JPH11148486A - Manufacture of vacuum pump and its device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vacuum pump excellent in corrosion resistance and heat radiation properties in the vacuum pump which is provided with a rotor and a stator, and performs a pumping action by means of impeller rotation. SOLUTION: At least either one of a rotor 1 and a stator 2, which are made out of aluminum as base material, is coated with a nitriding aluminum layer 4 excellent in corrosion resistance and heat radiation properties. By this constitution, the corrosion resistance of the rotor or the stator can be effectively made higher, and vacuum drawing of the corrosive gas for the rotor and the stator can be made usable, and concurrently, the rotor can be prevented from being overheated, and from being annealed because of overheating, and its performance can be enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vacuum pump such as a turbo molecular pump, a scroll pump, a mechanical booster pump, etc., which performs a pumping operation by blade rotation.
The present invention relates to a method and an apparatus for manufacturing such a vacuum pump.

[0002]

2. Description of the Related Art A conventional vacuum pump such as a turbo molecular pump which performs a pumping operation by blade rotation is known in which its rotor or stator is made of aluminum. Recently, the use of such a vacuum pump for evacuation of corrosive gases such as HF and HCl used for CVD and the like has been increasing.

[0003]

However, when such a vacuum pump is used to evacuate a corrosive gas, there arises a problem that the rotor or the stator is corroded by the corrosive gas. On the other hand, there is also a problem that when the vacuum pump exhausts an excessively large amount of gas, the rotor is overheated and becomes dull. In order to solve such a problem at once, a vacuum pump according to the present invention is obtained by attaching a material excellent in corrosion resistance and heat radiation to at least one of an aluminum-based rotor and a stator. The present invention proposes a method and an apparatus for manufacturing such a vacuum pump.

[0004]

That is, the present invention relates to a vacuum pump having a rotor and a stator and performing a pumping operation by blade rotation, wherein at least one of the rotor and the stator covers an aluminum substrate and its surface. And an aluminum nitride layer comprising:

[0005] Aluminum nitride is a ceramic material having high corrosion resistance.
In addition, it is not corroded by corrosive gas such as the above, has excellent surface thermal conductivity for effectively preventing dulling due to overheating of the rotor, and has properties of extremely high heat dissipation. Therefore, according to such a configuration, the corrosion resistance of the rotor or the stator can be effectively increased, and the rotor or the stator can be used for evacuation of corrosive gas, and overheating of the rotor and the dulling thereof can be prevented, and Can also be improved.

As a method of coating an aluminum base material with an aluminum nitride layer, a gas nitriding method, a plasma nitriding method, and an ion implantation method are specifically mentioned. Of these, the plasma nitriding method has the advantage that a large area can be nitrided while the nitriding temperature is kept low. It has the disadvantage of becoming non-uniform. Therefore, it has been difficult to apply this plasma nitriding method to a rotor or a stator of a vacuum pump having a complicated shape having a plurality of blades or steps. Therefore, in order to eliminate this drawback, the present invention proposes a method for making the thickness of the aluminum nitride layer uniform when the aluminum base material is coated with the aluminum nitride layer using the plasma nitriding method. .

That is, the present invention is a method for manufacturing a vacuum pump, which is applied to the vacuum pump according to claim 1 and has a step of forming an aluminum nitride layer by plasma nitriding. A step of forming an aluminum nitride layer by discharging the rotor or the stator from an anode disposed at an equal distance from the surface of the rotor or the stator within an error range of ± 6 mm. This is a method for manufacturing a pump.

In such a case, the anode faces each portion of the rotor or the stator at a substantially uniform distance, and the thickness of the aluminum nitride layer can be made uniform. Further, as an embodiment of a specific manufacturing apparatus capable of realizing the above-described manufacturing method, a housing capable of incorporating the rotor or the stator to be nitrided, and a structure in which the surface of the rotor or the stator incorporated in the housing is included. An anode comprising: an anode disposed at an equal distance within an error range of 6 mm; and a discharge circuit for generating an electric field between the anode and the rotor or the stator in order to discharge the anode or the rotor or the stator. No.

