JPH04295199A - Turbo molecular pump - Google Patents

Abstract

PURPOSE:To eliminate a need for a complicated control circuit and to reduce size and a cost. CONSTITUTION:A superconduction bearing comprising an upper permanent magnet 25 and an upper superconductor 26 is located between the upper part of a housing 1 and the upper part of a rotary shaft 2. A superconduction bearing comprising a lower permanent magnet 28 and a lower superconductor 29 is located between the lower part of the housing 1 and the lower part of the rotary shaft 2. As a result, the rotary shaft 2 is supported in a non-contact state to the inner side of the housing 1 through a pinning effect. Support of the under side of the rotary shaft 2 may be effected by means of an oil lubricating spherical spiral groove bearing.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved turbomolecular pump for achieving ultra-high vacuum conditions.

0002

2. Description of the Related Art Turbomolecular pumps as shown in FIG. 3 have conventionally been used to achieve ultra-high vacuum conditions in various experimental equipment or manufacturing equipment.

This turbo molecular pump includes a cylindrical housing 1 and a rotating shaft 2 supported inside the housing 1.
, a motor 3 for rotationally driving this rotating shaft 2, a moving blade body 4 supported by the rotating shaft 2, and a plurality of moving blades 5, 5 provided on the upper outer peripheral surface of this moving blade body 4. A cylindrical case 7 is provided surrounding the housing 1 and has an intake port 6 at one end, and a pump part 8 is supported by the inner circumferential surface of the case 7 together with the rotor blades 5. and an exhaust port 10 for discharging the gas sucked in from the intake port 6 by the pump section 8.

[0004] An upper magnetic ring 11 and a lower magnetic ring 12 are externally fitted and fixed at two positions on the upper and lower sides of the outer peripheral surface of the rotating shaft 2, respectively. Further, an upper radial electromagnet 13 is provided on the upper inner circumferential surface of the housing 1 at a portion facing the upper magnetic ring 11 to constitute an upper radial magnetic bearing 14. , the lower magnetic ring 1
A lower radial electromagnet 15 is provided in a portion facing 2 to constitute a lower radial magnetic bearing 16.

Further, a flange portion 20 made of a magnetic material is formed on the outer peripheral surface of the intermediate portion of the rotating shaft 2.
A pair of upper and lower thrust electromagnets 21 supported and fixed on the inner surface of the
, 21 are opposed to a flange portion 20 made of a magnetic material to constitute a thrust magnetic bearing 22.

The position of the rotating shaft 2 in the radial direction is determined by both upper and lower radial sensors 17 and 18 provided at two upper and lower positions on the inner surface of the housing 1. Each is detected by a thrust sensor 19 provided between the lower end surface and the bottom surface of the housing 1.

[0007] Signals representing the detected values of each sensor 17 to 19 are input to a controller (not shown), and this controller
Based on the signals from each of the sensors 17 to 19, energization to each of the electromagnets 13, 15, and 21 is controlled to maintain the rotating shaft 2 in a floating state. Therefore, the rotating shaft 2 can freely rotate at an extremely high speed without contacting any parts.

When the conventional turbo molecular pump constructed as described above is used, the motor 3 is energized while the rotary shaft 2 is maintained in a floating state by a signal from the controller. motor 3
When the rotary shaft 2 and the rotor blade body 4 rotate at high speed based on energization, the air sucked from the intake port 6 by the pump section 8 consisting of the rotor blades 5, 5 and stationary blades 9, 9 is transferred to the exhaust port 10. The part where the air inlet 6 is connected can be brought into an ultra-high vacuum state.

In FIG. 3, reference numerals 23 and 23 refer to parts that rotate together with the rotating shaft 2 and fixed parts that strongly rub against each other when power is stopped to each electromagnet 13, 15, 21 due to a power outage or the like. A touchdown bearing 24 is used to energize each electromagnet 13, 15, 21 and to prevent each sensor 17 to 1.
This is a connector for extracting the detection signal from 9.

0010

[Problems to be Solved by the Invention] However, in the case of the conventional turbo molecular pump that is configured and operates as described above, the structure is complicated because magnetic bearings are used to support the rotating shaft 2 in a floating state. Therefore, it was inevitable that production costs would increase.

That is, in order to maintain the rotating shaft 2 in a floating state by controlling the energization to each of the electromagnets 13, 15, and 21, each sensor 17 to 19 must be highly responsive and precise. Therefore, the controller that controls the energization of each electromagnet 13, 15, and 21 based on the signals from each sensor 17 to 19 must also be extremely responsive, which increases the manufacturing cost. .

