Vehicle braking control device

Abstract

To reduce power consumed by an electric motor when abnormality occurs in a main power supply and it is driven by an auxiliary power supply, in a brake control device.SOLUTION: A brake control device comprises: a pressurizing portion that increases wheel pressure; a control portion that drives the pressurizing portion; a main power supply that feeds power to the control portion; and an auxiliary power supply that feeds power to the control portion when the main power supply is in an abnormal condition. The pressurizing portion comprises: a fluid pump that is driven by an electric motor; a reflux path that connects a discharge portion and a suction portion of the fluid pump; a pressure-adjusting valve that is provided in the reflux path; and a hydraulic chamber that is connected to the reflux path. The control portion increases control pressure of the hydraulic chamber to increase the wheel pressure. When power is fed from the main power supply, the control portion drives the electric motor to generate a circulation flow of a brake liquid in the reflux path, and throttles it by the pressure-adjusting valve to increase the control pressure. However, when power is fed from the auxiliary power supply, the control portion closes the pressure-adjusting valve and drives the electric motor to move the brake liquid to the hydraulic chamber, thereby increasing the control pressure.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] The applicant has developed a braking control device for a vehicle powered by an electric motor, as described in Patent Document 1. Specifically, the device in Patent Document 1 includes a "pressure adjustment unit YC, which is composed of an electric pump DC and a solenoid valve UC, and which adjusts the brake fluid discharged by the electric pump to a regulated fluid pressure Pc by the solenoid valve UC and introduces the regulated fluid pressure Pc into a rear wheel cylinder," and a "master unit YM, which is composed of a master cylinder CM and a master piston PM, and which has a "master chamber Rm connected to the front wheel cylinder" and a "servo chamber Rs, into which the regulated fluid pressure Pc is introduced, and which applies to the master piston PM a forward force Fa that counteracts a backward force Fb applied to the master piston PM by the master chamber Rm."

[0003] Patent Document 2 discloses the following device for a hydraulic brake system equipped with a main power supply and an auxiliary power supply as on-board power sources, to prevent the voltage of the auxiliary power supply from falling below the minimum operating voltage of the hydraulic brake system in the event of an abnormality in the main power supply. The device is a hydraulic pressure generating device including a pump and a pump motor that drives the pump, and when the main power supply is normal, the pump motor is started by the main power supply in response to a braking request. However, when the main power supply cannot supply power to the hydraulic pressure generating device, the pump motor is continuously operated by the auxiliary power supply, regardless of whether a braking request is made. When the main power supply is abnormal, there are fewer opportunities for inrush current to flow. As a result, it is possible to prevent the voltage of the auxiliary power supply from falling below the minimum operating voltage.

[0004] However, in the device of Patent Document 2, even when there is no braking request, the pump motor (also called an "electric motor") continues to be driven by the auxiliary power supply. As a result, although the voltage drop due to the inrush current is suppressed, power consumption is not reduced. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2019-059294 [Patent Document 2] Japanese Patent Publication No. 2020-147185 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a braking control device that can reduce the power consumed by an electric motor when an abnormality occurs in the main power supply and the electric motor is driven by an auxiliary power supply. [Means for solving the problem]

[0007] The vehicle braking control device (SC) of the present invention comprises a pressure applying unit (CA, CB) that increases the wheel pressure (Pw) of the wheel cylinder (CW) of the vehicle, a control unit (EA, EB) that drives the pressure applying unit (CA, CB), a main power supply (BT) that supplies power to the control unit (EA, EB), and an auxiliary power supply (BU) that supplies power to the control unit (EA, EB) in place of the main power supply (BT) when the main power supply (BT) is abnormal. Here, the pressurizing section (CA, CB) comprises fluid pumps (QA, QB) driven by electric motors (MA, MB), return paths (HN, HL) connecting the discharge sections (Qo, Qp) of the fluid pumps (QA, QB) to the suction sections (Qi, Qj) of the fluid pumps (QA, QB), pressure regulating valves (UA, UB) provided in the return paths (HN, HL), and hydraulic chambers (Ru, Rw) connected to the return paths (HN, HL) between the discharge sections (Qo, Qp) and the pressure regulating valves (UA, UB).

[0008] In the vehicle brake control device (SC) according to the present invention, the control units (EA, EB) increase the wheel pressures (Pw) by increasing the control pressures (Pu, Pw) in the hydraulic chambers (Ru, Rw). In a first state in which power is supplied from the main power source (BT), the control units (EA, EB) drive the electric motors (MA, MB) to generate circulating flows (KN, KL) of brake fluid (BF) in the return paths (HK, HL), and increase the control pressures (Pu, Pw) by throttling the circulating flows (KN, KL) with the pressure regulator valves (UA, UB). In a second state in which power is supplied from the auxiliary power source (BU), the control units (EA, EB) close the pressure regulator valves (UA, UB) and drive the electric motors (MA, MB) to move brake fluid (BF) to the hydraulic chambers (Ru, Rw), thereby increasing the control pressures (Pu, Pw).

[0009] According to the above configuration, in the first state, the circulation flows KN and KL must be continuously generated, so the fluid pumps QA and QB continue to be driven. On the other hand, in the second state, the control pressures Pu and Pw are increased by the movement of brake fluid BF, so the fluid pumps QA and QB only need to be driven when necessary. Therefore, in the second state, the power consumption of the electric motors MA and MB is reduced when the control pressures Pu and Pw are increased.

[0010] The vehicle brake control device (SC) according to the present invention includes a check valve (GC) that blocks the flow of brake fluid (BF) from the pressure regulating valve (UA, UB) toward the discharge portion (Qo, Qp). control When the pressures (Pu, Pw) reach a target pressure (Pt) calculated in accordance with the braking demand (Bs) of the vehicle, power supply to the electric motors (MA, MB) is stopped.

[0011] According to the above configuration, the hydraulic pressure chambers Ru, Rw are sealed by the check valve GC and the pressure regulating valves UA, UB, so the control pressures Pu, Pw are not reduced. Therefore, even if the power supply to the electric motors MA, MB is completely stopped when the control pressures Pu, Pw reach the target pressure Pt, the control pressures Pu, Pw are maintained, thereby reducing the power consumption of the electric motors MA, MB. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic diagram for explaining a first embodiment of a braking control device SC. FIG. [Figure 2] FIG. 4 is a flowchart illustrating an example of a pressure regulation control process. [Figure 3] FIG. 4 is a schematic diagram for explaining a second embodiment of the braking control device SC. DETAILED DESCRIPTION OF THE INVENTION

[0013] <Symbols for components, etc., and suffixes at the end of the symbols> In the following description, components, calculation processes, signals, characteristics, and values ​​with the same symbols, such as "CW," have the same function. The suffixes "f" and "r" at the end of the symbols for each wheel are generic symbols that indicate whether the symbol relates to the front or rear wheel system. For example, a wheel cylinder CW provided on each wheel is written as a "front wheel cylinder CWf" and a "rear wheel cylinder CWr." Furthermore, the suffixes "f" and "r" at the end of the symbol can 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.

[0014] In the fluid path from the master cylinder CM to the wheel cylinder CW, 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, KL of the brake fluid BF, the side closer to the discharge ports Qo, Qp of the fluid pumps QA, QB (the side farther from the suction ports Qi, Qj) is referred to as the "upstream side," and the side closer to the suction ports Qi, Qj of the fluid pumps QA, QB (the side farther from the discharge ports Qo, Qp) is referred to as the "downstream side."

