Brake control device for a vehicle

Abstract

A brake control device of a vehicle is provided with a control cylinder into which a control piston is inserted, a servo pressure is generated by moving the control piston using an electric motor, a servo pressure sensor that detects the servo pressure, and a controller that controls the electric motor based on the servo pressure, the brake control device of the vehicle adjusts a wheel pressure of a wheel cylinder by the servo pressure. Also, the controller acquires an amount of discharged fluid from the control cylinder, calculates an estimated amount of fluid based on the servo pressure and a conversion map, and controls the electric motor based on a deviation between the amount of discharged fluid and the estimated amount of fluid. For example, the controller calculates a target pressure based on a brake request amount, calculates a standard amount of fluid based on the target pressure and the conversion map, and controls a rotation angle of the electric motor based on the standard amount of fluid and the deviation.

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 1 that, in order to enable the driver to recognize the change in load fluid loss characteristics by changing the braking force corresponding to the amount of brake pedal operation, when the load fluid loss characteristics change, includes: a motor drive cylinder 13; wheel cylinders 2b and 3b; a stroke sensor 11a for detecting the amount of brake pedal operation Ps; a target value setting circuit 33 for setting the target stroke St of the motor drive cylinder 13 according to the amount of brake pedal operation Ps; and a hydraulic compensation circuit 38 for correcting the target stroke St in the direction of reducing the deviation when a deviation occurs between the standard value Bo of the brake hydraulic pressure corresponding to the amount of brake pedal operation Ps and the actual brake hydraulic pressure B. The vehicle braking device 1 also includes a stroke limiting circuit 51 for suppressing the compensation value ΔB of the hydraulic compensation circuit 38 based on the amount of brake pedal operation Ps.

[0003] However, in the device of Patent Document 1, the target value setting circuit 33 uses a mapping diagram or the like to determine the target stroke St of the motor drive cylinder 13 corresponding to the corrected brake hydraulic pressure Bt. Here, the conversion mapping diagram from hydraulic pressure to electric cylinder stroke (i.e., the amount of brake fluid discharged from the electric cylinder) represents the relationship between the hydraulic pressure of the wheel cylinder and the amount of brake fluid (working fluid) supplied to the wheel cylinder. This relationship is called the "hydraulic-fluid volume characteristic". The hydraulic-fluid volume characteristic is basically determined by the rigidity of the brake caliper, friction components, etc., but it includes errors such as deviation and aging. These errors are caused by the presence or absence of gas in the device, wear of friction components, etc.

[0004] Patent Document 1: International Publication No. 2012 / 086162 Summary of the Invention

[0005] In view of the above-mentioned problems, the object of the present invention is to provide a technique that can compensate for errors in the conversion mapping diagram representing hydraulic-fluid volume characteristics in a braking control device of a vehicle in which hydraulic pressure is regulated by an electric motor.

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

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

[0008] Although errors are present in the conversion maps Zef, Zer, and Zek representing hydraulic-fluid volume characteristics, these errors can be appropriately compensated for based on the above configuration. Therefore, the volume of brake fluid BF discharged from the control cylinder CC is adjusted so that it is neither excessive nor insufficient relative to the target pressure Pt, thus improving the pressure regulation accuracy of the control cylinder CC (i.e., the electric cylinder DN) driven by the electric motor MA. Attached Figure Description

[0009] Figure 1 This is a schematic diagram illustrating a first embodiment of a vehicle's braking control device SA.

[0010] Figure 2 This is a flowchart used to illustrate the voltage regulation control process.

[0011] Figure 3 This is a block diagram used to illustrate the drive control of the electric cylinder DN.

[0012] Figure 4 This is a schematic diagram illustrating a second embodiment of the vehicle's braking control device SA. Detailed Implementation

[0013] <Symbols of constituent parts, etc., and the superscripts at the end of the symbols>

[0014] In the following description, components, processing units, signals, characteristics, and values ​​with the same symbol, such as "CW," have the same function. The subscripts "f" and "r" appended to the end of each wheel's symbol are general symbols indicating which system it relates to for the front or rear wheels. For example, in the wheel cylinder CW installed on each wheel, it is expressed as "front wheel cylinder CWf, rear wheel cylinder CWr." Furthermore, the subscripts "f" and "r" at the end of the symbol can be omitted. When the subscripts "f" and "r" are omitted, each symbol represents its general term. For example, "CW" is the general term for the wheel cylinders installed on the front and rear wheels of a vehicle. Additionally, "CW" as a general term is also expressed as "CW (=CWf, CWr)."

[0015] The brake control unit SA, hydraulic correction unit SZ, and wheel cylinder CW are connected via a fluid path (connection path HS). Furthermore, various components (CC, etc.) within the brake control unit SA and hydraulic correction unit SZ 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 actuators, hoses, etc. In the following description, connection path HS, reservoir path HR, input path HN, servo path HU, and replenishment path HH are fluid paths.

[0016] <First Embodiment of Braking Control Device SA>

[0017] Reference Figure 1 The diagram illustrates a first embodiment of a vehicle's braking control device SA. The braking control device SA is applied, for example, to hybrid vehicles or electric vehicles equipped with an electric motor for driving.

[0018] 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., a brake disc). A wheel cylinder CW is located within the brake caliper (not shown). Hydraulic pressure Pw (referred to as "wheel pressure") within the wheel cylinder CW presses the friction components (not shown) against the rotating component KT fixed to each wheel WH, thereby 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 described as a "device that generates frictional braking force Fe through wheel pressure Pw," or a "device that converts wheel pressure Pw into frictional braking force Fe."

[0019] The vehicle is equipped with a regenerative braking device KG. The regenerative braking device KG consists of a generator GN (“electric motor / generator,” or, also called a “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 is also the electric motor for driving. During regenerative braking, the electric 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, a 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, a 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.

[0020] 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 the "relative distance," or "inter-vehicle distance" if the object is a preceding vehicle) up to an object present in front of the vehicle. For example, a radar sensor, millimeter-wave sensor, or image sensor can be used as the object detection sensor SJ. In the driving assistance controller EJ, based on the detection result Sj (relative distance) from the object detection sensor SJ, the target acceleration Gs (the target value of the vehicle's acceleration in the longitudinal direction) is calculated. The driving assistance device KJ (especially the driving assistance controller EJ) is connected to a communication bus BS. The target acceleration Gs is transmitted to the braking control device SA via the communication bus BS. In the braking control device SA, the braking forces Fg and Fe are adjusted according to the target acceleration Gs. The result is the control of the vehicle's speed Vx (vehicle speed).

