WO2023171813A1

WO2023171813A1 - Braking control device for vehicles

Info

Publication number: WO2023171813A1
Application number: PCT/JP2023/009434
Authority: WO
Inventors: 啓介田中; 卓海老根; 俊哉渡邊
Original assignee: 株式会社アドヴィックス
Priority date: 2022-03-10
Filing date: 2023-03-10
Publication date: 2023-09-14
Also published as: JP2023131936A

Abstract

Provided is a braking control device comprising: an upper braking unit that outputs a supply pressure by restricting, with a pressure regulation valve, a circulation flow which has been discharged by a fluid pump driven by an electric motor; and a lower braking unit that is provided between the upper braking unit and a plurality of wheel cylinders and that outputs a wheel pressure by adjusting the supply pressure individually for each of the plurality of wheel cylinders. In the braking control device, the upper braking unit controls the pressure regulation valve on the basis of a requested pressure, which is requested for automatic pressurization control, when the lower braking unit carries out the automatic pressurization control under which the wheel pressure is automatically and individually increased. The requested pressure here is determined on the basis of the maximum value of necessary pressures respectively requested for the plurality of wheel cylinders.

Description

Vehicle braking control device

The present disclosure relates to a braking control device for a vehicle.

Patent Document 1 states that in order to improve the initial response of brake fluid pressure generation in control that stabilizes vehicle behavior by controlling the yaw moment of the vehicle (so-called sideslip prevention control), it is stated that ``the brake pedal is pressed by the driver.'' A first electric motor driven according to the amount of operation generates brake fluid pressure.A second electric motor generates brake fluid pressure to individually operate the wheel cylinders in a fluid path between the slave cylinder and the wheel cylinder. A yaw moment control device is disposed, and the slave cylinder is temporarily activated when the yaw moment control device starts operating. In the device of Patent Document 1, at the start of stability control control, a unit (referred to as an "upper braking unit") whose power source is a first electric motor (also referred to as an "upper electric motor") and a second electric motor (referred to as an "upper electric motor") are activated. The hydraulic pressure in the wheel cylinders (referred to as "wheel pressure") is increased by a unit powered by a unit (also referred to as "lower braking unit") powered by a "lower electric motor" (also referred to as "lower electric motor"), which improves the responsiveness of the wheel pressure increase. Ru. Incidentally, in a vehicle brake control device composed of two braking units, it is desired not only to improve wheel pressure increase responsiveness but also to reduce the size of the device.

JP2009-227023A

An object of the present invention is to provide a brake control device for a vehicle that is configured with two brake units and can be miniaturized.

The vehicle brake control device (SC) according to the present invention reduces the supply pressure (Pm ), which is arranged between the upper braking unit (SA) and a plurality of wheel cylinders (CW), and which outputs the supply pressure (Pm) to the plurality of wheel cylinders (CW). and a lower braking unit (SB) that individually adjusts and outputs wheel pressure (Pw) for each of the wheels.

In the vehicle braking control device (SC) according to the present invention, the upper braking unit (SA) performs automatic pressurization control in which the lower braking unit (SB) automatically and individually increases the wheel pressure (Pw). When executed, the pressure regulating valve (UA) is controlled based on the required pressure (Pe) required for the automatic pressurization control. Here, the required pressure (Pe) is determined based on the maximum value (MAX[Po]) of the required pressures (Po) required for each of the plurality of wheel cylinders (CW).

In the vehicle brake control device (SC) according to the present invention, the upper braking unit (SA) controls the electric motor (MA) based on the required flow rate (Qe) for achieving the required pressure (Pe). do. Here, the required flow rate (Qe) is determined based on the increasing gradient (kP) of the required pressure (Po) required for each of the plurality of wheel cylinders (CW).

According to the above configuration, the required pressure Pe, which is the basis for automatic pressurization control, is generated by the upper braking unit SA, and the individual adjustment of the wheel pressure Pw is performed by the lower braking unit SB. Since the small-sized lower braking unit SB can be adopted, the entire device can be downsized. Furthermore, in the upper braking unit SA, the required pressure Pe is generated at the necessary and minimum flow rate. This saves power in the upper braking unit SA.

1 is a schematic diagram for explaining the overall configuration of a vehicle JV equipped with a brake control device SC according to the present invention. It is a schematic diagram for explaining the example of composition of upper brake unit SA. It is a schematic diagram for explaining the example of composition of lower brake unit SB. It is a block diagram for explaining control of pressure regulating valve UA. It is a block diagram for explaining control of electric motor MA.

<Symbols of component parts, etc. and subscripts at the end of the symbol>
In the following description, components, arithmetic processing, signals, characteristics, and values having the same symbol, such as "CW", have the same function. The suffixes "f" and "r" attached to the end of the symbol for each wheel are comprehensive symbols indicating which system of the front and rear wheels the symbol relates to. For example, the wheel cylinders CW provided on each wheel are written as "front wheel cylinder CWf" and "rear wheel cylinder CWr." Furthermore, the subscripts "f" and "r" at the end of the symbol may be omitted. When the subscripts "f" and "r" are omitted, each symbol represents a generic term. For example, "CW" is a general term for wheel cylinders provided on the front and rear wheels of a vehicle.

In the fluid path from the master cylinder CM to the wheel cylinder CW, the side near the master cylinder CM (the side far from the wheel cylinder CW) is called the "upper part", and the side near the wheel cylinder CW (the side far from the master cylinder CM) ) is called the "lower part". In addition, in the circulation flows KN and KL of the brake fluid BF, the side closer to the discharge parts of the fluid pumps QA and QB (the side away from the suction parts) is called the "upstream side", and the side closer to the discharge parts of the fluid pumps QA and QB is called the "upstream side", The near side (the side away from the discharge part) is called the "downstream side."

The upper actuator YA of the upper braking unit SA (also referred to as the "upper fluid unit"), the lower actuator YB of the lower braking unit SB (also referred to as the "lower fluid unit"), and the wheel cylinder CW are connected to a fluid path (communication path HS). Connected at Further, in the upper and lower actuators YA and YB, various components (UA, etc.) are connected through fluid paths. Here, the "fluid path" is a path for moving the brake fluid BF, and includes piping, a flow path in an actuator, a hose, and the like. In the following description, the communication path HS, return path HK, return path HL, reservoir path HR, input path HN, servo path HV, pressure reduction path HG, etc. are fluid paths.

<Vehicle JV equipped with braking control device SC>
The overall configuration of a vehicle JV equipped with a brake control device SC according to the present invention will be described with reference to the schematic diagram of FIG.

The vehicle JV is equipped with front wheel and rear wheel braking devices SXf and SXr (=SX). The braking device SX includes a brake caliper CP, a friction member MS (for example, a brake pad), and a rotating member KT (for example, a brake disc). The brake caliper CP is provided with a wheel cylinder CW. The friction member MS is pressed against the rotating member KT fixed to each wheel WH by the hydraulic pressure Pw (referred to as "wheel pressure") in the wheel cylinder CW. As a result, a frictional braking force Fm is generated at the wheel WH. "Frictional braking force Fm" is a braking force generated by wheel pressure Pw.

The vehicle JV is equipped with a brake operation member BP and a steering operation member SH. The brake operation member BP (eg, brake pedal) is a member operated by the driver to decelerate the vehicle JV. The steering operation member SH (for example, a steering wheel) is a member operated by the driver to turn the vehicle JV.

