Brake control device of vehicle

Abstract

To provide a brake control device of a vehicle for adjusting a liquid pressure by an electric motor which compensates an error of a conversion map indicating liquid pressure-liquid amount characteristics.SOLUTION: A brake control device of a vehicle includes: a control cylinder for generating a servo pressure by inserting a control piston thereto and moving the control piston by an electric motor; a servo pressure sensor for detecting the servo pressure; and a controller for controlling the electric motor on the basis of the servo pressure, and adjusts a wheel pressure of a wheel cylinder by the servo pressure. The controller acquires a discharge liquid amount from the control cylinder, calculates an estimated liquid amount on the basis of the servo pressure and a conversion map, and controls the electric motor on the basis of deviation between a discharge liquid amount and an estimated liquid amount. For example, the controller calculates a target pressure on the basis of a brake request amount, calculates a standard liquid amount on the basis of a target pressure and the conversion map, and controls a rotation angle of the electric motor on the basis of the standard liquid amount and the deviation.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 the load fluid loss characteristic changes, a motor-driven cylinder 13, wheel cylinders 2b and 3b, a stroke sensor 11a for detecting a brake pedal operation amount Ps, and a target value setting circuit 33 for setting a target stroke St of the motor-driven cylinder 13 according to the brake pedal operation amount Ps are provided so that the braking force corresponding to the brake pedal operation amount can be changed to let the driver recognize the change in the load fluid loss characteristic. In a vehicle brake device 1 having a hydraulic compensation circuit 38 for correcting the target stroke St in a direction to reduce the deviation when a deviation occurs between a brake fluid pressure standard value Bo corresponding to the brake pedal operation amount Ps and an actual brake fluid pressure B, a stroke limiting circuit 51 for suppressing a compensation value ΔB by the hydraulic compensation circuit 38 based on the brake pedal operation amount Ps is provided, as described.

[0003] By the way, in the device of Patent Document 1, in the target value setting circuit 33, a map or the like is used to obtain the target stroke St of the motor-driven cylinder 13 corresponding to the corrected brake fluid pressure Bt. Here, the conversion map from the fluid pressure to the stroke of the electric cylinder (that is, the fluid volume of the brake fluid discharged from the electric cylinder) represents the relationship between the fluid pressure of the wheel cylinder and the fluid volume of the brake fluid (working fluid) supplied to the wheel cylinder. This relationship is called "fluid pressure-fluid volume characteristic". The fluid pressure-fluid volume characteristic is basically determined by the rigidity of the brake caliper, friction members, etc., but it includes errors such as variations and aging changes. These errors are caused by the presence or absence of gas in the device, wear of the friction members, etc.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0005] In view of the above problems, an object of the present invention is to provide a braking control device for a vehicle that adjusts hydraulic pressure by an electric motor, in which an error in a conversion map representing hydraulic pressure - hydraulic volume characteristics can be compensated for.

MEANS FOR SOLVING THE PROBLEMS

[0006] A braking control device (SA) for a vehicle according to the present invention includes a control cylinder (CC) in which a control piston (NC) is inserted and a servo pressure (Pa) is generated by moving the control piston (NC) by an electric motor (MA), a servo pressure sensor (PA) for detecting the servo pressure (Pa), and a controller (EA) for controlling the electric motor (MA) based on the servo pressure (Pa), and adjusts a wheel pressure (Pw) of a wheel cylinder (CW) by the servo pressure (Pa). Then, the controller (EA) acquires a discharge liquid volume (Ej) from the control cylinder (CC), calculates an estimated liquid volume (Ee) based on the servo pressure (Pa) and a conversion map (Zef, Zer, Zek), and controls the electric motor (MA) based on a deviation (hE) between the discharge liquid volume (Ej) and the estimated liquid volume (Ee).

[0007] In the braking control device (SA) for a vehicle according to the present invention, the controller (EA) calculates a target pressure (Pt) based on a braking demand amount (Bs), calculates a standard liquid volume (Es) based on the target pressure (Pt) and the conversion map (Zef, Zer, Zek), and controls a rotation angle (Ka) of the electric motor (MA) based on the standard liquid volume (Es) and the deviation (hE). Further, the controller (EA) sets a relationship between a volume of braking fluid flowing into the wheel cylinder (CW) and the wheel pressure (Pw) as the conversion map (Zef, Zer, Zek).

[0008] Although the conversion maps Zef, Zer, and Zek representing the hydraulic-fluid volume characteristics contain errors, according to the above configuration, the errors can be appropriately compensated. As a result, the volume of the brake fluid BF discharged from the control cylinder CC is adjusted accurately with respect to the target pressure Pt, so that the pressure regulation accuracy of the control cylinder CC (i.e., the electric cylinder DN) driven by the electric motor MA is improved.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0010] <Symbols of components, etc., and subscripts at the end of 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 wheel cylinder CWf, rear wheel wheel cylinder CWr". Furthermore, the subscripts "f" and "r" at the end of the symbol can 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)".

[0011] The braking 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 braking control device SA and the hydraulic pressure correction device SZ, various components (CC, etc.) are connected by fluid passages. Here, the "fluid passage" is a path for moving the brake fluid BF, and examples include pipes, flow paths in actuators, hoses, and the like. 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.

[0012] <First Embodiment of the Braking Control Device SA> With reference to the schematic diagram of FIG. 1, a first embodiment of the braking control device SA for a vehicle will be described. The braking control device SA is applied to, for example, a hybrid vehicle equipped with a driving electric motor or an electric vehicle.

[0013] Braking devices SX (= SXf, SXr) are provided for the front and rear wheels WHf, WHr (= WH) of the vehicle. The braking device SX is composed of a brake caliper, a friction member (e.g., a brake pad), and a rotating member KT (e.g., 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".

