Abstract:
An object is to provide a rotary electric machine capable of suppressing degradation of strength in high-speed rotation and reducing a torque ripple. 
     A rotor of a rotary electric machine according to the present invention includes a rotor core provided with a magnet insertion hole that forms a space into which a permanent magnet is inserted and a non-magnetic portion facing the space to form a part of the magnet insertion hole, wherein the non-magnetic portion is provided asymmetrically with respect to a d-axis.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a rotor of a rotary electric machine provided with a permanent magnet serving as a magnetic field source of the rotor and a rotary electric machine using the same. 
       BACKGROUND ART 
       [0002]    A rotary electric machine mounted on an electric vehicle, a hybrid vehicle, or the like is demanded to reduce a torque ripple. For example, PTL 1 discloses a stator structure of a rotary electric machine provided with a hole between a permanent magnet and the outer circumference in order to reduce a torque ripple. 
       CITATION LIST 
     Patent Literature 
       [0003]    PTL 1: JP 2008-278591 A 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0004]    However, if a hole is provided between the permanent magnet and the outer circumference as disclosed in PTL 1, a portion where a core width is extremely narrow may be generated between the outer circumference of the rotor and the permanent magnet. This may generate degradation in strength or torque in high-speed rotation. 
         [0005]    An object of the present invention is to provide a rotary electric machine capable of reducing a torque ripple while suppressing degradation of strength in high-speed rotation. 
       Solution to Problem 
       [0006]    In order to solve the problem, a rotor of a rotary electric machine according to the present invention includes a rotor core provided with a magnet insertion hole that forms a space into which a permanent magnet is inserted and a non-magnetic portion facing the space to form a part of the magnet insertion hole, wherein the non-magnetic portion is provided asymmetrically with respect to a d-axis. 
       Advantageous Effects of Invention 
       [0007]    According to the present invention, it is possible to reduce a torque ripple while suppressing degradation of strength in high-speed rotation. Other objects, configurations, and effects than those described above will become apparent by reading the following description of embodiments. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0008]      FIG. 1  is an enlarged view illustrating a region  80  of  FIG. 6  according to a first embodiment. 
           [0009]      FIG. 2  is a diagram illustrating torque ripple waveforms of a rotary electric machine according to the first embodiment and a rotary electric machine of the background art. 
           [0010]      FIG. 3  is an enlarged view illustrating a rotor for one pole in a rotary electric machine according to a modification of the first embodiment. 
           [0011]      FIG. 4  is an enlarged view illustrating a rotor  10  for one pole in a rotary electric machine according to a second embodiment. 
           [0012]      FIG. 5  is a diagram illustrating torque ripple amplitudes of the rotary electric machine according to the second embodiment and the rotary electric machine of the background art. 
           [0013]      FIG. 6  is a cross-sectional view illustrating a cross section as seen from an axial direction of the rotary electric machine according to the first embodiment. 
           [0014]      FIG. 7  is a diagram illustrating a rotor  11  of a rotary electric machine according to a third embodiment. 
           [0015]      FIG. 8  is an enlarged view illustrating a steel plate  300  for one pole in a rotor core  20  according to the third embodiment. 
           [0016]      FIG. 9  is an enlarged view illustrating a steel plate  310  for one pole in the rotor core  20  according to the third embodiment. 
           [0017]      FIG. 10  is a diagram illustrating main parts of a rotary electric machine  100  of the background art. 
           [0018]      FIG. 11  is a cross-sectional view as seen in an axial direction of the rotary electric machine  100  of the background art. 
           [0019]      FIG. 12  is an exterior view illustrating a rotor  10  in the rotary electric machine  100  of the background art. 
           [0020]      FIG. 13  is an enlarged view illustrating the rotor  10  for one pole in the rotary electric machine  100  of the background art. 
           [0021]      FIG. 14  is an enlarged view illustrating the rotor  10  for one pole in another configuration of the rotary electric machine  100  of the background art. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0022]    Embodiments of the present invention will now be described with reference to the accompanying drawings. While a specific example of the contents of the present invention is discussed in the following description, the present invention is not limited such a description. Various changes or modifications may be possible for a person ordinarily skilled in the art within the scope and spirit of the present invention as disclosed in this specification. Note that, for description purposes, like reference numerals denote like elements throughout overall drawings, and they will not be repeatedly description. 
         [0023]      FIG. 10  is a diagram illustrating main parts of a rotary electric machine  100  of the background art.  FIG. 10  is a diagram as seen in a radial direction of the rotary electric machine  100  and shows only one side with respect to a rotational axis (illustrated as a one-dotted chain line).  FIG. 11  is a cross-sectional view taken along a line A-A′ of  FIG. 10  in the axial direction.  FIG. 12  is an exterior view illustrating a rotor core  20 .  FIG. 13  is an enlarged view illustrating a configuration of a region  80  of  FIG. 11  in the rotary electric machine  100  of the background art. 
