Brake device

Abstract

To enhance controllability of wheel pressure by precisely adjusting a discharge amount of brake fluid from a pump.SOLUTION: A processing circuit executes required flow rate derivation processing M25 to derive a first required flow rate Qwr, which is a required flow rate value of brake fluid supplied to a first wheel cylinder based on a first map MP1r, a first target wheel pressure Ptr, and a wheel pressure Pwr, and a second required flow rate Qwf, which is a required flow rate value of brake fluid supplied to a second wheel cylinder based on a first map MP1f, a second target wheel pressure Ptf, and a wheel pressure Pwf. The processing circuit further executes a plurality of processes M29, M31, and M33 to increase the rotational speed of an electric motor 52 in proportion to the sum of the first required flow rate Qwr and the second required flow rate Qwf.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a braking device that generates braking force on vehicle wheels by controlling hydraulic pressure in wheel cylinders. [Background technology]

[0002] Patent Document 1 discloses a braking system including a pressure regulating unit and a controller for controlling the pressure regulating unit. The pressure regulating unit includes an electric pump that discharges brake fluid from an output port, a pressure regulating valve, and an adjustment passage located between the output port of the electric pump and the pressure regulating valve. The pressure regulating unit generates hydraulic pressure in the wheel cylinder according to the hydraulic pressure in the adjustment passage.

[0003] The controller sets a target rotation speed of the electric motor, which is the power source of the electric pump, based on the rate of increase in the amount of operation of the brake operating member by the driver or a correlation value thereof. Specifically, the controller increases the target rotation speed when the rate of increase or its correlation value is greater than 0 (zero). On the other hand, the controller decreases the target rotation speed when the rate of increase or its correlation value is less than 0 (zero). The controller then controls the discharge pressure of the brake fluid from the electric pump by driving the electric motor based on the target rotation speed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-1438 Summary of the Invention [Problem to be solved by the invention]

[0005] SUMMARY OF THE INVENTION An object of the present invention is to improve the controllability of the hydraulic pressure in the wheel cylinders by accurately setting the amount of brake fluid discharged from the electric pump. [Means for solving the problem]

[0006] A first aspect of a braking device for solving the above problems is applied to a vehicle in which the higher the wheel pressure, which is the hydraulic pressure in the wheel cylinder, the greater the braking force generated at the wheel. The braking device includes a reservoir tank for storing brake fluid, a pump having an electric motor as a power source and discharging brake fluid drawn from the reservoir tank through an output port, a return flow path connected to the output port for returning the brake fluid discharged from the output port to the reservoir tank, a pressure regulating valve provided in the return flow path, and a control device for controlling the pump and the pressure regulating valve, and the control device operates the pressure regulating valve to control an adjustment pressure, which is the brake fluid pressure in the portion of the return flow path between the output port and the pressure regulating valve, and generates the wheel pressure in the wheel cylinder according to the adjustment pressure. The control device executes a required flow rate derivation process that derives a required value of the flow rate of brake fluid when supplying brake fluid to the wheel cylinder based on cylinder characteristics that indicate the relationship between the amount of brake fluid supplied to the wheel cylinder and the wheel pressure, a target wheel pressure that is a target for the wheel pressure, and the wheel pressure, and a pump operation process that increases the rotation speed of the electric motor as the required flow rate increases.

[0007] A second aspect of the braking device for solving the above problem is applied to a vehicle having a first wheel and a second wheel as wheels, and wherein the braking force generated at the first wheel increases as the first wheel pressure, which is the hydraulic pressure in a first wheel cylinder, increases, and the braking force generated at the second wheel increases as the second wheel pressure, which is the hydraulic pressure in a second wheel cylinder, increases. The braking device includes a reservoir tank for storing brake fluid, a pump having an electric motor as a power source and discharging brake fluid drawn from the reservoir tank from an output port, a return flow path connected to the output port and returning the brake fluid discharged from the output port to the reservoir tank, a first pressure regulating valve provided in the return flow path, a second pressure regulating valve located in the return flow path on the opposite side of the first pressure regulating valve from the output port, and a control device for controlling the pump, the first pressure regulating valve, and the second pressure regulating valve. The control device operates the first pressure regulating valve to control an upstream regulating pressure, which is the brake fluid pressure in the portion of the return flow path between the output port and the first pressure regulating valve, and operates the first pressure regulating valve and the second pressure regulating valve to control a downstream regulating pressure, which is the brake fluid pressure in the portion of the return flow path between the first pressure regulating valve and the second pressure regulating valve, thereby generating the second wheel pressure in accordance with the upstream regulating pressure in the second wheel cylinder and generating the first wheel pressure in accordance with the downstream regulating pressure in the first wheel cylinder.The control device executes a first required flow rate derivation process that derives a required value of the flow rate of brake fluid when supplying brake fluid to the first wheel cylinder as a first required flow rate based on a first cylinder characteristic that indicates the relationship between the amount of brake fluid supplied to the first wheel cylinder and the first wheel pressure, a first target wheel pressure that is a target for the first wheel pressure, and the first wheel pressure; a second required flow rate derivation process that derives a required value of the flow rate of brake fluid when supplying brake fluid to the second wheel cylinder as a second required flow rate based on a second cylinder characteristic that indicates the relationship between the amount of brake fluid supplied to the second wheel cylinder and the second wheel pressure, a second target wheel pressure that is a target for the second wheel pressure, and the second wheel pressure; and a pump operation process that increases the rotation speed of the electric motor as the sum of the first required flow rate and the second required flow rate increases. [Effects of the Invention]

[0008] The braking device described above has the advantage of being able to improve the controllability of the wheel pressure by accurately adjusting the amount of brake fluid discharged from the pump. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing a schematic configuration of a vehicle equipped with a braking device according to a first embodiment. [Figure 2] FIG. 2 is a block diagram showing various processes executed to drive the electric motor provided in the braking device of the first embodiment. [Figure 3] FIG. 3 is a block diagram showing various processes executed to drive the first pressure regulating valve and the second pressure regulating valve provided in the braking device of the first embodiment. [Figure 4] FIG. 4 is a map showing the relationship between the target differential pressure and the current flowing through the solenoid of the first pressure regulating valve in the braking device of the first embodiment. [Figure 5] FIG. 5 is a map showing the relationship between the target differential pressure and the current flowing through the solenoid of the second pressure regulating valve in the braking device of the first embodiment. [Figure 6]FIG. 6 is a schematic diagram showing the first pressure regulating valve. [Figure 7] FIG. 7 is a diagram showing a schematic configuration of a vehicle equipped with a braking device according to the second embodiment. [Figure 8] FIG. 8 is a block diagram showing various processes executed to drive the electric motor provided in the braking device of the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] (First embodiment) A first embodiment of a braking device will be described below with reference to FIGS. 1 shows a vehicle equipped with a braking device 100. The vehicle has two first wheels 11a and two second wheels 11b as wheels. The vehicle also has friction brakes 15 in the same number as the wheels.

[0011] In the example shown in Fig. 1, the first wheel 11a is a rear wheel and the second wheel 11b is a front wheel. For example, if the vehicle is an electric vehicle capable of generating regenerative braking force, the first wheel 11a is a wheel that can apply regenerative braking force, while the second wheel 11b is a wheel that cannot apply regenerative braking force. Electric vehicles include hybrid vehicles and battery vehicles. Note that the vehicle equipped with the braking device 100 may be a vehicle other than an electric vehicle.

[0012] <Friction brake> The plurality of friction brakes 15 each generate a friction braking force at the corresponding wheels 11a, 11b. 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, friction 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 Pw, which is the hydraulic pressure in the wheel cylinders 16, increases. Therefore, the friction brakes 15 can generate a greater friction braking force at the wheels as the wheel pressure Pw increases.

[0013] In the following description, of the four wheel cylinders 16, the wheel cylinder 16 corresponding to the first wheel 11a corresponds to the "first wheel cylinder." The wheel cylinder 16 corresponding to the second wheel 11b corresponds to the "second wheel cylinder." The wheel pressure of the first wheel cylinder is sometimes referred to as the "first wheel pressure," and the wheel pressure of the second wheel cylinder is sometimes referred to as the "second wheel pressure."

[0014] <Brake device> The braking system 100 adjusts the friction braking force generated in the vehicle by controlling the wheel pressure Pw of the plurality of wheel cylinders 16. The braking system 100 includes a hydraulic pressure generating device 20, a brake actuator 80, and a control device 90. 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 90 controls the operation of the hydraulic pressure generating device 20 and the brake actuator 80.

[0015] <Liquid pressure generator> The hydraulic pressure generating device 20 has a reservoir tank 21, a brake operating member 22, a master device 30, and a pressurizing 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 when decelerating 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 pressure Pw in the multiple wheel cylinders 16 according to the amount of operation of the brake operating member 22.

[0017] <Master device> The master unit 30 includes a master cylinder 31, a stroke simulator 32, multiple flow paths 331, 332, and 333 connected to the master cylinder 31, and multiple control valves 341 and 342 that control the flow of brake fluid. The master unit 30 also includes an input hydraulic pressure sensor 353 as a sensor for detecting hydraulic pressure. A detection signal from the input hydraulic pressure sensor 353 is input to the control device 90.

[0018] The stroke simulator 32 is capable of generating a reaction force according 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 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.

[0019] The main cylinder 41 has a plate-shaped bottom wall 411, a cylindrical peripheral wall 412 extending from the bottom wall 411 along the axis 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.

[0020] 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 movement direction of the master piston 43, which is to the left in FIG. 1 and which reduces 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 which increases the volume of the master chamber Rm.

[0021] 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. Inside the main cylinder 41, the master chamber Rm, the first fluid chamber R1, and the servo chamber Rs are not connected to one another.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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. After this, 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.

[0029] The first flow path 331 connects the master chamber Rm to a second hydraulic circuit 82 of the brake actuator 80 (described later). The second flow path 332 connects the first fluid chamber R1 to a 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.

[0030] 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 90 is operating, the first control valve 341 is opened and the second control valve 342 is closed.

[0031] The input hydraulic pressure sensor 353 detects the hydraulic pressure in the second hydraulic chamber R2. For example, the input hydraulic pressure sensor 353 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 input hydraulic pressure sensor 353 will be referred to as the "input hydraulic pressure Pgs."

[0032] <Pressure unit> The pressurizing unit 50 includes a pump 51, a supply flow path 54, and a return flow path 55. The pump 51 is an electric pump powered by an electric motor 52. The pump 51 pressurizes brake fluid pumped from an input port 51a and discharges it from an output port 51b. The supply flow path 54 connects the reservoir tank 21 to the input port 51a. The return flow path 55 is connected to the output port 51b and returns the brake fluid discharged from the output port 51b to the reservoir tank 21. In the example shown in FIG. 1 , one end of the return flow path 55 is connected to the reservoir tank 21, but one end of the return flow path 55 may be connected to the supply flow path 54. Even if one end of the return flow path 55 is connected to the supply flow path 54, the return flow path 55 can return the brake fluid discharged from the output port 51b to the reservoir tank 21. A check valve 56 is provided in the return flow path 55. The check valve 56 regulates the brake fluid from flowing in the return passage 55 toward the output port 51b.

[0033] The pressurizing unit 50 includes a hydraulic pressure adjustment unit 60, a first servo pressure sensor 65, and a second servo pressure sensor 66. The hydraulic pressure adjustment unit 60 is installed in a portion of the return flow path 55 opposite the output port 51b, with the check valve 56 sandwiched between them. The hydraulic pressure adjustment unit 60 includes a first pressure adjustment valve 61 and a second pressure adjustment valve 62. The first pressure adjustment valve 61 and the second pressure adjustment valve 62 are normally-open linear solenoid valves. The second pressure adjustment valve 62 is installed in a portion of the return flow path 55 opposite the check valve 56, with the first pressure adjustment valve 61 sandwiched between them.

