JPH0234456A - Antiskid control device - Google Patents

Abstract

PURPOSE:To prevent a wheel speed from changing so as to improve a comfortableness to ride by providing a means which decreases a time change rate of increasing braking power of a braking means when a changing period of the wheel speed decreases smaller than a predetermined period. CONSTITUTION:A pressure of oil is generated in a master cylinder 21 by a step-in control of a brake pedal 20 and supplied to wheel cylinders 22a to 22d through actuators 6a to 6d, displaying brake power. Here by an antiskid control circuit 1 controlling the actuators 6a to 6d and a pressure of brake fluid, an antiskid control is performed. Here in the antiskid control circuit 1, in response to an output of a wheel speed detecting means detecting a wheel speed of each wheel, when a changing period of the wheel speed is discriminated to decrease smaller than a predetermined period, a time change rate of increasing the pressure of brake fluid is decreased, thus a fluctuation of the wheel speed is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an anti-skid control device that prevents wheels from locking during brake operation, and more particularly to an anti-skid control device that prevents fluctuations in wheel speed.

Conventional technology Anti-skid control devices hydraulically control the rotational speed of the wheels so that the slip ratio of the wheels reaches a value that generates the highest braking force in order to maintain the maximum braking force of the wheels against the road surface when the brake is depressed. It is a device. Slip rate S
, ■S is the traveling speed of the car, VW is the rotational speed of the wheels (
Hereinafter referred to as "wheel speed"), it is expressed by the first equation.

Therefore, in the conventional anti-skid control device, the wheel speed is determined by the wheel speed detecting means provided on each wheel, the traveling speed of the vehicle is estimated from these wheel speeds, and the first
The wheel speed is hydraulically controlled so that the slip ratio calculated from the equation becomes a slip ratio that provides the highest braking force, for example around 10% to 20%.

Problems to be Solved by the Invention However, in conventional anti-skid control devices, the control amount, that is, the gain, relative to the input amount to the control device is fixed. The anti-skid control circuit, braking means, wheels, transmission,
When considered as a control loop including wheel speed detection means,
The loop gain is not necessarily constant. Therefore, when the transmission is set to a high gear ratio, such as 1st or 2nd speed, the inertial mass of the wheels, that is, the load seen from the wheels toward the transmission, increases.
If the control gain of the anti-skid control circuit is kept constant, the control gain of the anti-skid control loop will become high, which may cause the wheel speed to fluctuate, resulting in poor ride comfort.

FIG. 5 is a timing chart for explaining conventional control in which the wheel speed oscillates. Figure 5 (1) shows changes in wheel speed, Figure 5 (2) shows changes in wheel cylinder oil pressure, that is, brake pressure, and Figure 5 (3) shows the state of the control signal sent from the anti-skid control circuit. At 0 time tll, which respectively represents , the brake pedal is depressed, the wheel cylinder oil pressure starts to rise, and the wheel speed starts to decrease. Then, when the anti-skid control start condition is satisfied at time t12, a pressure reduction control signal is output to the braking means, and the wheel cylinder oil pressure starts to decrease. However, if the inertial mass of the wheel is large, even if the wheel cylinder oil pressure decreases, the wheel speed shows no sign of recovery, so the pressure reduction control signal continues to be output. Then, when the wheel speed begins to show signs of recovery, the wheel cylinder oil pressure is in a very low state, so the wheel speed rapidly recovers.

If the degree of recovery is large, the anti-skid control circuit outputs a pressure increase control signal to suppress recovery of wheel speed. However, as described above, if the inertial mass of the wheel is large, recovery of the wheel speed cannot be suppressed.

As described above, when the inertial mass of the wheel is large, the response of the wheel speed to the ii control signal is delayed, resulting in overcontrol and vibration, or hunting, in the wheel speed.

The first threshold value THI in FIG. 5(2) indicates the oil pressure level at which the wheels begin to lock, and when the brake pressure becomes greater than this threshold value TH1, the wheels begin to lock. Therefore, the oil pressure difference ΔP1 is an increase in oil pressure due to overcontrol.

