JP2009222209A - Ball screw with spline - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ball screw with a spline capable of further preventing noise by eliminating a ball in a screw groove from riding on over the shoulder into a spline groove, while maintaining a size equal to that of a conventional ball screw with a spline. <P>SOLUTION: This ball screw with the spline is provided by forming a plurality of straight line-shaped male splines 5 extending in the axial direction by crossing with the screw groove 6 on a screw shaft 1. A spline nut is formed as a fitting type spline nut 3 for mutually fitting a female spline 14 and a male spline 5 of the screw shaft 1 by arranging the female spline 14 fitted to the male spline 5 on its inner peripheral surface. A resin coating as a shock absorbing material is applied to at last one of the female spline 14 or the male spline 5. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a ball screw with a spline.

As a ball screw with a spline, a screw shaft formed on the outer peripheral surface by intersecting a plurality of linear spline grooves extending in the axial direction with the screw groove, and a screw ball that passes through the screw shaft and corresponds to the screw groove of the screw shaft A screw nut with a circulation path, a spline nut that is passed through the screw shaft to form a spline ball circulation path for the spline groove of the screw shaft, and a screw ball circulation path of the screw nut. In addition, there is known one including a plurality of screw balls and a plurality of spline balls disposed in a spline ball circulation path of a spline nut (see Patent Document 1).
Japanese Patent Laid-Open No. 06-300106

  In the ball screw with a spline of Patent Document 1 described above, the screw groove and the spline groove intersect each other on the screw shaft, so that there is a risk of causing a so-called shoulder climbing in which the screw ball comes off the screw groove and rides on the spline groove. Furthermore, when the spline ball moves in the axial direction, it may collide with the corner of the spline groove to generate noise.

  An object of the present invention is to maintain a size equivalent to that of a conventional splined ball screw, while preventing the ball in the screw groove from climbing over the spline groove and further preventing noise. Is to provide.

  A splined ball screw according to the present invention includes a screw shaft having a screw groove formed on the outer peripheral surface, a screw nut having a screw ball passage formed through the screw shaft and corresponding to the screw groove of the screw shaft, A spline ball screw comprising a plurality of screw balls disposed in a screw ball circulation path of a screw nut and a spline nut passed through the screw shaft. The screw shaft intersects with a screw groove. A plurality of straight male splines extending in the axial direction are formed, and the spline nut is provided with a female spline fitted to the male spline on its inner peripheral surface, and the female spline and the male spline of the screw shaft Is a fitting spline nut that fits together, and at least one of the female spline or male spline has a resin coating as a cushioning material It has been subjected and is characterized in.

  The male spline and the female spline fitted to the male spline may be, for example, an involute spline (spline in which the cross-sectional shape of the spline is formed in an involute curve), such as an arc spline having a circular cross section or a square spline having a square shape. There may be.

  The resin coated on at least one of the female spline and the male spline may be any resin that can suppress impact, and is, for example, polyamide 11 or polyamide 12.

  For example, three or four male splines may be provided on the screw shaft at equal intervals or may be provided on the entire circumference.

  A spline ball screw, for example, is a state in which the spline nut is fixed so that it does not rotate or move to a fixed position in the axial direction, and the screw nut is supported so that it rotates at a fixed position in the axial direction but does not move. Used in.

  In the ball screw with a spline according to the present invention, it is preferable that the male spline has a shape with a large diameter in which the top surface is in contact with the inner bottom surface of the female spline.

  In this way, when a rotational moment is applied to the screw shaft, the fitting spline nut can support the moment load.

  By replacing the ball spline used in conventional ball screws with a mating spline that fits a female spline and a male spline, it is possible to prevent the ball from climbing over the shoulder. Moving in the axial direction may cause noise when the female spline and male spline are fitted together, and for this noise, at least one of the female spline or male spline must be coated with resin. Can be prevented. In addition, by changing the ball spline to a fitting spline, it is not necessary to provide a ball circulation path, a cage for holding the ball, and a retaining ring for fixing the cage in the axial direction on the spline nut. It can be manufactured at low cost while maintaining the same thickness as a conventional ball spline.

  According to the ball screw with a spline according to the present invention, the screw shaft is formed with a plurality of straight male splines that intersect the screw groove and extend in the axial direction, and the spline nut is formed on the inner peripheral surface of the male spline. A female spline that is fitted to the male spline, and a female spline and a male spline of the screw shaft are fitted to each other, and at least one of the female spline and the male spline is coated with a resin coating as a cushioning material. Therefore, the ball in the screw groove does not ride on the shoulder to the spline groove, and noise can be further prevented. Further, since the spline nut is changed from the conventional ball spline to the fitting type spline, it is not necessary to provide the ball circulation path, the retainer and the retaining ring in the spline nut, so that an inexpensive structure can be achieved.

  Embodiments of the present invention will be described below with reference to the drawings. In the following description, the left and right in FIG.

  FIG. 1 shows a longitudinal sectional view of the main part of a splined ball screw according to the present invention. FIG. 2 is an enlarged cross-sectional view of the spline nut and the screw shaft.

  The ball screw includes a steel screw shaft (1) extending in the left-right direction, a screw nut (2), a fitting spline nut (3), and a large number of screw balls (4).

  The screw shaft (1) is a solid shaft with a circular cross section. The screw shaft (1) has a single thread groove (male thread groove) (6) on the outer peripheral surface of the screw shaft (1), and a plurality of axial directions (left and right directions). The straight male spline (5) is formed.

