JP2008259359A - Outer rotor permanent magnet motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an outer rotor permanent magnet motor that easily brings a magnetic flux density into a sine curve shape without need for increasing the thickness of a permanent magnet in increasing the magnetic force of a magnetic pole. <P>SOLUTION: A reversed T-shape hole 14 is formed on a portion 13 having a magnetic pole of a rotor core 8, and in the hole 14, two permanent magnets 9a, 9b having different widths are stacked. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a rotor of an abduction type permanent magnet motor in which a permanent magnet is arranged in a hole formed in a portion where a magnetic pole of a rotor core is formed.

2. Description of the Related Art Conventionally, a rotor of a permanent magnet motor has been provided with a configuration in which a flat permanent magnet is inserted and disposed in a hole formed in a portion where a magnetic pole of an iron core is formed (see, for example, Patent Document 1).
On the other hand, in recent dehydrating washing machines, a method of driving an inverter of a permanent magnet motor is adopted, but the rotor is generally an abduction type, and in this abduction type permanent magnet motor, However, a configuration is adopted in which a hole is provided in a portion of the rotor core where the magnetic pole is formed, and a permanent magnet is inserted into the hole.
JP-A-8-182282

  In the rotor core of the outer rotation type permanent magnet motor used in the above-described washing machine for dehydration, a single permanent magnet is arranged in each hole. Therefore, the magnetic force of the permanent magnet is used for the purpose of increasing torque. In order to increase the strength, the thickness of the permanent magnet must be increased. However, flat permanent magnets undergo a manufacturing process in which magnetic powder is pressed and sintered, polished, and finished to a predetermined size, so that thick permanent magnets are difficult to manufacture and increase manufacturing costs. It was.

  In order to reduce driving noise in a washing machine that is also used as a dewatering machine, it is preferable to reduce the cogging torque of the electric motor. In order to reduce the cogging torque, it is effective that the magnetic flux density of each magnetic pole of the rotor core exhibits a sine curve shape. However, if the magnetic pole is composed of one flat permanent magnet, the magnetic flux density Becomes trapezoidal and difficult to make into a sine curve.

  The present invention has been made in view of the above circumstances. The purpose of the present invention is to increase the magnetic force of the magnetic pole without increasing the thickness of the permanent magnet, and to bring the magnetic flux density of the magnetic pole closer to a sine curve. An object of the present invention is to provide a rotor of an abduction type permanent magnet motor that is easy to operate.

  The present invention is characterized in that a plurality of permanent magnets are arranged in each hole of the rotor core so as to overlap in the radial direction of the rotor core.

  According to the present invention employing the above-described means, since a plurality of permanent magnets are arranged in the holes of the magnetic poles of the rotor core, when increasing the magnetic force, the thickness of each permanent magnet is increased. You don't have to. In addition, since each magnetic pole is composed of a plurality of permanent magnets, the magnetic flux density can be easily approximated to a sine curve.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings by applying it to a washing machine motor (a stirrer and a rotary drive source of a rotating tub) of a dehydrating washing machine.
FIG. 3 shows a stator 1 and a rotor 2 of an outer rotation type permanent magnet motor (brushless motor). Among them, the stator 1 includes a stator core 3 and a coil 4. Further, the stator core 3 is formed by laminating a large number of silicon steel plates, which are magnetic materials, and includes an annular yoke portion 3a and a large number of teeth portions 3b projecting radially from the outer peripheral portion thereof. The covering member 5 made of synthetic resin, which is an electrical insulating material, is formed by molding on substantially the entire outer surface.

A plurality of attachment portions 6 are formed on the inner peripheral portion of the covering member 5, whereby the stator 1 is attached to a motor attachment portion (not shown) of the dehydrating washing machine. The coils 4 are wound around the teeth 3b from the outer periphery of the covering member 5. The stator 1 is configured as described above.
On the other hand, the rotor 2 includes a frame 7, a rotor core 8, and a permanent magnet 9. Among them, the frame 7 is formed by pressing, for example, an iron plate that is a magnetic body, and has a circular main plate portion 7a and an annular peripheral side wall 7c that rises from the outer peripheral portion of the main plate portion 7a via the stepped portion 7b. And has a flat bottomed cylindrical shape.

  The rotor core 8 has an annular shape and is disposed on the inner peripheral portion of the peripheral side wall 7 c of the frame 7. Further, as shown in FIGS. 1 and 2, the rotor core 8 is slightly separated from the stepped portion 7b of the frame 7 in the axial direction (upward in the drawing) and slightly protrudes in the axial direction further than the peripheral side wall 7c. Are arranged to be. A plurality of resin through holes 10 are formed in the stepped portion 7b over the entire circumference. On the other hand, a shaft support insertion hole 11 is formed in the central portion of the main plate portion 7a as shown in FIG. Yes. And many ventilation holes 12 are radially formed in the part between this shaft support body insertion hole 11 and the step part 7b.

