1. A brake device, wherein the brake device comprises:

a brake piston that presses a brake member against a braked member that rotates together with a wheel;

a hydraulic system that urges the brake piston toward the braked member;

an electric system having a movable piece that urges the brake piston toward the member to be braked; and

a control device capable of performing a parking brake action using the hydraulic system and the electric system,

in the parking brake operation, the control device is configured to apply a pressing force of a predetermined value or more to the brake piston by both the hydraulic system and the electric system,

the prescribed value is larger than a maximum pressing force that the electric system can apply to the brake piston.

2. The braking device according to claim 1,

the electric system includes a feed screw member that advances and retracts the movable element with respect to the brake piston, and a motor that rotates the feed screw member,

in the parking brake operation, the control device is configured to control an operation of the electric motor.

3. The braking device according to claim 1 or 2,

the hydraulic system is configured to change the pressing force applied to the brake piston in accordance with an operation of a brake pedal by a user,

in the parking brake operation, the control device executes a notification process for prompting the user to perform a further operation of the brake pedal in accordance with the pressing force provided to the brake piston by the hydraulic system.

4. The braking device according to any one of claims 1 to 3,

the hydraulic system has a hydraulic pump that increases the pressing force applied to the brake piston,

in the parking brake operation, the control device is configured to control an operation of the hydraulic pump.

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

the control device is also capable of performing a parking brake release action using the hydraulic system and the electric system,

in the parking brake release operation, the control device retracts the movable element of the electric system from the brake piston while applying the pressing force to the brake piston by the hydraulic system.

Background

A brake device is disclosed in japanese patent application laid-open No. 2006-256578. The brake device includes a brake piston that presses a brake member against a member to be braked that rotates together with a wheel, an electric system that includes a movable element that presses the brake piston against the member to be braked, and a control device that can perform a parking brake operation using the electric system. The electric system includes a feed screw member that advances and retracts the movable element with respect to the brake piston, and an electric motor that rotates the feed screw member.

In the electric system of the brake device described in japanese patent application laid-open No. 2006-256578, the parking brake is actuated and released by rotating the feed screw member using the motor. In such a configuration, the motor needs to be selected according to the required braking force, and a motor with a relatively large output may be required. Generally, the size of the motor is increased in proportion to the output of the motor. Therefore, when a motor having a relatively large output is used, the size and weight of the brake device may be increased, which may cause various obstacles in the design of the vehicle.

Disclosure of Invention

In view of the above-described circumstances, the present specification provides a technique capable of reducing the output required for the electric system in the brake device.

The brake device disclosed in the present specification includes: a brake piston that presses a brake member against a braked member that rotates together with a wheel; a hydraulic system that urges a brake piston toward a member to be braked; an electric system having a movable element for pressing a brake piston against a member to be braked; and a control device capable of executing a parking brake operation using the hydraulic system and the electric system. In the parking brake operation, the control device is configured to apply a pressing force of a predetermined value or more to the brake piston by both the hydraulic system and the electric system. The predetermined value is larger than the maximum pressing force that the electric system can apply to the brake piston.

In the above-described brake device, the parking brake operation is performed using both the hydraulic system and the electric system. In the parking brake operation, a pressing force equal to or greater than a predetermined value corresponding to a required braking force is applied to the brake piston from both the hydraulic system and the electric system. The predetermined value is larger than the maximum pressing force that the electric system can apply to the brake piston. That is, by using both the electric system and the hydraulic system, it is possible to apply a pressing force to the brake piston that cannot be obtained by only the electric system. As a result, the output required by the electric system (i.e., the motor or the other actuator) can be relatively reduced with respect to the braking force required during the parking brake operation. Thus, the electric system can be configured to be relatively small, and the degree of freedom in designing the vehicle can be improved by reducing the size and weight of the brake device.

Drawings

Fig. 1 shows a block diagram of a brake device 10 of an electric vehicle of an embodiment.

Fig. 2 shows a circuit configuration of the hydraulic system 16 of the brake apparatus 10.

Fig. 3 is a flowchart showing an example of a series of processing of the parking brake operation performed by the brake device 10.

Fig. 4 is a flowchart showing another example of a series of processing for the parking brake operation performed by the brake device 10.

Fig. 5 is a flowchart showing an example of a series of processing for the parking brake release operation performed by the brake device 10.

Fig. 6 is a flowchart showing another example of a series of processing for the parking brake release operation performed by the brake device 10.