The turbomolecular pump of the present invention eliminates the above-mentioned disadvantages.

[0013]

[Means for Solving the Problems] The turbo-molecular pump of the present invention, like the conventional turbo-molecular pump described above, includes a housing, a rotating shaft supported inside the housing via a bearing, and the rotating shaft. a rotor blade body supported by the rotary shaft; a plurality of rotor blades provided on the outer peripheral surface of the rotor blade body; a case having an air intake port;
A plurality of stationary vanes are supported on the inner circumferential surface of the case and constitute a pump section together with the rotor blades, and an exhaust port is provided for discharging the gas sucked in from the intake port by the pump section. .

Further, in the turbo molecular pump according to claim 1 of the present invention, an annular upper permanent magnet supported and fixed to the upper outer peripheral surface of the rotating shaft, and the housing an upper superconductor supported and fixed on the inner peripheral surface of the upper permanent magnet at a portion opposite to the outer peripheral surface of the upper permanent magnet; and an upper coolant reservoir provided inside the housing at a portion that contacts the upper superconductor. , an annular lower permanent magnet supported and fixed to the lower outer circumferential surface of the rotating shaft; and a lower superconductor supported and fixed to a portion of the inner circumferential surface of the housing opposite to the outer circumferential surface of the lower permanent magnet. , a lower coolant reservoir provided inside the housing at a portion that contacts the lower superconductor, and an inlet for feeding the coolant into the lower coolant reservoir and the upper coolant reservoir. It is characterized by

Furthermore, in the turbo molecular pump according to claim 2, instead of omitting the lower permanent magnet, the lower superconductor, and the lower coolant reservoir, or the lower permanent magnet, the lower superconductor, and the lower cooling Along with the agent reservoir, an oil-lubricated spherical spiral groove bearing is provided between the lower end surface of the rotating shaft and the bottom surface of the housing.

[0016]

[Function] In the case of the turbo-molecular pump of the present invention constructed as described above, the rotating shaft can be maintained in a floating state regardless of the structure without using a complicated control circuit.

That is, in the case of the turbo molecular pump described in claim 1, due to the pinning effect between the upper permanent magnet and the upper superconductor, the outer peripheral surface of the upper permanent magnet and the inner surface of the upper superconductor are connected. At the same time, the distance between the outer circumferential surface of the lower permanent magnet and the inner circumferential surface of the lower superconductor is kept constant due to the pinning effect between the lower permanent magnet and the lower superconductor. remains constant.

Further, in the case of the turbo-molecular pump described in claim 2, due to the pinning effect between the upper permanent magnet and the upper superconductor, the outer peripheral surface of the upper permanent magnet and the inner surface of the upper superconductor are At the same time, the lower end of the rotating shaft is kept concentric with the housing due to the oil-lubricated spherical spiral groove bearing provided between the lower end surface of the rotating shaft and the bottom surface of the housing. , and maintained in a floating state.

As a result, in either structure, the rotating shaft supporting and fixing the permanent magnet is supported inside the housing in a non-contact manner.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a first embodiment of the present invention, which corresponds to the invention set forth in claim 1. This turbo molecular pump has a cylindrical housing 1, a rotating shaft 2 supported inside the housing 1, and a motor 3 for rotationally driving the rotating shaft 2, as in the case of the conventional structure described above. , a rotor blade body 4 supported by the rotating shaft 2, and this rotor blade body 4
a plurality of rotor blades 5, 5 provided on the outer peripheral surface of the housing 1, a cylindrical case 7 provided surrounding the housing 1 and having an intake port 6 at one end; A plurality of stator blades 9, 9 are supported and constitute a pump section 8 together with the rotor blades 5, 5, and the pump section 8 provides the air intake port 6.
It is provided with an exhaust port 10 for discharging the gas sucked in from the air.

Further, in the turbo molecular pump of the present invention, an annular upper permanent magnet 2 is provided on the upper outer peripheral surface of the rotating shaft 2.
5 is supported and fixed, and on the inner circumferential surface of the housing 1, at a portion facing the outer circumferential surface of the upper permanent magnet 25, there is an annular upper portion having an inner diameter slightly larger than the outer diameter of the upper permanent magnet 25. A superconductor 26 is supported and fixed. and,
An upper coolant reservoir 27 is provided inside the housing 1 at a portion that contacts the outer peripheral surface of the upper superconductor 26, so that the upper superconductor 26 can be cooled freely.

