Braking device

Abstract

To suppress generation of vibration in a pressure regulator during vehicle braking.SOLUTION: A braking device 100 comprises a master cylinder 30, a pressurizing unit 71, a second pressure regulator 78, and a first pressure regulator 77. Master chambers Rm1, Rm2 are formed in a cylinder 31 of the master cylinder 30 by master pistons 37, 38. In a situation where wheel pressure is generated by an increase in hydraulic pressure of the master chambers Rm1, Rm2 following the operation of the pressurizing unit 71 and the second pressure regulator 78, a control device 200 of the braking device 100 restricts a decrease in the hydraulic pressure of the master chambers Rm1, Rm2 when a request value of braking force is increased or maintained.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a braking device applied to a vehicle in which a braking force corresponding to hydraulic pressure in a wheel cylinder is generated at a wheel. [Background technology]

[0002] Patent Document 1 discloses an example of a braking device including a master cylinder, a pressurizing unit, and a pressure regulating valve. The master cylinder includes a master piston and an input piston connected to a brake pedal. A partition member is disposed between the master piston and the input piston in the cylinder, dividing the space between the master piston and the input piston into two chambers. One of the two chambers is a servo chamber divided by the master piston and the partition member, while the other is a separated chamber divided by the input piston and the partition member.

[0003] In a braking system, when high-pressure brake fluid generated by a pressurizing unit is supplied to a servo chamber, the hydraulic pressure in the servo chamber increases. This causes the master piston to move forward in response to the increased hydraulic pressure in the servo chamber. This increases the hydraulic pressure in the master chamber, causing brake fluid to be supplied from the master chamber to the wheel cylinders via a supply line. This increases the wheel pressure, which is the hydraulic pressure in the wheel cylinders, and generates braking force on the wheels. At this time, the control unit of the braking system operates a pressure regulating valve to adjust the hydraulic pressure of the brake fluid supplied to the servo chamber. In other words, by operating the pressure regulating valve, the control unit can control the hydraulic pressure in the master chamber and the wheel pressure in the master cylinder.

[0004] The braking device of Patent Document 1 further includes a brake actuator provided in the supply flow path. The brake actuator is configured to be able to adjust the wheel pressure regardless of the operation of the pressurizing unit and the pressure regulating valve. The wheel pressure generated by the operation of the pressurizing unit and the pressure regulating valve is referred to as the "upstream wheel pressure," and the wheel pressure generated by the operation of the brake actuator is referred to as the "downstream wheel pressure." The proportion of the wheel pressure that is accounted for by the upstream wheel pressure is referred to as the "first proportion," and the proportion of the wheel pressure that is accounted for by the downstream wheel pressure is referred to as the "second proportion."

[0005] When sudden braking is required, the control unit of the braking device operates the pressurizing unit, the pressure regulating valve, and the brake actuator so that the first rate is greater than the second rate. In this state, when the rate of increase of the target wheel pressure, which is the target value of the wheel pressure, falls below a predetermined rate, the control unit performs switching control to switch the upstream wheel pressure to the downstream wheel pressure so that the second rate is greater than the first rate. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2018-47807 Summary of the Invention [Problem to be solved by the invention]

[0007] After the above-described switching control is performed, the control unit may operate the pressurizing unit and the pressure regulating valve so that the first ratio increases again. When the pressure regulating valve is activated to increase the hydraulic pressure in the master chamber of the master cylinder, high-pressure brake fluid generated by the pressurizing unit passes through the pressure regulating valve. At this time, the opening of the pressure regulating valve, i.e., the position of the plunger relative to the valve seat within the pressure regulating valve, is adjusted by adjusting the magnitude of the current flowing through the pressure regulating valve's solenoid. The closer the distance between the valve seat and the plunger, the more difficult it is for the high-pressure brake fluid generated by the pressurizing unit to pass through the pressure regulating valve. As a result, the hydraulic pressure of the brake fluid passing through the pressure regulating valve decreases. When high-pressure brake fluid passes through the pressure regulating valve in this way, the high-pressure brake fluid presses the plunger of the pressure regulating valve, which may cause the plunger to vibrate within the pressure regulating valve. If the plunger vibrates within the pressure regulating valve, the pressure regulating valve will generate abnormal noise. [Means for solving the problem]

[0008] A braking device for solving the above problems is applied to a vehicle in which a braking force is generated at a wheel corresponding to wheel pressure, which is hydraulic pressure in a wheel cylinder. The braking device includes a master cylinder having a master chamber, a pressurizing unit for supplying high-pressure brake fluid, a pressure regulating valve for adjusting the hydraulic pressure of the brake fluid supplied from the pressurizing unit and supplying the adjusted brake fluid to the master cylinder to increase the hydraulic pressure in the master chamber, a supply flow path connected to the master chamber and serving as a brake fluid path for supplying brake fluid from the master chamber to the wheel cylinder, a brake actuator connected to the supply flow path and configured to adjust the wheel pressure, and a control device for controlling the pressurizing unit, the pressure regulating valve, and the brake actuator. The master cylinder includes a cylinder, an input piston connected to a brake pedal and moving forward when the brake pedal is operated, and moving backward, which is the opposite direction to the forward direction, when the brake pedal is operated, and a master piston located in the cylinder, further forward than the input piston, and defining the master chamber. The control device limits the decrease in the hydraulic pressure in the master chamber when the required braking force value increases or is maintained under conditions in which the wheel pressure is generated by an increase in hydraulic pressure in the master chamber due to the operation of the pressurizing unit and the pressure regulating valve. [Effects of the Invention]

[0009] The braking device has an effect of suppressing the occurrence of vibrations in the pressure regulating valve when braking the vehicle. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of a vehicle on which a braking device according to an embodiment is mounted. [Figure 2] FIG. 2 is a schematic diagram showing the configuration of a second hydraulic circuit provided in the braking device of FIG. [Figure 3] FIG. 3 is a block diagram showing an outline of a control device provided in the braking device of FIG. [Figure 4] FIG. 4 is a flowchart showing a series of processes executed by the control device shown in FIG. [Figure 5] FIG. 5 is a timing chart when the vehicle is braking. [Figure 6] FIG. 6 is a timing chart showing the timing of vehicle braking in a modified example of the braking device. DETAILED DESCRIPTION OF THE INVENTION

[0011] An embodiment of a braking device mounted on a vehicle will be described below with reference to FIGS. 1 shows a vehicle equipped with a braking device 100. The vehicle has two front wheels 11f and two rear wheels 11r. The vehicle also has friction brakes 15, the same number as the wheels, and a regenerative device 300 configured to be able to adjust the regenerative braking force FxRR generated at the two rear wheels 11r.

[0012] <Regenerative device> The regenerative device 300 includes a motor generator 301 and a regenerative control unit 302 that controls the motor generator 301. When the motor generator 301 functions as an electric motor, a driving force is transmitted from the motor generator 301 to the multiple rear wheels 11r. On the other hand, when the motor generator 301 functions as a generator, a regenerative braking force FxRR corresponding to the amount of power generated by the motor generator 301 is generated at the multiple rear wheels 11r.

[0013] An example of the regeneration control unit 302 is an electronic control device. In this case, the regeneration control unit 302 has a CPU and a memory. The memory stores a control program executed by the CPU. The regeneration control unit 302 operates the motor generator 301 by the CPU executing the control program.

[0014] The regenerative control unit 302 is configured to be able to send and receive various information to and from a control device 200 of the braking device 100, which will be described later, via an in-vehicle network. As will be described in detail later, when braking the vehicle, the regenerative control unit 302 adjusts the regenerative braking force FxRR by sending and receiving information to and from the control device 200.

