JPH01204850A - Antiskid controlling method - Google Patents

Abstract

PURPOSE:To make improvements in safety by installing such a means as detecting lateral acceleration in a car body and, when this lateral acceleration is more than the setting value and car speed is also more than that, it is so judged as in a J-turn state and thereby performing antiskid control with a characteristic conformed to this J-turn state. CONSTITUTION:A hydraulic control unit 5 consisting of a hydraulic holding valve, a pressure reducing valve and a pump, pumping out a liquid set free to a reservoir and feeding it to the upstream side of the hydraulic holding valve via an accumulator, or the like is installed in the point midway in a braking fluid pressure route ranging from a master cylinder 2 to a braking device 3. Then, each valve and this pump are controlled by an electronic control unit ECU 6 on the basis of output of a wheel speed sensor 7, making it control brake fluid pressure. In a suchlike antiskid device, when lateral acceleration G of a car body detected by a lateral G sensor 8 and car speed is also more than that, it is so judged as a J-turn state, and at the time of this judgment, antiskid control is made so as to be performed in accordance with a characteristic conformed to this J-turn state.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an anti-skid control method for a motor vehicle.

BACKGROUND ART In a hydraulic braking system for an automobile, when braking fluid pressure is supplied to each wheel's braking device by a braking operation and the fluid pressure in the braking device becomes pressurized, the pressure increases as the wheel speed decreases. The hydraulic pressure in the brake system is reduced, and after waiting for the wheel speed to recover due to the pressure reduction, the brake fluid pressure is increased again, and thereafter the same pressure reduction and pressure increase are repeated to ensure effective braking action. Various types of anti-skid devices for automobiles have been developed and disclosed, for example, in Japanese Patent Application Laid-Open No. 80-61354.

Problems to be Solved by the Invention In the above-mentioned anti-skid device, pressure reduction and pressurization are generally controlled by each wheel speed signal from a wheel speed sensor provided for each wheel. The braking hydraulic system is made up of multiple systems, such as dividing the two diagonal wheels into two independent systems, so that even if a defect occurs in one system, the other system can maintain braking power for the time being. Therefore, the lower wheel speed of the two wheels in the same system is selected, and the brake fluid pressure control for that system is performed at this lower wheel speed. It is common practice to prevent the wheels from locking up.

However, if the brakes are suddenly applied during a J-turn (a J-turn is a state in which the vehicle enters a curve at a predetermined speed or higher and makes a sharp turn, and is a term generally used in this industry), the above-mentioned situation may occur. When the anti-skid device is activated, the inner wheel almost floats due to the large wheel speed difference between the inner and outer wheels and the increased lateral acceleration, reducing the ground reaction force on the inner wheel.
The wheel speed on the inner wheel side is considerably lower than that on the outer wheel side, so control of reducing and increasing the brake fluid pressure is performed mainly based on the wheel speed on the inner wheel side. Then, as mentioned above, the ground reaction force on the inner wheel side is low, so the slight increase in brake fluid pressure causes the wheel speed to drop rapidly and become almost locked, and even if the pressure is reduced, the wheel speed does not recover easily and remains in a depressurized state. becomes longer, resulting in insufficient braking force as a whole, and the braking distance in the extreme situation of sudden braking during a J-turn becomes longer than intended, which is undesirable from a safety standpoint.

The present invention aims to solve the problems in conventional anti-skid control as described above.

Means for Solving the Problems The present invention provides an anti-skid control device for an automobile as described above, which includes means for detecting lateral acceleration of the vehicle body.
When the lateral acceleration of the vehicle body is equal to or higher than the set value and the vehicle speed is equal to or higher than the set value, the anti-skid control control unit determines that the J-turn is in progress, and changes the anti-skid control mode from normal mode to J-turn. The present invention is characterized by switching to a corresponding mode and performing anti-skid control based on the mode corresponding to the J-turn.

For operation In the above, when entering a curve at a speed higher than the set vehicle speed and making a sharp turn in a J-turn, the control unit determines that a J-turn is occurring based on the information on the lateral acceleration and vehicle speed, and performs anti-skid control. When the mode is changed to a mode adapted to a J-turn and a sudden braking operation is performed in the J-turn state, the vehicle speed, which is the reference value for the mode adapted to the J-turn, e.g. depressurization and pressurization control, is set to the normal mode. Anti Skid control is performed, which improves the effectiveness of the brakes during J-turns, shortens braking distance, and improves safety.

