JP2732873B2 - Anti-skid control device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anti-skid control device for preventing a wheel from being locked during a brake operation.

Conventional technology When the brake pedal is depressed strongly, it is provided on each wheel,
In some cases, the braking oil pressure supplied to the hydraulic braking means for braking the rotation of the wheel increases, and the wheel may fall into a locked state (a state in which the wheel speed becomes substantially zero). In this locked state, the braking ability of the wheels on the road surface is reduced, and the steering characteristics of the steering wheel are lost. Therefore, the anti-skid control device hydraulically controls each wheel so that the friction braking force of the wheel against the road surface has the highest slip ratio. This makes it possible to shorten the braking distance while maintaining the steering ability of the steering wheel high during the brake operation. Here, the slip ratio S is defined by the following equation, where VS is the running speed of the vehicle (hereinafter referred to as "vehicle speed") and VW is the rotational speed of the wheels (hereinafter referred to as "wheel speed"). You.

When the brake pedal is depressed strongly, the braking oil pressure supplied to the hydraulic braking means increases, and the wheel speed decreases accordingly.
If it further decreases, it will be in a locked state. The anti-skid control device controls the oil pressure supplied to the hydraulic braking means to reduce the pressure in order to prevent the wheels from being locked, and adjusts the wheel speed to a slip ratio (10% to 10%) at which the highest friction braking force is exerted.
20%).

FIG. 8 is a time chart for explaining a control state in the above-described conventional anti-skid control device. In FIG. 8, the brake pedal is strongly depressed,
As the vehicle speed indicated by line l3 decreases,
At time t11 when the wheel speed indicated by l4 decreases and the wheel acceleration becomes equal to or less than a predetermined value, a pressure reduction control signal is output. As a result, the braking oil pressure decreases during the period when the pressure reduction control signal is being output. The time at which the wheel speed goes in the recovery direction due to the output of the pressure reduction control signal and the wheel speed has sufficiently recovered
At t12, a pressure increase control signal for increasing the friction braking force of the wheel is output.

As the output timing of the pressure increase control signal, the pressure increase control signal may not be output when the wheel speed completely recovers, but may be output when the wheel acceleration reaches a predetermined acceleration.

As described above, in the conventional anti-skid control device, the output timing of the pressure increase control signal after the output of the pressure reduction control signal for preventing the wheel from locking is determined when the wheel speed is completely recovered. There is a case where it is output, and a case where it is output when the wheel acceleration reaches a predetermined acceleration. In the former case, since the pressure increase control signal is output after the wheel speed is completely recovered, the braking timing is delayed due to a time delay from the output of the pressure increase control signal to the generation of the friction braking force, It has the disadvantage that the braking distance is long.
If the pressure increase control signal is output at the time when the latter wheel acceleration reaches a predetermined value, the slip rate is not sufficiently recovered and the friction coefficient μ is not sufficiently high, so that the pressure is increased too much. Sometimes, there is a disadvantage that the turning performance of the vehicle is reduced.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described drawbacks.
An object of the present invention is to provide an anti-skid control device which outputs the signals in different times.

Means for Solving the Problems According to the present invention, in response to a wheel speed signal from a wheel speed sensor provided on each wheel of an automobile, the slip ratio at which the friction coefficient between the wheel and the road surface is maximized is set. In an anti-skid control device for controlling the wheel speed by hydraulic braking means provided on each wheel, after performing a pressure reduction control for reducing the hydraulic pressure supplied to the hydraulic braking means, the wheel acceleration becomes a first predetermined acceleration. A first pressure increasing means for performing pressure increasing control for a predetermined time during the recovery of the wheel speed exceeding the predetermined value, and a wheel acceleration falling below the second predetermined acceleration after the wheel acceleration exceeds the first predetermined acceleration. An anti-skid control device characterized by including a second pressure increasing means for performing a pressure increasing control for a predetermined time immediately after the wheel speed recovery.

