Patent Publication Number: US-2022224201-A1

Title: Motor coil cooling structure

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2021-002216 filed on Jan. 8, 2021, the disclosure of which is incorporated by reference herein. 
     BACKGROUND 
     Technical Field 
     The present disclosure relates to a motor coil cooling structure. 
     Related Art 
     Japanese Patent Application Laid-Open (JP-A) No. 2019-146388 discloses a structure for cooling coils housed in plural slots formed arrayed around a circumferential direction of a stator core of a motor. The motor includes a rotor core capable of rotating integrally with a rotation shaft, and the stator core provided opposing an outer peripheral portion of the rotor core. In the technology disclosed in JP-A No. 2019-146388, slot openings that are in communication with the plural slots extend along a rotation-axial direction at an inner peripheral face of the stator core, and the coils are directly cooled by oil flowing through the slot openings and along the respective slots. 
     However, accompanying advances in motor rotation speed and electromagnetic density (increased current), there is a demand to directly and uniformly cool coils disposed in slots formed in the stator core in an efficient manner. There is therefore room for improvement of coil cooling structures in this respect. 
     SUMMARY 
     The present disclosure provides a motor coil cooling structure capable of directly and uniformly cooling coils disposed in slots formed in a stator in an efficient manner. 
     A first aspect of the present disclosure is a motor coil cooling structure including a rotor core that is fixed to an outer circumference of a rotation shaft provided with an internal supply path through which coolant flows, and that includes a rotor-side flow path in communication with the supply path and passing through to a radial direction outer side of the rotor core; a stator core that is disposed at the radial direction outer side of the rotor core so as to form a space between the stator core and the rotor core, and that includes plural slots arrayed around a circumferential direction, each of the plural slots housing a coil; plural first flow paths that are formed in the stator core so as to include the slots and pass through the stator core in a radial direction; plural second flow paths that are formed in an upper portion of the stator core relative to the rotation shaft when an axial direction of the rotation shaft is disposed along a horizontal direction, the plural second flow paths being formed so as to include the slots and extend in a radial direction through the stator core, and passing through the stator core only at a radial direction outer circumferential side thereof; and a supply section configured to supply coolant from above the stator core when the axial direction of the rotation shaft is disposed along the horizontal direction. 
     The motor coil cooling structure of the above aspect includes the rotor core that is fixed to the outer circumference of the rotation shaft provided with the internal supply path through which the coolant flows, and that includes the rotor-side flow path in communication with the supply path and passing through (or penetrating) the radial direction outside of the rotor core, the stator core that is disposed at the radial direction outside of the rotor core so as to form a space between the stator core and the rotor core, and that houses the coils in the plural slots formed arrayed around the circumferential direction, and the plural first flow paths that are formed in the stator core so as to include the slots and pass through (or penetrate) the stator core in the radial direction. Accordingly, centrifugal force causes the coolant flowing through the supply path to be supplied into the plural first flow paths after passing through the rotor-side flow path. The coolant accordingly flows directly into each of the plural slots, thereby enabling the coils to be directly cooled. Such direct cooling of the coils enables efficient cooling of the coils. 
     Generally, when a vehicle is stationary and the motor has been switched off, the coolant drops under its own weight into an oil pan disposed below the motor. Thus, when the vehicle is restarted after a substantial amount of time has elapsed since the motor was switched off, the motor is actuated in a state in which the first flow paths in the stator core are filled with air. Note that in cases in which the motor is mounted transversely (i.e., in cases in which the axial direction of the rotation shaft is disposed in a horizontal direction), the coolant readily passes through and out of the first flow paths in the stator core at both side portions and a lower portion of the motor as a result of centrifugal force of the rotating rotor and the weight of the coolant itself. However, the coolant less readily passes through and out of the first flow paths in the stator core under its own weight at an upper portion of the motor. 
     In other words, in cases in which air remains above the coolant in the respective first flow paths in an upper portion of the stator core, an expulsion pressure directed from the radial direction inner side toward the first flow paths is required in order to expel this remaining air. However, it would be difficult to discharge this air with only the amount of coolant supplied as a result of the centrifugal force of the rotating rotor when the vehicle is restarted. 
