JP2010246301A - Rotor for permanent magnet type motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase the output torque of a motor by suppressing a leakage flux. <P>SOLUTION: The so-called magnet embedding type rotor embeds permanent magnets 4 and 5 in through-holes 12 formed in a rotor body 11. In the magnet embedded type rotor, a trench 13 as a notch exposing the magnet end faces 4B1 and 5A1 of the permanent magnets 4 and 5 to the outer periphery of the rotor body 11 positioned on a center line L between magnetic poles in the radial direction tying the central position C of the rotor body 11 and the central position D between the two adjacent magnetic poles M2 and m3, is formed. In the magnet embedding type rotor, the ends 11A1 and 11A2 of the external core 11A of the rotor body 11 facing the trench 13 are projected from the magnet end faces 4B1 and 5A1. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a rotor of a permanent magnet motor, and more particularly to a leakage magnetic flux reduction technique.

  A rotor (rotor) used in a permanent magnet electric motor (permanent magnet motor) using a permanent magnet in a magnetic circuit has, for example, a plurality of through holes in an iron core (rotor core) in which a plurality of donut-shaped silicon steel plates are laminated. There is a so-called magnet-embedded type rotor that is formed to penetrate in the axial direction at a predetermined interval in the circumferential direction and in which permanent magnets constituting magnetic poles are embedded in the respective through holes.

  In an embedded magnet type rotor, there are two permanent magnets for each magnetic pole for the purpose of reducing leakage flux and increasing linkage flux of the permanent magnet to improve output torque. There has been proposed a structure in which a bridge portion connected to an outer core portion for holding the permanent magnet is provided between them, and a groove portion for exposing a magnet end surface of the permanent magnet is provided between the magnetic poles (for example, Patent Document 1). Etc.).

JP-A-11-252840

  However, in the rotor described in Patent Document 1, magnetic flux may concentrate on the core corner portion of the outer core portion that is flush with the end surface of the magnet, and magnetic flux leakage may occur. Therefore, in this rotor, a reduction in the output torque of the electric motor is unavoidable due to leakage magnetic flux.

  Therefore, the present invention provides a rotor of a permanent magnet electric motor that can suppress leakage magnetic flux and improve the output torque of the electric motor.

  In the rotor of the permanent magnet electric motor of the present invention, on the outer periphery of the rotor body located on the radial center line between the magnetic poles connecting the center position of the rotor body and the center position between two adjacent magnetic poles, A groove that exposes the magnet end face of the permanent magnet is formed, and an outer peripheral end of the rotor body that faces the groove is projected from the magnet end face.

  According to the rotor of the permanent magnet electric motor of the present invention, when the outer peripheral end of the rotor body facing the groove formed in the outer peripheral part of the rotor main body is projected from the magnet end surface, the leakage magnetic flux leaks from the projecting portion. However, it is difficult to reach the end face of the permanent magnet facing the groove, the minimum magnetic flux density in the permanent magnet is increased, and the reverse magnetic field that demagnetizes the permanent magnet is reduced, so that the demagnetization resistance can be improved. Therefore, by using the rotor of the present invention for the electric motor, the current that can be supplied can be increased, and the output torque of the electric motor can be improved. Further, according to the present invention, the thickness of the permanent magnet can be reduced by the improvement in the demagnetization resistance, and the cost can be reduced.

FIG. 1 is a cross-sectional view of a rotor of the permanent magnet type electric motor according to the first embodiment. FIG. 2 is an enlarged view of a main part of the rotor of FIG. 1 showing an enlarged portion where a permanent magnet is embedded. FIG. 3 is an enlarged view of a main part of a portion where a groove is formed in the rotor of FIG. FIG. 4 is a characteristic diagram showing the minimum magnetic flux density in the magnet when a current is applied. FIG. 5 is a diagram showing a magnetic flux density distribution leaking from the outer core portion when a current is applied to a coil wound around the stator. FIG. 6 is a diagram showing the relationship between the extension amount of the extension portion and the minimum magnetic flux density when the extension portion which is the end portion of the outer core portion is extended. FIG. 7 is a diagram showing the interlinkage magnetic flux φa of the magnet when the extension amount of the extending portion is changed. 8A and 8B show the rotor of Comparative Example 1, in which FIG. 8A is a cross-sectional view thereof, and FIG. 8B is an enlarged view of a main part showing an enlarged portion where a permanent magnet is embedded. 9A and 9B show a rotor of Comparative Example 2, in which FIG. 9A is a cross-sectional view thereof, and FIG. 9B is an enlarged view of a main part showing an enlarged portion where a permanent magnet is embedded. FIG. 10 is an enlarged view of the outer core portion of the rotor according to the second embodiment. FIG. 11 is a diagram illustrating the third embodiment and showing an example in which the tip portion of the extending portion is inclined. FIG. 12 shows the third embodiment, and shows an example in which the tip of the extending portion is inclined. FIG. 13 shows the third embodiment, and shows an example in which the tip portion of the extending portion is inclined.

  Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings.

“Embodiment 1”
FIG. 1 is a cross-sectional view of a rotor of a permanent magnet type electric motor according to Embodiment 1, FIG. 2 is an enlarged view of a main part showing an enlarged portion of the rotor of FIG. 1 where a permanent magnet is embedded, and FIG. It is a principal part enlarged view of the site | part in which the groove part was formed among 1 rotors.

  A permanent magnet type electric motor (permanent magnet type motor) is a permanent magnet type AC motor having a stator as a stator and a rotor as a rotor. A stator (not shown) is formed as a cylindrical body in which a rotor is rotatably arranged, and has a structure in which a coil for generating a rotating magnetic field is wound around an inner portion of the stator.

  As shown in FIG. 1, the rotor 1 is formed as a laminated cylindrical body in which a plurality of disk-shaped magnetic bodies made of, for example, silicon steel plates are alternately stacked with an insulating material interposed therebetween. A rotation shaft (not shown) is inserted and fixed in the center hole 2 of the rotor 1. The rotor 1 is formed with two permanent magnets 3 to 10 that constitute a magnetic pole, and through holes 12 that embed the permanent magnets 3 to 10 in the rotor body 11.

  Sixteen permanent magnets 3 to 10 are provided because the number of magnetic poles is eight. The permanent magnets 3 to 10 have a substantially rectangular cross section and are formed as bar magnets having substantially the same length as the rotor axial direction length of the rotor 1. In this embodiment, two magnetic poles M1 to M8 are configured with two permanent magnets 3A, 3B to 10A, and 10B as one set. The eight magnetic poles M1 and M2 are configured by forming eight grooves 13 serving as notches on the outer peripheral portion of the rotor body 11 to form two permanent magnets 3A, 3B to 10A, and 10B as one set. It is formed as a convex portion having an arcuate tip shape.

  As shown in FIG. 2, the groove portion 13 is provided on a magnetic pole center line L in the radial direction connecting the center position C of the rotor body 11 and the center position D between two adjacent magnetic poles M2 and M3. It is formed by notching a part of the outer peripheral portion of the rotor body 11 so as to expose the magnet end faces 4B1, 5A1 of the adjacent permanent magnets 4B, 5A. The groove portions 13 are respectively provided at positions that divide the rotor body 11 into eight equal parts, and are formed from the outer peripheral portion toward the center position C and along the axial direction.

  Two through-holes 12 are formed in each part where the magnetic poles M1 to M8 are formed. The through hole 12 penetrates in the axial direction of the rotor body 11 and has one end opened to the groove 13. Between the two through holes 12 formed in each of the magnetic poles M1 to M8, the two permanent magnets 3A, 3B to 10A, 10B embedded in the through holes 12 are held, and a convex portion having an arc shape is formed. A bridge portion 11B that holds the outer core portion 11A is formed. The narrower the bridge portion 11B, the smaller the volume (the smaller the volume), the more it is possible to suppress the leakage magnetic flux.

  In the first embodiment, as shown in FIG. 3, the outer peripheral end of the rotor main body 11 facing the groove 13, that is, both end portions 11A1, 11A2 of the outer core portion 11A are projected from the magnet end surfaces 4A1, 4B1, 5A1, 5B1. ing. When the end portions 11A1 and 11A2 of the outer core portion 11A are extended portions that protrude from the magnet end surfaces 4B1 and 5A1 toward the center line L between the magnetic poles, the minimum magnetic flux density in the magnet can be increased, and anti-demagnetization performance. Can be improved.

