JPH0268253A - Antiskid controller - Google Patents

Abstract

PURPOSE:To control a variation in wheel speed due to an operating time lag in a selector valve by compensating output time through the output state when a switching signal is delivered to a hydraulic switching means controlling hydraulic pressure for a hydraulic braking means at each wheel. CONSTITUTION:Hydraulic pressure being fed to hydraulic braking means 22a-22d is controlled by each switching signal to hydraulic switching means 6a-6d. An antiskid controller 1 controls the hydraulic pressure being fed to these hydraulic braking means 22a-22d in direction of increasing frictional braking force between respective wheels 23a-23d and a road surface. The switching signal being delivered to the hydraulic switching means 6a-6d is compensated of its output time by an output state of the switching signal when the signal is delivered. For example, at a high friction factor passage, a pulse decompression switching signal combined with a so-called short time range decompression switching signal and a holding switching signal is outputted, but when a wheel starts its locking, decompression time is added as much as the preset time and outputted to a selector valve. Thus, any shortage of operation due to an operation time lag in the hydraulic switching means is obviated.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anti-skid control device that corrects the output time of a switching signal to a hydraulic switching device that controls the hydraulic pressure supplied to a hydraulic braking device.

A conventional anti-skid control device prevents an excessive increase in brake oil pressure to the hydraulic braking means due to sudden depression of the brake pedal, prevents wheel locking (a state in which the rotational speed of the wheels becomes almost zero), and This is a device that hydraulically controls the number of rotations per unit time (hereinafter referred to as "wheel speed") of each wheel so that the frictional braking force between each wheel and the road surface becomes the maximum slip ratio. Here, when VS is the traveling speed of the vehicle and VW is the wheel speed, the slip rate S is calculated by the first equation.

The anti-skid control device calculates the wheel speed of each wheel based on the wheel speed signal from the wheel speed sensor installed on each wheel of the car, and calculates the actual running speed of the car from the wheel speed of each wheel. The corresponding speed (hereinafter referred to as "vehicle speed") is estimated, and the slip ratio S calculated by the first formula from the wheel speed of each wheel and the vehicle speed is the slip ratio exerted by the highest braking force, for example 20%. The hydraulic braking means is controlled to maintain the front and back. That is, when the slip ratio S increases, the wheel speed is significantly lower than the vehicle speed, so an operation to reduce the hydraulic pressure supplied to the hydraulic braking means, that is, a pressure reduction operation is performed. Furthermore, in a state where the slip ratio S becomes small, the wheel speed approaches the vehicle body speed and the frictional braking force against the road surface decreases, so an operation to increase the hydraulic pressure to the hydraulic braking means, that is, a pressure increase operation is performed. be exposed.

The hydraulic pressure supplied to the hydraulic braking means is controlled by controlling a hydraulic pressure switching means such as an electromagnetically controlled directional switching valve (hereinafter referred to as a "switching valve").

Problems to be Solved by the Invention As described above, the hydraulic pressure supplied to the hydraulic braking means is controlled by switching the operating states of pressure increase, pressure decrease, and holding by the hydraulic pressure switching means.

The pressure increase, pressure decrease, and holding state are set by the position of the spool of the switching valve, and are set by the switching signal applied to the switching valve. That is, when the spool is set at the neutral position, it is in the holding state, moving the spool in one direction will result in a pressure increase operation, and further moving the spool in the other direction will result in a pressure reduction operation. In this way, it is possible to control the hydraulic pressure supplied to the hydraulic braking means by changing the position of the spool, but due to the inertia due to the mass of the spool, it is not possible to control the hydraulic pressure by moving the spool in synchronization with the switching signal. In other words, the hydraulic pressure supplied to the hydraulic braking means is supplied with a certain time delay, and especially when switching from pressure increase to pressure reduction or from pressure reduction to pressure increase, the distance the spool moves becomes longer, so the time delay is increased accordingly. becomes larger.

