JPH09208757A - Sealing device for direct acting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a sealing device of a direct acting device in which a component does not vaporize even under a high vacuum condition, expressing self- lubricating properties and excellent in durability by forming a polyolefin-based synthetic resin containing a specific amount of a vacuum pump oil having a vapor pressure below a specified value. SOLUTION: For example, a side seal 10, as a sealing device for sealing a space opening between a slider 2 and a guiding rail 1 by mounting on the slider 2 of a linear guiding device which is a direct acting device, is made by forming a polyolefin-based synthetic resin such as polyethylene containing 10-80wt.% of a vacuum pump oil consisting of one or more compounds having <=10<-5> Torr vapor pressure at 25 deg.C and selected from hexadecyldiphenyl ether, octadecyldiphenyl ether, eicosylnaphthalene, a monoalkyltetraphenyl ether and a dialkyltetraphenyl ether.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a seal device for a linear motion device, and more particularly to a seal device having a self-lubricating property that can be used in a vacuum.

[0002]

2. Description of the Related Art Conventionally, typical linear motion devices generally used include a linear guide device used as a linear motion guide device and a ball screw used as a linear motion drive device. For example, as shown in FIG. 5, the linear guide device includes a guide rail 1 which has a rolling element rolling groove 3 on the outer surface and extends in the axial direction, and a slider 2 which is assembled across the guide rail 1. Are known. Slider 2
Is composed of a slider body 2A and end caps 2B attached to both ends of the slider body 2A. The slider body 2A is provided on the inner side surfaces of the sleeves 4 so as to face the rolling element rolling groove 3 of the guide rail 1 and to roll rolling elements (not shown). In addition to having the groove, it has a rolling element return path (not shown) that penetrates the thick portion of the sleeve in the axial direction. On the other hand, the end cap 2B is the slider body 2A.
Has a curved path (not shown) that connects the rolling element rolling groove and the rolling element return path parallel to the rolling element rolling groove, the rolling element return path, and the curved paths at both ends to the rolling element. Circulation circuit is formed. A large number of rolling elements made of, for example, steel balls are loaded in a circulation circuit of the rolling elements.

[0003] The slider 2 assembled on the guide rail 1
The rolling elements smoothly move along the guide rails through the rolling of the rolling elements in the rolling elements rolling grooves facing each other, and during the movement, the rolling elements circulate while rolling in the rolling element circulation paths in the slider. Lubrication of rolling rolling elements has been performed by grease previously applied to the inner surface of the slider 2.

As shown in FIG. 6, a side seal 5 is attached to the end surface of each end cap 2B and an under seal 6 is attached to the lower surface of the slider 2 as a sealing device for sealing the opening between the slider 2 and the guide rail 1. This prevents foreign matter from entering from the outside and diffusion of the internal lubricant to the outside. For these conventional seals, a rubber seal such as NBR (acrylonitrile butadiene rubber) is generally used.

On the other hand, even in the case of a ball screw which is a linear drive device, although not shown, for example, plastic seals are attached to both ends of the ball screw nut as seal devices to allow foreign matter to enter from the outside and lubricate the inside. It is practiced to prevent the diffusion of the agent to the outside.

In the case of a ball screw, a plurality of balls loaded between the spiral thread groove provided on the outer peripheral surface of the screw shaft and the spiral thread groove provided on the inner peripheral surface of the ball screw nut are provided. The rotation of the screw shaft (or the ball screw nut) is converted into an axial displacement of the ball screw nut (or the screw shaft) via the shaft, and the sealing device is attached to the end of the ball screw nut. The sealing device is generally formed in a ring shape from a resin material such as polyacetal resin, has a convex portion that fits into the thread groove of the screw shaft on its inner peripheral surface, and has a radial notch (see FIG. (Cutting) is provided. Then, after opening the slit and expanding the ring and fitting it on the screw shaft, the seal mounting screw is screwed in from the outer peripheral surface of the end of the ball screw nut, and it is fixed by pressing the outer diameter surface of the sealing device inward. ing.

[0007]

SUMMARY OF THE INVENTION However, NBR
When a linear guide device equipped with a sealing device is used in a vacuum environment, volatile components in NBR, such as DOP [di- (2-ethylhexyl) phthalate] used as a plasticizer, evaporates and becomes a vacuum. As a result, the rubber seal device had to be used without being attached.

Therefore, as the linear guide device reciprocates, the lubricant is gradually discharged from both ends of the linear guide device, and the lubricant is consumed quickly, resulting in poor lubrication in a short time.

