JPH0624319A - Anti-skid brake device for vehicle - Google Patents

Abstract

PURPOSE:To prevent generation of synchronous vibration between plural wheels under ABS control. CONSTITUTION:Under ABS control, if a condition of locking tendency becoming stronger is detected when brake force rising control is not performed, control of reduction of the brake force is prohibited, and a brake force holding control condition, for example, is forcedly made during this prohibition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle anti-skid brake device.

[0002]

2. Description of the Related Art Recently, as is well known by the name of ABS device, many vehicles are equipped with an anti-skid brake device for preventing the wheels from locking during braking. In the ABS control, that is, the braking force control, there are at least two types of control modes, that is, a control for decreasing the braking force and a control for increasing the braking force, and in addition, there is also a control mode for holding the braking force.

Contrary to the ABS control, there is also known traction control in which when a wheel excessively rotates with respect to a road surface, braking force control is performed on the over-rotated wheel by decreasing the braking force and increasing the braking force. Has been. In this traction control, in order to prevent control hunting, when the wheel speed exceeds a predetermined threshold value twice within a predetermined time,
It has also been proposed to delay the start timing of the control for decreasing the braking force or the control for increasing the braking force (JP-A-1-14115).
(See Japanese Patent Publication No. 5).

[0004]

In the ABS control, the wheels may vibrate due to various factors during the braking force control. When such a vibration occurs, at least a plurality of wheels that are in a torque transmission relationship are synchronized with each other, and the braking force control is performed following this vibration. Or
The braking force is unnecessarily reduced, which is not preferable for securing a sufficient braking force.

The above-mentioned vibration of the wheel is caused, for example, by elastic deformation of the tire or by twisting of the drive system. This is particularly noticeable in the case of an all-wheel drive vehicle in which all the drive wheels have a torque transmission relationship.

Therefore, it is an object of the present invention to provide an anti-skid brake device for a vehicle which can prevent synchronous vibrations between a plurality of wheels.

[0007]

In order to achieve the above object, the present invention has the following configuration. That is, in a vehicle anti-skid brake device in which the braking force is controlled at least by the braking force decrease and the braking force increase to prevent the wheels from being locked on the road surface, a specific state in which the tendency of the wheels to lock becomes strong is detected. And a prohibiting unit that prohibits the control of the braking force decrease when the specific state is detected by the specific state detecting unit when the control of the braking force increase is not performed. It is provided as a configuration.

The specific state detecting means may detect a high peak at which the acceleration becomes substantially zero after the wheel exhibits the acceleration.

When the braking force control is set to further hold the braking force and the prohibiting means prohibits the braking force control, the braking force holding control state can be set.

The prohibition by the prohibiting means can be performed only for a predetermined time.

The vehicle may be an all-wheel drive vehicle in which all wheels are drive wheels.

The object to be prohibited by the prohibiting means can be all the channels for which the braking force control is independently performed.

[0013]

EFFECTS OF THE INVENTION It can be considered that the fact that the locking tendency of the wheel becomes strong when the braking force increase control is not performed is due to the wheel vibration. Therefore, in such a case, by prohibiting the control of the reduction of the braking force, the vibration cycle between the plurality of wheels is shifted without causing the braking force to be insufficient, and the uncomfortable longitudinal vibration of the vehicle body is prevented. be able to.

With the structure as described in claim 2, it is possible to promptly know that the vibration of the wheel is generated as a factor having excellent responsiveness such as acceleration as a parameter. The effect described in 1 can be obtained with good response.

By adopting the structure as described in claim 3, it is possible to obtain the effect of claim 1 while obtaining well-balanced prevention of insufficient braking force and prevention of wheel locking.

By adopting the structure as described in claim 4, it is preferable in order to surely return to the original ABS control by minimizing the time for preventing the synchronous vibration.

By adopting the structure as described in claim 5, it is preferable for preventing the synchronous vibration of the all-wheel drive vehicle in which the synchronous vibration is a problem.

With the structure as described in claim 6, the vibration cycle is shifted for each channel, and the effect of claim 1 can be further enhanced.

