Abstract:
The disclosure is directed to an electrical motor that includes a rotor and stator with improved cooling of the motor. The improved cooling is due to a convenient coil connecting structure of the stator. Outer and inner peripheral connectors connect the coil wound ends at the outer and inner peripheral sides of the stator, respectively. From this structure, heat sources, such as the connectors, are distributed to both the outer peripheral and inner peripheral sides of the stator core. In this manner, the motor may more effectively be cooled through the distributed heat sources.

Description:
This application claims priority to Japanese Patent Application No. 2005-169588, filed Jun. 9, 2005, the entire content of which is incorporated herein by reference. 
   TECHNICAL FIELD 
   The invention relates to electric motors. 
   BACKGROUND 
   Conventionally, a 3-phase motor has coil windings of a U phase coil, a V phase coil, and a W phase coil. Each coil winding of the U phase coil, V phase coil, and W phase coil of a 3-phase motor has a multiplicity of turns, and is connected to the wound final end by the outer peripheral side or the inner peripheral side of the stator core. The turns of the coil are connected by the outer side outer connector of the coil or the inner side inner connector of the coil in common with the neutral line to which each coil end is connected. 
   SUMMARY 
   The disclosure is directed to an electrical motor that includes a rotor and stator with improved cooling of the motor. The improved cooling is due to a convenient coil connecting structure of the stator. Outer and inner peripheral connectors connect the coil wound ends at the outer and inner peripheral sides of the stator, respectively. 
   For conventional technology, there is placement of the connectors on only the outer peripheral side of the stator core or the inner peripheral side. The connectors become concentrated on one side of the outer peripheral or inner peripheral side of the stator. 
   In one embodiment, the invention is directed to a motor that includes a rotor having a plurality of permanent magnets and a stator opposed to the rotor that includes a plurality of stator cores formed in an annulus. The motor also includes a coil that includes outer peripheral coil wound ends disposed on an outer peripheral side of the plurality of stator cores and inner peripheral wound ends on an inner peripheral side of the plurality of stator cores. Additionally, the motor includes a plurality of outer peripheral connectors that connect the outer peripheral coil wound ends via the outer peripheral side of the plurality of stator cores and a plurality of inner peripheral connectors that connect the inner peripheral coil wound ends via the outer peripheral side of the plurality of stator cores. 
   In another embodiment, the invention is directed to a motor including a rotor comprising a plurality of permanent magnets and means for conducting an electrical current around a plurality of stator cores adjacent to a periphery of a stator, wherein the means for conducting an electrical current comprises outer peripheral coil wound ends disposed on an outer peripheral side of the plurality of stator cores and inner peripheral wound ends on an inner peripheral side of the plurality of stator cores. The motor also includes means for connecting the outer peripheral coil wound ends at an outer peripheral side of the plurality of stator cores and means for connecting the inner peripheral coil wound ends at an inner peripheral side of the plurality of stator cores. 
   The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
       FIG. 1  is a cross-sectional view which shows an axial gap type motor whose connection structure is appropriate for this invention. 
       FIG. 2  is an example diagram of the coil connection structure of Embodiment 1 of this invention. 
       FIG. 3  is an example diagram of the connection sequence of the coil connection structure of  FIG. 2 . 
       FIG. 4  is an example diagram of the coil connection structure of Embodiment 2 of this invention. 
       FIG. 5  is an example diagram of the connection sequence of the coil connection structure of  FIG. 4 . 
       FIG. 6  is an example diagram of the connection sequence of the coil connection structures of Embodiments 3 and 4. 
       FIG. 7  illustrates the coil connection structure of Embodiment 5 of this invention, with (a) a cross-sectional example diagram for an odd number of coil stages, and (b) a cross-sectional example diagram for an even number of coil stages. 
       FIG. 8  illustrates the coil connection structure of a conventional 3-phase motor with (a) an example diagram of the outer peripheral connections and (b) an example diagram of the inner peripheral connections. 
