1. A heating device, comprising:

a rotating body;

a heating body that heats a material to be heated while rotating together with the rotating body and conveying the material to be heated between the heating body and the rotating body; and

and a contact mechanism that, in a state where the material to be heated is not present between the rotating body and the heating body after the material to be heated has passed between the rotating body and the heating body, brings the rotating body into contact with the heating body that heats the rotating body while rotating together with the rotating body at a center portion in a rotation axis direction, and brings both end portions in the rotation axis direction of the rotating body into contact with the heating body over a smaller range than at the center portion in the rotation axis direction.

2. The heating device according to claim 1,

in the non-existing state, the contact mechanism makes a contact width of the rotating body with the heating body in the rotation direction smaller at both ends in the rotation axis direction than at a center in the rotation axis direction.

3. The heating device according to claim 1,

the contact mechanism causes the rotating body to be in non-contact with the heating body at both ends in the rotation axis direction in the non-existing state.

4. A heating device, comprising:

a rotating body;

a heating body that heats a material to be heated while rotating together with the rotating body and conveying the material to be heated between the heating body and the rotating body; and

and a contact mechanism that, in a state where the material to be heated is not present between the rotating body and the heating body after the material to be heated has passed between the rotating body and the heating body, causes the rotating body to contact the heating body that heats the rotating body while rotating together with the rotating body at a central portion in the direction of the rotation axis, and forms a space between the rotating body and the heating body at both end portions in the direction of the rotation axis.

5. The heating device according to any one of claims 1 to 4,

the heating body is formed in a convex shape toward the rotating body at the center in the rotating shaft direction,

the contact mechanism moves the rotating body farther from the heating body in the non-existing state than in a heating state in which the material to be heated is heated between the rotating body and the heating body.

6. The heating device according to claim 5,

the rotating body is a roller having a diameter larger at both ends in the rotating axis direction than at a central portion in the rotating axis direction,

the recess dimension of the rotating body in the center portion in the rotation axis direction is smaller than the projection dimension of the heating body toward the rotating body in the center portion in the rotation axis direction.

7. The heating device according to any one of claims 1 to 6,

the contact mechanism, when the material to be heated having a larger dimension in the rotation axis direction than the material to be heated is conveyed after the material to be heated passes between the rotating body and the heating body, brings the rotating body into contact with the heating body that heats the rotating body while rotating together with the rotating body in the rotation axis direction center portion in an absence state in which the material to be heated is not present between the rotating body and the heating body, and brings each of both rotation axis direction end portions of the rotating body into contact with the heating body in a range smaller than a contact range in the rotation axis direction center portion.

8. A fixing device as the heating device according to any one of claims 1 to 7, wherein,

the rotating body is a pressure roller,

the fixing device fixes an image to a recording medium by applying pressure and heat to the recording medium while conveying the recording medium as the heated material between the pressure roller and the heating body.

9. The fixing device according to claim 8,

the heating body is formed in a convex shape toward the rotating body at the center in the rotating shaft direction,

the contact mechanism presses both ends of the pressure roller in a rotation axis direction toward the heating body in a heated state in which the recording medium is heated between the pressure roller and the heating body, and bends the pressure roller along the convex shape of the heating body,

in the non-existing state, the rotating body is kept away from the heating body.

10. An image forming apparatus includes:

a forming section that forms an image on the recording medium; and

the fixing device according to claim 8 or 9.

11. The image forming apparatus according to claim 10,

the contact mechanism of the fixing device, during the operation in the non-existing state, causes the pressure roller to contact the heating body that heats the pressure roller while rotating together with the pressure roller at a center portion in a rotation axis direction, and causes contact ranges of both end portions in the rotation axis direction of the pressure roller with the heating body to be smaller than a contact range at the center portion in the rotation axis direction.

12. A heating device, comprising:

a rotating body;

a heating body that heats a material to be heated while rotating together with the rotating body and conveying the material to be heated between the heating body and the rotating body; and

a contact mechanism that switches the rotating body between a first contact state and a second contact state in a state where the material to be heated is not present between the rotating body and the heating body after the material to be heated has passed between the rotating body and the heating body,

the first contact state is a state in which: the rotary body is brought into contact with the heating body that heats the rotary body while rotating together with the rotary body at a rotation axis direction center portion and a rotation axis direction one end portion, and a contact range of the rotary body with the heating body at the rotation axis direction other end portion is made smaller than a contact range at the rotation axis direction center portion,

the second contact state is a state in which: the rotating body is brought into contact with the heating body at the rotation axis direction center portion and the rotation axis direction other end portion, and a contact range with the heating body at the rotation axis direction one end portion is made smaller than a contact range at the rotation axis direction center portion.

13. The heating device according to claim 12,

the contact mechanism makes a contact width of the rotating body with the heating body in the rotation direction smaller at the other end portion in the rotation axis direction than at the center portion in the rotation axis direction in the first contact state, thereby making the contact range with the heating body smaller at the other end portion in the rotation axis direction than at the center portion in the rotation axis direction,

the contact mechanism makes a contact width of the rotating body with the heating body in the rotation direction smaller at one end portion in the rotation axis direction than at a center portion in the rotation axis direction in the second contact state, thereby making the contact range with the heating body smaller at the one end portion in the rotation axis direction than at the center portion in the rotation axis direction.

14. The heating device according to claim 12,

the contact mechanism causes the other end portion of the rotating body in the rotation axis direction to be in non-contact with the heating body in the first contact state,

the contact mechanism causes one end of the rotating body in the rotation axis direction to be in non-contact with the heating body in the second contact state.

15. A heating device, comprising:

a rotating body;

a heating body that heats a material to be heated while rotating together with the rotating body and conveying the material to be heated between the heating body and the rotating body; and

a contact mechanism that switches the rotating body between a first contact state and a second contact state in a state where the material to be heated is not present between the rotating body and the heating body after the material to be heated has passed between the rotating body and the heating body,

the first contact state is a state in which: the rotary body is brought into contact with the heating body that heats the rotary body while rotating together with the rotary body at a center portion in a rotation axis direction and one end portion in the rotation axis direction, and a space is formed between the rotary body and the heating body at the other end portion in the rotation axis direction,

the second contact state is a state in which: the rotating body is brought into contact with the heating body at the center in the rotation axis direction and the other end in the rotation axis direction, and a space is formed between the rotating body and the heating body at the one end in the rotation axis direction.

16. The heating apparatus according to any one of claims 12 to 15,

the contact mechanism has:

a first cam having a long diameter portion and a short diameter portion, the first cam being in contact with a first contacted portion disposed on one end side of the rotating body in the rotation axis direction; and

a second cam having a long diameter portion and a short diameter portion, the second cam being in contact with a second contacted portion disposed on the other end portion side of the rotating body in the rotating shaft direction,

the long diameter portion of the first cam is in contact with the first contacted portion at a first rotational position, the short diameter portion of the first cam is in contact with the first contacted portion at a second rotational position,

the short diameter portion of the second cam is in contact with the second contacted portion in the first rotational position, and the long diameter portion of the second cam is in contact with the second contacted portion in the second rotational position.

17. The heating device according to claim 16,

the first cam and the second cam are different in shape.

18. The heating apparatus according to any one of claims 12 to 17,

the contact mechanism rotates the rotating body a plurality of times in each of the first contact state and the second contact state, and switches between the first contact state and the second contact state.

19. The heating device according to claim 18,

the contact mechanism rotates the rotating body at the same rotation speed or the same rotation time in each of the first contact state and the second contact state, and switches between the first contact state and the second contact state.

20. The heating apparatus according to any one of claims 12 to 19,

the contact mechanism switches the rotating body between the first contact state and the second contact state in a non-existing state where the heated material is not present between the rotating body and the heating body when the heated material having a larger dimension in the rotation axis direction than the heated material is conveyed after the heated material passes between the rotating body and the heating body.

21. A fixing device as the heating device according to any one of claims 12 to 20, wherein,

the rotating body is a pressure roller,

the fixing device fixes an image to a recording medium by applying pressure and heat to the recording medium while conveying the recording medium as the heated material between the pressure roller and the heating body.

22. An image forming apparatus includes:

the fixing device according to claim 21; and

a forming section that forms an image on the recording medium.

23. The image forming apparatus according to claim 22,

the contact mechanism of the fixing device switches the pressure roller between a first contact state and a second contact state between jobs in the non-existing state.

Background

Patent document 1 discloses a fixing device including a heating rotating body heated by a heating member and a pressing rotating body which is in sliding contact with the heating rotating body and forms a fixing nip portion between the heating rotating body and the heating rotating body, wherein a recording sheet having an unfixed toner image transferred thereto is heated and pressed while being nipped and conveyed by the fixing nip portion, and the unfixed toner image is fixed to a surface of the recording sheet, and the fixing device is characterized in that a heat transfer member is provided so as to be capable of coming into contact with either one of the rotating bodies.

Patent document 1: japanese patent laid-open publication No. 2004-53674

When a material to be heated such as paper passes between a rotating body such as a pressure roller and the center portion in the rotation axis direction of a heating body such as a heating belt, the temperature of the center portion in the rotation axis direction of the rotating body is lower than the temperatures of both end portions in the rotation axis direction. This may cause temperature unevenness in the rotating shaft direction in the rotating body.

Disclosure of Invention

The present invention reduces temperature unevenness in the rotation axis direction of the rotating body in a short time after the material to be heated passes between the rotating body and the central portion in the rotation axis direction of the heating body, as compared with a configuration in which the contact range between the rotating body and the heating body is kept in the same state at the central portion in the rotation axis direction and at both end portions in the rotation axis direction in a state in which the material to be heated does not exist between the rotating body and the heating body after the material to be heated passes between the rotating body and the heating body.

A first aspect of the present invention is a heating device including: a rotating body; a heating body that heats a material to be heated while rotating together with the rotating body and conveying the material to be heated between the heating body and the rotating body; and a contact mechanism that, in a state where the material to be heated is not present between the rotating body and the heating body after the material to be heated has passed between the rotating body and the heating body, brings the rotating body into contact with the heating body that heats the rotating body while rotating together with the rotating body at a center portion in a rotation axis direction, and brings both end portions in the rotation axis direction of the rotating body into contact with the heating body over a range that is smaller than a range of contact at the center portion in the rotation axis direction.

According to a second aspect of the present invention, in the first aspect, the contact mechanism is configured to make a contact width of the rotating body with the heating body in the rotation direction smaller at both ends in the rotation axis direction than at a center portion in the rotation axis direction in the non-existing state.

According to a third aspect of the present invention, in the first aspect, the contact mechanism causes the rotating body to be out of contact with the heating body at both ends in the rotation axis direction in the non-existing state.

A fourth aspect of the present invention is a heating apparatus having: a rotating body; a heating body that heats a material to be heated while rotating together with the rotating body and conveying the material to be heated between the heating body and the rotating body; and a contact mechanism that, in a state where the material to be heated is not present between the rotating body and the heating body after the material to be heated has passed between the rotating body and the heating body, causes the rotating body to contact the heating body that heats the rotating body while rotating together with the rotating body at a central portion in the direction of the rotation axis, and forms a space between the rotating body and the heating body at both end portions in the direction of the rotation axis.

According to a fifth aspect of the present invention, in any one aspect of the first to fourth aspects, the heating body is formed in a convex shape toward the rotary body at a center portion in a rotation axis direction, and the contact mechanism moves the rotary body farther from the heating body in the non-existing state than in a heating state in which the material to be heated is heated between the rotary body and the heating body.

According to a sixth aspect of the present invention, in the fifth aspect, the rotating body is a roller having a diameter larger at both ends in the rotation axis direction than at a center portion in the rotation axis direction, and a recess dimension of the rotating body at the center portion in the rotation axis direction is smaller than a projection dimension of the heating body toward the rotating body side at the center portion in the rotation axis direction.

According to a seventh aspect of the present invention, in any one aspect of the first to sixth aspects, the contact mechanism makes the rotary body contact the heating body that heats the rotary body while rotating together with the rotary body at the center in the rotation axis direction in a state where the heated material is not present between the rotary body and the heating body when the heated material having a larger dimension in the rotation axis direction than the heated material is conveyed after the heated material passes between the rotary body and the heating body, and makes contact ranges of both ends in the rotation axis direction of the rotary body with the heating body smaller than a contact range at the center in the rotation axis direction.

