JPH1120673A - Braking force control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide in constitution with short pipe length such a function that brake fluid pressure higher than that of usual time is generated when urgent braking operation is actuated. SOLUTION: In this device, disposed is a pump 76 provided with a suction hole communicatable to a hydraulic passage 22 communicating to a master cylinder 18, and a delivery hole communicatable to wheel cylinders 50, 52. The first master cut valve 28 and the first relief valve 34 are arranged between the master cylinder 18 and the wheel cylinders 50, 52. The first master cut valve 28 is usually kept in opened condition. When urgent brake operation is actuated, the first master cut valve 28 is brought into closed condition, a suction valve 78 is opened, and the pump 76 is made into ON-condition. Relief pressure of the first relief valve 34 is set to a prescribed assist pressure Pa.

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 above-described conventional apparatus includes a master cylinder that generates a brake fluid pressure according to a brake operation amount. Also,
The above-described conventional device includes a reservoir tank for storing brake fluid, and a pump that sucks brake fluid from the reservoir tank and generates a brake fluid pressure higher than the master cylinder pressure PM _{/ C.} .

In the above-mentioned conventional apparatus, when a driver performs a normal brake operation, brake fluid is supplied to a wheel cylinder from a master cylinder.
In this case, the wheel cylinder pressure P _{W / C} is a hydraulic pressure corresponding to the brake operation amount. Further, in the above conventional device,
When the driver performs an emergency braking operation, the pump supplies brake fluid to the wheel cylinder. In this case, the wheel cylinder generates a wheel cylinder pressure P _{W / C which} is higher than the master cylinder pressure P _{M / C.}

[0004] A driver of a vehicle executes an emergency braking operation when it is desired to quickly increase the braking force. According to the above-described conventional braking force control device, when an emergency brake operation is performed, a larger brake fluid pressure can be supplied to the wheel cylinder than in a normal case. Therefore, according to the above-described conventional device, it is possible to appropriately respond to the driver's request.

[0005]

However, the above-mentioned conventional apparatus employs a configuration in which the pump sucks brake fluid from a reservoir tank. Therefore, in the above-described conventional apparatus, a path connecting the reservoir tank and the suction side of the pump is required in addition to a path connecting the master cylinder and the wheel cylinder and a path connecting the discharge side of the pump and the wheel cylinder. Is done. Therefore, in order to realize the above-described conventional apparatus, a long pipe was required.

The present invention has been made in view of the above points, and has a function of generating a larger brake fluid pressure than usual when an emergency brake operation is performed;
An object is to provide a braking force control device having a short pipe length.

[0007]

The above object is achieved by the present invention.
As described in the above, in a braking force control device having a pump having a suction hole that can communicate with a hydraulic pressure passage communicating with the master cylinder and a discharge hole that can communicate with the wheel cylinder, the master cylinder side and the wheel cylinder side are electrically connected. A brake fluid flowing from the wheel cylinder side to the master cylinder side only when the hydraulic pressure on the wheel cylinder side is higher than the hydraulic pressure on the master cylinder side and exceeds the first relief pressure. First control valve means for realizing a second state permitting the flow of air, and brake fluid discharged from the pump after realizing the second state when an emergency brake operation is performed by a driver. And a BA control unit for executing a brake assist control to be supplied to the wheel cylinder.

In the present invention, when the first control means realizes the first state, the master cylinder and the wheel cylinder are electrically connected. In this case, the wheel cylinder pressure can be controlled to be equal to the master cylinder pressure. First
When the control means realizes the second state, it is possible to generate a higher hydraulic pressure on the wheel cylinder side than on the master cylinder side. According to the brake assist control,
Under such circumstances, the brake fluid is supplied from the pump to the wheel cylin- ders. In this case, a wheel cylinder pressure higher than the master cylinder pressure can be generated in the wheel cylinder. In the present invention, the pump sucks the brake fluid from the hydraulic passage communicating with the master cylinder. In this case, since a pipe connecting the reservoir tank and the pump is unnecessary, the system is configured with a short pipe length.