[0015] The master cylinder CM, pressurizing units CA and CB, and wheel cylinders CW are connected by a fluid path (communication path HS). Furthermore, various components (UA, etc.) are connected to the pressurizing units CA and CB by fluid paths. Here, a "fluid path" is a path for moving brake fluid BF, and corresponds to piping, flow paths in the actuator, hoses, etc. In the following explanation, the communication path HS, return paths HK and HL, return path HT, reservoir path HR, servo path HV, pressure reduction path HG, etc. are fluid paths.

[0016] <First embodiment of braking control device SC> A first embodiment of a braking control device SC according to the present invention will be described with reference to the schematic diagram of FIG. 1. The braking control device SC according to the first embodiment is a brake-by-wire type device. That is, the braking control device SC can generate wheel pressure Pw independently in response to braking operations by the driver, etc. FIG. 1 is a schematic diagram of the configuration (particularly the upper fluid unit YU) described in Patent Document 1 (JP 2019-059294 A). Specifically, the diagram illustrates the components from the master cylinder CM described in the publication to each of the front and rear wheel cylinders CWf and CWr (for example, the wheel cylinders CWi and CWk in Patent Document 1).

[0017] A vehicle is provided with a brake operating member BP. The brake operating member (e.g., a brake pedal) BP is a member that the driver operates to decelerate the vehicle. The vehicle is also provided with front and rear wheel braking devices SXf, SXr (=SX). The braking device SX is composed of a brake caliper CP (=CPf, CPr), a friction member MS (e.g., a brake pad), and a rotating member KT (=KTf, KTr, e.g., a brake disc). The brake caliper CP is provided with a wheel cylinder CW (=CWf, CWr). A wheel piston NW (=NWf, NWr) is inserted into the wheel cylinder CW. Inside the wheel cylinder CW, a hydraulic chamber Rw (=Rwf, Rwr) is formed by the wheel piston NW. When the wheel pressure Pw (=Pwf, Pwr) is supplied from the brake control device SC to the hydraulic pressure chamber Rw (referred to as the "wheel chamber"), the friction member MS is pressed against the rotating member KT fixed to the wheel WH. This causes a frictional braking force Fm to be generated in the wheel WH. The "frictional braking force Fm" is the braking force generated by the wheel pressure Pw.

[0018] The vehicle is equipped with two power sources BT and BU as sources of power supply to the braking control device SC (particularly the controller EA, the pressure applying unit CA, etc.). The power source BT is called the "main power source" and is used for normal power supply. The power source BU is called the "auxiliary power source" and is used as an alternative power source in case of an abnormality in the main power source BT. Here, an abnormality in the main power source BT is also called "power source abnormality."

[0019] The brake control device SC employs a so-called front and rear type (also called "type II") as two braking systems. The brake control device SC is composed of a braking operation amount sensor BA, a stroke simulator SS, a master cylinder CM, a first pressure applying unit CA (also called "pressurizing unit"), and a first controller EA (also called "controller").

[0020] The braking operation amount sensor BA detects the operation amount Ba (braking operation amount) of the brake operating member BP. For example, an operation displacement sensor SP that detects the operation displacement Sp of the brake operating member BP is used as the braking operation amount sensor BA. Furthermore, a simulator pressure sensor PZ that detects the hydraulic pressure Pz (referred to as "simulator pressure") of the stroke simulator SS is used as the braking operation amount sensor BA. In other words, the braking operation amount Ba is a general term for signals that represent the driver's braking intention, and the braking operation amount sensor BA is a general term for sensors that detect the braking operation amount Ba. The braking operation amount Ba is input to the first controller EA.

[0021] An operating force Fp of the brake operating member BP is generated by a stroke simulator SS (also simply referred to as "simulator"). Since the brake control device SC is of a brake-by-wire type, the operating characteristics of the brake operating member BP (the relationship between the operating displacement Sp and the operating force Fp) are generated by the simulator SS. A simulator pressure sensor PZ is provided to detect a simulator pressure Pz. The simulator pressure Pz is a state quantity that represents the operating force Fp of the brake operating member BP.

[0022] A single master cylinder CM supplies a master pressure Pm to a front wheel cylinder CWf (particularly, a front wheel chamber Rwf) as a front wheel pressure Pwf. A master piston NM is inserted into the master cylinder CM. The interior of the master cylinder CM is divided into a master chamber Rm and a servo chamber Ru by the master piston NM. The master chamber Rm is connected to the hydraulic chamber Rwf (front wheel chamber) of the front wheel cylinder CWf via a front wheel communication passage HSf. The servo chamber Ru is connected to a pressurizing section CA via a servo passage HV (fluid passage). The pressure-receiving area rm (referred to as the "master area") of the master chamber Rm and the pressure-receiving area ru (referred to as the "servo area") of the servo chamber Ru are set equal (i.e., "rm = ru").

[0023] When braking is not in progress, the master piston NM is in its most retracted position (i.e., the position where the volume of the master chamber Rm is at its maximum). In this state, the master chamber Rm is in communication with the master reservoir RV (atmospheric pressure reservoir). When the brake operating member BP is operated, the servo pressure Pu in the servo chamber Ru increases, and the master piston NM moves forward (in the direction in which the volume of the master chamber Rm decreases and the volume of the servo chamber Ru increases). This movement blocks communication between the master chamber Rm and the master reservoir RV. Furthermore, when the master piston NM moves forward, the hydraulic pressure Pm (master pressure) in the master chamber Rm increases from "0 (atmospheric pressure)", and brake fluid BF is pumped out of the master chamber Rm. Here, since "rm = ru", "Pm = Pu" holds true.

[0024] [First pressure section CA] A first pressurizing unit CA (corresponding to a "pressurizing unit") generates a servo pressure Pu. The servo pressure Pu (corresponding to a "control pressure") is supplied to a servo chamber Ru (corresponding to a "hydraulic pressure chamber") of the master cylinder CM and a rear wheel chamber Rwr (corresponding to a "hydraulic pressure chamber") of the rear wheel cylinder CWr. The first pressurizing unit CA (also simply referred to as the "pressurizing unit") is composed of a first electric motor MA, a first fluid pump QA, a first pressure regulating valve UA, and a master pressure sensor PM.

[0025] A first fluid pump QA (also simply referred to as a "fluid pump") is driven by a first electric motor MA (also simply referred to as an "electric motor"). The electric motor MA is provided with a first rotation angle sensor KA (also simply referred to as a "rotation angle sensor") to detect a first rotation angle Ka (also simply referred to as a "rotation angle") of a rotor. The first rotation angle Ka (actual value) is input to a controller EA.

[0026] In the first fluid pump QA, the first suction port Qi and the first discharge port Qo are connected by a first return path HK (a fluid path, also simply referred to as the "return path"). The first suction port Qi (also simply referred to as the "suction port") of the fluid pump QA is also connected to the master reservoir RV via a reservoir path HR. A check valve GC is provided near the first discharge port Qo (also simply referred to as the "discharge port") of the fluid pump QA. More specifically, the check valve GC is disposed in the return path HK between the discharge port Qo and the pressure regulating valve UA. Furthermore, a normally open first pressure regulating valve UA is provided in the return path HK. The first pressure regulating valve UA (also simply referred to as the "pressure regulating valve") is a linear solenoid valve whose valve opening amount is continuously controlled based on the energization state (e.g., the supply current Ia).

[0027] In the pressurizing section CA, the electric motor MA and the pressure regulating valve UA are driven by the controller EA to generate a servo pressure Pu. The "servo pressure Pu" is the hydraulic pressure between the discharge section Qo of the fluid pump QA and the pressure regulating valve UA. In the brake control device SC, the front and rear wheel pressures Pwf and Pwr are increased by the servo pressure Pu. However, the pressure transmission paths from the servo pressure Pu to the front and rear wheel pressures Pwf and Pwr are different for the brake system associated with the front wheel WHf and the brake system associated with the rear wheel WHr.

