JPH06227384A - Antiskid control method - Google Patents

Abstract

PURPOSE:To provide a sufficient braking force, in a H-piping brake vehicle, by changing over the braking force of the rear wheels to select-high control, when the braking system of the front wheels is judged to be defective. CONSTITUTION:A braking pressure generator 1 is connected to the respective wheel brakes 41 to 44 of front wheels 31, 32 and rear wheels 33, 34 by means of a H-shaped piping through the two systems of pressure medium circuits that have been hydraulically separated. In the case where the surface of a road is frozen, when at least one of the rear wheels 33, 34 is in an antiskid condition, and the front wheels 31, 32 are in a nonantiskid condition, and also if this condition is continued for a prescribed period of time, it is judged that the braking system of the front wheels 31, 32 have failed. In this case, high- select control is carried out so as to be in accordance with wheel not indicating a lock tendency. As an alternative, the slip threshold of the rear wheel is changed for changing over the slip to deeper control, or the pressure-reducing pulse time is reduced for delaying the recovery from a slip tendency, so that a sufficient braking force can be obtained by either of the above methods.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anti-skid control for an H pipe braking vehicle.

[0002]

2. Description of the Related Art Conventionally, in anti-skid control of an H-pipe braking vehicle, the rear wheel secures the directional stability of the vehicle rather than the braking force, and one of the left and right wheels, which is easier to lock, is the brake for both wheels. The so-called select low control for simultaneously controlling the hydraulic pressure is performed.

[0003]

When the braking system for the front wheels fails, anti-skid control is performed only by the braking system for the rear wheels, the deceleration of the vehicle cannot be sufficiently obtained, and the stop distance increases. is there.

[0004]

OBJECT OF THE INVENTION The present invention relates to an H pipe braking vehicle,
An object of the present invention is to provide an anti-skid control method in which a sufficient braking force can be obtained even if the braking system of the front wheels fails.

[0005]

SUMMARY OF THE INVENTION The present invention is an anti-skid control method for an H-pipe braking vehicle, comprising at least one of:
If two rear wheels are in anti-skid control state and both front wheels are in non-anti-skid control state and a predetermined time has elapsed, the select low control of the rear wheels is stopped and the rear wheel control is performed by the select high control. A characteristic anti-skid control method, or at least one rear wheel is in an anti-skid control state, and both front wheels are in a non-anti-skid control state, and when a predetermined time has elapsed, the slip threshold of the rear wheel is changed, An anti-skid control method characterized by performing rear wheel control so that slip control is switched to deeper control than when normal front wheel control is performed, or at least 1.
When two rear wheels are in the anti-skid control state and both front wheels are in the non-anti-skid control state, the rear wheel control is performed so that the decompression pulse time is shorter than when the front wheel control is normal when the predetermined time has elapsed. The anti-skid control method characterized by the above, or when at least one rear wheel is in the anti-skid control state and both front wheels are in the non-anti-skid control state, and a predetermined time has elapsed, In the anti-skid control method, the rear wheel control is performed when the value does not exceed a predetermined value.

[0006]

Embodiments Embodiments will be described below with reference to the drawings. <A> First and second pressure medium circuits 2, 3 In the brake pressure generator 1, brake fluid pressure is generated from the brake pedal 11 and the master cylinder 12. As shown in FIG. 2, the brake pressure generator 1 includes a right front wheel 3 via a hydraulically separated first and second pressure medium circuits 21, 22.
1, the left front wheel 32, the right rear wheel 33, and the left rear wheel 34 are connected to the wheel brakes 41 to 44 by H-type pipes.
The auxiliary pressure source 6 is for supplying auxiliary hydraulic pressure to the pressure medium circuits 21 and 22, and includes the check valves 61 and 62 and the hydraulic pump 6.
3, 64, an electric motor 65 for driving them, and auxiliary reservoirs 66, 67. The auxiliary reservoirs 66 and 67 are connected to the suction sides of the hydraulic pumps 63 and 64 to supply the pressure medium. Auxiliary reservoir 66, 67
Are connected to the first return circuit 23 and the second return circuit 24, respectively, and collect the pressure medium.

