Bar-handle vehicle brake control apparatus

1. A bar-handle vehicle brake control apparatus comprising:

an acceleration acquiring part which acquires

a first acceleration corresponding to an acceleration that is on a straight line which connects a gravity center of a bar-handle vehicle and a front wheel axle and that is in an axle direction directed toward the front wheel axle, and

a second acceleration corresponding to an acceleration that is in a tangential direction at a point where the straight line intersects a circle which is centered at the front wheel axle; and

a control unit which controls a front wheel brake based on the acquired first acceleration and the acquired second acceleration.

2. The control apparatus of claim 1 ,

wherein control unit controls the front wheel brake so that the second acceleration becomes zero.

3. The control apparatus of claim 1 ,

wherein the control unit controls so that a hydraulic pressure at the front wheel brake is reduced when the hydraulic pressure at the front wheel brake needs to be reduced for a rear lift suppression and when a predetermined acceleration is generated in the bar-handle vehicle.

4. The control apparatus of claim 1 ,

wherein the control unit includes a determination part which determines whether or not there is a risk of occurrence of a rear lift based on the second acceleration and an axle-directed acceleration which is directed to the front wheel axle, and

wherein the determination part determines that a rear wheel is being lifted regardless of a component of the second acceleration when the axle-directed acceleration is equal to or smaller than a predetermined value.

5. The control apparatus of claim 1 ,

wherein the control unit controls the front wheel brake so that a vehicle body acceleration “a” of the bar-handle vehicle is in a relationship expressed by the following expression (1):

a≦g ×cos(θ+β)/sinθ  (1),

where g is a gravitational acceleration, where θ is an angle formed by the straight line which passes through the gravity center of the bar-handle vehicle and the front wheel axle and a road surface, and where β is an inclination angle of the road surface.

6. The control apparatus of claim 1 , wherein

the acceleration acquiring part acquires an acceleration G 1 ′ and an acceleration G 2 ′,

the acceleration G 1 ′ follows a longitudinal direction of the bar-handle vehicle,

the acceleration G 2 ′ follows a direction of gravity of the bar-handle vehicle,

an acceleration signal conversion part converts the accelerations G 1 ′ and G 2 ′ into accelerations G 1H and G 2H whose coordinate axes L 1 ′, L 2 ′ are parallel to coordinate axes of accelerations G 1 and G 2 which pass through the gravity center of the bar-handle vehicle, and

the accelerations G 1H and G 2H approximate to the accelerations G 1 ′ and G 2 ′ which pass through the gravity center of the bar-handle vehicle.

7. The control apparatus of claim 6 , wherein the coordinate axis of the acceleration G 1H is parallel to a straight line L 1 which connects the gravity center of the bar-handle vehicle with the front wheel axle, and the coordinate axis of the acceleration G 2H is a parallel to tangent L 2 at a point where the straight line L 1 intersects the circle which is centered at the front wheel axle.

8. The control apparatus of claim 7 , wherein accelerations G 1H , G 2H are obtained by expressions (4), (5),

G 1H = G 1 ′×cos φ+ G 2 ′×sin φ  (4)

G 2H = G 2 ′×sin φ+ G 2 ′×cos φ  (5)

where φ denotes a coordinate rotation angle.

9. The control apparatus of claim 8 , wherein

the acceleration G 2 is a difference between a component G 2A of a gravitational acceleration in the direction of the tangent and a component G 2B of a vehicle body acceleration in the direction of the tangent and is obtained by expression (6)

G 2 = G 2A − G 2B   (6), and

when the acceleration G 2 becomes a minus acceleration which is when the component G 2B of the vehicle body acceleration becomes larger than the component G 2A of the gravitational acceleration, there is a risk of occurrence of a rear lift.

10. The control apparatus of claim 9 , further comprising a pressure reduction area determination part which determines whether or not a pressure reduction control needs to be carried out on a front wheel brake to suppress occurrence of the rear lift based on the accelerations G 1 , G 2 , wherein it is determined that the pressure reduction control is to suppress the occurrence of the rear lift when the accelerations G 1 , G 2 reside in a pressure reduction area set where G 1 <0 and G 2 <0, as well as an area where the acceleration G 1 is equal to or smaller than a predetermined value X (X<0).

11. The control apparatus of claim 10 , wherein when the acceleration G 1 in the direction of the front wheel axle is equal to or smaller than the predetermined value X, it is determined that there is a risk of occurrence of the rear lift, and a rear lift suppression function is exhibited irrespective of a magnitude of the acceleration G 2 .

