JPH0672306A - Anti-skid brake device for vehicle - Google Patents

Abstract

PURPOSE:To execute precise brake pressure control without causing wrong operation at the time of high mu road travel. CONSTITUTION:In a case in which it is confirmed according to the output signal of a road surface state presuming means 35 that a travel road is not a high muroad, normal judgment control that judges the finish timing of the depressurization state of brake pressure according to vehicle w heel acceleration and a ship rate or the like is executed at a control means 39, and in a case in which it is confirmed that the travel road is a high mu road, in addition to the normal judgment control, the judgment control of the high mu road to judge the finish timing of the depressurization state of brake pressure according to the output signal of a change rate detecting means 36 is executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antiskid brake device for a vehicle, which prevents the wheels from locking during braking by controlling the brake pressure according to the slip ratio of the wheels.

[0002]

2. Description of the Related Art Conventionally, as shown, for example, in Japanese Examined Patent Publication No. 62-16857, at the time when it is confirmed that the wheel speed sharply decreases during braking and the acceleration becomes smaller than a preset value. At the time when the wheel brake pressure is reduced to execute the anti-skid control, and when the wheel acceleration changes from a negative state to a positive value or becomes larger than the reference acceleration set to a negative value, An anti-skid brake device for a vehicle is known which is configured to terminate the reduction of the brake pressure.

[0003]

SUMMARY OF THE INVENTION The above antiskid brake device changes the reference acceleration, which is a criterion for deciding whether or not to finish reducing the brake pressure, in accordance with the vehicle speed, so that the antiskid brake conforms to the road surface condition. Is configured to exercise control. However, two types of reference acceleration preset as described above are selected according to the wheel speed,
If the reference acceleration is compared with the wheel acceleration to determine the end timing of the brake pressure, there is a problem that the optimum brake pressure control corresponding to the running state of the vehicle cannot be executed.

That is, in the above-mentioned conventional anti-skid brake device, when the decrease amount of the wheel speed is small, it is determined that the traveling road is the high μ road, and the discrimination control during the high μ road traveling is executed. However, since it is difficult to accurately correspond the decrease amount of the wheel speed and the road surface μ of the traveling road, malfunction is likely to occur, and a precise brake adapted to the changing state of the wheel speed when traveling on the high μ road. There is a problem that pressure control cannot be executed.

The present invention has been made to solve the above problems, and is an anti-skid brake device for a vehicle capable of executing a precise brake pressure control when traveling on a high μ road without causing a malfunction. Is intended to provide.

[0006]

SUMMARY OF THE INVENTION The present invention is an anti-skid brake device for a vehicle equipped with a brake pressure adjusting means for adjusting the brake pressure during braking to perform anti-skid control. The control means for setting the operation timing of the brake pressure adjusting means, the road surface state estimating means for estimating the road surface μ of the traveling road, and the change rate detecting means for detecting the change rate of the wheel acceleration. When it is confirmed that the traveling road is not a high μ road according to the output signal of the road surface state estimating means, the normal end timing of the brake pressure reduction state is determined according to the wheel acceleration, the slip ratio, and the like. When the judgment control is executed and it is confirmed that the traveling road is a high μ road, the brake pressure is reduced according to the output signal of the change rate detection means in addition to the normal judgment control. Those that are configured to perform the determination control determines high μ road and end timing.

[0007]

According to the present invention having the above-mentioned structure, when it is confirmed that the traveling road is not the high μ road according to the output signal of the road surface state estimating means, the brake pressure is changed according to the acceleration of the wheel and the slip ratio. Normal determination control is performed to determine the end timing of the reduced pressure state of, while preventing the locking of the wheels,
The brake pressure reduction state can be terminated at an appropriate timing.

On the other hand, when it is confirmed that the traveling road is a high μ road, the brake pressure reduction state is ended in accordance with the output signal of the change rate detecting means in addition to the normal determination control. The determination control on the high μ road for determining the timing is executed, and the precise brake pressure control adapted to the changing state of the wheel speed can be executed during traveling on the high μ road without causing malfunction.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the overall configuration of an antiskid brake device for a vehicle according to an embodiment of the present invention. This vehicle is provided with left and right front wheels 1 and 2 that are driven wheels and left and right rear wheels 3 and 4 that are driving wheels, and the driving force of an engine 5 is from an automatic transmission 6 to a propeller shaft 7, a differential 8 and left and right. It is configured to be transmitted to the rear wheels 3 and 4 via the axles 9 and 10.

