JPH07165052A - Antiskid control method - Google Patents

Abstract

PURPOSE:To improve steerability or stability and to shorten a stopping distance by lessening the falling in of the wheel speed of either of a front and a rear wheel. CONSTITUTION:A value at which the wheel speed VF of a front wheel is less than prefixed acceleration G1 is obtained in every increase and decrease cycle Tn of the braking oil pressure of the front wheel, and slip limit speed V2 at the optional point of time (t) is computed on the previous value V (n-1) of the wheel speed VF and a present value Vn from the equation of V2=Vn-(V (n-1)-Vn). t/Tn, and the braking oil pressure of the rear wheel is controlled on the slip limit speed V2. Thus, the rear wheel is reduced in fixed braking oil pressure at the point of time when the indication of locking appears, and the large falling in of the wheel speed of the rear wheel can thereby be prevented for improving stability.

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 method for preventing wheels from locking even when a hard brake is applied.

[0002]

2. Description of the Related Art An anti-skid control device is a device for controlling a braking force so as to increase a friction coefficient between a wheel and a road surface on the basis of a wheel speed, a vehicle body speed, etc., and shortening a braking distance. .

Therefore, when the braking operation is performed by depressing the brake pedal, the wheels are about to lock, and the slip ratio between the wheels and the road surface increases, the pressure reduction control of the braking hydraulic pressure is performed. When the wheel speed is restored by this pressure reduction control, the braking hydraulic pressure is increased again, and such pressure reduction /
The pressure increasing operation and the holding operation are repeated, and the braking force is controlled so that the slip ratio becomes appropriate.

The pressure reduction control is started when the wheel speed falls below a predetermined slip reference. The slip reference is determined, for example, based on the vehicle speed obtained from the maximum value of the wheel speeds of the four wheels.
That is, for example, it is obtained by multiplying the vehicle body speed by a predetermined coefficient, for example, 0.85.

When the wheels are locked, if the wheels are front wheels, steerability deteriorates, and if the wheels are rear wheels, stability deteriorates.

[0006]

In the prior art as described above, since the pressure reduction control is started at the time when each wheel speed becomes equal to or less than the slip reference, the drop amount of the wheel speed becomes large, There is a problem in that both the steerability and the stability are reduced and the stopping distance is increased.

It is an object of the present invention to provide an anti-skid control method capable of reducing the amount of wheel speed drop, improving the steerability or stability, and shortening the stopping distance.

[0008]

SUMMARY OF THE INVENTION The present invention provides an anti-skid control method for making a lock decision when each wheel speed falls below a predetermined slip reference based on at least the vehicle body speed and reducing the braking hydraulic pressure of each wheel. A pair of front and rear wheels on the left and right sides of the vehicle body, and for each left and right side, control the braking hydraulic pressure of either the front wheel or the rear wheel based on the wheel speed and at least the slip reference. Then, the slip limit speed is calculated based on the acceleration of one of the wheels under the control, and the braking hydraulic pressure of either the front wheel or the rear wheel is calculated based on the wheel speed and at least the slip limit speed. It is an anti-skid control method that is characterized by performing control by means of the following method.

Further, the present invention is characterized in that the slip limit speed is calculated on the basis of the wheel speed at the time point when the drop acceleration of the wheel speed becomes equal to or less than a predetermined value and the sign of the lock appears.

[0010]

According to the present invention, the front and rear wheels on each of the left and right sides of the wheel are paired, and the braking hydraulic pressure of either the front wheel or the rear wheel is determined based on the wheel speed and at least the vehicle body speed. Control based on a predetermined slip reference, the slip limit speed is calculated based on the acceleration of any one of the wheels by this control, and the braking hydraulic pressure of the other wheel is at least the wheel speed. Control based on the slip limit speed.

In this way, the other wheel is not decompressed after being locked, but rather
Since the pressure reduction control is performed on the basis of the slip limit speed, the fluctuation of the wheel speed of the other wheel becomes small.

Therefore, when the slip limit speed is calculated for the front wheels, the rear wheels are controlled at the slip limit speed, a large drop in the wheel speed of the rear wheels can be prevented, and the stability is improved.

