Brake control device of vehicle

Abstract

To execute two systems of pressure adjustment by a brake control device having an electric cylinder.SOLUTION: A brake control device is applied to a vehicle having regenerative devices on front wheels. The device includes a control cylinder for generating a basic pressure using an electric motor as a power source, an electromagnetic valve for adjusting the basic pressure to an adjustment pressure, and a controller for controlling the electric motor and the electromagnetic valve, wherein a front wheel wheel pressure is controlled by the adjustment pressure, and a rear wheel wheel pressure is controlled by the basic pressure. The controller executes one of one system of pressure adjustment of making the adjustment pressure equal to the basic pressure and achieving total brake force according to a required brake amount, and two systems of pressure adjustment of making the adjustment pressure smaller than the basic pressure and achieving the total brake force in a state in which longitudinal distribution of the total brake force is maintained to a predetermined value. The brake control device calculates a first instruction pressure for controlling the adjustment pressure by the one system of pressure adjustment, and a second instruction pressure for controlling the adjustment pressure by the two systems of pressure adjustment, and selects one of the one system of pressure adjustment and the two systems of pressure adjustment, on the basis of comparison of the first instruction pressure with the second instruction pressure.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a braking control device for a vehicle. [Background technology]

[0002] Patent Document 1 describes a braking control device that can achieve both vehicle stability during braking and the amount of regenerative energy in a vehicle equipped with an energy regenerative device. Specifically, the braking control device is applied to a vehicle equipped with a regenerative generator on the front wheels, and includes an actuator that applies front wheel torque and rear wheel torque, and a controller that adjusts the front wheel torque and rear wheel torque separately. If the regenerative braking force Fg by the regenerative generator has not reached the maximum regenerative force Fx, which is the maximum value that can be generated, the controller determines the front wheel torque and the rear wheel torque to be zero. On the other hand, if the regenerative braking force Fg has reached the maximum regenerative force Fx, the controller increases the rear wheel torque from zero before increasing the front wheel torque from zero. Furthermore, when the regenerative braking force reaches the maximum regenerative force, the controller calculates a rear wheel reference force based on a required braking force corresponding to the vehicle's braking operation amount and the front / rear ratio of the braking force acting on the vehicle, calculates a complementary braking force based on the required braking force and the maximum regenerative force, and when the complementary braking force is equal to or less than the rear wheel reference force, maintains the front wheel torque at zero and increases the rear wheel torque based on the complementary braking force, and when the complementary braking force is greater than the rear wheel reference force, increases the front wheel torque based on the complementary braking force and the rear wheel reference force and increases the rear wheel torque based on the rear wheel reference force. The pressure regulation control described in Patent Document 1 is also called "two-system pressure regulation".

[0003] The applicant has developed a braking control device as described in Patent Document 2. The braking control device includes an electric cylinder 51 that discharges brake fluid from an output port 516 at a hydraulic pressure corresponding to the drive of an electric motor 513, a master cylinder 31 configured such that brake fluid flows out of the master chamber Rm as the master piston 43 moves with an increase in hydraulic pressure in the servo chamber Rs, and brake fluid flows into the master chamber Rm as the master piston 43 moves with a decrease in hydraulic pressure in the servo chamber Rs, a first flow path 331 that connects the master chamber Rm to the wheel cylinder 11 for the front wheels, a sixth flow path 58 that connects the output port 516 to the wheel cylinder 11 for the rear wheels, a fifth flow path 55 that connects the sixth flow path 58 to the servo chamber Rs, and a differential pressure regulating valve 551 provided in the fifth flow path 55 to regulate a differential pressure between a first hydraulic pressure, which is the hydraulic pressure in the sixth flow path 58, and a second hydraulic pressure, which is the hydraulic pressure in the servo chamber Rs. In the device of Patent Document 2, there is a restriction in the relationship between the first hydraulic pressure and the second hydraulic pressure. Even in a brake control device equipped with such an electric cylinder, it is desired to implement the above-mentioned two-system pressure regulation. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2019-137203 [Patent Document 2] Patent application No. 2022-197101 Summary of the Invention [Problem to be solved by the invention]

[0005] In view of the above problems, an object of the present invention is to provide a brake control device for a vehicle equipped with an electric cylinder, which is capable of performing dual-system pressure regulation. [Means for solving the problem]

[0006] The vehicle braking control device (SA) of the present invention is applied to a vehicle equipped with a regenerative device (KG) on the front wheels (WHf), and is equipped with a control cylinder (CC) that generates a base pressure (Pa) using an electric motor (MA) as a power source, an solenoid valve (UC) that adjusts the base pressure (Pa) to an adjusted pressure (Pb), and a controller (EA) that controls the electric motor (MA) and the solenoid valve (UC), and generates the base pressure (Pa) and the adjusted pressure (Pb) based on the required braking amount (Bs) of the vehicle, controls the hydraulic pressure (Pwf) in the front wheel cylinder (CWf) using the adjusted pressure (Pb), and controls the hydraulic pressure (Pwr) in the rear wheel cylinder (CWr) using the base pressure (Pa).

[0007] In the vehicle braking control device (SA) of the present invention, when the regenerative device (KG) generates a regenerative braking force (Fg), the controller (EA) can execute one of single-system pressure regulation in which the regulated pressure (Pb) is made equal to the base pressure (Pa) to achieve a total braking force (Fu) corresponding to the required braking amount (Bs), and dual-system pressure regulation in which the regulated pressure (Pb) is made smaller than the base pressure (Pa) to achieve the total braking force (Fu) while maintaining the front / rear distribution of the total braking force (Fu) at a predetermined value (hf), and calculates a first command pressure (P1sb) for controlling the regulated pressure (Pb) in the single-system pressure regulation and a second command pressure (P2sb) for controlling the regulated pressure (Pb) in the dual-system pressure regulation, and determines whether to select the single-system pressure regulation or the dual-system pressure regulation based on a comparison between the first command pressure (P1sb) and the second command pressure (P2sb). Specifically, the controller (EA) selects the one-system pressure regulation when the second command pressure (P2sb) is equal to or greater than the first command pressure (P1sb), and selects the two-system pressure regulation when the second command pressure (P2sb) is less than the first command pressure (P1sb).

[0008] According to the above configuration, the brake control device SA using the electric cylinder, which has a restriction on the adjustment of the adjustment pressure Pb, can perform dual-system pressure adjustment, thereby achieving both energy regeneration and vehicle stability. [Brief description of the drawings]

[0009] [Figure 1] 1 is a schematic diagram for explaining a first embodiment of a vehicle braking control device SA. [Diagram 2] FIG. 4 is a flow chart for explaining a pressure regulation control process. [Diagram 3] FIG. 4 is a characteristic diagram for explaining the operation of pressure regulation control. [Figure 4] FIG. 2 is a schematic diagram for explaining a second embodiment of a vehicle braking control device SA. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] <Symbols for components, etc. and suffixes at the end of the symbols> In the following description, components, arithmetic processes, signals, characteristics, and values ​​with the same symbol, such as "CW", have the same function. The suffixes "f" and "r" at the end of the symbol for each wheel are generic symbols that indicate whether it is related to the front or rear wheel system. For example, the wheel cylinder CW provided on each wheel is written as "front wheel cylinder CWf, rear wheel cylinder CWr". Furthermore, the suffixes "f" and "r" at the end of the symbol may be omitted. When the suffixes "f" and "r" are omitted, each symbol represents its generic name. For example, "CW" is a generic name for wheel cylinders provided on the front and rear wheels of a vehicle. In addition, "CW" as a generic name can also be written as "CW (= CWf, CWr)".

[0011] The brake control device SA, hydraulic pressure correction device SZ, and wheel cylinder CW are connected by a fluid path (communication path HS). Furthermore, in the brake control device SA and hydraulic pressure correction device SZ, various components (CC, UC, etc.) are connected by fluid paths. Here, the "fluid path" is a path for moving brake fluid BF, and corresponds to piping, flow paths in actuators, hoses, etc. In the following explanation, the communication path HS, reservoir path HR, input path HN, servo path HU, etc. are fluid paths.

[0012] <First embodiment of the brake control device SA> A first embodiment of a vehicle braking control device SA will be described with reference to the schematic diagram of Fig. 1. The braking control device SA is applied to, for example, a hybrid vehicle equipped with an electric motor for running, or an electric vehicle.

[0013] The front and rear wheels WHf, WHr (=WH) of the vehicle are provided with a braking device SX (=SXf, SXr). The braking device SX is composed of a brake caliper, a friction member (e.g., brake pad), and a rotating member KT (e.g., brake disc). The brake caliper (not shown) is provided with a wheel cylinder CW. A hydraulic pressure Pw (called "wheel pressure") in the wheel cylinder CW presses a friction member (not shown) against a rotating member KT fixed to each wheel WH, and a braking torque Tb is applied to the wheel. As a result, a frictional braking force Fe (also called "hydraulic braking force") is generated in the wheel WH. Therefore, the braking device SX can be said to be "a device that generates a frictional braking force Fe by the wheel pressure Pw" or "a device that converts the wheel pressure Pw into a frictional braking force Fe."

[0014] The vehicle is provided with a regenerative device KG. The regenerative device KG is composed of a generator GN for energy regeneration (also called an "electric motor / generator" or "regenerative generator"), a control unit EG for the regenerative device KG (also called a "regenerative controller"), and a regenerative storage battery (not shown). The regenerative generator GN also serves as an electric motor for running. In regenerative braking, the electric motor / generator GN operates as a generator, and the generated electric power is stored in the regenerative storage battery via the regenerative controller EG. At this time, a regenerative braking force Fg acts on the wheels. That is, the regenerative device KG can generate the regenerative braking force Fg. For example, the regenerative device KG is provided on the front wheels WHf. Therefore, the regenerative braking force Fg is generated in the front wheels WHf. The regenerative device KG (particularly, the regenerative controller EG) is connected to the communication bus BS.

