JPH09109870A - Anti-skid control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent generation of the cascade condition on a low μ road by surely detecting that the road surface is the low μ road based on the differential speed between the maximum wheel speed and the minimum wheel speed of all wheels and the difference in each mean wheel speed between right and left front wheels and right and left rear wheels. SOLUTION: When a vehicle is traveling, a signal processing device 10 selects the maximum wheel speed and the minimum wheel speed among all wheel speeds detected by wheel speed sensors S0 -S3 , and calculates the differential speed Δ S thereof. The difference in each mean wheel speed Δ Save between the right and left front wheels and the right and left rear wheels based on each wheel speed. When the frequency that the differential speed ΔS is above the prescribed value, and the difference Δ Save is below the prescribed value is below the prescribed value, it is judged that the vehicle is in the cascade condition on the low μ road. The low μcontrol which is the ABS control corresponding to the low μ road is realized. The cascade condition on the low μroad is prevented from being generated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle anti-skid control device, and more particularly to an anti-skid control device for a four-wheel drive vehicle that estimates the wheel cylinder hydraulic pressure of each wheel during ABS control.

[0002]

2. Description of the Related Art Generally, in an antiskid control device,
The skid state of the wheel is detected by the amount of depression of the wheel with respect to the vehicle body speed and the wheel acceleration / deceleration, and the brake fluid pressure is adjusted to an appropriate level accordingly. As a result, the skid of the wheel is maintained at an appropriate level, that is, in the region where the friction coefficient μ of the road surface is near the peak, so that the braking distance is shortened and the vehicle body stability and steering stability are secured high. . However, when controlling the pressure increase / decrease of the brake fluid, judging only by the behavior of the wheels and the vehicle body, the brake fluid pressure will be excessively reduced, or the pressurizing operation after the excessive reduction will not be performed accurately and the brake fluid pressure Occasionally a shortage condition occurred.

As a method for controlling the brake fluid pressure, an ON / OFF type solenoid valve is generally adopted. In this method, the solenoid valve is used to increase or decrease the brake fluid pressure in the wheel cylinder. The brake fluid pressure is controlled by performing In this case, the pressure increase / decrease characteristic of the brake hydraulic pressure changes depending on the master cylinder hydraulic pressure or the wheel cylinder hydraulic pressure, so the above problems may occur unless an accurate brake hydraulic pressure value is known. was there.

As a method for solving the above problem, it is preferable to use an actuator having a servo function as an actuator for directly controlling the brake fluid pressure.
Japanese Patent Publication No. 3-92463. However, since such an actuator is expensive, it is not very desirable in terms of cost.

[0005]

Therefore, conventionally, an actuator having a general ON / OFF type solenoid valve is used to estimate a brake fluid pressure value in a wheel cylinder under ABS control, and the brake fluid pressure is estimated. Although pressure control was performed, especially in a four-wheel drive vehicle, even though the braking road surface is a low μ road with a small friction coefficient μ, the friction coefficient μ
It is possible to detect a lock symptom even though it is erroneously determined to be a high μ road with a large number of wheels, and the lock symptom is shown even though the wheel speed of each wheel is in a cascade state in which the wheel speeds are almost uniform and sinking. However, there is a problem that the brake fluid pressure reduction command becomes a small brake fluid pressure reduction value assuming a road surface with a larger friction coefficient μ, wheel locking and improper skid occur and vehicle stability etc. is impaired. It was

The present invention has been made to solve the above problems, and reliably detects that the road surface is a low μ road, and prevents the occurrence of a cascade state on the low μ road. An object of the present invention is to obtain an anti-skid control device for a four-wheel drive vehicle capable of estimating the wheel cylinder hydraulic pressure of each wheel during ABS control.

[0007]

The present invention has a wheel speed sensor for detecting the wheel speed of each wheel, and the wheel of each wheel during ABS control from each wheel speed detected by the wheel speed sensor. In the anti-skid control device for estimating the cylinder hydraulic pressure, a selecting means for selecting the maximum wheel speed Vmax1 which is the maximum value and the minimum wheel speed Vmin which is the minimum value among the above wheel speeds, and the maximum wheel speed Vmax1.
Difference speed ΔS which is the difference between the minimum wheel speed Vmin and the minimum wheel speed Vmin, and a difference speed determination means for determining whether or not the difference speed ΔS is a predetermined value A or more; A difference ΔSave between the speed and the average wheel speed of the left and right rear wheels is calculated, and front and rear wheel difference speed determination means for determining whether or not the difference ΔSave is less than or equal to a predetermined value B. The difference speed determination means determines that ΔS is equal to or larger than the predetermined value A, and the difference ΔSave is equal to or larger than the predetermined value B.
When the frequency is less than or equal to a predetermined value Z by the front / rear wheel differential speed determination means, the cascade determination means determines that the vehicle is in the cascade state on the low μ road, and the cascade determination means determines the low μ road. When it is determined that the anti-skid control device is in the cascade state, the anti-skid control device is provided with a cascade control means for setting the low μ control which is the ABS control corresponding to the low μ road. is there.

In this way, it is possible to detect the variation in the wheel speeds by detecting that the difference speed ΔS is equal to or more than the predetermined value A, and to detect that the difference ΔSave is less than or equal to the predetermined value B. Therefore, the frequency of detecting that the wheel speed difference ΔSave between the front and rear wheels is almost 0 is the predetermined value Z.
By detecting the above, it is possible to detect the cascade state when the road surface μ of each wheel varies on a low μ road. Further, when such a cascade state is detected, since the road surface is a low μ road, ABS control corresponding to the low μ road is performed.
It is possible to prevent the cascade state on the low μ road. From these facts, in a vehicle, especially a four-wheel drive vehicle, it is possible to prevent erroneous determination of a high μ road on a low μ road where the road surface μ between the wheels varies, and it is also possible to prevent the low μ road. A cascade condition on the road can be prevented, the wheels can be prevented from locking, and skids can be generated appropriately.
The performance and reliability of BS control can be improved.

In the invention described in claim 2 of the present application, the cascade determination means of claim 1 is:
When the differential speed determining means determines that the differential speed ΔS is equal to or larger than the predetermined value A and the front and rear wheel differential speed determining means determines that the difference ΔSave is equal to or smaller than the predetermined value B, the count-up is performed. Other than that, it is characterized in that it has a count means for performing a countdown, and when the count value of the count means becomes equal to or greater than a predetermined value α, it is determined that the vehicle is in a cascade state on a low μ road.

As described above, by detecting that the difference speed ΔS is equal to or larger than the predetermined value A, the variation in the wheel speeds is detected, and the difference ΔSave is smaller than or equal to the predetermined value B. By measuring the frequency of detecting that the wheel speed difference ΔSave between the front and rear wheels is almost 0 by using the counting means, the cascade state is detected when the road surface μ of each wheel varies on a low μ road. can do. From this, vehicles, especially 4
In a wheel drive vehicle, it is possible to prevent erroneous determination as a high μ road on a low μ road where there is variation in the road surface μ between the wheels, and to prevent a cascade state on the low μ road, Since the wheel can be prevented from being locked and the skid can be appropriately generated, the ABS control performance and reliability can be improved.

In the invention described in claim 3 of the present application, when the differential speed determining means of claim 1 determines that the differential speed ΔS is equal to or more than a predetermined value A, a flag F
s is set, and the front-rear wheel differential speed determination means of claim 1 sets a flag Fave when it determines that the difference ΔSave is less than or equal to a predetermined value B, and the cascade determination means of claim 1 sets the flag Fs and The cascade control according to claim 1, further comprising a counting means for counting up when the flag Fave is all set and for counting down otherwise, and setting the flag Fcas when the count value of the counting means is equal to or more than a predetermined value α. The means is set to perform the low μ control when the flag Fcas is set.

As described above, the frequency of detecting the state in which both the flag Fs and the flag Fave are set is measured by using the counting means, so that the road surface μ of each wheel varies on a low μ road. It is possible to detect the cascade state of the case. From this, in a vehicle, particularly a four-wheel drive vehicle, it is possible to prevent a low μ road having a road surface μ variation between the wheels from being erroneously determined to be a high μ road, and to prevent the low μ road from being erroneously determined. Since it is possible to prevent the cascade state in the above and prevent the wheels from being locked and appropriately generate the skid, it is possible to improve the performance and reliability of the ABS control.

In the invention described in claim 4 of the present application, the cascade determination means of claim 1 is
Counts down when the differential speed determining means determines that the differential speed ΔS is equal to or greater than the predetermined value A, and the front and rear wheel differential speed determining means determines that the difference ΔSave is equal to or less than the predetermined value B. Has a counting means for counting up, and when the count value of the counting means becomes equal to or smaller than a predetermined value β which is smaller than the initial value of the counting means, it is determined that the vehicle is in a cascade state on a low μ road. Characterize.

As described above, by detecting that the difference speed ΔS is equal to or larger than the predetermined value A, the variation of the wheel speeds can be detected, and the difference ΔSave can be detected as being equal to or smaller than the predetermined value B. By measuring the frequency of detecting that the wheel speed difference ΔSave between the front and rear wheels is almost 0 by using the counting means, the cascade state is detected when the road surface μ of each wheel varies on a low μ road. can do. From this, vehicles, especially 4
In a wheel drive vehicle, it is possible to prevent erroneous determination as a high μ road on a low μ road where there is variation in the road surface μ between the wheels, and to prevent a cascade state on the low μ road, Since the wheel can be prevented from being locked and the skid can be appropriately generated, the ABS control performance and reliability can be improved.

In the invention described in claim 5 of the present application, when the differential speed determining means in claim 1 determines that the differential speed ΔS is a predetermined value A or more, a flag F
s is set, and the front-rear wheel differential speed determination means of claim 1 sets a flag Fave when it determines that the difference ΔSave is less than or equal to a predetermined value B, and the cascade determination means of claim 1 sets the flag Fs and When the flag Fave is all set, it has a count means that counts down and otherwise counts up, and sets the flag Fcas when the count value of the count means becomes a predetermined value β smaller than the initial value of the count means. However, the cascade control means according to claim 1 is set to perform the low μ control when the flag Fcas is set.

As described above, by measuring the frequency of detecting the state in which both the flag Fs and the flag Fave are set by using the counting means, there is a variation in the road surface μ of each wheel on a low μ road. It is possible to detect the cascade state of the case. From this, in a vehicle, particularly a four-wheel drive vehicle, it is possible to prevent a low μ road having a road surface μ variation between the wheels from being erroneously determined to be a high μ road, and to prevent the low μ road from being erroneously determined. Since it is possible to prevent the cascade state in the above and prevent the wheels from being locked and appropriately generate the skid, it is possible to improve the performance and reliability of the ABS control.

