Brake device

Abstract

The invention provides a brake device. The control unit (100) performs output calibration of the control pressure sensor (353) while moving the piston (512) of the electric cylinder (51) from the standby position in the backward direction (Zb) when confirming a deviation in the output of the control pressure sensor (353).

Description

Technical Field

[0001] The present invention relates to a braking device including an electric cylinder. Background Art

[0002] As a braking device including an electric cylinder, a device described in Patent Document 1 is known. The electric cylinder has a piston movably housed in a cylinder, a hydraulic chamber partitioned by the peripheral wall of the cylinder and the piston, and an electric motor that drives the piston. This braking device generates braking force by supplying the brake fluid discharged from the electric cylinder to a wheel cylinder. Further, this braking device includes a hydraulic sensor that detects the hydraulic pressure of the brake fluid discharged from the electric cylinder.

[0003] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2009-137376

[0004] The output characteristics of the hydraulic sensor provided in such a braking device may change depending on environmental conditions and the like. Further, there is a case where the detection accuracy of the hydraulic sensor decreases due to the change in the output characteristics. Summary of the Invention

[0005] The braking device that solves the above problems includes: a storage tank that stores brake fluid; an electric cylinder that discharges brake fluid by moving a piston in the cylinder according to the drive of an electric motor; a hydraulic sensor that detects the hydraulic pressure of the brake fluid discharged from the electric cylinder; and a control unit that controls the electric motor. Further, this braking device generates braking force on a wheel by supplying brake fluid to the wheel cylinder according to the discharge of the brake fluid from the electric cylinder. The electric cylinder of this braking device has: a hydraulic chamber partitioned by the peripheral wall of the cylinder and the piston; an input port that is an inlet of the brake fluid from the storage tank to the hydraulic chamber; and an output port that is an outlet of the brake fluid from the hydraulic chamber. Further, the electric cylinder is configured to open the input port when the piston is at the retracted limit position, but to close the input port by moving the piston from the retracted limit position in the forward direction, so that the hydraulic pressure in the hydraulic chamber increases and brake fluid is discharged from the output port. In addition, the control unit of this braking device holds the piston at a standby position when generation of braking force is not required, and the standby position is set between a position where the state of closing the input port and the state of opening the input port are switched and the retracted limit position. Further, when generation of braking force is required, the control unit controls the electric motor to move the piston in the forward direction from the standby position. Further, after commanding the electric motor to move the piston in the retracted direction compared to the standby position, the control unit executes a calibration process for calibrating the output of the hydraulic sensor. Here, the forward direction indicates the moving direction of the piston that reduces the volume of the hydraulic chamber. Further, the retracted direction here indicates the direction opposite to the forward direction. Further, the retracted limit position here indicates the position closest to the retracted direction in the movable range of the piston.

[0006] At the start of the calibration process, there is a possibility that a piston has not retracted to the standby position and the input port is not open. In contrast, during the calibration process, the control unit of the braking device performs output calibration of the hydraulic sensor after commanding the electric motor to move the piston in the backward direction compared to the standby position. Therefore, even if the input port is not open at the start of the calibration process, the possibility of the input port being open during the implementation of the output calibration is increased. Therefore, it is easy to perform output calibration of the hydraulic sensor on the premise that the hydraulic pressure is equivalent to the atmospheric pressure. Therefore, the braking device has the effect of easily maintaining the detection accuracy of the hydraulic sensor against changes in output characteristics.

[0007] Another braking device for solving the above problem includes: a storage tank for storing brake fluid; an electric cylinder for discharging brake fluid by moving a piston in the cylinder according to the drive of an electric motor; a hydraulic sensor for detecting the hydraulic pressure of the brake fluid discharged from the electric cylinder; and a control unit for controlling the electric motor. Moreover, this braking device generates a braking force on the wheel by supplying brake fluid to a wheel cylinder according to the discharge of brake fluid from the electric cylinder. The electric cylinder of this braking device has: a hydraulic chamber divided by the peripheral wall of the cylinder and the piston; an input port which is an inlet for brake fluid from the storage tank to the hydraulic chamber; and an output port which is an outlet for the brake fluid from the hydraulic chamber. Moreover, this electric cylinder is configured to open the input port when the piston is at the retracted limit position, but to close the input port by moving the piston from the retracted limit position in the forward direction, so that the hydraulic pressure in the hydraulic chamber increases and the brake fluid is discharged from the output port. And this braking device includes a release flow path for connecting the output port to the storage tank without passing through the hydraulic chamber, and a release valve for opening and closing the release flow path. In addition, the control unit of this braking device holds the piston at a standby position when the generation of braking force is not required, and this standby position is set between the position for switching between the state of closing the input port and the state of opening the input port and the retracted limit position. Moreover, when the generation of braking force is required, the control unit controls the electric motor to move the piston from the standby position in the forward direction. And this control unit performs a calibration process for implementing output calibration of the hydraulic sensor in a state where the release valve is open.

[0008] During the calibration process, the control unit of the braking device performs output calibration of the hydraulic sensor after making the release valve open. If the release valve is opened, the output port of the electric cylinder is connected to the storage tank via the release flow path. Therefore, regardless of whether the input port is open, the hydraulic pressure that is the detection object of the hydraulic sensor becomes equivalent to the atmospheric pressure. Therefore, it is possible to perform output calibration of the hydraulic sensor on the premise that the hydraulic pressure is equivalent to the atmospheric pressure. Therefore, the braking device has the effect of easily maintaining the detection accuracy of the hydraulic sensor against changes in output characteristics. Description of the Drawings

[0009] Figure 1 It is a diagram schematically showing an example of the configuration of the braking device according to the first embodiment and the second embodiment.

[0010] Figure 2 It is a flowchart of the calibration routine executed by the control unit included in the braking device according to the first embodiment.

