JP2018003923A - Ball screw device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology that can contribute to a workability and a cost reduction due to elimination of seal ridge processing for a helical shape that is specific to a ball screw and further can improve reliability in operation of the ball screw while reducing a dispersion of grease adhered to a nut end surface.SOLUTION: There are provided several balls rolling between a threaded shaft 10 and a nut 20, a seal 30 attached to at least one end part of the end parts in a nut moving direction. The seal 30 comprises at least a cylindrical part 32, a flange part 37 at an end part of the nut 20; a grease accumulated part 33 arranged at an inner peripheral surface of the cylindrical part 32 and a slot 34 extending from one end side of the cylindrical part 32 along an axis line X direction of the threaded shaft 10 and communicated with the grease accumulated part 33. An inner surface of the cylindrical part 32 is formed flat, the flat inner surface has a clearance S between it and a land part of the threaded shaft 10, and an external part of the cylindrical part 32 is provided with a cylindrical cover 31 covering the cylindrical part 32 with a specified space P.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a ball screw device provided with a slotted seal.

  As an example of a ball screw device provided with a slotted seal, Patent Document 1 discloses a ball screw device that more effectively prevents accumulation and scattering of excess grease in a nut. This ball screw device has a structure in which a cylindrical seal is attached to the end of the nut in the moving direction. The seal includes a cylindrical portion through which the screw shaft passes, and a flange portion that is provided on the side opposite to the one end side of the cylindrical portion and is fixed to the end portion of the nut. The seal surrounds the outer peripheral surface of the screw shaft and seal crests that enter the spiral groove of the screw shaft on the inside, and grease provided on the inner peripheral surface of the cylindrical portion so as to form a space with respect to the screw shaft It has a reservoir and a slit extending from the end surface on one end side of the cylindrical portion along the axial direction of the screw shaft and communicating with the grease reservoir. In this ball screw device, the grease inside the nut is discharged to the outer periphery of the cylindrical portion through the grease reservoir and slit of the seal. For this reason, excess grease in the nut is taken out to the outside at a position where the centrifugal force of the screw shaft is difficult to act, so that it does not scatter around.

JP2015-105665A

The ball screw device disclosed in Patent Document 1 pays attention only to grease scattering during shaft rotation, but the ball screw device may be used for nut rotation in addition to shaft rotation.
However, in the case of nut rotation, when the ball screw is stroked, excess grease discharged from the inside of the nut adheres to the end surface of the nut, and grease that cannot withstand centrifugal force is scattered by rotating at high speed. There has been no particular attention to this point in the past.
Further, in Patent Document 1, since the grease on the screw shaft is swept away by paying attention to the scattering of the grease when the screw shaft is rotated, there is a seal ridge that engages with the screw groove of the screw shaft on the inner periphery. Contact seals are provided.
However, such a ball screw device has a problem in terms of workability and cost because it requires a spiral seal ridge processing that is unique to the ball screw device.

  The present invention has been made paying attention to the above-mentioned problems, and the purpose thereof is to eliminate the need for the spiral seal thread processing unique to the ball screw, thereby contributing to workability and cost reduction. An object of the present invention is to provide a technique capable of improving the reliability of a ball screw while reducing the scattering of the adhered grease.

  In order to solve the above-described problem, a ball screw according to an aspect of the present invention includes a screw shaft having a spiral groove provided on an outer peripheral surface, a nut having a spiral groove provided on an inner peripheral surface, and through which the screw shaft passes. A plurality of balls rolling in a rolling path formed by the spiral groove of the screw shaft and the spiral groove of the nut, and attached to at least one of the end portions in the moving direction of the nut. A ball screw device including a seal, and the seal includes a tubular portion through which the screw shaft passes, and an outer periphery of the tubular portion on the other end side opposite to the one end side of the tubular portion. A flange portion that protrudes outward from the surface, and is fixed to an end portion of the nut; and is provided on an inner peripheral surface of the cylindrical portion so as to form a space with respect to the screw shaft. Grease reservoir and the axial direction of the screw shaft from one end side of the cylindrical portion At least a slit extending along the grease reservoir and communicating with the grease reservoir, and the inner surface of the cylindrical portion is formed in a flat shape, between the flat inner surface and the land portion of the screw shaft. Has a small radial gap, and a cylindrical cover is provided outside the cylindrical portion so as to cover the cylindrical portion with a predetermined space.

