Braking control device of vehicle

Abstract

To properly monitor actuation of a liquid pressure generation source of a braking control device.SOLUTION: A braking control device, which is applied to a vehicle provided with a reproduction device, includes: a liquid pressure generation part that individually adjusts first servo pressure and second servo pressure under the condition that the first servo pressure is higher than the second servo pressure so that liquid pressure of a wheel cylinder is controlled; a controller that calculates first target servo pressure and second target servo pressure corresponding to the first servo pressure and the second servo pressure on the basis of a required braking amount, and controls the liquid pressure generation part so that the first and second servo pressure match the first and second target servo pressure; and a first servo pressure sensor that detects the first servo pressure, as first detected servo pressure. In the braking control device, the controller, when executing cooperative control with the reproduction device, increases the first target servo pressure from zero, while keeping the second target servo pressure at zero, and determines an abnormality of the liquid pressure generation part on the basis of the first detected servo pressure and the first target servo pressure.SELECTED DRAWING: Figure 4

Description

[Technical field]

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

[0002] The applicant has developed a brake control device as described in Patent Document 1. The brake control device includes a "master unit having a master chamber connected to a front wheel cylinder and a servo chamber for applying a forward force to the master piston that is opposite to the backward force applied to the master piston by the master chamber," a "pressure adjustment unit for adjusting the brake fluid discharged by an electric pump to a first hydraulic pressure by a first solenoid valve, introducing the first hydraulic pressure into a rear wheel cylinder, and reducing and adjusting the first hydraulic pressure to a second hydraulic pressure by a second solenoid valve and introducing the second hydraulic pressure into the servo chamber," and a "regenerative coordination unit composed of an input piston interlocked with a brake operating member and an input cylinder fixed to the master cylinder, in which the gap between the master piston and the input piston is controlled by the second hydraulic pressure." As a result, the brake control device is shortened in the longitudinal direction and the brake hydraulic pressure of the front wheel system and the brake hydraulic pressure of the rear wheel system are individually controlled. Meanwhile, in the above brake control device, an electric motor or the like is used as a hydraulic pressure generating source. In such a device, it is necessary to check the operation of the hydraulic pressure generating source. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-137202 A Summary of the Invention [Problem to be solved by the invention]

[0004] In view of the above problems, an object of the present invention is to provide a brake control device that can appropriately monitor the operation of a hydraulic pressure generating source. [Means for solving the problem]

[0005] The vehicle braking control device (SC) of the present invention is applied to a vehicle equipped with a regenerative device (KG), and includes a hydraulic pressure generating unit (PU) that individually adjusts first and second servo pressures (Pa, Pb) on the condition that the first servo pressure (Pa) is equal to or higher than the second servo pressure (Pb) so as to control a hydraulic pressure (Pw) in a wheel cylinder (CW) of the vehicle, a controller (EA) that calculates first and second target servo pressures (Pat, Pbt) corresponding to the first and second servo pressures (Pa, Pb) based on braking requirements (Bs, Ba, Gs) of the vehicle, and controls the hydraulic pressure generating unit (PU) so that the first and second servo pressures (Pa, Pb) match the first and second target servo pressures (Pat, Pbt), and a first servo pressure sensor (PA) that detects the first servo pressure (Pa) as a first detected servo pressure (Pak).

[0006] In the vehicle brake control device (SC) according to the present invention, when the controller (EA) executes cooperative control with the regenerative device (KG), the controller (EA) increases the first target servo pressure (Pat) from zero (0) while maintaining the second target servo pressure (Pbt) at zero (0), and determines an abnormality in the hydraulic pressure generating unit (PU) based on the first detected servo pressure (Pak) and the first target servo pressure (Pat). For example, the controller (EA) calculates a deviation (hPa) between the first target servo pressure (Pat) and the first detected servo pressure (Pak), and determines an abnormality in the hydraulic pressure generating unit (PU) when the deviation (hPa) is greater than a threshold pressure (Ha). With the above configuration, the operation of the hydraulic pressure generating source PU is appropriately monitored, and when an abnormality occurs, it can be determined early. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic diagram for explaining a first embodiment of a brake control device SC. [Diagram 2] FIG. 13 is a schematic diagram for explaining a lower braking unit SZ. [Diagram 3] FIG. 4 is a flow chart for explaining a pressure regulation control process. [Figure 4]11 is a flow chart for explaining a suitability determination of a hydraulic pressure generating unit PU. FIG. [Diagram 5] FIG. 11 is a time series diagram for explaining the operation of suitability determination. [Figure 6] FIG. 4 is a schematic diagram for explaining a second embodiment of a brake control device SC. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] <Symbols for components, subscripts at the end of symbols, etc.> In the following description, components, calculation processes, signals, characteristics, and values ​​with the same symbol, such as "CW", have the same function. The suffixes "f" and "r" at the end of the symbol for each wheel are generic symbols that indicate whether it relates to the front or rear wheel system. For example, the wheel cylinder CW provided on each wheel is written as "front wheel cylinder CWf, rear wheel cylinder CWr". Furthermore, the suffixes "f" and "r" at the end of the symbol may be omitted. When the suffixes "f" and "r" are omitted, each symbol represents a generic term. For example, "CW" is a generic term for wheel cylinders provided on the front and rear wheels of a vehicle. In addition, "CW" as a generic term can also be written as "CW (= CWf, CWr)".

[0009] In the fluid path, the side closer to the master cylinder CM (the side farther from the wheel cylinder CW) is referred to as the "upper" side, and the side closer to the wheel cylinder CW (the side farther from the master cylinder CM) is referred to as the "lower" side. In addition, in the circulating flows KN, KZ of the brake fluid BF (working fluid), the side closer to the discharge parts of the fluid pumps QA, QZ (the side farther from the suction parts) is referred to as the "upstream side," and the side closer to the suction parts of the fluid pumps QA, QZ (the side farther from the discharge parts) is referred to as the "downstream side."

[0010] The upper actuator YA of the upper braking unit SA, the lower actuator YZ of the lower braking unit SZ, and the wheel cylinder CW are connected by a fluid path (communication path HS). Furthermore, in the upper and lower actuators YA and YZ, various components (UA, etc.) are connected by fluid paths. Here, the "fluid path" is a path for moving the brake fluid BF, and corresponds to piping, flow paths in the actuators, hoses, etc. In the following explanation, the communication path HS, reflux path HK, return path HZ, reservoir path HR, input path HN, servo path HC, pressure reduction path HG, etc. are fluid paths.

[0011] <Names of various hydraulic pressures> In the brake control device SC, the pressure of the brake fluid BF (also called "hydraulic pressure") is transmitted from the upper brake unit SA to the wheel cylinder CW via the lower brake unit SZ. The upper brake unit SA includes a hydraulic pressure generating unit PU as a pressure source. In the following explanation, the names of various hydraulic pressures are as follows. "Servo pressures Pa, Pb" are hydraulic pressures generated in the hydraulic pressure generating unit PU. "Supply pressure Ps" is hydraulic pressure transmitted (supplied) from the upper brake unit SA to the lower brake unit SZ. "Wheel pressure Pw" is hydraulic pressure transmitted (supplied) from the lower brake unit SZ to the wheel cylinder CW, and is the internal pressure of the wheel cylinder CW. "Master pressure Pm" is the internal pressure of the master cylinder CM. In the upper brake unit SA, in a configuration in which the supply pressure Ps is output from the master cylinder CM to the lower brake unit SZ, the master pressure Pm is the supply pressure Ps. On the other hand, in the upper brake unit SA, in a configuration in which the supply pressure Ps is directly output from the hydraulic pressure generating section PU to the lower brake unit SZ, the servo pressure Pa (or Pb) is the supply pressure Ps.

[0012] <Target value, actual value, and detected value> In hydraulic control, the "actual value" is controlled to approach and match the "target value". The actual value includes a "detected value" and an "estimated value". The detected value is a value detected by a hydraulic pressure sensor. The estimated value is a value calculated using a certain relationship from values ​​obtained as different physical quantities (various state quantities, etc.). For example, in hydraulic control using the pressure regulating valves UA and UB, the adjusted hydraulic pressure is uniquely determined according to the current supplied to the pressure regulating valves UA and UB. Therefore, "control to match the actual value with the target value" includes not only closed-loop control based on the detected value of the hydraulic pressure sensor (i.e., control in which the detected value is fed back), but also open-loop control (i.e., control in which the detected value is not fed back) by only adjusting a physical quantity different from the hydraulic pressure (e.g., supply current). In other words, "control to match the actual value with the target value" includes a configuration that does not have a hydraulic pressure sensor. In contrast, in suitability judgment, a hydraulic pressure sensor that detects the actual value is an essential component. In the following description, it will be clearly stated that it is a detected value by a hydraulic pressure sensor (detected servo pressure, detected supply pressure, etc.) as necessary.

[0013] <First embodiment of the brake control device SC> A first embodiment of a vehicle brake control device SC (particularly, an upper brake unit SA) will be described with reference to the schematic diagram of Fig. 1. The brake control device SC is composed of an upper brake unit SA and a lower brake unit SZ. For example, the brake control device SC is applied to a hybrid vehicle or an electric vehicle equipped with an electric motor for driving.

[0014] The front and rear wheels WHf, WHr (=WH) of the vehicle are provided with a braking device SX (=SXf, SXr). The braking device SX is composed of a brake caliper, a friction member (e.g., brake pad), and a rotating member KT (e.g., brake disc). The brake caliper (not shown) is provided with a wheel cylinder CW. A hydraulic pressure Pw (called "wheel pressure") in the wheel cylinder CW presses a friction member (not shown) against a rotating member KT fixed to each wheel WH, thereby applying a braking torque Tb to the wheel. As a result, a frictional braking force Fe (also called "hydraulic braking force") is generated in the wheel WH. Therefore, the braking device SX can be said to be "a device that generates a frictional braking force Fe by the wheel pressure Pw" or "a device that converts the wheel pressure Pw into a frictional braking force Fe."

[0015] The vehicle is provided with a regenerative device KG. The regenerative device KG is composed of a generator GN for energy regeneration (also called an "electric motor / generator" or "regenerative generator"), a control unit EG for the regenerative device KG (also called a "regenerative controller"), and a regenerative storage battery (not shown). The regenerative generator GN also serves as an electric motor for running. In regenerative braking, the electric motor / generator GN operates as a generator, and the generated electric power is stored in the regenerative storage battery via the regenerative controller EG. At this time, a regenerative braking force Fg acts on the wheels. That is, the regenerative device KG can generate the regenerative braking force Fg. For example, the regenerative device KG is provided on the front wheels WHf. Therefore, the regenerative braking force Fg is generated in the front wheels WHf. The regenerative device KG (particularly, the regenerative controller EG) is connected to the communication bus BS.

[0016] The vehicle is equipped with a driving assistance device KJ. The driving assistance device KJ executes automatic speed control. The driving assistance device KJ is composed of an object detection sensor SJ and a driving assistance controller EJ (also simply referred to as a "driving assistance controller"). The object detection sensor SJ detects a distance Sj (called a "relative distance" and also called an "inter-vehicle distance" when the object is a preceding vehicle) to an object present in front of the vehicle (including a preceding vehicle traveling in front of the vehicle). For example, a radar sensor, a millimeter wave sensor, an image sensor, or the like is adopted as the object detection sensor SJ. The driving assistance controller EJ calculates a target acceleration Gs of the vehicle (a target value of the vehicle body acceleration in the longitudinal direction of the vehicle) based on the detection result Sj (relative distance) of the object detection sensor SJ. The driving assistance device KJ (particularly, the driving assistance controller EJ) is connected to a communication bus BS. The target acceleration Gs is transmitted to the braking control device SC via the communication bus BS. The braking control device SC adjusts the braking forces Fg and Fe in accordance with the target acceleration Gs, thereby controlling the vehicle running speed Vx (vehicle speed).