[0011] Figure 3 It is a flowchart of the calibration routine executed by the braking unit included in the braking device according to the second embodiment. Detailed Embodiments

[0012] (First Embodiment)

[0013] According to Figures 1 to 3 , the first embodiment of the braking device will be described. In Figure 1 , together with the braking device 20 of the present embodiment, a plurality of wheels and a plurality of braking mechanisms 10 are shown. The plurality of wheels include two front wheels and two rear wheels. For example, Figure 1 the wheel FL represents the left front wheel, the wheel FR represents the right front wheel, the wheel RL represents the left rear wheel, and the wheel RR represents the right rear wheel.

[0014] <Configuration of the Braking Mechanism 10>

[0015] First, the configuration of the braking mechanism 10 will be described. One braking mechanism 10 is provided for each wheel. Each braking mechanism 10 includes a wheel cylinder 11 to which brake fluid is supplied, a rotating plate 12 that rotates integrally with the wheel, and a friction material 13 that is pressed against the rotating plate 12. The braking mechanism 10 presses the friction material 13 against the rotating plate 12 by the hydraulic pressure supplied to the wheel cylinder 11, thereby generating a braking force on the wheel.

[0016] <Configuration of the Braking Device 20>

[0017] Next, the configuration of the braking device 20 will be described. The braking device 20 includes a braking operation member 21, a hydraulic pressure generating device 22, a brake actuator 23, a storage tank 24, and a control unit 100. The braking operation member 21 is a member operated by the driver when braking the vehicle is required. An example of the braking operation member 21 is a brake pedal. The storage tank 24 is a tank for storing brake fluid. The storage tank 24 is open to the atmosphere. Therefore, the hydraulic pressure of the brake fluid in the storage tank 24 is approximately equal to the atmospheric pressure. The hydraulic pressure generating device 22 is a device that generates hydraulic pressure according to the operation of the braking operation member 21. The hydraulic pressure generating device 22 includes a main device 30 and a braking unit 50. The main device 30 can supply brake fluid to the brake actuator 23. The braking unit 50 can supply brake fluid to both the main device 30 and the brake actuator 23. The control unit 100 controls the operation of the braking device 20.

[0018] <Configuration of the main device 30>

[0019] Next, the configuration of the main device 30 will be described. The main device 30 includes a master cylinder 31 and a stroke simulator 32.

[0020] The master cylinder 31 includes a cylinder main body 41 and a cylinder head 42. In addition, the master cylinder 31 includes a master piston 43 and an input piston 44. Also, the master cylinder 31 includes a master spring 45 that presses on the master piston 43 and an input spring 46 that presses on the input piston 44. The master piston 43 and the input piston 44 can move relative to the cylinder main body 41 and the cylinder head 42.

[0021] The cylinder main body 41 of the master cylinder 31 has a plate-shaped bottom wall 411 and a first peripheral wall 412 that extends along the axis of the bottom wall 411 from the bottom wall 411. Also, the cylinder main body 41 has a second peripheral wall 413 that extends along the axis of the first peripheral wall 412 from the rear end of the first peripheral wall 412, and a first annular wall 414 that extends toward the axis of the second peripheral wall 413 from the rear end of the second peripheral wall 413. The first peripheral wall 412 and the second peripheral wall 413 are each cylindrical. A hole for inserting the rear end portion of the master piston 43 described later is formed in the first annular wall 414. The inner diameter of the first peripheral wall 412 is smaller than the inner diameter of the second peripheral wall 413.

[0022] In the cylinder main body 41, a master chamber Rm is partitioned by the bottom wall 411, the first peripheral wall 412, and the master piston 43. Hereinafter, in the master cylinder 31, Figure 1 the left side in [description], that is, the moving direction of the master piston 43 that reduces the volume of the master chamber Rm, is referred to as "front", and on the other hand, the opposite direction of the front is referred to as "rear". The rear is also the direction in which the volume of the master chamber Rm increases.

[0023] In the cylinder main body 41, a first liquid chamber R1 is partitioned by the second peripheral wall 413 and the master piston 43, and a servo chamber Rs is partitioned by the second peripheral wall 413, the first annular wall 414, and the master piston 43. The master chamber Rm is formed at a position near the front end of the master cylinder 31. The first liquid chamber R1 is formed rearward compared to the master chamber Rm. The servo chamber Rs is formed rearward compared to the first liquid chamber R1. Inside the cylinder main body 41, the master chamber Rm, the first liquid chamber R1, and the servo chamber Rs are not connected to each other.

[0024] The cylinder head 42 of the master cylinder 31 has a cylindrical third peripheral wall 421 and a second annular wall 422 that extends toward the axis of the third peripheral wall 421 from the rear end of the third peripheral wall 421. The third peripheral wall 421 is installed on the first annular wall 414 such that the axis coincides with the second peripheral wall 413 of the cylinder main body 41. A hole for inserting the rear end portion of the input piston 44 described later is provided in the second annular wall 422.

[0025] In the cylinder head 42, a second fluid chamber R2 is defined by the first annular wall 414 of the cylinder body 41, the third peripheral wall 421, and the input piston 44. Further, in the cylinder head 42, a third fluid chamber R3 is defined by the third peripheral wall 421, the second annular wall 422, and the input piston 44. In the master cylinder 31, the second fluid chamber R2 is formed rearward compared to the servo chamber Rs. Further, in the master cylinder 31, the third fluid chamber R3 is formed rearward compared to the second fluid chamber R2. In addition, inside the cylinder head 42, the second fluid chamber R2 and the third fluid chamber R3 are not connected to each other.

[0026] The master piston 43 is housed in the master cylinder 31 in a state of being in surface contact with the inner peripheral surface of the first peripheral wall 412 of the cylinder body 41, the inner peripheral surface of the second peripheral wall 413, and the inner peripheral surface of the first annular wall 414. Therefore, when the master piston 43 moves axially, the master piston 43 slides on the inner peripheral surface of the first peripheral wall 412, the inner peripheral surface of the second peripheral wall 413, and the inner peripheral surface of the first annular wall 414. The rear end portion of the master piston 43 protrudes rearward compared to the first annular wall 414 and is located inside the second fluid chamber R2.

