Brake control device of vehicle

Abstract

To provide a brake control device of a vehicle for individually adjusting liquid pressures of wheel cylinders of front and rear wheels which appropriately controls an electric motor and an electromagnetic valve.SOLUTION: A brake control device is applied to a vehicle having a regenerative device on front wheels, includes a control cylinder for generating a foundation pressure using an electric motor as a power source, an electromagnetic valve for adjusting the foundation pressure to an adjustment pressure, and a controller for controlling the electric motor and the electromagnetic valve, controls a front wheel pressure of a front wheel cylinder by the adjustment pressure, and controls a rear wheel pressure of a rear wheel cylinder by the foundation pressure. The controller calculates liquid amounts to be supplied to the front wheel and rear wheel cylinder as front wheel and rear wheel standard liquid amounts, on the basis of front wheel and rear wheel target pressures which are target values of the front wheel and rear wheel pressures, controls the electric motor on the basis of the front wheel and rear wheel standard liquid amounts, and controls the electromagnetic valve on the basis of the front wheel and rear wheel target pressures.SELECTED DRAWING: Figure 3

Description

Technical Field

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

Background Art

[0002] In Patent Document 1, when controlling the brake hydraulic pressure generated by the electro-hydraulic generating means by the rotation angle feedback of the electric motor, in order to maintain the relationship between the rotation angle and the generated brake hydraulic pressure constant, an electro-hydraulic generating means (23) that generates brake hydraulic pressure by the operation of an electric motor (32), and an electric motor control means (U) that controls the operation of the electric motor (32) are provided. The electric motor control means (U) calculates a target rotation angle of the electric motor (32) for generating a brake hydraulic pressure corresponding to the driver's brake operation amount in the electro-hydraulic generating means (23), and performs feedback control so that the actual rotation angle of the electric motor (32) matches the target rotation angle. A vehicle brake device, wherein the electric motor control means (U) includes a correction means (M5) for correcting the target rotation angle of the electric motor (32) based on the actual brake hydraulic pressure generated by the electro-hydraulic generating means (23) is described.

[0003] Specifically, in the device described in Patent Document 1, the stroke of the brake pedal 12 detected by the stroke sensor Sb is converted into a brake hydraulic pressure (target brake hydraulic pressure) to be generated in the slave cylinder 23 (also referred to as a "control cylinder"). The target brake hydraulic pressure is converted into a rotation angle (target rotation angle) of an electric motor 32 (also referred to as an "electric motor") of the slave cylinder 23. Then, based on the target rotation angle, the electric motor is controlled.

[0004] Incidentally, the applicant has developed a braking control device as described in Patent Document 2. The braking control device includes an electric cylinder 51 that discharges a hydraulic brake fluid corresponding to the drive of an electric motor 513 from an output port 516, and a master cylinder 31 configured such that brake fluid flows out of a master chamber Rm as a master piston 43 moves with an increase in the hydraulic pressure in a servo chamber Rs, while brake fluid flows into the master chamber Rm as the master piston 43 moves with a decrease in the hydraulic pressure in the servo chamber Rs. The braking control device also includes a first flow path 331 that connects the master chamber Rm and a wheel cylinder 11 for a front wheel, a sixth flow path 58 that connects the output port 516 and a wheel cylinder 11 for a rear wheel, a fifth flow path 55 that connects the sixth flow path 58 and the servo chamber Rs, and a differential pressure regulating valve 551 provided in the fifth flow path 55 for adjusting the differential pressure between a first hydraulic pressure that is the hydraulic pressure in the sixth flow path 58 and a second hydraulic pressure that is the hydraulic pressure in the servo chamber Rs. In such a device, control of not only the electric motor but also the differential pressure regulating valve (solenoid valve) is required.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] In view of the above problems, an object of the present invention is to provide a braking control device for a vehicle that individually adjusts the hydraulic pressures of wheel cylinders for front and rear wheels, in which an electric motor and a solenoid valve can be appropriately controlled.

Means for Solving the Problems

[0007] The braking control device (SA) for a vehicle according to the present invention is applied to a vehicle equipped with a regenerative device (KG) on the front wheels (WHf), and includes a control cylinder (CC) that generates a base pressure (Pa) using an electric motor (MA) as a power source, a solenoid valve (UC) that adjusts the base pressure (Pa) to an adjustment pressure (Pb), and a controller (EA) that controls the electric motor (MA) and the solenoid valve (UC). The adjustment pressure (Pb) controls the front wheel wheel pressure (Pwf) of the front wheel wheel cylinder (CWf), and the base pressure (Pa) controls the rear wheel wheel pressure (Pwr) of the rear wheel wheel cylinder (CWr).

[0008] In the braking control device (SA) for a vehicle according to the present invention, the controller (EA) calculates, as front and rear reference liquid amounts (Esf, Esr), the amount of liquid to be supplied to the front and rear wheel cylinders (CWf, CWr) based on the front and rear target pressures (Ptf, Ptr) which are the target values of the front and rear wheel pressures (Pwf, Pwr), controls the electric motor (MA) based on the front and rear reference liquid amounts (Esf, Esr), and controls the solenoid valve (UC) based on the front and rear target pressures (Ptf, Ptr).

[0009] In the braking control device (SA) for a vehicle according to the present invention, the controller (EA) acquires the discharged liquid amount (Ej) from the control cylinder (CC), calculates an estimated liquid amount (Ee) based on the base pressure (Pa) and the adjustment pressure (Pb), and controls the rotation angle (Ka) of the electric motor (MA) based on the deviation (hE) between the discharged liquid amount (Ej) and the estimated liquid amount (Ee). Further, the controller (EA) calculates a target differential pressure (St) based on the front and rear target pressures (Ptf, Ptr), and controls the valve current (Ic) supplied to the solenoid valve (UC) based on the target differential pressure (St).

[0010] The hydraulic pressure Pw generated in the wheel cylinder CW is determined according to the amount of fluid supplied to the wheel cylinder CW. Therefore, in the braking control device SA, the rotation angle Ka of the electric motor MA is controlled based on the relationship between the above hydraulic pressure and the amount of fluid (i.e., the hydraulic pressure - fluid amount characteristic). As a result, the amount of fluid required to achieve the basic pressure Pa is discharged from the electric cylinder DN (particularly, the control cylinder CC). Also, with respect to the pressure regulating valve UC, since the differential pressure Sa between the hydraulic pressure Pa on the side closer to the electric cylinder DN and the hydraulic pressure Pb on the side farther from the electric cylinder DN is determined according to the valve current Ic supplied to the pressure regulating valve UC, the pressure regulating valve UC is executed based on the target differential pressure St. According to the above configuration, in the braking control device SA that individually adjusts the hydraulic pressures of the wheel cylinders of the front and rear wheels by two-system pressure regulation, the electric motor MA and the pressure regulating valve UC are appropriately controlled. As a result, in two-system pressure regulation, the basic pressure Pa and the adjustment pressure Pb can be adjusted accurately.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0012] <Symbols of components, etc., and subscripts at the end of the symbols> In the following description, components, arithmetic processes, signals, characteristics, and values with the same symbol, such as "CW", have the same function. The subscripts "f" and "r" attached to the end of the symbol related to each wheel are inclusive symbols indicating whether it relates to the front or rear wheel system. For example, in the wheel cylinder CW provided for each wheel, it is expressed as "front wheel cylinder CWf, rear wheel cylinder CWr". Further, the subscripts "f" and "r" at the end of the symbol may be omitted. When the subscripts "f" and "r" are omitted, each symbol represents its general term. For example, "CW" is the general term for the wheel cylinders provided for the front and rear wheels of the vehicle. Also, the general term "CW" is also expressed as "CW(=CWf, CWr)".

[0013] The brake control device SA, the hydraulic pressure correction device SZ, and the wheel cylinder CW are connected by a fluid passage (communication passage HS). Further, in the brake control device SA and the hydraulic pressure correction device SZ, various components (CC, UC, etc.) are connected by the fluid passage. Here, the "fluid passage" is a path for moving the brake fluid BF, and pipes, flow paths in actuators, hoses, etc. are applicable. In the following description, the communication passage HS, the reservoir passage HR, the input passage HN, the servo passage HU, the supply passage HH, etc. are fluid passages.

[0014] <First Embodiment of Brake Control Device SA> With reference to the schematic diagram of FIG. 1, a first embodiment of the brake control device SA for a vehicle will be described. The brake control device SA is applied to, for example, a hybrid vehicle equipped with a driving electric motor or an electric vehicle.

[0015] The front and rear wheels WHf and WHr (= WH) of the vehicle are provided with a braking device SX (= SXf, SXr). The braking device SX is composed of a brake caliper, a friction member (for example, a brake pad), and a rotating member KT (for example, a brake disk). A wheel cylinder CW is provided in the brake caliper (not shown). By the hydraulic pressure Pw (referred to as "wheel pressure") in the wheel cylinder CW, a friction member (not shown) is pressed against the rotating member KT fixed to each wheel WH, and a braking torque Tb is applied to the wheel. As a result, a frictional braking force Fe (also referred to as "hydraulic braking force") is generated at the wheel WH. Therefore, the braking device SX can be referred to as "a device that generates a frictional braking force Fe by the wheel pressure Pw" or "a device that converts the wheel pressure Pw into the frictional braking force Fe".

[0016] The vehicle is provided with a regeneration device KG. The regeneration device KG is composed of a generator GN for energy regeneration (also referred to as "electric motor / generator" or "regeneration generator"), a control unit EG for the regeneration device KG (also referred to as "regeneration controller"), and a regeneration battery (not shown). The regeneration generator GN is also an electric motor for running. In regenerative braking, the electric motor / generator GN operates as a generator, and the generated electric power is stored in the regeneration battery via the regeneration controller EG. At this time, a regenerative braking force Fg acts on the wheel. That is, the regeneration device KG can generate a regenerative braking force Fg. For example, the regeneration device KG is provided on the front wheel WHf. Therefore, the regenerative braking force Fg is generated at the front wheel WHf. The regeneration device KG (particularly, the regeneration controller EG) is connected to the communication bus BS.

[0017] The vehicle is equipped with a driving assistance device KJ. In the driving assistance device KJ, automatic speed control is executed. The driving assistance device KJ is composed of an object detection sensor SJ and a controller EJ for driving assistance (simply referred to as the "driving assistance controller"). The object detection sensor SJ detects the distance Sj to an object existing in front of the host vehicle (including a preceding vehicle traveling in front of the host vehicle) (referred to as the "relative distance", and when the object is a preceding vehicle, it is also referred to as the "inter-vehicle distance"). For example, as the object detection sensor SJ, a radar sensor, a millimeter-wave sensor, an image sensor, etc. are adopted. Based on the detection result Sj (relative distance) of the object detection sensor SJ, the target acceleration Gs of the host vehicle (the target value of the vehicle body acceleration in the longitudinal direction of the host vehicle) is calculated by the driving assistance controller EJ. The driving assistance device KJ (especially the driving assistance controller EJ) is connected to the communication bus BS. The target acceleration Gs is transmitted to the braking control device SA via the communication bus BS. In the braking control device SA, the braking forces Fg and Fe are adjusted according to the target acceleration Gs. As a result, the traveling speed Vx of the vehicle (the vehicle body speed) is controlled.