[0015] <Friction brake> The plurality of friction brakes 15 each generate a friction braking force at a corresponding wheel. The friction brake 15 has a wheel cylinder 16, a rotating body 17, and a friction portion 18. Because the rotating body 17 rotates together with the wheel, the friction portion 18 presses against the rotating body 17, generating a friction braking force at the wheel. The force pressing the friction portion 18 against the rotating body 17 increases as the wheel pressure Pw, which is the hydraulic pressure in the wheel cylinder 16, increases. Therefore, the friction brake 15 can generate a greater friction braking force at the wheel as the wheel pressure Pw increases.

[0016] The friction braking force generated at the rear wheels 11r is called the "rear wheel friction braking force FxMR." The friction braking force generated at the front wheels 11f is called the "front wheel friction braking force FxMF." When the total braking force generated at the rear wheels 11r is called the "rear wheel braking force FxR," the sum of the regenerative braking force FxRR generated at the rear wheels 11r and the rear wheel friction braking force FxMR becomes the rear wheel braking force FxR. When the total braking force generated at the front wheels 11f is called the "front wheel braking force FxF," the front wheel braking force FxF is equal to the front wheel friction braking force FxMF. When the vehicle braking force is called the "vehicle braking force Fx," the sum of the rear wheel braking force FxR and the front wheel braking force FxF becomes the vehicle braking force Fx. Furthermore, the sum of the rear wheel friction braking force FxMR and the front wheel friction braking force FxMF is called the "vehicle friction braking force FxM."

[0017] <Brake device> The braking device 100 adjusts the vehicle braking force Fx by controlling the wheel pressure Pw of the plurality of wheel cylinders 16. The braking device 100 includes a hydraulic pressure generating device 20, a brake actuator 80, and a control device 200. The hydraulic pressure generating device 20 and the brake actuator 80 are each configured to be able to control the wheel pressure Pw of the plurality of wheel cylinders 16. The control device 200 controls the operation of the hydraulic pressure generating device 20 and the brake actuator 80.

[0018] <Liquid pressure generator> The hydraulic pressure generating device 20 includes a reservoir tank 21, a brake pedal 22, a stroke simulator 23, a master cylinder 30, a plurality of brake fluid flow paths 51, 52, 53, 54, and 55, a plurality of control valves 61 and 62, a plurality of hydraulic pressure sensors 65 and 66, and a pressure regulating device 70. The hydraulic pressure sensors 65 and 66 detect the hydraulic pressure of the brake fluid. Each of the hydraulic pressure sensors 65 and 66 outputs a detection signal corresponding to the detected hydraulic pressure to the control device 200.

[0019] The reservoir tank 21 stores brake fluid and is open to the atmosphere. The stroke simulator 23 can generate a reaction force in response to the operation of the brake pedal 22 by the driver.

[0020] <Master cylinder> The master cylinder 30 includes a cylinder 31 and a boot 33. The cylinder 31 has a bottom wall 311 and a cylindrical peripheral wall 312 extending from the bottom wall 311 along the axis of the bottom wall 311. The cylinder 31 may be formed of a single member or multiple members. The boot 33 is attached to a rear end portion 31a of the cylinder 31.

[0021] An input piston 35, a plurality of master pistons 37, 38, a partition member 39, and a plurality of master springs 41, 42 are provided in the internal space formed by the cylinder 31 and the boot 33.

[0022] The brake pedal 22 is connected to the input piston 35. The input piston 35 moves in response to the driver's braking operation. The amount of operation of the brake pedal 22 by the driver is called the "braking operation amount." In this case, the direction of movement of the input piston 35 when the braking operation amount is increasing due to the braking operation is called the "forward direction Za." On the other hand, the direction of movement of the input piston 35 when the braking operation amount is decreasing due to the braking operation is called the "reverse direction Zb." The reverse direction Zb is the opposite direction to the forward direction Za.

[0023] Each of the multiple master pistons 37, 38 is positioned further in the forward direction Za than the input piston 35. Of the multiple master pistons 37, 38, the first master piston 37 is positioned further in the forward direction Za than the second master piston 38. A first master chamber Rm1 is defined by the bottom wall 311 and peripheral wall 312 of the cylinder 31 and the first master piston 37. A second master chamber Rm2 is defined by the peripheral wall 312 of the cylinder 31 and the first master piston 37 and second master piston 38. In other words, the second master chamber Rm2 is positioned further in the backward direction Zb than the first master chamber Rm1. Furthermore, within the cylinder 31, the multiple master chambers Rm1, Rm2 are not connected to each other.

[0024] The position of the master pistons 37, 38 when wheel pressure Pw is not generated in the wheel cylinders 16 is referred to as the "standby position of the master pistons 37, 38." When the master pistons 37, 38 are located in the standby position, each of the master chambers Rm1, Rm2 is in communication with the reservoir tank 21. However, when the master pistons 37, 38 move in the forward direction Za from the standby position, as shown in FIG. 1, the first master piston 37 blocks communication between the first master chamber Rm1 and the reservoir tank 21. Similarly, the second master piston 38 blocks communication between the second master chamber Rm2 and the reservoir tank 21.

[0025] The second master piston 38 has a main body 381 and a protruding portion 382 that protrudes in the backward direction Zb from the main body 381. The outer diameter of the protruding portion 382 is smaller than the outer diameter of the main body 381. A space is provided between the rear end of the protruding portion 382 and the front end of the input piston 35.

[0026] A first chamber R1 having an annular shape is defined between the peripheral wall 312 of the cylinder 31 and the main body portion 381. The first chamber R1 is not connected to any of the plurality of master chambers Rm1, Rm2. The partitioning member 39 is located further in the forward direction Za than the input piston 35. More specifically, the partitioning member 39 is located between the main body 381 of the second master piston 38 and the input piston 35. The partitioning member 39 has an annular shape. The partitioning member 39 is attached to the peripheral wall 312 of the cylinder 31 with the protruding portion 382 of the second master piston 38 passing through the space inside the partitioning member 39.

[0027] The partitioning member 39 divides the space between the second master piston 38 and the input piston 35 into two chambers. One of the two chambers is a servo chamber Rs, and the other is a separation chamber Ra. The servo chamber Rs is divided by the second master piston 38 and the partitioning member 39. More specifically, the space between the main body 381 of the second master piston 38 and the partitioning member 39 is the servo chamber Rs. The separation chamber Ra is divided by the partitioning member 39 and the input piston 35. In other words, the separation chamber Ra is located on the opposite side of the partitioning member 39 from the servo chamber Rs. Within the cylinder 31, the servo chamber Rs and the separation chamber Ra are not connected to each other.

[0028] A second chamber R2, which is an annular space, is formed in the peripheral wall 312 of the cylinder 31 radially outward of the separated chamber Ra. The second chamber R2 is located further in the backward direction Zb than the servo chamber Rs. The second chamber R2 is always in communication with the reservoir tank 21. When no braking operation is being performed, the second chamber R2 is in communication with the separated chamber Ra via a path formed in the cylinder 31. On the other hand, when the input piston 35 moves in the forward direction Za due to an increase in the amount of braking operation associated with a braking operation, communication between the second chamber R2 and the separated chamber Ra via the path is blocked.

[0029] Of the multiple master springs 41, 42, the first master spring 41 is located in the first master chamber Rm1, and the second master spring 42 is located in the second master chamber Rm2. The first master piston 37 biases the first master piston 37 in the backward direction Zb. Therefore, when the first master piston 37 moves in the forward direction Za, the first master spring 41 is elastically compressed. The second master piston 38 biases the second master piston 38 in the backward direction Zb. Therefore, when the second master piston 38 moves in the forward direction Za, the second master spring 42 is elastically compressed.

