Nsk Corporation

Nnsk Ltd.

Toshiharu Kajita

Eiji Hayashi

Tsutomu Ohkubo

Hideyuki Sato

Hiroshi Fujita

Takayuki Yabe

A linear motion apparatus has a guide shaft including a spiral-shaped or linear-shaped rolling element rolling groove, a movable body including a spiral-shaped or linear-shaped rolling element rolling groove opposed to the rolling element rolling groove of the guide shaft, a large number of rolling elements rollably moving along a rolling element rolling passage formed between the rolling element rolling grooves of the guide shaft and movable body and, a rolling element return passage communicating with the rolling element rolling passage, wherein, in the portion of the rolling element rolling groove of the movable body that is adjacent to an open end of a rolling element return passage, an escape portion is formed by abrasive flow machining in such a manner that the grinding depth thereof increases gradually toward the open end of the rolling element return passage.

Linear motion apparatus and method for manufacturing thereof

A ball screw having: a screw shaft having a spiral ball rolling groove; a ball nut having a ball rolling groove corresponding to the ball rolling groove; and a large number of balls interposed between the ball rolling grooves so as to roll freely; wherein the ball rolling groove of at least one of the screw shaft and the ball nut is ground so that a maximum value component of a number of undulation peaks per lead in the ball rolling groove is not in a range of from 0.95 nm to 1.05 nm centered on an integral multiple nm of a number m of load balls per lead calculated by an expression: in which P is a distance between centers of the adjacent load balls disposed at substantially equal intervals in the ball rolling groove, dis a ball pitch circle diameter, and L is a lead.

Ball screw

A super finishing is carried out after grinding, so that surface roughness of a ball rolling groove of a screw shaft is made 0.12 &mgr;m or less in an average roughness (Ra). Separators having ball holding surfaces shaped in concave surface are disposed between balls respectively.

A ball nut has a dowel for circulating balls . A cage type retainer is disposed between a screw shaft and the ball nut which engages with the screw shaft through the ball . The retainer is provided with a plurality of elongated holes at a peripheral surface thereof to extend to an axial direction thereof so as to separate the balls from one another in a peripheral direction thereof and to hold the balls therein to be free to roll. The distance of a space between the screw shaft and the cage type retainer is set to be smaller than that of a space between the dowel and the cage type retainer n the radial direction of the screw shaft.

A single shaft type table feed device comprises a movable body and an auxiliary movable body,The movable body is supported by a guide rail,and can be freely moved by a feed screw shaft,in the axial direction thereof. The auxiliary movable body,includes an inside diameter portion through which the feed screw shaft,can be inserted. The auxiliary movable body,is supported by the guide rail,and freely movable in the axial direction thereof. The inside diameter portion,of the auxiliary movable body,is slidingly contacted with the feed screw shaft

Single shaft type table feed device

A ball screw device includes a screw shaft including a hollow hole, a vibration controlling mass member inserted into the hollow hole, a rubber member or a synthetic resin member which is interposed between the outer surface of the vibration controlling mass member and the inner surface of the hollow hole of the screw shaft to prevent contact between the vibration controlling mass member and hollow hole. Further, the ball screw device includes vibration controlling mass member hold rings respectively interposed between the outer surface of the vibration controlling mass member and the inner surface of the hollow hole of the screw shaft and providing two or more support points spaced from each other in the axial direction of the mass member, with slight clearances being provided at least between the outside diameter surfaces of the hold rings and the inside diameter surface of the hollow hole. A table drive device, which includes the ball screw device, is supported on a base member in parallel to the screw shaft and can be moved when a ball nut is rotationally driven by a drive motor disposed on the table.

Growing community of inventors

Gunma, Japan

Toshiharu Kajita