[0027] The input piston 44 is housed in the master cylinder 31 in a state of being in surface contact with the inner peripheral surface of the third peripheral wall 421 of the cylinder head 42 and the inner peripheral surface of the second annular wall 422. Therefore, when the input piston 44 moves axially, the input piston 44 slides on the inner peripheral surface of the third peripheral wall 421 and the inner peripheral surface of the second annular wall 422. The rear end portion of the input piston 44 protrudes rearward compared to the second annular wall 422. Moreover, a brake operation member 21 is connected to the rear end portion of the input piston 44. Therefore, the input piston 44 moves in a direction approaching the master piston 43 according to the operation amount of the brake operation member 21. In addition, in the second fluid chamber R2, a gap is formed between the input piston 44 and the master piston 43.

[0028] The master spring 45 is disposed in the master chamber Rm of the cylinder body 41. The master spring 45 presses the master piston 43 rearward. Therefore, if the master piston 43 moves forward, the master spring 45 is elastically compressed.

[0029] The input spring 46 is disposed in the second fluid chamber R2 of the cylinder head 42. The input spring 46 presses the input piston 44 rearward. Therefore, if the input piston 44 moves forward, the input spring 46 is elastically compressed.

[0030] In the master cylinder 31, the master chamber Rm is connected to the reservoir 24. Specifically, a portion of the master chamber Rm near the rear end is connected to the reservoir 24 via a port formed in the first peripheral wall 412 of the cylinder body 41. Therefore, when the master piston 43 moves from Figure 1When moving forward from the shown initial position, the main chamber Rm is not connected to the storage tank 24. As a result, as the main piston 43 moves forward, the hydraulic pressure in the main chamber Rm increases. For example, if the hydraulic pressure in the servo chamber Rs becomes high, the main piston 43 moves forward by the hydraulic pressure in the servo chamber Rs. Thus, the hydraulic pressure in the main chamber Rm increases.

[0031] The main chamber Rm is connected to the brake actuator 23 via the first flow path 331. That is, the first flow path 331 is a flow path that connects a part of the plurality of wheel cylinders 11 to the main chamber Rm. Specifically, the first flow path 331 connects the wheel cylinders 11 for the wheels FL and FR corresponding to the second wheel cylinder to the main chamber Rm. In addition, the first liquid chamber R1 and the second liquid chamber R2 are connected via the second flow path 332. And the third liquid chamber R3 is connected to the storage tank 24 via the third flow path 333. Therefore, when the input piston 44 moves forward, brake fluid is supplied from the storage tank 24 to the third liquid chamber R3. On the other hand, when the input piston 44 moves backward, brake fluid is discharged from the third liquid chamber R3 to the storage tank 24. In addition, the third flow path 333 connects the storage tank 24 and the second flow path 332.

[0032] A first control valve 341 is arranged in a portion between the connection point of the third flow path 333 on the second flow path 332 and the second liquid chamber R2. The first control valve 341 is a normally-closed solenoid valve. In addition, a second control valve 342 is provided in the third flow path 333. The second control valve 342 is a normally-open solenoid valve. When the control unit 100 of the braking device 20 operates, the first control valve 341 opens and the second control valve 342 closes.

[0033] On the other hand, a stroke simulator 32 provided together with the master cylinder 31 in the main device 30 generates a reaction force corresponding to the operation amount of the braking operation member 21. The stroke simulator 32 is arranged between the first liquid chamber R1 and the first control valve 341 on the second flow path 332. For example, the stroke simulator 32 has a piston (not shown) pressed from the back by a spring inside. In this case, if the piston inside the stroke simulator 32 is displaced against the pressure of the spring due to the inflow of brake fluid from the second flow path 332, the brake fluid generates pressure according to the displacement of the piston. Specifically, if, in a state where the first control valve 341 is open and the second control valve 342 is closed, the input piston 44 moves forward by the operation of the braking operation member 21, brake fluid flows into the stroke simulator 32. As a result, the same pressure is generated in the second liquid chamber R2 and the first liquid chamber R1 connected via the second flow path 332 by the stroke simulator 32.

[0034] <Composition of the braking unit 50>

[0035] Next, the configuration of the braking unit 50 will be described. The braking unit 50 includes an electric cylinder 51. The braking unit 50 can operate through the electric cylinder 51 to adjust the hydraulic pressure in the plurality of wheel cylinders 11.

[0036] The braking unit 50 includes a fourth flow path 54, a fifth flow path 55, and a sixth flow path 58. The fourth flow path 54 connects the electric cylinder 51 and the reservoir 24. The sixth flow path 58 connects the brake actuator 23 and the electric cylinder 51. That is, the sixth flow path 58 is a flow path that connects a part of the plurality of wheel cylinders 11 and the electric cylinder 51. Specifically, the sixth flow path 58 connects the wheel cylinders 11 for the wheels RL and RR corresponding to the first wheel cylinder and the electric cylinder 51. The fifth flow path 55 connects the servo chamber Rs of the master cylinder 31 and the sixth flow path 58. Moreover, the electric cylinder 51 is disposed between the fourth flow path 54 and the sixth flow path 58. The fourth flow path 54 is connected to the input port 515 of the electric cylinder 51. The sixth flow path 58 is connected to the output port 516 of the electric cylinder 51.

[0037] In addition, the braking unit 50 includes a release flow path 56 and a release valve 57. The release valve 57 is disposed in the release flow path 56. The release flow path 56 is a flow path that connects the reservoir 24 and the wheel cylinder 11 in a manner that bypasses the electric cylinder 51. Hereinafter, the two ends of the release flow path 56 will be respectively referred to as the first end and the second end. The first end of the release flow path 56 is connected to the fourth flow path 54. On the other hand, the second end of the release flow path 56 is connected to the sixth flow path 58. Specifically, the release flow path 56 connects between the reservoir 24 and the input port 515 on the fourth flow path 54 and between the output port 516 and the brake actuator 23 on the sixth flow path 58. The release valve 47 is a normally closed solenoid valve that opens and closes such a release flow path 56. That is, during the period when the control to open the release valve 57 is not performed, the release flow path 56 is closed.