According to a second aspect of the present invention, in the braking force control apparatus according to the first aspect, the brake assist control is such that the wheel cylinder pressure is increased by a predetermined assist pressure as compared with the master cylinder pressure. In addition, the braking force control device in which the first relief pressure is set to the assist pressure is effective in reflecting an increase or decrease in the brake operation amount in the wheel cylinder pressure during execution of the brake assist control. .

In the present invention, the second state is realized by the first control means during the execution of the brake assist control. According to the second state, the hydraulic pressure on the wheel cylinder side can be higher than the master cylinder pressure by the first relief pressure. During the execution of the brake assist control, a fluid pressure sufficiently higher than the master cylinder pressure is supplied from the pump to the wheel cylinder. Therefore, according to the brake assist control, the wheel cylinder pressure is controlled to a fluid pressure higher than the master cylinder by the first relief pressure.

The first relief pressure is set to an assist pressure to be added to the master cylinder pressure during the execution of the brake assist control. Therefore, during the execution of the brake assist control, the wheel cylinder pressure is controlled to a hydraulic pressure that is higher by a predetermined assist pressure than the master cylinder pressure. The master cylinder pressure increases and decreases as the brake operation amount increases and decreases. For this reason, the wheel cylinder pressure during execution of the brake assist control increases and decreases with an increase and decrease in the brake operation amount, while maintaining a value higher than the master cylinder pressure by the assist pressure.

According to a third aspect of the present invention, in the braking force control apparatus according to the second aspect, the second control valve means is disposed in series between the hydraulic passage and the wheel cylinder.
Control valve means, wherein the second control valve means has a third state in which the master cylinder side and the wheel cylinder side are in a conducting state, and a third state in which the wheel cylinder side hydraulic pressure is higher than the master cylinder side hydraulic pressure. And a fourth state in which the flow of brake fluid from the wheel cylinder side to the master cylinder side is allowed only when the pressure is higher than the relief pressure of the second relief pressure, and the second relief pressure is equal to the first relief pressure. The braking force control device having a higher pressure than the relief pressure is effective in executing a brake fluid pressure control different from the brake assist control.

In the present invention, when the first control valve means realizes the first state and the second control valve means realizes the third state, the master cylinder and the wheel cylinder become conductive. Hereinafter, this state is referred to as a normal state. When the state of the first control valve means changes from the above-described normal state to the second state, the hydraulic pressure on the wheel cylinder side is higher than the master cylinder side by the first relief pressure, that is, only the predetermined assist pressure. It is possible to generate a high hydraulic pressure. In the present invention, the brake assist control is realized by operating the pump under the above-described circumstances.

When the state of the second control valve means changes from the above-mentioned normal state to the fourth state, the second relief having a higher pressure than the first relief pressure is provided on the wheel cylinder side as compared with the master cylinder side. It is possible to generate a hydraulic pressure that is higher by the pressure. Therefore, operating the pump under the above conditions,
It is possible to realize a brake fluid pressure control for generating a large differential pressure between the master cylinder pressure and the wheel cylinder pressure as compared with the brake assist control.

According to a fourth aspect of the present invention, in the braking force control apparatus according to the third aspect, the wheel is moved from the master cylinder side by bypassing both the first control valve means and the second control valve means. The braking force control device including the check valve means that allows the flow of the brake fluid toward the cylinder side, when the master cylinder pressure is higher than the wheel cylinder pressure, the brake fluid control device that controls the brake fluid from the master cylinder to the wheel cylinder. It is effective in always allowing the flow.

In the present invention, during the execution of the brake fluid pressure control, that is, during the execution of the brake assist control or other brake fluid pressure control, the first control valve means or the second control valve means is controlled.
Control valve means prevents the flow of brake fluid from the master cylinder to the wheel cylinder. According to the present invention, the flow of the brake fluid from the master cylinder to the wheel cylinder is permitted by the check valve means even under the above-mentioned situation. Therefore, when a master cylinder pressure higher than the wheel cylinder pressure is generated during the execution of the brake fluid pressure control, the wheel cylinder pressure is reliably increased to the master cylinder pressure.

[0017]

FIG. 1 is a system configuration diagram of a part of a braking force control device according to an embodiment of the present invention. The braking force control device of the present embodiment includes a first system including a right front wheel FR and a left rear wheel RL, and a second system including a left front wheel FL and a right rear wheel RR. These two systems are substantially identical in configuration. Therefore, in the following description, only the configuration and operation of the first system will be described.

