Nsk Corporation

Takeshi Nakazawa

Yoshinori Mizumura

Tsutomu Ohkubo

Kazuo Miyaguchi

Soichiro Kato

Hiroki Yamaguchi

Nobumitsu Takahashi

Shirouji Yabe

Ryouichi Sato

Between two mutually adjoining load balls, there is interposed a retaining piecehaving two concave surfaceswhich are respectively opposed to the two adjoining load balls. The retaining piecehas an outside diameter dimension equal to or more than 0.5 times the outside diameter dimension of the load ball. Further, the retaining piecehas an outside diameter dimension which, when the retaining piecepasses through a screw groove circulation passage and a tube circulation passage, prevents the retaining piecefrom touching the inner walls of these screw groove circulation passage and tube circulation passage, or has an outside diameter dimension which is equal to or less than 0.9 times the outside diameter dimension of the load ball. Accordingly, it is possible to provide a ball screw mechanism which can prevent a retaining piece from interfering with the inner walls of circulation passages to circulate load balls stably to thereby prevent variations in torque as well as prevent the wear of the retaining piece to thereby enhance the durability thereof.

Ball screw mechanism

In a ball screw device comprising a screw shaft and a nut which make relative movement to each other through a multiplicity of balls, as well as in a linear motion device comprising an outer member and an inner member which make the relative movements to each other through the multiplicity of balls, a spacer having two concave surfaces facing respectively to balls, is disposed between the balls adjacent to each other. In one preferred form, the spacer has such a configuration that the balls adjacent to each other come into contact with at least three or more outer edge portions of the spacer or portions vicinal to the outer edges.

Ball screw device and linear motion device

A spacer between adjacent balls of, for example, a ball screw device or a linear motion device has an outer periphery that is concave such that the spacer is elastically deformed to be in substantially circular line contact with the adjacent balls and that a distance therebetween is variable.

In a ball screw device comprising a screw shaft and a nut which make relative movement to each other through a multiplicity of balls, as well as in a linear motion device comprising an outer member and an inner member which make the relative movements to each other through the multiplicity of balls, a spacer having two concave surfaces facing respectively to balls, is disposed between the balls adjacent to each other. A section of each of the concave surfaces of the spacer is formed of two circular arcs of which central positions deviate from each other to form a Gothic arch. The spacer has such a configuration that the balls adjacent to each other come into contact with outer edges thereof or portions vicinal to the outer edges. The spacer also has such a configuration that the balls adjacent to each other come into contact with at least three or more outer edge portions thereof or portions vicinal to the outer edges. The spacer may have a through-hole formed in a thinnest portion thereof.

Between two mutually adjoining load balls , there is interposed a retaining piece having two concave surfaces which are respectively opposed to the two adjoining load balls . The retaining piece has an outside diameter dimension equal to or more than 0.5 times the outside diameter dimension of the load ball . Further, the retaining piece has an outside diameter dimension which, when the retaining piece passes through a screw groove circulation passage and a tube circulation passage, prevents the retaining piece from touching the inner walls of these screw groove circulation passage and tube circulation passage, or has an outside diameter dimension which is equal to or less than 0.9 times the outside diameter dimension of the load ball. Accordingly, it is possible to provide a ball screw mechanism which can prevent a retaining piece from interfering with the inner walls of circulation passages to circulate load balls stably to thereby prevent variations in torque as well as prevent the wear of the retaining piece to thereby enhance the durability thereof.

In a ball screw device comprising a screw shaft and a nut which make relative movement to each other through a multiplicity of balls, as well as in a linear motion device comprising an outer member and an inner member which make the relative movements to each other through the multiplicity of balls, a spacer having two concave surfaces facing respectively to balls, is disposed between the balls adjacent to each other. A section of each of the concave surfaces of the spacer is formed of two circular arcs of which central positions deviate from each other to from a Gothic. The spacer has such a configuration that the balls adjacent to each other come into contact with outer edges thereof or portions vicinal to the outer edges. The spacer also has such a configuration that the balls adjacent to each other come into contact with at least three or more outer portions thereof or portions vicinal to the outer edges. The spacer may have a through-hole formed in a thinnest portion thereof.

Growing community of inventors

Maebashi, Japan

Takeshi Nakazawa