JPH1120637A - Braking force controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a braking force controller provided with a pump which supplies brake fluid suctioned from a master cylinder to a wheel cylinder so as to prevent master cylinder pressure from affecting pressure intensifying characteristics of wheel cylinder pressure. SOLUTION: This controller is provided with a pump 100 which suctions brake fluid from a liquid pressure passage 26 which communicates a master cylinder 18 with wheel cylinders 70, 72. A liquid pressure sensor 29 is communicated with the liquid pressure passage 26. When emergency brake operation is performed, brake assist control in which liquid pressure discharged from the pump 100 is supplied to wheel cylinders 74, 76 is done. Discharge capacity of the pump 100 changes according to master cylinder pressure. When wheel cylinder pressure is increased, pressure intensifying conditions are changed according to master cylinder pressure so that the changes of the discharge capacity of the pump 100 are offset.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a braking force control device, and more particularly to a braking force control device suitable for controlling a vehicle braking force.

[0002]

2. Description of the Related Art Conventionally, for example, Japanese Patent Laid-Open No.
As disclosed in Japanese Patent No. 0, there is known a braking force control device that generates a larger brake fluid pressure than normal when a brake pedal is depressed at a speed exceeding a predetermined speed.
The driver of the vehicle operates the brake pedal at a high speed when it is desired to quickly increase the braking force. According to the above-described conventional braking force control device, when such a braking operation (hereinafter, referred to as an emergency braking operation) is performed, a larger braking fluid pressure is generated as compared with a normal operation, so that the driver's demand can be appropriately adjusted. Braking force can be generated.

[0003]

A control for generating a larger brake fluid pressure than usual when an emergency brake operation is performed (hereinafter, this control is referred to as brake assist control) is performed, for example, by a master cylinder. System comprising a first on-off valve interposed between the pump and the wheel cylinder, a pump for supplying brake fluid sucked from the master cylinder side to the wheel cylinder, and a second on-off valve interposed between the pump and the master cylinder Can be implemented in

According to the above system, the first on-off valve is opened and the second on-off valve is closed, so that the master cylinder and the wheel cylinder are electrically connected and the master cylinder is closed. And the pump can be shut off. In this case, a wheel cylinder pressure P _{W / C} equal to the master cylinder pressure P _{M / C} can be generated in the wheel cylinder. As described above, according to the above-described system, the function as a normal brake device can be realized by realizing the above-described state.

According to the above system, the first on-off valve is closed, the second on-off valve is open, and
By operating the pump, the master cylinder and the wheel cylinder can be cut off, and the brake fluid in the master cylinder can be increased in pressure by the pump and supplied to the wheel cylinder. In this case, a high hydraulic pressure can be generated in the wheel cylinder as compared with the master cylinder pressure PM _{/ C.} Therefore, according to the above system,
By realizing the above-described state, the brake assist control can be executed.

The discharge capacity of a pump depends on its suction
The higher the liquid pressure supplied to the side, the higher the pressure. Follow
In the above system, the pump is
Da pressure P _{M / C}The higher the pressure, the higher the discharge capacity.
In the above system, the discharge capacity of the pump changes
During the execution of the brake assist control
Pressure P_{W / C}Changes in the pressure-increasing characteristics. Because of this,
In some systems, the brake assist control
Therefore, it was difficult to always obtain a constant pressure increasing characteristic.

The present invention has been made in view of the above points, and uses a system configuration including a pump for sucking brake fluid from a hydraulic passage communicating between a master cylinder and a wheel cylinder. It is an object of the present invention to provide a braking force control device capable of increasing the wheel cylinder pressure with a constant pressure increasing characteristic without being affected by the value of the braking force.

[0008]

The above object is achieved by the present invention.
And a brake for controlling the wheel cylinder pressure by supplying a brake fluid discharged from the pump to the wheel cylinder, the pump including a pump for sucking brake fluid from a hydraulic passage communicating the master cylinder and the wheel cylinder. A braking force control device that performs hydraulic pressure control, the braking force control device including pressure increasing condition changing means that changes a pressure increasing condition when supplying brake fluid from the pump to a wheel cylinder in accordance with a master cylinder pressure. Is done.

In the present invention, when an increase in the wheel cylinder pressure is required during the execution of the brake fluid pressure control, brake fluid discharged from the pump is supplied to the wheel cylinder. The master cylinder pressure is supplied to the suction side of the pump from a hydraulic passage. Therefore, the discharge capacity of the pump changes according to the master cylinder pressure. In the present invention, the pressure increasing condition during the execution of the brake fluid pressure control is changed according to the master cylinder pressure in order to offset the change in the discharge capacity of the pump. Therefore, the wheel cylinder pressure is always increased with a constant pressure increasing characteristic without being affected by the value of the master cylinder pressure.

[0010] The object of the present invention is as described in claim 2.
2. The braking force control device according to claim 1, wherein the pressure increasing condition changing means is achieved by a braking force control device that increases the pressure increasing time as the master cylinder pressure decreases. In the present invention, the discharge capacity of the pump decreases as the master cylinder pressure decreases. Further, in the present invention, the pressure increase time during execution of the brake fluid pressure control becomes longer as the master cylinder pressure is lower. If the pressure increase time is prolonged when the discharge capacity of the pump is reduced, fluctuations in the discharge capacity of the pump are offset, and a constant pressure increase characteristic is maintained. .

[0011] The above object is as described in claim 3.
2. The braking force control device according to claim 1, wherein the brake fluid pressure control is a brake assist control for generating a wheel cylinder pressure higher than a master cylinder pressure when an emergency braking operation is performed by a driver. This is achieved by a braking force control device.

In the present invention, the increase of the wheel cylinder pressure by the pump is performed during the execution of the brake assist control. The brake assist control may be executed in an environment where the master cylinder pressure is sufficiently increased. Further, the brake assist control may be executed in an environment where the master cylinder pressure is not so increased. Therefore,
The discharge capacity of the pump during execution of the brake assist control tends to show a relatively large change. According to the present invention,
The wheel cylinder pressure can always be increased with a constant pressure increase characteristic during the execution of the brake assist control without being affected by the change in the discharge capacity of the pump described above.

[0013] The above object is as described in claim 4.
4. The braking force control device according to claim 3, wherein after the brake assist control is started, a start pressure increase control for supplying brake fluid discharged from the pump to the wheel cylinder for a predetermined pressure increase time is executed. In addition, the pressure increasing condition changing means is achieved by a braking force control device that changes the pressure increasing condition of the start pressure increasing control according to a master cylinder pressure.

In the present invention, the wheel cylinder pressure is increased to a higher fluid pressure than the master cylinder pressure by executing the start pressure increase control after the brake assist control is started. The discharge capacity of the pump during execution of the start pressure increase control is affected by the master cylinder pressure. In the present invention, so that the change in the discharge capacity of the pump is offset,
The pressure increasing condition of the start pressure increasing control is changed according to the master cylinder pressure. For this reason, during execution of the start pressure increase control, the wheel cylinder pressure is always increased with a constant pressure increase characteristic.

[0015] The object of the present invention is as described in claim 5.
2. The braking force control device according to claim 1, wherein the pump is operated when a suction control valve disposed between the hydraulic passage and the pump is required to increase a wheel cylinder pressure. And, and pressure-increasing control means for performing pressure-increasing control to open the suction control valve,
The pressure increasing condition changing means is achieved by a braking force control device that increases a time during which the suction control valve is opened during execution of the pressure increasing control as the master cylinder pressure is lower.

In the present invention, the pump supplies brake fluid to the wheel cylinder pressure when the suction control valve is open. The discharge capacity of the pump decreases as the master cylinder pressure decreases. On the other hand, in the present invention, the opening time of the suction control valve becomes longer as the master cylinder pressure becomes lower. If the opening time of the suction control valve is prolonged when the discharge capacity of the pump is reduced, fluctuations in the discharge capacity of the pump are offset, and a constant pressure increasing characteristic is maintained.

