Braking device and method for controlling braking device

Abstract

A braking device (100) comprises: a hydraulic-pressure generating device (20) including an electric cylinder (51) having an electric motor; a braking actuator (70) having a retention valve (74); and a control device (200). The control device (200) is configured to derive a target rotation angle for the electric motor by feedback control based on the deviation between a servo-pressure detection value and a target servo pressure, and to drive the electric motor on the basis of the target rotation angle. The control device (200) is further configured so that in the situation where the braking actuator (70) is operated by braking control attendant on closure of the retention valve (74), the control device (200) lowers the feedback control gain compared to the situation where the braking actuator is not operated.

Description

Brake device and brake device control method

[0001] The present disclosure relates to a braking device applied to a vehicle that generates a braking force according to hydraulic pressure in a wheel cylinder, and a method for controlling the braking device.

[0002] Japanese Patent Application Laid-Open No. 2006-129999 discloses a braking device that generates braking force by adjusting hydraulic pressure in wheel cylinders. The braking device includes an electric cylinder powered by an electric motor, a hydraulic pressure control device, and an electronic control unit. The hydraulic pressure control device is provided in a hydraulic line connecting the electric cylinder and the wheel cylinder. The electronic control unit sets a target rotation angle of the electric motor through feedback control using the deviation between a servo pressure, which is the discharge pressure of the brake fluid from the electric cylinder, and a target servo pressure as an input. The electronic control unit adjusts the servo pressure by driving the electric motor based on the target rotation angle.

[0003] JP 2009-137377 A

[0004] The cylinder characteristics, which are the relationship between the amount of brake fluid discharged from the electric cylinder and the servo pressure, can change depending on the operating state of the hydraulic pressure control device. If the cylinder characteristics change, there is a risk that the accuracy of servo pressure adjustment will decrease.

[0005] A braking device according to a first aspect of the present disclosure is applied to a vehicle in which braking force is generated according to wheel pressure, which is hydraulic pressure in a wheel cylinder. The braking device includes a hydraulic pressure generating device, which is an electric cylinder having an electric motor and an output port, configured to adjust the discharge of brake fluid from the output port by adjusting the motor rotation angle, a servo pressure sensor detecting a servo pressure, which is the discharge pressure of the brake fluid from the electric cylinder, and a supply flow path through which brake fluid flows toward the wheel cylinder when the servo pressure increases, a connecting flow path connecting the supply flow path to the wheel cylinder, a brake actuator having a holding valve, which is a normally open solenoid valve, installed in the connecting flow path, and a control device. The hydraulic pressure generating device is configured to generate the wheel pressure in the wheel cylinder according to the servo pressure. The brake actuator is configured to restrict the supply of brake fluid from the hydraulic pressure generating device to the wheel cylinder by closing the holding valve. The control device is configured to derive a target rotation angle that is a target for the motor rotation angle by feedback control based on a deviation between a servo pressure detection value that is a detection value of the servo pressure sensor and a target servo pressure that is a target for the servo pressure, and to drive the electric motor based on the target rotation angle. The control device is further configured to lower a gain of the feedback control when the brake actuator is operated by braking control that involves closing the holding valve compared to when this is not the case.

[0006] A braking device according to a second aspect of the present disclosure is applied to a vehicle in which braking force is generated according to wheel pressure, which is hydraulic pressure in a wheel cylinder. The braking device includes a hydraulic pressure generating device, which is an electric cylinder having an electric motor and an output port, configured to adjust servo pressure, which is the brake fluid discharge pressure from the output port, by adjusting motor torque, which is the output torque of the electric motor; a servo pressure sensor for detecting the servo pressure; and a supply flow path through which brake fluid flows toward the wheel cylinder when the servo pressure increases. The hydraulic pressure generating device includes a connecting flow path connecting the supply flow path to the wheel cylinder and a holding valve, which is a normally open solenoid valve, installed in the connecting flow path; and a control device. The hydraulic pressure generating device is configured to generate the wheel pressure in the wheel cylinder according to the servo pressure. The brake actuator is configured to restrict the supply of brake fluid from the hydraulic pressure generating device to the wheel cylinder by closing the holding valve. The control device is configured to derive a target torque that is a target for the motor torque by performing feedback control based on a deviation between a servo pressure detection value that is a detection value of the servo pressure sensor and a target servo pressure that is a target for the servo pressure, and to drive the electric motor based on the target torque. The control device is further configured to vary a differential gain of the feedback control in accordance with an operating state of the hold valve when the brake actuator is operated by braking control that involves closing the hold valve.

[0007] According to a third aspect of the present disclosure, there is provided a method for controlling a braking device applied to a vehicle, which generates a braking force corresponding to a wheel pressure, i.e., hydraulic pressure in a wheel cylinder. The braking device includes a hydraulic pressure generating device, which is an electric cylinder having an electric motor and an output port, and which is configured to adjust the discharge of brake fluid from the output port by adjusting the motor rotation angle, i.e., the rotation angle of the electric motor. The hydraulic pressure generating device includes a servo pressure sensor that detects a servo pressure, i.e., the discharge pressure of the brake fluid from the electric cylinder, and a supply flow path through which brake fluid flows toward the wheel cylinder when the servo pressure increases. The hydraulic pressure generating device is configured to generate the wheel pressure in the wheel cylinder corresponding to the servo pressure. The brake actuator is configured to regulate the supply of brake fluid from the hydraulic pressure generating device to the wheel cylinder by closing the hold valve. The control method includes deriving a target rotation angle, which is a target for the motor rotation angle, by feedback control based on the deviation between a servo pressure detection value, which is a detection value of the servo pressure sensor, and a target servo pressure, which is a target for the servo pressure, driving the electric motor based on the target rotation angle, and lowering the gain of the feedback control when the brake actuator is operated by braking control involving closing the holding valve compared to when this is not the case.

[0008] According to a fourth aspect of the present disclosure, there is provided a method for controlling a braking device applied to a vehicle, which generates a braking force corresponding to a wheel pressure, which is a hydraulic pressure in a wheel cylinder. The braking device includes a hydraulic pressure generating device, which is an electric cylinder having an electric motor and an output port, and which is configured to adjust a servo pressure, which is a brake fluid discharge pressure from the output port, by adjusting the motor torque, which is the output torque of the electric motor. The hydraulic pressure generating device includes a servo pressure sensor for detecting the servo pressure and a supply flow path through which brake fluid flows toward the wheel cylinder when the servo pressure increases. The hydraulic pressure generating device is configured to generate the wheel pressure in the wheel cylinder corresponding to the servo pressure. The brake actuator is configured to regulate the supply of brake fluid from the hydraulic pressure generating device to the wheel cylinder by closing the hold valve. The control method includes deriving a target torque, which is a target for the motor torque, by performing feedback control based on the deviation between a servo pressure detection value, which is a detection value of the servo pressure sensor, and a target servo pressure, which is a target for the servo pressure, driving the electric motor based on the target torque, and varying a differential gain of the feedback control according to the operating state of the holding valve when the braking actuator is operated by braking control involving closing the holding valve.

[0009] FIG. 1 is a schematic diagram showing a vehicle equipped with a braking device of a first embodiment. FIG. 2 is a schematic diagram showing a brake actuator equipped in the braking device of FIG. 1. FIG. 3 is a block diagram showing various processes for driving an electric motor, which is a power source of an electric cylinder, in a first controller equipped in the braking device of FIG. 1. FIG. 4 is a flowchart showing a series of processes executed when determining a gain of feedback control when first braking control is being performed by a control device equipped in the braking device of FIG. 1. FIG. 5 is a flowchart showing a series of processes executed when determining a gain of feedback control when second braking control is being performed by a control device equipped in the braking device of FIG. 1. FIG. 6 is a block diagram showing various processes for driving an electric motor, which is a power source of an electric cylinder, in a first controller equipped in a braking device of a second embodiment. FIG. 7 is a flowchart showing a series of processes executed when determining a gain of feedback control when first braking control or second braking control is being performed by a control device equipped in the braking device of FIG. 6.

[0010] First Embodiment A first embodiment of a braking device mounted on a vehicle and a method for controlling the braking device will be described below with reference to FIGS. 1 to 5. FIG.

[0011] 1 shows a vehicle equipped with a braking device 100. The vehicle has wheels including two front wheels 11fl, 11fr and two rear wheels 11rl, 11rr. The vehicle also has friction brakes 15 in the same number as the wheels.

[0012] <Configuration of Friction Brake> The multiple friction brakes 15 each generate a braking force at the corresponding wheel. The friction brakes 15 have wheel cylinders 16, rotating bodies 17, and friction portions 18. Because the rotating bodies 17 rotate together with the wheels, braking force is generated at the wheels by pressing the friction portions 18 against the rotating bodies 17. The force pressing the friction portions 18 against the rotating bodies 17 increases as the wheel pressure, which is the hydraulic pressure in the wheel cylinders 16, increases. Therefore, the higher the wheel pressure, the greater the braking force the friction brakes 15 can generate at the wheels. The braking force generated on the vehicle by the operation of the friction brakes 15 is called the "friction braking force."

[0013] <Configuration of Brake Device> The brake device 100 adjusts the friction braking force generated in the vehicle by controlling the wheel pressures of the multiple wheel cylinders 16. The brake device 100 includes an upstream unit 110 and a downstream unit 120. Each of the upstream unit 110 and the downstream unit 120 is configured to be able to control the wheel pressures of the multiple wheel cylinders 16.