In particular, when anti-skid control is performed while driving on a road with a high friction coefficient, and the pressure is reduced from the pressure increase operation, the pressure reduction control time is shortened due to the above-mentioned operation delay, and the hydraulic pressure supplied to the hydraulic braking means is reduced. There may be cases where it is not possible to sufficiently reduce the pressure to the desired hydraulic pressure. Therefore, a problem arises in that insufficient pressure reduction causes a large drop in wheel speed.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an anti-skid control device that suppresses fluctuations in wheel speed caused by a delay in operation of a switching valve.

Means for Solving the Problems The present invention provides that the hydraulic pressure supplied to the hydraulic braking means provided for each wheel of an automobile is controlled by a switching signal to the hydraulic switching means, thereby increasing the frictional braking force between each wheel and the road surface. The anti-skid control device controls hydraulic pressure so that the slip ratio increases, and the anti-skid control device is characterized in that the output time of the switching signal is corrected depending on the output state of the switching signal when the switching signal is sent to the hydraulic pressure switching means. This is an anti-skid control device.

Operation In the present invention, a hydraulic brake means is provided for each wheel of the automobile, and the hydraulic pressure supplied to the hydraulic brake means is controlled by a switching signal to the hydraulic pressure switching means. The anti-skid control device controls the hydraulic pressure supplied to the hydraulic braking means in a direction that increases the frictional braking force between each wheel and the road surface. The output time of the switching signal sent to the hydraulic pressure switching means is corrected depending on the output state of the switching signal when the signal is sent.

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 2d are provided for each wheel and are sensors for detecting 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 circumference of the detection plate. For example, an electromagnetic pickup detects a signal with a frequency proportional to the wheel speed. Wheel speed sensors 2a to 2d
The wheel speed signal detected by the waveform shaping circuit 3a~
After the waveform is shaped into a pulse signal by 3d, the processing circuits 4a to 4a are realized by a microcomputer or the like.
4b.

The switch 2e is, for example, a brake switch that sends 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 suitable for the anti-skid control port 281. converted to level. The output of the level conversion circuit 3e is sent to processing circuits 4a and 4b.

The processing circuit 4a calculates the respective wheel speeds based on the wheel speed signals from the wheel speed sensor 2a provided on the right front wheel and the wheel speed sensor 2b provided on the left rear wheel, and then calculates the wheel speed of the larger wheel. The speed is transferred to the processing circuit 4a via the signal line sl1.

Similarly, the processing circuit 4b calculates the respective wheel speeds based on the wheel speed signals from the wheel speed sensor 2c provided on the left front wheel and the wheel speed sensor 2d provided on 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 calculation is 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 to 5d, and then applied to the solenoid coils provided in the switching valves 6a to 6d. Processing circuit 4a.

The solenoid relay drive signal sent from 4b is
! ! The output is applied to a product circuit 7, whose output is power amplified by a solenoid relay drive circuit 8, and then applied to a relay coil 9a of the solenoid relay. When the contact 9b is conductive, the battery voltage of the battery 11 is applied to the other end of the solenoid coil incorporated in the switching valves 6a to 6d via the contact 9b and the connection point 10.

The motor 12a is a motor for driving a hydraulic pump,
When the motor relay 13 is turned on, power is supplied from the battery 11 and control hydraulic pressure is generated. Processing circuits 4a, 4
The motor drive signal from b is given to the OR circuit 14,
When either of the motor drive signals from the processing circuits 4a, 4b becomes high level, the motor relay drive circuit 15 is turned on, and the motor relay 13 is also turned 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. Warning lamp 17
lights up to alert the driver if any abnormality occurs in the anti-skid control device.

A positive electrode of the battery 11 is connected to a power supply circuit 19 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 depressing the brake pedal 20 is applied to the wheel cylinders 22a to 22d via the switching valves 6a to 6d, and is applied to the wheel cylinders 23a to 22d.
- Decrease the rotation speed of 23d.