[0018] The vehicle is equipped with a braking operation member BP and various sensors (such as SP). The braking operation member BP (for example, a brake pedal) is an operation member for the driver to decelerate the vehicle. The vehicle is provided with an operation displacement sensor SP that detects the operation displacement Sp of the braking operation member BP. The operation displacement Sp is one of the state quantities (state variables) that indicates the operation amount of the braking operation member BP, and in a brake-by-wire type braking control device SA, it is a signal representing the driver's braking intention (that is, a braking instruction). In addition to the operation displacement sensor SP, as another state quantity representing the braking operation amount, the hydraulic pressure Pn in the input chamber Rn (described later) (referred to as the "input pressure") is adopted. The input pressure Pn is detected by the input pressure sensor PN. The operation displacement Sp, the input pressure Pn, etc. are collectively referred to as the "braking operation amount Ba". Also, the operation displacement sensor SP and the input pressure sensor PN that detect the operation displacement Sp and the input pressure Pn (that is, the braking operation amount Ba) are referred to as the "braking operation amount sensor BA".

[0019] The vehicle is equipped with various sensors for braking control such as anti-lock brake control and skid prevention control (i.e., individual control of each wheel pressure Pw). Specifically, each wheel WH is equipped with a wheel speed sensor VW that detects its rotational speed Vw (referred to as "wheel speed"). Also, a steering amount sensor that detects the steering amount Sw (e.g., operating angle) of a steering operation member (e.g., steering wheel), a yaw rate sensor that detects the yaw rate Yr of the vehicle, a longitudinal acceleration sensor that detects the longitudinal acceleration Gx (also referred to as "deceleration") of the vehicle, and a lateral acceleration sensor that detects the lateral acceleration Gy of the vehicle are provided (not shown above).

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

[0021] The braking control device SA (particularly, the brake controller EA) and the hydraulic pressure correction device SZ (particularly, the correction controller EZ) are connected to the communication bus BS. Signal transmission is performed among a plurality of controllers (EA, EZ, EG, EJ, etc.) through the communication bus BS. That is, the plurality of controllers can transmit signals (detection values, calculation values, control flags, etc.) to the communication bus BS and can receive signals from the communication bus BS.

[0022] <Configuration of the Braking Control Device SA> The configuration of the braking control device SA according to the first embodiment will be described. The braking control device SA generates a base pressure Pa and an adjustment pressure Pb in response to the operation of a braking operation member BP (brake pedal). Then, a supply pressure Pm and a base pressure Pa are output from the braking control device SA to the hydraulic pressure correction device SZ. In the hydraulic pressure correction device SZ, the supply pressure Pm and the base pressure Pa are adjusted, and finally, front-wheel and rear-wheel wheel pressures Pwf and Pwr are supplied to the front-wheel and rear-wheel wheel cylinders CWf and CWr. The braking control device SA is composed of a brake actuator YA and a brake controller EA.

[0023] ≪Brake Actuator YA≫ The brake actuator YA is composed of a hydraulic pressure generating unit PU, an apply unit AP, and an input unit NR.

[0024] [Hydraulic Pressure Generating Unit PU] The hydraulic pressure generating unit PU generates a basic pressure Pa and an adjustment pressure Pb using an electric motor MA as a power source. The hydraulic pressure generating unit PU is composed of an electric cylinder DN and a pressure regulating valve UC. Here, the electric cylinder DN includes an electric motor MA, a rotation angle sensor KA, a speed reducer GS, a conversion mechanism GH, a control cylinder CC, and a control piston NC.

[0025] The electric motor MA is a power source (pressurizing source) for generating the basic pressure Pa (hydraulic pressure generated by the electric cylinder DN). "Power" is the energy required to move the movable members (such as GS, GH, NC, etc.) in the electric cylinder DN. For example, power is defined as the energy per unit time (also referred to as "working rate") as a physical quantity. Rotational power (also referred to as "first rotational power") is output from the electric motor MA. The rotational power of the electric motor MA is the product of the shaft torque of the electric motor MA and the rotational speed of the electric motor MA (especially the motor shaft). Note that the linear power of a linear moving member (described later) is the product of the thrust of the linear moving member (the force acting in the direction of the central axis) and the linear speed of the linear moving member (the speed in the direction along the central axis).

[0026] As the electric motor MA, a three-phase brushless motor is adopted. The electric motor MA includes a motor coil, a motor shaft, and a rotation angle sensor KA. The motor coil is fixed to the motor housing. Electric power is supplied to the motor coil from a controller EA (particularly, a drive circuit DR). The motor shaft is rotatably supported with respect to the motor housing. A permanent magnet is fixed to the outer periphery of the motor shaft. In the three-phase brushless motor MA, the magnetic pole position of the permanent magnet (i.e., the motor rotation angle Ka) is detected by the rotation angle sensor KA (which also corresponds to the "liquid volume sensor"). Then, based on the rotation angle Ka of the motor shaft, the three-phase motor currents Im related to the U phase, V phase, and W phase (a general term for the currents flowing in the U phase, V phase, and W phase) are switched.

[0027] Specifically, the signal of the rotation angle Ka (which also corresponds to the "discharged liquid volume Ej" described later) detected by the rotation angle sensor KA is transmitted to the controller EA (particularly, a microprocessor MP). In the controller EA, according to the rotation angle Ka, the switching elements of the drive circuit DR (also referred to as the "inverter circuit") are driven. Thereby, the motor current Im flowing through the motor coil is switched, and the electric motor MA is driven. Then, the first rotational power is output from the electric motor MA to the speed reducer GS.

[0028] The first rotational power output from the electric motor MA is decelerated by the speed reducer GS. Specifically, the input shaft of the speed reducer GS and the motor shaft are fixed. Also, the output shaft of the speed reducer GS and the rotating member of the conversion mechanism GH are fixed. In the speed reducer GS, the speed input from the electric motor MA is decreased, and the torque input from the electric motor MA is increased. Then, the decelerated rotational power (also referred to as the "second rotational power") is output from the speed reducer GS to the conversion mechanism GH.

[0029] The conversion mechanism GH is composed of a rotating member that performs rotational motion and a linear motion member that performs linear motion. In the conversion mechanism GH, the second rotational power output from the speed reducer GS is input to the rotating member. Then, the rotational power input to the rotating member is converted into the linear power of the linear motion member. The conversion mechanism GH is also referred to as a "rotation-linear motion conversion mechanism". A rotation prevention member is engaged with the linear motion member. As a result, the rotational motion of the linear motion member is blocked, so the linear motion member moves along the rotation axis of the rotating member.

[0030] For example, a "ball screw" is adopted as the conversion mechanism GH. Specifically, in the ball screw mechanism, the rotating member, which is a shaft member, is fixed to the output shaft of the speed reducer GS. The rotating member is inserted into a linear motion member having a cylindrical shape. A ball screw groove is formed on the outer peripheral surface of the rotating member. Similarly, a ball screw groove is also formed on the inner peripheral surface of the linear motion member. A plurality of balls (steel balls) are fitted into the ball screw groove.

[0031] The linear power is transmitted to the control piston NC by the linear motion member of the conversion mechanism GH. The control piston NC is inserted into the control cylinder CC. Inside the control cylinder CC, a control chamber Rc (hydraulic chamber) is formed by the control piston NC. Specifically, the outer peripheral surface of the control piston NC and the inner peripheral surface of the control cylinder CC are sealed by two seal members SL. As a result, the control chamber Rc is made liquid-tight. The hydraulic pressure of the control cylinder CC (that is, the control chamber Rc) is the "basic pressure Pa". That is, in the electric cylinder DN, the electric motor MA is used as the power source, and the basic pressure Pa is output.

[0032] The control cylinder CC is connected to the servo chamber Ru (described later) of the apply unit AP via the servo path HU (fluid path). In addition, the control cylinder CC is connected to the rear wheel wheel cylinder CWr via the hydraulic pressure correction device SZ via the rear wheel connection path HSr (fluid path). The hydraulic pressure generating unit PU is provided with a basic pressure sensor PA to detect the basic pressure Pa (the generated hydraulic pressure of the electric cylinder DN).

[0033] Figure 1 shows a state where the electric cylinder DN is not generating the basic pressure Pa. The control cylinder CC is provided with a through hole between two seal members SL. The control piston NC is also provided with a through hole. A supply passage HH (fluid passage) connected to the master reservoir RV is connected to the through hole of the control cylinder CC. In the illustrated state, the control chamber Rc is connected to the master reservoir RV via the through hole and the supply passage HH, and the basic pressure Pa is "0 (atmospheric pressure)". The position of the control piston NC in this state is referred to as the "initial position". In the initial position, the control piston NC is displaced maximally in its retraction direction Hb, and the volume of the control chamber Rc is maximized.

[0034] When an increase in the basic pressure Pa is required, the rotational power of the electric motor MA is increased. This rotational power is transmitted to the conversion mechanism GH via the speed reducer GS and output as the linear power of the linear member. Then, the control piston NC is pressed by the linear member, and the control piston NC is moved in the forward direction Ha (the direction in which the volume of the control chamber Rc decreases). By this movement, first, the communication between the control chamber Rc and the master reservoir RV is blocked. When the control piston NC is further moved in the forward direction Ha, the basic pressure Pa (the internal pressure of the control chamber Rc) is increased from "0 (atmospheric pressure)". The braking fluid BF pressurized by the basic pressure Pa is output (pumped) from the control chamber Rc of the control cylinder CC.

[0035] When the maintenance of the basic pressure Pa is required, the rotation of the electric motor MA is stopped. The movement of the control piston NC is stopped, and the basic pressure Pa is maintained constant. When a decrease in the basic pressure Pa is required, the rotational power of the electric motor MA is decreased. Due to the basic pressure Pa, the electric motor MA rotates in the reverse direction, so the control piston NC is moved in the retraction direction Hb (the direction in which the volume of the control chamber Rc increases). At this time, since the braking fluid BF is returned toward the control chamber Rc, the basic pressure Pa is decreased.

[0036] In the servo circuit HU (a fluid circuit connecting the control room Rc and the servo room Ru), a pressure regulating valve UC (equivalent to an "electromagnetic valve") is provided. The pressure regulating valve UC is a normally open linear solenoid valve whose valve opening amount (lift amount) is continuously controlled according to the supplied current Ic (referred to as the "valve current"). The pressure regulating valve UC is also called a "differential pressure valve" for adjusting the hydraulic pressure difference (differential pressure). By the pressure regulating valve UC, the basic pressure Pa output from the electric cylinder DN is adjusted to the adjusted pressure Pb.

[0037] Specifically, the pressure regulating valve UC is composed of a valve body, a valve seat, and a solenoid. And the plunger of the solenoid is fixed to the valve body. When a current Ic is supplied to the coil of the solenoid, the plunger is attracted by the coil and a thrust is generated. By this thrust, the valve body is pushed toward the valve seat. As a result, the flow of the braking fluid BF from the control cylinder CC toward the servo room Ru is blocked. Consequently, since the basic pressure Pa is blocked by the pressure regulating valve UC, the pressure regulating valve UC can adjust the adjusted pressure Pb to be smaller than the basic pressure Pa. When no current Ic is supplied to the pressure regulating valve UC, the pressure regulating valve UC is in a fully open state, so the basic pressure Pa and the adjusted pressure Pb are equal (that is, "Pa = Pb" when "Ic = 0"). In the hydraulic pressure generating unit PU, a pressure sensor PB is provided between the pressure regulating valve UC and the servo room Ru to detect the adjusted pressure Pb.

