Vehicle braking control device

Abstract

To provide a brake control device for a vehicle that executes liquid pressure control including feedback control, which has a simple constitution.SOLUTION: A brake control device for a vehicle includes a first unit for outputting a supply pressure according to an operation amount of a brake operation member, a second unit which is provided between the first unit and a wheel cylinder, and adjusts the supply pressure and outputs a wheel pressure to the wheel cylinder, a communication bus for performing signal transmission between the first unit and the second unit, an operation amount sensor which is connected to the first unit and detects the operation amount, and a supply pressure sensor which is connected to the second unit and detects the supply pressure. The first unit calculates a target pressure on the basis of the operation amount, acquires the supply pressure from the second unit through the communication bus, and executes feedback control so that the supply pressure coincides with the target pressure.SELECTED DRAWING: Figure 4

Description

Technical Field

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

Background Art

[0002] The applicant has developed a braking control device for a vehicle as described in Patent Document 1. Patent Document 1 provides "a braking control device having a brake-by-wire configuration with good braking operation characteristics and in which two braking systems are fluidly separated during normal braking". Therefore, "the braking control device includes a first fluid passage to which two of the four wheel cylinders are connected, a second fluid passage to which another two of the four wheel cylinders are connected, a piston that fluidly separates the first and second fluid passages, a simulator that is fluidly separated from the first and second fluid passages and applies an operating force to a braking operation member, an electric pump connected to a reservoir, a pressure regulating valve that adjusts the braking fluid discharged by the electric pump to a regulated hydraulic pressure, a reflux passage that returns the braking fluid that has passed through the pressure regulating valve to the suction portion of the electric pump, a servo chamber that is fluidly separated from the first and second fluid passages and the simulator and adjusts the hydraulic pressure of the first and second fluid passages via the piston by the regulated hydraulic pressure, and a controller that controls the electric pump and the pressure regulating valve".

[0003] By the way, in the device of Patent Document 1, a pressure sensor for detecting the regulated hydraulic pressure is provided, and the pressure regulating valve is feedback-controlled so that the detected regulated hydraulic pressure approaches and matches the target hydraulic pressure. Thereby, highly accurate hydraulic pressure control is achieved. In such a braking control device, it is desired that the hydraulic pressure feedback control be executed with a simple configuration.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] An object of the present invention is to provide a vehicle brake control device that executes hydraulic control including feedback control and that has a simple configuration. [Means for solving the problem]

[0006] A vehicle brake control device (SC) according to the present invention includes a first unit (SA) that outputs a supply pressure (Pm) in response to an operation amount (Sp) of a brake operating member (BP), a second unit (SB) that is provided between the first unit (SA) and a wheel cylinder (CW) and adjusts the supply pressure (Pm) to output a wheel pressure (Pw) to the wheel cylinder (CW), 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) that detects the operation amount (Sp), and a supply pressure sensor (PM) connected to the second unit (SB) that detects the supply pressure (Pm). The first unit (SA) calculates a target pressure (Pt) based on the operation amount (Sp), obtains the supply pressure (Pm) from the second unit (SB) via the communication bus (BS), and performs feedback control to make the supply pressure (Pm) equal to the target pressure (Pt).

[0007] The second unit SB includes a supply pressure sensor PM so that independent wheel control, such as antilock brake control and anti-skid control, can be performed. The first unit SA acquires the supply pressure Pm via the communication bus BS. With the above configuration, one supply pressure sensor PM is shared by the pressure regulation control and the independent wheel control. This simplifies the overall configuration of the brake control device SC.

[0008] In the braking control device (SC) of the vehicle according to the present invention, the operation amount sensor (SP) is also connected to the second unit (SB). When the first unit (SA) cannot acquire the supply pressure (Pm) (FP = 1), the second unit (SB) calculates the target pressure (Pt) based on the operation amount (Sp), and adjusts the wheel pressure (Pw) based on the deviation (hP) between the target pressure (Pt) and the supply pressure (Pm). For example, when the supply pressure (Pm) is smaller than the target pressure (Pt), the second unit (SB) increases the wheel pressure (Pw) by an amount corresponding to the deviation (hP).

[0009] The above configuration is a simple configuration in which, even when the first braking unit SA cannot acquire the supply pressure Pm and cannot execute the above feedback control, the second braking unit SB compensates for the excess or deficiency (i.e., hydraulic error) of the supply pressure Pm and can ensure the pressure regulating accuracy of the wheel pressure Pw.

Brief Description of Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0011] <Symbols of components, etc., and subscripts 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 (UA, 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 the "operation amount sensor") includes two detection units SPa and SPb (referred to as the "first and second detection units"). That is, the detection of the operation displacement Sp is performed doubly, and the operation displacement sensor SP is redundant. The first detection unit SPa of the operation displacement sensor SP (referred to as the "first displacement detection unit") is connected to the first braking unit SA (particularly, the first control unit EA) by the first displacement signal line L Spa. On the other hand, the second detection unit SPb of the operation displacement sensor SP (referred to as the "second displacement detection unit") is connected to the second braking unit SB (particularly, the second control unit EB) by the second displacement signal line L Spb. Therefore, the signal Spa of the first detection unit SPa (referred to as the "first operation displacement") is directly input to the first control unit EA. On the other hand, the signal Spb of the second detection unit SPb (referred to as the "second operation displacement") is directly input to the second control unit EB. For example, the "signal lines L Spa and L Spb" are electric wires (wire harnesses) for signal transmission.

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

[0019] The vehicle JV is equipped with various sensors. For braking control (referred to as "individual wheel control") that individually controls the wheel pressure Pw of each wheel WH, such as antilock brake control and skid prevention control, the wheel WH is equipped with a wheel speed sensor VW that detects its rotational speed (wheel speed) Vw. Also, a steering angle sensor that detects the steering amount Sa (for example, the operation angle of the steering wheel), 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 are provided (not shown above). The signals of 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 (specifically, the second control unit EB) via their respective signal lines.

[0020] The vehicle JV is equipped with a braking control device SC. In the braking control device SC, a so-called front-rear type (also referred to as "Type II") is adopted as the two braking systems. The actual wheel pressure Pw is adjusted by the braking control device SC.

[0021] The braking control device SC is composed of two braking units SA and SB. The first braking 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 battery BT (braking battery) different from the drive battery BG as a power source. The second braking unit SB is composed of a second fluid unit YB and a second control unit EB. The second fluid unit YB is controlled by the second control unit EB using the battery BT as a power source, similar to the first braking unit SA.

[0022] The first braking unit SA (particularly, the first control unit EA) and the second braking unit SB (particularly, the second control unit EB) are connected to the communication bus BS. Further, a regenerative device KG (particularly, the regenerative control unit EG) is connected to the communication bus BS. The "communication bus BS" has a network structure in which a plurality of control units (also referred to as "controllers") are suspended from a communication line terminated at both ends. Signal transmission is performed among a plurality of controllers (EA, EB, EG, etc.) via the communication bus BS. That is, a plurality of controllers can transmit signals (detection values, calculation values, control flags, etc.) to the communication bus BS and can receive signals from the communication bus BS. For example, as the communication bus BS, a vehicle bus (an internal communication network that interconnects controllers in a vehicle) is adopted, and CAN is used as the serial communication protocol. The communication bus BS is composed of a communication line (e.g., a CAN cable) and microcontrollers for transmission and reception in each controller.

[0023] <First braking unit SA> With reference to the schematic diagram of FIG. 2, a configuration example of the first braking unit SA (corresponding to the "first unit") of the braking control device SC will be described. The first braking unit SA generates a supply pressure Pm in response to the operation of a braking operation member BP (brake pedal). The supply pressure Pm is finally supplied to the wheel cylinder CW via a connection path HS (fluid path) and the second braking unit SB. The first braking unit SA is composed 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 regulating part CA, and an input part NR.

[0025] [Apply part AP] In response to the operation of the braking operation member BP, a supply pressure Pm is output from the apply part AP. The apply part AP is composed of a tandem type master cylinder CM and primary and secondary master pistons NM, NS.

[0026] In the tandem master cylinder CM, primary and secondary master pistons NM and NS are inserted. The interior of the master cylinder CM is partitioned into four hydraulic chambers Rmf, Rmr, Ru, and Rs by the two master pistons NM and NS. The front-wheel and rear-wheel master chambers Rmf and Rmr (= Rm) are partitioned by one side bottom of the master cylinder CM and the master pistons NM and NS. Further, the interior of the master cylinder CM is partitioned into a servo chamber Ru and a reaction chamber Rs by the flange portion Tu of the master piston NM. The master chamber Rm and the servo chamber Ru are arranged to face 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 not braking, the master pistons NM and NS are at the 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 communicates with the master reservoir RV. Braking fluid BF is stored inside the master reservoir RV (which is an atmospheric pressure reservoir and is also simply referred to as the "reservoir"). When the braking operation member BP is operated, the master pistons NM and NS are moved in the forward direction Ha (the direction in which the volume of the master chamber Rm decreases). Due to this movement, the communication between the master chamber Rm and the reservoir RV is blocked. Then, when the master pistons NM and NS are further moved in the forward direction Ha, the front-wheel and rear-wheel supply pressures Pmf and Pmr (= Pm) are increased from "0 (atmospheric pressure)". As a result, the braking fluid BF pressurized to the supply pressure Pm is output (pumped) from the master chamber Rm of the master cylinder CM. Since the supply pressure Pm is the hydraulic pressure of the master chamber Rm, it is also referred to as the "master pressure".

