Vehicle brake control device

1. A vehicle brake control device comprising:

a wheel speed acquisition section configured to acquire a wheel speed of one of a front wheel and a rear wheel;

a wheel acceleration calculation section configured to calculate a wheel acceleration of the one wheel based on the wheel speed;

an anti-lock brake control section configured to execute an anti-lock brake control for the one wheel based on a slip amount based on the wheel speed and a vehicle speed;

a bad road determination section configured to determine whether or not a running road surface is a bad road based on the wheel acceleration; and

a bad road amount setting section configured to set a bad road amount for correcting the slip amount based on the determination result of the bad road determination section,

wherein the wheel acceleration calculation section calculates, as the wheel acceleration, a first wheel acceleration and a second wheel acceleration in which a high-frequency component is attenuated more than the first wheel acceleration,

wherein the bad road determination section determines that a running road surface is a bad road when the calculated first wheel acceleration is larger than a first boundary line in an area where the first wheel acceleration is larger than the second wheel acceleration, and wherein the bad road amount setting section increases the bad road amount as the calculated first wheel acceleration is larger when it is determined that a running road surface is a bad road.

2. The vehicle brake control device according to claim 1 ,

wherein the first boundary line has a step-like portion formed by:

a first line segment in which the first wheel acceleration is a constant first value;

a second line segment in which the first wheel acceleration is a constant second value larger than the first value;

a third line segment in which the second wheel acceleration is a constant third value and which connects the first line segment and the second line segment; and

a fourth line segment in which the second wheel acceleration is a constant fourth value larger than the third value and which extends from the second line segment.

3. The vehicle brake control device according to claim 2 ,

wherein the bad road determination section determines that a running road surface is a bad road when the calculated first wheel acceleration is larger than the first value and equal to or less than the second value, and the calculated second wheel acceleration is smaller than the third value, and the bad road amount setting section sets the bad road amount to a first bad road amount, and

wherein the bad road determination section determines that a running road surface is a bad road when the calculated first wheel acceleration is larger than the second value and the calculated second wheel acceleration is smaller than the fourth value, and the bad road amount setting section sets the bad road amount to a second bad road amount larger than the first bad road amount.

4. The vehicle brake control device according to claim 1 , wherein the bad road determination section determines that the running road surface is a bad road when the calculated first wheel acceleration is larger than the first boundary line in the area where the first wheel acceleration is larger than the second wheel acceleration and the first wheel acceleration increases.

5. The vehicle brake control device according to claim 1 , further comprising a changeover switch configured to switch a specification of the bad road determination.

6. The vehicle brake control device according to claim 5 , wherein the changeover switch is turned off when it is determined that there is no front wheel anti-lock brake execution or when it is determined that a vehicle acceleration is equal to or less than a predetermined value.

7. The vehicle brake control device according to claim 6 , when the changeover switch is turned off, the bad road determination section executes the had road determination only using a rear wheel acceleration.

8. The vehicle brake control device according to claim 5 , wherein the bad road determination section executes the bad road determination by selectively using one of a front wheel acceleration and a rear wheel acceleration when the changeover switch is turned on.

9. The vehicle brake control device according to claim 1 , wherein the wheel acceleration calculation section comprises:

a front wheel acceleration calculation section configured to calculate the first wheel acceleration by differentiating the front wheel speed and calculating the second wheel acceleration by differentiating a value obtained by filtering the front wheel speed by a low-pass filter, the second wheel acceleration has a value in which a high-frequency component is attenuated more than the first wheel acceleration; and

a rear wheel acceleration calculation section which calculates the first wheel acceleration by differentiating the rear wheel speed and calculating the second wheel acceleration by differentiating a value obtained by filtering the rear wheel speed by the low-pass filter, the second wheel acceleration has a value in which a high-frequency component is attenuated more than the first wheel acceleration.

10. The vehicle brake control device according to claim 1 , wherein

the anti-lock brake control section outputs an instruction for reducing braking force when the wheel accelerations of the front wheel and the rear wheel become 0 or less and the slip amount becomes larger than a control intervention threshold;

when the wheel accelerations become larger than 0 after pressure is reduced, the anti-lock brake control section outputs an instruction for maintaining braking force; and

when the wheel accelerations become 0 or less and the slip amount becomes a control intervention threshold or less after the braking force is maintained, the anti-lock brake control section outputs an instruction for increasing the braking force.