In order to solve such a problem of poor lubrication, the applicant of the present invention has previously filed an application for a sealing device made of a polymer member containing a lubricant (Japanese Patent Laid-Open No. 6-34691).
No. 9). This product uses a rubber-containing or synthetic resin-containing sealing device such as a side seal or under seal to be mounted on the slider of a linear guide device, and the lubricant that continuously exudes from the sealing device for a long period of time automatically It is designed to be supplied to the rolling element circulation circuit of the slider. However, even in this case, no particular consideration was given to the response to the vacuum environment.

On the other hand, in the case of the ball screw, since the ring-shaped sealing device is fixed to the ball screw nut by the set screw, the fitting gap between the screw groove of the screw shaft and the convex portion of the sealing device is large. Therefore, the fitting clearance does not always become zero, and there is a disadvantage that sufficient sealing performance cannot be obtained depending on the usage conditions of the ball screw.

In order to solve this point, the present applicant has applied for a ball screw seal device to which a lubricant-containing polymer member is applied (Japanese Utility Model Publication No. 7-4952). In this product, a ball screw nut is attached with a sealing device made of a polymer containing lubricant so that it can be slidably contacted with the thread groove of the screw shaft,
The lubricating oil is automatically and stably supplied over a long period of time. However, even in this case, no particular consideration was given to the response to the vacuum environment.

Therefore, the present invention has a problem of a sealing device in a linear motion drive device (collectively referred to as a linear motion device) including a linear motion guide device including the above-mentioned conventional linear guide device and a ball screw device. In order to provide a seal device for a direct-acting device that does not evaporate even when used in a vacuum environment and has a self-lubricating property that has a lubricant supply function by itself. The purpose is to

[0013]

A sealing device for a linear motion device according to the present invention which achieves the above-mentioned object is 10 ^-5 T at 25 ° C.
Vacuum pump oil having a vapor pressure of orr
It is formed by molding a polyolefin-based synthetic resin that is contained by weight.

Here, the vacuum pump oil may be composed of at least one of hexadecyl diphenyl ether, octadecyl diphenyl ether, eicosyl naphthalene, monoalkyl tetraphenyl ether and dialkyl tetraphenyl ether.

[0015]

Embodiments of the present invention will be described below. The seal device for a linear motion device according to the present invention contains a lubricant in advance and has a self-lubricating property which also has a lubricant supply function. First, the component composition will be described.

The lubricant used in the sealing device of the present invention is a vacuum pump oil having a vapor pressure of 10 ^-5 Torr or less at 25 ° C., specifically, hexadecyl diphenyl ether, octadecyl diphenyl ether, eicosylnaphthalene, monoalkyl. Tetraphenyl ether [the following structural formula (1)] and dialkyl tetraphenyl ether [the following structural formula (2)] are preferable, and these can be used alone or in combination.

[0017]

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[0018]

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As the vacuum pump oil having a vapor pressure of 10 ^-5 Torr or less at 25 ° C., in addition to the above, polyphenyl ether such as pentaphenyl ether, fluorine oil such as perfluoropolyether, or tetramethyl tetra There are also methylphenyl silicone oils such as phenyltrisiloxane, but since these have poor compatibility with polyolefin synthetic resins, it is not possible to obtain a molded product having a high oil content as in the sealing device according to the present invention. Even if it is possible, the compatibility with the polyolefin-based synthetic resin is poor, so that the oil leaks quickly and the oil leaks early.

Polyethylene, polypropylene, polymethylpentene and the like are suitable as the polyolefin synthetic resin which can be used in the sealing device of the linear motion device according to the present invention. Polyethylene has a number average molecular weight of 10,000 to 100
Low to medium molecular weight less than 0000 and number average molecular weight 1
An ultra high molecular weight compound having a molecular weight of 000000 to 6,000,000 is used alone or as a mixture as necessary. Among them, ultra-high molecular weight polyethylene has poor fluidity when dissolved,
It is premised on injection molding. In that case, 10% by weight or less is appropriate in the total composition, and if 5% by weight or more is added, necessary and sufficient mechanical strength can be obtained.