Further, the above object is achieved by a braking force control device according to claim 1 as described in claim 6.
The pump is a variable displacement pump, and the pressure increase condition changing means is achieved by a braking force control device that increases the discharge capacity of the pump as the master cylinder pressure decreases.

In the present invention, the discharge capacity of the pump tends to decrease as the master cylinder pressure decreases. In the present invention, the discharge capacity of the variable displacement pump is increased as the master cylinder pressure is lower so that the change is offset. When the discharge capacity of the variable displacement pump is changed as described above, a change in the discharge capacity of the pump is canceled, and a constant pressure increasing characteristic is maintained.

[0019]

FIG. 1 shows a system configuration diagram of a braking force control device according to an embodiment of the present invention. The braking force control device of this embodiment is a device suitable as a braking force control device mounted on a front engine / front drive type vehicle (FF vehicle). The braking force control device according to the present embodiment is controlled by an electronic control unit 10 (hereinafter, referred to as ECU 10).

The braking force control device includes a brake pedal 12. A brake switch 14 is provided near the brake pedal 12. Brake switch 14
Outputs an ON signal when the brake pedal 12 is depressed. The ECU 10 controls the brake switch 14
It is determined whether or not the brake pedal 12 is depressed based on the output signal.

The brake pedal 12 is connected to a vacuum booster 16. The vacuum booster 16
When the brake pedal 12 is depressed, an assist force Fa having a predetermined boosting ratio with respect to the brake depression force F is generated. A master cylinder 18 is fixed to the vacuum booster 16. A first hydraulic chamber 20 and a second hydraulic chamber 22 are formed inside the master cylinder 18. In the first hydraulic chamber 20 and the second hydraulic chamber 22, a master cylinder pressure PM _{/ C} is generated in accordance with the resultant force of the brake depression force F and the assist force Fa.

A reservoir tank 24 is provided above the master cylinder 18. The master cylinder 18 and the reservoir tank 24 are electrically connected only when the depression of the brake pedal 12 is released. A first hydraulic pressure passage 26 and a second hydraulic pressure passage 28 communicate with the first hydraulic pressure chamber 20 and the second hydraulic pressure chamber 22 of the master cylinder 18, respectively.

The first hydraulic passage 26 is provided with a hydraulic pressure sensor 29. The hydraulic pressure sensor 29 is connected to the first hydraulic pressure passage 26.
, That is, an electric signal pMC corresponding to the master cylinder pressure PM _{/ C} generated by the master cylinder 18. The output signal pMC of the hydraulic pressure sensor 29 is supplied to the ECU 10. The ECU 10 detects the master cylinder pressure PM _{/ C} based on the output signal pMC.

The first hydraulic passage 26 has a first master cut solenoid 30 (hereinafter referred to as SMC- ₁ 30) and a first reservoir cut solenoid 32 (hereinafter SRC- ₁ 32).
Is called). On the other hand, a second master cut solenoid 34 (hereinafter, SMC- ₂₎
34) and a second reservoir cut solenoid 36
(Hereinafter referred to as SRC- ₂₃₆ ).

Constant pressure release valves 38 and 40 are provided inside the SMC- ₁ 30 and the SMC- ₂ 34. SMC _-1
A hydraulic pressure passage 4 provided corresponding to the right rear wheel RR
2, and a hydraulic passage 44 provided corresponding to the left front wheel FL. Similarly, a hydraulic passage 46 provided corresponding to the left rear wheel RL and a hydraulic passage 48 provided corresponding to the right front wheel FR communicate with the SMC _- 234.

The SMC- ₁₃₀ and the SMC- ₂₃₄ each maintain the valve-open state in a normal state, and connect the first hydraulic passage 26 and the hydraulic passages 42 and 44 with a drive signal supplied from the ECU 10. Alternatively, it is a two-position solenoid valve that connects the second hydraulic passage 28 and the hydraulic passages 46 and 48 via the constant pressure release valves 38 and 40, respectively. The SRC _-1 32 and the SRC _-2 36 are two-position solenoid valves that maintain a closed state in a normal state and are opened when a drive signal is supplied from the ECU 10.

A check valve 50 is provided between the first hydraulic passage 26 and the hydraulic passages 42 and 44. The check valve 50 is
This is a one-way valve that allows only fluid flow from the first hydraulic pressure passage 26 to the hydraulic pressure passages 42 and 44. Similarly, a check valve 52 is provided between the second hydraulic passage 28 and the hydraulic passages 46 and 48. The check valve 52 is a one-way valve that allows only the flow of the fluid from the second hydraulic passage 28 to the hydraulic passages 46 and 48.

In the hydraulic passage 42 corresponding to the right rear wheel RR,
A right rear wheel holding solenoid 54 (hereinafter, referred to as SRRH 54) communicates therewith. Similarly, a left front wheel holding solenoid 56 (hereinafter referred to as SF) is provided in the hydraulic passage 44 corresponding to the left front wheel FL.
LH56) is a hydraulic passage 4 corresponding to the left rear wheel RL.
6 has a left rear wheel holding solenoid 58 (hereinafter, SRLH58).
), But also a hydraulic passage 48 corresponding to the right front wheel FR.
Is connected to a right front wheel holding solenoid 60 (hereinafter, referred to as SFRH60). Hereinafter, when these solenoids are collectively referred to, they are referred to as “holding solenoid S ** H”. The holding solenoid S ** H is a two-position solenoid valve that keeps the valve open in a normal state and is closed when a drive signal is supplied from the ECU 10.

The right rear wheel pressure reducing solenoid 62 (hereinafter, referred to as SRRR 62) communicates with the SRRH 54. Similarly, the SFLH 56 has a left front wheel pressure reducing solenoid 64 (hereinafter, referred to as SFLR 64), and the SRLH 58 has a left rear wheel pressure reducing solenoid 66 (hereinafter, referred to as SRLR 66).
Further, a right front wheel pressure reducing solenoid 68 (hereinafter, referred to as SFRR 68) communicates with the SFRH 60, respectively. Hereinafter, these solenoids are collectively referred to as “pressure reducing solenoid S ** R”. The pressure reducing solenoid S ** R is
The solenoid valve is a two-position solenoid valve that maintains a closed state in a normal state and is opened when a drive signal is supplied from the ECU 10.

Wheel cylinders 70, 72, 74, 76 communicate with the holding solenoids S ** H of the respective wheels. The wheel cylinders 70, 72, 74, 76
Are connected to check valves 78, 80, 82, 84, respectively. The check valves 78, 80, 82, 84 are connected to the hydraulic passages 42, 4 from the wheel cylinders 70, 72, 74, 76 side.
This is a one-way valve that allows only fluid flow toward the 4, 46, 48 side.

The SRRR 62 and the SFLR 64 communicate with a pressure reducing passage 88. Similarly, the SRLR 66 and the SFRR 68 communicate with the pressure reducing passage 90. Auxiliary reservoirs 92 and 94 communicate with the pressure reducing passages 88 and 90. The suction holes of the pumps 100 and 102 communicate with the auxiliary reservoirs 92 and 94 via check valves 96 and 98.
The suction holes of the pumps 100 and 102 are also provided with SRC- _13.
2 or SRC- ₂₃₆ is in communication.

When a drive signal is supplied from the ECU 10, the pumps 100 and 102 serve as auxiliary reservoirs 92 and 94.
Brake fluid stored in or SRC
Brake fluid guided through _-1 32 or SRC- ₂ 36 is discharged from the discharge hole. Pump 100,1
The discharge hole 02 communicates with the dampers 104 and 106. The dampers 104 and 106 absorb pulsations generated in the discharge pressures of the pumps 100 and 102. Dampers 104 and 106
Communicate with the hydraulic passages 44 and 46, respectively.

