JPH07269479A - Pump blade for vacuum pump - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a vane with high durability even in a corrosive atmosphere. [Constitution] A pump blade for a vacuum pump, which is made of carbon / carbon composite material. [Effect] A pump blade suitable for a vacuum pump, which is free from defects, corrosion, and water absorption and has sufficient strength, can be obtained, and a vacuum pump with higher durability can be manufactured. Further, it is possible to obtain a pump blade that is suitable for an oil rotary vacuum pump that uses pump oil for the purpose of improving exhaust performance and airtightness, has the above-mentioned durability and corrosion resistance, and does not damage the casing. Therefore, it is possible to manufacture an oil rotary vacuum pump having higher performance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a highly durable pump blade for a vacuum pump (hereinafter referred to as "vane").

[0002]

2. Description of the Related Art Vacuum pumps are widely used for various purposes. A vacuum pump used in an environment where corrosive gas is generated, such as a semiconductor manufacturing apparatus, is exposed to a corrosive environment at a portion that comes into contact with intake gas, so that durability of component parts is difficult to be exhibited. In particular, as a vane of a vacuum pump, although a metal vane has been widely used in the related art, its durability is insufficient and it is necessary to replace parts frequently, which has been a problem.

The use of a non-metallic material for the vane of a vacuum pump is disclosed in, for example, Japanese Patent Publication No. 50-11090 and Japanese Patent Laid-Open No. 62-276291. Japanese Patent Publication No. 50-11090 discloses a Goethe type oil rotary vacuum pump having a vane made of a material having a specific gravity of 0.8 to 5. The purpose is to obtain a high-speed rotating vacuum pump that obtains a desired ultimate pressure without causing seizure, for example, a vacuum pump having a rotation speed of 500 rpm or more. The specific gravity in the publication is 0.8 to 5
Bakelite, Teflon, Delrin,
Examples include plastic materials such as nylon (these are trade names), carbon, aluminum, and titanium. According to the publication, unlike a compressor, in the case of a vacuum pump, it is almost impossible to increase the amount of oil supply for the purpose of preventing wear and seizure by increasing the number of revolutions, and wear in a vacuum causes wear in the air. It is said to be larger than wear.

Japanese Unexamined Patent Publication (Kokai) No. 62-276291 discloses a rotary vane type pump which operates without lubrication.
As the vane material, graphite having a bending strength of 4 kg / mm ² or more or graphite impregnated with Pb and Sb or graphite reinforced with pitch, tar, carbon fiber, and ceramic fiber is disclosed. In the examples, graphite (HCB) is used as the vane material. -3
0) is used. The reason for this is that graphite has self-lubricating properties and does not cause galling due to adhesion even if oil is not supplied. However, from these technologies, vanes that exhibit high durability and corrosion resistance while maintaining sufficient exhaust performance in an environment with the generation of corrosive gas and that do not cause damage to the casing are still being developed. There wasn't. Especially suitable for oil rotary vacuum pumps that use pump oil for the purpose of improving exhaust performance and airtightness, no vane has been developed that has the above durability and corrosion resistance and does not cause damage to the casing. is the current situation.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a highly durable pump blade for a vacuum pump.

[Means for Solving the Problems]

The present invention resides in a pump vane for a vacuum pump (hereinafter referred to as "vane"), which is characterized by comprising a carbon / carbon composite material. Hereinafter, the carbon / carbon composite material in the present invention will be described in detail. In the present invention, the carbon / carbon composite material is a composite material mainly composed of carbon fiber and a carbonaceous matrix, and the fiber volume content thereof is usually 10 to 80% and the matrix volume content thereof is usually 2
0 to 90%, and the void volume ratio is usually 1 to 30%, preferably about 2 to 10%. The carbon / carbon composite material used in the present invention usually has a fiber volume content of 10-8.
0%, preferably 20-70%, more preferably 30-
65%. If the fiber volume content is less than the above range, the effect of fiber reinforcement is not sufficient, and a brittle material such as a carbon material disclosed in, for example, Japanese Patent Publication No. 50-11090 is used, and impact strength and fracture toughness are obtained. It becomes a vane material having a low value, and it cannot exhibit sufficient performance and durability as an oil rotary vacuum pump used in an environment where corrosive gas is generated.

The void volume ratio of the carbon / carbon composite material used in the present invention is usually 1 to 30%, preferably 2 to 25.
%, More preferably 5 to 25%. Here, if the void volume ratio is less than the above range, the vacuum pump oil cannot be sufficiently held, and sufficient performance and durability cannot be exhibited as an oil rotary vacuum pump.
On the other hand, when the void volume ratio exceeds the above range, the strength of the vane material is insufficient. The matrix volume content of the carbon / carbon composite material used in the present invention is determined by the fiber volume content and the void volume, and is usually 20 to 90%, preferably about 5 to 30%. is there. The bending strength of the carbon / carbon composite material used in the present invention is usually 4.5 kg / mm ² or more, preferably 8 kg.
/ Mm ² or more. The Izod impact value of the carbon / carbon composite material is usually 4 kg · cm / cm ² or more, preferably 8 kg · cm / cm ² or more. Furthermore, the Charpy impact value of the carbon / carbon composite material is usually 7 k.
g · cm / cm ² or more, preferably 10 kg · cm / c
m ² or more. Further, the carbon / carbon composite material used in the present invention preferably has a thermal expansion coefficient in at least one direction of less than 1.5 × 10 ⁻⁶ (° C. ⁻¹ ) at room temperature. More specifically, the coefficient of thermal expansion of the carbon / carbon composite material at room temperature is preferably smaller than 1.0 × 10 ⁻⁶ (° C. ⁻¹ ). Further, the coefficient of thermal expansion of the carbon / carbon composite material at room temperature is preferably smaller than 0.5 × 10 ⁻⁶ (° C. ⁻¹ ).

Although the vane according to the present invention can be sufficiently used for a non-lubricated vacuum pump, its performance is remarkably exhibited especially in an oil rotary type vacuum pump. The material of the member other than the vane of the vacuum pump of the present invention is not particularly limited, and a conventionally known material can be used. For example, carbon steel or cast iron can be used for the cylinder and rotor that come into contact with the vanes. Furthermore, the vacuum pump oil is not particularly limited as long as it can be used as a normal vacuum pump oil, and general mineral oil-based, synthetic oil-based pump oil, etc. can be used.

There is a vacuum pump called EC type as one kind of vacuum pump suitable for using the vane according to the present invention. An example of the vane suitable for this vacuum pump and its peripheral members will be described with reference to the drawings. FIG. 1 is a perspective view showing the shape of a vane, which is made of a carbon / carbon composite material.
FIG. 2 is a cross-sectional view showing an assembly of vanes, in which a plurality of vanes 1 are mounted on a rotor 3 via springs 2. Figure 3
FIG. 3 is a cross-sectional view showing a state where the vane assembly shown in FIG. 2 is mounted in a casing (cylinder), and the vane assembly rotates eccentrically. The vane in the upper part of the rotating diagram is pushed into the rotor, and the vane in the lower part is pushed out and is always in close contact with the inner wall of the casing.

Hereinafter, an example of the method for producing the carbon / carbon composite material used in the present invention will be described in detail. In the present invention, the carbon / carbon composite material means a composite material containing carbon fibers and a carbonaceous matrix as main constituent elements. As the carbon fiber, various fibers such as pitch-based, polyacrylonitrile-based, rayon-based or precursors thereof can be used. Particularly, pitch-based carbon fiber is preferable because it is easy to enhance abrasion resistance.

As the carbonaceous pitch which is a raw material of the pitch-based carbon fiber, coal-based or petroleum-based pitch having a softening point of usually 100 to 400 ° C., preferably 150 to 350 ° C. is used. As the carbonaceous pitch, either an optically isotropic pitch or an anisotropic pitch can be used, but particularly the content of the optically anisotropic phase is 60 to 10.
An optically anisotropic pitch within the range of 0% is preferably used. By melt-spinning the carbonaceous pitch by a known method, the average diameter is usually 5 to 100 μm, preferably 7
Obtain pitch fibers of ~ 30 μm. Next, the pitch fiber is placed in an oxidizing gas atmosphere, usually at 50 to 400 ° C., preferably 1
Infusibilizing treatment is performed within a temperature range of 00 to 350 ° C. to obtain infusibilized fiber. Examples of the oxidizing gas include air, oxygen, nitrogen compounds, sulfur compounds, halogens, and mixtures thereof. The infusibilizing treatment time is usually 10 minutes to 20 hours. The obtained infusibilized fiber is further subjected to an inert gas atmosphere, usually 350 to 3000 ° C., preferably 4
A so-called carbon fiber such as carbonized fiber or graphitized fiber can be obtained by treating within a temperature range of 00 to 2800 ° C. for 1 second to 5 hours.

The above-mentioned carbon fibers are usually used as a continuous fiber bundle of 500 to 25,000. Further, a one-way laminate, a two-dimensional woven fabric or a laminate thereof, a three-dimensional woven fabric, a mat-like molded product, a felt-shaped molded product, or the like, in which carbon fibers are molded into a shape close to a vane can be used. As a molding method, a conventionally known method can be used.