During anti-skid control, braking oil pressure generated by driving the motor 12a is supplied to the P valves 24b and 24d. When a pressure increase switching signal is sent from the anti-skid control circuit 1 to the switching valve 6a, the braking oil pressure generated in the oil pressure source 12 is transferred to the wheel cylinder 2 via pipes 25a and 26a.
2a. Furthermore, when the pressure reduction switching signal is sent to the switching valve 6a, the hydraulic pressure in the wheel cylinder 22a is returned to the reservoir tank 28 via the pipes 26a and 27.
The oil pressure inside the wheel cylinder 22a is lowered. Further, when the holding switching signal is sent to the switching valve 6a, the pipe line 25
The same applies to the switching valves 6b to 6d, in which all of the valves a, 26a, and 27 are shut off, and the oil pressure in the wheel cylinder 22a is maintained constant.

The P valves 24b and 24d are the rear wheel cylinders 22.
This is a valve for restricting the slope of the braking oil pressure supplied to the cylinders b and 22d rising from a predetermined value or higher.

FIG. 3 is a diagram for explaining the operation of the switching valve used in the present embodiment. FIG. 3 shows the case of a three-bottle, three-position switching valve, in which the boat PTI is piped to the P valve, the boat PT2 is piped to the wheel cylinder, and the boat PT3 is piped to the reservoir tank. In the holding state, all boats PT1 to PT3 are in a cutoff state. Then, when the pressure increasing position is set, the boat PTI and the boat PT2 are brought into conduction, and hydraulic pressure is supplied to the wheel cylinder. In addition, in a reduced pressure state, the boat P
T2 and boat PT3 are brought into conduction, and the hydraulic oil in the wheel cylinder is returned to the reservoir tank and depressurized. In this way, in order to switch from the increased pressure state to the reduced pressure state, it is necessary to go through the held state, so the switching time is longer than when switching from the held state to the reduced pressure state.

Next, correction of the output time of the switching signal will be explained. In particular, a case will be described in which there is a request to output a pressure reduction switching signal while the pressure increasing switching signal is being output. FIG. 4 is a functional block diagram for explaining the correction calculation of the pressure reduction switching signal. A wheel speed and a wheel acceleration, which is a time change rate of the wheel speed, are input to the control section 41 that outputs a switching signal. The control unit 41 selects and outputs a pressure increase, hold, or pressure decrease switching signal based on the wheel speed and wheel acceleration based on a table stored in the memory in advance. On normal roads, a pressure increase switching signal or a pressure reduction switching signal is output while a holding switching signal is being output.

On roads with a high friction coefficient, the wheel speed will recover with a short time decompression switching signal, so if the hydraulic pressure in the wheel cylinder is depressurized too much, the braking distance will lengthen and the braking force will feel like it has been temporarily lost. , which will worsen the control feeling. Therefore, on roads with a high friction coefficient, a pulse reduction switching signal is output that is a combination of a pressure reduction switching signal with a short time width and a holding switching signal, but when the wheels start to lock, a pressure increase switching signal with a short time width is output. If a pressure increase switching signal of a pulse pressure increase switching signal that is a combination of a holding switching signal and a holding switching signal is output, a delay in operation of the switching valve will become a problem. Therefore, the output time is corrected in the decompression time correction section 42 to prevent this operation delay. That is, the pressure increase switching signal currently being output to the pressure reduction time correction section 42 and the control section 41
When the pressure reduction request signal is inputted, a correction signal is outputted to the control section 411 to instruct the control section 4111 to correct the output time of the pressure reduction switching signal. When the control unit 41 receives this correction signal, the control unit 41 sets the decompression time to a predetermined time (for example, 4
~8rnsec) is added and output to the switching valve.

Next, the control state of anti-skid control will be explained using a timing chart. FIG. 5 is a timing chart for explaining the anti-skid control of this embodiment.

When the brake pedal 20 is strongly depressed, the state shown in FIG. 5 (3)
As shown in FIG. 5, the wheel cylinder oil pressure continues to rise, and the wheel speed decreases as shown in line 11 in FIG. 5(1).