         [0024]    As illustrated in  FIG. 10 , the rotary electric machine  100  includes a rotor  10 , a rotor core  20 , a stator  30 , a stator core  40 , an armature coil  50 , a permanent magnet  60 , and a shaft  70 . 
         [0025]    A plurality of stator slots  41  are disposed in the stator core  40  approximately at equal intervals in a circumferential direction as illustrated in  FIG. 11 , and the stator coil  50  is wound inside the stator slots  41  as illustrated in  FIG. 10 . As illustrated in  FIG. 12 , the rotor  10  is coaxially disposed in the inner circumference side of the stator core  40 , and a plurality of permanent magnets  60  are disposed in the rotor  10  approximately at equal intervals in the circumferential direction. As illustrated in  FIG. 13 , the permanent magnet  60  is inserted into a magnet insertion hole  120  provided in the rotor core  20 . A d-axis  110  is also illustrated. 
         [0026]    Note that, as illustrated in  FIG. 14 , the magnet insertion hole  120  may be bisected in the circumferential direction, so that two permanent magnets  60  are provided for one pole in the circumferential direction. 
         [0027]    In the following example, the configuration will be described for the region  80  of the rotor for one pole. The other pole may be symmetrically provided to obtain the same effects of the present invention. 
         [0028]    In the following examples, it is assumed that a rotation direction is counterclockwise as illustrated in  FIG. 11 . 
       Example 1 
       [0029]      FIG. 6  is a cross-sectional view illustrating a cross section as seen from the axial direction of the rotary electric machine according to the first embodiment.  FIG. 1  is an enlarged view illustrating the region  80  of  FIG. 6  according to the first embodiment. 
         [0030]    The rotor  10  has a rotor core  20 , a permanent magnet  60 , and a shaft  70  (refer to  FIG. 10 ). The rotor core  20  is formed by stacking a plurality of steel plates. Each of the steel plates is provided with a magnet insertion hole  120  by punching or the like. The permanent magnet  60  is stored in this magnet insertion hole  120 . The stator  30  (not shown) is disposed in the outer circumference side of the rotor  10  (refer to  FIG. 10 ). 
         [0031]    The rotor core  20  is provided with a non-magnetic portion  130  communicating with the magnet insertion hole  120 . In other words, the non-magnetic portion  130  is disposed in a position facing a space formed by the magnet insertion hole  120  to form a part of the magnet insertion hole  120 . 
         [0032]    According to this embodiment, a rotational direction of the rotor  10  is counterclockwise as illustrated in  FIG. 6 , and this counterclockwise direction is defined as a motor driving direction. As illustrated in  FIG. 1 , a position of the non-magnetic portion  130  is in a leading side in the rotational direction from the d-axis  110  as a center of a magnetic pole. When a motor is driven, a magnetic flux density in the rotation leading side of the rotor  10  is high. In addition, since the non-magnetic portion  130  is provided in the rotation leading side, influence on a torque ripple is significant. 
         [0033]    The non-magnetic portion  130  communicates with the magnet insertion hole  120  and can be provided without degrading manufacturability by forming integrally when punching from the steel plate. 
         [0034]    By providing the non-magnetic portion  130  in communication with the magnet insertion hole  120 , a loss caused by air resistance at the outer circumferential portion does not increase. Even in oil immersion for lubrication or cooling, a loss caused by stirring does not increase. 
         [0035]    The non-magnetic portion  130  is provided without forming an extremely narrow portion of the core width between the outer circumference of the rotor core  20  and the permanent magnet  60 . Therefore, it is possible to secure strength at high-speed rotation and avoid torque reduction because there is no intervention in the magnetic flux. 
         [0036]      FIG. 2  is a computation result of the torque ripple waveform. Compared to the waveform  200  in the case where the non-magnetic portion  130  is not provided, the waveform  210  in the case where the non-magnetic portion  130  is provided has a smaller amplitude, so that the torque ripple is reduced. Meanwhile, an average torque value does not change nearly between both cases. The cause of the torque ripple is the change in the magnetic resistance by the stator slot  41  shown in  FIG. 6 . However, by providing the non-magnetic portion communicating with the magnet insertion hole  120  according to this embodiment, an abrupt change of the magnetic resistance is alleviated. Therefore, as illustrated in  FIG. 2 , it is possible to reduce the torque ripple while maintaining the average torque value. 
         [0037]      FIG. 3  is an enlarged view illustrating the rotor for one pole of the rotary electric machine according to a modification of the first embodiment. The magnet insertion hole is bisected into a first magnet insertion hole  120   a  and a second magnet insertion hole  120   b  with respect to the d-axis  110  in the circumferential direction. In addition, the first permanent magnet  60   a  is stored in the first magnet insertion hole  120   a , and the second permanent magnet  60   b  is stored in the second magnet insertion hole  120   b.    
         [0038]    The non-magnetic portion  131  is formed to communicate with the first magnet insertion hole  120   a  in the leading side in the rotational direction. The non-magnetic portion  132  is formed to communicate with the second magnet insertion hole  120   b  in the lagging side in the rotational direction. The non-magnetic portion  131  is formed to be larger than the non-magnetic portion  132  in the circumferential direction. As a result, it is possible to effectively reduce the torque ripple. 
