JP2012205435A - Electric motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric motor including a proper structure which prevents the outflow of magnetic powder generated by the corrosion of permanent magnets to the exterior of a rotor.SOLUTION: Revet holes 29 are disposed between a rotation shaft hole 27 and magnet insertion holes 28 so as to be located on the inner sides of the magnet insertion holes 28 when viewed in the radial direction of a rotor core 11. The internal diameter of each rivet hole 29 is set so as to be larger than the shaft diameter of a revet 32 penetrating through the revet hole 29. Further, each revet hole 29 connects with the magnet insertion hole 28 through a communication path 33. Magnetic powder 38 generated by permanent magnets 12 due to hydrogen embrittlement blows out in the magnet insertion holes 28, however, the powder passes through the communication path 33 to be housed in a space formed between the rivet hole 29 and the rivet 32. Thus, the magnetic powder 38 is not likely to pop out to the exterior of the rotor core 11. Therefore, the operation of an electric compressor continues without causing failures in a compression mechanism and an electric motor.

Description

  The present invention relates to an electric motor including a permanent magnet embedded rotor.

  For example, a compressor used in a vehicle air conditioner includes an electric compressor in which an electric motor is housed inside a compressor housing as a drive source of a compression mechanism. The electric motor may be configured by a permanent magnet embedded type motor including a stator wound with a coil and a rotor in which a permanent magnet is embedded in a rotor core. The electric compressor is configured such that a refrigerant containing lubricating oil circulates from the periphery of the electric motor toward the compression mechanism in the housing. Water is present in the refrigerant used in the vehicle air conditioner. In particular, the piping used for the vehicle air conditioner is not easily influenced by bending, vibration of the vehicle, etc. so that the vehicle air conditioner can be easily mounted inside the vehicle having a complicated structure in a narrow space, such as a rubber tube. The tube is made of flexible material. For this reason, in the refrigerant circuit of the vehicle air conditioner, moisture that permeates from the piping is also added, and a large amount of moisture is present as compared with the electric compressors used in other devices.

  In the state where the temperature of the lubricating oil in the electric compressor is high due to the operation of the vehicle air conditioner, the moisture in the refrigerant circuit is diffused into the lubricating oil and the refrigerant, and causes less problems. However, when the temperature of the lubricating oil decreases, such as when the electric compressor is stopped, the saturated water concentration of the lubricating oil and the refrigerant decreases, and a large amount of free water is generated. A large amount of the lubricating oil stays in the gaps between the magnet insertion holes of the rotor core constituting the electric motor, and the free water generated from the lubricating oil may corrode the permanent magnets installed in the magnet insertion holes.

  On the other hand, rare earth magnets are often used as permanent magnets attached to the rotor core of an electric motor. The rare earth magnet is subjected to surface treatment such as nickel plating or aluminum plating to prevent corrosion, and is inserted into the magnet insertion hole of the rotor core and attached. However, the surface treatment part of the rare earth magnet may be scratched by the surface treatment part of the rare earth magnet rubbing against the inner wall surface of the magnet insertion hole due to the vibration of the electric motor itself or the vibration of the electric compressor. Moreover, since the magnet insertion hole of the rotor core is formed by punching each laminated steel plate, the magnet insertion hole is likely to be burred, and the burr may damage the surface treatment portion of the rare earth magnet. In addition, the surface treatment portion subjected to plating or the like cannot completely eliminate the generation of pinholes. For this reason, there is a possibility that the free water staying in the rotor core penetrates from scratches or pinholes in the surface treatment portion and corrodes the rare earth magnet.

  As the corrosion of the rare earth magnet by free water proceeds, the rare earth magnet absorbs hydrogen generated by the corrosion and expands and collapses due to hydrogen embrittlement. For this reason, the rare earth magnet collapsed by the collapse generates a large amount of fine magnet powder, and this magnet powder jumps out of the rotor from the minute gaps of the steel plates on which the rotor core is laminated by the pressure at the time of collapse. Since magnet powder contains iron, if it adheres and accumulates on the airtight terminals provided in the electric compressor, the terminal pins or between the terminal pins and the housing is short-circuited, the electric motor is turned off, or the housing is grounded. May cause problems.