[0038] <Configuration of the electric cylinder 51>

[0039] Next, the configuration of the electric cylinder 51 will be described. The electric cylinder 51 includes a cylinder 511, a piston 512, a first electric motor 513, and a conversion mechanism 514. The piston 512 is disposed in the cylinder 511 in a slidable state. The first electric motor 513 is the power source of the electric cylinder 51. The conversion mechanism 514 converts the rotational motion of the output shaft of the first electric motor 513 into the linear motion of the piston 512.

[0040] Inside the cylinder 511, a hydraulic chamber Re into which brake fluid is introduced is defined by the peripheral wall of the cylinder 511 and the piston 512. The position of the piston 512 inside the cylinder 511 can be changed by driving the first electric motor 513. Hereinafter, the moving direction of the piston 512 that reduces the volume of the hydraulic chamber Re is referred to as the "forward direction Za", and the direction opposite to the forward direction Za is referred to as the "backward direction Zb". The backward direction Zb is also the moving direction of the piston 512 that increases the volume of the hydraulic chamber Re. Further, hereinafter, the end portion of the backward direction Zb within the movable range of the piston 512 inside the cylinder 511 is referred to as the "backward limit position".

[0041] An input port 515 and an output port 516 are formed in the peripheral wall of the cylinder 511 as ports for connecting the hydraulic chamber Re to the outside. A through hole 517 is formed in the piston 512. The through hole 517 is formed at a position where the input port 515 can be connected to the hydraulic chamber Re when the piston 512 is at the backward limit position. Thus, when the piston 512 is at the backward limit position, the hydraulic chamber Re of the cylinder 511 is connected to the fourth flow path 54 via the input port 515 and the through hole 517. That is, the hydraulic chamber Re of the cylinder 511 communicates with the storage tank 24 via the input port 515 and the through hole 517. The input port 515 is configured to be open when the piston 512 is at the backward limit position, and is closed by the piston 512 when the piston 512 moves in the forward direction Za from the backward limit position. If the piston 512 moves in the forward direction Za even though the input port 515 is closed by the piston 512 in this way, the hydraulic pressure in the hydraulic chamber Re increases. In this way, the input port 515 is an inlet for the brake fluid from the storage tank 24 to the hydraulic chamber Re.

[0042] The output port 516 of the cylinder 511 is connected to the brake actuator 23 and the fifth flow path 55 via the sixth flow path 58. The output port 516 is always open regardless of the position of the piston 512. Therefore, when the input port 515 is closed by the piston 512, if the piston 512 moves in the forward direction Za, the brake fluid in the hydraulic chamber Re is discharged from the output port 516 to the outside of the cylinder 511. In this way, the output port 516 is an outlet for the brake fluid from the hydraulic chamber Re.

[0043] <Configuration of the Brake Actuator 23>

[0044] Next, the configuration of the brake actuator 23 will be described. The brake actuator 23 is configured to be able to independently adjust the hydraulic pressure of a plurality of wheel cylinders 11. The brake actuator 23 includes two pumps 631, 632 that use the second electric motor 64 as a power source.

[0045] The brake actuator 23 can increase the hydraulic pressure in the wheel cylinder 11 without increasing the hydraulic pressure regulated by the braking unit 50. In other words, the braking device 20 has a redundant configuration with the braking unit 50 on the upstream side and the brake actuator 23 on the downstream side.

[0046] The brake actuator 23 has hydraulic circuits of two systems, a first hydraulic circuit 611 and a second hydraulic circuit 612. Two wheel cylinders 11 for the wheels FL and FR are connected to the first hydraulic circuit 611. Two wheel cylinders 11 for the wheels RL and RR are connected to the second hydraulic circuit 612.

[0047] The first hydraulic circuit 611 is connected to the reservoir 24 via the first flow path 331 and the master chamber Rm. On the first hydraulic circuit 611, a first differential pressure regulating valve 621, which is a normally open type linear solenoid valve, is provided in the hydraulic path connecting the connection point with the first flow path 331 and the wheel cylinder 11.

[0048] The second hydraulic circuit 612 is connected to the reservoir 24 via the fourth flow path 54, the electric cylinder 51, and the sixth flow path 58. On the second hydraulic circuit 612, a second differential pressure regulating valve 622, which is a normally open type linear solenoid valve, is provided in the hydraulic path connecting the connection point with the sixth flow path 58 and the wheel cylinder 11.

[0049] A pump 631 is provided in the first hydraulic circuit 611. The pump 631 supplies brake fluid to the hydraulic path connecting the first differential pressure regulating valve 621 and the wheel cylinder 11. A pump 632 is provided in the second hydraulic circuit 612. The pump 632 supplies brake fluid to the hydraulic path connecting the second differential pressure regulating valve 622 and the wheel cylinder 11.

[0050] On the first hydraulic circuit 611, paths 65a and 65b having the same number as the wheel cylinders 11 connected to the first hydraulic circuit 611 are provided on the wheel cylinder 11 side compared with the first differential pressure regulating valve 621. Similarly, on the second hydraulic circuit 612, paths 65c and 65d having the same number as the wheel cylinders 11 connected to the second hydraulic circuit 612 are provided on the wheel cylinder 11 side compared with the second differential pressure regulating valve 622. Moreover, holding valves 66 that close valves when restricting the increase in the hydraulic pressure in the wheel cylinder 11 and pressure reducing valves 67 that open valves when reducing the hydraulic pressure are provided in the plurality of paths 65a to 65d. That is, the holding valves 66 are arranged in the hydraulic path on the wheel cylinder 11 side compared with the first differential pressure regulating valve 621 and the second differential pressure regulating valve 622. In addition, the plurality of holding valves 66 are normally open type solenoid valves, and the plurality of pressure reducing valves 67 are normally closed type solenoid valves.

