JPH01204852A - Antiskid controlling method - Google Patents

Abstract

PURPOSE:To make improvements in safety by finding a wheel speed difference between symmetrical two wheels, and when this wheel speed difference is more than the threshold value, it is so judges as a J-turn state, and making a controller perform 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 to the upstream side of the hydraulic holding valve via an accumulator, or the like is installing in the point midway in a braking fluid route ranging from a master cylinder 2 to a braking device 3. Each valve and the pump are controlled by an electronic control unit ECU 6 on the basis of output of a wheel speed sensor 7, making it control the braking fluid pressure. In a suchlike antiskid device, a wheel speed difference between symmetrical two wheels is found out, and when this wheel speed difference is more than the threshold value, it is so judged as a J-turn state by this ECU 6. At the time of this J-turn state judgement, antiskid control is made so as to be carried out 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 the braking device of each wheel by a braking operation and the hydraulic pressure in the braking device becomes pressurized, the braking is applied in response to a decrease in wheel speed. The hydraulic pressure inside the device was reduced, and after waiting for the wheel speed to recover due to the pressure reduction, the brake fluid pressure was increased again, and the same pressure reduction and increase were repeated thereafter to ensure effective braking action. Various anti-skid devices for automobiles have been developed in the past, and are disclosed, for example, in Japanese Patent Laid-Open No. 60-61354.

Problems to be Solved by the Invention In the above-mentioned anti-skid device, depressurization and pressurization are generally controlled based on the wheel speed signals of the wheel speed sensors 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 operates, the difference in wheel speed between the inner and outer wheels is large and the inner wheel almost floats due to 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 in L.

Means for Solving the Problems The present invention provides an anti-skid control device for an automobile as described above, in which an anti-skid control control unit determines the wheel speed difference between two left and right wheels, such as two diagonal wheels, and determines the wheel speed. If the difference is greater than the threshold, it is determined that the vehicle is in a J-turn, the anti-skid control mode is switched from the normal mode to a mode compatible with the J-turn, and the anti-skid control is performed in the mode compatible with the J-turn. It is characterized by:

In action 1, when the vehicle enters a curve at a speed higher than the set vehicle speed and makes a sharp turn in a J-turn, the control unit determines that the vehicle is in a J-turn state because the wheel speed difference between the left and right wheels exceeds the threshold value. However, in a mode adapted to a J-turn, for example, the pseudo vehicle speed determined by the calculation that is the basis of anti-skid control is set to a lower value than in the normal mode, or the wheel speed setting value that determines the timing of pressure reduction. Then, the wheel speed setting value that determines the timing of switching from depressurization to pressurization is switched to a mode lower than that in the normal mode, and during subsequent braking operations, anti-skid control is performed in a mode adapted to the J-turn.
It is possible to improve the effectiveness of the brake during a J turn, shorten the braking distance, and improve 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, 1 is a brake pedal, 2 is a mask 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 released into the reservoir and supplies it to the upstream side of the hydraulic pressure holding valve through an accumulator. Based on the wheel speed signal of the wheel speed sensor 7 that detects the wheel speed of the electronic control unit (hereinafter referred to as ECU) 6.
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 transferred to the brake device 3.
is supplied to the brake equipment 213, and the hydraulic pressure of the brake equipment 213 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 speed and the low peak value of the wheel speed, the pressure reducing valve is closed, and the pressure reducing valve is closed. 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 pressure holding valve to a set value to switch to pressurization.

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 master cylinder 2 to the brake device 3 of the wheel 4 is connected to, for example, the left front wheel and the right front wheel. The rear wheels are normally configured with two independent piping systems, such as the same piping for the front right wheel and the same piping for the left rear wheel, and each piping system is provided with one HO2, and the two wheels in the same system are Common brake fluid pressure control is performed by one HO2. Therefore, for the two wheels in the same system, the ECUS selects the one with the lower wheel speed, 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. By signaling the HO2 of the vehicle, 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 the braking operation during a J-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 performs a sudden steering at 82 points,
When sudden braking is applied at the BP point, not only will the error in the vehicle speed calculated from the wheel speed become large due to the difference in travel trajectories between the inner and outer wheels, but also the wheel speed at the initial stage of braking will change due to the decrease in ground reaction force on the inner wheel. The decrease is more rapid than that on the outer wheel side, and the brake fluid pressure is reduced at a relatively low state, and at the same time,
In a depressurized state, the ground reaction force on the inner wheel side is small, so it takes a long time for the wheel speed to recover to the set value, so the depressurized state becomes longer, and overall the brake effectiveness becomes worse than when braking in 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, during a J-turn, as shown in FIG. 4, the running trajectories of the front, rear, left, and right wheels are different, so that the so-called difference in wheel speed between the inner and outer wheels becomes large. Therefore, as shown in Figure 3, the wheel speed difference between the left and right wheels on the diagonal, such as the left front wheel and the right rear wheel, and the right front wheel and the left rear wheel, is determined, and if no braking operation has been performed yet, When the speed difference is equal to or greater than a threshold value, it is determined that the vehicle is in a J-turn state.

When braking, even if you are driving straight, on a split A road where the coefficient of friction between the left and right road surfaces is significantly different, the difference in wheel speed between the left and right wheels may become large. I can't tell if it's a road or not.

Therefore, in the case of a J-turn after braking, it is checked whether the above-mentioned wheel speed difference has been greater than the threshold value for a certain set time (for example, set to about 200m5ec). , it is determined that the J-turn state is present when it continues for a set time or longer. In other words, when braking on a (split) road, the anti-skid control repeatedly depressurizes and pressurizes the vehicle, so the wheel speed increases and decreases accordingly, and the wheel speed difference also increases and decreases significantly, and the wheel speed difference that exceeds the threshold value does not continue for a long time. Since this is impossible, by doing the above, it is possible to reliably determine a J-turn in a braking state.

However, if braking is performed before steering, it may be assumed that the braking effect has already taken effect and the vehicle has been considerably decelerated before the vehicle turns, and the determination as a J-turn may not be made.

The threshold value of the wheel speed difference is set to a decreasing function that decreases as the vehicle speed (pseudo vehicle speed Vν calculated from the wheel speed as described above) increases, as shown in FIG. 5, for example. It is appropriate that the threshold value of the wheel speed difference is set to, for example, 7 to 8 Km/H at low vehicle speeds and about 2 to 3 Km/H at high vehicle speeds.

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.

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 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 illustrating a J-turn state.
FIG. 5 is a diagram illustrating a wheel travel trajectory during a turn, and is a diagram showing an example of a threshold value of a wheel speed difference for determining a J-turn. 1... Brake pedal, 2... Mask cylinder, 3
...Brake device, 4.Wheel, 5.Hydraulic control unit, 6.Electronic control unit, 7.Wheel speed sensor. that's all

Claims (1)

[Claims] Anti-skid control equipment for automobiles repeats a control pattern that detects signs of wheel lock from the wheel speed during braking, reduces the brake fluid pressure, and then re-pressurizes the brake fluid after waiting for the wheel speed to recover. The control unit calculates the wheel speed difference between the left and right wheels, and when the wheel speed difference is equal to or greater than a threshold value, it determines that a J-turn is occurring and changes the anti-skid control from normal characteristics to characteristics corresponding to a J-turn. 1. An anti-skid control method comprising performing anti-skid control based on characteristics corresponding to the J-turn.