JP2003294042A - Rolling bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rolling bearing used both in an air and in a vacuum which can obtain the decreased amount of dusts to be generated regardless of use in an air or in a vacuum, and secure an excellent durability. <P>SOLUTION: A lubricating element of a lubrication composition 5 accommodated so as to partially cover a holder 4 for holding a ball 3 between an inner ring 1 and an outer ring 2 is constituted of lubricating grease and lubricating oil. Alkyl cyclopentane oil is employed as lubricating oil, which leads to increase in the strength of the lubricating composition 5 to improve durability. Fluorine oil is employed as a base oil of lubricating grease, which suppresses the generation of dusts in an air or in a vacuum so as to stably utilize the bearing used both in an air and in a vacuum for a long time. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an atmospheric / vacuum rolling bearing used in semiconductor manufacturing equipment.

[0002]

2. Description of the Related Art In semiconductor manufacturing equipment, a processing environment with a higher degree of cleanliness is required as the degree of integration of semiconductors increases. Is required. As one of the parts that strongly demand such low dust generation,
There is a rolling bearing incorporated in a robot that carries semiconductor substrates (wafers). Many of the transfer robots work in vacuum, but some work in the atmosphere, so
There is a demand for bearings that generate less dust in any environment. Further, since the bearing for the transfer robot is used under a high load in order to suppress the positional deviation of the substrate to be transferred, it is required to have low dust generation and durability under a high load.

In response to such a demand, as a rolling bearing for vacuum equipment, there is one described in JP-A-2000-87983. This bearing contains a solid lubricating composition in which a lubricating component is dispersed and held in a synthetic resin base material, and a small amount of oil gradually evaporates from the lubricating composition even under the action of centrifugal force during operation. Since it oozes out, the amount of dust generated in a vacuum is smaller than that of a bearing having a general structure filled with grease, which often oozes oil. By using an alkylcyclopentane-based oil having a high load bearing property as the base oil or the lubricating oil of the lubricating grease that constitutes the lubricating component, it is possible to obtain excellent durability even under a high load.

However, the above-mentioned bearing using the alkylcyclopentane oil has a property of producing a large amount of dust in the atmosphere, and therefore is not suitable for being incorporated in a transfer robot operating in the atmosphere.

Therefore, in many cases, equipment such as a transfer robot for the atmosphere incorporates a bearing using a fluorine-based oil as a base oil or a lubricating oil of a lubricating grease of a lubricating composition.
Although this bearing shows stable low dust generation in the air and vacuum, it has a drawback that the solidified lubricating composition does not have sufficient strength and is inferior in durability.

From the above, conventionally, bearings using alkylcyclopentane oil are incorporated in the vacuum transfer robot, and bearings using fluorine oil are incorporated in the atmospheric transfer robot. By using the two types of bearings properly, manufacturing of the bearings and management at the time of assembling become complicated, and there is a possibility that troubles such as confusing the two may occur.

[0007]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a rolling bearing for both atmosphere and vacuum which has a small amount of dust regardless of whether it is in the air or in a vacuum and has excellent durability. is there.

[0008]

In order to solve the above problems, the present invention is directed to a rolling bearing in which a solid lubricating composition in which lubricating oil and lubricating grease are dispersed and held in a synthetic resin base material is housed inside a bearing. In the above, a configuration in which an alkylcyclopentane oil is used as the lubricating oil and a fluorine oil is used as the base oil of the lubricating grease is adopted.

That is, by using an alkylcyclopentane-based oil having a strong molecular chain bonding force as the lubricating oil, the strength of the lubricating composition is increased and good durability is ensured even under high load. At the same time, by using a fluorine-based oil as the base oil of the lubricating grease, dust generation in the atmosphere and vacuum was suppressed.

An average molecular weight of 1 × 10
^{By using} a polyolefin powder of ^{6 to} 5 × 10 ⁶ , the strength of the lubricating composition is further increased to improve the durability, and the oil retaining property is improved to stabilize the exudation of the oil and to improve the dust generation amount. Can be reduced.

Polyethylene powder is preferably used as the polyolefin powder.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIGS. This rolling bearing is a deep groove ball bearing incorporated in a substrate transfer robot of a semiconductor manufacturing facility, and as shown in FIGS.
A plurality of balls 3, which are rolling elements, are housed in a gap between the outer ring 2 and the outer ring 2 and held by a cage 4, and a plurality of lubricating compositions 5 are housed so as to partially cover the cage 4. .

The lubricating composition 5 is a solid composition in which a lubricating component is dispersed and held in a synthetic resin base material, and is manufactured by the following method. That is, this lubricating composition 5 is obtained by uniformly mixing polyethylene powder as a base material, lubricating grease and a small amount of lubricating oil, and at a temperature not lower than the gel point of the polyethylene powder and not higher than the dropping point of the lubricating grease (150). ~
It is manufactured by heating to 200 ° C.) to disperse and retain a lubricating grease and a lubricating oil on a polyethylene powder base material, and cooling and solidifying the lubricating grease and the lubricating oil.

As the polyethylene powder, one having an average molecular weight of 1 × 10 ^{6 to} 5 × 10 ⁶ is used. By using such an ultra-high molecular weight polyolefin powder as a base material for holding a lubricating component, the strength of the lubricating composition 5 can be increased and the oil retaining property can be improved as compared with the case where a low molecular weight one is used. it can. And due to its excellent oil-holding power, the oil gradually and stably exudes even under the action of centrifugal force during bearing operation, and it is possible to reliably prevent oil from leaking from the inside of the bearing due to changes in atmospheric pressure. You can

As the base material holding the lubricating component,
The above-mentioned polyethylene powder is preferable, but it is also possible to use a polyolefin powder such as polypropylene or polybutene powder or a mixed powder obtained by mixing polyethylene powder with these. Also in such a case, it is preferable to use an ultra high molecular weight one.

