Patent Publication Number: US-2020303983-A1

Title: Stator and rotating electrical machine

Description:
This application is based on and claims the benefit of priority from Japanese Patent Application No. 2019-054836, filed on 22 Mar. 2019, the content of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a stator and a rotating electrical machine including the stator. 
     Related Art 
     In a rotating electrical machine including a rotor and a stator, the stator is configured with an iron core including a winding attached, and a stator frame attached to the outer surface of the stator. As one method of fixing the iron core to the stator frame, a method called shrink fitting is known (refer to, for example, Patent Document 1).
     Patent Document 1: Japanese Unexamined Utility Model Application, Publication No. H07-9070   

     SUMMARY OF THE INVENTION 
     In the above-described fixing by shrink fitting, the iron core and the stator frame are likely to be deformed, and thus magnetic characteristics may be deteriorated. Therefore, a stator and a rotating electrical machine having good magnetic characteristics are desired. 
     (1) In one aspect of the present disclosure, a stator includes a substantially cylindrical iron core including a winding attached inside, and a stator frame joined to the iron core via a first weld portion. In the stator, the iron core includes a groove portion extending along an axial direction and recessed from an outer circumferential surface of the iron core inward in a radial direction, and the first weld portion is formed at, on at least one edge in the axial direction of the iron core, mutually facing portions of an edge portion of the iron core and an inner circumferential surface of the stator frame. 
     (2) In another aspect of the present disclosure, a rotating electrical machine includes the stator according to (1) and a rotor disposed inside the stator and supported by a rotary shaft. 
     The one aspect of the present disclosure enables to provide a stator and a rotating electrical machine having good magnetic characteristics. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view for explaining a configuration of an electric motor  1  according to one embodiment. 
         FIG. 2  is an oblique view of a stator  20 . 
         FIG. 3  is an exploded oblique view of an iron core  21  and a stator frame  22  included in the stator  20 . 
         FIG. 4A  is a diagram for explaining the action generated at the time when the iron core  21  and the stator frame  22  are joined via a first weld portion W 1 . 
         FIG. 4B  is a diagram for explaining the action generated after the iron core  21  and the stator frame  22  are joined via the first weld portion W 1 . 
         FIG. 5A  is a diagram illustrating an example of a groove portion  212  of the iron core  21  joined via a second weld portion W 2 . 
         FIG. 5B  is a diagram illustrating another example of the groove portion  212  of the iron core  21  joined via the second weld portion W 2 . 
         FIG. 6A  is a diagram illustrating an example of each of the groove portions  212  disposed at every other position of teeth  211  of the iron core  21 . 
         FIG. 6B  is a diagram illustrating an example of each of the groove portions  212  disposed at a position between adjacent teeth  211  of the iron core  21 . 
         FIG. 7A  is a diagram illustrating an example of the groove portions  212  having triangular shapes in the cross section. 
         FIG. 7B  is a diagram illustrating an example of the groove portions  212  having substantially U shapes in the cross section. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     One embodiment of the present disclosure will be described below. All of the drawings attached to the present specification are schematic diagrams, and a shape, a scale, a length/width ratio and the like of each part are changed from the actual ones or exaggerated, so as to be easily understood. In the drawings, hatching of indicating a cross section of a member will be omitted as appropriate. 
     The electric motor  1  (rotating electrical machine) including the stator  20  of the present embodiment is described first.  FIG. 1  is a cross-sectional view for explaining the configuration of the electric motor  1  according to the one embodiment. It is noted that the configuration of the electric motor  1  shown in  FIG. 1  is merely one example, and any configuration is available as long as the stator  20  of the present embodiment is available. 
     In each of  FIG. 1  and other drawings, a coordinate system including the X axis and the Y axis orthogonal to each other is illustrated. In the present coordinate system, the X direction serves as the axial direction of the electric motor  1 , the Y direction serves as the radial direction thereof, and the R direction serves as the circumferential direction thereof. It is noted that the axial direction, the radial direction and the circumferential direction of the electric motor  1  respectively coincide with the axial directions, the radial directions and the circumferential directions of the stator  20 , the iron core  21  and the stator frame  22 , which are described below. 
