Vehicle braking control device

Abstract

To provide a braking control device, which can secure vehicle stability even if a regenerative device cannot perform energy regeneration.SOLUTION: A vehicle, to which a braking control device is applied, is configured so that a ratio of rear wheel friction brake force to front wheel friction brake force is equal to a predetermined value, in a state where wheel pressure of a front wheel is equal to wheel pressure of a rear wheel. The braking control device comprises an actuator that generates the front wheel friction brake force while adjusting the wheel pressure of the front wheel and generates rear wheel friction brake force while adjusting wheel pressure of the rear wheel, and a controller that controls the actuator. The controller, when a regenerative device can generate regenerative brake force, individually adjusts the wheel pressure of the front wheel and the wheel pressure of the rear wheel, on the regenerative brake force, so that the ratio of the total brake force of the rear wheel to the total brake force of the front wheel is equal to a predetermined value. If the regenerative device cannot generate the regenerative brake force, the controller adjusts the wheel pressure of the front wheel and the wheel pressure of the rear wheel so that the wheel pressure of the front wheel is equal to the wheel pressure of the rear wheel.SELECTED DRAWING: Figure 4

Description

[Technical Field]

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

[0002] In order to achieve both improved fuel economy and improved vehicle stability in regenerative cooperative control, the applicant has developed a braking control device that can simultaneously apply separate hydraulic pressures to the front and rear wheels using a single pressurizing system using an electric motor, as described in Patent Document 1. Specifically, the braking control device adjusts the front wheel brake hydraulic pressure (also referred to as "front wheel pressure") in the front wheel cylinders provided on the front wheels of the vehicle and the rear wheel brake hydraulic pressure (also referred to as "rear wheel pressure") in the rear wheel cylinders provided on the rear wheels of the vehicle, and includes a hydraulic pressure generation unit that adjusts the hydraulic pressure generated by the electric motor to an adjusted hydraulic pressure and applies the adjusted hydraulic pressure as rear wheel brake hydraulic pressure, and a hydraulic pressure correction unit that reduces and adjusts the adjusted hydraulic pressure to a corrected hydraulic pressure and applies the corrected hydraulic pressure as front wheel brake hydraulic pressure.

[0003] The braking control device described in Patent Document 1 improves vehicle stability in regenerative cooperative control when a regenerative device performs energy regeneration. It is desirable for the braking control device to ensure vehicle stability even when the regenerative device is unable to regenerate energy (for example, when the regenerative device fails). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2019-059458 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a braking control device for a vehicle that performs regenerative cooperative control, which can ensure vehicle stability even when a regenerative device is unable to perform energy regeneration. [Means for solving the problem]

[0006] The vehicle braking control device according to the present invention is applied to a vehicle (JV) equipped with a regenerative device (KC) on one of the front wheels (WHf) and the rear wheels (WHr), and includes an actuator (HU) that generates a front wheel friction braking force (Fmf) by adjusting a front wheel pressure (Pwf) in a front wheel cylinder (CWf) provided on the front wheels (WHf) and generates a rear wheel friction braking force (Fmr) by adjusting a rear wheel pressure (Pwr) in a rear wheel cylinder (CWf) provided on the rear wheels (WHr), and a controller (ECU) that controls the actuator (HU). The vehicle (JV) is configured so that a ratio (Km) of the rear wheel friction braking force (Fmr) to the front wheel friction braking force (Fmf) is a predetermined value (hb) when the front and rear wheel pressures (Pwf, Pwr) are equal.

[0007] In the vehicle braking control device according to the present invention, when the regenerative device (KC) is in a first state (FK=0) where it can generate a regenerative braking force (Fg), the controller (ECU) adjusts the front and rear wheel pressures (Pwf, Pwr) individually based on the regenerative braking force (Fg) so that the ratio of the total braking force (Fbf) of the rear wheels (WHr) to the total braking force (Fbf) of the front wheels (WHf) becomes the predetermined value (hb). Furthermore, when the regenerative device (KC) is in a second state (FK=1) where it cannot generate the regenerative braking force (Fg), the controller (ECU) adjusts the front wheel pressure (Pwf) and the rear wheel pressure (Pwr) so that they are equal.

[0008] According to the above configuration, even if the regenerative braking device KC malfunctions, the ratio of the rear wheel total braking force Fbr to the front wheel total braking force Fbf is maintained at a predetermined value hb, thereby making it possible to maintain vehicle stability even when the regenerative braking device KC malfunctions. [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] 1 is a schematic diagram for explaining a first embodiment of a braking control device SC. [Figure 3] FIG. 4 is a flowchart illustrating a process of regenerative cooperative control. [Figure 4] 3 is a time series diagram for explaining the operation of the regenerative cooperative control according to the first embodiment of the braking control device SC. FIG. [Figure 5] FIG. 4 is a schematic diagram for explaining a second embodiment of the braking control device SC. [Figure 6] FIG. 6 is a time series diagram for explaining the operation of the regenerative cooperative control according to the second embodiment of the braking control device SC. DETAILED DESCRIPTION OF THE INVENTION

[0010] <Symbols of components> In the following explanation, components, signals, values, and other elements with the same symbol, such as "CW," have the same function. The subscripts "f" and "r" added to the end of various symbols related to wheels are generic symbols that indicate whether the element relates to the front or rear wheels. Specifically, "f" indicates "element related to the front wheels," and "r" indicates "element related to the rear wheels." For example, a wheel cylinder CW is written as "front wheel cylinder CWf, rear wheel cylinder CWr." Furthermore, the subscripts "f" and "r" may be omitted. When omitted, each symbol represents its generic name.

[0011] <Vehicle JV equipped with braking control device SC> The overall configuration of a vehicle JV equipped with a braking control device SC according to the present invention will be described with reference to the schematic diagram of FIG.

[0012] The vehicle JV is a hybrid vehicle or an electric vehicle equipped with a drive electric motor. The drive electric motor also functions as a generator (electric power generator) for energy regeneration. The generator GNf is provided on the front wheels WHf. The generator GNf (also called a "front wheel generator") is controlled (driven) by a generator controller EGf. Here, a device including the generator GNf and its controller EGf is referred to as the "regeneration device KCf (or front wheel regeneration device KCf)." The vehicle JV is equipped with a storage battery BT for the regeneration device KCf. In other words, the regeneration device KCf also includes the storage battery BT.

[0013] When the electric motor / generator GNf operates as a drive electric motor (when the vehicle JV is accelerating), power is supplied to the electric motor / generator GNf from the storage battery BT via a regeneration device controller EGf (referred to as a "regeneration controller" or "front wheel regeneration controller"). On the other hand, when the electric motor / generator GNf operates as a generator (when the vehicle JV is decelerating), power generated by the generator GNf is stored in the storage battery BT via the regeneration controller EGf (so-called regenerative braking is performed). In regenerative braking, the generator GNf generates a front wheel regenerative braking force Fgf independently and separately from a friction braking force Fm, which will be described later.

[0014] A vehicle JV is equipped with front and rear wheel brake devices SXf, SXr (=SX). The brake device SX generates front and rear wheel friction braking forces Fmf, Fmr on the front wheels WHf and rear wheels WHr. The brake device SX includes a rotating member (e.g., a brake disc) KT and a brake caliper CP. The rotating member KT is fixed to the wheel WH, and the brake caliper CP is provided to sandwich the rotating member KT. The brake caliper CP is provided with a wheel cylinder CW. Pressurized braking fluid BF is supplied to the wheel cylinder CW from a brake control device SC. A friction member (e.g., a brake pad) MS is pressed against the rotating member KT by hydraulic pressure Pw (referred to as "wheel pressure") in the wheel cylinder CW. Because the rotating member KT and the wheel WH are fixed so as to rotate together, the frictional force generated at this time generates a frictional braking force Fm on the wheel WH. That is, the friction braking force Fm is generated by the friction between the rotating member KT and the friction member MS.

[0015] The vehicle JV is equipped with a brake operating member BP and various sensors (such as BA). The brake operating member (e.g., a brake pedal) BP is a member that the driver operates to decelerate the vehicle. The vehicle JV is provided with a brake operation amount sensor BA to detect the operation amount Ba (also referred to as the "braking operation amount") of the brake operating member BP. As the brake operation amount sensor BA, at least one of a simulator pressure sensor PS that detects the hydraulic pressure Ps (referred to as the "simulator pressure") of a stroke simulator SS (described later), an operation displacement sensor SP that detects the operation displacement Sp of the brake operating member BP, and an operation force sensor FP that detects the operation force Fp of the brake operating member BP is adopted. In other words, the operation amount sensor BA detects at least one of the simulator pressure Ps, the brake operation displacement Sp, and the brake operation force Fp as the braking operation amount Ba. The braking operation amount Ba is input to a controller ECU (also simply referred to as the "brake controller" or "controller") for the brake control device SC. The vehicle JV is equipped with various sensors including a wheel speed sensor VW that detects the rotational speed (wheel speed) Vw of the wheels WH. The detection signals (Ba, etc.) of these sensors are input to a braking controller ECU. The braking controller ECU calculates the vehicle speed Vx based on the wheel speed Vw.

