Brake control device for a vehicle

Abstract

The braking control device of the present invention is applied to a vehicle equipped with a regenerative braking device in the front wheels, and comprises: a control cylinder that generates a base pressure using an electric motor as a power source; a solenoid valve that adjusts the base pressure to a regulating pressure; and a controller that controls the electric motor and the solenoid valve to control the front wheel cylinder pressure of the front wheel cylinders by adjusting the pressure, and to control the rear wheel cylinder pressure of the rear wheel cylinders by using the base pressure. The controller calculates the required fluid volume to be supplied to the front and rear wheel cylinders as the front wheel standard fluid volume and the rear wheel standard fluid volume based on the front wheel target pressure and the rear wheel target pressure, respectively, and controls the electric motor based on the front wheel standard fluid volume and the rear wheel standard fluid volume, and controls the solenoid valve based on the front wheel target pressure and the rear wheel target pressure.

Description

Technical Field

[0001] This disclosure relates to a braking control device for a vehicle. Background Technology

[0002] Patent Document 1 describes a vehicle braking device that, in order to maintain a constant relationship between the rotation angle and the generated braking hydraulic pressure by controlling the braking hydraulic pressure generated by the electro-hydraulic generating unit through feedback of the rotation angle of the electric motor, comprises: an electro-hydraulic generating unit (23) that generates braking hydraulic pressure through the operation of an electric motor (32); and an electric motor control unit (U) that controls the operation of the electric motor (32). The electric motor control unit (U) calculates a target rotation angle of the electric motor (32) for the electro-hydraulic generating unit (23) to generate braking hydraulic pressure corresponding to the amount of braking operation by the driver, and performs feedback control to make the actual rotation angle of the electric motor (32) consistent with the target rotation angle. The electric motor control unit (U) includes a correction unit (M5) that corrects the target rotation angle of the electric motor (32) based on the actual braking hydraulic pressure generated by the electro-hydraulic generating unit (23).

[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 brake hydraulic pressure (target brake hydraulic pressure) to be generated by the driven cylinder 23 (also referred to as the "control cylinder"). The target brake hydraulic pressure is converted into the rotation angle (target rotation angle) of the electric motor 32 (also referred to as the "motor") of the driven cylinder 23. The electric motor is then controlled based on the target rotation angle.

[0004] In addition, the applicant is developing a braking control device as described in Patent Document 2. The braking control device includes: an electric cylinder 51 that ejects hydraulic brake fluid, corresponding to the drive of a motor 513, from an output port 516; a master cylinder 31, through the movement of a master piston 43 accompanying an increase in the hydraulic pressure of the servo chamber Rs, causing brake fluid to flow out of the master chamber Rm, and conversely, through the movement of a master piston 43 accompanying a decrease in the hydraulic pressure of the servo chamber Rs, causing brake fluid to flow into the master chamber Rm; a first flow path 331 connecting the master chamber Rm and a wheel cylinder 11 for the front wheels; a sixth flow path 58 connecting the output port 516 and a wheel cylinder 11 for the rear wheels; a fifth flow path 55 connecting the sixth flow path 58 and the servo chamber Rs; and a differential pressure regulating valve 551 provided in the fifth flow path 55, regulating the differential pressure between the first hydraulic pressure (servo chamber Rs) and the second hydraulic pressure (servo chamber Rs). In such a device, it is necessary not only to control the motor but also to control the differential pressure regulating valve (solenoid valve).

[0005] Patent Document 1: Japanese Patent Application Publication No. 2009-137377

[0006] Patent Document 2: Japanese Patent Application No. 2022-197101 Summary of the Invention

[0007] In view of the above-mentioned problems, the object of the present invention is to provide a vehicle braking control device that can appropriately control the motor and solenoid valve in a vehicle braking control device that separately adjusts the hydraulic pressure of the wheel cylinders of the front and rear wheels.

[0008] The vehicle braking control device (SA) of the present invention is applied to a vehicle having a regenerative device (KG) in the front wheel (WHf). The braking control device (SA) 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 a regulating pressure (Pb); and a controller (EA) that controls the electric motor (MA) and the solenoid valve (UC) to control the front wheel cylinder pressure (Pwf) of the front wheel cylinder (CWf) using the regulating pressure (Pb) and to control the rear wheel cylinder pressure (Pwr) of the rear wheel cylinder (CWr) using the base pressure (Pa).

[0009] In the vehicle braking control device (SA) of the present invention, the controller (EA) calculates the amount of fluid to be supplied to the front and rear wheel cylinders (CWf, CWr) as the standard fluid volume (Esf, Esr) for the front and rear wheels based on the target values ​​of the front and rear wheel cylinder pressures (Pwf, Pwr). The controller controls the motor (MA) based on the standard fluid volume (Esf, Esr) for the front and rear wheels, and controls the solenoid valve (UC) based on the target pressures (Ptf, Ptr) for the front and rear wheels.

[0010] In the vehicle braking control device (SA) of the present invention, the controller (EA) acquires the amount of fluid injected from the control cylinder (CC) (Ej), calculates the estimated amount of fluid (Ee) based on the base pressure (Pa) and the regulating pressure (Pb), and controls the rotation angle (Ka) of the motor (MA) based on the deviation (hE) between the injected amount of fluid (Ej) and the estimated amount of fluid (Ee). Furthermore, the controller (EA) calculates the target differential pressure (St) based on the target pressures (Ptf, Ptr) of the front and rear wheels, and controls the valve current (Ic) supplied to the solenoid valve (UC) based on the target differential pressure (St).

[0011] The hydraulic pressure Pw generated in wheel cylinder CW is determined based on the amount of fluid supplied to wheel cylinder CW. Therefore, in the brake control device SA, the rotation angle Ka of motor MA is controlled based on the aforementioned relationship between hydraulic pressure and fluid volume (i.e., hydraulic-fluid volume characteristics). This results in the injection of the required amount of fluid from electric cylinder DN (particularly control cylinder CC) to achieve the base pressure Pa. Furthermore, since the differential pressure Sa between the hydraulic pressure Pa on the side of the pressure regulating valve UC closest to electric cylinder DN and the hydraulic pressure Pb on the side furthest from electric cylinder DN is determined based on the valve current Ic supplied to the pressure regulating valve UC, the pressure regulating valve UC operates based on the target differential pressure St. According to the above structure, in the brake control device SA that separately regulates the hydraulic pressure of the wheel cylinders of the front and rear wheels through dual-system pressure regulation, motor MA and pressure regulating valve UC are appropriately controlled. As a result, in dual-system pressure regulation, the base pressure Pa and the regulating pressure Pb can be adjusted with high precision. Attached Figure Description

[0012] Figure 1 This is a schematic diagram illustrating a first embodiment of the vehicle's braking control device SA.

[0013] Figure 2 This is a flowchart used to illustrate the voltage regulation control process.

[0014] Figure 3 This is a block diagram used to illustrate the drive control of the electric cylinder DN.

[0015] Figure 4 This is a block diagram illustrating the drive control of the pressure regulating valve UC.

[0016] Figure 5 This is a schematic diagram illustrating a second embodiment of the vehicle's braking control device SA. Detailed Implementation

[0017] <Symbols of constituent parts, etc., and subscripts at the end of the symbols>

[0018] In the following explanation, components, processing units, signals, characteristics, and values ​​marked with the same symbols, such as "CW," have the same function. The subscripts "f" and "r" at the end of the symbols for each wheel are general symbols indicating which system of the front or rear wheels it relates to. For example, in the wheel cylinders CW installed on each wheel, it is written as "front wheel cylinder CWf, rear wheel cylinder CWr." Furthermore, the subscripts "f" and "r" at the end of the symbols 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 installed on the front and rear wheels of a vehicle. Additionally, "CW" as a general term is also written as "CW (=CWf, CWr)."

[0019] The brake control unit SA, the hydraulic correction unit SZ, and the wheel cylinder CW are connected via a fluid path (connecting path HS). Furthermore, within the brake control unit SA and the hydraulic correction unit SZ, various components (CC, UC, etc.) are connected via fluid paths. Here, "fluid path" refers to the path used to move the brake fluid BF, equivalent to piping, flow paths within the actuator, hoses, etc. In the following description, the connecting path HS, reservoir path HR, input path HN, servo path HU, and replenishment path HH are fluid paths.

[0020] <First Embodiment of Braking Control Device SA>

[0021] Reference Figure 1 The schematic diagram illustrates a first embodiment of the vehicle's braking control device SA. The braking control device SA is applied, for example, to hybrid vehicles or electric vehicles equipped with a driving motor.

[0022] The front and rear wheels WHf and WHr (=WH) of the vehicle are equipped with braking devices SX (=SXf, SXr). The braking device SX consists of a brake caliper, friction components (e.g., brake pads), and a rotating component KT (e.g., brake disc). A wheel cylinder CW is provided in the brake caliper (not shown). Through hydraulic pressure Pw within the wheel cylinder CW (referred to as "wheel cylinder pressure"), the friction components (not shown) are pressed against the rotating component KT fixed to each wheel WH, imparting a braking torque Tb to the wheel. As a result, a frictional braking force Fe (also called "hydraulic braking force") is generated at the wheel WH. Therefore, the braking device SX can be referred to as a "device that generates frictional braking force Fe through wheel cylinder pressure Pw" or a "device that converts wheel cylinder pressure Pw into frictional braking force Fe."

[0023] The vehicle is equipped with a regenerative braking device KG. The regenerative braking device KG consists of a generator GN (also called a "motor / generator" or "regenerative generator") for energy regeneration, a control unit EG (also called a "regenerative controller") for the regenerative braking device KG, and a regenerative battery (not shown). The regenerative generator GN also serves as the motor for driving. During regenerative braking, the motor / generator GN operates as a generator, and the generated electricity is stored in the regenerative battery via the regenerative controller EG. At this time, the regenerative braking force Fg is applied to the wheels. That is, the regenerative braking device KG can generate the regenerative braking force Fg. For example, the regenerative braking device KG is located at the front wheel WHf. Therefore, the regenerative braking force Fg is generated at the front wheel WHf. The regenerative braking device KG (specifically the regenerative controller EG) is connected to the communication bus BS.

[0024] The vehicle is equipped with a driving assistance device KJ. Automatic speed control is performed in the driving assistance device KJ. The driving assistance device KJ consists of an object detection sensor SJ and a driving assistance controller EJ (also simply called the "driving assistance controller"). The object detection sensor SJ detects the distance Sj (called "relative distance," or "inter-vehicle distance" if the object is a moving vehicle) of objects present in front of the vehicle (including vehicles traveling in front of it). For example, the object detection sensor SJ may be a radar sensor, a millimeter-wave sensor, or an image sensor. In the driving assistance controller EJ, the target acceleration Gs (the target value of the vehicle's acceleration in the longitudinal direction) is calculated based on the detection result Sj (relative distance) from the object detection sensor SJ. The driving assistance device KJ (specifically the driving assistance controller EJ) is connected to a communication bus BS. The target acceleration Gs is transmitted to the brake control device SA via the communication bus BS. In the brake control device SA, the braking forces Fg and Fe are adjusted according to the target acceleration Gs. As a result, the vehicle's speed Vx (vehicle speed) is controlled.

