Patent Publication Number: US-2022216774-A1

Title: Rotor of rotating electric machine and method of manufacturing rotor

Description:
TECHNICAL FIELD 
     The present invention relates to a rotor of a rotating electric machine including a rotor core and an end plate, and to a method of manufacturing the rotor. 
     BACKGROUND ART 
     In Patent Literature 1, description is made of a method of manufacturing a rotor of an electric motor. The rotor includes a laminated core and a pair of end plates arranged on both sides of the laminated core in an axial direction. This manufacturing method includes a step of fitting a rotation shaft into a through-hole of the end plate formed into a dish shape so as to have elasticity in a thickness direction, and a step of bringing the end plate into contact with an end portion of the laminated core under a state in which the end plate is elastically deformed. In Patent Literature 1, it is described that, according to this manufacturing method, a contact state between the end portion of the laminated core and the end plate can be kept by an elastic restoration force of the end plate. 
     CITATION LIST 
     Patent Literature 
     
         
         [PTL 1] JP 2008-178253 A 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     In the manufacturing method described above, the end plate is formed into a dish shape in advance. Accordingly, for example, when deformation such as warpage or distortion of the end plate occurs in the steps described above, a desired elastic force of the end plate cannot be obtained. Thus, the end plate and the laminated core are not always held in close contact with each other. As a result, there has been a problem in that a gap is formed between the end plate and the end portion of the laminated core in some cases. 
     The present invention has been made to solve the problem described above, and has an object to provide a rotor of a rotating electric machine capable of more reliably holding an end plate and a rotor core in close contact with each other, and to provide a method of manufacturing the rotor. 
     Solution to Problem 
     According to the present invention, there is provided a rotor of a rotating electric machine, including: a rotor core; an end plate provided at an end portion of the rotor core in an axial direction of the rotor core; and a shaft passing through the rotor core and the end plate along the axial direction, wherein the end plate includes: a flat plate portion that has an annular shape and is held in contact with the rotor core; and a warp portion that is formed more on an inner peripheral side of the end plate than the flat plate portion and is held in contact with the shaft, and wherein in a radial cross section of the end plate, the warp portion is warped so as to be apart from the rotor core as extending away from the flat plate portion. 
     According to the present invention, there is provided a method of manufacturing a rotor of a rotating electric machine, including a step of press-fitting a first press-fitted portion of a shaft, to which a rotor core is mounted, into a first through-hole of a first end plate that has a flat plate shape and is supported on a jig, the first press-fitted portion being located on one end side of the rotor core, wherein the jig includes: a flat surface portion configured to support the first end plate; a hole portion that is formed in a position surrounded by the flat surface portion, has a diameter larger than a diameter of the first through-hole and a diameter of the first press-fitted portion, and extends in a direction perpendicular to the flat surface portion; and a tapered surface formed between an inner peripheral surface of the hole portion and the flat surface portion. 
     Advantageous Effects of Invention 
     According to the present invention, it is possible to more reliably hold the end plate and the rotor core in close contact with each other. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a sectional view for illustrating a configuration of a rotor of a rotating electric machine according to a first embodiment of the present invention. 
         FIG. 2  is a sectional view for illustrating a portion II of  FIG. 1  in an enlarged manner. 
         FIG. 3  is a sectional view for illustrating a configuration of a rotor of a rotating electric machine according to a comparative example of the first embodiment of the present invention. 
         FIG. 4  is a plan view for illustrating a configuration of a first end plate to be used in a method of manufacturing the rotor of the rotating electric machine according to the first embodiment of the present invention. 
         FIG. 5  is a sectional view for illustrating a configuration of a first press-fitted portion of a shaft to be used in the method of manufacturing the rotor of the rotating electric machine according to the first embodiment of the present invention. 
         FIG. 6  is a sectional view for illustrating a portion VI of  FIG. 5  in an enlarged manner. 
         FIG. 7  is a plan view for illustrating a configuration of a second end plate to be used in the method of manufacturing the rotor of the rotating electric machine according to the first embodiment of the present invention. 
         FIG. 8  is a plan view for illustrating a portion VIII of  FIG. 7  in an enlarged manner. 
         FIG. 9  is a sectional view for illustrating a configuration of a second press-fitted portion of the shaft to be used in the method of manufacturing the rotor of the rotating electric machine according to the first embodiment of the present invention. 
         FIG. 10  is a sectional view for illustrating a step of manufacturing the rotor of the rotating electric machine according to the first embodiment of the present invention. 
