Axial Movement of Piston Rings in the Groove

Abstract

The axial movement of piston rings is presumed to be connected with the increase of a blow-by, engine noise, wear, ring breakage etc. The first and second ring movements in each groove, and the pressure changes in the combustion chamber (p₁) and in the space between the top and second ring (p₂) have been measured simultaneously in a high speed automobile engine, using the rectangular “floating” taper-face and L-type piston rings. The results are as follows: 1. The top ring lifts up when pressure p₁ becomes equal to p₂. In this case, however, gas leakage does not increase. As long as the top ring's posture is normal, it never lifts. 2. The second ring lifts up before TDC at higher than any critical speed because p₂ is very low and inertia force is large. In this case, gas leakage increases greatly. 3. In case of the taper face ring as a second one, the larger the taper angle, the lower the critical speed. 4. L-ring movement is complicated because it is laid in arch-shape on the lower surface of groove.