Vehicle braking control device

Abstract

To provide a vehicle brake control device capable of two system pressure regulation in which execution of anti-lock brake control can be satisfactorily performed.SOLUTION: A vehicle brake control device (SC) comprises: a first unit which outputs front wheel and rear wheel supply pressures (Pm, Pv) individually depending on an amount (Sp) of operation of a vehicle brake operation member (BP); and a second unit which is provided between the first unit and front wheel and rear wheel wheel cylinders (CWf, CWr), regulates the front wheel and rear wheel supply pressures (Pm, Pv), and outputs front wheel and rear wheel wheel pressures. When the second unit executes anti-lock brake control, the first unit communicates a part on which the front and wheel supply pressure (Pm) acts and a part on which the rear wheel supply pressure (Pv) acts with each other, and equalizes the front wheel and rear wheel supply pressures (Pm, Pv).SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] In Patent Document 1, in order to prevent the ABS from frequently operating due to excessive use of regenerative braking, a relative slip ratio is calculated from the difference between the maximum wheel speed of the front and rear wheels and the minimum wheel speed of the front wheels, and the vehicle speed, and a regenerative braking coefficient is calculated that decreases as the relative slip ratio increases, and the regenerative braking is performed by calculating the coefficient.The document describes that the magnitude of regenerative braking is reduced as the magnitude of the relative slip ratio increases.

[0003] Patent Document 2 describes that when ABS control intervenes during regenerative cooperative control, in order to prevent control interference, reduce the frequency of control re-intervention, and ensure the amount of regenerative energy, when ABS control intervenes during regenerative cooperative control, regenerative braking requests are stopped during ABS control intervention, and when ABS control transitions to a non-operating state, regenerative cooperative control is performed during ABS intervention, in which the system returns to regenerative cooperative control with a limited regenerative braking request, with the regenerative amount limited to a value that does not exceed the regenerative amount at the time of the previous ABS control intervention as the regenerative amount limiter.

[0004] The applicant has developed a braking control device, as disclosed in Patent Document 3, that can separately control the brake fluid pressure of the front wheel system (also referred to as "wheel pressure") and the brake fluid pressure of the rear wheel system in order to achieve a high level of both vehicle stability and energy regeneration in regenerative cooperative control. This braking control device combines two units. Specifically, an upper fluid unit YU (also referred to as "first unit") executes regenerative cooperative control and appropriately adjusts the wheel pressures of the front and rear wheels. A lower fluid unit YL (also referred to as "second unit"), located between the first unit and the wheel cylinder, executes ABS control (also referred to as "anti-lock brake control"). When executing anti-lock brake control, it is desirable to minimize the change in the supply pressure input to the second unit. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-095391 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-131306 [Patent Document 3] Japanese Patent Application Publication No. 2019-137202 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a vehicle brake control device capable of performing dual-system pressure regulation, which is capable of performing antilock brake control well. [Means for solving the problem]

[0007] A vehicle brake control device (SC) according to the present invention includes a first unit (SA) that outputs front and rear wheel supply pressures (Pm, Pv) separately in accordance with the operation amount (Sp) of a vehicle brake operating member (BP), and a second unit (SB) that is provided between the first unit (SA) and front and rear wheel cylinders (CWf, CWr) and adjusts the front and rear wheel supply pressures (Pm, Pv) to output front and rear wheel pressures (Pwf, Pwr). When the second unit (SB) executes antilock brake control, the first unit (SA) communicates a portion (pk) on which the front wheel supply pressure (Pm) acts with a portion (pj) on which the rear wheel supply pressure (Pv) acts, thereby equalizing the front and rear wheel supply pressures (Pm, Pv).

[0008] In the vehicle brake control device (SC) of the present invention, the first unit (SA) adjusts the pressure of the brake fluid (BF) discharged from the fluid pump (QA) to upstream and downstream servo pressures (Pj, Pk) using normally open upstream and downstream pressure regulating valves (UJ, UK) arranged in series with the circulating flow (KN) of brake fluid (BF) including the fluid pump (QA), outputs the front wheel supply pressure (Pm) using the hydraulic pressure on one side of the upstream and downstream servo pressures (Pj, Pk), and outputs the rear wheel supply pressure (Pv) using the hydraulic pressure on the other side of the upstream and downstream servo pressures (Pj, Pk).When the second unit (SB) executes antilock brake control, the first unit (SA) stops supplying current to the upstream pressure regulating valve (UJ) to equalize the front and rear wheel supply pressures (Pm, Pv).