         FIG. 11  is a sectional view for illustrating the step of manufacturing the rotor of the rotating electric machine according to the first embodiment of the present invention. 
         FIG. 12  is a sectional view for illustrating a portion XII of  FIG. 11  in an enlarged manner. 
         FIG. 13  is a sectional view for illustrating the step of manufacturing the rotor of the rotating electric machine according to the first embodiment of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     First Embodiment 
     Description is made of a rotor of a rotating electric machine according to a first embodiment of the present invention and a method of manufacturing the rotor. First, a configuration of the rotor of the rotating electric machine according to this embodiment is described with reference to  FIG. 1  and  FIG. 2 .  FIG. 1  is a sectional view for illustrating a configuration of a rotor  100  of the rotating electric machine according to this embodiment.  FIG. 2  is a sectional view for illustrating a portion II of  FIG. 1  in an enlarger manner. In  FIG. 1  and  FIG. 2 , radial cross sections of a rotor core  10 , a first end plate  20 , and a second end plate  30  are illustrated. In this embodiment, the rotor  100  of an interior permanent magnet (IPM) type including permanent magnets  14  embedded in the rotor is exemplified. 
     The rotor  100  illustrated in  FIG. 1  and  FIG. 2  is a component of a rotating electric machine of an inner rotor type. The rotating electric machine of the inner rotor type includes the rotor  100 , and a stator (not shown) arranged on an outer peripheral side of the rotor  100 . The rotor  100  is supported by a bearing (not shown) so as to be freely rotatable with respect to the stator. The rotor  100  includes the rotor core  10 , the first end plate  20 , the second end plate  30 , and a shaft  40 . The first end plate  20  is provided at one end portion of the rotor core  10  in an axial direction of the rotor core  10 . The second end plate  30  is provided at the other end portion of the rotor core  10  in the axial direction. The shaft  40  passes through the rotor core  10 , the first end plate  20 , and the second end plate  30  along the axial direction. 
     The shaft  40  includes a large-diameter portion  41  in a portion thereof in the axial direction. The large-diameter portion  41  has a diameter larger than diameters of other portions of the shaft  40 . The rotor core  10 , the first end plate  20 , and the second end plate  30  are fixed to the large-diameter portion  41 . The large-diameter portion  41  includes a first press-fitted portion  41   a  and a second press-fitted portion  41   b . The first press-fitted portion  41   a  is to be press-fitted into the first end plate  20 . The second press-fitted portion  41   b  is to be press-fitted into the second end plate  30 . Each of the first press-fitted portion  41   a  and the second press-fitted portion  41   b  is a part of the large-diameter portion  41  in the axial direction. As described later, first protrusions  42  are formed on an outer peripheral surface of the large-diameter portion  41  so as to extend in the axial direction. 
     The rotor core  10  is formed of a plurality of laminated electromagnetic steel sheets  11 . The rotor core  10  has a cylindrical shape as a whole. A through-hole  12  is formed in a center portion of the rotor core  10  so as to pass through the rotor core  10  in the axial direction. The large-diameter portion  41  of the shaft  40  is fitted into the through-hole  12  of the rotor core  10  through press-fitting or shrink-fitting. In this manner, the rotor core  10  is fixed to the shaft  40 . A plurality of magnet insertion holes  13  are formed more on an outer peripheral side of the rotor core  10  than the through-hole  12  so as to pass through the rotor core  10  in the axial direction. The permanent magnets  14  are inserted in the magnet insertion holes  13 , respectively. One end portion of each of the magnet insertion holes  13  in the axial direction is closed by the first end plate  20 . The other end portion of each of the magnet insertion holes  13  in the axial direction is closed by the second end plate  30 . 
     The first end plate  20  and the second end plate  30  each have a disk shape. The first end plate  20  and the second end plate  30  are each made of a non-magnetic material such as SUS304. The first end plate  20  and the second end plate  30  are each made of a non-magnetic material to prevent reduction in magnetic force due to leakage of a magnetic flux of each of the permanent magnets  14  through the first end plate  20  or the second end plate  30 . 
     A first through-hole  21  is formed in a center portion of the first end plate  20  so as to pass through the first end plate  20  in the axial direction. The first press-fitted portion  41   a  of the shaft  40  is press-fitted into the first through-hole  21 . In this manner, the first end plate  20  is fixed to the shaft  40 . 
