JPH0656022A - Anti-skid control method - Google Patents

Abstract

PURPOSE:To cope with the trouble of a brake control valve properly in a case in which it is detected that the opening/closing valve becomes out of order and is not closed, by stopping the anti-skid control of a rear wheel connected to a pressure medium circuit connected to the opening/closing valve that is out of order, conducting the front wheel anti-skid control alone. CONSTITUTION:In a case in which an opening/closing valve 24 does not become closed due to mechanical trouble, brake pressures at front and rear wheels 6, 7 become equal to each other naturally. If a vehicle having trouble such as this one travels on a road surface, the rear wheels slip and enter into anti- skid control action and decrease the brake pressure of the rear wheels. With this, front wheel brake pressure also comes to be led into pressure decrease. As a result, the rear wheel anti-skid control of a damaged system is stopped, and the opening/closing action of an outlet valve 22 by rear wheel anti-skid control is stopped. However, front wheel anti-skid control is conducted. As a result, anti-skid control is conducted as the vehicle whole.

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. We have invented an anti-skid control device that can be controlled independently (see Japanese Patent Laid-Open No. 3-169769).

[0003]

When the middle opening / closing valve of the three valves connected in series fails and cannot be closed, the braking pressures of the front wheels and the rear wheels diagonally opposite to each other become equal to each other. . The frictional resistance of the road surface differs between the left and right wheels, and if the rear wheels slip and the brake pressure is reduced, the brake pressure of the front wheels required for braking is also reduced. As a result, the braking force due to the failed system is significantly reduced.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an antiskid control method that can appropriately cope with a brake control valve failure.

[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. Front wheel brakes arranged in series between the inlet valve and the on-off valve in each pressure medium circuit;
In the anti-skid control device in which a rear wheel brake is diagonally connected between the on-off valve and the outlet valve and a control circuit for controlling the brake pressure of the front and rear wheels is provided via the pressure medium circuit, When it is detected that the valve has failed and cannot be closed, the anti-skid control of the rear wheels connected to the pressure medium circuit connected to the on-off valve of the failure is stopped and only the anti-skid control of the front wheels is performed.
The anti-skid control method is characterized by.

[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 Corresponding to Failure of Opening / Closing Valve Of the opening / closing valves, for example, when the opening / closing valve 24 is mechanically broken and cannot be closed, the brake pressures of the front wheels 6 and the rear wheels 7 are naturally equal. . When a vehicle with such a failure travels on the road surface in FIG. 3, the rear wheels slip and the anti-skid control operation is started to reduce the brake pressure of the rear wheels. Along with that, the brake pressure of the front wheels is also pulled and reduced. As a result, the braking pressure of the front wheels, which particularly contributes to braking, is reduced, and braking of the entire vehicle is weakened. Therefore, when the open / close valve 24 fails, the braking pressure of the front wheels, which particularly contributes to braking, is not reduced. Therefore, the antiskid control of the rear wheel of the defective system is stopped, and the opening / closing operation of the outlet valve 22 by the antiskid control of the rear wheel is stopped. However, anti-skid control of the front wheels is performed. As a result, the anti-skid control is performed for the entire vehicle, and the brake pressure of the front wheels can be secured, so that the braking of the vehicle is performed despite the failure of the on-off valve.

<C> Method for Detecting Failure of Opening / Closing Valve There are the following methods for detecting a failure of the opening / closing valve. (I) The total pressure increase of the front wheels is continuous several times (eg, twice), and
A method of detecting that the integrated value of the depressurization pulse width per skid cycle of the rear wheels is equal to or longer than a predetermined time (eg, 150 ms).
That is, when increasing the hydraulic pressure, it is performed stepwise, but if the slip tendency is not shown even if it is performed a predetermined number of times (eg, 10 times) or more (the pressure increase is not sufficient), the inlet valve is not changed stepwise. Control to take an open state and increase the pressure all at once (total increase) is taken. This state occurs when the pressure increase is not sufficiently obtained. For example, it may occur when the vehicle enters a low μ road to a high μ road. Therefore, in order to determine the failure of the pressure-increasing on-off valve, it is preferable to count the total number of times of increasing the pressure of the front wheels several times and detect that the pressure reduction of the rear wheels does not proceed in order to further improve the accuracy. Therefore, in one skid cycle, if the integrated value of the decompression pulse width (decompression operation time) exceeds a predetermined time, decompression is not sufficiently performed, and the on-off valve fails and the pressure medium of the front wheels is lost. It can be judged that it is flowing into the rear wheel.

(Ii) The number of times of pressure increase in yaw control is several tens of times (eg: 20 times) or more, and the integrated value of the pressure reducing pulse width per rear wheel skid cycle is a predetermined time (eg: 150 ms). How to detect the above. That is, when a large brake pressure difference is abruptly generated between the left and right wheels, a rotational moment is strongly applied to the vehicle. To prevent this,
To prevent the brake pressure from increasing suddenly, the yaw control is performed to increase the brake pressure in stages. The detection of this state occurs when the vehicle enters a road surface having different left and right frictional resistances as shown in FIG. Therefore, in order to determine the failure of the pressure increase / decrease valve, the number of times the brake pressure is increased is counted more than the normal number (for example, 20 times), and in order to further improve the accuracy, as in (i), It is good to detect that the pressure reduction of the rear wheels does not proceed. It should be noted that if the methods (i) and (ii) are used together, a more accurate determination can be made.

[0014]

As described above, the present invention can obtain the following special effects. <B> Even if the open / close valves 23 and 24 are broken and open, by stopping the anti-skid control of the rear wheels,
It is possible to suppress the decrease in brake pressure and enable anti-skid control. <B> The brake control required for the anti-skid control can be performed by using only six small control valves.

[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 with different left and right road friction

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 an anti-skid control device provided with a control circuit for controlling pressure, when it is detected that the on-off valve fails and cannot be closed, a rear wheel connected to a pressure medium circuit connected to the on-off valve with the failure is detected. The anti-skid control method is characterized in that the anti-skid control is stopped and only the anti-skid control of the front wheels is performed.