[0009] According to the above configuration, when antilock brake control is not performed, the front wheel and rear wheel supply pressures Pm, Pv are adjusted individually, ensuring the regenerative efficiency of the regenerative device KG and improving vehicle stability. On the other hand, when antilock brake control is performed, the front wheel and rear wheel supply pressures Pm, Pv are made equal, suppressing changes in the supply pressures Pm, Pv to the second brake unit SB. This allows the antilock brake control to be performed well, improving its performance. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic diagram illustrating an entire vehicle JV equipped with a braking control device SC. [Figure 2] 3 is a schematic diagram for explaining a configuration example of a first braking unit SA. FIG. [Figure 3] 4 is a schematic diagram for explaining a configuration example of a second braking unit SB. FIG. [Figure 4] FIG. 4 is a flow chart for explaining pressure regulation control. DETAILED DESCRIPTION OF THE INVENTION

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

[0061] In pressure regulation control, normal control and specific control are switched depending on whether or not antilock brake control (also called "ABS control") is being executed in the second brake unit SB. "Normal control" is control that corresponds to when ABS control is not being executed, and "specific control" is control that corresponds to when ABS control is being executed. The algorithm for pressure regulation control, including specific control, is programmed in the microprocessor MPa of the first controller EA.

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

[0063] The various braking forces are as follows: - "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.

[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, selecting a first mode in which the master piston NM and the brake operating member BP can be displaced separately. In the first mode, the front and rear wheel supply pressures Pm, Pv (i.e., front and rear wheel pressures Pwf, Pwr) are adjusted independently of the operation of the brake operating member BP. At this time, the operating force Fp of the brake operating member BP is generated by the stroke simulator SS.

[0065] In step S120, signals such as the first and second operation displacements Spa and Spb, the front wheel supply pressure Pm, the rear wheel supply pressure Pv, and the execution flag Fab are read. The operation displacement sensor SP is provided with two operation displacement detection units SPa and SPb (first and second detection units). The first operation displacement Spa (detection value of the first detection unit SPa) and the rear wheel supply pressure Pv (detection value of the rear wheel supply pressure sensor PV) are directly acquired through the first displacement signal line LSpa and the rear wheel supply pressure signal line LPv. The second operation displacement Spb (detection value of the second detection unit SPb) and the front wheel supply pressure Pm (detection value of the front wheel supply pressure sensor PM) are acquired (received) from the second controller EB via the communication bus BS. The "execution flag Fab" is a control flag that indicates whether or not ABS control is being executed in the second brake unit SB. The execution flag Fab is acquired from the second brake unit SB 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 calculated to be "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 calculated 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, the first controller EA determines "whether antilock brake control is being executed in the second brake unit SB" based on the execution flag Fab. The execution flag Fab (a control flag indicating the execution status of ABS control in the second brake unit SB) is "0" indicating that ABS control is not being executed, and "1" indicating that ABS control is being executed. The execution flag Fab is transmitted from the second controller EB to the communication bus BS. It is then received by the first controller EA from the communication bus BS.

[0069] The process of step S140 is referred to as "specific determination." If ABS control is not being executed, the specific determination is negative, and the process proceeds to step S150. On the other hand, if ABS control is being executed, the specific determination is positive, and the process proceeds to step S180.

[0070] <Normal control processing> The processing of steps S150 to S170 corresponds to normal control (pressure regulation control when ABS control is not being executed in second brake unit SB). In normal control, dual-system pressure regulation is performed in first brake unit SA.