[0015] The vehicle is equipped with a driving assistance device KJ. The driving assistance device KJ executes automatic speed control. The driving assistance device KJ is composed of an object detection sensor SJ and a driving assistance controller EJ (also simply referred to as a "driving assistance controller"). The object detection sensor SJ detects a distance Sj (called a "relative distance" and also called an "inter-vehicle distance" when the object is a preceding vehicle) to an object (including a preceding vehicle traveling in front of the vehicle) that exists in front of the vehicle. For example, a radar sensor, a millimeter wave sensor, an image sensor, or the like is adopted as the object detection sensor SJ. The driving assistance controller EJ calculates a target acceleration Gs of the vehicle (a target value of the vehicle body acceleration in the longitudinal direction of the vehicle) based on the detection result Sj (relative distance) of the object detection sensor SJ. The driving assistance device KJ (particularly, the driving assistance controller EJ) is connected to a communication bus BS. The target acceleration Gs is transmitted to the braking control device SA via the communication bus BS. In the brake control device SA, the braking forces Fg, Fe are adjusted in accordance with the target acceleration Gs, and as a result, the vehicle running speed Vx (vehicle speed) is controlled.

[0016] The vehicle is equipped with a brake operating member BP and various sensors (SP, etc.). The brake operating member BP (e.g., a brake pedal) is an operating member for the driver to decelerate the vehicle. The vehicle is provided with an operation displacement sensor SP that detects an operation displacement Sp of the brake operating member BP. The operation displacement Sp is one of state quantities (state variables) that indicate the operation amount of the brake operating member BP, and in a brake-by-wire type brake control device SA, it is a signal that indicates the driver's braking intention (i.e., a braking command). In addition to the operation displacement sensor SP, a hydraulic pressure Pn (referred to as "input pressure") in an input chamber Rn (described later) is adopted as another state quantity that indicates the braking operation amount. The input pressure Pn is detected by an input pressure sensor PN. The operation displacement Sp, the input pressure Pn, etc. are collectively referred to as the "braking operation amount Ba." Further, the operation displacement sensor SP and the input pressure sensor PN which detect the operation displacement Sp and the input pressure Pn (that is, the braking operation amount Ba) are referred to as a "braking operation amount sensor BA."

[0017] A vehicle is provided with various sensors for braking control (i.e., individual control of the wheel pressure Pw of each wheel) such as antilock brake control and skid prevention control. Specifically, each wheel WH is provided with a wheel speed sensor VW that detects its rotation speed Vw (called "wheel speed"). In addition, a steering amount sensor that detects the steering amount Sw (e.g., operation angle) of a steering operation member (e.g., steering wheel), a yaw rate sensor that detects the yaw rate Yr of the vehicle, a longitudinal acceleration sensor that detects the longitudinal acceleration Gx (also called "deceleration") of the vehicle, and a lateral acceleration sensor that detects the lateral acceleration Gy of the vehicle (all not shown).

[0018] The vehicle is equipped with a brake control device SA. The brake control device SA employs a so-called front and rear type (also called "type II") brake system as two systems. The wheel pressure Pw of each wheel cylinder CW is adjusted by the brake control device SA.

[0019] The brake control device SA (particularly, the brake controller EA) and the hydraulic pressure correction device SZ (particularly, the correction controller EZ) are connected to a communication bus BS. Signals are transmitted between the multiple controllers (EA, EZ, EG, EJ, etc.) via the communication bus BS. In other words, the multiple controllers can transmit signals (detection values, calculation values, control flags, etc.) to the communication bus BS and can receive signals from the communication bus BS.

[0020] <Configuration of the Brake Control Device SA> The configuration of the brake control device SA according to the first embodiment will be described. The brake control device SA generates a base pressure Pa and an adjustment pressure Pb in response to the operation of a brake operating member BP (brake pedal). Then, the brake control device SA outputs a supply pressure Pm and a base pressure Pa to a hydraulic pressure correction device SZ. The hydraulic pressure correction device SZ adjusts the supply pressure Pm and the base pressure Pa, and ultimately supplies front and rear wheel pressures Pwf and Pwr to the front and rear wheel cylinders CWf and CWr. The brake control device SA is composed of a brake actuator YA and a brake controller EA.

[0021] <Braking actuator YA> The brake actuator YA is composed of a hydraulic pressure generating unit PU, an apply unit AP, and an input unit NR.

[0022] [Hydraulic pressure generating unit PU] The hydraulic pressure generating unit PU uses an electric motor MA as a power source to generate a base pressure Pa and an adjustment pressure Pb. The hydraulic pressure generating unit PU is composed of an electric cylinder DN and a pressure regulating valve UC. Here, the electric cylinder DN includes an electric motor MA, a rotation angle sensor KA, a reducer GS, a conversion mechanism GH, a control cylinder CC, and a control piston NC.

[0023] The electric motor MA is a power source (pressurizing source) for generating the base pressure Pa (hydraulic pressure generated by the electric cylinder DN). "Power" refers to the energy required to move the movable members (GS, GH, NC, etc.) in the electric cylinder DN. For example, power is defined as a physical quantity, namely, energy per unit time (also called "power"). Rotational power (also called "first rotational power") is output from the electric motor MA. The rotational power of the electric motor MA is the shaft torque of the electric motor MA multiplied by the rotational speed of the electric motor MA (particularly, the motor shaft). The linear power of the linearly moving member (described later) is the thrust of the linearly moving member (force acting in the direction of the central axis) multiplied by the linear speed of the linearly moving member (speed in the direction along the central axis).

[0024] A three-phase brushless motor is adopted as the electric motor MA. The electric motor MA includes a motor coil, a motor shaft, and a rotation angle sensor KA. The motor coil is fixed to a motor housing. Power is supplied to the motor coil from a controller EA (particularly, a drive circuit DR). The motor shaft is rotatably supported with respect to the motor housing. A permanent magnet is fixed to the outer periphery of the motor shaft. In the three-phase brushless motor MA, the magnetic pole position of the permanent magnet (i.e., the rotation angle Ka) is detected by the rotation angle sensor KA. Then, a three-phase motor current Im (a collective term for the currents flowing through the U phase, V phase, and W phase) relating to the U phase, V phase, and W phase is switched based on the rotation angle Ka of the motor shaft.

[0025] Specifically, a signal of the rotation angle Ka detected by the rotation angle sensor KA is input to a braking controller EA (particularly, a microprocessor MP). The controller EA drives a switching element of a drive circuit DR (also called an "inverter circuit") according to the rotation angle Ka. This switches the motor current Im flowing through the motor coil, driving the electric motor MA. Then, rotational power is output from the electric motor MA to the reducer GS.

[0026] The reducer GS reduces the speed of the first rotational power output from the electric motor MA. Specifically, the input shaft of the reducer GS and the motor shaft are fixed. Also, the output shaft of the reducer GS and the rotating member of the conversion mechanism GH are fixed. In the reducer GS, the speed input from the electric motor MA is reduced and the torque input from the electric motor MA is increased. Then, the reduced rotational power (also referred to as "second rotational power") is output from the reducer GS to the conversion mechanism GH.

[0027] The conversion mechanism GH is composed of a rotating member that performs rotational motion and a linear member that performs linear motion. In the conversion mechanism GH, the rotational power output from the reducer GS is input to the rotating member. Then, the second rotational power input to the rotating member is converted into linear power of the linear member. The conversion mechanism GH is also called a "rotation / linear conversion mechanism." A rotation stopper member is engaged with the linear member. This prevents the rotational motion of the linear member, so that the linear member moves along the rotation axis of the rotating member.

[0028] For example, a "ball screw" is used as the conversion mechanism GH. Specifically, in the ball screw mechanism, a rotating member, which is a shaft member, is fixed to the output shaft of the reducer GS. The rotating member is inserted into a linear motion member having a cylindrical shape. A ball screw groove is formed on the outer circumferential surface of the rotating member. Similarly, a ball screw groove is also formed on the inner circumferential surface of the linear motion member. A plurality of balls (steel balls) are fitted into the ball screw groove.

[0029] A linear force is transmitted to the control piston NC by the linear motion member of the conversion mechanism GH. The control piston NC is inserted into the control cylinder CC. Inside the control cylinder CC, the control piston NC forms a control chamber Rc (hydraulic pressure chamber). In detail, the outer peripheral surface of the control piston NC and the inner peripheral surface of the control cylinder CC are sealed by two seal members SL. This makes the control chamber Rc liquid-tight. The hydraulic pressure in the control cylinder CC (i.e., the control chamber Rc) is the "base pressure Pa." That is, in the electric cylinder DN, the electric motor MA is used as the power source, and the base pressure Pa is output.

[0030] The control cylinder CC is connected to a servo chamber Ru (described later) of the apply unit AP via a servo path HU (fluid path). The control cylinder CC is also connected to a rear wheel cylinder CWr via a rear wheel connection path HSR (fluid path) and a hydraulic pressure correction device SZ. A base pressure sensor PA is provided in the hydraulic pressure generating unit PU to detect the base pressure Pa.

