JP2014236546A - Motor and pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology which achieves prevention of the occurence of an eddy current and reduction of an air gap between a motor stator and a motor rotor and protects the motor stator from a corrosive gas or a condensible gas.SOLUTION: A motor connected with a pump and used for a rotation driving source of the pump includes: a motor rotor which may rotate around a rotation axis; and a motor stator which is disposed at the outer side of the motor rotor and has a stator core and coil exposed portions formed at both ends of the stator core in a rotation axis direction. A non-conducting coating layer having the sealability is formed at a portion of the stator core which is exposed to an internal space of the motor and portions of the stator core which are located around the coil exposed portions.

Description

  The present invention relates to protection technology against corrosive or condensable gases for motor or pump components.

  A motor used as a driving source of a vacuum pump may handle a corrosive gas such as a chlorine-based gas or a fluorine-based gas or a condensable gas such as a solvent vapor / water vapor. Corrosion of the motor stator due to inflow of corrosive gas or condensable gas from the vacuum pump to the motor side becomes a problem. Therefore, conventionally, a motor called a canned motor has been widely used (for example, Patent Document 1 below). In the canned motor, a rotor chamber that separates the motor stator and the motor rotor is formed in order to seal the vacuum pump. The rotor chamber is separated from the motor stator by a partition fixed to the vacuum pump side, that is, a can. It is a sealed space. The can prevents corrosive gas or condensable gas from coming into contact with the motor stator. The can of the canned motor is made of nonmagnetic metal or resin.

  Since the metal can easily secures the strength, it can be formed with a smaller thickness than the resin can. For this reason, the space | gap of a motor stator and a motor rotor can be made comparatively small, and the fall of the motor efficiency by the leakage of magnetic flux can be suppressed. On the other hand, in the metal can, an eddy current is generated on the surface by the action of magnetic flux from the motor stator, and the motor efficiency decreases due to the loss at this time.

  Eddy currents do not occur in resin cans. On the other hand, since the resin can has a lower strength than the metal can, it is necessary to make the thickness larger than that of the metal can. For this reason, the space | gap of a motor stator and a motor rotor becomes large compared with metal cans, and the fall of the motor efficiency by the leakage of magnetic flux generate | occur | produces.

  For this reason, conventionally, metal cans have been used in AC motors in which the motor efficiency is greatly reduced when the gap is large. On the other hand, resin cans having a thickness of about 1.5 to 2.0 mm have been used in DC motors in which the effect of increasing the gap is smaller than in AC motors.

JP 2005-184958 A

However, the above method of use completely eliminates both the point that eddy currents, which are disadvantages of metal cans, and the relatively large gap between the motor stator and motor rotor, which are disadvantages of resin cans. It cannot be solved. Therefore, there is a demand for a technique that can protect the motor stator from corrosive gas or condensable gas while achieving both prevention of eddy current generation and reduction of the gap between the motor stator and the motor rotor. Such a problem is not limited to a vacuum pump, but is a problem common to various pumps that handle corrosive gas or condensable gas. Such a problem is not limited to pumps that handle gas, but is common to pumps that handle corrosive liquids. Further, it is desirable that not only the motor stator but also other components of the motor or components of the pump can be protected from corrosive gas, condensable gas or corrosive liquid.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as, for example, the following forms.

  The 1st form of this invention is connected with a pump, and is provided as a motor for using as a rotational drive source of a pump. The motor includes a motor rotor that can rotate around a rotation axis, a motor stator disposed outside the motor rotor, and includes a stator core and coil exposed portions formed at both ends of the stator core in the direction of the rotation axis. A motor stator. A coating layer having non-conductivity and sealing properties is formed in a portion of the stator core that is exposed to the internal space of the motor and around the coil exposed portion.

  According to such a motor, as an alternative to the can, by using a coating layer having non-conductivity and sealing properties, while preventing both generation of eddy currents and reducing the gap between the motor stator and the motor rotor, The motor stator can be protected from corrosive or condensable gases or corrosive liquids.

  As a second aspect of the present invention, in the first aspect, the coating layer may be formed by thermal spraying. According to this form, a coating layer can be formed easily. In addition, since the coating layer can be formed of various materials, the degree of freedom in selecting the coating layer material is high.

  As a third aspect of the present invention, in the first or second aspect, the periphery of the coil exposed portion may be covered with a molded resin member. The coating layer formed around the coil exposed portion may be formed in a portion of the resin member exposed to the internal space of the motor. According to this form, the coating layer around the coil exposed portion can be reinforced by the resin member. Therefore, even if the force acting on the coating layer (for example, when a motor is used in a vacuum pump, the compressive stress due to the pressure difference between the vacuum pressure in the vacuum pump and the atmospheric pressure) is large, it is necessary for the coating layer. Mechanical strength can be imparted.

