Patent Publication Number: US-2021184532-A1

Title: Rotary electric machine

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present application relates to the field of a rotary electric machine. 
     Description of the Related Art 
     In recent years, a reduction in size, an increase in power, and an increase in efficiency have been required for a rotary electric machine such as an electric motor or an electric generator. In order to meet these requirements, particularly, an in-vehicle motor adopts a distributed winding which uses substantially rectangular cross-section coils. A distributed winding stator, as it has a smooth distribution of rotating fields, is characterized by low noise, as compared with a concentrated winding stator. Also, the use of substantially rectangular cross-section coils improves the space factor of the coils, and has the effect of an increase in power, as compared with when configuring a winding by bundling round wires. On the other hand, an improvement in cooling performance is required in the course of the trend toward a reduction in size and an increase in power. 
     As a solution to these problems, for example, a stator winding described in PTL 1 shows a structure in which coil turn portions, each folded back at the top portion of a coil end, are formed in a U-shape and are radially disposed so as for their lateral faces to face the center, and empty spaces passing through from the inner circumference side to the outer circumference side are each provided between a coil turn portion and an adjacent coil turn portion at the top of another coil end. By adopting this kind of structure, a refrigerant passes through the empty spaces between the coil end portions, thereby leading to an improvement in cooling performance. 
     [PTL 1] Japanese Patent No. 5,770,074 
     The rotary electric machine disclosed in PTL 1, however, has a problem in that the refrigerant passes through between the coil ends, so that only a slight amount of the refrigerant comes into contact with coils, resulting in a deficiency in cooling performance. 
     SUMMARY OF THE INVENTION 
     The present application has been made to solve the above problem, and an object of the present application is to provide a rotary electric machine which is improved in cooling performance. 
     A rotary electric machine disclosed in the present application includes a rotor; and a stator which, being disposed opposite the rotor, has a stator core having a plurality of slots therein and a stator winding wound in the plurality of slots. In the rotary electric machine, the stator has a plurality of coil ends which are formed protruding from an axial end face of the stator core and between adjacent ones of which is provided a radial clearance passing through from the inner diameter side to the outer diameter side. The stator also includes a bus bar which, being disposed on the inner diameter side of the plurality of coil ends so as to occlude the clearances between the plurality of coil ends, guides a refrigerant, which is supplied from the radial direction of the stator, to the plurality of coil ends. 
     According to the rotary electric machine disclosed in the present application, it is possible to obtain the rotary electric machine which is improved in cooling performance. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view showing a stator of a rotary electric machine according to the first embodiment. 
         FIG. 2  is a front view showing a unit coil of the rotary electric machine according to the first embodiment. 
         FIG. 3A  is a top view of a bus bar of the rotary electric machine according to the first embodiment. 
         FIG. 3B  is a side view of the bus bar in  FIG. 3A . 
         FIG. 4  is a diagram showing an example of connection of the bus bar of the rotary electric machine according to the first embodiment. 
         FIG. 5A  is a top view of the rotary electric machine according to the first embodiment. 
         FIG. 5B  is a sectional view along the line A-A of  FIG. 5A . 
         FIG. 5C  is a side view as seen from the side B of  FIG. 5A . 
         FIG. 5D  is a top view showing a modification example of the rotary electric machine according to the first embodiment. 
         FIG. 5E  is a sectional view along the line C-C of  FIG. 5D . 
         FIG. 6  is a front view showing a rotary electric machine according to the second embodiment. 
         FIG. 7  is an enlarged top view showing a bus bar according to the third embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First Embodiment 
     Hereinafter, a description will be given, based on the drawings, of the first embodiment. In the individual drawings, identical signs represent identical or equivalent portions. 
       FIG. 1  is a perspective view showing a stator of a rotary electric machine according to the first embodiment. As shown in  FIG. 1 , a stator  1  includes an annular stator core  9 , a stator winding  10  wound on the stator core  9 , and ground insulation paper (not shown) fixed in slots  22 . 
