Patent ID: 7958875

Claim:
An internal combustion engine comprising: a cylinder head provided with an engine valve; a valve system including a camshaft provided with a valve cam for opening and closing the engine valve, the camshaft being rotationally driven by power of a crankshaft housed in a crank chamber; and a breather system provided with a breather chamber into which blow-by gas flows through an introduction space communicating with the crank chamber, wherein the camshaft is provided with a hollow part penetrating the camshaft in an axial direction of the camshaft, the breather chamber is constituted of an upstream-side breather chamber formed of the hollow part, and a downstream-side breather chamber into which the blow-by gas flows from the upstream-side breather chamber, and the hollow part opens to the introduction space at a first shaft end portion of the camshaft, and also opens to the downstream-side breather chamber at a second shaft end portion of the camshaft, wherein the downstream-side breather chamber has a volume-enlarged chamber surrounding and extending in the axial direction beyond the second shaft end portion of the camshaft.