JP2765217B2 - Anti-skid brake control method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an anti-skid brake control method for preventing locking of wheels during braking, and particularly to an anti-skid brake suitable for a four-wheel-drive vehicle. It relates to a brake control method.

(Prior Art) According to this kind of anti-skid brake control method,
During braking, the wheel speed of each wheel is detected by a wheel speed sensor, while the vehicle deceleration is detected by a deceleration sensor, and a pseudo vehicle speed of the vehicle is calculated based on the wheel speed and the vehicle deceleration. doing. Then, when the wheel speed of the wheel is too low with respect to the pseudo vehicle speed, and the rotation tendency has a locking tendency, the braking force of the wheel, that is, the braking force is reduced to eliminate the locking tendency. On the basis of the rotation tendency of the wheels, the brake pressure is repeatedly increased, held or reduced to control the wheel speed of each wheel to follow the pseudo vehicle speed, thereby preventing the locking of each wheel. I have. When the above-described anti-skid control is performed at the time of braking, steering performance can be reliably ensured, and a great effect can be exhibited in shortening the braking distance.

On the other hand, among the four-wheel drive (4WD) type vehicles to which the above-described anti-skid brake control method is applied, the drive system is switched from four-wheel drive to two-wheel drive (2WD), and the center differential is locked. In order to implement anti-skid control, some switches are equipped with a 4WD select switch, a center differential lock switch, etc. To control the brake pressure.

(Problems to be Solved by the Invention) In the above-described anti-skid brake control method, the anti-skid control is conventionally performed in consideration of the switching state of the 4WD select switch and the center differential lock switch. Even when a failure occurs in one of the select switch and the center differential lock switch, anti-skid control is not performed in order to secure running safety. That is, 4WD
When a failure occurs in the select switch or the center differential lock switch, the anti-skid control, that is, the operation of the system is immediately stopped.

Therefore, according to the conventional anti-skid brake control method, the automobile is running on a low μ road such as a snowy road or a frozen road with four-wheel drive, and the anti-skid control is performed along with braking in such a situation. If a failure occurs in the 4WD select switch or the center differential lock switch during the operation, the anti-skid control is immediately stopped. For this reason, when the anti-skid control is stopped under the above-described driving conditions and the brake control returns to the normal brake control, in this case, the braking force of each wheel, that is, the brake pressure becomes excessive, so that four drive When the vehicle is traveling at a high speed, the possibility that all of the four wheels are locked at the same time increases.

The present invention has been made on the basis of the above-described circumstances, and the object thereof is to provide a method for controlling an anti-skid control even when a failure occurs in a 4WD select switch.
It is an object of the present invention to provide an anti-skid brake control method that reliably prevents the lock of each wheel to ensure steering performance and is excellent in safety.

(Means for Solving the Problems) The present invention relates to an anti-skip brake control method applied to a vehicle having a 4WD select switch for switching between four-wheel drive and two-wheel drive as one of switches for setting a drive system. The vehicle speed is detected by a wheel speed sensor while the vehicle deceleration is detected by a deceleration sensor. During braking, a pseudo vehicle speed is calculated based on the wheel speed and the vehicle deceleration. Thus, when the tendency of the rotation of the wheels to be locked with respect to the pseudo vehicle speed is generated, the braking force of the wheels is controlled to eliminate the tendency of the wheels to be locked in accordance with the driving method set by the switch. In an anti-skid brake control method based on the assumption that the wheel speed of a wheel follows the pseudo vehicle speed, a storage step of storing a switching state of a switch; A determination step of determining the presence or absence of a failure; and, during the anti-skid control, when it is determined in the determination step that a failure has occurred in the switch, the switching state of the switch is maintained at the switching state immediately before the failure, and the anti-skid control is performed. And a continuation step to be continuously performed until the end.

Preferably, in addition to the 4WD select switch, the switch further includes a center differential lock switch for locking the center differential of the vehicle, and in this case, the storing step and the determining step store the switching state of the center differential lock switch and determine whether or not there is a failure. Judge each,
The continuation step is executed when a failure occurs in one of the 4WD select switch and the center differential lock switch.