An eighth aspect of the present invention is the heating device according to any one of the first to seventh aspects, wherein the rotating body is a pressure roller, and the fixing device fixes an image to a recording medium by pressing and heating the recording medium while conveying the recording medium as the material to be heated between the pressure roller and the heating body.

According to a ninth aspect of the present invention, in the eighth aspect, the heating body is formed in a convex shape toward the rotating body side at the center portion in the rotation axis direction, and the contact mechanism presses both end portions in the rotation axis direction of the pressure roller toward the heating body side in a heating state in which the recording medium is heated between the pressure roller and the heating body, and bends the pressure roller along the convex shape of the heating body, and in the non-existing state, separates the rotating body from the heating body.

A tenth aspect of the present invention is an image forming apparatus including: a forming section that forms an image on the recording medium; and the fixing device according to the eighth or ninth aspect.

An image forming apparatus according to an eleventh aspect of the present invention is the tenth aspect, wherein the contact mechanism of the fixing device contacts the pressure roller with a heating body that heats the pressure roller while rotating together with the pressure roller at a rotation axis direction center portion during the operation in the non-existing state, and a contact range between each of rotation axis direction both end portions of the pressure roller and the heating body is made smaller than a contact range at the rotation axis direction center portion.

A twelfth aspect of the present invention is a heating device including: a rotating body; a heating body that heats a material to be heated while rotating together with the rotating body and conveying the material to be heated between the heating body and the rotating body; and a contact mechanism that switches the rotating body between a first contact state and a second contact state in a state where the heated material is not present between the rotating body and the heating body after the heated material passes between the rotating body and the heating body, the first contact state being a state in which: the rotating body is brought into contact with the heating body that heats the rotating body while rotating together with the rotating body at a rotation axis direction center portion and a rotation axis direction one end portion, and a contact range of the rotating body with the heating body at a rotation axis direction other end portion is made smaller than a contact range at the rotation axis direction center portion, and the second contact state is a state in which: the rotating body is brought into contact with the heating body at the rotation axis direction center portion and the rotation axis direction other end portion, and a contact range with the heating body at the rotation axis direction one end portion is made smaller than a contact range at the rotation axis direction center portion.

In the heating apparatus according to a thirteenth aspect of the present invention, in the twelfth aspect, the contact mechanism is configured to, in the first contact state, the contact width of the rotating body in the rotating direction with the heating body is made smaller at the other end portion in the rotating axis direction than at the central portion in the rotating axis direction, whereby the contact range with the heating body at the other end portion in the rotation axis direction of the rotating body is made smaller than the contact range with the heating body at the center portion in the rotation axis direction, in the second contact state, a contact width of the rotating body with the heating body in the rotation direction is made smaller at one end portion in the rotation axis direction than at a central portion in the rotation axis direction, thereby making the contact range with the heating body at the rotation axis direction one end portion of the rotating body smaller than the contact range with the heating body at the rotation axis direction center portion.

In the heating device according to a fourteenth aspect of the present invention, in the twelfth aspect, the contact mechanism causes the other end portion of the rotating body in the rotation axis direction to be out of contact with the heating body in the first contact state, and causes the one end portion of the rotating body in the rotation axis direction to be out of contact with the heating body in the second contact state.

A fifteenth aspect of the present invention is a heating device including: a rotating body; a heating body that heats a material to be heated while rotating together with the rotating body and conveying the material to be heated between the heating body and the rotating body; and a contact mechanism that switches the rotating body between a first contact state and a second contact state in a state where the material to be heated is not present between the rotating body and the heating body after the material to be heated has passed between the rotating body and the heating body, the first contact state being a state in which: the rotating body is brought into contact with the heating body that heats the rotating body while rotating together with the rotating body at a center portion in a rotation axis direction and one end portion in the rotation axis direction, and a space is formed between the rotating body and the heating body at the other end portion in the rotation axis direction, and the second contact state is a state in which: the rotating body is brought into contact with the heating body at the center in the rotation axis direction and the other end in the rotation axis direction, and a space is formed between the rotating body and the heating body at the one end in the rotation axis direction.

According to a sixteenth aspect of the present invention, in any one of the twelfth to fifteenth aspects, the contact mechanism includes: a first cam having a long diameter portion and a short diameter portion, the first cam being in contact with a first contacted portion disposed on one end side of the rotating body in the rotation axis direction; and a second cam that is in contact with a second contacted portion disposed on the other end portion side in the rotation axis direction of the rotating body, and that has a long diameter portion and a short diameter portion, wherein the long diameter portion of the first cam is in contact with the first contacted portion at a first rotation position, the short diameter portion of the first cam is in contact with the first contacted portion at a second rotation position, the short diameter portion of the second cam is in contact with the second contacted portion at the first rotation position, and the long diameter portion of the second cam is in contact with the second contacted portion at the second rotation position.

In the heating device according to a seventeenth aspect of the present invention, in the sixteenth aspect, the first cam and the second cam have different shapes.

According to an eighteenth aspect of the present invention, in any one of the twelfth to seventeenth aspects, the contact mechanism switches between the first contact state and the second contact state while rotating the rotating body a plurality of times in each of the first contact state and the second contact state.

According to a nineteenth aspect of the present invention, in the eighteenth aspect, the contact mechanism rotates the rotating body at the same rotation speed or for the same rotation time in each of the first contact state and the second contact state, and switches between the first contact state and the second contact state.

According to a heating device of a twentieth aspect of the present invention, in any one of the twelfth aspect to the nineteenth aspect, the contact mechanism switches the rotating body between the first contact state and the second contact state in a state where the rotating body is not present between the rotating body and the heating body when the heated material having a larger dimension in the rotation axis direction than the heated material is conveyed after the heated material passes between the rotating body and the heating body.

A twenty-first aspect of the present invention is the heating device according to any one of the twelfth to twentieth aspects, wherein the rotating body is a pressure roller, and the fixing device fixes the image to the recording medium by pressing and heating the recording medium as the material to be heated while conveying the recording medium between the pressure roller and the heating body.

A twenty-second aspect of the present invention is an image forming apparatus including: the fixing device according to the twenty-first aspect; and a forming section that forms an image on the recording medium.

In an image forming apparatus according to a twenty-third aspect of the present invention, in the twenty-second aspect, the contact mechanism of the fixing device switches the pressure roller between a first contact state and a second contact state during the job as the non-existing state.

According to the configuration of the first aspect, the temperature unevenness in the rotation axis direction of the rotating body can be reduced in a short time after the material to be heated passes between the rotating body and the rotation axis direction center portion of the heating body, as compared with the configuration in which the contact range between the rotating body and the heating body is the same at the rotation axis direction center portion and both rotation axis direction end portions in the non-existing state.

According to the configuration of the second aspect, compared to a configuration in which the rotary body is not in contact with the heating body at both ends in the rotation axis direction in the absence state, the angle of one of the rotary body and the heating body with respect to the other is less likely to change.

According to the configuration of the third aspect, the temperature unevenness in the rotation axis direction of the rotating body can be reduced in a short time after the material to be heated passes between the rotating body and the rotation axis direction center portion of the heating body, as compared with the configuration in which the rotating body is in contact with the heating body at both ends in the rotation axis direction in the non-existing state.

According to the configuration of the fourth aspect, the temperature unevenness in the rotation axis direction of the rotating body can be reduced in a short time after the material to be heated passes between the rotating body and the rotation axis direction center portion of the heating body, as compared with the configuration in which the rotating body is in contact with the heating body at both ends in the rotation axis direction in the non-existing state.

According to the configuration of the fifth aspect, the contact range of the rotating body with the heating body at the center portion in the rotation axis direction can be adjusted by the distance by which the rotating body is away from the heating body.

According to the configuration of the sixth aspect, in the non-existing state, the contact range of the rotating body with the heating body at the both ends in the rotation axis direction is easily made smaller than the contact range at the center in the rotation axis direction, as compared with the configuration in which the recess dimension is larger than the protrusion dimension.

According to the configuration of the seventh aspect, in the absence state between the materials to be heated when the materials to be heated having a larger dimension in the rotation axis direction than the materials to be heated are conveyed after the materials to be heated have passed between the rotating body and the heating body, the effect of suppressing wrinkles in the materials to be heated being conveyed is more excellent than in the configuration in which the contact range between the rotating body and the heating body is the same at the center portion in the rotation axis direction and at both end portions in the rotation axis direction.

According to the configuration of the eighth aspect, compared to a configuration in which the contact range between the pressure roller and the heating body is the same at the center portion in the rotation axis direction and at both end portions in the rotation axis direction in the non-existing state, it is possible to suppress uneven fixing of an image.

According to the configuration of the ninth aspect, in the configuration in which the heating body is formed in the convex shape toward the rotary body side at the center portion in the rotary shaft direction, it is possible to suppress uneven fixing of an image in a heated state, as compared with the configuration in which the state in which the pressure roller is maintained along the rotary shaft direction.

According to the configuration of the tenth aspect, image defects can be suppressed as compared with a configuration in which the contact range of the pressure roller and the heating body is the same at the center portion in the rotation axis direction and at both end portions in the rotation axis direction in the non-existing state.

According to the configuration of the eleventh aspect, image defects can be suppressed as compared with a configuration in which the contact range between the pressure roller and the heating body is the same at the center portion in the rotation axis direction and at both end portions in the rotation axis direction during work.

According to the configuration of the twelfth aspect, the temperature unevenness in the rotation axis direction of the rotating body can be reduced in a short time after the material to be heated passes between the rotating body and the heating body at the center portion in the rotation axis direction, as compared with the configuration in which the state in which the rotating body and the heating body are in contact from the one end portion to the other end portion in the rotation axis direction is continued in the non-existing state.

According to the configuration of the thirteenth aspect, compared to a configuration in which the rotary body is not in contact with the heating body at both ends in the rotation axis direction in the absence state, the angle of one of the rotary body and the heating body with respect to the other is less likely to change.

According to the configuration of the fourteenth aspect, the temperature unevenness in the rotation axis direction of the rotating body can be reduced in a short time after the material to be heated passes between the rotating body and the heating body at the rotation axis direction center portion, as compared with the configuration in which the one end portion in the rotation axis direction and the other end portion in the rotation axis direction of the rotating body are simultaneously in contact with the heating body in the non-existing state.

According to the fifteenth aspect, as compared with the configuration in which the one end portion in the rotation axis direction and the other end portion in the rotation axis direction of the rotary body are simultaneously in contact with the heating body in the non-existing state, the temperature variation in the rotation axis direction of the rotary body can be reduced in a short time after the material to be heated passes between the rotary body and the heating body at the center portion in the rotation axis direction.

According to the configuration of the sixteenth aspect, the rotating body can be switched between the first contact state and the second contact state by rotating the first cam and the second cam between the first rotational position and the second rotational position.

According to the configuration of the seventeenth aspect, the degree of freedom in adjusting the positional relationship between the rotary body and the heating body in the first contact state and the second contact state is higher than that in a configuration in which a pair of cams having the same shape are used while changing their phases.

According to the eighteenth aspect, the temperature variation in the rotational direction of the rotating body can be reduced as compared with a configuration in which the rotating body rotates less than two revolutions in each of the first contact state and the second contact state.

According to the configuration of the nineteenth aspect, temperature unevenness in the rotation axis direction of the rotating body can be reduced as compared with a configuration in which the rotating body rotates at a different rotation speed or for a different rotation time in each of the first contact state and the second contact state.

According to the configuration of the twentieth aspect, in the absence of the heated material when the heated material having a larger dimension in the rotation axis direction than the heated material is conveyed after the heated material passes between the rotating body and the heating body, the effect of suppressing wrinkles in the conveyed heated material is more excellent than in the configuration in which the rotating body and the heating body are continued to be in contact with each other from one end portion to the other end portion in the rotation axis direction.

According to the configuration of the twenty-first aspect, it is possible to suppress uneven fixing of an image, as compared with a configuration in which the pressure roller and the heating body are kept in contact from one end portion to the other end portion in the rotation axis direction in the non-existing state.

According to the configuration of the twenty-second aspect, an image failure can be suppressed as compared with a configuration in which a state in which the pressure roller and the heating body are in contact from one end portion to the other end portion in the rotation axis direction is continued in an absent state.

According to the configuration of the twenty-third aspect, image defects can be suppressed as compared with a configuration in which the state in which the pressure roller and the heating body are in contact from one end portion to the other end portion in the rotation axis direction is continued during the job.