In such a manufacturing apparatus, in order to facilitate the work of disposing the anode, it is preferable that the anode is configured to be dividable into two or more.
In order to improve the corrosion resistance and heat dissipation by coating the surface of the aluminum base material constituting the rotor or the stator, a refractory metal layer other than aluminum nitride may be used. In this case, examples of the material of the high melting point metal layer include a simple substance of tungsten or rhenium, or an alloy containing any two or more of tungsten, rhenium, and molybdenum. In addition, in order to reduce the amount of rhenium which is particularly excellent in corrosion resistance but is expensive, and to obtain the same effect, it is preferable to form the above-mentioned single material or alloy into a multilayer structure. As a method for forming these refractory metal layers, it is preferable to use a chemical vapor deposition method.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIGS. FIG.
FIG. 1 is a schematic cross-sectional view showing an internal structure of a turbo molecular pump which is a vacuum pump of the present embodiment.

This turbo molecular pump comprises a stator 2 and
A cylindrical casing 10, a base frame 11 for supporting the casing 10, a motor housing 12 inside the casing 10 and fixed to the base frame 11,
A pair of ball bearings 13 respectively provided on the motor housing 12 and the base frame 11, a shaft 14 supported near both shaft ends by the ball bearings 13, and fixed to the shaft 14 so as to be integrally rotatable. And a rotor 1 housing a motor housing 12 on the inner periphery. The bearing is not limited to the ball bearing 13, but may be a magnetic levitation type bearing.

The rotor 1 has a plurality of rotor blades 15 protruding from the outer peripheral surface thereof and is made of aluminum as a base material 3. In addition, the stator 2 includes a plurality of stackable annular divided bodies 21 and a plurality of stator blades 22 protruding from the inner peripheral surface thereof. . This rotor wing 1
5 and the stator blades 22 are arranged alternately, and the gas sucked from the intake port 16 is supplied to the rotor blades 15 and the stator blades 2.
Blow off by interaction with the base frame 1
1 is configured to be capable of forcibly exhausting air from an exhaust port 17 provided in the apparatus.

[0013] In the turbo molecular pump having such a configuration,
The rotor 1 and the stator 2 of the present embodiment have a base material 3 made of aluminum and a surface coated with an aluminum nitride layer 4 as shown in a schematic partial cross section in FIG. FIG. 2 representatively shows a schematic outer shape of the rotor 1. Aluminum nitride is a ceramic material having high corrosion resistance, and HF, H
It is not eroded by corrosive gas such as Cl and has excellent heat conductivity and heat radiation. Therefore, according to the present embodiment, it is possible to increase the corrosion resistance of the rotor 1 and the stator 2 and effectively prevent overheating of the rotor 1.

Since it is not necessary to provide the stator 2 with heat radiation, only the rotor 1 is coated with the aluminum nitride layer 4 and the stator 2 is coated with another material having only excellent corrosion resistance. No problem. Next, a method of manufacturing the above-described turbo-molecular pump will be described in detail below, particularly focusing on a method of coating the surface of the rotor 1 with the aluminum nitride layer 4.

In the present embodiment, when the aluminum nitride layer 4 is coated on the surface of the rotor 1, a manufacturing apparatus 5A for nitriding whose schematic structure is shown in FIG. 3 is used. The manufacturing apparatus 5A includes a housing 5 capable of housing the rotor 1 to be nitrided.
1A, an anode 6A that can be arranged at an equal distance from the surface of the built-in rotor 1 within an error range of ± 6 mm, and an electric field is generated between the anode 6A and the rotor 1 to discharge the rotor 1 from the anode 6A. And a discharge circuit 8A.

The housing 51A has a cylindrical housing body 52A.
, A top cover 53A and a bottom cover 54A for closing both end surfaces of the housing body 52A, and a holder 55A projecting from the center of the bottom cover 54A and supporting the rotor 1. The anode 6A is a cylindrical member that is in close contact with the inner peripheral surface of the housing main body 52A and is supported by the bottom cover 54A, as shown in FIGS. It comprises a body 61A and a plurality of protrusions 62A protruding from the inner peripheral surface thereof and capable of being located between the rotor blades.