[0031] FIG. 1 illustrates a state in which the electric cylinder DN does not generate a base pressure Pa. The control cylinder CC has a through hole between two seal members SL. The control piston NC also has a through hole. A supply path HH connected to the master reservoir RV is connected to the through hole of the control cylinder CC. In the illustrated state, the control chamber Rc is connected to the master reservoir RV via the through hole and the supply path HH, and the base pressure Pa is "0 (atmospheric pressure)". The position of the control piston NC in this state is referred to as the "initial position". In the initial position, the control piston NC is displaced to its maximum in the backward direction Hb, and the volume of the control chamber Rc is maximum.

[0032] When it is necessary to increase the base pressure Pa, the rotational power of the electric motor MA is increased. The rotational power is transmitted to the conversion mechanism GH via the reducer GS and output as linear power of the linear motion member. Then, the control piston NC is pressed by the linear motion member, so that the control piston NC moves in the forward direction Ha (the direction in which the volume of the control chamber Rc decreases). This movement first blocks communication between the control chamber Rc and the master reservoir RV. When the control piston NC is further moved in the forward direction Ha, the base pressure Pa (the internal pressure of the control chamber Rc) is increased from "0 (atmospheric pressure)". Brake fluid BF pressurized to the base pressure Pa is output (pumped) from the control chamber Rc of the control cylinder CC.

[0033] When it is necessary to maintain the basal pressure Pa, the rotation of the electric motor MA is stopped. The movement of the control piston NC is stopped and the basal pressure Pa is maintained constant. When it is necessary to decrease the basal pressure Pa, the rotational power of the electric motor MA is decreased. The basal pressure Pa causes the electric motor MA to rotate in the reverse direction, so that the control piston NC is moved in the backward direction Hb (the direction in which the volume of the control chamber Rc increases). At this time, the brake fluid BF is returned toward the control chamber Rc, so that the basal pressure Pa is decreased.

[0034] A pressure regulating valve UC (corresponding to a "solenoid valve") is provided in the servo path HU (a fluid path connecting the control chamber Rc and the servo chamber Ru). The pressure regulating valve UC is a normally open linear solenoid valve whose valve opening amount (lift amount) is continuously controlled according to the supplied current Ic. The pressure regulating valve UC is also called a "differential pressure valve" because it adjusts the hydraulic pressure difference (differential pressure). The base pressure Pa output from the electric cylinder DN is adjusted to an adjustment pressure Pb by the pressure regulating valve UC.

[0035] In detail, the pressure regulating valve UC is composed of a valve body, a valve seat, and a solenoid. The plunger of the solenoid is fixed to the valve body. When a current Ic is supplied to the coil of the solenoid, the plunger is attracted to the coil, generating a thrust. The thrust pushes the valve body toward the valve seat. This prevents the flow of brake fluid BF from the control cylinder CC toward the servo chamber Ru. As a result, the pressure regulating valve UC blocks the base pressure Pa, so that the pressure regulating valve UC can adjust the adjustment pressure Pb to be smaller than the base pressure Pa. When the current Ic is not supplied to the pressure regulating valve UC, the pressure regulating valve UC is in a fully open state, so that the base pressure Pa and the adjustment pressure Pb are equal (i.e., when "Ic=0", "Pa=Pb"). In the hydraulic pressure generating unit PU, an adjustment pressure sensor PB is provided between the pressure regulating valve UC and the servo chamber Ru to detect the adjustment pressure Pb.

[0036] In the brake control device SA, there is a limit to the adjustment of the adjustment pressure Pb. As described above, the pressure regulating valve UC can prevent the inflow of the brake fluid BF pressurized to the base pressure Pa, and can make the adjustment pressure Pb smaller than the base pressure Pa. However, the pressure regulating valve UC cannot reduce the adjustment pressure Pb by itself. In other words, in order to reduce the adjustment pressure Pb, it is necessary to reduce the base pressure Pa.

[0037] [Apply Unit AP] The apply unit AP is composed of a single-type master cylinder CM and a master piston NM. The master piston NM is inserted into the single-type master cylinder CM. The interior of the master cylinder CM is divided into three hydraulic chambers Rm, Ru, and Rs by the master piston NM. The master chamber Rm is formed by the master cylinder CM and the master piston NM. Furthermore, the interior of the master cylinder CM is divided into a servo chamber Ru and a reaction chamber Rs by a flange portion Tu of the master piston NM. Here, the pressure-receiving area rm of the master chamber Rm and the pressure-receiving area ru of the servo chamber Ru are set to be equal.

[0038] The servo chamber Ru is supplied with an adjustment pressure Pb from the hydraulic pressure generating unit PU. The adjustment pressure Pb causes the apply unit AP to output a supply pressure Pm. When "Pb=0" (e.g., when braking is not being applied), the master piston NM is in the most retreated position (i.e., the position where the volume of the master chamber Rm is maximum). In this state, the master chamber Rm of the master cylinder CM is connected to the master reservoir RV. Brake fluid BF is stored inside the master reservoir RV (also called the "atmospheric pressure reservoir"). When the adjustment pressure Pb is increased from "0", the master piston NM is moved in the forward direction Da (the direction in which the volume of the master chamber Rm decreases). This movement blocks communication between the master chamber Rm and the master reservoir RV. Then, when the master piston NM is further moved in the forward direction Da, the supply pressure Pm (the internal pressure of the master chamber Rm, also called the "master pressure") is increased from "0 (atmospheric pressure)". As a result, brake fluid BF pressurized to the supply pressure Pm is output (pressurized and sent) from the master chamber Rm of the master cylinder CM to the hydraulic pressure correction device SZ. Note that since "rm=ru", if the sliding resistance of the seal member SL is ignored, "Pb=Pm".

[0039] [Input unit NR] The input unit NR realizes regenerative cooperative control. "Regenerative cooperative control" cooperates the friction braking force Fe (braking force due to wheel pressure Pw) and the regenerative braking force Fg (braking force due to regenerative generator GN) so that the kinetic energy of the vehicle can be efficiently recovered as electrical energy during braking. In regenerative cooperative control, the brake operating member BP is operated, but a state is created in which no wheel pressure Pw is generated. The input unit NR is composed of an input cylinder CN, an input piston NN, a first control valve VA, a second control valve VB, a stroke simulator SS, and an input pressure sensor PN.

[0040] The input cylinder CN is fixed to the master cylinder CM. An input piston NN is inserted into the input cylinder CN. The input piston NN is mechanically connected to a brake operating member BP (brake pedal) so as to move in conjunction with the movement of the brake operating member BP. There is a gap Ln (also called the "separation distance") between the end face of the input piston NN and the end face of the master piston NM. The separation distance Ln is adjusted by the adjustment pressure Pb, thereby achieving regenerative cooperative control.

[0041] The input chamber Rn of the input unit NR is connected to the reaction chamber Rs of the apply unit AP via an input path HN (fluid path). A normally closed first control valve VA is provided in the input path HN. The input path HN is connected to a master reservoir RV between the first control valve VA and the reaction chamber Rs via a reservoir path HR (fluid path). A normally open second control valve VB is provided in the reservoir path HR. An on-off type solenoid valve is used for the first and second control valves VA and VB. A stroke simulator SS is connected to the input path HN between the first control valve VA and the reaction chamber Rs.

[0042] When power is not supplied to the first and second control valves VA and VB, the first control valve VA is closed and the second control valve VB is open. When the first control valve VA is closed, the input chamber Rn is sealed and fluid-locked. This causes the master piston NM to be displaced integrally with the brake operating member BP. When the second control valve VB is opened, the stroke simulator SS and the reaction chamber Rs are connected to the master reservoir RV.

[0043] When power is supplied to the first and second control valves VA, VB, the first control valve VA is opened and the second control valve VB is closed. This allows the master piston NM to be displaced separately from the brake operating member BP. At this time, the input chamber Rn is connected to the stroke simulator SS, so that the operating force of the brake operating member BP is generated by the stroke simulator SS. In order to detect the input pressure Pn, an input pressure sensor PN is provided in the input path HN between the input chamber Rn and the first control valve VA. The input pressure Pn is also the hydraulic pressure in the stroke simulator SS.

[0044] <Braking controller EA> The brake actuator YA is controlled by the brake controller EA. The brake controller EA is composed of a microprocessor MP and a drive circuit DR. The brake controller EA is connected to a communication bus BS so that signals (detection values, calculation values, control flags, etc.) can be shared between the brake controller EA and other controllers (EZ, EG, etc.).

[0045] The brake controller EA directly receives various signals such as the operation displacement Sp (detection value of the operation displacement sensor SP), the input pressure Pn (detection value of the input pressure sensor PN), the base pressure Pa (detection value of the base pressure sensor PA), the adjustment pressure Pb (detection value of the adjustment pressure sensor PB), and the motor rotation angle Ka (detection value of the rotation angle sensor KA). Furthermore, the controller EA receives various signals such as the supply pressure Pm, the standard regenerative braking force Fz, the vehicle's traveling speed Vx (also called "vehicle speed"), and the target acceleration Gs from the communication bus BS. The brake controller EA also outputs a target regenerative braking force Fh (target value of the regenerative braking force Fg) to the communication bus BS. The regenerative controller EG controls the regenerative braking force Fg (actual value) based on the target regenerative braking force Fh (target value) acquired from the communication bus BS.

