JP2010273426A - Permanent magnet motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a permanent magnet motor for changing a magnetization amount of permanent magnets by applying an external magnetic field, which improves corrosion resistance of the permanent magnets and efficiently adjusts the magnetization amount of the permanent magnets. <P>SOLUTION: The permanent magnet motor includes: a stator having winding, a rotor 3 rotatably provided on the stator, permanent magnets 11 inserted in a magnet insertion holes 10 formed on a rotor core 9 of the rotor 3 and having a coercive force of a level at which the magnetization amount can be easily changed by a magnetic field generated in the winding. In the motor, an oxidation preventing layer 11a having low permittivity is formed on the surface of each of the permanent magnet 11. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a permanent magnet motor having a large number of permanent magnets in a rotor.

  This type of permanent magnet motor is used as a drive source for rotating the drum of a drum type washing machine, for example. In such a permanent magnet motor, the stator coil (winding) of the stator is chained according to the low-speed rotation (during washing and rinsing operation) and high-speed rotation (during dehydration) of the driving drum. It is desired to appropriately adjust the magnetic flux amount (magnetization amount) of the intersecting permanent magnets.

  However, the permanent magnet provided in the rotor of the permanent magnet motor is generally constituted by one type, and therefore the amount of magnetic flux of the permanent magnet is always constant. In this case, for example, if the permanent magnet provided in the rotor is composed only of a permanent magnet having a large coercive force, the induced voltage due to the permanent magnet during high-speed rotation (during dehydration operation) becomes extremely high, leading to dielectric breakdown of electronic components. There is a fear. On the other hand, if the permanent magnet provided in the rotor is composed only of a permanent magnet having a small coercive force, the output during low-speed rotation (during washing operation and rinsing operation) is reduced.

  Therefore, for example, in the permanent magnet motor described in Patent Document 1, two types of permanent magnets having different coercive forces are arranged inside the rotor, and among them, the magnetization state of the low coercive force permanent magnet is changed to an external magnetic field (stator). The amount of magnetization (the amount of magnetic flux) of the permanent magnet is adjusted by demagnetizing or magnetizing with a magnetic field generated by a current flowing through the coil.

  In addition, it is known that the surface of the permanent magnet provided in such a permanent magnet motor is subjected to metal plating to improve corrosion resistance in order to prevent corrosion (deterioration due to oxidation or chemical reaction) of the permanent magnet. (For example, refer to Patent Document 2).

JP 2006-280195 A JP 2007-300791 A

  When the magnetization state of the permanent magnet is changed (magnetization or demagnetization), the energization amount of the stator coil is made larger than normal (the energization amount when the rotor rotates), and the external magnetic field generated from the stator coil is changed. It is necessary to strengthen and apply a strong magnetic field to the permanent magnet. However, in the configuration in which the surface of the permanent magnet is metal-plated, an eddy current is generated in the metal-plated portion when an external magnetic field stronger than usual acts. The eddy current generated in this way acts to cancel the external magnetic field from the stator coil. Therefore, in order to change the magnetization state of the permanent magnet, the energization amount of the stator coil must be further increased, and the magnetization amount of the permanent magnet cannot be adjusted efficiently.

  The present invention has been made in view of the circumstances described above, and its purpose is to change the amount of magnetization of a permanent magnet by applying an external magnetic field, and to improve the corrosion resistance of the permanent magnet. An object of the present invention is to provide a permanent magnet motor capable of efficiently adjusting the amount of magnetization of the permanent magnet.

  The permanent magnet motor of the present invention is generated from the winding inserted into a stator provided with windings, a rotor provided rotatably with respect to the stator, and an insertion hole formed in a rotor core of the rotor. And a permanent magnet having a coercive force at a level at which the amount of magnetization can be easily changed by a magnetic field, and an anti-oxidation layer having a low magnetic permeability is formed on the surface of the permanent magnet.

  According to the permanent magnet motor of the present invention, since the anti-oxidation layer having a low magnetic permeability is formed on the surface of the permanent magnet, an external magnetic field is generated from the stator winding to change the magnetization amount of the permanent magnet. In addition, the generation of eddy currents on the surface of the permanent magnet can be avoided. Moreover, since the low magnetic permeability antioxidant layer has a function of preventing the permanent magnet from being oxidized, the corrosion resistance of the permanent magnet can be improved. Thereby, corrosion of a permanent magnet can be prevented and the amount of magnetization of the permanent magnet can be adjusted efficiently.