Each of the wheels 1 to 4 has a brake consisting of disks 11a to 14a which rotate integrally with the wheels 1 to 4 and calipers 11b to 14b which control the rotation of the disks 11a to 14a by receiving brake pressure. Device 11-
14 are provided, and these brake devices 11-14 are
It is controlled by the brake control system 15. The brake control system 15 is provided with a booster 17 for increasing the stepping force of the brake pedal 16 and a master cylinder 18 for generating a brake pressure according to the stepping force increased by the booster 17. There is.

The front wheel brake pressure line 19 led from the master cylinder 18 is branched into two paths, and the front wheel branch paths 19a and 19b are connected to the brake devices 11 and 12 of the left and right front wheels 1 and 2. Caliper 11
b and 12b, respectively. In the one front-wheel branch passage 19a leading to the brake device 11 for the left front wheel 1, an electromagnetic on-off valve 20a and an electromagnetic relief valve 20 are provided.
The 1st valve unit 20 which consists of b is arranged. Similarly to the first valve unit 20, an electromagnetic on-off valve 21 and an electromagnetic relief valve 21b are also provided on the other front wheel branch line 19b leading to the brake device 12 for the right front wheel 2. A 2-valve unit 21 is installed.

On the other hand, in the brake pressure line 22 for the rear wheels guided from the master cylinder 18, a third valve unit 23 including an electromagnetic opening / closing valve 23a and an electromagnetic relief valve 23b is installed. There is. Further, the brake pressure line 22 is branched into two paths on the downstream side of the third valve unit 23, and the rear wheel branch path 22a,
22b is a brake device 13 for the left and right rear wheels 3, 4,
Fourteen calipers 13b and 14b are respectively connected. The electromagnetic relief valves 20b, 21b, 23b
The brake oil discharged from the reservoir tank 1 of the master cylinder 18 is drained through a drain line (not shown).
8a.

Then, the above-mentioned first to third valve units 2
0, 21, 23 are independently driven and controlled by the control unit ECU, and the braking force of the braking device 11 for the left front wheel 1 and the braking device 12 for the right front wheel 2 is activated by the operation of the first and second valve units 20, 21. Are variably controlled, and by the operation of the third valve unit 23,
The braking force applied to the braking devices 13 and 14 of the left and right rear wheels 3 and 4 is variably controlled.

The control unit ECU has a detection signal of the brake switch 25 for detecting whether or not the brake pedal 16 is stepped on, a detection signal of wheel speed sensors 26-29 for detecting the rotation speeds of the wheels 1-4, and a steering wheel. A control signal for anti-skid brake control is generated based on the detection signal of the steering angle sensor 30 that detects the steering wheel operation angle, and this control signal is output to each of the first to third valve units 20, 21, 23. Left and right front wheels 1,
The first is the braking control for the slip of the rear wheel 2 and the rear wheels 3, 4.
-It is comprised so that it may carry out in parallel for every 3rd valve unit 20,21,23.

That is, the control unit EC
In U, as shown in FIG. 2, the wheel speed sensors 26-2
9, a vehicle body speed calculation stage 31 for calculating the traveling speed of the vehicle in accordance with the detection signal of 9, a correction unit 32 for correcting the wheel speed Vw in accordance with the output signal of the steering angle sensor 30, and slips of the wheels 1 to 4 The slip ratio calculating means 33 for calculating the ratio, the acceleration calculating means 34 for calculating the acceleration of each of the wheels 1 to 4, and the road surface state estimating means for estimating the road surface μ of the traveling road according to the output signal of the acceleration calculating means 34. And 35 are provided.

Further, the control unit ECU
Stores a change rate detecting means 36 for detecting a change rate of wheel acceleration, that is, an amount of change in acceleration per unit time according to the output signal of the acceleration calculating means 34, and various slip control threshold values as a map. A threshold storage means 37,
A threshold value reading means 38 for reading a threshold value corresponding to the running of the vehicle from the map and a control means 39 for controlling the brake pressure adjusting means composed of the brake control system 15 are provided.