In the present invention, the anti-skid control device obtains wheel speeds based on wheel speed signals output from wheel speed sensors provided on each wheel of the automobile. Each wheel of the vehicle is also provided with a hydraulic braking means for hydraulically controlling the rotation of the wheel. The anti-skid control device controls the wheel speed by the hydraulic braking means so that the slip rate at which the friction coefficient between the wheel and the road surface becomes the largest is obtained. After the hydraulic pressure supplied to the hydraulic braking means is reduced, the first pressure increasing means increases the hydraulic pressure supplied to the hydraulic braking means for a predetermined time during the recovery of the wheel speed when the wheel acceleration exceeds the first predetermined acceleration. Pressure increase control is performed. Then, after this pressure increase control is performed, the second pressure increase means immediately after the wheel acceleration exceeds the first predetermined acceleration, and immediately after the wheel speed recovers when the wheel acceleration falls below the second predetermined acceleration, Pressure increase control for increasing the oil pressure supplied to the oil pressure braking means for a predetermined time is performed.

FIG. 1 is a block diagram for explaining a hydraulic path of an anti-skid control device according to an embodiment of the present invention.
When the brake pedal 30 is depressed, a braking oil pressure is generated in the master cylinder 31, and the braking oil pressure is supplied to the three-position electromagnetic control valves 13a to 13d via the pipes p1 to p4, and further, the pipe p5
Are supplied to the wheel cylinders 33a to 33d through .about.p8.
As a result, the wheels 34a to 34d start braking, and the speed of the vehicle decreases.

The rotation speeds of the wheels 34a to 34d are detected by wheel speed sensors 1a to 1d.

When the anti-skid control circuit 4 determines that the anti-skid control start condition is satisfied, the anti-skid control circuit 4 applies the braking hydraulic pressure generated by the motor 17 to the master cylinder via the pipe p9.
At the same time, the three-position electromagnetic control valves 32a to 32d are controlled to increase, decrease, or hold the pressure, thereby controlling the brake hydraulic pressure of the wheel cylinders 33a to 33d. By this control, the slip ratio S of the wheels 34a to 34d is controlled so that the friction braking force is the highest value on the road surface.

FIG. 2 is a block diagram for explaining the electrical connection of the anti-skid control device according to one embodiment of the present invention.
Wheel speed sensors 1a to 1d provided for each wheel detect the rotation speed of the wheel, and the detection signal is sent to a waveform shaping circuit 5a to 5d.
Given to. The wheel speed sensors 1a to 1d are provided with a number of notches and projections at equal intervals in the circumferential direction of a detection plate made of a ferromagnetic material fixed to a wheel shaft, for example, and an electromagnetic pickup provided near the periphery of the detection plate. Alternatively, the sensor outputs a wheel speed signal having a frequency proportional to the wheel speed by an optical sensor.

The wheel speed signal is provided to the waveform shaping circuits 5a to 5d, and is shaped into a pulse signal, and then sent to the processing circuit 2.

The switch 7 is, for example, a brake switch for detecting whether or not the brake pedal 30 is depressed. The output of the switch 7 is converted to a suitable voltage in the anti-skid control circuit 4 by the level conversion circuit 8 and then processed. 2 is sent.

The power supply circuit 9 converts the voltage supplied from the battery 11 via the power supply switch 10 into a voltage used in the anti-skid control circuit 4.

The anti-skid control signal output from the processing circuit 2 is supplied to the solenoid drive circuits 12a to 12d, and after being amplified in power, sent to the three-position electromagnetic control valves 13a to 13d, where any one of pressure increase, pressure decrease, or holding is performed. State controlled.

When performing anti-skid control, the processing circuit 2 sets the three-position electromagnetic control valves 13a to 13d in a controllable state.
A signal for exciting the solenoid relay 15 is sent to the solenoid relay drive circuit 14. When the exciting current flows through the coil 15a of the solenoid relay 15, the contact 15b conducts, and the battery 11 is connected to the solenoid coils of the three-position current control valves 13a to 13d.
Is supplied.

The motor relay 16 is a motor for generating control hydraulic pressure.
When the motor relay drive signal amplified by the motor relay drive circuit 18 in the drive relay 17 excites the coil 16a, the contact 16b conducts and the motor 17 rotates.

The lamp 19 is turned on when the anti-skid control circuit 4 performs an abnormal operation. The alarm signal output from the processing circuit 2 is applied to the lamp 19 after the power is amplified by the lamp drive circuit 20.