     As it is difficult for the coolant to pass through and out of the first flow paths in the stator core at the upper portion of the motor, when, for example, the motor is subjected to a large travel load when the vehicle is restarted, the upper portion of the stator core is liable to undergo localized heating where the coolant cannot pass through and out readily, with the result that it may not be possible to achieve a uniform temperature distribution in the stator core. 
     The motor coil cooling structure of the present aspect includes the plural second flow paths that are formed in the portion of the stator core that is higher than the rotation shaft when the axial direction of the rotation shaft is disposed along the horizontal direction. Each of the plural second flow paths is formed so as to include the slot and extends in a radial direction through the stator core, and only passes through (or penetrates) the radial direction outer circumferential side of the stator core. The motor coil cooling structure also includes the supply section that supplies the coolant to the stator core from above when the axial direction of the rotation shaft is disposed along the horizontal direction. Accordingly, the coolant supplied from above the stator core is supplied into the second flow paths from the radial direction outer circumferential side. This enables the coolant to flow directly from the upper side to the lower side in the slots in the portion of the stator core higher than the rotation shaft, enabling the corresponding coils to directly and efficiently cooled. 
     As described above, the coils at the upper portion of the stator core may be efficiently cooled using both the first flow paths and the second flow paths, thereby enabling a uniform temperature distribution to be achieved in the stator core. 
     In the above aspect, configuration may be made wherein the second flow paths are formed on both sides of the respective first flow paths in the axial direction; and the motor coil cooling structure further includes one or more third flow paths formed within the stator core so as to place the second flow paths formed on respective sides of the corresponding first flow path in communication with each other. 
     The configuration described above further includes the one or more third flow paths formed within the stator core so as to place the second flow paths in communication with each other. The coolant accordingly flows through the plural second flow paths and the third flow paths, thereby facilitating circulation of the coolant within the stator core. 
     In the above aspect, configuration may be made wherein at least one third flow path of the one or more third flow paths passes through the stator core in the axial direction. 
     In the configuration described above, the at least one third flow path of the one or more third flow paths passes through (or penetrates) the stator core in the axial direction such that the coolant is discharged in the axial direction of the third flow path, thereby enabling the coolant to be even more efficiently circulated. 
     In the above aspect, configuration may be made wherein the coil includes two coil ends, each configuring a location jutting out from respective axial direction ends of the stator core; and of the one or more third flow paths, a third flow path positioned above the coil ends when the axial direction of the rotation shaft is disposed along the horizontal direction passes through the stator core in the axial direction. 
     In the configuration described above, the third flow path positioned above the coil ends passes through (or penetrates) the stator core in the axial direction. Thus, coolant passing through the third flow path positioned above the coil ends is discharged through a discharge port of the third flow path positioned above the coil ends. The coolant discharged through the discharge port accordingly flows toward the coil ends under its own weight, thereby enabling the coil ends to be cooled by this coolant. 
     In the above aspect, configuration may be made wherein the coil includes two coil ends, each configuring a location jutting out from respective axial direction ends of the stator core; and of the one or more third flow paths, a third flow path positioned below the coil ends when the axial direction of the rotation shaft is disposed along a horizontal direction passes through the stator core in the axial direction. 
     In the configuration described above, the third flow path positioned below the coil ends passes through (or penetrates) the stator core in the axial direction. Thus, coolant that has passed through the second flow paths is discharged through a discharge port of the third flow path positioned below the coil ends. This promotes the passage of fresh coolant supplied from the supply section into the second flow paths, thereby enabling cooling efficiency to be improved. 
     In the above aspect, configuration may be made wherein the plural first flow paths are provided at a central portion, in an axial direction, of the stator core. 
     In order to achieve a uniform temperature distribution in the stator core, it would for example be conceivable to provide a greater number of the first flow paths in an upper portion of the stator core. However, the greater the number of radially penetrating first flow paths that are provided, the smaller the amount of coolant available for each of the first flow paths, such that it becomes difficult to secure the aforementioned expulsion pressure. In the configuration described above, the first flow paths are provided at the axial direction central portion of the stator core where heat is generally liable to build up and cause the coils to become hot. This enables the coils to be efficiently cooled using a smaller number of the first flow paths. 
