Braking control device of vehicle

Abstract

To provide a braking control device which can identify an abnormality related to output reduction.SOLUTION: A braking control device includes: a braking unit that makes servo pressure Pa generated by a liquid pressure generation part match target servo pressure Pat calculated based on a required braking amount Bs to output supply pressure Ps, and adjusts liquid pressure Pw of a wheel cylinder by the supply pressure Ps; and a servo pressure sensor that detects the servo pressure Pa, as detected servo pressure Pak. The braking unit calculates a servo pressure deviation hPa that is a deviation between the detected servo pressure Pak and the target servo pressure Pat, and when the servo pressure deviation hPa is larger than a first threshold pressure Ha, determines that an abnormality occurs on the liquid pressure generation part. For instance, the braking unit calculates a target servo pressure gradient dPa corresponding to a variation per unit time of the target servo pressure Pat, and determines the first threshold pressure Ha on the basis of the target servo pressure gradient dPa.SELECTED DRAWING: Figure 4

Description

[Technical field]

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

[0002] Patent Document 1 describes that in order to maintain stable operability even when an abnormality occurs, "the vehicle brake system A comprises a master cylinder 10, a slave cylinder 30 that generates brake fluid pressure by moving pistons 35a, 35b together with a ball screw shaft 33b, normally open master cut valves 50a, 50b that connect / disconnect the slave cylinder 30 and the master cylinder 10, a first judgment unit that judges whether the electric motor 31 is controllable, and a control device that drives the electric motor 31 to retract the ball screw shaft 33b when an abnormality occurs and the first judgment unit judges that the electric motor 31 is controllable."

[0003] In Patent Document 1, a first judgment unit 62a (first judgment means) judges whether an abnormality in devices including the electric motor 31 and the master cut valves 50a, 50b is detected according to a signal input from a fault sensor 93, and judges whether the electric motor 31 is controllable or not. Here, the fault sensor 93 indicates each sensor installed to detect faults in the electric motor 31, the master cut valves 50a, 50b, the pressure sensors Pm, Pp, Ph, the stroke simulator S, etc. For example, the first judgment unit 62a judges whether the electric motor 31 is controllable or not based on a signal from the fault sensor 93 that detects a break in a three-phase AC line installed in the electric motor 31.

[0004] In addition to a state in which the device completely loses its function due to a breakdown, there are also cases in which performance is reduced. For example, if an electric motor (also called an "electric motor") breaks down, the device will completely lose its function. On the other hand, a situation may also occur in which the output of the device is reduced. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2015-013526 A Summary of the Invention [Problem to be solved by the invention]

[0006] In view of the above problems, an object of the present invention is to provide a braking control device that can identify an abnormality related to a decrease in output. [Means for solving the problem]

[0007] The vehicle braking control device (SC) of the present invention includes a braking unit (SA) that outputs a supply pressure (Ps) by matching a servo pressure (Pa) generated by a hydraulic pressure generating unit (PU) with a target servo pressure (Pat) calculated based on a braking demand (Bs), and adjusts the hydraulic pressure (Pw) of a wheel cylinder (CW) using the supply pressure (Ps), and a servo pressure sensor (PA) that detects the servo pressure (Pa) as a detected servo pressure (Pak).

[0008] In the vehicle brake control device (SC) of the present invention, the brake unit (SA) calculates a servo pressure deviation (hPa) which is the deviation between the detected servo pressure (Pak) and the target servo pressure (Pat), and determines an abnormality in the hydraulic pressure generating unit (PU) when the servo pressure deviation (hPa) is greater than a first threshold pressure (Ha). This allows the brake unit SA to identify a drop in output of the hydraulic pressure generating unit PU, which is its power source.

[0009] In the vehicle brake control device (SC) according to the present invention, the brake unit (SA) calculates a target servo pressure gradient (dPa) corresponding to the amount of change per unit time of the target servo pressure (Pat), and determines the first threshold pressure (Ha) based on the target servo pressure gradient (dPa). This allows the brake unit SA to avoid unnecessary abnormality determinations due to the responsiveness of the hydraulic pressure generating unit PU.

[0010] The vehicle brake control device (SC) according to the present invention includes a supply pressure sensor (PS) that detects the supply pressure (Ps) as a detected supply pressure (Psk). The brake unit (SA) then calculates a target supply pressure (Pst) corresponding to the supply pressure (Ps), calculates a supply pressure deviation (hPs) that is the deviation between the detected supply pressure (Psk) and the target supply pressure (Pst), and determines an abnormality in the brake unit (SA) when the supply pressure deviation (hPs) is greater than a second threshold pressure (Hs). This allows the brake unit SA to identify not only a decrease in output related to the hydraulic pressure generating section PU, but also a decrease in output of the entire brake unit SA.

[0011] In the vehicle brake control device (SC) according to the present invention, the brake unit (SA) calculates a target gradient (dPx) corresponding to the amount of change per unit time of at least one of the target servo pressure (Pat) and the target supply pressure (Pst), and determines the first and second threshold pressures (Ha, Hs) based on the target gradient (dPx). As described above, the brake unit SA can avoid unnecessary abnormality determinations due to the responsiveness of the hydraulic pressure generating unit PU. [Brief description of the drawings]

[0012] [Figure 1] FIG. 2 is a schematic diagram for explaining an 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] FIG. 4 is a flow chart for explaining the processing of the first and second suitability determinations. [Diagram 5] FIG. 4 is a time series diagram for explaining the operations of the first and second suitability determinations. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] <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)".

[0014] 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."

[0015] 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.

[0016] <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 pressure Pa" is the hydraulic pressure generated by the hydraulic pressure generating unit PU. "Supply pressure Ps" is the hydraulic pressure transmitted (supplied) from the upper brake unit SA to the lower brake unit SZ. "Wheel pressure Pw" is the 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 is the supply pressure Ps.

[0017] <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 solenoid valves UA and UZ, the adjusted hydraulic pressure is uniquely determined according to the current supplied to the solenoid valves UA and UZ. 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 requirement. In the following description, it will be clearly stated that the detected value is a hydraulic pressure sensor (detected servo pressure, detected supply pressure, etc.) as necessary.

[0018] <Embodiments of the Brake Control Device SC> An 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.

[0019] 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."

[0020] 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.

[0021] 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).

[0022] 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."

[0023] 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).

[0024] 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.

[0025] 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."

[0026] 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.

[0027] <Upper braking unit SA> The configuration of the upper braking unit SA (corresponding to "brake unit") 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.

[0028] <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.

[0029] [Apply Department AP] In response to the operation of the brake operating member BP, a supply pressure Ps (=Psf, Psr) is output from the apply section AP. The apply section AP is composed of a tandem master cylinder CM, and primary and secondary master pistons NM, NS.

[0030] A primary and secondary master pistons NM, NS are inserted into the tandem master cylinder CM. The interior of the master cylinder CM is divided into four hydraulic chambers Rmf, Rmr, Rc, and Rs by the two master pistons NM, NS. The front and rear wheel master chambers Rmf, Rmr (=Rm) are divided by the bottom of one side of the master cylinder CM and the master pistons NM, NS. 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. 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 Rmf, Rmr, Rc, and Rs are sealed from the master cylinder CM by a seal member SL.

[0031] When braking is not being applied, the master pistons NM, NS are in their most rearward 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 pistons NM, NS are 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 pistons NM, NS are further moved in the forward direction Da, the hydraulic pressures Pmf, Pmr (also called the "front and rear master pressures") in the front and rear master chambers Rmf, Rmr are increased from "0 (atmospheric pressure)". As a result, brake fluid BF pressurized to master pressure Pm (=Pmf, Pmr) is output (pressurized) from the master chamber Rm (=Rmf, Rmr) of the master cylinder CM to the lower brake unit SZ as front and rear wheel supply pressures Psf, Psr (=Ps).