[0034] Therefore, when brake fluid is being discharged from the output port 51b of the pump 51, the first pressure regulating valve 61 can adjust the pressure difference between a portion of the return flow path 55 between the first pressure regulating valve 61 and the check valve 56 and a portion of the return flow path 55 between the first pressure regulating valve 61 and the second pressure regulating valve 62. The second pressure regulating valve 62 can adjust the pressure difference between a portion of the return flow path 55 between the first pressure regulating valve 61 and the second pressure regulating valve 62 and a portion of the return flow path 55 between the second pressure regulating valve 62 and the end of the return flow path 55 on the reservoir tank 21 side. In other words, by operating the first pressure regulating valve 61, the upstream regulated pressure, which is the hydraulic pressure in the portion of the return flow path 55 between the first pressure regulating valve 61 and the check valve 56, is adjusted. In addition, by operating the first pressure regulating valve 61 and the second pressure regulating valve 62, the downstream regulated pressure, which is the hydraulic pressure in the portion of the reflux flow path 55 between the first pressure regulating valve 61 and the second pressure regulating valve 62, is adjusted.

[0035] The first servo pressure sensor 65 detects the discharge pressure of the brake fluid from the pump 51. For example, the first servo pressure sensor 65 is provided in a portion of the return flow path 55 between the check valve 56 and the first pressure regulating valve 61. In this case, it can also be said that the first servo pressure sensor 65 detects the upstream regulating pressure. In the following explanation, the fluid pressure based on the detection signal of the first servo pressure sensor 65 will be referred to as the "first servo pressure Pp."

[0036] The second servo pressure sensor 66 detects the hydraulic pressure of the brake fluid supplied from the pressurizing unit 50 to a first hydraulic circuit 81 of a brake actuator 80, which will be described later. For example, the second servo pressure sensor 66 is provided in a portion of the return flow path 55 between the first pressure regulating valve 61 and the second pressure regulating valve 62. In this case, it can also be said that the second servo pressure sensor 66 detects the downstream regulating pressure. In the following description, the hydraulic pressure based on the detection signal of the second servo pressure sensor 66 will be referred to as the "second servo pressure Po."

[0037] The portion of the reflux flow path 55 between the check valve 56 and the first pressure regulating valve 61 is connected to the servo chamber Rs of the master device 30 via a first connecting flow path 67. The portion of the reflux flow path 55 between the first pressure regulating valve 61 and the second pressure regulating valve 62 is connected to a first hydraulic circuit 81 of a brake actuator 80 (described later) via a second connecting flow path 68.

[0038] While the pump 51 is discharging brake fluid, the pressurizing unit 50 operates the hydraulic pressure adjusting unit 60 to supply brake fluid with adjusted pressure to the brake actuator 80 and the master cylinder 31. Specifically, the brake fluid adjusted by the first pressure adjusting valve 61 of the hydraulic pressure adjusting unit 60 is supplied from the first connecting flow path 67 to the servo chamber Rs of the master device 30. This increases the hydraulic pressure in the servo chamber Rs, causing the master piston 43 to move forward. This increases the hydraulic pressure in the master chamber Rm, causing brake fluid to be supplied from the master chamber Rm to the second hydraulic circuit 82 of the brake actuator 80. As a result, brake fluid is supplied to two wheel cylinders 16 (second wheel cylinders) connected to the second hydraulic circuit 82, among the multiple wheel cylinders 16. This increases the wheel pressure Pw (second wheel pressure) of the two wheel cylinders 16.

[0039] Furthermore, the brake fluid whose pressure is adjusted by the second pressure adjusting valve 62 of the fluid pressure adjusting unit 60 is supplied from the second connecting flow path 68 to the first fluid pressure circuit 81 of the brake actuator 80. Then, the brake fluid is supplied to two wheel cylinders 16 (first wheel cylinders) among the plurality of wheel cylinders 16 that are connected to the first fluid pressure circuit 81. As a result, the wheel pressure Pw (first wheel pressure) of the two wheel cylinders 16 is increased.

[0040] <Braking actuator> The brake actuator 80 includes a first hydraulic pressure circuit 81 and a second hydraulic pressure circuit 82. The first hydraulic pressure circuit 81 is disposed between the second connecting flow path 68 and the wheel cylinder 16 (first wheel cylinder) for the first wheel 11a. Therefore, the brake fluid that flows from the second connecting flow path 68 into the first hydraulic pressure circuit 81 is supplied to the wheel cylinder 16 (first wheel cylinder) for the first wheel 11a.

[0041] The second hydraulic circuit 82 is disposed between the first flow path 331 and the wheel cylinder 16 (second wheel cylinder) for the second wheel 11b. Therefore, the brake fluid that flows from the first flow path 331 into the second hydraulic circuit 82 is supplied to the wheel cylinder 16 (second wheel cylinder) for the second wheel 11b.

[0042] The second hydraulic pressure circuit 82 is provided with a master hydraulic pressure sensor 821 that detects the hydraulic pressure of the brake fluid supplied from the first flow path 331 to the second hydraulic pressure circuit 82. The master hydraulic pressure sensor 821 can detect the hydraulic pressure in the master chamber Rm. Hereinafter, the hydraulic pressure based on the detection signal of the master hydraulic pressure sensor 821 will also be referred to as the "master pressure Pmc."

[0043] <Control device> The control device 90 includes a processing circuit 91. An example of the processing circuit 91 is an electronic control device. In this case, the processing circuit 91 includes a CPU 92, a first memory 93, and a second memory 94. The first memory 93 stores a control program executed by the CPU 92 and various maps referenced by the CPU 92. The second memory 94 stores the results of calculations by the CPU 92. The CPU 92 executes the control program in the first memory 93, causing the processing circuit 91 to operate the hydraulic pressure generating device 20.

[0044] The control device 90 receives detection signals from a plurality of sensors included in the hydraulic pressure generating device 20. The plurality of sensors includes the above-described plurality of sensors 353, 65, 66, 821 and an operation amount sensor 221. The operation amount sensor 221 detects the amount of operation of the brake operating member 22 by the driver. The operation amount detected by the operation amount sensor 221 is referred to as the "braking operation amount Ba."

[0045] <Various processes for driving electric motors> With reference to FIG. 2, various processes executed by the processing circuit 91 to drive the electric motor 52 will be described.

[0046] The processing circuit 91 executes a required braking force derivation process M11, a target wheel pressure setting process M13, a standard supply rate derivation process M15, an estimated wheel pressure derivation process M17, an estimated fluid volume derivation process M19, and a compensation fluid volume derivation process M21. Furthermore, the processing circuit 91 executes a fluid volume conversion process M23, a required flow rate derivation process M25, a required flow rate derivation process M27, a target flow rate derivation process M29, a target rotation speed derivation process M31, and a rotation speed feedback process M33. Hereinafter, the rotation speed feedback process M33 will be referred to as the "rotation speed F / B process M33." The processing circuit 91 controls the discharge of brake fluid from the pump 51 by repeatedly executing these various processes M11 to M33 at predetermined control intervals.

[0047] <Required braking force calculation process> In the required braking force derivation process M11, the processing circuit 91 derives a vehicle braking force required value Fv. The vehicle braking force required value Fv is a required value of the vehicle braking force. The vehicle braking force is the sum of braking forces generated at the multiple wheels 11a, 11b. The processing circuit 91 derives the vehicle braking force required value Fv based on the input hydraulic pressure Pgs and the braking operation amount Ba.

[0048] The control device 90 may be instructed to decelerate the vehicle by another control device. In this case, in the required braking force derivation process M11, the processing circuit 91 derives the vehicle braking force corresponding to the instruction to decelerate the vehicle from the other control device as the vehicle braking force required value Fv.

[0049] <Target wheel pressure setting process> In the target wheel pressure setting process M13, the processing circuit 91 sets a target wheel pressure Pt, which is a target value for the wheel pressure Pw, based on the vehicle braking force requirement value Fv. In this embodiment, the processing circuit 91 sets a first target wheel pressure Ptr and a second target wheel pressure Ptf as the target wheel pressures Pt. The first target wheel pressure Ptr is a target value for the wheel pressure (first wheel pressure) of the wheel cylinder 16 for the first wheel 11a. The second target wheel pressure Ptf is a target value for the wheel pressure (second wheel pressure) of the wheel cylinder 16 for the second wheel 11b. For example, the processing circuit 91 sets the first target wheel pressure Ptr and the second target wheel pressure Ptf so that the ratio between the braking force generated at the first wheel 11a and the braking force generated at the second wheel 11b is a predetermined ratio.

[0050] When a regenerative braking force FvR is generated at the first wheel 11a, the processing circuit 91 sets the first target wheel pressure Ptr taking the regenerative braking force FvR into consideration. The braking force obtained by subtracting the regenerative braking force FvR from the target value of the braking force to be generated at the first wheel 11a is the target value of the frictional braking force to be generated at the first wheel 11a. The processing circuit 91 sets the wheel pressure corresponding to the target value of the frictional braking force to be generated at the first wheel 11a as the first target wheel pressure Ptr.

[0051] <Standard supply amount derivation process> In the standard supply amount derivation process M15, the processing circuit 91 derives a standard supply amount Es, which is a base value of the amount of brake fluid to be supplied to the wheel cylinder 16. The standard supply amount Es is the amount of brake fluid required to make the wheel pressure Pw equal to the target wheel pressure Pt. Therefore, the processing circuit 91 derives a standard supply amount Es such that the standard supply amount Es increases as the target wheel pressure Pt increases. In this embodiment, the processing circuit 91 derives a first standard supply amount Esr and a second standard supply amount Esf as the standard supply amount Es. The first standard supply amount Esr is the standard supply amount for the wheel cylinder 16 (first wheel cylinder) of the first wheel 11a. The second standard supply amount Esf is the standard supply amount for the wheel cylinder 16 (second wheel cylinder) of the second wheel 11b.

[0052] For example, the processing circuit 91 derives the first standard supply rate Esr and the second standard supply rate Esf based on a first map MP1. The first map MP1 is a map showing the relationship between the brake fluid pressure and the brake fluid amount. The wheel cylinder 16 of the first wheel 11a and the wheel cylinder 16 of the second wheel 11b have different volumes. Therefore, the first map MP1 includes a first map MP1r for the first wheel 11a and a first map MP1f for the second wheel 11b. The first map MP1r corresponds to a "first cylinder characteristic" that shows the relationship between the amount of brake fluid supplied to the wheel cylinder 16 (first wheel cylinder) of the first wheel 11a and the wheel pressure (first wheel pressure) of the wheel cylinder 16. The processing circuit 91 derives the brake fluid amount corresponding to the first target wheel pressure Ptr as the first standard supply rate Esr based on the first map MP1r for the first wheel 11a.

[0053] The first map MP1f corresponds to a "second cylinder characteristic" that indicates the relationship between the amount of brake fluid supplied to the wheel cylinder 16 (second wheel cylinder) of the second wheel 11b and the wheel pressure (second wheel pressure) of the wheel cylinder 16. The processing circuit 91 derives, based on the first map MP1f for the second wheel 11b, the amount of brake fluid corresponding to the second target wheel pressure Ptf as a second standard supply amount Esf.

[0054] <Estimated wheel pressure derivation process> In the estimated wheel pressure derivation process M17, the processing circuit 91 derives wheel pressures Pw, which are estimated values ​​of the wheel pressures of the multiple wheel cylinders 16. Specifically, the processing circuit 91 derives, as the wheel pressures Pw, a wheel pressure Pwr, which is an estimated value of the wheel pressure of the wheel cylinder 16 of the first wheel 11a, and a wheel pressure Pwf, which is an estimated value of the wheel pressure of the wheel cylinder 16 of the second wheel 11b. For example, the processing circuit 91 derives, as the wheel pressure Pwf, a hydraulic pressure corresponding to the first servo pressure Pp. Alternatively, for example, the processing circuit 91 derives, as the wheel pressure Pwr, a hydraulic pressure corresponding to the second servo pressure Po. In this case, the processing circuit 91 may derive, as the wheel pressure Pwf, a hydraulic pressure corresponding to the master pressure Pmc, instead of the first servo pressure Pp. Hereinafter, the wheel pressure Pwr may also be referred to as the "first wheel pressure Pwr," and the wheel pressure Pwf may also be referred to as the "second wheel pressure Pwf."

[0055] <Estimated fluid volume derivation process> In the estimated fluid volume derivation process M19, the processing circuit 91 derives an estimated fluid volume Ee, which is an estimate of the amount of brake fluid stored in the wheel cylinder 16. Specifically, the processing circuit 91 derives, as the estimated fluid volume Ee, a first estimated fluid volume Eer, which is the estimated fluid volume in the wheel cylinder 16 of the first wheel 11a, and a second estimated fluid volume Eef, which is the estimated fluid volume in the wheel cylinder 16 of the second wheel 11b.