The vehicle JV is equipped with various sensors (BA, etc.) listed below. Detection signals (Ba, etc.) from these sensors are input to controllers EA and EB and used for various controls.
- A brake operation amount sensor BA is provided that detects an operation amount Ba (referred to as "brake operation amount") of the brake operation member BP. For example, as the brake operation amount sensor BA, an operation displacement sensor SP that detects the operation displacement Sp of the brake operation member BP is provided. In addition, a simulator pressure sensor PZ that detects the hydraulic pressure Pz (referred to as "simulator pressure") of the stroke simulator SS is employed. In the brake control device SC, the brake operation amount Ba is a general term for signals representing the driver's braking intention, and the brake operation amount sensor BA is a general term for sensors that detect the brake operation amount Ba. The braking operation amount Ba is input to the upper controller EA.
- A wheel speed sensor VW is provided to detect the rotational speed Vw (wheel speed) of the wheel WH. Wheel speed Vw is input to lower controller EB. The lower controller EB calculates the vehicle speed Vx based on the wheel speed Vw. Further, the lower controller EB executes anti-lock brake control to prevent the wheels WH from locking and traction control to prevent the driving wheels WH from spinning based on the wheel speed Vw and the vehicle body speed Vx.
- A steering operation amount sensor SK is provided that detects an operation amount Sk (a steering operation amount, for example, a steering angle) of the steering operation member SH. The vehicle JV (particularly the vehicle body) is provided with a yaw rate sensor YR that detects the yaw rate Yr, a longitudinal acceleration sensor GX that detects the longitudinal acceleration Gx, and a lateral acceleration sensor GY that detects the lateral acceleration Gy. These sensor signals are input to the lower controller EB. The lower controller EB executes electronic stability control (ESC) that suppresses oversteer and understeer and stabilizes the yawing behavior of the vehicle JV.

The vehicle JV is equipped with a brake control device SC. The brake control device SC employs a front and rear type (also referred to as "Type II") as two brake systems. The actual wheel pressure Pw is adjusted by the brake control device SC.

The brake control device SC is composed of two brake units SA and SB. The upper braking unit SA includes an upper actuator YA (upper fluid unit) and an upper controller EA (upper control unit). Upper actuator YA is controlled by upper controller EA. A lower brake unit SB is arranged between the upper brake unit SA and the wheel cylinder CW. The lower braking unit SB includes a lower actuator YB (lower fluid unit) and a lower controller EB (lower control unit). Lower actuator YB is controlled by lower controller EB.

The upper braking unit SA (especially the upper controller EA) and the lower braking unit SB (especially the lower controller EB) are connected to the communication bus BS. The "communication bus BS" has a network structure in which a plurality of controllers (control units) hang from a communication line. A communication bus BS allows signal transmission between a plurality of controllers (EA, EB, etc.). That is, the plurality of controllers can transmit signals (detected values, calculated values, control flags, etc.) to the communication bus BS, and can receive signals from the communication bus BS.

<Upper braking unit SA>
An example of the configuration of the upper braking unit SA will be described with reference to the schematic diagram of FIG. 2. The upper brake unit SA generates a supply pressure Pm in response to operation of a brake operation member BP (brake pedal). The supply pressure Pm is finally supplied to the wheel cylinder CW via the communication path HS (fluid path) and the lower braking unit SB. The upper braking unit SA includes an upper actuator YA and an upper controller EA.

<<Upper actuator YA>>
The upper actuator YA includes an apply unit AP, a pressure adjustment unit CA, and an input unit NR.

[Apply unit AP]
In response to the operation of the brake operation member BP, the supply pressure Pm is output from the apply unit AP. The apply unit AP includes a tandem master cylinder CM, and primary and secondary master pistons NM and NS.

Primary and secondary master pistons NM and NS are inserted into the tandem master cylinder CM. The interior of the master cylinder CM is divided into four hydraulic chambers Rmf, Rmr, Ru, and Ro by two master pistons NM and NS. The front wheel and rear wheel master chambers Rmf and Rmr (=Rm) are defined by one side bottom of the master cylinder CM and the master pistons NM and NS. Further, the interior of the master cylinder CM is partitioned into a servo chamber Ru and a reaction force chamber Ro by the flange Tu of the master piston NM. The master chamber Rm and the servo chamber Ru are arranged to face each other with the collar Tu in between. These hydraulic chambers Rmf, Rmr, Ru, and Ro are sealed by a seal member SL. Note that the pressure receiving area rm of the master chamber Rm is equal to the pressure receiving area ru of the servo chamber Ru.

When not braking, the master pistons NM and NS are at the most retracted position (that is, 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 in communication with the master reservoir RV. Braking fluid BF is stored inside a master reservoir RV (also referred to as an "atmospheric pressure reservoir"). When the brake operation member BP is operated, the master pistons NM and NS are moved in the forward direction Ha (the direction in which the volume of the master chamber Rm decreases). Due to this movement, communication between the master chamber Rm and the master reservoir RV is cut off. Then, when the master pistons NM and NS are further moved in the forward direction Ha, the front wheel and rear wheel supply pressures Pmf and Pmr (=Pm) are increased from "0 (atmospheric pressure)". As a result, the brake fluid BF pressurized to the supply pressure Pm is output (forced) from the master chamber Rm of the master cylinder CM. Since the supply pressure Pm is the hydraulic pressure of the master chamber Rm, it is also called "master pressure."

[Pressure adjustment unit CA]
The pressure adjustment unit CA supplies the servo pressure Pu to the servo chamber Ru of the apply unit AP. The pressure regulating unit CA includes an upper electric motor MA, an upper fluid pump QA, and a pressure regulating valve UA.

An upper fluid pump QA (also simply referred to as a "fluid pump") is driven by an upper electric motor MA (also simply referred to as an "electric motor"). In the fluid pump QA, the suction section and the discharge section are connected by a reflux path HK (fluid path). Moreover, the suction part of the fluid pump QA is also connected to the master reservoir RV via the reservoir path HR. A check valve is provided at the discharge portion of the fluid pump QA.

A normally open pressure regulating valve UA is provided in the reflux path HK. The pressure regulating valve UA is a linear electromagnetic valve whose opening amount is continuously controlled based on the energization state (for example, the supply current Ia). The pressure regulating valve UA is also called a "differential pressure valve" because it regulates the hydraulic pressure difference (differential pressure) between its upstream side and its downstream side.

When the electric motor MA is driven and the brake fluid BF is discharged from the fluid pump QA, a circulation flow KN (indicated by a broken line arrow) of the brake fluid BF is generated in the reflux path HK. When the pressure regulating valve UA is fully open (the pressure regulating valve UA is of a normally open type and is not energized), the fluid pressure Pu between the discharge part of the fluid pump QA and the pressure regulating valve UA is lowered in the reflux path HK. (referred to as "servo pressure") is "0 (atmospheric pressure)". When the amount of current Ia (supplied current) to the pressure regulating valve UA is increased, the circulating flow KN (the flow of the brake fluid BF circulating in the recirculation path HK) is throttled by the pressure regulating valve UA. In other words, the pressure regulating valve UA narrows the flow path of the return flow path HK, and the orifice effect of the pressure regulating valve UA is exerted. As a result, the hydraulic pressure Pu 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) between the upstream hydraulic pressure Pu (servo pressure) and the downstream hydraulic pressure (atmospheric pressure) is generated with respect to the pressure regulating valve UA. The differential pressure is regulated by the current Ia supplied to the pressure regulating valve UA.

