JPH11263208A - Brake control system for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress an initial locking phenomenon caused by the releasing delay of brake liquid pressure by changing the operation condition of a slip suppressing means in a direction for facilitating the operation of the same when a brake state amount exceeds a specified level during traveling on a road surface having a low friction coefficient. SOLUTION: When processing is started, an ABS control start threshold value Sa and a target slip rate Sb are calculated (S38). By determining whether a friction coefficient μ is lower than a specified threshold value μ1 or not, the traveling of a vehicle on a low-μ road is determined. If the friction coefficient is lower than the specified threshold value μ 1, then the process moves to step S42 (S40). Then, determination is made as to whether a flag FBA is set or not (S42). If the flat FBA is set, since the vehicle is in an emergency brake control state during the low-μ traveling, the ABS control start threshold value Sa is corrected to be reduced, and the ABS start thereshold value Sa is changed in a direction for facilitating the interruption of ABS control (S44).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a vehicle brake control device.

[0002]

2. Description of the Related Art A general automobile is equipped with a booster (booster) for assisting a braking force generated by depressing a brake pedal. Here, especially for beginners,
In emergency situations, it may not be possible to perform enough steps. Therefore, an emergency braking device has been proposed for assisting the booster to obtain a stronger braking force.

On the other hand, in recent automobiles, when a driver performs a brake operation, it is detected whether or not the wheel is likely to be locked based on a wheel slip ratio, and when this state is detected, the brake fluid pressure of the wheel is released. An ABS (anti-skid brake system) device that suppresses locking of wheels by reducing the braking force is mounted.

Japanese Patent Application Laid-Open No. 4-135958 discloses an ABS control during turning of a vehicle in which a target slip ratio is changed in accordance with a depression state of a brake pedal.

[0005]

However, for example, when the vehicle is traveling on a road surface having a low coefficient of friction, the release of the brake fluid pressure is delayed due to a sudden braking operation, and the wheels are quickly locked. A phenomenon occurs (see FIG. 6), and the grip force of the tire on the road surface is lost.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above-described problems, and has as its object to provide a vehicle brake control device capable of improving the braking performance of an emergency brake device while suppressing an initial lock phenomenon caused by a delay in releasing brake fluid pressure. It is to be.

[0007]

In order to solve the above-mentioned problems and achieve the object, a vehicle brake control device according to the present invention has the following arrangement. That is, braking force assisting means for increasing the braking force of the wheel when the brake state amount is equal to or more than a predetermined amount, and slip suppressing means for reducing the braking force when the wheel slip ratio is equal to or more than a predetermined value to suppress wheel slip. A brake control device for a vehicle, comprising: when traveling on a road surface having a low coefficient of friction, when the brake state amount is equal to or more than a predetermined amount, the slip suppression unit is configured to easily operate the slip suppression unit. A changing means for changing the operating condition of the means is provided.

Preferably, the changing means changes the predetermined value so that the predetermined value becomes smaller when the brake state amount becomes equal to or more than a predetermined amount.

Preferably, the slip suppressing means is provided on a first valve for increasing or decreasing a brake fluid pressure in a brake fluid passage in accordance with the slip ratio, and provided on a downstream side of the first valve. A second valve for reducing the brake fluid pressure, and controlling the opening and closing of the first and second valves to reduce the braking force of the wheels.

[0010] Preferably, the apparatus further comprises a judging means for judging an emergency when it is necessary to increase the braking force when the braking state amount is equal to or more than a predetermined amount.

Preferably, the brake state amount is a brake pedal depression amount and a brake pedal depression speed by a driver.

[0012]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. [Mechanical Configuration of ABS Control Device] FIG. 1 is a block diagram showing a mechanical configuration of the ABS control device according to the present embodiment.

As shown in FIG. 1, the vehicle according to the present embodiment comprises:
Left and right front wheels 11 and 12 are driven wheels, and left and right rear wheels 13 and 14.
Are drive wheels, and the output torque of the engine 15 is transmitted from the automatic transmission 16 to the left and right rear wheels 13 and 14 via the propeller shaft 17, the differential device 18 and the left and right drive shafts 19 and 20. ing.

Each of the wheels 11 to 14 is provided with a disk 21a to 24a which rotates integrally with the wheel and a caliper 21b to 24b which brakes the rotation of the disk 21a to 24a by receiving a braking pressure. Apparatus 21-24
Is provided.

