JPH08290762A - Anti-skid control device - Google Patents

Abstract

PURPOSE: To provide an anti-skid control device which gives a braking force through maximum utilization of the friction between a tire and road surface by controlling the wheel slip ratio so that the road surface μ becomes near the maximum at an early stage of brake application and reduce the amount of liquid consumption with the controlling operations by holding the liquid pressure in a wheel cylinder when the applicable wheel attains near the lock pressure. CONSTITUTION: An electronic control device 10 controls normally open solenoid valves 21-24, normally closed solenoid valves 31-34, and an electric motor 5 on the basis of the sensing signals given by a stop switch 9 and wheel speed sensors 8a-8d and increases, decreases, or retain the brake pressure applied to wheel cylinders 7a-7d. For stepped boosting of the brake pressure, a plurality of output patterns are set in compliance with the size of the oil pressure gradient applied to the wheels FR-RL. When the output pattern having a low gradient is selected, judgement that the wheels FR-RL have reached near the lock pressure is passed when the calculated value of slip ratio exceeds the specified threshold. Thereafter the oil pressures applied to the wheels FR-RL are held in a constant condition for a certain period of time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention prevents wheel lock by selecting a control mode based on the slip ratio and the wheel acceleration, which indicates how much the wheel is slipping relative to the speed of the vehicle body when the vehicle brake is operated. The present invention relates to an anti-skid control device for performing and controlling brake pressure.

[0002]

2. Description of the Related Art Conventionally, when wheels are locked during sudden braking of a vehicle, the vehicle is swayed to a high friction coefficient (high μ) side of the road surface depending on road surface conditions, so that directional stability of the vehicle is impaired.
Therefore, when the brake fluid pressure applied to the wheel cylinders during the sudden braking becomes equal to or higher than the lock pressure, the hydraulic pressure applied to the wheels is controlled to prevent the wheels from being locked.

8. Specifically, an anti-skid for controlling the braking force by reducing, increasing, or holding the hydraulic pressure applied to the wheel cylinder according to the wheel speed and the wheel acceleration so that the wheel does not lock during sudden braking. A control device is known, and as shown in Japanese Patent Laid-Open No. 62-205849, this control device has a threshold value for each of the combinations of the slip ratio and the wheel acceleration and changes the control pattern according to a control map. A method of performing brake control is disclosed. In the method of changing the control pattern of the anti-skid by this control map, the hydraulic pressure is increased or decreased too much because the pressure increase, pressure decrease, and holding modes are switched depending on the threshold value of the control map. Also, when the slip ratio or the wheel acceleration fluctuates near the threshold for switching the control map, the control pattern is frequently changed, the solenoid valve is operated, and the amount of brake fluid used for braking is increased. Loud valve operating noise.

Further, on a uniform road surface μ having a uniform road surface friction coefficient (which is shown below with the road surface μ), a slip curve (μ-S curve) consisting of a slip ratio and the road surface μ shows that the wheel speed changes when the tire torque fluctuates. Since it fluctuates, there is a problem that the wheel speed fluctuates greatly in the vicinity of the lock pressure, which is near the maximum value of the road surface μ.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to prevent excessive increase or decrease in hydraulic pressure due to control map switching when switching control modes by a control map based on wheel slip ratio and wheel acceleration. In addition to preventing this, if the wheel slip ratio or wheel acceleration fluctuates near the threshold for switching the control pattern, the control pattern is frequently changed and the number of solenoid valve actuations increases. It is intended to reduce the noise of the solenoid valve operating due to the operation of the various solenoid valves and to suppress the consumption of the brake fluid.

[0006]

In order to solve the above problems, the antiskid control device of the present invention uses a wheel speed detecting means (8a, 8b, 8c, 8c) for detecting the wheel speed of a wheel.
8d), a wheel speed calculating means (S12) for calculating a wheel speed based on the output of the wheel speed detecting means, a wheel acceleration calculating means (S13) for calculating a wheel acceleration based on a calculated value of the wheel speed calculating means, and the wheel. Slip rate calculating means (S2A) for calculating the slip rate of the wheel based on the calculated value of the speed calculating means, and the hydraulic pressure applied to the wheel based on the slip rate calculated by the slip ratio calculating means and the wheel acceleration calculated by the wheel acceleration calculating means. In an anti-skid control device provided with control mode selection means (S20) including at least a step pressure increase consisting of a combination of pressure increase and holding, and a step pressure decrease consisting of a combination of pressure decrease and holding,
For the step pressure increase, a plurality of output patterns are provided according to the magnitude of the hydraulic pressure gradient applied to the wheel, and when a step pressure increase pattern having a low hydraulic pressure gradient is selected from among the plurality of patterns, calculation is performed by the slip ratio calculation means. When the calculated slip ratio value is equal to or greater than a predetermined threshold value, a lock pressure determining means (S2B) for determining that the wheel has reached the vicinity of the lock pressure is provided, and the lock pressure determining means determines the lock pressure. In this case, the hydraulic pressure applied to the wheels is forcibly maintained in a constant state for a fixed time.

