JPH05157090A - Turbo-molecular pump - Google Patents

Abstract

PURPOSE:To prevent a situation that a fixed blade deformed due to dynamic lift generated at the time of entry into the atmosphere is brought into contact with a rotary blade to break a turbine. CONSTITUTION:A stepped portion 2e is formed in an inner circumferential supporter 2a of a rotary blade group 2. An axial distance d3 between an inner circumferential supporter 4a of a fixed blade group 4 and the inner circumferential supporter 2a in the stepped portion 2e, which faces to the inner circumferential supporter 4a on a suction port 5 side, is set shorter than an axial distance d2 between a suction port end 4d on the inner circumferential side of a fixed blade 4c and an exhaust port end 2d on the inner circumferential side of a rotary blade 2c.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a turbo molecular pump used for continuous exhaust of gas under medium vacuum or low vacuum, including generation and maintenance of high vacuum and ultra-high vacuum. ..

[0002]

2. Description of the Related Art FIG. 3 shows an example of a conventional turbo molecular pump. In this structure, a rotor blade group 2 projecting from the outer circumference of a rotor 1 and a fixed blade group 4 projecting from the inner circumference of a stator 3 are alternately arranged in multiple stages in the rotation axis m direction to form a turbine T.
The turbine T is configured to be able to perform an exhaust action from the intake port 5 toward the exhaust port 6. The rotary blade group 2 of each stage is formed by projecting a large number of rotary blades 2c at outer circumferential equiangular positions of an annular inner support 2a formed integrally with the rotor 1. The fixed blade group 4 is formed by forming a large number of fixed blades 4c at an equiangular position between an outer peripheral side support 4a and an inner peripheral side support 4b which form an annular shape. When the description of the fixed blade group 4 is captured, as shown in FIG. 4, a blade portion is cut out by etching at the central portion of a thin annular plate made of stainless steel or aluminum, and the cut portion is pressed. The fixed blade 4c is formed by performing bending processing. At that time, an annular outer peripheral side support 4a and an annular outer peripheral side support 4b are formed at the portions left uncut on the inner and outer peripheral sides. The outer peripheral side support 4a of the fixed blade group 4 is held between the spacers 3a laminated on the inner periphery of the outer cylinder, so that the fixed blade group 4 is supported on the stator 3 side. The fixed blade group 4 is divided in half at the time of assembling, and is assembled in an annular shape while being inserted into both sides of the rotor 1.

[0003]

By the way, the turbine T performs an exhaust action by rotating the rotary vane group 2 at a high speed in a vacuum of 1 Torr or less, and its rotational speed is usually 20000-90000 rpm. The peripheral speed at the tip of the rotor 2c reaches 200 to 400 m / s. During this operation, when the atmosphere rushes into the pump due to an erroneous operation and the internal pressure rises sharply, a strong swirling air flow u is generated around the fixed blade 4c as shown in FIG. v indicates the rotation direction of the rotary blade 2c at that time. And, by the air flow u,
Lifting force F is generated on the fixed blade 4c, and the fixed blade 4c is deformed together with the outer peripheral side support 4a toward the intake port 5 side as shown by an imaginary line in FIG. At that time, in the conventional turbo molecular pump, as shown in the same figure, between the inner peripheral side intake port end 4d of the fixed blade 4c and the inner peripheral side exhaust port end 2d of the rotary blade 2c formed by bending. The axial separation distance d ₂ of the rotor blade group 2 facing the inner support 4b of the fixed blade group 4 and the inner support 4b of the fixed blade group 4c on the intake port 5 side is equal to the amount by which the fixed blade 4c is twisted. It is smaller than the axial separation distance d ₁ from the inner support 2a. Therefore, when the deformation based on the above-mentioned lift force F occurs, the fixed blade 4c contacts the rotary blade 2c before the fixed blade inner peripheral side support 4b contacts the rotary blade inner peripheral side support 2a. The blades 4c, 2c mesh with each other and the turbine T is damaged, resulting in a serious accident.

Therefore, in the past, the fixed blades 4c were so arranged that the deformation of the fixed blades 4c was sufficiently small even if there was an entry into the atmosphere.
Or make the blades thick enough to reduce the deformation.
Such a situation was avoided by determining whether the axial separation distance d ₂ between c and the rotary blade 2c is sufficiently wide.

However, in the above-mentioned method, the space between the fixed blade 4c and the rotary blade 2c is narrowed, and the exhaust flow path is narrowed, resulting in a drawback that the exhaust speed is lowered. There is. Further, the method (1) has a drawback that the axial interval between the rotary blade groups (2) becomes large, and accordingly the bearing portion for supporting the rotor (1) also needs to be made large, which leads to an increase in size of the entire pump.

The present invention has been made in view of such a problem, and it is possible to effectively protect the turbine from the inrush to the atmosphere without lowering the exhaust speed and increasing the size of the pump. The purpose is to provide a turbo molecular pump.

[0007]

The present invention adopts the following constitution in order to achieve the above object.

That is, in the turbo molecular pump according to the present invention, the rotor blade group supported by the rotor through the annular inner peripheral side support, and the stator supported by the outer peripheral side support and the inner peripheral side support. In a turbo molecular pump comprising a fixed blade group and a rotating blade group and a fixed blade group which are alternately arranged in multiple stages in the axial direction to form a turbine, The axial separation distance between the inner peripheral side support and the inner peripheral side support of the rotary vane group facing on the intake port side is defined as the inner peripheral side intake port end of the fixed blade and the inner peripheral side exhaust port of the rotary blade. It is characterized in that it is smaller than the axial separation distance from the end.

