JPH0656021A - Anti-skid control method for front wheel drive vehicle - Google Patents

Abstract

PURPOSE:To provide the control method of front wheel brake pressure at the time of engine stop in the case of the anti-skid control of a front wheel drive vehicle. CONSTITUTION:In the case of a front wheel drive vehicle, when engine stop is detected during travel, front wheel anti-lock control is changed over to normal brake control, and anti-skid control is conducted only for the brake control of rear wheels 5, 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antiskid control method for a front wheel drive vehicle.

[0002]

2. Description of the Related Art Recently, various anti-skid control devices have been developed which suppress the locking and slipping of wheels by controlling the pressure reduction, pressure retention and pressure increase of a brake pressure by electronic control means.
In particular, the present applicant has previously found that the pressure medium circuits were previously piped in two series in a diagonal manner, three valves were connected in series to each, and the brake pressures of the front and rear wheels were separated by a total of as few as six valves. Invented an anti-skid control device that can be controlled independently (see Japanese Patent Laid-Open No. 3-169769).

[0003]

When the front-wheel drive vehicle stalls during running, the front wheels are locked by the engine brake, so that the anti-skid control works and the brake pressure of the front wheels decreases. Along with that, in the anti-skid control device having the above six valves, the brake pressure of the rear wheels also decreases. As a result, the brake control based on the brake pressure is not performed.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an anti-skid control method capable of appropriately performing brake control when a front-wheel drive vehicle stalls during running.

[0005]

According to the present invention, two pressure medium circuits are provided from the master cylinder to the pressure medium return circuit, and an inlet valve, an on-off valve and an outlet valve are provided in each pressure medium circuit. Arranged in series, the front wheel brake is connected between the inlet valve and the opening / closing valve in each pressure medium circuit, and the rear wheel brake is connected between the opening / closing valve and the outlet valve in a diagonal manner, Anti-skid control device for front-wheel drive vehicle equipped with a control circuit that controls the brake pressure of the front and rear wheels via the medium circuit, when the engine stop is detected while the vehicle is running, the anti-skid control of the front wheel brake is prohibited. Then, the anti-skid control method of the front-wheel drive vehicle is characterized in that the anti-skid control of the brakes of the rear wheels is performed by returning to the normal brake control.

[0006]

Embodiments Embodiments will be described below with reference to the drawings. <A> First and second pressure medium circuits 2, 3 The brake pressure generator 1 is composed of a power booster 8, a master cylinder 9 and a reservoir 17. The brake pressure generator 1 includes wheel brakes 41, 61 for a left front wheel 4, a right front wheel 6 and a right rear wheel 5, and a left rear wheel 7 via hydraulically separated first and second pressure medium circuits 2, 3. , 51, 71 are connected in a diagonal manner. The auxiliary pressure source 10 is for supplying auxiliary hydraulic pressure to the pressure medium circuits 2 and 3.
The check valves 11 and 12, the hydraulic pumps 13 and 14, an electric motor 15 that drives these, and auxiliary reservoirs 25 and 26. The auxiliary reservoirs 25 and 26 are connected to the suction sides of the hydraulic pumps 13 and 14 to supply the pressure medium. The auxiliary reservoirs 25 and 26 are connected to the return circuits 18b and 1
8a are respectively connected to collect the pressure medium.

<B> Inlet valves 19, 20, open / close valves 23, 2
4, outlet valves 21, 22 inlet valves 19, 20, opening / closing valves 23, 24 and outlet valves 21, 2
2 are connected in series in the pressure medium circuit. That is,
The inlet valves 19 and 20 are the master cylinder 9, the check valve 11,
It is connected to 12. The outlet valves 21 and 22 are connected to the return circuits 18b and 18a, respectively. Each valve 19-
Reference numeral 24 has a function as a 2-port 2-position directional control valve that operates electromagnetically. A block diagram of the control system for controlling these valves 19-24 is shown in FIG. This control system includes a sensor 31 for measuring the rotation speed of wheels, an input device 32, a processing device 33 for performing antiskid control processing, an output device 34, and a hydraulic pressure control device 35. The inlet valves 19, 20 and the on-off valves 23, 24 are in the open position in the non-actuated position, and the outlet valves 21, 22
Is normally closed.