[0016] The vehicle JV is equipped with a brake control device SC so as to execute so-called regenerative cooperative control (control in which the regenerative braking force Fg and the friction braking force Fm are operated in cooperation with each other). The brake control device SC employs a so-called front and rear type (also called "type II") brake system as two systems. The brake control device SC supplies wheel pressure Pw to the brake device SX (particularly, wheel cylinder CW) via the front and rear wheel connection paths HSf and HSR in accordance with the operation amount Ba of the brake operating member BP. The brake control device SC is composed of a fluid unit HU (also called "actuator") including a master cylinder CM, and a brake controller ECU.

[0017] The hydraulic unit HU is controlled by a brake controller ECU. The brake controller ECU is composed of a microprocessor MP that processes signals and a drive circuit DD that drives the solenoid valves and the electric motor. The brake controller ECU is connected to a regenerative device controller EGf via a communication bus BS. Therefore, information (detected values, calculated values) is shared between these controllers. For example, a target regenerative braking force Fhf is calculated by the brake controller ECU and sent to the regenerative controller EGf. A limit regenerative braking force Fxf and an operation flag FK are determined by the regenerative controller EGf and sent to the brake controller ECU. The brake controller ECU receives inputs such as the braking operation amount Ba, wheel speed Vw, limit regenerative braking force Fx, and an operation flag FK (a control flag indicating the operation state of the regenerative device KCf). Based on these signals, the brake controller ECU controls the hydraulic unit HU.

[0018] <First embodiment of braking control device SC> A first embodiment of the brake control device SC (particularly, a configuration example of the fluid unit HU) will be described with reference to the schematic diagram of FIG. 2. The brake control device SC includes a fluid unit HU as a pressure source for increasing the hydraulic pressure (wheel pressure) Pw of the four wheel cylinders CW. In the illustrated brake control device SC, the fluid unit HU and the master cylinder CM are integrated. The brake control device SC also employs a front / rear type (also called "type II") brake system. The fluid unit HU is composed of an apply unit AU including the master cylinder CM, and a pressurizing unit KU.

[0019] The apply unit AU and the pressurizing unit KU are controlled by a brake controller ECU. Specifically, the controller ECU receives the braking operation amount Ba (at least one of the simulator pressure Ps, operation displacement Sp, and operation force Fp), the master pressure Pm, the second servo pressure Pb, and the front wheel limit regenerative braking force Fxf. Based on these signals, the controller ECU calculates drive signals Va and Vb for the first and second on-off valves VA and VB, drive signals Ua and Ub for the first and second pressure regulating valves UA and UB, a drive signal Ma for the electric motor MA, and a front wheel target regenerative braking force Fhf. The solenoid valves VA, VB, UA, and UB constituting the hydraulic unit HU and the electric motor MA are controlled (driven) in accordance with the drive signals Va, Vb, Ua, Ub, and Ma.

[0020] As will be described later, the hydraulic unit HU, wheel cylinders CW, etc. are connected by the reservoir path HR, communication path HS (= HSf, HSR), input path HN, servo path HV, and return path HK. These are fluid paths through which the brake fluid BF moves. Fluid paths (HS, etc.) include fluid piping, flow paths within the hydraulic unit HU, hoses, etc.

[0021] <<Apply Unit AU>> The apply unit AU is composed of a master reservoir RV, a master cylinder CM, a master piston NM, a master spring DM, an input cylinder CN, an input piston NN, an input spring DN, first and second on-off valves VA and VB, a stroke simulator SS, and a simulator pressure sensor PS.

[0022] The master reservoir (also called the "atmospheric pressure reservoir") RV is a tank for hydraulic fluid, and stores brake fluid BF therein. The master reservoir RV is connected to the master cylinder CM (particularly, the master chamber Rm).

[0023] The master cylinder CM is a cylinder member having a bottom. A master piston NM is inserted into the master cylinder CM, and the interior is sealed with a seal member SL to form a master chamber Rm. The master cylinder CM is of a so-called single type. A master spring DM is provided in the master chamber Rm to pressurize the master piston NM in the backward direction Hb (the direction in which the volume of the master chamber Rm increases, which is the opposite direction to the forward direction Ha). The master chamber Rm is ultimately connected to the front wheel cylinder CWf via the front wheel communication passage HSf and a hydraulic pressure modulator MJ. When the master piston NM moves in the forward direction Ha (the direction in which the volume of the master chamber Rm decreases), brake fluid BF is pumped from the fluid unit HU (particularly the master cylinder CM) toward the front wheel cylinder CWf at hydraulic pressure Pm. The hydraulic pressure Pm in the master chamber Rm is referred to as the "master pressure."

[0024] The master piston NM is provided with a flange Tp. This flange Tp further divides the interior of the master cylinder CM into a servo chamber Ru and a rear chamber Ro. The servo chamber Ru is disposed opposite the master chamber Rm across the master piston NM. The rear chamber Ro is sandwiched between the master chamber Rm and the servo chamber Ru and is disposed therebetween. The servo chamber Ru and the rear chamber Ro are also sealed by the seal member SL, as described above.

[0025] For example, the pressure-receiving area ru of the flange portion Tp of the master piston NM (i.e., the pressure-receiving area of ​​the servo chamber Ru, also called the "servo area") and the pressure-receiving area rm of the end portion of the master piston NM (i.e., the pressure-receiving area of ​​the master chamber Rm, also called the "master area") are set to be equal. In this case, the hydraulic pressure Pa (first servo pressure) in the servo chamber Ru and the hydraulic pressure Pm (master pressure) in the master chamber Rm are statically equal, ignoring friction and other factors.

[0026] The input cylinder CN is fixed to the master cylinder CM. An input piston NN is inserted inside the input cylinder CN and sealed with a seal member SL to form an input chamber Rn. The input piston NN is mechanically connected to the brake operating member BP via a clevis (U-shaped link). A flange Tn is provided on the input piston NN. An input spring DN is provided between the flange Tn and the mounting surface of the input cylinder CN relative to the master cylinder CM. The input spring DN presses the input piston NN in the backward direction Hb.

[0027] When the input piston NN and the master piston NM are pressed most in the backward direction Hb, there is a gap Ks (also referred to as a "separation distance") between the input piston NN and the master piston NM. The gap Ks creates a state in which the wheel pressure Pw does not change even when a displacement Sp of the brake operating member BP occurs. In other words, by separating the input piston NN and the master piston NM with the gap Ks, the brake control device SC is configured as a brake-by-wire system, and regenerative cooperative control can be achieved.

[0028] The apply unit AU is provided with hydraulic chambers: an input chamber Rn, a servo chamber Ru, a rear chamber Ro, and a master chamber Rm. Here, the "hydraulic chambers" are chambers filled with brake fluid BF and sealed with a seal member SL. The volume of each hydraulic chamber is changed by the movement of the input piston NN and the master piston NM. The hydraulic chambers are arranged along the central axis Jm of the master cylinder CM in the order of input chamber Rn, servo chamber Ru, rear chamber Ro, and master chamber Rm, from the side closest to the brake operating member BP.

[0029] The input chamber Rn and the rear chamber Ro are connected via an input path HN. A first on-off valve VA is provided in the input path HN. The input path HN is connected to a master reservoir RV via a reservoir path HR between the rear chamber Ro and the first on-off valve VA. A second on-off valve VB is provided in the reservoir path HR. The first and second on-off valves VA and VB are two-position solenoid valves (also called "on-off valves") having an open position (communicating state) and a closed position (blocking state). A normally closed solenoid valve is used as the first on-off valve VA. A normally open solenoid valve is used as the second on-off valve VB. The first and second on-off valves VA and VB are driven (controlled) by drive signals Va and Vb from a brake controller ECU.

[0030] A stroke simulator (also simply referred to as "simulator") SS is connected to the rear chamber Ro. An operating force Fp of the brake operating member BP is generated by the simulator SS. A piston and an elastic body (e.g., a compression spring) are provided inside the simulator SS. When brake fluid BF flows into the simulator SS, the piston is pushed by the brake fluid BF. A force is applied to the piston by the elastic body in a direction that prevents the inflow of brake fluid BF, thereby generating an operating force Fp of the brake operating member BP. The operating characteristics of the brake operating member BP (the relationship between the operating displacement Sp and the operating force Fp) are formed by the simulator SS.

[0031] A simulator pressure sensor PS is provided to detect the hydraulic pressure (referred to as "simulator pressure") Ps of the simulator SS. The simulator pressure Ps is a state quantity equivalent to the operation force Fp, and is also the hydraulic pressure in the input chamber Rn and the rear chamber Ro. The simulator pressure sensor PS is one of the above-mentioned braking operation amount sensors BA, and the simulator pressure Ps is input to the controller ECU for the brake control device SC as the braking operation amount Ba.

[0032] In addition to the simulator pressure sensor PS, the fluid unit HU is provided with a braking operation amount sensor BA, which includes an operation displacement sensor SP that detects the operation displacement Sp of the brake operating member BP and / or an operation force sensor FP that detects the operation force Fp of the brake operating member BP. That is, the braking operation amount sensor BA is at least one of the simulator pressure sensor PS, the operation displacement sensor SP (stroke sensor), and the operation force sensor FP. Therefore, the braking operation amount Ba is at least one of the simulator pressure Ps, the operation displacement Sp, and the operation force Fp.

