JPS63159695A - Turbo molecular pump - Google Patents

Abstract

PURPOSE:To improve performance, by forming a rotor blade in an exhaust port side to a smaller diameter and a stator blade, positioned being opposed to the rotor blade, to a divided ring while a fixed wall, to which the rotor blade approaches, in the internal periphery of the stator blade. CONSTITUTION:A bottom part rotor blade 7B forms its outside diameter D smaller than the outside diameter D0 of an upper part rotor blade 7A. A stator blade 8B in a position, opposed to the bottom part rotor blade 7B, is formed by a two-divided ring. The stator blade 8B forms in its internal periphery a blade wall 8a and a fixed wall 8b opposed to the rotor blade 7B. Accordingly, an effective exhaust speed is obtained in a wide pressure region by enabling a rotor 3 to reasonably light decrease its weight.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application 1] The present invention relates to a high-performance turbomolecular pump with improved rotor and stator structures.

[Prior Art] A turbomolecular pump achieves high vacuum through the mechanical exhaust action of a row of turbine blades formed by rotor blades and stator blades arranged alternately in the axial direction. The structure consists of rotor (turbine) blades that are integrally or separately protruding from the rotor around a rotor that is rotatably arranged in a casing, and a rotor (turbine) blade that is oriented in the opposite direction between the rotor blades, the outer periphery of which is held by a spacer. The stator (turbine) blades inserted in the turbine are stacked in an appropriate number of stages from the intake port to the exhaust port. In this type of turbomolecular pump, the outer diameter of each rotor blade is constant in the axial direction for convenience in manufacturing and assembly.

[Problems to be Solved by the Invention] Generally speaking, in a turbomolecular pump, the gas compression performance becomes more important toward the exhaust port, and for this reason, the rotor blade length on the exhaust port side is made shorter than that on the intake port side. I try to keep it short. In addition, in the case of a turbomolecular pump, the compression ratio of the gas taken in from the intake port is sequentially compressed in the turbine blade rows and sent to the blade row on the exhaust port side until the exhaust gas is sucked into the back pump is very high. It is useful to shorten the rotor blades on the exhaust port side in order to reduce the flow path of the turbine blades on the exhaust port side.

For these reasons, conventional turbomolecular pumps
The rotor blade length is changed in the axial direction and the blade length is shortened on the exhaust port side, but under the above-mentioned condition where the rotor blade outer diameter is constant, shortening the rotor blade length will inevitably result in a shorter rotor blade length. The outer diameter of the rotor body on which the rotor blades are protruded becomes large on the exhaust port side. However, when a turbomolecular pump is in operation, it rotates at extremely high speeds, and each part of the rotor is subject to extremely large stress due to centrifugal force (proportional to the square of the radius). In order to prevent this part from breaking, it is necessary to increase the thickness of the rotor and to suppress the rotor rotational speed to a certain limit. In other words, in the conventional rotor configuration in which the outer diameter of the rotor on the exhaust port side is large, it is necessary to reduce the weight of the rotor, increase its rotation speed, and improve the performance of the turbomolecular pump so that it can work effectively over a wide pressure range. The result is contradictory to the request.

The present invention focuses on these problems and attempts to make it easier to improve the performance of this type of turbomolecular pump by reducing the outer diameter of the rotor on the exhaust port side, where the centrifugal force is most applied. It is something that you do.

[Means for Solving the Problems] As a means for achieving the above-mentioned object, the present invention provides a turbine blade array in which rotor blades protruding from the rotor and stator blades whose outer peripheries are held by spacers are arranged alternately. In the turbo molecular pump comprising the rotor blade, the one on the exhaust port side is formed to have a small diameter, and the stator blade facing the rotor blade on the exhaust port side is formed into a split ring, and the stator blade is formed into a split ring. The present invention is characterized in that a fixed wall is formed on the inner periphery to which the rotor blades are brought close.

[Operation] With this configuration, the outer diameter of the rotor blade is made small on the exhaust port side where the rotor blade length is shortened, so the outer diameter of the rotor can be made small at this portion. If the outer diameter of the rotor on the exhaust port side is small, the centrifugal force applied during pump operation will be small, so the entire rotor can be made smaller in diameter and thinner, making it lighter in weight. Combined, it becomes possible to increase the rotor rotational speed without difficulty. In addition, the stator blade in the part facing the rotor blade on the exhaust port side, which has a reduced diameter, is
Because it is a split ring, the rotor blades can be assembled and set from the side of the protruding rotor without any problems, and in this installed state, the fixed wall formed on the inner periphery comes close to the rotor blades. A necessary narrow flow path is formed between the rotor blade and the rotor blade.

[Example] Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

The drawings schematically show the inside of a turbomolecular pump according to the present invention with improved rotor and stator structures, and its configuration is as follows. A cylindrical casing 2 is erected on a base 1, and a bell-shaped rotor 3 is rotatably disposed within the casing 2. This rotor 3 has a small diameter part 3a, a middle diameter part 3b, and a large diameter part 3 from the upper part to the lower part.
C, and is fixed to one end of the rotor set 4 and rotated integrally with the shaft 4 around its axis. In this case, the rotor shaft 4 protrudes from the upper end of a motor housing M that is packaged into one assembly and is removably attached to the center of the base 1.

