JP2024011639A - Braking control device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suitably control an electric motor in a braking control device in which operating force of a braking operation member is assisted by using the electric motor as a pressurization source.

SOLUTION: A braking control device includes: a master cylinder that outputs master pressure in accordance with operation amount of a braking operation member; a negative pressure booster for assisting operating force of the braking operation member in accordance with the operation amount by using negative pressure; a negative pressure sensor for detecting booster negative pressure of the negative pressure booster; a fluid unit that comprises a fluid pump driven by the electric motor and a pressure regulating valve, increases the master pressure and supplies the master pressure to a wheel cylinder as wheel pressure; and a controller that controls the fluid unit. When the booster negative pressure is small, the controller performs control on the basis of the booster negative pressure, so as to increase rotational frequency of the electric motor compared to when the booster negative pressure is large.

SELECTED DRAWING: Figure 4

COPYRIGHT: (C)2024,JPO&INPIT

Description

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

Patent Document 1 discloses that in order to improve the brake feeling when the brake pedal is depressed with more than a predetermined pedal force in a state where the negative pressure of the negative pressure booster is decreasing, the braking operation of the brake pedal 5 is changed. The pedal force sensor is equipped with a master cylinder 35 that can output master cylinder pressure according to the pressure, a vacuum booster 30 that supports input to the master cylinder 35 with negative pressure, and a pump 70 that supports the master cylinder pressure by pressurizing the pump. A target wheel cylinder pressure is set based on the master cylinder pressure acquired by the master cylinder pressure sensor 75 when the pedal force acquired by step 15 exceeds a preset standard braking operation force, and based on the set target wheel cylinder pressure. It is described that the pump 70 is controlled by

Patent Document 2 discloses an engine automatic stop/restart control means and an engine 1 intake negative pressure control means for preventing a decrease in braking force even when the engine intake negative pressure decreases. A vehicle equipped with a booster (depression force assisting means) 14 that assists the driver's brake depressing force by utilizing the pressure applied by the driver, and a pressurization control unit 21 that generates a required brake fluid pressure by a pump driven by an electric motor 26. In the brake control unit (ECU) 13, when the vehicle is running in a state where restarting of the engine 1 cannot be confirmed after the restart conditions are established, and the negative pressure of the booster 14 is equal to or higher than the set value (negative pressure It is described that when the assist force of the booster 14 is insufficient, the brake fluid pressure is increased by the pressurization control unit 21 to compensate for the lack of assist force provided by the booster 14.

Patent Documents 1 and 2 disclose that when the negative pressure in the negative pressure booster (referred to as "booster negative pressure") is insufficient, an electric motor is used as a pressure source to assist the driver's operating force of a brake operating member. It is stated that. In this situation, it is necessary that the electric motor be properly controlled so that the assistance provided by the electric motor can be carried out in just the right amount.

Japanese Patent Application Publication No. 2009-120124 Japanese Patent Application Publication No. 2013-060164

An object of the present invention is to provide a brake control device for a vehicle in which the electric motor is used as a pressure source to assist the operation force of a brake operation member, in which the electric motor can be suitably controlled.

A brake control device (SC) for a vehicle according to the present invention includes a master cylinder (CM) that outputs a master pressure (Pm) according to an operation amount (Ba) of a brake operation member (BP), and a master cylinder (CM) that outputs a master pressure (Pm) according to an operation amount (Ba) of a brake operation member (BP), and a master cylinder (CM) that outputs a master pressure (Pm) according to an operation amount (Ba) of a brake operation member (BP). (Ba), a negative pressure booster (VB) that assists the operating force (Fp) of the brake operating member (BP), and a negative pressure sensor that detects the booster negative pressure (Pv) of the negative pressure booster (VB). (PV), a fluid pump (QB) driven by an electric motor (MB), and a pressure regulating valve (UB). It includes a fluid unit (HU) that supplies the cylinder (CW), and a controller (ECU) that controls the fluid unit (HU). The controller (ECU) controls the rotation speed (Na) of the electric motor (MB) based on the booster negative pressure (Pv). For example, the controller (ECU) increases the rotation speed (Na) when the booster negative pressure (Pv) is small compared to when the booster negative pressure (Pv) is large.

In control in which the electric motor is used as a pressure source to assist the operation force of the brake operation member (ie, assist control), the more the booster negative pressure Pv is insufficient, the greater the differential pressure Sj is required. According to the above configuration, when the booster negative pressure Pv is insufficient, the motor rotation speed Na is controlled to be increased. Thereby, the brake fluid BF is sufficiently discharged from the fluid pump QB, so that the differential pressure Sj is reliably secured.

In the vehicle brake control device (SC) according to the present invention, the controller (ECU) increases the rotation speed (Na) based on the amount of change (dB) of the operation amount (Ba) over time. When the amount of change in operation dB is large, it may be difficult for the negative pressure booster VB to generate an assisting force. According to the above configuration, even if a sudden operation (braking operation with a large operation change amount dB) is performed, a sufficient differential pressure Sj is ensured with a high response.

1 is a schematic diagram for explaining the entire vehicle equipped with a brake control device SC. FIG. 3 is a schematic diagram for explaining a configuration example of a fluid unit HU. It is a characteristic diagram for explaining the outline of low negative pressure assistance control. It is a flowchart for explaining the process of low negative pressure assistance control.

<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 circulating flow KL of the brake fluid BF in the fluid unit HU, the side closer to the discharge part of the fluid pump QB (the side away from the suction part) is called the "upstream side", and the side closer to the suction part of the fluid pump QB is called the "upstream side". The side (the side away from the discharge part) is called the "downstream side".

The master cylinder CM, fluid unit HU, and wheel cylinder CW are connected through a fluid path (communication path HS). Furthermore, in the fluid unit HU, various components (UB, 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 HL, decompression path HG, etc. are fluid paths.

<Vehicle equipped with braking control device SC>
The overall configuration of a vehicle equipped with a brake control device SC according to the present invention will be described with reference to the schematic diagram of FIG. For example, a hybrid type vehicle is adopted. That is, the vehicle includes an internal combustion engine IC (also simply referred to as an "engine") and a traveling electric motor MD (simply referred to as a "travel motor") as a prime mover (a device that converts energy into mechanical work). Alternatively, two different power sources (also referred to as "drive motors") are provided. The traveling motor MD also functions as a generator for energy regeneration during vehicle deceleration, so it is also called a "motor generator." Furthermore, the running motor MD can also function as a starter for the internal combustion engine IC.