The reflux passage HK is located between the discharge part of the fluid pump QA (specifically, the downstream part of the check valve) and the pressure regulating valve UA, and is connected to the servo chamber Ru via the servo passage HV (fluid passage). connected to. Therefore, the servo pressure Pu is introduced (supplied) into the servo chamber Ru. As the servo pressure Pu increases, the master pistons NM and NS are pressed in the forward direction Ha, and the hydraulic pressures Pmf and Pmr (front and rear wheel supply pressures) in the front and rear wheel master chambers Rmf and Rmr are increased.

Front wheel and rear wheel communication paths HSf and HSr (=HS) are connected to the front wheel and rear wheel master chambers Rmf and Rmr (=Rm). The front wheel and rear wheel communication paths HSf and HSr are connected to the front and rear wheel cylinders CWf and CWr (=CW) via the lower braking unit SB (particularly the lower actuator YB). Therefore, the front wheel and rear wheel supply pressures Pmf and Pmr are supplied from the upper braking unit SA to the front wheel and rear wheel cylinders CWf and CWr. Here, the front wheel supply pressure Pmf and the rear wheel supply pressure Pmr are equal (ie, "Pmf=Pmr").

[Input unit NR]
Although the brake operation member BP is operated by the input unit NR so as to realize regeneration cooperative control, a state is created in which no wheel pressure Pw is generated. "Regenerative cooperative control" is a system that regenerates friction braking force Fm (braking force due to wheel pressure Pw) and regeneration so that the kinetic energy possessed by the vehicle JV can be efficiently recovered into electric energy by a motor/generator (not shown) during braking. This is to cooperate with the braking force Fg (braking force by the motor/generator). The input unit NR includes an input cylinder CN, an input piston NN, an introduction valve VA, a release valve VB, a stroke simulator SS, and a simulator hydraulic sensor PZ.

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 the brake operation member BP (brake pedal) via a clevis (U-shaped link) so as to be interlocked with the brake operation member BP. The end face of the input piston NN and the end face of the primary master piston NM have a gap Ks (also referred to as "separation displacement"). Regeneration cooperative control is realized by adjusting the separation distance Ks by the servo pressure Pu.

The input chamber Rn of the input unit NR is connected to the reaction force chamber Ro of the apply unit AP via an input path HN (fluid path). The input path HN is provided with a normally closed type introduction valve VA. The input path HN is connected to the master reservoir RV via the reservoir path HR between the introduction valve VA and the reaction force chamber Ro. A normally open open valve VB is provided in the reservoir path HR. The introduction valve VA and the release valve VB are on-off type solenoid valves. A stroke simulator SS (also simply referred to as a "simulator") is connected to an input path HN between the introduction valve VA and the reaction force chamber Ro.

When power is not supplied to the introduction valve VA and the release valve VB, the introduction valve VA is closed and the release valve VB is opened. By closing the introduction valve VA, the input chamber Rn is sealed and fluid-locked. Thereby, the master pistons NM and NS are displaced integrally with the brake operation member BP. Further, by opening the release valve VB, the simulator SS is communicated with the master reservoir RV. 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. Thereby, the master pistons NM and NS can be displaced separately from the brake operation member BP. At this time, since the input chamber Rn is connected to the stroke simulator SS, the operating force Fp of the brake operating member BP is generated by the simulator SS. A simulator pressure sensor PZ is provided in the input path HN between the introduction valve VA and the reaction force chamber Ro so as to detect the hydraulic pressure Pz (simulator pressure) in the simulator SS. In addition, since the simulator pressure Pz is also the internal pressure of the input chamber Rn, it is also a state quantity representing the operating force Fp of the brake operating member BP.

The state in which the master pistons NM, NS and the brake operation member BP are displaced separately (when the electromagnetic valves VA, VB are energized) is called the "first mode (or by-wire mode)". In the first mode, the brake control device SC functions as a brake-by-wire type device (that is, a device that can generate frictional braking force Fm independently in response to the driver's braking operation). Therefore, in the first mode, the wheel pressure Pw is generated independently of the operation of the brake operation member BP. On the other hand, a state in which the master pistons NM, NS and the brake operation member BP are displaced together (when the electromagnetic valves VA, VB are not energized) is called a "second mode (or manual mode)." In the second mode, the wheel pressure Pw is linked to the driver's braking operation. In the input unit NR, one of the first mode (by-wire mode) and the second mode (manual mode) is selected depending on whether or not power is supplied to the introduction valve VA and the release valve VB.

≪Upper controller EA≫
Upper actuator YA is controlled by 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 (detected values, calculated values, control flags, etc.) can be shared with other controllers (EB, etc.).

A braking operation amount Ba is input to the upper controller EA. The brake operation amount Ba is a general term for state quantities representing the operation amount of the brake operation member BP. As the braking operation amount Ba, a detection signal Sp (operation displacement) of the operation displacement sensor SP and a detection signal Pz (simulator pressure) of the simulator pressure sensor PZ are directly input from the braking operation amount sensor BA to the upper controller EA. Further, the supply pressure Pm and the like are input to the upper controller EA via the communication bus BS. "Supply pressure Pm" is the output pressure of the upper actuator YA. The supply pressure Pm is detected by a supply pressure sensor PM provided in the lower actuator YB, and is transmitted from the lower controller EB.

A pressure regulation control algorithm is programmed into the upper controller EA (particularly the microprocessor MP). "Pressure adjustment control" is control for adjusting the supply pressure Pm (ultimately the wheel pressure Pw). The pressure regulation control is executed based on the braking operation amount Ba (operation displacement Sp, simulator pressure Pz), supply pressure Pm, and the like. Specifically, based on the pressure regulation control algorithm, the drive circuit DR drives the electric motor MA that constitutes the upper actuator YA and various electromagnetic valves (UA, etc.). The drive circuit DR includes an H-bridge circuit using switching elements (eg, MOS-FET) to drive the electric motor MA. The drive circuit DR is also equipped with switching elements to drive various electromagnetic valves (UA, etc.). In addition, the drive circuit DR includes a motor current sensor (not shown) that detects a current Im supplied to the electric motor MA (referred to as "motor current"), and a motor current sensor (not shown) that detects a current Ia supplied to the pressure regulating valve UA (referred to as "pressure regulating valve current"). A pressure regulating valve current sensor (not shown) is included to detect the current. Note that electric motor MA is provided with a rotation angle sensor (not shown) that detects rotation angle Ka (referred to as "motor rotation angle") of its rotor. Then, the motor rotation speed Na is calculated based on the motor rotation angle Ka.

In the upper controller EA, a target current It (target value) corresponding to the pressure regulating valve current Ia (actual value) is calculated based on the braking operation amount Ba. The pressure regulating valve UA is controlled so that the pressure regulating valve current Ia approaches and matches the target current It. Further, in the upper controller EA, a target rotational speed Nt (target value) corresponding to the motor rotational speed Na (actual value) is calculated based on the braking operation amount Ba. In controlling the electric motor MA, the motor current Im is controlled so that the actual rotational speed Na approaches and matches the target rotational speed Nt. Specifically, if "Nt>Na", the motor current Im is increased so that the motor rotation speed Na increases, and if "Nt<Na", the motor current Im is increased so that the motor rotation speed Na is decreased. Im is decreased. Based on these control algorithms, a drive signal Ma for controlling the electric motor MA and drive signals Ua, Va, Vb for controlling the various electromagnetic valves UA, VA, VB are calculated. Then, the switching elements of the drive circuit DR are driven according to the drive signal (Ma, etc.), and the electric motor MA and the solenoid valves UA, VA, and VB are controlled.