     As described above, the present disclosure is capable of directly and uniformly cooling the coils disposed in the slots formed in the stator in an efficient manner. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-section illustrating an axial direction central portion of a motor structure according to a first exemplary embodiment. 
         FIG. 2  is a perspective view locally illustrating a structure of a stator according to the first exemplary embodiment. 
         FIG. 3  is an enlarged cross-section of relevant portions appearing in  FIG. 1 , illustrating a flow of cooling oil after rotation of a motor according to the first exemplary embodiment. 
         FIG. 4  is an enlarged cross-section of relevant portions, illustrating a flow of cooling oil after rotation at an axial direction upper portion and lower portion of a motor structure according to the first exemplary embodiment. 
         FIG. 5  is a top-down view of a motor according to the first exemplary embodiment. 
         FIG. 6  is a perspective view locally illustrating a structure of a stator according to a second exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Detailed explanation follows regarding a first exemplary embodiment according to the present disclosure, with reference to  FIG. 1  to  FIG. 5 . Note that to aid explanation, in  FIG. 1 , the arrow UP indicates an upward direction with respect to a motor  12 , and a direction perpendicular to the page surface corresponds to an axial direction of a rotation shaft  14  of the motor  12 . Namely, the motor  12  according to the present exemplary embodiment is mounted transversely in a vehicle (i.e., disposed such that the axial direction of the rotation shaft  14  runs along a horizontal direction). Moreover, to aid explanation, the arrow D in  FIG. 2  indicates the axial direction of the rotation shaft. 
     Also to aid explanation, in  FIG. 1 ,  FIG. 3 , and  FIG. 4 , coils  38  are illustrated somewhat smaller than in reality, whereas gaps P between slots  36  and the coils  38  (first flow paths  40  and second flow paths  50 ) are illustrated larger somewhat than in reality. Also to aid explanation, in  FIG. 1  to  FIG. 4 , cooling oil is represented by arrows, and the flow of the cooling oil along the respective flow paths is also represented by arrows. 
     A coil cooling structure  10  of the motor  12  according to the first exemplary embodiment is employed in a motor installed in a vehicle such as a hybrid vehicle or an electric vehicle (not illustrated in the drawings). The motor  12  is employed as a source of motive force in the vehicle. As illustrated in  FIG. 1 , the motor  12  according to the first exemplary embodiment includes a substantially circular cylinder shaped rotor  20  fixed to an outer circumferential face of the circular cylindrical rotation shaft  14  so as to rotate integrally with the rotation shaft  14 , and a substantially annular stator  30  disposed at a radial direction outer side of the rotor  20  with a space G therebetween. 
     The rotor  20  includes a circular cylinder shaped rotor core  22 , and plural permanent magnets (not illustrated in the drawings) internally provided to the rotor core  22 . The stator  30  includes a stator core  32  configured by an annular magnetic body, and the coils  38  provided to the stator core  32 . Note that the rotor core  22  and the stator core  32  are each formed by, for example, stacking plural punched electromagnetic steel plates along the axial direction of the rotation shaft  14  so as to form an integral unit. 
     Attraction force and repulsion force arising due to a rotating magnetic field generated by the coils  38  acts on the plural permanent magnets so as to cause the rotor core  22  (or rotor  20 ) to rotate in one direction about the rotation shaft  14 . As previously mentioned, an outer circumferential face of the rotor core  22  and an inner circumferential face of the stator core  32  oppose each other in a radial direction across the space G. The space G has a predetermined width (namely, has a constant radial direction width). 
     A supply path  18  through which cooling oil serving as a coolant flows is formed extending through the interior of the rotation shaft  14  in the axial direction. The supply path  18  is connected to a supply device  48  serving as a supply section for supplying the cooling oil. Plural (for example four) circular openings  16 , serving as cooling oil outlets, are formed in the outer circumferential face of the rotation shaft  14  at an axial direction central portion of the rotation shaft  14 . 
     Plural (for example four) branch flow paths  28 , serving as rotor-side flow paths into which the cooling oil flows from the supply path  18  via the openings  16 , are formed in inner portions of the rotor core  22 . The respective branch flow paths  28  are configured by through-holes with circular cross-section profiles formed by punching the electromagnetic steel plates configuring the rotor core  22 . As a result, plural circular openings  24 ,  26  (for example four of each), serving as inlets and outlets (of the branch flow paths  28 ) for the cooling oil, are respectively formed in an inner circumferential face and an outer circumferential face of an axial direction central portion of the rotor core  22 . 