The braking force control device of this embodiment includes wheel speed sensors 108, 110, 112, 114. Each of the wheel speed sensors 108, 110, 112, and 114 outputs a pulse signal at a cycle corresponding to the rotation speed of each wheel. The output signals of the wheel speed sensors 108, 110, 112, 114 are E
It is supplied to CU10. ECU10 detects the rotational speed V _W of each wheel based on the output signal of the wheel speed the wheel speed sensors 108, 110, 112, 114.

Next, the operation of the braking force control device according to the present embodiment will be described with reference to FIGS.
The braking force control device according to the present embodiment switches the state of various solenoid valves disposed in the hydraulic circuit to provide a function as a normal brake device (hereinafter, referred to as a normal brake function) and an anti-lock brake. A function as a system (hereinafter referred to as an ABS function) and a function to generate a wheel cylinder pressure P _{W / C} higher than the master cylinder pressure P _{M / C} (hereinafter referred to as a brake assist function) are realized. I do.

FIG. 1 shows control for realizing the normal brake function (hereinafter referred to as normal brake control) or A
The state realized during execution of control for realizing the BS function (hereinafter, referred to as ABS control) is shown. Hereinafter, the state shown in FIG. 1 is referred to as a normal brake state. During the execution of the normal brake control, as shown in FIG. 1, all the solenoid valves provided in the braking force control device are turned off.
According to the normal brake state, the wheel cylinders 70, 72, 74, 76 of all the wheels communicate with the master cylinder 18. In this case, the wheel cylinder pressure P _{W / C} of each wheel is
The pressure is always controlled to be equal to the master cylinder pressure PM _{/ C.} Therefore, according to the normal brake state shown in FIG. 1, the normal brake function can be realized.

During execution of the ABS control, as shown in FIG. 1, SMC- ₁ 30, SRC- ₂ 32, SMC- ₁ 34 and SR
The C- ₂₃₆ is turned off and the pumps 100 and 1 are turned off.
02 is activated and the holding solenoid S ** H
And the pressure reducing solenoid S ** R is appropriately driven according to the request of the ABS. Hereinafter, a state realized during the execution of the ABS control is referred to as an ABS state.

According to the ABS state, the master cylinder pressure P _{M / C} can be guided to all four hydraulic passages 42, 44, 46, 48 provided corresponding to the respective wheels. In this state, when the holding solenoid S ** H is opened and the pressure reducing solenoid S ** R is closed, the wheel cylinder pressure P _{W / C} of each wheel is directed toward the master cylinder pressure P _{M / C.} Pressure can be increased. Hereinafter, this state is referred to as (i) pressure increase mode. In the above state, the holding solenoid S *
When both * H and the pressure reducing solenoid S ** R are closed, the wheel cylinder pressure P _{W / C} of each wheel can be maintained. Hereinafter, this state is referred to as (ii) holding mode.
Further, in the above state, when the holding solenoid S ** H is closed and the pressure reducing solenoid S ** R is opened, the wheel cylinder pressure P _{W / C} of each wheel can be reduced. . Hereinafter, this state is referred to as (iii) decompression mode.

When the ABS control is started, the ECU 10
Implements (i) the pressure increasing mode, (ii) the holding mode, and (iii) the pressure reducing mode as appropriate for each wheel so that an excessive slip rate does not occur in each wheel. When the holding solenoid S ** H and the pressure reducing solenoid S ** R are controlled as described above, the wheel cylinder pressures P _{W / C of} all wheels are controlled.
Is controlled to an appropriate pressure without causing an excessive slip rate on the corresponding wheel. As described above, according to the above control, the ABS function can be realized in the braking force control device.

FIGS. 2 to 4 show control (hereinafter referred to as BA) for realizing a brake assist function (hereinafter referred to as a BA function).
(Referred to as control). ECU
The control unit 10 starts the BA control so as to generate a larger braking force than usual when an emergency braking operation is performed by the driver. During the execution of the BA control, the ECU 10
Thus, any of the states shown in FIGS. 2 to 4 is appropriately realized.

FIG. 2 shows an assist pressure increasing state realized during execution of the BA control. The assist pressure increase state is BA
This is realized when it is necessary to increase the wheel cylinder pressure P _{W / C} of each wheel during execution of the control. In the system of this embodiment, the assist pressure increasing state is as shown in FIG.
SMC- ₁ 30, SRC- ₁ 32, SMC- ₂ 34 and SR
_Turn on C- ₂₃₆ (SMC- ₁₃₀ and SMC _- 234)
Is closed, SRC- ₁ 32 and SRC- ₂₃₆ are open, and the pumps 100 and 102 are turned on.

According to the assist pressure increasing state, the master cylinder 18 and the suction holes of the pumps 100 and 102 communicate with each other. In this case, the pumps 100 and 102 can suck the brake fluid from the master cylinder 18 and discharge the high-pressure brake fluid to the hydraulic passages 42 and 44 or the hydraulic passages 46 and 48. According to the assist pressure increasing state, the hydraulic passages 42, 44 and the hydraulic passages 46, 4
8 is separated from the master cylinder 18 by constant pressure release valves 38 and 40 built in the SMC- ₁ 30 or SMC- ₂ 34, respectively. In this case, the pumps 100, 10
2 is supplied to the hydraulic passage 4
The wheels are supplied to wheel cylinders 70, 72, 74, 76 via the wheels 2, 44, 46, 48.

Therefore, according to the assist pressure increasing state shown in FIG. 1, the brake fluid in the master cylinder 18 is pumped by the pumps 100 and 102 so that the wheel cylinder pressure P _{W / C} of each wheel is reduced by the master cylinder. The pressure can be increased to a higher hydraulic pressure than the pressure PM _{/ C.} FIG. 3 shows an assist pressure holding state realized during execution of the BA control. The assist pressure increasing state is realized when it is necessary to maintain the wheel cylinder pressure P _{W / C} of each wheel during execution of the BA control. In the system of this embodiment, the assist pressure holding state is, as shown in FIG. 3, the SMC- ₁₃₀ and the SMC- _2.
34 is turned on (valve closed state) and the pump 10
This is realized by turning on 0 and 102.

According to the assist pressure holding state, SRC- ₁₃
2 and SRC _- 236 allow the suction holes of pumps 100 and 102 and master cylinder 18 to be shut off. In this case, the pumps 100 and 102 cannot suck the brake fluid from the master cylinder 18. In addition, ABSs are provided inside the auxiliary reservoirs 92 and 94.
Before the control is started, the brake fluid is not stored. Therefore, when the assist pressure holding state is realized, the pumping of the brake fluid by the pumps 100 and 102 is stopped. Therefore, according to the assist pressure holding state, the wheel cylinder pressures P _{W / C} of all the wheels can be held at a constant value.

FIG. 4 shows a reduced assist pressure state realized during execution of the BA control. The assist pressure reduction state is BA
This is realized when it is necessary to reduce the wheel cylinder pressure P _{W / C} of each wheel during execution of the control. In this embodiment,
The assist pressure reduction state is realized by turning off all the solenoids as shown in FIG. According to the reduced assist pressure state, SRC- ₁ 32 and SRC- ₂ 36 are closed. In this case, the pumps 100 and 102 cannot pump the brake fluid. Further, according to the assist pressure reduction state, the wheel cylinders 7
0, 72, 74, and 76 are SMC- ₁ 30 or SMC3
4 and communicate with the master cylinder 18. For this reason,
According to the assist pressure reduction state, the wheel cylinder pressure P _{W / C} of all wheels can be reduced with the master cylinder pressure P _{M / C} as a lower limit.

