JPH09249111A - Anti-skid control device - Google Patents

Abstract

(57) An object of the present invention is to provide an anti-skid control device capable of improving the braking performance of a vehicle while suppressing the yaw torque applied to the vehicle on a split road. A control mode for controlling a solenoid valve for adjusting brake hydraulic pressure is set for each wheel based on a wheel speed or the like calculated from a detection result of a wheel speed sensor, and it is determined that the vehicle is traveling on a split road (step 401-Y), the control mode of the high hydraulic side wheel (high μ wheel) is reset (steps 407 to 423) so that the increase of the brake hydraulic pressure of the high hydraulic side wheel is limited, so that the left and right wheels are reset. It prevents the difference in braking force from becoming too large. However, when the vehicle body deceleration D and the vehicle body speed V detected by the front-rear G sensor are smaller than the predetermined values Da and Va (step 403-Y, step 405-Y), even if the braking force is different between the left and right wheels Since the influence on the stability is small, the normal control is performed without limiting the hydraulic pressure. This makes it possible to improve braking performance without impairing steering stability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anti-skid control device for preventing wheel lock during braking of a wheel, and particularly to braking performance and steering on a traveling road (hereinafter referred to as a split road) having different friction coefficients between the left and right wheels. The present invention relates to those that are compatible with stability.

[0002]

2. Description of the Related Art Conventionally, in this type of device, the rear wheel is so-called select low control for controlling the braking force of both the left and right wheels in the same manner in accordance with the wheel on the side of large slip,
The front wheels are subjected to so-called independent control, which independently controls the braking force of each wheel.

That is, when the front and rear wheels are independently controlled, the braking performance is the best on a road surface (uniform road) where the friction coefficients are substantially equal on the left and right, but on the split road, the braking force between the left and right wheels is increased. The yaw moment is generated from the difference, and there is a problem that the steering stability of the vehicle is impaired because the vehicle tries to spin in the direction of the road surface (high μ road) on the high friction coefficient side where braking force is large. When the select low control is used, the braking force of the wheels on the high μ road side (high μ wheels) is reduced on the split road, the difference in braking force between the left and right wheels is reduced, and the yaw moment is suppressed, improving steering stability. However, on a uniform road, since the braking force is controlled to be low, there is a problem that a sufficient braking force cannot be obtained and the braking distance is extended. For this reason, the front wheels, which generate a relatively large braking force during braking, employ independent control, in which each wheel produces the largest braking force, and the select low control, which applies only to the rear wheels. It is a balance with stability.

However, even in this device, since the front wheels are independently controlled, the yaw torque may exceed the allowable range on a split road where the friction coefficient greatly differs between the left and right sides, and sufficient steering stability can be obtained. I couldn't.
On the other hand, in Japanese Unexamined Patent Publication No. 6-107156, in addition to the above device, it is determined whether or not the vehicle is traveling on a split road based on the pressure difference between the braking force of the front wheels, and the vehicle is traveling on the split road. In this case, a device in which a limit control for limiting the braking force of the high μ wheel is added is disclosed.

With this device, braking performance equivalent to that of the above device can be ensured on a uniform road, and further, on a split road,
The steering stability can be further improved.

[0006]

However, in this device, the magnitude of the braking force when it is judged that the vehicle is traveling on the split road depends on the road surface condition (difference in friction coefficient between the high μ road and the low μ road, etc.). When it is judged that the vehicle is traveling on a split road, it does not depend on the magnitude of the braking force at that time,
The increase in the braking force of high μ wheels is uniformly limited. For this reason, if the limit control is started when the braking force on the high μ wheels is relatively small and there is still room for steering stability, the limit control can be performed even though the braking force on the high μ wheels can be increased. As a result, the braking force of the high μ wheel is suppressed to an unnecessarily low level because the pressure is not sufficiently increased by the above, and as a result, the braking distance on the split road is unnecessarily extended.

Therefore, in order to solve the above problems, it is an object of the present invention to provide an anti-skid control device capable of improving the braking performance of the vehicle while suppressing the yaw torque applied to the vehicle on the split road. And

[0008]

In the anti-skid control device according to claim 1 of the present invention made to achieve the above object, the braking force control means adjusts the braking force of the control device during vehicle braking. Then, control is performed so that excessive slip does not occur between each wheel and the road surface.

