Four-wheel steering motor vehicle

• US 4,971,174 A
• Filed: 03/17/1989
• Issued: 11/20/1990
• Est. Priority Date: 03/17/1988
• Status: Expired due to Fees

• Current Assignee: Honda Giken Kogyo Kabushiki Kaisha (Honda Motor Company)
• Original Assignee: Honda Giken Kogyo Kabushiki Kaisha (Honda Motor Company)
• Inventors: Iwagawa, Yoshihiro, Yahagi, Toshio, Abe, Masaru, Kohata, Takashi
• Primary Examiner(s): Marmor, Charles A.
• Assistant Examiner(s): BOEHLER, ANNE MARIE M
• Application Number:
  US07/325,214
• Time in Patent Office: 613 Days
• Field of Search: 180/140, 280/91, 303/92, 303/96, 303/100, 303/111
• US Class Current: 180/408
• CPC Class Codes: B60T 2260/022 Rear-wheel steering; Four-wheel steering
• CPC Class Codes: B60T 8/1755 Brake regulation specially adapted to control the stability of the vehicle, e.g. taking into account yaw rate or transverse acceleration in a curve road vehicle drive control systems for control of driving stability otherwise than by controlling a particular sub-unit B60W30/02
• CPC Class Codes: B60T 8/32 responsive to a speed condition, e.g. acceleration or deceleration using electrical circuitry or regulation means B60T8/17 ; B60T8/28 takes precedence; electric devices on electrically propelled vehicles indicating the wheel slip B60L3/10; measuring linear or angular speed per se G01P3/00
• CPC Class Codes: B62D 7/148 provided with safety devices
• CPC Class Codes: B62D 7/1581 characterised by comprising an electrical interconnecting system between the steering control means of the different axles
• 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 four-wheel steering motor vehicle adapted to prevent a steering ratio of the rear wheels to the front wheels from varying at the time of sudden braking when the pressure of a brake liquid is reduced by an antilock brake unit. This vehicle includes a front wheel steering unit for steering the front wheels in accordance with angular movement of a steering wheel, a rear wheel steering unit for steering the rear wheels, steering control unit for determining a target steering angle of the respective rear wheels based on a vehicle speed and a front wheel steering angle and for controlling the rear wheel steering unit in such a manner that the rear wheel steering unit steers the rear wheel until a rear wheel steering angle reaches the target value, an antilock brake unit for calculating a slip coefficient of each wheel based on a sensed rotating speed of each wheel and for reducing the pressure of a brake liquid being supplied to a brake of the individual wheel when the slip coefficient of the wheel exceeds a predetermined value. The steering control unit controls the rear wheel steering unit so as to substantially prevent the rear wheel steering angle from varying when the pressure to the brake liquid is reduced by the antilock brake unit.

Claims

1. A four-wheel steering motor vehicle, comprising:

(a) a front wheel steering unit for steering front wheels in accordance with angular movement of a steering wheel;

(b) a rear wheel steering unit for steering rear wheels;

(c) steering control means for determining a target steering angle of the rear wheels based on a vehicle speed and a front wheel steering angle and for controlling said rear wheel steering unit in such a manner that said rear wheel steering unit steers the rear wheels until a rear wheel steering angle reaches said target value;

(d) an antilock brake unit for calculating a slip coefficient of each of the wheels based on a rotating speed of each said wheel and for reducing the pressure of a brake liquid being applied to a brake of the wheel when the slip coefficient of the wheel exceeds a predetermined value; and

(e) said steering control means being operable to control said rear wheel steering unit so as to substantially prevent the rear wheel steering angle from varying in response to a change of the vehicle speed, when said antilock brake unit is operative.

2. A four-wheel steering motor vehicle according to claim 1, wherein said steering control means is adapted to determine a steering phase and a steering ratio of the rear wheels with respect to the front wheels based on the vehicle speed for calculating said target steering angle of the rear wheels, said steering control means being adapted to substantially prevent the steering ratio from varying when the antilock brake unit is operative.

3. A four-wheel steering motor vehicle according to claim 1, wherein said steering control means includes a driver circuit for driving a motor operatively connected with said rear wheel steering unit, a rear wheel steering angle processing circuit for determining a target steering angle of the rear wheels to output an operative signal to said driver circuit, and a correcting circuit for correcting a value of the vehicle speed so as to substantially prevent the same from varying and for issuing an output signal to said rear wheel steering processing circuit.

4. A four-wheel steering motor vehicle according to claim 1, wherein said antilock brake unit is provided with a sensor for detecting a rotating speed of the wheels, said steering control means being adapted to calculate the vehicle speed based on an output signal from said sensor.

5. A four-wheel steering motor vehicle according to claim 1, wherein said steering control means includes a driver circuit for driving a motor operatively connected with said rear wheel steering unit, a rear wheel steering angle processing circuit for determining the target steering angle of the rear wheels to output an operative signal to said driver circuit, and a memory gate circuit gate for memorizing said target steering angle of the rear wheels outputted from said rear wheel steering angle processing circuit, said memory gate circuit being adapted to output said memorized target steering angle of the rear wheels to said driver circuit when said antilock brake unit is operative.