[0021] 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 an operating component used by the driver to decelerate the vehicle. The vehicle is equipped with an operating displacement sensor SP that detects 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 operating amount of the brake operating component BP. In a brake control device SA of the in-line control type, it is a signal indicating the driver's braking intention (i.e., brake indication). In addition to the operating displacement sensor SP, the hydraulic pressure Pn (called "input pressure") of the input chamber Rn (described later) is also used as another state quantity to indicate the braking operation amount. 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 operating displacement sensor SP and the input pressure sensor PN that detect the operating displacement Sp and input pressure Pn (i.e., brake operation amount Ba) are referred to as "brake operation amount sensor BA".

[0022] The vehicle is equipped with various sensors for braking control, such as anti-lock braking and anti-skid control (i.e., individual control of each wheel pressure Pw). Specifically, each wheel WH is equipped with a wheel speed sensor VW that detects its rotational speed Vw (referred to as "wheel speed"). In addition, there are steering input sensors that detect the steering input Sw (e.g., steering angle) of steering operation components (e.g., steering wheel), yaw rate sensors that detect the vehicle's yaw rate Yr, front and rear acceleration sensors that detect the vehicle's front and rear acceleration Gx (also referred to as "deceleration"), and lateral acceleration sensors that detect the vehicle's lateral acceleration Gy (the above structures are not shown).

[0023] The vehicle is equipped with a brake control unit SA. The brake control unit SA employs a dual-system braking system, also known as a front-rear type (or "Type II") system. The brake control unit SA adjusts the wheel pressure Pw of each wheel cylinder CW.

[0024] 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.

[0025] <Composition of Braking Control Device SA>

[0026] The configuration of the brake control device SA according to the first embodiment will be described. The brake control device SA generates a servo pressure Pa based on the operation of the brake operating component BP (brake pedal). Then, the brake control device SA outputs a supply pressure Pm and a servo pressure Pa to the hydraulic correction device SZ. In the hydraulic correction device SZ, the supply pressure Pm and the servo pressure Pa are adjusted, ultimately supplying the front wheel and rear wheel cylinders CWf and CWr with wheel pressures Pwf and Pwr, respectively. The brake control device SA consists of a brake actuator YA and a brake controller EA.

[0027] <<Brake Actuator YA>>

[0028] The brake actuator YA consists of a hydraulic generation unit PU, a running unit AP, and an input unit NR.

[0029] [Hydraulic generation unit PU]

[0030] The hydraulic generating unit PU uses an electric motor MA as its power source to generate servo pressure Pa. The hydraulic generating unit PU is also known as the "electric cylinder DN". The electric cylinder DN includes an electric motor MA, a rotation angle sensor KA, a reducer GS, a conversion mechanism GH, a control cylinder CC, and a control piston NC.

[0031] The electric motor MA is a power source (pressurization source) used to generate servo 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, as a physical quantity, is defined as the energy per unit time (also called "power"). Rotational power (also called "first rotational power") is output from the electric motor MA. The rotational power of the electric motor MA is obtained by multiplying the shaft torque of the electric motor MA by the rotational speed of the electric motor MA (specifically, the motor shaft). Furthermore, 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 central axis).

[0032] The electric motor MA is a three-phase brushless motor. The electric motor MA includes a motor coil, a motor shaft, and a rotation angle sensor KA. The motor coil is fixed to the motor housing. Power is supplied to the motor coil from the controller EA (specifically the drive circuit DR). The motor shaft is rotatably supported on the motor housing. A permanent magnet is fixed to the outer circumference of the motor shaft. In the three-phase brushless motor MA, the rotation angle sensor KA (also equivalent to a "fluid level sensor") detects the magnetic pole position of the permanent magnet (i.e., the motor rotation angle Ka). Then, based on the rotation angle Ka of the motor shaft, the three-phase motor current Im (the total current flowing through the U, V, and W phases) is switched.

[0033] Specifically, the rotation angle Ka (also equivalent to "discharge 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 known as the "inverter circuit") are driven according to the rotation angle Ka. This switches the motor current Im flowing through the motor coil, driving the electric motor MA. Then, the electric motor MA outputs the first rotational power to the reducer GS.

[0034] The first rotational power output from the electric motor MA is reduced by a speed reducer GS. Specifically, the input shaft of the speed reducer GS is fixed to the motor shaft. Furthermore, the output shaft of the speed reducer GS is fixed to the rotating component of the conversion mechanism GH. In the speed reducer GS, the speed input from the electric motor MA is reduced, and the torque input from the electric motor MA is increased. Then, the reduced rotational power (also called the "second rotational power") is output from the speed reducer GS to the conversion mechanism GH.

[0035] 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 rotary power output from the reducer GS is input to the rotating component. Then, the rotary power input to the rotating component is converted into the linear power of the linear component. The conversion mechanism GH is also called a "rotation / linear conversion mechanism". An anti-rotation component engages with the linear component. As a result, the rotational motion of the linear component is stopped, and therefore the linear component moves along the rotation axis of the rotating component.

[0036] For example, the conversion mechanism GH employs a ball screw. Specifically, in the 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. Ball screw grooves are formed on the outer circumferential surface of the rotating component. Similarly, ball screw grooves are also formed on the inner circumferential surface of the linearly moving component. Multiple balls (steel balls) are embedded in the ball screw grooves.

[0037] 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, a control chamber Rc (hydraulic chamber) is formed by the control piston NC. 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. This makes the control chamber Rc hydraulically sealed. The hydraulic pressure of the control cylinder CC (i.e., the control chamber Rc) is a servo pressure Pa. That is, in the electric cylinder DN, the electric motor MA is used as the power source, outputting a servo pressure Pa.

[0038] The control cylinder CC is connected to the servo chamber Ru (described later) of the operating unit AP via the servo circuit HU (fluid circuit). Furthermore, the control cylinder CC is connected to the rear wheel cylinder CWr via the rear wheel connection circuit HSr (fluid circuit) and the hydraulic correction device SZ. A servo pressure sensor PA is installed in the hydraulic generation unit PU to detect the servo pressure Pa (the hydraulic pressure generated by the electric cylinder DN).

[0039] exist Figure 1 The diagram illustrates the state where the electric cylinder DN has not generated the servo pressure Pa. A through-hole is provided between the two sealing components SL in the control cylinder CC. Additionally, a through-hole is provided in the control piston NC. A supply path HH (fluid path) connecting to the main reservoir RV is connected to the through-hole of the control cylinder CC. In the illustrated state, the control chamber Rc is connected to the main reservoir RV via the through-hole and supply path HH, and the servo 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, while the volume of the control chamber Rc is at its maximum.

[0040] When an increase in servo pressure Pa is required, the rotational power of the electric motor MA is increased. This rotational power is transmitted to the conversion mechanism GH via the reducer GS and output as linear power to the direct-acting component. Then, the control piston NC is pressed by the direct-acting component, causing the control piston NC to move in the forward direction Ha (the direction in which the volume of the control chamber Rc decreases). This movement first disconnects the connection between the control chamber Rc and the main reservoir RV. If the control piston NC moves further in the forward direction Ha, the servo pressure Pa (the internal pressure of the control chamber Rc) increases from "0 (atmospheric pressure)". The brake fluid BF, pressurized to the servo pressure Pa, is output (pressurized) from the control chamber Rc of the control cylinder CC.

