JPH03159859A - Anti-skid braking method - Google Patents

Abstract

PURPOSE:To shorten the braking distance by providing a pressure boosting/ reducing map equipped with a rapid boosting mode besides brake pressure reducing mode, retaining mode, and boosting mode, and putting the appropriate control mode in effect on the basis of the wheel acceleration/deceleration and the slip amount during anti-skid control. CONSTITUTION:When anti-lock brake control is put in effect, the brake pressure in a wheel brake 6 for the wheel on which lock tendency is generated, is reduced by a brake pressure adjusting device 5 to be interposed in a brake circuit, and thereafter the brake pressure is boosted or retain. This brake pressure adjusting device 5 makes control on the basis of the outputs of a wheel speed sensor 9 and a brake switch 10 with the aid of an electronic controller 8. Therein a pressure boosting/reducing map is provided which shall be equipped as brake pressure control modes with a rapid boosting mode besides the reducing mode, retaining mode, and boosting mode. This rapid boosting mode shall be selected when the wheel acceleration/deceleration is over a positive acceleration value as specified and when the slip amount is below its specified value.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an anti-skid braking method for preventing wheels from locking during braking of a motor vehicle.

(Prior art) This type of anti-skid braking method prevents wheel slippage during braking while a car is running on a low μ road such as a rain-wet road or snowy road, or when driving on a high μ road. Among other things, it is effective in preventing wheel slippage, that is, locking, caused by sudden braking.This prevents the vehicle from skidding during braking, ensures its steering stability, and improves braking. The distance can also be shortened.

In fact, when implementing the anti-skid braking method, the wheel speed and reference vehicle speed are determined, the amount of wheel slip is calculated from the deviation of these, and the wheel brake is adjusted so that this amount of slip becomes optimal. This will control the pressure.

To explain this brake pressure control more specifically, when the amount of slip of a wheel increases during braking and a tendency to lock occurs, the brake pressure of that wheel is first reduced to release the tendency to lock. Ru. And after this,
By increasing or maintaining the brake pressure based on the amount of slip at that time, or decreasing the pressure as necessary, it becomes possible to stop the vehicle without causing the vehicle to skid.

(Problem to be Solved by the Invention) As described above, conventionally, after the anti-skid brake control is started and the brake pressure of a wheel that is prone to locking is once reduced, the brake is applied at a constant rate. I was trying to increase the pressure. However, with such a brake pressure increasing mote, even if the wheel acceleration/deceleration takes a large positive acceleration value, the brake pressure is only increased at a constant rate, so the brake pressure of the wheel is increased. As a result, the braking distance reduction efficiency could not be improved.

To explain this point further, first, it is known that the equation of motion of the wheel is determined by the following equation.

Iα=rFB −TB Here, ■ is the inertia of the wheel, α is the angular velocity of the wheel, r
is the radius of the wheel, FB is the braking force (frictional force with the road surface), TB
indicate the brake torque, respectively.

Here, when the wheel acceleration/deceleration takes a large positive acceleration value, it means that the angular velocity α of the wheel takes a large positive value, and in this case, the brake torque T
B This indicates that the brake pressure is too low. If the brake pressure is low in this way, as mentioned above, the braking of that wheel will not work effectively, and as a result,
The braking distance of a car becomes long.

This invention was made based on the above-mentioned circumstances, and
The purpose of this is to reduce the brake pressure of a wheel that has a tendency to lock, and then increase the brake pressure optimally according to the rotational trend of that wheel, thereby greatly shortening the braking distance. The purpose is to provide a method for skid braking that is possible.

(Means for Solving the Problems) In the anti-slip braking method of the present invention, each control mode of brake pressure is divided into a pressure reduction mode, a holding mode, and a pressure increase mode based on the relationship between wheel acceleration/deceleration and slip amount. A pressure increase/decrease map is prepared in advance, and during anti-skid brake control, a control mode selected from the pressure increase/decrease map is implemented based on the wheel acceleration/deceleration and slip amount at that time to control the brake pressure. The pressure increase/decrease map is selected and executed when the wheel acceleration/deceleration is greater than or equal to a positive predetermined acceleration value and the slip amount is less than or equal to a predetermined value, and the braking is performed more quickly than in the pressure increase mode mentioned above. It further includes a rapid pressure increase mode to increase the pressure.

(Operation) According to the anti-skid braking method described above,
In the pressure increase/decrease map, a rapid pressure mode is provided separately in addition to the pressure increase mode, so when the wheel acceleration/deceleration exceeds a predetermined positive acceleration value, the rapid pressure mode is implemented and the brake pressure is quickly increased. You can make the brakes work more effectively by pressing the brakes. In addition, when surge pressure mode 1 is selected, there is a condition that the amount of slip is less than a predetermined value, so when the amount of slip is large, surge pressure mode is implemented, which may lead to wheel locking. Nor.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 schematically shows the structure of an anti-skid brake device installed in an automobile, and this anti-skid brake device is equipped with a tandem mask cylinder l equipped with a vacuum brake booster. This mask cylinder l is actuated by a brake pedal 2.

