Patent ID: 7765969

Claim:
A vertical internal combustion engine comprising: a hollow crankcase having a crank chamber formed therein; a transmission case attached to the crankcase and having a belt chamber formed therein; a valve train chamber disposed below the transmission case; a crankshaft enclosed in the crank chamber and oriented with a center axis thereof substantially vertically extended; a driven mechanism including a driven shaft which is rotatively driven by the crankshaft, said driven shaft disposed within the valve train chamber; and a belt-drive transmission mechanism held in a belt chamber and including a flexible belt comprising rubber for transmitting power of the crankshaft to the driven shaft and lubricated with oil; wherein the belt chamber communicates with the crank chamber by way of vent holes, the transmission case is provided with a barrier member disposed between the vent holes and the belt in the belt chamber so as to deflect a flow of an oil-containing gas flowing from the crank chamber into the belt chamber such that the oil-containing gas flows in directions deviating from a direction toward the belt; wherein the oil-containing gas flows between the crank chamber and the belt chamber substantially only through a first set of vent holes, and the gas flows between the valve train chamber and the belt chamber substantially only through a second set of vent holes.