Electric steering system for automobiles

• US 4,741,409 A
• Filed: 06/25/1987
• Issued: 05/03/1988
• Est. Priority Date: 06/25/1987
• Status: Expired due to Term

• Current Assignee: Delphi Technologies, Inc. (BorgWarner Incorporated)
• Original Assignee: General Motors Corporation (Motors Liquidation Co. GUC Trust)
• Inventors: Westercamp, Kenneth L., Hallman, Steven J.
• Primary Examiner(s): Love, John J.
• Assistant Examiner(s): McGiehan, Donn
• Application Number:
  US07/066,655
• Time in Patent Office: 313 Days
• Field of Search: 180/140, 180/148, 180/152, 180/153, 180/79.1, 74/388 PS, 74/422
• US Class Current: 180/413
• CPC Class Codes: B62D 5/001 Mechanical components or aspects of steer-by-wire systems, not otherwise provided for in this maingroup
• CPC Class Codes: B62D 5/003 Backup systems, e.g. for manual steering B62D5/30 takes precedence
• CPC Class Codes: B62D 7/09 characterised by means varying the ratio between the steering angles of the steered wheels varying the ratio automatically depending on driving conditions B62D6/00

Abstract

An electric steering system for automobiles includes a tubular main housing disposed on a transverse axis of the vehicle between two steerable road wheels. A left steering rack is slidably disposed in the main housing and connected to the left road wheel. A right steering rack is slidably disposed in the main housing and connected to the right road wheel. A pair of reversible electric motors at opposite ends of the main housing drive the steering racks independently of each other through corresponding pinion drive assemblies. The inboard end of the left steering rack telescopes into a bore in the inboard end of the right steering rack. The inboard end of the left steering rack has an annular shoulder which is captured in the bore by a rack rack nut on the inboard end of the right steering rack so that withdrawal of the left steering rack from the bore is prevented. The telescopic connection permits enough relative movement between the steering racks to allow an electronic control to optimally position each road wheel during steering maneuvers but is sufficiently small that the wheels can be acceptably steered together by one motor if the other becomes inoperative.

Claims

1. In combination with an automobile having at least one pair of steerable road wheels each pivotable independently of the other about a corresponding one of a pair of steering axes of said automobile, a manual steering implement on said automobile, and an electronic control connected to said steering implement operative to convert a manual steering input to said implement into at least two electric current outputs corresponding to said steering input,

an electric steering system comprising:

a tubular main housing on said automobile aligned on a transverse axis thereof between said pair of steerable road wheels,

a first steering rack disposed in said main housing for bodily shiftable movement in opposite directions along said transverse axis and including an inboard end and an outboard end,

a second steering rack disposed in said main housing for bodily shiftable movement in opposite directions along said transverse axis and including an inboard end and an outboard end,

means connecting said outboard end of each of said first and said second steering racks to a corresponding one of said steerable road wheels so that bodily shiftable movement of each of said first and said second steering racks effects steering pivotal movement of said corresponding steerable road wheel,

a first reversible electric motor mounted on said main housing and connected to one of said electric current outputs whereby said first motor is selectively energized by said electronic control,

a second reversible electric motor mounted on said main housing and connected to the other of said electric current outputs whereby said second motor is selectively energized by said electronic control,

first reversible reduction gear means between said first motor and said first steering rack operative when said first motor is energized to bodily shift said first steering rack along said transverse axis and to back drive said first motor when said first motor is deenergized and said first steering rack is forcibly bodily shifted along said transverse axis,

second reversible reduction gear means between said second motor and said second steering rack operative when said second motor is energized to bodily shift said second steering rack along said transverse axis and to back drive said second motor when said second motor is deenergized and said second steering rack is forcibly bodily shifted along said transverse axis,

means on said inboard end of said first steering rack and on said inboard end of said second steering rack defining a telescopeable sliding connection between said first and said second steering racks, and

stop means on each of said first and said second steering racks operative to limit said relative telescopeable sliding movement to a predetermined dimension so that attempted relative movement beyond said predetermined dimension is accompanied by positive driving engagement of one of said first and said second steering racks on the other.

