Electrical power-assisted steering systems

• US 6,194,849 B1
• Filed: 05/13/1998
• Issued: 02/27/2001
• Est. Priority Date: 09/13/1996
• Status: Expired due to Fees

• Current Assignee: Lucas Industries Limited (Zeppelin - Stiftung der Stadt Friedrichshafen)
• Original Assignee: Lucas Industries Limited (Zeppelin - Stiftung der Stadt Friedrichshafen)
• Inventors: Wilson-Jones, Russell, Wilkes, Mark Anthony, Appleyard, Michael, Horton, Steven John, Ironside, John Michael
• Primary Examiner(s): MARTIN, DAVID S
• Application Number:
  US09/068,746
• Time in Patent Office: 1,021 Days
• Field of Search: 318/8-12, 318/15, 318/254, 318/439, 318/138, 318/432-434
• US Class Current: 318/15
• CPC Class Codes: B62D 5/0406 including housing for electronic control unit
• CPC Class Codes: B62D 5/0484 for reaction to failures, e.g. limp home
• CPC Class Codes: H02K 11/21 Devices for sensing speed or position, or actuated thereby specially adapted for machines having non-mechanical commutating devices H02K29/06, H02K29/14
• CPC Class Codes: H02K 11/215 Magnetic effect devices, e.g. Hall-effect or magneto-resistive elements
• CPC Class Codes: H02K 11/24 Devices for sensing torque, or actuated thereby H02K11/27 takes precedence
• CPC Class Codes: H02K 11/33 Drive circuits, e.g. power electronics H02K11/38 takes precedence
• CPC Class Codes: H02K 2203/03 Machines characterised by the wiring boards, i.e. printed circuit boards or similar structures for connecting the winding terminations
• CPC Class Codes: H02K 2211/03 Machines characterised by circuit boards, e.g. pcb
• CPC Class Codes: H02K 5/225 Terminal boxes or connection arrangements specially adapted for submersible motors H02K5/132
• CPC Class Codes: H02K 7/1166 comprising worm and worm-wheel structural association with bearings specially adapted for worm gear drives H02K7/081
• CPC Class Codes: Y02E 10/72 Wind turbines with rotation axis in wind direction

Abstract

An electrical power-assisted steering system comprising a brushless electric motor which has a plurality of phase windings connected at a star point and in which a switching device such as a relay is provided in at least one phase of the motor, the switching device being movable between a closed position in which current is able to flow in the phase winding and an open position which prevents current flowing in the respective phase in the event of a fault.

Claims

1. An electrical power-assisted steering system for a vehicle comprising an electric motor connected through a gearbox to act on a steering mechanism of the vehicle, in which the electric motor is a brushless motor having a plurality of phase windings connected at a star point, and wherein a switching means is provided in at least one phase of the motor, the switching means being movable between a closed position in which current is able to flow in the phase winding, and an open position which prevents current flowing in the respective phase winding of the motor and wherein the switching means is provided at the star point of the motor and opening of the switching means isolate the phase winding from the star point.

2. An electrical power assisted steering system according to claim 1, wherein the switching means comprises a solid state relay.

3. An electrical power assisted steering system according to claim 1, wherein a switching means is provided in each phase of the motor to allow each phase to be isolated from the star point independently.

4. An electrical power assisted steering system according to claim 1, wherein the electric motor comprises a 3-phase motor and the switching means comprises a pair of relay contacts operated by a single relay coil so that two of the three phases can be isolated from the third phase which is common to both relay contacts.