   

   DETAILED DESCRIPTION 
     FIG. 1  is a cross-sectional view which shows an axial gap type motor wherein the coil connection structure of this invention is appropriate. The axial gap type motor provides a rotary axis  1 , a rotor  2 , a stator  3 , and a motor case  11 . Motor case  11  is formed from a front side case  11   a , a rear side case  11   b , and from an outer case  11   c  which is bolt joined to both side cases  11   a  and  11   b.    
   The rotary axis  1  is rotatably supported by the first bearing  5  which is established on the front side case  11   a  and the second bearing  6  which is established on the rear side case  11   b . In addition, a rotary sensor  7 , which detects the axis rotation count, is established on the rear end of the rotary axis  1 . 
   Rotor  2  is fixed to rotating axis  1 , and has a plurality of permanent magnets  9  inserted at the facing surface with stator  3 . The permanent magnets  9  are disposed along the direction of the circumference of the rotor  2 . The permanent magnets  9  generate a repelling force and attractive force to the rotating magnetic flux which is imparted from the stator  3 . So as to rotate the rotary axis  1  at the center, rotor  2  is formed with a rotor base  8  by an electromagnetic steel plate (strong magnetic metal). 
   The plurality of permanent magnets  9  are arranged so that adjacent surface magnetic poles (N pole, S pole) are alternately different. Between the rotor  2  and stator  3  a gap exists which is called the air gap, with no mutual contacts. 
   Stator  3  is fixed to the rear side case  11   b , and is formed by the stator core which provides the tooth  12  and the coil  13 , or means for conducting an electrical current, and by the back yoke  17 . The above-mentioned coil winding  13  is wound on the tooth  12  by the insulator (not illustrated). In addition, the stator  3  is maintained by the rear side case  11   b  by means of this back yoke  17 . 
     FIG. 2  is an explanation diagram of the coil connections structure of the motor of Embodiment 1. As shown in  FIG. 2 , the stator core  10  is formed as an annulus on the periphery of the rotating axis (not illustrated) and has a plurality of coils  13  in the peripheral direction along this annulus. This plurality of coils is arranged at approximately equal intervals in the peripheral direction. The coils are formed by winding coil wire (wire) for every phase by means of an insulator (not illustrated) on the boundary of every tooth  12 , which projects in the direction of the stator (not illustrated). 
   The plurality of coils  13  have 3-phase coils, and provide respectively 4 coils per phase as in the U phase coil (U 1 ˜U 4 ), the V phase coil (V 1 ˜V 4 ), and the W phase coil (W 1 ˜W 4 ). Each coil of the U phase, V phase, and W phase has outer peripheral coil wound ends  31   u   1 ˜ 31   u   4 ,  31   v   1 ˜ 31   v   4 , and  31   w   1 ˜ 31   w   4  on the outer peripheral side of the stator core  10 . For the inner peripheral side, there are the inner peripheral coil wound ends  32   u   1 ˜ 32   u   4 ,  32   v   1 ˜ 32   v   4 , and  32   w   1 ˜ 32   w   4  on the inner peripheral side of the stator  10 . 
   The outer peripheral coil wound ends  31   u   1 ,  31   u   4 ,  31   v   1 ,  31   v   4 ,  31   w   1 , and  31   w   4  are connected by the outer peripheral connectors  21   u ,  21   v , and  21   w , or means for connecting the outer peripheral coil wound ends, which are arranged on the outer peripheral side of the stator core  10 . The remaining outer peripheral coil wound end parts  31   u   2 ,  31   u   3 ,  31   v   2 ,  31   v   3 ,  31   w   2 , and  31   w   3  are connected by the outer peripheral connector  24 . This outer peripheral connector  24  combines with the neutral wire. 
   The inner peripheral coil wound ends  32   u   1 ,  32   u   2 ,  32   v   1 ,  32   v   2 ,  32   w   1 , and  32   w   2  are connected by the inner peripheral connectors  22   ua ,  22   va , and  22   wa , or means for connecting the inner peripheral coil wound ends, which are arranged on the inner peripheral side of the stator core  10 . The remaining inner peripheral coil wound ends  32   u   3 ,  32   u   4 ,  32   v   3 ,  32   v   4 ,  32   w   3 , and  32   w   4  are connected by the inner peripheral connectors  22   ub ,  22   vb , and  22   wb , which are arranged on the inner peripheral side of the stator core  10 . 