[0056] For example, the processing circuit 91 derives the first estimated fluid volume Eer and the second estimated fluid volume Eef based on the first map MP1. In this case, the processing circuit 91 derives the brake fluid volume corresponding to the first wheel pressure Pwr as the first estimated fluid volume Eer based on the first map MP1r for the first wheel 11a. The processing circuit 91 derives the brake fluid volume corresponding to the second wheel pressure Pwf as the second estimated fluid volume Eef based on the first map MP1f for the second wheel 11b.

[0057] <Compensation liquid volume derivation process> In the compensation fluid volume derivation process M21, the processing circuit 91 derives the deviation between the standard supply volume Es and the estimated fluid volume Ee as the compensation fluid volume Eh. The compensation fluid volume Eh is the excess or deficiency of brake fluid required to make the wheel pressure Pw equal to the target wheel pressure Pt. Therefore, when the wheel pressure Pw is lower than the target wheel pressure Pt, the compensation fluid volume Eh is a positive value. On the other hand, when the wheel pressure Pw is higher than the target wheel pressure Pt, the compensation fluid volume Eh is a negative value. In this embodiment, the processing circuit 91 derives a first compensation fluid volume Ehr and a second compensation fluid volume Ehf as the compensation fluid volume Eh. The first compensation fluid volume Ehr is the compensation fluid volume for the wheel cylinder 16 of the first wheel 11a. The second compensation fluid volume Ehf is the compensation fluid volume for the wheel cylinder 16 of the second wheel 11b. The processing circuit 91 derives the first compensation fluid volume Ehr by subtracting the first estimated fluid volume Eer from the first standard supply volume Esr, and the processing circuit 91 derives the second compensation fluid volume Ehf by subtracting the second estimated fluid volume Eef from the second standard supply volume Esf.

[0058] <Liquid volume conversion processing> In the fluid volume conversion process M23, the processing circuit 91 converts the amount of brake fluid supplied to the wheel cylinder 16 into the flow rate of brake fluid in the flow path. The flow rate of brake fluid is the increase in the amount of brake fluid supplied per unit time. Therefore, the processing circuit 91 converts the standard supply rate Es into a standard flow rate Qs. For example, the processing circuit 91 derives the standard flow rate Qs by time-differentiating the standard supply rate Es. In this embodiment, the processing circuit 91 derives the first standard flow rate Qsr by time-differentiating the first standard supply rate Esr. The processing circuit 91 derives the second standard flow rate Qsf by time-differentiating the second standard supply rate Esf.

[0059] The processing circuit 91 also converts the compensation fluid volume Eh into a compensation flow rate Qh. For example, the processing circuit 91 derives the compensation flow rate Qh by time-differentiating the compensation fluid volume Eh. Therefore, when the difference between the target wheel pressure Pt and the wheel pressure Pw is increasing, a positive value is derived as the compensation flow rate Qh. When the difference between the target wheel pressure Pt and the wheel pressure Pw is decreasing, a negative value is derived as the compensation flow rate Qh.

[0060] In this embodiment, the processing circuit 91 derives the first compensation flow rate Qhr by differentiating the first compensation fluid volume Ehr with respect to time, and the processing circuit 91 derives the second compensation flow rate Qhf by differentiating the second compensation fluid volume Ehf with respect to time.

[0061] <Required flow rate derivation process> In the required flow rate derivation process M25, the processing circuit 91 derives a brake amount corresponding to the standard supply rate Es and the compensation fluid rate Eh as a required flow rate Qw, which is a required value for the flow rate of brake fluid to the wheel cylinders 16. In this embodiment, the processing circuit 91 derives the required flow rate Qw based on the standard flow rate Qs and the compensation flow rate Qh. For example, the processing circuit 91 derives the sum of the standard flow rate Qs and the compensation flow rate Qh as the required flow rate Qw. In this embodiment, the processing circuit 91 derives a first required flow rate Qwr and a second required flow rate Qwf as the required flow rate Qw. The first required flow rate Qwr is the required flow rate for the wheel cylinder 16 of the first wheel 11a. The second required flow rate Qwf is the required flow rate for the wheel cylinder 16 of the second wheel 11b. In this case, the processing circuit 91 may derive the sum of the first standard flow rate Qsr and the first compensation flow rate Qhr as the first required flow rate Qwr. The processing circuit 91 may derive the sum of the second standard flow rate Qsf and the second compensation flow rate Qhf as the second required flow rate Qwf.

[0062] In the required flow rate derivation process M25, both the first required flow rate Qwr and the second required flow rate Qwf are derived. Therefore, the required flow rate derivation process M25 includes a "first required flow rate derivation process" that derives the first required flow rate Qwr and a "second required flow rate derivation process" that derives the second required flow rate Qwf.

[0063] <Required flow rate derivation process> In the essential flow rate derivation process M27, the processing circuit 91 derives the essential flow rate Qu, which is the flow rate of brake fluid to the wheel cylinder 16 required to achieve the target wheel pressure Pt. The processing circuit 91 selects the higher of the first target wheel pressure Ptr and the second target wheel pressure Ptf as the selected hydraulic pressure. The processing circuit 91 then derives the essential flow rate Qu so that the higher the selected hydraulic pressure, the larger the essential flow rate Qu.

[0064] For example, the processing circuit 91 derives the essential flow rate Qu based on a second map MP2. The second map MP2 is a map showing the relationship between the wheel pressure Pw and the flow rate of brake fluid. In this case, the processing circuit 91 derives the flow rate of brake fluid corresponding to the selected hydraulic pressure as the essential flow rate Qu based on the second map MP2.

[0065] <Target flow rate derivation process> In the target flow rate derivation process M29, the processing circuit 91 derives a target flow rate Qt, which is a target value for the flow rate of brake fluid in the reflux flow path 55. The processing circuit 91 derives the target flow rate Qt based on the first required flow rate Qwr, the second required flow rate Qwf, and the required flow rate Qu. For example, when the sum of the first required flow rate Qwr and the second required flow rate Qwf is equal to or greater than 0 (zero), the processing circuit 91 derives the sum of the first required flow rate Qwr, the second required flow rate Qwf, and the required flow rate Qu as the target flow rate Qt. When the sum of the first required flow rate Qwr and the second required flow rate Qwf is less than 0 (zero), the processing circuit 91 derives the required flow rate Qu as the target flow rate Qt.

[0066] <Target rotation speed derivation process> In the target rotation speed derivation process M31, the processing circuit 91 derives, based on the target flow rate Qt, a target rotation speed Ntt that is a target value for the rotation speed Nt of the electric motor 52 that is the power source of the pump 51. For example, the processing circuit 91 derives the target rotation speed Ntt so that the target rotation speed Ntt increases as the target flow rate Qt increases.

[0067] <Rotational speed feedback processing> In the rotation speed F / B process M33, the processing circuit 91 drives the electric motor 52 based on the target rotation speed Ntt. For example, the processing circuit 91 derives a command value Imt for the electric motor 52 by feedback control using as input the deviation between the target rotation speed Ntt and the rotation speed Nt of the electric motor 52. An example of the rotation speed Nt used here is the rotation speed of the rotating shaft of the electric motor 52 based on a detection signal from a rotation angle sensor provided in the electric motor 52. The processing circuit 91 drives the electric motor 52 by operating a driver circuit for the electric motor 52 based on the command value Imt.

[0068] As described above, the command value Imt is derived according to the target rotation speed Ntt. The target rotation speed Ntt is set based on the first required flow rate Qwr and the second required flow rate Qwf. Therefore, the target flow rate derivation process M29, the target rotation speed derivation process M31, and the rotation speed F / B process M33 constitute an example of a "pump operation process" that increases the rotation speed of the electric motor 52 as the sum of the first required flow rate Qwr and the second required flow rate Qwf increases.

[0069] <Various processes for driving the first pressure regulating valve> 3 to 6, various processes executed by the processing circuit 91 to drive the first pressure regulating valve 61 will be described.

[0070] The processing circuit 91 executes a first target differential pressure derivation process M41, a first passing flow rate derivation process M42, a first standard current derivation process M43, a first differential pressure deviation derivation process M47, and a first compensation current derivation process M49. Furthermore, the processing circuit 91 executes a first target current derivation process M51 and a first current feedback process M53. Hereinafter, the first current feedback process M53 will be referred to as a "first current F / B process M53." The processing circuit 91 controls the aperture of the first pressure regulating valve 61 by repeatedly executing these various processes M41 to M53 at predetermined control intervals.

[0071] <First target differential pressure derivation process> In the first target differential pressure derivation process M41, the processing circuit 91 derives a first target differential pressure Stj. The first target differential pressure Stj is a target value of the differential pressure between a portion of the return flow passage 55 between the first pressure regulating valve 61 and the check valve 56 and a portion of the return flow passage 55 between the first pressure regulating valve 61 and the second pressure regulating valve 62. The portion of the return flow passage 55 between the first pressure regulating valve 61 and the check valve 56 is indirectly connected to the wheel cylinder 16 of the second wheel 11b. Furthermore, the portion of the return flow passage 55 between the first pressure regulating valve 61 and the second pressure regulating valve 62 is connected to the wheel cylinder 16 of the first wheel 11a. Therefore, the processing circuit 91 derives a target value corresponding to the difference between the first target wheel pressure Ptr and the second target wheel pressure Ptf as the first target differential pressure Stj. For example, the processing circuit 91 derives the first target differential pressure Stj by subtracting the first target wheel pressure Ptr from the second target wheel pressure Ptf.

[0072] <First passing flow rate derivation process> In the first passing flow rate derivation process M42, the processing circuit 91 derives a first estimated passing flow rate Qr1. The first estimated passing flow rate Qr1 is an estimated value of the amount of brake fluid passing through the first pressure regulating valve 61. The processing circuit 91 derives the first estimated passing flow rate Qr1 based on the first required flow rate Qwr and the second required flow rate Qwf derived in the required flow rate derivation process M25 and the required flow rate Qu derived in the required flow rate derivation process M27. For example, the processing circuit 91 can derive the first estimated passing flow rate Qr1 by referring to the following relational expression (D1). In the relational expression (D1), "QwfA" is the product of the second required flow rate Qwf and "-1". As a result, the processing circuit 91 derives the first estimated passing flow rate Qr1 so that it increases as the product QwfA increases. Furthermore, the processing circuit 91 derives the first estimated passing flow rate Qr1 so that the first estimated passing flow rate Qr1 increases as the first required flow rate Qwr increases.

[0073] Qr1 = MAX(Qwr, 0)+MAX(QwfA, 0)+Qu …(D1) In the above relational expression (D1), "MAX(Qwr, 0)" corresponds to the increase in the first wheel pressure Pwr, and "MAX(QwfA, 0)" corresponds to the decrease in the second wheel pressure Pwf. The required flow rate Qu is the minimum amount of brake fluid that is returned to the reservoir tank 21 via the return flow path 55 when the pump 51 is operated. When the first wheel pressure Pwr is increased, the greater the increase in the first wheel pressure Pwr, the greater the amount of brake fluid that passes through the first pressure regulating valve 61. When the second wheel pressure Pwf is decreased, the brake fluid that has flowed out of the servo chamber Rs flows toward the reservoir tank 21 via the first pressure regulating valve 61. Therefore, the greater the decrease in the second wheel pressure Pwf, the greater the amount of brake fluid that passes through the first pressure regulating valve 61.

[0074] <First reference current derivation process> In the first standard current derivation process M43, the processing circuit 91 derives a first standard current Isj, which is a current value corresponding to the first target differential pressure Stj. The first standard current Isj is a current that corresponds to the first target differential pressure Stj and is passed through the solenoid of the first pressure regulating valve 61. The processing circuit 91 derives the first standard current Isj based on the first estimated through flow rate Qr1 and the first target differential pressure Stj. For example, the processing circuit 91 derives the first standard current Isj so that it increases as the first target differential pressure Stj increases. Alternatively, for example, the processing circuit 91 derives the first standard current Isj so that it increases as the first estimated through flow rate Qr1 decreases.

