Ball screw mechanism and steering device

Patent metadata

Field	Value
Publication number	US-9446788-B2
Application number	US-201514693315-A
Country	US
Kind code	B2
Filing date	Apr 22, 2015
Priority date	May 9, 2014
Publication date	Sep 20, 2016
Grant date	Sep 20, 2016

Abstract

A ball screw mechanism includes: a rack shaft, on the outer peripheral surface of which a spiral rack screw groove is formed; a cylindrical nut, on the inner peripheral surface of which a spiral nut groove that faces the rack screw groove is formed; and a plurality of balls disposed in a rolling passage that is a space surrounded by the rack screw groove and the nut groove. The nut is provided with: shift portions provided at both ends of the nut groove to shift the track of the nut groove in the axial direction of the rack shaft from the rack screw groove and to displace the nut groove to be deeper in the radial direction of the rack shaft as the track is shifted; a circulation passage that connects between the shift portions; and passage entrances that each connect between the shift portion and the circulation passage.

First claim

What is claimed is:

1. A ball screw mechanism comprising:
a screw shaft, on an outer peripheral surface of which a spiral screw shaft-side rolling groove is formed;
a cylindrical nut, on an inner peripheral surface of which a spiral nut-side rolling groove that faces the screw shaft-side rolling groove is formed; and
a plurality of balls disposed in a rolling passage that is a space surrounded by the screw shaft-side rolling groove and the nut-side rolling groove, wherein
the nut is provided with:
shift portions provided at both ends of the nut-side rolling groove to shift a track of the nut-side rolling groove in an axial direction of the screw shaft from the screw shaft-side rolling groove and to displace the nut-side rolling groove to be deeper in a radial direction of the screw shaft as the track of the nut-side rolling groove is shifted;
a circulation passage that connects between the shift portions provided at both ends of the nut-side rolling groove; and
passage entrances that are each an entrance of a passage that connects between the shift portion and the circulation passage, and

the passage entrances are each positioned, in the axial direction of the screw shaft, between a starting position of the shift portion and a position facing an outermost periphery of a screw thread that is adjacent to the screw shaft-side rolling groove which faces the starting position of the shift portion.

2. The ball screw mechanism according to claim 1 , wherein
the shift portions are formed at both ends of the nut-side rolling groove so as to shift a track of the shift portions toward a rolling groove that is adjacent to the nut-side rolling groove.

3. The ball screw mechanism according to claim 1 , further comprising:
a sleeve externally fitted on the nut, wherein
the circulation passage is formed on an outer periphery of the nut.

4. The ball screw mechanism according to claim 2 , further comprising:
a sleeve externally fitted on the nut, wherein
the circulation passage is formed on an outer periphery of the nut.

5. The ball screw mechanism according to claim 1 , wherein
the passage entrances are each formed, in the axial direction of the screw shaft, at such a position as to face an outermost periphery of a screw thread of the screw shaft that is adjacent to the screw shaft-side rolling groove which faces the shift portion.

6. The ball screw mechanism according to claim 2 , wherein
the passage entrances are each formed, in the axial direction of the screw shaft, at such a position as to face an outermost periphery of a screw thread of the screw shaft that is adjacent to the screw shaft-side rolling groove which faces the shift portion.

7. The ball screw mechanism according to claim 3 , wherein
the passage entrances are each formed, in the axial direction of the screw shaft, at such a position as to face an outermost periphery of a screw thread of the screw shaft that is adjacent to the screw shaft-side rolling groove which faces the shift portion.

8. The ball screw mechanism according to claim 4 , wherein
the passage entrances are each formed, in the axial direction of the screw shaft, at such a position as to face an outermost periphery of a screw thread of the screw shaft that is adjacent to the screw shaft-side rolling groove which faces the shift portion.

9. The ball screw mechanism according to claim 1 , wherein
the passage entrances are each positioned, in an axial direction of the nut, between a starting position of the shift portion and a position of an elevated portion of a screw thread that is adjacent to the nut-side rolling groove to which the shift portion is connected.