A brake control system for operating the brake devices 21 to 24 includes a main booster 27 and a sub-booster 47 for increasing the depressing force of the brake pedal 26 by the driver, and a depressing force increased by the boosters 27 and 47. And a master cylinder 28 that generates a braking pressure according to the The front wheel brake pressure supply line 29 extending from the master cylinder 28 is branched into a left front wheel brake pressure supply line 29a and a right front wheel brake pressure supply line 29b, and the calipers 21a, 2
2b. Left front wheel braking pressure supply line 29
a includes an electromagnetic on-off valve 30a and an electromagnetic relief valve 30b.
And a second valve unit 31 including an electromagnetic on-off valve 31a and an electromagnetic relief valve 31b is provided on the right front wheel braking pressure supply line 29b.

A third valve unit 30 comprising an electromagnetic on-off valve 33a and an electromagnetic relief valve 33b is connected to a rear wheel braking pressure supply line 32 extending from the master cylinder 28.
Is provided. The rear wheel braking pressure supply line 32 is connected to the left rear wheel braking pressure supply line 32a and the right rear wheel braking pressure supply line 3 downstream of the third valve unit 33.
2b, and are connected to the calipers 23a and 24b of each of the brake devices 23 and 24.

In this embodiment, the first valve unit 30
, A second channel for adjusting the braking pressure of the brake device 21 of the right front wheel 12 by operating the second valve unit 31, and a third valve for adjusting the braking pressure of the brake device 21 of the left front wheel 11 by the operation of By the operation of the unit 33, the brake devices 23, 2 for the left and right rear wheels 13, 14 are provided.
And a third channel for adjusting the braking pressure of the control unit 4. The respective channels are controlled independently of each other. Then, the first to third valve units 30, 31,
33 adjusts the braking pressure.

The control 34 for controlling the first to third channels includes a brake state signal from a brake sensor 35 for detecting whether or not the brake pedal 26 is depressed, a depression amount and a depression speed of the brake pedal, 1
Wheel speed sensors 37 to 40 for detecting rotation speeds of 1 to 14
, And a steering angle signal (steering amount, steering speed) from the steering angle sensor 41 are input, and ABS control is performed in parallel for each channel.

The control unit 34 controls each wheel 11
The first to third valve units 30, 31, and 33 control the increase and decrease of the braking pressure of each of the wheels 11 to 14 based on the predetermined ABS control start threshold value based on the wheel speeds of the wheels.
The S control start threshold is corrected or the correction is prohibited, and the first to third
Opening / closing valves 30a, 31 of valve units 30, 31, 33
The opening and closing of the relief valves a, 33a and the relief valves 30b, 31b, 33b are controlled by duty control.
The brake fluid discharged from the relief valves 30b, 31b, 33b is returned to the reservoir tank 28a of the master cylinder 28 via a drain line (not shown). [Mechanical Configuration of Emergency Brake Control Device] For convenience of explanation, the brake control by the normal booster (main booster) is hereinafter referred to as “boost control”, and the assist control for the emergency booster is referred to as “emergency control”. Brake control ".

FIG. 2 is a block diagram showing a mechanical configuration of the vehicle emergency brake control device according to the embodiment of the present invention.

As shown in FIG. 2, the emergency brake control device for a vehicle according to the present embodiment includes a main booster 27 and a sub booster 47 connected in series. The main booster 27 and the sub booster 47 are provided between the brake pedal 26 and the master cylinder 28.

The main booster 27 includes a diaphragm 27a urged leftward in the figure by a return spring in a shell, and a diaphragm chamber 27b partitioned by the diaphragm 27a has a vacuum pressure or a vacuum pressure in an intake manifold of the engine. The vacuum pressure from the vacuum pump is supplied via a check valve 59.

Similarly, the sub-booster 47 includes a diaphragm 47a urged leftward in the figure by a return spring in a shell, and an air chamber 57 is connected to a diaphragm chamber 47b partitioned by the diaphragm 47a. I have.

The air chamber 57 has a check valve 5
Vacuum pressure is supplied via the vacuum valve 9 and the vacuum valve 55, and atmospheric pressure is supplied via an atmospheric pressure valve 49. These vacuum valves 5
5 and the atmospheric pressure valve 49 are duty solenoid valves, and the opening degree of each of the valves 49 and 55 is duty-controlled by the control unit 34. As will be described later, the control unit 34 changes the boost ratio of the sub booster 47 to the main booster by controlling the opening of each valve. The control unit 34 includes a general central processing unit (CPU), a ROM for storing control programs and the like, a RAM for storing vehicle speed, brake depression amount, and the like, a clock timer, and the like.