  In addition, the magnet powder that has jumped out of the rotor is also carried to the compression mechanism side by the refrigerant, which may cause damage to the sliding portion and the bearing portion of the compression mechanism. Such a problem of hydrogen embrittlement of the rare earth magnet due to free water is particularly remarkable when the vehicle air conditioner is used in a hot and humid environment. In addition to electric compressors, in electric motors used in other general devices, moisture penetrates rare earth magnets through scratches and pinholes in the surface treatment section of rare earth magnets, and hydrogen in rare earth magnets. May cause brittleness.

  For example, Patent Document 1 discloses a technique for forming rivet fixing holes on both sides in the circumferential direction of a permanent magnet insertion hole of a rotor for the purpose of positioning a permanent magnet inserted into the permanent magnet insertion hole of the rotor. Yes. Therefore, in order to fix the rotor and the end plates in contact with both end faces of the rotor, the two rivets passed through the rivet fixing holes can be positioned by restricting the permanent magnets on both sides. . The rivet fixing holes formed on both sides in the circumferential direction of the permanent magnet insertion hole in Patent Document 1 temporarily stores magnet powder that may be generated due to hydrogen embrittlement when a rare earth magnet is used as the permanent magnet, and the rotor. It is estimated that the outflow can be expected to be suppressed.

JP 2007-181254 A (see FIGS. 24 to 28)

  In order to position the permanent magnet, the rivet fixing hole of Patent Document 1 must be formed at a position adjacent to the permanent magnet insertion hole different from the normal formation position, and to balance the magnetic circuit. It must be formed on both sides of the permanent magnet insertion hole in the circumferential direction. That is, the number of rivet fixing holes required is twice as many as normally required, and the number of rivets must be used twice as well. Further, since the rivet fixing hole is close to the permanent magnet, the rivet needs to be made of a non-magnetic material so that magnetic flux leakage can be prevented, leading to a problem of increasing costs. Moreover, when the influence on a magnetic circuit is considered, there exists a problem that the diameter of a rivet fixing hole cannot be enlarged and the accommodation capacity of magnet powder cannot be improved. Furthermore, when magnet powder containing iron is accommodated in the rivet fixing hole, the presence of the magnet powder may affect the magnetic circuit. Therefore, the rivet fixing hole of Patent Document 1 is not suitable as a configuration that accommodates rare earth magnet magnet powder generated due to hydrogen embrittlement and prevents the magnet powder from flowing out of the rotor.

  This invention provides the electric motor provided with the suitable structure which can prevent the outflow of the magnet powder generate | occur | produced by corrosion of a permanent magnet to the exterior of a rotor.

  The first aspect includes a rotating shaft, a rotor fixed to the rotating shaft, and a stator disposed around the rotor and wound with a coil. The rotor includes a rotor core and both end surfaces of the rotor core. An end plate that is in contact with the rotor core, a permanent magnet inserted into the rotor core, and a rivet that fastens the rotor core and the end plate, and the rotor core includes a rotation shaft hole into which the rotation shaft is inserted. An electric motor having a magnet insertion hole that is formed around the rotation shaft hole and into which the permanent magnet is inserted, and a rivet hole that is formed around the rotation shaft hole and into which the rivet is inserted. The diameter of the hole is larger than the shaft diameter of the rivet, and the rotor core has a communication path that connects the magnet insertion hole and the rivet hole.

  According to the first aspect, since the magnet powder of the permanent magnet generated by the corrosion can be accommodated in the rivet hole, it is possible to reliably prevent the magnet powder from flowing out of the rotor core. Moreover, since the rivet hole and the magnet insertion hole are formed at positions away from being connected via the communication path, the magnetic circuit of the permanent magnet is not affected.

  According to a second aspect of the present invention, the rotor and the stator are disposed inside a housing of an electric compressor, and the rotating shaft is connected to a compression mechanism of the electric compressor. According to the second aspect of the present invention, particularly in an electric compressor having a large influence of free water, it is possible to reliably prevent problems such as a short circuit at an airtight terminal or damage to a compression mechanism and a bearing portion caused by magnet powder.

  According to a third aspect of the present invention, the rivet hole is disposed radially inward of the rotor core with respect to the magnet insertion hole. According to the third aspect, since the rivet hole is provided at a position away from the magnet insertion hole, the rivet is formed of a magnetic material, or the inner diameter of the rivet hole is increased to increase the magnet powder holding capacity. However, there is no fear of affecting the magnetic circuit of the permanent magnet.

