Vehicle braking control device

Abstract

To simplify the configuration of a brake control device capable of two system pressure regulation.SOLUTION: A brake control device comprises: a first unit which outputs a front wheel supply pressure and a rear wheel supply pressure individually depending on an amount of operation of a brake operation member; a second unit which is provided between the first unit and front wheel and rear wheel wheel cylinders, regulates the front wheel supply pressure and the rear wheel supply pressure, and outputs front wheel and rear wheel wheel pressures; a communication bus which performs signal transmission between the first unit and the second unit; an operation amount sensor which is connected to the first unit, and detects an operation amount; a front wheel supply pressure sensor which is connected to the second unit, and detects the front wheel supply pressure; and a rear wheel supply pressure sensor which is connected to the first unit, and detects the rear wheel supply pressure. The first unit acquires the front wheel supply pressure via the communication bus from the second unit, calculates front wheel and rear wheel target pressures on the basis of the operation amount, performs feedback control so that the front wheel supply pressure is coincident with the front wheel target pressure, and performs feedback control so that the rear wheel supply pressure is coincident with the rear wheel target pressure.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] The applicant has developed a brake control device as disclosed in Patent Document 1, which has a reduced longitudinal dimension and allows for separate control of the brake fluid pressure in the front wheel system and the brake fluid pressure in the rear wheel system. Specifically, the brake control device in Patent Document 1 includes "a master unit having a master chamber connected to the front wheel cylinder and a servo chamber that applies a forward force to the master piston that counteracts the backward force applied to the master piston by the master chamber," "a pressure adjustment unit that adjusts brake fluid discharged from an electric pump to a first fluid pressure using a first solenoid valve, introduces the first fluid pressure into the rear wheel cylinder, and reduces and adjusts the first fluid pressure to a second fluid pressure using a second solenoid valve and introduces the second fluid pressure into the servo chamber," and "a regenerative coordination unit that includes an input piston that operates in conjunction with a brake operating member and an input cylinder fixed to the master cylinder, and in which the gap between the master piston and the input piston is controlled by the second fluid pressure." Here, adjusting the brake fluid pressure of the front wheel system and the brake fluid pressure of the rear wheel system to the same level is called "single-system pressure regulation," while adjusting them separately is called "dual-system pressure regulation."In a brake control device that can achieve dual-system pressure regulation, it is desirable to not only reduce the longitudinal dimension but also simplify the configuration. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-137202 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a vehicle brake control device capable of dual-system pressure regulation, the configuration of which can be simplified. [Means for solving the problem]

[0005] A vehicle brake control device (SC) according to the present invention comprises a first unit (SA) that outputs front and rear wheel supply pressures (Pm, Pv) individually in accordance with an operation amount (Sp) of a vehicle brake operating member (BP), a second unit (SB) that is provided between the first unit (SA) and front and rear wheel cylinders (CWf, CWr) and adjusts the front and rear wheel supply pressures (Pm, Pv) to output front and rear wheel pressures (Pwf, Pwr), a communication bus (BS) that transmits signals between the first unit (SA) and the second unit (SB), an operation amount sensor (SP) connected to the first unit (SA) and detecting the operation amount (Sp), a front wheel supply pressure sensor (PM) connected to the second unit (SB) and detecting the front wheel supply pressure (Pm), and a rear wheel supply pressure sensor (PV) connected to the first unit (SA) and detecting the rear wheel supply pressure (Pv).

[0006] In the vehicle braking control device (SC) according to the present invention, the first unit (SA) acquires the front wheel supply pressure (Pm) from the second unit (SB) via the communication bus (BS). Then, the first unit (SA) calculates front and rear wheel target pressures (Ptf, Ptr) based on the manipulated variable (Sp), and executes feedback control to make the front wheel supply pressure (Pm) coincide with the front wheel target pressure (Ptf), and also executes feedback control to make the rear wheel supply pressure (Pv) coincide with the rear wheel target pressure (Ptr). With this configuration, the front wheel supply pressure Pm is shared by multiple controls, simplifying the entire device.

[0007] In the vehicle brake control device (SC) according to the present invention, when the first unit (SA) cannot acquire the front wheel supply pressure (Pm) or when the first unit (SA) cannot acquire the rear wheel supply pressure (Pv), the first unit (SA) determines a common target pressure (Px) by equalizing the front wheel target pressure (Ptf) and the rear wheel target pressure (Ptr), and communicates the portion (pk) on which the front wheel supply pressure (Pm) acts with the portion (pj) on which the rear wheel supply pressure (Pv) acts, thereby executing feedback control to make the rear wheel supply pressure (Pv) equal to the common target pressure (Px). The above configuration is a simple configuration that can execute hydraulic pressure feedback control even when one of the front wheel and rear wheel supply pressures Pm and Pv cannot be acquired.

[0008] For example, the first unit (SA) adjusts the pressure of the brake fluid (BF) discharged by the fluid pump (QA) to upstream and downstream servo pressures (Pj, Pk) using normally open upstream and downstream pressure regulating valves (UJ, UK) arranged in series with the circulating flow (KN) of brake fluid (BF) including the fluid pump (QA), and outputs the front wheel supply pressure (Pm) using the hydraulic pressure on one side of the upstream and downstream servo pressures (Pj, Pk), and outputs the rear wheel supply pressure (Pv) using the hydraulic pressure on the other side of the upstream and downstream servo pressures (Pj, Pk). The first unit (SA) acquires the front wheel supply pressure (Pm) from the second unit (SB) via the communication bus (BS), calculates front and rear wheel target pressures (Ptf, Ptr) based on the manipulated variable (Sp), and feedback-controls the one-side hydraulic pressure so that the front wheel supply pressure (Pm) coincides with the front wheel target pressure (Ptf), and feedback-controls the other-side hydraulic pressure so that the rear wheel supply pressure (Pv) coincides with the rear wheel target pressure (Ptr). With this configuration, the front wheel supply pressure Pm is shared by multiple controls, thereby simplifying the entire device.

[0009] In the vehicle brake control device (SC) according to the present invention, when the first unit (SA) cannot obtain the front wheel supply pressure (Pm) or when the first unit (SA) cannot obtain the rear wheel supply pressure (Pv), the first unit (SA) determines a common target pressure (Px) by equalizing the front wheel target pressure (Ptf) and the rear wheel target pressure (Ptr), stops the supply of current to the upstream pressure regulating valve (UJ), and drives the downstream pressure regulating valve (UK) by feedback control so that the rear wheel supply pressure (Pv) coincides with the common target pressure (Px). The above configuration is a simple configuration that can perform hydraulic pressure feedback control even when one of the front and rear wheel supply pressures Pm and Pv cannot be obtained. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic diagram illustrating an entire vehicle JV equipped with a braking control device SC. [Figure 2] 3 is a schematic diagram for explaining a configuration example of a first braking unit SA. FIG. [Figure 3] 4 is a schematic diagram for explaining a configuration example of a second braking unit SB. FIG. [Figure 4] 10 is a flowchart for explaining pressure regulation control including specific control when acquisition of front wheel supply pressure Pm is abnormal. [Figure 5] 10 is a flow chart for explaining pressure regulation control including specific control when the acquisition of rear wheel supply pressure Pv is abnormal. [Figure 6] FIG. 4 is a block diagram for explaining drive control of a first actuator YA. DETAILED DESCRIPTION OF THE INVENTION

[0011] <Symbols for components, etc., and suffixes at the end of the symbols> In the following description, components, calculation processes, signals, characteristics, and values ​​with the same symbols, such as "CW," have the same function. The suffixes "f" and "r" at the end of the symbols for each wheel are generic symbols that indicate whether the symbol relates to the front or rear wheel system. For example, a wheel cylinder CW provided on each wheel is written as a "front wheel cylinder CWf" and a "rear wheel cylinder CWr." Furthermore, the suffixes "f" and "r" at the end of the symbol can be omitted. When the suffixes "f" and "r" are omitted, each symbol represents a generic term. For example, "CW" is a generic term for wheel cylinders provided on the front and rear wheels of a vehicle.

[0012] In the fluid path from the master cylinder CM to the wheel cylinder CW, the side closer to the master cylinder CM (the side farther from the wheel cylinder CW) is referred to as the "upper side," and the side closer to the wheel cylinder CW (the side farther from the master cylinder CM) is referred to as the "lower side." Also, in the circulating flows KN, KL of brake fluid BF in the first and second fluid units YA, YB, the side closer to the discharge ports of the first and second fluid pumps QA, QB (the side farther from the suction ports) is referred to as the "upstream side," and the side closer to the suction ports of the first and second fluid pumps QA, QB (the side farther from the discharge ports) is referred to as the "downstream side."

[0013] The first hydraulic unit YA of the first brake unit SA, the second hydraulic unit YB of the second brake unit SB, and the wheel cylinder CW are connected by a fluid path (communication path HS). Furthermore, in the first and second hydraulic units YA and YB, various components (UJ, UK, etc.) are connected by fluid paths. Here, the "fluid path" is a path for moving the brake fluid BF, and corresponds to piping, flow paths in the actuator, hoses, etc. In the following explanation, the communication path HS, reflux path HK, return path HL, reservoir path HR, input path HN, servo path HV, pressure reduction path HG, etc. are fluid paths.

[0014] <Vehicle JV equipped with braking control device SC> With reference to the schematic diagram of FIG. 1, the overall configuration of a vehicle JV equipped with a braking control device SC according to the present invention will be described. The vehicle JV is a hybrid vehicle or an electric vehicle equipped with an electric motor for driving. The vehicle JV is equipped with a regenerative device KG. The regenerative device KG is composed of a generator GN and a control unit EG for the regenerative device (also referred to as a "regenerative controller"). The generator GN is also an electric motor for driving. In regenerative braking, the electric motor / generator GN operates as a generator, and the generated electric power is stored in a storage battery BG via the regenerative controller EG. For example, the regenerative device KG is provided on the front wheels WHf. In this configuration, the regenerative device KG generates a regenerative braking force Fg on the front wheels WHf.

[0015] A vehicle JV is equipped with front and rear wheel braking devices SXf, SXr (=SX). The braking device SX is composed of a brake caliper CP, a friction member MS (e.g., brake pad), and a rotating member (e.g., brake disc) KT. The brake caliper CP is provided with a wheel cylinder CW. The hydraulic pressure Pw (referred to as "wheel pressure") in the wheel cylinder CW presses the friction member MS against the rotating member KT fixed to each wheel WH. This generates a braking force Fm on the wheel WH. The braking force generated by the wheel pressure Pw is referred to as the "friction braking force Fm."

[0016] The vehicle JV is equipped with a brake operating member BP and various sensors (such as SP). The brake operating member (e.g., brake pedal) BP is a member that the driver operates to decelerate the vehicle JV. The vehicle JV is provided with an operation displacement sensor SP that detects the operation displacement Sp of the brake operating member BP. The operation displacement Sp is one of the state quantities (state variables) that indicate the operation amount (braking operation amount) of the brake operating member BP, and in a brake-by-wire type brake control device SC, it is a signal that indicates the driver's intention to brake (i.e., a braking command).

[0017] The operation displacement sensor SP (corresponding to an "operation amount sensor") includes two detection units SPa and SPb (referred to as "first and second detection units"). That is, the operation displacement Sp is detected in two ways, making the operation displacement sensor SP redundant. The first detection unit SPa (referred to as "first displacement detection unit") of the operation displacement sensor SP is connected to the first braking unit SA (particularly, the first control unit EA) by a first displacement signal line LSpa. On the other hand, the second detection unit SPb (referred to as "second displacement detection unit") of the operation displacement sensor SP is connected to the second braking unit SB (particularly, the second control unit EB) by a second displacement signal line LSpb. Therefore, the signal Spa (referred to as "first operation displacement") of the first displacement detection unit SPa is directly input to the first control unit EA. On the other hand, the signal Spb (referred to as "second operation displacement") of the second displacement detection unit SPb is directly input to the second control unit EB. For example, "signal lines LSpa, LSpb" are electric wires (wire harnesses) for transmitting signals.

[0018] In addition to the operation displacement sensor SP, the hydraulic pressure Ps (referred to as "simulator pressure") of the stroke simulator SS is adopted as another state quantity representing the braking operation amount. The simulator pressure Ps is detected by a simulator pressure sensor PS. The simulator pressure sensor PS is connected to the first brake unit SA (particularly, the first control unit EA) by a simulator pressure signal line LPs. Therefore, the simulator pressure Ps is directly input to the first control unit EA. The simulator pressure Ps is a state quantity equivalent to the operating force of the brake operating member BP.