  As a 4th form of this invention, the film layer formed in the circumference | surroundings of a coil exposure part in the 1st or 2nd form may be formed in the surface of a coil exposure part. According to such a configuration, the coil exposed portion can be sealed from corrosive gas, condensable gas, or corrosive liquid with a simple configuration.

  The fifth aspect of the present invention is provided as a pump including the motor according to any one of the first to fourth aspects. According to such a pump, the same effects as those of the first to fourth embodiments are obtained.

  As a sixth aspect of the present invention, in the fifth aspect, a magnetic bearing for magnetically supporting the main shaft of the pump may be disposed on at least one side of both sides in the direction of the rotation axis of the motor. A coating layer may be formed on the electromagnet side of the magnetic bearing. According to this embodiment, the magnetic bearing can be suitably protected from corrosive gas, condensable gas, or corrosive liquid.

  As a seventh aspect of the present invention, in the sixth aspect, the space between the motor and the magnetic bearing may be filled with a molded resin member. A coating layer may be formed at a site on the main shaft side of the resin member filled in the space. According to this embodiment, the coating layer around the coil exposed portion of the electromagnet of the magnetic bearing can be reinforced by the resin member. Therefore, even if the force acting on the coating layer is large, the mechanical strength necessary for the coating layer can be imparted.

The present invention provides a method for protecting a motor stator from a corrosive gas, a condensable gas, or a corrosive liquid, a pump member, a corrosive gas, a condensable gas, or a corrosive liquid. It can be realized in various forms such as a protection method.

It is explanatory drawing which shows schematic structure of the motor of the vacuum pump as 1st Example of this invention. It is explanatory drawing which shows schematic structure of the motor of the vacuum pump as 2nd Example. It is explanatory drawing which shows schematic structure of the motor of the vacuum pump as 3rd Example.

A. First embodiment:
FIG. 1 shows a schematic configuration of a motor 200 used in the vacuum pump 20. In FIG. 1, the cross section containing the rotating shaft AL which the vacuum pump 20 has is shown. In this embodiment, the vacuum pump 20 is used in a semiconductor product manufacturing process. The motor 200 is connected to the vacuum pump 20 and is used as a rotational drive source of the vacuum pump 20. The vacuum pump 20 includes a pump main shaft 21 and a bearing 61. The pump main shaft 21 is supported by a bearing 61 and another bearing (not shown), and is driven to rotate about the rotation axis AL by the motor 200.

  The motor 200 includes a motor stator 210 (hereinafter also simply referred to as a stator 210), a motor rotor 220 (hereinafter also simply referred to as a rotor 220), and a stator frame 240. The stator frame 240 includes a frame body 241 and side plates 242. The frame body 241 has a cylindrical shape in which an internal space is formed along the rotation axis AL. The side plate 242 has a disc shape and closes an opening at one end of the frame main body 241. The stator 210 and the rotor 220 are accommodated in the internal space of the stator frame 240.

  The stator 210 has a configuration in which a coil is mounted on the stator core 211a. At both ends of the stator 210 in the direction of the rotational axis AL, the coil mounted on the stator core 211a protrudes outward in the direction of the rotational axis AL of the stator core 211a to form a coil exposed portion 211b. The stator 210 is fixed to the stator frame 240 concentrically with the rotation axis AL by fitting the stator core 211a inside the frame main body 241. The stator core 211a can be formed by laminating silicon steel plates, for example. The rotor 220 is disposed concentrically with the rotation axis AL inside the stator 210 and is directly connected to the pump main shaft 21 of the vacuum pump 20.

  The periphery of the coil exposed portion 211b, that is, the space between the stator core 211a and the stator frame 240 is covered with a molded resin member 280. The resin member 280 is formed up to the same position as the surface of the stator core 211a on the rotation axis AL side in the direction orthogonal to the rotation axis AL.

A coating layer 270 is formed on the surface of the portion exposed to the internal space of the motor 200 in the stator core 211a and the resin member 280, in other words, on the surface facing the rotor 220. The coating layer 270 can be formed of any material having non-conductivity and sealing properties, for example, ceramic or resin. If the coating layer 270 is formed of ceramic, the mechanical strength of the coating layer 270 can be increased. In the present embodiment, the coating layer 270 is made of Al ₂ O ₃ . In this embodiment, the coating layer 270 is formed by thermal spraying. By thermal spraying, the coating layer 270 can be easily formed. In addition, since the coating layer 270 can be formed of various materials, the degree of freedom in selecting the material of the coating layer 270 can be increased.