[0017] The vehicle is equipped with a brake operating member BP and various sensors (SP, etc.). The brake operating member BP (e.g., a brake pedal) is an operating member for the driver to decelerate the vehicle. The vehicle is provided with an operation displacement sensor SP that detects an operation displacement Sp of the brake operating member BP. The operation displacement Sp is one of state quantities (state variables) that indicate the operation amount of the brake operating member BP, and in a brake-by-wire type brake control device SC, it is a signal that indicates the driver's braking intention (i.e., a braking command). In addition to the operation displacement sensor SP, a hydraulic pressure Pn (referred to as "input pressure") in an input chamber Rn (described later) is adopted as another state quantity that indicates the braking operation amount. The input pressure Pn is detected by an input pressure sensor PN. The operation displacement Sp, the input pressure Pn, etc. are collectively referred to as the "braking operation amount Ba". Further, the operation displacement sensor SP and the input pressure sensor PN which detect the operation displacement Sp and the input pressure Pn (that is, the braking operation amount Ba) are referred to as a "braking operation amount sensor BA."

[0018] A vehicle is provided with various sensors for braking control, such as anti-lock brake control and anti-skid control, which individually controls the wheel pressure Pw of each wheel. Specifically, each wheel WH is provided with a wheel speed sensor VW that detects its rotation speed Vw (referred to as "wheel speed"). In addition, a steering amount sensor that detects the steering amount Sa (e.g., operation angle) of a steering operation member (e.g., a steering wheel), a yaw rate sensor that detects the yaw rate Yr of the vehicle, a longitudinal acceleration sensor that detects the longitudinal acceleration Gx (also referred to as "deceleration") of the vehicle, and a lateral acceleration sensor that detects the lateral acceleration Gy of the vehicle are provided (all not shown).

[0019] The vehicle is equipped with a brake control device SC. The brake control device SC employs a so-called front and rear type (also called "type II") brake system as two systems. The wheel pressure Pw of each wheel cylinder CW is adjusted by the brake control device SC.

[0020] The brake control device SC is composed of two brake units SA, SZ. The upper brake unit SA is composed of an upper actuator YA and an upper controller EA. The upper actuator YA is controlled by the upper controller EA. The lower brake unit SZ is composed of a lower actuator YZ and a lower controller EZ. The lower actuator YZ is controlled by the lower controller EZ. Here, the upper and lower actuators YA, YZ are also referred to as "upper and lower fluid units." Moreover, the upper and lower controllers EA, EZ are also referred to as "upper and lower control units."

[0021] The upper braking unit SA (particularly, the upper controller EZ) and the lower braking unit SZ (particularly, the lower controller EZ) are connected to a communication bus BS. Signals are transmitted between the multiple controllers (EA, EZ, EG, EJ, etc.) via the communication bus BS. In other words, the multiple controllers can transmit signals (detection values, calculation values, control flags, etc.) to the communication bus BS and can receive signals from the communication bus BS.

[0022] <Upper braking unit SA> The configuration of the upper braking unit SA will be described. The upper braking unit SA generates a supply pressure Ps in response to the operation of the brake operating member BP (brake pedal). The supply pressure Ps is output (supplied) to the lower braking unit SZ (ultimately, the wheel cylinder CW). The upper braking unit SA is composed of an upper actuator YA and an upper controller EA.

[0023] <Upper actuator YA> The upper actuator YA (upper fluid unit) is composed of an apply part AP, a hydraulic pressure generating part PU, and an input part NR.

[0024] [Apply Department AP] In response to the operation of the brake operating member BP, the apply section AP outputs the front wheel supply pressure Psf. The apply section AP is composed of a single-type master cylinder CM and a master piston NM.

[0025] A master piston NM is inserted into the single-type master cylinder CM. The interior of the master cylinder CM is divided into three hydraulic chambers Rm, Rc, and Rs by the master piston NM. The master chamber Rm is divided by the bottom of the master cylinder CM and the master piston NM. Furthermore, the interior of the master cylinder CM is divided into a servo chamber Rc and a reaction chamber Rs by a flange portion Tu of the master piston NM. In other words, the master chamber Rm and the servo chamber Rc are arranged to face each other with the flange portion Tu in between. Here, the pressure receiving area rm of the master chamber Rm and the pressure receiving area rc of the servo chamber Rc are made equal. The hydraulic chambers Rm, Rc, and Rs are sealed from the master cylinder CM by a seal member SL.

[0026] When braking is not being applied, the master piston NM is in the most retreated position (i.e., the position where the volume of the master chamber Rm is maximum). In this state, the master chamber Rm of the master cylinder CM is connected to the master reservoir RV. Brake fluid BF is stored inside the master reservoir RV (also called the "atmospheric pressure reservoir"). When the brake operating member BP is operated, the master piston NM is moved in the forward direction Da (the direction in which the volume of the master chamber Rm decreases). This movement blocks communication between the master chamber Rm and the master reservoir RV. Then, when the master piston NM is further moved in the forward direction Da, the hydraulic pressure Pm (also called the "master pressure") in the master chamber Rm is increased from "0 (atmospheric pressure)". As a result, the brake fluid BF pressurized to the master pressure Pm is output (pressurized and fed) from the master chamber Rm of the master cylinder CM to the lower brake unit SZ as the front wheel supply pressure Psf.

[0027] [Hydraulic pressure generating unit PU] The hydraulic pressure generating unit PU uses one electric motor MA as a power source to individually generate first and second servo pressures Pa, Pb. The hydraulic pressure generating unit PU supplies the first servo pressure Pa to the rear wheel cylinder CWr, and individually supplies the second servo pressure Pb to the servo chamber Rc of the apply unit AP. The first servo pressure Pa is output to the lower braking unit SZ as the rear wheel supply pressure Psr. The hydraulic pressure generating unit PU is composed of the electric motor MA, the fluid pump QA, and the first and second pressure regulating valves UA, UB.

[0028] The electric motor MA drives the fluid pump QA. The electric motor MA is a power source for generating the first and second servo pressures Pa and Pb. The electric motor MA and the fluid pump QA are included in the upper brake unit SA, and therefore are also referred to as the "upper electric motor MA" and the "upper fluid pump QA."

[0029] In the fluid pump QA, the suction portion Qi and the discharge portion Qo are connected by a return passage HK (fluid passage). The suction portion Qi of the fluid pump QA is connected to the master reservoir RV via a reservoir passage HR. A check valve is provided at the discharge portion Qo of the fluid pump QA.

[0030] Two pressure regulating valves UA and UB are provided in series in the return flow path HK. Specifically, a normally open second pressure regulating valve UB is provided in the return flow path HK. A normally open first pressure regulating valve UA is provided between the second pressure regulating valve UB and the discharge part Qo of the fluid pump QA. Therefore, in the circulation flow KN (indicated by the dashed arrow) of the brake fluid BF, the first pressure regulating valve UA is disposed upstream (closer to the discharge part Qo of the fluid pump QA) of the second pressure regulating valve UB. The first and second pressure regulating valves UA and UB are linear solenoid valves whose valve opening amount (lift amount) is continuously controlled according to the energized state (for example, the supply currents Ia and Ib). The first and second pressure regulating valves UA and UB are also called "differential pressure valves" because they adjust the hydraulic pressure difference (differential pressure) between their upstream and downstream sides.

[0031] When the fluid pump QA is driven by the electric motor MA, a circulating flow KN of brake fluid BF (a flow of brake fluid BF circulating within the return flow path HK) is generated in the return flow path HK, which includes the fluid pump QA and the first and second pressure regulating valves UA and UB. The fluid pressure Pb (second servo pressure) between the first pressure regulating valve UA and the second pressure regulating valve UB is controlled by the second pressure regulating valve UB. Furthermore, the fluid pressure Pa (first servo pressure) between the first pressure regulating valve UA and the discharge portion Qo of the fluid pump QA is controlled by the first pressure regulating valve UA.

[0032] When the second pressure regulating valve UB is fully open (when not energized, since the second pressure regulating valve UB is of the normally open type), the second servo pressure Pb is "0 (atmospheric pressure)." When the current Ib (also referred to as the "second pressure regulating valve current") supplied to the second pressure regulating valve UB is increased, the flow path of the return flow path HK is narrowed by the second pressure regulating valve UB. The upstream fluid pressure Pb (second servo pressure) is increased from the downstream fluid pressure (atmospheric pressure "0") by the second pressure regulating valve UB. The second servo pressure Pb is adjusted by the second pressure regulating valve current Ib.

[0033] Similarly, when the first pressure regulating valve UA is in a fully open state (when not energized because the first pressure regulating valve UA is of a normally open type), the first servo pressure Pa is equal to the second servo pressure Pb. When the current Ia (also referred to as the "first pressure regulating valve current") supplied to the first pressure regulating valve UA is increased, the circulation flow KN is throttled by the first pressure regulating valve UA. The upstream hydraulic pressure Pa (first servo pressure) is increased from the downstream hydraulic pressure Pb (second servo pressure) by the first pressure regulating valve UA. The first servo pressure Pa is adjusted by the first pressure regulating valve current Ia. In terms of the magnitude relationship between the first servo pressure Pa and the second servo pressure Pb, the first servo pressure Pa is always equal to or greater than the second servo pressure Pb (i.e., "Pa≧Pb"). In other words, the execution of the pressure regulating control (described later) is premised on the first servo pressure Pa being equal to or greater than the second servo pressure Pb.

[0034] In the brake control device SC, a regenerative braking force Fg is generated at the front wheels WHf. Since "Pa ≧ Pb", the front wheel pressure Pwf is adjusted by the second servo pressure Pb, and the rear wheel pressure Pwr is adjusted by the first servo pressure Pa. In the brake system related to the front wheels WHf, the return path HK is connected to the servo chamber Rc of the master cylinder CM via a servo path HC (fluid path) between the first pressure regulating valve UA and the second pressure regulating valve UB. With an increase in the second servo pressure Pb introduced (supplied) to the servo chamber Rc, the master piston NM is pressed in the forward direction Da, and the internal pressure Pm (master pressure) of the master chamber Rm is increased. A front wheel connection path HSf (fluid path) is connected to the master chamber Rm. The front wheel connection path HSf is connected to the front wheel cylinder CWf via the lower brake unit SZ. Therefore, in the front wheel braking system, the master pressure Pm generated by the second servo pressure Pb is supplied to the front wheel cylinder CWf as the front wheel supply pressure Psf. That is, in the front wheel braking system, the second servo pressure Pb is transmitted to the front wheel cylinder CWf in the order of "Pb → Pm (= Psf) → Pwf". Here, since "rc = rm", if the sliding resistance of the seal member SL is ignored, "Pb = Pm (= Psf) = Pwf".

[0035] In the brake control device SC, the rear wheel pressure Pwr is adjusted by the first servo pressure Pa. In the brake system related to the rear wheel WHr, the return path HK is connected to the rear wheel connection path HSR (fluid path) between the discharge part Qo and the first pressure regulating valve UA. The rear wheel connection path HSR is connected to the rear wheel cylinder CWr via the lower brake unit SZ. Therefore, in the rear wheel brake system, the first servo pressure Pa is supplied directly (i.e., not via the master cylinder CM) to the rear wheel cylinder CWr as the rear wheel supply pressure Psr. In other words, in the rear wheel brake system, the first servo pressure Pa is transmitted to the rear wheel cylinder CWr in the order of "Pa (= Psr) → Pwr". Here, "Pa (= Psr) = Pwr".