[0028] [Pressure regulating unit CA] The pressure regulating unit CA supplies a servo pressure Pu to the servo chamber Ru of the application unit AP. The pressure regulating unit CA is composed of a first electric motor MA, a first fluid pump QA, and a pressure regulating valve UA.

[0029] The first fluid pump QA is driven by the first electric motor MA. In the first fluid pump QA, the suction part and the discharge part are connected by a reflux passage HK (fluid passage). Further, the suction part of the first fluid pump QA is also connected to the master reservoir RV via a reservoir passage HR. A check valve is provided at the discharge part of the first fluid pump QA.

[0030] A normally open pressure regulating valve UA is provided in the reflux passage HK. The pressure regulating valve UA is a linear solenoid valve whose valve opening amount is continuously controlled based on an energized state (for example, supply current). Since the pressure regulating valve UA adjusts the hydraulic pressure difference (differential pressure) between its upstream side and downstream side, it is also referred to as a "differential pressure valve".

[0031] When the braking fluid BF is discharged from the first fluid pump QA, a circulating flow KN (indicated by a broken line arrow) of the braking fluid BF is generated in the reflux passage HK. When the pressure regulating valve UA is in a fully open state (since the pressure regulating valve UA is a normally open type, when not energized), in the reflux passage HK, the hydraulic pressure Pu (referred to as "servo pressure") between the discharge part of the first fluid pump QA and the pressure regulating valve UA is "0 (atmospheric pressure)". When the energization amount (supply current) to the pressure regulating valve UA is increased, the circulating flow KN (the flow of the braking fluid BF circulating in the reflux passage HK) is restricted by the pressure regulating valve UA. In other words, the flow passage of the reflux passage HK is narrowed by the pressure regulating valve UA, and the orifice effect by the pressure regulating valve UA is exerted. Thereby, the hydraulic pressure Pu on the upstream side of the pressure regulating valve UA is increased from "0". That is, in the circulating flow KN, a hydraulic pressure difference (differential pressure) between the upstream side hydraulic pressure Pu (servo pressure) with respect to the pressure regulating valve UA and the downstream side hydraulic pressure (atmospheric pressure) is generated. The differential pressure is adjusted by the energization amount to the pressure regulating valve UA.

[0032] The reflux passage HK is connected to the servo chamber Ru via a servo passage HV (fluid passage) at a position between the discharge part of the first fluid pump QA and the pressure regulating valve UA. Therefore, the servo pressure Pu is introduced (supplied) into the servo chamber Ru. Due to the increase in the servo pressure Pu, the master pistons NM, NS are pressed in the forward direction Ha (the direction in which the volume of the master chamber Rm decreases), and the hydraulic pressures Pmf, Pmr (front wheel, rear wheel supply pressures) in the front wheel and rear wheel master chambers Rmf, Rmr are increased.

[0033] Front wheels, and in the front and rear wheel master chambers Rmf and Rmr (= Rm), front and rear wheel communication paths HSf and HSr (= HS) are connected. The front and rear wheel communication paths HSf and HSr are connected to the front and rear wheel wheel cylinders CWf and CWr (= CW) via the second braking unit SB (in particular, the second fluid unit YB). Therefore, the front and rear wheel supply pressures Pmf and Pmr are supplied from the first braking unit SA to the front and rear wheel wheel cylinders CWf and CWr. Here, the front wheel supply pressure Pmf and the rear wheel supply pressure Pmr are equal (i.e., "Pmf = Pmr").

[0034] [Input unit NR] By the input unit NR, the braking operation member BP is operated so as to achieve regenerative cooperative control, but a state in which the wheel pressure Pw is not generated is created. "Regenerative cooperative control" is to cooperate the frictional braking force Fm (the braking force by the wheel pressure Pw) and the regenerative braking force Fg (the braking force by the generator GN) so that the kinetic energy of the vehicle JV can be efficiently recovered as electric energy during braking. The input unit NR is composed of an input cylinder CN, an input piston NN, an introduction valve VA, an open valve VB, a stroke simulator SS, and a simulator hydraulic pressure sensor PS.

[0035] The input cylinder CN is fixed to the master cylinder CM. The input piston NN is inserted into the input cylinder CN. The input piston NN is mechanically connected to the braking operation member BP via a clevis (U-shaped link) so as to be interlocked with the braking operation member BP (brake pedal). The end face of the input piston NN and the end face of the primary piston NM have a gap Ks (also referred to as "separation displacement"). By adjusting the separation distance Ks by the servo pressure Pu, regenerative cooperative control is achieved.

[0036] The input chamber Rn of the input section NR is connected to the reaction force chamber Rs of the apply section AP via an input passage HN (fluid passage). A normally closed introduction valve VA is provided in the input passage HN. The input passage HN is connected to the master reservoir RV via a reservoir passage HR between the introduction valve VA and the reaction force chamber Rs. An open valve VB of normally open type is provided in the reservoir passage HR. The introduction valve VA and the open valve VB are on-off type solenoid valves. A stroke simulator SS (simply referred to as "simulator" also) is connected to the input passage HN between the introduction valve VA and the reaction force chamber Rs.

[0037] When power supply (power feeding) is not performed to the introduction valve VA and the open valve VB, the introduction valve VA is closed and the open valve VB is opened. By closing the introduction valve VA, the input chamber Rn is sealed and fluid-locked. Thereby, the master pistons NM, NS are displaced integrally with the braking operation member BP. Also, by opening the open valve VB, the simulator SS is communicated with the master reservoir RV. When power supply (power feeding) is performed to the introduction valve VA and the open valve VB, the introduction valve VA is opened and the open valve VB is closed. Thereby, the master pistons NM, NS can be displaced separately from the braking operation member BP. At this time, since the input chamber Rn is connected to the stroke simulator SS, the operating force Fp of the braking operation member BP is generated by the simulator SS.

[0038] The state in which the master pistons NM, NS and the brake operating member BP are displaced separately (when the solenoid valves VA, 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 pistons NM, NS and the brake operating member BP are displaced together (when the solenoid valves VA, 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 operation modes, the first mode (by-wire mode) or 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.

[0039] 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.

[0040] <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 with other controllers (EB, EG, etc.).

[0041] The first controller EA and the first detection unit SPa of the operation displacement sensor SP are connected via a signal line L Spa for the first detection unit SPa. Also, the first controller EA and the simulator pressure sensor PS are connected via a signal line L Ps for the simulator pressure sensor PS. The first operation displacement Spa and the simulator pressure Ps are directly input to the first controller EA through these signal lines L Spa and L Ps.

[0042] A pressure control algorithm is programmed in the first controller EA (particularly, the first microprocessor MPa). "Pressure control" is control for adjusting the supply pressure Pm (and as a result, the wheel pressure Pw), and includes regenerative cooperative control. The pressure control is executed based on the first and second operation displacements Spa and Spb, the simulator pressure Ps, the supply pressure Pm, and the maximum regenerative braking force Fx.

[0043] Based on the pressure control algorithm, the first drive circuit DRa drives the first electric motor MA that constitutes the first actuator YA and various solenoid valves (such as UA). In the first drive circuit DRa, an H-bridge circuit is formed by switching elements (for example, MOS-FETs) to drive the first electric motor MA. Also, the first drive circuit DRa is provided with switching elements to drive various solenoid valves (such as UA). In addition, the first drive circuit DRa includes a motor current sensor (not shown) for detecting the supply current Im (actual value) to the first electric motor MA and a first current sensor (not shown) for detecting the supply current Ia (actual value, referred to as the "first supply current") to the pressure regulating valve UA. Note that a rotational speed sensor (not shown) for detecting the rotational speed Na (actual value) of the first electric motor MA is provided. A rotational angle sensor (not shown) for detecting the rotational angle Ka (actual value) may be provided for the first electric motor MA, and the motor rotational speed Na may be calculated based on the motor rotational angle Ka.

[0044] In the first controller EA, based on the operation displacement Sp (operation amount), a first target current Ita (target value) corresponding to the first supply current Ia is calculated. Then, the first supply current Ia is controlled to approach and match the first target current Ita (so-called current feedback control). Also, in the first controller EA, based on the operation displacement Sp, a target rotation speed Nta (target value) corresponding to the actual rotation speed Na is calculated. Then, the motor supply current Im is controlled 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 Ua, Va, Vb for controlling various solenoid valves UA, VA, VB are calculated. Then, according to the drive signals (such as Ma), the switching elements of the first drive circuit DRa are driven, and the first electric motor MA and the solenoid valves UA, VA, VB are controlled.