[0041] When maintaining the servo pressure Pa is necessary, the rotation of the electric motor MA is stopped. The movement of the control piston NC is stopped, maintaining the servo pressure Pa at a constant level. When a reduction in servo pressure Pa is needed, the rotational power of the electric motor MA is reduced. Due to the servo pressure Pa, the electric motor MA rotates in the reverse direction, thus the control piston NC moves backward in the direction Hb (the direction in which the volume of the control chamber Rc increases). Because the brake fluid BF returns towards the control chamber Rc, the servo pressure Pa decreases.

[0042] [Running Unit AP]

[0043] The operating unit AP consists of a single-cylinder master cylinder CM and a master piston NM. The master piston NM is inserted into the single-cylinder master cylinder CM. The interior of the master cylinder CM is divided into three hydraulic chambers Rm, Ru, and Rs by the master piston NM. The master cylinder CM and the master piston NM form the main chamber Rm. In addition, the interior of the master cylinder CM is divided into a servo chamber Ru and a reaction chamber Rs by the flange Tu of the master 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.

[0044] The hydraulic generating unit PU (electric cylinder DN) supplies servo pressure Pa to the servo chamber Ru. Through the servo pressure Pa, the operating unit AP outputs supply pressure Pm. Here, "supply pressure Pm" is the internal pressure of the main chamber Rm, also known as "main pressure". When "Pa=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)".

[0045] Brake fluid BF is stored inside the main reservoir RV (also known as the "atmospheric reservoir"). If the servo pressure Pa increases from "0", the master piston NM moves in the forward direction Da (the direction in which the volume of the master chamber Rm decreases). This movement disconnects the main chamber Rm from the main reservoir RV. Then, if the master piston NM moves further in the forward direction Da, the supply pressure Pm (main pressure) increases from "0 (atmospheric pressure)". Thus, brake fluid BF, pressurized to the supply pressure Pm, is output (pressurized) from the master cylinder CM's 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 "Pa=Pm".

[0046] [Input Unit NR]

[0047] Regenerative coordinated control is achieved through the input unit NR. "Regenerative coordinated control" aims to efficiently recover the vehicle's kinetic energy into electrical energy during braking, coordinating the friction braking force Fe (braking force based on wheel pressure Pw) and the regenerative braking force Fg (braking force based on the regenerative device KG). In regenerative coordinated control, a state occurs where the braking actuation component BP is operated, but wheel pressure Pw is not generated. 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.

[0048] Input cylinder CN is fixed to master cylinder CM. Input piston NN is inserted into input cylinder CN. Input piston NN is mechanically connected to brake operating component BP to coordinate with the action of brake operating component BP (brake pedal). There is a gap Ln (also called "separation distance") between the end face of input piston NN and the end face of master piston NM. Regenerative coordinated control is achieved by adjusting the separation distance Ln using servo pressure Pa.

[0049] The input chamber Rn of the input unit NR is connected to the reaction chamber Rs of the operating unit AP via the input path HN (fluid path). A normally closed first control valve VA is installed in the input path HN. Between the first control valve VA and the reaction chamber Rs, the input path HN is connected to the main reservoir RV via the reservoir path HR (fluid path). A normally open second control valve VB is installed in the reservoir path HR. The first and second control valves VA and 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.

[0050] When no power is supplied to the first and second control valves VA and VB, the first control valve VA is closed, and the second control valve VB is open. The closure of the first control valve VA seals the input chamber Rn, achieving fluid locking. This causes the main piston NM to move integrally with the braking operating component BP. Furthermore, the opening of the second control valve VB connects the stroke simulator SS and the reaction chamber Rs to the main reservoir RV.

[0051] When power is supplied to the first and second control valves VA and VB, the first control valve VA opens and the second control valve VB closes. This allows the main piston NM to move independently of the braking actuation component BP. At this time, the input chamber Rn is connected to the stroke simulator SS, so the operating force of the braking actuation component BP is generated through 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.

[0052] <<Brake Controller EA>>

[0053] 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 so that it can share signals (detected values, calculated values, control flags, etc.) with other controllers (EZ, EG, EJ, etc.).

[0054] The brake controller EA directly inputs various signals, including the operating displacement Sp (detected by the operating displacement sensor SP), input pressure Pn (detected by the input pressure sensor PN), servo pressure Pa (detected by the servo pressure sensor PA), and motor rotation angle Ka (detected by the rotation angle sensor KA). Additionally, it inputs various signals to the controller EA from the communication bus BS, such as the supply pressure Pm, standard regenerative braking force Fz, vehicle speed Vx, and target acceleration Gs. Furthermore, 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, in the regenerative controller EG, the actual regenerative braking force Fg is controlled based on the target regenerative braking force Fh (target value) obtained from the communication bus BS.

[0055] In the brake controller EA (especially the microprocessor MP), a voltage regulation control algorithm is programmed. "Voltage regulation control" is used to regulate the wheel pressure Pw (=Pwf, Pwr), including regenerative coordination control. Voltage regulation control is performed based on the various signals mentioned above (Sp, Pa, etc.). Based on the voltage regulation control algorithm, the electric motor MA and various solenoid valves (VA, etc.) are driven by the drive circuit DR. An inverter circuit is constructed in the drive circuit DR using switching elements (e.g., MOS-FETs) to drive the electric motor MA. Furthermore, the drive circuit DR is equipped with switching elements to drive various solenoid valves. Additionally, the drive circuit DR includes a motor current sensor (not shown) that detects the supply current Im (motor current) to the electric motor MA. A rotation angle sensor KA is provided in the electric motor MA to detect the position Ka (rotation angle) of the motor shaft.

[0056] In the brake controller EA, the drive signals Va and Vb of the first and second control valves VA and VB, and the drive signal Ma of the electric motor MA, are calculated. Then, the aforementioned switching elements are driven according to the various drive signals (Ma, etc.). Specifically, in the control of the solenoid valves, power is supplied to the first and second control valves VA and VB based on the drive signals Va and Vb. This opens the first control valve VA and closes the second control valve VB. Furthermore, the drive signal Ma is determined based on a pressure regulation control algorithm, and the electric motor MA is controlled based on the drive signal Ma.

[0057] <Hydraulic Correction Device SZ>

[0058] 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 connection 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 connection circuit HSr), the servo 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 servo pressure Pa, and outputs the hydraulic pressures Pwf and Pwr (front and rear wheel pressures) for the front and rear wheel cylinders CWf and CWr, respectively.