  As shown in FIG. 4, the rotor core 8 is formed by splicing a plurality (for example, six) of unit cores 8a formed by laminating a large number of, for example, silicon steel plates, which are magnetic bodies punched in a substantially arc shape. Thus, holes 14 are respectively formed in portions 13 of the rotor core 8 that form magnetic poles (for example, 48 poles in total). As shown in FIG. 1, the hole 14 has a depth that reaches from the lower end surface that is one end surface portion of the rotor core 8 in the axial direction to the upper end surface that is the opposite end surface portion, and is opened. As shown in FIG. 5, the inner peripheral side (stator core 3 side) of the rotor core 8 has a substantially convex planar shape with a narrow width. Further, in the hole 14, an outwardly recessed portion 15 is formed at the center of the outer peripheral side inner surface.

  For such a rotor core 8, the permanent magnet 9 is composed of two permanent magnets 9a and 9b having different widths as shown in FIG. As shown in FIGS. 1 and 2, the wide permanent magnet 9a is inserted and disposed in the wide portion 14a on the outer peripheral side of the hole 14 of the rotor core 8, and the narrow permanent magnet 9b is It is inserted and arranged in the narrow portion 14b on the circumferential side. In a state where both the permanent magnets 9 a and 9 b are disposed in the hole 14, a part thereof, for example, the upper end surface in the figure is flush with the upper end surface of the rotor core 8 and is exposed to the outside. The permanent magnets 9a and 9b may be inserted into the holes 14 after being bonded.

  The frame 7, the rotor core 8, and the permanent magnets 9 a and 9 b constituting the rotor 2 are integrated by a mold resin 16. FIG. 6 shows a mold 17 of the mold resin 16. As shown in FIG. 6, the molding die 17 includes a lower die 18 and an upper die 19 that covers the lower die 18. The lower mold 18 has a convex portion 20 protruding from the base surface 18a, and the rotor core 8 in which the permanent magnets 9a and 9b are inserted into the holes 14 is disposed on the outer periphery of the convex portion 20 of the lower mold 18. The frame 7 is put on from above.

  Further, the upper die 19 is put on the frame 7 and is clamped as shown in FIG. In this clamping state, the rotor core 8 and the permanent magnets 9 a and 9 b are in contact with the base surface 18 a of the lower mold 18. After the mold clamping, for example, a thermoplastic resin 16 is injected and filled into the cavity 21 between the lower mold 18 and the upper mold 19. The injection direction of the resin 16 is from the upper mold 19 side toward the lower mold 18 side as indicated by an arrow A in FIG. 7, that is, the side in which the rotor core 8 of the frame 7 is incorporated in FIG. There is a gate (not shown) on the opposite side.

  As a result, as shown in FIG. 1, the resin 16 passes through the resin through hole 10 of the step portion 7 b of the frame 7 and between the rotor core 8 and the step portion 7 b of the frame 7. The gap between the hole 14 and the two permanent magnets 9a, 9b and the recess 15 are filled to enclose the permanent magnets 9a, 9b from the outside, and between the rotor core 8 and the step 7b of the frame 7 As shown in FIG. 2, the valley portions 22 between the portions 13 forming the magnetic poles of the rotor core 8 are filled as shown in FIG. The outer surface side of the step 7b opposite to the above is also filled and formed into an annular shape.

  At that time, the resin 16 wraps around the shaft support 23 as an insert part from another gate (not shown) to the shaft support insertion hole 11 of the frame 7 as shown in FIG. A plurality of ribs 24 that are shaped to hold and extend radially around the periphery are formed. Thus, the frame 7, the rotor core 8, and the permanent magnets 9 a and 9 b are integrally fixed by the resin 16, the shaft support 23 is held, and the plurality of ribs 24 are formed, whereby the rotor 2 is manufactured. . The molding die 17 removes the upper die 19 and picks up the entire rotor 2 from the lower die 18 when the resin 16 is cured.

  Now, in the portion 13 forming the magnetic poles of the rotor core 8, the surface (inner peripheral surface) 13a facing the stator core 3 has a medium-high height as shown in FIGS. It is formed in a circular arc convex shape. Further, the portions 13 are separated from each other by a valley portion 22, but the side portions 13b on both sides along the circumferential direction among the peripheral side portions of the hole 14 are set to have a thickness of 0.5 mm or less. Yes. And since the hole 14 has convex shape, as shown to FIG. 9 (a-3), the trough part 22 has become the convex shape of the reverse direction to the hole 14, In the portion 13, the interval between the permanent magnets 9 a on the outer peripheral side is narrower than the interval between the permanent magnets 9 b on the inner peripheral side.