[0032] [Hydraulic pressure generating unit PU] A servo pressure Pa is supplied to a servo chamber Rc of the apply unit AP by a hydraulic pressure generating unit PU. The hydraulic pressure generating unit PU is composed of an electric motor MA, a fluid pump QA, and a pressure adjusting valve UA.

[0033] The electric motor MA drives the fluid pump QA. The electric motor MA is a power source for generating the servo pressure Pa. 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."

[0034] 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.

[0035] A normally open pressure regulating valve UA is provided in the return passage HK. The pressure regulating valve UA is a linear solenoid valve whose opening amount is continuously controlled based on the energized state (e.g., the supply current Ia). The pressure regulating valve UA is also called a "differential pressure valve" because it adjusts the hydraulic pressure difference (differential pressure) between its upstream and downstream sides.

[0036] When the brake fluid BF is discharged from the fluid pump QA, a circulation flow KN (indicated by a dashed arrow) of the brake fluid BF is generated in the return path HK. When the pressure regulating valve UA is in a fully open state (when not energized because the pressure regulating valve UA is of a normally open type), the fluid pressure Pa (called "servo pressure") between the discharge part Qo of the fluid pump QA and the pressure regulating valve UA in the return path HK is "0 (atmospheric pressure)". When the current Ia (also called "pressure regulating valve current") supplied to the pressure regulating valve UA is increased, the pressure regulating valve UA throttles the circulation flow KN (the flow of the brake fluid BF circulating in the return path HK). In other words, the pressure regulating valve UA narrows the flow path of the return path HK, and the orifice effect of the pressure regulating valve UA is exerted. As a result, the fluid pressure Pa on the upstream side of the pressure regulating valve UA is increased from "0". That is, in the circulating flow KN, a hydraulic pressure difference (differential pressure) is generated between the hydraulic pressure Pa (servo pressure) on the upstream side and the hydraulic pressure (atmospheric pressure) on the downstream side with respect to the pressure regulating valve UA. The differential pressure is adjusted by the amount of current Ia supplied to the pressure regulating valve UA.

[0037] The return path HK is connected to the servo chamber Rc via a servo path HC (fluid path) between the discharge portion Qo of the fluid pump QA and the pressure regulating valve UA. Therefore, the servo pressure Pa is introduced (supplied) to the servo chamber Rc. As the servo pressure Pa increases, the master pistons NM, NS are pressed forward in the direction Da (the direction in which the volume of the master chamber Rm decreases), and the hydraulic pressures Pmf, Pmr (front and rear master pressures) in the front and rear master chambers Rmf, Rmr increase.

[0038] The front and rear wheel master chambers Rmf, Rmr (=Rm) are connected to the front and rear wheel communication passages HSf, HSR (=HS). The front and rear wheel communication passages HSf, HSR (fluid passages) are connected to the front and rear wheel wheel cylinders CWf, CWr (=CW) via the lower brake unit SZ (particularly, the lower fluid unit YZ). Therefore, the master pressure Pm is supplied as the supply pressure Ps from the upper brake unit SA to the wheel cylinder CW. Here, the front wheel supply pressure Psf (=Pmf) and the rear wheel supply pressure Psr (=Pmr) are equal (i.e., "Psf=Psr").

[0039] The hydraulic pressure generating unit PU is provided with a servo pressure sensor PA to detect the servo pressure Pa. The servo pressure Pa detected by the servo pressure sensor PA is referred to as a "detected servo pressure Pak." The detected servo pressure Pak is input to the upper controller EA.

[0040] [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.

[0041] 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.

[0042] 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. Regenerative cooperative control is realized by adjusting the separation distance Ks by the servo pressure Pa. Note that, like the hydraulic chambers Rm, Rc, and Rs, the input chamber Rn is also sealed by a seal member SL.

[0043] 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.

[0044] 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.

[0045] When power is supplied 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.

[0046] 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 called 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 power failure). In the first operation mode Mm (also called the "manual mode"), the input chamber Rn is fluidically locked, so that the master pistons NM, NS move integrally with the brake operating member BP. In the first operation mode Mm, the supply pressure Ps is generated by the operating force Fp of the brake operating member BP (i.e., "Ps = Pm"). That is, in the first operation mode Mm, the supply pressure Ps is generated by the muscle force of the driver as a power source. At this time, the operating force Fp is applied by the rigidity (i.e., elastic deformation of the brake caliper, friction member, brake piping, etc.) of the brake device SX (a device that generates a frictional braking force Fe by the wheel pressure Pw).

[0047] 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 pistons NM, NS can move separately from the brake operating member BP. In the second operation mode Ms, the supply pressure Ps is generated by the servo pressure Pa. 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.

[0048] <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.).

[0049] The upper controller EA receives various sensor signals such as the operation displacement Sp, the input pressure Pn, and the detected servo pressure Pak. 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 outputs the target regenerative braking force Fh (target value of the regenerative braking force Fg), a first suitability flag FL (control flag indicating the operating state of the hydraulic pressure generating unit PU), a second suitability flag FM (control flag indicating the operating state of the upper brake unit SA), 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.

[0050] 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 servo pressure Pa, and ultimately for adjusting the wheel pressure Pw (=Pwf, Pwr). Pressure regulation control includes regenerative cooperative control. Pressure regulation control is performed based on the various signals (Sp, etc.) mentioned above.

[0051] The hydraulic pressure generating unit PU (MA, UA, 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, 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 a pressure regulation valve current sensor (not shown) that detects a current Ia (pressure regulation valve current) supplied to the pressure regulation valve UA. 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.

[0052] In the upper controller EA, a target current Iat is calculated based on the braking operation amount Ba (a collective term for Sp and Pn). The "target current Iat" is a target value corresponding to the pressure regulating valve current Ia (actual value). In the upper controller EA, the pressure regulating valve current Ia detected by the pressure regulating valve current sensor is controlled so as to approach and match the target current Iat.

[0053] 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.

[0054] The target rotation speed Nt takes into consideration the minimum flow rate of the pressure regulating valve UA and the minimum rotation speed of the electric motor MA. The "minimum flow rate" is the minimum flow rate required for the pressure regulating valve UA 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.

[0055] In the upper controller EA, a drive signal Ma for controlling the electric motor MA and drive signals Ua, Va, Vb for controlling the various solenoid valves UA, VA, VB are calculated based on the above control algorithm. Then, the switching elements of the drive circuit DR are driven in response to the drive signal (Ma, etc.), thereby controlling the electric motor MA and the solenoid valves UA, VA, VB.

[0056] <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.

[0057] The front and rear wheel master pressures Pmf and Pmr 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=Pmf, Psr=Pmr"). 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.

[0058] <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.

[0059] A control valve UZ (=UZf, UZr) is provided in the communication passage HS (=HSf, HSR). The control valve UZ is a normally open linear solenoid valve (differential pressure valve) like the pressure regulating valve UA. 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 pressures Pwf, Pwr can be individually adjusted by the front and rear wheel control valves UZf, UZr.

[0060] 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.

[0061] 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".

[0062] 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 orifice effect at that time increases the hydraulic pressure Pp (referred to as the "regulating pressure") at the lower part of the control valve UZ from the hydraulic pressure Ps (supply pressure) at the upper part of the control valve UZ. As with the servo pressure Pa, 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.