[0038] In the braking control device SA, there are limitations in adjusting the adjusted pressure Pb. As described above, the pressure regulating valve UC can block the inflow of the braking fluid BF pressurized to the basic pressure Pa and make the adjusted pressure Pb smaller than the basic pressure Pa. However, the pressure regulating valve UC alone cannot decrease the adjusted pressure Pb. That is, in order to decrease the adjusted pressure Pb, a decrease in the basic pressure Pa is required.

[0039] [Application Unit AP] The apply unit AP is composed of a single-type master cylinder CM and a master piston NM. The single-type master cylinder CM has the master piston NM inserted therein. The interior of the master cylinder CM is partitioned by the master piston NM into three hydraulic chambers Rm, Ru, and Rs. The master chamber Rm is formed by the master cylinder CM and the master piston NM. Further, the interior of the master cylinder CM is partitioned by the flange portion Tu of the master piston NM into a servo chamber Ru and a reaction chamber Rs. 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.

[0040] The adjustment pressure Pb is supplied from the hydraulic pressure generating unit PU to the servo chamber Ru. From the apply unit AP, a supply pressure Pm (corresponding to the "adjustment pressure Pb") is output by the adjustment pressure Pb. Here, the "supply pressure Pm" is the internal pressure of the master chamber Rm and is also referred to as the "master pressure". When "Pb = 0" (for example, during non-braking), the master piston NM is at the most retracted position (i.e., the position where the volume of the master chamber Rm is maximum). In this state, the master chamber Rm of the master cylinder CM communicates with the master reservoir RV. For this reason, the master pressure Pm is "0 (atmospheric pressure)".

[0041] The braking fluid BF is stored inside the master reservoir RV (also referred to as the "atmospheric pressure reservoir"). When the adjustment pressure Pb is increased from "0", the master piston NM moves in the forward direction Da (the direction in which the volume of the master chamber Rm decreases). By this movement, the communication between the master chamber Rm and the master reservoir RV is blocked. And when the master piston NM further moves in the forward direction Da, the supply pressure Pm (master pressure) is increased from "0 (atmospheric pressure)". Thereby, the braking fluid BF pressurized to the supply pressure Pm is output (pumped) from the master chamber Rm of the master cylinder CM toward the hydraulic pressure correction device SZ. Note that since "rm = ru", if the sliding resistance of the seal member SL is ignored, "Pb = Pm".

[0042] [Input unit NR] The input unit NR realizes regenerative cooperative control. "Regenerative cooperative control" is to cooperate the frictional braking force Fe (the braking force caused by the wheel pressure Pw) and the regenerative braking force Fg (the braking force caused by the regenerator KG) so that the kinetic energy of the vehicle can be efficiently recovered as electrical energy during braking. In regenerative cooperative control, the braking operation member BP is operated, but a state where the wheel pressure Pw is not generated is created. The input unit NR is composed of an input cylinder CN, an input piston NN, a first control valve VA, a second control valve VB, a stroke simulator SS, and an input pressure sensor PN.

[0043] The input cylinder CN is fixed to the master cylinder CM. The input piston NN is inserted into the input cylinder CN. The input piston NN is mechanically connected to the braking operation member BP so as to be interlocked with the movement of the braking operation member BP (brake pedal). The end face of the input piston NN and the end face of the master piston NM have a clearance Ln (also referred to as "separation distance"). By adjusting the separation distance Ln by the adjustment pressure Pb, regenerative cooperative control is realized.

[0044] The input chamber Rn of the input unit NR is connected to the reaction chamber Rs of the apply unit AP via an input passage HN (fluid passage). A normally closed first control valve VA is provided in the input passage HN. The input passage HN is connected to the master reservoir RV via a reservoir passage HR (fluid passage) between the first control valve VA and the reaction chamber Rs. A normally open second control valve VB is provided in the reservoir passage HR. On-off type solenoid valves are adopted for the first and second control valves VA and VB. A stroke simulator SS is connected to the input passage HN between the first control valve VA and the reaction chamber Rs.

[0045] When no power is supplied to the first and second control valves VA and VB, the first control valve VA is closed and the second control valve VB is opened. By closing the first control valve VA, the input chamber Rn is sealed and fluid-locked. As a result, the master piston NM is displaced integrally with the braking operation member BP. Also, by opening the second control valve VB, the stroke simulator SS and the reaction chamber Rs communicate with the master reservoir RV.

[0046] When power is supplied to the first and second control valves VA and VB, the first control valve VA opens and the second control valve VB closes. As a result, the master piston NM can be displaced separately from the braking operation member BP. At this time, since the input chamber Rn is connected to the stroke simulator SS, the operating force of the braking operation member BP is generated by the stroke simulator SS. An input pressure sensor PN is provided between the input chamber Rn and the first control valve VA so as to detect the input pressure Pn. Note that the input pressure Pn is also the hydraulic pressure in the stroke simulator SS.

[0047] ≪Braking Controller EA≫ The braking actuator YA is controlled by the braking controller EA. The braking controller EA is composed of a microprocessor MP and a drive circuit DR. The controller EA is connected to a communication bus BS so that signals (detection values, calculation values, control flags, etc.) can be shared with other controllers (EZ, EG, EJ, etc.).

[0048] Various signals such as the operating displacement Sp (detection value of the operating displacement sensor SP), the input pressure Pn (detection value of the input pressure sensor PN), the base pressure Pa (detection value of the base pressure sensor PA), and the motor rotation angle Ka (detection value of the rotation angle sensor KA) are directly input to the braking controller EA. Further, various signals such as the supply pressure Pm, the specified regenerative braking force Fz, the vehicle body speed Vx, and the target acceleration Gs are input to the controller EA from the communication bus BS. Also, a target regenerative braking force Fh (target value of the regenerative braking force Fg) is output from the braking controller EA to the communication bus BS. Note that in the regenerative controller EG, the regenerative braking force Fg (actual value) is controlled based on the target regenerative braking force Fh (target value) acquired from the communication bus BS.

[0049] The braking controller EA (particularly, the microprocessor MP) has a pressure control algorithm programmed therein. "Pressure control" is control for adjusting the wheel pressure Pw (= Pwf, Pwr) and includes regenerative cooperative control. The pressure control is executed based on the various signals (Sp, Pa, etc.) described above. Based on the pressure control algorithm, the drive circuit DR drives the electric motor MA and various solenoid valves (UC, VA, etc.). The drive circuit DR is configured with an inverter circuit using a switching element (e.g., MOS-FET) to drive the electric motor MA. Also, the drive circuit DR is provided with switching elements to drive the various solenoid valves. In addition, the drive circuit DR includes a motor current sensor (not shown) for detecting the supply current Im (motor current) to the electric motor MA. The electric motor MA is provided with a rotation angle sensor KA for detecting the position Ka (rotation angle) of the motor shaft.

[0050] In the braking controller EA, drive signals Va, Vb for the first and second control valves VA, VB, drive signal Uc for the pressure regulating valve UC, and drive signal Ma for the electric motor MA are calculated. Then, the switching elements are driven according to the various drive signals (Uc, Ma, etc.). Specifically, in the control of the solenoid valves, power supply to the first and second control valves VA, VB is performed based on the drive signals Va, Vb. As a result, the first control valve VA is opened and the second control valve VB is closed. In addition, based on the pressure control algorithm, the drive signals Uc, Ma are determined. Then, the pressure regulating valve UC is controlled based on the drive signal Uc, and the electric motor MA is controlled based on the drive signal Ma.

[0051] <Hydraulic correction device SZ> A hydraulic pressure correction device SZ is provided between the braking control device SA and the wheel cylinder CW. The anti-lock brake control, traction control, anti-skid control, etc. are executed by the hydraulic pressure correction device SZ. In the braking system related to the front wheels WHf (i.e., the front wheel connection path HSf), the supply pressure Pm is supplied from the master cylinder CM to the hydraulic pressure correction device SZ. On the other hand, in the braking system related to the rear wheels WHr (i.e., the rear wheel connection path HSr), the base pressure Pa is directly supplied from the hydraulic pressure generating unit PU to the hydraulic pressure correction device SZ. In the hydraulic pressure correction device SZ, the supply pressure Pm and the base pressure Pa are adjusted (increased or decreased) and output as the hydraulic pressures Pwf and Pwr of the front and rear wheel cylinders CWf and CWr (front and rear wheel pressures).

[0052] The hydraulic pressure correction device SZ is composed of a correction actuator YZ and a correction controller EZ. Since the configuration of the correction actuator YZ is well-known, its description is omitted. A supply pressure sensor PM is provided in the correction actuator YZ to detect the supply pressure Pm. The adjustment pressure Pb is transmitted as the supply pressure Pm via the master piston NM. Therefore, the supply pressure Pm corresponds to the adjustment pressure Pb, and the supply pressure sensor PM corresponds to the adjustment pressure sensor PB. In other words, the supply pressure Pm is an example of the adjustment pressure Pb, and the supply pressure sensor PM is an example of the adjustment pressure sensor PB.

[0053] When the regenerative cooperative control is executed, the operation of the correction actuator YZ is stopped. Therefore, during the execution of the regenerative cooperative control, the adjustment pressure Pb is transmitted to the front wheel cylinder CWf as the front wheel pressure Pwf via the supply pressure Pm, while the base pressure Pa is directly transmitted to the rear wheel cylinder CWr as the rear wheel pressure Pwr. That is, in the front wheel braking system, "Pb = Pm = Pwf", and in the rear wheel braking system, "Pa = Pwr".

[0054] The correction controller EZ is connected to the braking controller EA via the communication bus BS. The correction controller EZ receives the wheel speed Vw detected by the wheel speed sensor VW and the supply pressure Pm detected by the supply pressure sensor PM. Then, based on the wheel speed Vw, the traveling speed Vx (vehicle body speed) of the vehicle is calculated in the correction controller EZ. The vehicle body speed Vx and the supply pressure Pm are transmitted to the braking controller EA through the communication bus BS.

[0055] <Pressure adjustment control process> Referring to the flowchart of FIG. 2, an example of the pressure adjustment control process will be described. In the pressure adjustment control, the regenerative cooperation control between the regenerator KG and the braking control device SA is executed. In the regenerative cooperation control, the adjustment pressure Pb is made smaller than the base pressure Pa, so that the total braking force Fu is achieved according to the required braking amount Bs while the front-rear distribution of the total braking force Fu is maintained at a predetermined value hf. In this control, since the front-wheel wheel pressure Pwf and the rear-wheel wheel pressure Pwr are adjusted individually, it is also called "two-system pressure adjustment".

[0056] ≪Various braking forces≫ The various braking forces in the description of the pressure adjustment control are as follows. - "Total braking force Fu" is the actual braking force acting on the entire vehicle. The target value corresponding to the total braking force Fu is "target total braking force Fv". - "Frictional braking force Fe (hydraulic braking force)" is the braking force actually generated by the wheel pressure Pw. The target value corresponding to the frictional braking force Fe is "target frictional braking force Fn". - "Regenerative braking force Fg" is the braking force actually generated by the regenerator KG. The target value corresponding to the regenerative braking force Fg is "target regenerative braking force Fh". The target regenerative braking force Fh is calculated by the braking control device SA (especially the braking controller EA) and transmitted to the regenerator KG (especially the regenerative controller EG) via the communication bus BS. In the regenerator KG, the generator GN is controlled by the regenerative controller EG so that the actual regenerative braking force Fg approaches and matches the target regenerative braking force Fh. - The "standard regenerative braking force Fz" is the maximum value (limit value) of the regenerative braking force Fg that the regenerator KG can generate. Therefore, the regenerator KG can generate the regenerative braking force Fg within the range from "Fg = 0" to the standard regenerative braking force Fz. The standard regenerative braking force Fz is calculated by the regenerator KG (especially the regeneration controller EG) and transmitted to the braking control device SA (especially the braking controller EA) via the communication bus BS. Note that the standard regenerative braking force Fz can be restricted according to the driving conditions of the vehicle (e.g., the friction coefficient of the driving road).