  When the rotor 2 is assembled as an electric motor together with the stator 1, the circuit board 25 attached to the stator 2 faces the upper end surface of the rotor core 8 as shown in FIG. 1. The circuit board 25 is provided with a magnetic sensor 26 for detecting the rotational position of the rotor 2 by the magnetic detection of the permanent magnet 9.

  The magnetic sensor 26 is composed of a Hall element or the like, and detects the magnetism of the permanent magnet 9a on the outer peripheral side. That is, the outer peripheral side permanent magnet 9a has opposite magnetic poles adjacent to each other as shown in FIGS. 9A-2 and 9A-3, and between the adjacent permanent magnets 9a, FIG. Leakage magnetic flux as shown by arrow B in (a-2) is generated. As shown in FIG. 9 (a-1), the leakage magnetic flux reverses in the middle, so that the reversal of the magnetic pole is detected with a certain threshold value. The magnetic sensor 26 detects the polarity inversion and outputs a position detection signal. In a motor control circuit unit (not shown), the position of the rotor 2 is calculated by a detection signal from the magnetic sensor 26, and the rotation of the rotor 2 is controlled by driving the coil 4 of the stator core 3 with an inverter.

According to the above configuration, the following excellent effects can be obtained.
(1) Since the hole 14 is formed in the portion 13 of the rotor core 8 where the magnetic pole is formed, and a plurality of, for example, two permanent magnets 9a and 9b are disposed in the hole 14, let's increase the magnetic force at the magnetic pole. In this case, the magnetic force of the individual permanent magnets 9a and 9b can be increased without increasing the thickness of the individual permanent magnets 9a and 9b so much, and a significant increase in manufacturing cost can be avoided.

In addition, the magnetic flux density of each of the permanent magnets 9a and 9b is trapezoidal, but the combined magnetic flux density when superimposed is closer to a sine curve as shown in FIG. For this reason, generation | occurrence | production of cogging torque reduces and it can contribute to noise reduction.
That is, FIG. 8A shows a case where the permanent magnets 9a and 9b have the same width and the same magnetic flux density, but the resultant magnetic flux density approaches a sine curve from a trapezoidal shape.

  FIG. 8B shows the case where the widths of the two permanent magnets 9a and 9b are made different (the magnetic flux density is the same) as in this embodiment, but the combined magnetic flux density when they are stacked is shown in FIG. It comes closer to the sine curve than (a). FIG. 8C shows the case where the magnetic flux density of the two permanent magnets 9a is made higher than that of the permanent magnets 9, but in this case, it becomes closer to a sine curve. It should be noted that the permanent magnets 9a and 9b are made different in thickness and the constituent materials of the permanent magnets 9a and 9b are made different so that the respective magnetic forces are different, thereby making the resultant magnetic flux density closer to a sine curve. May be.

  (2) Since the surface 13a of the portion 13 forming the magnetic pole that faces the stator core 3 has an arcuate convex shape, the magnetic flux density linked to the coil 4 of the stator core 3 is further increased by a sine curve. The generation of cogging torque is further reduced.

(3) When the interval between the magnetic poles of the rotor core 8 is narrowed, the leakage magnetic flux between the magnetic poles increases. For this reason, it is preferable in view of the generated torque to increase the interval between the magnetic poles as shown in FIGS. 9B-2 and 9B-3 with one permanent magnet 9, but the interval between the magnetic poles is reduced. If it is widened, as shown in FIG. 9 (b-1), the change in the leakage magnetic flux density between the magnetic poles becomes gradual, which may cause an error in the output timing of the position detection signal by the magnetic sensor 26.
However, in the present embodiment, the widths of the two permanent magnets 9a and 9b arranged at the respective magnetic poles are made different so that the wide permanent magnet 9a is arranged on the side farther from the stator core 3 (outer peripheral side) and narrow. Since the permanent magnets 9b are arranged on the side closer to the stator core 3 (inner peripheral side), even if the spacing between the permanent magnets 9a arranged on the outer peripheral side is narrowed, the spacing between the permanent magnets 9b arranged on the inner peripheral side is A wide state is obtained.

  In this way, with respect to the permanent magnet 9a on the outer peripheral side, the spacing between the adjacent permanent magnets 9a is narrow and the effect of suppressing magnetic flux leakage is small, but instead, as shown in FIG. 9 (a-1). As a result, the change in leakage magnetic flux density becomes abrupt, and the position detection accuracy by the magnetic sensor 26 is improved. The permanent magnet 9b on the side of the stator core 3 directly affects the generated torque, but the permanent magnet 9b has a large separation distance between adjacent permanent magnets 9b. However, leakage of magnetic flux can be suppressed, and reduction of generated torque can be prevented as much as possible.

