JP2016156487A - Ball screw - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ball screw which efficiently improves lubricity of balls moved on a load raceway in conjunction with action of the ball screw without increasing the size of the ball screw.SOLUTION: A ball screw includes: a screw shaft 10 in which a spiral groove 11 is provided on an outer peripheral surface; a nut 20 in which a spiral groove 21 is provided on an inner peripheral surface; a circulation member 22; and balls 30. A grease retaining groove 25 for retaining grease is formed between the spiral grooves 21, 21 in an axial direction of the nut 20 on the inner peripheral surface of the nut 20.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a ball screw.

Conventionally, a ball screw having a configuration in which a plurality of balls interposed between a spiral groove provided on a screw shaft and a spiral groove provided on a nut is circulated by a circulation member is known.
In such a ball screw, a technique for holding grease in the ball screw for lubrication is disclosed (see Patent Documents 1 and 2).
Patent Document 1 discloses a ball screw in which a spiral groove for holding grease is formed in a land portion (outer diameter portion) of a screw shaft. Patent Document 2 discloses a technique in which a space portion is formed between circuits and grease is applied to the space portion.

JP 2000-326857 A JP 2008-19932 A

  However, in the ball screw disclosed in Patent Document 1, since the groove for holding the grease is provided on the screw shaft, the grease must be supplied over the entire area of the groove. There was room for improvement. In addition, the ball screw disclosed in Patent Document 1 is applied to a steering mechanism and used for nut rotation-axis movement. In the case of a mechanism that uses a screw shaft by rotating it, grease is applied by centrifugal force. Since the grease scatters around, the grease does not reach the spiral groove, and the effect of improving the lubricating performance cannot be obtained.

  In addition, the ball screw disclosed in Patent Document 2 has a structure in which “two pitches or more” circulation paths are provided and grease holding spaces are provided between the circuits. It needs to be long. As a result, there is a demerit that the nut stroke of the ball screw must be shortened or the apparatus incorporating the ball screw must be made long.

  Accordingly, the present invention has been made paying attention to the above-mentioned problems, and an object of the present invention is to provide a ball screw that can improve the lubricity of a ball in a load trajectory associated with the operation of the ball screw without increasing the size. There is.

In one aspect of the ball screw for achieving the above object, a screw shaft having a spiral groove on an outer peripheral surface, a nut having a spiral groove on an inner peripheral surface, and a nut attached to the nut, A circulation member that communicates with a load raceway formed by a spiral groove and a spiral groove of the nut, and a ball that is arranged to roll in the load raceway and the circulation member,
On the inner peripheral surface of the nut, a grease holding groove for holding grease is formed between the spiral grooves in the axial direction of the nut.

Here, in the ball screw, the grease holding groove may form a spiral groove of the same lead as the spiral groove of the nut.
Further, in the ball screw in which the grease retaining groove forms a spiral groove of the same lead as the spiral groove of the nut, the grease retaining groove may be formed on the entire inner peripheral surface in the axial direction of the nut. .
In the ball screw, the grease retaining groove may have a tapered shape having a large radial cross section.

In the ball screw, the grease retaining groove may communicate with the spiral groove.
In the ball screw, a grease supply hole that penetrates the nut in a radial direction may communicate with the grease holding groove.

  ADVANTAGE OF THE INVENTION According to this invention, the ball screw which improves the lubricity of the ball | bowl in the load track | orbit accompanying the operation | movement of a ball screw efficiently can be provided, without enlarging.

It is sectional drawing which follows the axial direction which shows the structure in embodiment with a ball screw. It is sectional drawing which follows the axial direction which shows the structure of the nut in embodiment with a ball screw.

  In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of embodiments of the present invention. However, it will be apparent that one or more embodiments may be practiced without such specific details. In other instances, well-known structures and devices are schematically shown in order to simplify the drawing.

Hereinafter, embodiments of a ball screw according to the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view along the axial direction showing the configuration of the ball screw of the present embodiment. FIG. 2 is a cross-sectional view along the axial direction showing the configuration of the nut of the ball screw of the present embodiment.

(Constitution)
As shown in FIG. 1, the ball screw of this embodiment includes a screw shaft 10, a nut 20, a ball 30, and a circulation member 22. The nut 20 is fitted to the screw shaft 10 with a predetermined gap, and the inner diameter of the nut 20 is larger than the outer diameter of the screw shaft 10. The nut 20 has a substantially cylindrical shape, and a flange for fixing the ball screw is provided at an end of the nut 20.
Further, the flange is provided with a grease greasing hole 26 that penetrates the outer peripheral surface 20a and the inner peripheral surface 20b of the nut 20 in the radial direction, and a nipple 27 is provided at the opening on the outer peripheral surface 20a side. ing.

  A spiral spiral groove 11 having a substantially semicircular cross section is provided on the outer peripheral surface 10 a of the screw shaft 10. The nut 20 is provided with a spiral groove 21 having the same lead as the spiral groove 11 and having a substantially semicircular cross section on the inner peripheral surface 10b. All of these semicircular shapes have a radius of curvature larger than the radius of the ball 30. The ball 30 is arranged to roll in a load track having a substantially circular cross section formed by the spiral grooves 11 and 21.

  With such a configuration, the ball 30 rolls in the track S as the screw shaft 10 rotates relative to the nut 20, and the nut 20 moves in the axial direction of the screw shaft 10 with respect to the screw shaft 10. It is possible to move linearly.