  According to a fourth aspect of the present invention, the permanent magnet has a coating layer made of a corrosion-resistant material on the surface. According to the fourth aspect, the permanent magnet can be prevented from being corroded by forming the coating layer, and the lifetime of the permanent magnet can be further extended.

  According to a fifth aspect of the present invention, the permanent magnet is a rare earth magnet. According to the fifth aspect, in a rare earth magnet that absorbs hydrogen generated by corrosion and easily collapses due to hydrogen embrittlement, the influence of magnet powder can be effectively prevented.

  In the present invention, magnet powder generated by corrosion of the permanent magnet can be temporarily stored in the rivet hole away from the magnet insertion hole, so that the magnet powder is surely prevented from flowing out of the rotor core of the electric motor. be able to.

It is a longitudinal cross-sectional view which shows the outline | summary of a scroll compressor. It is a front view which shows the end surface of a rotor core. It is a front view which shows the end surface of the rotor core which inserted the permanent magnet in the magnet insertion hole. It is an enlarged view of the magnet insertion hole and rivet hole which inserted the permanent magnet shown in FIG. FIG. 4 is a sectional view taken along line AA in FIG. 3.

  An embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows an example in which the present invention is applied to a scroll type electric compressor (hereinafter simply referred to as an electric compressor) of a vehicle air conditioner, and an outline of the electric compressor will be described below. The electric compressor has a sealed housing in which a front housing 1 and a rear housing 2 are fixed together by a plurality of bolts 3. Both the housings 1 and 2 are made of a metallic material such as aluminum or an aluminum alloy. A suction port 4 is formed in the housing 2, and a discharge port 5 is formed in the housing 1. The suction port 4 and the discharge port 5 are each connected to an external refrigerant circuit (not shown).

  A scroll type compression mechanism 6 and an electric motor 7 for driving the compression mechanism 6 are accommodated in the interiors 2A of the housings 1 and 2. The electric motor 7 includes a rotating shaft 8 that is rotatably supported by a housing 2 via a bearing, a rotor 9 that is fixed to the rotating shaft 8, and an outer periphery of the rotor 9, and a stator 10 that is fixed to the inner wall of the housing 2. It is comprised by. The rotor 9 includes, as main elements, a rotor core 11 constituted by a laminated steel plate in which thin steel plates made of a plurality of magnetic bodies are laminated, and a plurality of permanent magnets 12, and the stator 10 includes a coil 13 wound in three phases. Have.

  The permanent magnet 12 is composed of a rare earth magnet, and a neodymium magnet, a samarium cobalt magnet, or other types of rare earth magnets can be used. As shown in FIGS. 3 and 4, a coating layer 12A and a surface modification layer (not shown) are formed on the surface of the permanent magnet 12 from an inorganic material such as nickel or aluminum as a corrosion-resistant material. .

  The compression mechanism 6 includes, as main elements, a fixed scroll 14 fixed to the inner walls of the housings 1 and 2 and a movable scroll 15 disposed to face the fixed scroll 14. A variable volume compression chamber 16 for compressing the refrigerant is formed between the fixed scroll 14 and the movable scroll 15. The movable scroll 15 is connected to an eccentric pin 18 of the rotary shaft 8 via a bearing and an eccentric bush 17 so as to swing according to the rotation of the rotary shaft 8 and change the volume of the compression chamber 16. ing.

  On the other hand, an inverter housing 20 that forms the inverter accommodating chamber 19 is joined and fixed to a part of the outer peripheral wall of the housing 2. An inverter 21 and an airtight terminal 22 for driving the motor are attached to the outer peripheral wall of the housing 2 in the inverter accommodating chamber 19. The airtight terminal 22 is electrically connected to the inverter 21 through the connector 23 on the inverter side in the inverter accommodating chamber 19, and is pulled out from the coil 13 of the stator 10 through the cluster block 24 in the interior 2 </ b> A of the housing 2. It is electrically connected to a lead wire (not shown). Therefore, when the coil 21 of the electric motor 7 is energized from the inverter 21 through the airtight terminal 22, the rotor 9 is rotated and the compression mechanism 6 is operated by the rotating shaft 8.

  As shown in FIGS. 2 to 5, in the rotor core 11 constituting the rotor 9, the rotating shaft hole 27 and the permanent magnet 12 are inserted from one end face 25 toward the other end face 26 by gap fitting. A magnet insertion hole 28 and four rivet holes 29 are formed as through holes. The rotation shaft hole 27 is formed concentrically at the center of the rotor core 11, and the rotation shaft 8 is fitted into the rotation shaft hole 27 by press-fitting or the like and fixed so as to be integrated. The magnet insertion hole 28 and the rivet hole 29 are arranged around the rotation shaft hole 27 at equal intervals.

