JPS62282193A - Turbo molecular pump - Google Patents

Abstract

PURPOSE:To prevent degradation of the rotary performance by supporting a rotary member having a rotor blade by means of a lower bearing in the central protion of a mortor. CONSTITUTION: A rotor 4 of a motor is shrinkage fitted over an outer cylindrical section of a rotary shaft 15. The lower end of an inside post section 17 of the rotary shaft 15 is supported by a spherical spiral groove bearing 12 and it is positioned in the central portion of a rotor 4 of the motor. Consequently, even when the electromagnetic force or the electromagnetic balance force between the stator and the rotor of the motor is produced in the horizontal direction, these external force passes through the supporting point of the lower bearing 12 thereby the degradation of the rotary performance is prevented.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention [Field of Application for V Business Owners] This invention relates to a turbo molecular pump (vacuum molecular pump) device for realizing high vacuum equipment such as semiconductor manufacturing equipment, for example. It is.

[Conventional technology]

Magazine (Ameri
can vacuuz 5ociety (1983)
Pages 224-227, “A New type”
of turbomolecular vacuum
There was something published in "ump bearing").

In general, the present inventor has improved the bearing for supporting the rotating body in the specification of Utility Model Application No. 1983-78395. FIG. 4 is a longitudinal sectional view showing the turbomolecular pump device. In the figure, (1) is a rotor blade that sucks fluid, and is provided on the outer periphery of a rotating body that rotates about a rotating shaft (c). (2) is a stator blade arranged opposite to the rotor blade (1), and is attached to the inner wall of the cylindrical casing (3) of the device. (4) is a rotor of an electric motor that drives a rotating body composed of rotor blades (1) and a rotating shaft (A), and is attached, for example, to the rotating shaft α by shrink fitting or the like. (5) is the stator of the electric motor, and the frame (1
It is fixed at 1. (c), α4 is the rotation axis of the rotating body 0
It is a bearing that rotatably supports υ, and for example, supports the rotating shaft αQ at its lower and upper parts. Normally @ is a spherical spiral groove bearing, and α is a touchdown bearing.

(7) is an exhaust port for exhausting the fluid (11a), (ll'b) inside the device, for example, air in many cases, to the outside of the device. (9) is a base that supports the entire device. (2) is a spherical spiral groove bearing (A) which is the lower bearing of the rotating body.
It is a lubricating oil necessary for this purpose, and oil with a very low saturated vapor pressure of, for example, 10 TOrr or less at room temperature is usually used.

αQ is a flange for attaching a turbo-molecular pump device, and is attached to a device body that requires high vacuum, such as a semiconductor I-made @ Sumire.

Next, the operation of the turbo-molecular pump device configured as described above will be explained.

When a turbomolecular pump device attached to equipment that requires high vacuum is rotated at high speed, usually at about 100 rpm, via an electric motor (4), (51), The fluid inside the device body (l
la )+ (l], b) is exhausted to the outside air through the gap between the rotor blade (1) and the stator blade (2), and the pressure inside the device gradually decreases to achieve a high vacuum. Normally, the rotor blades (1) and stator blades (2) are designed to have a specially designed shape, and even in a unidirectional flow molecular pump device, the pressure is reduced to the flange of the device that requires a high vacuum. The pressure is lower at αQ, and the pressure increases as it approaches the exhaust port side (7) 0 Normally, the number of rotor blades (1),
That is, the greater the number of stages, the higher the vacuum can be achieved. However, the higher the rotation speed, the better the performance and the smaller and lighter device.

Let's talk about rotational performance. Before the rotating body rotates, that is, when stopped, the rotating body has a touchdown bearing 0 station placed at the top,
It is supported by the spherical spiral groove bearing (2) which is the lower bearing. When the rotating body supported in this way is driven by the electric motors (4) and (5), in the low rotational speed range, both bearings C121 , (14) and rotated. However, when the rotational speed increases and reaches a certain number of rotations, usually several thousand rpm or more, the rotating body automatically detaches from the upper touchdown bearing α4) due to the gyroscopic effect of the rotating body, and rotates without contact. There are many things to do.

The lower bearing (■) is still in metal contact when it is stopped, but when the rotating body is rotated, it draws lubricating oil into the spherical spiral groove bearing (2), forming a hydrodynamic bearing. Rotates in a vesi bearing state.

[Problem that the invention seeks to solve]

In conventional turbo molecular pump devices, the lower bearing is located below the electric motor, so the electromagnetic force or electromagnetic unbalance force between the stator (5) and rotor (4) of the electric motor is acts as a horizontal disturbance. For example, by delaying the rotation speed at which the upper touchdown bearing α → becomes non-contact), due to this electromagnetic force or electromagnetic unbalanced force, there is a large amount of image capture in the low rotation speed range, which damages the lower bearing (6). This invention was made to solve the above-mentioned problems. The object of the present invention is to provide a turbomolecular pump device that can prevent rotational performance from deteriorating due to force.

[Failure to solve the problem]

A turbo-molecular pump device according to the present invention includes a casing having stator blades, a rotating body having a rotor blade disposed opposite to the stator blade and sucking fluid during rotation, a rotor formed on the rotating body, and a rotor formed on the rotating body. An electric motor that has a stator disposed opposite to the rotor and rotates a rotating body;
In a turbomolecular pump device equipped with an upper bearing that supports the rotating body at its upper part and a lower bearing that supports the rotating body at its lower part, the lower bearing supports the rotating body at the center of the electric motor. be.