[0025] The vehicle is equipped with a brake operating component BP and various sensors (SP, etc.). The brake operating component BP (e.g., the brake pedal) is the operating component used by the driver to decelerate the vehicle. A displacement sensor SP is installed on the vehicle to detect the operating displacement Sp of the brake operating component BP. The operating displacement Sp is one of the state quantities (state variables) that display the amount of operation of the brake operating component BP, and in a brake control device SA of in-line control type, it is a signal indicating the driver's braking intention (i.e., brake indication). In addition to the displacement sensor SP, hydraulic pressure Pn (referred to as "input pressure") in the input chamber Rn (described later) is used as another state quantity to indicate the amount of braking operation. The input pressure Pn is detected by the input pressure sensor PN. The operating displacement Sp, input pressure Pn, etc., are collectively referred to as "brake operation amount Ba". Furthermore, the displacement sensor SP and the input pressure sensor PN, which detect the operating displacement Sp and the input pressure Pn (i.e., brake operation amount Ba), are referred to as "brake operation amount sensor BA".

[0026] The vehicle is equipped with various sensors for braking control such as anti-lock braking and anti-skid control (i.e., individual control of the pressure Pw in each wheel cylinder). Specifically, each wheel WH is equipped with a wheel speed sensor VW that detects its rotational speed Vw (referred to as "wheel speed"). In addition, there is a steering input sensor that detects the steering input Sw (e.g., operating angle) of steering operation components (e.g., steering wheel), a yaw rate sensor that detects the vehicle's yaw rate Yr, a front and rear acceleration sensor that detects the vehicle's front and rear acceleration Gx (also referred to as "deceleration"), and a lateral acceleration sensor that detects the vehicle's lateral acceleration Gy (the above are not shown).

[0027] The vehicle is equipped with a brake control device SA. Within the brake control device SA, a dual-system braking system is employed, employing a so-called front-rear type (also known as "Type II") braking system. The brake control device SA regulates the wheel cylinder pressure Pw of each wheel cylinder CW.

[0028] The braking control unit SA (especially the braking controller EA) and the hydraulic correction unit SZ (especially the correction controller EZ) are connected to the communication bus BS. Signals are transmitted between multiple controllers (EA, EZ, EG, EJ, etc.) via the communication bus BS. That is, multiple controllers can send signals (detected values, calculated values, control flags, etc.) to the communication bus BS and can receive signals from the communication bus BS.

[0029] <Structure of Braking Control Device SA>

[0030] The structure of the brake control device SA according to the first embodiment will be described. The brake control device SA generates a base pressure Pa and an adjustment pressure Pb based on the operation of the brake operating component BP (brake pedal). Furthermore, the brake control device SA outputs a supply pressure Pm and a base pressure Pa to the hydraulic correction device SZ. In the hydraulic correction device SZ, the supply pressure Pm and the base pressure Pa are adjusted, ultimately supplying the front wheel cylinder pressure Pwf and the rear wheel cylinder pressure Pwr to the front wheel cylinder CWf and the rear wheel cylinder CWr, respectively. The brake control device SA consists of a brake actuator YA and a brake controller EA.

[0031] Brake Actuator YA

[0032] The brake actuator YA consists of a hydraulic generation unit PU, an application unit AP, and an input unit NR.

[0033] [Hydraulic generation unit PU]

[0034] The hydraulic generating unit PU uses the motor MA as a power source to generate a base pressure Pa and a regulating pressure Pb. The hydraulic generating unit PU consists of an electric cylinder DN and a pressure regulating valve UC. Here, the electric cylinder DN includes a motor MA, a rotation angle sensor KA, a reducer GS, a conversion mechanism GH, a control cylinder CC, and a control piston NC.

[0035] The motor MA is the power source (pressurization source) used to generate the base pressure Pa (the hydraulic pressure generated by the electric cylinder DN). "Power" is the energy required to move the movable parts (GS, GH, NC, etc.) in the electric cylinder DN. For example, power is defined as the energy per unit time (also called "power"). Rotational power (also called "first rotational power") is output from the motor MA. The rotational power of the motor MA is obtained by multiplying the shaft torque of the motor MA by the rotational speed of the motor MA (specifically, the motor shaft). Additionally, the linear power of the direct-acting parts (described later) is obtained by multiplying the thrust of the direct-acting parts (the force acting in the direction of the central axis) by the linear velocity of the direct-acting parts (the velocity along the direction of the central axis).

[0036] The motor MA is a three-phase brushless motor. The motor MA includes a motor coil, a motor shaft, and a rotation angle sensor KA. The motor coil is fixed to the motor housing. Power is supplied to the motor coil from the controller EA (specifically the drive circuit DR). The motor shaft is supported so that it can rotate relative to the motor housing. A permanent magnet is fixed to the outer circumference 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 (also equivalent to a "fluid level sensor"). Furthermore, based on the rotation angle Ka of the motor shaft, the three-phase motor current Im (the total current flowing in the U, V, and W phases) is switched.

[0037] Specifically, the rotation angle Ka (also equivalent to "dispensing volume Ej (described later)") detected by the rotation angle sensor KA is transmitted to the controller EA (specifically, the microprocessor MP). In the controller EA, the switching elements of the drive circuit DR (also called the "inverter circuit") are driven according to the rotation angle Ka. This switches the motor current Im flowing in the motor coil, driving the motor MA. Furthermore, the first rotational power is output from the motor MA to the reducer GS.

[0038] The first rotational power output from the motor MA is reduced in speed via the reducer GS. Specifically, the input shaft of the reducer GS is fixed to the motor shaft. Furthermore, the output shaft of the reducer GS and the rotating parts of the conversion mechanism GH are fixed. In the reducer GS, the speed input from the motor MA decreases, and the torque input from the motor MA increases. Moreover, the reduced rotational power (also referred to as the "second rotational power") is output from the reducer GS to the conversion mechanism GH.

[0039] The conversion mechanism GH consists of a rotating component that performs rotary motion and a linear component that performs linear motion. In the conversion mechanism GH, a second rotational power output from the reducer GS is input to the rotating component. Furthermore, the rotational power input to the rotating component is converted into linear power for the linear component. The conversion mechanism GH is also referred to as a "rotation / linear conversion mechanism". An anti-rotation component engages with the linear component. This prevents the rotational motion of the linear component, thus causing it to move along the rotation axis of the rotating component.

[0040] For example, the conversion mechanism GH employs a ball screw. Specifically, in a ball screw mechanism, a rotating component, serving as a shaft member, is fixed to the output shaft of the reducer GS. The rotating component is inserted into a linearly moving component that has a cylindrical shape. A ball screw groove is formed on the outer circumferential surface of the rotating component. Similarly, a ball screw groove is also formed on the inner circumferential surface of the linearly moving component. Multiple balls (steel balls) are embedded in the ball screw grooves.

[0041] Linear power is transmitted to the control piston NC via the direct-acting component of the conversion mechanism GH. The control piston NC is inserted into the control cylinder CC. Inside the control cylinder CC, the control piston NC forms a control chamber Rc (hydraulic chamber). Specifically, the outer circumferential surface of the control piston NC and the inner circumferential surface of the control cylinder CC are sealed by two sealing components SL. Thus, the control chamber Rc becomes hydraulically sealed. The hydraulic pressure of the control cylinder CC (i.e., the control chamber Rc) is the "base pressure Pa". That is to say, in the electric cylinder DN, the motor MA becomes the power source, outputting the base pressure Pa.

[0042] The control cylinder CC is connected to the servo chamber Ru (described later) of the application unit AP via the servo path HU (fluid path). Additionally, the control cylinder CC is connected to the rear wheel cylinder CWr via the rear wheel connecting path HSr (fluid path) and the hydraulic correction device SZ. A base pressure sensor PA is installed in the hydraulic generation unit PU to detect the base pressure Pa (the hydraulic pressure generated by the electric cylinder DN).

[0043] exist Figure 1 The diagram shows the state where the electric cylinder DN has not generated the base pressure Pa. In the control cylinder CC, a through-hole is provided between the two sealing components SL. Additionally, a through-hole is provided in the control piston NC. The through-hole in the control cylinder CC is connected to a supply path HH (fluid path) that connects to the main reservoir RV. In the illustrated state, the control chamber Rc is connected to the main reservoir RV via the through-hole and the supply path HH, and the base pressure Pa is "0 (atmospheric pressure)". The position of the control piston NC in this state is called the "initial position". In the initial position, the control piston NC displaces to its maximum extent in its backward direction Hb, and the volume of the control chamber Rc is at its maximum.

[0044] When an increase in base pressure Pa is required, the rotational power of motor MA increases. This rotational power is transmitted to the conversion mechanism GH via reducer GS and output as linear power to the direct-acting component. Furthermore, by pressing the control piston NC using the direct-acting component, the piston NC is moved in the forward direction Ha (the direction in which the volume of control chamber Rc decreases). This movement first disconnects the connection between control chamber Rc and the main reservoir RV. If the control piston NC moves further in the forward direction Ha, the base pressure Pa (the internal pressure of control chamber Rc) increases from "0 (atmospheric pressure)". Brake fluid BF, pressurized to the base pressure Pa, is output (pumped) from control chamber Rc of control cylinder CC.

[0045] When the base pressure Pa needs to be maintained, the rotation of motor MA stops. The movement of control piston NC stops, and the base pressure Pa remains constant. When the base pressure Pa needs to be reduced, the rotational power of motor MA decreases. Due to the base pressure Pa, motor MA rotates in the reverse direction, thus causing control piston NC to move in the backward direction Hb (the direction in which the volume of control chamber Rc increases). At this time, brake fluid BF returns towards control chamber Rc, thus reducing the base pressure Pa.

[0046] A pressure regulating valve UC (equivalent to a "solenoid valve") is installed in the servo path HU (the fluid path connecting the control chamber Rc and the servo chamber Ru). The pressure regulating valve UC is a normally open linear solenoid valve that continuously controls the valve opening amount (lift) according to the supplied current Ic (called the "valve current"). In order to regulate the hydraulic differential (differential pressure), the pressure regulating valve UC is also called a "differential pressure valve". The pressure regulating valve UC adjusts the base pressure Pa output from the electric cylinder DN to the regulating pressure Pb.