The braking force control device of the present embodiment is a braking force control device for diagonal piping (X piping). The braking force control device 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. The brake switch 14 outputs an ON signal when the brake pedal 12 is depressed. The ECU 10 controls the brake pedal 12 based on the output signal of the brake switch 14.
It is determined whether or not is depressed.

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 and a second hydraulic chamber are formed inside the master cylinder 18. In each of these hydraulic chambers, 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 20 is provided above the master cylinder 18. The master cylinder 18 and the reservoir tank 20 are electrically connected only when the depression of the brake pedal 12 is released. A first hydraulic passage 22 and a second hydraulic passage 24 communicate with the first hydraulic chamber and the second hydraulic chamber of the master cylinder 18, respectively. The first hydraulic passage 22 communicates with a first hydraulic circuit. On the other hand, the second hydraulic passage 22 communicates with a second hydraulic circuit (not shown).

The first hydraulic passage 22 is provided with a hydraulic pressure sensor 26. The hydraulic pressure sensor 26 is connected to the first hydraulic pressure passage 22.
, 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 26 is supplied to the ECU 10. The ECU 10 detects the master cylinder pressure PM _{/ C} based on the output signal pMC.

A high pressure passage 30 communicates with the first hydraulic passage 22 via a first master cut valve 28. The first master cut valve 28 maintains the valve open state in a normal state, and the ECU 1
This is a two-position solenoid valve that is closed when a drive signal is supplied from 0. The first master cut valve 28 includes:
The check valve 32 and the first relief valve 34 are arranged in parallel. The check valve 32 is connected to the high pressure passage 3 from the hydraulic passage 22 side.
This is a one-way valve that allows only the flow of brake fluid toward the zero side.

The first relief valve 34 is connected to the high pressure passage 3
Only when the hydraulic pressure on the zero side is higher than the first relief pressure compared to the hydraulic pressure on the hydraulic pressure passage 22 side, the flow of the brake fluid from the high pressure passage 30 toward the hydraulic pressure passage 22 is reduced. Allowable constant pressure release valve. The brake fluid pressure control device of the present embodiment is characterized in that the first relief pressure of the first relief valve 34 is set to a predetermined assist pressure described later.

The high pressure passage 30 communicates with control hydraulic pressure passages 40 and 42 via holding valves 36 and 38. Holding valve 3
Numerals 6 and 38 are two-position solenoid valves that maintain a valve open state in a normal state and are closed when a drive signal is supplied from the ECU 10. Check valves 44 and 46 are arranged in parallel with the holding valves 36 and 38, respectively. Check valve 44, 4
Reference numeral 6 denotes a one-way valve that allows only the flow of brake fluid from the control hydraulic pressure passages 40 and 42 toward the high-pressure passage 30.

The control hydraulic passage 40 has a proportioning
Left rear wheel R via valve 48 (hereinafter referred to as PV48)
L is communicated with the wheel cylinder 50. On the other hand, the control liquid
The pressure passage 42 communicates with the wheel cylinder 52 of the right front wheel FR.
doing. The PV 48 is supplied to the control hydraulic pressure passage 40
Brake fluid pressure P_BIf is less than the specified value,
Rake fluid pressure P_BIs supplied to the wheel cylinder 50 as it is,
On the other hand, the brake fluid pressure P supplied to the control fluid pressure passage 40_B
Is greater than a predetermined value, the brake fluid pressure P _BPredetermined
Valve machine that supplies the wheel cylinder 50 with attenuation at the ratio of
It is fine.

In the system of this embodiment, the left rear wheel RL
Near the front right wheel FR and the wheel speed sensor 5
4,56 are provided. The wheel speed sensor 54 outputs a pulse signal at a cycle corresponding to the wheel speed Vw of the left rear wheel RL. On the other hand, the wheel speed sensor 56 detects the wheel speed V of the right front wheel FR.
A pulse signal is output at a cycle corresponding to w. Output signals of the wheel speed sensors 54 and 56 are supplied to the ECU 10.
The ECU 10 determines the left rear wheel RL based on these output signals.
And the wheel speed Vw of the right front wheel FR are detected.