[0075] Here, the first estimated through flow rate Qr1 increases as the second required flow rate Qwf decreases. Specifically, when the second required flow rate Qwf is a negative value, the first estimated through flow rate Qr1 increases compared to when the second required flow rate Qwf is a positive value. The first standard current Isj decreases as the first estimated through flow rate Qr1 increases. Therefore, when the first target wheel pressure Ptr is constant, the processing circuit 91 increases the first standard current Isj in the required flow rate derivation process M25 as the second required flow rate Qwf decreases.

[0076] In this embodiment, the processing circuit 91 derives the first reference current Isj based on a third map MP3 shown in FIG. 4 . The third map MP3 is a map showing the relationship between the first target differential pressure Stj and the current flowing through the solenoid of the first pressure regulating valve 61. The first pressure regulating valve 61 is a normally-open linear solenoid valve. Therefore, the larger the current flowing through the solenoid, the smaller the opening of the first pressure regulating valve 61. The smaller the opening of the first pressure regulating valve 61, the larger the differential pressure. Therefore, the third map MP3 corresponds to the “pressure regulating valve characteristics” that show the relationship between the first target differential pressure Stj and the opening of the first pressure regulating valve 61. The third map MP3 is stored in advance in a first memory 93 of the processing circuit 91.

[0077] 4, the third map MP3 includes a plurality of pressure regulating valve characteristics corresponding to the first estimated through flow rate Qr1. In any of the plurality of pressure regulating valve characteristics, the current increases as the first target differential pressure Stj increases.

[0078] Of the multiple pressure regulator valve characteristics, the reference pressure regulator valve characteristic Zr0 is the pressure regulator valve characteristic when the first estimated throughflow rate Qr1 is 0 (zero). In FIG. 4, the reference pressure regulator valve characteristic Zr0 is indicated by a dashed line. Of the multiple pressure regulator valve characteristics, the increasing pressure regulator valve characteristic Zr1 is the pressure regulator valve characteristic when the first estimated throughflow rate Qr1 is greater than 0 (zero). In other words, the increasing pressure regulator valve characteristic Zr1 is the pressure regulator valve characteristic when the first estimated throughflow rate Qr1 is greater than the reference pressure regulator valve characteristic Zf0. In this embodiment, multiple increasing pressure regulator valve characteristics Zr1 are prepared.

[0079] When the first estimated through flow rate Qr1 is 0 (zero), the processing circuit 91 selects the reference pressure regulating valve characteristic Zr0 and derives a current corresponding to the first target differential pressure Stj as the first standard current Isj based on the reference pressure regulating valve characteristic Zr0.

[0080] When the first estimated throughflow rate Qr1 is greater than 0 (zero), the processing circuit 91 selects the increasing pressure regulating valve characteristic Zr1. At this time, the processing circuit 91 selects the increasing pressure regulating valve characteristic Zr1 corresponding to the first estimated throughflow rate Qr1 from among a plurality of increasing pressure regulating valve characteristics Zr1. Then, the processing circuit 91 derives a current corresponding to the first target differential pressure Stj as the first reference current Isj based on the selected increasing pressure regulating valve characteristic Zr1.

[0081] The first estimated through flow rate Qr1 is derived according to the second required flow rate Qwf. The smaller the second required flow rate Qwf, the larger the first estimated through flow rate Qr1. Therefore, when the second required flow rate Qwf is small, the processing circuit 91 derives the first reference current Isj based on the increasing pressure regulation valve characteristic Zr1, among the multiple increasing pressure regulation valve characteristics Zr1, which is used when the first estimated through flow rate Qr1 is larger than when the second required flow rate Qwf is large.

[0082] The reason for changing the pressure regulating valve characteristics in accordance with the first estimated through flow rate Qr1 will be described with reference to FIG. 6. FIG. 6 is a schematic diagram of the first pressure regulating valve 61. The first pressure regulating valve 61 is a normally-open linear solenoid valve. Therefore, in the first pressure regulating valve 61, an electromagnetic force corresponding to the magnitude of the current flowing through the solenoid acts on the plunger 61a. As the electromagnetic force acting on the plunger 61a increases, the amount of brake fluid passing through the first pressure regulating valve 61 and heading toward the second pressure regulating valve 62, out of the brake fluid heading toward the first pressure regulating valve 61 in the return flow path 55, decreases, while the amount of brake fluid heading toward the servo chamber Rs via the first connecting flow path 67 increases.

[0083] When the brake fluid discharged from the pump 51 to the return flow path 55 passes through the first pressure regulating valve 61, the greater the flow rate of the brake fluid into the first pressure regulating valve 61, the more the plunger 61a is pushed in a direction that increases the opening degree of the first pressure regulating valve 61. Therefore, in order to prevent the opening degree of the first pressure regulating valve 61 from increasing, it is preferable to increase the electromagnetic force acting on the plunger 61a as the flow rate of the brake fluid into the first pressure regulating valve 61 increases.

[0084] When the second wheel pressure Pwf is reduced, the brake fluid in the servo chamber Rs of the master unit 30 is returned to the return flow path 55 from the first connecting flow path 67. In this case, the brake fluid passing through the first pressure regulating valve 61 includes both the brake fluid discharged from the pump 51 to the return flow path 55 and the brake fluid returned from the servo chamber Rs. As a result, the flow rate of brake fluid into the first pressure regulating valve 61, i.e., the flow rate of brake fluid passing through the first pressure regulating valve 61, is greater than when the second wheel pressure Pwf is not reduced.

[0085] When the second wheel pressure Pwf is increased, a portion of the brake fluid discharged from the pump 51 to the return flow path 55 is supplied to the servo chamber Rs via the first connecting flow path 67, while the remainder passes through the first pressure regulating valve 61. As a result, the flow rate of brake fluid into the first pressure regulating valve 61, i.e., the flow rate of brake fluid passing through the first pressure regulating valve 61, becomes smaller than when the second wheel pressure Pwf is not increased.

[0086] As described above, the greater the decrease in the second wheel pressure Pwf, the greater the first estimated through flow rate Qr1. Therefore, by increasing the current flowing through the solenoid of the first pressure regulating valve 61 as the first estimated through flow rate Qr1 increases, the accuracy of adjusting the hydraulic pressure in the portion of the return flow path 55 between the first pressure regulating valve 61 and the second pressure regulating valve 62 can be improved.

[0087] Therefore, in this embodiment, the processing circuit 91 selects a pressure regulating valve characteristic corresponding to the first estimated through flow rate Qr1 in the third map MP3 shown in Fig. 4. Then, the processing circuit 91 derives the first reference current Isj based on the selected pressure regulating valve characteristic.

[0088] <First differential pressure deviation derivation process> 3, in the first differential pressure deviation derivation process M47, the processing circuit 91 derives a first differential pressure deviation hSj, which is the deviation between the second target wheel pressure Ptf and the first servo pressure Pp. For example, the processing circuit 91 derives the first differential pressure deviation hSj by subtracting the first servo pressure Pp from the second target wheel pressure Ptf.

[0089] <First compensation current derivation process> In the first compensation current derivation process M49, the processing circuit 91 derives a first compensation current Ihj based on the first differential pressure deviation hSj. The first compensation current Ihj is a current that flows through the solenoid of the first pressure regulating valve 61 to correct the discrepancy between the first target differential pressure Stj and the first actual differential pressure Saj. The processing circuit 91 derives the first compensation current Ihj so that the larger the first differential pressure deviation hSj, the larger the first compensation current Ihj.

[0090] For example, the processing circuit 91 derives the first compensation current Ihj based on a fourth map MP4. The fourth map MP4 is a map showing the relationship between the differential pressure deviation and the current. In this case, when the absolute value of the first differential pressure deviation hSj is equal to or less than a predetermined value, the processing circuit 91 derives 0 (zero) as the first compensation current Ihj. When the absolute value of the first differential pressure deviation hSj is equal to or less than the predetermined value, it is determined that there is almost no deviation between the first target differential pressure Stj and the first actual differential pressure Saj. When the first differential pressure deviation hSj is a positive value and the absolute value of the first differential pressure deviation hSj is greater than the predetermined value, the processing circuit 91 derives a positive value as the first compensation current Ihj. Specifically, the processing circuit 91 derives the first compensation current Ihj so that the larger the first differential pressure deviation hSj, the larger the first compensation current Ihj. When the first differential pressure deviation hSj is a negative value and the absolute value of the first differential pressure deviation hSj is greater than a predetermined value, the processing circuit 91 derives a negative value as the first compensation current Ihj. Specifically, the processing circuit 91 derives the first compensation current Ihj so that the smaller the first differential pressure deviation hSj is, the smaller the first compensation current Ihj becomes.

[0091] <First target current derivation process> In the first target current derivation process M51, the processing circuit 91 derives a first target current Itj, which is a target value of the current to be passed through the solenoid of the first pressure regulating valve 61. The processing circuit 91 derives the sum of the first standard current Isj and the first compensation current Ihj as the first target current Itj.

[0092] This first target current Itj corresponds to the "instructed opening" that is the instruction value for the opening of the first pressure regulating valve 61. Because the first pressure regulating valve 61 is a normally open linear solenoid valve, it can be said that the processing circuit 91 reduces the instruction opening as the first estimated through flow rate Qr1 increases. In other words, it can be said that the first norm current derivation process M43, the first compensation current derivation process M49, and the first target current derivation process M51 constitute an example of an "opening adjustment process."

[0093] <First current feedback processing> In the first current F / B processing M53, the processing circuit 91 operates the first pressure regulating valve 61 based on the first target current Itj and the actual current Ij flowing through the solenoid of the first pressure regulating valve 61. Specifically, the processing circuit 91 operates the first pressure regulating valve 61 by feedback control using the deviation between the first target current Itj and the current Ij as an input.

[0094] <Various processes for driving the second pressure regulating valve> With reference to FIG. 3, various processes executed by the processing circuit 91 to drive the second pressure regulating valve 62 will be described.

[0095] The processing circuit 91 executes a second target differential pressure derivation process M61, a second passing flow rate derivation process M62, a second standard current derivation process M63, a second differential pressure deviation derivation process M67, and a second compensation current derivation process M69. Furthermore, the processing circuit 91 executes a second target current derivation process M71 and a second current feedback process M73. Hereinafter, the second current feedback process M73 will be referred to as a "second current F / B process M73." The processing circuit 91 controls the aperture of the second pressure regulating valve 62 by repeatedly executing these various processes M61 to M73 at predetermined control intervals.

[0096] <Second target differential pressure derivation process> In the second target differential pressure derivation process M61, the processing circuit 91 derives the second target differential pressure Stk. The second target differential pressure Stk is a target value of the differential pressure between the portion of the return flow passage 55 between the first pressure regulating valve 61 and the second pressure regulating valve 62 and the portion of the return flow passage 55 between the first pressure regulating valve 61 and the end of the return flow passage 55 on the reservoir tank 21 side. The hydraulic pressure in the portion of the return flow passage 55 between the first pressure regulating valve 61 and the second pressure regulating valve 62 can be considered to be equal to the first wheel pressure Pwr. Furthermore, the portion of the return flow passage 55 between the second pressure regulating valve 62 and the end of the return flow passage 55 on the reservoir tank 21 side is atmospheric pressure. Therefore, the processing circuit 91 derives the first target wheel pressure Ptr as the second target differential pressure Stk.

[0097] <Second passing flow rate derivation process> In the second passing flow rate derivation process M62, the processing circuit 91 derives a second estimated passing flow rate Qr2. The second estimated passing flow rate Qr2 is an estimate of the amount of brake fluid passing through the second pressure regulating valve 62. The processing circuit 91 derives the second estimated passing flow rate Qr2 based on the first required flow rate Qwr and the second required flow rate Qwf derived in the required flow rate derivation process M25 and the required flow rate Qu derived in the required flow rate derivation process M27. For example, the processing circuit 91 can derive the second estimated passing flow rate Qr2 by referring to the following relational expression (D2). In the relational expression (D2), "QwrA" is the product of the first required flow rate Qwr and "-1", and "QwfA" is the product of the second required flow rate Qwf and "-1". As a result, the processing circuit 91 derives the second estimated passing flow rate Qr2 so that it increases as the product QwfA increases. Furthermore, the processing circuit 91 derives the first estimated passing flow rate Qr1 so that the first estimated passing flow rate Qr1 increases as the product QwrA increases.