According to the anti-skid brake control method of the present invention, even if the 4WD select switch fails during the anti-skid control, the switching state of the 4WD select switch immediately before the failure is maintained, and the anti-skid control is performed. 4W
In accordance with the drive system set by the D select switch, the operation is continuously executed until the end, that is, the vehicle stops or the tendency to lock the wheels is eliminated. That is, in the anti-skid brake control method of the present invention,
During the anti-skid control, the anti-skid control is released immediately after the failure of the 4WD select switch,
There is no transition to normal foot brake control.

Further, when a center differential lock switch is also considered in addition to the 4WD select switch, even if a failure occurs in the center differential lock switch during the anti-skid control, the anti-skid control is continued until the end thereof.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

Referring to FIG. 1, there is schematically shown an anti-skid brake device applied to a 2WD / 4WD selection type automobile. First, a brief description of the power transmission path of an automobile will be given. In the case of 4WD, the driving force of the engine 1 is transmitted through a transmission 2, a front differential (not shown), and a front wheel drive shaft 3 to the left and right front wheels 4L. , 4R, and to the left and right rear wheels 5L, 5R via a transmission 2, a center differential (not shown), a propeller shaft 6, a rear differential 7, and a rear wheel drive shaft 8,
Is transmitted. In the case of 2WD, the driving force of the engine 1 is limited to the front wheels 4L and 4L.
R or one of the rear wheels 5L, 5R.

A wheel brake 9 is mounted on each of the front wheel 4 and the rear wheel 5, and these wheel brakes 9 are connected to a hydraulic brake circuit 10.

The hydraulic brake circuit 10 includes a tandem-type master cylinder 12 with a vacuum brake booster operated by a brake pedal 11, and a front wheel brake line 13 is provided from one pressure chamber (not shown) of the master cylinder 12. A rear wheel brake line 14 extends from the other pressure chamber (not shown). The front and rear wheel brake lines 13 and 14 extend through the control valve device 15, and the front wheel brake line 13 is connected to the wheel brakes 9 of the respective front wheels 4, with the distal end branched left and right. The rear brake line 14 is also connected to the wheel brakes 9 of the rear wheels 5 with the leading end branched right and left.

In the front wheel brake line 13, anti-skid valve devices 16 are interposed at portions of the corresponding front wheel branched toward the wheel brake 9, respectively. In the site before branching, 1
Two anti-skid valve devices 16 are inserted.

Further, a hydraulic pump 17 is connected to the control valve device 15, and the hydraulic pump 17 pressurizes the hydraulic fluid sucked from the hydraulic fluid tank 18 to a predetermined pressure, and during the anti-skid brake control, It can be supplied to the wheel brake 9 of each wheel via the control valve device 15.

That is, when the anti-skid control is started during braking,
Each wheel brake 9 has a hydraulic pump, not a hydraulic fluid from the master cylinder 12, due to the operation of the control valve device 15.
The dynamic pressure from 17 is supplied, and the brake pressure in the wheel brake 9, that is, the braking force, can be controlled by appropriately operating each anti-skid valve device 16. .

In order to control the brake pressure of each wheel brake 9 by the above-described anti-skid control, a wheel speed sensor 19 is disposed on each of the wheels 4, 5, and a wheel speed signal from the wheel speed sensor 19 is transmitted to a controller. Supplied to 20.

In addition to the wheel speed sensor 19, a deceleration sensor 21 for detecting the vehicle body deceleration GS and various switches for setting the driving system of the vehicle are connected to the controller 20. These switches include a 4WD select switch 22 for selecting 2WD and 4WD, a center differential lock switch 23 for locking the function of the center differential, a rear differential lock switch 24 for locking the function of the rear differential 7, and the like. The sensor signal and the switching signal from the deceleration sensor 21 and each switch are also supplied to 20.

In FIG. 1, a return line from each wheel brake 9 to the hydraulic fluid tank 18 is not shown in order to simplify the drawing.