The brake pedal 26 and the master cylinder 28
Are connected by a rod 28a extending through the center of each of the diaphragms 27a, 47a provided in the main booster 27 and the sub-booster 47. The center of both diaphragms 27a, 47a is connected to the rod 28a. Have been combined.

Therefore, both diaphragm chambers 27b, 47b
Becomes negative pressure, the center of each of the diaphragm chambers 27b and 47b is displaced rightward in the figure against the urging force of each return spring, and this displacement causes the emergency brake pressure in addition to the depression force of the brake pedal 26. Added to rod 28a.

The depressing force of the brake pedal is applied to the piston of the master cylinder 28 by multiplying the boost pressure of the main booster 27 and the emergency brake pressure of the sub booster 47, and makes the emergency brake pressure by the sub booster 47 variable. This changes the overall boost pressure.

The front wheel braking pressure supply line 29 extending from the master cylinder 28 is connected to the left front wheel braking pressure supply line 29.
a and a right front wheel braking pressure supply line 29b, which is connected to the calipers 21b and 22b of each of the brake devices 21 and 22.

The rear wheel braking pressure supply line 32 extending from the master cylinder 28 is a left rear wheel braking pressure supply line 32.
a and a braking pressure supply line 32b for the right rear wheel, and are connected to the calipers 23b and 24b of the respective brake devices 23 and 24.

In addition, the same components as those of the ABS control device shown in FIG.

The control unit 34 has a brake state signal from a brake sensor 35 and an air chamber 57.
A chamber pressure signal from a pressure sensor 58 for detecting the internal pressure, a vehicle speed signal from a vehicle speed sensor 71 for detecting the vehicle speed, and an accelerator depression amount signal from an accelerator stroke sensor 74 for detecting the depression amount of an accelerator pedal 73 are input. You. The control unit 34 outputs a vacuum pressure control signal and an atmospheric pressure control signal for controlling a duty solenoid for the vacuum valve 55 and the atmospheric pressure valve 49.

As the brake sensor, a pedal pressure sensor or the like may be applied in addition to the stroke sensor.

The control unit 34 calculates the depression amount and the depression speed of the brake pedal based on the brake state signal of the brake pedal. When the pedal depression amount and the pedal depression speed become larger than predetermined threshold values, a boost ratio (emergency brake pressure) in the sub booster 47 is determined, and a target pressure value in the air chamber 57 is set to obtain the boost ratio. Then, the duty ratio between the vacuum pressure control signal and the atmospheric pressure control signal to be output to the vacuum valve 55 and the atmospheric pressure valve 49 is calculated from the target pressure value, and the vacuum is adjusted so that the pressure value in the air chamber 57 approaches the target pressure value. The duty of the valve 55 and the atmospheric pressure valve 49 is controlled. This duty control employs a form of feedback control that approaches the target pressure value using the vacuum pressure and the atmospheric pressure.

Further, in addition to the device using the pneumatic actuator of the present embodiment, a configuration using a hydraulic actuator may be adopted. In this case, an emergency brake hydraulic valve may be interposed downstream of the master cylinder in place of the vacuum valve, the atmospheric pressure valve, the sub booster, and the air chamber. [Control procedure of emergency brake control device] Next, a control procedure by the emergency brake control device of the present embodiment will be described.

FIG. 3 is a flowchart showing a control procedure of the emergency brake control device according to this embodiment.

As shown in FIG. 3, when the process is started,
In step S2, the control unit 34 takes in a brake state signal from the brake sensor 35. In step S4, the stepping amount and stepping speed of the brake pedal 26 by the driver are calculated from the brake state signal. In step S6, it is determined whether the flag FBA has been reset. This flag FBA indicates whether or not emergency brake control is being performed. If FBA is set (FBA = 1), the emergency brake control state is set, and if FBA is not set (FBA
= 0) Indicates an emergency brake non-control state. Step S6
If the flag FBA is reset, the process proceeds to step S8, and it is determined whether or not the emergency brake control start condition is satisfied.
The condition for starting the emergency brake control is as follows.
Is determined based on whether or not the stepping amount and the stepping speed have become equal to or greater than a predetermined threshold. If the emergency brake control start condition is satisfied in step S8, the flag FBA is set in step S10, and the openings of the atmospheric pressure valve and the vacuum valve are set in steps S12 and S14 so as to have a predetermined boost ratio.

