JPH0656023A - Anti-skid controller - Google Patents

Abstract

PURPOSE:To lessen the shortage of brake force in the case of an anti-skid controller equipped with a step difference detecting means. CONSTITUTION:When vehicle wheels pass a step difference during braking, the speed of the vehicle wheels is reduced, and vehicle acceleration becomes smaller than a set value (time point 1), and moreover, when it becomes less than a threshold within a set time, it is detected that there is a step difference (time point 2). When the step difference is detected, a duty control ratio is sought on the basis of the size of vehicle body deceleration. Afterwards, anti- skid control is started (time point 3), and at the initial stage of depressurization start, an actuator is driven on the basis of its duty control ratio, so a depressurization incline is virtually gentled. Afterwards, the vehicle wheel speed is recovered due to step difference passing, and retention and pulse pressure increase are conducted, so a small initial depressurization quantity will do, and a brake distance becoming long is avoided. Even in the case of step difference decision having been wrong, the vehicle wheels do not fall into a lock state as anti-skid control itself is not made to be finished.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antiskid control device having a partial low μ road detecting means.

[0002]

2. Description of the Related Art An anti-skid control device equipped with a means for detecting a step, which is a type of partial low μ road, is disclosed in Japanese Patent Laid-Open No. 2-24.
No. 9752. In the anti-skid control device described in this publication, the determination of the step is
After the wheel has passed the step, and therefore at least the first
The anti-skid control is ended when the step is detected after the end of the depressurization for the second time. If a wheel passes through a step during braking, the wheel lifts up from the road surface and the friction coefficient of the road surface becomes partially equal to 0, and the driving force based on the friction force is lost and the wheel speed decreases, causing slippage. Becomes excessive, anti-skid control is started, and sudden pressure reduction is performed. However, the decrease in the wheel speed when passing the step is a temporary phenomenon, and the wheel speed always increases after passing the step, so that the anti-skid control does not need to be originally performed. When passing a step, useless anti-skid control is performed to reduce the pressure, which causes a problem that the braking distance is unnecessarily extended. Therefore, in the anti-skid control device described in the above publication, the anti-skid control is terminated when it is detected as a step.

[0003]

However, even in the anti-skid control device described in the above publication, it is not possible to completely avoid the extension of the braking distance. FIG. 6 shows changes in wheel speed and brake fluid pressure when a vehicle equipped with the anti-skid control device passes a step during braking. If the wheel passes through the step during braking, anti-skid control is started (time point Q1), and a sudden pressure reduction is performed. After that, at time Q2, it is detected that there is a step, and the anti-skid control is ended. In this case, the decompression accompanying the start of the anti-skid control is completely executed, so the braking force becomes insufficient and the braking distance becomes long.

In order to solve this problem, it is possible to delay the pressure reduction at the start of the anti-skid control. However, if the anti-kid control is started in a state where the vehicle deceleration is large (when the anti-skid control is started on a high μ road surface with a high road friction coefficient μ), it may be erroneously determined as a step. Therefore, as shown in FIG. 7, if the anti-skid control is terminated based on an erroneous determination, there is a problem that the slip becomes excessive.

Although the steps on the road surface have been described above, the same phenomenon occurs when passing through a manhole, a crossing wastewater channel, etc., and therefore these are collectively referred to as a partial low μ road. In other words, a partial low μ road has a road surface friction coefficient of a short portion in the traveling direction of the vehicle which is significantly lower than that of the other portions or becomes 0, and once the vehicle passes through this portion during braking, wheel slippage occurs once. A road surface that grows in size but recovers after a short time.

According to the present invention, when the vehicle is braking, the wheels are partially low μ
When passing a road, it is possible to avoid unnecessary braking of the braking distance due to execution of unnecessary anti-skid control, and the start of anti-skid control on a high μ road is mistaken for a partial low μ road. If the determination is made, it is an object to obtain an anti-skid control device capable of avoiding slip as much as possible.