The invention according to claim 6 of the present application has a wheel speed sensor for detecting the wheel speed of each wheel, and A is calculated from each wheel speed detected by the wheel speed sensor.
In an anti-skid control device that estimates the wheel cylinder hydraulic pressure of each wheel during BS control, an ABS that determines whether or not at least one wheel is in an ABS control state
It is a difference between the judging means, a selecting means for selecting the maximum wheel speed Vmax1 which is the maximum value among the wheel speeds and the minimum wheel speed Vmin which is the minimum value, and the difference between the maximum wheel speed Vmax1 and the minimum wheel speed Vmin. The difference speed ΔS is calculated, and the difference speed ΔS is less than or equal to a predetermined value C, and ΔS determining means is used to calculate the acceleration of each wheel from the wheel speeds. The wheel acceleration determining means for determining whether the vehicle speed is equal to or less than a predetermined value D, the estimated vehicle body speed calculating means for calculating an estimated vehicle body speed which is an estimated value of the vehicle body speed from the wheel speeds, and the estimated vehicle body speed calculating means. From the calculated estimated vehicle speed, the descending speed of the estimated vehicle speed is high μ
The vehicle body deceleration judging means for judging whether or not the value is equal to or more than a predetermined value E corresponding to the value on the road, and the ABS judging means for judging that at least one wheel is in the ABS control state in a predetermined control cycle. , And the above-mentioned difference acceleration ΔS is below a predetermined value C, the above-mentioned ΔS determining means determines, and all the wheel acceleration of each wheel is below a predetermined value D, the above-mentioned wheel acceleration determining means determines, and the estimated vehicle body speed. If the vehicle body deceleration determining means determines that the descending speed is equal to or higher than a predetermined value E continuously for a predetermined value T or more, the cascade determining means determines that the vehicle is in a cascade state on a low μ road, When the cascade determination means determines that it is in the cascade state on the low μ road, the cascade control means is set to perform the low μ control which is the ABS control corresponding to the low μ road. There is provided a Nchisukiddo controller.

As described above, it is detected that the ABS control is being performed, and that the estimated vehicle body speed lowering speed is equal to or higher than the value corresponding to the high μ road, and all four wheels are not skid on the road surface. While detecting the gripping situation,
By detecting a state where the wheel acceleration is small such that the road surface is on a low μ road and the behavior of the wheel is in a cascade state, and the state is continued for a predetermined time T or more, the cascade state on the low μ road is detected. It is possible to detect, and it is also possible to detect a cascade state on a low μ road where there is no variation in the friction coefficient μ of the road surface between the wheels. Furthermore, when such a cascade state is detected, since the road surface is a low μ road, the ABS control corresponding to the low μ road is performed, so that the cascade state on the low μ road can be prevented. . From these facts, in a vehicle, especially a four-wheel drive vehicle, it is possible to prevent erroneous determination of a high μ road on a low μ road where the road surface μ between the wheels varies, and it is also possible to prevent the low μ road. Since the cascade state on the road can be prevented, the wheels can be prevented from being locked, and the skid can be appropriately generated, the performance and reliability of the ABS control can be improved.

In the invention according to claim 7 of the present application, the cascade determination means according to claim 6 is:
If at least one wheel is in the ABS control state, the above A
The BS determining means makes a determination, and the differential speed ΔS is a predetermined value C.
The ΔS determining means determines that the following is true, and the wheel acceleration determining means determines that all of the calculated wheel accelerations are equal to or less than the predetermined value D, and the estimated vehicle body speed lowering speed is on a high μ road. If the vehicle body deceleration determining means determines that the vehicle body deceleration determining means is equal to or greater than a predetermined value E corresponding to a value, the counting means resets to an initial value otherwise, and the count value of the counting means is a predetermined value γ. The above is characterized in that the vehicle is determined to be in the cascade state on the low μ road.

In this way, it is detected that the ABS control is in progress, and that the estimated vehicle body speed lowering speed is equal to or higher than the value corresponding to the high μ road, and all four wheels are not skid on the road surface. While detecting the gripping situation,
By detecting a state in which the wheel acceleration is small such that the road surface is a low μ road and shows the behavior of wheels in a cascade state, and by measuring and detecting that the state has continued for a predetermined time T or more by using the counting means, It is possible to detect the cascade state on the low μ road, and it is also possible to detect the cascade state on the low μ road where there is no variation in the friction coefficient μ of the road surface between the wheels. Therefore, in a vehicle, particularly a four-wheel-drive vehicle, it is possible to prevent a low μ road from being erroneously determined to be a high μ road, prevent a cascade state on the low μ road, and lock wheels. Therefore, the skid can be appropriately generated and the ABS control performance and reliability can be improved.

In the invention described in claim 8 of the present application, the ABS judging means of claim 6 sets the flag Fabs when judging that at least one wheel is in the ABS control state, The ΔS determination means of item 6 sets the flag Fs1 when it determines that the differential speed ΔS is less than or equal to the predetermined value C, and the wheel acceleration determination means of claim 6 has all the calculated wheel accelerations equal to or less than the predetermined value D. If it is determined that there is a flag, the flag Facc is set, and the vehicle body deceleration determining means according to claim 6 determines that the estimated vehicle body speed has a high decrease μ.
The flag Fdec is set when it is determined that the value is equal to or more than the predetermined value E corresponding to the value on the road, and the cascade determination means of the above-mentioned claim 6 counts when the flag Fabs, the flag Fs1, the flag Facc and the flag Fdec are all set. Up,
Other than that, it has counting means for resetting to the initial value,
The flag Fcas is set when the count value of the counting means becomes equal to or larger than a predetermined value γ, and the cascade control means according to claim 6 is set to perform the low μ control when the flag Fcas is set. And

As described above, the flag Fabs, the flag Fs1,
By detecting a state in which the flag Facc and the flag Fdec are all set, and measuring and detecting that the state has continued for a predetermined time T or longer by using the counting means,
It is possible to detect the cascade state on the low μ road, and it is also possible to detect the cascade state on the low μ road where there is no variation in the friction coefficient μ of the road surface between the wheels. Therefore, in a vehicle, particularly a four-wheel-drive vehicle, it is possible to prevent a low μ road from being erroneously determined to be a high μ road, prevent a cascade state on the low μ road, and lock wheels. Therefore, the skid can be appropriately generated and the ABS control performance and reliability can be improved.

In the invention described in claim 9 of the present application, the cascade determination means of claim 6 is:
If at least one wheel is in the ABS control state, the above A
The BS determining means makes a determination, and the differential speed ΔS is a predetermined value C.
The ΔS determining means determines that the following is true, and the wheel acceleration determining means determines that all of the calculated wheel accelerations are equal to or less than the predetermined value D, and the estimated vehicle body speed lowering speed is on a high μ road. If the vehicle body deceleration determination means determines that the vehicle body deceleration determination means is equal to or greater than a predetermined value E corresponding to the value, the count means resets to an initial value otherwise, and the count value of the count means is equal to the count value of the count means. It is characterized in that the vehicle is determined to be in a cascade state on a low μ road when the value is equal to or smaller than a predetermined value δ which is smaller than the initial value.

In this way, it is detected that the ABS control is in progress, and that the estimated vehicle body speed lowering speed is equal to or higher than the value corresponding to the high μ road, and all four wheels are not skid on the road surface. While detecting the gripping situation,
By detecting a state in which the wheel acceleration is small such that the road surface is a low μ road and shows the behavior of wheels in a cascade state, and by measuring and detecting that the state has continued for a predetermined time T or more by using the counting means, It is possible to detect the cascade state on the low μ road, and it is also possible to detect the cascade state on the low μ road where there is no variation in the friction coefficient μ of the road surface between the wheels. Therefore, in a vehicle, particularly a four-wheel-drive vehicle, it is possible to prevent a low μ road from being erroneously determined to be a high μ road, prevent a cascade state on the low μ road, and lock wheels. Therefore, the skid can be appropriately generated and the ABS control performance and reliability can be improved.

In the invention according to claim 10 of the present application, the ABS judging means according to claim 6 sets the flag Fabs when judging that at least one wheel is in the ABS control state, The ΔS determination means of item 6 sets the flag Fs1 when it determines that the differential speed ΔS is less than or equal to the predetermined value C, and the wheel acceleration determination means of claim 6 has all the calculated wheel accelerations equal to or less than the predetermined value D. The flag Facc is set when it is determined that there is, and the flag Facc is set.
The vehicle body deceleration determining means sets the flag Fdec when it determines that the descending speed of the estimated vehicle body speed is equal to or more than the predetermined value E corresponding to the value on the high μ road, and the cascade determining means of the above-mentioned claim 6 When the Fabs, the flag Fs1, the flag Facc, and the flag Fdec are all set, the counter has a count means for counting down, and the other means for resetting to an initial value. The count value of the count means is smaller than the initial value of the count means. The flag Fcas is set when the value is δ or less, and the cascade control means of the sixth aspect is set to perform the low μ control when the flag Fcas is set.

In this way, the flags Fabs, Fs1,
By detecting a state in which the flag Facc and the flag Fdec are all set, and measuring and detecting that the state has continued for a predetermined time T or longer by using the counting means,
It is possible to detect the cascade state on the low μ road, and it is also possible to detect the cascade state on the low μ road where there is no variation in the friction coefficient μ of the road surface between the wheels. Therefore, in a vehicle, particularly a four-wheel-drive vehicle, it is possible to prevent a low μ road from being erroneously determined to be a high μ road, prevent a cascade state on the low μ road, and lock wheels. Therefore, the skid can be appropriately generated and the ABS control performance and reliability can be improved.

In the invention according to claim 11 of the present application, when the cascade control means according to any one of claims 1 to 10 determines that the cascade determination means is in a cascade state on a low μ road. , When setting to calculate the estimated vehicle body speed based on the maximum wheel speed which is the maximum value among the wheel speeds, and the cascade determination means does not determine that it is in the cascade state on the low μ road,
It is characterized in that the estimated vehicle body speed is set based on the maximum wheel speed which is the maximum value among the wheel speeds and the wheel speeds other than the maximum wheel speed.

As described above, when the cascade state on the low μ road is detected, the road surface is a low μ road, and therefore, the estimated vehicle body speed Vref is set based on the maximum wheel speed to set the estimated vehicle body speed. It is possible to prevent the speed Vref from being calculated excessively, and it is possible to prevent the cascade state on the low μ road. As a result, the wheels can be prevented from locking and skids can be appropriately generated, so that the performance and reliability of the ABS control can be improved.

In the invention described in claim 12 of the present application, when the cascade control means of claim 11 does not determine that the cascade determination means is in the cascade state on the low μ road, The estimated vehicle body speed is set based on an average value of the maximum wheel speed that is the maximum value among the wheel speeds and the wheel speed that is the next largest value of the maximum wheel speed.