[0033] <Pressure unit KU> The pressurizing unit KU adjusts the hydraulic pressure Pwf (front wheel pressure) in the front wheel cylinder CWf and the hydraulic pressure Pwr (rear wheel pressure) in the rear wheel cylinder CWr independently and individually. However, in terms of the magnitude relationship between the front wheel pressure Pwf and the rear wheel pressure Pwr, the front wheel pressure Pwf is equal to or less than the rear wheel pressure Pwr. The pressurizing unit KU includes an electric motor MA, a fluid pump QA, first and second pressure regulating valves UA and UB, and a servo pressure sensor PB.

[0034] The hydraulic pump QA is driven by an electric motor MA, and the hydraulic fluid BF discharged by the hydraulic pump QA increases the wheel pressure Pw. Therefore, the electric motor MA is the power source for increasing the hydraulic pressure (wheel pressure) Pw in the wheel cylinder CW. The electric motor MA is controlled by the brake controller ECU in response to a drive signal Ma.

[0035] The suction port of the fluid pump QA is connected to the master reservoir RV via a reservoir line HR. The suction port and discharge port of the fluid pump QA are also connected via a return path HK. Therefore, when the electric motor MA is driven, a circulating flow KN of brake fluid BF is generated in the return path HK by the brake fluid BF discharged by the fluid pump QA (see the dashed arrows in the figure). Here, the side of the circulating flow KN closer to the discharge port of the fluid pump QA is referred to as the "upstream side," and the side further away is referred to as the "downstream side."

[0036] Two pressure regulating valves UA and UB are provided in series in the return flow path HK. Specifically, a first pressure regulating valve UA is provided in the return flow path HK. A second pressure regulating valve UB is provided between the first pressure regulating valve UA and the discharge port of the fluid pump QA. Therefore, in the return flow KN, the second pressure regulating valve UB is disposed upstream of the first pressure regulating valve UA. The first and second pressure regulating valves UA and UB are linear solenoid valves (also called "proportional valves" or "differential pressure valves") whose valve opening amount (lift amount) is continuously controlled based on the energization state (e.g., supply current). Normally open solenoid valves are used as the first and second pressure regulating valves UA and UB. The first and second pressure regulating valves UA and UB are controlled by a braking controller ECU based on drive signals Ua and Ub.

[0037] The hydraulic pressure Pa between the first pressure regulating valve UA and the second pressure regulating valve UB is regulated only by the first pressure regulating valve UA. The hydraulic pressure Pa is referred to as the "first servo pressure." In the braking system for the front wheels WHf, the return path HK is connected to the servo chamber Ru through the servo path HV between the first pressure regulating valve UA and the second pressure regulating valve UB. Therefore, the first servo pressure Pa is supplied to the servo chamber Ru. The first servo pressure Pa presses the master piston NM, generating a master pressure Pm. The master pressure Pm is supplied to the front wheel cylinder CWf. In other words, the first servo pressure Pa ultimately generates the front wheel pressure Pwf. A master pressure sensor PM is provided in the pressurizing unit KU to detect the master pressure Pm.

[0038] The hydraulic pressure Pb between the fluid pump QA and the second pressure regulating valve UB is controlled by both the first and second pressure regulating valves UA and UB. The hydraulic pressure Pb is referred to as the "second servo pressure." In the braking system for the rear wheel WHr, the return path HK is connected to the rear wheel cylinder CWr between the fluid pump QA (particularly the discharge portion) and the second pressure regulating valve UB via the rear wheel connection path HSR and the hydraulic pressure modulator MJ. In other words, the second servo pressure Pb is supplied directly to the rear wheel cylinder CWr, and the rear wheel pressure Pwr is generated by the second servo pressure Pb. The pressurizing unit KU is provided with a servo pressure sensor PB (also referred to as the "second servo pressure sensor") to detect the second servo pressure Pb.

[0039] When the electric motor MA is driven and the fluid pump QA is operating, a circulation flow KN of brake fluid BF is generated through the fluid pump QA and the first and second pressure regulating valves UA and UB (a flow that circulates in the order "QA → UB → UA → QA"). When no power is supplied to the first and second pressure regulating valves UA and UB and they are fully open, the first and second servo pressures Pa and Pb are both approximately "0 (atmospheric pressure)" (i.e., "Ia = Ib = 0" and "Pa = Pb = 0"). Here, pressure loss when the first and second pressure regulating valves UA and UB are fully open is ignored.

[0040] When the second pressure regulating valve UB is de-energized, power begins to be supplied to the first pressure regulating valve UA, and the amount of power Ia increases, causing the first pressure regulating valve UA to throttle the circulation flow KN. This causes the first servo pressure Pa to increase from "0." In this state, when power begins to be supplied to the second pressure regulating valve UB, and the amount of power Ib increases, the second pressure regulating valve UB further throttles the circulation flow KN. This causes the second servo pressure Pb to increase from the first servo pressure Pa. In other words, the first servo pressure Pa is a differential pressure with respect to "0 (atmospheric pressure)" and is regulated only by the first pressure regulating valve UA. Meanwhile, the second servo pressure Pb is a differential pressure with respect to the first servo pressure Pa and is regulated by the first and second pressure regulating valves UA and UB. Therefore, in terms of the magnitude relationship between the first servo pressure Pa and the second servo pressure Pb, the second servo pressure Pb is always equal to or greater than the first servo pressure Pa (i.e., "Pb≧Pa"). When no power is supplied to the second pressure regulating valve UB and it is fully open, the first servo pressure Pa and the second servo pressure Pb are made equal (that is, "Ib=0" and "Pa=Pb").

[0041] A hydraulic pressure modulator MJ is provided between the brake control device SC and the front and rear wheel cylinders CWf, CWr so that the front and rear wheel pressures Pwf, Pwr can be individually controlled at each wheel cylinder CW. Inside the hydraulic pressure modulator MJ, the front and rear wheel communication paths HSf, HSR are each branched into two paths that are connected to the front and rear wheel cylinders CWf, CWr. The hydraulic pressure modulator MJ controls each wheel pressure Pw for anti-lock brake control, vehicle stability control, etc., independently and individually. Note that the hydraulic pressure modulator MJ is not activated during service brake (service brake) application.

[0042] <Operation of the brake control device SC> When braking is not being applied (for example, when the brake operating member BP is not being operated), the master piston NM is pressed by the master spring DM and returned to its initial position (the position where it has been moved furthest in the backward direction Hb). In this state, the master chamber Rm and the master reservoir RV are in communication, and the hydraulic pressure Pm (master pressure) in the master chamber is "0 (atmospheric pressure)." Furthermore, when the master piston NM is in its initial position, there is a gap Ks between the input piston NN and the master piston NM. When braking is not being applied, the first and second pressure regulating valves UA and UB are open, so the first and second servo pressures Pa and Pb are "0 (atmospheric pressure)."

[0043] During braking (i.e., when the brake operating member BP is operated), the first on-off valve VA is opened and the second on-off valve VB is closed. That is, the input chamber Rn and the rear chamber Ro are connected, and the rear chamber Ro is disconnected from the master reservoir RV. As the operating amount Ba of the brake operating member BP increases, the input piston NN is moved forward in the forward direction Ha, and brake fluid BF is discharged from the input chamber Rn. The discharged brake fluid BF is absorbed by the stroke simulator SS, increasing the hydraulic pressure Pn (input pressure) in the input chamber Rn and the hydraulic pressure Po (rear pressure) in the rear chamber Ro, and generating an operating force Fp on the brake operating member BP. At this time, the first and second pressure regulating valves UA and UB are controlled in accordance with the braking operating amount Ba (at least one of the simulator pressure Ps, operating displacement Sp, and operating force Fp), and the first and second servo pressures Pa and Pb are increased.

[0044] Since the first servo pressure Pa is supplied to the servo chamber Ru, the master piston NM is pressed and moved in the forward direction Ha. As the master piston NM moves in the forward direction Ha, the master pressure Pm increases. Then, brake fluid BF adjusted to the master pressure Pm is supplied to the front wheel cylinder CWf, increasing its internal pressure Pwf. Also, brake fluid BF adjusted to the second servo pressure Pb is supplied to the rear wheel cylinder CWr, increasing its internal pressure Pwr. In other words, the front wheel pressure Pwf is adjusted to be equal to the first servo pressure Pa, and the rear wheel pressure Pwr is adjusted to be equal to the second servo pressure Pb. At this time, due to the constraints of the fluid unit HU (particularly the pressurizing unit KU), the front wheel pressure Pwf (= Pa) can be adjusted within a range equal to or less than the rear wheel pressure Pwr (= Pb).

[0045] The braking control device SC is of a brake-by-wire type and performs regenerative cooperative control. Because there is a gap Ks between the input piston NN and the master piston NM, the relative positional relationship between the input piston NN and the master piston NM can be adjusted arbitrarily within the range of this gap Ks by controlling the first servo pressure Pa. For example, when only the braking force Fgf from the front wheel regenerative device KCf is required, Pa is set to "0" and the master pressure Pm is left at "0." Because the front wheel pressure Pwf is not increased and remains at "0," no braking force (front wheel friction braking force) Fmf is generated due to friction between the rotating member KT and the friction member MS. Therefore, the total front wheel braking force Fbf is generated solely by the front wheel regenerative braking force Fgf.

