Patent ID: 7886711

Claim:
An oil drain structure, characterized in that: an inner-side space of a chain cover is formed by being surrounded by a side wall of an engine block on a side on which a timing chain that transmits rotation of a crankshaft to a camshaft is arranged, and by an inner wall of the chain cover that covers the timing chain; there is provided a partition that partitions the inner-side space into an oil drain passage that guides lubrication oil toward an oil pan and a chain arranged space in which the timing chain is arranged; the partition is formed by bringing a rib provided on the inner wall of the chain cover into contact with a rib provided on the side wall of the engine block; and an opening is formed in a portion of the partition by separating a portion of the rib provided on the side wall of the engine block from a portion of the rib provided on the inner wall of the chain cover.