[0057] ≪Various hydraulic pressures≫ The various hydraulic pressures in the description of the pressure regulation control are as follows. - The "basic pressure Pa" is the output of the electric cylinder DN (i.e., the internal pressure of the control chamber Rc). The basic pressure Pa is detected (acquired) by the basic pressure sensor PA. - The "regulated pressure Pb" is the hydraulic pressure obtained by regulating the basic pressure Pa with the pressure regulating valve UC. The regulated pressure Pb is detected (acquired) by the regulated pressure sensor PB. Alternatively, the regulated pressure Pb may be detected (acquired) by the supply pressure sensor PM. Therefore, the supply pressure Pm corresponds to one of the regulated pressures Pb, and the supply pressure sensor PM corresponds to one of the regulated pressure sensors PB. - The "rear wheel target pressure Ptr" corresponds to the target value for controlling the basic pressure Pa (actual value). Also, the "front wheel target pressure Ptf" corresponds to the target value for controlling the regulated pressure Pb. This is based on the fact that the rear wheel wheel pressure Pwr is adjusted by the basic pressure Pa and the front wheel wheel pressure Pwf is adjusted by the regulated pressure Pb.

[0058] In the hydraulic pressure transmission in the braking control device SA, there are various resistances such as the pipe friction resistance in the fluid passage, the resistance as the orifice of the solenoid valve, and the sliding resistance of the seal member SL. In the feedback control related to the hydraulic pressure, the actual value is controlled to match the target value. Considering the above resistances, it is desirable that the comparison between the actual value and the target value be made at the same part. In the following description, this comparison is made at the wheel cylinder CW. That is, the rear wheel target pressure Ptr is determined to correspond to the rear wheel wheel pressure Pwr. And the rear wheel wheel pressure Pwr (actual value) is determined from the base pressure Pa (the detected value of the base pressure sensor PA) with the hydraulic pressure corresponding to the above resistance compensated. Similarly, the front wheel target pressure Ptf is determined to correspond to the front wheel wheel pressure Pwf. And the front wheel wheel pressure Pwf (actual value) is determined from the adjusted pressure Pb (the detected value of the adjusted pressure sensor PB) with the hydraulic pressure corresponding to the above resistance compensated.

[0059] In the pressure regulation control, first, power is supplied to the first and second control valves VA and VB. The normally closed first control valve VA is opened, and the normally open second control valve VB is closed. As a result, the master piston NM and the braking operation member BP can be displaced separately, so the front and rear wheel wheel pressures Pwf and Pwr can be adjusted independently of the operation of the braking operation member BP. At this time, the operating force of the braking operation member BP is generated by the stroke simulator SS.

[0060] In step S110, various signals are read by the braking controller EA. In the braking controller EA, the braking operation amount Ba (a general term for Sp and Pn), the target acceleration Gs, the base pressure Pa, the adjusted pressure Pb, and the reference regenerative braking force Fz are acquired. The braking operation amount Ba and the target acceleration Gs are collectively referred to as the "braking required amount Bs". The braking required amount Bs is a state quantity representing the braking requirement for the vehicle. The base pressure Pa is acquired by the base pressure sensor PA. The adjusted pressure Pb is acquired by at least one of the adjusted pressure sensor PB and the supply pressure sensor PM. The reference regenerative braking force Fz is determined by the regenerative device KG (particularly, the regenerative controller EG) and received by the braking controller EA via the communication bus BS.

[0061] In step S120, based on the braking demand amount Bs and the operation map Zfv, the target total braking force Fv (the target value of the total braking force Fu acting on the entire vehicle) is calculated. The target total braking force Fv is calculated as "0" according to the operation map Zfv when the braking demand amount Bs is less than a predetermined amount bo. And when the braking demand amount Bs is greater than or equal to the predetermined amount bo, the target total braking force Fv is calculated so as to increase from "0" as the braking demand amount Bs increases. Here, the "predetermined amount bo" is preset as a predetermined value (constant) (see the target total braking force calculation block FV above).

[0062] In step S130, the rear wheel target pressure Ptr and the front wheel target pressure Ptf for performing two-system pressure regulation are calculated based on the target total braking force Fv and the standard regenerative braking force Fz. In two-system pressure regulation, the base pressure Pa and the adjustment pressure Pb are adjusted individually. Specifically, the adjustment pressure Pb is decreased from the base pressure Pa. For this reason, the front wheel target pressure Ptf is smaller than the rear wheel target pressure Ptr (that is, "Ptr < Ptf"). In two-system pressure regulation, the front and rear wheel target pressures Ptf and Ptr are determined by dividing into the following three cases.

[0063] Case (1): When the target total braking force Fv is less than or equal to the standard regenerative braking force Fz, the target regenerative braking force Fh is made equal to the target total braking force Fv, and the front and rear wheel target frictional braking forces Fnf and Fnr are made "0". That is, when "Fv ≦ Fz", "Fh = Fv, Fnf = Fnr = 0" is determined.

[0064] Case (2): When the target total braking force Fv is greater than the standard regenerative braking force Fz and less than or equal to the value "Fz / hf" obtained by dividing the standard regenerative braking force Fz by the distribution ratio hf, the target regenerative braking force Fh is made equal to the target total braking force Fv. And the front wheel target frictional braking force Fnf is made "0", and the rear wheel target frictional braking force Fnr is determined as the value obtained by subtracting the target regenerative braking force Fh (= Fz) from the target total braking force Fv, respectively. That is, when "Fz < Fv ≦ (Fz / hf)", "Fh = Fz, Fnf = 0, Fnr = Fv - Fh = Fv - Fz" is determined.

[0065] Here, the "distribution ratio hf" is the ratio of the target front-wheel braking force (i.e., the sum of the target regenerative braking force Fh and the target front-wheel frictional braking force Fnf) to the target total braking force Fv (resulting in the total braking force Fu). The distribution ratio hf (also referred to as the "front-wheel ratio") is preset as a predetermined value (constant) based on the specifications of the vehicle (such as the center-of-gravity position, wheelbase, etc.). Note that the distribution ratio hf is equal to the ratio of the front-wheel frictional braking force Fef to the total braking force Fu when the regenerative braking force Fg does not act and the front-wheel wheel pressure Pwf and the rear-wheel wheel pressure Pwr are equal. That is, when "Fg = 0, Pwf = Pwr", "hf = Fef / Fu = Fef / (Fef + Fer)".

[0066] Case (3): When the target total braking force Fv is greater than the value "Fz / hf" obtained by dividing the standard regenerative braking force Fz by the distribution ratio hf, the target regenerative braking force Fh is made equal to the target total braking force Fv. Then, the target front-wheel frictional braking force Fnf is calculated by subtracting the target regenerative braking force Fh from the value "hf·Fv" obtained by multiplying the target total braking force Fv by the front-wheel ratio hf. Also, the target rear-wheel frictional braking force Fnr is calculated by multiplying the target total braking force Fv by the value obtained by subtracting the distribution ratio hf from "1". That is, when "Fv > (Fz / hf)", "Fh = Fz, Fnf = hf·Fv - Fh, Fnr = (1 - hf)·Fv" is determined.

[0067] Next, based on the target rear-wheel frictional braking force Fnr, the target rear-wheel pressure Ptr is calculated. That is, based on the specifications of the rear-wheel braking device SXr, the target rear-wheel frictional braking force Fnr is converted into the target rear-wheel pressure Ptr. Similarly, based on the target front-wheel frictional braking force Fnf, the target front-wheel pressure Ptf is calculated. That is, based on the specifications of the front-wheel braking device SXf, the target front-wheel frictional braking force Fnf is converted into the target front-wheel pressure Ptf. Note that the specifications of the braking device SX (= SXf, SXr) include the pressure-receiving area of the wheel cylinder CW, the effective braking radius of the rotating member KT (brake disk), the friction coefficient of the friction member (brake pad), the effective radius of the wheel WH (tire), etc.

[0068] In case (1) where 「Fv≦Fz」, the front and rear wheel target pressures Ptf and Ptr are both maintained at 「0」 so that the energy is recovered to the maximum extent by the regeneration device KG. And in case (2) where 「Fz<Fv≦(Fz / hf)」, with the front wheel target pressure Ptf (and as a result, the front wheel wheel pressure Pwf) maintained at 「0」, the rear wheel target pressure Ptr (and as a result, the rear wheel wheel pressure Pwr) is increased from 「0」 so that the front-rear distribution of the total braking force Fu quickly reaches a predetermined ratio hf. Further, in case (3) where 「Fv>(Fz / hf)」, with the state of 「Ptr>Ptf」, the front and rear wheel target pressures Ptf and Ptr are both increased so that the front-rear distribution of the total braking force Fu is maintained at a predetermined ratio hf.

[0069] In step S140, based on the rear wheel target pressure Ptr and the front wheel target pressure Ptf, the electric motor MA and the pressure regulating valve UC are controlled. Specifically, when the regenerative cooperative control is executed, the basic pressure Pa is controlled by the electric cylinder DN (particularly, the electric motor MA) so that the rear wheel wheel pressure Pwr approaches and matches the rear wheel target pressure Ptr. Also, the differential pressure Sa (also referred to as the 「actual differential pressure」) between the basic pressure Pa and the regulating pressure Pb is controlled by the pressure regulating valve UC so that the front wheel wheel pressure Pwf approaches and matches the front wheel target pressure Ptf. Specifically, the valve current Ic is adjusted so that the target differential pressure St calculated from the front and rear wheel target pressures Ptf and Ptr approaches and matches the actual differential pressure Sa calculated from the basic pressure Pa and the regulating pressure Pb. Here, the basic pressure Pa is acquired by the basic pressure sensor PA. Also, the regulating pressure Pb is acquired by at least one of the regulating pressure sensor PB and the supply pressure sensor PM.

[0070] <Drive control of electric cylinder DN> Referring to the block diagram of FIG. 3, the details of the drive control of the electric cylinder DN in step S140 will be described. The electric cylinder DN (particularly, the electric motor MA) is controlled based on the front wheel target pressure Ptf, the rear wheel target pressure Ptr, the base pressure Pa, the adjustment pressure Pb, and the motor rotation angle Ka. The drive control of the electric motor MA is composed of a wheel pressure calculation block PW, a hydraulic pressure / liquid volume conversion block ZE, a discharged liquid volume calculation block EJ, a reference value calculation block KS, a correction value calculation block KH, a target rotation angle calculation block KT, and a rotation angle feedback control block KF.