[0019] The vehicle JV is equipped with various sensors. For braking control (referred to as "independent wheel control") that individually controls the wheel pressure Pw of each wheel WH, such as antilock brake control and anti-skid control, each wheel WH is equipped with a wheel speed sensor VW that detects its rotational speed (wheel speed) Vw. The vehicle JV is also equipped with a steering amount sensor that detects the steering amount Sa (e.g., the steering wheel angle), a yaw rate sensor that detects the vehicle's yaw rate Yr, a longitudinal acceleration sensor that detects the vehicle's longitudinal acceleration Gx, and a lateral acceleration sensor that detects the vehicle's lateral acceleration Gy (all not shown). The signals for the wheel speed Vw, steering amount Sa, yaw rate Yr, longitudinal acceleration Gx, and lateral acceleration Gy are input to the second braking unit SB (particularly, the second control unit EB) via their respective signal lines.

[0020] The vehicle JV is equipped with a brake control device SC. The brake control device SC employs a so-called front and rear type (also called "type II") brake system as two brake systems. The brake control device SC adjusts the actual wheel pressure Pw.

[0021] The brake control device SC is composed of two brake units SA and SB. The first brake unit SA is composed of a first fluid unit YA and a first control unit EA. The first fluid unit YA is controlled by the first control unit EA using a storage battery BT (braking storage battery) separate from the drive storage battery BG as its power source. The second brake unit SB is composed of a second fluid unit YB and a second control unit EB. Like the first brake unit SA, the second fluid unit YB is controlled by the second control unit EB using the storage battery BT as its power source.

[0022] The first brake unit SA (particularly, the first control unit EA) and the second brake unit SB (particularly, the second control unit EB) are connected to a communication bus BS. The regenerative device KG (particularly, the regenerative control unit EG) is also connected to the communication bus BS. The "communication bus BS" has a network structure in which multiple control units (also called "controllers") hang from communication lines terminated at both ends. Signals are transmitted between the multiple controllers (EA, EB, EG, etc.) via the communication bus BS. That is, the multiple controllers can transmit signals (detected values, calculated values, control flags, etc.) to the communication bus BS and can receive signals from the communication bus BS. For example, a vehicle bus (an internal communication network that interconnects controllers within a vehicle) is used as the communication bus BS, and CAN is used as the serial communication protocol. The communication bus BS is composed of communication lines (e.g., CAN bus cables) and transmitting / receiving microcontrollers in each controller.

[0023] <First braking unit SA> An example of the configuration of the first brake unit SA (corresponding to the "first unit") of the brake control device SC will be described with reference to the schematic diagram of FIG. 2. The first brake unit SA generates front and rear wheel supply pressures Pm and Pv in response to operation of the brake operating member BP (brake pedal). The front and rear wheel supply pressures Pm and Pv are ultimately supplied to the front and rear wheel cylinders CWf and CWr via a communication path HS (fluid path) and a second brake unit SB. The first brake unit SA is made up of a first fluid unit YA and a first control unit EA.

[0024] <First fluid unit YA> The first fluid unit YA (also referred to as the "first actuator") is composed of an apply part AP, a pressure adjustment part CA, and an input part NR.

[0025] [Apply Department AP] In response to operation of the brake operating member BP, the apply section AP outputs a front wheel supply pressure Pm, which is composed of a single master cylinder CM and a master piston NM.

[0026] A master piston NM is inserted into the single-type master cylinder CM. The master piston NM divides the interior of the master cylinder CM into three hydraulic chambers Rm, Ru, and Rs. The master chamber Rm is divided by the bottom of one side of the master cylinder CM and the master piston NM. The interior of the master cylinder CM is further divided into a servo chamber Ru and a reaction chamber Rs by a flange portion Tu of the master piston NM. In other words, the master chamber Rm and the servo chamber Ru are arranged opposite each other with the flange portion Tu in between. Here, the pressure-receiving area rm of the master chamber Rm and the pressure-receiving area ru of the servo chamber Ru are made equal.

[0027] When braking is not in progress, the master piston NM is in its most retracted 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 in communication with the master reservoir RV. Brake fluid BF is stored inside the master reservoir RV (an atmospheric pressure reservoir, also simply referred to as the "reservoir"). When the brake operating member BP is operated, the master piston NM is moved forward in the Ha direction (a direction in which the volume of the master chamber Rm decreases). This movement blocks communication between the master chamber Rm and the reservoir RV. When the master piston NM is further moved forward in the Ha direction, the front wheel supply pressure Pm increases from "0 (atmospheric pressure)." As a result, brake fluid BF pressurized to the front wheel supply pressure Pm is output (pressurized and fed) from the master chamber Rm of the master cylinder CM. Because the front wheel supply pressure Pm is the hydraulic pressure of the master chamber Rm, it is also referred to as the "master pressure." [Pressure Regulating Unit CA] The pressure adjusting unit CA supplies rear wheel supply pressure Pv to the rear wheel cylinder CWr and downstream servo pressure Pk to the servo chamber Ru of the apply unit AP. The pressure adjusting unit CA is composed of a first electric motor MA, a first fluid pump QA, and upstream and downstream pressure adjusting valves UJ and UK.

[0028] A first electric motor MA drives a first fluid pump QA. The suction and discharge ports of the first fluid pump QA are connected by a return passage HK (fluid passage). The suction port of the first fluid pump QA is also connected to a master reservoir RV via a reservoir passage HR. A check valve is provided at the discharge port of the first fluid pump QA.

[0029] Two pressure regulating valves UJ, UK are provided in series in the return path HK. Specifically, a normally open downstream pressure regulating valve UK is provided in the return path HK. A normally open upstream pressure regulating valve UJ is provided between the downstream pressure regulating valve UK and the discharge port of the fluid pump QA. Therefore, in the circulating flow KN of brake fluid BF, the upstream pressure regulating valve UJ is located upstream (closer to the discharge port of the fluid pump QA) of the downstream pressure regulating valve UK. The upstream and downstream pressure regulating valves UJ, UK are linear solenoid valves whose valve opening (lift amount) is continuously controlled based on the energization state (e.g., supply currents Ij, Ik). The upstream and downstream pressure regulating valves UJ, UK are also called "differential pressure valves" because they adjust the hydraulic pressure difference between their upstream and downstream sides.

[0030] When the first electric motor MA drives the first fluid pump QA, a circulation flow KN (indicated by the dashed arrow) of brake fluid BF is generated in the return path HK through the fluid pump QA and the upstream and downstream pressure regulating valves UJ and UK. The fluid pressure Pk between the upstream pressure regulating valve UJ and the downstream pressure regulating valve UK (referred to as the "downstream servo pressure") is controlled by the downstream pressure regulating valve UK. The fluid pressure Pj between the upstream pressure regulating valve UJ and the discharge port of the first fluid pump QA (referred to as the "upstream servo pressure") is controlled by the upstream pressure regulating valve UJ.

[0031] When the downstream pressure regulating valve UK is fully open (the downstream pressure regulating valve UK is normally open and therefore not energized), the downstream servo pressure Pk is "0 (atmospheric pressure)." When the amount of electricity (supply current Ik) to the downstream pressure regulating valve UK is increased, the downstream pressure regulating valve UK throttles the circulation flow KN (the flow of brake fluid BF circulating in the return flow path HK). In other words, the downstream pressure regulating valve UK narrows the flow path of the return flow path HK, and the downstream pressure regulating valve UK exerts an orifice effect. As a result, a differential pressure sPk (referred to as the "downstream differential pressure") is generated between the downstream hydraulic pressure (atmospheric pressure) and the upstream hydraulic pressure Pk (downstream servo pressure) for the downstream pressure regulating valve UK. The downstream differential pressure sPk is adjusted by the amount of electricity (supply current Ik) to the downstream pressure regulating valve UK.

[0032] Similarly, when the upstream pressure regulating valve UJ is fully open (the upstream pressure regulating valve UJ is normally open and therefore not energized), the upstream servo pressure Pj is equal to the downstream servo pressure Pk. When the amount of energization (supply current Ij) to the upstream pressure regulating valve UJ is increased, the upstream pressure regulating valve UJ throttles the circulation flow KN (the flow of brake fluid BF circulating in the return flow path HK). In other words, the upstream pressure regulating valve UJ narrows the flow path of the return flow path HK, thereby exerting an orifice effect. This generates a differential pressure sPj (referred to as the "upstream differential pressure") between the downstream hydraulic pressure Pk (downstream servo pressure) and the upstream hydraulic pressure Pj (upstream servo pressure) for the upstream pressure regulating valve UJ. The upstream differential pressure sPj is adjusted by the amount of energization (supply current Ij) to the upstream pressure regulating valve UJ. In terms of the magnitude relationship between the upstream servo pressure Pj and the downstream servo pressure Pk, the upstream servo pressure Pj is always equal to or greater than the downstream servo pressure Pk (i.e., "Pj≧Pk"). Here, when no power is supplied to the upstream pressure regulating valve UJ and it is in a fully open state, the upstream and downstream servo pressures Pj and Pk are made equal (i.e., "Pj=Pk").

[0033] The hydraulic pressure supplied from the first brake unit SA to the second brake unit SB is referred to as the "supply pressure." In the brake control device SC, the transmission path of the supply pressure is different between the brake system related to the front wheels WHf and the brake system related to the rear wheels WHr. In the brake system related to the front wheels WHf, the return path HK is connected to the servo chamber Ru via a servo path HV (fluid path) at a point pk between the upstream pressure regulating valve UJ and the downstream pressure regulating valve UK. Therefore, the downstream servo pressure Pk is introduced (supplied) to the servo chamber Ru. As the downstream servo pressure Pk increases, the master piston NM is pressed in the forward direction Ha, and the hydraulic pressure Pm (front wheel supply pressure) in the master chamber Rm increases. A front wheel connection path HSf is connected to the front wheel cylinder CWf via the second brake unit SB (particularly, the second fluid unit YB). Therefore, in the braking system for the front wheels WHf of the brake control device SC, the downstream servo pressure Pk is supplied to the front wheel cylinders CWf via the master cylinder CM as the front wheel supply pressure Pm. However, since "ru = rm", "Pk = Pm = Pwf" holds.

[0034] In the brake system for the rear wheels WHr, the return path HK is connected to the rear wheel cylinder CWr via the rear wheel connection path HSR (fluid path) and the second brake unit SB (particularly, the second fluid unit YB) at a location pj between the discharge port of the first fluid pump QA and the upstream pressure regulating valve UJ. Therefore, in the brake system for the rear wheels WHr of the brake control device SC, the upstream servo pressure PJ is directly supplied to the rear wheel cylinder CWr as the rear wheel supply pressure Pv (i.e., "Pj = Pv = Pwr").

[0035] A rear wheel supply pressure sensor PV (also referred to as a "servo pressure sensor") is provided in the rear wheel connection path HSr to detect the rear wheel supply pressure Pv (=Pj). The rear wheel supply pressure sensor PV is connected to the first controller EA by a rear wheel supply pressure signal line LPv (also referred to as a "servo pressure signal line"). Therefore, a signal of the rear wheel supply pressure Pv is directly input to the first controller EA.

[0036] [Input NR] The input unit NR operates the brake operating member BP to realize regenerative cooperative control, but creates a state in which wheel pressure Pw is not generated. "Regenerative cooperative control" coordinates the friction braking force Fm (braking force due to wheel pressure Pw) and the regenerative braking force Fg (braking force due to generator GN) so that the kinetic energy of the vehicle JV can be efficiently recovered as electrical energy during braking. The input unit NR is composed of an input cylinder CN, an input piston NN, an intake valve VA, an open valve VB, a stroke simulator SS, and a simulator hydraulic pressure sensor PS.

[0037] 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 the brake operating member BP (brake pedal) via a clevis (U-shaped link) so that it moves in conjunction with the brake operating member BP. There is a gap Ks (also called "separation displacement") between the end face of the input piston NN and the end face of the master piston NM. Regenerative cooperative control is achieved by adjusting the separation distance Ks using the downstream servo pressure Pk.

[0038] 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 inlet valve VA is provided in the input path HN. The input path HN is connected to the master reservoir RV via a reservoir path HR between the inlet valve VA and the reaction chamber Rs. A normally open release valve VB is provided in the reservoir path HR. The inlet valve VA and the release valve VB are on-off solenoid valves. A stroke simulator SS (also simply referred to as "simulator") is connected to the input path HN between the inlet valve VA and the reaction chamber Rs.