[0059] The hydraulic correction device SZ consists of a correction actuator YZ and a correction controller EZ. Since the configuration of the correction actuator YZ is well-known, its description is omitted. A supply pressure sensor PM is installed in the correction actuator YZ to detect the supply pressure Pm. The servo pressure Pa is transmitted as the supply pressure Pm via the main piston NM. Therefore, the supply pressure Pm is equivalent to the servo pressure Pa, and the supply pressure sensor PM is equivalent to the servo pressure sensor PA. In other words, the supply pressure Pm is an example of the servo pressure Pa, and the supply pressure sensor PM is an example of the servo pressure sensor PA.

[0060] When regenerative coordinated control is executed, the operation of the correction actuator YZ is stopped. Therefore, during the execution of regenerative coordinated control, the servo pressure Pa is transmitted to the front wheel cylinder CWf as the front wheel pressure Pwf via the supply pressure Pm, and on the other hand, it is directly transmitted to the rear wheel cylinder CWr as the rear wheel pressure Pwr. That is, in the front wheel braking system, "Pa=Pm=Pwf", and in the rear wheel braking system, "Pa=Pwr".

[0061] The correction controller EZ is connected to the brake controller EA via the communication bus BS. The correction controller EZ receives the wheel speed Vw detected by the wheel speed sensor VW and the supply pressure Pm detected by the supply pressure sensor PM. Furthermore, the correction controller EZ calculates the vehicle speed Vx (vehicle body speed) based on the wheel speed Vw. The vehicle speed Vx and the supply pressure Pm are then transmitted to the brake controller EA via the communication bus BS.

[0062] <Processing of Voltage Regulation Control>

[0063] Reference Figure 2 The flowchart illustrates an example of voltage regulation control. In voltage regulation control, regenerative coordination control is performed between the regenerative braking device KG and the braking control device SA. In regenerative coordination control, adjustments are made to coordinate the regenerative braking force Fg with the frictional braking force Fe, thereby achieving a total braking force Fu corresponding to the required braking force Bs.

[0064] <<Various Braking Forces>>

[0065] The various braking forces described in the pressure regulation control instructions are as follows.

[0066] - "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".

[0067] - "Frictional braking force Fe (hydraulic braking force)" is the actual braking force generated by the wheel pressure Pw. The target value corresponding to frictional braking force Fe is "target frictional braking force Fn".

[0068] - "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 generator GN is controlled by the regenerative controller EG to make the actual regenerative braking force Fg close to and consistent with the target regenerative braking force Fh.

[0069] - "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. In addition, 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).

[0070] <<Various Hydraulics>>

[0071] The various hydraulic systems described in the pressure regulation control instructions are as follows.

[0072] - "Servo pressure Pa" is the output of the electric cylinder DN (i.e., the internal pressure of the control chamber Rc). The servo pressure Pa is detected (acquired) by the servo pressure sensor PA.

[0073] - "Target pressure Pt" is equivalent to the target value used to control the servo pressure Pa (actual value).

[0074] 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 throttling orifice acting as a solenoid valve, and sliding resistance of the sealing component SL. In feedback control involving hydraulics, control is performed to make the actual value match the target value; however, considering the aforementioned resistances, it is desirable 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 target pressure Pt is determined to correspond to the wheel pressure Pw. Furthermore, based on the servo pressure Pa (the detected value of the servo pressure sensor PA), the wheel pressure Pw (actual value) is determined by compensating for the hydraulic pressure equivalent to the aforementioned resistances.

[0075] In pressure regulation control, power is first supplied to the first and second control valves VA and VB. The normally closed first control valve VA is opened, and the normally open second control valve VB is closed. This allows the main piston NM and the brake operating component BP to move independently, thus enabling the adjustment of the front and rear wheel pressures Pwf and Pwr 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.

[0076] In step S110, various signals are read by the brake controller EA. The brake controller EA acquires the braking operation quantity Ba (a collective term for Sp and Pn), target acceleration Gs, servo pressure Pa, and standard regenerative braking force Fz. The braking operation quantity Ba and target acceleration Gs are collectively referred to as the "braking requirement quantity Bs." The braking requirement quantity Bs is a state quantity representing the braking requirement for the vehicle. The servo pressure Pa is acquired through at least one of the servo pressure sensor PA and the supply pressure sensor PM. The standard regenerative braking force Fz is determined by the regenerative device KG (specifically, the regenerative controller EG) and received by the brake controller EA via the communication bus BS.

[0077] 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 requirement Bs and the calculation mapping Zfv. According to the calculation mapping Zfv, if the braking requirement Bs is less than a predetermined amount bo, the target total braking force Fv is calculated as "0". Furthermore, if the braking requirement Bs is greater than or equal to the predetermined amount bo, the target total braking force Fv is calculated to increase from "0" as the braking requirement Bs increases. Here, the "predetermined amount bo" is preset to a predetermined value (constant) (refer to the target total braking force calculation block FV above).

[0078] In step S130, the target pressure Pt is calculated based on the target total braking force Fv and the standard regenerative braking force Fz to perform regenerative coordinated control. "Target pressure Pt" is the target value of the wheel pressure Pw, which is the target value used to control the servo pressure Pa. In step S130, the sum Fnt (also called "target sum") of the target regenerative braking force Fh and the target friction braking force Fn is first calculated. Here, "target sum Fnt" is the sum of the front wheel target friction braking force Fnf and the rear wheel target friction braking force Fnr (i.e., "Fnt = Fnf + Fnr"). Then, the target pressure Pt is determined based on the following two cases.

[0079] Case (1): When the target total braking force Fv is less than the standard regenerative braking force Fz, the target regenerative braking force Fh is made equal to the target total braking force Fv, and the sum of the target friction braking forces Fn, Fnt (target sum), is "0". That is, in the case of "Fv≤Fz", it is determined that "Fh=Fv, Fnt=0".

[0080] Case (2): When the target total braking force Fv is greater than the standard regenerative braking force Fz, the target regenerative braking force Fh is made equal to the standard regenerative braking force Fz, and the target total Fnt is "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 "Fv>Fz", it is determined that "Fh=Fz, Fnt=Fv-Fh=Fv-Fz".

[0081] Next, the target pressure Pt is calculated based on the target sum Fnt. Specifically, the target pressure Pt is determined based on the specifications of the braking device SX (=SXf, SXr) to satisfy the target sum Fnt. That is, in the case of "Fv≤Fz" (1), the target pressure Pt is determined to be "0". In contrast, in the case of "Fv>Fz" (2), the target pressure Pt is determined by the fact that the total Fnt (target sum) of the target friction braking force Fn is equal to the value "Fv-Fh". Here, the "specifications of the braking device SX" include the pressure 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.