     As shown in  FIG. 1 , the electric motor  1  includes a frame  10 , the stator  20  and a rotor  30 . The frame  10 , which is an exterior member of the electric motor  1 , includes a frame body  11 , a shaft hole  12  and a bearing  13 . The frame body  11  is a housing for enclosing and holding the stator  20 . The frame body  11  holds the rotor  30  via the bearing  13 . The frame body  11  includes a supply port  14 , a discharge port  15  and a hole part  16 . The supply port  14  is an opening for supplying a refrigerant to a passage  23  (to be described below) of the stator frame  22 , and is connected to a supply pipe (not shown) of the refrigerant. The discharge port  15  is an opening for discharging the refrigerant circulated through the passage  23 , and is connected to a discharge pipe (not shown) of the refrigerant. The hole part  16  is an opening through which a power line  27  drawn out from the iron core  21  pierces. The shaft hole  12  is a hole through which a rotary shaft  32  (to be described below) pierces. The bearing  13  is a member for rotatably supporting the rotary shaft  32 . 
     The stator  20  is a composite member configured to form a rotating magnetic field for rotating the rotor  30 . The stator  20  is formed in a cylindrical shape as a whole, and is fixed inside the frame  10 . The stator  20  includes the iron core  21  and the stator frame  22 . 
     The iron core  21  is a member allowing a winding  26  to be attached inside. The iron core  21  is formed in a cylindrical shape, and is disposed inside the stator frame  22  in the stator  20 . The iron core  21  has a plurality of the teeth  211  (refer to  FIG. 2 ) on the inner surface thereof. The winding  26  is attached to the teeth  211 . It is noted that the winding  26  partially protrudes from the both ends of the iron core  21  in the axial direction (X direction) of the iron core  21 . The iron core  21  is integrated by, for example, laminating a plurality of thin plates such as electromagnetic steel plates to form a laminated body, and joining the laminated body such as by bonding, bolting or calking. 
     The stator frame  22  is a member for holding the iron core  21  inside thereof. The stator frame  22  is formed in a cylindrical shape. As will be described below, the iron core  21  is joined to the stator frame  22  via a weld portion (not shown). As shown in  FIG. 1 , the stator frame  22  of the present embodiment includes, on the outer surface, the passage  23  for cooling the heat transmitted from the iron core  21 . The passage  23  is a single or multiple spiral groove(s) formed on the outer surface of the stator frame  22 . The refrigerant (not shown) supplied through the supply port  14  of the frame body  11  (frame  10 ) circulates through the passage  23  spirally along the outer surface of the stator frame  22 , and thereafter is discharged to the outside through the discharge port  15  of the frame body  11 . 
     Examples of the material for the stator frame  22  include carbon steel, a steel member for electromagnetic steel plate, and stainless steel. It is noted that the stator frame  22  may be made of any material as long as the stator frame  22  is able to be welded to the iron core  21 . The inner circumferential side of the stator frame  22  to be joined to the iron core  21  by welding may be made of iron material, and the outer circumferential side thereof may be made of non-iron material. 
     The power line  27  electrically connected to the winding  26  is drawn out from the iron core  21  of the stator  20 . The power line  27  is connected to a power supply (not shown) installed outside the electric motor  1 . In an example, during when the electric motor  1  operates, a three-phase alternating current is supplied to the iron core  21 , thereby forming a rotating magnetic field for rotating the rotor  30 . 
     The rotor  30  is a component configured to be rotated by magnetic interaction with the rotating magnetic field formed by the stator  20 . The rotor  30  is disposed inside the stator  20 . The rotor  30  includes a rotor body  31  and the rotary shaft  32 . The rotor body  31  is configured with a plurality of permanent magnets (not shown), to generate a rotational force by the rotating magnetic field formed by the stator  20 . 
     The rotary shaft  32  is a member for supporting the rotor body  31 . The rotary shaft  32  is inserted so as to pierce through the axial center of the rotor body  31 , and is fixed to the rotor body  31 . The rotary shaft  32  is rotatably supported by the bearing  13  provided in the frame  10 . The rotary shaft  32  pierces through the shaft hole  12 , and is connected to a power transmission mechanism, a speed reduction mechanism and the like (not shown) disposed outside. 
     In the electric motor  1  shown in  FIG. 1 , when a three-phase alternating current is supplied to the stator  20  (iron core  21 ), the magnetic interaction generated between the stator  20  and the rotor  30  where the rotating magnetic field is formed generates a rotational force to the rotor body  31 , and the rotational force is output to the outside via the rotary shaft  32 . It is noted that although the electric motor  1  is a synchronous motor in the present embodiment, the electric motor  1  may be, for example, an induction motor. 