In this way, when the cascade state on the low μ road is not detected, the estimated vehicle body speed Vref is calculated based on the average value of the maximum wheel speed and the wheel speed of the next largest value of the maximum wheel speed. By setting so that it is possible to prevent the estimated vehicle body speed Vref from being calculated excessively, it is possible to realize high braking performance.
As a result, the wheels can be prevented from locking and skids can be appropriately generated, so that the performance and reliability of the ABS control can be improved.

In the invention described in claim 13 of the present application, if the cascade control means of the above-mentioned claim 11 and claim 12 determines that the above-mentioned cascade determination means is in a cascade state on a low μ road. Further, it is characterized in that a criterion for detecting the lock symptom is set so that the lock symptom of each wheel can be easily detected, and the wheel cylinder hydraulic pressure reduction amount is set to be large. In this way, when the cascade condition on the low μ road is detected, the judgment criterion that the wheel is the lock sign is set so that the lock sign of each wheel can be easily detected, and the wheel cylinder hydraulic pressure reduction amount is increased. And low μ
It is possible to prevent a cascade condition on the road. From these facts, in a vehicle, particularly a four-wheel drive vehicle, the cascade state on the low μ road can be detected and prevented, the wheel can be prevented from being locked, and the skid can be appropriately generated. Performance and reliability can be improved.

In the invention according to claim 14 of the present application, when the cascade control means according to claim 13 determines that the cascade determination means is in a cascade state on a low μ road, the wheel acceleration is increased. Is the threshold TH3
In the pressurization start condition that the pressurization of the wheel cylinder hydraulic pressure is started when it exceeds the threshold value, the threshold value TH3 is set to be larger than that in the case where it is not determined that the cascade state is on the low μ road. To do. In this way, when detecting the cascade state on the low μ road, since the road surface is the low μ road, in order to make it easier to detect the lock sign of each wheel, while setting the determination standard for detecting the lock sign,
It is possible to prevent the cascade state on the low μ road by increasing the pressure reduction amount of the wheel cylinder hydraulic pressure by continuing the pressure reduction signal of the wheel cylinder hydraulic pressure for a longer time. From these facts, in a vehicle, especially a four-wheel drive vehicle, it is possible to detect and prevent a cascade state on a low μ road, prevent wheel lock, and appropriately generate skids. And reliability can be improved.

In the invention according to claim 15 of the present application, the cascade control means according to claims 13 and 14 determines that the cascade determination means is in a cascade state on a low μ road. In this case, in the pressurization start condition that the pressurization of the wheel cylinder hydraulic pressure is started when the differential value of the wheel acceleration exceeds the threshold value TH4, it is more than that in the case where it is not determined that the cascade state is on the low μ road. The feature is that the threshold value TH4 is set large.
In this way, when the cascade condition on a low μ road is detected, the road surface is a low μ road, so the judgment criteria for detecting the lock sign are set and the wheel is set so that the lock sign of each wheel can be easily detected. It is possible to prevent the cascade state on the low μ road by increasing the pressure reduction amount of the wheel cylinder hydraulic pressure by continuing the pressure reduction signal of the cylinder hydraulic pressure for a longer time. From these facts, in a vehicle, especially a four-wheel drive vehicle, it is possible to detect and prevent a cascade state on a low μ road, prevent wheel lock, and appropriately generate skids. And reliability can be improved.

The invention as set forth in claim 16 of the present application has a wheel speed sensor for detecting a wheel speed of each wheel, and ABS control is performed from each wheel speed detected by the wheel speed sensor. In the anti-skid control device for estimating the wheel cylinder hydraulic pressure of each wheel, the maximum wheel speed Vmax1 which is the maximum value and the minimum wheel speed Vmin which is the minimum value among the wheel speeds are selected, and the maximum wheel speed Vm is selected.
The difference speed ΔS, which is the difference between ax1 and the minimum wheel speed Vmin, is calculated, and it is determined whether or not the difference speed ΔS is equal to or more than a predetermined value A. The difference ΔSave from the average wheel speed of the wheels is calculated, and the difference ΔSa
It is determined whether ve is equal to or less than a predetermined value B, it is determined that the difference speed ΔS is greater than or equal to a predetermined value A, and the difference ΔSave is less than or equal to a predetermined value B in a predetermined control cycle. When the frequency is equal to or higher than the predetermined value Z, it is determined that the vehicle is in the cascade state on the low μ road, and when it is determined that the vehicle is in the cascade state on the low μ road, the low μ control which is the ABS control corresponding to the low μ road. The present invention provides an anti-skid control device characterized by being set so as to perform.

In this way, by detecting that the speed difference ΔS is greater than or equal to the predetermined value A, it is possible to detect the variation in the wheel speeds and also detect that the difference ΔSave is less than or equal to the predetermined value B. Therefore, the frequency of detecting that the wheel speed difference ΔSave between the front and rear wheels is almost 0 is the predetermined value Z.
By detecting the above, it is possible to detect the cascade state when the road surface μ of each wheel varies on a low μ road. Further, when such a cascade state is detected, since the road surface is a low μ road, ABS control corresponding to the low μ road is performed.
It is possible to prevent the cascade state on the low μ road. From these facts, in a vehicle, especially a four-wheel drive vehicle, it is possible to prevent erroneous determination of a high μ road on a low μ road where the road surface μ between the wheels varies, and it is also possible to prevent the low μ road. A cascade condition on the road can be prevented, the wheels can be prevented from locking, and skids can be generated appropriately.
The performance and reliability of BS control can be improved.

The invention as set forth in claim 17 of the present application has a wheel speed sensor for detecting the wheel speed of each wheel, and ABS control is performed from each wheel speed detected by the wheel speed sensor. In the anti-skid control device for estimating the wheel cylinder hydraulic pressure of each wheel, at least 1
It is determined whether or not one of the wheels is in the ABS control state, and the maximum wheel speed Vmax1 which is the maximum value among the above wheel speeds,
The minimum wheel speed Vmin, which is the minimum value, is selected, the difference speed ΔS, which is the difference between the maximum wheel speed Vmax1 and the minimum wheel speed Vmin, is calculated, and it is determined whether the difference speed ΔS is less than or equal to a predetermined value C. Then, the acceleration of each wheel is calculated from the wheel speeds, it is determined whether or not all the calculated wheel accelerations are equal to or less than a predetermined value D, and the estimated vehicle body speed that is an estimated value of the vehicle body speed is calculated from the wheel speeds. The speed is calculated, and from the calculated estimated vehicle speed, it is determined whether or not the descending speed of the estimated vehicle speed is equal to or higher than a predetermined value E corresponding to the value on the high μ road, and at least in a predetermined control cycle. It is determined that one wheel is in the ABS control state, the differential speed ΔS is less than or equal to a predetermined value C, and all the wheel acceleration of each wheel is less than or equal to a predetermined value D, and the estimated vehicle body If the descending speed of the speed is equal to or higher than the predetermined value E When the set time continuously exceeds the predetermined value T, it is determined that the low-μ road is in the cascade state, and when it is determined that the low-μ road is in the cascade state, the ABS control corresponds to the low-μ road. The present invention provides an anti-skid control device characterized by performing low μ control.

As described above, it is detected that the ABS control is being performed, and that the estimated vehicle body speed lowering speed is equal to or higher than the value corresponding to the high μ road, and all four wheels are not skid on the road surface. While detecting the gripping situation,
By detecting a state where the wheel acceleration is small such that the road surface is on a low μ road and the behavior of the wheel is in a cascade state, and the state is continued for a predetermined time T or more, the cascade state on the low μ road is detected. It is possible to detect, and it is also possible to detect a cascade state on a low μ road where there is no variation in the friction coefficient μ of the road surface between the wheels. Furthermore, when such a cascade state is detected, since the road surface is a low μ road, the ABS control corresponding to the low μ road is performed, so that the cascade state on the low μ road can be prevented. . From these facts, in a vehicle, especially a four-wheel drive vehicle, it is possible to prevent erroneous determination of a high μ road on a low μ road where the road surface μ between the wheels varies, and it is also possible to prevent the low μ road. Since the cascade state on the road can be prevented, the wheels can be prevented from being locked, and the skid can be appropriately generated, the performance and reliability of the ABS control can be improved.

[0038]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described in detail based on an embodiment shown in the drawings. 1 is a schematic control system diagram showing a first embodiment of an anti-skid control device of the present invention, and FIG. 2 is a schematic block diagram showing a first embodiment of the device of the present invention. Therefore, first, the outline of the first embodiment of the apparatus of the present invention will be described with reference to FIGS. 1 and 2.

The control object of the anti-skid control device according to the first embodiment of the present invention shown in FIGS. 1 and 2 is a four-wheel drive vehicle, and corresponds to the master cylinder 1 and the left and right front wheels and the left and right rear wheels, respectively. Wheel cylinders 2A, 2B, 2
While the inlet valves 3A, 3B, 3C, 3D made up of ON / OFF type electromagnetic valves are arranged between C and 2D, the outlet valves 4A, 4B made up of ON / OFF type electromagnetic valves from the wheel cylinders 2A to 2D are arranged. Four
A recirculation line 7 is provided for recirculating to the master cylinder 1 via C, 4D and pump motor 6. A buffer chamber 8 is arranged between the outlet valves 4A to 4D of the reflux line 7 and the pump motor 6. The symbols A, B, C, and D indicating the wheel cylinder, the inlet valve, and the outlet valve indicate the left and right front wheels and the left and right rear wheels of the vehicle, respectively.

The wheel speed sensors S0, S1, S2, S3 are connected to a signal processing device 10 which will be described later, and the wheel speed sensors S0, S1, S2, S3 detect the respective speeds of the left and right front wheels and the left and right rear wheels. The detected speed is sent to the signal processing device 10 as a wheel speed signal.

The signal processing device 10 comprises a microcomputer, and as shown in FIG.
Differential speed determination unit 12, front and rear wheel differential speed determination unit 13, flag F
The cas operation unit 14 and the solenoid command output unit 15 are provided, and the predetermined processing is performed on the wheel speed signal to perform the inlet valves 3A to 3D and the outlet valve 4.
Actuators ACT0, ACT1, A with A to 4D
The compression / decompression signal Si is output to CT2 and ACT3. The subscript i is i = 0, 1, 2, 3 and indicates the left and right front wheels and the left and right rear wheels of the vehicle, respectively, together with the subscripts 0, 1, 2, and 3 indicating the wheel speed sensors and actuators. Further, in FIG. 1, except for the master cylinder 1 and the signal processing device 10, an arbitrary one of the four wheels of a four-wheeled vehicle is shown as an example, and the reference numeral 4 is necessary for the explanation. It shows a circle.

