JP2012080658A - Permanent magnet motor and washing machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a permanent magnet motor where demagnetization and magnetization of a permanent magnet with a small coercive force have little effect on magnetic flux between a plurality of split cores of a rotor.SOLUTION: A permanent magnet motor has a rotor that includes a plurality of split cores arranged circumferentially and formed into an approximately annular shape. Each of the split cores has a plurality of magnet insertion slots into which permanent magnets are inserted so as to form magnetic poles. The rotor is rotatable relative to a stator. Permanent magnets with a relatively large coercive force are inserted into the magnet insertion slots located near boundaries among the split cores, and at least one permanent magnet with a relatively small coercive force is inserted into the magnet insertion slot located elsewhere than near the boundaries.

Description

  The present invention relates to a permanent magnet motor having a plurality of types of permanent magnets inside a rotor core and a washing machine.

  In this type of permanent magnet motor, the amount of magnetic flux (interlinkage magnetic flux) of the permanent magnet interlinked with the stator winding according to the load driven by the permanent magnet motor (for example, the drum of a drum type washing and drying machine). Proper adjustment is desired.

  However, the permanent magnet provided in 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 only a permanent magnet having a large coercive force is used, the induced voltage due to the permanent magnet at the time of high-speed rotation becomes extremely high, which may cause dielectric breakdown of electronic components. On the other hand, if it comprises only a permanent magnet with a small coercive force, the output at the time of low speed rotation will fall.

  Therefore, for example, in the permanent magnet motor described in Patent Document 1, permanent magnets having different coercive forces are arranged inside the rotor core, and the magnetization state of the permanent magnets having a small coercive force is changed to the external by armature reaction. The amount of magnetic flux of the permanent magnet is adjusted by demagnetizing or increasing the magnetic field (magnetic field generated by the current flowing through the stator winding).

JP 2009-284746 A

  However, in the permanent magnet motor described in Patent Document 1, for example, when the core of the rotor is divided and formed, the magnetization of the permanent magnet having a small coercive force is demagnetized and increased, and the magnetic flux between the cores is reduced. Because of differences, motor noise may occur.

  The present invention has been made in view of the above-described circumstances, and its purpose is a permanent magnet that does not affect the magnetic flux between the rotor cores even when the magnetization of the permanent magnet having a small coercive force is in a demagnetized state or a magnetized state. It is providing the washing machine provided with the motor and the said permanent magnet motor.

  In the permanent magnet motor according to the embodiment, a stator having a plurality of teeth wound with windings and a plurality of divided cores are arranged in the circumferential direction to form a substantially ring shape, and each of the divided cores is permanent. A magnet having a plurality of magnet insertion openings for forming magnetic poles by inserting magnets, the rotor being provided rotatably with respect to the stator, and a magnet in the vicinity of the boundary between the divided cores of the magnet insertion openings A permanent magnet having a relatively large coercive force is inserted into the insertion port, and at least one permanent magnet having a relatively low coercive force is inserted into a magnet insertion port other than the vicinity of the boundary.

1 is a perspective view schematically showing an overall configuration of a permanent magnet motor according to Embodiment 1 of the present invention. FIG. The perspective view which expands and shows a part of rotor Schematic schematic showing a part of the rotor and stator expanded linearly Longitudinal side view schematically showing the internal structure of the washing machine Block diagram schematically showing electrical connection of permanent magnet motor

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a perspective view schematically showing the overall configuration of a permanent magnet motor 1 (outer rotor type brushless motor). The permanent magnet motor 1 includes a stator 2 and a rotor 3 provided on the outer periphery thereof.

  The stator 2 includes a stator core 4 having a plurality of teeth 4a projecting radially on the outer peripheral portion, and a stator winding 5 wound around each tooth 4a. The stator core 4 includes a plurality of cores 4A formed by laminating and caulking a plurality of silicon steel plates that are punched and formed of soft magnetic materials, and engaging protrusions formed at one end of the core 4A. It is formed by being connected to each other by engaging with each other in an engaging recess formed at the end of each. The surface of the stator core 4 is covered with PET resin (mold resin) except for the outer peripheral surface (tip surface of each tooth 4a) that forms a gap with the inner peripheral surface of the rotor 3. A plurality of attachment portions 6 made of this PET resin are integrally formed on the inner peripheral portion of the stator 2. These attachment portions 6 are provided with a plurality of screw holes, and by fixing these attachment portions 6, the stator 2 is fixed to the back surface of the water tub 25 (see FIG. 4) of the washing machine 21 in this case. It has come to be. The stator winding 5 consists of three phases and is wound around each tooth 4a.