[0051] The first hydraulic circuit 611 and the second hydraulic circuit 612 are respectively connected to reservoir tanks 681, 682 that temporarily store the brake fluid flowing out from the wheel cylinder 11 via the pressure reducing valve 67 when the pressure reducing valve 67 is opened. The plurality of reservoir tanks 681, 682 are connected to pumps 631, 632 via suction flow paths 691, 692.

[0052] The reservoir tank 681 is connected to the liquid path connecting the first differential pressure regulating valve 621 and the master chamber Rm via a tank side flow path 701. The reservoir tank 682 is connected to the liquid path connecting the connection point of the second hydraulic circuit 612 and the sixth flow path 58 and the second differential pressure regulating valve 622 via a tank side flow path 702.

[0053] The plurality of pumps 631, 632 can draw the brake fluid in the storage tank 24 via the reservoir tanks 681, 682. The plurality of pumps 631, 632 discharge the drawn brake fluid into the liquid path between the first differential pressure regulating valve 621 and the second differential pressure regulating valve 622 and the holding valve 66. Hereinafter, the liquid paths between this liquid path and the pumps 631, 632 are respectively referred to as intermediate liquid paths 711, 712.

[0054] <Detection system of the braking device 20>

[0055] The braking device 20 has a detection system composed of a plurality of sensors. The plurality of sensors constituting the detection system include a stroke sensor SE1, a rotation angle sensor SE2, a master hydraulic pressure sensor 351, an input hydraulic pressure sensor 352, and a control pressure sensor 353.

[0056] The stroke sensor SE1 detects the operation amount of the brake operation member 21. The rotation angle sensor SE2 detects the rotation angle of the first electric motor 513 that is the power source of the electric cylinder 51. The rotation angle of the first electric motor 513 based on the detection value of the rotation angle sensor SE2 is referred to as "motor rotation angle θmt".

[0057] The master hydraulic pressure sensor 351 detects the hydraulic pressure in the master chamber Rm. For example, the master hydraulic pressure sensor 351 is provided in the first flow path 331. The hydraulic pressure in the master chamber Rm based on the detection value of the master hydraulic pressure sensor 351 is referred to as "master pressure".

[0058] The input hydraulic pressure sensor 352 detects the hydraulic pressure in the second liquid chamber R2. For example, the input hydraulic pressure sensor 352 is connected at a position between the first control valve 341 and the second liquid chamber R2 on the second flow path 332. The hydraulic pressure of the second liquid chamber R2 based on the detection value of the input hydraulic pressure sensor 352 is referred to as "input hydraulic pressure".

[0059] The control pressure sensor 353 is a hydraulic pressure sensor that detects the hydraulic pressure of the brake fluid discharged by the electric cylinder 51. For example, the control pressure sensor 353 is provided near the output port 516 in the electric cylinder 51. As an example, inFigure 1 A configuration is shown in which a control pressure sensor 353 is connected between a release valve 57 and an output port 516 on a release flow path 56. The discharge hydraulic pressure of the electric cylinder 51 based on the detection value of the control pressure sensor 353 is referred to as "control pressure Psc". In the present embodiment, the control pressure sensor 353 corresponds to a hydraulic pressure sensor that detects the hydraulic pressure of the brake fluid discharged by the electric cylinder 51.

[0060] <Configuration of Control Unit 100>

[0061] The braking device 20 includes a control unit 100. The control unit 100 is, for example, an electronic control device. In this case, the control unit 100 has a CPU and a memory. The memory stores a control program executed by the CPU. Detection signals of the respective sensors constituting the detection system of the braking device 20 are input to the control unit 100. The control unit 100 controls the operations of the hydraulic pressure generating device 22 and the brake actuator 23 by executing the control program by the CPU. More specifically, the control unit 100 controls the first control valve 341, the second control valve 342, the release valve 57, and the first electric motor 513 of the electric cylinder 51 of the hydraulic pressure generating device 22. In addition, the control unit 100 controls various solenoid valves (621, 622, 66, 77) and the second electric motor 64 of the brake actuator 23.

[0062] <Drive Control of Electric Cylinder 51>

[0063] Next, the drive control of the electric cylinder 51 executed by the control unit 100 will be described. When the driver performs a vehicle start operation, power is supplied to the braking device 20. Moreover, the control unit 100 receives the power supply and starts up.

[0064] After startup, the control unit 100 performs drive preparation processing for the electric cylinder 51. During the drive preparation processing, the control unit 100 first commands the first electric motor 513 of the electric cylinder 51 to rotate in the direction in which the piston 512 moves in the backward direction Zb. If this command is continued, the piston 512 moves in the backward direction Zb until it reaches the backward limit position. When the piston 512 reaches the backward limit position, the movement of the piston 512 is mechanically restricted, so the load on the first electric motor 513 increases. The control unit 100 confirms that the piston 512 has reached the backward limit position based on the increase in the current value of the first electric motor 513 accompanying the increase in the load. If it is confirmed that the backward limit position has been reached, the control unit 100 temporarily stops the rotation of the first electric motor 513. Next, the control unit 100 commands the first electric motor 513 to rotate by a specified rotation amount Xm in the direction in which the piston 512 moves in the forward direction Za. As a result, the piston 512 moves a specified amount in the forward direction Za from the backward limit position. Thereafter, the position of the piston 512 at this time is recorded as the standby position. In addition, the movement position of the piston 512 that switches between the state where the input port 515 is open and the state where it is closed by the piston 512 is recorded as the pressure application start position. The specified rotation amount Xm is set such that the position in the backward direction Zb compared to the pressure application start position and in the forward direction Za compared to the backward limit position becomes the standby position. Further, in order to improve the responsiveness of the braking device 20, it is preferable to set the position close to the pressure application start position as the standby position within the range where the input port 515 is reliably opened.