The prime mover control device GC provided in the vehicle includes an internal combustion engine IC, a driving electric motor MD, and an electronic control unit ECG for the prime mover (also referred to as a "prime mover controller"). In an internal combustion engine IC, fuel such as gasoline is combusted, and mechanical work is obtained by the combustion gas generated thereby. The driving motor MD generates power using an on-vehicle storage battery as an energy source. The internal combustion engine IC and the driving motor MD are controlled by a prime mover controller ECG.

A controller ECG of the prime mover control device GC and a brake electronic control unit ECU (also referred to as a "brake controller") of the brake control device SC are connected via a communication bus BS. Various signals (Aa, Pv, FV, etc.) are shared between the prime mover controller ECG and the brake controller ECU through the communication bus BS.

In an internal combustion engine IC (for example, a gasoline engine), an intake negative pressure is generated. Intake negative pressure is the pressure within the intake pipe (intake manifold) generated by the lowering of the engine piston. Intake negative pressure increases when the engine is idling with the throttle closed or under low load, and decreases when the throttle is fully open.

The vehicle is equipped with an acceleration operation member AP. The acceleration operation member AP (for example, an accelerator pedal) is a member operated by the driver to accelerate the vehicle. The acceleration operation member AP is provided with an acceleration operation amount sensor AA that detects its operation amount Aa (acceleration operation amount). The acceleration operation amount Aa is one of state quantities (state variables) that indicates the degree of operation of the acceleration operation member AP. The acceleration operation amount Aa detected by the acceleration operation amount sensor AA is input to the prime mover controller ECG. The prime mover controller ECG adjusts the output (as a result, the driving force of the wheels) of the prime mover (internal combustion engine IC, travel motor MD) based on the acceleration operation amount Aa. Further, the acceleration operation amount Aa is output to the communication bus BS and acquired by the brake controller ECU.

The prime mover controller ECG performs an operation to generate intake negative pressure in response to a request from the brake control device SC (particularly, the brake controller ECU). Intake negative pressure is stored in the negative pressure booster VB as booster negative pressure Pv. When booster negative pressure Pv decreases, the assisting force of negative pressure booster VB decreases, so intake negative pressure is generated by prime mover controller ECG in response to a request signal (for example, request flag FV) from brake control device SC. Ru. Specifically, generation of intake negative pressure is instructed from the brake control device SC to the prime mover control device GC via the request flag FV. The "request flag FV" is a control flag, and when it is "0", it is instructed that the generation of intake negative pressure is not necessary, and when it is "1", it is instructed that the generation of intake negative pressure is necessary. For example, when the internal combustion engine IC is in a stopped state, the request flag FV switches from "0" to "1", so that the internal combustion engine IC is started (started) by the starter ST (or drive motor MD). and negative intake pressure is generated.

≪Size relationship of booster negative pressure Pv≫
The booster negative pressure Pv is generated as a negative (-) value when atmospheric pressure is the reference value "0 (zero)". However, when discussing the magnitude of the values, including the sign of the booster negative pressure Pv may complicate the explanation. Therefore, below, the magnitude relationship will be explained based on the absolute value of the booster negative pressure Pv. Therefore, "the booster negative pressure Pv is large" means that the absolute value (magnitude) of the booster negative pressure Pv is large, lowering from atmospheric pressure and approaching vacuum. Conversely, "the booster negative pressure Pv is small" means that the absolute value (magnitude) of the booster negative pressure Pv is small and closer to atmospheric pressure.

The vehicle is equipped with a braking device. The braking device includes a brake caliper, a friction member (for example, a brake pad), and a rotating member KT (for example, a brake disc). The brake caliper (not shown) is provided with a wheel cylinder CW. A friction member (not shown) is pressed against a 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, braking force is generated at the wheel WH.

The vehicle is equipped with a brake operation member BP. The brake operation member BP (eg, brake pedal) is a member operated by the driver to decelerate the vehicle. The brake operation member BP is provided with an operation displacement sensor SP that detects its operation displacement Sp. The operation displacement Sp is one of state quantities (state variables) that indicates the degree of operation of the brake operation member BP.

The vehicle is equipped with various sensors in order to individually control the wheel pressure Pw of each wheel WH, such as anti-lock brake control and skid prevention control. Specifically, the wheel WH is equipped with a wheel speed sensor VW that detects its rotational speed Vw (wheel speed). Additionally, a steering amount sensor (not shown) that detects the steering amount Sa of a steering operation member (for example, a steering wheel), a yaw rate sensor (not shown) that detects the yaw rate Yr of the vehicle, and a longitudinal acceleration sensor that detects the longitudinal acceleration Gx of the vehicle. A sensor (not shown) and a lateral acceleration sensor (not shown) that detects the lateral acceleration Gy of the vehicle are provided. The signals of wheel speed Vw, steering amount Sa, yaw rate Yr, longitudinal acceleration Gx, and lateral acceleration Gy are input to the brake controller ECU.

The vehicle is equipped with a brake control device SC. The brake control device SC employs a so-called 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 includes a master cylinder CM, a negative pressure booster VB, a fluid unit HU, and a brake controller ECU.

A tandem type master cylinder CM is adopted. Specifically, a primary master piston NM and a secondary master piston NN are inserted into the master cylinder CM. The interior of the master cylinder CM is divided into two hydraulic chambers Rmf and Rmr (=Rm) by the two master pistons NM and NN. The front wheel and rear wheel hydraulic pressure chambers Rmf and Rmr are referred to as "front wheel and rear wheel master chambers." The master pistons NM and NN are moved in conjunction with the brake operation member BP via the operation rod RD.

When the brake operation member BP is not operated (non-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 maximized). In this state, the master chamber Rm of the master cylinder CM and the master reservoir RV are in communication. The master reservoir RV is also called an "atmospheric pressure reservoir" and is a tank for working fluid, in which brake fluid BF is stored.