   From this construction, each respective coil of the U phase, V phase, and W phase is serially connected. In this embodiment, there is assumed a structure produced from the outside by the establishment of the outside produced parts  23   u ,  23   v , and  23   w  by the outer peripheral connectors  21   u ,  21   v , and  21   w.    
     FIG. 3  is an explanation diagram of the connection sequence for the series connections of  FIG. 2 . As shown in  FIG. 3 , for the U phase coil, there is passage through the inner peripheral side from coil U 1  to coil U 2  (inner peripheral connector  22   ua ), and passage through the outer peripheral side (outer peripheral connector  24 ) from coil U 2  to coil U 3 , and passage through the inner peripheral side (inner peripheral connector  22   ub ) from coil U 3  to coil U 4 , and passage through the outer peripheral side (outer peripheral connector  21   u ) for from coil U 4  to coil U 1 . All these passages are respectively connected. Thus, when serially connected, for every phase, there is alternately an outer peripheral connector and an inner peripheral connector. 
   Because the outer peripheral connectors  21   u ,  21   v ,  21   w , and  24  and the inner peripheral connectors  22   u ,  22   v , and  22   w , which are heat sources, do not concentrate in one direction by distributing to the outer peripheral side and the inner peripheral side of the stator  10 , there is no great heat generated only on one side of either the outer peripheral side or the inner peripheral side of the stator core  10 . Accordingly, it is possible to improve the cooling of the motor. 
   In addition, by having serial connections which serially connect alternately using outer peripheral connector and inner peripheral connectors, it is possible to arrange evenly the overlapping count of busbars. It is possible also for the turns of the coil winding to be made the same (30.5 t) using all of the U phase coils (U 1 ˜U 4 ), V phase coils (V 1 ˜V 4 ), and the W phase coils (W 1 ˜W 4 ). 
   However, as shown in  FIG. 8 , when there are connections only by the outer peripheral connectors or the inner peripheral connectors, the overlapping count of the busbars reaches a maximum of 4. Because the heat sources in these parts are concentrated, the connectors become locally heated to a high degree. By alternately serially connecting, using the outer peripheral connectors and the inner peripheral connectors, as shown in  FIG. 2 , it is possible to curtail the maximum of the overlapping count of the busbars to 3. It is then possible to control the locally high heat that the connectors experience. Thus, it is possible to improve the motor&#39;s cooling performance. 
   Additionally, as shown in  FIG. 8(   a ), when there is connection only with the inner peripheral connector, because the take-out part is located on the inner peripheral side of the stator core, when there is wiring from this take-out part to outside the motor&#39;s case, there is the necessity of locating the wires (take-out line) in the radial direction of the motor. This part of the motor becomes long in the axial direction, but as shown in  FIG. 2 , by establishing take-out parts  23   u ,  23   v , and  23   w  at the outer peripheral connectors  21   u ,  21   v , and  21   w , because it is possible to wire directly to the outside of the motor from the outer peripheral of the stator core, it is possible to prevent a lengthening of the motor in the axial direction. 
     FIG. 4  is an explanation diagram of the coil connection structure of the motor of Embodiment 2. In this embodiment, as shown in  FIG. 4 , there is an inner peripheral take-out structure which establishes inner peripheral take-out parts  25   u ,  25   v , and  25   w  at the inner peripheral connectors  22   u ,  22   v , and  22   w.    
   Every coil of the U phase, V phase and W phase has inner peripheral coil wound ends  32   u   1 ˜ 32   u   4 ,  32   v   1 ˜ 32   v   4 , and  32   w   1 ˜ 32   w   4  on the inner periphery of the stator core  20 , and outer peripheral coil wound ends  31   u   1 ˜ 31   u   4 ,  31   v   1 ˜ 31   v   4 , and  31   w   1 ˜ 31   w   4  on the outer periphery of the stator core  20 . 