     The first end plate  20  includes a flat plate portion  22  that is held in contact with an end surface  10   a  of the rotor core  10  on one end side in the axial direction. The flat plate portion  22  has an annular shape. As a matter of course, the flat plate portion  22  is provided more on the outer peripheral side than the first press-fitted portion  41   a  of the shaft  40 . The flat plate portion  22  is provided around an entire periphery of the first press-fitted portion  41   a  in a circumferential direction of the first press-fitted portion  41   a . A surface of the flat plate portion  22  and the end surface  10   a  of the rotor core  10  are held in surface contact with each other without a gap. An outer peripheral-side end portion of the flat plate portion  22 , that is, an outer peripheral-side end portion  20   a  of the first end plate  20  is located more on an inner peripheral side of the rotor core  10  than an outer peripheral surface of the rotor core  10  when seen along the axial direction. 
     Further, the first end plate  20  includes a warp portion  23  formed more on the inner peripheral side than the flat plate portion  22  and arranged more on the outer peripheral side than the first press-fitted portion  41   a  of the shaft  40 . An inner peripheral-side end portion of the warp portion  23 , that is, an inner peripheral-side end portion  20   b  of the first end plate  20  is held in contact with an outer peripheral surface of the first press-fitted portion  41   a . The warp portion  23  is provided around an entire periphery of the first press-fitted portion  41   a  in the circumferential direction of the first press-fitted portion  41   a . In the radial cross section of the first end plate  20  as illustrated in  FIG. 1  and  FIG. 2 , the warp portion  23  is warped so as to be apart from the end surface  10   a  of the rotor core  10  as extending away from the flat plate portion  22 , that is, extending closer to the shaft  40 . Further, in the radial cross section described above, the warp portion  23  is connected to the flat plate portion  22  smoothly and continuously, and is curved so as to protrude on the rotor core  10  side. A width of the warp portion  23 , that is, a radial dimension of the warp portion  23  is smaller than a width of the flat plate portion  22 , that is, a radial dimension of the flat plate portion  22 . 
     Owing to the presence of the warp portion  23 , the flat plate portion  22  is pressed onto the end surface  10   a  of the rotor core  10  by an elastic force of the first end plate  20  itself with the inner peripheral-side end portion  20   b  of the first end plate  20  serving as a fulcrum. Accordingly, the flat plate portion  22  is held in close contact with the end surface  10   a  of the rotor core  10  without a gap. 
     Similarly to the first end plate  20 , a second through-hole  31  is formed in a center portion of the second end plate  30  so as to pass through the second end plate  30  in the axial direction. The second press-fitted portion  41   b  of the shaft  40  is press-fitted into the second through-hole  31 . In this manner, the second end plate  30  is fixed to the shaft  40 . 
     The second end plate  30  includes a flat plate portion  32  that is held in contact with an end surface  10   b  of the rotor core  10  on the other end side in the axial direction. The flat plate portion  32  has an annular shape. As a matter of course, the flat plate portion  32  is provided more on the outer peripheral side than the second press-fitted portion  41   b  of the shaft  40 . The flat plate portion  32  is provided around an entire periphery of the second press-fitted portion  41   b  in a circumferential direction of the second press-fitted portion  41   b . A surface of the flat plate portion  32  and the end surface  10   b  of the rotor core  10  are held in surface contact with each other without a gap. An outer peripheral-side end portion of the flat plate portion  32 , that is, an outer peripheral-side end portion  30   a  of the second end plate  30  is located more on an inner peripheral side of the rotor core  10  than an outer peripheral surface of the rotor core  10  when seen along the axial direction. 
     Further, the second end plate  30  includes a warp portion  33  formed more on the inner peripheral side than the flat plate portion  32  and arranged more on the outer peripheral side than the second press-fitted portion  41   b  of the shaft  40 . An inner peripheral-side end portion of the warp portion  33 , that is, an inner peripheral-side end portion  30   b  of the second end plate  30  is held in contact with an outer peripheral surface of the second press-fitted portion  41   b . The warp portion  33  is provided around an entire periphery of the second press-fitted portion  41   b  in the circumferential direction of the second press-fitted portion  41   b . In the radial cross section of the second end plate  30  as illustrated in  FIG. 1 , the warp portion  33  is warped so as to be apart from the end surface  10   b  of the rotor core  10  as extending away from the flat plate portion  32 , that is, extending closer to the shaft  40 . Further, in the radial cross section described above, the warp portion  33  is connected to the flat plate portion  32  smoothly and continuously, and is curved so as to protrude on the rotor core  10  side. A width of the warp portion  33 , that is, a radial dimension of the warp portion  33  is smaller than a width of the flat plate portion  32 , that is, a radial dimension of the flat plate portion  32 . 