The wheel speed sensors S0 to S3 are connected to the basic control amount calculation unit 11, and the basic control amount calculation unit 11 is connected to the differential speed determination unit 12, the front and rear wheel differential speed determination unit 13, and the solenoid command output unit 15. The differential speed determination unit 12 and the front and rear wheel differential speed determination unit 13 are connected to the flag Fcas operating unit 14, and the flag Fcas operating unit 14 is connected to the solenoid command output unit 15.

The basic control amount calculation unit 11 is based on the wheel speed signals input from the wheel speed sensors S0 to S3, and the wheel speed SPEE of each wheel representing the behavior of the wheel and the vehicle body.
Di is calculated, and the calculated wheel speed SPEEDi is output to the solenoid command output unit 15. Where wheel speed SP
The method of calculating EEDi is known and wheel speed SPE is known.
As an example of a method for calculating EDi, from the number m of pulse signals from the wheel speed sensor generated within a predetermined time Δt,
It is calculated from the following formula (1). SPEEDi = m / Δt × a (1) In the above formula (1), a is a proportional constant. Further, the basic control amount calculation unit 11 further outputs the calculated wheel speed SPEEDi of each wheel to the differential speed determination unit 12 and the front and rear wheel differential speed determination unit 13.

The differential speed determination unit 12 has a maximum wheel speed Vmax1 that is the maximum value and a minimum wheel speed Vmi that is the minimum value among the wheel speeds input from the basic control amount calculation unit 11.
n is selected, and the maximum wheel speed Vmax1 and the minimum wheel speed Vmin are selected.
The difference speed ΔS which is the difference between the difference speed ΔS and the difference speed ΔS is a predetermined value A or more, for example, 2 km / h or more, the difference speed ΔS is a predetermined value A or more Set the flag Fs. In a four-wheel drive vehicle, when four wheels are restrained and a cascade state occurs on a low μ road, the four wheels have almost the same speed. However, if the road surface μ of each wheel varies, the wheel speed between the wheels varies due to the influence of the differential gear. Therefore, as described above, the differential speed determination unit 12 detects the variation in the wheel speed, and detects the cascade state when the road surface μ of each wheel varies on the low μ road.

The front / rear wheel differential speed determination unit 13 calculates the average wheel speed of the front wheels and the average wheel speed of the rear wheels from the wheel speeds input from the basic control amount calculation unit 11, and calculates the calculated average. ΔSave, which is the difference in wheel speed, is calculated from the following equation (2). ΔSave = | (SPEED0 + SPEED1) / 2- (SPEED2 + SPEED3) / 2 | ………………………… (2) SPEED0 is the wheel speed of the left front wheel, and SPEED
ED1 is the wheel speed of the right front wheel, SPEED2 is the wheel speed of the left rear wheel, and SPEED3 is the wheel speed of the right rear wheel.

When ΔSave calculated by the above equation (2) is less than or equal to a predetermined value B, for example, 2 km / h or less, Δ
A front / rear wheel differential speed determination flag Fave indicating that Save is less than or equal to a predetermined value B is set. In a four-wheel drive vehicle,
When the vehicle is in a cascade state on a road surface having a low friction coefficient μ, there is a characteristic that the wheel speed difference between the front and rear wheels is almost 0, and when the LSD is provided between the front and rear wheels, the characteristic is particularly remarkable. . Therefore, the front / rear wheel differential speed determination unit 1
3 is the wheel speed difference ΔSave between the front and rear wheels as described above.
Is detected to be almost 0, and the cascade state on the low μ road is detected.

The flag Fcas operating unit 14 determines the differential speed determination flag Fs and the front / rear wheel differential speed determination flag Fave.
When it is detected that all are set, the built-in detection counter CTR1 is incremented. In other cases, that is, any one of the differential speed determination flag Fs and the front and rear wheel differential speed determination flag Fave is not set. When this is detected, the detection counter CTR1 is decremented. In this way, the flag Fcas operating unit 14 measures, using the detection counter CTR1, the frequency at which the state in which the differential speed determination flag Fs and the front and rear wheel differential speed determination flag Fave are all set is detected.

If the counter value of the detection counter CTR1 is equal to or greater than the predetermined value α, for example, the control cycle is 8 msec, the flag Fcas operating section 14 sets the counter value to 0.2 s.
It becomes 25 or more indicating ec, that is, the differential speed determination flag F
When the frequency of detecting the state in which s and the front and rear wheel speed difference determination flag Fave are all set is equal to or greater than the predetermined value Z, it is determined that the vehicle is in the cascade state on the low μ road, and the cascade determination flag Fcas is set. Further, the flag Fcas operating unit 14 inputs the estimated vehicle body speed Vref calculated from the solenoid command output unit 15, and if the estimated vehicle body speed (Vref) _n-1 in the previous control cycle is 0, the cascade determination flag Fcas. To reset. As described above, the flag Fcas operating unit 14 causes the cascade determination flag Fcas.
By setting, A
The low μ control which is the BS control is applied to the solenoid command output unit 1
Have 5 done.

The solenoid command output unit 15 calculates the estimated vehicle body speed Vref from the wheel speed SPEEDi input from the basic control amount calculation unit 11. Here, a method for calculating the estimated vehicle body speed Vref is known, and the estimated vehicle body speed Vr is calculated.
As an example of a method of calculating ef, a method of calculating the estimated vehicle body speed Vref by a value obtained by applying a low-pass filter to the maximum wheel speed Vmax1 which is the maximum value among the wheel speeds of each wheel is known, and the following (3) Calculate from the formula. (Vref) _n = (Vref) _n-1 + K × {Vmax1− (Vref) _n-1 } (3) In the above equation (3), K is the filter time (K <1). , (Vref) _n is the Vref value in the current control cycle, and (Vref) _n-1 is the Vref value in the previous control cycle.

Further, the solenoid command output section 15 is
Wheel speed SP input from the basic control amount calculation unit 11
From EEDi and the estimated vehicle speed Vref calculated above, for example, Vref-SPEEDi ≧ TH1 = (3 + Vref / 32) km / h and d / dt (SPEEDi) ≦ −TH2 = −1.5g
(Hereinafter, g indicates gravitational acceleration), it is determined that the lock sign is detected, and each actuator ACT0 to AC is detected.
The pressure increasing / decreasing signal Si is set and output so as to reduce the brake fluid pressure with respect to T3, and when no other lock sign is detected, the pressure increasing / decreasing signal Si is increased to maintain or hold the brake fluid pressure. And output. The above TH1
Is the above (Vref-S) for determining that there is a lock sign.
It is a threshold value for PEEDi) and TH1> 0. The TH2 is a threshold for the {d / dt (SPEEDi)} for judging the lock sign, and TH2> 0.

If the pressure increase / decrease signal Si from the solenoid command output unit 15 is "pressure decrease", the actuators ACT0 to ACT
The outlet valves 4A to 4D of CT3 are opened and the inlet valves 3A to 3D are closed, and the pressurizing / depressurizing signal Si from the solenoid command output unit 16 is "hold".
If so, the outlet valves 4A to 4D and the inlet valves 3A to 3D are closed, and if the pressure increasing / decreasing signal Si from the solenoid command output unit 16 is "pressurized",
The inlet valves 3A to 3D are opened and the outlet valves 4A to 4D are closed.

Here, the solenoid command output unit 15 monitors whether or not the cascade determination flag Fcas is set, and when the cascade determination flag Fcas is set, the low μ control is set. A CAS control unit 16 is provided for switching to.

When the cascade determination flag Fcas is not set, the CAS control unit 16 determines the maximum wheel speed Vmax1 which is the maximum value among the wheel speed SPEEDi input from the basic control amount calculation unit 11 and the Vmax1. The next largest wheel speed Vmax2 is selected, and the estimated vehicle body speed Vref is calculated based on the average value of the Vmax1 and Vmax2.
For example, in the above equation (3), Vmax1 is (Vmax1 + Vm
Ax2) / 2 is substituted, and the estimated vehicle body speed Vref is set to be calculated as a function f (Vmax1, Vmax2) of Vmax1 and Vmax2. In addition, the threshold value TH1 for determining the lock sign is set to (3 + Vref
/ 32), similarly, the threshold value TH2 is set to, for example, 1.5 g as described above.

On the other hand, the cascade determination flag Fca
When s is set, it is considered that the road surface is a low μ road, so that the estimated vehicle body speed Vref is Vm based on the maximum wheel speed Vmax1 so that the estimated vehicle body speed Vref is not calculated too small.
For example, the threshold TH1 for determining the lock sign is set to be calculated as the function f (Vmax1) of ax1 by using the above formula (3).
The value is reduced from (3 + Vref / 32) to (2 + Vref / 32), and the threshold value TH2 is also reduced from, for example, 1.5 g to 1.2 g to make it easier to detect the lock sign of each wheel. As described above, a criterion for detecting a lock symptom is set.

Here, in general, during recovery from the skid state of the wheel, when the wheel acceleration is small, the pressure reduction signal or the hold signal in the pressure increase / decrease signal Si is extended, and in the previous control cycle. The pressure increase / decrease signal Si is a pressure decrease signal or a hold signal, and d / d
t (SPEEDi) ≦ TH3, and d ² / dt ² (SPEED
When EDi) ≤TH4, the pressure reducing signal or the holding signal is continuously output. The TH3 is TH3> 0 and the TH4 is TH4> 0.

Therefore, when the cascade determination flag Fcas is not set, the CAS control unit 16 sets the TH3 to 2 g and the TH4 to (0.5 g / 1 control cycle time), and the cascade determination flag Fcas is set. If is set, for example, TH3 above is set to 3g,
Set TH4 to (1g / 1 control cycle time),
The pressure reduction signal of the wheel cylinder hydraulic pressure is maintained for a long time so that the pressure reduction amount of the wheel cylinder hydraulic pressure is increased.

The differential speed judging unit 12 constitutes a selecting means and a differential speed judging means, and the front and rear wheel differential speed judging unit 13 is provided.
Represents the front / rear wheel differential speed determination means, the flag Fcas operating unit 14 forms the cascade determination means according to any one of claims 1 to 5, and the detection counter CTR1 includes the counting means according to any one of claims 2 to 5. The CAS control unit 16 constitutes a cascade control means.

Next, FIGS. 3 and 4 are flowcharts showing an operation example of the anti-skid control device shown in FIG. 2, and the first embodiment of the present invention will be described with reference to FIGS. 3 and 4. An operation example of the device will be described. In FIG.
First, in step S1, the basic control amount calculation unit 11 calculates the wheel speed SPEEDi of each wheel and uses the calculated wheel speed SPEEDi as the differential speed determination unit 12, the front and rear wheel differential speed determination unit 13, and the solenoid command output unit. Output to 15.