[0047] In detail, the pressure regulating valve UC consists of a valve core, a valve seat, and a solenoid. The plunger of the solenoid is fixed to the valve core. When a current Ic is supplied to the coil of the solenoid, the plunger is attracted by the coil, generating a thrust. This thrust pushes the valve core towards the valve seat. This impedes the flow of brake fluid BF from the control cylinder CC to the servo chamber Ru. As a result, since the base pressure Pa is blocked by the pressure regulating valve UC, the pressure regulating valve UC can adjust the regulating pressure Pb to be lower than the base pressure Pa. Furthermore, when no current Ic is supplied to the pressure regulating valve UC, the pressure regulating valve UC is fully open, so the base pressure Pa is equal to the regulating pressure Pb (i.e., "Pa = Pb" when "Ic = 0"). In the hydraulic generation unit PU, a regulating pressure sensor PB is installed between the pressure regulating valve UC and the servo chamber Ru to detect the regulating pressure Pb.

[0048] In the brake control unit SA, there are limitations to the adjustment of the regulating pressure Pb. As mentioned above, the pressure regulating valve UC can prevent the inflow of brake fluid BF pressurized to the base pressure Pa, thus making the regulating pressure Pb lower than the base pressure Pa. However, the pressure regulating valve UC alone cannot reduce the regulating pressure Pb. That is, in order to reduce the regulating pressure Pb, the base pressure Pa needs to be reduced.

[0049] [Applying Unit AP]

[0050] The application unit AP consists of a single-unit main cylinder CM and a main piston NM. The main piston NM is inserted into the single-unit main cylinder CM. The interior of the main cylinder CM is divided into three hydraulic chambers Rm, Ru, and Rs by the main piston NM. The main chamber Rm is formed by the main cylinder CM and the main piston NM. Furthermore, the interior of the main cylinder CM is divided into a servo chamber Ru and a reaction chamber Rs by the flange Tu of the main piston NM. Here, the pressure-bearing area rm of the main chamber Rm is equal to the pressure-bearing area ru of the servo chamber Ru.

[0051] The hydraulic generating unit PU supplies a regulating pressure Pb to the servo chamber Ru. By regulating the pressure Pb, the application unit AP outputs a supply pressure Pm (equivalent to "regulating pressure Pb"). Here, "supply pressure Pm" is the internal pressure of the main chamber Rm, also known as "main pressure". When "Pb = 0" (e.g., during non-braking), the main piston NM is in its final retracted position (i.e., the position where the main chamber Rm has the largest volume). In this state, the main chamber Rm of the master cylinder CM is connected to the main reservoir RV. Therefore, the main pressure Pm is "0 (atmospheric pressure)".

[0052] Brake fluid BF is stored inside the master reservoir RV (also known as the "atmospheric reservoir"). If the regulating pressure Pb 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). This movement disconnects the connection between the master chamber Rm and the master reservoir RV. Furthermore, if the master piston NM moves further in the forward direction Da, the supply pressure Pm (master pressure) increases from "0 (atmospheric pressure)". Thus, brake fluid BF, pressurized to the supply pressure Pm, is pumped from the master cylinder CM through the master chamber Rm towards the hydraulic correction device SZ. Furthermore, since "rm = ru", if the sliding resistance of the sealing component SL is ignored, then "Pb = Pm".

[0053] [Input Unit NR]

[0054] Regenerative coordinated control is achieved through the input unit NR. "Regenerative coordinated control" involves coordinating the friction braking force Fe (based on wheel cylinder pressure Pw) and the regenerative braking force Fg (based on the regenerative device KG) during braking to efficiently recover the vehicle's kinetic energy into electrical energy. In regenerative coordinated control, although the braking actuation component BP is activated, a state where wheel cylinder pressure Pw is not generated occurs. The input unit NR consists of the input cylinder CN, the input piston NN, the first control valve VA, the second control valve VB, the stroke simulator SS, and the input pressure sensor PN.

[0055] 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 brake operating component BP (brake pedal) in a manner that links their operation. There is a gap Ln (also called "separation distance") between the end face of the input piston NN and the end face of the master piston NM. The separation distance Ln is adjusted by regulating the pressure Pb, thereby achieving regenerative coordinated control.

[0056] The input chamber Rn of the input unit NR is connected to the reaction chamber Rs of the application unit AP via the input path HN (fluid path). A normally closed first control valve VA is installed in the input path HN. The input path HN is connected to the main reservoir RV via the reservoir path HR (fluid path) between the first control valve VA and the reaction chamber Rs. A normally open second control valve VB is installed in the reservoir path HR. The first control valve VA and the second control valve VB are 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.

[0057] When no power is supplied to the first control valve VA and the second control valve VB, the first control valve VA is closed and the second control valve VB is open. With the first control valve VA closed, the input chamber Rn is sealed and fluid-locked. As a result, the main piston NM and the brake operating component BP are displaced integrally. Furthermore, with the second control valve VB open, the stroke simulator SS and the reaction chamber Rs are connected to the main reservoir RV.

[0058] When power is supplied to the first control valve VA and the second control valve VB, the first control valve VA opens and the second control valve VB closes. This allows the main piston NM to move separately from the braking actuation component BP. At this time, since the input chamber Rn is connected to the stroke simulator SS, the operating force of the braking actuation component BP is generated by the stroke simulator SS. An input pressure sensor PN is installed on the input path HN between the input chamber Rn and the first control valve VA to detect the input pressure Pn. Furthermore, the input pressure Pn is also the hydraulic pressure within the stroke simulator SS.

[0059] Brake Controller EA

[0060] The brake actuator YA is controlled by the brake controller EA. The brake controller EA consists of a microprocessor MP and a drive circuit DR. The controller EA is connected to the communication bus BS to enable the sharing of signals (detected values, calculated values, control flags, etc.) with other controllers (EZ, EG, EJ, etc.).

[0061] The brake controller EA receives various signals directly, including the operating displacement Sp (detected by the operating displacement sensor SP), input pressure Pn (detected by the input pressure sensor PN), base pressure Pa (detected by the base pressure sensor PA), and motor rotation angle Ka (detected by the rotation angle sensor KA). Furthermore, the controller EA receives various signals from the communication bus BS, including supply pressure Pm, standard regenerative braking force Fz, vehicle speed Vx, and target acceleration Gs. Additionally, the brake controller EA outputs the target regenerative braking force Fh (the target value of the regenerative braking force Fg) from the communication bus BS. Moreover, the regenerative controller EG controls the actual regenerative braking force Fg based on the target regenerative braking force Fh (target value) obtained from the communication bus BS.

[0062] In the brake controller EA (specifically the microprocessor MP), a pressure regulation control algorithm is programmed. "Pressure regulation control" is used to regulate the wheel cylinder pressure Pw (=Pwf, Pwr), including regenerative coordination control. Pressure regulation control is executed based on the various signals mentioned above (Sp, Pa, etc.). Based on the pressure regulation control algorithm, the drive circuit DR drives the motor MA and various solenoid valves (UC, VA, etc.). In the drive circuit DR, an inverter circuit is constructed using switching elements (e.g., MOS-FETs) to drive the motor MA. Additionally, the drive circuit DR includes switching elements to drive various solenoid valves. Furthermore, the drive circuit DR includes a motor current sensor (not shown) that detects the supply current Im (motor current) supplied to the motor MA. A rotation angle sensor KA is installed in the motor MA to detect the position Ka (rotation angle) of the motor shaft.

[0063] In the brake controller EA, the drive signals Va and Vb of the first control valve VA and the second control valve VB, the drive signal Uc of the pressure regulating valve UC, and the drive signal Ma of the motor MA are calculated. Furthermore, the aforementioned switching elements are driven according to these various drive signals (Uc, Ma, etc.). Specifically, in the control of the solenoid valves, power is supplied to the first control valve VA and the second control valve VB based on the drive signals Va and Vb. As a result, the first control valve VA opens, and the second control valve VB closes. Moreover, the drive signals Uc and Ma are determined based on the pressure regulation control algorithm. Furthermore, the pressure regulating valve UC is controlled based on the drive signal Uc, and the motor MA is controlled based on the drive signal Ma.

[0064] <Hydraulic Correction Device SZ>

[0065] A hydraulic correction device SZ is installed between the brake control unit SA and the wheel cylinder CW. The hydraulic correction device SZ performs anti-lock braking control, traction control, and anti-skid control. In the braking system involving the front wheel WHf (i.e., the front wheel connecting circuit HSf), the supply pressure Pm is supplied from the master cylinder CM to the hydraulic correction device SZ. On the other hand, in the braking system involving the rear wheel WHr (i.e., the rear wheel connecting circuit HSr), the base pressure Pa is directly supplied from the hydraulic generation unit PU to the hydraulic correction device SZ. The hydraulic correction device SZ adjusts (increases or decreases) the supply pressure Pm and the base pressure Pa, providing the hydraulic outputs Pwf and Pwr (front wheel cylinder pressure and rear wheel cylinder pressure) for the front wheel cylinder CWf and rear wheel cylinder CWr, respectively.

[0066] The hydraulic correction device SZ consists of a correction actuator YZ and a correction controller EZ. Since the structure 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 regulating pressure Pb is transmitted as the supply pressure Pm via the main piston NM. Therefore, the supply pressure Pm is equivalent to the regulating pressure Pb, and the supply pressure sensor PM is equivalent to the regulating pressure sensor PB. In other words, the supply pressure Pm is an example of the regulating pressure Pb, and the supply pressure sensor PM is an example of the regulating pressure sensor PB.

[0067] When regenerative coordinated control is executed, the operation of the corrective actuator YZ stops. Therefore, during the execution of regenerative coordinated control, the regulating pressure Pb is transmitted to the front wheel cylinder CWf via the supply pressure Pm as the front wheel cylinder pressure Pwf, while the base pressure Pa is directly transmitted to the rear wheel cylinder CWr as the rear wheel cylinder pressure Pwr. That is, in the front wheel braking system, "Pb = Pm = Pwf", and in the rear wheel braking system, "Pa = Pwr".

[0068] 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. Furthermore, the correction controller EZ calculates the vehicle speed Vx (body speed) based on the wheel speed Vw. The vehicle speed Vx and supply pressure Pm are then transmitted to the brake controller EA via the communication bus BS.

[0069] <Processing of Voltage Regulation Control>

[0070] Reference Figure 2The flowchart illustrates an example of pressure regulation control. In pressure regulation control, regenerative coordination control is performed between the regenerative device KG and the braking control device SA. In this coordinated regenerative control, by making the regulating pressure Pb less than the base pressure Pa, the total braking force Fu is maintained at a predetermined value hf, thus achieving a total braking force Fu corresponding to the requested braking amount Bs. Because the front wheel cylinder pressure Pwf and the rear wheel cylinder pressure Pwr are adjusted separately in this control, it is also referred to as "dual-system pressure regulation."