     Owing to the presence of the warp portion  33 , the flat plate portion  32  is pressed onto the end surface  10   b  of the rotor core  10  by an elastic force of the second end plate  30  itself with the inner peripheral-side end portion  30   b  of the second end plate  30  serving as a fulcrum. Accordingly, the flat plate portion  32  is held in close contact with the end surface  10   a  of the rotor core  10  without a gap. 
     As described above, the flat plate portion  22  of the first end plate  20  is held in close contact with the end surface  10   a  of the rotor core  10 , and the flat plate portion  32  of the second end plate  30  is held in close contact with the end surface  10   b  of the rotor core  10 . That is, the rotor core  10  is pressed by the first end plate  20  and the second end plate  30  from both end sides of the rotor core  10  in the axial direction. With this configuration, during operation of the rotating electric machine, the electromagnetic steel sheets  11  located at both end portions of the rotor core  10  in the axial direction can be prevented from being vibrated by an electromagnetic force. Further, axial positions of the permanent magnets  14  can be thus regulated. Accordingly, noise caused during operation of the rotating electric machine can be suppressed. 
     Here, with reference to a comparative example, description is made of a state in which the first end plate  20  and the second end plate  30  are not held in close contact with the rotor core  10 .  FIG. 3  is a sectional view for illustrating a configuration of a rotor  200  of a rotating electric machine according to a comparative example of this embodiment. Also in the configuration of the comparative example illustrated in  FIG. 3 , the first end plate  20  and the second end plate  30  are fixed to the shaft  40  through press-fitting. However, in the configuration of the comparative example, an outer peripheral side of the first end plate  20  and an outer peripheral side of the second end plate  30  are warped in a direction of separating from the rotor core  10 . As a result, a gap  201  is formed between the first end plate  20  and the end surface  10   a  of the rotor core  10 , and a gap  202  is formed between the second end plate  30  and the end surface  10   b  of the rotor core  10 . This is because the first end plate  20  and the second end plate  30  each having a flat plate shape before press-fitting are deformed by stress caused at the time of press-fitting. It is known that, when a force is locally applied to a periphery of a center hole of a flat plate-like member such as the first end plate  20  or the second end plate  30  and then the flat plate-like member is press-fitted to a columnar member such as the shaft  40 , an outer peripheral side of the flat plate-like member is warped to a side opposite to a direction of applying the force to the flat plate-like member. Under the state as illustrated in  FIG. 3 , during operation of the rotating electric machine, the electromagnetic steel sheets  11  located at the both end portions of the rotor core  10  in the axial direction are vibrated by the electromagnetic force. In addition, the axial positions of the permanent magnets  14  cannot be regulated. 
     Next, description is made of a method of manufacturing the rotor of the rotating electric machine according to this embodiment with reference to  FIG. 4  to  FIG. 13 .  FIG. 4  is a plan view for illustrating a configuration of the first end plate  20  to be used in the method of manufacturing the rotor of the rotating electric machine according to this embodiment.  FIG. 4  is an illustration of the configuration of the first end plate  20  as a component before assembly of the rotor  100 . 
     As illustrated in  FIG. 4 , the first end plate  20  has a disk shape and a flat plate shape. The first through-hole  21 , into which the first press-fitted portion  41   a  of the shaft  40  is to be press-fitted, is formed in the center portion of the first end plate  20 . The first through-hole  21  has a perfectly circular sectional shape. That is, a protrusion protruding radially inward and a recessed portion recessed radially outward are not formed on an inner peripheral surface of the first through-hole  21 . 
       FIG. 5  is a sectional view for illustrating a configuration of the first press-fitted portion  41   a  of the shaft  40  to be used in the method of manufacturing the rotor of the rotating electric machine according to this embodiment.  FIG. 5  is an illustration of a sectional configuration of the shaft  40  as a component before assembly of the rotor  100 , which is taken along a plane perpendicular to the axial direction.  FIG. 6  is a sectional view for illustrating a portion VI of  FIG. 5  in an enlarged manner. 