<C> Front and rear wheel brakes 41, 5
1, 61, 71 In the first pressure medium circuit 2, the wheel brake 41 of the left front wheel 4 is connected to the pressure medium circuit between the inlet valve 19 and the opening / closing valve 23. The wheel brake 51 of the right rear wheel 5 is diagonally connected to the pressure medium circuit between the on-off valve 23 and the outlet valve 21. Similarly, the second pressure medium circuit 3
At the wheel brake 61 of the right front wheel 6, the inlet valve 2
0 and the on-off valve 24 are connected to the pressure medium circuit.
The wheel brake 71 of the left rear wheel 7 is diagonally connected to the pressure medium circuit between the opening / closing valve 24 and the outlet valve 22. Since the on-off valves 23 and 24 separate the brake pressures of the rear wheels 5 and 7 from the brake pressures of the front wheels 4 and 6,
Independently controlled.

An example of anti-skid control will be shown below. <A> Example of anti-skid control on a road surface having different left and right frictional resistances The anti-skid control when the road surface conditions for contacting the left and right wheels are different will be described (see FIG. 3). The pressure generated from the brake pressure generator 1 by depressing the brake pedal 16 reaches the wheel brakes 41, 51, 61, 71 through the first and second pressure medium circuits 2, 3.
The front wheels 4, 6 and the rear wheels 5, 7 are braked. On the road surface where the left side surface is frozen, the friction coefficient μ of the left wheel is 0.2,
Assume that the right wheel is on an asphalt road and the coefficient of friction μ is 0.8. In this case, the anti-skid control needs to adjust the brake pressure of each wheel and the brake pressure on the low friction coefficient side to secure the braking force and the steering stability. That is, if the left side of the vehicle has a low coefficient of friction, the left front wheel 4
When the slip tendency is detected, the inlet valve 19 is closed based on this detection signal, and the opening / closing valve 23 remains in the open position, which is the non-operating state, and thereafter the brake is applied by opening / closing the inlet / outlet valves 19 and 21. The pressure is controlled. Therefore, the brake pressure of the right rear wheel 5 belonging to the first pressure medium circuit 2 is equal to the left front wheel 4
It is decompressed at about the same pressure.

On the other hand, the second right front wheel 6 is on the high friction coefficient side
In the pressure medium circuit 3, the slip tendency of the left rear wheel 7 that contacts the low friction road surface is detected first, and the open / close valve 24 in the normally open state is closed based on this detection signal, and the right side that requires further pressure increase. Only the brake pressure of the front wheels 6 is increased. When the slip tendency of the right front wheel 6 is detected, the inlet valve 20 is closed, the brake of the right front wheel 6 is kept in the pressure holding state, and the recovery or progress of the slip tendency is monitored. Until the pressure holding state of the right front wheel 6, the on-off valve 24 continues to be in the normally closed state, and the brake pressure of the left rear wheel 7 is held together with the closed position of the outlet valve 22, or the left rear wheel 7 slips. As the tendency progresses, the pressure is reduced by the opening operation of the outlet valve 22. When the slip tendency of the right front wheel 6 continues, the opening / closing valve 24 is switched to the open position to reduce the brake pressure of the right front wheel 6. At this time, the outlet valve 22 is also opened and closed to control the hydraulic pressure of the left rear wheel 7. Next, when the slip tendency of the left rear wheel 7 is recovered and pressure increase is required, the outlet valve 22 is closed and the on-off valve 24 is switched to introduce pressure via the inlet valve 20. Hereinafter, except when the pressure reduction of the right front wheel 6 is required, the brake pressure of the right front wheel 6 is controlled by opening / closing the inlet valve 20, and the brake pressure of the left rear wheel 7 is controlled by the switching valve 24 and the outlet valve 2.
Each of them is independently controlled by the opening / closing operation of 2. In the anti-skid control, it is preferable to increase the brake pressure of the front wheels to mainly contribute to braking, and to reduce the brake pressure of the rear wheels to prevent stability, that is, skid. The present invention allows this control with only three valves.

