Vehicle braking control device

Abstract

To provide a brake control device for a vehicle that is composed of two control devices connected to each other by communication, which can appropriately perform pressure regulation control at the time of communication abnormality.SOLUTION: A brake control device 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 for detecting the operation amount, and a supply pressure sensor for detecting the supply pressure. In the brake control device, when the signal transmission is abnormal, the second unit calculates a target pressure on the basis of the operation amount, and adjusts the wheel pressure on the basis of a deviation between the target pressure and the supply pressure.SELECTED DRAWING: Figure 4

Description

[Technical Field]

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

[0002] Patent Document 1 describes that, with the aim of "fully demonstrating the function of increasing brake fluid pressure even when a communication abnormality occurs in the operation of the VSA device regarding the operating state information of the VSA device," "vehicle braking system 10 comprises ESB device 16 that generates brake fluid pressure by operating brake motor 72, VSA device 18 that adjusts the brake fluid pressure by operating pump motor 135, CAN communication medium 33 used when communicating operating state information regarding VSA device 18 to ESB device 16, and first braking control unit 77 that performs pressurization control to increase the brake fluid pressure in the fluid supply flow path to VSA device 18 by operating brake motor 72 when ESB device 16 receives operation in-progress information indicating that VSA device 18 is operating via CAN communication medium 33. First braking control unit 77 continues to perform the pressurization control even when it recognizes that a communication abnormality has occurred in the operation state information."

[0003] In the device of Patent Document 1, if a communication abnormality occurs while the ESB device (also referred to as the "first brake unit") is receiving information from the VSA device (also referred to as the "second brake unit") via communication that the VSA device is operating, the ESB device continues to increase the brake fluid pressure. That is, the device of Patent Document 1 anticipates a situation in which a communication abnormality occurs while operation information of the second brake unit is being transmitted to the first brake unit. Therefore, the first brake unit can determine that the second brake unit is operating. However, once the operation of the first and second brake units is terminated, the operation status of the first and second brake units cannot be determined in the event of a communication abnormality. Therefore, it is desirable for a vehicle brake control device to be able to properly perform brake control when a communication abnormality occurs and it becomes impossible to determine each other's operation status. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-147614 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a vehicle brake control device that is configured with two brake units connected by communication, and that is capable of appropriately performing pressure regulation control even when communication abnormality occurs. [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 accordance with 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) that detects the operation amount (Sp), and a supply pressure sensor (PM) that detects the supply pressure (Pm).

[0007] In the vehicle brake control device (SC) according to the present invention, when there is an abnormality in the signal transmission, the second unit (SB) calculates a target pressure (Pt) based on the manipulated variable (Sp) and adjusts the wheel pressure (Pw) based on a 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 equivalent to the deviation (hP).

[0008] If there is an abnormality in signal transmission between the two brake units SA and SB, their operating conditions cannot be determined from each other. According to the above configuration, the second brake unit SB calculates the target pressure Pt and determines the hydraulic pressure deviation hP. The wheel pressure Pw is then adjusted based on the hydraulic pressure deviation hP. The hydraulic pressure deviation hP calculated by the second brake unit SB is a state quantity that represents the deviation between the target value of the supply pressure under normal conditions (i.e., the target pressure Pt) and the actual supply pressure Pm. By adjusting based on the hydraulic pressure deviation hP, pressure regulation control is performed appropriately even when the operating condition of the first brake unit SA cannot be determined. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic diagram illustrating an entire vehicle JV equipped with a braking control device SC. [Figure 2] 3 is a schematic diagram for explaining a configuration example of a first braking unit SA. FIG. [Figure 3] 4 is a schematic diagram for explaining a configuration example of a second braking unit SB. FIG. [Figure 4] FIG. 4 is a flowchart illustrating a pressure regulation control process. [Figure 5] FIG. 4 is a block diagram for explaining drive control of a pressure regulating valve UA. [Figure 6] FIG. 3 is a block diagram for explaining drive control of a control valve UB. DETAILED DESCRIPTION OF THE INVENTION

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

[0011] 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."

[0012] 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.

[0013] <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.

[0014] 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."

[0015] 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).

[0016] The operation displacement sensor SP (corresponding to an "operation amount sensor") includes two detection units SPa and SPb (referred to as "first and second detection units"). That is, the operation displacement Sp is detected in two ways, making the operation displacement sensor SP redundant. The first detection unit SPa (referred to as "first displacement detection unit") of the operation displacement sensor SP is connected to the first braking unit SA (particularly, the first control unit EA) by a first displacement signal line LSpa. On the other hand, the second detection unit SPb (referred to as "second displacement detection unit") of the operation displacement sensor SP is connected to the second braking unit SB (particularly, the second control unit EB) by a second displacement signal line LSpb. Therefore, the signal Spa (referred to as "first operation displacement") of the first displacement detection unit SPa is directly input to the first control unit EA. On the other hand, the signal Spb (referred to as "second operation displacement") of the second displacement detection unit SPb is directly input to the second control unit EB. For example, "signal lines LSpa, LSpb" are electric wires (wire harnesses) for transmitting signals.

[0017] In addition to the operation displacement sensor SP, the hydraulic pressure Ps (referred to as "simulator pressure") of the stroke simulator SS is adopted as another state quantity representing the braking operation amount. The simulator pressure Ps is detected by a simulator pressure sensor PS. The simulator pressure sensor PS is connected to the first brake unit SA (particularly, the first control unit EA) by a simulator pressure signal line LPs. Therefore, the simulator pressure Ps is directly input to the first control unit EA. The simulator pressure Ps is a state quantity equivalent to the operating force of the brake operating member BP.

[0018] The vehicle JV is equipped with various sensors. For braking control (referred to as "independent wheel control") that individually controls the wheel pressure Pw of each wheel WH, such as antilock brake control and anti-skid control, each wheel WH is equipped with a wheel speed sensor VW that detects its rotational speed (wheel speed) Vw. The vehicle JV is also equipped with a steering amount sensor that detects the steering amount Sa (e.g., the steering wheel angle), a yaw rate sensor that detects the vehicle's yaw rate Yr, a longitudinal acceleration sensor that detects the vehicle's longitudinal acceleration Gx, and a lateral acceleration sensor that detects the vehicle's lateral acceleration Gy (all not shown). The signals for the wheel speed Vw, steering amount Sa, yaw rate Yr, longitudinal acceleration Gx, and lateral acceleration Gy are input to the second braking unit SB (particularly, the second control unit EB) via their respective signal lines.

[0019] The vehicle JV is equipped with a brake control device SC. The brake control device SC employs a so-called front and rear type (also called "type II") brake system as two brake systems. The brake control device SC adjusts the actual wheel pressure Pw.

[0020] The brake control device SC is composed of two brake units SA and SB. The first brake unit SA is composed of a first fluid unit YA and a first control unit EA. The first fluid unit YA is controlled by the first control unit EA using a storage battery BT (braking storage battery) separate from the drive storage battery BG as its power source. The second brake unit SB is composed of a second fluid unit YB and a second control unit EB. Like the first brake unit SA, the second fluid unit YB is controlled by the second control unit EB using the storage battery BT as its power source.

[0021] The first brake unit SA (particularly, the first control unit EA) and the second brake unit SB (particularly, the second control unit EB) are connected to a communication bus BS. The regenerative device KG (particularly, the regenerative control unit EG) is also connected to the communication bus BS. The "communication bus BS" has a network structure in which multiple control units (also called "controllers") hang from communication lines terminated at both ends. Signals are transmitted between the multiple controllers (EA, EB, EG, etc.) via the communication bus BS. That is, the multiple controllers can transmit signals (detected values, calculated values, control flags, etc.) to the communication bus BS and can receive signals from the communication bus BS. For example, a vehicle bus (an internal communication network that interconnects controllers within a vehicle) is used as the communication bus BS, and CAN is used as the serial communication protocol. The communication bus BS is composed of communication lines (e.g., CAN bus cables) and transmitting / receiving microcontrollers in each controller.

[0022] <First braking unit SA> An example of the configuration of the first brake unit SA (corresponding to the "first unit") of the brake control device SC will be described with reference to the schematic diagram of FIG. 2. The first brake unit SA generates a supply pressure Pm in response to operation of the brake operating member BP (brake pedal). The supply pressure Pm is ultimately supplied to the wheel cylinder CW via a communication path HS (fluid path) and a second brake unit SB. The first brake unit SA is made up of a first fluid unit YA and a first control unit EA.

