Cover structure of plug hole

A cover structure of a plug hole of a cylinder head cover of an engine, the cover structure comprising:

• a plug cap detachably attached to the plug hole;
• an outer cover covering at least an upper surface of the plug cap;
• and
• a seal member provided on an upper surface of the cylinder head cover and surrounding a periphery of the plug hole,
• wherein the outer cover has a projection portion projected toward the cylinder head cover,
• wherein the seal member is pressed to the upper surface of the cylinder head cover by the projection portion;
• wherein the projection portion is a first projection portion,
• wherein the outer cover further has a second projection portion located radially inside the first projection portion and projecting toward the cylinder head cover,
• wherein the seal member has a first convex portion and a second convex portion respectively facing the first projection portion and the second projection portion,
• wherein the plug cap has a disk portion enlarged in a radial direction,
• wherein the disk portion has a peripheral projection projecting downwardly at an outer circumferential edge thereof, and
• wherein the outer cover, the plug cap, and the seal member are configured such that, when the plug cap is attached to the plug hole:
• (a) the peripheral projection is inserted between the first convex portion and the second convex portion,
• (b) the first projection portion presses the first convex portion downwardly, and
• (c) the second projection portion faces the second convex portion and substantially contacts with an upper surface of the disk portion.