FIG. 3 is a time chart for explaining the control according to the present invention. At a time t1 at which the wheel speed indicated by the line l2 starts to decrease along with the decrease of the vehicle speed of the line l1 and the wheel acceleration, which is a temporal change rate of the wheel speed, exceeds a predetermined deceleration (negative acceleration), the anti-skid control circuit Reference numeral 4 outputs a pressure reduction control signal for lowering the braking oil pressure to prevent the wheels from being locked. Decompression control signal is output during a period of time T _D until the recovery deceleration wheel acceleration is predetermined.

Brake hydraulic pressure is reduced, the start wheel speed recovery, at a first predetermined acceleration G wheel speed recovery during the time t2 exceeds _A the wheel acceleration is predetermined, first pressure boosting means in the processing circuit 2 pre-determined time During the period of T _I1 , a first pressure increase control signal is output. The output of the first pressure increase control signal increases the braking oil pressure, and suppresses a decrease in the frictional braking force of the wheel on the road surface. After the wheel acceleration reaches the maximum wheel acceleration G _max, the wheel acceleration is started lowering, upon reaching the time t3 immediately after the wheel speed recovery was One drops below a second predetermined acceleration G _B the predetermined second pressure increase The means outputs a second pressure increase control signal for a predetermined time T _I2 . By outputting the first and second pressure increase control signals, the wheel speed becomes smaller than the vehicle speed.
Braking is performed while maintaining the slip ratio that exhibits the highest braking force.

Next, the control according to the present invention will be described in more detail with reference to a flowchart. FIG. 4 is a schematic flow chart of the anti-skid control processing executed in the processing circuit 2, and FIGS. 5 to 7 are flow charts for executing the control according to the present invention. First, in FIG. 4, when the processing circuit 2 starts processing, in step g1, initialization processing such as clearing of a memory area and resetting of a flag are performed. When the initialization process is completed, the process proceeds to step g2, and the wheel speed of each wheel is calculated based on a wheel speed signal from a wheel speed sensor provided for each wheel. Then, the process proceeds to step g3, where the wheel acceleration is calculated from the time rate of change of the wheel speed. Step
In g4, a vehicle speed corresponding to the actual running speed of the vehicle is obtained. The vehicle speed is obtained by estimating the maximum wheel speed among the wheel speeds of the wheels as the vehicle speed.

When the wheel speed, the wheel acceleration, and the vehicle body speed are calculated by the processes in steps g2 to g4, the process proceeds to step g5, and it is determined whether or not the anti-skid control is executed. If the anti-skid control is not executed, go to step g6
The brake hydraulic pressure generated by depressing the brake pedal 30 is supplied to the wheel cylinders 33a to 33d as they are. During the anti-skid control, the process proceeds to step g7, and the anti-skid control process described later is executed. The above processing is performed at predetermined time intervals.

The embodiment for executing the flowchart shown in FIG.
The maximum wheel acceleration after the output of the pressure increase control signal is detected, and the remaining time obtained by subtracting the output time of the first pressure increase control signal from the total pressure increase time obtained based on the maximum wheel acceleration is used as a second increase. Control is performed as the output time of the pressure control signal.

First, in step s1, it is determined whether or not the anti-skid control is currently being executed.
Since there is no need to judge the start of anti-skid control,
Proceed to step s4. If the anti-skid control is not performed in step s1, the process proceeds to step s2, and it is determined whether the start condition of the anti-skid control is satisfied. As a start condition of the anti-skid control, for example, when the wheel is locked or when the wheel speed becomes lower than the predetermined rotation speed and the wheel deceleration is larger than the predetermined deceleration, it is determined that the anti-skid control start condition is satisfied. I do. If the start condition of the anti-skid control is satisfied, the process proceeds to step s3, and a pressure reducing flag for causing the wheel cylinder to perform the pressure reducing control is set in a predetermined memory area of the processing circuit 4.

If it is determined in step s2 that the start condition of the anti-skid control is not satisfied, the process proceeds to step s5, in which the brake hydraulic pressure generated in the master cylinder 31 by the depression of the brake pedal is transmitted to the wheel cylinders 33a to 33d. To do so, the three-position electromagnetic control valves 13a to 13d are set to the pressure increasing position.

In step s4, the braking condition of the anti-skid control is determined. For example, when the foot is released from the brake pedal, or when the vehicle speed becomes 5 km / H or less, the anti-skid control is released. If the condition for terminating the anti-skid control is not satisfied in step s4, the process proceeds to step s6, in which a flag for controlling the increase or decrease in the hydraulic pressure of the wheel cylinders 33a to 33d is determined.