When the rotor 1 is incorporated in the apparatus, the following procedure is performed. First, after the rotor 1 is supported by the holder 55A, the half body 62A of the anode 6A is removed so as to cover the rotor 1 from the outer periphery. After being brought close to each other and integrated, the anode 6A is fixed to the bottom cover 54A. In this state, the plurality of protrusions 62A are located between the rotor blades 15, and the anodes 6A are arranged at an equal distance from the surface of the rotor 1 within an error range of ± 6 mm. Then, the housing body 52A is externally fitted to the anode 6A from above, and the bottom cover 54A
Then, the rotor 1 is hermetically sealed in the housing 51A by attaching the canopy 53A to the upper end surface of the housing main body 52A.

Thereafter, when performing nitriding, the housing 5
In order to make the inside of 1A a nitrogen atmosphere, a nitrogen gas or an ammonia gas is introduced from a gas inlet 56A provided in a canopy 53A, and a gas outlet 57 provided in a bottom cover 54A.
A gas is derived from A. In this way, the gas is always supplied into the housing 51A and circulated. On this occasion,
The temperature suitable for nitriding is set in advance by the heater 7 disposed so as to cover the outer surface of the housing 51A. Then, the discharge circuit 8
A discharges between the anode 6A and the rotor 1 by A to perform plasma nitriding.

In this way, the anode 6A faces each part of the rotor 1 at a substantially uniform distance, and the thickness of the aluminum nitride layer 4 can be made uniform. Further, as described above, the anode 6A is made of a pair of half bodies 62A.
Therefore, the work of incorporating the rotor 1 into the manufacturing apparatus 5A and installing the anode 6A can be easily performed.

FIG. 5 is a schematic sectional view showing a manufacturing apparatus 5B for nitriding the stator 2 in a state where the stator 2 is incorporated.
This manufacturing apparatus 5B has a housing 51B that can house the stator 2 to be nitrided, and ± 6 m from the surface of the built-in stator 2.
An anode 6B that can be disposed at an equal distance within an error range of m, and a discharge circuit 8B that generates an electric field between the anode 6B and the stator 2 so as to discharge the anode 6B to the stator 2. .

The housing 51B includes a housing main body 52B having a cylindrical bottom cover 54B and a canopy 53B for closing an end surface of the housing main body 52B. The anode 6B is
Plural divided disk-shaped divided bodies 61B and each divided body 61
B includes a plurality of protrusions 62B protruding from the outer periphery and positioned between the stator blades 22. The lowermost divided body 61B is not provided with a projection 62B.

When the stator 2 is built in this apparatus, the following procedure is performed. First, the divided body 61B positioned at the lowermost end is placed at the center of the bottom cover 54B. Since the stator 2 is originally configured to be able to be divided and stacked, the divided body 21 of the stator 2 is placed on the bottom lid 54B. Next, the divided body 61B of the anode 6B is placed on the divided body 61B of the anode 6B which has been arranged first. Then, the divided body 21 of the stator 2 is placed on the divided body 21 of the stator 2 which is arranged first. In this manner, the divided body 61B of the anode 6B and the divided body 21 of the stator 2 are laminated in an alternate order, and a state is formed in which the protrusion 62B of the anode 6B enters between the stator blades 22. Are arranged equidistant from the surface of the stator 2 within an error range of ± 6 mm. Then, by attaching a canopy 53B to the housing body 52B, the stator 2 is hermetically sealed inside the housing 51B.

The nitriding operation is the same procedure as in the case of the rotor 1. The manufacturing apparatus 5B can also make the thickness of aluminum nitride uniform, and since the anode 6B is composed of the plurality of divided bodies 61B as described above, the stator 2 can be incorporated into the manufacturing apparatus 5B. ,
The work of installing the anode 6B can be facilitated. The above-described manufacturing apparatus is not limited to the illustrated example, and for example, the division shape of the anode may be changed as long as the effect of simplifying the assembling operation is obtained.

Next, a second embodiment of the present invention will be described with reference to FIGS.
This will be described with reference to FIG. The same members as those in the first embodiment are denoted by the same reference numerals. This embodiment is a turbo-molecular pump having a structure similar to that of the first embodiment. However, as shown in FIG. 6, a high melting point metal layer 9 is formed on the surface of an aluminum base material 3 constituting its rotor 101 and stator 102. Is coated. In this case, the refractory metal layer 9 in this case is made of an alloy of tungsten, rhenium, and molybdenum.