[0071] Various braking forces

[0072] The various braking forces described in the pressure regulation control instructions are as follows.

[0073] "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".

[0074] "Frictional braking force Fe (hydraulic braking force)" is the actual braking force generated by the wheel cylinder pressure Pw. The target value corresponding to the frictional braking force Fe is "target frictional braking force Fn".

[0075] "Regenerative braking force Fg" is the actual braking force generated by the regenerative braking device 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 (specifically the braking controller EA) and sent to the regenerative braking device KG (specifically the regenerative controller EG) via the communication bus BS. In the regenerative braking device KG, the regenerative controller EG controls the generator GN to make the actual regenerative braking force Fg close to and consistent with the target regenerative braking force Fh.

[0076] The "standard regenerative braking force Fz" is the maximum (limit) value of the regenerative braking force Fg that the regenerative device KG can generate. Therefore, the regenerative device KG can generate 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 (specifically the regenerative controller EG) and transmitted to the brake control device SA (specifically the brake controller EA) via the communication bus BS. Furthermore, the standard regenerative braking force Fz can be limited according to the vehicle's driving conditions (e.g., the coefficient of friction of the road surface).

[0077] Various hydraulic systems

[0078] The various hydraulic systems described in the pressure regulation control instructions are as follows.

[0079] "Base pressure Pa" is the output of the electric cylinder DN (i.e., the internal pressure of the control chamber Rc). The base pressure Pa is detected (acquired) by the base pressure sensor PA.

[0080] "Regulating pressure Pb" is the hydraulic pressure obtained by adjusting the base pressure Pa through the pressure regulating valve UC. The regulating pressure Pb is detected (acquired) by the regulating pressure sensor PB. Alternatively, the regulating pressure Pb can also be detected (acquired) by the supply pressure sensor PM. Therefore, the supply pressure Pm is equivalent to one of the regulating pressures Pb, and the supply pressure sensor PM is equivalent to one of the regulating pressure sensors PB.

[0081] "Rear wheel target pressure Ptr" corresponds to the target value used to control the basic pressure Pa (actual value). Additionally, "front wheel target pressure Ptf" corresponds to the target value used to control the regulating pressure Pb. This is based on regulating the rear wheel cylinder pressure Pwr through the basic pressure Pa and regulating the front wheel cylinder pressure Pwf through the regulating pressure Pb.

[0082] In the hydraulic transmission of the brake control device SA, various resistances exist, such as pipe friction resistance in the fluid path, resistance of the solenoid valve acting as a throttle orifice, and sliding resistance of the sealing component SL. In feedback control involving hydraulics, control is performed so that the actual value matches the target value. However, considering the aforementioned resistances, it is preferable to compare the actual value and the target value at the same location. In the following explanation, this comparison is performed at the wheel cylinder CW. That is, the rear wheel target pressure Ptr is determined to correspond to the rear wheel cylinder pressure Pwr. Furthermore, the rear wheel cylinder pressure Pwr (actual value) is compensated for with a hydraulic amount equivalent to the aforementioned resistance, determined based on the base pressure Pa (the detection value of the base pressure sensor PA). Similarly, the front wheel target pressure Ptf is determined to correspond to the front wheel cylinder pressure Pwf. Furthermore, the front wheel cylinder pressure Pwf (actual value) is compensated for with a hydraulic amount equivalent to the aforementioned resistance, determined based on the regulating pressure Pb (the detection value of the regulating pressure sensor PB).

[0083] In pressure regulation control, power is first supplied to the first control valve VA and the second control valve VB. The normally closed first control valve VA is opened, and the normally open second control valve VB is closed. Therefore, since the main piston NM and the brake operating component BP can be displaced separately, the front wheel cylinder pressure Pwf and the rear wheel cylinder pressure Pwr can be adjusted independently of the operation of the brake operating component BP. At this time, the operating force of the brake operating component BP is generated by the stroke simulator SS.

[0084] In step S110, various signals are read in through the brake controller EA. The brake controller EA acquires the braking operation quantity Ba (a collective term for Sp and Pn), target acceleration Gs, base pressure Pa, regulating pressure Pb, and standard regenerative braking force Fz. The braking operation quantity Ba and target acceleration Gs are collectively referred to as the "brake request quantity Bs." The brake request quantity Bs is a state quantity representing the braking request to the vehicle. The base pressure Pa is acquired by the base pressure sensor PA. The regulating pressure Pb is acquired by at least one of the regulating pressure sensor PB and the supply pressure sensor PM. The standard regenerative braking force Fz is determined by the regeneration device KG (specifically the regeneration controller EG) and received by the brake controller EA via the communication bus BS.

[0085] In step S120, the target total braking force Fv (the target value of the total braking force Fu acting on the entire vehicle) is calculated based on the braking request quantity Bs and the calculation mapping Zfv. The target total braking force Fv is calculated as "0" according to the calculation mapping Zfv if the braking request quantity Bs is less than a predetermined quantity bo. Furthermore, if the braking request quantity Bs is greater than or equal to the predetermined quantity bo, the target total braking force Fv is calculated to increase from "0" as the braking request quantity Bs increases. Here, the "predetermined quantity bo" is preset to a predetermined value (constant) (refer to the target total braking force calculation block FV above).

[0086] In step S130, the target rear wheel pressure Ptr and the target front wheel pressure Ptf for performing dual-system pressure regulation are calculated based on the target total braking force Fv and the standard regenerative braking force Fz. In dual-system pressure regulation, the base pressure Pa and the regulating pressure Pb are adjusted separately. Specifically, the regulating pressure Pb is obtained by reducing the base pressure Pa. Therefore, the target front wheel pressure Ptf is less than the target rear wheel pressure Ptr (i.e., "Ptr < Ptf"). In dual-system pressure regulation, the target front wheel pressure Ptf and the target rear wheel pressure Ptr are determined in three cases.

[0087] Case (1): When the target total braking force Fv is below the standard regenerative braking force Fz, the target regenerative braking force Fh is equal to the target total braking force Fv, and the target friction braking force Fnf of the front wheel and the target friction braking force Fnr of the rear wheel are "0". That is, in the case of "Fv≤Fz", it is determined that "Fh=Fv、Fnf=Fnr=0".

[0088] Case (2): When the target total braking force Fv is greater than the standard regenerative braking force Fz, and the value obtained by dividing the standard regenerative braking force Fz by the distribution ratio hf, "Fz / hf", is less than or equal to the target total braking force Fv, the target regenerative braking force Fh is equal to the target total braking force Fv. Moreover, the target friction braking force Fnf of the front wheel is determined to be "0", and the target friction braking force Fnr of the rear wheel is determined to be the value obtained by subtracting the target regenerative braking force Fh (=Fz) from the target total braking force Fv. That is, in the case of "Fz < Fv ≤ (Fz / hf)", "Fh = Fz, Fnf = 0, Fnr = Fv - Fh = Fv - Fz" is determined.

[0089] 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 friction braking force Fnf) to the target total braking force Fv (which results in the total braking force Fu). The distribution ratio hf (also known as the "front wheel ratio") is preset to a specified value (constant) based on the vehicle's specifications (center of gravity position, wheelbase, etc.). Furthermore, the distribution ratio hf is equal to the ratio of the front wheel friction braking force Fef to the total braking force Fu when the regenerative braking force Fg is not applied and the front wheel cylinder pressure Pwf is equal to the rear wheel cylinder pressure Pwr. That is, in the case of "Fg = 0, Pwf = Pwr", it is "hf = Fef / Fu = Fef / (Fef + Fer)".

[0090] 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 equal to the target total braking force Fv. Moreover, the target friction braking force Fnf of the front wheel 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. In addition, the target friction braking force Fnr of the rear wheel is calculated by multiplying the value obtained by subtracting the distribution ratio hf from "1" by the target total braking force Fv. That is, when "Fv>(Fz / hf)", it is determined that "Fh=Fz, Fnf=hf•Fv-Fh, Fnr=(1-hf)•Fv".

[0091] Next, the target rear wheel pressure Ptr is calculated based on the target rear wheel friction braking force Fnr. That is, based on the specifications of the rear wheel brake system SXr, the target rear wheel friction braking force Fnr is converted into the target rear wheel pressure Ptr. Similarly, the target front wheel pressure Ptf is calculated based on the target front wheel friction braking force Fnf. That is, based on the specifications of the front wheel brake system SXf, the target front wheel friction braking force Fnf is converted into the target front wheel pressure Ptf. In addition, the specifications of the brake system SX (=SXf, SXr) correspond to the pressure-bearing area of ​​the wheel cylinder CW, the effective braking radius of the rotating component KT (brake disc), the friction coefficient of the friction component (brake pad), and the effective radius of the wheel WH (tire), etc.

[0092] In the case of "Fv≤Fz" (1), the target pressure Ptf of the front wheel and the target pressure Ptr of the rear wheel are both maintained at "0" so that energy can be recovered to the maximum extent through the regeneration device KG. Moreover, in the case of "Fz<Fv≤(Fz / hf)" (2), while the target pressure Ptf of the front wheel (resulting in the front wheel cylinder pressure Pwf) is maintained at "0", the target pressure Ptr of the rear wheel (resulting in the rear wheel cylinder pressure Pwr) increases from "0" so that the front-rear distribution of the total braking force Fu quickly reaches the specified ratio hf. Furthermore, in the case of "Fv>(Fz / hf)" (3), while "Ptr>Ptf", both the target pressure Ptf of the front wheel and the target pressure Ptr of the rear wheel increase so that the front-rear distribution of the total braking force Fu is maintained at the specified ratio hf.

[0093] In step S140, the motor MA and the pressure regulating valve UC are controlled based on the rear wheel target pressure Ptr and the front wheel target pressure Ptf. Specifically, when performing regenerative coordinated control, the base pressure Pa is controlled by the electric cylinder DN (specifically the motor MA) so that the rear wheel cylinder pressure Pwr approaches and matches the rear wheel target pressure Ptr. Furthermore, the differential pressure Sa (also called the "actual differential pressure") between the base pressure Pa and the regulating pressure Pb is controlled by the pressure regulating valve UC so that the front wheel cylinder 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 based on the front wheel target pressure Ptf and the rear wheel target pressure Ptr approaches and matches the actual differential pressure Sa calculated based on the base pressure Pa and the regulating pressure Pb. Here, the base pressure Pa is obtained by the base pressure sensor PA. Additionally, the regulating pressure Pb is obtained by at least one of the regulating pressure sensor PB and the supply pressure sensor PM.

