JP3328325B2 - Anti-skid brake system for all-wheel drive vehicles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anti-skid brake device for an all-wheel drive vehicle.

[0002]

2. Description of the Related Art Recently, as is well known by the name of an ABS device, an anti-skid brake device for preventing wheels from locking during braking has been mounted on many vehicles. At the time of the ABS control, that is, the braking force control, there are at least two types of control modes, that is, the control of the braking force decrease and the control of the braking force increase.

[0003] Whether or not the wheels are locked can usually be determined by a slip value (lock value) obtained from the pseudo vehicle body speed theoretically obtained and the actual wheel speed.
Therefore, it can be determined whether or not to start the braking force control by determining whether or not the slip value has exceeded a predetermined threshold value. In this case, the larger the pseudo vehicle speed is set to a larger value, the stronger the tendency of the wheels to be locked, and the control mode is such that the braking force is reduced.

The deceleration of a wheel can be easily and accurately obtained by differentiating the wheel speed detected by a wheel speed sensor, while the deceleration of the wheel indicates the behavior of the wheel quite accurately. Becomes From such a viewpoint, it can be determined whether or not to start the ABS control by determining whether or not the wheel deceleration exceeds a predetermined threshold value.

On the other hand, in an all-wheel drive vehicle in which all wheels are drive wheels, for example, in a four-wheel drive vehicle, the pseudo vehicle speed is set to 4
It is common practice to set the maximum driving wheel speed among the two driving wheel speeds. In other words, on the assumption that all the drive wheels are not locked at the same time, the maximum drive wheel speed closest to the value indicating the vehicle speed is set as the pseudo vehicle speed (Japanese Utility Model Laid-Open No. 63-46276). reference).

[0006]

The ABS control is started when the condition that the locking tendency of the wheels is strong is satisfied, and the above-mentioned condition used for determining the locking tendency as the starting condition is determined. The wheel deceleration and the slip value indicate a certain temporary behavior of the wheel.

Therefore, starting the ABS control by judging the locking tendency based only on the deceleration and the slip value may unnecessarily lower the braking force due to the influence of noise or the like. For example, since the tire that forms the contact surface with the road surface is an elastic body, it exhibits a large deceleration momentarily at the beginning of braking, and then exhibits a behavior such that the deceleration becomes small thereafter (tire rolling back phenomenon). As a result, a situation in which the ABS control is started and the braking force is unnecessarily reduced is likely to occur.

Further, in an all-wheel drive vehicle, since each drive wheel is directly connected to each other, it is likely to vibrate under the influence of the behavior of the other wheels, particularly to vibrate at the time of braking. Cause it to start.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an anti-skid brake device for an all-wheel drive vehicle which prevents ABS control from being erroneously started. .

[0010]

Means for Solving the Problems To achieve the above object, the present invention has the following configuration. That is, in an anti-skid brake device of an all-wheel drive vehicle in which all wheels are set as drive wheels and braking force control is performed so that the wheels do not lock during braking, vehicle speed detecting means for detecting vehicle speed Wheel speed detecting means for detecting a rotation speed of a wheel; deviation determining means for calculating a deviation between a vehicle speed detected by the vehicle speed detecting means and a wheel speed detected by the wheel speed detecting means; An integrating means for integrating the deviation determined by the means for a predetermined number of times; a starting means for starting the braking force control when the integrated value integrated by the integrating means satisfies a starting condition of not less than a predetermined value; And a prohibition unit for prohibiting the start of the braking force control based on the integrated value when the acceleration detection unit detects the acceleration of the vehicle.

The start of the braking force control based on the integrated value can be executed on condition that the brake operation has been performed, and also can be executed on condition that the accelerator is fully closed.

[0012]

The integrated value obtained by the integrating means becomes an integrated value indicating how much the deviation between the vehicle speed and the wheel speed has decreased within a predetermined time, while the deviation temporarily increases due to vibration or the like. However, the integrated value does not increase so much. Therefore, by setting that the integrated value is equal to or larger than a predetermined value as the start condition of the ABS control, it is extremely effective in preventing a situation in which the ABS control is erroneously started.