If the flag FBA has been set in step S6, the flow advances to step S16 to determine whether or not the emergency brake control end condition has been satisfied. The emergency brake control termination condition is determined based on whether the depression amount and the depression speed of the brake pedal 26 have become equal to or less than a predetermined threshold. If the emergency brake control end condition is satisfied in step S16, the atmospheric pressure valve and the vacuum valve are closed in steps S18 and S20, and the flag FBA is determined in step S22.
Reset.

If the emergency brake start condition is not satisfied in step S8, the atmospheric pressure valve and the vacuum valve are closed in steps S24 and S26. [Control Procedure of ABS Control Apparatus] Next, a control procedure by the ABS control apparatus will be described.

FIGS. 4 and 5 show the ABS according to this embodiment.
It is a flowchart which shows the control procedure of a control apparatus.

As shown in FIGS. 4 and 5, when the process is started, in step S32, a signal is input from each sensor. In step S34, a friction coefficient μ of the road surface is calculated. In step S36, the slip ratio of each wheel is calculated. In step S38, an ABS control start threshold value Sa and a target slip ratio Sb are calculated. In step S40, it is determined whether or not the vehicle is traveling on a low μ road by determining whether or not the friction coefficient μ calculated in step S34 is equal to or smaller than a predetermined threshold μ1. If the friction coefficient μ is equal to or smaller than the predetermined threshold μ1 in step S40, the process proceeds to step S42, and if the friction coefficient μ exceeds the predetermined threshold μ1, the process proceeds to step S46 in FIG.

In the step S42, it is determined whether or not the flag FBA is set. If the flag FBA has been reset in step S42, the process proceeds to step S46.

If the flag FBA has been set in step S42, the process proceeds to step S44. Since the emergency brake control state is in effect when the vehicle is traveling on a low μ road, the ABS control start threshold value Sa is reduced as shown in FIG. Then, the ABS start threshold value Sa is changed in a direction that facilitates the intervention in the ABS control.

Thus, when the emergency brake device operates during traveling on a low μ road, the initial lock phenomenon due to the release delay of the brake fluid pressure can be suppressed, and the braking performance of the emergency brake device can be improved.

In step S46, it is determined whether the flag FABS has been reset. The flag FABS indicates whether or not the ABS control is being performed. When the ABS is set (FABS = 1), the ABS control state is set, and when the ABS is reset (FABS = 0), the ABS non-control state is set.
If the flag FABS is reset in step S46, the process proceeds to step S48, and it is determined whether or not the wheel slip ratio S is equal to or greater than the ABS control start threshold value Sa. The slip ratio S of each wheel is calculated, for example, from the average value of the slip ratio of each wheel. In step S48, the slip ratio S of the wheel is ABS.
If it is equal to or greater than the start threshold value Sa, the process proceeds to step S50,
ABS is set, and in step S52, each of the brake devices 21
The brake pressure is reduced to ２４24 so that the slip ratio S converges to the target slip ratio Sb.

If the flag FABS is set in step S46, the flow advances to step S54 to determine whether or not the wheel slip ratio S is equal to or less than the target slip ratio Sb. In step S54, the slip rate S of the wheel is set to the target slip rate Sb.
If not, the process proceeds to step S56, in which the first to third valve units 30, 31, 33 use the brake devices 21 to 2 respectively.
4 to increase the slip to the target slip ratio Sb
To converge.

In step S58, it is determined whether or not the continuous pressure increase time t has exceeded a predetermined time t1. Step S
If the continuous pressure increase time t does not exceed the predetermined time t1 at 58, the routine returns, and at step S58, the continuous pressure increase time t
Has elapsed for a predetermined time t1 or more, the flag FABS is reset in step S60, and the routine returns.

If the wheel slip ratio S exceeds the target slip ratio Sb in step S54, step S62.
In step S62, it is determined whether or not the difference between the wheel slip ratio S and the target slip ratio Sb is equal to or greater than a predetermined value α. If it is determined in step S62 that the difference between the wheel slip ratio S and the target slip ratio Sb is equal to or larger than the predetermined value α, the process proceeds to step S6.
In 4, the first to third valve units 30, 31, and 33 reduce the braking pressure to each of the brake devices 21 to 24 so that the slip ratio S converges to the target slip ratio Sb.