At this time, the braking force control means controls each front wheel independently, but when the running state determining means determines that the vehicle is traveling on a split road, the braking force controlling means causes the road surface on the side having a large friction coefficient. Wheels traveling on (high μ road) (high μ
Limit the increase in braking force on the wheels. However, when the acceleration (deceleration) in the direction opposite to the traveling direction of the vehicle detected by the vehicle body deceleration detection means is smaller than a predetermined value, the first
Prohibiting means prohibits the operation of the braking force limiting means.

That is, as a result of repeated experiments, it was found that when the vehicle is braked on the split road, if the deceleration of the vehicle is below a predetermined value, the operational stability of the vehicle is not impaired. The above is used to limit the increase in the braking force of the high μ wheel by the braking force limiting means only when the vehicle is traveling on the split road and the deceleration is larger than the predetermined value.

For this reason, when the vehicle is braked on the split road, the control according to the road surface friction force is performed for each wheel until the predetermined deceleration is reached.
Within a range that does not impair steering stability, the pressure is rapidly increased until sufficient braking force is applied, and after the braking force is sufficiently increased and reaches a predetermined deceleration, the braking force of the high μ wheel is increased. Since the increase in pressure is limited, the braking force of the high μ wheel does not become larger than necessary.

Therefore, according to the anti-skid control device of the present invention, since each front wheel is independently controlled during traveling on a uniform road, it is possible to obtain a sufficient braking force according to the friction coefficient with the road surface. During traveling on a split road, the braking force of the high μ wheels is limited, the braking force that is largely biased to the high μ wheels is not applied, and the yaw torque applied to the vehicle is suppressed, so steering stability can be ensured. Moreover, when traveling on split roads, regardless of the road surface condition, it is possible to always secure the braking performance as much as possible without impairing the steering stability, and to achieve an anti-skid control with an excellent balance of braking force and steering stability. realizable.

Further, the deceleration at which the braking performance is ensured without impairing the steering stability is peculiar to the vehicle, and in the case of a four-wheel drive vehicle, it has the same magnitude regardless of the restraint state of the center differential. Therefore, if the device is provided in a four-wheel drive vehicle, the braking effect can be made substantially the same regardless of the restrained state of the center differential.

Further, in the anti-skid control device according to the second aspect, when the vehicle body speed detected by the vehicle body speed detecting means is smaller than a predetermined value, the second prohibiting means,
The operation of the brake limiting means is prohibited. That is, when the vehicle speed is sufficiently low (less than a predetermined speed), even if the braking force by the left and right front wheels is different, the yaw torque generated thereby has a small effect on the steering stability. You don't have to.

Therefore, by adding this condition,
The braking performance can be further improved without impairing the steering stability.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an overall configuration diagram of an anti-skid control device of the present embodiment applied to a front-wheel steering / front-wheel drive four-wheel vehicle.

In FIG. 1, the brake pedal 20 is connected to a master cylinder 28 via a vacuum booster 21, and when the driver depresses the brake pedal 20, hydraulic pressure is generated in the master cylinder 28. This oil pressure is applied to each wheel (left front wheel FL, right front wheel FR, left rear wheel RL, right rear wheel RR).
Wheel cylinders 31, 32, 33, 34 provided in
Is supplied to the vehicle to generate a braking force for braking the rotation of the wheels FL to RR. A stop switch 10 for detecting the presence or absence of a depressing operation is arranged near the brake pedal 20, and the detection signal from the stop switch 10 is an electronic control circuit (ECU) 8
0 has been entered.

The master cylinder 28 has two pressure chambers (not shown) for generating brake hydraulic pressures of the same pressure, and supply pipes 40 and 50 are connected to the respective pressure chambers. The supply pipe 40 branches into communication pipes 41 and 42. The communication pipe 41 is connected to a brake pipe 43 that communicates with the wheel cylinder 31 via an electromagnetic valve 60a. Similarly, the communication pipe 42 is connected to a brake pipe 44 communicating with the wheel cylinder 34 via an electromagnetic valve 60c.

The supply pipe 50 also has a connection relationship similar to that of the supply pipe 40 and is branched into communication pipes 51 and 52. Communication pipe 51
Is connected to a brake pipe 53 communicating with the wheel cylinder 32 via an electromagnetic valve 60b. Similarly, the communication pipe 52 is connected to the wheel cylinder 3 via the solenoid valve 60d.
3 is connected to a brake pipe 54.