[0036] In the hydraulic pressure generating unit PU, the first servo pressure Pa and the second servo pressure Pb are individually adjusted, thereby individually adjusting the front wheel supply pressure Psf and the rear wheel supply pressure Psr. However, since the second servo pressure Pb is equal to or lower than the first servo pressure Pa, the front wheel supply pressure Psf is equal to or lower than the rear wheel supply pressure Psr. By individually adjusting the first and second servo pressures Pa and Pb, the front and rear wheel pressures Pwf and Pwr are individually controlled.

[0037] The hydraulic pressure generating unit PU is provided with first and second servo pressure sensors PA and PB to detect the first and second servo pressures Pa and Pb. The first and second servo pressures Pa and Pb (actual values) detected by the first and second servo pressure sensors PA and PB are referred to as "first and second detected servo pressures Pak and Pbk." The first and second detected servo pressures Pak and Pbk are input to the upper controller EA.

[0038] [Input NR] The input unit NR realizes regenerative cooperative control. "Regenerative cooperative control" cooperates the frictional braking force Fe (braking force due to wheel pressure Pw) and the regenerative braking force Fg (braking force due to regenerative generator GN) so that the kinetic energy possessed by the vehicle during braking can be efficiently recovered as electrical energy. In regenerative cooperative control, the input unit NR operates the brake operating member BP, but creates a state in which the wheel pressure Pw is not generated.

[0039] The input unit NR is composed of an input cylinder CN, an input piston NN, an introduction valve VA, a release valve VB, a stroke simulator SS, and an input pressure sensor PN.

[0040] The input cylinder CN is fixed to the master cylinder CM. An input piston NN is inserted into the input cylinder CN. The input piston NN is mechanically connected to a brake operating member BP (brake pedal) via a clevis (U-shaped link) so as to move in conjunction with the movement of the brake operating member BP. There is a gap Ks (also called "separation displacement") between the end face of the input piston NN and the end face of the master piston NM. The separation distance Ks is adjusted by the first servo pressure Pa, thereby achieving regenerative cooperative control. Like the hydraulic chambers Rm, Rc, and Rs, the input chamber Rn is also sealed by a seal member SL.

[0041] The input chamber Rn of the input unit NR is connected to the reaction chamber Rs of the apply unit AP through an input path HN (fluid path). A normally closed type introduction valve VA is provided in the input path HN. The input path HN is connected to the master reservoir RV through a reservoir path HR (fluid path) between the introduction valve VA and the reaction chamber Rs. A normally open type release valve VB is provided in the reservoir path HR. An on-off type solenoid valve is used for the introduction valve VA and the release valve VB. A stroke simulator SS is provided in the input path HN between the introduction valve VA and the reaction chamber Rs. An input pressure sensor PN is provided in the input path HN between the input chamber Rn and the introduction valve VA to detect the hydraulic pressure Pn (input pressure) in the input chamber Rn. The input pressure Pn detected by the input pressure sensor PN is input to the upper controller EA as the braking operation amount Ba.

[0042] When no power is supplied to the introduction valve VA and the release valve VB, the introduction valve VA is closed and the release valve VB is open. When the introduction valve VA is closed, the input chamber Rn is sealed and fluid locked. This causes the master piston NM to be displaced integrally with the brake operating member BP. When the release valve VB is opened, the stroke simulator SS and the reaction chamber Rs are connected to the master reservoir RV.

[0043] When power is supplied (powered) to the introduction valve VA and the release valve VB, the introduction valve VA is opened and the release valve VB is closed. This allows the master piston NM to be displaced separately from the brake operating member BP. At this time, the input chamber Rn is connected to the stroke simulator SS, so that the operating force Fp of the brake operating member BP is generated by the stroke simulator SS. In detail, the volume of the input chamber Rn is reduced by operating the brake operating member BP, and brake fluid BF is discharged from the input chamber Rn. The discharged brake fluid BF flows into the stroke simulator SS. An elastic body (e.g., a compression spring) is provided inside the stroke simulator SS and generates a force that prevents the inflow of brake fluid BF. This generates the operating force Fp of the brake operating member BP.

[0044] In the input unit NR, the operation mode of the brake operating member BP when no power is supplied to the introduction valve VA and the release valve VB is referred to as the "first operation mode Mm". The first operation mode Mm is used when the hydraulic pressure generating device PU is stopped due to an abnormality (including when the power supply fails). In the first operation mode Mm (also called the "manual mode"), the input chamber Rn is fluidically locked, so that the master piston NM moves integrally with the brake operating member BP. In the first operation mode Mm, the front wheel supply pressure Psf is generated by the operating force Fp of the brake operating member BP, and the rear wheel supply pressure Psr is not generated (i.e., "Psf=Pm, Psr=0"). In other words, in the first operation mode Mm, the front wheel supply pressure Psf is generated using the driver's muscle force as a power source. At this time, the operating force Fp is applied by the stiffness (that is, the elastic deformation of the brake caliper, friction members, brake piping, etc.) of the front wheel braking device SXf (a device that generates a friction braking force Fef by the wheel pressure Pwf).

[0045] In contrast, the operation mode of the brake operating member BP in the input section NR when the introduction valve VA and the release valve VB are supplied with electricity is called the "second operation mode Ms". The second operation mode Ms is used when the hydraulic pressure generating device PU is in operation. In the second operation mode Ms (also called the "by-wire mode"), the brake fluid BF discharged from the input chamber Rn flows into the stroke simulator SS, so that the master piston NM can move separately from the brake operating member BP. In the second operation mode Ms, the supply pressure Ps is generated by the servo pressures Pa and Pb. That is, the driver's muscle force (i.e., the operating force Fp) is not used as a power source for generating the servo pressure. Therefore, the operating force Fp of the brake operating member BP is applied by the stroke simulator SS.

[0046] <Upper controller EA> The upper actuator YA is controlled by the upper controller EA. The upper controller EA is composed of a microprocessor MP and a drive circuit DR. The upper controller EA is connected to a communication bus BS so that signals (detection values, calculation values, control flags, etc.) can be shared between the upper controller EA and various controllers (EZ, EG, EJ, etc.).

[0047] The upper controller EA receives various sensor signals such as the operation displacement Sp, the input pressure Pn, the first and second detected servo pressures Pak and Pbk. Furthermore, the upper controller EA receives various signals such as the target acceleration Gs, the detected supply pressure Psk, and the limit regenerative braking force Fx from the communication bus BS. The upper controller EA also outputs a target regenerative braking force Fh (target value of the regenerative braking force Fg), a suitability flag FL (a control flag indicating the operating state of the hydraulic pressure generating unit PU), and the like to the communication bus BS. The regenerative controller EG controls the regenerative braking force Fg (actual value) based on the target regenerative braking force Fh (target value) acquired from the communication bus BS.

[0048] The upper controller EA (particularly the microprocessor MP) is programmed with a pressure regulation control algorithm. "Pressure regulation control" is a control for controlling the first and second servo pressures Pa and Pb, and ultimately for adjusting the front and rear wheel pressures Pwf and Pwr (=Pw). Pressure regulation control includes regenerative cooperative control. Pressure regulation control is performed based on the various signals (Sp, etc.) mentioned above.

[0049] The hydraulic pressure generating unit PU (MA, UA, UB, etc.) is driven by the drive circuit DR based on the pressure regulation control algorithm. In the drive circuit DR, an H-bridge circuit is configured with switching elements (e.g., MOS-FET) to drive the electric motor MA. The drive circuit DR is also provided with switching elements to drive various solenoid valves (UA, UB, etc.). In addition, the drive circuit DR includes a motor current sensor (not shown) that detects a supply current Im (also called "motor current") to the electric motor MA, and first and second pressure regulating valve current sensors (not shown) that detect currents Ia and Ib (first and second pressure regulating valve currents) supplied to the first and second pressure regulating valves UA and UB. The electric motor MA is provided with a rotation speed sensor (not shown) that detects its rotation speed Na. Alternatively, the electric motor MA may be provided with a rotation angle sensor (not shown) that detects a rotation angle Ka, and the motor rotation speed Na may be calculated based on the detected motor rotation angle Ka. The motor rotation speed Na may also be estimated based on the motor current Im.

[0050] In the upper controller EA, the first and second target currents Iat, Iat are calculated based on the braking operation amount Ba (a collective term for Sp and Pn). The "first and second target currents Iat, Ibt" are target values ​​corresponding to the first and second pressure regulating valve currents Ia, Ib (actual values). In the upper controller EA, the first and second pressure regulating valve currents Ia, Ib detected by the first and second pressure regulating valve current sensors are controlled so as to approach and match the first and second target currents Iat, Ibt.

[0051] In the upper controller EA, a target rotation speed Nt is calculated based on the operation displacement Sp. The "target rotation speed Nt" is a target value corresponding to the motor rotation speed Na (actual value). For example, the operation displacement Sp is time-differentiated to calculate the operation speed dS. Then, when the operation displacement Sp increases, the target rotation speed Nt is determined to be larger as the operation speed dS (increase in the operation displacement Sp per unit time) increases. Also, when the operation displacement Sp decreases or is maintained constant, the target rotation speed Nt is decreased.

[0052] The target rotation speed Nt takes into consideration the minimum flow rate of the first and second pressure regulating valves UA and UB and the minimum rotation speed of the electric motor MA. The "minimum flow rate" is the minimum flow rate required for the first and second pressure regulating valves UA and UB to function. The "minimum rotation speed" is the minimum value of the speed at which the electric motor MA can rotate stably. Taking into consideration the minimum flow rate and the minimum rotation speed, a lower limit speed nt (a predetermined value set in advance) is set for the target rotation speed Nt. In other words, when the target rotation speed Nt is equal to or greater than the lower limit speed nt, no restriction is imposed by the lower limit speed nt, and the calculated target rotation speed Nt is used as is. On the other hand, when the target rotation speed Nt is less than the lower limit speed nt, the target rotation speed Nt is determined to be the lower limit speed nt. The motor current Im is then controlled so that the motor rotation speed Na approaches and matches the target rotation speed Nt.

[0053] Based on the above control algorithm, the upper controller EA calculates a drive signal Ma for controlling the electric motor MA, and drive signals Ua, Ub, Va, Vb for controlling the various solenoid valves UA, UB, VA, VB. Then, in response to the drive signal (Ma, etc.), the switching elements of the drive circuit DR are driven to control the electric motor MA and the solenoid valves UA, UB, VA, VB.

[0054] The upper brake unit SA according to the first embodiment is applied to a vehicle in which a regenerative device KG is provided on the front wheels WHf. That is, in addition to the front wheel friction braking force Fef, a regenerative braking force Fg acts on the front wheels WHf. In the hydraulic pressure generating section PU, the first servo pressure Pa and the second servo pressure Pb, which is equal to or lower than the first servo pressure Pa, are individually adjusted. Therefore, the front wheel pressure Pwf is controlled by the second servo pressure Pb, and the rear wheel pressure Pwr is controlled by the first servo pressure Pa. As a result, although there is a restriction that the front wheel pressure Pwf must be equal to or lower than the rear wheel pressure Pwr, each can be controlled separately.

[0055] <Lower Brake Unit SZ> The configuration of the lower braking unit SZ will be described with reference to the schematic diagram of Fig. 2. The lower braking unit SZ is a general-purpose unit for performing anti-lock brake control, traction control, anti-skid control, etc. In addition, the lower braking unit SZ performs complementary control. The "complementary control" compensates for a shortage of the supply pressure Ps from the upper braking unit SA.