[0082] In step S140, the electric motor MA is controlled based on the target pressure Pt. Specifically, the resistance on the hydraulic transmission path (such as the sliding resistance of the sealing component SL) is first considered, and the wheel pressure Pw is calculated based on the servo pressure Pa. Here, the servo pressure Pa is obtained by at least one of the servo pressure sensor PA and the supply pressure sensor PM. Then, the servo pressure Pa is controlled by driving the electric cylinder DN (especially the electric motor MA) so that the wheel pressure Pw (the calculated actual value) approaches and matches the target pressure Pt (the target value).

[0083] <Drive Control of Electric Cylinder DN>

[0084] Reference Figure 3 The block diagram illustrates the details of the drive control of the electric cylinder DN (i.e., the processing in step S140). The electric cylinder DN (especially the electric motor MA) is controlled based on the target pressure Pt, servo pressure Pa, and motor rotation angle Ka. The drive control of the electric motor MA consists of a wheel pressure calculation block PW, a hydraulic / fluid quantity conversion block ZE, a discharge fluid quantity calculation block EJ, a reference value calculation block KS, a correction value calculation block KH, a target rotation angle calculation block KT, and a rotation angle feedback control block KF.

[0085] In the wheel pressure calculation block PW, the wheel pressure Pw is calculated based on the servo pressure Pa. As mentioned above, the target pressure Pt is determined to correspond to the wheel pressure Pw. Therefore, the wheel pressure Pw is determined based on the resistance in the hydraulic transmission path and the servo pressure Pa.

[0086] In the hydraulic / fluid volume conversion block ZE, the conversion (conversion) from hydraulic pressure to fluid volume is performed. "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 fluid volume conversion block ZE contains front-wheel and rear-wheel conversion maps Zef and Zer (equivalent to "conversion maps"). These conversion maps Zef and Zer represent 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 and rear-wheel conversion maps Zef and Zer are pre-determined through experiments and analysis and stored in the controller EA.

[0087] In the hydraulic-fluid quantity characteristic (the nonlinear characteristic of wheel pressure Pw), when the wheel pressure Pw is small, a larger amount of fluid is required to generate that wheel pressure Pw compared to when the wheel pressure Pw is large. Conversely, when the wheel pressure Pw is large, a smaller amount of fluid can generate the wheel pressure Pw compared to when the wheel pressure Pw is small. That is, in the hydraulic-fluid quantity characteristic, the fluid quantity increases with an increase in wheel pressure Pw in an "upward" manner. The nonlinearity of the hydraulic-fluid quantity characteristic is based on the fact that the rigidity characteristics (e.g., the rigidity of brake calipers, friction components, etc.) in the braking system SX (=SXf, SXr) are nonlinear. Since the rigidity characteristics are different in the front wheel braking system SXf and the rear wheel braking system SXr, separate front wheel and rear wheel conversion mapping diagrams Zef and Zer are set.

[0088] The hydraulic / fluid quantity conversion block ZE contains a standard fluid quantity calculation block ES and an estimated fluid quantity calculation block EE. In the standard fluid quantity calculation block ES, the standard fluid quantity Es is calculated based on the target pressure Pt and the front wheel and rear wheel conversion mapping diagrams Zef and Zer. The "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.

[0089] In detail, within the standard fluid volume calculation block ES, the front wheel standard fluid volume Esf is calculated based on the target pressure Pt and the front wheel conversion 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 target pressure Pt. Similarly, within the standard fluid volume calculation block ES, the rear wheel standard fluid volume Esr is calculated based on the target pressure Pt and the rear wheel conversion mapping Zer. "Rear wheel standard fluid volume Esr" is the amount of fluid that should flow into the rear wheel cylinder CWr to achieve the target pressure Pt. Then, the front wheel standard fluid volume Esf and the rear wheel standard fluid volume Esr are added 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.

[0090] In the estimated fluid volume calculation block EE, the estimated fluid volume Ee is calculated based on the wheel pressure Pw and the front-wheel and rear-wheel conversion mappings Zef and Zer. "Estimated fluid volume Ee" refers to 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 wheel pressure Pw. Specifically, the estimated front wheel fluid volume Eef is calculated based on the wheel pressure Pw and the front wheel conversion mapping Zef (i.e., the hydraulic-fluid volume characteristics of the front wheel cylinder CWf). Similarly, the estimated rear wheel fluid volume Eer is calculated based on the rear wheel pressure Pw and the rear wheel conversion mapping Zer (i.e., the hydraulic-fluid volume characteristics of the rear wheel cylinder CWr). Then, the estimated front wheel fluid volume Eef and the estimated rear wheel fluid volume Eer are added 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 volume Eef for the front wheel and the estimated fluid volume Eer for the rear wheel, and is the inferred fluid volume flowing from the control cylinder CC into the wheel cylinder CW. Furthermore, since the wheel pressure Pw is derived from the servo pressure Pa, it can be said that "the estimated fluid volume Ee is calculated based on the servo pressure Pa and the front and rear wheel conversion mapping diagrams Zef and Zer".

[0091] In the discharge volume calculation block EJ, the discharge volume Ej is calculated based on the motor rotation angle Ka (actual value). "Discharge volume Ej" is the actual amount (volume) of brake fluid BF ejected (discharged) from the electric cylinder DN (i.e., control cylinder CC). In the discharge volume calculation block EJ, the rotation angle Ka is converted into the discharge volume Ej based on the specifications of the electric cylinder DN. 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.

[0092] In the discharge volume calculation block EJ, the discharge volume Ej (the volume of liquid discharged 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. Moreover, the discharge 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 discharge volume Ej from the control cylinder CC, they are collectively referred to as "liquid volume sensors". That is, in the discharge volume calculation block EJ, the discharge volume Ej is determined based on the detection results of the liquid volume sensors KA and SN.

[0093] In the reference value calculation block KS, the reference value Ks is determined based on the standard fluid volume Es (=Esf+Esr). The "reference value Ks" is a state variable used to determine the target value for controlling the electric motor MA. Specifically, the reference value Ks is a state variable converted from the standard fluid volume Es to a dimension (i.e., a physical quantity) from the standard fluid volume Es to the rotation angle of the electric motor MA. For example, the dimension (physical quantity) of the reference value Ks can be any one of the following: the dimension of the fluid volume, the dimension of the displacement of the control piston NC, or the dimension of the rotation angle of the electric motor MA. In the electric cylinder DN, the specifications of the constituent components are known. In the reference value calculation block KS, the standard fluid 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 reference value Ks is determined to be larger as the standard fluid volume Es increases.