[0046] An algorithm for pressure regulation control is programmed in the brake controller EA (particularly, the microprocessor MP). The "pressure regulation control" is a control for adjusting the wheel pressure Pw (=Pwf, Pwr) and includes regenerative cooperative control. The pressure regulation control is executed based on the above-mentioned various signals (Sp, Pa, etc.). Based on the pressure regulation control algorithm, the electric motor MA and various solenoid valves (UC, VA, etc.) are driven by the drive circuit DR. In the drive circuit DR, an H-bridge circuit (inverter circuit) is configured with switching elements (e.g., MOS-FET) to drive the electric motor MA. The drive circuit DR is also provided with switching elements to drive the various solenoid valves. In addition, the drive circuit DR includes a motor current sensor (not shown) that detects the supply current Im (motor current) to the electric motor MA. The electric motor MA is provided with a rotation angle sensor KA to detect the position Ka (rotation angle) of the motor shaft.

[0047] In the braking controller EA, drive signals Va, Vb of the first and second control valves VA, VB, a drive signal Uc of the pressure regulating valve UC, and a drive signal Ma of the electric motor MA are calculated. Then, the switching elements are driven in response to the various drive signals (Uc, Ma, etc.). Specifically, in the control of the solenoid valves, power is supplied to the first and second control valves VA, VB based on the drive signals Va, Vb. As a result, the first control valve VA is opened and the second control valve VB is closed. In addition, the drive signals Uc, Ma are determined based on an algorithm for pressure regulation control. Then, the pressure regulating valve UC is controlled based on the drive signal Uc, and the electric motor MA is controlled based on the drive signal Ma.

[0048] <Hydraulic pressure correction device SZ> A hydraulic pressure correction device SZ is provided between the brake control device SA and the wheel cylinder CW. Antilock brake control, traction control, anti-skid control, etc. are performed by the hydraulic pressure correction device SZ. In the brake system related to the front wheels WHf (i.e., the front wheel connecting path HSf), a supply pressure Pm is supplied from the master cylinder CM to the hydraulic pressure correction device SZ. On the other hand, in the brake system related to the rear wheels WHr (i.e., the rear wheel connecting path HSr), a base pressure Pa is directly supplied from a hydraulic pressure generating unit PU to the hydraulic pressure correction device SZ. The supply pressure Pm and base pressure Pa are adjusted (increased or decreased) by the hydraulic pressure correction device SZ, and are output to the front and rear wheel cylinders CWf and CWr as front and rear wheel pressures Pwf and Pwr.

[0049] The hydraulic pressure correction device SZ is composed of a correction actuator YZ and a correction controller EZ. The configuration of the correction actuator YZ is well known, so a description thereof will be omitted. The correction actuator YZ is provided with a supply pressure sensor PM to detect the supply pressure Pm. The adjustment pressure Pb is transmitted as the supply pressure Pm via the master piston NM. Therefore, the supply pressure Pm corresponds to the adjustment pressure Pb, and the supply pressure sensor PM corresponds to the adjustment pressure sensor PB. In other words, the supply pressure Pm is an example of the adjustment pressure Pb, and the supply pressure sensor PM is an example of the adjustment pressure sensor PB.

[0050] When the regenerative braking cooperative control is executed, the operation of the correction actuator YZ is stopped. Therefore, during the execution of the regenerative braking cooperative control, the adjustment pressure Pb is transmitted to the front wheel cylinder CWf as the front wheel pressure Pwf via the supply pressure Pm, and the base pressure Pa is transmitted directly to the rear wheel cylinder CWr as the rear wheel pressure Pwr. Therefore, in the front wheel braking system, "Pb = Pm = Pwf" and in the rear wheel braking system, "Pa = Pwr".

[0051] The correction controller EZ is connected to the brake controller EA via a communication bus BS. The wheel speed Vw detected by the wheel speed sensor VW and the supply pressure Pm detected by the supply pressure sensor PM are input to the correction controller EZ. The correction controller EZ calculates the vehicle running speed Vx (body speed) based on the wheel speed Vw. The body speed Vx and the supply pressure Pm are transmitted to the brake controller EA via the communication bus BS.

[0052] <Pressure regulation control processing> An example of the pressure regulation control process will be described with reference to the flow chart of FIG. 2. In the pressure regulation control, a regenerative cooperative control between the regenerative device KG and the brake control device SA is executed. Furthermore, the regenerative cooperative control includes one-way pressure regulation and two-way pressure regulation. In the one-way pressure regulation, the base pressure Pa and the adjustment pressure Pb are made equal to each other, and a total braking force Fu corresponding to the required braking amount Bs is achieved. In the one-way pressure regulation, the base pressure Pa and the adjustment pressure Pb are adjusted collectively, and therefore the one-way pressure regulation is also called "collectively adjusted pressure regulation." In contrast, in the two-way pressure regulation, the adjustment pressure Pb is made smaller than the base pressure Pa, and therefore a total braking force Fu corresponding to the required braking amount Bs is achieved while the front / rear distribution of the total braking force Fu is maintained at a predetermined value hf. In the two-way pressure regulation, the base pressure Pa and the adjustment pressure Pb are adjusted individually, and therefore the one-way pressure regulation is also called "individual pressure regulation." In the regenerative cooperative control, one of single-system pressure regulation and dual-system pressure regulation is selected and executed to accommodate the limitations arising from the configuration of the braking control device SA described above (i.e., the inability to reduce the regulated pressure Pb by the pressure regulating valve UC alone).

[0053] ≪Various braking forces≫ The various braking forces in the description of pressure regulation control are as follows. - "Total braking force Fu" is the actual braking force acting on the entire vehicle. A target value corresponding to the total braking force Fu is "target total braking force Fv." - "Friction braking force Fe (hydraulic braking force)" is the braking force actually generated by the wheel pressure Pw. A target value corresponding to the friction braking force Fe is "target friction braking force Fn." - "Regenerative braking force Fg" is the braking force actually generated by the regenerative device KG. A target value corresponding to the regenerative braking force Fg is "target regenerative braking force Fh." The target regenerative braking force Fh is calculated by the braking control device SA (particularly, the braking controller EA) and transmitted to the regenerative device KG (particularly, the regenerative controller EG) via the communication bus BS. In the regenerative device KG, the regenerative controller EG controls the generator GN so that the actual regenerative braking force Fg approaches and matches the target regenerative braking force Fh. - The "standard regenerative braking force Fz" is the maximum value (limit value) of the regenerative braking force Fg that the regenerative device KG can generate. Therefore, the regenerative device KG can generate a regenerative braking force Fg in the range from "Fg=0" to the standard regenerative braking force Fz. The standard regenerative braking force Fz is calculated by the regenerative device KG (particularly, the regenerative controller EG) and transmitted to the brake control device SA (particularly, the brake controller EA) via the communication bus BS. The standard regenerative braking force Fz can be limited depending on the driving conditions of the vehicle (e.g., the friction coefficient of the road).

[0054] <Various hydraulic pressures> The various hydraulic pressures are divided into hydraulic pressures in single-system pressure regulation and hydraulic pressures in dual-system pressure regulation. Hydraulic pressures related to single-system pressure regulation have "first" added to their names. Hydraulic pressures related to dual-system pressure regulation have "second" added to their names. The various hydraulic pressures in the explanation of pressure regulation control are as follows: The "first command basal pressure P1sa" corresponds to a target value for controlling the basal pressure Pa (actual value) in the single-system pressure regulation. - The "second indicated basal pressure P2sa" is a target value for controlling the basal pressure Pa (actual value) in the dual pressure regulation. The "first command regulated pressure P1sb" corresponds to a target value for controlling the regulated pressure Pb (actual value) in the single-system pressure regulation. The "second command regulated pressure P2sb" corresponds to a target value for controlling the regulated pressure Pb (actual value) in the dual-system pressure regulation.

[0055] In the pressure regulation control, either the single-system pressure regulation or the dual-system pressure regulation is ultimately executed. "Basal pressure Pa" is the actual value of the final output of the electric cylinder DN (i.e., the internal pressure of the control chamber Rc). That is, the basal pressure Pa is the discharge pressure of the electric cylinder DN regardless of whether it is a single-system pressure regulating system or a dual-system pressure regulating system. The basal pressure Pa is detected (acquired) by the basal pressure sensor PA. The "target basal pressure Pta" corresponds to a target value for controlling the basal pressure Pa (actual value). One of the first indicated basal pressure P1sa and the second indicated basal pressure P2sa is adopted as the target basal pressure Pta. - "Adjusted pressure Pb" is the actual value of the final fluid pressure obtained by adjusting the basal pressure Pa by the pressure regulating valve UC. That is, the adjusted pressure Pb is the fluid pressure adjusted by the pressure regulating valve UC regardless of whether the system is a single-system pressure regulating system or a dual-system pressure regulating system. The adjusted pressure Pb is detected (acquired) by the adjusted pressure sensor PB. Alternatively, the adjusted pressure Pb may be detected (acquired) by the supply pressure sensor PM. Therefore, the supply pressure Pm corresponds to one of the adjusted pressures Pb, and the supply pressure sensor PM corresponds to one of the adjusted pressure sensors PB. The "target basal pressure Ptb" corresponds to a target value for controlling the basal pressure Pb (actual value). One of the first command basal pressure P1sb and the second command basal pressure P2sb is used as the target basal pressure Pta.

[0056] In pressure regulation control, first, power is supplied to the first and second control valves VA, VB. The normally closed first control valve VA is opened, and the normally open second control valve VB is closed. This allows the master piston NM and the brake operating member BP to be displaced separately, so that the front and rear wheel pressures Pwf, Pwr can be adjusted independently of the operation of the brake operating member BP. At this time, the operating force of the brake operating member BP is generated by the stroke simulator SS.

