JPH07172278A - Anti-skid control method - Google Patents

Abstract

PURPOSE:To provide an anti-skid control method whereby control performance can be enhanced in the early stage of control. CONSTITUTION:The speed and acceleration of each wheel are computed (n2) and subjected to a synchronous process (n3) and then the speed and acceleration of the vehicle body are estimated (n4), and, when the speed of either one of the wheels is not greater than a slip reference (n5) and the acceleration of the wheel is not greater than a reference for the start of decompression (n6), the wheel is recognized as being locked, and the coefficient mu of friction between the wheels and the road surface is determined (n7) according to the lowest value of the accelerations of the remaining wheels. The amount by which braking hydraulic pressure is reduced in the early stage of control is set according to the result and anti-skid control is performed (n8).

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 controlling a slip ratio between a wheel and a road surface to shorten a braking distance and ensure stability and steerability.

[0002]

2. Description of the Related Art An anti-skid control device is a device for controlling a slip ratio between a wheel and a road surface on the basis of a wheel speed, a vehicle body speed, etc. to shorten a braking distance and ensure stability and steerability. is there.

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 is optimized.

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

In performing the anti-skid control as described above, in the prior art, the friction coefficient μ between the wheel and the road surface is not detected until the above-mentioned control is performed, and therefore the road surface is initially in the initial stage of the control. Since I do not know μ,
The control was performed on the assumption that the μ was high.

[0006]

In the prior art as described above, if the assumed road surface μ is different from the actual road surface μ, proper control cannot be performed at the start of control, and it is assumed that the value μ is high but low. If it is μ, the amount of pressure reduction will be insufficient, the drop in wheel speed will be large, and the steerability will decrease, and if it is assumed to be low μ, if it is high μ, the hydraulic pressure will be reduced too much, There is a problem that the braking force is insufficient.

An object of the present invention is to provide an anti-skid control method capable of improving control performance in the initial stage of control.

[0008]

SUMMARY OF THE INVENTION According to the present invention, each wheel speed is determined to be below a predetermined slip reference based on at least the vehicle body speed to perform lock determination, and the braking hydraulic pressure of each wheel is determined according to the determination result. In the anti-skid control method of decompressing, when the lock determination is performed on any one of the wheels, the friction coefficient between the wheels and the road surface is determined based on the smallest value of the wheel deceleration of the remaining wheels. The anti-skid control method is characterized by making a determination and changing at least the pressure reduction amount of the braking hydraulic pressure in accordance with the determination result.

According to the present invention, the front and rear wheels on each of the left and right sides of the vehicle body are made into a pair, and when the lock determination is made by one of the front and rear wheels on each of the left and right sides, the other wheel is determined. It is characterized in that the friction coefficient is determined based on the wheel deceleration.

Furthermore, according to the present invention, each wheel speed becomes equal to or less than a predetermined slip reference based on the vehicle body speed, lock determination is performed, and the braking hydraulic pressure of each wheel is reduced according to the determination result. In the skid control method, the wheel speed is detected at each predetermined cycle, and the wheel deceleration obtained from the wheel speed is stored for a predetermined time. The anti-skid control method is characterized in that the coefficient of friction between the wheel and the road surface is determined based on the wheel deceleration, and at least the pressure reduction amount of the braking hydraulic pressure is changed in accordance with the determination result.

Further, according to the present invention, anti-skid is performed in which each wheel speed is equal to or less than a predetermined slip reference based on the vehicle body speed to perform a lock determination, and the braking hydraulic pressure of each wheel is reduced according to the determination result. In the control method, the vehicle body speed is detected for each predetermined cycle, the vehicle body deceleration is calculated from the vehicle body speed, and when the lock determination is performed on at least one of the wheels, the determination is performed. Anti-skid control, characterized in that the coefficient of friction between the wheel and the road surface is determined based on the vehicle body deceleration at the time of breaking, and at least the pressure reduction amount of the braking hydraulic pressure is changed according to the determination result. Is the way.

