JPH04370394A - Vacuum pump - Google Patents

Abstract

PURPOSE:To improve exhaust efficiency relating to light gas. CONSTITUTION:In the case of a vacuum pump provided with a rotor blade 5 and a stator blade 6, the rotor blade 5 is formed of titanium alloy and surface- treated with plating or oxide film. By thus forming the rotary blade 5 of the titanium alloy, rotational speed of the vacuum pump can be increased, and exhaust efficiency of the vacuum pump relating to light gas can be substantially improved.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vacuum pump that evacuates a vacuum chamber or the like.

0002

2. Description of the Related Art In conventional vacuum pumps, such as turbomolecular pumps, Al alloys (duralumin, etc.) are used for rotating bodies such as rotor blades because of their high specific strength (tensile strength/density). Furthermore, when a vacuum pump is used in a magnetic field, an Al alloy uses a rotating body made of ceramic because the temperature rises due to the generation of eddy currents and the tensile strength decreases. Furthermore, when gallium gas is used in semiconductor manufacturing, precipitation hardening stainless steel is sometimes used since Al alloys deteriorate due to corrosion. On the other hand, an Al alloy is generally used for the stator blades (fixed blades), and in special cases such as when used for gallium gas as mentioned above, the above stainless steel may be used.

0003

[Problem to be Solved by the Invention] However, in such conventional vacuum pumps, when an Al alloy is used for the rotor blades, the circumferential speed (rotational speed at the maximum diameter) during rotation is usually 300 to 350 m/s, and hydrogen (1600 m/s) and helium (130 m/s) have high molecular speeds.
0 m/s). Furthermore, when ceramic is used for the rotor blades, machinability is poor, and even if machining is possible, it is very difficult to join various parts when assembling the rotor blades from a large number of parts. Furthermore, since ceramic is porous and has a large surface roughness, the surface area becomes large and gas tends to adhere to it, which gets mixed into the exhaust gas during operation and reduces the exhaust performance. In addition, when stainless steel is used for rotor blades, it has a high specific strength like Al alloy, but its weight is large, which increases the load on the bearings that support rotation, which causes a problem in that the durability of the bearings deteriorates. . Therefore, it is an object of the present invention to solve the above problems.

0004

[Means for Solving the Problems] In order to solve the above problems, the present invention provides rotor blades provided on a rotating rotor;
In a vacuum pump equipped with a stator blade fixedly provided on a casing side, the rotor blade is formed of a titanium alloy and the surface thereof is plated or surface-treated with an oxide film, and the stator blade is formed of a titanium alloy. The rotor blades and the stator blades are formed of a titanium alloy, and the stator blades are further provided with a heating means for heating the stator blades. be.

[0005]

Embodiments Hereinafter, embodiments of the present invention will be described based on the drawings. FIG. 1 is a diagram of a turbomolecular pump showing an embodiment of the vacuum pump according to the present invention. In the figure, a casing 1 is formed with an inlet port 2 and a discharge port 3, and a rotor 4 is housed within the casing 1. Rotor blades 5 are formed on the rotor 4 toward the inner peripheral wall surface of the casing 1, and stator blades 6 are formed opposite to the rotor blades 5.
is attached to the inner peripheral wall surface of the casing 1 via a spacer 7. The rotor 4 is rotated by a motor 8 housed in the casing 1, so that the rotor blades 5 rotate at a high speed relative to the stator blades 6. Also,
The suction port 2 is connected to an opening (not shown) in the working chamber. The rotor blade 5 is made of a titanium alloy, and its surface is treated with Ni-based plating or an oxide film formed using oxygen, fluorine, or the like.

[0006] Such a turbomolecular pump has a rotor 4
When the rotor blades 5 are rotationally driven by the motor 8, the rotor blades 5 rotate at a high speed relative to the stator blades 6. Due to the cooperation between the rotor blades 5 and the stator blades 6, molecules such as gas and moisture in the working chamber are removed. is inhaled from the suction port 2 and discharged from the discharge port 3.
discharge from. By the way, since the rotor blades 5 are made of titanium alloy, their specific strength is extremely high, making it possible to significantly increase the rotational speed, and the peripheral speed to 40.
The speed can be set to about 0 to 450 m/s. For this reason, not only nitrogen whose gas movement speed is 450 m/s,
The exhaust efficiency of the aforementioned hydrogen and helium can also be greatly increased. Furthermore, unlike Al alloys, titanium alloys do not generate eddy currents in a magnetic field, so even if they are used in a strong magnetic field, the temperature will not rise and the tensile strength will not decrease, making it possible to use the titanium alloys. Furthermore, the titanium alloy surface was coated with Ni.
Because the surface is treated with chlorine-based plating or oxide film, it is free from chlorine-based,
There is no problem even if fluorine-based gas is exhausted.