[0056] The master pressure Pm and the first servo pressure Pa are input to the lower braking unit SZ from the upper braking unit SA as the front and rear wheel supply pressures Psf and Psr (i.e., "Psf=Pm, Psr=Pa"). The front and rear wheel supply pressures Psf and Psr (=Ps) are then adjusted (increased or decreased) by the lower braking unit SZ, and are output as hydraulic pressures Pwf and Pwr (front and rear wheel pressures) of the front and rear wheel cylinders CWf and CWr. The lower braking unit SZ is composed of a lower actuator YZ and a lower controller EZ.

[0057] <Lower actuator YZ> The lower actuator YZ (lower fluid unit) is provided between the upper actuator YA and the wheel cylinder CW in the communication passage HS. The lower actuator YZ is composed of a control valve UZ, a supply pressure sensor PS, a fluid pump QZ, an electric motor MZ, a pressure regulating reservoir RZ, an inlet valve VI, and an outlet valve VO.

[0058] A control valve UZ (=UZf, UZr) is provided in the communication path HS (=HSf, HSR). The control valve UZ is a normally open linear solenoid valve (differential pressure valve) like the pressure regulating valves UA, UB. The front and rear wheel control valves UZf, UZr enable the front and rear wheel pressures Pwf, Pwr to be increased from the front and rear wheel supply pressures Psf, Psr. In the lower braking unit SZ, the front and rear wheel control valves UZf, UZr enable the front and rear wheel pressures Pwf, Pwr to be individually adjusted.

[0059] Front and rear wheel supply pressure sensors PSf, PSr (=PS) are provided on the upper part of the control valve UZ (the part of the communication passage HS closer to the upper actuator YA) to detect the front and rear wheel supply pressures Psf, Psr (=Ps). The supply pressure Ps (=Psf, Psr) detected by the supply pressure sensor PS (=PSf, PSr) is referred to as the "detected supply pressure Psk (=Pskf, Pskr)." The detected supply pressure Psk is input to the lower controller EZ. Here, the rear wheel supply pressure sensor PSr can be omitted.

[0060] The upper and lower parts of the control valve UZ (=UZf, UZr) are connected by a return path HZ (=HZf, HZr). A fluid pump QZ (=QZf, QZr) and a pressure regulating reservoir RZ (=RZf, RZr) are provided in the return path HZ (fluid path). The fluid pump QZ is driven by an electric motor MZ. The electric motor MZ is a power source for increasing the supply pressure Ps (=Psf, Psr). The electric motor MZ and the fluid pump QZ are included in the lower braking unit SZ, and are therefore also referred to as the "lower electric motor MZ" and the "lower fluid pump QZ".

[0061] When the electric motor MZ is driven, the fluid pump QZ sucks the brake fluid BF from the upper part of the control valve UZ and discharges it to the lower part of the control valve UZ. As a result, a circulating flow KZ (indicated by dashed arrows) of the brake fluid BF, which includes the pressure regulating reservoir RZ, is generated in the communication path HS and the return path HZ. When the flow path of the communication path HS is narrowed by the control valve UZ and the circulating flow KZ of the brake fluid BF is throttled, the hydraulic pressure Pp (referred to as the "regulating pressure") at the lower part of the control valve UZ is increased from the hydraulic pressure Ps (supply pressure) at the upper part of the control valve UZ due to the orifice effect at that time. As with the first and second servo pressures Pa and Pb, the relationship between the supply pressure Ps and the regulating pressure Pp is such that the regulating pressure Pp is equal to or greater than the supply pressure Ps (i.e., "Pp≧Ps"). In other words, the regulating pressure Pp can be increased from the supply pressure Ps.

[0062] Inside the lower actuator YZ, the front and rear wheel communication passages HSf and HSR are branched into two and connected to the front and rear wheel cylinders CWf and CWr. A normally open inlet valve VI and a normally closed outlet valve VO are provided for each wheel cylinder CW so that each wheel pressure Pw can be adjusted individually. Specifically, the inlet valve VI is provided in the branched communication passage HS (i.e., on the side closer to the wheel cylinder CW with respect to the branching part of the communication passage HS). The communication passage HS is connected to the pressure regulating reservoir RZ via a pressure reducing passage HG (fluid passage) at a lower part of the inlet valve VI (a part of the communication passage HS closer to the wheel cylinder CW). An outlet valve VO is provided in the pressure reducing passage HG. An on-off type solenoid valve is used as the inlet valve VI and the outlet valve VO. The wheel pressure Pw can be adjusted individually for each wheel by the inlet valve VI and the outlet valve VO.

[0063] When the inlet valve VI and the outlet valve VO are not energized and are not operating, the inlet valve VI is opened and the outlet valve VO is closed. In this state, the wheel pressure Pw is equal to the regulating pressure Pp. The wheel pressure Pw is independently adjusted for each wheel cylinder CW by driving the inlet valve VI and the outlet valve VO. To decrease the wheel pressure Pw, the inlet valve VI is closed and the outlet valve VO is opened. The inflow of the brake fluid BF into the wheel cylinder CW is prevented and the brake fluid BF in the wheel cylinder CW flows out to the pressure regulating reservoir RZ, so that the wheel pressure Pw is decreased. To increase the wheel pressure Pw, the inlet valve VI is opened and the outlet valve VO is closed. The outflow of the brake fluid BF into the pressure regulating reservoir RZ is prevented and the regulating pressure Pp from the pressure regulating valve UZ is supplied to the wheel cylinder CW, so that the wheel pressure Pw is increased. However, the upper limit of the increase is the regulated pressure Pp. To maintain the wheel pressure Pw, the inlet valve VI and the outlet valve VO are both closed. Since the wheel cylinder CW is fluidically sealed, the wheel pressure Pw is maintained constant.

[0064] <Lower Controller EZ> The lower actuator YZ is controlled by a lower controller EZ (lower control unit). The lower controller EZ, like the upper controller EA, is composed of a microprocessor MP and a drive circuit DR. The lower controller EZ is connected to a communication bus BS. Therefore, the upper controller EA and the lower controller EZ can share signals via the communication bus BS.

[0065] The lower controller EZ (particularly, the microprocessor MP) receives inputs of sensor signals such as the operation displacement Sp, the detected supply pressure Psk, the wheel speed Vw, the steering amount Sa, the yaw rate Yr, the longitudinal acceleration Gx, and the lateral acceleration Gy. Furthermore, the lower controller EZ receives inputs of the target acceleration Gs, the target supply pressure Pst, the suitability flag FL, and the like from the communication bus BS. The lower controller EZ calculates the vehicle's traveling speed Vx (also called the "vehicle speed") based on the wheel speed Vw. The lower controller EZ executes antilock brake control (so-called ABS control) that suppresses locking of the wheels WH, traction control that suppresses the spinning of the drive wheels, and anti-skid control (so-called ESC) that suppresses understeer and oversteer to improve the directional stability of the vehicle. Furthermore, in addition to the above controls, the lower controller EZ executes complementary control (described later) to deal with abnormalities in the brake control device SC (particularly, the hydraulic pressure generating unit PU).

[0066] The lower controller EZ drives the electric motor MZ and various solenoid valves (UZ, etc.) constituting the lower actuator YZ by the drive circuit DR according to a control algorithm programmed in the microprocessor MP. In the drive circuit DR of the lower controller EZ, an H-bridge circuit is configured with switching elements (e.g., MOS-FET) to drive the electric motor MZ. The drive circuit DR is also provided with switching elements to drive the various solenoid valves (UZ, etc.). In addition, the drive circuit DR includes a motor current sensor (not shown) that detects the supply current In to the electric motor MZ, and a control valve current sensor IZ (not shown) that detects the current Iz (referred to as the "control valve current") supplied to the control valve UZ. Based on the control algorithm, the drive signal Mz of the electric motor MZ, the drive signal Uz of the control valve UZ, the drive signal Vi of the inlet valve VI, and the drive signal Vo of the outlet valve VO are calculated. Then, based on the drive signal (Uz, etc.), the electric motor MZ and the solenoid valves UZ, VI, and VO are controlled by the drive circuit DR.

[0067] <Pressure regulation control processing> An example of the pressure regulation control process will be described with reference to the flow chart in Fig. 3. The pressure regulation control includes regenerative cooperative control between the regenerative device KG and the brake control device SC, as well as suitability judgment of the hydraulic pressure generating unit PU and complementary control. In suitability judgment, it is determined whether "the operation of the hydraulic pressure generating unit PU is normal or abnormal." If the hydraulic pressure generating unit PU breaks down and is abnormal, the shortage of supply pressure Ps is compensated for by complementary control in the lower brake unit SZ. Pressure regulation control excluding complementary control is executed by the upper controller EA, and complementary control is executed by the lower controller EZ.

[0068] In describing the processing example, the following is assumed. The regenerative device KG is provided only on the front wheels WHf. Therefore, the regenerative braking force Fg acts on the front wheels WHf but not on the rear wheels WHr. When the brake control device SC operates normally, the lower actuator YZ is not driven, and only the upper actuator YA is driven. Therefore, when the upper brake unit SA is normal, the wheel pressure Pw is adjusted only by the upper actuator YA, so that the supply pressure Ps and the wheel pressure Pw are the same (i.e., "Ps=Pw"). In the upper actuator YA, the pressure receiving area rm (also called the "master area") of the master chamber Rm and the pressure receiving area rc (also called the "servo area") of the servo chamber Rc are set to be equal (i.e., "rm = rc"). Therefore, if the friction of the seal member SL is ignored, in the static state, "Pm = Pb". The rear wheel supply pressure sensor PSr is omitted. Therefore, the supply pressure sensor PS is the front wheel supply pressure sensor PSf, and the detected supply pressure Psk is the front wheel detected supply pressure Pskf. Here, the supply pressure sensor PS is built into the lower actuator YZ, and the detected supply pressure Psk is input to the lower controller EZ. Furthermore, the detected supply pressure Psk is acquired by the upper controller EA through the communication bus BS.

[0069] The various braking forces are as follows: - "Vehicle body total braking force Fu" is the actual braking force acting on the entire vehicle. A target value corresponding to the vehicle body total braking force Fu is "target total braking force Fv." - "Friction braking force Fe (hydraulic braking force)" is the braking force actually generated by the wheel pressure Pw. A target value corresponding to the friction braking force Fe is "target friction braking force Fn." - "Regenerative braking force Fg" is the braking force actually generated by the regenerative device KG. A 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 upper braking unit SA (particularly, the upper controller EA) and transmitted to the regenerative device KG (particularly, the regenerative controller EG) via the communication bus BS. In the regenerative device KG, the regenerative controller EG controls the generator GN so that the actual regenerative braking force Fg approaches and matches the target regenerative braking force Fh. - "Limit regenerative braking force Fx" is the maximum value (limit value) of the regenerative braking force Fg that the regenerative device KG can generate. Therefore, the regenerative device KG can generate a regenerative braking force Fg in the range from "Fg=0" to the limit regenerative braking force Fx. The limit regenerative braking force Fx is calculated by the regenerative device KG (particularly, the regenerative controller EG) and transmitted to the upper braking unit SA (particularly, the upper controller EA) via the communication bus BS. The upper controller EA grasps the operating status of the regenerative device KG based on the limit regenerative braking force Fx.

