JPH06341444A - Solid lubricant film and forming method thereof - Google Patents

Abstract

PURPOSE:To improve homogeneity and quality of coating in a rolling bearing by forming island-likely distributed coating out of fine particles of polytetrafluoroethylene having decided means grain diameter. CONSTITUTION:For example, in the inner ring 1, the outer ring 2, and the rolling bodies 3 of a deep groove ball bearing, island-likely distributed fixed lubricating coating 1a-3a made of fine particles of polytetrafluoroethylene (PTFE) having means particle diameter under 4mum on the raceway surface of the inner and outer rings 1, 2 and the surface of the rolling bodies. For forming the coating, after soaking the bearing pats 1-3 or the finished product of the bearing in a processing liquid in which PTFE fine particles are dispersed in an organic solvent and modulated, they are dried in the atmosphere. Further the means molecular weight of PTFE is set as 1X10<6>-8X10<6>. Consequently the crystal construction of PTFE is left as it is, and original lubrication performance is maintained without being spoiled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid lubricating coating for rolling bearings used in semiconductor manufacturing equipment, vacuum equipment and the like, and a method for forming the solid lubricating coating.

[0002]

2. Description of the Related Art Generally, solid lubricants are used for lubricating rolling bearings used in vacuum equipment, semiconductor manufacturing facilities and the like. Currently, as solid lubricants, layered substances such as molybdenum disulfide, soft metals such as gold, silver and lead, PTFE (polytetrafluoroethylene: average molecular weight of 1 × 10 ⁵ or more, mainly 1 × 10 ⁶ to 1) Polymers such as polyimide (× 10 ⁷ ) and polyimide are widely used, and these are usually subjected to coating treatment by sputtering or ion plating.

[0003]

According to the sputtering or ion plating method, processing equipment centering on a vacuum chamber is required. Moreover, the processing time is about 2 hours at the minimum including the pre-processing and post-processing such as vacuum exhaustion and cooling, and the production efficiency is extremely low. Further, the shape, size, number of objects to be processed, the shape of the processing jig, etc. are restricted by the shape, size, etc. inside the vacuum container. recently,
A load lock system is being adopted for the purpose of shortening the evacuation and cooling time, but the cost is increased because the device becomes expensive.

Further, in the compound or polymer sputtering method, when the target material (solid lubricant) is subjected to the sputtering action, the original crystal structure of the target material is flung out in a partially cut state and the target material (solid lubricant) is ejected to the object to be processed. Due to the adhesion, the original excellent lubricity of the target material may be somewhat impaired.

For the above reasons, the applicant of the present invention is
An object to be treated is dipped in a treatment liquid prepared by dispersing FE in an organic solvent, and then dried to form an island-shaped solid lubricating coating made of PTFE (Japanese Patent Application No. 2000-242242). No. 4-106392). According to the coating film forming method (hereinafter referred to as dipping method) of this application, a solid lubricating coating film which is superior in lubricity and low dust generation easily by using simple processing equipment as compared with the sputtering or ion plating method. Could be formed. Further, since the cycle time required for the coating treatment is short and a large amount of objects to be treated can be treated at the same time, the production efficiency in the coating treatment process can be improved.

However, according to the above dipping method, PTFE
In order to maintain the dispersibility of the particles, it was necessary to carry out the coating treatment while constantly stirring the treatment liquid. Therefore, a difference occurs in the adhered state of the PTFE particles between the surface of the object to be processed facing the flow of the processing liquid and the surface that is behind the flow of the processing liquid, resulting in a positional variation of the treatment film and a variation between the objects to be treated. Could be the cause of. Further, it has been relatively difficult to form a uniform coating on the narrow gap on the surface of the object to be processed or on the inner surface of the small object to be processed.

An object of the present invention is to solve the above-mentioned problems in the PTFE solid lubricating coating and the method for forming the same.

[0008]

The solid lubricating coating of claim 1 has an island-like distribution of fine particles of polytetrafluoroethylene having an average particle diameter of 4 μm or less.

A second aspect of the present invention is the solid lubricating coating of the first aspect, wherein the polytetrafluoroethylene has an average molecular weight of 1 ×.
10 ⁶ to 8 × 10 ⁶ .