[0039] When power is not supplied to the introduction valve VA and the release valve VB, the introduction valve VA is closed and the release valve VB is open. When the introduction valve VA is closed, the input chamber Rn is sealed and fluid locked. As a result, the master piston NM is displaced integrally with the brake operating member BP. When the release valve VB is open, the simulator SS is connected to the master reservoir RV. When power is supplied to the introduction valve VA and the release valve VB, the introduction valve VA is opened and the release valve VB is closed. As a result, the master piston NM can be displaced separately from the brake operating member BP. At this time, the input chamber Rn is connected to the stroke simulator SS, and the operating force Fp of the brake operating member BP is generated by the simulator SS.

[0040] The state in which the master piston NM and the brake operating member BP are displaced separately (when the solenoid valves VA and VB are energized) is called the "first mode (or by-wire mode)." In the first mode, the brake control device SC functions as a brake-by-wire type device (i.e., a device that can generate a frictional braking force Fm independently of the driver's braking operation). Therefore, in the first mode, the wheel pressure Pw is generated independently of the operation of the brake operating member BP. On the other hand, the state in which the master piston NM and the brake operating member BP are displaced together (when the solenoid valves VA and VB are not energized) is called the "second mode (or manual mode)." In the second mode, the wheel pressure Pw is linked to the driver's braking operation. The input unit NR selects one of the first mode (by-wire mode) and the second mode (manual mode) depending on whether or not power is supplied to the introduction valve VA and the release valve VB. If a power failure occurs in the braking control device SC (for example, failure of the storage battery BT), the input unit NR goes into the second mode.

[0041] A simulator pressure sensor PS is provided in the input line HN between the introduction valve VA and the reaction force chamber Rs to detect the hydraulic pressure Ps (simulator pressure) in the simulator SS. The simulator pressure sensor PS is connected to the first control unit EA by a simulator pressure signal line LPs. Therefore, the simulator pressure Ps is directly input to the first control unit EA via the simulator pressure signal line LPs.

[0042] <First control unit EA> The first actuator YA is controlled by a first control unit EA (also referred to as the "first controller"). The first controller EA is composed of a first microprocessor MPa and a first drive circuit DRa. The first controller EA is connected to a communication bus BS so that signals (detected values, calculated values, control flags, etc.) can be shared between the first controller EA and various controllers (EB, EG, etc.).

[0043] The first controller EA and the first detection unit SPa of the operation displacement sensor SP are connected via a signal line LSpa for the first detection unit SPa. The first controller EA and the rear wheel supply pressure sensor PV are connected via a signal line LPv for the rear wheel supply pressure sensor PV. The first controller EA and the simulator pressure sensor PS are connected via a signal line LPs for the simulator pressure sensor PS. Therefore, the first controller EA directly receives the first operation displacement Spa via the signal line LSpa, the rear wheel supply pressure Pv via the signal line LPv, and the simulator pressure Ps via the signal line LPs.

[0044] The first controller EA (particularly, the first microprocessor MPa) is programmed with a pressure regulation control algorithm. "Pressure regulation control" is a control for adjusting the front and rear wheel supply pressures Pm and Pv (resulting in front and rear wheel pressures Pwf and Pwr), and includes regenerative cooperative control. The pressure regulation control is performed based on the first and second operation displacements Spa and Spb, the simulator pressure Ps, the front and rear wheel supply pressures Pm and Pv, and the maximum regenerative braking force Fx.

[0045] Based on the pressure regulation control algorithm, the first drive circuit DRa drives the first electric motor MA constituting the first actuator YA and various solenoid valves (UJ, UK, etc.). The first drive circuit DRa includes an H-bridge circuit configured with switching elements (e.g., MOS-FETs) to drive the first electric motor MA. The first drive circuit DRa also includes switching elements to drive the various solenoid valves (UJ, UK, etc.). Additionally, the first drive circuit DRa includes a motor current sensor (not shown) that detects the supply current Im (actual value) to the first electric motor MA, and upstream and downstream current sensors (not shown) that detect the supply currents Ij and Ik (actual values, referred to as "upstream and downstream currents") to the upstream and downstream pressure regulation valves UJ and UK. The first electric motor MA is provided with a rotation speed sensor (not shown) that detects its rotation speed Na (actual value). The first electric motor MA may be provided with a rotation angle sensor (not shown) that detects the rotation angle Ka (actual value), and the motor rotation speed Na may be calculated based on the motor rotation angle Ka.

[0046] The first controller EA calculates upstream and downstream target currents Itj and Itk (target values) corresponding to the upstream and downstream currents Ij and Ik based on the operation displacement Sp (operation amount). The upstream and downstream currents Ij and Ik are then controlled so as to approach and match the upstream and downstream target currents Itj and Itk (so-called current feedback control). The first controller EA also calculates a target rotation speed Nta (target value) corresponding to the actual rotation speed Na based on the operation displacement Sp. The first controller EA controls the motor supply current Im so that the actual rotation speed Na approaches and matches the target rotation speed Nta (so-called rotation speed feedback control). Based on these control algorithms, a drive signal Ma for controlling the first electric motor MA and drive signals Uj, Uk, Va, and Vb for controlling the various solenoid valves UJ, UK, VA, and VB are calculated. Then, in response to the drive signal (Ma, etc.), the switching elements of the first drive circuit DRa are driven to control the first electric motor MA and the solenoid valves UJ, UK, VA, VB.

[0047] <Second braking unit SB> An example of the configuration of the second braking unit SB (corresponding to the "second unit") of the braking control device SC will be described with reference to the schematic diagram of Fig. 3. The second braking unit SB is a general-purpose unit (device) for performing independent control of each wheel, such as anti-lock brake control, traction control, and anti-skid control.

[0048] The second brake unit SB is supplied with front and rear wheel supply pressures Pm and Pv from the first brake unit SA. Specifically, in the brake system for the front wheels WHf (i.e., the front wheel connecting path HSf), the front wheel supply pressure Pm is supplied from the master cylinder CM. On the other hand, in the brake system for the rear wheels WHr (i.e., the rear wheel connecting path HSR), the rear wheel supply pressure Pv is supplied from the pressure adjusting unit CA. The front and rear wheel supply pressures Pm and Pv are then adjusted (increased or decreased) by the second brake unit SB and output as hydraulic pressures Pwf and Pwr (front and rear wheel pressures) in the front and rear wheel cylinders CWf and CWr. The second brake unit SB is composed of a second fluid unit YB and a second control unit EB.

[0049] <Second fluid unit YB> The second fluid unit YB (also referred to as the "second actuator") is provided in the communication path HS between the first actuator YA and the wheel cylinder CW. The second actuator YB is composed of a front wheel supply pressure sensor PM, a control valve UB, a second fluid pump QB, a second electric motor MB, a pressure regulating reservoir RB, an inlet valve VI, and an outlet valve VO.

[0050] Front and rear wheel control valves UBf, UBr (=UB) are provided in the front and rear wheel communication passages HSf, HSR (=HS). The control valve UB is a normally open linear solenoid valve (differential pressure valve), as are the upstream and downstream pressure regulating valves UJ, UK. The front and rear wheel control valves UBf, UBr enable the front and rear wheel pressures Pwf, Pwr to be increased individually from the front and rear wheel supply pressures Pm, Pv.

[0051] The front wheel supply pressure sensor PM is provided above the front wheel control valve UBf (at a portion of the communication passage HSf near the first actuator YA) so as to detect the actual hydraulic pressure Pm (front wheel supply pressure) supplied from the first actuator YA (particularly, the master chamber Rm). The front wheel supply pressure sensor PM is also referred to as a "master pressure sensor" and is built into the second actuator YB. The front wheel supply pressure sensor PM is connected to the second brake unit SB (particularly, the second control unit EB) by a front wheel supply pressure signal line LPm. In other words, the signal of the front wheel supply pressure Pm is directly input to the second control unit EB.

[0052] The front and rear wheel return paths HLf, HLr (=HL) connect the upper portions of the front and rear wheel control valves UBf, UBr (portions of the communication paths HS closer to the first actuator YA) with the lower portions of the front and rear wheel control valves UBf, UBr (portions of the communication paths HS closer to the wheel cylinders CW). The front and rear wheel return paths HLf, HLr are provided with front and rear wheel fluid pumps QBf, QBr (=QB) and front and rear wheel pressure regulating reservoirs RBf, RBr (=RB). The second fluid pump QB is driven by a second electric motor MB.

[0053] When the second electric motor MB is driven, the second fluid pump QB draws brake fluid BF from the top of the control valve UB and discharges it from the bottom of the control valve UB. As a result, a circulating flow KL of brake fluid BF (i.e., front and rear wheel circulating flows KLf and KLr, indicated by dashed arrows) containing the pressure regulating reservoir RB is generated in the communication line HS and the return line HL. When the control valve UB narrows the flow path of the communication line HS and throttles the circulating flow KL of brake fluid BF, the orifice effect created increases the hydraulic pressures Pqf and Pqr (referred to as "front and rear wheel regulating pressures") below the control valve UB from the hydraulic pressures Pm and Pv (front and rear wheel supply pressures) above the control valve UB. In other words, in the circulation flow KL, the hydraulic pressure difference (differential pressure) between the hydraulic pressures Pm, Pv (supply pressures) downstream of the control valve UB and the hydraulic pressures Pqf, Pqr (adjustment pressures) upstream of the control valve UB is adjusted by the control valve UB. Note that in terms of the magnitude relationship between the front and rear wheel supply pressures Pm, Pv and the front and rear wheel adjustment pressures Pqf, Pqr, the front and rear wheel adjustment pressures Pqf, Pqr are equal to or greater than the front and rear wheel supply pressures Pm, Pv (i.e., "Pqf≧Pm, Pqr≧Pv"). As explained above, the mechanism by which the adjustment pressure Pq is generated in the second actuator YB is the same as the mechanism by which the servo pressures Pj, Pk are generated in the first actuator YA.

[0054] Inside the second actuator YB, the front and rear wheel communication passages HSf and HSR are each branched into two, which are connected to the front and rear wheel cylinders CWf and CWr. A normally-open inlet valve VI and a normally-closed outlet valve VO are provided for each wheel cylinder CW so that each wheel pressure Pw can be individually adjusted. Specifically, the inlet valve VI is provided in the branched communication passage HS (i.e., on the side of the communication passage HS closer to the wheel cylinder CW). The communication passage HS is connected to the pressure-regulating reservoir RB via a pressure-reducing passage HG below the inlet valve VI (the portion of the communication passage HS closer to the wheel cylinder CW). An outlet valve VO is provided in the pressure-reducing passage HG. The inlet valve VI and the outlet valve VO are on-off solenoid valves. The inlet valve VI and the outlet valve VO allow the wheel pressure Pw to be individually reduced from the front and rear wheel adjustment pressures Pm and Pv at each wheel.

[0055] When the inlet valve VI and the outlet valve VO are not powered and are not operating, the inlet valve VI is open and the outlet valve VO is closed. In this state, the wheel pressure Pw is equal to the regulated pressure Pq. By driving the inlet valve VI and the outlet valve VO, the wheel pressure Pw is independently regulated for each wheel cylinder CW. To decrease the wheel pressure Pw, the inlet valve VI is closed and the outlet valve VO is opened. The inflow of brake fluid BF into the wheel cylinder CW is blocked, and the brake fluid BF in the wheel cylinder CW flows out to the pressure regulating reservoir RB, thereby decreasing the wheel pressure Pw. To increase the wheel pressure Pw (however, the increase can be limited to the front and rear wheel regulated pressures Pqf and Pqr), the inlet valve VI is opened and the outlet valve VO is closed. The brake fluid BF is prevented from flowing out to the pressure regulating reservoir RB, and the regulated pressure Pq from the pressure regulating valve UB is supplied to the wheel cylinder CW, increasing the wheel pressure Pw. To maintain the wheel pressure Pw, both the inlet valve VI and the outlet valve VO are closed. Since the wheel cylinder CW is fluidly sealed, the wheel pressure Pw is maintained constant.

[0056] <Second control unit EB> The second actuator YB is controlled by a second control unit EB (also referred to as a "second controller"). Similar to the first controller EA, the second controller EB is composed of a second microprocessor MPb and a second drive circuit DRb. The second controller EB is connected to a communication bus BS. Therefore, the first controller EA and the second controller EB can share signals via the communication bus BS.