[0014] <Configuration of Upstream Unit> The upstream unit 110 includes a hydraulic pressure generating device 20 and a first controller 210 that controls the hydraulic pressure generating device 20. The first controller 210 constitutes a part of the control device 200 of the braking device 100. The first controller 210 will be described later.

[0015] The hydraulic pressure generating device 20 includes a reservoir tank 21, a brake operating member 22, a brake sensor 23, a master device 30, and an electric pressure unit 50. The reservoir tank 21 stores brake fluid and is open to the atmosphere.

[0016] The brake operating member 22 is a member that is operated by the driver of the vehicle to adjust the deceleration of the vehicle. An example of the brake operating member 22 is a brake pedal. The driver's operation of the brake operating member 22 is referred to as a "braking operation." When a braking operation is being performed, the hydraulic pressure generating device 20 can generate wheel pressures in the multiple wheel cylinders 16 that correspond to the amount of operation of the brake operating member 22.

[0017] The brake sensor 23 detects information related to the driver's operation of the brake operating member 22. For example, the brake sensor 23 detects the amount of operation of the brake operating member 22 by the driver as information related to the operation of the brake operating member 22. Hereinafter, the amount of operation based on the detection signal of the brake sensor 23 will be referred to as the "braking operation amount Ba."

[0018] <Master Device> The master device 30 includes a master cylinder 31, a stroke simulator 32, a plurality of flow paths 331, 332, and 333 connected to the master cylinder 31, and a plurality of control valves 341 and 342 that control the flow of brake fluid. The master device 30 includes a hydraulic pressure sensor 351 that detects the hydraulic pressure of the brake fluid.

[0019] The stroke simulator 32 is capable of generating a reaction force corresponding to the amount of operation of the brake operating member 22. The master cylinder 31 includes a main cylinder 41, a cover cylinder 42, a master piston 43, and an input piston 44. The master piston 43 and the input piston 44 can each move relative to the main cylinder 41 and the cover cylinder 42. The master cylinder 31 includes a master spring 45 that biases the master piston 43, and an input spring 46 that biases the input piston 44.

[0020] The main cylinder 41 has a plate-shaped bottom wall 411, a cylindrical peripheral wall 412 extending from the bottom wall 411 in the thickness direction of the bottom wall 411, and a first annular wall 413 extending from the rear end of the peripheral wall 412 toward the axis of the peripheral wall 412. A hole is formed in the first annular wall 413, into which the rear end of a master piston 43 (described later) is inserted.

[0021] Within the main cylinder 41, a master chamber Rm is defined by a bottom wall 411, a peripheral wall 412, and a master piston 43. Hereinafter, in the master cylinder 31, the leftward direction in FIG. 1, i.e., the direction in which the master piston 43 moves to reduce the volume of the master chamber Rm, will be referred to as the "forward" direction. On the other hand, the opposite direction to the forward direction will be referred to as the "rearward" direction. The rearward direction is also the direction in which the volume of the master chamber Rm increases.

[0022] A first fluid chamber R1 is defined behind the master chamber Rm within the main cylinder 41 by the peripheral wall 412 and the master piston 43. A servo chamber Rs is defined behind the first fluid chamber R1 within the main cylinder 41 by the peripheral wall 412, the first annular wall 413, and the master piston 43. Within the main cylinder 41, the master chamber Rm, the first fluid chamber R1, and the servo chamber Rs are not connected to one another.

[0023] The cover cylinder 42 has a cylindrical peripheral wall 421 and a second annular wall 422 extending from the rear end of the peripheral wall 421 toward the axis of the peripheral wall 421. The peripheral wall 421 is attached to the first annular wall 413 so that its axis coincides with that of the peripheral wall 412 of the main cylinder 41. The second annular wall 422 has a hole into which the rear end of the input piston 44 (described later) is inserted.

[0024] Within the cover cylinder 42, a second fluid chamber R2 is defined by the peripheral wall 421, the second annular wall 422, and the first annular wall 413 of the main cylinder 41. In the master cylinder 31, the second fluid chamber R2 is located rearward of the servo chamber Rs.

[0025] The master piston 43 is housed in the master cylinder 31 in surface contact with the inner circumferential surface of the peripheral wall 412 of the main cylinder 41 and the inner circumferential surface of the first annular wall 413. Therefore, when the master piston 43 moves in the axial direction, the master piston 43 slides on the inner circumferential surface of the peripheral wall 412 and the inner circumferential surface of the first annular wall 413. The rear end of the master piston 43 protrudes rearward beyond the first annular wall 413 and is located in the second fluid chamber R2.

[0026] The input piston 44 is housed in the master cylinder 31 in surface contact with the inner circumferential surface of the second annular wall 422 of the cover cylinder 42. Therefore, when the input piston 44 moves in the axial direction, the input piston 44 slides on the inner circumferential surface of the second annular wall 422. The rear end of the input piston 44 protrudes rearward beyond the second annular wall 422. The brake operating member 22 is connected to the rear end of the input piston 44. In the second fluid chamber R2, a gap is formed between the input piston 44 and the master piston 43. When the brake operating member 22 is operated, the input piston 44 moves in a direction approaching the master piston 43.

[0027] The master spring 45 is disposed between the bottom wall 411 of the main cylinder 41 and the master piston 43. The master spring 45 biases the master piston 43 rearward, so when the master piston 43 moves forward, the master spring 45 is elastically compressed.

[0028] The input spring 46 is disposed between the first annular wall 413 of the main cylinder 41 and the input piston 44. The input spring 46 biases the input piston 44 rearward, so that when the input piston 44 moves forward, the input spring 46 is elastically compressed.

[0029] In the master cylinder 31, the master chamber Rm is connected to the reservoir tank 21. More specifically, a portion of the master chamber Rm near the rear end is connected to the reservoir tank 21 via a port formed in the peripheral wall 412 of the main cylinder 41. Therefore, when the master piston 43 moves forward from the initial position shown in FIG. 1, the connection between the master chamber Rm and the reservoir tank 21 is released. From this point on, the hydraulic pressure in the master chamber Rm increases as the master piston 43 moves forward. For example, when the hydraulic pressure in the servo chamber Rs increases, the hydraulic pressure in the servo chamber Rs moves the master piston 43 forward. This increases the hydraulic pressure in the master chamber Rm.

[0030] The first flow path 331 connects a second hydraulic circuit 712 of the brake actuator 70 (described later) to the master chamber Rm. The second flow path 332 connects the first fluid chamber R1 to the third flow path 333. The stroke simulator 32 is also connected to the second flow path 332. The third flow path 333 connects the second fluid chamber R2 to the reservoir tank 21.

[0031] The first control valve 341 is a normally closed solenoid valve. The second control valve 342 is a normally open solenoid valve. The first control valve 341 is provided in a portion of the third flow path 333 closer to the second liquid chamber R2 than the connection point with the second flow path 332. The second control valve 342 is provided in a portion of the third flow path 333 on the opposite side of the connection point with the second flow path 332 from the first control valve 341. When the control device 200 is operating, the first control valve 341 is opened and the second control valve 342 is closed.

[0032] The hydraulic pressure sensor 351 detects the hydraulic pressure in the second hydraulic chamber R2. For example, the hydraulic pressure sensor 351 is provided in a portion of the third flow path 333 between the connection point with the second hydraulic chamber R2 and the first control valve 341. In the following description, the hydraulic pressure based on the detection signal of the hydraulic pressure sensor 351 will be referred to as the "input hydraulic pressure Pgs."

[0033] 1, the pressure unit 50 includes an electric cylinder 51. The pressure unit 50 can adjust the wheel pressures of the plurality of wheel cylinders 16 by operating the electric cylinder 51.

[0034] The pressurizing unit 50 has brake fluid flow paths including a fourth flow path 54, a fifth flow path 55, and a sixth flow path 56. The fourth flow path 54 is connected to an input port 515 of the electric cylinder 51 and the reservoir tank 21. The fifth flow path 55 is connected to a servo chamber Rs of the master cylinder 31 and an output port 516 of the electric cylinder 51. The sixth flow path 56 is connected to a first hydraulic pressure circuit 711 of the brake actuator 70 (described later) and the fifth flow path 55. Therefore, the electric cylinder 51 can supply brake fluid discharged from the output port 516 to both the servo chamber Rs and the first hydraulic pressure circuit 711.

[0035] The pressurizing unit 50 includes a differential pressure adjustment valve 551 installed in a portion of the fifth flow path 55 closer to the servo chamber Rs than the connection point with the sixth flow path 56. The differential pressure adjustment valve 551 is a normally open linear solenoid valve that adjusts the differential pressure between a portion of the fifth flow path 55 closer to the servo chamber Rs than the differential pressure adjustment valve 551 and a portion of the fifth flow path 55 closer to the electric cylinder 51 than the differential pressure adjustment valve 551. The pressurizing unit 50 can adjust the amount of brake fluid supplied to the servo chamber Rs, i.e., the hydraulic pressure in the servo chamber Rs, by adjusting the command opening of the differential pressure adjustment valve 551.

[0036] A check valve 552 is provided in parallel with the differential pressure adjustment valve 551 in the fifth flow path 55. The check valve 552 allows the flow of brake fluid from the servo chamber Rs toward the electric cylinder 51. On the other hand, the check valve 552 restricts the flow of brake fluid from the electric cylinder 51 toward the servo chamber Rs.