FIG. 5 shows changes that occur in the master cylinder pressure P _{M / C} and the wheel cylinder pressure P _{W / C} when the driver performs an emergency brake operation. When the driver performs an emergency braking operation, the master cylinder pressure P _{M / C} sharply increases as shown by a broken line in FIG. 5. Based on the output signal pMC of the hydraulic pressure sensor 29, the ECU 10 increases the master cylinder pressure PM _{/ C} rapidly and
If it can be recognized that the pressure has been increased to a sufficiently large value, it is determined that the emergency braking operation has been performed. And ECU1
If 0 determines that the emergency braking operation has been performed, then the BA control is started.

When the BA control is started in the braking force control device, first, (I) a start pressure increasing mode is executed (period in FIG. 5). The start pressure increase mode uses a predetermined duty ratio Duty
1 is realized by repeating the assist pressure increasing state shown in FIG. 2 and the assist pressure holding state shown in FIG. More specifically, SMC- ₁₃₀ and SMC- ₂₃
4 is maintained in the ON state (valve closed state), and the pumps 100, 1
02 in operation and SRC _-1 32 and S
This is realized by repeatedly turning on / off the RC _- 236 at a predetermined duty ratio Duty1.

The start pressure increase mode is a predetermined pressure increase time T _STA
It is continuously executed during The pressure increase time T _STA is set to a time necessary for increasing the wheel cylinder pressure P _{W / C} by a predetermined assist pressure Pa compared to the master cylinder pressure P _{M / C.} The predetermined assist pressure Pa is a pressure required to generate a predetermined assist deceleration G ₀ to the vehicle. Therefore, when the start pressure increase mode is executed, the vehicle is provided with a deceleration G + G ₀ larger by a predetermined assist deceleration G ₀ than the deceleration G generated by the normal brake control.
Occurs.

In the braking force control device, when the (I) start pressure increasing mode is completed, (II) the assist pressure increasing mode, (III) the assist pressure decreasing mode, One of the IV) assist pressure holding mode, the (V) assist pressure gradual increase mode, and the (VI) assist pressure gradual decrease mode are executed. FIG. 6 shows an example of a map referred to by the ECU 10 in order to determine a mode to be executed after the start pressure increase mode. In FIG. 6, the horizontal axis represents the hydraulic pressure sensor 2.
9 is the change rate ΔpMC of the output signal pMC.

If a positive rate of change occurs in the master cylinder pressure PM _{/ C} at the end of the start pressure increase mode, it can be determined that the driver is requesting a larger braking force. When a change rate ΔpMC exceeding a predetermined value K ₁ (> 0) occurs when the start pressure increase mode ends, the ECU 10 determines that the driver is requesting a larger braking force. In this case, the ECU 10 determines the mode to be executed after the start pressure increasing mode to be (II) the assist pressure increasing mode.

If a negative rate of change occurs in the master cylinder pressure PM _{/ C} at the end of the start pressure increase mode, it can be determined that the driver has requested a decrease in the braking force. The ECU 10 determines that the driver is requesting a decrease in the braking force if the rate of change ΔpMC that is lower than the predetermined value K ₂ (<0) occurs when the start pressure increase mode ends. In this case, the ECU 10 determines the mode to be executed after the start pressure increasing mode to (III) the assist pressure decreasing mode.

When the start pressure increase mode ends, the
Star cylinder pressure P_{M / C}Where the rate of change is not large
If it is, determine that the driver is requesting the maintenance of braking force
be able to. The ECU 10 terminates the start pressure increase mode.
K_Two≦ ΔpMC ≦ K ₁Change rate ΔpMC that satisfies
The driver demands that the braking force be maintained
Judge that there is. In this case, the ECU 10 controls the start pressure increasing mode.
(IV) Assist pressure holding mode
To decide.

(II) The assist pressure increasing mode is when the brake operation amount is greatly increased at the end of the above-described start pressure increasing mode, or when the assist pressure holding mode described later is being executed or the assist pressure is gradually increased. This is executed when the brake operation amount is greatly increased during execution of the mode (FIG. 5).
Medium period). The assist pressure increasing mode is realized by repeating the assist pressure increasing state shown in FIG. 2 and the assist pressure holding state shown in FIG. 3 at a predetermined duty ratio Duty2. Note that the duty ratio Duty2 used in the assist pressure increase mode may be the same as or different from the duty ratio Duty1 used in the start pressure increase mode. According to the assist pressure increasing mode, when the brake operation amount is greatly increased, the wheel cylinder pressure P _{W / C} of each wheel is rapidly increased in a region higher than the master cylinder pressure P _{M / C.} Can be pressed.

FIG. 7 shows an example of a map referred to by the ECU 10 to determine the mode to be executed during the execution of the assist pressure increasing mode. In FIG. 7, the horizontal axis represents the rate of change ΔpMC of the output signal pMC of the hydraulic pressure sensor 29.
During execution of the assist pressure increasing mode, the master cylinder pressure P
_If the increase in _{M / C} continues, it can be determined that the driver is requesting a larger braking force. ECU
10 is a predetermined value K during execution of the assist pressure increasing mode.
_If a change rate ΔpMC exceeding ₃ (> 0) occurs, it is determined that the driver is requesting a larger braking force. In this case, the ECU 10 continuously sets the mode to be executed to the assist pressure increasing mode.

Also, during execution of the assist pressure increasing mode,
If a large increase has not occurred in master cylinder pressure PM _{/ C} , it can be determined that the driver no longer requests an increase in the braking force. The ECU 10 determines that the rate of change Δ exceeding a predetermined value K ₃ (> 0) during execution of the assist pressure increasing mode.
If pMC has not occurred, it is determined that the driver has not requested an increase in the braking force. In this case, the ECU 10
The mode to be executed is determined as the assist pressure holding mode.

(III) The assist pressure reducing mode is used when the brake operation amount is greatly reduced at the end of the above-described start pressure increasing mode, or during the execution of the assist pressure holding mode described later or the assist pressure gradual decreasing mode. Is executed when the brake operation amount is greatly reduced during the execution of the operation (the period in FIG. 5). In the assist pressure reducing mode, the assist pressure holding state shown in FIG.
This is realized by repeating the assist pressure reduction state shown in FIG. More specifically, SRC _-1 32 and SRC _-2 36 are maintained in the off state (valve closed state), pumps 100 and 102 are maintained in the operating state, and SMC _-13
This is realized by repeatedly turning on and off 0 and SMC _- 234 at a predetermined duty ratio Duty3. According to the assist pressure reduction mode, when the brake operation amount is greatly reduced, the wheel cylinder pressure P _{W / C} of each wheel is
With the master cylinder pressure P _{M / C} as the lower limit, the pressure can be rapidly reduced.

FIG. 8 shows an example of a map referred to by the ECU 10 to determine a mode to be executed during execution of the assist pressure reducing mode. In FIG. 8, the horizontal axis represents the rate of change ΔpMC of the output signal pMC of the hydraulic pressure sensor 29.
During execution of the assist pressure reducing mode, the master cylinder pressure P
_{If the M / C} continues to decrease, it can be determined that the driver is requesting a smaller braking force. ECU
10 is a predetermined value K during execution of the assist pressure increasing mode.
_{If a} change rate ΔpMC lower than ₄ (<0) occurs, it is determined that the driver is requesting a smaller braking force. In this case, the ECU 10 continuously sets the mode to be executed to the assist pressure reducing mode.

Also, during execution of the assist pressure reducing mode,
If the master cylinder pressure P _{M / C} has not significantly decreased, it can be determined that the driver no longer requests a decrease in the braking force. During execution of the assist pressure reducing mode, the ECU 10 determines that the rate of change Δ below a predetermined value K ₄ (<0).
If pMC has not occurred, it is determined that the driver has not requested a decrease in the braking force. In this case, the ECU 10
The mode to be executed is determined as the assist pressure holding mode.