[0098] Qr2 = MAX(QwrA, 0)+MAX(QwfA, 0)+Qu …(D2) In the above relational expression (D2), "MAX(QwrA, 0)" corresponds to the decrease in the first wheel pressure Pwr, and "MAX(QwfA, 0)" corresponds to the decrease in the second wheel pressure Pwf. The required flow rate Qu is the minimum amount of brake fluid returned to the reservoir tank 21 via the return flow path 55 when the pump 51 is operated. When the first wheel pressure Pwr is reduced, the greater the amount of reduction, the greater the amount of brake fluid passing through the second pressure regulating valve 62. When the second wheel pressure Pwf is reduced, the brake fluid flowing out of the servo chamber Rs flows toward the reservoir tank 21 via the first pressure regulating valve 61 and the second pressure regulating valve 62. Therefore, the greater the amount of reduction in the second wheel pressure Pwf, the greater the amount of brake fluid passing through the second pressure regulating valve 62.

[0099] <Second reference current derivation process> In the second standard current derivation process M63, the processing circuit 91 derives a second standard current Isk, which is a current value corresponding to the second target differential pressure Stk. The second standard current Isk is a current that corresponds to the second target differential pressure Stk and flows through the solenoid of the second pressure regulating valve 62. The processing circuit 91 derives the second standard current Isk based on the second estimated through flow rate Qr2 and the second target differential pressure Stk. For example, the processing circuit 91 derives the second standard current Isk so that it increases as the second target differential pressure Stk increases. Alternatively, for example, the processing circuit 91 derives the second standard current Isk so that it increases as the second estimated through flow rate Qr2 decreases.

[0100] In this embodiment, the processing circuit 91 derives the second reference current Isk based on a fifth map MP5 shown in FIG. 5 . The fifth map MP5 is a map that shows the relationship between the second target differential pressure Stk and the current flowing through the solenoid of the second pressure regulating valve 62. The second pressure regulating valve 62 is a normally-open linear solenoid valve. Therefore, the larger the current flowing through the solenoid, the smaller the aperture of the second pressure regulating valve 62. The smaller the aperture of the second pressure regulating valve 62, the larger the differential pressure. The fifth map MP5 is pre-stored in the first memory 93 of the processing circuit 91. The fifth map MP5 is also referred to as a “second pressure regulating valve characteristic” that shows the relationship between the second target differential pressure Stk and the aperture of the second pressure regulating valve 62.

[0101] 5, the fifth map MP5 includes a plurality of second pressure regulating valve characteristics corresponding to the second estimated through flow rate Qr2. In any of the plurality of second pressure regulating valve characteristics, the current increases as the second target differential pressure Stk increases.

[0102] Of the multiple second pressure regulating valve characteristics, the reference pressure regulating valve characteristic Zf0 is the second pressure regulating valve characteristic when the second estimated throughflow rate Qr2 is 0 (zero). In FIG. 5, the reference pressure regulating valve characteristic Zf0 is indicated by a dashed line. Of the multiple second pressure regulating valve characteristics, the increasing pressure regulating valve characteristic Zf1 is the second pressure regulating valve characteristic when the second estimated throughflow rate Qr2 is greater than 0 (zero). In other words, the increasing pressure regulating valve characteristic Zf1 is the second pressure regulating valve characteristic when the second estimated throughflow rate Qr2 is greater than the reference pressure regulating valve characteristic Zf0. In this embodiment, multiple increasing pressure regulating valve characteristics Zf1 are prepared.

[0103] When the second estimated through flow rate Qr2 is 0 (zero), the processing circuit 91 selects the reference pressure regulating valve characteristic Zf0. Then, the processing circuit 91 derives a current corresponding to the second target differential pressure Stk as the second standard current Isk based on the reference pressure regulating valve characteristic Zf0.

[0104] When the second estimated throughflow rate Qr2 is greater than 0 (zero), the processing circuit 91 selects the increasing pressure regulating valve characteristic Zf1. At this time, the processing circuit 91 selects the increasing pressure regulating valve characteristic Zf1 corresponding to the second estimated throughflow rate Qr2 from among a plurality of increasing pressure regulating valve characteristics Zf1. Then, the processing circuit 91 derives a current corresponding to the second target differential pressure Stk as the second reference current Isk based on the selected increasing pressure regulating valve characteristic Zf1.

[0105] The second estimated throughflow rate Qr2 is derived based on the first required flow rate Qwr and the second required flow rate Qwf. The smaller the sum of the first required flow rate Qwr and the second required flow rate Qwf, the larger the second estimated throughflow rate Qr2. Therefore, when the sum of the first required flow rate Qwr and the second required flow rate Qwf is small, the processing circuit 91 derives the second reference current Isk based on the increasing pressure regulation valve characteristic Zf1, among multiple increasing pressure regulation valve characteristics Zf1, that is used when the second estimated throughflow rate Qr2 is larger than when the sum is large.

[0106] <Second differential pressure deviation derivation process> 3, in the second differential pressure deviation derivation process M67, the processing circuit 91 derives a second differential pressure deviation hSk, which is the deviation between the first target wheel pressure Ptr and the second servo pressure Po. For example, the processing circuit 91 derives the second differential pressure deviation hSk by subtracting the second servo pressure Po from the first target wheel pressure Ptr.

[0107] <Second compensation current derivation process> In the second compensation current derivation process M69, the processing circuit 91 derives a second compensation current Ihk based on the second differential pressure deviation hSk. The second compensation current Ihk is a current that flows through the solenoid of the second pressure regulating valve 62 to correct the discrepancy between the second target differential pressure Stk and the second actual differential pressure Sak. The processing circuit 91 derives the second compensation current Ihk so that the larger the second differential pressure deviation hSk, the larger the second compensation current Ihk.

[0108] For example, the processing circuit 91 derives the second compensation current Ihk based on a sixth map MP6. The sixth map MP6 is a map showing the relationship between the differential pressure deviation and the current. In this case, when the absolute value of the second differential pressure deviation hSk is equal to or less than a predetermined value, the processing circuit 91 derives 0 (zero) as the second compensation current Ihk. When the absolute value of the second differential pressure deviation hSk is equal to or less than the predetermined value, it is assumed that there is almost no deviation between the second target differential pressure Stk and the second actual differential pressure Sak. When the second differential pressure deviation hSk is a positive value and the absolute value of the second differential pressure deviation hSk is greater than the predetermined value, the processing circuit 91 derives a positive value as the second compensation current Ihk. Specifically, the processing circuit 91 derives the second compensation current Ihk so that the second compensation current Ihk increases as the second differential pressure deviation hSk increases. When the second differential pressure deviation hSk is negative and the absolute value of the second differential pressure deviation hSk is greater than a predetermined value, the processing circuit 91 derives a negative value as the second compensation current Ihk. Specifically, the processing circuit 91 derives the second compensation current Ihk so that the smaller the second differential pressure deviation hSk is, the smaller the second compensation current Ihk becomes.

[0109] <Second target current derivation process> In the second target current derivation process M71, the processing circuit 91 derives a second target current Itk, which is a target value of the current to be passed through the solenoid of the second pressure regulating valve 62. The processing circuit 91 derives the second target current Itk as the sum of the second reference current Isk and the second compensation current Ihk. This second target current Itk can also be said to be an instruction value for the opening degree of the second pressure regulating valve 62.

[0110] <Second current feedback processing> In the second current F / B processing M73, the processing circuit 91 operates the second pressure regulating valve 62 based on the second target current Itk and the actual current Ik flowing through the solenoid of the second pressure regulating valve 62. Specifically, the processing circuit 91 operates the second pressure regulating valve 62 by feedback control using the deviation between the second target current Itk and the current Ik as an input.

[0111] <Actions and Effects of This Embodiment> (1-1) The processing circuit 91 of the control device 90 controls the upstream regulated pressure and the downstream regulated pressure by operating the hydraulic pressure adjustment unit 60. The upstream regulated pressure is the brake hydraulic pressure in the portion of the return flow path 55 between the check valve 56 and the first pressure adjustment valve 61. The downstream regulated pressure is the brake hydraulic pressure in the portion of the return flow path 55 between the first pressure adjustment valve 61 and the second pressure adjustment valve. The braking device 100 equipped with the processing circuit 91 can generate a wheel pressure corresponding to the upstream regulated pressure in the wheel cylinder 16 of the second wheel 11b. The braking device 100 can generate a wheel pressure corresponding to the downstream regulated pressure in the wheel cylinder 16 of the first wheel 11a.

[0112] When controlling the operation of the pump 51, the processing circuit 91 derives a first required flow rate Qwr through a first required flow rate derivation process. The processing circuit 91 also derives a second required flow rate Qwf through a second required flow rate derivation process. The processing circuit 91 then drives the electric motor 52 so that the rotation speed Nt of the electric motor 52 increases as the sum of the first required flow rate Qwr and the second required flow rate Qwf increases.

[0113] The larger the sum of the first required flow rate Qwr and the second required flow rate Qwf, the larger the total amount of brake fluid required by the multiple wheel cylinders 16. Furthermore, the higher the rotation speed Nt of the electric motor 52, the larger the amount of brake fluid discharged from the pump 51. Therefore, the processing circuit 91 increases the amount of brake fluid discharged from the pump 51 as the sum of the first required flow rate Qwr and the second required flow rate Qwf increases. On the other hand, if this sum is relatively small, the total amount of brake fluid required by the multiple wheel cylinders 16 is not that large. Therefore, in such a case, the processing circuit 91 can relatively reduce the amount of brake fluid discharged from the pump 51. In other words, the braking system 100 accurately adjusts the amount of brake fluid discharged from the pump 51. Therefore, the braking system 100 can improve the controllability of the wheel pressure Pw of the multiple wheel cylinders 16.

[0114] (1-2) The processing circuit 91 executes the standard supply rate derivation process M15 to derive a first standard supply rate Esr based on a first map MP1r corresponding to the first cylinder characteristic. The processing circuit 91 executes the estimated fluid rate derivation process M19 and the compensation fluid rate derivation process M21 to derive a first compensation fluid rate Ehr based on the first map MP1r. The processing circuit 91 then executes the required flow rate derivation process M25 to derive a brake fluid flow rate corresponding to the first standard supply rate Esr and the first compensation fluid rate Ehr as a first required flow rate Qwr.

[0115] The first standard supply rate Esr corresponds to a feedforward term corresponding to the first target wheel pressure Ptr. The first compensation fluid volume Ehr corresponds to a feedback term that corrects the discrepancy between the first target wheel pressure Ptr and the actual wheel pressure Pwr. The processing circuit 91 derives the first required flow rate Qwr based on the first standard supply rate Esr and the first compensation fluid volume Ehr. This allows the processing circuit 91 to derive the first required flow rate Qwr with higher accuracy compared to deriving the first required flow rate Qwr without using the first compensation fluid volume Ehr.

[0116] (1-3) The processing circuit 91 executes the standard supply rate derivation process M15 to derive a second standard supply rate Esf based on a first map MP1f corresponding to the second cylinder characteristic. The processing circuit 91 executes the estimated fluid rate derivation process M19 and the compensation fluid rate derivation process M21 to derive a second compensation fluid rate Ehf based on the first map MP1f. The processing circuit 91 then executes the required flow rate derivation process M25 to derive a brake fluid flow rate corresponding to the second standard supply rate Esf and the second compensation fluid rate Ehf as a second required flow rate Qwf.

[0117] The second standard supply rate Esf corresponds to a feedforward term corresponding to the second target wheel pressure Ptf. The second compensation fluid volume Ehf corresponds to a feedback term that corrects the discrepancy between the second target wheel pressure Ptf and the actual wheel pressure Pwf. The processing circuit 91 derives the second required flow rate Qwf based on the second standard supply rate Esf and the second compensation fluid volume Ehf. This allows the processing circuit 91 to derive the second required flow rate Qwf with higher accuracy than when the second required flow rate Qwf is derived without using the second compensation fluid volume Ehf.