[0023] <First fluid unit YA> The first fluid unit YA (also referred to as the "first actuator") is composed of an apply part AP, a pressure adjustment part CA, and an input part NR.

[0024] [Apply Department AP] In response to operation of the brake operating member BP, a supply pressure Pm is output from the apply section AP, which is composed of a tandem master cylinder CM and primary and secondary master pistons NM and NS.

[0025] Primary and secondary master pistons NM and NS are inserted into the tandem master cylinder CM. The interior of the master cylinder CM is divided into four hydraulic chambers Rmf, Rmr, Ru, and Rs by the two master pistons NM and NS. The front and rear wheel master chambers Rmf and Rmr (= Rm) are divided by the bottom of one side of the master cylinder CM and the master pistons NM and NS. The interior of the master cylinder CM is further divided into a servo chamber Ru and a reaction chamber Rs by the flange Tu of the master piston NM. The master chamber Rm and the servo chamber Ru are arranged opposite each other with the flange 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.

[0026] When braking is not in progress, the master pistons NM and NS are in their most retracted position (i.e., the position where the volume of the master chamber Rm is maximum). In this state, the master chamber Rm of the master cylinder CM is in communication with the master reservoir RV. Brake fluid BF is stored inside the master reservoir RV (an atmospheric pressure reservoir, also simply referred to as the "reservoir"). When the brake operating member BP is operated, the master pistons NM and NS are moved forward in the Ha direction (a direction in which the volume of the master chamber Rm decreases). This movement blocks communication between the master chamber Rm and the reservoir RV. When the master pistons NM and NS are further moved forward in the Ha direction, the front and rear wheel supply pressures Pmf and Pmr (= Pm) are increased from "0 (atmospheric pressure)." As a result, brake fluid BF pressurized to the supply pressure Pm is output (pressurized and fed) from the master chamber Rm of the master cylinder CM. The supply pressure Pm is the hydraulic pressure in the master chamber Rm, and is therefore also called the "master pressure."

[0027] [Pressure Regulating Unit CA] A servo pressure Pu is supplied to the servo chamber Ru of the apply unit AP by a pressure adjusting unit CA, which is composed of a first electric motor MA, a first fluid pump QA, and a pressure adjusting valve UA.

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

[0029] A normally open pressure regulating valve UA is provided in the return path HK. The pressure regulating valve UA is a linear solenoid valve whose opening amount is continuously controlled based on the energization state (e.g., supply current). The pressure regulating valve UA adjusts the hydraulic pressure difference (differential pressure) between its upstream and downstream sides, so it is also called a "differential pressure valve."

[0030] When the first fluid pump QA discharges brake fluid BF, a circulating flow KN (indicated by the dashed arrow) of brake fluid BF is generated in the return path HK. When the pressure regulating valve UA is fully open (when not energized, since the pressure regulating valve UA is normally open), the fluid pressure Pu (referred to as "servo pressure") between the discharge port of the first fluid pump QA and the pressure regulating valve UA in the return path HK is "0 (atmospheric pressure)." When the amount of electricity (supply current) to the pressure regulating valve UA is increased, the pressure regulating valve UA throttles the circulating flow KN (the flow of brake fluid BF circulating in the return path HK). In other words, the pressure regulating valve UA narrows the flow path of the return path HK, thereby exerting an orifice effect. As a result, the fluid pressure Pu upstream of the pressure regulating valve UA increases from "0." That is, in the circulating flow KN, a hydraulic pressure difference (differential pressure) is generated between the hydraulic pressure Pu (servo pressure) on the upstream side and the hydraulic pressure (atmospheric pressure) on the downstream side with respect to the pressure regulating valve UA. This differential pressure is adjusted by the amount of current supplied to the pressure regulating valve UA.

[0031] The return path HK is connected to the servo chamber Ru via a servo path HV (fluid path) at a location between the discharge port of the first fluid pump QA and the pressure regulating valve UA. Therefore, the servo pressure Pu is introduced (supplied) to the servo chamber Ru. As the servo pressure Pu increases, the master pistons NM and NS are pressed forward Ha (in the direction in which the volume of the master chamber Rm decreases), and the hydraulic pressures Pmf and Pmr (front and rear wheel supply pressures) in the front and rear master chambers Rmf and Rmr increase.

[0032] The front and rear wheel master chambers Rmf and Rmr (=Rm) are connected to the front and rear wheel communication passages HSf and HSR (=HS). The front and rear wheel communication passages HSf and HSR are connected to the front and rear wheel cylinders CWf and CWr (=CW) via the second brake unit SB (particularly, the second fluid unit YB). Therefore, the front and rear wheel supply pressures Pmf and Pmr are supplied from the first brake unit SA to the front and rear 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").

[0033] [Input NR] The input unit NR operates the brake operating member BP to realize regenerative cooperative control, but creates a state in which wheel pressure Pw is not generated. "Regenerative cooperative control" coordinates the friction braking force Fm (braking force due to wheel pressure Pw) and the regenerative braking force Fg (braking force due to generator GN) so that the kinetic energy of the vehicle JV can be efficiently recovered as electrical energy during braking. The input unit NR is composed of an input cylinder CN, an input piston NN, an intake valve VA, an open valve VB, a stroke simulator SS, and a simulator hydraulic pressure sensor PS.

[0034] The input cylinder CN is fixed to the master cylinder CM. An input piston NN is inserted into the input cylinder CN. The input piston NN is mechanically connected to the brake operating member BP (brake pedal) via a clevis (U-shaped link) so that it moves in conjunction with the brake operating member BP. There is a gap Ks (also called "separation displacement") between the end face of the input piston NN and the end face of the primary piston NM. Regenerative cooperative control is achieved by adjusting the separation distance Ks using the servo pressure Pu.

[0035] The input chamber Rn of the input unit NR is connected to the reaction chamber Rs of the apply unit AP via an input path HN (fluid path). A normally closed inlet valve VA is provided in the input path HN. The input path HN is connected to the master reservoir RV via a reservoir path HR between the inlet valve VA and the reaction chamber Rs. A normally open release valve VB is provided in the reservoir path HR. The inlet valve VA and the release valve VB are on-off solenoid valves. A stroke simulator SS (also simply referred to as "simulator") is connected to the input path HN between the inlet valve VA and the reaction chamber Rs.

[0036] When power is not supplied to the introduction valve VA and the release valve VB, the introduction valve VA is closed and the release valve VB is open. When the introduction valve VA is closed, the input chamber Rn is sealed and fluid locked. As a result, the master pistons NM and NS are displaced integrally with the brake operating member BP. When the release valve VB is open, the simulator SS is connected to the master reservoir RV. When power is supplied to the introduction valve VA and the release valve VB, the introduction valve VA is opened and the release valve VB is closed. As a result, the master pistons NM and NS can be displaced separately from the brake operating member BP. At this time, the input chamber Rn is connected to the stroke simulator SS, and the operating force Fp of the brake operating member BP is generated by the simulator SS.

[0037] 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.

[0038] 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.

[0039] <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.).

[0040] The first controller EA and the first detection unit SPa of the operation displacement sensor SP are connected via a signal line LSpa for the first detection unit SPa. The first controller EA and the simulator pressure sensor PS are connected via a signal line LPs 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 LSpa and LPs.

[0041] The first controller EA (particularly, the first microprocessor MPa) is programmed with a pressure regulation control algorithm. "Pressure regulation control" is a control for adjusting the supply pressure Pm (and consequently the wheel pressure Pw), and includes regenerative cooperative control. The pressure regulation control is performed based on the first and second operation displacements Spa and Spb, the simulator pressure Ps, the supply pressure Pm, and the maximum regenerative braking force Fx.

[0042] The first drive circuit DRa drives the first electric motor MA constituting the first actuator YA and various solenoid valves (UA, etc.) based on a pressure regulation control algorithm. The first drive circuit DRa includes an H-bridge circuit configured with switching elements (e.g., MOS-FETs) to drive the first electric motor MA. The first drive circuit DRa also includes switching elements to drive the various solenoid valves (UA, etc.). Additionally, the first drive circuit DRa includes a motor current sensor (not shown) that detects the supply current Im (actual value) to the first electric motor MA, and a first current sensor (not shown) that detects the supply current Ia (actual value, referred to as the "first supply current") to the pressure regulation valve UA. The first electric motor MA is provided with a rotation speed sensor (not shown) that detects its rotation speed Na (actual value). The first electric motor MA may also be provided with a rotation angle sensor (not shown) that detects the rotation angle Ka (actual value), and the motor rotation speed Na may be calculated based on the motor rotation angle Ka.