[0030] The first flow path 51 connects the first master chamber Rm1 with a first hydraulic circuit 811 of the brake actuator 80, which will be described later. The state in which the first master chamber Rm1 and the first flow path 51 are in communication with each other is maintained regardless of the position of the first master piston 37. The second flow path 52 connects the second master chamber Rm2 with a second hydraulic circuit 812 of the brake actuator 80, which will be described later. The state in which the second master chamber Rm2 and the second flow path 52 are in communication with each other is maintained regardless of the position of the second master piston 38. In other words, the first flow path 51 and the second flow path 52 correspond to "supply flow paths," which are brake fluid paths for supplying brake fluid from the master chambers Rm1, Rm2 to the wheel cylinders 16.

[0031] The third flow path 53 connects the first chamber R1 and the second chamber R2. The stroke simulator 23 is connected to the third flow path 53. A first control valve 61 is provided in a portion of the third flow path 53 between a connection point 53a with the stroke simulator 23 and a connection point with the second chamber R2. The first control valve 61 is a normally open solenoid valve.

[0032] The fourth flow path 54 connects the third flow path 53 and the separated chamber Ra. More specifically, the fourth flow path 54 connects the separated chamber Ra to a portion of the third flow path 53 between a connection point 53a with the stroke simulator 23 and the first control valve 61. A second control valve 62 is provided in the fourth flow path 54. The second control valve 62 is a normally closed solenoid valve.

[0033] The fifth flow path 55 connects the servo chamber Rs with a regulator 76 of the pressure regulating device 70, which will be described later. That is, the fifth flow path 55 corresponds to a "pressure regulating flow path" which is a brake fluid path connected to the servo chamber Rs.

[0034] The first hydraulic pressure sensor 65 detects the hydraulic pressure of the brake fluid flowing in the portion of the third flow path 53 between a connection point 53a with the stroke simulator 23 and a connection point 53b with the fourth flow path 54. The second hydraulic pressure sensor 66 detects the hydraulic pressure of the brake fluid flowing in the fifth flow path 55. Because the fifth flow path 55 is connected to the servo chamber Rs, it can be said that the second hydraulic pressure sensor 66 detects the hydraulic pressure in the servo chamber Rs. Hereinafter, the hydraulic pressure based on the detection signal of the first hydraulic pressure sensor 65 will be referred to as the "simulator pressure Psm." The hydraulic pressure based on the detection signal of the second hydraulic pressure sensor 66 will be referred to as the "servo pressure Psv."

[0035] <Pressure Regulator> The pressure regulating device 70 includes a pressurizing unit 71, a regulator 76, a first pressure regulating valve 77, and a second pressure regulating valve 78. The first pressure regulating valve 77 is a normally open linear solenoid valve. The second pressure regulating valve 78 is a normally closed linear solenoid valve.

[0036] The pressurizing unit 71 generates high-pressure brake fluid. For example, the pressurizing unit 71 includes a servo pump 73 powered by a first electric motor 72, an accumulator 74 that accumulates high-pressure brake fluid, and an accumulator pressure sensor 75. The accumulator pressure sensor 75 detects the fluid pressure in the accumulator 74. The fluid pressure based on the detection signal of the accumulator pressure sensor 75 is referred to as the "accumulator pressure Paq." In the pressurizing unit 71, when the accumulator pressure Paq falls below a predetermined pressure, brake fluid is supplied from the servo pump 73 to the accumulator 74. This allows the accumulator 74 to accumulate high-pressure brake fluid.

[0037] The regulator 76 is a mechanical regulator. High-pressure brake fluid is supplied to the regulator 76 from the accumulator 74. As described above, the regulator 76 is connected to the servo chamber Rs in the master cylinder 30 via the fifth flow path 55. Therefore, the regulator 76 can supply high-pressure brake fluid to the servo chamber Rs via the fifth flow path 55.

[0038] When brake fluid is supplied to the servo chamber Rs through the fifth flow path 55 by operation of the regulator 76, the opening of the second pressure regulating valve 78 is adjusted with the first pressure regulating valve 77 closed. The operation of the second pressure regulating valve 78 adjusts the hydraulic pressure of the brake fluid flowing into the fifth flow path 55 through the regulator 76. That is, when the hydraulic pressure in the servo chamber Rs is to be increased, the second pressure regulating valve 78 adjusts the hydraulic pressure of the brake fluid supplied from the pressurizing unit 71. Then, the brake fluid whose hydraulic pressure has been adjusted by the second pressure regulating valve 78 is supplied to the servo chamber Rs through the fifth flow path 55. That is, the first pressure regulating valve 77 can increase the hydraulic pressure in the master chambers Rm1, Rm2 by supplying the brake fluid whose hydraulic pressure has been adjusted to the master cylinder 30.

[0039] On the other hand, when the regulator 76 is operated to cause the brake fluid in the servo chamber Rs to flow out of the cylinder 31 via the fifth flow path 55, the opening of the first pressure regulating valve 77 is adjusted with the second pressure regulating valve 78 closed. By operating the first pressure regulating valve 77 in this manner, the outflow of brake fluid from the servo chamber Rs via the fifth flow path 55 is adjusted.

[0040] <Operation of the hydraulic pressure generator> The operation of the hydraulic pressure generating device 20 when the pressurizing unit 71 is activated to supply brake fluid from the hydraulic pressure generating device 20 to the plurality of wheel cylinders 16 will be described.

[0041] The first control valve 61 is opened, and the second control valve 62 is closed. This establishes communication between the first chamber R1 and the separation chamber Ra within the master cylinder 30, while disabling communication between the first chamber R1 and the reservoir tank 21. In this state, the first pressure regulating valve 77 and the second pressure regulating valve 78 of the pressurizing unit 71 operate, causing brake fluid supplied from the accumulator 74 to the regulator 76 to be supplied to the servo chamber Rs of the master cylinder 30 via the fifth flow path 55. This increases the hydraulic pressure in the servo chamber Rs, causing the master pistons 37 and 38 to move in the forward direction Za. This then disables communication between the reservoir tank 21 and the master chambers Rm1 and Rm2, increasing the hydraulic pressure in the master chambers Rm1 and Rm2. This allows brake fluid to be supplied from the first master chamber Rm1 to the wheel cylinder 16 for the front wheel 11f via the first hydraulic circuit 811 of the brake actuator 80. Similarly, brake fluid is supplied from the second master chamber Rm2 to the wheel cylinder 16 for the rear wheel 11r via the second hydraulic circuit 812 of the brake actuator 80. As a result, the wheel pressures Pw in the plurality of wheel cylinders 16 each increase.

[0042] The hydraulic pressure in the servo chamber Rs can be reduced by operating the first pressure regulating valve 77 and the second pressure regulating valve 78. When the hydraulic pressure in the servo chamber Rs is reduced by operating the first pressure regulating valve 77 and the second pressure regulating valve 78, the master pistons 37, 38 move in the rearward direction Zb. This reduces the hydraulic pressure in each of the master chambers Rm1, Rm2. This causes brake fluid to flow out of the wheel cylinders 16, thereby reducing the wheel pressure Pw in each of the wheel cylinders 16.

[0043] The operation modes of the first pressure regulating valve 77 and the second pressure regulating valve 78 are controlled by the manner of the driver's braking operation. For example, when the vehicle friction braking force FxM is increased by braking, the first pressure regulating valve 77 and the second pressure regulating valve 78 operate to increase the hydraulic pressure in the servo chamber Rs, i.e., the servo pressure Psv. At this time, a plunger in the second pressure regulating valve 78 operates based on the commanded opening for the second pressure regulating valve 78. Specifically, a current corresponding to the commanded opening flows through the solenoid of the second pressure regulating valve 78, and an electromagnetic force corresponding to the commanded opening acts on the plunger. In this state, high-pressure brake fluid supplied from the accumulator 74 flows into the housing of the second pressure regulating valve 78. Therefore, the plunger is subjected to both the electromagnetic force acting on the plunger and the force from the high-pressure brake fluid. At this time, if the force acting on the plunger from the high-pressure brake fluid is large, the plunger may vibrate.

