1. A photoelectric sensor comprising a light projector and a light receiver which are independent of each other,

the projector includes:

a light emitting unit that generates a projection beam; and

a power supply circuit that receives supply of electric power via a 1 st power supply line and a 2 nd power supply line connected to the outside of the projector and supplies necessary electric power to the light emitting unit,

one end of a 3 rd power line is connected between the power circuit and the 1 st power line,

the light receiver includes:

a 1 st switching element connected to the other end of the 3 rd power line, for outputting a 1 st output signal;

a 2 nd switching element connected to the other end of the 3 rd power line, for outputting a 2 nd output signal; and

and a detection circuit for switching the on state of each of the 1 st switching element and the 2 nd switching element according to the intensity of the detected light.

2. The photosensor of claim 1,

the photoelectric sensor further includes a connection unit to which power from an external power source is input and which outputs the 1 st output signal and the 2 nd output signal,

the 1 st power line extends from the light projector to the connecting portion,

the 2 nd power supply line extends from the light receiver to the connecting portion.

3. The photosensor according to claim 1 or 2,

the detection circuit switches the 1 st switching element and the 2 nd switching element to different conduction states according to the detected intensity of light.

4. A light projector which is combined with light receivers configured independently of each other to form a photoelectric sensor, the light projector comprising:

a light emitting unit that generates a projection beam; and

a power supply circuit that receives supply of electric power via a 1 st power supply line and a 2 nd power supply line connected to the outside of the projector and supplies necessary electric power to the light emitting unit,

one end of a 3 rd power line is connected between the power circuit and the 1 st power line,

the light receiver includes:

a 1 st switching element connected to the other end of the 3 rd power line, for outputting a 1 st output signal;

a 2 nd switching element connected to the other end of the 3 rd power line, for outputting a 2 nd output signal; and

and a detection circuit for switching the on state of each of the 1 st switching element and the 2 nd switching element according to the intensity of the detected light.

Background

As an example of a sensor for detecting the presence or intrusion of an object, a photoelectric sensor is known. The photoelectric sensor irradiates light from the light projecting section, and the light receiving section detects that the irradiated light has changed to some extent due to the detection medium. Photoelectric sensors are broadly classified into transmission type, reflection type, distance setting type, and the like. In contrast to the reflective type and distance setting type photosensors, the light projecting section and the light receiving section are arranged at substantially the same position, and in the transmissive type photosensors, the light projecting section and the light receiving section are arranged in a separated state.

Various sensors including a photoelectric sensor are key devices for realizing FA (Factory Automation), and the operation of various devices and/or devices is controlled based on the detection results of the various sensors. On the other hand, there are cases where some sort of failure occurs in each sensor, and when some sort of failure occurs in this manner, it is necessary to detect the occurrence of the failure.

For example, japanese patent application laid-open No. 2009-098735 (patent document 1) discloses a sensor system in which a plurality of transmission type photosensors are connected to a PLC via a slave device (slave), wherein, in the case of implementing a sensor abnormality diagnosis method using switching of the amount of projected light, the load of a user program on the PLC side is reduced, and abnormality detection of the photosensors can be performed in real time. More specifically, the sensor abnormality diagnosis unit attached to the slave of the PLC disclosed in patent document 1 switches the amount of projected light and detects an abnormality of the photoelectric sensor based on the relationship between the amounts of received light at that time.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 2009-098735

Disclosure of Invention

Problems to be solved by the invention

In the configuration disclosed in patent document 1, it is necessary to install a sensor abnormality diagnosis unit in the slave device of the PLC, and it is preferable to connect a plurality of transmission type photosensors through a single slave device.

The purpose of the present invention is to realize a configuration capable of detecting an abnormality with a simple configuration in a transmission-type photosensor.

Means for solving the problems

According to one aspect of the present invention, there is provided a photoelectric sensor including a light projector and a light receiver which are independent of each other. The light projector includes: a light emitting unit that generates a projection beam; and a power supply circuit which receives the supply of electric power via a 1 st power supply line connected to the outside of the projector and supplies necessary electric power to the light emitting section. The light receiver includes: a 1 st switching element connected to a 2 nd power supply line connected to an outside of the light receiver, for outputting a 1 st output signal; a 2 nd switching element connected to the 2 nd power supply line for outputting a 2 nd output signal; and a detection circuit for switching the conduction state of each of the 1 st switching element and the 2 nd switching element according to the intensity of the detected light. A3 rd power line is provided, one end of the 3 rd power line is electrically connected to the 1 st power line inside the projector, and the other end is electrically connected to the 2 nd power line outside the light receiver.

Preferably, the light projector further includes: a 3 rd switching element arranged between one end of the 3 rd power supply line and the 1 st power supply line; and a monitoring circuit which controls the conduction state of the 3 rd switching element.

