JP2000085564A - Braking force control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a braking force control device which can prevent a creep grown (so-called muffled sound) generated in a creep running time, in a vehicle furnished with an automatic transmission. SOLUTION: In a braking force control device having a brake booster device 2 which is operated to boost a master cylinder 5 by utilizing the fluid pressure from a fluid pressure source 7, by operating a brake operating member 1, a function to increase the hysteresis of the brake booster device 2 according to the turning condition of the vehicle is given to the brake booster device 2.

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 for a vehicle, and more particularly, to a vehicle equipped with an automatic transmission, which is capable of reducing creep groan (so-called goo noise) generated during creep running. The present invention relates to a braking force control device that can prevent the braking force.

[0002]

2. Description of the Related Art Conventionally, a brake booster for boosting a master cylinder by using a fluid pressure of a fluid pressure source is known (for example, see Japanese Patent No. 2581969).
In an automatic transmission type vehicle equipped with a brake device having such a booster, when the vehicle is stopped and held in a traveling range of the automatic transmission (a state in which creep traveling is possible),
Since it is necessary to generate a braking torque (brake pressure) that overcomes the torque of the vehicle, it is necessary to continue to depress the brake pedal with a certain depressing force.

[0003]

However, the driver often unconsciously loosens the pedal force, and when the pedal force is loosened and the balance between the driving torque and the braking torque is barely attained, the pad and the pad are unintentionally reduced. A stick-slip phenomenon occurs in the disk rotor, and so-called creep grown occurs. For this reason, in order to prevent the occurrence of creep grown, the pedal force must not be excessively reduced, and the driver must always maintain the predetermined pedal force,
It was one of the factors of fatigue. Therefore, the present invention provides a brake control device that increases the hysteresis of the brake booster when the vehicle is stopped and held in the traveling range of the automatic transmission, thereby stopping the vehicle even if the brake pedal is slightly loosened more than usual. It is an object of the present invention to provide a braking force control device capable of maintaining a holding state and preventing the occurrence of creep grown, and solving the above problems.

According to the present invention, a throttle generating means is provided in a low-pressure flow path for recirculating a fluid from a brake booster to a reservoir, and the fluid from the brake booster is supplied via the throttle generating means in accordance with a running state of the vehicle. By returning to the reservoir, the hysteresis of the brake booster is increased. Therefore, when the vehicle is stopped and held in the driving range (creep running) of the automatic transmission, even if the pedal force is slightly loosened, the vehicle remains stopped and creeping groan (so-called goo noise) is prevented. Is done.

[0005]

SUMMARY OF THE INVENTION Therefore, the technical solution adopted by the present invention is to provide a brake doubling mechanism for operating a master cylinder using a fluid pressure from a fluid pressure source by operating a brake operating member. A brake force control device provided with a force device, wherein a function of increasing a hysteresis of the brake booster depending on a running state of a vehicle is provided to the brake booster, wherein a brake operation is performed. A brake force control device provided with a brake booster that boosts a master cylinder using a fluid pressure from a fluid pressure source by operating a member, wherein a fluid is returned from the brake booster to a reservoir. A throttle generating means for performing a throttle function according to the running state of a vehicle in a low-pressure flow path. It is.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an overall configuration diagram of a first embodiment relating to the present brake force control device, and FIG. Flowchart for increasing the hysteresis,
FIG. 3 is an explanatory diagram of the hysteresis of the brake booster.

In FIG. 1, 1 is a brake pedal as a brake operating member, 2 is a brake booster, 3 is an inlet port of the brake booster, 4 is a return port of the brake booster, and 5 is a master cylinder ( M /
C), 6 are wheel cylinders (W / C), 7 is an accumulator (ACC), 8 is a pump, 9 is a motor (M) for driving the pump, 10 is a reservoir, 11 is a solenoid valve, and 12 is a throttle generating means. Reference numeral 13 denotes a speed sensor for detecting a wheel speed and the like. Reference numeral 14 denotes an electronic control unit (ECU). The motor 9, the solenoid valve 11, and the speed sensor 13 are electrically connected to the electronic control unit 14. Further, the motor 9 is operated when the pressure in the accumulator 7 drops below a predetermined pressure, so that a predetermined pressure is constantly accumulated in the accumulator 7. The brake booster and the master cylinder are disclosed in, for example, the aforementioned Patent No.
The configuration is the same as that described in No. 1969 and other conventionally known components, and the description of these configurations and operations will be omitted.

The solenoid valve 11 is a two-position switching type solenoid valve that switches the flow path between the positions A and B in accordance with a signal from the electronic control unit according to a flowchart described later. Is switched to the position B when the control for increasing the hysteresis is started. A return flow path 16 from a low-pressure flow path 15 that returns from the return port 4 of the brake booster 2 to the reservoir 10
The throttle 12 is disposed in the return passage 16 and the electromagnetic valve 11 is provided at a branch point between the two passages.
Is disposed, and the flow of the fluid is returned by the valve to the flow path 16.
It can be switched to. The throttle valve is formed by the action of the solenoid valve 11 and the throttle 12, and the hysteresis of the brake booster can be increased.

In this brake force control device, when the brake pedal 1 is depressed, a predetermined hydraulic pressure flows from the accumulator 7 into the brake booster 2 through the inlet port 3 and is boosted according to the brake pedal depression force. The hydraulic pressure is supplied to the master cylinder 5 and the output pressure from the master cylinder is supplied to the wheel cylinder 6 to operate the brake. When the brake pedal 1 is released, the brake fluid in the wheel cylinder 6 returns to the reservoir 10 through the master cylinder, the return port 4 through the flow path in the brake booster, and the solenoid valve 11 in the A position. , Brakes are released.

When the reference speed of the vehicle detected by the speed sensor 13 is equal to or lower than a predetermined speed and the vehicle is in either the stop holding state or the creep running state, the solenoid valve is controlled by a signal from the electronic control unit 14. 11
Switches to the B position. In this state, brake pedal 1
When the brake pedal is depressed, a predetermined hydraulic pressure flows from the accumulator 7 into the brake booster 2, and the hydraulic pressure boosted according to the brake pedal depression force is supplied to the master cylinder 5, and the output pressure from the master cylinder 5 Is supplied to the wheel cylinder 6 to operate the brake. When the brake pedal is released, the brake fluid in the wheel cylinder 6 is returned to the master cylinder 5, the return port 4 via the flow passage in the brake booster 2, the solenoid valve 11 in the B position, and the throttle 1
It returns to the reservoir 10 via 2 and the brake is released. At this time, the hysteresis of the brake booster can be increased by the action of the solenoid valve 11 switched to the position B and the throttle 12 provided in the return flow passage 16, and the travel range of the automatic transmission (creep travel). When the vehicle is stopped and held, the stopped state of the vehicle is maintained even if the pedal force is slightly loosened, so that the generation of a creep groon (so-called goo noise) can be prevented.

A control flow for switching the solenoid valve 11 will be described with reference to FIG. When the present program is started, it is determined in step S1 whether or not the reference speed of the vehicle detected by the speed sensor 13 is equal to or lower than a predetermined speed (for example, 5 km / h or lower). That is, in this step, it is determined whether the vehicle is in the stop holding state or the creep running state, and if it is determined that the vehicle is in the stop holding state or the creep running state, the process proceeds to step S2. In step S2, it is determined whether the brake pedal 1 is depressed. Here, brake pedal 1
It is determined whether or not the vehicle is stopped by stepping on. In this step, if the brake pedal 1 is depressed and the brake switch is turned on, the process proceeds to step S3, where the two-position switching type solenoid valve 11 is switched to the position B, and the return fluid from the brake booster is returned. Channel 16 → throttle 1
It returns to the reservoir 10 via 2 to increase the hysteresis of the brake booster.

The state in which the hysteresis of the brake booster 2 becomes large will be described with reference to the hysteresis diagram of the brake booster shown in FIG. 3. In the graph of FIG. 3, F represents the brake pedal force, P represents the brake pressure (oil pressure), P1 is a brake pressure at which a creep phenomenon occurs. A conventional brake booster depresses a brake pedal, and when a predetermined pedaling force is exceeded, the brake fluid pressure starts to increase. Further, as the pedaling force increases, the brake pressure exceeds a brake pressure P1 at which creep occurs. The pressure is increased to a predetermined brake pressure P2, and the vehicle is brought into a braking state, and the brake pressure P2 at that time is maintained.
This vehicle braking state is maintained until the pedaling force of the brake pedal is loosened and the force is reduced to F1 in the drawing, in other words, the brake pressure is reduced to the creep pressure P1. When the brake pressure drops to P1, the balance between the driving torque and the braking torque reaches a critical state, and in this state, a stick-slip phenomenon occurs in the pad and the disk rotor, and the vehicle starts creep running, so-called creep grown occurs. . That is, creep running starts in a state where the pedaling force of the brake pedal 1 has decreased to F1, and a creep groon occurs. As described above, the conventional brake booster has the hysteresis indicated by A, B, C, and D in the figure.