[0046] <Regenerative Cooperative Control Processing> The regenerative cooperative control process will be described with reference to the flow chart in Figure 3. In "regenerative cooperative control," the regenerative braking force Fgf by the generator GNf and the friction braking force Fmf by the brake control device SC are controlled in coordination so that the kinetic energy of the vehicle JV during braking is efficiently recovered (regenerated) as electrical energy. The regenerative cooperative control algorithm is programmed in the microprocessor MP of the brake controller ECU.

[0047] <Total braking force Fb, friction braking force Fm, and set distribution Km> The actual braking force of the vehicle JV as a whole is referred to as the "vehicle body total braking force Fu." In other words, the vehicle body total braking force Fu (actual value) is the sum of the braking forces acting on the body of the vehicle JV. In addition, the sum of the braking forces acting on the front and rear wheels WHf and WHr (also referred to as the "total braking force") is referred to as the "front and rear wheel total braking forces Fbf and Fbr." Therefore, the sum of the front and rear wheel total braking forces Fbf and Fbr is the vehicle body total braking force Fu.

[0048] The braking forces actually generated by the front and rear wheel pressures Pwf and Pwr are referred to as "front and rear wheel friction braking forces Fmf and Fmr." In the first embodiment, no regenerative braking force is applied to the rear wheels WHr, so the rear wheel total braking force Fbr (actual value) coincides with the rear wheel friction braking force Fmr (actual value). Note that when no regenerative braking force Fgf is generated by the regenerative device KCf, the front wheel total braking force Fbf (actual value) coincides with the front wheel friction braking force Fmf (actual value).

[0049] In the vehicle JV, when the front and rear wheel pressures Pwf and Pwr are equal, the ratio Km (referred to as the "set distribution") of the rear wheel friction braking force Fmr to the front wheel friction braking force Fmf is set to a predetermined value hb (also referred to as the "reference value"). Specifically, the set distribution Km is determined to be the predetermined value hb based on the specifications of the front and rear wheel braking devices SXf and SXr (=SX) of the vehicle JV (pressure receiving area of ​​the wheel cylinder CW, effective braking radius of the rotating member KT, friction coefficient of the friction member MS, etc.). The predetermined value (reference value) hb is a constant set in advance.

[0050] <Regenerative Cooperative Control> First, we will explain the regenerative cooperative control when the operating state of the regenerative device KCf is appropriate. Here, the state in which the operation of the regenerative device KCf is appropriate is referred to as the "first state," and the state in which the operation is inappropriate is referred to as the "second state." In the first state, the regenerative device KCf can regenerate the kinetic energy of the vehicle JV and generate a regenerative braking force Fgf. On the other hand, in the second state, the regenerative device KCf cannot regenerate the kinetic energy of the vehicle JV and cannot generate a regenerative braking force Fgf.

[0051] The first and second states are transmitted from the regeneration controller EGf to the braking controller ECU via the communication bus BS via an operation flag FK. Here, the operation flag FK is a control flag that indicates whether the operation state of the regeneration device KCf is appropriate. Specifically, the operation flag FK indicates proper operation (first state) with a value of "0" and improper operation (second state) with a value of "1."

[0052] In step S110, signals such as the braking operation amount Ba, master pressure Pm, second servo pressure Pb, vehicle speed Vx, and operation flag FK are read. The operation amount Ba is calculated based on the detected value of the operation amount sensor BA (simulator pressure sensor PS, operation displacement sensor SP, operation force sensor FP, etc.). The master pressure Pm is calculated based on the detected value of the master pressure sensor PM. The second servo pressure Pb is calculated based on the detected value of the servo pressure sensor PB. The vehicle speed Vx is calculated based on the wheel speed Vw (detected value of the wheel speed sensor VW). Also, "FK=0 (first state)" is received from the regeneration controller EGf.

[0053] In step S120, a target vehicle body posture force Fv is calculated based on the braking operation amount Ba. The "target vehicle body posture force Fv" is a target value corresponding to the total braking force Fu (vehicle body total braking force) acting on the vehicle body. The target vehicle body posture force Fv is calculated to be "0" based on the braking operation amount Ba and the calculation map Zfv when the braking operation amount Ba is less than a predetermined amount bo. When the braking operation amount Ba is equal to or greater than the predetermined amount bo, the target vehicle body posture force Fv is calculated to increase from "0" as the braking operation amount Ba increases from "0". Here, the predetermined amount bo is a preset value (constant) that represents the play of the brake operating member BP.

[0054] In step S130, front and rear wheel required braking forces Fqf, Fqr (=Fq) are calculated based on the target vehicle body position force Fv. The "front and rear wheel required braking forces Fqf, Fqr" are target values ​​corresponding to the sums Fbf, Fbr (total front and rear wheel braking forces) of the braking forces actually acting on the front wheels WHf and rear wheels WHr. Therefore, the front wheel required braking force Fqf is a target value corresponding to the sum of the regenerative braking force Fgf (actual braking force by the regenerative device KCf) and the front wheel friction braking force Fmf (actual braking force by the front wheel wheel pressure Pwf). Furthermore, the rear wheel required braking force Fqr is a target value corresponding to the rear wheel friction braking force Fmr (actual braking force by the rear wheel pressure Pwr). In addition, in the braking control device SC, the braking forces of the left and right wheels are calculated as the same value, so the front wheel required braking force Fqf corresponds to the two wheels at the front of the vehicle (i.e., the two front wheels WHf), and the rear wheel required braking force Fqr corresponds to the two wheels at the rear of the vehicle (i.e., the two rear wheels WHr).

[0055] In step S130, the front and rear wheel required braking forces Fqf and Fqr are calculated so that the following two conditions are satisfied. 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 the "required distribution") of the rear wheel required braking force Fqr to the front wheel required braking force Fqf matches a predetermined value hb (=Km) (i.e., "Kq = Fqr / Fqf = hb = Km, where the predetermined value hb is a preset constant"). Specifically, in step S130, the required distribution Kq is set to a predetermined value hb (that is, the set distribution Km), and the required front and rear wheel braking forces Fqf, Fqr are calculated according to the following equation (1). Fqf = Fv / (1 + hb), and Fqr = Fv hb / (1 + hb) ...Equation (1)

[0056] In step S140, the limit regenerative braking force Fxf is acquired. The "limit regenerative braking force Fxf" is the maximum value (limit value) of the regenerative braking force Fgf that can be generated by the regenerative device KCf, and is also referred to as the "front wheel limit regenerative braking force." In other words, the limit regenerative braking force Fxf is a state quantity that represents the limit of the regenerative braking force Fgf of the front wheels WHf.

[0057] The limit regenerative braking force Fxf is restricted by the operating state of the front wheel regenerative device KCf. Therefore, the limit regenerative braking force Fxf is determined based on the operating state of the regenerative device KCf. Specifically, the operating state of the regenerative device KCf corresponds to at least one of the rotation speed Ngf of the front wheel generator GNf, the state (temperature, etc.) of the front wheel regenerative controller EGf (particularly, power transistors such as IGBTs), and the state (charge acceptance amount, temperature, etc.) of the storage battery BT. The limit regenerative braking force Fxf is determined (calculated) by the regenerative controller EGf and acquired by the brake controller ECU via the communication bus BS. For example, the front wheel regenerative controller EGf determines the front wheel limit regenerative braking force Fxf in the following manner.

[0058] The limit regenerative braking force Fxf (the upper limit value of the regenerative braking force Fgf) is determined based on the characteristic Zfx (calculation map) of block X140. This is because the amount of regeneration (and as a result, the regenerative braking force Fgf) by the regenerator KCf is determined by the rating of the power transistor (such as IGBT) of the regenerative controller EGf and the amount of charge that can be received by the battery BT (the remaining amount obtained by subtracting the current charge amount from the full charge amount). Specifically, in the calculation map Zfx, when the rotational speed Ngf of the front-wheel generator GNf is equal to or higher than the first predetermined speed vo, the regenerative power (work rate) by the regenerator KCf is made constant (that is, the product of the limit regenerative braking force Fxf and the rotational speed Ngf is made constant), and the limit regenerative braking force Fxf is determined. Therefore, when "Ngf ≧ vo", as the rotational speed Ngf decreases, the limit regenerative braking force Fxf is calculated to increase in an inverse proportion to the rotational speed Ngf. Also, when the rotational speed Ngf decreases, the amount of regeneration decreases. Thus, in the calculation map Zfx, when the rotational speed Ngf is less than the second predetermined speed vp, the limit regenerative braking force Fxf is calculated to decrease as the rotational speed Ngf decreases. Furthermore, when the rotational speed Ngf is extremely low, energy regeneration becomes impossible. Hence, in the calculation map Zfx, when the rotational speed Ngf is less than the third predetermined speed vq, the limit regenerative braking force Fxf is calculated to be "0". In addition, to prevent excessive deceleration slip (in extreme cases, wheel lock) from occurring in the front wheel WHf due to the regenerative braking force Fgf, a preset upper limit value fxf is provided in the calculation map Zfx (that is, "vp ≦ Ngf < vo" and "Fxf = fxf"). The first, second, and third predetermined speeds vo, vp, vq, and the upper limit value fxf are preset predetermined values (constants).