Further, if the difference between the wheel slip ratio S and the target slip ratio Sb is smaller than the predetermined value α in step S62, it is determined in step S66 whether the wheel acceleration Δv is equal to or greater than the first value va. I do. If the wheel acceleration Δv is equal to or greater than the first value va in step S66, each of the brake devices 21 to 2 is controlled by the first to third valve units 30, 31, and 33.
The slip rate S is made to converge to the target slip rate Sb by increasing the braking pressure to S4.

If the wheel acceleration Δv is smaller than the first value va in step S66, the process proceeds to step S70.
It is determined whether the wheel acceleration Δv is equal to or less than a second value vb.
If the wheel acceleration Δv is equal to or smaller than the second value vb in step S70, the first to third valve units 3 are set in step S72.
The brake pressure applied to each of the brake devices 21 to 24 is reduced by 0, 31, and 33 to converge the slip ratio S to the target slip ratio Sb. On the other hand, if the wheel acceleration Δv exceeds the second value vb in step S70, the braking pressure to each of the brake devices 21 to 24 is held by the first to third valve units 30, 31, and 33 in step S74.

It should be noted that the present invention can be applied to a modification or modification of the above embodiment without departing from the spirit thereof.

[0051]

As described above, according to the first aspect of the present invention, when traveling on a road surface having a low friction coefficient, when the brake state amount exceeds a predetermined amount, the slip suppressing means is easily activated. By changing the operating condition of the slip suppressing means in the direction, the initial locking phenomenon due to the release delay of the brake fluid pressure can be suppressed even when the emergency brake control state is made while traveling on a road surface with a low friction coefficient, and the emergency braking device According to the second aspect of the present invention, when the brake state amount is equal to or more than the predetermined amount, the operating condition of the slip suppression means can be easily changed by changing the predetermined value to be small. Can be changed.

According to the third aspect of the present invention, by controlling the opening and closing of the first and second valves to reduce the braking force on the wheels, it is possible to easily control using the existing ABS control device.

According to the fourth aspect of the present invention, when the braking state amount is equal to or more than the predetermined amount, the emergency braking control device is operated only in an emergency by determining that the emergency is required to increase the braking force. it can.

According to the fifth aspect of the present invention, the emergency state can be reliably determined because the brake state amount is the amount of depression of the brake pedal by the driver and the depression speed of the brake pedal.

[0055]

[Brief description of the drawings]

FIG. 1 is a block diagram showing a mechanical configuration of an ABS control device according to the present embodiment.

FIG. 2 is a block diagram showing a mechanical configuration of the vehicle emergency brake control device according to the embodiment of the present invention.

FIG. 3 is a flowchart showing a control procedure of the emergency brake control device according to the embodiment.

FIG. 4 is a flowchart showing a control procedure of the ABS control device according to the embodiment.

FIG. 5 is a flowchart showing a control procedure of the ABS control device according to the embodiment.

FIG. 6 is a diagram illustrating a method of correcting an ABS control start threshold value in the ABS control according to the embodiment.

[Explanation of symbols]

 21 to 24 brake device 30 first valve unit 31 second valve unit 33 third valve unit 34 control unit

Claims (5)

[Claims] 1. A braking force assisting means for increasing a braking force of a wheel when a braking state amount is equal to or more than a predetermined amount, and suppressing a wheel slip by reducing the braking force when a wheel slip ratio is equal to or more than a predetermined value. A brake control device for a vehicle, comprising: a slip control unit; and wherein the vehicle is running on a road surface having a low friction coefficient, and when the brake state amount exceeds a predetermined amount, the slip control unit is easily operated. A brake control device for a vehicle, further comprising changing means for changing an operation condition of the slip suppressing means. 2. The brake control device for a vehicle according to claim 1, wherein the change unit changes the predetermined value to be smaller when the brake state amount becomes equal to or more than a predetermined amount. . A first valve for increasing or decreasing the brake fluid pressure in the brake fluid passage according to the slip ratio; and a brake valve provided on the downstream side of the first valve. 3. A brake control device for a vehicle according to claim 2, further comprising: a second valve for reducing the pressure of the vehicle, and controlling opening and closing of the first and second valves to reduce a braking force of a wheel. 4. The vehicle according to claim 1, further comprising a determination unit configured to determine an emergency when it is necessary to increase the braking force when the brake state amount is equal to or more than a predetermined amount. Brake control device. 5. The brake control apparatus for a vehicle according to claim 4, wherein the brake state quantity is a stepping amount of a brake pedal and a stepping speed of the brake pedal by a driver.