[0094] <Drive Control of Electric Cylinder DN>

[0095] Reference Figure 3The block diagram below details the drive control of the electric cylinder DN in step S140. The electric cylinder DN (specifically the motor MA) is controlled based on the front wheel target pressure Ptf, the rear wheel target pressure Ptr, the base pressure Pa, the regulating pressure Pb, and the motor rotation angle Ka. The drive control of the motor MA consists of a wheel cylinder pressure calculation module PW, a hydraulic / fluid volume conversion module ZE, an ejection fluid volume calculation module EJ, a reference value calculation module KS, a correction value calculation module KH, a target rotation angle calculation module KT, and a rotation angle feedback control module KF.

[0096] In the wheel cylinder pressure calculation module PW, the rear wheel cylinder pressure Pwr is calculated based on the base pressure Pa. Additionally, the front wheel cylinder pressure Pwf is calculated based on the regulating pressure Pb. As mentioned above, the target pressure Pt is determined to correspond to the wheel cylinder pressure Pw. Therefore, based on the resistance in the hydraulic transmission path, the rear wheel cylinder pressure Pwr is calculated based on the base pressure Pa, and the front wheel cylinder pressure Pwf is calculated based on the regulating pressure Pb. Furthermore, in the front wheel cylinder pressure Pwf and the rear wheel cylinder pressure Pwr, since the transmission paths of the base pressure Pa and the regulating pressure Pb are different, resistance compensation is considered. Specifically, since the regulating pressure Pb is transmitted to the front wheel cylinder CWf via the master cylinder CM and the master piston NM, the sliding resistance of the sealing component SL is considered in the calculation of the front wheel cylinder pressure Pwf. However, since the base pressure Pa is directly supplied to the rear wheel cylinder CWr, the sliding resistance of the sealing component SL does not need to be considered.

[0097] The hydraulic / fluid volume conversion module ZE performs the conversion (conversion) from hydraulic pressure to fluid volume. "Hydraulic pressure" refers to the pressure in wheel cylinder CW, and "fluid volume" refers to the volume of brake fluid BF within wheel cylinder CW. The hydraulic / fluid volume conversion module ZE includes front wheel conversion mapping Zef and rear wheel conversion mapping Zer (equivalent to "conversion mapping"). These conversion mappings Zef and Zer demonstrate the relationship between the hydraulic pressure Pw generated in wheel cylinder CW and the fluid volume of brake fluid BF within wheel cylinder CW (also known as "hydraulic-fluid volume characteristics"). Furthermore, the front wheel conversion mapping Zef and rear wheel conversion mapping Zer are pre-determined through experiments and analysis and stored in the controller EA.

[0098] In the hydraulic-fluid quantity characteristic (the nonlinear characteristic of wheel cylinder pressure Pw), when the wheel cylinder pressure Pw is small, a larger fluid quantity is required to generate the wheel cylinder pressure Pw compared to when it is large. Conversely, when the wheel cylinder pressure Pw is large, a smaller fluid quantity can generate the wheel cylinder pressure Pw compared to when it is small. In other words, in the hydraulic-fluid quantity characteristic, the increase in fluid quantity relative to the wheel cylinder pressure Pw increases with an "upward convex" characteristic. The nonlinearity of the hydraulic-fluid quantity characteristic is based on the nonlinearity of the rigidity characteristics of the braking system SX (=SXf, SXr) (e.g., the rigidity of the brake caliper, friction components, etc.). In the front wheel braking system SXf and the rear wheel braking system SXr, due to the different rigidity characteristics, the front wheel conversion mapping Zef and the rear wheel conversion mapping Zer are set separately.

[0099] The hydraulic / fluid quantity conversion module ZE includes a standard fluid quantity calculation module ES and an inferred fluid quantity calculation module EE. In the standard fluid quantity calculation module ES, the standard fluid quantity Es is calculated based on the target pressure Pt (=Ptf, Ptr) and the front wheel conversion mapping Zef and the rear wheel conversion mapping Zer. "Standard fluid quantity Es" is the amount (volume) of brake fluid BF that should flow into the front wheel cylinder CWf and the rear wheel cylinder CWr to achieve the target pressure Pt. In other words, the standard fluid quantity Es is the target value of the fluid quantity that should be supplied from the control cylinder CC to the wheel cylinder CW.

[0100] In detail, in the standard fluid volume calculation module ES, the front wheel standard fluid volume Esf is calculated based on the front wheel target pressure Ptf and the front wheel conversion mapping Zef. "Front wheel standard fluid volume Esf" is the amount of fluid (the volume of brake fluid BF) that should flow into the front wheel cylinder CWf to achieve the front wheel target pressure Ptf. Similarly, in the standard fluid volume calculation module ES, the rear wheel standard fluid volume Esr is calculated based on the rear wheel target pressure Ptr and the rear wheel conversion mapping Zef. "Rear wheel standard fluid volume Esr" is the amount of fluid that should flow into the rear 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 to determine the standard fluid volume Es (i.e., "Es = Esf + Esr"). In other words, the standard fluid volume Es is the sum of the front wheel standard fluid volume Esf and the rear wheel standard fluid volume Esr.

[0101] In the inferred fluid volume calculation module EE, the inferred fluid volume Ee is calculated based on "the front wheel cylinder pressure Pwf calculated from the regulating pressure Pb", "the rear wheel cylinder pressure Pwr calculated from the base pressure Pa", and "the front wheel conversion mapping Zef and the rear wheel conversion mapping Zer". "Inferred fluid volume Ee" is the amount (volume) of brake fluid BF that should have been supplied to the front wheel cylinder CWf and the rear wheel cylinder CWr to generate the cylinder pressure Pw (= Pwf, Pwr). Specifically, the front wheel inferred fluid volume Eef is calculated based on the front wheel cylinder pressure Pwf and the front wheel conversion mapping Zef (i.e., the hydraulic-fluid volume characteristics of the front wheel cylinder CWf). Similarly, the rear wheel inferred fluid volume Eer is calculated based on the rear wheel cylinder pressure Pwr and the rear wheel conversion mapping Zer (i.e., the hydraulic-fluid volume characteristics of the rear wheel cylinder CWr). Then, the estimated fluid volume Eef for the front wheel is added to the estimated fluid volume Eer for the rear wheel to determine the estimated fluid volume Ee (i.e., "Ee = Eef + Eer"). In other words, the estimated fluid volume Ee is the sum of the estimated fluid volumes Eef for the front wheel and Eer for the rear wheel, and it represents the estimated fluid volume flowing from the control cylinder CC into the front wheel cylinder CWf and the rear wheel cylinder CWr. Furthermore, since the front wheel cylinder pressure Pwf and the rear wheel cylinder pressure Pwr are derived from the base pressure Pa and the regulating pressure Pb, the estimated fluid volume Ee can be calculated in the "Estimated Fluid Volume Calculation Module EE" based on the base pressure Pa, the regulating pressure Pb, and the transformation mappings Zef and Zer.

[0102] In the injection fluid volume calculation module EJ, the injection fluid volume Ej is calculated based on the motor rotation angle Ka (actual value). "Injection fluid volume Ej" is the actual amount (volume) of brake fluid BF discharged (ejected) from the electric cylinder DN (i.e., control cylinder CC). In the injection fluid volume calculation module EJ, the rotation angle Ka is converted into the injection fluid volume Ej based on the specifications of the electric cylinder DN. Furthermore, the specifications of the electric cylinder DN include the reduction ratio of the reducer GS, the lead of the conversion mechanism GH (the displacement of the linearly moving part per revolution of the rotating part), and the pressure area of ​​the control piston NC, etc.

[0103] In the liquid volume calculation module EJ, the liquid volume Ej (the volume of liquid delivered from the control cylinder CC) can also be obtained using the piston stroke Sn. Specifically, a stroke sensor SN is installed in the electric cylinder DN to acquire the displacement (piston stroke) of the control piston NC. Then, the liquid volume Ej is determined based on the piston stroke Sn and the pressure area of ​​the control piston NC. Since the rotation angle sensor KA and the stroke sensor SN are used to determine the liquid volume Ej ejected from the control cylinder CC, they are collectively referred to as "liquid volume sensors". That is, in the liquid volume calculation module EJ, the liquid volume Ej is determined based on the detection results of the liquid volume sensors KA and SN.

[0104] In the reference value calculation module KS, the reference value Ks is determined based on the standard liquid volume Es (=Esf+Esr). The "reference value Ks" is a state variable used to determine the target value for controlling the motor MA. Specifically, the reference value Ks is a state variable that converts the standard liquid volume Es into a dimension (i.e., a physical quantity) representing the rotation angle from the standard liquid volume Es to the motor MA. For example, the dimension (physical quantity) of the reference value Ks can be any one of the following: the dimension of the liquid volume, the dimension of the displacement of the control piston NC, or the dimension of the rotation angle of the motor MA. In the electric cylinder DN, the specifications of the constituent components are known. In the reference value calculation module KS, the standard liquid volume Es is converted into the reference value Ks based on the specifications of the electric cylinder DN (reduction ratio of the reducer GS, lead of the conversion mechanism GH, pressure area of ​​the control piston NC, etc.). Therefore, the larger the standard liquid volume Es, the larger the determined reference value Ks is.

[0105] In the correction value calculation module KH, the correction value Kh is calculated based on the inferred fluid volume Ee and the injected fluid volume Ej. Although the front wheel conversion mapping Zef and the rear wheel conversion mapping Zer are preset, they contain errors such as deviation and aging. These errors arise from factors such as the presence or absence of gas inside the braking device SX, and wear of friction components. The "correction value Kh" is a state variable used to compensate for these errors. In the correction value calculation module KH, the deviation hE (fluid volume deviation) between the inferred fluid volume Ee and the injected fluid volume Ej is calculated. For example, the fluid volume deviation hE is determined by subtracting the inferred fluid volume Ee from the injected fluid volume Ej (i.e., "hE = Ej - Ee"). Then, the fluid volume deviation hE is converted into a quantity (physical quantity) with the same dimensions 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 fluid volume deviation hE, the larger the determined correction value Kh; the smaller the fluid volume deviation hE, the smaller the determined correction value Kh.

[0106] In the target rotation angle calculation module 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 of the rotation angle Ka used to control the motor MA. For example, the reference value Ks and the correction value Kh are added together to determine the indicated value Ku (i.e., "Ku = Ks + Kh"). The "indicated value Ku" is equivalent to the intermediate target value used to determine the target rotation angle Kt. Here, the physical quantity (dimensions) of the indicated value Ku is the same as that of the reference value Ks and the correction value Kh.