[0057] The second controller EB (particularly, the second microprocessor MPb) receives inputs of the wheel speed Vw, steering amount Sa, yaw rate Yr, longitudinal acceleration Gx, and lateral acceleration Gy. The second controller EB calculates the vehicle speed Vx based on the wheel speed Vw. The second controller EB executes the following independent controls for each wheel. Specifically, the independent controls for each wheel include antilock brake control (so-called ABS control) that suppresses locking of the wheels WH, traction control that suppresses spin of the drive wheels, and anti-skid control (so-called ESC) that suppresses understeer and oversteer to improve the directional stability of the vehicle.

[0058] The second drive circuit DRb drives the second electric motor MB constituting the second actuator YB and various solenoid valves (UB, etc.) in accordance with a control algorithm programmed in the second microprocessor MPb. The second drive circuit DRb includes an H-bridge circuit configured with switching elements (e.g., MOS-FETs) to drive the second electric motor MB. The second drive circuit DRb also includes switching elements to drive the various solenoid valves (UB, etc.). In addition, the second drive circuit DRb includes a motor current sensor (not shown) that detects the supply current In (actual value) to the second electric motor MB, and a second current sensor (not shown) that detects the supply current Ib (actual value, referred to as the "second supply current") to the control valve UB. Based on the control algorithm of the second microprocessor MPb, a drive signal Ub for the control valve UB, a drive signal Vi for the inlet valve VI, a drive signal Vo for the outlet valve VO, and a drive signal Mb for the second electric motor MB are calculated. Then, based on the drive signal (Ub, etc.), the second electric motor MB and the solenoid valves UB, VI, and VO are controlled by the second drive circuit DRb.

[0059] The second controller EB and the second detection unit SPb of the operation displacement sensor SP are connected via a signal line LSpb (e.g., a wire harness) for the second detection unit SPb. Furthermore, the second controller EB and the front wheel supply pressure sensor PM are connected via a signal line LPm (e.g., a signal pin) for the front wheel supply pressure sensor PM. Therefore, the second operation displacement Spb is directly input to the second controller EB via the signal line LSpb, and the front wheel supply pressure Pm is directly input to the second controller EB via the signal line LPm. Then, the second operation displacement Spb and the front wheel supply pressure Pm are transmitted from the second controller EB to the first controller EA via the communication bus BS. That is, the first controller EA acquires the second operation displacement Spb and the front wheel supply pressure Pm from the second controller EB via the communication bus.

[0060] <Pressure regulation control processing> An example of the pressure regulation control process will be described with reference to Figures 4 to 6. In the brake control device SC, dual-system pressure regulation is achieved by the first brake unit SA. "Dual-system pressure regulation" is pressure regulation control in which the front and rear wheel pressures Pwf, Pwr are regulated independently and individually. In contrast to dual-system pressure regulation, pressure regulation control in which the front and rear wheel pressures Pwf, Pwr are regulated equally is called "single-system pressure regulation." In regenerative cooperative control, dual-system pressure regulation improves regenerative efficiency and optimizes the distribution of braking force between the front and rear wheels compared to single-system pressure regulation.

[0061] The pressure regulation control includes not only regenerative cooperative control but also specific control that responds to abnormal conditions. "Specific control" is pressure regulation control that is performed when the first braking unit SA (particularly the first controller EA) is unable to acquire either the front wheel supply pressure Pm (detection signal from the front wheel supply pressure sensor PM) or the rear wheel supply pressure Pv (detection signal from the rear wheel supply pressure sensor PV). The pressure regulation control algorithm, including specific control, is programmed in the microprocessor MPa of the first controller EA. In the explanation, the case where the signals of the front and rear wheel regulated pressures Pm and Pv cannot be properly acquired is referred to as "acquisition abnormality."

[0062] In describing the example process, the following assumptions are made: The regenerative device KG is provided only on the front wheels WHf, so that the regenerative braking force Fg acts on the front wheels WHf but not on the rear wheels WHr. In the first actuator YA, the pressure-receiving area rm (also called the "master area") of the master chamber Rm and the pressure-receiving area ru (also called the "servo area") of the servo chamber Ru are set equal. Therefore, "rm = ru", and in a static state, "Pk = Pm" (here, friction of the seal member SL, etc. is ignored). The front wheel supply pressure sensor PM is built into the second braking unit SB, and the front wheel supply pressure Pm is input to the first braking unit SA via the communication bus BS. On the other hand, the rear wheel supply pressure sensor PV is built into the first braking unit SA, and the rear wheel supply pressure Pv is input directly to the first braking unit SA.

[0063] The various braking forces are as follows: The "vehicle body total braking force Fu" is the actual braking force acting on the entire vehicle JV. The target value corresponding to the vehicle body total braking force Fu is the "target vehicle body force Fv." - "Friction braking force Fm" is the braking force that is actually generated according to the wheel pressure Pw. A target value corresponding to the friction braking force Fm 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 first braking unit SA (particularly, the first controller) 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 "limit regenerative braking force Fx" is the maximum value (limit value) of the regenerative braking force Fg that can be generated by the regenerative device KG. Therefore, the regenerative device KG generates a regenerative braking force Fg within a range (limit) up to the limit regenerative braking force Fx. The limit regenerative braking force Fx is calculated by the regenerative device KG (particularly, the regenerative controller EG) and transmitted to the first braking unit SA (particularly, the first controller EA) via the communication bus BS.

[0064] <Pressure regulation control including specific control when abnormalities occur in the acquisition of front wheel supply pressure Pm> The entire pressure regulation control will be described with reference to the flow chart of Figure 4. The pressure regulation control includes specific control to deal with abnormalities in the acquisition of the front wheel supply pressure Pm. The following processing is performed by the first controller EA.

[0065] In step S110, power is supplied to the inlet valve VA and the release valve VB. As a result, the normally closed inlet valve VA is opened, and the normally open release valve VB is closed, selecting a first mode in which the master piston NM and the brake operating member BP can be displaced separately. In the first mode, the front and rear wheel supply pressures Pm, Pv (i.e., front and rear wheel pressures Pwf, Pwr) are adjusted independently of the operation of the brake operating member BP. At this time, the operating force Fp of the brake operating member BP is generated by the stroke simulator SS.

[0066] In step S120, signals such as the first and second operation displacements Spa and Spb, the front wheel supply pressure Pm, and the rear wheel supply pressure Pv are read. The operation displacement sensor SP is provided with two operation displacement detection units SPa and SPb (first and second detection units). The first operation displacement Spa (detection value of the first detection unit SPa) and the rear wheel supply pressure Pv (detection value of the rear wheel supply pressure sensor PV) are directly acquired through the first displacement signal line LSpa and the rear wheel supply pressure signal line LPv. The second operation displacement Spb (detection value of the second detection unit SPb) and the front wheel supply pressure Pm (detection value of the front wheel supply pressure sensor PM) are acquired (received) from the second controller EB via the communication bus BS.

[0067] In step S120, the operation displacement Sp is calculated based on the first and second operation displacements Spa and Spb. Specifically, the average value of the first and second operation displacements Spa and Spb is determined as the operation displacement Sp (i.e., "Sp = (Spa + Spb) / 2"). Furthermore, if one of the first and second operation displacements Spa and Spb cannot be obtained, the operation displacement Sp is determined based on the other that can be obtained (i.e., "Sp = Spa" or "Sp = Spb"). Since the operation displacement sensor SP is redundant, the operation displacement Sp is determined based on at least one of the first and second operation displacements Spa and Spb. The operation displacement Sp is transmitted from the first controller EA to the communication bus BS.

[0068] In step S130, a target vehicle body posture force Fv (a target value of the braking force acting on the entire vehicle) is calculated based on the operation displacement Sp and the calculation map Zfv. When the operation displacement Sp is less than a predetermined displacement so, the target vehicle body posture force Fv is set to "0" according to the calculation map Zfv. When the operation displacement Sp is equal to or greater than the predetermined displacement so, the target vehicle body posture force Fv is set to increase from "0" as the operation displacement Sp increases from "0". Here, the "predetermined displacement so" is a preset value (constant) that represents the play of the brake operating member BP.

[0069] In step S140, the first controller EA determines whether the front wheel supply pressure Pm is properly acquired. This determination process is referred to as an "acquisition determination" for the front wheel supply pressure Pm. If the first braking unit SA can normally acquire (receive) the supply pressure Pm, the acquisition determination is affirmative, and the process proceeds to step S150. On the other hand, if the front wheel supply pressure Pm cannot be properly acquired, the acquisition determination is negative, and the process proceeds to step S180. For example, the cause of an abnormal acquisition of the front wheel supply pressure Pm is at least one of "a failure of the front wheel supply pressure sensor PM," "a disconnection of the communication line of the communication bus BS," "a failure of the communication microcontroller (particularly the receiving unit) of the first controller EA," and "a failure of the communication microcontroller (particularly the transmitting unit) of the second controller EB."

[0070] In step S140, if the acquisition determination is affirmative, the determination flag FM (also referred to as the "acquisition flag") is set to "0." On the other hand, if the acquisition determination is negative, the acquisition flag FM is set to "1." The "acquisition flag FM" is a control flag that indicates whether the front wheel supply pressure Pm can be acquired in the first brake unit SA. With the acquisition flag FM, "0" represents a normal state, and "1" represents an abnormal state. If the communication bus BS is normal, the acquisition flag FM is transmitted from the first controller EA to the communication bus BS.

[0071] <Normal control processing> The processing of steps S150 to S170 corresponds to normal control. "Normal control" is pressure regulation control when the operation of the brake control device SC is normal. Therefore, the following processing corresponds to the case where the front wheel supply pressure Pm is received normally. In normal control, two-system pressure regulation is performed by the first brake unit SA.

[0072] In step S150, front-wheel and rear-wheel required braking forces Fqf, Fqr (=Fq) are calculated based on the target vehicle body position force Fv. Specifically, the front-wheel and rear-wheel required braking forces Fqf, Fqr are calculated so that the following two conditions are satisfied. The "front-wheel required braking force Fqf" is a target value of the total braking force acting on the front wheels WHf. Therefore, the front-wheel required braking force Fqf is equal to the sum of the target regenerative braking force Fh and the front-wheel target frictional braking force Fnf (i.e., "Fqf = Fh + Fnf"). The "rear-wheel required braking force Fqr" is a target value of the total braking force acting on the rear wheels WHr. Therefore, the rear-wheel required braking force Fqr is equal to the rear-wheel target frictional braking force Fnr (i.e., "Fqr = Fnf"). Condition 1: The sum of the front wheel required braking force Fqf and the rear wheel required braking force Fqr matches the target vehicle body position force Fv (that is, "Fv=Fqf+Fqr"). Condition 2: The ratio Kq (referred to as "requested distribution") of the rear wheel required braking force Fqr to the front wheel required braking force Fqf must match a predetermined value hb (i.e., "Kq = Fqr / Fqf = hb"). Here, the predetermined value hb is the ratio of the rear wheel friction braking force Fmr to the front wheel friction braking force Fmf when the regenerative braking force Fg is "0". Therefore, the predetermined value hb is a constant that is set in advance based on the specifications of the braking device SX. The front and rear wheel required braking forces Fqf and Fqr are determined by the following equation (1) so as to satisfy conditions 1 and 2. Fqf = Fv / (1 + hb), and Fqr = Fv hb / (1 + hb) ...Equation (1)

[0073] Furthermore, in step S150, a target regenerative braking force Fh and front-wheel and rear-wheel target frictional braking forces Fnf and Fnr are calculated based on the front-wheel and rear-wheel required braking forces Fqf and Fqr and the limit regenerative braking force Fx. Specifically, the target regenerative braking force Fh is determined to be a value equal to or less than the limit regenerative braking force Fx. For example, when the front-wheel required braking force Fqf is equal to or less than the limit regenerative braking force Fx, the target regenerative braking force Fh is set equal to the front-wheel required braking force Fqf, the front-wheel target frictional braking force Fnf is set to "0", and the rear-wheel frictional braking force Fnr is set equal to the rear-wheel required braking force Fqr (i.e., when "Fqf≦Fx", "Fh=Fqf, Fnf=0, Fnr=Fqr"). On the other hand, when the front wheel required braking force Fqf is greater than the limit regenerative braking force Fx, the target regenerative braking force Fh is set equal to the limit regenerative braking force Fx, the front wheel target frictional braking force Fnf is set to the value obtained by subtracting the limit regenerative braking force Fx (=Fh) from the front wheel required braking force Fqf, and the rear wheel frictional braking force Fnr is set equal to the rear wheel required braking force Fqr (i.e., when "Fqf>Fx", "Fh=Fx, Fnf=Fqf-Fx=Fqf-Fh, Fnr=Fqr").

