Electric power steering system over-speed energizing brake system

• US 8,177,018 B2
• Filed: 09/30/2009
• Issued: 05/15/2012
• Est. Priority Date: 09/30/2009
• Status: Expired due to Fees

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations LLC (General Motors Company)
• Inventors: Coleman, Brian C., Mielke, Christopher J., Doerr, George E.
• Primary Examiner(s): Dickson, Paul N
• Assistant Examiner(s): POTTER, WESLEY A
• Application Number:
  US12/570,483
• Publication Number:
  US 20110073404A1
• Time in Patent Office: 958 Days
• Field of Search: 180/444, 188/184, 188/185, 188/186, 192/105.CD, 192/103.A, 192/103.B
• US Class Current: 180/444
• CPC Class Codes: B62D 5/04 electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear

Abstract

A bi-directional over-speed energizing brake system which implements automatically in the event an electric power steering system is in an over-speed condition. For rotational speeds of a rotating component exceeding a predetermined rotational speed threshold, centrifugal force acting on brake arms of a braking assembly overcome biasing by springs such that the brake arms will frictionally engage a non-rotating brake ring to thereby slow the rotational speed of the rotating component.

Claims

1. An over-speed energizing brake system for an electric power steering system, said power steering system having rotatable components and non-rotatable components with respect to the motor vehicle, said over-speed energizing brake system comprising:

a brake ring having an annular braking surface; and

a braking assembly disposed in concentric relation to said braking surface, said braking assembly selectively engaging said braking surface in response to rotation of said braking assembly with respect to said brake ring, wherein for rotation speeds of said braking assembly not exceeding a predetermined rotation speed threshold then said braking assembly does not engage said braking surface, and wherein for rotation speeds of said braking assembly exceeding the predetermined rotation speed threshold then said braking assembly engages said braking surface, wherein the engagement is an energizing braking engagement which acts to slow the rotational speed of said braking assembly;

wherein said brake ring is adapted for connection to a non-rotatable component of the electric power steering system;

wherein said braking assembly is adapted for connection to a rotatable component of the electric power steering system; and

wherein said braking assembly comprises;

a base;

a plurality of brake arms pivotally connected to said base;

at least one biasing spring biasing said plurality of brake arms toward said base;

wherein said base is adapted for connection to the rotatable component of the electric power steering system;

wherein for rotation speeds of said base not exceeding the predetermined rotation speed threshold then said brake arms do not engage said braking surface, and wherein for rotation speeds of said base exceeding the predetermined rotation speed threshold then said brake arms engage said braking surface, wherein the engagement is an energizing braking engagement which acts to slow the rotational speed of said braking assembly;

wherein said plurality of brake arms comprises;

at least one pair of brake arms which provide bi-directional braking of said braking assembly with respect to said brake ring;

wherein a first brake arm thereof has a pivot location which is disposed angularly lagging its engagement with said braking surface when said base rotates in a clockwise direction at a speed exceeding said threshold; and

wherein a second brake arm thereof has a pivot location which is disposed angularly lagging its engagement with said braking surface when said base is rotating in a counterclockwise direction at a speed exceeding said threshold;

wherein said at least one pair of brake arms comprises a plurality of pairs of brake arms which are mutually spaced apart on said base

wherein said at least one biasing spring comprises a plurality of biasing springs retained by said base, one biasing spring, respectively, for each pair of brake arms;

wherein each said brake arm has a contact foot structured for said engagement with said braking surface, each contact foot being disposed distally from the respective pivot connection of the respective brake arm to said base;

wherein said base is annular and has a periphery; and

said plurality of pairs of brake arms comprises three pairs of brake arms which are mutually spaced apart substantially equidistantly on the periphery of said base.