<B> Brake control at the time of stall during traveling When the front wheel drive vehicle stalls during traveling on a road surface having a low friction coefficient such as a frozen road surface, the front wheels are in the engine braking state. In FIG. 4, when the engine stalls at time t ₁ , the front wheel speed is rapidly decelerated to the locked state. On the other hand, the rear wheel speed becomes almost the same as the vehicle body speed (see FIG. 4 (B)). The reason is that the engine brake locks the front wheels, and the anti-skid control reduces the brake pressure on the front wheels to reduce slip. In order to reduce the brake pressure of the front wheels, the inlet valves 19 and 20 are closed, the opening / closing valves 23 and 24, and the outlet valves 21 and 22 are opened. As a result, the brake pressure on the rear wheels is also reduced. If this state continues, the hydraulic pressures of the front and rear wheels both decrease, and the brake control by the brake pressure becomes ineffective (see FIG. 4C). Further, since the anti-skid control continues, the motor 15 rotates insignificantly and continues until time t ₂ when the vehicle body stops, so that the driver feels poor (see FIG. 4A). In order to prevent this, when an engine stall is detected, the anti-skid control of the brake pressure of the front wheels is switched to the normal brake control, and the anti-skid control of only the brake pressure of the rear wheels is performed. That is, the inlet valves 19 and 20 are
Always open. Then, the on-off valves 23 and 24 and the outlet valves 21 and 22 perform anti-skid control. With this control, the normal brake control is performed on the front wheels,
There is no meaningless brake decompression. Since the anti-skid control is performed on the rear wheels, it is possible to accurately control even when the wheels are in a slip state.

<C> Method for detecting engine stall There are various methods for detecting engine stall. As an example,
If the signals from the wheel speed sensors for both the left and right front wheels continue in a pulseless state for a certain time or more, for example, one second or more, it is determined that the engine is stalled. That is, the sine wave signal from the wheel speed sensor becomes a square wave in the input circuit and is input to the arithmetic unit.
The frequency becomes 0 when the vehicle is stopped or locked. In other words, there is no pulse. Alternatively, the engine stall may be determined by detecting the alternator signal.
That is, the alternator signal is different when the engine is rotating and when the engine is stalled. The engine stall can be determined by detecting this voltage difference.

[0013]

As described above, the present invention can obtain the following special effects. <B> In an anti-skid control device that controls with a total of six front-wheel drive valves, even if an engine stall occurs, the anti-skid control of the front wheels should be switched to normal brake control and only the anti-skid control of the rear wheels should be performed. Thus, control equivalent to that of 3 channels becomes possible.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a pressure medium circuit of an anti-skid device.

FIG. 2 is a block diagram of a control device of an anti-skid device.

[Fig. 3] Wheel layout diagram in which left and right road surface friction is separated

FIG. 4 is a diagram showing changes in brake pressure, wheel speed, etc. when the front wheels are stalled.

Claims (1)

[Claims] 1. A pressure medium circuit of two systems is provided from a master cylinder to a pressure medium return circuit, and an inlet valve, an on-off valve and an outlet valve are arranged in series in each pressure medium circuit, and each pressure medium circuit is arranged. A front wheel brake is connected between the inlet valve and the on-off valve in the circuit, and a rear wheel brake is connected between the on-off valve and the outlet valve in a diagonal manner, and front and rear wheel brakes are connected via the pressure medium circuit. In the anti-skid control device for a front-wheel drive vehicle provided with a control circuit for controlling the pressure, when the engine stop is detected while the vehicle is running, the anti-skid control of the front wheel brake is prohibited and the normal brake control is restored. An anti-skid control method for a front-wheel drive vehicle, which is characterized in that only anti-skid control of the brakes of the rear wheels is performed.