Four-wheel-steered vehicle control system

• US 5,201,382 A
• Filed: 03/29/1991
• Issued: 04/13/1993
• Est. Priority Date: 03/30/1990
• Status: Expired due to Fees

• Current Assignee: Mazda Motor Corporation
• Original Assignee: Mazda Motor Corporation
• Inventors: Nakashima, Takashi, Ohmura, Hiroshi, Murai, Takeshi, Edahiro, Takeshi, Akita, Ryuya
• Primary Examiner(s): HILL, MITCHELL
• Application Number:
  US07/677,528
• Time in Patent Office: 746 Days
• Field of Search: 180/197, 180/140, 180/142, 364/426.02, 364/426.03, 303/92, 74/866
• US Class Current: 180/197
• CPC Class Codes: B60K 28/16 responsive to, or preventing, skidding of wheels brake control systems for vehicle drive stability B60T8/1755; arrangements responsive to a speed condition for adjusting wheel braking force B60T8/32; control of vehicle driving stability otherwise than by controlling the propulsion unit only B60W30/02; preventing wheel slippage by reducing power in rail vehicles B61C15/00
• CPC Class Codes: B60T 2260/022 Rear-wheel steering; Four-wheel steering
• CPC Class Codes: B60T 8/175 Brake regulation specially adapted to prevent excessive wheel spin during vehicle acceleration, e.g. for traction control safety devices for propulsion unit control responsive to, or preventing, skidding of wheels B60K28/16
• 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: B62D 7/148 provided with safety devices
• CPC Class Codes: B62D 7/159 characterised by computing methods or stabilisation processes or systems, e.g. responding to yaw rate, lateral wind, load, road condition

Abstract

A front drive vehicle is provided with a four-wheel steering system and a traction control system. A control system for the vehicle detects whether a failure occurs in the traction control system, and causes the rear wheel turning mechanism to turn the rear wheels according to corrected rear wheel turning characteristics when it is determined that a failure occurs in the traction control system. The corrected rear wheel turning characteristics are shifted toward the reverse phase side with respect to the original rear wheel turning characteristics.

Claims

1. A vehicle control system for a vehicle which has front and rear wheels, the front wheels being driving wheels, and is provided with a four-wheel steering system comprising a front wheel turning mechanism which turns the front wheels in response to turning a steering wheel, a rear wheel turning mechanism which turns the rear wheels and a four-wheel steering control means which causes the rear wheel turning mechanism to turn the rear wheels according to first predetermined rear wheel turning characteristics, and a traction control system comprising a slip ratio detecting means for detecting a slip ratio of the front wheels with respect to the road surface where the slip ratio is a function of the relative rotational speeds of the front and rear wheels and a driving force control means which controls the driving force of the front wheels so that the slip ratio of the front wheels converges on a target slip ratio when the slip ratio of the front wheels as detected by the slip ratio detecting means exceeds a preset value where the target slip ratio represents a value that the slip ratio should be converted to after the slip ratio exceed said preset value where the preset value is greater than the target value of the slip ratio, the vehicle control system characterized by having

a failure detecting means which detects that a failure occurs in the traction control system, and

a rear wheel turning characteristic changing means which controls the four-wheel-steering control means to cause the rear wheel turning mechanism to turn the rear wheels according to second rear wheel turning characteristics when the failure detecting means detects that a failure occurs in the traction control system, the second rear wheel turning characteristics being shifted toward a reverse phase side with respect to the first rear wheel turning characteristics where the reverse phase side occurs when the rear wheels are turned in the direction opposite to that of the front wheels.

2. A vehicle control system as defined in claim 1 further comprising

another failure detecting means which detects that a failure occurs in the four-wheel steering system, and

a target slip ratio changing means which increases the target slip ratio when said another failure detecting means detects that a failure occurs in the four-wheel steering system.

