In an ac generator having a claw-pole type rotor, a stator winding has a plurality of front and rear coil ends. Each of the rear coil ends has an inside bent portion extending radially outward from the inner periphery of the rear end of the stator core and an inside main portion extending axially from the bent portion to form a backwardly expanding space around the rotor.
The present ac alternator application is based on and claims priority from Japanese Patent Application Hei 10-79412 filed on Mar. 26, 1998, the contents of which are incorporated herein by reference.
A rotor of a conventional brushless alternator has a pair of pole cores having a base portion and a plurality of claw pole pieces extending axially from the base portion disposed at opposite ends of the rotor. A stator core of conventional ac generators have a plurality of coil ends extending from opposite ends thereof to surround the circumference of the claw poles. A centrifugal cooling fan is fixed to an end of the rotor to cool the plurality of coil ends.
It has been found that fan noise is caused when circulating air C1, as shown in FIG. 2, driven by such a centrifugal cooling fan is interrupted by inner peripheral surfaces C2 of the coil ends surrounding the centrifugal fan.
A main object of the brushless ac generator is to provide an improved structure for reducing fan noise and noise generated when cooling air is interrupted by the coil ends, thereby improving cooling efficiency.
According to the ac generator, each of the rear coil ends of a stator winding has an air guiding inside surface. The air guiding inside surface is composed of an inside bent portion inclining or expanding radially outward from the inner periphery of the rear end of the stator core and an inside main portion extending axially from the bent portion to form a backwardly expanding space around a rear portion of the rotor. As a result, cooling air is guided by the inside surface to expand so that the speed and density of the cooling air can be regulated.