Device for controlling a reaction force using an electric motor to provide a steering assistance force in a hydraulic power steering system

• US 5,931,256 A
• Filed: 07/25/1997
• Issued: 08/03/1999
• Est. Priority Date: 06/27/1994
• Status: Expired due to Fees

• Current Assignee: Mercedes-Benz Ludwigsfelde GmbH (Mercedes-Benz Group AG)
• Original Assignee: Mercedes-Benz AG (Mercedes-Benz Group AG)
• Inventors: Langkamp, Bernd
• Primary Examiner(s): BOEHLER, ANNE MARIE M
• Application Number:
  US08/900,511
• Time in Patent Office: 739 Days
• Field of Search: 180/400, 180/417, 180/421, 180/422, 180/423, 180/443, 180/446, 180/404, 180/405, 180/406, 180/407
• US Class Current: 180/422
• CPC Class Codes: B62D 5/0463 calculating assisting torque from the motor based on driver input
• CPC Class Codes: B62D 5/06 fluid, i.e. using a pressurised fluid for most or all the force required for steering a vehicle
• CPC Class Codes: B62D 6/008 Control of feed-back to the steering input member, e.g. simulating road feel in steer-by-wire applications

Abstract

A device for the parameter-dependent control of a reaction force at an operating element, in particular a steering wheel of a motor vehicle, of a hydraulic power steering system. In this case, a parameter-dependent additional force is generated by an electric motor in addition to a hydraulically generated servo positioning force.

Claims

1. A hydraulic power steering system for a vehicle, comprising:

an operating element used by a driver of the vehicle;

steered wheels operated by said operating element;

a mechanical drive transmission having first and second parts movable relative to one another to a limited extent counter to a spring force, said first and second parts moving relative to one another;

a servo valve arranged between a hydraulic pressure source and a relatively pressureless hydraulic reservoir, said servo valve being controlled by the relative movement of said first and second parts;

a hydraulic servo motor coupled to the steered wheels of the vehicle and being controlled via said servo valve;

an electric motor drivingly coupled to the operating element; and

a control unit for controlling said electric motor to provide a force in accordance with input signals received by said control unit from at least one of a force measuring sensor arranged between the hydraulic servo motor and the steered wheels, and pressure sensors arranged to detect a hydraulic pressure difference present at the hydraulic servo motor.

2. The hydraulic power steering system according to claim 1, wherein said first part is an operating-element-side part and said electric motor is drivingly coupled to said operating-element-side part.

3. A steering system according to claim 1, wherein said first and second parts form a steering shaft, a rotor of the electric motor being formed by the first part of the steering shaft arranged adjacent the operating element relative to the second part.

4. A steering system according to claim 1, wherein the electric motor generates an auxiliary force acting to control the steered wheels in a same direction as a servo positioning force of the hydraulic servo motor.

5. A steering system according to claim 1, wherein said electric motor generates an additional force counteracting a servo positioning force of the hydraulic servomotor.

6. A steering system according to claim 1, further comprising a further sensor detecting a manual force parameter of said operating element, said further sensor being coupled to said control unit.