Drawings

Fig. 1 is a schematic diagram showing the configuration of the image forming apparatus according to the first and fourth embodiments.

Fig. 2 is a schematic diagram showing the structure of the heating belt of the first and fourth embodiments.

Fig. 3 is a schematic diagram showing the structure of the pressure roller according to the first and fourth embodiments.

Fig. 4 is a schematic view showing a state in which the pressure roller of the first and fourth embodiments is located at the nip position.

Fig. 5 is a schematic view showing a state in which the pressure roller of the first embodiment is located at the center contact position.

Fig. 6 is a schematic diagram showing a state in which the pressure roller of the first embodiment is located at the separated position.

Fig. 7 is a front view showing the structure of the contact mechanism of the first embodiment.

Fig. 8 is a perspective view showing the structure of the contact mechanism of the first embodiment.

Fig. 9 is a schematic diagram showing the structure of the cam of the first embodiment.

Fig. 10 is a graph showing a relationship between a rotational position of the cam and an amount of press-fitting into the cam follower in the first embodiment.

Fig. 11 is a block diagram showing the hardware configuration of the control device of the first and fourth embodiments.

Fig. 12 is a block diagram showing an example of the functional configuration of the control device of the first and fourth embodiments.

Fig. 13 is a diagram for explaining a preceding job, a subsequent job, and a concept between jobs in the case where a plurality of jobs are executed by the image forming apparatuses of the first and fourth embodiments.

Fig. 14 is a graph showing the relationship between the axial position of the pressure roller and the temperature in the first embodiment.

Fig. 15 is a schematic view showing a contact state of the pressure roller with the heating belt at both end portions in the axial direction in a case where the pressure roller of the second embodiment is located at the center contact position.

Fig. 16 is a schematic view showing a contact state of the pressure roller with the heating belt at the axial center portion in the case where the pressure roller of the second embodiment is located at the center contact position.

Fig. 17 is a schematic diagram for illustrating a difference in size of recording media between a preceding job and a succeeding job in the image forming apparatuses of the third and sixth embodiments.

Fig. 18A is a schematic view showing a state in which the pressure roller of the fourth embodiment is located at the first contact position.

Fig. 18B is a schematic diagram showing a state in which the pressure roller of the fourth embodiment is located at the second contact position.

Fig. 19 is a front view showing the structure of the contact mechanism of the fourth embodiment.

Fig. 20 is a perspective view showing the structure of the contact mechanism of the fourth embodiment.

Fig. 21 is a schematic diagram showing the structure of a cam according to the fourth embodiment.

Fig. 22 is a graph showing a relationship between a rotational position of the cam and an amount of press-fitting into the cam follower in the fourth embodiment.

Fig. 23 is a graph showing the relationship between the axial direction position and the temperature of the pressure roller of the fourth embodiment.

Fig. 24 is a graph showing the relationship between the axial position and the temperature of the pressure roller in the state where the pressure roller of the fourth embodiment is located at the first contact position.

Fig. 25 is a graph showing the relationship between the axial position of the pressure roller and the temperature in a state where the pressure roller of the fourth embodiment is located at the second contact position.

Fig. 26 is a schematic view showing a contact state of the pressure roller with the heating belt at the axial end portion in the case where the pressure roller of the fifth embodiment is located at the first contact position and the second contact position.

Fig. 27 is a schematic view showing a contact state of the pressure roller with the heating belt at the axial center portion in the case where the pressure roller is located at the first contact position and the second contact position in the fifth embodiment.

Description of the reference symbols

10: an image forming apparatus; 14: a forming section; 16: a fixing device (an example of a heating device); 40: a pressure roller (an example of a rotating body); 46: a space; 60: a heating belt (an example of a heating body); 70: a contact mechanism; p2: a recording medium (an example of a material to be heated); 71: a first cam; 72: a second cam.

Detailed Description

Hereinafter, an example of an embodiment of the present invention will be described with reference to the drawings.

First embodiment

(image Forming apparatus 10)

First, the configuration of the image forming apparatus 10 according to the present embodiment will be described. Fig. 1 is a schematic diagram showing the configuration of an image forming apparatus 10 according to the present embodiment.

As shown in fig. 1, the image forming apparatus 10 includes a first conveying unit 11, a second conveying unit 12, a forming unit 14, and a fixing device 16. The first conveying unit 11 has a function of conveying the recording medium P1. Specifically, as shown in fig. 1, the first conveying section 11 includes a winding-out roller (unwinding roller)22, a winding-up roller (winding roller)24, and a winding-up roller (winding roller) 26.

The recording medium P1 is wound around the wind-out roller 22 in advance. The unwinding roller 22 winds out the wound recording medium P1 by rotating. The winding roller 26 is wound around the recording medium P1 between the unwinding roller 22 and the winding roller 24. Thereby, a conveyance path of the recording medium P1 from the wind-out roller 22 to the wind-up roller 24 is determined. The take-up roller 24 is a roller that takes up the recording medium P1. The take-up roller 24 is rotationally driven by a driving unit (not shown). Thereby, the recording medium P1 is wound by the winding-up roller 24, and the recording medium P1 is wound out by the winding-out roller 22. Thereby, the recording medium P1 is conveyed from the wind-out roller 22 to the wind-up roller 24. As an example of the recording medium P1, a hot-pressed foil is used.

The forming section 14 has a function of forming an image on the recording medium P1. Specifically, the formation portion 14 is an ejection portion that ejects liquid droplets. More specifically, the forming portion 14 is constituted by a head as an ejection portion that ejects ink droplets as liquid droplets.

The second conveying unit 12 has a function of conveying the recording medium P2 as an example of the material to be heated. The second conveying unit 12 includes, for example, a conveying roller pair 13. In the second conveying section 12, the recording medium P2 is conveyed to the fixing device 16 in accordance with the timing at which the image formed on the recording medium P1 is conveyed to the fixing device 16 (specifically, a contact area 50S described later). As an example of the recording medium P2, for example, paper is used. Here, the recording medium P1 is roll paper, but the recording medium P2 is cut paper. In addition, the recording medium P1 hardly affects the temperature of the fixing device 16 (specifically, the temperature of the pressure roller 40), and the effect of the temperature decrease of the fixing device 16 due to the heated material mainly depends on the recording medium P2.

The fixing device 16 transfers and fixes the image formed on the recording medium P1 onto the recording medium P2. The specific configuration of the fixing device 16 will be described later.

The forming portion 14 may be an electrophotographic image forming portion that forms a toner image as an image. In the electrophotographic image forming unit, a toner image is formed on the recording medium P2 through various steps such as charging, exposure, development, and transfer.

The forming unit 14 may form an image directly on the recording medium P2. In this case, for example, the fixing device 16 fixes the image formed on the recording medium P2 onto the recording medium P2.

(fixing device 16)

The fixing device 16 shown in fig. 1 is an example of a heating device. As shown in fig. 1, the fixing device 16 has a pressure roller 40 and a heating belt 60, and the fixing device 16 presses and heats the recording medium P1 and the recording medium P2 while conveying the recording medium P1 and the recording medium P2 between the pressure roller 40 and the heating belt 60, thereby fixing the image of the recording medium P1 to the recording medium P2.

In this way, the fixing device 16 functions as a heating device that heats the recording medium P2, which is an example of a material to be heated. More specifically, the fixing device 16 includes a contact mechanism 70 (see fig. 7) and a control device 50 (see fig. 7) in addition to the pressure roller 40 and the heating belt 60. Hereinafter, a specific configuration of each part of the fixing device 16 will be described.

(pressure roller 40 and heating belt 60)

The heating belt 60 shown in fig. 1 is an example of a heating body. The pressure roller 40 shown in fig. 1 is an example of a rotating body. The pressure roller 40 and the heating belt 60 are disposed opposite to each other. In the present embodiment, as shown in fig. 1, the heating belt 60 is disposed on the lower side of the pressure roller 40, for example.

The heating belt 60 is formed in a ring shape, specifically, a jointless shape. A heating unit (not shown) that heats the heating belt 60 is provided on at least one of the inner circumferential side and the outer circumferential side of the heating belt 60. As the heating portion, for example, a heating portion that heats the heating belt 60 by a heating element that generates heat by joule heat generated by an internal resistance, a heating portion such as a lamp that heats the heating belt 60 by radiant heat, or the like is used.

As shown in fig. 1, a spacer 66 serving as a support portion is provided on the inner periphery of the heating belt 60 on the side of the pressure roller 40. As shown in fig. 2, the liner 66 has a length along the width of the heating belt 60. The pad 66 has a bearing surface 66A facing the pressure roller 40 side (i.e., the upper side). The support surface 66A supports the inner peripheral surface of the heating belt 60. The pad 66 is formed in a convex shape toward the pressure roller 40 at the center portion in the belt width direction. Thereby, the entire heating belt 60 is formed in a convex shape toward the pressure roller 40 (i.e., upward) at the center portion in the belt width direction.

The belt width direction is a direction (specifically, a perpendicular direction) intersecting with the rotation direction of the heating belt 60. The belt width direction may be a direction along the rotation axis direction (hereinafter referred to as axial direction) of the pressure roller 40.

As shown in fig. 3, the pressure roller 40 is a roller having a larger diameter at both end portions in the axial direction than at a central portion. Specifically, the outer diameter of the pressure roller 40 gradually increases from the center portion in the axial direction toward both end portions. The outer diameter of the pressure roller 40 is continuously increased from the center portion in the axial direction toward both end portions. In this way, by making the diameter of the both end portions in the axial direction of the pressure roller 40 larger than the central portion, the conveying speed of the pressure roller 40 to the recording medium P2 becomes faster at the both end portions in the width direction than at the central portion. Thus, tension acts from the center of the recording medium P2 in the width direction toward both ends, and wrinkles in the recording medium P2 are suppressed.

The recess dimension at the axial center portion of the pressure roller 40 (see fig. 3) is smaller than the projection dimension toward the pressure roller 40 side at the axial center portion of the heating belt 60 (see fig. 2). The depression of the pressure roller 40 is a dimension along the radial direction from the outer peripheral surface of the axial end portion to the outer peripheral surface of the axial center portion of the pressure roller 40 (see fig. 3). In other words, the depression size of the pressing roller 40 is a difference in radius between the maximum radius and the minimum radius of the pressing roller 40. The protruding dimension of the heating belt 60 is a dimension along the radial direction from the outer peripheral surface of the end portion in the belt width direction to the outer peripheral surface of the central portion in the belt width direction of the heating belt 60. The protruding dimension of the heating belt 60 can also be understood as a difference in height between the end portion in the belt width direction and the central portion in the belt width direction at the support surface 66A of the spacer 66.

As shown in fig. 1 and 4, the pressing roller 40 is pressed against the heating belt 60. Thereby, a contact area 50S (i.e., a fixing nip) where the heating belt 60 contacts the pressure roller 40 is formed. In other words, the contact region 50S is a region formed between the heating belt 60 and the pressing roller 40.

As described later, the pressure roller 40 is moved by the contact mechanism 70 between a contact position (hereinafter referred to as a nip position) shown in fig. 1 and 4, a contact position (hereinafter referred to as a center contact position) shown in fig. 5, and a separation position shown in fig. 6. The pressing roller 40 is pressed against the heating belt 60 at a nip position shown in fig. 4.

The pressure roller 40 is driven to rotate by a driving unit 42 (see fig. 7). The heating belt 60 rotates following the pressure roller 40. Thus, the heating belt 60 heats the recording medium P2 while rotating together with the pressure roller 40 and being conveyed with the pressure roller 40 across the recording medium P2.

That is, in the fixing device 16, the recording medium P2 introduced into the contact region 50S is conveyed while being pressed between the heating belt 60 and the pressing roller 40, and the image of the recording medium P1 is fixed to the recording medium P2 by the pressing force and heat generated by the heating belt 60. In this way, in the present embodiment, the recording medium P2 passes through the contact region 50S (i.e., between the heating belt 60 and the pressure roller 40), thereby fixing the image of the recording medium P1.

The axial center of the pressure roller 40 substantially coincides with the center of the heating belt 60 in the belt width direction. The recording medium P2 is conveyed by the heating belt 60 and the pressure roller 40 in a state in which the width direction center substantially coincides with the axial direction center of the pressure roller 40 and the belt width direction center of the heating belt 60 (i.e., center alignment).