[0045] <Second braking unit SB> Referring to the schematic diagram of FIG. 3, a configuration example of the second braking unit SB (corresponding to the "second unit") of the braking control device SC will be described. The second braking unit SB is a general-purpose unit (device) for performing independent wheel control such as anti-lock braking control, traction control, and skid prevention control for each wheel. In addition, in the second braking unit SB, complementary control is executed. The "complementary control" compensates for the excess or deficiency of the supply pressure Pm caused by the abnormality of the first braking unit SA.

[0046] The front-wheel and rear-wheel supply pressures Pmf, Pmr (= Pm) are supplied to the second braking unit SB from the first braking unit SA. Then, in the second braking unit SB, the front-wheel and rear-wheel supply pressures Pmf, Pmr are adjusted (increased or decreased) and output as the hydraulic pressures Pwf, Pwr (front-wheel and rear-wheel wheel pressures) of the front-wheel and rear-wheel wheel cylinders CWf, CWr. The second braking unit SB is composed of a second fluid unit YB and a second control unit EB.

[0047] ≪Second fluid unit YB≫ The second fluid unit YB (also referred to as the "second actuator") is provided between the first actuator YA and the wheel cylinder CW in the communication path HS. The second actuator YB is composed of a 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.

[0048] The front-wheel and rear-wheel control valves UBf, UBr (= UB) are provided in the front-wheel and rear-wheel communication paths HSf, HSr (= HS). The control valve UB is a normally open linear solenoid valve (differential pressure valve) similar to the pressure regulating valve UA. By the control valve UB, the wheel pressure Pw can be individually increased from the supply pressure Pm in the front and rear wheel systems.

[0049] The front-wheel and rear-wheel supply pressure sensors PMf, PMr (= PM) are provided at the upper parts of the front-wheel and rear-wheel control valves UBf, UBr (the part of the communication path HS close to the first actuator YA) so as to detect the actual hydraulic pressures Pmf, Pmr (front-wheel and rear-wheel supply pressures) supplied from the first actuator YA (especially, the front-wheel and rear-wheel master chambers Rmf, Rmr). The supply pressure sensor PM is also referred to as the "master pressure sensor" and is built into the second actuator YB. The front-wheel and rear-wheel supply pressure sensors PMf, PMr are connected to the second brake unit SB (especially, the second control unit EB) by the front-wheel and rear-wheel supply pressure signal lines LPmf, LPmr (= LPm). That is, the signals of the front-wheel and rear-wheel supply pressures Pmf, Pmr (= Pm) are directly input to the second control unit EB. Since the front-wheel supply pressure Pmf and the rear-wheel supply pressure Pmr are substantially the same, either one of the front-wheel and rear-wheel supply pressure sensors PMf, PMr may be omitted. For example, in a configuration where the rear-wheel supply pressure sensor PMr is omitted, only the front-wheel supply pressure Pmf is detected by the front-wheel supply pressure sensor PMf and directly input to the second control unit EB.

[0050] The front wheel, rear wheel return paths HLf, HLr (=HL) connect the upper parts of the front wheel and rear wheel control valves UBf, UBr (the part of the communication path HS closer to the first actuator YA) and the lower parts of the front wheel and rear wheel control valves UBf, UBr (the part of the communication path HS closer to the wheel cylinder CW). The front wheel, rear wheel return paths HLf, HLr are provided with front wheel, rear wheel fluid pumps QBf, QBr (=QB) and front wheel, rear wheel pressure regulating reservoirs RBf, RBr (=RB). The second fluid pump QB is driven by the second electric motor MB.

[0051] When the second electric motor MB is driven, the second fluid pump QB sucks the brake fluid BF from the upper part of the control valve UB and discharges it to the lower part of the control valve UB. As a result, a circulating flow KL of the brake fluid BF (i.e., the front wheel, rear wheel circulating flows KLf, KLr, indicated by the dashed arrows) including the pressure regulating reservoir RB is generated in the communication path HS and the return path HL. When the flow path of the communication path HS is narrowed by the control valve UB and the circulating flow KL of the brake fluid BF is restricted, the hydraulic pressure Pq (referred to as the "adjusted pressure") at the lower part of the control valve UB is increased from the hydraulic pressure Pm (supply pressure) at the upper part of the control valve UB due to the orifice effect at that time. In other words, in the circulating flow KL, the pressure difference (differential pressure) between the downstream hydraulic pressure Pm (supply pressure) and the upstream hydraulic pressure Pq (adjusted pressure) with respect to the control valve UB is adjusted by the control valve UB. Note that in the magnitude relationship between the supply pressure Pm and the adjusted pressure Pq, the adjusted pressure Pq is equal to or higher than the supply pressure Pm (i.e., "Pq≧Pm"). As described above, the mechanism for generating the adjusted pressure Pq in the second actuator YB is the same as the mechanism for generating the servo pressure Pu in the first actuator YA.

[0052] Inside the second actuator YB, the front and rear wheel connection paths HSf and HSr are each branched into two and connected to the front and rear wheel cylinder CWf and CWr. In order to be able to adjust each wheel pressure Pw individually, a normally open inlet valve VI and a normally closed outlet valve VO are provided for each wheel cylinder CW. Specifically, the inlet valve VI is provided in the branched connection path HS (that is, the side closer to the wheel cylinder CW with respect to the branch portion of the connection path HS). The connection path HS is connected to the pressure regulating reservoir RB via a pressure reducing path HG at the lower part of the inlet valve VI (the portion of the connection path HS closer to the wheel cylinder CW). And an outlet valve VO is arranged in the pressure reducing path HG. As the inlet valve VI and the outlet valve VO, on-off type solenoid valves are adopted. By the inlet valve VI and the outlet valve VO, the wheel pressure Pw can be individually reduced from the supply pressure Pm at each wheel.

[0053] When power is not supplied to the inlet valve VI and the outlet valve VO and their operations are stopped, the inlet valve VI is opened and the outlet valve VO is closed. In this state, the wheel pressure Pw is equal to the adjustment pressure Pq. By driving the inlet valve VI and the outlet valve VO, the wheel pressure Pw is adjusted independently for each wheel cylinder CW. To reduce the wheel pressure Pw, the inlet valve VI is closed and the outlet valve VO is opened. The inflow of the 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, so the wheel pressure Pw is reduced. To increase the wheel pressure Pw (however, the upper limit of the increase is up to the adjustment pressure Pq), the inlet valve VI is opened and the outlet valve VO is closed. The outflow of the brake fluid BF to the pressure regulating reservoir RB is blocked and the adjustment pressure Pq from the pressure regulating valve UB is supplied to the wheel cylinder CW, so the wheel pressure Pw is increased. To hold 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.

[0054] ≪Second Control Unit EB≫ The second actuator YB is controlled by the second control unit EB (also referred to as the "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 the communication bus BS. Therefore, the first controller EA and the second controller EB can share signals via the communication bus BS.

[0055] Wheel speed Vw, steering amount Sa, yaw rate Yr, longitudinal acceleration Gx, and lateral acceleration Gy are input to the second controller EB (specifically, the second microprocessor MPb). Based on the wheel speed Vw, the vehicle body speed Vx is calculated by the second controller EB. The following independent wheel controls are executed by the second controller EB. Specifically, as the independent wheel controls, an anti-lock brake control (so-called ABS control) for suppressing the locking of the wheel WH, a traction control for suppressing the wheelspin of the driving wheels, and a skid prevention control (so-called ESC) for suppressing understeer and oversteer to improve the directional stability of the vehicle are executed.

[0056] According to the control algorithm programmed in the second microprocessor MPb, the second drive circuit DRb drives the second electric motor MB that constitutes the second actuator YB, and various solenoid valves (such as UB). In the second drive circuit DRb, an H-bridge circuit is constituted by switching elements (for example, MOS-FETs) to drive the second electric motor MB. Also, the second drive circuit DRb is provided with switching elements to drive various solenoid valves (such as UB). 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, the drive signal Ub of the control valve UB, the drive signal Vi of the inlet valve VI, the drive signal Vo of the outlet valve VO, and the drive signal Mb of the second electric motor MB are calculated. Then, based on the drive signals (such as Ub), the second drive circuit DRb controls the second electric motor MB and the solenoid valves UB, VI, and VO.

[0057] The second controller EB and the second detection unit SPb of the operation displacement sensor SP are connected via a signal line LSpb for the second detection unit SPb. Also, the second controller EB and the supply pressure sensor PM are connected via a signal line LPm (for example, a signal pin) for the supply pressure sensor PM. Therefore, the second operation displacement Spb is directly input to the second controller EB through the signal line LSpb, and the supply pressure Pm is directly input to the second controller EB through the signal line LPm. Then, the second operation displacement Spb and the supply pressure Pm are transmitted from the second controller EB to the first controller EA through the communication bus BS. That is, in the first controller EA, the second operation displacement Spb and the supply pressure Pm are acquired from the second controller EB through the communication bus.

[0058] In the second controller EB, in addition to the above-described individual wheel independent control, complementary control is executed to cope with abnormalities in the braking control device SC. In the complementary control, the performance degradation of the first braking unit SA is compensated by the second braking unit SB.

