Vehicle having secondarily steered front and rear wheels

• US 4,970,646 A
• Filed: 11/10/1988
• Issued: 11/13/1990
• Est. Priority Date: 11/12/1987
• Status: Expired due to Term

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Kawagoe, Kenji, Mouri, Hiroshi, Mori, Kazunori, Kuroki, Junsuke, Sugasawa, Fukashi
• Primary Examiner(s): Black, Thomas G.
• Application Number:
  US07/269,698
• Time in Patent Office: 733 Days
• Field of Search: 364/424.05, 180/140-143, 180/79.1, 280/91, 74/388 P
• US Class Current: 701/42
• CPC Class Codes: B62D 7/14 the pivotal axes being situated in more than one plane transverse to the longitudinal centre line of the vehicle, e.g. all-wheel steering

Abstract

A method of steering a vehicle having a set of steerable front wheels and a set of steerable rear wheels. The front and rear wheels are both secondarily steered in addition to a main steer of the front wheels caused by an operation of a front wheel steering gear in response to an operation of a steering wheel. The method comprises providing to the front wheels a secondary steer angle corresponding to at least a differentiated value of a steer angle of a steering wheel in such a way as to increase an overall steer angle of the front wheels and providing to the rear wheels a secondary steer angle proportional to the steer angle of the steering wheel and in the same direction as the steer angle of the front wheels.

Claims

1. A method of steering a vehicle having a set of steerable front wheels and a set of steerable rear wheels which are both secondarily steered upon main steering of the front wheels by operation of a steering wheel, the method comprising:

providing to said front wheels a secondary steer angle corresponding to at least a differentiated value of a steering wheel operation, to increase an overall steer angle of said front wheels; and

providing, with a time-lag of a first order, to said rear wheels a secondary steer angle proportional to said steering wheel operation and of the same phase as said steer angle of said front wheels.

2. A method as set forth in claim 1 wherein said differentiated value of said steering wheel operation is a differentiated value of a steer angle of said steering wheel.

3. A method as set forth in claim 2 wherein said said secondary steer angle of said front wheels is related to a vehicle speed.

4. A method as set forth in claim 3 wherein said first mentioned providing comprises detecting said steer angle of said steering wheel and said vehicle speed and computing a front wheel secondary steer target angle δ

f and a rear wheel secondary steer target angle δ

r from the following formulas,

space="preserve" listing-type="equation">δ

f=Kf·

θ

+Tf·

θ

##EQU2## where θ

is a steer angle of the steering wheel, θ

is a differentiated value of the steer angle θ

, Kf and Kr are proportional constants which are functions of vehicle speed, Tf is a differential constant which is a function of vehicle speed, and τ

is a time constant which is a function of a vehicle speed.

5. A method as set forth in claim 4 wherein said first mentioned providing further comprises detecting a front wheel secondary steer actual angle δ

F and a rear wheel secondary steer actual angle δ

R, and controlling the front and rear wheel steer so that δ

f=δ

F and δ

r=δ

R are attained.

6. A method as set forth in claim 1 wherein said first mentioned providing comprises detecting said steer angle of said steering wheel and said vehicle speed and computing a front wheel secondary steer target angle δ

f from the following formula,

space="preserve" listing-type="equation">δ

f=Tf·

θ

where Tf is a differential constant which is a function of vehicle speed and θ

is a differentiated value of a steer angle θ

of said steering wheel.

7. A method as set forth in claim 6 wherein said first mentioned providing further comprises detecting a front wheel secondary steer actual angle δ

F and controlling the front wheel secondary steer so that δ

f=δ

F is attained.

8. A method as set forth in claim 7 wherein said second mentioned providing is performed so that said secondary steer angle of said rear wheels is directly proportional to a steer angle of said steering wheel.