[0063] 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.

[0064] 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.

[0065] <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.

[0066] 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 first and second suitability flags FL and FM, 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 (hydraulic pressure generating unit PU, etc.).

[0067] 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.

[0068] <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 first and second suitability judgments and complementary control in addition to the regenerative cooperative control between the regenerative device KG and the braking control device SC. The first and second suitability judgments judge whether "the device is operating normally or abnormally." If a device failure occurs and there is an abnormality, the shortage of the supply pressure Ps is compensated for by complementary control in the lower braking unit SZ. The pressure regulation control except for the complementary control is executed by the upper controller EA, and the complementary control is executed by the lower controller EZ.

[0069] In describing the example process, the following assumptions are made: 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, "Pa = Pm". 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.

[0070] 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.

[0071] 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 of the brake operating member BP 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).

[0072] 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.

[0073] 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 detected servo pressure Pak, 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.

[0074] In step S110, the lower controller EZ acquires the braking demand amount Bs (generic term for Ba and Gs), the target supply pressure Pst, and the first and second suitability flags FL and FM. The "target supply pressure Pst" is a target value corresponding to the supply pressure Ps. The "first suitability flag FL" is a control flag indicating whether the operation of the hydraulic pressure generating unit PU is normal or abnormal. For example, when the hydraulic pressure generating unit PU is normal, "FL=0" is determined, and when the hydraulic pressure generating unit PU is abnormal, "FL=1" is determined. The "second suitability flag FM" is a control flag indicating whether the operation of the upper brake unit SA is normal or abnormal. For example, when the upper brake unit SA is normal, "FM=0" is determined, and when the upper brake unit SA is abnormal, "FM=1" is determined. The target supply pressure Pst and the first and second suitability flags FL and FM are transmitted from the upper controller EA to the communication bus BS.

[0075] 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).

[0076] In step S130, in order to execute the regenerative cooperative control, a target regenerative braking force Fh and a target frictional braking force Fn are calculated based on the target total braking force Fv and the limit regenerative braking force Fx. Specifically, the target regenerative braking force Fh is determined to be a value equal to or less than the limit regenerative braking force Fx. For example, when the target vehicle body position dynamics 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 vehicle body position dynamics Fv, and the target frictional braking force Fn is determined to be "0" (i.e., when "Fv≦Fx", "Fh=Fv, Fn=0"). On the other hand, when the target vehicle deadlock force Fv is greater than the limit regenerative braking force Fx, the target regenerative braking force Fh is set equal to the limit regenerative braking force Fx, and the target frictional braking force Fn is determined to be "a value obtained by subtracting the limit regenerative braking force Fx (=Fh) from the target vehicle deadlock force Fv" (i.e., when "Fv>Fx", "Fh=Fx, Fn=Fv-Fx=Fv-Fh"). The target regenerative braking force Fh is transmitted from the upper controller EA to the regenerative controller EG via the communication bus BS. Then, the regenerative controller EG controls the generator GN so that the actual regenerative braking force Fg approaches and coincides with the target regenerative braking force Fh.

[0077] In step S140, a target servo pressure Pat is calculated based on the target frictional braking force Fn. The "target servo pressure Pat" is a target value corresponding to the servo pressure Pa (actual value). The target servo pressure Pat is converted from the target frictional braking force Fn based on the specifications of the braking device SX. Furthermore, since the servo pressure Pa is transmitted to the wheel cylinder CW via the master cylinder CM, the sliding resistance of the seal member SL is taken into consideration in calculating the target servo pressure Pat. 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), etc.

[0078] In step S150, it is determined whether "the hydraulic pressure generating unit PU is abnormal." That is, in step S150, it is determined whether "the servo pressure Pa generated by the hydraulic pressure generating unit PU is insufficient or sufficient." The process of step S150 is referred to as "first suitability determination." If the first suitability determination is negative (i.e., if the hydraulic pressure generating unit PU is normal and sufficient servo pressure Pa is generated), the first suitability flag FL is set to "0" and the process proceeds to step S160. On the other hand, if the first suitability determination is positive (i.e., if the hydraulic pressure generating unit PU has failed and the servo pressure Pa is insufficient), the first suitability flag FL is set to "1" and the process proceeds to step S200. Note that the case where the first suitability determination is positive is referred to as "first abnormality."

[0079] In step S160, it is determined whether "the upper brake unit SA is abnormal or not." That is, in step S160, it is determined whether "the supply pressure Ps output from the upper brake unit SA is insufficient or sufficient." The process of step S160 is referred to as "second suitability determination." If the second suitability determination is negative (i.e., if the upper brake unit SA is normal and a sufficient supply pressure Ps is output), the second suitability flag FM is set to "0" and the process proceeds to step S170. On the other hand, if the second suitability determination is positive (i.e., if the upper brake unit SA has broken down and the supply pressure Ps is insufficient), the second suitability flag FM is set to "1" and the process proceeds to step S230. Note that the case where the second suitability determination is positive is referred to as "second abnormality."

[0080] When a first abnormality is determined, the hydraulic pressure generating unit PU, which is the pressure source (power source) of the upper brake unit SA, is abnormal, so naturally the upper brake unit SA is abnormal. That is, the first abnormality is a state in which the servo pressure Pa cannot be generated sufficiently, and therefore the supply pressure Ps cannot be generated either. On the other hand, when a second abnormality is determined, the hydraulic pressure generating unit PU is normal, but the upper brake unit SA is abnormal. That is, the second abnormality is a state in which the servo pressure Pa is being generated appropriately, but the supply pressure Ps is not being generated sufficiently. The first and second suitability determinations will be described in detail later.

[0081] <Normal control> When the upper brake unit SA including the hydraulic pressure generating unit PU operates normally, the processes of steps S170 to S190 are executed. This process is called "normal control." In normal control, in step S170, the upper actuator YA (particularly, the hydraulic pressure generating unit PU) is driven by the upper controller EA. This controls the servo pressure Pa to approach and coincide with the target servo pressure Pat.

[0082] Specifically, first, the electric motor MA is driven. This generates a circulating flow KN including the fluid pump QA and the pressure regulating valve UA. A target rotation speed Nt of the electric motor MA is calculated based on the operation speed dS. Then, the supply current Im (motor current) to the electric motor MA is controlled so that the motor rotation speed Na approaches and coincides with the target rotation speed Nt.

[0083] Next, the pressure regulating valve UA is controlled based on the target servo pressure Pat so that the servo pressure Pa (actual value) approaches and matches the target servo pressure Pat (target value). For example, based on the detected servo pressure Pak detected by the servo pressure sensor PA, control is performed so that the detected servo pressure Pak (detected value) approaches and matches the target servo pressure Pat (target value). Since the servo pressure Pa and the pressure regulating valve current Ia have a unique relationship, the target current Iat is calculated based on the target servo pressure Pat. Then, the drive circuit DR is controlled so that the pressure regulating valve current Ia (detected value) detected by the pressure regulating valve current sensor approaches and matches the target current Iat (target value). Furthermore, the pressure regulating valve current Ia is finely adjusted based on the detected servo pressure Pak so as to compensate for the hydraulic pressure error. That is, in the adjustment of the servo pressure Pa, a so-called feedback control (closed loop control) related to the hydraulic pressure is performed. In addition, since the servo pressure Pa and the supply pressure Ps have a predetermined relationship (if the sliding resistance of the sealing member SL is ignored, the relationship is "Pa = Ps"), in feedback control, the detected supply pressure Psk (detected value) detected by the supply pressure sensor PS may be controlled to approach and match the target servo pressure Pat.