[0014] The vehicle is equipped with a regenerative device KG. The regenerative device KG is composed of a generator GN for energy regeneration (also referred to as an "electric motor / generator" or a "regenerative generator"), a control unit EG for the regenerative device KG (also referred to as a "regenerative controller"), and a regenerative battery (not shown). The regenerative generator GN is also an electric motor for driving. During regenerative braking, the electric motor / generator GN operates as a generator, and the generated electric power is stored in the regenerative battery via the regenerative controller EG. At this time, a regenerative braking force Fg acts on the wheels. That is, the regenerative device KG can generate the regenerative braking force Fg. For example, the regenerative device KG is provided on the front wheels WHf. Therefore, the regenerative braking force Fg is generated at the front wheels WHf. The regenerative device KG (particularly, the regenerative controller EG) is connected to the communication bus BS.

[0015] The vehicle is equipped with a driving support device KJ. In the driving support device KJ, automatic speed control is executed. The driving support device KJ is composed of an object detection sensor SJ and a controller EJ for driving support (also simply referred to as a "driving support controller"). The object detection sensor SJ detects the distance Sj (referred to as the "relative distance" and also as the "inter-vehicle distance" when the object is a preceding vehicle traveling in front of the host vehicle) to an object existing in front of the host vehicle (including a preceding vehicle traveling in front of the host vehicle). 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 (the target value of the vehicle body acceleration in the longitudinal direction of the host vehicle) of the host vehicle is calculated by the driving support controller EJ. The driving support device KJ (particularly, the driving support 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 (vehicle body speed) of the vehicle is controlled.

[0016] 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 (referred to as the "input pressure") in the input chamber Rn (described later) is adopted. The input pressure Pn is detected by an 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".

[0017] The vehicle is equipped with various sensors for braking control such as antilock brake control and skid prevention control (that is, 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 the "wheel speed"). Also, a steering amount sensor that detects the steering amount Sw (for example, the operation angle) of the steering operation member (for example, a steering wheel), a yaw rate sensor that detects the yaw rate Yr of the vehicle, a longitudinal and lateral acceleration sensor that detects the longitudinal and lateral acceleration Gx (also referred to as the "deceleration") of the vehicle, and a lateral acceleration sensor that detects the lateral acceleration Gy of the vehicle are provided (not shown above).

[0018] 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 the "II type") is adopted as the two braking systems. The braking control device SA adjusts the wheel pressure Pw of each wheel cylinder CW.

[0019] 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. Signals are transmitted among a plurality of controllers (EA, EZ, EG, EJ, etc.) via 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.

[0020] <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 servo pressure Pa in response to the operation of the braking operation member BP (brake pedal). Then, the supply pressure Pm and the servo 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 servo pressure Pa are adjusted, and finally, the 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 braking actuator YA and a brake controller EA.

[0021] ≪Braking actuator YA≫ The braking actuator YA is composed of a hydraulic pressure generation unit PU, an apply unit AP, and an input unit NR.

[0022] [Hydraulic pressure generation unit PU] The hydraulic pressure generation unit PU generates a servo pressure Pa using an electric motor MA as a power source. The hydraulic pressure generation unit PU is also referred to as an "electric cylinder DN". 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.

[0023] The electric motor MA is a power source (pressure source) for generating the servo 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 called "power rate") as a physical quantity. Rotational power (also called "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 member (described later) is the product of the thrust of the linear member (the force acting in the direction of the central axis) and the linear speed of the linear member (the speed in the direction along the central axis).

[0024] 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 (especially 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 a "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 are switched.

[0025] 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 (especially a microprocessor MP). In the controller EA, according to the rotation angle Ka, the switching elements of the drive circuit DR (also called an "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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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 servo pressure Pa. That is, in the electric cylinder DN, the electric motor MA is used as the power source, and the servo pressure Pa is output.

[0030] The control cylinder CC is connected to a servo chamber Ru (described later) of an apply unit AP via a servo passage HU (fluid passage). Further, the control cylinder CC is connected to a rear-wheel wheel cylinder CWr via a rear-wheel communication passage HSr (fluid passage) and a hydraulic pressure correction device SZ. A servo pressure sensor PA is provided in a hydraulic pressure generation unit PU so as to detect a servo pressure Pa (hydraulic pressure generated by an electric cylinder DN).

[0031] FIG. 1 illustrates a state in which the electric cylinder DN is not generating the servo pressure Pa. A through hole is provided in the control cylinder CC between two seal members SL. A through hole is also provided in the control piston NC. A supply passage HH (fluid passage) connected to a master reservoir RV is connected to the through hole of the control cylinder CC. In the illustrated state, a control chamber Rc is connected to the master reservoir RV via the through hole and the supply passage HH, and the servo pressure Pa is "0 (atmospheric pressure)". The position of the control piston NC in this state is referred to as the "initial position". At 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.

[0032] When an increase in the servo pressure Pa is required, the rotational power of the electric motor MA is increased. The rotational power is transmitted to a conversion mechanism GH via a speed reducer GS and output as linear power of a 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 servo pressure Pa (the internal pressure of the control chamber Rc) is increased from "0 (atmospheric pressure)". The braking fluid BF pressurized by the servo pressure Pa is output (pressure-fed) from the control chamber Rc of the control cylinder CC.

[0033] When it is necessary to maintain the servo pressure Pa, the rotation of the electric motor MA is stopped. The movement of the control piston NC stops, and the servo pressure Pa is maintained constant. When it is necessary to decrease the servo pressure Pa, the rotational power of the electric motor MA is decreased. Due to the servo 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). Since the brake fluid BF is returned toward the control chamber Rc, the servo pressure Pa is decreased.