  The magnet insertion hole 28 is configured by a magnet insertion space 30 having a rectangular cross section and a through-hole 31 for preventing leakage of magnetic fluxes connected to both sides in the circumferential direction of the rotor core 11 with respect to the magnet insertion space 30 (FIG. 2). (See FIG. 4). The vertical width, the horizontal width, and the length of the magnet insertion hole 28 in the magnet insertion space 30 are set to be larger than the vertical width, the horizontal width, and the length of the permanent magnet 12 formed in the rectangular parallelepiped. . As shown in FIG. 2, the vertical width indicates the distance in the circumferential direction of the rotor core 11 when viewed from the end face 25 side of the rotor core 11, and the horizontal width indicates the distance in the radial direction of the rotor core 11. Further, the length indicates a distance extending from the end face 25 side of the rotor core 11 to the end face 26 side. Therefore, the permanent magnet 12 inserted into the magnet insertion hole 28 by the clearance fit is mounted in a form embedded in the magnet insertion hole 28.

  As shown in FIG. 2, the rivet hole 29 is disposed between the rotary shaft hole 27 and the magnet insertion hole 28 so as to be inside the magnet insertion hole 28 when viewed in the radial direction of the rotor core 11. The inner diameter D1 of the rivet hole 29 is set larger than the shaft diameter D2 of the rivet 32 that passes through the rivet hole 29 (see FIG. 4). The rivet hole 29 is connected to the magnet insertion space 30 of the magnet insertion hole 28 by a communication path 33. Since the rivet hole 29 is connected by the communication path 33, the rivet hole 29 can be arranged at a position close to the rotary shaft hole 27 away from the magnet insertion hole 28, which has an influence on the magnetic circuit. It can be lost. Further, since the rivet hole 29 is disposed at a position that does not affect the magnetic circuit, the rivet 32 can be a commercial product made of a magnetic material or the like.

  The end surfaces 25 and 26 of the rotor core 11 have end plates 36 and 37 each having holes 34 and 35 formed so as to coincide with the rivet holes 29 after the permanent magnet 12 is mounted in the magnet insertion hole 28. (See FIG. 5). The rivet 32 passes through the holes 34 and 35 of the end plates 36 and 37 and the rivet hole 29 of the rotor core 11 and is riveted. The rotor core 11 and the end plates 36 and 37 are firmly fixed by fastening the rivets 32, and the rotor 9 is configured.

The embodiment of the present invention configured as described above has the following operations and effects.
During the operation of the electric compressor in the vehicle air conditioner, the refrigerant sucked from the suction port 4 flows from the electric motor 7 side to the compression mechanism 6, is compressed by the compression mechanism 6, and is discharged from the discharge port 5 to the external refrigerant circuit (FIG. Not shown). The lubricating oil that circulates in the refrigerant circuit together with the refrigerant is in a state where the temperature of the lubricating oil is high during the operation of the electric compressor, so a lot of moisture present in the electric compressor is absorbed in the lubricating oil and the refrigerant, which causes a problem. It is rare to become.

  When the electric compressor is stopped, the temperature of the lubricating oil is lowered, so that the saturated water concentration of the lubricating oil is lowered and a large amount of free water is generated. Lubricating oil that is a source of free water stays inside the electric compressor and also stays around the rotor 9. The lubricating oil staying in the rotor 9 permeates and stays around the rotor core 11 and even in a slight gap between the laminated steel plates constituting the rotor core 11. Since the coating layer 12A is formed on the surface of the permanent magnet 12 mounted in the magnet insertion hole 28 of the rotor core 11, it prevents the permeation of free oil generated from the lubricating oil or lubricating oil into the permanent magnet 12. Yes.

  However, the permanent magnet 12 has friction of the permanent magnet 12 due to vibration during operation of the electric compressor, scratches on the coating layer 12A generated when the permanent magnet 12 is mounted, or pinholes generated when the coating layer 12A is formed. May exist. For this reason, the free water generated from the lubricating oil staying in the rotor core 11 may penetrate into the scratches and pinholes and corrode the permanent magnet 12. Since the hydrogen generated by the progress of corrosion of the permanent magnet 12 is occluded in the permanent magnet 12, the permanent magnet 12 collapses due to hydrogen embrittlement and generates a large amount of fine magnet powder 38 (see FIGS. 3 and 5). ).