[0044] <Braking actuator> The brake actuator 80 is configured to be able to individually adjust the wheel pressures Pw of the multiple wheel cylinders 16, independent of the hydraulic pressure generator 20. The brake actuator 80 has a first hydraulic pressure circuit 811 and a second hydraulic pressure circuit 812. The first hydraulic pressure circuit 811 is connected to the first flow path 51 and has two wheel cylinders 16 for the front wheels 11f connected to it. The second hydraulic pressure circuit 812 is connected to the second flow path 52 and has two wheel cylinders 16 for the rear wheels 11r connected to it.

[0045] As shown in FIG. 2, the second hydraulic circuit 812 has a connecting flow path 82 connected to the second flow path 52, and a differential pressure control valve 83 installed in the connecting flow path 82. The connecting flow path 82 is a brake fluid path connecting the two wheel cylinders 16 for the rear wheels 11r to the second flow path 52. The differential pressure control valve 83 is a normally open linear solenoid valve. The differential pressure control valve 83 can adjust the differential pressure between the portion of the connecting flow path 82 on the second flow path 52 side and the portion on the wheel cylinder 16 side. For example, the differential pressure control valve 83 can generate a larger differential pressure as the current flowing through its solenoid increases.

[0046] The portion of the connecting flow path 82 closer to the wheel cylinder 16 than the differential pressure control valve 83 branches into two paths 82a and 82b. The path 82a is connected to one of the wheel cylinders 16 for the two rear wheels 11r, while the path 82b is connected to the other of the wheel cylinders 16 for the two rear wheels 11r. A holding valve 84 is installed in each of the two paths 82a and 82b. The holding valve 84 is a normally open solenoid valve. When the holding valve 84 is closed, the holding valve 84 restricts an increase in the wheel pressure Pw in the wheel cylinder 16 for the rear wheel 11r.

[0047] The second hydraulic circuit 812 has a reduced pressure reservoir 85 that stores brake fluid, and a reduced pressure fluid path 86 connected to the reduced pressure reservoir 85. The reduced pressure fluid path 86 is a brake fluid path that connects the reduced pressure reservoir 85 to the portions of the paths 82a and 82b that are closer to the wheel cylinder 16 than the retention valve 84. A pressure reducing valve 87, which is a normally closed solenoid valve, is installed in each of the portions of the reduced pressure fluid path 86 that are connected to the path 82a and the path 82b.

[0048] The second hydraulic circuit 812 has a pump 89 and a return fluid path 90. The pump 89 is powered by a second electric motor 88. The pump 89 pumps up the brake fluid in the reduced-pressure reservoir 85 and discharges the brake fluid to a portion of the connecting flow path 82 between the differential pressure control valve 83 and the holding valve 84. The return fluid path 90 is a brake fluid path that is connected to the reduced-pressure reservoir 85 and a portion of the connecting flow path 82 that is closer to the second flow path 52 than the differential pressure control valve 83.

[0049] The configuration of the first hydraulic pressure circuit 811 is substantially the same as the configuration of the second hydraulic pressure circuit 812. Therefore, a detailed description of the configuration of the first hydraulic pressure circuit 811 will be omitted here. The first hydraulic pressure circuit 811 includes a differential pressure control valve 83, a plurality of holding valves 84 and a pressure reducing valve 87, a pressure reducing reservoir 85, and a pump 89 powered by a second electric motor 88.

[0050] <Control device> The control device 200 will be described with reference to FIGS. Detection signals from a plurality of sensors are input to the control device 200. The plurality of sensors includes a manipulation amount sensor 221 in addition to a plurality of hydraulic pressure sensors 65, 66, 75. The manipulation amount sensor 221 detects the amount of braking manipulation. Then, the control device 200 operates the hydraulic pressure generating device 20 and the brake actuator 80 based on the detection signals from the plurality of sensors 65, 66, 75, 221.

[0051] The control device 200 includes a plurality of electronic control devices. Hereinafter, the electronic control devices are referred to as "ECUs." Each of the plurality of ECUs is configured to be able to send and receive various information and commands via an in-vehicle network 230. Of the plurality of ECUs, a first ECU 210 controls the hydraulic pressure generating device 20, and a second ECU 220 controls the brake actuator 80.

[0052] Each of the multiple ECUs 210, 220 has a CPU, a first memory, and a second memory. The first memory stores a control program executed by the CPU. The second memory stores the calculation results of the CPU. The CPU of the first ECU 210 is CPU 211. The first memory of the first ECU 210 is first memory 212. The second memory of the first ECU 210 is second memory 213.

[0053] The braking device 100 can generate the wheel pressure Pw by operating the hydraulic pressure generating device 20. The braking device 100 can also generate the wheel pressure Pw by operating the brake actuator 80. Hereinafter, the wheel pressure Pw generated by operation of the hydraulic pressure generating device 20 will be referred to as the "upstream wheel pressure Pw1." The wheel pressure Pw generated by operation of the brake actuator 80 will be referred to as the "downstream wheel pressure Pw2." Increasing the upstream wheel pressure Pw1 by operation of the hydraulic pressure generating device 20 will also be referred to as "upstream pressurization." Increasing the downstream wheel pressure Pw2 by operation of the brake actuator 80 will also be referred to as "downstream pressurization."

[0054] <Braking control> An example of a series of processes executed by the control device 200 when adjusting the vehicle friction braking force FxM will be described with reference to Fig. 4. When the vehicle is braking, the series of processes shown in Fig. 4 is repeatedly executed at every predetermined control cycle.

[0055] In step S11, the control device 200 derives a requested vehicle braking force FxRq, which is a requested value of the vehicle braking force Fx. When the driver is performing a braking operation, the control device 200 derives a braking force corresponding to the amount of braking operation as the requested vehicle braking force FxRq. In addition, deceleration of the vehicle may be requested from another control device. In this case, the control device 200 derives a braking force corresponding to the deceleration of the vehicle requested by the other control device as the requested vehicle braking force FxRq.

[0056] In the following step S13, the control device 200 determines whether or not a condition for prioritizing upstream pressurization over downstream pressurization is met. In the braking system 100, when the wheel pressure Pw is increased, the responsiveness of the hydraulic pressure generating device 20 is higher than the responsiveness of the brake actuator 80. On the other hand, the accuracy of adjusting the downstream wheel pressure Pw2 by the brake actuator 80 is higher than the accuracy of adjusting the upstream wheel pressure Pw1 by the hydraulic pressure generating device 20. Therefore, when the rate of increase in the required vehicle braking force FxRq is relatively high, it is preferable to prioritize upstream pressurization over downstream pressurization.

[0057] Therefore, in the control device 200, for example, a judgment increase speed ΔFxth is set as a criterion for determining whether or not the increase speed ΔFxRq of the required vehicle braking force FxRq is large. If the increase speed ΔFxRq is equal to or greater than the judgment increase speed ΔFxth, it is determined that the condition for prioritizing upstream pressurization over downstream pressurization is met. On the other hand, if the increase speed ΔFxRq is less than the judgment increase speed ΔFxth, it is determined that the condition for prioritizing upstream pressurization over downstream pressurization is not met.