     The stator  20  in the electric motor  1  of the present embodiment is described next. In the drawings of the embodiment to be described below, the illustration of the winding  26  attached to the teeth  211  of the iron core  21 , the passage  23  provided on the outer surface of the stator frame  22 , and the like are omitted.  FIG. 2  is an oblique view of the stator  20 .  FIG. 3  is an exploded oblique view of the iron core  21  and the stator frame  22  included in the stator  20 .  FIG. 4A  is a diagram for explaining the action generated at the time when the iron core  21  and the stator frame  22  are joined via the first weld portion W 1 .  FIG. 4B  is a diagram for explaining the action generated after the iron core  21  and the stator frame  22  are joined via the first weld portion W 1 . Each of  FIG. 4A  and  FIG. 4B  is a plan view of a part of the stator  20  shown in  FIG. 2  viewed from the axial direction (X direction), as an example. 
     As shown in  FIG. 2 , in the stator  20 , the iron core  21  is held inside the stator frame  22  in the radial direction (Y direction). The iron core  21  has the plurality of teeth  211  on the inner surface thereof, which are disposed away from one another in the circumferential direction (R direction) and protrude inward in the radial direction (Y direction). The winding  26  (refer to  FIG. 1 ) is attached to gaps between teeth  211 ,  211  adjacent in the circumferential direction (R direction). 
     The iron core  21  has, on the outer circumferential surface thereof, the plurality of groove portions  212  recessed from the outer circumferential surface inward in the radial direction. The groove portions  212  are disposed at the positions corresponding to the teeth  211  of the iron core  21 . In the present embodiment, each of the groove portions  212  is disposed at a center in the circumferential direction (R direction) of each of the root portions of the teeth  211 . As shown in  FIG. 3 , each of the groove portions  212  is disposed from one edge portion  21   a  through to the other edge portion  21   b  in the axial direction (X direction) of the iron core  21 . 
     As shown in  FIG. 2 , the iron core  21  inserted in the stator frame  22  is joined at the mutually facing portions of the edge portion  21   a  and an inner circumferential surface  221  of the stator frame  22  via the first weld portion W 1 . The groove portions  212  of the iron core  21  are not joined to the stator frame  22  via the first weld portion W 1 . The first weld portion W 1  is formed by joining the mutually facing portions of the edge portion  21   a  of the iron core  21  and the internal circumferential surface  221  of the stator frame  22  by, for example, laser welding. 
     The iron core  21  is joined also at the mutually facing portions of the edge portion  21   b  not shown of the iron core  21  positioned opposite to the edge portion  21   a  and the inner circumferential surface  221  of the stator frame  22  via the first weld portion W 1 . That is, the iron core  21  of the present embodiment is joined to the stator frame  22  via the first weld portion W 1  at the edge portion  21   a  and the edge portion  21   b  respectively in the axial direction (X direction). 
     As shown in  FIG. 4A , when the iron core  21  and the stator frame  22  are joined via the first weld portion W 1 , the iron core  21  is distorted in the illustrated arrow directions by the heat of welding. The distortion is dispersed by the groove portions  212  disposed on the outer circumferential surface of the iron core  21 , thereby enabling to suppress the deterioration in magnetic characteristics caused by the deformation of the iron core  21 . If the whole circumferences of the mutually facing portions of the edge portion  21   a  ( 21   b ) of the iron core  21  without the groove portions  212  provided and the internal circumferential surface  221  of the stator frame  22  are welded to each other, the distortion caused in the iron core  21  is not dispersed, unlike in  FIG. 4A . For this reason, the deformation of the iron core  21  may deteriorate the magnetic characteristics. In the stator  20  of the present embodiment, the mutually facing portions of the edge portion  21   a  ( 21   b ) of the iron core  21  except the groove portions  212  provided on the outer circumferential surface of the iron core  21  and the inner circumferential surface  221  of the stator frame  22  are joined via the first weld portion W 1 , thereby enabling to suppress the deterioration in magnetic characteristics caused by the deformation of the iron core  21 . 