     The stator core  9  includes therein the circumferentially arranged slots  22 . The stator winding  10  is wound in the plurality of slots  22 . A plurality of coil ends  24  are formed protruding from an axial end face of the stator core  9 . Radial clearances  21 , which pass through from the inner diameter side to the outer diameter side of the coil ends  24 , are each provided between adjacent ones of the plurality of coil ends  24 . A bus bar  13  is disposed on the inner diameter side of a plurality of ones of the coil ends  24 . The bus bar  13  is provided so as to occlude the clearances  21 , each between adjacent ones of the plurality of the coil ends  24 . Also, the bus bar  13  electrically connects terminal wires  25  together. 
       FIG. 2  is a front view showing a unit coil of the rotary electric machine according to the first embodiment. A unit coil  12  is an annular coil, and the stator winding  10  includes a plurality of the unit coils  12 . The unit coils  12  each have a coil slot portion  23  to be fixed in the slot  22  of the stator core  9 , the coil end  24  which protrudes from the slot  22  of the stator core  9  and is connected to another coil end  24  protruding from a circumferentially different slot  22 , and the terminal wire  25  which, axially protruding from the slot  22  of the stator core  9 , is for connecting with another unit coil  12  of the stator winding  10 . 
     Also, the stator winding  10  has at least one bus bar  13  which electrically connects the terminal wires  25  of a plurality of ones of the unit coils  12  together, and the unit coils  12  and the bus bar  13  configure the stator winding  10 . The stator winding  10  and the bus bar  13  are different parts of the same material, for example, a metal containing copper. 
       FIG. 3A  is a top view of the bus bar of the rotary electric machine according to the first embodiment. Also,  FIG. 3B  is a side view of the bus bar in  FIG. 3A . Furthermore,  FIG. 4  is a diagram showing an example of connection of the bus bar of the rotary electric machine according to the first embodiment. 
     As shown in  FIG. 3A , the bus bar  13  has a circular arc shape such as to follow the inner diameter of the coil ends  24  as seen from the top (in the axial direction). Also, as shown in  FIG. 3B , the bus bar  13  is formed in a substantially U-shape as seen from the side and has two end portions  11 . As shown in  FIG. 4 , the end portions  11  of the bus bar  13  are each electrically connected to the terminal wire  25  of the unit coil  12  by TIG welding, laser welding, or the like. The bus bar  13  connects two of the terminal wires  25 , for example, six slots away from each other. The stator winding  10  is integrated by connecting the two terminal wires  25 , for example, six slots away from each other, with the bus bar  13  and by connecting the terminal wires  25  together. 
       FIG. 5A  is a top view of the rotary electric machine according to the first embodiment. Also,  FIG. 5B  is a sectional view along the line A-A of  FIG. 5A , and  FIG. 5C  is a side view as seen from the side B of  FIG. 5A . Furthermore,  FIG. 5D  is a top view showing a modification example of the rotary electric machine according to the first embodiment, and  FIG. 5E  is a sectional view along the line C-C of  FIG. 5D .  FIGS. 5B, 5C, and 5E  are illustrations focused on the coil end  24 , wherein a rotor  2  and a rotary shaft  3  which are disposed inside the inner periphery of the stator  1  are omitted from illustration. 
     As shown in  FIG. 5A , a rotary electric machine  50  includes the rotor  2 , which has the rotatably supported rotary shaft  3 , and the stator  1  disposed opposite the outer periphery of the rotor  2 . 
     As shown in  FIGS. 5A and 5C , the radial clearances  21  passing through from the inner diameter side to the outer diameter side are each provided between adjacent coil ends  24 . The bus bar  13 , being disposed on the inner diameter side of the stator  1 , is disposed in a position in which it occludes the clearances  21  between the coil ends  24 . With this configuration, a radially sprayed refrigerant is restrained from passing through the clearances  21  between the coil ends  24 , and the refrigerant is guided to the coil ends  24  along the bus bar  13 , so that the refrigerant comes into sufficient contact with the coil ends  24 , leading to an improvement in cooling performance. 