Polypropylene has a number average molecular weight of 1,000.
Although it is possible to use those having an oil content of from 0 to 400000, if the oil content is high as in the composition of the present invention, the mechanical strength becomes too low by itself. Therefore, ultrahigh molecular weight polyethylene is added for the purpose of improving the mechanical strength. May be. Also, polyamide, polycarbonate, polybutylene terephthalate, polyphenylene sulfide, polyether sulfone, polyether ether ketone, polyamide imide,
A thermoplastic resin such as polystyrene or ABS resin can be used. Alternatively, a thermosetting resin such as unsaturated polyester resin, urea resin, melamine resin, phenol resin, polyimide resin, or epoxy resin can be used.

Polymethylpentene having a number average molecular weight of 600,000 to 2,000,000 is preferably used. The oil content of the seal device of the linear motion device of the present invention is 10
To 80% by weight, more preferably 30 to 70% by weight
Is appropriate. When the oil content is less than 10% by weight, the amount of lubricating oil exuded is small, resulting in poor lubrication between the lubricated members of the linear motion device and wear of the sealing device. If it exceeds 80% by weight, the mechanical strength required for the sealing device cannot be obtained.

The seal device of the linear motion device of the present invention having the above-mentioned composition of components is composed of a vacuum pump oil having a vapor pressure of 10 ^-5 Torr or less at 25 ° C. and a polyolefin-based synthetic resin. Even when used in vacuum, the seal itself does not volatilize oil or the like. Therefore,
The function as a seal can be maintained for a long period of time without deteriorating the degree of vacuum of the use atmosphere.

Further, the vacuum pump oil held inside the seal gradually exudes and contacts the guide rail of the linear guide device which is the lubricated member of the linear motion device or the contact surface between the screw shaft of the ball screw and the rolling element. An oil film is formed on the seal to develop the self-lubricating property of the sealing device itself, and at the same time, it functions as a lubricant supply device that supplies oil to the rolling elements via the guide rails or screw shafts. Therefore, the linear motion device used in a vacuum atmosphere is stably lubricated for a long period of time.

Next, an embodiment of the sealing device of the present invention will be described. (Embodiment 1) This embodiment is an example applied to a seal device of a linear guide device as a linear motion device.

A side seal 10 as a sealing device for a linear guide device having the shape shown in FIG. 1 was injection-molded using a paste-like mixture obtained by mixing the following components as an injection molding material. The shape and dimensions of the end cap 2B were almost the same. That is, it has a substantially U-shaped outer shape and a pair of mounting screw insertion holes 11. In addition, the inner surface of the concave portion is provided with a protruding portion 12 that comes into close contact with the rolling element rolling groove 3 of the guide rail 1.

Low and medium molecular weight polyethylene: PZ50U
[Mitsubishi Yuka Co., Ltd.], 15 wt% ultra high molecular weight polyethylene: Miperon (registered trademark) XM
220 [Mitsui Petrochemical Co., Ltd.] 10 wt% octadecyl diphenyl ether: Neovac SY
[Muramatsu Oil Research Institute Co., Ltd.], 75% by weight (Example 2) This example is also an example applied to a sealing device of a linear guide device as a linear motion device.

The side seal 10 of the linear guide device having the shape shown in FIG. 1 was injection-molded using a paste mixture prepared by mixing the following components in 10% by weight of the ultrahigh molecular weight polyethylene as an injection molding material.

Polymethylpentene: TPX (registered trademark) DX-845 [Mitsui Petrochemical Co., Ltd.], 20% by weight dialkyl tetraphenyl ether [Structural formula (2)]: S-3230 [Muramatsu Petroleum Research Institute Co., Ltd.] Made],
70% by weight (Comparative Example 1) This is a comparative example with respect to Examples 1 and 2 above.

A paste-like mixture obtained by mixing the following components with the same components as above is used as an injection molding material.
Side seal 10 of the linear guide device having the shape shown in FIG.
Was injection molded.

Low / Medium Molecular Weight Polyethylene: PZ50U
[Mitsubishi Yuka Co., Ltd.], 15 wt% ultra high molecular weight polyethylene: Miperon (registered trademark) XM
220 [manufactured by Mitsui Petrochemical Co., Ltd.], 10% by weight paraffinic mineral oil: FBKRO100 [manufactured by Nippon Oil Co., Ltd.], 75% by weight A: Storage test in vacuum Example 1, Example 2 and Comparative Example Each side seal 10 having a composition of 1 was used as a sample, and a standing test in vacuum was conducted under the following conditions for comparison.

Temperature: 25 ° C. Vacuum degree: 10 ^-2 Torr time: 10 hours The results are shown in Table 1.