[0057] In step S110, various signals are read in the brake controller EA. The brake controller EA acquires the braking operation amount Ba (collectively Sp and Pn), the target acceleration Gs, the base pressure Pa, the regulated pressure Pb, and the standard regenerative braking force Fz. The braking operation amount Ba and the target acceleration Gs are collectively referred to as the "braking demand amount Bs." The braking demand amount Bs is a state amount that represents a braking demand for the vehicle. The base pressure Pa is acquired by the base pressure sensor PA. The regulated pressure Pb is acquired by at least one of the regulated pressure sensor PB and the supply pressure sensor PM. The standard regenerative braking force Fz is determined by the regenerative device KG (particularly, the regenerative controller EG) and is received by the brake controller EA via the communication bus BS.

[0058] In step S120, a target total braking force Fv (a target value of the total braking force Fu acting on the entire vehicle) is calculated based on the braking demand Bs and the calculation map Zfv. When the braking demand Bs is less than a predetermined amount bo, the target total braking force Fv is calculated to be "0" according to the calculation map Zfv. When the braking demand Bs is equal to or greater than the predetermined amount bo, the target total braking force Fv is calculated to increase from "0" as the braking demand Bs increases. Here, the "predetermined amount bo" is preset as a predetermined value (constant) (see target total braking force calculation block FV).

[0059] In step S130, a first command base pressure P1sa and a first command adjustment pressure P1sb (corresponding to "first command pressure") for performing single-system pressure adjustment are calculated based on the target total braking force Fv and the standard regenerative braking force Fz. In single-system pressure adjustment, the base pressure Pa and the adjustment pressure Pb are made equal, so that the first command base pressure P1sa and the first command adjustment pressure P1sb are equal (i.e., "P1sa = P1sb"). In step S130, first, a sum Fnt (also called "target sum") of the target regenerative braking force Fh and the target frictional braking force Fn is calculated. Here, the "target sum Fnt" is the sum of the front wheel target frictional braking force Fnf and the rear wheel target frictional braking force Fnr (i.e., "Fnt = Fnf + Fnr"). In single-system pressure adjustment, the command pressures P1sa and P1sb are determined in the following two cases.

[0060] Case (1): When the target total braking force Fv is equal to or less than the standard regenerative braking force Fz, the target regenerative braking force Fh is set equal to the target total braking force Fv, and the sum Fnt (target sum) of the target frictional braking forces Fn is set to 0. That is, when "Fv≦Fz", "Fh=Fv, Fnt=0" is determined.

[0061] Case (2): When the target total braking force Fv is larger than the standard regenerative braking force Fz, the target regenerative braking force Fh is set equal to the standard regenerative braking force Fz, and the target sum Fnt is set to a value obtained by subtracting the target regenerative braking force Fh (=Fz) from the target total braking force Fv. In other words, when Fv>Fz, Fh=Fz, Fnt=Fv-Fh=Fv-Fz is determined.

[0062] Next, command pressures P1sa and P1sb are calculated based on the target sum Fnt. Specifically, the command pressures P1sa and P1sb are determined based on the specifications of the braking device SX (=SXf, SXr) so that the target sum Fnt is satisfied under the condition of "P1sa=P1sb". That is, in the case (1) of "Fv≦Fz", the command pressures P1sa and P1sb are determined to be "0". On the other hand, in the case (2) of "Fv>Fz", the command pressures P1sa and P1sb are determined so that "P1sa=P1sb" is satisfied and the sum Fnt (target sum) of the target frictional braking forces Fn is equal to the value "Fv-Fh". Here, the "specifications of the braking device SX" include the pressure-receiving area of ​​the wheel cylinder CW, the effective braking radius of the rotating member KT, the friction coefficient of the friction material, and the effective radius of the wheel WH.

[0063] In step S140, a second instruction base pressure P2sa and a second instruction adjustment pressure P2sb (corresponding to the "second instruction pressure") for performing two-system pressure regulation are calculated based on the target total braking force Fv and the standard regenerative braking force Fz. In two-system pressure regulation, since the base pressure Pa and the adjustment pressure Pb are adjusted individually, the second instruction base pressure P2sa and the second instruction adjustment pressure P2sb are different. In particular, since the adjustment pressure Pb is decreased from the base pressure Pa, the second instruction adjustment pressure P2sb is smaller than the second instruction base pressure P2sa (i.e., "P2sa > P2sb"). In two-system pressure regulation, the instruction pressures P2sa and P2sb are determined in the following three cases.

[0064] Case (3): When the target total braking force Fv is less than or equal to the standard regenerative braking force Fz, the target regenerative braking force Fh is made equal to the target total braking force Fv, and the front and rear wheel target frictional braking forces Fnf and Fnr are set to "0". That is, when "Fv ≦ Fz", "Fh = Fv, Fnf = Fnr = 0" is determined.

[0065] Case (4): When the target total braking force Fv is greater than the standard regenerative braking force Fz and less than or equal to the value "Fz / hf" obtained by dividing the standard regenerative braking force Fz by the distribution ratio hf, the target regenerative braking force Fh is made equal to the target total braking force Fv. Then, the front wheel target frictional braking force Fnf is set to "0", and the rear wheel target frictional braking force Fnr is determined to be the value obtained by subtracting the target regenerative braking force Fh (= Fz) from the target total braking force Fv. That is, when "Fz < Fv ≦ (Fz / hf)", "Fh = Fz, Fnf = 0, Fnr = Fv - Fh = Fv - Fz" is determined.

[0066] Here, the "allocation ratio hf" is the ratio of the front wheel target braking force (i.e., the sum of the target regenerative braking force Fh and the front wheel target frictional braking force Fnf) to the target total braking force Fv (resulting in a total braking force Fu). The allocation ratio hf (also called the "front wheel ratio") is preset as a predetermined value (constant) based on the vehicle specifications (center of gravity position, wheelbase, etc.). The allocation ratio hf is equal to the ratio of the front wheel frictional braking force Fef to the total braking force Fu when the regenerative braking force Fg is not acting and the front wheel pressure Pwf and the rear wheel pressure Pwr are equal. In other words, when "Fg=0, Pwf=Pwr", "hf=Fef / Fu=Fef / (Fef+Fer)".

[0067] Case (5): When the target total braking force Fv is greater than the value "Fz / hf" obtained by dividing the standard regenerative braking force Fz by the distribution ratio hf, the target regenerative braking force Fh is set equal to the target total braking force Fv. The front wheel target frictional braking force Fnf is calculated by subtracting the target regenerative braking force Fh from the value "hf·Fv" obtained by multiplying the target total braking force Fv by the front wheel ratio hf. The rear wheel target frictional braking force Fnr is calculated by multiplying the target total braking force Fv by the value obtained by subtracting the distribution ratio hf from "1". In other words, when "Fv>(Fz / hf)", "Fh=Fz, Fnf=hf·Fv-Fh, Fnr=(1-hf)·Fv" are determined.

[0068] Next, the second command base pressure P2sa is calculated based on the rear wheel target frictional braking force Fnr. That is, the rear wheel target frictional braking force Fnr is converted into the second command base pressure P2sa based on the specifications of the rear wheel brake device SXr. Similarly, the second command adjustment pressure P2sb is calculated based on the front wheel target frictional braking force Fnf. The front wheel target frictional braking force Fnf is converted into the second command adjustment pressure P2sb based on the specifications of the front wheel brake device SXf. As above, the specifications include the pressure-receiving area of ​​the wheel cylinder CW, the effective braking radius of the rotating member KT (brake disc), the friction coefficient of the friction member (brake pad), the effective radius of the wheel WH (tire), and the like. Note that the adjustment pressure Pb is transmitted to the front wheel cylinder CWf via the master cylinder CM and the master piston NM, so that the sliding resistance of the seal member SL can be taken into account in the calculation of the second command adjustment pressure P2sb.

[0069] In the two - system pressure regulation, when "Fv≦Fz" (case (3)), the second commanded base pressure P2sa and the second commanded adjustment pressure P2sb are both maintained at "0" so that the energy is maximally recovered by the regenerative device KG. And when "Fz < Fv≦(Fz / hf)" (case (4)), with the second commanded adjustment pressure P2sb (and as a result, the front - wheel wheel pressure Pwf) maintained at "0", the second commanded base pressure P2sa (and as a result, the rear - wheel wheel pressure Pwr) is increased from "0" so that the front - rear distribution of the total braking force Fu quickly reaches a predetermined ratio hf. Further, when "Fv > (Fz / hf)" (case (5)), the second commanded base pressure P2sa and the second commanded adjustment pressure P2sb are both increased in a state of "P2sa > P2sb" so that the front - rear distribution of the total braking force Fu is maintained at the predetermined ratio hf.

[0070] In step S150, it is determined whether "the second commanded adjustment pressure P2sb is smaller than the first commanded adjustment pressure P1sb". If the second commanded adjustment pressure P2sb is less than the first commanded adjustment pressure P1sb and the determination in step S150 is affirmative, two - system pressure regulation is selected and the process proceeds to step S160. If the second commanded adjustment pressure P2sb is greater than or equal to the first commanded adjustment pressure P1sb and the determination in step S150 is negative, one - system pressure regulation is selected and the process proceeds to step S170.

[0071] In step S160, two - system pressure regulation (individual pressure regulation) is executed. In two - system pressure regulation, the base pressure Pa and the adjustment pressure Pb are individually adjusted by the electric cylinder DN and the pressure - regulating valve UC. Specifically, the second commanded base pressure P2sa is adopted as the final target value Pta (target base pressure) for controlling the base pressure Pa. Also, the second commanded adjustment pressure P2sb is adopted as the final target value Ptb (target adjustment pressure) for controlling the adjustment pressure Pb. That is, in step S160, "Pta = P2sa, Ptb = P2sb" is determined.