[0107] The correction value Kh is a state variable used to ensure that the rear wheel cylinder pressure Pwr matches the target rear wheel pressure Ptr. In other words, the correction based on the reference value Ks of the correction value Kh is equivalent to feedback control related to the brake fluid BF quantity. Furthermore, the correction based on the correction value Kh also functions as feedback control related to hydraulic pressure. This is based on the principle that "the inferred fluid quantity Ee is calculated from the hydraulic pressure Pwf and Pwr (actual value)" and "if the fluid quantity is optimized, the hydraulic pressure is also optimized." In the brake control unit SA, through feedback control based on the correction value Kh, the rear wheel cylinder pressure Pwr is controlled to be close to and consistent with the target rear wheel pressure Ptr.

[0108] In the target rotation angle calculation module KT, the target rotation angle Kt is calculated based on the indicated value Ku. Specifically, the indicated value Ku is converted into the dimensions (physical quantity) of the motor rotation angle Ka using the specifications of the components of the electric cylinder DN (reduction ratio of the reducer GS, lead of the conversion mechanism GH, etc.) to determine the target rotation angle Kt. The responsiveness of the motor MA can be considered when determining the target rotation angle Kt. For example, a constraint is imposed on the response speed of the target rotation angle Kt (i.e., the change per unit time) using the response model of the motor MA. This is based on the scenario where, even if a phased change in the target rotation angle Kt is calculated, the motor MA cannot keep up with that target rotation angle Kt. In any case, in the target rotation angle calculation module KT, the target rotation angle Kt, as the final target value, is determined based on the reference value Ks and the correction value Kh.

[0109] In the rotation angle feedback control module KF, the motor MA is controlled based on the target rotation angle Kt and the actual motor rotation angle Ka. Specifically, the drive signal Ma of the motor MA is determined so that the motor rotation angle Ka (actual value) obtained by the rotation angle sensor KA is close to and consistent with the target rotation angle Kt (target value) (i.e., the deviation hK between the target value Kt and the actual value Ka is close to "0"). Moreover, in the drive circuit DR (inverter circuit), the current Im (motor current) supplied to the motor MA is adjusted based on the motor drive signal Ma. That is, the rotation angle feedback control module KF performs so-called rotation angle feedback control.

[0110] In the brake control unit SA, the rotation angle Ka of the motor MA is converted into the displacement of the control piston NC by the conversion mechanism GH. The control cylinder CC ejects a fluid volume (the volume of brake fluid BF) corresponding to the displacement of the control piston NC from the wheel cylinder CW. Furthermore, based on the hydraulic-fluid volume characteristic of the wheel cylinder CW, the wheel cylinder pressure Pw is determined by the fluid volume flowing into the wheel cylinder CW. Since the hydraulic-fluid volume characteristic is the fluid volume consumed by the wheel cylinder CW to generate the wheel cylinder pressure Pw, it is also called the "fluid consumption characteristic."

[0111] In the brake control unit SA, the target rotation angle Kt is determined based on the standard rear wheel fluid volume Esr calculated from the target rear wheel pressure Ptr and the standard front wheel fluid volume Esf calculated from the target front wheel pressure Ptf. Then, the motor MA is controlled so that the actual rotation angle Ka matches the target rotation angle Kt. Consequently, to achieve the base pressure Pa, an appropriate amount of brake fluid BF is injected from the electric cylinder DN (specifically the control cylinder CC).

[0112] As a hydraulic-fluid volume characteristic (fluid consumption characteristic), the front wheel conversion mapping Zef and rear wheel conversion mapping Zer pre-stored in the brake controller EA (especially the microprocessor MP) contain errors caused by the presence of gas (such as air) within the device, wear of friction components, etc. Specifically, in the presence of gas, more fluid is required to achieve the same hydraulic pressure compared to the absence of gas. Furthermore, in cases of high wear on friction components, the same hydraulic pressure can be achieved with less fluid compared to cases of low wear.

[0113] In the brake control unit SA, a correction value Kh is determined to compensate for errors in the conversion maps Zef and Zer. The correction value Kh is determined based on the rear wheel inferred fluid volume Eer (the inferred fluid volume flowing into the rear wheel cylinder CWr) calculated from the base pressure Pa, the front wheel inferred fluid volume Eef (the inferred fluid volume flowing into the front wheel cylinder CWf) calculated from the regulating pressure Pb, and the actual fluid volume Ej (the ejected fluid volume) ejected from the control cylinder CC. Here, the ejected fluid volume Ej is obtained from the fluid volume sensors KA and SN. When calculating the inferred fluid volume Ee, the same conversion maps Zef and Zer as those used for calculating the standard fluid volume Es are used. Therefore, the correction value Kh, based on the deviation hE between the inferred fluid volume Ee and the ejected fluid volume Ej, represents the error contained in the conversion maps Zef and Zer. Since the target rotation angle Kt is determined by correcting the reference value Ks with the correction value Kh, the effects of the aforementioned errors are corrected.

[0114] The fluid volume deviation hE is determined by subtracting the inferred fluid volume Ee from the ejected fluid volume Ej (i.e., "hE = Ej - Ee"). When the ejected fluid volume Ej is larger than the inferred fluid volume Ee (i.e., "Ej > Ee, hE > 0"), the conversion maps Zef and Zer are offset relative to the true value by decreasing in the direction of the vertical axis (the axis of hydraulic pressure). In other words, in the conversion maps Zef and Zer, the fluid volume is determined to be smaller than the true value under the same hydraulic pressure. Therefore, correction is performed by adding the correction value Kh calculated based on the fluid volume deviation hE to the reference value Ks calculated based on the standard fluid volume Es, thereby increasing the target rotation angle Kt. Conversely, when the ejected fluid volume Ej is smaller than the inferred fluid volume Ee (i.e., "Ej < Ee, hE < 0"), the conversion maps Zef, Zer, and Zek are offset relative to the true value by increasing in the direction of the vertical axis (the axis of hydraulic pressure). In other words, in the conversion mappings Zef and Zer, under the same hydraulic pressure, the fluid volume is determined to be larger than the true value. Therefore, correction is performed by decreasing the target rotation angle Kt using a correction value Kh calculated based on the fluid volume deviation hE. Furthermore, including the sign, the larger the fluid volume deviation hE, the larger the correction value Kh is determined to be. Through correction based on the fluid volume deviation hE, the amount Ej (ejected fluid volume) of brake fluid BF discharged from the electric cylinder DN (especially the control cylinder CC) is adjusted precisely relative to the target pressures Ptf and Ptr. As a result, high-precision adjustment can be achieved through the electric cylinder DN to ensure that the rear wheel cylinder pressure Pwr matches the rear wheel target pressure Ptr.

[0115] <Drive control of pressure regulating valve UC>

[0116] Reference Figure 4 The block diagram below details the drive control of the pressure regulating valve UC in step S140. 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 regulating pressure Pb. The drive control of the pressure regulating valve UC consists of a target differential pressure calculation module ST, an indication current calculation module IS, an actual differential pressure calculation module SA, a differential pressure deviation calculation module HS, a compensation current calculation module IH, a target valve current calculation module IT, and a current feedback control module IF.

[0117] In the target differential pressure calculation module ST, the target differential pressure St is calculated based on the rear wheel target pressure Ptr and the front wheel target pressure Ptf. The "target differential pressure St" is the target value of the hydraulic difference (differential pressure) generated by the pressure regulating valve UC. Specifically, considering the aforementioned resistance, the target differential pressure St is determined by subtracting the front wheel target pressure Ptf from the rear wheel target pressure Ptr.

[0118] In the indicating current calculation module IS, the indicating current Is is calculated based on the target differential pressure St and the pre-set calculation mapping Zis. "Indicating current Is" is the target value corresponding to the valve current Ic (actual value) supplied to the pressure regulating valve UC. According to the calculation mapping Zis, the larger the target differential pressure St, the larger the indicating current Is is determined to be.

[0119] In the actual differential pressure calculation module SA, the actual differential pressure Sa is calculated based on the base pressure Pa and the regulating pressure Pb. The "actual differential pressure Sa" is the hydraulic difference (actual differential pressure) actually generated by the pressure regulating valve UC. Specifically, the actual differential pressure Sa is determined by subtracting the regulating pressure Pb from the base pressure Pa (i.e., "Sa = Pa - Pb"). Here, the base pressure Pa is detected by the base pressure sensor PA. Additionally, the regulating pressure Pb is detected by at least one of the regulating pressure sensor PB and the supply pressure sensor PM.

[0120] In the differential pressure deviation calculation module HS, the differential pressure deviation hS is calculated based on the target differential pressure St and the actual differential pressure Sa. "Differential pressure deviation hS" is the deviation between the target differential pressure St and the actual differential pressure Sa, equivalent to the error in the control of the pressure regulating valve UC. If a valve current Ic equal to the indicating current Is is supplied to the pressure regulating valve UC, the actual differential pressure Sa should ideally match the target differential pressure St. However, an error hS is actually generated. 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").

[0121] In the compensation current calculation module IH, the compensation current Ih is calculated based on the differential pressure deviation hS and the pre-set calculation mapping Zih. The "compensation current Ih" is used to compensate for the aforementioned error hS, ensuring that the actual differential pressure Sa matches the target differential pressure St. According to the calculation mapping Zih, the larger the differential pressure deviation hS, the larger the compensation current Ih is determined to be. Furthermore, a dead zone is set in the calculation mapping Zih.

[0122] In the target valve current calculation module IT, the target valve current It is calculated based on the indicating 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 target valve current It is determined by adding the compensation current Ih to the indicating current Is (i.e., "It = Is + Ih"). In the target valve current calculation module IT, the target valve current It is determined by the compensation current Ih to ensure that the actual differential pressure Sa is close to and consistent with the target differential pressure St.

[0123] For example, when the target differential pressure St is greater than the actual differential pressure Sa, the actual differential pressure Sa is insufficient. In the differential pressure deviation calculation module HS, since the differential pressure deviation hS is determined to be a positive value, the compensation current Ih is determined to be a positive value according to the calculation mapping Zih. In the target valve current calculation module IT, since the target valve current It increases from the indicating current Is through the compensation current Ih, the insufficient actual differential pressure Sa increases to match the target differential pressure St. Conversely, when the target differential pressure St is less than the actual differential pressure Sa, the actual differential pressure Sa is excessive, so the differential pressure deviation hS is determined to be a negative value. Therefore, the compensation current Ih is also determined to be a negative value, and the target valve current It decreases from the indicating current Is. As a result, the excessive actual differential pressure Sa decreases to match the target differential pressure St. That is, through the compensation current Ih, the differential pressure deviation hS (error) approaches "0" and matches it.

