JP2006275000A - Magnetic bearing type rotary vacuum pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic bearing type vacuum pump not magnetizing an inner ring of a bearing at a time of pump assembly and preventing following rotation of the inner ring in pump operation. <P>SOLUTION: A rotor 4 having a rotary blade 21 formed thereon is attached on a shaft 2 having a motor rotor 3 of a DC blushless motor built therein. A rotating body which consists of the rotor 4 and the shaft 2 is supported by electromagnets 51, 52, 53 constructing a magnetic bearing without contact. The shaft 2 is installed to be inserted through emergency mechanical bearings 27, 28 provided on a stator 5. The inner ring 27b and a rolling elements 27a of the mechanical bearing 27 is formed out of nonmagnetic material or soft magnetic material. As a result, the inner ring 27b is not magnetized due to influence of magnetic force of the motor rotor 3 at a time of pump assembly, and following rotation of the inner ring 27b of the mechanical bearing 27 can be prevented in pump operation. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a magnetic bearing type rotary vacuum pump.

  Conventionally, a turbo molecular pump using a magnetic bearing is known as a magnetic bearing type rotary vacuum pump. In such a turbo molecular pump, a DC brushless motor may be used as a rotation drive motor. In a DC brushless motor, a permanent magnet is built in the motor rotor. In the case of a magnetic bearing type turbo molecular pump, a mechanical bearing such as a ball bearing is provided as a protective bearing that supports the rotating body when the support of the rotating body by the magnetic bearing is turned off. In recent years, in order to improve the performance of protective bearings, protective bearings using ceramics as rolling elements have been proposed (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 10-176714

  By the way, since the rotating shaft provided with the motor rotor is arranged so as to be inserted through the protective bearing, the permanent magnet in the motor rotor passes near the protective bearing when the pump is assembled. Since the inner ring of the protective bearing is formed of a steel material that is easily magnetized, the inner ring may be magnetized when the rotating shaft is inserted. Since the rotating shaft is generally made of steel, if the inner ring is magnetized, the inner ring is supported by a magnetic bearing, even though the rotating shaft that rotates at high speed and the inner ring are not in contact with each other. Is accompanied by rotation with the rotation axis.

  When the rolling element is a steel material, the rolling element is also dragged to the inner ring by a magnetic force, so the frictional resistance is increased and it is difficult for the rolling element to occur. However, when the rolling element is a non-magnetic material such as ceramics, the inner ring Since only the magnetic force is dragged, there is a problem that the rotation of the protective bearing is liable to occur.

According to the first aspect of the present invention, there is provided a rotating body provided with a rotation-side exhaust means, a fixed-side exhaust means that cooperates with the rotation-side exhaust means to generate an exhaust action, and a magnetic bearing that supports the rotation body in a non-contact manner. And a motor rotor provided on the rotating shaft of the rotating body and having a permanent magnet, and a mechanical bearing that supports the rotating body when the rotating shaft is inserted inside the bearing inner ring and is not supported by the magnetic bearing. The magnetic bearing type rotary vacuum pump is characterized in that the inner ring and the rolling element of the mechanical bearing are formed of a nonmagnetic material or a soft magnetic material.
According to a second aspect of the present invention, in the magnetic bearing type vacuum rotary pump according to the first aspect, a pair of mechanical bearings are provided so as to sandwich the motor rotor along the rotating shaft. And the rolling element was formed with the nonmagnetic material or the soft magnetic material.

  According to the present invention, the inner ring and the rolling element of the mechanical bearing are formed of a non-magnetic material or a soft magnetic material, so that the inner ring of the bearing is not magnetized when the pump is assembled, and the inner ring is prevented from being rotated during the pump operation. can do.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings. FIG. 1 shows an embodiment of a magnetic bearing type rotary vacuum pump according to the present invention, and is a sectional view showing a schematic configuration of a pump body 1 of a magnetic bearing type turbo molecular pump. The magnetic bearing type turbo molecular pump shown in FIG. 1 includes a 5-axis control type magnetic bearing, and the stator 5 is provided with electromagnets 51 and 52 constituting a radial magnetic bearing and an electromagnet 53 constituting an axial magnetic bearing. It has been.

