Patent Publication Number: US-2009230807-A1

Title: Stator for rotating electric machine

Description:
TECHNICAL FIELD 
     The present invention relates to a stator for a rotating electric machine, and in particular, to a structure of a stator that reduces a loss by eddy currents. 
     BACKGROUND ART 
     As a stator for a rotating electric machine including the stator and a rotor, conventionally, there has been disclosed a stator formed in such a manner that an integral laminated coil is inserted into a slot between a plurality of teeth provided in a stator core. In the integral laminated coil, for example, two sets of coil laminated bodies each having a plurality of linear and thin conductors laminated are integrally formed by resin molding. The thin conductors are laminated so as to be close to a sectional area of the slot in a direction orthogonal to a rotating shaft, so that an area ratio of a sectional area occupied by the coil to a sectional area of the slot. (hereinafter, referred to as a space factor) can be improved. With regard to a structure of the stator for the rotating electric machine described above, there is a technique disclosed in the following publication. 
     Japanese Patent Laying-Open No. 2001-178053 discloses a stator for a rotating electric machine which can be reduced in size and improved in workability in such a manner that a length of a coil end is reduced. The stator for the rotating electric machine includes a stator core, and stator coils attached to a plurality of slots formed between teeth of the stator core. The stator coil is formed in such a manner that two sets of linear and thin conductors, which are laminated, are integrally molded into one by an insulating resin. The stator coil is constituted of a laminated coil piece having connection ends formed at two ends of the conductor, and first and second connection coil pieces formed in such a manner that laminated thin conductors are integrally molded into one by an insulating resin. In the thin conductors of the laminated coil piece inserted into the plurality of slots of the stator core with the tooth being interposed therebetween, one ends are connected by the thin conductors of the first connection coil piece so as to hold the tooth, and the other ends are connected by the thin conductors of the second connection coil so as to hold the tooth with the thin conductors laminated in a radial direction of the stator core being displaced one by one in the radial direction. The stator has a feature in that the stator coil is formed while being wound around the tooth as described above. 
     The stator for the rotating electric machine disclosed in this publication can be reduced in size and improved in workability in such a manner that the length of the coil end is reduced. 
     In the stator for the rotating electric machine disclosed in the foregoing publication, however, there arises a problem that eddy currents occur by a leakage flux passing through the slot when the rotating electric machine is in operation. The leakage flux passes so as to transverse the slot in the circumferential direction. The leakage flux is generated in an increasing amount as nearer to the tip side of the tooth. Accordingly, in the laminated coil in the slot, eddy currents occur in accordance with the passage of the leakage flux. Accordingly, there arises a problem that the passage of the generated eddy currents through the thin conductors causes Joule heat to occur, thereby increasing the loss. 
     It may also be possible to further laminate the laminated coils in an identical turn. However, when the laminated coil has its both ends connected to a connecting coil piece, each of the laminated coil plates is connected also electrically at the connection portions. This may cause the eddy currents to entirely circulate via each of the laminated coil plates. Consequently, there arises a problem that the loss by the eddy currents cannot be suppressed. 
     In the stator for the rotating electric machine disclosed in the foregoing publication, none of such problems are taken into consideration. Therefore, it is impossible to suppress the loss by the eddy currents. 
     DISCLOSURE OF THE INVENTION 
     An object of the present invention is to provide a stator for a rotating electric machine that suppresses a loss by eddy currents. 
     A stator for a rotating electric machine according to an aspect of the present invention is a stator for a rotating electric machine including a rotor and the stator. The stator includes: a stator core having a plurality of slots in a direction parallel to a rotating shaft of the rotating electric machine; a plurality of coil plate laminated bodies formed in such a manner that a plurality of coil plates each having an insulating member attached to at least one side are laminated in a radial direction; and connection members connecting the coil plate laminated bodies inserted into different ones of the slots. The stator has at least one of a first shape in which at least two of the connection members are provided so as to cross each other as seen from the direction parallel to the rotating shaft and a second shape in which each one of the coil plates is formed by integrally combined first member and second member each having a substantially flat shape and being bent in a front-back direction as seen from the radial direction. 