<Lower braking unit SB>
An example of the configuration of the lower brake unit SB of the brake control device SC will be described with reference to the schematic diagram of FIG. 3. The lower braking unit SB is a general-purpose unit (device) for performing anti-lock brake control, traction control, skid prevention control, etc. In the traction control and the skid prevention control, the wheel pressure Pw of each wheel cylinder CW is automatically increased independently of the operation of the brake operation member BP. Furthermore, in these controls, each wheel pressure Pw is adjusted individually. Therefore, controls in which the wheel pressure Pw is automatically and individually increased, such as traction control and skid prevention control, are collectively referred to as "automatic pressurization control."

The lower brake unit SB is supplied with front wheel and rear wheel supply pressures Pmf and Pmr (=Pm) from the upper brake unit SA. Then, the lower braking unit SB adjusts (increases or decreases) the front wheel and rear wheel supply pressures Pmf and Pmr, and finally the hydraulic pressures Pwf and Pwr of the front and rear wheel cylinders CWf and CWr (front and rear wheel output as wheel pressure). The lower braking unit SB includes a lower actuator YB and a lower controller EB.

≪Lower actuator YB≫
The lower actuator YB is provided between the upper actuator YA and the wheel cylinder CW in the communication path HS. The lower actuator YB includes a supply pressure sensor PM, a control valve UB, a lower fluid pump QB, a lower electric motor MB, a pressure regulating reservoir RB, an inlet valve VI, and an outlet valve VO.

Front wheel and rear wheel control valves UBf and UBr (=UB) are provided in the front and rear wheel communication paths HSf and HSr (=HS). The control valve UB is a normally open linear solenoid valve (differential pressure valve) like the pressure regulating valve UA. The control valve UB allows the wheel pressure Pw to be increased individually for the front and rear wheel systems from the supply pressure Pm.

The front wheel and rear wheel supply pressure sensors PMf and PMr (=PM) detect the actual hydraulic pressures Pmf and Pmr (front and rear wheel supply pressures) supplied from the upper actuator YA (especially the front and rear wheel master chambers Rmf and Rmr). ) is provided to detect. The supply pressure sensor PM is also called a "master pressure sensor" and is built into the lower actuator YB. Signals of front wheel and rear wheel supply pressures Pmf and Pmr (=Pm) are directly input to the lower controller EB and output to the communication bus BS. Note that since the front wheel supply pressure Pmf and the rear wheel supply pressure Pmr are substantially the same, either one of the front wheel and rear wheel supply pressure sensors PMf and PMr may be omitted. For example, in a configuration where the rear wheel supply pressure sensor PMr is omitted, only the front wheel supply pressure Pmf is detected by the front wheel supply pressure sensor PMf.

The front wheel and rear wheel return paths HLf and HLr (=HL) connect the upper part of the front wheel and rear wheel control valves UBf and UBr (the part of the communication path HS on the side closer to the upper actuator YA), the front wheel and rear wheel control valves UBf, The lower part of the UBr (the part of the communication path HS on the side closer to the wheel cylinder CW) is connected. The front wheel and rear wheel return paths HLf and HLr are provided with front wheel and rear wheel lower fluid pumps QBf and QBr (=QB), and front and rear wheel pressure regulating reservoirs RBf and RBr (=RB). The lower fluid pump QB is driven by the lower electric motor MB.

When the lower electric motor MB (also simply referred to as the "electric motor") is driven, the brake fluid BF is sucked in from the upper part of the control valve UB by the lower fluid pump QB (also simply referred to as the "fluid pump"). It is discharged to the lower part of the control valve UB. As a result, the communication path HS and the return path HL have a circulating flow KL of the brake fluid BF (i.e., a circulating flow KLf of the brake fluid BF including the fluid pump QB, the control valve UB, and the pressure regulating reservoir RB). , KLr (indicated by the dashed arrow) occurs. When the flow path of the communication passage HS is narrowed by the control valve UB and the circulation flow KL of the brake fluid BF is throttled, the hydraulic pressure Pq (referred to as "adjustment pressure") at the lower part of the control valve UB is reduced due to the orifice effect at that time. is increased from the hydraulic pressure Pm (supply pressure) above the control valve UB. In other words, in the circulating flow KL, the hydraulic pressure difference (differential pressure) between the downstream hydraulic pressure Pm (supply pressure) and the upstream hydraulic pressure Pq (adjustment pressure) with respect to the control valve UB is adjusted by. Note that in terms of the magnitude relationship between the supply pressure Pm and the adjustment pressure Pq, the adjustment pressure Pq is greater than or equal to the supply pressure Pm (that is, "Pq≧Pm"). As explained above, the mechanism for generating the adjustment pressure Pq in the lower actuator YB is the same as the mechanism for generating the servo pressure Pu in the upper actuator YA.

Inside the lower actuator YB, the front wheel and rear wheel connecting paths HSf and HSr are branched into two, respectively, and connected to the front wheel 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 path HS (that is, on the side closer to the wheel cylinder CW with respect to the branched portion of the communication path HS). The communication path HS is connected to the pressure regulating reservoir RB via the pressure reduction path HG (fluid path) at the lower part of the inlet valve VI (the portion of the communication path HS on the side closer to the wheel cylinder CW). An outlet valve VO is arranged in the pressure reduction path HG. On-off type solenoid valves are employed as the inlet valve VI and outlet valve VO. By means of the inlet valve VI and the outlet valve VO, the wheel pressure Pw can be individually reduced from the regulation pressure Pq (or supply pressure Pm) at each wheel. As a result, anti-lock brake control, traction control, sideslip prevention control, etc. are executed.

If power is not supplied to the inlet valve VI and outlet valve VO and their operation is stopped, the inlet valve VI is opened and the outlet valve VO is closed. In this state, wheel pressure Pw is equal to adjustment pressure Pq. By driving the inlet valve VI and the outlet valve VO, the wheel pressure Pw is adjusted independently for each wheel cylinder CW. In order to reduce the wheel pressure Pw, the inlet valve VI is closed and the outlet valve VO is opened. The brake fluid BF is prevented from flowing into the wheel cylinder CW, and the brake fluid BF in the wheel cylinder CW flows out to the pressure regulating reservoir RB, so that the wheel pressure Pw is reduced. In order to increase the wheel pressure Pw, the inlet valve VI is opened and the outlet valve VO is closed. The brake fluid BF is prevented from flowing into the pressure regulating reservoir RB, and the regulating pressure Pq from the pressure regulating valve UB is supplied to the wheel cylinder CW, so that the wheel pressure Pw is increased. Here, the upper limit of increase in wheel pressure Pw is adjustment pressure Pq. In order to maintain the wheel pressure Pw, both the inlet valve VI and the outlet valve VO are closed. Since the wheel cylinder CW is fluidly sealed, the wheel pressure Pw is maintained constant.

≪Lower controller EB≫
The lower actuator YB is controlled by the lower controller EB. Like the upper controller EA, the lower controller EB includes a microprocessor MP and a drive circuit DR. The lower controller EB is connected to the communication bus BS, so that the upper controller EA and the lower controller EB can share signals via the communication bus BS.

