1. Field of the Invention
The present invention relates to an electric rotating machine used as a motor or an alternator in a vehicle.
2. Description of Related Art
Generally, a vehicle-mounted electric rotating machine includes a rotor rotatable around a rotating shaft, a stator core formed with slots arranged along the circumferential direction of the stator core so as to face the outer periphery of the rotor, and a stator coil constituted of a plurality of coil wires wound around the slots. The coil wire includes in-slot portions accommodated in the slots which are different in their circumferential positions, and turn portions each connecting two adjacent ones of the coil wires. The turn portions form a coil end at each of both axial ends of the stator coil, the coil end projecting axially outward from the end surface of the stator coil.
Since the stator coil of the electric rotating machine having such a structure increases in temperature when it operates, various countermeasures for the temperature increase have been proposed. For example, Japanese Patent Application Laid-open No. 2001-195302 (Patent document 1) describes installing an oil jacket on each of both end surfaces of the stator core so as to surround the coil end, providing an oil chamber between the oil jacket and the end surface, and passing coolant to the oil chamber to cool the coil end.
Further, Japanese Patent Application Laid-open No. 2004-180376 (Patent document 2) describes disposing, above the coil end, a gutter including a coolant supply opening through which coolant to be supplied to the surface of the coil end is taken and a guide connected to the coolant supply opening to guide coolant discharged from the coolant supply opening in order that coolant is guided to a desired direction to efficiently cool the coil end.
In the case of Patent document 1, the coolant passage is a closed space, and when the oil chamber is filled with coolant, the entire surface of the coil end becomes wet by coolant so that it is cooled. However, the cooling structure described in Patent document 1 needs a coolant supply pump, because the coolant passage has a relatively large fluid resistance. This increases manufacturing cost.
In the case of Patent document 2, since coolant flowing in from the coolant supply opening and flowing out from the guide flows down on the surface of the coil end by the action of the gravity, it is likely that some parts of the surface of the coil end do not become wet, causing the cooling to be non-uniform. Generally, the envelope surface of a coil end of a stator of an electric rotating machine is not flat, and accordingly, the non-uniform cooling tends to occur easily.