Further, the vehicle body speed of the present invention is obtained by selecting the maximum value of the wheel speeds in each predetermined cycle and limiting the rate of change of the maximum value to be within a predetermined value. It is characterized by

[0013]

According to the present invention, when any one of the wheels is below the slip reference determined based on at least the vehicle speed and the lock determination is performed, the remaining wheel deceleration of each wheel is determined. , The friction coefficient between the wheel and the road surface is determined based on the smallest value, and the pressure reduction amount of the braking hydraulic pressure of the one wheel is changed according to the determined friction coefficient. Among the wheels, the friction coefficient closest to the actual road surface can be obtained from the smallest value of the wheel deceleration, and since this friction coefficient is used in the initial control of the one wheel, Can also set the optimum pressure reduction amount, and the control performance is improved.

Further, preferably, a pair of front and rear wheels on each of the left and right sides of the vehicle body is used, and when a lock determination is made on one of the front and rear wheels on each of the left and right sides, a determination is made on the other wheel. The pressure reduction amount of the braking hydraulic pressure of the one wheel is changed according to the friction coefficient determined based on the wheel deceleration. By determining the friction coefficient on each of the left and right sides in this way, a more accurate friction coefficient can be estimated when the road surface conditions on the left and right are different, such as the road shoulder and the road surface. Will be improved.

Further, according to the present invention, when the wheel lock determination is performed, the braking hydraulic pressure of the locked wheel is corresponding to the friction coefficient determined based on the wheel deceleration previous by a predetermined time. The amount of reduced pressure is changed. This method is effective even when the wheels are locked almost at the same time, and the friction coefficient thus estimated is used in the initial control of the locked wheels, so that the control performance in the initial control is improved.

According to the present invention, the vehicle body speed is detected for each predetermined period, the vehicle body deceleration is calculated from the vehicle body speed, and the lock determination is performed on at least one of the wheels. The pressure reduction amount of the braking hydraulic pressure for one wheel is changed according to the friction coefficient determined based on the vehicle body deceleration at that time. Since the friction coefficient obtained based on the deceleration of the vehicle body having a small fluctuation range is used in the initial stage of the control of the locked wheels, the control performance in the initial stage of the control is improved.

Further preferably, the vehicle speed is
It is selected as the maximum value of the wheel speeds for each predetermined cycle, and is obtained by limiting the rate of change of the maximum value so as to be within a predetermined value. In this way, the vehicle speed is estimated by limiting the maximum value that can be decelerated in terms of vehicle performance, so if deceleration above the maximum value is detected when sudden braking is applied, the maximum speed is limited. Since the friction coefficient is determined in this manner, it is possible to prevent the determination of μ that is larger than necessary.

[0018]

1 is a block diagram showing the electrical construction of an anti-skid control device in which the present invention is implemented, and FIG. 2 is a diagram of a brake hydraulic pressure piping route of the anti-skid control device. 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 the like provided near the circumference of the detection plate. These wheel speed sensors 1a-1
The wheel speed signal from d is given to the waveform shaping circuits 5a to 5d in the anti-skid control circuit 4, shaped into pulse signals, and then inputted to the processing circuit 2.

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 stabilized by the power circuit 9 and then supplied.

The processing circuit 2 is based on the input result input as described above, and the three-position electromagnetic control valves 32a-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 state, a pressure-decreasing state, or a holding state.

Further, the processing circuit 2 outputs the output to the relay coil 16a of the relay 16 via the motor relay drive circuit 18, and thereby the motor for generating the braking hydraulic pressure is connected to the relay switch 16b of the relay 16. 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 depressed, braking hydraulic pressure is generated in the master cylinder 31, and the braking hydraulic pressure passes through the lines P1 to P4 and the three-position electromagnetic control valve 32a. ~ 32d, and further pipeline P5
Through P8 to the wheel cylinders 33a-33d. 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 condition for starting the anti-skid control is 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. This allows the wheels 34a
The slip ratio of ~ 34d is controlled to a value 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 of the embodiment of the present invention. When the brake pedal 30 is depressed at time t11,
As shown in FIG. 3 (4), the braking hydraulic pressure starts to increase. This increases the wheel acceleration to the negative side, and FIG.
As shown in (2), it becomes less than or equal to the decompression start reference G11 that is predetermined at time t12, and further in FIG.
When the wheel speed indicated by the reference sign L13 becomes equal to or lower than the predetermined slip reference L11, the time t13 corresponds to the friction coefficient μ estimated as described later, and FIG.
As shown by, the pressure reduction control of the braking hydraulic pressure is started.