[0043] The first controller EA calculates a first target current Ita (target value) corresponding to the first supply current Ia based on the operation displacement Sp (operation amount). The first supply current Ia is then controlled so as to approach and match the first target current Ita (so-called current feedback control). The first controller EA also calculates a target rotation speed Nta (target value) corresponding to the actual rotation speed Na based on the operation displacement Sp. The motor supply current Im is then 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 the various solenoid valves UA, VA, VB are calculated. The switching elements of the first drive circuit DRa are then driven in response to the drive signals (Ma, etc.), thereby controlling the first electric motor MA and the solenoid valves UA, VA, VB.

[0044] <Second braking unit SB> An example of the configuration of the second braking unit SB (corresponding to the "second unit") of the braking control device SC will be described with reference to the schematic diagram in Figure 3. The second braking unit SB is a general-purpose unit (device) for performing independent control of each wheel, such as anti-lock brake control, traction control, and anti-skid control. In addition, the second braking unit SB performs complementary control. The "complementary control" compensates for any excess or deficiency in the supply pressure Pm caused by an abnormality in the first braking unit SA.

[0045] The second brake unit SB is supplied with front and rear wheel supply pressures Pmf and Pmr (=Pm) from the first brake unit SA. The second brake unit SB then adjusts (increases or decreases) the front and rear wheel supply pressures Pmf and Pmr and outputs them as hydraulic pressures Pwf and Pwr (front and rear wheel pressures) for the front and rear wheel cylinders CWf and CWr. The second brake unit SB is composed of a second fluid unit YB and a second control unit EB.

[0046] <Second fluid unit YB> The second fluid unit YB (also referred to as the "second actuator") is provided in the communication passage HS between the first actuator YA and the wheel cylinder CW. 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.

[0047] Front and rear wheel control valves UBf and UBr (=UB) are provided in the front and rear wheel communication passages HSf and HSR (=HS). The control valves UB are normally open linear solenoid valves (differential pressure valves) like the pressure regulating valve UA. The control valves UB allow the wheel pressure Pw to be increased individually from the supply pressure Pm in the front and rear wheel systems.

[0048] Front and rear wheel supply pressure sensors PMf, PMr (=PM) are provided above the front and rear wheel control valves UBf, UBr (at the portion of the communication passage HS closer to the first actuator YA) to detect actual hydraulic pressures Pmf, Pmr (front and rear wheel supply pressures) supplied from the first actuator YA (particularly, front and rear wheel master chambers Rmf, Rmr). The supply pressure sensor PM is also referred to as a "master pressure sensor" and is built into the second actuator YB. The front and rear wheel supply pressure sensors PMf, PMr are connected to the second brake unit SB (particularly, the second control unit EB) by front and rear wheel supply pressure signal lines LPmf, LPmr (=LPm). In other words, the signals of the front 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 and rear wheel supply pressure sensors PMf and PMr may be omitted. For example, in a configuration in which 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 input directly to the second control unit EB.

[0049] The front and rear wheel return paths HLf, HLr (=HL) connect the upper portions of the front and rear wheel control valves UBf, UBr (portions of the communication paths HS closer to the first actuator YA) with the lower portions of the front and rear wheel control valves UBf, UBr (portions of the communication paths HS closer to the wheel cylinders CW). The front and rear wheel return paths HLf, HLr are provided with front and rear wheel fluid pumps QBf, QBr (=QB) and front and rear wheel pressure regulating reservoirs RBf, RBr (=RB). The second fluid pump QB is driven by a second electric motor MB.

[0050] When the second electric motor MB is driven, the second fluid pump QB draws brake fluid BF from the top of the control valve UB and discharges it to the bottom of the control valve UB. As a result, a circulating flow KL of brake fluid BF (i.e., front and rear wheel circulating flows KLf and KLr, indicated by dashed arrows) containing the pressure regulating reservoir RB is generated in the communication line HS and the return line HL. When the control valve UB narrows the flow path of the communication line HS and throttles the circulating flow KL of brake fluid BF, the resulting orifice effect increases the hydraulic pressure Pq (referred to as the "regulating pressure") below the control valve UB from the hydraulic pressure Pm (supply pressure) above the control valve UB. In other words, the hydraulic pressure difference (differential pressure) between the hydraulic pressure Pm (supply pressure) downstream of the control valve UB and the hydraulic pressure Pq (regulating pressure) upstream of the control valve UB is adjusted by the control valve UB. In terms of the magnitude relationship between the supply pressure Pm and the adjustment pressure Pq, the adjustment pressure Pq is equal to or greater than the supply pressure Pm (i.e., "Pq≧Pm"). As described above, the mechanism by which the adjustment pressure Pq is generated in the second actuator YB is the same as the mechanism by which the servo pressure Pu is generated in the first actuator YA.

[0051] Inside the second actuator YB, the front and rear wheel communication passages HSf and HSR are each branched into two passages connected to the front and rear wheel cylinders CWf and CWr. A normally-open inlet valve VI and a normally-closed outlet valve VO are provided for each wheel cylinder CW so that each wheel pressure Pw can be individually adjusted. Specifically, the inlet valve VI is provided in the branched communication passage HS (i.e., on the side of the communication passage HS closer to the wheel cylinder CW). The communication passage HS is connected to the pressure-regulating reservoir RB via a pressure-reducing passage HG below the inlet valve VI (the portion of the communication passage HS closer to the wheel cylinder CW). An outlet valve VO is provided in the pressure-reducing passage HG. The inlet valve VI and the outlet valve VO are on-off solenoid valves. The inlet valve VI and the outlet valve VO allow the wheel pressure Pw to be individually reduced from the supply pressure Pm at each wheel.

[0052] When the inlet valve VI and the outlet valve VO are not energized and are deactivated, the inlet valve VI is open and the outlet valve VO is closed. In this state, the wheel pressure Pw is equal to the regulated pressure Pq. The wheel pressure Pw is independently adjusted for each wheel cylinder CW by operating the inlet valve VI and the outlet valve VO. To decrease the wheel pressure Pw, the inlet valve VI is closed and the outlet valve VO is opened. This prevents brake fluid BF from flowing into the wheel cylinder CW and causes the brake fluid BF in the wheel cylinder CW to flow out to the pressure regulating reservoir RB, thereby decreasing the wheel pressure Pw. To increase the wheel pressure Pw (up to the regulated pressure Pq), the inlet valve VI is opened and the outlet valve VO is closed. The brake fluid BF is prevented from flowing out to the pressure regulating reservoir RB, and the regulated pressure Pq from the pressure regulating valve UB is supplied to the wheel cylinder CW, increasing the wheel pressure Pw. To maintain the wheel pressure Pw, both the inlet valve VI and the outlet valve VO are closed. Since the wheel cylinder CW is fluidly sealed, the wheel pressure Pw is maintained constant.

[0053] <Second control unit EB> The second actuator YB is controlled by a second control unit EB (also referred to as a "second controller"). Similar to the first controller EA, the second controller EB is composed of a second microprocessor MPb and a second drive circuit DRb. The second controller EB is connected to a communication bus BS. Therefore, the first controller EA and the second controller EB can share signals via the communication bus BS.

[0054] The second controller EB (particularly, the second microprocessor MPb) receives inputs of the wheel speed Vw, steering amount Sa, yaw rate Yr, longitudinal acceleration Gx, and lateral acceleration Gy. The second controller EB calculates the vehicle speed Vx based on the wheel speed Vw. The second controller EB executes the following independent controls for each wheel. Specifically, the independent controls for each wheel include antilock brake control (so-called ABS control) that suppresses locking of the wheels WH, traction control that suppresses spin of the drive wheels, and anti-skid control (so-called ESC) that suppresses understeer and oversteer to improve the directional stability of the vehicle.

