JPS63259192A - Turbo molecular pump - Google Patents

Abstract

PURPOSE:To suppress a lubricant from generating its dissolved gas and to easily attain a high vacuum, by providing a thrust/radial bearing part to be arranged in the intermediate part of a motor shaft and an end part of the motor shaft to be arranged being fitted to a fluid sealed chamber. CONSTITUTION:Stationary blades 2 are provided in multiple stages in the axial line direction in a casing 1. While moving blades 4, provided in the periphery of a rotor 3, are rotatably provided through a motor shaft 5. And a pump provides a thrust/radial bearing part, which comprises a thrust receiving member 7, radial receiving member 9 and a supporting member 8 provided being opposed to these thrust receiving member 7 and radial receiving member 9, to be arranged in the intermediate part of the motor shaft 5. Further the pump arranges an end part of the motor shaft 5 to be inserted and fitted to a fluid sealed chamber 10. In this way, the pump enables a lubricant to be suppressed from generating its dissolved gas further a high vacuum to be easily attained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention has a rotor supported in a casing interior for generating a high vacuum containing no bearing lubricant, particularly lubricating oil. This invention relates to vacuum pumps, particularly turbomolecular pumps that require high-speed rotation.

[Conventional technology]

Generally, semiconductor manufacturing equipment, electron microscope equipment, vapor deposition equipment, high vacuum furnaces, vacuum tube manufacturing equipment, etc. require a highly purified vacuum, and for this reason, a vacuum pump is always provided as an accessory device.

There are various types of vacuum pumps in which a rotor is supported within a casing to generate a high degree of vacuum, such as oil diffusion vacuum pumps, turbomolecular pumps, positive displacement vacuum pumps, and axial flow vacuum pumps. There are things that are often used,
They are used depending on their purpose.

Among these, turbomolecular pumps and axial flow vacuum pumps are easy to start up and can be applied to a wide range of vacuum degrees, so they have become popular in a wide range of fields with the development of precision processing technology. These turbomolecular pumps have pressure values in the molecular pressure range of 1O-2 to 10-
” In order to increase the pressure of mm11g to 4, the number of rotations should be approximately 2.
It is known that special problems often occur in rotor support because the rotor rotates at high rotational speeds with a maximum rotation of 0.0 OOr, p, m or more.

Conventional turbo-molecular pumps rotate rotary blades arranged at intervals between fixed blades at a high speed of rotation per minute, providing momentum in a certain direction to gas molecules to perform vacuum evacuation, resulting in high-speed rotation. The electric motor for this purpose is supplied with electric power using electric gC at a frequency higher than the maximum operating frequency. In addition, bearings for high-speed rotation are important parts that greatly contribute to the reliability of the pump, and lubricating oil is normally supplied to the bearings from a lubricating oil reservoir provided at the bottom of the pump casing to prevent wear and seizure of the bearings. It is prevented.

As mentioned above, turbomolecular pumps are vacuum pumps with excellent properties that can easily achieve ultra-high vacuums, but since they use lubricating oil in the bearings, the lubricating oil must be removed when the pump is stopped. The lubricant decomposes due to the mechanical contact that occurs locally in the bearing during operation, producing low molecular weight molecules that diffuse into the vacuum chamber. Turbomolecular pumps using magnetic bearings were sometimes used for vacuum equipment that required.

[Problem that the invention seeks to solve]

When the rotor is supported by a bearing in a conventional turbo-molecular pump, the rolling bearing or ball bearing used is often used with an oil or grease lubricant for solid contact, and the lubricant circuit is used to support the rotor. However, it is difficult to ensure proper lubrication and sufficient cooling of this bearing device, and oil lubrication such as grease tends to cause oil mist to get mixed into the vacuum, resulting in extremely short lifespan, and the bearing Hydrocarbons such as lubricant vapor or lubricant thin air are generated due to the local heat generation phenomenon caused by solid-solid contact, and the vapor tends to diffuse toward the high vacuum side, causing severe deterioration of the lubricant. In addition to requiring an expensive heating process over a long period of time when restarting the pump, hydrocarbons in a vacuum have the disadvantage of reducing the resistance to electrical flash, especially for bearings. If a metal material is used for the pole, the deformation will be large, and if the lubricant deteriorates, the release of radiant heat will decrease, the cooling effect will decrease, and the durability will be lost. The problem becomes even more serious as the bearing comes into solid contact with the bearing and the bearing reaches the end of its life after a predetermined operating period.