More preferably, the monitoring circuit operates by receiving power supplied via the 1 st power supply line.

More preferably, the projector further includes a detector that monitors a state of the projection beam irradiated from the light emitting unit, and the monitoring circuit maintains the 3 rd switching element in an on state when the projection beam is irradiated in a predetermined state.

Preferably, the photosensor further includes a connection portion to which power from an external power source is input, and which outputs a 1 st output signal and a 2 nd output signal. The 1 st power line extends from the projector to the connecting portion, and the 2 nd power line extends from the light receiver to the connecting portion.

According to another aspect of the present invention, there is provided a light projector which constitutes a photoelectric sensor in combination with light receivers which are constructed independently of each other. The light projector includes: a light emitting unit that generates a projection beam; and a power supply circuit which receives the supply of electric power via a 1 st power supply line connected to the outside of the projector and supplies necessary electric power to the light emitting section. The light receiver includes: a 1 st switching element connected to a 2 nd power supply line connected to an outside of the light receiver, for outputting a 1 st output signal; a 2 nd switching element connected to the 2 nd power supply line for outputting a 2 nd output signal; and a detection circuit for switching the conduction state of each of the 1 st switching element and the 2 nd switching element according to the intensity of the detected light. A3 rd power line is provided, one end of the 3 rd power line is electrically connected to the 1 st power line inside the projector, and the other end is electrically connected to the 2 nd power line outside the light receiver.

According to another aspect of the present invention, there is provided a photosensor including a light projector and a light receiver which are independent of each other, the light projector including: a light emitting unit that generates a projection beam; and a power supply circuit that receives supply of electric power via a 1 st power supply line and a 2 nd power supply line connected to an outside of the projector and supplies necessary electric power to the light emitting unit, wherein one end of a 3 rd power supply line is connected between the power supply circuit and the 1 st power supply line, and the light receiver includes: a 1 st switching element connected to the other end of the 3 rd power line, for outputting a 1 st output signal; a 2 nd switching element connected to the other end of the 3 rd power line, for outputting a 2 nd output signal; and a detection circuit that switches on states of the 1 st switching element and the 2 nd switching element according to intensity of the detected light.

According to another aspect of the present invention, there is provided a light projector that constitutes a photoelectric sensor in combination with light receivers that are configured independently of each other, the light projector including: a light emitting unit that generates a projection beam; and a power supply circuit that receives supply of electric power via a 1 st power supply line and a 2 nd power supply line connected to an outside of the projector and supplies necessary electric power to the light emitting unit, wherein one end of a 3 rd power supply line is connected between the power supply circuit and the 1 st power supply line, and the light receiver includes: a 1 st switching element connected to the other end of the 3 rd power line, for outputting a 1 st output signal; a 2 nd switching element connected to the other end of the 3 rd power line, for outputting a 2 nd output signal; and a detection circuit that switches on states of the 1 st switching element and the 2 nd switching element according to intensity of the detected light.

Effects of the invention

According to the present invention, a transmissive photosensor capable of detecting an abnormality with a simple configuration can be realized.

Drawings

Fig. 1 is a schematic diagram showing a state in which a transmissive photosensor of the present embodiment is arranged.

Fig. 2 is a schematic diagram showing the structure of the transmission type photosensor of the present embodiment.

Fig. 3 is a schematic diagram showing an example of a wiring structure of a photosensor according to the related art of the present invention.

Fig. 4 is a diagram showing a change in an output signal when a disconnection occurs in the photoelectric sensor according to the related art of the present invention.

Fig. 5 is a schematic diagram showing an example of the wiring structure of the photosensor according to the present embodiment.

Fig. 6 is a diagram showing changes in output signals when a disconnection occurs in the photoelectric sensor according to the present embodiment.

Fig. 7 is a schematic diagram showing an example of the wiring structure of the photosensor according to variation 1 of the present embodiment.

Fig. 8 is a schematic diagram showing an example of the wiring structure of the photosensor according to variation 2 of the present embodiment.

Detailed Description

Embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same or corresponding portions are denoted by the same reference numerals, and description thereof will not be repeated.

< A. application example of photoelectric sensor >

First, an application example of the transmission type photosensor 1 of the present embodiment will be described.

Fig. 1 is a schematic diagram showing a state in which the transmission type photosensor 1 of the present embodiment is arranged. Fig. 1 shows an example of detecting a workpiece 12 conveyed on a conveyor 10. More specifically, the photosensor 1 includes a light projector 2, a light receiver 4, and a controller 6. The light projector 2 and the light receiver 4 other than the controller 6 are also sometimes referred to as "photosensors". The light projector 2 and the light receiver 4 are arranged independently of each other, and the light projector 8 irradiated from the light projector 2 is received by the light receiver 4. That is, the projector 2 and the light receiver 4 are each constituted by different housings.