     As illustrated in  FIG. 5  and  FIG. 6 , a plurality of first protrusions  42  are formed on the outer peripheral surface of the first press-fitted portion  41   a  of the shaft  40  so as to protrude radially outward. As illustrated in  FIG. 1 , each of the first protrusions  42  extends along the axial direction to a portion of the large-diameter portion  41  of the shaft  40  to be press-fitted into the rotor core  10 . The first protrusions  42  each have a function of securing a fixing force exerted when the shaft  40  is press-fitted into the rotor core  10 , and a function of securing a fixing force exerted when the shaft  40  is press-fitted into the first end plate  20 . Between two adjacent first protrusions  42 , a recessed portion  43  is formed. The recessed portion  43  is capable of accommodating chips of the rotor core  10  chipped off by the first protrusions  42  at the time of press-fitting. A plurality of sets each including two first protrusions  42  and one recessed portion  43  are provided on the outer peripheral surface of the large-diameter portion  41  at equal intervals in the circumferential direction. 
     Here, D 1  represents a diameter of the first through-hole  21  of the first end plate  20  illustrated in  FIG. 4 . D 2  represents a diameter of a cylindrical portion of the first press-fitted portion  41   a  including no first protrusion  42  and no recessed portion  43 . D 3  represents a diameter of a circumscribed circle that has a center on a center axis of the shaft  40  and circumscribes the plurality of first protrusions  42 . In this case, the diameter D 1 , the diameter D 2 , and the diameter D 3  satisfy a relation of D 2 &lt;D 1 &lt;D 3 . When the above-mentioned relation is satisfied, the fixing force exerted when the first press-fitted portion  41   a  of the shaft  40  is press-fitted into the first end plate  20  is secured by the first protrusions  42 . 
       FIG. 7  is a plan view for illustrating a configuration of the second end plate  30  to be used in the method of manufacturing the rotor of the rotating electric machine according to this embodiment.  FIG. 7  is an illustration of the configuration of the second end plate  30  as a component before assembly of the rotor  100 .  FIG. 8  is a plan view for illustrating a portion VIII of  FIG. 7  in an enlarged manner. 
     As illustrated in  FIG. 7  and  FIG. 8 , the second end plate  30  has a disk shape and a flat plate shape. The second through-hole  31 , into which the large-diameter portion  41  of the shaft  40  is to be press-fitted, is formed in the center portion of the second end plate  30 . A plurality of second protrusions  34  protruding radially inward are formed on an inner peripheral surface of the second through-hole  31 . 
       FIG. 9  is a sectional view for illustrating a configuration of the second press-fitted portion  41   b  of the shaft  40  to be used in the method of manufacturing the rotor of the rotating electric machine according to this embodiment.  FIG. 9  is an illustration of a sectional configuration of the shaft  40  as a component before assembly of the rotor  100 , which is taken along a plane perpendicular to the axial direction. 
     As illustrated in  FIG. 9 , the second press-fitted portion  41   b  has a perfectly circular sectional shape. That is, a protrusion protruding radially outward and a recessed portion recessed radially inward are not formed on an outer peripheral surface of the second press-fitted portion  41   b.    
     Here, in the second through-hole  31  of the second end plate  30  illustrated in  FIG. 7 , D 4  represents a diameter of a cylindrical portion of the second through-hole  31  including no second protrusions  34 . D 5  represents a diameter of an inscribed circle that has a center on a center axis of the second through-hole  31  and is inscribed in the plurality of second protrusions  34 . D 6  represents a diameter of the second press-fitted portion  41   b . In this case, the diameter D 4 , the diameter D 5 , and the diameter D 6  satisfy a relation of D 5 &lt;D 6 &lt;D 4 . When the above-mentioned relation is satisfied, the fixing force exerted when the shaft  40  is press-fitted into the second end plate  30  is secured by the second protrusions  34 . The diameter D 6  of the second press-fitted portion  41   b  may be equal to the diameter D 2  of the first press-fitted portion  41   a . The diameter D 4  of the second through-hole  31  may be equal to the diameter D 1  of the first through-hole  21 . 