11. The vehicle brake control device according to claim 1 , wherein

the wheel anti-lock brake control section calculates the wheel slip amount (SA) by the following equation:

SA=Vc−Vw−BA

BA is a wheel bad road amount set by the bad road amount setting section, Vc is the vehicle speed and Vw is the wheel speed.

12. The vehicle brake control device according to claim 1 , wherein the bad road determination section determines a bad road determination by selectively using one of a front wheel acceleration and a rear wheel acceleration at least based on information on whether or not the anti-lock brake control for the front wheel is executed and the vehicle acceleration.

13. The vehicle brake control device according to claim 12 , wherein

the bad road determination section executes the bad road determination by using the front wheel acceleration when the anti-lock brake control for the front wheel is not executed and the vehicle acceleration is larger than a predetermined value; and

when executing the bad road determination by using the front wheel acceleration, the bad road determination section executes the bad road determination based on a first boundary line where the first wheel acceleration increases as the second wheel acceleration increases when the anti-lock brake control for the rear wheel is executed.

14. The vehicle brake control device according to claim 13 , wherein

when executing the bad road determination by using the front wheel acceleration, the bad road determination section executes the bad road determination based on a second boundary line where the first wheel acceleration increases as the second wheel acceleration increases when the anti-lock brake control for the rear wheel is not executed.

15. The vehicle brake control device according to claim 14 , wherein

the bad road determination section determines that a running road is a bad road when the calculated first wheel acceleration is smaller than the second boundary line in an area where the first wheel acceleration is smaller than the second wheel acceleration.

16. The vehicle brake control device according to claim 1 , wherein

the bad road determination section executes the bad road determination by selectively using one of q front wheel acceleration and a rear wheel acceleration when a changeover switch is turned on; and

when the changeover switch is turned off, the bad road determination section does not execute the bad road determination using the front wheel acceleration but executes only the bad road determination using the rear wheel acceleration.

17. A vehicle brake control device comprising:

a wheel speed acquisition section configured to acquire a wheel speed of one of a front wheel and a rear wheel;

a wheel acceleration calculation section configured to calculate a wheel acceleration of the one wheel based on the wheel speed;

an anti-lock brake control section configured to execute an anti-lock brake control for the one wheel based on a slip amount based on the wheel speed and a vehicle speed;

a bad road determination section configured to determine whether or not a running road surface is a bad road based on the wheel acceleration; and

a bad road amount setting section configured to set a bad road amount for correcting the slip amount based on the determination result of the bad road determination section,

wherein the wheel acceleration calculation section calculates, as the wheel acceleration, a first wheel acceleration and a second wheel acceleration in which a high-frequency component is attenuated more than the first wheel acceleration,

wherein the bad road determination section determines that a running road surface is a bad road when the calculated first wheel acceleration is smaller than a second boundary line in an area where the first wheel acceleration is smaller than the second wheel acceleration, and

wherein the bad road amount setting section increases the bad road amount as the calculated first wheel acceleration is smaller when it is determined that a running road surface is a bad road.

18. The vehicle brake control device according to claim 17 ,

wherein the second boundary line has a step-like portion formed by:

a fifth line segment in which the first wheel acceleration is a constant fifth value;

a sixth line segment in which the first wheel acceleration is a constant sixth value smaller than the fifth value;

a seventh line segment in which the second wheel acceleration is a constant seventh value and which connects the fifth line segment and the sixth line segment; and

an eighth line segment in which the second wheel acceleration is a constant eighth value smaller than the seventh value and which extends from the sixth line segment.

19. The vehicle brake control device according to claim 18 ,

wherein the bad road determination section determines that a running road surface is a bad road when the calculated first wheel acceleration is smaller than the fifth value and equal to or larger than the sixth value, and the calculated second wheel acceleration is larger than the seventh value, and the bad road amount setting section sets the bad road amount to a third bad road amount, and

wherein the bad road determination section determines that a running road surface is a bad road when the calculated first wheel acceleration is smaller than the sixth value and the calculated second wheel acceleration is larger than the eighth value, and the bad road amount setting section sets the bad road amount to a fourth bad road amount larger than the third bad road amount.