[0059] <Pressure regulation control processing> An example of the pressure regulation control process will be described with reference to Figures 4 to 6. The pressure regulation control includes not only regenerative cooperative control but also complementary control to deal with a state in which the supply pressure Pm is not properly acquired by the first braking unit SA (particularly the first controller EA) (also referred to as "acquisition abnormality"). The pressure regulation control algorithm is programmed in the microprocessors MPa and MPb of the first and second controllers EA and EB.

[0060] The first controller EA acquires the supply pressure Pm from the second controller EB via the communication bus BS. Here, the communication bus BS is composed of a communication line and a transmitting / receiving (communication) microcontroller in the first and second controllers EA and EB. Therefore, an abnormality in acquiring the supply pressure Pm occurs due to a break in the communication line, a malfunction of the communication microcontroller, etc. A state in which an abnormality exists in the communication bus BS and it is unable to function normally is called a "communication abnormality." Therefore, an abnormality in acquiring the supply pressure Pm is caused by a communication abnormality.

[0061] In describing the processing example, the following is assumed. 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. When the braking control device SC operates normally, the second actuator YB is not driven, and only the first actuator YA is driven. Therefore, when the braking control device SC operates normally, the wheel pressure Pw is adjusted only by the first actuator YA, so that the wheel pressure Pw and the supply pressure Pm are equal (i.e., "Pm = Pw"). 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, "Pm = Pu" (where friction of the seal member SL is ignored). - The supply pressure sensor PM is built into the second actuator YB and connected to the second controller EB by a signal line LPm. The first controller EA acquires the supply pressure Pm from the second controller EB through the communication bus BS. - In the second actuator YB, the rear wheel supply pressure sensor PMr is omitted, and only the front wheel supply pressure sensor PMf is provided as the supply pressure sensor PM. Therefore, only the front wheel supply pressure Pmf is adopted as the signal of the supply pressure Pm.

[0062] The various braking forces are as follows. - The "total vehicle body braking force Fu" is the actual braking force acting on the entire vehicle JV. The target value corresponding to the total vehicle body braking force Fu is the "target vehicle body braking force Fv". - The "frictional braking force Fm" is the braking force actually generated according to the wheel pressure Pw. The target value corresponding to the frictional braking force Fm is the "target frictional braking force Fn". - The "regenerative braking force Fg" is the braking force actually generated by the regenerator KG. The target value corresponding to the regenerative braking force Fg is the "target regenerative braking force Fh". The target regenerative braking force Fh is calculated by the first braking unit SA (especially the first controller) and transmitted to the regenerator KG (especially the regeneration controller EG) via the communication bus BS. In the regenerator KG, the generator GN is controlled by the regeneration controller EG so that the actual regenerative braking force Fg approaches and matches the target regenerative braking force Fh. - The "limiting regenerative braking force Fx" is the maximum value (limit value) of the regenerative braking force Fg that the regenerator KG can generate. Therefore, in the regenerator KG, the regenerative braking force Fg is generated within the range (limit) up to the limiting regenerative braking force Fx. The limiting regenerative braking force Fx is calculated by the regenerator KG (especially the regeneration controller EG) and transmitted to the first braking unit SA (especially the first controller EA) via the communication bus BS.

[0063] Referring to the flowchart of FIG. 4, the overall pressure regulation control will be described. The pressure regulation control includes the following two aspects according to the operating state of the first braking unit SA. The first is the pressure regulation control when the operation of the braking control device SC is normal (referred to as the "normal state"), which is called "normal control". The second is the pressure regulation control when an abnormal acquisition of the supply pressure Pm occurs in the first braking unit SA (referred to as the "abnormal state"), which is called "complementary control". In "complementary control", the excess or deficiency of the supply pressure Pm from the first braking unit SA due to the abnormal acquisition of the supply pressure Pm is compensated by the second braking unit SB.

[0064] In step S110, the first controller EA supplies power (powers) to the inlet valve VA and the release valve VB. As a result, the normally closed inlet valve VA is opened, the normally open release valve VB is closed, and the first mode in which the master pistons NM, NS and the braking operation member BP can be displaced separately is selected. In the first mode, the supply pressure Pm (i.e., the wheel pressure Pw) is adjusted independently of the operation of the braking operation member BP. At this time, the operating force Fp of the braking operation member BP is generated by the stroke simulator SS.

[0065] In step S120, the first controller EA reads signals such as the first and second operation displacements Spa, Spb, and the supply pressure Pm (= Pmf). The operation displacement sensor SP is provided with two operation displacement detection parts SPa, SPb (the first and second detection parts). The first operation displacement Spa (the detection value of the first detection part SPa) is directly acquired through the first displacement signal line L Spa. The second operation displacement Spb (the detection value of the second detection part SPb) and the supply pressure Pm (the detection value of the supply pressure sensor PM) are acquired from the second controller EB via the communication bus BS.

[0066] In step S120, the first controller EA calculates the operation displacement Sp 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"). Also, when one of the first and second operation displacements Spa and Spb cannot be obtained, the operation displacement Sp is determined by the other obtainable side (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 second controller EB via the communication bus BS.

[0067] In step S130, based on the operation displacement Sp and the calculation map Zfv, the target vehicle body braking force Fv (the target value of the braking force acting on the entire vehicle) is calculated. The target vehicle body braking force Fv is determined to be "0" when the operation displacement Sp is less than the predetermined displacement so according to the calculation map Zfv. And when the operation displacement Sp is greater than or equal to the predetermined displacement so, as the operation displacement Sp increases from "0", the target vehicle body braking force Fv is determined to increase from "0". Here, the "predetermined displacement so" is a preset value (constant) representing the play of the braking operation member BP.

[0068] In step S140, the first controller EA determines whether the supply pressure Pm is properly obtained. This determination process is referred to as the "acquisition determination". When the first braking unit SA can normally obtain (receive) the supply pressure Pm, the acquisition determination is affirmed and the process proceeds to step S150. On the other hand, when the supply pressure Pm cannot be properly obtained, the acquisition determination is negated and the process proceeds to step S180. For example, the cause of the abnormal acquisition of the supply pressure Pm is at least one of "disconnection of the communication line", "malfunction of the communication microcontroller (especially the receiving part) of the first controller EA", and "malfunction of the communication microcontroller (especially the transmitting part) of the second controller EB".

[0069] In step S140, when the acquisition determination is affirmed, the determination flag FP (also referred to as the "acquisition flag") is determined to be "0". On the other hand, when the acquisition determination is negated, the acquisition flag FP is determined to be "1". The "acquisition flag FP" is a control flag indicating the availability of acquiring the supply pressure Pm in the first braking unit SA. In the acquisition flag FP, "0" represents the normal state where acquisition is performed normally, and "1" represents the abnormal state where there is an abnormality in acquisition. The acquisition flag FP is transmitted from the first controller EA to the second controller EB via the communication bus BS when the communication bus BS is normal.

[0070] ≪Processing of Normal Control≫ The processing in steps S150 to S170 corresponds to normal control including regenerative cooperative control (pressure regulating control when the supply pressure Pm is received normally). This processing is executed by the first controller EA. For example, in normal control, only the first actuator YA is driven.

[0071] In step S150, based on the target vehicle body braking force Fv and the limit regenerative braking force Fx, the target regenerative braking force Fh and the target frictional braking force Fn are calculated. Specifically, the target regenerative braking force Fh is determined as a value less than or equal to the limit regenerative braking force Fx. For example, when the target vehicle body braking force Fv is less than or equal to the limit regenerative braking force Fx, the target regenerative braking force Fh is made equal to the target vehicle body braking force Fv, and the target frictional braking force Fn is determined to be "0" (i.e., when "Fv≦Fx", then "Fh = Fv, Fn = 0"). On the other hand, when the target vehicle body braking force Fv is greater than the limit regenerative braking force Fx, the target regenerative braking force Fh is made equal to the limit regenerative braking force Fx, and the target frictional braking force Fn is determined to be "the value obtained by subtracting the limit regenerative braking force Fx (=Fh) from the target vehicle body braking force Fv" (i.e., when "Fv > Fx", then "Fh = Fx, Fn = Fv - Fx = Fv - Fh"). The target regenerative braking force Fh is transmitted from the first controller EA to the regenerative controller EG via the communication bus BS. Then, the generator GN is controlled by the regenerative controller EG so that the actual regenerative braking force Fg approaches and matches the target regenerative braking force Fh.

[0072] In step S160, based on the target frictional braking force Fn, the target pressure Pt (= Ptf, Ptr) is calculated. The "target pressure Pt" is the target value corresponding to the supply pressure Pm. Also, during normal operation of the braking control device SC, since "Pm = Pw", the target pressure Pt is also the target value corresponding to the wheel pressure Pw. Specifically, the target pressure Pt is based on specifications of the braking device SX etc. (such as the pressure receiving area of the wheel cylinder CW, the effective braking radius of the rotating member KT, the friction coefficient of the friction member MS, the effective radius of the wheel (tire), etc.), and the target frictional braking force Fn is determined by being converted into the dimension of the supply pressure Pm (that is, the wheel pressure Pw). Note that since "Pmf = Pmr", the front-wheel target pressure Ptf and the rear-wheel target pressure Ptr are determined to be equal values (that is, "Ptf = Ptr").

