JP5483684B2 - Molecular pump - Google Patents

Description

  The present invention relates to a molecular pump suitable for evacuation in a strong magnetic field.

  When evacuation is performed in a device that generates a strong magnetic field such as an accelerator or a fusion device, the turbo molecular pump or the complex molecular pump that performs evacuation is exposed to a strong magnetic field.

  In a strong magnetic field, eddy currents are generated in the rotor and rotating shaft that rotate at high speed in these molecular pumps, causing a brake and heat generation phenomenon against rotation, which makes operation difficult.

  Conventionally, when a molecular pump is used in a magnetic field, a magnetic shield such as iron is placed outside the molecular pump to form a magnetic shield. There were problems such as difficulty in fixing means to the molecular pump body.

  In addition, the applicant firstly, in the vacuum pump that compresses and exhausts the gas by rotating the rotating member in the fixed member fixed in the casing, the casing and / or the fixing member is made of a magnetic material. An application for a vacuum pump constructed was filed (see Patent Document 1).

FIG. 3 is a perspective sectional view of a complex molecular pump as an example of a conventional vacuum pump.

  The composite molecular pump is composed of an upper turbo molecular pump part and a thread groove pump part provided below the turbo molecular pump part. 6a is an intake port and 7a is an exhaust port.

  Reference numeral 2c denotes a stator of the thread groove pump portion, 3c denotes a spacer of the turbo molecular pump portion, and 4a denotes a pump housing.

  In the composite molecular pump of Patent Document 1, both or either one of the fixing member of the stator 2c and the spacer 3c and the housing 4a are formed of an iron-based magnetic permeable material.

  However, the structure of the magnetic shield disclosed in Patent Document 1 has a problem in that it is insufficient to cope with a strong magnetic field.

Japanese Patent Laid-Open No. 01-190991

  In the present invention, there is no risk of interference with peripheral devices, there is no problem in fixing to the molecular pump body, and the magnetic pump is completely evacuated in a strong magnetic field over the entire length of the molecular pump. An object is to provide a suitable molecular pump.

The present invention is to achieve the above object, in a composite molecular pump formed more becomes rotating body and the screw groove pump section rotor which is continuously provided on the lower of the turbo molecular pump portion rotor Toko and the rotary shaft, the thread groove pump portion rotor And a casing made of a soft magnetic material having a high saturation magnetic flux density and a high permeability, and the casing surrounds the thread groove pump section stator. And a bottom plate that connects the stator and the inner wall of the casing and connects the lower end opening of the casing with the soft magnetic material. It was blocked.

  According to the present invention, in a molecular pump that operates in a strong magnetic field, there is no risk of interference with peripheral devices, there is no problem in fixing to the molecular pump body, and the magnetic shield is completely covered over the entire length of the molecular pump. This has the effect of providing a molecular pump having the applied structure.

It is a longitudinal cross-sectional view of Example 1 of the molecular pump of the present invention. It is a longitudinal cross-sectional view of Example 2 of the molecular pump of the present invention. It is a perspective sectional view of an example of the conventional molecular pump.

  The example of the form for carrying out the present invention is shown below.

  Example 1 of the molecular pump of the present invention will be described with reference to FIG.

  FIG. 1 is a longitudinal sectional view of a composite molecular pump 1 according to the present invention in which a thread groove pump portion S is continuously provided below a turbo molecular pump portion T. FIG.

  Reference numeral 2 denotes a rotor made of an aluminum alloy. On the rotor 2, rotor blades 2A of a turbo molecular pump portion are formed radially and projecting outward from the rotor 2 in multiple stages.

  A thread groove pump portion rotor 2B is formed in a cylindrical shape below the rotor 2.

  Reference numeral 3 denotes a bearing housing. The bearing housing 3 has a built-in bearing structure that rotatably supports a rotating shaft 21 fixed at the shaft center of the rotor 2, and rotationally drives the rotating shaft 21. Built-in electric motor.

  The rotor 2, the rotating shaft 21 and the like form a rotating body of the complex molecular pump 1.

  Reference numeral 4 denotes a base portion of the complex molecular pump 1 which fixes the bearing housing 3.

  The side portion of the base portion 4 includes an exhaust port 4A of the composite molecular pump 1 and connection portions such as electric wiring and cooling water piping.

  Reference numeral 5 denotes a stator of the thread groove pump part S, which is disposed close to the outer peripheral surface of the thread groove pump part rotor 2B, and has a thread groove 5A on the inner periphery. The stator 5 is made of an aluminum alloy or the like.

  A casing 6 is formed of a soft magnetic material having a high saturation magnetic density and high magnetic permeability, such as silicon steel or iron alloy such as permalloy.