The workpiece 12 blocks light from the projector 2, so that the light receiving state (detected light amount) of the light receiver 4 changes, and the presence or absence of the workpiece 12 can be detected from the change.

As described later, the controller 6 may give an instruction for controlling the timing and the irradiation state of the projection beam 8 from the projector 2 to the controller 6.

< B. Structure of photoelectric sensor >

Next, the structure of the transmission type photosensor 1 of the present embodiment will be described. Fig. 2 is a schematic diagram showing the structure of the transmission type photosensor 1 of the present embodiment.

Referring to fig. 2, projector 2 of photosensor 1 includes light-emitting unit 22 and power supply circuit 24. The power supply circuit 24 receives power supplied from an external power supply and supplies power necessary for a predetermined voltage to the light emitting unit 22. The Light Emitting unit 22 is composed of a Light Emitting element such as an LED (Light Emitting Diode) and a lens, and generates the Light beam 8 to be irradiated to the detection medium.

The light receiver 4 of the photosensor 1 includes a light receiving portion 42, a detection circuit 44, and a signal output circuit 46. The light receiving unit 42 is composed of a light receiving element such as a photodiode, and outputs a signal corresponding to the intensity of the incident light beam 8 when the light beam 8 from the light projector 2 enters. The detection circuit 44 outputs a signal corresponding to the light incident state and the light shielded state based on the signal from the light receiving unit 42. The signal output circuit 46 outputs a detection signal to the controller 6 (fig. 1) and the like based on the signal from the light receiving section 42.

< C. Wiring Structure and problems arising in the Wiring Structure >

Next, a wiring structure of the photosensor 101 according to the related art of the present invention will be described, and a problem caused by the wiring structure will be described.

Fig. 3 is a schematic diagram showing an example of a wiring structure of the photosensor 101 according to the related art of the present invention. Referring to fig. 3, a photosensor 101 according to the related art of the present invention includes a projector 102 and a light receiver 104, which supply power and output signals via a connection unit 130. That is, the connection portion 130 is inputted with power from an external power source, and output signals OUT1 and OUT2 (1 st and 2 nd output signals) are outputted from the connection portion 130.

The light emitting unit 22 of the light projector 102 is substantially the same as the light emitting unit 22 of the light projector 2 of the photosensor 1, and the light receiving unit 42, the detection circuit 44, and the signal output circuit 46 of the light receiver 104 are substantially the same as the light receiving unit 42, the detection circuit 44, and the signal output circuit 46 of the light receiver 4. On the other hand, the power supply circuit 124 of the projector 102 receives power supplied from an external power supply and supplies power of a predetermined voltage to the light emitting unit 22.

The photoelectric sensor 101 of the related art of the present invention and the photoelectric sensor 1 of the present embodiment (details will be described later) each output two signals as detection signals. By using these two signals, a possible failure in the light receiver 104 and the light receiver 4 can be detected. The method of detecting such a defect will be described in detail later.

In the wiring structure of the light projector 102, the power supply potential VCC supplied to the connection unit 130 is connected to one end of the power supply circuit 124 of the light projector 102 via the power supply line 131, and the ground potential GND supplied to the connection unit 130 is connected to the other end of the power supply circuit 124 of the light projector 102 via the ground line 132.

In the wiring structure of the light receiver 104, the power supply potential VCC supplied to the connection portion 130 is connected to one end of the signal output circuit 46 of the light receiver 104 via the power supply line 133, and the ground potential GND supplied to the connection portion 130 is connected to the other end of the signal output circuit 46 of the light receiver 104 via the ground line 134.

Although not shown, the power supplied from the power supply line 133 and the ground line 134 may be supplied to the detection circuit 44. In this case, the power supply line 133 and the ground line 134 are also connected to a power supply circuit not shown.

The transistor 462 and the transistor 466 are connected in parallel with the power supply potential VCC supplied to the signal output circuit 46.

One end of the transistor 462 is connected to the 1 st signal line 135. The potential appearing on the 1 st signal line 135 becomes the output signal OUT 1. That is, the transistor 462 corresponds to the 1 st switching element connected to the power supply line 133 (2 nd power supply line) connected to the outside of the light receiver 104 and outputting the output signal OUT1 (1 st output signal).

Similarly, one end of the transistor 466 is connected to the 2 nd signal line 136. The potential appearing on the 2 nd signal line 136 becomes the output signal OUT 2. That is, the transistor 466 corresponds to a 2 nd switching element connected to the power supply line 133 (2 nd power supply line) connected to the outside of the light receiver 104 and outputting the output signal OUT2 (2 nd output signal).