According to a third aspect of the present invention, in the method for forming a solid lubricating coating, the object to be treated is immersed in a treatment liquid prepared by dispersing fine particles of polytetrafluoroethylene having an average particle diameter of 4 μm or less in an organic solvent. It is dried to form a solid lubricating coating made of the polytetrafluoroethylene on the surface of the object to be treated.

A method for forming a solid lubricating coating according to a fourth aspect is the method for forming a solid lubricating coating according to the third aspect, wherein the polytetrafluoroethylene has an average molecular weight of 1 × 10 ⁶ to 8 × 10 ^6.
It is what

[0012]

[Function] The solid lubricating coating is PTF with an average particle size of 4 μm or less.
It is composed of E fine particles, and the crystal structure of PTFE is maintained as it is without being destroyed.

Further, the PTFE fine particles having an average particle diameter of 4 μm or less have extremely good dispersibility in an organic solvent, and the treatment liquid in which the PTFE fine particles are dispersed can be easily stirred before the treatment. The suspended state (state in which the PTFE fine particles are dispersed in an appropriate and uniform manner) is maintained.

[0014]

EXAMPLES Examples in which the present invention is applied to a rolling bearing will be described below.

The deep groove ball bearing shown in FIG. 1 comprises an inner ring 1, an outer ring 2, a plurality of rolling elements 3 interposed between the inner and outer rings 1, 2 and a cage 4 for holding the rolling elements 3 at equal circumferential intervals. And inside
On the rolling surfaces of the outer rings 1 and 2 and on the surface of the rolling element 3, polytetrafluoroethylene (P
Solid lubricating coatings 1a, 2a, 3 composed of fine particles of TFE)
a is formed.

These solid lubricating coatings have an average particle size of 4 μm.
It is formed by immersing a bearing component or a completed bearing product in a treatment liquid prepared by dispersing the following PTFE fine particles in an organic solvent for about 10 seconds, and then drying this in the atmosphere. The PTFE fine particles having an average particle diameter of 4 μm or less have good dispersibility in an organic solvent, and a treatment liquid in which the PTFE fine particles are dispersed is in a suspended state (the PTFE fine particles are appropriately dispersed by simply stirring before treatment). The state of being evenly dispersed) is maintained for a long time. Therefore, it is not necessary to stir the treatment liquid during the coating treatment, and positional variation of the treated coating due to the stirring, variation between the objects to be treated, etc. are unlikely to occur. Further, since the PTFE fine particles have good dispersibility, it is possible to form a uniform coating on a narrow gap on the surface of the object to be processed, an inner surface of the small object to be processed, or the like.

The average particle size of PTFE is 0.5 μm.
Hereinafter, it is desirable to use one having an average molecular weight of 1 × 10 ⁶ to 8 × 10 ⁶ . As the organic solvent, for example, a fluorine-based inert liquid (all hydrogen of hydrocarbons is replaced by fluorine; CFC-based solvent is not included), alcohol, mineral spirits (solvent obtained by fractionating crude oil) One, saturated hydrocarbon with 8 to 10 carbon atoms, boiling point 150
It is preferable to use a material having a temperature of up to 205 ° C). In this example, PTFE has an average particle size of 0.3 μm and an average molecular weight of 2
~ 8 × 10 ⁶ (for example, PTFE manufactured by Kitamura Co., Ltd.
Dispersion KD-300AS), and mineral spirits (for example, White Spirits LAWS manufactured by Shell Japan Co., Ltd.) are used as an organic solvent. And above K
The finished bearing was dipped in a treatment liquid (referred to as an immersion treatment liquid A) obtained by diluting D-300AS with White Spirits LAWS to an appropriate concentration.

In this embodiment, the solid lubricating coating is formed on the rolling surfaces of the inner and outer races 1 and 2 and the surface of the rolling element 3, but the solid lubricating coating is formed on at least the surface of the rolling element 3. Good. Further, in the figure, the solid lubricating coatings 1a, 2a are formed on the entire outer surfaces of the inner and outer rings 1, 2, respectively.
As shown in FIG. 2, a portion such as a fitting surface where the solid lubricating coating is originally unnecessary should be removed before the final product. Furthermore, the bearing type is not limited to deep groove ball bearings,
Widely applicable to rolling bearings in general.