  (4) The two permanent magnets 9a and 9b arranged on each magnetic pole of the rotor core 8 are magnetized with different magnetic poles in the thickness direction as shown in FIG. 9 (a-3). For this reason, in the permanent magnets 9a and 9b, as shown by the arrow C in FIG. 9 (a-3), the magnetic flux leaks on the side portions in the width direction using the side portion of the hole 14 as a magnetic path. In the present embodiment, the thickness of both side portions of the hole 14 is set to 0.5 mm or less in the portion 13 forming the magnetic pole of the rotor core 8. If the thickness is about 0.5 mm, the magnetic saturation occurs, the leakage magnetic flux can be suppressed to a constant level, and the strength of the side portion of the hole 14 can be secured.

  (5) Since one end surfaces of the two permanent magnets 9a and 9b arranged in the hole 14 are exposed, the end surfaces of the permanent magnets 9a and 9b are moved together with the one end surface of the rotor core 8 when the mold resin 16 is formed. The lower mold 18 can be positioned in contact with the base surface 18a. For this reason, even if the permanent magnet 9 is comprised from the two permanent magnets 9a and 9b, the positional relationship with respect to the rotor core 8 of the permanent magnets 9a and 9b is stabilized.

The present invention is not limited to the embodiment described above and shown in the drawings, and can be expanded or modified as follows.
The permanent magnet 9 is not limited to the one constituted by the two permanent magnets 9a and 9b, and may be constituted by three or more permanent magnets.
The plurality of permanent magnets constituting the permanent magnet 9 may have different thicknesses. In this case, all of the plurality of permanent magnets may have different thicknesses, or the permanent magnets with different thicknesses may be mixed in the same permanent magnet.
The plurality of permanent magnets constituting the permanent magnet 9 may be made of different materials. Various materials such as ferrite, samarium cobalt, iron-chromium-cobalt, and manganese aluminum are conceivable.

The fragmentary sectional view of the rotor which shows one Embodiment of this invention Partial perspective view of rotor Perspective view showing the overall configuration of the electric motor partially broken Top view of the entire rotor core Partial exploded perspective view of the rotor Sectional drawing showing the molding process of the rotor by the mold Cross-sectional view showing resin filling into mold The figure which shows the synthetic magnetic flux density in the case of comprising from a plurality of permanent magnets with a comparative example The figure which shows the leakage magnetic flux in the case of comprising from a plurality of permanent magnets with a comparative example

Explanation of symbols

  In the drawings, 1 is a stator, 2 is a rotor, 3 is a stator iron core, 4 is a coil, 8 is a rotor iron core, 9a and 9b are permanent magnets, 13 is a portion forming a magnetic pole, 14 is a hole, 16 is Resin, 17 is a mold, and 26 is a magnetic sensor.

Claims (8)

In a rotor of an abduction type permanent magnet motor that has an annular shape surrounding the stator core from the outside and includes a rotor core having a hole in a portion forming a magnetic pole, and a permanent magnet is disposed in the hole of the core. ,
A rotor of an abduction type permanent magnet motor, wherein a plurality of permanent magnets are disposed in each hole of the rotor core so as to overlap in the radial direction of the rotor core.   The rotor of an outer rotation type permanent magnet motor according to claim 1, wherein the plurality of permanent magnets arranged in each hole have different thicknesses in the radial direction.   The rotor of an outer rotation type permanent magnet motor according to claim 1, wherein the plurality of permanent magnets arranged in each hole have different widths in a direction along a circumferential direction.   4. The rotor of an abduction type permanent magnet motor according to claim 3, wherein a plurality of permanent magnets arranged in each hole are positioned more radially outward of the rotor core.   The rotor of an outer rotation type permanent magnet motor according to any one of claims 1 to 4, wherein the plurality of permanent magnets arranged in each hole are made of different materials.   The surface of the part that forms the magnetic pole of the rotor core that faces the stator core is formed in an arcuate convex shape. Rotor.   The portions constituting the magnetic poles of the rotor core are provided apart from each other, and the thickness of both side portions in the direction along the circumferential direction of the peripheral side portions of the holes is set to 0.5 mm or less. The rotor of an abduction type permanent magnet motor according to any one of claims 1 to 6.   The rotor of an outer rotation type permanent magnet motor according to any one of claims 1 to 7, wherein the permanent magnet is integrated with the rotor core by molding resin so that a part of the permanent magnet is exposed.

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