JPH08310375A - Anti-skid controller - Google Patents

Abstract

(57) [Abstract] [Purpose] On a low μ road surface, prevent the early operation of the wheels due to the four wheels falling, and improve the accuracy of the estimated vehicle speed. [Structure] Wheel cylinders (51, 52, 53, 5)
4), hydraulic pressure generating means (2), hydraulic pressure switching means (ACT),
Whether the road surface friction coefficient is a low friction coefficient in the hydraulic pressure control device including the wheel speed detection means (41, 42, 43, 44), the estimated vehicle body speed calculation means (AS), and the hydraulic pressure control means (BC). A road surface friction coefficient determining means (JM) for determining whether the traveling road surface before control is a road surface having a low friction coefficient is used to reduce or maintain the brake pressure of any one of the rear wheels. An anti-skid control device for a vehicle, characterized in that an estimated vehicle body speed is obtained based on wheel speeds.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anti-skid control device for controlling a braking force on each wheel to prevent locking, and more particularly to producing an estimated vehicle body speed which is a reference for anti-skid control.

[0002]

2. Description of the Related Art Conventionally, an anti-skid control device has been known as a device for preventing wheel lock during braking of a vehicle. This control device controls each wheel depending on how much the vehicle wheel speed decreases with respect to the vehicle speed. Wheel lock is prevented by increasing, reducing, and holding the hydraulic pressure. Here, the vehicle speed that is the reference speed of the anti-skid control must be estimated from the wheel speed so that it is as close as possible to the actual vehicle speed, and the estimated vehicle speed estimated from the wheel speed is the same as the actual vehicle speed. If it is significantly different, accurate anti-skid control (ABS control) will not be possible. For example, in a two-wheel drive vehicle, when braking is applied, the front wheels first fall, and then the rear wheels fall. It is known that the estimated vehicle body speed, which is the standard for anti-skid control, is created with the non-driving wheels as the standard in order to make it as close as possible to the actual vehicle body speed. The anti-skid control is started when the vehicle wheel speed difference is generated or when the vehicle body acceleration of a certain threshold value or more occurs. on the other hand,
In a four-wheel-drive vehicle or a two-wheel-drive vehicle that performs ideal braking force distribution, when braking is applied, the front wheels first fall, and then the rear wheels fall, but
The difference in wheel speed between the front wheels and the rear wheels is smaller than that in the former case, which makes it difficult to enter control. As a result, the control start is delayed because the control start is not performed until the wheel speed drops considerably. For example, low coefficient of friction (hereinafter referred to as low μ)
When the brake pedal is slowly increased on the road surface (during slow braking), the estimated vehicle speed becomes lower than the actual vehicle speed before anti-skid control is entered, and proper slip control cannot be performed, resulting in an early locking tendency. However, it is difficult to create an accurate estimated vehicle speed, which becomes a problem. Regarding a method of creating an estimated vehicle speed when traveling on a low μ road surface, for example, as disclosed in Japanese Patent Publication No. 4-55905, the braking force is released and released for one of the rear wheels during anti-skid control. There is disclosed a method of detecting the wheel speed and performing anti-skid control as a reference vehicle speed. This is to prevent the estimated vehicle speed from dropping by releasing the braking force of either one of the rear wheels during the anti-skid control.

[0003]

When braking (slow braking) in which a braking force is gently applied on a low μ road surface, the wheel speed also gently decreases, so that a difference in wheel speed between the front wheels and the rear wheels hardly occurs. In addition, it is difficult to detect the locked state of the wheels because the vehicle body acceleration is not sufficient, and the locked state cannot be detected until the wheel speed decreases considerably, and the control start is delayed, and as a result, all the wheels tend to lock at the same time. Could be.

Therefore, an object of the present invention is to prevent all the wheels from locking at the same time due to the delay of the control start due to the fact that the locking tendency cannot be detected until the wheel speed is considerably reduced during traveling on a low μ road surface. It is an object of the present invention to prevent an inadvertent drop of the estimated vehicle speed, which serves as a reference for control, and to improve the accuracy of creating the estimated vehicle speed.