[0007]

According to the present invention, in the slip curve consisting of the slip ratio and the road surface μ, since the wheel speed fluctuates when the tire torque fluctuates, the threshold value for the lock pressure determination is set at a place slightly lower than the maximum value of the road surface μ. The hydraulic pressure can be maintained near the lock pressure by controlling the hydraulic pressure so that it does not exceed the maximum value of the road surface μ when it exceeds this threshold value. Can be prevented.

By thus maintaining the hydraulic pressure applied to the wheel cylinder for a certain period of time, the number of times the solenoid valve is operated can be reduced, and the operating noise associated with the operation of the solenoid valve can be reduced.

Further, since the braking force is maintained, the brake is applied with a constant deceleration feeling, and the feeling during brake operation is improved.

By suppressing the amount of brake fluid consumed during brake operation, the amount of consumed fluid can be reduced, and the electric motor for driving the pump for pumping the brake fluid from the reservoir can be eliminated. By eliminating the motor, it is also possible to have an inexpensive system configuration.

[0011]

Embodiments of the present invention will be described below. FIG. 1 shows the configuration of an anti-skid control device according to an embodiment of the present invention. The master cylinder 1 which is a hydraulic pressure generator driven by the brake pedal 11 and wheels (right front wheel FR,
The left front wheel FL, the right rear wheel RR, and the left rear wheel RL) are provided with solenoid valves 21, 22, 23, 24, and 3 in hydraulic paths connected to wheel cylinders 7a, 7b, 7c, 7d provided respectively.
1, 32, 33, 34, pumps 4a, 4b, an electric motor 5 for driving the pumps, and reservoirs 6a, 6b are interposed. The outputs of the stop switch 9 and the wheel speed sensors 8a, 8b, 8c, 8d that detect the rotation of the wheels are input to an input port of an electronic control unit 10 that is a hydraulic pressure control device that controls hydraulic pressure. This electronic control unit 10
Determines the state of the wheels and whether or not the vehicle is being braked by the input signal, and the two-port normally open solenoid valves 21, 2
2, 23, 24 and normally closed solenoid valves 31, 32, 33, 3
4 and the electric motor 5 are controlled.

When the hydraulic pressure applied to the wheels is reduced in this system configuration, the solenoid valves 21 to 24 are turned on so that the hydraulic pressure does not fluctuate in the pedals and the hydraulic path between the master cylinder and the wheel cylinders is cut off. At the same time, the solenoid valves 31 to 34 are turned on to release the hydraulic pressure applied to the wheel cylinders to the reservoirs 6a to 6b, and the pumps 4a to 4b are driven by the electric motor 5 to return the hydraulic pressure to the master cylinder side. To maintain this hydraulic pressure, the electromagnetic valves 31 to 34 are turned off from the above-described state to cut off the flow path of the brake fluid and keep the hydraulic pressure constant.

On the other hand, when increasing the pressure, the solenoid valves 21 to 24 and 31 to 34 are turned off to turn the brake pedal 1 on.
Step 1 is pressed to apply the hydraulic pressure generated by the master cylinder 1 to the wheel cylinders 7a and 7b via the solenoid valves 21 to 24 to operate the brake. During the anti-skid control, the electric motor 5 is driven to operate the pump 4. In this way, the normally open solenoid valves 21 to 24 and the normally closed solenoid valves 31 to 34 are controlled to be turned on and off to increase, reduce, or maintain the brake pressure applied to the wheel cylinders 7a to 7d. You can
Also, by adjusting the time interval of the on / off of the solenoid valve, it is possible to create a step pressure increase consisting of pressure increase and hold. In this step pressure increase, the pressure increase time is short and the pressure increase gradient is small. There are pulse pressure increase and dither pressure increase with long pressure increase time and large pressure increase gradient. Further, it is possible to set a step pressure reduction (shown as pulse pressure reduction) consisting of pressure reduction and holding so that the gradient of the hydraulic pressure applied to the wheel cylinders is controlled to be gradually increased or gradually decreased.

Wheel speed sensor 8 for detecting wheel rotation
Reference numerals a, 8b, 8c and 8d denote electromagnetic induction type sensors each including a toothed rotor that rotates with the rotation of each wheel and a pickup that is provided so as to face the tooth portion of the rotor.
A device that outputs a voltage having a frequency proportional to the rotation speed of each wheel is used and is input to the electronic control unit 10.