Wheel speed Vw, steering operation amount Sk, yaw rate Yr, longitudinal acceleration Gx, and lateral acceleration Gy are input to the lower controller EB (particularly the microprocessor MP). The lower controller EB calculates the vehicle speed Vx based on the wheel speed Vw. Automatic pressurization control is executed in the lower controller EB. Specifically, the automatic pressurization control includes at least one of traction control, which suppresses the spinning of the drive wheels, and electronic stability control (ESC), which suppresses understeer and oversteer to improve the directional stability of the vehicle. executed.

The lower electric motor MB and various electromagnetic valves (UB, etc.) that constitute the lower actuator YB are driven by the lower controller EB. The drive circuit DR of the lower controller EB includes an H-bridge circuit using switching elements (eg, MOS-FET) to drive the lower electric motor MB. Further, the drive circuit DR is equipped with switching elements to drive various electromagnetic valves (UB, etc.). Based on a control algorithm programmed in the microprocessor MP, a drive signal Ub for the control valve UB, a drive signal Vi for the inlet valve VI, a drive signal Vo for the outlet valve VO, and a drive signal Mb for the lower electric motor MB are calculated. The lower electric motor MB and the solenoid valves UB, VI, and VO are controlled by the drive circuit DR based on the drive signal (Ub, etc.).

<Control of pressure regulating valve UA>
An example of control processing of the pressure regulating valve UA will be described with reference to the block diagram of FIG. 4. The pressure regulating valve UA regulates the servo pressure Pu, and finally the supply pressure Pm (=Pw). The pressure regulating valve UA is controlled by a required pressure calculation block PO, a required pressure calculation block PE, a command pressure calculation block PS, a target pressure calculation block PT, a command current calculation block IS, a hydraulic pressure deviation calculation block PH, a compensation current calculation block IH, and a current feedback control block IF. For example, the processes of the required pressure calculation block PO and the required pressure calculation block PE are executed by the lower controller EB, and other processes (PS, PT, etc.) are executed by the upper controller EA.

In the required pressure calculation block PO, the required pressure Po corresponding to the wheel pressure Pw of each wheel cylinder CW is calculated based on the wheel speed Vw, steering operation amount Sk, yaw rate Yr, lateral acceleration Gy, etc. “Required pressure Po” is a target value for each wheel cylinder CW that is required to execute automatic pressurization control. Here, automatic pressurization control is a general term for traction control and skid prevention control, and increases each wheel pressure Pw automatically and individually.

In the required pressure calculation block PO, in traction control, based on the comparison result between the vehicle body speed Vx calculated from the wheel speed Vw and the wheel speed Vw of the driving wheel, the idle state of the driving wheel (for example, the wheel speed of the driving wheel) is determined. Acceleration slip, which is the difference between speed Vw and vehicle speed Vx, is calculated. Then, the required pressure Po is determined for each drive wheel so that the idle state of the drive wheels is suppressed. Therefore, if the vehicle JV is a two-wheel drive vehicle, two required pressures Po are calculated. Furthermore, if the vehicle JV is a four-wheel drive vehicle, four required pressures Po are calculated.

Further, in the required pressure calculation block PO, the degree of stability of the vehicle JV is calculated in the skid prevention control based on the vehicle body speed Vx, the steering operation amount Sk, the yaw rate Yr, and the lateral acceleration Gy. Specifically, the comparison result of the target behavior calculated from the vehicle body speed Vx and the steering operation amount Sk and the actual behavior calculated from the yaw rate Yr and the lateral acceleration Gy (for example, the difference between the target behavior and the actual behavior ), the steering characteristics (degree of understeer/oversteer) of the vehicle JV is calculated. Then, the required pressure Po corresponding to each wheel pressure Pw is determined so that understeer and oversteer are suppressed. That is, in the sideslip prevention control, four required pressures Po are calculated.

In the required pressure calculation block PE, the required pressure Pe is calculated based on the required pressure Po. "Required pressure Pe" is a target value required to execute automatic pressurization control. Specifically, among the plurality of required pressures Po, the maximum one is determined as the required pressure Pe (that is, "Pe=MAX(Po)"). Alternatively, the required pressure Pe may be determined by adding the predetermined pressure pe to the maximum value of the plurality of required pressures Po (ie, "Pe=MAX(Po)+pe"). Here, the "predetermined pressure pe" is a preset predetermined value (constant). In any case, the required pressure Pe is determined based on the maximum value of the required pressure Po. The required pressure Pe is transmitted from the lower controller EB to the communication bus BS and received by the upper controller EA.

In the command pressure calculation block PS, the command pressure Ps is calculated based on the braking operation amount Ba. "Instruction pressure Ps" is a target value corresponding to supply pressure Pm, and is an intermediate target value for calculating target pressure Pt, which is the final target value. The command pressure Ps is calculated to increase as the braking operation amount Ba increases according to a preset calculation map Zps.

In the target pressure calculation block PT, the target pressure Pt is calculated based on the command pressure Ps and the required pressure Pe. "Target pressure Pt" is the final target value corresponding to supply pressure Pm (resultingly, wheel pressure Pw). Specifically, the larger of the command pressure Ps and the required pressure Pe is determined as the target pressure Pt (ie, "Pt=MAX(Ps, Pe)"). Therefore, when "Ps>Pe" and the command pressure Ps is adopted as the target pressure Pt, the target pressure Pt is the target value corresponding to the wheel pressure Pw that should be achieved according to the braking operation amount Ba. It is. Further, when "Ps<Pe" and the required pressure Pe is adopted as the target pressure Pt, the target pressure Pt is a target value corresponding to the wheel pressure Pw required for automatic pressurization control.

In the instruction current calculation block IS, the instruction current Is is calculated based on the target pressure Pt and a preset calculation map Zis. The "instruction current Is" is a target value corresponding to the supply current Ia of the pressure regulating valve UA, which is necessary for achieving the target pressure Pt. According to the calculation map Zis, the instruction current Is is determined to increase as the target pressure Pt increases. The command current calculation block IS corresponds to feedforward control based on the target pressure Pt.

In the hydraulic pressure deviation calculation block PH, a deviation hP (hydraulic pressure deviation) between the target pressure Pt and the supply pressure Pm is calculated. Specifically, the supply pressure Pm is subtracted from the target pressure Pt to determine the hydraulic pressure deviation hP (ie, "hP=Pt-Pm").

In the compensation current calculation block IH, the compensation current Ih is calculated based on the hydraulic pressure deviation hP and a preset calculation map Zih. Although the instruction current Is is calculated in accordance with the target pressure Pt, an error may occur between the target pressure Pt and the supply pressure Pm. "Compensation current Ih" is for compensating for (reducing) this error. The compensation current Ih is determined to increase according to the calculation map Zih as the hydraulic pressure deviation hP increases. Specifically, when the target pressure Pt is larger than the supply pressure Pm and the hydraulic pressure deviation hP has a positive sign, a positive compensation current Ih is determined so that the instruction current Is is increased. On the other hand, when the target pressure Pt is smaller than the supply pressure Pm and the hydraulic pressure deviation hP has a negative sign, a negative compensation current Ih is determined so that the instruction current Is is decreased. Here, a dead zone is provided in the calculation map Zih. The compensation current calculation block IH corresponds to feedback control based on the supply pressure Pm.

A compensation current Ih is added to the instruction current Is to calculate a target current It (ie, "It=Is+Ih"). "Target current It" is the final target value of the current supplied to the pressure regulating valve UA. That is, the target current It is determined as the sum of the instruction current Is, which is a feedforward term, and the compensation current Ih, which is a feedback term. Therefore, drive control of the pressure regulating valve UA is configured by feedforward control (processing of the instruction current calculation block IS) and feedback control (processing of the compensation current calculation block IH) in the hydraulic pressure.