  On the other hand, the rotating body includes a rotor 4 in which a plurality of stages of rotating blades 21 are formed, and a shaft 2 to which the rotor 4 is fixed and which constitutes a rotating shaft of the rotating body. A motor rotor 3 containing a permanent magnet is incorporated in the shaft 2, and a motor stator 6 is provided on the stator side. Further, on the stator side, radial displacement sensors 71 and 72 constituting a radial displacement sensor and an axial displacement sensor 73 constituting an axial displacement sensor are provided.

  Reference numerals 27 and 28 denote emergency mechanical bearings. When the rotor 4 is not magnetically levitated, the rotor 4 is supported by these mechanical bearings 27 and 28. The mechanical bearing 27 constrains the movement of the rotor 4 in the radial direction (x-axis and y-axis) in an emergency, and the mechanical bearing 28 includes the radial direction in two axes (x-axis and y-axis) and the axial direction in one axis ( z axis) is constrained.

  In the casing 20, a plurality of fixed wings 23 are provided in the axial direction (the vertical direction in the figure), which are alternately arranged with respect to the rotary wings 21. A pumping action is generated by rotationally driving a rotating body composed of the shaft 2 and the rotor 4 while being supported in a non-contact manner by the electromagnets 51, 52, 53. The receptacle 25 provided in the stator 5 is connected to a cable that connects the pump body 1 and a controller (not shown) that drives and controls the pump body 1.

  2A and 2B are views for explaining the motor rotor 3 and the mechanical bearing 27. FIG. 2A is a cross-sectional view of the motor rotor 3 portion of the shaft 2, and FIG. 2B is a cross-sectional view of the mechanical bearing 27 portion. FIG. 2C is a cross-sectional view when a conventional mechanical bearing 127 is used instead of the mechanical bearing 27. A DC brushless motor is used for the motors 3 and 6 of the present embodiment, and the motor rotor 3 is provided with permanent magnets 31 and 32. The permanent magnets 31 and 32 are magnetized in the shaft radial direction, the permanent magnet 31 is magnetized so that the shaft side becomes an N pole, and the permanent magnet 32 is magnetized so that the shaft side becomes an S pole. As a result, in the state shown in FIG. 2A, the motor rotor 3 has an S pole on the right side and an N pole on the left side.

  On the other hand, in the mechanical bearing 27 shown in FIG. 2B, ceramics are used for the rolling element 27a, and a nonmagnetic material is used for the inner ring 27b. As the nonmagnetic material, ceramics having high hardness and high toughness such as silicon nitride and zirconia, titanium alloys, and the like are used. Further, a soft magnetic material such as austenitic stainless steel may be used instead of the nonmagnetic material. On the other hand, the material used for the outer ring 27c may be a magnetic material or a non-magnetic material, and may be a ferromagnetic material such as conventionally used bearing steel or martensitic stainless steel. In the present embodiment, the rolling element 27a is made of ceramics, but a nonmagnetic material or soft magnetic material similar to the inner ring 27b may be used.

  When assembling the pump, first, after the electromagnets 51, 52, 53, the motor stator 6, and the displacement sensors 71, 72 are assembled in the stator 5, the shaft 2 to which the rotor 4 is fixed is shown by the arrow from the mechanical bearing 27 side. Are inserted into the stator 5 and assembled (see FIG. 3). At this time, when the shaft 2 is inserted inside the mechanical bearing 27, the motor rotor 3 provided with the permanent magnets 31 and 32 passes near the inner ring 27 b of the mechanical bearing 27. Further, the motor rotor 3 may contact the inner ring 27b.

  Therefore, if the inner ring 127b is made of a magnetic material such as bearing steel like the mechanical bearing 127 used in the conventional turbo molecular pump, the inner ring 127b is magnetized due to the magnetic force of the motor rotor 3. There was a case (see FIG. 2C). In the inner ring 127b shown in FIG. 2 (c), when the motor rotor 3 passes, the portions facing the permanent magnets 31 and 32 (shaded portions) are magnetized. When the shaft 2 made of steel is rotated in such a magnetized state, the inner ring 127b is rotated in the same direction as the shaft 2 due to the magnetic force.