[0070] In the pressure regulation control, the second operation mode Ms is adopted as the operation mode of the brake operating member BP. For example, the operation mode is switched from the first operation mode Mm to the second operation mode Ms when the brake control device SC is started (or when braking starts).

[0071] In the second operation mode Ms, power is supplied to the inlet valve VA and the release valve VB, the normally closed inlet valve VA is opened, and the normally open release valve VB is closed. In the second operation mode Ms, the brake operating member BP can be displaced separately from the master piston NM, so that the front and rear wheel pressures Pwf, Pwr can be adjusted independently of the operation of the brake operating member BP. At this time, the operating force Fp of the brake operating member BP is generated by the stroke simulator SS.

[0072] In step S110, various signals are read in the upper and lower controllers EA and EZ. The upper controller EA acquires the braking operation amount Ba (a collective term for Sp and Pn), the target acceleration Gs, the first and second detected servo pressures Pak and Pbk, the detected supply pressure Psk, and the limit regenerative braking force Fx. The braking operation amount Ba and the target acceleration Gs are referred to as the "braking demand amount Bs." The braking demand amount Bs is a state quantity that represents a braking demand for the vehicle, and is a collective term for the braking operation amount Ba and the target acceleration Gs.

[0073] In step S110, the lower controller EZ acquires the braking demand amount Bs (collectively referring to Ba and Gs), the target supply pressure Pst, and the suitability flag FL. The "target supply pressure Pst" is a target value corresponding to the supply pressure Ps. The "suitability flag FL" is a control flag indicating whether the operation of the hydraulic pressure generating unit PU of the upper brake unit SA is normal or abnormal. For example, if the hydraulic pressure generating unit PU is normal, "FL=0" is determined, and if the hydraulic pressure generating unit PU is abnormal, "FL=1" is determined. The target supply pressure Pst and the suitability flag FL are transmitted from the upper controller EA to the communication bus BS.

[0074] In step S120, a target total braking force Fv (a target value of vehicle body total braking force Fu acting on the entire vehicle) is calculated based on the braking demand Bs and the calculation map Zfv. When the braking demand Bs is less than a predetermined amount bo, the target total braking force Fv is calculated to be "0" according to the calculation map Zfv. When the braking demand Bs is equal to or greater than the predetermined amount bo, the target total braking force Fv is calculated to increase from "0" as the braking demand Bs increases. Here, the "predetermined amount bo" corresponds to the play of the brake operating member BP, etc., and is set in advance as a predetermined value (constant) (see total braking force calculation block FV).

[0075] In step S130, in order to execute the regeneration cooperative control, based on the target total braking force Fv and the limit regenerative braking force Fx, the target regenerative braking force Fh and the front and rear wheel target frictional braking forces Fnf, Fnr (= Fn) are calculated. Specifically, for the braking force Fu of the entire vehicle, the ratio of the braking forces (including the regenerative braking force Fg) generated by the front and rear wheels WHf, WHr (also referred to as "braking force distribution") is optimized, and the target values Fh, Fn of the braking force are determined in three cases.

[0076] Case (1): When the target total braking force Fv is less than or equal to the limit regenerative braking force Fx, the target regenerative braking force Fh is made equal to the target total braking force Fv, and the front and rear wheel target frictional braking forces Fnf, Fnr are made "0". That is, when "Fv ≦ Fx", "Fh = Fv, Fnf = Fnr = 0" is determined.

[0077] Case (2): When the target total braking force Fv is greater than the limit regenerative braking force Fx and less than or equal to the value "Fx / hf" obtained by dividing the limit regenerative braking force Fx by the front wheel ratio hf, the target regenerative braking force Fh is made equal to the target total braking force Fv. Then, the front wheel target frictional braking force Fnf is made "0", and the rear wheel target frictional braking force Fnr is determined to be the value obtained by subtracting the target regenerative braking force Fh (= Fx) from the target total braking force Fv. That is, when "Fx < Fv ≦ (Fx / hf)", "Fh = Fx, Fnf = 0, Fnr = Fv - Fh = Fv - Fx" is determined. Here, the "front wheel ratio hf" is the ratio of the front wheel target braking force (that is, the sum of the target regenerative braking force Fh and the front wheel target frictional braking force Fnf) to the target total braking force Fv. The front wheel ratio hf is preset as a predetermined value (constant) based on the specifications of the vehicle (such as the center of gravity position, wheelbase, etc.).

[0078] Case (3): When the target total braking force Fv is greater than the value "Fx / hf" obtained by dividing the limit regenerative braking force Fx by the front wheel ratio hf, the target regenerative braking force Fh is set equal to the target total braking force Fv. The front wheel target frictional braking force Fnf is calculated by subtracting the target regenerative braking force Fh from the value "hf·Fv" obtained by multiplying the target total braking force Fv by the front wheel ratio hf. The rear wheel target frictional braking force Fnr is calculated by multiplying the value obtained by subtracting the front wheel ratio hf from "1" by the target total braking force Fv. In other words, when "Fv>(Fx / hf)", "Fh=Fx, Fnf=hf·Fv-Fh, Fnr=(1-hf)·Fv" are determined.

[0079] In step S140, the first and second target servo pressures Pat, Pbt are calculated based on the target frictional braking force Fn. The "first and second target servo pressures Pat, Pbt" are target values ​​corresponding to the first and second servo pressures Pa, Pb (actual values). Since "Pa≧Pb", the first target servo pressure Pat is calculated from the rear wheel target frictional braking force Fnr based on the specifications of the braking device SX. Similarly, the second target servo pressure Pbt is calculated from the front wheel target frictional braking force Fnf based on the specifications of the braking device SX. Furthermore, since the second servo pressure Pb is transmitted to the front wheel cylinder CWf via the master cylinder CM, the sliding resistance of the seal member SL is taken into account in the calculation of the second target servo pressure Pbt. The specifications of the braking device SX include the pressure-receiving area of ​​the wheel cylinder CW, the effective braking radius of the rotating member KT (brake disc), the friction coefficient of the friction member (brake pad), the effective radius of the wheel WH (tire), and the like.

[0080] In the regenerative cooperative control, the first and second target servo pressures Pat, Pbt are determined as follows with an increase in the braking demand Bs. In case (1), the first and second target servo pressures Pat, Pbt are both maintained at "0" so that the regenerative device KG recovers the maximum amount of energy. In case (2), the first target servo pressure Pat (resulting in rear wheel pressure Pwr) is increased from "0" while the second target servo pressure Pbt (resulting in front wheel pressure Pwf) is maintained at "0" so that the braking force distribution quickly reaches a predetermined ratio (i.e., front wheel ratio hf). In case (3), the first and second target servo pressures Pat, Pbt are both increased so that the braking force distribution is maintained at the predetermined ratio hf.

[0081] In step S150, it is determined whether "the hydraulic pressure generating unit PU is abnormal." The process of step S150 is referred to as "suitability determination." If the suitability determination is negative (i.e., the hydraulic pressure generating unit PU is normal), the suitability flag FL is set to "0," and the process proceeds to step S160. If the hydraulic pressure generating unit PU is normal, the lower actuator YZ is stopped. On the other hand, if the suitability determination is positive (i.e., the hydraulic pressure generating unit PU has failed), the suitability flag FL is set to "1," and the process proceeds to step S170. The suitability determination will be described in detail later.

[0082] In step S160, the upper actuator YA (particularly, the hydraulic pressure generating unit PU) is driven by the upper controller EA. As a result, the first and second servo pressures Pa and Pb are controlled to approach and match the first and second target servo pressures Pat and Pbt. Specifically, first, the electric motor MA is driven. As a result, a circulating flow KN is generated that includes the fluid pump QA and the first and second pressure regulating valves UA and UB. A target rotation speed Nt of the electric motor MA is calculated based on the operation speed dS. Then, a supply current Im (motor current) to the electric motor MA is controlled so that the motor rotation speed Na approaches and matches the target rotation speed Nt.

[0083] Based on the first and second target servo pressures Pat, Pbt, the first and second pressure regulating valves UA, UB are controlled so that the first and second servo pressures Pa, Pb (actual values) approach and match the first and second target servo pressures Pat, Pbt (target values). For example, based on the first and second detected servo pressures Pak, Pbk detected by the first and second servo pressure sensors PA, PB, control is performed so that the first and second detected servo pressures Pak, Pbk (detected values) approach and match the first and second target servo pressures Pat, Pbt (target values). Specifically, since the first and second servo pressures Pa, Pb and the first and second pressure regulating valve currents Ia, Ib have a unique relationship, the first and second target currents Iat, Ibt are calculated based on the first and second target servo pressures Pat, Pbt. The drive circuit DR is controlled so that the first and second pressure regulating valve currents Ia, Ib (detected values) detected by the pressure regulating valve current sensor approach and match the first and second target currents Iat, Ibt (target values). Furthermore, the first and second pressure regulating valve currents Ia, Ib are finely adjusted based on the first and second detected servo pressures Pak, Pbk so as to compensate for hydraulic pressure errors. That is, in adjusting the first and second servo pressures Pa, Pb, so-called feedback control (closed loop control) related to hydraulic pressure is executed. Furthermore, since the second servo pressure Pb and the supply pressure Ps have a predetermined relationship (the relationship is "Pb = Ps" if the sliding resistance of the seal member SL is ignored), in the feedback control, the detected supply pressure Psk (detected value) detected by the supply pressure sensor PS may be controlled so as to approach and match the second target servo pressure Pbt. In this configuration, the second servo pressure sensor PB may be omitted.

[0084] When the first and second pressure regulating valve currents Ia and Ib corresponding to the first and second target servo pressures Pat and Pbt are supplied, the first and second servo pressures Pa and Pb are achieved as a result of the unique relationship described above. For this reason, open-loop control may be performed in which the first and second detected servo pressures Pak and Pbk are not used. In this configuration, the first and second servo pressure sensors PA and PB are not required. However, since the first servo pressure sensor PA is required for suitability determination (described later), at least the first servo pressure sensor PA is provided in the brake control device SC. Note that when the hydraulic pressure generating unit PU is normal (when step S150 is negative and "FL=0"), the lower actuator YZ is stopped, so "Pwf=Psf=Pm, Pwr=Psr=Pa".

[0085] If an abnormality is determined in the suitability determination in step S150, the operation of the regenerative device KG is stopped in step S170. For example, "Fh=0" or "FL=1" is sent from the upper controller EA to the regenerative controller EG, and power generation by the generator GN in the regenerative device KG is stopped. As a result, the regenerative braking force Fg is set to "0" and the regenerative cooperative control is terminated. Also, in step S170, the hydraulic pressure generating unit PU is stopped. Therefore, the first and second servo pressures Pa and Pb are set to "0".

[0086] Furthermore, in step S170, the operation mode of the brake operating member BP is switched from the second operation mode Ms (by-wire mode) to the first operation mode Mm (manual mode). By stopping the supply of power to the solenoid valves VA and VB, the normally closed inlet valve VA is closed and the normally open release valve VB is opened. Since the input chamber Rn is fluidically locked, the master piston NM and the brake operating member BP are displaced together, and the front wheel supply pressure Psf due to the operation of the brake operating member BP is output from the upper brake unit SA. In other words, the supply pressure Psf (=Pm) from the upper brake unit SA is generated by the driver's muscle force (i.e., the operating force Fp). At this time, the operating force Fp of the brake operating member BP is generated by the rigidity (i.e., the elastic deformation of the brake caliper, friction members, brake piping, etc.) of the front wheel braking device SXf (a device that generates a front wheel friction braking force Fef by the front wheel pressure Pwf). Incidentally, since the hydraulic pressure generating unit PU is stopped, the rear wheel supply pressure Psr (=Pa) is not generated.