[0084] In step S180, the second operation mode Ms is selected in the operation mode of the input unit NR. As a result, the operation force Fp is generated by the stroke simulator SS, and the supply pressure Ps is controlled separately from the operation displacement Sp. In step S190, the lower actuator YZ is stopped. Therefore, the state of "Pa=Pm=Ps=Pw" is maintained.

[0085] <First abnormality control> When the first suitability judgment in step S150 judges that the hydraulic pressure generating unit PU is abnormal (i.e., the servo pressure Pa is insufficient), the process of steps S200 to S220 is executed. This process is called "first abnormality control". In the first abnormality control, in step S200, the operation of the regenerative device KG is stopped. For example, "Fh=0" or "FL=1" is transmitted from the upper controller EA to the regenerative controller EG, and the regenerative device KG stops generating electricity by the generator GN. As a result, the regenerative braking force Fg is set to "0", and the regenerative cooperative control is terminated. Since the operation of the regenerative device KG is stopped, the target frictional braking force Fn is set to be equal to the target vehicle body force Fv (i.e., "Fn=Fv"). Also, in step S200, the hydraulic pressure generating unit PU is stopped. Therefore, the servo pressure Pa is set to "0".

[0086] In step S210, the first operation mode Mm is selected as the operation mode of the input unit NR. That is, the power supply to the solenoid valves VA and VB is stopped, and the input chamber Rn is fluidically locked. As a result, the master piston NM and the brake operating member BP are displaced together, and the supply pressure Ps is generated by operating the brake operating member BP. That is, the supply pressure Ps (=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 brake device SX (a device that generates a frictional braking force Fe by the wheel pressure Pw).

[0087] In step S220, the lower braking unit SZ executes complementary control to compensate for the shortage of the supply pressure Ps relative to the target supply pressure Pst and to reduce the operation force Fp by the driver. The complementary control is started in response to "FL=1". In the complementary control, a target supply pressure Pst, which is a target value of the supply pressure Ps to be supplied to the lower braking 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 target servo pressure Pat. Since the target servo pressure Pat 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] Based on the target supply pressure Pst and the detected supply pressure Psk (=Pskf), a deviation hPs therebetween (also referred to as a "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 to be output from the upper actuator YA.

[0089] Based on the supply pressure deviation hPs, the lower actuator YZ (MZ, UZ, etc.) is driven. 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. Based on the supply pressure deviation hPs and a preset calculation map (not shown), a target current Is is calculated. 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 matches 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 (=Pw) ​​is output from the lower actuator YZ as the wheel pressure Pw (actual value) (i.e., "Pw=Ps+hPs").

[0091] In the case of a first abnormality in which the servo pressure Pa is insufficient, the hydraulic pressure generating unit PU is stopped and the first operation mode Mm is selected. The supply pressure Ps (=Pm) is generated only by the operating force Fp of the brake operating member BP applied by the driver. 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. This compensates for the shortage of the supply pressure Pa and reduces the operating force Fp.

[0092] <Second abnormality control> If the first suitability determination in step S150 is negative but the second suitability determination in step S160 is positive (i.e., the servo pressure Pa is sufficient but the supply pressure Ps is insufficient), the processing of steps S230 to S250 is executed. This processing is called "second abnormality control." In the second abnormality, the hydraulic pressure generating unit PU is normal but the upper brake unit SA is abnormal. This situation occurs when an abnormality occurs in the hydraulic pressure transmission path from the hydraulic pressure generating unit PU to the lower brake unit SZ. For example, this occurs when the sliding resistance increases in the seal member SL of the master cylinder CM, when resistance increases in the fluid path, etc.

[0093] In the second abnormality control, in step S230, the operation of the hydraulic pressure generating unit PU is continued as in step S170. Also, in step S240, the second operation mode Ms is selected in the input unit NR as in step S180. In step S250, the complementary control is executed by the lower brake unit SZ as in step S220. The complementary control is as described above, and therefore will not be described again. When the hydraulic pressure generating unit PU is normal but the desired supply pressure Ps is not output from the upper brake unit SA for some reason (i.e., during the second abnormality), the same operation as in the normal control (continuation of the hydraulic pressure generating unit PU and the second operation mode Ms) is executed, while the complementary control is executed in the lower brake unit SZ. As a result, the operation characteristic (Sp-Fp characteristic) of the brake operating member BP is not changed, and discomfort to the driver is avoided. Furthermore, the shortage of the supply pressure Ps is compensated for by the complementary control, so sufficient vehicle deceleration is ensured.

[0094] In the case of the second abnormality in which the servo pressure Pa is sufficient but the supply pressure Ps is insufficient, the performance and characteristics are ensured to be the same as those of normal control by continuing the operation of the hydraulic pressure generating unit PU, selecting the second operation mode Ms, and performing complementary control in the lower brake unit SZ. For this reason, even in the case of the second abnormality, the regenerative cooperative control can be continued. However, since it is an abnormal state, the regenerative cooperative control may be stopped. In other words, in the regenerative cooperative control in the second abnormality, either a configuration in which the regenerative device KG continues to operate or a configuration in which the regenerative device KG is stopped may be selected. In addition, in the configuration in which the regenerative device KG is stopped, "Fh=0" or "FM=1" is transmitted from the upper controller EA to the regenerative controller EG.

[0095] In the brake control device SC, the presence or absence of a device abnormality is determined in two stages. Specifically, a first suitability judgment is made to judge whether there is an abnormality in the hydraulic pressure generating unit PU, and a second suitability judgment is made to judge whether there is an abnormality in the upper brake unit SA. Device abnormalities can occur not only in the power source such as the electric motor MA, but also in the hydraulic pressure transmission path. In the brake control device SC, abnormalities are identified in two ways, improving reliability and identifying the part where the abnormality has occurred. Therefore, an appropriate abnormality procedure can be selected depending on the abnormal part. In other words, the abnormality is dealt with appropriately.

[0096] In the brake control device SC, the service brake (also called "service brake") is executed by using the hydraulic pressure generating unit PU as a power source. That is, when the brake control device SC is normal and anti-lock brake control, traction control, anti-skid control, etc. are not executed, the lower actuator YZ (particularly, the electric motor MZ and the control valve UZ) are stopped, and only the upper brake unit SA is operating. Then, when the hydraulic pressure generating unit PU cannot generate the servo pressure Pa appropriately (that is, when the first abnormality is judged), the hydraulic pressure generating unit PU is stopped. In the case of the first abnormality, the servo pressure Pa cannot be obtained appropriately even if the hydraulic pressure generating unit PU is supplied with electricity. At this time, the operation mode of the brake operating member BP is set to the first operation mode Mm, and the supply pressure Ps (=Pm) is generated by using the muscle force of the driver as a power source. Furthermore, the supply pressure Ps is amplified by the complementary control in the lower brake unit SZ, and the wheel pressure Pw is generated. As a result, the operating force Fp by the driver is reduced, and the vehicle deceleration is ensured.

[0097] On the other hand, when the hydraulic pressure generating unit PU is operating normally but the supply pressure Ps is not appropriately output from the upper brake unit SA (i.e., when the second abnormality is determined), the hydraulic pressure generating unit PU is operated. The second abnormality occurs when resistance increases in the hydraulic pressure transmission path, but in the case of the second abnormality in which the hydraulic pressure generating unit PU is operating normally, the abnormal state may be eliminated. For this reason, the hydraulic pressure generating unit PU is not stopped and its operation continues. At this time, the operation mode of the brake operating member BP is set to the second operation mode Ms, and its operation characteristics are not changed. The decrease in the supply pressure Ps is compensated for by complementary control in the lower brake unit SZ. This prevents the driver from feeling uncomfortable and ensures the vehicle deceleration.