  As shown in FIGS. 1 and 2, the rotor 3 has a structure in which a frame 10, a rotor core 11, and a plurality of types of permanent magnets 12 having different coercive forces are integrated with a mold resin (not shown). . The frame 10 is formed into a flat bottomed cylindrical shape by pressing, for example, an iron plate, which is a magnetic body, and has a circular main plate portion and an annular periphery that rises from the outer peripheral portion of the main plate portion via a talk portion. And a side wall. A shaft attaching portion 16 for attaching a rotating shaft is provided at the center of the main plate portion.

The rotor core 11 is formed by laminating and caulking a plurality of silicon steel plates, which are soft magnetic bodies punched and formed in a substantially annular shape, and is disposed on the inner peripheral portion of the peripheral side wall of the frame 10. The inner peripheral surface of the rotor core 11 (the surface that faces the outer peripheral surface of the stator (the outer peripheral surface of the stator core 4) and forms a gap between the stator core 4) is circular toward the inner side. It is formed in a concavo-convex shape having a plurality of convex portions 11a protruding in an arc shape. Each of the plurality of convex portions 11a is formed with one rectangular magnet insertion slot 11b penetrating through the rotor core 11 in the axial direction (stacking direction of the silicon steel plates). 11 b has a configuration in which the rotor core 11 is annularly arranged.

  The permanent magnet 12 is, for example, two types of permanent magnets: a low coercivity permanent magnet (hereinafter referred to as “low coercivity magnet 12a”) and a high coercivity permanent magnet (hereinafter referred to as “high coercivity magnet 12b”). By inserting into the magnet insertion slot 11b of the rotor core 11, the convex part 11a of the rotor core 11 is made into a magnetic pole. The low coercive force magnet 12a is, for example, a samakoba (samarium / cobalt) magnet having a low coercive force (the coercive force of the samakova magnet is 350 kA / m or less). The high coercive force magnet 11b is, for example, a neodymium magnet having a high coercive force (the coercive force of the neodymium magnet is 700 kA / m or more). Note that the Samakoba magnet is the low coercive force magnet 12a and the neodymium magnet is the high coercive force magnet 12b because the external magnetic field (stator winding 5 is changed from the stator 2 (stator winding 5) to the armature reaction. When a magnetic field generated by a flowing current) is applied, a samacoba magnet is used as a low coercivity magnet on the basis that the magnetization amount of a neodymium magnet does not change with a current that can change the magnetization amount of the samacoba magnet. The 12a and neodymium magnets are referred to as high coercivity magnets 12b.

The configuration of the rotor core 11 and the arrangement of the permanent magnets 12 are shown in FIG. FIG. 3 is a schematic schematic view showing a part of the rotor 3 and the stator 2 expanded linearly. The plurality of split cores 11A are formed by being connected to each other by inserting and engaging the engaging convex portion 13a formed at one end portion with the engaging concave portion 13b formed at the other end portion. The rotor core 11 is formed by combining six divided cores 11A. Each of the split cores 11A has eight convex portions 11a that form magnetic poles, and low coercivity magnets are inserted into the eight magnet insertion openings 11b so that the magnetic poles alternately have N and S poles. 12a or high coercive force magnet 12b is inserted and arranged. Here, the high coercivity magnets 12b are disposed in the magnet insertion openings 11b at both ends of the split core 11A, and the low coercivity magnets 12a are disposed in at least one magnet insertion opening 11b other than both ends.

  For example, the low coercive force magnet 12a is disposed in the fourth magnet insertion slot 11b when viewed from one side (left side) of the split core 11A, and the high coercivity magnet 12b is disposed in the other magnet insertion slot 11b. Specifically, the high coercivity magnet 12b (“large N”), the high coercivity magnet 12b (“large S”), the high coercivity magnet 12b (“large N”), the low coercivity magnet 12a (“small S”), The high coercive force magnet 12a ("large N"), the high coercive force magnet 12a ("large S"), the high coercive force magnet 12a ("large N"), and the high coercive force magnet 12a ("large S") are arranged in this order. .

  Similarly, the other divided cores 11A are sequentially arranged with a low coercive force magnet 12a and a high coercive force magnet 12b.