[0055] The second drive circuit DRb drives the second electric motor MB constituting the second actuator YB and various solenoid valves (UB, etc.) in accordance with a control algorithm programmed in the second microprocessor MPb. The second drive circuit DRb includes an H-bridge circuit configured with switching elements (e.g., MOS-FETs) to drive the second electric motor MB. The second drive circuit DRb also includes switching elements to drive the various solenoid valves (UB, etc.). In addition, the second drive circuit DRb includes a motor current sensor (not shown) that detects the supply current In (actual value) to the second electric motor MB, and a second current sensor (not shown) that detects the supply current Ib (actual value, referred to as the "second supply current") to the control valve UB. Based on the control algorithm of the second microprocessor MPb, a drive signal Ub for the control valve UB, a drive signal Vi for the inlet valve VI, a drive signal Vo for the outlet valve VO, and a drive signal Mb for the second electric motor MB are calculated. Then, based on the drive signal (Ub, etc.), the second electric motor MB and the solenoid valves UB, VI, and VO are controlled by the second drive circuit DRb.

[0056] 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. Furthermore, the second controller EB and the supply pressure sensor PM are connected via a signal line LPm (e.g., a signal pin) for the supply pressure sensor PM. Therefore, the second operation displacement Spb is directly input to the second controller EB via the signal line LSpb, and the supply pressure Pm is directly input to the second controller EB via the signal line LPm. The second operation displacement Spb and the supply pressure Pm are then transmitted from the second controller EB to the first controller EA via the communication bus BS. In other words, the first controller EA acquires the second operation displacement Spb and the supply pressure Pm from the second controller EB via the communication bus.

[0057] In addition to the independent control of each wheel, the second controller EB also performs complementary control to deal with abnormalities in the brake control device SC. In the complementary control, the performance degradation of the first brake unit SA is compensated for by the second brake unit SB.

[0058] <Pressure regulation control processing> An example of the voltage regulation control process will be described with reference to Figures 4 to 6. The voltage regulation control includes not only regenerative cooperative control but also complementary control to deal with abnormalities in the communication bus BS (also called "communication abnormalities"). The communication bus BS is composed of a communication line (for example, a CAN bus cable) and communication microcontrollers in the first and second controllers EA and EB. A communication abnormality occurs due to a break in the communication line, a failure in the communication microcontrollers in the first and second controllers EA and EB, etc.

[0059] If a communication abnormality occurs between the first and second brake units SA and SB (particularly the first and second controllers EA and EB), the second brake unit SB will be unable to grasp the operating state of the first brake unit SA. For example, if the communication abnormality is caused by a failure in the communication line, the first brake unit SA will be unable to perform closed-loop control (i.e., feedback control) based on the supply pressure Pm, but will be able to perform open-loop control (i.e., feedforward control). On the other hand, if the communication abnormality is caused by a failure in the first controller EA and the first brake unit SA loses all its function, the supply pressure Pm will be generated solely by the driver's muscle force. Complementary control is used to address this situation. Below, we will explain the pressure regulation control in the first brake unit SA and the pressure regulation control in the second brake unit SB separately. The pressure regulation control algorithm is programmed in the microprocessors MPa and MPb of the first and second controllers EA and EB, respectively.

[0060] In describing the example process, the following assumptions are made: The regenerative device KG is provided only on the front wheels WHf, so that the regenerative braking force Fg acts on the front wheels WHf but not on the rear wheels WHr. 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 is 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 via 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 used as the signal of the supply pressure Pm.

[0061] The various braking forces are as follows: - "Vehicle body total braking force Fu" is the actual braking force acting on the entire vehicle JV. A target value corresponding to the vehicle body total braking force Fu is "target vehicle body position force Fv." - "Friction braking force Fm" is the braking force that is actually generated according to the wheel pressure Pw. A target value corresponding to the friction braking force Fm is "target friction braking force Fn." - "Regenerative braking force Fg" is the braking force actually generated by the regenerative device KG. A target value corresponding to the regenerative braking force Fg is "target regenerative braking force Fh." The target regenerative braking force Fh is calculated by the first braking unit SA (particularly, the first controller) and transmitted to the regenerative device KG (particularly, the regenerative controller EG) via the communication bus BS. In the regenerative device KG, the regenerative controller EG controls the generator GN so that the actual regenerative braking force Fg approaches and matches the target regenerative braking force Fh. The "limit regenerative braking force Fx" is the maximum value (limit value) of the regenerative braking force Fg that can be generated by the regenerative device KG. Therefore, the regenerative device KG generates a regenerative braking force Fg within a range (limit) up to the limit regenerative braking force Fx. The limit regenerative braking force Fx is calculated by the regenerative device KG (particularly, the regenerative controller EG) and transmitted to the first braking unit SA (particularly, the first controller EA) via the communication bus BS.

[0062] <Pressure regulation control flow> The overall voltage regulation control will be described with reference to the flow chart in Figure 4. The voltage regulation control includes two types of control depending on the operating state of the communication bus BS. The first is voltage regulation control when signal transmission through the communication bus BS is normal (referred to as "normal state"), and is called "normal control." The second is voltage regulation control when there is an abnormality in signal transmission through the communication bus BS (referred to as "abnormal state"), and is called "complementary control." The complementary control is performed by the second braking unit SB.

[0063] The pressure regulation control in the first braking unit SA will now be described. The following processing is performed by the first controller EA.

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

[0065] In step S120, signals such as the first and second operational displacements Spa and Spb, and the supply pressure Pm (=Pmf) are read. The operational displacement sensor SP is provided with two operational displacement detection units SPa and SPb (first and second detection units). The first operational displacement Spa (detection value of the first detection unit SPa) is directly acquired through the first displacement signal line LSpa. The second operational displacement Spb (detection value of the second detection unit SPb) and the supply pressure Pm (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 operation displacement Sp is calculated based on the first and second operation displacements Spa and Spb. Specifically, the average value of the first and second operation displacements Spa and Spb is determined as the operation displacement Sp (i.e., "Sp = (Spa + Spb) / 2"). Furthermore, if one of the first and second operation displacements Spa and Spb cannot be obtained, the operation displacement Sp is determined based on the other that can be obtained (i.e., "Sp = Spa" or "Sp = Spb"). Since the operation displacement sensor SP is redundant, the operation displacement Sp is determined based on at least one of the first and second operation displacements Spa and Spb. The operation displacement Sp is transmitted from the first controller EA to the communication bus BS.

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

[0068] In step S140, it is determined whether signal transmission via communication is normal. This determination process is referred to as "suitability determination." The suitability of communication is determined by determining whether "the first braking unit SA is capable of sending and receiving signals via the communication bus BS." If all signals can be sent and received, the suitability determination is affirmative, and the process proceeds to step S150. On the other hand, if there is an abnormality in the signal transmission and reception, the suitability determination is negative, and the process proceeds to step S180.

[0069] In step S140, if the suitability determination is affirmative, the determination flag FT is set to "0." On the other hand, if the suitability determination is negative, the determination flag FT is set to "1." The "determination flag FT" is a control flag that indicates the suitability of the communication function. With the determination flag FT, "0" indicates a normal state, and "1" indicates an abnormal communication state.

[0070] <Normal control process in first braking unit SA> The normal control will now be described. The normal control is a pressure regulation control when all operations of the braking control device SC are normal. The processing of steps S150 to S170 corresponds to the normal control. This processing is executed by the first controller EA. For example, in the normal control, only the first actuator YA is driven.

[0071] In step S150, a target regenerative braking force Fh and a target frictional braking force Fn are calculated based on the target vehicle body position dynamics Fv and the limit regenerative braking force Fx. Specifically, the target regenerative braking force Fh is determined to be a value equal to or less than the limit regenerative braking force Fx. For example, if the target vehicle body position dynamics Fv is equal to or less than the limit regenerative braking force Fx, the target regenerative braking force Fh is set equal to the target vehicle body position dynamics Fv, and the target frictional braking force Fn is determined to be "0" (i.e., if "Fv≦Fx", "Fh=Fv, Fn=0"). On the other hand, when the target vehicle body position dynamics Fv is greater than the limit regenerative braking force Fx, the target regenerative braking force Fh is set equal to the limit regenerative braking force Fx, and the target 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 position dynamics Fv" (i.e., when "Fv > Fx," "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. The regenerative controller EG then controls the generator GN so that the actual regenerative braking force Fg approaches and matches the target regenerative braking force Fh.