[0118] (1-4) If the rotation speed Nt of the electric motor 52 is higher than necessary, the upstream adjustment pressure in the portion of the return flow path 55 between the check valve 56 and the first pressure regulating valve 61 is likely to become high. Therefore, in order to appropriately adjust the second wheel pressure Pwf, it is necessary to increase the current flowing through the solenoid of the first pressure regulating valve 61. In this regard, in the present embodiment, the rotation speed Nt of the electric motor 52 is optimized, so it is not necessary to increase the current flowing through the solenoid of the first pressure regulating valve 61. Therefore, in the braking system 100, an increase in power consumption in the hydraulic pressure generating device 20 can be suppressed.

[0119] (1-5) By executing the required flow rate derivation process M25, the processing circuit 91 derives, as the second required flow rate Qwf, a required value of the flow rate of brake fluid when supplying brake fluid to the wheel cylinder 16 based on the first map MP1f corresponding to the second cylinder characteristic, the second target wheel pressure Ptf, and the second wheel pressure Pwf. The processing circuit 91 derives, as the first required flow rate Qwr, a required value of the flow rate of brake fluid when supplying brake fluid to the wheel cylinder 16 based on the first map MP1r corresponding to the first cylinder characteristic, the first target wheel pressure Ptr, and the first wheel pressure Pwr. The processing circuit 91 then reduces the instructed opening of the first pressure regulating valve 61 so that the larger the first required flow rate Qwr is and the smaller the second required flow rate Qwf is.

[0120] As described above, the smaller the second required flow rate Qwf, the larger the passing flow rate, which is the flow rate of brake fluid passing through the first pressure regulating valve 61. The larger the first required flow rate Qwr, the larger the passing flow rate of the first pressure regulating valve 61. Furthermore, the larger the passing flow rate, the stronger the force with which the brake fluid pushes the plunger 61a in the direction increasing the opening of the first pressure regulating valve 61. When the second required flow rate Qwf is a negative value, the passing flow rate of the first pressure regulating valve 61 is larger than when the second required flow rate Qwf is a positive value. When the first required flow rate Qwr is a positive value, the passing flow rate of the first pressure regulating valve 61 is larger than when the first required flow rate Qwr is a negative value. Therefore, when the second required flow rate Qwf is a negative value, the first estimated passing flow rate Qr1 is derived so that it is larger than when the second required flow rate Qwf is a positive value. Furthermore, when the first required flow rate Qwr is a positive value, the first estimated passing flow rate Qr1 is derived so that it is larger than when the first required flow rate Qwr is a negative value. The larger the first estimated passing flow rate Qr1, the larger the current flowing through the solenoid of the first pressure regulating valve 61. As a result, the controllability of the opening degree of the first pressure regulating valve 61 is improved. In this way, when the accuracy of the opening degree of the first pressure regulating valve 61 is improved, the controllability of the second wheel pressure Pwf is improved.

[0121] Therefore, the braking system 100 can improve the controllability of the second wheel pressure Pwf by optimizing the instructed opening degree for the first pressure regulating valve 61. Furthermore, the increased accuracy of the opening degree of the first pressure regulating valve 61 increases the accuracy of regulating the second servo pressure Po, which is the hydraulic pressure in the portion of the return flow path 55 between the first pressure regulating valve 61 and the second pressure regulating valve 62. Therefore, the braking device 100 can also increase the controllability of the first wheel pressure Pwr.

[0122] (1-6) The processing circuit 91 selects a characteristic corresponding to the first estimated through flow rate Qr1 from among the multiple pressure regulating valve characteristics Zr0, Zr1 shown in FIG. 4. Specifically, when the first estimated through flow rate Qr1 is 0 (zero), the processing circuit 91 selects the reference pressure regulating valve characteristic Zr0. When the second target wheel pressure Ptf is decreased, the second required flow rate Qwf becomes smaller than 0 (zero). The greater the decrease in the second target wheel pressure Ptf, the greater the first estimated through flow rate Qr1. When the first target wheel pressure Ptr is increased, the first required flow rate Qwr becomes larger than 0 (zero). The greater the increase in the first target wheel pressure Ptr, the greater the first estimated through flow rate Qr1. The processing circuit 91 selects the increasing pressure regulating valve characteristic Zr1 corresponding to the first estimated through flow rate Qr1. That is, the processing circuit 91 selects the increasing pressure regulating valve characteristic Zr1 in consideration of the amount of decrease in the second target wheel pressure Ptf and the amount of increase in the first target wheel pressure Ptr. Based on the selected characteristic, the processing circuit 91 derives the first reference current Isj that correlates with the command opening of the first pressure regulating valve 61.

[0123] The processing circuit 91 derives the first standard current Isj based on the pressure regulating valve characteristics corresponding to the first estimated through flow rate Qr1 at that time. Subsequently, the processing circuit 91 derives the first target current Itj based on the first standard current Isj. Then, the processing circuit 91 operates the first pressure regulating valve 61 based on the first target current Itj. Therefore, the processing circuit 91 can control the first pressure regulating valve 61 with high accuracy.

[0124] (1-7) The smaller the sum of the first required flow rate Qwr and the second required flow rate Qwf, the smaller the opening degree that the processing circuit 91 instructs the second pressure regulating valve 62 to be. As described above, the smaller the sum of the first required flow rate Qwr and the second required flow rate Qwf, the larger the passing flow rate, which is the flow rate of brake fluid passing through the second pressure regulating valve 62. Furthermore, the larger the passing flow rate through the second pressure regulating valve 62, the greater the force with which the brake fluid pushes the plunger of the second pressure regulating valve 62 in a direction that increases the aperture of the second pressure regulating valve 62. When the sum of the first required flow rate Qwr and the second required flow rate Qwf is negative, the passing flow rate through the second pressure regulating valve 62 is larger than when the sum is positive. Therefore, when the sum is negative, the second estimated passing flow rate Qr2 is calculated so that it is larger than when the sum is positive. Furthermore, the larger the second estimated passing flow rate Qr2, the larger the current flowing through the solenoid of the second pressure regulating valve 62. As a result, the controllability of the aperture of the second pressure regulating valve 62 is improved. In this way, when the accuracy of the aperture of the second pressure regulating valve 62 is improved, the controllability of the first wheel pressure Pwr is improved.

[0125] Therefore, the braking system 100 can improve the controllability of the first wheel pressure Pwr by optimizing the instructed opening degree for the second pressure regulating valve 62. (Second embodiment) A second embodiment of the braking device will be described with reference to Figures 7 and 8. The second embodiment differs from the first embodiment in part of the configuration of the pressurizing unit of the hydraulic pressure generating device, and in part of the control of the electric motor and pressure regulating valve that are the power source for the pump. In the following explanation, parts that differ from the first embodiment will be mainly described, and the same components as those in the first embodiment will be assigned the same reference numerals and redundant explanations will be omitted.

[0126] <Pressure unit of hydraulic pressure generator> As shown in FIG. 7, the pressurizing unit 50A includes a pump 51, a supply flow path 54, a return flow path 55, a hydraulic pressure adjusting section 60A, and a first servo pressure sensor 65.

[0127] The fluid pressure adjustment unit 60A is provided in a portion of the return flow path 55 between the check valve 56 and the end portion on the reservoir tank 21 side. The fluid pressure adjustment unit 60A has a pressure adjustment valve 61A, which is a normally open linear solenoid valve. In the return flow path 55, a connection point with the first connection flow path 67 is referred to as a first connection point 55a, and a connection point with the second connection flow path 68 is referred to as a second connection point 55b. In this case, the pressure adjustment valve 61A is disposed in a portion of the return flow path 55 between the first connection point 55a and the second connection point 55b and the end portion on the reservoir tank 21 side.

[0128] When the pump 51 is discharging brake fluid, the pressurizing unit 50A operates the hydraulic pressure adjusting unit 60A to supply brake fluid at a regulated pressure to the brake actuator 80 and the master cylinder 31. Specifically, a portion of the brake fluid whose pressure is regulated by the pressure adjusting valve 61A of the hydraulic pressure adjusting unit 60A is supplied from the second connecting flow path 68 to the first hydraulic pressure circuit 81 of the brake actuator 80. As a result, the brake fluid is supplied to two of the multiple wheel cylinders 16 that are connected to the first hydraulic pressure circuit 81, and the wheel pressure Pw of those two wheel cylinders 16 increases.

[0129] Of the brake fluid whose pressure is adjusted by the pressure regulating valve 61A, the brake fluid that does not flow into the second connecting flow path 68 is supplied from the first connecting flow path 67 to the servo chamber Rs of the master device 30. Then, the fluid pressure in the servo chamber Rs increases, causing the master piston 43 to move forward. This increases the fluid pressure in the master chamber Rm, and brake fluid is supplied from the master chamber Rm to the second hydraulic circuit 82 of the brake actuator 80. As a result, brake fluid is supplied to two of the multiple wheel cylinders 16 that are connected to the second hydraulic circuit 82, and the wheel pressure Pw of those two wheel cylinders 16 increases.

[0130] <Various processes for driving electric motors> With reference to FIG. 8, various processes executed by the processing circuit 91 to drive the electric motor 52 will be described.

[0131] The processing circuit 91 executes a required braking force derivation process M11, a target wheel pressure setting process M13A, a standard supply rate derivation process M15A, an estimated wheel pressure derivation process M17A, an estimated fluid volume derivation process M19A, and a compensation fluid volume derivation process M21A. Furthermore, the processing circuit 91 executes a fluid volume conversion process M23A, a required flow rate derivation process M25A, a required flow rate derivation process M27A, a target flow rate derivation process M29A, a target rotation speed derivation process M31, and a rotation speed feedback process M33. The processing circuit 91 controls the discharge of brake fluid from the pump 51 by repeatedly executing these various processes at predetermined control intervals.

[0132] Of the above processes, the target wheel pressure setting process M13A, standard supply volume derivation process M15A, estimated wheel pressure derivation process M17A, estimated fluid volume derivation process M19A, compensation fluid volume derivation process M21A, fluid volume conversion process M23A, required flow rate derivation process M25A, essential flow rate derivation process M27A, and target flow rate derivation process M29A differ in content from the first embodiment. Therefore, the content of these processes will be described below. Meanwhile, a description of processes that are the same as those in the first embodiment will be omitted.

[0133] <Target wheel pressure setting process> In the target wheel pressure setting process M13A, the processing circuit 91 sets the target wheel pressure Pt based on the vehicle braking force requirement value Fv. The target wheel pressure Pt set here is a common target value for the first wheel cylinder and the second wheel cylinder.

[0134] When a regenerative braking force FvR is generated at the first wheel 11a, the processing circuit 91 sets the target wheel pressure Pt taking the regenerative braking force FvR into consideration. The braking force obtained by subtracting the regenerative braking force FvR from the vehicle braking force request value Fv is the target value of the frictional braking force. The processing circuit 91 sets the wheel pressure according to the target value of the frictional braking force as the target wheel pressure Pt.

[0135] <Standard supply amount derivation process> In the standard supply amount derivation process M15A, the processing circuit 91 derives a standard supply amount Es based on the target wheel pressure Pt. The standard supply amount Es is the amount of brake fluid required to make the wheel pressures Pw in all wheel cylinders 16 equal to the target wheel pressure Pt. Therefore, the processing circuit 91 derives the standard supply amount Es so that it increases as the target wheel pressure Pt increases.

[0136] For example, the processing circuit 91 derives the first standard supply rate Esr and the second standard supply rate Esf based on the above-mentioned first map MP1. The processing circuit 91 derives the brake fluid amount corresponding to the target wheel pressure Pt as the first standard supply rate Esr based on the first map MP1r for the first wheel 11a. The processing circuit 91 derives the brake fluid amount corresponding to the target wheel pressure Pt as the second standard supply rate Esf based on the first map MP1f for the second wheel 11b. Then, the processing circuit 91 derives the sum of the first standard supply rate Esr and the second standard supply rate Esf as the standard supply rate Es.

[0137] <Estimated wheel pressure derivation process> In the estimated wheel pressure derivation process M17A, the processing circuit 91 derives the wheel pressure Pw, which is an estimated value of the wheel pressure. Here, the processing circuit 91 derives the wheel pressure Pw assuming that the wheel pressures in all the wheel cylinders 16 are the same. For example, the processing circuit 91 derives the hydraulic pressure corresponding to the first servo pressure Pp as the wheel pressure Pw.