Further, an annular lower permanent magnet 28 is fixed to the lower outer peripheral surface of the rotating shaft 2, and a portion of the inner peripheral surface of the housing 1 that faces the outer peripheral surface of the lower permanent magnet 28 is provided with a ring-shaped lower permanent magnet 28. Again, an annular lower superconductor 29 having an inner diameter slightly larger than the outer diameter of the lower permanent magnet 28 is supported and fixed. This lower superconductor 29 faces the lower side surface of the lower permanent magnet 28 in the axial direction. Further, a lower coolant reservoir 30 is provided inside the housing 1 at a portion that contacts the outer peripheral surface of the lower superconductor 29, so that the lower superconductor 29 can be cooled freely.

Further, an inlet port 31 is formed on the outer peripheral surface of the housing 1, and the inlet port 31, the upper coolant reservoir 27, and the lower coolant reservoir 30 are connected to each other.
These are communicated through passages 32 and 33, so that a coolant such as liquid nitrogen can be freely fed into the upper and lower coolant reservoirs 27 and 30, respectively.

In the case of the turbomolecular pump of the present invention constructed as described above, during operation, both the upper and lower coolant reservoirs 27
, 30, to keep both the upper and lower superconductors 26, 29 in a superconducting state, and to connect these superconductors 26, 29 and both upper and lower permanent magnets 25,
28 to create a pinning effect.

The pinning effect refers to a phenomenon in which a force acts between a superconductor and a permanent magnet in a direction that maintains the distance between the superconductor and the permanent magnet at a constant value. That is, when a superconductor and a permanent magnet are placed facing each other, when the distance between them exceeds the above-mentioned certain value, an attractive force acts on both, and when the distance between them is less than the above-mentioned certain value, A repulsive force acts between the two. Note that the above-mentioned attractive force and repulsive force are referred to as pinning force.

As mentioned above, both the upper and lower superconductors 26,
As a result of a pinning effect occurring between 29 and both the upper and lower permanent magnets 25 and 28, the distance between the outer peripheral surface of the upper permanent magnet 25 and the inner peripheral surface of the upper superconductor 26 is kept constant, and at the same time, The radial and axial distances between the outer circumferential surface and lower end surface of the lower permanent magnet 28 and the lower superconductor 29 are kept constant.

Since the positioning of the rotating shaft 2 by the pinning effect is performed automatically, there is no need for sensors, electromagnets, or controllers for detecting the radial direction position and thrust direction position of the rotating shaft 2, which is troublesome. The rotating shaft 2 can be maintained in a floating state without using any control circuit.

In the illustrated embodiment, the motor 3 for rotationally driving the rotating shaft 2 is located at the middle of the rotating shaft 2.
It is provided between the upper permanent magnet 25 and upper superconductor 26 and the lower permanent magnet 28 and lower superconductor 29. By installing the motor 3 in such a position, the distance between the upper and lower superconductors 26 and 29 can be made longer than when the motor 3 is installed at the end of the rotating shaft 2. It is possible to improve the rigidity and downsize the turbomolecular pump.

Next, FIG. 2 shows a second embodiment of the present invention, which corresponds to the invention set forth in claim 2. In the case of this embodiment, from the structure of the first embodiment described above, the lower permanent magnet 28, the lower superconductor 29, and the lower coolant reservoir 30 are omitted, and instead of the lower end surface of the rotating shaft 2 and the bottom surface of the housing 1. between, supporting radial load and thrust load,
An oil-lubricated spherical spiral groove bearing 34 is provided.

This oil-lubricated spherical spiral groove bearing 34 is as follows:
A spherical concave surface 35 formed on the bottom surface of the housing 1 and a spherical convex surface 3 formed on the lower end of the rod 36 at the lower end of the rotating shaft 2
7 and facing each other. Oil 38 is interposed between the opposing surfaces 35 and 37, and a spiral groove 39 is formed in at least one of the spherical convex surface 37 and the spherical concave surface 35.

In the case of the oil-lubricated spherical spiral groove bearing 34 constructed in this manner, as the spherical convex surface 37 rotates together with the rotating shaft 2, dynamic pressure is generated between the spherical convex surface 37 and the spherical concave surface 35. The lower end of the rotating shaft 2 is held concentrically with respect to the housing 1 and in a floating state.

