Electric steering apparatus

• US 4,967,618 A
• Filed: 10/24/1989
• Issued: 11/06/1990
• Est. Priority Date: 04/17/1987
• Status: Expired

• Current Assignee: Nippon Seiko Kabushiki Kaisha (NSK Limited)
• Original Assignee: Nippon Seiko Kabushiki Kaisha (NSK Limited)
• Inventors: Matsumoto, Sakae, Ichikawa, Mitsuo
• Primary Examiner(s): NOT, DEFINED
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US07/426,033
• Time in Patent Office: 378 Days
• Field of Search: 74/89.15, 74/383, 74/409, 74/424.8 R, 74/441, 74/493, 74/495, 280/775
• US Class Current: 74/493
• CPC Class Codes: B62D 1/181 with power actuated adjustment, e.g. with position memory
• CPC Class Codes: Y10T 74/19623 Backlash take-up
• CPC Class Codes: Y10T 74/19902 Screw and nut

Abstract

An electric steering apparatus which effects position adjustment by electric drive has a screw shaft parallel to upper and lower columns. A nut member rotatably supported by a housing fixed to a bracket is fixed against movement in the axial direction of the screw shaft and threadably engaged with a screw portion provided at one end of the screw shaft. In a preferred embodiment the other end of the screw shaft is pivotally connected to the upper column for pivotal movement relative to the bracket in the direction of tilt. The nut member is self-aligning in the housing, and the nut member is rotatively driven by an electric motor to move the screw shaft in the axial direction and thereby move the upper column, whereby position adjustment can be accomplished. The apparatus is provided with a back-lash preventing device in which the screw shaft is pressed against the nut member in a radial direction and the threadably engaged portions of the screw shaft and the nut member are urged against each other.

Claims

1. An electric steering apparatus comprising:

a lower column fixed to a vehicle body and having a housing provided thereon;

an upper column having a tilting pivot portion and a screw shaft pivot portion, said upper column being pivotally attached to said lower column at said tilting pivot portion so as to be tiltable with respect to said lower column;

a lower shaft rotatably received in said lower column and having a first end and a second end, said first end being connected to a steering gear;

an upper shaft rotatably received in said upper column for tilting with said upper column and having a first end connected to a steering wheel and a second end connected to said second end of said lower shaft through a universal joint such that an angle formed between respective axes of said upper and lower shafts may be changed by tilting of said upper shaft with said upper column;

a screw shaft having a non-threaded first end portion pivotally connected directly to said screw shaft pivot portion of said upper column, and a second end portion formed with a screw thread;

nut means rotatable by an electric motor and having a threaded portion engaged with said screw thread of said screw shaft;

antifriction bearing means mounted in said housing and comprising two inner races provided on a surface of said nut means, two outer races fitted in said housing, and two groups of rolling members provided between said inner races and said outer races, said antifriction bearing means being mounted in said housing in such a manner as to support said nut means for rotation relative to said screw thread and as to prevent said nut means from moving in an axial direction of said lower column and from moving in a direction perpendicular to said lower column, said screw shaft thus moving in the axial direction of said lower column upon rotation of said nut means by said motor while pivoting relative to said screw shaft pivot portion;

aligning means for aligning a rotational axis of said nut means with an axis of said screw shaft during said pivoting of said screw shaft; and

back-lack eliminating means for eliminating back-lash by pressing on an outer surface of said screw shaft such that said screw thread presses against said threaded portion of said nut means.

2. An electric steering apparatus according to claim 1, wherein said aligning means includes said outer races of said antifriction bearing means, and said outer races are configured such that said rolling members of said antifriction bearing means shift along said outer races in accordance with the pivoting movement of said screw shaft.

3. An electric steering apparatus according to claim 1, wherein said aligning means includes curved inner portions of said housing, and said outer races of said antifriction bearing means are configured to shift along said curved inner portions in accordance with the pivoting movement of said screw shaft.

4. An electric steering apparatus according to claim 1, wherein said back-lash eliminating means also presses said first end portion of said screw shaft toward said screw shaft pivot portion of said housing.