When the brake operation member BP is operated, the master pistons NM and NS are moved in the forward direction (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, the front and rear wheel master pressures Pmf and Pmr (=Pm), which are the internal pressures of the front and rear wheel master chambers Rmf and Rmr, become "0 (large)". atmospheric pressure). As a result, the brake fluid BF pressurized to the master pressure Pm is output (forced) from the master chamber Rm of the master cylinder CM. When the brake operation member BP is returned, the master pistons NM and NN are moved in the backward direction (direction in which the volume of the master chamber Rm increases) opposite to the forward direction, and the brake fluid BF is returned toward the master cylinder CM. It will be done.

The front wheel and rear wheel master chambers Rmf and Rmr (=Rm) of the tandem type master cylinder CM and the front wheel and rear wheel cylinders CWf and CWr (=CW) are the front wheel and rear wheel communication paths HSf and HSr (=HS). connected by. The communication path HS is a fluid path that connects the master cylinder CM and the wheel cylinder CW. The front wheel and rear wheel communication paths HSf and HSr are respectively branched into two in the fluid unit HU and connected to the front wheel and rear wheel cylinders CWf and CWr.

The master cylinder CM is provided with a negative pressure booster VB. The negative pressure booster VB is a booster that uses intake negative pressure to assist the operating force Fp of the brake operating member BP. Negative pressure booster VB is arranged between brake operation member BP and master cylinder CM. The inside of the negative pressure booster VB is divided into two gas chambers Rv and Ro by a diaphragm Dm. The gas chamber Rv is referred to as a "negative pressure chamber" and the gas chamber Ro is referred to as an "atmospheric pressure chamber."

Negative pressure chamber Rv is arranged on the master cylinder CM side in negative pressure booster VB. Intake negative pressure is introduced (supplied) into the negative pressure chamber Rv from the internal combustion engine IC (in particular, the intake manifold) via the negative pressure hose VH, and is stored therein. The internal pressure of the negative pressure chamber Rv is the booster negative pressure Pv.

Atmospheric pressure chamber Ro is arranged on the side of brake operation member BP in negative pressure booster VB. Inside the atmospheric pressure chamber Ro, the valve body Vt is connected to the operating rod RD. When the brake operation member BP is not operated, the valve body Vt is closed. In this state, the atmospheric pressure in the atmospheric pressure chamber Ro is equal to the atmospheric pressure Pv (booster negative pressure) in the negative pressure chamber Rv.

When the brake operating member BP is operated and the operating rod RD is moved in the forward direction toward the master cylinder CM, the valve body Vt is opened. As a result, outside air (atmospheric pressure) is introduced into the atmospheric pressure chamber Ro. The pressure in the atmospheric pressure chamber Ro approaches atmospheric pressure, and a pressure difference occurs between it and the booster negative pressure Pv, which is the pressure in the negative pressure chamber Rv. Due to this pressure difference, a thrust force in the direction of the master cylinder CM (that is, in the forward direction) acts on the diaphragm Dm. The thrust assists the operating force Fp of the brake operating member BP. That is, in the negative pressure booster VB, the operating force Fp of the brake operating member BP is reduced due to the pressure difference between the booster negative pressure Pv and the atmospheric pressure.

The negative pressure booster VB (in particular, the negative pressure chamber Rv) is provided with a booster negative pressure sensor PV (also simply referred to as a "negative pressure sensor") to detect the booster negative pressure Pv. As described above, the smaller the booster negative pressure Pv, the closer the internal pressure of the negative pressure chamber Rv is to the atmospheric pressure "0", which means that the negative pressure in the negative pressure booster VB is insufficient. Conversely, the larger the booster negative pressure Pv, the closer the internal pressure of the negative pressure chamber Rv is to a vacuum, and the negative pressure in the negative pressure booster VB is sufficient. The booster negative pressure Pv signal is input to the brake controller ECU.

A fluid unit HU is provided between the master cylinder CM and the wheel cylinder CW. The fluid unit HU is a device for executing independent control of each wheel, such as anti-lock brake control, traction control, and skid prevention control. In addition, in the fluid unit HU, when the booster negative pressure Pv of the negative pressure booster VB decreases, in addition to the negative pressure booster VB, the braking operation force Fp is assisted. This control is called "low negative pressure assist control."

The fluid unit HU can increase the master pressure Pm output from the master cylinder CM and supply the wheel pressure Pw to the wheel cylinder CW. The fluid unit HU is controlled by a brake electronic control unit ECU (brake controller). The brake controller ECU is connected to the prime mover controller ECG via a communication bus BS. A communication bus BS performs signal transmission between a plurality of controllers (ECU, ECG, 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.

<Fluid unit HU>
An example of the configuration of the fluid unit HU will be described with reference to the schematic diagram of FIG. 2. The fluid unit HU is a device for executing low negative pressure assist control. Front wheel and rear wheel master pressures Pmf and Pmr (=Pm) are supplied to the fluid unit HU from the master cylinder CM. The fluid unit HU then adjusts (increases or decreases) the front and rear wheel master pressures Pmf and Pmr, and outputs them as hydraulic pressures Pwf and Pwr (front and rear wheel pressures) of the front and rear wheel cylinders CWf and CWr. Ru.

The fluid unit HU is provided between the master cylinder CM and the wheel cylinder CW in the communication path HS. The fluid unit HU includes a master pressure sensor PM, a pressure regulating valve UB, a fluid pump QB, an electric motor MB, a pressure regulating reservoir RB, an inlet valve VI, and an outlet valve VO.

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

The front wheel and rear wheel master pressure sensors PMf and PMr (=PM) detect the actual hydraulic pressures Pmf and Pmr (front and rear wheel master pressures) supplied from the master cylinder CM (especially the front wheel and rear wheel master chambers Rmf and Rmr). ) are provided above the front and rear wheel pressure regulating valves UBf and UBr (at the communication path HS near the master cylinder CM). Master pressure sensor PM is built into fluid unit HU. Signals of front wheel and rear wheel master pressures Pmf and Pmr (=Pm) are input to the brake controller ECU. Note that since the front wheel master pressure Pmf and the rear wheel master pressure Pmr are substantially the same, either one of the front wheel and rear wheel master pressure sensors PMf and PMr may be omitted. For example, in a configuration where the rear wheel master pressure sensor PMr is omitted, only the front wheel master pressure Pmf is detected by the front wheel master pressure sensor PMf.

