Vehicular brake control apparatus and vehicular brake control method

• US 6,598,946 B2
• Filed: 07/19/2001
• Issued: 07/29/2003
• Est. Priority Date: 07/31/2000
• Status: Expired due to Term

• Current Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Nagae, Akira
• Primary Examiner(s): Schwartz, Christopher P.
• Application Number:
  US09/907,757
• Publication Number:
  US 20020014799A1
• Time in Patent Office: 740 Days
• Field of Search: 180/244, 180/249, 303/190, 303/3, 303/15, 303/20, 701/81, 701/89
• US Class Current: 303/190
• CPC Class Codes: B60K 17/3462 with means for changing distribution of torque between front and rear wheels
• CPC Class Codes: B60K 17/35 including arrangements for suppressing or influencing the power transfer, e.g. viscous clutches differential gearing with locking devices F16H48/20
• CPC Class Codes: B60K 23/0808 for varying torque distribution between driven axles, e.g. by transfer clutch
• CPC Class Codes: B60T 2270/12 for all-wheel drive vehicles
• CPC Class Codes: B60T 8/1769 specially adapted for vehicles having more than one driven axle, e.g. four-wheel drive vehicles
• CPC Class Codes: B60T 8/322 Systems specially adapted for vehicles driven by more than one axle, e.g. Four Wheel-Drive vehicles
• CPC Class Codes: B60W 2510/0638 Engine speed
• CPC Class Codes: B60W 2520/105 Longitudinal acceleration
• CPC Class Codes: B60W 2520/125 Lateral acceleration
• CPC Class Codes: B60W 2520/14 Yaw
• CPC Class Codes: B60W 2520/28 Wheel speed
• CPC Class Codes: B60W 2540/10 Accelerator pedal position
• CPC Class Codes: B60W 2540/12 Brake pedal position

Abstract

A vehicle is equipped with a coupling such as, for example, a center differential or a variable clutch, that transmits a driving force from an engine to a front-wheel drive shaft and a rear-wheel drive shaft while allowing a difference in rotational speed therebetween and a brake controller that individually controls braking forces to be applied to wheels in accordance with a running state of the vehicle. A vehicular brake controller prohibits braking force control from being started if the coupling is in its locked state or when the coupling causes a relatively great connecting strength to exist between the front-wheel and rear-wheel drive shafts. While braking force control is being performed by the brake controller, braking force control is continued even if there is a command to cause the coupling to be locked or to achieve the great coupling strength.

Claims

1. A vehicular brake control apparatus comprising:

a connecting state coupling interposed between a front-wheel drive shaft that transmits a driving force to a front-wheel side and a rear-wheel drive shaft that transmits a driving force to a rear-wheel side, and that changes a connecting state between the front-wheel drive shaft and the rear-wheel drive shaft;

brakes, each of which is provided in a corresponding one of wheels to apply a braking force to the corresponding one of the wheels; and

a brake controller that performs operation control of the brakes in accordance with a running state of the vehicle and that controls braking forces to be applied to the wheels individually, wherein the brake controller;

(a) prohibits brake control if conditions for starting brake control by the brake controller have been fulfilled during a period in which the coupling causes a great connecting strength to act between the front-wheel drive shaft and the rear-wheel drive shaft, and

(b) continues brake control if the connecting state between the front-wheel drive shaft and the rear-wheel drive shaft has been changed during perfoarmance of the brake control such that the great connecting strength acts between the front-wheel drive shaft and the rear-wheel drive shaft while brake control is being performed by the brake controller.

2. The brake control apparatus according to claim 1, wherein the brake controller prohibits brake control from being started if conditions for starting brake control by the brake controller have been fulfilled when the coupling is in a locked state in which relative rotation between the front-wheel drive shaft and the rear-wheel drive shaft is locked.

3. The brake control apparatus according to claim 1, wherein the brake controller continues brake control if the connecting strength between the front-wheel drive shaft and the rear-wheel drive shaft has temporarily become the great connecting strength while brake control is being performed by the brake controller.

4. The brake control apparatus according to claim 3, wherein the brake controller continues brake control if the connecting strength between the front-wheel drive shaft and the rear-wheel drive shaft has become the great connecting strength as a result of a changeover operation of the coupling between two-wheel-drive and four-wheel-drive modes while brake control is being performed by the brake controller.

5. The brake control apparatus according to claim 1, wherein the brake controller performs brake control without prohibiting the brake control if the vehicle is running at a speed higher than a threshold while the connecting strength between the front-wheel drive shaft and the rear-wheel drive shaft is the great connecting strength.

6. The brake control apparatus according to claim 1, wherein the brake controller performs brake control without prohibiting the brake control if a road surface has a friction coefficient smaller than a reference value while the connecting strength between the front-wheel drive shaft and the rear-wheel drive shaft is the great connecting strength.

7. The brake control apparatus according to claim 1, wherein the brake controller individually controls braking forces to be applied to the wheels such that a turning behavior of the vehicle is stabilized, if turning behavior of the vehicle is in a predetermined state.

8. The brake control apparatus according to claim 1, wherein the connecting state coupling includes a lockable differential.

9. The brake control apparatus according to claim 1, wherein the connecting state coupling includes a variable clutch mechanism.

10. A brake control method for a vehicle having (a) a connecting state coupling interposed between a front-wheel drive shaft that transmits a driving force to a front-wheel side and a rear-wheel drive shaft that transmits the driving force to a rear-wheel side, and that changes a connecting state between the front-wheel drive shaft and the rear-wheel drive shaft, (b) brakes, each of which is provided in a corresponding one of wheels to apply a braking force to the corresponding one of the wheels, and (c) a controller that performs operation control of the brakes in accordance with a running state of the vehicle and that controls braking forces to be applied to the wheels individually, comprising the steps of:

prohibiting brake control if conditions for starting brake control by the brake controller have been fulfilled during a period in which the coupling causes a great connecting strength to act between the front-wheel drive shaft and the rear-wheel drive shaft; and

continuing brake control by the brake controller if the connecting state between the front-wheel drive shaft and the rear-wheel drive shaft has been changed during performance of the brake control such that the great connecting strength acts between the front-wheel drive shaft and the rear-wheel drive shaft, while brake control is being performed by the brake controller.

11. The brake control method according to claim 10, wherein performance of the brake control is continued if the connecting strength between the front-wheel drive shaft and the rear-wheel drive shaft has temporarily become the great connecting strength while brake control is being performed by the brake controller.

12. The brake control method according to claim 11, wherein performance of the brake control is continued if the connecting strength between the front-wheel drive shaft and the rear-wheel drive shaft has become the great connecting strength as a result of a changeover operation of the coupling between two-wheel-drive and four-wheel-drive modes while brake control is being performed by the brake controller.

13. The brake control method according to claim 10, wherein the brake control is prohibited from being started if conditions for starting brake control by the brake controller have been fulfilled when the coupling is in a locked state in which relative rotation between the front-wheel drive shaft and the rear-wheel drive shaft is locked.

14. The brake control method according to claim 10, wherein the brake control is not prohibited if the vehicle is running at a speed higher than a threshold while the connecting strength between the front-wheel drive shaft and the rear-wheel drive shaft is the great connecting strength.

15. The brake control method according to claim 10, wherein the brake control is not prohibited if a road surface has a friction coefficient smaller than a reference value while the connecting strength between the front-wheel drive shaft and the rear-wheel drive shaft is the great connecting strength.

16. The brake control method according to claim 10, wherein the controller individually controls braking forces to be applied to the wheels such that a turning behavior of the vehicle is stabilized, if turning behavior of the vehicle is in a predetermined state.