In the current feedback control block IF, the drive signal Ua is calculated based on the target current It (target value) and the supply current Ia (actual value) so that the supply current Ia approaches and matches the target current It. Ru. Here, the supply current Ia is detected by a pressure regulating valve current sensor IA provided in the drive circuit DR. In the current feedback control block IF, if "It>Ia", the drive signal Ua is determined so that the supply current Ia increases. On the other hand, if "It<Ia", the drive signal Ua is determined so that the supply current Ia decreases. That is, in the current feedback control block IF, feedback control regarding current is executed. Therefore, the drive control of the pressure regulating valve UA includes feedback control related to current in addition to feedback control related to hydraulic pressure.

The brake control device SC is equipped with two brake units SA and SB. One is the upper brake unit SA, which outputs the supply pressure Pm according to the operation amount Ba of the brake operation member BP. The other one is the lower braking unit SB, which individually adjusts the supply pressure Pm to each of the plurality of wheel cylinders CW and outputs the wheel pressure Pw. The lower braking unit SB is provided between the upper braking unit SA and the plurality of wheel cylinders CW.

The lower braking unit SB includes a lower electric motor MB, a lower fluid pump QB, a plurality of electromagnetic valves (VI, VO, etc.), and a lower controller EB. Automatic pressurization control is executed by controlling the electric motor MB and a plurality of electromagnetic valves by the lower controller EB. The automatic pressurization control is a control that automatically and individually increases the wheel pressure Pw, and includes, for example, traction control, skid prevention control, and the like. In the lower controller EB, when performing automatic pressurization control, a required pressure Pe for automatic pressurization control is calculated. The required pressure Pe is a target value corresponding to the maximum wheel pressure Pw required to perform automatic pressurization control. For example, in the automatic pressurization control, the lower controller EB calculates the required pressure Po for each of the plurality of wheel cylinders CW, and the maximum value thereof is determined as the required pressure Pe. Alternatively, the required pressure Pe may be determined by adding a predetermined pressure pe (a preset constant) to this maximum value. In any case, the required pressure Pe is calculated based on the maximum value of the required pressure Po.

The upper braking unit SA includes an upper electric motor MA, an upper fluid pump QA, a pressure regulating valve UA, and an upper controller EA. Upper controller EA controls electric motor MA and pressure regulating valve UA. Then, the circulating flow KN (also referred to as "upper circulating flow") discharged by the fluid pump QA driven by the electric motor MA is throttled by the pressure regulating valve UA, thereby adjusting the supply pressure Pm. When automatic pressurization control is executed in the lower brake unit SB, the upper controller EA controls the pressure regulating valve UA based on the required pressure Pe. That is, in the upper controller EA, the pressure regulating valve UA is driven so that the supply pressure Pm approaches and matches the required pressure Pe.

Specifically, when the required pressure Pe required to execute automatic pressurization control is larger than the command pressure Ps calculated from the braking operation amount Ba, the target current It is set based on the required pressure Pe (=Pt). The pressure regulating valve current Ia approaches and is controlled to match the target current It. As a typical example, when the brake operation member BP is not operated (that is, when the brake operation amount Ba is "0"), the pressure regulating valve UA is controlled based on the required pressure Pe. Note that the command pressure Ps is determined to increase as the braking operation amount Ba increases.

In the brake control device SC, the required pressure Pe necessary for automatic pressurization control is generated by the upper brake unit SA. Since the upper brake unit SA can also handle sudden operation of the brake operation member BP, its rated output is sufficiently satisfactory even in automatic pressurization control. Since the required pressure Pe necessary for the automatic pressurization control is supplied from the upper braking unit SA, the lower braking unit SB is not required to have a considerable level of responsiveness in the automatic pressurization control. Therefore, the lower braking unit SB (particularly the electric motor MB and the fluid pump QB) is downsized. Note that individual control of the automatic pressurization control (adjustment of each wheel Pw) is performed by the lower braking unit SB (particularly the inlet valve VI and the outlet valve VO). Furthermore, the reduction in wheel pressure Pw during automatic pressurization control is achieved by moving the brake fluid BF from the wheel cylinder CW to the pressure regulating reservoir RB, but since the volume of the pressure regulating reservoir RB is finite, , the electric motor MB is driven so that the brake fluid BF is returned to the upper part of the inlet valve VI (between the control valve UB and the inlet valve VI). Therefore, during execution of automatic pressurization control, a circulating flow KL (also referred to as a "lower circulating flow") is generated by the lower electric motor MB and the lower fluid pump QB.

When the required pressure Pe is realized by the upper braking unit SA (that is, when the supply pressure Pm reaches the required pressure Pe), in the lower braking unit SB, power is not supplied to the control valve UB, and its fully open state is maintained. maintained. On the other hand, if the supply pressure Pm from the upper braking unit SA is insufficient with respect to the required pressure Pe, power is supplied to the control valve UB and the lower circulation flow KL is throttled to compensate for this shortage (i.e. The hydraulic pressure "Pe-Pm (=hP)" is supplemented by the lower braking unit SB.

<Control of electric motor MA>
An example of control processing for upper electric motor MA will be described with reference to the block diagram in FIG. 5 . For example, electric motor MA may be driven at a predetermined rotation speed na. However, as explained below, when the electric motor MA is driven based on the flow rate of the brake fluid BF, power saving is achieved.

The electric motor MA is controlled by a required pressure gradient calculation block KP, a required flow rate calculation block QE, a liquid volume conversion block PR, a liquid volume deviation calculation block RH, a commanded flow rate calculation block QS, a compensation flow rate calculation block QH, and a target flow rate calculation block QT. , a target rotational speed calculation block NT, and a rotational speed feedback control block NF. For example, the processes of the required pressure gradient calculation block KP and the required flow rate calculation block QE are executed by the lower controller EB, and other processes (PR, RH, etc.) are executed by the upper controller EA.

In the required pressure gradient calculation block KP, an increasing gradient kP (also referred to as "target increasing gradient") is calculated based on the required pressure Po. Specifically, the required pressure Po in each wheel cylinder CW is differentiated with respect to time, and each increasing slope (the amount of increase in the required pressure Po per unit time) is determined as the increasing slope kP. Therefore, "increase gradient kP" is a target value corresponding to the actual increase gradient (increase amount per unit time) of wheel pressure Pw. Note that when the necessary pressure Po is maintained at a constant value or when the necessary pressure Po is decreased, the increasing gradient kP is determined to be "0".

In the required flow rate calculation block QE, the required flow rate Qe is calculated based on the increasing slope kP (target increasing slope) corresponding to each wheel cylinder CW. The "required flow rate Qe" is the flow rate of the brake fluid BF necessary to execute automatic pressurization control. Specifically, the required flow rate Qe is determined based on the sum ΣkP (total value) of the increasing gradient kP of each wheel cylinder CW. Specifically, the required flow rate calculation block QE adds each of the increasing gradients kP to calculate the total value ΣkP. Then, according to a preset calculation map Zqe, the required flow rate Qe is determined to increase as the total value ΣkP increases. The requested flow rate Qe is transmitted from the lower controller EB to the communication bus BS and received by the upper controller EA.