[0065] Thereafter, the control unit 100 determines the presence or absence of a braking requirement based on the detection signal of the stroke sensor SE1 or the like. When it is determined that there is no braking requirement, the control unit 100 holds the piston 512 of the electric cylinder 51 at the standby position. On the other hand, if it is determined that there is a braking requirement, the control unit 100 drives the first electric motor 513 to move the piston 512 in the forward direction Za. When the piston 512 moves in the forward direction Za from the standby position, the input port 515 is closed by the piston 512. Then, the brake fluid in the hydraulic chamber Re is pressed by the piston 512 and discharged from the output port 516. The braking device 20 thereby supplies brake fluid to the wheel cylinders 11 of each wheel FL, FR, RL, RR to generate braking force. Further, if the braking requirement is released during the generation of the braking force, the control unit 100 drives the first electric motor 513 to move the piston 512 in the backward direction Zb to the standby position.

[0066] <Output Calibration of the Control Pressure Sensor 353>

[0067] As described above, the braking device 20 includes a control pressure sensor 353 that detects the hydraulic pressure of the brake fluid discharged from the electric cylinder 51, that is, the control pressure Psc. The control unit 100 calculates the control pressure Psc based on the output of the control pressure sensor 353. Hereinafter, the control pressure Psc calculated by the control unit 100 based on the output of the control pressure sensor 353 is referred to as the detected value of the control pressure Psc.

[0068] The output characteristics of the control pressure sensor 353 are temperature-dependent. Moreover, due to the change in the output characteristics of the control pressure sensor 353 caused by temperature, the detected value of the control pressure Psc may deviate from the actual value. In the braking device 20 of the present embodiment, output calibration of the control pressure sensor 353 is performed to correct the deviation of the detected value of the control pressure Psc caused by such a change in the output characteristics.

[0069] In Figure 2 FIG. shows a flowchart of a calibration routine executed by the control unit 100 for output calibration of the control pressure sensor 353. The control unit 100 repeatedly executes this routine at a predetermined control cycle during the operation of the braking device 20.

[0070] If this routine is started, the control unit 100 first determines the presence or absence of a braking request in step S100. For example, the control unit 100 determines that there is a control request when the detected value of the operation amount of the braking operation member 21 by the stroke sensor SE1 is not "0".

[0071] When there is a braking request (S100: Yes), the control unit 100 advances the process to step S110. Then, in step S110, the control unit 100 sets the value of the calibration request flag F to "0", and then ends the process of this routine in the current control cycle. The calibration request flag F is a flag that indicates that the output calibration of the control pressure sensor 353 is in progress when the value is "1".

[0072] On the contrary, when there is no braking request (S100: No), the control unit 100 advances the process to step S120. In step S120, the control unit 100 determines whether the value of the calibration request flag F is "1". Moreover, when the value of the calibration request flag F is "0" (No), the control unit 100 advances the process to step S130, and when it is "1" (Yes), the control unit 100 advances the process to step S160.

[0073] When the process enters step S130, in this step S130, the control unit 100 determines whether there is a deviation in the detected value of the control pressure Psc by the control pressure sensor 353. When there is no braking requirement, the control unit 100 controls the first electric motor 513 to make the position of the piston 512 of the electric cylinder 51 the standby position. At the standby position, since the input port 515 is open, the hydraulic chamber Re of the electric cylinder 51 communicates with the storage tank 24. The control pressure Psc at this time becomes a value equivalent to the atmospheric pressure. Therefore, when the deviation amount of the detected value of the control pressure Psc from the value equivalent to the atmospheric pressure is equal to or greater than a specified threshold value, the control unit 100 determines that there is a deviation in the detected value of the control pressure Psc.

[0074] When it is determined that there is no deviation in the detected value of the control pressure Psc (S130: No), the control unit 100 directly ends the processing of this example routine. In contrast, when it is determined that there is a deviation in the detected value of the control pressure Psc (S130: Yes), the control unit 100 causes the process to enter step S140.

[0075] In step S140, the control unit 100 sets the value of the calibration request flag F to "1". In addition, in the next step S150, the control unit 100 commands the piston 512 to retract from the standby position. That is, the control unit 100 commands the first electric motor 513 to move the piston 512 to a position in the retraction direction Zb compared with the standby position. Then, after this command, the control unit 100 ends the processing of this example routine in this control cycle.

[0076] On the other hand, when the process enters step S160, in this step S160, the control unit 100 determines whether the retraction of the piston 512 commanded in step S150 is completed. For example, when the rotation amount of the first electric motor 513 after the command in step S150 reaches a specified amount, it is determined that the retraction of the piston 512 is completed. Moreover, when the retraction of the piston 512 is not completed (No), the control unit 100 directly ends the processing of this example routine in this control cycle. On the other hand, when the retraction of the piston 512 is completed (Yes), the control unit 100 causes the process to enter step S170.

[0077] In step S170, the control unit 100 performs output calibration of the control pressure sensor 353. For example, the control unit 100 calculates the deviation amount of the output based on the average value of the output of the control pressure sensor 353 within a predetermined period. Moreover, thereafter, the control unit 100 corrects the output of the control pressure sensor 353 by this deviation amount. In addition, in the case of this embodiment, the output calibration of the control pressure sensor 353 requires multiple control cycles.

[0078] Next, in step S180, the control unit 100 determines whether the output calibration of the control pressure sensor 353 is completed in this control cycle. Moreover, when the output calibration is not completed (No), the control unit 100 directly ends the processing of this routine in this control cycle. On the other hand, when the output calibration is completed (Yes), the control unit 100 sets the value of the calibration request flag F to "0" in step S110, and then ends the processing of this routine in this control cycle.

[0079] <Function and Effect of Embodiment>

[0080] The function and effect of this embodiment will be described.

[0081] During the operation of the braking device 20, when the control unit 100 confirms the deviation of the output of the control pressure sensor 353, it performs the output calibration of the control pressure sensor 353. This output calibration is performed on the premise of opening the input port 515 of the electric cylinder 51.