[0059] In step S150, a target regenerative braking force Fhf 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 Fxf. The "target regenerative braking force Fhf" is a target value corresponding to the actual regenerative braking force Fgf to be realized by the regenerative device KCf provided on the front wheels WHf. Furthermore, the "front-wheel and rear-wheel target frictional braking forces Fnf and Fnr (=Fn)" are target values ​​corresponding to the actual front-wheel and rear-wheel frictional braking forces Fmf and Fmr (=Fm) to be realized by the brake control device SC.

[0060] In step S150, it is determined whether the front wheel required braking force Fqf is greater than the limit regenerative braking force Fxf (referred to as "limit determination"). If the front wheel required braking force Fqf is equal to or less than the limit regenerative braking force Fxf (i.e., if the limit determination is negative), the target regenerative braking force Fhf is calculated to be equal to the front wheel required braking force Fqf, and the front wheel target frictional braking force Fnf is calculated to be "0". Furthermore, the rear wheel target frictional braking force Fnr is calculated to be equal to the rear wheel required braking force Fqr. That is, in step S150, if "Fqf≦Fxf", it is determined that "Fhf=Fqf, Fnf=0, Fnr=Fqr".

[0061] On the other hand, if the front wheel required braking force Fqf is greater than the limit regenerative braking force Fxf (i.e., if the limit determination is positive), the target regenerative braking force Fhf is calculated to be equal to the limit regenerative braking force Fxf, and the front wheel target frictional braking force Fnf is calculated to be equal to the front wheel required braking force Fqf minus the limit regenerative braking force Fxf. The rear wheel target frictional braking force Fnr is calculated to be equal to the rear wheel required braking force Fqr. That is, in step S150, if "Fqf>Fxf", it is determined that "Fhf=Fxf, Fnf=Fqf-Fxf, Fnr=Fqr".

[0062] The target regenerative braking force Fhf calculated in step S150 is transmitted from the braking controller ECU to the regenerative controller EGf via the communication bus BS. Then, the front wheel generator GNf is controlled by the front wheel regenerative controller EGf so that the actual front wheel regenerative braking force Fgf approaches and matches the target regenerative braking force Fhf.

[0063] In step S160, front and rear wheel target pressures Ptf, Ptr (=Pt) are calculated based on the front and rear wheel target frictional braking forces Fnf, Fnr (=Fn). The front and rear wheel target pressures Ptf, Ptr are target values ​​corresponding to the front and rear wheel pressures Pwf, Pwr (=Pw). The target pressures Pt (=Ptf, Ptr) are determined by simply converting the target frictional braking forces Fn (=Fnf, Fnr) into the dimension of the wheel pressures Pw (=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.). Note that since the front wheel pressure Pwf is equal to the master pressure Pm, the front wheel target pressure Ptf is also the target value of the master pressure Pm. Furthermore, since the rear wheel pressure Pwr is equal to the second servo pressure Pb, the target rear wheel pressure Ptr is also the target value of the second servo pressure Pb.

[0064] 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 brake controller ECU drives the electric motor MA and the first and second pressure regulating valves UA, UB to control the front and rear wheel pressures Pwf, Pwr to approach and match the front and rear wheel target pressures Ptf, Ptr. Specifically, first, the electric motor MA is driven to generate a circulation flow KN that includes the fluid pump QA and the first and second pressure regulating valves UA, UB. Then, based on the front wheel target pressure Ptf and the master pressure Pm (the value detected by the master pressure sensor PM), the first pressure regulating valve UA is hydraulically feedback controlled so that the master pressure Pm (= Pwf) matches the front wheel target pressure Ptf. In other words, the current Ia (also referred to as the "first current") supplied to the first pressure regulating valve UA is adjusted so that the deviation hPf between the master pressure Pm and the front wheel target pressure Ptf becomes "0". Furthermore, the second pressure regulating valve UB is hydraulically feedback controlled based on the rear wheel target pressure Ptr and the second servo pressure Pb (the value detected by the servo pressure sensor PB) so that the second servo pressure Pb (= Pwr) matches the rear wheel target pressure Ptr. In other words, the current Ib (also referred to as the "second current") supplied to the second pressure regulating valve UB is adjusted so that the deviation hPr between the second servo pressure Pb and the rear wheel target pressure Ptr becomes "0".

[0065] <<Control when the regenerative device KCf is malfunctioning>> Next, we will explain what happens when the regenerative device KCf installed on the front wheels WHf is not operating properly (for example, when the regenerative device KCf fails). When the regenerative device KCf is not operating properly (i.e., in the second state), the generator GNf cannot generate regenerative braking force Fgf. The second state is transmitted from the regenerative controller EGf via the communication bus BS by "FK=1".

[0066] For example, the second state is determined based on the state of the regeneration controller EGf, such as the temperature. When the temperature Tg of the regeneration controller EGf is higher than a predetermined temperature tg, the second state is determined. Similarly, when the temperature Tb of the storage battery BT is higher than a predetermined temperature tb, the second state is determined. Note that the predetermined temperatures tg and tb are threshold values ​​for determination, and are preset values ​​(constants).

[0067] From the calculation cycle in which "FK=1 (second state)" is received, "Fhf=0, Fnf=Fqf, Fnr=Fqr" is calculated in step S150. Accordingly, in step S160, the front wheel target pressure Ptf is determined to match the rear wheel target pressure Ptr. In other words, the front wheel target pressure Ptf is increased so that the front wheel target pressure Ptf and the rear wheel target pressure Ptr are made equal. In increasing the front wheel target pressure Ptf, a limit is imposed on the time change amount dPf by a predetermined gradient kf. The predetermined gradient kf is a predetermined value (constant) that is set in advance.

[0068] In step S170, the wheel pressure Pw (actual value) is adjusted based on the target pressure Pt (target value). Specifically, the current Ia (first current) supplied to the first pressure regulating valve UA is increased in accordance with an increase in the front wheel target pressure Ptf. At this time, the increase gradient (time change amount) dPf of the front wheel target pressure Ptf is limited to a predetermined gradient kf, so that the first current Ia is gradually increased. As a result, the front wheel pressure Pwf is gradually increased.

[0069] Furthermore, in step S170, the supply current Ib (second current) to the second pressure regulating valve UB is reduced in response to the increase in the first current Ia. The difference sPt between the front wheel target pressure Ptf and the rear wheel target pressure Ptr (= "Ptr - Ptf", referred to as the "target pressure difference") is reduced toward "0", and the second current Ib is adjusted based on the target pressure difference sPt. Specifically, as the target pressure difference sPt is gradually reduced, the second current Ib is gently reduced. Finally, the second current is set to "0", and the second pressure regulating valve UB is brought into a fully open state. This forcibly makes the first servo pressure Pa (= Pwf) and the second servo pressure Pb (= Pwr) the same.

[0070] In the braking control device SC, in the case of the first state (i.e., when energy regeneration by the regenerator KCf is possible), based on the front-wheel regenerative braking force Fgf, the front-wheel target pressure Ptf and the rear-wheel target pressure Ptr are individually calculated so that the required distribution Kq (i.e., "Fqr / Fqf") matches a predetermined value hb (i.e., the set distribution Km). That is, in the first state, since the regenerative braking force Fgf can be generated in the front wheel WHf, the front-wheel target pressure Ptf is determined to be smaller than the rear-wheel target pressure Ptr (i.e., the state of "Pwf<Pwr"). Then, based on the front-wheel and rear-wheel target pressures Ptf and Ptr, the front-wheel wheel pressure Pwf and the rear-wheel wheel pressure Pwr are adjusted to be different. Therefore, in the first state, the total front-wheel braking force Fbf matches the sum of the front-wheel regenerative braking force Fgf and the front-wheel frictional braking force Fmf, and the total rear-wheel braking force Fbr matches the rear-wheel frictional braking force Fmr (i.e., "Fbf=Fgf+Fmf, Fbr=Fmr"). Also, since the ratio (actual value) of the total rear-wheel braking force Fbr to the total front-wheel braking force Fbf is controlled to match the required distribution Kq (target value), it is the predetermined value hb (i.e., "Fbr / Fbf=Kq=Km=hb").

[0071] When transitioning from the first state to the second state (i.e., when energy regeneration by the regenerator KCf becomes impossible), the front-wheel target pressure Ptf and the rear-wheel target pressure Ptr are determined to be equal. As a result, the front-wheel wheel pressure Pwf and the rear-wheel wheel pressure Pwr are adjusted to match. Specifically, the energization to the second pressure regulating valve UB is stopped, and the second pressure regulating valve UB is set to the fully open state. Thereby, the first servo pressure Pa (=Pm=Pwf) and the second servo pressure Pb (=Pwr) are forcibly made equal, and "Pwf=Pwr" is achieved.

[0072] In the vehicle JV, the specifications of the front and rear wheel braking devices SXf and SXr are set to satisfy "Km = hb." Therefore, when the regenerative device KCf is in a malfunctioning state (e.g., a failure state) and the regenerative braking force Fgf is not generated, "Pwf = Pwr" is set, and the ratio of the rear wheel braking force Fmr (i.e., the rear wheel friction braking force Fmr) to the total front wheel braking force Fbf (i.e., the front wheel friction braking force Fmf) is maintained at the set distribution Km (i.e., the predetermined value hb). Therefore, even in the second state, this ratio does not change, so the directional stability of the vehicle JV is maintained. In addition, sufficient braking force can be ensured.

