JP2018141468A - Ball Screw - Google Patents

Abstract

The present invention provides a ball screw that not only realizes an improved permissible rotational speed and lowers operating noise, but also supports a wide variety of variations at a low cost. SOLUTION: A screw shaft 10, a nut 20, and a circulation component 30 for returning a ball from the end point of the track to the start point, and the circulation component 30 is arranged in contact with the outer flat surface of the nut 20. The main body portion 31 is formed of a pair of leg portions 32 and 32 that are provided on the outer flat surface and are inserted into a pair of circulation holes 23 each having a cylindrical shape. Is inserted in a direction perpendicular to the axial direction of the nut 20 with respect to the circulation hole 23 provided in the outer flat surface, and the main body 31 is disposed in contact with the outer flat surface. [Selection] Figure 1

Description

  The present invention relates to a ball screw.

The ball screw is disposed between a nut having a spiral groove formed on the inner peripheral surface, a screw shaft having a spiral groove formed on the outer peripheral surface, and a raceway formed by the spiral groove of the nut and the spiral groove of the screw shaft. And the ball
A ball return path for returning the ball from the end point of the track to the start point, and the nut moves relative to the screw shaft as the ball rolls in the track. As the ball return path of the ball screw, a return tube method is often adopted because it is easy to assemble.

However, with the conventional return tube type ball screw, with the recent high rotation of the ball screw, the speed at which the ball collides with the return tube increases and the collision energy increases, so that the return tube and thread groove ( (Including both shoulders of the thread groove).
Therefore, in order to prevent this damage, and to improve the permissible rotational speed and reduce the operating noise, a technology equipped with a return tube that scoops the ball in the tangential direction of the screw shaft and the lead angle direction of the screw groove is disclosed in Patent Literature 1 and 2.

The technique disclosed in Patent Document 1 is not made of metal in view of the complicated shape of the return tube for scooping up the ball in the tangential direction of the screw shaft and the lead angle direction of the screw groove,
This technology uses a return tube made of synthetic resin.

The technique disclosed in Patent Document 2 is a technique in which a through hole inclined along a spiral groove is provided in a nut, and an end portion that forms a linear shape of a return tube is inserted into the hole.

JP 2010-38196 A Japanese Utility Model Publication No. 6-69502

However, the technique described in Patent Document 1 requires a mold for producing a return tube made of synthetic resin, and it is necessary to manufacture a huge amount of molds in order to meet various ball screw specifications. Arise. As a result, the manufacturing cost may increase.

Further, in the technique described in Patent Document 2, in order to open an oblique hole in a nut, a general 4-axis machining center cannot be used, and expensive equipment (for example, a 5-axis machining center) is used.
Is necessary, and there are significant restrictions on facilities. As a result, there is a room for improvement because there is a possibility of increasing capital investment.
In addition, as shown in FIG. 6, instead of making an oblique hole in the nut 120, a technique for making a large hole 123 in the nut 120 into which the end of the return tube 130 can be inserted obliquely can be considered. However, when the interval between the adjacent spiral grooves 121 and 121 is narrow, the hole 123 is formed in the nut 12.
It interferes with the spiral groove of 0, which is not preferable.

Therefore, the present invention has been made paying attention to the above-mentioned problems, and its purpose is not only to realize an increase in the allowable rotational speed and a reduction in operating noise, but also a ball screw that can be used for a wide variety of variations at a low cost. Is to provide.

A certain aspect of the ball screw for achieving the above object includes a nut having a spiral groove formed on the inner peripheral surface, a screw shaft having a spiral groove formed on the outer peripheral surface, a spiral groove of the nut, and a spiral groove of the screw shaft. A ball disposed between the tracks formed in the above, and a circulation part that forms a ball return path for returning the ball from the end point of the track to the start point,
The circulation part is provided in a U-shaped cylindrical main body portion arranged in contact with the outer flat surface of the nut, and is inserted into a pair of circulation holes provided on the outer flat surface, each having a cylindrical shape. The leg portion is inserted in a direction perpendicular to the axial direction of the nut with respect to the circulation hole provided in the outer flat surface of the nut, and the main body portion is the outer side. It is placed in contact with a flat surface.

Here, in the ball screw, a connecting portion between the main body portion and the leg portion may be inside the nut.
Moreover, in the said ball screw, the fitting shape which mutually fits may be formed in each edge part of the said main-body part and the said leg part.
In the ball screw, the circulation hole may be provided with a countersink for positioning the leg.

  According to one aspect of the present invention, it is possible to provide a ball screw that not only achieves an increase in the allowable rotational speed and reduces operating noise, but also supports a wide variety of variations at a low cost.