[0071] In the wheel pressure calculation block PW, the rear wheel wheel pressure Pwr is calculated based on the base pressure Pa. Also, the front wheel wheel pressure Pwf is calculated based on the adjustment pressure Pb. As described above, the target pressure Pt is determined to correspond to the wheel pressure Pw. Therefore, based on the resistance in the hydraulic transmission path, the rear wheel wheel pressure Pwr is calculated from the base pressure Pa, and the front wheel wheel pressure Pwf is calculated from the adjustment pressure Pb, respectively. Note that since the transmission paths of the base pressure Pa and the adjustment pressure Pb are different between the front wheel wheel pressure Pwf and the rear wheel wheel pressure Pwr, this is taken into account for resistance compensation. Specifically, since the adjustment pressure Pb is transmitted to the front wheel wheel cylinder CWf via the master cylinder CM and the master piston NM, the sliding resistance of the seal member SL is considered in the calculation of the front wheel wheel pressure Pwf. However, since the base pressure Pa is directly supplied to the rear wheel wheel cylinder CWr, it is not necessary to consider the sliding resistance of the seal member SL.

[0072] In the hydraulic pressure - liquid volume conversion block ZE, the conversion (conversion) from hydraulic pressure to liquid volume is performed. "Hydraulic pressure" is the pressure in the wheel cylinder CW, and "liquid volume" is the volume of the brake fluid BF in the wheel cylinder CW. In the hydraulic pressure - liquid volume conversion block ZE, front - wheel and rear - wheel conversion maps Zef, Zer (corresponding to the "conversion map") are set. In the conversion maps Zef, Zer, the relationship between the hydraulic pressure Pw generated in the wheel cylinder CW and the liquid volume of the brake fluid BF in the wheel cylinder CW (also referred to as "hydraulic pressure - liquid volume characteristic") is expressed. Note that the front - wheel and rear - wheel conversion maps Zef, Zer are obtained in advance through experiments, analysis, etc. and stored in the controller EA.

[0073] In the hydraulic pressure - liquid volume characteristic (non - linear characteristic of the wheel pressure Pw), when the wheel pressure Pw is small, compared with the case when the wheel pressure Pw is large, a larger amount of liquid volume is required to generate the wheel pressure Pw. Conversely, when the wheel pressure Pw is large, the wheel pressure Pw can be generated with a small amount of liquid volume compared with the case when the wheel pressure Pw is small. That is, in the hydraulic pressure - liquid volume characteristic, the liquid volume increases with a "convex upward" characteristic with respect to the increase in the wheel pressure Pw. The non - linearity of the hydraulic pressure - liquid volume characteristic is based on the fact that the rigidity characteristics (for example, the rigidity of the brake caliper, friction members, etc.) in the braking device SX (= SXf, SXr) are non - linear. Since the rigidity characteristics are different between the front - wheel braking device SXf and the rear - wheel braking device SXr, the front - wheel and rear - wheel conversion maps Zef, Zer are set individually.

[0074] The hydraulic pressure - liquid volume conversion block ZE includes a standard liquid volume calculation block ES and an estimated liquid volume calculation block EE. In the standard liquid volume calculation block ES, based on the target pressure Pt (= Ptf, Ptr) and the front - wheel and rear - wheel conversion maps Zef, Zer, the standard liquid volume Es is calculated. The "standard liquid volume Es" is the amount (volume) of the brake fluid BF that should flow into the front - wheel wheel cylinder CWf and the rear - wheel wheel cylinder CWr to achieve the target pressure Pt. In other words, the standard liquid volume Es is the target value of the liquid volume that should be supplied from the control cylinder CC to the wheel cylinder CW.

[0075] Specifically, in the standard fluid volume calculation block ES, the front-wheel standard fluid volume Esf is calculated based on the front-wheel target pressure Ptf and the front-wheel conversion map Zef. The "front-wheel standard fluid volume Esf" is the volume of fluid (brake fluid BF) that should flow into the front-wheel wheel cylinder CWf to achieve the front-wheel target pressure Ptf. Similarly, in the standard fluid volume calculation block ES, the rear-wheel standard fluid volume Esr is calculated based on the rear-wheel target pressure Ptr and the rear-wheel conversion map Zer. The "rear-wheel standard fluid volume Esr" is the volume of fluid that should flow into the rear-wheel wheel cylinder CWr to achieve the rear-wheel target pressure Ptr. Then, the front-wheel standard fluid volume Esf and the rear-wheel standard fluid volume Esr are added together to determine the standard fluid volume Es (i.e., "Es = Esf + Esr"). That is, the standard fluid volume Es is the sum of the front-wheel standard fluid volume Esf and the rear-wheel standard fluid volume Esr.

[0076] In the estimated liquid volume calculation block EE, an estimated liquid volume Ee is calculated based on "the front wheel wheel pressure Pwf calculated from the adjustment pressure Pb", "the rear wheel wheel pressure Pwr calculated from the basic pressure Pa", and "the front wheel and rear wheel conversion maps Zef and Zer". The "estimated liquid volume Ee" is the amount (volume) of the brake fluid BF that should have already been supplied to the front wheel wheel cylinder CWf and the rear wheel wheel cylinder CWr in order to generate the wheel pressure Pw (= Pwf, Pwr). Specifically, based on the front wheel wheel pressure Pwf and the front wheel conversion map Zef (i.e., the hydraulic pressure - liquid volume characteristics of the front wheel wheel cylinder CWf), a front wheel estimated liquid volume Eef is calculated. Similarly, based on the rear wheel wheel pressure Pwr and the rear wheel conversion map Zer (i.e., the hydraulic pressure - liquid volume characteristics of the rear wheel wheel cylinder CWr), a rear wheel estimated liquid volume Eer is calculated. Then, the front wheel estimated liquid volume Eef and the rear wheel estimated liquid volume Eer are added together to determine the estimated liquid volume Ee (i.e., "Ee = Eef + Eer"). That is, the estimated liquid volume Ee is the sum of the front wheel estimated liquid volume Eef and the rear wheel estimated liquid volume Eer, and is the liquid volume estimated to have flowed from the control cylinder CC into the front and rear wheel cylinders CWf and CWr. Since the front and rear wheel pressures Pwf and Pwr are derived from the basic pressure Pa and the adjustment pressure Pb, it can be said that "in the estimated liquid volume calculation block EE, the estimated liquid volume Ee is calculated based on the basic pressure Pa, the adjustment pressure Pb, and the conversion maps Zef and Zer".

[0077] In the discharged liquid volume calculation block EJ, a discharged liquid volume Ej is calculated based on the motor rotation angle Ka (actual value). The "discharged liquid volume Ej" is the amount (volume) of the brake fluid BF actually discharged (discharged) from the electric cylinder DN (i.e., the control cylinder CC). In the discharged liquid volume calculation block EJ, based on the specifications of the electric cylinder DN, the rotation angle Ka is converted into the discharged liquid volume Ej. The specifications of the electric cylinder DN include the reduction ratio of the speed reducer GS, the lead of the conversion mechanism GH (the displacement of the linear member per rotation of the rotating member), the pressure receiving area of the control piston NC, etc.

[0078] In the discharge liquid volume calculation block EJ, the piston stroke Sn may be used to obtain the discharge liquid volume Ej (the volume of liquid sent out from the control cylinder CC). Specifically, the electric cylinder DN is provided with a stroke sensor SN for obtaining the displacement (piston stroke) of the control piston NC. Then, based on the piston stroke Sn and the pressure receiving area of the control piston NC, the discharge liquid volume Ej is determined. Since the rotation angle sensor KA and the stroke sensor SN are used to determine the discharge liquid volume Ej from the control cylinder CC, they are collectively referred to as the "liquid volume sensor". That is, in the discharge liquid volume calculation block EJ, the discharge liquid volume Ej is determined based on the detection results of the liquid volume sensors KA and SN.

[0079] In the reference value calculation block KS, based on the standard liquid volume Es (= Esf + Esr), the reference value Ks is determined. The "reference value Ks" is a state quantity (variable) for determining the target value for controlling the electric motor MA. Specifically, the reference value Ks is a state variable obtained by converting the standard liquid volume Es into the dimension (i.e., physical quantity) from the standard liquid volume Es to the rotation angle of the electric motor MA. For example, as the dimension (physical quantity) of the reference value Ks, any one of the dimension of the liquid volume, the dimension of the displacement of the control piston NC, and the dimension of the rotation angle of the electric motor MA can be adopted. In the electric cylinder DN, the specifications of the components are known. In the reference value calculation block KS, based on the specifications of the electric cylinder DN (reduction ratio of the speed reducer GS, lead of the conversion mechanism GH, pressure receiving area of the control piston NC, etc.), the standard liquid volume Es is converted into the reference value Ks. Therefore, the reference value Ks is determined to increase as the standard liquid volume Es increases.

[0080] In the correction value calculation block KH, a correction value Kh is calculated based on the estimated liquid volume Ee and the discharged liquid volume Ej. The front and rear wheel conversion maps Zef and Zer are preset, but they include errors such as variations and aging changes. These errors are caused by the presence or absence of gas inside components such as the braking device SX and the wear of friction members. The "correction value Kh" is a state quantity (variable) for compensating for these errors. In the correction value calculation block KH, a deviation hE (liquid volume deviation) between the estimated liquid volume Ee and the discharged liquid volume Ej is calculated. For example, the estimated liquid volume Ee is subtracted from the discharged liquid volume Ej to determine the liquid volume deviation hE (i.e., "hE = Ej - Ee"). Then, the liquid volume deviation hE is converted to the same dimension (physical quantity) as the reference value Ks based on the specifications of the components of the electric cylinder DN, and the correction value Kh is determined. Therefore, the larger the liquid volume deviation hE, the larger the correction value Kh is determined, and the smaller the liquid volume deviation hE, the smaller the correction value Kh is determined.

[0081] In the target rotation angle calculation block KT, a target rotation angle Kt is calculated based on the reference value Ks and the correction value Kh. The "target rotation angle Kt" is the final target value for controlling the rotation angle Ka of the electric motor MA. For example, the reference value Ks and the correction value Kh are added to determine an instruction value Ku (i.e., "Ku = Ks + Kh"). The "instruction value Ku" corresponds to an intermediate target value for determining the target rotation angle Kt. Here, the physical quantity (dimension) of the instruction value Ku is the same as the physical quantities of the reference value Ks and the correction value Kh.

[0082] The correction value Kh is a state quantity for making the rear wheel wheel pressure Pwr match the rear wheel target pressure Ptr. In other words, the correction of the reference value Ks based on the correction value Kh corresponds to feedback control related to the liquid volume of the brake fluid BF. Also, the correction by the correction value Kh functions as feedback control related to hydraulic pressure. This is based on "the estimated liquid volume Ee is obtained from the hydraulic pressures Pwf and Pwr (actual values)" and "when the liquid volume is optimized, the hydraulic pressure is also optimized". In the braking control device SA, through the feedback control based on the correction value Kh, the rear wheel wheel pressure Pwr is controlled to approach and match the rear wheel target pressure Ptr.

[0083] In the target rotation angle calculation block KT, the target rotation angle Kt is calculated based on the command value Ku. Specifically, using the specifications of the components of the electric cylinder DN (such as the reduction ratio of the speed reducer GS and the lead of the conversion mechanism GH), the command value Ku is converted into the dimension (physical quantity) of the motor rotation angle Ka, and the target rotation angle Kt is determined. When determining the target rotation angle Kt, the responsiveness of the electric motor MA can be considered. For example, through the response model of the electric motor MA, a limit is imposed on the response speed (i.e., the amount of change per unit time) of the target rotation angle Kt. This is based on the fact that even if a stepwise changing target rotation angle Kt is calculated, the electric motor MA cannot follow it. In any case, in the target rotation angle calculation block KT, based on the reference value Ks and the correction value Kh, the target rotation angle Kt, which is the final target value, is determined.