An alkylated cyclopentane oil is used as the lubricating oil. The alkylcyclopentane-based oil has a strong binding force of the molecular chain and thus has excellent load resistance, and its strength can be increased by adding it to the lubricating composition 5.

Further, the lubricating grease uses a fluorine-based oil as its base oil. During the operation of the bearing, this fluorinated oil mainly exudes from the lubricating composition 5.

That is, in this bearing, the lubricating component of the lubricating composition 5 is composed of lubricating grease and lubricating oil, and since fluorine-based oil is used as the base oil of the lubricating grease, it is in the atmosphere and in vacuum. In addition to having stable and low dust generation, it is also excellent in durability because an alkylcyclopentane oil is used as a lubricating oil.

In order to confirm the characteristics of the bearing of the above-mentioned embodiment, a dust generation characteristic test and a durability test were conducted. In each test, in addition to the bearing of the embodiment (bearing A), a vacuum type (bearing B) having only a lubricating grease containing an alkylcyclopentane-based oil as a base oil as a lubricating component of the lubricating composition, and a fluorine-based one. As a comparative example, a lubricant having only oil as a base oil and mainly used in the atmosphere (bearing C) was prepared. Table 1 shows the composition of the lubricating composition of each test bearing.

[0020]

[Table 1]

The amount of polyethylene in each test bearing was 40 wt.
40% by weight means that as the amount of polyethylene contained in the lubricating composition increases, the hardness when solidified increases.
This is because sufficient strength is secured by the above.

The content of the alkylcyclopentane type oil in the bearing A is set to 5 wt% in order to reduce the amount of the expensive oil used as much as possible.

(1) Dust Generation Characteristic Test A dust generation amount measurement tester was used to measure the amount of dust generation while operating each test bearing under the following conditions in air and vacuum. The test results in air are shown in FIG.

[0024]

As is apparent from FIG. 2, the bearing B for vacuum is used.
In contrast, the amount of dust generated in the atmosphere is large, whereas the amount of dust generated in the bearing A of the embodiment is at the same level as that of the bearing C for the atmosphere, and the bearing A uses the alkylcyclopentane oil in the lubricating composition. It was confirmed that even if it was included, it was suitable for use in the atmosphere.

Although not shown in the drawings, it was also confirmed in a test in vacuum that the amount of dust generated by the bearing A was as small as that of the bearing B for vacuum.

(2) Durability test Since the bearing life tends to be shorter in vacuum than in air, a test was conducted to compare the life in vacuum. The test uses a vacuum durability tester to measure the friction torque while operating with a high load applied to each test bearing, which is close to the actual operating conditions, and the sum of the measured friction torque is 10 ^-2.
The life time was defined as the time when it reached Nm. The test results are shown in FIG. The arrow in the figure indicates that the test was terminated halfway.

(Test conditions) Axial load: 83.4 N Rotation speed: 2500 rpm Atmosphere temperature: Room temperature Vacuum degree: 10 ^-6 Torr or less

As is clear from FIG. 3, the bearing A according to the embodiment has a life of 1.5 times or more that of the bearing C, similarly to the bearing B, and the alkylcyclopentane oil contained in the lubricating composition is 5 wt%. It was found that even a small amount has an effect of sufficiently improving durability.

Needless to say, the present invention can be applied not only to the ball bearing as in the embodiment but also to a rolling bearing using rollers as rolling elements. Further, the application thereof is not limited to the substrate transfer robot of the semiconductor manufacturing facility, but can be widely used for both atmosphere and vacuum.

[0031]

As described above, in the rolling bearing of the present invention, the alkylcyclopentane oil is used as the lubricating oil and the fluorine oil is used as the base oil of the lubricating grease in the lubricating composition housed inside the bearing. Because it was
It has a long life even under a heavy load, generates little dust in the air and vacuum, and can be used stably for a long time as both air and vacuum.

Therefore, even when the bearing for the atmosphere and the bearing for the vacuum are separately used, the necessity is eliminated, and the management at the time of manufacturing and assembling the bearing is simplified, so that there is no trouble of mistakenly selecting the type of the bearing. In addition, there are cost advantages due to standardization.

Further, since the alkylcyclopentane type oil can obtain good characteristics by adding a small amount thereof, the manufacturing cost is higher than that of the conventional vacuum bearing which uses this expensive oil as the base oil or the lubricating oil of the lubricating grease. Can also be cheaper.

[Brief description of drawings]

FIG. 1A is a vertical sectional front view of a rolling bearing according to an embodiment, and b is a cross-sectional view taken along line BB of a.

FIG. 2 is a view showing dust generation characteristics of the bearing of FIG. 1 in the atmosphere in comparison with a conventional bearing.

FIG. 3 is a diagram showing durability of the bearing of FIG. 1 in a vacuum in comparison with a conventional bearing.

[Explanation of symbols]

1 inner ring 2 outer ring 3 balls 4 cage 5 Lubricating composition

Claims (3)

[Claims] 1. A rolling bearing in which a solid lubricating composition in which a lubricating oil and a lubricating grease are dispersed and held in a synthetic resin base material is housed inside a bearing, wherein an alkylcyclopentane oil is used as the lubricating oil, and the lubricating grease is used. Rolling bearings, each of which uses a fluorine-based oil as the base oil. 2. The synthetic resin base material has an average molecular weight of 1 × 1.
A polyolefin powder of 0 ^{6 to} 5 × 10 ⁶ is used.
Rolling bearing described in. 3. The rolling bearing according to claim 2, wherein the polyolefin powder is polyethylene powder.