10. The ball screw mechanism according to claim 2 , wherein
the passage entrances are each positioned, in an axial direction of the nut, between a starting position of the shift portion and a position of an elevated portion of a screw thread that is adjacent to the nut-side rolling groove to which the shift portion is connected.

11. The ball screw mechanism according to claim 3 , wherein
the passage entrances are each positioned, in an axial direction of the nut, between a starting position of the shift portion and a position of an elevated portion of a screw thread that is adjacent to the nut-side rolling groove to which the shift portion is connected.

12. The ball screw mechanism according to claim 1 , wherein
the outermost periphery of the screw thread of the screw shaft is formed on a cylindrical surface.

13. The ball screw mechanism according to claim 2 , wherein
the outermost periphery of the screw thread of the screw shaft is formed on a cylindrical surface.

14. The ball screw mechanism according to claim 3 , wherein
the outermost periphery of the screw thread of the screw shaft is formed on a cylindrical surface.

15. The ball screw mechanism according to claim 5 , wherein
the outermost periphery of the screw thread of the screw shaft is formed on a cylindrical surface.

16. A steering device comprising:
a ball screw mechanism including a steered shaft of a vehicle that acts as a screw shaft, a cylindrical nut provided with a spiral nut-side rolling groove that faces a spiral screw shaft-side rolling groove formed on an outer peripheral surface of the steered shaft, and a plurality of balls disposed in a rolling passage that is a space surrounded by the screw shaft-side rolling groove and the nut-side rolling groove;
a motor that applies torque to the nut; and
a speed reduction mechanism that transmits rotary torque of the motor to the nut, wherein
the ball screw mechanism according to claim 1 is used as the ball screw mechanism.

17. A steering device comprising:
a ball screw mechanism including a steered shaft of a vehicle that acts as a screw shaft, a cylindrical nut provided with a spiral nut-side rolling groove that faces a spiral screw shaft-side rolling groove formed on an outer peripheral surface of the steered shaft, and a plurality of balls disposed in a rolling passage that is a space surrounded by the screw shaft-side rolling groove and the nut-side rolling groove;
a motor that applies torque to the nut; and
a speed reduction mechanism that transmits rotary torque of the motor to the nut, wherein
the ball screw mechanism according to claim 2 is used as the ball screw mechanism.

18. A steering device comprising:
a ball screw mechanism including a steered shaft of a vehicle that acts as a screw shaft, a cylindrical nut provided with a spiral nut-side rolling groove that faces a spiral screw shaft-side rolling groove formed on an outer peripheral surface of the steered shaft, and a plurality of balls disposed in a rolling passage that is a space surrounded by the screw shaft-side rolling groove and the nut-side rolling groove;
a motor that applies torque to the nut; and
a speed reduction mechanism that transmits rotary torque of the motor to the nut, wherein
the ball screw mechanism according to claim 3 is used as the ball screw mechanism.

19. A steering device comprising:
a ball screw mechanism including a steered shaft of a vehicle that acts as a screw shaft, a cylindrical nut provided with a spiral nut-side rolling groove that faces a spiral screw shaft-side rolling groove formed on an outer peripheral surface of the steered shaft, and a plurality of balls disposed in a rolling passage that is a space surrounded by the screw shaft-side rolling groove and the nut-side rolling groove;
a motor that applies torque to the nut; and
a speed reduction mechanism that transmits rotary torque

Assignees

• Jtekt Corp

Inventors

• Yamaguchi Masashi

Classifications

• F16H2025/2081

  Parallel arrangement of drive motor to screw axis · CPC title

• B62D5/0448 Primary

  Ball nuts · CPC title

• F16H25/2223

  Cross over deflectors between adjacent thread turns, e.g. S-form deflectors connecting neighbouring threads · CPC title

• Y10T74/19767

  Return path geometry · CPC title

• B62D5/0424

  the axes of motor and final driven element of steering gear, e.g. rack, being parallel · CPC title