Patent ID: 6857406

Claim:
A valve driving device for an engine comprising, a camshaft produced by casting and formed with one center cam and two side cams which are different from the center cam in lift amount, with the center cam being centrally located between the side cams in an axial direction of the camshaft, a tappet assembly slidably fitted in a tappet guide hole formed in the engine and abutting on one of the center cam and the side cams to drive a valve, and including a center tappet adapted to abut on the center cam and side tappets adapted to abut on the side cams, the center tappet being slidably connected to the side tappets in a sliding direction of the tappet, one of the center tappet and the side tappets being connected to a valve shaft of the valve, a lock mechanism which selectively locks or unlocks the center tappet and the side tappets with or from each other so that the tappet assembly is driven by the center cam when the lock mechanism locks the center tappet and the side tappets with each other and the tappet assembly is driven by the side cams when the lock mechanism unlocks the center tappet and the side tappets from each other, wherein one cam of the center cam and the side cams is dimensioned so that a cam portion thereof over a predetermined angle range except for a cam nose section thereof is smaller than a base circle of the other cam in profile.