JP2012229729A - Ball screw - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily align a lip part of a seal with a screw shaft in a peripheral direction when mounting the contact seal at an axial direction end of a nut in a ball screw.SOLUTION: A seal cap 5 fixed with the seal 4 thereto is fixed to a mounting part 12 of the nut 1 to mount the seal 4 on the nut 1. Three planar parts 13 are formed at different positions in a peripheral direction on an outer peripheral surface of the mounting part 12. The seal cap 5 includes an annular part 51 externally fitted to the mounting part 12, and an inward flange part 52. In the annular part 51, three through screw holes (through-holes) 51a are formed at the same positions as the three planar parts 13. The annular part 51 of the seal cap 5 is externally fitted to the mounting part 12 of the nut 1 and the though screw holes 51a are aligned with the planar parts 13 to screw small screws 7. Accordingly, the seal 4 is mounted on the nut 1, and the lip part 41 of the seal 4 and the screw shaft 2 are aligned with each other in the peripheral direction.

Description

  The present invention is arranged 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 groove formed by the spiral groove of the nut and the spiral groove of the screw shaft. And a ball screw provided with ring-shaped seals disposed at both axial ends of a nut.

A ball screw used in a machine tool, an injection molding machine, a semiconductor device manufacturing apparatus, or the like 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, and a spiral groove of the nut. And a ball disposed between the raceway grooves formed by the spiral grooves of the screw shaft.
Since the ball of such a ball screw rolls in the groove along with the rotational movement of the screw shaft, if foreign matter such as dust or abrasion powder adhering to the screw shaft enters the nut, the foreign matter that has entered the nut Can hinder the rolling motion of the ball and cause damage such as seizure.
In order to prevent foreign matter from entering the nut, ring-shaped seals are arranged at both axial ends of the nut.

In Patent Document 1, an attachment portion in which a V groove (a circumferential groove having a V-shaped cross section) is formed on an outer peripheral surface is formed at an axial end portion of a nut of a ball screw, and a seal is attached to the attachment portion in advance. Fixing the seal cap is described. The seal is a contact seal that has a lip portion having an inner peripheral edge shape similar to the cross-sectional shape perpendicular to the axis of the screw shaft, and is in sliding contact with the screw shaft.
The seal cap has an annular portion that is fitted onto the outer peripheral surface of the nut attachment portion, and an attachment screw hole that penetrates from the outer peripheral surface in the radial direction is formed in the annular portion. The seal cap is fixed to the nut by screwing a set screw into the mounting screw hole of the annular portion and pressing the conical surface at the tip of the conical surface against the pressing slope that forms the V groove of the mounting portion. .
Thereby, since the circumferential position (phase) of the lip portion can be arbitrarily set when the seal is fixed, it becomes possible to accurately match the inner peripheral edge shape of the lip portion and the cross-sectional shape perpendicular to the axis of the screw shaft. It is described that the sealing performance of the contact seal can be improved.

JP 2008-261403 A

However, in the ball screw described in Patent Document 1, it is necessary to perform the operation of aligning the seal lip portion and the screw shaft in the circumferential direction while rotating the seal cap and checking the tip of the lip portion. It takes time and is difficult to adjust to an optimal position where good dustproofness and sealing performance can be obtained.
SUMMARY OF THE INVENTION An object of the present invention is to make it easy to align a seal lip portion and a screw shaft in the circumferential direction when a contact seal is attached to an axial end of a ball screw nut.

In order to solve the above-mentioned problems, the present invention is formed by 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 screw having a ball disposed between the raceway grooves and a ring-shaped seal disposed at both axial ends of the nut, wherein the seal is similar to the cross-sectional shape perpendicular to the axis of the screw shaft. A contact seal having a lip portion having an inner peripheral edge shape and in sliding contact with a screw shaft, and having the following configurations (1) to (4).
(1) Flat portions perpendicular to the radial direction of the nut are provided at three or more positions that are different in the circumferential direction of the outer peripheral surface of the mounting portion that is the axial end portion of the nut.
(2) Consists of an annular part fitted on the mounting part and an inward flange part provided at one end in the axial direction of the annular part to fix the seal, and penetrates at the same position as the flat part of the annular part. A seal cap having a hole and fixed to the mounting portion after fixing the seal is provided, and the axial dimension of the seal cap is a dimension at which the seal is disposed at a set position in the axial direction.
(3) The seal is arranged so that the inner peripheral edge shape of the lip portion corresponds to the cross-sectional shape perpendicular to the axis of the screw shaft in a state where the through hole of the seal cap is aligned with the flat portion of the nut. It is fixed to the orientation flange.
(4) The seal cap is fixed to the nut with a fixing screw inserted from the through hole fitting the annular portion to the mounting portion and aligned with the flat portion.