Example Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows an example of an anti-skid device to which the present invention is applied. In FIG. 1, l is a brake pedal, 2 is a master cylinder, and 3 is a brake device for a wheel 4. 3, there is a hydraulic pressure holding valve that closes the hydraulic pressure supply from the mask cylinder 3 to the brake device 3, and a reservoir for storing the braking hydraulic pressure of the brake device 3 when the hydraulic pressure holding valve is closed. A hydraulic control unit (hereinafter referred to as HU) 5 is provided, which includes a pressure reducing valve that releases the liquid to the reservoir, and a pump that pumps out the liquid that has escaped to the reservoir and supplies it to the upstream side of the hydraulic pressure holding valve via a cumulator 7. An electronic control unit (hereinafter referred to as ECU) 6 based on a wheel speed signal from a wheel speed sensor 7 that detects the wheel speed of 4.
issues signals to control the operation of the six valves and pumps of the HU, and performs braking hydraulic pressure control as described below.

That is, 1. Normally, the hydraulic pressure holding valve is open and the pressure reducing valve is closed. When the brake pedal 1 is depressed and the mask cylinder 2 is activated, the braking hydraulic pressure passes through the hydraulic pressure holding valve and is applied to the brake equipment fi.
3, and the hydraulic pressure of the brake device 3 increases. As the hydraulic pressure of the brake device 3 increases, a braking force is generated and the wheel speed of the wheels 4 decreases, but when the rate of decrease reaches the set value, E
The CUS issues a holding signal, the hydraulic pressure holding valve closes, shutting off the hydraulic pressure supply from the mask cylinder 2, and the hydraulic pressure of the brake device 3 is maintained at the current state.

When the wheel speed further decreases to a certain set value, which will be described later, in the state where the hydraulic pressure is maintained, the ECUS issues an open signal to the pressure reducing valve to open the pressure reducing valve, and the fluid in the brake device 3 flows into the reservoir. Perform depressurization.

The liquid flowing into the reservoir is sent to the accumulator by the operation of the pump.

When the pressure of the brake device 3 is reduced, the wheel speed of the wheels 4 gradually recovers due to the ground reaction force and approaches the vehicle body speed. When the wheel speed recovers to a predetermined value, the ECUS gives a closing signal to the pressure reducing valve. An open signal is given to the hydraulic pressure holding valve, the pressure reducing valve is closed and the liquid pressure holding valve is opened, and the liquid pumped up by the pump and stored in the accumulator is supplied to the brake device 3 through the hydraulic pressure holding valve and applied. As a result, the wheel speed decreases again, and after that, by repeating pressure reduction and pressure increase as described above, efficient braking is achieved at a predetermined vehicle body deceleration without causing wheel lock. It will be done.

In the above, ECUS calculates and estimates the vehicle speed from the highest wheel speed among the four wheels on the front, rear, left and right sides, and sets the pressure reducing valve opening signal to a value lower by a predetermined value or a predetermined percentage with respect to the vehicle speed. When the wheel speed changes from decreasing to increasing due to the opening of the pressure reducing valve, for example, when the wheel speed recovers by a predetermined percentage with respect to the difference between the vehicle body speed and the low peak value of the wheel speed, the pressure reducing valve is closed and the hydraulic pressure is The control timing for pressure reduction and pressurization is determined from the vehicle body speed and wheel speed obtained from the high-selected wheel speed, such as setting the holding valve to a set value for switching to pressurization.

Also, although Fig. 1 shows the anti-skid control system for only one of the four wheels, in reality, the brake hydraulic pressure piping from the mask cylinder 2 to the brake device 3 of the wheel 4 is divided into 5, for example, the left front wheel and the right front wheel. The rear wheels are usually configured with two independent piping systems, with the same piping for the right front wheel and the other same piping for the left rear wheel, and each piping system is equipped with one HU5, and the two wheels in the same system are Common brake fluid pressure control is performed by one HU5. Therefore, the ECUS selects the lower wheel speed for the two wheels in the same system, and determines the control timing for depressurization and pressurization of the two wheels in that system based on the low selected wheel speed and the vehicle speed listed in 1. By issuing a signal to the HU5 of the system, an anti-skid operation is obtained in which wheel locking never occurs.

If the above-mentioned anti-skid control in the normal running state, ie, the normal state, is performed during a braking operation during a co-turn, significant inconvenience will occur.

That is, as shown in Fig. 2, in a J-turn state where the vehicle enters a curve at a certain speed or higher and makes a sudden steering at the SP point,
When a sudden wheel movement is applied at the BP point, not only does the error in the vehicle speed calculated from the wheel speed become large due to the difference in travel trajectory between the inner and outer wheels, but also the inner wheel's ground reaction force decreases, causing the wheels to move faster at the beginning of braking. The speed decreases more rapidly than that of the outer wheels, and the brake fluid pressure is reduced at a relatively low pressure.In the reduced pressure state, the inner wheels have less ground reaction force, so it takes less time for the wheel speed to recover to the set value. Therefore, the depressurization state becomes longer, and overall the effectiveness of the brake becomes worse than when braking under normal driving conditions.