It is a top view which shows the structure in a certain aspect of a ball screw. It is a figure which shows the structure in a certain aspect of a ball screw, (a) is the fragmentary sectional view seen from the axial direction, (b) is the fragmentary sectional view seen from the side surface. It is a top view which shows the structure of the circulation component in a certain aspect with a ball screw. It is a figure which shows the structure of the circulation component in the aspect with a ball screw, (a) is sectional drawing of the main-body part along the track | orbit of a ball | bowl, (b) is a top view of a leg part, (c) is the front of a leg part. (D) is sectional drawing of the leg part along the track | orbit of a ball | bowl, (e), (f) is a side view of the main-body part and leg part as a modification. It is a figure which shows the structure in a certain aspect of a ball screw, (a) is the fragmentary sectional view seen from the axial direction of the nut, (b) is a side view of a nut. It is sectional drawing which shows an example of the installation aspect of the circulation component of the conventional ball screw.

Hereinafter, embodiments of the ball screw will be described with reference to the drawings.
FIG. 1 is a plan view showing the configuration of an embodiment of a ball screw. 2A and 2B are diagrams showing a configuration in a certain aspect of the ball screw, in which FIG. 2A is a partial cross-sectional view seen from the axial direction, and FIG. 2B is a partial cross-sectional view seen from the side. FIG. 3 is a plan view showing the configuration of the circulating component in an embodiment with a ball screw. 4A and 4B are diagrams showing the configuration of the circulating component in a certain aspect of the ball screw, where FIG. 4A is a cross-sectional view of the main body along the track of the ball, FIG. 4B is a plan view of the leg, and FIG. ) Is a front view of the leg, (d) is a cross-sectional view of the leg along the track of the ball, and (e) and (f) are side views of the main body and the leg as modified examples. FIG. 5 is a view showing the configuration of a certain aspect of the ball screw, in which (a) is a partial cross-sectional view seen from the axial direction of the nut, and (b) is a side view of the nut.

  As shown in FIGS. 1 and 2, a ball screw 1 according to this embodiment includes a screw shaft 10 having a spiral groove 11 formed on the outer peripheral surface, a nut 20 having a spiral groove formed on the inner peripheral surface, and a rolling element. As a ball B and a circulating component 30. The circulating component 30 is fixed to the nut 20 by a mounting component 40. The balls are disposed so as to be able to roll in a raceway formed by a spiral groove 11 of the screw shaft 10 and a spiral groove (not shown) of the nut 20 and in a ball return path formed by the circulating component 30. Yes.

  As shown in FIGS. 1 and 2, a part of the outer peripheral portion of the nut 20 is a concave portion 21, and the bottom surface is an outer flat surface 22 to which the circulating component 30 is attached. A pair of through holes (circulation holes) 23, 23 are formed on the outer flat surface 22 of the nut 20.

  Here, as shown in FIG. 3 and FIG. 4, the circulating component 30 is composed of a main body 31 machined with metal (stainless steel, brass, carbon, etc.), not a synthetic resin, and a pair of parts installed at both ends thereof. The leg portion 32 is formed. That is, the circulating component 30 is formed by cutting a short cylindrical body at both end portions 31b and 31b of a main body 31 (FIG. 4A) formed by bending a long cylindrical body into a U shape. Two leg portions (FIG. 4B) 32, 32 are connected to end portions 32a, 32a.

  Further, as shown in FIGS. 4C and 4D, when the circulating component 30 is installed in the through hole 23 provided in the outer flat surface 22 of the nut 20, the leg portion 32 inserted into the through hole 23. Is inserted in the direction perpendicular to the axial direction of the nut 20 with respect to the circulation hole 23.

  Further, a tongue 32c for scooping up the ball B in the tangential direction is formed at the other end 32b of the leg 32. In addition, when installing the circulation component 30 in the through-hole 23, the lower surface (surface on the leg 32 side) 31b of the main body 31 is a surface that contacts the outer flat surface 22 of the nut 20 (see FIG. 4A). ).

  Here, the joining mode of the main body 31 and the leg 32 is not particularly limited as long as it does not adversely affect the rolling of the ball, but as a modification, the end 32a of the leg 32 and the end of the main body 31 are used. It is good also as a shape which 31a engages. Specifically, as shown in FIG. 4 (e), the end portion 32a of the leg portion 32 may be tapered, and the end portion 31a of the main body portion 31 may be reversely tapered, as shown in FIG. 4 (f). As shown, a convex portion may be provided at the end portion 32 a of the leg portion 32, and a concave portion may be provided at the end portion 31 a of the main body portion 31.