In the present invention, the carbonaceous matrix includes those obtained by heat treatment of organic precursors and those obtained by vapor phase pyrolysis of hydrocarbons and the like. The organic precursors include thermoplastic ones and thermosetting ones. A typical example of the thermoplastic organic precursor is carbonaceous pitch. The carbonaceous pitch includes coal-based or petroleum-based pitch having a softening point of usually 100 to 400 ° C, preferably 200 to 350 ° C.
As the pitch for the matrix, either an optically isotropic pitch or an anisotropic pitch can be used, but the optically anisotropic pitch has a content of the optically anisotropic phase in the range of 60 to 100%. Are particularly preferably used. After the above-mentioned thermoplastic organic precursor is impregnated into a carbon fiber, in particular, a molded body of carbon fiber, carbonization treatment is performed to produce a primary molded body. The carbonization treatment can be carried out under normal pressure, but is usually carried out under pressure or under press. The carbonization under pressure is performed by using a hot isostatic press, etc., with an inert gas of 50 to 1000.
0 kg / cm ² , preferably 100 to 2000 kg / c
Pressurized to a pressure within the range of about m ² , usually 400 to 200
It is carried out in a temperature range of 0 ° C., preferably about 500 to 1500 ° C. Carbonization under the press, usually 10~500kg / cm ² in air by the device, such as a hot press, preferably under a uniaxial pressure in a range of about 20 to 200 kg / cm ^2, 400 to 2,000 ° C., preferably 500 ~ 15
The temperature is within the range of about 00 ° C.

Examples of the thermosetting organic precursor include carbonizable resins, specifically, carbonizable thermoplastic resins such as phenol resins and furan resins. The curing temperature of these thermosetting resins is usually 80 to 200 ° C, preferably 110 to 150 ° C. The thermosetting organic precursor is impregnated into a carbon fiber, preferably a carbon fiber molded body, and cured within the above curing temperature range, and optionally 140 to 140
After the post-heat treatment within the temperature range of 180 ° C., the carbonization treatment is performed, whereby the primary molded body can be manufactured. The carbonization treatment is usually 200 to 3000 ° C., preferably 50.
It can be carried out in a temperature range of 0 to 2500 ° C. under vacuum, reduced pressure, an inert gas atmosphere or a reducing atmosphere. Specific examples of the inert gas include those commonly used as inert gases such as nitrogen, argon, and helium, and examples of the reducing gas include hydrogen and carbon monoxide. When the thus obtained primary molded article has the desired physical properties of the carbon / carbon composite material, such as density, matrix volume content or void volume, etc., the primary molded article is processed as it is or after polishing. You can use it as a vane. When the primary molded body does not have the desired physical properties of the carbon / carbon composite material, such as density, matrix volume content or void volume ratio, the primary molded body is further impregnated with the above-mentioned organic precursor. It is also possible to obtain a carbon / carbon composite material having desired physical properties by carrying out carbonization treatment once or performing treatment for depositing pyrolytic carbon one or more times.

The treatment of depositing pyrolytic carbon as used herein is a method of vapor-decomposing hydrocarbons or the like in the vapor phase to form carbon, which is generally called chemical vapor deposition (CVD). Is. Specifically, for example, hydrocarbons such as methane, ethane, acetylene, propane, benzene, natural gas, etc., or at least one of these hydrocarbons diluted with an inert gas or hydrogen is used as a raw material, and pyrolytic carbon is added to the primary compact. Let it deposit. At this time, the thermal decomposition temperature is usually 700 to 3000 ° C., preferably 800 to 250.
It is within the range of 0 ° C. The thermal decomposition may be carried out at normal pressure, but it is preferably reduced pressure, specifically 0.5 to 100 Torr, preferably 0.5 to 50.
It is desirable to be in the range of about Torr.

[0016]

According to the present invention, it is possible to obtain a vane that exhibits high durability and corrosion resistance while maintaining sufficient exhaust performance in an environment in which corrosive gas is generated, and that does not damage the casing. , A more durable vacuum pump can be manufactured. Further, according to the present invention, a vane suitable for an oil rotary vacuum pump using pump oil for the purpose of improving exhaust performance and airtightness, and having the above-mentioned durability and corrosion resistance and not causing damage to the casing. As a result, the oil rotary vacuum pump having higher performance can be manufactured.