The control hydraulic pressure passages 40 and 42 communicate with the low pressure passage 62 via pressure reducing valves 58 and 60, respectively.
The pressure reducing valves 58 and 60 maintain the valve closed state in a normal state,
This is a two-position solenoid valve that is opened when a drive signal is supplied from the solenoid valve 10. The low-pressure passage 62 communicates with an auxiliary reservoir 64. The auxiliary reservoir 64 has a piston 66 and a spring 68 therein. The auxiliary reservoir 64 can store a predetermined amount of brake fluid therein by elastically deforming the spring 68.

A suction passage 72 communicates with the auxiliary reservoir 64 via a check valve 70. The suction passage 72 communicates with the suction side of the pump 76 via a check valve 74, and communicates with the hydraulic passage 22 via a suction valve 78.
The suction valve 78 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 EUC 10. The discharge side of the pump 76 is
It communicates with 0. The pump 30 includes a reservoir tank 64
Alternatively, the brake fluid is sucked from the suction passage 72 and the sucked brake fluid is discharged at a predetermined discharge pressure into the high pressure passage 30.
Can be discharged.

Next, the operation of the braking force control device according to the present embodiment will be described with reference to FIGS. FIG.
3 shows a flowchart of an example of a main routine executed by the ECU 10 in the braking force control device of the present embodiment.
The routine shown in FIG. 2 is repeatedly started each time the processing is completed. In the routine shown in FIG. 2, first, the process of step 80 is executed.

In step 80, it is determined whether or not the driver has performed an emergency braking operation. When the driver performs a brake operation for the purpose of emergency braking, the brake pedal 12 is depressed at high speed and greatly. In this case, the master cylinder pressure P _{M / C} reaches a large value with a steep pressure increase gradient. Therefore, in this embodiment, when the master cylinder pressure PM _{/ C} suddenly reaches a large value, it can be determined that the driver has performed the emergency braking operation.

In step 80, when the output signal pMC of the hydraulic pressure sensor 26 exceeds a predetermined value and the rate of change dpMC / dt exceeds the predetermined value, it is determined that the emergency braking operation has been performed. You. The process of step 80 is repeatedly executed until it is determined that the emergency brake operation has been executed. All the solenoid valves included in the braking force control device are turned off while the processing of step 80 is repeated. In this case, the braking force control device is maintained in the state shown in FIG.

According to the state shown in FIG. 1, the master cylinder 18 communicates with the wheel cylinders 50, 52 via the high pressure passage 30 and the control hydraulic pressure passages 40, 42. In this case, the wheel cylinder pressure P of the left rear wheel RL and the right front wheel FR
_{The W / C} is controlled using the master cylinder 18 as a hydraulic pressure source. Therefore, according to the state shown in FIG. 1, the wheel cylinder pressure P _{W / C} corresponding to the brake operation amount can be generated in the wheel cylinders 50 and 52 as in the normal brake device. As described above, according to the braking force control device of the present embodiment, when the driver does not perform the emergency braking operation, that is, when the driver performs the normal braking operation, the function as the normal braking device is performed. Can be realized.

When the emergency braking operation is performed by the driver, the condition of step 80 is satisfied, and then the process of step 82 is performed. In step 82, a process is executed in which the first master cut valve 28 is closed (ON state), the suction valve 78 is opened (ON state), and the pump 76 is ON.

In the system of this embodiment, the first master
When the cut valve 28 is closed, the first relief valve 3
As long as the valve 4 is not opened, the hydraulic passage 22
The flow of brake fluid toward the side is blocked. this
In this case, the hydraulic pressure in the high-pressure passage 30 is
That is, the master cylinder pressure P_{M / C}High pressure compared to
Can be. The relief valve 28 is connected to the hydraulic pressure of the high pressure passage 30.
Is the master cylinder pressure P _{M / C}The first relief pressure is
The valve opens when the pressure exceeds the limit. Therefore, the first master
When the valve 28 is in the closed state, the hydraulic pressure on the high pressure passage 30 side is
Is the master cylinder pressure P_{M / C}1st relief pressure compared to
Higher hydraulic pressures can be achieved.