2. An electric power steering system of a motor vehicle, comprising:

rotatable electric power steering components which are rotatable with respect to the motor vehicle;

non-rotatable electric power steering components which are non-rotatable with respect to the motor vehicle; and

an over-speed energizing brake system comprising;

a brake ring having an annular braking surface; and

a braking assembly disposed in concentric relation to said braking surface, said braking assembly selectively engaging said braking surface in response to rotation of said braking assembly with respect to said brake ring, wherein for rotation speeds of said braking assembly not exceeding a predetermined rotation speed threshold then said braking assembly does not engage said braking surface, and wherein for rotation speeds of said braking assembly exceeding the predetermined rotation speed threshold then said braking assembly engages said braking surface, wherein the engagement is an energizing braking engagement which acts to slow the rotational speed of said braking assembly;

wherein said brake ring is connected to a selected non-rotatable component of the electric power steering system; and

wherein said braking assembly is connected to a selected rotatable component of the electric power steering system.

3. The electric power steering system of claim 2, wherein said braking assembly comprises:

a base;

a plurality of brake arms pivotally connected to said base;

at least one biasing spring biasing said plurality of brake arms toward said base;

wherein said base is connected to the selected rotatable component of the electric power steering system; and

wherein for rotation speeds of said base not exceeding the predetermined rotation speed threshold then said brake arms do not engage said braking surface, and wherein for rotation speeds of said base exceeding the predetermined rotation speed threshold then said brake arms engage said braking surface, wherein the engagement is an energizing braking engagement which acts to slow the rotational speed of said braking assembly.

4. The electric power steering system of claim 3, wherein said plurality of brake arms comprises:

at least one pair of brake arms which provide bi-directional braking of said braking assembly with respect to said brake ring;

wherein a first brake arm thereof has a pivot location which is disposed angularly lagging its engagement with said braking surface when said base rotates in a clockwise direction at a speed exceeding said threshold; and

wherein a second brake arm thereof has a pivot location which is disposed angularly lagging its engagement with said braking surface when said base is rotating in a counterclockwise direction at a speed exceeding said threshold.

5. The electric power steering system of claim 4, wherein said at least one pair of brake arms comprises a plurality of pairs of brake arms which are mutually spaced apart on said base.

6. The electric power steering system of claim 5, wherein the electric power steering system further comprises an electric motor, wherein the non-rotating component is connected with a housing of said electric motor, and wherein the rotating component is connected with a shaft of said electric motor.

10. The electric power steering system of claim 5, wherein the electric power steering system further comprises a gear box and a rack, wherein the non-rotating component is connected with housing of said gear box, and wherein the rotating component is connected with said rack.

7. The electric power steering system 6, wherein said at least one biasing spring comprises a plurality of biasing springs retained by said base, one biasing spring, respectively, for each pair of brake arms.

8. The electric power steering system claim 7, wherein each said brake arm has a contact foot structured for said engagement with said braking surface, each contact foot being disposed distally from the respective pivot connection of the respective brake arm to said base.

9. The electric power steering system of claim 8, wherein:

said base is annular and has a periphery; and

said plurality of pairs of brake arms comprises three pairs of brake arms which are mutually spaced apart substantially equidistantly on the periphery of said base.

11. The electric power steering system 10, wherein said at least one biasing spring comprises a plurality of biasing springs retained by said base, one biasing spring, respectively, for each pair of brake arms.

12. The electric power steering system claim 11, wherein each said brake arm has a contact foot structured for said engagement with said braking surface, each contact foot being disposed distally from the respective pivot connection of the respective brake arm to said base.

13. The electric power steering system of claim 12, wherein:

said base is annular and has a periphery; and

said plurality of pairs of brake arms comprises three pairs of brake arms which are mutually spaced apart substantially equidistantly on the periphery of said base.

14. A method for selectively braking a rotating component of an electric power steering system, comprising the steps of:

applying braking to a rotating component of the power steering system if the rotation speed of the rotating component exceeds a predetermined rotational speed threshold;

wherein said step of applying is automatically responsive to centrifugal force of the rotating component.