Such a high melting point metal is not affected by gases such as HF and HCl used for CVD and the like. In particular, rhenium is a noble metal and has the same corrosion resistance as gold. In addition, the refractory metal has a higher heat radiation property than aluminum. Therefore, according to the present embodiment, the corrosion resistance of the rotor 101 or the stator 102 can be effectively increased,
In addition to being usable for evacuation of corrosive gas, overheating of the rotor 101 and its dulling due to the overheating can be prevented, and the performance can be improved.

In order to form such a high melting point metal layer 9, a chemical vapor deposition method is used in this embodiment. Then
Briefly, the method is, for example, tungsten is reduced by hydrogen reduction of WF ₆ , rhenium is reduced by hydrogen reduction of ReF ₆ , and molybdenum is reduced by hydrogen reduction of MoF ₆ . The steps of a typical chemical vapor deposition method will be specifically described with reference to the flowchart of FIG. In this step, the rotor 101 or the stator 102 is housed in a reaction tube (not shown).
First, the aluminum base material 3 forming the rotor 101 or the stator 102 is placed on a heater (not shown) in the reaction tube (step S1), and is evacuated to remove impurity gas in the reaction tube (step S2).

Next, a gas is introduced into the reaction tube. The gas is an inert gas such as hydrogen gas or argon, or a nitrogen gas (step S3). Of course, it may be kept in an evacuated state. Next, the temperature of the substrate 3 is increased (Step S4). The temperature is any temperature between 270C and 450C. Among them, 310 ° C. to 360 ° C. is most desirable.

When the temperature reaches a predetermined temperature, the inside of the reaction tube is evacuated again (step S5). This step is not necessary when the temperature is raised in the state of evacuation. At this time, care should be taken so that hydrogen gas does not particularly remain in the reaction tube. Next, the exhaust port is closed once, and WF ₆ , ReF ₆ , or MoF
₆ is sealed in a fixed amount. Then, for example, the state is held for about 30 minutes. The amount of gas varies depending on the capacity of the reaction tube, but in this embodiment, the gas is sealed so as to be 2 Torr. The larger the gas amount, the better (step S6). This step improves the adhesion between the base material 3 and the high melting point metal layer 9.

Then, a film forming process is performed (Step S7).
As a preferable condition at this time, the pressure in the reaction tube is set at 0.1.
Torr to any pressure of 10 Torr, H ₂ gas flow rate of any flow of 30 to 4000 CCM, WF
_The flow rate of ₆ + ReF ₆ + MoF ₆ is an arbitrary flow rate from 10 to 400 CCM. As more preferable conditions, WF _6, ReF _6, the total gas or WF of MoF _6, H _2
6 , layer 9 formed by intermittently flowing ReF ₆ and MoF ₆
Is improved. Gas Flow Time and Layer 9 Formed
Is approximately proportional to the thickness of the layer 9 (in this embodiment, about 0.5 μm to 50 μm) by controlling the gas flow time.
(Any thickness of 0 μm).

Thereafter, the gas in the reaction tube is replaced with N ₂ , Ar or the like, the heater is stopped, and the temperature is cooled to room temperature, and then the formed rotor 101 or stator 102 is taken out (step S8). Next, the unnecessary high melting point metal layer 9 attached to the rotor 101 or the stator 102 taken out is removed.
For example, it is removed by wet etching (step S
9). As an etchant, for example, a hydrogen peroxide solution is suitable. As the masking method, bind rubber or the like is used.

If the refractory metal layer 9 is formed by using the chemical vapor deposition method as described above, the refractory metal layer 9 can be made to have a polycrystalline structure by controlling the deposition conditions, so that the heat dissipation can be further improved. . The refractory metal layer may be made of tungsten or rhenium alone or an alloy containing any two or more of tungsten, rhenium and molybdenum, and is not limited to the second embodiment. Further, a metal layer of another material is further formed on the surface of the metal layer thus formed, so that a high melting point metal layer 10 having a multilayer structure is formed.
9 (see FIG. 8). In this way, the amount of rhenium that is excellent in corrosion resistance but expensive can be reduced, and the same effect can be obtained.