[0073] Furthermore, in the brake control device SC, the increase in the front wheel target pressure Ptf due to malfunction of the regenerative device KCf is not sudden but is performed smoothly. Specifically, the time change (increase gradient) dPf of the front wheel target pressure Ptf is limited to a predetermined gradient kf (a preset constant). Then, the first current Ia is gradually increased based on the front wheel target pressure Ptf. At the same time, the second current Ib is gradually decreased based on the difference sPt (target pressure difference) between the front wheel target pressure Ptf and the rear wheel target pressure Ptr. When transitioning from the first state to the second state, "Pwf = Pwr" is smoothly achieved, so a sudden change in the vehicle body acceleration Gx is suppressed and a deterioration in ride comfort is avoided. In addition, disturbances in vehicle behavior can also be avoided.

[0074] <Operation of the Brake Control Device SC in the Regenerative Cooperative Control According to the First Embodiment> The operation of the regenerative cooperative control (particularly the calculation of the front and rear wheel target pressures Ptf and Ptr) of the braking control device SC according to the first embodiment will be described with reference to the time series diagram of Figure 4 (a diagram showing the transition of various state quantities over time T). In the regenerative cooperative control, the actual values ​​Pwf and Pwr are controlled to match the target values ​​Ptf and Ptr, so the diagram of the target pressure Pt and the diagram of the wheel pressure Pw overlap.

[0075] In the example, it is assumed that: The regenerative device KCf is provided only on the front wheels WHf. Therefore, the regenerative braking force Fgf and the friction braking force Fmr act on the front wheels WHf, and only the friction braking force Fmr acts on the rear wheels WHr. In the brake control device SC, the pressure receiving area ru of the servo chamber Ru is equal to the pressure receiving area rm of the master chamber Rm, so the master pressure Pm is equal to the first servo pressure Pa. - The front wheel pressure Pwf (= Pm) is adjusted by the first servo pressure Pa. The first servo pressure Pa is feedback-controlled so that the master pressure Pm (detected value of the master pressure sensor PM) coincides with the front wheel target pressure Ptf.

[0076] At time t0, operation of the brake operating member BP begins. Accordingly, from time t0, the front and rear wheel required braking forces Fqf, Fqr are increased in accordance with the increase in the braking operation amount Ba. From time t0, the rear wheel target friction braking force Fnr is increased, and the rear wheel target pressure Ptr is increased. From time t0 to time t1, the front wheel required braking force Fqf is equal to or less than the limit regenerative braking force Fxf, so the front wheel target friction braking force Fnf remains at "0". Therefore, the front wheel target pressure Ptf is set to "0".

[0077] At time t1, "Fqf = Fxf". After time t1, the front wheel target friction braking force Fnf is increased in accordance with an increase in the braking operation amount Ba, and the front wheel target pressure Ptf is increased. At time t2, the brake operating member BP is held. After time t2, the generator rotation speed Ngf decreases as the vehicle speed Vx decreases, so the limit regenerative braking force Fxf is increased (see the calculation map Zfx in Figure 3). Therefore, the front wheel regenerative braking force Fgf increases, and the front wheel target pressure Ptf is decreased.

[0078] At time t3, the rotation speed Ngf of the front wheel generator GNf decreases to the first predetermined speed vo, and the limit regenerative braking force Fxf reaches the upper limit value fxf. After time t3, the state of "Fxf = fxf (predetermined upper limit value)" is maintained, and the front wheel target pressure Ptf is calculated to be constant.

[0079] At time t4, the regenerative device KCf enters a malfunctioning state (e.g., a failure state) and is unable to generate regenerative braking force Fgf. At time t4, the operation flag FK sent from the regenerative controller ECf to the controller ECU is switched from "0 (first state)" to "1 (second state)." At time t4, the front wheel pressure Pwf begins to increase based on the operation flag FK. Specifically, the front wheel target pressure Ptf is increased while being limited by a predetermined gradient kf (a preset constant). As a result, the current value Ia (first current) to the first pressure regulating valve UA is gradually increased, and the current value Ib (second current) to the second pressure regulating valve UB is gradually decreased.

[0080] At time t5, the second current Ib is set to "0" and the second pressure regulating valve UB is set to a fully open state. As a result, the first servo pressure Pa and the second servo pressure Pb become equal, and the front wheel pressure Pwf and the rear wheel pressure Pwr become equal. Since "Ib = 0" continues from time t5 onwards, the state of "Pwf = Pwr" is maintained. At time t6, the brake operating member BP, which had been held, is returned. Accordingly, the front and rear wheel pressures Pwf and Pwr are reduced towards "0".

[0081] <Second embodiment of braking control device SC> A second embodiment of the brake control device SC will be described with reference to the schematic diagram of Fig. 5. In a vehicle JV equipped with the brake control device SC according to the first embodiment, a regenerative device KCf is provided on the front wheels WHf. Conversely, in a vehicle JV equipped with the brake control device SC according to the second embodiment, a regenerative device KCr is provided on the rear wheels WHr, as indicated by the dashed lines and bracketed symbols in the schematic diagram of Fig. 1. The regenerative device KCr (also referred to as the "rear wheel regenerative device KCr") includes a generator GNr (also referred to as the "rear wheel generator"), a controller EGr for the generator GNr, and a storage battery BT for the regenerative device KCr.

[0082] In a vehicle JV equipped with a brake control device SC according to the second embodiment, no regenerative braking force is generated on the front wheels WHf, and only the regenerative braking force Fgr is generated on the rear wheels WHr. Therefore, in the second embodiment of the brake control device SC, the first servo pressure Pa is supplied to the rear wheel cylinder CWr, and the second servo pressure Pb is supplied to the servo chamber Ru. The following describes the differences between the first and second embodiments. Note that the first and second embodiments are the same except for the differences.

[0083] In the brake control device SC according to the second embodiment, in the brake system for the front wheels WHf, the return path HK is connected to the servo chamber Ru through the servo path HV between the discharge port of the fluid pump QA and the second pressure regulating valve UB. Therefore, the second servo pressure Pb is supplied to the servo chamber Ru. The second servo pressure Pb generates a master pressure Pm via the master piston NM. The master pressure Pm is supplied to the front wheel cylinder CWf, and ultimately the front wheel pressure Pwf is generated by the second servo pressure Pb.

[0084] In the braking system for the rear wheel WHr, the return path HK is connected to the rear wheel cylinder CWr between the first pressure regulating valve UA and the second pressure regulating valve UB via the rear wheel connection path HSR and the hydraulic pressure modulator MJ. Therefore, the first servo pressure Pa is directly supplied to the rear wheel cylinder CWr. Therefore, the rear wheel pressure Pwr is generated by the first servo pressure Pa. The pressurizing unit KU is provided with a servo pressure sensor PA (also referred to as the "first servo pressure sensor") to detect the first servo pressure Pa.

[0085] In the second embodiment, in the first state, the front wheel target pressure Ptf and the rear wheel target pressure Ptr are individually calculated based on the rear wheel regenerative braking force Fgr so that the required allocation Kq (i.e., "Fqr / Fqf") matches a predetermined value hb (i.e., set allocation Km). Then, the front wheel pressure Pwf and the rear wheel pressure Pwr are adjusted to be different based on the front and rear wheel target pressures Ptf and Ptr. In other words, in the first state, the front wheel total braking force Fbf matches the front wheel friction braking force Fmf, and the rear wheel total braking force Fbr matches the sum of the rear wheel regenerative braking force Fgf and the rear wheel friction braking force Fmr (i.e., "Fbf = Fmf, Fbr = Fgr + Fmr"). As in the first embodiment, the ratio (actual value) of the rear wheel total braking force Fbr to the front wheel total braking force Fbf is controlled to match the required distribution Kq (target value), and is therefore a predetermined value hb (i.e., "Fbr / Fbf=Kq=Km=hb").

[0086] Next, the regenerative cooperative control according to the second embodiment will be described with reference to the flow diagram of Fig. 3. The regenerative cooperative control in the second embodiment corresponds to the process in steps S140 and S150, where "front wheels" is replaced with "rear wheels", and the suffix "f" at the end of the symbols is replaced with "r", and the suffix "r" is replaced with "f".

[0087] In step S140, a limit regenerative braking force Fxr of the rear wheels WHr is calculated and acquired based on a calculation map similar to the calculation map Zfx and the rotation speed Ngr of the rear wheel generator GNr (or vehicle speed Vx). Then, in step S150, a limit determination is made as to whether the rear wheel required braking force Fqr is greater than the limit regenerative braking force Fxr. If the rear wheel required braking force Fqr is equal to or less than the limit regenerative braking force Fxr, the target regenerative braking force Fhr is calculated to be equal to the rear wheel required braking force Fqr, the front wheel target frictional braking force Fnf is calculated to be equal to the front wheel required braking force Fqf, and the rear wheel target frictional braking force Fnr is calculated to be "0." That is, if "Fqr≦Fxr," it is determined that "Fhr=Fqr, Fnf=Fqf, Fnr=0."