[0074] In step S160, front and rear wheel target pressures Ptf, Ptr are calculated based on the front and rear wheel target friction braking forces Fnf, Fnr (=Fn). The front and rear wheel target pressures Ptf, Ptr are determined by converting the target friction braking force Fn into the dimensions of front and rear wheel supply pressures Pm, Pv (i.e., front and rear wheel pressures Pwf, Pwr) based on the specifications of the braking device SX, etc. (pressure-receiving area of ​​the wheel cylinder CW, effective braking radius of the rotating member KT, friction coefficient of the friction member MS, effective radius of the wheel (tire) etc.). Since the front wheel supply pressure Pm is equal to the front wheel pressure Pwf and the rear wheel supply pressure Pv is equal to the rear wheel pressure Pwr, the front and rear wheel target pressures Ptf, Ptr are also target values ​​of the front and rear wheel wheel pressures Pwf, Pwr.

[0075] In step S170, the front and rear wheel pressures (actual values) Pwf, Pwr are adjusted based on the front and rear wheel target pressures Ptf, Ptr (target values). The first controller EA drives the first electric motor MA and the upstream and downstream pressure regulating valves UJ, UK, and controls the front and rear wheel pressures Pwf, Pwr to approach and match the front and rear wheel target pressures Ptf, Ptr. Specifically, in step S170, the electric motor MA is driven to generate a circulation flow KN that includes the fluid pump QA and the upstream and downstream pressure regulating valves UJ, UK. Then, based on the front wheel target pressure Ptf and the front wheel supply pressure Pm, the downstream pressure regulating valve UK is hydraulically feedback controlled so that the front wheel supply pressure Pm (=Pwf) matches the front wheel target pressure Ptf. In other words, the supply current Ik (actual value, also referred to as the "downstream current") to the downstream pressure regulating valve UK is adjusted so that the deviation hPf (referred to as the "front wheel deviation") between the front wheel supply pressure Pm and the front wheel target pressure Ptf becomes "0". Furthermore, the upstream pressure regulating valve UJ is hydraulically feedback controlled based on the rear wheel target pressure Ptr and the rear wheel supply pressure Pv so that the rear wheel supply pressure Pv (= Pwr) matches the rear wheel target pressure Ptr. In other words, the supply current Ij (actual value, also referred to as the "upstream current") to the upstream pressure regulating valve UJ is adjusted so that the deviation hPr (referred to as the "rear wheel deviation") between the rear wheel supply pressure Pv and the rear wheel target pressure Ptr becomes "0".

[0076] <<Specific control processing>> The pressure regulation control (i.e., specific control) when the front wheel supply pressure Pm is not received normally by the first brake unit SA will be described. The processing of steps S180 to S210 corresponds to the specific control. In the specific control, one-path pressure regulation is performed by the first brake unit SA.

[0077] If the determination in step S140 is negative, the power supply to the upstream pressure regulating valve UJ is stopped in step S180, and the upstream pressure regulating valve UJ is opened. Because the upstream pressure regulating valve UJ is a normally open solenoid valve, stopping the power supply causes it to be fully open. In step S180, a switch is made from dual-system pressure regulation to single-system pressure regulation.

[0078] In step S190, a sum Fnt (also referred to as "target sum") of the target regenerative braking force Fh and the target frictional braking force Fn is calculated based on the target vehicle body position dynamics Fv and the limit regenerative braking force Fx. 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 step S190, similar to the processing in step S150, the target regenerative braking force Fh is determined to be a value equal to or less than the limit regenerative braking force Fx. For example, if the target vehicle body position dynamics Fv is equal to or less than the limit regenerative braking force Fx, the target regenerative braking force Fh is made equal to the target vehicle body position dynamics Fv, and the sum Fnt of the target frictional braking forces Fn is set to "0" (i.e., if "Fv≦Fx", "Fh=Fv, Fnt=0"). Furthermore, when the target vehicle body position dynamics Fv is greater than the limit regenerative braking force Fx, the target regenerative braking force Fh is set equal to the limit regenerative braking force Fx, and the target sum Fnt is set to "a value obtained by subtracting the target regenerative braking force Fh (=Fx) from the target vehicle body position dynamics Fv" (i.e., when "Fv>Fx", "Fh=Fx, Fnt=Fv-Fh=Fv-Fx"). The target regenerative braking force Fh is transmitted from the first controller EA to the communication bus BS.

[0079] In step S200, the common target pressure Px is calculated based on the target sum Fnt. Specifically, the common target pressure Px is determined based on the specifications of the braking device SX and the like (pressure-receiving area of ​​the wheel cylinder CW, effective braking radius of the rotating member KT, friction coefficient of the friction member MS, effective radius of the wheel (tire) etc.) so that "Ptf = Ptr" and the target sum Fnt are satisfied. Therefore, if "Fv ≦ Fx", the common target pressure Px (= Ptf = Ptr) is determined to be "0". Also, if "Fv > Fx", the common target pressure Px is determined under the condition of "Ptf = Ptr" so that the sum Fnt (target sum) of the target frictional braking forces Fn corresponding to the common target pressure Px becomes equal to the value "Fv - Fh". In the specific control, "Ptf = Ptr", so the "common target pressure Px" is a common target value unified for the front and rear wheel braking systems corresponding to the front and rear wheel supply pressures Pm and Pv. In other words, while the front and rear wheel target pressures Ptf and Ptr are target values ​​in two-system pressure regulation, the common target pressure Px is a target value in one-system pressure regulation.

[0080] In step S200, the target regenerative braking force Fh may be set to "0" when the acquisition of the front wheel supply pressure Pm is abnormal. In other words, when the first brake unit SA is unable to acquire the front wheel supply pressure Pm normally, the operation of the regenerative device KG is stopped. When "Fh = 0", the common target pressure Px is calculated based on the specifications of the brake device SX, etc., in the same manner as above, so that "Ptf = Ptr, Fnf + Fnr = Fv" is satisfied.

[0081] In step S210, the first actuator YA is driven based on the common target pressure Px and the rear wheel supply pressure Pv. In the pressure regulating section CA, the upstream pressure regulating valve UJ is fully open, so the upstream servo pressure Pj and the downstream servo pressure Pk are made equal. That is, since the state is "Pk = Pm = Pwf = Pj = Pv = Pwr," the downstream pressure regulating valve UK is hydraulically feedback controlled so that the rear wheel supply pressure Pv approaches and matches the common target pressure Px. Specifically, the supply current Ik (downstream current) to the downstream pressure regulating valve UK is adjusted so that the deviation hPx (referred to as the "common deviation") between the rear wheel supply pressure Pv and the common target pressure Px becomes "0."

[0082] The brake control device SC is a brake-by-wire type device that can independently control the operation of the brake operating member BP (brake pedal) and the hydraulic pressure (wheel pressure Pw) of the wheel cylinder CW. The first brake unit SA is provided with a master chamber Rm and a servo chamber Ru. The master chamber Rm and the servo chamber Ru are hydraulic chambers defined by a master cylinder CM and a master piston NM. In the first brake unit SA (particularly, the pressure adjusting section CA), two linear solenoid valves UJ and UK (upstream and downstream pressure adjusting valves) adjust the upstream and downstream servo pressures Pj and Pk individually. In the brake system related to the front wheels WHf, the downstream servo pressure Pk is adjusted based on the operation displacement Sp and the front wheel supply pressure Pm. When the downstream servo pressure Pk is supplied to the servo chamber Ru, the front wheel supply pressure Pm is output from the master chamber Rm, and the front wheel pressure Pwf is ultimately adjusted. Meanwhile, in the braking system for the rear wheels WHr, the upstream servo pressure Pj is adjusted based on the operation displacement Sp and the rear wheel supply pressure Pv. The upstream servo pressure Pj is supplied directly from the pressure regulating unit CA to the rear wheel cylinder CWr as the rear wheel supply pressure Pv. In the first braking unit SA, hydraulic pressure feedback control is executed according to the front and rear wheel supply pressures Pm and Pv so that the front and rear wheel supply pressures Pm and Pv approach and match the front and rear wheel target pressures Ptf and Ptr calculated based on the operation displacement Sp. With the above configuration, the first braking unit SA achieves dual-system pressure regulation.

[0083] The second brake unit SB is a general-purpose unit for executing independent wheel control, such as anti-lock brake control and anti-skid control. Since information on the front wheel supply pressure Pm is essential for executing independent wheel control, the second actuator YB incorporates a front wheel supply pressure sensor PM, which is directly connected to the second controller EB. The first controller EA acquires the front wheel supply pressure Pm through the communication bus BS to execute the above-mentioned hydraulic pressure feedback control. Since one front wheel supply pressure sensor PM is shared by the first brake unit SA and the independent wheel control by the second brake unit SB, the configuration is simpler than a device in which a front wheel supply pressure sensor PM is provided for each of the first and second brake units SA and SB. In other words, the brake control device SC executes pressure regulation control, including feedback control, but the configuration is simplified.

[0084] Furthermore, in the brake control device SC, if an acquisition abnormality occurs in the front wheel supply pressure Pm, the first brake unit SA (particularly the first controller EA) is unable to execute feedback control of the front wheel supply pressure Pm. Therefore, the first brake unit SA stops supplying power to the upstream pressure regulating valve UJ and switches from dual-system pressure regulation to single-system pressure regulation. This places the system in a state where Pj = Pk, and the downstream pressure regulating valve UK is feedback-controlled based on the rear wheel supply pressure Pv. At this time, the front wheel target pressure Ptf and the rear wheel target pressure Ptr are calculated equally. Therefore, the target values ​​of the front and rear wheel supply pressures Pm and Pv are determined as a common target value Px (common target pressure) unified for the front and rear wheel systems. Even when an acquisition abnormality occurs in the front wheel supply pressure Pm, feedback control continues based on the rear wheel supply pressure Pv that can be acquired, ensuring the accuracy of the pressure regulation control. Even during specific control when the acquisition of the front wheel supply pressure Pm is abnormal, the first mode is selected in the first brake unit SA, so the operation characteristics of the brake operating member BP do not change.

[0085] The brake control device SC employs a configuration in which the front wheel supply pressure sensor PM is included in the second brake unit SB (referred to as the "former configuration"), which allows both pressure regulation control and individual wheel independent control using a single front wheel supply pressure sensor PM. Conversely, a configuration in which the front wheel supply pressure sensor PM is included in the first brake unit SA (referred to as the "latter configuration") is also possible. However, the former configuration is more advantageous than the latter configuration in terms of functional distribution and fail-safe. In the latter configuration, when performing individual wheel independent control, the second brake unit SB must acquire the front wheel supply pressure Pm through the communication bus BS. However, if a communication abnormality occurs, the second brake unit SB cannot acquire the front wheel supply pressure Pm, making it impossible to perform individual wheel independent control. On the other hand, in the former configuration, even if a communication abnormality occurs, the second brake unit SB can acquire the front wheel supply pressure Pm, making it possible to perform individual wheel independent control. Furthermore, as described above, the first braking unit SA can execute feedback control in the pressure regulation control even if it cannot acquire the front wheel supply pressure Pm. Therefore, the former configuration is superior in terms of functional distribution, fail-safe, etc.

[0086] <Pressure regulation control including specific control when rear wheel supply pressure Pv is abnormally acquired> Specific control for dealing with abnormalities in the acquisition of rear wheel supply pressure Pv will be described with reference to the flow chart of Figure 5. The processes (S110 to S130 and S150 to S200) with the same symbols as those described with reference to the flow chart of Figure 4 have the same content, so their description will be omitted. Below, the differences will be described.

[0087] In step S240, the first controller EA determines whether the rear wheel supply pressure Pv is properly acquired. This determination process is referred to as an "acquisition determination" for the rear wheel supply pressure Pv. If the first braking unit SA can normally acquire the rear wheel supply pressure Pv, the acquisition determination is affirmative, and the process proceeds to step S150. On the other hand, if the rear wheel supply pressure Pv cannot be properly acquired, the acquisition determination is negative, and the process proceeds to step S180. For example, since the rear wheel supply pressure sensor PV is built into the first actuator YA, the cause of the abnormal acquisition of the rear wheel supply pressure Pv is a "failure of the rear wheel supply pressure sensor PV."