     Namely, the respective branch flow paths  28  pass through or penetrate the rotor core  22  in radial directions (in a radiating pattern), such that the openings  16  in the rotation shaft  14  and the openings  24  in the rotor core  22  are in communication with each other. Thus, a centrifugal force arising as the rotor  20  rotates causes the cooling oil to flow from the supply path  18  into the respective branch flow paths  28 , flow through the inside of the rotor core  22 , and flow out to the space G. As a result, the rotor core  22  and the permanent magnets are cooled by the cooling oil. 
     Teeth  34  and the slots  36  extend along the axial direction, and are formed alternately around the circumferential direction of the stator core  32 . Namely, in the stator core  32 , plural (for example twenty) slots  36  are formed arranged around the circumferential direction, and the respective coils  38  are wound around the teeth  34  so as to be disposed in the slots  36 . Two axial direction end portions of each of the coils  38  respectively project out from two axial direction end faces of the stator core  32 . In the following explanation, these projecting portions are referred to as “coil ends  38 A”. 
     The respective coils  38  are electrically connected to a power source unit (not illustrated in the drawings), and a three-phase alternating current flows from this power source unit. The respective coils  38  generate the rotating magnetic field as a result. Insulating paper (not illustrated in the drawings) is stuffed into the gaps P between the slots  36  and the coils  38 . Note that the insulating paper is not provided in the gaps P at an axial direction central portion of the stator core  32 . 
     Namely, first flow paths  40  through which the cooling oil flows in order to cool the respective coils  38  are formed by the respective gaps P of the stator core  32  where the insulating paper is not provided. Specifically, grooves  34 A extending along the axial direction are formed in the teeth  34  in order to configure the respective slots  36 . As illustrated in  FIG. 2  and  FIG. 3 , plural circular first openings  42 ,  44  (for example twenty of each) configuring inlets and outlets (of the first flow paths  40 ) for the cooling oil are thereby respectively formed in an inner circumferential face and at an outer circumferential face at the axial direction central portion of the stator core  32 . 
     Namely, the respective first flow paths  40  formed at the axial direction central portion of the stator core  32  include the corresponding slots  36  (i.e., the corresponding gaps P) and each pass through or penetrate the stator core  32  in a radial direction (so as to form a radiating pattern). Thus, as illustrated in  FIG. 2  and  FIG. 3 , the centrifugal force arising as the rotor  20  rotates causes cooling oil that has flowed into the space G to flow into the first flow paths  40  through the first openings  42 , flow along the first flow paths  40 , and flow out through the first openings  44 . The coils  38  disposed in the slots  36  are thereby directly cooled by the cooling oil. 
     The cooling oil may also be supplied to the outer circumferential face of the stator core  32 . Namely, as illustrated in  FIG. 1 , a shower pipe  46  capable of supplying cooling oil from above the stator core  32  is disposed at an upper side (namely, the radial direction outer side) of the stator core  32 . The shower pipe  46  is connected to the supply device  48  that includes an oil pump (not illustrated in the drawings). Note that the shower pipe  46  functions as part of the supply device  48 . 
     Driving of the oil pump of the supply device  48  is controlled by a control device  49  serving as a control unit installed in the vehicle. Cooling oil is supplied (i.e., sprinkled from above) onto an upper portion of the outer circumferential face of the stator core  32  under the control of the control device  49 . 
     A section of the stator core  32  positioned above the rotation shaft  14  includes second flow paths  50  provided within the stator core  32 . The second flow paths  50  are provided for cooling, out of the coils  38 , plural (for example five) neighboring coils  38  around the circumferential direction, centered on the coil  38  positioned at the uppermost side. Note that insulating paper is not provided in the gaps P where the second flow paths  50  are formed. 