In the liquid volume conversion block PR, the target liquid volume Rt and the actual liquid volume Rj are calculated based on the target pressure Pt and the supply pressure Pm. In the liquid amount conversion block PR, the target pressure Pt is converted into a target liquid amount Rt, and the supply pressure Pm is converted into an actual liquid amount Rj, based on a preset calculation map Zpr. Here, the "target fluid amount Rt" is the fluid amount (volume of the brake fluid BF to be transferred to the wheel cylinder CW) necessary to achieve the target pressure Pt. Moreover, the "actual liquid amount Rj" is the amount of liquid that has already flowed into the wheel cylinder CW in order to generate the supply pressure Pm (resultingly, the wheel pressure Pw).

In the liquid volume deviation calculation block RH, a deviation hR (referred to as "liquid volume deviation") between the target liquid volume Rt and the actual liquid volume Rj is calculated. Specifically, the actual liquid amount Rj is subtracted from the target liquid amount Rt to determine the liquid amount deviation hR (ie, "hR=Rt-Rj"). “Liquid amount deviation hR” is a target value of the amount of liquid (volume) that should flow into the wheel cylinder CW in the future in order to achieve the target pressure Pt.

In the instructed flow rate calculation block QS, the instructed flow rate Qs is calculated based on the target liquid amount Rt. Specifically, the target liquid amount Rt is differentiated with respect to time, and the commanded flow rate Qs is determined (ie, "Qs=d(Rt)/dt"). The commanded flow rate calculation block QS corresponds to feedforward control in flow rate control.

A compensation flow rate calculation block QH calculates a compensation flow rate Qh based on the liquid volume deviation hR. Specifically, the liquid volume deviation hR is time-differentiated to determine the compensation flow rate Qh (ie, "Qh=d(hR)/dt"). The compensation flow rate calculation block QH corresponds to feedback control in flow rate control.

A target flow rate calculation block QT calculates a target flow rate Qt based on the required flow rate Qe, the instructed flow rate Qs, and the compensation flow rate Qh. "Target flow rate Qt" is a final target value in which the flow rate necessary for achieving the target pressure Pt and executing automatic pressurization control in the lower braking unit SB is estimated. Specifically, the required flow rate Qe, the instructed flow rate Qs, and the compensation flow rate Qh are added together to determine the target flow rate Qt (ie, "Qt=Qe+Qs+Qh"). Therefore, when automatic pressurization control is not executed in the lower braking unit SB, since "Qe=0", the target flow rate Qt is calculated as the sum of the commanded flow rate Qs and the compensation flow rate Qh. .

In the target rotation speed calculation block NT, the target rotation speed Nt is calculated based on the target flow rate Qt. "Target rotation speed Nt" is a target value corresponding to rotation speed Na (actual value) of electric motor MA. Specifically, the target rotation speed Nt is determined to increase as the target flow rate Qt increases, based on the discharge amount of the fluid pump QA (the volume of the brake fluid BF discharged per rotation). 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 required flow rate for the pressure regulating valve UA to regulate the servo pressure Pu, and is set in advance. Moreover, the "minimum rotation speed" is the minimum value of the rotation speed at which the electric motor MA can continue to rotate stably. Taking these things into consideration, a lower limit rotation speed nt (predetermined value set in advance) is provided for the target rotation speed Nt. Therefore, when the target rotational speed Nt calculated based on the target flow rate Qt is equal to or higher than the lower limit rotational speed nt, the restriction by the lower limit rotational speed nt is not performed, and the calculated target rotational speed Nt is used as is. On the other hand, when the target rotational speed Nt calculated based on the target flow rate Qt is less than the lower limit rotational speed nt, the target rotational speed Nt is determined to be the lower limit rotational speed nt (ie, "Nt=nt").

In the rotation speed feedback control block NF, based on the target rotation speed Nt (target value) and the motor rotation speed Na (actual value), the motor rotation speed Na approaches and matches the target rotation speed Nt. A drive signal Ma is calculated. Here, the motor rotation speed Na is calculated based on a detection value Ka (rotation angle) of a rotation angle sensor KA provided in the electric motor MA. Specifically, the motor rotation angle Ka is time differentiated to determine the motor rotation speed Na. In the rotation speed feedback control block NF, if "Nt>Na", the drive signal Ma is determined so that the actual rotation speed Na increases. On the other hand, if "Nt<Na", the drive signal Ma is determined so that the actual rotational speed Na decreases. That is, in the rotation speed feedback control block NF, feedback control related to the motor rotation speed is executed.

In the lower braking unit SB, a required liquid amount Qe required to execute automatic pressurization control is calculated. Specifically, the required flow rate Qe is the flow rate of the brake fluid BF necessary to achieve the required pressure Pe, and is the volume of the brake fluid BF per unit time to be transferred to the plurality of wheel cylinders CW. For example, in the lower braking unit SB, the necessary pressure Po required to execute automatic pressurization control is calculated for each wheel cylinder CW. In each of the plurality of wheel cylinders CW, an increasing gradient kP, which is the amount of change over time when the required pressure Po increases, is calculated. Then, the sum of the increasing gradients kP of each wheel cylinder CW (total value ΣkP) is determined as the required flow rate Qe.

In the upper braking unit SA, the electric motor MA is controlled based on the target rotation speed Nt calculated from the required flow rate Qe. Specifically, the current Im supplied to the electric motor MA is controlled so that the actual rotation speed Na of the electric motor MA approaches and matches the target rotation speed Nt. That is, since the target rotational speed Nt is calculated based on the required pressure Po in the lower braking unit SB, the required pressure Po is achieved in the upper braking unit SA with the minimum necessary flow rate. As a result, even in a configuration in which the required pressure Pe for automatic pressurization control is generated by the upper brake unit SA, the power consumption of the upper brake unit SA (particularly, the electric motor MA) is suppressed.

In the upper braking unit SA, in order to realize the required pressure Pe, the target rotation speed Nt is determined to be a predetermined rotation speed na (a preset constant), and the actual rotation speed Na of the electric motor MA is set to a predetermined rotation speed. It may be driven to approach and match na. However, the configuration in which the target rotational speed Nt is determined based on the required pressure Po has a greater power saving effect than the configuration in which "Nt=na".

As explained above, in the brake control device SC, the required pressure Pe, which is the basis for automatic pressurization control, is generated by the upper brake unit SA, and the individual adjustment of the wheel pressure Pw is performed by the lower brake unit SB. Thereby, a small lower brake unit SB can be adopted as the brake control device SC. As a result, the entire device can be made smaller.

Further, in the upper braking unit SA, the required pressure Pe is generated using the necessary and minimum flow rate. Thereby, in the brake control device SC, in addition to reducing the size of the lower brake unit SB, it is possible to reduce the power consumption of the upper brake unit SA. That is, in the brake control device SC, the overall configuration is optimized by the division of roles between the upper and lower brake units SA and SB.

<Other embodiments>
Other embodiments will be described below. Other embodiments also provide the same effects as described above (device miniaturization, power saving, etc.).

In the embodiment described above, the required pressure Pe was calculated by the lower braking unit SB and sent to the upper braking unit SA. Alternatively, the required pressure Pe may be calculated by the upper braking unit SA. Since signals such as wheel speed Vw and yaw rate Yr are input to the lower braking unit SB, the determination of the start/end of automatic pressurization control and the calculation of each required pressure Po are performed by the lower braking unit SB. be exposed. However, since the upper and lower braking units SA and SB share the signal via the communication bus BS, the required pressure Pe can be calculated by the upper braking unit SA. Therefore, the required pressure Pe is calculated by either the upper braking unit SA or the lower braking unit SB based on the required pressure Po.