     According to the present invention, by a leakage flux passing in the circumferential direction in a slot, eddy currents around the magnetic flux direction occur at respective surface layer portions of the coil plates laminated in the radial direction. Even when the eddy currents occur due to the leakage flux passing the slot in the coil plate laminated body inserted into the slot, by allowing the connection members (for example, transition members) to cross each other, paths can be provided so that the eddy currents from the coil plate laminated bodies inserted into different slots flow in the opposite directions relative to each other. Accordingly, by providing a first shape so that eddy currents in opposite directions relative to each other flow in the paths of eddy currents formed because of a leakage flux over the coil plate laminated bodies inserted into different slots, the eddy currents can be cancelled. Alternatively, even when eddy currents occur, paths can be provided so that the eddy currents formed in the coil plates flow in the direction opposite to each other, by the first and second members each provided with a bent portion. Specifically, the coil plate is formed by the integrally combined first and second. members each having a portion bent in the front-back direction as seen from the radial direction. The leakage flux passes in the circumferential direction in the slot. That is, when opposing ends of the first and second members are joined, in the coil plate, an electric circulation path having a portion with a crossing portion substantially in a figure of eight as seen from the direction in which the magnetic flux passes is formed by the first and second members. Therefore, even when eddy currents occur in the surface layer portion of the coil plate by a leakage flux, a path can be provided so that the eddy currents flow in the directions opposite to each other by the crossing portion. Thus, the eddy currents can be cancelled. By canceling the eddy currents, generation of Joule heat can be suppressed. Accordingly, a stator for a rotating electric machine that suppresses a loss by eddy currents can be provided. 
     Preferably, the stator for the rotating electric machine has the second shape. The first member and the second member have their respective bent portions positioned near a center between openings at opposing ends of the slot. 
     According to the present invention, as the first member and the second member have their respective bent portions positioned near a center between openings at opposing ends of the slot, the magnitude of the eddy currents occurring at front and rear of the bent portions can be made substantially the same. The coil plate is formed by the integrally combined first and second members each having a portion bent in the front-back direction as seen from the radial direction. That is, when opposing ends of the first and second members are joined, in the coil plate, an electric path crossing substantially in a figure of eight as seen from the direction in which the magnetic flux passes is formed by the first and second members. Therefore, even when eddy currents occur in the surface layer portion of the coil plate by a leakage flux, a path can be provided so that the eddy currents flow in the directions opposite to each other by the crossing portion. Thus, by allowing the eddy currents passing in the front and rear of the bent portions to be substantially the same, the eddy currents can more surely be cancelled each other. Accordingly, the loss by the eddy currents can further be suppressed. 
     Further preferably, the stator for the rotating electric machine has the second shape. The coil plate has at least a first formation portion where a front-side plane of the first member and a back-side plane of the second member are in close contact with each other, and a second formation portion where a back-side plane of the first member and a front-side plane of the second member are in close contact with each other. 
     According to the present invention, when opposing ends of the first and second members are joined, in the coil plate, an electric path crossing substantially in a figure of eight as seen from the direction in which the magnetic flux passes is formed by the first and second members. Thus, a path can be provided so that the eddy currents flow in the directions opposite to each other. Furthermore, by the formation of the first and second formation portions, the first and second portions will be in close contact with each other, and therefore the coil plate will not become large in size in the radial direction. Accordingly, an increase in the size of the stator can be suppressed. 
     Further preferably, the stator for the rotating electric machine has the first shape. The coil plate is formed by two sets of laminated coil plate groups formed in such a manner that a plurality of laminated coil plates having substantially same shape as the coil plate as seen from the lamination direction are laminated. The plurality of connection members are two connection members respectively connected to the two sets of laminated coil plate groups. The two connection members respectively connect the laminated coil plate groups and two sets of laminated coil plate groups of an adjacent turn. 
     According to the present invention, by providing two connection members connecting to the laminated coil plate groups of the adjacent turn so that they cross each other, it becomes possible to allow an eddy current to flow in a direction from the laminated coil plate group of one turn toward the connection member, and further, an eddy current to flow in a direction from the laminated coil plate group of the other turn toward the connection member. That is, paths can be provided so that the eddy currents from the adjacent laminated coil plate groups inserted into different slots flow in the opposite directions relative to each other. Thus, the eddy currents can be canceled, whereby generation of Joule heat can be suppressed and the loss by the eddy currents can be suppressed. 
     Further preferably, the two connection members are inserted at a position on a center side of the rotating shaft, at least in the slot. 
     According to the present invention, the leakage flux tends to occur in an increasing amount as nearer to the axial center side. Accordingly, by providing the first shape on the center side of the rotating shaft, the eddy currents occurring in a large amount can be cancelled. Thus, generation of Joule heat can be suppressed and the loss by the eddy currents can be suppressed. 
     Further preferably, a coil of an identical turn is formed by the coil plates. 
     According to the present invention, by providing the second shape to the coil plates forming the coil of an identical turn, the second shape can be formed in each of the coil plate for each turn. Therefore, the eddy currents respectively occurring in the coil plates for each turn can be cancelled, whereby generation of Joule heat can further be suppressed. Accordingly, a loss by the eddy currents can further be suppressed. 
     Further preferably, the coil plates are inserted at a position on a center side of the rotating shaft, at least in the slot. 
     According to the present invention, the leakage flux tends to occur in an increasing amount as nearer to the axial center side. Accordingly, by providing the first or second shape on the center side of the rotating shaft, the eddy currents occurring in a large amount can be cancelled. Thus, generation of Joule heat can be suppressed and the loss by the eddy currents can be suppressed. 