Known proportioning valves 59 and 49 are installed in the brake pipes 54 and 44 connected to the wheel cylinders 33 and 34, respectively. The proportioning valves 59 and 49 control the brake hydraulic pressure supplied to the rear wheels RL and RR to bring the braking force distribution of the front and rear wheels FL to RR close to ideal.

Solenoid valves 60a, 60c, 60b, 60d
Is a 3-port 3-position solenoid valve, and at the position A in FIG. 1, the communication pipes 41, 42, 51, 52 and the brake pipe 4 are shown.
3, 44, 53, 54, respectively, and at the B position, the communication pipes 41, 42, 51, 52, the brake pipe 4
3, 44, 53, 54 and branch pipes 47, 48, 57, 58 are all blocked. Further, in the C position, the brake pipes 43, 44, 53, 54 and the branch pipes 47, 48, 57, 5 are
8 and 8 respectively.

The branch pipes 47 and 48 are both connected to the discharge pipe 81, and the branch pipes 57 and 58 are both connected to the discharge pipe 91. These discharge pipes 81 and 91 are respectively connected to the reservoirs 93a and 9a.
3b. The reservoirs 93a and 93b temporarily store the brake fluid discharged from the wheel cylinders 31 to 34 when the solenoid valves 60a to 60d are in the C position. Therefore, the wheel cylinders 31 to 34
The brake hydraulic pressure is increased when the solenoid valves 60a to 60d are in the A position, is held when it is in the B position, and is reduced when it is in the C position.

The pumps 99a, 99b are for pumping up the brake fluid accumulated in the reservoirs 93a, 93b and returning it to the master cylinder 28 side, and the check valves 97a, 98a, 97b, 98b are reservoirs. This is to prevent the brake fluid pumped up from 93a, 93b from flowing back to the reservoirs 93a, 93b side again.

Further, electromagnetic pickup type wheel speed sensors 71, 72, 73 and 74 are installed on the respective wheels FL to RR, and accelerations in the traveling direction of the vehicle body applied to the vehicle body are provided at appropriate positions on the vehicle body ( A front and rear G sensor 12 for detecting the front and rear G) is attached, and the detection signals of the wheel speed sensors 71 to 74 and the front and rear G sensor 12 are E
It is input to the CU80. In addition, this front and rear G sensor 1
2 corresponds to the vehicle body deceleration detecting means.

The ECU 80 is composed of a well-known microcomputer mainly composed of a CPU, a ROM and a RAM, and based on detection signals from the front and rear G sensor 12, the stop switch 10 and the wheel speed sensors 71 to 74, an electromagnetic valve. By generating drive signals for driving 60a to 60d, anti-skid control processing is executed to control the brake hydraulic pressure of each wheel cylinder 31 to 34 so that each wheel FL to RR does not slip excessively.

The anti-skid control process executed by the ECU 80 will be described below with reference to the flow charts shown in FIGS. First, FIG. 2 is a flowchart showing the main routine of the anti-skid control processing. In addition,
This process is started when an ignition switch (not shown) is turned on.

When this process is activated, first, step 20
In No. 1, the solenoid valves 60a to 60d are set to the A position so that the hydraulic pressures of the wheel cylinders 31 to 34 are increased according to the hydraulic pressure generated in the master cylinder 28, and various flags and various counters described later are initialized. To do. In the following step 203, the wheel speeds and accelerations of the wheels FL to RR are calculated based on the detection signals from the wheel speed sensors 71 to 74, and the maximum wheel speed is set as the vehicle body speed V. In the next step 205, the front and rear G
Based on the detection signal from the sensor 12, the vehicle body deceleration D, which is the acceleration in the direction opposite to the traveling direction of the vehicle body, is calculated.

In the following step 207, the pressure increasing times TupFL and TupFR for which the solenoid valves 60a and 60b were set to the A position between the previous control and the present control, and the solenoid valves 60a and 60b to the C position. Calculate the set depressurization times TdwFL and TdwFR respectively, and continue with Step 2
At 09, based on the calculation result at step 207, it is determined which of the front wheels FL and FR is the high hydraulic side wheel (the wheel on the high brake hydraulic pressure side) by the high hydraulic side wheel determination routine described later.

In the following step 211, step 203
Based on the wheel velocities and accelerations of the wheels FL to RR calculated in, the control modes (increase pressure, hold,
Decompression). Since this process is a well-known process, detailed description thereof will be omitted. The control mode set here is merely numerical data in the ECU 80,
This step does not drive the solenoid valves 60a-60d.

