COVER MEMBER FASTENING METHOD AND FASTENING STRUCTURE FOR A HEAD COVER

Provided are a cover member fastening method and a fastening structure whereby the surface area in contact with an engine body is decreased, minimizing the transmission of vibrations to the cover member. Said fastening method and fastening structure also minimize deformation of the cover member while securely affixing abutting parts that need to be firmly fixed in place. The provided fastening structure uses a fastening member (7) to fasten a head cover (2) to a cylinder head (1) so as to cover the top surface of said cylinder head (1). Abutting parts (27) that abut against the top surface of the cylinder head (1) are formed on the inside surface of the head cover (2). The bottom surfaces of head-cover-side fastening boss parts (26) protrude farther than the bottom surface of a head-cover-side attachment flange (22). The surface area (A) of the bottom surfaces of the head-cover-side fastening boss parts (26) equals or approximates a minimum contact area (A min ) obtained by dividing the required axial fastening force (N) of the fastening member (7) by a stress tolerance (Ãa) determined by the material that the head cover (2) is made of.