  Further, when the circulating component 30 is installed in the through hole 23 provided in the outer flat surface 22 of the nut 20, a connection portion (joint portion between the end portion 31 a and the end portion 32 a) between the main body portion 31 and the leg portion 32 is provided. It is installed so as to be located inside the nut 20 (on the axial center side from the surface of the nut 20). By doing in this way, the area which the circulation component 30 protrudes with respect to the outer diameter of the nut 20 is small, and the ball screw 1 can be made compact.

  Further, as shown in FIGS. 5A and 5B, the through hole 23 formed in the nut 20 is formed in a spiral groove (parallel to the spiral groove of the screw shaft 10) formed on the inner peripheral surface of the nut 20. It is provided with an oval opening in a direction perpendicular to the axial direction of the nut 20, not obliquely along the axis. The through holes 23 and 23 are seats in which the other end portion (end portion on the side where the tongue portion 32c is formed) 32b of the leg portion 32 of the circulating component 30 abuts on an edge portion other than the ball trajectory. The feeding portion 23a is formed in a U shape. The width d of the countersunk portion 23 a is substantially the same as the width d of the other leg portion 32 b of the circulating component 30. Further, the tongue portion 32c formed at the other end portion 32b of the leg portion 32 is inserted into the counterbore portion 23a. Thereafter, the main body 31 is joined to the leg 32, and the circulating component 30 may be installed in the through-hole insert 23.

  Thus, according to this embodiment, since the through-hole 23 is provided in the direction orthogonal to the axial direction of the nut 20, it is only necessary to open a simple slot without using an expensive machine tool. It is possible to provide a ball screw of a tangential scooping type corresponding to a wide variety of variations at low cost.

  In addition, since the structure of the circulating component 30 used in the present embodiment is a structure that scoops up the ball in the tangential direction, the impact force generated when the ball hits the other end 32b of the circulating component 30 can be weakened. it can. As a result, it is effective in improving the allowable rotational speed of the ball screw 1 and reducing the operating sound of the ball screw 1.

In addition, the circulating component 30 used in the present embodiment includes a main body 31 and a leg 32, and can be manufactured at low cost by merely machining a cylindrical member bent with a single radius of curvature. . In particular, since the tongue 32c provided on the leg portion 32 can be processed in the same manner as a conventional circulation tube, it is not necessary to newly manufacture a cutting tool or a jig. Therefore, the manufacturing cost is not increased.
In addition, since the main body and the leg are separated, a short cylindrical body made of cold-rolled steel sheet is formed as a leg, and carburizing or carbonitriding is performed to partially improve the strength. it can.

  Furthermore, since the counterbore 23a is provided in the through hole 23, the positioning of the leg 32 in the through hole 23 is appropriately performed, which contributes to the reduction of the operation sound of the ball screw 1.

  Therefore, it is possible to provide a ball screw that not only realizes an increase in the permissible rotational speed and lowers the operating noise, but also supports a wide variety of variations at a low cost.

DESCRIPTION OF SYMBOLS 1 Ball screw 10 Screw shaft 11 Spiral groove (of screw shaft) 20 Nut 21 Recessed portion (of nut) 22 Outer flat surface of (nut) 23 Through hole (circulation hole) of (nut)
30 Circulating parts 31 Body part (of circulating parts) 31a End part 31b Lower surface of body part (contact surface with outer flat surface of nut)
32 (circulation part) leg part 32a (one) end part 32b (other) end part 32c tongue part 40 attachment parts

Claims (4)

A nut having a spiral groove formed on the inner peripheral surface; a screw shaft having a spiral groove formed on the outer peripheral surface; and a ball disposed between a spiral groove of the nut and a spiral groove of the screw shaft; A circulation part that forms a ball return path for returning the ball from the end point of the track to the start point,
The circulation part is provided in a U-shaped cylindrical main body portion arranged in contact with the outer flat surface of the nut, and is inserted into a pair of circulation holes provided on the outer flat surface, each having a cylindrical shape. Consisting of a pair of legs,
The leg portion is inserted in a direction orthogonal to the axial direction of the nut with respect to the circulation hole provided on the outer flat surface of the nut, and the main body portion is disposed in contact with the outer flat surface. And ball screw. The ball screw according to claim 1, wherein a connection portion between the main body portion and the leg portion is inside the nut. The ball screw according to claim 1, wherein a fitting shape that fits each other is formed at each end of the main body portion and the leg portion. The ball screw according to any one of claims 1 to 3, wherein the circulation hole is provided with a countersink portion for alignment of the leg portion.

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