Vehicle braking control system

Abstract

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

Description

Technical Field

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

Background Art

[0002] In Patent Document 1, in order to improve the braking feeling when the brake pedal is depressed with a force of a predetermined value or more in a state where the negative pressure of the vacuum booster is decreased, a master cylinder 35 capable of outputting a master cylinder pressure in response to a braking operation of the brake pedal 5, a vacuum booster 30 that assists the input to the master cylinder 35 by negative pressure, and a pump 70 that assists the master cylinder pressure by pump pressurization are provided. When the braking force obtained by the braking force sensor 15 exceeds a preset reference braking operation force, a target wheel cylinder pressure is set based on the master cylinder pressure obtained by the master cylinder pressure sensor 75, and the pump 70 is controlled based on the set target wheel cylinder pressure.

[0003] In Patent Document 2, even when the intake negative pressure of the engine decreases, for the purpose of preventing a decrease in braking force, an engine automatic stop / restart control means, a booster (tread force assist means) 14 that assists the driver's brake tread force using the intake negative pressure of the operating engine 1, and a pressurization control unit 21 that generates a required brake hydraulic pressure by a pump driven by an electric motor 26. In a braking control device (ECU) 13 of a vehicle provided with, when the vehicle is running in a state where the restart of the engine 1 cannot be confirmed after the restart condition is satisfied, and when the negative pressure of the booster 14 is equal to or higher than a set value (negative pressure shortage), the pressurization control unit 21 pressurizes the brake hydraulic pressure to compensate for the shortage of the assist force by the booster 14.

[0004] Patent documents 1 and 2 describe using an electric motor as a pressure source to assist the driver's braking force when the negative pressure in a negative pressure booster (referred to as "booster negative pressure") is insufficient. In this situation, it is necessary that the electric motor be appropriately controlled so that the assistance provided by the electric motor is neither excessive nor insufficient. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2009-120124 [Patent Document 2] Japanese Patent Publication No. 2013-060164 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] The object of the present invention is to provide a vehicle braking control device in which an electric motor is used as a pressure source to assist the operating force of a braking operating member, and in which the electric motor can be suitably controlled. [Means for solving the problem]

[0007] The vehicle braking control device (SC) according to the present invention comprises a master cylinder (CM) that outputs a master pressure (Pm) according to the amount of operation (Ba) of a braking operating member (BP), a negative pressure booster (VB) that assists the operating force (Fp) of the braking operating member (BP) according to the amount of operation (Ba) by negative pressure, a negative pressure sensor (PV) that detects the booster negative pressure (Pv) of the negative pressure booster (VB), a fluid unit (HU) which is composed of a fluid pump (QB) driven by an electric motor (MB) and a pressure regulating valve (UB) that increases the master pressure (Pm) and supplies it to a wheel cylinder (CW) as wheel pressure (Pw), and a controller (ECU) that controls the fluid unit (HU). The controller (ECU) controls the rotational speed (Na) of the electric motor (MB) based on the booster negative pressure (Pv). For example, the controller (ECU) increases the rotational speed (Na) when the booster negative pressure (Pv) is small compared to when the booster negative pressure (Pv) is large.

[0008] In a control system where an electric motor is used as a pressure source and the operating force of the braking mechanism is assisted (i.e., assisted control), a larger differential pressure Sj is required the more insufficient the booster negative pressure Pv is. According to the above configuration, when the booster negative pressure Pv is insufficient, the motor rotation speed Na is controlled to increase. As a result, sufficient brake fluid BF is discharged from the fluid pump QB, and the differential pressure Sj is reliably secured.

[0009] In the vehicle braking control device (SC) according to the present invention, the controller (ECU) increases the rotational speed (Na) based on the amount of change (dB) of the manipulated variable (Ba) with respect to time. When the amount of change of the manipulated variable dB is large, it may be difficult for the assisting force of the negative pressure booster VB to be generated. With the above configuration, even if a sudden operation (braking operation with a large amount of change of the manipulated variable dB) is performed, a sufficient differential pressure Sj is ensured with high responsiveness. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic diagram illustrating the overall structure of a vehicle equipped with a braking control system (SC). [Figure 2] This is a schematic diagram illustrating an example configuration of a fluid unit HU. [Figure 3] This is a characteristic diagram illustrating the overview of low negative pressure-assisted control. [Figure 4] This is a flowchart illustrating the process of low negative pressure assist control. [Modes for carrying out the invention]

[0011] <Symbols for constituent components, etc., and subscripts at the end of the symbols> In the following explanation, components, calculation processes, signals, characteristics, and values ​​that are denoted by the same symbol, such as "CW," represent the same function. The subscripts "f" and "r" at the end of the symbols related to each wheel are general symbols indicating whether they relate to the front or rear wheel system. For example, a wheel cylinder CW provided on each wheel is written as "front wheel cylinder CWf" and "rear wheel cylinder CWr." Furthermore, the subscripts "f" and "r" at the end of the symbols may be omitted. When the subscripts "f" and "r" are omitted, each symbol represents a general term. For example, "CW" is a general term for the wheel cylinders provided on the front and rear wheels of a vehicle.

[0012] In the fluid path from the master cylinder CM to the wheel cylinder CW, the side closer to the master cylinder CM (the side further from the wheel cylinder CW) is referred to as the "upper part," and the side closer to the wheel cylinder CW (the side further from the master cylinder CM) is referred to as the "lower part." Furthermore, in the circulating flow KL of the brake fluid BF in the fluid unit HU, the side closer to the discharge port of the fluid pump QB (the side further from the suction port) is referred to as the "upstream side," and the side closer to the suction port of the fluid pump QB (the side further from the discharge port) is referred to as the "downstream side."

[0013] The master cylinder CM, fluid unit HU, and wheel cylinder CW are connected by a fluid passage (connecting passage HS). Furthermore, various components (UB, etc.) in the fluid unit HU are connected by fluid passages. Here, a "fluid passage" is a path for moving the brake fluid BF, and includes piping, flow paths within actuators, hoses, etc. In the following explanation, the connecting passage HS, return passage HL, pressure reducing passage HG, etc., are fluid passages.