FIGS. 2 and 3 are diagrams showing other embodiments of the vacuum pump according to the present invention. In this embodiment, the rotor blades 5 are made of an Al alloy, and the stator blades 6 are made of a titanium alloy. As shown in FIG. 2, a heating wire 10 (heating means) such as a tungsten wire is built into the stator blade 6 and embedded by known means such as casting or cladding. The stator blade 6 is adjacent to the spacer 7
The circumferential portion 6a sandwiched between them is formed in a continuous semicircular shape as shown in FIG. stator blades 6 are formed. As shown in FIG.
are all connected around the periphery of the connector 12, and one end is connected to the connector 12.
The other end of the heating wire 10 and the other end of the other heating wire 11 are respectively connected to the + and - poles of a power source (not shown).

In this embodiment, heating wires 10, 11
When electricity is applied to heat the stator blades 6, the surface of the titanium alloy that makes up the stator blades 6 sublimates, and the sublimated titanium molecules adhere to the surfaces of the rotor blades 5 and parts inside the pump.
By chemically reacting and bonding with molecules of a light gas such as hydrogen, this molecule exerts a pumping effect on the light gas (the so-called titanium getter effect). Therefore, in addition to the conventional mechanical pumping action, the chemical adsorption pumping action can greatly increase the light gas pumping efficiency. In this embodiment, the stator blades 6 themselves are made of a titanium alloy, but unlike this, the stator blades 6 themselves are made of an Al alloy, and a titanium alloy wire is wound around it in a coil shape. A thin film of titanium alloy may be formed on the surface. Furthermore, the stator blades 6 coated with titanium alloy may be formed in only one stage, or in any combination such as every other stage, every second stage, or all stages.

[0009] Note that the first and second embodiments described above may be implemented in combination. In this case, it is possible to significantly increase the exhaust efficiency for light gases, and since no eddy currents occur, it is suitable for use in magnetic fields, and it also has improved corrosion resistance against gases such as gallium, chlorine, and fluorine. can be done.

0010

[Effects of the Invention] As explained above, according to the present invention, by forming the rotor blades from a titanium alloy, the specific strength of the rotor blades becomes extremely high, making it possible to significantly increase the rotational speed. Therefore, the exhaust efficiency for light gas can be significantly increased. Furthermore, unlike Al alloys, titanium alloys do not generate eddy currents, so even when used in a magnetic field, the temperature will not rise and the tensile strength will not decrease, making them suitable.

Furthermore, by forming the stator blades from a titanium alloy and by providing heating means for heating the stator blades, in addition to the conventional mechanical pumping action,
As a titanium getter pump, it is possible to perform a pumping action on light gases by chemical adsorption, so it is possible to significantly increase pumping efficiency. Furthermore, by forming the rotor blades and stator blades from a titanium alloy and by providing a heating means to heat the stator blades, it is possible to further significantly increase the exhaust efficiency for light gases, and there is no eddy current. Therefore, it is suitable for use in a magnetic field, and corrosion resistance against gases such as gallium, chlorine, and fluorine can be improved.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a turbo-molecular pump to which an embodiment of the vacuum pump according to the present invention is applied.

FIG. 2 is an enlarged cross-sectional view of essential parts showing another embodiment of the vacuum pump according to the present invention.

3 is an overall plan view of the stator blades 6 in FIG. 2. FIG.

[Explanation of symbols]

1 Casing 4 Rotor 5 Rotor blade 6 Stator blades 10, 11 Heating wire (heating means)

Claims (3)

[Claims] 1. A vacuum pump comprising rotor blades provided on a rotating rotor and stator blades fixedly provided on a casing side, wherein the rotor blades are formed of a titanium alloy and the surface thereof is plated or coated with an oxide film. A vacuum pump characterized by surface treatment. 2. In a vacuum pump comprising rotor blades provided on a rotating rotor and stator blades fixedly provided on a casing side, the stator blades are formed of a titanium alloy, and the stator blades are heated. A vacuum pump characterized by being equipped with a heating means. 3. A vacuum pump comprising rotor blades provided on a rotating rotor and stator blades fixedly provided on a casing side, wherein the rotor blades and stator blades are formed of a titanium alloy, and the stator blades are made of a titanium alloy. A vacuum pump characterized by being provided with a heating means for heating.