[0098] <Processing of the first and second suitability judgments> The first and second suitability judgment processes (steps S150 and S160) will be described with reference to the flow diagram of FIG. 4. In the first suitability judgment, it is judged whether "the operation of the hydraulic pressure generating unit PU is abnormal (i.e., whether the servo pressure Pa is sufficient or not)". In the second suitability judgment, it is judged whether "the operation of the upper braking unit SA is abnormal (i.e., whether the supply pressure Ps is sufficient or not)". The first and second suitability judgments are also called "first and second abnormality judgments". Although the state quantities used in the first and second suitability judgments are different, the processes are basically the same. The first and second suitability judgments are executed by the upper controller EA.

[0099] <First suitability test> The first suitability determination for identifying a shortage of the servo pressure Pa is performed based on the deviation hPa between the target servo pressure Pat and the detected servo pressure Pak (referred to as the "servo pressure deviation").

[0100] In step S310, the target servo pressure Pat and the detected servo pressure Pak are read in. The target servo pressure Pat is a target value related to the servo pressure Pa calculated from the braking demand amount Bs. The detected servo pressure Pak is the detection result of the servo pressure sensor PA.

[0101] In step S320, a target servo pressure gradient dPa is calculated based on the target servo pressure Pat. The "target servo pressure gradient dPa" is a value equivalent to the amount of change in the target servo pressure Pat per unit time (also simply referred to as "time change amount"). For example, the absolute value of the target servo pressure Pat is time-differentiated to determine the target servo pressure gradient dPa (time change amount related to the servo pressure Pa). Since the target servo pressure Pat is calculated based on the braking demand Bs, the target servo pressure gradient dPa may be calculated from the braking demand Bs. When the target servo pressure Pat is maintained constant, the target servo pressure gradient dPa is "0".

[0102] In step S330, a first threshold pressure Ha is calculated based on the target servo pressure gradient dPa. The "first threshold pressure Ha" is a threshold value for determining an abnormality in the hydraulic pressure generating unit PU. The first threshold pressure Ha is determined to be larger as the target servo pressure gradient dPa is larger, according to a preset calculation map Zha. That is, when the target servo pressure gradient dPa is large, the first threshold pressure Ha is made larger compared to when the target servo pressure gradient dPa is small. A lower limit pressure ha is set for the first 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).

[0103] 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. Then, the start of braking triggers the start of operation of the hydraulic pressure generating unit PU. Since the response of the hydraulic pressure generating unit PU (particularly the electric motor MA) is limited, the servo pressure deviation hPa may increase instantaneously when the hydraulic pressure generating unit PU is started. In such a situation, the first threshold pressure Ha is determined based on the target servo pressure gradient dPa so that an abnormality is not unnecessarily determined. That is, when the target servo pressure gradient dPa is large, the first threshold pressure Ha is determined to be large, thereby avoiding an abnormality being unnecessarily determined.

[0104] In step S340, the deviation hPa (servo pressure deviation) between the target servo pressure Pat and the detected servo pressure Pak is calculated. Specifically, the detected servo pressure Pak is subtracted from the 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 detected servo pressure Pak relative to the target servo pressure Pat.

[0105] In step S350, it is determined whether the servo pressure deviation hPa is greater than the first threshold pressure Ha. If the servo pressure deviation hPa is equal to or less than the first threshold pressure Ha, the result in step S350 is negative, and the process proceeds to step S360. In step S360, the hydraulic pressure generating unit PU is determined to be normal, and the first suitability flag FL is set to "0." On the other hand, if the servo pressure deviation hPa is greater than the first threshold pressure Ha, the result in step S350 is positive, and the process proceeds to step S370.

[0106] In step S370, 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 S350 was first made positive.

[0107] In step S380, it is determined whether the duration Tk is greater than a first predetermined time ta based on the duration Tk. Here, the "first predetermined time ta" is a threshold value related to the duration Tk, and is a preset predetermined value (constant). If the duration Tk is equal to or less than the first predetermined time ta and step S380 is negative, the process proceeds to step S360. On the other hand, if the duration Tk exceeds the first predetermined time ta and step S380 is positive, the process proceeds to step S390. In step S390, an abnormality (i.e., a first abnormality) of the hydraulic pressure generating unit PU is identified, and the first suitability flag FL is set to "1."

[0108] In the first suitability judgment (first abnormality judgment), even if the servo pressure deviation hPa exceeds the first threshold pressure Ha, an abnormality in the hydraulic pressure generating unit PU is not immediately judged. An abnormality in the hydraulic pressure generating unit PU is judged when the state in which the servo pressure deviation hPa is greater than the first threshold pressure Ha continues for a first predetermined time ta. In the lower braking unit SZ, execution of complementary control is started by switching the first suitability flag FL from "0" to "1".

[0109] <<Second suitability judgment>> The second suitability judgment for identifying a shortage of the supply pressure Ps is executed based on the deviation hPs between the target supply pressure Pst and the detected supply pressure Psk (referred to as "supply pressure deviation"). In the explanation of the first suitability judgment, the following is replaced with the explanation of the second suitability judgment: "target servo pressure Pat" with "target supply pressure Pst", "detected servo pressure Pak" with "detected supply pressure Psk", "servo pressure deviation hPa" with "supply pressure deviation hPs", "target servo pressure gradient dPa" with "target supply pressure gradient dPs", "computation map Zha" with "computation map Zhs", "first threshold pressure Ha" with "second threshold pressure Hs", "first predetermined time ta" with "second predetermined time ts", and "first suitability flag FL" with "second suitability flag FM". Furthermore, the symbols in square brackets in FIG. 4 correspond to the second suitability judgment. Below, the processing of the second suitability judgment will be briefly explained.

[0110] In step S310, the target supply pressure Pst and the detected supply pressure Psk are read. The target supply pressure Pst is a target value related to the supply pressure Ps, and the detected supply pressure Psk is a detection result of the supply pressure sensor PS. In step S320, a target supply pressure gradient dPs is calculated based on the target supply pressure Pst. The "target supply pressure gradient dPs" is a value corresponding to the amount of change per unit time of the target supply pressure Pst (absolute value). Here, when the target supply pressure Pst is constant, the target supply pressure gradient dPs is determined to be "0". In step S330, a second threshold pressure Hs is calculated based on the target supply pressure gradient dPs (amount of change per time related to the supply pressure Ps). The "second threshold pressure Hs" is a threshold value for determining an abnormality of the upper brake unit SA. The second threshold pressure Hs is determined to be larger as the target supply pressure gradient dPs is larger according to a preset calculation map Zhs. Similarly to the above, in order to avoid unnecessary abnormality determination, the second threshold pressure Hs is determined based on the target supply pressure gradient dPs. Note that the second threshold pressure Hs also has a lower limit pressure that is a preset predetermined value (constant).

[0111] In step S340, a deviation hPs (supply pressure deviation) between the target supply pressure Pst and the detected supply pressure Psk is calculated (i.e., "hPs=Pst-Psk"). The supply pressure deviation hPs is a shortage of the detected supply pressure Psk relative to the target supply pressure Pst. In step S350, it is determined whether the supply pressure deviation hPs is greater than the second threshold pressure Hs. If the supply pressure deviation hPs is equal to or less than the second threshold pressure Hs, step S350 is negative, and the process proceeds to step S360. In step S360, the upper brake unit SA is identified as normal, and the second suitability flag FM is set to "0". On the other hand, if the supply pressure deviation hPs is greater than the second threshold pressure Hs, step S350 is positive, and the process proceeds to step S370.