<B> Input Valve, Output Valve The input valves 51 and 52 are connected in parallel to the first pressure medium circuit 21, and are connected to the first return circuit 23 via the output valves 54 and 55. The input valve 53 includes the second pressure medium circuit 22.
And is connected to the second return circuit 24 via the output valve 56. Each of the input valves and the output valves 51 to 56 has a function as a 2-port 2-position directional control valve that operates electromagnetically. In the non-actuated position, the input valves 51-53 are in the open position and the output valves 54-56 are in the normally closed position.

<C> Control of Valves The ABS hydraulic unit 7 is composed of the input valves, the output valves 51 to 56, and the auxiliary pressure source 6, and controls the braking of the wheels 31 to 34. The ABS hydraulic unit 7 is electrically controlled by an electronic control unit 8. The electronic control unit 8 reads the output of the wheel speed sensors 91 to 94 of each wheel, measures the rotation speed of each wheel, and performs anti-skid (ABS) control. The electronic control unit 8 has an input unit 81 for inputting the signals from the wheel speed sensors 91 to 94, a processing unit 82 for performing anti-skid control processing, and an output unit 83. The output from this output unit 83 is an ABS hydraulic unit. Control 7

The anti-skid control method will be described below. <A> Normal control method When the brake pedal 11 is depressed and the master cylinder 12
The hydraulic pressure generated from the first and second pressure medium circuits 2,
3 through the wheel brakes 41-44, front wheel 3
1, 32 and the rear wheels 33, 34 are braked. If the coefficient of friction of the road surface is small, the wheels will start to slip. The wheel rotation speed is measured from the output signals of the wheel speed sensors 91 to 94, and the slip state of the wheel is judged from the deviation from the vehicle body speed. If the wheels are slipping, it is necessary to adjust the wheel brake pressure of the wheels to ensure braking force and steering stability. That is, when the slip tendency of the front wheels is detected,
Based on this detection signal, the input valve is closed and the output valve is opened to control the brake pressure. When the wheel grips the road surface, it closes the output valve and releases the input valve to increase brake pressure and increase braking force. In this way, anti-skid control is performed on a road surface that tends to slip.

<B> Failure detection method for front wheel braking system For example, when the entire road surface is frozen and all are normal, all wheels are in anti-skid control operation. But,
If there is a failure in the front wheel system, this normal operation will not occur,
Braking is reduced. In particular, if the front wheel system fails, sufficient braking force cannot be obtained. As a method of detecting this failure, if the entire road surface is frozen, all wheels may be in anti-skid control state, but both front wheels are in control state while both rear wheels are in control state. If it is, the possibility that there is a failure in the brake control system of the front wheels increases. However, since there is a possibility that it is temporarily in the uncontrolled state, if the uncontrolled state persists for a predetermined period by measuring the passage of time in this uncontrolled state, the front wheel control system has failed. to decide. Further, by adding a condition that the vehicle body deceleration does not exceed the set value to the above conditions, the detection accuracy can be improved. The method of detecting the controlled state and the non-controlled state is performed in the anti-skid control process, for example. Usually, the wheels tend to lock from the braking state, and the control state is determined when the pressure reducing mode is entered. After that, if the control is continued, the control state is maintained. On the other hand, the non-controlled state is the normal traveling state (for example, when braking is stopped) or the normal braking (braking when the wheels are not in the lock tendency).