[0087] In step S180, the lower brake unit SZ executes complementary control. The complementary control is started in response to "FL=1". The complementary control compensates for the shortage of the supply pressure Ps. Specifically, a target supply pressure Pst, which is a target value of the supply pressure Ps to be supplied to the lower brake unit SZ, is calculated. The target supply pressure Pst is determined by compensating for the sliding resistance of the seal member SL with respect to the second target servo pressure Pbt. Since the second target servo pressure Pbt is calculated from the braking demand amount Bs, the target supply pressure Pst may be determined from the braking demand amount Bs (collectively, Ba and Gs). Here, the target supply pressure Pst is calculated by the upper controller EA and acquired by the lower controller EZ. Alternatively, the target supply pressure Pst may be calculated by the lower controller EZ based on the same method as the upper controller EA.

[0088] When the hydraulic pressure generating unit PU is normal, the front wheel supply pressure Psf and the rear wheel supply pressure Psr are adjusted separately. However, when the hydraulic pressure generating unit PU is abnormal, the regenerative cooperative control is stopped, so the front wheel target supply pressure Pstf and the rear wheel target supply pressure Pstr are determined to be equal (i.e., "Pst=Pstf=Pstr"). Furthermore, based on the target supply pressure Pst and the detected supply pressure Psk (=Pskf), a deviation hPs therebetween (also called "supply pressure deviation") is calculated. Specifically, the detected supply pressure Psk is subtracted from the target supply pressure Pst to determine the supply pressure deviation hPs (i.e., "hPs=Pst-Psk"). The supply pressure deviation hPs represents a shortage of the supply pressure Ps that should be output from the upper actuator YA.

[0089] Then, in step S180, the lower actuator YZ (MZ, UZ, etc.) is driven based on the supply pressure deviation hPs. The electric motor MZ is driven, and the brake fluid BF is discharged from the fluid pump QZ. This generates a circulating flow KZ of the brake fluid BF in the communication path HS and the return path HZ. A target current Is is calculated based on the supply pressure deviation hPs and a preset calculation map (not shown). The "target current Is" is a target value corresponding to the current Iz (control valve current) supplied to the control valve UZ. The target current Is is determined to be larger according to the calculation map as the supply pressure deviation hPs is larger. The drive signal Uz is calculated so that the control valve current Iz (detected value) approaches and coincides with the target current Is (target value). Here, the control valve current Iz is detected by a control valve current sensor (not shown) provided in the drive circuit DR of the lower controller EZ.

[0090] By throttling the circulating flow KZ by the control valve UZ, the regulated pressure Pp (=Pw) ​​is increased by an amount corresponding to the supply pressure deviation hPs from the supply pressure Ps. The increased regulated pressure Pp is output from the lower actuator YZ as the wheel pressure Pw (actual value) (i.e., "Pw=Ps+hPs").

[0091] When an abnormality is determined in the hydraulic pressure generating unit PU, the hydraulic pressure generating unit PU is stopped and the first operation mode Mm is selected. The front wheel supply pressure Psf (=Pm) is generated only by the operating force Fp of the brake operating member BP by the driver, and the rear wheel supply pressure Psr (=Pa) is "0". However, in the brake control device SC, a wheel pressure Pw corresponding to the braking demand amount Bs can be generated by complementary control in the lower brake unit SZ.

[0092] <Conformity assessment of hydraulic pressure generating unit PU> The suitability judgment process (the process of step S150) will be described with reference to the flow diagram of Fig. 4. In the suitability judgment, it is judged whether "the operation of the hydraulic pressure generating unit PU is abnormal or not." The suitability judgment is also called "abnormality judgment." The suitability judgment is always performed by the upper controller EA when the hydraulic pressure generating unit PU is operating.

[0093] In the hydraulic pressure generating unit PU, the first servo pressure Pa is equal to or greater than the second servo pressure Pb. In the regenerative cooperative control, the first servo pressure Pa is increased from "0" before the second servo pressure Pb is increased. For this reason, the operation of the hydraulic pressure generating unit PU is monitored (i.e., the suitability judgment) based on the state quantities Pat and Pak related to the first servo pressure Pa. The suitability judgment can also be made based on the state quantities Pbt and Pbk related to the second servo pressure Pb. However, by adopting the state quantities Pat and Pak related to the first servo pressure Pa for the suitability judgment, an abnormality in the hydraulic pressure generating unit PU can be quickly judged. Specifically, the suitability judgment is made based on the deviation hPa between the first target servo pressure Pat and the first detected servo pressure Pak (referred to as the "servo pressure deviation").

[0094] In step S210, the first target servo pressure Pat and the first detected servo pressure Pak are read in. The first target servo pressure Pat is a target value for the first servo pressure Pa calculated from the braking demand amount Bs. The first detected servo pressure Pak is the detection result of the first servo pressure sensor PA.

[0095] In step S220, a target gradient dPa is calculated based on the first target servo pressure Pat. The "target gradient dPa" is a value equivalent to the amount of change in the first target servo pressure Pat per unit time (also simply referred to as the "time change amount"). For example, the absolute value of the first target servo pressure Pat is time-differentiated to determine the target gradient dPa. Since the first target servo pressure Pat is calculated based on the braking demand Bs, the target gradient dPa may be calculated from the braking demand Bs. Note that when the first target servo pressure Pat is maintained constant, the target gradient dPa is "0".

[0096] In step S230, a threshold pressure Ha is calculated based on the target gradient dPa. The "threshold pressure Ha" is a threshold value for determining an abnormality in the hydraulic pressure generating unit PU. The threshold pressure Ha is determined in accordance with a preset calculation map Zha so that the greater the target gradient dPa, the greater the threshold pressure Ha. That is, when the target gradient dPa is large, the threshold pressure Ha is made larger compared to when the target gradient dPa is small. A lower limit pressure ha is set for the threshold pressure Ha. The lower limit pressure ha is a predetermined value (constant) that is set in advance (see threshold pressure calculation block HA of the blowing section).

[0097] The brake control device SC is a so-called on-demand type device that operates in response to a braking request. Therefore, when braking is not being applied, the hydraulic pressure generating unit PU is stopped, and the start of braking is a trigger to start the operation of the hydraulic pressure generating unit PU. Since the response of the hydraulic pressure generating unit PU (especially the electric motor MA) is limited, the servo pressure deviation hPa may increase instantaneously when the hydraulic pressure generating unit PU is started. In addition, an increase in the servo pressure deviation hPa may also occur when the second servo pressure Pb (=Pwf) is suddenly decreased while the first servo pressure Pa (=Pwr) is being maintained or decreased. In such a situation, the threshold pressure Ha is determined based on the target gradient dPa so that an abnormality is not unnecessarily determined.

[0098] In step S240, the deviation hPa (servo pressure deviation) between the first target servo pressure Pat and the first detected servo pressure Pak is calculated based on them. Specifically, the first detected servo pressure Pak is subtracted from the first target servo pressure Pat to determine the servo pressure deviation hPa (i.e., "hPa = Pat - Pak"). The servo pressure deviation hPa represents the shortage of the first detected servo pressure Pak with respect to the first target servo pressure Pat.

[0099] In step S250, it is determined whether the servo pressure deviation hPa is greater than the threshold pressure Ha. If the servo pressure deviation hPa is equal to or less than the threshold pressure Ha, the result in step S250 is negative, and the process proceeds to step S260. In step S260, the hydraulic pressure generating unit PU is identified as being normal, and the suitability flag FL is set to "0." On the other hand, if the servo pressure deviation hPa is greater than the threshold pressure Ha, the result in step S250 is positive, and the process proceeds to step S270.

[0100] In step S270, the duration Tk is calculated. The duration Tk is the time during which the state of "hPa>Ha" continues. In other words, the duration Tk is the time that has elapsed since the determination in step S250 was first made positive.

[0101] In step S280, it is determined whether the duration Tk is greater than a predetermined time ta based on the duration Tk. Here, the "predetermined time ta" is a threshold value related to the duration Tk, and is a preset predetermined value (constant). If the duration Ta is equal to or less than the predetermined time ta and step S280 is negative, the process proceeds to step S260. On the other hand, if the duration Tk exceeds the predetermined time ta and step S280 is positive, the process proceeds to step S290. In step S290, an abnormality in the hydraulic pressure generating unit PU is identified and the suitability flag FL is set to "1."

[0102] In the suitability judgment (abnormality judgment), even if the servo pressure deviation hPa exceeds the threshold pressure Ha, the hydraulic pressure generating unit PU is not immediately judged to be abnormal. If the state in which the servo pressure deviation hPa is greater than the threshold pressure Ha continues for a predetermined time ta, the hydraulic pressure generating unit PU is judged to be abnormal. In the lower braking unit SZ, the suitability flag FL switches from "0" to "1", and the execution of complementary control is started.

[0103] In regenerative cooperative control, the first servo pressure Pa is increased from "0" before the second servo pressure Pb is increased from "0", so that the operation of the hydraulic pressure generating unit PU is monitored by the first detected servo pressure Pak. This monitoring is performed not only at start-up (i.e., when the vehicle is stopped) but also when the vehicle is running. For example, when the hydraulic pressure generating unit PU is operating and the first servo pressure Pa is generated, monitoring is always performed. Since the operation of the hydraulic pressure generating source PU is appropriately monitored, if an abnormality occurs in the hydraulic pressure generating source PU, the abnormality is immediately determined.

[0104] <Conformity judgment operation> The operation of suitability determination will be described with reference to the time series diagram of Fig. 5 (a diagram showing the transition of state quantities over time T). The suitability (normal or abnormal) of the hydraulic pressure generating unit PU is determined based on the first target servo pressure Pat (target value) and the first detected servo pressure Pak (detected value). In the suitability determination, if "(Pat-Pak) ≦ Ha", the hydraulic pressure generating unit PU is determined to be normal, and if "(Pat-Pak) > Ha", the hydraulic pressure generating unit PU is determined to be abnormal.

[0105] "(Pat-Pak)≦Ha" can be modified to "Pak≧(Pat-Ha)". Therefore, the suitability judgment can be expressed as follows. If the hydraulic pressure obtained by subtracting the threshold pressure Ha from the first target servo pressure Pat is the "lower limit pressure", the hydraulic pressure generating unit PU is normal when the first detected servo pressure Pak is equal to or higher than the lower limit pressure "Pat-Ha". Here, the region from the first target servo pressure Pat to the lower limit pressure "Pat-Ha" is referred to as the "allowable range Xa". In the suitability judgment, the allowable range Xa is determined (set) based on the first target servo pressure Pat and the threshold pressure Ha. Then, when the first detected servo pressure Pak transitions within the allowable range Xa, the hydraulic pressure generating unit PU is judged to be normal. On the other hand, when the first detected servo pressure Pak transitions outside the allowable range Xa, the hydraulic pressure generating unit PU is judged to be abnormal.

[0106] The suitability determination is always performed when the hydraulic pressure generating unit PU is operating (i.e., when the first servo pressure Pa is increased, maintained, or decreased). Alternatively, the suitability determination may be performed only when the hydraulic pressure generating unit PU is increasing pressure. In this case, a value equivalent to the increase in the first target servo pressure Pat per unit time (the amount of change over time when the hydraulic pressure is increasing) is used for the target gradient dP. In any case, the operation of the hydraulic pressure generating unit PU is always monitored, not only at start-up, but at least when the first servo pressure Pa is increasing.