     It is assumed that, as shown in  FIG. 4B , after the iron core  21  and the stator frame  22  are joined via the first weld portion W 1 , a crack C is generated partially in the first weld portion W 1 . It is conceivable that the crack C propagates in one of or both directions of the illustrated arrows, but in either case, the propagation is suppressed by the groove portions  212  disposed in the vicinity. Accordingly, in the stator  20  of the present embodiment, even in the case where the crack C is generated partially in the first weld portion W 1 , the crack C is prevented from propagating in a wide range. If the whole circumferences of the mutually facing portions of the edge portion  21   a  ( 21   b ) of the iron core  21  without the groove portions  212  provided and the internal circumferential surface  221  of the stator frame  22  are welded to each other, the crack C is not able to be suppressed from propagating, and accordingly the crack C has possibility of propagating in a wide range. However, since the stator  20  of the present embodiment includes the groove portions  212  on the outer circumferential surface of the iron core  21 , the crack C generated in the first weld portion W 1  is able to be suppressed from propagating. 
     In the stator  20  of the present embodiment described above, the iron core  21  and the stator frame  22  are hardly deformed as compared with the case of fixing by shrink fitting, and accordingly the stator  20  has better magnetic characteristics. In addition, the iron core  21  is able to be more easily fitted into the stator frame  22 , as compared with the case of fixing by shrink fitting. 
     As a method of fixing an iron core to a stator frame, joining with an adhesive is known. However, in the joining with an adhesive, the adhesive strength depends on the surface conditions of the iron core and the stator frame, and the gaps between the iron core and the stator frame need to be controlled uniformly. On the other hand, in the stator  20  of the present embodiment, the joining strength of the first weld portion W 1  less depends on the surface conditions of the iron core  21  and the stator frame  22 , and the accuracy of the gaps between the iron core  21  and the stator frame  22 . Therefore, in the stator  20  of the present embodiment, the iron core  21  and the stator frame  22  are able to be joined more stably. 
     As another method of fixing an iron core to a stator frame, key engagement is known. However, in the key engagement, since a key groove needs to be provided on a stator frame, the number of machining steps increases. On the other hand, in the stator  20  of the present embodiment, a step such as of providing a key groove on the stator frame  22  is not required, and thus the number of machining steps is able to be suppressed. 
     In the stator  20  of the present embodiment, the groove portions  212  of the iron core  21  are disposed from the one edge portion  21   a  through to the other edge portion  21   b  in the axial direction (X direction) of the iron core  21 . Therefore, when the iron core  21  and the stator frame  22  are joined via the first weld portion W 1 , the distortion occurring in the iron core  21  is able to be dispersed in a wider range. It is noted that the groove portions  212  may not be disposed through between the both edge portions in the axial direction of the iron core  21 . In an example, the groove portions  212  may be disposed in the vicinity of the one edge portion  21   a  in the axial direction of the iron core  21 , and in the vicinity of the other edge portion  21   b , respectively. 
     In the stator  20  of the present embodiment, each of the groove portions  212  of the iron core  21  is disposed at a center of each of the root portions of the teeth  211 . It is conceivable that, in the iron core  21 , the portion where each of the groove portions  212  is arranged has less magnetic fluxes passing through the inside thereof. However, each of the groove portions  212  is disposed at a center of each of the root portions of the teeth  211  where the magnetic fluxes easily pass, thereby enabling to minimize the influence caused by the decrease of the magnetic fluxes. It is noted that, as will be described below, the positions where the groove portions  212  are disposed in the iron core  21  may be other positions than the root portions of the teeth  211 . 
     Another embodiment of the iron core  21  is described next. Each of  FIG. 5A  and  FIG. 5B  is a diagram illustrating an example of each of the groove portions  212  of the iron core  21  joined via the second weld portion W 2 . Each of  FIG. 5A  and  FIG. 5B  is a plan view of a part of the iron core  21  viewed from the axial direction (X direction). As described above, the iron core  21  is integrated by laminating a plurality of thin plates such as electromagnetic steel plates to form a laminated body, and joining the laminated body such as by bonding, bolting or calking. In the present example to be described below, the iron core  21  is integrated by welding the groove portions  212  of the iron core  21 . 
     In the iron core  21  shown in  FIG. 5A , one corner (the left side in the drawing) on the bottom surface side of each of the groove portions  212  is joined via the second weld portion W 2 . The second weld portion W 2  is disposed from the one edge portion  21   a  through to the other edge portion  21   b  in the axial direction (X direction) of the iron core  21  serving as a laminated body (refer to  FIG. 3 ). It is noted that, in the iron core  21  shown in  FIG. 5A , the other corner (the right side in the drawing) on the bottom surface side of each of the groove portions  212  may be joined via the second weld portion W 2 . 