The differential speed determination unit 12 determines the wheel speed SPEED input from the basic control amount calculation unit 11 in step S2.
Among i, the maximum wheel speed Vmax1 which is the maximum value and the minimum wheel speed Vmin which is the minimum value are selected, and in step S3, the differential speed ΔS is calculated. Is the calculated differential speed ΔS 2 km / h or more? Check whether or not it is 2 km / h or more (YE
S), the process proceeds to step S5, and in step S5, the differential speed Δ
Differential speed determination flag F indicating that S is equal to or greater than the predetermined value A
After setting s, the process proceeds to step S6. If ΔS is not 2 km / h or more in step S3 (NO), the process proceeds to step S4, and in step S4, the differential speed determination flag F
After resetting s, the process proceeds to step S6.

In step S6, the front / rear wheel differential speed determination unit 13 determines the average wheel speed (SPEED) of the front wheels from the wheel speeds SPEEDi input from the basic control amount calculation unit 11.
ED0 + SPEED1) / 2 and the average wheel speed of the rear wheels (SPE
ED2 + SPEED3) / 2 is calculated, and ΔSave, which is the difference between the calculated average wheel speeds, is calculated from the above equation (2). When the calculated ΔSave is 2 km / h or less (YES), in step S8, Front / rear wheel differential speed determination unit 13
Sets the front / rear wheel differential speed determination flag Fave indicating that ΔSave is equal to or less than the predetermined value B, and then proceeds to step S9. If ΔSave is not less than 2 km / h in step S6 (NO), the front / rear wheel differential speed determination unit 13 resets the front / rear wheel differential speed determination flag Fave in step S7, and the process proceeds to step S9.

In step S9, the flag Fcas operating unit 14 checks whether or not the differential speed determination flag Fs and the front / rear wheel differential speed determination flag Fave are all set, and when it is detected that they are all set. (YES), the process proceeds to step S11, and step S11
Then, the flag Fcas operating unit 14 determines that the estimated vehicle body speed Vref is calculated too small, and the detection counter CT is detected.
After incrementing R1, the process proceeds to step S12.
When it is detected in step S9 that any one of the differential speed determination flag Fs and the front and rear wheel differential speed determination flag Fave is not set (NO), step S1
0, and in step S10, the flag Fcas operating unit 14
Judges that the estimated vehicle body speed Vref is not calculated too small, decrements the detection counter CTR1 and proceeds to step S12.

In step S12, the flag Fcas operating unit 14 checks the counter value of the detection counter CTR1. If the counter value is a predetermined value α or more, for example, if the control cycle is 8 msec, the counter value is 0.2 sec. 25 (the maximum counter value of the detection counter CTR1 is 2
55 and the minimum value is 0) (YE
S), the process proceeds to step S13, and in step S13, the flag Fcas operating unit 14 determines that the vehicle is in the cascade state on the low μ road, and the cascade determination flag indicating that the cascade state on the low μ road is detected. After setting Fcas, the process proceeds to step S14. Also, in step S12,
If the counter value is not 25 or more (NO), step S
Proceed to 14.

In step S14, the flag Fcas operating unit 14 sets the estimated vehicle body speed (Vref) _n-1 calculated by the solenoid command output unit 15 in the previous control cycle to 0.
If (Vref) _n-1 is 0 (YES), the flag Fcas operating unit 1 is checked in step S15.
4 resets the cascade determination flag Fcas, and then proceeds to step S16 in FIG. Also, in step S14,
If (Vref) _n-1 is not 0 (NO), the process proceeds to step S16 in FIG.

In step S16 of FIG. 4, the CAS control unit 16 checks whether or not the cascade determination flag Fcas is set. If the cascade determination flag Fcas is not set (NO), the process proceeds to step S17, and CAS is executed. In step S17, the control unit 16 selects the maximum wheel speed Vmax1 that is the maximum value among the wheel speeds SPEEDi input from the basic control amount calculation unit 11 and the wheel speed Vmax2 that is the next highest Vmax1 and that Vmax1. The estimated vehicle speed Vref is calculated based on the average value of Vmax2.
For example, in the above equation (3), Vmax1 is (Vmax1 + Vm
The estimated vehicle body speed Vref is calculated by replacing it with ax2) / 2.
Next, in step S18, the CAS control unit 16 sets the threshold value TH1 for determining the lock symptom to (3 + V).
ref / 32), the threshold value TH2 is set to 1.5 g in step S19, and the process proceeds to step S23.

If the cascade determination flag Fcas is set in step S16 (YES), the process proceeds to step S20, and the CAS control unit 16 proceeds to step S20.
Then, the wheel speed SP input from the basic control amount calculation unit 11
The maximum wheel speed Vmax1 which is the maximum value among the EEDi is selected, and the estimated vehicle body speed Vref is calculated based on the maximum wheel speed Vmax1. Next, the CAS control unit 16 sets the threshold value TH1 to (2 + Vref / 32) in step S21, sets the threshold value TH2 to 1.2 g in step S22, and proceeds to step S23.

In step S23, the solenoid command output unit 15 checks whether or not a lock sign is detected. If a lock sign is detected (YES), the process proceeds to step S24, and in step S24, the solenoid command output unit 15 is detected. Is
The pressure reduction or holding signal Si is output to the actuator ACTi, and this flow ends. If no lock sign is detected in step S23 (NO), step S2
5, the CAS control unit 16 checks in step S25 whether or not the cascade determination flag Fcas is set. If the cascade determination flag Fcas is not set (NO), then the CAS control unit 16 proceeds to step S26. 16 is 2 g of the threshold value TH3 in step S26.
And the threshold value TH4 is set in step S27.
(0.5 g / 1 control cycle time) and proceed to step S30.

If the cascade determination flag Fcas is set in step S25 (YES), the process proceeds to step S28, and the CAS control unit 16 proceeds to step S28.
Then, the threshold value TH3 is set to 3 g, and step S2
In step 9, the threshold value TH4 is set to (1 g / 1 control cycle time), and the process proceeds to step S30.

The solenoid command output unit 15 executes step S
At 30, the pressure increase / decrease signal Si in the previous control cycle is the pressure decrease signal or the hold signal, and d / dt (SPEED
i) ≦ TH3 and d ² / dt ² (SPEED i) ≦ TH4
It is checked whether or not the pressure reduction or holding signal Si is continuously output and extended. If the pressure reduction or holding signal Si is not continuously output and extended (NO), the process proceeds to step S31 and step S31. Then, the pressurization signal Si is output to the actuator ACTi, and this flow ends. Step S3
If the pressure reduction or holding signal Si is continuously output and extended at 0 (YES), the process proceeds to step S32 and step S32.
At 32, the solenoid command output unit 15 outputs the pressure reduction or holding signal Si to the actuator ACTi, and the present flow ends.

As described above, in the device according to the first embodiment of the present invention, in the four-wheel drive vehicle, when the four wheels are restrained and the cascade state occurs on the low μ road, the four wheels are Although the speeds are almost the same, if there is variation in the road surface μ among the wheels, the wheel speed between the wheels also varies due to the influence of the differential gear. Further, when cascading on a road surface having a low friction coefficient μ, there is a characteristic that the wheel speed difference between the front and rear wheels is almost 0. Therefore, the variation in the wheel speed is detected, and the road surface of each wheel on the low μ road is detected. It is possible to detect the cascade state when there is a variation in μ, and it is possible to detect that the wheel speed difference ΔSave between the front and rear wheels is almost 0, and to detect the cascade state on the low μ road.

Furthermore, when the cascade state on the low μ road as described above is detected, since the road surface is the low μ road,
It is set to calculate the estimated vehicle body speed Vref based on the maximum wheel speed Vmax1 so that the estimated vehicle body speed Vref is not calculated too small, and a determination is made to detect the lock symptom so that the lock symptom of each wheel can be easily detected. It is possible to prevent the cascade state on the low μ road by setting the reference and performing the low μ control for increasing the pressure reduction amount of the wheel cylinder hydraulic pressure by continuing the pressure reduction signal of the wheel cylinder hydraulic pressure for a longer time. From these facts, in vehicles, especially in four-wheel-drive vehicles, high μ on low μ roads where the road μ between wheels varies
It is possible to prevent erroneous determination as a road, detect and prevent a cascade state on the low μ road, prevent wheel lock, and appropriately generate skids. The control performance and reliability can be improved.

Here, in the anti-skid control device of the first embodiment, the detection counter CTR1 is incremented when it detects that the differential speed determination flag Fs and the front and rear wheel differential speed determination flag Fave are all set. When it counts up and detects a state in which at least one of the differential speed determination flag Fs and the front and rear wheel differential speed determination flag Fave is not set, it is decremented and counted down, but the differential speed determination flag Fs and the front and rear wheel differential speed determination flag Fave. When it detects that all are set, it decrements and counts down, and the differential speed determination flag Fs
Alternatively, when a state in which even one of the front and rear wheel differential speed determination flag Fave is not set is detected, it may be incremented and counted up.

In this case, the flag Fcas operating section 14 determines that the counter value of the detection counter CTR1 is smaller than a predetermined value β which is a value smaller than the initial value of the detection counter CTR1,
That is, when the frequency at which the state in which the differential speed determination flag Fs and the front and rear wheel differential speed determination flag Fave are all set is detected is equal to or greater than the predetermined value Z, it is determined that the vehicle is in the cascade state on the low μ road, and the cascade determination flag is set. Set Fcas.

Next, in the anti-skid control device according to the first embodiment, it is possible to detect the cascade state on the low μ road where the friction coefficient μ of the road surface between the wheels varies. , Friction coefficient of road surface between wheels μ
It is not possible to detect a cascade state on a low μ road where there is no variation in Therefore, an anti-skid control device according to a second embodiment of the present invention that can detect a cascade state on a low μ road where there is no variation in the friction coefficient μ of the road surface between the wheels will be described.

FIG. 5 is a schematic block diagram showing an anti-skid control device according to a second embodiment of the present invention. FIG. 5 shows an anti-skid control device according to the second embodiment of the present invention with reference to FIG. The outline will be described. The second book
The schematic control system diagram showing the anti-skid control device of the embodiment is the same as that of FIG. 2 except that the signal processing device 10 is replaced with the signal processing device 30, and therefore the description thereof is omitted. Also,
5, the same components as those in FIG. 2 are designated by the same reference numerals, and the description thereof will be omitted here, and only the differences from FIG. 2 will be described.

The difference between FIG. 5 and FIG. 2 is that the signal processing device 10 of FIG. 2 does not include the differential speed determination unit 12 and the front and rear wheel differential speed determination unit 13, and the four wheels grip without skidding. ΔS determination unit 31 for detecting the state
And from the wheel acceleration in the process of recovering from the skid state,
A wheel acceleration determination unit 32 that determines whether the road surface is a low μ road and the vehicle is in a cascade state, and an estimated vehicle body speed Vre
A vehicle body deceleration determination unit 33 that determines whether the inclination of f is a depression corresponding to a high μ road or more, and an ABS determination unit 34 that determines whether the ABS control is being performed. .

