BALL SCREW MECHANISM

• US 20100043583A1
• Filed: 08/21/2009
• Published: 02/25/2010
• Est. Priority Date: 08/21/2008
• Status: Active Grant

• Current Assignee: SMC Kabushiki Kaisha
• Original Assignee: SMC Kabushiki Kaisha
• Inventors: Fukano, Yoshihiro, Sugiyama, Toru, Imamura, Masaki
• Granted Patent: US 8,584,546 B2
• Time in Patent Office: Days
• US Class Current: 74/424.870
• CPC Class Codes: F16H 25/2219 Axially mounted end-deflectors
• CPC Class Codes: Y10T 74/19772 Rolling element deflector

Abstract

A ball screw mechanism is equipped with a ball screw shaft formed from a metallic material, a displacement nut inserted over an outer circumferential side of the ball screw shaft, steel balls installed between a first screw groove formed on the ball screw shaft and a second screw groove formed in the displacement nut, and a pair of first and second return members, through which the steel balls are circulated between one end side and another end side of the displacement nut. The first and second return members include main body parts mounted respectively onto one end and another end of the displacement nut, and cylindrical parts that project outwardly with respect to the main body parts. A return passage, through which the steel balls are circulated, is formed inside of the main body parts and the cylindrical parts.

Claims

1. A ball screw mechanisms comprising:

a ball screw shaft having a first ball screw groove engraved on an outer circumferential surface thereof;

a nut member formed in a cylindrical shape and having a second ball screw groove on an inner circumferential surface thereof, the nut member being disposed on an outer circumferential side of the ball screw shaft, and being screw-engaged with respect to the ball screw shaft via balls which are installed between the second ball screw groove and the first ball screw groove; and

a circulation member connected respectively to both ends of the nut member along an axial direction thereof, for circulating the balls through a circulation passage provided on an exterior of the nut member from one end side in a displacement direction of the nut member to the another end side thereof,

wherein the circulation member includes a main body part installed on the nut member and a cylindrical part connected to the main body part.

2. The ball screw mechanism according to claim 1, wherein the circulation passage is formed inside of the main body part and the cylindrical part, both ends of the circulation passage being connected respectively to the second ball screw groove.

3. The ball screw mechanism according to claim 1, wherein the circulation member includes a pair of circulation members, which are installed respectively into mounting portions, having outer circumferential surfaces thereof cutout in the one end and the other end of the nut member, the circulation members covering the outer circumferential side of the ball screw shaft, which is inserted through the interior of the nut member.

4. The ball screw mechanism according to claim 3, wherein the circulation passage includes:

a first passage provided in the main body part and connected to an end of the second ball screw groove; and

a second passage formed in the cylindrical part and extending along the axial direction of the cylindrical part.

5. The ball screw mechanism according to claim 4, wherein the first passage and the second passage are connected together substantially perpendicularly, and the cylindrical part of one circulation member and the cylindrical part of another circulation member are connected to each other such that the second passages thereof communicate with each other.

6. The ball screw mechanism according to claim 1, wherein, in the main body part, the interior wall surface facing the ball screw shaft is formed in an arcuate shape at a same radius of curvature as the inner circumferential surface of the nut member.

7. The ball screw mechanism according to claim 6, wherein a projection is disposed on an inner wall surface of the main body part, which projects outwardly with respect to the inner wall surface facing the circulation passage, the projection being disposed in parallel with the circulation passage, and the inside surface facing the circulation passage is connected with the circulation passage and is formed with a semicircular shape in cross section.

8. The ball screw mechanism according to claim 7, wherein the balls are guided by the projection when the balls move from the circulation passage into the second ball screw groove, and when the balls move from the second ball screw groove into the circulation passage.

9. The ball screw mechanism according to claim 5, wherein the first passage is formed in a helical shape connected to an end of the second ball screw groove, thereby forming a rolling groove together with the second ball screw groove.

10. The ball screw mechanism according to claim 1, wherein in the circulation member, the cylindrical part is detachably connected to the main body part.