[0084] In the rotation angle feedback control block KF, the electric motor MA is controlled based on the target rotation angle Kt and the actual motor rotation angle Ka. Specifically, the motor rotation angle Ka (actual value) acquired by the rotation angle sensor KA is made to approach and match the target rotation angle Kt (target value) (i.e., the deviation hK between the target value Kt and the actual value Ka approaches "0"), and the drive signal Ma of the electric motor MA is determined. Then, in the drive circuit DR (inverter circuit), based on the motor drive signal Ma, the current Im (motor current) supplied to the electric motor MA is adjusted. That is, in the rotation angle feedback control block KF, so-called rotation angle feedback control is executed.

[0085] In the braking control device SA, the rotation angle Ka of the electric motor MA is converted into the displacement of the control piston NC by the conversion mechanism GH. The amount of liquid (the volume of the braking fluid BF) corresponding to the displacement of the control piston NC is discharged from the control cylinder CC to the wheel cylinder CW. Then, according to the liquid pressure - liquid volume characteristic of the wheel cylinder CW, the wheel pressure Pw is determined by the amount of liquid flowing into the wheel cylinder CW. The liquid pressure - liquid volume characteristic is the amount of liquid consumed in the wheel cylinder CW to generate the wheel pressure Pw, and is also referred to as the "consumed liquid volume characteristic".

[0086] In the braking control device SA, the target rotation angle Kt is determined based on the rear-wheel standard liquid volume Esr calculated from the rear-wheel target pressure Ptr and the front-wheel standard liquid volume Esf calculated from the front-wheel target pressure Ptf. Then, the electric motor MA is controlled so that the actual rotation angle Ka matches the target rotation angle Kt. As a result, an appropriate amount of brake fluid BF is discharged from the electric cylinder DN (particularly, the control cylinder CC) in order to achieve the base pressure Pa.

[0087] As the hydraulic pressure - liquid volume characteristics (consumed liquid volume characteristics), the front-wheel and rear-wheel conversion maps Zef, Zer pre-stored in the brake controller EA (particularly, the microprocessor MP) include errors caused by the presence of gas (such as air) in the device, wear of friction members, etc. Specifically, when gas is present, more liquid volume is required to achieve the same hydraulic pressure compared to the case where no gas is present. Also, when the wear of the friction members is large, the same hydraulic pressure is achieved with less liquid volume compared to the case where the wear is small.

[0088] In the braking control device SA, a correction value Kh is determined so as to compensate for the errors in the conversion maps Zef, Zer. The correction value Kh is determined based on the rear-wheel estimated liquid volume Eer (the liquid volume estimated to have flowed into the rear-wheel wheel cylinder CWr) calculated from the base pressure Pa, the front-wheel estimated liquid volume Eef (the liquid volume estimated to have flowed into the front-wheel wheel cylinder CWf) calculated from the adjustment pressure Pb, and the liquid volume Ej (discharged liquid volume) actually discharged from the control cylinder CC. Here, the discharged liquid volume Ej is acquired by the liquid volume sensors KA, SN. The same conversion maps Zef, Zer as those for calculating the standard liquid volume Es are used for calculating the estimated liquid volume Ee. Therefore, the correction value Kh based on the deviation hE between the estimated liquid volume Ee and the discharged liquid volume Ej represents the error included in the conversion maps Zef, Zer. Since the reference value Ks is corrected by the correction value Kh and the target rotation angle Kt is determined, the influence of the above errors is corrected.

[0089] The liquid volume deviation hE is determined by subtracting the estimated liquid volume Ee from the discharged liquid volume Ej (i.e., "hE = Ej - Ee"). When the discharged liquid volume Ej is larger than the estimated liquid volume Ee (i.e., when "Ej > Ee, hE > 0"), the conversion maps Zef and Zer are shifted so as to be reduced in the direction of the vertical axis (the axis of liquid pressure) with respect to the true value. That is, in the conversion maps Zef and Zer, at the same liquid pressure, the liquid volume is determined to be smaller than the true value. Therefore, the correction value Kh calculated from the liquid volume deviation hE is added to the reference value Ks calculated from the standard liquid volume Es, so that the target rotation angle Kt is corrected to be larger. On the other hand, when the discharged liquid volume Ej is smaller than the estimated liquid volume Ee (i.e., when "Ej < Ee, hE < 0"), the conversion maps Zef, Zer, and Zek are shifted so as to be enlarged in the direction of the vertical axis (the axis of liquid pressure) with respect to the true value. That is, in the conversion maps Zef and Zer, at the same liquid pressure, the liquid volume is determined to be larger than the true value. Therefore, the target rotation angle Kt is corrected to be smaller by the correction value Kh calculated from the liquid volume deviation hE. Note that the correction value Kh is determined to be larger as the liquid volume deviation hE is larger, including the positive and negative signs. By the correction based on the liquid volume deviation hE, the amount Ej (discharged liquid volume) of the brake fluid BF discharged from the electric cylinder DN (particularly, the control cylinder CC) is adjusted without excess or deficiency with respect to the target pressures Ptf and Ptr. As a result, the electric cylinder DN can adjust the rear wheel wheel pressure Pwr with high precision so as to match the rear wheel target pressure Ptr.

[0090] <Drive control of the pressure regulating valve UC> With reference to the block diagram of FIG. 4, the details of the drive control of the pressure regulating valve UC in step S140 will be described. The pressure regulating valve UC is controlled based on the front wheel target pressure Ptf, the rear wheel target pressure Ptr, the base pressure Pa, and the adjustment pressure Pb. The drive control of the pressure regulating valve UC is composed of a target differential pressure calculation block ST, an indicated current calculation block IS, an actual differential pressure calculation block SA, a differential pressure deviation calculation block HS, a compensation current calculation block IH, a target valve current calculation block IT, and a current feedback control block IF.

[0091] In the target differential pressure calculation block ST, based on the rear wheel target pressure Ptr and the front wheel target pressure Ptf, the target differential pressure St is calculated. The "target differential pressure St" is the target value of the hydraulic pressure difference (differential pressure) generated by the pressure regulating valve UC. Specifically, after considering the above resistance, the front wheel target pressure Ptf is subtracted from the rear wheel target pressure Ptr to determine the target differential pressure St.

[0092] In the indicated current calculation block IS, based on the target differential pressure St and a preset calculation map Zis, the indicated current Is is calculated. The "indicated current Is" is the target value corresponding to the valve current Ic (actual value) supplied to the pressure regulating valve UC. The indicated current Is is determined according to the calculation map Zis such that it increases as the target differential pressure St increases.

[0093] In the actual differential pressure calculation block SA, based on the base pressure Pa and the adjustment pressure Pb, the actual differential pressure Sa is calculated. The "actual differential pressure Sa" is the hydraulic pressure difference (actual differential pressure) actually generated by the pressure regulating valve UC. Specifically, the adjustment pressure Pb is subtracted from the base pressure Pa to determine the actual differential pressure Sa (i.e., "Sa = Pa - Pb"). Here, the base pressure Pa is detected by the base pressure sensor PA. Also, the adjustment pressure Pb is detected by at least one of the adjustment pressure sensor PB and the supply pressure sensor PM.

[0094] In the differential pressure deviation calculation block HS, based on the target differential pressure St and the actual differential pressure Sa, the differential pressure deviation hS is calculated. The "differential pressure deviation hS" is the deviation between the target differential pressure St and the actual differential pressure Sa and corresponds to the error in the control of the pressure regulating valve UC. When a valve current Ic equal to the indicated current Is is supplied to the pressure regulating valve UC, originally the actual differential pressure Sa should be equal to the target differential pressure St. However, in reality, an error hS occurs. Specifically, the differential pressure deviation hS is determined by subtracting the actual differential pressure Sa from the target differential pressure St (i.e., "hS = St - Sa").

[0095] In the compensation current calculation block IH, the compensation current Ih is calculated based on the differential pressure deviation hS and a preset calculation map Zih. The "compensation current Ih" is for compensating the above error hS to make the actual differential pressure Sa match the target differential pressure St. The compensation current Ih is determined according to the calculation map Zih such that the larger the differential pressure deviation hS, the larger it becomes. Note that a dead zone is provided in the calculation map Zih.

[0096] In the target valve current calculation block IT, the target valve current It is calculated based on the command current Is and the compensation current Ih. The "target valve current It" is the final target value of the valve current Ic supplied to the pressure regulating valve UC. Specifically, the compensation current Ih is added to the command current Is to determine the target valve current It (i.e., "It = Is + Ih"). In the target valve current calculation block IT, the target valve current It is determined such that the actual differential pressure Sa approaches and matches the target differential pressure St by the compensation current Ih.

[0097] For example, when the target differential pressure St is larger than the actual differential pressure Sa, the actual differential pressure Sa is insufficient. In the differential pressure deviation calculation block HS, since the differential pressure deviation hS is determined as a positive-signed value, the compensation current Ih is determined as a positive-signed value according to the calculation map Zih. In the target valve current calculation block IT, the target valve current It is increased from the command current Is by the compensation current Ih, so that the insufficient actual differential pressure Sa is increased to match the target differential pressure St. Conversely, when the target differential pressure St is smaller than the actual differential pressure Sa, the actual differential pressure Sa is excessive, so the differential pressure deviation hS is determined as a negative-signed value. Thereby, the compensation current Ih is also determined as a negative-signed value, and the target valve current It is decreased from the command current Is. As a result, the excessive actual differential pressure Sa is decreased to match the target differential pressure St. That is, the differential pressure deviation hS (error) approaches and matches "0" by the compensation current Ih.

[0098] In the current feedback control block IF, the drive signal Uc of the pressure regulating valve Uc is determined so that the actual valve current Ic approaches and matches the target valve current It (that is, the deviation hI between the target value It and the actual value Ic approaches "0"). Then, in the drive circuit DR, power is supplied to the pressure regulating valve UC based on the drive signal Uc. That is, in the current feedback control block IF, so-called current feedback control is executed. Note that the valve current Ic is detected by the valve current sensor IC provided in the drive circuit DR.

[0099] The pressure regulating valve UC (a linear solenoid valve) has its valve opening amount adjusted according to the supplied valve current Ic. And by adjusting the valve opening amount, the hydraulic pressure Pa (basic pressure) on the side closer to the electric cylinder DN, the hydraulic pressure Pb (adjusting pressure) on the side farther from the electric cylinder DN, and the hydraulic pressure difference Sa with respect to the pressure regulating valve UC are controlled. For this reason, in the braking control device SA, the valve current Ic of the pressure regulating valve UC is controlled based on the differential pressure St (target differential pressure) to be generated by the pressure regulating valve UC. Further, the valve current Ic is finely adjusted so as to reduce the error hS (differential pressure deviation), which is the difference between the actually generated differential pressure Sa (actual differential pressure) and the target differential pressure St. Thereby, the basic pressure Pa generated in the electric cylinder DN is accurately adjusted to the adjusting pressure Pb by the pressure regulating valve UC.

