Nsk Corporation

Kazuo Miyaguchi

Yoshinori Mizumura

Takeshi Nakazawa

Soichiro Kato

Hiroki Yamaguchi

Tsutomu Ohkubo

Nobumitsu Takahashi

Shirouji Yabe

Ryouichi Sato

Toshiaki Yamaguchi

Daisuke Maruyama

Noriaki Sekiya

Toshiyuki Iehisa

Toshikazu Yabe

Ken Namimatsu

Akio Sakai

Daisuke Kuroiwa

Shigeharu Kobayashi

Osamu Ideta

Tetsuo Matsumoto

Shuichi Kobayashi

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.

A ball screw apparatus is provided with a screw shaft having a spiral ball screw groove, a nut member having a screw groove, and a plurality of balls. A smoothly continuous worked portion is formed at a portion of the screw groove by grinding a corner portion between the screw groove and a connecting way. The worked portion is formed such that the distance between the screw grooves is gradually reduced regarding an advancing direction of the ball entering from the connecting way in between the screw grooves. This worked portion extends from an end of the connecting way in a circumferential direction of the nut member and within a range of 90&deg; from the corner portion along the circumferential direction of the nut member.

Ball screw apparatus

A ball screw apparatus comprises a screw shaft, a nut, and a plurality of balls. A first helical groove is formed at an outer peripheral surface of the screw shaft. A second helical groove is formed at an inner peripheral surface of the nut. A rolling contact way of balls is defined by the first helical groove and the second helical groove facing each other. A connecting way formed of a tube for connecting a part and another part of the rolling contact way is provided on the nut. An endlessly communicating circuit is defined by the connecting way and the rolling contact way. Each of the balls is endlessly arranged in the circuit. A smoothly continuous machined portion is formed by cutting out an angular portion between the helical groove and the connecting way of the nut.

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.

A lubricating apparatus for a ball screw which can sufficiently lubricate even in a high load usage is disposed between a ball nut and a screw shaft, and a polymer member containing a lubricant being mainly in slidable contact with an outer diameter portion of the screw shaft is mounted to at least any one of both ends of the ball nut and a space including a ball not-passing space in an inner portion of the ball nut. The polymer member prevents the lubricant attached to the thread groove of the screw shaft from being scraped off during oscillations of the screw shaft, such that the lubricant attached to the thread groove can be efficiently maintained.

Lubricating apparatus for ball screw

A ball screw device of a ball-circulating-part embedded type includes: a screw shaft having a helical thread groove on an outer peripheral surface thereof; a ball nut having a thread groove provided on an inner peripheral surface thereof in correspondence with the thread groove of the screw shaft, the screw shaft being loosely fitted in the inner peripheral surface of the ball nut; and a multiplicity of balls rotatably fitted between the two thread grooves and adapted to circulate while being guided by a ball-circulating part fitted in the ball nut wherein the ball nut has a retaining recess on an outer peripheral surface thereof, wherein at least a portion of a fitted outward surface of the ball-circulating part is substantially flush with the outer peripheral surface of the ball nut in a vicinity of the fitted outward surface of the ball-circulating part, and wherein there is provided a circulating-part holding member for fixing the ball-circulating part to the ball nut by being fitted over the outer peripheral surface of the ball nut and covering the fitted outward surface of the ball-circulating part, the circulating-part holding member having a projection for engaging the retaining recess of the ball nut.

Ball screw device of ball-circulating-part embedded type

In a ball screw device which provides a screw shaft including a ball screw groove in the outer peripheral surface, a ball nut including a ball screw groove formed in the inner peripheral surface opposite to the ball screw groove of the screw shaft, a plurality of balls fitted between the ball screw grooves of the screw shaft and ball nut, and a tube type circulation path for circulating these balls, the ball screw device can reduce the moment of inertia of a rotary portion of the device so as to facilitate the use of the ball screw device of a nut rotation type. Further, the ball screw device further provides an oil supplying structure which includes a first oil supplying hole formed in the outer race of the rolling bearing and passing through the outer race from the outer peripheral surface thereof to the inner peripheral surface thereof, and a second oil supplying hole formed in the ball nut, passing through the ball nut from the outer peripheral surface thereof to the inner peripheral surface thereof and also communicating with the first oil supplying hole through an annular gap. The oil supplying structure can supply oil even while the ball screw device is in operation, and eliminate the mounting and removal of an oil supplying pipe when supplying the oil.

Ball screw device with means for maintaining balance

An internal-circulation-type ball screw having simple construction and high productivity is provided. A ball nut has one or more through holes and one or more constrictions, which are formed around its outer peripheral surface so as to span the openings of respective through holes. One or more deflectors are put in respective through holes and fixed by fitting corresponding deflector-locking springs onto the constrictions. Each deflector-locking spring is a thin plate spring having a substantially C-shaped cross section with a concave portion in the middle. When the deflector-locking spring is fitted onto the constriction, the concave portion thereof presses the deflector in the through hole toward the threaded shaft. Thus, the deflector is fixed to the ball nut.

Internal-circulation-type ball screw device

A preliminary thrusting mechanism for a screw device serves to achieve not only constant position type preliminary thrusting but also constant pressure type preliminary thrusting. The preliminary thrusting mechanism includes as essential components a screw shaft having a spirally extending screw groove formed axially along the outer surface thereof, a first nut threadably engaged with the screw shaft, a second nut operatively connected to the first nut in series and threadably engaged with the screw shaft, a rotation stopping unit for preventing the second nut from being rotated relative to the first nut, a thrusting unit including a thrusting member adapted to impart to the first nut and the second nut a certain intensity of thrusting power effective in the opposite direction for allowing them to be displaced away from each other in the axial direction, and a stopping unit for preventing the thrusting member from being displaced further when the thrusting member is displaced by a predetermined distance. In practice, the thrusting unit includes a liquid pressure source, a liquid pressure supplying path and a pressure chamber, and the stopping unit includes flanges each serving to prevent further displacement of the thrusting member.

Preliminary thrusting mechanism for a screw device

An external circulation type ball thread device includes a threaded shaft having a ball thread groove in the outer surface; a ball nut having a ball thread groove in the inner surface; and a number of balls fitted between those ball thread grooves, the balls being circulated while being led in a ball circulating tube which is secured to the outer surface of the ball nut with a tube retaining member. In the device, the ball nut has in the outer surface a tube supporting groove which is formed along the ball circulating tube which is arranged inclined with respect to the axis of the threaded shaft, to support the bottom of the ball circulating tube, and an annular groove which is formed across the tube supporting groove; and the tube retaining member is made of an elastic thin plate in such a manner that the tube retaining member is substantially C-shaped in section so as to be fitted in the annular groove, and has an engaging groove which is engaged with the ball circulating tube. Thus, the device is simple in structure and high in productivity.

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Maebashi, Japan

Kazuo Miyaguchi