  The magnet powder 38 generated from the permanent magnet 12 is ejected into the magnet insertion space 30 of the magnet insertion hole 28, and is formed between the communication path 33 and the rivet 32 of the rivet hole 29 due to the formation of the communication path 33. Contained in the space. The pressure at the time of generation of the magnet powder 38 is also applied between the laminated steel plates in the magnet insertion hole 28. However, since the gap between the laminated steel plates is extremely small, all the magnet powder passes through the communication path 33 and passes through the rivet holes 29. Is housed in. Since the rivet hole 29 is closed by the end plates 36 and 37, there is no possibility that the magnet powder 38 flows outside the rivet hole 29. Therefore, since there is no possibility that the magnet powder 38 jumps out of the rotor 9, there is no problem with the compression mechanism 6 and the electric motor 7, and the operation of the electric compressor can be continued.

  Since the rivet hole 29 can be freely disposed at a position away from the magnet insertion hole 28 so as not to affect the magnetic circuit, the inner diameter of the rivet hole 29 is set to be large, A large space can be formed between the two. Therefore, the accommodation space for the magnet powder 38 caused by hydrogen embrittlement can be expanded, and the accommodation capacity can be further increased.

  The present invention is not limited to the configuration of the embodiment of the present invention described above, and various modifications are possible within the scope of the gist of the present invention, and the present invention is implemented in other embodiments as follows. Is possible.

(1) In the embodiment of the present invention, the permanent magnet 12 is mounted in the magnet insertion hole 28 by a clearance fit. Can also be implemented.
(2) When the permanent magnet 12 is mounted in the magnet insertion hole 28 by a clearance fit, the permanent magnet 12 that does not form the coating layer 12A can be used.
(3) The present invention can be implemented even if the permanent magnet 12 is not limited to a rare earth magnet, and other types of magnets are used.
(4) In the embodiment of the present invention, an example of implementation in a scroll type electric compressor has been shown. However, the electric compressor may be a reciprocating type such as a vane type or screw type rotary compressor, a swash type or a wobble type. The present invention can be implemented in an electric compressor in which an electric motor is built in a compressor.
(5) The present invention is not limited to an electric compressor of a vehicle air conditioner, but is applied to, for example, an electric motor used for an electric compressor other than a vehicle air conditioner for home use or a mechanical device other than an electric compressor. It can be implemented in the electric motor used.

DESCRIPTION OF SYMBOLS 1, 2 Housing 4 Intake port 5 Discharge port 6 Compression mechanism 7 Electric motor 9 Rotor 10 Stator 11 Rotor core 12 Permanent magnet 12A Coating layer 13 Coil 14 Fixed scroll 15 Movable scroll 22 Airtight terminal 28 Magnet insertion hole 29 Rivet hole 30 Magnet insertion space 31 Gap part 32 Rivet 33 Communication path 36, 37 End plate 38 Magnet powder

Claims (5)

A rotating shaft; a rotor fixed to the rotating shaft; and a stator disposed around the rotor and wound with a coil. The rotor is in contact with a rotor core and both end faces of the rotor core. An end plate, a permanent magnet inserted into the rotor core, and a rivet that fastens the rotor core and the end plate, the rotor core having a rotation shaft hole into which the rotation shaft is inserted, and the rotation shaft hole In an electric motor having a magnet insertion hole that is drilled around and inserted into the permanent magnet, and a rivet hole that is drilled around the rotation shaft hole and into which the rivet is inserted,
The electric motor according to claim 1, wherein a diameter of the rivet hole is larger than a shaft diameter of the rivet, and the rotor core has a communication path that connects the magnet insertion hole and the rivet hole.   The electric motor according to claim 1, wherein the rotor and the stator are disposed inside a housing of an electric compressor, and the rotating shaft is connected to a compression mechanism of the electric compressor.   The electric motor according to claim 1, wherein the rivet hole is disposed radially inward of the rotor core with respect to the magnet insertion hole.   The electric motor according to any one of claims 1 to 3, wherein the permanent magnet has a coating layer made of a corrosion-resistant material on a surface thereof.   The electric motor according to claim 1, wherein the permanent magnet is a rare earth magnet.

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