The controller 20 includes a wheel speed sensor 19 and a deceleration sensor 21.
The anti-skid control described above, that is, the operation of the control valve device 15 and each of the anti-skid valve devices 16 is controlled based on the sensor signals from the sensors and the switching states of various switches. An example of the routine is shown in FIG.

Therefore, the ABS main routine will be described below with reference to FIG.

ABS Main Routine First, in step S1, the wheel speed VW of each wheel is read by each wheel speed sensor 19, and the next step
In S2 and S3, the type 2 failure flag F2 and the type 3 failure flag F
3 is set or not, that is, 1 is set in these flags F2 and F3.
Is set or not. Here, the determinations in steps S2 and S3 are still negative (No), and the vehicle deceleration GS is read by the deceleration sensor 21 in the next step S4.

Thereafter, in step S5, it is determined whether or not 1 is set in the first failure flag F1. However, here, the determination is still negative, and therefore, the process proceeds to step S6, and the above-described 4WD select is performed. After the switching states of the switch 22, the center differential lock switch 23, and the rear differential lock switch 24 are read, in the next step S7, one of the wheel speeds VW of the respective wheels read in step S1 is selected as the reference wheel speed VWS. . Here, as the reference wheel speed VW, for example, when the vehicle is running in 4WD, each wheel speed VW
Of the above, the second or third wheel speed from the top is selected,
On the other hand, when the vehicle is traveling by 2WD, the wheel speed of the non-driven wheel is selected.

In step S8, it is determined whether or not to start the anti-skid control, that is, whether the ABS control should be started. Specifically, at least one of the other wheel speeds VW with respect to the already obtained reference wheel speed VWS is determined. It is determined whether or not the wheel has decreased to a predetermined value ΔVW or more and a locking tendency has occurred in the wheel. Here, if the brake pedal (not shown) of the vehicle is not depressed, that is, if the braking has not been started, the determination in step S8 is negative, so the process returns to step S1.
The above steps are repeated.

If the determination in step S8 is positive (Yes) and at least one of the wheels has a tendency to lock, and the anti-skid control is started, in the next step S9, the pseudo vehicle speed VRE
F and the friction coefficient of the road surface, that is, the road surface μ are estimated. In the case of this embodiment, the pseudo vehicle speed VREF is obtained by the reference wheel speed VWS, the calculated deceleration Gk obtained from the reference wheel speed VW, and the deceleration sensor 21 as shown in the block diagram of FIG. The vehicle body deceleration GS is calculated in consideration of the vehicle body deceleration GS. That is, the reference wheel speed VW S selected from the wheel speeds VW of the respective wheels is supplied to the calculation unit 25 that calculates the pseudo vehicle speed VREF as the reference wheel speed VF after being subjected to the filtering process. The VF is supplied to the calculation unit 25 as the calculated deceleration Gk by receiving the differential processing. on the other hand,
The vehicle body deceleration GS obtained by the deceleration sensor 21 is also supplied to the calculation unit 25 after being subjected to a filtering process. In FIG. 3, the subscripts FL, FR, RL, R added to the wheel speed VW
R indicates that the wheel speed is that of the front left wheel, front right wheel, rear left wheel, rear right wheel.

The arithmetic unit 25 calculates the pseudo vehicle speed VREF in consideration of the reference vehicle speed VF, the calculated deceleration Gk, and the vehicle deceleration GS, while estimating the road surface μ. Specifically, the reference vehicle speed VF is normally set as the pseudo vehicle speed VREF, but immediately after the start of the ABS control, the calculated deceleration G
If k is too large for normal braking, it can be estimated that the reference wheel speed VWS itself is also slipping. Therefore, in the situation described above,
Instead of setting the reference vehicle speed VF as the pseudo vehicle speed VREF, in this case, immediately after the start of the ABS control, it is assumed that the vehicle decelerates at a predetermined deceleration for a predetermined time, and The vehicle speed VREF is calculated, and after a predetermined time has elapsed since the start of the ABS control, the deceleration sensor 21
The pseudo vehicle speed VREF is calculated based on the vehicle deceleration GS from the vehicle. When the values of the calculated deceleration Gk and the vehicle deceleration GS return to normal ranges, the reference vehicle speed VF is adopted as the pseudo vehicle speed VREF.