[0017]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. (Example 1) Modulus of elasticity 25 ton / mm ² , average fiber length 5
A non-woven fabric of petroleum pitch-based carbon fiber having 0 mm and a phenol resin were mixed and molded, and cured to obtain a plate-shaped CFRP. Next, this was carbonized at 1000 ° C. for 1 hour to obtain a primary molded body. Then, the primary compact was subjected to densification treatment for impregnation with petroleum pitch and carbonization treatment three times to obtain a plate-like, non-woven fabric-reinforced carbon / carbon composite material having various physical properties shown in Table 1 below.

[0018]

[Table 1]

The above-mentioned carbon / carbon composite material was machined into blades (vanes) for an oil rotary vacuum pump and incorporated into the oil rotary vacuum pump. Using the oil rotary vacuum pump having the vane of the above carbon / carbon composite material, a steady operation was performed at a vacuum degree of 10 ⁻³ Torr in a corrosive gas atmosphere containing a silane-based gas, and after 1000 hours, the vane was taken out to examine the state. As a result, no defects, corrosion, abnormal wear, etc. were observed.

(Comparative Example 1) An operation test of an oil rotary vacuum pump was conducted in the same manner as in Example 1 except that a cast iron vane was used, and the vane was taken out and examined for its condition. It was also found that the vane had a bite, and further use was impossible.

(Examples 2 to 4 and Comparative Examples 2 to 4) A plain weave of petroleum pitch-based carbon fibers having an elastic modulus of 40 ton / mm ² and an optically anisotropic pitch having a softening point of 280 ° C. were alternately laminated. Was uniaxially pressure-molded at 700 ° C. to prepare a plate-shaped primary molded body. Next, this primary compact was subjected to densification treatment by impregnation with petroleum pitch and carbonization treatment three times to obtain a carbon / carbon composite material having the physical properties shown in Table 2 below.

[0022]

[Table 2]

The above carbon / carbon composite material was machined into vanes for an oil rotary vacuum pump and incorporated into an oil rotary vacuum pump having a cast iron or aluminum casing. As a comparative example, a sliding carbon material was used. The test was conducted using the following vanes as shown in Table 3 below.

[0024]

[Table 3]

As a result, the oil rotary vacuum pump using the vanes according to the present invention (Examples 2 to 4) could be operated without any abnormality. On the other hand, sliding carbon material (Comparative Example 2
The oil rotary type vacuum pump using ~ 4) as a vane was unusable because the vane was scratched or the casing was scratched and scratched.

(Example 5 and Comparative Example 5) Methane was used as a raw material for the primary molded body obtained in Example 1 to obtain 1300.
Densification treatment was performed by depositing pyrolytic carbon at 50 ° C. and 50 Torr to obtain a plate-like nonwoven fabric-reinforced carbon / carbon composite material having the following physical properties.

[0027]

[Table 4]

The non-woven fabric reinforced carbon / carbon composite material was machined into an oil rotary vacuum pump blade and incorporated into an oil rotary vacuum pump. Using the oil rotary vacuum pump having the vane of the above carbon / carbon composite material, a steady operation was performed at a vacuum degree of 10 ⁻³ Torr in a corrosive gas atmosphere containing a silane-based gas, and after 1000 hours, the vane was taken out to examine the state. As a result, no defects, corrosion, abnormal wear, etc. were observed. On the other hand, when a similar test was conducted using a vane made of an asbestos-based FRP material, the vane itself had a dimensional change due to water absorption, and further use was impossible.

[Brief description of drawings]

FIG. 1 is a perspective view showing an example of the shape of a vane.

FIG. 2 is a cross-sectional view showing an example of a vane assembly.

3 is a cross-sectional view showing a state where the assembly of FIG. 2 is installed in a casing.

[Explanation of symbols]

 1 vane 2 spring 3 rotor 4 casing

Front page continued (72) Inventor Mitsuru Yahagi 2500 Hagien, Chigasaki-shi, Kanagawa ULVAC Seiki Co., Ltd., Chigasaki Plant (72) Inventor Katsunori Naka, 3313 Ueno, Yokogawa-cho, Aira-gun, Kagoshima Aruba Seiki Co., Ltd. Kagoshima Plant ( 72) Inventor Shunichi Tateno 3313 Uenogawa-cho, Aira-gun, Kagoshima Inside the Kagoshima factory of Arbac Seiki Co., Ltd. (72) Kiho Hayada 8 Chidori-cho, Naka-ku, Yokohama, Kanagawa Nippon Oil & Oil Co., Ltd. (72) Inventor Takeshi Kono 8 Chidori-cho, Naka-ku, Yokohama-shi, Kanagawa Nihon Sekiyu Co., Ltd. Central Technology Research Institute

Claims (1)

[Claims] 1. A pump blade for a vacuum pump, comprising a carbon / carbon composite material.