     Further preferably, an end of the coil plate and an end of the connection member are joined to each other using a paste-like joining material containing a metal nanoparticle coated with an organic substance and an organic solvent. 
     According to the present invention, the joining portion of the coil plate end and the connection member (e.g., a transition member) is joined using a paste-like joining material containing a metal nanoparticle coated with an organic substance and an organic solvent. As for the joining material, when the organic substance serving as a protective layer is decomposed by application of heat, the metal nanoparticle starts sintering at a low temperature. Therefore, it becomes possible to allow the sintering temperature to be lower than a melting temperature of an insulating material. On the other hand, after the sintering, the metal nanoparticle is in a metal bonding state and is not melted until the temperature approaches a eutectic temperature of metal and a material for the coil plate (e.g., about 1000° C. for a eutectic temperature of silver and copper). Using such a joining material to join the joining portion, the temperature at the time of joining becomes lower than the melting temperature of the insulating material. Therefore, deterioration in an insulating performance of the insulating member can be suppressed. Furthermore, after joining, the melting temperature of the joining portion becomes sufficiently higher than the heat generated when the rotating electric machine is in operation. Therefore, deterioration in the joining strength can be suppressed. 
     Further preferably, the joining material sinters at a temperature lower than a melting temperature of an insulating member used for the stator. 
     According to the present invention, as the joining material sinters at the temperature lower than the melting temperature of the insulating material used for the stator, heat is not applied to the stator until the insulating material is melted at the time of joining. Therefore, deterioration in the insulating performance by the heat at the time of joining can be suppressed. 
     Further preferably, the metal nanoparticle is a nanoparticle of a metal being one of gold, silver, copper, and platinum. 
     According to the present invention, by using the paste-like joining material containing metal nanoparticle of one of gold, silver, copper and platinum, heat is not applied to the stator until the insulating material is melted at the time of joining. Therefore, deterioration in the insulating performance at the time of joining can be suppressed. 
     Further preferably, the insulating member is one of an insulating film and a coating film of insulation coating. 
     According to the present invention, by laminating the coil plates so that one of an insulating film and a coating film of insulation coating is interposed therebetween, the coil plates can be more surely insulated from each other by the insulation film or the coating film. By allowing the insulation film and the coating film to be as thin as possible, the insulating performance and the space factor are allowed to be compatible. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a stator according to a first embodiment. 
         FIG. 2  is a perspective view showing coil plates and transition members incorporated to a tooth. 
         FIG. 3  shows flows of magnetic fluxes between a rotor and the stator. 
         FIGS. 4A and 4B  are perspective views showing the coil plates and the transition member in a first embodiment. 
         FIGS. 5A and 5B  show paths of eddy currents in the coil plates. 
         FIG. 6  shows an appearance of a U-shaped coil plate laminated body in a second embodiment. 
         FIG. 7  is an illustration (No.  1 ) showing the structure of transition members in the second embodiment. 
         FIG. 8  is an illustration (No.  2 ) showing the structure of transition members in the second embodiment. 
         FIG. 9  shows paths of eddy currents in a coil plate laminated body. 
         FIG. 10  shows paths of eddy currents in coil plate laminated bodies and the transition members. 
     
    
    
     BEST MODES FOR CARRYING OUT THE INVENTION 
     Hereinafter, an embodiment of the present invention is described with reference to the drawings. In the following description, identical parts are denoted by identical reference symbols. Designations and functions thereof are also the same. Accordingly, detailed description thereof is not repeated. 
     First Embodiment 
     A stator according to the present embodiment is a stator for a rotating electric machine constituted of the stator and a rotor including a permanent magnet. In the present embodiment, the stator is a stator for a three-phase AC (Alternating Current) synchronous rotating electric machine in which the number of poles is 21. However, the present invention should be applied to any stator with wound coils, and the number of poles is not particularly limited to 21. Furthermore, the present invention is not limitedly applied to the stator for the three-phase AC synchronous rotating electric machine. 
     As shown in  FIG. 1 , a stator  100  is constituted of a stator core  102 , coil plate laminated bodies  138  and  144 , transition member laminated bodies  110  and  112 , and bus bars  114 . Transition member laminated bodies  110  and  112  are held by a holding member  158 . 
     Stator core  102  is formed into a hollow cylindrical shape. In stator core  102 , through slots  106  extending in a direction parallel with a rotating shaft are formed in a predetermined number along a circumferential direction of stator core  102 . In stator core  102 , further, teeth  104  are formed in a predetermined number between slots  106  so as to be opposed to an axial center of the rotating shaft. The predetermined number corresponds to the number of poles. In the present embodiment, the number of slots  106  to be formed and the number of teeth  104  to be formed are  21 , respectively. In the present embodiment, stator core  102  is formed in such a manner that a plurality of electromagnetic steel plates are laminated. 