[0028] In the braking system for the front wheels WHf, the return path HK is connected to the servo chamber Ru via a servo path HV at a location Bv between the discharge port Qo of the fluid pump QA and the pressure regulating valve UA. Therefore, servo pressure Pu is supplied to the servo chamber Ru. As the servo pressure Pu increases, the master piston NM is pressed forward (in the direction in which the volume of the master chamber Rm decreases), and the hydraulic pressure Pm (master pressure) in the master chamber Rm increases. A master pressure sensor PM is provided in the pressurizing section CA to detect the master pressure Pm.

[0029] The master chamber Rm is connected to the front wheel chamber Rwf of the front wheel cylinder CWf by the front wheel communication passage HSf via the hydraulic pressure modulator MJ. Therefore, the master pressure Pm is supplied from the master chamber Rm of the master cylinder CM to the front wheel chamber Rwf of the front wheel cylinder CWf as the front wheel pressure Pwf. Here, the hydraulic pressure modulator MJ is a general-purpose unit for performing antilock brake control, etc. When the hydraulic pressure modulator MJ is not performing antilock brake control, etc., the servo pressure Pu, master pressure Pm, and front wheel pressure Pwf are all equal (i.e., Pu = Pm = Pwf).

[0030] In the brake system for the rear wheels WHr, the return path HK is connected to the rear wheel connection path HSR at a location Bv between the discharge port Qo of the fluid pump QA and the pressure regulating valve UA. The rear wheel connection path HSR is connected to the rear wheel chamber Rwr of the rear wheel cylinder CWr via a hydraulic pressure modulator MJ. Therefore, in the brake system for the rear wheels WHr, servo pressure Pu is directly supplied to the rear wheel chamber Rwr of the rear wheel cylinder CWr. Similarly to the above, when anti-lock brake control or the like is not being performed by the hydraulic pressure modulator MJ, the servo pressure Pu and the rear wheel pressure Pwr are equal (i.e., "Pu = Pwr").

[0031] When power is supplied from the controller EA, the pressurizing unit CA (particularly the electric motor MA and the pressure regulating valve UA) is driven to generate the servo pressure Pu. The controller EA receives power from either the main power supply BT or the auxiliary power supply BU. However, the method of pressurization in the pressurizing unit CA differs depending on which of these power supplies is selected. The state in which power is supplied to the controller EA from the main power supply BT is referred to as the "first state," and the state in which power is supplied to the controller EA from the auxiliary power supply BU is referred to as the "second state." The braking control device SC normally selects the first state, but selects the second state in the event of a power supply abnormality.

[0032] <Pressurization method when power is supplied from the main power BT> This section describes a pressurization method when power is supplied to the brake control device SC (particularly the pressurization unit CA) from the main power supply BT (i.e., the first state). In the first state, the servo pressure Pu is increased by throttling the circulating flow KN of brake fluid BF discharged by the fluid pump QA driven by the electric motor MA using the pressure regulating valve UA. This pressurization method is called the "dynamic pressure method or dynamic pressurization." "Dynamic pressure" is the pressure that occurs when a flowing fluid (e.g., brake fluid BF) is obstructed. Dynamic pressurization (pressurization by dynamic pressure) will be described in detail below.

[0033] The electric motor MA drives the fluid pump QA. When the fluid pump QA discharges brake fluid BF, a circulating flow KN (indicated by the dashed arrow) of brake fluid BF is generated in the return path HK. When the pressure regulating valve UA is fully open (when not energized, since the pressure regulating valve UA is normally open), the fluid pressure Pu (servo pressure) between the discharge port Qo of the fluid pump QA and the pressure regulating valve UA in the return path HK is zero (atmospheric pressure). When the amount of current Ia (supply current) to the pressure regulating valve UA is increased, the pressure regulating valve UA throttles the circulating flow KN (the flow of brake fluid BF circulating in the return path HK), obstructing the flow of the circulating flow KN. In other words, the pressure regulating valve UA narrows the flow path of the return path HK, creating an orifice effect. This increases the fluid pressure Pu (servo pressure) upstream of the pressure regulating valve UA from zero. That is, in the circulating flow KN, a hydraulic pressure difference (differential pressure) is generated between the hydraulic pressure Pu (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 pressure regulating valve UA adjusts the differential pressure between its upstream and downstream sides, and is therefore also called a "differential pressure valve." The differential pressure is adjusted by the amount of current Ia (e.g., the supply current) applied to the pressure regulating valve UA. When the servo pressure Pu reaches the desired hydraulic pressure (i.e., the target pressure Pt), the amount of current Ia is maintained constant.

[0034] A check valve GC is provided in the return path HK. The check valve GC allows the flow of brake fluid BF (i.e., the flow of the circulating flow KN) from the pressure regulating valve UA toward the suction port Qi (in the direction of the dashed arrow), but blocks the flow of brake fluid BF in the opposite direction, from the pressure regulating valve UA toward the discharge port Qo. In other words, the check valve GC prevents the backflow of brake fluid BF in the return path HK.

[0035] <Pressurization method when power is supplied from the auxiliary power supply BU> The following describes a pressurization method in which, instead of the main power supply BT, power is supplied to the brake control device SC (particularly, the pressurization unit CA) from the main power supply BT (i.e., the second state). In the second state, the pressure regulating valve UA is fully closed, and the entire amount of brake fluid BF discharged by the fluid pump QA driven by the electric motor MA is moved to the servo chamber Ru and the rear wheel chamber Rwr, thereby increasing the servo pressure Pu. Specifically, the brake fluid BF is sucked from the master reservoir RV into the fluid pump QA. Then, the entire amount of the sucked brake fluid BF is discharged to the servo chamber Ru and the rear wheel chamber Rwr. In other words, the fluid pump QA moves the brake fluid BF from the master reservoir RV to the servo chamber Ru and the rear wheel chamber Rwr. This pressurization method is called the "static pressure method or static pressurization." Contrary to dynamic pressure, "static pressure" is the pressure when there is no flow (or when there is only a slight flow). Static pressurization (pressurization by static pressure) will be explained in detail below.

[0036] Power is supplied to the normally open pressure regulating valve UA, completely closing the pressure regulating valve UA. The electric motor MA drives the fluid pump QA, causing brake fluid BF to be discharged from the fluid pump QA. All of the brake fluid BF discharged from the fluid pump QA is transferred to the servo chamber Ru and the rear wheel chamber Rwr. Because the brake control device SC and the brake device SX are rigid, the amount (volume) of brake fluid BF flowing from the fluid pump QA into the hydraulic chambers Ru and Rwr increases, thereby increasing the servo pressure Pu. When the servo pressure Pu (i.e., the wheel pressure Pw) reaches the desired hydraulic pressure (i.e., the target pressure Pt), the electric motor MA stops rotating, and the discharge of brake fluid BF from the fluid pump QA is terminated. At this time, the check valve GC and the pressure regulating valve UA are closed, fluidically locking the hydraulic chambers Ru and Rwr. Therefore, even if the power supply to the electric motor MA is stopped, the servo pressure Pu is maintained.

[0037] <First Controller EA> The pressurizing unit CA is controlled by a first controller EA (corresponding to a "control unit"). Specifically, the controller EA adjusts the power supplied to the electric motor MA and the pressure regulating valve UA using the main power supply BT or the auxiliary power supply BU as a power supply source. The controller EA is composed of a microprocessor MP and a drive circuit DR.

