Cylinder block

A cylinder block including a water jacket for maintaining an engine at a proper temperature during operation thereof, comprising:

• a plurality of cylinders formed within the cylinder block so that pistons are respectively inserted into the cylinders;
• and,
• a heat sink formed in the water jacket and enclosing side surfaces of the plural cylinders,
• wherein the heat sink has a band shape and is continuously formed along outer surfaces of the plural cylinders,
• wherein the heat sink has a curvature formed along the outer surfaces of the cylinders and is bent in a shape such that a plurality of rectangular concave-convex structures is continuously adjacent to each other along the outer surfaces of the plural cylinders, and each of the rectangular concave-convex structures of the heat sink has a stepped cross-section and each said stepped cross-section is in a shape of alternatively protruding towards the outer surfaces of the plural cylinders and protruding outwards of the outer surfaces of the plural cylinders, so that heat transfer from the heat sink to cooling water is maximized, and
• wherein the heat sink has a heat transfer coefficient larger than the water jacket.