An example of outputting mutually inverted values as two output signals corresponding to the intensity of light is shown in the photosensor 1 according to the present embodiment. That is, two signals inverted to each other are output as detection signals.

A gate of the transistor 462 is connected to the drive line 442 from the detection circuit 44, and a gate of the transistor 466 is input to the drive line 446 connected to the drive line 442 via the inverter circuit 444. The detection circuit 44 drives the drive line 442 in accordance with a detection signal from the light receiving section 42. Since the drive line 446 is connected to the output of the inverting circuit 444 of the input drive line 442, the drive line 442 and the drive line 446 are driven complementarily to each other. For example, if a predetermined amount of light received is detected in the light receiving unit 42, the driving line 442 is activated, while the driving line 446 is inactivated. On the other hand, if the light receiving unit 42 does not detect a predetermined amount of light, the drive line 442 is inactive, and the drive line 446 is active. Thus, one drive line is activated, while the other drive line is deactivated. That is, the detection circuit 44 switches the transistor 462 (1 st switching element) and the transistor 466 (2 nd switching element) to different conduction states according to the intensity of the detected light.

In this way, the detection circuit 44 switches the on states of the transistor 462 (1 st switching element) and the transistor 466 (2 nd switching element) according to the intensity of the detected light.

By using such output logic, for example, when the output signal OUT1 is Hi (active state/high potential) when the light receiving unit 42 detects a predetermined amount of received light, the output signal OUT2 is Low (inactive state/Low potential). Conversely, when the light receiving unit 42 does not detect the predetermined amount of light, the output signal OUT1 is Low and the output signal OUT2 is Hi.

The relationship between the output signal OUT1 and the output signal OUT2 and the amount of light received may be reversed. That is, when the light receiving unit 42 detects a predetermined amount of received light, the output signal OUT1 is Low (inactive state/Low potential), and the output signal OUT2 is Hi (active state/high potential).

The controller 6 (see fig. 1) can detect the presence or absence of an abnormality based on the combination of the values of the output signal OUT1 and the output signal OUT 2.

The light projector 102 and the light receiver 104 may be connected to each other via a terminal provided in the connection unit 130. A plurality of cables may be connected to each other as a cable connecting the connection unit 130 and the light projector 102 and/or a cable connecting the connection unit 130 and the light receiver 104. In such a case, the cables may be connected to the connection unit 130, the cables may be connected to each other, and the cables may be connected to the light projector 102 or the light receiver 104 via arbitrary connectors.

In such a wiring structure, there is a possibility that a wire connecting the connection portion 130 to the light projector 102 or the light receiver 104 may be broken. In particular, the longer the distance from the connection portion 130, the more likely the disconnection occurs.

A function of detecting disconnection in the photosensor 101 shown in fig. 3 will be described. Fig. 4 is a diagram showing a change in an output signal when a disconnection occurs in the photosensor 101 of the related art of the present invention. Fig. 4 shows the output results of the output signal OUT1 and the output signal OUT2 in the case where the detection medium is not present (light incident state) and the case where the detection medium is present (light shielded state), respectively, for (a) the case where the power line 133 of the light receiver 104 is disconnected, (B) the case where the ground line 134 of the light receiver 104 is disconnected, (C) the case where the 1 st signal line 135 is disconnected, (D) the case where the 2 nd signal line 136 is disconnected, (E) the case where the power line 131 of the light projector 102 is disconnected, and (F) the case where the ground line 132 of the light projector 102 is disconnected, except for a normal state where no disconnection occurs.

In a normal state where no disconnection occurs, in the case where no detection medium is present (light-in state: no detection medium), the output signal OUT1 is at a high potential (Hi), and the output signal OUT2 is at a Low potential (Low). On the other hand, when the detection medium is present (light-shielded state: presence of detection medium), the output signal OUT1 is at Low potential (Low) and the output signal OUT2 is at high potential (Hi). The presence or absence of the detection medium is determined based on these output signals.

(A) When the power supply line 133 of the photo-detector 104 is disconnected, no power is supplied to output the output signal OUT1 and the output signal OUT2, and therefore, the output signal OUT1 and the output signal OUT2 are both maintained at a Low potential (Low) regardless of the presence or absence of the detection medium. In this state, the value of the output signal OUT1 and the value of the output signal OUT2 are not mutually inverted, and thus an abnormality can be detected.

(B) When the ground line 134 of the photodetector 104 is disconnected, the transistor 462 and the transistor 466 are in a non-conductive state because power is not supplied to the photodetector 104, and therefore, both the output signal OUT1 and the output signal OUT2 are Low (Low). Therefore, the value of the output signal OUT1 and the value of the output signal OUT2 are not mutually inverted between the high potential (Hi) and the Low potential (Low), and an abnormality can be detected.