When the anti-skid control starts, since the pressure reduction flag is set in step s3, the process proceeds from step s7 to step s8, and the brake hydraulic pressure of the wheel cylinders 33a to 33d is reduced. In step s7, when the condition for terminating the pressure reduction control, that is, when the wheel speed starts to show signs of recovery, the process proceeds to step s9, and a holding flag for maintaining the oil pressure of the wheel cylinders 33a to 33d constant is set. When the setting of the holding flag is completed, the process proceeds to step s20, and the holding ending condition is determined.

Holding termination condition beyond the acceleration G _B the predetermined shown in Figure 3 the wheel acceleration satisfy by then below its acceleration G _B. If the holding end condition is not satisfied, the process proceeds to step s21, and the maximum wheel acceleration from the start of the holding control to the present is stored. In step s22,
When the wheel acceleration exceeds a first predetermined acceleration G _A the predetermined is determined, the process proceeds from step s23 and step s24 to step s11, the first pressure-increasing control signal is output.
When the first pressure-increasing control signal is output, the count of the pressure increasing time T _I1 is started at step s24. And
In step s22, the wheel acceleration becomes the first predetermined acceleration G _A
If the following become or the pressure increasing time T _I1 has passed a predetermined time, the process proceeds to step s10, is switched to the pressure increasing control color retention control.

Thereafter, it is determined in step s20 whether or not the above-described holding end condition is satisfied.
Proceeding to 25, a pressure increase flag for pressure increase control is set. In step s26, Zenzo pressure boosting period T _I based on the maximum wheel acceleration G _max determined at step s21 is determined. When the total pressure increase time T _I is obtained, the remaining pressure increase time T _I2 is calculated in step s27 according to the second equation.

T _I2 = T _I −T _I1 (2) When the pressure increase time T _I2 is calculated, the process proceeds from step s12 to step s13, and the second pressure increase control signal is output. In step s12, the pressure increasing time T _I2 has elapsed, step s1
Proceeding to 4, the pulse pressure increase flag for the pulse pressure increase for gradually increasing the brake oil pressure is set.

When the pulse pressure increase control is started, the process proceeds from step s15 to step s16, where a pressure increase pulse having a predetermined time width is output, and the brake oil pressure is gradually increased. And
In step s15, the pulse pressure increase ending condition, for example, when the wheel speed becomes lower than the predetermined rotation speed, and when the wheel deceleration becomes larger than the predetermined deceleration, the pulse pressure increase control is ended and the process proceeds to step s17. In step s17, a pressure reduction flag for performing pressure reduction control is set, and the flow advances to step s8, where a pressure reduction control signal is output.

Next, another embodiment of the present invention will be described. Since another embodiment described below is realized by changing only the step group F in the flow chart shown in FIG. 5, FIG. 6 shows only the step group F in the flow chart of FIG. Since the processing is the same, the description is omitted.

When the holding flag is set in step s9 of FIG. 5, the process proceeds to step s30 of the flowchart shown in FIG. In the process of step s30, the same holding end condition as that of step s20 is determined. If the holding end condition is not satisfied, the process proceeds to step s31, and the maximum wheel acceleration after the start of the holding control is stored. Then, the process proceeds when the wheel acceleration in step s32 exceeds a first predetermined acceleration G _A stipulated in advance from step s33 to step s11, the output pressure increase control signal, pressure control is performed first increase. Then, if the wheel acceleration is equal to or less than the first predetermined acceleration G _A, or the first
When the pressure increase control has passed for a predetermined time, the process proceeds to step s10, a holding control signal is output, and the first pressure increase control ends.

Thereafter, at step s30, it is determined to be satisfied holding end condition, the process proceeds to step s34, with pressure increase flag is excisional, in step s35, based on the maximum wheel acceleration G _max stored in step s31 A fixed pressure increase time is set. When the pressure increase time setting is completed, the process proceeds from step s12 to step s13, and the second
A pressure increase control signal is output. Then, when the pressure increase time set in step s35 has elapsed, it is determined in step s12 that the pressure increase control has ended.

As described above, in this embodiment, between the second pressure increase is set based on the maximum wheel acceleration G _max. Since the maximum wheel acceleration _Gmax is considered to indicate an insufficient amount of the braking oil pressure, the second wheel pressure increasing time is set based on the maximum wheel acceleration _Gmax , so that the maximum wheel acceleration Gmax can be adjusted according to the insufficient braking oil pressure. The pressure increase time can be set.