[0038] The controller EA receives inputs such as the braking operation amount Ba, master pressure Pm, and rotation angle Ka. The braking operation amount Ba is a general term for a state quantity that represents the operation amount of the brake operating member BP. Specifically, the detection signal Sp (operation displacement) of the operation displacement sensor SP and the detection signal Pz (simulator pressure) of the simulator pressure sensor PZ are input as the braking operation amount Ba. To control the pressure regulating valve UA and the electric motor MA, the master pressure Pm (detection value of the master pressure sensor PM) and the motor rotation angle Ka (detection value of the rotation angle sensor KA) are input.

[0039] Furthermore, a required deceleration Gs is input to the controller EA. The required deceleration Gs is a required value for decelerating the vehicle. The controller EA is connected to a communication bus BS so that signals (detected values, calculated values, control flags, etc.) can be shared with other controllers. For example, the required deceleration Gs is calculated by a driving assistance device and transmitted to the controller EA via the communication bus BS. Alternatively, the required deceleration Gs is instructed to the brake control device SC by a device (also referred to as an "external operation device") separate from the brake operating member BP.

[0040] The controller EA (particularly the microprocessor MP) is programmed with a pressure regulation control algorithm. "Pressure regulation control" is control for adjusting the servo pressure Pu (ultimately the wheel pressure Pw). Pressure regulation control includes the dynamic and static pressurization described above. Pressure regulation control is performed based on the braking operation amount Ba (operation displacement Sp, simulator pressure Pz) and the required deceleration Gs. Here, the braking operation amount Ba and the required deceleration Gs are collectively referred to as the "braking request amount Bs." The braking request amount Bs is an input value for instructing (requesting) the wheel pressure Pw to be generated by the brake control device SC.

[0041] Based on a pressure regulation control algorithm, the drive circuit DR drives the electric motor MA and the pressure regulating valve UA that constitute the pressurizing unit CA. The drive circuit DR includes an H-bridge circuit configured with switching elements (e.g., MOS-FET) to drive the electric motor MA. The drive circuit DR also includes a switching element to drive the pressure regulating valve UA. In addition, the drive circuit DR includes a motor current sensor (not shown) that detects the supply current Im (actual value) to the electric motor MA, and a current sensor (not shown) that detects the supply current Ia (actual value, referred to as the "supply current") to the pressure regulating valve UA.

[0042] In pressure regulation control, a target pressure Pt is calculated based on the braking demand Bs. In control of the pressure regulating valve UA during dynamic pressurization, a target current It (target value) corresponding to the supply current Ia of the pressure regulating valve UA is calculated based on the target pressure Pt. The supply current Ia is then controlled to approach and match the target current It. In control of the electric motor MA during dynamic pressurization, a target rotation speed Nt (target value) corresponding to the actual rotation speed Na is calculated based on the target pressure Pt. The motor supply current Im is then controlled so that the actual rotation speed Na approaches and matches the target rotation speed Nt. The motor rotation speed Na is calculated based on the motor rotation angle Ka.

[0043] Based on the dynamic pressurization control algorithm, a drive signal Ma for controlling the electric motor MA and a drive signal Ua for controlling the pressure regulating valve UA are calculated. Then, in response to the drive signals (Ma, etc.), the switching elements of the drive circuit DR are driven to control the electric motor MA and the pressure regulating valve UA.

[0044] In the control of the pressure regulating valve UA during static pressurization, a predetermined current ia is supplied. This completely closes the pressure regulating valve UA. The "predetermined current ia" is a predetermined value (constant) that is sufficient to maintain the pressure regulating valve UA in a completely closed state. In the control of the electric motor MA during static pressurization, a target current In (target value) corresponding to the supply current Im of the electric motor MA is calculated based on the target pressure Pt. The supply current Im is then controlled to approach and match the target current In. Alternatively, a target angle Kn (target value) corresponding to the rotation angle Ka of the electric motor MA is calculated based on the target pressure Pt. The actual rotation angle Ka (the value detected by the rotation angle sensor KA) is then controlled to approach and match the motor target angle Kn.

[0045] Based on the control algorithm for static pressurization, a drive signal Ma for controlling the electric motor MA and a drive signal Ua for controlling the pressure regulating valve UA are calculated. Then, the switching elements constituting the H-bridge of the drive circuit DR are driven in response to the drive signal Ma. Note that during static pressurization, the pressure regulating valve UA is completely closed by the drive signal Ua.

[0046] <Pressure regulation control processing> The pressure regulation control process will be described with reference to the flow chart in Figure 2. Pressure regulation control is the control of servo pressure Pu (and consequently wheel pressure Pw) based on braking demand Bs (Ba, Gs, etc.). The pressure regulation control algorithm is programmed in the microprocessor MP of the first controller EA.

[0047] In step S110, various signals (Ba, Gs, etc.) are read. The braking operation amount Ba (Sp, Pz, etc.) is obtained from the braking operation amount BA (SP, PZ, etc.). The required deceleration Gs is obtained from a driving assistance device or the like via the communication bus BS. The suitability flag FB is obtained from a power supply monitoring device via the communication bus BS. The suitability flag FB is a control flag indicating the suitability of the main power supply BT, and "0" indicates that "the main power supply BT is normal" and "1" indicates that "the main power supply BT is abnormal." In addition, the supply voltage Vd (also referred to as "power supply voltage") of the controller EA is obtained. The power supply voltage Vd is detected by a power supply voltage sensor VD (not shown) provided in the drive circuit DR.

[0048] In step S120, a required braking amount Bs is calculated based on the braking operation amount Ba and the required deceleration Gs. For example, the braking operation amount Ba and the required deceleration Gs are compared in terms of vehicle deceleration, and the larger of them is determined as the required braking amount Bs. The required braking amount Bs is a value for indicating the servo pressure Pu (=Pw) ​​required by the brake control device SC.

[0049] Furthermore, in step S120, the target pressure Pt is calculated based on the braking demand amount Bs and the calculation map Zpt. The "target pressure Pt" is the target value corresponding to the servo pressure Pu (actual value). The target pressure Pt is calculated to be "0" according to the calculation map Zpt when the braking demand amount Bs is less than a predetermined amount bo. When the braking demand amount Bs is greater than or equal to the predetermined amount bo, the target pressure Pt is calculated to increase from "0" as the braking demand amount Bs increases from "0". Here, the "predetermined amount bo" is a preset predetermined value (constant).

[0050] In step S130, it is determined whether the main power supply BT is normal or not. This determination is referred to as a "feasibility determination". For example, the feasibility determination is made based on a feasibility flag FB transmitted from a power supply monitoring device (not shown) through the communication bus BS. When "FB = 0" and the main power supply BT is normal (in the first state), the main power supply BT is adopted as the power supply for the pressurizing unit CA. The feasibility determination is affirmed, and the process proceeds to step S140. On the other hand, when "FB = 1" and the main power supply BT is abnormal (in the second state), the auxiliary power supply BU is adopted as the power supply for the pressurizing unit CA instead of the main power supply BT. The feasibility determination is negated, and the process proceeds to step S160.

[0051] The feasibility determination may also be made based on the power supply voltage Vd. The power supply voltage Vd is the voltage that can be supplied to the pressurizing unit CA (UA, MA, etc.) and is detected by the power supply voltage sensor VD. Specifically, the suitability of the main power supply BT is determined based on whether the power supply voltage Vd is greater than or equal to a predetermined voltage vd. When the power supply voltage Vd is greater than or equal to the predetermined voltage vd, the first state is determined; when the power supply voltage Vd is less than the predetermined voltage vd, the second state is determined. Here, the predetermined voltage vd is a threshold value for the feasibility determination and is a preset predetermined value (constant). When "Vd ≥ vd", the feasibility determination is affirmed, and the process proceeds to step S140. On the other hand, when "Vd < vd", the feasibility determination is negated, and the process proceeds to step S160.