5. An electric steering apparatus comprising:

a lower column fixed to a vehicle body and having a housing provided thereon;

an upper column telescopically connected to said lower column;

a lower shaft rotatably received in said lower column and having a first end and a second end, said first end being connected to a steering gear;

an upper shaft rotatably received in said upper column for movement with said upper column relative to said lower column and having a first end connected to a steering wheel and a second end connected to said second end of said lower shaft such that the connected second ends may move axially but not rotatably relative to each other;

a screw shaft having a non-threaded first end portion connected to said upper column and a second end portion formed with a screw thread;

nut means rotatable by an electric motor and having a threaded portion engaged with said screw thread of said screw shaft;

antifriction bearing means mounted in said housing and comprising two inner races provided on a surface of said nut means, two outer races fitted in said housing, and two groups of rolling members provided between said inner races and said outer races, said antifriction bearing means supporting said nut means in such a manner as to prevent said nut means from moving in an axial direction of said lower column but to permit said nut means to rotate relative to said screw shaft, said screw shaft thus moving in the axial direction of said lower column upon rotation of said nut means by said motor;

first back-lash eliminating means for eliminating back-lash by pressing an outer surface of said screw shaft so that said screw thread of said screw shaft presses against said threaded portion of said nut means; and

second back-lash eliminating means for eliminating back-lash by pressing said antifriction bearing means so that each said inner race presses against a corresponding said outer race through an associated one of said groups of rolling members.

6. An electric steering apparatus according to claim 5, wherein said second back-lash eliminating means comprises male and female threaded members engaged with one another and threadably adjustable for pressing against said antifriction bearing means to eliminate backlash associated with said antifriction bearing means.

7. An electric steering apparatus comprising:

a lower column fixed to a vehicle body;

an upper column having a tilting pivot portion and a screw shaft pivot portion, said upper column being pivotally attached to said lower column at said tilting pivot portion so as to be tiltable with respect to said lower column;

a lower shaft rotatably received in said lower column and having a first end and a second end, said first end being connected to a steering gear;

an upper shaft rotatably received in said upper column for tilting movement with said upper column and having a first end connected to a steering wheel and a second end connected to said second end of said lower shaft through a universal joint such that an angle formed between respective axes of said upper and lower shafts may be changed by tilting of said upper shaft with said upper column;

a screw shaft having a non-threaded first end portion pivotally connected directly to said screw shaft pivot portion of said upper column, and a second end portion formed with a screw thread;

nut means rotatable by an electric motor and having a threaded portion engaged with said screw thread of said screw shaft;

antifriction bearing means supporting said nut means for rotating relative to said screw thread and in such a manner as to prevent said nut means from moving in an axial direction of said lower column and from moving in a direction perpendicular to said lower column, said screw shaft thus being movable in the axial direction of said lower column upon rotation of said nut means by said electric motor while pivoting relative to said screw shaft pivot portion;

aligning means for aligning a rotational axis of said nut means with the axis of said screw shaft during movement of said screw shaft; and

pressing means for pressing said antifriction bearing means to eliminate back-lash.

8. An electric steering apparatus according to claim 7, including a housing provided on said lower column, and wherein:

said antifriction bearing means comprises two inner races provided on a surface of said nut means, two outer races fitted in said housing, and two groups of rolling members provided between said inner and outer races, and

said pressing means comprises male and female threaded members engaged with one another and threadably adjustable for pressing against said antifriction bearing means to eliminate back-lash associated with said antifriction bearing means.

9. An electric steering apparatus according to claim 7, wherein said aligning means includes said outer races of said antifriction bearing means, and said outer races are configured such that said rolling members of said antifriction bearing means shift along said outer races in accordance with the pivoting movement of said screw shaft.

10. An electric steering apparatus according to claim 7, including a housing provided on said lower column, and wherein said aligning means includes curved inner portions of said housing, and said outer races of said antifriction bearing means are configured to shift along said curved inner portions in accordance with the pivoting movement of said screw shaft.