[0014] <Vehicles equipped with a braking control system (SC)> Referring to the schematic diagram in Figure 1, the overall configuration of a vehicle equipped with the braking control device SC according to the present invention will be described. For example, a hybrid type vehicle is employed. That is, the vehicle is equipped with two different power sources as prime movers (devices that convert energy into mechanical work): an internal combustion engine IC (also simply called the "engine") and a traction electric motor MD (also simply called the "trailer" or "drive motor"). The traction motor MD also functions as a generator for regenerating energy during vehicle deceleration, and is therefore also referred to as a "motor generator." Furthermore, the traction motor MD can also function as a starter for the internal combustion engine IC.

[0015] The engine control system (GC) installed in the vehicle consists of an internal combustion engine IC, a drive electric motor (MD), and an electronic control unit (ECG) for the engine (also called the "engine controller"). In the internal combustion engine IC, fuel such as gasoline is burned, and mechanical work is obtained from the combustion gases produced. The drive motor (MD) generates power using an onboard battery as its energy source. The internal combustion engine IC and the drive motor (MD) are controlled by the engine controller (ECG).

[0016] The motor control unit GC's controller ECG and the braking electronic control unit ECU (also called the "braking controller") of the braking control unit SC are connected via the communication bus BS. Various signals (Aa, Pv, FV, etc.) are shared between the motor controller ECG and the braking controller ECU via the communication bus BS.

[0017] In an internal combustion engine IC (for example, a gasoline engine), intake negative pressure is generated. The intake negative pressure is the pressure in the intake pipe (intake manifold) generated by the downward movement of the engine piston. The intake negative pressure increases during idling and at low loads when the throttle is closed, and decreases when the throttle is fully open.

[0018] The vehicle is equipped with an acceleration operation member AP. The acceleration operation member AP (for example, an accelerator pedal) is a member that the driver operates to accelerate the vehicle. An acceleration operation amount sensor AA for detecting the operation amount Aa (acceleration operation amount) of the acceleration operation member AP is provided. The acceleration operation amount Aa is one of the state quantities (state variables) indicating 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. In the prime mover controller ECG, the output of the prime mover (internal combustion engine IC, traveling motor MD) (and as a result, the driving force of the wheels) is adjusted based on the acceleration operation amount Aa. Also, the acceleration operation amount Aa is output to the communication bus BS and acquired by the brake controller ECU.

[0019] In the prime mover controller ECG, the operation of generating intake negative pressure is executed in response to a request from the brake control device SC (particularly, the brake controller ECU). The intake negative pressure is stored as the booster negative pressure Pv in the negative pressure booster VB. When the booster negative pressure Pv decreases, since the assisting force of the negative pressure booster VB decreases, the intake negative pressure is generated by the prime mover controller ECG in response to a request signal (for example, a request flag FV) from the brake control device SC. Specifically, the generation of the 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 "0" indicates that the generation of intake negative pressure is unnecessary, and "1" indicates that the generation of intake negative pressure is necessary. For example, when the internal combustion engine IC is in a stopped state, the internal combustion engine IC is started (activated) by the starter ST (or the traveling motor MD) by switching the request flag FV from "0" to "1", and the intake negative pressure is generated.

[0020] ≪Magnitude relationship of the booster negative pressure Pv≫ The booster negative pressure Pv is generated as a negative (-) value when the atmospheric pressure is set as the reference value "0 (zero)". However, when discussing the magnitude of the value, including the sign of the booster negative pressure Pv can make the explanation complicated. Therefore, hereinafter, the magnitude relationship will be explained based on the absolute value of the booster negative pressure Pv. Accordingly, "the booster negative pressure Pv is large" means that the absolute value (magnitude) of the booster negative pressure Pv is large, it has dropped more from the atmospheric pressure, and it is approaching a vacuum. Conversely, "the booster negative pressure Pv is small" means that the absolute value (magnitude) of the booster negative pressure Pv is small and it is approaching the atmospheric pressure.

[0021] The vehicle is equipped with a braking device. The braking device is composed of a brake caliper, a friction member (e.g., a brake pad), and a rotating member KT (e.g., a brake disc). A wheel cylinder CW is provided in the brake caliper (not shown). Due to the hydraulic pressure Pw ("wheel pressure") in the wheel cylinder CW, a friction member (not shown) is pressed against the rotating member KT fixed to each wheel WH. Thereby, a braking force is generated on the wheel WH.

[0022] The vehicle is equipped with a braking operation member BP. The braking operation member BP (e.g., a brake pedal) is a member that the driver operates to decelerate the vehicle. An operation displacement sensor SP for detecting the operation displacement Sp is provided on the braking operation member BP. The operation displacement Sp is one of the state quantities (state variables) indicating the degree of operation of the braking operation member BP.

[0023] The vehicle is equipped with various sensors to individually control the wheel pressure Pw of each wheel WH for anti-lock braking control, anti-skid control, etc. Specifically, each wheel WH is equipped with a wheel speed sensor VW to detect its rotational speed Vw (wheel speed). In addition, a steering amount sensor (not shown) is provided to detect the steering amount Sa of the steering control member (e.g., steering wheel), a yaw rate sensor (not shown) is provided to detect the vehicle's yaw rate Yr, a longitudinal acceleration sensor (not shown) is provided to detect the vehicle's longitudinal acceleration Gx, and a lateral acceleration sensor (not shown) is provided to detect the vehicle's lateral acceleration Gy. The signals for wheel speed Vw, steering amount Sa, yaw rate Yr, longitudinal acceleration Gx, and lateral acceleration Gy are input to the braking controller ECU.

[0024] The vehicle is equipped with a braking control system SC. The braking control system SC employs a so-called front and rear type (also called "Type II") braking system with two separate braking systems. The actual wheel pressure Pw is adjusted by the braking control system SC. The braking control system SC consists of a master cylinder CM, a vacuum booster VB, a fluid unit HU, and a braking controller ECU.

[0025] A tandem type master cylinder CM is employed. Specifically, a primary master piston NM and a secondary master piston NN are inserted into the master cylinder CM. The two master pistons NM and NN divide the inside of the master cylinder CM into two hydraulic chambers Rmf and Rmr (=Rm). The front wheel and rear wheel hydraulic chambers Rmf and Rmr are referred to as the "front wheel and rear wheel master chambers." The master pistons NM and NN are moved in conjunction with the braking operating member BP via the operating rod RD.