Description of reference numerals

10: brake device

12: brake pedal

14: master cylinder

18: brake actuator

16: hydraulic system

20: control device

24: hydraulic sensor

26: liquid storage container

28: hydraulic pump

30. 32, 34: electromagnetic valve

36. 37: check valve

40: electric system

42: electric motor

52: braked component

54: brake component

56: brake piston

58: feed screw member

59: cylinder body

60: brake caliper

61. 63: pipeline

62: movable part

64: brake oil

Detailed Description

In one embodiment of the present technology, the electric system may include a feed screw member that advances and retracts the movable element with respect to the brake piston, and a motor that rotates the feed screw member. In this case, the control device may be configured to control the operation of the electric motor during the parking brake operation. However, the electric system is not limited to the system of the above-described embodiment, and may have various configurations as long as the movable element can be advanced and retracted with respect to the brake piston.

In an embodiment of the present technology, the hydraulic system may be configured to change the pressing force applied to the brake piston in accordance with an operation of the brake pedal 12 by a user. In this case, the control device may execute a notification process for prompting the user to further operate the brake pedal in accordance with the pressing force applied to the brake piston by the hydraulic system during the parking brake operation. That is, in the parking brake action, the control device may indirectly control the action of the hydraulic system via the user, rather than directly controlling the action of the hydraulic system. The notification processing described herein is not particularly limited, and may be processing that is perceived by at least one of the visual, auditory, and tactile senses of the user.

In one embodiment of the present technology, the hydraulic system may have a hydraulic pump that increases the pressing force applied to the brake piston. In this case, the control device may be configured to control the operation of the hydraulic pump during the parking brake operation. According to such a configuration, the control device can perform the parking brake operation without requiring a user's operation in particular by directly controlling the operation of the hydraulic system.

In one embodiment of the present technology, the control device may be configured to perform the parking brake release operation using a hydraulic system and an electric system. In this case, the control device may retract the movable element of the electric system from the brake piston while applying the pressing force to the brake piston by the hydraulic system during the parking brake release operation. In the parking brake operation, a pressing force that cannot be achieved by only the electric system is applied to the brake piston. As a result, when the parking brake is released, an excessive reaction force acts on the mover from the brake piston, and if only the electric system is used, the parking brake may not be released. Therefore, even in the parking brake release operation, the control device uses both the hydraulic system and the electric system, thereby reliably releasing the parking brake. That is, by applying a pressing force to the brake piston by the hydraulic system, the reaction force acting on the movable element from the brake piston is reduced or eliminated. By operating the electric system in this state, the movable element can be reliably retracted from the brake piston.

In the above embodiment, the control means may indirectly control the operation of the hydraulic system in the parking brake release operation via the user. That is, during the parking brake release operation, the control device may execute a notification process for prompting the user to further operate the brake pedal based on the pressing force applied to the brake piston by the hydraulic system. Alternatively, the control device may directly control the operation of the hydraulic system in the parking brake release operation. That is, the control device may be configured to control the operation of the hydraulic pump provided in the hydraulic system during the parking brake release operation.

Representative, non-limiting examples of the present disclosure are described in detail below with reference to the accompanying drawings. This detailed description is merely intended to show those skilled in the art the details of preferred embodiments for practicing the present disclosure, and is not intended to limit the scope of the invention. In addition, additional features and disclosures disclosed below may be utilized separately or in conjunction with other features and techniques to provide further improved vehicle bodies.

In addition, combinations of features and steps disclosed in the following detailed description are not essential to practice of the present disclosure in the broadest sense, and are described merely to describe particularly representative specific examples of the present disclosure. Furthermore, the various features of the representative examples described above and below, as well as those of the aspects set forth in the independent and dependent claims, are not intended to be combined in the order in which the specific examples described herein, or recited herein, are combined in order to provide additional and useful embodiments of the present disclosure.

All the features described in the specification and/or claims are disclosed individually and independently as limitations on specific matters disclosed and claimed at the beginning of the application, in addition to the configurations of the features described in the embodiments and/or claims. Further, the description of all the numerical ranges and groups or sets is intended to disclose intermediate structures thereof as limitations to specific matters disclosed and claimed at the time of application.

Examples

A brake device 10 for a vehicle as an embodiment of the present technology is explained with reference to the drawings. It is assumed that the brake apparatus 10 of the present embodiment is mainly employed in an electric vehicle. However, the structure described in the present embodiment is not limited to being applied to a brake device for an electric vehicle, and can be applied to brake devices for various vehicles such as an engine vehicle, for example.