Then, during the time WOI from time to to time t1, a pulse depressurization switching signal for avoiding wheel locking is output. Thereafter, the holding switching signal is output until time t2, and the wheel cylinder oil pressure is reduced during the period during which the pressure reducing switching signal is output, and then kept constant. As a result of the wheel cylinder oil pressure being reduced by the output of the pressure reduction switching signal, as shown in Fig. 5 (1)
), the wheel speed begins to recover around time t1, and as shown in FIG. 5(2), when the wheel acceleration exceeds the acceleration G2, a hold switching signal is output.

When the wheel speed almost recovers at time t2, a pressure increase switching signal is output for time rWW23 in order to increase the wheel cylinder oil pressure and increase the braking force. After time t3, a pulse pressure increase switching signal for gradually increasing the wheel cylinder oil pressure is output.

When the wheel speed starts to drop at time t5, when the wheel speed gradually decreases and the wheel cylinder oil pressure gradually increases, a pulse depressurization switching signal is output to avoid wheel locking.

Next, a case where the pressure reduction output means is corrected will be explained.

In the state where the pressure increase switching signal is being output from time t7, as shown by line 12 in FIG. When the pressure decreases below a predetermined pressure reduction reference acceleration Gl (for example, -2G to -2.5G, where G is gravitational acceleration), the output signal is switched from the pressure increase switching signal to the pressure reduction switching signal at time t8. However, as described above, due to the delay in the operation of the switching valve, the compensation time KT for compensating for the delay in operation of the switching valve is set to just before C at the output time M1, which is normally output as a pulse pressure reduction switching signal, and the pressure reduction switching continues until time t9. A signal is output. In this way, by performing the pulse pressure reduction operation just before the time corresponding to the operation delay of the switching valve, insufficient pressure reduction can be prevented.

FIG. 6 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 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 circuit 4a, 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, there is no need to judge whether to start the anti-skid control. Proceed to step S4.

If anti-skid control is not being performed in step S1, the process proceeds to step S2, where it is determined whether conditions for starting anti-skid control are satisfied. The anti-skid control start condition is, for example, when the wheels are locked or the wheel speed is lower than a predetermined rotation speed, and it is determined whether the wheel deceleration (negative wheel acceleration) is greater than the predetermined deceleration. If the conditions for starting the anti-skid control are met, the process proceeds to step S3, where a decompression flag for causing the wheel cylinder to perform decompression operation f% is stored in a predetermined memory area of the processing circuit 1a. Set.

In step S2, the anti-skid system 0'Ilt!
: If it is determined that the conditions for starting are not met, the process proceeds to step s20, and the switching valve 6a is set to the pressure increasing position so that the hydraulic pressure generated in the master cylinder by pressing the brake pedal is directly transmitted to the wheel cylinder. is set to

In step S4, the condition for ending the anti-skid control is determined. For example, in step S4, the anti-skid control is canceled 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, the process proceeds to step S5, where a flag (flag) determination is performed to control the increase/decrease of the wheel cylinder oil pressure.

When the anti-skid control starts, since the pressure reduction flag is set in step S3, the process advances to step S6, and then to step S7, where the wheel cylinder 22
a is pulse depressurized. In step s6, when the pulse depressurization operation end condition is met, that is, the wheel acceleration exceeds the predetermined acceleration G2 and the wheel speed begins to show signs of recovery, the process proceeds to step s8. In step S8, a flag is set to keep the oil pressure of the wheel cylinder 22a constant. When the holding flag is set, the process proceeds from step s9 to step slo, where a holding switching signal is output to the switching valve 6a and the wheel cylinder oil pressure is kept constant.

In step S9, when the wheel acceleration exceeds the acceleration G2 and then falls below the acceleration G2, the holding end condition is satisfied. When the holding end condition is met, steps s9 to 5 are performed.
11, a pressure increase flag for increasing the oil pressure of the wheel cylinder 22a is set. Wheel cylinder 22
The output time of the switching signal for increasing the pressure a is set by the value of the wheel acceleration after the pressure is decreased. And step S1
2 to step s13, the wheel cylinder 22a
The hydraulic pressure inside is increased. When the pressure increase setting time ends, the process proceeds from step s12 to step s14, where a pulse pressure increase flag is set to gradually increase the pressure in the wheel cylinder 22a.