2. The steering system recited in claim 1 wherein:

said means on said inboard end of said first steering rack and on said inboard end of said second steering rack defining a telescopeable sliding connection between said first and second second steering racks includes

means defining a blind bore extending longitudinally from said inboard end of said first steering rack to a bottom wall of said bore, and

means on said second steering rack at said inboard end thereof defining an outside cylindrical surface slidably received in said blind bore.

3. The steering system recited in claim 2 wherein:

said stop means on each of said first and said second steering racks operative to limit said relative telescopeable sliding movement to a predetermined dimension includes

an end wall on said inboard end of said second steering rack engageable on said bottom wall of said bore to limit relative telescopeable collapse between said first and said second steering racks,

a rack nut on said first steering rack at the open end of said blind bore, and

means defining an annular shoulder on said second steering rack engageable on said rack nut to limit relative telescopeable extension between said first and said second steering racks.

4. In combination with an automobile having a front pair of road wheels steerable independently of each other about corresponding ones of a pair of front steering axes of said automobile and a rear pair of road wheels steerable independently of each other about corresponding ones of a pair of rear steering axes of said automobile, a manual steering implement on said automobile, and an electronic control connected to said steering implement operative to convert a manual steering input to said implement into four electric current outputs corresponding to said steering input,

an electric steering system comprising:

a front tubular main housing on said automobile aligned on a front transverse axis thereof between said front pair of steerable road wheels,

a rear tubular main housing on said automobile aligned on a rear transverse axis thereof between said rear pair of steerable road wheels,

a first steering rack disposed in each of said front and said rear main housings for bodily shiftable movement in opposite directions along the corresponding one of said front and said rear transverse axes and each including an inboard end and an outboard end,

a second steering rack disposed in each of said front and said rear main housings for bodily shiftable movement in opposite directions along the corresponding one of said front and said rear transverse axes and each including an inboard end and an outboard end,

means connecting said outboard end of each of said first and said second steering racks to a corresponding one of said front and said rear steerable road wheels so that bodily shiftable movement of each of said first and said second steering racks effects steering pivotal movement of said corresponding steerable road wheel,

a front pair of reversible electric motors mounted on said front main housing and connected to respective ones of said four electric current outputs whereby each of said front pair of motors is selectively energized by said electronic control independently of the other,

a rear pair of reversible electric motors mounted on said rear main housing and connected to respective ones of said four electric current outputs whereby each of said rear pair of motors is selectively energized by said electronic control independently of the other,

a reversible reduction gear train between each of said electric motors of said front and said rear pairs of motors and respective ones of said first and said second steering racks operative when a corresponding one of said electric motors is energized to bodily shift said respective steering rack along a corresponding one of said front and said rear transverse axes and to back drive said corresponding motor when said corresponding motor is deenergized and said respective steering rack is forcibly bodily shifted along said corresponding one of said front and said rear transverse axes,

means on each of said first steering racks defining a blind bore extending longitudinally from said inboard end thereof to a bottom wall of said bore,

means on each of said second steering racks defining an outer cylindrical wall adjacent said inboard end projecting into said blind bore in the corresponding one of said first steering racks

means on each of said second steering racks defining a longitudinally spaced pair of annular shoulders on said outer cylindrical wall each having an outside cylindrical surface slidably engaging said blind bore in a corresponding one of said first steering racks whereby each of said second steering racks is telescopeable relative to said corresponding one of said first steering racks along said front and said rear transverse axes,

means on said inboard end of each of said second steering racks defining an end wall engageable on said bottom wall of said bore in a corresponding one of said first steering racks to limit relative telescopeable collapse between said first and said second steering racks, and

a rack nut on each of said first steering racks at an open end of said blind bore therein projecting into an annulus between said blind bore and said outer cylindrical wall of a corresponding one of said second steering racks,

one of said annular shoulders on each of said second steering racks being engageable on a corresponding one of said rack nuts to limit relative telescopeable extension between said first and said second steering racks.