         [0039]    Note that a place where the non-magnetic portions  130  to  132  are disposed communicates with the magnet insertion hole  120 . Therefore, resin or the like may be filled in order to hold the permanent magnet  60 . 
       Example 2 
       [0040]      FIG. 4  is an enlarged view illustrating a rotor  10  for one pole in the rotary electric machine according to a second embodiment. 
         [0041]    In this embodiment, assuming that the rotational direction is counterclockwise, that is, a motor driving direction, a circumferential position of the non-magnetic portion  130  is set to an electric angle range between φ 1 =12° and   2 =38° in a rotation leading direction from the d-axis  110  as a center of the magnetic pole. When a motor is driven, a magnetic flux density in the rotation leading side of the rotor  10  is high. In addition, since the non-magnetic portion  130  is provided in the rotation leading side, influence on the torque ripple is significant. 
         [0042]      FIG. 5  illustrates a relationship between electric angle positions from the d-axis in the rotation leading side end and the rotation lagging side end of the non-magnetic portion  130  and the torque ripple amplitude. It is recognized that, when the electric angle from the d-axis is smaller than 12° in the torque ripple amplitude  220  of the rotation leading side end position of the non-magnetic portion  130 , and the electric angle from the d-axis is larger than of 38° in the torque ripple amplitude  230  of the rotation lagging side end position of the non-magnetic portion  130 , the torque ripple amplitudes  220  and  230  in both cases are higher than the torque ripple amplitude  240  in the case where no non-magnetic portion is provided. 
         [0043]    According to this embodiment, the circumferential position of the non-magnetic portion  130  has an electric angle range between 12° and 38° in the rotation leading direction from the d-axis  110 . As a result, it is possible to effectively reduce the torque ripple. 
       Example 3 
       [0044]      FIG. 7  is a diagram illustrating a rotor  11  of a rotary electric machine according to a third embodiment. As illustrated in  FIG. 7 , the rotor core  20  is formed by alternately stacking a plurality of steel plates  300  and  310 . 
         [0045]      FIG. 8  is an enlarged view illustrating the steel plate  300  for one pole in the rotor core  20  according to the third embodiment.  FIG. 9  is an enlarged view illustrating the steel plate  310  for one pole in the rotor core  20  according to the third embodiment. 
         [0046]    The non-magnetic portion  133  of the steel plate  300  is disposed in the rotation leading side relative to the non-magnetic portion  134  of the steel plate  310 . The non-magnetic portion  134  of the steel plate  310  is disposed in the rotation lagging side relative to the non-magnetic portion  133  of the steel plate  300 . 
         [0047]    Comparing  FIGS. 8 and 9 ,  FIG. 8  is a cross-sectional view illustrating the non-magnetic portion  133  having a slightly wide width provided in the rotation leading side, and  FIG. 9  is a cross-sectional view illustrating the non-magnetic portion  134  having a slightly narrow width provided in the rotation lagging side. By alternately stacking them, it is possible to obtain the rotor core  20  having an intermediate characteristic between both cross sections. 
         [0048]    According to this embodiment, it is possible to reduce a desired order harmonic component when the torque is affected overlappingly by the harmonics in addition to the slot due to an influence of the power source and the like. 
         [0049]    Note that the circumferential position of the non-magnetic portion and the number of the combined non-magnetic portions may be determined by performing computation and measurement depending on a desired characteristic. In addition, the number of the stacks is not limited to one, but a plurality of stacks may be provided. Furthermore, in order to secure a holding strength of the permanent magnet, the number of the stacked steel plates may be determined without providing the non-magnetic portion. 
       REFERENCE SIGNS LIST 
       [0000]    
       
           10  . . . rotor 
           20  . . . rotor core 
           30  . . . stator 
           40  . . . stator core 
           41  . . . stator slot 
           50  . . . armature coil 
           60  . . . permanent magnet 
           60   a  . . . first permanent magnet 
           60   b  . . . second permanent magnet 
           70  . . . shaft 
           80  . . . region 
           100  . . . rotary electric machine 
           110  . . . d-axis 
           120  . . . magnet insertion hole 
           120   a  . . . first magnet insertion hole 
           120   b  . . . second magnet insertion hole 
           130  . . . non-magnetic portion 
           131  . . . non-magnetic portion 
           132  . . . non-magnetic portion 
           200  . . . torque waveform in case where no non-magnetic portion  130  is provided 
           210  . . . torque waveform in case where non-magnetic portion  130  is provided 
           220  . . . torque ripple amplitude in rotation leading side end position of non-magnetic portion 
           230  . . . torque ripple amplitude in rotation lagging side end position of non-magnetic portion 
           240  . . . torque ripple amplitude in case where no non-magnetic portion is provided 
           300  . . . steel plate 
           310  . . . steel plate