[0052] ≪Dynamic Pressurization During Power Supply from the Main Power Supply BT≫ In the first state where the main power supply BT is normal (when power to the pressurizing unit CA is supplied by the main power supply BT), pressurization by the dynamic pressure is carried out in steps S140 and S150.

[0053] In step S140, a target rotation speed Nt (target value) is calculated based on the target pressure Pt. Specifically, the target rotation speed Nt is determined based on a preset calculation map so that the target rotation speed Nt increases as the target pressure Pt increases. Alternatively, the target rotation speed Nt may be determined to a predetermined value (constant) that is set in advance. Then, the electric motor MA is driven so that the actual rotation speed Na approaches and matches the target rotation speed Nt. Here, the actual motor rotation speed Na is determined by time-differentiating the motor rotation angle Ka.

[0054] In step S150, a target current It (target value) corresponding to the supply current Ia of the pressure regulating valve UA is calculated based on the target pressure Pt. Specifically, based on a preset calculation map, the target current It is determined so that it increases as the target pressure Pt increases. Then, current feedback control is executed so that the supply current Ia, which is the detection value of the supply current sensor IA, approaches and matches the target current It.

[0055] Furthermore, the pressure regulating valve UA is controlled so that the master pressure Pm (actual value) approaches and matches the target pressure Pt (target value). Specifically, first, a deviation hP between the target pressure Pt and the master pressure Pm (referred to as a "hydraulic pressure deviation") is calculated based on the target pressure Pt and the master pressure Pm (i.e., "hP = Pt - Pm"). Then, the target current It of the pressure regulating valve UA is adjusted based on the hydraulic pressure deviation hP. In other words, in the control of the pressure regulating valve UA during dynamic pressurization, feedback control (master loop) based on the master pressure Pm is added to the current feedback control (slave loop) so that the master pressure Pm approaches and matches the target pressure Pt.

[0056] <Static pressure when power is supplied from the auxiliary power supply BU> In the second state where the main power supply BT is abnormal (when the power to the pressurizing unit CA is supplied by the auxiliary power supply BU), pressurization by the static pressure is performed in steps S160 and S170.

[0057] In step S160, a predetermined current ia (a predetermined value set in advance) is supplied to the pressure regulating valve UA to close the pressure regulating valve UA. By supplying the predetermined current ia, the pressure regulating valve UA is maintained in a fully closed state, and the circulation flow KN cannot be generated in the return path HK.

[0058] In step S170, a target current In (target value) corresponding to the supply current Im of the electric motor MA is calculated based on the target pressure Pt. Specifically, based on a preset calculation map, the motor target current In is determined to increase as the target pressure Pt increases. Then, current feedback control is executed so that the supply current Im, which is the detection value of the motor current sensor IM, approaches and matches the target current In.

[0059] Furthermore, the electric motor MA is controlled so that the master pressure Pm (actual value) approaches and matches the target pressure Pt (target value). Specifically, as in the case of dynamic pressurization, a deviation hP (hydraulic pressure deviation) between the target pressure Pt and the master pressure Pm is calculated based on the target pressure Pt and the master pressure Pm (i.e., "hP = Pt - Pm"). Then, the target current In of the electric motor MA is adjusted based on the hydraulic pressure deviation hP. In other words, in the control of the electric motor MA in static pressurization, feedback control (master loop) based on the master pressure Pm is added to the current feedback control (slave loop) so that the master pressure Pm approaches and matches the target pressure Pt.

[0060] In step S170, the electric motor MA may be controlled based on the rotation angle Ka. In this control, a target angle Kn (target value) corresponding to the rotation angle Ka of the electric motor MA is calculated. Specifically, based on a preset calculation map, the motor target angle Kn is determined to increase as the target pressure Pt increases. Then, rotation angle feedback control is executed so that the rotation angle Ka, which is the value detected by the rotation angle sensor KA, approaches and matches the motor target angle Kn. Furthermore, similarly to the above, the motor target angle Kn is adjusted based on the hydraulic pressure deviation hP. That is, in the control of the electric motor MA during static pressurization, a cascade configuration is adopted in which hydraulic pressure feedback control (master loop) based on the master pressure Pm is added to rotation angle feedback control (slave loop).

[0061] When the brake control device SC is driven by the main power supply BT (first state), dynamic pressurization is performed. Dynamic pressurization offers excellent pressure regulation accuracy, but consumes a large amount of power. This is because the electric motor MA must be continuously driven to continuously generate the circulating flow KN. Therefore, when the brake control device SC is driven by the auxiliary power supply BU (second state), static pressurization is performed instead of dynamic pressurization. Static pressurization involves transferring the entire amount of brake fluid BF from the fluid pump QA to the hydraulic chambers Ru (servo chamber) and Rwr (rear wheel chamber), thereby reducing the power consumption of the electric motor MA. In addition, a check valve GC is provided in the return path HK, and the hydraulic chambers Ru and Rwr are fluid-locked (fluid-tightly sealed) by the pressure regulating valve UA and the check valve GC. Therefore, the servo pressure Pu (=Pwf, Pwr) can be maintained even when the power supply to the electric motor MA is completely stopped (state "Im = 0"). In the braking control device SC, the power consumption of the auxiliary power supply BU is suppressed, so the capacity of the auxiliary power supply BU is reduced, which allows the device as a whole to be made smaller.

[0062] <Second embodiment of braking control device SC> A second embodiment of a brake control device SC according to the present invention will be described with reference to the schematic diagram of Fig. 3. The brake control device SC according to the second embodiment is a device in which master pressure Pm is pumped from a master cylinder CM in response to operation of a brake operating member BP by a driver. While a brake-by-wire system is adopted in the first embodiment, this is not adopted in the second embodiment. Therefore, in the second embodiment, the operating force Fp of the brake operating member BP is generated by the rigidity of the brake control device SC, the brake device SX, etc.

[0063] FIG. 3 (particularly, the second pressurizing unit CB) schematically illustrates the lower fluid unit YL of Patent Document 1 (JP 2019-059294 A). The pressurizing unit CB is a general-purpose device for performing antilock brake control (also known as ABS control), anti-skid control (also known as ESC), and traction control. FIG. 3 illustrates the area from the master cylinder CM to one wheel cylinder CW.

[0064] In the first embodiment, the servo pressure Pu (control pressure) generated by the first pressurizing unit CA is supplied to the front wheel cylinder CWf via the master cylinder CM / master piston NM as the front wheel pressure Pwf, and to the rear wheel cylinder CWr directly to the rear wheel chamber Rwf. In the second embodiment, the wheel pressure Pw (corresponding to "control pressure") generated by the second pressurizing unit CB is supplied directly to the front and rear wheel chambers Rwf, Rwr (=Rw) (corresponding to "hydraulic chambers") of the front and rear wheel cylinders CWf, CWr (=CW). The following mainly describes the differences from the first embodiment.

[0065] As in the first embodiment, in the second embodiment, the vehicle is provided with a brake operating member BP and a braking device SX. The vehicle is also provided with two power supply sources: a main power supply BT and an auxiliary power supply BU. The braking control device SC (particularly, the controller EB, the pressure unit CB, etc.) is supplied with power from the main power supply BT or the auxiliary power supply BU. When power is supplied from the main power supply BT (i.e., when the main power supply BT is normal), it is in a first state, and when power is supplied from the auxiliary power supply BU (i.e., when an abnormality occurs in the main power supply BT), it is in a second state.

