Combined oil ring

3:

• The combined oil ring according to claim 2, wherein
• a difference between the inclined angles of the upper inclined surface and the lower inclined surface (Δθ=θ2−θ1) is defined to be at least 5 degrees or more and 20 degrees or less.

4:

• The combined oil ring according to claim 1, wherein
• the anti-tilt device has contact surfaces on inner peripheral sides of the upper side rail and the lower side rail contacting with the upper seating tab portion and the lower seating tab portion respectively being formed in an asymmetrical shape with respect to a center line substantially in parallel to a horizontal direction of the piston.

6:

• The combined oil ring according to claim 4, wherein
• in a position where the inner peripheral upper portion and the inner peripheral lower portion are continuous with each other, there is a linear portion substantially in parallel to the axial direction.

7:

• The combined oil ring according to claim 5, wherein
• the radius R of the inner peripheral upper arcuate portion is defined to be ⅓ or more of an axial dimension of the side rail.

8:

• The combined oil ring according to claim 1, wherein
• each in the pair of upper and lower side rails has a tapered shape linearly expanding from up to down of the piston in the sectional shape of the sliding contact portion taken along the axial direction of the piston,
• the tapered shape has an angle of 8 to 12 degrees with respect to the axial direction of the piston and an apex of the tapered shape is located within 0.15 mm from a lower end of the side rails.

9:

• The combined oil ring according to claim 8, wherein
• the apex of the tapered shape is formed in a linear portion extending substantially in parallel to the axial direction of the piston.