[0073] In step S170, the first controller EA controls the first actuator YA so that the supply pressure Pm (actual value) approaches and matches the target pressure Pt (target value). Specifically, the first electric motor MA is driven, and the braking fluid BF is discharged from the first fluid pump QA. As a result, a circulating flow KN of the braking fluid BF is generated in the reflux path HK. Then, the pressure regulating valve UA is driven, and the circulating flow KN is throttled to generate the servo pressure Pu. In the driving of the first actuator YA, the pressure regulating valve UA is controlled by feedback control based on the supply pressure Pm so that the supply pressure Pm approaches the target pressure Pt.

[0074] ≪Processing of Complementary Control≫ Although the operation of the supply pressure sensor PM is normal, the pressure regulation control (that is, complementary control) when the supply pressure Pm is not normally received by the first braking unit SA will be described. The complementary control is executed to compensate for the excess or deficiency of the supply pressure Pm from the first braking unit SA. The processing of steps S190 and S200 by the second braking unit SB corresponds to the complementary control.

[0075] If the acquisition determination in step S140 is negative, then in step S180, the operation of the regeneration device KG is stopped. For example, "Fh = 0" or "FP = 1" is transmitted from the first controller EA to the regeneration controller EG, and in the regeneration device KG, the power generation by the generator GN is stopped. As a result, the regenerative braking force Fg is set to "0", and the regenerative cooperative control is terminated. Alternatively, if a communication abnormality occurs in the first braking unit SA, the operation stop signal is not transmitted, so the regeneration controller EG cannot acquire the target regenerative braking force Fh. Based on this, the regeneration controller EG identifies an abnormal state and stops the power generation by the generator GN. Therefore, if an acquisition abnormality of the supply pressure Pm occurs, the regenerative braking force Fg is set to "0", and the regenerative cooperative control is terminated. In step S180, since the operation of the regeneration device KG is stopped, the target frictional braking force Fn is made equal to the target vehicle body braking force Fv (i.e., "Fn = Fv").

[0076] In step S190, the target pressure Pt is acquired by the first and second controllers EA and EB. Here, the target pressure Pt of the first controller EA and the target pressure Pt of the second controller EB are determined as the same value. In step S190, since "Fh = 0, Fg = 0", the target frictional braking force Fn is equal to the target vehicle body braking force Fv (i.e., "Fn = Fv"). Therefore, the operation displacement Sp and the target frictional braking force Fn calculated according to the calculation map Zfv are converted into the target pressure Pt and determined based on the specifications of the braking device SX and the like. For example, the target pressure Pt is calculated in the same way based on the operation displacement Sp by each of the first and second controllers EA and EB. In the "same way", in a state where the regenerative braking force Fg is not generated, the same calculation map Zfv is adopted to calculate the target pressure Pt. However, the calculation map Zfv used by the first controller EA and the calculation map Zfv used by the second controller EB do not have to exactly match, and it is sufficient if they are approximate. Also, the target pressure Pt calculated by the first controller EA may be acquired by the second controller EB via the communication bus BS. Alternatively, the target pressure Pt calculated by the second controller EB may be acquired by the first controller EA via the communication bus BS.

[0077] When an acquisition abnormality occurs due to a disconnection of the communication line, the signal transmission of the first and second operation displacements Spa and Spb via the communication bus BS cannot be performed. In this situation, in the first controller EA, since the second operation displacement Spb cannot be acquired, the first operation displacement Spa is determined as the operation displacement Sp. Also, in the second controller EB, since the first operation displacement Spa cannot be acquired, the second operation displacement Spb is determined as the operation displacement Sp. If the operation displacement sensor SP is operating normally, the first operation displacement Spa and the second operation displacement Spb are substantially equal.

[0078] From the above, in step S190, the target pressure Pt is obtained (or calculated) by any of the above methods in both the first and second controllers EA and EB. That is, the respective target pressures Pt in the first and second controllers EA and EB are calculated using the same or approximate calculation maps as in the case of "Fh = 0" in normal control. Therefore, in any case, the target pressure Pt of the first braking unit SA and the target pressure Pt of the second braking unit SB are substantially equal values.

[0079] In step S190, based on the target pressure Pt, both the first actuator YA and the second actuator YB are driven. Specifically, the first actuator YA is controlled by the first controller EA in a method in which feedback control based on the supply pressure Pm from step S170 is omitted. A detailed description of the driving method of the first actuator YA will be omitted.

[0080] In step S200, based on the target pressure Pt and the supply pressure Pm, a deviation hP (referred to as "hydraulic pressure deviation") between the target pressure Pt and the supply pressure Pm is calculated. Specifically, the supply pressure Pm is subtracted from the target pressure Pt to determine the hydraulic pressure deviation hP (that is, "hP = Pt - Pm"). And in step S200, the second actuator YB is controlled by the second controller EB based on the hydraulic pressure deviation hP. The "hydraulic pressure deviation hP" is a state quantity representing the difference between the supply pressure (that is, the target pressure Pt) to be output from the first braking unit SA and the actually generated supply pressure Pm. Therefore, when the supply pressure Pm is smaller than the target pressure Pt and an increase in the supply pressure Pm is required (that is, when the hydraulic pressure deviation hP is greater than "0"), the hydraulic pressure deviation hP is a target value for compensating for the shortage of the supply pressure Pm and increasing the wheel pressure Pw. Also, when the supply pressure Pm is greater than the target pressure Pt and a decrease in the supply pressure Pm is required (that is, when the hydraulic pressure deviation hP is smaller than "0"), the hydraulic pressure deviation hP is a target value for compensating for the excessive supply pressure Pm and decreasing the wheel pressure Pw.

[0081] When the supply pressure Pm is smaller than the target pressure Pt and an increase in the wheel pressure Pw is required, the second electric motor MB and the control valve UB are driven. Specifically, the second electric motor MB is driven, and the braking fluid BF is discharged from the second fluid pump QB. As a result, a circulating flow KL of the braking fluid BF is generated in the communication path HS and the return path HL. When the hydraulic pressure deviation hP is equal to or greater than the pressure increase predetermined deviation hp, the supply pressure Pm is increased by the amount of the hydraulic pressure deviation hP by the control valve UB. Here, the "pressure increase predetermined deviation hp" is a preset positive predetermined value (constant). The adjustment to increase from the supply pressure Pm is called "pressure increase control" in the complementary control.

[0082] In the pressure increase control, the control valve UB is driven, and the circulating flow KL is throttled, thereby generating a hydraulic pressure difference between the upstream side and the downstream side of the control valve UB. As a result, the adjustment pressure Pq, which is the upstream side hydraulic pressure, is increased from the supply pressure Pm, which is the downstream side hydraulic pressure. That is, in the drive of the second actuator YB, the control valve UB is controlled so that the differential pressure between the adjustment pressure Pq and the supply pressure Pm (i.e., the hydraulic pressure "Pq - Pm") becomes the hydraulic pressure deviation hP. Since the adjustment pressure Pq is equal to the wheel pressure Pw, from the second actuator YB, a hydraulic pressure obtained by adding an actual hydraulic pressure corresponding to the hydraulic pressure deviation hP (target value) to the supply pressure Pm (actual value) is output as the wheel pressure Pw (actual value) (i.e., "Pw = Pm + hP"). In the pressure increase control, when the supply pressure Pm is smaller than the target pressure Pt, the control valve UB is appropriately driven, so that the wheel pressure Pw is increased by an amount corresponding to the hydraulic pressure deviation hP from the supply pressure Pm.

[0083] On one hand, when the supply pressure Pm is greater than the target pressure Pt and a decrease in the wheel pressure Pw is required, the second electric motor MB, the inlet valve VI, and the outlet valve VO are driven. Specifically, when the hydraulic pressure deviation hP is less than the decompression predetermined deviation hq, the supply pressure Pm is decreased by an amount corresponding to the hydraulic pressure deviation hP by the inlet valve VI and the outlet valve VO and output as the wheel pressure Pw (i.e., "Pw = Pm - hP"). Here, the "decompression predetermined deviation hq" is a preset negative constant value. The adjustment of decreasing from the supply pressure Pm is called "decompression control" in the complementary control. In the decompression control, when the supply pressure Pm is greater than the target pressure Pt, the inlet valve VI and the outlet valve VO are appropriately driven (for example, in the same driving method as the anti-lock brake control), and the wheel pressure Pw is decreased from the supply pressure Pm by the amount of the hydraulic pressure deviation hP. The second electric motor MB is driven to return the hydraulic fluid BF from the pressure regulating reservoir RB to the upper part of the control valve UB.

[0084] The configuration of the braking control device SC and the pressure regulating control are summarized. The braking control device SC is a brake-by-wire type device in which the operation of the braking operation member BP (brake pedal) and the hydraulic pressure of the wheel cylinder CW (wheel pressure Pw) can be controlled independently. Specifically, in the first braking unit SA, one of the first mode (by-wire mode) in which the master piston NM and the braking operation member BP are displaced separately by the input unit NR and the second mode (manual mode) in which the master piston NM and the braking operation member BP are displaced integrally is selected. Thereby, in the first mode, the operation displacement Sp and the supply pressure Pm are independent, and in the second mode, the operation displacement Sp and the supply pressure Pm are interlocked. Since the supply pressure Pm is supplied as the wheel pressure Pw, when the first mode is selected, the wheel pressure Pw is controlled independently of the operation of the braking operation member BP.