In the system of this embodiment, the suction valve 78
Is in the valve open state, the brake fluid on the hydraulic passage 22 side reaches the suction side of the pump 74. When the pump 76 is turned on in this state, the pump 76 sucks the brake fluid from the hydraulic passage 22 and discharges the sucked brake fluid to the high-pressure passage 30. The pump 76
It has the ability to generate a higher hydraulic pressure than the master cylinder pressure PM _{/ C.} Therefore, when the processing of step 82 is executed, the first master cut valve 28 is closed, the suction valve 78 is opened, and the pump 76 is turned on. The internal pressure of the high-pressure passage 30 is increased to a hydraulic pressure that is higher by a first relief pressure than the master cylinder pressure PM _{/ C.}

As described above, according to the braking force control apparatus of the present embodiment, after the driver performs the emergency braking operation, the first relief pressure in the high-pressure passage 30 is higher than the master cylinder pressure PM _{/ C.} Only a high brake fluid pressure P _B can be generated. Therefore, according to the braking force control device of the present embodiment, after the driver performs the emergency braking operation,
A high wheel cylinder pressure P _{W / C} can be generated in the wheel cylinders 50 and 52 as compared with normal times. Less than,
As described above, the wheel cylinder pressure P which is higher than normal
Control for generating _{W / C} is referred to as brake assist control (BA control).

In step 84, it is determined whether or not the BA control end condition is satisfied. It is determined that the BA control end condition is satisfied when the vehicle speed V is sufficiently reduced and when the driver releases the brake operation. In this step 84, specifically, when the vehicle speed V calculated based on the wheel speed Vw falls below the predetermined speed α, and when the output signal pMC of the hydraulic pressure sensor 26 becomes a sufficiently small value Or brake switch 1
When the output signal of No. 4 changes from on to off, it is determined that the BA control end condition has been satisfied. The process of step 84 is repeatedly executed until it is determined that the BA control end condition is satisfied. While the process of step 84 is repeatedly executed, the braking force control device continuously executes the BA control.

FIG. 3 shows the high pressure passage 30 during the execution of the BA control.
Of an example of a change appearing in the brake fluid pressure P _B (solid line), and shows during execution of the BA control an example of a change generated in the master cylinder pressure P _{M / C} and (dashed line). As described above, during execution of the BA control, the master cylinder pressure P _{M / C}
Only the first relief pressure high-pressure brake fluid pressure P _B produced as compared with. In this embodiment, the first relief pressure is BA
The predetermined assist pressure Pa to be generated during the execution of the control is set. Therefore, as shown in FIG. 3, during execution of the BA control, the brake fluid pressure P _{B in} the high-pressure passage 30 is constantly controlled to a fluid pressure higher than the master cylinder pressure PM _{/ C} by the assist pressure Pa.

The high pressure passage 30 is provided with a master cylinder pressure P _{M / C}
When the brake fluid pressure P _{B that} is higher by the assist pressure Pa than that of the master cylinder pressure P _{M / C} is introduced into the high-pressure passage 30, a large deceleration is generated in the vehicle. Occurs. Hereinafter, the deceleration generated in response to the master cylinder pressure P _{M / C} is referred to as a normal deceleration G _0, and the deceleration generated due to the assist pressure Pa is referred to as an assist deceleration G
a.

In this embodiment, the assist pressure Pa (that is, the first relief pressure) is set so that the assist deceleration Ga is about 0.3 G. For this reason,
During the execution of the BA control, the vehicle normally receives the deceleration G _0.
Deceleration about 0.3 G larger than that of Usually deceleration G _0, by the master cylinder pressure P _{M / C} is increased or decreased, i.e., varies by the brake operation amount is increased or decreased by the driver. At this time, the deceleration of the vehicle is
While the assist deceleration G ₀ is maintained at approximately 0.3 G, it varies according to the increase or decrease of the brake operation amount. Therefore, according to the braking force control device of the present embodiment, it is possible to increase or decrease the deceleration of the vehicle according to the driver's intention while maintaining the substantially constant assist deceleration Ga during the execution of the BA control. .

If it is determined in step 84 that the condition for terminating the BA control is satisfied, the process proceeds to step 86. In step 86, the first master cut valve 2
8 is opened (off state), the suction valve 78 is closed (off state), and the pump 76 is turned off. When the process of step 86 is performed, the braking force control device enters the state shown in FIG.
It returns to a state where it can function as a normal brake device.
When the process of step 86 is performed, the current routine ends.