[0082] However, when the control unit 100 releases the braking request, it controls the first electric motor 513 to return the piston 512 to the standby position. However, considering that the piston 512 does not fully return to the standby position and stops at a position in the forward direction Za compared to the standby position. At this time, since the input port 515 is not opened, residual pressure is generated in the hydraulic chamber Re. In a state where such residual pressure is generated, it is not possible to appropriately perform the output calibration of the control pressure sensor 353.

[0083] In contrast, in the case of this embodiment, when the control unit 100 confirms the deviation of the output of the control pressure sensor 353, it first commands the first electric motor 513 to move the piston 512 in the backward direction Zb compared to the standby position. Moreover, the control unit 100 performs the output calibration of the control pressure sensor 353 based on the output of the control pressure sensor 353 after this command. That is, after the control unit 100 commands the first electric motor 513 to move the piston 512 in the backward direction Zb compared to the standby position, it performs the calibration process of performing the output calibration of the control pressure sensor 353. In such a case, even before the implementation of the output calibration, if the piston 512 stops at a position in the forward direction Za compared to the standby position and residual pressure is generated in the hydraulic chamber Re, the possibility of opening the input port 515 during the output calibration is increased. Thus, it is not easy to inappropriately perform the output calibration in a state where the input port 515 is not opened. Therefore, the braking device 20 of this embodiment has the effect of easily maintaining the detection accuracy of the control pressure sensor 353 in the case of output characteristic changes.

[0084] When the generation of braking force is not required, the electric cylinder 51 is controlled to an open input port 515 state, so that the control pressure Psc becomes a value equivalent to the atmospheric pressure. Thus, if the detected value of the hydraulic pressure of the control pressure sensor 353 at this time deviates from the value equivalent to the atmospheric pressure, it can be determined that there is a deviation in the output of the control pressure sensor 353. In contrast, when the difference between the detected value of the hydraulic pressure by the control pressure sensor 353 and the value equivalent to the atmospheric pressure is above the threshold during the operation of the braking device 20, the control unit 100 performs a calibration process. Therefore, during the operation of the braking device 20, when the output of the control pressure sensor 353 deviates due to the surrounding temperature or the like, the deviation can be quickly corrected.

[0085] In addition, when the generation of braking force is required during the execution of the calibration process, the control unit 100 immediately aborts the calibration process at that moment. Therefore, it is not easy for the generation of braking force to be delayed due to the implementation of the calibration process.

[0086] Furthermore, the control unit 100 retracts the piston 512 to the retraction limit value during the drive preparation process of the electric cylinder 51. During such a drive preparation process, when the piston 512 moves in the retraction direction Zb compared to the standby position, the control unit 100 also performs output calibration of the control pressure sensor 353.

[0087] (Second Embodiment)

[0088] Next, a second embodiment of the braking device will be described in detail with reference to Figure 3 together.

[0089] <Output Calibration of Control Pressure Sensor 353>

[0090] The hardware of the braking device in this embodiment is the same as that of Figure 1 The content of the calibration process of the braking device in this embodiment is different from that of the first embodiment.

[0091] In Figure 3 FIG. shows a flowchart of a calibration routine executed by the control unit 100 of the braking device 20 in this embodiment. The control unit 100 repeatedly executes this routine at a predetermined control cycle during the operation of the braking device 20.

[0092] If this routine is started, the control unit 100 first determines the presence or absence of a braking request in step S200. Then, when there is a braking request (Yes), the control unit 100 proceeds to step S210, and when there is no braking request (No), the control unit 100 proceeds to step S230.

[0093] In step S210, the control unit 100 sets the value of the calibration requirement flag F to "0". Then, in step S220, the control unit 100 instructs the closing of the release valve 57, and then ends the processing of this routine in this control cycle.

[0094] On the other hand, in step S230, the control unit 100 determines whether the value of the calibration requirement flag F is "1". Moreover, when the value of the calibration requirement flag F is "0" (No), the control unit 100 advances the processing to step S240, and when it is "1" (Yes), the control unit 100 advances the processing to step S270.

[0095] In step S240, the control unit 100 determines whether there is a deviation in the detected value of the control pressure Psc by the control pressure sensor 353. When it is determined that there is no deviation in the detected value of the control pressure Psc (S240: No), the control unit 100 directly ends the processing of this routine in this control cycle. In contrast, when it is determined that there is a deviation in the detected value of the control pressure Psc (S240: Yes), the control unit 100 advances the processing to step S250.

[0096] In step S250, the control unit 100 sets the value of the calibration requirement flag F to "1". Then, in the next step S260, the control unit 100 instructs the opening of the release valve 57, and then ends the processing of this routine in this control cycle.

[0097] On the other hand, in step S270, the control unit 100 is the same as Figure 2 step S170 of, and performs a calibration process. Then, in step S280, the control unit 100 determines whether the calibration process is completed. Moreover, when the calibration process is completed (Yes), the control unit 100 advances the processing to the above step S210, and when it is not completed (No), it directly ends the processing of this routine in this control cycle.

[0098] <Effect of the Embodiment>

[0099] The operation and effect of this embodiment will be described.

[0100] In the present embodiment, when the control unit 100 also confirms a deviation in the output of the control pressure sensor 353 during the operation of the braking device 20, the control unit 100 performs output calibration of the control pressure sensor 353. When performing output calibration, the control unit 100 opens the release valve 57. When the release valve 57 is opened, the output port 516 of the electric cylinder 51 communicates with the storage tank 24 via the release flow path 56. As a result, regardless of whether the input port 515 of the electric cylinder 51 is open or not, the control pressure Psc becomes a value equivalent to the atmospheric pressure. Therefore, in the braking device 20 of the present embodiment as well, similar to the first embodiment, there is an effect that it is easy to maintain the detection accuracy of the control pressure sensor 353 against changes in output characteristics. In addition, when the calibration process is completed and when the generation of braking force is required during the calibration process, the control unit 100 quickly closes the release valve 57.

[0101] (Other embodiments)

[0102] The above embodiment can be modified as follows. The present embodiment and the following modification examples can be implemented in combination with each other within a technically consistent range.

