JPH08240223A - Direct acting type bearing and method for forming lubricating thin film thereof - Google Patents

Abstract

PURPOSE: To restrain dust deposition and improve a lubricating property by forming a lubricating thin film made of fluoline containing copolymer having functional group on a rail and the track surface of a movable body or the like in a direct acting type bearing provided with the shaft-like rail, a tubular movable body externally fitted on the bearing and a plurality of rolling bodies rolled and circulated. CONSTITUTION: A direct acting bearing is provided with an axial rail 1, a tubular body 2 externally fitted on the rail 1 and a plurality of rolling bodies (balls) 4 disposed between both 1, 2, rolled and circulated along with the relative motion of both 1, 2. A plurality of loading ball rolling paths of a part of two opposed straight grooves formed respectively formed on the rail 1 and movable body 2 are formed so that ball 4 groups existing in these ball rolling paths are rollingly held by a retainer 3. Then, a lubricating film 16 made of fluoline containing copolymer having functional group is formed on the surfaces of the grooves of the rail 1 and movable body 2, annular grooves of the retainer 3 and balls 4, so that dust deposition is restrained and a lubricating property is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direct acting type bearing, and particularly to a vacuum environment where ordinary grease and oil cannot be used,
The present invention relates to a direct acting bearing suitable for use in a clean environment and a corrosive environment.

[0002]

2. Description of the Related Art The environment described above includes, for example, a carrier system installed inside a semiconductor manufacturing apparatus. In such an environment, when grease is used as a lubricant for a linear motion type bearing, Due to the evaporation of the oil content, problems such as deterioration of the lubrication function and pollution of the use environment occur.

In such a case, conventionally, a soft metal such as gold, silver, lead, or copper is mainly used on at least one of the track surface of the shaft-shaped rail or the cylindrical moving body or the surface of the rolling element, or the like. A solid lubricant such as carbon or molybdenum disulfide is coated in a film shape.

[0004]

By the way, in the case of the coating film made of the above-mentioned solid lubricant, the coating film is peeled off little by little due to the contact with the rolling element, and the dust generation state becomes lower than that when grease is used. However, the level is unsuitable especially in a clean environment. In particular, the amount of dust generated increases under high load conditions.

Further, the applicant of the present application coats a component of a linear motion type bearing with a solid lubricant in which a binder is mixed with a fluororesin, and in this case, the solid lubricant is coated more than the conventional example. You will be able to reduce dust by orders of magnitude. However, even with this coating film, when a relatively large radial load is applied, in addition to peeling and chipping, dust generation due to abrasion remarkably increases, and the dust generation life is shortened.

Moreover, if the coating film peels off or is lost as described above, the lubrication action between the respective components of the direct acting type bearing is reduced, and the metal and metal are likely to be in contact with each other. , Wear of each component is accelerated, etc.
There is a problem in terms of life.

Further, in an environment where a corrosive gas is present, as described above, the peeling of the coating film and the components at the missing portions are corroded.

Therefore, it is an object of the present invention to suppress dust generation and improve lubricity in a direct acting type bearing so that a long life can be achieved.

[0009]

The linear motion type bearing of the present invention comprises:
It is provided with a shaft-shaped rail, a cylindrical moving body that is fitted onto the rail, and a plurality of rolling elements that are arranged between the rail and the moving body and are circulated and circulated by their relative sliding movements. The rail and the moving body are made of metal, and a lubricating thin film made of a fluorine-containing polymer having a functional group is formed on at least track surfaces of the rail and the moving body.

The linear bearing of the present invention comprises a shaft-shaped rail,
A cylindrical moving body fitted on the outside of the rail, and a plurality of rolling elements arranged between the rail and the moving body to be circulated and circulated in accordance with their relative sliding movements. The moving body is made of metal, the rolling body is made of ceramics, and a lubricating thin film made of a fluorine-containing polymer having a functional group is formed on at least the rail and the raceway surface of the moving body.

The above-mentioned thin film is preferably 0.2 μm or less and set in the vicinity thereof. The thin film in this case can be formed from a lubricating oil obtained by diluting a mixture with perfluoropolyether (PFPE) or its derivative with a diluting solvent to 0.25 mass%.