[0058] In step S13, if the control device 200 determines that the condition for prioritizing upstream pressurization over downstream pressurization is met (S13: YES), the control device 200 proceeds to step S51. On the other hand, if the control device 200 determines that the condition for prioritizing upstream pressurization over downstream pressurization is not met (S13: NO), the control device 200 proceeds to step S15.

[0059] In step S15, the control device 200 derives a required frictional braking force FxMTr based on the required vehicle braking force FxRq. The required frictional braking force FxMTr is a required value of the vehicle frictional braking force FxM. For example, the control device 200 derives the required frictional braking force FxMTr by subtracting the regenerative braking force FxRR from the required vehicle braking force FxRq.

[0060] In the following step S17, the control device 200 derives a target wheel pressure PwTr, which is a target value of the wheel pressure Pw, based on the required frictional braking force FxMTr. For example, the control device 200 derives the target wheel pressure PwTr so that the target wheel pressure PwTr increases as the required frictional braking force FxMTr increases.

[0061] In the next step S19, the control device 200 determines whether the upstream wheel pressure Pw1 is generated. If the control device 200 determines that the upstream wheel pressure Pw1 is generated (S19: YES), the control device 200 proceeds to step S31. On the other hand, if the control device 200 determines that the upstream wheel pressure Pw1 is not generated (S19: NO), the control device 200 proceeds to step S21.

[0062] In step S21, the control device 200 sets a target upstream wheel pressure Pw1Tr and a target downstream wheel pressure Pw2Tr based on the target wheel pressure PwTr. The target upstream wheel pressure Pw1Tr is a target value for the upstream wheel pressure Pw1. The target downstream wheel pressure Pw2Tr is a target value for the downstream wheel pressure Pw2. For example, the control device 200 sets the target downstream wheel pressure Pw2Tr to the product of the target wheel pressure PwTr and a predetermined coefficient α. The predetermined coefficient α is set to a value greater than 0 (zero) and less than 1. In this case, the control device 200 sets the wheel pressure obtained by subtracting the target downstream wheel pressure Pw2Tr from the target wheel pressure PwTr to the target upstream wheel pressure Pw1Tr. Thereafter, the control device 200 proceeds to step S37.

[0063] In step S31, the control device 200 determines whether the target wheel pressure PwTr is decreasing. If the control device 200 determines that the target wheel pressure PwTr is decreasing (S31: YES), the process proceeds to step S33. On the other hand, if the control device 200 determines that the target wheel pressure PwTr is not decreasing (S31: NO), the process proceeds to step S35.

[0064] In step S33, the control device 200 reduces the target upstream wheel pressure Pw1Tr and the target downstream wheel pressure Pw2Tr. At this time, the control device 200 reduces the target upstream wheel pressure Pw1Tr and the target downstream wheel pressure Pw2Tr so that the sum of the target upstream wheel pressure Pw1Tr and the target downstream wheel pressure Pw2Tr remains equal to the target wheel pressure PwTr. Then, the control device 200 proceeds to step S37.

[0065] In step S35, the control device 200 sets the target downstream wheel pressure Pw2Tr after limiting the decrease in the target upstream wheel pressure Pw1Tr. In this embodiment, the control device 200 limits the decrease in the target upstream wheel pressure Pw1Tr by maintaining the target upstream wheel pressure Pw1Tr. For example, the control device 200 derives the wheel pressure obtained by subtracting the target upstream wheel pressure Pw1Tr from the target wheel pressure PwTr as the target downstream wheel pressure Pw2Tr. Therefore, when the target wheel pressure PwTr is increasing, the control device 200 can increase the target downstream wheel pressure Pw2Tr while maintaining the target upstream wheel pressure Pw1Tr. Then, the control device 200 proceeds to step S37.

[0066] In step S37, the control device 200 operates the hydraulic pressure generator 20 based on the target upstream wheel pressure Pw1Tr. Specifically, the first ECU 210 of the control device 200 sets a servo pressure corresponding to the target upstream wheel pressure Pw1Tr to the target servo pressure PsvTr. The target servo pressure PsvTr is a target value for the servo pressure Psv. The first ECU 210 drives the first pressure regulating valve 77 and the second pressure regulating valve 78 so that the servo pressure Psv becomes the target servo pressure PsvTr.

[0067] In the next step S39, the control device 200 operates the brake actuator 80 based on the target downstream wheel pressure Pw2Tr. Specifically, the second ECU 220 of the control device 200 drives the second electric motor 88 to discharge brake fluid from the pump 89, while driving the differential pressure control valve 83. At this time, the second ECU 220 applies a current corresponding to the target downstream wheel pressure Pw2Tr to the solenoid of the differential pressure control valve 83.

[0068] In the following step S41, the control device 200 determines whether or not the downstream wheel pressure Pw2 can be adjusted. As described above, the downstream wheel pressure Pw2 is adjusted with higher accuracy than the upstream wheel pressure Pw1. Therefore, when regenerative cooperative control is performed in the braking device 100, the downstream wheel pressure Pw2 is adjusted in accordance with an increase or decrease in the regenerative braking force FxRR. In other words, if it is not possible to increase or decrease the downstream wheel pressure Pw2, the braking device 100 cannot perform regenerative cooperative control.

[0069] Therefore, in step S41, the control device 200 determines that it is not possible to adjust the downstream wheel pressure Pw2 if at least one of the following conditions (A1) and (A2) is met.

[0070] (A1) The target downstream wheel pressure Pw2Tr is 0 (zero). (A2) An abnormality occurs in at least one of the brake actuator 80 and the second ECU 220.

[0071] When the control device 200 determines that the downstream wheel pressure Pw2 is adjustable (S41: YES), the process proceeds to step S43. On the other hand, when the control device 200 determines that the downstream wheel pressure Pw2 is not adjustable (S41: NO), the process proceeds to step S59.

[0072] In step S43, the control device 200 permits the regenerative control unit 302 to generate the regenerative braking force FxRR. After that, the control device 200 temporarily ends the series of processes.

[0073] In step S51, the control device 200 derives a required frictional braking force FxMTr based on the required vehicle braking force FxRq. For example, the control device 200 sets the required vehicle braking force FxRq to the required frictional braking force FxMTr. In other words, if the condition for prioritizing upstream pressure application over downstream pressure application is met, the regenerative cooperative control is not performed.

[0074] In the following step S53, the control device 200 derives the target wheel pressure PwTr based on the required friction braking force FxMTr, similar to the above step S17. In the next step S55, the control device 200 sets a target upstream wheel pressure Pw1Tr and a target downstream wheel pressure Pw2Tr. For example, the control device 200 sets the target upstream wheel pressure Pw1Tr to the target wheel pressure PwTr, and sets the target downstream wheel pressure Pw2Tr to 0 (zero).

[0075] Then, in step S57, the control device 200 operates the hydraulic pressure generating device 20 based on the target upstream wheel pressure Pw1Tr, similar to step S37. Then, the control device 200 proceeds to step S59.

[0076] In step S59, the control device 200 prohibits the regenerative control unit 302 from generating the regenerative braking force FxRR. After that, the control device 200 temporarily ends the series of processes.

[0077] <Actions and Effects of This Embodiment> The operation and effects of this embodiment will be described with reference to FIG. As shown in (A), (B), (C), and (D) of FIG. 5, at timing t10, a braking request is issued to the vehicle, for example, when the driver starts a braking operation. Then, the control device 200 increases the requested vehicle braking force FxRq in accordance with the braking request. In the example shown in FIG. 5, during the period from timing t10 ​​to timing t11, the rate of increase ΔFxRq of the requested vehicle braking force is equal to or greater than the judgment rate of increase ΔFxth. In this case, sudden braking is requested of the vehicle. Therefore, the control device 200 determines that the conditions for prioritizing upstream pressure increase over downstream pressure increase are met.