[0007]

The gist of the present invention is as follows: (1) Brake fluid pressure control means for keeping the slip ratio of a wheel within an appropriate range by increasing or decreasing the brake fluid pressure. (2) Partial low μ road detection means for detecting that the road is a partial low μ road while passing through the partial low μ road, and (3) the partial low μ road is detected by the partial low μ road detection means, and At least when the vehicle body deceleration is small, the pressure reducing gradient reducing means for substantially grading the pressure reducing gradient is included.

[0008]

When a vehicle equipped with the anti-skid control device of the present invention passes through a partial low μ road during braking, the wheel speed decreases and the slip becomes excessive, so the anti-skid control is started and the brake fluid pressure is increased. It is reduced by the brake fluid pressure control means. However, during the passage of the partial low μ road, that is, before the start of the anti-skid control or during the depressurization at the beginning of the control, the partial low μ road may be a partial low μ road.
It is detected by the road detecting means, and the pressure reducing gradient is made gentle by the pressure reducing gradient reducing means.

The depressurization gradient may be made gentle regardless of the magnitude of the vehicle body deceleration, or may be made gentle only when the vehicle body deceleration is small. However, in the former case, it is only necessary to correctly detect that the vehicle is on a partial low μ road.However, as described above, when an erroneous determination is made that the vehicle is on a partially low μ road when the vehicle deceleration is large. Has a demerit that slip becomes excessive because the pressure reduction amount by the pressure reduction control becomes insufficient by making the pressure reduction gradient gentle. Moreover, the influence of the erroneous determination becomes particularly large when the vehicle body deceleration is large. Therefore, when the depressurization gradient is made gentle regardless of the magnitude of the vehicle body deceleration, it is desirable to make the degree of graduation relatively small when the vehicle body deceleration is large. For the same reason, the latter mode in which the decompression gradient is not made gentle when the vehicle deceleration is large and is made gentle only when the vehicle deceleration is small may be possible.

In order to substantially make the depressurization gradient gentle, for example, switching between depressurization and holding may be repeated after the partial low μ road is detected, or the flow passage area of the brake fluid may be narrowed. However, the depressurization may be switched to the holding for a set time during the depressurization. Even in the latter case, if the decompression and the holding are considered equally, the decompression gradient is substantially gentle.

The anti-skid control is started when the wheel speed decreases and the slip becomes excessive, and the pressure is reduced. Then, when the decompression amount reaches a certain amount, the wheel speed starts to increase, and the decompression is terminated accordingly. on the other hand,
Similarly, the anti-skid control is started when the vehicle passes through the partial low μ road during braking, but the wheel speed starts to increase after passing through the partial low μ road. This is not because the amount of pressure reduction reached the required amount, but because the road passed through the partial low μ road. In other words, the decompression is terminated when the wheel passes through the partial low μ road regardless of the decompression amount. Therefore, by making the decompression gradient gentle, it is possible to reduce the decompression amount until the decompression is completed after passing through the partial low μ road.

[0012]

According to the anti-skid control device of the present invention, the fact that the road is a partial low μ road means that the road is passing through the partial low μ road, that is, before the start of the first pressure reduction or during the pressure reduction. When it is detected and at least the deceleration of the vehicle body is small, the depressurization gradient is made gentle. Therefore, it is possible to suppress unnecessary depressurization and prevent the braking distance from increasing.

Moreover, since the anti-skid control is not ended only by substantially reducing the depressurization gradient, the anti-skid control is performed even if it is erroneously determined that the road is a partial low μ road. That is, it is possible to favorably prevent the slip of the wheels from being significantly increased and the braking distance to be extended.

In particular, when the vehicle body deceleration is large, in a mode in which the degree of depressurization gradient is moderated or is not moderated, it is erroneously detected as a partial low μ road during traveling on a high μ road. Also, it is possible to better prevent the slip from becoming excessive due to the lack of the reduced pressure amount.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 4 shows a hydraulic brake device equipped with an anti-skid control device according to an embodiment of the present invention. 10 _FL ,
10 _FR is the left and right front wheels of the automobile, and 10 _RL and 10 _RR are the left and right rear wheels. These wheels are provided with brakes operated by brake cylinders 20 _FL , 20 _FR , 20 _RL , and 20 _RR , respectively.