(IV) In the assist pressure holding mode, a large increase or decrease in the brake operation amount occurs at the end of the above-described start pressure increasing mode or during execution of the assist pressure increasing mode or the assist pressure decreasing mode described above. It is executed when it is detected that there is not, and after the assist pressure gradual increase mode or the assist pressure gradual decrease mode described later is executed for a predetermined period (period in FIG. 5).

The assist pressure holding mode is realized by maintaining the assist pressure holding state shown in FIG.
According to the assist pressure holding mode, the wheel cylinder pressure P _{W / C} of each wheel can be maintained at a constant value when the brake operation amount does not greatly change. FIG. 9 shows an example of a map that the ECU 10 refers to to determine a mode to be executed during the execution of the assist pressure holding mode.
In FIG. 9, the horizontal axis represents the output signal p of the hydraulic pressure sensor 29.
The change rate of MC is ΔpMC. The vertical axis indicates the output value pMCSTA at the time of change from the output signal pMC of the hydraulic pressure sensor 29.
Is the value obtained by subtracting. The change-time output value pMCSTA is the value of the output signal pMC output from the hydraulic pressure sensor 29 when the assist pressure holding mode is started. Therefore,
In FIG. 9, the vertical axis corresponds to the amount of change in the output signal pMC in the increasing direction after the start of the assist pressure holding mode.

If the master cylinder pressure P _{M / C} sharply increases during the execution of the assist pressure holding mode, it can be determined that the driver has requested a sharp increase in the braking force. E
CU10, after the assist pressure holding mode is started, before the predetermined time T _MODE1 elapses, change exceeding a predetermined value P ₁ in the output signal pMC (i.e., pMC-pMCSTA
> P ₁ changes to meet) is generated, and, the rate of change ΔpMC at the time the change occurs is a driver if it exceeds the ₅ (> 0) a predetermined value K requires an increase of rapid braking force Judge that In this case, the ECU 10 changes the mode to be executed from the assist pressure holding mode to the assist pressure increasing mode.

If the master cylinder pressure P _{M / C} drops rapidly during execution of the assist pressure holding mode, it can be determined that the driver has requested a sharp decrease in the braking force. E
CU10, after the assist pressure holding mode is started, before the predetermined time T _MODE1 elapses, decreases the output signal pMC exceeds a predetermined value P ₄ (i.e., pMC-pMCSTA
<Until reduction) and P ₄ is satisfied, and the rate of change ΔpMC at the time the drop has occurred is the driver when below the predetermined value K ₆ (<0) to request a reduction in the sudden braking amount Judge that In this case, the ECU 10 changes the mode to be executed from the assist pressure holding mode to the assist pressure reducing mode.

If the master cylinder pressure P _{M / C} gradually increases during the execution of the assist pressure holding mode, it can be determined that the driver has requested a gradual increase in the braking force. After the assist pressure holding mode is started, the ECU 10 does not satisfy the above-described condition for shifting to the assist pressure increasing mode or the assist pressure decreasing mode, and outputs a predetermined time T _MODE1 to the output signal pMC continuously. Value P ₂ (0 <
Changes exceeding P ₂ <P ₁ (i.e., pMC-pMC)
If the change meets the STA> P ₂₎ has occurred, it is determined that the driver is requesting a moderate increase in the braking force. In this case, the ECU 10 changes the mode to be executed from the assist pressure holding mode to the assist pressure gradual increase mode.

If the master cylinder pressure P _{M / C} is gradually decreasing during execution of the assist pressure holding mode, it can be determined that the driver has requested a gentle decrease in the braking force. After the assist pressure holding mode is started, the ECU 10 does not satisfy the above-described condition for shifting to the assist pressure increasing mode or the assist pressure decreasing mode, and outputs a predetermined time T _MODE1 to the output signal pMC continuously. Value P ₃ (0>
P _3> P ₄₎ decreases below (i.e., pMC-pMC
If the STA <lowering satisfying P ₃₎ has occurred, it is determined that the driver is requesting a moderate reduction of the braking force. In this case, the ECU 10 changes the mode to be executed from the assist pressure holding mode to the assist pressure gradual decrease mode.

Further, during execution of the assist pressure holding mode,
Master cylinder pressure P_{M / C}When there is no significant change in
Can determine that the driver has requested the braking force to be maintained.
You. The ECU 10 has started the assist pressure holding mode.
After that, the change amount of the output signal pMC becomes a predetermined value P_TwoAnd P_ThreeBetween
(Ie, P_Three≤pMC-pMCSTA≤
P _TwoIs satisfied), the driver requests the holding of the braking force.
Judge that you are. In this case, the ECU 10
The torsion pressure holding mode is maintained as a mode to be executed.

(V) The assist pressure gradual increase mode is executed when a gradual increase in the brake operation amount is detected during execution of the assist pressure holding mode, as described above. When the execution of the assist pressure gradual increase mode is requested, the ECU 10 maintains the braking force control device in the assist pressure increase state shown in FIG. 2 for a predetermined short time T _MODE2 . And the ECU 10
As long as a sudden increase in the brake operation amount is not detected, after a predetermined time T _MODE2 has elapsed, the assist pressure gradual increase mode is ended and the assist pressure holding mode is started again. According to the assist pressure gradual increase mode, the wheel cylinder pressure P _{W / C} of each wheel can be increased intermittently when the brake operation amount is gently increased.

FIG. 10 shows an example of a map referred to by the ECU 10 to determine the mode to be executed during the execution of the assist pressure gradual increase mode. In FIG. 10, the horizontal axis represents the change rate ΔpMC of the output signal pMC of the hydraulic pressure sensor 29. The vertical axis indicates the amount of change pMC-pMCST that has occurred in the output signal pMC after the start of the assist pressure gradual increase mode.
A.

If the master cylinder pressure P _{M / C} sharply increases during execution of the assist pressure gradual increase mode, it can be determined that the driver has requested a rapid increase in the braking force. E
CU10, after the assist pressure moderately increasing mode is started, before the predetermined time T _MODE2 has elapsed, change exceeding a predetermined value P ₅ to the output signal pMC (i.e., pMC-pMCSTA
> P ₅ changes satisfying) is generated, and the rate of change ΔpMC at the time the change occurs is a driver when the difference exceeds the predetermined value K ₇ (> 0) requires an increase in sudden braking force Judge that In this case, the ECU 10 changes the mode to be executed from the assist pressure gradual increase mode to the assist pressure increase mode.

If a rapid increase in master cylinder pressure P _{M / C} is not recognized during execution of the assist pressure gradual increase mode,
It can be determined that the driver has not requested a rapid increase in the braking force. If the above-described condition for shifting to the assist pressure increasing mode is not satisfied before the predetermined time T _MODE2 has elapsed after the assist pressure gradual increasing mode has been started, the ECU 10 determines that the driver has a sudden braking amount. Is determined not to require an increase. In this case, the ECU 10 changes the mode to be executed from the assist pressure gradual increase mode to the assist pressure holding mode.

(VI) The assist pressure moderation mode is as described above.
Of the brake operation amount during execution of the assist pressure holding mode.
Executed when a gradual decrease is detected (Fig.
while). When execution of the assist pressure moderation mode is requested,
The ECU 10 determines a predetermined short time T _MODE3Only braking force control
Is maintained in the assist pressure reduced state shown in FIG. So
Then, the ECU 10 detects a sharp decrease in the brake operation amount.
Unless known, T_MODE3After elapse,
Terminate the cyst pressure moderate mode and restart the assist pressure holding mode.
Start loading. According to the assist pressure moderation mode,
When the operation amount is gradually reduced,
Wheel cylinder pressure P_{W / C}Can be depressurized intermittently.
Wear.

FIG. 11 shows an example of a map referred to by the ECU 10 to determine the mode to be executed during the execution of the assist pressure gradual decrease mode. In FIG. 11, the horizontal axis represents the rate of change ΔpMC of the output signal pMC of the hydraulic pressure sensor 29. The vertical axis represents the amount of change pMC-pMCST that has occurred in the output signal pMC after the start of the assist pressure moderation mode.
A.

If the master cylinder pressure P _{M / C} sharply decreases during execution of the assist pressure moderate mode, it can be determined that the driver has requested a sharp decrease in the braking force. E
CU10, after the assist pressure moderately decreasing mode is started, before the predetermined time T _MODE3 elapses, decreases exceeding a predetermined value P ₆ to the output signal pMC (i.e., pMC-pMCSTA
<Drop) occurs satisfying P _6, and the rate of change ΔpMC at the time the drop has occurred is the driver when below the predetermined value K ₈ (<0) requesting a reduction in sudden braking force Judge that there is. In this case, the ECU 10 changes the mode to be executed from the assist pressure gradual increase mode to the assist pressure decrease mode.

If the master cylinder pressure P _{M / C} does not suddenly decrease during execution of the assist pressure moderate mode,
It can be determined that the driver has not requested a rapid decrease in the braking force. If the above-mentioned condition for shifting to the assist pressure reducing mode is not satisfied before the predetermined time T _MODE3 has elapsed after the assist pressure gradual decrease mode is started, the ECU 10 determines that the driver has a sudden braking amount. Judge that no reduction is requested. In this case, the ECU 10 changes the mode to be executed from the assist pressure gradual decrease mode to the assist pressure holding mode.

As described above, according to the braking force control device of the present embodiment, when the driver performs an emergency braking operation, the BA control is executed to thereby control the wheel cylinder pressure P _{W / C of} each wheel. Can be increased to a pressure higher than the master cylinder pressure PM _{/ C.} Further, according to the braking force control device of the present embodiment, during the execution of the BA control, an increase or decrease in the driver's brake operation amount is detected based on the output signal pMC of the hydraulic pressure sensor 29, and the brake operation amount is detected. , The wheel cylinder pressure P _{W / C} can be increased or decreased. Therefore, according to the braking force control device of the present embodiment,
During the execution of the BA control, the braking force can be increased or decreased according to the driver's intention.

Next, referring to FIG. 12 to FIG.
A characteristic portion of the braking force control device according to the embodiment will be described. FIG.
2 is the discharge capacity of the pumps 100 and 102 and the master
Cylinder pressure P_{M / C}The relationship is shown below. Braking force control of this embodiment
In the control device, on the suction side of the pumps 100 and 102,
The first hydraulic passage 26 and the second hydraulic passage 28
Linda pressure P _{M / C}Is supplied. Pumps 100, 102
The higher the hydraulic pressure guided to the suction side, the higher the discharge
Demonstrate the ability to go out. Therefore, the discharge of the pumps 100 and 102
As shown in FIG. 12, the master cylinder pressure P_{M / C}
Becomes higher as the pressure becomes higher.

Using the pumps 100 and 102 as hydraulic pressure sources,
Cylinder pressure P_{W / C}When increasing the pressure of a wheel cylinder,
Pressure P_{W / C}Means that pumps 100 and 102 have high discharge capacity
The pressure is increased at a steep gradient as it runs. Therefore, the BA control
Wheel cylinder pressure P during line_{W / C}Pressure increase gradient,
Specifically, the braking force control device is in the assist pressure increasing state.
Cylinder pressure P_{W / C}Pressure gradient appearing on
Is the master cylinder pressure P _{M / C}The higher the pressure, the steeper the
Become.

The braking force control device of the present embodiment realizes the wheel cylinder pressure P
_{Although the} pressure increase gradient appearing in the _{W / C} is affected by the master cylinder pressure P _{M / C} as described above, (I) the start pressure increase mode, (II) the assist pressure pressure increase mode, and (V The characteristic is that the wheel cylinder pressure P _{W / C} is constantly increased with constant characteristics along with the execution of the assist pressure gradual increase mode.

FIG. 13 is a flowchart showing a part of a main routine executed by the ECU 10. The ECU 10
By executing a series of processes shown in FIG. 13, (I) when execution of the start pressure increase mode is required, the assist pressure P is always constant without being affected by the master cylinder pressure PM _{/ C.}
a is generated. A series of processing shown in FIG. 13 is executed under the condition that the execution condition of the BA control is satisfied. FIG.
Are started from step 120.

At step 120, it is determined whether execution of the start pressure increase mode is requested. The start pressure increase mode is requested immediately after the execution condition of the BA control is satisfied. If it is determined in step 120 that the start pressure increase mode has not been requested, it can be determined that the start pressure increase mode has already been executed. In this case, other processes not shown in FIG. 13 are performed thereafter. On the other hand, if it is determined that the start pressure increase mode is required, then step 122
Is performed.

At step 122, the output signal pMC of the hydraulic pressure sensor 29 is stored as the output value pMCSTA at the time of change. According to the above processing, the output value at the time of change pMCSTA
The output signal pM at the time when the start pressure increase mode is started
C is stored. In step 124, the pressure increase time T _STA
Is calculated. The pressure increase time T _STA is a time during which the start pressure increase mode should be continued as described above. In the present step 124, the pressure increase time T _STA is set to the change-time output value pMCSTA.
Is calculated based on

FIG. 14 shows an example of a map that defines the relationship between the pressure increase time T _STA and the output value at change pMC. ECU1
In the step 124, the pressure increase time T _STA is calculated according to the map shown in FIG. According to the map shown in FIG. 14, the pressure increase time T _STA is equal to the change-time output value pMCSTA.
Is set to a shorter time as is larger. In step 126, control for repeating the assist pressure increasing state shown in FIG. 2 and the assist pressure holding state shown in FIG. 3 at a predetermined duty ratio Duty1 (hereinafter referred to as Duty pressure increasing control) is started. After the processing of step 126 is performed, thereafter, the wheel cylinder pressure P _{W / C} of each wheel starts increasing at a predetermined pressure increasing gradient.

In step 128, the above-mentioned step 126
Is executed, the pressure increase time T _STAHas passed
Is determined. The process of step 128 is performed by
T_{ST A}Is repeatedly executed until it is determined that
You. As a result, the pressure increase time T_STAIs determined to have passed
In this case, the process of step 130 is performed next. Stay
In step 130, the Duty started in step 126 above
The pressure increase control is ended. The process of step 130 is executed
The wheel cylinder pressure P_{W / C}Pressure is stopped
You. When the above process is completed, the process shown in FIG.
Other processing is executed.

[0082] According to the above processing, after the execution of the start pressurizing mode is requested, for a predetermined pressure increasing time T _STA Du
By executing the ty pressure increase control, the wheel cylinder pressure P _{W / C}
Can be increased. In the system of the present embodiment, the pumps 100 and 102
The larger A is, the higher the discharge capacity is exhibited during execution of the start pressure increase mode. Therefore, in order to generate a constant assist pressure Pa by performing the start pressurizing mode, as the change time output value pMCSTA is large, it is necessary to shorten the pressure increasing time T _{ST A.}

In this embodiment, the map shown in FIG. 14 is set such that the pressure increase time T _STA becomes shorter as the change-time output value pMCSTA becomes larger, as described above. Further, in the map shown in FIG. 14, the pressure increase time T _STA is
It is determined so that changes appearing in the discharge characteristics of the pumps 100 and 102 can be appropriately offset. Therefore,
According to the braking force control device of the present embodiment, by executing the start pressure increase mode, a constant assist pressure Pa can always be generated without being affected by the master cylinder pressure PM _{/ C.}

FIG. 15 is a flowchart showing a part of a main routine executed by the ECU 10. The ECU 10
By executing the series of processes shown in FIG. 15, (II) when the execution of the assist pressure increasing mode is required, the wheel cylinder pressure P _{W /} is not affected by the master cylinder pressure P _{M / C. C} is constantly increased with a constant pressure increasing tendency. A series of processes shown in FIG. 15 is executed under the condition that the execution condition of the BA control is satisfied. A series of processes shown in FIG.

