Patent ID: 8171910

Claim:
A cast iron cylinder liner having a shape of cylinder hollow to be enclosed in a cylinder block main body made of aluminum alloy by enclosing-casting method, which comprises a plurality of strip-shaped plane surfaces circularly extending in a circumferential direction of the cylinder liner, the circular strip-shaped plane surfaces being formed on an outer circumferential surface of the cylinder liner at intervals in the axis direction, and a plurality of circumferential grooves extending in the circumferential direction, the circumferential grooves being formed between the adjacent strip-shaped plane surfaces, each of the circumferential grooves of the cylinder liner in an axial sectional view comprising: a first circumferential groove comprising, a first slant surface whose diameter is gradually reduced with moving from an outer circumferential edge of a strip-shaped plane surface existing in one end side in an axial direction of the cylinder liner to an inner circumferential end to undercut a support portion of the strip-shaped plane surface, a first curved surface whose diameter is gradually reduced with moving from the inner circumferential end of the first slant surface, and a second slant surface whose diameter is gradually increased with moving from an inner circumferential end of the first curved surface to the other end side in the axial direction of the cylinder liner and which faces the first slant surface, the first slant surface, the first curved surface and the second slant surface being continuously linked to each other in this order to form a shape of “J” of the alphabet in sectional view; and a second circumferential groove comprising, a third slant surface which continuously links to an outer circumferential end of the second slant surface and whose diameter is gradually reduced with moving to the other end side in the axial direction of the cylinder liner, a second curved surface whose diameter is gradually increased with moving from an inner circumferential end of the third slant surface, and a fourth slant surface whose diameter is increased with moving from an outer circumferential end of the second curved surface to the one end side in the axial direction of the cylinder liner, which faces the third slant surface and whose outer circumference end links to an outer circumferential end of an adjacent strip-shaped plane surface existing in the other end side in an axial direction of the cylinder liner to undercut a support portion of the strip-shaped plane surface, the third slant surface, the second curved surface and the fourth slant surface being continuously linked to each other in this order to form a shape of “J” of the alphabet in sectional view.