     In  FIG. 5B , the arrows shown pointing in the direction of the bus bar  13  indicate the direction in which the refrigerant is sprayed or the direction in which the refrigerant diffuses. As shown in  FIG. 5B , when the refrigerant is strayed from the inner diameter side to the outer diameter side, the refrigerant is diffused by hitting against the bus bar  13 , and the refrigerant can thus be brought into wide contact with the coil ends  24 , enabling an improvement in cooling performance 
     Also, the bus bar  13  guides the refrigerant, which is supplied from the radial direction of the stator  1 , to the plurality of coil ends  24 . The refrigerant is supplied from the inner diameter side of the stator  1 , specifically, from, for example, the rotor  2  side. 
       FIG. 5D  is a top view showing a modification example of the rotary electric machine according to the first embodiment, and  FIG. 5E  is a sectional view along the line C-C of  FIG. 5D . In the region in which the bus bar  13  is disposed on the inner diameter side of the plurality of coil ends  24 , the respective bases of the coil ends  24  protruding from the slots  22  of the stator core  9  cannot be changed in position. When the coil end  24  is erected normal to the stator core  9  as shown in  FIG. 5B , there is also a possibility that the bus bar  13  may come out to the inner diameter side beyond an end face  27  of the stator core  9 . Consequently, in the region in which the bus bar  13  is disposed, as shown in  FIGS. 5D and 5E , the position of the coil ends  24  may be inclined to the outer diameter side. 
     Specifically, an inner diameter side face  26  of the coil end  24  has a first lateral face  28  on the side of a top portion  30  of the coil end  24  and a second lateral face  29  on the side of the end face  27  of the stator core  9 , and the coil end  24  may be provided so that the first lateral face  28  is positioned farther in the outer diameter direction than the second lateral face  29 , that is, is provided on the outer diameter side. 
     Owing to the above configuration, the coil ends  24  can be reduced in size, enabling an improvement in cooling performance without an increase in size. 
     Also, the bus bar  13  may be disposed closer in the axial direction to the stator core  9  side than to the top portion  30  of the coil end  24 . The bus bar  13  is disposed closer in the axial direction to the stator core  9  side than to the top portion  30  of the coil end  24 , thereby enabling the refrigerant to be guided among the coil ends  24 , leading to an improvement in cooling performance. 
     Furthermore, the bus bar  13  may be disposed on the outer diameter side of the inner diameter surface of the stator  1 . This configuration enables an improvement in cooling performance without an interference with the rotor  2 . 
     Also, the bus bar  13 , being rectangular in section, may be disposed so that the lateral face thereof crosses the radial direction of the stator  1 . The bus bar  13  can receive the refrigerant on its surface, so that the amount of refrigerant supplied to the coil ends  24  increases, enabling a further improvement in cooling performance. 
     Also, the bus bar  13  is formed in a circular arc along the inner diameter of the coil ends  24 . The bus bar  13  is formed in a circular arc along the inner diameter of the coil ends  24 , thereby increasing the area of the coil ends  24  with which the refrigerant comes into contact, leading to an improvement in cooling performance. 
     Also, the surface of the bus bar  13  has thereon an insulating film. The distance required to insulate the bus bar  13  from the coil ends  24  can be reduced by using a member having an insulating film around the bus bar  13 . That is, the bus bar  13  can be disposed adjacent to the coil ends  24 , so that the refrigerant comes into sufficient contact with the coil ends  24 , leading to an improvement in cooling performance. 
     Also, the stator winding  10  has a plurality of annular coils, and at least a pair of ones of the plurality of annular coils are connected together via the bus bar  13 . 