On the contrary, when the slip limit speed is calculated for the rear wheels, the front wheels are controlled at the slip limit speed, a large drop in the wheel speed of the front wheels can be prevented, and the steerability is improved.

Further, according to the present invention, the slip limit speed is calculated based on the wheel speed at the time when the acceleration of the wheel speed falls below a predetermined value and a sign of lock appears.

[0015]

1 is a block diagram showing the electrical construction of an anti-skid controller in which the present invention is implemented, and FIG. 2 is a piping path diagram of a braking hydraulic pressure of the anti-skid controller. The wheel speed sensors 1a to 1d provided on the wheels 34a to 34d detect the rotation speeds of the wheels 34a to 34d, respectively.

These wheel speed sensors 1a to 1d are, for example, in the circumferential direction of a ferromagnetic detection plate fixed to the wheel shaft.
A large number of notches and protrusions are provided at equal intervals, and a wheel speed signal having a frequency proportional to the rotation speed of the wheel is derived by an electromagnetic pickup or an optical sensor provided near the circumference of the detection plate. Has been done. The wheel speed signals from the wheel speed sensors 1a to 1d are given to the waveform shaping circuits 5a to 5d in the anti-skid control circuit 4, and after being waveform shaped into pulse signals, the processing circuit 2 realized by a microcomputer or the like. Entered in.

The processing circuit 2 also includes a brake pedal 30.
The output from the switch 7 that detects that the
The level conversion circuit 8 causes the anti-skid control circuit 4
It is input after being converted to a voltage level suitable for the inside. In each circuit in this anti-skid control circuit 4,
The voltage from the battery 11 input via the power switch 10 is supplied after being stabilized by the power circuit 9.

The processing circuit 2 is based on the input result input as described above, and the three-position electromagnetic control valves 32a to 32 are provided.
The actuators 13a to 13d configured by d and the wheel cylinders 33a to 33d are drive-controlled to perform an anti-skid control operation. That is, via the solenoid relay drive circuit 14, the relay coil 1 of the relay 15
5a is excited, whereby the relay switch 15b becomes conductive. A high level voltage is commonly applied to one input of each of the actuators 13a to 13d via the relay switch 15b. Control outputs from the processing circuit 2 are given to the other inputs of the actuators 13a to 13d via the solenoid drive circuits 12a to 12d, respectively. As a result, the three-position electromagnetic control valves 32a to 32d control the braking hydraulic pressure to either a pressure-increasing or pressure-decreasing state or a holding state.

Further, the processing circuit 2 outputs an output to a relay coil 16a of the relay 16 via a motor relay drive circuit 18, and thereby a motor for generating a braking hydraulic pressure connected to a relay switch 16b of the relay 16 is provided. 17
Are driven and controlled. Furthermore, the processing circuit 2 turns on the warning lamp 19 via the lamp driving circuit 20 when an abnormality occurs in the anti-skid control.

Referring to FIG. 2, when the brake pedal 30 is stepped on, braking hydraulic pressure is generated in the master cylinder 31, and the braking hydraulic pressure passes through the pipe lines P1 to P4 and the three-position solenoid control valve is operated. 32a to 32d, and the conduit P
It is supplied to the wheel cylinders 33a to 33d via 5 to P8. As a result, the wheels 34a to 34d are braked and the vehicle body speed is reduced.

When the anti-skid control circuit 4 determines that the conditions for starting the anti-skid control are satisfied, the braking hydraulic pressure generated by the motor 17 is transferred to the conduit P.
9 to the master cylinder 31, and the three-position electromagnetic control valves 32a to 32d are controlled to either increase pressure, reduce pressure, or hold the wheel cylinders 33a to.
The braking hydraulic pressure of 33d is controlled. As a result, the wheels 34
The slip ratios a to 34d are controlled to values at which a high friction braking force acts on the road surface.

FIG. 3 is a timing chart for explaining the anti-skid control operation. In FIG. 3A, the solid line VF is the front wheel speed, the broken line VR is the rear wheel speed, VS is the vehicle body speed, and VSI is the estimated vehicle body speed.
The control pattern of the front wheels will be described below.

