CYLINDER BLOCK STRUCTURE

摘要

PROBLEM TO BE SOLVED: To provide a cylinder block structure with lightweight by swallowing a water jacket and reducing excessive weight by providing a down oil passage part. SOLUTION: A cylinder block structure comprises a cylinder 8 having an upper peripheral wall u covered with a water jacket 9. A down oil passage part W is formed to be projected to the outside of each of the water jacket 9 and the cylinder 8 to flow oil from a cylinder head H down on a side of a crank chamber 5. In the down oil passage 7 of the down oil passage part W, a section of a lower flow passage below the water jacket 9 is expanded on the side of the cylinder 8, compared with an upper flow passage opposed to the water jacket 9.