The slip reference L11 is set to 85% of the vehicle body speed Vs indicated by reference numeral L12, for example. Further, the reduced pressure amount is set to be smaller on a road having a high friction coefficient, in which the wheel easily follows the road surface and the wheel speed is rapidly recovered.

Therefore, when the friction coefficient μ is high, FIG.
The decompression time W1 is set short as indicated by the solid line in (3), and when the friction coefficient μ is low, the decompression time W2 is set long as indicated by the broken line in FIG. 3 (3). The wheel acceleration and the wheel speed are recovered by such pressure reduction control, the pressure reduction control is terminated at time t14 or t20, and the control shifts to the holding control.

However, when the drop in the wheel speed is large, the wheel acceleration does not converge even if the pressure reducing control is switched to the holding control, and at time t15 the pressure increasing start reference G12 or more is reached, and at time t16 the peak value is reached. Then, at time t17, the pressure is again less than the pressure increase start reference G12. At this time, the anti-skid control circuit 4 increases the braking hydraulic pressure for a pressure increase time corresponding to the peak value of the wheel acceleration at the time t16 and the friction coefficient μ.

The pressure increasing time is set longer as the friction coefficient μ is higher and the peak value of the wheel acceleration at the time t16 is higher. Therefore, when the friction coefficient μ is high, the pressure increase time is set to be long as indicated by reference numeral W3, and when the friction coefficient μ is low, the pressure increase time is set to be short as indicated by reference numeral W4.

In this way, the wheel acceleration is based on the reference G11, G.
When it is within 12, thereafter, as shown at times t18 and t19, the braking hydraulic pressure is pulse-increased at every predetermined constant period W11.

FIG. 4 is a timing chart for explaining changes in wheel speed and wheel acceleration with respect to a difference in friction coefficient μ. In this figure, the change of the front wheels is indicated by reference symbol F, and the change of the rear wheels is indicated by reference symbol R. Time t
When the brake pedal 30 is depressed at 11, FIG.
The braking hydraulic pressure starts to rise as shown in Fig. 4, and the braking hydraulic pressure of the front wheels gradually increases, while the braking hydraulic pressure of the rear wheels rises to a predetermined value in the same way as the front wheels, and then crawls when it rises to the predetermined value. It becomes a state. In this way, a hydraulic pressure control valve (not shown), which is a so-called P valve, which secures the running stability by suppressing the braking hydraulic pressure of the rear wheel more than the front wheel and locking the front wheel in advance, is provided in the conduit P2. , P4.

As described above, as the braking hydraulic pressure rises,
The wheel speed is as shown in FIG. 4 (2), and the wheel acceleration is as shown in FIG. 4 (3). In these figures, the solid line shows the case of the high μ road, the broken line shows the case of the low μ road, and Vs shows the vehicle speed. From these figures, it is understood that the decrease in the wheel speed is faster on the low μ road than on the high μ road, and the low μ road is more likely to be locked. Further, it can be said that it is understood that the front wheel is more likely to lock due to the action of the P valve.

As described above with reference to FIG. 3, when the wheel acceleration falls below the depressurization start reference G11 and the wheel speed falls below the slip reference L11, the depressurization control is performed and the depressurization time W1 (see FIG. 3C). ) Is set corresponding to each friction coefficient μ. Conventionally, the friction coefficient μ is not detected and is unknown until the anti-skid control is performed, and therefore the decompression time W1 is set assuming that the friction coefficient μ is generally high at the initial stage of control. If it is assumed that the value of μ is high and the value of μ is low, the amount of pressure reduction, that is, the pressure reduction time W1 is insufficient, and the drop of the wheel speed becomes large. As described below, the friction coefficient is determined even from the initial stage of control, and the depressurization time W1 is changed in accordance with the determination result for each μ, so the steering performance at the initial stage of control is improved.