[0034] [Apply Unit AP] The apply unit AP is composed of a single-type master cylinder CM and a master piston NM. The master piston NM is inserted into the single-type master cylinder CM. 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.

[0035] The servo pressure Pa is supplied to the servo chamber Ru from a hydraulic pressure generating unit PU (electric cylinder DN). From the apply unit AP, a supply pressure Pm is output by the servo pressure Pa. Here, the "supply pressure Pm" is the internal pressure of the master chamber Rm and is also referred to as the "master pressure". When "Pa = 0" (for example, during non-braking), the master piston NM is in 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)".

[0036] Inside the master reservoir RV (also referred to as the "atmospheric pressure reservoir"), the brake fluid BF is stored. When the servo pressure Pa increases from "0", the master piston NM moves in the forward direction Da (the direction in which the volume of the master chamber Rm decreases). Due to this movement, the communication between the master chamber Rm and the master reservoir RV is blocked. Then, when the master piston NM further moves in the forward direction Da, the supply pressure Pm (master pressure) increases from "0 (atmospheric pressure)". As a result, the brake fluid BF pressurized by the supply pressure Pm is output (pumped) from the master chamber Rm of the master cylinder CM toward the hydraulic pressure correction device SZ. Since "rm = ru", if the sliding resistance of the seal member SL is ignored, "Pa = Pm".

[0037] [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.

[0038] 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). There is a gap Ln (also referred to as the "separation distance") between the end face of the input piston NN and the end face of the master piston NM. By adjusting the separation distance Ln by the servo pressure Pa, the regenerative cooperative control is realized.

[0039] The input chamber Rn of the input unit NR is connected to the reaction chamber Rs of the apply unit AP via the input path HN (fluid path). A normally-closed first control valve VA is provided in the input path HN. The input path HN is connected to the master reservoir RV via a reservoir path HR (fluid path) between the first control valve VA and the reaction chamber Rs. A normally-open second control valve VB is provided in the reservoir path HR. The first and second control valves VA and VB employ on-off type solenoid valves. A stroke simulator SS is connected to the input path HN between the first control valve VA and the reaction chamber Rs.

[0040] 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.

[0041] When power is supplied to the first and second control valves VA and VB, the first control valve VA is opened and the second control valve VB is closed. 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 in the input path HN so as to detect the input pressure Pn. Note that the input pressure Pn is also the hydraulic pressure in the stroke simulator SS.

[0042] ≪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 as to share signals (detection values, calculation values, control flags, etc.) with other controllers (EZ, EG, EJ, etc.).

[0043] Various signals such as the operation displacement Sp (detection value of the operation displacement sensor SP), the input pressure Pn (detection value of the input pressure sensor PN), the servo pressure Pa (detection value of the servo pressure sensor PA), and the motor rotation angle Ka (detection value of the rotation angle sensor KA) are directly input to the brake controller EA. Further, various signals such as the supply pressure Pm, the standard 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, the target regenerative braking force Fh (target value of the regenerative braking force Fg) is output from the brake 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.

[0044] An algorithm for pressure regulation control is programmed in the brake controller EA (particularly, the microprocessor MP). "Pressure regulation control" is control for adjusting the wheel pressure Pw (= Pwf, Pwr) and includes regenerative cooperative control. The pressure regulation control is executed based on the above various signals (Sp, Pa, etc.). Based on the algorithm for pressure regulation control, the drive circuit DR drives the electric motor MA and various solenoid valves (VA, etc.). In the drive circuit DR, an inverter circuit is configured by switching elements (for example, MOS-FETs) to drive the electric motor MA. Also, the drive circuit DR is provided with switching elements to drive 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. A rotation angle sensor KA is provided on the electric motor MA to detect the position Ka (rotation angle) of the motor shaft.

[0045] In the braking controller EA, drive signals Va and Vb for the first and second control valves VA and VB, and a drive signal Ma for the electric motor MA are calculated. Then, according to various drive signals (such as Ma), the switching elements are driven. Specifically, in the control of the solenoid valve, power supply to the first and second control valves VA and VB is performed based on the drive signals Va and 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 regulating control algorithm, the drive signal Ma is determined, and the electric motor MA is controlled based on the drive signal Ma.

[0046] <Hydraulic pressure correction device SZ> A hydraulic pressure correction device SZ is provided between the braking control device SA and the wheel cylinder CW. By means of the hydraulic pressure correction device SZ, anti-lock braking control, traction control, skid prevention control, etc. are executed. In the braking system related to the front wheel 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 wheel WHr (i.e., the rear wheel connection path HSr), the servo 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 servo pressure Pa are adjusted (increased or decreased) and output as the hydraulic pressures Pwf and Pwr (front and rear wheel hydraulic pressures) of the front and rear wheel cylinders CWf and CWr.

[0047] 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 known, its description is omitted. A supply pressure sensor PM is provided in the correction actuator YZ to detect the supply pressure Pm. The servo pressure Pa is transmitted as the supply pressure Pm via the master piston NM. Therefore, the supply pressure Pm corresponds to the servo pressure Pa, and the supply pressure sensor PM corresponds to the servo pressure sensor PA. In other words, the supply pressure Pm is an example of the servo pressure Pa, and the supply pressure sensor PM is an example of the servo pressure sensor PA.

[0048] When the regeneration cooperative control is executed, the operation of the correction actuator YZ is stopped. Therefore, during the execution of the regeneration cooperative control, the servo pressure Pa is transmitted as the front wheel wheel pressure Pwf to the front wheel wheel cylinder CWf via the supply pressure Pm, while it is directly transmitted as the rear wheel wheel pressure Pwr to the rear wheel wheel cylinder CWr. That is, in the front wheel braking system, "Pa = Pm = Pwf", and in the rear wheel braking system, "Pa = Pwr".