The vehicle body speed calculating means 31 is configured to obtain a pseudo vehicle speed Vr by a conventionally known method based on the wheel speed Vw obtained from the detection signals of the wheel speed sensors 26 to 29. Further, the correction means 32 is
In order to correct the wheel speed on the turning inner wheel side, which is smaller than that on the turning outer wheel side, a correction value obtained by multiplying the detection values of the wheel speed sensors 26 to 29 by a correction coefficient corresponding to the steering angle is used. The deviation of the wheel speed due to the turning of the vehicle is eliminated by adding it to the detected value of.

The correction amount of the wheel speed is limited to the range of the maximum correction value set corresponding to the vehicle speed, and when the value calculated by the correction means 32 exceeds the maximum correction value, Each wheel speed is corrected based on this maximum correction value. This maximum correction value is Rmax
Is a predetermined value (600) set in advance as shown in the following equation.
Is divided by the pseudo vehicle speed Vr.

Maximum correction value (Rmax) = 600 / Vr [km / h] Further, the slip ratio calculating means 33 is corrected by the pseudo vehicle speed Vr obtained by the vehicle body speed calculating means 31 and the correcting means 32. Based on the wheel speed Vw, the slip ratio S is calculated for each wheel 1 to 4 as shown in the following equation.

Slip rate (S) = (wheel speed Vw / pseudo vehicle speed Vr) × 100 [%] Further, the acceleration calculating means 34 calculates the difference between the previous value and the current value of the wheel speed Vw in the sampling cycle Δt ( For example, the acceleration of the wheel speed Vw is calculated by converting the value divided by 7 ms) into the gravitational acceleration.

The road surface state estimating means 35 estimates the road surface μ of the traveling road, and the estimation operation will be described with reference to the flowchart shown in FIG. When this estimation operation starts, first, in step S1, various data are read, and then in step S2, it is determined whether or not the ABS control flag F indicating that the anti-skid control is currently being executed is set to 1. To judge.

The ABS control flag F is set to 1 when, for example, it is confirmed that at least one of the wheels is in a locking tendency, and when the brake switch 25 is switched from the ON state to the OFF state. Is reset to 0. When it is confirmed in step S2 that the ABS control flag F is not set to 1, the process proceeds to step S3, in which 3 indicating a high μ road is set as the value MU of the road surface μ of the traveling road.

If it is confirmed in step S2 that the ABS control flag F is set to 1, the process proceeds to step S4 and the previous cycle (see FIG.
The minimum value DW of the wheel acceleration in the cycle shown in
It is determined whether it is smaller than 20G. This step S
If YES is determined in step 4, the process proceeds to step S5, and the maximum value AW of the wheel acceleration in the previous cycle is 10
It is determined whether or not the value is larger than G, and if the result of this determination is NO, in step S6, 1 indicating a low μ road is set as the value MU of the road surface μ of the traveling road.

On the other hand, when it is confirmed in step S4 that the minimum value DW of the wheel acceleration is -20 G or more, it is determined in step S7 whether the maximum value AW of the wheel acceleration is larger than 20 G. To judge. If the result of this determination is YES, the process proceeds to step S3, in which 3 indicating a high μ road is set as the value MU of the road surface μ of the traveling road. Further, in step S7, the maximum value AW of the wheel acceleration is
Is confirmed to be 20 G or less, in step S8, 2 indicating a medium μ road is set as the value MU of the road surface μ of the traveling road.

The threshold value reading means 38, based on the output signals of the vehicle body speed calculating means 31 and the road surface state estimating means 35,
The accelerations, slip rates and acceleration change rates of the wheels 1 to 4 corresponding to the current running state are read from the map stored in the threshold value storage means 37, and these values are used to start the anti-skid control and hold and reduce the brake pressure. It is also output to the control means 39 as a threshold value for determining the timing of pressure increase.

The map of the threshold value of the wheel acceleration is high μ
Wheels 1 to 4 in each road surface condition of road, medium μ road and low μ road
Is a value that is obtained in advance as a value that causes a lock, for example, (high μ road threshold, medium μ road threshold, low μ road threshold) = (− 1.5G, −1.0G, −0.5G ) Is set.