[0037] 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 slidably provided within the cylinder 511. The first electric motor 513 is a power source for the electric cylinder 51. The conversion mechanism 514 converts the rotation of the output shaft of the first electric motor 513 into linear movement of the piston 512.

[0038] A hydraulic pressure chamber Re, into which brake fluid is introduced, is defined inside the cylinder 511 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 direction of linear movement of the piston 512 when reducing the volume of the hydraulic pressure chamber Re will be referred to as the "forward direction Za," and the direction opposite to the forward direction Za will be referred to as the "rearward direction Zb." The rearward direction Zb is also the direction of linear movement of the piston 512 when increasing the volume of the hydraulic pressure chamber Re.

[0039] Ports, including an input port 515 and an output port 516, connecting the hydraulic chamber Re to the outside are formed in the peripheral wall of the cylinder 511. A through-hole 517 is formed in the piston 512. The through-hole 517 is positioned so that the input port 515 and the hydraulic chamber Re can communicate with each other when the piston 512 is in the most retracted position. As a result, when the piston 512 is in the most retracted position, the hydraulic chamber Re of the cylinder 511 communicates with the reservoir tank 21 via the through-hole 517, the input port 515, and the fourth flow path 54. The input port 515 is open when the piston 512 is in the most retracted position and is closed by the piston 512 when the piston 512 moves forward in the forward direction Za from the most retracted position. Even after the input port 515 is closed by the piston 512, the hydraulic pressure in the hydraulic chamber Re increases when the piston 512 moves forward in the forward direction Za.

[0040] The output port 516 is connected to the master cylinder 31 and the sixth flow path 56 via the fifth flow path 55. 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, the piston 512 moves in the forward direction Za within the cylinder 511 in response to the drive of the first electric motor 513, causing the brake fluid in the hydraulic chamber Re to be discharged from the output port 516 to the fifth flow path 55. On the other hand, the piston 512 moves in the backward direction Zb within the cylinder 511 in response to the drive of the first electric motor 513, causing the brake fluid in the fifth flow path 55 to be drawn into the hydraulic chamber Re through the output port 516.

[0041] In the hydraulic pressure generating device 20, when brake fluid is discharged from the output port 516 of the electric cylinder 51, the brake fluid flows through the fifth flow path 55. A portion of the brake fluid flowing through the fifth flow path 55 flows toward the wheel cylinders 16 for the rear wheels 11rl and 11rr via the sixth flow path 56. The remaining brake fluid flows into the servo chamber Rs of the master device 30. As a result, the hydraulic pressure in the servo chamber Rs increases, causing the master piston 43 to move forward, increasing the hydraulic pressure in the master chamber Rm. As a result, the brake fluid in the master chamber Rm flows through the first flow path 331 toward the wheel cylinders 16 for the front wheels 11fl and 11fr. In other words, the first flow path 331 and the sixth flow path 56 correspond to a "supply flow path" through which brake fluid flows toward the wheel cylinders 16 when the discharge pressure of the brake fluid from the electric cylinder 51 increases.

[0042] On the other hand, when the electric cylinder 51 is drawing brake fluid through the output port 516, brake fluid flows out from each of the wheel cylinders 16 for the rear wheels 11rl, 11rr and the wheel cylinders 16 for the front wheels 11fl, 11fr. As a result, brake fluid flows through the sixth flow path 56 toward the fifth flow path 55. Also, brake fluid flows through the first flow path 331 toward the master chamber Rm. As a result, the hydraulic pressure in the master chamber Rm increases, causing the master piston 43 to move in the backward direction Zb. As a result, brake fluid in the servo chamber Rs flows out into the fifth flow path 55. As a result, brake fluid flows through the fifth flow path 55 toward the electric cylinder 51.

[0043] The pressurizing unit 50 includes a servo pressure sensor 58 and a rotation angle sensor 59. The servo pressure sensor 58 detects the servo pressure, which is the hydraulic pressure of the brake fluid discharged from the output port 516 of the electric cylinder 51. The rotation angle sensor 59 detects the motor rotation angle, which is the rotation angle of the output shaft of the first electric motor 513. Hereinafter, the servo pressure based on the detection signal of the servo pressure sensor 58 will be referred to as the "servo pressure detection value Ps." The motor rotation angle based on the detection signal of the rotation angle sensor 59 will be referred to as the "rotation angle detection value θ."

[0044] <Downstream Unit> The downstream unit 120 includes a brake actuator 70 and a second controller 220 that controls the brake actuator 70. The second controller 220 constitutes a part of the control device 200 of the braking device 100. The second controller 220 will be described later.

[0045] 1 and 2, the brake actuator 70 is configured to be able to adjust the differential pressure between the servo pressure and the wheel pressure. The brake actuator 70 is connected to the first flow path 331 and the sixth flow path 56. Specifically, the brake actuator 70 has a first hydraulic pressure circuit 711 and a second hydraulic pressure circuit 712. The first hydraulic pressure circuit 711 is connected to the sixth flow path 56 and is also connected to the two wheel cylinders 16 for the rear wheels 11rl, 11rr. The second hydraulic pressure circuit 712 is connected to the first flow path 331 and is also connected to the two wheel cylinders 16 for the front wheels 11fl, 11fr.

[0046] 2 , the first hydraulic pressure circuit 711 has a connection flow path 721 connected to the sixth flow path 56. The second hydraulic pressure circuit 712 has a connection flow path 722 connected to the first flow path 331. The connection flow path 721 is a brake fluid path that connects the two wheel cylinders 16 for the rear wheels 11rl, 11rr to the sixth flow path 56. The connection flow path 722 is a brake fluid path that connects the two wheel cylinders 16 for the front wheels 11fl, 11fr to the first flow path 331.

[0047] Each of the plurality of connection flow paths 721, 722 is provided with a differential pressure control valve 73, which is a normally-open linear solenoid valve. The differential pressure control valve 73 installed in the connection flow path 721 can adjust the differential pressure between a portion of the connection flow path 721 closer to the sixth flow path 56 and a portion of the connection flow path 721 closer to the wheel cylinder 16. The differential pressure control valve 73 installed in the connection flow path 722 can adjust the differential pressure between a portion of the connection flow path 722 closer to the first flow path 331 and a portion of the connection flow path 722 closer to the wheel cylinder 16. For example, the differential pressure control valve 73 can generate a larger differential pressure as the current flowing through its solenoid increases.

[0048] A portion of the connecting flow path 721 closer to the wheel cylinder 16 than the differential pressure control valve 73 branches into two paths 72a and 72b. The path 72a is connected to the wheel cylinder 16 for the left rear wheel 11rl, while the path 72b is connected to the wheel cylinder 16 for the right rear wheel 11rr. A portion of the connecting flow path 722 closer to the wheel cylinder 16 than the differential pressure control valve 73 branches into two paths 72c and 72d. The path 72c is connected to the wheel cylinder 16 for the left front wheel 11fl, while the path 72d is connected to the wheel cylinder 16 for the right front wheel 11fr.

[0049] A retention valve 74 is provided in each of the multiple paths 72a to 72d. The retention valve 74 is a normally open solenoid valve. When the retention valve 74 is closed, the supply of brake fluid to the wheel cylinder 16 corresponding to that retention valve 74 is restricted. In other words, an increase in wheel pressure is restricted. A bypass fluid path 85 that bypasses the retention valve 74 is connected to each of the multiple paths 72a to 72d. A check valve 86 is provided in each of the multiple bypass fluid paths 85 to restrict the flow of brake fluid in the bypass fluid path 85 from the differential pressure control valve 73 toward the wheel cylinder 16.

[0050] The first hydraulic circuit 711 has a reduced-pressure reservoir 751 that stores brake fluid and a reduced-pressure fluid path 761 that is connected to the reduced-pressure reservoir 751. The second hydraulic circuit 712 has a reduced-pressure reservoir 752 that stores brake fluid and a reduced-pressure fluid path 762 that is connected to the reduced-pressure reservoir 752. The reduced-pressure fluid path 761 is a brake fluid path that connects the reduced-pressure reservoir 751 to portions of the paths 72a and 72b that are closer to the wheel cylinder 16 than the retention valve 74. The reduced-pressure fluid path 762 is a brake fluid path that connects the reduced-pressure reservoir 752 to portions of the paths 72c and 72d that are closer to the wheel cylinder 16 than the retention valve 74. Pressure reducing valves 77 are respectively installed in the portion of pressure reducing fluid passage 761 connected to passage 72a, the portion of pressure reducing fluid passage 761 connected to passage 72b, the portion of pressure reducing fluid passage 762 connected to passage 72c, and the portion of pressure reducing fluid passage 762 connected to passage 72d. Pressure reducing valves 77 are normally closed solenoid valves. When pressure reducing valves 77 are opened, brake fluid in wheel cylinders 16 flows into pressure reducing reservoirs 751 and 752 via pressure reducing fluid passages 761 and 762.

[0051] The first hydraulic circuit 711 has a pump 791. The second hydraulic circuit 712 has a pump 792. The multiple pumps 791, 792 are electric pumps powered by the second electric motor 78. The pumps 791, 792 pump up brake fluid from the reduced pressure reservoirs 751, 752 and discharge the brake fluid into the connecting flow paths 721, 722 between the differential pressure control valve 73 and the pressure retention valve 74.