[0085] The first braking unit SA is provided with a master cylinder CM, a master chamber Rm partitioned by a master piston NM inserted into the master cylinder CM, and a servo chamber Ru. Then, when the servo pressure Pu supplied to the servo chamber Ru is increased, a supply pressure Pm is output from the master chamber Rm. When the entire device is normal, the first mode is selected in the first braking unit SA. Then, the servo pressure Pu is adjusted based on the operation displacement Sp and the supply pressure Pm. As a result, the supply pressure Pm is adjusted, and finally, the wheel pressure Pw is adjusted. Specifically, in the first braking unit SA, a target pressure Pt is calculated based on the operation displacement Sp, and the servo pressure Pu is adjusted so that the supply pressure Pm approaches and matches the target pressure Pt. That is, in the first braking unit SA, hydraulic feedback control is executed so that the output supply pressure Pm approaches the target pressure Pt calculated with the operation displacement Sp as an input.

[0086] The second braking unit SB is a general-purpose unit for performing individual wheel control such as anti-lock braking control and skid prevention control. Since information on the supply pressure Pm is essential for performing individual wheel control, the supply pressure sensor PM is built into the second actuator YB and directly connected to the second controller EB. Then, in the first controller EA, the supply pressure Pm is acquired through the communication bus BS in order to execute the above-mentioned hydraulic feedback control. Since one supply pressure sensor PM is shared for the hydraulic feedback control in the first braking unit SA and the individual wheel control in the second braking unit SB, the configuration is made simpler compared to a device in which a supply pressure sensor PM is provided for each of the first and second braking units SA and SB. That is, in the braking control device SC, hydraulic control including feedback control is executed, but its configuration is simplified.

[0087] Furthermore, in the brake control device SC, even if the supply pressure sensor PM is operating normally, if an acquisition abnormality of the supply pressure Pm occurs, in the first brake unit SA (particularly, the first controller EA), the information on the supply pressure Pm becomes unavailable. Therefore, in the first brake unit SA, open-loop control (i.e., feed-forward control) can be executed, but closed-loop control (i.e., feedback control) based on the supply pressure Pm cannot be executed. As a result, an error may occur between the target pressure Pt and the supply pressure Pm. For this reason, also in the second brake unit SB, based on the operation displacement Sp, the target pressure Pt is calculated, and the deviation hP between the target pressure Pt and the supply pressure Pm is determined. The hydraulic pressure deviation hP calculated in the second brake unit SB is equal to the hydraulic pressure error in the first brake unit SA. In other words, the hydraulic pressure deviation hP is a state quantity representing the excess or deficiency of the supply pressure Pm. Therefore, so that the hydraulic pressure error (i.e., excess or deficiency) of the supply pressure Pm is compensated, adjustment (increase or decrease) of the wheel pressure Pw is performed by the complementary control (i.e., pressure increase control and pressure decrease control) in the second brake unit SB. By the complementary control, the actual supply pressure Pm is compensated without excess or deficiency, so that the pressure regulation control is appropriately performed even during an acquisition abnormality. That is, in the brake control device SC, even if its operation is abnormal, the accuracy of the pressure regulation control is ensured by the complementary control. Note that even when the complementary control is executed, in the first brake unit SA, the first mode is selected.

[0088] In the complementary control in the second brake unit SB, the pressure decrease control may be omitted and only the pressure increase control may be executed. This is based on the fact that in the complementary control, it is most important to compensate for the decrease in the wheel pressure Pw. In addition, when the inlet valve VI and the outlet valve VO are operated, noise and vibration may occur. Therefore, by omitting the pressure decrease control, the quietness of the brake control device SC can be improved.

[0089] The brake control device SC employs a configuration in which one supply pressure sensor PM is incorporated in the second actuator YB (referred to as the "former configuration"), but the opposite configuration, in which the supply pressure sensor PM is incorporated in the first actuator YA (referred to as the "latter configuration"), is also possible. In the latter configuration, when performing complementary control, the second controller EB needs to acquire the supply pressure Pm from the first controller EA via the communication bus BS. However, the former configuration is more advantageous than the latter configuration in terms of functional distribution and fail-safe. For example, in the latter configuration, if a communication abnormality occurs, the second brake unit SB (particularly the second controller EB) cannot acquire the supply pressure Pm. As a result, complementary control based on the supply pressure Pm cannot be performed. Furthermore, the supply pressure Pm is required for the second brake unit SB to perform independent wheel control, but if the supply pressure Pm cannot be acquired, independent wheel control cannot be performed. Therefore, the former configuration is advantageous in terms of functional distribution, fail-safe, etc.

[0090] <Drive control of pressure regulating valve UA> The details of the drive control of the pressure regulating valve UA (particularly the processing of steps S170 and S200) will be described with reference to the block diagram of Figure 5. The drive control processing is executed by the first controller EA. The pressure regulating valve UA adjusts the servo pressure Pu, and ultimately the supply pressure Pm.

[0091] The drive control of the pressure regulating valve UA in step S170 (ie, the control when the brake control device SC is normal) is made up of a command current calculation block IS, a hydraulic pressure deviation calculation block HP, a compensation current calculation block IH, and a first current feedback control block IFA.

[0092] In the command current calculation block IS, a command current Isa is calculated based on a target pressure Pt and a preset calculation map Zis. The "command current Isa" is a target value related to the supply current Ia (first supply current) of the pressure regulating valve UA required to achieve the target pressure Pt. According to the calculation map Zis, it is determined that the command current Isa increases as the target pressure Pt increases. The command current calculation block IS corresponds to feedforward control based on the target pressure Pt.

[0093] In the hydraulic pressure deviation calculation block HP, a deviation hP (hydraulic pressure deviation) between the target pressure Pt and the supply pressure Pm is calculated. Specifically, the supply pressure Pm is subtracted from the target pressure Pt to determine the hydraulic pressure deviation hP (i.e., "hP = Pt - Pm").

[0094] In the compensation current calculation block IH, a compensation current Ih is calculated based on the hydraulic pressure deviation hP and a preset calculation map Zih. The command current Isa is calculated corresponding to the target pressure Pt, but there may be an error between the target pressure Pt and the supply pressure Pm. The "compensation current Ih" is for compensating (reducing) this error. The compensation current Ih is determined to increase as the hydraulic pressure deviation hP increases according to the calculation map Zih. Specifically, when the target pressure Pt is greater than the supply pressure Pm and the hydraulic pressure deviation hP has a positive sign, a positive-sign compensation current Ih is determined so that the command current Isa increases. On the other hand, when the target pressure Pt is less than the supply pressure Pm and the hydraulic pressure deviation hP has a negative sign, a negative-sign compensation current Ih is determined so that the command current Isa decreases. Here, a dead zone is provided in the calculation map Zih. Also, the compensation current calculation block IH corresponds to feedback control based on the supply pressure Pm.

[0095] For the indicated current Isa, a compensation current Ih is added, and a first target current Ita is calculated (i.e., "Ita = Isa + Ih"). The "first target current Ita" is the final target value of the current supplied to the pressure regulating valve UA. That is, the first target current Ita is determined as the sum of the feedforward term Isa and the feedback term Ih. Therefore, the drive control of the pressure regulating valve UA is constituted by feedforward control (processing of the indicated current calculation block IS) and feedback control (processing of the compensation current calculation block IH) in terms of hydraulic pressure.

[0096] In the first current feedback control block IFA, based on the first target current Ita (target value) and the first supply current Ia (actual value), a first drive signal Ua is calculated so that the first supply current Ia approaches and matches the first target current Ita. Here, the first supply current Ia is detected by a first supply current sensor IA provided in the first drive circuit DRa. In the first current feedback control block IFA, if "Ita > Ia", the first drive signal Ua is determined so that the first supply current Ia increases. On the other hand, if "Ita < Ia", the first drive signal Ua is determined so that the first supply current Ia decreases. That is, in the first current feedback control block IFA, feedback control related to current is executed. Therefore, in the drive control of the pressure regulating valve UA, in addition to the feedback control related to hydraulic pressure, feedback control related to current is provided.

[0097] When an acquisition abnormality occurs in the supply pressure Pm (i.e., the process of step S200), in the first controller EA, the indicated current Isa is calculated, but since the hydraulic pressure deviation hP cannot be calculated, the compensation current Ih is not calculated (i.e., "Ih = 0"). As a result, the indicated current Isa is determined as the target current Ita (i.e., "Ita = Isa"). During acquisition abnormality, in the drive control of the pressure regulating valve UA, feedback control based on the supply pressure Pm is not executed, and only feedforward control based on the target pressure Pt is executed.

[0098] <Drive Control of Control Valve UB> Referring to the block diagram of FIG. 6, the detailed drive control of the control valve UB in the complementary control (i.e., the process of step S200) will be described. The process of the complementary control is executed by the second controller EB. Before it is determined that there is an abnormality in obtaining the supply pressure Pm (i.e., when "FP = 0"), the operation of the second actuator YB is stopped. When the acquisition determination in step S140 is negated and an acquisition abnormality is determined (i.e., the switching point from "FP = 0" to "FP = 1"), the complementary control is started by the second actuator YB.