     Coil plate laminated bodies  138  and  144  are inserted into slot  106  formed in stator core  102 . Coil plate laminated bodies  138  and  144  are formed in such a manner that a plurality of I-shaped coil plates are laminated in the radial direction. It is to be noted that coil plate laminated bodies  138  and  144  are only required to be laminated from a back yoke side toward an axial center side of stator core  102 , while the lamination is not particularly limited to the radial direction. For example, coil plate laminated bodies  138  and  144  may have such a configuration that a plurality of I-shaped coil plates are laminated so that a width direction of the coil plates is orthogonal to a wall face of tooth  104  in slot  106 . In the present embodiment, while each coil plate is described to have an I-shape, its shape is not particularly limited to an I-shape as long as a portion inserted into the slot is in an I-shape. For example, the coil plate may be in a U-shape. 
     An insulating film is attached to at least one side of the I-shaped coil plate. It is to be noted that a coating film of insulation coating may be attached in place of the insulating film. A material for the insulating film is not particularly limited as long as the insulating film has a thickness capable of ensuring insulation between the coil plates. The insulating film is a polyimide film, for example. Coil plate laminated bodies  138  and  144  are formed in such a manner that the coil plates are laminated with the insulating film interposed therebetween. 
     As shown in  FIG. 2 , among two coil plate laminated bodies  138  and  144  inserted into slots  106  positioned on opposing sides of each tooth  104 , coil plate laminated bodies  138  and  144  adjacent to identical tooth  104  are connected to each other by transition member laminated bodies  110  and  112 . Transition member laminated body  112  is connected to tooth  104  on its top side as seen in  FIG. 2 . Transition member laminated body  110  is incorporated to tooth  104  on its bottom side as seen in  FIG. 2 . Coil ends are formed by transition member laminated bodies  110  and  112 . 
     Transition member laminated bodies  110  and  112  are respectively formed by a plurality of transition members  160  and  162  being laminated. Transition members  160  and  162  connect between the ends of coil plates forming two coil plate laminated bodies  138  and  144  positioned on the opposing sides of tooth  104  (i.e., inserted into different slots). 
     Transition member  160 , being a constituent of transition member laminated body  110 , connects coil plates  128  and  130  of an identical turn. Transition member  162 , being a constituent of transition member laminated body  112 , connects coil plates  128  and  132  of adjacent turns. 
     Thus, by transition member laminated bodies  110  and  112  being incorporated to two coil plate laminated bodies  138  and  144  positioned on the opposing sides of tooth  104 , a coil is spirally wound around the tooth by a predetermined number of turns (ten turns in the present embodiment). It is to be noted that winding directions of the coils wound around respective teeth  104  are all the same. 
     Herein, ends of a coil wound around tooth  104  by ten turns are: a coil plate end  134  on the side closest to the shaft center and being connected to none of transition members  162 ; and a coil plate end  136  on the side farthest from the shaft center and being not connected to transition member  162 . 
     Referring again to  FIG. 1 , to each of these coil plate ends, one end of bus bar  114  is connected. The other end of bus bar  114  is connected to an end of a coil that is wound around another teeth and that is of an identical phase (i.e., a coil plate laminated body inserted into a different slot). Thus, in stator core  102 , coils of ten turns respectively corresponding to U phase, V phase and W phase are wound around respective teeth. 
     Terminal members  122  to  126  are provided at the ends of coils of respective phases. Here, coil plate end  116  and terminal member  122  correspond to the ends of U-phase coil, coil plate end  118  and terminal member  124  correspond to the ends of V-phase coil, and coil plate end  120  and terminal member  126  correspond to the ends of W-phase coil. Coil plate ends  116  to  120  are connected to each other. It is to be noted that coil plate ends  116  to  120  may not be connected to each other and a terminal member may be provided to each end. 
     The coil plate ends are connected to transition members  160  and  162  and bus bar  114  using a joining material. In the present embodiment, the joining material is a paste-like joining material containing a metal nanoparticle coated with an organic substance and an organic solvent (hereinafter, referred to as a metal nanoparticle paste). The metal nanoparticle is a nanoparticle of metal, e.g., one of gold, silver, copper and platinum. In the present embodiment, description will be given of use of, for example, a paste-like joining material containing a silver nanoparticle coated with an organic substance and an organic solvent (hereinafter, referred to as a silver nanoparticle paste). As for the silver nanoparticle paste, when the organic substance serving as a protective layer is decomposed by application of heat, the silver nanoparticle starts sintering at a low temperature. Therefore, the sintering temperature is low, i.e., about 260° C., which is lower than a melting temperature of an insulating material such as PPS (polyphenylene sulfide). On the other hand, after the sintering, the silver nanoparticle is in a metal bonding state and is not melted until the temperature approaches a eutectic temperature (about 1000° C.) of metal silver and copper which is a material for the coil plate. It is to be noted that a joining material containing the metal nanoparticle is a well-known technique; therefore, detailed description thereof will not be given. 