[0052] Each of the multiple hydraulic circuits 711, 712 has a return flow path 80 and a valve mechanism 81. The return flow path 80 is a brake fluid path that connects a portion of the connecting flow paths 721, 722 that is closer to the flow paths 56, 331 than the differential pressure control valve 73 and pressure-reducing reservoirs 751, 752. The valve mechanism 81 is integrated with the pressure-reducing reservoirs 751, 752. The valve mechanism 81 allows the flow of brake fluid from the return flow path 80 toward the flow paths 56, 331, while restricting the flow of brake fluid from the flow paths 56, 331 toward the pressure-reducing reservoirs 751, 752. However, when the pumps 791, 792 are operated while the pressure-reducing reservoirs 751, 752 are empty, the valve mechanism 81 allows the flow of brake fluid from the flow paths 56, 331 through the return flow path 80.

[0053] The second hydraulic pressure circuit 712 is provided with a hydraulic pressure sensor 83 that detects the hydraulic pressure of the brake fluid that has flowed into the second hydraulic pressure circuit 712 from the first flow path 331. The hydraulic pressure sensor 83 is connected to a portion of the connecting flow path 722 that is closer to the first flow path 331 than the differential pressure control valve 73. The first flow path 331 is connected to the master chamber Rm of the master unit 30. Therefore, it can be said that the hydraulic pressure sensor 83 detects the hydraulic pressure of the brake fluid discharged from the master chamber Rm. Hereinafter, the hydraulic pressure based on the detection signal of the hydraulic pressure sensor 83 will be referred to as the "master pressure detection value Pmc."

[0054] <Overview of Control Device> As shown in Fig. 1, the control device 200 of the braking device 100 can operate the hydraulic pressure generating device 20 and the brake actuator 70 based on detection signals from multiple sensors 351, 58, 59, and 83. For example, the control device 200 adjusts the motor rotation angle of the first electric motor 513 to adjust the brake fluid discharged from the output port 516. This allows the control device 200 to control the servo pressure. In this state, the control device 200 operates the brake actuator 70 to adjust the wheel pressures of the multiple wheel cylinders 16. This allows the control device 200 to adjust the frictional braking force generated at the multiple wheels.

[0055] The braking control performed by the control device 200 includes a first braking control and a second braking control. The first braking control is a control that does not require a sudden increase in wheel pressure. The second braking control is a control that may require a sudden increase in wheel pressure.

[0056] An example of the first braking control is antilock brake control. Hereinafter, antilock brake control will be referred to as "ABS." ABS is a braking control that is initiated when a deceleration slip occurs at a wheel while braking force is being applied to that wheel. In such an ABS, the control device 200 controls the servo pressure based on a required braking force, which is a braking force required of the brake device 100. The control device 200 also adjusts the friction braking force generated at the wheel where deceleration slip occurs by driving the holding valve 74, the pressure reducing valve 77, and the pumps 791 and 792 corresponding to that wheel.

[0057] In a first braking control represented by an ABS, at least one of the plurality of holding valves 74 may be closed. When the first braking control is initiated, the cylinder characteristics, which are the relationship between the amount of brake fluid discharged from the electric cylinder 51 and the servo pressure, may change. Specifically, when the holding valve 74 is closed, the amount of increase in servo pressure when brake fluid is discharged from the electric cylinder 51 is more likely to be large compared to when all of the plurality of holding valves 74 are open. This tendency becomes stronger as the number of holding valves 74 that are closed increases.

[0058] Examples of the second braking control are traction control, anti-skid control, and anti-rollover control. Hereinafter, traction control will be referred to as "TCS" and anti-skid control will be referred to as "ESC." When such second braking control is being performed, there may be periods when a rapid increase in wheel pressure is required and periods when a rapid increase in wheel pressure is not required. For example, a rapid increase in wheel pressure is likely to be required at the start of the second braking control. In the TCS or ESC, at least one of the multiple pressure retention valves 74 may be closed.

[0059] <Configuration of Control Device> The control device 200 includes the above-described first controller 210 and second controller 220. The multiple controllers 210, 220 can transmit and receive various information and commands to and from each other via an in-vehicle network 230.

[0060] The first controller 210 has a first processing circuit 211. The second controller 220 has a second processing circuit 221. An example of the processing circuits 211, 221 is an electronic control device. In this case, each of the multiple processing circuits 211, 221 has a CPU and a memory that stores a control program executed by the CPU. The first processing circuit 211 operates the hydraulic pressure generating device 20 by the CPU executing the control program stored in the memory. The second processing circuit 221 operates the brake actuator 70 by the CPU executing the control program stored in the memory.

[0061] <Control of Electric Cylinder> The control of the electric cylinder 51 executed by the first processing circuit 211 will be described with reference to FIG.

[0062] The first processing circuit 211 executes a required braking force derivation process M11, a target servo pressure setting process M13, a hydraulic pressure feedforward process M15, a hydraulic pressure feedback process M17, a gain setting process M19, and a target servo pressure correction process M21. Furthermore, the first processing circuit 211 executes a target conversion process M23 and a rotation angle feedback process M25. Hereinafter, the hydraulic pressure feedforward process M15 will be referred to as "hydraulic pressure F / F process M15." The hydraulic pressure feedback process M17 will be referred to as "hydraulic pressure F / B process M17." The rotation angle feedback process M25 will be referred to as "rotation angle F / B process M25."

[0063] <Required Braking Force Derivation Process> The first processing circuit 211 executes a required braking force derivation process M11 at every predetermined control cycle. In the required braking force derivation process M11, the first processing circuit 211 derives a required frictional braking force FmR, which is a required value of the frictional braking force to be generated by the vehicle. For example, when the driver is operating the brake operating member 22, the first processing circuit 211 derives the required braking force FR so that the required braking force FR increases as the braking operation amount Ba increases. Furthermore, for example, when deceleration of the vehicle is requested by another control device, the first processing circuit 211 derives a value corresponding to the vehicle deceleration requested by the other control device as the required braking force FR. The first processing circuit 211 then derives the required frictional braking force FmR by subtracting the regenerative braking force Fr generated by the vehicle from the required braking force FR. When the regenerative braking force Fr is 0 (zero), the first processing circuit 211 derives the required braking force FR as the required frictional braking force FmR.

[0064] When the second braking control is being performed, the second controller 220 may request the first controller 210 to generate a servo pressure. In this case, the first processing circuit 211 derives a value corresponding to the servo pressure requested by the second controller 220 as the requested frictional braking force FmR.

[0065] <Target Servo Pressure Setting Process> The first processing circuit 211 executes a target servo pressure setting process M13 at every predetermined control cycle. In the target servo pressure setting process M13, the first processing circuit 211 derives a target servo pressure PsT, which is a target value of the servo pressure, based on the required frictional braking force FmR. For example, the first processing circuit 211 derives the target servo pressure PsT such that the target servo pressure PsT increases as the required frictional braking force FmR increases.

[0066] <Hydraulic Pressure F / F Processing> The first processing circuit 211 executes a hydraulic pressure F / F processing M15 at every predetermined control cycle. In the hydraulic pressure F / F processing M15, the first processing circuit 211 derives a standard servo pressure Psb, which is a standard value of the servo pressure, based on the target servo pressure PsT. For example, the first processing circuit 211 derives the standard servo pressure Psb so that the standard servo pressure Psb increases as the target servo pressure PsT increases.

[0067] <Hydraulic Pressure F / B Processing> The first processing circuit 211 executes hydraulic pressure F / B processing M17 at every predetermined control cycle. In the hydraulic pressure F / B processing M17, the first processing circuit 211 derives a servo pressure compensation value Psh by feedback control using the deviation between the servo pressure detection value Ps and the target servo pressure PsT as an input. Hereinafter, the feedback control using the deviation between the servo pressure detection value Ps and the target servo pressure PsT as an input will be referred to as "hydraulic pressure F / B control."

[0068] For example, the first processing circuit 211 performs PID control as hydraulic pressure F / B control. PID control includes proportional control, integral control, and differential control. The gain used in proportional control is called "proportional gain." The gain used in integral control is called "integral gain." The gain used in differential control is called "differential gain." The proportional gain, integral gain, and differential gain are "gains of hydraulic pressure F / B control."

[0069] In this embodiment, the first processing circuit 211 derives the compensation value Psh by using the gain set in a gain setting process M19 (described later) as the gain for hydraulic pressure feedback control. <Gain Setting Process> The first processing circuit 211 executes the gain setting process M19 at each predetermined control cycle when a predetermined change condition is met. In the gain setting process M19, the first processing circuit 211 sets the gains for hydraulic pressure feedback control, i.e., the proportional gain, integral gain, and derivative gain. As will be described in detail later, when the first braking control or the second braking control is being performed, the second controller 220 transmits gain information, which is information related to the gain for hydraulic pressure feedback control, to the first controller 210. The first processing circuit 211 sets the gain for hydraulic pressure feedback control based on this gain information.

[0070] For example, the first processing circuit 211 determines that a predetermined change condition is met when the first braking control is initiated. In the gain setting process M19 when the first braking control is being implemented, the first processing circuit 211 sets the gain of the hydraulic pressure F / B control to a value lower than the gain before the first braking control is initiated. For example, when ABS, which is an example of the first braking control, is being implemented, the first processing circuit 211 sets the derivative gain of the hydraulic pressure F / B control to a value lower than the value before the ABS is initiated. In this case, the first processing circuit 211 may lower at least one of the proportional gain and the integral gain compared to the value before the ABS is initiated. Alternatively, the first processing circuit 211 may maintain the proportional gain and the integral gain at the value before the ABS is initiated.