[0138] <Estimated fluid volume derivation process> In the estimated fluid volume derivation process M19A, the processing circuit 91 derives an estimated fluid volume Ee, which is an estimate of the amount of brake fluid stored in the wheel cylinder 16. In this embodiment, the processing circuit 91 derives the estimated fluid volume Ee as the sum of the first estimated fluid volume Eer and the second estimated fluid volume Eef. The first estimated fluid volume Eer is the estimated fluid volume in the wheel cylinder 16 of the first wheel 11a. The second estimated fluid volume Eef is the estimated fluid volume in the wheel cylinder 16 of the second wheel 11b. The method of deriving the first estimated fluid volume Eer and the second estimated fluid volume Eef is the same as in the first embodiment described above.

[0139] <Compensation liquid volume derivation process> In the compensation fluid volume derivation process M21A, the processing circuit 91 derives the compensation fluid volume Eh based on the standard supply volume Es and the estimated fluid volume Ee. For example, the processing circuit 91 derives the compensation fluid volume Eh by subtracting the estimated fluid volume Ee from the standard supply volume Es.

[0140] <Liquid volume conversion processing> In the fluid volume conversion process M23A, the processing circuit 91 converts the brake fluid volume into a flow rate of the brake fluid. Specifically, the processing circuit 91 converts the standard supply volume Es into a standard flow rate Qs, and converts the compensation fluid volume Eh into a compensation flow rate Qh. For example, the processing circuit 91 derives the standard flow rate Qs as a value obtained by differentiating the standard supply volume Es with respect to time, and derives the compensation fluid volume Eh with respect to time as a value obtained by differentiating the compensation fluid volume Qh with respect to time.

[0141] <Required flow rate derivation process> In the required flow rate derivation process M25A, the processing circuit 91 derives the amount of brake fluid corresponding to the standard supply rate Es and the compensation fluid rate Eh as a required flow rate Qw, which is the required value of the flow rate of brake fluid to the wheel cylinder 16. In this embodiment, the processing circuit 91 derives the required flow rate Qw based on the standard flow rate Qs and the compensation flow rate Qh. For example, the processing circuit 91 derives the sum of the standard flow rate Qs and the compensation flow rate Qh as the required flow rate Qw.

[0142] <Required flow rate derivation process> In the essential flow rate derivation process M27A, the processing circuit 91 derives the essential flow rate Qu as the total flow rate of brake fluid to the multiple wheel cylinders 16 required to achieve the target wheel pressure Pt. Specifically, the processing circuit 91 derives the essential flow rate Qu so that it increases as the target wheel pressure Pt increases.

[0143] For example, the processing circuit 91 derives the required flow rate Qu based on a second map MP2A. The second map MP2A is a map showing the relationship between the wheel pressure Pw and the flow rate of brake fluid. In this case, the processing circuit 91 derives the flow rate of brake fluid corresponding to the target wheel pressure Pt as the required flow rate Qu based on the second map MP2A.

[0144] <Target flow rate derivation process> In the target flow rate derivation process M29A, the processing circuit 91 derives the target flow rate Qt based on the required flow rate Qw and the required flow rate Qu. For example, when the required flow rate Qw is greater than 0 (zero), the processing circuit 91 derives the sum of the required flow rate Qw and the required flow rate Qu as the target flow rate Qt. When the required flow rate Qw is equal to or less than 0 (zero), the processing circuit 91 derives the required flow rate Qu as the target flow rate Qt.

[0145] <Various processes for driving the pressure regulating valve> The processing circuit 91 controls the pressure regulating valve 61A. In this case, the processing circuit 91 controls the pressure regulating valve 61A by executing a process equivalent to the process for driving the second pressure regulating valve 62 in the first embodiment.

[0146] Specifically, the processing circuit 91 derives the target differential pressure StA by executing processing equivalent to the second target differential pressure derivation processing M61. The target differential pressure StA is a target value of the differential pressure between a portion of the reflux flow path 55 between the check valve 56 and the pressure regulating valve 61A and a portion of the reflux flow path 55 between the pressure regulating valve 61A and the end of the reflux flow path 55 on the reservoir tank 21 side. The hydraulic pressure in the portion of the reflux flow path 55 between the check valve 56 and the pressure regulating valve 61A can be considered to be equal to the wheel pressure Pw. Furthermore, the portion of the reflux flow path 55 between the pressure regulating valve 61A and the end of the reflux flow path 55 on the reservoir tank 21 side is atmospheric pressure. Therefore, the processing circuit 91 may derive the target wheel pressure Pt as the target differential pressure StA.

[0147] The processing circuit 91 executes a process equivalent to the second passing flow rate derivation process M62, thereby The estimated passing flow rate QrA is derived. The estimated passing flow rate QrA is an estimated value of the amount of brake fluid passing through the pressure regulating valve 61A. The processing circuit 91 derives the estimated passing flow rate QrA based on the required flow rate Qw derived in the required flow rate derivation process M25A and the required flow rate Qu derived in the required flow rate derivation process M27A. For example, when the required flow rate Qw is equal to or greater than 0 (zero), the processing circuit 91 derives the required flow rate Qu as the estimated passing flow rate QrA. When the required flow rate Qw is less than 0 (zero), the processing circuit 91 derives the sum of the product of the required flow rate Qw and "-1" and the required flow rate Qu as the estimated passing flow rate QrA.

[0148] The processing circuit 91 executes processing equivalent to the second standard current derivation processing M63 to derive a standard current IsA, which is a current value corresponding to the target differential pressure StA. The standard current IsA is a current corresponding to the target differential pressure StA and passed through the solenoid of the pressure regulating valve 61A. The processing circuit 91 derives the standard current IsA based on the estimated through flow rate QrA and the target differential pressure StA. For example, the processing circuit 91 derives the standard current IsA so that it increases as the target differential pressure StA increases. Alternatively, for example, the processing circuit 91 derives the standard current IsA so that it increases as the estimated through flow rate QrA decreases. In this case, the processing circuit 91 may derive the standard current IsA using a map such as that shown in FIG. 5.

[0149] The processing circuit 91 executes a process equivalent to the second differential pressure deviation derivation process M67 to derive a differential pressure deviation hSA, which is the deviation between the target wheel pressure Pt and the first servo pressure Pp. For example, the processing circuit 91 derives the differential pressure deviation hSA by subtracting the first servo pressure Pp from the target wheel pressure Pt.

[0150] The processing circuit 91 derives the compensation current IhA based on the differential pressure deviation hSA by executing a process equivalent to the second compensation current derivation process M69. In this case, the processing circuit 91 may derive the compensation current IhA based on the sixth map MP6 shown in FIG.

[0151] The processing circuit 91 executes processing equivalent to the second target current derivation processing M71 to derive a target current ItA, which is a target value of the current to be passed through the solenoid of the pressure regulating valve 61A. In this case, the processing circuit 91 derives the target current ItA based on the reference current IsA and the compensation current IhA. For example, the processing circuit 91 derives the sum of the reference current IsA and the compensation current IhA as the target current ItA. This target current ItA can also be considered to be an indication value of the opening degree of the pressure regulating valve 61A.

[0152] Then, the processing circuit 91 executes processing equivalent to the second current F / B processing M73 to operate the pressure regulating valve 61A based on the target current ItA and the actual current IA flowing through the solenoid of the pressure regulating valve 61A. Specifically, the processing circuit 91 operates the pressure regulating valve 61A by feedback control using the deviation between the target current ItA and the current IA as an input.

[0153] <Actions and Effects of This Embodiment> (2-1) The processing circuit 91 of the control device 90 controls the adjustment pressure by operating the hydraulic pressure adjustment unit 60A. The adjustment pressure is the brake hydraulic pressure in the portion of the return flow path 55 between the check valve 56 and the pressure adjustment valve 61A. The braking device 100 equipped with the processing circuit 91 can generate a wheel pressure Pw corresponding to the adjustment pressure in either the wheel cylinder 16 of the first wheel 11a or the wheel cylinder 16 of the second wheel 11b.

[0154] When controlling the operation of the pump 51, the processing circuit 91 derives the required flow rate Qw by a required flow rate derivation process M25A. Then, the processing circuit 91 drives the electric motor 52 so that the rotation speed Nt of the electric motor 52 increases as the required flow rate Qw increases.

[0155] The larger the required flow rate Qw, the larger the amount of brake fluid required by the multiple wheel cylinders 16. Furthermore, the higher the rotation speed Nt of the electric motor 52, the larger the amount of brake fluid discharged from the pump 51. Therefore, the processing circuit 91 increases the amount of brake fluid discharged from the pump 51 as the required flow rate Qw increases. On the other hand, if the required flow rate Qw is relatively small, the amount of brake fluid required by the multiple wheel cylinders 16 is not that large. Therefore, in such a case, the processing circuit 91 can relatively reduce the amount of brake fluid discharged from the pump 51. In other words, the braking system 100 accurately adjusts the amount of brake fluid discharged from the pump 51. Therefore, the braking system 100 can improve the controllability of the wheel pressure Pw of the multiple wheel cylinders 16.

[0156] (2-2) The processing circuit 91 executes a standard supply rate derivation process M15A to derive a standard supply rate Es based on the first maps MP1r and MP1f corresponding to the wheel-cylinder relationship. Then, the processing circuit 91 executes a required flow rate derivation process M25A to derive a required flow rate Qw, which is a brake fluid flow rate corresponding to the standard supply rate Es and the compensation fluid rate Eh.

[0157] The standard supply rate Es corresponds to a feedforward term corresponding to the target wheel pressure Pt. The compensation fluid volume Eh corresponds to a feedback term that corrects the discrepancy between the target wheel pressure Pt and the actual wheel pressure Pw. The processing circuit 91 derives the required flow rate Qw based on the standard supply rate Es and the compensation fluid volume Eh. This allows the processing circuit 91 to derive the required flow rate Qw with higher accuracy compared to when the required flow rate Qw is derived without using the compensation fluid volume Eh.

[0158] (2-3) By executing the required flow rate derivation process M25A, the processing circuit 91 derives the required value of the flow rate of brake fluid when supplying brake fluid to the wheel cylinder 16 based on the first map MP1, the target wheel pressure Pt, and the wheel pressure Pw as the required flow rate Qw. The processing circuit 91 can then reduce the instructed opening of the pressure regulating valve 61A as the required flow rate Qw decreases.

[0159] The smaller the required flow rate Qw, the larger the passing flow rate, which is the flow rate of brake fluid passing through the pressure regulating valve 61A. Furthermore, the larger the passing flow rate through the pressure regulating valve 61A, the greater the force with which the brake fluid pushes the plunger of the pressure regulating valve 61A in the direction increasing the opening of the pressure regulating valve 61A. When the required flow rate Qw is a negative value, the passing flow rate through the pressure regulating valve 61A is larger than when the required flow rate Qw is a positive value. Therefore, when the required flow rate Qw is a negative value, the estimated passing flow rate QrA is derived so that the passing flow rate is larger than when the required flow rate Qw is a positive value. Furthermore, the larger the estimated passing flow rate QrA, the greater the current flowing through the solenoid of the pressure regulating valve 61A. As a result, the controllability of the opening of the pressure regulating valve 61A is improved. In this way, when the accuracy of the opening of the pressure regulating valve 61A is improved, the controllability of the wheel pressure Pw is improved.

[0160] Therefore, the braking system 100 can improve the controllability of the wheel pressure Pw by optimizing the instructed opening degree of the pressure regulating valve 61A. <Example of change> 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.

[0161] In the first embodiment, the processing circuit 91 may derive the first required flow rate Qwr without using the first compensation fluid volume Ehr. In this case, the processing circuit 91 may derive the first required flow rate Qwr as the flow rate of brake fluid derived based on the first standard supply volume Esr in the first required flow rate derivation process.

[0162] Furthermore, when the wheel pressure Pwr is lower than the first target wheel pressure Ptr, the processing circuit 91 may derive the first required flow rate Qwr by adding a positive offset value to the brake fluid flow rate derived based on the first standard supply rate Esr. On the other hand, when the wheel pressure Pwr is higher than the first target wheel pressure Ptr, the processing circuit 91 may derive the first required flow rate Qwr by subtracting a positive offset value from the brake fluid flow rate derived based on the first standard supply rate Esr. In other words, when the wheel pressure Pwr deviates from the first target wheel pressure Ptr, the processing circuit 91 may derive the first required flow rate Qwr by correcting the brake fluid flow rate derived based on the first standard supply rate Esr.