Therefore, multiple stages of rotor blades 7A and 7B are stacked and arranged around the rotor 3 in the casing 2, alternating with stator blades 8A and 8B from the intake port 5 at the upper end to the exhaust port 6 at the lower end, A row of turbine blades is configured to provide axial exhaust flow. Here, the rotor blades 7A located on the upper intake port side (hereinafter referred to as "upper rotor blades") are ring-shaped molded separately from the rotor 3, and are formed at the small and medium diameter portions of the rotor 3, respectively. 3a and 3b. In this part, while the blade length of the upper rotor blade 7A is gradually changed toward the exhaust port side,
Its outer diameter is kept at a constant Do. On the other hand, the rotor blade (hereinafter referred to as "lower rotor blade") 7B located on the lower exhaust port side is carved directly on the outer circumferential surface of the large diameter portion 3C of the rotor 3, and has a thicker blade and a shorter blade length. It is made into a short piece. The outer diameter of this lower rotor blade 7B is
The outer diameter Do of the upper rotor blade 7A is reduced.

Further, the stators g8A and 8B arranged alternately with the rotor blades 7A and 7B are arranged between ring-shaped spacers 9A and 9B stacked on the inner circumference of the casing 2, each having an outer circumference 8L.
8n is held and positioned and fixed. Among these, the stator blade 8A located opposite the upper rotor blade 7A is formed from an integral ring, while the stator blade 8B located opposite the lower rotor blade 7B is formed from a split ring. In other words, when setting this stator g8B around the lower rotor blade 7B, which has a smaller diameter than the upper rotor blade 7A, the pair of half blades are brought together from the side of the rotor 3 with the casing 2 removed. Make sure to incorporate it.

These stators J18B have a blade wall 8a inserted between the rotor m7B and forming a stator turbine blade, and a fixed wall 8b opposed to the rotor blade 7B formed on the inner periphery of the stator J18B. , the fixed wall 8 in its assembled state
The tip of the rotor blade 7B is close to b, forming a narrow flow path 10 there.

First of all, the turbomolecular pump with the above configuration is
In addition, it is possible to reasonably reduce the weight of the rotor 3. In other words, if the present invention is not applied to this type of pump, the outer diameter of its lowermost end must be expanded to approximately Do, but in this case, the maximum outer diameter of the rotor 3 is reduced to a smaller size;D( D<Do). Therefore, the centrifugal force acting on this portion is reduced, and the wall thickness necessary for strength can be reduced, and as a result, the weight of the rotor 3 as a whole can be reduced. By making the rotor 3 smaller in diameter and lighter in weight, mechanical and strength restrictions on the rotation of the rotor are relaxed, and the number of rotations thereof can be increased.

Also, if you adopt this new rotor and stator configuration,
On the premise of increasing the rotor rotational speed, it becomes possible to realize a turbomolecular pump that can effectively pump air in a wide pressure range. In other words, the upper turbine blade row formed by the large-diameter, long-span upper rotor blade 7A and the opposing stator blade 8A is effective in the molecular flow region, and as the rotor speed increases, the upper rotor blade 7A is effective in the molecular flow region. Increase the pumping speed. On the other hand, the lower turbine blade cascade, which is formed by the rotor blade 7B with a small diameter and short blade length and the stator blade 8B that opposes it and creates a narrow flow path 10 between them by its fixed wall 8b, is effective in the viscous flow region. In addition to exhibiting 1;, it also plays the role of further compressing the gas that is compressed by the upper turbine blade row and flows into the blade row. Therefore, when the rotor rotational speed is increased, the pumping speed in the viscous flow region increases in this part, and sufficient compression performance is ensured for pumping in the molecular flow region.

As described above, according to the turbomolecular pump according to the present invention, by improving the configuration of its rotor and stator, a high-performance pump that operates effectively in a wide range of pressures can be realized.

In the illustrated embodiment, the structure of the lower part of the rotor is different from that of the upper part, but the lower rotor blade 7B may be a turbine blade of the same type as the upper rotor blade 7A.

[Effects of the Invention] As described above, in the present invention, by improving the rotor and stator structures on the exhaust port side, the rotor can be made smaller and lighter, and its rotation speed can be increased, making it effective in a wide pressure range. A high-performance turbomolecular pump that exhibits a pumping speed of

[Brief explanation of the drawing]

The drawing is a sectional view of a turbomolecular pump according to an embodiment of the present invention.

Claims (1)

[Claims] In a turbo-molecular pump in which rotor blades protruding from a rotor and stator blades whose outer periphery is held by a spacer are alternately arranged to form a turbine blade row, one of the rotor blades on the exhaust port side is formed to have a small diameter. In addition, a turbo molecular pump characterized in that the stator blade facing the rotor blade on the exhaust port side is a split ring, and a fixed wall is formed on the inner periphery of the stator blade to which the rotor blade is brought close. .