Two master cylinder side brake pipes 3, 4 extend from the mask cylinder l, and these mask cylinder side brake pipes 3.4 extend through the brake pressure adjustment device 5, and are connected to the front wheel FW and the rear wheel. It is connected to the RW wheel brake 6 via a corresponding branch brake line 7. In this embodiment, the brake line 3 is connected from the brake pressure regulator 5 to the wheel brakes 6 of the front right wheel and the rear left wheel via two brake lines 7, respectively. The conduit 4 is connected from the brake pressure adjustment device 5 to the wheel brakes 6 of the left front wheel and the right rear wheel via the remaining two brake conduits 7, respectively.

That is, the brake pipes extending from the mask cylinder 1 to each wheel brake 6 are arranged in a so-called diagonal split system.

The brake pressure adjustment device 5 is configured to
When one wheel tends to lock and anti-skid brake control (ABS) is started, by reducing the brake pressure in the wheel brake 6 for that wheel,
The locking tendency of the wheels is released, and then the brake pressure is increased or maintained depending on the rotational trend of the wheels.

As the above-mentioned brake pressure adjustment device 5 is known to have various structures, a description of the brake pressure adjustment device will be omitted here, but the operation of this type of brake pressure adjustment device 5 is basically It is designed to be controlled by an electronic controller 8. Therefore, the electronic controller 8 is electrically connected to a wheel speed sensor 9 that detects the wheel speed of each front wheel FW and each rear wheel RW, a brake switch IO that detects depression of the brake pedal 2, etc. . Therefore, the electronic controller 8 receives sensor signals from the wheel speed sensor 9 and the brake switch 10, and outputs an operation control signal to the brake pressure regulating device 5 based on these sensor signals.

Next, the functions of the electronic controller 8 will be explained.
This electronic controller 8 is basically an ABS controller as shown in FIG.
Follow the flowchart as shown in the main routine.
perform its functions; That is, in step Sl, the wheel speed VW and wheel acceleration/deceleration GVW of the front wheel FW and rear wheel RW are calculated based on the sensor signals from each wheel speed sensor 9, respectively.

More specifically, in the case of this embodiment, the wheel speed sensor 9 is composed of a gear-shaped disk that rotates together with the wheel, and a pickup coil that is fixed opposite to the tooth surface of this disk. Therefore, each wheel speed sensor 9 outputs a pulse signal every time it detects each tooth of the disk. Then, the electronic controller 8 receives pulse signals from each wheel speed sensor 9, and
Calculate the angular velocity of the wheel from the time interval of pulse signal generation,
By multiplying this by the wheel radius, the wheel speed VW of each wheel, that is, the front wheel FW and the rear wheel RW, is calculated. The wheel speed VW determined in this way is temporarily stored in a memory (not shown) within the electronic controller 8. Then, the wheel speed VWn calculated this time and the wheel speed V calculated last time are calculated.
Based on Wn-1, the wheel acceleration/deceleration GVW (VWn - VWn-1) of each of the front wheels FW and rear wheels RW is calculated and determined.

In the next step S2, a reference vehicle speed VREF is calculated and determined. In this case, the reference vehicle speed VREF is set to A.D. during braking. First, considering whether the BS is in operation or not,
A reference wheel speed SVW is determined from each wheel speed VW, and based on this reference wheel speed SVw, the road surface μ on which the vehicle is traveling is determined.
Actually, considering the value of wheel acceleration/deceleration GVW,
You will be asked for it. Regarding the determination of whether or not the ABS is in operation, first, when the ABS main routine is started by depressing the brake pedal 2, it is assumed that the ABS is not in operation and the car is traveling on a so-called high μ road. Assuming that the
After this, when the reference vehicle speed VREF is a predetermined speed (for example, 10 km/h or more), and as shown in FIG. 3, the deviation H between the reference vehicle speed VREF and the wheel speed VW is a predetermined value. When the value becomes larger than the above value, it is determined that ABS is in operation.

Moreover, once the ABS operation is started, this 10 ABS operation will be continued until a predetermined control condition is established.

Once the reference vehicle speed VREF has been determined in this manner, the process proceeds to the next step S3, and in this step S3, the slip amount Δ■ of each wheel is calculated and determined.