[0072] In step S160, a target pressure Pt (=Ptf, Ptr) is calculated based on the target frictional braking force Fn. The "target pressure Pt" is a target value corresponding to the supply pressure Pm. Furthermore, since "Pm=Pw" holds when the brake control device SC is operating normally, the target pressure Pt is also a target value corresponding to the wheel pressure Pw. Specifically, the target pressure Pt is determined by converting the target frictional braking force Fn into the dimension of the supply pressure Pm (i.e., the wheel pressure Pw) based on the specifications of the braking device SX and the like (pressure-receiving area of ​​the wheel cylinder CW, effective braking radius of the rotating member KT, friction coefficient of the friction member MS, effective radius of the wheel (tire) etc.). Note that since "Pmf=Pmr", the front wheel target pressure Ptf and the rear wheel target pressure Ptr are determined to be equal values ​​(i.e., "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 coincides with the target pressure Pt (target value). Specifically, the supply pressure Pm is acquired from the second controller EB via the communication bus BS. The first electric motor MA is driven, and brake fluid BF is discharged from the first fluid pump QA. This generates a circulating flow KN of brake fluid BF in the return path HK. The pressure regulating valve UA is then driven, and the circulating flow KN is throttled, thereby generating a servo pressure Pu. When the first actuator YA is driven, 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 in the first braking unit SA when a communication error occurs>> The following describes the pressure regulation control in the first braking unit SA when communication does not function normally (i.e., when a communication abnormality occurs). If the appropriateness determination in step S140 is negative, operation of the regenerative device KG is stopped in step S180. If communication between the first controller EA and the regenerative controller EG is functioning properly, "Fh=0" or "FT=1" is sent from the first controller EA to the regenerative controller EG, and power generation by the generator GN in the regenerative device KG is stopped. However, if the communication function of the first controller EA is malfunctioning, the regenerative controller EG cannot obtain the target regenerative braking force Fh. Based on this, the regenerative controller EG identifies a communication abnormality and stops power generation by the generator GN. In either case, when a communication abnormality occurs, the regenerative braking force Fg is set to "0" and the regenerative cooperative control is terminated.

[0075] In step S190, a determination is made as to whether the first brake unit SA is operable (referred to as a "operability determination"). For example, if everything is normal except for the inability to acquire the supply pressure Pm via communication, it is determined that the first brake unit SA is operable (i.e., the "operability determination" is affirmative). However, if the drive voltage Ve of the first brake unit SA (the voltage that can be applied to the first controller EA and the first actuator YA) has dropped below a predetermined voltage Ve, it is determined that the first brake unit SA is inoperable (i.e., the "operability determination" is negative). Here, the "drive voltage Ve" is detected by a drive voltage sensor (not shown) provided in the first drive circuit DRa. The "predetermined voltage Ve" is a threshold value for the ability determination, and is a predetermined value (constant) that is set in advance. If the ability determination is affirmative, the process proceeds to step S200. On the other hand, if the ability determination is negative, the process proceeds to step S220.

[0076] In step S200, the first controller EA cannot acquire a signal of the second operation displacement Spb, and therefore the operation displacement Sp is calculated based on the first operation displacement Spa. Specifically, the first operation displacement Spa is determined as the operation displacement Sp (i.e., "Sp = Spa"). Furthermore, in step S200, the target pressure Pt is calculated based on the operation displacement Sp (= Spa) and the calculation map Zfv. Since the target regenerative braking force Fh is determined to be "0" and the target frictional braking force Fn is equal to the target vehicle body position force Fv, in the calculation map Zfv, the target vehicle body position force Fv (the vertical axis of the calculation map Zfv) is replaced with the target frictional braking force Fn. Therefore, the target frictional braking force Fn calculated based on the operation displacement Sp is converted into the dimension of the supply pressure Pm based on the specifications of the brake device SX, and the target pressure Pt is determined.

[0077] In step S210, the first actuator YA is driven only by feedforward control using the target pressure Pt. When a communication abnormality occurs, the supply pressure Pm cannot be obtained, and therefore feedback control according to the supply pressure Pm is omitted.

[0078] If the result of the determination in step S190 is negative, the power supply to the inlet valve VA and the release valve VB is stopped and the operation mode of the input unit NR is switched to the second mode in step S220, whereby the master piston NM is moved in conjunction with the brake operating member BP.

[0079] In step S230, the power supply to the first electric motor MA and the pressure regulating valve UA is reduced. Except when power cannot be supplied to the first braking unit SA at all, when power can be supplied, the power supply to the components (UA, MA, etc.) included in the first braking unit SA (particularly the pressure regulating unit CA) that increase the supply pressure Pm is reduced compared to normal control. In other words, when the first braking unit SA is in an abnormal state, the power supply to the pressure regulating unit CA is stopped or the first electric motor MA is driven at a reduced rotation speed nx (for example). Note that when the communication abnormality is due to a loss of function of the first controller EA, power cannot be supplied to the components of the first actuator YA, so the input unit NR is set to the second mode and output from the pressure regulating unit CA is stopped (i.e., "Pu = 0").

[0080] <Complementary control processing> The complementary control will be described. The complementary control is a pressure regulation control in the second braking unit SB when a communication abnormality occurs. The processing of steps S310 to S370 corresponds to the complementary control. The complementary control is executed by the second controller EB.

[0081] In step S310, the second controller EB reads various signals such as the first and second operation displacements Spa and Spb, the supply pressure Pm (=Pmf), and the judgment flag FT. The second operation displacement Spb (the detection value of the second displacement detection unit SPb) is acquired via the signal line LSpb. Similarly, the supply pressure Pm (the detection value of the supply pressure sensor PM) is acquired via the signal line LPm. The first operation displacement Spa and the judgment flag FT are read from the communication bus BS. Note that in the event of a communication abnormality, the second controller EB cannot acquire signals such as the first operation displacement Spa and the judgment flag FT.

[0082] In step S320, the second controller EB performs a suitability determination of "whether signal transmission via communication is normal or not" in the same manner as in step S140. If the second brake unit SB is able to send and receive signals via the communication bus BS, the suitability determination is affirmative, and the process returns to step S310. In this case, complementary control is not executed. If signal reception and transmission are not possible, the process proceeds to step S330. In step S320, if the suitability determination is affirmative, the determination flag FU is set to "0," indicating a normal state. On the other hand, if the second brake unit SB is unable to send and receive signals and the suitability determination is negative, the determination flag FU is set to "1," indicating an abnormal state.

[0083] In step S330, the operation of the regeneration device KG is stopped. For example, "Fh=0" is transmitted from the second controller EB to the regeneration controller EG, and the power generation of the generator GN in the regeneration device KG is stopped (i.e., "Fg=0"). Alternatively, "FU=1" may be transmitted, and the operation of the generator GN may be stopped.

[0084] In step S340, the operation displacement Sp is calculated. In the event of a communication abnormality, the second controller EB cannot receive the signal of the first operation displacement Spa, and therefore the second operation displacement Spb is determined as the operation displacement Sp (i.e., "Sp = Spb"). Furthermore, in step S340, the target vehicle body position force Fv is calculated based on the operation displacement Sp (= Spb) and a method similar to that in step S130. Here, "a similar method" means that the target vehicle body position force Fv is calculated using a similar calculation map Zfv in a state where the regenerative braking force Fg is not generated (i.e., a state where "Fh = 0, Fg = 0"). However, the calculation map Zfv used in the first controller EA and the calculation map Zfv used in the second controller EB do not need to be completely identical, and it is sufficient if they are similar to each other.

[0085] In step S350, the target frictional braking force Fn is converted into a dimension of the supply pressure Pm based on the specifications of the braking device SX, etc., to determine the target pressure Pt. The target pressure Pt in the second controller EB, like the target pressure Pt in the first controller EA, is a target value corresponding to the operation displacement Sp (=Spb) and the supply pressure Pm calculated based on a calculation map (Zfv, etc.). Therefore, the target pressure Pt in step S350 is substantially the same as the target pressure Pt in step S200.