[0088] On the other hand, when the rear wheel required braking force Fqr is greater than the limit regenerative braking force Fxr, the target regenerative braking force Fhr is calculated to be equal to the limit regenerative braking force Fxr, the front wheel target frictional braking force Fnf is calculated to be equal to the front wheel required braking force Fqf, and the rear wheel target frictional braking force Fnr is calculated to be equal to the rear wheel required braking force Fqr minus the limit regenerative braking force Fxr. That is, when "Fqr > Fxr," the following is determined: "Fhr = Frf, Fnf = Fqf, Fnr = Fqr - Fxr." The target regenerative braking force Fhr is then transmitted from the brake controller ECU to the rear wheel regenerative controller EGr via the communication bus BS. The regenerative controller EGr controls the rear wheel generator GNr so that the actual rear wheel regenerative braking force Fgr approaches and matches the target regenerative braking force Fhr.

[0089] <Operation of the Brake Control Device SC in Regenerative Cooperative Control According to the Second Embodiment> The operation of the braking control device SC according to the second embodiment (particularly the calculation of the front and rear wheel target pressures Ptf and Ptr) during regenerative cooperative control will be described with reference to the time series diagram of Figure 6 (a diagram showing the transition of various state quantities over time T). During regenerative cooperative control, the actual values ​​Pwf and Pwr are controlled to match the target values ​​Ptf and Ptr, so the diagram of the target pressure Pt and the diagram of the wheel pressure Pw overlap.

[0090] In the example, it is assumed that: The regenerative braking device KCr is provided only on the rear wheels WHr. Therefore, only the friction braking force Fmf acts on the front wheels WHf, and the regenerative braking force Fgr and the friction braking force Fmr act on the rear wheels WHr. In the braking control device SC, the pressure-receiving area ru of the servo chamber Ru is equal to the pressure-receiving area rm of the master chamber Rm. Therefore, "Pb = Pm". The front wheel pressure Pwf (= Pm) is adjusted by the second servo pressure Pb. The second servo pressure Pb is feedback-controlled so that the master pressure Pm (detected value of the master pressure sensor PM) coincides with the front wheel target pressure Ptf.

[0091] At time u0, operation of the brake operating member BP begins. Accordingly, from time u0, the front and rear wheel required braking forces Fqf and Fqr are increased in accordance with the increase in the braking operation amount Ba. From time t0, the front wheel target frictional braking force Fnf is increased, and the front wheel target pressure Ptf is increased. From time u0 to time u1, the rear wheel required braking force Fqr is equal to or less than the limit regenerative braking force Fxr, so the rear wheel target frictional braking force Fnr remains at "0". From time u1 onwards, the state becomes "Fqr > Fxr", so the rear wheel target frictional braking force Fnr is increased in accordance with the increase in the braking operation amount Ba, and the rear wheel target pressure Ptr is increased.

[0092] At time u3, the regenerative device KCr enters a malfunctioning state (e.g., a failure state), and rear wheel regenerative braking force Fgr cannot be generated. At time u3, the operation flag FK is switched from "0 (first state)" to "1 (second state)." At time u3, an increase in the rear wheel pressure Pwr begins based on the transition of the operation flag FK. Specifically, the rear wheel target pressure Ptr is increased so as to match the front wheel target pressure Ptf while being limited by a predetermined gradient kr (a preset constant). As a result, the supply current Ia (first current) to the first pressure regulating valve UA is gradually increased, and the supply current Ib (second current) to the second pressure regulating valve UB is gradually decreased. In the second embodiment, the first current Ia is gradually increased based on the rear wheel target pressure Ptr. At the same time, the second current Ib is gradually reduced based on the target pressure difference sPt (=Ptf-Ptr) between the target front wheel pressure Ptf and the target rear wheel pressure Ptr.

[0093] At time u4, the power supply (energization) to the second pressure regulating valve UB is completely stopped, and the second pressure regulating valve UB is set to a fully open state. As a result, the first servo pressure Pa and the second servo pressure Pb become equal, and the front wheel pressure Pwf and the rear wheel pressure Pwr match. Since "Ib = 0" continues from time u4 onwards, the state of "Pwf = Pwr" is maintained. At time u5, the brake operating member BP, which had been held, is returned. Accordingly, the front and rear wheel pressures Pwf and Pwr are reduced towards "0".

[0094] <Summary of each embodiment> An embodiment of the brake control device SC will be summarized below. A vehicle JV to which the brake control device SC is applied is provided with a regenerative device KC (KCf or KCr) on one of the front wheels WHf and the rear wheels WHr. The vehicle JV is configured so that when the front and rear wheel wheel pressures Pwf and Pwr are equal (i.e., when Pwf = Pwr), the ratio Km of the rear wheel friction braking force Fmr to the front wheel friction braking force Fmf becomes a predetermined value hb.

[0095] The braking control system SC is composed of an actuator HU and a controller ECU. The actuator HU (fluid unit) adjusts the hydraulic pressure Pwf (front wheel pressure) in the front wheel cylinder CWf. The front wheel pressure Pwf generates a front wheel friction braking force Fmf. The actuator HU also adjusts the hydraulic pressure Pwr (rear wheel pressure) in the rear wheel cylinder CWr. The rear wheel pressure Pwr generates a rear wheel friction braking force Fmr. The controller ECU controls the actuator HU. In other words, the front and rear wheel pressures Pwf and Pwr are adjusted by the controller ECU via the actuator HU.

[0096] When the regenerative device KC is operating properly and can regenerate the kinetic energy of the vehicle JV by the regenerative device KC and can generate a regenerative braking force Fg (i.e., in the case of the first state), the controller ECU individually adjusts the regenerative braking force Fg and the front and rear wheel pressures Pwf and Pwr so that the ratio of the total braking force Fbr of the rear wheels WHr (the sum of the braking forces acting on the rear wheels WHr) to the total braking force Fbf of the front wheels WHf (the sum of the braking forces acting on the front wheels WHf) becomes a predetermined value hb. On the other hand, when the regenerative device KC is not operating properly and cannot regenerate the kinetic energy of the vehicle JV by the regenerative device KC and can no longer generate a regenerative braking force Fg (i.e., in the case of the second state), the controller ECU adjusts the front wheel pressure Pwf and the rear wheel pressure Pwr so that they are equal.

[0097] The brake control device SC executes regenerative cooperative control (control in which the regenerative braking force Fg and the friction braking force Fm cooperate with each other). In the regenerative cooperative control, the target regenerative braking forces Fhf, Fhr (resulting in regenerative braking forces Fgf, Fgr) and the target pressures Ptf, Ptr (resulting in wheel pressures Pwf, Pwr) are determined so that the ratio Kq (requested distribution) of the rear wheel required braking force Fqr to the front wheel required braking force Fqf is maintained at a predetermined value hb (predetermined constant). Furthermore, in the vehicle JV, when the front wheel pressure Pwf and the rear wheel pressure Pwr are the same, the specifications of the brake device SX are set so that the ratio Km (set distribution) of the rear wheel friction braking force Fmr (braking force due to the rear wheel pressure Pwr) to the front wheel friction braking force Fmf (braking force due to the front wheel pressure Pwf) becomes a predetermined value hb (i.e., "Km = Fmr / Fmf = hb"). Therefore, even when the vehicle transitions from the first state to the second state, the front wheel pressure Pwf and the rear wheel pressure Pwr are adjusted to be equal to each other, so that the ratio of the total rear wheel braking force Fbr to the total front wheel braking force Fbf is maintained constant at the predetermined value hb. Therefore, even when the regenerative device KC cannot perform energy regeneration, vehicle stability can be ensured.

[0098] Furthermore, in the brake control device SC, when the front and rear wheel pressures Pwf and Pwr are made to match, the increase gradient of the hydraulic pressure on the increasing side is limited. Specifically, in a vehicle JV in which a regenerative device KCf is provided on the front wheels WHf, the time change (increase gradient) dPf of the front wheel target pressure Ptf is limited to a predetermined gradient kf (a preset constant), and the front wheel target pressure Ptf (resulting in the front wheel pressure Pwf) is increased. Conversely, in a vehicle JV in which a regenerative device KCr is provided on the rear wheels WHr, the time change (increase gradient) dPr of the rear wheel target pressure Ptr is limited to a predetermined gradient kr (a preset constant), and the rear wheel target pressure Ptr (resulting in the rear wheel pressure Pwr) is increased. By limiting the time change dP when the target pressure Pt is increased, the front and rear wheel pressures Pwf and Pwr are made to match smoothly. Therefore, a sudden change in the vehicle body acceleration Gx is suppressed, and as a result, a decrease in the ride comfort of the vehicle JV can be avoided.

[0099] For example, the actuator HU may be a "fluid pump QA driven by an electric motor MA," and The fluid pump QA is configured with "first and second pressure regulating valves UA and UB provided in the return passage HK connecting the suction port and discharge port of the fluid pump QA." The first and second pressure regulating valves UA and UB regulate the first and second servo pressures Pa and Pb. Specifically, the first servo pressure Pa is regulated only by the first pressure regulating valve UA, and the second servo pressure Pb is regulated by both the first and second pressure regulating valves UA and UB.

[0100] In a vehicle JV in which a regenerative device KCf (particularly, a generator GNf) is provided on the front wheels WHf, the first servo pressure Pa is transmitted to the front wheel cylinders CWf via the master piston NM to adjust the front wheel pressure Pwf, and the second servo pressure Pb is supplied directly to the rear wheel cylinders CWr to adjust the rear wheel pressure Pwr. In other words, in a vehicle JV in which the regenerative device KCf is provided on the front wheels WHf, "Pwf≦Pwr" holds, so when the operation of the regenerative device KCf is proper (i.e., in the first state), the front wheel pressure Pwf is adjusted to be smaller than the rear wheel pressure Pwr.