The method of forming a lubricating thin film for a linear motion bearing according to the present invention is a lubricating oil comprising a fluorine-containing polymer having a functional group in at least rolling and sliding parts of each component of the assembled linear motion bearing. And a step of removing the mixture contained therein by heating the film-shaped lubricating oil.

[0013]

In the direct acting type bearing of the present invention, the lubricating element is a lubricating thin film having fluidity which does not cause abrasion as well as peeling and missing like the coating film of the conventional solid lubricant. Moreover, since this lubricating thin film does not have a form in which the lubricating oil is sealed inside the direct acting bearing as in the conventional case, there is no fear of external leakage thereof.

In such a lubricating thin film of the present invention, even if a relatively large radial load is applied, the sliding contact between the respective constituent elements does not become a non-lubricating contact state between the metals, and the entire surface of the constituent elements is always maintained. Since the state of adherence is maintained without interruption, the rolling and sliding of each component of the linear motion bearing will always be performed via the lubricating oil, and the lubrication action between the rolling elements will be stable. Will be maintained.

In particular, when the thickness of the thin film is specified, excellent results can be obtained with respect to both dust generation and lubricity. This film thickness can be easily set by specifying the lubricating oil that is the base for forming the thin film.

Further, in the method for forming a lubricating thin film of a linear motion bearing according to the present invention, a thin film of a lubricating oil made of a fluorine-containing polymer having a functional group is provided for the dust-generating property and the lubricating property with respect to the site where the oil film is formed. It is possible to satisfactorily form a film having an excellent film thickness for both.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below based on the embodiments shown in the drawings. 1 to 3 relate to an embodiment of the present invention. FIG. 1 is a vertical sectional view of a direct acting ball bearing, FIG. 2 is a horizontal sectional view of FIG. 1, and FIG. 3 is a horizontal sectional view of a rail. is there.

In the figure, A is a direct-acting ball bearing, 1 is a rail made of a cylindrical shaft, 2 is a moving body made of a cylindrical member, 3 is a retainer made of press, 4 is a ball, and 5 is a holding cylinder. is there.

The rail 1 is made of JIS standard SUS440C, and linear grooves 6 along the axial direction are provided over the entire length at six positions on the outer circumferential surface of the rail.

The moving body 2 is also JIS standard SUS44.
Tracks for the load circulating ball row and the no-load circulating ball row, which are made of 0C and are arranged at six circumferential positions in the axially intermediate region of the inner peripheral surface so as to face the adjacent grooves 6 of the rail 1 in the radial direction. Grooves 91 and 92 are provided.

The cage 3 is made of JIS standard SUS304, and has a cylindrical shape curved along a part of the inner peripheral surface of the moving body 2. Both end portions thereof are supported by the holding cylinder 5. Six laterally elongated annular grooves 3 each in the central area
1, 32 are provided symmetrically. The straight portion of the annular groove 31 has a bottom that is penetrated and has no bottom, and is used for the load circulation ball row 41. The annular groove 32 has a bottom and is used for the unloaded circulation ball row 42.

The above-described two linear grooves 6 and 91 facing each other on the rail 1 side and the moving body 2 side form a pair to form a total of six load ball transfer paths 12. The group of balls 4 existing in the ball transfer path 12 is located in the bottomless straight portion of the annular groove 31 of the cage 3. Further, the groove 92 of the moving body 2 and the bottomed portion of the annular groove 32 of the cage 3 form a pair to form a total of six ball circulators 13 for no load.
Each of the six ball transfer paths 12 and each of the six ball circulation paths 13 adjacent to the six ball transfer paths 12 are communicatively connected to each other to form a ball circulation circuit. Therefore, as the rail 1 and the moving body 2 slide relative to each other in the axial direction, the group of balls 4 rolls and circulates between the ball transfer path 12 and the ball circulation path 13. .

