Cooling structure for internal combustion engine

A cooling system for an internal combustion engine in which:

• a spacer is fitted inside a water jacket which is formed to surround peripheries of three or more cylinder bores arranged one after another on a cylinder row line of a cylinder block of the internal combustion engine;
• and a cooling condition of the cylinder bores is controlled by regulating a flow of cooling water in the water jacket by use of the spacer, wherein
• the cylinder bores comprise end-portion cylinder bores situated respectively in opposite end portions in a direction of the cylinder row line, and one or more intermediate cylinder bores other than the end-portion cylinder bores, and
• the spacer is configured so that cooling performances for the intermediate cylinder bores are higher than those for the end-portion cylinder bores, wherein
• the spacer comprises a spacer main body part for regulating the flow of the cooling water in the water jacket, and
• the spacer main body part has a smaller thickness in a radial direction in portions facing the intermediate cylinder bores than in portions facing the end-portion cylinder bores.

A cooling system for an internal combustion engine in which:

• a spacer is fitted inside a water jacket which is formed to surround peripheries of three or more cylinder bores arranged one after another on a cylinder row line of a cylinder block of the internal combustion engine;
• and a cooling condition of the cylinder bores is controlled by regulating a flow of cooling water in the water jacket by use of the spacer, wherein
• the cylinder bores comprise end-portion cylinder bores situated respectively in opposite end portions in a direction of the cylinder row line, and one or more intermediate cylinder bores other than the end-portion cylinder bores, and
• the spacer is configured so that cooling performances for the intermediate cylinder bores are higher than those for the end-portion cylinder bores, wherein
• the spacer comprises a spacer main body part for regulating the flow of the cooling water in the water jacket, and
• a passage of the cooling water between an inner peripheral surface of the spacer main body part and an inner wall surface of the water jacket has a larger cross-sectional area in portions facing the intermediate cylinder bores than in portions facing the end-portion cylinder bores.