In the following step 213, since the antiskid control is favorably performed according to the road surface condition, step 20
Step 21 is performed based on the calculated value and the set value in 3 to 211.
The control mode of the front wheels FL and FR set in 1 is reset. In the following step 215, the control mode of the rear wheels RL and RR is reset by the select low control. That is,
The slip ratios of the rear wheels RL and RR are calculated from the wheel speed and the vehicle body speed that are the calculation results in step 203, and the control mode on the side with the larger slip ratio is changed to the same as the control mode on the side with the smaller slip ratio. Set.

At step 217, steps 211 to 2 are performed.
Based on the control mode set in 15, the solenoid valve 60a
After executing the solenoid valve driving process for driving the to 60d, the process returns to the step 203, and thereafter, the processes of the steps 203 to 207 are repeatedly executed. In this solenoid valve drive processing, when the control mode is the holding mode, the wheel cylinders 31 to 3 are
The solenoid valves 60a to 60d are driven to the B position in order to maintain the hydraulic pressure of No.4. When the control mode is the decompression mode,
After being driven to the C position for a predetermined period, the remaining position is driven to the B position. Further, when the control mode is the pressure increasing mode, it is driven to the position A for a predetermined period every predetermined period, and is driven to the B position at other times.
By driving to the position, duty output is performed. Then, when the control mode is the slow pressure increasing mode set in the front wheel control routine described later, the duty output is performed at the A position and the B position as in the normal pressure increasing mode.
The period for driving to the A position is shortened. That is, in the slow pressure increasing mode, the brake hydraulic pressure is gradually increased as compared with the normal pressure increasing mode.

When anti-skid control is not being performed, all solenoid valves 6 are operated regardless of the control mode setting.
Set 0a to 60d to the A position. Further, the anti-skid control is started when the brake pedal 20 is operated and one of the wheels FL to RR becomes equal to or higher than a predetermined slip ratio, and thereafter, the operation of the brake pedal 20 is released, or It ends when it is confirmed that the vehicle has stopped.

Next, the high oil pressure side wheel determination routine executed in step 209 will be described with reference to the flow chart shown in FIG. When this process is started, first, step 30
At 1, it is determined whether or not anti-skid control is in progress. If the anti-skid control is not in progress, the process proceeds to step 302, and the cumulative value ΔTu of the pressure increase time difference, which will be described later, is set.
p, after clearing the cumulative value ΔTdw of the depressurization time difference,
In the following step 303, the right front wheel flag FFR indicating that the right front wheel FR is a high hydraulic pressure side wheel and the left front wheel flag FFL indicating that the left front wheel FL is a high hydraulic pressure side wheel are both reset and the main routine is executed. Return.

On the other hand, when it is determined in step 301 that the anti-skid control is being performed, the process proceeds to step 305, and the pressure increase time TupFR of the solenoid valve 60b and the pressure increase of the solenoid valve 60a, which are the calculation results in step 207, are obtained. Based on the time TupFL, the cumulative value ΔTup of the pressure increase time difference from the start of the anti-skid control to the present is obtained, and in the subsequent step 307, similarly, the pressure reduction time TdwFR, TdwFL of the solenoid valves 60b, 60a is set. Based on this, the cumulative value ΔTdw of the pressure reduction time difference is obtained.

In the following step 309, it is determined whether or not the value obtained by subtracting the cumulative value ΔTdw of the pressure reduction time difference from the cumulative value ΔTup of the pressure increase time difference is equal to or larger than a predetermined value Ta. If the value is equal to or greater than the predetermined value Ta, it is determined that the front right wheel FR is the high hydraulic side wheel while the vehicle is traveling on the split road, and step 31
At 1, the right front wheel flag FFR is set and the left front wheel flag FFL is reset, and then the process returns to the main routine.

That is, the difference ΔTup-ΔTdw between the accumulated value of the pressure increase time difference and the accumulated value of the pressure decrease time difference is large means that the solenoid valve 6 is operated from the time when the anti-skid control is started until the present time.
0a indicates that the solenoid valve 60b is increasing pressure for a longer period of time, or the solenoid valve 60a is reducing pressure for a longer period of time than the solenoid valve 60b. If the right front wheel FR whose hydraulic pressure is controlled can be determined to be the high hydraulic side wheel, and if the difference is equal to or greater than the predetermined value Ta, the left and right front wheels FL, FR are traveling on a split road with greatly different friction coefficients. You can judge that.
The high oil pressure side wheels correspond to the high μ wheels traveling on the high μ road having a large road surface friction coefficient, and the low oil pressure side wheels correspond to the low μ wheels traveling on the low μ road having a small road surface friction coefficient.