[0071] In step S150, front-wheel and rear-wheel required braking forces Fqf, Fqr (=Fq) are calculated based on the target vehicle body position force Fv. Specifically, the front-wheel and rear-wheel required braking forces Fqf, Fqr are calculated so that the following two conditions are satisfied. The "front-wheel required braking force Fqf" is a target value of the total braking force acting on the front wheels WHf. Therefore, the front-wheel required braking force Fqf is equal to the sum of the target regenerative braking force Fh and the front-wheel target frictional braking force Fnf (i.e., "Fqf = Fh + Fnf"). The "rear-wheel required braking force Fqr" is a target value of the total braking force acting on the rear wheels WHr. Therefore, the rear-wheel required braking force Fqr is equal to the rear-wheel target frictional braking force Fnr (i.e., "Fqr = Fnf"). Condition 1: The sum of the front wheel required braking force Fqf and the rear wheel required braking force Fqr matches the target vehicle body position force Fv (that is, "Fv=Fqf+Fqr"). Condition 2: The ratio Kq (referred to as "requested distribution") of the rear wheel required braking force Fqr to the front wheel required braking force Fqf must match a predetermined value hb (i.e., "Kq = Fqr / Fqf = hb"). Here, the predetermined value hb is the ratio of the rear wheel friction braking force Fmr to the front wheel friction braking force Fmf when the regenerative braking force Fg is "0". Therefore, the predetermined value hb is a constant that is set in advance based on the specifications of the braking device SX. The front and rear wheel required braking forces Fqf and Fqr are determined by the following equation (1) so as to satisfy conditions 1 and 2. Fqf = Fv / (1 + hb), and Fqr = Fv hb / (1 + hb) ...Equation (1)

[0072] Furthermore, in step S150, a target regenerative braking force Fh and front-wheel and rear-wheel target frictional braking forces Fnf and Fnr are calculated based on the front-wheel and rear-wheel required braking forces Fqf and Fqr and the limit regenerative braking force Fx. Specifically, the target regenerative braking force Fh is determined to be a value equal to or less than the limit regenerative braking force Fx. For example, when the front-wheel required braking force Fqf is equal to or less than the limit regenerative braking force Fx, the target regenerative braking force Fh is set equal to the front-wheel required braking force Fqf, the front-wheel target frictional braking force Fnf is set to "0", and the rear-wheel frictional braking force Fnr is set equal to the rear-wheel required braking force Fqr (i.e., when "Fqf≦Fx", "Fh=Fqf, Fnf=0, Fnr=Fqr"). On the other hand, when the front wheel required braking force Fqf is greater than the limit regenerative braking force Fx, the target regenerative braking force Fh is set equal to the limit regenerative braking force Fx, the front wheel target frictional braking force Fnf is set to the value obtained by subtracting the limit regenerative braking force Fx (=Fh) from the front wheel required braking force Fqf, and the rear wheel frictional braking force Fnr is set equal to the rear wheel required braking force Fqr (i.e., when "Fqf>Fx", "Fh=Fx, Fnf=Fqf-Fx=Fqf-Fh, Fnr=Fqr").

[0073] In step S160, front and rear wheel target pressures Ptf, Ptr are calculated based on the front and rear wheel target friction braking forces Fnf, Fnr (=Fn). The front and rear wheel target pressures Ptf, Ptr are determined by converting the target friction braking force Fn into the dimensions of front and rear wheel supply pressures Pm, Pv (i.e., front and rear wheel pressures Pwf, Pwr) based on the specifications of the braking device SX, etc. (pressure-receiving area of ​​the wheel cylinder CW, effective braking radius of the rotating member KT, friction coefficient of the friction member MS, effective radius of the wheel (tire) etc.). Since the front wheel supply pressure Pm is equal to the front wheel pressure Pwf and the rear wheel supply pressure Pv is equal to the rear wheel pressure Pwr, the front and rear wheel target pressures Ptf, Ptr are also target values ​​of the front and rear wheel wheel pressures Pwf, Pwr.

[0074] In step S170, the front and rear wheel pressures Pwf, Pwr (actual values) are adjusted based on the front and rear wheel target pressures Ptf, Ptr (target values). The first controller EA drives the first electric motor MA and the upstream and downstream pressure regulating valves UJ, UK, and controls the front and rear wheel pressures Pwf, Pwr to approach and match the front and rear wheel target pressures Ptf, Ptr. Specifically, in step S170, the electric motor MA is driven to generate a circulation flow KN that includes the fluid pump QA and the upstream and downstream pressure regulating valves UJ, UK. Then, based on the front wheel target pressure Ptf and the front wheel supply pressure Pm, the downstream pressure regulating valve UK is hydraulically feedback controlled so that the front wheel supply pressure Pm (=Pwf) matches the front wheel target pressure Ptf. In other words, the supply current Ik (actual value, also referred to as the "downstream current") to the downstream pressure regulating valve UK is adjusted so that the deviation hPf (referred to as the "front wheel deviation") between the front wheel supply pressure Pm and the front wheel target pressure Ptf becomes "0". Furthermore, the upstream pressure regulating valve UJ is hydraulically feedback controlled based on the rear wheel target pressure Ptr and the rear wheel supply pressure Pv so that the rear wheel supply pressure Pv (= Pwr) matches the rear wheel target pressure Ptr. In other words, the supply current Ij (actual value, also referred to as the "upstream current") to the upstream pressure regulating valve UJ is adjusted so that the deviation hPr (referred to as the "rear wheel deviation") between the rear wheel supply pressure Pv and the rear wheel target pressure Ptr becomes "0".