[0005]

In order to achieve the above object, a vehicle anti-skid control device of the present invention shown in FIG. 1 includes a right front wheel (FR), a left front wheel (FL), and a right rear wheel. Wheel cylinders (51, 52, 53, 5) attached to each of the wheels (RR) and the left rear wheel (RL) to apply braking force
4), hydraulic pressure generating means (2) for supplying brake pressure to each of the wheel cylinders, hydraulic pressure switching means (ACT) interposed between the hydraulic pressure generating means and the wheel cylinder, and each wheel Wheel speed detecting means for detecting speed (4
1, 42, 43, 44), an estimated vehicle body speed calculation means (AS) for determining a vehicle body speed which serves as a reference for hydraulic control from the information by the wheel speed detection means, the information by the wheel speed detection means and the estimated vehicle body speed calculation means. In a hydraulic control device equipped with hydraulic control means (BC) for operating hydraulic pressure switching means based on information to control hydraulic pressure, road surface friction for determining whether or not the friction coefficient of a traveling road surface is a low friction coefficient. A coefficient determining means (JM) is provided, and when the road surface friction coefficient determining means determines that the running road surface before control is a road surface having a low friction coefficient, the hydraulic pressure controlling means applies a brake pressure to one of the rear wheels. The antiskid control device for a vehicle is characterized in that an output of decompression or holding is made and an estimated vehicle speed is obtained based on the wheel speed.

Further, as described in claim 2, the right front wheel (FR), the left front wheel (FL), and the right rear wheel (RR) of the vehicle,
Wheel cylinders (51, 52, 53, 54) mounted on each of the left rear wheels (RL) to apply a braking force, hydraulic pressure generating means (2) for supplying a brake pressure to each of the wheel cylinders, and this hydraulic pressure Hydraulic pressure switching means (ACT) interposed between the generating means and the wheel cylinder, and wheel speed detecting means (41, 42, 43, 4) for detecting the wheel speed of each wheel.
4) Estimated vehicle speed calculation means (A) for determining the vehicle speed that serves as a reference for hydraulic pressure control from the information obtained by the wheel speed detection means.
S), a hydraulic pressure control device including hydraulic pressure control means (BC) for operating the hydraulic pressure switching means to control the hydraulic pressure based on the information from the wheel speed detecting means and the information from the estimated vehicle body speed calculating means, A road surface friction coefficient judging means (AS) for judging whether or not the friction coefficient is a low friction coefficient is provided, and the traveling road surface before hydraulic pressure control is judged to be a road surface having a low friction coefficient by this road surface friction coefficient judging means. If the wheel speed of the rear wheel is more than the value calculated by the estimated vehicle speed calculation means for a certain period of time, the hydraulic pressure control means outputs the brake pressure of one of the rear wheels to reduce or maintain the brake pressure. An anti-skid control device for a vehicle, characterized in that an estimated vehicle body speed is obtained based on the speed.

[0007]

In the anti-skid control device having the above structure, when it is determined that the road surface has a low friction coefficient, the braking force of any one of the rear wheels is reduced or maintained to recover the wheel speed. It is possible to prevent all four wheels from locking at the same time and to start the control accurately, so that it is possible to improve the accuracy of the estimated vehicle body speed that is the reference of the control. Also, if the wheel speed is restored by decompressing or holding one of the rear wheels, the wheel speed of the other rear wheel will drop due to the influence of the differential in a four-wheel drive vehicle and the wheel speed will decrease. It is possible to prevent the four wheels from locking at the same time because a difference occurs and the control is easily performed.

Further, as described in claim 2, when the road surface has a low coefficient of friction and the wheel speed of the rear wheel deviates from the value calculated by the estimated vehicle speed calculation means for a certain period of time, the rear wheel By decompressing or maintaining the braking force of one of the wheels, the wheel speed is recovered, the four wheels are prevented from becoming locked at the same time, and accurate control can be started. The accuracy of speed can be improved.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 shows an anti-skid control device according to an embodiment of the present invention, which includes a master cylinder 2a and a booster 2.
b, hydraulic pressure generator 2 driven by brake pedal 3, right front wheel FR, left front wheel FL, right rear wheel RR, wheel cylinders 51 to 54 arranged on the left rear wheel RL, respectively Pumps 21, 22 and reservoir 2 are provided in the pressure path.
3, 24 and solenoid valves 31 to 38 are interposed.