As described above, according to this embodiment, the pseudo vehicle speed V
In calculating the REF, not only the wheel speed VW but also the calculated deceleration Gk and the vehicle body deceleration GS are taken into account. The speed VREF can be accurately calculated.

Further, the road surface μ is estimated from the magnitude of the calculated deceleration Gk or the vehicle body deceleration GS and the change trend thereof. That is, if the value of the deceleration is large, it can be estimated that the road surface μ is also large, and conversely, if the deceleration is small, the road surface μ can also be estimated to be small.

When the pseudo vehicle speed VREF and the road surface μ are estimated in step S9 as described above, in the next steps S10 and S11, the wheel speed VW of each wheel with respect to the pseudo vehicle speed VREF is calculated.
Is calculated based on the slip rate, and based on the slip rate, the brake pressure control of each wheel, that is, the control valve device 15 is adjusted so that the slip rate of each wheel becomes an optimal value.
And operation control of each anti-skid valve device 16 is implemented,
Thereby, the lock of the wheel which tends to lock can be released.

Thereafter, in the next step S12, it is determined whether or not 1 has been set to the abnormality flag F0. However, here, the determination is no, and after a failure diagnosis routine in step S13 described later, By repeating the above-described steps, the brake pressure of each wheel is controlled to increase, maintain, or reduce the pressure in accordance with the rotation trend of the wheel. As a result, each wheel speed VW is made to follow the pseudo vehicle speed VREF. The lock of each wheel can be prevented.

In the case of this embodiment, in controlling the brake pressure of each wheel in step S11, not only the road surface μ estimated in step S9 but also the switching state of each switch read in step S6 is taken into consideration. Has become. Specifically, when the above-described anti-skid control is started while the vehicle is traveling in 4WD, the front-wheel drive system and the rear-wheel drive system are in a prosperous state. If the braking force on the wheel side is controlled independently, the torsional torque in the drive system will increase, which may cause the front and rear wheel speeds VW to oscillate. Therefore, in this embodiment, when controlling the brake pressure of each wheel, for example, a locking tendency occurs in the rear wheel 5R as shown in FIG. 4, and the rear wheels 5L, 5L, When the brake pressure of the 5R is reduced, the brake pressure of the front wheel 4R on the same side as the rear wheel 5R is also reduced by the predetermined pressure DP at the same time. With this configuration, during the anti-skid control, the brake pressure reduction control on the front wheel side and the rear wheel side can be performed in the same phase, so that the vibration of each wheel speed VW is effectively suppressed. be able to. In the case of 2WD, it goes without saying that the brake pressures of the left and right front wheels 4 and both rear wheels 5 are independently controlled during the anti-skid control.

In the above case, the 4WD select switch 22 is turned on, but in addition to the 4WD select switch 22, the center differential lock switch 23 is also turned on to lock the center differential. ,
Vibration is likely to occur at each wheel speed VW for the above-described reason. In such a switching state of the switch, when controlling the brake pressure of each wheel, the brake pressure is set to a more relaxed side than in the case described above. In addition to the above two switches 22 and 23, the rear differential lock switch 24 is also turned on, and when the rear differential 7 is locked, the brake of each wheel is The pressure is
Further, it is controlled on the loosening side.

Next, details of the above-described failure diagnosis routine performed in step S13 are shown in FIG.
The failure diagnosis routine will be described.

First, in step S20 shown in FIG. 5, sensor values from the wheel speed sensors 19 and the deceleration sensors 21 and the switching states of the switches 22, 23, and 24 are stored in a memory. In the next step S21, the average value GAVE of the vehicle body deceleration GS obtained by the deceleration sensor 21 is calculated and stored in the memory. Here, the average value GAVE of the vehicle body deceleration GS is obtained by adding the value of the vehicle body deceleration GS up to a predetermined time before each execution of step S21 when the ABS main routine of FIG. 1 is repeatedly executed. Then, it can be obtained by taking the average value.