[0107] FIG. 5 illustrates an example of the suitability judgment when the first target servo pressure Pat increases at a constant target gradient dPa with the passage of time T. The shaded area is the allowable range Xa. The threshold pressure Ha changes according to the target gradient dPa, but in this example, the threshold pressure Ha is a constant value. Three examples of the transition of the first detected servo pressure Pak are shown in (a), (b), and (c).

[0108] At time t0, braking is started, and the braking demand amount Bs is increased from "0". Accordingly, the first target servo pressure Pat is increased from "0". Immediately after time t0, a target gradient dPa (amount of change in the first target servo pressure Pat per unit time) is calculated based on the first target servo pressure Pat. Then, a threshold pressure Ha is determined based on the target gradient dPa. The threshold pressure Ha is calculated to be larger as the target gradient dPa is larger. The threshold pressure Ha is compared with the deviation hPa between the first target servo pressure Pat and the first detected servo pressure Pak (the detection value of the first servo pressure sensor PA). That is, it is determined whether the first detected servo pressure Pak is within the allowable range Xa.

[0109] ≪Transition example (a)≫ As in transition example (a), when the first detected servo pressure Pak increases from "0" within the permissible range Xa and then transitions within the permissible range Xa, the servo pressure deviation hPa continues to be equal to or less than the threshold pressure Ha. In other words, since the first detected servo pressure Pak follows the first target servo pressure Pat, the result in step S250 is NO, and it continues to be determined that "the hydraulic pressure generating unit PU is normal (FL=0)."

[0110] ≪Transition example (b)≫ As in the transition example (b), when the first detected servo pressure Pak does not increase from "0" within the allowable range Xa (i.e., when the rise of the first detected servo pressure Pak is delayed), the count of the duration Tk is started at the time t1 when the first detected servo pressure Pak transitions to the outside of the allowable range Xa. After that, the state where the first detected servo pressure Pak is out of the allowable range Xa (i.e., the state where the servo pressure deviation hPa is larger than the threshold pressure Ha) continues for a predetermined time ta. At the time t2, the result of step S280 is affirmative, and it is determined that "the hydraulic pressure generating unit PU is abnormal (FL=1)". At the time t2, the supply of power to the hydraulic pressure generating unit PU is terminated, and the hydraulic pressure generating unit PU is stopped. Also, at the time t2, the supply of power to the solenoid valves VA and VB is stopped, and the operation mode is switched from the second operation mode Ms to the first operation mode Mm.

[0111] ≪Transition example (c)≫ As in transition example (c), the first detected servo pressure Pak rises from "0" within the allowable range Xa, but then falls outside the allowable range Xa. From time t3 when the first detected servo pressure Pak transitions outside the allowable range Xa, the duration Tk is calculated. As in transition example (b), when the state in which the first detected servo pressure Pak transitions outside the allowable range Xa (i.e., the state of "hPa>Ha") continues for a predetermined time ta, an abnormality in the hydraulic pressure generating unit PU is determined. Then, the above-mentioned measures (stopping the hydraulic pressure generating unit PU and switching to the first operation mode Mm) are executed.

[0112] Even if the first detected servo pressure Pak once deviates from the permissible range Xa, if it re-enters the permissible range Xa, the calculation of the duration Tk is reset and returned to "Tk = 0." After that, when the first detected servo pressure Pak deviates from the permissible range Xa again, counting of the duration Tk is started from that point.

[0113] <Second embodiment of the brake control device SC> A second embodiment of the vehicle brake control device SC will be described with reference to the schematic diagram of FIG. 6. The first embodiment is applied to a vehicle equipped with a regenerative generator GN on the front wheels WHf. In contrast, the second embodiment is applied to a vehicle equipped with a regenerative generator GN on the rear wheels WHr. Since the first and second servo pressures Pa and Pb generated by the hydraulic pressure generating unit PU are constrained by "Pa≧Pb", in the second embodiment, the front wheel pressure Pwf is controlled by the first servo pressure Pa, and the rear wheel pressure Pwr is controlled by the second servo pressure Pb.

[0114] The configurations of the apply unit AP, input unit NR, hydraulic pressure generating unit PU, upper controller EA, and lower brake unit SZ in the second embodiment are the same as those in the first embodiment. The differences are the hydraulic pressure transmission paths of the first and second servo pressures Pa and Pb, and the calculation method of the first and second target servo pressures Pat and Pbt related to the regenerative cooperative control. Explanations of the parts that are the same as those in the first embodiment will be omitted.

[0115] <Hydraulic pressure transmission path: Connection of hydraulic pressure generating unit PU> In the second embodiment, since the regenerative braking force Fg is generated at the rear wheel WHr, the front wheel pressure Pwf is adjusted by the first servo pressure Pa, and the rear wheel pressure Pwr is adjusted by the second servo pressure Pb. That is, in the front wheel braking system, the return path HK is connected to the servo chamber Rc between the discharge part Qo and the first pressure regulating valve UA via the servo path HC. The master pressure Pm is adjusted by the first servo pressure Pa supplied to the servo chamber Rc. Therefore, in the front wheel braking system, the master pressure Pm generated by the first servo pressure Pa is supplied to the front wheel cylinder CWf as the front wheel supply pressure Psf. In the rear wheel braking system, the return path HK is connected to the rear wheel connection path HSr between the first pressure regulating valve UA and UB. Therefore, in the rear wheel braking system, the second servo pressure Pb is directly supplied to the rear wheel cylinder CWr as the rear wheel supply pressure Psr.

[0116] <Regenerative Cooperative Control: Determination of the 1st and 2nd target servo pressures Pat and Pbt> In the pressure adjustment control (particularly, regenerative cooperative control) according to the second embodiment, the target regenerative braking force Fh and the front and rear wheel target frictional braking forces Fnf, Fnr are determined based on the target total braking force Fv and the limit regenerative braking force Fx in the following three cases. Then, based on the specifications of the braking device SX, the front and rear wheel target frictional braking forces Fnf, Fnr are converted into first and second target servo pressures Pat, Pbt. The main difference is that the "front wheel ratio hf" in the first embodiment is replaced with a "rear wheel ratio hr" in the second embodiment.

[0117] Case (4): When the target total braking force Fv is equal to or less than the limit regenerative braking force Fx, the target regenerative braking force Fh is set equal to the target total braking force Fv, and the front and rear wheel target frictional braking forces Fnf, Fnr are set to 0. That is, when "Fv≦Fx", it is determined that "Fh=Fv, Fnf=Fnr=0".

[0118] Case (5): When the target total braking force Fv is greater than the limit regenerative braking force Fx and is less than or equal to the value "Fx / hr" obtained by dividing the limit regenerative braking force Fx by the rear wheel ratio hr, the target regenerative braking force Fh is made equal to the target total braking force Fv. Then, the front wheel target frictional braking force Fnf is determined as the value obtained by subtracting the target regenerative braking force Fh (= Fx) from the target total braking force Fv, and the rear wheel target frictional braking force Fnr is determined to be "0". That is, when "Fx < Fv ≦ (Fx / hr)", "Fh = Fx, Fnf = Fv - Fh = Fv - Fx, Fnr = 0" is determined. Note that the "rear wheel ratio hr" is the ratio of the rear wheel target braking force (i.e., the sum of the target regenerative braking force Fh and the rear wheel target frictional braking force Fnr) to the target total braking force Fv, and is a predetermined value (constant) set in advance based on vehicle specifications.

[0119] Case (6): When the target total braking force Fv is greater than the value "Fx / hr" obtained by dividing the limit regenerative braking force Fx by the rear wheel ratio hr, the target regenerative braking force Fh is made equal to the target total braking force Fv. Then, the front wheel target frictional braking force Fnf is calculated by multiplying the target total braking force Fv by the value obtained by subtracting the rear wheel ratio hr from "1". Also, the rear wheel target frictional braking force Fnr is calculated by subtracting the target regenerative braking force Fh from the value "hr·Fv" obtained by multiplying the target total braking force Fv by the rear wheel ratio hr. That is, when "Fv > (Fx / hr)", "Fh = Fx, Fnf = (1 - hr)·Fv, Fnr = hr·Fv - Fh" is determined.

[0120] In the regenerative cooperation control according to the second embodiment, as the braking demand amount Bs increases, the first and second target servo pressures Pat and Pbt are determined as follows. In case (4), both the first and second target servo pressures Pat and Pbt are maintained at "0" so that energy is maximally recovered by the regenerative device KG. And in case (5), with the second target servo pressure Pbt (and as a result, the rear wheel wheel pressure Pwr) maintained at "0", the first target servo pressure Pat (and as a result, the front wheel wheel pressure Pwf) is increased from "0" so that the braking force distribution quickly reaches a predetermined ratio (i.e., the rear wheel ratio hr). In case (6), both the first and second target servo pressures Pat and Pbt are increased so that the braking force distribution is maintained at the predetermined ratio hr.

[0121] As in the first embodiment, in the second embodiment, the first servo pressure Pa is increased from "0" before the second servo pressure Pb. Therefore, the suitability of the hydraulic pressure generating unit PU is always determined based on the first target servo pressure Pat and the first detected servo pressure Pak when the hydraulic pressure generating unit PU is in operation. That is, because the operation of the hydraulic pressure generating source PU is appropriately monitored, any abnormality in the hydraulic pressure generating source PU is identified at an early stage.

[0122] <Other embodiments> Other embodiments will be described below. The other embodiments also provide the same effects as those described above (such as appropriately monitoring the operation of the hydraulic pressure generating unit PU and identifying an abnormality in the hydraulic pressure generating unit PU at an early stage).

[0123] In the above-described embodiment, the target values ​​of various braking forces (Fv, Fx, Fh, Fn, etc.) are calculated in the dimension of the longitudinal forces acting on the vehicle. Alternatively, they may be calculated in the dimension of the deceleration of the vehicle or the torque of the wheels WH. This is based on the fact that state quantities from the longitudinal forces to the vehicle deceleration (referred to as "state quantities related to forces") are equivalent. Therefore, the first and second target servo pressures Pat, Pbt are calculated based on state quantities related to forces from the longitudinal forces acting on the vehicle to the vehicle deceleration.

[0124] In the above-described embodiment, the hydraulic pressure generating unit PU is exemplified as one in which the circulating flow KN of the brake fluid BF discharged by the fluid pump QA is throttled by the pressure regulating valves UA and UB to regulate the first and second servo pressures Pa and Pb (so-called reflux type configuration). Alternatively, the first servo pressure Pa may be generated by increasing or decreasing the volume inside the cylinder by a piston directly driven by an electric motor, and the first servo pressure Pa may be further adjusted to the second servo pressure Pb (≦Pa) by the pressure regulating valve (so-called configuration combining an electric cylinder and a linear valve).

[0125] In the above embodiment, in the apply section AP, the pressure receiving area rm (master area) of the master chamber Rm and the pressure receiving area rc (servo area) of the servo chamber Rc are set to be equal. The master area rm and the servo area rc do not have to be equal. In a configuration in which the master area rm and the servo area rc are different, hydraulic pressure conversion is possible based on the ratio of the servo area rc to the master area rm.