Then, proceeding from step s15 to step s16,
A pressure increase pulse having a predetermined time width is sent from the processing circuit 4a to the solenoid drive circuit 5a, and the switching valve 6a performs the pressure increase operation for a time corresponding to the pulse width given from the solenoid drive circuit 5a.

In step s15, the pulse pressure increase termination condition is met, that is, when the wheels start to lock or when the wheel speed is below the slip reference speed and the wheel acceleration is equal to the pressure reduction reference acceleration G1.
When the pressure decreases below , the process proceeds from step S15 to step s17, and a depressurization flag is set.

When the pulse pressure reduction flag is set, the process proceeds to step s18, where it is determined whether the switching signal at the time of output of the pressure reduction switching signal is a pressure increase switching signal. If it is a pressure increase switching signal, the process proceeds to step s19, where a count value KT corresponding to the time for compensating for the operation delay of the switching valve 6a is added to a preset count [Ml] as the output time of the pressure reduction switching signal. , the output time of the pressure reduction switching signal is corrected. If the switching signal at the time of outputting the pressure reduction switching signal is not the pressure increase switching signal in step s18, the output time is not corrected.If the output time is corrected in step s19, the process advances to step S7 and pulse reduction is output. Ru.

As described above, when the switching signal immediately before outputting the pressure reduction switching signal is the pressure increase switching signal, the time required to compensate for the operation delay of the switching valve 6a is added to the pressure reduction time, thereby eliminating the need for wheels due to insufficient pressure reduction. It is possible to prevent such a decline from occurring.

In the above embodiment, the case where the switching signal immediately before the output of the pressure reduction switching signal is the pressure increase switching signal has been explained, but the switching valve also operates when the switching signal immediately before the output of the pressure increase switching signal is the pressure reduction switching signal. Since a delay occurs, the output time of the pressure increase switching signal may be corrected.

Effects of the Invention As described above, according to the present invention, it is possible to prevent insufficient operation due to a delay in the operation of the hydraulic pressure switching means, and it is possible to improve the accuracy of controlling the hydraulic pressure supplied to the hydraulic braking means. Further, since the hydraulic pressure supplied to the hydraulic braking means can be accurately controlled, anti-skid control can be performed smoothly.

[Brief Description of the Drawings] Fig. 1 is an electrical block diagram of an anti-skid control device which is an embodiment of the present invention, and Fig. 2 illustrates a hydraulic path of an anti-skid control device which is an embodiment of the present invention. 3 is a diagram for explaining the operation of the switching valve used in this embodiment, FIG. 4 is a functional block diagram for explaining the correction calculation of the pressure reduction switching signal, and FIG. 5 is a diagram for explaining the operation of the switching valve used in this embodiment. FIG. 6 is a flow chart for explaining the anti-skid control of this embodiment. 1...Anti-skid control circuit, 2a-2d...Wheel speed sensor, 3a-3d...Waveform shaping circuit, 4a4b
...Processing circuit, 5a-5d...Solenoid drive circuit, 6a-6d...Switching valve, 9...Solenoid relay 11...Battery, 12...Hydraulic pressure source, 13...Motor relay 15... Motor relay drive circuit, 19.
...Power supply circuit, 21...Master cylinder, 22a~
22d...Wheel cylinder agent Patent attorney Keiichi Saikyo Figure 3 Wheel cylinder No. 4

Claims (1)

[Claims] The hydraulic pressure supplied to the hydraulic braking means provided for each wheel of the automobile is controlled by a switching signal to the hydraulic switching means, and the frictional braking force between each wheel and the road surface is increased. An anti-skid control device that controls hydraulic pressure to maintain a slip ratio, wherein the output time of the switching signal is corrected depending on the output state of the switching signal when the switching signal is sent to the hydraulic pressure switching means. Anti-skid control device.