[0078] Therefore, the control device 200 derives the wheel pressure Pw corresponding to the required vehicle braking force FxRq as the target upstream wheel pressure Pw1Tr. Then, the control device 200 operates the pressurizing unit 71, the first pressure regulating valve 77, and the second pressure regulating valve 78 so that the servo pressure Psv increases in response to an increase in the target upstream wheel pressure Pw1Tr.

[0079] As a result, the servo pressure Psv increases at a speed corresponding to the target upstream wheel pressure Pw1Tr. In this case, the hydraulic pressure in the servo chamber Rs increases, causing the master pistons 37, 38 to move in the forward direction Za. This increases the hydraulic pressure in the first master chamber Rm1 and the second master chamber Rm2, and brake fluid is supplied from the first master chamber Rm1 and the second master chamber Rm2 to the wheel cylinders 16. As a result, as shown in FIG. 5B, the upstream wheel pressure Pw1 is generated in the wheel cylinders 16, and the wheel pressure Pw in the wheel cylinders 16 increases.

[0080] 5(C), the target downstream wheel pressure Pw2Tr is 0 (zero), so the downstream wheel pressure Pw2 is not generated in the plurality of wheel cylinders 16. In the example shown in Fig. 5, the downstream wheel pressure Pw2 is not generated during the period from timing t10 ​​to timing t12. Therefore, during this period, the control device 200 prohibits the generation of the regenerative braking force FxRR, as shown in Fig. 5(D).

[0081] From timing t12, the required vehicle braking force FxRq is reduced by, for example, reducing the braking operation amount. Furthermore, the target upstream wheel pressure Pw1Tr is equal to the target wheel pressure PwTr. Therefore, the control device 200 reduces the target wheel pressure PwTr and the target upstream wheel pressure Pw1Tr. The control device 200 then operates the pressurizing unit 71, the first pressure regulating valve 77, and the second pressure regulating valve 78 so that the servo pressure Psv decreases in accordance with the decrease in the target upstream wheel pressure Pw1Tr.

[0082] Then, in response to the decrease in the servo pressure Psv, the wheel pressures Pw in the plurality of wheel cylinders 16, that is, the upstream wheel pressure Pw1, are decreased as shown in FIG. 5(B). The required vehicle braking force FxRq increases again from timing t13 thereafter. In the example shown in FIG. 5, the required vehicle braking force FxRq increases from timing t13 to timing t15. During the period from timing t13 to timing t14, the rate of increase ΔFxRq of the required vehicle braking force is equal to or greater than the criterion rate of increase ΔFxth. Therefore, the control device 200 determines that the condition for prioritizing upstream pressurization over downstream pressurization is met. The control device 200 then derives the wheel pressure Pw corresponding to the required vehicle braking force FxRq as the target upstream wheel pressure Pw1Tr. The control device 200 then operates the pressurization unit 71, the first pressure regulating valve 77, and the second pressure regulating valve 78 so that the servo pressure Psv increases in accordance with the increase in the target upstream wheel pressure Pw1Tr.

[0083] 5, the required vehicle braking force FxRq is maintained from timing t11 to timing t12, so the increase rate ΔFxRq of the required vehicle braking force is less than the determined increase rate ΔFxth. At timing t11, the target upstream wheel pressure Pw1Tr is equal to the target wheel pressure PwTr, so the target downstream wheel pressure Pw2Tr is 0 (zero). In other words, the target downstream wheel pressure Pw2Tr is lower than the first product, which is the product of the target wheel pressure PwTr and the predetermined coefficient α.

[0084] Consider a comparative example in which the target downstream wheel pressure Pw2Tr and the target upstream wheel pressure Pw1Tr are set so that the target downstream wheel pressure Pw2Tr becomes the first product during the period from timing t11 to timing t12. In this comparative example, when the condition for prioritizing upstream pressurization over downstream pressurization is not met, the target downstream wheel pressure Pw2Tr and the target upstream wheel pressure Pw1Tr are set so that the downstream ratio is greater than the upstream ratio. The upstream ratio is the ratio of the upstream wheel pressure Pw1 to the wheel pressure Pw. The downstream ratio is the ratio of the downstream wheel pressure Pw2 to the wheel pressure Pw. On the other hand, in this comparative example, when the condition for prioritizing upstream pressurization over downstream pressurization is met, the target downstream wheel pressure Pw2Tr and the target upstream wheel pressure Pw1Tr are set so that the upstream ratio is greater than the downstream ratio.

[0085] Therefore, during the period from timing t11 to timing t12, the target downstream wheel pressure Pw2Tr is increased while the target upstream wheel pressure Pw1Tr is decreased. As a result, the upstream wheel pressure Pw1 is replaced with the downstream wheel pressure Pw2 while the wheel pressure Pw is maintained. In this case, in the comparative example, the downstream wheel pressure Pw2 is generated from timing t11, making it possible to permit the generation of the regenerative braking force FxRR.

[0086] However, at timing t13 when the increase in the required vehicle braking force FxRq begins, the target upstream wheel pressure Pw1Tr is lower than the target wheel pressure PwTr. Therefore, from timing t13 to timing t14, the target upstream wheel pressure Pw1Tr and the target downstream wheel pressure Pw2Tr are set so that the upstream proportion increases while the downstream proportion decreases. In this case, the target upstream wheel pressure Pw1Tr is increased while the target downstream wheel pressure Pw2Tr is decreased so that the difference between the target upstream wheel pressure Pw1Tr and the target wheel pressure PwTr decreases. As a result, the increase in the servo pressure Psv from timing t13 to timing t14 is greater than in the case of this embodiment.

[0087] When the servo pressure Psv is increased, the amount of brake fluid flowing into the housing of the second pressure regulating valve 78 in the pressure regulating device 70 increases. The brake fluid flowing into the housing of the second pressure regulating valve 78 is high-pressure brake fluid supplied from the accumulator 74. Therefore, in the second pressure regulating valve 78, the force of the high-pressure brake fluid flowing into the housing causes the plunger to vibrate. The amplitude of the plunger vibration increases as the flow rate of the high-pressure brake fluid flowing into the housing increases. Furthermore, when the amplitude of the plunger vibration is large, the noise generated in the second pressure regulating valve 78 due to the plunger vibration increases.

[0088] In contrast, in this embodiment, the control device 200 does not decrease the hydraulic pressure in the servo chamber Rs when the required vehicle braking force FxRq is increased or maintained under the condition that the upstream wheel pressure Pw1 is generated by increasing the hydraulic pressure in the servo chamber Rs. In other words, the control device 200 prohibits the upstream wheel pressure Pw1 from being replaced with the downstream wheel pressure Pw2 under the condition that the required vehicle braking force FxRq is increased or maintained under the condition that the upstream wheel pressure Pw1 is generated by increasing the hydraulic pressure in the servo chamber Rs.

[0089] Therefore, during the period from timing t13 to timing t14, the increase in the hydraulic pressure in the master chambers Rm1, Rm2 and the servo chamber Rs, i.e., the servo pressure Psv, can be made smaller than in the comparative example. This prevents the amplitude of the plunger vibration in the second pressure regulating valve 78 from increasing. Therefore, the control device 200 can prevent abnormal noise from being generated from the second pressure regulating valve 78 when increasing the servo pressure Psv during vehicle braking.

[0090] 5, the rate of increase ΔFxRq of the required vehicle braking force FxRq decreases as the required vehicle braking force FxRq increases. That is, from timing t14 onwards, the rate of increase ΔFxRq becomes less than the criterion rate of increase ΔFxth. Therefore, in the period from timing t14 to timing t15, the control device 200 determines that the condition for prioritizing upstream pressure increase over downstream pressure increase is not met.