The present invention is not limited only to the above-described embodiment. For example, the present invention only needs to be a vacuum pump that performs a pumping action by blade rotation, and has similar effects when applied to a scroll pump, a mechanical booster pump, and the like other than the turbo molecular pump.
In addition, various modifications can be made without departing from the spirit of the present invention.

[0033]

As described above, according to the vacuum pump of the present invention, at least one of the aluminum-based rotor and the stator is provided with an aluminum nitride layer or a material having excellent corrosion resistance and heat dissipation. Since the high melting point metal layer is coated, the corrosion resistance of the rotor and the stator can be increased, and the overheating of the rotor can be effectively prevented. In addition, overheating of the rotor and its dulling can be prevented, and the performance can be improved.

When the aluminum nitride layer is coated, the rotor or the stator is discharged in an atmosphere of nitrogen from an anode disposed equidistantly within ± 6 mm from the surface of the rotor or the stator to be nitrided. In a method of manufacturing a vacuum pump having a step of forming an aluminum nitride layer by forming the aluminum nitride layer with a uniform thickness on a rotor or stator having a complex shape having a plurality of blades or steps. Can be coated.

Further, a manufacturing apparatus capable of realizing the above-described manufacturing method includes a housing capable of incorporating the rotor or the stator to be nitrided, and an error range of ± 6 mm from the surface of the incorporated rotor or stator within the housing. And an electric discharge circuit for generating an electric field between the anode and the rotor or the stator in order to discharge the anode or the rotor or the stator from the anode. If it is configured so as to be able to be divided into a plurality of parts, it is possible to facilitate the operation when the rotor or the stator is built in and the anode is provided.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a turbo-molecular pump showing first and second embodiments of the present invention.

FIG. 2 is a partial schematic cross-sectional view showing a schematic cross section of the rotor of the embodiment.

FIG. 3 is a longitudinal sectional view schematically showing a rotor nitriding manufacturing apparatus of the embodiment.

FIG. 4 is a schematic sectional view taken along line AA in FIG. 3;

FIG. 5 is a vertical cross-sectional view schematically showing a stator nitriding manufacturing apparatus of the embodiment.

FIG. 6 is a partial schematic cross-sectional view showing a schematic cross section of a rotor according to a second embodiment of the present invention.

FIG. 7 is a flowchart for explaining a chemical vapor deposition method in the embodiment.

FIG. 8 is a partial schematic cross-sectional view showing a schematic cross section of a rotor according to a modification of the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 101 ... Rotor 2, 102 ... Stator 3 ... Aluminum base material 4 ... Aluminum nitride layer 5A, 5B ... Manufacturing apparatus 6A, 6B ... Anode 51A, 51B ... Housing Body 8A, 8B ... discharge circuit 9, 109 ... high melting point metal layer

Claims (5)

[Claims] 1. A vacuum pump having a rotor and a stator and performing a pumping action by blade rotation, wherein at least one of the rotor and the stator comprises an aluminum substrate and an aluminum nitride layer covering the surface thereof. Vacuum pump. 2. A method for manufacturing a vacuum pump applied to the vacuum pump according to claim 1, comprising a step of forming an aluminum nitride layer by plasma nitriding, wherein the rotor is nitrided in a nitrogen atmosphere. Or a process for forming an aluminum nitride layer by discharging the rotor or the stator from an anode disposed equidistantly within an error range of ± 6 mm from the surface of the stator. . 3. A vacuum pump manufacturing apparatus applied to the vacuum pump according to claim 1 and used for forming an aluminum nitride layer by plasma nitriding, wherein a housing capable of incorporating the rotor or stator to be nitrided. And an anode which is disposed in the housing and which can be arranged at an equal distance from the surface of the built-in rotor or stator within an error range of ± 6 mm, and an anode and the rotor or stator which are discharged from the anode to the rotor or stator. An apparatus for manufacturing a vacuum pump, comprising: a discharge circuit for generating an electric field therebetween. 4. The vacuum pump manufacturing apparatus according to claim 3, wherein the anode is configured to be dividable into two or more. 5. A vacuum pump having a rotor and a stator and performing a pumping action by blade rotation, wherein at least one of the rotor and the stator has an aluminum substrate and a layer of a high melting point metal formed on the surface thereof. And a vacuum pump comprising: