JP2000168539A - Brake pressure control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of a creep groan by connecting a braking device and a reservoir while brake pressure reaches from first prescribed brake pressure to second prescribed brake pressure. SOLUTION: Vehicle speed is taken from a wheel speed sensor 10 and whether vehicle speed is reference speed or below is judged. When vehicle speed is the reference speed or below, brake hydraulic pressure is detected by a hydraulic pressure sensor 7 and whether hydraulic pressure is creep groan generation starting hydraulic pressure within an electronic control device or below 13 is judged. When hydraulic pressure is creep groan generation starting hydraulic pressure or below, a hold valve 4 is closed, a decay valve 5 is opened, brake fluid within a wheel cylinder 6 is refluxed to a reservoir 8 and pressure reduction is performed. Next, whether brake hydraulic pressure is creep groan extinguishing hydraulic pressure within the electronic control device 13 or below is judged. When brake hydraulic pressure becomes extinguishing hydraulic pressure or below, the hold valve 4 is opened, the decay valve 5 is closed and a brake state is returned to a normal brake state. As a result, generation of creep groan can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brake pressure control device for a vehicle, and more particularly, to a vehicle equipped with an automatic transmission, which reduces a creep groan (so-called goo noise) generated during creep running. The present invention relates to a brake pressure control device that can prevent the brake pressure.

[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 has been known (for example, see Japanese Patent Application Laid-Open No. 9-267738). 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), a braking torque that overcomes the vehicle torque. Since it is necessary to generate (brake pressure), the driver needs 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. The stick-slip phenomenon occurs in the disk rotor, and abnormal noise called 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 a predetermined pedal force, which is one of the factors of fatigue. Accordingly, the present invention provides a brake pressure control device capable of preventing the occurrence of creep groan by reducing the chance that the balance between the driving torque and the braking torque is in a bare state when the vehicle is stopped and held in the traveling range of the automatic transmission. And to solve the above problems.

[0004] According to the present invention, while the driver holds the vehicle stopped,
Based on the signal from the hydraulic pressure sensor, the starting pressure of the creep grown and the pressure at which the creep grown disappears are detected and stored in the electronic control unit. During the next stop and hold, the brake is released, and the signal from the hydraulic pressure sensor is released. When the creep groon start hydraulic pressure is detected, the hold valve is closed and the decay valve is opened to rapidly reduce the brake fluid pressure from the creep groon start hydraulic pressure to the creep grown extinguishing hydraulic pressure. Provided is a brake pressure control device that can suppress the occurrence of a groon. If the vehicle is stopped and held in the traveling range (creep traveling) of the automatic transmission, even if the pedal effort is slightly loosened, a creep groon (a so-called goo Sound) is prevented.

[0005]

For this reason, the technical solution adopted by the present invention is the first predetermined brake pressure and the first predetermined brake pressure.
Setting a second predetermined brake pressure lower than the predetermined brake pressure, and connecting the brake device and the reservoir until the brake pressure reaches the second predetermined brake pressure from the first predetermined brake pressure in the brake pressure reduction process A brake pressure control device characterized by comprising a normally open type hold valve located between the master cylinder and the brake device, and a normally open type decay valve located between the brake device and the reservoir. A brake pressure control device comprising a brake device and a reservoir connected by closing a hold valve and opening a decay valve.

[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. 2 uses a wheel speed sensor. FIG. 3 is a flow chart for detecting a creep groon generation start fluid pressure and a creep grone disappearance fluid pressure, and FIG. FIG. 5 is a flowchart for releasing the brake hydraulic pressure, FIG. 5 is an explanatory diagram of hysteresis of the brake booster, and FIG. 6 is an explanatory diagram of hysteresis of the conventional brake booster. The present embodiment is configured by adding a hydraulic pressure sensor, a vibration sensor, and a stroke sensor to a conventionally known circulation type antilock control device. Since the configuration can be used, manufacturing costs can be reduced.

In FIG. 1, 1 is a brake pedal as a brake operating member, 2 is a vacuum booster as a brake booster, 3 is a master cylinder (M / C),
4 is a hold valve, 5 is a decay valve, 6 is a wheel cylinder (W / C), 7 is a hydraulic pressure sensor, 8 is a reservoir, 9 is a pump, 10 is a wheel speed sensor for detecting wheel speed, 11 is a vibration sensor, Reference numeral 12 denotes a stroke sensor for the piston in the reservoir 8, and 13 denotes an electronic control unit (EC
U), a pump driving motor (not shown), a hold valve 4, a decay valve 5, a hydraulic pressure sensor 7, a wheel speed sensor 10, a vibration sensor 11, and a stroke sensor 1.
2 is electrically connected to the electronic control unit 13 by an electric signal path shown in the figure. The structure of the brake booster and the master cylinder are the same as those of the conventionally known brake booster, and the description of these structures and operations is omitted.