[0088] In step S240, if the acquisition determination is affirmative, the determination flag FV (also referred to as the "acquisition flag") is set to "0." On the other hand, if the acquisition determination is negative, the acquisition flag FV is set to "1." The "acquisition flag FV" is a control flag that indicates whether the rear wheel supply pressure Pv can be acquired in the first brake unit SA. With the acquisition flag FV, "0" represents a normal state, and "1" represents an abnormal state. The acquisition flag FV is transmitted from the first controller EA to the second controller EB via the communication bus BS.

[0089] In step S250, the first actuator YA is driven based on the common target pressure Px and the front wheel supply pressure Pm. In step S250, the upstream pressure regulating valve UJ is fully open, so the upstream servo pressure Pj and the downstream servo pressure Pk are made equal. That is, since "Pk = Pm = Pwf = Pj = Pv = Pwr" is true, the downstream pressure regulating valve UK is hydraulically feedback controlled so that the front wheel supply pressure Pm approaches and matches the common target pressure Px. Specifically, the supply current Ik (downstream current) to the downstream pressure regulating valve UK is adjusted so that the deviation hPx (similar to the above, referred to as the "common deviation") between the front wheel supply pressure Pm and the common target pressure Px becomes "0."

[0090] As with the case where an abnormality occurs in the acquisition of the front wheel supply pressure Pm, when an abnormality occurs in the acquisition of the rear wheel supply pressure Pv in the brake control device SC, the first brake unit SA (particularly the first controller EA) is unable to execute feedback control of the rear wheel supply pressure Pv. Therefore, the first brake unit SA stops supplying power to the upstream pressure regulating valve UJ and switches from dual-system pressure regulation to single-system pressure regulation. This places the system in a state where Pj = Pk, and the downstream pressure regulating valve UK is feedback-controlled based on the available front wheel supply pressure Pm. At this time, the front and rear wheel target pressures Ptf and Ptr are calculated equally and determined as a common target pressure Px (a common target value unified between the front and rear wheel brake systems). Since feedback control continues even when an abnormality occurs in the acquisition of the rear wheel supply pressure Pv, the accuracy of the pressure regulation control is ensured. Even during specific control when an abnormality occurs in the acquisition of the rear wheel supply pressure Pv, the first brake unit SA selects the first mode, so the operation characteristics of the brake operating member BP do not change.

[0091] <Drive control of first actuator YA> The drive control of the first actuator YA (particularly the processing of steps S170, S210, and S250) will be described in detail with reference to the block diagram of Figure 6. The drive control processing is executed by the first controller EA. In the drive control of the first actuator YA, the first electric motor MA is driven to generate a circulating flow KN of brake fluid BF including the upstream and downstream pressure regulating valves UJ, UK, and the first fluid pump QA.

[0092] <Downstream pressure regulating valve UK drive control> The drive control of the downstream pressure regulating valve UK will now be described. The drive processing for the downstream pressure regulating valve UK is composed of a downstream command current calculation block ISK, a downstream deviation calculation block HPK, a downstream compensation current calculation block IHK, and a downstream current feedback control block IFK.

[0093] The downstream command current calculation block ISK calculates the downstream command current Isk based on the front wheel target pressure Ptf and a preset calculation map Zsk. The "downstream command current Isk" is a target value for the supply current Ik (downstream current) of the downstream pressure regulating valve UK required to achieve the front wheel target pressure Ptf. The downstream command current Isk is determined to increase as the front wheel target pressure Ptf increases according to the calculation map Zsk. The downstream command current calculation block ISK corresponds to feedforward control based on the front wheel target pressure Ptf.

[0094] The downstream deviation calculation block HPK calculates the deviation hPf (front wheel deviation) between the front wheel target pressure Ptf and the front wheel supply pressure Pm (i.e., wheel pressure Pwf). Specifically, the front wheel deviation hPf is calculated by subtracting the front wheel supply pressure Pm from the front wheel target pressure Ptf (i.e., "hPf=Ptf-Pm").

[0095] The downstream compensation current calculation block IHK calculates the downstream compensation current Ihk based on the front wheel deviation hPf and a preset calculation map Zhk. The downstream command current Isk is calculated in accordance with the front wheel target pressure Ptf, but an error may occur between the front wheel target pressure Ptf and the front wheel supply pressure Pm. The "downstream compensation current Ihk" is intended to compensate for (reduce) this error. The downstream compensation current Ihk is determined in accordance with the calculation map Zhk so as to increase as the front wheel deviation hPf increases. Specifically, when the front wheel target pressure Ptf is greater than the front wheel supply pressure Pm and the front wheel deviation hPf has a positive sign, a positive downstream compensation current Ihk is determined so as to increase the downstream command current Isk. On the other hand, when the front wheel target pressure Ptf is smaller than the front wheel supply pressure Pm and the front wheel deviation hPf has a negative sign, a negative downstream compensation current Ihk is determined so as to decrease the downstream command current Isk. Here, the calculation map Zhk is provided with a dead zone. The downstream compensation current calculation block IHK corresponds to feedback control based on the front wheel supply pressure Pm.

[0096] For the downstream-side indicated current Isk, a downstream-side compensation current Ihk is added, and a downstream-side target current Itk is calculated (i.e., "Itk = Isk + Ihk"). The "downstream-side target current Itk" is the final target value of the current supplied to the downstream-side pressure regulating valve UK. Therefore, the drive control of the downstream-side pressure regulating valve UK is composed of feedforward control and feedback control.

[0097] In the downstream-side current feedback control block IFK, based on the downstream-side target current Itk (target value) and the downstream-side current Ik (actual value), a downstream-side drive signal Uk is calculated so that the downstream-side current Ik approaches and matches the downstream-side target current Itk. Here, the downstream-side current Ik is detected by a downstream-side current sensor IK provided in the first drive circuit DRa. In the downstream-side current feedback control block IFK, if "Itk > Ik", the drive signal Uk is determined so that the downstream-side current Ik increases. On the other hand, if "Itk < Ik", the drive signal Uk is determined so that the downstream-side current Ia decreases. That is, in the downstream-side current feedback control block IFK, feedback control related to the current is executed. Therefore, in the drive control of the downstream-side pressure regulating valve UK, in addition to the feedback control related to the hydraulic pressure, feedback control related to the current is provided, and the downstream-side servo pressure Pk (= Pm = Pwf) is controlled to match the front-wheel target pressure Ptf.

[0098] ≪Drive Control of Upstream-Side Pressure Regulating Valve UJ≫ The drive control of the upstream-side pressure regulating valve UJ will be described. The downstream-side pressure regulating valve UK is controlled based on the front-wheel target pressure Ptf, while the upstream-side pressure regulating valve UJ is controlled based on the difference sPt between the front-wheel target pressure Ptf and the rear-wheel target pressure Ptr. In addition, the upstream-side pressure regulating valve UJ is controlled based on feedback control related to the rear-wheel supply pressure Pv. Other than these, it is the same as the downstream-side pressure regulating valve UK, so the common parts will be briefly described. The drive process related to the upstream-side pressure regulating valve UJ is composed of a target differential pressure calculation block SPT, an upstream-side indicated current calculation block ISJ, an upstream-side deviation calculation block HPJ, an upstream-side compensation current calculation block IHJ, and an upstream-side current feedback control block IFJ.

[0099] The target differential pressure calculation block SPT calculates a target differential pressure sPt based on the front and rear wheel target pressures Ptf and Ptr. The "target differential pressure sPt" is a target value for the differential pressure to be generated by the upstream pressure regulating valve UJ (the difference between the upstream hydraulic pressure and the downstream hydraulic pressure in the upstream pressure regulating valve UJ). Specifically, the target differential pressure sPt is determined by subtracting the front wheel target pressure Ptf from the rear wheel target pressure Ptr (i.e., "sPt = Ptr - Ptf (≧0)"). The upstream pressure regulating valve UJ increases the downstream servo pressure Pk (= Pm) by an amount equivalent to the target differential pressure sPt to generate the upstream servo pressure Pj (= Pv).

[0100] The upstream command current calculation block ISJ calculates the upstream command current Isj based on the target differential pressure spt and a preset calculation map Zsj. The "upstream command current Isj" is a target value for the supply current Ij (upstream current) of the upstream pressure regulating valve UJ required to achieve the target differential pressure spt. According to the calculation map Zsj, the upstream command current Isj is determined to increase as the target differential pressure spt increases. The upstream command current calculation block ISJ corresponds to feedforward control based on the target differential pressure spt.

[0101] The upstream deviation calculation block HPJ calculates the deviation hPr (rear wheel deviation) between the rear wheel target pressure Ptr and the rear wheel supply pressure Pv (i.e., the rear wheel pressure Pwr). Specifically, the rear wheel deviation hPr is calculated by subtracting the rear wheel supply pressure Pv from the rear wheel target pressure Ptr (i.e., "hPr = Ptr - Pv").

[0102] The upstream compensation current calculation block IHJ calculates the upstream compensation current Ihj based on the rear wheel deviation hPr and a preset calculation map Zhj. The "upstream compensation current Ihj" is used to compensate for (reduce) the error between the rear wheel target pressure Ptr and the rear wheel supply pressure Pv. The upstream compensation current Ihj is determined in accordance with the calculation map Zhj so as to increase as the rear wheel deviation hPr increases. The upstream compensation current calculation block IHJ corresponds to feedback control based on the rear wheel supply pressure Pv.

[0103] The upstream compensation current Ihj is added to the upstream command current Isj to calculate the upstream target current Itj (i.e., "Itj = Isj + Ihj"). The "upstream target current Itj" is the final target value of the current supplied to the upstream pressure regulating valve UJ. Therefore, the drive control of the upstream pressure regulating valve UJ is composed of feedforward control and feedback control.

[0104] The upstream current feedback control block IFJ calculates the upstream drive signal Uj based on the upstream target current Itj (target value) and the upstream current Ij (actual value) so that the upstream current Ij approaches and matches the upstream target current Itj. The upstream current Ij is detected by an upstream current sensor IJ provided in the first drive circuit DRa. The upstream current feedback control block IFJ executes feedback control related to the current. Therefore, the drive control of the upstream pressure regulating valve UJ includes feedback control related to the hydraulic pressure as well as feedback control related to the current, and the upstream servo pressure Pj (=Pv=Pwr) is controlled to match the rear wheel target pressure Ptr.

[0105] If an abnormality occurs in the acquisition of the front wheel supply pressure Pm, the front wheel target pressure Ptf and the rear wheel target pressure Ptr are made equal, and a common target pressure Px is calculated. Then, the functions of the blocks related to the upstream pressure regulating valve UJ (i.e., SPT, ISJ, HPJ, IHJ, IFJ) are stopped, and power supply to the upstream pressure regulating valve UJ is stopped (i.e., "Ik = 0"). The blocks related to the downstream pressure regulating valve UK (particularly ISK, HPK) adopt the common target pressure Px instead of the front wheel target pressure Ptf, and adopt the rear wheel supply pressure Pv instead of the front wheel supply pressure Pm. That is, the downstream command current calculation block ISK calculates the downstream command current Isk based on the common target pressure Px. Furthermore, the downstream deviation calculation block HPK calculates a common deviation hPx (hydraulic pressure deviation corresponding to the common target pressure Px) based on the common target pressure Px and the rear wheel supply pressure Pv (i.e., "hPx = Px - Pv"). The downstream compensation current calculation block IHK then calculates a downstream compensation current Ihk based on the common deviation hPx and the calculation map Zhk. If the front wheel supply pressure Pm cannot be acquired normally, the braking control device SC stops supplying power to the upstream pressure regulating valve UJ and continues feedback control according to the rear wheel supply pressure Pv that can be acquired. Therefore, the accuracy of the pressure regulation control is ensured even when the rear wheel supply pressure Pv is abnormally acquired.

[0106] When an abnormality occurs in the acquisition of the rear wheel supply pressure Pv, similar to the abnormality in the acquisition of the front wheel supply pressure Pm, the front wheel target pressure Ptf and the rear wheel target pressure Ptr are made equal to calculate the common target pressure Px. Then, the function of the block related to the upstream pressure regulating valve UJ is stopped, and the supply of current to the upstream pressure regulating valve UJ is stopped (i.e., "Ik = 0"). In the block related to the downstream pressure regulating valve UK, the common target pressure Px is used instead of the front wheel target pressure Ptf. That is, the downstream command current calculation block ISK calculates the downstream command current Isk based on the common target pressure Px, and the downstream deviation calculation block HPK calculates the common deviation hPx based on the common target pressure Px (i.e., "hPx = Px - Pm"). Then, the downstream compensation current calculation block IHK calculates the downstream compensation current Ihk based on the common deviation hPx and the calculation map Zhk. In the braking control device SC, if the rear wheel supply pressure Pv cannot be obtained normally, the power supply to the upstream pressure regulating valve UJ is stopped and feedback control continues according to the available front wheel supply pressure Pm, thereby ensuring the accuracy of the pressure regulation control even when the front wheel supply pressure Pm is not obtained normally.