[0026] When the braking mechanism BP is not operated (non-braking), the master pistons NM and NS are in their most retracted position (i.e., the position where the volume of the master chamber Rm is maximum). In this state, the master chamber Rm of the master cylinder CM and the master reservoir RV are in communication. The master reservoir RV is also called the "atmospheric pressure reservoir" and is a tank for the working fluid, storing the braking fluid BF inside.

[0027] When the braking operating 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). This movement disconnects the communication between the master chamber Rm and the master reservoir RV. When the master pistons NM and NS are moved further in the forward direction, the internal pressures of the front and rear wheel master chambers Rmf and Rmr, respectively, the front and rear wheel master pressures Pmf and Pmr (=Pm), increase from "0 (atmospheric pressure)". As a result, the brake fluid BF, pressurized to the master pressure Pm, is output (pressurized) from the master chamber Rm of the master cylinder CM. When the braking operating member BP is returned, the master pistons NM and NN are moved in the reverse direction (the direction in which the volume of the master chamber Rm increases), opposite to the forward direction, and the brake fluid BF is returned towards the master cylinder CM.

[0028] The front and rear wheel master chambers Rmf and Rmr (=Rm) of the tandem-type master cylinder CM, and the front and rear wheel cylinders CWf and CWr (=CW) are connected by the front and rear wheel connecting passages HSf and HSr (=HS). The connecting passage HS is a fluid passage that connects the master cylinder CM and the wheel cylinder CW. Within the fluid unit HU, the front and rear wheel connecting passages HSf and HSr each branch into two and connect to the front and rear wheel cylinders CWf and CWr.

[0029] The master cylinder CM is equipped with a negative pressure booster VB. The negative pressure booster VB is a power assist device that uses intake negative pressure to assist the operating force Fp of the braking operating member BP. The negative pressure booster VB is positioned between the braking operating member BP and the master cylinder CM. The inside of the negative pressure booster VB is divided into two gas chambers Rv and Ro by a diaphragm Dm. Gas chamber Rv is referred to as the "negative pressure chamber," and gas chamber Ro is referred to as the "atmospheric pressure chamber."

[0030] The vacuum chamber Rv is located on the master cylinder CM side in the vacuum booster VB. Intake vacuum pressure is introduced (supplied) to the vacuum chamber Rv from the internal combustion engine IC (especially the intake manifold) via the vacuum hose VH, and is stored there. The internal pressure of the vacuum chamber Rv is the booster vacuum pressure Pv.

[0031] The atmospheric pressure chamber Ro is located on the side of the braking operating member BP in the negative pressure booster VB. Within the atmospheric pressure chamber Ro, the valve body Vt is coupled to the operating rod RD. When the braking operating 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.

[0032] When the braking operating member BP is operated and the operating rod RD is moved forward toward the master cylinder CM, the valve body Vt opens. This introduces outside air (atmospheric pressure) into the atmospheric pressure chamber Ro. The pressure in the atmospheric pressure chamber Ro approaches atmospheric pressure, creating a pressure difference between it and the booster negative pressure Pv, which is the pressure in the negative pressure chamber Rv. This pressure difference causes a thrust force to act on the diaphragm Dm in the direction of the master cylinder CM (i.e., the forward direction). This thrust force assists the operating force Fp of the braking operating member BP. In other words, in the negative pressure booster VB, the operating force Fp of the braking operating member BP is reduced by the pressure difference between the booster negative pressure Pv and atmospheric pressure.

[0033] The negative pressure booster VB (especially the negative pressure chamber Rv) is equipped with a booster negative pressure sensor PV (also simply called a "negative pressure sensor") to detect the booster negative pressure Pv. As mentioned above, the smaller the booster negative pressure Pv, the closer the internal pressure of the negative pressure chamber Rv is to atmospheric pressure "0", indicating insufficient negative pressure in the negative pressure booster VB. Conversely, the larger the booster negative pressure Pv, the closer the internal pressure of the negative pressure chamber Rv is to a vacuum, indicating sufficient negative pressure in the negative pressure booster VB. The booster negative pressure Pv signal is input to the braking controller ECU.

[0034] A fluid unit HU is installed between the master cylinder CM and the wheel cylinder CW. The fluid unit HU is a device for performing independent control of each wheel, such as anti-lock brake control, traction control, and anti-skid control. In addition, when the booster vacuum Pv of the vacuum booster VB decreases, the fluid unit HU provides assistance to the vacuum booster VB by increasing the braking force Fp. This control is referred to as "low vacuum assist control".

[0035] The fluid unit HU can increase the master pressure Pm output from the master cylinder CM and supply wheel pressure Pw to the wheel cylinder CW. The fluid unit HU is controlled by the braking electronic control unit ECU (braking controller). The braking controller ECU is connected to the prime mover controller ECG via a communication bus BS. Signal transmission between multiple controllers (ECU, ECG, etc.) is performed via the communication bus BS. In other words, multiple controllers can send signals (detected values, calculated values, control flags, etc.) to the communication bus BS and can also receive signals from the communication bus BS.

[0036] <Fluid Unit HU> Referring to the schematic diagram in Figure 2, an example configuration of the fluid unit HU will be explained. The fluid unit HU is a device for performing low negative pressure assist control. The fluid unit HU is supplied with front wheel and rear wheel master pressures Pmf and Pmr (=Pm) from the master cylinder CM. The fluid unit HU then adjusts (increases or decreases) the front wheel and rear wheel master pressures Pmf and Pmr, and outputs them as hydraulic pressures Pwf and Pwr (front wheel and rear wheel pressures) for the front wheel and rear wheel cylinders CWf and CWr.

[0037] The fluid unit HU is installed in the communication passage HS between the master cylinder CM and the wheel cylinder CW. The fluid unit HU consists of 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.

[0038] Front and rear wheel pressure regulating valves UBf and UBr (=UB) are installed in the front and rear wheel connecting passages HSf and HSr (=HS). Pressure regulating valve UB is a normally open type linear solenoid valve (differential pressure valve). Pressure regulating valve UB allows the wheel pressure Pw to be individually increased from the master pressure Pm in the front and rear wheel systems.