  Next, the configuration of the washing machine 21 including the permanent magnet motor 1 configured as described above will be described. FIG. 4 is a longitudinal side view schematically showing the internal configuration of the washing machine 21.

  The outer box 22 forming the outer shell of the washing machine 21 has a laundry entrance 23 opened in a circular shape on the front surface. The laundry entrance 23 is opened and closed by a door 24. Inside the outer box 22, a bottomed cylindrical water tank 25 having a closed back surface is disposed, and the permanent magnet motor 1 (stator 2) is screwed to the center of the back surface of the water tank 25. It is fixed. The rotating shaft 26 of the permanent magnet motor 1 has a rear end portion (right end portion in FIG. 4) fixed to the shaft mounting portion 16 of the permanent magnet motor 1 (rotor 3), and a front end portion (in FIG. 4). The left end) protrudes into the water tank 25. A bottomed cylindrical drum 27 whose rear surface is closed is fixed to the front end of the rotating shaft 26 so as to be coaxial with the water tank 25, and this drum 27 is driven by the permanent magnet motor 1. It rotates integrally with the rotor 3 and the rotating shaft 26. The drum 27 is provided with a plurality of flow holes 28 through which air and water can flow, and a plurality of baffles 29 for scraping and unraveling the laundry in the drum 27.

  A water supply valve 30 is connected to the water tank 25, and water is supplied into the water tank 25 when the water supply valve 30 is opened. Further, a drain hose 32 having a drain valve 31 is connected to the water tank 25, and when the drain valve 31 is opened, water in the water tank 25 is discharged.

  A ventilation duct 33 extending in the front-rear direction is provided below the water tank 25. A front end portion of the ventilation duct 33 is connected to the water tank 25 via the front duct 34, and a rear end portion is connected to the water tank 25 via the rear duct 35. A blower fan 36 is provided at the rear end of the ventilation duct 33, and the air in the water tank 25 is blown from the front duct 34 into the ventilation duct 33 by the blowing action of the blower fan 36 as indicated by an arrow. And is returned to the water tank 25 through the rear duct 35.

  An evaporator 37 is disposed on the front end side inside the ventilation duct 33, and a condenser 38 is disposed on the rear end side. The evaporator 37 and the condenser 38 constitute a heat pump 40 together with the compressor 39 and a throttle valve (not shown), and the air flowing through the ventilation duct 33 is dehumidified by the evaporator 37 and heated by the condenser 38. And is circulated in the water tank 25.

  An operation panel 41 is provided on the front surface of the outer box 22 above the door 24. The operation panel 41 is provided with a plurality of operation switches (not shown) for setting a driving course and the like. ing. The operation panel 41 is composed mainly of a microcomputer and is connected to a control circuit unit 42 (corresponding to a control unit) that controls the overall operation of the drum-type washing and drying machine 21, and the control circuit unit 42 is connected to the operation panel 41. Various operation courses are executed while controlling the drive of the permanent magnet motor 1, the water supply valve 30, the drain valve 31, the compressor 39, the throttle valve, etc.

  Further, a magnetic sensor 43 (see FIG. 5) that detects the magnetism of the permanent magnet 12 is disposed at a portion facing the permanent magnet 12 in the permanent magnet motor 1. The magnetic sensor 43 is mounted on a circuit board (not shown) attached to the stator 2 side. As shown in FIG. 5, the control circuit unit 42 calculates the rotational position of the rotor 3 based on the detection signal from the magnetic sensor 43. Then, by driving the inverter circuit 44 in which six IGBTs 44a (only two are shown in FIG. 7) are connected in a three-phase bridge by the gate drive signal G according to the calculation result, the stator winding 5 The rotor 3 is rotated while controlling energization.

  Next, the operation of the washing machine 21 provided with the permanent magnet motor 1 as described above will be described.

  When the control circuit unit 42 energizes the stator winding 5 via the inverter circuit 44, an external magnetic field (magnetic field generated by a current flowing through the stator winding 5) due to the armature reaction is generated by the permanent magnets 12a, 12b will be acted upon. Of these permanent magnets 12a and 12b, the magnetization state of the high coercivity magnet 12b does not change, but the magnetization state of the low coercivity magnet 12a is demagnetized or increased by an external magnetic field due to this armature reaction. Thereby, the magnetic flux amount (interlinkage magnetic flux amount) linked to the stator winding 5 can be increased or decreased. Therefore, in the present embodiment, the control circuit unit 42 switches the magnetization state of the low coercive force magnet 12a for each operation process (washing process, dehydration process, drying process) by controlling the energization of the stator winding 5. To run. Here, the operation content in each driving process will be described in order.