(contact mechanism 70)

The contact mechanism 70 shown in fig. 7 and 8 is a mechanism for bringing the pressure roller 40 into contact with the heating belt 60. Specifically, the contact mechanism 70 moves the pressure roller 40 between a nip position shown in fig. 1, 4, 7, and 8, a center contact position shown in fig. 5, and a separation position shown in fig. 6.

More specifically, as shown in fig. 7 and 8, the contact mechanism 70 includes a pair of lever portions 80, a pair of cams 72, a camshaft 74, a camshaft gear 76, a transmission gear 78, and a driving portion 79 (see fig. 7). In addition, in fig. 7 and 8, one rod portion 80 of the pair of rod portions 80 is shown, and one cam 72 of the pair of cams 72 is shown.

The pair of lever portions 80 are displacement portions that displace the pressure roller 40. The pair of lever portions 80 are disposed on one end side and the other end side in the axial direction of the pressure roller 40, respectively. Specifically, as shown in fig. 7, each lever portion 80 includes a lever 82, a support member 84, a spring portion 86, and a cam follower 88.

The lever 82 is supported at one end portion thereof to the main body of the fixing device 16 so as to be rotatable via a fulcrum 82A, and the fulcrum 82A is disposed upstream (rightward in fig. 7) in the conveying direction with respect to the pressure roller 40.

The lever 82 extends obliquely upward from the fulcrum 82A toward the downstream side in the conveying direction (the left side in fig. 7), bends toward the upper side of the pressure roller 40, and extends toward the downstream side in the conveying direction (the left side in fig. 7) from the bent portion 82B. The cam follower 88 is formed in a roller shape and is rotatably attached to the curved portion 82B of the lever 82.

The supporting member 84 rotatably supports the pressure roller 40. The support member 84 is provided at the other end of the lever 82 so that the pressure roller 40 can move in a direction of approaching the heating belt 60 (downward in fig. 7) and in the opposite direction (upward in fig. 7) within a predetermined range.

The spring portion 86 is formed of a coil spring and is provided between the lever 82 and the support member 84. The spring portion 86 presses the support member 84 in the approaching direction by its elastic force.

The cam shaft 74 is a rotary shaft extending in the axial direction of the pressure roller 40 on the upper side of the pressure roller 40 and the lever 82. The cam shaft 74 is rotatably supported by the apparatus main body of the fixing apparatus 16.

The pair of cams 72 are fixed to one end side and the other end side in the axial direction of the cam shaft 74, respectively. As shown in fig. 9, each of the cams 72 includes: a short diameter portion 90; a first long diameter portion 91 having a longer radial length from the camshaft 74 (i.e., the rotation center) than the short diameter portion 90; and a second long diameter portion 92 having a longer radial length from the camshaft 74 than the short diameter portion 90 and shorter than the first long diameter portion 91.

As shown in fig. 7, each cam 72 contacts each cam follower 88, and the contact position of the cam 72 with the cam follower 88 changes according to the rotation angle of the cam shaft 74. The pair of cams 72 have the same shape.

The camshaft gear 76 is fixed to one axial end of the camshaft 74. The transmission gear 78 is rotatably supported on the apparatus main body of the fixing apparatus 16 in a state of meshing with the cam shaft gear 76.

The driving section 79 drives the transmission gear 78 to rotate. Specifically, the driving unit 79 is constituted by a stepping motor that rotates the transmission gear 78 forward and backward, for example.

Further, in the contact mechanism 70, the driving portion 79 rotates the transmission gear 78 (specifically, normal rotation and reverse rotation), whereby the driving force is transmitted to the camshaft 74 via the camshaft gear 76, and the camshaft 74 and the cam 72 rotate.

By the rotation of the cam 72, the contact position with the cam follower 88 is changed among the short diameter portion 90, the first long diameter portion 91, and the second long diameter portion 92. The pressure roller 40 is located at the separated position shown in fig. 6 by the contact of the short diameter portion 90 of the cam 72 with the cam follower 88. The pressure roller 40 is in non-contact with the heating belt 60 from one axial end portion to the other axial end portion at the separation position.

When the short diameter portion 90 of the cam 72 contacts the cam follower 88, the amount a of press-fitting of the cam 72 into the cam follower 88 is minimized as shown in fig. 10.

When the cam 72 rotates and the first long diameter portion 91 of the cam 72 contacts the cam follower 88, the lever 82 rotates about the fulcrum 82A, and the pressure roller 40 moves to the nip position shown in fig. 4. At the nip position, both end portions of the pressure roller 40 in the axial direction are pressed toward the heating belt 60 by the elastic force of the spring portion 86. Thereby, the pressure roller 40 is bent along the convex shape of the heating belt 60. As a result, the pressure roller 40 comes into contact with the heating belt 60 from one axial end portion to the other axial end portion at the nip position, and a contact region 50S is formed.

When the first long diameter portion 91 of the cam 72 contacts the cam follower 88, the amount of press-fitting C of the cam 72 into the cam follower 88 is maximized as shown in fig. 10.

When the cam 72 further rotates and the second long diameter portion 92 of the cam 72 contacts the cam follower 88, the lever 82 rotates about the fulcrum 82A, and the pressure roller 40 moves to the center contact position shown in fig. 5. At the center contact position, the pressure roller 40 contacts the heating belt 60 at the axial center portion, and the contact ranges of the respective axial end portions with the heating belt 60 are smaller than the contact range of the axial center portion. Specifically, at the center contact position, the pressure roller 40 is in contact with the heating belt 60 at the center portion in the axial direction, and is not in contact with the heating belt 60 at both end portions in the axial direction.

In other words, at the center contact position, the pressure roller 40 contacts the heating belt 60 at the axial center portion, and a space 46 is formed between the pressure roller 40 and both axial end portions of the heating belt 60.

When the second long diameter portion 92 of the cam 72 contacts the cam follower 88, as shown in fig. 10, the press-in amount B of the cam 72 with respect to the cam follower 88 is an intermediate value between the press-in amount a and the press-in amount C. Therefore, the pressing roller 40 is farther at the center contact position than at the nip position and closer than at the separation position with respect to the heating belt 60.

The configuration in which the contact range between each of the two axial end portions and the heating belt 60 is smaller than the contact range at the axial center portion is a concept including the configuration in which the contact range is 0 (zero) as described above.

As described above, the contact mechanism 70 causes the pressing roller 40 to contact and separate from the heating belt 60. In other words, the contact mechanism 70 can be said to be a mechanism that displaces the pressure roller 40 to change the distance between the rotational axis of the pressure roller 40 and the rotational axis of the heating belt 60.

(control device 50)

The control device 50 controls the operations of the respective parts including the driving part 79 in the fixing device 16. In the present embodiment, the control device 50 is configured as a device that controls the operations of each unit of the image forming apparatus 10. The control device 50 may be configured to control at least the operation of the driving unit 79. Fig. 11 is a block diagram showing a hardware configuration of the control device 50.

As shown in fig. 11, the control device 50 has a function as a computer, and includes a CPU (Central Processing Unit) 51, a ROM (Read Only Memory) 52, a RAM (Random Access Memory) 53, a Memory 54, a user interface 55, a communication interface 56, and an I/O Unit 57. The respective units of the control device 50 are communicably connected to each other via a bus 59.

The CPU 51 is a central processing unit, and executes various programs and controls the respective units. That is, the CPU 51 reads out the program from the ROM52 or the memory 54 and executes the program with the RAM 53 as a work area. The CPU 51 controls each unit of the image forming apparatus 10 and performs various arithmetic processes in accordance with programs recorded in the ROM52 or the memory 54.

The ROM52 stores various programs and various data. The RAM 53 temporarily stores programs or data as a work area. The memory 54 is a storage unit such as an HDD (Hard Disk Drive) or an SSD (Solid State Drive), and stores various programs including an operating system and various data.

The user interface 55 is an interface when the user uses the image forming apparatus 10. The user interface 55 includes an input unit such as a button or a touch panel, and a display unit such as a liquid crystal display. The user is an instruction person who instructs execution of a job.

The communication interface 56 is an interface for communicating with a user terminal such as a personal computer. As a communication method of the communication interface 56, wired or wireless is used. As a communication standard of the communication interface 56, for example, ethernet (registered trademark), FDDI, Wi-Fi (registered trademark), or the like is used. The I/O unit 57 connects the CPU 51 to each unit of the image forming apparatus 10.

When executing the program, the control device 50 uses the hardware resources to realize various functions. The functional configuration realized by the control device 50 will be described. Fig. 12 is a block diagram showing an example of the functional configuration of the control device 50.

As shown in fig. 12, the control device 50 has an acquisition unit 50A and a control unit 50B as functional configurations. Each functional configuration is realized by the CPU 51 reading out and executing a control program stored in the ROM52 or the memory 54.

The acquisition unit 50A acquires an execution instruction to execute a job and job information related to the job. The acquisition unit 50A acquires information such as the size (specifically, the size in the conveying direction and the width direction), the number of sheets, and the conveying speed of the recording medium P2 designated in the job as job information related to the job. The job is a processing unit of an image forming operation executed in response to one instruction by an instruction person. The instructor specifies the size, the number, the conveyance speed, and the like of the recording medium P2 during the job.

For example, an instruction to execute a job is input through a user terminal that can communicate via the communication interface 56, and the acquisition unit 50A acquires the instruction to execute the job. Alternatively, a job may be generated by reading a document with a reading device (specifically, a scanner), and the acquisition unit 50A may acquire an instruction to execute the job.

When the acquisition unit 50A acquires an instruction to execute a job, the control unit 50B controls each unit of the image forming apparatus 10 including the fixing device 16 to execute the job. At this time, the control unit 50B performs control for heating the heating belt 60 and rotating the pressure roller 40 for each part of the fixing device 16 including the driving unit 42. The control unit 50B controls the driving unit 79 (see fig. 7) of the contact mechanism 70 in the fixing device 16 so that the pressure roller 40 is positioned at the nip position (see fig. 4).

In addition, when the execution of the job is completed, the control section 50B controls the driving of the driving section 79 so that the pressure roller 40 is located at the separation position. At this time, the control section 50B controls each section of the fixing device 16 including the driving section 42 to stop the heating of the heating belt 60 and the rotation of the pressure roller 40.

When the acquiring unit 50A continuously acquires a plurality of jobs, the control unit 50B controls the drive of the driving unit 79 so that the pressure roller 40 is positioned at the center contact position between the jobs (see fig. 5). At this time, the control section 50B controls each section of the fixing device 16 including the driving section 42 during the job so as to maintain the heating of the heating belt 60 and the rotation of the pressure roller 40.

The case of continuously acquiring jobs corresponds to, for example, acquiring one job before the execution of the other job is completed. As shown in fig. 13, a job executed earlier among a plurality of jobs successively acquired by the acquisition unit 50A is referred to as a preceding job, and a job executed immediately after the preceding job is referred to as a subsequent job. The period between the preceding operation and the subsequent operation is referred to as an inter-operation period.

Here, the inter-job state is a state in which the recording medium P2 is not present in the contact area 50S. That is, in a state where the recording medium P2 is not present between the pressure roller 40 and the heating belt 60 (hereinafter, referred to as a non-present state) after the recording medium P2 passes between the pressure roller 40 and the heating belt 60, the control section 50B controls the driving section 79 such that the pressure roller 40 is located at the center contact position.

(action of the first embodiment)

Next, the operation of the first embodiment will be explained.

According to the image forming apparatus 10 of the first embodiment, when the acquisition unit 50A acquires the instruction to execute the job, the control unit 50B (see fig. 12) of the control apparatus 50 controls each unit of the image forming apparatus 10 to execute the job. At this time, the control unit 50B controls each unit of the fixing device 16 including the driving unit 42 to heat the heating belt 60 and rotate the pressure roller 40. The control unit 50B controls the driving unit 79 of the contact mechanism 70 in the fixing device 16 so that the pressure roller 40 is positioned at the nip position (see fig. 4).

Thereby, the contact mechanism 70 moves the pressure roller 40 from the separation position to the nip position. As a result, both axial end portions of the pressure roller 40 are pressed toward the heating belt 60, and the pressure roller 40 bends in a convex shape along the heating belt 60. Thereby, a contact region 50S is formed between the pressure roller 40 and the heating belt 60.