[0019]

Embodiments of the present invention will be described below with reference to the accompanying drawings. Description of FIG. 1 1FR is the right front wheel, 1FL is the left front wheel, 1RR is the right rear wheel, 1
RL is the left rear wheel. Reference numeral 2 denotes an engine, and the torque generated by the engine 2 is transmitted to the center differential 5 via the clutch 3 and the transmission 4. The generated torque of the engine 2 transmitted to the center differential 5 is transmitted to the left and right rear wheels 1RR, 1RL via the propeller shaft 6 and the differential device 7, and then via the left and right drive shafts 8R or 8L. At the same time, the engine 2 transmitted to the center differential 5
After passing through the propeller shaft 9 and the differential device 10, the generated torque is transmitted to the left and right front wheels 1FR, 1FL via the left and right drive shafts 11R or 11L. In this way, the automobile is a four-wheel drive vehicle in which all four wheels 1FR to 1RL are drive wheels.

Each of the wheels 1FR to 1RL is provided with a braking device 12FR to 12RL. In the embodiment, each of the brake devices 12FR to 12RL is a disk brake including a disk that rotates integrally with a wheel and a caliper that incorporates a wheel cylinder.

Reference numeral 13 is a brake fluid pressure adjusting device, and this fluid pressure adjusting device 13 is provided with pipes 14, 15, 16 or 1.
Brake device 12FR to 12RL for each wheel via
And are connected independently. A brake hydraulic pressure from a master cylinder (not shown) is supplied to the hydraulic pressure adjusting device 13, and the hydraulic pressures supplied to the pipes 14 to 17 are controlled independently during ABS control. , A braking force decrease (liquid pressure decrease), a braking force increase (liquid pressure increase), and a braking force holding (liquid pressure holding) state are switched. Of course, when the ABS control is not performed, the hydraulic pressure adjusting device 13 supplies the brake hydraulic pressure from the master cylinder to each of the breaking devices 12FR to 12RL as it is. In addition,
Since the hydraulic pressure adjusting device 13 itself which performs such an operation is well known, further description will be omitted.

U is a control unit constructed by using a micro computer, and at least signals from respective sensors or switches S1 to S6 are inputted to the control unit U, while the control unit U outputs hydraulic pressure. Adjusting device 1
A predetermined control signal is output to 3. Each of the sensors S1 to S1
S4 is a wheel speed sensor that independently detects the driving wheel speeds of the driving wheels 1FR to 1RL.

Description of FIG . 2 The content of the ABS control by the control unit U will be described with reference to FIG. In this ABS control, Phase 0, Phase 1, Phase 2, Phase 3, Phase 5
Is used, and its meaning is as follows. Phase 0: Means that non-ABS control is in progress. Phase 1: means increasing pressure (increasing braking force). Phase 2: means holding (holding braking force) after non-ABS control or after pressure increase. Phase 3: means decompression (reduction of braking force). Phase 5: Retaining after depressurization. The slip value indicating the locking tendency of the wheels is determined by, for example, the following equation, and the estimation of the pseudo vehicle body speed will be described later. Of course, the smaller the slip value is, the stronger the locking tendency of the drive wheels is, and the braking force is reduced (the brake fluid pressure is reduced) by the ABS control. "Slip value = (wheel speed / pseudo vehicle speed) x 100%"

In the following description, the acceleration is when the speed is increasing due to the positive acceleration, and the deceleration is when the speed is decreasing due to the negative acceleration. That is, in the following description, a large acceleration means that the speed increases to a large extent, and a large deceleration means that the speed decreases to a large extent.

Based on the above, the ABS control is not performed until the time point t1, and the wheel speed, that is, the drive wheel speed is gradually reduced from the pseudo vehicle speed as the brake fluid pressure increases. To go. Due to the decrease in the drive wheel speed, the deceleration of the drive wheel speed increases to a predetermined value as the ABS control start condition at time t1, that is, time A.

The ABS control is started from the time point A, but it is performed by first maintaining the brake hydraulic pressure. Even during this holding, the driving wheel speed decreases, and when the slip value decreases to a predetermined threshold value as shown at time B, the pressure is reduced. Due to this pressure reduction, the degree of decrease in the drive wheel speed becomes weaker, and the deceleration becomes near 0 at the time C. At the time point C when the deceleration is near 0, the holding is performed, whereby the drive wheel speed gradually increases, and at the time point D, the slip value returns to the predetermined threshold value. From this point D,
The pressure is increased, but the pressure is rapidly increased in the initial stage and then gradually increased.

