STEERING SYSTEM

• US 20180281843A1
• Filed: 03/28/2018
• Published: 10/04/2018
• Est. Priority Date: 04/04/2017
• Status: Active Grant

• Current Assignee: Jtekt Corporation (Toyota Motor Corporation)
• Original Assignee: Jtekt Corporation (Toyota Motor Corporation)
• Inventors: ASAKURA, Toshihiro, NAKAYAMA, Takuya
• Granted Patent: US 10,661,824 B2
• Time in Patent Office: Days
• CPC Class Codes: B62D 3/126 characterised by the rack
• CPC Class Codes: B62D 5/0403 characterised by constructional features, e.g. common housing for motor and gear box
• CPC Class Codes: B62D 5/0424 the axes of motor and final driven element of steering gear, e.g. rack, being parallel
• CPC Class Codes: B62D 5/0448 Ball nuts
• CPC Class Codes: F16H 2025/2081 Parallel arrangement of drive motor to screw axis
• CPC Class Codes: F16H 2025/2096 using endless flexible members
• CPC Class Codes: F16H 2057/02034 Gearboxes combined or connected with electric machines structural association with electric machines H02K7/116
• CPC Class Codes: F16H 25/2204 with balls
• CPC Class Codes: F16H 25/24 Elements essential to such mechanisms, e.g. screws, nuts F16H25/22 takes precedence
• CPC Class Codes: F16H 55/171 Toothed belt pulleys
• CPC Class Codes: F16H 55/48 manufactured exclusively or in part of non-metallic material, e.g. plastics F16H55/38, F16H55/42, F16H55/46 take precedence ; manufacture of wooden wheels B27H7/00
• CPC Class Codes: F16H 57/02 Gearboxes; Mounting gearing therein
• CPC Class Codes: F16H 7/023 with belts having a toothed contact surface or regularly spaced bosses or hollows for slipless or nearly slipless meshing with complementary profiled contact surface of a pulley toothed belts F16G1/28, F16G5/20

Abstract

A steering system with a reduced number of parts is provided. A driven pulley has a radially outer portion, a radially inner portion, and a connection portion that connects the radially outer portion and the radially inner portion to each other. The radially inner portion is provided with a plurality of slits at equal intervals in the circumferential direction. A plurality of retention portions are provided at portions of the radially inner portion between the slits. Lug portions are provided on the inner surface of the distal ends of the retention portions. A groove is provided in the outer peripheral surface of a ball screw nut. The lug portions of the retention portions are fitted with the groove of the ball screw nut.

Claims

1. A steering system comprising:

a motor;

a steered shaft that is reciprocally movable in an axial direction;

a ball screw nut threadably engaged with the steered shaft via a plurality of balls; and

a speed reducer that has a driven pulley into which the ball screw nut is inserted so that the driven pulley is fixed to an outer peripheral surface of the ball screw nut, a drive pulley fixed so as to be rotatable together with a rotary shaft of the motor, and a belt wound between the driven pulley and the drive pulley, wherein

the outer peripheral surface of the ball screw nut is provided with a groove that extends along a circumferential direction of the ball screw nut, and an inner peripheral surface of the driven pulley is provided with a lug portion to be fitted with the groove.

2. The steering system according to claim 1, wherein

the driven pulley has a cylindrical radially outer portion around which the belt is wound, a radially inner portion disposed inside the radially outer portion and attached so as to be rotatable together with the ball screw nut, and a connection portion that connects the radially outer portion and the radially inner portion to each other in a radial direction.

3. The steering system according to claim 2, wherein:

the radially inner portion is provided with slits provided at equal intervals in the circumferential direction to extend in the axial direction; and

the lug portion is provided at portions of the radially inner portion between the slits and on an inner peripheral surface of distal end portions of the radially inner portion that are opposite to the connection portion.

4. The steering system according to claim 1, further comprising:

a rack housing that houses the ball screw nut and the speed reducer; and

a bearing that supports the ball screw nut so as to be rotatable with respect to an inner peripheral surface of the rack housing, wherein

the groove is provided at an end portion of a portion of the ball screw nut to which the driven pulley is fixed, the end portion being closer to a portion of the ball screw nut to which the bearing is fixed.

5. The steering system according to claim 1, further comprising:

a rack housing that houses the ball screw nut and the speed reducer; and

a bearing that supports the ball screw nut so as to be rotatable with respect to an inner peripheral surface of the rack housing, wherein

the groove is provided at an end portion of a portion of the ball screw nut to which the driven pulley is fixed, the end portion being opposite to a portion of the ball screw nut to which the bearing is fixed.

6. The steering system according to claim 1, wherein:

the outer peripheral surface of the ball screw nut is provided with a key groove that extends in the axial direction; and

the inner peripheral surface of the driven pulley is provided with a key portion that extends in the axial direction to be fitted with the key groove.

7. The steering system according to claim 1, wherein:

the outer peripheral surface of the ball screw nut is provided with an abutment portion that is located adjacent to the groove in the axial direction and that has a surface that is orthogonal to or oblique with respect to the axial direction of the ball screw nut; and

an end portion of the driven pulley in the axial direction abuts against the abutment portion.

8. The steering system according to claim 1, wherein:

the belt has helical teeth; and

the driven pulley has helical teeth corresponding to the helical teeth of the belt.