By the way, the cross section of the groove 6 of the rail 1 and the groove 91 of the moving body 2 is formed in a circulator arc shape, but it may be a Gothic arch shape. In this case, the cross section of each groove is formed in a V shape, and the balls 4 are supported by four-point contact with the pair of grooves 6 and 91 facing each other. The two slopes of each of the grooves 6 and 91 are formed as gentle curved surfaces. It should be noted that the circumscribed circle diameter of the group of balls 4 with the balls 4 applied to the grooves 6 of the rail 1 and the inscribed circle diameter of the group of balls 4 with the balls 4 applied to the grooves 91 of the moving body 2 respectively. By adjusting the difference between and a predetermined preload is applied, the pair of grooves 6, 9
1 is used to support the ball 4 in four-point contact.

The above-mentioned rail 1, moving body 2 and ball 4
Are formed of a corrosion resistant material. Examples of the corrosion resistant material include a martensitic stainless steel such as JIS standard SUS440C described above, and a metal material obtained by subjecting precipitation hardening stainless steel such as JIS standard SUS630 to an appropriate hardening heat treatment. For light load applications, austenitic stainless steel such as JIS standard SUS304 may be used.

The rail 1, the moving body 2 and the ball 4
As the corrosion resistant material, a ceramic material can be used in addition to the metal material. As the ceramic material, yttria (Y ₂ O ₃ ) and alumina (Al ₂ O ₃ ) are used as a sintering aid, and aluminum nitride (Al
N), titanium oxide (TiO ₂ ), spinel (MgAl ₂ O)
₄ ) mainly composed of silicon nitride (Si ₃ N ₄ ), alumina (Al ₂ O ₃ ), silicon carbide (SiC),
Zirconia (ZrO ₂ ), aluminum nitride (AlN) and the like can be used. The retainer 3 is, for example, JIS
In addition to the standard SUS304, brass, titanium material and the like are preferably used, but synthetic resin material can also be used. Examples of the synthetic resin material include fluororesins such as polytetrafluoroethylene (hereinafter abbreviated as PTFE), ethylene tetrafluoroethylene (ETFE), polyether ether ketone (PEEK), polyphenylene sulfide (PPS), and polyether. Sulfone (PE
It is also possible to use engineering plastics such as S) and nylon 46. Reinforcing fibers such as glass fibers may be added to these resins.

The groove 6 of the rail 1 and the groove 9 of the moving body 2
1. On the surface of the annular groove 32 and the ball 4 of the cage 3,
A thin film 16 of lubricating oil is formed by coating. The thin film 16 may be formed on the entire outer peripheral surface of the rail 1.

The thin film 16 is made of a fluorine-containing polymer having a functional group and is made of a lubricating oil in the form of a film, and the fluorine-containing polymer is preferably a fluoropolyether polymer or a polyfluoroalkyl polymer. . The fluoropolyether polymer has a unit represented by the general formula (X is an integer of 1 to 4) of -C _X F _2X -O- as a main structural unit, and each has a number average molecular weight of 1,000 to 50,000. There are things to do. Examples of the polyfluoroalkyl polymer include those represented by the following chemical formula 1. Further, the above-mentioned functional group is preferably one having a high affinity for a metal (for example, an epoxy group, an amino group, a carboxyl group, a hydroxyl group, a mercapto group, an isocyanate group, a sulfone group or an ester group), and for example, the following chemical formula 2 , 3 are listed. Such fluoropolymers may be used alone or in combination of two or more kinds. In that case, it is desirable to take care so that the combined groups react with each other to make the polymer have a higher molecular weight so as to obtain a thin film having more excellent abrasion resistance.

[0028]

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[0029]

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[0030]

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More specifically, the above-mentioned thin film 16 is a mixture with perfluoropolyether (PFPE) or a derivative thereof, specifically, for example, the product name FONBLIN Y standard of Montecatini Co., Fomblin emulsion (FE20, EM04) or Fomblin Z derivative (FONBLIN Z DEAL, FONBLIN Z DIAC, FONBLI)
NZ DISOC, FONBLIN Z DOL, FONBLIN Z DOLTX2000, FON
BLIN Z TETRAOL) is preferably used. Since all of these examples have a high concentration and have a very poor affinity for metals, it is difficult to deposit them in a film form as they are. Therefore, the following method is applied to form the thin film 16. When the above-mentioned Fomblin Z derivative is used in a vacuum environment, it may harm the vacuum exhaust system. Therefore, it is preferable to consider the usage environment.