The perspective view of the permanent magnet motor which shows the 1st Embodiment of this invention Enlarged perspective view of the main part Perspective view of permanent magnet 1 shows a schematic configuration of a drum type washing machine, (a) is a longitudinal side view, (b) is a longitudinal rear view.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view schematically showing the overall configuration of a permanent magnet motor 1 (outer rotor type brushless DC motor).
The permanent magnet motor 1 includes a stator 2 and a rotor 3 provided so as to be rotatable with respect to the stator. The stator 2 includes a stator core 5 having a large number (36 in this case) of magnetic pole teeth 4 on the outer periphery, a stator coil 6 (corresponding to a winding) wound around each magnetic pole tooth 4, and a synthetic resin. The mounting portion 7 is provided. The permanent magnet motor 1 is fixedly attached to, for example, the rear surface portion 23a (see FIG. 4) of the water tank 23 via the attachment portion 7. In this case, the stator core 5 is composed of divided cores 5A divided into six equal parts in the circumferential direction, and these six divided cores 5A are connected. Accordingly, one divided core 5A has six magnetic pole teeth 4, and three adjacent magnetic pole teeth 4 correspond to three phases U, V, and W.

  The rotor 3 includes a shallow container-like magnetic body frame 8 having an annular wall 8a on the outer peripheral portion, an annular rotor core 9 disposed on the inner peripheral portion of the annular wall 8a, and the rotor core 9 with a rotor. It has a configuration including permanent magnets 11 and 12 having different coercive forces arranged as magnets. The permanent magnets 11 and 12 are inserted into a large number (in this case, 48) of magnet insertion holes 10 (see FIG. 2) that are formed in the rotor core 9 and open in a rectangular shape. A rotating shaft 25 (see FIG. 4) is coupled to the shaft mounting portion 13 provided at the center of the frame 8. In this case, the rotor core 9 is composed of divided cores 9A divided into six equal parts in the circumferential direction, and these six divided cores 9A are connected. Accordingly, one divided core 9A is configured by inserting and arranging eight permanent magnets 11 and 12 in eight magnet insertion holes 10 so that N-pole and S-pole magnetic poles are alternately formed. Yes.

  The permanent magnets 11 and 12 are composed of a permanent magnet 11 that is a low coercive force permanent magnet and a permanent magnet 12 that is a high coercive force permanent magnet. In this case, the low coercive force permanent magnet 11 has a coercive force smaller than that of the high coercive force permanent magnet 12, and the magnetization amount can be easily changed by a magnetic field (external magnetic field) generated from the stator coil 6. Has coercivity.

  Specifically, the permanent magnet 11 having a small coercive force is composed of, for example, an alnico magnet (aluminum / nickel / cobalt magnet, the coercive force of the alnico magnet is 350 kA / m or less) that has a low coercive force. The alnico magnet 11 is formed by sintering alnico magnet powder. As shown in FIG. 3, an oxide film 11a is formed on the surface of the alnico magnet 11 as an anti-oxidation layer having a low magnetic permeability. In this case, the oxide film 11a is formed with a thickness of several microns. The oxide film 11a is formed by subjecting the surface of the alnico magnet 11 to heat treatment and altering the surface of the alnico magnet 11.

  The oxide film 11a formed in this way contains an oxide of magnetic powder or metal powder that constitutes the Alnico magnet 11. However, such an oxide is not formed continuously in a planar shape on the surface of the alnico magnet 11, but is formed in a non-uniformly scattered state. Therefore, unlike the configuration in which the surface of the permanent magnet is plated with metal (the configuration in which the metal is continuous in a planar shape on the surface of the permanent magnet), the electrical continuity through the magnetic powder or the oxide of the metal powder on the surface of the Alnico magnet 11. Is unlikely to occur.

  The permanent magnet 12 having a high coercivity and a high coercivity is composed of, for example, a neodymium magnet having a high coercivity (the coercivity of a neodymium magnet is 700 kA / m or more). The neodymium magnet 12 is formed by sintering neodymium magnet powder, and a metal plating layer (not shown) is formed on the surface of the neodymium magnet 12 by, for example, nickel or aluminum. Thereby, the corrosion resistance of the neodymium magnet 12 is improved, and corrosion of the neodymium magnet 12 (deterioration due to oxidation or chemical reaction) is prevented.