[0101] On the other hand, in a vehicle JV in which the regenerative device KCr (particularly the generator GNr) is provided on the rear wheels WHr, the second servo pressure Pb is transmitted to the front wheel cylinder CWf via the master piston NM to adjust the front wheel pressure Pwf, and the first servo pressure Pa is supplied directly to the rear wheel cylinder CWr to adjust the rear wheel pressure Pwr. In other words, in a vehicle JV in which the regenerative device KCr is provided on the rear wheels WHr, "Pwf≧Pwr" holds, so when the operation of the regenerative device KCr is proper (i.e., in the first state), the rear wheel pressure Pwr is adjusted to be smaller than the front wheel pressure Pwf.

[0102] In the above configuration, when the regenerative device KC malfunctions, "Pwf = Pwr" is achieved by de-energizing the second pressure regulating valve UB. When de-energizing the second pressure regulating valve UB, the current value Ib is gradually reduced and finally set to "0." This ensures a smooth increase in hydraulic pressure during the transition from the first state to the second state, thereby avoiding a sudden change in the vehicle body acceleration Gx and ensuring a comfortable ride. [Explanation of symbols]

[0103] JV...vehicle, SC...brake control device, SXf, SXr...front and rear wheel brake devices, CP...brake caliper, CW...wheel cylinder, KT...rotating member (brake disc), MS...friction member (brake pad), CM...master cylinder, NM...master piston, Rm...master chamber, Ru...servo chamber, HU...fluid unit (actuator), UA, UB...first and second pressure regulating valves, MA...electric motor, QA...fluid pump, ECU...controller for brake control device (brake controller), KCf, KCr...front and rear wheel regenerative device, GNf, GNr...front and rear wheel generators, EGf, EGr...controller for front and rear wheel regenerative device (front and rear wheel regenerative controller), BS...communication bus, Fu...total vehicle Braking force (actual value), Fv...target vehicle braking force (target value), Fbf, Fbr...front and rear wheel total braking force (actual value), Fqf, Fqr...front and rear wheel required braking force (target value), Fxf, Fxr...front and rear wheel limit regenerative braking force, Fmf, Fmr...front and rear wheel friction braking force (actual value), Fnf, Fnr...front and rear wheel target friction braking force (target value), Ptf, Ptr...front Wheel, rear wheel target pressure (target value), Pwf, Pwr...front wheel, rear wheel pressure (actual value), Pa, Pb...first and second servo pressure (actual value), Pm...master pressure (actual value), hb...predetermined value (reference value), Km...set distribution (=hb), Kq...requested distribution (=hb), PM...master pressure sensor, PA, PB...first and second servo pressure sensors (first and second servo pressure sensors).

Claims

1. A vehicle braking control device that is applied to a vehicle that has front wheels and rear wheels as wheels and has a regenerative device on the front wheels, an actuator that generates a front wheel friction braking force by adjusting a front wheel pressure in a front wheel cylinder provided on the front wheel, and generates a rear wheel friction braking force by adjusting a rear wheel pressure in a rear wheel cylinder provided on the rear wheel; a controller for controlling the actuator; Equipped with the vehicle is configured so that a ratio of the rear wheel friction braking force to the front wheel friction braking force becomes a predetermined value when the front wheel and rear wheel wheel pressures are equal, the vehicle includes a plurality of the front wheels and a plurality of the rear wheels, The actuator is a hydraulic pressure modulator capable of adjusting the wheel pressure of each of the plurality of wheels; a front wheel connecting path and a rear wheel connecting path; a pressure unit that generates brake fluid pressure to be supplied to the front wheel connection path and the rear wheel connection path, the hydraulic pressure modulator is connected to the front wheel connection path and the rear wheel connection path; the front wheel communication passage is branched into a plurality of front wheel branch passages inside the hydraulic pressure modulator, and the plurality of front wheel branch passages are connected to the plurality of front wheel cylinders, respectively; the rear wheel communication passage is branched into a plurality of rear wheel branch passages inside the hydraulic pressure modulator, and the plurality of rear wheel branch passages are connected to the plurality of rear wheel cylinders, respectively; the pressurizing unit includes a fluid pump, a first pressure regulating valve, and a second pressure regulating valve; a suction portion of the fluid pump connected to a master reservoir via a reservoir passage, and a discharge portion of the fluid pump connected to the suction portion via a return passage; the first pressure regulating valve is provided in the return flow path, and the second pressure regulating valve is provided in a portion of the return flow path between the first pressure regulating valve and the discharge port, the pressurizing unit is configured to generate brake fluid pressure to be supplied to the front wheel connecting passage by a first servo pressure that is the brake fluid pressure in a portion of the return passage between the first pressure regulating valve and the second pressure regulating valve, and to generate brake fluid pressure to be supplied to the rear wheel connecting passage by a second servo pressure that is the brake fluid pressure in a portion of the return passage between the second pressure regulating valve and the discharge port, The controller When the regenerative device is in a first state in which it can generate a regenerative braking force, the first pressure regulating valve and the second pressure regulating valve are actuated based on the regenerative braking force to adjust the first servo pressure and the second servo pressure, respectively, so that the front wheel pressure is smaller than the rear wheel pressure, and the front wheel pressure and the rear wheel pressure are individually adjusted so that the ratio of the total braking force of the rear wheels to the total braking force of the front wheels becomes the predetermined value; In a second state in which the regenerative device cannot generate the regenerative braking force, the second pressure regulating valve is brought into a fully open state so that the first servo pressure and the second servo pressure are equal to each other, thereby adjusting the front wheel pressure and the rear wheel pressure to be equal to each other; A vehicle braking control device that, when the vehicle transitions from the first state to the second state during braking, adjusts the front wheel pressure so that the increase gradient, which is the amount of increase in the front wheel pressure per unit time, is limited to a predetermined gradient until the front wheel pressure becomes equal to the rear wheel pressure.

2. A vehicle braking control device that is applied to a vehicle that has front wheels and rear wheels as wheels and has a regenerative device on the rear wheels, an actuator that generates a front wheel friction braking force by adjusting a front wheel pressure in a front wheel cylinder provided on the front wheel, and generates a rear wheel friction braking force by adjusting a rear wheel pressure in a rear wheel cylinder provided on the rear wheel; a controller for controlling the actuator; Equipped with the vehicle is configured so that a ratio of the rear wheel friction braking force to the front wheel friction braking force becomes a predetermined value when the front wheel and rear wheel wheel pressures are equal, the vehicle includes a plurality of the front wheels and a plurality of the rear wheels, The actuator is a hydraulic pressure modulator capable of adjusting the wheel pressure of each of the plurality of wheels; a front wheel connecting path and a rear wheel connecting path; a pressure unit that generates brake fluid pressure to be supplied to the front wheel connection path and the rear wheel connection path, the hydraulic pressure modulator is connected to the front wheel connection path and the rear wheel connection path; the front wheel communication passage is branched into a plurality of front wheel branch passages inside the hydraulic pressure modulator, and the plurality of front wheel branch passages are connected to the plurality of front wheel cylinders, respectively; the rear wheel communication passage is branched into a plurality of rear wheel branch passages inside the hydraulic pressure modulator, and the plurality of rear wheel branch passages are connected to the plurality of rear wheel cylinders, respectively; the pressurizing unit includes a fluid pump, a first pressure regulating valve, and a second pressure regulating valve; a suction portion of the fluid pump connected to a master reservoir via a reservoir passage, and a discharge portion of the fluid pump connected to the suction portion via a return passage; the first pressure regulating valve is provided in the return flow path, and the second pressure regulating valve is provided in a portion of the return flow path between the first pressure regulating valve and the discharge port, the pressurizing unit is configured to generate brake fluid pressure to be supplied to the rear wheel connecting passage by a first servo pressure that is the brake fluid pressure in a portion of the return passage between the first pressure regulating valve and the second pressure regulating valve, and to generate brake fluid pressure to be supplied to the front wheel connecting passage by a second servo pressure that is the brake fluid pressure in a portion of the return passage between the second pressure regulating valve and the discharge port, The controller When the regenerative device is in a first state in which it can generate a regenerative braking force, the first pressure regulating valve and the second pressure regulating valve are actuated based on the regenerative braking force so that the ratio of the total braking force of the rear wheels to the total braking force of the front wheels becomes the predetermined value, thereby individually adjusting the wheel pressures of the front wheels and the rear wheels so that the wheel pressure of the front wheels is greater than the wheel pressure of the rear wheels; In a second state in which the regenerative device cannot generate the regenerative braking force, the second pressure regulating valve is brought into a fully open state so that the first servo pressure and the second servo pressure are equal to each other, thereby adjusting the front wheel pressure and the rear wheel pressure to be equal to each other; When the vehicle transitions from the first state to the second state during braking, the rear wheel pressure is adjusted so that the increase gradient, which is the amount of increase in the rear wheel pressure per unit time, is limited to a predetermined gradient until the rear wheel pressure becomes equal to the front wheel pressure.

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