[0075] <<Specific control processing>> The processing of steps S180 to S210 corresponds to the specific control (pressure adjustment control when ABS control is being executed by the second brake unit SB). In the specific control, one-path pressure adjustment is performed by the first brake unit SA.

[0076] The specific determination in step S140 positive When this occurs, in step S180, the power supply to the upstream pressure regulating valve UJ is stopped, and the upstream pressure regulating valve UJ is opened. Because the upstream pressure regulating valve UJ is a normally open solenoid valve, it is placed in a fully open state when the power supply is stopped. This switches from dual-system pressure regulation to single-system pressure regulation.

[0077] In step S190, a sum Fnt (also referred to as "target sum") of the target regenerative braking force Fh and the target frictional braking force Fn is calculated based on the target vehicle body position dynamics Fv and the limit regenerative braking force Fx. Here, the "target sum Fnt" is the sum of the front wheel target frictional braking force Fnf and the rear wheel target frictional braking force Fnr (i.e., "Fnt = Fnf + Fnr"). In step S190, similar to the processing in step S150, the target regenerative braking force Fh is determined to be a value equal to or less than the limit regenerative braking force Fx. For example, if the target vehicle body position dynamics Fv is equal to or less than the limit regenerative braking force Fx, the target regenerative braking force Fh is made equal to the target vehicle body position dynamics Fv, and the sum Fnt of the target frictional braking forces Fn is set to "0" (i.e., if "Fv≦Fx", "Fh=Fv, Fnt=0"). Furthermore, if the target vehicle body position dynamics Fv is greater than the limit regenerative braking force Fx, the target regenerative braking force Fh is set equal to the limit regenerative braking force Fx, and the target sum Fnt is set to "a value obtained by subtracting the target regenerative braking force Fh (=Fx) from the target vehicle body position dynamics Fv" (i.e., if "Fv > Fx", "Fh = Fx, Fnt = Fv - Fh = Fv - Fx"). The target regenerative braking force Fh is transmitted to the communication bus BS.

[0078] In step S200, the common target pressure Px is calculated based on the target sum Fnt. Specifically, the common target pressure Px is determined based on the specifications of the braking device SX and the like (pressure-receiving area of ​​the wheel cylinder CW, effective braking radius of the rotating member KT, friction coefficient of the friction member MS, effective radius of the wheel (tire) etc.) so that "Ptf = Ptr" and the target sum Fnt are satisfied. Therefore, if "Fv ≦ Fx", the common target pressure Px (= Ptf = Ptr) is determined to be "0". Also, if "Fv > Fx", the common target pressure Px is determined under the condition of "Ptf = Ptr" so that the sum Fnt (target sum) of the target frictional braking forces Fn corresponding to the common target pressure Px becomes equal to the value "Fv - Fh". In the specific control, "Ptf = Ptr", so the "common target pressure Px" is a common target value unified for the front and rear wheel braking systems corresponding to the front and rear wheel supply pressures Pm and Pv. In other words, while the front and rear wheel target pressures Ptf and Ptr are target values ​​in two-system pressure regulation, the common target pressure Px is a target value in one-system pressure regulation.

[0079] In step S200, the target regenerative braking force Fh may be determined to be "0" when ABS control is being executed. In other words, when ABS control is started in the first brake unit SA, the operation of the regenerative device KG is stopped. Even when "Fh = 0", the common target pressure Px is calculated based on the specifications of the brake device SX and the like so as to satisfy "Ptf = Ptr, Fnf + Fnr = Fv", as described above.