     A multipoint simultaneous joining process is performed by applying pressure so as to sandwich in the radial direction the coil ends of all the coil plate laminated bodies, having bus bars  114  or terminal members  122  to  126  and transition member laminated bodies  110  and  112  incorporated, and increasing the temperature. 
     By the increase in the temperature, the protective layer coating the silver nanoparticle contained in the silver nanoparticle paste is decomposed, and the silver nanoparticle sinters. By the application of the pressure, gas and the like in the paste generated by the decomposition of the protective layer are eliminated from the joining portion. The joining portion is joined by metal bonding of the sintering of the silver nanoparticle paste. Therefore, after the joining process, the joining portion is not melted until the temperature is increased to about 1000° C. corresponding to a melting point of metal silver. It is to be noted that the protective layer with which the silver nanoparticle is coated is decomposed at about 260° C.; therefore, the metal nanoparticle sinters at a low temperature after the protective layer is decomposed at about 260° C. Accordingly, the application of the heat is continued until the temperature reaches a predetermined temperature of about 260° C. which is lower than a temperature at which an insulating film applied to the coil plate or resin insulator  140  is melted. 
     A mold process is performed by injection molding of resin or the like to the coil end portion of stator  100  after the joining is completed. Here, stator core  102  is coated with resin (not shown), except for the outer peripheral face and the terminals of terminal members  122  to  126 . 
     In the rotating electric machine including stator  100  structured as described above and a rotor (not shown), when AC power is supplied to each of terminal members  122  to  126 , a magnetic field corresponding to the supplied power is generated. The rotor obtains a rotating force on the basis of the generated magnetic field, and rotates thereby. 
     Here, as shown in  FIG. 3 , a leakage flux passes along the circumferential direction in slot  106 . Accordingly, in each of the coil plates constituting coil plate laminated bodies  138  and  144  laminated in the radial direction in slot  106 , eddy currents corresponding to passage of the leakage current occur. As shown in  FIG. 3 , the leakage flux tends to occur in an increasing amount as nearer to the tip side of tooth  104 . There exists a problem that the eddy currents generated by the passage of leakage flux pass through the coil plate laminated bodies, whereby Joule heat is generated and the loss becomes greater. 
     This problem may possibly be addressed by further laminating coil plates forming an identical turn. However, when coil plates has their both ends connected to transition members  160  and  162 , each of the laminated coil plates is connected also electrically at the connection portions. This may cause the eddy currents to entirely circulate via each of the laminated coil plates. Consequently, there may be a case where the loss by the eddy currents cannot be suppressed. 
     Here, the present invention is characterized in that stator  100  has such a shape in which one coil plate is formed by integrally combined first and second members each having a substantially flat shape and being bent in the front-back direction as seen from the radial direction. This shape formed by the integrally combined first and second members corresponds to the aforementioned “second shape”. 
     More specifically, as shown in  FIGS. 4A and 4B , I-shaped coil plates  128  and  130  forming an identical turn are each formed by integrally combined two coil plate constituting members  200  and  202  having substantially flat shape. It is to be noted that coil plate constituting members  200  and  202  respectively correspond to the first member and the second member. Coil plate constituting members  200  and  202  each have a portion bent in the front-back direction as seen from the radial direction (i.e., the lamination direction). 
     Coil plates  128  and  130  each have at least: a formation portion  210  where a front-side plane (axial center side: left side in  FIGS. 4A and 4B ) of coil plate constituting member  200  and a back-side plane (back yoke side: right side in  FIGS. 4A and 4B ) of coil plate constituting member  202  are in close contact with each other; and a formation portion  212  where a back-side plane of coil plate constituting member  200  and a front-side plane of coil plate constituting member  202  are in close contact with each other. It is to be noted that coil plates  128  and  130  are only required to have a crossing portion as seen at least from the direction in which magnetic fluxes pass (the circumferential direction of the slot). 
     The bent portions of coil plate constituting members  200  and  202  are each provided with a notch portion formed to match the bent portion formed in the other coil plate constituting member. Combining coil plate constituting members  200  and  202  so that their notch portions and bent portions match each other, integrated and substantially flat coil plates  128  and  130  are formed. 
     Further, an insulating film is attached to at least one side of coil plate constituting members  200  and  202 . It is to be noted that a coating film of insulation coating may be attached in place of the insulating film. The insulating film is applied to at least one of two opposed faces in a thickness direction of coil plate constituting members  200  and  202 . 
     The bent portions of coil plate constituting members  200  and  202  are provided at a position near the center between openings at opposing ends of slot  106 . 