  The magnet insertion hole 10 of the rotor core 9 into which the alnico magnet 11 and the neodymium magnet 12 are inserted is larger than the dimensions of the alnico magnet 11 and the neodymium magnet 12, and the alnico magnet inserted into the magnet insertion hole 10. 11 and the neodymium magnet 12 are filled with a resin (for example, PBT (polybutylene terephthalate) of a thermoplastic resin). As a result, in addition to the above-described oxide film 11a which is an anti-oxidation layer having a low magnetic permeability, a resin layer 14 is further formed on the surface of the alnico magnet 11 as an anti-oxidation layer having a low magnetic permeability. . In addition to the above-described metal plating layer, a resin layer 14 is formed on the surface of the neodymium magnet 12 as an anti-oxidation layer having a low magnetic permeability. The resin layer 14 prevents the alnico magnet 11 and the neodymium magnet 12 from directly contacting the rotor core 9 (the inner surface of the magnet insertion hole 10). In addition, the alnico magnet 11 and the neodymium magnet 12 are integrally fixed to the rotor core 9 by the resin layer 14.

  In the permanent magnet motor 1, 12 U-phase stator coils 6 wound around the 12 magnetic pole teeth 4 of the rotor core 9 are connected in series and 12 V wound around the 12 magnetic pole teeth 4. The phase stator coils 6 are connected in series, and the 12 W-phase stator coils 6 wound around the 12 magnetic pole teeth 4 are connected in series, and these series circuits are star-connected. It has become.

Next, the configuration of the drum type washing machine 21 including the permanent magnet motor 1 configured as described above will be described. FIG. 4A is a longitudinal side view showing a schematic configuration of the drum type washing machine 21, and FIG. 4B is a longitudinal rear view showing the schematic configuration of the drum type washing machine 21.
A water tank 23 is disposed in the outer box 22 of the drum type washing machine 21. The water tank 23 has a bottomed cylindrical shape in which a rear surface portion 23a (right end surface portion in FIG. 4A) as one end portion is closed, and is elastic by a damper mechanism (not shown) in a state where the axial direction is substantially horizontal. Is supported. In the water tank 23, a drum 24 is rotatably disposed as a rotating tank. The drum 24 also has a bottomed cylindrical shape in which a rear surface portion 24a (right end surface portion in FIG. 4A) which is one end portion is closed, and is disposed in a state where the axial direction is substantially horizontal. Although not shown, the peripheral wall of the drum 24 has a large number of holes through which water and air can be passed. In addition, a door for opening and closing a laundry doorway formed by the front side opening of the water tub 23 and the drum 24 is provided on the front surface portion 22 a of the outer box 22. As a result, the laundry can be taken into and out of the drum 24 through the laundry entrance.

  On the back surface of the rear surface portion 23 a of the water tank 23, the above-described permanent magnet motor 1 is disposed as a drive source for rotating the drum 24. The rotating shaft 25 connected to the rotor 3 of the permanent magnet motor 1 is connected to the rear surface portion 24 a of the drum 24. Therefore, the drum type washing machine 21 is a direct drive system in which the drum 24 is directly driven to rotate by the permanent magnet motor 1. In this case, the drum 24 corresponds to a load that is rotationally driven by the permanent magnet motor 1.

  In this way, the permanent magnet motor 1 provided in the drum type washing machine 21 is controlled through an inverter circuit by a control device including a microcomputer as control means (not shown). This control device has a function of controlling the overall operation of the drum type washing machine 21, including a function of controlling a washing operation including a washing process, a rinsing process, and a dehydration process (final dehydration process) which will be described later.

Next, the operation of the drum type washing machine 21 provided with the permanent magnet motor 1 as described above will be described.
When starting the washing operation, the control device first performs a washing process. In the washing process, the control device opens a water supply valve (not shown) connected to the water tank 23 and performs a water supply operation for supplying and storing water in the water tank 23 and thus in the drum 24. Next, the control device rotates the drum 24 forward and backward at a low rotation speed (for example, 50 to 60 rpm) by the permanent magnet motor 1 in a state where the detergent is put in the water tank 23. Thereby, the control device performs a washing operation for washing the laundry stored in the drum 24. After performing the washing operation for a predetermined time, the control device opens the drain valve (not shown) connected to the discharge port (not shown) of the water tank 23 in a state where the drum 24 is stopped. A draining operation is performed to discharge the water inside the drum 24 to the outside of the machine.

  Next, the control device performs intermediate dehydration in the washing process. In this intermediate dehydration, the control device rotates the drum 24 in one direction at a high speed (for example, 1500 rpm) by the permanent magnet motor 1. Thereby, the laundry in the drum 24 is centrifugally dehydrated. Moisture discharged from the laundry is discharged from the outlet to the outside of the machine.