[0124] In the current feedback control module IF, a drive signal Uc for the pressure regulating valve Uc is determined to make the actual valve current Ic approach and match the target valve current It (i.e., to make the deviation hI between the target value It and the actual value Ic close to "0"). Then, in the drive circuit DR, power is supplied to the pressure regulating valve UC based on the drive signal Uc. In other words, so-called current feedback control is performed in the current feedback control module IF. Furthermore, the valve current Ic is detected by a valve current sensor IC located in the drive circuit DR.

[0125] The pressure regulating valve UC (linear solenoid valve) adjusts its opening amount according to the supplied valve current Ic. Furthermore, by adjusting this opening amount, the pressure regulating valve UC controls the hydraulic pressure Pa (base pressure) on the side closer to the electric cylinder DN, the hydraulic pressure Pb (regulating pressure) on the side farther from the electric cylinder DN, and the hydraulic differential Sa. Therefore, in the brake control device SA, the valve current Ic of the pressure regulating valve UC is controlled based on the differential pressure St (target differential pressure) that should be generated by the pressure regulating valve UC. Moreover, the valve current Ic is fine-tuned to reduce the difference between the actual generated differential pressure Sa (actual differential pressure) and the target differential pressure St, i.e., the error hS (differential pressure deviation). Thus, through the pressure regulating valve UC, the base pressure Pa generated by the electric cylinder DN is precisely adjusted to the regulating pressure Pb.

[0126] Furthermore, if the regulating pressure Pb is adjusted to match the front wheel target pressure Ptf, the amount of fluid supplied to the front wheel cylinder CWf will change, thus affecting the base pressure Pa (and consequently, the rear wheel cylinder pressure Pwr). However, when adjusting the base pressure Pa, the front wheel target pressure Ptf and the regulating pressure Pb are considered in addition to the rear wheel target pressure Ptr and the base pressure Pa. That is, the change in base pressure Pa caused by the change in regulating pressure Pb is compensated for by a feedback control loop (i.e., a closed loop) via the correction value Kh. Therefore, even if the regulating pressure Pb changes, the rear wheel cylinder pressure Pwr is adjusted to match the rear wheel target pressure Ptr.

[0127] <Second Embodiment of Braking Control Device SA>

[0128] Reference Figure 5 The schematic diagram illustrates a second embodiment of the vehicle's braking control device SA. In this second embodiment, the motor MA and the pressure regulating valve UC are controlled using the same method as in the first embodiment.

[0129] In the first embodiment, the regulating pressure Pb is transmitted as the supply pressure Pm via the master cylinder CM and the master piston NM. That is, in the hydraulic transmission path, the applying unit AP and the hydraulic generating unit PU are configured in series. Alternatively, the applying unit AP and the hydraulic generating unit PU can be configured in parallel. In the second embodiment, the applying unit AP (especially the master cylinder CM) and the hydraulic generating unit PU are directly connected to the hydraulic correction device SZ (especially the correction actuator YZ).

[0130] Specifically, in the brake control device SA of the second embodiment, a shut-off valve VM, a simulator valve VS, and a connecting valve VC are provided instead of the input unit NR. The shut-off valve VM is a normally open on / off solenoid valve, while the simulator valve VS and the connecting valve VC are normally closed on / off solenoid valves. The shut-off valve VM is located in the front wheel connection path HSf connecting the master cylinder CM (particularly the master chamber Rm) and the front wheel cylinder CWf. The stroke simulator SS is connected to the front wheel connection path HSf between the master cylinder CM and the shut-off valve VM via the simulator valve VS.

[0131] The front wheel connecting path HSf, the rear wheel connecting path HSR (the fluid path connecting the front wheel cylinder CWf and the rear wheel cylinder CWr), and the control cylinder CC (especially the control chamber Rc) are connected via the connecting path HV (fluid path). The connecting path HV is also the fluid path connecting the front wheel connecting path HSf and the rear wheel connecting path HSf. A pressure regulating valve UC and a connecting valve VC are installed in the connecting path HV.

[0132] As described above, in the pressure regulating valve UC, the thrust of the solenoid hinders the flow of brake fluid BF from the control cylinder CC towards the front wheel cylinder CWf. Therefore, the pressure regulating valve UC can adjust the regulating pressure Pb (i.e., the front wheel cylinder pressure Pwf) to be lower than the base pressure Pa (i.e., the rear wheel cylinder pressure Pwr).

[0133] That is, the pressure regulating valve UC is positioned in the hydraulic transmission path from the control cylinder CC to the front wheel cylinder CWf. Furthermore, the regulated pressure Pb, reduced from the base pressure Pa by the pressure regulating valve UC, is transmitted as the front wheel cylinder pressure Pwf to the front wheel cylinder CWf. Conversely, the base pressure Pa is transmitted as the rear wheel cylinder pressure Pwr to the rear wheel cylinder CWr. Moreover, the regulated pressure Pb cannot be reduced by the pressure regulating valve UC alone; a reduction in the regulated pressure Pb requires a reduction in the base pressure Pa.

[0134] During pressure regulation control, power is supplied to the shut-off valve VM, simulator valve VS, and connecting valve VC. This closes the shut-off valve VM and opens the simulator valve VS and connecting valve VC. The connection between the main chamber Rm and the front wheel cylinder CWf is severed, and regulating pressure Pb is supplied to the front wheel cylinder CWf. Furthermore, since the main chamber Rm is connected to the stroke simulator SS, the operating force of the brake operating component BP (brake pedal) is generated by the stroke simulator SS. Additionally, the regulating pressure sensor PB can be located in the hydraulic generation unit PU or in the correction actuator YZ. In the configuration where the regulating pressure sensor PB is located in the correction actuator YZ, the regulating pressure Pb is acquired by the brake controller EA via the communication bus BS.

[0135] In the second embodiment, the same regenerative coordination control as in the first embodiment is performed. Specifically, the base pressure Pa generated by the electric cylinder DN is regulated to a regulating pressure Pb by the pressure regulating valve UC. In the second embodiment, the same effect as in the first embodiment is achieved (appropriate control of the motor MA and the pressure regulating valve UC for dual-system pressure regulation).

[0136] <Other implementations of the braking control device SA, etc.>

[0137] Other embodiments of the brake control device SA equipped with an electric cylinder DN will be described. These other embodiments achieve the same effects as described above.

[0138] In the aforementioned embodiment of the brake control device SA, the base pressure Pa is obtained as the detection result of the base pressure sensor PA, which is installed at the ejection section of the electric cylinder DN. Alternatively, the base pressure sensor PA can be installed in the hydraulic transmission path from the control cylinder CC to the rear wheel cylinder CWr. In either case, the base pressure Pa used for calculating the fluid volume Ee and the actual differential pressure Sa is based on the actual value detected by the base pressure sensor PA.

[0139] Similarly, the regulating pressure Pb is obtained based on the detection result of the regulating pressure sensor PB, which is located between the pressure regulating valve UC and the servo chamber Ru. Alternatively, the regulating pressure sensor PB can be located in the hydraulic transmission path from the control cylinder CC to the front wheel cylinder CWf (e.g., refer to the supply pressure sensor PM). In either case, the regulating pressure Pb used in the calculation of the fluid volume Ee and the actual differential pressure Sa is based on the actual value detected by the regulating pressure sensor PB.

[0140] In the aforementioned embodiment of the brake control device SA, the injection fluid volume Ej is obtained based on the detection results of at least one of the rotation angle sensor KA and the stroke sensor SN. That is, the injection fluid volume Ej is calculated based on the displacement Sn of the control piston NC obtained from the motor rotation angle Ka, piston stroke Sn, etc. Alternatively, a flow sensor can be provided to detect the flow rate (volume per unit time) of the brake fluid injected from the control cylinder CC, and the injection fluid volume Ej can be obtained based on the detection value of the flow sensor. For example, an ultrasonic or electromagnetic flow sensor can be used. In either case, the injection fluid volume Ej (actual value) is based on the detection result of the flow sensor that detects the amount of brake fluid BF injected from the electric cylinder DN.

[0141] In the aforementioned embodiment of the brake control device SA, the target pressure Pt (=Ptf, Ptr) is determined as a target value corresponding to the wheel cylinder pressure Pw (=Pwf, Pwr). That is, the point where the target value is compared with the actual value (also called the "comparison point") is the wheel cylinder CW. Alternatively, the comparison point can be any point in the hydraulic transmission path from the ejection part of the electric cylinder DN to the wheel cylinder CW. For example, the detection point of the base pressure sensor PA or the regulating pressure sensor PB can also be used as the comparison point. In this structure, the target pressures Ptf and Ptr compensate for the hydraulic component caused by the aforementioned resistance and are determined to correspond to the base pressure Pa and the regulating pressure Pb. In pressure regulation control, regardless of the location of the comparison point between the target value and the actual value, the front wheel target pressure Ptf and the rear wheel target pressure Ptr are the target values ​​used to control the base pressure Pa and the regulating pressure Pb, and the standard fluid volume Es is determined based on the front wheel target pressure Ptf and the rear wheel target pressure Ptr, while the inferred fluid volume Ee is determined based on the base pressure Pa and the regulating pressure Pb. In addition, the target differential pressure St is determined based on the front wheel target pressure Ptf and the rear wheel target pressure Ptr, while the actual differential pressure Sa is determined based on the base pressure Pa and the adjustment pressure Pb.

[0142] In the aforementioned embodiment of the brake control device SA, a disc brake is used as the brake device SX. Alternatively, a drum brake can also be used as the brake device SX. In the drum brake device SX, the rotating component KT fixed to the wheel WH is the brake drum, and the friction component is the brake pads adhered to the brake shoes. In the drum brake device SX, similarly to the disc brake device SX, the brake pads (friction components) are pressed against the brake drum (rotating component) by the wheel cylinder pressure Pw of the wheel cylinder CW, thereby generating a frictional braking force Fe.

[0143] In the aforementioned embodiment of the brake control device SA, target values ​​for various braking forces (Fv, Fz, Fh, Fn, etc.) are calculated using the dimensions (corresponding physical quantities) of the front and rear forces acting on the vehicle. Alternatively, calculations can be performed using the dimensions of vehicle acceleration or the torque of the wheel WH. This is based on the equivalence of the state quantities (called "force-related state quantities") from the front and rear forces to vehicle acceleration. Therefore, target pressures Ptf, Ptr, etc., are calculated based on the braking request quantity Bs via the force-related state quantities from the front and rear forces acting on the vehicle to vehicle deceleration.