As shown in fig. 1, the brake device 10 includes a member to be braked 52, a brake member 54, and a brake piston 56. The braked member 52 is configured to be fixed to the wheel so as not to rotate relative thereto, and to rotate together with the wheel. The braking member 54 is supported to be able to advance and retreat with respect to the member 52 to be braked, and is pressed against the member 52 to be braked by the braking piston 56. When the braking member 54 is pressed against the braked member 52, a frictional force is generated between the braked member 52 and the braking member 54, and the braked member 52 (i.e., the wheel) is braked.

The member to be braked 52 is a disc-shaped brake disc, and the braking member 54 is a pair of brake pads facing each other with the brake disc interposed therebetween, but is not particularly limited. The brake member 54 (i.e., a pair of brake pads) is disposed in the brake caliper 60 together with the brake piston 56. The brake caliper 60 is mounted on a suspension (not shown) and has a cylinder 59 that houses the brake piston 56. Thus, the brake device 10 of the present embodiment has the configuration of a disc brake. However, as another embodiment, the brake device 10 may have a drum brake configuration. In this case, the braked member 52 may be a brake drum, and the brake member 54 may be one or more brake shoes disposed in the brake drum.

The brake device 10 includes a brake pedal 12, a hydraulic system 16, an electric system 40, and a control device 20. The brake pedal 12 is an operation member operated by a user, and is disposed in a driver's seat of the vehicle. The brake pedal 12 is connected to the caliper 60 via an oil pressure circuit including the hydraulic system 16. When the user operates the brake pedal 12, the hydraulic pressure corresponding to the operation amount thereof is transmitted to the caliper 60. In the brake caliper 60, the brake piston 56 presses the braking member 54 against the braked member 52. Thereby, the braked member 52 (i.e., the wheel) is braked.

The specific structure of the hydraulic system 16 is not particularly limited. The hydraulic system 16 of the present embodiment includes, for example, a master cylinder 14 and a brake actuator 18. The master cylinder 14 is one of the boosting devices, and is inserted between the brake pedal 12 and the caliper 60. The operating force applied to the brake pedal 12 is amplified by the master cylinder 14 and transmitted to the brake piston 56 of the brake caliper 60. The brake actuator 18 includes a hydraulic pump 28 and the like (see fig. 2), and is capable of controlling the hydraulic pressure (i.e., braking force) supplied to the brake caliper 60 regardless of the operation applied to the brake pedal 12. The operation of the brake actuator 18 is controlled by a control device 20.

The structure of the brake actuator 18 is explained with reference to fig. 2. The structure described here is an example, and the brake actuator 18 is not limited thereto. As shown in fig. 2, the brake actuator 18 includes a reservoir 26, a hydraulic pump 28, a hydraulic pressure sensor 24, a plurality of solenoid valves 30, 32, 34, a plurality of check valves 36, 37, a plurality of pipes 61, 63, and brake oil 64. Fig. 2 also shows a brake actuator 18 corresponding to one brake caliper 60 of the vehicle. The brake device 10 according to the present embodiment may include a plurality of brake calipers 60, and is not particularly limited, and in this case, the hydraulic system 16 shown in fig. 2 may be provided for each brake caliper 60. The plurality of conduits 61, 63 includes a first conduit 61 and a second conduit 63. The reservoir 26 is a container that temporarily stores the excess brake oil 64.

The hydraulic pressure sensor 24 is provided in a first line 61 that connects the master cylinder 14 and the reservoir 26, and detects the hydraulic pressure (pressure of brake oil) supplied from the master cylinder 14. The specific structure of the hydraulic pressure sensor 24 is not particularly limited. The hydraulic pressure sensor 24 may be a member capable of directly or indirectly measuring the hydraulic pressure in the first line 61. The hydraulic pressure sensor 24 is connected to the control device 20, and the detection result of the hydraulic pressure sensor 24 is input to the control device 20. A check valve 36 is provided between the hydraulic pressure sensor 24 and the reservoir 26 in the first pipe 61. The check valve 36 inhibits the direct flow of brake oil 64 from the master cylinder 14 to the reservoir 26.

The plurality of solenoid valves 30, 32, 34 include a first solenoid valve 30, a second solenoid valve 32, and a third solenoid valve 34. The individual solenoid valves 30, 32, 34 are controlled by the control device 20. The first solenoid valve 30 and the second solenoid valve 32 are normally open valves that are normally open and closed when power is supplied. The third electromagnetic valve 34 is a normally closed valve that is closed at normal times and opened when power is supplied. The first and second solenoid valves 30 and 32 are interposed between the master cylinder 14 and the brake caliper 60, and the third solenoid valve 34 is interposed between the brake caliper 60 and the reservoir 26. Normally, the first and second solenoid valves 30, 32 are opened, and the third solenoid valve 34 is closed. In this state, the hydraulic pressure generated by the master cylinder 14 is transmitted to the brake piston 56 of the brake caliper 60.