An actuator 30 is interposed between the hydraulic pressure generator 2 and the wheel cylinders 51 to 54.
In this actuator 30, solenoid valves 31, 32 and 33, 34 are installed in a hydraulic pressure passage connecting one output port of the master cylinder 2a and each of the wheel cylinders 51, 54, and a pump is provided between these solenoid valves 31, 32 and 33, 34. 21 is interposed. Similarly, solenoid valves 35, 36 and 37, 38 are provided in the hydraulic passages connecting the other output port of the master cylinder 2a and the wheel cylinders 52, 53, respectively, and the pump 22 is provided between them and the master cylinder 2a. It is installed. The pumps 21 and 22 are driven by the electric motor 20, and a brake pressure boosted to a predetermined pressure is supplied to these hydraulic pressure passages.

The discharge side hydraulic pressure passages of the normally closed electromagnetic valves 32 and 34 are connected to the pump 21 via the reservoir 23, and the discharge side hydraulic pressure passages of the electromagnetic valves 36 and 38 are connected to the pump 22 via the reservoir 24. Has been done. Reservoirs 23 and 24 each include a piston and a spring, and solenoid valves 32, 34, 36,
The brake fluid, which is recirculated from the valve 38 through the discharge-side fluid pressure passage, is stored therein, and the brake fluid is supplied when the pumps 21 and 22 are operated.

The solenoid valves 31 to 38 are two-port two-position solenoid valves, and each wheel cylinder 51 to 54 communicates with the hydraulic pressure generator 2 and the pump 21 or 22 when the solenoid coil is not energized (hereinafter referred to as OFF). ing. When the solenoid coil is energized (hereinafter referred to as "ON"), the wheel cylinders 51 to 54 are disconnected from the hydraulic pressure generator 2 and the pumps 21 and 22 and communicate with the reservoirs 23 to 24. The check valves are wheel cylinders 51 to 5
4 and the reservoirs 23 and 24 to allow the return to the hydraulic pressure generator 2 side, and to block the flow in the opposite direction.

By turning on and off the voltage applied to the solenoid valves 31 to 38 in this manner, the wheel cylinder 5
The brake pressures 1 to 54 can be increased, reduced, or held. That is, when the solenoids of the solenoid valves 31 to 38 are turned off, the brake pressure is supplied to the wheel cylinders 51 to 54 from the hydraulic pressure generator 2 and the pumps 21 and 22 to increase the pressure, and when the solenoids of the solenoid valves 31 to 38 are turned on, the brake pressure is communicated with the reservoirs 23 and 24 to reduce the pressure. To do. The brake pressure can be held when the solenoids of the solenoid valves 31, 33, 35, 37 are turned on and the other solenoids are turned off. Therefore, by adjusting the time interval for energizing the solenoid, step pressure increase (pulse pressure increase) that combines pressure increase and hold, or step pressure decrease (pulse pressure decrease) that combines pressure decrease and hold
It is possible to control so as to gradually increase or decrease the hydraulic pressure.

The solenoid valves 31 to 38 are electronic control units 1
0, and each solenoid valve and the electric motor 20 are controlled. Each wheel is provided with wheel speed sensors 41 to 44, which are wheel speed detecting means for detecting the wheel speed, and are input to the electronic control unit 10 together with the brake switch 45. As the wheel speed sensor, a toothed rotor that is rotated by the rotation of each wheel and an electromagnetic induction type sensor that is provided so as to face the tooth portion of the rotor are provided. It outputs a voltage.

The electronic control unit 10 is, as shown in FIG.
CPU14, ROM15, which are mutually connected through a bus,
A microcomputer 11 including a RAM 16, a timer 17, an input port 12 and an output port 13 is provided. The output signals of the wheel speed sensors 41 to 44 and the brake switch 45 are input to the CPU 14 from the input port 12 via the amplifier circuits 18a to 18e. In addition, from the output port 13 to the drive circuit 19a
A control signal is output to the electric motor 20 via
Control signals are output to the solenoid valves 31 to 38 via the drive circuits 19b to 19i. In the microcomputer 11, the ROM 15 stores a program for anti-skid control, and the CPU 14 executes the program when an ignition switch (not shown) is turned on. The RAM 16 temporarily stores variable data necessary for executing the program.