[0072] In step S170, one-system pressure adjustment (collectively adjusted pressure) is performed. In the two-system pressure adjustment, the basal pressure Pa and the adjusted pressure Pb are adjusted together by only the electric cylinder DN. Specifically, the first command basal pressure P1sa is adopted as the final target value Pta (target basal pressure) for controlling the basal pressure Pa. Also, the first command adjusted pressure P1sb is adopted as the final target value Ptb (target adjusted pressure) for controlling the adjusted pressure Pb. That is, in step S170, "Pta=Ptb=P1sa=P1sb" is determined.

[0073] In step S180, the electric motor MA and the pressure regulator valve UC are controlled based on the target base pressure Pta and the target adjustment pressure Ptb. Specifically, in the braking system related to the rear wheel cylinder CWr, when the regenerative cooperative control is executed, the electric cylinder DN (particularly the electric motor MA) is driven so that the base pressure Pa (detection value of the base pressure sensor PA) approaches and coincides with the target base pressure Pta, regardless of whether the single-system pressure regulation or the dual-system pressure regulation is performed.

[0074] On the other hand, in the braking system related to the front wheel cylinder CWf, in the regenerative cooperative control in the single-system pressure regulation, no power is supplied to the pressure regulating valve UC. That is, the pressure regulating valve UC is fully opened, and the regulated pressure Pb is made equal to the base pressure Pa. In contrast, in the regenerative cooperative control in the dual-system pressure regulation, the pressure regulating valve UC is driven so that the differential pressure sPj (also called "actual differential pressure") between the base pressure Pa and the regulated pressure Pb approaches and coincides with the differential pressure sPt (also called "target differential pressure") between the target base pressure Pta and the target regulated pressure Ptb. Specifically, the target current It to the pressure regulating valve UC is determined based on the target differential pressure sPt (=Pta-Ptb). Then, the target current It is corrected so that the actual differential pressure sPj (=Pa-Pb) becomes "0". As a result, the pressure regulating valve UC is controlled so that the regulated pressure Pb (the detection value of the regulated pressure sensor PB and / or the supply pressure sensor PM) approaches and coincides with the target regulated pressure Ptb.

[0075] The amount of regeneration of the generator GN (resulting in regenerative braking force Fg) is limited by the rating of the power transistors (IGBT, etc.) constituting the regeneration controller EG and the charge acceptance of the battery. For example, the generator GN is controlled so that the amount of regeneration is a predetermined power (electrical energy per unit time). When the power (power) is constant, the regenerative braking torque by the generator GN (resulting in regenerative braking force Fg) is inversely proportional to the rotation speed Ng of the generator GN (i.e., the vehicle speed Vx). Furthermore, when the rotation speed Ng of the generator GN decreases, the amount of regeneration decreases and the regenerative braking force Fg decreases. For this reason, as the vehicle travel speed Vx decreases, the standard regenerative braking force Fz increases once and is then limited to the upper limit value fz. Then, just before the vehicle stops, the standard regenerative braking force Fz decreases as the vehicle speed Vx decreases.

[0076] As described above, in the brake control device SA, there is a limit in the relationship between the basal pressure Pa and the regulated pressure Pb. Specifically, the brake control device SA can increase the regulated pressure Pb up to the basal pressure Pa (i.e., the upper limit of the regulated pressure Pb is the basal pressure Pa). However, once the regulated pressure Pb increases, it cannot be decreased unless the basal pressure Pa is decreased. In other words, the pressure regulating valve UC can prevent the regulated pressure Pb from increasing, but cannot decrease the regulated pressure Pb. This is because, in the configuration of the brake control device SA, the servo chamber Ru is not connected to a low-pressure portion such as the master reservoir RV.

[0077] In consideration of these, the brake control device SA determines whether to perform single-path pressure regulation or dual-path pressure regulation based on a comparison between the first command regulating pressure P1sb and the second command regulating pressure P2sb. When the second command regulating pressure P2sb is less than the first command regulating pressure P1sb (i.e., when "P1sb>P2sb"), the regulating pressure Pb has room to be increased, so dual-path pressure regulation is selected. On the other hand, when the second command regulating pressure P2sb is equal to or greater than the first command regulating pressure P1sb (i.e., when "P1sb≦P2sb"), the regulating pressure Pb needs to be reduced, so single-path pressure regulation is selected. As a result, in the brake control device SA, energy is sufficiently regenerated by the regenerating device KG, and, if possible, dual-path control is performed, thereby ensuring the running stability of the vehicle.

[0078] <Pressure regulation control operation> The operation, action, and effect of the pressure regulation control will be described with reference to the characteristic diagram of FIG. 3. FIG. 3(a) shows the characteristic of the standard regenerative braking force Fz in the regenerative device KG. The standard regenerative braking force Fz is the limit value of the regenerative braking force Fg that can be generated, and transitions along the characteristic Zfz. Specifically, the standard regenerative braking force Fz increases as the rotation speed Ng (i.e., the vehicle speed Vx) decreases until the rotation speed Ng of the generator GN reaches the first predetermined speed no. Then, when the rotation speed Ng is in the range from the first predetermined speed no to the second predetermined speed np, the standard regenerative braking force Fz is limited to the upper limit value fz. When the rotation speed Ng becomes smaller than the second predetermined speed np, the standard regenerative braking force Fz decreases as the rotation speed Ng decreases.

[0079] Assume that the required braking amount Bs is gradually increased from "0" and then maintained constant. The braking force distribution diagram (relationship between the front wheel braking force Fxf and the rear wheel braking force Fxr) in FIG. 3(b) corresponds to the characteristic diagram in FIG. 3(a). In FIG. 3(a) and (b), the state (operating point) at each time point is shown in [ ]. Note that the characteristic Cho (also called the "reference characteristic") in FIG. 3(b) is the relationship between the front wheel braking force Fxf and the rear wheel braking force Fxr in the state of "Fg=0" and "Pwf=Pwr", and represents "hf=Fxf / (Fxf+Fxr)".

[0080] At time t0, braking begins. At the beginning of braking, "P1sb>P2sb" is satisfied, and dual-system pressure adjustment is performed. At time t0, "Fg=0" and "Fxf=Fxr=0". Until time t1, there is a margin in the standard regenerative braking force Fz relative to the target total braking force Fv, so dual-system pressure adjustment in case (3) is performed. As a result, the target total braking force Fv is achieved only by the regenerative braking force Fg, and the front and rear wheel friction braking forces Fef and Fer are "0". Therefore, the operating point in the braking force distribution diagram transitions from the origin O along the X-axis.

[0081] At time t1, the target total braking force Fv reaches the standard regenerative braking force Fz (value fo). After time t1, dual-system pressure adjustment in case (4) is performed. As a result, the operating point increases along the Y-axis from point (A) toward point (B) on the reference characteristic Cho. That is, dual-system pressure adjustment quickly causes the front / rear distribution of the total braking force Fu to reach a predetermined ratio hf. When the front / rear distribution of the total braking force Fu reaches the reference characteristic Cho, dual-system pressure adjustment in case (5) is performed. As a result, the front and rear wheel braking forces Fxf and Fxr are increased while the front / rear distribution of the total braking force Fu is maintained at a preset predetermined ratio hf. That is, the operating point transitions from point (B) to point (C) along the reference characteristic Cho.

[0082] At time t2, an increase in the standard regenerative braking force Fz caused by a decrease in the vehicle speed Vx makes it necessary to decrease the second command regulating pressure P2sb. However, there is a limit to the relationship between the base pressure Pa and the regulating pressure Pb. For this reason, the pressure regulation control is switched from dual-system pressure regulation to single-system pressure regulation, and the single-system pressure regulation in case (2) is performed. The operating point deviates from the reference characteristic Cho and transitions from point (C) to point (D) along the constant acceleration line.

[0083] At time t3, the standard regenerative braking force Fz reaches the upper limit value fz. At this time, the required braking amount Bs is maintained at a constant value, and the regenerative braking force Fg is constant at the upper limit value fz, so the operating point remains at point (D). At time t4, due to a decrease in the vehicle speed Vx, the standard regenerative braking force Fz (and therefore the regenerative braking force Fg) is reduced. At time t4, a so-called replacement operation between the regenerative braking force Fg and the frictional braking force Fe is started. In the replacement operation, the decrease in the regenerative braking force Fg is compensated for by an increase in the frictional braking force Fe. The operating point transitions from point (D) toward point (C). After that, the vehicle stops and "Fg = 0", so the operating point transitions to point (C) on the reference characteristic Cho.

[0084] When the amount of regenerative energy is limited to a certain extent, such as in the early stage of braking (i.e., when "P1sb>P2sb"), the dual-system pressure regulation is selected as the pressure regulation control. This ensures the amount of regenerative energy and appropriately maintains the front / rear distribution of the total braking force Fu, improving the running stability of the vehicle.

[0085] When the amount of energy that can be regenerated increases with a decrease in the vehicle's traveling speed Vx (body speed) (i.e., when "P1sb≦P2sb"), the pressure regulation control is switched from dual pressure regulation to single pressure regulation. This allows the vehicle's kinetic energy to be fully recovered as electrical energy. In single pressure regulation, the front / rear distribution of the total braking force Fu is determined on a case-by-case basis as a result of changes in the regenerative braking force Fg. However, since the vehicle speed Vx has already decreased in this situation, the priority of driving stability is not that high.