[0086] In step S360, a deviation hP between the target pressure Pt and the supply pressure Pm (referred to as the "hydraulic pressure deviation") is calculated based on the target pressure Pt and the supply pressure Pm. Specifically, the supply pressure Pm is subtracted from the target pressure Pt to determine the hydraulic pressure deviation hP (i.e., "hP = Pt - Pm"). Because the target pressure Pt calculated by the first brake unit SA and the target pressure Pt calculated by the second brake unit SB are equivalent, the hydraulic pressure deviation hP is a state quantity that represents the difference between the supply pressure that should be output from the first brake unit SA (i.e., the target pressure Pt at the first brake unit SA) and the actually generated supply pressure Pm. Therefore, when the supply pressure Pm is smaller than the target pressure Pt and the hydraulic pressure deviation hP is greater than "0," the hydraulic pressure deviation hP is a target value for increasing the supply pressure Pm. Also, when the supply pressure Pm is greater than the target pressure Pt and the hydraulic pressure deviation hP is smaller than "0", the hydraulic pressure deviation hP is a target value for reducing the supply pressure Pm.

[0087] In step S370, the second actuator YB is driven based on the hydraulic pressure deviation hP to adjust (increase or decrease) the wheel pressure Pw. When the supply pressure Pm is lower than the target pressure Pt and an increase in the wheel pressure Pw is necessary (i.e., when the hydraulic pressure deviation hP is greater than "0"), the second electric motor MB and the control valve UB are driven. Specifically, the second electric motor MB is driven and brake fluid BF is discharged from the second fluid pump QB. This generates a circulating flow KL of brake fluid BF in the communication path HS and the return path HL. Then, when the hydraulic pressure deviation hP is equal to or greater than a predetermined pressure-boosting deviation hp, the control valve UB increases the supply pressure Pm by an amount equivalent to the hydraulic pressure deviation hP. Here, the "predetermined pressure-boosting deviation hp" is a preset positive value (constant). The adjustment to increase the supply pressure Pm is referred to as "pressure-boosting control" in the complementary control.

[0088] In pressure increase control, the control valve UB is driven to throttle the circulating flow KL, thereby generating a pressure difference between the upstream and downstream sides of the control valve UB. As a result, the upstream hydraulic pressure, regulated pressure Pq, is increased from the downstream hydraulic pressure, supply pressure Pm. In other words, when the second actuator YB is driven, the control valve UB is controlled so that the pressure difference between the regulated pressure Pq and the supply pressure Pm (i.e., hydraulic pressure "Pq - Pm") becomes equal to the hydraulic pressure deviation hP. Because the regulated pressure Pq is equal to the wheel pressure Pw, the second actuator YB outputs the hydraulic pressure obtained by adding the actual hydraulic pressure corresponding to the hydraulic pressure deviation hP (target value) to the supply pressure Pm (actual value) as the wheel pressure Pw (i.e., "Pw = Pm + hP"). In pressure increase control, when the supply pressure Pm is lower than the target pressure Pt, the control valve UB is driven appropriately to increase the wheel pressure Pw from the supply pressure Pm by the hydraulic pressure deviation hP.

[0089] On the other hand, when the supply pressure Pm is greater than the target pressure Pt and a reduction 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 predetermined pressure reduction deviation hq, the inlet valve VI and the outlet valve VO reduce the supply pressure Pm by an amount equivalent to the hydraulic pressure deviation hP, and output the reduced pressure as the wheel pressure Pw (i.e., "Pw = Pm - hP"). Here, the "predetermined pressure reduction deviation hq" is a predetermined negative value (constant). The adjustment to reduce the supply pressure Pm is referred to as "pressure reduction control" in the complementary control. In pressure reduction 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 a manner similar to antilock brake control) to reduce the wheel pressure Pw from the supply pressure Pm by the hydraulic pressure deviation hP. The second electric motor MB is driven to return the brake fluid BF from the pressure regulating reservoir RB to the top of the control valve UB.

[0090] If an abnormality occurs in the operation of the first brake unit SA (particularly the first controller EA) and a communication abnormality occurs, the supply pressure Pm output from the first brake unit SA may decrease. In extreme cases, the first brake unit SA may lose its function, and the supply pressure Pm may be generated from the first brake unit SA solely by the driver's muscle force. Even in such a situation, the second brake unit SB compensates for the decrease in supply pressure Pm in the complementary control. Specifically, the second brake unit SB determines the target pressure Pt based on the operation displacement Sp and the same calculation map Zfv as the first brake unit SA. Therefore, the target pressure Pt in the second brake unit SB is the target value of the supply pressure Pm in the normal control. If the supply pressure Pm output from the first brake unit SA decreases, the hydraulic pressure deviation hP is determined to be a positive value. Then, the second brake unit SB increases the supply pressure Pm by an amount equivalent to the hydraulic pressure deviation hP and outputs the increased pressure as the wheel pressure Pw. The wheel pressure Pw output at this time is equivalent to the wheel pressure Pw in normal control. That is, the drop in the supply pressure Pm is appropriately compensated for by the complementary control (particularly the pressure increase control).

[0091] Furthermore, a communication error may occur due to a disconnection of the communication line, etc. In this case, the first brake unit SA is operable, but the supply pressure Pm cannot be acquired, and therefore hydraulic pressure feedback control cannot be performed. This may result in an error between the target pressure Pt and the supply pressure Pm. Since the hydraulic pressure deviation hP at the second brake unit SB is equal to this hydraulic pressure error, the wheel pressure Pw is adjusted (increased or decreased) by complementary control (i.e., pressure increase control and pressure decrease control) to compensate for the hydraulic pressure error caused by the communication error.

[0092] As explained above, the complementary control compensates for the difference (i.e., hydraulic pressure deviation hP) between the supply pressure that should be output if the first brake unit SA and communication functions are normal (i.e., target pressure Pt) and the actual supply pressure Pm. When a communication abnormality occurs, the second brake unit SB cannot grasp the operating state of the first brake unit SA, but the complementary control compensates for the actual supply pressure Pm without excess or deficiency. As a result, the accuracy of the pressure regulation control is ensured even when a communication abnormality occurs.

[0093] In the complementary control by the second brake unit SB, the pressure reduction control may be omitted and only the pressure increase control may be executed. This is because the most important aspect of complementary control is to compensate for the decrease in 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 reduction control, the quietness of the brake control device SC may be improved.

[0094] <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 S210) 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.

[0095] The drive control of the pressure regulating valve UA is composed 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.

[0096] The command current calculation block IS calculates the command current Isa based on the target pressure Pt and a preset calculation map Zis. The "command current Isa" is a target value for 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, the command current Isa is determined to increase as the target pressure Pt increases. The command current calculation block IS corresponds to feedforward control based on the target pressure Pt.

[0097] The hydraulic pressure deviation calculation block HP calculates the deviation hP (hydraulic pressure deviation) between the target pressure Pt and the supply pressure Pm. Specifically, the hydraulic pressure deviation hP is determined by subtracting the supply pressure Pm from the target pressure Pt (i.e., "hP = Pt - Pm").

[0098] The compensation current calculation block IH calculates the compensation current Ih 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 an error may occur between the target pressure Pt and the supply pressure Pm. The "compensation current Ih" is used to compensate for (reduce) 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 compensation current Ih is determined to increase the command current Isa. On the other hand, when the target pressure Pt is smaller than the supply pressure Pm and the hydraulic pressure deviation hP has a negative sign, a negative compensation current Ih is determined to decrease the command current Isa. Here, a dead band is provided in the calculation map Zih. The compensation current calculation block IH corresponds to feedback control based on the supply pressure Pm.

[0099] 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 composed of, in terms of hydraulic pressure, feedforward control (the process of the indicated current calculation block IS) and feedback control (the process of the compensation current calculation block IH).

[0100] 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.

[0101] When a communication abnormality occurs due to a disconnection of the communication line or the like (i.e., the process of step S210), in the first controller EA, the supply pressure Pm cannot be obtained. For this reason, 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 a communication 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.

[0102] <Drive Control of Control Valve UB> With reference to the block diagram of Fig. 6, the details of the drive control of the control valve UB in the complementary control (particularly the processing of steps S360 and S370) will be described. The complementary control processing is executed by the second controller EB. Before a communication abnormality is determined (i.e., when "FT = 0, FU = 0"), the operation of the second actuator YB is stopped. When the appropriateness determination in step S320 is negative and a communication abnormality state is determined (i.e., when "FU = 0" is switched to "FU = 1"), complementary control is started by the second actuator YB. Note that in the case of a communication abnormality, the second controller EB cannot receive the determination flag FT and the first operation displacement Spa determined by the first controller EA.