Further, the difference between FIG. 5 and FIG. 2 is that the flag Fcas operating unit 14 in FIG. 2 determines that the ΔS determination unit 31, the wheel acceleration determination unit 32, and the vehicle body deceleration determination. The cascade state on the low μ road is detected based on the determination by the unit 33 and the determination by the ABS determination unit 34, whereby the flag Fcas operating unit 14 in FIG. 2 is set as the flag Fcas operating unit 35. Further, the solenoid command output unit 15 of FIG. 2 outputs the calculated estimated vehicle body speed Vref to the vehicle body deceleration determination unit 33, outputs the pressure increase / decrease signal Si to the actuator ACTi, and the ABS determination unit 34.
Since it is also output to the solenoid command output unit 15, the solenoid command output unit 15 of FIG. Accordingly, the signal processing device 10 of FIG.
It is set to 0.

In FIG. 5, the signal processing device 30 is composed of a microcomputer, and has a basic control amount computing unit 11, Δ
An S determination unit 31, a wheel acceleration determination unit 32, a vehicle body deceleration determination unit 33, an ABS determination unit 34, a flag Fcas operating unit 35, and a solenoid command output unit 36 are provided, and predetermined processing is performed on the wheel speed signal to Inlet valve 3A ~
3D and the actuators ACT0, ACT1, ACT2, AC having the outlet valves 4A to 4D
The pressure increasing / decreasing signal Si is output to T3.

The wheel speed sensors S0 to S3 are connected to the basic control amount calculation unit 11, and the basic control amount calculation unit 11 changes by Δ.
The S determination unit 31, the wheel acceleration determination unit 32, and the solenoid command output unit 36 are connected, and the ΔS determination unit 31, the wheel acceleration determination unit 32, the vehicle body deceleration determination unit 33, and the ABS determination unit 3 are connected.
4 is connected to the flag Fcas operating unit 35, and the flag Fcas operating unit 35 is connected to the solenoid command output unit 36. Further, the solenoid command output unit 36 is connected to the vehicle body deceleration determination unit 33 and the ABS determination unit 34.

The basic control amount calculation section 11 calculates the calculated wheel speed SPEEDi of each wheel from the ΔS determination section 31,
It outputs to the wheel acceleration determination unit 32 and the solenoid command output unit 36. The ΔS determination unit 31 selects the maximum wheel speed Vmax1 which is the maximum value and the minimum wheel speed Vmin which is the minimum value among the wheel speeds SPEEDi input from the basic control amount calculation unit 11, and the maximum wheel speed Vmax1. Difference speed ΔS, which is the difference between the minimum wheel speed Vmin and the minimum wheel speed Vmin. Indicating Δ
The S determination flag Fs1 is set. As described above, the ΔS determination unit 31 determines that the four wheels of the four-wheeled vehicle are 4
It is detected that each wheel speed of the wheel is within a predetermined range.

The wheel acceleration determining section 32 is arranged to detect the wheel speed SPEEDi input from the basic control amount calculating section 11.
To calculate the wheel acceleration ACCELi,
When the wheel acceleration ACCELi is less than or equal to the predetermined value D,
For example, when the weight is 5 g or less, the wheel acceleration ACCELi indicates that the wheel acceleration determination flag F is less than or equal to a predetermined value D.
Set acc. When the road surface is on a high μ road, the wheel acceleration is large while the wheel is recovering from the skid state, but the behavior of the wheel on a low μ road in a cascade state is that the wheel acceleration is small and the road surface μ is small, so It is characterized by slow recovery. From this, the wheel acceleration determination unit 32 detects a state in which the calculated wheel acceleration ACCELi is small.

The vehicle body deceleration determination unit 33 differentiates the estimated vehicle body speed Vref in the previous cycle input from the solenoid command output unit 36 to calculate the vehicle body deceleration, and the calculated vehicle body deceleration is high μ. Predetermined value E corresponding to the road
When the acceleration is a positive value and the deceleration direction is a negative value and is −0.6 g or less, it is indicated that the absolute value of the vehicle deceleration is equal to or greater than a predetermined value E. The deceleration determination flag Fdec is set. Thus, the vehicle body deceleration determination unit 33 detects that the descending speed of the estimated vehicle body speed Vref indicated by the vehicle body deceleration is equal to or higher than the value E corresponding to the high μ road.

The ABS determining section 34 detects that the pressure reduction signal Si is output from the solenoid command output section 36 to any one of the actuators ACTi, and when it detects the output of the pressure reduction signal Si, the built-in timer counter TM.
After setting the counter value of R to a predetermined initial value φ, for example, 250 corresponding to 2 seconds, the timer counter TMR is decremented. When the pressure reduction signal Si is not output from the solenoid command output unit 36 to any of the actuators ACTi, the timer counter TMR is decremented. Then, when the counter value of the timer counter TMR is not 0, the ABS determination unit 34 sets the ABS determination flag Fabs indicating that the ABS control is being performed. It can be determined that the ABS control is being performed within a predetermined time from the latest pressure reduction signal Si output from the solenoid command output unit 36. From this, the ABS determination unit 34 determines that the ABS control is being performed within a predetermined time after the pressure reduction is generated in all of the four wheels.

The flag Fcas operating section 35 uses the ΔS
When it is detected that the determination flag Fs1, the wheel acceleration determination flag Facc, the vehicle body deceleration determination flag Fdec, and the ABS determination flag Fabs are all set, the built-in detection counter CTR2 is incremented, otherwise, That is, the ΔS determination flag Fs
1. When it is detected that any one of the wheel acceleration determination flag Facc, the vehicle body deceleration determination flag Fdec, and the ABS determination flag Fabs is not set, the detection counter CTR2 is reset to 0 which is an initial value. To do. In this way, the flag Fcas operating unit 35 determines that ΔS
The detection counter CTR2 is used to measure the time when the determination flag Fs1, the wheel acceleration determination flag Facc, the vehicle body deceleration determination flag Fdec and the ABS determination flag Fabs are all set continuously.

Further, the flag Fcas operating section 35 sets the counter value of the detection counter CTR2 to a predetermined value γ or more indicating the predetermined time T, for example, if the control cycle is 8 msec, the counter value is set to 25 or more indicating 0.2 sec. That is, Δ
When the time when the S determination flag Fs1, the wheel acceleration determination flag Facc, the vehicle body deceleration determination flag Fdec, and the ABS determination flag Fabs are all continuously detected for a predetermined value T or more, the vehicle is cascaded on a low μ road. When it is determined that the state is in the state, the cascade determination flag Fcas is set.

Further, the flag Fcas operating section 35 is configured to estimate the vehicle body speed V calculated from the solenoid command output section 36.
When ref is input and the estimated vehicle speed (Vref) _n-1 in the previous control cycle is 0 or the ABS determination flag Fabs is reset, the cascade determination flag Fcas is reset. In this way, the flag Fcas operating unit 3
5 sets the cascade determination flag Fcas to cause the solenoid command output unit 36 to perform low μ control which is ABS control assuming the low μ road shown in the first embodiment.

The solenoid command output unit 36 outputs the calculated estimated vehicle body speed Vref to the vehicle body deceleration judgment unit 33 and outputs the pressure increase / decrease signal Si to the ABS judgment unit 34, except for the CAS control unit 16 described above. This is the same as the solenoid command output unit 15 of the first embodiment having the above.

The ΔS determination section 31 constitutes ΔS determination means, the wheel acceleration determination section 32 constitutes wheel acceleration determination means, the vehicle body deceleration determination section 33 constitutes vehicle body deceleration determination means, and the ABS determination is made. The section 34 constitutes an ABS judging means, the flag Fcas operating section 35 constitutes a cascade judging means according to claims 6 to 10, and the solenoid command output section 36 constitutes an estimated vehicle body speed calculating means.

Next, FIGS. 6 and 7 are flow charts showing the first half of the operation example of the anti-skid control device shown in FIG. The flow chart showing the latter half of the operation example of the anti-skid control device shown in FIG. 5 is the same as the flow chart of FIG. 4 in the first embodiment except that the solenoid command output unit 15 is replaced with the solenoid command output unit 36. Are the same, so I will omit them,
An operation example in the apparatus according to the second embodiment of the present invention will be described with reference to FIGS. 6 and 7. In FIG. 6, the basic control amount calculation unit 11 first calculates the wheel speed SPEEDi of each wheel in step S50, and calculates the calculated wheel speed SP.
EEDi is output to the ΔS determination unit 31, the wheel acceleration determination unit 32, and the solenoid command output unit 36.

Next, the ABS judging section 34 carries out step S5.
1, the solenoid command output unit 36 in the previous control cycle
From any of the actuators ACTi to check whether or not there is a pressure reduction request for outputting the pressure reduction signal Si, and if there is a pressure reduction request (YES), the timer counter TMR is set to the initial value 250 in step S52. After that, the process proceeds to step S53. Also, in step S51,
If there is no pressure reduction request (NO), the process proceeds to step S53. In step S53, the ABS determination unit 34 determines the counter value of the timer counter TMR (timer counter TMR).
Is decremented by 0) and the process proceeds to step S54.

In step S54, the ABS determination unit 34 checks whether or not the counter value of the timer counter TMR is 0, and when it is 0 (NO), in step S55, A
It is determined that the BS control is not in progress, and the ABS determination flag Fab
After resetting s, the process proceeds to step S57. If it is not 0 in step S54 (YES), step S56.
Then, it is determined that the ABS control is being performed, the ABS determination flag Fabs is set, and then the process proceeds to step S57.

In step S57, the vehicle body deceleration determination unit 33 calculates the vehicle body deceleration by differentiating the estimated vehicle body speed Vref calculated in the previous control cycle by the solenoid command output unit 36, and calculates the vehicle body deceleration d / When dt (Vref) is a negative value in the deceleration direction, it is checked whether or not it is -0.6 g or less. If it is not -0.6 g or less (NO), step S5
At 8, the vehicle body deceleration determination unit 33 resets the vehicle body deceleration determination flag Fdec, and proceeds to step S60. Further, in step S57, when the weight is −0.6 g or less (Y
ES), in step S59, the vehicle body deceleration determination unit 33 sets the vehicle body deceleration determination flag Fdec, and proceeds to step S60.

Next, the ΔS determination section 31 determines in step S60.
, The maximum wheel speed Vmax1 which is the maximum value among the wheel speeds SPEEDi input from the basic control amount calculation unit 11
And the minimum wheel speed Vmin which is the minimum value are calculated, and in step S61, the differential speed ΔS is calculated, and it is checked whether the calculated differential speed ΔS is 2 km / h or less, and ΔS is 2 km / h or less. If not (NO), the process proceeds to step S62, and in step S62, after the ΔS determination flag Fs1 indicating that the differential speed ΔS is equal to or less than the predetermined value C is reset, the step S6 is performed.
Proceed to 4. If the speed is 2 km / h or less in step S61 (YES), the process proceeds to step S63 and step S6.
In 3, the ΔS determination unit 31 sets the ΔS determination flag Fs1 and then proceeds to step S64.

