Development of Low Friction Axial-Type Lip Seals

Reducing the torque of the crankshaft seal of a light vehicle engine is required to improve fuel efficiency. A sprung radial fluoro rubber lip is one of the representative seal types for this application, although axial-silicone-rubber-type lip seals are widely used in diesel engines of buses and trucks. This type of oil seal has low torque because the primary lip load is low. In terms of reliability, it is durable against contamination between the lip and slinger while the shaft is rotating; thus, it has a long life span [1]. This axial-type lip seal was applied to the gasoline engine of a light vehicle to achieve low friction and high reliability. A slight oil leak was observed for the conventional slinger at high shaft speed. To resolve this issue, a new slinger that can prevent leakage has been developed. To clarify the phenomenon, direct observations of the leakage and evaluation of lip followability were conducted. For the developed slinger, the reduction of the gap between the lip and slinger at high shaft speed was confirmed in the evaluation of lip followability. The torque of the developed axial-type lip seal was 60% lower than that of conventional radial-type lip seal. The axial-type lip seal applicable to light vehicle engines has been developed, which features low friction and high reliability.