FIG. 3 shows the solid lubricating coatings 1a, 2a, 3 described above.
The distribution state of a (11a in the figure) is schematically shown. P dispersed in the immersion treatment liquid A
TFE fine particles (average particle size 0.3 μm) adhere to the surface of the base material 11 to form discontinuous islands 12. The average film thickness of the solid lubricating coating 11a is about 0.3 μm. Each island 12 is formed by one dispersed PTFE fine particle or an aggregate of a plurality of PTFE fine particles.
The crystal structure of FE remains as it is without being destroyed. This is in sharp contrast to the uniform distribution of the solid lubricating coating formed by sputtering of PTFE and the change in the molecular structure of the original PTFE. In such a solid lubricating coating 11a, the excellent lubricating performance originally possessed by the PTFE is maintained without being impaired. A concave space 13 is formed between the islands 12. The convex island 12 is scraped off by the contact with the mating surface 15 to generate the lubricating powder 12a (FIG. 11C), but this lubricating powder 12a
Enters into the concave space portion 13 and is transferred to that portion (FIG. 3D). In this way, as a result of the lubricant powder 12a scraped off from the surface of the solid lubricating coating 11a being captured by the space 13 between the islands 12, the amount of dust generated by the bearing becomes extremely small.

FIG. 4a shows a deep groove ball bearing # 608 (the product of this embodiment:
A plurality of bearings (denoted as bearing A) (80-9
(0 pieces) Histogram of coating weight per bearing after coating treatment, FIG. 4b shows deep groove ball bearing # 608 (comparative product: bearing B) coated with the immersion treatment liquid B shown below.
A coating weight histogram obtained in the same manner as above is shown. As shown in the figure, the weight variation of the bearing A is the same as that of the bearing B.
It was extremely small compared to. Further, as a result of observing the surface of the coating after the coating treatment, in the bearing A, uniform coating formation was observed in each part of the bearing, but in the bearing B, local variation in adhesion was observed. Further, the immersion treatment liquid A maintained the suspended state of the PTFE fine particles even after being left standing for several hours after the initial stirring, whereas the immersion treatment liquid B did not precipitate the PTFE particles within 1 minute after the stirring. Can be seen, and PT
Agitation of the treatment liquid was required to suppress the precipitation of FE particles.

{Immersion treatment liquid A: bearing A}

PTFE: average particle size 0.3 μm, average molecular weight 2-8 × 10 ⁶

(PTA dispersion made by Kitamura Co., Ltd. KD-
300AS)

Organic solvent: Mineral spirit

(White Spirits LAWS manufactured by Shell Japan Co., Ltd.)

{Immersion treatment liquid B: bearing B}

PTFE: average particle size 15 μm, average molecular weight 3 × 10 ⁵

(Mitsui DuPont Fluorochemical Co., Ltd.
MP1300)

Organic solvent: acetone (reagent)

FIG. 5 shows the results of a dusting test conducted on the bearing A and the bearing B. The test was carried out by rotating the bearing A or the bearing B under the following conditions and detecting dust by a dust detector arranged directly below the bearing.
As shown in FIG. 6A, the bearing A has a very low amount of dust generation per 10 hours of 1 to 2 and is stable, while the bearing B has a low amount of dust generation and a high amount of dust generation. The amount of dust generated varied between bearings. The same figures b and c show that the bearing B produced a large amount of dust. The amount of dust generated by the bearing B in FIG. 6B was (150/150 h), and the amount of dust generated by the bearing B in FIG. 3C was (210/150 h). In addition, the tendency of the change in the amount of dust generation with time is different between FIG. B and FIG. ), Conversely, in the same figure, the amount of coating film is too large and the amount of dust is high due to excessive lubrication (particularly, much dust is generated in the latter period).