Next, in step S64, the wheel acceleration determination unit 32 differentiates the wheel speed SPEEDi input from the basic control amount calculation unit 11 to calculate the wheel acceleration ACCELi, and the calculated wheel acceleration ACCELi is 5 g. It is checked whether or not it is equal to or less than 5 g (NO), and if it is not equal to or less than 5 g (NO), the wheel acceleration determination flag Facc is reset in step S65, and then the process proceeds to step S67 in FIG. If it is 5 g or less in step S64 (YES), step S6
At 6, the wheel acceleration determination flag Facc is set,
It progresses to step S67 of FIG.

In step S67 of FIG. 7, the flag F
The cas operating unit 35 checks whether or not the ABS determination flag Fabs, the vehicle body deceleration determination flag Fdec, the ΔS determination flag Fs1, and the wheel acceleration determination flag Facc are all set, and the ABS determination flag Fabs, the vehicle body reduction flag When it is detected that any one of the speed determination flag Fdec, the ΔS determination flag Fs1 and the wheel acceleration determination flag Facc is not set (NO), the process proceeds to step S68, and in step S68, the flag Fcas operating unit 35
The detection counter CTR2 is reset to 0 which is an initial value, and the process proceeds to step S70. In addition, step S67
When it is detected that all are set (YE
S), the process proceeds to step S69, and in step S69, the flag Fcas operating unit 35 increments the detection counter CTR2, and then proceeds to step S70.

In step S70, the flag Fcas operating section 35 checks the counter value of the detection counter CTR2, and the counter value is equal to or more than the predetermined value γ indicating the predetermined time T,
For example, when the control cycle is set to 8 msec and the counter value becomes 25 (which indicates the maximum value of the detection counter CTR2 is 255 and the minimum value is 0) indicating 0.2 sec (YES), the process proceeds to step S71. Go to step S
In 71, the flag Fcas operating unit 35 determines that the vehicle is in the cascade state on the low μ road, and indicates that the cascade state on the low μ road is detected.
After setting, the process proceeds to step S72. If the counter value is not 25 or more in step S70 (N
O), and proceeds to step S72.

In step S72, the flag Fcas operating unit 35 sets the estimated vehicle body speed (Vref) _n-1 calculated by the solenoid command output unit 36 in the previous control cycle to 0.
Or if the ABS determination flag Fabs is reset. If (Vref) _n-1 is 0 or if the ABS determination flag Fabs is reset (YES), step Proceed to S73, step S7
3, the flag Fcas operating unit 35 resets the cascade determination flag Fcas, and then executes step S16 of FIG.
The following processing is performed. Further, in step S72, (Vr
ef) When _n-1 is not 0 and the ABS determination flag Fabs is not reset (NO), step S of FIG.
The processing after 16 is performed. In the case of the second embodiment, the processing from step S16 of FIG. 4 is performed by replacing the solenoid command output unit 15 of FIG. 4 with the solenoid command output unit 36.

As described above, in the device according to the second embodiment of the present invention, when the road surface is a high μ road, the wheel acceleration is large while the wheel is recovering from the skid state, but the road surface is a low μ road. The behavior of the wheels in the cascade state on the road is that the wheel acceleration is small and the road surface μ is small, so that the recovery from the skid is slow. From this fact, it is detected that the ABS control is in progress, and that the estimated vehicle speed Vref lowering speed is equal to or higher than the value corresponding to the high μ road, and all four wheels grip on the road surface without skidding. While detecting the situation where the road surface is low μ, the wheel acceleration ACCELi that shows the behavior of the wheels in the cascade state on the low μ road is detected to be small, and it is detected that the state has continued for a predetermined time T or more. By doing so, the cascade state on the low μ road can be detected. In this way, it is possible to detect a cascade state on a low μ road where there is no variation in the friction coefficient μ of the road surface between the wheels.

Furthermore, when the cascade state on the low μ road as described above is detected, the road surface is the low μ road.
It is set to calculate the estimated vehicle body speed Vref based on the maximum wheel speed Vmax1 so that the estimated vehicle body speed Vref is not calculated too small, and a determination is made to detect the lock symptom so that the lock symptom of each wheel can be easily detected. It is possible to prevent the cascade state on the low μ road by performing the above-mentioned low μ control in which the reference is set and the pressure reduction signal of the wheel cylinder hydraulic pressure is continued for a longer time to increase the pressure reduction amount of the wheel cylinder hydraulic pressure. From these facts, in vehicles, especially in four-wheel-drive vehicles, high μ on low μ roads where the road μ between wheels varies
It is possible to prevent erroneous determination as a road, detect and prevent a cascade state on the low μ road, prevent wheel lock, and appropriately generate skids. The control performance and reliability can be improved.

Here, in the antiskid control device of the second embodiment, the detection counter CTR2 is A
When it detects that the BS determination flag Fabs, the ΔS determination flag Fs1, the wheel acceleration determination flag Facc, and the vehicle body deceleration determination flag Fdec are all set, it increments and counts up, and the ABS determination flag Fabs, the ΔS determination flag Fs1, and the wheel acceleration. When it is detected that at least one of the determination flag Facc and the vehicle body deceleration determination flag Fdec is not set, the initial value 0 is reset.
When the BS determination flag Fabs, the ΔS determination flag Fs1, the wheel acceleration determination flag Facc, and the vehicle body deceleration determination flag Fdec are all set, they are decremented and counted down, and the ABS determination flag Fabs, the ΔS determination flag Fs1, and the wheel acceleration determination are performed. If it is detected that at least one of the flag Facc and the vehicle body deceleration determination flag Fdec is not set, it may be reset to a predetermined initial value.

In this case, the flag Fcas operating unit 35 determines that the counter value of the detection counter CTR2 is less than or equal to a predetermined value δ which is a value smaller than the initial value of the detection counter CTR2,
That is, the ABS determination flag Fabs and the ΔS determination flag Fs
1. When the time when the wheel acceleration determination flag Facc and the vehicle body deceleration determination flag Fdec are all set continuously is longer than a predetermined value T, it is determined that the vehicle is in the cascade state on the low μ road, Cascade judgment flag Fcas
Set

In the first and second embodiments, the CAS control unit 16 has the cascade determination flag Fca.
When s is not set, the estimated vehicle body speed Vref may be calculated based on a wheel speed smaller than the wheel speed Vmax2 or the maximum wheel speed Vmax1. Further, the thresholds TH1 and TH2 can be set freely according to the vehicle and the like, and the estimated vehicle speed Vref
May be set non-linearly with respect to. As described above, various modifications of the present invention are conceivable, and it goes without saying that the scope of the present invention is not limited to the above-described embodiments and should be defined by the scope of the claims.

[Brief description of the drawings]

FIG. 1 is a schematic control system diagram showing a first embodiment of an anti-skid control device of the present invention.

FIG. 2 is a schematic block diagram showing a first embodiment of an anti-skid control device of the present invention.

FIG. 3 is a flowchart showing an operation example of the anti-skid control device shown in FIG.

FIG. 4 is a flowchart showing an operation example of the anti-skid control device shown in FIG.

FIG. 5 is a schematic block diagram showing a second embodiment of the anti-skid control device of the present invention.

6 is a flowchart showing an operation example of the anti-skid control device shown in FIG.

7 is a flowchart showing an operation example of the anti-skid control device shown in FIG.

[Explanation of symbols]

 10, 30 Signal processing device 11 Basic control amount calculation unit 12 Differential speed determination unit 13 Front / rear wheel differential speed determination unit 14, 35 Flag Fcas operating unit 15 Solenoid command output unit 16 CAS control unit 31 ΔS determination unit 32 Wheel acceleration determination unit 33 Vehicle body deceleration determination unit 34 ABS determination unit S0, S1, S2, S3 Wheel speed sensor ACT0, ACT1, ACT2, ACT3 Actuator CTR1, CTR2 detection counter TMR timer counter

Claims (17)