   The inner peripheral coil wound ends  32   u   1 ,  32   u   4 ,  32   v   1 ,  32   v   4 ,  32   w   1 , and  32   w   4  are connected by the inner peripheral connectors  22   u ,  22   v , and  22   w . The remaining inner peripheral coil wound ends  32   u   2 ,  32   u   3 ,  32   v   2 ,  32   v   3 ,  32   w   2 ,  32   w   3  are connected by the inner peripheral connector  26 . This inner peripheral connector combines with the neutral line  26 . 
   The outer peripheral coil wound ends  31   u   1 ,  31   u   2 ,  31   v   1 ,  31   v   2 ,  31   w   1 , and  31   w   2  are connected by the outer peripheral connectors  21   ua ,  21   va ,  21   wa . The remaining outer peripheral coil wound ends  31   u   3 ,  31   u   4 ,  31   v   3 ,  31   v   4 ,  31   w   3 , and  31   w   4  are connected by  21   ub ,  21   vb , and  21   wb . From this arrangement, each coil, for respectively the U phase, V phase, and W phase, is serially connected. 
     FIG. 5  is an explanation diagram of the wire connections sequence when there are the serial connections of  FIG. 4 . As shown in  FIG. 5 , when it is the case of the U phase coil, there are respective connections by passage through the outer peripheral side (outer peripheral connector  21   ua ) from coil U 1  to coil U 2 , there is a passage through the inner peripheral side (inner peripheral connector  26 ) from coil U 2  to coil U 3 , there is passage through the outer (outer peripheral connector  21   ub ) peripheral side from coil U 3  to coil U 4 , and there is passage through the inner peripheral side from coil U 4  to coil U 1  (inner peripheral connector  22   u ). Thus, when serially connected, for every phase, there is alternation between the inner peripheral connectors and the outer peripheral connectors. 
   Because the inner peripheral connectors  22   u ,  22   v ,  22   w , and  26  and the outer peripheral connectors  21   u ,  21   v , and  21   w , which are heat sources, are not concentrated in one direction by distribution to the inner peripheral side and outer peripheral side of the stator core  10 , there is no high heat concentration only in one direction of the inner peripheral side or the outer peripheral side of the stator core  20 . Thus, there can be improvement in the cooling of the motor. 
   In addition, by having serial connectors which connect in series using alternately the inner peripheral connector and the outer peripheral connector, it is possible to arrange the overlapping count of busbars evenly. It is possible also for the turns of the coil winding to be made the same (30.5 t) using all of the U phase coils (U 1 ˜U 4 ), V phase coils (V 1 ˜V 4 ), and the W phase coils (W 1 ˜W 4 ). 
   However, as shown in  FIG. 8 , when there are connections only by the outer peripheral connectors or the inner peripheral connectors, the overlapping count of the busbars reaches a maximum of 4. Because the heat sources in these parts are concentrated, the connectors become locally greatly heated. By alternately serially connecting, using the outer peripheral connectors and the inner peripheral connectors, as shown in  FIG. 4 , it is possible to curtail the maximum of the overlapping count of the busbars to three counts. It is then possible to control, or reduce, the locally high heat concentration that the connectors experience. Therefore, it is possible to improve the motor&#39;s cooling with this configuration. 
     FIG. 6  is an explanation diagram of the wire connection sequence of the coil connection sequence of Embodiments 3 and 4. As shown in  FIG. 6 , also when there are established respectively 6 coils for the U phase, V phase, and W phase, there is alternate repetition of the sequence of the connecting parts, the outer peripheral side and the inner peripheral side as in the outer peripheral connectors→inner peripheral connectors or the inner peripheral connectors→outer peripheral connectors. 
   For example, the connection sequence for the U phase coil (U 1 ˜U 6 ) is as follows. When it is the case of serial connections from coil UI to coil U 6 , as shown in  FIG. 6(   a ), there are respective connections through a sequence through the inner peripheral side (inner peripheral connector) from coil U 1  to coil U 2 , through the outer peripheral side (outer peripheral connector) from coil U 2  to coil U 3 , through the inner peripheral side (inner peripheral connector) from coil U 3  to coil U 4 , through the outer peripheral side (outer peripheral connector) from coil U 4  to coil U 5 , through the inner peripheral side (inner peripheral connector) from coil U 5  to coil U 6 , and through the outer peripheral side (outer peripheral connector) from coil U 6  to coil U 1 . Or, there are respective connections when there is passage from coil U 1  to coil U 2 , and afterwards, by repeating the inner peripheral→outer peripheral sequence, there is passage through the inner peripheral side from coil U 6  to coil U 1 . 