[0112] In step S370, the duration Tk is calculated. The duration Tk is the time during which the state "hPs>Hs" continues. In step S380, it is determined whether the duration Tk is greater than the second predetermined time ts based on the duration Tk. Here, the "second predetermined time ts" is a preset predetermined value (constant). If the duration Tk is equal to or less than the second predetermined time ts and step S380 is negative, the process proceeds to step S360. On the other hand, if the duration Tk exceeds the second predetermined time ts and step S380 is positive, the process proceeds to step S390. In step S390, an abnormality (i.e., a second abnormality) of the upper braking unit SA is identified, and the second suitability flag FM is set to "1."

[0113] In the relationship between the first and second suitability judgments, the first and second threshold pressures Ha and Hs are determined so as to prevent a situation in which the first suitability judgment is positive and the second suitability judgment is negative. Since "rc=rm" is established in the braking control device SC, during pressure increase, the supply pressure Ps (=Pm) is smaller than the servo pressure Pa by an amount of hydraulic pressure equivalent to the sliding resistance of the seal member SL. For this reason, the second threshold pressure Hs is set to a value equal to or greater than the first threshold pressure Ha. When the servo pressure deviation hPa is greater than the first threshold pressure Ha, the supply pressure deviation hPs is always greater than the second threshold pressure Hs, so the above situation is reliably avoided.

[0114] The first suitability determination is performed based on the servo pressure deviation hPa, and therefore not only a simple malfunction but also an abnormality related to a decrease in the output of the hydraulic pressure generating unit PU can be identified. Similarly, the second suitability determination is performed based on the supply pressure deviation hPs, and therefore a decrease in the output of the upper brake unit SA as a whole can be determined.

[0115] <1st and 2nd suitability judgment operations> The operations of the first and second suitability determinations will be described with reference to the time series diagram of FIG. 5 (a diagram showing transitions of state quantities with the passage of time T).

[0116] <First suitability test> The first suitability judgment determines whether the hydraulic pressure generating unit PU is suitable (normal or abnormal) based on the target servo pressure Pat (target value) and the detected servo pressure Pak (detected value of the servo pressure sensor PA). In the first suitability judgment, 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.

[0117] "(Pat-Pak)≦Ha" can be modified to "Pak≧(Pat-Ha)". Therefore, the first suitability judgment can be expressed as follows. If the hydraulic pressure obtained by subtracting the first threshold pressure Ha from the target servo pressure Pat is the "first lower limit pressure", the hydraulic pressure generating unit PU is normal when the detected servo pressure Pak is equal to or higher than the first lower limit pressure "Pat-Ha". Here, the region from the target servo pressure Pat to the first lower limit pressure "Pat-Ha" is referred to as the "first allowable range Xa". In the suitability judgment, the first allowable range Xa is determined (set) based on the target servo pressure Pat and the first threshold pressure Ha. Then, when the detected servo pressure Pak transitions within the first allowable range Xa, it is judged that the hydraulic pressure generating unit PU is normal. On the other hand, when the detected servo pressure Pak transitions outside the first allowable range Xa, it is judged that the hydraulic pressure generating unit PU is abnormal.

[0118] The first suitability judgment is always performed when the hydraulic pressure generating unit PU is operating (i.e., when the servo pressure Pa is increased, maintained, or decreased). Alternatively, the suitability judgment 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 target servo pressure Pat per unit time (the amount of change over time when the hydraulic pressure is increasing) is adopted for the target servo gradient dPa. 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 servo pressure Pa is increasing.

[0119] FIG. 5 illustrates an example of the first suitability judgment when the target servo pressure Pat increases with the passage of time T at a constant target servo pressure gradient dPa. The shaded area is set as the first allowable range Xa. The first threshold pressure Ha changes according to the target servo pressure gradient dPa, but in the example, the first threshold pressure Ha is a constant value. Three examples (a), (b), and (c) of the transition of the detected servo pressure Pak are shown.

[0120] At time t0, braking is started, and the braking demand amount Bs is increased from "0". Accordingly, the target servo pressure Pat is increased from "0". Immediately after time t0, a target servo pressure gradient dPa (amount of change in the target servo pressure Pat per unit time) is calculated based on the target servo pressure Pat (absolute value). Then, a first threshold pressure Ha is determined based on the target servo pressure gradient dPa. The first threshold pressure Ha is calculated to be larger as the target servo pressure gradient dPa is larger. The first threshold pressure Ha is compared with the deviation hPa between the target servo pressure Pat and the detected servo pressure Pak (the detection value of the servo pressure sensor PA). That is, it is determined whether the detected servo pressure Pak is within the first permissible range Xa.

[0121] ≪Transition example (a)≫ As in transition example (a), when the detected servo pressure Pak increases from "0" within the first permissible range Xa and then continues to transition within the first permissible range Xa, the servo pressure deviation hPa continues to be equal to or less than the first threshold pressure Ha. In other words, since the detected servo pressure Pak follows the 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)."

[0122] ≪Transition example (b)≫ As in the transition example (b), when the detected servo pressure Pak does not increase from "0" within the first permissible range Xa (i.e., when the rise of the detected servo pressure Pak is delayed), the count of the duration Tk is started at the time t1 when the detected servo pressure Pak transitions to the outside of the first permissible range Xa. After that, the state where the detected servo pressure Pak is out of the first permissible range Xa (i.e., the state where the servo pressure deviation hPa is larger than the first threshold pressure Ha) continues for the first predetermined time ta. At the time t2, the result of step S380 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.

[0123] ≪Transition example (c)≫ As in transition example (c), the detected servo pressure Pak rises from "0" within the first permissible range Xa, but then falls outside the first permissible range Xa. From time t3 when the detected servo pressure Pak transitions outside the first permissible range Xa, the duration Tk is calculated. As in transition example (b), when the state in which the detected servo pressure Pak transitions outside the first permissible range Xa (i.e., the state of "hPa>Ha") continues for the first predetermined time ta, an abnormality is determined in the hydraulic pressure generating unit PU. Then, the above-mentioned abnormality measures (stopping the hydraulic pressure generating unit PU and switching to the first operation mode Mm) are executed.

[0124] Even if the detected servo pressure Pak once deviates from the first permissible range Xa, if the detected servo pressure Pak re-enters the first permissible range Xa, the calculation of the duration Tk is reset and returned to "Tk = 0." If the detected servo pressure Pak subsequently deviates from the first permissible range Xa again, counting of the duration Tk is started from that point.

[0125] <<Second suitability judgment>> The second suitability judgment determines whether the upper brake unit SA is normal or abnormal based on the target supply pressure Pst (target value) and the detected supply pressure Psk (detected value of the supply pressure sensor PS). In the second suitability judgment, if "(Pst-Psk)≦Hs", the upper brake unit SA is determined to be normal.

[0126] As above, the symbols in the square brackets in Fig. 5 correspond to the second suitability judgment. In addition, in the explanation of the first suitability judgment, the following are replaced with the "target servo pressure Pat" as the "target supply pressure Pst", the "detected servo pressure Pak" as the "detected supply pressure Psk", the "servo pressure deviation hPa" as the "supply pressure deviation hPs", the "target servo pressure gradient dPa" as the "target supply pressure gradient dPs", the "calculation map Zha" as the "calculation map Zhs", the "first threshold pressure Ha" as the "second threshold pressure Hs", the "first predetermined time ta" as the "second predetermined time ts", the "first suitability flag FL" as the "second suitability flag FM", and the "first allowable range Xa" as the "second allowable range Xs", respectively, to correspond to the explanation of the second suitability judgment. Hereinafter, the operation of the second suitability judgment will be briefly explained.