Next, FIG. 2 will be described. The electronic control unit 10 includes a CPU 1 connected to each other via a bus.
4, a ROM 15, a RAM 16, a timer 17, an input port 22 and an output port 23, and a microcomputer 20. The wheel speed sensors 8a, 8b, 8
The signals of c, 8d and the stop switch 9 are amplified by the amplifier circuit 18
Each of the input ports 22 is input to the CPU 14 via a, 18b, 18c, 18d and 18e. Further, from the output port 23 to the solenoid valve drive circuits 19b, 19c, 19d, 19e, 19f, 19g, 1
9h, 19i through the respective solenoid valves 21, 22, 2
A control signal is output to 3, 24, 31, 32, 33, and 34, and the electric motor 5 is driven via the electric motor drive circuit 19a. In the microcomputer 20, the ROM 15 stores a control program for anti-skid control. When the ignition switch (not shown) of the vehicle is turned on and the microcomputer 20 is supplied with power, the ROM 15 is stored in the ROM 15. The program starts running. In addition, RAM16
Is for temporarily storing variable data necessary for program execution.

In the embodiment configured as described above, when an ignition switch (not shown) of the vehicle is turned on and power is supplied to the microcomputer 20, a program corresponding to the flowchart shown in FIG. 3 is executed. To be executed.

Here, FIG. 3 will be described. When power is first supplied to the microcomputer 20, the microcomputer 20 is initialized in step S10, and various calculation values, various wheel speeds Vw, and RAM values such as wheel acceleration DVw are cleared and initialized. To be done. In step S11, the state of the input port 22 of the microcomputer 20, which is the input of the stop switch, is read. In step S12, the wheel speed sensors 8a, 8b, 8
The wheel speed Vw of each wheel is calculated from the output signals of c and 8d, and the process proceeds to step S13 to calculate the wheel acceleration DVw from the calculated wheel speed value. Next, in step S14, an estimated vehicle speed calculation for estimating the vehicle speed, which is the reference for starting the anti-skid control, from the calculated wheel speed value is performed. In the next step S15, road surface determination is performed, and the road surface state during traveling is calculated. In step S16, it is determined whether or not anti-skid control is started, and in step S17, it is determined whether or not anti-skid control is started. When the anti-skid control is started, step S18
Is executed, and if control is not started, step S
Move to 19. In step S18, the control mode of the anti-skid control is selected, and control output of any one of the pressure reducing, pressure increasing, and holding states is performed. The details will be described with reference to FIG. In the next step S19, control for driving the electric motor is performed, and the process returns to step S11 to repeat the process.

Next, FIG. 4 will be described. In FIG. 4, the antiskid control mode is selected and the control output of the selected mode is performed. In step S20, predetermined threshold values V _SN , V _{SH of the} wheel speed (in the present embodiment, threshold values of the wheel speed having slip ratios of 9% and 13% with respect to the estimated vehicle speed V _S0 , respectively). And wheel acceleration G1, G2 (-2
G, 2G) is set and a mode in which patterns of pressure reduction, pressure increase, and holding are respectively combined from the control threshold map shown in FIG. 6 is created. In this embodiment, the control mode is selected from the pressure reduction mode, the pulse pressure reduction mode including pressure reduction and holding, and the pulse pressure increase mode including pressure increasing and holding. Further, in the pulse pressure increasing mode, the pressure increasing time control output having a high pressure increasing gradient, the dither pressure increasing control output having a pressure increasing gradient lower than the pressure increasing time control output, and the pressure increasing gradient higher than the dither pressure increasing control output are included. Includes a low pulse boost output of. After the control mode is selected in step S20, it is determined in step S21 whether the pressure reduction mode is set. In the pressure reduction mode, the pressure reduction control output is performed in step S22, and when not in the pressure reduction mode, the process proceeds to step S23. In step S23, it is determined whether or not the pulse pressure reduction mode is in effect. If the pulse pressure reduction mode is selected, pulse pressure reduction output is performed in step S24. If not, the process proceeds to step S25. In step S25, the control pattern in the pulse pressure increasing mode is selected. In the present embodiment, the control pattern is selected such that the previous pressure reduction mode is the pressure increase mode, the pressure increase time control output is output for the first time, and the dither pressure increase control output is output when a step is determined by road surface determination. One of the three control patterns is selected so as to perform pressure output. In step S26, it is determined whether or not the control pattern in the pulse pressure increasing mode is the pressure increasing time control output,
In the case of the pressure increase time control output, the pressure increase time control is performed in step S27, and when it is not the pressure increase time control output, the process proceeds to step S28. In step S28, it is determined whether or not it is the dither pressure increase control output. If it is the dither pressure increase control output, the dither pressure increase control is performed in step S29. If it is not the dither pressure increase output, the process proceeds to step S2A. Step S2A
Then, the slip ratio is calculated, and the lock pressure determination control is executed in the next step S2B.