Further, the threshold value TH2 is the oil pressure level at which the wheel speed starts to recover, and when the oil pressure becomes lower than this threshold value T+-42, the wheel speed rapidly recovers. Therefore, the oil pressure difference ΔP2
is the pressure reduction due to overcontrol.

SUMMARY OF THE INVENTION An object of the present invention is to provide an anti-skid control device that prevents vibrations in wheel speed and improves riding comfort even when the gear ratio of a transmission is set to a high gear ratio.

Means for Solving the Problems The present invention provides: a braking means that is provided on a vehicle body and brakes each wheel, a wheel speed detection means that detects the wheel speed of each of the wheels, and a system that responds to the output of the wheel speed detection means. The anti-skid control device is characterized in that the anti-skid control device includes means for reducing a time rate of change for increasing the braking force of the braking means when the cycle of fluctuation of the wheel speed becomes smaller than a predetermined cycle.

Further, the present invention provides an anti-skid control n''At characterized in that the period of fluctuation of the wheel speed is detected based on the period of control of the braking means.

Operation In the present invention, each wheel is provided with a braking means for braking the rotation of the wheel, and a wheel speed detection means for detecting the wheel speed of each wheel. Then, when the wheel speed detected by the wheel speed detection means fluctuates at a cycle smaller than a predetermined cycle, the braking force applied to the braking means is gently controlled.

Further, in the present invention, the cycle of wheel speed fluctuation is determined by detecting the cycle of controlling the braking means.

Embodiment FIG. 1 is an electrical block diagram of an anti-skid control device which is an embodiment of the present invention. The anti-skid control circuit 1 is provided, for example, in a vehicle interior or a rear trunk. Wheel speed sensors 2a to 2 as wheel speed detection means
d is a senna provided for each wheel to detect the wheel speed.

The wheel speed sensors 2a to 2d each include a detection plate made of a ferromagnetic material, in which a large number of notches and protrusions are formed at equal intervals in the circumferential direction, is fixed to a wheel shaft, and is provided near the entire circumference of the detection plate. For example, an electromagnetic pickup detects a signal with a frequency proportional to the wheel speed. Wheel speed sensor 2a
After the wheel speed signal detected by ~2d is waveform-shaped into a pulse signal by waveform shaping circuits 3a~3d,
It is applied to processing circuits 4a and 4b realized by microcomputers or the like.

The switch 2e is, for example, a brake switch that sends out a signal indicating that the brake pedal has been depressed, and the output signal of the switch 2e is given to a level conversion circuit 3e, so that the signal level is adjusted to a voltage that is compatible with the anti-skid control circuit 1. converted to level. The output of the level conversion circuit 3e is sent to processing circuits 4a and 4b.

The processing circuit 4a includes a wheel speed sensor 2a attached to the front right wheel and a wheel speed sensor 2 attached to the rear left wheel.
After determining the respective wheel speeds based on the wheel speed signals from the wheel speed signals from the wheel speed signals from the wheel speed signals from the wheel speed signals sent from the wheel speed signals from the wheel speed signals from the wheel speed signals sent from the wheel speed signals from the wheel speed signals from the wheel speed signals from the wheel speed signals from the wheel speed signals from the wheel speed signals to the processing circuit 4b, the higher wheel speed is transferred to the processing circuit 4b via the signal line S11.

Similarly, the processing circuit 4b calculates the respective wheel speeds based on the wheel speed signals from the wheel speed sensor 2c attached to the left front wheel and the wheel speed sensor 2d attached to the right rear wheel, and then selects the larger one. The wheel speed is transferred to the processing circuit 4a via the signal line S12.

The processing circuits 4a and 4b estimate, for example, the larger wheel speed from the transferred wheel speeds and the wheel speeds calculated within each processing circuit as the controlled vehicle body speed. Anti-skid control calculations are performed based on this controlled vehicle speed and each wheel speed, and wheel cylinder oil pressure is controlled.

The control signals output from the processing circuits 4a, 4b are power-amplified by the solenoid drive circuits 5a-5d, and then given to the solenoid coils provided in the actuators 6a-6d. The solenoid relay drive signals sent out from the processing circuits 4a and 4b are given to the AND circuit 7, and the output thereof is power amplified by the solenoid relay drive circuit 8, and then sent to the relay coil 9 of the solenoid relay 9.
given to a. When the contact 9b becomes conductive, the battery voltage of the battery 11 is applied to the other ends of the solenoid coils incorporated in the actuators 6a to 6d via the contact 9b and the connection point 10.