The forming unit 14 forms an image on the recording medium P1 conveyed by the first conveying unit 11 shown in fig. 1. The recording medium P1 on which the image is formed is conveyed to the contact area 50S by the first conveying portion 11.

The recording medium P2 is conveyed to the contact area 50S by the second conveying portion 12 in accordance with the timing at which the image formed on the recording medium P1 is conveyed to the contact area 50S.

Then, the fixing device 16 presses and heats the recording medium P1 and the recording medium P2 while conveying the recording medium P1 and the recording medium P2 between the pressing roller 40 and the heating belt 60, thereby fixing the image of the recording medium P1 to the recording medium P2.

In addition, when the recording medium P2 is heated between the pressure roller 40 and the heating belt 60, the pressure roller 40 maintains a state of contact with the heating belt 60 while maintaining a state of deflection along the convex shape of the heating belt 60. That is, in the present embodiment, in the heated state in which the recording medium P2 is heated between the pressure roller 40 and the heating belt 60, the contact mechanism 70 presses both axial end portions of the pressure roller 40 toward the heating belt 60, and bends the pressure roller 40 along the convex shape of the heating belt 60.

In the present embodiment, when the acquiring unit 50A acquires a plurality of jobs continuously, the control unit 50B controls the driving of the driving unit 79 of the contact mechanism 70 so that the pressure roller 40 is positioned at the center contact position between the preceding job and the succeeding job (see fig. 5). At this time, the control section 50B controls each section of the fixing device 16 including the driving section 42 during the job so as to maintain the heating of the heating belt 60 and the rotation of the pressure roller 40.

Thus, in the non-existing state, the contact mechanism 70 brings the pressure roller 40 into contact with the heating belt 60 that heats the pressure roller 40 at the axial center portion, and brings the pressure roller 40 into non-contact with the heating belt 60 at the axial both end portions (this operation is hereinafter referred to as a recovery operation). Thereby, the axial center portion of the pressure roller 40 is heated by the heating belt 60, and the axial both end portions of the pressure roller 40 are not heated.

Here, when a plurality of jobs are continuous, the following is considered: in the preceding job, a recording medium P2 (hereinafter, referred to as a small-sized recording medium P2) having a smaller width-direction dimension than the width-direction dimension of the contact region 50S is used, and in the subsequent job, a recording medium P2 (hereinafter, referred to as a large-sized recording medium P2) having a larger width-direction dimension than the width-direction dimension of the recording medium P2 used in the preceding job is used (see fig. 17). For example, the width-direction dimension of the recording medium P2 used in the subsequent job is equal to the width-direction dimension of the contact region 50S (specifically, a dimension slightly smaller than the width-direction dimension of the contact region 50S).

In the preceding job, when the small-sized recording medium P2 passes through the contact region 50S, the heat of the heating belt 60 is transmitted to the pressing roller 40 via the recording medium P2 at the center portion in the belt width direction. On the other hand, at both ends of the heating belt 60 in the belt width direction, the heat of the heating belt 60 is not transmitted to the pressure roller 40 via the recording medium P2. Therefore, as shown by the broken line in fig. 14, the temperature is lower at the center portion in the axial direction of the pressure roller 40 than at both end portions in the axial direction.

In the non-existing state (i.e., during the operation), the contact range between the pressure roller 40 and the heating belt 60 is the same at the axial center portion and both axial end portions (hereinafter referred to as a first configuration), and the temperature is maintained at a lower level at the axial center portion of the pressure roller 40 than at both axial end portions in the subsequent operation (the state shown by the broken line in fig. 14).

In this way, since temperature unevenness occurs in the axial direction of the pressure roller 40, the difference in outer diameter between the axial direction both ends of the pressure roller 40 with respect to the axial direction center portion becomes large due to thermal expansion at the axial direction both ends of the pressure roller 40. As a result, when the large-sized recording medium P2 passes through the contact region 50S in the subsequent operation, the conveyance speed of the recording medium P2 is excessively higher at both ends in the width direction than at the center portion, and wrinkles may occur in the recording medium P2.

Further, since temperature unevenness occurs in the axial direction of the pressure roller 40, there is a possibility that fixing unevenness of an image may occur in the width direction of the recording medium P2 in a subsequent operation.

In contrast, in the recovery operation of the present embodiment, during the operation, the central portion of the pressure roller 40 in the axial direction is heated by the heating belt 60, and the both end portions of the pressure roller 40 in the axial direction are not heated. Therefore, after the recording medium P2 passes between the pressure roller 40 and the axial center portion of the heating belt 60, the temperature variation in the axial direction of the pressure roller becomes smaller in a short time as compared with the first configuration. That is, the temperature distribution shown by the solid line in fig. 14 is restored in a short time.

As described above, according to the configuration of the present embodiment, the temperature unevenness in the axial direction of the pressure roller is reduced in a short time. Therefore, as compared with the first configuration, in the subsequent operation, the wrinkles of the recording medium P2 due to the difference in the outer diameters of the axial direction both end portions and the axial direction central portion of the pressure roller 40 can be suppressed. Further, according to the configuration of the present embodiment, compared to the first configuration, the fixing unevenness of the image generated in the width direction of the recording medium P2 is suppressed in the subsequent job. Therefore, according to the configuration of the present embodiment, a failure of the image formed on the recording medium P2 is suppressed in the subsequent job as compared with the first configuration.

In particular, in the recovery operation of the present embodiment, the pressure roller 40 is not in contact with the heating belt 60 at both axial ends during the operation. Therefore, as compared with a configuration in which the pressure roller 40 is in contact with the heating belt 60 during the job (hereinafter referred to as a second configuration), the temperature variation in the axial direction of the pressure roller becomes smaller in a short time after the recording medium P2 passes between the pressure roller 40 and the axial center portion of the heating belt 60.

Further, in the recovery operation of the present embodiment, a space 46 is formed between the pressure roller 40 and both axial end portions of the heating belt 60 during the operation (see fig. 5). Therefore, as compared with the second configuration, air flows more easily between the pressure roller 40 and the both axial end portions of the heating belt 60, and the temperature variation in the axial direction of the pressure roller becomes small in a short time after the recording medium P2 passes between the pressure roller 40 and the axial center portion of the heating belt 60.

In the present embodiment, the entire heating belt 60 is formed in a convex shape toward the pressure roller 40 (i.e., upward) in the center portion in the belt width direction. The pressure roller 40 is distant from the nip position with respect to the heating belt 60 at the center contact position, so as to be in non-contact with the heating belt 60 at both end portions in the axial direction while maintaining contact with the heating belt 60 at the central portion in the axial direction.

In this way, in the present embodiment, the heating belt 60 is formed in a convex shape toward the pressure roller 40 at the center portion in the belt width direction. Therefore, the contact range with the heating belt 60 at the axial center portion of the pressure roller 40 can be adjusted by the distance of the pressure roller 40 from the heating belt 60.

In the present embodiment, the recess dimension (see fig. 3) at the axial center portion of the pressure roller 40 is smaller than the projection dimension (see fig. 2) of the axial center portion of the heating belt 60 toward the pressure roller 40. Therefore, in comparison with a configuration in which the recess dimension is larger than the protrusion dimension, it is easy to make the contact range between each of the axial direction both end portions of the pressure roller 40 and the heating belt 60 smaller than the contact range at the axial direction center portion during the work.

In the present embodiment, in a heated state in which the recording medium P2 is heated between the pressure roller 40 and the heating belt 60, the contact mechanism 70 presses both axial end portions of the pressure roller 40 toward the heating belt 60, and bends the pressure roller 40 along the convex shape of the heating belt 60.

Therefore, in the configuration in which the heating belt 60 is formed in a convex shape toward the pressure roller 40 side at the axial center portion, it is possible to suppress uneven fixing of the image to the recording medium in the heated state, as compared with the configuration in which the pressure roller 40 is maintained in the state along the axial direction.

Second embodiment

Next, a second embodiment will be explained. Note that the same reference numerals are given to the same components as those in the first embodiment, and the description thereof will be omitted as appropriate.

In the first embodiment, the pressure roller 40 is configured as follows in the second embodiment, while contacting the heating belt 60 at the center in the axial direction at the center contact position (see fig. 5) and not contacting the heating belt 60 at both ends in the axial direction.

That is, in the second embodiment, the pressing roller 40 is in contact with the heating belt 60 at the center contact position at the axial center portion, and is in contact with the heating belt 60 at both end portions in the axial direction over a smaller contact range with the heating belt 60 than at the axial center portion. Specifically, at the center contact position, the contact width W1 (see fig. 15) at both axial end portions in the rotational direction (i.e., the circumferential direction) of the pressure roller 40 and the heating belt 60 is smaller than the contact width W2 (see fig. 16) at the axial center portion.

The operation of the second embodiment will be described below.

In the present embodiment, when the acquiring unit 50A acquires a plurality of jobs continuously, the control unit 50B controls the drive of the drive unit 79 of the contact mechanism 70 so that the pressure roller 40 is positioned at the center contact position between the jobs. At this time, the control section 50B controls each section of the fixing device 16 including the driving section 42 during the job so as to maintain the heating of the heating belt 60 and the rotation of the pressure roller 40.

Thus, in the non-existing state of the contact mechanism 70, the pressure roller 40 is brought into contact with the heating belt 60 that heats the pressure roller 40 at the axial center portion, and the contact width in the rotation direction of the pressure roller 40 and the heating belt 60 is made smaller at the axial both end portions than at the axial center portion

Thus, the amount of heat at both axial end portions of the pressure roller 40 is smaller than the amount of heat at the axial center portion of the pressure roller 40.

Therefore, after the recording medium P2 passes between the pressure roller 40 and the axial center portion of the heating belt 60, the temperature variation in the axial direction of the pressure roller becomes smaller in a short time as compared with the first configuration.

As described above, according to the configuration of the present embodiment, since the temperature variation in the axial direction of the pressure roller is reduced in a short time, the wrinkles of the recording medium P2 due to the difference in the outer diameters of the axial direction both end portions and the axial direction central portion of the pressure roller 40 are suppressed in the subsequent operation, as compared with the first configuration. Further, according to the configuration of the present embodiment, compared to the first configuration, the fixing unevenness of the image generated in the width direction of the recording medium P2 is suppressed in the subsequent job. Thus, according to the configuration of the present embodiment, a failure of an image formed on the recording medium P2 is suppressed in the subsequent job as compared with the first configuration.

In the recovery operation of the present embodiment, the pressure roller 40 is in contact with the heating belt 60 at the center and both ends in the axial direction during the operation, and therefore one of the pressure roller 40 and the heating belt 60 is supported by the other. Therefore, compared to a configuration in which the pressure roller 40 is not in contact with the heating belt 60 at both axial ends during operation, the angle of one of the pressure roller 40 and the heating belt 60 with respect to the other is less likely to vary.

In the recovery operation of the present embodiment, the pressure roller 40 is in contact with the heating belt 60 at the center and both ends in the axial direction during the operation, and therefore, the heating belt 60 can be stably rotated following the pressure roller 40, as compared with a configuration in which the pressure roller 40 is not in contact with the heating belt 60 at both ends in the axial direction during the operation.

Third embodiment

Next, a third embodiment will be explained. Note that the same reference numerals are given to the same components as those in the first embodiment, and the description thereof will be omitted as appropriate.

As described above, in the first embodiment, when the acquiring unit 50A acquires a plurality of jobs continuously, the control unit 50B controls the driving unit 79 so that the pressure roller 40 is positioned at the center contact position between the jobs, whereas in the third embodiment, the following configuration is adopted.

That is, in the third embodiment, when the acquiring unit 50A acquires a plurality of jobs consecutively, the control unit 50B controls the driving unit 79 so that the pressure roller 40 is positioned at the center contact position during a job in which the width-directional size of the recording medium P2 used in the succeeding job is larger than the width-directional size of the recording medium P2 used in the preceding job (hereinafter, referred to as "the case where the size of the succeeding medium is large"), as shown in fig. 17.

In other words, after the recording medium P2 passes through the contact region 50S, the recovery operation is performed in the non-existing state between the recording media P2 when the recording medium P2 having a larger dimension in the width direction than the recording medium P2 is conveyed.

Thus, in this non-existing state, the contact mechanism 70 brings the pressure roller 40 into contact with the heating belt 60 that heats the pressure roller 40 at the axial center portion, and brings the pressure roller 40 into non-contact with the heating belt 60 at the axial both end portions. Thereby, the axial center portion of the pressure roller 40 is heated by the heating belt 60, and the axial both end portions of the pressure roller 40 are not heated.

