US 4,577,716 A · Servo steering system

Abstract

A power steering system for vehicles is disclosed using an electric servomotor. The servomotor is energized for power assist in executing turns and for reducing the drag of the servomotor during the return of the dirigible wheels to the straight ahead position. A torque transducer operatively coupled with the steering wheel shaft and the steering gear generates a torque signal corresponding to the torque applied by the driver to the steering wheel. A lost motion coupling is provided between the servomotor and the steering gear and a lost motion transducer is operatively coupled therewith to develop a signal corresponding to lost motion. The torque signal and the lost motion signal are combined differentially and the resultant signal is applied to the servo amplifier for energization of the servomotor. When the driver turns the steering wheel, the torque signal predominates and the servomotor is energized to provide power assist. When the driver releases the steering wheel, the torque signal drops to zero and the lost motion signal controls the energization of the servomotor to overcome its resistance to the return of the dirigible wheels to the straight ahead position. A second configuration provides a compact unit of cylindrical symmetry.

Claims26

Dependent claims

In a vehicle power steering system of the type comprising dirigible wheels, a manual input means, an electric servomotor, a steering gear, means for generating a torque signal corresponding to torque transmitted by said manual input means, and control means adapted to control energization of said servomotor in accordance with the torque signal, the improvement comprising:

restoring means responsive to turning of the dirigible wheels toward a straight ahead direction for controlling the energization of the servomotor to reduce its resistance to the turning of the dirigible wheels toward the straight ahead direction.

A vehicle power steering system comprising:

a manual input shaft,
an output means for driving a steering gear,
an electric servo motor mounted coaxially with said manual input shaft and having a tubular output shaft operatively connected through speed reduction means to said output means,
means for generating a torque signal corresponding to torque transmitted by said manual input shaft,
control means adapted to control energization of said servomotor in accordance with the torque signal,
a first displacement transmitting tubular shaft coaxial with and between the tubular output shaft and the manual input shaft operably connected with said output means for rotation therewith,
said means for generating a torque signal being an angular displacement sensor with one input member operably connected for rotation with said manual input shaft and a remaining input member operably connected for rotation with said first displacement transmitting tubular shaft.

4 more elements

Dependencies are inferred from the claim text.

Servo steering system

Life of this patent

Servo steering system

Life of this patent

Abstract

Claims26