PURPOSE: To reduce cost and weight and to more surely prevent oscillation of a timing chain cover.

CONSTITUTION: An edge of an integrally moulded timing chain cover 25 is fastened and fixed by bolt holes 17 provided on the edge at roughly regular intervals and fixed by bolt holes 21 and 22 provided at a roughly central part of the timing chain cover 25. Consequently, oscillation due to an engine main body is prevented all over the timing chain cover 25. In the meantime, it is fixed by bolt holes 20 and 24 provided as near a sprocket as possible. Consequently, local oscillation of the timing chain cover locally generated at a part of the sprocket is concentrically prevented. Accordingly, by synergism of prevention of oscillation from the engine main body and local oscillation of the sprocket part, it is possible to surely prevent oscillation of the whole of the timing chain cover 25.