[0091] Therefore, the control device 200 increases the target downstream wheel pressure Pw2Tr from timing t14 onwards. In this case, the control device 200 increases the target downstream wheel pressure Pw2Tr so that the sum of the target downstream wheel pressure Pw2Tr and the target upstream wheel pressure Pw1Tr becomes equal to the target wheel pressure PwTr.

[0092] As a result, downstream wheel pressure Pw2 is generated at timing t14. Therefore, as shown in (D) of Figure 5, control device 200 permits regenerative control unit 302 to generate regenerative braking force FxRR. In other words, regenerative cooperative control can be performed from timing t14 onwards.

[0093] The required vehicle braking force FxRq is reduced from timing t16 onwards, so that the control device 200 reduces the target downstream wheel pressure Pw2Tr and the target upstream wheel pressure Pw1Tr.

[0094] In this embodiment, the following effects can be further obtained. (1) Within the cylinder 31 of the master cylinder 30, the servo chamber Rs and the separation chamber Ra are arranged with a partition member 39 sandwiched between them. If the increase in hydraulic pressure in the master chambers Rm1, Rm2 and the servo chamber Rs is large, the partition member 39 may be slightly displaced in the reverse direction Zb. For example, when the driver applies the brakes, the greater the braking operation, the higher the separation pressure, which is the hydraulic pressure in the separation chamber Ra. As a result, the separation pressure may be higher than the hydraulic pressure in the servo chamber Rs. If the hydraulic pressure in the servo chamber Rs is increased in this state, the hydraulic pressure in the servo chamber Rs will become higher than the separation pressure. This reversal of the magnitude relationship between the hydraulic pressure in the servo chamber Rs and the separation pressure may cause the partition member 39 to be slightly displaced in the reverse direction Zb.

[0095] When the partitioning member 39 is displaced in the backward direction Zb, the volume of the separation chamber Ra decreases. Consequently, the separation pressure increases in response to the reduction in the volume of the separation chamber Ra. The separation chamber Ra is partitioned by the partitioning member 39 and the input piston 35. Therefore, when the separation pressure changes, the input piston 35 vibrates due to the change in separation pressure. The brake pedal 22 is connected to the input piston 35. At this time, if the driver operates the brake pedal 22, the vibration of the input piston 35 is transmitted to the driver via the brake pedal 22. That is, the vibration caused by the increase in the hydraulic pressure in the master chambers Rm1 and Rm2 is transmitted to the driver via the brake pedal 22.

[0096] In the comparative example described above, the hydraulic pressure in the master chambers Rm1, Rm2, and the servo chamber Rs increases significantly during the period from timing t13 to timing t14 in FIG. 5. This also increases the amount of increase in the separation pressure. As a result, the amplitude of vibration of the input piston 35 tends to increase. If the vibration of the input piston 35 is transmitted to the driver via the brake pedal 22, the driver may feel uncomfortable.

[0097] In this regard, in the braking system 100, when an increase in the servo pressure Psv generates the upstream wheel pressure Pw1, the hydraulic pressures in the master chambers Rm1, Rm2, and the servo chamber Rs are not decreased if the required vehicle braking force FxRq is increased or maintained. Therefore, the increase in the servo pressure Psv is smaller than in the comparative example during the period from timing t13 to timing t14 in FIG. 5. As a result, the displacement of the partition member 39 in the rearward direction Zb caused by the increase in the hydraulic pressure in the servo chamber Rs is suppressed, thereby suppressing the increase in the separation pressure. Therefore, in the braking system 100, the vibration of the input piston 35 caused by the increase in the hydraulic pressure in the master chambers Rm1, Rm2, and the servo chamber Rs is prevented from being transmitted to the brake pedal 22.

[0098] (2) Consider a case where both the target upstream wheel pressure Pw1Tr and the target downstream wheel pressure Pw2Tr are increased during the period from timing t14 to timing t15. In this case, the downstream wheel pressure Pw2 becomes lower than in this embodiment. As a result, the maximum value of the regenerative braking force FxRR that can be generated in the vehicle becomes smaller.

[0099] In this regard, after timing t14, the control device 200 increases the target downstream wheel pressure Pw2Tr while maintaining the target upstream wheel pressure Pw1Tr. Therefore, the control device 200 can relatively increase the downstream wheel pressure Pw2. This relatively increases the maximum value of the regenerative braking force FxRR that can be generated in the vehicle. The greater the regenerative braking force FxRR that is generated, the higher the energy efficiency of the vehicle. Therefore, the control device 200 can increase the energy efficiency of the vehicle when braking the vehicle.

[0100] <Example of change> The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other within the scope of technical compatibility.

[0101] The control device 200 may increase both the upstream wheel pressure Pw1 and the downstream wheel pressure Pw2 during the period from timing t14 to timing t15 in FIG. 5, provided that the upstream wheel pressure Pw1 is not decreased.

[0102] The condition for prioritizing upstream pressurization over downstream pressurization may include a condition other than the condition that the increase rate ΔFxRq of the required vehicle braking force is equal to or greater than the criterion increase rate ΔFxth. For example, the condition for prioritizing upstream pressurization may include the condition that the upstream wheel pressure Pw1 is less than a predetermined pressure.

[0103] The control device 200 may allow a decrease in the hydraulic pressure in the master chambers Rm1, Rm2 if the decrease can be limited when the required frictional braking force FxMTr is not reduced under the condition that the upstream wheel pressure Pw1 is generated by an increase in the hydraulic pressure in the master chambers Rm1, Rm2 due to the operation of the pressurizing unit 71 and the second pressure regulating valve 78. In other words, the control device 200 may allow the upstream wheel pressure Pw1 to be replaced with the downstream wheel pressure Pw2 when the required frictional braking force FxMTr is not reduced under the condition that the upstream wheel pressure Pw1 is generated by an increase in the hydraulic pressure in the master chambers Rm1, Rm2 due to the operation of the pressurizing unit 71 and the second pressure regulating valve 78.

[0104] Here, the phenomenon of vibration occurring in the second pressure regulating valve 78 when the hydraulic pressure in the master chambers Rm1, Rm2 increases as a result of operation of the second pressure regulating valve 78 is likely to occur when the pressurizing unit 71 is at a high temperature. For example, when the oil temperature, which is the temperature of the brake fluid in the pressurizing unit 71, increases, the temperature of the pressurizing unit 71 increases. The oil temperature in the pressurizing unit 71 can be detected based on the detection signal of the accumulator pressure sensor 75. Of course, if an oil temperature sensor is provided in the pressurizing unit 71, the detection value of the oil temperature sensor can be used as the oil temperature.

[0105] Therefore, when the oil temperature is equal to or higher than the threshold value, the control device 200 determines that the pressurizing unit 71 has a high temperature. When the control device 200 replaces the upstream wheel pressure Pw1 with the downstream wheel pressure Pw2 under the condition that the pressurizing unit 71 has a high temperature, the control device 200 may reduce the rate at which the upstream wheel pressure Pw1 decreases compared to when the control device 200 replaces the upstream wheel pressure Pw1 with the downstream wheel pressure Pw2 under the condition that the pressurizing unit 71 has not a high temperature.

[0106] Figure 6 shows a timing chart for the case where the process of replacing the upstream wheel pressure Pw1 with the downstream wheel pressure Pw2 is executed in this manner. In Figure 6(B), the change in the upstream wheel pressure Pw1 in the modified example is shown by a solid line, and the change in the upstream wheel pressure Pw1 in a comparative example for the modified example is shown by a dashed line. In Figure 6(C), the change in the downstream wheel pressure Pw2 in the modified example is shown by a solid line, and the change in the downstream wheel pressure Pw2 in a comparative example for the modified example is shown by a dashed line. The comparative example here is a case where the rate of decrease of the upstream wheel pressure Pw1 is not slowed down even when the pressurizing unit 71 is at a high temperature.