[0080] In step S210, the first actuator YA is driven based on the common target pressure Px and the rear wheel supply pressure Pv. In the pressure regulating section CA, the upstream pressure regulating valve UJ is fully open, so the upstream servo pressure Pj and the downstream servo pressure Pk are made equal. That is, since the state is "Pk = Pm = Pwf = Pj = Pv = Pwr," the downstream pressure regulating valve UK is hydraulically feedback controlled so that the rear wheel supply pressure Pv approaches and matches the common target pressure Px. Specifically, the supply current Ik (downstream current) to the downstream pressure regulating valve UK is adjusted so that the deviation hPx (referred to as the "common deviation") between the rear wheel supply pressure Pv and the common target pressure Px becomes "0."

[0081] The brake control device SC is a brake-by-wire type device that can independently control the operation of the brake operating member BP (brake pedal) and the hydraulic pressure (wheel pressure Pw) of the wheel cylinder CW. The first brake unit SA is provided with a master chamber Rm and a servo chamber Ru. The master chamber Rm and the servo chamber Ru are hydraulic chambers defined by a master cylinder CM and a master piston NM. In the first brake unit SA (particularly, the pressure adjusting section CA), two linear solenoid valves UJ and UK (upstream and downstream pressure adjusting valves) adjust the upstream and downstream servo pressures Pj and Pk individually. In the brake system related to the front wheels WHf, the downstream servo pressure Pk is adjusted based on the operation displacement Sp and the front wheel supply pressure Pm. When the downstream servo pressure Pk is supplied to the servo chamber Ru, the front wheel supply pressure Pm is output from the master chamber Rm, and the front wheel pressure Pwf is ultimately adjusted. Meanwhile, in the braking system for the rear wheels WHr, the upstream servo pressure Pj is adjusted based on the operation displacement Sp and the rear wheel supply pressure Pv. The upstream servo pressure Pj is supplied directly from the pressure regulating unit CA to the rear wheel cylinder CWr as the rear wheel supply pressure Pv. In the first braking unit SA, hydraulic pressure feedback control is executed according to the front and rear wheel supply pressures Pm and Pv so that the front and rear wheel supply pressures Pm and Pv approach and match the front and rear wheel target pressures Ptf and Ptr calculated based on the operation displacement Sp. With the above configuration, the first braking unit SA achieves dual-system pressure regulation.

[0082] The second brake unit SB is a general-purpose unit for performing antilock brake control (ABS control) and the like. When ABS control is performed by the second brake unit SB, the first brake unit SA stops supplying power to the upstream pressure regulating valve UJ and switches from dual-system pressure regulation to single-system pressure regulation. This results in a state where Pj = Pk. In other words, the individual adjustment of the front wheel supply pressure Pm and the rear wheel supply pressure Pv is eliminated. Since the front wheel supply pressure Pm and the rear wheel supply pressure Pv are adjusted equally, changes in the hydraulic pressures Pm and Pv input to the second brake unit SB are suppressed. As a result, the control performance of the ABS control can be improved. In single-system pressure regulation, the target values ​​of the front and rear wheel supply pressures Pm and Pv are determined as the same target value Px (common target pressure) for both the front and rear wheel systems. The downstream pressure regulating valve UK is then feedback-controlled based on the common target pressure Px and the rear wheel supply pressure Pv.

[0083] <Application to a vehicle JV with a regenerative device KG mounted on the rear wheels WHr> In the above-described embodiment, a vehicle (referred to as a "front-wheel regenerative vehicle") is assumed in which the regenerative device KG is provided on the front wheels WHf but not on the rear wheels WHr. Alternatively, the braking control device SC may be applied to a vehicle (referred to as a "rear-wheel regenerative vehicle") in which the regenerative device KG is provided on the rear wheels WHr but not on the front wheels WHf. The differences will be explained below.

[0084] In the braking control device SC applied to a rear-wheel regenerative vehicle, as shown in the schematic diagram of FIG. 2, the servo path HV is connected to the return path HK at a point pj, and the rear-wheel connecting path HSr is connected to the return path HK at a point pk. That is, the upstream servo pressure Pj is supplied to the servo chamber Ru, and the downstream servo pressure Pk is supplied to the rear wheel cylinder CWr (i.e., "Pj = Pm = Pwf, Pk = Pv = Pwr"). Also, in the pressure regulation control process (particularly, dual-path pressure regulation) of FIG. 4, when "Fqr≦Fx" is satisfied, the front and rear wheel target frictional braking forces Fnf and Fnr are calculated as "Fh = Fqr, Fnf = Fqf, Fnr = 0." On the other hand, when "Fqf > Fx," the following are determined: "Fh = Fx, Fnf = Fqf, Fnr = Fqr - Fx = Fqr - Fh." The front and rear wheel target friction braking forces Fnf and Fnr are then converted into front and rear wheel target pressures Ptf and Ptr (where Ptf≧Ptr). The single-system pressure adjustment process is the same for front and rear wheel regenerative vehicles.