In this embodiment thus constructed, the program is executed when an ignition switch (not shown) is turned on. When the program is executed, the processing shown in FIG. 4 is performed.

Therefore, FIG. 4 will be described. First, in step 101, the microcomputer 11 is initialized, and various calculation values, an estimated vehicle body speed VS0 serving as a reference vehicle speed for control, a wheel speed VW, a wheel acceleration DVW, and the like are cleared. Next, at step 102, the wheel speed V of each wheel is determined by the output signals of the wheel speed sensors 41 to 44.
W is calculated, and in step 103, the wheel acceleration DVW is calculated from the calculated value by the wheel speed calculation. In the next step 104, it is determined whether or not the anti-skid control (ABS control) is being performed. If the control is being performed, step 105 is performed.
When control is not in progress (before control), in-control road surface friction coefficient estimation is performed in step S107, and the routine jumps to step. In step S105, pre-control road surface friction coefficient estimation (pre-control road surface μ estimation) is performed to set the friction coefficient of the traveling road surface to high μ, medium μ or low μ, and in step 106, rear wheel one wheel decompression is performed. Make a request decision. Pre-control road friction estimation in step 105 and step 107
The in-control road surface friction estimation may be performed by calculation based on the information based on the wheel speed, or may be determined by using an acceleration sensor. In the next step 108, it is determined whether or not ABS control is in progress. If it is in control, step 111
And before the control, step 109 is executed. At step 109, the ABS control start condition is judged and
If the S control start condition is satisfied, step 111 is executed and A
If the BS control start condition is not satisfied, step 110 is executed. In step 110, it is determined whether or not the rear wheel / single wheel pressure reduction request flag set in the rear wheel / single wheel pressure reduction request flag is set. If the rear wheel / single wheel pressure reduction request flag is set, step 111 is executed, If not set, the process jumps to step 117. When the control start condition is satisfied, step 111 selects one of the pulse pressure increasing, pressure reducing, and holding control modes. Next, it is judged in step 112 whether the control mode selected in step 111 is the pressure reducing mode. If the selected mode is the pressure reducing mode, the pressure reducing output is performed in step 113. When the mode is other than the pressure reducing mode, it is determined in step 114 whether or not the pulse pressure increasing mode is set. When the mode is the pulse pressure increasing mode, the pulse pressure increasing output is performed in step 115. In the case other than the above, step 1 is performed.
Hold output is performed at 16. Next, in step 117, it is judged whether or not the process of repeating the same process for four wheels is completed, and if the process for repeating four wheels is not completed, step 1
Returning to 02, the same process is repeated. If all four wheels have been processed, step 118 is executed, the estimated vehicle speed VS0 calculation for determining the vehicle speed that serves as the reference for anti-skid control is determined from the information from the wheel speed sensor, and the process returns to step 102. Repeat the process.

The estimated vehicle body speed VS0 is set according to the flowchart of FIG. First, at step 201, the maximum value of the wheel speeds of the four wheels is obtained every control cycle (5 ms in this embodiment), and the maximum wheel speed VW0 is obtained.
(n). Also, (n) represents the value at the time of n cycles, and n
Is an integer of 1 or more. Next, at step 202, it is judged whether or not the road surface μ is high μ, and if it is high μ, at step 203 a deceleration αDW is set to a predetermined value, for example 1.1 G.
(G indicates gravitational acceleration) is set. Step 20
If 2 is not determined to be high μ, step 204 is executed,
This time, it is determined whether or not it is medium μ. If it is determined to be medium μ here, for example, 0.6 G is set as the deceleration αDW in step 205, otherwise it is determined to be low μ,
In step 206, for example, 0.4 G is set as the deceleration αDW. After αG is set to 0.5 G in step 207, the estimated vehicle speed VSO is set in step 208.
(n) is calculated. That is, VW0 (n), which is the maximum wheel speed obtained in step 201, and estimated vehicle speed VSO (n-1) at the previous control cycle, which is a value obtained by adding the product of acceleration αUP and control cycle time T (VSO (n -1) + αUP * T) and the value obtained by subtracting the product of deceleration αDW and control cycle time T from the estimated vehicle speed VSO (n-1) at the previous control cycle (VSO (n
The intermediate value of the three values of (-1) -αDW * T) is calculated and used as the estimated vehicle speed VSO (n). The MED shown in FIG. 5 is a function for obtaining an intermediate value. In the next step 209, the maximum wheel speed VW0 (n) of the four wheels and the estimated vehicle body speed VSO (n) are compared, and VW0 (n) is estimated vehicle body speed VSO.
If it is smaller than (n), the αDW continuous selection counter is counted in step 210, and if it is larger, the αDW continuous selection counter is cleared in step 211.

Next, the rear wheel / one wheel pressure reduction request determination of FIG. 6 will be described. In step 301, it is determined whether or not the rear wheels are being calculated. If the rear wheels are being calculated, step 302 is performed. If the rear wheels are not being calculated (front wheels are being calculated), the rear wheel one wheel pressure reduction request determination is made. finish. In step 302, it is determined whether or not the friction coefficient of the road surface before control is a low μ road surface, and if it is a low μ road surface, step 303 is performed,
Otherwise, jump to step 308. In step 303, it is determined whether or not the αDW continuous selection counter has passed a predetermined time (360 ms in this embodiment). That is, here, it is determined whether or not the wheel speed of the rear wheels has been separated from the estimated vehicle body speed for a certain period of time, and if the separated state has passed a predetermined time, step 304 is performed, and if the predetermined time has not passed, Performs step 308. In step 304, it is determined whether or not there is a pressure reduction request for both of the rear wheels. If there is no pressure reduction request for both wheels, step 305 is performed, and if there is a pressure reduction request for both wheels, step 3 is performed.
Perform 08. In step 305, the wheel speeds of the rear wheels are compared, and in steps 306 and 307, the pressure reduction request flag for the rear wheels is set so as to reduce the pressure on the low wheel speed side. For example, if the wheel speed on the right side of the rear wheels is smaller than that on the left side, the right wheel decompression request flag is set, and if the wheel speed on the left side of the rear wheels is smaller than that on the right side, one wheel on the left side is set. Set the pressure reduction request flag. In step 308, both rear wheels and one wheel pressure reduction request flag are cleared. In this way, pressure reduction is requested on the side of the rear wheels with low wheel speed, and pressure reduction output is performed, but it is desirable to maintain the braking force for a certain period of time after pressure reduction, and the inner wheel side of the rear wheels is selected while the vehicle is turning. It is desirable to be done.

FIG. 7 shows an embodiment of an output pattern when one rear wheel one wheel pressure reduction is requested. By first performing pressure reduction output and then holding output for a certain period of time, it is possible to prevent a decrease in wheel speed. desirable.

Further, FIG. 8 shows a waveform when a rear wheel one wheel decompression request judgment is made in a four-wheel drive vehicle. When the braking force on the low wheel speed side of the rear wheel is reduced after the low μ road surface judgment is made. As a result, the wheel speed of the target wheel becomes faster due to the influence of the differential, the difference between the left and right wheel speeds becomes large, and the effect of easily entering control is produced.

When low μ is detected as described above, or when low μ is detected and the state where the wheel speed of the rear wheels deviates from the estimated vehicle body speed continues for a certain period of time, one of the rear wheels is depressurized or held. By doing so, the wheel speed is recovered and early locking is prevented. Also, in four-wheel drive vehicles, the wheel speed of the rear wheel that does not reduce or maintain pressure drops due to the influence of the differential, and the left-right speed difference between the rear wheels makes it easier to enter control, preventing early locking and ensuring accurate control. It can be done and an accurate estimated vehicle speed can be made.

[0024]

As described above, in the vehicle anti-skid control device according to the present invention, even if the braking force is gently applied when traveling on a low μ road surface, the control can be performed by depressurizing or holding one of the rear wheels. It is possible to prevent all wheels from tending to lock at the same time without delaying the start, and to make an accurate estimated vehicle body speed.

Further, in the case of a four-wheel drive vehicle, the wheel speed of the rear wheels on the side that is not depressurized or maintained drops due to the influence of the differential, and a speed difference between the front and rear wheels occurs, which makes it easier to enter control and stabilizes. Braking can be secured.

[Brief description of drawings]

FIG. 1 is a block diagram showing an outline of an anti-skid control device for a four-wheel drive vehicle according to the present invention.

FIG. 2 is an overall configuration diagram of an anti-skid control device for a four-wheel drive vehicle according to the present invention.

FIG. 3 is a block diagram showing a configuration of the electronic control device of FIG.

FIG. 4 is a flowchart showing an outline of anti-skid control in one embodiment of the present invention.

5 is a flowchart showing details of an estimated vehicle body speed calculation shown in FIG.

FIG. 6 is a flowchart showing details of one rear wheel / one wheel pressure reduction request determination shown in FIG. 4.

FIG. 7 is a diagram showing an embodiment of an output pattern at the time of determining a rear wheel / one wheel pressure reduction request according to the present invention.

FIG. 8 is a diagram showing an effect when a rear wheel / one wheel pressure reduction request determination according to the present invention is performed in a four-wheel drive vehicle.

[Explanation of symbols]

 2: Liquid pressure generating device 2a: Master cylinder 2b: Booster 3: Brake pedal 10: Electronic control device 20: Electric motor 21, 22: Pump 23, 24: Reservoir 30: Liquid pressure control device (actuator) 31-38: Electromagnetic Valve (solenoid) 41-44: Wheel speed sensor 51-54: Wheel cylinder

Claims (2)

[Claims] 1. A wheel cylinder mounted on each of a front wheel and a rear wheel of a vehicle for applying a braking force, a hydraulic pressure generating means for supplying a brake pressure to each of the wheel cylinders, and the hydraulic pressure generating means and the wheel cylinder. Hydraulic pressure switching means interposed therebetween, wheel speed detecting means for detecting the wheel speed of each of the wheels, and estimated vehicle speed calculating means for determining a vehicle speed that serves as a reference for hydraulic control based on information from the wheel speed detecting means. A friction coefficient of a traveling road surface in a hydraulic pressure control device including hydraulic pressure control means for operating the hydraulic pressure switching means to control hydraulic pressure based on information from the wheel speed detection means and information from the estimated vehicle body speed calculation means. Is provided with a road surface friction coefficient determining means for determining whether or not the traveling road surface before control is a road surface having a low friction coefficient. In this case, the hydraulic pressure control means outputs an output for reducing or holding the brake pressure of any one of the rear wheels, and the estimated vehicle body speed is obtained based on the wheel speed. 2. A wheel cylinder mounted on each of a front wheel and a rear wheel of a vehicle for applying a braking force, a hydraulic pressure generating means for supplying a brake pressure to each of the wheel cylinders, the hydraulic pressure generating means and the wheel cylinder. Hydraulic pressure switching means interposed therebetween, wheel speed detecting means for detecting the wheel speed of each of the wheels, and estimated vehicle speed calculating means for determining a vehicle speed that serves as a reference for hydraulic control based on information from the wheel speed detecting means. A friction coefficient of a traveling road surface in a hydraulic pressure control device including hydraulic pressure control means for operating the hydraulic pressure switching means to control hydraulic pressure based on information from the wheel speed detection means and information from the estimated vehicle body speed calculation means. Is provided with a road surface friction coefficient judging means for judging whether or not the friction coefficient is low, and the road surface friction coefficient judging means judges that the traveling road surface before the hydraulic control is a road surface with a low friction coefficient. If the state in which the wheel speed of the rear wheels deviates from the value calculated by the estimated vehicle body speed calculation means continues for a certain period of time, the hydraulic pressure control means outputs or reduces the brake pressure of any one of the rear wheels. ,
An anti-skid control device for a vehicle, wherein an estimated vehicle body speed is obtained based on the wheel speed.