The hold valve 4 is a conventionally-known normally-open two-position switching valve, and the decay valve 5 is a conventionally-known normally-closed two-position switching valve. Therefore, the valves 4 and 5 are opened and closed according to the signal output from the electronic control unit 13, and the hold valve 4 is closed and the decay valve 5 is opened and the brake fluid is opened until the pressure from the creep grown generation start fluid pressure to the creep grown disappearance fluid pressure is reached. Reduce pressure rapidly. By doing so, it is possible to change the hysteresis of the brake booster and suppress the occurrence of creep grown.
The hydraulic pressure sensor 7 is a sensor for detecting a brake hydraulic pressure, and a conventionally known one is used.

The vibration sensor 11 is a known vibration sensor capable of detecting a vibration of a brake device, a brake fluid pressure, a vehicle body, or a suspension. It is also possible to use sensors. When the wheel speed sensor is used as the vibration sensor and the waveform exceeds the normal voltage range and becomes larger than the vibration determination threshold based on the waveform from the wheel speed sensor, the vibration level is higher than the reference. , A signal may be output (see FIG. 2).

The reservoir 8 has a function of allowing the brake fluid from the wheel cylinder 6 to flow when the decay valve 5 is opened, and when the pump 9 operates, the brake fluid in the reservoir 8 is pumped to the master cylinder. . A piston 8b urged upward in the drawing by a spring 8a is provided in a cylinder constituting the reservoir 8.
Are slidably disposed in a liquid-tight state, and a liquid chamber 8c is defined in the cylinder by the piston 8b.
The liquid chamber 8c is connected to the pump 9 and the decay valve 5. The piston 8b is provided with a stroke sensor 12 for detecting the stroke of the piston 8b. When the stroke sensor 12 detects that the stroke of the piston 8b is maximum, the pump 9 is operated by a signal from the electronic control unit 13 to pump the brake fluid in the fluid chamber 8c to the master cylinder. In addition,
The pump 9 also operates during the antilock control, and has the function of pumping up the brake fluid in the reservoir.

In this brake pressure control device, when the brake pedal 1 is depressed, the hydraulic pressure generated in the master cylinder 3 flows into the wheel cylinder 6 via the open hold valve 4 to operate the brake. When the brake pedal 1 is released, the brake fluid in the wheel cylinder 6 returns to the master cylinder via the hold valve 4,
The brake is released. The speed detected by the wheel speed sensor 10 is equal to or lower than a predetermined speed, and the vibration sensor 11
When the vibration level detected from the pressure sensor is equal to or higher than a predetermined value and the signal from the hydraulic pressure sensor 7 becomes the creep grown generation start hydraulic pressure, the hold valve 4 is closed, the decay valve 5 is opened, and the brake in the wheel cylinder 6 is opened. The pressure is reduced until the creep groon disappears. By this operation, even when the pedal force is slightly loosened while the vehicle is stopped and held in the traveling range (creep traveling) of the automatic transmission, the generation of creep grown (so-called goo noise) is prevented. The depressurized brake fluid amount is absorbed by the reservoir 8, but when the brake fluid amount exceeds a certain amount, the pump operation signal is input to the electronic control unit 13 by a signal from the stroke sensor 12 and returned to the master cylinder by the pump 9. .

Referring to FIGS. 3 and 4, the control for preventing the generation of creep grone will be described. FIG. 3 is a flow chart for detecting a creep glow generation start fluid pressure and a creep grone extinguishing fluid pressure. 5 is a flowchart for changing the hysteresis of the brake booster. In FIG. 3, when the control for detecting the creep grown generation start fluid pressure P1 and the creep grown extinction fluid pressure P3 is started, in step S1, the wheel speed sensor 10
The speed of the vehicle is determined from whether the vehicle speed is equal to or lower than the reference speed (V = 5 km / h). If the vehicle speed is equal to or lower than the reference speed, the process proceeds to step S2. It is determined whether or not the level is higher than the standard. The vibration level can be detected as shown in FIG. 2 based on the waveform from the wheel speed sensor instead of the vibration sensor.