[0071] In this embodiment, while a first braking control such as an ABS is being performed, the second controller 220 transmits gain information to the first controller 210. Then, the first processing circuit 211 sets the value indicated by the gain information as the gain of the hydraulic pressure F / B control.

[0072] If the first processing circuit 211 changes the gain of the hydraulic pressure F / B control in conjunction with the execution of the first braking control, the first processing circuit 211 determines that a predetermined change condition is met when the first braking control ends, and then returns the gain of the hydraulic pressure F / B control to the value before the start of the first braking control.

[0073] Further, for example, the first processing circuit 211 determines that a predetermined change condition is met when the second braking control is being performed. In the gain setting process M19 when the second braking control is being performed, the first processing circuit 211 sets the gain of the hydraulic pressure F / B control based on the latest gain information transmitted from the second controller 220. When the second braking control is being performed, the first processing circuit 211 varies the proportional gain of the gain of the hydraulic pressure F / B control. At this time, the first processing circuit 211 may also vary at least one of the integral gain and the derivative gain. Furthermore, the first processing circuit 211 may hold the integral gain and the derivative gain.

[0074] If the first processing circuit 211 changes the gain of the hydraulic pressure F / B control in conjunction with the execution of the second braking control, the first processing circuit 211 determines that a predetermined change condition is met when the second braking control ends, and then returns the gain of the hydraulic pressure F / B control to the value before the second braking control started.

[0075] <Target Servo Pressure Correction Process> The first processing circuit 211 executes a target servo pressure correction process M21 at each predetermined control cycle. In the target servo pressure correction process M21, the first processing circuit 211 derives a target servo pressure correction value PsTa as the sum of the standard servo pressure Psb and the compensation value Psh.

[0076] <Target Conversion Process> The first processing circuit 211 executes the target conversion process M23 each time it executes the target servo pressure correction process M21 to derive the target servo pressure modification value PsTa. In the target conversion process M23, the first processing circuit 211 derives a target rotation angle θT, which is a target value for the motor rotation angle of the first electric motor 513. For example, the first processing circuit 211 converts the target servo pressure modification value PsTa into a motor rotation angle and derives the target rotation angle θT.

[0077] The first processing circuit 211 stores a first reference characteristic which is the relationship between the motor rotational angle and servo pressure of the first electric motor 513 when all of the plurality of holding valves 74 of the brake actuator 70 are open. The first processing circuit 211 derives the motor rotational angle corresponding to the target servo pressure correction value PsTa based on the first reference characteristic, and sets the derived motor rotational angle as the target rotational angle θT. In this way, the first processing circuit 211 can derive the target rotational angle θT such that the target rotational angle θT increases as the target servo pressure correction value PsTa increases.

[0078] <Rotation Angle Feedback Processing> The first processing circuit 211 executes rotation angle feedback processing M25 at every predetermined control cycle. In the rotation angle feedback processing M25, the first processing circuit 211 derives a motor current command value Imt, which is the current for the first electric motor 513, by feedback control using as input the deviation between the rotation angle detection value θ and the target rotation angle θT. The first processing circuit 211 then operates the driver circuit for the first electric motor 513 in accordance with a drive signal based on the command value Imt. This allows the first processing circuit 211 to drive the first electric motor 513 based on the target rotation angle θT. Hereinafter, feedback control using as input the deviation between the rotation angle detection value θ and the target rotation angle θT will be referred to as "rotation angle feedback control."

[0079] <First Gain Information Transmission Process> The first gain information transmission process executed by the second controller 220 while the first braking control is being performed will be described with reference to Fig. 4. The first gain information transmission process is a series of processes for transmitting gain information to the first controller 210. The second processing circuit 221 repeatedly executes the first gain information transmission process at each predetermined control period.

[0080] In step S11, the second processing circuit 221 determines whether the first braking control is being performed. If the second processing circuit 221 determines that the first braking control is being performed (S11: YES), the second processing circuit 221 proceeds to step S13. If the second processing circuit 221 determines that the first braking control is not being performed (S11: NO), the second processing circuit 221 temporarily ends the first gain information transmission process.

[0081] In step S13, the second processing circuit 221 obtains the number of wheels to be controlled by the first braking control. The wheel pressures in the wheel cylinders 16 for the wheels to be controlled by the first braking control are adjusted by the brake actuators 70. At this time, the pressure retention valves 74 for the wheels to be controlled may be closed to adjust the wheel pressure. Therefore, the number of wheels to be controlled by the first braking control is the same as the number of pressure retention valves 74 that are closed during the first braking control.

[0082] In the next step S15, the second processing circuit 221 determines a gain for the hydraulic pressure F / B control based on the number of wheels to be controlled by the first braking control. For example, the second processing circuit 221 sets a value smaller than the value before the start of the first braking control as the derivative gain of the hydraulic pressure F / B control. In this case, the second processing circuit 221 lowers the derivative gain as the number increases.

[0083] In the next step S17, the second processing circuit 221 transmits information indicating the gain determined in step S15 as gain information to the first controller 210. Thereafter, the second processing circuit 221 temporarily ends the first gain information transmission process.

[0084] <Second Gain Information Transmission Process> The second gain information transmission process executed by the second controller 220 while the second braking control is being performed will be described with reference to Fig. 5. The second gain information transmission process describes a series of processes for transmitting gain information to the first controller 210. The second processing circuit 221 repeatedly executes the second gain information transmission process at each predetermined control period.

[0085] In step S31, the second processing circuit 221 determines whether the second braking control is being performed. If the second processing circuit 221 determines that the second braking control is being performed (S31: YES), the second processing circuit 221 proceeds to step S33. If the second processing circuit 221 determines that the second braking control is not being performed (S31: NO), the second processing circuit 221 temporarily ends the second gain information transmission process.

[0086] In step S33, the second processing circuit 221 derives the increase speed dPw of the wheel pressures of the plurality of wheel cylinders. For example, the second processing circuit 221 derives the increase speed dPw of the target values ​​of the wheel pressures of the plurality of wheel cylinders. In the following step S35, the second processing circuit 221 selects the maximum value of the increase speeds dPw as the maximum increase speed dPwMax.

[0087] Then, in step S37, the second processing circuit 221 determines whether the maximum increase speed dPwMax is equal to or greater than the determination speed dPwth. The determination speed dPwth is a criterion for determining whether the increase speed of the wheel pressure is high. If the second processing circuit 221 determines that the maximum increase speed dPwMax is equal to or greater than the determination speed dPwth (S37: YES), the second processing circuit 221 proceeds to step S39. If the second processing circuit 221 determines that the maximum increase speed dPwMax is less than the determination speed dPwth (S37: NO), the second processing circuit 221 proceeds to step S41.

[0088] In step S39, the second processing circuit 221 determines a relatively high gain for the hydraulic pressure F / B control. For example, the second processing circuit 221 determines a relatively high proportional gain among the gains for the hydraulic pressure F / B control. If the proportional gain when neither the first braking control nor the second braking control is being performed is defined as a reference value, the second processing circuit 221 may determine the reference value as the proportional gain. That is, when the second processing circuit 221 determines that the maximum increase speed dPwMax is equal to or greater than the determination speed dPwth during the second braking control, the second processing circuit 221 may set the proportional gain among the gains for the hydraulic pressure F / B control to a value higher than that during the first braking control. Then, the second processing circuit 221 proceeds to step S43.

[0089] In step S41, the second processing circuit 221 determines a lower gain for the hydraulic pressure F / B control compared to when the maximum increase speed dPwMax is equal to or greater than the threshold speed dPwth. For example, the second processing circuit 221 determines a lower proportional gain among the gains for the hydraulic pressure F / B control compared to when the maximum increase speed dPwMax is equal to or greater than the threshold speed dPwth. If the proportional gain when neither the first braking control nor the second braking control is being performed is defined as a reference value, the second processing circuit 221 may determine a value lower than the reference value as the proportional gain. Then, the second processing circuit 221 proceeds to step S43.

[0090] In step S43, the second processing circuit 221 transmits information indicating the gain determined in step S39 or step S41 as gain information to the first controller 210. Thereafter, the second processing circuit 221 temporarily ends the second gain information transmission process.

[0091] <Functions and Effects of the Present Embodiment> (1-1) The first cylinder characteristic, which is the relationship between the motor rotation angle of the first electric motor 513 and the servo pressure, correlates with the amount of brake fluid discharged from the electric cylinder 51. The first cylinder characteristic when all of the retention valves 74 are open is referred to as the first reference characteristic. The first cylinder characteristic when at least one of the retention valves 74 is closed differs from the first reference characteristic. Therefore, when the electric cylinder 51 is operated based on the first reference characteristic, closing at least one of the retention valves 74 reduces the controllability of the servo pressure compared to when all of the retention valves 74 are open. For example, when the target servo pressure PsT is changed, it tends to take a long time for the detected servo pressure Ps to converge to the target servo pressure PsT. In other words, the amount of change in servo pressure relative to the amount of brake fluid discharged from the electric cylinder 51 tends to be large, making hunting, overshoot, undershoot, and the like more likely to occur. As a result, it tends to take a long time for the detected servo pressure Ps to converge to the target servo pressure PsT.