Next, an example of a method for forming the above-mentioned lubricating oil thin film 16 will be described.

(A) After the rail 1, the moving body 2, the cage 3 and the ball 4 are assembled to complete the direct-acting ball bearing A, the presence of the ball 4 between the rail 1 and the moving body 2. At the location where the lubricating oil is prepared, a few drops of the prepared lubricating oil are injected by a spoid or the like, and the lubricating oil is film-shaped to slide on the rail 1, the moving body 2, and the cage 3.
And the rolling and sliding parts of the ball 4 are covered (supplying process). The supply of the lubricating oil may be applied by spraying, or may be immersed in the lubricating oil storage tank. The lubricating oil prepared here is, for example, fomblin emulsion FE.
20 (Fomblin concentration of 20 mass%) was diluted with an appropriate diluent solvent to a Fomblin concentration of 0.25 mass%. The above-mentioned diluent solvent may be a volatile one such as a methanol solution, an alcohol solution or water.

(B) The entire direct-acting ball bearing A coated with the lubricating oil is heated at 40 to 50 ° C. for about 3 minutes to remove a solvent such as a methanol solution contained in the lubricating oil (drying treatment).

(C) After that, depending on the ambient temperature of the operating environment of the direct acting ball bearing A, for example, it is heated at 150 to 300 degrees for 15 to 30 minutes (finish drying treatment).

The steps (a) and (b) may be repeated several times as necessary, and the film thickness of the lubricating oil thin film 16 is finally set to, for example, 0.2 μm or less.

By doing so, the thin film 16 of the lubricating oil can be formed in a suitable film thickness on the parts of the components of the direct acting ball bearing A that are in contact with each other. Then, if the solvent is removed as described above, unnecessary dust-generating components during the operation of the direct-acting ball bearing A are eliminated. In addition, a thin film 16 of lubricating oil
Since the film thickness is set to be extremely thin, almost no dust is generated by the oil component. Furthermore, the final heat treatment makes it possible to eliminate dust generation in the use environment.

Next, regarding the above-mentioned lubricating oil, the relationship between the dilution concentration and the amount of dust generated in the initial stage of rotation in the direct acting ball bearing,
The relationship between the number of times of repeating the supply process and the drying process (the number of times of dipping) when forming the thin film 16 and the dust generation amount in the initial stage of rotation of the direct acting ball bearing, and the relationship between the presence or absence of the derivative molecule and the dust generation life are respectively described. I'm investigating it, so I'll explain.

The test uses the apparatus shown in FIG. In the figure, 60 is a test direct-acting ball bearing, 61 is a rail, 62 is a case, 63 is a particle monitor, 64 is a load weight, and M ₁ and M ₂ are load weight drive motors.

The test conditions are as follows.

-Reciprocating speed: 20 to 30 mm / s-Load: Radial load 50 N-Stroke: 100 mm-Atmosphere: Atmosphere, inside clean bench (class 10) -Environmental temperature: Room temperature-Measuring conditions: Particle diameter 0.1 μm or more, The direct-acting ball bearing used in the test for the number of dust particles of 0.3 μm or more is model S manufactured by Koyo Seiko Co., Ltd.
It is ESDM10ST5.

The test time is 10 hours (h) at the beginning of the operation.
And Lubricating oil is Fomblin emulsion FE20
Fomblin concentration (mass%) of "5",
What was diluted with a dilution solvent (ethyl alcohol or water) in four stages of "2", "0.5", and "0.25" is used. The method of forming the thin film 16 is the method described above. However, after the supply treatment and the drying treatment are repeated twice, finish drying (170 ° C., 15 minutes) is performed.

The result is 0.25 as shown in Table 1 below.
The amount of dust generated when it is set to mass% is much smaller than the others.

[0044]

[Table 1]

The test time is 10 hours (h) at the beginning of the operation.
And The number of repetitions of the supply process and the drying process is
There are four levels of "4", "3", "2", and "1".
The lubricating oil is the same as that described above (the fomblin concentration of the fomblin emulsion FE20 is 0.25 mass.
% Diluted).

