US Patent 10060532 Oil seal

An oil seal, which is provided on an outer circumference of a crankshaft to prevent leakage of two fluids such as a lubricating oil and an engine oil, includes: a first seal that seals a flywheel side; a second seal that seals an engine side; a pressure release hole provided to at least one of the first seal and the second seal so that a space surrounded by the first seal, the second seal and the crankshaft is in communication with one of the flywheel side and the engine side through the pressure release hole; and a partitioning lip provided between the first seal and the second seal to divide the space.