The coating layer 270 functions as a partition wall that separates the stator 210 and the rotor 220, and prevents corrosive or condensable gas flowing into the motor 200 from the vacuum pump 20 from coming into contact with the stator 210. Thereby, the stator 210 can be protected from corrosive gas or condensable gas. The thickness of the coating layer 270 can be set to an arbitrary thickness smaller than 1.5 mm. By so doing, the gap between the stator 210 and the rotor 220 can be reduced as compared with the case where the stator 210 is protected using a resin can. Therefore, a decrease in motor efficiency due to magnetic flux leakage can be suppressed. In the present embodiment, the thickness of the coating layer 270 is set to 0.5 mm or less. Thereby, a decrease in motor efficiency due to magnetic flux leakage is remarkably suppressed.

  In the present embodiment, the surface of the rotor 220 facing the stator 210 is subjected to rust prevention coating, and a rust prevention coating film 290 is formed. On this surface, a coating layer similar to the coating layer 270 may be formed instead of the rust preventive coating film 290. In this way, rusting of the rotor 220 can be prevented for a longer period.

  According to the motor 200, the stator 210 can be protected from corrosive gas or condensable gas without using a can. Furthermore, since the coating layer 270 has non-conductivity, no eddy current is generated. Further, by forming the coating layer 270 thin, the gap between the stator 210 and the rotor 220 can be made extremely small. As a result, a decrease in motor efficiency due to magnetic flux leakage can be suitably suppressed. That is, according to the motor 200, the stator 210 can be protected from corrosive gas or condensable gas while achieving both prevention of eddy current generation and reduction of the gap between the stator 210 and the rotor 220.

  Further, according to the motor 200, the periphery of the coil exposed portion 211 b is covered with the resin member 280, and the coating layer 270 is formed on the surface of the resin member 280. Therefore, compared with the case where the coating layer 270 is formed on the surface of the coil exposed portion 211b, the coating layer 270 around the coil exposed portion 211b can be reinforced by the resin member 280. Therefore, even when the compressive stress due to the differential pressure between the vacuum pressure of the vacuum pump 20 and the atmospheric pressure is large, the coating layer 270 can be given mechanical strength that can withstand the compressive stress.

The sealing property of the coating layer 270 described above can be confirmed by a motor leak test. The leak test can be performed as follows. First, the helium leak detector is connected to the motor 200, and the internal space of the motor 200 is evacuated. Next, helium gas is sprayed from the outside of the motor 200. Then, the leak amount from the outside to the inside of the motor 200 is confirmed by a helium leak detector. If the leak amount is 5.0 × 10 ⁻³ Pa · m ³ / sec or less, it can be said that the coating layer 270 has a sealing property. The reference value of the leak amount may be set more severely, for example, 1.3 × 10 ⁻⁷ Pa · m ³ / sec or less.

B. Second embodiment:
FIG. 2 shows a schematic configuration of a motor 300 as the second embodiment. In FIG. 2, the same components as those of the motor 200 as the first embodiment are denoted by the same reference numerals as those in FIG. The motor 300 does not have the resin member 280. Due to this point, the formation place of the coating layer 370 corresponding to the coating layer 270 of the first embodiment is different from that of the first embodiment. As shown in the drawing, the coating layer 370 is formed on the surface of the portion of the stator core 211a that is exposed to the internal space of the motor 200 and the surface of the coil exposed portion 211b. According to such a configuration, the configuration of the motor 300 can be simplified. In the motor 300, the mechanical strength of the coating layer 370 formed on the surface of the coil exposed portion 211b can withstand the compressive stress acting on the coating layer 370 (for example, the vacuum pressure, the material, the thickness, etc. of the coating layer 370). Can be employed).

C. Third embodiment:
FIG. 3 shows a schematic configuration of the motor 400 used in the vacuum pump 420 as the third embodiment. The motor 400 includes a stator 410 having a stator core 411a and a coil exposed portion 411b, and a frame body 441. On both sides of the stator 410 in the rotation axis AL direction, radial magnetic bearings 451 and 461 for magnetically supporting the pump main shaft 421 in the radial direction are arranged. Radial sensors 455 and 465 for detecting the position of the pump main shaft 421 in the radial direction are disposed outside the radial magnetic bearings 451 and 461 in the rotation axis AL direction. An axial magnetic bearing 471 that magnetically supports the pump main shaft 421 in the axial direction is disposed on the opposite side of the radial sensor 455 in the rotational axis AL direction from the radial magnetic bearing 451. In the space between the stator 410 and the radial magnetic bearings 451 and 461 and the space between the radial magnetic bearings 451 and 461 and the radial sensors 455 and 466 in the rotation axis AL direction, a molded resin member 480 is formed. Is filled.