[0103] In the complementary control, the wheel pressure Pw is adjusted based on the hydraulic pressure deviation hP. The complementary control includes pressure increase control, which increases the wheel pressure Pw, and pressure decrease control, which decreases the wheel pressure Pw. In the complementary control, a dead band is provided in the range where the hydraulic pressure deviation hP is greater than a predetermined pressure decrease deviation hq (a preset negative constant) and smaller than a predetermined pressure increase deviation hp (a preset positive constant). 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 decrease control block PG.

[0104] The hydraulic pressure deviation calculation block HP calculates the deviation hP between the target pressure Pt and the supply pressure Pm. The processing of the hydraulic pressure deviation calculation block HP is the same as that of the hydraulic pressure 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 to determine the hydraulic pressure deviation hP (i.e., "hP = Pt - Pm"). The target pressure Pt is calculated in the second brake unit SB based on a method similar to the method for calculating the target pressure Pt in the first brake unit SA. More specifically, the target pressure Pt is calculated based on a calculation map (Zfv, etc.) that is the same as or similar to the calculation map used in the processing of steps S130 to S160 when "Fh = 0" or the processing of step S200. In the complementary control, the hydraulic pressure deviation hP is treated as a target value for the differential pressure between the supply pressure Pm and the wheel pressure Pw.

[0105] When the supply pressure Pm is smaller than the target pressure Pt (more specifically, when the hydraulic pressure deviation hP is equal to or greater than the predetermined pressure increase deviation hp and exceeds the dead band of the complementary control), the second target current calculation block IBT calculates a second target current Itb based on the hydraulic pressure deviation hP and a preset calculation map Zib. The "second target current Itb" is a target value for the supply current Ib (second supply current) of the control valve UB required to generate a differential pressure equivalent 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 that of the command current calculation block IS described above (i.e., feedforward control based on hydraulic pressure).

[0106] 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 a 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 current similar to the above-described 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 process of boost control.

[0107] 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 decompression predetermined deviation hq and exceeds the dead zone of the complementary control), in the decompression control block PG, the inlet valve VI and the outlet valve VO are controlled. In the decompression control block PG, the drive signals Vi and Vo of the inlet valve VI and the outlet valve VO are determined so that the supply pressure Pm is decreased by an amount corresponding to the hydraulic pressure deviation hP. The decompression control block PG corresponds to the process of decompression control.

[0108] Although the drive control of the above-described control valve UB is open-loop control, it may be configured as closed-loop control including feedback control related to hydraulic pressure. In this configuration, a pressure regulating sensor (not shown) is provided at the lower part of the control valve UB so as to detect the regulated pressure Pq. Then, the second target current Itb is finely adjusted based on the deviation between the supply pressure Pm and the regulated pressure Pq in the same manner as the above-described compensation current calculation block IH.

[0109] <Configuration of Two-System Pressure Regulation> In the above-described embodiment, when the brake control device SC is in a normal state, the operation of the second actuator YB is stopped and only the first actuator YA is driven. In this case, the front and rear wheel supply pressures Pmf and Pmr (=Pm) are equal, and therefore the front and rear wheel pressures Pwf and Pwr (=Pw) ​​are equal. This type of pressure regulation control is referred to as "single-system pressure regulation." In the single-system pressure regulation configuration, the second actuator YB is not driven during normal control, so the target pressure Ptm (referred to as "target supply pressure") corresponding to the supply pressure Pm and the target pressure Ptw (referred to as "target wheel pressure") corresponding to the wheel pressure Pw are equal (i.e., "Pt=Ptm=Ptw").

[0110] Instead of the single-system pressure regulation configuration, when the brake control device SC is in a normal state, a second actuator YB may be driven in addition to the first actuator YA to separately regulate the front and rear wheel pressures Pwf, Pwr. Specifically, the first actuator YA supplies the same supply pressures Pmf, Pmr (=Pm) to the second actuator YB. The second actuator YB then regulates the wheel pressure of one system corresponding to a wheel equipped with a regenerative device KG (e.g., the front wheel pressure Pwf) to be smaller than the wheel pressure of the other system corresponding to a wheel not equipped with a regenerative device KG (e.g., the rear wheel pressure Pwr). Pressure regulation control in which the front and rear wheel pressures Pwf, Pwr are independently and individually regulated by driving the second actuator YB is referred to as "dual-system pressure regulation." In regenerative cooperative control, dual-system pressure regulation improves regenerative efficiency and optimizes braking force distribution between the front and rear wheels compared to single-system pressure regulation.

[0111] In a dual-system pressure regulation configuration, the second actuator YB is driven even in a normal state, so the target pressure Ptm (target supply pressure) corresponding to the supply pressure Pm differs from the target pressure Ptw (target wheel pressure) corresponding to the wheel pressure Pw. For this reason, the first actuator YA executes feedforward control and feedback control so that the supply pressure Pm (= Pmf, Pmr) approaches and matches the target supply pressure Ptm. Then, the second actuator YB executes feedforward control based on pressure differences hPf, hPr (referred to as "front and rear wheel target pressure differences") between the front and rear wheel target wheel pressures Ptwf, Ptwr and the target supply pressure Ptm (or actual supply pressure Pm).

[0112] Complementary control is also applied in the dual-system pressure regulation configuration. When a communication abnormality is determined (i.e., when the determination flags FT and FU are switched to "1"), the regenerative cooperative control is terminated and the generation of regenerative braking force Fg is stopped. In complementary control, the second actuator YB adjusts (increases or decreases) the supply pressure Pm (actual value) by an amount equivalent to the hydraulic pressure deviation hP (target value) so as to compensate for any excess or deficiency in the supply pressure Pm output from the first brake unit SA. Even in the dual-system pressure regulation configuration, as in the single-system pressure regulation configuration, pressure regulation control is appropriately executed in the event of a communication abnormality, and any excess or deficiency in the supply pressure Pm from the first brake unit SA is compensated for by an appropriate amount.

[0113] <Other embodiments> Other embodiments will be described below, which also provide the same effects as those described above (such as the execution of appropriate pressure regulation control when a communication abnormality occurs).

[0114] In the above-described embodiment, the target values ​​of various braking forces (Fv, Fx, Fh, Fn, etc.) are calculated in terms of the longitudinal force acting on the vehicle JV. Alternatively, they may be calculated in terms of the deceleration of the vehicle JV or the torque of the wheels WH. This is based on the fact that state quantities (referred to as "state quantities related to force") from the longitudinal force acting on the vehicle JV to the deceleration of the vehicle JV are equivalent. Therefore, the target pressure Pt is calculated based on state quantities related to the force from the longitudinal force acting on the vehicle JV to the deceleration of the vehicle JV.

[0115] In the above-described embodiment, a front-rear type brake system is used as the two-system brake system. Alternatively, a diagonal type (also called "X type") brake system may be used as the two-system brake 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 a configuration in which dual-system pressure regulation is used, the brake system is limited to the front-rear type.

[0116] In the above-described embodiment, the supply pressure sensor PM is built into the second actuator YB and connected to the second controller EB. The supply pressure sensor PM may have two detectors, similar to the operation displacement sensor SP, which are connected to the first and second controllers EA and EB. In this configuration, even during a communication abnormality, the first controller EA can acquire the supply pressure Pm and execute feedback control related to the supply pressure Pm. Therefore, the hydraulic pressure error described above does not occur, and complementary control to compensate for this error is not executed. Therefore, in the complementary control, complementary control (particularly, pressure increase control) is executed only when a communication abnormality occurs and the performance of the first brake unit SA is degraded. In other words, in this configuration, pressure reduction control is omitted in the complementary control.

[0117] 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.

[0118] 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).

[0119] 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.

[0120] In the above-described embodiment, the pressure receiving area rm (master area) of the master chamber Rm and the pressure receiving area ru (servo area) of the servo chamber Ru in the apply section AP are set equal. The master area rm and the servo area ru do not have to be equal. In a configuration in which the master area rm and the servo area ru are different, it is possible to perform a conversion calculation between the supply pressure Pm and the servo pressure Pu based on the ratio of the servo area ru to the master area rm (i.e., conversion based on "Pm·rm=Pu·ru").