     The refrigerant is sprayed from the inner diameter side toward the outer diameter side of the coil ends  24 . The refrigerant is diffused by hitting against the bus bar  13 , and comes into sufficient contact with the coil ends  24 , leading to an improvement in cooling performance. 
     As above, according to the rotary electric machine  50  of the first embodiment, it is possible to obtain the rotary electric machine  50  wherein the refrigerant is guided to the coil ends  24  along the bus bar  13 , so that the refrigerant comes into sufficient contact with the coil ends  24 , leading to an improvement in the cooling performance for the coil ends  24 . 
     Second Embodiment 
       FIG. 6  is a front view showing a rotary electric machine according to the second embodiment. In the second embodiment, a description will be given of only different points from those in the first embodiment, omitting the description of configurations identical to those in the first embodiment. Also, in  FIG. 6 , the arrows shown pointing in the direction of the bus bar  13  indicate the direction in which the refrigerant is sprayed or the direction in which the refrigerant flows. 
     As shown in  FIG. 6 , in the rotary electric machine  50  of the second embodiment, the stator  1  is installed so that the direction of the rotary shaft  3  of the rotor  2  is positioned in the horizontal direction. In the second embodiment, a refrigerant which is, for example, a cooling oil is sprayed from the outer diameter side toward the inner diameter side of the coil ends  24 . The refrigerant is supplied, for example, from the side of a motor case (not shown) which holds the stator  1 . According to the rotary electric machine  50  of the second embodiment, the refrigerant sprayed from above, as seen in the horizontal direction, drips down the bus bars  13  by gravity and comes into sufficient contact with the coil ends  24 , thus leading to an improvement in cooling performance. 
     Also, a plurality of the bus bars  13  are disposed on the inner diameter side of the coil ends  24 , and the plurality of bus bars  13  are disposed in a range of 90 degrees or more centered on the rotary shaft  3  of the rotor  2 . 
     The plurality of bus bars  13  are provided and disposed in a range of 90 degrees or more centered on the rotary shaft  3  of the rotor  2 , thereby enabling the refrigerant sprayed from above to trickle down the bus bars  13  and come into contact with the left and right coil ends  24 , leading to an improvement in cooling performance. 
     Furthermore, a configuration may be such that the bus bar  13  is disposed below the rotary shaft  3 , as seen in the horizontal direction, and that a temperature detector  14  is installed on the bus bar  13  disposed below as seen in the horizontal direction. In this case, the temperature detector  14  is installed on the lower side on which the refrigerant is unlikely sprayed, and thereby it is possible to measure the temperature of the bus bar  13  which, as the refrigerant is not sprayed thereon, is high in temperature. 
     The stator  1  has thereon the temperature detector  14 , wherein at least one bus bar  13  is disposed below the rotary shaft  3 , as seen in the horizontal direction, and at least one temperature detector  14  is installed on the bus bar  13  disposed below as seen in the horizontal direction. 
     Third Embodiment 
       FIG. 7  is an enlarged top view showing a bus bar according to the third embodiment. In the third embodiment, a description will be given of only different points from those in the second embodiment. As shown in  FIG. 7 , the bus bar  13  has a straight portion  15 , and the temperature detector  14  is installed on the straight portion  15 . The temperature detector  14  is installed on the straight portion  15 , so that it is easy to stabilize the state of contact between the temperature detector  14  and the bus bar  13 , leading to an improvement in temperature detection accuracy. 
     Although the present application is described above in terms of various exemplary embodiments and implementations, it should be understood that the various features, aspects, and functionality described in one or more of the individual embodiments are not limited in their applicability to the particular embodiment with which they are described, but instead can be applied, alone or in various combinations, to one or more of the embodiments. 
     It is therefore understood that numerous modifications which have not been exemplified can be devised without departing from the scope of the present application. For example, at least one of the constituent components may be modified, added, or eliminated. At least one of the constituent components mentioned in at least one of the preferred embodiments may be selected and combined with the constituent components mentioned in another preferred embodiment.