[0107] <Application to a vehicle JV with a regenerative device KG mounted on the rear wheels WHr> In the above-described embodiment, a vehicle (referred to as a "front-wheel regenerative vehicle") is assumed in which the regenerative device KG is provided on the front wheels WHf but not on the rear wheels WHr. Alternatively, the braking control device SC may be applied to a vehicle (referred to as a "rear-wheel regenerative vehicle") in which the regenerative device KG is provided on the rear wheels WHr but not on the front wheels WHf. Differences will be explained below. Note that the symbols in [ ] in the block diagram of FIG. 6 correspond to the braking control device SC for a rear-wheel regenerative vehicle.

[0108] In the braking control device SC applied to a rear-wheel regenerative vehicle, as shown in the schematic diagram of FIG. 2, the servo path HV is connected to the return path HK at a point pj, and the rear-wheel connecting path HSr is connected to the return path HK at a point pk. That is, the upstream servo pressure Pj is supplied to the servo chamber Ru, and the downstream servo pressure Pk is supplied to the rear wheel cylinder CWr (i.e., "Pj = Pm = Pwf, Pk = Pv = Pwr"). In addition, in the pressure regulation control process (particularly the dual-path pressure regulation process) shown in FIGS. 4 and 5, when "Fqr≦Fx" is satisfied, the front and rear wheel target frictional braking forces Fnf and Fnr are calculated as follows: "Fh = Fqr, Fnf = Fqf, Fnr = 0" is determined. On the other hand, when "Fqf > Fx," the following is determined: "Fh = Fx, Fnf = Fqf, Fnr = Fqr - Fx = Fqr - Fh" is determined. Then, the front and rear wheel target friction braking forces Fnf and Fnr are converted into front and rear wheel target pressures Ptf and Ptr (where "Ptf≧Ptr").

[0109] Furthermore, in FIG. 6 , the downstream command current calculation block ISK and the downstream deviation calculation block HPK receive the rear wheel target pressure Ptr instead of the front wheel target pressure Ptf. That is, the downstream command current Isk is determined based on the rear wheel target pressure Ptr and the calculation map Zsk, and the downstream deviation calculation block HPK calculates the rear wheel deviation hPr by "hPr = Ptr - Pv." The downstream compensation current calculation block IHK calculates the downstream compensation current Ihk based on the rear wheel deviation hPr. The target deviation calculation block SPT calculates the target differential pressure sPt by "sPt = Ptf - Ptr (≧0)." The upstream deviation calculation block HPJ receives the front wheel target pressure Ptf instead of the rear wheel target pressure Ptr. Therefore, the upstream deviation calculation block HPJ calculates the front wheel deviation hPf by "hPf = Ptf - Pm." Then, an upstream compensation current calculation block IHJ calculates an upstream compensation current Ihj based on the front wheel deviation hPf. The single-system pressure adjustment process is the same for front-wheel and rear-wheel regenerative vehicles.

[0110] In a vehicle equipped with a regenerative device KG (=KGf, KGr) on both the front and rear wheels WHf and WHr, one of the two configurations described above is adopted depending on the magnitude of the regenerative energy of the regenerative devices. Specifically, a brake control device SC for a front-wheel regenerative vehicle is applied to a vehicle in which the regenerative energy of the front-wheel regenerative device KGf is greater than that of the rear-wheel regenerative device KGf. Conversely, a brake control device SC for a rear-wheel regenerative vehicle is applied to a vehicle in which the regenerative energy of the front-wheel regenerative device KGf is smaller than that of the rear-wheel regenerative device KGf.

[0111] To summarize the above, in the first brake unit SA, normally open upstream and downstream pressure regulating valves UJ and UK are arranged in series in the circulating flow KN of brake fluid BF including the fluid pump QA. The upstream and downstream pressure regulating valves UJ and UK regulate the pressure of the brake fluid BF discharged by the fluid pump QA to upstream and downstream servo pressures Pj and Pk. The front wheel supply pressure Pm is output based on the hydraulic pressure on one side of the upstream and downstream servo pressures Pj and Pk. The rear wheel supply pressure Pv is output based on the hydraulic pressure on the other side of the upstream and downstream servo pressures Pj and Pk.

[0112] When the brake control device SC operates normally, the first brake unit SA performs dual-system pressure adjustment processing in the following order: Front and rear wheel required braking forces Fqf, Fqr are calculated based on the operation displacement Sp so as to satisfy conditions 1 and 2 (i.e., equation (1)) above. Front and rear wheel target frictional braking forces Fnf, Fnr are calculated based on the front and rear wheel required braking forces Fqf, Fqr, taking into account front and rear wheel target regenerative braking forces Fhf, Fhr. The front and rear wheel target frictional braking forces Fnf, Fnr are converted to front and rear wheel target pressures Ptf, Ptr based on the specifications of the front and rear wheel brake devices SXf, SXr. Based on the front and rear wheel target pressures Ptf, Ptr, the "hydraulic pressure on one side of the upstream and downstream servo pressures Pj, Pk" and the "hydraulic pressure on the other side of the upstream and downstream servo pressures Pj, Pk" are controlled. Specifically, one-side hydraulic pressure is adjusted by feedback control based on the front wheel supply pressure Pm so that the front wheel supply pressure Pm coincides with the front wheel target pressure Ptf, and the other-side hydraulic pressure is adjusted by feedback control based on the rear wheel supply pressure Pv so that the rear wheel supply pressure Pv coincides with the rear wheel target pressure Ptr.

[0113] The rear wheel supply pressure sensor PV is built into the first brake unit SA. On the other hand, the front wheel supply pressure sensor PM is built into the second brake unit SB to execute independent control of each wheel. Therefore, the first brake unit SA obtains the front wheel supply pressure Pm from the second brake unit SB via the communication bus BS. The signal Pm of the front wheel supply pressure sensor PM is used not only for independent control of each wheel but also for feedback control of the two-system pressure regulation, making the device simple.

[0114] When the first braking unit SA cannot acquire the front wheel supply pressure Pm, the first braking unit SA equates the front wheel target pressure Ptf with the rear wheel target pressure Ptr to determine the common target pressure Px (a common target value corresponding to the front and rear wheel supply pressures Pm and Pv) (i.e., "Px = Ptf = Ptr"). Furthermore, the supply of electricity to the upstream pressure regulating valve UJ is stopped and the valve is fully opened. The downstream pressure regulating valve UK is controlled so that the rear wheel supply pressure Pv and the common target pressure Px coincide. In other words, the downstream pressure regulating valve UK is driven in response to feedback control based on the rear wheel supply pressure Pv. Similarly, when the first braking unit SA cannot acquire the rear wheel supply pressure Pv, the common target pressure Px is determined as "Ptf = Ptr." The supply of electricity to the upstream pressure regulating valve UJ is stopped and the valve is fully opened. The downstream pressure regulating valve UK is controlled so that the front wheel supply pressure Pm and the common target pressure Px coincide. That is, the downstream pressure regulating valve UK is driven in response to feedback control based on the front wheel supply pressure Pm. In the brake control device SC, even if an acquisition abnormality occurs in either the front wheel or rear wheel supply pressure Pm, Pv, hydraulic pressure feedback control can be performed, so pressure regulation accuracy is appropriately ensured. In other words, the brake control device SC has a simple configuration that can ensure pressure regulation accuracy through hydraulic pressure feedback control even when the front wheel supply pressure Pm or the rear wheel supply pressure Pm is not acquired.

[0115] <Other embodiments> Other embodiments will be described below. The other embodiments also provide the same effects as those described above (such as simplified configuration and ensuring pressure regulation accuracy in the event of an abnormality).

[0116] In the above-described embodiment, the target values ​​of various braking forces (Fv, Fx, Fh, Fn, etc.) were calculated in terms of longitudinal forces acting on the vehicle JV. Alternatively, they may be calculated in terms of deceleration of the vehicle JV or torque of the wheels WH. This is based on the fact that state quantities (referred to as "force-related state quantities") from longitudinal forces acting on the vehicle JV to vehicle deceleration are equivalent. Therefore, the target pressures Ptf, Ptr, and Px are calculated based on state quantities related to forces from longitudinal forces acting on the vehicle JV to deceleration of the vehicle JV.

[0117] In the above-described embodiment, the pressure regulating unit CA is exemplified as one that adjusts the front and rear wheel supply pressures Pm, Pv by throttling the circulating flow KN of brake fluid BF discharged by the fluid pump QA using the upstream and downstream pressure regulating valves UJ, UK (a so-called reflux type configuration). Alternatively, the pressure regulating unit CA may adjust the front and rear wheel supply pressures Pm, Pv based on the pressure accumulated in an accumulator (a so-called accumulator type configuration). Alternatively, the front and rear wheel supply pressures Pm, Pv may be adjusted by increasing or decreasing the volume within a cylinder using a piston directly driven by an electric motor (a so-called electric cylinder type configuration). In either configuration, the pressure regulating unit CA receives feedback of the detected values ​​Pm, Pv of the front and rear wheel supply pressure sensors PM, PV, and electrically adjusts them.

[0118] In the above-described embodiment, 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 in the apply section AP are set 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 front wheel supply pressure Pm and the downstream servo pressure Pk (or the upstream servo pressure Pj) is possible based on the ratio between the servo area ru and the master area rm (i.e., conversion based on "Pm·rm=Pk·ru (or Pj·ru)").

[0119] In the above-described embodiment, the first brake unit SA outputs the front wheel supply pressure Pm via the master cylinder CM. That is, the apply unit AP and the pressure adjustment unit CA are arranged in series in the hydraulic pressure transmission path, and the downstream servo pressure Pk supplied from the pressure adjustment unit CA is transmitted as the front wheel supply pressure Pm via the master piston NM. This configuration is referred to as a "series configuration." Instead of the series configuration, the apply unit AP and the pressure adjustment unit CA may be arranged in parallel. This configuration is referred to as a "parallel configuration." In the parallel configuration, the apply unit AP (particularly, the master cylinder CM) and the pressure adjustment unit CA are each directly connected to the second actuator YB. In the first mode, "connection between the pressure adjustment unit CA and the second actuator YB" is selected, and in the second mode, "connection between the apply unit AP and the second actuator YB" is selected. For example, this selection is achieved by a solenoid valve (referred to as a "switching valve"). In the first mode of this configuration, the front and rear wheel supply pressures Pm and Pv generated by the pressure adjusting unit CA are directly output as the front and rear wheel supply pressures Pm and Pv without passing through the apply unit AP. At this time, the apply unit AP is connected to the stroke simulator SS, and the operating force Fp of the brake operating member BP is generated by the simulator SS. On the other hand, in the second mode, the hydraulic pressure in the master chamber Rm generated by operating the brake operating member BP is output as the front wheel supply pressure Pm. At this time, the apply unit AP is disconnected from the simulator SS.

[0120] In the brake control device SC, regardless of whether it is configured in series or parallel, in the transmission paths of the front and rear wheel supply pressures Pm and Pv, a fluid path (a path through which brake fluid BF moves, referred to as a "communication path") connects between the portion where the front wheel supply pressure Pm acts and the portion where the rear wheel supply pressure Pv acts. A normally open solenoid valve (referred to as a "communication valve") is provided in the communication path. When the brake control device SC operates normally, the communication valve is closed and the communication path is blocked. As a result, the front wheel and rear wheel supply pressures Pm and Pv are individually adjusted, and dual-system pressure regulation is performed. On the other hand, when an acquisition abnormality occurs in the front wheel and rear wheel supply pressures Pm and Pv, the communication valve is opened and the portions related to the front wheel and rear wheel supply pressures Pm and Pv are placed in a communication state. As a result, the front wheel and rear wheel supply pressures Pm and Pv are adjusted to the same hydraulic pressure, and single-system pressure regulation is performed. Here, the portions on which the front and rear wheel supply pressures Pm and Pv act (referred to as "action portions") include the sources of the front and rear wheel supply pressures Pm and Pv, the transmission paths (fluid paths, hydraulic chambers), and the like. The action portions include not only portions on which the front and rear wheel supply pressures Pm and Pv act directly, but also portions on which the force generated by the front and rear wheel supply pressures Pm and Pv acts via a member (e.g., master piston NM). For example, in the configuration shown in FIG. 2, portions pj and pk correspond to the action portions, and the upstream pressure regulating valve UJ corresponds to the communication valve. Here, the rear wheel supply pressure Pv acts directly on portion pj, while the front wheel supply pressure Pm acts indirectly on portion pk via the master piston NM.