As a result, as shown in Table 2 below, the amount of dust generated when the number of repetitions is 2 times or less is significantly smaller than the others.

[0047]

[Table 2]

The film thickness of each thin film 16 for each number of repetitions was estimated based on the mass increase of the ball. In this case, after the thin film 16 is obtained, the direct acting ball bearing A is disassembled and the amount of increase in the mass of the ball is measured. The results are shown in Table 3 below.

[0049]

[Table 3]

Specific gravity of film: 1.88 g / cm ³ Surface area of ball: 0.495 cm ^{2 In view of} this result and the above results, the thickness of the thin film 16 should be 0.2 μm or less. It can be said that it is preferable. However, even if it is 0.2 μm or less, if it is too thin, the lubricity at the sliding contact portion between the metal materials may be deteriorated, so it can be said that it is preferable to set it in the vicinity of 0.2 μm or less.

There is no limitation because the test time is the dusting life. The dust generation life is 10 when the amount of dust generated from the direct acting ball bearing is
In a situation where the number is 00 / 0.1 cf or more, the time is measured up to the time when the measurement is performed 10 times in succession. The measurement is 10
Minute interval.

The test uses three example products, a comparative product and a conventional product. The example product uses a lubricating oil obtained by diluting Fomblin emulsion FE20 with a diluting solvent (ethyl alcohol or water) to a Fomblin concentration of 0.25 mass%, and three of the same specifications are used.
The comparative product is Fomblin Z25 diluted solvent (Galden S
V90) is used to dilute the fomblin concentration to 0.25 mass%. That is, the lubricating oil of the example product contains the derivative, and the lubricating oil of the comparative product does not contain the derivative. The conventional product has a coating film formed on the rail, the track surface of the moving body, and the surface of the ball. This coating film is obtained by dispersing and mixing polytetrafluoroethylene (PTFE) in a binder made of thermosetting synthetic resin.

The results are shown in Table 4 below. When the radial load is 50 N, the load resistance of the example product is about 10 times that of the comparative product and the conventional product.
It can be said to be advantageous especially when used under high load conditions.
By the way, the amount of dust generated by the conventional coating film is much smaller than that of other general solid lubricant coating films. The reason why such a result is obtained is that the thin film 16 of the lubricating oil, which is the product of this embodiment, has fluidity, and the rail, the moving body, and the ball are always in the state of passing through the lubricating oil. It can be said that, in addition to peeling or lack of the lubricant coating film, wear does not occur.

[0054]

[Table 4]

As shown in Table 5 below, there was almost no difference in the amount of dust generated during the initial 10 hours of operation between the example product and the comparative product.

[0056]

[Table 5]

From these results, it was found that the lubricating oil for forming the thin film 16 was also excellent in load bearing property if it contained a derivative molecule.

As shown by the results of each of the above-mentioned tests, as the thin film 16, it is necessary to specify the properties of the lubricating oil used, the method of forming the thin film, the film thickness after formation, etc., to some extent. It will be seen that it is important in loadability.

By the way, a thin film 1 made of the lubricating oil (diluted Fomblin emulsion FE20) described above.
In the direct-acting type ball bearing A in which 6 is formed, when at least the rail 1, the moving body 2 and the ball 4 are made of a corrosion-resistant metal material, when an unbalanced load acts or the like, corrosion occurs in the sliding contact portion when it is unfavorable. There is a possibility that The reason is that if a part of the thin film 16 is scraped off when an unbalanced load is applied, the surfaces of the rail 1, the moving body 2, and the ball 4 (oxidized surface on the metal surface) are exposed. Then, the adhesion wear of the metal materials occurs here, but when such adhesion wear occurs, the surfaces of the rail 1, the moving body 2 and the ball 4 also have a new surface (a pure surface not oxidized). Since the metal surface is exposed, this new surface may react with fluorine in the components of the lubricating oil and be corroded. In addition, a gas of a fluorine component may be generated due to a catalytic action during adhesion wear. On the other hand, if at least the balls 4 in the direct-acting ball bearing A are made of a ceramic material, the adhesive wear as described above does not occur, so that there is no concern about corrosion or gas generation as described above.
Therefore, it can be said that the structure of the direct-acting ball bearing A, at least the balls 4 of which are made of a ceramic material, is superior to the structure of which all the balls 4 are made of a metal material.