[0086] As described above, in the brake control device SA using the electric cylinder DN, although there are restrictions on the adjustment of the adjustment pressure Pb, single-path pressure adjustment and dual-path pressure adjustment are appropriately selected based on the required braking amount Bs (resulting in a total braking force Fu) and the operating state of the regenerative device KG. In other words, even a brake control device SA that employs the electric cylinder DN can perform dual-path pressure adjustment. As a result, the brake control device SA can ensure both the amount of energy regeneration and the improvement of vehicle stability.

[0087] <Second embodiment of the brake control device SA> A second embodiment of the vehicle brake control device SA will be described with reference to the schematic diagram of Fig. 4. In the second embodiment, similarly to the first embodiment, one-way pressure regulation and two-way pressure regulation can be selectively performed.

[0088] In the first embodiment, the adjustment pressure Pb is transmitted as the supply pressure Pm via the master cylinder CM and the master piston NM. That is, the apply unit AP and the hydraulic pressure generating unit PU are arranged in series in the hydraulic pressure transmission path. Alternatively, the apply unit AP and the hydraulic pressure generating unit PU may be arranged in parallel. In the second embodiment, the apply unit AP (particularly, the master cylinder CM) and the hydraulic pressure generating unit PU are each directly connected to the hydraulic pressure correcting device SZ (particularly, the correcting actuator YZ).

[0089] Specifically, in the brake control device SA according to the second embodiment, a shutoff valve VM, a simulator valve VS, and a communication valve VC are provided instead of the input unit NR. The shutoff valve VM is a normally open type on-off solenoid valve, and the simulator valve VS and the communication valve VC are normally closed type on-off solenoid valves. The shutoff valve VM is provided in a front wheel communication passage HSf that connects the master cylinder CM (particularly, the master chamber Rm) and the front wheel cylinder CWf. The stroke simulator SS is connected to the front wheel communication passage HSf between the master cylinder CM and the shutoff valve VM via the simulator valve VS.

[0090] The front and rear wheel communication passages HSf and HSR (fluid passages connected to the front and rear wheel cylinders CWf and CWr) are connected to the control cylinder CC (particularly, the control chamber Rc) via a communication passage HV (fluid passage). The communication passage HV is also a fluid passage connecting the front and rear wheel communication passages HSf and HSf. A pressure regulating valve UC and a communication valve VC are provided in the communication passage HV.

[0091] When the pressure regulation control is performed, power is supplied to the shutoff valve VM, the simulator valve VS, and the communication valve VC. As a result, the shutoff valve VM is closed, and the simulator valve VS and the communication valve VC are opened. The connection between the master chamber Rm and the front wheel cylinder CWf is cut off, and the regulation pressure Pb is supplied to the front wheel cylinder CWf. Since the master chamber Rm is connected to the stroke simulator SS, the operating force of the brake operating member BP (brake pedal) is generated by the stroke simulator SS. The regulation pressure sensor PB may be provided in the hydraulic pressure generating unit PU or in the correction actuator YZ. In a configuration in which the regulation pressure sensor PB is provided in the correction actuator YZ, the regulation pressure Pb is acquired by the brake controller EA via the communication bus BS.

[0092] As described above, the pressure regulating valve UC prevents the flow of brake fluid BF from the control cylinder CC toward the front wheel cylinder CWf by the thrust of the solenoid. This allows the pressure regulating valve UC to adjust the adjustment pressure Pb (i.e., the front wheel pressure Pwf) to be smaller than the base pressure Pa (i.e., the rear wheel pressure Pwr). That is, the pressure regulating valve UC is provided in the hydraulic pressure transmission path from the control cylinder CC to the front wheel cylinder CWf. The adjustment pressure Pb, which is adjusted by the pressure regulating valve UC to reduce the base pressure Pa, is transmitted to the front wheel cylinder CWf as the front wheel pressure Pwf. On the other hand, the base pressure Pa is transmitted to the rear wheel cylinder CWr as the rear wheel pressure Pwr. Note that the adjustment pressure Pb cannot be reduced by the pressure regulating valve UC alone, and a reduction in the base pressure Pa is essential to reduce the adjustment pressure Pb.

[0093] In the second embodiment, the regenerative cooperative control similar to that in the first embodiment is executed. Specifically, the base pressure Pa generated by the electric cylinder DN is adjusted to the adjustment pressure Pb by the pressure regulating valve UC. At this time, the adjustment pressure Pb can be increased up to the base pressure Pa, but the reduction of the adjustment pressure Pb requires the reduction of the base pressure Pa. For this reason, in the second embodiment, whether to execute the single-path pressure adjustment or the dual-path pressure adjustment is determined based on a comparison between the first command adjustment pressure P1sb and the second command adjustment pressure P2sb. When the second command adjustment pressure P2sb is less than the first command adjustment pressure P1sb, the adjustment pressure Pb has room to increase, so the dual-path pressure adjustment is selected. On the other hand, when the second command adjustment pressure P2sb is equal to or greater than the first command adjustment pressure P1sb, the single-path pressure adjustment is selected. In the second embodiment, the same effects as those in the first embodiment (execution of the dual-path pressure adjustment, securing of the amount of energy regeneration, improvement of vehicle stability, etc.) are achieved.

[0094] <Other embodiments of the brake control device SA> Another embodiment of the brake control device SA including the electric cylinder DN will be described. The other embodiments also provide the same effects as those described above.

[0095] In the above-described embodiment of the brake control device SA, a disc-type brake device SX is used as the brake device SX. Alternatively, a drum-type brake device SX may be used as the brake device SX. In a drum-type brake device SX, the rotating member KT fixed to the wheel WH is a brake drum, and the friction member is a brake lining attached to a brake shoe. In the drum-type brake device SX, as in the disc-type brake device SX, the wheel pressure Pw of the wheel cylinder CW presses the brake lining (friction member) against the brake drum (rotating member), generating a frictional braking force Fe.

[0096] In the hydraulic pressure transmission in the brake control device SC, various resistances exist, such as the pipe friction resistance of the fluid path, the resistance as the orifice of the solenoid valve, the sliding resistance of the seal member SL, etc. In the feedback control related to the hydraulic pressure, the actual value is controlled so as to match the target value, but considering the above resistance, the actual value and the target value need to be compared at the same part. In the above-mentioned embodiment, the basal pressure Pa (the detection value of the basal pressure sensor PA) was controlled so as to approach and match the target basal pressure Pta. Also, the adjustment pressure Pb (the detection value of the adjustment pressure sensor PB and / or the supply pressure sensor PM) was controlled so as to approach and match the target adjustment pressure Ptb. That is, the part where the target value and the actual value are compared (also called the "comparison part") is the part where the servo pressure sensor PA or the like is provided. Instead of this, the comparison part may be any part from the discharge part of the electric cylinder DN to the wheel cylinder CW in the path where the hydraulic pressure is transmitted. For example, the wheel cylinder CW is used as the comparison portion, the target basal pressure Pta and the target adjusted pressure Ptb are determined to correspond to the wheel pressure Pw (actual value), and the wheel pressure Pw is estimated from the basal pressure Pa and the adjusted pressure Pb after the hydraulic pressure component due to the resistance is compensated for. In pressure adjustment control, regardless of the location of the comparison portion between the target value and the actual value, the first and second command basal pressures P1sa, P2sa are target values ​​for controlling the basal pressure Pa (actual value), and the first and second command adjusted pressures P1sb, P2sb are target values ​​for controlling the adjusted pressure Pb (actual value).

[0097] In the embodiment of the brake control device SA described above, the target values ​​of various braking forces (Fv, Fz, Fh, Fn, etc.) are calculated in the dimension of the longitudinal force acting on the vehicle (corresponding physical quantity). Alternatively, they may be calculated in the dimension of the acceleration of the vehicle or the torque of the wheels WH. This is based on the fact that state quantities from the longitudinal force to the vehicle acceleration (referred to as "state quantities related to force") are equivalent. Therefore, the target pressures Pta, Ptb, etc. are calculated based on the braking demand amount Bs via state quantities related to forces from the longitudinal force acting on the vehicle to the deceleration of the vehicle.

[0098] In the above-described embodiment of the brake control device SA, the pressure regulating valve UC is provided in the servo path HU or the communication path HV. Alternatively, the pressure regulating valve UC may be provided in the front wheel communication path HSf. Specifically, the pressure regulating valve UC is disposed in the front wheel communication path HSf between a portion to which the base pressure Pa is transmitted and the front wheel cylinder CWf. In either case, the pressure regulating valve UC is provided in the hydraulic pressure transmission path from the control cylinder CC to the front wheel cylinder CWf. The regulated pressure Pb, which is reduced from the base pressure Pa by the pressure regulating valve UC, is transmitted to the front wheel cylinder CWf as the front wheel pressure Pwf.

[0099] In the first embodiment of the brake control device SA described above, in the apply unit AP, the pressure receiving area rm (master area) of the master chamber Rm and the pressure receiving area ru (servo area) of the servo chamber Ru are set to be equal. The master area rm and the servo area ru do not have to be equal. In a configuration in which the master area rm and the servo area ru are different, a conversion calculation between the supply pressure Pm (master pressure) and the base pressure Pa is possible based on the area ratio between the servo area ru and the master area rm (i.e., conversion based on "Pm·rm=Pa·ru"). In a configuration in which the supply pressure sensor PM is used as the adjustment pressure sensor PB and the supply pressure Pm is used as the adjustment pressure Pb, the supply pressure Pm is converted to the adjustment pressure Pb based on the above area ratio.

