Patent ID: 7228751
Filing Date: 2007-06-12
Classification: F16H,Y10T

Abstract:
1. A ball screw mechanism comprising: a ball screw shaft of a metal material having a first ball screw groove engraved on an outer circumference thereof, said first ball screw groove having solely a semicircular cross section conforming in shape to surfaces of balls disposed in said first ball screw groove, without other grooves, profiles or clearances being formed in said first ball screw groove; and a nut member of a resin material being screwed onto said ball screw shaft via balls between said first ball screw groove and a second ball screw groove formed in said nut member, wherein rotation of said nut member is restricted, and said nut member is displaceable in an axial direction of said ball screw shaft, wherein a pair of oil sumps is formed on only said second ball screw groove of said nut member, said oil sumps extending along a circumferential surface of said second ball screw groove on respective sides of said balls, and being separated by a predetermined length from a bottom of said second ball screw groove, wherein said oil sumps comprise a pair of respective oil-retaining recesses formed and recessed into said nut member, each of said oil-retaining recesses being recessed a predetermined depth from said circumferential surface of said second ball screw groove, wherein openings of said oil-retaining recesses facing said balls are covered by said surfaces of said balls, and wherein a clearance is formed at said bottom of said second ball screw groove, between said second ball screw groove and said ball in said second ball screw groove.