  The casing 6 includes an upper casing 6 </ b> A that fits a ring-shaped spacer T <b> 1 on an inner peripheral portion thereof to form a shell portion of the turbo molecular pump portion T, and a lower casing 6 </ b> B that covers the thread groove pump portion stator 5.

  Reference numeral 6C denotes an intake port.

  In this embodiment, the lower casing 6B is formed to have a diameter larger than that of the upper casing 6A, and a flange 5B provided on the stator 5 is brought into contact with a stepped portion that transitions from the upper casing 6A to the lower casing 6B, whereby a bolt 6D. And the stator 5, the bearing housing 3 fixed to the stator 5, the rotary shaft 21 rotatably supported by the bearing housing 3, and the rotation via the bolt 6 </ b> D and the flange 5 </ b> B. A pump body P including a rotor 2 fixed to a shaft 21 and a base portion 4 fixed to the stator 5 is supported by the casing 6, and a lower end portion of a lower casing 6 B of the casing 6 is a base portion 4 of the pump body P. It is formed to extend further downward.

  6E is an opening provided in the side wall portion of the lower casing 6B of the casing 6, and the exhaust port 4A, cooling water piping, electric wiring, and the like are inserted through the opening 6E.

  Next, the usage and effects of the complex molecular pump 1 of the present embodiment will be described.

  The complex molecular pump 1 is used to evacuate inside a device that generates a strong magnetic field such as an accelerator or a fusion device.

  The rotor 2 of the pump body P, which is the main part of the complex molecular pump 1, and the rotating body of the rotating shaft are surrounded by a casing 6 made of a soft magnetic material that extends downward from the base portion 4 of the pump body P. Therefore, the pumping operation of the molecular pump can be performed safely without worrying about braking action or heat generation even in a strong magnetic field.

  In this embodiment, the lower end portion of the casing 6 is formed to extend downward from the base portion 4 of the pump body P. However, the lower end portion of the casing 6 is connected to the rotor 2 and the rotary shaft of the pump body P. The above-described operation can be achieved if it is located at least below the rotating body.

  Embodiment 2 of the molecular pump of the present invention will be described with reference to FIG.

  FIG. 2 is a longitudinal sectional view of the complex molecular pump 11 of the present embodiment.

  The composite molecular pump 11 is different from the composite molecular pump 1 in that a bottom plate 7 made of an iron alloy of a soft magnetic material is attached to the casing 6 of the composite molecular pump 1 of the first embodiment.

  As described above, by providing a shield against the magnetic field also in the lower part of the pump body P, the capability of the molecular pump in a strong magnetic field is further improved. In particular, when the magnetic field direction is not perpendicular to the rotation axis of the molecular pump, that is, when there is a magnetic field component in the rotation axis direction, the capability is improved.

  When the composite molecular pump 1 is exposed to a stronger magnetic field in the rotational direction, a short pipe (not shown) of an intake pipe made of a soft magnetic material is provided between the intake port 6C of the molecular pump 1 and the exhausted system. ) May be interposed.

  Moreover, although the said Example showed the case of the composite molecular pump, this may consist only of a turbo molecular pump.

  The molecular pump of the present invention is used for evacuation in a device that generates a strong magnetic field such as an accelerator or a fusion device.

1,11 Molecular pump (complex molecular pump)
2 Rotor 4 Base part 5 Stator (Thread groove pump part stator)
6 Casing 6E Opening 7 Bottom plate P Pump body S Thread groove pump part T Turbo molecular pump part

Claims (3)

In the composite molecular pump formed more becomes rotating body and the screw groove pump section rotor which is continuously provided on the lower of the turbo molecular pump portion rotor Toko and the rotary shaft, the thread groove pump portion stator provided outside of the thread groove pumping rotor, A casing made of a soft magnetic material having a high saturation magnetic flux density and high magnetic permeability is provided outside the turbo molecular pump unit rotor, and the casing surrounds the thread groove pump unit stator and extends downward to form a lower end of the rotating body. While extending below the part ,
Connecting the stator and the inner wall of the casing;
A molecular pump , wherein a lower end opening of the casing is closed by a bottom plate formed of the soft magnetic material .   A base portion of the molecular pump is continuously provided at a lower portion of the stator, and a pipe communicating with the base portion is formed so as to pass through an opening provided in a side wall portion of the casing. The molecular pump according to claim 1. 3. The molecular pump according to claim 1, wherein a short pipe of an intake pipe made of a soft magnetic material having a high saturation magnetic flux density and high permeability is connected to an intake port portion of the molecular pump.

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