When the vibration level from the vibration sensor 11 is equal to or higher than the reference, the process proceeds to step S3, where the brake fluid pressure at that time is detected by the fluid pressure sensor and stored in the electronic control unit. That is, in this step, the creep grown generation start hydraulic pressure P1 is detected and stored. Next, in step S4, it is determined whether or not the vibration from the vibration sensor 11 is below the vibration level reference. When the vibration is below the reference, the brake fluid pressure at that time is detected by the fluid pressure sensor and stored in the electronic control unit. Keep it. That is, in this step, the creep grone extinction fluid pressure P3 is detected and stored. As described above, the creep grown generation start fluid pressure P1 and the creep grone disappearance fluid pressure P3 are detected and stored in accordance with the above flowchart. It should be noted that the creep groon generation start fluid pressure P1 and the creep grone extinction fluid pressure P3
Varies depending on the friction coefficient μ of the friction material. Therefore, it is necessary to detect the value at the time of system initialization or periodically and change the memory value in the electronic control unit.

On the other hand, when the flowchart for changing the hysteresis of the brake booster shown in FIG. 4 is started, the vehicle speed is fetched from the wheel speed sensor 10 in step SS1, and this vehicle speed is equal to or less than the reference speed (V = V). 5km
/ H), and if the speed is equal to or less than the reference speed, the process proceeds to step SS2, where the brake fluid pressure at that time is detected by the fluid pressure sensor 7, and the fluid pressure is stored in the electronic control unit 13 and stored. It is determined whether or not the creep grown generation start pressure P1 is equal to or lower than the set pressure P1. When the pressure is equal to or lower than the creep grown generation start pressure, the process proceeds to step SS3, where the hold valve 4 is closed, the decay valve 5 is opened, the brake fluid in the wheel cylinder 6 is returned to the reservoir 8, and the brake fluid pressure is reduced.

Next, at step SS4, it is determined again whether or not the brake fluid pressure at that time is equal to or less than the creep grown extinction fluid pressure P3 stored in the electronic control unit 13. 4 is opened and the decay valve 5 is closed to return to the normal braking state.
In this way, the state in which the balance between the driving torque and the braking torque is barely reduced by loosening the pedaling force, that is, by avoiding the hydraulic pressure at which the creep grone is generated, the generation of the creep grone can be prevented.

The state of changing the hysteresis of the brake booster 2 will be described with reference to the drawings. FIG. 5 is a hysteresis diagram of the brake booster according to the present invention, and FIG. 6 is a hysteresis of the conventional brake booster. FIG. In the figure, F is the brake pedal force, P is the brake pressure (fluid pressure), P1
Is the creep groon generation start fluid pressure, and P3 is the creep grown disappearance fluid pressure. The conventional brake booster is
As shown in FIG. 6, the brake pedal is stepped on, and when the pedal pressure exceeds a predetermined pedaling force F2, the brake fluid pressure starts to increase. As the pedaling force further increases, the brake pressure is increased linearly, and the vehicle enters a braking state. Is maintained. This vehicle braking state is maintained until the pedaling force of the brake pedal is loosened, the force is reduced to F1 in the figure, and the brake pressure is reduced to the creep grown generation start hydraulic 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. . This creep grown continues to be generated until the pedaling force of the brake pedal 1 decreases to F2 and the brake fluid pressure becomes the creep grone disappearing oil pressure P2, and disappears when the brake fluid pressure falls below the brake fluid pressure P2.

Therefore, in order to prevent the above-described creep grown from occurring, in the present embodiment, the hold valve 4 and the decay valve 5 are actuated until the depression force of the brake pedal 1 falls from F1 to F2. During this time, the brake fluid pressure is maintained at the creep grown extinction fluid pressure P3, thereby avoiding the last minute balance between the driving torque and the braking torque. To prevent the occurrence of That is, in the present embodiment, when the brake fluid pressure decreases to P1 in a state where the reference speed of the vehicle is equal to or lower than the predetermined speed as shown in FIG. 5, the hold valve and the decay valve are switched to reduce the brake fluid pressure to P3. , P
When the pressure becomes 3, the hold valve 4 and the decay valve 5 are returned to the normal brake operation state, thereby preventing the occurrence of creep grown (that is, in this state, the brake booster is a, b, c in FIG. Hysteresis shown in d, e, f, and g).

As described above, in the above-described embodiment, the occurrence of creep can be suppressed in a wide range, and when the driver stops and holds the vehicle in the traveling range (creep traveling) of the automatic transmission, the driver unconsciously Even if the pedal force is loosened, it is possible to reliably prevent creep grown.

Next, a second embodiment will be described. In the second embodiment, a full power type antilock control device
It is an example using the creep grown occurrence prevention system of the embodiment. The embodiment of the present invention will be described with reference to the drawings. FIG. 7 is an overall configuration diagram of a brake force pressure control device according to a second embodiment, in which a reduced fluid amount is released to a reservoir 25 in the atmosphere. With the configuration, the stroke sensor provided in the reservoir, which is required in the first embodiment, becomes unnecessary. In the present embodiment, the opening and closing timings of the hold valve and the decay valve are the same as those in the first embodiment, and the description of their control modes will be omitted. The same members as those in the first embodiment are denoted by the same reference numerals.