  First, in the washing process, the control circuit unit 42 opens the water supply valve 30 to supply water into the water tank 25, and then rotates the drum 27 to perform washing. In this washing process, it is necessary to rotate the drum 27 with high torque in order to scoop up the laundry containing water, but the rotation speed may be low. Therefore, the control circuit unit 42 controls energization of the stator winding 5 by the inverter circuit 44 so that the magnetization state of the low coercive force magnet 12a is increased. As a result, the amount of magnetic flux acting on the stator winding 5 is large (the magnetic force is strong), so that the drum 27 can be rotated at high torque and low speed.

  Next, in the dehydration process, the control circuit unit 42 opens the drain valve 31 to discharge the water in the water tank 25, and then dehydrates moisture contained in the laundry by rotating the drum 27 at a high speed. In this dewatering process, it is necessary to rotate the drum 27 at a high speed in order to improve the dewatering efficiency, but the torque may be small. Therefore, the control circuit unit 42 controls energization of the stator winding 5 by the inverter circuit 44 so that the magnetization state of the low coercive force magnet 12a is demagnetized. As a result, the amount of magnetic flux acting on the stator winding 5 is reduced (the magnetic force is weak), so that the drum 27 can be rotated at a low torque and a high speed.

  Finally, in the drying process, the control circuit unit 42 dries the laundry by driving the blower fan 36 and the heat pump 40 and rotating the drum 27. In this drying process, the control circuit unit 42 controls the energization of the stator winding 5 by the inverter circuit 44 so that the magnetization state of the low coercive force magnet 12a is increased in preparation for the next washing process. . Thereby, it can be set as the state which increased the magnetic flux amount which acts on the stator coil | winding 5, and can make it easy to rotate the drum 27 at high torque low speed in the next washing process.

  As described above, according to the permanent magnet motor 1 of the present embodiment, the magnetization state of the low coercive force magnet 12a among the two types of permanent magnets 12a and 12b having different coercive forces is reduced by the external magnetic field due to the armature reaction. By magnetizing or magnetizing, it is possible to adjust the amount of magnetic flux of the permanent magnet 12 according to the load to be driven (in this embodiment, the drum 27 of the washing machine 21). As a result, the amount of magnetic flux of the permanent magnet 12 can be appropriately varied, and insulation breakdown during high speed rotation and output reduction during low speed rotation can be prevented.

Further, the permanent magnet 12 inserted and arranged in the magnet insertion openings 11b at both ends of the split core 11A is assumed to be a high coercivity magnet 12b, and the low coercivity magnets 12a are arranged in the magnet insertion openings 11b other than both ends. . Thereby, since there is no low coercivity magnet 12a at both ends of the split core 11A, the magnetic flux between the split cores 11A does not change when the low coercivity magnet 12a is in a magnetized state or a demagnetized state. Therefore, vibration and noise of the permanent magnet motor 1 can be suppressed.

Further, according to the configuration of the present embodiment, since the low coercive force magnet 12a is formed as far as possible from both ends, changes in magnetic flux between the divided cores 11A can be further suppressed.

Moreover, since the arrangement of the low coercivity magnets 12a and the high coercivity magnets 12b is made constant in each divided core 11A, the manufacturing of the permanent magnet motor 1 can be simplified, and at the same time, the change in the gap magnetic flux density during rotation. Can be made constant, and rotation with little fluctuation can be made possible. In addition, since the arrangement of the low coercivity magnets 12a is the same in each divided core 11A, the magnetization state of the low coercivity magnets 12a can be easily and efficiently changed.

(Other embodiments)
The present invention is not limited to the above-described embodiments, and can be modified or expanded as follows.

  Although the number of magnetic poles (number of convex portions 11a) of the divided core 11A is 8 and the number of divided cores 11A is 6, the present invention is not limited to this, and a high coercive force is provided in the magnet insertion openings 11b at both ends of the divided core 11A. If the magnet 12b is arrange | positioned, the number can be set arbitrarily.