     As illustrated in  FIG. 2 , the second flow paths  50  are formed on both axial direction sides of the first flow paths  40  at locations corresponding to these five coils  38 . As illustrated in  FIG. 2  and  FIG. 4 , the second flow paths  50  are formed with plural circular second openings  52  serving as inlets for the cooling oil (into the second flow paths  50 ) in the outer circumferential face of the stator core  32 . Namely, the second flow paths  50  formed in the stator core  32  each extend in a radial direction (so as to form a radiating pattern) through the stator core  32  including at the respective slots  36  (gaps P), and only pass through or penetrate the radial direction outer circumferential side (namely, the shower pipe  46  side) of the stator core  32 . Namely, as illustrated in  FIG. 4 , in order to prevent backflow, the second flow paths  50  do not pass through or penetrate through to the rotor  20  side of the stator core  32 . 
     As described above, the first flow paths  40  are formed at the axial direction central portion, and the second flow paths  50  are formed on both axial direction sides of the corresponding first flow paths  40 .  FIG. 5  is a top-down view of the motor  12 . The arrow D in  FIG. 5  indicates the axial direction of the rotation shaft  14 . In  FIG. 5 , the first openings  44  of the first flow paths  40  are indicated by hatching in order to better distinguish them from the second openings  52  of the second flow paths  50 .  FIG. 5  is a diagram illustrating the stator  30  in  FIG. 1  as viewed from above. Six of the second openings  52  of the second flow paths  50  are illustrated in the stator core  32  in  FIG. 5 . However, in the present exemplary embodiment, in reality the second openings  52  of the second flow paths  50  (second flow paths  50 ) are also provided on both axial direction sides of the non-illustrated first flow paths  40  adjacent to the not-illustrated first flow paths  40  located at the upper side and lower side of the page of  FIG. 5 , to give a total of ten of the second openings  52 . 
     As illustrated in  FIG. 5 , the first openings  44  of the first flow paths  40  are formed at uniform intervals around the axial direction central portion of the outer circumferential face of the stator core  32 . The second openings  52  of the second flow paths  50  are formed on both axial direction sides of the five circumferential-direction neighboring first openings  44  centered on the uppermost first opening  44 . 
     As illustrated in  FIG. 2  and  FIG. 4 , the stator core  32  includes two third flow paths  60  that place the second flow paths  50  formed on both axial direction sides of the corresponding first flow path  40  in communication with each other. The two third flow paths  60  are formed so as to extend along the axial direction within the stator core  32 . The flow path provided on the radial direction side corresponding to the rotor  20  is referred to as a third flow path  60 A, and the flow path provided on the outer circumferential side of the stator core  32  is referred to as a third flow path  60 B. As illustrated in  FIG. 2 , the third flow path  60 B, provided on the outer circumferential side penetrates the stator core  32  in the axial direction, is provided with circular discharge ports  62  in both axial direction end faces (i.e., coil end  38 A sides) of the stator core  32 . Note that the third flow paths  60  are flow paths formed so as to be in communication with the corresponding second flow paths  50 , but not to be in communication with the corresponding first flow path  40 . 
     Cooling oil supplied from the shower pipe  46  directly cools the stator core  32 , and also directly cools the respective coils  38  disposed in the five circumferential-direction neighboring slots  36  centered on the coil  38  positioned on the uppermost side. Specifically, cooling oil supplied from the shower pipe  46  flows into the second flow paths  50  through the second openings  52  and circulates inside the second flow paths  50 . Cooling oil that has flowed into the second flow paths  50  then flows into the third flow paths  60 A,  60 B, and circulates inside the second flow paths  50  and the third flow paths  60 A,  60 B. Cooling oil that has flowed into the third flow path  60 B positioned on the outer circumferential side is discharged through the respective discharge ports  62 . Thus, the outer circumferential face of the section of the stator core  32  positioned above the rotation shaft  14  and the respective coils  38  that are disposed in the five circumferential-direction neighboring slots  36  centered on the coil  38  positioned on the uppermost side are directly cooled by the cooling oil. 
     The coil cooling structure  10  of the motor  12  of the first exemplary embodiment is configured in the above manner. Next, explanation follows regarding operation and effects of the coil cooling structure  10  of the motor  12  configured in the above manner. 
     After the vehicle has become stationary and the motor  12  has been switched off, the cooling oil drops under its own weight into an oil pan (not illustrated in the drawings) disposed below the motor  12 . Thus, when the vehicle is restarted after a substantial amount of time has elapsed since the motor  12  was switched off, the motor  12  is actuated in a state in which the first flow paths  40  in the stator  30  are certain to be filled with air. 