In the present embodiment, when the width-directional size of the recording medium P2 used in the subsequent job is smaller than the width-directional size of the recording medium P2 used in the preceding job, the recovery operation is not performed during the preceding job. Specifically, for example, the control unit 50B controls the drive unit 79 so that the pressure roller 40 is positioned at the separation position.

Further, the control unit 50B determines, for example, the width-directional size of the recording medium P2 as the job information. The control unit 50B may determine the width-directional size of the recording medium P2 based on the detection result of the detection unit such as a sensor.

Here, when the size of the succeeding medium is large, the portions of the pressure roller 40 on both axial end sides come into contact with the recording medium P2 in the succeeding operation as compared with the preceding operation. Thus, when the difference in the outer diameters of the axial direction both end portions and the axial direction center portion of the pressure roller 40 is increased due to thermal expansion at the axial direction both end portions of the pressure roller 40, the conveyance speed of the recording medium P2 is likely to be faster at the both end portions in the width direction than at the center portion.

Therefore, when the size of the succeeding medium is large, the recording medium P2 is likely to wrinkle during the succeeding operation in a configuration in which control is performed to position the pressure roller 40 at the center contact position (hereinafter referred to as a third configuration) as compared to a configuration in which the contact range of the pressure roller 40 with the heating belt 60 is the same at the center portion in the axial direction and both end portions in the axial direction.

In contrast, in the present embodiment, the drive unit 79 is controlled so that the pressure roller 40 is positioned at the center contact position during the job when the size of the downstream medium is large, and therefore, the effect of suppressing the wrinkles of the recording medium P2 being conveyed is better than in the third configuration.

In the third embodiment described above, the recovery action is performed when the size of the succeeding medium is large, but the present invention is not limited thereto. For example, the following structure may be adopted: when the temperature difference between the center portion and at least one of the both end portions of the pressure roller 40 in the axial direction becomes equal to or greater than a predetermined threshold value as a result of the preceding operation, the return operation is executed. In this case, the recovery operation is performed based on information obtained by measuring the temperatures of the central portion and both end portions of the pressure roller 40 in the axial direction by a detection portion such as a temperature sensor, for example. Further, the temperature difference of the pressure roller 40 may be predicted from the number of sheets of the recording medium P2 on which the job is executed in the preceding job, and the recovery operation may be executed based on this information.

Fourth embodiment

Next, a fourth embodiment will be explained. The image forming apparatus 10, the fixing device 16, and the heating belt 6 are configured in the same manner as in the first embodiment, and therefore, the description thereof is omitted. As will be described later, the contact mechanism 70 moves the pressure roller 40 between the contact position shown in fig. 1 and 4 (hereinafter referred to as a nip position), the first contact position shown in fig. 18A, the second contact position shown in fig. 18B, and the separation position shown in fig. 6, but otherwise has the same configuration as the first embodiment.

(contact mechanism 70)

The contact mechanism 70 shown in fig. 7 and 20 is a mechanism for bringing the pressure roller 40 into contact with the heating belt 60. Specifically, the contact mechanism 70 moves the pressure roller 40 between the nip position shown in fig. 1, 4, 7, and 20, the first contact position shown in fig. 18A, the second contact position shown in fig. 18B, and the separation position shown in fig. 6.

More specifically, as shown in fig. 7 and 20, the contact mechanism 70 includes a pair of lever portions 80, a first cam 71A, a second cam 72A, a cam shaft 74, a cam shaft gear 76, a transmission gear 78, and a driving portion 79 (see fig. 7). In addition, in fig. 7 and 20, one lever portion 80 of the pair of lever portions 80 is shown, and the first cam 71A of the first cam 71A and the second cam 72A is shown.

The pair of lever portions 80 are displacement portions that displace the pressure roller 40. The pair of rod portions 80 are disposed on one end side and the other end side in the axial direction of the pressure roller 40, respectively. Specifically, as shown in fig. 7, each lever portion 80 includes a lever 82, a support member 84, a spring portion 86, and a cam follower 88.

The lever 82 is supported at one end portion thereof by the apparatus main body of the fixing apparatus 16 so as to be rotatable about a fulcrum 82A disposed upstream (rightward in fig. 7) in the conveying direction with respect to the pressure roller 40.

The lever 82 extends obliquely upward from the fulcrum 82A toward the downstream side in the conveying direction (the left side in fig. 7), bends toward the upper side of the pressure roller 40, and extends toward the downstream side in the conveying direction (the left side in fig. 7) from the bent portion 82B. The cam follower 88 is formed in a roller shape and is rotatably attached to the curved portion 82B of the lever 82.

The supporting member 84 rotatably supports the pressure roller 40. The support member 84 is provided at the other end of the lever 82 so that the pressure roller 40 can move in a direction of approaching the heating belt 60 (downward in fig. 7) and in the opposite direction (upward in fig. 7) within a predetermined range.

The spring portion 86 is formed of a coil spring and is provided between the lever 82 and the support member 84. The spring portion 86 presses the support member 84 in the approaching direction by its elastic force.

The cam shaft 74 is a rotary shaft extending in the axial direction of the pressure roller 40 on the upper side of the pressure roller 40 and the lever 82. The cam shaft 74 is rotatably supported by the apparatus main body of the fixing apparatus 16.

The first cam 71A shown in fig. 21 is fixed to one end side in the axial direction of the cam shaft 74. The second cam 72A shown in fig. 22 is fixed to the other end side in the axial direction of the cam shaft 74. The first cam 71A and the second cam 72A are in contact with the respective cam followers 88. Specifically, the first cam 71A contacts the cam follower 88 (hereinafter, sometimes referred to as the cam follower 881) disposed on one end side in the axial direction of the pressure roller 40, and the second cam 72A contacts the cam follower 88 (hereinafter, sometimes referred to as the cam follower 882) disposed on the other end side in the axial direction of the pressure roller 40. The cam follower 881 is an example of the first contacted portion. The cam follower 882 exemplifies a second contacted portion.

As shown in fig. 21 and 22, the first cam 71A and the second cam 72A have a first contact portion 91A, a second contact portion 92A, a third contact portion 93A, and a fourth contact portion 94A, respectively. The lengths of the first contact portion 91A, the second contact portion 92A, the third contact portion 93A, and the fourth contact portion 94A from the camshaft 74 (i.e., the rotation center) in the radial direction (hereinafter referred to as radial lengths) are sequentially longer. The second contact portion 92A is an example of a short diameter portion. The third contact portion 93A is an example of a long diameter portion.

In the first cam 71A, a first contact portion 91A, a second contact portion 92A, a fourth contact portion 94A, and a third contact portion 93A are arranged in this order in the clockwise direction in fig. 21 with reference to the first contact portion 91A. On the other hand, in the second cam 72A, the first contact portion 91A, the third contact portion 93A, the fourth contact portion 94A, and the second contact portion 92A are arranged in this order in the clockwise direction in fig. 22 with reference to the first contact portion 91A. In this way, in the second cam 72A, the third contact portion 93A is disposed between the first contact portion 91A and the fourth contact portion 94A, and the second contact portion 92A is disposed between the fourth contact portion 94A and the first contact portion 91A as viewed in the clockwise direction in fig. 22. Therefore, for example, compared to a configuration in which both the third contact portion 93A and the second contact portion 92A are arranged between the first contact portion 91A and the fourth contact portion 94A, the change in the outer diameter of the second cam 72A from the first contact portion 91A to the fourth contact portion 94A and the change in the outer diameter of the fourth contact portion 94A to the first contact portion 91A can be suppressed to be small. In addition, in the first cam 71A, the second contact portion 92A is disposed between the first contact portion 91A and the fourth contact portion 94A, and the third contact portion 93A is disposed between the fourth contact portion 94A and the first contact portion 91A as viewed in the clockwise direction in fig. 21. Therefore, for example, compared to a configuration in which both the third contact portion 93A and the second contact portion 92A are arranged between the first contact portion 91A and the fourth contact portion 94A, the change in the outer diameter of the first cam 71A from the first contact portion 91A to the fourth contact portion 94A and the change in the outer diameter of the fourth contact portion 94A to the first contact portion 91A can be suppressed to be small. Thereby, the movement of the pressure roller 40 between the nip position and the separation position becomes smooth.

The first contact portion 91A of the first cam 71A and the first contact portion 91A of the second cam 72A are arranged at the same position in the circumferential direction of the cam shaft 74. In addition, the third contact portion 93A of the first cam 71A and the second contact portion 92A of the second cam 72A are arranged at the same position in the circumferential direction of the camshaft 74. In addition, the second contact portion 92A of the first cam 71A and the third contact portion 93A of the second cam 72A are arranged at the same position in the circumferential direction of the camshaft 74. In addition, the fourth contact portion 94A of the first cam 71A and the fourth contact portion 94A of the second cam 72A are arranged at the same position in the circumferential direction of the camshaft 74.

As described above, in the first cam 71A and the second cam 72A, the first contact portion 91A, the second contact portion 92A, the third contact portion 93A, and the fourth contact portion 94A are arranged differently, and thus the first cam 71A and the second cam 72A are different in shape.

Further, the contact positions of the first cam 71A and the second cam 72A with respect to the respective cam followers 88 are switched in accordance with the rotational position of the camshaft 74. Specifically, the first cam 71A and the second cam 72A are in a predetermined reference rotational position (position a in fig. 21 and 22), and the first contact portions 91A thereof are in contact with the respective cam followers 88. In the first rotational position (position B in fig. 21) in which the first cam 71A is rotated by a predetermined angle from the reference rotational position, the third contact portion 93A contacts the cam follower 881. In addition, the second contact portion 92A of the first cam 71A is in contact with the cam follower 881 at a second rotational position (position C in fig. 21) rotated by a predetermined angle from the first rotational position. Then, the fourth contact portion 94A of the first cam 71A is in contact with the cam follower 881 at a third rotational position (position D in fig. 21) rotated by a predetermined angle from the second rotational position.

On the other hand, in the first rotational position (position B in fig. 22), the second contact portion 92A of the second cam 72A contacts the cam follower 882. In addition, when the second cam 72A is at the second rotational position (position C in fig. 22), the third contact portion 93A thereof contacts the cam follower 882. In the third rotational position (position D in fig. 22), the fourth contact portion 94A of the second cam 72A contacts the cam follower 882.

The camshaft gear 76 is fixed to one axial end of the camshaft 74. The transmission gear 78 is rotatably supported on the apparatus main body of the fixing apparatus 16 in a state of meshing with the cam shaft gear 76.

The driving section 79 drives the transmission gear 78 to rotate. Specifically, the driving unit 79 is constituted by a stepping motor that rotates the transmission gear 78 forward and backward, for example.

In the contact mechanism 70, the drive portion 79 rotates the transmission gear 78 (specifically, normal rotation and reverse rotation), and the drive force is transmitted to the camshaft 74 via the camshaft gear 76, whereby the camshaft 74 rotates.

As described above, by the rotation of the cam shaft 74, the contact positions of each of the first cam 71A and the second cam 72A with respect to each of the cam followers 88 are changed among the first contact portion 91A, the second contact portion 92A, the third contact portion 93A, and the fourth contact portion 94A. The pressure roller 40 is located at the separated position shown in fig. 6 by the first contact portion 91A of each of the first cam 71A and the second cam 72A coming into contact with each of the cam followers 88. The pressure roller 40 is in non-contact with the heating belt 60 from one axial end portion to the other axial end portion at the separation position.

When the cam shaft 74 rotates and the fourth contact portions 94A of the first cam 71A and the second cam 72A contact the cam followers 88, the lever 82 rotates about the fulcrum 82A, and the pressure roller 40 moves to the nip position shown in fig. 4. At the nip position, both end portions of the pressure roller 40 in the axial direction are pressed toward the heating belt 60 by the elastic force of the spring portion 86. Thereby, the pressure roller 40 is bent along the convex shape of the heating belt 60. As a result, the pressure roller 40 comes into contact with the heating belt 60 from one axial end portion to the other axial end portion at the nip position, and forms a contact region 50S.

When the fourth contact portion 94A of each of the first cam 71A and the second cam 72A contacts each of the cam followers 88, the amount of press-fitting of each of the first cam 71A and the second cam 72A into each of the cam followers 88 becomes maximum.