When the brake pedal 30 is depressed at time t1, the braking hydraulic pressure starts rising. As a result, the wheel acceleration increases to the negative side, and as shown in FIG. 3 (2), the pressure reduction start reference G1 predetermined at time t2, for example, −20.
m / sec ² or less and will, as further shown at time t3 in FIG. 3 (1), the wheel speed VF is less slip reference V1 to predetermined, from the time t3, FIG. 3
As shown in (3), the pressure reduction control of the braking hydraulic pressure is started.

The slip reference V1 is obtained by, for example, multiplying an estimated vehicle body speed VSI obtained by performing a filter calculation on a higher wheel speed among the wheel speeds of non-driving wheels at the time of braking by a predetermined coefficient, for example, 0.85. Is required.

By the pressure reduction control, the wheel acceleration and the wheel speed VF are recovered, and when the wheel acceleration exceeds the pressure reduction start reference G1, the pressure reduction control is ended at the time t4.

With respect to the repetition of the front wheel control pattern as described above, a value at which the wheel speed VF of the front wheel is equal to or less than a predetermined acceleration (for example, decompression start reference G1) is obtained for each cycle of increasing / decreasing the braking hydraulic pressure. Previous value V (n-1)
And the slip limit speed V2 is calculated from the current value Vn. This calculation formula is such that, if the period from the previous value V (n-1) to the current value Vn is Tn and the elapsed time is t, then V2 = Vn- (V (n-1) -Vn) .t / It is represented by Tn (1).

In the present invention, the slip limit speed V2 thus obtained from one of the paired front wheels or rear wheels on the same side which is locked first is used, and the wheel speed of the other wheel is set to this slip limit. When the speed becomes equal to or lower than the speed V2, the braking hydraulic pressure is reduced by a predetermined constant pressure, and when the lock determination is made based on the slip reference V1 and the depressurization start reference G1, the braking hydraulic pressure is greatly reduced as described above. In the following description, the wheel that is locked in advance will be described as a front wheel for simplification of description.

FIG. 4 is a flow chart for explaining the antiskid control operation. At step n1, initialization processing of the values of the register for storing the wheel speed and the vehicle body speed is performed, and at step n2, when a predetermined calculation timing is set every 5 msec, for example, the process proceeds to step n3. At step n3, each wheel speed and wheel acceleration is calculated from the detection results of the wheel speed sensors 1a to 1d. In step n4, the vehicle body speed VSI is calculated by estimating as described above from the wheel speed obtained in step n3.

At step n5, it is judged whether or not the conditions for starting the anti-skid control are satisfied. The control start condition is, for example, that the brake pedal 30 is depressed and the vehicle body speed VS is a predetermined value, for example, 5
This is the case, for example, when it is over km / h. When the condition for starting the anti-skid control is not satisfied, the process proceeds to step n6, the three-position electromagnetic control valves 32a to 32d of the actuators 13a to 13d are set to the pressure increasing position, and the anti-skid is not controlled. Return to step n2. Therefore, the braking hydraulic pressure generated in the master cylinder 31 by the depression of the brake pedal 30 is
3a to 33d are directly transmitted, and a normal braking operation is performed.

When the condition for starting the anti-skid control is satisfied in step n5, the process proceeds to step n7, and the slip limit speed V2 is calculated when either the front wheel or the rear wheel is locked. It At step n8, the braking hydraulic pressure of the front wheels is controlled,
In step n9, the braking hydraulic pressure of the rear wheels is controlled, and the process returns to step n2.

FIG. 5 is a flow chart for explaining in detail the control operation of the braking hydraulic pressure of the front wheels in step n8. In step m1, it is determined whether or not the wheel speed obtained in step n3 is equal to or less than the slip reference V1 created based on the estimated vehicle body speed VSI obtained in step n4. In m2, it is determined whether or not the wheel acceleration obtained in step n3 is less than or equal to the predetermined acceleration (decompression start reference) G1, and if so, the process proceeds to step m3, where the braking hydraulic pressure is reduced, Go to step n9 of 4. Further, in step m1, the wheel speed is the slip reference V1.
If not, or if the wheel acceleration is not less than or equal to the predetermined acceleration G1 in step m2, the process goes to step m4 to increase the braking hydraulic pressure, and the process goes to step n9 in FIG.