According to the ball screw of the present invention, the annular portion of the seal cap after the seal is fixed is externally fitted to the mounting portion of the nut, and the through hole of the seal cap is aligned with the flat portion, thereby the lip of the seal The part and the screw shaft are aligned in the circumferential direction. In this state, the seal is attached to the nut by inserting a fixing screw from the through hole and pressing and fixing the fixing screw to the flat portion. Therefore, it is possible to easily align the seal lip portion and the screw shaft in the circumferential direction.

  According to the ball screw of the present invention, when the contact seal is attached to the axial end portion of the nut, the circumferential alignment between the seal lip portion and the screw shaft can be easily performed.

It is sectional drawing which shows a part of ball screw equivalent to one Embodiment of this invention. They are the front view (a) which shows the state before attaching a seal | sticker to a nut with the ball screw of FIG. 1, and AA sectional drawing (b) of (a). It is the front view (a) which shows the seal cap which comprises the ball screw of FIG. 1, and AA sectional drawing (b) of (a). It is a front view which shows the state which fixed the seal | sticker to the seal cap of FIG. It is a front view which shows the ball screw to which the seal | sticker was attached by fixing the seal cap of the state of FIG. 4 to a nut. It is the front view (a) which shows the 2nd seal | sticker in the case of attaching two seals, and the front view (b) which shows the state by which the 2 seals were fixed to the seal cap of FIG. It is a front view which shows the 3rd sticker in the case of attaching 3 stickers.

Embodiments of the present invention will be described below.
As shown in FIG. 1, the ball screw of this embodiment includes a nut 1, a screw shaft 2, a ball 3, a seal 4, a seal cap 5, and a machine screw 6 that fixes the seal 4 to the seal cap 5. , And a small screw (fixing screw) 7 for fixing the seal cap 5 to the nut 1.
A spiral groove 11 is formed on the inner peripheral surface of the nut 1, and a spiral groove 21 is formed on the outer peripheral surface of the screw shaft 2. The ball 3 is disposed between the raceway groove formed by the spiral groove 11 of the nut 1 and the spiral groove 21 of the screw shaft 2.
The seal 4 is a contact seal that has a lip portion 41 having an inner peripheral edge shape similar to the cross-sectional shape perpendicular to the axis of the screw shaft 2 and is in sliding contact with the screw shaft 2. An annular base portion 42 is formed on the outer peripheral side of the lip portion 41.

The outer diameter of the end portion in the axial direction of the nut 1 is formed smaller than the other portion, and this small diameter portion serves as an attachment portion 12 to which the seal cap 5 is attached. As shown in FIGS. 2 (a) and 2 (b), on the outer peripheral surface of the mounting portion 12, there are three flat portions 13 at the same position in the axial direction and at different positions in the circumferential direction.
Is formed. The plane portion 13 is formed as a plane perpendicular to the radial direction of the nut 1. The distal end portion of the machine screw 7 is formed on a plane parallel to the plane portion 13.

As shown in FIGS. 1 and 3, the seal cap 5 includes an annular portion 51 that is fitted on the attachment portion 12 of the nut 1, and an inward flange portion 52 that is provided at one axial end of the annular portion 51. Three through screw holes (through holes) 51 a are formed on the other end side in the axial direction of the annular portion 51 at the same position as the three flat portions 13 formed in the attachment portion 12.
In the inward flange portion 52, three through screw holes 52a for fixing the seal 4 with the machine screws 6 are formed at the same positions as the three through screw holes 51a in the circumferential direction. The axial dimension L of the seal cap 5 is such a dimension that the seal 4 is attached to a set position in the axial direction in a state where the seal cap 5 is fixed to the nut 1 after fixing the seal 4.

When attaching the seal 4 to the axial end portion of the nut 1, first, as shown in FIG. 4, the base portion 42 of the seal 4 is fixed to the inward flange portion 52 of the seal cap 5 with the machine screw 6.
In the base 42 of the seal 4, three through screw holes 42 a are formed at the same position as the three through screw holes 52 a of the inward flange 52. The three through screw holes 42a are formed in a state in which the seal cap 5 in which the seal 4 is fixed to each through screw hole 42a through the machine screw 6 is fitted onto the nut 1 and the through screw hole 51a is aligned with the flat surface portion 13 The inner peripheral edge shape of the portion 41 is arranged so as to match the cross-sectional shape perpendicular to the axis of the screw shaft 2.

Next, as shown in FIGS. 5 and 1, the annular portion 51 of the seal cap 5 to which the seal 4 is fixed is fitted on the mounting portion 12 of the nut 1, and the through screw hole 51 a is aligned with the flat portion 13. Then, a small screw 7 having a flat tip is screwed into the through screw hole 51a, and the tip is pressed against the flat portion 13.
As a result, the seal cap 5 to which the seal 4 is fixed is fixed to the nut 1, and the inner peripheral edge shape of the lip portion 41 of the seal 4 matches the axially perpendicular cross-sectional shape of the screw shaft 2. That is, the lip portion 41 of the seal 4 and the screw shaft 2 are aligned in the circumferential direction.