[0085] In a vehicle equipped with a regenerative device KG (=KGf, KGr) on both the front and rear wheels WHf and WHr, one of the two configurations described above is adopted depending on the magnitude of the regenerative energy of the regenerative devices. Specifically, a brake control device SC for a front-wheel regenerative vehicle is applied to a vehicle in which the regenerative energy of the front-wheel regenerative device KGf is greater than that of the rear-wheel regenerative device KGf. Conversely, a brake control device SC for a rear-wheel regenerative vehicle is applied to a vehicle in which the regenerative energy of the front-wheel regenerative device KGf is smaller than that of the rear-wheel regenerative device KGf.

[0086] <Other embodiments> Other embodiments will be described below, which also provide the same effect as above (good execution of ABS control).

[0087] In the above-described embodiment, the target values ​​of various braking forces (Fv, Fx, Fh, Fn, etc.) were calculated in terms of longitudinal forces acting on the vehicle JV. Alternatively, they may be calculated in terms of deceleration of the vehicle JV or torque of the wheels WH. This is based on the fact that state quantities (referred to as "force-related state quantities") from longitudinal forces acting on the vehicle JV to vehicle deceleration are equivalent. Therefore, the target pressures Ptf, Ptr, and Px are calculated based on state quantities related to forces from longitudinal forces acting on the vehicle JV to deceleration of the vehicle JV.

[0088] In the above-described embodiment, the pressure regulating unit CA is exemplified as one that adjusts the front and rear wheel supply pressures Pm, Pv by throttling the circulating flow KN of brake fluid BF discharged by the fluid pump QA using the upstream and downstream pressure regulating valves UJ, UK (a so-called reflux type configuration). Alternatively, the pressure regulating unit CA may adjust the front and rear wheel supply pressures Pm, Pv based on the pressure accumulated in an accumulator (a so-called accumulator type configuration). Alternatively, the front and rear wheel supply pressures Pm, Pv may be adjusted by increasing or decreasing the volume within a cylinder using a piston directly driven by an electric motor (a so-called electric cylinder type configuration). In either configuration, the pressure regulating unit CA receives feedback of the detected values ​​Pm, Pv of the front and rear wheel supply pressure sensors PM, PV, and electrically adjusts them.

[0089] In the above-described embodiment, the pressure receiving area rm (master area) of the master chamber Rm and the pressure receiving area ru (servo area) of the servo chamber Ru in the apply section AP are set equal. The master area rm and the servo area ru do not have to be equal. In a configuration in which the master area rm and the servo area ru are different, a conversion calculation between the front wheel supply pressure Pm and the downstream servo pressure Pk (or the upstream servo pressure Pj) is possible based on the ratio between the servo area ru and the master area rm (i.e., conversion based on "Pm·rm=Pk·ru (or Pj·ru)").

[0090] In the above-described embodiment, the first brake unit SA outputs the front wheel supply pressure Pm via the master cylinder CM. That is, the apply unit AP and the pressure adjustment unit CA are arranged in series in the hydraulic pressure transmission path, and the downstream servo pressure Pk supplied from the pressure adjustment unit CA is transmitted as the front wheel supply pressure Pm via the master piston NM. This configuration is referred to as a "series configuration." Instead of the series configuration, the apply unit AP and the pressure adjustment unit CA may be arranged in parallel. This configuration is referred to as a "parallel configuration." In the parallel configuration, the apply unit AP (particularly, the master cylinder CM) and the pressure adjustment unit CA are each directly connected to the second actuator YB. In the first mode, "connection between the pressure adjustment unit CA and the second actuator YB" is selected, and in the second mode, "connection between the apply unit AP and the second actuator YB" is selected. For example, this selection is achieved by a solenoid valve (referred to as a "switching valve"). In the first mode of this configuration, the front and rear wheel supply pressures Pm and Pv generated by the pressure adjusting unit CA are directly output as the front and rear wheel supply pressures Pm and Pv without passing through the apply unit AP. At this time, the apply unit AP is connected to the stroke simulator SS, and the operating force Fp of the brake operating member BP is generated by the simulator SS. On the other hand, in the second mode, the hydraulic pressure in the master chamber Rm generated by operating the brake operating member BP is output as the front wheel supply pressure Pm. At this time, the apply unit AP is disconnected from the simulator SS.