     Note that in cases in which the motor  12  is disposed horizontally, cooling oil readily passes through and out of the first flow paths  40  in the stator  30  at two side portions and a lower portion of the motor  12  as a result of centrifugal force arising as the rotor  20  rotates, as well as the weight of the cooling oil itself. However, the cooling oil less readily passes through and out of the first flow paths  40  in the stator  30  under its own weight at an upper portion of the motor  12 . 
     In other words, in cases in which air remains above the cooling oil inside the first flow paths  40  in the upper portion of the stator core  32 , an expulsion pressure directed from the radial direction inside toward the inside of these first flow paths  40  is required in order to expel this remaining air. It would be difficult to discharge this air with only the amount of cooling oil supplied through the first openings  42  under the centrifugal force of the rotating rotor  20  when the vehicle is restarted. 
     As it is difficult for the cooling oil to pass through and out of the first flow paths  40  in the stator core  32  at the upper portion of the motor  12  as described above, cooling oil that has flowed out toward the upper side through the branch flow paths  28  of the rotor core  22  could pool in the space G between the rotor core  22  and the stator core  32  and be drew into the rotor  20  as the rotor  20  rotates, causing loss as a result of drag as the rotor  20  rotates. 
     Moreover, when the motor  12  is subjected to a large travel load when the vehicle is restarted, the upper portion of the stator core  32  is liable to undergo localized heating where the cooling oil cannot pass through and out readily, with the result that it may not be possible to achieve a uniform temperature distribution in the stator core  32 . 
     However, the coil cooling structure  10  of the motor  12  according to the present exemplary embodiment includes the plural second flow paths  50  that are formed in the stator core  32  at positions above the rotation shaft  14  when the axial direction of the rotation shaft  14  is disposed along the horizontal direction. The second flow paths  50  each extend in a radial direction through the stator core  32  while including the slots  36 , and only penetrate the radial direction outer circumferential side of the stator core  32 . The coil cooling structure  10  also includes the supply device  48  that supplies cooling oil to the stator core  32  from above when the axial direction of the rotation shaft  14  is disposed along the horizontal direction. This enables cooling oil to be supplied from above the stator core  32  prior to the rotor  20  rotating, such that the supplied cooling oil flows (backflows) through the plural first openings  44  of the first flow paths  40  at the upper portion of the stator core  32  under its own weight. This cooling oil fills the inside of the first flow paths  40 . Namely, any air inside the first flow paths  40  is pushed into the space G by the cooling oil so as to be discharged from the inside of the first flow paths  40  (i.e. the air is bled out from the first flow paths  40 ). 
     Since the cooling oil readily passes through and out of the first flow paths  40  at the upper portion of the stator  30  as a result, the coils  38  disposed in the slots  36  may be directly cooled in an efficient manner, and the occurrence of loss as a result of drag or the like as the rotor  20  rotates may be suppressed or prevented. 
     Moreover, cooling oil can also be supplied from above the stator core  32  as the rotor  20  rotates, and this cooling oil supplied from above the stator core  32  as the rotor  20  rotates is supplied into the second flow paths  50  through the second openings  52  provided on the radial direction outer circumferential face. Thus, coolant flows directly from the upper side to the lower side in the slots  36  in the section of the stator core  32  positioned above the rotation shaft  14 , namely at the upper portion of the stator core  32 , thereby enabling the corresponding coils  38  to be directly cooled in an efficient manner. 
     As described above, the coils  38  at the upper portion of the stator core  32  can be efficiently cooled using both the first flow paths  40  and the second flow paths  50 , thereby enabling a uniform temperature distribution to be achieved in the stator core  32 . 
     Moreover, in the coil cooling structure  10  of the motor  12  according to the first exemplary embodiment, the plural first flow paths  40  are provided at the axial direction central portion of the stator core  32 . In order to achieve a uniform temperature distribution in the stator core  32 , it would for example be conceivable to provide a greater number of the first flow paths  40  in the upper portion of the stator core  32 . However, the greater the number of radially penetrating first flow paths  40  that are provided, the smaller the amount of cooling oil available for each of the first flow paths  40 , such that it becomes difficult to secure the aforementioned expulsion pressure. In the coil cooling structure  10  of the motor  12  according to the first exemplary embodiment, the first flow paths  40  are provided at the axial direction central portion where heat is generally liable to build up and cause the coils to become hot. This enables the coils  38  to be efficiently cooled using a smaller number of the first flow paths  40 . 