The present invention is not limited to the above embodiment. For example, other types of direct-acting ball bearings described in the embodiment, for example, a saddle-type moving body straddling a square rail is provided,
The present invention can be applied to linear motion type bearings such as so-called linear motion guides.

[0061]

In the linear motion type bearing of the present invention, since a thin film of lubricating oil having fluidity without wear is used in addition to peeling and loss like a coating film of a conventional solid lubricant, a relatively large radial bearing is used. Even when a load is applied, the sliding contact between the components does not become a non-lubricating metal-to-metal contact state, but always comes into sliding contact through lubricating oil, which significantly reduces dust generation and lubricity. Will be improved. In this way, not only dust from the thin film of lubricating oil but also dust from each component can be suppressed, and it is possible to contribute to the improvement of operation stability.

Therefore, when the linear motion bearing of the present invention is used in a place where high precision processing is required, for example, in the semiconductor manufacturing process, it is difficult to obstruct the clean atmosphere, which contributes to improvement in the yield of semiconductor manufactured products. it can.

In particular, when the thickness of the thin film is specified, excellent results can be obtained with respect to both dust generation and lubricity. This film thickness can be easily set by specifying the lubricating oil that is the base for forming the thin film.

Further, in the method for forming a thin film of a lubricating oil of a linear motion type bearing of the present invention, a thin film of a lubricating oil made of a fluorine-containing polymer having a functional group is lubricated at a portion where an oil film is to be formed, in an amount that does not generate dust. As the amount that does not hinder the action can be adhered well, there is almost no dust generation, and the lubricating action between each component can be stably obtained, and the service life of the linear bearing can be extended. You will be able to achieve it.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a direct acting ball bearing according to an embodiment of the present invention.

2 is a cross-sectional view of FIG.

FIG. 3 is a cross-sectional view of the rail.

FIG. 4 is a schematic diagram of a test apparatus used for measuring the amount of dust generated from the bearing.

[Explanation of symbols]

 A Direct acting ball bearing 1 Rail 2 Moving body 3 Cage 4 Ball 6 Axle groove 91 Moving body groove 31 Cage annular groove 12 Ball transfer path 13 Ball circulation path 16 Thin film of lubricating oil

Claims (5)

[Claims] 1. A shaft-shaped rail, a cylindrical moving body fitted onto the shaft-shaped rail, and a plurality of rollers arranged between the rail and the moving body and rotatably circulated along with their relative sliding movements. A linear motion bearing comprising a rolling element, wherein the rail and the moving body are formed of metal, and a lubricating thin film made of a fluorine-containing polymer having a functional group is formed on at least track surfaces of the rail and the moving body. A direct-acting type bearing characterized in that 2. A shaft-shaped rail, a cylindrical moving body fitted onto the shaft-shaped rail, and a plurality of rollers arranged between the rail and the moving body and rotatively circulated along with their relative sliding movements. A linear motion bearing comprising a rolling element, wherein the rail and the moving body are formed of metal, the rolling element is formed of ceramics, and a fluorine-containing polymer having a functional group on at least the rail and the raceway surface of the moving body. A direct-acting bearing, wherein a lubrication thin film made of is formed. 3. The direct acting bearing according to claim 1, wherein the thin film has a thickness of 0.2 μm or less and is set in the vicinity thereof. 4. The thin film is formed by a lubricating oil prepared by diluting a mixture of perfluoropolyether (PFPE) or its derivative with a diluent solvent to 0.25 mass%. Direct acting type bearing. 5. A step of depositing a lubricating oil composed of a fluorine-containing polymer having a functional group in a film shape on at least rolling and sliding parts of each component of the assembled direct acting type bearing, and A method of forming a lubricating thin film for a linear motion bearing, comprising the step of removing the mixture contained therein by heating the above-mentioned lubricating oil.