| 摘要 |
PROBLEM TO BE SOLVED: To provide a combination oil ring capable of certainly preventing relative rotation of side rails and a spacer expander, securing sealability of the upper and lower faces and the peripheral faces of the side rails and having excellent installability, and to provide manufacturing method for the side rail. SOLUTION: This combination oil ring 1 comprises the two side rails 3, 4 and the spacer expander 5. The upper face 4a of the side rail 4 on the lower side is formed with a recess 6 opened on the inner circumferential side by pressing, and the inner circumferential side of the recess 6 is formed with a protrusion 7. The protrusion 7 has 0.05-0.15 mm projection, a maximum length in the circumferential direction of 0.5-(a distance between adjacent lug parts of the spacer expander 5-0.05) mm, and 3-30 mm distance from an abutment end face 2a of the side rail 4 to the center of the protrusion 7. A side rail lower face 4b portion opposite to the recess 6 is a flat surface. The lower face of the side rail 3 on the upper side is formed with a recess, and the inner circumference is formed with a protrusion.
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