     Moreover, the coil cooling structure  10  of the motor  12  according to the first exemplary embodiment also includes the two third flow paths  60  that are formed in the stator core  32  and that place the corresponding second flow paths  50  in communication with each other. The cooling oil flows through the second flow paths  50  and the third flow paths  60 , thereby facilitating circulation of cooling oil within the stator core  32 . 
     Moreover, in the coil cooling structure  10  of the motor  12  according to the first exemplary embodiment, the third flow path  60 B provided on the outer circumferential side penetrates the stator core  32  in the axial direction, such that cooling oil is discharged in the axial direction through the third flow path  60 B. This enables the cooling oil to be even more efficiently circulated. 
     Moreover, in the coil cooling structure  10  of the motor  12  according to the first exemplary embodiment, the third flow path  60 B provided on the outer circumferential side, namely the third flow path  60 B positioned above the coil ends  38 A penetrates the stator core  32  in the axial direction. Thus, cooling oil passing through the third flow path  60 B positioned above the coil ends  38 A is discharged through the discharge ports  62  of the third flow path  60 B positioned above the coil ends  38 A. The cooling oil discharged through the discharge ports  62  flows toward the coil ends  38 A under its own weight, thereby enabling the coil ends  38 A to be cooled by this cooling oil. 
     Note that although the third flow path  60 B provided on the outer circumferential side, namely the third flow path  60 B positioned above the coil ends  38 A, penetrates the stator core  32  in the axial direction in the first exemplary embodiment, the present disclosure is not limited thereto. 
     Next, detailed explanation follows regarding a second exemplary embodiment according to the present disclosure, with reference to  FIG. 6 . As illustrated in  FIG. 6 , in a coil cooling structure  10 - 2  of a motor  12  according to the second exemplary embodiment, the third flow path  60 A provided on the side of the rotor  20  in the radial direction, namely the third flow path  60 A provided below the coil ends  38 A, penetrates the stator core  32  in the axial direction. Specifically, the third flow path  60 A provided on the rotor  20  side is provided with circular discharge ports  62  similar to those illustrated in  FIG. 2  at both axial direction ends (on the coil end  38 A sides) of the stator core  32 , such that the third flow path  60 A penetrates the stator core  32  in the axial direction. 
     Thus, cooling oil that has passed through the second flow paths  50  is also discharged through the discharge ports  62  of the third flow path  60  positioned below the coil ends  38 A. This promotes the passage of fresh cooling oil supplied into the second flow paths  50  from the supply device  48 , thereby enabling cooling efficiency to be improved. 
     The coil cooling structures  10 ,  10 - 2  of the motor  12  according to the first exemplary embodiment and second exemplary embodiment have been described above with reference to the drawings. However, the coil cooling structures  10 ,  10 - 2  of the motor  12  according to the first exemplary embodiment and second exemplary embodiment are not limited to those illustrated in the drawings, and suitable design modifications may be implemented within a range not departing from the spirit of the present disclosure. For example, cooling oil is merely one example of a coolant, and a liquid coolant other than cooling oil may be employed to cool the coils  38  and the like. 
     Moreover, although an example has been given in which the respective openings  16 ,  24 ,  26 ,  42 ,  44 ,  52  and the discharge ports  62  are circular in shape, there is no limitation thereto, and these openings may formed in other shape, for example, be square in shape. 
     Although two of the third flow paths  60  are provided as an example, there is no limitation thereto, and for example three or more of the third flow paths  60  may be provided. Moreover, although an example has been given in which only one of the third flow paths  60  is provided so as to penetrate the stator core  32  in the axial direction, there is no limitation thereto, and configuration may be such that both or neither of the third flow paths  60  penetrate the stator core  32  in the axial direction. Moreover, there is no particular limitation to the route of the third flow paths  60  as long as the third flow paths  60  may be provided so as to place the plural second flow paths  50  in communication with each other without being in communication with the first flow paths  40 .