[0039] Front and rear wheel master pressure sensors PMf and PMr (=PM) are installed above the front and rear wheel pressure regulating valves UBf and UBr (in the communication passage HS on the side closer to the master cylinder CM) to detect the actual fluid pressure Pmf and Pmr (front and rear wheel master pressure) supplied from the master cylinder CM (particularly the front and rear wheel master chambers Rmf and Rmr). The master pressure sensor PM is built into the fluid unit HU. The signals for the front and rear wheel master pressures Pmf and Pmr (=Pm) are input to the braking controller ECU. Since the front wheel master pressure Pmf and the rear wheel master pressure Pmr are essentially the same, either the front or rear wheel master pressure sensors PMf or 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.

[0040] The upper part of the front and rear wheel pressure regulating valves UBf and UBr (the part of the communication passage HS closer to the master cylinder CM) and the lower part of the front and rear wheel pressure regulating valves UBf and UBr (the part of the communication passage HS closer to the wheel cylinder CW) are connected by the front and rear wheel return passages HLf and HLr. The front and rear wheel fluid pumps QBf and QBr (=QB) and the front and rear wheel pressure regulating reservoirs RBf and RBr (=RB) are provided in the front and rear wheel return passages HLf and HLr. The fluid pump QB is driven by an electric motor MB.

[0041] When the electric motor MB is driven, the fluid pump QB draws the brake fluid BF into the upper part of the pressure regulating valve UB and discharges it to the lower part of the pressure regulating valve UB. This creates a circulating flow KL of brake fluid BF (i.e., the front and rear wheel circulating flows KLf and KLr, indicated by the dashed arrows) in the connecting passage HS and the return passage HL, including the fluid pump QB and the pressure regulating reservoir RB. When the flow path of the connecting passage HS is narrowed by the pressure regulating valve UB, and the circulating flow KL of brake fluid BF is restricted, the orifice effect causes the hydraulic pressure Pq ("regulating pressure") at the lower part of the pressure regulating valve UB to increase from the hydraulic pressure Pm (master pressure) at the upper part of 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 (regulating pressure) with respect to the pressure regulating valve UB is regulated by the pressure regulating valve UB. Furthermore, regarding the relationship between the master pressure Pm and the regulating pressure Pq, the regulating pressure Pq is greater than or equal to the master pressure Pm (i.e., "Pq ≥ Pm").

[0042] Inside the fluid unit HU, the front and rear wheel connecting passages HSf and HSr are each branched into two, and connected to the front and rear wheel cylinders CWf and CWr, respectively. To allow individual adjustment of each wheel pressure Pw, a normally open inlet valve VI and a normally closed outlet valve VO are provided for each wheel cylinder CW. Specifically, the inlet valve VI is located in the branched connecting passage HS (i.e., on the side of the connecting passage HS closer to the wheel cylinder CW at the branching point). The connecting passage HS is connected to the pressure regulating reservoir RB via a pressure reducing passage HG at the lower part of the inlet valve VI (the part of the connecting passage HS closer to the wheel cylinder CW). The outlet valve VO is located in the pressure reducing passage HG. On / off type solenoid valves are used as the inlet valve VI and the outlet valve VO. The inlet valve VI and the outlet valve VO allow the wheel pressure Pw to be individually reduced from the regulated pressure Pq at each wheel.

[0043] The wheel pressure Pw is independently adjusted for each wheel cylinder CW by driving the inlet valve VI and the outlet valve VO. To decrease the wheel pressure Pw, the inlet valve VI is closed and the outlet valve VO is opened. This prevents the inflow of brake fluid BF into the wheel cylinder CW, and the brake fluid BF in the wheel cylinder CW flows out to the pressure regulating reservoir RB, thus decreasing the wheel pressure Pw. To increase the wheel pressure Pw, the inlet valve VI is opened and the outlet valve VO is closed. This prevents the outflow of brake fluid BF to the pressure regulating reservoir RB, and the regulating pressure Pq from the pressure regulating valve UB is supplied to the wheel cylinder CW, thus increasing the wheel pressure Pw. Here, the upper limit of the increase in wheel pressure Pw is up to the regulating pressure Pq. To maintain the wheel pressure Pw, both the inlet valve VI and the outlet valve VO are closed. The wheel cylinder CW is fluidically sealed, so the wheel pressure Pw is maintained at a constant level.

[0044] If power is not supplied to the inlet valve VI and the outlet valve VO, and their operation is stopped, the inlet valve VI will open and the outlet valve VO will close. In this state, the wheel pressure Pw is equal to the regulated pressure Pq (i.e., "Pq = Pw").

[0045] The fluid unit HU is controlled by the brake controller ECU. The brake controller ECU consists 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.

[0046] The braking controller ECU (specifically the microprocessor MP) receives inputs of wheel speed Vw, steering amount Sa, yaw rate Yr, longitudinal acceleration Gx, and lateral acceleration Gy. Based on the wheel speed Vw, the braking controller ECU calculates the vehicle speed Vx. The braking controller ECU then performs the following independent wheel controls. Specifically, these independent wheel controls include anti-lock braking control (so-called ABS control) to prevent wheel lock, traction control to suppress wheelspin of the drive wheels, and anti-skid control (so-called ESC) to improve the vehicle's directional stability by suppressing understeer and oversteer. In addition, the braking controller ECU receives a signal of booster vacuum Pv detected by the vacuum sensor PV, and based on the booster vacuum Pv, the low vacuum assist control described above is performed.

[0047] In the braking controller ECU, the drive circuit DR is controlled according to a control algorithm programmed into the microprocessor MP. Specifically, the drive circuit DR drives the electric motor MB and various solenoid valves (UB, etc.) that constitute the fluid unit HU. The drive circuit DR has an H-bridge circuit made up of switching elements (e.g., MOS-FETs) to drive the electric motor MB. The drive circuit DR is also equipped with switching elements to drive various solenoid valves (UB, etc.). In addition, the drive circuit DR includes a motor current sensor (not shown) that detects the supply current In (actual value) to the electric motor MB, and a current sensor (not shown) that detects the supply current Ib (actual value, referred to as "supply current") to the pressure regulating valve UB. Based on the control algorithm of the microprocessor MP, the drive signal Ub for the pressure regulating valve UB, the drive signal Vi for the inlet valve VI, the drive signal Vo for the outlet valve VO, and the drive signal Mb for the electric motor MB are calculated. Then, based on the drive signal (Ub, etc.), the drive circuit DR controls the electric motor MB and the solenoid valves UB, VI, and VO.

