JP2011147288A - Rotor of synchronous motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rotor of a synchronous motor for achieving the highly efficient and inexpensive synchronous motor with low noise and high power. <P>SOLUTION: The rotor of the synchronous motor includes a permanent magnet of a plastic magnet of rare earth (SmFeN) being a material with a high magnetic characteristic (resin material including powder of rare earth magnet), which is arranged on a surface of the rotor and is oriented or magnetized with pole anisotropy. A non-magnetic member is arranged at the back of the permanent magnet. When thickness in a radial direction of the permanent magnet is set to be D and magnetic pole width of the rotor to be W, a relation of D/W≥0.3 is satisfied. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a rotor of a synchronous motor having a permanent magnet in the rotor.

  Synchronous motors used for blowers of household electrical products often use plastic magnet ring magnets for the rotor from the viewpoint of light weight, low cost, and low noise. In particular, a polar-oriented magnet that applies an extremely anisotropic magnetic field from the outside at the time of manufacturing the ring magnet is often used. This is because, as viewed from the stator iron core, there is no need to dispose the iron core as the back yoke on the back surface of the magnet, so that the number of parts can be reduced and the weight can be reduced at the same time.

  Further, since the magnetic flux density distribution waveform on the rotor surface becomes sinusoidal due to the anisotropic orientation, it is possible to suppress the generation of induced voltage distortion and cogging torque that cause vibration and noise of the synchronous motor.

  Magnets often used in these synchronous motors are often ferrite, and the performance of magnets is insufficient for applications that require high output, high efficiency, and downsizing.

  On the other hand, by using a plastic magnet made of a rare earth magnet with higher performance, it is possible to achieve higher output, higher efficiency, and smaller size. However, since these materials (rare earth magnets) are expensive, it is often the case that a thin magnet is attached to the surface of the iron core of the magnetic material, contrary to the above. In this case, in addition to the increase in the number of parts and the weight, it is necessary to ensure sufficient reliability with respect to the adhesion between the metal material and the resin material. In addition, when using thin ring magnets, the magnet orientation is often radial orientation, which causes an increase in cogging torque, an increase in torque ripple due to distortion of the induced voltage of the synchronous motor, etc. It becomes a factor.

  On the other hand, a technique has been proposed in which a rare earth plastic magnet in a ring shape is oriented close to the polar anisotropy different from the radial orientation in the vicinity (between the poles) where the magnetic pole is switched.

  That is, in the method of orienting a hollow cylindrical anisotropic bonded magnet, when forming an anisotropic bonded magnet using a mold, the cylindrical axis cavity of the mold is made of a high permeability object. A cylindrical core is provided, and an anisotropic bonded magnet raw material is filled in a cylindrical cavity formed on the outer periphery of the core. In the cavity on the cross section perpendicular to the central axis, the core section is oriented in the main section. By applying an orienting magnetic field so that the normal direction of the outer circumference is in the normal direction, the distribution of the surface magnetic flux density in the normal direction of the anisotropic bonded magnet after magnetization is equal, while the orientation of the magnetic pole In the transition zone where the magnetic field changes, by gradually reversing the orientation magnetic field in the tangential direction, the absolute value of the surface magnetic flux density in the normal direction of the anisotropic bonded magnet after magnetization is increased with respect to the increase in electrical angle. Gradually decreasing and increasing distribution By generating an orientation magnetic field so that an alignment treatment method of the anisotropic bonded magnet motor, characterized in that for alignment treatment anisotropic bonded magnet has been proposed (e.g., see Patent Document 1).

  In the hollow cylindrical anisotropic bonded magnet, the surface magnetic flux density in the normal direction in the cross section perpendicular to the axis of the anisotropic bonded magnet is the same as the surface magnetic flux density in the normal direction in the main section of the magnetic pole period. In the transition section in which the magnetic pole directions change, the absolute value of the surface magnetic flux density in the normal direction gradually decreases and gradually increases as the electrical angle increases. It has been proposed (see, for example, Patent Document 2).