[0163] In the first embodiment, the processing circuit 91 may derive the second required flow rate Qwf without using the second compensation fluid volume Ehf. In this case, the processing circuit 91 may derive the second required flow rate Qwf as the flow rate of brake fluid derived based on the second standard supply volume Esf in the second required flow rate derivation process.

[0164] When the wheel pressure Pwf is lower than the second target wheel pressure Ptf, the processing circuit 91 may derive the second required flow rate Qwf by adding a positive offset value to the brake fluid flow rate derived based on the second standard supply rate Esf. On the other hand, when the wheel pressure Pwf is higher than the second target wheel pressure Ptf, the processing circuit 91 may derive the second required flow rate Qwf by subtracting a positive offset value from the brake fluid flow rate derived based on the second standard supply rate Esf. In other words, when the wheel pressure Pwf deviates from the second target wheel pressure Ptf, the processing circuit 91 may derive the second required flow rate Qwf by correcting the brake fluid flow rate derived based on the second standard supply rate Esf.

[0165] In the second embodiment, the processing circuit 91 may derive the required flow rate Qw without using the compensation fluid volume Eh. In this case, the processing circuit 91 may derive the required flow rate Qw as a flow rate of brake fluid based only on the standard supply volume Es out of the standard supply volume Es and the compensation fluid volume Eh in the required flow rate derivation process M25A.

[0166] Furthermore, when the wheel pressure Pw is lower than the target wheel pressure Pt, the processing circuit 91 may increase the required flow rate Qw by adding a positive offset value to the brake fluid flow rate based only on the standard supply rate Es out of the standard supply rate Es and the compensation fluid rate Eh. On the other hand, when the wheel pressure Pw is higher than the target wheel pressure Pt, the processing circuit 91 may decrease the required flow rate Qw by subtracting a positive offset value from the brake fluid flow rate based only on the standard supply rate Es out of the standard supply rate Es and the compensation fluid rate Eh. In other words, when the wheel pressure Pw deviates from the target wheel pressure Pt, the processing circuit 91 may derive the required flow rate Qw by correcting the brake fluid flow rate based only on the standard supply rate Es out of the standard supply rate Es and the compensation fluid rate Eh.

[0167] The first cylinder characteristic does not have to be the first map MP1r shown in Figures 2 and 8, as long as it shows the relationship between the amount of brake fluid supplied to the first wheel cylinder and the first wheel pressure Pwr. For example, the first cylinder characteristic may be a relational expression that shows the relationship between the amount of brake fluid supplied to the first wheel cylinder and the first wheel pressure Pwr.

[0168] The second cylinder characteristic does not have to be the first map MP1f shown in Figures 2 and 8, as long as it shows the relationship between the amount of brake fluid supplied to the second wheel cylinder and the second wheel pressure Pwf. For example, the second cylinder characteristic may be a relational expression that shows the relationship between the amount of brake fluid supplied to the second wheel cylinder and the second wheel pressure Pwf.

[0169] In the first embodiment, the hydraulic pressure generator 20 may connect a portion of the return flow passage 55 between the check valve 56 and the first pressure regulating valve 61 to the first hydraulic pressure circuit 81 of the brake actuator 80 via a connecting flow passage. Also, the hydraulic pressure generator 20 may connect a portion of the return flow passage 55 between the first pressure regulating valve 61 and the second pressure regulating valve 62 to the servo chamber Rs of the master unit 30 via a connecting flow passage. In this case, the hydraulic pressure generator 20 can be mounted on an electric vehicle that is capable of applying regenerative braking force to the second wheel 11b but is not capable of applying regenerative braking force to the first wheel 11a.

[0170] In the above embodiments, the brake fluid is supplied to the second hydraulic circuit 82 of the brake actuator 80 via the master device 30, but this is not limiting. For example, the hydraulic pressure generating device may be configured to directly supply the brake fluid discharged from the pump 51 to the second hydraulic circuit 82.

[0171] The vehicle to which the braking device 100 is applied may be a vehicle having at least one front wheel and at least one rear wheel. The processing circuit 91 is not limited to a circuit having a CPU and ROM and executing software processing. In other words, the processing circuit 91 may have any one of the following configurations (a), (b), and (c):

[0172] (a) The processing circuit 91 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 configured to cause the CPU to execute processes. The memory, i.e., computer-readable medium, includes any available medium that can be accessed by a general-purpose or special-purpose computer.

[0173] (b) The processing circuit 91 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."

[0174] (c) The processing circuitry 91 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.

[0175] <Other technical ideas> The technical ideas that can be understood from the above-described embodiments and modifications will be described. [Appendix 1] It is preferable that the control device derives a required flow rate, which is a required value of the flow rate of brake fluid when supplying brake fluid to the wheel cylinder, based on a target wheel pressure, which is a target for the wheel pressure, and the difference between the target wheel pressure and the wheel pressure.

[0176] [Appendix 2] The control device is a brake fluid supply amount to the wheel cylinder corresponding to the target wheel pressure is calculated as a standard supply amount based on the cylinder characteristics; When the wheel pressure is lower than the target wheel pressure, the standard supply amount is increased to derive the required flow rate. When the wheel pressure is higher than the target wheel pressure, it is preferable to derive the required flow rate by correcting the standard supply amount by decreasing it.

[0177] [Appendix 3] The control device deriving a first required flow rate, which is a required value of a flow rate of brake fluid when supplying brake fluid to the first wheel cylinder, based on a first target wheel pressure, which is a target of the first wheel pressure, and a difference between the first target wheel pressure and the first wheel pressure; It is preferable to derive a second required flow rate, which is a required value of the flow rate of brake fluid when supplying brake fluid to the second wheel cylinder, based on a second target wheel pressure, which is a target for the second wheel pressure, and the difference between the second target wheel pressure and the second wheel pressure.

[0178] [Appendix 4] The control device deriving a supply amount of brake fluid to the first wheel cylinder according to the first target wheel pressure as a first standard supply amount based on the first cylinder characteristic; When the first wheel pressure is lower than the first target wheel pressure, the first standard supply amount is increased and corrected to derive the first required flow rate; When the first wheel pressure is higher than the first target wheel pressure, it is preferable to derive the first required flow rate by correcting the first standard supply amount by decreasing it.

[0179] [Appendix 5] The control device deriving a supply amount of brake fluid to the second wheel cylinder corresponding to the second target wheel pressure as a second standard supply amount based on the second cylinder characteristic; When the second wheel pressure is lower than the second target wheel pressure, the second standard supply amount is increased to derive the second required flow rate; When the second wheel pressure is higher than the second target wheel pressure, it is preferable to derive the second required flow rate by correcting the second standard supply amount by decreasing it.

[0180] 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]

[0181] 11a,11b...Wheel 16...Wheel cylinder 21...Reservoir tank 51...Pump 51b...Output port 52...Electric motor 55...reflux flow path 61...First pressure regulating valve 61A... Pressure regulating valve 62...Second pressure regulating valve 90...Control device 91...Processing circuit 92...CPU 93...First memory 94...Second memory 100...braking device

Claims

1. It is applied to vehicles in which the higher the wheel pressure, which is the hydraulic pressure in the wheel cylinder, the greater the braking force generated at the wheel. a reservoir tank in which brake fluid is stored; a pump having an electric motor as a power source and configured to pump up brake fluid from the reservoir tank and discharge the pumped brake fluid from an output port; a return flow path connected to the output port and configured to return the brake fluid discharged from the output port to the reservoir tank; a pressure regulating valve provided in the reflux flow path; a control device for controlling the pump and the pressure regulating valve; the control device operates the pressure regulating valve to control an adjustment pressure, which is a brake fluid pressure in a portion of the return flow passage between the output port and the pressure regulating valve; a braking device that generates the wheel pressure corresponding to the adjusted pressure in the wheel cylinder, The control device a required flow rate derivation process for deriving a required value of the flow rate of brake fluid when supplying brake fluid to the wheel cylinder based on a cylinder characteristic indicating the relationship between the amount of brake fluid supplied to the wheel cylinder and the wheel pressure, a target wheel pressure that is a target for the wheel pressure, and the wheel pressure; and executing a pump operation process for increasing the rotation speed of the electric motor as the required flow rate increases. A braking device characterized by:

2. The control device a brake fluid supply amount to the wheel cylinder corresponding to the target wheel pressure is calculated as a standard supply amount based on the cylinder characteristics; deriving a compensation fluid amount as a brake fluid excess or deficiency amount in the wheel cylinder for making the wheel pressure equal to the target wheel pressure based on the cylinder characteristics; In the required flow rate derivation process, a flow rate of brake fluid corresponding to the standard supply amount and the compensation fluid amount is derived as the required flow rate.

2. The braking device of claim 1.

3. The control device derives an estimated fluid amount of brake fluid to be supplied to the wheel cylinder according to the wheel pressure based on the cylinder characteristics, and derives a deviation between the standard fluid amount and the estimated fluid amount as the compensation fluid amount.

3. The braking device according to claim 2.

4. The present invention is applied to a vehicle that includes a first wheel and a second wheel as wheels, and in which the braking force generated at the first wheel increases as the first wheel pressure, which is the hydraulic pressure in a first wheel cylinder, increases, and the braking force generated at the second wheel increases as the second wheel pressure, which is the hydraulic pressure in a second wheel cylinder, increases, a reservoir tank in which brake fluid is stored; a pump having an electric motor as a power source and configured to pump up brake fluid from the reservoir tank and discharge the pumped brake fluid from an output port; a return flow path connected to the output port and configured to return the brake fluid discharged from the output port to the reservoir tank; a first pressure regulating valve provided in the reflux flow path; a second pressure adjustment valve disposed in a portion of the reflux passage opposite the output port across the first pressure adjustment valve; a control device that controls the pump, the first pressure regulating valve, and the second pressure regulating valve; the control device operates the first pressure regulating valve to control an upstream regulating pressure, which is the brake fluid pressure in a portion of the return flow path between the output port and the first pressure regulating valve, and operates the first pressure regulating valve and the second pressure regulating valve to control a downstream regulating pressure, which is the brake fluid pressure in a portion of the return flow path between the first pressure regulating valve and the second pressure regulating valve; a braking device that generates the second wheel pressure in the second wheel cylinder according to the upstream adjustment pressure and generates the first wheel pressure in the first wheel cylinder according to the downstream adjustment pressure, The control device a first required flow rate derivation process for deriving a required value of the flow rate of brake fluid when supplying brake fluid to the first wheel cylinder as a first required flow rate based on a first cylinder characteristic indicating a relationship between the amount of brake fluid supplied to the first wheel cylinder and the first wheel pressure, a first target wheel pressure that is a target for the first wheel pressure, and the first wheel pressure; a second required flow rate derivation process for deriving a required value of the flow rate of brake fluid when supplying brake fluid to the second wheel cylinder as a second required flow rate based on a second cylinder characteristic indicating the relationship between the amount of brake fluid supplied to the second wheel cylinder and the second wheel pressure, a second target wheel pressure that is a target for the second wheel pressure, and the second wheel pressure; a pump operation process for increasing the rotation speed of the electric motor as the sum of the first required flow rate and the second required flow rate increases; A braking device characterized by:

5. The control device deriving a supply amount of brake fluid to the first wheel cylinder corresponding to the first target wheel pressure as a first standard supply amount based on the first cylinder characteristic; deriving a first compensation fluid amount, which is an excess or deficiency of brake fluid in the first wheel cylinder for making the first wheel pressure equal to the first target wheel pressure, based on the first cylinder characteristic; In the first required flow rate derivation process, a flow rate of brake fluid corresponding to the first standard supply rate and the first compensation fluid rate is derived as the first required flow rate; deriving a supply amount of brake fluid to the second wheel cylinder corresponding to the second target wheel pressure as a second standard supply amount based on the second cylinder characteristic; deriving a second compensation fluid amount, which is an excess or deficiency of brake fluid in the second wheel cylinder for making the second wheel pressure equal to the second target wheel pressure, based on the second cylinder characteristic; In the second required flow rate derivation process, a flow rate of brake fluid corresponding to the second standard supply rate and the second compensation fluid rate is derived as the second required flow rate.

5. The braking device according to claim 4.

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