[0048] During low-negative-pressure-assisted control, the inlet valve VI and outlet valve VO are not driven (power is not supplied), while the electric motor MB and pressure regulating valve UB are driven. Therefore, the inlet valve VI remains open and the outlet valve VO remains closed, and the regulated pressure Pq is output from the fluid unit HU as the wheel pressure Pw. In other words, in low-negative-pressure-assisted control, the regulated pressure Pq and the wheel pressure Pw are equal.

[0049] <Low negative pressure assist control> Referring to the characteristic diagram in Figure 3, the overview of low negative pressure assist control will be explained. In the characteristic diagram, the change in wheel pressure Pw (hydraulic pressure of the wheel cylinder CW) is plotted in relation to the amount Ba of the braking operating member BP operated by the driver. Here, the braking operating amount Ba is a state quantity (state variable) that represents the degree of operation of the braking operating member BP, and corresponds to at least one of the operating displacement Sp and the operating force Fp.

[0050] The assistance of the driver's braking force Fp by a negative pressure booster VB is called "negative pressure assistance." Negative pressure assistance reduces the operating force Fp required to generate master pressure Pm (and consequently wheel pressure Pw). The increase of the hydraulic pressure Pm (master pressure) generated by the master cylinder CM by a fluid pump QB (i.e., electric pump) driven by an electric motor MB (i.e., low negative pressure assistance control) is called "electric pump assistance." Because electric pump assistance increases the wheel pressure Pw from the master pressure Pm, the braking force Fp required to generate the wheel pressure Pw is reduced.

[0051] In Figure 3, the characteristic line Cho represents the braking characteristics of the braking control device SC. Specifically, the characteristic line Cho represents the characteristics of the wheel pressure Pw that should be generated in response to the braking operation amount Ba. The characteristic line Cha represents the characteristics when neither negative pressure assistance nor electric pump assistance is provided. Specifically, the characteristic line Cha represents the characteristics when the master pressure Pm (and consequently the wheel pressure Pw) is generated solely by the driver's muscle strength. These characteristics are determined by geometrical parameters such as the lever ratio of the braking operation member BP, and the pressure-receiving area of ​​the cylinder CM and CW.

[0052] Characteristic line Chb represents the characteristics when electric pump assistance is not performed and only negative pressure assistance is applied. In other words, characteristic line Chb represents the relationship between the master pressure Pm and the braking amount Ba when the fluid unit HU is not operating but the negative pressure booster VB is operating. Characteristic line Chb is expressed as a characteristic parallel to characteristic line Cha, starting from the limit point (G). Here, the limit point (G) is also called the "modulation point" and is the point where the negative pressure assistance reaches its limit (maximum value). At the limit point (G), the assisting force generated by the negative pressure booster VB (the force assisting the driver's operating force Fp) reaches its upper limit. Therefore, negative pressure assistance can be performed in the region between characteristic line Cha and characteristic line Chb.

[0053] Above characteristic curve Chb, low-negative-pressure assist control is performed by the fluid unit HU. When the braking manipulator Ba is greater than the value Bg corresponding to the limit point (G) (referred to as the "limit manipulator"), electric pump assist is provided by the low-negative-pressure assist control. This can compensate for the decrease in the increasing gradient of wheel pressure Pw (the change in wheel pressure Pw with respect to braking manipulator Ba) even when the braking manipulator Ba exceeds the limit manipulator Bg. As a result, wheel pressure Pw can be generated along characteristic curve Cho.

[0054] For example, if the braking operation amount Ba is value ba and is relatively small (i.e., "Ba ≤ Bg"), low negative pressure assist control is not performed. In this case, the master pressure Pm (value pa) output from the master cylinder CM is supplied directly to the wheel cylinder CW as the wheel pressure Pw (value pa). On the other hand, if the braking operation amount Ba is value bb and is relatively large (i.e., "Ba > Bg"), low negative pressure assist control is performed. In this case, the master pressure Pm (value pb) output from the master cylinder CM is increased by 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.

[0055] The limit point (G) (coordinates (Bg,Pg)) varies depending on the magnitude of the booster negative pressure Pv. When the booster negative pressure Pv decreases (i.e., when the booster negative pressure Pv approaches atmospheric pressure "0"), the limit point (G) moves along the characteristic curve Cho toward the origin O (coordinates (0,0)). On the other hand, when the booster negative pressure Pv increases (i.e., when the booster negative pressure Pv approaches vacuum), the limit point (G) moves along the characteristic curve Cho toward the origin O (coordinates (0,0)). Therefore, the conditions under which negative pressure-assisted control is performed (i.e., the limiting variable Bg) depend on the booster negative pressure Pv.

[0056] <Processing of low negative pressure assist control> Referring to the flow diagram in Figure 4, the process of low negative pressure assist control (also simply called "assist control") will be explained. In assist control, the master pressure Pm is increased by the fluid unit HU in response to 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, thereby increasing the master pressure Pm, which is then output as wheel pressure Pw to the wheel cylinder CW. The assist control algorithm is programmed into the microprocessor MP of the brake controller ECU. Therefore, assist control is executed by the brake control device SC (particularly the brake controller ECU).

[0057] In step S110, detection signals (Ba, Pv, etc.) from various sensors (BA, PV, etc.) are acquired. The braking amount Ba detected by the braking amount sensor BA is acquired. "Braking amount Ba" is a general term for state quantities that represent the degree of operation of the braking operating member BP. "Braking amount sensor BA" is a general term for sensors that detect these quantities. Specifically, the operating displacement Sp of the braking operating member BP and the operating force Fp of the braking operating member BP correspond to the braking amount Ba. The operating displacement sensor SP that detects the operating displacement Sp and the operating force sensor FP that detects the operating force Fp correspond to the braking amount sensor BA. In other words, in step S110, the braking amount Ba is determined based on at least one of the operating displacement Sp detected by the operating displacement sensor SP and the operating force Fp detected by the operating force sensor FP, and is loaded into the assist control algorithm.