[0100] <Summary of the embodiment> The brake control device SA is applied to a vehicle equipped with a regenerative device KG on the front wheels WHf. The brake control device SA is composed of a control cylinder CC, a pressure regulating valve UC (solenoid valve), and a brake controller EA. Here, the control cylinder CC generates a base pressure Pa using an electric motor MA as a power source, the pressure regulating valve UC adjusts the base pressure Pa to an adjusted pressure Pb, and the controller EA controls the electric motor MA and the pressure regulating valve UC. The brake control device SA generates the base pressure Pa and the adjusted pressure Pb based on the required braking amount Bs of the vehicle, controls the hydraulic pressure Pwf of the front wheel cylinder CWf with the adjusted pressure Pb, and controls the hydraulic pressure Pwr of the rear wheel cylinder CWr with the base pressure Pa.

[0101] For example, the brake control device SA has a master chamber Rm and a servo chamber Ru which face each other via a master piston NM. The control cylinder CC is connected to the servo chamber Ru and the rear wheel cylinder CWr, the master chamber Rm is connected to the front wheel cylinder CWf, and the pressure regulating valve UC is disposed between the control cylinder CC and the servo chamber Ru. With this configuration, the hydraulic pressure Pwf (front wheel pressure) in the front wheel cylinder CWf is controlled by the regulating pressure Pb, and the hydraulic pressure Pwr (rear wheel pressure) in the rear wheel cylinder CWr is controlled by the base pressure Pa.

[0102] In the brake control device SA, the controller EA can execute one of the single-path pressure regulation and the dual-path pressure regulation when the regenerative device KG generates a regenerative braking force Fg (i.e., when regenerative cooperative control is executed). Here, the single-path pressure regulation achieves the total braking force Fu according to the required braking amount Bs by making the regulated pressure Pb equal to the base pressure Pa. Meanwhile, the dual-path pressure regulation achieves the total braking force Fu in a state in which the regulated pressure Pb is made smaller than the base pressure Pa and the front / rear distribution of the total braking force Fu is maintained at a predetermined value hf (a distribution ratio set in advance). The controller EA calculates a first command regulated pressure P1sb (first command pressure) for controlling the regulated pressure Pb in the single-path pressure regulation, and a second command regulated pressure P2sb (second command pressure) for controlling the regulated pressure Pb in the dual-path pressure regulation. Then, based on a comparison between the first command regulated pressure P1sb and the second command regulated pressure P2sb, it is determined whether to select the single-path pressure regulation or the dual-path pressure regulation.

[0103] Specifically, the controller EA selects the single-system adjustment pressure when the second command adjustment pressure P2sb is equal to or greater than the first command adjustment pressure P1sb, and selects the dual-system adjustment pressure when the second command adjustment pressure P2sb is less than the first command adjustment pressure P1sb. In other words, the smaller of the first command adjustment pressure P1sb and the second command adjustment pressure P2sb is selected, and control corresponding to the selected command adjustment pressure between the single-system adjustment pressure and the dual-system adjustment pressure is executed.

[0104] In the braking control device SA, the basic pressure Pa is output from the electric cylinder DN by the power of the electric motor MA. Then, the basic pressure Pa is decreased and adjusted by the pressure regulating valve UC to the adjusted pressure Pb. The pressure regulating valve UC operates so as to prevent an increase in the adjusted pressure Pb, and forms a state in which the adjusted pressure Pb is less than the basic pressure Pa. In the braking control device SA including the electric cylinder DN, the pressure regulating valve UC alone cannot decrease the adjusted pressure Pb. When the traveling speed Vx (vehicle body speed) decreases due to braking, the possible regenerative braking force Fg (that is, the standard regenerative braking force Fz) increases. At this time, in order to decrease the adjusted pressure Pb to increase the regenerative braking force Fg, it is necessary to decrease the basic pressure Pa.

[0105] In the braking control device SA, the single-line pressure regulation and the two-line pressure regulation are appropriately switched according to the vehicle situation (that is, the degree of increase in the required braking amount Bs and the operating state of the regenerator KG). Specifically, in the braking control device SA, based on the comparison between the first indicated regulated pressure P1sb and the second indicated regulated pressure P2sb, it is selected whether to execute the single-line pressure regulation or the two-line pressure regulation. When the second indicated regulated pressure P2sb is less than the first indicated regulated pressure P1sb, the two-line pressure regulation is determined, and when the second indicated regulated pressure P2sb is greater than or equal to the first indicated regulated pressure P1sb, the single-line pressure regulation is determined. This is based on the fact that "P2sb < P1sb" in a state where the generation of the regenerative braking force Fg is restricted and the increase in the adjusted pressure Pb is possible, and "P2sb ≥ P1sb" in a state where it is necessary to decrease the adjusted pressure Pb as the regenerative braking force Fg increases.

[0106] In the brake control device SA, immediately after the start of braking, the target total braking force Fv (resulting in the total braking force Fu) is gradually increased, and in a situation where the traveling speed Vx is relatively high, the dual-system pressure adjustment is executed. As a result, the vehicle stability is improved and energy regeneration is performed. After that, when the traveling speed Vx decreases due to braking, the single-system pressure adjustment is executed, so that energy is sufficiently regenerated. In the single-system pressure adjustment, the front / rear distribution of the total braking force Fu is determined as a result of the regenerative braking force Fg. However, since the traveling speed Vx is decreasing when the single-system pressure adjustment is executed, the energy regeneration is prioritized over the vehicle stability. In the brake control device SA, the single-system pressure adjustment and the dual-system pressure adjustment are appropriately switched according to the traveling state of the vehicle. In other words, in the brake control device SA using the electric cylinder DN, which has a restriction on the adjustment of the adjustment pressure Pb, the dual-system pressure adjustment can be appropriately executed. As a result, both the energy regeneration and the vehicle stability are achieved. [Explanation of symbols]

[0107] SA...Brake control device, SX...Brake device, BP...Brake operation member (brake pedal), BF...Brake fluid (hydraulic fluid), YA...Brake actuator, EA...Brake controller, BS...Communication bus, CM...Master cylinder, CW...Wheel cylinder, AP...Apply unit, NR...Input unit, PU...Fluid pressure generating unit, DN...Electric cylinder, MA...Electric motor, NC...Control piston, CC...Control cylinder, Rc...Control chamber (fluid pressure chamber of CC), UC...Pressure regulating valve (corresponding to solenoid valve), VA, VB...First and second control valves, SP...Operation displacement sensor, Sp...Operation displacement (detected value of SP), PN...Input pressure sensor, Pn...Input pressure (detected value of PN), BA...Brake operation amount sensor (generic term for SP and PN), Ba...Brake operation amount (generic term for Sp and Pn, detected value of BA), Gs...Target acceleration, Bs...Brake demand amount (total of Ba and Gs) nominal), Pa...basal pressure (output of DN, detected value of PA), Pta...target basal pressure (final target value for controlling Pa), PA...basal pressure sensor, P1sa...first indicated basal pressure (target value for controlling Pa with single-system pressure regulation), P2sa...second indicated basal pressure (target value for controlling Pa with dual-system pressure regulation), Pb...adjusted pressure (result of pressure regulation by UC, detected value of PB), Ptb...target adjusted pressure (final target value for controlling Pb), PB...adjusted pressure sensor, P1sb...first indicated adjusted pressure (target value for controlling Pb with single-system pressure regulation, equivalent to the first indicated pressure), P2sb...second indicated adjusted pressure (target value for controlling Pb with dual-system pressure regulation, equivalent to the second indicated pressure), Pm...supply pressure (detected value of PM, equivalent to Pb), PM...supply pressure sensor (equivalent to PB), Pwf, Pwr...front and rear wheel pressures.

Claims

1. A vehicle brake control device is applied to a vehicle equipped with a regenerative device on a front wheel, and includes a control cylinder that generates a base pressure using an electric motor as a power source, a solenoid valve that adjusts the base pressure to an adjustment pressure, and a controller that controls the electric motor and the solenoid valve, and generates the base pressure and the adjustment pressure based on a required braking amount of the vehicle, controls the hydraulic pressure of a front wheel cylinder by the adjustment pressure, and controls the hydraulic pressure of a rear wheel cylinder by the base pressure. The controller: When the regenerative device generates a regenerative braking force, one of a single-system pressure regulation in which the regulated pressure is made equal to the base pressure to achieve a total braking force corresponding to the required braking amount, and a two-system pressure regulation in which the regulated pressure is made smaller than the base pressure to achieve the total braking force while maintaining the front / rear distribution of the total braking force at a predetermined value, can be performed. Calculating a first command pressure for controlling the regulated pressure in the single-system pressure regulating system and a second command pressure for controlling the regulated pressure in the dual-system pressure regulating system; A braking control device for a vehicle that determines whether to select the single-system pressure regulation or the dual-system pressure regulation based on a comparison between the first command pressure and the second command pressure.

2. 2. The vehicle brake control device according to claim 1, A braking control device for a vehicle, wherein the controller selects the single-system pressure regulation when the second command pressure is equal to or greater than the first command pressure, and selects the dual-system pressure regulation when the second command pressure is less than the first command pressure.

3. A vehicle braking control device according to claim 1 or 2, A master chamber and a servo chamber are disposed opposite each other via a master piston, A vehicle braking control device, wherein the control cylinder is connected to the servo chamber and the rear wheel cylinder, the master chamber is connected to the front wheel cylinder, and the solenoid valve is disposed between the control cylinder and the servo chamber.

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