[0091] Regardless of whether the brake control device SC is configured in series or parallel, in the transmission paths of the front and rear wheel supply pressures Pm and Pv, a fluid path (a path through which brake fluid BF moves, referred to as a "communication path") connects between the portion where the front wheel supply pressure Pm acts and the portion where the rear wheel supply pressure Pv acts. A normally open solenoid valve (referred to as a "communication valve") is provided in the communication path. When ABS control is not being executed, the communication valve is closed and the communication path is blocked. As a result, the front wheel and rear wheel supply pressures Pm and Pv are individually regulated, and dual-system pressure regulation is performed. On the other hand, when ABS control is being executed, the communication valve is opened, and the portions related to the front wheel and rear wheel supply pressures Pm and Pv are placed in a communication state. As a result, the front wheel and rear wheel supply pressures Pm and Pv are regulated with the same hydraulic pressure, and single-system pressure regulation is performed. Here, the portions on which the front and rear wheel supply pressures Pm and Pv act (referred to as "action portions") include the sources of the front and rear wheel supply pressures Pm and Pv, the transmission paths (fluid paths, hydraulic chambers), and the like. The action portions include not only portions on which the front and rear wheel supply pressures Pm and Pv act directly, but also portions on which the force generated by the front and rear wheel supply pressures Pm and Pv acts via a member (e.g., master piston NM). For example, in the configuration shown in FIG. 2, portions pj and pk correspond to the action portions, and the upstream pressure regulating valve UJ corresponds to the communication valve. Here, the rear wheel supply pressure Pv acts directly on portion pj, while the front wheel supply pressure Pm acts indirectly on portion pk via the master piston NM.

[0092] <Summary of the embodiment> The following summarizes an embodiment of the brake control device SC: The brake control device SC is a brake-by-wire type device that can independently adjust the operation displacement Sp of the brake operating member BP and the hydraulic pressure Pw (wheel pressure) of the wheel cylinder CW.

[0093] The brake control device SC is equipped with a "first brake unit SA (first unit) that outputs front and rear wheel supply pressures Pm, Pv individually in accordance with the operation amount Sp of the brake operating member BP," and a "second brake unit SB (second unit) that is provided between the first brake unit SA and the front and rear wheel cylinders CWf, CWr, and that adjusts the front and rear wheel supply pressures Pm, Pv to output front and rear wheel pressures Pwf, Pwr." In the brake control device SC, when the second brake unit SB executes antilock brake control, the first brake unit SA communicates between a portion pk on which the front wheel supply pressure Pm acts and a portion pj on which the rear wheel supply pressure Pv acts, thereby making the front wheel target pressure Ptf and the rear wheel target pressure Ptr equal.

[0094] For example, in the first brake unit SA, normally open upstream and downstream pressure regulating valves UJ and UK are arranged in series in the circulating flow KN of brake fluid BF including a fluid pump QA. The upstream and downstream pressure regulating valves UJ and UK regulate the pressure of the brake fluid BF discharged by the fluid pump QA to upstream and downstream servo pressures Pj and Pk. The front wheel supply pressure Pm is output based on the hydraulic pressure on one side of the upstream and downstream servo pressures Pj and Pk. The rear wheel supply pressure Pv is output based on the hydraulic pressure on the other side of the upstream and downstream servo pressures Pj and Pk.

[0095] When ABS control is not being performed in the second brake unit SB, the first brake unit SA adjusts the upstream and downstream servo pressures Pj and Pk separately, thereby performing dual-system pressure regulation. However, when ABS control is being performed in the second brake unit SB, the first brake unit SA performs single-system pressure regulation. Specifically, in single-system pressure regulation, the front wheel target pressure Ptf and the rear wheel target pressure Ptr are made equal to determine the common target pressure Px (a common target value corresponding to the front and rear wheel supply pressures Pm and Pv) (i.e., "Px = Ptf = Ptr"). Furthermore, the upstream pressure regulator valve UJ is de-energized and fully opened. The downstream pressure regulator valve UK is controlled so that the rear wheel supply pressure Pv and the common target pressure Px coincide. In other words, the downstream pressure regulator valve UK is driven in response to feedback control based on the rear wheel supply pressure Pv.