Next, still another embodiment of the present invention will be described.
As in the case described above, the embodiment described below uses the step group F
Will be described, and other processes will be omitted. In the above embodiment, between the second pressure increase based on the maximum wheel acceleration G _max is set, in this embodiment first
The total pressure increasing time is determined based on the pressure reducing time of the pressure reducing control output immediately before the pressure increasing control.

Step s40 is a process for measuring the decompression time T _D. When the pressure reduction control ends, the process proceeds to step s41, and the same holding end condition as in the above-described embodiment is determined. If the holding end condition is not satisfied, the process proceeds to step s42. Step s
42 to step s44 are the above-described steps s22 to s24
This is exactly the same processing as.

If it is determined in step s41 that the holding end condition has been satisfied, the process proceeds to step s45, in which a hydraulic pressure flag for pressure increase control is set. When excisional intensification flag is completed, the process proceeds to step s46, the total pressure increasing time T _I is determined based on the timed decompression time T _D in step s40. The second pressure increase between T _I2 from total pressure increasing time T _I minus first pressure increasing time T _I1 in step s47 is calculated on the basis of the third expression.

T _I2 = T _I −T _I1 (3) When this second pressure increase time T _I2 is calculated, the process proceeds from step s12 to step s13, and the second pressure increase control signal is output.

In this embodiment, since the pressure increase control time is determined based on the pressure decrease control time, the optimum pressure increase time can be set even when the friction coefficient of the road surface changes.

Although the above embodiment has been described assuming that the anti-skid control processing is performed by one processing circuit 2 shown in FIG. 2, the present invention is not limited to this. Two processing circuits, for example, the right front wheel and the left The rear wheel may be configured to perform anti-skid control calculation by one processing circuit, and the left front wheel and the right rear wheel may be configured to perform anti-skid control calculation by another processing circuit. The same processing as in the case of one processing circuit is performed. In this case, in calculating the wheel speed, the wheel acceleration, and the vehicle speed, which are the basis of the anti-skid control calculation, the wheel speed and the like are transferred between the respective processing circuits.

Effects of the Invention As described above, according to the present invention, in the pressure increase control performed after the pressure decrease control, the pressure increase control is output in two parts, and the first pressure increase is performed during the recovery of the wheel speed. Since the braking oil pressure can be increased to some extent, the stopping distance can be reduced without lowering the turning characteristics of the vehicle.

[Brief description of the drawings]

FIG. 1 is a block diagram for explaining a hydraulic path of an anti-skid control device according to one embodiment of the present invention, and FIG. 2 is a block diagram for explaining electric connection of the anti-skid control device according to one embodiment of the present invention. FIGS. 3 and 4 are timing charts for explaining the control according to the present invention, FIG. 4 is a schematic flow chart of the anti-skid control processing executed in the processing circuit 2, and FIGS. 5 to 7 are the control according to the present invention. FIG. 8 is a timing chart for explaining the conventional anti-skid control. 1a to 1d wheel speed sensor, 2 processing circuit, 4 anti-skid control circuit, 13a to 13d three-position solenoid control valve

 ──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-57-158153 (JP, A) JP-A-49-44195 (JP, A) JP-A-56-116540 (JP, A) JP-A-1- 197160 (JP, A) Japanese Utility Model Showa 57-83061 (JP, U)

Claims (1)

(57) [Claims] 1. A method according to claim 1, further comprising the step of: responding to a wheel speed signal from a wheel speed sensor provided on each wheel of the vehicle, providing a slip ratio at which the coefficient of friction between the wheel and the road surface is maximized. In the anti-skid control device for controlling the wheel speed by the hydraulic braking means, after the pressure reduction control for reducing the hydraulic pressure supplied to the hydraulic braking means is performed, the wheel speed is being recovered after the wheel acceleration exceeds the first predetermined acceleration. A first pressure increasing means for performing pressure increasing control for a predetermined time, and after the wheel acceleration exceeds the first predetermined acceleration, immediately after the wheel speed recovers when the wheel acceleration falls below the second predetermined acceleration, An anti-skid control device comprising: a second pressure increasing means for performing pressure increasing control for a predetermined time.