The front wheel and rear wheel return paths HLf and HLr (=HL) allow the front wheel and rear wheel pressure regulating valves UBf and the upper part of the UBr (portion of the communication path HS near the master cylinder CM), the front wheel and rear wheel pressure regulating 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 fluid pumps QBf and QBr (=QB), and front and rear wheel pressure regulating reservoirs RBf and RBr (=RB). Fluid pump QB is driven by electric motor MB.

When the electric motor MB is driven, the fluid pump QB sucks the brake fluid BF from the upper part of the pressure regulating valve UB and discharges it to the lower part of the pressure regulating valve UB. As a result, the communication path HS and the return path HL include the fluid pump QB and the pressure regulating reservoir RB, and the circulation flow KL of the brake fluid BF (that is, the front wheel and rear wheel circulation flows KLf, KLr). , indicated by the dashed arrow) occurs. When the flow path of the communication path HS is narrowed by the pressure regulating valve UB and the circulating flow KL of the brake fluid BF is throttled, the hydraulic pressure Pq (referred to as "adjusted pressure") at the lower part of the pressure regulating valve UB is reduced due to the orifice effect at that time. is increased from the hydraulic pressure Pm (master pressure) above the pressure regulating valve UB. In other words, in the circulating flow KL, the hydraulic pressure difference Sj (differential pressure) between the downstream hydraulic pressure Pm (master pressure) and the upstream hydraulic pressure Pq (adjusted pressure) with respect to the pressure regulating valve UB is Adjusted by UB. Note that in terms of the magnitude relationship between the master pressure Pm and the adjusted pressure Pq, the adjusted pressure Pq is greater than or equal to the master pressure Pm (ie, "Pq≧Pm").

Inside the fluid unit HU, the front and rear wheel communication paths HSf and HSr are branched into two, respectively, and connected to the front and rear wheel cylinders CWf and CWr. A normally open inlet valve VI and a normally closed outlet valve VO are provided for each wheel cylinder CW so that each wheel pressure Pw can be adjusted individually. Specifically, the inlet valve VI is provided in the branched communication 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 passage HS is connected to the pressure regulating reservoir RB via the pressure reduction passage HG at the lower part of the inlet valve VI (the portion of the communication passage 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 regulating pressure Pq at each wheel.

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 up to 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.

When power is not supplied to the inlet valve VI and the 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 (ie, "Pq=Pw").

The fluid unit HU is controlled by a brake controller ECU. The brake controller ECU is composed of a microprocessor MP and a drive circuit DR. The brake controller ECU can share signals with the prime mover controller ECG via the communication bus BS.

A wheel speed Vw, a steering amount Sa, a yaw rate Yr, a longitudinal acceleration Gx, and a lateral acceleration Gy are input to the brake controller ECU (particularly the microprocessor MP). The brake controller ECU calculates the vehicle speed Vx based on the wheel speed Vw. The brake controller ECU executes independent control for each wheel as listed below. Specifically, as independent control for each wheel, anti-lock brake control (so-called ABS control) that prevents wheel locking, traction control that suppresses spin of the drive wheels, and control that suppresses understeer and oversteer to control the vehicle. Skid prevention control (so-called ESC) is executed to improve the directional stability of the vehicle. In addition, a signal of the booster negative pressure Pv detected by the negative pressure sensor PV is input to the brake controller ECU, and the above-described low negative pressure assist control is executed based on the booster negative pressure Pv.

In the brake controller ECU, the drive circuit DR is controlled according to a control algorithm programmed in the microprocessor MP. Specifically, the drive circuit DR drives the electric motor MB and various electromagnetic valves (UB, etc.) that constitute the fluid unit HU. The drive circuit DR includes an H-bridge circuit using switching elements (eg, MOS-FET) to drive the electric motor MB. Further, the drive circuit DR is equipped with switching elements to drive various electromagnetic valves (UB, etc.). In addition, the drive circuit DR includes a motor current sensor (not shown) that detects the current In (actual value) supplied to the electric motor MB, and a current Ib (actual value) supplied to the pressure regulating valve UB (actual value). A current sensor (not shown) that detects the current (referred to as "current") is included. Based on the control algorithm of the microprocessor MP, a drive signal Ub for the pressure regulating 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 electric motor MB are calculated. The 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.).

Note that when executing the low negative pressure assist control, the inlet valve VI and the outlet valve VO are not driven (power supplied), but the electric motor MB and the pressure regulating valve UB are driven. Therefore, the inlet valve VI maintains the open state and the outlet valve VO maintains the closed state, so the adjusted pressure Pq is output from the fluid unit HU as the wheel pressure Pw. That is, in the low negative pressure assist control, the adjustment pressure Pq and the wheel pressure Pw are equal.

<Low negative pressure assist control>
An overview of the low negative pressure assist control will be described with reference to the characteristic diagram in FIG. 3. In the characteristic diagram, changes in the wheel pressure Pw (hydraulic pressure in the wheel cylinder CW) are plotted against the operation amount Ba of the brake operation member BP by the driver. Here, the brake operation amount Ba is a state quantity (state variable) expressing the degree of operation of the brake operation member BP, and corresponds to at least one of the operation displacement Sp and the operation force Fp.

Assisting the driver's braking force Fp by the negative pressure booster VB is referred to as "negative pressure assisting." The negative pressure assist reduces the operating force Fp for generating the master pressure Pm (as a result, the wheel pressure Pw). The hydraulic pressure Pm (master pressure) generated by the master cylinder CM is increased by the fluid pump QB (i.e., electric pump) driven by the electric motor MB as a power source (i.e., low negative pressure assist control). However, it is called "electric pump assistance". Since the wheel pressure Pw is increased from the master pressure Pm by the electric pump assistance, the braking operation force Fp required to generate the wheel pressure Pw is reduced.

In FIG. 3, a characteristic line Cho expresses the braking characteristic by the braking control device SC. That is, the characteristic line Cho is the characteristic of the wheel pressure Pw that should be generated in response to the braking operation amount Ba. The characteristic line Cha is the characteristic when neither negative pressure assistance nor electric pump assistance is performed. That is, the characteristic line Cha is a characteristic when the master pressure Pm (resultingly, the wheel pressure Pw) is generated only by the driver's muscular strength. The characteristics are determined by geometrical specifications such as the lever ratio of the brake operating member BP and the pressure receiving areas of the cylinders CM and CW.