[0049] The correction controller EZ is connected to the brake controller EA via the communication bus BS. The wheel speed Vw detected by the wheel speed sensor VW and the supply pressure Pm detected by the supply pressure sensor PM are input to the correction controller EZ. Then, in the correction controller EZ, the running speed Vx (vehicle body speed) of the vehicle is calculated based on the wheel speed Vw. The vehicle body speed Vx and the supply pressure Pm are transmitted to the brake controller EA through the communication bus BS.

[0050] <Pressure regulation control process> With reference to the flowchart of FIG. 2, an example of the pressure regulation control process will be described. In the pressure regulation control, the regeneration cooperative control between the regeneration device KG and the brake control device SA is executed. In the regeneration cooperative control, the regenerative braking force Fg and the frictional braking force Fe are adjusted to cooperate so that the total braking force Fu corresponding to the required braking amount Bs is achieved.

[0051] ≪Various braking forces≫ The various braking forces in the description of the pressure regulation control are as follows. - The "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 the "target total braking force Fv". - The "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 the "target frictional braking force Fn". - The "regenerative braking force Fg" is the braking force actually generated by the regenerative device KG. The target value corresponding to the regenerative braking force Fg is the "target regenerative braking force Fh". The target regenerative braking force Fh is calculated by the braking control device SA (particularly, the braking controller EA) and transmitted to the regenerative device KG (particularly, the regenerative controller EG) via the communication bus BS. In the regenerative device 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 regenerative device KG can generate. Therefore, the regenerative device 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 regenerative device KG (particularly, the regenerative controller EG) and transmitted to the braking control device SA (particularly, the braking controller EA) via the communication bus BS. Note that the standard regenerative braking force Fz can be limited according to the driving conditions of the vehicle (e.g., the friction coefficient of the road surface).

[0052] ≪Various hydraulic pressures≫ The various hydraulic pressures in the description of the pressure control are as follows. - The "servo pressure Pa" is the output of the electric cylinder DN (i.e., the internal pressure of the control chamber Rc). The servo pressure Pa is detected (acquired) by the servo pressure sensor PA. - The "target pressure Pt" corresponds to the target value for controlling the servo pressure Pa (actual value).

[0053] In the hydraulic pressure transmission in the braking control device SA, there are various resistances such as the pipe friction resistance in the fluid path, 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 control is performed so that the actual value matches the target value. Considering the above resistances, it is desirable that the comparison between the actual value and the target value is made at the same part. In the following description, this comparison is made at the wheel cylinder CW. That is, the target pressure Pt is determined to correspond to the wheel pressure Pw. And the wheel pressure Pw (actual value) is determined from the servo pressure Pa (the detected value of the servo pressure sensor PA) after compensating for the hydraulic pressure corresponding to the above resistances.

[0054] In pressure 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 that the front and rear 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.

[0055] 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 servo pressure Pa, 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 demand amount Bs". The braking demand amount Bs is a state quantity representing the braking demand for the vehicle. The servo pressure Pa is acquired by at least one of the servo pressure sensor PA and the supply pressure sensor PM. The reference regenerative braking force Fz is determined by the regenerator KG (particularly, the regenerative controller EG) and received by the braking controller EA via the communication bus BS.

[0056] In step S120, based on the braking demand amount Bs and the calculation 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 to be "0" according to the calculation map Zfv when the braking demand amount Bs is less than the predetermined amount bo. Then, when the braking demand amount Bs is equal to or greater than the predetermined amount bo, the target total braking force Fv is calculated 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).

[0057] In step S130, the target pressure Pt is calculated based on the target total braking force Fv and the standard regenerative braking force Fz so that regenerative cooperative control is executed. The "target pressure Pt" is the target value of the wheel pressure Pw and is the target value for controlling the servo pressure Pa. In step S130, first, the sum Fnt (also referred to as the "target sum") of the target regenerative braking force Fh and the target frictional braking force Fn is calculated. Here, the "target sum Fnt" is the sum of the front-wheel target frictional braking force Fnf and the rear-wheel target frictional braking force Fnr (i.e., "Fnt = Fnf + Fnr"). Then, the target pressure Pt is determined in two cases as follows.

[0058] 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 sum Fnt (target sum) of the target frictional braking force Fn is made "0". That is, when "Fv ≦ Fz", "Fh = Fv, Fnt = 0" is determined.

[0059] Case (2): When the target total braking force Fv is greater than the standard regenerative braking force Fz, the target regenerative braking force Fh is made equal to the standard regenerative braking force Fz, and the target sum Fnt is made "the value obtained by subtracting the target regenerative braking force Fh (= Fz) from the target total braking force Fv". That is, when "Fv > Fz", "Fh = Fz, Fnt = Fv - Fh = Fv - Fz" is determined.

[0060] Next, based on the target sum Fnt, the target pressure Pt is calculated. Specifically, the target pressure Pt is determined based on the specifications of the braking device SX (= SXf, SXr) so that the target sum Fnt is satisfied. That is, in case (1) where "Fv ≦ Fz", the target pressure Pt is determined to be "0". In contrast, in case (2) where "Fv > Fz", the target pressure Pt is determined so that the total Fnt (target sum) of the target frictional braking force Fn is equal to the value "Fv - Fh". Here, the "specifications of the braking device SX" 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), and the effective radius of the wheel WH.