Due to the pressure increase, the deceleration of the drive wheel speed at time E again increases to the predetermined value set as the ABS control start condition. As a result, after the brake fluid pressure is maintained, when the slip value decreases to a predetermined threshold value at time F, pressure reduction is performed. Then, the brake fluid pressure is maintained from the time point G corresponding to the time point C.

The above is the outline of the ABS control, and the period from the end of the phase 5 (starting pressure increase), which is maintained after decompression, to the end of the next phase 5, is one control cycle. However, this one cycle is only for the start of ABS control.
From the start of holding Phase 2 to the end of Phase 5 (because the ABS control is started from Phase 2). The threshold value when the phase is changed is changed according to the road surface μ (friction coefficient), and a specific setting example of the threshold value according to the road surface μ is shown in the following table.

[0029]

[Table 1]

Description of FIGS . 3 and 4 FIG. 3 is a flowchart showing an example of control according to the present invention. In the following description, P indicates a step. First, at P1, signals from the sensors S1 to S4 are input, and then at P2, the acceleration / deceleration of each drive wheel is calculated based on each drive wheel speed.

At P3, it is judged if the ABS control is currently being performed. If the determination in P3 is NO,
Since it is an area unrelated to the control of the present invention, it is possible to directly
Will be When the result of the determination in P3 is YES, it is determined in P4 whether or not the braking force is currently increased (the brake fluid pressure is increased) (the phase 1 control state described above). Determining whether or not). When the determination in P4 is YES, the tendency of the wheels to lock becomes stronger under the control condition, so the routine is returned as it is.

When the determination in P4 is NO, it is determined in P5 whether or not the high peak is detected. As shown in FIG. 4, this high peak shows an acceleration in which the driving wheel speed that is decreasing is increasing, and then becomes the behavior when the acceleration becomes zero. In this way, the high peak is
It is caused by the vibration of the wheels, and after the acceleration becomes almost zero, it also shows a large deceleration.
Therefore, if the determination in P5 is YES, then P6 continues.
At, it is determined whether a large deceleration has occurred.

If the result of the determination in P6 is YES, it means that the wheel is vibrating, and in P7, the braking force reduction (reduction of the brake hydraulic pressure) is prohibited, and the braking force is forcibly maintained ( (Holds the brake fluid pressure at the current level)
Is controlled. Thereafter, in P8, it is determined whether or not a predetermined time has elapsed after the prohibition of the braking force reduction control in P7 was started. When the determination in P8 is NO, the process returns to P7, and when the determination in P8 is YES, the return is performed.
Will be

The above-described control of FIG. 3 is performed for all channels (pipes 14 to 17) whose hydraulic pressures are controlled independently.

Although the embodiment has been described above, whether or not the tendency of the wheels to lock becomes stronger can be determined based on the slip value. In the embodiment, the maximum drive wheel speed among the four drive wheel speeds is set as the pseudo vehicle speed for slip value calculation.

[Brief description of drawings]

FIG. 1 is an overall system diagram showing an embodiment of the present invention.

FIG. 2 is a time chart showing an example of ABS control.

FIG. 3 is a flow chart showing a control example for prohibiting control of braking force reduction.

FIG. 4 is an explanatory diagram showing a high peak.

[Explanation of symbols]

 1FR to 1FL: drive wheel 12FR to 12FL: brake device 13: hydraulic pressure adjusting device 14 to 17: brake pipe S1 to S4: sensor (drive wheel speed) U: control unit

Claims (6)

[Claims] 1. An anti-skid brake device for a vehicle, wherein at least a braking force control is performed by a braking force decrease and a braking force increase to prevent a wheel from locking on a road surface. Specific state detecting means for detecting a state, and prohibiting means for prohibiting the control of the braking force decrease when the specific state is detected by the specific state detecting means when the control for increasing the braking force is not performed. And an anti-skid brake for vehicles characterized by
Ki device. 2. The specific state detection means according to claim 2, which detects a high peak at which the acceleration becomes substantially zero after the wheel shows the acceleration. 3. The braking force holding control state according to claim 1, wherein the braking force control is set to further hold the braking force, and when the inhibition is performed by the inhibiting means. 4. The method according to claim 1, wherein the prohibition is performed only for a predetermined time. 5. The vehicle according to claim 1, which is an all-wheel drive vehicle in which all wheels are drive wheels. 6. The device according to claim 1, wherein all the channels for which the braking force control is independently performed are the targets to be inhibited by the inhibiting means.