Brake cylinders 20 _FL , 20 _FR , 20 _RL
Normally, the brake fluid pressure generated in the master cylinder 32 in response to the operation of the brake pedal 30 is transmitted to and 20 _RR. However, since this brake fluid pressure is excessive in relation to the friction coefficient of the road surface, Wheel 10 _FL , 1
When the slip ratio such as 0 _FR , 10 _RL , 10 _RR, etc. increases beyond the proper range, the anti-skid controller 34 controls the brake fluid pressure. Anti-skid controller 3
4 is a wheel speed sensor 40 _FL , 40 _FR , 40 _RL , 40 _RR ,
It comprises actuators 50 _FL , 50 _FR , 50 _RL , 50 _RR and a control unit 58. A brake switch 59 for detecting depression of the brake pedal 30 is also connected to the controller 58. Actuator 50 _FL , 50 _FR , 5
The 0 _RL and 50 _RR are equipped with a power hydraulic pressure source, a reservoir, a 3-position solenoid valve, etc., and the 3-position solenoid valve controls the brake fluid pressure by switching between a pressure increasing position, a holding position, and a pressure reducing position. It is a thing.

The control unit 58 is mainly composed of a computer, and its configuration is conceptually shown in FIG. The vehicle speed deceleration calculation means 60 includes a wheel speed sensor 4
The vehicle speed, the vehicle deceleration, the wheel acceleration, etc. are calculated based on the output values of 0 _FL , 40 _FR , 40 _RL , and 40 _RR , and these output values are used for the partial low μ road detection means 62 and the pressure reduction gradient reduction means. 64, and is supplied to the brake fluid pressure control means 66. The partial low μ road detection means 62 detects that the road is a partial low μ road or the like based on the wheel acceleration or the like, and the output signal thereof is supplied to the pressure reduction gradient reduction means 64.

In the present embodiment, the partial low μ road detecting means 62 detects a step, and the fact that it is a step, that is, that the vehicle is passing through a step means that the front wheels 10 _FL , 10 _FR.
Regarding, regarding the front wheels 10 _FL and 10 _FR , within a certain time (for example, within 12 ms) after the wheel acceleration of the front wheels 10 _FL and 10 _FR becomes a certain value G ₁ or less.
Is detected when the wheel acceleration falls below the threshold value of -10 G. In this embodiment, the step is detected before the start of the anti-skid control.

Further, the front wheels 10 _FL and 10 _FR have a predetermined time (for example, 100 m) after being detected as a step.
In s), the step detection ends, such as the fact that the rear wheels 10 _RL and 10 _RR have been detected to have passed the step, that the anti-skid control has ended, and that it was determined that the step was incorrect. When the condition is satisfied, the step detection is ended. Here, it is determined that the step determination is erroneous because the condition that the wheel acceleration exceeds the threshold value 10G within the set time after the step is determined when the depressurization time becomes equal to or more than the set value is satisfied. For example, if there is no

The step detection for the rear wheels 10 _RL and 10 _RR is
This is performed by starting the anti-skid control on the rear wheels 10 _RL , 10 _RR within a fixed time period after the step is detected on the front wheels 10 _FL , 10 _FR . This is because, when it is determined that there is a step difference based on the acceleration of the wheels as described above, the determination for the front wheels 10 _FL and 10 _FR is relatively accurate, but the rear wheels 10 _FL and 10 _FR are relatively accurate. _RL ,
This is because it is difficult to make an accurate determination for 10 _RR . Since the rear wheel load becomes smaller than the front wheel load due to the load transfer during braking, the braking force of the rear wheels 10 _RL and 10 _RR is
It is smaller than the braking force of 0 _FL , 10 _FR , and the wheel deceleration at the time of passing a step is not as large as that of the front wheels 10 _FL , 10 _FR , so it is difficult to distinguish from the normal anti-skid control and the step determination is accurate. It is difficult to do.