As shown in FIG. 4, the P valve generally applies a higher braking oil pressure to the front wheels than to the rear wheels, and therefore the front wheels often lock earlier than the rear wheels. Utilizing the fact that there are wheels that are fast and wheels that are locked in this way, in one embodiment of the present invention, if a lock determination is made for any one of the wheels, the remaining wheels The friction coefficient μ is determined based on the smallest value of the wheel deceleration. The friction coefficient μ is
For example, if the vehicle body acceleration is 0.1 G, it becomes 0.1. Therefore, among the wheels, the wheel having the smallest wheel deceleration is closest to the vehicle body deceleration, and therefore the closest friction coefficient μ can be obtained. .

FIG. 5 is a flow chart for explaining the above-mentioned anti-skid control operation. At step n1, initialization processing such as the contents stored in the register and the count value of the counter is performed. At step n2, the wheel speed and wheel acceleration of each wheel are calculated. At step n3, for example, the cycle of this anti-skid control operation is 5 m.
The process waits until a predetermined calculation timing for each sec is reached, and when the calculation timing is reached, the process proceeds to step n4. In step n4, the vehicle body speed and the vehicle body acceleration are estimated and obtained from the wheel speed and the wheel acceleration obtained in step n2, and the process proceeds to step n5.

In step n5, it is judged whether or not the wheel speed of any one of the wheels has become equal to or less than the slip reference L11, and if so, the process proceeds to step n6, and the wheel acceleration of the one wheel is further determined. Is equal to or less than the depressurization start reference G11, and if so, it is determined that one wheel is locked, and the process proceeds to step n7, where the remaining wheel deceleration of each wheel is based on the smallest value. Then, the coefficient of friction μ between the wheel and the road surface is determined, and the pressure reduction amount of the braking hydraulic pressure at the initial stage of control, that is, the pressure reduction time W1 in FIG. 3 (3) is set according to the determination result, and the process proceeds to step n8. , Anti-skid control is performed, and the process returns to step n2.

In step n5, the slip reference L11
When it is not below, or when it is not below the pressure reduction start reference G11 in step n6, it is determined that none of the wheels are locked, and the process proceeds to step n9, where antiskid control is not performed and step n2 is not performed. Return to.

When the lock determination is performed on any one wheel in this manner, the pressure reduction at the initial stage of control of the one wheel is performed in accordance with the friction coefficient μ determined based on the smallest value of the remaining wheel deceleration of each wheel. Since the amount is set, it is possible to set the optimum amount of pressure reduction from the initial braking of the one wheel, and it is possible to improve the control performance.

In addition, for example, in a snowy road, the snow is melted in the center of the road surface, the snow remains on the road shoulders, and the left wheel runs while stepping on the snow on the road shoulders.
The right side where the snow is melted becomes high μ, and the left side where the snow remains is low μ, so that μ may be different between the left and right sides. Therefore, in another embodiment of the present invention, if the front and rear wheels on each of the left and right sides of the vehicle body are paired, and on each of these left and right sides, the lock determination is made by either one of the front and rear wheels, whichever is the case. The friction coefficient μ is determined based on the wheel deceleration of the other wheel.

FIG. 6 is a flow chart for explaining the anti-skid control operation of another embodiment of the present invention in such a case. Steps m1 to m4 are the same as steps n1 to n4 in the above-mentioned flowchart, and therefore the description thereof will be omitted. In step m5, the wheel speed of either the front or rear wheel on the left or right side becomes the slip reference L11 or less. If it is below the slip reference L11, the process proceeds to step m6. It is determined whether or not the wheel acceleration of the wheel is below the pressure reduction start reference G11, and if so, step m7.
Then, after the flag F1 indicating that anti-skid control is to be performed on one side is set to 1, the process proceeds to step m8, where one wheel and the road surface are selected based on the wheel deceleration of the front or rear wheel on the other side. The friction coefficient μX is determined, and the routine goes to Step m9.