[0061] In step S140, the electric motor MA is controlled based on the target pressure Pt. Specifically, first, the resistance in the hydraulic transmission path (such as the sliding resistance of the seal member SL) is considered, and the wheel pressure Pw is calculated from the servo pressure Pa. Here, the servo pressure Pa is acquired by at least one of the servo pressure sensor PA and the supply pressure sensor PM. Then, the servo pressure Pa is controlled so that the wheel pressure Pw (the calculated actual value) approaches and matches the target pressure Pt (the target value) by driving the electric cylinder DN (particularly, the electric motor MA).

[0062] <Drive control of the electric cylinder DN> Referring to the block diagram of FIG. 3, the details of the drive control of the electric cylinder DN (that is, the process of step S140) will be described. The electric cylinder DN (particularly, the electric motor MA) is controlled based on the target pressure Pt, the servo pressure Pa, 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 / hydraulic volume conversion block ZE, a discharged hydraulic 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.

[0063] In the wheel pressure calculation block PW, the wheel pressure Pw is calculated based on the servo pressure Pa. As described above, the target pressure Pt is determined to correspond to the wheel pressure Pw. Therefore, the wheel pressure Pw is determined from the servo pressure Pa based on the resistance in the hydraulic transmission path.

[0064] 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 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 characteristics") 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.

[0065] In the hydraulic pressure - liquid volume characteristics (non - linear characteristics 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 characteristics, 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 characteristics is based on the fact that the rigidity characteristics (e.g., 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.

[0066] 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 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.

[0067] Specifically, in the standard fluid volume calculation block ES, the front-wheel standard fluid volume Esf is calculated based on the target pressure Pt and the front-wheel conversion map Zef. The "front-wheel standard fluid volume Esf" is the volume of the fluid (brake fluid BF) that should flow into the front-wheel wheel cylinder CWf to achieve the target pressure Pt. Similarly, in the standard fluid volume calculation block ES, the rear-wheel standard fluid volume Esr is calculated based on the target pressure Pt and the rear-wheel conversion map Zer. The "rear-wheel standard fluid volume Esr" is the volume of the fluid that should flow into the rear-wheel wheel cylinder CWr to achieve the target pressure Pt. 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.

[0068] In the estimated fluid volume calculation block EE, the estimated fluid volume Ee is calculated based on the wheel pressure Pw and the front-wheel and rear-wheel conversion maps Zef and Zer. The "estimated fluid volume Ee" is the volume (amount) of the brake fluid BF that should already have been supplied to the front-wheel wheel cylinder CWf and the rear-wheel wheel cylinder CWr to generate the wheel pressure Pw. Specifically, based on the wheel pressure Pw and the front-wheel conversion map Zef (i.e., the hydraulic pressure - fluid volume characteristics of the front-wheel wheel cylinder CWf), the front-wheel estimated fluid volume Eef is calculated. Similarly, based on the rear-wheel wheel pressure Pw and the rear-wheel conversion map Zer (i.e., the hydraulic pressure - fluid volume characteristics of the rear-wheel wheel cylinder CWr), the rear-wheel estimated fluid volume Eer is calculated. Then, the front-wheel estimated fluid volume Eef and the rear-wheel estimated fluid volume Eer are added together to determine the estimated fluid volume Ee (i.e., "Ee = Eef + Eer"). That is, the estimated fluid volume Ee is the sum of the front-wheel estimated fluid volume Eef and the rear-wheel estimated fluid volume Eer, and is the volume of the fluid estimated to have flowed from the control cylinder CC into the wheel cylinder CW. Note that since the wheel pressure Pw is derived from the servo pressure Pa, it can be said that "the estimated fluid volume Ee is calculated based on the servo pressure Pa and the front-wheel and rear-wheel conversion maps Zef and Zer".

[0069] In the discharge liquid volume calculation block EJ, the discharge liquid volume Ej is calculated based on the motor rotation angle Ka (actual value). The "discharge liquid volume Ej" is the amount (volume) of the braking fluid BF actually discharged (ejected) from the electric cylinder DN (i.e., the control cylinder CC). In the discharge liquid volume calculation block EJ, the rotation angle Ka is converted into the discharge liquid volume Ej based on the specifications of the electric cylinder DN. 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 motion member per one rotation of the rotating member), the pressure receiving area of the control piston NC, and the like.

[0070] In the discharge liquid volume calculation block EJ, the piston stroke Sn may be used to obtain the discharge liquid volume Ej (the amount of liquid sent out from the control cylinder CC). Specifically, a stroke sensor SN for obtaining the displacement (piston stroke) of the control piston NC is provided in the electric cylinder DN. 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 sensors". 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.

[0071] In the reference value calculation block KS, a reference value Ks is determined based on the standard liquid volume Es (= Esf + Esr). The "reference value Ks" is a state quantity (variable) for determining a 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 dimensions (i.e., physical quantities) 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 constituent members are known. In the reference value calculation block KS, the standard liquid volume Es is converted into the reference value Ks based on the specifications of the electric cylinder DN (such as the reduction ratio of the speed reducer GS, the lead of the conversion mechanism GH, the pressure receiving area of the control piston NC, etc.). Therefore, the reference value Ks is determined to increase as the standard liquid volume Es increases.

[0072] 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-wheel 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 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 into the same dimension (physical quantity) as the reference value Ks based on the specifications of the constituent members of the electric cylinder DN, and the correction value Kh is determined. Therefore, the correction value Kh is determined to increase as the liquid volume deviation hE increases, and the correction value Kh is determined to decrease as the liquid volume deviation hE decreases.

[0073] In the target rotation angle calculation block KT, the 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 the indicated value Ku (i.e., "Ku = Ks + Kh"). The "indicated value Ku" corresponds to an intermediate target value for determining the target rotation angle Kt. Here, the physical quantity (dimension) of the indicated value Ku is the same as those of the reference value Ks and the correction value Kh.