  According to one aspect of the present invention, since a spiral seal ridge processing unique to a ball screw is not required, it is possible to contribute to workability and cost reduction, and while reducing grease scattering adhering to a nut end face, The reliability of the screw can be increased.

It is a side view which cuts and shows a schematic structure of a ball screw device concerning an embodiment of the present invention partially. It is a figure which shows schematic structure of the seal | sticker used for the ball screw apparatus which concerns on embodiment of this invention, (a) is sectional drawing which follows an axial direction, (b) is a part which shows the positional relationship with a screw shaft It is sectional drawing.

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.
Embodiments of the present invention will be described below with reference to the drawings.

Embodiment
(Constitution)
As shown in FIG. 1, the ball screw device 1 according to the embodiment of the present invention includes a screw shaft 10, a nut 20, a plurality of balls (not shown), and a seal 30.
The nut 20 has a cylindrical shape (for example, a cylindrical shape) in which a through hole is formed, and is installed so that the screw shaft 10 passes through the through hole.
A spiral groove 11 is provided on the outer peripheral surface of the screw shaft 10. Although not shown in detail in FIG. 1, a spiral groove (not shown) is also provided on the inner peripheral surface of the nut 20 with leads similar to the spiral groove 11. A rolling path (not shown) in which a plurality of balls 25 roll is formed by the spiral groove 11 of the screw shaft 10 and the spiral groove 21 of the nut 20.

In the ball screw device 1 having such a configuration, the nut 20 and the screw shaft 10 are relatively movable via a ball that is arranged in the rolling path and rolls.
Although not shown in detail, the screw shaft 10 is rotatably supported by a machine base (not shown) on which the ball screw device 1 is installed, and is connected to a rotational drive source (not shown) such as a motor. Has been. Also, a flange 22 is formed at one end of the nut 20, and a moving body (not shown) such as a moving table that is driven forward and backward by the ball screw device 1 is mounted through the flange 22. Therefore, the moving body is driven to advance and retract through the nut 20 by the rotation of the screw shaft 10.

[seal]
As shown in FIG. 1, the seal 30 is attached to at least a rear end portion in the moving direction of the nut 20. Here, as described above, in the ball screw device 1 in which the nut 20 moves forward and backward with respect to the screw shaft 10, the front and rear of the moving direction are relatively changed. The seals 30 (30A, 30B) are preferably attached to both ends of the direction. In the present embodiment, the seal 30 (30A) is attached to one end portion of both ends of the nut 20 in the moving direction, and the seal 30 (30B) is attached to the other end portion. The seal 30 is made of a resin material such as a high molecular weight polyethylene resin.

  As shown in FIGS. 1 and 2, the seal 30 has a cylindrical portion 32 provided with a through-hole through which the screw shaft 10 passes, and a cylindrical portion on the other end side opposite to one end side of the cylindrical portion 32. The flange portion 37 is provided so as to protrude outward from the outer peripheral surface of the shaped portion 32 and is fixed to the end portion of the nut 20. The seal 30 has an end of the nut 20 in a state in which the flange portion 37 is fitted in a recess provided in the end portion of the nut 20 in the axial direction and the cylindrical portion 32 protrudes from the end portion of the nut 20 in the axial direction. It is fixed to the part.

[Grease reservoir]
Further, the seal 30 has a grease reservoir 33 provided on the inner peripheral surface of the cylindrical portion 32 so as to form a space with respect to the screw shaft 10. The grease reservoir 33 is formed such that the inner peripheral surface thereof increases in diameter from one end side (side exposed from the nut 20) of the cylindrical portion 32 toward the other end side (flange portion 37 side). That is, as shown in FIG. 2B, the seal 30 has an inner diameter on one end side of the cylindrical portion 32 that is in contact with the land portion 12 of the screw shaft 10, and the other end of the cylindrical portion 32. The inner diameter on the side is larger than the inner diameter on one end side of the cylindrical portion 32.