  The screw nut (2) includes a cylindrical metal nut body (8) and a pair of annular synthetic resin end caps (9) attached to both axial end faces of the nut body (8). ing. The end cap (9) is composed of a short cylindrical ring having the same shape, and is fixed to both end surfaces in the axial direction of the nut body (8) using a coupling tool such as a bolt (not shown). The nut (2) is fitted to the outer periphery of the screw shaft (1) with a slight gap in the radial direction.

A single thread groove (female thread groove) (10) corresponding to the male thread groove (6) is formed on the inner peripheral surface of the nut body (8). The space between the female thread groove (10) of the nut body (8) and the thread groove (6) of the screw shaft (1) facing this is the main passage (11) where the ball (4) rolls. It has become. A return passage (12) is formed at one location on the peripheral wall of the nut body (8). The return passage (12) includes a through hole having a circular cross section that penetrates the nut body (8) over the entire length in the axial direction.
A groove-shaped direction changing path (13) for communicating the main passage (11) and the return passage (12) is formed on the end face of each end cap (9) on the nut body (8) side.

  The screw ball (4) is disposed in the main passage (11), the return passage (12), and the direction changing passage (13), and the screw ball (4) rolling on the main passage (11) is a screw shaft. It is designed to guide the relative rotation of (1) and the screw nut (2). A screw ball circulation path is constituted by the main path (11), the return path (12), and the direction changing path (13).

  The fitting spline nut (3) has a plurality of involute shaped female splines on its inner peripheral surface formed at equal intervals in the circumferential direction, and the screw shaft (1) has a female spline on its outer peripheral surface. A male spline (5) having an involute shape slidably meshed with the spline is formed. The interval between the male splines (5) is set to such a narrow width that the screw balls (4) cannot ride on.

  As shown in FIG. 3, the top surface (5a) of the male spline (5) has a large diameter contact with the inner bottom surface (14a) of the female spline (14). The male spline (5) and the female spline (14) is coated with a polyamide-based resin (for example, polyamide 11 or polyamide 12).

  The above ball screw, for example, fixes the spline nut (3) so that it does not rotate or move to a fixed position in the axial direction, and rotates the screw nut (2) at a fixed position in the axial direction but does not move. It is used in a state of being supported so as not to.

  By rotating the screw nut (2) in the above-described state, the screw shaft (1) moves linearly in the axial direction without rotating by using the spline nut (3) as a guide.

  At this time, in the portion of the screw nut (2), the screw ball (4) rolling in the main passage (11) is changed in direction by the direction changing path (13) of one end cap (9). Screw nut (4) that has been introduced into the return passage (12) of the nut body (8), moved in the return passage (12) toward the other end cap (9), and moved through the return passage (12). Is changed in the direction change path (13) of the other end cap (9) and introduced into the main path (11). Thus, the screw ball (4) is circulated through the screw ball circulation path. The portion of the spline nut (3) is moved in the axial direction along the male spline (5) as the screw nut (2) rotates.

  In the portion of the screw nut (2), the distance between the male splines (5) is narrow enough to prevent the screw ball (4) from climbing, so the screw ball in the male thread groove (6) There is no risk that (4) shoulders on the spline groove (7). Furthermore, if the conventional ball spline is changed to a mating spline, there is a risk that noise will occur when the female spline (14) and the male spline (5) are fitted together due to the movement of the spline nut (3). Since the female spline (14) and the male spline (5) are coated with a polyamide resin serving as a buffer material, noise can be reduced. In addition, the spline nut (3) can move in the axial direction without providing a ball circulation path, a cage for holding the ball, and a retaining ring for fixing the cage in the axial direction. Thus, the nut (3) can be manufactured at low cost. Furthermore, since the top surface (5a) of the male spline (5) has a large diameter, when a rotational moment is applied to the screw shaft (1), the moment can be supported.

  In this embodiment, the female spline (14) formed on the fitting spline nut (3) and the male spline (5) formed on the screw shaft (1) are described as having an involute shape. The shape is not limited to the involute shape, and the female spline may be formed in a square shape having a substantially rectangular cross section or an arc shape having a substantially semicircular shape.

FIG. 1 is a longitudinal sectional view of a main part of a ball screw with splines showing an embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view taken along line II-II in FIG. FIG. 3 is an enlarged view of a main part showing large diameter matching between a male spline and a female spline.

Explanation of symbols

(1) Screw shaft
(2) Screw nut
(3) Spline nut
(4) Screw balls
(5) Male spline
(5a) Top surface of male spline
(6) Male thread groove
(7) Spline groove
(10) Female thread groove
(11) Main passage
(12) Return passage
(13) Direction change path
(14) Female spline
(14a) Inner bottom of female spline

Claims (2)

A screw shaft in which a screw groove is formed on the outer peripheral surface; a screw nut in which a screw shaft is passed and a screw ball circulation path corresponding to the screw groove of the screw shaft is formed; and a screw ball circulation path of the screw nut In a ball screw with a spline comprising a plurality of screw balls disposed on the screw shaft and a spline nut passed through the screw shaft,
The screw shaft is formed with a plurality of linear male splines that intersect the screw groove and extend in the axial direction, and the spline nut is provided with a female spline that is fitted to the male spline on its inner peripheral surface. It is a fitting spline nut in which a female spline and a male spline of a screw shaft are fitted together, and at least one of the female spline or the male spline is provided with a resin coating as a cushioning material. Ball screw with spline.   2. The splined ball screw according to claim 1, wherein the male spline has a shape with a large diameter that abuts the top surface thereof in contact with the inner bottom surface of the female spline.

Images