[0107] In this modified example, compared to the comparative example, the increase in the upstream wheel pressure Pw1 when the upstream wheel pressure Pw1 is increased again at timing t21 can be reduced. In other words, the increase in the hydraulic pressure in the master chambers Rm1, Rm2 and the servo chamber Rs can be reduced. This reduces the vibration of the second pressure regulating valve 78 when the hydraulic pressure in the master chambers Rm1, Rm2 and the servo chamber Rs is increased.

[0108] The pressurizing unit may have a different configuration from the pressurizing unit 71 shown in FIG. 1 as long as it is capable of supplying high-pressure brake fluid. For example, the pressurizing unit may not have the accumulator 74. In this case, the pressurizing unit supplies brake fluid discharged from the servo pump 73 to the servo chamber Rs. The pressurizing unit may also have an electric cylinder instead of a pump.

[0109] The master cylinder may have a different configuration from the master cylinder 30 shown in Fig. 1 as long as the master chamber is partitioned inside. For example, the master cylinder may have a configuration in which brake fluid whose pressure is adjusted by the operation of the second pressure regulating valve 78 is supplied to the master chamber.

[0110] The brake actuator may have a configuration different from that shown in FIG. 2, as long as it is capable of individually adjusting the wheel pressures Pw of the plurality of wheel cylinders 16. The vehicle may be equipped with a regenerative device that can generate regenerative braking force on the front wheels 11f.

[0111] The control device 200 is not limited to a device that includes a CPU and ROM and executes software processing. In other words, the control device 200 may have any of the following configurations (a), (b), and (c):

[0112] (a) The control device 200 includes 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 that 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.

[0113] (b) The control device 200 includes 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."

[0114] (c) The control device 200 includes 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 among the various processes.

[0115] <Other technical ideas> The technical concepts that can be understood from the above-described embodiments and modifications will be described below. [Note 1] The pressurizing unit preferably has an accumulator for storing high-pressure brake fluid.

[0116] [Appendix 2] The vehicle is equipped with a regenerative device that generates regenerative braking force at the wheels, It is preferable that the control device permits the regenerative device to generate a regenerative braking force at the wheel on the condition that the downstream wheel pressure is generated.

[0117] The expression "at least one" used herein means "one or more" of the desired options. As an example, the expression "at least one" used herein 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 herein means "only one option" or "any combination of two or more options" if the number of options is three or more. [Explanation of symbols]

[0118] 11f,11r…wheels 15...Friction brake 16...Wheel cylinder 20...Liquid pressure generator 22...Brake pedal 30...Master cylinder 31...Cylinder 35...Input piston 37,38...Master piston 39...Partition member 51...First flow path (an example of a supply flow path) 52...Second flow path (an example of a supply flow path) 55...fifth flow path (an example of a pressure adjustment flow path) 70...Pressure regulator 71...Pressure unit 74...Accumulator 77...First pressure regulating valve 78...Second pressure regulating valve 80...Braking actuator 100...braking device 200...Control device 300...Regenerative device Ra…Separate room Rm1, Rm2...Master room Rs...Servo room

Claims

1. This applies to vehicles where braking force is generated at the wheels according to the wheel pressure, which is the hydraulic pressure in the wheel cylinder. a master cylinder having a master chamber; a pressure unit that supplies high-pressure brake fluid; a pressure regulating valve that adjusts the hydraulic pressure of the brake fluid supplied from the pressurizing unit and supplies the brake fluid whose hydraulic pressure has been adjusted to the master cylinder, thereby increasing the hydraulic pressure in the master chamber; a supply passage that is connected to the master chamber and serves as a brake fluid passage for supplying brake fluid from the master chamber to the wheel cylinder; a brake actuator connected to the supply flow path and configured to adjust the wheel pressure; a control device that controls the pressurizing unit, the pressure regulating valve, and the brake actuator, The master cylinder is A cylinder; an input piston connected to a brake pedal, which moves in a forward direction when the amount of operation of the brake pedal increases, and moves in a backward direction, which is the opposite direction to the forward direction, when the amount of operation of the brake pedal decreases; a master piston located in the cylinder in the forward direction relative to the input piston and defining the master chamber, The control device In a situation where the wheel pressure is generated by an increase in the hydraulic pressure in the master chamber due to the operation of the pressurizing unit and the pressure regulating valve, if the required value of the braking force is increased or maintained, a decrease in the hydraulic pressure in the master chamber is limited. Braking device.

2. a pressure adjusting passage for supplying brake fluid, the pressure of which has been adjusted by the pressure adjusting valve, into the master cylinder; The master cylinder has a servo chamber and a separation chamber formed therein, and the pressure adjustment passage is connected to the servo chamber. a partition member is provided in the cylinder and positioned further in the forward direction than the input piston, the servo chamber is a chamber defined by the master piston and the partition member, and is located in the rearward direction relative to the master chamber, the separated chamber is a chamber defined by the partition member and the input piston, and is located on the opposite side of the partition member from the servo chamber, When the input piston moves in the forward direction, the volume of the separation chamber decreases, whereas when the input piston moves in the backward direction, the volume of the separation chamber increases, The master cylinder is configured such that when the hydraulic pressure in the servo chamber increases, the master piston moves in the forward direction, thereby increasing the hydraulic pressure in the master chamber and discharging brake fluid from the master chamber to the supply flow path, and when the hydraulic pressure in the servo chamber decreases, the master piston moves in the backward direction, thereby decreasing the hydraulic pressure in the master chamber and allowing brake fluid to flow from the supply flow path into the master chamber.

2. The braking device of claim 1.

3. the wheel pressure generated by the operation of the pressurizing unit and the pressure regulating valve is an upstream wheel pressure, and the wheel pressure generated by the operation of the brake actuator is a downstream wheel pressure, The control device prohibits the upstream wheel pressure from being replaced with the downstream wheel pressure when the required value of the braking force is increased or maintained under a condition in which the upstream wheel pressure is generated by an increase in the hydraulic pressure in the master chamber due to the operation of the pressurizing unit and the pressure regulating valve.

2. The braking device of claim 1.

4. the wheel pressure generated by the operation of the pressurizing unit and the pressure regulating valve is an upstream wheel pressure, and the wheel pressure generated by the operation of the brake actuator is a downstream wheel pressure, the control device is configured to allow the upstream wheel pressure to be replaced with the downstream wheel pressure when the required value of the braking force is increased or maintained under a condition in which the upstream wheel pressure is generated by an increase in the hydraulic pressure in the master chamber due to the operation of the pressurizing unit and the pressure regulating valve, When the control device replaces the upstream wheel pressure with the downstream wheel pressure under a condition where it is determined that the pressurizing unit is at a high temperature, the control device reduces the rate at which the upstream wheel pressure decreases compared to when the control device replaces the upstream wheel pressure with the downstream wheel pressure under a condition where it is determined that the pressurizing unit is not at a high temperature.

2. The braking device of claim 1.

5. The control device When the rate of increase in the required value of the braking force is equal to or greater than a determined rate of increase, the wheel pressure is increased by adjusting the hydraulic pressure in the master chamber in accordance with the operation of the pressurizing unit and the pressure regulating valve; When the rate of increase in the required value of the braking force is less than the determined rate of increase, the hydraulic pressure in the master chamber is maintained by operating the pressurizing unit and the pressure regulating valve, and the wheel pressure is increased by operating the brake actuator. The braking device according to any one of claims 1 to 4.

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