Further, the map of the threshold value of the slip ratio is
As will be described later, it is obtained in advance by experiments or the like as a value for setting the timing for reducing or increasing the brake pressure according to the vehicle speed and the like. For example, (high speed threshold, medium speed threshold, low speed threshold) = ( 95%, 90%, 85%). On the other hand, the threshold value of the acceleration change rate indicates whether or not the brake pressure reduction control is terminated when it is confirmed that the traveling road is a high μ road according to the output signal of the road surface state estimating means 35. It is obtained in advance by experiments or the like as a value that serves as a criterion for the determination.

The control means 39 controls the acceleration AW of the wheel immediately after the start of braking in response to the depression operation of the brake pedal 6, and
The threshold value of the acceleration read by the threshold value reading means 38 is compared, and when the acceleration AW of the wheels 1 to 4 falls below the threshold value, a control signal for holding the brake pressure is generated. Also,
Slip rate S of wheels 1 to 4 after holding brake pressure
Is compared with the threshold value of the slip ratio read by the threshold value reading means 38, and when the slip ratio S of the wheels 1 to 4 falls below the threshold value, a control signal for reducing the brake pressure is generated.

Then, the control signal is input to the brake control system 15, and in the brake control system 15, the first to third valve units 20, 21, 2 are provided.
The electromagnetic on-off valves 20a, 21a, 23a of No. 3 and the electromagnetic relief valves 20b, 21b, 23b are controlled to be opened / closed by duty control, respectively, whereby the braking force corresponding to the slip state is applied to the front wheels 1, 2 and the rear wheels 3, 4 It is supposed to be generated.

When anti-skid control is not performed, the first to third valve units 20, 2 are
The control signal of the brake pressure is not output to 1 and 23, and the electromagnetic opening / closing valves 20a, 21a and 23a are held in the open state, while the electromagnetic relief valves 20b, 21b and 23b are held.
Is kept closed. This allows the brake pedal 16
The brake pressure generated in the master cylinder 18 according to the stepping force of the brake cylinder is supplied to the brake devices 11 to 14 of the left and right front wheels 1 and 2 and the rear wheels 3 and 4 via the brake pressure lines 19 and 22, and the brake pedal 16 The brake pressure corresponding to the stepping force is directly applied to the wheels 1 to 4.

Next, the basic control operation of the anti-skid brake device will be described with reference to FIG. The increase / decrease control of the brake pressure is performed by the first to third valve units 20,
This is performed for each of the units 21 and 23. Here, the first valve unit 20 for the left front wheel 1 will be described as an example.

When the brake pedal 16 is depressed at time To in FIG. 4, the brake pressure generated in the master cylinder 18 gradually increases, and the braking force reduces the wheel speed Vw of the left front wheel 1. The acceleration AW of the wheel speed Vw is calculated by the acceleration calculating means 34 and read by the threshold reading means 38.
1.5G ". Then, at time Ta, the wheel speed V
When the acceleration AW of w falls below the threshold value "-1.5 G", the phase shifts from the phase 0, which is a non-control state of the anti-skid control, to the control state of the phase 2, and the anti-skid control of the first cycle is started. It

As described above, in the first cycle of the anti-skid control, the threshold value of the high μ road is read by the road surface state estimating means 34 as the threshold value of the deceleration DW. This is because the road surface μ of the traveling road cannot be estimated in the first cycle, and when a threshold value on a low μ road, for example, “−0.5 G” is used as the threshold value, the acceleration AW of the wheel 1 is slightly reduced. In this case, the situation will be less than or equal to the threshold value, and as a result, the antiskid control will be frequently started.

The anti-skid control is started from the phase 2 for holding the brake pressure, the control for the phase 3 for reducing the brake pressure after the holding is executed at the time Tb, and the brake pressure after the depressurization is executed at the time Tc. After the control of the phase 4 for holding is executed, the anti-skid control of the first cycle ends at time Td.