[0074] The correction value Kh is a state quantity for making the wheel pressure Pw coincide with the target pressure Pt. 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 the hydraulic pressure. This is based on "the estimated liquid volume Ee being obtained from the wheel pressure Pw (actual value)" and "the hydraulic pressure being optimized when the liquid volume is optimized". In the braking control device SA, the servo pressure Pa is controlled so that the wheel pressure Pw approaches and coincides with the target pressure Pt by the feedback control based on the correction value Kh.

[0075] In the target rotation angle calculation block KT, the target rotation angle Kt is calculated based on the indicated value Ku. Specifically, using the specifications of the components of the electric cylinder DN (the reduction ratio of the speed reducer GS, the lead of the conversion mechanism GH, etc.), the indicated 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 the electric motor MA cannot follow the stepwise changing target rotation angle Kt even if it is calculated. Anyway, in the target rotation angle calculation block KT, the target rotation angle Kt, which is the final target value, is determined based on the reference value Ks and the correction value Kh.

[0076] 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 approaches and matches the target rotation angle Kt (target value) (that is, 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), the current Im (motor current) supplied to the electric motor MA is adjusted based on the motor drive signal Ma. That is, in the rotation angle feedback control block KF, so-called rotation angle feedback control is executed.

[0077] <<Modification Example>> In the above-described embodiment, in the standard liquid volume calculation block ES and the estimated liquid volume calculation block EE, the front wheel conversion map Zef and the rear wheel conversion map Zer are separately provided as calculation maps for converting hydraulic pressure into liquid volume. Then, the front wheel standard liquid volume Esf and the rear wheel standard liquid volume Esr are calculated separately, and the front wheel estimated liquid volume Eef and the rear wheel estimated liquid volume Eer are determined separately. Instead of this, as a calculation map for converting hydraulic pressure into liquid volume, a conversion map Zek (also referred to as an "integrated conversion map") in which the front wheel and rear wheel conversion maps Zef and Zer are integrated may be adopted (refer to the characteristics shown by the broken line). Even in the integrated conversion map Zek, the relationship between hydraulic pressure and liquid volume is defined. In a configuration in which the integrated conversion map Zek is adopted, the reference value Ks is determined based on the target pressure Pt and the standard liquid volume Es calculated from the integrated conversion map Zek. Similarly, the correction value Kh is determined based on the servo pressure Pa (that is, the wheel pressure Pw) and the estimated liquid volume Ee calculated from the integrated conversion map Zek. Note that the integrated conversion map Zek is also obtained in advance by experiments, analysis, etc., similar to the front wheel and rear wheel conversion maps Zef and Zer.

[0078] <<Operation and Effect>> 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 brake 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 hydraulic 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 hydraulic 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".

[0079] In the braking control device SA, the target rotation angle Kt is determined based on the standard liquid volume Es calculated from the target pressure Pt. 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 (specifically, the control cylinder CC) to achieve the target pressure Pt.

[0080] As the hydraulic pressure - liquid volume characteristic (consumed liquid volume characteristic), the conversion maps Zef, Zer, and Zek pre - stored in the brake controller EA (specifically, 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 there is no gas. 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.

[0081] In the braking control device SA, a correction value Kh is determined so as to compensate for errors in the conversion maps Zef, Zer, and Zek. The correction value Kh is determined based on an estimated liquid volume Ee (the liquid volume estimated to have flowed into the wheel cylinder CW) calculated from the servo pressure Pa and an actual discharged liquid volume Ej (discharged liquid volume) from the control cylinder CC. Here, the discharged liquid volume Ej is acquired by a liquid volume sensor (KA, SN, etc.). The same conversion maps Zef, Zer, and Zek 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, and Zek. Since the reference value Ks is corrected by the correction value Kh to determine the target rotation angle Kt, the influence of the above error is corrected.

[0082] 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, Zer, and Zek are shifted so as to be reduced in the direction of the vertical axis (the axis of hydraulic pressure) with respect to the true value. That is, in the conversion maps Zef, Zer, and Zek, at the same hydraulic 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 hydraulic pressure) with respect to the true value. That is, in the conversion maps Zef, Zer, and Zek, at the same hydraulic 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 braking fluid BF discharged from the electric cylinder DN (particularly, the control cylinder CC) is adjusted without excess or deficiency with respect to the target pressure Pt. As a result, the servo pressure Pa is adjusted with high precision by the electric cylinder DN so that the wheel pressure Pw matches the target pressure Pt.

[0083] <Second Embodiment of the Braking Control Device SA> With reference to the schematic diagram of FIG. 4, a second embodiment of the braking control device SA for a vehicle will be described. Also in the second embodiment, the electric motor MA of the electric cylinder DN is controlled by the same method as in the first embodiment.

[0084] In the first embodiment, the servo pressure Pa was transmitted as the supply pressure Pm via the master cylinder CM and the master piston NM. That is, in the hydraulic transmission path, the application unit AP and the hydraulic pressure generating unit PU were arranged in series. Instead of this configuration, the application unit AP and the hydraulic pressure generating unit PU may be arranged in parallel. In the second embodiment, each of the application unit AP (particularly, the master cylinder CM) and the hydraulic pressure generating unit PU is directly connected to the hydraulic pressure correction device SZ (particularly, the correction actuator YZ).

[0085] 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 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.

[0086] The front wheels, the front-wheel and rear-wheel communication paths HSf, HSr (fluid paths connected to the front-wheel and rear-wheel 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. A communication valve VC is provided in the communication path HV.