12. The control apparatus of claim 10 , wherein the pressure reduction control is carried out on the front wheel brake so that acceleration “a” is in a relationship expressed by expression (1)

a≦g ×cos(θ+β)sin θ.   (1)

13. The control apparatus of claim 12 , wherein

during deceleration of the bar-handle vehicle, when the acceleration G 2 is detected by an acceleration sensor becomes minus acceleration G 2 and the component G 2B of the vehicle body acceleration takes a larger value than that of the component G 2A of the gravitational acceleration, the pressure reduction area determination part determines that the pressure reduction control for suppression of the occurrence of the rear lift is necessary,

an acceleration determination part further determines whether or not a predetermined acceleration is being generated based on the acceleration “a,” and when the acceleration determination part determines that the acceleration “a” is being generated, a request for pressure reduction control for suppression of the occurrence of the rear lift is made by a pressure reduction control part, and a pressure reduction control signal Pb which signals that the pressure reduction control should be carried out on the front wheel brake is outputted to a control selection part by a rear lift suppression control part,

then, the control selection part selects the pressure reduction control for suppression of the occurrence of the rear lift as the control of highest priority when a pressure reduction control signal Pa of an ABS control has not yet been inputted thereinto, and controls a hydraulic unit for pressure reduction at the front wheel brake.

14. The control apparatus of claim 1 , wherein

the acceleration acquiring part further acquires an axle-direction acceleration toward the front wheel axel, the axel-direction acceleration being on the straight line which connects the gravity center of the bar-handle vehicle and the front wheel axle, and

the control unit controls the front wheel brake based on the tangential second acceleration and the axel-direction acceleration.

15. A bar-handle vehicle brake control apparatus comprising:

an acceleration acquiring part which acquires a tangential acceleration at a point where a straight line which connects a gravity center of a bar-handle vehicle and a front wheel axle intersects a circle which is centered at the front wheel axle; and

a control unit which controls a front wheel brake based on the tangential acceleration,

wherein the control unit selects either a pressure reduction control in an ABS control or a pressure reduction control for a rear lift suppression, which has a larger pressure reduction pulse, in preference to a holding control in the ABS control and a pressure increase control in the ABS control.

16. A bar-handle vehicle brake control apparatus, comprising an acceleration acquiring part which acquires

a first acceleration corresponding to an acceleration that is on a straight line which connects a gravity center of a bar-handle vehicle and a ground contact point of a front wheel and that is in a ground-contact-point direction directed toward the ground contact point of the front wheel, and

a second acceleration corresponding to an acceleration that is in a tangential direction at a point where the straight line intersects a circle which is centered at the ground contact point of the front wheel; and

a control unit which controls a front wheel brake based on the acquired first acceleration and the acquired second acceleration.

17. The control apparatus of claim 16 ,

wherein the control unit controls the front wheel brake so that the second acceleration becomes zero.

18. The control apparatus of claim 16 ,

wherein the control unit controls so that a hydraulic pressure at the front wheel brake is reduced when the hydraulic pressure at the front wheel brake needs to be reduced for a rear lift suppression and when a predetermined acceleration is generated in the bar-handle vehicle.

19. The control apparatus of claim 16 ,

wherein the control unit includes a determination part which determines whether or not there is a risk of occurrence of a rear lift based on the second acceleration and a ground contact point-directed acceleration which is directed to the ground contact point of the front wheel, and

wherein the determination part determines that a rear wheel is being lifted regardless of a component of the second acceleration when the ground contact point-directed acceleration is equal to or smaller than a predetermined value.

20. The control apparatus of claim 16 ,

wherein, when the bar-handle vehicle is decelerated, the control unit controls the front wheel brake so that a vehicle body acceleration “a” of the bar-handle vehicle is in a relationship expressed by the following expression (2):

a≦g ×cos(θ1+β)/sin θ1  (2),

where g is a gravitational acceleration, where θ 1 is an angle formed by the straight line which passes through the gravity center of the bar-handle vehicle and the ground contact point of the front wheel and a road surface, and where β is an inclination angle of the road surface.

21. The control apparatus of claim 16 , wherein

the acceleration acquiring part further acquires a ground-contact-point-direction acceleration toward the ground contact point, the ground-contact-point-direction acceleration being on the straight line which connects the gravity center of the bar-handle vehicle and the ground contact point of the front wheel, and

the control unit controls the front wheel brake based on the second acceleration and the ground-contact-point-direction acceleration.

22. A bar-handle vehicle brake control apparatus, comprising

an acceleration acquiring part which acquires a tangential acceleration at a point where a straight line which connects a gravity center of a bar-handle vehicle and a ground contact point of a front wheel intersects a circle which is centered at the ground contact point of the front wheel; and

a control unit which controls a front wheel brake based on the tangential acceleration,

wherein the control unit selects either a pressure reduction control in an ABS control or a pressure reduction control for a rear lift suppression, which has a larger pressure reduction pulse, in preference to a holding control in the ABS control and a pressure increase control in the ABS control.