  However, in the mechanical bearing 27 of the present embodiment, since the rolling elements 27a and the inner ring 27b are formed of a nonmagnetic material or a soft magnetic material, the inner ring 27b is magnetized even if the motor rotor 3 passes when the rotating body is assembled. There is nothing to do. As a result, the accompanying rotation of the inner ring 27b can be prevented, and the generation of noise and the deterioration of the mechanical bearing 27 due to the accompanying rotation can be prevented. Conventionally, the assembling work has to be performed with care so that the inner ring 127b is not magnetized, so that work efficiency is reduced and skill is required. However, the turbo molecular pump of the present embodiment does not require a reduction in work efficiency or a special skill level.

  In the case of the turbo molecular pump shown in FIG. 1, since the shaft 2 is structured to be inserted into the stator 5 from the mechanical bearing 27 side, the inner ring and the rolling elements of the mechanical bearing 27 are made of a nonmagnetic material or a soft magnetic material. did. However, if the shaft 2 has a structure that can be inserted from both the upper and lower directions, the inner ring and the rolling element can be formed of a nonmagnetic material or a soft magnetic material for both the mechanical bearings 27 and 28. good.

  In the embodiment described above, the magnetic bearing type turbo molecular pump has been described as an example. However, the magnetic bearing type rotary vacuum pump is not limited to the magnetic bearing type turbo molecular pump, and may be applied to, for example, a drag pump. it can.

  In the correspondence between the embodiment described above and the elements of the claims, the rotary blade 21 is a rotary-side exhaust means, the fixed blade 23 is a fixed-side exhaust means, the shaft 2 is a rotary shaft, the shaft 2 and the rotor 4. Each constitutes a rotating body. The above description is merely an example, and when interpreting the invention, there is no limitation or restriction on the correspondence between the items described in the above embodiment and the items described in the claims.

1 shows an embodiment of a magnetic bearing type rotary vacuum pump according to the present invention, and is a cross-sectional view showing a schematic configuration of a pump body 1 of a magnetic bearing type turbo molecular pump. It is a figure explaining the motor rotor 3 and the mechanical bearing 27, (a) is sectional drawing of the part of the motor rotor 3 of the shaft 2, (b) is sectional drawing of the part of the mechanical bearing 27, (c) is a substitute of the mechanical bearing 27 It is sectional drawing at the time of using the conventional mechanical bearing 127. It is a figure explaining pump assembly.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pump main body 2 Shaft 3 Motor rotor 4 Rotor 5 Stator 6 Motor stator 21 Rotary blade 23 Fixed blade 27, 28, 127 Mechanical bearing 27a Rolling element 27b, 127b Inner ring 27c Outer ring 31, 32 Permanent magnet 51, 52, 53 Electromagnet

Claims (2)

A rotating body provided with a rotation-side exhaust means;
Fixed-side exhaust means for generating an exhaust action in cooperation with the rotation-side exhaust means;
A magnetic bearing for supporting the rotating body in a non-contact manner;
A motor rotor provided on a rotating shaft of the rotating body and having a permanent magnet;
In the magnetic bearing type rotary vacuum pump provided with a mechanical bearing that supports the rotating body when the rotating shaft is inserted inside a bearing inner ring and is not supported by the magnetic bearing,
A magnetic bearing type rotary vacuum pump, wherein an inner ring and a rolling element of the mechanical bearing are formed of a nonmagnetic material or a soft magnetic material. In the magnetic bearing type rotary vacuum pump according to claim 1,
A pair of the mechanical bearings are provided so as to sandwich the motor rotor along the rotating shaft, and the inner ring and the rolling element are formed of a nonmagnetic material or a soft magnetic material for any of the pair of mechanical bearings. Magnetic bearing type rotary vacuum pump.

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