In FIG. 1, reference numeral 21 denotes a hydro booster,
22 is an accumulator, 23 is a check valve, 24 is a pump,
Reference numeral 25 denotes an open-to-atmosphere reservoir, reference numeral 26 denotes a hydro-booster switching valve, and the same reference numerals used in the first embodiment denote the same members. The hydro booster 21 is a known type that can supply the hydraulic pressure controlled in proportion to the pedaling force of the brake pedal from the accumulator 22 to the wheel cylinder 6 side, and the description of the configuration and operation will be omitted.

A predetermined hydraulic pressure is always stored in the accumulator 22, and when the hydraulic pressure in the accumulator is reduced, the pump 24 is operated as needed to store the predetermined hydraulic pressure. The hydro booster switching valve 26 is A,
The B2 position switching valve has a function of connecting the master cylinder 3 and the hold valve 4 at the time of the A position, and has a function of connecting the hydrobooster 21 and the hold valve 4 at the time of the B position.

In this brake pressure control device, when the brake pedal 1 is depressed, the hydraulic pressure controlled in proportion to the depression force of the bouquet pedal 1 by the action of the hydro booster 21 acts on the master cylinder 3 from the accumulator 22.
The output pressure from the master cylinder 3 flows into the wheel cylinder 6 via the position A of the hydraulic booster switching valve 26 → the open hold valve 4 to operate the brake. When the brake pedal 1 is released, the brake fluid in the wheel cylinder 6 flows through the hold valve 4 → the hydro booster switching valve 26 → the master cylinder 3 to the reservoir 25.
And the brake is released. During braking,
When the antilock control is started, the hydro booster switching valve 26 is switched to the position B, and the hold valve and the decay valve are controlled to open and close to execute the antilock control. This anti-lock control is the same as the conventional anti-lock control, and a detailed description thereof will be omitted.

When the vehicle is stopped with the brake pedal depressed, the vehicle speed detected by the wheel speed sensor 11 is equal to or lower than a predetermined speed (V = 5 km / h) and detected by the vibration sensor 11. When the vibration level is equal to or higher than the predetermined value, when the signal from the hydraulic pressure sensor 7 reaches the creep grown generation start hydraulic pressure P1, the hold valve 4 is closed, the decay valve 5 is opened, and the brake fluid in the wheel cylinder 6 is creep-grown extinguished The pressure is returned to the reservoir 25 until the pressure becomes the pressure, and the brake fluid pressure is reduced. By this operation, even when the pedal force is slightly loosened while the vehicle is stopped and held in the traveling range (creep traveling) of the automatic transmission, the generation of creep grown (so-called goo noise) is prevented.

[0024]

As described in detail above, according to the present invention,
When the driver depresses the brake pedal and holds the vehicle stopped, the pedal depresses and the hold valve is closed and the decay valve is closed during the period from the start of creep grown generation to the end of creep grone disappearance when the creep groon start hydraulic pressure is reached. By opening the valve and reducing the brake fluid pressure, it is possible to achieve an excellent operation and effect that the generation of creep grown can be reliably suppressed.

[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 an explanatory diagram for detecting a creep grown generation vibration from a wheel speed.

FIG. 3 is a flow chart for detecting a creep groon generation start fluid pressure and a creep grone disappearing fluid pressure.

FIG. 4 is a flowchart for changing the hysteresis of the brake booster.

FIG. 5 is a hysteresis diagram of the brake booster according to the present invention.

FIG. 6 is a hysteresis diagram of a conventional brake booster.

FIG. 7 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 Vacuum booster 3 Master cylinder 4 Hold valve 5 Decay valve 6 Wheel cylinder 7 Fluid pressure sensor 8 Reservoir 9 Pump 10 Wheel speed sensor 11 Vibration sensor 12 Stroke sensor 13 Electronic control unit

Claims (2)

[Claims] A first predetermined brake pressure and a second predetermined brake pressure lower than the first predetermined brake pressure are set, and the brake pressure is reduced from a first predetermined brake pressure to a second predetermined brake pressure in a brake pressure reduction process. A brake pressure control device, wherein a brake device and a reservoir are connected until the brake pressure is reached. And a normally open decay valve located between the master cylinder and the brake device, and a normally open decay valve located between the brake device and the reservoir. The brake pressure control device according to claim 1, wherein the brake device and the reservoir are connected by opening a valve.