In each of the following steps S22 to S25, it is determined whether the 4WD select switch 22, the center differential lock switch 23, the rear differential lock switch 24, and the deceleration sensor 21 are abnormal.
For example, it is determined whether or not a signal line connecting each switch and the controller 20 has a failure such as a disconnection.

If all of the determinations in steps S22 to S25 are negative, the process returns to step S1 and the above-described steps are repeated.

However, if any one of the determinations in steps S22 to S24 becomes positive (Yes),
Proceeding to step S26, in this step, the first-class failure flag F1 is set to 1, and then in step S27, the abnormal flag F0 is set to 1.

On the other hand, if the determination in step S25 is positive, in the next step S28, it is determined whether the driving method of the vehicle is 4WD or 2WD. Here, the driving method is 4
If it is a WD, the process proceeds to step S29, where 1 is set to the second type failure flag F2, and then step S27 is performed. On the other hand, when the driving method is 2WD, after the type 3 failure flag F3 is set to 1 in step S30, step S27 is performed.

Accordingly, after any of the above-described steps S26, S29, and S30 is performed, the process returns to the ABS main routine of FIG. 1, and when this main routine is performed, steps S2, S3, and S3 are performed.
Since any one of the determinations in S5 is positive, according to the failure flag, steps S31 to S33, that is, the first
The seed-to-third-type failsafe control is performed. That is, when the type 1 flag F1 is set to 1 and the determination in step S5 becomes positive, the ABS is controlled to proceed to step S9 through the execution of type 1 fail-safe control from step S5 to step 31. The main routine is performed. On the other hand, if one of the type 2 and type 3 failure flags F2 and F3 is set to 1 and one of the determinations in steps S2 and S3 is positive, the corresponding step is performed from that step.
After execution of S32 or S33, ABS
The main routine will be performed. In the failure diagnosis routine described above, if any of the first to third failure flags F1, F2, and F3 is set to 1, the fifth failure flag is set.
Since the abnormality flag F0 is set to 1 in step S27 in the figure, if the ABS main routine is thereafter executed, the determination in step S12 becomes positive, and thus the failure diagnosis routine in step S13 Is bypassed.

The first to third types of fail-safe control are shown in FIGS. 6 to 8, respectively, and these fail-safe controls will be sequentially described below.

Type 1 fail-safe control This type 1 fail-safe control is, as is clear from the above description, 4 W in the failure diagnosis routine of FIG.
This is performed when a failure occurs in any of the D select switch 22, the center differential lock switch 23, and the rear differential lock switch 24. First, the step shown in FIG.
In S40, it is determined whether the ABS control is being performed. For example, this determination is performed by checking whether or not the wheel speed VW of each wheel has converged within a predetermined deviation with respect to the pseudo vehicle body speed VREF.

If the determination in step S40 is positive, the next step S41 is performed, and the 4WD select switch 2
2. Even if a failure occurs in either the center differential lock switch 23 or the rear differential lock switch 24, the switching state of each of the switches 22, 23, 24 before the failure occurs is maintained. Specifically, in step S20 of FIG.
By reading the switching states of the switches 22, 23, and 24 stored in the memory, the switching states of the switches 22, 23, and 24 before the failure can be maintained.

From step S41, the process proceeds to step S9 in the ABS main routine in FIG. 2, and this step transition step is repeatedly performed.

In the process of repeatedly executing the ABS main routine via the first type fail-safe control in step S31, if the determination in step S40 in FIG. 6 is negative, the process proceeds to step S42. In this step, the alarm lamp 26 (see FIG. 1) is turned on and the operation of the anti-skid brake device, that is, the system is stopped, and a failure code corresponding to the failure flag is output. The ABS main routine is forcibly terminated.

As is apparent from the above-described first-type fail-safe control, during the ABS control, the 4WD select switch 22, the center differential lock switch 23, and the rear differential lock switch 24
Even if a failure occurs in any of the above, the ABS control is not immediately stopped, and until the ABS control ends, taking into consideration the switching state of the various switches 22, 23, 24 before the failure, the Control will be continued. That is, as shown in FIG. 9, a change in the wheel speed VW during the ABS control is shown.
During the control, at time t1, even if any of the switches 22, 23, and 24 fails, the control of the wheel speed VW by the ABS control is performed as follows.
As indicated by the broken line, the control is continued until the end of the control.