[0066] The brake control device SC performs automatic braking control in addition to anti-lock brake control and anti-skid control. The automatic braking control automatically decelerates the vehicle based on the required deceleration Gs from the driving assistance device to avoid a collision with an obstacle or to mitigate damage in the event of a collision. In addition, in the automatic braking control, the vehicle is decelerated based on the required deceleration Gs instructed by an external operation device. The brake control device SC is composed of a braking operation amount sensor BA, a master cylinder CM, a second pressurizing unit CB (also simply referred to as the "pressurizing unit"), and a second controller EB (also simply referred to as the "controller").

[0067] The braking operation amount sensor BA is an operation displacement sensor SP that detects the operation displacement Sp of the brake operating member BP. The braking operation amount sensor BA also uses a master pressure sensor PM that detects the hydraulic pressure Pm (master pressure) in the master chamber Rm of the master cylinder CM. The braking operation amount Ba is input to a second controller EB.

[0068] A master piston NM is inserted into the master cylinder CM, forming a master chamber Rm. A brake operating member BP is connected to the master piston NM, and the master piston NM moves in conjunction with the operation of the brake operating member BP. The master cylinder CM (particularly, the master chamber Rm) and the wheel cylinder CW (particularly, the wheel chamber Rw) are connected by a communication path HS. As the master piston NM moves, a master pressure Pm is supplied from the master cylinder CM to the wheel cylinder CW as wheel pressure Pw. A second pressurizing section CB is provided between the master cylinder CM and the wheel cylinder CW.

[0069] [Second pressure section CB] The master pressure Pm is individually adjusted (increased or decreased) for each wheel cylinder CW by a second pressurizing unit CB (corresponding to a "pressurizing unit"), and supplied as wheel pressure Pw to the wheel chamber Rw of the wheel cylinder CW. The pressurizing unit CB is powered by a controller EB. As described above, in the second embodiment, the pressurizing method of the pressurizing unit CB differs depending on whether power is supplied from the main power supply BT or the auxiliary power supply BU. Note that a first state is when power is supplied to the controller EB from the main power supply BT, and a second state is when power is supplied to the controller EB from the auxiliary power supply BU. The second pressurizing unit CB is composed of a second electric motor MB, a second fluid pump QB, a second pressure regulating valve UB, a pressure regulating reservoir RB, an inlet valve VI, an adjustment pressure sensor PP, and an outlet valve VO.

[0070] A second fluid pump QB (also simply referred to as a "fluid pump") is driven by a second electric motor MB (also simply referred to as an "electric motor"). The electric motor MB is provided with a second rotation angle sensor KB (also simply referred to as a "rotation angle sensor") to detect a second rotation angle Kb (also simply referred to as a "rotation angle") of the rotor. The actual rotation angle Kb is input to a controller EB.

[0071] A normally open second pressure regulating valve UB is provided in the communication passage HS. The second pressure regulating valve UB (also simply referred to as the "pressure regulating valve") is a linear solenoid valve whose valve opening amount is continuously controlled based on the energization state (for example, the supply current Ib). An upper portion Bm (the side closer to the master cylinder CM) of the communication passage HS and a lower portion Bw (the side closer to the wheel cylinder CW) of the communication passage HS are connected to the pressure regulating valve UB by a return passage HT (fluid passage). A second fluid pump QB is provided in the return passage HT. In addition, a pressure regulating reservoir RB is provided in the return passage HT on the side of the suction portion Qj of the fluid pump QB.

[0072] As in the first embodiment, in the second embodiment, a second reflux path HL (also simply referred to as the "reflux path") connecting the second suction port Qj and the second discharge port Qp in the fluid pump QB is formed by a part of the communication path HS and the return path HT. In addition, a check valve GC is provided in the reflux path HL near the discharge port Qp. More specifically, a check valve is disposed in the reflux path HL (particularly the return path HT) between the discharge port Qp and the pressure regulating valve UB. In other words, the reflux path HL includes the fluid pump QB, the check valve GC, the pressure regulating valve UB, and the pressure regulating reservoir RB. The reflux path HL is connected to the wheel chamber Rw of the wheel cylinder CW by the communication path HS between the pressure regulating valve UB and the check valve GC.

[0073] In the communication line HS, a normally open inlet valve VI is provided below the pressure regulating valve UB. A regulation pressure sensor PP is provided in the communication line HS between the pressure regulating valve UB and the inlet valve VI to detect the hydraulic pressure Pp (referred to as "regulation pressure") regulated by the pressure regulating valve UB and the like. Below the inlet valve VI, the communication line HS is connected to a return line HT (i.e., a reflux line HL) at a point Bg between the suction port Qj of the fluid pump QB and the pressure regulating reservoir RB via a pressure reduction line HG (fluid line). A normally closed outlet valve VO is provided in the pressure reduction line HG. On-off solenoid valves are used as the inlet valve VI and the outlet valve VO. An inlet valve VI and an outlet valve VO are provided for each wheel cylinder CW so that each wheel pressure Pw can be individually adjusted.

[0074] <Dynamic pressure in the first state> In the first state, power is supplied from the main power supply BT to the controller EB and the pressurizing unit CB. In the first state, pressurization is performed by dynamic pressure, as described above. At this time, power is not supplied to the inlet valve VI and the outlet valve VO. Therefore, the inlet valve VI is open and the outlet valve VO is closed.

[0075] When the electric motor MB is driven, the fluid pump QB draws brake fluid BF from the upper portion Bm of the pressure regulating valve UB and discharges it to the lower portion Bw of the pressure regulating valve UB. This generates a second circulation flow KL (indicated by dashed arrows and simply referred to as the "circulation flow") of brake fluid BF, which contains the pressure regulating reservoir RB, in the second reflux path HL (comprised of the communication path HS and the return path HL and simply referred to as the "reflux path"). When the pressure regulating valve UB narrows the flow path of the communication path HS and throttles the circulation flow KL of brake fluid BF, the resulting orifice effect increases the hydraulic pressure Pp (regulation pressure) in the lower portion Bw of the pressure regulating valve UB from the hydraulic pressure Pm (master pressure) in the upper portion of the pressure regulating valve UB. In other words, the pressure difference (differential pressure) between the hydraulic pressure Pm (master pressure) downstream of the pressure regulating valve UB and the hydraulic pressure Pp (regulation pressure) upstream of the pressure regulating valve UB is adjusted by the pressure regulating valve UB. In terms of the magnitude relationship between the master pressure Pm and the adjustment pressure Pp, the adjustment pressure Pp is equal to or greater than the master pressure Pm (i.e., "Pp≧Pm"). The difference between the first pressurizing unit CA and the second pressurizing unit CB is that the servo pressure Pu is increased from "0 (atmospheric pressure)", while the adjustment pressure Pp is increased from the master pressure Pm. However, in the first state, the adjustment pressure Pp is increased by dynamic pressurization, the same as the servo pressure Pu.

[0076] <Static pressure in the second state> In the second state, the controller EB and the pressurizing unit CB are supplied with power from the auxiliary power supply BU instead of the main power supply BT. In the second state, pressurization is performed by static pressure, as described above. As described above, no power is supplied to the inlet valve VI and the outlet valve VO, the inlet valve VI is open, and the outlet valve VO is closed.