[Claims] 1. An anti-skid controller having a wheel speed sensor for detecting a wheel speed of each wheel, and estimating a wheel cylinder hydraulic pressure of each wheel during ABS control from each wheel speed detected by the wheel speed sensor. In the above, the maximum wheel speed Vmax1 which is the maximum value among the above wheel speeds
And a selecting means for selecting the minimum wheel speed Vmin which is the minimum value, and a differential speed ΔS which is a difference between the maximum wheel speed Vmax1 and the minimum wheel speed Vmin, and the differential speed ΔS is a predetermined value A or more. A difference speed determination means for determining whether or not the difference ΔSave between the average wheel speed of the left and right front wheels and the average wheel speed of the left and right rear wheels is calculated from the wheel speeds, and whether the difference ΔSave is equal to or less than a predetermined value B. Front and rear wheel differential speed determining means for determining whether or not the differential speed determining means determines that the differential speed ΔS is a predetermined value A or more in a predetermined control cycle, and the difference ΔSave is a predetermined value B or less. If the frequency of the front-rear wheel differential speed determination means becomes equal to or greater than a predetermined value Z, the cascade determination means determines that the vehicle is in the cascade state on the low μ road, and the cascade determination means determines that the vehicle is on the low μ road. Determined to be in cascade , Anti-skid control apparatus characterized by comprising a cascade control unit be configured to perform low μ control which is a ABS control corresponding to the low μ road. 2. The anti-skid control device according to claim 1, wherein the cascade determination means includes the differential speed ΔS.
Is greater than or equal to the predetermined value A, the differential speed determination means determines that
In addition, the front-rear wheel differential speed determination means counts up when the difference ΔSave is less than or equal to the predetermined value B, and otherwise has count means for counting down, and the count value of the count means is the predetermined value α. When it becomes above, it is judged that the vehicle is in the cascade state on the low μ road. 3. The anti-skid control device according to claim 1, wherein when the differential speed determination means determines that the differential speed ΔS is equal to or more than a predetermined value A, a flag Fs is set.
The front-rear wheel differential speed determination means sets a flag Fave when it determines that the difference ΔSave is less than or equal to a predetermined value B, and the cascade determination means counts up when the flag Fs and the flag Fave are all set. Other than that, it has a count means for counting down, and when the count value of the count means becomes equal to or greater than a predetermined value α, sets a flag Fcas, and the cascade control means sets the flag Fcas.
The anti-skid control device is set to perform the above low μ control when is set. 4. The anti-skid control device according to claim 1, wherein the cascade determination means sets the differential speed ΔS.
Is greater than or equal to the predetermined value A, the differential speed determination means determines that
In addition, the front-rear wheel differential speed determination means counts down when the difference ΔSave is less than or equal to the predetermined value B, and otherwise has count means for counting up, and the count value of the count means is the count means. The anti-skid control device is characterized in that it is determined that the vehicle is in a cascade state on a low μ road when the value becomes equal to or smaller than a predetermined value β which is smaller than the initial value of. 5. The anti-skid control device according to claim 1, wherein when the differential speed determination means determines that the differential speed ΔS is equal to or more than a predetermined value A, a flag Fs is set,
The front-rear wheel differential speed determination means sets a flag Fave when it determines that the difference ΔSave is less than or equal to a predetermined value B, and the cascade determination means counts down when the flag Fs and the flag Fave are all set, and otherwise. Has a counting means for counting up, and sets a flag Fcas when the count value of the counting means becomes a predetermined value β smaller than an initial value of the counting means, and the cascade control means sets the flag Fcas. Anti-skid control device characterized by setting so as to perform the above-mentioned low μ control 6. An anti-skid control device having a wheel speed sensor for detecting a wheel speed of each wheel, and estimating a wheel cylinder hydraulic pressure of each wheel during ABS control from each wheel speed detected by the wheel speed sensor. In the above, in at least one wheel, ABS determining means for determining whether or not the wheel is in the ABS control state, and the maximum wheel speed Vmax1 which is the maximum value among the above wheel speeds.
And a selecting means for selecting the minimum wheel speed Vmin which is the minimum value, and a differential speed ΔS which is the difference between the maximum wheel speed Vmax1 and the minimum wheel speed Vmin, and the differential speed ΔS is not more than a predetermined value C. .DELTA.S determining means for determining whether or not the wheel acceleration, and wheel acceleration determining means for calculating acceleration of each wheel from the wheel speeds and determining whether or not all of the calculated wheel accelerations are equal to or less than a predetermined value D, From the estimated vehicle body speed calculation means for calculating the estimated vehicle body speed, which is an estimated value of the vehicle body speed from the wheel speeds, and the estimated vehicle body speed calculated by the estimated vehicle body speed calculation means, The vehicle body deceleration determining means for determining whether or not it is equal to or more than a predetermined value E corresponding to the value in, and the ABS determining means determines that at least one wheel is in the ABS control state in a predetermined control cycle,
Further, the ΔS determination means determines that the differential speed ΔS is less than or equal to the predetermined value C, and the wheel acceleration determination means determines that all the wheel accelerations of the wheels are less than or equal to the predetermined value D, and the estimated vehicle body speed The time for which the vehicle body deceleration determining means determines that the descending speed is equal to or higher than the predetermined value E continuously exceeds the predetermined value T.
When the above is the case, the cascade determination means for determining the cascade state on the low μ road, and the ABS determination corresponding to the low μ road when the cascade determination means determines the cascade state for the low μ road. An anti-skid control device comprising: a cascade control unit configured to perform μ control. 7. The anti-skid control device according to claim 6, wherein the cascade determination means determines that at least one wheel is in an ABS control state, and the differential speed ΔS is predetermined. The ΔS determination means determines that the value is less than or equal to C, and the wheel acceleration determination means determines that all the calculated wheel accelerations are equal to or less than the predetermined value D, and the estimated vehicle body speed lowering speed is high μ road. If the vehicle body deceleration determination means determines that the vehicle body deceleration determination means is greater than or equal to a predetermined value E corresponding to the value in the above, the count value for resetting to the initial value is provided. An anti-skid control device, which determines that the vehicle is in a cascade state on a low μ road when the value is γ or more. 8. The anti-skid control device according to claim 6, wherein the ABS determining means sets a flag Fabs when determining that at least one wheel is in an ABS control state, and the ΔS determining means sets a difference. Speed ΔS is a predetermined value C
If it is determined that the following, the flag Fs1 is set, and if the calculated wheel accelerations are all less than or equal to the predetermined value D, the wheel acceleration determination means sets the flag Facc. When it is determined that the descending speed of the vehicle body speed is equal to or higher than the predetermined value E corresponding to the value on the high μ road, the flag Fdec is set, and the cascade determination means sets all the flags Fabs, flag Fs1, flag Facc and flag Fdec. When the count value of the count means is increased, the count value of the other means is reset to an initial value, and when the count value of the count means becomes equal to or larger than a predetermined value γ, a flag Fcas is set. An anti-skid control device, characterized in that it is set to perform the above-mentioned low μ control when set. 9. The anti-skid control device according to claim 6, wherein the cascade determination means determines that at least one wheel is in an ABS control state, and the differential speed ΔS is predetermined. The ΔS determination means determines that the value is less than or equal to C, and the wheel acceleration determination means determines that all the calculated wheel accelerations are equal to or less than the predetermined value D, and the estimated vehicle body speed lowering speed is high μ road. In the case where the vehicle body deceleration determination means determines that the vehicle body deceleration determination means is equal to or greater than the predetermined value E corresponding to the value in, the count value is reset to the initial value. An anti-skid control device characterized by determining that the vehicle is in a cascade state on a low μ road when the value is equal to or smaller than a predetermined value δ smaller than the initial value of the means. 10. The anti-skid control device according to claim 6, wherein when the ABS determination means determines that at least one wheel is in an ABS control state, a flag Fabs.
If the ΔS determination means determines that the differential speed ΔS is less than or equal to a predetermined value C, a flag Fs1 is set, and the wheel acceleration determination means determines that all calculated wheel accelerations are less than or equal to a predetermined value D. If the determination is made, the flag Facc is set, and if the vehicle body deceleration determination means determines that the descending speed of the estimated vehicle body speed is equal to or higher than the predetermined value E corresponding to the value on the high μ road, the flag Fdec is set and the cascade determination is made. The means has a counting means that counts down when the flags Fabs, the flag Fs1, the flag Facc, and the flag Fdec are all set, and resets to the initial value otherwise, and the count value of the counting means is the initial value of the counting means. When the flag Fcas is smaller than the predetermined value δ, the flag Fcas is set, and the cascade control means performs the low μ control when the flag Fcas is set. Setting antiskid control device which is characterized in that. 11. The anti-skid control device according to claim 1, wherein the cascade control means determines that the cascade determination means is in a cascade state on a low μ road. When the estimated vehicle body speed is calculated based on the maximum wheel speed which is the maximum value among the wheel speeds, and the cascade determination means does not determine that the vehicle is in the cascade state on the low μ road, An anti-skid control device, characterized in that the estimated vehicle body speed is set based on a maximum wheel speed which is the maximum value among the wheel speeds and a wheel speed other than the maximum wheel speed. 12. The anti-skid control device according to claim 11, wherein when the cascade control means does not determine that the cascade determination means is in a cascade state on a low μ road, An anti-skid control device, wherein the estimated vehicle body speed is set based on an average value of a maximum wheel speed that is the maximum value and a wheel speed that is the next largest value of the maximum wheel speed. 13. The anti-skid control device according to claim 11 or 12, wherein the cascade control means further determines that the cascade determination means is in a cascade state on a low μ road. An anti-skid control device characterized by setting a criterion for detecting a lock symptom so as to make it easier to detect a lock symptom of each wheel, and setting a large reduction amount of the wheel cylinder hydraulic pressure. 14. The anti-skid control device according to claim 13, wherein when the cascade control means determines that the cascade determination means is in a cascade state on a low μ road, the wheel acceleration is a threshold value TH3. In the pressurization start condition that the pressurization of the wheel cylinder hydraulic pressure is started when it exceeds the threshold value, the threshold value TH3 is set to be larger than that in the case where it is not determined that the cascade state is on the low μ road. Anti-skid control device. 15. The anti-skid control device according to claim 13 or 14, wherein when the cascade control means determines that the cascade determination means is in a cascade state on a low μ road, Under the pressurization start condition that the pressurization of the wheel cylinder hydraulic pressure is started when the differential value of the wheel acceleration exceeds the threshold value TH4, the threshold value is higher than that in the case where it is not determined that the cascade state is on the low μ road. An anti-skid control device characterized by setting a large value TH4. 16. An anti-skid control device having a wheel speed sensor for detecting a wheel speed of each wheel, and estimating a wheel cylinder hydraulic pressure of each wheel during ABS control from each wheel speed detected by the wheel speed sensor. In the above, the maximum wheel speed Vmax1 which is the maximum value among the above wheel speeds
And a minimum wheel speed Vmin which is the minimum value, and a difference speed ΔS which is a difference between the maximum wheel speed Vmax1 and the minimum wheel speed Vmin is calculated. Whether or not the difference speed ΔS is a predetermined value A or more. Then, a difference ΔSave between the average wheel speed of the left and right front wheels and the average wheel speed of the left and right rear wheels is calculated from the wheel speeds, and it is determined whether the difference ΔSave is equal to or less than a predetermined value B. In the control cycle, it is determined that the speed difference ΔS is equal to or greater than the predetermined value A, and the difference ΔSave is equal to the predetermined value B.
When the frequency of determining that it is less than or equal to a predetermined value Z or more, it is determined that the vehicle is in the cascade state on the low μ road, and when it is determined that the vehicle is in the cascade state on the low μ road, the ABS corresponding to the low μ road is determined. An anti-skid control device characterized by being set to perform low μ control which is control. 17. An anti-skid control device having a wheel speed sensor for detecting a wheel speed of each wheel, and estimating a wheel cylinder hydraulic pressure of each wheel during ABS control from each wheel speed detected by the wheel speed sensor. , It is determined whether or not at least one wheel is in the ABS control state, and the maximum wheel speed Vmax1 which is the maximum value among the above wheel speeds is determined.
And the minimum wheel speed Vmin which is the minimum value, and the difference speed ΔS which is the difference between the maximum wheel speed Vmax1 and the minimum wheel speed Vmin is calculated, and whether or not the difference speed ΔS is less than or equal to a predetermined value C Then, the acceleration of each wheel is calculated from the wheel speeds, and it is determined whether or not all the calculated wheel accelerations are equal to or less than a predetermined value D, which is an estimated value of the vehicle body speed from the wheel speeds. The estimated vehicle body speed is calculated, and it is determined from the calculated estimated vehicle body speed whether or not the descending speed of the estimated vehicle body speed is equal to or higher than a predetermined value E corresponding to the value on the high μ road. , It is determined that at least one wheel is in an ABS control state, the differential speed ΔS is less than or equal to a predetermined value C, and all wheel accelerations of each wheel are less than or equal to a predetermined value D, and Estimated vehicle speed descending speed is equal to or higher than a predetermined value E When the time for determining that there is a certain value continuously exceeds the predetermined value T, it is determined that the low μ road is in the cascade state, and when it is determined that the low μ road is in the cascade state, the ABS control corresponding to the low μ road is performed. An anti-skid control device characterized by performing low μ control.