[0033]

[Table 1]

The weight reduction rate of each sample after leaving for 10 hours was
It was recognized that Comparative Example 1 was remarkably large. It is considered that this is due to evaporation of paraffinic mineral oil, which is a constituent of the seal, in a vacuum environment. On the other hand, in Examples 1 and 2, the weight reduction rate was very small, on the order of hundreds.

B: Running test of linear guide device in vacuum Each side seal 10 having the composition of the above-mentioned Examples 1, 2 and Comparative Example 1 was used as a sample and mounted on the linear guide device. A reciprocating running test was performed in a vacuum under the conditions, and the results were compared.

When mounting the side seal 10,
As shown in FIG. 2, the protector 15 which is a metal plate for reinforcement is arranged on the outside, and a metal sleeve is attached to the mounting hole 11 to the end cap 2B as a spacer to prevent the side seal 10 from being crushed by tightening the screw. While preventing it, the slider 2 was screwed and attached to the end cap end face.

Linear guide device; slider width 20 m
m, length 27 mm, height 10 mm Running stroke length; 20 mm Feed rate; 100 mm / sec Lubrication; Only with lubricating oil supplied from the side seals.

Degree of vacuum: 10 ^-2 Torr The results are shown in Table 2.

[0039]

[Table 2]

In both Examples 1 and 2, no abnormality was found even after 1000 hours of running. On the other hand, in Comparative Example 1, seizure occurred due to poor lubrication after running for 50 hours.

Next, an embodiment in which the sealing device of the present invention is applied to a ball screw device as a linear motion device will be described. The paste-like mixture obtained by mixing the components of (Example 3) with the following components was used as an injection molding material, as shown in FIGS.
The seal 20 as the ball screw sealing device shown in FIG. The shape is a ring shape having a slightly longer axial length, and has a convex portion 20a fitted to the thread groove 21a of the screw shaft 21 on the inner peripheral surface, and a slit 22 for cutting the ring on one side surface thereof. It is provided. An annular peripheral groove 2 into which a garter spring 23 is fitted is provided on the outer peripheral surface of the seal 20.
4 are formed. Further, a cylindrical reinforcing member 25 is fitted in a position where it does not interfere with the circumferential groove 24 (only one place is shown).

The seal 20 is opened by opening the slit 22 to expand the ring and fitted into the screw shaft 21, and then fitted into the recess 27 of the end surface of the ball screw nut 26, and the mounting screw 28 screwed from the side surface of the nut. It is fixed by engaging the tip with the reinforcing member 25. By elastically tightening the seal 20 expanded and attached by the slit 22 with the garter spring 23, the thread groove 2 of the screw shaft 21
The fitting gap between 1a and the convex portion 20a on the inner circumference of the seal 20 is maintained at zero or less. Then, a spiral thread groove 21a provided on the outer peripheral surface of the screw shaft 21, a spiral thread groove 26a provided on the inner peripheral surface of the ball screw nut 26, and a plurality of balls 28 loaded between the both grooves. Lubricant gradually exuding from the ball seal 20 is automatically supplied to the contact surface with and to suppress an increase in frictional resistance. Since the tightening force of the seal mounting screw 29 is not directly applied to the seal 20, it is possible to use the seal 20 made of a soft lubricant-containing polymer containing a large amount of lubricant.

Low and medium molecular weight polyethylene: PZ50U
[Mitsubishi Yuka Co., Ltd.], 20% by weight ultra high molecular weight polyethylene: Miperon (registered trademark) XM
220 [manufactured by Mitsui Petrochemical Co., Ltd.], 10 wt% Eicosylnaphthalene: Lion diffusion pump oil S [manufactured by Lion Co., Ltd.], 70 wt% (Comparative Example 2) This is a comparative example to Example 3.

A ball screw seal 20 having the shape shown in FIGS. 3 and 4 was injection-molded by using a paste-like mixture obtained by mixing the following components with the same components as in (1) and (2) below.

Low and medium molecular weight polyethylene: PZ50U
[Mitsubishi Yuka Co., Ltd.], 20% by weight ultra high molecular weight polyethylene: Miperon (registered trademark) XM
220 [manufactured by Mitsui Petrochemical Co., Ltd.], 10 wt% paraffinic mineral oil: FBKRO100 [manufactured by Nippon Oil Co., Ltd.], 70 wt% C: leaving test in vacuum The composition of Example 3 and Comparative Example 2 described above was used. Using each of the side seals 20 included in the sample as a sample, a standing test in vacuum was performed under the following conditions for comparison.