[0094] In the correction value calculation block KH, the correction value Kh is calculated based on the estimated fluid volume Ee and the discharged fluid volume Ej. Although the front and rear wheel conversion mapping diagrams Zef and Zer are preset, they contain errors such as deviation and aging. These errors are caused by the presence or absence of gas inside the braking device SX, wear of friction components, etc. The "correction value Kh" is a state quantity (variable) used to compensate for these errors. In the correction value calculation block KH, the deviation hE (fluid volume deviation) between the estimated fluid volume Ee and the discharged fluid volume Ej is calculated. For example, the fluid volume deviation hE is determined by subtracting the estimated fluid volume Ee from the discharged fluid volume Ej (i.e., "hE = Ej - Ee"). Then, based on the specifications of the components of the electric cylinder DN, the fluid volume deviation hE is converted to the same dimension (physical quantity) as the reference value Ks to determine the correction value Kh. Therefore, the larger the determined fluid volume deviation hE, the larger the correction value Kh, and the smaller the determined fluid volume deviation hE, the smaller the correction value Kh.

[0095] In the target rotation angle calculation block KT, the target rotation angle Kt is calculated based on the reference value Ks and the correction value Kh. The "target rotation angle Kt" is the final target value of the rotation angle Ka used to control the electric motor MA. For example, adding the reference value Ks and the correction value Kh determines 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 the physical quantity of the reference value Ks and the correction value Kh.

[0096] The correction value Kh is a state variable used to make the wheel pressure Pw consistent with the target pressure Pt. In other words, the correction of the reference value Ks based on 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 hydraulics. This is based on "calculating the estimated fluid quantity Ee from the actual wheel pressure Pw" and "if the fluid quantity is optimized, the hydraulics are also optimized." In the brake control unit SA, through feedback control based on the correction value Kh, the servo pressure Pa is controlled so that the wheel pressure Pw approaches and matches the target pressure Pt.

[0097] In the target rotation angle calculation block 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 electric motor MA can be considered when determining the target rotation angle Kt. For example, a constraint is imposed on the response speed (i.e., the change per unit time) of the target rotation angle Kt using the response model of the electric motor MA. This is based on the assumption that even if a step-like change in the target rotation angle Kt is calculated, the electric motor MA cannot follow it. In any case, in the target rotation angle calculation block KT, the final target value, i.e., the target rotation angle Kt, is determined based on the reference value Ks and the correction value Kh.

[0098] In the rotation angle feedback control block KF, the electric motor MA is controlled based on the target rotation angle Kt and the actual motor rotation angle Ka. Specifically, the drive signal Ma of the electric motor MA is determined in a way that makes the motor rotation angle Ka (actual value) obtained by the rotation angle sensor KA close to and consistent with the target rotation angle Kt (target value) (i.e., so that the deviation hK between the target value Kt and the actual value Ka is close to "0"). Then, in the drive circuit DR (inverter circuit), the current Im (motor current) supplied to the electric motor MA is adjusted based on the motor drive signal Ma. That is, in the rotation angle feedback control block KF, so-called rotation angle feedback control is performed.

[0099] <<Variation Examples>>

[0100] In the above embodiment, in the standard fluid volume calculation block ES and the estimated fluid volume calculation block EE, a front wheel conversion mapping diagram Zef and a rear wheel conversion mapping diagram Zer are separately set as calculation mapping diagrams for converting hydraulic pressure into fluid volume. Furthermore, the standard fluid volume Esf of the front wheel and the standard fluid volume Esr of the rear wheel are calculated separately, and the estimated fluid volume Eef of the front wheel and the estimated fluid volume Eer of the rear wheel are determined separately. Alternatively, as the calculation mapping diagram for converting hydraulic pressure into fluid volume, a conversion mapping diagram Zek (also called an "integrated conversion mapping diagram") integrating the front and rear wheel conversion mapping diagrams Zef and Zer can be used (refer to the characteristics shown by the dashed line). The relationship between hydraulic pressure and fluid volume is also defined in the integrated conversion mapping diagram Zek. In the configuration using the integrated conversion mapping diagram Zek, the reference value Ks is determined based on the standard fluid volume Es calculated from the target pressure Pt and the integrated conversion mapping diagram Zek. Similarly, the correction value Kh is determined based on the estimated fluid volume Ee calculated from the servo pressure Pa (i.e., wheel pressure Pw) and the integrated conversion mapping diagram Zek. In addition, similar to the front and rear wheel transformation mappings Zef and Zer, the integrated transformation mapping Zek is obtained in advance through experiments and analysis.

[0101] <<Function / Effect>>

[0102] In the brake control unit SA, the rotation angle Ka of the electric motor MA is converted into the displacement of the control piston NC via the conversion mechanism GH. A volume of brake fluid (BF) corresponding to the displacement of the control piston NC is discharged from the control cylinder CC to the wheel cylinder CW. Furthermore, the wheel pressure Pw is determined by the volume of fluid flowing into the wheel cylinder CW based on the hydraulic-fluid volume characteristics of the wheel cylinder CW. Since the hydraulic-fluid volume characteristics refer to the volume of fluid consumed in the wheel cylinder CW to generate the wheel pressure Pw, it is also called the "fluid consumption characteristic."

[0103] In the brake control unit SA, the target rotation angle Kt is determined based on the standard fluid volume Es calculated according to the target pressure Pt. Then, the electric motor MA is controlled so that the actual rotation angle Ka matches the target rotation angle Kt. Thus, in order to achieve the target pressure Pt, an appropriate amount of brake fluid BF is discharged from the electric cylinder DN (especially the control cylinder CC).

[0104] As hydraulic-fluid volume characteristics (fluid consumption characteristics), the conversion mappings Zef, Zer, and Zek pre-stored in the brake controller EA (especially the microprocessor MP) contain errors caused by the presence of gas (air, etc.) 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, when wear of friction components is significant, the same hydraulic pressure can be achieved with less fluid compared to when wear is minimal.

[0105] In the brake control unit SA, a correction value Kh is determined to compensate for errors in the conversion maps Zef, Zer, and Zek. The correction value Kh is determined based on the estimated fluid volume Ee (presumably the fluid volume flowing into the wheel cylinder CW) calculated from the servo pressure Pa and the actual fluid volume Ej (discharge volume) discharged from the control cylinder CC. Here, the discharge volume Ej is obtained from fluid volume sensors (KA, SN, etc.). The calculation of the estimated fluid volume Ee uses the same conversion maps Zef, Zer, and Zek as the calculation of the standard fluid volume Es. Therefore, the correction value Kh, based on the deviation hE between the estimated fluid volume Ee and the discharge volume Ej, shows the error included in the conversion maps Zef, Zer, and Zek. 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 can be corrected.