When the cam shaft 74 further rotates and the third contact portion 93A of the first cam 71A and the second contact portion 92A of the second cam 72A contact the respective cam followers 88, the lever 82 rotates about the fulcrum 82A, and the pressure roller 40 moves to the first contact position shown in fig. 18A. The pressure roller 40 is in contact with the heating belt 60 at one end portion and the central portion in the axial direction at the first contact position, and the contact range with the heating belt 60 at the other end portion in the axial direction is smaller than the contact range at the central portion in the axial direction. Specifically, the pressure roller 40 is in contact with the heating belt 60 at one end portion and the central portion in the axial direction at the first contact position, and is not in contact with the heating belt 60 at the other end portion in the axial direction.

In other words, the pressure roller 40 is in contact with the heating belt 60 at one end portion and the central portion in the axial direction at the first contact position, and forms the space 46 between the pressure roller 40 and the heating belt 60 at the other end portion in the axial direction.

When the cam shaft 74 rotates and the second contact portion 92A of the first cam 71A and the third contact portion 93A of the second cam 72A contact the cam followers 88, the lever 82 rotates about the fulcrum 82A, and the pressure roller 40 moves to the second contact position shown in fig. 18B. The pressure roller 40 is in contact with the heating belt 60 at the other end portion and the central portion in the axial direction at the second contact position, and the contact range with the heating belt 60 at the one end portion in the axial direction is smaller than the contact range at the central portion in the axial direction. Specifically, the pressure roller 40 is in contact with the heating belt 60 at the other end portion and the central portion in the axial direction at the second contact position, and is not in contact with the heating belt 60 at one end portion in the axial direction.

In other words, the pressure roller 40 contacts the heating belt 60 at the other end portion and the central portion in the axial direction at the second contact position, and a space 46 is formed between the pressure roller 40 and the heating belt 60 at one end portion in the axial direction.

As described above, the configuration in which the contact range with the heating belt 60 is smaller at the axial end portions than at the axial center portion is a concept including a configuration in which the contact range is 0 (zero).

As described above, the contact mechanism 70 causes the pressing roller 40 to contact and separate from the heating belt 60. In other words, the contact mechanism 70 can be said to be a mechanism that displaces the pressure roller 40 to change the distance between the rotational axis of the pressure roller 40 and the rotational axis of the heating belt 60.

(control device 50)

The control device 50 is not described in detail in the same manner as described in the first embodiment. When the acquiring portion 50A acquires a plurality of jobs continuously, the control portion 50B controls the driving of the driving portion 79 so that the pressure roller 40 is alternately positioned at the first contact position (see fig. 18A) and the second contact position (see fig. 18B) between the jobs.

The case of continuously acquiring jobs corresponds to, for example, acquiring one job before the execution of the other job is completed. As shown in fig. 13, a job executed earlier among a plurality of jobs successively acquired by the acquisition unit 50A is referred to as a preceding job, and a job executed immediately after the preceding job is referred to as a subsequent job. The period between the preceding operation and the subsequent operation is referred to as an inter-operation period.

Here, the inter-job state is a state in which the recording medium P2 is not present in the contact area 50S. That is, in a state where the recording medium P2 is not present between the pressure roller 40 and the heating belt 60 (hereinafter, referred to as a non-present state) after the recording medium P2 passes between the pressure roller 40 and the heating belt 60, the control section 50B controls the drive section 79 so that the pressure roller 40 is alternately positioned at the first contact position (see fig. 18A) and the second contact position (see fig. 18B). Specifically, the control unit 50B controls the drive unit 79 to rotate the pressure roller 40 a plurality of times in each of the state where the pressure roller 40 is located at the first contact position and the state where the pressure roller 40 is located at the second contact position (see fig. 18B).

More specifically, the control unit 50B controls the drive unit 79 to rotate the pressure roller 40 for the same rotation time in each of the state where the pressure roller 40 is located at the first contact position and the state where the pressure roller 40 is located at the second contact position (see fig. 18B). The control unit 50B may control the driving of the driving unit 79 such that the heating belt 60 rotates at the same rotational speed in each of the state where the pressure roller 40 is located at the first contact position and the state where the pressure roller is located at the second contact position (see fig. 18B).

(operation of the fourth embodiment)

Next, an operation of the fourth embodiment will be described.

According to the image forming apparatus 10 of the fourth embodiment, when the acquisition unit 50A acquires an instruction to execute a job, the control unit 50B (see fig. 12) of the control apparatus 50 controls each unit of the image forming apparatus 10 to execute the job. At this time, the control unit 50B controls each unit of the fixing device 16 including the driving unit 42 to heat the heating belt 60 and rotate the pressure roller 40. The control unit 50B controls the driving unit 79 of the contact mechanism 70 in the fixing device 16 so that the pressure roller 40 is positioned at the nip position (see fig. 4).

Thereby, the contact mechanism 70 moves the pressure roller 40 from the separation position to the nip position. As a result, both axial end portions of the pressure roller 40 are pressed toward the heating belt 60, and the pressure roller 40 bends in a convex shape along the heating belt 60. Thereby, a contact region 50S is formed between the pressure roller 40 and the heating belt 60.

The forming unit 14 forms an image on the recording medium P1 conveyed by the first conveying unit 11 shown in fig. 1. The recording medium P1 on which the image is formed is conveyed to the contact area 50S by the first conveying portion 11.

The recording medium P2 is conveyed to the contact area 50S by the second conveying portion 12 in accordance with the timing at which the image formed on the recording medium P1 is conveyed to the contact area 50S.

Then, the fixing device 16 presses and heats the recording medium P1 and the recording medium P2 while conveying the recording medium P1 and the recording medium P2 between the pressure roller 40 and the heating belt 60, thereby fixing the image of the recording medium P1 to the recording medium P2.

When the recording medium P2 is heated between the pressure roller 40 and the heating belt 60, the pressure roller 40 maintains a state of contact with the heating belt 60 while maintaining a state of bending along the convex shape of the heating belt 60. That is, in the present embodiment, in the heated state in which the recording medium P2 is heated between the pressure roller 40 and the heating belt 60, the contact mechanism 70 presses both axial end portions of the pressure roller 40 toward the heating belt 60, and bends the pressure roller 40 along the convex shape of the heating belt 60.

In the present embodiment, when the acquiring unit 50A acquires a plurality of jobs continuously, the control unit 50B controls the driving of the driving unit 79 of the contact mechanism 70 so that the pressure roller 40 is alternately positioned at the first contact position (see fig. 18A) and the second contact position (see fig. 18B) between the preceding job and the succeeding job. At this time, the control section 50B controls each section of the fixing device 16 including the driving section 42 during the job so as to maintain the heating of the heating belt 60 and the rotation of the pressure roller 40.

Thus, in the non-existing state, the contact mechanism 70 switches the pressure roller 40 between the first contact state (see fig. 18A) and the second contact state (see fig. 18B) (hereinafter, this operation is referred to as a return operation). The first contact state is a state in which: the pressure roller 40 is brought into contact with the heating belt 60 that heats the pressure roller 40 while rotating together with the pressure roller 40 at the axial center portion and one axial end portion, and the contact range with the heating belt 60 at the other axial end portion of the pressure roller 40 is made smaller than the contact range at the axial center portion. Specifically, in the first contact state, the other end portion of the pressure roller 40 in the axial direction of the pressure roller 40 is not in contact with the heating belt 60.

The second contact state is a state in which the pressure roller 40 is brought into contact with the heating belt 60 that heats the pressure roller 40 while rotating together with the pressure roller 40 at the axial center portion and the axial other end portion, and the contact range of the pressure roller 40 with the heating belt 60 at the axial one end portion is made smaller than the contact range at the axial center portion. Specifically, in the second contact state, the pressure roller 40 is not in contact with the heating belt 60 at one end portion in the axial direction of the pressure roller 40. In this way, by switching the heating belt 60 between the first contact state (see fig. 18A) and the second contact state (see fig. 18B), the amount of heat at the axial both end portions of the pressure roller 40 is smaller than the amount of heat at the axial center portion of the pressure roller 40.

Here, when a plurality of jobs are continuous, the following is considered: in the preceding job, a recording medium P2 (hereinafter referred to as a small-sized recording medium P2) whose width-directional dimension is smaller than that of the contact region 50S in the width direction is used, and in the subsequent job, a recording medium P2 (hereinafter referred to as a large-sized recording medium P2) whose width-directional dimension is larger than that of the recording medium P2 used in the preceding job is used (see fig. 17). As an example, the width-directional dimension of the recording medium P2 used in the subsequent job is equal to the width-directional dimension of the contact region 50S (specifically, a dimension slightly smaller than the width-directional dimension of the contact region 50S).

In the preceding job, when the small-sized recording medium P2 passes through the contact region 50S, the heat of the heating belt 60 is transmitted to the pressing roller 40 via the recording medium P2 at the center portion in the belt width direction. On the other hand, at both ends of the heating belt 60 in the belt width direction, the heat of the heating belt 60 is not transmitted to the pressure roller 40 via the recording medium P2. Therefore, as shown by the broken line in fig. 23, the temperature is lower at the center portion in the axial direction of the pressure roller 40 than at both end portions in the axial direction.

In the configuration in which the pressure roller 40 and the heating belt 60 are continuously in contact from one end portion to the other end portion in the axial direction in the non-existing state (i.e., during the work) (hereinafter referred to as the first configuration), the temperature is maintained in a state in which the axial center portion of the pressure roller 40 is lower than both end portions in the axial direction in the subsequent work (the state shown by the broken line in fig. 23).

In this way, since temperature unevenness occurs in the axial direction of the pressure roller 40, the difference in outer diameter between the axial direction both end portions and the axial direction center portion of the pressure roller 40 becomes large due to thermal expansion at the axial direction both end portions of the pressure roller 40. As a result, when the large-sized recording medium P2 passes through the contact region 50S in the succeeding operation, the conveyance speed of the recording medium P2 is excessively higher at both ends in the width direction than at the center portion, and hence wrinkles may be generated in the recording medium P2 in the succeeding operation.

Further, since temperature unevenness occurs in the axial direction of the pressure roller 40, image fixing unevenness may occur in the width direction of the recording medium P2 in the subsequent operation.

In contrast, in the return operation of the present embodiment, the pressure roller 40 is switched between the first contact state and the second contact state. In the first contact state, the axial center portion and one axial end portion of the pressure roller 40 are heated by the heating belt 60, while the other axial end portion of the pressure roller 40 is not heated. Therefore, as shown in fig. 24, the temperature rises at the axial center portion of the pressure roller 40, and falls at the axial other end portion of the pressure roller 40.

In the second contact state, the axial center portion and the axial other end portion of the pressure roller 40 are heated by the heating belt 60, and the axial one end portion of the pressure roller 40 is not heated. Therefore, as shown in fig. 25, the temperature rises at the axial center portion of the pressure roller 40, and falls at the axial one end portion of the pressure roller 40.

Thus, after the recording medium P2 passes between the pressure roller 40 and the axial center portion of the heating belt 60, the temperature variation in the axial direction of the pressure roller is reduced in a shorter time than in the first configuration.

As described above, according to the configuration of the present embodiment, since temperature variation in the axial direction of the pressure roller is reduced in a short time, wrinkles of the recording medium P2 due to the difference in the outer diameters of the axial direction both end portions and the axial direction central portion of the pressure roller 40 are suppressed in the subsequent operation, as compared with the first configuration. Further, according to the configuration of the present embodiment, compared to the first configuration, the fixing unevenness of the image generated in the width direction of the recording medium P2 is suppressed in the subsequent job. Thus, according to the configuration of the present embodiment, a failure of an image formed on the recording medium P2 is suppressed in the subsequent job as compared with the first configuration.

In particular, in the recovery operation of the present embodiment, the other end portion and one end portion in the axial direction of the pressure roller 40 are alternately out of contact with the heating belt 60 during the operation. Therefore, as compared with a configuration in which the other end portion and one end portion in the axial direction of the pressure roller 40 are simultaneously in contact with the heating belt 60 during the work (hereinafter, referred to as a second configuration), the temperature variation in the axial direction of the pressure roller becomes small in a short time after the recording medium P2 passes between the pressure roller 40 and the axial center portion of the heating belt 60.