[0092] Therefore, when the brake actuator 70 is operated by the first braking control that involves closing the holding valve 74, the control device 200 lowers the gain of the hydraulic pressure F / B control compared to when all of the holding valves 74 are open. This prevents an increase in the time required for the servo pressure detection value Ps to converge to the target servo pressure PsT, even if the target servo pressure PsT is changed while the first braking control is being performed. In other words, the occurrence of hunting, overshoot, undershoot, and the like is suppressed. Therefore, the control device 200 can prevent a decrease in the accuracy of servo pressure adjustment depending on the operating state of the brake actuator 70.

[0093] (1-2) For example, when the control device 200 is implementing ABS, which is an example of first braking control, the control device 200 lowers the gain of the hydraulic pressure F / B control compared to before the ABS started. This allows the control device 200 to prevent a decrease in the accuracy of servo pressure adjustment due to the implementation of ABS. In other words, the control device 200 can prevent hunting, overshoot, undershoot, and the like from occurring.

[0094] (1-3) When the gain of the hydraulic pressure feedback control is reduced, the rate of increase in the servo pressure is less likely to increase. The ABS is a braking control that is initiated when wheel pressure and servo pressure are generated in multiple wheel cylinders 16. Therefore, a sudden increase in the servo pressure is less likely to be required while the ABS is in operation.

[0095] Therefore, when the ABS is started, the control device 200 lowers the gain of the hydraulic pressure F / B control. In other words, when a rapid increase in servo pressure is not required, the control device 200 can prevent a decrease in the accuracy of servo pressure adjustment caused by the closure of the pressure retention valve 74. In other words, the control device 200 can prevent hunting, overshoot, undershoot, and the like from occurring.

[0096] (1-4) The greater the number of retention valves 74 that are closed among the multiple retention valves 74, the greater the increase in servo pressure relative to the discharge rate of brake fluid from the electric cylinder 51. Therefore, the control device 200 lowers the gain of the hydraulic pressure F / B control as the number of retention valves 74 that are closed during the implementation of the first braking control. This allows the control device 200 to prevent a decrease in the accuracy of servo pressure adjustment even when the number of retention valves 74 that are closed during the implementation of the first braking control. In other words, the control device 200 can prevent hunting, overshoot, undershoot, and the like from occurring.

[0097] (1-5) When the second braking control is being performed, the rate of increase dPw of the wheel pressure may become equal to or greater than the threshold rate dPwth. If the gain of the hydraulic pressure F / B control is reduced because the pressure retention valve 74 is closed when the rate of increase dPw is equal to or greater than the threshold rate dPwth, the rate of increase of the wheel pressure is unlikely to become large.

[0098] Therefore, when the control device 200 determines that the increase rate dPw of the wheel pressure is equal to or greater than the threshold speed dPwth during the second braking control, it increases the gain of the hydraulic pressure F / B control compared to when it determines that the increase rate dPw is less than the threshold speed dPwth. This allows the control device 200 to quickly increase the servo pressure and wheel pressure when a rapid increase in wheel pressure is required during the second braking control.

[0099] On the other hand, during execution of the second braking control, the wheel pressure increase rate dPw may become less than the threshold speed dPwth. In such a case, the control device 200 reduces the gain of the hydraulic pressure F / B control compared to when the increase rate dPw is equal to or greater than the threshold speed dPwth. This allows the control device 200 to prevent a decrease in the accuracy of servo pressure adjustment. In other words, the control device 200 can prevent hunting, overshoot, undershoot, and the like from occurring.

[0100] Second Embodiment A second embodiment of the braking device will be described with reference to Figures 6 and 7. In the second embodiment, the control method of the first electric motor and the like differ from the first embodiment. In the following description, differences from the first embodiment will be mainly described, and the same reference numerals will be used to designate the same components as those in the first embodiment, and redundant description will be omitted.

[0101] The control of the electric cylinder 51 will be described with reference to Fig. 6. The first processing circuit 211 executes a required braking force derivation process M11 and a target servo pressure setting process M13, as well as a reference torque setting process M31, a hydraulic pressure feedback process M33, a gain setting process M35, a target torque derivation process M37, and a command process M39. Hereinafter, the hydraulic pressure feedback process M33 will be referred to as "hydraulic pressure F / B process M33."

[0102] <Reference Torque Setting Process> The first processing circuit 211 executes a reference torque setting process M31 at every predetermined control cycle. In the reference torque setting process M31, the first processing circuit 211 sets a reference motor torque Tmb based on the target servo pressure PsT. The reference motor torque Tmb is a reference value of the motor torque, which is the output torque of the first electric motor 513. For example, the first processing circuit 211 sets the reference motor torque Tmb to a value obtained by converting the target servo pressure PsT into motor torque. In this way, the first processing circuit 211 can set the reference motor torque Tmb so that the reference motor torque Tmb increases as the target servo pressure PsT increases.

[0103] <Hydraulic Pressure Feedback Processing> The first processing circuit 211 executes hydraulic pressure feedback processing M33 at every predetermined control cycle. In hydraulic pressure feedback processing M33, the first processing circuit 211 derives a servo pressure compensation value Psh by hydraulic pressure feedback control using the deviation between the servo pressure detection value Ps and the target servo pressure PsT as an input. One example of hydraulic pressure feedback control is PID control. PID control includes proportional control, integral control, and differential control. The gain used in proportional control is the "proportional gain." The gain used in integral control is the "integral gain." The gain used in differential control is the "differential gain." In this embodiment, the first processing circuit 211 performs hydraulic pressure feedback control using the gain set in gain setting processing M35, which will be described later.

[0104] The first processing circuit 211 converts the compensation value Psh into a motor torque and sets the resulting value as the motor torque compensation value Tmh. This allows the first processing circuit 211 to set the motor torque compensation value Tmh to a value corresponding to the deviation between the detected servo pressure value Ps and the target servo pressure PsT.

[0105] <Gain Setting Process> When a predetermined change condition is met, the first processing circuit 211 executes a gain setting process M35 at every predetermined control cycle. In the gain setting process M35, the first processing circuit 211 sets a proportional gain, an integral gain, and a derivative gain for the hydraulic pressure feedback control. For example, when the first braking control is being performed, the second controller 220 transmits gain information to the first controller 210. The first processing circuit 211 sets a derivative gain for the hydraulic pressure feedback control based on this gain information. For example, when the second braking control is being performed, the second controller 220 transmits gain information to the first controller 210. The first processing circuit 211 sets a proportional gain and an integral gain for the hydraulic pressure feedback control based on this gain information.

[0106] The first processing circuit 211 determines that a predetermined change condition is met when the first braking control is started. In the gain setting process M35 when the first braking control is being performed, the first processing circuit 211 varies the derivative gain depending on the operating state of the retention valves 74 of the brake actuator 70. For example, when all of the retention valves 74 are closed, the first processing circuit 211 lowers the derivative gain compared to when at least one of the retention valves 74 is open.

[0107] When the first braking control ends, the first processing circuit 211 returns the derivative gain of the hydraulic pressure F / B control to the value it had before the first braking control started. When the second braking control is being performed, the first processing circuit 211 determines that a predetermined change condition is met. In the gain setting process M35 when the second braking control is being performed, the first processing circuit 211 sets the proportional gain and integral gain of the hydraulic pressure F / B control based on the latest gain information transmitted from the second controller 220. At this time, it is preferable that the first processing circuit 211 maintains the derivative gain.

[0108] If the gains of the hydraulic pressure F / B control are changed in conjunction with the execution of the second braking control, the first processing circuit 211 determines that a predetermined change condition is met when the second braking control ends, and then returns the proportional gain and integral gain of the hydraulic pressure F / B control to the values ​​before the second braking control started.

[0109] <Target Torque Derivation Process> The first processing circuit 211 executes a target torque derivation process M37 at every predetermined control period. In the target torque derivation process M37, the first processing circuit 211 derives the target torque TmT as the sum of the standard motor torque Tmb and the motor torque compensation value Tmh. The target torque TmT is the target motor torque of the first electric motor 513.

[0110] <Command Processing> The first processing circuit 211 executes command processing M39 at every predetermined control cycle. In command processing M39, the first processing circuit 211 sets the motor current command value Imt to a motor current corresponding to the target torque TmT. As a result, the first processing circuit 211 can set a larger current value as the target torque TmT increases. The first processing circuit 211 then operates the driver circuit for the first electric motor 513 in accordance with a drive signal based on the command value Imt. As a result, the first processing circuit 211 can drive the first electric motor 513 based on the target torque TmT.

[0111] <Gain Information Transmission Process> The gain information transmission process executed by the second controller 220 while the first braking control or the second braking control is being performed will be described with reference to Fig. 7. The gain information transmission process is a series of processes for transmitting gain information to the first controller 210. The second processing circuit 221 repeatedly executes the gain information transmission process at each predetermined control period.

[0112] In step S51, the second processing circuit 221 determines whether the first braking control is being performed. If the second processing circuit 221 determines that the first braking control is being performed (S51: YES), the second processing circuit 221 proceeds to step S53. If the second processing circuit 221 determines that the first braking control is not being performed (S51: NO), the second processing circuit 221 proceeds to step S61.

[0113] In step S53, the second processing circuit 221 executes a process for determining a derivative gain of the hydraulic pressure F / B control. In this process, the second processing circuit 221 acquires the operating states of the plurality of holding valves 74 provided in the brake actuator 70. When at least one of the plurality of holding valves 74 is open, the second processing circuit 221 determines a first value as the derivative gain. An example of the first value is the same value as the derivative gain before the start of the first brake control. When all of the plurality of holding valves 74 are closed, the second processing circuit 221 sets a second value smaller than the first value as the derivative gain. After executing this determination process, the second processing circuit 221 proceeds to step S55.