     In this embodiment, the first press-fitted portion  41   a  and the second press-fitted portion  41   b  are different from each other in configuration, and the first end plate  20  and the second end plate  30  are different from each other in configuration. That is, the plurality of first protrusions  42  are formed on the outer peripheral surface of the first press-fitted portion  41   a , whereas a protrusion and a recessed portion are not formed on the outer peripheral surface of the second press-fitted portion  41   b . Further, a protrusion and a recessed portion are not formed on the inner peripheral surface of the first through-hole  21  of the first end plate  20 , whereas the plurality of second protrusions  34  are formed on the inner peripheral surface of the second through-hole  31  of the second end plate  30 . This is because the plurality of first protrusions  42  are not formed in the axial direction in an entire region of the large-diameter portion  41  to be press-fitted into the rotor core  10 , and thus do not reach the second press-fitted portion  41   b . When the shaft  40  is press-fitted into the rotor core  10 , the inner peripheral surface of the rotor core  10  is chipped off by the first protrusions  42 . When the first protrusions  42  are formed so as to be prevented from reaching the second press-fitted portion  41   b , the chips of the rotor core  10  can be kept inside the rotor core  10 . 
     However, the second press-fitted portion  41   b  may have the same configuration as that of the first press-fitted portion  41   a , and the second end plate  30  may have the same configuration as that of the first end plate  20 . That is, similarly to the first press-fitted portion  41   a , the first protrusions  42  may also be formed on the outer peripheral surface of the second press-fitted portion  41   b . Further, similarly to the first through-hole  21 , the second through-hole  31  may also have a perfectly circular sectional shape. Alternatively, similarly to the second through-hole  31 , the second protrusions  34  may also be formed on the inner peripheral surface of the first through-hole  21 . Further, similarly to the second press-fitted portion  41   b , the first press-fitted portion  41   a  may also have a perfectly circular sectional shape. 
     Next, description is made of steps of manufacturing the rotor  100  of the rotating electric machine according to this embodiment.  FIG. 10 ,  FIG. 11 , and  FIG. 13  are sectional views for illustrating the steps of manufacturing the rotor  100  of the rotating electric machine according to this embodiment.  FIG. 12  is a sectional view for illustrating a portion XII of  FIG. 11  in an enlarged manner. In  FIG. 10  to  FIG. 13 , as part of the steps of manufacturing the rotor  100 , a step of press-fitting the first press-fitted portion  41   a  of the shaft  40  into the first end plate  20  is illustrated. In the step illustrated in  FIG. 10  to  FIG. 13 , the second end plate  30  is already mounted to the second press-fitted portion  41   b  through press-fitting. However, a step of press-fitting the second press-fitted portion  41   b  into the second end plate  30  may be performed after the step of press-fitting the first press-fitted portion  41   a  into the first end plate  20 . The step of press-fitting the second press-fitted portion  41   b  into the second end plate  30  can be performed in the same manner as that of the step of press-fitting the first press-fitted portion  41   a  into the first end plate  20 . 
       FIG. 10  is an illustration of a state before the shaft  40  is press-fitted into the first end plate  20 . As illustrated in  FIG. 10 , in the step of press-fitting the first press-fitted portion  41   a  of the shaft  40  into the first end plate  20 , first, the first end plate  20  having a flat plate shape is supported on a jig  50 . The jig  50  includes a flat surface portion  51  and a hole portion  52 . The flat surface portion  51  is configured to support the first end plate  20 . The hole portion  52  is formed in a position surrounded by the flat surface portion  51 , has a cylindrical shape, and extends in a direction perpendicular to the flat surface portion  51 . When D 7  represents a diameter of the hole portion  52 , the diameter D 7  satisfies a relation of D 7 &gt;D 1  and a relation of D 7 &gt;D 2 . A tapered surface  53  is formed along an entire periphery of a corner portion between the flat surface portion  51  and an inner peripheral surface of the hole portion  52 . The first end plate  20  is positioned so that a center of the hole portion  52  and a center of the first through-hole  21  match each other when seen from the direction perpendicular to the flat surface portion  51 . 
       FIG. 11  and  FIG. 12  are each an illustration of a state in the course of press-fitting the shaft  40  into the first end plate  20 . As illustrated in  FIG. 11  and  FIG. 12 , the first press-fitted portion  41   a  of the shaft  40  is gradually press-fitted into the first through-hole  21  of the first end plate  20 . At this time, the inner peripheral-side end portion  20   b  of the first end plate  20  is deformed by stress caused as a result of press-fitting of the shaft  40 . That is, the inner peripheral-side end portion  20   b  of the first end plate  20  is deformed along the tapered surface  53  with an inner peripheral edge portion  51   a  of the flat surface portion  51  serving as a fulcrum. In this manner, the inner peripheral-side end portion  20   b  of the first end plate  20  is warped in a direction of press-fitting the shaft  40 . Thus, the warp portion  23  is formed on an inner peripheral side of the first end plate  20 . Meanwhile, the outer peripheral-side end portion  20   a  of the first end plate  20  rises from the flat surface portion  51  with the inner peripheral edge portion  51   a  serving as a fulcrum. A gap  54  is formed between the outer peripheral-side end portion  20   a  and the flat surface portion  51 . With those configurations, the first end plate  20  is deformed, as a whole, into a coned disc-spring shape protruding in the direction of separating from the rotor core  10 . 