[0103] · In Figure 2 step S150, it is also possible to command the piston 512 to retreat to the retreat limit position. In this case, for Figure 2 the determination of the completion of the retreat in step S160, it can be determined based on an increase in the current value of the first electric motor 513.

[0104] · Figure 2 The content of the calibration process in step S170 of Figure 3 and the calibration process in step S270 of

[0105] can also be appropriately changed. For example, it is also possible to calculate the deviation amount of the output based on the instantaneous value of the output of the control pressure sensor 353 and perform the calibration process. Figure 2 or Figure 3 it is also possible to perform output calibration of the main hydraulic sensor 351 together with the control pressure sensor 353 through the calibration routine of

[0106] · As long as the configuration of the braking device 20 includes an electric cylinder 51 and a hydraulic sensor that detects the hydraulic pressure of the brake fluid discharged from the electric cylinder 51, it can also be a configuration different from Figure 1 .

[0107] · The braking unit 50 of the first embodiment may not include the release flow path 56 and the release valve 57. In this case, it is preferable to arrange the control pressure sensor 353 provided in the release flow path 56 in the portion between the second differential pressure adjustment valve 622 provided in the fifth flow path 55 or the sixth flow path 58 and the output port 516 of the electric cylinder 51. Figure 1 ​

[0108] · When performing the calibration process of the control pressure sensor 353, as a method of making the control pressure Psc equivalent to the atmospheric pressure, it is also possible to selectively use the piston 512 or the relief valve 57 according to specified conditions. For example, during driving, the relief valve 57 can be used to make the control pressure Psc equivalent to the atmospheric pressure to perform the calibration process of the control pressure sensor 353. On the other hand, during parking, the piston 512 can be used to make the control pressure Psc equivalent to the atmospheric pressure to perform the calibration process of the control pressure sensor 353.

[0109] · The control unit 100 can be configured as one or more processors that operate according to a computer program, one or more dedicated hardware circuits such as dedicated hardware that performs at least a part of various processes, or a circuit including a combination thereof. As the dedicated hardware, for example, an ASIC as an application-specific integrated circuit can be cited. The processor includes a CPU, and memories such as a RAM and a ROM, and the memories store program codes or commands configured to cause the CPU to execute processes. The memory, i.e., the storage medium, includes all available media that can be accessed by a general-purpose or dedicated computer.

Claims

1. A braking device, comprising: a storage tank for storing brake fluid; an electric cylinder for discharging brake fluid by moving a piston in a cylinder according to the drive of an electric motor; A hydraulic sensor that detects the hydraulic pressure of the brake fluid discharged from the electric cylinder; and a control unit that controls the electric motor. The braking device generates a braking force on the wheel by supplying brake fluid to the wheel cylinder according to the discharge of the brake fluid from the electric cylinder. The electric cylinder has: a hydraulic chamber partitioned by the peripheral wall of the cylinder and the piston; an input port that is an inlet for the brake fluid from the storage tank to the hydraulic chamber. And an output port that is an outlet for the brake fluid from the hydraulic chamber. The electric cylinder is configured such that when the moving direction of the piston that reduces the volume of the hydraulic chamber is set as the forward direction, the opposite direction of the forward direction is set as the backward direction, and the position closest to the backward direction in the movable range of the piston is set as the backward limit position, the input port is opened when the piston is at the backward limit position, but the input port is closed by the piston moving from the backward limit position to the forward direction, so that the hydraulic pressure in the hydraulic chamber increases and brake fluid is discharged from the output port. When the generation of braking force is not required, the control unit holds the piston at a standby position that is set between the position where the input port is switched between the closed state and the open state and the backward limit position. When the generation of braking force is required, the control unit controls the electric motor to move the piston from the standby position to the forward direction. And after the control unit commands the electric motor to move the piston in the backward direction compared to the standby position, the control unit performs a calibration process for calibrating the output of the hydraulic sensor.

2. A braking device includes: a storage tank for storing brake fluid; an electric cylinder for discharging brake fluid by moving a piston in a cylinder according to the drive of an electric motor; A hydraulic sensor that detects the hydraulic pressure of the brake fluid discharged from the electric cylinder; and a control unit that controls the electric motor. The braking device generates a braking force on the wheel by supplying brake fluid to the wheel cylinder according to the discharge of the brake fluid from the electric cylinder. The electric cylinder has: a hydraulic chamber partitioned by the peripheral wall of the cylinder and the piston; an input port that is an inlet for the brake fluid from the storage tank to the hydraulic chamber. And an output port that is an outlet for the brake fluid from the hydraulic chamber. The electric cylinder is configured such that when the moving direction of the piston that reduces the volume of the hydraulic chamber is set as the forward direction, the opposite direction of the forward direction is set as the backward direction, and the position closest to the backward direction in the movable range of the piston is set as the backward limit position, the input port is opened when the piston is at the backward limit position, but the input port is closed by the piston moving from the backward limit position to the forward direction, so that the hydraulic pressure in the hydraulic chamber increases and brake fluid is discharged from the output port. The braking device includes a release flow path that connects the output port to the storage tank without passing through the hydraulic chamber, and a release valve that opens and closes the release flow path. When the generation of braking force is not required, the control unit holds the piston at a standby position, which is set between the position for switching between the state of closing the input port and the state of opening the input port and the retraction limit position. When the generation of braking force is required, the control unit controls the electric motor to move the piston from the standby position in the forward direction. Furthermore, the control unit executes a calibration process for calibrating the output of the hydraulic sensor in a state where the release valve is open.

3. The braking device according to claim 1 or 2, wherein when the difference between the detected value of the hydraulic pressure by the hydraulic sensor when the generation of braking force is not required and the value equivalent to the atmospheric pressure is equal to or greater than a threshold value, the control unit executes the calibration process.

4. The braking device according to claim 1 or 2, wherein when the generation of braking force is required during the execution of the calibration process, the control unit aborts the calibration process.

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