Steering control method for a motor vehicle with a differential

• US 5,253,728 A
• Filed: 08/13/1992
• Issued: 10/19/1993
• Est. Priority Date: 08/26/1991
• Status: Expired due to Term

• Current Assignee: Fuji Jukogyo KK (Subaru Corp.)
• Original Assignee: Fuji Jukogyo KK (Subaru Corp.)
• Inventors: Mouri, Toyohiko, Matsuno, Kouji
• Primary Examiner(s): Focarino, Margaret A.
• Assistant Examiner(s): MATTIX, CARLA
• Application Number:
  US07/928,776
• Time in Patent Office: 432 Days
• Field of Search: 180/140, 180/141, 180/142, 180/79, 180/79.1, 180/249, 364/424.05
• US Class Current: 180/446
• CPC Class Codes: B60K 23/04 for differential gearing
• CPC Class Codes: B62D 5/0463 calculating assisting torque from the motor based on driver input
• CPC Class Codes: B62D 5/0472 for damping vibrations

Abstract

A steering control method for a motor vehicle with a differential. The quantity and direction of a torque displacement in the state in which restricting means is locked are calculated. When the direction of the torque displacement is from an outside wheel to an inside wheel, a restricting torque is set at zero. On the other hand, when the direction of the torque displacement is from the inside wheel to the outside wheel, the ratio between the load displacement magnitudes of a front axle is calculated. A front axle driving torque is calculated from a transmission gear position, an engine speed and a throttle opening degree. The restricting torque is calculated so that a torque distribution to the inside and outside wheels may become substantially equal to a load distribution to them. The correction amount of a steering assist force is calculated from the restricting torque, and the mass offset of a wheel tire, the diameter of the wheel tire and a steering gear ratio. A hydraulic controller is driven on the basis of the restricting torque calculated above. A steering correction controller is driven on the basis of the correction amount of the steering assist force calculated above.

Claims

1. A steering control method for a motor vehicle having, an engine mounted on said motor vehicle, a differential provided between a left front wheel and a right front wheel for absorbing a speed difference of said left and right front wheels, restricting means mounted on said differential for controlling a torque distribution to said left and right front wheels, a steering wheel operatively connected to said wheels for steering said motor vehicle, an electric motor connected with said steering wheel for assisting an operation of said steering wheel, a torsion torque sensor connected to said steering wheel for detecting a torsion torque of said steering wheel and for producing a torsion torque signal, a vehicle speed sensor for detecting a vehicle speed and for generating a vehicle speed signal, an engine speed sensor for detecting an engine speed and for generating an engine speed signal, a throttle sensor for detecting an opening degree of a throttle valve in said engine and for producing a degree signal, a gear position sensor for detecting a position of selected gears and for generating a position signal, a lateral G sensor mounted on said motor vehicle for detecting a lateral acceleration and for generating a lateral G signal, and a longitudinal G sensor mounted on said motor vehicle for detecting a longitudinal acceleration and for generating a longitudinal G signal, an improvement of the control method which comprises the steps of:

deriving an amount and a direction of a torque displacement from said lateral and longitudinal G signals when said restricting means is locked;

deactivating said restricting means when said direction of said torque displacement is from the outside wheel to the inside wheel;

calculating a load distribution to said left and right wheels when said direction of said torque displacement is from said inside wheel to said outside wheel;

computing a driving torque from a map storing data in a function of said position signal, said engine speed signal and said degree signal;

determining a restricting torque from said load distribution and said driving torque;

actuating said restricting means in accordance with said restricting torque;

deciding a correction amount from said restricting torque and characteristic values of said motor vehicle; and

correcting an assist force by said electric motor so as to improve a traction performance and to attain an optimum control of said steering wheel without fluctuation.

2. The method according to claim 1, wherein said characteristic values are a mass offset and a diameter of a wheel tire, and a steering gear ratio.