  When the intermediate dehydration is completed, the control device proceeds to the rinsing process. In the rinsing process, the control device first performs the water supply operation again in a state where the rotation of the drum 24 is stopped, and supplies and stores water in the water tank 23 and thus in the drum 24. Next, the control device performs a rinsing operation. In the rinsing operation, the control device performs the same control as the above-described washing operation except that no detergent is used. That is, the control device performs the rinsing operation of the laundry in the drum 24 for a predetermined time by rotating the drum 24 forward and backward at a low rotation speed (for example, 50 to 60 rpm) by the permanent magnet motor 1. Thereafter, the control device performs the same drainage operation as described above. Hereinafter, the control device repeats a water supply operation, a rinsing operation, and a draining operation similar to those described above, and ends the rinsing process.

  Next, the control device performs a dehydration process. In the dehydration process, the control device rotates the drum 24 in one direction at a high speed (for example, 1000 rpm) by the permanent magnet motor 1. Thereby, the laundry in the drum 24 is centrifugally dehydrated. Moisture discharged from the laundry is discharged from the outlet to the outside of the machine. When the above dehydration operation is performed for a predetermined time, the control device completes the dehydration process and ends the washing operation.

  Here, in the washing operation in the washing process described above, the rotation speed of the drum 24 (permanent magnet motor 1) is low (50 to 60 rpm), and the permanent magnet motor 1 requires low speed rotation and high torque. Therefore, in the water supply operation before the washing operation, the control device performs a magnetizing process so as to increase the magnetization amount (magnetic flux amount) of the alnico magnet 11 of the permanent magnet motor 1.

  Specifically, the control device increases the energization amount of the stator coil 6 (for example, applies a voltage of +500 V), generates an external magnetic field in the stator coil 6, and acts on the alnico magnet 11. As a result, the amount of magnetization of the alnico magnet 11 is increased, and the amount of magnetization is maintained even when the application of voltage is canceled. Here, an oxide film 11 a is formed on the surface of the alnico magnet 11 as an anti-oxidation layer having a low magnetic permeability. For this reason, even when an external magnetic field stronger than normal (when the rotor 3 rotates in the washing operation) is applied to the alnico magnet 11 during this magnetizing process, an eddy current hardly occurs on the surface of the alnico magnet 11.

  By increasing the magnetization state (magnetization amount) of the alnico magnet 11 in this way, the magnetic flux of the entire rotor 3 acting on the stator 2 increases. In this state, the permanent magnet motor 1 can exhibit a high torque by rotating the drum 24 at a low speed and executing a washing operation. During this washing process, since the normal operating voltage (energization amount) to the stator coil 6 is in the range of about ± 200 V, the amount of magnetization does not change even with the low coercivity Alnico magnet 11. .

  Next, in the intermediate dehydration process of the washing process, the rotation speed of the drum 24 (permanent magnet motor 1) is high (1500 rpm), and the permanent magnet motor 1 requires low torque and high speed rotation. Therefore, the control device performs demagnetization processing in order to reduce the magnetization amount (magnetic flux amount) of the alnico magnet 11 of the permanent magnet motor 1 in the draining operation before the intermediate dehydration.

  Specifically, the control device reduces the energization amount of the stator coil 6 (applies a voltage slightly higher than −500 V, for example), generates an external magnetic field in the stator coil 6, and acts on the alnico magnet 11. As a result, the amount of magnetization of the alnico magnet 11 is reduced, and the amount of magnetization is maintained even when the application of voltage is canceled. Here, an oxide film 11 a is formed on the surface of the alnico magnet 11 as an anti-oxidation layer having a low magnetic permeability. Therefore, even when an external magnetic field stronger than normal (when the rotor 3 rotates in the washing operation) is applied to the alnico magnet 11 during the demagnetization process, eddy current is hardly generated on the surface of the alnico magnet 11.

  By demagnetizing the magnetization state (magnetization amount) of the alnico magnet 11 in this way, the magnetic flux of the entire rotor 3 acting on the stator 2 is reduced. In this state, the permanent magnet motor 1 is suitable for low torque and high speed rotation by rotating the drum 24 at a high speed and performing intermediate dehydration. Even during this intermediate dehydration, the normal operating voltage (energization amount) to the stator coil 6 is in the range of about ± 200 V, so the amount of magnetization does not change even with the low coercivity Alnico magnet 11. .