[0106] The liquid volume deviation hE is determined by subtracting the estimated liquid volume Ee from the discharged liquid volume Ej (i.e., "hE = Ej - Ee"). When the discharged liquid volume Ej is greater than the estimated liquid volume Ee (i.e., when "Ej > Ee, hE > 0"), the conversion maps Zef, Zer, Ze deviate from the true value in a way that shrinks in the direction of the vertical axis (the axis of hydraulic pressure). That is, in the conversion maps Zef, Zer, Zek, at the same hydraulic pressure, the liquid volume is determined to be smaller than the true value. Therefore, by adding the correction value Kh calculated based on the liquid volume deviation hE to the reference value Ks calculated based on the standard liquid volume Es, the target rotation angle Kt is corrected to increase. In contrast, when the discharged liquid volume Ej is smaller than the estimated liquid volume Ee (i.e., when "Ej < Ee, hE < 0"), the conversion maps Zef, Zer, Zek deviate from the true value in a way that expands in the direction of the vertical axis (the axis of hydraulic pressure). That is, in the conversion maps Zef, Zer, Zek, at the same hydraulic pressure, the liquid volume is determined to be larger than the true value. Therefore, the target rotation angle Kt is corrected to decrease by the correction value Kh calculated based on the liquid volume deviation hE. In addition, the correction value Kh includes positive and negative signs and is determined to be larger as the liquid volume deviation hE becomes larger. Through the correction based on the liquid volume deviation hE, the amount Ej (discharged liquid volume) of the brake fluid BF discharged from the electric cylinder DN (especially the control cylinder CC) is adjusted so as not to be excessive or insufficient with respect to the target pressure Pt. As a result, the servo pressure Pa is adjusted with high precision by the electric cylinder DN so that the wheel pressure Pw coincides with the target pressure Pt.

[0107] <Second Embodiment of the Brake Control Device SA>

[0108] Refer to Figure 4 the schematic diagram to describe the second embodiment of the brake control device SA for a vehicle. In the second embodiment, the electric motor MA of the electric cylinder DN is also controlled by the same method as in the first embodiment.

[0109] In the first embodiment, the servo pressure Pa is transmitted as the supply pressure Pm via the master cylinder CM and the master piston NM. That is, on the hydraulic pressure transmission path, the operation unit AP and the hydraulic pressure generation unit PU are arranged in series. Instead of this configuration, the operation unit AP and the hydraulic pressure generation unit PU can be arranged in parallel. In the second embodiment, the operation unit AP (especially the master cylinder CM) and the hydraulic pressure generation unit PU are directly connected to the hydraulic pressure correction device SZ (especially the correction actuator YZ) respectively.

[0110] Specifically, in the braking control device SA according to 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 on the front wheel connection line HSf, which connects the master cylinder CM (particularly the master chamber Rm) to the front wheel cylinder CWf. The stroke simulator SS is connected to the front wheel connection line HSf between the master cylinder CM and the shut-off valve VM via the simulator valve VS.

[0111] The front and rear wheel connection lines HSf and HSR (fluid lines connecting the front and rear wheel cylinders CWf and CWr) are connected to the control cylinder CC (especially the control chamber Rc) via the connecting line HV (fluid line). The connecting line HV is also the fluid line connecting the front wheel connection line HSf and the rear wheel connection line HSr. A connecting valve VC is installed in the connecting line HV.

[0112] 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, supplying servo pressure Pa 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 through the stroke simulator SS. The servo pressure sensor PA can be located either in the hydraulic generation unit PU or in the correction actuator YZ. In the configuration where the servo pressure sensor PA is located in the correction actuator YZ, the servo pressure Pa is obtained from the brake controller EA via the communication bus BS.

[0113] In the second embodiment, the same regeneration coordination control as in the first embodiment is also performed, achieving the same effect (error compensation for the conversion map of hydraulic-fluid volume characteristics).

[0114] <Other implementations of the brake control device SA, etc.>

[0115] Other embodiments of the brake control device SA equipped with an electric cylinder DN will be described. The same effects described above are achieved in these other embodiments.

[0116] In the aforementioned embodiment of the brake control device SA, the servo pressure Pa is obtained based on the detection result of the servo pressure sensor PA, which is installed at the discharge section of the electric cylinder DN. Alternatively, the servo pressure sensor PA can be installed along the hydraulic transmission path from the control cylinder CC to the wheel cylinder CW (for example, referring to the supply pressure sensor PM). In either case, the servo pressure Pa used for estimating the fluid volume Ee is based on the actual value detected by the servo pressure sensor PA.

[0117] In the aforementioned embodiment of the brake control device SA, the discharge 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 discharge fluid volume Ej is calculated based on the motor rotation angle Ka and the displacement Sn of the control piston NC obtained from the piston stroke Sn, etc. Alternatively, a flow sensor can be provided to detect the flow rate (fluid volume per unit time) from the control cylinder CC, and the discharge 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 discharge fluid volume Ej (actual value) is based on the detection result of the fluid volume sensor that detects the discharge amount of brake fluid BF from the electric cylinder DN.

[0118] In the embodiment of the aforementioned brake control device SA, the target pressure Pt is determined to be a target value corresponding to the wheel pressure Pw (actual value). That is, the location (also called the "comparison location") for comparing the target value and the actual value is the wheel cylinder CW. Alternatively, the comparison location can be any position in the path of hydraulic pressure transmission from the discharge section of the electric cylinder DN to the wheel cylinder CW. For example, the detection location of the servo pressure sensor PA can also be used as the comparison location. In this configuration, the target pressure Pt is determined to correspond to the servo pressure Pa (actual value) by compensating for the hydraulic pressure component caused by the aforementioned resistance. In pressure regulation control, regardless of the location of the comparison location between the target value and the actual value, the target pressure Pt is the target value used to control the servo pressure Pa. Furthermore, the standard fluid volume Es is determined based on the target pressure Pt, and the estimated fluid volume Ee is determined based on the servo pressure Pa. Moreover, the actual hydraulic pressure (Pa, Pw, etc.) corresponding to the target pressure Pt is controlled to be close to and consistent with the target pressure Pt.

[0119] 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 attached to the brake shoes. In the drum brake device SX, similar to the disc brake device SX, the wheel pressure Pw of the wheel cylinder CW presses the brake pads (friction components) against the brake drum (rotating component), thereby generating a frictional braking force Fe.

[0120] In the aforementioned embodiment of the braking control device SA, target values ​​for various braking forces (Fv, Fz, Fh, Fn, etc.) are calculated using the dimensions of the front and rear forces acting on the vehicle (corresponding physical quantities). Alternatively, calculations can be performed using the dimensions of the vehicle's 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 the vehicle's acceleration. Therefore, based on the braking requirement Bs, the target pressure Pt is calculated via the force-related state quantities from the front and rear forces acting on the vehicle to the vehicle's deceleration.