[Effect]

Since the lower bearing in this invention supports the rotating body at the center of the electric motor, it prevents horizontal electromagnetic force or electromagnetic unbalanced force between the stator and rotor of the electric motor from becoming a moment that would knock down the rotating body. Prevents disturbance from acting on the rotating body.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
As shown in the figure, the lower part of the rotating shaft (4) is formed into, for example, a double cylindrical shape, and the rotor (4) of the electric motor is attached to the outer cylindrical part (end) of this rotating shaft by shrink fitting or the like. The spherical surface of the lower end of the rotary shaft is supported by a spiral groove bearing (6), and its position is located at the center of the rotor (4) of the electric motor.

In a turbomolecular pump mounted in this way, even if electromagnetic force or electromagnetic unbalance force between the stator and rotor of the electric motor occurs in the horizontal direction, these external forces will be applied to the lower bearing ( Since it is configured to pass through the support point according to (a), it does not create a moment that would knock down the rotating body. Therefore, compared to the conventional device, the rotation speed at which the touchdown bearing and the rotating body are not in contact becomes faster, and the electromagnetic force or electromagnetic imbalance force does not act on the rotating body as a disturbance, resulting in stable rotation. Furthermore, in the case of damage to the lower bearing, it is advantageous because the whirling, especially in the low rotation speed range, is reduced, and the life of the bearing is extended.

Another embodiment of the invention is shown in FIG. In the figure, α
η is a rotating body that has rotor blades (1) on its outer periphery and has, for example, a recess formed around the rotation axis αυ; For example, a rotor of an electric motor integrally formed with the rotating body (17) on the peripheral wall of the recess,
It has a built-in permanent magnet and is fixed. The wire is a stator (
(2) is an intake hole, @ is a lower bearing box, and Yu is a cooling fin. Even in this curved turbo molecular pump device, by supporting the rotating body with the lower bearing at the center of the motor, it is possible to prevent a reduction in rotational performance due to electromagnetic force or electromagnetic unbalanced force of the motor. Furthermore, in this embodiment, since the rotor 09 is arranged inside the rotating body 07), the structure of the rotating body αη can be made simpler than before, and it can withstand a larger centrifugal force than before. Therefore, it becomes possible to further increase the rotation speed of the rotating body αη. Therefore, the performance required of the turbo-molecular pump device is also improved.

Still another embodiment of the invention is shown in FIG.

In this figure, (19a) and (x9''0) are the magnetic shafts installed at the upper bearing (upper bearing), which prevent the rotating body from wobbling in the radial direction. This is a repulsion type non-contact magnetic bearing that can be configured as follows.With such a structure, in addition to the young fruit of the 8 examples above, a function is added to ensure that the rotating body is always maintained during rotation. Therefore, a turbo-molecular pump device with excellent rotational performance (as in the above embodiment) is obtained.

[Young fruit of invention]

As described above, according to the present invention, there is provided a casing having stator blades, a rotating body having rotor blades arranged opposite to the stator blades and sucking fluid during rotation, a rotor formed on this rotating body, and this rotor. A turbo-molecular pump device comprising a stator disposed facing the rotor, an electric motor for rotating the rotor, an upper bearing for supporting the rotor at its upper part, and a lower bearing for supporting the rotor at its lower part. By supporting the rotating body in the center of the electric motor with the lower bearing, it is possible to prevent a decrease in rotational performance due to the electromagnetic force or electromagnetic unbalanced force of the electric motor, thereby providing a turbo molecular pump device with excellent rotational performance. There is an effect that can be done.

[Brief explanation of drawings]

FIG. 1 is a vertical sectional view showing a turbo molecular pump device according to an embodiment of the present invention, FIGS. 21'il and 3 are longitudinal sectional views showing other embodiments of the invention, and FIG. 0 (1)... Rotor g, +21... Stator X, (3
) ... casing, (4) ... motive stator,
(5)...Electric motor rotor, 0■...Lower bearing, a
■... Upper bearing, (to)... Rotating shaft. In the drawings, the same reference numerals indicate the same or equivalent parts.

Claims (5)

[Claims] (1) A casing having stator blades, a rotating body having rotor blades disposed opposite to the stator blades and sucking fluid during rotation, a rotor formed on the rotor, and a rotor disposed facing the rotor. In the turbo molecular pump device, the turbo molecular pump device includes a stator provided therein, an electric motor that rotates the rotary body, an upper bearing that supports the rotary body at its upper part, and a lower bearing that supports the rotary body at its lower part. A turbo molecular pump device characterized in that a lower bearing supports the rotating body at a central portion of the electric motor. (2) The rotating body has a recess formed around the rotating shaft, and the electric motor is supported by a peripheral wall of the recess, and a rotor formed in the rotary body, and a motor is disposed in the recess facing the rotor. The turbo-molecular pump device according to claim 1, characterized in that it has a stator. (3) The turbo-molecular pump device according to claim 1 or 2, wherein the upper bearing is a touchdown bearing, and the lower bearing is a spherical spiral groove bearing. (4) The upper bearing has a magnetic bearing that prevents the rotating body from wobbling in the radial direction.
The turbomolecular pump device according to any one of items 1 to 3. (5) The turbo-molecular pump device according to claim 4, wherein the magnetic bearing is a repulsion type magnetic bearing.