Furthermore, even when magnetic bearings are used, although magnetic bearings require an extremely complex control device, the magnetic bearing effect is completely lost during normal power loss, Uμ, or power outage, and rotation during high-speed rotation. The disadvantage is that the blades cannot be supported, and for this reason, turbomolecular pumps that use magnetic bearings must be equipped with an emergency battery and an emergency power generation flywheel as a countermeasure in the event of a power outage. -411 as there is no means to release heat from the body side.
However, it cannot be said that the vacuum pump has safety advantages.

The present invention aims to eliminate these conventional drawbacks, and allows for proper lubrication without solid contact, no local heat generation, suppresses the generation of decomposition gas from the lubricant, and ensures stable rotation without deterioration. The purpose of this project is to provide a highly reliable and durable turbomolecular pump in a simple and inexpensive form that enables ultra-high-speed operation of the pump and easily generates a clean high vacuum. be.

(Means for Solving the Problems) The present invention provides stator blades provided in multiple stages in the axial direction within a casing, and stator blades provided on the outer periphery of a rotor located between the stator blades and located at the center of the casing. In order to freely rotate the rotor blades as a rotating body via the motor shaft, the rotating body is rotatably supported by a radial bearing part and a thrust bearing part, each having a groove for generating dynamic pressure, provided on the motor shaft. In a turbo molecular pump, a thrust/radial bearing section consisting of a thrust receiving member, a radial receiving member, and a supporting member installed opposite these is provided in the middle part of the motor shaft, and the end of the motor shaft is fitted into a fluid enclosure chamber. This is a turbo-molecular pump characterized by the fact that it is inserted.

Embodiment C] The embodiment of the present invention will be explained with reference to the example of FIG. In a turbo molecular pump, the rotor blades 4 provided on the outer periphery of a rotor 3 located at the center of the casing are rotatably rotatable via a motor shaft 5. a thrust receiving member 7 with a groove 6;
That is, a thrust receiving member 7 attached to the rotor 3, a supporting member 8 facing the thrust receiving member 7, and a sleeve-shaped radial shaft provided at the intermediate portion of the motor shaft 5 and having a herringbone-shaped groove 61 formed on the outer peripheral surface. A thrust radial bearing section consisting of a receiving member 9 and a supporting member 18 provided opposite thereto is provided, and the end of the motor shaft is fitted into a fluid enclosure chamber 10 to form a turbo molecular pump.

In this case, the end of the motor shaft may also be rotatably supported by a radial bearing portion consisting of a sleeve 1G having a herringbone groove 61 formed on its outer circumferential surface and a support member 17 into which the sleeve 16 is fitted. At least one or both of the thrust radial bearing section or the radial bearing section consisting of the sleeve 16 and the support section 17 is made of a ceramic sintered body.

The thrust radial bearing portion is provided on the rotor 3 and includes a thrust receiving member 7 in which a spiral groove 6 is formed, a supporting member 8 corresponding to the thrust receiving member 7, and a cylindrical supporting member 18 of the radial receiving member 9. and a radial receiving member 9 that fits into the inner circumferential surface of the cylindrical supporting member 18 and has a herringbone groove 61 formed on its outer circumferential surface. A magnetic fluid is sealed in the gap formed and a magnet 11 is used to control the magnetic fluid.

It should be noted that the motor shaft 5 has a herringbone-shaped groove 6 on the outer circumferential surface at the intermediate portion and the shaft end. 17.1, each having a smooth surface.
It is best to deploy it in parallel to 8.