The motor 12 is a motor for driving a hydraulic pump, and when the motor relay 13 is turned on, power is supplied from the battery 11 and control hydraulic pressure is generated.

The motor drive signals from the processing circuits 4a and 4b are given to the OR circuit 14, and when either motor drive signal from the processing circuits 4a or 4b becomes high level, the motor relay drive circuit 15 is turned on and the motor relay 13 is turned on. Also turns on. When a lamp drive signal from the processing circuit 4a or 4b is applied to the lamp drive circuit 16, the alarm lamp 17 is turned on. The warning lamp 17 lights up when any abnormality occurs in the anti-skid control device to alert the driver.

The positive electrode of the battery 11 is connected to one power supply circuit via a power switch 18. The power supply circuit 19 converts the battery voltage into a desired voltage, and then supplies the converted voltage to each circuit.

FIG. 2 is a block diagram for explaining a hydraulic path of an anti-skid control device according to an embodiment of the present invention. Hydraulic pressure generated in the master cylinder 21 by depression of the brake pedal 20 is applied to the wheel cylinders 22a to 22d via the actuators 6a to 6d, thereby reducing the rotational speed of the wheels 23a to 23d.

During actuator control, the braking oil pressure generated by the motor 12 is supplied to the master cylinder 21,
Anti-skid control circuit 1 and actuators 6a to 6
By the control signal given to d, the wheel cylinder 2
The brake hydraulic pressure supplied to wheels 2a to 22d is controlled to
Controls the rotation speed of a to 23d. P valve 24b, 24
d is a valve for limiting the upward slope when the oil pressure supplied to the rear wheel cylinders 22b and 22d exceeds a predetermined value. FIG. 3 is a timing chart for explaining control to prevent wheel speed vibration. The anti-skid control in this embodiment is performed for each wheel, and in order to simplify the explanation below, the control for the front right wheel 23a will be explained, and the explanation for the other wheels will be omitted. Figure 3 (1) shows the right front wheel 2.
3a shows the change in wheel speed, FIG. 3 (2) shows the change in the oil pressure in the wheel cylinder 22a, and FIG. 3 (3) shows the change in the output state of the control signal output to the actuator 6a at time 0. When the brake pedal 20 is depressed at t1, the brake pressure generated in the master cylinder 21 is applied to the wheel cylinder 22a, and as shown in FIG. It rises until the time t2 when it is satisfied. As the oil pressure increases, the right front wheel 2 as shown in Fig. 3 (1)
The wheel speed of wheel 3a decreases, and even if the pressure reduction control signal is output from time t2, the wheel speed continues to decrease due to the inertial mass of the wheel. When the five-wheel deceleration (negative wheel acceleration) and slip rate exceed predetermined values, a holding control signal is output, and at time t3 when the wheel speed starts to recover and the wheel acceleration exceeds the predetermined value, the wheel speed is increased. A pressure increase control signal is output to suppress sudden recovery.

In this way, when the pressure increase control signal is output at time t3, the wheel speed eventually reaches its peak and starts to decrease again. Then, when the wheel deceleration and slip rate exceed a predetermined value, a pressure reduction control signal is output in the same manner as described above. By outputting the pressure reduction control signal, the wheel speed starts to recover again, and when the wheel acceleration exceeds a predetermined value as described above, a pressure increase control signal is output.

If the inertial mass of the wheels is large, such as when the gearbox is set to a high reduction gear ratio such as 1st or 2nd gear, braking control is performed excessively, causing hunting in the wheel speed as described above. cause

Therefore, in this embodiment, the time W34 from time 3 when the first pressure increase control signal is output to time t4 when the second pressure increase control signal is output is measured, and this time W3
4 is shorter than the predetermined vibration time T, it is determined that hunting is occurring, and control is performed to prevent wheel speed vibration.