Therefore, in order to prevent the above-mentioned creep grown from occurring, in this embodiment, the throttle generating means increases the hysteresis of the brake booster as follows, and the pedaling force of the brake pedal 1 is reduced. F smaller than F1
The braking torque is made larger than the driving torque until the brake pedal drops to 2, and even if the pedaling force of the brake pedal 1 decreases slightly,
To be able to prevent the occurrence of creep grown. In this example, when it is determined that the reference speed of the vehicle is equal to or lower than the predetermined speed and the vehicle is in either the stop holding state or the creep running state, the electromagnetic valve 11 switches to the position B,
As a result, the return of the brake fluid from the brake booster 2 to the reservoir is restricted by the throttle 12, the braking force is reduced to F2, and the braking state is maintained until the brake pressure decreases to the creep pressure P1 ( That is, in this state, the brake booster has the hysteresis shown in a, b, e, and f in the figure).

As described above, according to the present invention, it is possible to suppress the occurrence of creep in a wide range of brake pedaling force from F0 to F2 as compared with the conventional brake booster, and the driver can reduce the traveling range of the automatic transmission. When the vehicle is stopped and held during (creep running), even if the pedal effort is unconsciously loosened, no creep occurs until the brake effort is reduced to F2, which is lower than the conventional F1. This can prevent the occurrence of creep grown.

Next, a second embodiment will be described. In the second embodiment, the return passage is eliminated as shown in FIG. 4, and a throttle 12a is incorporated in a solenoid valve 11 provided in the low-pressure passage. This is the same as the embodiment. In this embodiment, the throttle function can be generated only by switching the solenoid valve 11 in the same manner as in the first embodiment, so that a special return flow path is not required and the configuration is simplified.

[0016]

As described in detail above, according to the present invention,
A throttle generating means is provided in a low-pressure flow path for recirculating fluid from the brake booster to the reservoir, and the fluid from the fluid pressure booster is returned to the reservoir via the throttle generating means according to the traveling state of the vehicle, thereby increasing the brake boost. When the hysteresis of the power device is increased and the vehicle is stopped and held in the traveling range (creep traveling) of the automatic transmission, even if the pedal effort is slightly loosened, the vehicle remains stopped and the creep grown ( An excellent action and effect that the generation of so-called goo noise can be prevented can be achieved.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a brake force pressure control device according to a first embodiment.

FIG. 2 is a flowchart for increasing the hysteresis of the brake booster.

FIG. 3 is an explanatory diagram of hysteresis of a brake booster.

FIG. 4 is an overall configuration diagram of a brake force pressure control device according to a second embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Brake pedal 2 Brake booster 3 Inlet port 4 Return port 5 Master cylinder 6 Wheel cylinder 7 Accumulator 8 Pump 9 Motor 10 Reservoir 11 Solenoid valve 12 Throttle 13 Speed sensor 14 Electronic control device 15 Low pressure flow path 16 Return flow path

Claims (3)

[Claims] 1. A brake force control device comprising a brake booster (2) for operating a master cylinder (5) by using a fluid pressure from a fluid pressure source (7) by operating a brake operating member (1). A brake force control device, wherein the brake booster 2 is provided with a function of increasing the hysteresis of the brake booster 2 depending on the running state of the vehicle. 2. A brake force control device comprising a brake booster for operating a master cylinder 5 by using a fluid pressure from a fluid pressure source 7 by operating a brake operating member 1. A braking force control device comprising: a throttle generating means (12) for performing a throttle function according to a running state of a vehicle, in a low-pressure flow path (15) for recirculating fluid from a brake booster (2) to a reservoir (10). 3. The low pressure flow path 1 for recirculating fluid from the brake booster 2 to the reservoir 10.
A braking force control device comprising: a throttle (12) provided in a return flow path (16) branched from the inside of (5); and an electromagnetic valve (11) for switching between a low pressure flow path and a return flow path.