The hydraulic pump 28 is provided on a second pipe line 63 extending from the reservoir 26, and is connected to the brake caliper 60 via the second electromagnetic valve 32. A check valve 37 is provided downstream of the hydraulic pump 28. The check valve 37 prohibits the flow of the brake oil 64 from the master cylinder 14 to the reservoir 26 via the hydraulic pump 28 when the hydraulic pump 28 is not operating. The operation of the hydraulic pump 28 is controlled by the control device 20. The control device 20 is capable of supplying a desired hydraulic pressure to the brake caliper 60 regardless of the operation of the brake pedal 12 by the user by controlling the hydraulic pump 28. In this case, the control device 20 closes the first electromagnetic valve 30 and drives the hydraulic pump 28. When the pressure is reduced thereafter, the control device 20 stops the driving of the hydraulic pump 28 and opens the first and third electromagnetic valves 30 and 34.

Returning to fig. 1, the electric system 40 includes a movable element 62, a feed screw member 58, and an electric motor 42. The movable member 62 is configured to advance and retract with respect to the brake piston 56. The movable element 62 is a nut-shaped member having an internal thread that engages with the feed screw member 58, but is not particularly limited. The feed screw member 58 is a feed screw that advances and retracts the movable element 62 with respect to the brake piston 56, and is configured to be rotationally driven by the motor 42. When the motor 42 rotates the feed screw member 58, the movable piece 62 advances and retreats relative to the brake piston 56. Thereby, the movable element 65 can press the brake piston 56 against the brake member 54, whereby the brake member 54 is pressed against the braked member 52. Here, the pitch of the thread of the feed screw member 58 is sufficiently small, and even if a reaction force is applied from the brake piston 56 to the movable element 62, the movable element 62 does not move. The operation of the electric system 40, in particular the operation of the electric motor 42, is controlled by the control device 20. The configuration of the electric system 40 described here is an example. The electric system 40 is not limited to the system of the above-described embodiment, and may have various configurations as long as the movable element 62 can be advanced and retracted relative to the brake piston 56.

The control device 20 can perform the parking brake operation and the parking brake release operation by controlling the operations of the electric system 40 and the hydraulic system 16. The parking brake operation is an operation of applying a parking brake to the vehicle, and the parking brake release operation is an operation of releasing the parking brake applied to the vehicle. During the parking brake operation, a pressing force equal to or greater than a predetermined value corresponding to a required braking force is applied to the brake piston 56 from both the hydraulic system 16 and the electric system 40. The predetermined value is larger than the maximum pressing force that the electric system 40 can apply to the brake piston 56. That is, by using both the electric system 40 and the hydraulic system 16, it is possible to apply a pressing force to the brake piston 56 that cannot be obtained by only the electric system 40. As a result, the output required by the electric system 40 (i.e., the motor 42 or other actuator) can be relatively reduced with respect to the braking force required during the parking brake operation. Accordingly, the electric system 40 can be configured to be relatively small, and the degree of freedom in designing the vehicle can be improved by reducing the size and weight of the brake device 10.

On the other hand, during the parking brake release operation, the controller 20 retracts the movable element 62 of the electric system 40 from the brake piston 56 while applying a pressing force to the brake piston 56 by the hydraulic system 16. In the parking brake operation described above, a pressing force that cannot be achieved with only the electric system 40 is applied to the brake piston 56. As a result, when the parking brake is released, an excessive reaction force acts on the brake piston 56, and if only the electric system 40 is used, the parking brake may not be released. Therefore, during the parking brake release operation, the control device 20 uses both the hydraulic system 16 and the electric system 40, thereby reliably releasing the parking brake. That is, by applying a pressing force to the brake piston 56 by the hydraulic system 16, the reaction force acting on the movable element 62 from the brake piston 56 is reduced or eliminated. By operating the electric system 40 in this state, the movable element 62 can be reliably retracted from the brake piston 56.