Further, the fluid filled chamber 1o includes lubricating oil, grease,
It is filled with a viscous fluid such as a lubricant or a magnetic fluid, and is sectioned and arranged at a position in the casing where the end of the motor shaft is inserted.

Further, as the radial receiving member 9, the motor shaft 5
A herringbone-shaped groove 6. is formed on the outer circumferential surface of the sleeve. forming a gauging or bearing member 18
Although it is used, it can also be provided outside the stepped part formed on the motor shaft 5 or on the outer periphery of the motor shaft. In this case, consideration may be given to filling the gap formed between the two with grease, oil, or, if it is difficult to retain these, magnetic fluid to improve the sealing effect of the motor chamber.

Although it is considered that the surface opposite to the surface with the hydrodynamic pressure generating groove is a smooth surface, it is possible to form a spiral groove 6 or a herringbone groove 61 as the dynamic pressure generating groove. Hard ceramic material such as SiC sintered body, B
It is preferable to form the thrust radial bearing part or the radial bearing part using an α-3iC sintered body containing eO or a 5isNa* viscous body.

In the figure, 12 is a drive motor, 13 is a power supply connector, 14 is a discharge port, and 15 is a suction port.

In the example shown in FIG. 2, a sleeve-shaped radial bearing member 9 provided with a herringbone-shaped groove 61 as a thrust radial bearing portion is fixed to the motor shaft 5 and inserted into the cylindrical support member 18. A magnetic fluid is sealed in the gap formed by forming a bearing member 8 corresponding to a flange-shaped thrust receiving member, and a magnet made of a permanent magnet or a secondary conductor holds and controls the magnetic fluid. 11 to provide both a sealing effect and a thrust/radial bearing function.

The rotor 3, which is a rotating body with moving blades 4, is rotatable by the motor shaft 5, and the mass balance is carried out on the radial bearing part, which is composed of a thrust radial bearing part with a groove for generating dynamic pressure, a sleeve 1G, and a support member 17. It maintains good fluid balance and magnetic balance, rotates smoothly, and can operate at extremely high speeds.

In this case, a spiral groove 6 for generating dynamic pressure is formed in the thrust bearing member 7 constituting the bearing, and the other surface is a smooth plane to serve as the thrust bearing. A herringbone groove 6I for generating dynamic pressure is formed on either the outer circumferential surface of the sleeve in 5 or the cylindrical surface of the through hole of the hollow cylindrical support, and the other surface is formed into a smooth cylindrical surface. In both embodiments, there is a spiral groove 6 for supporting the thrust load;
Herringbone groove to support radial loads 6. The groove width is approximately 3 to 50 μm. In addition, the surface with this hydrodynamic pressure generating groove is made into a smooth flat land surface with an overall waviness of 0.3 μm or less and a maximum surface roughness of 0.1 μm, and is then shot blasted to a depth of 3 to 50 μm. This is a spiral-shaped groove machined.

Bearings that utilize the hydrodynamic effect are made of hard ceramic materials, and the grooves for generating hydrodynamic pressure can be machined with high precision. It is maintained even in the generated state, and moreover, it can be started,
It can be used effectively and with durability even if the load is to a certain extent even against fixed friction that occurs when stopping.

In the example shown in Fig. 3, the thrust/radial bearing part is of a type in which the end surface with the dynamic pressure generating groove formed is provided on the supporting member side to serve both thrust and radial functions, and is provided at the end of the motor shaft. It is designed to provide an effective bearing function with the radial bearing section. In the example shown in Fig. 4, a sleeve-shaped radial bearing member fixed to the motor shaft 5 and a plate-shaped thrust bearing member are combined into a single unit for thrust and thrust bearing.
It was used as a radial bearing.

In each of the embodiments, the fluid chamber 10 is filled with a viscous fluid such as lubricating oil or a magnetic fluid, and is protruded from the casing. It can also be replaced with gas,
In a dynamic pressure thrust bearing including the thrust bearing member 7, the frictional resistance is small even if the viscosity is a little high, and in a radial bearing, since the gap is constant, the viscosity immediately becomes resistance, so a thicker viscosity is used on the thrust side. It is better to use a small lubricant on the radial side.