[0058] In step S110, the booster negative pressure Pv detected by the negative pressure sensor PV is further acquired. The 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 used 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.

[0059] In step S120, the limit point (G) is determined based on the booster negative pressure Pv. The negative pressure booster VB generates an assisting force against the operating force Fp based on the booster negative pressure Pv, and the limit point (G) is the point where this assisting force reaches its limit (see Figure 3). In step S120, the limit operating amount Bg is set as the limit point (G). Here, the "limit operating amount Bg" corresponds to the braking operating amount Ba at which the electric pump assist begins. Specifically, the limit operating amount Bg is calculated based on the booster negative pressure Pv, the specifications of the negative pressure booster VB (pressure-receiving area of ​​the diaphragm Dm, etc.), and the specifications of the master cylinder CM and wheel cylinder CW (pressure-receiving area of ​​various cylinders CM and CW, etc.). The limit operating amount Bg is determined to be larger as the booster negative pressure Pv increases.

[0060] In step S130, the calculation map Zst is set based on the limit operating amount Bg calculated from the booster negative pressure Pv, as shown in the calculation map setting block ZST. The "calculation map Zst" is a calculation characteristic related to the control of the pressure regulating valve UB for adjusting the regulating pressure Pq (i.e., wheel pressure Pw). For example, in step S130, the relationship between the braking operating amount Ba and the target differential pressure St (also called the "target differential pressure characteristic") is determined as the calculation map Zst. Here, the target differential pressure St is the target value for the differential pressure Sj (actual value) between the regulating pressure Pq (=Pw) ​​and the master pressure Pm.

[0061] 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 negative pressure assist region is expanded. As the demand for assist control decreases, the calculation map Zst (target differential pressure characteristic) is set to make it more difficult to perform the control. 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 negative pressure assist region is reduced. As the demand for assist control increases, the calculation map Zst is set to make it easier to perform the control (see Figure 3 above).

[0062] 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 is "0" when the braking amount Ba is less than or equal to the limit amount Bg. When the braking amount Ba is greater than the limit amount Bg, the calculation map Zst is set so that the target differential pressure St increases as the braking amount Ba increases. The limit amount Bg is determined to be smaller as the booster negative pressure Pv decreases and larger as the booster negative pressure Pv increases. For this reason, the calculation map Zst is set to shift parallel along the X-axis (horizontal axis) in the direction of decrease 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 amount Ba, the target differential pressure St is calculated to be larger as the booster negative pressure Pv decreases and smaller as the booster negative pressure Pv increases. In other words, in assist control, even with the same braking operation amount Ba, the target differential pressure St is determined to be larger when the booster negative pressure Pv is small compared to when the booster negative pressure Pv is large.

[0063] In step S140, the necessity of assistive control is determined based on the braking operation amount Ba and the booster negative pressure Pv. Specifically, the necessity is determined based on whether the braking operation amount Ba is greater than or equal to the determination operation amount Bh, which is set based on the booster negative pressure Pv. Here, the determination operation amount Bh is a value that is smaller than the limit operation amount Bg by a predetermined amount bh (constant) (i.e., "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 assistive control is not necessary, the process returns to step S110. On the other hand, if the braking operation amount Ba is greater than the determination operation amount Bh and it is determined that assistive control is necessary, the process proceeds to step S150.

[0064] The need for assistive control is determined by a judgment variable Bh that is a predetermined amount bh smaller than the limit variable Bg, thereby improving the responsiveness of the control. The master pressure Pm is actually increased by assistive control only when the target differential pressure St is calculated to be greater than "0" (i.e., "Ba > Bg"). However, since starting the electric motor MB takes time, the execution of assistive control (especially the starting of the electric motor MA) begins before the braking variable Ba becomes greater than or equal to the limit variable Bg. This suppresses the time delay required to start the electric motor MB.

[0065] In step S150, the target differential pressure St (a 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.

[0066] In step S160, the target rotational speed Nt for the electric motor MB is calculated based on the booster negative pressure Pv. The "target rotational speed Nt" is a target value that corresponds to the actual rotational speed Na (also called "motor rotational speed") of the electric motor MB. First, as shown in the indicated rotational speed calculation block NS, the indicated rotational speed Ns is calculated based on the booster negative pressure Pv and a preset calculation map Zns. The "indicated rotational speed Ns" is one of the target values ​​for calculating the target rotational speed Nt. In the calculation map Zns, the indicated rotational speed Ns is determined to increase as the booster negative pressure Pv decreases. The calculation map Zns is provided with an upper limit rotational speed nj and a lower limit rotational speed nk for the indicated rotational speed Ns. The upper and lower limit rotational speeds nj and nk are preset predetermined values ​​(constants).

[0067] The calculation map Zns of the indicated rotational speed calculation block NS can be set in two stages, as shown by the dashed line characteristic. Specifically, when the booster negative pressure Pv is greater than or equal to a predetermined negative pressure po, the indicated rotational speed Ns is determined to the first predetermined rotational speed nk (initial value and lower limit). On the other hand, when the booster negative pressure Pv decreases and falls below the predetermined negative pressure po, the indicated rotational speed Ns is increased from the first predetermined rotational speed nk and determined to the second predetermined rotational speed nj (upper limit). The predetermined negative pressure po is a predetermined value (constant) set in advance. Note that the indicated rotational speed Ns may be increased in multiple stages as the booster negative pressure Pv decreases.

[0068] In any case, in step S160, the indicated rotational speed Ns increases in accordance with the decrease in booster negative pressure Pv. Therefore, when the booster negative pressure Pv is small, the indicated rotational speed Ns is calculated to be larger compared to when the booster negative pressure Pv is large.

[0069] Next, in step S160, the braking amount Ba is differentiated with respect to time to calculate the change in braking amount Ba with respect to time dB (also called the "operation change amount"). For example, the operating speed dS, which is the change in operating displacement Sp with respect to time, is used as the operation change amount dB. Then, the target rotational 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 the pre-set calculation map Znu. The "rotational speed increase amount Nu" is the target value for increasing the target rotational speed Ns. The calculation map Znu is set to an upper limit increase amount nm for the rotational speed increase amount Nu. The upper limit increase amount nm is a pre-set predetermined value (constant). The rotational speed increase amount Nu is added to the target rotational speed Ns to calculate the final target value, the target rotational speed Nt (i.e., "Nt = Ns + Nu").

[0070] The operation map Znu of the increase amount calculation block NU can be set in two steps, like the characteristics shown by the dashed line. Specifically, when the amount of operation change dB is less than the predetermined speed do, the rotation speed increase amount Nu is determined to be "0". Therefore, when "dB < do", the indicated rotation speed Ns is calculated as the target rotation speed Nt as it is (i.e., "Nt = Ns"). On the other hand, when the amount of operation change dB is equal to or greater than the predetermined speed do, the rotation speed increase amount Nu is increased from "0" and determined to be the predetermined increase amount nm. Therefore, the predetermined increase amount nm (which is "= Nu", a preset constant) is added to the indicated rotation speed Ns to calculate the target rotation speed Nt (i.e., "Nt = Ns + nm"). Note that the indicated rotation speed Ns may be increased in multiple steps as the amount of operation change dB increases.

[0071] In step S170, the electric motor MB is controlled (driven) based on the target rotation speed Nt and the 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 so that the actual value Na approaches and matches the target value Nt. Here, the motor rotation speed Na is calculated based on the detection value (motor rotation angle) of the 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. The supply current Im to the electric motor MB (also referred to as "motor current") is adjusted by the motor drive signal Mb. When "Nt > Na", the motor current Im is increased so that the motor rotation speed Na increases. On the other hand, when "Nt < Na", the motor current Im is decreased so that the motor rotation speed Na decreases.

[0072] 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 required 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. Further, in step S180, based on the target current It (target value) and the supply current Ib (actual value), a drive signal Ub (pressure regulating valve drive signal) is determined so that the supply current Ib approaches and matches the target current It. 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 matches the target differential pressure St. In a configuration equipped with a hydraulic sensor for detecting the regulated pressure Pq, the target current It may be finely adjusted based on the hydraulic differential pressure Sj (actual value of the differential pressure) between the regulated pressure Pq (detected value) and the master pressure Pm (detected value).

[0073] In the boost control, the greater the shortage of the booster negative pressure Pv, the greater the actual differential pressure Sj required, so the target differential pressure St is calculated to be large. For this reason, in the braking control device SC, when the booster negative pressure Pv is small (i.e., when the booster negative pressure Pv is insufficient), the target rotational speed Nt is determined to be greater than when the booster negative pressure Pv is large (i.e., when the booster negative pressure Pv is sufficient). Thereby, the discharge of the braking fluid BF from the fluid pump QB is sufficiently performed, so the actual differential pressure Sj is surely ensured.

[0074] To ensure a sufficient actual differential pressure Sj, it is 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 (i.e., when the booster negative pressure Pv is relatively large, for example, when "Pv≧po"), the electric motor MB is driven at a rotational speed Na greater than necessary. This presents a problem in terms of the power consumption of the electric motor MB. In the braking control device SC, the target rotational speed Nt is determined according to the booster negative pressure Pv, thus suppressing the power consumption of the braking control device SC.

[0075] Furthermore, in the braking control device SC, the target rotational speed Nt is increased in accordance with the increase in the time-varying amount dB (operation change amount) of the braking operating member BP. As described above, in the negative pressure booster VB, air is introduced into the atmospheric pressure chamber Ro through the valve body Vt, and an assisting force is generated by the pressure difference between the internal pressure of the negative pressure chamber Rv (booster negative pressure Pv) and the internal pressure of the atmospheric pressure chamber Ro (ultimately atmospheric pressure). When the operation change amount dB is large, a sufficient amount (volume) of outside air (atmosphere) may not be able to pass through the valve body Vt. In other words, when the operation change amount dB is large, it is difficult to generate an assisting force from the negative pressure booster VB. For this reason, in the braking control device SC, when the operation change amount dB is large, the motor rotational speed Na is increased compared to when the operation change amount dB is small. Even when sudden operation (braking operation with a large operation change amount dB) is performed, a sufficient actual differential pressure Sj is ensured with high response by increasing the motor rotational speed Na.

[0076] <Other Embodiments> Other embodiments will be described below. The same effects as described above will be achieved in the other embodiments as well. In the embodiment described above, the braking control device SC was applied to a hybrid vehicle. Alternatively, it may be applied to a vehicle equipped only with an internal combustion engine IC (e.g., a gasoline vehicle) or a vehicle equipped only with a traction motor MD (i.e., an electric vehicle). In vehicles without an internal combustion engine IC, an electric vacuum pump is provided, and this electric vacuum pump generates a booster vacuum Pv.

[0077] In the above-described embodiment, based on the operation change amount dB, the target rotational speed Nt was adjusted to increase. The increase adjustment of the target rotational speed Nt based on the operation change amount dB may be executed only when the booster negative pressure Pv is smaller than the negative pressure threshold value px. That is, in this increase adjustment, a permission condition based on the booster negative pressure Pv is added. Here, the negative pressure threshold value px is a preset predetermined value (constant). Specifically, the increase adjustment is prohibited when the booster negative pressure Pv is greater than or equal to the negative pressure threshold value px (that is, in the case of "Pv≥px"). In this case, even if the operation change amount dB is large, the increase adjustment is not performed, and the indicated rotational speed Ns is determined as the target rotational speed Nt. This is because when the booster negative pressure Pv is sufficient, such a large actual differential pressure Sj is not required. On the other hand, when the booster negative pressure Pv is less than the negative pressure threshold value px (that is, in the case of "Pv<px"), the increase adjustment is permitted. In this case, in the rotation speed increase amount calculation block NU, the rotation speed increase amount Nu is calculated based on the operation change amount dB, and the total value "Ns+Nu" of the indicated rotational speed Ns and the rotation speed increase amount Nu is determined as the target rotational speed Nt. Thereby, since the motor rotational speed Ns is increased, a sufficient actual differential pressure Sj corresponding to the rapid operation of the braking operation member BP is generated.