[0019]

[Table 1]

Next, the lock pressure determination control of FIG. 5 will be described. In step S30, it is determined whether the lock pressure determination control has been performed with the previous output pattern. If the lock pressure determination control was previously performed, the process proceeds to step S33, and if the lock pressure determination control is not performed, steps S31 and S3.
In step 2, both the lock pressure determination control flag and the determination time counter are cleared, and step S33 is executed. Step S33
Then, the lock pressure determination time is counted. Next, in step S34, if the lock pressure determination time, which is the time from when the lock pressure determination control is started, is within a predetermined time, step S35 is executed. If the predetermined time is exceeded, step S3A is performed. Step S3
In A and S3B, the lock pressure determination control flag and the determination time counter are cleared, and the process proceeds to step S38. Step S
At 35, it is determined whether or not the slip ratio exceeds a predetermined slip ratio (slip ratio 5% in this embodiment) set lower than the maximum value of the road surface μ. If the slip ratio exceeds the predetermined slip ratio, at step S36. Clear the lock pressure determination time counter. If it does not exceed the predetermined slip ratio, the process proceeds to step S37. In step S37, the lock pressure determination control flag is set, and the lock pressure determination control is started by this flag. In step S38, it is determined whether or not the lock pressure determination control flag turned on in step S37 is set. If the lock pressure determination control flag is set, the holding output is performed in step S39. If the lock pressure determination control flag is not set, the flow of the program for performing the pulse pressure increase control in step S3C is followed.

[0021]

As described above, according to the present invention, since the slip ratio of the wheel is controlled so that the road surface μ is close to the maximum value at the initial stage of braking, the friction between the tire and the road surface is maximized. It becomes possible to add a braking force. Also,
By holding the hydraulic pressure of the wheel cylinder when the wheels reach the vicinity of the lock pressure, it is possible to effectively utilize the braking force between the tire and the road surface and reduce the amount of liquid consumed by the control.

Further, when the wheel reaches the lock pressure, the hydraulic pressure applied to the wheel is maintained and the recovery of the wheel speed is observed. Therefore, the number of times the solenoid valve is operated can be reduced, and the operation noise associated with the operation of the solenoid valve is reduced. Since the brake operates with a certain deceleration feeling, the feeling during brake operation is improved.

Furthermore, by suppressing the amount of brake fluid consumed on the wheels during brake operation, the amount of brake fluid returned to the master cylinder can be reduced, and a pump for pumping the brake fluid and a pump can be provided. Since the electric motor to be driven can be eliminated, the pump and the electric motor can be eliminated so that an inexpensive system configuration can be obtained.

[Brief description of drawings]

FIG. 1 is a system configuration diagram of an anti-skid control device according to an embodiment of the present invention.

FIG. 2 is an internal configuration diagram of an electronic control unit according to an embodiment of the present invention.

FIG. 3 is a flowchart showing the overall processing of an anti-skid control program in an embodiment of the present invention.

FIG. 4 is a flowchart showing selection and output of the anti-skid control mode shown in FIG. 3 in the embodiment of the present invention.

FIG. 5 is a flowchart showing lock pressure determination control of the anti-skid control shown in FIG. 4 in the embodiment of the present invention.

[Explanation of symbols]

 1: master cylinder 4a, 4b: pump 5: electric motor 6a, 6b: reservoir 7a, 7b, 7c, 7d: wheel cylinder 8a, 8b, 8c, 8d: wheel speed sensor 9: stop switch 10: electronic control unit 11: Brake pedals 21, 22, 23, 24: Normally open solenoid valves 31, 32, 33, 34: Normally closed solenoid valves

Claims (1)

[Claims] 1. A wheel speed detecting means for detecting a wheel speed of a wheel, a wheel speed calculating means for calculating a wheel speed based on an output of the wheel speed detecting means, and a wheel acceleration for calculating a calculated value of the wheel speed calculating means. Wheel acceleration calculation means, slip ratio calculation means for calculating the slip ratio of the wheel based on the calculation value of the wheel speed calculation means, slip ratio calculated by the slip ratio calculation means, and wheel acceleration calculated by the wheel acceleration calculation means In the anti-skid control device provided with the control mode selecting means for controlling the hydraulic pressure applied to the wheels on the basis of at least a step pressure increase consisting of a combination of pressure increase and holding, and a step pressure decrease consisting of a combination of pressure decrease and holding, The pressure is provided with a plurality of output patterns set according to the magnitude of the hydraulic pressure gradient applied to the wheels, If a step pressure increase pattern having a low oil pressure gradient is selected, the wheels are determined to have reached the lock pressure vicinity when the value calculated by the slip ratio calculation means is equal to or greater than a predetermined threshold value. An anti-skid control characterized by comprising a lock pressure determining means, and when the lock pressure determining means determines the lock pressure, the hydraulic pressure applied to the wheels is forcibly held in a constant state for a fixed time. apparatus.