In this embodiment, the motor 3 is provided around the rod 36. Furthermore, unlike magnetic bearings or superconducting bearings using superconductors, the oil-lubricated spherical spiral groove bearing 34 does not lose its bearing force instantaneously due to a power outage or disappearance of the superconducting state. Unlike the example and the first embodiment, no touchdown bearing is provided at the lower part of the rotating shaft 2.

Furthermore, the oil-lubricated spherical spiral groove bearing 34 is not only provided in place of omitting the lower permanent magnet 28, the lower superconductor 29, and the lower coolant reservoir 30, but also is provided in place of the lower permanent magnet 28, the lower superconductor 29, and the lower coolant reservoir 30. It may be provided in addition to the lower coolant reservoir 30 and configured to support larger radial loads and thrust loads. Other configurations and operations are the same as those of the first embodiment described above, so equivalent parts are given the same reference numerals and redundant explanations will be omitted.

Various superconducting materials can be used as the superconductor for constructing the turbomolecular pump of the present invention. For example, yttrium-based superconducting materials include a normal conducting phase in the superconducting phase of YBa2Cu3On, which is generally called the 123 phase. A material uniformly mixed with fine powder of Y2BaCuOn called 211 phase can be preferably used because it can obtain a large pinning force.

[0035]

[Effects of the Invention] Since the turbomolecular pump of the present invention is constructed and operates as described above, expensive sensors and troublesome control circuits are not required, and the pump can be manufactured inexpensively and compactly.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing a first embodiment of the present invention.

FIG. 2 is a longitudinal sectional view showing the second embodiment.

FIG. 3 is a vertical cross-sectional view showing a conventional example.

[Explanation of symbols]

1 Housing 2 Rotation axis 3 Motor 4. Moving blade body 5 Moving blade 6 Intake port 7 Case 8 Pump part 9 Shizuka 10 Exhaust port 11 Upper magnetic ring 12 Lower magnetic ring 13 Upper radial electromagnet 14 Upper radial magnetic bearing 15 Lower radial electromagnet 16 Lower radial magnetic bearing 17 Upper radial sensor 18 Lower radial sensor 19 Thrust sensor 20 Flange part 21 Thrust electromagnet 22 Thrust magnetic bearing 23 Touchdown bearing 24 Connector 25 Upper permanent magnet 26 Upper superconductor 27 Upper coolant reservoir 28 Lower permanent magnet 29 Lower superconductor 30 Lower coolant reservoir 31 Infeed port 32 Passage 33 Passage 34 Oil lubricated spherical spiral groove bearing 35 Spherical concave surface 36 Rod 37 Spherical convex surface 38 Oil 39 Spiral groove

Claims (2)

[Claims] Claim 1: A housing, a rotating shaft supported inside the housing via a bearing, a motor for rotationally driving the rotating shaft, a moving blade body supported by the rotating shaft, and a rotary blade body supported by the rotating shaft, A plurality of rotor blades provided on the outer peripheral surface of the blade body, a case provided surrounding the housing and having an intake port at one end, and supported on the inner peripheral surface of the case together with the rotor blades. In a turbo molecular pump comprising a plurality of stator vanes constituting a pump section and an exhaust port for discharging gas sucked in from the intake port by the pump section,
an annular upper permanent magnet supported and fixed on the upper outer peripheral surface of the rotating shaft; an upper superconductor supported and fixed on a portion of the inner peripheral surface of the housing that faces the outer peripheral surface of the upper permanent magnet; an upper coolant reservoir provided inside the housing at a portion that contacts the upper superconductor; an annular lower permanent magnet supported and fixed to the lower outer peripheral surface of the rotating shaft; and an inner periphery of the housing. a lower superconductor supported and fixed on a portion facing the outer circumferential surface of the lower permanent magnet; a lower coolant reservoir provided inside the housing at a portion in contact with the lower superconductor; A turbo-molecular pump comprising a coolant reservoir and an inlet for feeding coolant into the upper coolant reservoir. 2. Instead of omitting the lower permanent magnet, the lower superconductor, and the lower coolant reservoir, or together with the lower permanent magnet, the lower superconductor, and the lower coolant reservoir, the lower end surface of the rotating shaft and the bottom surface of the housing are combined. The turbo-molecular pump according to claim 1, further comprising an oil-lubricated spherical spiral groove bearing provided therebetween.