That is, a pulse pressure increase control signal is output that repeatedly outputs a pressure increase control signal having a predetermined pulse width in order to gradually increase the brake pressure supplied to the wheel cylinder 22a rather than rapidly. In this way, by gradually increasing the brake pressure of the wheel cylinder 23a, it is possible to lower the control gain in the anti-skid control circuit and prevent wheel speed hunting in the anti-skid control loop.

The pulse pressure increase control signal during time W45 from time t4 to time t5 during which control to prevent wheel speed vibration is performed is the same as the normal pulse pressure increase control signal output during time W67 between time t6 and time t7. are distinguished. That is, the pulse pressure increase control signal that is output to prevent vibrations in wheel speed has a shorter output cycle and a shorter pulse width for pressure increase control than a normal pulse pressure increase control signal. By doing so, the brake pressure can be increased more smoothly relative to the normal pulse pressure increase control signal.

FIG. 4 is a flowchart for explaining anti-skid control according to an embodiment of the present invention.

Note that, in order to simplify the explanation, the control for the fifth right front wheel 23a will be described below, but the control for the other wheels is exactly the same.

When the anti-skid control is executed in the processing circuits 4a and 4b, it is first determined in step s1 whether or not the anti-skid control is currently being executed, and if the anti-skid control is currently being executed, it is necessary to determine whether to start the anti-skid control. Since there is no one, the process advances to step s5. If anti-skid control is not performed in step s1, step s2
Then, it is determined whether the conditions for starting anti-skid control are satisfied. As the anti-skid starting condition, it is determined, for example, if the wheels are locked, or if the wheel speed is lower than a predetermined rotational speed, and if the wheel deceleration is greater than the predetermined current speed.

If the conditions for starting the anti-skid control are met, the process proceeds to step s3, where a pressure reduction flag is set in a predetermined memory area of the processing circuit 4 to cause the wheel cylinder to perform a pressure reduction operation.

In step S5, the conditions for ending the anti-skid control are determined, and the anti-skid control is canceled, for example, when the foot is released from the brake pedal or when the vehicle speed becomes 5 km/h or less. If the anti-skid control termination condition is not satisfied in step S5, the process proceeds to step S6, where a flag for controlling increase/decrease in wheel cylinder oil pressure is determined.

If it is determined in step S2 that the conditions for starting anti-skid control are not met, and in step S
If it is determined in step 5 that the anti-skid control termination conditions are met, the process proceeds to step s4, in which the actuator rotor a is activated so that the hydraulic pressure generated in the master cylinder by pressing the brake pedal is transmitted to the wheel cylinder. The solenoid control valve is set to the pressure increase position.

When anti-skid control is started, since the pressure reduction flag has already been set in step s3, step s
7, and further in step s8, a pressure reduction control signal for reducing the pressure in the wheel cylinder 22a is output.

After the pressure reduction control signal is output in step s8, when it is determined in step s7 that the end condition for the pressure reduction operation, that is, the wheel speed has begun to show signs of recovery, the process proceeds from step S7 to step s9, and the wheel cylinder 22a is
A hold flag is set to keep the oil pressure constant. Then, proceed from step slo to step all,
A holding control signal is output to the actuator 6a, and the wheel cylinder pressure is kept constant.

In step slO, if it is determined that the wheel speed starts to increase and the wheel acceleration exceeds a predetermined value and satisfies the holding end conditions, steps s1O to s12
Then, it is determined whether or not wheel speed hunting occurs.

That is, it is determined whether the time W34 in FIG. 3(3) is shorter than the predetermined vibration time T. However, when this step s12 is executed for the first time, the counter M remains set to zero, so the process proceeds from step s12 to step s13 and the pressure increase flag is set. Then, in step s14, a counter corresponding to the vibration time T is set in the counter M. Then, the process proceeds from step s14 to step s15, and further proceeds to step s16, where a pressure increase control signal is output and the oil pressure in the wheel cylinder 22a is increased.

In step s15, when the pressure increase end condition, for example, the oil pressure has recovered to a predetermined value, the process proceeds to step s17, where a first pulse pressure increase flag is set to gradually increase the pressure in the wheel cylinder 22a. and,
Proceeding from step s18 to step s19, a pressure increase pulse having a predetermined time width is sent from the processing circuit 4 to the solenoid drive circuit 5 at regular intervals, and the actuator 6a is driven by the pulse width given from the solenoid drive circuit 5a. Perform pressure increase operation for the corresponding amount of time.