On the other hand, in step 309, the cumulative value difference ΔT
When it is determined that up-ΔTdw is smaller than the predetermined value Ta, the process proceeds to step 313, and this time, the difference ΔT of the accumulated values.
It is determined whether up-ΔTdw is less than or equal to a predetermined value-Ta. If the value is equal to or less than the predetermined value -Ta, it is determined that the left front wheel FL is a high hydraulic side wheel while traveling on a split road, the right front wheel flag FFR is reset and the left front wheel flag FFL is set in step 315, and then the main routine is executed. Return to.

In step 313, the cumulative value difference ΔT
When it is determined that up-ΔTdw is larger than the predetermined value -Ta, there is no significant difference in the brake hydraulic pressure applied to the left and right front wheels FL and FR, that is, it is assumed that the vehicle is traveling on a uniform road.
After resetting the flags FFL and FFR in step 303,
Return to the main routine.

That is, according to this processing, when the vehicle is traveling on the split road during the anti-skid control, one of the flags FFR or FFL corresponding to the high hydraulic side wheel is set,
If the vehicle is traveling on a uniform road, both flags FFR and FFL are reset. Next, the front wheel control routine executed in step 217 will be described with reference to the flowchart shown in FIG.

When this processing is started, first, step 40
At 1, it is determined whether either the right front wheel flag FFR or the left front wheel flag FFL is set. If either is set, it is determined that the vehicle is running on a split road, and the process proceeds to step 403. To do.

In step 403, it is judged whether or not the vehicle body deceleration D calculated in step 205 is smaller than a predetermined value Da, and if it is more than the predetermined value Da, the process proceeds to step 405, and in step 405, It is determined whether or not the vehicle body speed V obtained in step 203 is smaller than the predetermined value Va, and if it is equal to or larger than the predetermined value Va, the high hydraulic side wheel (that is, the front wheel corresponding to the flag set in step 209) Assuming that the increase in hydraulic pressure needs to be limited, step 4
Move to 07.

In step 407, it is judged whether or not the control mode of the high oil pressure side wheels set in step 211 is the pressure increasing mode. If it is the pressure increasing mode, step 409 is executed.
Move to In step 409, it is determined whether the control mode of the low hydraulic pressure side wheel (that is, the front wheel corresponding to the flag reset in step 209) is the pressure reducing mode. If the control mode is the pressure reducing mode, the process proceeds to step 411. hand,
After incrementing the counter CT1, the process proceeds to step 413.

In step 413, it is judged whether or not the value of the counter CT1 is within the range of the predetermined value K1 or more and less than the predetermined value K2, and if it is within the range, the process proceeds to step 415 and the high hydraulic pressure side. After resetting the wheel control mode to the decompression mode, the routine returns to the main routine. On the other hand, if the value of the counter CT1 is not within the above range, the process proceeds to step 421 and the control mode of the high hydraulic side wheel is reset to the holding mode. After setting, return to the main routine.

If it is determined in the previous step 409 that the control mode of the low hydraulic pressure side wheel is not the pressure reducing mode, the process proceeds to step 417, the counter CT1 is cleared, and then the process proceeds to step 419. In step 419, it is determined whether or not the control mode of the low hydraulic pressure side wheels is the holding mode. If the control mode is the holding mode, the process proceeds to step 421, and as described above, the control mode of the high hydraulic pressure side wheels is set. After resetting to the holding mode, the routine returns to the main routine. On the other hand, if the control mode is not the holding mode but the pressure increasing mode, the routine proceeds to step 423, and the control mode of the high hydraulic side wheels is reset to the slow pressure increasing mode. After that, it returns to the main routine.

When it is determined in the previous step 401 that neither the right front wheel flag FFR nor the left front wheel flag FFL is set, it is determined in step 403 that the vehicle body deceleration D is smaller than the predetermined value Da. When it is determined, in step 405, it is determined that the vehicle body speed V is smaller than the predetermined value Va, and when it is determined in step 407 that the high hydraulic side wheel control mode is not the pressure increasing mode. Shifts to step 425, clears the counter CT1, and then returns to the main routine.