In step m9, the wheel speed of either the front or rear wheel on either the left or right side is the slip reference L1.
It is determined whether or not it has become 1 or less, the process proceeds to step m10, and the wheel acceleration of the one wheel is the decompression start reference G11.
It is determined whether or not the following is true, and if so, in step m11, after the flag F2 indicating that anti-skid control is to be performed for the other side is set to 1, the process proceeds to step m12, and the wheels and road surface on the other side are set. The coefficient of friction μY between and is determined. Since it is possible that the wheels on one side are already locked, in this case, the braking force on one side is extremely small, and therefore the friction coefficient μ obtained from the wheel deceleration of either the front or rear wheel on the other side is The value of
Therefore, the friction coefficient μY is obtained by averaging the detected friction coefficient μ and then subtracting the friction coefficient μX obtained on the one side. Therefore, this calculation formula is μY = 2μ−μX. When the friction coefficient μY is calculated by such a formula,
Move to step m13.

Further, at step m5, when the wheel speeds of the front and rear wheels on either the left or right side are not both equal to or less than the slip reference L11, or at step m6 the wheel accelerations of both wheels start the decompression. If it is not below the reference G11, the process directly proceeds to m13. Similarly, when the wheels are not locked at steps m9 and m10, the process directly proceeds to step m13.

In step m13, it is judged whether or not at least one of the flags F1 and F2 is 1, and if so, in step m14, one side corresponds to the friction coefficient μX and the initial braking is performed. The anti-skid control is performed to reduce the hydraulic pressure, and the other side is anti-skid controlled to reduce the initial braking hydraulic pressure corresponding to the friction coefficient μY, and the process returns to step m2. Step m1
When the flags F1 and F2 are not both in step 3, the antiskid control is not performed in step m15, and the process returns to step m2.

In this way, the friction coefficient μ
By determining X and μY, it is possible to more accurately estimate the friction coefficient between the road surface and the wheels when the road surface conditions on the left and right are different.

As another embodiment of the present invention, the wheel speed is detected at a predetermined cycle, for example, a cycle of 5 msec, and the wheel deceleration obtained from the wheel speed is stored for a predetermined time, for example, 100 msec. When the lock determination is performed, the coefficient of friction μ between the wheel and the road surface is determined based on the wheel deceleration that has been performed for the predetermined time.
Is determined, and the pressure reduction amount of the initial braking hydraulic pressure is set according to the determination result.

FIG. 7 is a flow chart for explaining the anti-skid control operation of still another embodiment of the present invention in such a case. It should be noted that this is almost similar to the flowchart of FIG. 5, and the same portions are denoted by the same reference numerals. The difference is that in step n7a, the friction coefficient μ is determined based on the wheel deceleration before a certain period of time, and in other steps, the same control operation as in FIG. 5 is performed.

According to this method, it is possible to deal with the case where the wheels are locked substantially at the same time, so that the control performance at the initial stage of control can be further improved.

Further, also in this embodiment, the front and rear wheels on each of the left and right sides are set as a pair, and the wheel deceleration before each time is calculated for each of the left and right sides by a predetermined time, and based on the wheel deceleration, The coefficient of friction μ between the wheels and the road surface may be determined.

FIG. 8 is a flow chart for explaining the anti-skid control operation of another embodiment of the present invention in such a case. It should be noted that this is almost similar to the flowchart of FIG. 6, and the same portions are denoted by the same reference numerals. The difference is that in step m8a, the friction coefficient μX is determined based on the wheel deceleration on either the left or right side before a certain period of time, and at step m12a, the friction coefficient μ is on the other side of the left or right side before the certain period of time. It is calculated based on the wheel deceleration of.

Therefore, in FIG. 6, step m
5, m6; m9, m10, for each of the left and right sides, it is determined whether or not one of the front and rear wheels is locked. However, in this embodiment,
Even if both the front and rear wheels are locked at the same time, the left and right friction coefficients can be calculated.