An example of the parking brake operation will be described with reference to fig. 3. The process of fig. 3 is started by the user performing a predetermined operation to turn on the parking brake operation (yes at step S10). First, in step S12, the control device 20 compares the detected pressure P1 detected by the hydraulic pressure sensor 24 with a predetermined first pressure threshold Pth 1. The detected pressure P1 at this time depends on the operation of the brake pedal 12 by the user. The first pressure threshold Pth1 is a value determined according to the pressing force required for the parking brake on the brake piston 56. That is, if the detected pressure P1 reaches the first pressure threshold Pth1, it means that the sum of the pressing force against the brake piston 56 by the hydraulic system 16 and the pressing force against the brake piston 56 by the electric system 40 is equal to or greater than the pressing force required for the parking brake. At this time, the pressing force against the brake piston 56 by the electric system 40 may be sufficiently smaller than the pressing force against the brake piston 56 by the hydraulic system 16. The first pressure threshold Pth1 is stored in the control device 20 in advance.

If it is determined that the detected pressure P1 is equal to or greater than the first pressure threshold Pth1 (yes in step S12), the control device 20 proceeds to the process of step S14. On the other hand, if it is determined that the detected pressure P1 is lower than the first pressure threshold Pth1 (no in step S12), the control device 20 recognizes that the hydraulic pressure is insufficient, and proceeds to the process of step S22. In step S22, the control device 20 executes notification processing for the user. This notification process prompts the user to make a further operation of the brake pedal 12 (i.e., further depression of the brake pedal 12). After executing the notification processing, the control device 20 returns to the processing of step S12 again.

Here, the specific form of the notification treatment is not particularly limited. The notification process may be a process that is perceived by at least one of the vision, the hearing, and the touch of the user. Examples of the processing to be perceived by the user's vision include lighting a predetermined lamp or displaying a predetermined message or graphic on a display. As the processing to be perceived by the auditory sense of the user, for example, a predetermined notification sound or a voice message is output. As the process to be sensed by the tactile sense of the user, for example, an operation member such as a steering wheel or a brake pedal 12 is vibrated.

When the process proceeds to step S14, the control device 20 controls the motor 42 of the electric system 40 to rotate in the forward direction. Thereby, the feed screw member 58 rotates in the forward direction, and the movable element 62 advances toward the brake piston 56. At this time, the brake piston 56 is already pressed against the brake member 54 by the hydraulic pressure, and is disposed apart from the movable element 62 in front of the movable element 62. Therefore, the load acting on the motor 42 is small. In other words, it is sufficient that the motor 42 has a relatively small output. Next, the process proceeds to step S16.

In step S16, the control device 20 compares the detected pressure P1 and the first pressure threshold Pth1 again. If the detected pressure P1 is equal to or higher than the first pressure threshold Pth1 (yes in step S16), the control device 20 recognizes that the parking brake operation can be continued, and proceeds to the process of step S18. On the other hand, when the detected pressure P1 is lower than the first pressure threshold Pth1 (no in step S16), the control device 20 recognizes that the operation of the brake pedal 12 by the user is insufficient, and proceeds to the process of step S24. In step S24, the control device 20 executes notification processing to the user. This notification processing prompts the user to further operate the brake pedal 12, similarly to the notification processing of step S22 described above. After executing the notification processing, the control device 20 returns to the processing of step S16 again.

When proceeding to the process of step S18, the control device 20 compares the current a1 of the motor 42 with the first current threshold Ath 1. Thereby, the control device 20 determines whether or not the movable element 62 abuts on the brake piston 56. That is, when the movable element 62 abuts against the brake piston 56 and the motor 42 is locked, the current a1 of the motor 42 is greatly increased. Therefore, the control device 20 can determine that the movable element 62 is in contact with the brake piston 56 when the current a1 of the motor 42 exceeds the first current threshold Ath 1. When the current a1 of the motor 42 exceeds the first current threshold Ath1 (yes in step S18), the control device 20 proceeds to the process of step S20. On the other hand, when the current a1 of the motor 42 is lower than the first current threshold Ath1 (no in step S18), the process returns to step S16. That is, the comparison process of the detected pressure P1 in step S16 and the comparison process of the current a1 in step S18 are performed again. Here, the contact state of the movable element 62 with the brake piston 56 may be recognized based on other indexes, not limited to the current a1 of the motor 42.