If the conditions for ending pulse pressure increase are met in step s18, the process proceeds to step s20, where a pressure reduction flag is set.

Then, the process proceeds from step s20 to step s8, and a pressure reduction control signal is output, so that the wheel cylinder 22a
oil pressure decreases.

The series of controls described above are executed, and at the same time step s6 is performed in which flags are determined at predetermined fixed time intervals, the counter value set in the counter M is decremented by 1. Each time step s6, which performs flag determination processing, is executed, the counter M is decremented by 1, and the processing specified by the flag is performed.

When the holding end condition is satisfied in step slo, the process proceeds from step slo to step s12, where the counter value of the counter M is determined. In other words, if the counter M is zero, it is determined that the control period is longer than the vibration time T, and it is determined that hunting of the wheel speed has not occurred. However, if the counter M is not zero, the control period is determined to be longer than the vibration time T. It is determined that it is shorter than the vibration time T, and it is determined that hunting has occurred in the wheel speed. Note that once the counter M reaches zero, the count value is no longer decremented.

If it is determined that hunting has occurred in the wheel speed, the process proceeds from step S12 to step s21, where a second pulse pressure increase flag is set to distinguish it from the normal pulse pressure increase control described above. When the second pulse pressure increase flag is set, the process advances to step s22 and the counter M is cleared. If the second pulse pressure increase flag is set in step s21, then in step s18, as output at time W45 in FIG. 3(2), the output cycle is shorter than the normal pulse pressure increase control signal, and the pulse A short control signal is output.

As described above, when hunting is detected in the wheel speed, the pressure increase control signal with a short pulse width is outputted at a shorter cycle than the normal pulse pressure increase control signal to smoothly increase the pressure in the wheel cylinder 22a. , it is possible to suppress the occurrence of wheel speed hunting.

In this embodiment, as a means of detecting the occurrence of hunting, the time from when a pressure increase control signal is output to when the next pressure increase control signal is output is measured, and if the time is shorter than a predetermined time, Although it is determined that hunting has occurred in The time from the time when the wheel speed becomes the lowest to the time when the next wheel speed becomes the lowest may be measured, or the cycle of the peak value when the wheel speed becomes the highest may be measured.

Effects of the Invention As described above, according to the present invention, when a change in wheel speed is detected, the braking means is controlled to gradually increase the braking force, so that the change in wheel speed can be effectively suppressed. , the ride comfort of a car can be significantly improved.

[Brief explanation of the drawing]

Fig. 1 is a diagram of a blower of an anti-skid control device according to an embodiment of the present invention, Fig. 2 is a block diagram for explaining the hydraulic path of the anti-skid control device according to the present invention, and Fig. 3 is a wheel diagram of the anti-skid control device according to the present invention. FIG. 4 is a timing chart for explaining control to prevent speed vibration. FIG. 4 is a flow chart for explaining anti-skid control which is an embodiment of the present invention.
FIG. 5 is a timing chart for explaining conventional control in which wheel speeds fluctuate. 1...Anti-skid control circuit, 2a-2d...Wheel speed sensor, 3a-3d...Waveform shaping circuit, 4a. 4b... Processing circuit, 5a-5d... Solenoid drive circuit, 6a-6d... Actuator, 9... Solenoid relay, 11... Battery, 12... Motor, 13... Motor relay , 15...Motor relay drive circuit, 19...Power supply circuit, 21...Master cylinder, 22a-22d...Wheel cylinder agent Patent attorney Keiichi Nishikyo Figure 2 Figure 2 t3 bt6 Figure dragon 11

Claims (2)

[Claims] (1) Braking means provided on the vehicle body for braking each wheel, wheel speed detection means for detecting the wheel speed of each wheel, and varying the wheel speed in response to the output of the wheel speed detection means. An anti-skid control device comprising means for reducing a time rate of change of increasing the braking force of the braking means when the cycle becomes smaller than a predetermined cycle. (2) The anti-skid control device according to claim 1, wherein the period of fluctuation of the wheel speed is detected based on the period of control of the braking means.