[0096] In the brake control device SC, when ABS control is not performed in the second brake unit SB, the first brake unit SA performs two-way pressure regulation (individual adjustment of the front and rear wheel supply pressures Pm and Pv), which ensures the regenerative efficiency of the regenerative device KG and maintains a good front / rear braking force ratio, thereby improving vehicle stability. Also, in the brake control device SC, when ABS control is performed in the second brake unit SB, the first brake unit SA equalizes the front and rear wheel supply pressures Pm and Pv, thereby suppressing changes in the supply pressures Pm and Pv to the second brake unit SB. This allows ABS control to be performed well, improving its performance. [Explanation of symbols]

[0097] SC...Brake control device, KG...Regeneration device, BP...Brake operating member (brake pedal), SA...First brake unit (first unit), SB...Second brake unit (second unit), YA...First fluid unit (first actuator), YB...Second fluid unit (second actuator), EA...First control unit (first controller), EB...Second control unit (second controller), BS...Communication bus, CM...Master cylinder, CW...Wheel cylinder, AP...Apply section, NR...Input section, CA...Pressure adjustment section, UJ, UK...Upstream and downstream pressure adjustment valves, MA, MB... First and second electric motors, QA, QB...first and second fluid pumps, VA...inlet valve, VB...release valve, UB...control valve, SP...operation displacement sensor (operation amount sensor), PM, PV...front and rear wheel supply pressure sensors, Sp, Spa, Spb...operation displacement (operation amount), Pm, Pv...front and rear wheel supply pressure, Pj, Pk...upstream and downstream servo pressure, Pq...adjustment pressure, Pw...wheel pressure, Ptf, Ptr...front and rear wheel target pressure (target value corresponding to Pm, Pv), Px...common target pressure (common target value corresponding to Pm and Pv when "Ptf = Ptr"), Fab...ABS control execution flag.

Claims

[Claim 1] a first unit that outputs pressures to be supplied to the front wheels and the rear wheels individually in accordance with an amount of operation of a brake operating member of the vehicle; a second unit provided between the first unit and the front and rear wheel cylinders, the second unit adjusting the pressures supplied to the front and rear wheels and outputting wheel pressures for the front and rear wheels; In a braking control device for a vehicle, The first unit adjusts the pressure of the brake fluid discharged by the fluid pump to upstream and downstream servo pressures using normally open upstream and downstream pressure regulating valves arranged in series with the circulating flow of brake fluid including the fluid pump, and outputs the front wheel supply pressure using one of the upstream and downstream servo pressures, and outputs the rear wheel supply pressure using the other of the upstream and downstream servo pressures, The second unit is a front wheel inlet valve that is installed in a front wheel path that transmits the front wheel supply pressure to the front wheel cylinder, and that is closed when restricting an increase in the front wheel pressure; an outlet valve for a front wheel that opens when the wheel pressure of the front wheel is reduced; a pressure regulating reservoir for the front wheels that stores brake fluid flowing out from the front wheel cylinder through the open outlet valve for the front wheels; a second fluid pump for front wheels that pumps up brake fluid from the pressure regulating reservoir for the front wheels and discharges the brake fluid to a portion of the front wheel path between the inlet valve for the front wheels and the first unit; a rear wheel inlet valve that is installed in a rear wheel path that transmits the rear wheel supply pressure to the rear wheel cylinder, and that closes when restricting an increase in the rear wheel pressure; an outlet valve for a rear wheel that opens when the wheel pressure of the rear wheel is reduced; a pressure regulating reservoir for the rear wheels that stores brake fluid flowing out from the rear wheel cylinder through the outlet valve for the rear wheels that is open; a second fluid pump for the rear wheels that pumps up brake fluid from the pressure regulating reservoir for the rear wheels and discharges the brake fluid to a portion of the rear wheel path between the inlet valve for the rear wheels and the first unit, When the second unit executes antilock brake control, The first unit stops the supply of current to the upstream pressure regulating valve to equalize the pressures supplied to the front and rear wheels.

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