[0127] If the hydraulic pressure obtained by subtracting the second threshold pressure Hs from the target supply pressure Pst is defined as the "second lower limit pressure," the upper brake unit SA is normal when the detected supply pressure Psk is equal to or higher than the second lower limit pressure "Pst-Hs." Similarly, the region from the target supply pressure Pst to the second lower limit pressure "Pst-Hs" is referred to as the "second permissible range Xs." In the second suitability determination, the second permissible range Xs is determined (set) based on the target supply pressure Pst and the second threshold pressure Hs. Then, when the detected supply pressure Psk transitions within the second permissible range Xs, it is determined that the upper brake unit SA is normal. On the other hand, when the detected supply pressure Psk transitions outside the second permissible range Xs, it is determined that the upper brake unit SA is abnormal. In detail, when the state in which the detected supply pressure Psk transitions outside the second permissible range Xs (ie, the state of "hPs>Hs") continues for a second predetermined time ts, an abnormality is determined in the upper brake unit SA.

[0128] The methods of the first and second suitability tests are the same. However, the measures taken after an abnormality is determined to be present are different from those for the first suitability test. Even if an abnormality is determined in the second suitability test, operation of the hydraulic pressure generating unit PU continues, and the second operation mode Ms is maintained. However, the supplementary control in the lower brake unit SZ is executed in the second abnormality as well as in the first abnormality.

[0129] <Another embodiment of the brake control device SC> Other embodiments of the brake control device SC will be described below. The other embodiments also provide the same effects as those described above (identification of output reduction abnormality, identification of the abnormality occurrence location and corresponding measures, etc.).

[0130] In the above embodiment, the first threshold pressure Ha is determined based on the servo pressure gradient dPa corresponding to the change amount per unit time of the servo pressure Pa, and the second threshold pressure Hs is determined based on the supply pressure gradient dPs corresponding to the change amount per unit time of the supply pressure Ps. A predetermined relationship exists between the servo pressure Pa and the supply pressure Ps. Therefore, the first and second threshold pressures Ha and Hs may be determined based on the change amount per unit time of at least one of the servo pressure Pa and the supply pressure Ps (also referred to as the "target gradient dPx"). In other words, the target gradient dPx can be said to be a general term for the target servo pressure gradient dPa and the target supply pressure gradient dPs. For example, the larger of the target servo pressure gradient dPa and the target supply pressure gradient dPs is determined as the target gradient dPx. Alternatively, the average value of the target servo pressure gradient dPa and the target supply pressure gradient dPs may be determined as the target gradient dPx. In any case, in the upper braking unit SA, the first and second threshold pressures Ha, Hs are set according to a target gradient dPx calculated from at least one of the servo pressure Pa and the supply pressure Ps. Here, the first and second threshold pressures Ha, Hs are set to be larger as the target gradient dPx is larger.

[0131] 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 target servo pressure Pat and the target supply pressure Pst are calculated based on state quantities related to forces from the longitudinal forces acting on the vehicle to the vehicle deceleration.

[0132] In the above embodiment, a front-rear type is used as the two braking systems. Alternatively, a diagonal type (also called "X type") may be used as the two braking systems. In this configuration, one of the two master chambers Rm is connected to the left front wheel cylinder and the right rear wheel cylinder, and the other of the two master chambers Rm is connected to the right front wheel cylinder and the left rear wheel cylinder.

[0133] In the above embodiment, a tandem type master cylinder CM is exemplified. Instead of this, a single type master cylinder CM may be adopted. In this configuration, the secondary master piston NS is omitted. And, one master chamber Rm is connected to four wheel cylinders CW. In this configuration, the supply pressure Ps (=Pm) is output from one master cylinder CM.

[0134] In a configuration in which a single-type master cylinder CM is used, the master chamber Rm may be connected to the front wheel cylinder CWf, and the servo pressure Pa may be directly supplied from the hydraulic pressure generating unit PU to the rear wheel cylinder CWr. In this configuration, the front wheel supply pressure Psf (=Pm) is output from the master cylinder CM. On the other hand, the rear wheel supply pressure Psr (=Pa) is output from the hydraulic pressure generating unit PU.

[0135] In the above-described embodiment, the hydraulic pressure generating unit PU is exemplified as one in which the servo pressure Pa is adjusted by throttling the circulating flow KN of the brake fluid BF discharged by the fluid pump QA with the pressure regulating valve UA (so-called reflux type configuration). Alternatively, the hydraulic pressure generating unit PU may adjust the servo pressure Pa by increasing or decreasing the volume inside a cylinder with a piston directly driven by an electric motor (so-called electric cylinder type configuration). Even in the electric cylinder type, the hydraulic pressure generating unit PU (particularly the electric motor) operates when there is a braking request corresponding to the braking request amount Bs, just like the reflux type. In other words, the hydraulic pressure generating unit PU is of an on-demand type.

[0136] 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 (also called the "area ratio") of the servo area rc to the master area rm. In this configuration, the first and second threshold pressures Ha and Hs are determined based on the area ratio so that a situation does not occur in which the first suitability judgment is affirmed and the second suitability judgment is denied. Furthermore, conversion based on the area ratio is also performed in the calculation of the target gradient dPx.

[0137] In the above-described embodiment, 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 servo pressure Pa 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 servo pressure Pa generated by the hydraulic pressure generating unit PU is outputted 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 (master pressure) in the master chamber Rm generated by operating the brake operating member BP is output as the supply pressure Ps. At this time, since the apply unit AP is disconnected from the stroke simulator SS, 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.).

[0138] In the above-described embodiment, the brake control device SC is applied to a vehicle in which the front wheels WHf are provided with the regenerative device KG and in which the regenerative cooperative control is executed. In a vehicle in which the regenerative cooperative control is executed, the regenerative device KG may be provided in at least one of the front wheels WHf and the rear wheels WHr. The brake control device SC may also be applied to a vehicle in which the regenerative device KG is omitted and in which the regenerative cooperative control is not executed. In other words, the brake control device SC may be applied to various vehicles, regardless of whether or not the regenerative cooperative control is executed.

[0139] <Summary of the embodiment> The following is a summary of an embodiment of the brake control device SC. The brake control device SC 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 (Sp, Ba, Gs, etc.).

[0140] The brake control device SC is equipped with an upper brake unit SA (corresponding to a "brake unit") and a servo pressure sensor PA. In the upper brake unit SA, a supply pressure Ps is output by matching the servo pressure Pa generated by the hydraulic pressure generating unit PU with a target servo pressure Pat calculated based on a braking demand amount Bs, and the hydraulic pressure Pw of the wheel cylinder CW is adjusted by the supply pressure Ps. In addition, the servo pressure Pa is detected by the servo pressure sensor PA as a detected servo pressure Pak.

[0141] In the upper brake unit SA of the brake control device SC, a servo pressure deviation hPa, which is the deviation between the detected servo pressure Pak and the target servo pressure Pat, is calculated. If the servo pressure deviation hPa is greater than the first threshold pressure Ha, an abnormality in the hydraulic pressure generating unit PU is determined. This allows a drop in the output of the hydraulic pressure generating unit PU, which is the pressure source for the upper brake unit SA, to be appropriately identified.