As still another embodiment of the present invention,
When the vehicle body speed is detected in a predetermined cycle, for example, every 5 mmsec, the vehicle body deceleration is calculated from the vehicle body speed, and if the lock determination is performed on at least one of the wheels, the determination is made. The friction coefficient μ between the vehicle body and the road surface is determined based on the vehicle body deceleration at the time when it is performed, and the pressure reduction amount of the braking hydraulic pressure at the initial stage of control is set according to the determination result.

The vehicle speed is estimated from each wheel speed. During control, the wheel speed does not exceed the vehicle body speed, and the maximum value of each wheel speed is considered to be the value closest to the vehicle body speed, so the vehicle body speed is selected as the maximum value of the wheel speeds. . However, since the wheel speeds of all the wheels suddenly decrease when the vehicle is suddenly braked on a low μ road, in this case, the vehicle body deceleration is limited to the maximum allowable deceleration.

The maximum allowable deceleration is determined from the vehicle body performance, and can be obtained from an experimental value under the best possible braking condition. The braking conditions include dry asphalt road surface, high-grip tires that are not worn, and a ride only for the driver with no load.

FIG. 9 is a flow chart for explaining the anti-skid control operation of still another embodiment of the present invention in such a case. It should be noted that this is similar to the flowchart of FIG. 5, and the same portions are denoted by the same reference numerals. The difference is that step n5. When the lock determination is made in n6, the process proceeds to step n11, and it is determined whether or not the deceleration that is the value obtained by inverting the vehicle body acceleration obtained in step n4 is a value exceeding the maximum allowable deceleration. If it is, the vehicle body deceleration is limited to the maximum allowable deceleration in step n12, and then the process proceeds to step n7b. If not, the process directly proceeds to step n7b.
In step n7b, the friction coefficient μ is determined based on the vehicle body deceleration obtained as described above, and the control operation similar to that in FIG. 5 is performed in other steps.

As described above, the friction coefficient μ is determined by the vehicle body deceleration with a small fluctuation range in which the vehicle body deceleration is limited by the maximum allowable deceleration.
Is determined and the locked wheel is initially controlled in accordance with the friction coefficient μ, so that the control performance at the initial stage of the control can be improved.

[0056]

As described above, according to the present invention, the conventional control of the anti-skid control, that is, the first reduction of the braking hydraulic pressure is high because the friction coefficient μ between the wheel and the road surface is unknown. Although the pressure reduction amount was set assuming μ, the lock timing of each wheel is deviated, and if the lock determination is made for any one of the wheels, the wheels of the remaining wheels are The friction coefficient μ is determined based on the smallest value of deceleration. Since at least the pressure reduction amount of the braking hydraulic pressure is changed in accordance with the result of this determination, the initial control can be optimally performed, and particularly the initial steering performance is improved, and therefore the safety is improved.

Further, preferably, the front and rear wheels on the left and right sides are set as a pair, and the lock determination is performed on each side. Therefore, when the lock determination is performed on either one of the front and rear wheels on each of the left and right sides, the friction coefficient μ is determined based on the deceleration of the other wheel. This makes it possible to more accurately determine the friction coefficient between the road surface and the wheels even when the road surface conditions on the left and right are different, such as when snow melts in the center of the road surface and snow remains on the shoulders of the road. be able to.

Further, according to the present invention, when the lock determination is performed, the coefficient of friction between the road surface and the wheel is determined based on the wheel deceleration that has been set for a predetermined time, and the determination result is dealt with. Then, at least the pressure reduction amount of the braking hydraulic pressure is changed. This method is effective even when the wheels are locked almost at the same time, and the control performance at the initial stage of control can be further improved.