FIG. 6 is a flow chart for explaining in detail the control operation of the braking hydraulic pressure for the rear wheels in step n9. In step s1, it is judged whether or not the wheel speed is equal to or lower than the slip limit speed V2, and if so, the process moves to step s2, the constant hydraulic pressure is reduced, and the process moves to step s3. In step s3, it is determined whether the wheel speed is equal to or lower than the slip reference V1, and if so, the process proceeds to step s4, and the wheel acceleration is the predetermined acceleration G.
It is determined whether or not it is 1 or less, and if so, that is, if the wheel speed has dropped significantly, step s5
Then, similarly to the front wheels, a relatively large pressure reduction control of the braking hydraulic pressure is performed, and the process returns to step n2 in FIG.

In step s3, the slip reference V
When it is not less than 1 and when it is not less than the predetermined acceleration G1 in step s4, that is, when the drop of the wheel speed is suppressed by the relatively small pressure reducing control in step s2, the pressure reducing control in step s5 is not performed, and the process is performed directly. 4. Go to step n2 of 4. If the wheel speed is not equal to or lower than the slip limit speed V2 in step s1, the process proceeds to step s6, the braking hydraulic pressure increase control is performed, and the process returns to step s2 in FIG.

FIG. 7 is a flow chart for explaining the calculation operation of the slip limit speed V2. In step k1, it is judged whether or not the wheel acceleration has become equal to or less than the predetermined value G1, and if so, the process proceeds to step k2, in which the wheel speed VF of the front wheels at that time is updated to the current value Vn and held. It At this time, the previously input value is moved to the previous value V (n-1), and the previous value V (n-
1) is updated. When the current value Vn and the previous value V (n-1) are updated in this way, the process proceeds to step k3. If the wheel acceleration is not less than or equal to the predetermined value G1 in step k1, the values Vn and V (n-1) are not updated and the process proceeds to step k3.

At step k3, the slip limit speed V2 is calculated from the current value Vn and the previous value V (n-1) as V2 = Vn- (V (n-1) -Vn) .t / as described above.
The operation is performed by the formula of Tn, and the next operation starts.

As described above, the slip limit speed V2 is obtained from the control of the front wheels, and the braking hydraulic pressure of the rear wheels is controlled with reference to this slip limit speed V2. Therefore, a predetermined braking is applied before the rear wheels are locked. By reducing the hydraulic pressure, it is possible to prevent a large drop in the wheel speed of the rear wheels,
Therefore, stability can be improved.

As another embodiment of the present invention, it is also possible to obtain the slip limit speed V2 from the control of the rear wheels and control the front wheels on the basis of the slip limit speed V2. As a result, the predetermined braking hydraulic pressure is reduced before the front wheels are locked, whereby a large drop in the wheel speed of the front wheels can be prevented, and therefore the steerability can be improved.

However, when the slip limit speed V2 of the front wheels is calculated from the rear wheels in this way, in the vehicle equipped with the rear wheel hydraulic pressure adjusting device (abbreviated as P valve), the rear wheels are prevented from preceding locking. Therefore, the slip limit speed V2 of the front wheels cannot be obtained from the rear wheels,
When the front wheels are locked in advance, the slip limit speed V2 of the front wheels cannot be obtained. Therefore, in another embodiment of the present invention, in such a case, the slip limit speed V2 of the front wheels is set to a value lower than the speed of the rear wheels by a constant value, as described below.

FIG. 8 shows a slip limit speed V of another embodiment of the present invention when the above-mentioned P valve is mounted.
6 is a flowchart for explaining a second calculation operation.
At step p1, it is judged whether or not the rear wheels are locked. When the rear wheels are locked, the routine proceeds to step p2, where the limit speed calculation shown in step k3 of FIG. 7 of the above-described embodiment is performed and V2 = Vn. − (V (n−1) −Vn) · t / Tn
The slip limit speed V2 of the front wheels is obtained by the following equation. When the rear wheel is not locked in step p1, the rear wheel wheel speed VR that is rotating following the road surface is obtained by multiplying the rear wheel wheel speed VR by a predetermined value k1. The slip limit speed V2 is a value obtained by subtracting the offset amount k2 from the speed VR at a predetermined ratio. Therefore, this arithmetic expression is expressed by V2 = VR- (k1 · VR + k2) (2).