  According to these, the cogging torque can be reduced, and the increase in vibration and noise of the synchronous motor can be suppressed even when a high magnetic force magnet is used.

  In a polar anisotropic ring magnet, the magnetization direction is the normal direction at the magnetic pole position, the tangential direction at the intermediate position between the adjacent magnetic poles, and an equiangular pitch element between the magnetic pole position and the adjacent intermediate position. A method has been proposed in which the magnetic flux density distribution on the rotor surface is made closer to a sine wave by making the magnetization directions of adjacent elements have a certain angular difference when divided into two (see, for example, Patent Documents). 3).

Japanese Patent Laid-Open No. 2004-23085 JP 2004-56835 A JP-A-2005-44820

  However, in the motor using the anisotropic bonded magnet for a motor described in Patent Documents 1 and 2, although the cogging torque of the rotor can be reduced, a back yoke of the rotor core is necessary. There are many issues such as ensuring the manufacturing cost and the reliability of adhesion.

  In order to suppress the vibration and noise of the synchronous motor, it is effective to smooth the magnetic flux density distribution on the rotor surface, and it is an effective means to use a magnet with polar orientation or magnetization. . However, since the rare earth magnet is an expensive material as described above, it is necessary to make the shape and amount of use suitable for the required performance in order to reduce the product cost.

  In Patent Document 3, there is a description that the inner diameter of the ring-shaped permanent magnet is set to a certain value or more. In other words, if the thickness of the ring-shaped permanent magnet exceeds a certain value, the surface magnetic flux density saturates, so it is desirable to make it less than that, but if the back yoke is not used on the back of the permanent magnet, the thickness of the permanent magnet is If the thickness is too thin, polar anisotropic orientation is not sufficiently formed inside the permanent magnet, so that the magnetic properties of the permanent magnet cannot be fully utilized.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a rotor for realizing a synchronous motor having low noise, high output, high efficiency, and low cost.

A rotor of a synchronous motor according to the present invention includes a rare earth permanent magnet arranged on the rotor surface and oriented or magnetized in an anisotropic direction, and a nonmagnetic member is arranged on the back of the permanent magnet. Yes,
When the radial thickness of the permanent magnet is D and the magnetic pole width of the rotor is W,
D / W ≧ 0.3
It is characterized by satisfying the relationship.

  The synchronous motor rotor according to the present invention can realize a low-noise, high-efficiency, low-cost synchronous motor rotor by using the minimum necessary materials by optimizing the size of the permanent magnet. It becomes possible.

FIG. 3 shows the first embodiment and is a cross-sectional view of a rotor 100 of the synchronous motor. The figure which expanded a part of FIG. FIG. 5 shows the first embodiment, and shows electromagnetic field analysis results in a state where a magnetic body 200 is arranged with a constant gap 30 provided on the outer periphery of the rotor 100. FIG. 4 shows the first embodiment, and shows a gap magnetic flux density distribution waveform obtained from the electromagnetic field analysis result of FIG. 3. The figure which shows Embodiment 1 and shows the result of having calculated | required the magnetic flux magnetic flux density by electromagnetic field analysis at the time of changing the magnet thickness and the magnetic pole number of the rotor 100 with a table | surface. FIG. 5 is a diagram illustrating the first embodiment, and is a diagram illustrating, in a graph, the result of obtaining the gap magnetic flux density by electromagnetic field analysis when the magnet thickness and the number of magnetic poles of the rotor 100 are changed. The figure which shows Embodiment 1, and is a figure which shows a magnet thickness / magnetic pole width when changing the magnet thickness of the rotor from which the number of magnetic poles differs. FIG. 5 is a diagram illustrating the first embodiment and is a diagram illustrating a relationship between magnet thickness / magnetic pole width and air gap magnetic flux density in a graph.