In addition, when accelerating, particularly when accelerating on slippery roads such as snowy roads, even in an all-wheel drive vehicle, a considerable amount of drive wheels slip. At this time, there is a case where the rotation speed of another drive wheel increases after a delay from the increase in the rotation speed of a certain drive wheel. In such a case, the integrated value increases in a relatively short time and exceeds a predetermined value. It will be easy. However, according to the present invention, the ABS control is not started based on the integrated value at the time of acceleration at which the integrated value is not expected to accurately reflect the lock of the wheel. It can be further prevented.

The configuration as described in claim 2 or 3 is preferable for further preventing erroneous start of the ABS control.

[0015]

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

Each of the wheels 1FR to 1RL is provided with a brake 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 having a built-in wheel cylinder.

Numeral 13 denotes a brake fluid pressure adjusting device, which is connected to a pipe 14, 15, 16 or 1
7, brake devices 12FR to 12RL for each wheel
And are connected independently. The brake fluid pressure from a master cylinder (not shown) is supplied to the fluid pressure adjusting device 13. In the ABS control, the fluid pressure supplied to the pipes 14 to 17 is independently controlled. In addition, three states of a braking force decrease (fluid pressure decrease), a braking force increase (hydraulic pressure increase), and a braking force holding (hydraulic pressure holding) 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 brake devices 12FR to 12RL as it is. In addition,
Since the fluid pressure adjusting device 13 itself that performs such an operation is well known, further description is omitted.

U is a control unit constructed by using a microcomputer. The control unit U receives signals from at least each sensor or switches S1 to S6, while the control unit U receives a hydraulic pressure. Adjustment device 1
3, a predetermined control signal is output. Each of the above sensors S1 to S1
S4 is a wheel speed sensor that independently detects the drive wheel speed of each of the drive wheels 1FR to 1RL. The switch S5 is a brake for detecting whether the brake pedal is depressed or not.
Key switch. The switch S6 is an accelerator switch for detecting whether the accelerator is fully closed or below.

Description of FIG . 2 The contents 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 the meaning is as follows. Phase 0: means that non-ABS control is being performed. Phase 1: means pressure increase (braking force increase). Phase 2: Holding after non-ABS control or after pressure increase (braking force holding). Phase 3: Means pressure reduction (braking force reduction). Phase 5: means holding after decompression. The slip value indicating the tendency to lock the wheels is determined, for example, by the following equation. The estimation of the pseudo vehicle speed will be described later. Of course, the smaller the slip value, the stronger the tendency to lock the drive wheels, indicating that the braking force is reduced (the brake fluid pressure is reduced) by the ABS control. "Slip value = (wheel speed / pseudo vehicle speed) x 100%"

On the premise of the above, the ABS control is not performed until time t1, and the wheel speed, that is, the driving wheel speed increases as the brake fluid pressure increases (generally, the maximum driving wheel speed). Speed). Due to the decrease in the drive wheel speed, at time t1, that is, at the time A, the deceleration of the drive wheel speed increases to a predetermined value as the ABS control start condition.

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

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

The above is an outline of the ABS control. One cycle of control is a period from the end of the phase 5 (start of pressure increase) to be maintained after the pressure reduction to the end of the next phase 5. However, this one cycle is a failure only when the ABS control starts.
The period 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 in accordance with the road surface μ (coefficient of friction), and specific examples of the threshold value in accordance with the road surface μ are shown in the following table.

[0024]

[Table 1]

The illustration 3 in FIG. 3, flow showing a control example of the present invention - are bets, - Cha
In the following description, P indicates a step. In the following description, the acceleration is a value when the speed is increasing with a positive acceleration, and the deceleration is a value when the speed is decreasing with a negative acceleration. That is, in the following description, a large acceleration means that the degree of speed increase is large, and a large deceleration means that the degree of speed decrease is large.

First, at P1, the brake switch S
By checking the signal from 5, it is determined whether or not the brake pedal is depressed. Y in P1 discrimination
In the case of ES, at P2, it is determined whether or not the accelerator is fully closed. If the determination in P2 is YES, P3
In, it is determined whether or not the vehicle is accelerating. This determination as to whether or not the vehicle is accelerating can be made, for example, by checking whether or not one driving wheel speed or a plurality of (for example, all) driving wheel speeds are increasing. Of course, the detection of the acceleration can be performed by a known appropriate method such as an increase in the accelerator opening.