[0099] In the complementary control, the wheel pressure Pw is adjusted based on the hydraulic pressure deviation hP. The complementary control includes a pressure increasing control for increasing the wheel pressure Pw and a pressure decreasing control for decreasing the wheel pressure Pw. In the complementary control, a dead zone is provided in the range where "the hydraulic pressure deviation hP is larger than the pressure decreasing predetermined deviation hq (a preset negative constant) and smaller than the pressure increasing predetermined deviation hp (a preset positive constant)".

[0100] The drive control of the control valve UB in the complementary control is composed of a hydraulic pressure deviation calculation block HP, a second target current calculation block IBT, a second current feedback control block IFB, and a pressure decreasing control block PG.

[0101] In the hydraulic pressure deviation calculation block HP, the deviation hP between the target pressure Pt and the supply pressure Pm is calculated. The process of the hydraulic pressure deviation calculation block HP is the same as the process of the deviation calculation block HP of the first controller EA. Specifically, the supply pressure Pm is subtracted from the target pressure Pt calculated based on the operation displacement Sp, and the hydraulic pressure deviation hP is determined (i.e., "hP = Pt - Pm"). Here, the target pressure Pt is calculated by the second braking unit SB based on the same method as the calculation method of the target pressure Pt in the first braking unit SA. Specifically, the target pressure Pt is calculated based on an operation map (such as Zfv) that is the same as or approximate to the operation map adopted in the processes of steps S130 to S160 when "Fh = 0" or the process of step S190. In the complementary control, the hydraulic pressure deviation hP is treated as the target value of the differential pressure between the supply pressure Pm and the wheel pressure Pw.

[0102] When the supply pressure Pm is smaller than the target pressure Pt (specifically, when the hydraulic pressure deviation hP is greater than or equal to the predetermined pressure increase deviation hp and exceeds the dead zone of the supplementary control), the second target current calculation block IBT calculates the second target current Itb based on the hydraulic pressure deviation hP and a preset calculation map Zib. The "second target current Itb" is the target value related to the supply current Ib (second supply current) of the control valve UB, which is necessary to generate a differential pressure corresponding to the hydraulic pressure deviation hP by the control valve UB. The second target current Itb is determined to increase as the hydraulic pressure deviation hP increases according to the calculation map Zib. The processing of the second target current calculation block IBT is the same as the processing of the aforementioned command current calculation block IS (i.e., feedforward control based on hydraulic pressure).

[0103] In the second current feedback control block IFB, based on the second target current Itb (target value) and the second supply current Ib (actual value), the second drive signal Ub is calculated so that the second supply current Ib approaches and matches the second target current Itb. Here, the second supply current Ib is detected by the second supply current sensor IB provided in the second drive circuit DRb. In the second current feedback control block IFB, if "Itb > Ib", the second drive signal Ub is determined so that the second supply current Ib increases. On the other hand, if "Itb < Ib", the second drive signal Ub is determined so that the second supply current Ib decreases. In the second current feedback control block IFB, feedback control related to the current similar to that of the aforementioned first current feedback control block IFA is executed. The second target current calculation block IBT and the second current feedback control block IFB correspond to the processing of the pressure increase control.

[0104] When the supply pressure Pm is greater than the target pressure Pt (specifically, when the hydraulic pressure deviation hP is less than or equal to the predetermined decompression deviation hq and exceeds the dead zone of the complementary control), the inlet valve VI and the outlet valve VO are controlled by the pressure reduction control block PG. In the pressure reduction control block PG, the drive signals Vi and Vo of the inlet valve VI and the outlet valve VO are determined such that the supply pressure Pm is reduced by an amount corresponding to the hydraulic pressure deviation hP. The pressure reduction control block PG corresponds to the process of pressure reduction control.

[0105] Although the drive control of the control valve UB described above is open-loop control, it may be configured as closed-loop control including feedback control related to hydraulic pressure. In this configuration, a pressure adjustment sensor (not shown) is provided at the lower part of the control valve UB so as to detect the adjustment pressure Pq. Then, in the same manner as the above-described compensation current calculation block IH, the second target current Itb is finely adjusted based on the deviation between the supply pressure Pm and the adjustment pressure Pq.

[0106] <Configuration of two-system pressure regulation> In the above-described embodiment, in the normal state of the braking control device SC, the operation of the second actuator YB is stopped and only the first actuator YA is driven. In this case, since the front-wheel and rear-wheel supply pressures Pmf and Pmr (= Pm) are equal, the front-wheel and rear-wheel wheel pressures Pwf and Pwr (= Pw) are equal. Such pressure regulation control is called "one-system pressure regulation". In the configuration of one-system pressure regulation, in normal control, since the second actuator YB is not driven, the target pressure Ptm corresponding to the supply pressure Pm (referred to as the "target supply pressure") and the target pressure Ptw corresponding to the wheel pressure Pw (referred to as the "target wheel pressure") are the same (that is, "Pt = Ptm = Ptw").

[0107] Instead of the system pressure regulation configuration, when the braking control device SC is normal, in addition to the first actuator YA, the second actuator YB may be driven so that the front and rear wheel pressures Pwf and Pwr are adjusted separately. Specifically, the same supply pressures Pmf and Pmr (= Pm) are supplied from the first actuator YA to the second actuator YB. Then, by the second actuator YB, the wheel pressure on one side corresponding to the wheel equipped with the regeneration device KG (for example, the front wheel pressure Pwf) is adjusted to be lower than the wheel pressure on the other side corresponding to the wheel not equipped with the regeneration device KG (for example, the rear wheel pressure Pwr). By driving the second actuator YB, the pressure regulation control in which the front and rear wheel pressures Pwf and Pwr are independently and individually adjusted is called "two-system pressure regulation". In the regenerative coordination control, compared with the one-system pressure regulation, the two-system pressure regulation improves the regenerative efficiency and optimizes the braking force distribution between the front and rear wheels.

[0108] In the two-system pressure regulation configuration, since the second actuator YB is driven even in the normal state, the target pressure Ptm (target supply pressure) corresponding to the supply pressure Pm and the target pressure Ptw (target wheel pressure) corresponding to the wheel pressure Pw are different. Therefore, in the first actuator YA, feedforward control and feedback control are executed so that the supply pressure Pm (= Pmf, Pmr) approaches and matches the target supply pressure Ptm. Then, in the second actuator YB, feedforward control is executed based on the differential pressures hPf and hPr (referred to as "front and rear wheel target differential pressures") between the front and rear wheel target wheel pressures Ptwf and Ptwr and the target supply pressure Ptm (or the actual supply pressure Pm).

[0109] Even in the configuration of two-system pressure regulation, complementary control is applied. When acquisition abnormality is determined (i.e., when the determination flag FP is switched to "1"), the regenerative cooperative control is terminated and the generation of the regenerative braking force Fg is stopped. In the complementary control, the supply pressure Pm (actual value) is adjusted (increased or decreased) by the second actuator YB by an amount corresponding to the hydraulic pressure deviation hP (target value) so as to compensate for the excess or deficiency of the supply pressure Pm output from the first braking unit SA. Even in the configuration of two-system pressure regulation, as in the configuration of one-system pressure regulation, when acquisition abnormality occurs, the pressure regulation control is appropriately executed and the excess or deficiency of the supply pressure Pm from the first braking unit SA is compensated by an appropriate amount.

[0110] <Other Embodiments> Hereinafter, other embodiments will be described. Also in other embodiments, the same effects as above (simplification of the configuration, ensuring of the pressure regulation accuracy at the time of acquisition abnormality, etc.) are achieved.

[0111] In the above-described embodiment, the target values (Fv, Fx, Fh, Fn, etc.) of various braking forces are calculated in the dimension of the longitudinal and lateral forces acting on the vehicle JV. Instead, it may be calculated in the dimension of the deceleration of the vehicle JV or the torque of the wheel WH. This is based on the fact that the state quantities from the longitudinal and lateral forces to the vehicle deceleration (referred to as "state quantities related to force") are equivalent. Therefore, the target pressure Pt is calculated based on the state quantities related to force from the longitudinal and lateral forces acting on the vehicle JV to the vehicle deceleration.

[0112] In the above-described embodiment, a front-rear type is adopted as the two-system braking system. Instead, a diagonal type (also referred to as "X type") may be adopted as the two-system braking system. In this configuration, one of the two master chambers Pm is connected to the left front wheel cylinder and the right rear wheel cylinder, and the other of the two master chambers Pm is connected to the right front wheel cylinder and the left rear wheel cylinder. However, in the configuration adopting two-system pressure regulation, the braking system is limited to the front-rear type.