Here, the nut 20 is provided with one or more circulation members 22 (two in the present embodiment) as a mechanism for returning the ball 30 to the previous load track on the outer peripheral surface 20a. The circulation member 22 is provided through the nut 20 so as to connect one end of the load track and the other end of the load track before the second winding. Therefore, the ball 30 rolling on the load track toward the circulation member 22 is lifted into the circulation member 22, and the ball 30 is passed through the circulation member 22 to return to the load track before the second winding (before the two leads). Thus, the ball 30 can be circulated. In this way, an infinite circulation path which is a closed circuit is formed outside the screw shaft 10 by the load track and the circulation member 22.
In addition to the tube-type circulation member described above, circulation methods such as a top type, an end deflector type, an end cap type, and an SRC type can be employed as the circulation type using the circulation member.

<Grease retaining groove>
On the inner peripheral surface 20 b of the nut 20, a grease holding groove 25 for holding grease is formed between the spiral grooves 21 and 21 in the axial direction of the nut 20. The grease holding groove 25 may be formed in a linear shape at least between the spiral grooves 21 and 21 in the axial direction of the nut 20 and parallel to the spiral grooves 21 and 21 as shown in FIG. It is preferable that the spiral grooves of the same lead as the spiral grooves 21 and 21 are used.
Further, as shown in FIG. 2, the grease retaining groove 25 forms a spiral groove with the same lead as the spiral grooves 21, 21 and is formed on the entire inner peripheral surface 20 b in the axial direction of the nut 20. More preferred. Here, “the entire inner circumferential surface in the axial direction” refers to the entire area in the axial direction of the inner circumferential surface 20 b excluding the groove portions 23 that accommodate the seals 40 provided at both axial end portions of the nut 20.

[Grease retention groove shape]
Although not shown, the cross-sectional shape of the grease retaining groove 25 may be semicircular like the spiral groove 21, or may be rectangular, triangular, or tapered. If the cross-sectional shape of the grease holding groove 25 is a semicircular shape, the formation of the grease holding groove 25 is efficient. An increase in processing cost can be suppressed, and the effect is more remarkable. When the cross-sectional shape of the grease retaining groove 25 is a semicircular shape, it is more preferable that the grease retaining groove 25 is formed by a single arc. Further, even if the grease holding groove 25 has a rectangular cross-sectional shape, it can be easily formed. Furthermore, if the cross-sectional shape of the grease retaining groove 25 is a taper, particularly a large taper in the radial direction, the opening is narrow, so that the grease retaining force by the grease retaining groove 25 is increased, and the grease retaining groove 25 can be used for a long time. Lubricating oil can be supplied.

Although not shown, the grease retaining groove 25 may communicate with the spiral groove 21. With such a configuration, the grease can be sufficiently supplied to the spiral groove 21.
Further, the grease holding groove 25 may be communicated with a grease supply hole 26 provided in the nut 20. With this configuration, grease can be supplied to the grease holding groove 25 from the nipple 27 at any time, and the efficiency is high.

In the ball screw of the present embodiment, the grease holding groove 25 is provided on the inner peripheral surface 20 b of the nut 20, so that the spiral groove 11 of the screw shaft 10 and the grease are rotated along with the relative rotation of the screw shaft 10 and the nut 20. Grease is supplied to the spiral groove 11 when the holding groove 25 communicates. In the ball screw of this embodiment, the amount of grease that can be held in the nut 20 is increased by providing the grease holding groove 25 regardless of whether it is linear or spiral. Further, by forming the grease holding groove 25 between the spiral grooves 21 and 21, it is not necessary to increase the length of the nut 20.
Therefore, grease can be efficiently supplied to the ball rolling groove, and even when the screw shaft rotates, the present invention does not impair the lubricating performance because the grease is present in the nut.
As a result, there is no need for a special configuration for supplying grease to the inside, and therefore it is possible to provide a ball screw that efficiently improves the lubricity of the ball in the load track accompanying the operation of the ball screw without increasing the size. it can.

  The ball screw of this embodiment is suitable for a ball screw used for a machine tool, an injection molding machine, and a semiconductor manufacturing apparatus, for example.

  Although the present invention has been described above with reference to specific embodiments, it is not intended that the present invention be limited by these descriptions. From the description of the invention, other embodiments of the invention will be apparent to persons skilled in the art, along with various variations of the disclosed embodiments. Therefore, it is to be understood that the claims encompass these modifications and embodiments that fall within the scope and spirit of the present invention.

10 Screw shaft 11 Spiral groove 20 Nut 21 Spiral groove 22 Circulating member 25 Grease holding groove 30 Ball (rolling element)

Claims (6)

A screw shaft having a spiral groove on the outer peripheral surface, a nut having a spiral groove on the inner peripheral surface, and a load track mounted on the nut and formed by the spiral groove of the screw shaft and the spiral groove of the nut A circulation member communicating with the ball, and a ball disposed so as to be able to roll in the load track and the circulation member,
A ball screw, wherein a grease retaining groove for retaining grease is formed between the spiral grooves in the axial direction of the nut on an inner peripheral surface of the nut.   The ball screw according to claim 1, wherein the grease retaining groove forms a spiral groove of the same lead as the spiral groove of the nut.   The ball screw according to claim 2, wherein the grease retaining groove is formed on the entire inner peripheral surface in the axial direction of the nut.   The ball screw according to any one of claims 1 to 3, wherein a cross-sectional shape of the grease retaining groove is a large tapered shape in a radial direction.   The ball screw according to claim 1, wherein the grease retaining groove communicates with the spiral groove.   The ball screw according to any one of claims 1 to 5, wherein a grease supply hole penetrating the nut in a radial direction communicates with the grease holding groove.

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