The termination of the step detection for the rear wheels 10 _RL , 10 _RR is carried out when substantially the same conditions as the conditions for the front wheels 10 _FL , 10 _FR are satisfied, but the respective set values and threshold values relate to the front wheels. It is set to a value smaller than the condition. Also, when it is detected that the step determination on the front wheels 10 _FL and 10 _FR is incorrect, the step detection is ended.

When the partial low μ road is detected, the pressure reducing gradient reducing means 64 obtains the duty control ratio from the table of FIG. 3 based on the vehicle deceleration and supplies the signal to the brake hydraulic pressure controlling means 66. Is. As shown in FIG. 3, the duty control ratio is such that the decompression time is short and the holding time is long when the vehicle deceleration is small, and the decompression time is long and the holding time is short when the vehicle deceleration is large. It has been decided.

The brake fluid pressure control means 66 controls the vehicle speed,
The brake cylinders 20 _FL , 20 _FR , 2 are set so that the slip ratio of the wheels is kept within an appropriate range based on the wheel speed and the like.
It controls the liquid pressure of 0 _RL and 20 _RR . Further, the pressure reduction gradient is controlled based on the output signal of the pressure reduction gradient reducing means 64 and the like. That is, the actuators 50 _FL , 50 _FR , 5
The 0 _RL and 50 _RR are made to perform pressure reduction and holding of the duty control ratio shown in FIG. 3 only once.

A case where a vehicle equipped with the above-mentioned brake device passes a step will be described with reference to FIG. When the front wheels 10 _FL and 10 _FR pass through the step during braking, the wheel speed decreases and the wheel acceleration decreases. At time P1, the wheel acceleration Gw becomes smaller than the set value G ₁ . At a time point P2 within 12 ms from the time point P1, the wheel acceleration is equal to or less than the threshold value -10 G, and thus it is detected as a step. When the step is detected, the duty control ratio is obtained from FIG. 3 based on the magnitude of the vehicle body deceleration. afterwards,
The anti-skid control is started at the time point P3 when the wheel speed becomes equal to or lower than the reference wheel speed. At the beginning of the pressure reduction, the actuators 50 _FL and 50 _FR are driven based on the above duty control ratio. In the case shown in the figure, since the vehicle body deceleration is small, the holding time is long and the depressurization gradient is loosened to a large extent. After that, similar to the normal anti-skid control, sudden pressure reduction, holding, and pulse pressure increase are performed, but if the condition that the wheel acceleration is 10 G or more is satisfied during the step detection (time point P4), the anti-skid control is performed. The skid control is ended and the step detection is ended.

In this way, if the step is detected, the duty control ratio is obtained based on the table of FIG. 3, and the pressure reduction gradient is made substantially gentle. Meanwhile, front wheels 10 _FL , 1
When 0 _FR passes through the step, the wheel speed is recovered, and accordingly, the holding and the pulse pressure increase are sequentially performed, and in the conventional case shown by the broken line (by the anti-skid control device described in Japanese Patent Laid-Open No. 2-249752). When compared to the case), less braking force is needed.

Next, a case where it is detected that a step difference has been passed when it is not actually a step difference will be described with reference to FIG. Similarly to the above, at time P5, the wheel acceleration Gw becomes equal to or less than the set value G ₁ and at time P6, it is detected that there is a step. Further, at time P7, the anti-skid control is started, and the pressure reduction gradient is controlled according to the magnitude of the vehicle body deceleration. In this case, since the vehicle body deceleration is large, the decompression gradient is made less gentle, and the decompression is performed with a substantially steeper gradient than when the vehicle body deceleration is small. Then, as in the case above, sudden decompression, holding,
Pulse pressure boosting is performed. However, in this case, since the wheel acceleration does not become 10 G or more within the set time after the step is detected, it is determined that the step determination is an erroneous determination, and the step detection is ended. Control continues.