Therefore, according to this embodiment, when the ABS control is performed, even if a failure occurs in various switches 22, 23, and 24,
Since the ABS control can be continued until the end thereof, even if the vehicle is running on a low μ road with 4WD at the time of the failure, the ABS control is not undesirably stopped without being stopped. Therefore, a situation in which the four wheels are locked at the same time can be reliably prevented, and the steering performance at that time can be sufficiently ensured, and the braking distance can be shortened.

Second-type fail-safe control This second-type fail-safe control is performed as described in the failure diagnosis routine of FIG.
In addition, this is performed when the drive system at the time of the failure is 4WD. In this case, in step S50 of FIG. 7, as in step S40 of FIG. 6, it is determined whether the ABS control is being performed. Is determined, and if the determination is positive, the next step S5
1 is implemented. In step S51, the vehicle deceleration GS stored in the memory in step S21 in FIG. 5 is used as the vehicle deceleration GS to be read in step S4 in FIG.
After returning to step S9 of the ABS main routine of FIG. 1, the pseudo vehicle speed VREF is calculated, and the road surface μ is estimated. Will be repeated. Therefore, even if such a deceleration sensor 21 fails,
Instead of the vehicle deceleration GS, the average value GAVE immediately before the failure
The anti-skid control can be continued by accurately obtaining the pseudo vehicle speed VREF and the road surface μ.

In the process of repeatedly executing the ABS main routine via the type 2 fail-safe control, step S5
If the determination of 0 is negative, the ABS main routine is forcibly terminated through the execution of step S52 similar to step S42 of FIG.

Third-Type Fail-Safe Control This third-type fail-safe control is executed when the deceleration sensor 21 fails, as in the case of the second-type fail-safe control described above. In other words, the drive system at the time of failure is not 4WD but 2WD. In this case, in step S60 in FIG.
Similar to the case of step S40 of FIG. 6 and step S50 of FIG. 7, it is determined whether or not the ABS control is being performed. If the determination is positive, the next step S61 is performed. In this step S61, the calculated deceleration Gk shown in FIG. 3 is adopted as the vehicle body deceleration GS to be read in step S4 in FIG. That is, in this case, the calculated deceleration Gk is obtained by differentiating the reference wheel speed VWS, and in the case of 2WD, the wheel speed of the non-driving wheel is selected as the reference wheel speed VWS. Therefore, the calculated deceleration Gk accurately represents the vehicle body deceleration. Thereafter, from step S51, the process returns to step S9 of the ABS main routine in FIG. 1, and the pseudo vehicle speed VREF is calculated, the road surface μ is estimated, and the steps after this step are repeated. become. Therefore, even in this case, by using the calculated deceleration Gk instead of the vehicle deceleration GS, the pseudo vehicle speed VREF and the road surface μ can be accurately obtained, and the anti-skid control can be continued.

In the process of repeatedly executing the ABS main routine via the type 3 fail-safe control, step S6
If the determination of 0 is negative, the ABS main routine is forcibly terminated through the execution of step S62 similar to step 42 of FIG. 6 and step S52 of FIG.

Therefore, as apparent from the above description, even if a failure of the deceleration sensor 21 occurs at the time point t1 in FIG. 9 during the ABS control, the type 2 fail-safe control or the type 3 fail-safe Through the control, the ABS main routine is continued until the end of the control. When continuing the ABS main routine, the deceleration sensor 21
The average value GAVE of the vehicle body deceleration GS immediately before the failure or the calculated deceleration Gk obtained by differentiating the reference vehicle body speed VF is used instead of the vehicle body deceleration GS detected by the deceleration sensor 21. Even if the vehicle body deceleration GS cannot be obtained in the above, the pseudo vehicle body speed VREF and the road surface μ obtained in step S9 become appropriate values. Therefore, even in this case, the brake pressure of each wheel should be optimally controlled. Becomes possible. Therefore, at the time of failure, even if the car is traveling on a low μ road, without stopping the ABS control undesirably, the optimal ABS control can be continued until the end thereof, so that the locking of the wheels can be reliably prevented, The steering performance can be sufficiently ensured, and the braking distance can be reduced.