  Next, in the rinsing operation of the rinsing process, the rotational speed of the drum 24 (permanent magnet motor 1) is low (50 to 60 rpm) as in the washing operation of the rinsing process. Therefore, in the water supply operation before the rinsing operation, the control device performs a magnetizing process similar to that described above in order to increase the magnetization amount of the alnico magnet 11. In such a state where the magnetization is increased, the control device performs a rinsing operation.

  In the dehydration process, the rotation speed of the drum 24 (permanent magnet motor 1) is high (1000 rpm) as in the intermediate dehydration process of the washing process, and the permanent magnet motor 1 requires low torque and high speed rotation. Therefore, the control device performs the same demagnetization process as described above in order to reduce the magnetization amount (magnetic flux amount) of the alnico magnet 11 in the draining operation in the rinsing process before the dehydration process. In this way, the control device performs the dehydration process in a state where the magnetization amount of the alnico magnet 11 is demagnetized.

  As described above, according to the present embodiment, the oxide film 11 a is formed on the surface of the alnico magnet 11 constituting the permanent magnet motor 1 as an anti-oxidation layer having a low magnetic permeability. Therefore, when an external magnetic field is generated from the stator coil 6 to change the magnetization amount of the alnico magnet 11, it is possible to avoid an eddy current from being generated on the surface of the alnico magnet 11. In addition, since the oxide film 11a is not only a low magnetic permeability layer but also an anti-oxidation layer (a layer having a function of preventing oxidation and alteration of the alnico magnet 11), the corrosion resistance of the alnico magnet 11 is improved. Can do. Thereby, corrosion of the alnico magnet 11 can be prevented and the amount of magnetization of the alnico magnet 11 can be adjusted efficiently.

  Moreover, the loss (loss) of the external magnetic field which acts on the alnico magnet 11 can be suppressed, the adjustment of the magnetization amount of the alnico magnet 11 can be stabilized, and the adjustment accuracy can be improved.

  Further, a resin layer 14 was further formed on the surface of the alnico magnet 11 as an anti-oxidation layer having a low magnetic permeability. Thereby, generation | occurrence | production of the eddy current on the surface of the Alnico magnet 11 at the time of a magnetizing process and a demagnetizing process can be suppressed further, and the adjustment efficiency and adjustment precision of the magnetization amount of the Alnico magnet 11 can be improved further. Further, according to the configuration in which the resin layer 14 is filled in the gap between the alnico magnet 11 and the magnet insertion hole 10, the alnico magnet 11 is vibrated by an external magnetic field when the magnetization amount of the alnico magnet 11 is adjusted. Can be prevented.

  Further, since the surface of the neodymium magnet 12 having a high coercive force that does not change the amount of magnetization, that is, the neodymium magnet 12 that does not need to suppress the generation of eddy current, is subjected to a metal plating process to form a metal plating layer. Corrosion of the magnet 12 can be prevented.

  The alnico magnet 11 and the neodymium magnet 12 are covered with the resin layer 14 and are electrically insulated from the rotor core 9 (magnet insertion hole 10 portion). Thereby, it is possible to prevent the magnetization amount after adjustment of the alnico magnet 11 and the original magnetization amount of the neodymium magnet 12 from changing.

(Second Embodiment)
Hereinafter, a second embodiment of the present invention will be described. In addition, description is abbreviate | omitted about the same part as the above-mentioned 1st Embodiment, and only a different part is demonstrated.
In the present embodiment, the surface of the Alnico magnet 11 having a low coercive force is impregnated with a rust preventive agent, so that the surface of the Alnico magnet 11 is provided with a low magnetic permeability antioxidant layer (a layer impregnated with a rust preventive agent). It is formed with a thickness of micron.

  In this case, a rust preventive agent using silicon oil as a solvent is used, and the surface of the alnico magnet 11 is impregnated with the rust preventive agent by immersing the alnico magnet 11 therein. In addition, as a rust preventive agent, it is not restricted to what uses silicon oil as a solvent, A various rust preventive agent can be used. Further, the surface of the alnico magnet 11 may be impregnated with the rust preventive agent by applying the rust preventive agent to the surface of the alnico magnet 11 instead of immersing the alnico magnet 11 in the rust preventive agent.