As described above, according to the braking force control device of the present embodiment, when the driver performs a normal braking operation, the function as a normal braking device can be realized, and the driver can perform the normal braking operation. When an emergency brake operation is performed, a function of generating a deceleration that is larger than usual and that increases or decreases in accordance with the driver's brake operation can be realized without performing complicated control. Therefore, according to the system configuration of the present embodiment, an inexpensive and highly safe braking force control device can be realized.

In the above embodiment, when the first master cut valve 28 is in the open state, the "first state" of the first embodiment is changed to the "first state" when the first master cut valve 28 is in the closed state. In some cases, the "second state" of the first aspect is realized, and the first master cut valve 28 and the first relief valve 34 correspond to the "first control valve means" of the first aspect. ing. In the above embodiment,
The “BA control means” according to claim 1 is realized by the ECU 10 executing the processing of steps 80 and 82.

Incidentally, in the above embodiment, the first
Although the master cut valve 28 is an open / close valve and the first relief valve 34 is disposed in parallel with the first master cut valve 28, the present invention is not limited to this. The function of the first relief valve 34 may be incorporated in the valve 28. Next, a second embodiment of the present invention will be described with reference to FIGS.

FIG. 4 is a system configuration diagram of the braking force control device according to the present embodiment. In FIG. 4, the same components as those shown in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. The braking force control device according to the present embodiment includes an ECU 9
0 is provided. The ECU 90 executes a control routine shown in FIG. Further, the braking force control device of the present embodiment includes a second master cut valve 92 disposed in series with the first master cut valve 28 between the hydraulic passage 22 and the high pressure passage 30. Further, the braking force control device according to the present embodiment includes a second relief valve 9 disposed in parallel with the second master cut valve 92.
4 and a check valve 96 that bypasses both the first master cut valve 28 and the second master cut valve 92.

The second master cut valve 92 is a two-position solenoid valve that keeps the valve open in a normal state and closes when a drive signal is supplied from the ECU 90. Further, the second relief valve 94 is configured to supply the hydraulic fluid from the high pressure passage 30 only when the hydraulic pressure on the high pressure passage 30 side is higher than the hydraulic pressure on the hydraulic pressure passage 22 side and exceeds the second relief pressure. This is a one-way valve that allows the flow of brake fluid toward the pressure passage 22 side. In the present embodiment, the second relief pressure is set to a value sufficiently larger than the first relief pressure. More specifically, the second relief pressure, the high pressure passage 30 side is set to a value capable of generating a brake fluid pressure P _B sufficient to the wheel locked while the vehicle is running.

FIG. 5 shows a flowchart of an example of a main routine executed by the ECU 90 in the braking force control device according to the present embodiment. The routine shown in FIG. 5 is repeatedly started each time the processing is completed. In FIG. 5, steps that execute the same processing as the steps shown in FIG. 2 are denoted by the same reference numerals, and description thereof will be omitted or simplified. In the routine shown in FIG. 5, first, the process of step 100 is executed.

In step 100, it is determined whether or not a request for VSC control has occurred. The VSC control generates a braking force on the front wheel on the turning outer wheel when a spin state of the vehicle is detected, and controls the left and right front wheels and the rear wheel on the turning inner wheel when a drift state of the vehicle is detected. This is control for generating power. In this step 100, VS
If it is determined that the request for the C control has occurred, the process of step 102 is executed next.

In step 102, the first master cut valve 28 is opened (off state), the second master cut valve 92 is closed (on state), and the suction valve 78 is opened (on state). And the process of turning on the pump 76 is executed. In the system of the present embodiment, when the first master cut valve 28 is in the open state and the second master cut valve 92 is in the closed state, unless the second relief valve 94 is opened, the high pressure passage The flow of brake fluid from the side 30 toward the hydraulic passage 22 is prevented. Under these circumstances, when the intake valve 78 is opened and the pump 76 is turned on, the hydraulic pressure in the high-pressure passage 30 is higher than the hydraulic pressure in the hydraulic passage 22 by the second relief pressure. It can be hydraulic. Therefore, step 10
When the second process is executed, the subsequent high-pressure passage 30, the brake fluid pressure P _B is generated enough to the left rear wheel RL and a right front wheel FR and locked while the vehicle is running.