At the time of anti-skid control on the high μ road, the wheel speed changes rapidly, and the influence of the delay of the hydraulic control becomes relatively larger than that on the low μ road. Even if the step is erroneously detected, if the vehicle deceleration is large, the depressurization is performed at a relatively steep gradient, and thus the insufficient depressurization amount is satisfactorily avoided.
Further, unlike the control by the conventional device, the anti-skid control cannot be ended when the step is detected, so that excessive slip is favorably avoided.

As in the above two control examples, a step is detected before the start of the anti-skid control, and the pressure reduction gradient is substantially moderated at the beginning of the anti-skid control to wait for the wheel speed to recover. The extension of the braking distance due to unnecessary decompression is favorably avoided. Moreover, when the vehicle body deceleration is large, the degree to which the decompression gradient is made gentle is reduced, and therefore, even if the step determination is erroneous, the decompression amount will not be insufficient.

Further, since the duty control ratio determined based on FIG. 3 is output at the beginning of depressurization, the holding state is maintained for the set time, and the depressurization gradient is well controlled. In order to control the depressurization gradient, it is possible to repeat depressurization and holding for a very short period of time, or to change the flow passage area of the brake fluid, but in the former case, a solenoid valve with good response is used. In the latter case, there is a problem in that the flow rate control valve must be separately provided, resulting in an increase in cost and a heavy weight.
On the other hand, as in the present embodiment, when the depressurization gradient is substantially moderated by switching to the holding state at the beginning of depressurization for a certain period of time, an inexpensive solenoid valve with poor responsiveness may be used. It is possible to satisfactorily control the pressure reduction gradient.

Further, the pressure reduction gradient is substantially made gentle by holding the pressure reduction at the beginning of the pressure reduction, and the rapid pressure reduction is performed after the pressure retention is completed. Therefore, in the unlikely event that the step difference is erroneously determined, rapid depressurization will be performed, so compared with the case where the depressurization gradient is made gentle by repeating depressurization and holding, or by narrowing the flow passage area. It is possible to satisfactorily prevent the wheel from becoming locked due to insufficient decompression.

Next, the detection of the step difference in the rear wheels 10 _RL and 10 _RR and the hydraulic control associated therewith will be described. Regarding the rear wheels 10 _RL and 10 _RR , the rear wheels 10 _FL and 10 _FR fall within the set time range after it is detected that the front wheels 10 _FL and 10 _FR are passing the step.
_{When the} anti-skid control is started for _RL and 10 _RR , it is detected that the vehicle is passing a step. Here, the set time range is determined based on the vehicle speed V and the wheel base L. That is, theoretically, after the front wheel passes the step and the rear wheel passes the step after a lapse of time (L / V), the set range is set as a range before and after the time L / V. . In this embodiment, the vehicle body speed V is 2
When it is 2.2 m / sec (80 km / h) or more, the setting range is set to 0 to 50 ms, and when it is less than 22.2 m / sec, it is set to 0 to 100 ms.

When a step is detected with respect to the rear wheels 10 _RL and 10 _RR , the duty control ratio is obtained based on the magnitude of the vehicle body deceleration similarly to the front wheels 10 _FL and 10 _FR. Based on the actuator 50 _RL , 5
0 _RR is driven. After that, normal anti-skid control by rapid pressure reduction, holding, and pulse pressure increase is performed. Further, when the above-mentioned step detection end condition is satisfied, the step detection is ended.

As described above, when the anti-skid control is started for the rear wheels within a certain period of time after the front wheel is detected as a step, it is detected that the rear wheel is passing the step. However, there is a possibility that the step detection on the front wheels is incorrect. That is, even if the step detection on the front wheels is erroneous, if the above conditions are satisfied on the rear wheels, it is detected that there is a step on the rear wheels, and the pressure reduction gradient is moderated according to the vehicle deceleration. However, after that, when it is detected that the step detection on the front wheels is an erroneous determination, the step detection on the front wheels is ended and the step detection on the rear wheels is also ended. In addition, when the step detection on the front wheels is correct, if the rear wheels satisfy the above condition and it is detected that the rear wheels are the step, it is very unlikely that the step detection on the rear wheels is erroneous.