Further, according to the present invention, the vehicle body speed is detected for each predetermined period, the vehicle body deceleration is calculated from the vehicle body speed, and the lock determination is performed on at least one of the wheels. The friction coefficient between the road surface and the wheels is determined based on the vehicle body deceleration at the time when the determination is made, and at least the decompression amount of the braking hydraulic pressure is changed according to the determination result. Since the fluctuation range of the vehicle body deceleration is small, it is possible to more accurately determine the friction coefficient between the road surface and the wheels.

Further preferably, the vehicle speed is
For each predetermined cycle, the maximum value of the wheel speed is selected, and the change rate of the maximum value is limited so that it is within a predetermined value, so it is limited by the maximum value that can be decelerated in terms of vehicle performance. When the value above the predetermined value is detected, the friction coefficient is determined based on the maximum value, so that it is possible to prevent the determination of μ that is larger than necessary.

[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 of the embodiment of the present invention.

FIG. 4 is a timing chart for explaining changes in wheel speed and wheel acceleration with respect to a difference in friction coefficient μ.

FIG. 5 is a flowchart for explaining an anti-skid control operation of an embodiment of the present invention in which the friction coefficient μ is determined based on the minimum value of wheel deceleration of wheels other than locked wheels.

FIG. 6 is a flow chart for explaining an anti-skid control operation of another embodiment of the present invention for determining the friction coefficient μ on each of the left and right sides in FIG.

FIG. 7: Friction coefficient μ based on wheel deceleration before a certain time
9 is a flow chart for explaining an anti-skid control operation of still another embodiment of the present invention for determining whether or not.

8 is a flow chart for explaining an anti-skid control operation of another embodiment of the present invention for determining the friction coefficient μ on each of the left and right sides in FIG.

FIG. 9 is a flow chart for explaining an anti-skid control operation of still another embodiment of the present invention for determining the friction coefficient μ based on the vehicle deceleration.

[Explanation of symbols]

 1a-1d Wheel speed sensor 2 Processing circuit 3a, 3b Acceleration sensor 4 Anti-skid control circuit 13a-13d Actuator

Claims (5)

[Claims] 1. An anti-skid control method in which each wheel speed is equal to or less than a predetermined slip reference based on a vehicle body speed, lock determination is performed, and the braking hydraulic pressure of each wheel is reduced according to the determination result. When the lock determination is performed on any one of the wheels, the friction coefficient between the wheels and the road surface is determined based on the smallest value of the wheel deceleration of each remaining wheel, and the determination result is dealt with. Then, at least the pressure reduction amount of the braking hydraulic pressure is changed. 2. A pair of front and rear wheels on each of the left and right sides of the vehicle body, and when a lock determination is made on one of the front and rear wheels on each of the left and right sides, the wheel reduction of the other wheel is performed. The antiskid control method according to claim 1, wherein the friction coefficient is determined based on a speed. 3. An anti-skid control method in which each wheel speed is equal to or less than a predetermined slip reference based on the vehicle body speed, lock determination is performed, and the braking hydraulic pressure of each wheel is reduced according to the determination result. , The wheel speed is detected for each predetermined cycle, and the wheel deceleration obtained from the wheel speed is stored for a predetermined time. When the lock determination is performed, the wheel deceleration before the predetermined time is stored. The anti-skid control method is characterized in that the friction coefficient between the wheel and the road surface is determined based on the above, and at least the pressure reduction amount of the braking hydraulic pressure is changed according to the determination result. 4. An anti-skid control method in which each wheel speed is equal to or less than a predetermined slip reference based on a vehicle body speed, lock determination is performed, and the braking hydraulic pressure of each wheel is reduced according to the determination result. When the vehicle body deceleration is calculated at predetermined intervals and the vehicle body deceleration is calculated from the vehicle body speed, and the lock determination is made on at least one of the wheels, the time at which the determination is made. In the anti-skid control method, the friction coefficient between the wheel and the road surface is determined based on the vehicle deceleration, and at least the pressure reduction amount of the braking hydraulic pressure is changed according to the determination result. 5. The vehicle body speed is selected as a maximum value of the wheel speeds for each predetermined cycle, and the change rate of the maximum value is limited so as to be within a predetermined value. The anti-skid control method according to claim 4.