       FIG. 13  is an illustration of a state after completion of press-fitting the shaft  40  into the first end plate  20 . As illustrated in  FIG. 13 , of the first end plate  20 , an outer peripheral-side portion with respect to the warp portion  23  is sandwiched between the end surface  10   a  of the rotor core  10  and the flat surface portion  51  of the jig  50 , and thus is deformed into a flat plate shape. In this manner, the flat plate portion  22  is formed in the first end plate  20 . The flat plate portion  22  is pressed, by an elastic force of the first end plate  20  itself, onto the end surface  10   b  of the rotor core  10  with the inner peripheral-side end portion  20   b  serving as a fulcrum. Accordingly, the flat plate portion  22  is held in close contact with the end surface  10   a  of the rotor core  10  without a gap. In this case, the elastic force of the first end plate  20  is obtained as a result of deformation of the first end plate  20  itself into a coned disc-spring shape, which is caused along with press-fitting of the shaft  40 . The first end plate  20  is deformed into a coned disc-spring shape mainly by an influence of the tapered surface  53  formed on the jig  50 . 
     In the method of manufacturing the rotor of the electric motor described in Patent Literature 1, the end plate that is formed into a coned disc-spring shape in advance before press-fitting is used in order to hold a rotor core and the end plate in close contact with each other. However, in this manufacturing method, when the end plate is press-fitted to the shaft, the end plate may be warped to a side opposite to the rotor core. Accordingly, the end plate may vary in shape widely, and a desired elastic force of the end plate cannot be obtained in some cases. As a result, there has been a problem in that a gap is formed between the end plate and the rotor core in some cases. Moreover, the step of forming the end plate into a coned disc-spring shape is additionally required. Accordingly, there has also been a problem in that manufacturing cost of the rotor is increased along with an increase in the number of manufacturing steps. 
     Further, normally, in order to hold the end plate having a flat plate shape in close contact with the rotor core in the rotating electric machine, another component such as a rivet or a boss has been required. Accordingly, there has been a problem in that the manufacturing cost of the rotor is increased along with an increase in the number of components and the increase in the number of manufacturing steps. 
     In contrast, in this embodiment, each of the first end plate  20  and the second end plate  30  is held, by its own elastic force, in close contact with the rotor core  10  without a gap. With this configuration, during operation of the rotating electric machine, the electromagnetic steel sheets  11  located at the both end portions of the rotor core  10  in the axial direction can be prevented from being vibrated by the electromagnetic force. Further, the axial positions of the permanent magnets  14  can be thus regulated. Accordingly, the noise caused during operation of the rotating electric machine can be suppressed. Moreover, in this embodiment, components each having a flat plate shape can be used as the first end plate  20  and the second end plate  30 , and it is not required to add another component such as a rivet or a boss. Thus, simplification of the steps of manufacturing the rotor  100 , and reduction in manufacturing cost of the rotor  100  can be achieved. 
     As described above, the rotor  100  of the rotating electric machine according to this embodiment includes the rotor core  10 , the first end plate  20 , and the shaft  40 . The first end plate  20  is provided at the end portion of the rotor core  10  in the axial direction of the rotor core  10 . The shaft  40  passes through the rotor core  10  and the first end plate  20  along the axial direction. The first end plate  20  includes the flat plate portion  22  having an annular shape, and the warp portion  23 . The flat plate portion  22  is held in contact with the rotor core  10 . The warp portion  23  is formed more on the inner peripheral side than the flat plate portion  22 , and is held in contact with the shaft  40 . In the radial cross section of the first end plate  20 , the warp portion  23  is warped so as to be apart from the rotor core  10  as extending away from the flat plate portion  22 . Here, the first end plate  20  is an example of an end plate. 
     With this configuration, the flat plate portion  22  of the first end plate  20  is pressed onto the rotor core  10  by the elastic force of the first end plate  20  itself. Thus, with the configuration described above, the first end plate  20  and the rotor core  10  can be held in close contact with each other more reliably. 