  FIG. 4 shows the minimum magnetic flux density in the magnet when a current is applied. The A line represents the rotor of the first embodiment, the B line represents the rotor of Comparative Example 1, and the C line represents the rotor of Comparative Example 2. . As shown in FIG. 8, the rotor 14 of Comparative Example 1 includes one magnetic pole M <b> 1 to M <b> 8 with one permanent magnet 3 to 10, and the permanent magnet 3 to 10 includes the outer core portion 11 </ b> A and the outer core portion. The structure is such that it is held by both bridge portions 11B and 11C connected to 11A, and a groove portion 13 is formed between the magnetic poles M1 to M8. Unlike the first embodiment, the rotor 14 of Comparative Example 1 does not expose the magnet end face to the groove 13, and the magnet end face is covered with the bridge portions 11 </ b> B and 11 </ b> C. As shown in FIG. 9, the rotor of Comparative Example 2 is the same as that of Embodiment 1 except that the end portions 11A1 and 11A2 of the outer core portion 11A are flush with the magnet end surfaces 4B1 and 5A1. It is assumed that the rotor widths of the first embodiment, comparative example 1 and comparative example 2 are adjusted so that they have the same size and have the strength capable of the same operation.

  When the permanent magnets 3 to 8 are below the nick point (indicated by X in FIG. 4) of the material, the permanent magnets are permanently demagnetized to reduce the generated magnetic flux. In order to generate the output torque of the electric motor, not only the magnetic flux but also the current is required. Therefore, it is necessary to increase the input current in order to increase the output torque. In the rotor of the first embodiment, when the minimum magnetic flux density is the same, the current that can be input is larger than that of the rotors of Comparative Example 1 and Comparative Example 2 (in the order of C1, B1, and A1), and the output torque is large. Become.

  In addition, the rotor of the first embodiment has a minimum magnetic flux density larger than that of the rotors of comparative example 1 and comparative example 2 in all current conditions, and the demagnetization resistance is improved. As a result, according to the rotor of the first embodiment, the thickness of the permanent magnet can be reduced as much as the demagnetization resistance is improved, and the cost can be reduced. The minimum magnetic flux density is difficult to demagnetize when the value is large, and is easily demagnetized when the value is small. In general, in a rotor, it is necessary to increase the thickness of a magnet in order to achieve equivalent demagnetization resistance. However, this increases costs. In the rotor of the first embodiment, the minimum magnetic flux density can be increased and the demagnetization resistance can be improved, so that it is not necessary to increase the thickness of the magnet and the cost is not increased.

  FIG. 5 is a diagram showing a magnetic flux density distribution leaking from the outer core portion when a current is applied to a coil wound around the stator. 5 shows the change in magnetic flux density in the rotor radial direction of the rotor of Embodiment 1, and the C line in FIG. 5 shows the change in magnetic flux density in the rotor radial direction of the rotor of Comparative Example 2. The R line in FIG. 5 indicates the radial direction of the rotor.

  In the rotor of Comparative Example 2, the region indicated by the hatched portion in the graph of FIG. 5 is a reverse magnetic field that demagnetizes the magnet corner. On the other hand, in the rotor of the first embodiment, the reverse magnetic field that demagnetizes the magnet corners is small. Therefore, as shown in FIG. 4, the rotor of the first embodiment has a smaller minimum magnetic flux density in the magnet than the rotor of the comparative example 2, and can improve the demagnetization resistance.

  FIG. 6 is a diagram showing the relationship between the extension amount of the extension portion and the minimum magnetic flux density when the extension portions which are the end portions 11A1 and 11A2 of the outer core portion 11A are extended. A line A in FIG. 6 shows the rotor of the first embodiment, and a line C in FIG. If the extension amount of the extending portion is increased even a little, the minimum magnetic flux density in the magnet becomes larger than that of the rotor of Comparative Example 2, and the demagnetization resistance is improved. Thereby, when the rotor of Embodiment 1 is used for a motor, the current that can be applied can be increased, and the output torque can be increased. Moreover, in the rotor of Embodiment 1, the thickness of the permanent magnet can be reduced by an amount corresponding to the improvement of the demagnetization resistance, and a cost reduction effect can be obtained.