〔Effect of the invention〕

The present invention provides a thrust/radial bearing section consisting of a thrust receiving member, a radial receiving member, and a supporting member installed opposite to these in the intermediate portion of the motor shaft, and the end of the motor shaft is fitted into a fluid enclosure chamber. By inserting OI, it is possible to minimize the generation of decomposition gas from lubricating oil that occurs with conventional balls and bearings, and it also has the effect of sealing in grease and oil lubricants, while reducing the surface area in contact with the outside. Since the amount of evaporation is smaller than other bearings, the amount of evaporation is extremely small, making it easy to retain the lubricant. It is also possible to accurately seal the atmosphere side and the vacuum system, and the bearing action can be effectively exerted. There is no local solid contact with the thrust bearing or radial bearing that supports the body's own weight (there is no heat generation phenomenon even if oil or grease lubrication is used, and the generation of decomposed gas from the lubricant is suppressed to the utmost, There are no problems caused by deterioration or wear and tear of the lubricant.
Constructs a durable turbo-molecular pump that enables stable rotor operation at ultra-high speeds and easily achieves high vacuum. A durable turbo-molecular pump that can operate well with strong damping action and large unbalance. Simple and inexpensive form. This has the effect of making it significantly more compact.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of an embodiment of the present invention, FIG. 2 is a partially enlarged cutaway side view, and FIGS. 3 and 4 are longitudinal sectional views of other embodiments. 1...Casing, 2...Stator blade, 3...Rotor,
4... Moving blade, 5... Motor shaft, 6, 6I... Groove,
7... Thrust receiving member, 8... Supporting member, 9...
Radial receiving member, lO...Fluid enclosure chamber, 11...Magnet, 16...Sleeve, f7. I8...Supporting member.

Claims (6)

[Claims] (1) The stator blades are provided in multiple stages in the axial direction within the casing, and the rotor blades located between the stator blades and provided on the outer periphery of the rotor located at the center of the casing are connected to the rotating body via the motor shaft. In a turbo molecular pump, the rotating body is rotatably supported by a radial bearing section and a thrust bearing section, each having a groove for generating dynamic pressure, provided on the motor shaft. A turbo-molecular pump characterized by having a thrust radial bearing portion consisting of a receiving member, a radial receiving member, and a supporting member installed opposite these, and having a motor shaft end inserted into a fluid enclosure chamber. . (2) The thrust/radial bearing section includes a thrust receiving member that is disposed opposite to the rotor and has a spiral dynamic pressure generating groove formed therein, and a cylindrical support of a supporting portion corresponding to the thrust receiving member and a radial receiving member. The turbo according to claim 2, which comprises a member and a sleeve that fits into the inner circumferential surface of the cylindrical support member and has a herringbone-shaped dynamic pressure generating groove formed on the outer circumferential surface. molecular pump. (3) the thrust radial bearing encloses a magnetic fluid in a gap formed between the rotating member and its support;
The turbo-molecular pump according to claim 1 or 2, comprising a magnet for controlling the magnetic fluid. (4) The motor shaft has a sleeve having a herringbone-shaped dynamic pressure generating groove formed on the outer circumferential surface fixed to the intermediate portion and the shaft end, and each sleeve is attached to a smooth surface supporting portion. 4. A turbomolecular pump according to any one of claims 1 to 3, wherein the turbomolecular pump is equipped with a turbomolecular pump according to any one of claims 1 to 3. (5) The fluid chamber is one in which a viscous fluid such as lubricating oil or grease or a magnetic fluid is sealed, and is divided and arranged at a position of the casing where the end of the motor shaft is inserted. A turbomolecular pump according to any one of the ranges 1 to 4. (6) Claims 1 to 5, wherein the thrust radial bearing portion is made of a ceramic sintered body.
A turbomolecular pump according to any one of the following paragraphs.