(C) When the 1 st signal line 135 is disconnected, the output signal OUT1 becomes electrically open, and therefore both the output signal OUT1 and the output signal OUT2 are Low (Low). Therefore, the value of the output signal OUT1 and the value of the output signal OUT2 are not mutually inverted between the high potential (Hi) and the Low potential (Low), and an abnormality can be detected.

(D) When the 2 nd signal line 136 is disconnected, the output signal OUT2 becomes electrically open, and therefore, when the detection medium is not present (no detection medium), the output signal OUT1 becomes high (Hi) and the output signal OUT2 becomes Low (Low). On the other hand, in the case where the detection medium is present (presence of the detection medium), both the output signal OUT1 and the output signal OUT2 are Low (Low). In the case where there is no detection medium, the combination of the same values as in the normal state is obtained, and therefore, the detection cannot be performed in this state, but when the detection state changes, the value of the output signal OUT1 and the value of the output signal OUT2 are not inverted between the high potential (Hi) and the Low potential (Low), and thus, an abnormality can be detected.

As described above, an abnormality can be detected regardless of which wire connected to the photodetector 104 is broken. In addition, even if the logics shown in fig. 4 are reversed, the same relationship holds. In this case, the output signal OUT1 in the table may be referred to as the output signal OUT2 instead, and the output signal OUT2 may be referred to as the output signal OUT1 instead.

On the other hand, it is impossible to detect an abnormality in a broken wire generated in a wire connected to the projector 102. Specifically, the state is such that the projection beam 8 is not irradiated from the projector 102 in any of (E) the case where the power supply line 131 of the projector 102 is disconnected and (F) the case where the ground line 132 of the projector 102 is disconnected. In this state, the light receiver 104 cannot distinguish whether the detection medium is present and the projection beam 8 is shielded or the projection beam 8 is not irradiated from the light projector 102. This state is constant regardless of the presence or absence of the detection medium.

That is, even if some trouble occurs in the path through which the power is supplied to the projector 102 and the irradiation of the projected beam 8 is disabled, the output signal OUT1 and the output signal OUT2 corresponding to the light-shielded state are output from the light receiver 104, and therefore, a normal state and an abnormal state cannot be distinguished. That is, even if the detection state changes, the abnormality cannot be detected.

The transmission type photosensor 1 according to the present embodiment is configured to be able to detect disconnection that may occur in the lead wire connected to the projector 102 as described above.

< D > one of the structures for solving the problems >

Next, an example of the wiring structure of the photosensor 1 of the present embodiment will be described.

Fig. 5 is a schematic diagram showing an example of the wiring structure of the photosensor 1 of the present embodiment. Referring to fig. 5, the photoelectric sensor 1 of the present embodiment includes a light projector 2 and a light receiver 4, which supply power and output signals via a connection unit 30.

The photosensor 1 of the present embodiment outputs two signals that are inverted to each other as a detection signal. By using the two signals inverted to each other, it is possible to detect not only the light receiver 4 but also a possible defect occurring in the light projector 2. The method of detecting such a defect will be described in detail later. The projector 2 includes a signal output circuit 26 in addition to the light emitting unit 22 and the power supply circuit 24. The signal output circuit 26 is a circuit that outputs a signal corresponding to the state of the projector 2.

With regard to the wiring structure of the light projector 2, the power supply potential VCC supplied to the connection unit 30 is input to the signal output circuit 26 of the light projector 2 via the power supply line 31, and is also connected to one end of the power supply circuit 24. The ground potential GND supplied to the connection unit 30 is input to the signal output circuit 26 of the projector 2 via the ground line 32, and is also connected to the other end of the power supply circuit 24. That is, the power supply circuit 24 of the projector 2 receives power supply via the power supply line 31 (1 st power supply line) connected to the outside of the projector 2 and the ground line 32. In the photoelectric sensor 1 of the present embodiment, the power supply line 31 and the ground line 32 extend to the connection portion 30.

The power supply potential VCC supplied to the signal output circuit 26 is connected to the transistor 262.

The power supply circuit 24 of the projector 2 includes a monitor circuit 25, and the monitor circuit 25 also operates by receiving power supplied via a power supply line 31 (1 st power supply line) and a ground line 32. A drive line 266 is arranged between the gate of the transistor 262 and the monitor circuit 25. The monitor circuit 25 controls the on state of the transistor 262 (3 rd switching element). That is, the monitoring circuit 25 activates or deactivates the drive lines 266 depending on the state of the light projector 2. More specifically, the drive line 266 is maintained in the active state as long as the projector 2 is in a healthy state or as long as power is supplied to the power supply circuit 24.

In the wiring structure of the light receiver 4, the secondary power line 38 is connected to the power line 33 of the light receiver 4 at the connection portion 30. That is, the power supply potential VCC supplied to the signal output circuit 26 is supplied to the signal output circuit 46 via the secondary power supply line 38 and the power supply line 33 after passing through the transistor 262 of the signal output circuit 26. In this way, the light receiver 4 includes a transistor 262 (3 rd switching element) disposed between one end of the secondary power line 38 (3 rd power line) and the power line 31 (1 st power line).

The circuit configuration of the signal output circuit 46 of the photodetector 4 and the wiring configuration between the 1 st signal line 35 and the 2 nd signal line 36 are the same as those in fig. 3, and therefore detailed description thereof will not be repeated.

As shown in fig. 5, the photoelectric sensor 1 is provided with a secondary power line 38 (3 rd power line), and one end of the secondary power line 38 is electrically connected to the power line 31 (1 st power line) inside the projector 2, and the other end is electrically connected to the power line 33 (2 nd power line) outside the light receiver 4. In addition, the power supply line 33 (2 nd power supply line) and the ground line 34 extend to the connection portion 30. By adopting such a configuration, the accuracy of abnormality detection such as disconnection can be improved as compared with the related art as described above.

The controller 6 (see fig. 1) can detect the presence or absence of an abnormality based on the combination of the values of the output signal OUT1 and the output signal OUT 2. As one of the detected abnormalities, there is a disconnection in the lead wire connecting the connection unit 30 and the light projector 2 or the light receiver 4 as described above.

The function of detecting a disconnection in the photosensor 1 shown in fig. 5 will be described below. Fig. 6 is a diagram showing changes in output signals when a disconnection occurs in the photosensor 1 of the present embodiment. Fig. 6 shows the output results of the output signal OUT1 and the output signal OUT2 in the case where the detection medium is not present (light-in state) and the case where the detection medium is present (light-shielded state), respectively, for (a) the case where the power supply line 33 of the light receiver 4 is disconnected, (B) the case where the ground line 34 of the light receiver 4 is disconnected, (C) the case where the 1 st signal line 35 is disconnected, (D) the case where the 2 nd signal line 36 is disconnected, (E) the case where the power supply line 31 of the light projector 2 is disconnected, (F) the case where the ground line 32 of the light projector 2 is disconnected, (G) the case where the secondary power supply line 38 of the light projector 2 is disconnected, except for a normal state where no disconnection occurs.

As shown in fig. 6, according to the photosensor 1 of the present embodiment, in a normal state in which no disconnection occurs, the presence or absence of a detection medium can be determined from the output signal OUT1 and the output signal OUT2, as in the above-described related art photosensor 101.

As shown in fig. 6, the photoelectric sensor 1 of the present embodiment can detect an abnormality in any of (a) a case where the power supply line 33 of the light receiver 4 is disconnected, (B) a case where the ground line 34 of the light receiver 4 is disconnected, (C) a case where the 1 st signal line 35 is disconnected, and (D) a case where the 2 nd signal line 36 is disconnected, as in the photoelectric sensor 101 of the related art described above.

Further, according to the photoelectric sensor 1 of the present embodiment, unlike the photoelectric sensor 101 of the related art described above, it is possible to detect an abnormality in either (E) a case where the power supply line 31 of the projector 2 is disconnected or (F) a case where the ground line 32 of the projector 2 is disconnected.

More specifically, (E) in the case where the power supply line 31 of the projector 2 is disconnected, since power is no longer supplied to any of the projector 2 and the light receiver 4, power for outputting the output signal OUT1 and the output signal OUT2 also does not exist. As a result, regardless of the presence or absence of the detection medium, both the output signal OUT1 and the output signal OUT2 are maintained at the Low potential (Low). In this state, the value of the output signal OUT1 and the value of the output signal OUT2 are not mutually inverted values, and therefore an abnormality can be detected.

(F) When the ground line 32 of the projector 2 is disconnected, the power supply circuit 24 of the projector 2 is no longer supplied with power, and therefore the monitoring circuit 25 for activating the transistor 262 also stops operating. As a result, the path for supplying power to the photodetector 4 via the secondary power supply line 38 is cut off, and the output signal OUT1 and the output signal OUT2 are both maintained at the Low potential (Low) regardless of the presence or absence of the detection medium. In this state, the value of the output signal OUT1 and the value of the output signal OUT2 are not mutually inverted values, and therefore an abnormality can be detected.

In the photoelectric sensor 1 of the present embodiment, the secondary power supply line 38 is added as a lead wire for connecting the connection unit 30 and the projector 2, as compared with the photoelectric sensor 101 shown in fig. 3. Although there is a possibility that the secondary power line 38 is broken, the secondary power line 38 can be also detected as broken.

(G) When the secondary power supply line 38 of the projector 2 is disconnected, the path for supplying power from the projector 2 to the photodetector 4 is cut off, and the output signal OUT1 and the output signal OUT2 are both maintained at a Low potential (Low) regardless of the presence or absence of the detection medium. In this state, the value of the output signal OUT1 and the value of the output signal OUT2 are not mutually inverted values, and therefore an abnormality can be detected.

In addition, even if the logics shown in fig. 6 are reversed, the same relationship holds. In this case, the output signal OUT1 in the table may be referred to as the output signal OUT2 instead, and the output signal OUT2 may be referred to as the output signal OUT1 instead.

As described above, in the photoelectric sensor 1 of the present embodiment, even when any one of the lead wires connecting the connection unit 30 and the light emitter 2 and the lead wire connecting the connection unit 30 and the light receiver 4 is broken, the abnormality can be reliably detected.

< E. modification >

The following modifications can be adopted for the photosensor 1 of the present embodiment.

(e 1: monitor Circuit)

The state of the projector 2 can be monitored more precisely by the monitoring circuit 25 of the power supply circuit 24 shown in fig. 5. For example, a situation is assumed in which dirt adheres to the lens surface (light irradiation surface) of the light emitting section 22 of the projector 2 or the light emitting element constituting the light emitting section 22 has a reduced light flux amount due to its lifetime. The monitoring circuit 25 may be provided with a function of detecting such an abnormal event.

Fig. 7 is a schematic diagram showing an example of the wiring structure of the photosensor 1A of modification 1 of the present embodiment. Referring to fig. 7, in a photoelectric sensor 1A according to modification 1 of the present embodiment, an irradiation state detection sensor 23 is disposed at a position close to a light emitting portion 22 of a projector 2A. The irradiation state detection sensor 23 corresponds to a detector for monitoring the state of the projected beam 8 irradiated from the light emitting unit 22. More specifically, the irradiation state detection sensor 23 is formed of a photodiode or the like, determines whether or not the intensity or illuminance of the light beam 8 irradiated from the light emitting unit 22 of the light projector 2A is equal to or higher than a predetermined value, and outputs the detection result to the monitoring circuit 25A.

In the monitoring circuit 25A, when the irradiation beam 8 is irradiated in a predetermined state, the transistor 262 (3 rd switching element) is maintained in an on state. More specifically, in the monitoring circuit 25A, the drive line 266 is switched to the inactive state (Low) when the detection result from the irradiation state detection sensor 23 indicates that the intensity of the projection beam 8 is lower than the predetermined value, regardless of the supply of the predetermined power from the power supply circuit 24 to the light emitting unit 22. Thus, the transistor 262 is in a non-conducting state, and thus a path for supplying power to the light receiver 4 is cut off. As a result, regardless of the presence or absence of the detection medium, both the output signal OUT1 and the output signal OUT2 become Low (Low), and are detected as an abnormality.

Fig. 7 shows an example of monitoring the intensity of the projected beam 8 emitted from the light emitting unit 22 of the projector 2A as a typical example, but the present invention is not limited to this, and any state of the projector 2 may be monitored. Examples of the objects to be monitored include ambient temperature, internal temperature, quality (voltage value, voltage fluctuation rate, and the like) of an external power supply, and capacity of an electrolytic capacitor mounted on the power supply circuit 24.

In addition, the voltage of the light projecting circuit may be monitored. When a light emitting element such as an LED is turned off, the driving voltage of the light projector circuit is lowered, and therefore, the voltage reduction may be monitored to set the output signal of the light projector to Low.

(e 2: simplified structure)

The photoelectric sensor 1 of the present embodiment described above has the following structure: by including the light projector 2 and the light receiver 4 in the path up to the output of the output signal OUT1 and the output signal OUT2, an abnormality such as a disconnection is detected. With such a technical idea, the circuit configuration of the projector 2 can be further simplified. An example of simplifying the circuit configuration of the projector 2 will be described below.

Fig. 8 is a schematic diagram showing an example of the wiring structure of the photosensor 1B of modification 2 of the present embodiment. Referring to fig. 8, in a photosensor 1B according to modification 2 of the present embodiment, the circuit configuration of a signal output circuit 26B of a projector 2B is simplified. More specifically, the transistor 262 and the like are omitted, and one end of the secondary power supply line 38 is electrically connected to the power supply line 31. Even with such a simple circuit configuration, it is possible to detect a disconnection occurring in the power supply line 31 or the like.

(e 3: short-circuit detection function)

In the above description, the function of detecting a disconnection that may occur in the lead wires connecting the connection unit 30 and the light projector 2 or the light receiver 4 has been described, but a short circuit that may occur between these lead wires can also be detected.