[0144] In the aforementioned embodiment of the brake control device SA, the pressure regulating valve UC is located in either the servo path HU or the connecting path HV. Alternatively, the pressure regulating valve UC may be located in the front wheel connecting path HSf. Specifically, in the front wheel connecting path HSf, the pressure regulating valve UC is positioned between the point where the base pressure Pa is transmitted and the front wheel cylinder CWf. In either case, the pressure regulating valve UC is located in the hydraulic transmission path from the control cylinder CC to the front wheel cylinder CWf. Furthermore, through the pressure regulating valve UC, the adjusted pressure Pb, reduced from the base pressure Pa, is transmitted as the front wheel cylinder pressure Pwf to the front wheel cylinder CWf.

[0145] In the first embodiment of the aforementioned braking control device SA, in the application unit AP, the pressure-bearing area rm (main area) of the main chamber Rm and the pressure-bearing area ru (servo area) of the servo chamber Ru are set to be equal. The main area rm and the servo area ru may also be unequal. In structures where the main area rm and the servo area ru are different, a conversion calculation between the supply pressure Pm (main pressure) and the base pressure Pa can be performed based on the area ratio of the servo area ru to the main area rm (i.e., a conversion based on "Pm•rm=Pa•ru"). Furthermore, in a structure that uses the supply pressure sensor PM as the regulating pressure sensor PB and the supply pressure Pm as the regulating pressure Pb, the supply pressure Pm is converted into the regulating pressure Pb based on the aforementioned area ratio.

[0146] <Summary of Implementation Methods>

[0147] The brake control unit SA is applied to vehicles equipped with a regenerative braking device KG in the front wheel cylinder CWf. The brake control unit SA consists of a control cylinder CC, a pressure regulating valve UC (solenoid valve), and a brake controller EA. Here, the control cylinder CC generates a base pressure Pa powered by a motor MA, the pressure regulating valve UC adjusts the base pressure Pa to a regulating pressure Pb, and the controller EA controls the motor MA and the pressure regulating valve UC. The brake control unit SA generates the base pressure Pa and the regulating pressure Pb based on the vehicle's requested braking amount Bs. The regulating pressure Pb controls the hydraulic pressure Pwf of the front wheel cylinder CWf, while the base pressure Pa controls the hydraulic pressure Pwr of the rear wheel cylinder CWr. Furthermore, the regulating pressure Pb is lower than the base pressure Pa.

[0148] For example, the brake control unit SA has a main chamber Rm and a servo chamber Ru opposed to each other via a main piston NM. Furthermore, the control cylinder CC is connected to the servo chamber Ru and the rear wheel cylinder CWr. Additionally, the main chamber Rm is connected to the front wheel cylinder CWf, and a pressure regulating valve UC is disposed between the control cylinder CC and the servo chamber Ru. According to this structure, the hydraulic pressure Pwf (front wheel cylinder pressure) of the front wheel cylinder CWf is controlled by adjusting the pressure Pb, and the hydraulic pressure Pwr (rear wheel cylinder pressure) of the rear wheel cylinder CWr is controlled by the base pressure Pa.

[0149] In the brake control device SA, the controller EA calculates the amount of fluid to be supplied to the rear wheel cylinder CWr based on the rear wheel target pressure Ptr, which is used to control the base pressure Pa, as the standard fluid volume Esr for the rear wheel. It also calculates the amount of fluid to be supplied to the front wheel cylinder CWf based on the front wheel target pressure Ptf, which is used to control the regulating pressure Pb, as the standard fluid volume Esf for the front wheel. Furthermore, the controller EA controls the motor MA based on the front wheel standard fluid volume Esf and the rear wheel standard fluid volume Esr. Simultaneously, the controller EA controls the pressure regulating valve UC based on the rear wheel target pressure Ptr and the front wheel target pressure Ptf.

[0150] The wheel cylinder pressure Pw is determined by the amount (volume) of brake fluid BF flowing into the wheel cylinder CW. Therefore, the brake control device SA is equipped with front wheel conversion mapping Zef and rear wheel conversion mapping Zer. The conversion mappings Zef and Zer correspond to the relationship between the hydraulic pressure Pw (wheel cylinder pressure) generated in the wheel cylinder CW and the volume (volume) of brake fluid BF supplied to the wheel cylinder CW, i.e., the hydraulic-volume characteristic (volume exhibits an upward convex nonlinear characteristic relative to hydraulic pressure). Specifically, in the conversion mappings Zef and Zer, the increase in standard fluid volumes Esf and Esr relative to the increase in target pressures Ptf and Ptr, and the increase in inferred fluid volumes Eef and Eer relative to the increase in actual hydraulic pressures Pa and Pb are determined.

[0151] In the brake control unit SA, hydraulic pressure (Ptf, Ptr, Pa, Pb, etc.) is converted into fluid volume (Esf, Esr, Eef, Eer, etc.) through conversion mappings Zef and Zer. Specifically, the standard fluid volume Es (i.e., the sum of the front wheel standard fluid volume Esf and the rear wheel standard fluid volume Esr) is determined based on the front wheel target pressure Ptf, the rear wheel target pressure Ptr, and the front wheel conversion mappings Zef and Zer. Furthermore, the rotation angle Ka of the motor MA is controlled based on the standard fluid volume Es. Since the standard fluid volume Es is equivalent to the amount of fluid that the control cylinder CC should inject to achieve the front wheel target pressure Ptf and the rear wheel target pressure Ptr, the required amount of brake fluid BF is injected from the electric cylinder DN (especially the control cylinder CC).

[0152] The front wheel conversion mapping Zef and the rear wheel conversion mapping Zer are pre-stored in the controller EA (specifically, the microprocessor MP) as defined characteristics. However, errors occur in the conversion mappings Zef and Zer due to factors such as gases (air, etc.) present inside the braking device SX, and wear of friction components. In the braking control device SA, a correction value Kh is calculated to compensate for the errors in the conversion mappings Zef and Zer. Specifically, based on the front wheel conversion mapping Zef, the fluid quantity Eef (presumed front wheel fluid quantity) to be supplied to the front wheel cylinder CWf is calculated and inferred based on the regulating pressure Pb. Similarly, based on the rear wheel conversion mapping Zer, the fluid quantity Eer (presumed rear wheel fluid quantity) to be supplied to the rear wheel cylinder CWr is calculated and inferred based on the base pressure Pa. Furthermore, the actual fluid quantity Ej (ejected fluid quantity) ejected from the control cylinder CC is obtained through the detection value of the fluid quantity sensor. Here, the base pressure Pa (actual value) is obtained by a base pressure sensor (PA, etc.), and the regulating pressure Pb (actual value) is obtained by a regulating pressure sensor (PB, PM, etc.). Additionally, the actual ejected fluid volume Ej is obtained from a fluid volume sensor (KA, SN, etc.). Then, the sum of the inferred fluid volume Eef for the front wheels and the inferred fluid volume Eer for the rear wheels is calculated as the inferred fluid volume Ee. The correction value Kh is calculated based on the deviation hE (fluid volume deviation) between the inferred fluid volume Ee and the ejected fluid volume Ej. Furthermore, since the fluid volume deviation hE is a state quantity (physical quantity) converted to the dimension of the reference value Ks, a larger fluid volume deviation hE results in a larger correction value Kh.

[0153] As described above, the transformation maps Zef and Zer used to calculate the reference value Ks contain errors, but the correction value Kh characterizes the errors contained in the transformation maps Zef and Zer. In the brake control device SA, the reference value Ks is corrected by the correction value Kh to determine the target rotation angle Kt. As a result, the amount Ej (injected fluid volume) of brake fluid BF injected (discharged) by the electric cylinder DN (especially the control cylinder CC) is precisely adjusted relative to the target pressures Ptf and Ptr. Consequently, the pressure adjustment accuracy of the electric cylinder DN is improved.

[0154] In controller EA, the target valve current It is calculated based on the target differential pressure St calculated from the target front wheel pressure Ptf and the target rear wheel pressure Ptr, and controlled to ensure that the valve current Ic (actual value) supplied to the pressure regulating valve UC matches the target valve current It (target value). Furthermore, in controller EA, the actual differential pressure Sa is calculated based on the base pressure Pa and the regulating pressure Pb, and the deviation hS between the target differential pressure St and the actual differential pressure Sa is determined. Then, in controller EA, the target valve current It is adjusted to make the differential pressure deviation hS "0".

[0155] The pressure regulating valve UC adjusts the differential pressure Sa (actual differential pressure) 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, based on the supplied valve current Ic. In the brake 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 that should be generated by the pressure regulating valve UC). Furthermore, since there is an error in the adjustment of the actual differential pressure Sa, the target valve current It (resulting in the valve current Ic) is finely adjusted in the brake control device SA based on the differential pressure deviation hS (the deviation between the target differential pressure St and the actual differential pressure Sa). Therefore, the pressure regulation accuracy based on the pressure regulating valve UC is improved.

[0156] If the regulating pressure Pb is adjusted to match the front wheel cylinder pressure Paf with the front wheel target pressure Ptf, it will affect the base pressure Pa. However, since the base pressure Pa is adjusted based on the correction value Kh, the change in base pressure Pa caused by the change in regulating pressure Pb is compensated for each time. That is, even if the regulating pressure Pb changes, the base pressure Pa is adjusted to match the rear wheel cylinder pressure Pwr with the rear wheel target pressure Ptr.

[0157] As explained above, in the braking control device SA, which independently adjusts the wheel cylinder pressures Pwf and Pwr of the front and rear wheels (CWf and CWr) through dual-system pressure regulation, the motor MA and pressure regulating valve UC are appropriately controlled. This allows for high-precision adjustment of the base pressure Pa and the regulating pressure Pb within the dual-system pressure regulation. As a result, the vehicle's driving stability is improved while ensuring sufficient energy regeneration.

Claims

1. A braking control device for a vehicle, applied to a vehicle equipped with a regenerative braking device in the front wheels, the braking control device comprising: a control cylinder that generates a base pressure using an electric motor as a power source; a solenoid valve that adjusts the base pressure to a regulating pressure; and a controller that controls the electric motor and the solenoid valve to control the front wheel cylinder pressure of the front wheel cylinders via the regulating pressure, and to control the rear wheel cylinder pressure of the rear wheel cylinders via the base pressure. The controller calculates the required fluid volume to be supplied to the front and rear wheel cylinders based on the target pressures of the front and rear wheels, using these as the standard fluid volumes for the front and rear wheels. It then controls the motor based on these standard fluid volumes and controls the solenoid valve based on the target pressures of the front and rear wheels. The aforementioned target pressure for the front wheel and target pressure for the rear wheel are the target values ​​for the front wheel cylinder pressure and the rear wheel cylinder pressure, respectively.

2. The vehicle braking control device according to claim 1, wherein, The controller acquires the amount of liquid ejected from the control cylinder, calculates and estimates the amount of liquid based on the base pressure and the regulating pressure, and controls the rotation angle of the motor based on the deviation between the amount of liquid ejected and the estimated amount of liquid.

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

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