In the embodiment described above, the increasing slope kP and the required flow rate Qe were calculated in the lower braking unit SB, and the required flow rate Qe was sent to the upper braking unit SA. Alternatively, the increasing gradient kP and the required flow rate Qe may be calculated by the upper braking unit SA. Similarly to the above, since signals are shared between the upper braking unit SA and the lower braking unit SB, the increased gradient kP and the required flow rate Qe are calculated by either the upper or lower braking unit SA or SB. .

In the above-described embodiment, front and rear brake systems were used as the two brake systems. Instead, a diagonal type (also referred to as "X type") may be adopted 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. Connected to the rear wheel cylinder.

In the above-described 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. One master chamber Rm is connected to four wheel cylinders CW. In this configuration, the same supply pressures Pmf and Pmr (=Pm) are output from the master cylinder CM.

In a configuration in which a single master cylinder CM is employed, the master chamber Rm may be connected to the front wheel cylinder CWf, and the pressure regulating unit CA may be directly connected to the rear wheel cylinder CWr. In this configuration, the master cylinder CM outputs the front wheel supply pressure Pmf to the front wheel cylinder CWf as the front wheel pressure Pwf. On the other hand, the servo pressure Pu is output from the pressure regulating unit CA to the rear wheel cylinder CWr as the rear wheel supply pressure Pmr.

In the above embodiment, in the apply unit AP, 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 to be equal. The master area rm and the servo area ru do not have to be equal. In a configuration where the master area rm and the servo area ru are different, it is possible to convert the supply pressure Pm and the servo pressure Pu based on the ratio of the servo area ru and the master area rm (i.e., "Pm・rm= Conversion based on "Pu・ru").

<Summary of embodiments>
The embodiments of the brake control device SC will be summarized below. The brake control device SC includes "an upper brake unit SA that outputs a supply pressure Pm by throttling a circulating flow KN (upper circulating flow) discharged by a fluid pump QA driven by an electric motor MA with a pressure regulating valve UA";"Lower braking unit SB is arranged between upper braking unit SA and a plurality of wheel cylinders CW, and outputs wheel pressure Pw by individually adjusting supply pressure Pm to each of the plurality of wheel cylinders CW", will be provided.

In the lower braking unit SB, automatic pressurization control (a general term for traction control and skid prevention control) that increases the wheel pressure Pw automatically and individually is executed. In this case, in the upper brake unit SA, the pressure regulating valve UA is controlled based on the required pressure Pe required for automatic pressurization control. Here, the required pressure Pe is a target value corresponding to the maximum value of each wheel pressure Pw required for automatic pressurization control. For example, the required pressure Po required for each of the plurality of wheel cylinders CW is calculated, and the required pressure Pe is determined based on the maximum value of the plurality of required pressures Po.

The control of the pressure regulating valve UA in the upper brake unit SA will be summarized. In the upper brake unit SA, the pressure regulating valve UA is controlled based on the required pressure Pe. Specifically, when the required pressure Pe is larger than the command pressure Ps calculated from the braking operation amount Ba, the supply pressure Pm is controlled to approach and match the required pressure Pe. In the brake control device SC, the pressure (that is, the required pressure Pe) that is the source of automatic pressurization control is generated in the upper brake unit SA. Since the rated output of the upper braking unit SA is capable of responding to sudden braking, it has sufficient responsiveness to automatic pressurization control. Since the required pressure Pe is supplied by the upper brake unit SA, the lower brake unit SB is made smaller.

When automatic pressurization control is executed, power is supplied to the lower electric motor MB in order to return the brake fluid BF that has flowed into the pressure regulating reservoir RB to the upper part of the inlet valve VI. However, since the required pressure Pe is supplied from the upper braking unit SA, there is no need to further increase the supply pressure Pm at the lower braking unit SB. Therefore, in the lower braking unit SB, power is not supplied to the control valve UB. However, when the upper braking unit SA cannot supply the required pressure Pe, power is supplied to the control valve UB so as to compensate for the shortage of the supply pressure Pm with respect to the required pressure Pe. Therefore, the control valve UB is controlled based on the difference hP between the required pressure Pe and the supply pressure Pm.

The control of electric motor MA in upper braking unit SA will be summarized. In the upper brake unit SA, an electric motor MA is driven to generate a circulating flow KN of the brake fluid BF, which includes the fluid pump QA and the pressure regulating valve UA. For example, the electric motor MA is driven at a constant speed of a predetermined rotation speed na. Alternatively, in the upper braking unit SA, the electric motor MA is controlled based on the required flow rate Qe for achieving the required pressure Pe. Specifically, based on the above-mentioned required pressure Po, the increasing slope kP (the amount of increase per unit time of the required pressure Po) is calculated, and the required flow rate Qe is calculated based on the increasing slope kP. For example, the required flow rate Qe is determined based on the sum ΣkP of the increasing gradients kP in each wheel cylinder CW. In the upper braking unit SA, a target rotational speed Nt is calculated based on the required flow rate Qe. Then, the actual rotation speed Na of the electric motor MA is controlled based on the target rotation speed Nt. The electric motor MA is controlled at the minimum necessary rotation speed based on the required flow rate Qe required for automatic pressurization control. Therefore, the power consumption of the upper braking unit SA is suppressed.

When the automatic pressurization control is executed by the brake control device SC, the required pressure Pe for the automatic pressurization control is generated in the upper braking unit SA, and each wheel pressure Pw is equal to or lower than the required pressure Pe, and the required pressure Pe for the automatic pressurization control is generated in the lower braking unit. SB (in particular, inlet valve VI and outlet valve VO) are individually regulated. At this time, in the upper braking unit SA, the required pressure Pe is generated at a flow rate necessary for automatic pressurization control (ie, required flow rate Qe). For example, when the brake operation member BP is not operated, the brake operation amount Ba is "0", and the automatic pressurization control is not executed, both the upper and lower brake units SA and SB are Operation is stopped and wheel pressure Pw is not generated. In this state, when automatic pressurization control is executed in the lower braking unit SB, not only the lower braking unit SB is operated, but also the upper braking unit SA is operated to supply the required pressure Pe. . In the brake control device SC, various roles are shared between the upper and lower brake units SA and SB, so that the entire device can be downsized and save power.

Claims

an upper braking unit that outputs supply pressure by throttling a circulating flow discharged by a fluid pump driven by an electric motor using a pressure regulating valve;
a lower braking unit that is disposed between the upper braking unit and the plurality of wheel cylinders, and outputs wheel pressure by individually adjusting the supply pressure to each of the plurality of wheel cylinders;
In a braking control device for a vehicle comprising:
When the lower braking unit executes automatic pressurization control that increases the wheel pressure automatically and individually, the upper braking unit controls the pressure regulating valve based on the required pressure required for the automatic pressurization control. A vehicle braking control device that controls the
The braking control device for a vehicle according to claim 1,
A braking control device for a vehicle, wherein the required pressure is determined based on a maximum value of required pressures required for each of the plurality of wheel cylinders.
In the vehicle braking control device according to claim 1 or 2,
The upper brake unit is a brake control device for a vehicle that controls the electric motor based on a required flow rate to achieve the required pressure.
In the vehicle braking control device according to claim 3,
A braking control device for a vehicle, wherein the required flow rate is determined based on an increasing gradient of required pressure required for each of the plurality of wheel cylinders.