[0100] Note that when the adjusting pressure Pb is adjusted to match the front wheel target pressure Ptf, the amount of hydraulic fluid supplied to the front wheel wheel cylinder CWf changes, thus affecting the basic pressure Pa (and as a result, the rear wheel wheel pressure Pwr). However, in adjusting the basic pressure Pa, in addition to the rear wheel target pressure Ptr and the basic pressure Pa, the front wheel target pressure Ptf and the adjusting pressure Pb are also considered. That is, the change in the basic pressure Pa caused by the change in the adjusting pressure Pb is compensated by a feedback control loop (i.e., a closed loop) via the correction value Kh. For this reason, even when the adjusting pressure Pb changes, the rear wheel wheel pressure Pwr is adjusted to match the rear wheel target pressure Ptr.

[0101] <Second Embodiment of the Braking Control Device SA> Referring to the schematic diagram of FIG. 5, a second embodiment of the braking control device SA for a vehicle will be described. Also in the second embodiment, the electric motor MA and the pressure regulating valve UC are controlled in the same manner as in the first embodiment.

[0102] In the first embodiment, the adjustment pressure Pb was transmitted as the supply pressure Pm via the master cylinder CM and the master piston NM. That is, the apply unit AP and the hydraulic pressure generating unit PU were arranged in series in the hydraulic pressure transmission path. Instead of this configuration, the apply unit AP and the hydraulic pressure generating unit PU may be arranged in parallel. In the second embodiment, each of the apply unit AP (particularly, the master cylinder CM) and the hydraulic pressure generating unit PU is directly connected to the hydraulic pressure correcting device SZ (particularly, the correction actuator YZ).

[0103] Specifically, in the braking control device SA according to the second embodiment, instead of the input unit NR, a shut-off valve VM, a simulator valve VS, and a communication valve VC are provided. The shut-off valve VM is a normally open on-off solenoid valve, and the simulator valve VS and the communication valve VC are normally closed on-off solenoid valves. The shut-off valve VM is provided in the front wheel communication path HSf that connects the master cylinder CM (particularly, the master chamber Rm) and the front wheel cylinder CWf. The stroke simulator SS is connected via the simulator valve VS to the front wheel communication path HSf between the master cylinder CM and the shut-off valve VM.

[0104] The front wheels, the front and rear wheel communication paths HSf, HSr (fluid paths connected to the front and rear wheel cylinders CWf, CWr), and the control cylinder CC (particularly, the control chamber Rc) are connected via a communication path HV (fluid path). The communication path HV is also a fluid path that connects the front wheel communication path HSf and the rear wheel communication path HSf. The communication path HV is provided with a pressure regulating valve UC and a communication valve VC.

[0105] As described above, in the pressure regulating valve UC, the flow of the brake fluid BF from the control cylinder CC toward the front wheel wheel cylinder CWf is blocked by the thrust of the solenoid. As a result, the pressure regulating valve UC can adjust the regulated pressure Pb (i.e., the front wheel wheel pressure Pwf) to be smaller than the base pressure Pa (i.e., the rear wheel wheel pressure Pwr).

[0106] That is, the pressure regulating valve UC is provided in the hydraulic pressure transmission path from the control cylinder CC to the front wheel wheel cylinder CWf. Then, the regulated pressure Pb decreased from the base pressure Pa by the pressure regulating valve UC is transmitted to the front wheel wheel cylinder CWf as the front wheel wheel pressure Pwf. On the other hand, the base pressure Pa is transmitted to the rear wheel wheel cylinder CWr as the rear wheel wheel pressure Pwr. Note that the decrease of the regulated pressure Pb is not possible only by the pressure regulating valve UC, and the decrease of the base pressure Pa is essential for the decrease of the regulated pressure Pb.

[0107] When the pressure regulating control is executed, power is supplied to the shut-off valve VM, the simulator valve VS, and the communication valve VC. As a result, the shut-off valve VM is closed, and the simulator valve VS and the communication valve VC are opened. The connection between the master chamber Rm and the front wheel wheel cylinder CWf is blocked, and the regulated pressure Pb is supplied to the front wheel wheel cylinder CWf. Further, since the master chamber Rm is connected to the stroke simulator SS, the operating force of the braking operation member BP (brake pedal) is generated by the stroke simulator SS. Note that the regulated pressure sensor PB may be provided in the hydraulic pressure generating unit PU or may be provided in the correction actuator YZ. In the configuration in which the regulated pressure sensor PB is provided in the correction actuator YZ, the regulated pressure Pb is acquired by the braking controller EA via the communication bus BS.

[0108] Also in the second embodiment, the same regeneration cooperative control as in the first embodiment is executed. Specifically, the base pressure Pa generated by the electric cylinder DN is adjusted to the regulated pressure Pb by the pressure regulating valve UC. Also in the second embodiment, the same effect (appropriately controlling the electric motor MA and the pressure regulating valve UC for two-system pressure regulation) as in the first embodiment is achieved.

[0109] <Other Embodiments of Brake Control Device SA, etc.> Another embodiment of the brake control device SA including the electric cylinder DN will be described. Even in other embodiments, the same effects as described above are achieved.

[0110] In the above-described embodiment of the brake control device SA, the base pressure Pa was obtained as the detection result of the base pressure sensor PA provided in the discharge part of the electric cylinder DN. Instead of this, the base pressure sensor PA can be provided in the hydraulic pressure transmission path from the control cylinder CC to the rear wheel cylinder CWr. In any case, the base pressure Pa used in the calculation of the estimated liquid volume Ee and the actual differential pressure Sa is based on the actual value detected by the base pressure sensor PA.

[0111] Similarly, the adjustment pressure Pb was obtained by the detection result of the adjustment pressure sensor PB provided between the pressure regulating valve UC and the servo chamber Ru. Instead of this, the adjustment pressure sensor PB can be provided in the hydraulic pressure transmission path from the control cylinder CC to the front wheel cylinder CWf (for example, refer to the supply pressure sensor PM). In any case, the adjustment pressure Pb used in the calculation of the estimated liquid volume Ee and the actual differential pressure Sa is based on the actual value detected by the adjustment pressure sensor PB.

[0112] In the above-described embodiment of the brake control device SA, the discharge liquid volume Ej was obtained by the detection result of at least one of the rotation angle sensor KA and the stroke sensor SN. That is, the discharge liquid volume Ej was calculated based on the displacement Sn of the control piston NC obtained from the motor rotation angle Ka, the piston stroke Sn, etc. Instead of this, a flow rate sensor for detecting the flow rate from the control cylinder CC (the liquid volume per unit time) may be provided, and the discharge liquid volume Ej may be obtained from the detection value of the flow rate sensor. For example, as the flow rate sensor, an ultrasonic type, an electromagnetic type, etc. are adopted. In any case, the discharge liquid volume Ej (actual value) is based on the detection result of the liquid volume sensor that detects the discharge amount of the brake fluid BF from the electric cylinder DN.

[0113] In the above-described embodiment of the braking control device SA, the target pressure Pt (= Ptf, Ptr) was determined as a target value corresponding to the wheel pressure Pw (= Pwf, Pwr). That is, the part where the target value and the actual value are compared (also referred to as the "comparison part") was the wheel cylinder CW. Instead of this, the comparison part may be any location from the discharge part of the electric cylinder DN to the wheel cylinder CW in the path through which the hydraulic pressure is transmitted. For example, as the comparison part, the detection part of the base pressure sensor PA or the adjustment pressure sensor PB may be adopted. In this configuration, the target pressures Ptf, Ptr are determined so that the hydraulic pressure component due to the above resistance is compensated and corresponds to the base pressure Pa and the adjustment pressure Pb. In the pressure control, regardless of where the comparison part between the target value and the actual value is located, the front and rear wheel target pressures Ptf, Ptr are target values for controlling the base pressure Pa and the adjustment pressure Pb, and the standard liquid volume Es is determined based on the front and rear wheel target pressures Ptf, Ptr, and the estimated liquid volume Ee is determined based on the base pressure Pa and the adjustment pressure Pb. Also, the target differential pressure St is determined based on the front and rear wheel target pressures Ptf, Ptr, and the actual differential pressure Sa is determined based on the base pressure Pa and the adjustment pressure Pb.

[0114] In the above-described embodiment of the braking control device SA, a disk-type braking device SX was adopted. Instead of this, a drum-type braking device SX may be adopted. In the drum-type braking device SX, the rotating member KT fixed to the wheel WH is a brake drum, and the friction member is a brake lining attached to the brake shoe. Also in the drum-type braking device SX, similar to the disk-type braking device SX, the brake lining (friction member) is pressed against the brake drum (rotating member) by the wheel pressure Pw of the wheel cylinder CW, and the frictional braking force Fe is generated.

[0115] In the above-described embodiment of the braking control device SA, the target values of various braking forces (Fv, Fz, Fh, Fn, etc.) are calculated in the dimension of the longitudinal force acting on the vehicle (the corresponding physical quantity). Instead of this, they may be calculated in the dimension of the acceleration of the vehicle or the dimension of the torque of the wheel WH. This is based on the equivalence of the state quantities from the longitudinal force to the vehicle acceleration (referred to as "state quantities related to force"). Therefore, the target pressures Ptf, Ptr, etc. are calculated via the state quantities related to force from the longitudinal force acting on the vehicle to the deceleration of the vehicle based on the braking demand amount Bs.

[0116] In the above-described embodiment of the braking control device SA, the pressure regulating valve UC is provided in the servo passage HU or the communication passage HV. Instead of this, the pressure regulating valve UC may be provided in the front-wheel connection passage HSf. Specifically, in the front-wheel connection passage HSf, the pressure regulating valve UC is arranged between the portion where the base pressure Pa is transmitted and the front-wheel wheel cylinder CWf. In any case, the pressure regulating valve UC is provided in the hydraulic pressure transmission path from the control cylinder CC to the front-wheel wheel cylinder CWf. And the regulated pressure Pb reduced and adjusted from the base pressure Pa is transmitted to the front-wheel wheel cylinder CWf as the front-wheel wheel pressure Pwf by the pressure regulating valve UC.

[0117] In the first embodiment of the above-described braking control device SA, in the apply unit AP, the pressure receiving area rm (master area) of the master chamber Rm and the pressure receiving area ru (servo area) of the servo chamber Ru are set to be equal. The master area rm and the servo area ru do not have to be equal. In a configuration where the master area rm and the servo area ru are different, based on the area ratio between the servo area ru and the master area rm, the conversion calculation between the supply pressure Pm (master pressure) and the base pressure Pa is possible (i.e., the conversion based on "Pm·rm = Pa·ru"). And in a configuration where the supply pressure sensor PM is adopted as the regulated pressure sensor PB and the supply pressure Pm is adopted as the regulated pressure Pb, the supply pressure Pm is converted into the regulated pressure Pb based on the above area ratio.

[0118] <Summary of the embodiment> The braking control device SA is applied to a vehicle equipped with a regenerative device KG on the front wheels WHf. The braking control device SA is composed of a control cylinder CC, a pressure regulating valve UC (electromagnetic valve), and a brake controller EA. Here, the control cylinder CC generates a basic pressure Pa using an electric motor MA as a power source, the pressure regulating valve UC adjusts the basic pressure Pa to an adjusted pressure Pb, and the controller EA controls the electric motor MA and the pressure regulating valve UC. The braking control device SA generates the basic pressure Pa and the adjusted pressure Pb based on the required braking amount Bs of the vehicle, and controls the hydraulic pressure Pwf of the front wheel wheel cylinder CWf with the adjusted pressure Pb, while controlling the hydraulic pressure Pwr of the rear wheel wheel cylinder CWr with the basic pressure Pa. Note that the adjusted pressure Pb is smaller than the basic pressure Pa.