   When there is serial connection of the sequence from coil U 1  to coil U 2 , coil U 3  to coil U 4 , coil U 5  to coil U 6 , and when there is parallel connection from coil U 1 , coil U 4  and coil U 4  and parallel connection from coil U 2 , coil U 3 , and coil U 5 , as shown in  FIG. 6(   b ), the serial connections are respectively connected by passage through the inner peripheral side (inner peripheral connections), and the parallel connections are respectively connected by passage through the outer peripheral side (outer peripheral connections). Or, the serial connections are respectively connected through the outer peripheral side (outer peripheral connections), and the parallel connections are respectively connected through the inner peripheral side (inner peripheral connections). 
     FIG. 7  shows the coil connection structure of Embodiment 5, with (a) as a cross-sectional explanation diagram for when the coil stage count is odd, and with (b) as a cross-sectional explanation diagram for when the coil stage count is even. The coil stage count is the layer count of the coil winding  13  which is wound as layers on the tooth  12 . When the coil winding  13  is wound in 2 layers on the tooth  12 , the coil stage count is  2 . 
   As shown in  FIG. 7 , assuming that the stage count for every coil is odd, there is take-out from the rotor side (not illustrated) the end of the coil winding  13  of the stator core&#39;s inner peripheral side, that is, from the projection end side of the tooth  12 . There is arrangement of the end connector  16   a  of the coil winding  13  of the stator core&#39;s inner peripheral side at intervals by the wall  11   d  which is used for cooling which is formed on the motor rotation axis side within the motor case  11 . There is arranged the end connector  16   b  of the coil winding  13  of the stator core&#39;s outer peripheral side at intervals of the case outer peripheral surface within the motor case  11  and the back yoke  17 ,  FIG. 7   a.    
   In addition, assuming an even number for the stage count of each coil, there is take-out of the end of the coil winding  13  in both directions of the stator core&#39;s inner peripheral. side and stator core&#39;s outer peripheral side, that is, from the base of the tooth  12 . There is arrangement of the end connector  16   a  of the coil winding  13  of the stator core&#39;s inner peripheral side at intervals of the wall  11   d  which is used for cooling inside the motor case  11  and the back yoke  17 . There is arrangement of the end connector  16   b  of the coil winding  13  of the stator core&#39;s outer peripheral side at intervals of the case&#39;s outer peripheral side surface within the motor case  11  and the back yoke  17 ,  FIG. 7   b.    
   In this way, when there are respective connections of the coil winding from the top of the stator core&#39;s inner peripheral side and from the bottom of the stator core&#39;s outer peripheral side, the coil stage count is odd, but when there is connection from both the stator core&#39;s inner peripheral side and the stator core&#39;s outer peripheral side, the coil stage count is even. For the case where the coil is connected with the inner peripheral connector, from the effect of the cooling fin which is located on the stator core&#39;s inner peripheral side, space efficiency is improved, when the take-out of the coil winding is at the projection end of the teeth (stator side). 
   On the one hand, at the stator core&#39;s outer peripheral side, because the connector is below the coil, it is permissible to perform take-out of the coil winding from the base side of the teeth. If the coil stage count is odd, because the winding start and winding end become up and down, it is possible to satisfy the previously described conditions. The effect is to be able to miniaturize the entire motor by doing away with space by miniaturizing the coil connectors. 
   In this case, by starting the winding of the coil winding from the outer peripheral side, because it is possible to place the end on the outer peripheral side, there is improvement in connection operability with the outer peripheral busbars. 
   Moreover, in the embodiment, there was an explanation using a 3-phase motor, but the phase count is not limited to this number, and this invention is appropriate for motors with phase counts greater than three phases. 
   Various embodiments of the invention have been described. These and other embodiments are within the scope of the following claims.