FIG. 4 shows in detail the calculation routine for the slip amount ΔV. In this calculation routine, step S30
0, S 304, it is determined whether the ABS is in operation and whether the road 7-j on which the vehicle is traveling is being detected as a rough road. These determinations ensure accurate ABS operation and
This is for smooth braking, and the conditions for starting ABS operation are as described above. In addition, detection of a rough road means, for example, detecting an uneven state of the road surface based on the vibration period of the wheel acceleration/deceleration GVW. To explain further,
If the vehicle speed is so low that ABS operation does not start, or if a rough road is detected at low vehicle speed, there is a risk that the detected wheel speed VW will include a large detection error, and the slip amount ΔV, which will be described later, may be affected. In some cases, the correction may actually be undesirable. Therefore, steps S300, S3
In step 04, it is determined whether or not there is the above-mentioned risk.

If the determination result in step S300 is negative (N), the process advances to step S301, and in step S301, the reference vehicle body speed VREF determined in step S2 is set to a predetermined value XRP. It is determined whether or not the speed is below P (for example, 60 km/h). At high speeds, the influence of the detection error on the wheel speed VW is small, so the process proceeds to step 8306, but on the other hand, the reference vehicle speed VREF is set to the predetermined value X IIThl'
In the following cases, the process advances to S302, and in this step S302, the correction value DDV of the slip amount ΔV is set to 0.
Set to .

On the other hand, if the ABS is in operation, no rough road has been detected, and the reference vehicle speed VREF is equal to or higher than the predetermined value XR[{F (for example, 60 km/h) as described above, Step 8306 is executed, where:
It is determined whether the road on which the vehicle is traveling is a low μ road. Regarding this determination, when the AS main routine is started as described above, it is assumed that the traveling road is a high μ road, but the road surface μ estimated from the wheel acceleration/deceleration GVW obtained in step S12 When it is larger than a predetermined value, it is determined that the road is low μ.

In step S306, if it is determined that the road is not a low μ road, the process advances to step S308, and this step S3
At step 08, a correction value DDV corresponding to the reference vehicle speed VREF is read from the high μ road table. A table for high μ roads is shown in FIG. As is clear from Fig. 5, when the reference vehicle speed VREF is 60 km/h or less,
The correction value DD■ is set to a negative value, and on the other hand,
When the reference vehicle speed VREF is 60 km/h or less, the correction value DDV is set to a positive value.

On the other hand, if the determination in step 8306 is positive (Y), the process advances to step S310, and this step S310
Then, the correction value DDV corresponding to the reference vehicle speed VREF is read from the low μ road table. The table for low μ road is
It is shown in FIG. As is clear from Fig. 6, since the reference vehicle speed VREF is a little less than 80 km/h,
If the reference vehicle speed VREF is 40 km/h or less, the correction value DDV is set to a positive value, and if the reference vehicle speed VREF is 40 km/h or less, the correction value DDV is set to a negative value.

As described above, steps S301 and S30
8 and S310, the correction value DDV is determined, and from this correction value DDV, the wheel speed VW of each wheel already determined in steps Sl and S2, and the reference vehicle body speed VREF, the correction value is calculated for each wheel using the following formula. The slip amount Δ■ is calculated and determined respectively.

ΔV=VREF-VW-DDV When the d calculation routine of the slip amount ΔV is completed, next
The process advances to step S4 in the BS main routine. In step S4, the brake pressure control mode is determined from the slip amount ΔV and the wheel acceleration/deceleration GVW by referring to the brake pressure increase/decrease map stored in advance in the memory of the electronic controller 8, that is, the basic pressure increase/decrease map. It is determined. The basic pressure increase/decrease map is shown in FIG. 7, in which each control mode is shown divided by solid lines. In Fig. 7, in the pressure increase mode, for example, 0.5 kg/
The brake pressure is increased by cm2, and in the pressure reduction mode, the brake pressure is reduced by a predetermined value.

Furthermore, in the hold mode, the brake pressure is held at that value.

In the case of the present invention, the basic pressure increase/decrease map includes a rapid pressure increase mode in addition to the above-mentioned pressure increase and pressure decrease modes. This sudden pressure mode is set in a region where the slip amount ΔV is below a predetermined value and the wheel acceleration/deceleration GVW is above a positive predetermined travel value, as indicated by diagonal lines in FIG.

When the brake pressure control mode is set in step S4 described above, the process proceeds to step S5.

In this step S5, according to the set control mode,
When the brake pressure adjustment device 5 mentioned above is activated, actually,
The brake pressure of the wheel brake 6 of each wheel is reduced, maintained, or rapidly increased.

The above-mentioned ABS main routine is repeatedly executed once the ABS operation is started, as described above, until the ABS operation termination condition is satisfied. The amount Δ■ and the brake pressure of the wheel brake 6 are as follows with respect to time:
It changes as shown in FIG. That is, when the wheel speed VW deviates from the reference vehicle body speed VREF, the wheel tends to lock, and the slip amount ΔV increases, the pressure reduction mode is implemented by the brake pressure adjustment device 5 based on the basic pressure increase/decrease map shown in FIG. .