[0114] In step S55, the second processing circuit 221 transmits information indicating the differential gain determined in step S53 as gain information to the first controller 210. Thereafter, the second processing circuit 221 temporarily ends the gain information transmission process.

[0115] In step S61, the second processing circuit 221 determines whether the second braking control is being performed. If the second processing circuit 221 determines that the second braking control is being performed (S61: YES), the second processing circuit 221 proceeds to step S63. If the second processing circuit 221 determines that the second braking control is not being performed (S61: NO), the second processing circuit 221 temporarily ends the gain information transmission process.

[0116] In step S63, the second processing circuit 221 executes a process for determining the proportional gain and integral gain of the hydraulic pressure F / B control. The content of this process is substantially the same as the series of processes from step S33 to S41 shown in FIG. 5. Therefore, a detailed description of this process will be omitted. After the second processing circuit 221 determines the proportional gain and integral gain through this process, the process proceeds to step S65.

[0117] In step S65, the second processing circuit 221 transmits information indicating the proportional gain and integral gain determined in step S63 as gain information to the first controller 210. Thereafter, the second processing circuit 221 temporarily ends the gain information transmission process.

[0118] <Functions and Effects of the Present Embodiment> (2-1) The second cylinder characteristic, which is the relationship between the motor torque of the first electric motor 513, which correlates with the amount of brake fluid discharged from the electric cylinder 51, and the servo pressure, when all of the retention valves 74 are open, is referred to as the second reference characteristic. The second cylinder characteristic when at least one of the retention valves 74 is closed differs from the second reference characteristic. Therefore, when the electric cylinder 51 is operated based on the second reference characteristic, if at least one of the retention valves 74 is closed, the controllability of the servo pressure decreases compared to when all of the retention valves 74 are open. The greater the number of closed retention valves 74, the greater the degree of decrease in controllability of the servo pressure. When the controllability of the servo pressure decreases, it tends to take a longer time for the detected servo pressure value Ps to converge to the target servo pressure PsT when the target servo pressure PsT is changed. In other words, the amount of change in servo pressure relative to the amount of brake fluid discharged by the electric cylinder 51 tends to increase, which makes it more likely that hunting, overshooting, undershooting, etc. will occur. As a result, it tends to take a long time for the detected servo pressure value Ps to converge to the target servo pressure PsT.

[0119] Generally, the differential control of hydraulic pressure feedback control functions to predict future changes in the servo pressure, which is the object of control, and to suppress the occurrence of overshoot. In other words, in cases where the servo pressure would change suddenly with proportional control and integral control alone, the differential control plays a role in suppressing the sudden change in the servo pressure.

[0120] As described above, when the holding valve 74 is closed, the change in servo pressure relative to the amount of brake fluid discharged from the electric cylinder 51 is likely to be larger than when the holding valve 74 is open. In other words, when the holding valve 74 is closed while brake fluid is being discharged from the electric cylinder 51, the absolute value of the value calculated by the differential control is likely to be larger than when the holding valve 74 is open. As a result, the role of suppressing sudden changes in the servo pressure may become excessive, making it more difficult for the detected servo pressure value Ps to converge to the target servo pressure PsT. Therefore, when the holding valve 74 is closed, the differential gain can be lowered compared to when the holding valve 74 is open, making it easier for the detected servo pressure value Ps to converge to the target servo pressure PsT more quickly. However, when the holding valve 74 is open, the differential gain can be increased to make the detected servo pressure value Ps converge to the target servo pressure PsT more quickly.

[0121] Therefore, in this embodiment, when the brake actuator 70 is operated by the first braking control that involves closing the retention valve 74, the control device 200 varies the derivative gain of the hydraulic pressure F / B control in accordance with the operating state of the retention valve 74. This prevents an increase in the time required for the servo pressure detection value Ps to converge to the target servo pressure PsT when the servo pressure detection value Ps deviates from the target servo pressure PsT while the first braking control is being performed. In other words, the occurrence of hunting, overshoot, undershoot, and the like is prevented. Therefore, the control device 200 can prevent a decrease in the accuracy of servo pressure adjustment depending on the operating state of the brake actuator 70.

[0122] (2-2) When all of the retention valves 74 are closed during the first braking control, the control device 200 reduces the derivative gain compared to when at least one of the retention valves 74 is open. In other words, when the deviation between the second cylinder characteristic and the second reference characteristic is relatively large, the control device 200 reduces the derivative gain compared to when the deviation between the second cylinder characteristic and the second reference characteristic is not so large. By varying the derivative gain during the first braking control in this way, the control device 200 can effectively suppress the occurrence of hunting, overshoot, undershoot, and the like.

[0123] (2-3) When the second braking control is being performed, the rate of increase dPw of the wheel pressure may become equal to or greater than the threshold rate dPwth. If the proportional gain and integral gain of the hydraulic pressure F / B control are reduced because the holding valve 74 is closed when the rate of increase dPw is equal to or greater than the threshold rate dPwth, the rate of increase of the wheel pressure is unlikely to become large.

[0124] Therefore, when the control device 200 determines that the increase rate dPw of the wheel pressure is equal to or greater than the threshold speed dPwth during the second braking control, it sets the proportional gain and the integral gain higher than when it determines that the increase rate dPw is less than the threshold speed dPwth. This allows the control device 200 to quickly increase the servo pressure and the wheel pressure when a rapid increase in the wheel pressure is required during the second braking control.

[0125] On the other hand, during execution of the second braking control, the wheel pressure increase rate dPw may become less than the threshold speed dPwth. In such a case, the control device 200 reduces the proportional gain and the integral gain compared to when the increase rate dPw is equal to or greater than the threshold speed dPwth. This allows the control device 200 to prevent a decrease in the accuracy of servo pressure adjustment. In other words, the control device 200 can prevent hunting, overshoot, undershoot, and the like from occurring.

[0126] (Modifications) The above-described embodiments can be modified as follows: The above-described embodiments and the following modifications can be combined with each other within the scope of technical compatibility.

[0127] In the first embodiment, the control device 200 may not change the gain of the hydraulic pressure F / B control when the second braking control is being performed. In the second embodiment, the control device 200 may change only one of the proportional gain and the integral gain of the hydraulic pressure F / B control when the second braking control is being performed. Furthermore, the control device 200 may not change the proportional gain and the integral gain of the hydraulic pressure F / B control when the second braking control is being performed.

[0128] The proportional gain when neither the first braking control nor the second braking control is being performed is defined as the reference value. In this case, the control device 200 may set the proportional gain higher than the reference value when it determines that the maximum increase speed dPwMax is equal to or greater than the determination speed dPwth while the second braking control is being performed.

[0129] In the first embodiment, when the first braking control is being performed, the control device 200 does not need to change the gain of the hydraulic pressure F / B control depending on the number of closed hold valves 74. In the first embodiment, when the first braking control is being performed, the control device 200 may lower the proportional gain of the gain of the hydraulic pressure F / B control compared to before the start of the first braking control. In this case, it is preferable that the control device 200 lower the proportional gain during the first braking control than when the second braking control is being performed.

[0130] In the second embodiment, when at least one of the plurality of retention valves 74 is closed while the first braking control is being performed, the control device 200 may lower the derivative gain compared to when all of the plurality of retention valves 74 are open. When at least one of the plurality of retention valves 74 is closed while the first braking control is being performed, the control device 200 may lower the derivative gain as the number of closed retention valves 74 increases.

[0131] In the above embodiments, the control device 200 lowers the derivative gain based on the operating state of the hold valve 74 while the first braking control is being performed, and raises the proportional gain and the integral gain based on the rate of increase dPw of the wheel pressure while the second braking control is being performed, but this is not limiting. For example, the control device 200 may change the control gain based on the operating state of the hold valve 74 and the rate of increase dPw of the wheel pressure regardless of whether the first braking control and the second braking control are being performed.

[0132] For example, the control device 200 may change the control gain as follows: When all of the plurality of retention valves 74 are closed, the control device 200 lowers the derivative gain compared to when at least one of the plurality of retention valves 74 is open. In a situation where the derivative gain is not lowered in this way, the control device 200 increases the proportional gain and the integral gain when it determines that the increasing speed dPw of the wheel pressure is equal to or greater than the determination speed dPwth.

[0133] Furthermore, for example, the control device 200 may change the control gains as follows: When all of the plurality of retention valves 74 are closed, the control device 200 lowers the derivative gain compared to when at least one of the plurality of retention valves 74 is open. Regardless of whether all of the plurality of retention valves 74 are closed, the control device 200 increases the proportional gain and the integral gain when it is determined that the increasing speed dPw of the wheel pressure is equal to or greater than the determination speed dPwth.

[0134] The braking control includes front / rear braking force distribution control, which restricts an increase in friction braking force generated at the rear wheels. When the front / rear braking force distribution control is performed, the holding valves 74 for the rear wheels 11rl and 11rr are closed. Therefore, the front / rear braking force distribution control is also an example of the first braking control.

[0135] Therefore, in the first embodiment, when the control device 200 performs front / rear braking force distribution control, the gain of the hydraulic pressure F / B control may be lower than that before the start of the front / rear braking force distribution control. In the first embodiment, the hydraulic pressure F / B control does not have to include at least one of integral control and differential control as long as it includes proportional control.