Normally, a short circuit between the lead of the power supply potential VCC and the lead of the ground potential GND can be detected based on the magnitude of the amount of current supplied. In addition, in the case of a short circuit between the lead of the power supply potential VCC or the ground potential GND and the lead of the output signal OUT1 or the output signal OUT2, the output signal OUT1 or the output signal OUT2 indicates a value corresponding to the state in many cases, and therefore, the occurrence of an abnormality can be detected from the values of the output signal OUT1 and the output signal OUT 2.

In addition, an additional circuit for facilitating detection of a short circuit may be provided in one or both of the signal output circuit 26 of the projector 2 and the signal output circuit 46 of the light receiver 4.

(e 4: shading instruction input)

In the above-described configuration of the photoelectric sensor shown in fig. 5, 7, and 8, the number of wires connected between the light projector 2, 2A, 2B and the connection unit 30 is 3, and 1 wire is smaller than 4 wires connecting the light receiver 4 and the connection unit 30. It is reasonable and economical to use the same number of cables for covering the number of wires from the connecting portion 30 to the 2, 2A, 2B and the number of wires for covering the number of wires from the connecting portion 30 to the light receptor 4. In the above example, it is also possible to connect each of the light emitters 2, 2A, 2B and the light receiver 4 from the connection portion 30 with a cable including 4 wires.

In the case of using such a cable including 4 wires, the remaining 1 wire may be used for another purpose for the light projector 2, 2A, 2B.

For example, a command for controlling the timing or the irradiation state of the projection beam 8 from the light emitters 2, 2A, 2B may be given from the controller 6 or the like. For example, when the command from the controller 6 is activated, a command (light-shielding command input) for shielding (mask) the irradiation of the projection beam 8 from the light projectors 2, 2A, 2B may be considered. By using such a light shielding command input, it is possible to prevent a situation in which the detection medium is erroneously detected in some jobs or the like.

(e 5: output signal)

In the above description, the output signal OUT1 and the output signal OUT2 have been shown as being inverted from each other, but the present invention is not limited to such a configuration. For example, the output signal OUT1 and the output signal OUT2 may both output the same value. Further, a signal of a predetermined operating frequency may be output as a single output signal.

When both the output signal OUT1 and the output signal OUT2 are made to output the same value, the disconnection of the signal line causes different values to be output, and thus an abnormality can be detected. For example, when any one of the output signal OUT1 and the output signal OUT2 is at a Low potential (Low), the Low potential and the Low-holding potential are both Low and Low, and therefore an abnormal state cannot be detected, but the abnormal state can be detected by detecting a change in the state of the medium.

< F. advantage >

According to the photoelectric sensor of the present embodiment, compared to the photoelectric sensor of the related art, it is possible to reliably detect a disconnection occurring in either the light emitter or the light receiver by merely adding 1 wire between the connection portion and the light emitter.

According to the photoelectric sensor of the present embodiment, the presence or absence of an abnormality can be detected in real time based on the combination of the values of the output signals, and therefore, it is not necessary to install complicated logic or the like for detecting an abnormality in a controller or the like.

According to the photoelectric sensor of the present embodiment, it is possible to detect not only an abnormality caused by a disconnection of the wire from the connection portion to the light projector but also an abnormality in the light projector. For example, by using the irradiation state detection sensor as described above, it is possible to detect a state in which the projection light beam cannot be appropriately irradiated, such as a case where the light beam amount decreases due to the service life of the light emitting element or a case where the lens is stained, and to externally output the abnormal state.

In general, in the case of a configuration in which the input line is used for checking the normal operation at an arbitrary timing, such as when the light projection is stopped, the power supply line, the ground line, the light projector input line, the light receiver signal line, and the light receiver signal line need to be 5 terminals in total, but the port can be used efficiently and effectively because the photoelectric sensor according to the present embodiment can use 4 terminals.

The embodiments disclosed herein are considered to be illustrative in all respects, rather than restrictive. The scope of the present invention is defined by the claims rather than the above description, and includes all modifications equivalent in meaning to the claims and within the scope.

Description of the reference symbols

1, 1A, 1B, 101: a photosensor; 2, 2A, 2B, 102: a light projector; 4,104: a light receptor; 6: a controller; 8: projecting a light beam; 10: a conveyor; 12: a workpiece; 22: a light emitting section; 23: an irradiation state detection sensor; 24, 124: a power supply circuit; 25, 25A: a monitoring circuit; 26, 26B, 46: a signal output circuit; 30, 130: a connecting portion; 31, 33, 131, 133: a power line; 32, 34, 132, 134: a ground line; 35, 135: a 1 st signal line; 36, 136: a 2 nd signal line; 38: a secondary power line; 42: a light receiving section; 44: a detection circuit; 262, 462, 466: a transistor; 266, 442, 446: driving a wire; 444: an inverter circuit; GND: a ground potential; OUT1, OUT 2: and outputting the signal.