Therefore, in the present invention, by providing a method that can easily and reliably determine whether or not it is in a J-turn state,
When it is determined by this method that the ECUS is in a J-turn state, the set value of the wheel speed for determining the control timing of the pressure reduction and pressurization is changed from the set value in the normal state to the J-turn state corresponding to the J-turn state. By switching to the turn mode, it is possible to eliminate the problem of deterioration of brake effectiveness as described above.

That is, the J-turn judgment uses the lateral G sensor 8 that detects the lateral acceleration of the vehicle body, and as shown in FIG. If the lateral acceleration is above the set value, then check whether the vehicle speed is above the set value (for example, set to about 30/H). is checked, and when the lateral acceleration is equal to or higher than the set value and the relative vehicle speed is equal to or higher than the set value, it is determined that the vehicle is in a J-turn state.

For the lateral G sensor 8, as shown in FIG. 4, for example, a pole-shaped movable contact 82 having a mass M is loosely fitted in a case 81 fixed to the vehicle body so as to be movable in the vehicle width direction. A spring 8 that presses the movable contact 82 in one direction.
3 is provided, and the movable contact 8 is moved by the spring force of the spring 83.
2 is pressed against a fixed contact 84 fixed to a case 81, and two of these structures are fixed to the vehicle body with the right and left sides reversed.

In such a lateral G sensor, if the force pushing the movable contact 82 to the left by the spring force of the spring 83 is F, and its initial set force is FO, then the vehicle body will have a rightward lateral acceleration -
(When this occurs, the movable contact 82d is
The car π・M that is about to move to the right side is the spring 83
The initial set force Fo is smaller than (−”M+
When Fo > O), the movable contact 82 is held in a state in which the fixed α is in contact with the fixed contact 84, that is, in an on state.

0), the movable contact 82 compresses the spring 83, moves to the right, and is balanced by a force F. This movement causes the movable contact 82 to move away from the fixed contact 84 and turn off, and this off signal allows it to be detected that the lateral acceleration has exceeded the set value.

In addition, in Fig. 3, to detect whether the vehicle speed is above a set value, it is generally possible to use vehicle speed information from a speedometer that is normally installed in a car, but as mentioned above, E
Since the CU 6 constantly calculates the vehicle speed VV in a pseudo manner based on the wheel speed signal from the wheel speed sensor 7, it is best to use the vehicle speed VV to detect whether the vehicle speed is higher than a set value. It's simple.

In this way, when the ECU 6 determines that the J-turn state is present, the anti-skid control is set to the J-turn mode. By switching to a mode in which the set value of the wheel speed that should be re-pressurized is lowered compared to the normal state, or the calculation method of the vehicle speed is changed and the value of the vehicle body speed Vv, which is the reference for control, is lowered. , it is possible to shorten the time in the depressurized state, improve the effectiveness of the brakes, and shorten the braking distance.

The lateral G sensor 8 is not limited to the embodiment shown in FIG. 4, and may be of any conventionally known type.

Effects of the Invention As described above, according to the present invention, it is possible to accurately determine whether the vehicle is in a J-turn state using extremely simple measures, and to switch the anti-skid control in the vehicle to a preferable characteristic corresponding to the J-turn state. This can improve safety during J-turns, and can have a great practical effect.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of the control system of an anti-skid device to which the method of the present invention is applied, Fig. 2 is a diagram explaining a J-turn state, Fig. 3 is a flowchart showing an example of the method of the present invention, and Fig. 4 is a diagram of the invention. FIG. 2 is a cross-sectional view showing an example of the structure of a lateral G sensor used in the present invention. l...brake pedal, 2...mask cylinder, 3
... Brake device, 4... Wheel, 5... Hydraulic control unit, 6... Electronic control unit, 7... Wheel speed sensor, 8
...Lateral G sensor.

Claims (1)

[Claims] During braking, an anti-skid control system for automobiles repeats a control pattern in which the brake fluid pressure is depressurized by detecting a sign of wheel lock based on the wheel speed, and then re-pressurized after waiting for the wheel speed to recover. A means for detecting lateral acceleration is provided, and when the lateral acceleration of the vehicle body is equal to or higher than a set value and the vehicle speed is equal to or higher than the set value, the anti-skid control control unit determines that the vehicle is in a J-turn state and performs anti-skid control. An anti-skid control method characterized by switching skid control from a normal characteristic to a characteristic corresponding to a J-turn, and performing anti-skid control based on the characteristic corresponding to the J-turn.