If the determination in P3 is NO, in P4, the driving wheel speed is subtracted from the vehicle speed (a pseudo vehicle speed, in this embodiment, the maximum wheel speed is set as the pseudo vehicle speed among the four driving wheel speeds). The deviation DV is calculated. Then
At P5, the deviation DV is integrated. Thereafter, in P6, it is determined whether the integrated DV is equal to or greater than a predetermined value.

If the determination in P6 is NO, in P7, it is determined whether or not a large deceleration greater than a predetermined value has occurred in the driving wheels. If the determination in P7 is NO, in P8, it is determined whether a predetermined time has elapsed from the start of the integration in P5. If the determination in P8 is NO, the process returns to P4, and the deviation DV continues to be accumulated in this way.

When the determination at P6 is YES, or at P7
If the determination is YES, in P9, the aforementioned AB
S control is started. In the determination of P7, a slip value may be used instead of the deceleration. If the determination in P8 is YES, it means that the integrated DV has not reached a predetermined value or more. In this case, the process returns to P1 without starting the ABS control.

When the determination in P1 is NO, when the determination in P2 is NO, and when the determination in P3 is YES, the process shifts to P10 to determine whether a large deceleration has occurred in the driving wheels. (Same as P7). If the determination in P10 is YES, ABS control is started in P9,
When the determination in P10 is NO, the control is returned without starting the ABS control.

Description of FIG . 4 Of the above- described control contents, attention will be given to P3 to P7 in FIG. 3 and further detailed description will be made with reference to FIG. First,
At the time t11 due to acceleration, the drive wheels start to slip (become over-rotated with respect to the road surface). The solid line indicates the drive wheel speed of one drive wheel, and the broken line indicates the drive of another drive wheel. Indicates the wheel speed. The drive wheel speed indicated by the solid line shows a relatively large upward trend, while another drive wheel speed shows a gentler upward trend. Such a phenomenon is unlikely to occur on a road surface having a large friction coefficient, but tends to occur on a slippery road surface such as a snowy road. As described above, while the increasing tendency of the drive wheel speed is considerably different, when the vehicle speed (pseudo-vehicle speed) is set as the maximum drive wheel speed, the integrated DV becomes a predetermined value or more at time t12, which is a relatively short time, and is indicated by a broken line. It is determined that the drive wheel corresponding to the drive wheel speed indicated by lock has been locked, and the ABS control is started.

However, since the start of the ABS control based on the integrated DV is prohibited during acceleration, a situation in which the ABS control is erroneously started during acceleration as shown in FIG. 4 is prevented. In addition, by performing the determination of P1 and P2, it is possible to more accurately determine whether or not the vehicle is accelerating, to more accurately grasp the state where the ABS control is not required, and to erroneously start the ABS control. Is more reliably prevented. The start of the ABS control based on the integrated DV may be prohibited even when the vehicle is turning.

[Brief description of the drawings]

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

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

FIG. 3 is a flowchart showing a control example for determining whether to start ABS control.

FIG. 4 is a time chart for schematically explaining the control example shown in FIG. 3 while focusing on acceleration.

[Explanation of symbols]

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

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B60T 8/58

Claims (3)

(57) [Claims] 1. An anti-skid brake system for an all-wheel drive vehicle in which all wheels are driven wheels and braking force control is performed so that the wheels do not lock during braking. Vehicle speed detection means, wheel speed detection means for detecting the rotation speed of the wheels, deviation determination means for calculating the deviation between the vehicle speed detected by the vehicle speed detection means and the wheel speed detected by the wheel speed detection means, Integrating means for integrating the deviation determined by the deviation determining means for a predetermined number of times; and starting means for starting the braking force control when an integrated value integrated by the integrating means satisfies a starting condition of not less than a predetermined value. And acceleration detecting means for detecting acceleration of the vehicle, and prohibiting means for prohibiting start of the braking force control based on the integrated value when the acceleration detecting means detects acceleration of the vehicle. To Characteristic anti-skid brake device for all-wheel drive vehicles 2. A method according to claim 1, wherein said braking force control based on the integrated value starts, blurring - is executed on condition that the key has been operated, and characterized in that
Anti-skid brake device for all-wheel drive vehicles . 3. The method of claim 1, wherein the start of the braking force control based on the integrated value, the accelerator is performed subject to the limitation that fully closed, that
Anti-skid brake device for all-wheel drive vehicles .