That is, in steps 401 to 407 of this processing, it is judged whether or not the increase in the hydraulic pressure of the high hydraulic side wheels is restricted. When the vehicle is traveling on a uniform road, the vehicle body deceleration D and the vehicle body speed V are determined. Is sufficiently small, and even if the braking forces of the front wheels FL and FR are different between the left and right, if the yaw torque generated thereby has a small effect on the steering stability, if the high hydraulic side wheels are not in the pressure boosting mode, Judge that it is not necessary to limit In this case, since the solenoid valves 60a and 60b are driven according to the control mode set according to the slip state of each wheel in step 211, the front wheel F
Maximum braking force is generated in L and FR.

Otherwise, steps 409-42
The control for restricting the increase of the hydraulic pressure of the high hydraulic side wheel is performed by means of 3. However, when the low hydraulic side wheel is in the pressure increasing mode, the high hydraulic side wheel is reset to the slow pressure increasing mode to set the low hydraulic side. When the low-hydraulic side wheels are in the holding mode or the depressurizing mode, the control mode of the high-hydraulic side wheels is restored to the same as that of the low-hydraulic side wheels by selecting low control. Set.

The counter CT1 measures the period during which the high hydraulic side wheels are kept in the pressure increasing mode and the low hydraulic side wheels are kept in the depressurizing mode. During this period, the road surface friction coefficient on the split road is left and right. The larger the difference, the longer the length. Therefore, when the value of the counter CT1 is smaller than the predetermined value K1,
Assuming that the difference between the left and right road surface friction coefficients is small, the holding mode is set so that the hydraulic pressure of the high hydraulic side wheels is not excessively limited. When the value of CT1 becomes equal to or larger than the predetermined value K2, the holding mode is reset to suppress the deterioration of the braking performance of the vehicle due to the selection low control being selected for a long time. Is also weakening the limit.

As described above, the control mode for the high hydraulic side wheels set to the pressure increasing mode in step 211 is any one of the pressure reducing mode, the holding mode, and the slow pressure increasing mode depending on the control mode of the low hydraulic side wheels. Since the solenoid valves 60a to 60d are driven according to the reset control mode, the braking force of the high-hydraulic side wheels does not increase more than necessary, and the vehicle is not braked on the split road. The applied yaw torque is well suppressed.

In each of the above processes, step 21
1, 217 are braking force control means, and steps 207, 209.
Is a running state determination means, steps 401, 407 to 425
Is the braking force limiting means, step 403 is the first inhibiting means, and step 405 is the second inhibiting means.

As described above, according to the anti-skid control device of this embodiment, since the front wheels FL and FR are independently controlled when traveling on a uniform road, a sufficient braking force can be obtained and the split road can be obtained. High hydraulic side wheels (high μ
Since the hydraulic pressure of the wheels is limited according to the control mode of the low hydraulic side wheels (low μ wheels), the yaw torque applied to the vehicle is suppressed, and good steering stability can be secured.

Even when the vehicle runs on a split road, even if the vehicle body deceleration D and the vehicle body speed V are sufficiently small and the braking forces of the front wheels FL and FR are different between left and right, the yaw torque generated thereby has an effect on the steering stability. When it is small, the hydraulic pressure of the high hydraulic side wheels is not limited, so that the hydraulic pressure of the high hydraulic side wheels will not be kept unnecessarily low and a sufficient braking force can always be secured. .

That is, regardless of the vehicle body deceleration D, in the conventional device that limits the pressure increase of the high hydraulic side wheels as soon as it is judged that the vehicle is traveling on the split road, as shown by the dotted line in FIG. Even if the vehicle hydraulic deceleration D does not reach the hydraulic pressure at which the vehicle body deceleration D reaches the predetermined value Da and there is a margin in steering stability, the hydraulic pressure is almost maintained, so that sufficient braking force cannot be obtained. However, in this embodiment, even if it is determined that the vehicle is traveling on the split road, the hydraulic pressure of the high hydraulic side wheels is increased as usual while the vehicle body deceleration D is smaller than the predetermined value Da and the steering stability can be sufficiently ensured. Since the pressure increase is limited after the predetermined value Da is reached, a sufficient braking force can be obtained by the high hydraulic side wheels, and the pressure is not increased more than necessary and the steering stability is not impaired. .