As will be understood from the foregoing description, in the parking brake operation shown in fig. 3, the pressing force required for the parking brake is generated from the hydraulic system 16 to the brake piston 56 by operating the brake pedal 12 by the user. Therefore, while the parking brake operation is being performed (after step S12), the user needs to continue depressing the brake pedal 12 and continue generating the hydraulic pressure equal to or higher than the first pressure threshold Pth 1. Therefore, the control device 20 prompts the user to further operate the brake pedal 12 by continuously monitoring the detected pressure P1 during the execution of the parking brake action and executing the above notification process as necessary. As described above, in the parking brake operation shown in fig. 3, the control device 20 indirectly controls the operation of the hydraulic system 16 via the user, rather than directly controlling the operation of the hydraulic system 16.

When the process proceeds to step S20, control device 20 stops driving motor 42. Thus, the positions of the movable element 62 and the brake piston 56 are locked in a state where a sufficient pressing force is applied to the brake piston 56. Next, in step S21, the hydraulic system 16 is depressurized by releasing the operation of the brake pedal 12 by the user. At this time, the control device 20 may prompt the user to cancel the operation of the brake pedal 12 by notifying the user that the parking brake operation is completed. Through the above steps, the parking brake operation is ended.

In the above-described parking brake operation, the start of the motor 42 (step S14) may be performed in parallel with the first pressure comparison (step S12) immediately after the parking brake operation is turned on. In addition, the depressurization of the hydraulic system 16 (step S21) may be performed simultaneously with the stop of the motor 42 (step S20). Alternatively, after the hydraulic system 16 is depressurized (i.e., after step S21), the motor 42 may be stopped (step S20).

Next, another example of the parking brake operation will be described with reference to fig. 4. The process of fig. 4 is started by the user performing a predetermined operation to turn on the parking brake operation (yes at step S50). First, in step S52, the control device 20 drives the hydraulic pump 28 of the hydraulic system 16.

Next, in step S54, the control device 20 compares the pump pressure P2 with a predetermined first pressure threshold Pth 1. The pump pressure P2 at this time is a pressure supplied to the brake caliper 60 by driving the hydraulic pump 28. The pump pressure P2 can be directly detected, but can be estimated based on the rotation speed of the hydraulic pump 28. However, the detection of the pump pressure P2 of the hydraulic pump 28 is not limited to this form, and may be performed directly by a hydraulic pressure sensor (not shown) provided between the hydraulic pump 28 and the brake caliper 60, for example. Alternatively, in the case where it is clear from the design that the pump pressure P2 exceeds the first pressure threshold Pth1 by driving the hydraulic pump 28, the process of step S54 can be omitted.

If it is determined that the pump pressure P2 is equal to or greater than the first pressure threshold Pth1 (yes in step S54), the control device 20 recognizes that the parking brake operation can be continued, and proceeds to the process of step S56. On the other hand, if it is determined that the pump pressure P2 is lower than the first pressure threshold Pth1 (no in step S54), the control device 20 recognizes that the hydraulic pressure is insufficient, and after a predetermined time has elapsed, executes the process of step S54 again.

When the process proceeds to step S56, the control device 20 controls the motor 42 of the electric system 40 to rotate in the forward direction. In this process, the feed screw member 58 rotates in the forward direction and the movable element 62 advances toward the brake piston 56, similarly to the process of step S14 described above. At this time, the brake piston 56 is already pressed against the brake member 54 by the hydraulic pressure, and is disposed apart from the movable element 62 in front of the movable element 62.

In step S58, the control device 20 compares the current a1 of the motor 42 with the first current threshold Ath 1. This process is the same as the process of step S18 described above. When the current a1 of the motor 42 exceeds the first current threshold Ath1 (yes in step S58), the control device 20 recognizes that the movable element 62 is in contact with the brake piston 56, and proceeds to the process of step S60. On the other hand, when the current a1 of the motor 42 is lower than the first current threshold Ath1 (no in step S58), the control device 20 recognizes that the movable element 62 is not in contact with the brake piston 56, and after a predetermined time has elapsed, the process of step S58 is executed again. Here, the contact state of the movable element 62 with the brake piston 56 may be recognized based on other indexes, not limited to the current a1 of the motor 42.

When the process proceeds to step S60, the control device 20 stops driving the hydraulic pump 28. Next, in step S61, the controller 20 opens the first solenoid valve 30 and the third solenoid valve 34, thereby depressurizing the hydraulic system 16. Then, in step S62, control device 20 stops driving of motor 42. Thus, the positions of the movable element 62 and the brake piston 56 are locked in a state where a sufficient pressing force is applied to the brake piston 56. Through the above steps, the parking brake operation is ended.

As will be understood from the foregoing description, in the parking brake operation shown in fig. 4, the operation of the hydraulic pump 28 is directly controlled by the control device 20, and the pressing force required for the parking brake is generated from the hydraulic system 16 to the brake piston 56. Therefore, the parking brake of the vehicle can be implemented without particularly requiring the operation of the user.

In the parking brake operation, the start of the motor 42 (step S56) may be started immediately after the parking brake operation is turned on, and may be executed in parallel with the pressure comparison (step S54). Additionally or alternatively, the stopping of the motor 42 (step S62) may be performed simultaneously with or prior to the stopping of the hydraulic pump 28 (step S60).

In the parking brake actuation described above, the pump pressure P2 may include a pressure generated by a user operating the brake pedal 12. At this time, the operation of the brake pedal 12 by the user may be performed before the driving of the hydraulic pump 28. That is, the hydraulic pump 28 can supplement the hydraulic pressure generated by the user operating the brake pedal 12 with a shortage amount.

An example of the parking brake release operation will be described with reference to fig. 5. The process of fig. 5 is started by the user performing a predetermined operation to turn on the parking brake release operation (yes at step S30).

First, in step S32, the control device 20 compares the detected pressure P1 detected by the hydraulic pressure sensor 24 with the second pressure threshold Pth 2. The second pressure threshold Pth2 at this time is a pressing force corresponding to the reaction force acting on the mover 62 from the brake piston 56 in the parking brake state. That is, if the detected pressure P1 reaches the second pressure threshold Pth2, the reaction force acting on the brake piston 56 decreases or disappears. The second pressure threshold Pth2 is stored in the control device 20 in advance. Strictly speaking, the required second pressure threshold Pth2 varies according to the parking brake action that is performed last. Therefore, the control device 20 can determine and store the second pressure threshold Pth2 required for releasing the parking action each time the parking action is performed.

If it is determined that the detected pressure P1 is equal to or greater than the second pressure threshold Pth2 (yes in step S32), the control device 20 proceeds to the process of step S34. On the other hand, if it is determined that the detected pressure P1 is lower than the second pressure threshold Pth2 (no in step S32), the control device 20 recognizes that the hydraulic pressure is insufficient, and proceeds to the process of step S42. In step S42, the control device 20 executes notification processing for the user. This notification processing prompts the user to further operate the brake pedal 12, similarly to the notification processing (step S22, step S24 in fig. 3). After executing the notification processing, the control device 20 returns to the processing of step S32 again.

When the process proceeds to step S34, the control device 20 controls the motor 42 of the electric system 40 to rotate in the reverse direction. Thereby, the feed screw member 58 rotates in the reverse direction, and the movable element 62 is retracted from the brake piston 56. At this time, the reaction force acting on the brake piston 56 by the parking brake action has been reduced or eliminated by the hydraulic pressure. By operating the motor 42 in this state, the movable element 62 can be reliably retracted from the brake piston 56. Next, the process proceeds to step S36.

In step S36, the control device 20 compares the current a1 of the motor 42 with the second current threshold Ath 2. Thereby, the control device 20 determines whether or not the movable element 62 has moved to the retreat limit position and has come into contact with the stopper. That is, when the movable element 62 abuts against the stopper at the reverse limit position and the motor 42 is locked, the current a1 of the motor 42 is greatly increased. Therefore, the control device 20 can determine that the movable element 62 is in contact with the stopper when the current a1 of the motor 42 exceeds the second current threshold Ath 2. When the current a1 of the motor 42 exceeds the second current threshold Ath2 (yes in step S36), the control device 20 proceeds to the process of step S38. On the other hand, when the current a1 of the motor 42 is lower than the second current threshold Ath2 (no in step S36), it is recognized that the movable element 62 is not in contact with the stopper, and the process of step S36 is repeatedly executed. Here, the current a1 of the motor 42 is not limited, and a case where the movable element 62 abuts against the stopper (or a case where the movable element 62 is sufficiently retracted from the brake piston 56) may be recognized based on another index.

When the process proceeds to step S38, control device 20 stops driving motor 42. Next, in step S40, the hydraulic system 16 is depressurized by releasing the operation of the brake pedal 12 by the user. At this time, the control device 20 may prompt the user to cancel the operation of the brake pedal 12 by notifying the user that the parking brake releasing operation is completed. Through the above steps, the parking brake release operation is ended.

As will be understood from the foregoing description, in the parking brake release operation shown in fig. 5, the pressing force necessary for releasing the parking brake is generated from the hydraulic system 16 to the brake piston 56 by operating the brake pedal 12 by the user. Therefore, the control device 20 prompts the user to perform further operation of the brake pedal 12 by performing the above notification processing as needed during execution of the parking brake release action. As described above, in the parking brake operation shown in fig. 5, the control device 20 indirectly controls the operation of the hydraulic system 16 via the user, rather than directly controlling the operation of the hydraulic system 16.

Another example of the parking brake release operation is described with reference to fig. 6. The process of fig. 6 is started by the user performing a predetermined operation to turn on the parking brake release operation (yes at step S80). First, in step S82, the control device 20 drives the hydraulic pump 28 of the hydraulic system 16.

Next, in step S84, the control device 20 compares the pump pressure P2 with the second pressure threshold Pth 2. If it is determined that the pump pressure P2 is equal to or greater than the second pressure threshold Pth2 (yes in step S84), the control device 20 proceeds to the process of step S86. On the other hand, if it is determined that the pump pressure P2 is lower than the second pressure threshold Pth2 (no in step S84), the control device 20 recognizes that the hydraulic pressure is insufficient, and executes the process of step S84 again after a predetermined time has elapsed. In the parking brake release operation, the pump pressure P2 can be estimated from the rotation speed of the hydraulic pump 28, for example.

When the process proceeds to step S86, the control device 20 controls the motor 42 of the electric system 40 to rotate in the reverse direction. In this process, the feed screw member 58 rotates in the reverse direction and the movable element 62 retracts from the brake piston 56, similarly to the process of step S34 described above. At this time, the reaction force acting on the brake piston 56 by the parking brake action has been reduced or eliminated by the hydraulic pressure. By operating the motor 42 in this state, the movable element 62 can be reliably retracted from the brake piston 56. Next, the process proceeds to step S88.

In step S88, the control device 20 compares the current a1 of the motor 42 with the second current threshold Ath 2. This process is the same as the process of step S36 described above. When the current a1 of the motor 42 exceeds the second current threshold Ath2 (yes in step S88), the controller 20 determines that the movable element 62 is in contact with the stopper at the rearward limit position, and proceeds to the process of step S90. On the other hand, when the current a1 of the motor 42 is lower than the second current threshold Ath2 (no in step S88), it is recognized that the movable element 62 is not in contact with the stopper, and the process of step S88 is repeatedly executed. Here, the current a1 of the motor 42 is not limited, and a case where the movable element 62 abuts against the stopper at the retreat limit position (or a case where the movable element 62 is sufficiently retreated from the brake piston 56) may be recognized based on another index.

When the process proceeds to step S90, control device 20 stops driving motor 42. Next, in step S92, the control device 20 stops driving the hydraulic pump 28. Then, in step S94, the control device 20 opens the first solenoid valve 30 and the third solenoid valve 34, thereby depressurizing the hydraulic system 16. Through the above steps, the parking brake release operation is ended.

As will be understood from the foregoing description, in the parking brake operation shown in fig. 6, the operation of the hydraulic pump 28 is directly controlled by the control device 20, and a pressing force required for releasing the parking brake is generated from the hydraulic system 16 to the brake piston 56. Therefore, the parking brake release operation can be performed without particularly requiring an operation by the user.

In the parking brake release operation, the start of the motor 42 (step S86) may be started immediately after the parking brake operation is turned on, and may be executed in parallel with the pressure comparison (step S84). Alternatively, the stop of the hydraulic pump 28 (step S92) may be performed simultaneously with or prior to the stop of the motor 42 (step S90).

As described above, the pump pressure P2 is a pressure supplied to the brake caliper 60 by driving the hydraulic pump 28. In the parking brake release action described above, the pump pressure P2 may include a pressure generated by the user operating the brake pedal 12. At this time, the operation of the brake pedal 12 by the user may be performed before the driving of the hydraulic pump 28. Therefore, the hydraulic pressure generated in the brake caliper 60 by the user operating the brake pedal 12 can be supplemented by the hydraulic pump 28 by an insufficient amount.

The parking brake operation according to the present technology may be performed for all parking brakes at a time, or may be performed only for the parking brake in a specific situation. The specific situation is not particularly limited, and examples thereof include situations in which a braking force larger than usual is required, such as a case of parking on a road surface having a slope such as a slope. For example, the determination of the slope may be performed by referring to information such as a G sensor incorporated in the vehicle, a traveling brake fluid pressure at the time of parking, and GPS position information.

As a modification of the present technology, the control device 20 may be provided with a stroke sensor capable of detecting the stroke position of the brake piston 56. By referring to the stroke position, it can be recognized that the braking force required for the parking brake action has been applied to the braked member 52.