[0121] In the above-described embodiment, the first brake unit SA outputs the supply pressure Pm via the master cylinder CM. That is, the apply unit AP and the pressure adjustment unit CA are arranged in series in the hydraulic pressure transmission path, and the servo pressure Pu supplied from the pressure adjustment unit CA is transmitted as the supply pressure Pm via the master piston NM. Alternatively, the apply unit AP and the pressure adjustment unit CA may be arranged in parallel. Specifically, the apply unit AP (particularly, the master cylinder CM) and the pressure adjustment unit CA are each directly connected to the second actuator YB. In the first mode, the connection between the pressure adjustment 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 of this configuration, the servo pressure Pu generated in the pressure adjustment unit CA is directly output as the supply pressure Pm without passing through the apply unit AP. In this mode, the apply unit AP is connected to the stroke simulator SS, and the operating force Fp of the brake operating member BP is generated by the simulator SS. On the other hand, in the second mode, the hydraulic pressure in the master chamber Rm generated by operating the brake operating member BP is output as the supply pressure Pm. In this mode, the apply unit AP is disconnected from the simulator SS.

[0122] In the above-described embodiment, the brake control device SC is applied to a vehicle JV that does not have a regenerative device KG on the rear wheels WHr. The brake control device SC may also be applied to a vehicle JV that has a regenerative device KG on the rear wheels WHr.

[0123] <Summary of the embodiment> The brake control device SC is a brake-by-wire type device that can independently adjust the operation displacement Sp (operation displacement) of the brake operating member BP and the hydraulic pressure Pw (wheel pressure) of the wheel cylinder CW.

[0124] The brake control device SC includes a "first brake unit SA (first unit) that outputs a supply pressure Pm in accordance with 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 detects the operation displacement Sp (operation amount)," and a "supply pressure sensor PM that detects the supply pressure Pm." The first brake unit SA selects either a first mode in which the operation displacement Sp and the supply pressure Pm are independent, or a second mode in which the operation displacement Sp and the supply pressure Pm are linked. This allows the brake control device SC to function as a brake-by-wire device.

[0125] When the operation of the brake control device SC is normal (for example, when signal transmission is normal), the first mode (by-wire mode) is selected in the first brake unit SA, and normal control is executed. In normal control, a target pressure Pt is calculated based on the operation displacement Sp, and the supply pressure Pm is controlled so as to approach the target pressure Pt. Specifically, feedback control (closed-loop control) based on the supply pressure Pm is executed so that the supply pressure Pm coincides with the target pressure Pt. In addition to the feedback control, feedforward control (open-loop control) based on the target pressure Pt is also executed in normal control.

[0126] In the brake control device SC, if there is an abnormality in signal transmission (i.e., communication), the second brake unit SB calculates a target pressure Pt based on the operation displacement Sp (particularly, the second operation displacement Spb). Here, the calculation of the target pressure Pt in the second brake unit SB is performed in the same manner as the calculation of the target pressure Pt in the first brake unit SA. Therefore, the target pressures Pt calculated in the first and second brake units SA and SB are substantially equal. Then, in the second brake unit SB, the wheel pressure Pw is adjusted based on the deviation hP between the target pressure Pt and the supply pressure Pm. Specifically, in the second brake unit SB, if 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. On the other hand, in the second brake unit SB, if the supply pressure Pm is larger than the target pressure Pt, the wheel pressure Pw is decreased by an amount corresponding to the deviation hP. Furthermore, in the complementary control, the wheel pressure Pw may not be decreased, but may be increased. This is because compensating for a decrease in the wheel pressure Pw is of utmost importance. In a configuration in which the wheel pressure Pw is only increased and the decrease is prohibited, the inlet valve VI and the outlet valve VO are not driven when adjusting the wheel pressure Pw, thereby improving the quietness of the brake control device SC.

[0127] If information cannot be transmitted between the first and second controllers EA and EB, even if an abnormality occurs in the first brake unit SA, the first brake unit SA cannot notify the second brake unit SB of this condition. In other words, if a communication abnormality occurs, the second brake unit SB cannot grasp the operating state of the first brake unit SA. For example, if the first brake unit SA (particularly the first controller EA) fails and a communication abnormality occurs, the operation of the first brake unit SA may be completely stopped. In this case, the first brake unit SA (particularly the input unit NR) is set to the second mode (manual mode), and the supply pressure Pm is not generated electrically but is generated using the driver's muscle power as a power source (corresponding to the case where step S190 is negative). Also, even if the operation of the first brake unit SA is not completely stopped, the output Pm from the first brake unit SA may be significantly lower than the target value Pt.

[0128] In the complementary control, in response to various abnormalities, if the supply pressure Pm output from the first brake unit SA is appropriate, no complementation is performed, but only if the supply pressure Pm is inappropriate, the supply pressure Pm is compensated for exactly. The hydraulic pressure deviation hP calculated by the second brake unit SB represents the deviation between the supply pressure that should be output (i.e., the target pressure Pt) and the actual supply pressure Pm (i.e., the amount of excess or deficiency of the supply pressure Pm relative to the target pressure Pt) if the brake control device SC, including signal transmission, is normal. Therefore, in the complementary control based on the hydraulic pressure deviation hP, the excess or deficiency of the supply pressure Pm is adjusted (increased or decreased) and output from the second brake unit SB as the wheel pressure Pw. As a result, even if the operating state of the first brake unit SA cannot be determined due to a communication abnormality, the second brake unit SB can appropriately perform pressure adjustment control.

[0129] For example, in the brake control device SC, the operation displacement sensor SP is connected to both the first and second brake units SA and SB, but the supply pressure sensor PM is connected only to the second brake unit SB. In this configuration, the first brake unit SA obtains the supply pressure Pm from the second brake unit SB via the communication bus BS. Therefore, if there is an abnormality in the signal transmission, the first brake unit SA cannot use the information on the supply pressure Pm and cannot perform feedback control. In the first brake unit SA, the supply pressure Pm is adjusted only by feedforward control, which can cause errors in the wheel pressure Pw. However, the wheel pressure Pw is appropriately adjusted by the above-mentioned complementary control, ensuring good accuracy of the pressure adjustment control. [Explanation of symbols]

[0130] SC...Brake control device, KG...Regeneration device, BP...Brake operating member (brake pedal), SA...First braking unit (first unit), SB...Second braking unit (second unit), YA...First fluid unit (first actuator), YB...Second fluid unit (second actuator), EA...First control unit (first controller), EB...Second control unit (second controller), BS...Communication bus, CM...Master cylinder, CW...Wheel cylinder, AP...Apply section, NR...Input section, CA...Pressure adjustment section, UA...Adjustment Pressure valve, UB...control valve, MA, MB...first and second electric motors, QA, QB...first and second fluid pumps, VA...inlet 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...adjusted pressure, Pw...wheel pressure, Pt...target pressure (target value corresponding to Pm), hP...hydraulic pressure deviation (hydraulic pressure difference between Pt and Pm), FT...suitability flag (determination result of step S140), FU...suitability flag (determination result of step S320).

Claims

1. a first unit that outputs a supply pressure in accordance with an operation amount of a brake operating member; a second unit provided between the first unit and a wheel cylinder, the second unit adjusting the supply pressure and outputting a wheel pressure to the wheel cylinder; a communication bus for transmitting signals between the first unit and the second unit; an operation amount sensor for detecting the operation amount; a supply pressure sensor for detecting the supply pressure; In a braking control device for a vehicle, the operation amount sensor includes a first detection unit that outputs a signal indicating the operation amount to the first unit, and a second detection unit that outputs a signal indicating the operation amount to the second unit, the supply pressure sensor outputs a signal of the supply pressure to the second unit, the first unit acquires the supply pressure from the second unit via the communication bus; the first unit calculates a target pressure based on the manipulated variable and operates by feedback control to bring the supply pressure closer to the target pressure; If there is an abnormality in the signal transmission, A braking control device for a vehicle, wherein the first unit calculates a target pressure based on the operation amount and operates by feedforward control based on the target pressure, and the second unit calculates the target pressure based on the operation amount and adjusts the wheel pressure based on the deviation between the target pressure and the supply pressure.

2. 2. The vehicle brake control device according to claim 1, The second unit increases the wheel pressure by an amount corresponding to the deviation when the supply pressure is lower than the target pressure.

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