[0087] During the execution of the pressure control, 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 servo pressure Pa 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 servo pressure sensor PA may be provided in the hydraulic pressure generation unit PU or in the correction actuator YZ. In the configuration where the servo pressure sensor PA is provided in the correction actuator YZ, the servo pressure Pa is acquired by the brake controller EA via the communication bus BS.

[0088] Also in the second embodiment, the same regeneration cooperative control as in the first embodiment is executed, and the same effect (error compensation of the conversion map representing the hydraulic pressure - hydraulic volume characteristics) is achieved.

[0089] <Other embodiments of the brake control device SA, etc.> Another embodiment of the brake control device SA including the electric cylinder DN will be described. Also in other embodiments, the same effects as described above are achieved.

[0090] In the embodiment of the brake control device SA described above, the servo pressure Pa was acquired as the detection result of the servo pressure sensor PA provided in the discharge portion of the electric cylinder DN. Instead of this, the servo pressure sensor PA can be provided in the hydraulic pressure transmission path from the control cylinder CC to the wheel cylinder CW (for example, refer to the supply pressure sensor PM). In any case, the servo pressure Pa used for the calculation of the estimated hydraulic volume Ee is based on the actual value detected by the servo pressure sensor PA.

[0091] In the above-described embodiment of the braking control device SA, the discharge liquid volume Ej was obtained based on 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 (liquid volume per unit time) from the control cylinder CC may be provided, and the discharge liquid volume Ej may be obtained from the detection value of the flow rate sensor. For example, an ultrasonic type, an electromagnetic type, etc. are adopted as the flow rate sensor. 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 braking liquid BF from the electric cylinder DN.

[0092] In the above-described embodiment of the braking control device SA, the target pressure Pt was determined as a target value corresponding to the wheel pressure Pw (actual value). 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, the detection part of the servo pressure sensor PA may be adopted as the comparison part. In this configuration, the target pressure Pt is determined so as to compensate for the hydraulic pressure component due to the above resistance and correspond to the servo pressure Pa (actual value). In the pressure regulation control, regardless of where the comparison part between the target value and the actual value is located, the target pressure Pt is the target value for controlling the servo pressure Pa. Also, the standard liquid volume Es is determined based on the target pressure Pt, and the estimated liquid volume Ee is determined based on the servo pressure Pa. Furthermore, the actual hydraulic pressure (Pa, Pw, etc.) corresponding to the target pressure Pt is controlled to approach and match the target pressure Pt.

[0093] 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, similarly 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.

[0094] In the above-described embodiment of the braking control device SA, the target values (Fv, Fz, Fh, Fn, etc.) of various braking forces were 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 vehicle acceleration or the dimension of the torque of the wheel WH. This is based on the fact that the state quantities from the longitudinal force to the vehicle acceleration (referred to as "state quantities related to force") are equivalent. Therefore, the target pressure Pt is calculated via the state quantities related to force from the longitudinal force acting on the vehicle to the vehicle deceleration based on the braking demand amount Bs.

[0095] The above-described braking control device SA was applied to a vehicle in which a regeneration device KG is provided for the front wheel WHf and regenerative cooperative control is executed. In a vehicle in which regenerative cooperative control is executed, the regeneration device KG may be provided for at least one of the front wheel WHf and the rear wheel WHr. Also, the braking control device SA can be applied to a vehicle in which the regeneration device KG is omitted and regenerative cooperative control is not executed. That is, the braking control device SA can be applied to various vehicles regardless of the presence or absence of regenerative cooperative control.

[0096] In the first embodiment of the braking control device SA described above, 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, conversion calculation between the supply pressure Pm (master pressure) and the servo pressure Pa is possible (that is, conversion based on "Pm·rm = Pa·ru"). And in a configuration where the supply pressure sensor PM is adopted as the servo pressure sensor PA and the supply pressure Pm is adopted as the servo pressure Pa, the supply pressure Pm is converted into the servo pressure Pa based on the above area ratio.

[0097] <Summary of the embodiment> The braking control device SA of the vehicle adjusts the wheel pressure Pw of the wheel cylinder CW by the servo pressure Pa. The braking control device SA is provided with a control cylinder CC, a control piston NC, an electric motor MA, a servo pressure sensor (PA, PM, etc.), a liquid amount sensor (KA, SN, etc.), and a controller EA.

[0098] The control piston NC is inserted into the control cylinder CC. By moving the control piston NC by the power of the electric motor MA, the control cylinder CC generates the servo pressure Pa. The servo pressure sensor (PA, PM, etc.) detects and acquires the servo pressure Pa (actual value). The liquid amount sensor (KA, SN, etc.) detects and acquires the actual liquid amount Ej of the brake fluid BF sent out from the control cylinder CC. The controller EA calculates a target pressure Pt for controlling the servo pressure Pa based on the braking required amount Bs of the vehicle, and controls the rotation angle (Ka) of the electric motor MA based on the target pressure Pt and the servo pressure Pa.

[0099] In the controller EA, the volume of the braking fluid BF discharged from the control cylinder CC is obtained as the discharged liquid volume Ej. Also, based on the servo pressure Pa and the conversion maps Zef, Zer, Zek, an estimated liquid volume Ee that is presumed to have flowed into the wheel cylinder CW is calculated. Then, the electric motor MA is controlled based on the deviation hE between the estimated liquid volume Ee and the discharged liquid volume Ej. Here, the conversion maps Zef, Zer, Zek are preset in the controller EA as the relationship between the volume (liquid volume) of the braking fluid BF that has flowed into the wheel cylinder CW and the wheel pressure Pw.