  Of the stator 410, the radial magnet bearings 451, 461 on the electromagnet side (the radially outer fixed side portion), the radial sensors 455, 465, and the resin member 480, the surfaces facing the pump main shaft 421 are arranged in the direction of the rotation axis AL. A coating layer 470 is formed along the entire surface. A coating layer 495 is formed on the electromagnet side of the axial magnetic bearing 471. Furthermore, in this embodiment, the coating layer 490 is also formed around the pump main shaft 421 over the entire region facing the coating layer 470. The coating layers 470, 490, and 495 correspond to the coating layer 270 of the first embodiment. According to this configuration, in addition to the stator core 411a, various components of the vacuum pump 420 can be protected from corrosive gas or condensable gas. If the magnetic bearing 461 is provided on the end (not shown in FIG. 3) side of the pump main shaft 421 opposite to the motor 400, the coating layer 470 is formed only on the radial magnetic bearing 451 side. Good. Further, the resin member 480 can be omitted. In this case, for example, the coating layer 470 may be formed in a region exposed to corrosive gas or condensable gas in the radial magnetic bearings 451, 461 and the like.

D. Variations:
D-1. Modification 1:
The coating layers 270, 370, 470, 490, and 495 are not limited to the structure formed by thermal spraying, and may be formed by any film forming method such as sputtering.

D-2. Modification 2:
The various embodiments described above are not limited to vacuum pumps, and can be applied to various pumps that handle corrosive gas or condensable gas. For example, you may apply embodiment mentioned above to the air blower which is 1 type of a gas pump in a broad sense. Of course, the above-described embodiment is applicable not only to a gas pump but also to various liquid pumps that handle corrosive liquids.

  The embodiments of the present invention have been described above based on some examples. However, the above-described embodiments of the present invention are for facilitating the understanding of the present invention and limit the present invention. It is not a thing. The present invention can be changed and improved without departing from the gist thereof, and the present invention includes the equivalents thereof. In addition, any combination or omission of each constituent element described in the claims and the specification is possible within a range where at least a part of the above-described problems can be solved or a range where at least a part of the effect is achieved. It is.

20, 420 ... Vacuum pump 21, 421 ... Pump main shaft 61 ... Bearing 200, 300, 400 ... Motor 210, 410 ... Motor stator 211a, 411a ... Stator core 211b, 411b ... Coil exposed part 220 ... Motor rotor 240 ... Stator frame 241, 441 ... Frame body 242 ... Side plate 270,370 ... Coating layer 280,480 ... Resin member 290 ... Anti-rust coating film 451,461 ... Radial magnetic bearing 455,465 ... Radial sensor 470,490,495 ... Coating layer 471 ... Axial magnetic bearing AL ... Rotation axis

Claims (7)

A motor connected to a pump and used as a rotational drive source of the pump,
A motor rotor capable of rotating around a rotation axis;
A motor stator disposed outside the motor rotor, the motor stator having a stator core and coil exposed portions formed at both ends of the stator core in the direction of the rotation axis; and
The motor in which the coating layer which has nonelectroconductivity and a sealing property was formed in the site | part exposed to the internal space of the said motor of the said stator core, and the circumference | surroundings of the said coil exposure part. The motor according to claim 1,
The coating layer is a motor formed by thermal spraying. The motor according to claim 1 or 2,
The periphery of the coil exposed portion is covered with a molded resin member,
The said coating layer formed in the circumference | surroundings of the said coil exposure part is formed in the site | part exposed to the internal space of the said motor among the said resin members. The motor according to claim 1 or 2,
The coating layer formed around the coil exposed portion is formed on a surface of the coil exposed portion.   The pump provided with the motor as described in any one of Claims 1 thru | or 4. The pump according to claim 5, wherein
A magnetic bearing for magnetically supporting the main shaft of the pump is disposed on at least one side of the motor in the direction of the rotation axis.
The coating layer is formed on the electromagnet side of the magnetic bearing. The pump according to claim 6, wherein
The space between the motor and the magnetic bearing is filled with a molded resin member,
The said coating layer is formed in the site | part by the side of the said main shaft of the said resin member with which the said space was filled. Pump.

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