     By combining coil plate constituting members  200  and  202 , at opposing end portions  206  of coil plates  128  and  130 , fitting portions corresponding to the shape of respective ends of transition members  160  and  162  are formed. In the present embodiment, transition member  162  is fitted to two fitting portions in the bottom direction of  FIGS. 4A and 4B , while transition member  160  is fitted to two fitting portions in the top direction of  FIGS. 4A and 4B . 
     Referring to  FIGS. 5A and 5B . the function of the stator for the rotating electric machine according to the present embodiment having the above-described structure will be described. 
     By the supply of electric power to the stator, a magnetic field is generated and a rotor rotates. Along with the generation of the magnetic flux, a leakage flux passes in the circumferential direction in slot  106 . Here, to coil plate  128  in slot  106 , the magnetic flux passes in the direction shown in  FIG. 5A . Accordingly, in coil plate constituting members  200  and  202 , eddy currents flow around the direction in which the magnetic flux passes, via the joining portions with transition members  160  and  162 , as shown by the dashed-line arrows in  FIG. 5A . Here, the eddy currents flow through the surface layer portion of coil plate  128 . Therefore, by coil plate constituting members  200  and  202 , an electric circulation path having a portion crossing substantially in a figure of eight as seen from the direction in which the magnetic flux passes is formed. 
     When the eddy currents pass through the front layer portion of coil plate  128 , in coil plate constituting member  202 , as shown by the dashed-line arrows in  FIG. 5B , eddy currents flow in opposite directions by the bent portion of coil plate constituting member  202 . Thus, the eddy currents are cancelled. By the cancellation of the eddy currents, generation of Joule heat is suppressed and the loss by the eddy currents is suppressed. 
     As above, according to the stator for the rotating electric machine according to the present embodiment, even when eddy currents occur in the coil plate laminated body inserted into a slot by a leakage flux passing through the slot, a path can be provided by the bent portion of the coil plate constituting member so that eddy currents flow in directions opposite to each other. Thus, the eddy currents can be cancelled. By the cancellation of the eddy currents, generation of Joule heat is suppressed. Accordingly, the stator for the rotating electric machine that suppresses the loss by the eddy currents can be provided. 
     By the provision of the bent portions of the coil plate constituting members at the positions near the center between the openings at the opposing ends of the slot, the magnitude of the eddy currents occurring at front and rear of the bent portions can be made substantially the same. As a result, the eddy currents can more surely be cancelled each other. Accordingly, the loss by the eddy currents can further be suppressed. 
     As the formation portions are formed so that the coil plate constituting members are in close contact with each other, the size of the coil plate in the radial direction is not increased. As a result, an increase in size of the stator can be suppressed. 
     The joining portion of the coil plate end and the transition member is joined using the paste-like joining material containing a silver nanoparticle coated with an organic substance and an organic solvent. In the joining material, when the organic substance serving as a protective layer is decomposed by application of heat, the silver nanoparticle starts sintering at a low temperature. Therefore, the sintering temperature can be made lower than a melting temperature of an insulating material. On the other hand, after the sintering, the silver nanoparticle is in a metal bonding state and is not melted until the temperature approaches a eutectic temperature (about 1000° C.) of silver and a material for the coil plate. Using such a joining material to join the joining portion, the temperature at the time of joining becomes lower than the melting temperature of the insulating material. Therefore, deterioration in an insulating performance of the insulating member can be suppressed. Furthermore, after joining, the melting temperature of the joining portion becomes sufficiently higher than the heat generated when the rotating electric machine is in operation. Therefore, deterioration in the joining strength can be suppressed. 
     As the joining material sinters at the temperature lower than the melting temperature of the insulating material used for the stator, heat is not applied to the stator until the insulating material is melted at the time of joining. Therefore, deterioration in the insulating performance by the heat at the time of joining can be suppressed. 
     By laminating the coil plates so that one of an insulating film and a coating film of insulation coating is interposed therebetween, the coil plates can be more surely insulated from each other by the insulation film or the coating film. By allowing the insulation film and the coating film to be as thin as possible, the insulating performance and the space factor are allowed to be compatible. 
     Preferably, the shape formed by coil plate constituting members  200  and  202  is provided on the axial center side. Thus, in the portion where leakage flux occurs in a large amount, the flow of eddy currents can be cancelled and whereby generation of Joule heat can further be suppressed. Accordingly, the loss by the eddy currents can be suppressed. 
     Alternatively, the shape formed by coil plate constituting members  200  and  202  may be provided in every coil plate for each turn. Thus, the eddy currents can be cancelled in each turn to further suppress generation of Joule heat. Accordingly, the loss by the eddy currents can be suppressed. 