Next, the control of the phase 1 for increasing the brake pressure again is executed from the time point Td to start the anti-skid control of the second cycle, and thereafter, the second cycle is performed through the above-mentioned phases 2 to 4. When finished,
The anti-skid control after the third cycle is repeatedly executed.

At the time of execution of the phase 2 hold control,
Wheel 1 by slip ratio calculation means 33 from wheel speed Vw
The slip ratio S is calculated and this value is compared with the threshold value read by the threshold value reading means 38 in accordance with the vehicle speed. For example, when the value of 95% at high speed is read as the threshold value of the slip ratio, the slip ratio S is 95%.
At the time point Tb when the pressure falls below the lower limit, the phase 2 shifts to the phase 3 and the pressure reduction control of the brake pressure is started. That is,
The relief valve 20b of the first valve unit 20 is turned on / off according to a predetermined duty ratio, whereby the brake pressure is reduced with a predetermined gradient, the braking force is gradually reduced, and the rotational force of the wheel 1 is recovered.

At time Tc, when the acceleration AW of the wheel 1 reaches the threshold value read by the threshold value reading means, for example, 0, the phase shifts from phase 3 to phase 4, and the brake pressure is maintained at the reduced pressure level. During phase 4, the wheel speed Vw increases again. Then, when the holding control in the phase 4 is executed, the threshold value read by the threshold value reading means 38 and the slip ratio S of the wheel 1 are compared by the control means 39, and the holding state of the brake pressure should be changed to the pressure increasing state. It is determined whether or not the slip ratio S has increased to a threshold value or more, and at time Td, the phase shifts from phase 4 to phase 1, and the second cycle anti-skid brake control is started.

Next, the setting operation of the end timing for ending the brake pressure reduction state in the phase 3 will be described with reference to the flowchart shown in FIG. That is, in step S11, it is determined whether or not the flag F3 indicating that the control state is currently in phase 3 is set to 1.

The flag F3 is set to 1 when the phase 2 holding control execution state shifts to the phase 3 pressure reduction control execution state. If the decision result in the step S11 is YES, the process advances to a step S12, and it is decided whether or not the road surface μ of the traveling road estimated by the road surface state estimating means 35 is a value corresponding to a high μ road. .

When it is determined NO in step S12 and it is confirmed that the road is a medium μ road or a low μ road, the acceleration AW of the wheel 1 is determined from the acceleration threshold value (0) in step S13. By executing the normal determination control, it is determined whether or not the depressurized state is ended by determining whether or not

As a result of the above judgment, when it is confirmed that the depressurized state is to be ended, in step S14, the control signal for ending the depressurized state of the brake pressure and shifting to the holding state is applied. After outputting to the control means 15, the flag F3 is set to 0 in step S15.
Reset to. On the other hand, if it is determined NO in step S13 and it is confirmed that the brake pressure reduction control should not be terminated, the process directly returns.

Further, YES in step S12.
If it is determined that the traveling road is a high μ road, it is determined in step S16 whether the acceleration AW of the wheel 1 is larger than the acceleration threshold value (0). If the determination result is NO, step S1
7, it is determined whether the rate of change AW ′ of the wheel acceleration is larger than the rate of change threshold value (20).
Normal judgment control for judging whether or not to end the depressurized state is executed.

If YES is determined in one of the steps S16 and 17, the above step S1
If the brake pressure reduction state is terminated and the determination is NO in both steps S16 and S17, it is determined that the brake pressure reduction control should not be terminated, and the routine returns.

As described above, when the vehicle runs on the medium μ road or the low μ road, the end timing of the pressure reducing control is determined according to the acceleration AW of the wheel, and when the vehicle runs on the high μ road, the wheel acceleration AW and its change rate. Since the end timing of the pressure reducing control is determined according to both of AW 'and the control state for determining the end timing of the pressure reducing control is changed according to the output signal of the road surface state estimating means 35, it is configured to Appropriate anti-skid control according to the road surface μ can be executed.