<C> Control method when the front wheel braking system has a failure In the case of antilock (ABS) control, the rear wheels are controlled so as to secure directional stability of the vehicle rather than braking force. That is, so-called select low control is performed in which the brake fluid pressure of both wheels is controlled simultaneously with reference to one of the right and left rear wheels that is easily locked. Therefore, if there is a failure in the braking of the front wheels in the H piping vehicle, the braking force is secured only by the rear wheels. Therefore, when there is a failure in the front wheels, which is important for the braking force, only the rear wheels are controlled, and sufficient braking cannot be obtained. Therefore, when a failure is detected, the control of the rear wheels is switched to the following methods (1) to (3) to increase the braking force. (1) Stop the select low control of the rear wheels and switch to the select high control. That is, normally, when either of the left and right wheels of the rear wheel shows a lock tendency, the control (select low control) is performed according to the wheel having the lock tendency. By switching this method, the control (select high control) is performed according to the wheel that does not show the middle lock tendency of the left and right wheels, and the braking force of the rear wheel is increased. (2) Change the slip threshold of the rear wheels and switch the slip to a deeper level than when the front wheels are normal. That is, normally, the rear wheel has a shallower slip threshold than the front wheel (slip threshold is a reference value for determining a locking tendency when the slip threshold is exceeded). By switching this method to deepen this slip threshold (about the same as the front wheels), the slip of the rear wheels is deepened and the braking force is increased. (3) The time of the pressure reducing pulse is made shorter than that in the case where the front wheels are normal. That is, by reducing the time of the decompression pulse,
The recovery from the slip tendency of the wheel is delayed more than usual, and the braking force is increased. However, when the deceleration is equal to or higher than the predetermined value, the control may not be switched to prevent the wheels from locking too strongly.

<D> Failure detection and processing The procedure for failure detection and processing switching of the front wheel system will be described. It is checked whether or not both front wheels are in a non-controlled state (S1). If both front wheels are in control, the braking force is sufficient, so
There is no problem, the failure timer is cleared (S4), and normal processing (S8) is performed. When both front wheels are in the non-controlled state, the process proceeds to step S2 in order to check the control state of both the rear wheels. When at least one rear wheel is in the non-controlled state, all the wheels are in the non-controlled state, so that the normal brake control is performed, the count of the failure timer is decremented (countdown, S4), and the normal processing (S8) is performed. When both the rear wheels are in the control state, there is a possibility that the braking system of the front wheels will fail, so the failure timer is counted up (S3), and the value of the failure timer is compared with a predetermined value (S6). The predetermined value is a time interval at which anti-skid control can be confirmed, and is, for example, several hundred ms. As a result of this comparison, when the value of the failure timer has not reached the predetermined value, the normal processing (S8) is performed. If the value of the failure timer is equal to or greater than the predetermined value, it is determined that the braking system of the front wheels is defective, and the normal anti-skid control method is switched to the processing for increasing the braking force of the rear wheels (S7). By the above control method, even if the front wheel braking system has a failure, a sufficient braking force can be secured.

[0013]

According to the present invention, the following special effects can be obtained. <B> By changing the anti-skid control method at the time of front wheel failure, high deceleration can be obtained. <B> Since front wheel failure is detected by the anti-lock control state of the front and rear wheels, no special hardware is required,
Easy to do.

[Brief description of drawings]

FIG. 1 is a schematic diagram of H-type piping.

FIG. 2 is a schematic diagram of ABS control.

FIG. 3 is a block diagram of an electronic control unit.

[Fig. 4] Flow chart for detection of system failure

Claims (4)

[Claims] 1. An anti-skid control method for an H-pipe braking vehicle, wherein at least one rear wheel is in an anti-skid control state, both front wheels are in a non-anti-skid control state, and when a predetermined time has elapsed, An anti-skid control method characterized by stopping select low control and performing rear wheel control with select high control. 2. An anti-skid control method for an H-pipe braking vehicle, wherein at least one rear wheel is in an anti-skid control state, both front wheels are in a non-anti-skid control state, and when a predetermined time has elapsed, the rear wheel An anti-skid control method characterized by changing the slip threshold and performing rear wheel control so that slip control is switched to deeper control than when normal front wheel control is performed. 3. An anti-skid control method for an H-pipe braking vehicle, wherein at least one rear wheel is in an anti-skid control state, both front wheels are in a non-anti-skid control state, and when a predetermined time has elapsed, the front wheel control is performed. An anti-skid control method characterized in that the rear wheel control is performed so that the pressure reducing pulse time is shorter than that in the normal case. 4. An anti-skid control method according to any one of claims 1 to 3, wherein at least one rear wheel is in an anti-skid control state and both front wheels are non-anti-skid. An anti-skid control method, characterized in that the rear wheel control is performed when a predetermined time has elapsed in the skid control state and when the vehicle body deceleration does not exceed a predetermined value.