As described above, since it is accurately determined whether or not the rear wheels 10 _RL and 10 _RR are passing through a step, it is possible to satisfactorily control the decreasing gradient of the brake fluid pressure of the rear wheels, and thus the vehicle. The stability can be improved. Further, if it is detected that the step difference in the front wheel is erroneous, the step difference detection in the rear wheel is also ended, so that the influence of the erroneous determination in the rear wheel can be reduced.

In this embodiment, the step detection on the front wheels is detected before the start of the anti-skid control. However, the anti-skid control may be detected together with the detection before the start of the anti-skid control or instead of the detection. It is also possible to detect during decompression after the start. In this case, the pressure reduction gradient is relaxed at the time when a step is detected during pressure reduction.

Further, in this embodiment, the degree of loosening of the decompression gradient can be changed based on the magnitude of the vehicle body deceleration, and even when the vehicle body deceleration is large, the decompression gradient by the normal anti-skid control is changed. Although it is made more gradual, when the vehicle body deceleration is large, it is possible to prevent the pressure reduction gradient from being loosened or to make it more steep than the normal pressure reduction gradient by the anti-skid control.

Further, in this embodiment, when the anti-skid control is started for the rear wheels within the set time range after it is detected that the front wheels are stepped, it is judged that the rear wheels are passing the step. However, when the anti-skid control is started for the rear wheels within the set time range after the anti-skid control is started for the front wheels, it may be determined that there is a step.

In addition to the above conditions, the step determination condition for the rear wheels may be that the rear wheel acceleration is smaller than a negative threshold value larger than the front wheel acceleration threshold value.

Further, with respect to the rear wheels, the level difference may be determined under the same conditions as the front wheels. However, even in that case, it is better to change the threshold value and the like from those for the front wheels.

Although not specifically exemplified, the present invention can be carried out in variously modified and improved modes based on the knowledge of those skilled in the art without departing from the scope of the claims.

[Brief description of drawings]

FIG. 1 is a diagram showing changes in front wheel speed and brake fluid pressure when a vehicle equipped with a brake device including an anti-skid control device according to an embodiment of the present invention passes through a step.

FIG. 2 is a diagram showing changes in front wheel speed and brake fluid pressure when antiskid control is started during braking of the vehicle on a high μ road.

FIG. 3 is a table showing a relationship between wheel deceleration and duty control ratio stored in a ROM of the anti-skid control device.

FIG. 4 is a schematic diagram showing a configuration of a brake device of the above embodiment.

FIG. 5 is a diagram conceptually showing the structure of a control unit in the above embodiment.

FIG. 6 is a diagram showing changes in wheel speed and brake fluid pressure when a vehicle equipped with a conventional anti-skid control device passes a step.

FIG. 7 is a block diagram of the conventional anti-skid control device.
Wheel speed when it is mistakenly determined to be a step,
It is a figure which shows the change of brake hydraulic pressure.

[Explanation of symbols]

20 _FL , 20 _FR , 20 _RL , 20 _RR Brake cylinder 50 _FL , 50 _FR , 50 _RL , 50 _RR Actuator 34 Anti-skid control device 60 Vehicle deceleration calculation means 62 Partial low μ road detection means 64 Decompression gradient reduction means 66 Brake fluid pressure control means

Claims (1)

[Claims] 1. A brake fluid pressure control means for keeping a slip ratio of a wheel within an appropriate range by increasing and decreasing a brake fluid pressure, and a portion for detecting a partial low μ road while passing through a partial low μ road. A low μ road detection means, and a pressure reduction gradient reduction means for substantially gentle pressure reduction gradient when the partial low μ road is detected by the partial low μ road detection means and at least the vehicle body deceleration is small An anti-skid control device characterized in that