  The extension amount of the extension portion is 0.1 ≦ Y / X ≦ 0.35, where the length Y of the extension portion is 1 when the distance X from the magnet end surface 5A1 to the center line L between the magnetic poles is 1. It is desirable to do. When the extension amount of the extension portion is 0.1 or more, the minimum magnetic flux density is larger than that of the rotor of Comparative Example 2. Therefore, the lower limit of the extension amount of the extending portion is set to 0.1 or more.

  FIG. 7 shows the interlinkage magnetic flux φa of the magnet when the extension amount of the extending portion is changed. A line A in FIG. 7 shows the rotor of the first embodiment, and a line C in FIG. The interlinkage magnetic flux φa of the magnet decreases as the extension amount of the extending portion increases. This is because when the amount of extension increases, the magnetic flux easily flows through the adjacent magnetic poles, and the leakage magnetic flux increases. Compared with the rotor of Comparative Example 2, the interlinkage magnetic flux of the magnet is improved when the amount of extension is 0.35 or less. Therefore, the upper limit of the extension amount of the extending portion is set to 0.35 or less. As described above, when the extension amount of the extension portion is set to 0.1 ≦ Y / X ≦ 0.35, the linkage flux φa can be improved while ensuring the demagnetization resistance performance, so that the output torque is further improved. be able to.

  As described above, according to the rotor of the permanent magnet type electric motor of the first embodiment, when the outer peripheral end portion of the rotor body facing the groove formed in the outer peripheral portion of the rotor body is protruded from the magnet end surface, the protruding portion Leakage magnetic flux that leaks from the magnet becomes difficult to reach the end face of the permanent magnet facing the groove, and the minimum magnetic flux density in the permanent magnet is increased and the reverse magnetic field that demagnetizes the permanent magnet is reduced, thereby improving the anti-demagnetization performance. Can do. Therefore, by using the rotor of the present invention for an electric motor, the current that can be supplied can be increased, and the output torque of the electric motor can be improved. Further, according to the present invention, the thickness of the permanent magnet can be reduced by the improvement in the demagnetization resistance, and the cost can be reduced.

  Further, according to the rotor of the permanent magnet type electric motor of the first embodiment, since the outer peripheral end portion of the rotor body is an extended portion that protrudes from the magnet end surface toward the center line between the magnetic poles, the rotor is formed when the groove portion is formed. By leaving a part of the outer peripheral portion of the main body, the extending portion can be easily formed.

  Further, according to the rotor of the permanent magnet type electric motor of the first embodiment, when the length Y of the extending portion is set to 1 as the distance X from the magnet end surface to the center line between the magnetic poles, 0.1 ≦ Y / Since X ≦ 0.35, the reverse magnetic field due to the leakage magnetic flux from the extending portion can be reduced, the anti-demagnetization performance can be secured, and the linkage flux can be improved.

“Embodiment 2”
FIG. 10 is an enlarged view of the outer core portion of the rotor according to the second embodiment. In the second embodiment, the lengths of both end portions 11A1 and 11A2 of the outer core portion 11A are different from each other at both end portions of each magnetic pole 4 with respect to the example in which the same length is used in the first embodiment. Specifically, in FIG. 10A, the left end portion 11A1 is an extending portion across the central bridge portion 11B, and the right end portion 11A2 is flush with the magnet end surface 4B1. In FIG. 10 (B), only the right side is extended contrary to FIG. 10 (A).

  This is because an electric vehicle using a motor as a drive source can cope with different torques required for power running and regeneration. Power running refers to converting electrical energy into mechanical energy (kinetic energy) (operating as a motor). Regeneration refers to converting mechanical energy into electrical energy (operating as a generator).