When the slip limit speed V2 is calculated in this way, the routine proceeds to step p4, where it is judged whether or not the front wheels are about to be locked based on the slip limit speed V2 obtained in step p2 or p3. If it is determined that the wheels are locked, then the process proceeds to step p5, where the front wheels are controlled to proceed to the next operation. If it is not determined in step p4 that the front wheels are about to be locked, the front wheels are not controlled and the next operation is performed.

In this way, even if the P valve is provided, it is possible to prevent the wheel speed VF of the front wheels from dropping significantly and to improve the steerability.

[0042]

As described above, according to the present invention, the slip limit is determined from the control result of the braking hydraulic pressure of either the front wheel or the rear wheel, with the front and rear wheels on the left and right sides of the vehicle body as a pair. The speed is detected, and the braking hydraulic pressure of the other wheel is controlled based on this slip limit speed.

When one wheel is a front wheel and the other wheel is a rear wheel, the braking hydraulic pressure of the front wheel is controlled based on a slip reference, a slip limit speed is calculated from the control result, and the slip limit speed is calculated based on the slip limit speed. Control the rear wheels. As a result, the braking hydraulic pressure of the rear wheels is not increased until the rear wheels are locked, and is reduced when the sign of lock appears before the wheel speed drops significantly. It is possible to prevent the stability of the vehicle from being lowered due to a large decrease in speed.

If one wheel is the rear wheel and the other wheel is the front wheel, the braking hydraulic pressure of the rear wheel is controlled based on the slip reference, and the slip limit speed is calculated from the control result,
The front wheels are controlled based on this slip limit speed. As a result, the control of the braking hydraulic pressure of the front wheels is reduced at the time when the sign of the lock appears, so that it is possible to prevent the deterioration of the steerability of the vehicle caused by the decrease in the wheel speed of the front wheels.

By thus reducing the drop in the wheel speed of one of the front and rear wheels, either the stability or the steerability can be improved and the stopping distance can be shortened.

[Brief description of drawings]

FIG. 1 is a block diagram showing an electrical configuration of an anti-skid control device in which the present invention is implemented.

FIG. 2 is a piping path diagram of a braking hydraulic pressure of the anti-skid control device of FIG.

FIG. 3 is a timing chart for explaining an anti-skid control operation.

FIG. 4 is a flowchart for explaining an anti-skid control operation.

5 is a flow chart for explaining in detail a control operation of a front wheel braking hydraulic pressure in step n8 of FIG. 4. FIG.

FIG. 6 is a flow chart for explaining in detail the control operation of the braking hydraulic pressure of the rear wheels in step n9 of FIG.

FIG. 7 is a flowchart for explaining a calculation operation of a slip limit speed V2 according to an embodiment of the present invention.

FIG. 8 is a flowchart for explaining a calculation operation of a slip limit speed V2 according to another embodiment of the present invention when a P valve is mounted.

[Explanation of symbols]

 1a-1d Wheel speed sensor 2 Processing circuit 4 Anti-skid control circuit 13a-13d Actuator 30 Brake pedal 32a-32d Three-position electromagnetic control valve 33a-33d Wheel cylinder

Claims (2)

[Claims] 1. An anti-skid control method in which a lock determination is made when each wheel speed falls below a predetermined slip reference based on the vehicle body speed, and the braking hydraulic pressure of each wheel is reduced. The front and rear wheels on each side are paired, and the braking hydraulic pressure on either the front wheel or the rear wheel is set for each left and right side.
Control based on the wheel speed and at least the slip reference, calculate the slip limit speed based on the acceleration of the one of the wheels by the control, the braking hydraulic pressure of the other of the front wheel or the rear wheel An anti-skid control method is characterized in that control is performed based on the wheel speed and at least the slip limit speed. 2. The slip limit speed is calculated on the basis of the wheel speed at the time when the acceleration of the wheel speed falls below a predetermined value and a sign of lock appears. Skid control method.