[0077] In the second state, power is supplied to the normally open pressure regulating valve UB, causing the pressure regulating valve UB to be completely closed. The electric motor MB drives the fluid pump QB, causing the fluid pump QB to discharge brake fluid BF. The entire amount of brake fluid BF discharged from the fluid pump QB is moved to the wheel chamber Rw. More specifically, the brake fluid BF is sucked into the fluid pump QB from the master cylinder CM (particularly the master chamber Rm). The entire amount of sucked brake fluid BF is then discharged into the wheel chamber Rw. The brake fluid BF flows into the master chamber Rm from the master reservoir RV via a cup seal. In other words, the fluid pump QB moves the brake fluid BF from the master reservoir RV to the wheel chamber Rw via the master cylinder CM.

[0078] Because the brake control device SC and the brake device SX have rigidity, the adjustment pressure Pp (corresponding to the "control pressure") gradually increases as the amount (volume) of brake fluid BF flowing from the fluid pump QB into the hydraulic chamber Rw increases. When the adjustment pressure Pp (i.e., wheel pressure Pw) reaches the desired hydraulic pressure (i.e., target pressure Pt), the electric motor MB stops rotating and the discharge of brake fluid BF from the hydraulic pump QB ends. At this time, the check valve GC and the pressure regulator valve UB are closed, fluidically locking the wheel chamber Rw. Therefore, the wheel pressure Pw is maintained even if the power supply to the electric motor MB is stopped.

[0079] <Second controller EB> The second controller EB (corresponding to a "controller") controls the second pressurizing unit CB based on the braking demand Bs. Specifically, the second controller EB uses the main power supply BT or the auxiliary power supply BU as a power supply source to adjust the power supplied to the second electric motor MB and the second pressure regulating valve UB. Like the first controller EA, the second controller EB is composed of a microprocessor MP and a drive circuit DR.

[0080] The controller EB receives inputs of the braking operation amount Ba, the regulated pressure Pp, the rotation angle Kb, the suitability flag FB, the power supply voltage Vd, etc. As the braking operation amount Ba, the detection signal Sp (operation displacement) of the operation displacement sensor SP and the detection signal Pm (master pressure) of the master pressure sensor PM are acquired. To control the pressure regulating valve UB and the electric motor MB, the regulated pressure Pp (detection value of the regulated pressure sensor PP) and the rotation angle Kb (detection value of the rotation angle sensor KB) are acquired. The controller EB also acquires the required deceleration Gs. Furthermore, to identify an abnormality in the main power supply BT, the controller EB acquires the suitability flag FB (control flag indicating the suitability of the main power supply BT) and the power supply voltage Vd (detection value of the power supply voltage sensor VD).

[0081] The controller EB is connected to a communication bus BS so that signals (detected values, calculated values, control flags, etc.) can be shared with other controllers. For example, the required deceleration Gs is calculated by a driving assistance device and transmitted to the controller EB via the communication bus BS. Alternatively, the required deceleration Gs is commanded by an external operation device different from the brake operating member BP. The suitability flag FB is transmitted from the power supply monitoring device to the controller EB via the communication bus BS.

[0082] An algorithm for pressure regulation control is programmed in the controller EB (particularly the microprocessor MP). The pressure regulation control according to the second embodiment is also a control for adjusting the wheel pressure Pw. Specifically, this is indicated by [ ] in FIG. 2. In the second embodiment, too, in the first state, dynamic pressurization is performed in steps S140 and S150. On the other hand, in the second state, static pressurization is performed in steps S160 and S170. The methods for dynamic and static pressurization are the same as those in the first embodiment, and therefore will not be described further.

[0083] Furthermore, in the second embodiment, when antilock brake control, anti-skid control, etc. are performed, the wheel pressure Pw in each wheel cylinder CW is individually adjusted by the normally open inlet valve VI and the normally closed outlet valve VO. To reduce the wheel pressure Pw, the inlet valve VI is closed and the outlet valve VO is opened. The inflow of brake fluid BF into the wheel cylinder CW is blocked, and the brake fluid BF in the wheel cylinder CW flows out to the pressure regulating reservoir RB, thereby reducing the wheel pressure Pw. To increase the wheel pressure Pw (up to the regulated pressure Pp), the inlet valve VI is opened and the outlet valve VO is closed. The outflow of brake fluid BF to the pressure regulating reservoir RB is blocked, and the regulated pressure Pp from the pressure regulating valve UB is supplied to the wheel cylinder CW, thereby increasing the wheel pressure Pw. To maintain the wheel pressure Pw, both the inlet valve VI and the outlet valve VO are closed. Since the hydraulic pressure chamber Rw of the wheel cylinder CW is fluidly sealed, the wheel pressure Pw is maintained constant.

[0084] In the second embodiment, similarly to the above, dynamic pressurization is performed when driven by the main power supply BT (first state), and static pressurization is performed when driven by the auxiliary power supply BU (second state). In static pressurization, the wheel pressure Pw is pressurized by transferring the entire amount of brake fluid BF from the fluid pump QB to the wheel pressure Pw, thereby reducing the power consumption of the electric motor MB. In addition, a check valve GC is provided in the return path HL (part of the communication path HS and the return path HT), so the wheel chamber Rw, which serves as a fluid chamber, is fluidically locked (sealed) by the pressure regulating valve UB and the check valve GC. Therefore, the wheel pressure Pw can be maintained even when the power supply to the electric motor MB is completely stopped. Therefore, in the brake control device SC, the power consumption of the auxiliary power supply BU is suppressed, similarly to the above, and the capacity of the auxiliary power supply BU is reduced. As a result, the entire device is made more compact.

[0085] <Other embodiments> Other embodiments will be described below, which also achieve the same effects as those described above (power saving, size reduction, etc. of the auxiliary power supply BU).

[0086] In the first embodiment described above, a single-type master cylinder CM is used, and the servo pressure Pu is transmitted to the front wheel chamber Rwf via the master cylinder CM / master piston NM, and directly to the rear wheel chamber Rwr. Alternatively, a tandem-type master cylinder CM may be used, and the servo pressure Pu may be transmitted to the front wheels and the rear wheel chambers Rwf and Rwr via the master cylinder CM / master piston NM. In this configuration, a diagonal type (also called an "X type") may be used as the two-system braking system. Note that in the second embodiment, either a front-rear type or a diagonal type may be used as the braking system.

[0087] In the first embodiment described above, the pressure-receiving area rm (master area) of the master chamber Rm and the pressure-receiving area ru (servo area) of the servo chamber Ru are set equal. Even if the master area rm and the servo area ru are different, the conversion between the master pressure Pm and the servo pressure Pu can be calculated based on the ratio of the servo area ru to the master area rm. Therefore, the master area rm and the servo area ru do not need to be equal.

[0088] In the second embodiment described above, the second pressurizing unit CB is provided with an adjustment pressure sensor PP to detect the adjustment pressure Pp. However, the adjustment pressure sensor PP may be omitted. This is because the adjustment pressure Pp (i.e., the hydraulic pressure difference between the master pressure Pm and the adjustment pressure Pp) is determined by the current Ib supplied to the second pressure regulating valve UB.

[0089] <Summary of the embodiment> An embodiment of the brake control device SC is summarized below. The brake control device SC includes pressurizing units CA and CB that increase the wheel pressure Pw in the wheel cylinders CW of the vehicle, control units EA and EB that drive the pressurizing units CA and CB, a main power supply BT that supplies power to the control units EA and EB, and an auxiliary power supply BU that supplies power to the control units EA and EB in place of the main power supply BT when the main power supply BT is abnormal. Furthermore, the pressurizing units CA and CB of the brake control device SC include fluid pumps QA and QB driven by electric motors MA and MB, return paths HN and HL that connect discharge ports Qo and Qp of the fluid pumps QA and QB to suction ports Qi and Qj of the fluid pumps QA and QB, pressure adjustment valves UA and UB provided in the return paths HN and HL, and hydraulic pressure chambers Ru and Rw connected to the return paths HN and HL between the discharge ports Qo and Qp and the pressure adjustment valves UA and UB. In the braking control device SC, the control units EA and EB increase the control pressures Pu and Pw in the hydraulic chambers Ru and Rw, thereby increasing the wheel pressure Pw. Here, the "hydraulic pressure chamber" corresponds to the servo chamber Ru in the first embodiment and the wheel chamber Rw in the first and second embodiments. Also, the "control pressure" corresponds to the servo pressure Pu in the first embodiment and the wheel pressure Pw in the first and second embodiments.