Embodiment 1 FIG.
1 to 8 are diagrams showing the first embodiment. FIG. 1 is a cross-sectional view of a rotor 100 of a synchronous motor, FIG. 2 is an enlarged view of part of FIG. 1, and FIG. The figure which shows the electromagnetic field analysis result of the state which provided the fixed air gap 30 and has arrange | positioned the magnetic body 200, FIG. 4 is a figure which shows the air gap magnetic flux density distribution waveform obtained from the electromagnetic field analysis result of FIG. FIG. 6 is a table showing the results obtained by electromagnetic field analysis of the gap magnetic flux density when the thickness and the number of magnetic poles of the rotor 100 are changed. FIG. 6 shows the gap magnetic flux density when the magnet thickness and the number of magnetic poles of the rotor 100 are changed. FIG. 7 is a graph showing the results obtained by electromagnetic field analysis, FIG. 7 is a table showing the magnet thickness / magnetic pole width when the magnet thickness of the rotor with different number of magnetic poles is changed, and FIG. 8 is the magnet thickness / magnetic pole. Graph showing the relationship between width and air gap magnetic flux density A.

  The rotor 100 of the synchronous motor according to the present embodiment shown in FIG. 1 is composed of a magnet 10 (permanent magnet) having a high magnetic force. This magnet 10 is polar-oriented or magnetized, and the magnetic flux inside the magnet 10 enters from the surface of the rotor 100, most of which does not come out to the inner diameter side of the magnet 10 and is again in the rotor 100. Go out to the surface. For this reason, the rotor 100 according to the present embodiment has less need for a back yoke made of a magnetic material such as an iron core serving as a magnetic path inside the magnet 10.

  The magnet 10 may be simply called a magnet.

  The broken line in FIG. 1 indicates the magnetic flux inside the magnet. The magnetic flux is directed from the N pole to the S pole.

  The rotor 100 shown in FIG. 1 is used for a synchronous motor for a blower mounted on an air conditioner, for example.

  For example, a rare earth (SmFeN) plastic magnet (resin material containing rare earth magnet powder), which is a material having high magnetic properties, is used for the magnet 10.

  The diameter of the rotor 100 is 49 mm, for example.

  The magnet 10 is a ring magnet, and its thickness D (see FIG. 2) is, for example, 4.35 mm.

  The number of poles of the rotor 100 configured by the ring magnet 10 is, for example, 12 poles. However, the number of poles of the rotor 100 is not limited to 12 poles.

  A method for manufacturing the rotor 100 shown in FIG. 1 will be briefly described. The rotor 100 of the present embodiment is manufactured by injection molding. At the time of injection molding, the polar-oriented magnet 10 is molded by applying a polar anisotropic magnetic field inside the mold.

  In order to obtain the magnetic flux density distribution on the surface of the rotor 100, as shown in FIG. 3, the magnetic body 200 (iron core) is arranged with a gap 30 (gap) having a constant radial dimension on the outer periphery of the rotor 100. The electromagnetic field analysis was performed in the state. In addition, the dimension (diameter direction) of the space | gap 30 was 0.4 mm. Further, the inside of the magnet 20 is a non-magnetic material 40 (for example, air).

  In the electromagnetic field analysis, the residual magnetic flux density Br of the magnet 10 was set to 0.57T. Here, the unit T is Tesla, and 1 Tesla is defined as “magnetic flux density of one weber per square meter in a plane perpendicular to the direction of magnetic flux”.

  In FIG. 3, the magnetic flux diagram obtained by the electromagnetic field analysis is also shown, and the state of the polar orientation of the magnet 10 can be seen.

  FIG. 4 shows a magnetic flux density distribution waveform of the air gap 30 between the rotor 100 and the outer magnetic body 200 at this time. In FIG. 4, the horizontal axis represents the circumferential angle (electrical angle) [deg] in the air gap 30, and the vertical axis represents the magnetic flux density [T] of the air gap 30 (denoted as air gap magnetic flux density [T] in FIG. 4). Therefore, FIG. 4 shows a magnetic flux density distribution waveform of the gap 30 for approximately one magnetic pole.