The characteristic line Chb is the characteristic when electric pump assistance is not performed and only negative pressure assistance is performed. That is, the characteristic line Chb is the relationship between the master pressure Pm and the braking operation amount Ba when the fluid unit HU is not operating but the negative pressure booster VB is operating. The characteristic line Chb is expressed as a characteristic parallel to the characteristic line Cha, starting from the limit point (G). Here, the limit point (G) is also called a "modulation point" and is the point at which assistance by negative pressure reaches its limit (maximum value). At the limit point (G), the assisting force (force assisting the driver's operating force Fp) generated by the negative pressure booster VB becomes the upper limit. Therefore, negative pressure assistance can be performed in the region sandwiched between the characteristic line Cha and the characteristic line Chb.

Above the characteristic line Chb, low negative pressure assist control is performed by the fluid unit HU. When the braking operation amount Ba is larger than a value Bg (referred to as "limit operation amount") corresponding to the limit point (G), electric pump assistance is performed by low negative pressure assistance control. Thereby, even if the braking operation amount Ba exceeds the limit operation amount Bg, the decrease in the increase gradient of the wheel pressure Pw (the amount of change in the wheel pressure Pw with respect to the braking operation amount Ba) can be compensated for. Thereby, the wheel pressure Pw can be generated along the characteristic line Cho.

For example, when the braking operation amount Ba is the value ba and is relatively small (that is, when "Ba≦Bg"), the low negative pressure assist control is not executed. In this case, master pressure Pm (value pa) output from master cylinder CM is supplied as is to wheel cylinder CW as wheel pressure Pw (value pa). On the other hand, when the braking operation amount Ba is the value bb and is relatively large (that is, when "Ba>Bg"), the low negative pressure assist control is executed. In this case, the master pressure Pm (value pb) output from the master cylinder CM is increased by the value sb by the fluid unit HU, and the hydraulic pressure "pb+sb" is supplied to the wheel cylinder CW as the wheel pressure Pw.

The limit point (G) (coordinates (Bg, Pg)) varies depending on the magnitude of booster negative pressure Pv. When the booster negative pressure Pv becomes smaller (that is, the booster negative pressure Pv approaches atmospheric pressure "0"), the limit point (G) moves to the origin O (coordinates (0, 0)) along the characteristic line Cho. Move closer. On the other hand, when the booster negative pressure Pv increases (that is, the booster negative pressure Pv approaches vacuum), the limit point (G) moves away from the origin O (coordinates) (0, 0)) along the characteristic line Cho. Move like this. Therefore, the conditions under which the negative pressure assist control is executed (that is, the limit operation amount Bg) depends on the booster negative pressure Pv.

<Processing of low negative pressure assist control>
The process of low negative pressure assist control (also simply referred to as "assist control") will be described with reference to the flowchart of FIG. 4. In the assisting control, the master pressure Pm is increased by the fluid unit HU in accordance with the booster negative pressure Pv. Specifically, the circulating flow KL generated by the fluid pump QB (electric pump) driven by the electric motor MB is throttled by the pressure regulating valve UB, so that the master pressure Pm is increased and the pressure is applied to the wheel cylinder CW. It is output as wheel pressure Pw. The assist control algorithm is programmed into the microprocessor MP of the brake controller ECU. Therefore, the assistance control is executed by the brake control device SC (particularly the brake controller ECU).

In step S110, detection signals (Ba, Pv, etc.) of various sensors (BA, PV, etc.) are acquired. The brake operation amount Ba detected by the brake operation amount sensor BA is acquired. “Brake operation amount Ba” is a general term for state quantities representing the degree of operation of the brake operation member BP. Further, "braking operation amount sensor BA" is a general term for sensors that detect these. Specifically, the operation displacement Sp of the brake operation member BP and the operation force Fp of the brake operation member BP correspond to the brake operation amount Ba. Further, the operation displacement sensor SP that detects the operation displacement Sp and the operation force sensor FP that detects the operation force Fp correspond to the braking operation amount sensor BA. In other words, in step S110, the braking operation amount Ba is determined based on at least one of the operation displacement Sp detected by the operation displacement sensor SP and the operation force Fp detected by the operation force sensor FP. , loaded into the assist control algorithm.

In step S110, the booster negative pressure Pv detected by the negative pressure sensor PV is further acquired. Booster negative pressure Pv is detected as a relative pressure with respect to atmospheric pressure. In other words, the booster negative pressure Pv corresponds to the pressure difference between the internal pressure of the negative pressure chamber Rv and the external pressure (atmospheric pressure). An absolute pressure sensor may be employed as the booster negative pressure sensor PV. In this configuration, an atmospheric pressure sensor is provided, and the difference between the atmospheric pressure detected by the sensor and the intake negative pressure (absolute pressure) is determined as the booster negative pressure Pv.

In step S120, a limit point (G) is determined based on booster negative pressure Pv. The negative pressure booster VB generates an auxiliary force against the operating force Fp using the booster negative pressure Pv, and the limit point (G) is the point at which the auxiliary force reaches its limit (see FIG. 3). In step S120, the limit operation amount Bg is set as the limit point (G). Here, the "limit operation amount Bg" corresponds to the braking operation amount Ba at which electric pump assistance is started. Specifically, the specifications of the booster negative pressure Pv and the negative pressure booster VB (pressure receiving area of diaphragm Dm, etc.), the specifications of master cylinder CM and wheel cylinder CW (pressure receiving area of various cylinders CM and CW, etc.) Based on this, the limit operation amount Bg is calculated. The limit operation amount Bg is determined to increase as the booster negative pressure Pv increases.

In step S130, as shown in a calculation map setting block ZST, a calculation map Zst is set based on the limit operation amount Bg calculated from the booster negative pressure Pv. The "calculation map Zst" is a calculation characteristic related to the control of the pressure regulating valve UB for adjusting the regulation pressure Pq (namely, the wheel pressure Pw). For example, in step S130, the relationship between the target differential pressure St and the braking operation amount Ba (also referred to as "target differential pressure characteristic") is determined as the calculation map Zst. Here, the target differential pressure St is a target value for the differential pressure Sj (actual value) between the adjusted pressure Pq (=Pw) and the master pressure Pm.

The limit point (G) increases along the characteristic line Cho as the booster negative pressure Pv increases. The characteristic line Chb is moved upward and the area of negative pressure assistance is expanded. Since the request for execution of the assistance control decreases, the calculation map Zst (target differential pressure characteristic) is set so that the control becomes difficult to execute. Conversely, the limit point (G) decreases along the characteristic line Cho as the booster negative pressure Pv decreases. The characteristic line Chb is moved downward and the area of negative pressure assistance is reduced. Since the number of requests for execution of assistance control increases, the calculation map Zst is set to facilitate execution of this control (see FIG. 3 above).

As shown in the calculation map setting block ZST, the calculation map Zst (target differential pressure characteristic) is set so that the target differential pressure St becomes "0" when the braking operation amount Ba is less than the limit operation amount Bg. Ru. The calculation map Zst is set such that when the brake operation amount Ba is larger than the limit operation amount Bg, the target differential pressure St increases as the brake operation amount Ba increases. The lower the booster negative pressure Pv, the smaller the limit operation amount Bg is determined, and the larger the booster negative pressure Pv is determined, the larger the limit operation amount Bg is determined. Therefore, the calculation map Zst is set to move in parallel along the X-axis (horizontal axis) in the decreasing direction of the X-axis (to the left in the figure) as the booster negative pressure Pv decreases. That is, in the calculation map Zst, for the same braking operation amount Ba, the target differential pressure St is calculated such that the smaller the booster negative pressure Pv is, the larger the target differential pressure St is, and the larger the booster negative pressure Pv is, the smaller the target differential pressure St is. Calculated. In other words, in the assist control, even if the braking operation amount Ba is the same, when the booster negative pressure Pv is small, the target differential pressure St is determined to be larger than when the booster negative pressure Pv is large. be done.

In step S140, it is determined whether or not assistance control is necessary based on the braking operation amount Ba and the booster negative pressure Pv. Specifically, the necessity is determined based on "whether or not the braking operation amount Ba is larger than the determination operation amount Bh" based on the determination operation amount Bh set based on the booster negative pressure Pv. . Here, the "judgment operation amount Bh" is a value smaller than the limit operation amount Bg by a predetermined amount bh (constant) (ie, "Bh=Bg-bh"). If the braking operation amount Ba is less than or equal to the determination operation amount Bh and it is determined that execution of the assistance control is unnecessary, the process returns to step S110. On the other hand, if the brake operation amount Ba is larger than the determination operation amount Bh and it is determined that the assistance control needs to be performed, the process proceeds to step S150.

The responsiveness of the control is improved by determining whether or not assistance control is necessary based on the determination operation amount Bh that is smaller than the limit operation amount Bg by a predetermined amount bh. The master pressure Pm is actually increased by the assisting control when the target differential pressure St is calculated to be larger than "0" (that is, when "Ba>Bg"). However, since it takes time to start the electric motor MB, execution of the assisting control (in particular, starting the electric motor MA) is started before the braking operation amount Ba becomes equal to or greater than the limit operation amount Bg. This suppresses the time delay required for starting the electric motor MB.

In step S150, a target differential pressure St (target value corresponding to the actual hydraulic pressure difference Sj) is calculated based on the braking operation amount Ba and the calculation map Zst set in step S130. The target differential pressure St is determined to increase as the braking operation amount Ba increases based on the calculation map Zst.

In step S160, a target rotation speed Nt for electric motor MB is calculated based on booster negative pressure Pv. The "target rotation speed Nt" is a target value corresponding to the actual rotation speed Na (also referred to as "motor rotation speed") of the electric motor MB. First, as shown in the command rotation speed calculation block NS, the command rotation speed Ns is calculated based on the booster negative pressure Pv and a preset calculation map Zns. "Instructed rotation speed Ns" is one of the target values for calculating the target rotation speed Nt. In the calculation map Zns, the commanded rotation speed Ns is determined to be larger as the booster negative pressure Pv is smaller. The calculation map Zns is provided with an upper limit rotation speed nj and a lower limit rotation speed nk of the command rotation speed Ns. The upper limit and lower limit rotational speed nj, nk are predetermined values (constants) set in advance.

The calculation map Zns of the command rotation speed calculation block NS can be set in two stages, as shown by the characteristic shown by the broken line. Specifically, when the booster negative pressure Pv is equal to or higher than the predetermined negative pressure po, the commanded rotation speed Ns is determined to be the first predetermined rotation speed nk (an initial value and a lower limit value). On the other hand, when the booster negative pressure Pv decreases and becomes less than the predetermined negative pressure po, the commanded rotation speed Ns is increased from the first predetermined rotation speed nk and determined to the second predetermined rotation speed nj (upper limit value). Ru. The predetermined negative pressure po is a predetermined value (constant) set in advance. Note that the commanded rotation speed Ns may be increased in multiple stages as the booster negative pressure Pv decreases.

In any case, in step S160, the commanded rotation speed Ns is increased in accordance with the decrease in the booster negative pressure Pv. Therefore, when the booster negative pressure Pv is small, the command rotation speed Ns is calculated to be larger than when the booster negative pressure Pv is large.

Next, in step S160, the brake operation amount Ba is differentiated with respect to time, and the amount of change dB (also referred to as "operation change amount") of the brake operation amount Ba with respect to time is calculated. For example, the operation speed dS, which is the amount of change over time in the operation displacement Sp, is used as the amount of change in operation dB. Then, the command rotation speed Ns calculated based on the booster negative pressure Pv is increased based on the operation change amount dB. Specifically, as shown in the increase amount calculation block NU, the rotational speed increase amount Nu is calculated based on the operation change amount dB and a preset calculation map Znu. The "rotation speed increase amount Nu" is a target value for increasing the commanded rotation speed Ns. The calculation map Znu is provided with an upper limit increase amount nm of the rotation speed increase amount Nu. The upper limit increase amount nm is a predetermined value (constant) set in advance. The rotation speed increase amount Nu is added to the command rotation speed Ns to calculate the target rotation speed Nt, which is the final target value (ie, "Nt=Ns+Nu").

The calculation map Znu of the increase amount calculation block NU can be set in two stages as shown by the broken line. Specifically, when the operation change amount dB is less than the predetermined speed do, the rotation speed increase amount Nu is determined to be "0". Therefore, when "dB<do", the commanded rotation speed Ns is directly calculated as the target rotation speed Nt (that is, "Nt=Ns"). On the other hand, when the operation change amount dB is equal to or greater than the predetermined speed do, the rotational speed increase amount Nu is increased from "0" and determined to be the predetermined increase amount nm. Therefore, the target rotation speed Nt is calculated by adding a predetermined increase amount nm ("=Nu", a preset constant) to the command rotation speed Ns (that is, "Nt=Ns+nm"). Note that the commanded rotation speed Ns may be increased in multiple steps as the amount of change in operation dB increases.

In step S170, electric motor MB is controlled (driven) based on target rotation speed Nt and actual rotation speed Na (motor rotation speed). In step S170, based on the target rotation speed Nt (target value) and the motor rotation speed Na (actual value), the drive signal Mb (motor drive signal ) is determined. Here, the motor rotation speed Na is calculated based on a detection value (motor rotation angle) of a rotation angle sensor provided in the electric motor MB. Specifically, the motor rotation angle is differentiated with respect to time to determine the motor rotation speed Na. A supply current Im (also referred to as "motor current") to the electric motor MB is adjusted by a motor drive signal Mb. In the case of "Nt>Na", motor current Im is increased so that motor rotation speed Na increases. On the other hand, if "Nt<Na", the motor current Im is decreased so that the motor rotation speed Na is decreased.

In step S180, the pressure regulating valve UB is controlled (driven) based on the target differential pressure St. In step S180, the target current It is calculated based on the target differential pressure St and a preset calculation map Zit (not shown). The "target current It" is a target value corresponding to the supply current Ib (actual value) of the pressure regulating valve UB, which is necessary to generate the target differential pressure St. The target current It is determined to increase as the target differential pressure St increases according to the calculation map Zit. Furthermore, in step S180, based on the target current It (target value) and the supply current Ib (actual value), the drive signal Ub (pressure regulating valve drive signal) is determined. Here, the supply current Ib to the pressure regulating valve UB (also referred to as "pressure regulating valve current") is detected by a current sensor provided in the drive circuit DR. The pressure regulating valve current Ib is adjusted by the pressure regulating valve drive signal Ub. When "It>Ib", the pressure regulating valve current Ib is increased, and when "It<Ib", the pressure regulating valve current Ib is decreased. By controlling the pressure regulating valve current Ib to match the target current It, the actual differential pressure Sj (actual differential pressure) approaches and is adjusted to match the target differential pressure St. In addition, in a configuration equipped with a hydraulic pressure sensor that detects the adjusted pressure Pq, the target current is determined based on the hydraulic pressure difference Sj (actual value of the differential pressure) between the adjusted pressure Pq (detected value) and the master pressure Pm (detected value). It may be fine-tuned.

In the assist control, the smaller the booster negative pressure Pv is, the larger the actual differential pressure Sj is required, so the target differential pressure St is calculated to be larger. Therefore, in the brake control device SC, when booster negative pressure Pv is small (i.e., booster negative pressure Pv is insufficient), when booster negative pressure Pv is large (i.e., booster negative pressure Pv is insufficient), The target rotational speed Nt is determined to be larger than that in the case where the engine is running. Thereby, the brake fluid BF is sufficiently discharged from the fluid pump QB, so that the actual differential pressure Sj is reliably secured.

In order to ensure a sufficient actual differential pressure Sj, it is also possible to always set the target rotational speed Nt to a large value (for example, the upper limit rotational speed nj). However, in this configuration, when the booster negative pressure Pv is sufficient (that is, when the booster negative pressure Pv is relatively large, for example, when "Pv≧po"), the electric motor MB operates more than necessary. It is driven at rotation speed Na. Therefore, there is a problem in terms of power consumption of the electric motor MB. In the brake control device SC, the target rotation speed Nt is determined according to the booster negative pressure Pv, so power consumption of the brake control device SC is suppressed.

Furthermore, in the brake control device SC, the target rotational speed Nt is increased in accordance with an increase in the time change amount dB (operation change amount) of the brake operation member BP. As described above, in the negative pressure booster VB, the atmosphere is introduced into the atmospheric pressure chamber Ro through the valve body Vt, and the internal pressure of the negative pressure chamber Rv (booster negative pressure Pv) and the internal pressure of the atmospheric pressure chamber Ro (eventually , atmospheric pressure), a supporting force is generated. When the amount of change in operation dB is large, a sufficient amount (volume) of outside air (atmosphere) may not be able to pass through the valve body Vt. That is, when the amount of change in operation dB is large, it is difficult for the negative pressure booster VB to generate an assisting force. Therefore, in the brake control device SC, when the amount of change in operation dB is large, the motor rotation speed Na is made larger than when the amount of change in operation dB is small. Even if a sudden operation (braking operation with a large amount of change in operation dB) is performed, a sufficient actual differential pressure Sj is ensured with high response by increasing the motor rotation speed Na.

<Other embodiments>
Other embodiments will be described below. Other embodiments also provide the same effects as described above.
In the embodiments described above, the brake control device SC was applied to a hybrid vehicle. Alternatively, the present invention may be applied to a vehicle (for example, a gasoline vehicle) that includes only an internal combustion engine IC as a power source, or a vehicle (that is, an electric vehicle) that includes only a driving motor MD as a power source. Note that a vehicle without an internal combustion engine IC is equipped with an electric negative pressure pump, and the booster negative pressure Pv is generated by the electric negative pressure pump.

In the embodiment described above, the target rotation speed Nt was adjusted to increase based on the amount of change in operation dB. The increase adjustment of the target rotational speed Nt based on the amount of change in operation dB may be performed only when the booster negative pressure Pv is smaller than the negative pressure threshold px. That is, in the increase adjustment, a permission condition based on the booster negative pressure Pv is added. Here, the negative pressure threshold px is a predetermined value (constant) set in advance. Specifically, the increase adjustment is prohibited when the booster negative pressure Pv is equal to or higher than the negative pressure threshold px (ie, when "Pv≧px"). In this case, even if the amount of change in operation dB is large, the increase adjustment is not performed, and the commanded rotation speed Ns is determined as the target rotation speed Nt. This is because when the booster negative pressure Pv is sufficient, a considerable actual differential pressure Sj is not required. On the other hand, when the booster negative pressure Pv is less than the negative pressure threshold px (that is, in the case of "Pv<px"), the increase adjustment is permitted. In this case, the increase calculation block NU calculates the rotation speed increase amount Nu based on the operation change amount dB, and the total value "Na+Nu" of the command rotation speed Ns and the rotation speed increase amount Nu is the target rotation speed. It is determined as the number Nt. As a result, the motor rotational speed Na is increased, so that a sufficient actual differential pressure Sj corresponding to the sudden operation of the brake operation member BP is generated.