Temperature: 25 ° C. Vacuum degree: 10 ^-2 Torr time: 10 hours The results are shown in Table 3.

[0047]

[Table 3]

The weight reduction rate of each sample after leaving for 10 hours was
It was recognized that Comparative Example 2 was remarkably large. It is considered that this is due to evaporation of paraffinic mineral oil, which is a constituent of the seal, in a vacuum environment. On the other hand, in Example 3, the weight reduction rate was very small, on the order of hundreds.

D: Driving test of ball screw in vacuum Each side seal 20 having the composition of the above-mentioned Example 3 and Comparative Example 2 was used as a sample, and each side seal 20 was attached to the ball screw, and in a vacuum under the following conditions. The reciprocating drive test of the ball screw nut 26 was performed and compared.

Ball screw; lead 10 mm, screw shaft diameter 1
5 mm nut running length; 500 mm feeding speed; 50 mm / sec lubrication; only by the lubricating oil supplied from the seal 20.

Degree of vacuum: 10 ^-2 Torr The results are shown in Table 4.

[0052]

[Table 4]

In Example 3, no abnormality was found even after driving for 1000 hours. On the other hand, in Comparative Example 2, seizure occurred due to poor lubrication after running for 80 hours. The seal device of the linear motion device of the present invention is not limited to the linear guide device, but may be a linear motion device of a type such as a linear ball spline device or a linear ball bushing device that performs linear motion using balls or rollers. Can be suitably applied to.

Further, the linear guide device is not limited to the type of the embodiment, and for example, the rolling groove of the load rolling element may be other than the single-sided rolling groove, and the rolling element may be a roller instead of a ball.

Furthermore, the sealing device for the linear motion device of the present invention is
The ball screw of the embodiment is not limited, and various other types of ball screws can be suitably applied. Further, the sealing device applied to the ball screw is not limited to the one with slits, but may be a continuous seal in the circumferential direction, and is applicable regardless of the presence or absence of a reinforcing member for the seal, the shape of the reinforcing member, or the like.

[0056]

As described above, according to the first aspect of the present invention.
According to the seal device of the direct-acting device according to, the vapor pressure is 25 ° C.
Since the vacuum pump oil is extremely low at 10 ^-5 Torr or less and is molded by mixing it with a polyolefin synthetic resin, the components will evaporate even if it is installed in a linear motion device and used in a vacuum environment. There is no. In addition, the lubricant gradually exudes from the lubricant-containing polymer member itself over time, and is automatically supplied to the contact moving surface of the linear motion member to form an oil film to exhibit self-lubricating property. As a result, even in a high vacuum environment, good lubrication can be achieved for a long period of time, and a long-life linear motion device can be provided.

Further, according to the invention of claim 2, the vacuum pump oil comprises at least one of hexadecyl diphenyl ether, octadecyl diphenyl ether, eicosyl naphthalene, monoalkyl tetraphenyl ether and dialkyl tetraphenyl ether. Therefore, it is possible to mold a seal device having a high compatibility with a polyolefin-based synthetic resin and a high oil content, and as a result, it is possible to provide a long-acting linear motion device capable of supplying a lubricant for a long period of time. Play.

[Brief description of drawings]

FIG. 1 is a front view of an embodiment of a sealing device according to the present invention.

FIG. 2 is a perspective view of a linear guide device to which the sealing device of FIG. 1 is attached.

FIG. 3 is a side view of another embodiment of the sealing device according to the present invention.

FIG. 4 is a side view showing a half section of a ball screw to which the sealing device of FIG. 3 is attached.

FIG. 5 is a perspective view of a conventional linear guide device.

FIG. 6 is a perspective view showing a lower surface side of the linear guide device of FIG.

[Explanation of symbols]

 1 Guide rail 2 Slider 3 Rolling element rolling groove 10 Sealing device 20 Sealing device 21 Screw shaft 26 Ball screw nut

Claims (2)

[Claims] 1. A sealing device for a linear motion device, which is formed by molding a polyolefin synthetic resin containing 10 to 80% by weight of vacuum pump oil having a vapor pressure of 10 ⁻⁵ Torr or less at 25 ° C. 2. The linear motion device according to claim 1, wherein the vacuum pump oil comprises at least one of hexadecyl diphenyl ether, octadecyl diphenyl ether, eicosyl naphthalene, monoalkyl tetraphenyl ether and dialkyl tetraphenyl ether. Sealing device.