[0126] In the above embodiment, in the upper brake unit SA, the supply pressure Ps is outputted via the master cylinder CM. That is, the apply unit AP and the hydraulic pressure generating unit PU are arranged in series in the hydraulic pressure transmission path, and the first servo pressure Pa (or the second servo pressure Pb) supplied from the hydraulic pressure generating unit PU is generated as the supply pressure Ps via the master piston NM. Alternatively, the apply unit AP and the hydraulic pressure generating unit PU may be arranged in parallel. Specifically, the apply unit AP (particularly, the master cylinder CM) and the hydraulic pressure generating unit PU are each directly connected to the lower actuator YZ. Then, in the second operation mode Ms, "connection between the hydraulic pressure generating unit PU and the lower actuator YZ" is selected, and in the first operation mode Mm, "connection between the apply unit AP and the lower actuator YZ" is selected. For example, the selection is achieved by an on-off solenoid valve (referred to as a "switching valve"). In the second operation mode Ms in this configuration, the first servo pressure Pa (or the second servo pressure Pb) generated by the hydraulic pressure generating unit PU is output as the supply pressure Ps without passing through the apply unit AP. At this time, the apply unit AP is connected to the stroke simulator SS, and the operating force Fp of the brake operating member BP is generated by the stroke simulator SS. On the other hand, in the first operation mode Mm, the hydraulic pressure Pm in the master chamber Rm generated by operating the brake operating member BP is output as the supply pressure Ps. At this time, the apply unit AP is disconnected from the stroke simulator SS, and the operating force Fp is generated by the rigidity of the braking device SX (elastic deformation of the brake caliper, friction members, brake piping, etc.).

[0127] <Summary of the embodiment> The following is a summary of an embodiment of the brake control device SC. The brake control device SC is applied to a vehicle equipped with a regenerative device KG, and is a brake-by-wire type device that can independently adjust the operation displacement Sp of the brake operating member BP and the hydraulic pressure Pw (wheel pressure) of the wheel cylinder CW. The hydraulic pressure generating unit PU of the brake control device SC is an on-demand type, and operates when there is a braking request corresponding to the braking request amount Bs.

[0128] The brake control device SC is composed of a hydraulic pressure generating unit PU, a controller EA, and a first servo pressure sensor PA to control the hydraulic pressure Pw (wheel pressure) of the wheel cylinder CW. The hydraulic pressure generating unit PU adjusts the first and second servo pressures Pa, Pb individually on the condition that the first servo pressure Pa is equal to or higher than the second servo pressure Pb. The controller EA calculates first and second target servo pressures Pat, Pbt corresponding to the first and second servo pressures Pa, Pb based on the braking demand amount Bs (general term for Ba and Gs). Furthermore, the controller EA controls the hydraulic pressure generating unit PU so that the first and second servo pressures Pa, Pb (actual values) match the first and second target servo pressures Pat, Pbt (target values). The first servo pressure sensor PA detects the first servo pressure Pa (actual value) as a first detected servo pressure Pak (detected value).

[0129] In the brake control device SC, when executing cooperative control with the regenerative device KG, the controller EA increases the first target servo pressure Pat from "0" while maintaining the second target servo pressure Pbt at "0 (zero)". Furthermore, the controller EA determines an abnormality in the hydraulic pressure generating unit PU based on the first detected servo pressure Pak and the first target servo pressure Pat. For example, the controller EA calculates a deviation hPa between the first target servo pressure Pat and the first detected servo pressure Pak. Then, when the deviation hPa is equal to or less than a threshold pressure Ha, the controller EA determines that the hydraulic pressure generating unit PU is normal, and when the deviation hPa is greater than the threshold pressure Ha, the controller EA determines that the hydraulic pressure generating unit PU is abnormal.

[0130] In a configuration in which two electric motors are used as the power source in the hydraulic pressure generating unit, there is no restriction (constraint) on the individual adjustment of the first servo pressure Pa and the second servo pressure Pb. However, in the hydraulic pressure generating unit PU used in the brake control device SC, the first and second servo pressures Pa, Pb are generated using a single electric motor MA as the power source. For this reason, the constraint on the configuration of the hydraulic pressure generating unit PU is that "the first servo pressure Pa is equal to or greater than the second servo pressure Pb." In other words, the prerequisite for individually generating the first and second servo pressures Pa, Pb is determined by the configuration of the hydraulic pressure generating unit PU.

[0131] In a vehicle in which a regenerative device KG (particularly, a regenerative generator GN) is provided on the front wheels WHf, it is sufficient that "Pwf≦Pwr" is satisfied in the regenerative cooperative control. That is, the wheel pressure Pwr of the rear wheels WHr, which are not provided with the regenerative device KG, is increased from "0" before the wheel pressure Pwf of the front wheels WHf, which are provided with the regenerative device KG and on which the regenerative braking force Fg acts, is increased from "0". For this reason, the front wheel pressure Pwf is adjusted by the second servo pressure Pb, and the rear wheel pressure Pwr is adjusted by the first servo pressure Pa. Then, in the regenerative cooperative control, the first servo pressure Pa is increased from "0" while the second servo pressure Pb is maintained at "0", so that the rear wheel pressure Pwr is increased from "0" while the front wheel pressure Pwf is maintained at "0" (see case (2)).

[0132] Conversely, in a vehicle equipped with a regenerative device KG (particularly, a regenerative generator GN) on the rear wheels WHr, it is sufficient that "Pwf ≧ Pwr" is satisfied in the regenerative cooperative control. Since this is the opposite of a vehicle equipped with a regenerative device KG on the front wheels WHf, the front wheel pressure Pwf is adjusted by the first servo pressure Pa, and the rear wheel pressure Pwr is adjusted by the second servo pressure Pb. In the regenerative cooperative control, the first servo pressure Pa is increased from "0" while the second servo pressure Pb is maintained at "0", thereby increasing the front wheel pressure Pwf from "0" while the rear wheel pressure Pwr is maintained at "0" (see case (5)).

[0133] Before the wheel pressure of the wheel equipped with the regenerative device KG is increased from "0", the wheel pressure of the wheel not equipped with the regenerative device KG is increased from "0". In the hydraulic pressure generating unit PU, the first servo pressure Pa can be adjusted to be greater than the second servo pressure Pb. Therefore, the wheel pressure of the wheel not equipped with the regenerative device KG is adjusted by the first servo pressure Pa, and the wheel pressure of the wheel equipped with the regenerative device KG is adjusted by the second servo pressure Pb. Then, in the regenerative cooperative control with the regenerative device KG, the first servo pressure Pa is increased from "0" before the second servo pressure Pb.

[0134] In order to quickly determine whether the hydraulic pressure generating unit PU is suitable (normal or abnormal), operation monitoring of the hydraulic pressure generating unit PU (i.e., suitability determination) is performed based on the first detected servo pressure Pak detected by the first servo pressure sensor PA. Here, when the first servo pressure Pa is generated, suitability determination is performed at all times. In other words, monitoring of the operation of the hydraulic pressure generating unit PU is performed not only at start-up (i.e., when the vehicle is stopped) but also when the vehicle is running. Because the operation of the hydraulic pressure generating source PU is appropriately monitored, in the unlikely event that an abnormality occurs in the hydraulic pressure generating source PU, the abnormality can be determined early.

[0135] Furthermore, in the controller EA of the brake control device SC, a target gradient dPa corresponding to the amount of change per unit time of the first target servo pressure Pat (absolute value) is calculated. The larger the target gradient dPa, the larger the threshold pressure Ha is set. Since the hydraulic pressure generating unit PU is of an on-demand type, when there is no braking request, the hydraulic pressure generating unit PU is stopped. Then, in response to a braking request, the hydraulic pressure generating unit PU is started. The hydraulic pressure generating unit PU has a limited response. For example, even if the braking request amount Bs increases sharply when the hydraulic pressure generating unit PU is started, the rotation speed of the electric motor MA cannot be increased in a stepwise manner. In the brake control device SC, the threshold pressure Ha is determined based on the target gradient dPa. In detail, the larger the target gradient dPa, the larger the threshold pressure Ha is set. This avoids unnecessary identification of an abnormality due to the response of the hydraulic pressure generating unit PU.

[0136] In the brake control device SC, when an abnormality is determined in the hydraulic pressure generating unit PU, the hydraulic pressure generating unit PU is stopped. At this time, the operation mode is switched from the second operation mode Ms to the first operation mode Mm. In the first operation mode Mm, the master pressure Pm, which is powered by the muscle force of the driver, is output as the supply pressure Ps (particularly, the front wheel supply pressure Psf). In the lower brake unit SZ, complementary control is executed to amplify the supply pressure Ps (=Pm). Specifically, the control valve UZ is driven based on the deviation hPs (supply pressure deviation) between the target supply pressure Pst and the detected supply pressure Psk (detection value of the supply pressure sensor PS). As a result, the wheel pressure Pw is increased by the supply pressure deviation hPs from the supply pressure Ps. That is, in the complementary control, the wheel pressure Pw is compensated by only the necessary amount. [Explanation of symbols]

[0137] SC...Brake control device, KG...Regenerative device, GN...Regenerative generator (motor / generator), EG...Regenerative controller (KG controller), BP...Brake operation member (brake pedal), SA, SZ...Upper and lower braking units, YA, YZ...Upper and lower actuators, EA, EZ...Upper and lower controllers, BS...Communication bus, CM...Master cylinder, CW...Wheel cylinder, AP...Apply section, NR...Input section, PU...Fluid pressure generation section, UA, UB...First and second pressure regulating valves, UZ...Control valve, MA, MZ...Upper and lower electric motors, QA, QZ...Upper and lower fluid pumps, VA...Inlet valve, VB...Release valve, SS...Stroke simulator, SP...Operation displacement sensor, Sp...Operation displacement (detected value of SP), Ba...Braking operation amount, Gs...Target deceleration, Bs...Braking demand amount (collectively referred to as Ba and Gs), Pa, Pb...First and second servo pressures (fluid pressures output from PU), Pat, Pbt: 1st and 2nd target servo pressure (target value corresponding to Pa and Pb), PA, PB: 1st and 2nd servo pressure sensor, Pak, Pbk: 1st and 2nd detected servo pressure (Pa and Pb detected by PA and PB), hPa: servo pressure deviation (difference between Pat and Pak), Ps: supply pressure (fluid pressure output from YA and input to YZ), Pst: target supply pressure (target value corresponding to Ps), PS: supply pressure sensor, Psk: detected supply pressure (detected by PS) Hydraulic pressure output), hPs...supply pressure deviation (difference between Pst and Psk), Pp...adjusted pressure, Pw...wheel pressure, FL...suitability flag (result of suitability judgment related to PU), Ha...threshold pressure (threshold for suitability judgment), Xa...tolerable range (area where abnormality is not judged), dPa...target gradient (amount of change in Pat over time), Mm...first operation mode (operation mode in which Fp is generated by SX), Ms...second operation mode (operation mode in which Fp is generated by SS).

Claims

1. A vehicle brake control device is applied to a vehicle equipped with a regenerative device, and includes a hydraulic pressure generating unit that adjusts first and second servo pressures individually on condition that a first servo pressure is equal to or higher than a second servo pressure so as to control hydraulic pressures in wheel cylinders of the vehicle, a controller that calculates first and second target servo pressures corresponding to the first and second servo pressures based on a braking request amount of the vehicle, and controls the hydraulic pressure generating unit so that the first and second servo pressures coincide with the first and second target servo pressures, and a first servo pressure sensor that detects the first servo pressure as a first detected servo pressure, The controller: When performing cooperative control with the regenerative device, the first target servo pressure is increased from zero while the second target servo pressure is maintained at zero, A brake control device for a vehicle that determines an abnormality in the hydraulic pressure generating unit based on the first detected servo pressure and the first target servo pressure.

2. 2. The vehicle brake control device according to claim 1, The controller: A brake control device for a vehicle, which calculates a deviation between the first target servo pressure and the first detected servo pressure, and determines that an abnormality exists in the hydraulic pressure generating unit when the deviation is larger than a threshold pressure.

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