That is, as shown by the solid line in FIG. 3, the brake pressure is reduced and the tendency of the wheels to lock is eliminated. After that, when the wheel speed VW recovers, the brake pressure is adjusted according to each control mode of pressure increase, hold, or pressure decrease mode of the basic pressure increase/decrease map selected based on the wheel acceleration/deceleration GVW and slip amount ΔV at that time. As shown by the solid line in FIG. 3, the wheel speed vW is increased while repeatedly increasing or maintaining the pressure (of course, reducing the pressure as necessary).
1, that is, the vehicle speed is reduced. In this case, the control mode to be implemented is as shown by the broken line in FIG.
It will be implemented to follow the selection path of pressure increase, hold and pressure reduction mode.

l6 In the case of this invention, since the basic pressure increase/decrease map is equipped with the rapid pressure increase mode as described above, A
When the operation of the BS is started, if the values of the wheel acceleration/deceleration GVW and the slip amount ΔV satisfy the conditions for the rapid pressure mode,
This sudden pressure mode is selected and implemented. Here, the conditions for selecting the rapid pressure mode are as described above and as is clear from FIG. 7, when the wheel acceleration/deceleration GVW is greater than a positive predetermined acceleration value, ,
This means that the brake pressure is too small as shown by the broken line in Fig. 3, so in this case, the rapid pressure mode is implemented to recover the brake pressure, that is, to suppress the increase.
The speed can be increased as shown by the broken line in the figure. As a result,
Even if the brake pressure is reduced more than necessary, by implementing the rapid pressure increase mode, the braking distance can be prevented from becoming longer and the efficiency of shortening the braking distance can be improved. In this case, the control mode to be implemented follows the selection path of rapid pressure increase, pressure increase, holding, and pressure reduction mode, as shown by the dashed line in FIG.

17 By the way, one of the conditions for selecting the rapid pressure mode is that the slip amount ΔV is smaller than a predetermined value. Therefore, if the slip amount Δ■ is large and the wheels are likely to lock In such a situation, the rapid pressure increase mode is not implemented, which effectively prevents the wheels from locking.

(Effects of the Invention) As explained above, according to the anti-skid braking method of the present invention, the brake pressure can be set in a pressure reduction mode, a holding mode, and a pressure increase mode based on the relationship between the wheel acceleration/deceleration and the amount of slip. Therefore, a pressure increase/decrease map that also includes a sudden pressure mode is prepared in advance, and during anti-skid brake control, the corresponding control mode is implemented from the pressure increase/decrease map based on the wheel acceleration/deceleration and slip amount at that time to adjust the brake pressure. Therefore, when the sudden pressure mode is selected and executed during anti-skid brake control, the brake pressure can be quickly increased to make braking work effectively, and as a result, 18! +. It is possible to shorten the braking distance. In addition, when the sudden pressure mode is selected, there is also a condition that the amount of slip is less than a predetermined value, so there is no possibility that the sudden pressure mode will be implemented when the amount of slip is large and cause the wheels to lock. , anti-skid brake control can be performed reliably and stably.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. Flowchart, FIG. 3 is a diagram showing changes in vehicle speed, slip amount, and brake pressure over time during ABS operation, FIG. 4 is a flowchart of the slip amount calculation routine, and FIGS. 5 and 6 are diagrams showing the flowchart of FIG. 4. For purposes of explanation, FIG. 7 is a graph showing the relationship between the slip amount correction value and the reference vehicle speed, and FIG. 7 is a diagram showing a basic pressure increase/decrease map. l...Mask cylinder, 5...Brake pressure adjustment device, 6...Wheel brake, 8...Electronic controller, l9 9...Wheel tracking sensor, 10...Flexible switch, FW...Front wheel , RW...Rear wheel.

Claims (1)

[Claims] In addition to determining the wheel speed and reference vehicle speed of the vehicle, the amount of wheel slip is determined based on the deviation between the reference vehicle speed and the wheel speed, and the brake pressure of the wheels is controlled to optimize the amount of wheel slip. In the anti-skid braking method described above, a pressure increase/decrease map is prepared in advance that divides the brake pressure into a pressure reduction mode, a holding mode, and a pressure increase mode based on the relationship between the wheel acceleration/deceleration and the amount of slip. During the anti-skid brake control, the brake pressure is controlled by implementing the corresponding control mode from the pressure increase/decrease map based on the wheel acceleration/deceleration and slip amount at that time, and among the above control modes, the wheel acceleration/deceleration The brake system includes a rapid pressure increase mode that is selected and executed when the brake is greater than or equal to a positive predetermined acceleration value and the amount of slip is less than or equal to a predetermined value. An anti-skid braking method characterized by: