Head cover having lubrication structure

1. A head cover having a lubrication structure, and having a box shape, the head cover comprising:

a side wall;

a lower surface side which is opened, and which includes a lower surface circumference portion that is fixed to an upper portion of an engine;

a lubrication opening which is opened in an upward direction, and which is disposed on an outer side of the head cover; and

a lubrication passage extending from the side wall in an outward direction, and connecting the lubrication opening and an inside of the head cover.

2. The head cover as claimed in claim 1 , wherein the lubrication passage is divided into an upper section and a lower section; the lower section of the lubrication passage is integrally formed with the head cover; and the lubrication opening is formed in an upper divided member which constitutes the upper section.

3. The head cover as claimed in claim 2 , wherein the upper divided member includes a mounting seat portion which has a predetermined thickness, which is provided near the lubrication passage, and which is joined with the lower section; and the mounting seat portion protrudes inside the lubrication passage.

4. The head cover as claimed in claim 1 , wherein the head cover further comprises a bolt boss portion which is formed in the lower surface circumference portion, into which a bolt for fixing the head cover on the upper portion of the engine is inserted; and the lubrication passage is formed near the bolt boss portion.