The present invention is not limited to the above-described embodiment, and various modifications are possible. For example, the device for implementing the anti-skid brake control method of the present invention is not limited to the configuration shown in FIG. 1, and the method of the present invention can be implemented even if the structure of the device is appropriately changed. It is.

(Effects of the Invention) As described above, according to the anti-skid brake control method of the present invention, 4W for setting the driving system of the vehicle
Even if the D select switch or the center differential lock switch fails during the anti-skid control, the switching state of the switch before the failure is maintained, and the anti-skid control is performed according to the driving method set by the switch. Continued until the end. Therefore, for example, in a situation where the anti-skid control is started while traveling on a low μ road with four-wheel drive, even if the 4WD select switch or the center differential lock switch fails, the anti-skid control is immediately released and the normal foot control is released. It does not return to the brake control, so that even in such a running condition with four-wheel drive, it is possible to reliably prevent the wheels from being locked, to ensure sufficient steering characteristics, and to control the braking. Excellent effects such as a great effect on shortening the distance.

[Brief description of the drawings]

1 shows an embodiment of the present invention, FIG. 1 is a schematic configuration diagram of an anti-skid brake device, FIG. 2 is a flowchart showing an ABS main routine, and FIG. FIG. 4 is a block diagram for explaining the estimation of the road surface μ, FIG. 4 is a diagram showing an example of brake pressure control by 4WD, FIG. 5 is a flowchart showing a failure diagnosis routine, and FIG. FIG. 7 is a flowchart showing a second type fail-safe control, FIG. 8 is a flowchart showing a third type fail-safe control, and FIG. 9 is a diagram showing wheel speeds and vehicle bodies during ABS control. It is the graph which showed the behavior of the deceleration. 4 Front wheel 5 Rear wheel 9 Wheel brake 12
... master cylinder, 15 ... control valve device, 16 ... anti-skid valve device, 19 ... wheel speed sensor, 20 ... controller, 21 ... deceleration sensor, 22 ... 4WD select switch, 23 ... center Differential lock switch, 24 ... Rear differential lock switch, 26 ... Alarm lamp.

Continuation of front page (56) References JP-A-62-251264 (JP, A) JP-A-60-25836 (JP, A) JP-A-62-94461 (JP, A) JP-A-61-232955 (JP) JP-A-60-45457 (JP, A) JP-A-1-82971 (JP, U) JP-A-1-74959 (JP, U) JP-A-62-195568 (JP, U) (58) Surveyed field (Int.Cl. ⁶ , DB name) B60T 8/58 B60T 8/66 B60T 8/92

Claims (2)

(57) [Claims] The present invention is applied to an automobile having a 4WD select switch for switching between four-wheel drive and two-wheel drive as one of switches for setting a drive system, and detecting wheel speed of each wheel by a wheel speed sensor. On the other hand, the vehicle body deceleration is detected by the deceleration sensor, and during braking, the pseudo vehicle speed is calculated based on the wheel speed and the vehicle deceleration. When
In an anti-skid brake control method for controlling the braking force of the wheels to eliminate the tendency of locking the wheels according to the driving method set by the switch, whereby the wheel speeds of the wheels follow the pseudo vehicle speed, A storage step of storing a switching state of the switch; a determining step of determining whether there is a failure of the switch; and during anti-skid control, when it is determined that the switch has failed in the determining step, A continuation step of maintaining the switching state in the switching state immediately before the failure and continuously performing the anti-skid control until the end thereof. 2. The switch according to claim 1, further comprising a center differential lock switch for locking a Santa differential of the vehicle, wherein said storing step and said determining step store the switching state of said center differential lock switch and determine whether or not there is a failure. The anti-skid brake control method according to claim 1, wherein the continuation step is performed when a failure occurs in one of the 4WD select switch and the center differential lock switch.