In step 132, it is determined whether or not the assist pressure increasing mode is required. As described above, the assist pressure increasing mode is required when the driver performs a brake operation intended to sharply increase the braking force. When it is determined that the assist pressure increasing mode is required as a result of the above determination, the routine proceeds to step 134.
Is performed.

In step 134, the output signal pMC output from the hydraulic pressure sensor 29 at that time is fetched. In step 136, a duty ratio Duty2 used during execution of the assist pressure increasing mode is calculated. In this step 136, the duty ratio Duty2 is calculated based on the output signal pMC.

FIG. 16 shows an example of a map defining the relationship between the duty ratio Duty2 and the output signal pMC. ECU1
In the step 136, the duty ratio Duty2 is calculated according to the map shown in FIG. According to the map shown in FIG. 16, the duty ratio Duty2 is set to a smaller value as the output signal pMC is larger, that is, as the master cylinder pressure PM _{/ C} is higher.

At step 138, the duty ratio Duty2
Then, the control for repeating the assist pressure increasing state shown in FIG. 2 and the assist pressure holding state shown in FIG. 3, that is, the Duty increasing control using the duty ratio Duty2 is started.
Note that Duty 2 is the ratio of the time during which the braking force control device is in the assist pressure increasing state in one cycle. When the process of step 138 is executed, the wheel cylinder pressure P _{W / C} of each wheel starts increasing at a predetermined pressure increasing gradient. When the above processing ends, other processing not shown in FIG. 13 is performed thereafter.

In the main routine of this embodiment, if it is determined in step 132 that the assist pressure increasing mode is not required, the process of step 140 is executed. In step 140, the Duty pressure increase control started in step 138 is ended. This step 140
Is executed, the increase of the wheel cylinder pressure P _{W / C} is stopped. After the above processing is completed,
The other processing not shown in FIG.

According to the above-described processing, only when the assist pressure increase mode is required, the duty increase control using the duty ratio Duty 2 is executed, so that the wheel cylinder pressure P
_{W / C} pressure can be increased. In the system of the present embodiment, the pumps 100 and 102 exhibit a higher discharge capacity during execution of the assist pressure increasing mode as the output signal pMC is larger. Therefore, in order to obtain a constant pressure increasing gradient during execution of the assist pressure increasing mode, it is necessary to reduce the duty ratio Duty2 as the output signal pMC increases.

In the present embodiment, the map shown in FIG. 16 is set such that the larger the output signal pMC, the shorter the duty ratio Duty2 becomes, as described above. Further, in the map shown in FIG. 16, the duty ratio Duty2 is determined so that changes appearing in the discharge characteristics of the pumps 100 and 102 can be appropriately offset. Therefore, according to the braking force control device of the present embodiment, the wheel cylinder pressure P _{W is} always maintained at a constant pressure increase gradient without being affected by the master cylinder pressure P _{M / C} during the execution of the assist pressure increase mode. _{/ C}
Can be increased.

FIG. 17 is a flowchart showing a part of a main routine executed by the ECU 10. The ECU 10
By executing a series of processes shown in FIG. 17, (V) when execution of the assist pressure gradual increase mode is requested, the wheel cylinder pressure P _{W /} is not affected by the master cylinder pressure P _{M / C. C} is constantly increased stepwise by a constant value. A series of processes shown in FIG. 17 is executed under the condition that the execution condition of the BA control is satisfied. A series of processes shown in FIG.

In step 142, it is determined whether or not the assist pressure gradual increase mode is required. As described above, the assist pressure gradual increase mode is required when the driver performs a brake operation intended to gradually increase the braking force. If it is determined that the assist pressure gradual increase mode is required as a result of the above determination, then the routine proceeds to step 14.
4 is executed. On the other hand, if it is determined that the assist pressure gradual increase mode is not requested, other processing not shown in FIG. 17 is performed thereafter.

At step 144, the output signal pMC output from the hydraulic pressure sensor 29 at that time is fetched. In step 146, when the assist pressure gradual increase mode is required, a time T _MODE2 for maintaining the braking force control device in the assist pressure increase state is calculated. Step 14
In 6, the predetermined time T _MODE2 is calculated based on the output signal pMC.

FIG. 18 shows the _relationship between the predetermined time T _MODE2 and the output signal p.
4 shows an example of a map that defines a relationship with MC. ECU10
Calculates the predetermined time T _MODE2 in step 146 according to the map shown in FIG. According to the map shown in FIG. 18, the predetermined time T _MODE2 is set to be shorter as the output signal pMC is larger, that is, as the master cylinder pressure PM _{/ C} is higher.

In step 148, the braking force control device is
A process for increasing the assist pressure shown in FIG. 2 is executed.
You. When the process of step 148 is executed,
Wheel cylinder pressure P_{W / C}Starts increasing at the specified pressure gradient.
You. In step 150, the process of step 148 is performed.
After execution, a predetermined time T _MODE2Whether or not
Separated. The processing in step 148 is performed for a predetermined time T
_MODE2Is repeatedly executed until it is determined that
You. As a result, the predetermined time T _MODE2Is determined to have passed
Then, the process of step 152 is executed next.

In step 152, a process is executed for bringing the braking force control device into the assist pressure holding state shown in FIG. When the process of step 152 is executed, the increase in the wheel cylinder pressure P _{W / C} is stopped. Upon completion of the above processing, other processing not shown in FIG. 17 is performed. According to the above processing, when the assist pressure gradual increase mode is required, the wheel cylinder pressure P _{W / C} can be increased stepwise only for the predetermined short time T _MODE2 . In the system of the present embodiment, the pumps 100 and 102 exhibit a higher discharge capacity during execution of the assist pressure increasing mode as the output signal pMC is larger. Therefore, in order to increase the wheel cylinder pressure P _{W / C} by a constant value in the assist pressure gradual increase mode, it is necessary to shorten the predetermined time T _MODE2 as the output signal pMC increases.

In this embodiment, the map shown in FIG. 18 is set such that the larger the output signal pMC, the shorter the predetermined time T _MODE2 as described above. Further, FIG.
In the map shown in FIG. 8, the predetermined time T _MODE2 is set so that changes appearing in the discharge characteristics of the pumps 100 and 102 can be appropriately offset. Therefore, according to the braking force control device of the present embodiment, by executing the assist pressure gradual increase mode, the wheel cylinder pressure P _{W / C is} always fixed by a constant value without being affected by the master cylinder pressure P _{M / C.} Can be increased.

As described above, according to the braking force control apparatus of this embodiment, although the discharge capacity of the pumps 100 and 102 fluctuates according to the master cylinder pressure PM _{/ C} , (I) the starting pressure increase Depending on the mode, a constant assist pressure Pa can always be generated, and (II) the wheel cylinder pressure P _{W / C} can be increased with a constant pressure increasing gradient during execution of the assist pressure increasing mode. (V) The wheel cylinder pressure P _{W / C} can always be increased by a constant value in the assist pressure gradual increase mode. For this reason, according to the braking force control device of the present embodiment, it is possible to generate a braking force with stable characteristics during the execution of the BA control.