  When the output torque of the power running is large, when the rotor rotates counterclockwise as indicated by an arrow F in FIG. 10, the left permanent magnet 4A that is the rotation direction is easily demagnetized. Therefore, the demagnetization resistance is improved by extending the end 11A1 of the outer core portion 11A on the rotor rotation direction side (the side on which the one permanent magnet 4A that rotates in advance) in each magnetic pole M2 extends from the magnet end surface 4A1. Let Then, the opposite side (right side) end portion 11A2 does not extend from the magnet end surface 4B1 of the other permanent magnet 4B or reduces the amount of extension, thereby suppressing the reduction of the interlinkage magnetic flux. Thereby, the reduction | decrease of a linkage flux can be suppressed, ensuring a demagnetization performance as a motor. Therefore, the rotor of the permanent magnet electric motor of Embodiment 2 can be used for a motor for an electric vehicle that requires different torques for power running and regeneration.

“Embodiment 3”
11 to 13 show the third embodiment, and show an example in which the tip portion of the extending portion is inclined. In Embodiment 3, the front-end | tip part of an extension part is inclined with respect to a magnet end surface.

  In FIG. 11, the tip of the outer core portion 11A provided on the outer side of the permanent magnet 4A (extending portion) 11A1 is not inclined as a plane parallel to the magnet end surface 4A1, but as an inclined surface 15. Yes. The inclined surface 15 in FIG. 11A is an inclined surface toward the magnet end surface 4A1, the inclined surface 15 in FIG. 11B is an inclined surface away from the magnet end surface 4A1, and the inclined surface 15 in FIG. The slope is even tighter.

  In FIG. 12, the tip of the end portion 11A1 of the outer core portion 11A is inclined so as to be a bent portion that approaches the magnet end surface 4A1. In FIG. 12B, the tip is sharper than that in FIG.

  In FIG. 13, the tip of the end portion 11A1 of the outer core portion 11A is inclined so as to be a bent portion that is bent in the rotor radial direction. In FIG. 13 (A), the tip is a convex shape facing the rotor radial direction, in FIG. 13 (B), the tip is sharpened, and in FIG. 13 (C), the tip is in the rotor radial direction. The shape is slightly inclined.

  In the third embodiment, even if the distal end portion of the extending portion is inclined with respect to the magnet end surface, like the rotor of the first embodiment, the leakage magnetic flux can be suppressed and the output torque of the electric motor can be improved.

  The present invention can be used for a rotor of a permanent magnet type electric motor.

DESCRIPTION OF SYMBOLS 1 ... Rotor 3-10 (3A, 3B-10A, 10B) ... Permanent magnet 4A1, 4B1, 5A1, 5B1 ... Magnet end surface 11 ... Rotor main body (rotor main body)
11A ... Outer core part (outer peripheral part of rotor main body)
11A1, 11A2 ... End of outer core (outer peripheral end of rotor body)
12 ... Through hole 15 ... Inclined surface M1-M8 ... Magnetic pole

Claims (5)

In the rotor of the permanent magnet type electric motor having a plurality of through holes that penetrate the rotor body in the axial direction and are formed at predetermined intervals in the rotation direction, and in which permanent magnets are embedded in each of the through holes,
A groove portion that exposes a magnet end surface of the permanent magnet on an outer peripheral portion of the rotor body located on a radial center line between the magnetic poles connecting the center position of the rotor body and the center position between two adjacent magnetic poles. Form the
A rotor of a permanent magnet electric motor, wherein an outer peripheral end portion of the rotor main body facing the groove portion is projected from the magnet end surface. The rotor of the permanent magnet type electric motor according to claim 1,
A rotor of a permanent magnet electric motor, wherein an outer peripheral end portion of the rotor main body is an extending portion that protrudes from the magnet end surface toward the center line between the magnetic poles. It is a rotor of the permanent magnet type electric motor according to claim 2,
Permanent magnet characterized in that the length Y of the extending portion is 0.1 ≦ Y / X ≦ 0.35 when the distance X from the magnet end surface to the center line between the magnetic poles is 1. Rotor of electric motor. The rotor of the permanent magnet type electric motor according to claim 2 or 3,
A rotor of a permanent magnet type electric motor characterized in that the length of the extending portion is different at both ends of each magnetic pole. It is a rotor of the permanent magnet type electric motor according to any one of claims 2 to 4,
A rotor of a permanent magnet electric motor, wherein a tip portion of the extending portion is inclined with respect to the magnet end surface.

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