     Second Embodiment 
     Hereinafter, a stator for a rotating electric machine according to a second embodiment of the present invention will be described. The stator for the rotating electric machine according to the present embodiment is different from the above-described stator for the rotating electric machine according to the first embodiment in that it includes a U-shaped coil plate instead of the I-shaped coil plates and transition member  160 . The other configurations are the same as those of above-described stator  100  for the rotating electric machine according to the first embodiment. They are denoted by identical reference symbols. Their functions are also the same. Accordingly, detailed description thereof is not repeated. 
     In the present embodiment, as shown in  FIG. 6 , a plurality of U-shaped coil plates are laminated to form coil plate laminated body  201 . Opposing ends of coil plate laminated body  201  are respectively inserted into slots  106  positioned at opposing sides of tooth  104 , so that coil plate laminated body  201  is incorporated to stator core  102  by bridging over tooth  104 . 
     To the opposing ends of coil plate laminated body  201 , a transition member laminated body  112  is incorporated. Coil plate laminated body  201  is formed by lamination of a plurality of coil plates corresponding to each turn. As transition member laminated body  112  is incorporated, connection is established with the end of coil plate laminated body of an adjacent turn. Thus, the coils in a predetermined number of turns are wound around tooth  104 . 
     The plurality of coil plates corresponding to each turn are formed by a plurality of laminated coil plate groups. The plurality of laminated coil plate groups are formed by lamination of a plurality of U-shaped laminated coil plates. An insulation film is attached to at least one side of the laminated coil plate. It is to be noted that a coating film. of insulation coating may be attached in place of the insulating film. The laminated coil plate and the coil plate are formed by lamination so that an insulating film is interposed therebetween. 
     The present embodiment is characterized in that stator  100  has a shape in which at least two connection members are provided so as to cross each other as seen from a direction parallel to the rotating shaft. This shape in which at least two connection members are provided so as to cross each other corresponds to the aforementioned “first shape”. 
     More specifically, a coil plate is formed by two sets of laminated coil plate groups formed in such a manner that a plurality of laminated coil plates having substantially the same shape as the coil plate as seen from the lamination direction are laminated. The plurality of transition members are two transition members respectively connected to the two sets of laminated coil plate groups. The two transition members respectively connect the laminated coil plate groups and two sets of laminated coil plate groups of an adjacent turn. Here, the two transition members are provided so that they cross each other as seen from a direction parallel to the rotating shaft. 
     As shown in  FIGS. 7 and 8 , a U-shaped coil plate  250  inserted on the very tip side of tooth  104  is the coil plate of the first turn (hereinafter also referred to as  1 T). Coil plate  250  is formed by a plurality of coil plate groups  260  and  262 . A plurality of U-shaped laminated coil plates, which are substantially in the same shape as coil plate  250  as seen from the lamination direction, are laminated to form respective laminated coil plate groups  260  and  262 . It is to be noted that part of laminated coil plates among laminated coil plate groups  260  and  262  are provided with notch portions at their ends, whereby concave shapes to which ends of transition members can fit are formed at the ends of the U-shaped coil plate. The joining portion of the coil plate end and the transition member is joined using the above-described paste-like joining material, and a specific description thereof will not be repeated herein. 
     U-shaped coil plate  252  is the coil plate of the second turn (hereinafter also referred to as  2 T). Coil plate  252  is formed by laminated coil plate groups  264  and  266 . U-shaped coil plate  254  is the coil plate of the third-turn (hereinafter also referred to as  3 T). 
     Here, coil plate  250  of  1 T and coil plate  252  of  2 T are connected by two transition members  256  and  258 . Two transition members  256  and  258  connect two sets of laminated coil plate groups  260  and  262  and two sets of laminated coil plate groups  264  and  266  of an adjacent turn. That is, transition member  256  connects laminated coil plate group  260  of  1 T and laminated coil plate group  266  of  2 T. Transition member  258  connects laminated coil plate group  262  of  1 T and laminated coil plate group  264  of  2 T. 
     While it has been assumed in the present embodiment that the crossing shape of the transition members are provided in transition members  256  and  258  between  1 T and  2 T, it is not so specifically limited. For example, it may also be possible to provide a crossing shape in two transition members connecting turns subsequent to  2 T. 
     Also, while it has been described in the present embodiment that transition member  258  is positioned on the axial outward side relative to transition member  256 , it may not so limited and transition member  256  may be positioned on the axial outward side relative to transition member  258 . 
     Referring to  FIGS. 9 and 10 , the function of the stator according to the present embodiment having the above-described structure will be described. Referring to  FIG. 10 , while the description will be given assuming that transition member  256  is positioned on the axial outward side relative to transition member  258 , the same effect can be attained when transition member  258  is positioned on the axial outward side relative to transition member  256 . 
     As shown in  FIG. 9 , when a leakage flux passes in the circumferential direction in slot  106 , in the surface layer portions of two laminated coil plate groups  260  and  262  forming coil plate  250  forming the coil of an identical turn, eddy currents flow (in the directions indicated by solid-line arrows) around the direction in which the magnetic flux passes. 