[0121] <Summary of the embodiment> The following summarizes an embodiment of the brake control device SC: The brake control device SC is a brake-by-wire type device that can independently adjust the operation displacement Sp of the brake operating member BP and the hydraulic pressure Pw (wheel pressure) of the wheel cylinder CW.

[0122] The brake control device SC is equipped with a "first brake unit SA (first unit) that outputs front and rear wheel supply pressures Pm and Pv individually in accordance with the operation amount Sp of the brake operating member BP," a "second brake unit SB (second unit) that is provided between the first brake unit SA and the front and rear wheel cylinders CWf and CWr and adjusts the front and rear wheel supply pressures Pm and Pv to output front and rear wheel pressures Pwf and Pwr," a "communication bus BS that transmits signals between the first brake unit SA and the second brake unit SB," an "operation displacement sensor SP (operation amount sensor) connected to the first brake unit SA and that detects the operation displacement Sp (operation amount)," a "front wheel supply pressure sensor PM connected to the second brake unit SB and that detects the front wheel supply pressure Pm," and a "rear wheel supply pressure sensor PV connected to the first brake unit SA and that detects the rear wheel supply pressure Pv." In the first brake unit SA, the front wheel supply pressure Pm is acquired from the second brake unit SB via the communication bus BS, and the front and rear wheel target pressures Ptf and Ptr are calculated based on the operation amount Sp, and feedback control is performed so that the front wheel supply pressure Pm coincides with the front wheel target pressure Ptf, and feedback control is also performed so that the rear wheel supply pressure Pv coincides with the rear wheel target pressure Ptr.

[0123] The second brake unit SB is a general-purpose unit for performing independent wheel control, such as anti-lock brake control and anti-skid control. Therefore, in order to perform these controls, the second brake unit SB is equipped with a front wheel supply pressure sensor PM. The first brake unit SA acquires the front wheel supply pressure Pm from the second brake unit SB via the communication bus BS, and uses this for feedback control of one of the two pressure regulation systems. In the brake control device SC, hydraulic pressure sensors are distributed and shared among multiple controls. This reduces the number of sensors in the entire device, simplifying its overall configuration.

[0124] In the brake control device SC, when the first brake unit SA cannot acquire the front wheel supply pressure Pm, the front wheel target pressure Ptf and the rear wheel target pressure Ptr are calculated to be equal and determined as the common target pressure Px. Here, the common target pressure Px is a common hydraulic pressure target value for the front and rear supply pressures when "Ptf = Ptr." Then, the portion pk on which the front wheel supply pressure Pm acts and the portion pj on which the rear wheel supply pressure Pv acts are connected, and feedback control is performed based on the rear wheel supply pressure Pv so that the rear wheel supply pressure Pv coincides with the common target pressure Px. In the brake control device SC, when the first brake unit SA cannot acquire the rear wheel supply pressure Pv, the common target pressure Px is similarly determined based on the operation amount Sp, the front wheels, the portions on which the rear wheel supply pressure Pm, and Pv act (e.g., portions pk and pj) are connected, and feedback control is performed based on the front wheel supply pressure Pm so that the front wheel supply pressure Pm coincides with the common target pressure Px.

[0125] In the brake control device SC, if an acquisition abnormality occurs in either the front or rear wheel supply pressure Pm or Pv, hydraulic pressure feedback control corresponding to the acquisition abnormality cannot be executed. Therefore, in the event of an acquisition abnormality, the brake control device switches from dual-system pressure regulation to single-system pressure regulation so that the front wheel supply pressure Pm and the rear wheel supply pressure Pv are equal. In this switching, the front wheel and rear wheel supply pressures Pm and Pv are forcibly equalized by the communication state of a communication valve (e.g., the upstream pressure regulation valve UJ), rather than by adjusting the front wheel and rear wheel supply pressures Pm and Pv to be equal. If an acquisition abnormality occurs in either the front wheel or rear wheel supply pressure Pm or Pv and only the other of these pressures can be acquired, hydraulic pressure feedback control is executed based on the signal from the other available pressure. Because the brake control device SC has a simple configuration, it is unable to continue dual-system pressure regulation in the event of an acquisition abnormality in the hydraulic pressure signal. However, the brake control device SC can continue hydraulic pressure feedback control, thereby ensuring good pressure regulation control accuracy. [Explanation of symbols]

[0126] SC...Brake control device, KG...Regeneration device, BP...Brake operating member (brake pedal), SA...First braking unit (first unit), SB...Second braking unit (second unit), YA...First fluid unit (first actuator), YB...Second fluid unit (second actuator), EA...First control unit (first controller), EB...Second control unit (second controller), BS...Communication bus, CM...Master cylinder, CW...Wheel cylinder, AP...Apply section, NR...Input section, CA...Pressure adjustment section, UJ, UK...Upstream and downstream pressure adjustment valves, MA, MB...First and second electric motors, QA, QB...First and second fluid pumps, VA...Inlet valve, VB...Release valve, UB...Control valve, SP...Operation displacement sensor (operating operation amount sensor), PM, PV...front wheel, rear wheel supply pressure sensor, Sp, Spa, Spb...operation displacement (operation amount), Pm, Pv...front wheel, rear wheel supply pressure, Pj, Pk...upstream, downstream servo pressure, Pq...adjusted pressure, Pw...wheel pressure, Ptf, Ptr...front wheel, rear wheel target pressure (target value corresponding to Pm, Pv), Px...common target pressure (common target value corresponding to Pm, Pv when "Ptf = Ptr"), sPt...target differential pressure (difference between Ptf and Ptr), hPf...front wheel deviation (difference between Ptf and Pm), hPr...rear wheel deviation (difference between Ptr and Pv), hPx...common deviation (difference between Px and Pm or Pv), FM...Pm acquisition flag (determination result of step S140), FV...Pv acquisition flag (determination result of step S240).

Claims

1. a first unit that outputs pressures to be supplied to the front wheels and the rear wheels individually in accordance with an amount of operation of a brake operating member of the vehicle; a second unit provided between the first unit and the front and rear wheel cylinders, the second unit adjusting the pressures supplied to the front and rear wheels and outputting wheel pressures for the front and rear wheels; a communication bus for transmitting signals between the first unit and the second unit; an operation amount sensor connected to the first unit and configured to detect the operation amount; a front wheel supply pressure sensor connected to the second unit and configured to detect the front wheel supply pressure; a rear wheel supply pressure sensor connected to the first unit and configured to detect the rear wheel supply pressure; In a braking control device for a vehicle, The first unit is The front wheel supply pressure is acquired from the second unit via the communication bus; Calculating front and rear wheel target pressures based on the operation amount; a feedback control is performed so that the front wheel supply pressure is made to coincide with the front wheel target pressure, and a feedback control is performed so that the rear wheel supply pressure is made to coincide with the rear wheel target pressure, The first unit is When the front wheel supply pressure cannot be obtained, The front wheel target pressure and the rear wheel target pressure are set equal to each other to determine a common target pressure; A vehicle braking control device that communicates the portion on which the front wheel supply pressure acts with the portion on which the rear wheel supply pressure acts, and performs feedback control so that the rear wheel supply pressure coincides with the common target pressure.

2. a first unit that outputs pressures to be supplied to the front wheels and the rear wheels individually in accordance with an amount of operation of a brake operating member of the vehicle; a second unit provided between the first unit and the front and rear wheel cylinders, the second unit adjusting the pressures supplied to the front and rear wheels and outputting wheel pressures for the front and rear wheels; a communication bus for transmitting signals between the first unit and the second unit; an operation amount sensor connected to the first unit and configured to detect the operation amount; a front wheel supply pressure sensor connected to the second unit and configured to detect the front wheel supply pressure; a rear wheel supply pressure sensor connected to the first unit and configured to detect the rear wheel supply pressure; In a braking control device for a vehicle, The first unit is The front wheel supply pressure is acquired from the second unit via the communication bus; Calculating front and rear wheel target pressures based on the operation amount; a feedback control is performed so that the front wheel supply pressure is made to coincide with the front wheel target pressure, and a feedback control is performed so that the rear wheel supply pressure is made to coincide with the rear wheel target pressure, The first unit is If the rear wheel supply pressure cannot be obtained, The front wheel target pressure and the rear wheel target pressure are set equal to each other to determine a common target pressure; a brake control device for a vehicle that communicates a portion on which the front wheel supply pressure acts with a portion on which the rear wheel supply pressure acts, and executes feedback control so that the front wheel supply pressure coincides with the common target pressure;

3. A first unit that outputs pressure to supply to the front and rear wheels individually according to the amount of operation of the brake operating member of the vehicle. and a second unit provided between the first unit and the front and rear wheel cylinders, the second unit adjusting the pressures supplied to the front and rear wheels and outputting wheel pressures for the front and rear wheels; a communication bus for transmitting signals between the first unit and the second unit; an operation amount sensor connected to the first unit and configured to detect the operation amount; a front wheel supply pressure sensor connected to the second unit and configured to detect the front wheel supply pressure; a rear wheel supply pressure sensor connected to the first unit and configured to detect the rear wheel supply pressure; A braking control device for a vehicle comprising: The first unit is The pressure of the brake fluid discharged by the fluid pump is adjusted to the upstream and downstream servo pressures by normally open upstream and downstream pressure regulating valves arranged in series with the circulating flow of brake fluid including the fluid pump, and the front wheel supply pressure is output by the hydraulic pressure on one side of the upstream and downstream servo pressures, and the rear wheel supply pressure is output by the hydraulic pressure on the other side of the upstream and downstream servo pressures, The first unit is The front wheel supply pressure is acquired from the second unit via the communication bus; Calculating front and rear wheel target pressures based on the operation amount; feedback control of the one-side hydraulic pressure so that the front wheel supply pressure coincides with the front wheel target pressure; feedback control of the other-side hydraulic pressure so that the rear wheel supply pressure coincides with the rear wheel target pressure; When the front wheel supply pressure cannot be obtained, The first unit is The front wheel target pressure and the rear wheel target pressure are set equal to each other to determine a common target pressure; a braking control device for a vehicle that stops energization of the upstream pressure regulating valve and drives the downstream pressure regulating valve by feedback control so that the rear wheel supply pressure coincides with the common target pressure;

4. a first unit that outputs pressures to be supplied to the front wheels and the rear wheels individually in accordance with an amount of operation of a brake operating member of the vehicle; a second unit provided between the first unit and the front and rear wheel cylinders, the second unit adjusting the pressures supplied to the front and rear wheels and outputting wheel pressures for the front and rear wheels; a communication bus for transmitting signals between the first unit and the second unit; an operation amount sensor connected to the first unit and configured to detect the operation amount; a front wheel supply pressure sensor connected to the second unit and configured to detect the front wheel supply pressure; a rear wheel supply pressure sensor connected to the first unit and configured to detect the rear wheel supply pressure; A braking control device for a vehicle comprising: The first unit is The pressure of the brake fluid discharged by the fluid pump is adjusted to the upstream and downstream servo pressures by normally open upstream and downstream pressure regulating valves arranged in series with the circulating flow of brake fluid including the fluid pump, and the front wheel supply pressure is output by the hydraulic pressure on one side of the upstream and downstream servo pressures, and the rear wheel supply pressure is output by the hydraulic pressure on the other side of the upstream and downstream servo pressures, The first unit is The front wheel supply pressure is acquired from the second unit via the communication bus; Calculating front and rear wheel target pressures based on the operation amount; The one-side hydraulic pressure is fed back so that the front wheel supply pressure coincides with the front wheel target pressure. Control and feedback control of the other-side hydraulic pressure so that the rear wheel supply pressure coincides with the rear wheel target pressure; If the rear wheel supply pressure cannot be obtained, The first unit is The front wheel target pressure and the rear wheel target pressure are set equal to each other to determine a common target pressure; a braking control device for a vehicle that stops energization of the upstream pressure regulating valve and drives the downstream pressure regulating valve by feedback control so that the pressure supplied to the front wheels coincides with the common target pressure;

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