{Test conditions}

Room temperature: 25 ° C Vacuum degree: 10 ^-5 Pa or less

Rotation speed: 50 rpm

Thrust load: 9.8N

Maximum contact pressure: 960 MPa

Even when the above-mentioned immersion treatment liquid A was replaced with a fluorine-based inert liquid (Sumitomo 3M Fluorinert), isopropyl alcohol, and ethylene glycol, the same results as with the bearing A were obtained.

The case where the present invention is applied to a rolling bearing has been described above. However, the present invention is not limited to rolling bearings and can be widely applied to sliding or rolling elements in general. For example, sliding bearings, ball screws, etc. Can be similarly applied. Further, although the above description relates to the immersion method, a solid lubricating coating is prepared by spraying a treatment liquid obtained by dispersing polytetrafluoroethylene fine particles having an average particle diameter of 4 μm or less in an organic solvent onto the surface of the treatment object. Can also be formed.

[0038]

The present invention has the following effects.

(1) The solid lubricating coating of the present invention is composed of PTFE fine particles having an average particle size of 4 μm or less, and the crystalline structure of PTFE is left as it is, so that the original excellent lubricating performance of PTFE is maintained. To be done. Moreover, since it has an island-like distribution, it is also excellent in low dust generation.

(2) The PTFE fine particles having an average particle size of 4 μm or less have good dispersibility in an organic solvent, and the treatment liquid prepared by dispersing them is suspended simply by stirring before the treatment. The state (the state in which the PTFE fine particles are dispersed in an appropriate and uniform manner) is maintained for a long time. Therefore, it is not necessary to stir the treatment liquid during the coating treatment, and positional variation of the treated coating due to the stirring, variation between the objects to be treated, etc. are unlikely to occur.

(3) Since the PTFE fine particles have a good dispersibility, it is possible to form a uniform coating on a narrow gap on the surface of the object to be treated or on the inner surface of a small object to be treated.

(4) Since the particle size is small, the area of adhesion of PTFE per unit weight to the object to be treated is increased, and stable lubricating performance and low dust generation are exhibited.

(5) Compared to the sputtering or ion plating method, a solid lubricating coating having excellent performance can be easily formed by using simple processing equipment. Further, since the forming method of the present invention has a short cycle time required for the film treatment and can process a large amount of film forming products at the same time, it can greatly contribute to the improvement of the production efficiency in the step of forming the solid lubricating film. it can.

[Brief description of drawings]

FIG. 1 is a sectional view showing a deep groove ball bearing (bearing A) according to an embodiment.

FIG. 2 is a cross-sectional view showing a state of the deep groove ball bearing shown in FIG. 1 when a solid lubricating coating such as a fitting surface is removed.

FIG. 3 is a plan view (FIG. A) and a sectional view (FIG. B, FIG. C, FIG. D) schematically showing a distribution state of the solid lubricating coating in FIGS. 1 and 2.

FIG. 4 is a coating weight histogram for a bearing A according to an example (FIG. A), and a coating weight histogram for a bearing B according to a comparative product (FIG. B).

FIG. 5 is a diagram showing a change over time in the amount of dust generated for bearing A (FIG. A), and a diagram showing a change over time in the amount of dust generated for bearing B (FIG. B, c).

[Explanation of symbols]

 1 Inner ring 1a Solid lubrication film 2 Outer ring 2a Solid lubrication film 3 Rolling element 3a Solid lubrication film

Claims (4)

[Claims] 1. A solid lubricating coating having an island-like distribution composed of fine particles of polytetrafluoroethylene having an average particle diameter of 4 μm or less. 2. The solid lubricating coating according to claim 1, wherein the polytetrafluoroethylene has an average molecular weight of 1 × 10 ⁶ to 8 × 10 ⁶ . 3. A polytetrafluoroethylene fine particle having an average particle size of 4 μm or less is immersed in a treatment liquid obtained by dispersing fine particles of the polytetrafluoroethylene in an organic solvent, and then this is dried to obtain the above polytetrafluoroethylene. A method for forming a solid lubricating coating comprising forming an island-shaped solid lubricating coating made of fine particles on the surface of the object to be treated. 4. The method for forming a solid lubricating coating according to claim 3, wherein the polytetrafluoroethylene has an average molecular weight of 1 × 10 ⁶ to 8 × 10 ⁶ .