[0009]

With this structure, the atmosphere rushes into the pump while the rotary blades are rotating at high speed, and a strong lift is generated on the fixed blades, which deforms the inner peripheral side toward the intake port side. However, the distance between the inner peripheral side support and the inner peripheral side support of the rotary blade is smaller than the distance between the inner peripheral side intake port end of the fixed blade and the inner peripheral side exhaust port end of the rotary blade. Since it is set to
The inner-side support of the fixed blade comes into contact with the inner-side support of the rotating blade before the fixed blade comes into contact with the rotating blade. Then, the inner peripheral side support of the fixed blade will not be further deformed after being attached to the inner peripheral side support of the rotary blade, and will continue to slide relative to the inner peripheral side support of the rotary blade at that position. Therefore, the fixed blade is also held at that position, and it is prohibited to approach the rotor blade side any further. Therefore, this can reliably avoid the situation where the fixed blade and the rotating blade come into contact with each other when entering the atmosphere.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.
Will be described. It should be noted that parts common to those in FIGS. 3 to 6 are denoted by the same reference numerals, and description thereof will be partially omitted.

This turbo-molecular pump has a fixed blade group 4 similar to the conventional one. That is, this fixed blade group 4 is
A portion of the thin annular circular plate made of stainless steel or aluminum as shown in FIG. 4 which becomes the blade is cut out by an etching method, and the cut portion is bent by press working to form the fixed blade 4c. In addition to being formed, an annular outer peripheral side support 4a and an inner peripheral side support 4b are formed at the portions left uncut on the inner and outer peripheries, respectively. In addition, the rotary blade group 2 also has the same structure as the rotor 1
The annular inner support 2a is formed integrally with the outer peripheral support 2a at the same angular position as the outer periphery of the inner support 2a. By bulging toward the side as shown in FIG.
e is integrally formed. By providing this step portion 2e on the lower surface of the inner peripheral side support 2a, the step portion 2e
The inner peripheral side support 4b of the fixed blade 4c corresponding to the portion, and the rotary blade 2c facing the inner peripheral side support 4b on the intake port 5 side.
The axial dimension d ₃ of the inner peripheral side support 2a of the
It is designed to be smaller than the axial separation distance d ₂ between the inner peripheral side intake port end 4d and the inner peripheral side exhaust port end 2d of the rotary blade 2c.

With such a structure, the rotor blade 2
The atmosphere rushes into the pump while c is rotating at a high speed, and a strong lift F is generated on the fixed blade 4c as shown by the imaginary line in FIG. Even if it is deformed to the intake port 5 side as shown by the line, by setting d ₃ <d ₂ , the inner peripheral side support 4b of the fixed blade 4c is provided before the fixed blade 4c contacts the rotary blade 2c. Rotor 2c
It can be brought into contact with the inner peripheral side support 2a at the stepped portion 2e. Then, the inner support 4b of the fixed blade 4c does not deform further after being in contact with the inner support 2a of the rotary blade 2c, and slides relative to the inner support 2a at that position. Since it continues, the fixed blade 4c is also held at that position, and it is prohibited to approach the rotary blade 2c further. Therefore, this structure can reliably avoid contact between the fixed blade 4c and the rotary blade 2c. As described above, this turbo-molecular pump can effectively protect the turbine T from damage at the time of entry into the atmosphere without lowering the exhaust speed or increasing the size of the pump itself. In other words, assuming that the robustness of the turbine T is the same level as that of the conventional pump, the pumping speed of the pump according to the present embodiment can be improved more than that of the conventional pump, and the pump itself is relatively small. The effect that it can be realized is exhibited.

Although the embodiment has been described with reference to the magnetic bearing type turbo-molecular pump, it goes without saying that the present invention can be applied to other bearing types as well. Further, the configuration of each unit is not limited to the illustrated example, and various modifications can be made without departing from the spirit of the present invention.

[0014]

According to the present invention, by performing the dimension setting described above, even if a lift is generated on the fixed blade due to atmospheric rush and the like, and the deformation occurs toward the intake port side, the fixed blade contacts the rotary blade. Prior to this, the inner peripheral side support of the fixed blade can be brought into sliding contact with the inner peripheral side support of the rotary blade. Therefore, it is possible to obtain an effect that it is possible to reliably protect the turbine from damage caused by contact with the rotating blades by prohibiting the fixed blades from being deformed to a certain extent or more.

[Brief description of drawings]

FIG. 1 is an overall vertical sectional view showing an embodiment of the present invention.

FIG. 2 is an enlarged view of a main part of FIG.

FIG. 3 is an overall vertical sectional view corresponding to FIG. 1 showing a conventional example.

FIG. 4 is a perspective view showing a fixed blade group used in the conventional example.

FIG. 5 is a development view for explaining the interaction between the fixed blade and the rotary blade of the conventional example.

FIG. 6 is an enlarged view of a main part of FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Rotor 2 ... Rotor blade group 2a ... Inner peripheral side support 2c ... Rotor blade 2d ... Inner peripheral side exhaust port end 3 ... Stator 4 ... Fixed blade group 4a ... Outer peripheral side support 4b ... Inner peripheral side support 4c ... Fixed blade 4d ... inner circumferential side inlet end d _2, d ₃ ... axial distance m ... rotation axis T ... turbine

Claims (1)

[Claims] 1. A rotary vane group supported by a rotor through an annular inner peripheral support, and a fixed blade group supported by a stator through an outer peripheral support and an inner peripheral support. In a turbo molecular pump in which the rotating blade group and the fixed blade group are alternately arranged in multiple stages in the axial direction to form a turbine, the inner peripheral side support of a fixed blade group and the intake port side The axial separation distance between the inner peripheral side support of the rotating blade group facing each other in the axial direction is defined as the axial separation distance between the inner peripheral side intake port end of the fixed blade and the inner peripheral side exhaust port end of the rotary blade. Turbo molecular pump characterized by being made smaller than.