In determining the target rotational speed Nt, the increase adjustment according to the amount of change in operation dB may be omitted. In this configuration, the command rotation speed Ns is calculated as the target rotation speed Nt (that is, "Nt=Ns" always). In any case, the target rotation speed Nt is set when the booster negative pressure Pv is small (i.e., the booster negative pressure Pv is insufficient) and when the booster negative pressure Pv is large (i.e., the booster negative pressure Pv is insufficient). (if sufficient).

<Summary of embodiments>
The embodiments of the brake control device SC will be summarized below.
The brake control device SC includes a master cylinder CM that outputs a master pressure Pm according to the operation amount Ba of the brake operation member BP, and a negative pressure that assists the operation force Fp of the brake operation member BP according to the operation amount Ba with negative pressure. Controls the pressure booster VB, the negative pressure sensor PV that controls the booster negative pressure Pv of the negative pressure booster VB, the fluid unit HU that increases master pressure Pm and supplies it to the wheel cylinder CW as wheel pressure Pw, and the fluid unit HU. A controller ECU is provided. Here, the fluid unit HU includes a fluid pump QB driven by an electric motor MB and a pressure regulating valve UB. Therefore, the electric motor MB and the pressure regulating valve UB are controlled by the controller ECU. Note that booster negative pressure Pv is supplied to the negative pressure booster VB by an internal combustion engine IC or an electric negative pressure pump.

In the brake control device SC, the controller ECU controls the rotation speed Na (motor rotation speed) of the electric motor MB based on the booster negative pressure Pv. Specifically, the controller ECU controls the rotation speed Na of the electric motor MB to be larger when the booster negative pressure Pv is small than when the booster negative pressure Pv is large. That is, as the booster negative pressure Pv decreases (decreases), the target rotation speed Nt of the electric motor MB is increased. Then, the electric motor MB is controlled so that the actual rotation speed Na matches the target rotation speed Nt.

In the negative pressure assist control executed by the brake control device SC, the required differential pressure Sj increases as the booster negative pressure Pv decreases. Therefore, in the brake control device SC, when the booster negative pressure Pv is small, the target rotation speed Nt (as a result, the motor rotation speed Na) is made larger than when the booster negative pressure Pv is large. By adjusting the motor rotation speed Na to increase, a sufficient flow rate of the brake fluid BF for generating the differential pressure Sj is ensured, so that the assisting force by the assisting control is generated in just the right amount (i.e., appropriately). .

In the controller ECU of the brake control device SC, based on the operation amount Ba (for example, operation displacement Sp) of the brake operation member BP, the amount of change dB (the amount of operation change, for example, operation speed dS) of the operation amount Ba with respect to time is determined. is calculated. Then, the motor rotation speed Na is increased based on the operation change amount dB. When the amount of change in operation dB of the brake operation member BP is large, the auxiliary force by the negative pressure booster VB is less likely to be generated than when the amount of change in operation dB is small. Therefore, the motor rotation speed Na is increased as the operation change amount dB increases. Thereby, even if a sudden operation is performed, the assisting force by the assisting control is appropriately controlled.

When the booster negative pressure Pv is large, it is not necessary to increase the motor rotation speed Na in accordance with the amount of operation change dB. Therefore, when the booster negative pressure Pv is equal to or higher than the negative pressure threshold value px (a preset constant), increasing adjustment of the motor rotation speed Na is prohibited. That is, the increase adjustment of the motor rotational speed Na based on the amount of change in operation dB is permitted and executed only when the booster negative pressure Pv is smaller than the predetermined negative pressure threshold px. Since the incremental adjustment is performed only when necessary, the reliability of the assist control can be improved.

SC...Brake control device, CM...Master cylinder, VB...Negative pressure booster, CW...Wheel cylinder, HU...Fluid unit, ECU...Brake controller (electronic control unit for SC), AP...Acceleration operation member (accelerator pedal), AA... Acceleration operation amount sensor, Aa... Acceleration operation amount, BP... Brake operation member (brake pedal), BA... Brake operation amount sensor, Ba... Brake operation amount, dB... Operation change amount (temporal change amount of Ba), BS ...Communication bus, UB...Pressure regulating valve, MB...Electric motor, QB...Fluid pump, PM...Master pressure sensor, Pm...Master pressure, Pq...Adjustment pressure, Pw...Wheel pressure, PV...Negative pressure sensor, Pv...Booster negative Pressure, Sj...Differential pressure (actual fluid pressure difference between Pm and Pq), St...Target differential pressure (target value related to Sj), Ns...Instructed rotation speed, Nt...Target rotation speed, Nu...Rotation speed increase amount, Na...Actual rotation speed (motor rotation speed).

Claims (3)

a master cylinder that outputs master pressure according to the amount of operation of the brake operation member;
a negative pressure booster that uses negative pressure to assist the operating force of the brake operating member according to the operating amount;
a negative pressure sensor that detects booster negative pressure of the negative pressure booster;
a fluid unit configured with a fluid pump driven by an electric motor and a pressure regulating valve, increasing the master pressure and supplying it to the wheel cylinder as wheel pressure;
a controller that controls the fluid unit;
In a braking control device for a vehicle comprising:
The controller is a braking control device for a vehicle that controls the rotation speed of the electric motor based on the booster negative pressure. The braking control device for a vehicle according to claim 1,
The controller is a braking control device for a vehicle that increases the rotational speed when the booster negative pressure is small compared to when the booster negative pressure is large. In the vehicle braking control device according to claim 2,
The controller is a braking control device for a vehicle that increases the rotational speed based on the amount of change in the manipulated variable over time.