By the way, in the above embodiment, (I)
In order to always keep the assist pressure Pa generated by the start pressure increase mode at a constant value, the pressure increase time T _STA is changed according to the master cylinder pressure PM _{/ C} , but the assist pressure Pa is set to a constant value. The technique is not limited to this. That is, the assist pressure Pa can be set to a constant value by, for example, changing the duty ratio Duty1 used during the execution of the start pressure increase mode based on the output signal pMC. Also, the assist pressure Pa is
The constant values can also be obtained by configuring the variable capacity pumps 00 and 102 and changing the pump capacity according to the master cylinder pressure PM _{/ C.}

Further, in the above embodiment, (II) in order to always obtain a constant pressure increasing gradient during the execution of the assist pressure increasing mode, the duty ratio is changed according to the master cylinder pressure PM _{/ C.}
Although Duty 2 is changed, the method for obtaining a constant pressure increase gradient is not limited to this. Similarly, in the above embodiment, (V) in order to constantly increase the wheel cylinder pressure P _{W / C} by a constant value in the assist pressure gradual increase mode, a predetermined time T according to the master cylinder pressure PM _{/ C. Although MODE2} is to be changed, the method for obtaining a constant pressure increase is not limited to this. The above-described constant pressure increasing gradient and the constant pressure increasing amount can also be obtained, for example, by configuring the pumps 100 and 102 with variable displacement pumps and changing the pump displacement according to the master cylinder pressure PM _{/ C.} Can be.

Although the above embodiment aims at obtaining a stable pressure increase characteristic during the execution of the BA control, the application of the present invention is not limited to the combination with the BA control. Using the cylinder pressure P as the hydraulic pressure source
It can be widely applied to brake fluid pressure control for increasing _{W / C.} In the above embodiment, the ECU 1
0 corresponds to steps 122, 124, 134, 136 and
By executing the processes of 144 and 146, the "pressure increasing condition changing means" according to claim 1 is realized.

In the above embodiment, the ECU 1
0 corresponds to steps 122, 124, 134 and 136 described above.
By executing the above processing, the "pressure increasing condition changing means" according to claim 2 is realized. Further, in the above embodiment, the pressure increase time T _STA corresponds to the “pressure increase condition” of the fourth aspect, and the ECU 10 executes the processing of steps 122 and 124 to execute the pressure increase time T _STA. The "pressure increasing condition changing means" described in 4 is realized.

In the above embodiment, SRC _-1
32 and the SRC- ₂₃₆ correspond to the "suction control valve" of the fifth aspect, and the ECU 10 realizes the assist pressure increasing state by means of the "pressure increasing control means" of the fifth aspect. Are the above steps 122, 124, 134,
By executing the processes of 136, 144 and 146, the "pressure increasing condition changing means" according to claim 5 is realized.

[0105]

As described above, according to the first, second, fifth and sixth aspects of the present invention, during execution of the brake fluid pressure control, the brake hydraulic pressure control is not affected by the master cylinder pressure. The wheel cylinder pressure can be increased with a constant pressure increasing characteristic. According to the third aspect of the invention, it is possible to always increase the wheel cylinder pressure with a constant pressure increase characteristic without being affected by the master cylinder pressure during the execution of the brake assist control.

According to the fourth aspect of the present invention, after the brake assist control is started, the start pressure increase control is executed to keep the wheel cylinder pressure constant without being affected by the master cylinder pressure. The pressure can be increased by the pressure increasing characteristics described above.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram of a braking force control device according to an embodiment of the present invention.

FIG. 2 is a diagram showing an assist pressure increasing state of the braking force control device shown in FIG. 1;

FIG. 3 is a diagram showing an assist pressure holding state of the braking force control device shown in FIG. 1;

FIG. 4 is a diagram showing a reduced assist pressure state of the braking force control device shown in FIG. 1;

5 is a diagram illustrating changes that occur in a master cylinder pressure PM _{/ C} and a wheel cylinder pressure _{PW / C} when an emergency braking operation is performed in the braking force control device illustrated in FIG. 1;

FIG. 6 is a table showing a control mode executed after a start pressure increase mode when BA control is executed in the braking force control device shown in FIG. 1;

FIG. 7 is a table showing a control mode executed next to the assist pressure increasing mode when BA control is executed in the braking force control device shown in FIG. 1;

FIG. 8 is a table showing a control mode executed next to the assist pressure reduction mode when BA control is executed in the braking force control device shown in FIG. 1;

FIG. 9 is a table showing a control mode executed next to the assist pressure holding mode when BA control is executed in the braking force control device shown in FIG. 1;

FIG. 10 is a table showing a control mode executed next to the assist pressure gradual increase mode when BA control is executed in the braking force control device shown in FIG. 1;

11 is a table showing a control mode that is executed after the assist pressure gradual decrease mode when BA control is executed in the braking force control device shown in FIG. 1;

12 is a view showing a relationship between a discharge capacity of a pump provided in the braking force control device shown in FIG. 1 and a master cylinder pressure P _{M / C.}

FIG. 13 is a flowchart showing a series of processing executed when a start pressure increase mode is requested in one embodiment of the present invention.

FIG. 14 is an example of a map referred to in a series of processes shown in FIG. 13;

FIG. 15 is a flowchart showing a series of processes executed when an assist pressure increasing mode is requested in one embodiment of the present invention.

FIG. 16 is an example of a map referred to in a series of processes shown in FIG. 15;

FIG. 17 is a flowchart showing a series of processes executed when an assist pressure gradual increase mode is requested in one embodiment of the present invention.

FIG. 18 is an example of a map referred to in a series of processes shown in FIG. 17;

[Explanation of symbols]

Reference Signs List 10 Electronic control unit (ECU) 12 Brake pedal 18 Master cylinder 26 First hydraulic passage 28 Second hydraulic passage 29 Hydraulic pressure sensor 70, 72, 74, 76 Wheel cylinder 100, 102 Pump PM _{/ C} master cylinder pressure pMC Output signal ΔpMC change rate

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hideyuki Aizawa 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation (72) Inventor Masahiro Hara 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation

Claims (6)

[Claims] A brake for sucking brake fluid from a hydraulic passage communicating the master cylinder and the wheel cylinder, and a brake for controlling the wheel cylinder pressure by supplying the brake fluid discharged from the pump to the wheel cylinder; A braking force control device for executing hydraulic pressure control, comprising: a pressure increasing condition changing means for changing a pressure increasing condition when supplying brake fluid from the pump to a wheel cylinder in accordance with a master cylinder pressure. Power control device. 2. The braking force control device according to claim 1, wherein the pressure increasing condition changing means increases the pressure increasing time as the master cylinder pressure decreases. 3. The braking force control device according to claim 1, wherein the brake fluid pressure control generates a wheel cylinder pressure that is higher than a master cylinder pressure when an emergency braking operation is performed by a driver. A braking force control device, which is a brake assist control. 4. The brake control apparatus according to claim 3, wherein after the brake assist control is started, the brake fluid discharged from the pump is supplied to the wheel cylinder for a predetermined pressure increase time. And the pressure increasing condition changing means changes the pressure increasing condition of the start pressure increasing control according to a master cylinder pressure. 5. The braking force control device according to claim 1, wherein a suction control valve disposed between the hydraulic passage and the pump and a wheel cylinder pressure increase are required. Pressure increase control means for performing pressure increase control for operating a pump and opening the suction control valve, wherein the pressure increase condition changing means increases the pressure increase as the master cylinder pressure decreases. A braking force control device, wherein the time during which the suction control valve is opened during execution of control is prolonged. 6. The braking force control device according to claim 1, wherein the pump is a variable displacement pump, and the pressure increasing condition changing means increases the discharge capacity of the pump as the master cylinder pressure decreases. Characteristic braking force control device.