[Gap]
The cross-sectional shape of the conventional seal has a Gothic arch-shaped seal crest formed in accordance with the cross-sectional shape of the spiral groove 11 being a Gothic arch shape. On the other hand, in this embodiment, as shown in FIGS. 1 and 2B, the cross-sectional shape of the seal 30 (cross-sectional shape of the inner surface of the cylindrical portion 32) facing the spiral groove 11 is formed flat. , Seal mountain is not formed.
This eliminates the need for a spiral seal ridge processing that is unique to a ball screw, thereby contributing to workability and cost reduction.

Moreover, as shown in FIG. 1 and FIG. 2B, between the flat inner surface and the land portion of the screw shaft (the land portion 12 between the spiral grooves 11 and 11 of the screw shaft 10 and the seal 30). Between the inner peripheral surface of the cylindrical portion 32, there is a fine radial gap S.
The gap size S is preferably 0.3 mm or less.
Grease that adheres to the shaft can be plated to a certain thickness by the seal provided with such a gap, and excess grease that adheres to the surface of the screw shaft is effectively returned into the nut, so that excess grease can be obtained. Can be discharged within a predetermined range.

[cover]
As shown in FIG. 1, a cylindrical cover 31 is provided that covers a cylindrical portion 32 where a seal crest of the seal 30 is not formed with a predetermined space P.

  The cover 31 is larger in diameter than the outer diameter of the cylindrical portion 32 and longer than the axial length of the cylindrical portion 32, and has a diameter from the outer periphery of the end of the covering portion 31a. And a disc portion 31b formed integrally in the direction. And the screw hole 31c provided in the disc part 31b and the screw hole 51 provided in the side surface of the nut 20 are connected, the screw 50 is screwed together, and it is integrally fixed to the end part of the nut 20. .

If there is no seal thread inserted into the screw groove 11 of the screw shaft 10 as in this embodiment, the grease remaining in the screw groove 11 of the screw shaft 10 cannot be swept away, and the ball screw is stroked. The excess grease discharged from the nut 20 is accumulated in the predetermined space P from which the grease is projected, but since the periphery is covered with the cover 31, the grease is not scattered when the nut is rotated.
Furthermore, since the screw shaft 10 does not rotate, there is no need to carefully sweep away the grease on the shaft. That is, the absence of a seal ridge is a grease that contributes to the lubrication of the ball screw as it is, and the lubrication surface is improved.

[Slot]
As shown in FIGS. 1 and 2, the seal 30 extends along the axis X direction of the screw shaft 10 from the end face 36 on one end side of the cylindrical portion 32 so as to be parallel to the axis X of the screw shaft 10. And a slit 34 communicating with the grease reservoir 33 on the flange portion 37 side. The slit 34 has a discharge port (not shown) through which grease is pushed out from the grease reservoir 33 and discharged at the end on the flange portion 37 side.
Thus, since the slit 34 is provided along the direction of the axis X of the screw shaft 10, the seal 30 can be easily manufactured by injection molding, which leads to cost reduction.
Six slots 34 are provided at equal intervals in the circumferential direction of the cylindrical portion 32. However, the number of slots 34 may be other numbers in consideration of each function described later. Further, it is preferable that all the slots 34 communicate with the grease reservoir 33, but a slot 34 that does not communicate with the grease reservoir 33 may be provided.

[Cylindrical part]
As shown in FIGS. 1 and 2, the seal 30 has an overhang length La of an overhang portion (projection portion) from the end surface 36 on one end side of the cylindrical portion 32 to the flange portion 37 so that one lead of the screw shaft 10 is one lead. It is shorter than the length Lb and is 0.7 times or more the length Lb of one lead of the screw shaft 10 (Lb> La ≧ Lb × 0.7).
Here, the range of the overhang length La will be described. The longer the overhanging length La is, the more force is applied to the base of the overhanging portion from the end surface 36 on one end side of the cylindrical portion 32 to the flange portion 37. The side is likely to be bent. In particular, in the seal 30 in which one end side of the tubular portion 32 is divided by a plurality of slits 34, the one end side of the tubular portion 32 is more easily bent.

  On the other hand, the longer the overhanging length La, the more the grease discharged from the inside of the nut 20 through the slit 34 to the outer periphery of the cylindrical portion 32 can be stored in the outer periphery of the cylindrical portion 32. The grease discharged to the outer periphery of the portion 32 flows to the screw shaft 10 through the end face 36 on the one end side of the cylindrical portion 32, so that the scattering of grease caused by the rotation of the screw shaft 10 can be suppressed.