According to the present embodiment, since a layer impregnated with a rust preventive agent is formed on the surface of the Alnico magnet 11 as an anti-oxidation layer having a low magnetic permeability, an external magnetic field is generated from the stator coil 6 to generate the Alnico magnet 11. When changing the amount of magnetization, it is possible to avoid the generation of eddy currents on the surface of the alnico magnet 11. Thereby, the magnetization amount of the alnico magnet 11 can be adjusted efficiently.
Moreover, corrosion of the alnico magnet 11 can be prevented by the rust preventive agent impregnated on the surface of the alnico magnet 11.

(Other embodiments)
In addition, this invention is not limited only to each above-mentioned embodiment, For example, it can deform | transform or expand as follows.
Rather than forming a layer impregnated with an oxide film 11a or a rust inhibitor as a low-permeability antioxidant layer on the surface of the low-coercivity alnico magnet 11, a low-permeability low-permeability magnetic layer is formed on the surface of the alnico magnet 11. Only the resin layer 14 may be formed as the antioxidant layer.
An oxide film or an antirust agent may be formed on the surface of the high coercive neodymium magnet 12 as an anti-oxidation layer having a low magnetic permeability.

  The resin layer 14 does not need to cover the entire surface of the Alnico magnet 11 when the surface of the Alnico magnet 11 is formed with an oxide film 11a or a rust preventive agent impregnated as an anti-oxidation layer having a low magnetic permeability. You may form so that a part of surface may be covered to such an extent that it does not contact the rotor core 9 (magnet insertion hole 10 part). Moreover, also about the neodymium magnet 12, the resin layer 14 does not need to cover the whole surface of the neodymium magnet 12, and may be formed so that a part of the surface may be covered.

The permanent magnets constituting the permanent magnet motor 1 are not limited to the Alnico magnets 11 and the neodymium magnets 12. When the former magnetization amount is changed, the permanent magnets 1 and 2 are kept to such an extent that the latter magnetization state is not affected. If there is a difference in magnetic force, it can be appropriately selected and used.
The alnico magnet 11 and the neodymium magnet 12 may be arranged alternately as shown in FIGS. 1 and 2 or may be arranged irregularly. Moreover, you may comprise all the permanent magnets which comprise the permanent magnet motor 1 with the alnico magnet 11. FIG.
The number of divisions of the stator core 5 and the rotor core 9 can be changed as appropriate.

The permanent magnet motor 1 of the present invention is not used as a driving source for the drum 24 of the above-described drum type washing machine 21 in which the axial direction is the horizontal direction, for example, in the rotary tub of a vertical washing machine in which the axial direction is the vertical direction. It can also be applied as a drive source.
The present invention is not limited to the outer rotor type permanent magnet motor 1 described above, but can also be applied to an inner rotor type permanent magnet motor.

  In the drawings, 1 is a permanent magnet motor, 2 is a stator, 3 is a rotor, 6 is a stator coil (winding), 9 is a rotor core, 11 is an alnico magnet (low coercive force permanent magnet), and 11a is an oxide film (low magnetic permeability). ), 12 is a neodymium magnet (high coercivity permanent magnet), 14 is a resin layer (low permeability antioxidant layer), and 10 is a magnet insertion hole (insertion hole).

Claims (5)

A stator with windings;
A rotor provided rotatably with respect to the stator;
A permanent magnet that is inserted into an insertion hole formed in the rotor core of the rotor and has a coercive force at a level that can easily change the amount of magnetization by a magnetic field generated from the winding;
A permanent magnet motor comprising an anti-oxidation layer having a low magnetic permeability formed on the surface of the permanent magnet.   The permanent magnet motor according to claim 1, wherein an oxide film is formed on the surface of the permanent magnet as the anti-oxidation layer having a low magnetic permeability.   2. The permanent magnet motor according to claim 1, wherein the low magnetic permeability antioxidant layer is formed on the surface of the permanent magnet by impregnating the surface of the permanent magnet with a rust inhibitor. The insertion hole opens larger than the permanent magnet,
The permanent magnet motor according to any one of claims 1 to 3, wherein a resin layer is formed on the surface of the permanent magnet as the low-permeability antioxidant layer. The permanent magnet is
A high coercivity permanent magnet,
The coercive force is smaller than that of the high coercive force permanent magnet, and the coercive force comprises a low coercive force permanent magnet having a level of coercive force that can be easily changed by the magnetic field generated from the winding,
The surface of the high coercive force permanent magnet is subjected to metal plating,
The permanent magnet motor according to any one of claims 1 to 4, wherein the low-permeability permanent magnet is provided with an anti-oxidation layer having a low magnetic permeability.

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