[0100] The estimated liquid volume Ee is calculated based on the conversion maps Zef, Zer, Zek. If the conversion maps Zef, Zer, Zek are accurate, the estimated liquid volume Ee and the discharged liquid volume Ej will match. If there is an error in the conversion maps Zef, Zer, Zek, the two will not match. That is, the deviation hE (liquid volume deviation) between the estimated liquid volume Ee and the discharged liquid volume Ej represents the error of the conversion maps Zef, Zer, Zek. In the braking control device SA, the electric motor MA is controlled based on the liquid volume deviation hE so as to compensate for the error.

[0101] Specifically, the electric motor MA is controlled as follows. Based on the target pressure Pt calculated from the braking demand amount Bs and the conversion maps Zef, Zer, Zek, a standard liquid volume Es is calculated. The standard liquid volume Es is the target value of the liquid volume that should flow into the wheel cylinder CW. Based on the servo pressure Pa and the conversion maps Zef, Zer, Zek, the estimated liquid volume Ee is calculated. The estimated liquid volume Ee is the estimated value of the liquid volume that is presumed to have flowed into the wheel cylinder CW. Then, the reference value Ks calculated from the standard liquid volume Es is corrected based on the comparison result hE (liquid volume deviation) between the estimated liquid volume Ee (estimated value) and the discharged liquid volume Ej (detected value), and the target rotation angle Kt of the electric motor MA is determined. Further, the supply current Im to the electric motor MA is adjusted so that the motor rotation angle Ka matches the target rotation angle Kt. Here, the discharged liquid volume Ej is obtained from the detected value of a liquid volume sensor (such as KA, SN, etc.).

[0102] The conversion maps Zef, Zer, and Zek are pre-stored as predetermined characteristics in the controller EA (especially the microprocessor MP). However, due to the gas (such as air) existing inside the braking device SX and the like, and the wear of the friction member, etc., the conversion maps Zef, Zer, and Zek contain errors. The liquid volume deviation hE is generated due to such errors. In the braking control device SA, based on the liquid volume deviation hE, the target rotation angle Kt of the electric motor MA is corrected so as to compensate for the errors of the conversion maps Zef, Zer, and Zek. That is, in the braking control device SA, the electric motor MA is controlled based on the liquid volume deviation hE.

[0103] Specifically, the liquid volume deviation hE is derived by subtracting the estimated liquid volume Ee from the discharged liquid volume Ej. When the discharged liquid volume Ej is larger than the estimated liquid volume Ee (that is, when the liquid volume deviation hE has a positive sign), the liquid volume discharged from the electric cylinder DN is insufficient and the servo pressure Pa is insufficient. In this situation, the target rotation angle Kt is corrected to increase so that the motor rotation angle Ka becomes larger. On the other hand, when the discharged liquid volume Ej is smaller than the estimated liquid volume Ee (that is, when the liquid volume deviation hE has a negative sign), the liquid volume discharged from the electric cylinder DN is excessive and the servo pressure Pa is excessive. In this situation, the target rotation angle Kt is corrected to decrease so that the motor rotation angle Ka becomes smaller. By adjusting the motor rotation angle Ka according to the liquid volume deviation hE, the liquid volume discharged from the electric cylinder DN (especially the control cylinder CC) is adjusted without excess or deficiency with respect to the target pressure Pt. As a result, the pressure regulation accuracy by the electric cylinder DN is improved.

Explanation of symbols

[0104] 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 (=PU), MA…Electric motor, NC…Control piston, CC…Control cylinder, Rc…Control chamber (hydraulic pressure chamber of CC), VA, VB…First, second control valves, SP…Operation displacement sensor, Sp…Operation displacement (detection value of SP), Pa…Servo pressure (output of DN), PA…Servo pressure sensor, Pt…Target pressure (target value corresponding to Pa), PM…Supply pressure sensor (corresponding to PA), Pm…Supply pressure (detection value of PM and corresponding to Pa), Pw…Wheel pressure, Esf, Esr…Front wheel, rear wheel standard fluid volume, Es…Standard fluid volume (sum of Esf and Esr), Eef, Eer…Front wheel, rear wheel estimated fluid volume, Ee…Estimated fluid volume (sum of Eef and Eer), Ej…Discharged fluid volume (fluid volume sent out from CC), Ks…Reference value, Kh…Correction value, Ka…Motor rotation angle (detection value of KA and also corresponding to Ej), KA…Rotation angle sensor (also corresponding to fluid volume sensor), Kt…Target rotation angle (target value corresponding to Ka), Zef…Front wheel conversion map, Zer…Rear wheel conversion map, Zek…Integrated conversion map, SN…Stroke sensor (corresponding to fluid volume sensor), Sn…Piston stroke (detection value of SN and corresponding to Ej).

Claims

1. A braking control device for a vehicle, comprising: a control cylinder in which a control piston is inserted and a servo pressure is generated by moving the control piston by an electric motor; a servo pressure sensor for detecting the servo pressure; and a controller for controlling the electric motor based on the servo pressure, wherein the servo pressure adjusts a wheel pressure of a wheel cylinder. The controller of the braking control device for a vehicle acquires a discharge liquid amount from the control cylinder, calculates an estimated liquid amount based on the servo pressure and a conversion map, and controls the electric motor based on a deviation between the discharge liquid amount and the estimated liquid amount.

2. In the braking control device for a vehicle according to Claim 1, the controller calculates a target pressure based on a braking demand amount, calculates a standard liquid amount based on the target pressure and the conversion map, and controls a rotation angle of the electric motor based on the standard liquid amount and the deviation.

3. In the braking control device for a vehicle according to Claim 1 or Claim 2, the controller sets a relationship between a volume of braking fluid flowing into the wheel cylinder and the wheel pressure as the conversion map.

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