Patent ID: 7392893

Claim:
A power unit cooling device for a power unit having a power source and a power transmission mechanism disposed within a casing of the power unit, comprising: a centrifugal fan having a front side and a rear side, disposed within the casing and configured so that air introduced from the front side of the centrifugal fan is allowed to flow through an interior of the casing by a blow-off action of the centrifugal fan; wherein the centrifugal fan is mounted on a rotary shaft of a heat generating rotating device that generates heat during operation; a flow dividing mechanism connected to the centrifugal fan for dividing a part of an air flow to be blown off radially outwardly and a part of an air flow to be blown off axially towards the rear side of the centrifugal fan; and the centrifugal fan includes: a base plate integrally connected to the rotary shaft of the heat-generating rotating device; a plurality of fins on an outer periphery edge portion of the base plate; a blow-off hole penetrating axially through the base plate between a pair of adjacent fins; and a guide wall disposed between the adjacent fins to conduct air flowing radially outward over the base plate into the blow-off hole; wherein the heat generating rotating device is a centrifugal clutch that transmits a rotating power to an outer rotor that is connected to a driven side of the clutch when the number of revolutions of an inner rotor connected to the power source has reached a predetermined number of revolutions; wherein the centrifugal clutch includes an inlet port for conducting air blown-off axially towards the rear side of the centrifugal fan into an interior of the centrifugal clutch; and a discharge port for discharging the air from the interior of the centrifugal clutch to an exterior of the centrifugal clutch; wherein the centrifugal clutch is interposed between an input side of the power transmission mechanism, which is for transmitting engine power to a driving wheel, and an engine crank shaft the centrifugal fan being mounted on an input side of the centrifugal clutch, and wherein the air blown off radially outward by the centrifugal fan is fed to the interior of the casing, while the air flowing axially backward as a divided air flow from the centrifugal fan is fed to the interior of the centrifugal clutch.