     In the iron core  21  shown in  FIG. 5B , the both corners on the bottom surface side of each of the groove portions  212  are respectively joined via the second weld portions W 2 . Also in the present aspect, each of the second weld portions W 2  is disposed from the one edge portion  21   a  through to the other edge portion  21   b  in the axial direction of the iron core  21  serving as a laminated body. The iron core  21  is joined by the method shown in  FIG. 5A  or  FIG. 5B , thereby enabling to integrate more firmly the laminated body formed by laminating a plurality of thin plates such as electromagnetic steel plates. 
     The one embodiment of the present disclosure has been described so far. The present disclosure is not limited to the above-described embodiment. Various modifications and changes are available as in the modifications to be described below. Such modifications and changes are also within the technical scope of the present disclosure. The above effects in the embodiment are described merely as the most preferable effects generated by the present disclosure. The effects generated by the present disclosure are not limited to those described in the embodiment. It is noted that although the above-described embodiment and the modifications to be described below are available in any combination thereof, the detailed description will be omitted. 
     (Modifications) 
       FIG. 6A  is a diagram illustrating the example of each of the groove portions  212  disposed at every other position of the teeth  211  of the iron core  21 .  FIG. 6B  is a diagram illustrating the example of each of the groove portions  212  disposed at a position between teeth  211  adjacent in the circumferential direction (R direction) of the iron core  21 . Each of  FIG. 6A  and  FIG. 6B  is a plan view of a part of the iron core  21  viewed from the axial direction (X direction). As shown in  FIG. 6A , each of the groove portions  212  may be disposed at every other position in the circumferential direction of the teeth  211  of the iron core  21 . Also in this case, each of the groove portions  212  is disposed at a center in the circumferential direction of each of the root portions of the teeth  211 . It is noted that in the case of the iron core  21  having a large diameter, each of the groove portions  212  may be disposed at every third position or more in the circumferential direction of the teeth  211  of the iron core  21 . 
     As shown in  FIG. 6B , each of the groove portions  212  may be disposed at a position between teeth  211  adjacent in the circumferential direction (R direction) of the iron core  21 . Although, in the example shown in  FIG. 6B , each of the groove portions  212  is disposed at an intermediate position of adjacent teeth  211  of the iron core  21 , the present invention is not limited thereto. Each of the groove portions  212  may be disposed close to one of adjacent teeth  211  of the iron core  21  therebetween. Alternatively, a plurality of groove portions  212  may be disposed between adjacent teeth  211  of the iron core  21 . The configuration shown in  FIG. 6B  may be combined with, for example, the configuration in which each of the groove portions  212  is disposed at a center of each of the root portions of the teeth  211 . 
       FIG. 7A  is a diagram illustrating the example of the groove portions  212  having triangular shapes in the cross section.  FIG. 7B  is a diagram illustrating the example of the groove portions  212  having substantially U shapes in the cross section. Each of  FIG. 7A  and  FIG. 7B  is a plan view of a part of the iron core  21  viewed from the axial direction (X direction). As shown in  FIG. 7A , the groove portions  212  may be formed in triangular shapes in the cross section. Alternatively, as shown in  FIG. 7B , the groove portions  212  may be formed in substantially U shapes in the cross section. In the case of the groove portions  212  having substantially U shapes in the cross section as shown in  FIG. 7B , when the iron core  21  and the stator frame  22  are joined via the first weld portion W 1 , the stress caused by heat hardly concentrates on the corners of the bottom surface sides of the groove portions  212 . Therefore, the distortion of the iron core  21  caused by the heat of welding is able to be suppressed more effectively. It is noted that the cross sectional shape of the groove portions  212  is not limited to a triangular shape or a substantially U shape, and may be, for example, a semicircular shape or a semielliptical shape. 
     In the configuration of the iron core  21  of the present embodiment, either the mutually facing portions of the edge portion  21   a  and the inner circumferential surface  221  of the stator frame  22  or the mutually facing portions of the edge portion  21   b  and the inner circumferential surface  221  of the stator frame  22  may be joined via the first weld portion W 1 . The insides of the groove portions  212  may be filled with resin. Also in the case of such a configuration, the crack generated in the first weld portion W 1  is able to be suppressed from propagating. 
     EXPLANATION OF REFERENCE NUMERALS 
       1 : ELECTRIC MOTOR,  20 : STATOR,  21 : IRON CORE,  22 : STATOR FRAME,  211 : TOOTH,  212 : GROOVE PORTION,  221 : INNER CIRCUMFERENTIAL SURFACE (STATOR FRAME), W 1 : FIRST WELD PORTION, W 2 : SECOND WELD PORTION