[0119] For example, the braking control device SA has a master chamber Rm and a servo chamber Ru facing each other via a master piston NM. And the control cylinder CC is connected to the servo chamber Ru and the rear wheel wheel cylinder CWr. Also, the master chamber Rm is connected to the front wheel wheel cylinder CWf, and the pressure regulating valve UC is arranged between the control cylinder CC and the servo chamber Ru. With this configuration, the hydraulic pressure Pwf (front wheel wheel pressure) of the front wheel wheel cylinder CWf is controlled by the adjusted pressure Pb, and the hydraulic pressure Pwr (rear wheel wheel pressure) of the rear wheel wheel cylinder CWr is controlled by the basic pressure Pa.

[0120] In the braking control device SA, the controller EA calculates the liquid volume to be supplied to the rear wheel wheel cylinder CWr as the rear wheel standard liquid volume Esr based on the rear wheel target pressure Ptr for controlling the basic pressure Pa, and calculates the liquid volume to be supplied to the front wheel wheel cylinder CWf as the front wheel standard liquid volume Esf based on the front wheel target pressure Ptf for controlling the adjusted pressure Pb. Then, the controller EA controls the electric motor MA based on the front and rear wheel standard liquid volumes Esf, Esr. At the same time, the controller EA controls the pressure regulating valve UC based on the rear wheel target pressure Ptr and the front wheel target pressure Ptf.

[0121] The wheel pressure Pw is determined by the amount (liquid volume) of the braking fluid BF flowing into the wheel cylinder CW. For this reason, the braking control device SA is provided with front-wheel and rear-wheel conversion maps Zef and Zer. The conversion maps Zef and Zer correspond to the hydraulic pressure-liquid volume characteristics (non-linear characteristics in which the liquid volume with respect to the hydraulic pressure is "convex upward"), which are the relationships between the hydraulic pressure Pw (wheel pressure) generated in the wheel cylinder CW and the liquid volume (volume) of the braking fluid BF supplied to the wheel cylinder CW. Specifically, in the conversion maps Zef and Zer, the increase rates of the standard liquid volumes Esf and Esr with respect to the increase in the target pressures Ptf and Ptr, and the increase rates of the estimated liquid volumes Eef and Eer with respect to the increase in the actual hydraulic pressures Pa and Pb are determined.

[0122] In the braking control device SA, the hydraulic pressures (such as Ptf, Ptr, Pa, and Pb) are converted and calculated into liquid volumes (such as Esf, Esr, Eef, and Eer) by the conversion maps Zef and Zer. That is, based on the front-wheel and rear-wheel target pressures Ptf and Ptr and the front-wheel and rear-wheel conversion maps Zef and Zer, the standard liquid volume Es (that is, the sum of the front-wheel and rear-wheel standard liquid volumes Esf and Esr) is determined. Then, based on the standard liquid volume Es, the rotation angle Ka of the electric motor MA is controlled. Since the standard liquid volume Es corresponds to the amount of the braking fluid BF that the control cylinder CC should discharge in order to achieve the front-wheel and rear-wheel target pressures Ptf and Ptr, the necessary amount of the braking fluid BF is discharged from the electric cylinder DN (particularly, the control cylinder CC).

[0123] The front-wheel and rear-wheel conversion maps Zef and Zer are pre-stored in the controller EA (specifically, the microprocessor MP) as predetermined characteristics. However, due to the gas (such as air) present inside components like the braking device SX and the wear of friction members, errors occur in the conversion maps Zef and Zer. In the braking control device SA, a correction value Kh is calculated to compensate for the errors in the conversion maps Zef and Zer. Specifically, based on the front-wheel conversion map Zef, the estimated liquid volume Eef (front-wheel estimated liquid volume) supplied to the front-wheel wheel cylinder CWf is calculated from the adjustment pressure Pb. Also, based on the rear-wheel conversion map Zer, the estimated liquid volume Eer (rear-wheel estimated liquid volume) supplied to the rear-wheel wheel cylinder CWr is calculated from the base pressure Pa. Furthermore, the actual discharged liquid volume Ej (discharged liquid volume) from the control cylinder CC is obtained from the detected value of the liquid volume sensor. Here, the base pressure Pa (actual value) is obtained by a base pressure sensor (such as PA), the adjustment pressure Pb (actual value) is obtained by an adjustment pressure sensor (PB, PM, etc.), and the discharged liquid volume Ej (actual value) is obtained by a liquid volume sensor (KA, SN, etc.). Then, the sum of the front-wheel estimated liquid volume Eef and the rear-wheel estimated liquid volume Eer is calculated as the estimated liquid volume Ee, and based on the deviation hE (liquid volume deviation) between the estimated liquid volume Ee and the discharged liquid volume Ej, the correction value Kh is calculated. Note that since the correction value Kh is a state quantity in which the liquid volume deviation hE is converted to the dimension (physical quantity) of the reference value Ks, it is determined to increase as the liquid volume deviation hE increases.

[0124] As described above, although the conversion maps Zef and Zer used in the calculation of the reference value Ks contain errors, the correction value Kh represents the errors contained in the conversion maps Zef and Zer. In the braking control device SA, the reference value Ks is corrected by the correction value Kh, and the target rotation angle Kt is determined. As a result, the amount Ej (discharged liquid volume) of the braking fluid BF discharged (ejected) by the electric cylinder DN (specifically, the control cylinder CC) is adjusted accurately with respect to the target pressures Ptf and Ptr. Consequently, the pressure adjustment accuracy by the electric cylinder DN is improved.

[0125] In controller EA, a target valve current It is calculated based on a target differential pressure St calculated from the front wheel and rear wheel target pressures Ptf and Ptr, and the valve current Ic (actual value) supplied to the pressure regulating valve UC is controlled to match the target valve current It (target value). Further, in controller EA, an actual differential pressure Sa is calculated from a base pressure Pa and an adjustment pressure Pb, and a deviation hS between the target differential pressure St and the target differential pressure St is determined. Then, in controller EA, the target valve current It is adjusted so that the differential pressure deviation hS becomes "0".

[0126] The pressure regulating valve UC adjusts a differential pressure Sa (actual differential pressure) between a hydraulic pressure Pa on the side closer to the electric cylinder DN and a hydraulic pressure Pb on the side farther from the electric cylinder DN with respect to the pressure regulating valve UC according to the supplied valve current Ic. In the braking control device SA, the valve current Ic of the pressure regulating valve UC is controlled based on the target differential pressure St (the differential pressure to be generated by the pressure regulating valve UC). Further, since an error is included in the adjustment of the actual differential pressure Sa, in the braking control device SA, the target valve current It (and as a result, the valve current Ic) is finely adjusted based on the differential pressure deviation hS (the deviation between the target differential pressure St and the actual differential pressure Sa). Thereby, the pressure regulation accuracy by the pressure regulating valve UC is improved.

[0127] When the adjustment pressure Pb is adjusted so that the front wheel wheel pressure Paf matches the front wheel target pressure Ptf, it affects the base pressure Pa. However, since the base pressure Pa is adjusted according to the correction value Kh, the change in the base pressure Pa caused by the change in the adjustment pressure Pb is compensated each time. That is, even when the adjustment pressure Pb changes, the base pressure Pa is adjusted so that the rear wheel wheel pressure Pwr matches the rear wheel target pressure Ptr.

[0128] As described above, in the braking control device SA that individually adjusts the wheel pressures Pwf and Pwr of the front and rear wheel cylinders CWf and CWr by two-system pressure regulation, the electric motor MA and the pressure regulating valve UC are preferably controlled. Thereby, in two-system pressure regulation, the base pressure Pa and the adjustment pressure Pb are adjusted with high precision. As a result, while ensuring the amount of regenerated energy, the running stability of the vehicle is improved.

Explanation of Symbols

[0129] SA… Brake control device, SX… Brake device, BP… Brake operation member (brake pedal), BF… Brake fluid (working fluid), YA… Brake actuator, EA… Brake controller, BS… Communication bus, CM… Master cylinder, CW… Wheel cylinder, AP… Apply unit, NR… Input unit, PU… Hydraulic pressure generating unit, DN… Electric cylinder, MA… Electric motor, NC… Control piston, CC… Control cylinder, Rc… Control chamber (hydraulic pressure chamber of CC), UC… Pressure regulating valve (solenoid valve), VA, VB… First, second control valves, SP… Operation displacement sensor, Sp… Operation displacement (detection value of SP), Pwf, Pwr… Front, rear wheel pressure (actual value), Ptf… Front wheel target pressure (target value corresponding to Pwf and target value for controlling Pb), Ptr… Rear wheel target pressure (target value corresponding to Pwr and target value for controlling Pa), Pa… Basic pressure (output of DN), PA… Basic pressure sensor, Pb… Adjusted pressure (pressure regulating result of UC), PB… Adjusted pressure sensor, Pm… Supply pressure (detection value of PM and equivalent to Pb), PM… Supply pressure sensor (equivalent to PB), Esf, Esr… Front, rear wheel standard liquid volume, Es… Standard liquid volume (sum of Esf and Esr), Eef, Eer… Front, rear wheel estimated liquid volume, Ee… Estimated liquid volume (sum of Eef and Eer), Ej… Discharged liquid volume (liquid volume sent out from CC), Ks… Reference value, Kh… Correction value, Ka… Motor rotation angle (detection value of KA and also equivalent to Ej), KA… Rotation angle sensor (also equivalent to liquid volume sensor), Kt… Target rotation angle (target value corresponding to Ka), St… Target differential pressure (target value of hydraulic pressure difference in UC), Sa… Actual differential pressure (actual value of hydraulic pressure difference in UC), hS… Differential pressure deviation (difference between St and Sa), Is… Indicating current, Ih… Compensation current, It… Target valve current (target value corresponding to Ic), Ic… Valve current (detection value of IC), IC… Valve current sensor, Sn… Piston stroke (detection value of SN and equivalent to Ej), SN… Stroke sensor (equivalent to liquid volume sensor).

Claims

1. Applied to a vehicle equipped with a regenerative device on the front wheels, comprising a control cylinder that generates a basic pressure using an electric motor as a power source, a solenoid valve that adjusts the basic pressure to an adjustment pressure, and a controller that controls the electric motor and the solenoid valve, and controlling the front-wheel wheel pressure of the front-wheel wheel cylinder with the adjustment pressure and controlling the rear-wheel wheel pressure of the rear-wheel wheel cylinder with the basic pressure, in a braking control device for a vehicle. The controller calculates, as front-wheel and rear-wheel standard liquid amounts, the liquid amounts to be supplied to the front-wheel and rear-wheel wheel cylinders based on front-wheel and rear-wheel target pressures that are target values of the front-wheel and rear-wheel wheel pressures, controls the electric motor based on the front-wheel and rear-wheel standard liquid amounts, and controls the solenoid valve based on the front-wheel and rear-wheel target pressures, a braking control device for a vehicle.

2. In the braking control device for a vehicle according to Claim 1. The controller acquires the discharged liquid amount from the control cylinder, calculates an estimated liquid amount based on the basic pressure and the adjustment pressure, and controls the rotation angle of the electric motor based on the deviation between the discharged liquid amount and the estimated liquid amount, a braking control device for a vehicle.

3. A braking control device for a vehicle according to Claim 1 or Claim 2, wherein the controller calculates a target differential pressure based on the front-wheel and rear-wheel target pressures and controls the valve current supplied to the solenoid valve based on the target differential pressure, a braking control device for a vehicle.

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