[0078] In the determination of the target rotational speed Nt, the increase adjustment according to the operation change amount dB may be omitted. In this configuration, the indicated rotational speed Ns is calculated as the target rotational speed Nt (that is, always, "Nt=Ns"). In any case, the target rotational speed Nt is determined to be larger when the booster negative pressure Pv is small (that is, when the booster negative pressure Pv is insufficient) compared to when the booster negative pressure Pv is large (that is, when the booster negative pressure Pv is sufficient).

[0079] <Summary of the Embodiment> Hereinafter, the embodiments of the braking control device SC will be summarized. The braking control device SC includes a master cylinder CM that outputs a master pressure Pm according to the operating amount Ba of the braking operating member BP, a negative pressure booster VB that assists the operating force Fp of the braking operating member BP according to the operating amount Ba using negative pressure, a negative pressure sensor PV that sets the booster negative pressure Pv of the negative pressure booster VB, a fluid unit HU that increases the master pressure Pm and supplies it to the wheel cylinder CW as wheel pressure Pw, and a controller ECU that controls the fluid unit HU. Here, the fluid unit HU consists of 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. The booster negative pressure Pv is supplied to the negative pressure booster VB by an internal combustion engine IC or an electric negative pressure pump.

[0080] In the braking control system SC, the controller ECU controls the rotational speed Na (motor speed) of the electric motor MB based on the booster vacuum Pv. Specifically, when the booster vacuum Pv is low, the controller ECU controls the rotational speed Na of the electric motor MB to be higher than when the booster vacuum Pv is high. In other words, as the booster vacuum Pv decreases, the target rotational speed Nt of the electric motor MB increases. The electric motor MB is then controlled so that the actual rotational speed Na matches the target rotational speed Nt.

[0081] In the negative pressure assist control performed by the braking control device SC, the required differential pressure Sj increases as the booster negative pressure Pv decreases. Therefore, when the booster negative pressure Pv is small, the braking control device SC increases the target rotational speed Nt (and consequently the motor rotational speed Na) compared to when the booster negative pressure Pv is large. By adjusting the motor rotational speed Na to increase, a sufficient flow rate of the braking fluid BF is ensured to generate the differential pressure Sj, so that the assist force from the assist control is generated without excess or deficiency (i.e., appropriately).

[0082] In the controller ECU of the braking control device SC, the change in the operating amount Ba (e.g., operating displacement Sp) of the braking operating member BP with respect to time is calculated in dB (operating change amount, e.g., operating speed dS). Then, the motor rotation speed Na is increased based on the operating change amount dB. When the operating change amount dB of the braking operating member BP is large, the assisting force from the negative pressure booster VB is less likely to be generated compared to when the operating change amount dB is small. For this reason, the motor rotation speed Na is increased in accordance with the increase in the operating change amount dB. As a result, even when sudden operation is performed, the assisting force from the assisting control is appropriately controlled.

[0083] When the booster negative pressure Pv is large, an increase in motor speed Na in accordance with the change in operating amount dB is unnecessary. Therefore, if the booster negative pressure Pv is greater than or equal to the negative pressure threshold px (a preset constant), the motor speed Na increase adjustment is prohibited. In other words, the motor speed Na increase adjustment based on the change in operating amount dB is permitted and executed only when the booster negative pressure Pv is less than the predetermined negative pressure threshold px. Since this increase adjustment is executed only when necessary, the reliability of the assistive control can be improved. [Explanation of Symbols]

[0084] SC... Brake control device, CM... Master cylinder, VB... Vacuum booster, CW... Wheel cylinder, HU... Fluid unit, ECU... Brake controller (electronic control unit for SC), AP... Acceleration operating member (accelerator pedal), AA... Acceleration operating amount sensor, Aa... Acceleration operating amount, BP... Brake operating member (brake pedal), BA... Brake operating amount sensor, Ba... Brake operating amount, dB... Operation change amount (time 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... Regulating pressure, Pw... Wheel pressure, PV... Vacuum sensor, Pv... Booster vacuum, Sj... Differential pressure (actual fluid pressure difference between Pm and Pq), St... Target differential pressure (target value related to Sj), Ns... Indicated rotational speed, Nt... Target rotational speed, Nu... Rotational speed increase amount, Na... Actual rotational speed (motor rotational speed).

Claims

1. A master cylinder that outputs master pressure according to the amount of operation of the braking operating member, A negative pressure booster assists the operating force of the braking operating member according to the amount of operation by negative pressure, A negative pressure sensor for detecting the negative pressure of the negative pressure booster, A fluid unit comprising a fluid pump driven by an electric motor and a pressure regulating valve, which increases the master pressure and supplies it to the wheel cylinder as wheel pressure, A controller for controlling the fluid unit, In a braking control device for a vehicle equipped with, The controller is a vehicle braking control device that, in controlling the rotational speed of the electric motor, increases the rotational speed when the booster negative pressure is small compared to when the booster negative pressure is large, and increases the rotational speed based on the amount of change of the manipulated variable with respect to time.

2. A master cylinder that outputs master pressure according to the amount of operation of the braking operating member, A negative pressure booster assists the operating force of the braking operating member according to the amount of operation by negative pressure, A negative pressure sensor for detecting the negative pressure of the negative pressure booster, A fluid unit comprising a fluid pump driven by an electric motor and a pressure regulating valve, wherein the master pressure is increased by adjusting the opening degree of the pressure regulating valve while the fluid pump is running, and supplied to the wheel cylinder as wheel pressure, A controller for controlling the fluid unit, In a braking control device for a vehicle equipped with, The aforementioned controller, Based on the booster negative pressure, the limit operating amount, which is the operating amount at which the assisting effect of the negative pressure booster reaches its limit, is calculated. When the aforementioned operating amount increases, control of the rotational speed of the electric motor based on the booster negative pressure is initiated from a stage before the operating amount reaches the aforementioned limit operating amount. A vehicle braking control device that controls the opening degree of the pressure regulating valve when the manipulated amount is greater than or equal to the limit manipulated amount after the start of control of the rotational speed of the electric motor.

3. In the vehicle braking control device described in Claim 2, The controller is a vehicle braking control device that, in controlling the rotational speed of the electric motor, increases the rotational speed when the booster negative pressure is small compared to when the booster negative pressure is large, and increases the rotational speed based on the amount of change of the manipulated variable with respect to time.

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