Cylinder head with coolant passage passing around outside of cylinder head fixing bolt boss and directing coolant flow toward squish area cooling passage portion.

摘要

An internal combustion engine has a cylinder block formed with first and second cylinder bores, and first and second pistons are fitted in the bores and reciprocate in them. A cylinder head is affixed to the cylinder block and defines first and second combustion chambers in cooperation with the first and second pistons and cylinder bores. This cylinder head is formed with a portion which in cooperation with a portion of the first piston defines a squish area of the first combustion chamber, with a cylinder fixing bolt hole boss being located between the first portion and the second portion of the cylinder head, and being disposed towards the side of the cylinder head on the side of the squish area. Further, the cylinder head is formed with a side wall defining one side of a coolant passage which substantially follows through the cylinder head proximate to the squish area so that a first portion of the coolant passage directly cools the squish area. A second portion of the coolant passage passes around the boss at least between it and the side wall of the cylinder head, and directs flow of coolant through it to the first coolant passage portion. Optionally, this second coolant passage portion may also pass around the other side of the boss.