  The arrangement of the permanent magnets 12 of the split core 11A is not limited to the above embodiment, and various modes can be adopted as long as the high coercive force magnet 12b is arranged in the magnet insertion port 11b at the end of the split core 11A. . For example, in the first embodiment, the low coercive force magnet 12a is disposed at the portion farthest from both ends of the split core 11A. However, if the magnet is not disposed at the magnet insertion ports 11b at both ends of the split core 11A, You may arrange | position to 11b. Moreover, although the arrangement | positioning of the low coercive force magnet 12a of each division | segmentation core 11A was made into the Example of the same position in each division | segmentation core 11A, arrangement | positioning may differ by each division | segmentation core 11A. In addition, although one low coercive force magnet 12a of each divided core 11A is arranged, a plurality of pieces can be arranged. Further, when a plurality of low coercivity magnets 12a are arranged in each divided core 11A, the low coercivity magnets 12a and the high coercivity magnets 12b may be arranged alternately, or the low coercivity magnets 12a may be arranged continuously. Good. In order to easily change the magnetization state of the low coercive force magnet 12a, it is preferable that the high coercive force magnet 12b be disposed next to at least one of the low coercive force magnets 12a.

  In addition, although the low coercive force magnet 12a is a Samacoba magnet and the high coercive force magnet 12b is a neodymium magnet, it is not limited thereto. When the external magnetic field (magnetic field generated by the current flowing through the stator winding 5) is applied from the stator 2 (stator winding 5) due to the armature reaction, the amount of magnetization of the low coercivity magnet 12a is changed. Any permanent magnet can be used as long as the low coercivity magnet 12a and the high coercivity magnet 12b are selected on the basis that the magnetization amount of the high coercivity magnet 12b does not change with a current that can be applied. For example, as the low coercive force magnet 12a, an alnico magnet, a ferrite magnet, a neodymium magnet having a small coercive force, or the like can be employed. Further, as the high coercive force magnet 12b, it is also possible to employ a summer coke magnet having a large coercive force.

  Further, the permanent magnet 12 is not limited to two types, and may be composed of three types of permanent magnets with large, medium and small coercive force, or composed of a plurality of types of permanent magnets such as four types and five types. May be. Also in this case, the change in the magnetic flux between the divided cores 11A can be minimized by disposing permanent magnets having a relatively large coercive force at both ends of the divided cores 11A.

  The means for adjusting the amount of magnetic flux of the permanent magnet 12 is not limited to the configuration in which the energization of the stator winding 5 is controlled by the inverter circuit 44. For example, a winding different from the stator winding 5 is provided. A configuration may be adopted in which energization of the winding is controlled.

  The permanent magnet motor 1 of the present invention can be applied not only to the above-described washing machine 21 but also to a washing / drying machine having a drying function and a vertical washing machine in which the axial direction of the rotating tub is vertical. Further, the present invention can be applied not only to the outer rotor type permanent magnet motor 1 as described above but also to an inner rotor type motor in which a rotor is provided on the inner periphery of the stator. Furthermore, the permanent magnet motor 1 of the present invention can be applied to various motors such as a compressor driving motor mounted on an air conditioner or the like.

  In the drawings, 1 is a permanent magnet motor, 3 is a rotor, 11 is a rotor core, 11A is a split core, 11a is a projection, 11b is a magnet insertion slot, 12a is a low coercivity magnet, 12b is a high coercivity magnet, 21 Denotes a washing machine, and 42 denotes a control circuit unit (control unit).

Claims (5)

A stator having a plurality of teeth wound with windings;
A plurality of divided cores are arranged in the circumferential direction to form a substantially ring shape, and each of the divided cores has a plurality of magnet insertion openings for inserting a permanent magnet to form a magnetic pole, and is rotatable with respect to the stator And a rotor provided in
A permanent magnet having a relatively large coercive force is inserted into a magnet insertion port near the boundary between the divided cores among the magnet insertion ports, and a permanent magnet having a relatively small coercive force is inserted into a magnet insertion port other than the vicinity of the boundary. At least one permanent magnet motor is inserted.   A permanent magnet having a relatively large coercive force is inserted into at least one of the magnet insertion ports arranged next to the magnet insertion port in which the permanent magnet having a relatively small coercive force is inserted. The permanent magnet motor according to claim 1.   The permanent magnet motor according to claim 1, wherein the magnet having a relatively large coercive force and the magnet having a relatively small coercive force are alternately arranged.   4. A magnetizing amount control means for generating an exciting current in the winding of the stator to change the magnetizing amount of the relatively small coercive permanent magnet. The permanent magnet motor of any one of Claims. A permanent magnet motor according to claim 4,
The magnetizing amount control means changes the magnetizing amount of the permanent magnet having a relatively small coercive force for each operation process.

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