Further, in the above-mentioned embodiment, the case where the invention is applied to the front-wheel drive vehicle has been described, but it may be applied to the four-wheel drive vehicle.
In particular, when the center differential has a restraint mechanism, if the center differential is restrained, the brake torque will sneak between the front and rear wheels, and a greater braking force will be exerted than when the center differential is free. Even if the same anti-skid control is performed when restrained and when free, the braking effectiveness differs.

That is, when the center differential is free and the braking performance and the steering stability are well balanced, an excessive braking force acts when the center differential is restrained, so that the steering stability on the split road is deteriorated. On the contrary, when the center differential is restrained, if the braking performance and the steering stability are well balanced,
When the center differential is free, the braking force is controlled weakly, so that the braking distance is extended.

However, if the anti-skid control device of this embodiment is used, hydraulic pressure is not limited until the vehicle body deceleration D reaches a predetermined value Da, as shown in FIG. Although the hydraulic pressures of the high hydraulic side wheels are different, after the vehicle body speed D reaches a predetermined value Da, the vehicle body deceleration is controlled to be almost constant by the restriction of the hydraulic pressure. Regardless of the restraint state, the braking effect is almost constant.

In the above embodiment, the slip state of the front wheels FL, FR is detected based on the control mode of the front wheels FL, FR, but the slip state of the front wheels FL, FR can be changed by various methods other than this. Can be detected. For example, the slip state may be detected by comparing the wheel speed detected by the wheel speed sensors 71, 72 with the vehicle speed.

In this embodiment, the counter CT1 counts the period during which the control mode for the high hydraulic side wheels is the pressure increasing mode and the control mode for the low hydraulic side wheels is the depressurizing mode.
Although the slip states of the front wheels FL and FR are compared based on the value and the control mode of the high-hydraulic side wheels is reset, the slip states can be compared by various other methods. For example, the slip states of the left and right front wheels FL and FR may be compared based on the pressure increase time difference ΔTup and the pressure decrease time difference ΔTdw calculated in steps 305 and 307 of FIG.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an anti-skid control device of an embodiment.

FIG. 2 is a flowchart showing a main routine of anti-skid control processing of the embodiment.

FIG. 3 is a flowchart showing a high hydraulic pressure side wheel determination routine of an anti-skid control process.

FIG. 4 is a flowchart showing a front wheel control routine of anti-skid control processing.

FIG. 5 is an explanatory diagram showing effects of the embodiment.

FIG. 6 is an explanatory diagram showing an effect when the embodiment is applied to a four-wheel drive vehicle.

[Explanation of symbols]

10 ... Stop switch 12 ... Front and rear G sensor 2
0 ... Brake pedal 21 ... Vacuum booster 28 ... Master cylinder 31-34 ... Wheel cylinder 40, 50 ... Supply pipe 41, 42, 51, 52 ... Communication pipe 43, 44, 5
3, 54 ... Brake pipe 47, 48, 57, 58 ... Branch pipe 59, 49 ... Proportioning valve 60a-60d ... Electromagnetic valve 71-74 ... Wheel speed sensor 80 ... ECU 81, 91 ... Discharge pipe 93a, 93
b ... Reservoir 97a, 98a, 97b, 98b ... Check valve 99
a, 99b ... Pump

Claims (2)

[Claims] 1. A braking device capable of individually adjusting the braking forces of the left and right front wheels, and the braking force of the braking device is adjusted during vehicle braking,
Based on the behavior of the left and right front wheels, the braking force control means that controls so that excessive slip does not occur between each wheel and the road surface, and on the split road where the left and right wheels have different friction coefficients between the wheel and the road surface When the traveling state determining means determines that the vehicle is traveling on a split road, the braking force of a wheel traveling on a road surface having a large friction coefficient is determined. In an anti-skid control device equipped with a braking force limiting means for limiting an increase in pressure, a vehicle body deceleration detecting means for detecting acceleration in a direction opposite to a traveling direction of the vehicle, and a vehicle body deceleration detecting means for detecting the acceleration. An anti-skid control device comprising: a first prohibiting means for prohibiting the operation of the braking force limiting means when the acceleration is smaller than a predetermined value. 2. The anti-skid control device according to claim 1, further comprising a vehicle body speed detecting means for detecting a vehicle body speed, and a vehicle body speed detected by the vehicle body speed calculating means being smaller than a predetermined value. An anti-skid control device comprising: second prohibiting means for prohibiting the operation of the brake limiting means.