That is, a high μ value that prevents the wheels from locking easily.
When the vehicle is traveling on a road, since the determination control for determining the end timing of the pressure reduction control corresponding to the change rate of the wheel deceleration AW 'is added, the change state of the wheel acceleration AW is properly predicted to increase the wheel acceleration AW. When it is confirmed that the wheel lock state is in a recovery tendency, the pressure reduction control is terminated in advance to execute a precise brake control adapted to the change state of the wheel speed. It is possible to effectively prevent the wheels from locking while sufficiently exerting the braking force. As a result, it is possible to prevent the brake pressure from being reduced more than necessary and improve the braking performance when traveling on a high μ road where wheel slip is easily eliminated.

On the other hand, when the vehicle is traveling on a medium μ road or a low μ road where the tendency of wheel locking tends to occur, the normal judgment control for judging the end timing of the pressure reducing control according to the acceleration AW of the wheel is executed. Since it is configured as described above, the pressure reduction control of the brake pressure does not end early unlike the case where the predictive control according to the change rate AW 'of the wheel deceleration is executed. The pressure reduction control can be ended at various timings.

In the above embodiment, the normal judgment control for judging the end timing of the pressure reduction control is executed according to the acceleration AW of the wheels, but according to the slip ratio S of the wheels. The determination control may be performed, or the determination control may be performed based on both the wheel acceleration AW and the slip ratio S.

[0048]

As described above, according to the present invention, when the vehicle runs on a medium μ road or a low μ road, the normal determination control for determining the end timing of the pressure reducing control according to the acceleration of the wheels and the like is executed. When traveling on a high μ road, in addition to the normal determination control described above, the high μ road determination control for determining the end timing of the pressure reduction control according to the change rate of the wheel acceleration is configured to be executed, so that the wheels are locked. When traveling on a difficult high-μ road, by determining the end timing of the front pressure control in accordance with the change rate of the wheel deceleration, the change state of the wheel acceleration is properly predicted and the wheel acceleration tends to increase. If it is confirmed that the wheel lock state is in a recovery tendency, the above pressure reduction control is ended in advance, and by doing so, precise brake pressure control adapted to the changing state of the wheel speed is executed, and the braking force is To It is possible to effectively suppress the locking of the wheels while sufficiently exerting the effect.

Further, when the vehicle is traveling on a medium μ road or a low μ road where the tendency of wheel locking tends to occur, the normal judgment control for judging the end timing of the pressure reducing control according to the acceleration of the wheels is executed. Since the brake pressure reduction control does not end early as in the case where the predictive control according to the change rate of the wheel deceleration is executed, the wheel lock is reliably prevented and the pressure reduction is performed at an appropriate timing. There is an advantage that the control can be ended.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an overall configuration of a vehicle anti-skid brake device according to the present invention.

FIG. 2 is a block diagram showing a configuration of a control unit of the antiskid brake device.

FIG. 3 is a flowchart showing an operation of estimating a road surface μ of a traveling road.

FIG. 4 is a time chart showing a control operation of the anti-skid brake device.

FIG. 5 is a flowchart showing a determination operation for determining the end timing of the brake pressure reduction control.

[Explanation of symbols]

 1-4 Wheels 15 Brake control system (brake pressure adjusting means) 35 Road surface state estimating means 36 Change rate detecting means 39 Control means

Front page continuation (72) Inventor Tetsuya Tachihata 3-1, Fuchu-cho Shinchi, Aki-gun, Hiroshima Mazda Co., Ltd. (72) Inventor Keisumi Masumi 3-3-1 Fuchu-cho, Aki-gun, Hiroshima Nardeck Co., Ltd.

Claims (1)

[Claims] 1. An anti-skid brake device for a vehicle, comprising a brake pressure adjusting means for adjusting a brake pressure during braking to execute an anti-skid control, wherein the brake pressure adjusting means operates in accordance with a running state of the vehicle. It has a control means for setting timing, a road surface state estimating means for estimating the road surface μ of the traveling road, and a change rate detecting means for detecting a change rate of the wheel acceleration, and the control means outputs the road surface state estimating means. When it is confirmed that the road is not a high μ road according to the signal, normal judgment control is executed to judge the end timing of the brake pressure reduction state according to the wheel acceleration and slip ratio. When it is confirmed that the road is a high μ road, in addition to the normal determination control, the end timing of the brake pressure reduction state is determined according to the output signal of the change rate detection means. An anti-skid brake device for a vehicle, which is configured to perform determination control of a μ road.