[0090] In the brake control device SC, in the first state where power is supplied from the main power source BT, the electric motors MA and MB are driven, generating circulating flows KN and KL of brake fluid BF in the return paths HK and HL. The circulating flows KN and KL are then throttled by the pressure regulating valves UA and UB (i.e., the flow paths of the return paths HK and HL are narrowed), thereby increasing the control pressures Pu and Pw. That is, in the first state, the control pressures Pu and Pw are increased by the dynamic pressure of the brake fluid BF. In terms of the fluid volume balance of the brake fluid BF, most of the amount of brake fluid BF discharged by the fluid pumps QA and QB passes through the pressure regulating valves UA and UB, but some of it moves to the hydraulic chambers Ru and Rw, thereby increasing the control pressures Pu and Pw. Furthermore, when the control pressures Pu and Pw are maintained constant, the entire amount of brake fluid BF discharged by the fluid pumps QA and QB is moved through the pressure regulating valves UA and UB and circulated as circulation flows KN and KL. In either case, in the first state, during braking, the fluid pumps QA and QB (i.e., the electric motors MA and MB) continue to rotate.

[0091] In the brake control device SC, in the second state where power is supplied from the auxiliary power source BU, the pressure regulating valves UA and UB are closed. The electric motors MA and MB are driven, and brake fluid BF is transferred from the fluid pumps QA and QB to the hydraulic chambers Ru and Rw, thereby increasing the control pressures Pu and Pw. In other words, in the second state, the control pressures Pu and Pw are increased by the static pressure of the brake fluid BF. In terms of the fluid volume balance of the brake fluid BF, the entire amount of brake fluid BF discharged by the fluid pumps QA and QB is transferred to the hydraulic chambers Ru and Rw, thereby increasing the control pressures Pu and Pw. Therefore, when the control pressures Pu and Pw are maintained constant, the rotation of the fluid pumps QA and QB (i.e., the electric motors MA and MB) is stopped. When it is necessary to decrease the control pressures Pu and Pw, the current supplied to the pressure regulating valves UA and UB is reduced, and the pressure regulating valves UA and UB are slightly opened.

[0092] The brake control device SC switches the method of applying control pressures Pu and Pw (ultimately, wheel pressure Pw) depending on whether it is powered by the main power source BT or the auxiliary power source BU. Specifically, when it is powered by the main power source BT (first state), dynamic application, which has excellent pressure regulation accuracy, is used. In dynamic application, the circulating flows KN and KL of brake fluid BF discharged from the fluid pumps QA and QB are throttled by pressure regulation valves (linear solenoid valves) UA and UB, thereby increasing the wheel pressure Pw. However, dynamic application requires that the fluid pumps QA and QB continue to operate. In order to reduce power consumption, the brake control device SC switches from dynamic application to static application when it is powered by the auxiliary power source BU (second state). In static application, the wheel pressure Pw is increased by moving brake fluid BF from the fluid pumps QA and QB to the hydraulic chambers Ru and Rw. Therefore, in the second state, the fluid pumps QA and QB (i.e., the electric motors MA and MB) are driven only when necessary. Static pressurization consumes less power than dynamic pressurization, allowing the auxiliary power supply BU to be made smaller. In other words, the braking control device SC appropriately selects the pressurization method in response to switching of the power supply source, thereby ensuring pressure regulation accuracy and reducing power consumption at the same time.

[0093] Furthermore, the brake control device SC is provided with check valves GC in the return paths HK and HL. The check valves GC allow the flow of brake fluid BF from the pressure regulating valves UA and UB toward the intake ports Qi and Qj, but prevent the flow of brake fluid BF from the pressure regulating valves UA and UB toward the discharge ports Qo and Qp. In other words, the generation of circulating flows KN and KL is permitted, but their reverse flow is prevented. In the second state, the control units EA and EB stop the rotation of the electric motors MA and MB and stop the supply of power to the electric motors MA and MB when the control pressures Pu and Pw reach the target pressures Pt. Here, the target pressures Pt are calculated according to the vehicle braking demand Bs. In the first state, even if the control pressures Pu and Pw reach the target pressures Pt, the supply of power to the electric motors MA and MB continues so that the electric motors MA and MB continue to rotate.

[0094] In the brake control device SC, in the second state, the hydraulic chambers Ru and Rw are sealed (fluid lock) by the check valve GC and the pressure regulating valves UA and UB. Therefore, the control pressures Pu and Pw will not decrease unless the pressure regulating valves UA and UB are opened. Therefore, even if the power supply to the electric motors MA and MB is completely stopped, the control pressures Pu and Pw are maintained. This allows the brake control device SC to save power. Note that the power supply to the electric motors MA and MB is only required to compensate for leakage from the pressure regulating valves UA and UB, etc. [Explanation of symbols]

[0095] SC...brake control device, BT...main power supply, BU...auxiliary power supply, BP...brake operation member (brake pedal), CW...wheel cylinder, CA, CB...pressurizing section, EA, EB...controller, CM...master cylinder, NM...master piston, UA, UB...pressure regulating valve, MA, MB...electric motor, QA, QB...fluid pump, Qi, Qj...suction section of fluid pump, Qo, Qp...discharge section of fluid pump, HN, HL...return path, PM...pressure sensor, PP...adjusted pressure sensor, Pt...target pressure, Pu...servo pressure (an example of control pressure), Pm...master pressure, Pp...adjusted pressure, Pw...wheel pressure (an example of control pressure), Bs...required braking amount, Ba...braking operation amount, Gs...required deceleration, Ru...servo chamber (an example of a hydraulic chamber), Rw...wheel chamber (an example of a hydraulic chamber), Rm...master chamber.

Claims

1. a pressure applying unit that increases wheel pressure in a wheel cylinder of the vehicle; a control unit that drives the pressure unit; a main power supply that supplies power to the control unit; an auxiliary power supply that supplies power to the control unit in place of the main power supply when the main power supply is abnormal; In a braking control device for a vehicle, the pressurizing unit includes a fluid pump driven by an electric motor, a return flow path connecting a discharge portion of the fluid pump and a suction portion of the fluid pump, a pressure regulating valve provided in the return flow path, and a hydraulic chamber connected to the return flow path between the discharge portion and the pressure regulating valve, The control unit increasing the control pressure of the hydraulic chamber to increase the wheel pressure; In a first state in which power is supplied from the main power supply, the electric motor is driven to generate a circulating flow of brake fluid in the return path, and the circulating flow is throttled by the pressure regulating valve to increase the control pressure; In a second state in which power is supplied from the auxiliary power source, the vehicle braking control device closes the pressure regulating valve and drives the electric motor to move brake fluid to the hydraulic chamber, thereby increasing the control pressure.

2. 2. A vehicle braking control device according to claim 1, a check valve that blocks the flow of brake fluid from the pressure regulating valve toward the discharge port, A vehicle braking control device, wherein, in the second state, the control unit stops supplying power to the electric motor when the control pressure reaches a target pressure calculated in accordance with the braking demand of the vehicle.

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