3. A vehicle control system for a vehicle which has front and rear wheels, the front wheels being driving wheels, and is provided with a four-wheel steering system comprising a front wheel turning mechanism which turns the front wheels in response to turning a steering wheel, a rear wheel turning mechanism which turns the rear wheels and a four-wheel-steering control means which causes the rear wheel turning mechanism to turn the rear wheels according to first predetermined rear wheel turning characteristics, and a traction control system comprising a slip ratio detecting means for detecting a slip ratio of the front wheels with respect to the road surface where the slip ratio is a function of the relative rotational speeds of the front and rear wheels and a driving force control means which controls the driving force of the front wheels so that the slip ratio of the front wheels converges on a target slip ratio when the slip ratio of the front wheels as detected by the slip ratio detecting means exceeds a preset value where the target slip ratio represents a value that the slip ratio should be converted to after the slip ratio exceeds said preset value where the preset value is greater than the target value of the slip ratio, the vehicle control system characterized by having

a failure detecting means which detects that a failure occurs in the four-wheel steering system, and

a target slip ratio changing means which increases the target slip ratio when the failure detecting means detects that a failure occurs in the four-wheel steering system.

4. A vehicle control system for a vehicle which has front and rear wheels, the rear wheels being driving wheels, and is provided with a four-wheel steering system comprising a front wheel turning mechanism which turns the front wheels in response to turning a steering wheel, a rear wheel turning mechanism which turns the rear wheels and a four-wheel-steering control means which causes the rear wheel turning mechanism to turn the rear wheels according to first predetermined rear wheel turning characteristics, and a traction control system comprising a slip ratio detecting means for detecting a slip ratio of the rear wheels with respect to the road surface where the slip ratio is a function of the relative rotational speeds of the front and rear wheels and a driving force control means which controls the driving force of the drear wheels so that the slip ratio of the rear wheels converges on a target slip ratio when the slip ratio of the rear wheels as detected by the slip ratio detecting means exceeds a preset value where the target slip ratio represents a value that the slip ratio should be converted to after the slip ratio exceeds said preset value where the preset value is greater than the target value of the slip ratio, the vehicle control system characterized by having

a failure detecting means which detects that a failure occurs in the traction control system, and

a rear wheel turning characteristic changing means which controls the four-wheel-steering control means to cause the rear wheel turning mechanism to turn the rear wheels according to second rear wheel turning characteristics when the failure detecting means detects that a failure occurs in the traction control system, the second rear wheel turning characteristics being shifted toward a same phase side with respect to the first rear wheel turning characteristics where the same phase side occurs when the rear wheels are turned in the same direction as that of the front wheels.

5. A vehicle control system as defined in claim 4 further comprising

another failure detecting means which detects that a failure occurs in the four-wheel steering system, and

a target slip ratio changing means which reduces the target slip ratio when said another failure detecting means detects that a failure occurs in the four-wheel steering system.

6. A vehicle control system for a vehicle which has front and rear wheels, the rear wheels being driving wheels, and is provided with a four-wheel steering system comprising a front wheel turning mechanism which turns the front wheels in response to turning a steering wheel, a rear wheel turning mechanism which turns the rear wheels and a four-wheel-steering control means which causes the rear wheel turning mechanism to turn the rear wheels according to first predetermined rear wheel turning characteristics, and a traction control system comprising a slip ratio detecting means for detecting a slip ratio of the rear wheels with respect to the road surface where the slip ratio is a function of the relative rotational speeds of the front and rear wheels and a driving force control means which controls the driving force of the rear wheels so that the slip ratio of the rear wheels converges on a target slip ratio when the slip ratio of the rear wheels as detected by the slip ratio detecting means exceeds a preset value where the target slip ratio represents a value that the slip ratio should be converted to after the slip ratio exceeds said preset value where the preset value is greater than the target value of the slip ratio, the vehicle control system characterized by having

a failure detecting means which detects that a failure occurs in the four-wheel steering system, and

a target slip ratio changing means which reduces the target slip ratio when the failure detecting means detects that a failure occurs in the four-wheel steering system.