[0142] In the upper braking unit SA, a target servo pressure gradient dPa corresponding to the amount of change in the target servo pressure Pat per unit time (for example, the time differential value of the absolute value of the target servo pressure Pat) is calculated. Then, a first threshold pressure Ha is determined based on the target servo pressure gradient dPa. Specifically, the first threshold pressure Ha is determined so as to increase as the target servo pressure gradient dPa increases.

[0143] Since the hydraulic pressure generating unit PU is of an on-demand type, when there is no braking request (when not braking), the hydraulic pressure generating unit PU is stopped. Then, when a braking request is generated, the hydraulic pressure generating unit PU is started at the same time. The hydraulic pressure generating unit PU has a limited response. For example, when the hydraulic pressure generating unit PU is started, even if the braking request amount Bs increases suddenly, the rotation speed of the electric motor MA cannot be increased in a stepwise manner. In the brake control device SC, the first threshold pressure Ha is set based on the target servo pressure gradient dPa, so that it is possible to avoid unnecessary determination of a decrease in output of the hydraulic pressure generating unit PU (i.e., a first abnormality).

[0144] The brake control device SC is further provided with a supply pressure sensor PS that detects the supply pressure Ps as a detected supply pressure Psk. In the upper brake unit SA, a target supply pressure Pst corresponding to the supply pressure Ps is calculated. Also, a supply pressure deviation hPs, which is the deviation between the detected supply pressure Psk and the target supply pressure Pst, is calculated. Then, if the supply pressure deviation hPs is larger than a second threshold pressure Hs, an abnormality in the upper brake unit SA is determined. This makes it possible to identify a decrease in output of the upper brake unit SA as a whole.

[0145] In the upper brake unit SA, abnormality judgment of the hydraulic pressure generating unit PU and abnormality judgment of the upper brake unit SA as a whole are performed separately. That is, in addition to monitoring the hydraulic pressure generating unit PU, which is the power source (i.e., first suitability judgment), the hydraulic pressure transmission path in the upper brake unit SA is also monitored (i.e., second suitability judgment). Since abnormality monitoring is performed doubly, the reliability of the suitability judgment is improved. In addition, the part where the abnormality has occurred can be identified.

[0146] In the upper braking unit SA of the brake control device SC, the hydraulic pressure generating unit PU is used as a pressure source (power source) to electrically generate the wheel pressure Pw. In the case of a first abnormality (i.e., when the hydraulic pressure generating unit PU is abnormal), the upper braking unit SA cannot output a sufficient supply pressure Ps, so the hydraulic pressure generating unit PU is stopped. Then, the operation mode is switched from the second operation mode Ms to the first operation mode Mm. As a result, the supply pressure Ps is generated by the muscle force of the driver.

[0147] In contrast, in the case of a second abnormality (i.e., the hydraulic pressure generating unit PU is normal but the upper brake unit SA is abnormal), there is a possibility that the abnormality will be resolved, so the hydraulic pressure generating unit PU is activated and the supply pressure Ps is generated by the servo pressure Pa. At this time, the operation mode remains in the second operation mode Ms. By maintaining the operation mode, any discomfort felt by the driver is suppressed. In this way, the brake control device SC can appropriately select the treatment depending on the location where the abnormality occurs.

[0148] In the upper braking unit SA, a target gradient dPx corresponding to the amount of change per unit time of at least one of the target servo pressure Pat (absolute value) and the target supply pressure Pst (absolute value) is calculated. Then, the first and second threshold pressures Ha and Hs are determined based on the target gradient dPx. For example, the larger of the servo pressure gradient dPa corresponding to the amount of change per unit time of the target servo pressure Pat and the supply pressure gradient dPs corresponding to the amount of change per unit time of the target supply pressure Pst is determined as the target gradient dPx. Then, the first and second threshold pressures Ha and Hs are determined to be larger as the target gradient dPx is larger.

[0149] As described above, since the hydraulic pressure generating unit PU is of the on-demand type, the responsiveness of the hydraulic pressure generating unit PU may unnecessarily determine that the output is insufficient at the time of startup. In the braking control device SC, the first and second threshold pressures Ha, Hs are set based on the target gradient dPx (a collective term for dPa and dPs), thereby preventing such unnecessary determinations.

[0150] The brake control device SC is provided with a lower brake unit SZ between the upper brake unit SA and the wheel cylinder CW. When the lower brake unit SZ determines that there is an abnormality in the hydraulic pressure generating unit PU or the upper brake unit SA, the supply pressure Ps is increased and output to the wheel cylinder CW. For example, in the lower brake unit SZ, the supply pressure Ps is increased by the supply pressure deviation hPs. This compensates for the shortage of the supply pressure Ps by the wheel pressure Pw, so that the vehicle deceleration according to the braking demand Bs can be ensured. In addition, when the hydraulic pressure generating unit PU is stopped, the operating force Fp can be reduced. [Explanation of symbols]

[0151] 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...Hydraulic pressure generating section (YA pressure source), U A...Second pressure regulating valve, 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 (generic term for Ba and Gs), Pa...Servo pressure (hydraulic pressure output from PU), Pat...Target servo pressure (target value corresponding to Pa), PA...Servo pressure sensor, Pak...Detection sensor Servo pressure (Pa detected by PA), hPa...Servo pressure deviation (difference between Pat and Pak), Ps...Supply pressure (hydraulic 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 (Ps detected by PS), hPs...Supply pressure deviation (difference between Pst and Psk), Pp...Adjusted pressure, Pw...Wheel pressure, FL...1st suitability flag (result of 1st suitability judgment related to PU), FM...2nd suitability flag (related to SA) result of second suitability judgment), Ha, Hs...first and second threshold pressures (threshold values ​​for first and second suitability judgment), Xa, Xs...first and second tolerance ranges (areas where first and second abnormalities are not judged), dPa...target servo pressure gradient (amount of change over time in Pat), dPs...target supply pressure gradient (amount of change over time in Pst), dPx...target gradient (generic term for dPa and dPs), 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 brake control device for a vehicle, comprising: a brake unit that outputs a supply pressure by making a servo pressure generated by a hydraulic pressure generating unit coincide with a target servo pressure calculated based on a braking request amount, and adjusts hydraulic pressure in a wheel cylinder by the supply pressure; and a servo pressure sensor that detects the servo pressure as a detected servo pressure, The braking unit comprises: A brake control device for a vehicle, which calculates a servo pressure deviation which is a deviation between the detected servo pressure and the target servo pressure, and determines that an abnormality exists in the hydraulic pressure generating unit when the servo pressure deviation is larger than a first threshold pressure.

2. 2. The vehicle brake control device according to claim 1, The braking unit comprises: A vehicle brake control device which calculates a target servo pressure gradient corresponding to an amount of change in the target servo pressure per unit time, and determines the first threshold pressure based on the target servo pressure gradient.

3. 2. A vehicle brake control device according to claim 1, a supply pressure sensor that detects the supply pressure as a detected supply pressure, The braking unit comprises: A vehicle braking control device that calculates a target supply pressure corresponding to the supply pressure, calculates a supply pressure deviation which is the deviation between the detected supply pressure and the target supply pressure, and determines an abnormality in the braking unit if the supply pressure deviation is greater than a second threshold pressure.

4. 4. The vehicle brake control device according to claim 3, The braking unit comprises: A braking control device for a vehicle that calculates a target gradient corresponding to an amount of change per unit time of at least one of the target servo pressure and the target supply pressure, and determines the first and second threshold pressures based on the target gradient.

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