  Since the magnet 10 has an anisotropic orientation, the magnetic flux density distribution waveform of the air gap 30 has a sine wave shape.

  Further, the maximum value of the magnetic flux density at this time is about 0.59T.

  For example, in the case of a radially oriented ring magnet (hereinafter simply referred to as a magnet), the thickness D is 4.35 mm, the air gap 30 is 0.4 mm, and even if an iron core is disposed inside the magnet, The magnetic flux density of the air gap 30 is about 0.53 T, and does not become higher than the residual magnetic flux density Br (0.57 T) of the magnet.

  On the other hand, in the rotor 100 of the present embodiment, a numerical value equal to or higher than the residual magnetic flux density Br (0.57 T) of the material used for the magnet 10 (rare earth (SmFeN) plastic magnet) is obtained (FIG. 4). reference).

  For the rotor 100 of the present embodiment, the gap magnetic flux density when the thickness of the magnet 10 and the number of magnetic poles of the rotor 100 were changed was obtained by electromagnetic field analysis. The results are shown in FIG. 5 (table) and FIG. 6 (graph). When changing the number of magnetic poles with the thickness of the magnet 10, the outer diameter of the magnet 10 (rotor 100) is made constant. The magnet 10 had six thicknesses D of 2.00, 2.40, 2.80, 3.20, 4.35, and 5.50 mm.

  Since the rotor 100 of the present embodiment has 12 poles and an outer diameter of 49 mm, the magnetic pole width W (see FIG. 2) is 12.8 mm. Since the outer diameter of the magnet 10 (rotor 100) is constant, the magnetic pole width W is inversely proportional to the number of magnetic poles.

  From FIG. 5 and FIG. 6, the air gap magnetic flux density is decreased by reducing the thickness D of the magnet 10 and increased by increasing the thickness. It can also be seen that the gap magnetic flux density is higher when the number of magnetic poles of the rotor 100 is larger.

  From the results of electromagnetic field analysis shown in FIGS. 5 and 6, a numerical value obtained by dividing the thickness of the magnet 10 by the width of the magnetic pole is obtained for each analysis result, and is shown in a table in FIG. FIG. 8 shows a graph in which the horizontal axis represents the magnet thickness / magnetic pole width and the gap magnetic flux density represents the vertical axis. From this, it can be seen that the air gap magnetic flux density exhibits a characteristic that generally rides on one curve with respect to the magnet thickness / magnetic pole width.

  Referring to FIG. 8, if the magnet thickness / magnetic pole width (D / W) value is 0.3 or more, the residual magnetic flux density Br (0.57 T) of the material can be obtained by using a rare earth rare earth ring magnet alone. It is not necessary to use a back yoke made of a magnetic material such as an iron core, which is usually disposed inside a magnet (permanent magnet).

  As a result, for example, a process such as bonding between a back yoke using a metal material and a plastic magnet becomes unnecessary, and the number of parts of the rotor 100 can be reduced, and at the same time, a magnet (permanent magnet) is damaged due to heat shock or the like. Can also prevent. Further, the weight of the rotor 100 can be reduced.

  As an application example of the present invention, application to a synchronous motor used in a blower is possible.

  10 magnets, 100 rotors.

Claims (2)

Arranged on the rotor surface, comprising a rare earth permanent magnet with polar orientation or magnetization, and a non-magnetic member arranged on the back of the permanent magnet,
When the radial thickness of the permanent magnet is D and the magnetic pole width of the rotor is W,
D / W ≧ 0.3
The rotor of the synchronous motor characterized by satisfying the relationship   The synchronous motor rotor according to claim 1, wherein the permanent magnet is a resin material containing a rare earth magnet powder and has a ring shape.

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