As described above, according to the ball screw of this embodiment, the seal cap 5 to which the seal 4 is fixed is fixed to the nut 1 with the small screw 6, whereby the lip portion 41 of the seal 4, the screw shaft 2, Are aligned in the circumferential direction. That is, according to the ball screw of this embodiment, it is possible to easily align the lip portion 41 of the seal 4 and the screw shaft 2 in the circumferential direction.
In this embodiment, the three flat portions 13 are formed at the same position in the axial direction of the outer peripheral surface of the mounting portion 12. However, if the positions are different in the circumferential direction, They may be formed at different positions in the axial direction. Moreover, the arrangement | positioning in the circumferential direction of the plane part provided 3 or more may be equally spaced, and may be different.

In this embodiment, the seal cap 5 is fixed to the nut 1 by screwing the small screw 7 and the through screw hole 51a. However, the seal cap 5 may be fixed by screwing the set screw and the through screw hole 51a. .
In this embodiment, the seal cap 5 is fixed to the nut 1 with a small screw 7 having a flat tip. However, as a screw having a flat tip, other than the “flat tip” defined in the JIS standard, “ The tip of the screw may have a ring shape and the center portion may be recessed as in the case of a “dent”.
Furthermore, in this embodiment, one seal 4 is attached to each end of the nut 1 in the axial direction. However, the seal mounting structure using the seal cap of the present invention is attached to each end of the nut in the axial direction. The present invention can also be applied when a plurality of seals are attached.

An example of attaching two seals will be described with reference to FIG. In this example, as shown in FIG. 6A, as the second seal 4A, a through screw hole 42b is provided at a position shifted by θ1 with respect to the through screw hole 42a of the first seal 4. Then, as shown in FIG. 6B, the two seals 4 and 4A are overlapped with the through screw holes 42a and 42b and overlapped with the inward flange portion 52 of the seal cap 5 with the small screw 6. Fix it. The seal cap 5 in this state is fixed to the nut 1 by the method described above.
Here, θ1 is when the inner peripheral shape of the lip portion 41 of the second seal 4A and the cross-sectional shape perpendicular to the axis of the screw shaft 2 match when the second seal 4A is fixed to the first seal 4. Is the angle.

When three seals are attached, for example, as shown in FIG. 7, a through screw hole 42c is provided as a third seal 4B at a position shifted by θ2 with respect to the through screw hole 42b of the second seal 4A. Use the provided one. Then, the three seals 4, 4 </ b> A, 4 </ b> B are fixed to the inward flange portion 52 of the seal cap 5 with the small screw 6 in a state where the through screw holes 42 a, 42 b are overlapped with each other. The seal cap 5 in this state is fixed to the nut 1 by the method described above.
Here, θ2 is when the inner peripheral shape of the lip portion 41 of the third seal 4B and the cross-sectional shape perpendicular to the axis of the screw shaft 2 match when the third seal 4B is fixed to the second seal 4A. Is the angle.
Thus, when installing multiple seals, in order to obtain good dustproof and sealing properties, it is necessary to install each seal at an optimal position shifted by a predetermined angle that matches the cross-sectional shape perpendicular to the axis in the circumferential direction. There is.

DESCRIPTION OF SYMBOLS 1 Nut 11 Spiral groove of nut 12 Mounting part 13 Plane part 2 Screw shaft 21 Spiral groove of screw shaft 3 Ball 4 Seal 4A Seal 4B Seal 41 Lip part 42 Base part 42a Through screw hole 42b Through screw hole 42c Through screw hole 5 Seal cap 51 Annular part 51a Through screw hole (through hole)
52 Inward flange 52a Through screw hole 6 Machine screw 7 Machine screw (fixing screw)

Claims (1)

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 the spiral groove of the nut and the raceway groove formed by the spiral groove of the screw shaft; A ball screw provided with ring-shaped seals disposed at both axial ends of the nut,
The seal is a contact seal having a lip portion having an inner peripheral edge shape similar to the cross-sectional shape perpendicular to the axis of the screw shaft, and is in sliding contact with the screw shaft, and is a periphery of the outer peripheral surface of the mounting portion including the axial end of the nut. In three or more places that are different positions in the direction, a plane portion perpendicular to the radial direction of the nut is provided,
It consists of an annular part fitted around the mounting part and an inward flange part provided at one end in the axial direction of the annular part to fix the seal, and has a through hole at the same position as the flat part of the annular part. And a seal cap fixed to the mounting portion after fixing the seal,
The axial dimension of the seal cap is a dimension at which the seal is arranged at a set position in the axial direction.
The seal is formed on the inward flange so that the inner peripheral edge shape of the lip portion corresponds to the cross-sectional shape perpendicular to the axis of the screw shaft with the through hole of the seal cap aligned with the flat portion of the nut. The seal cap is fixed to the nut with a fixing screw that is externally fitted to the mounting portion and inserted from the through hole that matches the flat surface portion. Ball screw.

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