     The method of manufacturing the rotor  100  of the rotating electric machine according to this embodiment includes the step of press-fitting the first press-fitted portion  41   a  of the shaft  40 , to which the rotor core  10  is mounted, into the first through-hole  21  of the first end plate  20  that has a flat plate shape and is supported on the jig  50 . The first press-fitted portion  41   a  is located on one end side of the rotor core  10 . The jig  50  includes the flat surface portion  51 , the hole portion  52 , and the tapered surface  53 . The flat surface portion  51  is configured to support the first end plate  20 . The hole portion  52  is formed in the position surrounded by the flat surface portion  51 , and has the diameter D 7  larger than the diameter D 1  of the first through-hole  21  and the diameter D 2  of the first press-fitted portion  41   a . The hole portion  52  extends in the direction perpendicular to the flat surface portion  51 . The tapered surface  53  is formed between the inner peripheral surface of the hole portion  52  and the flat surface portion  51 . 
     With this configuration, in the step of press-fitting the first press-fitted portion  41   a  into the first through-hole  21 , the inner peripheral-side end portion of the first end plate  20  is deformed along the tapered surface  53 . Thus, the first end plate  20  is deformed, as a whole, into a coned disc-spring shape. After completion of press-fitting the first press-fitted portion  41   a  into the first through-hole  21 , the first end plate  20  is pressed onto the rotor core  10  by the elastic force of the first end plate  20  itself. Thus, the first end plate  20  and the rotor core  10  can be held in close contact with each other more reliably. 
     Further, in the method of manufacturing the rotor  100  of the rotating electric machine according to this embodiment, the first protrusions  42  are formed on the outer peripheral surface of the first press-fitted portion  41   a , and the first through-hole  21  has a perfectly circular sectional shape. With this configuration, the fixing force exerted between the first end plate  20  and the shaft  40  can be secured by the first protrusions  42 . 
     Further, in the method of manufacturing the rotor  100  of the rotating electric machine according to this embodiment, the first press-fitted portion  41   a  has a perfectly circular sectional shape, and the second protrusions  34  are formed on the inner peripheral surface of the first through-hole  21 . With this configuration, the fixing force exerted between the first end plate  20  and the shaft  40  can be secured by the second protrusions  34 . 
     Further, the method of manufacturing the rotor  100  of the rotating electric machine according to this embodiment further includes the step of press-fitting the second press-fitted portion  41   b  of the shaft  40  into the second through-hole  31  of the second end plate  30  that has a flat plate shape and is supported on the jig  50 , the second press-fitted portion  41   b  being located on the other end side of the rotor core  10 . The first protrusions  42  are formed on the outer peripheral surface of the first press-fitted portion  41   a . The first through-hole  21  has a perfectly circular sectional shape. The second press-fitted portion  41   b  has a perfectly circular sectional shape. The second protrusions  34  are formed on the inner peripheral surface of the second through-hole  31 . With this configuration, the fixing force exerted between the first end plate  20  and the shaft  40  can be secured by the first protrusions  42 , and the fixing force exerted between the second end plate  30  and the shaft  40  can be secured by the second protrusions  34 . 
     The present invention is not limited to the embodiment described above, and various modifications can be made thereto. For example, in the embodiment described above, the rotor  100  of the IPM type is given as an example. However, the present invention is applicable to rotors of various types such as a surface permanent magnet (SPM) type, a consequent type and an inset type. 
     REFERENCE SIGNS LIST 
     
         
         
           
               10  rotor core,  10   a ,  10   b  end surface,  11  electromagnetic steel sheets,  12  through-hole,  13  magnet insertion hole,  14  permanent magnet,  20  first end plate,  20   a  outer peripheral-side end portion,  20   b  inner peripheral-side end portion,  21  first through-hole,  22  flat plate portion,  23  warp portion,  30  second end plate,  30   a  outer peripheral-side end portion,  30   b  inner peripheral-side end portion,  31  second through-hole,  32  flat plate portion,  33  warp portion,  34  second protrusion,  40  shaft,  41  large-diameter portion,  41   a  first press-fitted portion,  41   b  second press-fitted portion,  42  first protrusion,  43  recessed portion,  50  jig,  51  flat surface portion,  51   a  inner peripheral edge portion,  52  hole portion,  53  tapered surface,  54  gap,  100 ,  200  rotor,  201 ,  202  gap