[0121] The aforementioned brake control device SA is applied to vehicles equipped with a regenerative braking device KG on the front wheel (WHf) and capable of performing regenerative coordination control. In vehicles performing regenerative coordination control, it is sufficient that at least one of the front wheel (WHf) and the rear wheel (WHr) has a regenerative braking device KG. Furthermore, the brake control device SA can also be applied to vehicles that omit the regenerative braking device KG and are therefore unable to perform regenerative coordination control. That is, the brake control device SA can be applied to various vehicles regardless of the presence or absence of regenerative coordination control.

[0122] In the first embodiment of the braking control device SA described above, in the operating 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 configurations where the main area rm and the servo area ru are different, a conversion calculation between the supply pressure Pm (main pressure) and the servo 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 configuration where the supply pressure sensor PM is used as the servo pressure sensor PA and the supply pressure Pm is used as the servo pressure Pa, the supply pressure Pm is converted to the servo pressure Pa based on the aforementioned area ratio.

[0123] <Summary of Implementation Methods>

[0124] The vehicle's brake control unit SA adjusts the wheel pressure Pw of the wheel cylinder CW via servo pressure Pa. The brake control unit SA is equipped with a control cylinder CC, a control piston NC, an electric motor MA, servo pressure sensors (PA, PM, etc.), fluid volume sensors (KA, SN, etc.), and a controller EA.

[0125] The control piston NC is inserted into the control cylinder CC. Powered by the electric motor MA, the control piston NC moves, thereby generating a servo pressure Pa in the control cylinder CC. A servo pressure sensor (PA, PM, etc.) detects and acquires the actual value of the servo pressure Pa. A fluid level sensor (KA, SN, etc.) detects and acquires the actual volume Ej of the brake fluid BF delivered from the control cylinder CC. The controller EA calculates the target pressure Pt for controlling the servo pressure Pa based on the vehicle's braking requirement Bs, and controls the rotation angle (Ka) of the electric motor MA based on the target pressure Pt and the servo pressure Pa.

[0126] In controller EA, the volume of brake fluid BF discharged from control cylinder CC is obtained as the discharge volume Ej. Furthermore, based on servo pressure Pa and transformation maps Zef, Zer, and Zek, the estimated volume Ee, presumably flowing into wheel cylinder CW, is calculated. Then, the electric motor MA is controlled based on the deviation hE between the estimated volume Ee and the discharge volume Ej. Here, the transformation maps Zef, Zer, and Zek, representing the relationship between the volume (volume) of brake fluid BF flowing into wheel cylinder CW and wheel pressure Pw, are preset in controller EA.

[0127] The estimated liquid volume Ee is calculated based on the transformation maps Zef, Zer, and Zek. If the transformation maps Zef, Zer, and Zek are accurate, the estimated liquid volume Ee matches the discharged liquid volume Ej. If the transformation maps Zef, Zer, and Zek contain errors, the two are inconsistent. That is, the deviation hE (liquid volume deviation) between the estimated liquid volume Ee and the discharged liquid volume Ej represents the error in the transformation maps Zef, Zer, and Zek. In the braking control device SA, to compensate for this error, the electric motor MA is controlled based on the liquid volume deviation hE.

[0128] Specifically, the electric motor MA is controlled as follows: Based on the target pressure Pt calculated according to the braking requirement Bs and the conversion mappings Zef, Zer, and Zek, the standard fluid volume Es is calculated. The standard fluid volume Es is the target value of the fluid volume that should flow into the wheel cylinder CW. Based on the servo pressure Pa and the conversion mappings Zef, Zer, and Zek, the estimated fluid volume Ee is calculated. The estimated fluid volume Ee is an estimate of the fluid volume that is presumed to flow into the wheel cylinder CW. Then, based on the comparison result hE (fluid volume deviation) between the estimated fluid volume Ee (estimated value) and the discharged fluid volume Ej (detected value), the reference value Ks calculated based on the standard fluid volume Es is corrected, and the target rotation angle Kt of the electric motor MA is determined. Furthermore, the supply current Im to the electric motor MA is adjusted so that the motor rotation angle Ka is consistent with the target rotation angle Kt. Here, the discharged fluid volume Ej is obtained based on the detection value of the fluid volume sensor (KA, SN, etc.).

[0129] The conversion mappings Zef, Zer, and Zek are pre-stored as defined characteristics in the controller EA (specifically, the microprocessor MP). However, due to factors such as gases (air, etc.) present inside the braking device SX, and wear of friction components, errors are introduced into the conversion mappings Zef, Zer, and Zek. The fluid quantity deviation hE arises from these errors. In the braking control device SA, to compensate for the errors in the conversion mappings Zef, Zer, and Zek, the target rotation angle Kt of the electric motor MA is corrected based on the fluid quantity deviation hE. In other words, in the braking control device SA, the electric motor MA is controlled based on the fluid quantity deviation hE.

[0130] In detail, the liquid volume deviation hE is derived by subtracting the estimated liquid volume Ee from the discharged liquid volume Ej. When the discharged liquid volume Ej is larger than the estimated liquid volume Ee (i.e., when the liquid volume deviation hE is positive), the liquid volume discharged from the electric cylinder DN is insufficient, and the servo pressure Pa is insufficient. In this case, the target rotation angle Kt is increased to correct for this, thus increasing the motor rotation angle Ka. On the other hand, when the discharged liquid volume Ej is smaller than the estimated liquid volume Ee (i.e., when the liquid volume deviation hE is negative), the liquid volume discharged from the electric cylinder DN is excessive, and the servo pressure Pa is excessive. In this case, the target rotation angle Kt is decreased to correct for this, thus decreasing the motor rotation angle Ka. By adjusting the motor rotation angle Ka according to the liquid volume deviation hE, the liquid volume discharged from the electric cylinder DN (especially the control cylinder CC) is adjusted to be neither excessive nor insufficient relative to the target pressure Pt. As a result, the pressure regulation accuracy based on the electric cylinder DN can be improved.

Claims

1. A braking control device for a vehicle, comprising: a control cylinder for insertion of a control piston, wherein a servo pressure is generated by moving the control piston using an electric motor; a servo pressure sensor for detecting the servo pressure; and a controller for controlling the electric motor based on the servo pressure, wherein the braking control device adjusts the wheel pressure of a wheel cylinder using the servo pressure, wherein... The controller obtains the discharge volume from the control cylinder, calculates and estimates the volume based on the servo pressure and conversion mapping, and controls the electric motor based on the deviation between the discharge volume and the estimated volume.

2. The vehicle braking control device according to claim 1, wherein, The controller calculates the target pressure based on the braking requirement, calculates the standard liquid volume based on the target pressure and the conversion mapping, and controls the rotation angle of the electric motor based on the standard liquid volume and the deviation.

3. The braking control device for a vehicle according to claim 1 or 2, wherein, The controller sets the relationship between the volume of brake fluid flowing into the wheel cylinder and the wheel pressure as the aforementioned conversion mapping diagram.

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