[0113] In the above-described embodiment, the pressure regulating unit CA is exemplified as one that adjusts the servo pressure Pu by throttling the circulating flow KN of brake fluid BF discharged by the fluid pump QA with the pressure regulating valve UA (a so-called reflux-type configuration). Alternatively, the pressure regulating unit CA may adjust the pressure accumulated in an accumulator with a linear solenoid valve (a so-called accumulator-type configuration). Furthermore, the servo pressure Pu may be adjusted by increasing or decreasing the volume inside a cylinder with a piston directly driven by an electric motor (a so-called electric cylinder-type configuration). Because the output of the electric motor is proportional to the supply current, feedforward control based on the target pressure Pt is possible, similar to the pressure regulating valve UA. In either configuration, the pressure regulating unit CA feeds back the supply pressure Pm as an output signal, electrically adjusting the hydraulic pressure Pu (servo pressure) in the servo chamber Ru.

[0114] In the above-described embodiment, a tandem type master cylinder CM is exemplified. However, a single type master cylinder CM may be employed instead. In this configuration, the secondary master piston NS is omitted. One master chamber Rm is connected to four wheel cylinders CW. In this configuration, the master cylinder CM outputs the same supply pressures Pmf and Pmr (=Pm).

[0115] In a configuration in which a single-type master cylinder CM is used, the master chamber Rm may be connected to the front wheel cylinder CWf, and the servo pressure Pu may be directly supplied from the pressure adjusting unit CA to the rear wheel cylinder CWr. In this configuration, the master cylinder CM outputs a front wheel supply pressure Pmf. Meanwhile, the pressure adjusting unit CA outputs the servo pressure Pu as a rear wheel supply pressure Pmr.

[0116] In the above-described embodiment, in the apply unit AP, the pressure-receiving area rm (master area) of the master chamber Rm and the pressure-receiving area ru (servo area) of the servo chamber Ru were set to be equal. The master area rm and the servo area ru do not have to be equal. In a configuration where the master area rm and the servo area ru are different, conversion calculation between the supply pressure Pm and the servo pressure Pu is possible based on the ratio between the servo area ru and the master area rm (i.e., conversion based on "Pm·rm = Pu·ru").

[0117] In the above-described embodiment, in the first braking unit SA, the supply pressure Pm was output via the master cylinder CM. That is, in the hydraulic transmission path, the apply unit AP and the pressure regulating unit CA were arranged in series, and the servo pressure Pu supplied from the pressure regulating unit CA was transmitted as the supply pressure Pm via the master piston NM. Instead of this, the apply unit AP and the pressure regulating unit CA may be arranged in parallel. Specifically, each of the apply unit AP (particularly, the master cylinder CM) and the pressure regulating unit CA is directly connected to the second actuator YB. Then, in the first mode, "the connection between the pressure regulating unit CA and the second actuator YB" is selected, and in the second mode, "the connection between the apply unit AP and the second actuator YB" is selected. For example, this selection is achieved by an on-off solenoid valve (referred to as a "switching valve"). In the first mode in this configuration, the servo pressure Pu generated in the pressure regulating unit CA is directly output as the supply pressure Pm 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 braking operation 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 the operation of the braking operation member BP is output as the supply pressure Pm. At this time, the apply unit AP is disconnected from the simulator SS.

[0118] In the above-described embodiment, the braking control device SC was applied to a vehicle JV not equipped with the regeneration device KG on the rear wheels WHr. The braking control device SC may also be applied to a vehicle JV equipped with the regeneration device KG on the rear wheels WHr.

[0119] <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.

[0120] The brake control device SC includes a first brake unit SA (first unit) that outputs a supply pressure Pm in response to an operation displacement Sp (operation amount) of a brake operating member BP, a second brake unit SB (second unit) that is provided between the first brake unit SA and the wheel cylinder CW and that adjusts the supply pressure Pm and outputs a wheel pressure Pw to the wheel cylinder CW, 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) that is connected to the first brake unit SA and detects the operation displacement Sp (operation amount), and a supply pressure sensor PM that is connected to the second brake unit SB and detects the supply pressure Pm. In the brake control device SC, the first brake unit SA calculates a target pressure Pt based on the operation displacement Sp, and acquires the supply pressure Pm from the second brake unit SB via the communication bus BS. The first brake unit SA then performs feedback control so that the supply pressure Pm coincides with the target pressure Pt.

[0121] The second brake unit SB (particularly the second actuator YB) includes a supply pressure sensor PM so that independent wheel control, such as anti-lock brake control and anti-skid control, can be performed. The first brake unit SA does not include a supply pressure sensor PM, and a signal of the supply pressure Pm is input via the communication bus BS. In the brake control device SC, one supply pressure sensor PM is shared for various controls, such as pressure regulation control and independent wheel control (anti-lock brake control, anti-skid control, etc.). This simplifies the overall configuration of the brake control device SC.

[0122] In the braking control device SC, the operation displacement sensor SP is connected not only to the first braking unit SA but also to the second braking unit SB. When the first braking unit SA cannot acquire the supply pressure Pm (specifically, when the supply pressure sensor PM is normal but the first braking unit SA cannot acquire the signal Pm from the supply pressure sensor PM), in the second braking unit SB, the target pressure Pt is calculated based on the operation displacement Sp. Then, the wheel pressure Pw is adjusted based on the deviation hP between the target pressure Pt and the supply pressure Pm. For example, in the second braking unit SB, when the supply pressure Pm is smaller than the target pressure Pt, the wheel pressure Pw is increased by an amount corresponding to the deviation hP.

[0123] The situation where the supply pressure sensor PM is operating normally but the supply pressure Pm cannot be acquired by the first braking unit SA is caused by an abnormality in the communication bus BS. When the supply pressure Pm cannot be acquired by the first braking unit SA, the above feedback control cannot be executed, and in the pressure regulation control, only the feedforward control is executed. Therefore, the supply pressure Pm output from the first braking unit SA may include an error with respect to the target pressure Pt.

[0124] In the braking control device SC, since the operation displacement sensor SP is connected to both the first and second braking units SA and SB, even if an abnormality occurs in the communication bus BS, the first and second braking units SA and SB can acquire the operation displacement Sp. Further, in the second braking unit SB, the target pressure Pt is calculated based on a method similar to the method for calculating the target pressure Pt in the first braking unit SA. For example, in the second braking unit SB, the target pressure Pt is calculated based on the same or an approximate calculation map as the calculation map of the first braking unit SA. Therefore, the target pressure Pt calculated by the second braking unit SB and the target pressure Pt calculated by the first braking unit SA are substantially the same. When the braking control device SC is normal (i.e., when there is no abnormality in acquiring the supply pressure Pm), the hydraulic pressure deviation hP calculated by the first braking unit SA is equal to the hydraulic pressure deviation hP calculated by the second braking unit SB. In other words, the hydraulic pressure deviation hP in the second braking unit SB represents the hydraulic pressure error caused by the non-execution of feedback control. Therefore, in the second braking unit SB, based on this hydraulic pressure deviation hP, an appropriate amount is increased or decreased with respect to the supply pressure Pm and output as the wheel pressure Pw. As a result, even when the braking control device SC is malfunctioning and the supply pressure Pm cannot be acquired by the first braking unit SA, the accuracy of hydraulic pressure control is ensured.

[0125] In particular, in a situation where a sufficient supply pressure Pm is not generated, there is a concern about insufficient deceleration of the vehicle JV. In the braking control device SC, when the supply pressure Pm is smaller than the target pressure Pt, the wheel pressure Pw is increased from the supply pressure Pm by a pressure corresponding to the hydraulic pressure deviation hP. As a result, an appropriate wheel pressure Pw is ensured, so that in the vehicle JV, deceleration according to the driver's braking instruction (i.e., the operation displacement Sp) is achieved. The braking control device SC is configured to ensure the pressure regulation accuracy of the wheel pressure Pw even when the supply pressure Pm cannot be acquired, and the configuration is simple.

Description of Reference Signs

[0126] SC…Brake control device, KG…Regenerative device, BP…Brake operation member (brake pedal), SA…First brake unit (first unit), SB…Second brake 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 part, NR…Input part, CA…Pressure regulating part, UA…Pressure regulating valve, UB…Control valve, MA, MB…First, second electric motors, QA, QB…First, second fluid pumps, VA…Introduction valve, VB…Release valve, SP…Operation displacement sensor (operation amount sensor), PM…Supply pressure sensor, Sp, Spa, Spb…Operation displacement (operation amount), Pm…Supply pressure, Pu…Servo pressure, Pq…Adjustment pressure, Pw…Wheel pressure, Pt…Target pressure (target value corresponding to Pm), hP…Hydraulic pressure deviation (hydraulic pressure difference between Pt and Pm), FP…Acquisition flag (judgment result of step S140).

Claims

【Claim 1】 A first unit that outputs a supply pressure according to the operation amount of a braking operation member; A second unit provided between the first unit and a wheel cylinder, which adjusts the supply pressure and outputs a wheel pressure to the wheel cylinder; A communication bus for signal transmission between the first unit and the second unit; An operation amount sensor connected to the first unit for detecting the operation amount; A supply pressure sensor connected to the second unit for detecting the supply pressure; In a braking control device for a vehicle comprising: The supply pressure detected by the supply pressure sensor is a supply pressure detection value; The operation amount sensor is also connected to the second unit; ​ ​ ​ ​ ​ ​ ​

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