     When transition member  256  and bus bar  114  are connected to opposing ends of laminated coil plate groups  260  and  262 , the coil plates are connected at their ends also electrically. Therefore, an eddy current flow is formed from one end  272  of laminated coil plate group  260  toward coil end portion  270  in the downward direction in  FIG. 9 . Furthermore, at coil end portion  270 , an eddy current flow is formed from one end  272  side to the other end  274  side. Furthermore, an eddy current flow is formed toward the other end  274  of laminated coil plate group  260  in the upward direction in  FIG. 9 . 
     Additionally, an eddy current flow is formed from the other end  274  of laminated coil plate group  260  to one end  276  of laminated coil plate group  262 . An eddy current flow is formed from one end  276  of laminated coil plate group  262  toward coil end portion  278  in the downward direction in  FIG. 9 . Furthermore, at coil end portion  278 , an eddy current flow is formed from one end  276  side to the other end  280  side. Furthermore, an eddy current flow is formed from coil end portion  278  toward the other end  280  of laminated coil plate group  262  in the upward direction in  FIG. 9 . An eddy current flow is formed from the other end  280  of laminated coil plate group  262  to one end  280  of laminated coil plate group  262 . Such eddy current flow paths are similarly formed in two laminated coil plate groups  264  and  266  forming coil plate  252 . Therefore, detailed description thereof will not be repeated herein. 
     In this connection, by arranging transition members  256  and  258  to have a crossing shape, as shown in  FIG. 10 , an eddy current flows in the downward direction in  FIG. 10  (the direction indicated by dashed-line arrow), from one end  272 , which is the side where transition member  256  is not connected, of laminated coil plate group  260  (of which tip planes are indicated by hatched portions) to coil end portion  270 . Furthermore, an eddy current flows via coil end portion  270  toward the other end  274  of laminated coil plate group  260 . 
     Also, an eddy current flows in the downward direction in  FIG. 10  (the direction indicated by dashed-line arrow), from one end  276 , which is the side where transition member  258  is connected, of laminated coil plate group  262  to coil end portion  278 . Furthermore, an eddy current flows via coil end portion  278  toward the other end  280  of laminated coil plate group  262 . 
     Similarly, an eddy current flows in the downward direction in  FIG. 10  (the direction indicated by dashed-line arrow), from one end  282 , which is the side where transition member  258  is connected, of laminated coil plate group  264  (of which tip planes are indicated by hatched portions) to the coil end portion. Furthermore, an eddy current flows via the coil end portion toward the other end  284  of laminated coil plate group  264 . 
     Also, an eddy current flows in the downward direction in  FIG. 10  from one end  286 , which is the side where transition member  256  is not connected, of laminated coil plate group  266  to the coil end portion. Furthermore, an eddy current flows via the coil end portion toward the other end  288  of laminated coil plate group  266 . 
     Here, in transition member  256 , the eddy current in the direction from end  288  of laminated coil plate group  266  and the eddy current in the direction from end  274  of laminated coil plate group  260  flow. That is, as the crossing shape of transition member  256  and transition member  258  is provided to the stator, in transition member  256 , the eddy currents in the directions opposite to each other flow. This allows the eddy currents to be cancelled, and whereby generation of Joule heat is suppressed. Accordingly, the loss by the eddy currents can be suppressed. 
     As described above, according to the stator for the rotating electric machine of the present embodiment, by providing the two transition members connecting to the laminated coil plate groups of adjacent turns so as to cross each other, it becomes possible to allow an eddy current to flow in the direction from the laminated coil plate groups of one turn toward the transition member, and an eddy current to flow also from the direction from the laminated coil plate group of the other turn toward the transition member. That is, paths can be provided so that the eddy currents from adjacent laminated coil plate groups inserted into different slots can flow in opposite directions relative to each other. Thus, the eddy currents can be cancelled, whereby generation of Joule heat can be suppressed and the loss by the eddy currents can be suppressed. 
     It is to be noted that, preferably, the crossing shape of the transition members is desirably provided on the rotating shaft center side. This allows cancellation of eddy current flow in a portion where a leakage flux occurs in a large amount, and therefore generation of Joule heat can further be suppressed. Accordingly, the loss by the eddy currents can be suppressed. 
     While the present embodiment has been applied to the stator including the U-shaped coil plate laminated body, it is not so limited. That is, it may be applied to a stator including an I-shaped coil plate laminated body. Also, it may be applied to a stator including, instead of or in addition to the crossing shape of the transition members, an I-shaped coil plate laminated body which is integrally formed by a combination of two coil plate constituting members each having a portion bent in the front-back direction as seen from the radial direction, as described in the first embodiment. That is, it is only required that at least one of the first and second shapes is applied to the stator. 
     It should be understood that the embodiments disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications and changes within the meaning and scope equivalent to the terms of the claims.