[0136] In the second embodiment, the hydraulic pressure feedback control does not have to include proportional control or integral control as long as it includes differential control. The hydraulic pressure generating device may have a configuration different from the hydraulic pressure generating device 20 shown in Fig. 1 as long as it includes the electric cylinder 51. For example, the hydraulic pressure generating device may be configured to supply brake fluid discharged from the electric cylinder 51 directly to the second hydraulic pressure circuit 712 without passing through the master cylinder 31.

[0137] The processing circuits 211 and 221 are not limited to those including a CPU and a ROM and executing software processing. That is, the control device may have any one of the following configurations (a), (b), and (c).

[0138] (a) The processing circuits 211 and 221 include one or more processors that execute various processes according to a computer program. The processor includes a CPU and memory such as RAM and ROM. The memory stores program code or instructions configured to cause the CPU to execute processes. Memory, i.e., computer-readable media, includes any available media that can be accessed by a general-purpose or special-purpose computer.

[0139] (b) The processing circuits 211, 221 include one or more dedicated hardware circuits that perform various processes. Examples of dedicated hardware circuits include application specific integrated circuits (ASICs) or FPGAs. ASIC is an abbreviation for "Application Specific Integrated Circuit." FPGA is an abbreviation for "Field Programmable Gate Array."

[0140] (c) The processing circuits 211 and 221 each include one or more processors that execute some of the various processes in accordance with a computer program, and one or more dedicated hardware circuits that execute the remaining processes of the various processes.

[0141] It should be noted that the expression "at least one" used in this specification means "one or more" of the desired options. As an example, the expression "at least one" used in this specification means "only one option" or "both of two options" if the number of options is two. As another example, the expression "at least one" used in this specification means "only one option" or "any combination of two or more options" if the number of options is three or more.

Claims

1. A braking device applied to a vehicle that generates a braking force according to wheel pressure, which is hydraulic pressure in a wheel cylinder, comprising: a hydraulic pressure generating device, which is an electric cylinder having an electric motor and an output port, and configured so that the discharge of brake fluid from the output port can be adjusted by adjusting the motor rotation angle, which is the rotation angle of the electric motor; a hydraulic pressure generating device having a servo pressure sensor that detects the servo pressure, which is the discharge pressure of the brake fluid of the electric cylinder, and a supply flow path through which brake fluid flows toward the wheel cylinder when the servo pressure increases; a brake actuator having a connecting flow path that connects the supply flow path and the wheel cylinder, and a holding valve, which is a normally open solenoid valve, installed in the connecting flow path; and a control device, wherein the hydraulic pressure generating device is configured to generate the wheel pressure in the wheel cylinder according to the servo pressure, and the brake actuator is configured so that the supply of brake fluid from the hydraulic pressure generating device to the wheel cylinder can be restricted by closing the holding valve, and the control device A braking device configured to derive a target rotation angle that is a target for the motor rotation angle by feedback control based on the deviation between a servo pressure detection value that is a detection value of the servo pressure sensor and a target servo pressure that is a target for the servo pressure, and to drive the electric motor based on the target rotation angle, wherein the control device is further configured to lower the gain of the feedback control when the brake actuator is operated by braking control that involves closing the holding valve, compared to when this is not the case.

2. A braking device according to claim 1, wherein the braking control is a first braking control, the control device is capable of implementing a second braking control that may cause the rate of increase in the wheel pressure to be equal to or greater than a judgment speed, and the control device is further configured to, during implementation of the second braking control, when it is determined that the rate of increase in the wheel pressure is equal to or greater than the judgment speed, make the gain higher than when it is determined that the rate of increase is less than the judgment speed.

3. The braking device according to claim 2, wherein the second braking control is a control that may close at least one of the plurality of holding valves, and the control device is further configured to, even when at least one of the plurality of holding valves is closed during the implementation of the second braking control, if it determines that the rate of increase in the wheel pressure is equal to or greater than the judgment speed, make the gain higher than when it determines that the rate of increase is less than the judgment speed.

4. A braking device according to claim 2, wherein the first braking control is a control that prevents the rate of increase of the wheel pressure from exceeding the determination speed.

5. A braking device applied to a vehicle in which a braking force is generated according to wheel pressure, which is the hydraulic pressure in a wheel cylinder, comprising: a hydraulic pressure generating device, which is an electric cylinder having an electric motor and an output port, and configured so that servo pressure, which is the discharge pressure of brake fluid from the output port, can be adjusted by adjusting motor torque, which is the output torque of the electric motor; a hydraulic pressure generating device having a servo pressure sensor that detects the servo pressure and a supply flow path through which brake fluid flows toward the wheel cylinder when the servo pressure increases; a brake actuator having a connecting flow path that connects the supply flow path and the wheel cylinder and a holding valve that is a normally open solenoid valve installed in the connecting flow path; and a control device, wherein the hydraulic pressure generating device is configured to generate the wheel pressure in the wheel cylinder according to the servo pressure, and the brake actuator is configured so that the supply of brake fluid from the hydraulic pressure generating device to the wheel cylinder can be restricted by closing the holding valve, and the control device a control device for controlling the brake actuator based on a brake control that closes the brake valve, the control device being further configured to vary a differential gain of the feedback control in accordance with the operating state of the brake valve, when the brake actuator is operated by brake control that involves closing the brake valve; 6. The braking device according to claim 5, wherein the control device is further configured to lower the differential gain when the holding valve is closed during execution of the braking control compared to when the holding valve is open.

7. A braking device as set forth in claim 5, wherein the wheel cylinder is one of a plurality of wheel cylinders, the retention valve is one of a plurality of retention valves corresponding to the plurality of wheel cylinders, and the control device is further configured to lower the differential gain when all of the plurality of retention valves are closed during execution of the braking control compared to when at least one of the plurality of retention valves is open.

8. A braking device as claimed in any one of claims 5 to 7, wherein the braking control is a first braking control, the control device is capable of implementing a second braking control that may cause the rate of increase in the wheel pressure to be equal to or greater than a judgment speed, and the control device is further configured to, when it is determined that the rate of increase in the wheel pressure is equal to or greater than the judgment speed during implementation of the second braking control, make at least one of the proportional gain and the integral gain of the feedback control higher than when it is determined that the rate of increase is less than the judgment speed.

9. A braking device as described in claim 8, wherein the second braking control is a control that may close at least one of the plurality of holding valves, and the control device is further configured to, even when at least one of the plurality of holding valves is closed during implementation of the second braking control, if it determines that the rate of increase in the wheel pressure is equal to or greater than the judgment speed, make at least one of the proportional gain and integral gain of the feedback control higher than when it determines that the rate of increase is less than the judgment speed.

10. A braking device according to claim 8, wherein the first braking control is a control that prevents the rate of increase of the wheel pressure from exceeding the determination speed.

11. A control method for a braking device applied to a vehicle in which a braking force is generated according to wheel pressure, which is hydraulic pressure in a wheel cylinder, the braking device comprising: a hydraulic pressure generating device, which is an electric cylinder having an electric motor and an output port, and configured so that the discharge of brake fluid from the output port can be adjusted by adjusting the motor rotation angle, which is the rotation angle of the electric motor; a hydraulic pressure generating device having a servo pressure sensor that detects the servo pressure, which is the discharge pressure of the brake fluid of the electric cylinder, and a supply flow path through which brake fluid flows toward the wheel cylinder when the servo pressure increases; a connecting flow path that connects the supply flow path and the wheel cylinder, and a brake actuator having a holding valve, which is a normally open solenoid valve, installed in the connecting flow path; the hydraulic pressure generating device is configured to generate the wheel pressure in the wheel cylinder according to the servo pressure; and the brake actuator is configured so that the supply of brake fluid from the hydraulic pressure generating device to the wheel cylinder can be restricted by closing the holding valve; and the control method comprises: A method for controlling a braking device, comprising: deriving a target rotation angle that is a target for the motor rotation angle by feedback control based on a deviation between a servo pressure detection value that is a detection value of the servo pressure sensor and a target servo pressure that is a target for the servo pressure; driving the electric motor based on the target rotation angle; and when the brake actuator is operated by braking control that involves closing the holding valve, lowering a gain of the feedback control compared to when this is not the case.

12. A control method for a braking device applied to a vehicle in which a braking force is generated according to wheel pressure, which is hydraulic pressure in a wheel cylinder, the braking device comprising: a hydraulic pressure generating device, which is an electric cylinder having an electric motor and an output port, and configured to be able to adjust servo pressure, which is the discharge pressure of brake fluid from the output port, by adjusting motor torque, which is the output torque of the electric motor; a hydraulic pressure generating device having a servo pressure sensor that detects the servo pressure and a supply flow path through which brake fluid flows toward the wheel cylinder when the servo pressure increases; a connecting flow path that connects the supply flow path and the wheel cylinder, and a brake actuator having a holding valve, which is a normally open solenoid valve, installed in the connecting flow path; the hydraulic pressure generating device is configured to generate the wheel pressure in the wheel cylinder according to the servo pressure; and the brake actuator is configured to be able to regulate the supply of brake fluid from the hydraulic pressure generating device to the wheel cylinder by closing the holding valve; and the control method comprises: A method for controlling a braking device, comprising: deriving a target torque that is a target for the motor torque by performing feedback control based on a deviation between a servo pressure detection value that is a detection value of the servo pressure sensor and a target servo pressure that is a target for the servo pressure; driving the electric motor based on the target torque; and, when the brake actuator is operated by braking control that involves closing the retention valve, varying a differential gain of the feedback control in accordance with the operating state of the retention valve.

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