In step 104, the holding valves 36, 38 and the pressure reducing valves 58, 60 are controlled according to the VSC control request. When the process of step 104 is executed, an appropriate wheel cylinder pressure P _{W / C} according to the request of the VSC control is generated in the wheel cylinders 50 and 52. Step 1
At 06, it is determined whether or not the end condition of the VSC control is satisfied. In this step 106, it is determined that the VSC control termination condition has been satisfied, for example, when the spin state or the drift state of the vehicle has converged. If it is determined in step 106 that the condition for terminating the VSC control is not satisfied, the process of step 104 is performed again. On the other hand, when it is determined that the termination condition of the VSC control is satisfied, the process of step 108 is executed next.

In step 108, processing for returning the braking force control device to the normal state shown in FIG. 1, specifically, processing for turning off all the solenoid valves and turning off the pump 76 is executed. Is done. When the process of step 108 is performed, the braking force control device returns to a state where it can function as a normal brake device again. This step 10
When the process of step 8 is completed, the current routine is completed.

In this routine, in step 100, V
If it is determined that the SC control request has not been issued, it is next determined in step 80 whether or not the emergency brake operation has been performed. As a result, if it is determined that the emergency brake operation has not been performed, the process of step 100 is performed again. While the processing of steps 100 and 80 is repeatedly executed, the braking force control device is maintained in a normal state shown in FIG. 1, that is, a state in which a function as a normal brake device can be realized.

In this routine, if it is determined in step 80 that the emergency brake operation has been performed, then the process of step 82, ie, the process for starting the BA control, is performed, and then step 110 Is performed. In step 110, it is determined whether or not a request for VSC control has occurred. As a result, if it is determined that a request for VSC control has occurred, the process of step 102 is executed to start VSC control. On the other hand, V
If it is determined that a request for SC control has not occurred, then in step 84, it is determined whether a BA control end condition has been satisfied.

In this routine, at step 84, BA
If it is determined that the control termination condition is not satisfied,
The process of step 110 is executed again. On the other hand, if it is determined in step 84 that the BA control end condition has been satisfied, then the process of step 108, that is,
A process for bringing the braking force control device into a normal state is executed.

According to the above processing, the VSC
If the control is required, it is possible to generate a high pressure of the brake fluid pressure P _B sufficient to each wheel locked in the high-pressure passage 30, when an emergency brake operation is performed by the driver, the master It is possible to generate a wheel cylinder pressure P _{W / C} that is higher than the cylinder pressure P _{M / C} by a predetermined assist pressure Pa (that is, a first relief pressure). Thus, according to the braking force control device of the present embodiment,
A function for executing the same BA control as in the first embodiment,
The function of executing the control can be realized with a simple configuration.

In the braking force control device of the present embodiment, BA
During the execution of the control and the execution of the VSC control, one of the first master cut valve 28 and the second master cut valve 92 is closed. Therefore, during the execution of the BA control and the execution of the VSC control, even if a master cylinder pressure PM _{/ C} higher than the hydraulic pressure in the high-pressure passage 30 is generated in the hydraulic passage 22, the brake is not applied. Fluid flows through the first master cut valve 28 and the second master cut valve 92 to the high pressure passage 3.
It does not flow to the zero side.

However, the braking force control device of this embodiment includes the check valve 96 that bypasses both the first master cut valve 28 and the second master cut valve 92. For this reason, when the master cylinder pressure PM _{/ C} higher than the hydraulic pressure in the high-pressure passage 30 is generated in the hydraulic passage 22 during the execution of the BA control and the execution of the VSC control, The master cylinder pressure P on the hydraulic passage 22 side via the check valve 96
_{M / C} can be supplied to the high pressure passage 30 side.

In the above embodiment, the second master cut valve 92 and the second relief valve 94 are provided in the third embodiment.
And the second control valve means described above.
The “third state” according to claim 3 when the master cut valve 92 is in the open state, and the “fourth state” according to claim 3 when the second master cut valve 92 is in the closed state. Are respectively realized.

