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In the seal ring used for the rotating portion of the automatic transmission, we have developed a seal ring in which the wear of the ring is reduced to 1/10 under PV-value of 12MPa · m/s and equivalent at PV-value of 30MPa·m/s and also the frictional torque of the rotating portion is reduced to 1/2 when compared with the conventional PTFE seal ring. This has been achieved by means of improvement of the oil pocket's shape, size, and the distance between oil pockets equally spaced on the side surface of the seal ring.

In automotive automatic transmissions, seal rings made of cast iron or polytetrafluoroethylene (PTFE) have conventionally been installed between the rotary shaft and housing to prevent oil leakage. Recent trends have indicated that there is an increase in the number of cars with automatic transmissions (1)*, and leakage past the seal rings has become more critical from a functional view point. In this presentation, the leakage phenomena will be discussed, and seal rings with an improved shape and material will be introduced. The result of this design is a lower rate of leakage.