Further, in the recovery operation of the present embodiment, the space 46 is alternately formed between the other end portion in the axial direction and the one end portion in the axial direction of the pressure roller 40 and the heating belt 60 during the operation. Therefore, as compared with the second configuration, air easily flows in the space 46 between the pressure roller 40 and the heating belt 60 at the other end portion and the one end portion in the axial direction, and the temperature variation in the axial direction of the pressure roller becomes small in a short time after the recording medium P2 passes between the pressure roller 40 and the heating belt 60 at the center portion in the axial direction.

In the present embodiment, the control unit 50B controls the driving unit 79 such that the pressure roller 40 rotates a plurality of times in each of the state where the pressure roller 40 is located at the first contact position and the state where the pressure roller 40 is located at the second contact position (see fig. 18B). Thus, the contact mechanism 70 switches the pressure roller 40 between the first contact state and the second contact state while rotating the pressure roller a plurality of times in each of the first contact state and the second contact state.

Therefore, the temperature variation in the rotational direction of the pressure roller 40 is smaller than that in the configuration in which the heating belt 60 rotates less than two times in each of the first contact state and the second contact state.

In the present embodiment, the control unit 50B controls the driving unit 79 such that the pressure roller 40 rotates for the same rotation time in each of the state where the pressure roller 40 is located at the first contact position and the state where the pressure roller 40 is located at the second contact position (see fig. 18B).

Thus, the contact mechanism 70 switches the pressure roller 40 between the first contact state and the second contact state while rotating for the same rotation time in each of the first contact state and the second contact state.

Therefore, the temperature unevenness in the rotational direction of the pressure roller 40 is smaller than in a configuration in which the heating belt 60 is rotated for different rotation times in each of the first contact state and the second contact state.

In the present embodiment, the first cam 71A and the second cam 72A are different in shape. Therefore, the degree of freedom in adjustment of the positional relationship of the pressure roller 40 and the heating belt 60 in the first contact state and the second contact state is high as compared with a structure used by changing the phase of a pair of cams of the same shape.

In the present embodiment, in a heated state in which the recording medium P2 is heated between the pressure roller 40 and the heating belt 60, the contact mechanism 70 presses both axial end portions of the pressure roller 40 toward the heating belt 60, and bends the pressure roller 40 along the convex shape of the heating belt 60.

Therefore, in the configuration in which the heating belt 60 is formed in a convex shape toward the pressure roller 40 side at the axial center portion, uneven fixing of the image to the recording medium in the heated state is suppressed, as compared with the configuration in which the pressure roller 40 is maintained in the state along the axial direction.

Fifth embodiment

Next, a fifth embodiment will be explained. Note that the same reference numerals are given to the same components as those of the fourth embodiment, and the description thereof will be omitted as appropriate.

In the fourth embodiment, the pressure roller 40 is in contact with the heating belt 60 at one end portion and the central portion in the axial direction and is not in contact with the heating belt 60 at the other end portion in the axial direction at the first contact position (see fig. 18A). The pressure roller 40 is configured as follows in a second contact position (see fig. 18B) in which the other end portion and the central portion in the axial direction are in contact with the heating belt 60 and the one end portion in the axial direction is not in contact with the heating belt 60.

That is, in the fifth embodiment, the pressure roller 40 is in contact with the heating belt 60 at one end portion and the central portion in the axial direction at the first contact position, and is in contact with the heating belt 60 at the other end portion in the axial direction so that the contact range with the heating belt 60 is smaller than the contact range at the central portion in the axial direction. Specifically, at the first contact position, the contact width W1 (see fig. 26) of the pressure roller 40 at the other end portion in the axial direction in the rotational direction (i.e., the circumferential direction) of the heating belt 60 is smaller than the contact width W2 (see fig. 27) at the central portion in the axial direction.

The pressure roller 40 is in contact with the heating belt 60 at the other end portion and the central portion in the axial direction at the second contact position, and is in contact with the heating belt 60 at one end portion in the axial direction so that the contact range with the heating belt 60 is smaller than the contact range with the central portion in the axial direction. Specifically, at the second contact position, the contact width W1 (see fig. 26) of the pressure roller 40 at one axial end portion in the rotational direction (i.e., circumferential direction) of the heating belt 60 is smaller than the contact width W2 (see fig. 27) at the axial center portion.

The operation of the fifth embodiment will be described below.

In the present embodiment, when the acquiring portion 50A acquires a plurality of jobs continuously, the control portion 50B controls the driving of the driving portion 79 of the contact mechanism 70 so that the pressure roller 40 is alternately positioned at the first contact position and the second contact position between the jobs. At this time, the control section 50B controls each section of the fixing device 16 including the driving section 42 during the job so as to maintain the heating of the heating belt 60 and the rotation of the pressure roller 40.

Thus, in the non-existing state, the contact mechanism 70 switches the pressure roller 40 between the following first contact state and the following second contact state (hereinafter, this operation is referred to as a return operation). The first contact state is a state in which: the pressure roller 40 is brought into contact with the heating belt 60 that heats the pressure roller 40 while rotating together with the pressure roller 40 at the axial center portion and one axial end portion, and the contact range with the heating belt 60 at the other axial end portion of the pressure roller 40 is made smaller than the contact range at the axial center portion. Specifically, in the first contact state, the other end portion of the pressure roller 40 in the axial direction of the pressure roller 40 is not in contact with the heating belt 60.

The second contact state is a state in which: the pressure roller 40 is brought into contact with the heating belt 60 that heats the pressure roller 40 while rotating together with the pressure roller 40 at the axial center portion and the axial other end portion, and the contact range of the pressure roller 40 with the heating belt 60 at the axial one end portion is made smaller than the contact range at the axial center portion. Specifically, in the second contact state, the pressure roller 40 is not in contact with the heating belt 60 at one end portion in the axial direction of the pressure roller 40. By thus switching the heating belt 60 between the first contact state (see fig. 18A) and the second contact state (see fig. 18B), the amount of heat at both axial end portions of the pressure roller 40 is smaller than the amount of heat at the axial center portion of the pressure roller 40.

Therefore, after the recording medium P2 passes between the pressure roller 40 and the heating belt 60 at the axial center portion, the temperature variation in the axial direction of the pressure roller becomes smaller in a short time as compared with the first configuration.

As described above, according to the configuration of the present embodiment, since temperature variation in the axial direction of the pressure roller is reduced in a short time, wrinkles of the recording medium P2 due to the difference in the outer diameters of the axial direction both end portions and the axial direction central portion of the pressure roller 40 are suppressed in the subsequent operation, as compared with the first configuration. Further, according to the configuration of the present embodiment, compared to the first configuration, the fixing unevenness of the image generated in the width direction of the recording medium P2 is suppressed in the subsequent job. Thus, according to the configuration of the present embodiment, a failure of an image formed on the recording medium P2 is suppressed in the subsequent job as compared with the first configuration.

In the recovery operation of the present embodiment, the pressure roller 40 is in contact with the heating belt 60 at the center and both ends in the axial direction during the operation, and therefore one of the pressure roller 40 and the heating belt 60 is supported by the other. Therefore, compared to a configuration in which the pressure roller 40 is not in contact with the heating belt 60 at both axial ends during operation, the angle of one of the pressure roller 40 and the heating belt 60 with respect to the other is less likely to vary.

In the recovery operation of the present embodiment, the pressure roller 40 is in contact with the heating belt 60 at the center and both ends in the axial direction during the operation, and therefore the heating belt 60 is stably rotated following the pressure roller 40, as compared with a configuration in which the pressure roller 40 is not in contact with the heating belt 60 at both ends in the axial direction during the operation.

Sixth embodiment

Next, a sixth embodiment will be explained. Note that the same reference numerals are given to the same components as those of the fourth embodiment, and the description thereof will be omitted as appropriate.

As described above, in the fourth embodiment, when the acquiring unit 50A acquires a plurality of jobs continuously, the control unit 50B controls the driving unit 79 so that the pressure roller 40 is positioned at the second contact position between the jobs, whereas the sixth embodiment is configured as follows.

That is, in the sixth embodiment, when the acquiring unit 50A acquires a plurality of jobs continuously, the control unit 50B controls the driving unit 79 so that the pressure roller 40 is alternately positioned at the first contact position (see fig. 18A) and the second contact position (see fig. 18B) between jobs in which the width-directional size of the recording medium P2 used in the subsequent job is larger than the width-directional size of the recording medium P2 used in the preceding job (hereinafter, referred to as "the case where the size of the subsequent medium is large"), as shown in fig. 17.

In other words, after the recording medium P2 passes through the contact region 50S, the recovery operation is performed in the non-existing state between the recording media P2 when the recording medium P2 having a larger dimension in the width direction than the recording medium P2 is conveyed.

In the present embodiment, when the size in the width direction of the recording medium P2 used in the subsequent job is smaller than the size in the width direction of the recording medium P2 used in the preceding job, the recovery operation is not performed between the jobs. Specifically, for example, the control unit 50B controls the drive unit 79 so that the pressure roller 40 is positioned at the separation position.

Further, the control unit 50B determines, for example, the width-directional size of the recording medium P2 as the job information. The control unit 50B may determine the width-directional size of the recording medium P2 based on the detection result of the detection unit such as a sensor.

Here, when the size of the succeeding medium is large, the portions of the pressure roller 40 on both axial end sides come into contact with the recording medium P2 in the succeeding operation as compared with the preceding operation. Therefore, when the difference in the outer diameters of the axial direction both end portions and the axial direction center portion of the pressure roller 40 becomes large due to thermal expansion at the axial direction both end portions of the pressure roller 40, the conveying speed of the recording medium P2 is likely to be faster at the both end portions in the width direction than at the center portion.

Therefore, when the size of the downstream medium is large, the recording medium P2 is likely to wrinkle during the subsequent operation in a configuration in which the pressure roller 40 and the heating belt 60 are continuously in contact from one end portion to the other end portion in the axial direction (hereinafter referred to as a third configuration).

In contrast, in the present embodiment, since the recovery operation is performed between jobs when the size of the succeeding medium is large, the effect of suppressing wrinkles of the recording medium P2 being conveyed is better than in the third configuration.

In the sixth embodiment described above, the recovery operation is performed when the size of the succeeding medium is large, but the present invention is not limited thereto. For example, the following structure may be adopted: when the temperature difference between the center portion and at least one of the both end portions in the axial direction of the pressure roller 40 is equal to or greater than a predetermined threshold value as a result of the preceding operation, the return operation is executed. In this case, for example, the recovery operation is performed based on information obtained by measuring the temperatures of the central portion and both end portions of the pressure roller 40 in the axial direction by a detection portion such as a temperature sensor. Further, the temperature difference of the pressure roller 40 may be predicted from the number of sheets of the recording medium P2 on which the job is executed in the preceding job, and the recovery operation may be executed based on this information.

(other embodiments)

In embodiments 1 to 3 described above, when a plurality of jobs are executed, the contact mechanism 70 performs the return operation while the pressure roller 40 is positioned at the center contact position (see fig. 5) during the jobs. For example, the following structure may be adopted: in the case of executing a single job, the contact mechanism 70 positions the pressure roller 40 at the separated position after the recovery operation is performed after the job execution is ended. In this configuration, in the case where the job is executed immediately after the execution of the single job is completed, the influence of the temperature unevenness in the axial direction of the pressure roller is suppressed.

In embodiments 4 to 6 described above, the recovery operation is performed between jobs when a plurality of jobs are executed, but the present invention is not limited thereto. For example, the following structure may be adopted: in the case of executing a single job, the contact mechanism 70 positions the pressure roller 40 at the separated position after the recovery operation is performed after the job execution is ended. In this configuration, in the case where the job is executed immediately after the execution of the single job is completed, the influence of the temperature unevenness in the axial direction of the pressure roller is suppressed.

Further, the following structure may be adopted: in the case where a job is executed immediately after the execution of the job is completed, the job is executed after a recovery action is performed before the job is executed.

Further, the following configuration may be adopted: the recovery action is performed among the recording media P2 in a single job.

In the above embodiment, the pressure roller 40 is used as an example of the rotating body, but the present invention is not limited thereto. For example, the rotating body may be a pressing belt.

In the above embodiment, the heating tape 60 is used as an example of the heating body, but the present invention is not limited thereto. For example, a heating roller or the like may be used as an example of the heating body.

The present invention is not limited to the above-described embodiments, and various modifications, alterations, and improvements can be made without departing from the scope of the invention. For example, the above-described modification can be configured by appropriately combining a plurality of the modifications.