By the way, in the above embodiment, the second
Although the master cut valve 92 is an open / close valve and a second relief valve 94 is arranged in parallel with the second master cut valve 92, the present invention is not limited to this. The function of the second relief valve 94 may be incorporated in the valve 92. Further, in the above embodiment, the BA control and the VSC control are realized, but the brake fluid pressure control combined with the BA control is not limited to the VSC control. That is,
The brake fluid pressure control combined with the BA control may be, for example, a known traction control control that generates a braking force on a drive wheel when an excessive drive torque is generated and suppresses idling of the drive wheel.

[0060]

As described above, according to the first aspect of the present invention, while adopting a system configuration with a short pipe length, a normal function of generating a wheel cylinder pressure according to a brake operation amount is compared with a normal function. And a brake assist function of generating a high wheel cylinder pressure.

According to the second aspect of the invention, during execution of the brake assist control, the wheel cylinder pressure is increased to a hydraulic pressure higher than the master cylinder by a predetermined assist pressure without performing complicated control, that is, Thus, the hydraulic pressure can be controlled to be higher by the assist pressure than the hydraulic pressure corresponding to the brake operation amount. According to the third aspect of the present invention, a brake assist control for controlling the wheel cylinder pressure to a hydraulic pressure higher by a predetermined assist pressure than the master cylinder pressure, and a master cylinder pressure and a wheel cylinder pressure are provided. Brake fluid pressure control that should generate a large differential pressure compared to the assist pressure can be realized together.

According to the present invention, when a master cylinder pressure higher than the wheel cylinder pressure is generated during the execution of the brake fluid pressure control, the wheel cylinder pressure is reliably reduced to the master cylinder pressure. Pressure can be increased.

[Brief description of the drawings]

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

FIG. 2 is a flowchart of an example of a main routine executed in the braking force control device according to the first embodiment of the present invention.

A [3] change of the brake fluid pressure P _B that occurs in the brake force control apparatus according to a first embodiment of the present invention (solid line) and a change in the master cylinder pressure P _{M / C} (dashed line).

FIG. 4 is a system configuration diagram of a part of a braking force control device according to a second embodiment of the present invention.

FIG. 5 is a flowchart of an example of a main routine executed in a braking force control device according to a second embodiment of the present invention.

[Explanation of symbols]

 10, 90 Electronic control unit (ECU) 28 First master cut valve 34 First relief valve 50, 52 Wheel cylinder 76 Pump 78 Suction valve 92 Second master cut valve 94 Second relief valve

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

Claims (4)

[Claims] 1. A braking force control device having a pump having a suction hole communicating with a hydraulic pressure passage communicating with a master cylinder and a discharge hole communicating with a wheel cylinder, wherein the master cylinder side and the wheel cylinder side are electrically connected. A brake fluid flowing from the wheel cylinder side to the master cylinder side only when the hydraulic pressure on the wheel cylinder side is higher than the hydraulic pressure on the master cylinder side and exceeds the first relief pressure. First control valve means for realizing a second state permitting the flow of the vehicle, and when an emergency brake operation is performed by the driver,
BA control means for executing brake assist control for supplying brake fluid discharged from the pump to the wheel cylinder after realizing the second state. 2. The braking force control device according to claim 1, wherein the brake assist control is a control to increase a wheel cylinder pressure by a predetermined assist pressure as compared with a master cylinder pressure. Wherein the relief pressure is set to the assist pressure. 3. The braking force control device according to claim 2, further comprising: a second control valve disposed between the hydraulic passage and the wheel cylinder in series with the control valve. The valve means is in a third state in which the master cylinder side and the wheel cylinder side are in a conductive state, and the fluid pressure on the wheel cylinder side is higher than the second relief pressure in comparison with the fluid pressure on the master cylinder side. And a fourth state in which the flow of the brake fluid from the wheel cylinder side to the master cylinder side is realized only when the second relief pressure is higher than the first relief pressure. A braking force control device, characterized in that: 4. The braking force control device according to claim 3, wherein the flow of the brake fluid from the master cylinder side to the wheel cylinder side bypasses both the first control valve means and the second control valve means. A braking force control device comprising: a check valve means for allowing.