Here, since the protruding length La from the end surface 36 on one end side of the cylindrical portion 32 to the flange portion 37 is shorter than the length Lb of one lead of the screw shaft, the seal 30 has a cylindrical portion 32. It is possible to suppress the bending of the one end side. As a result, it is possible to suppress problems caused by bending of one end side of the cylindrical part 32, that is, problems that one end side of the cylindrical part 32 contacts the screw shaft 10 and leads to heat generation of the ball screw device 1 and early wear of the seal 30. Therefore, the reliability of the ball screw device 1 can be improved.
Further, since the protruding length La from the end surface 36 on one end side of the cylindrical portion 32 to the flange portion 37 of the seal 30 is 0.7 times or more the length Lb of one lead of the screw shaft 10, The grease discharged from the inside of the nut 20 to the outer periphery of the cylindrical portion 32 through the grease reservoir 33, the discharge port, and the slit 34 of the seal 30 can be stored in the outer periphery of the cylindrical portion 32. Thereby, since the grease discharged | emitted on the outer periphery of the cylindrical part 32 flows into the screw shaft 10 through the end surface 36 of the one end side of the cylindrical part 32, it can suppress the excess in nut 20 Grease accumulation and scattering can be prevented more efficiently.

As described above, in the ball screw device 1 according to the present embodiment, the grease in the nut 20 is transferred to the grease reservoir 33 and the discharge port of the seal 30B provided at the rear end in the moving direction of the nut 20. , And the slot 34 is discharged to the outer periphery of the cylindrical portion 32. For this reason, the excess grease in the nut 20 is taken out to the outside at a position where the centrifugal force of the screw shaft 10 hardly acts, so that it does not scatter around. Then, the screw 50 is screwed into the screw hole 51 of the nut 20 through the cover 31 to fix the cover to the end of the nut. As a result, surplus grease is guided to the cover 31 provided in the flange 22 via the slit 34, so that the surplus grease that does not contribute to lubrication in the nut 20 is prevented from adhering to the screw shaft 10, and Scattering can be effectively suppressed.
In particular, since the slit 34 and the grease reservoir 33 communicate with each other, the seal 30 installed on the front side in the moving direction of the nut effectively removes excess grease adhering to the surface of the screw shaft 10 into the nut 20. Can be returned to.

In the ball screw device 1 according to the embodiment, the overhang length La in the cylindrical portion of the seal 30 is Lb> La ≧ Lb × 0.7. Reliability can be improved while preventing scattering more efficiently. In addition, the seal 30 and the ball screw device 1 can be made compact.
Further, since the slit 34 is provided along the axial direction of the cylindrical seal 30, the seal 30 can be easily manufactured by injection molding, which leads to cost reduction of the ball screw device 1 and the seal 30.

  The ball screw device of the present invention can be used for a semiconductor element, a liquid crystal display panel manufacturing device, a transfer device, and other devices used in a clean environment.

DESCRIPTION OF SYMBOLS 1 Ball screw apparatus 10 Screw shaft 11 Turning groove 20 Nut 30 Seal 31 Cover 32 Cylindrical part 33 Grease storage part 34 Slot 36 End surface 37 Flange part 50 Screw 51 Screw hole

Claims (1)

A screw shaft provided with a spiral groove on the outer peripheral surface;
A nut provided with a spiral groove on the inner peripheral surface and through which the screw shaft passes;
A plurality of balls rolling in a rolling path formed by the spiral groove of the screw shaft and the spiral groove of the nut;
A ball screw device including a seal attached to at least one of the end portions of the nut in the moving direction,
The seal is
A cylindrical portion through which the screw shaft passes;
A flange portion provided on the other end side opposite to the one end side of the cylindrical portion so as to protrude outward from the outer peripheral surface of the cylindrical portion, and fixed to an end portion of the nut;
A grease reservoir provided on an inner peripheral surface of the cylindrical portion so as to form a space with respect to the screw shaft;
A slit extending along the axial direction of the screw shaft from one end side of the cylindrical portion and communicating with the grease reservoir,
The inner surface of the cylindrical part is formed flat,
There is a fine radial gap between the flat inner surface and the land portion of the screw shaft,
A ball screw device comprising: a cylindrical cover that covers the cylindrical part with a predetermined space outside the cylindrical part.

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