What is an oil seal?

What is an oil seal?

An oil seal is simply a mechanical component used to seal oil. To ensure smooth operation, friction points in machinery are often oiled, and oil seals are used to prevent this oil from leaking through the gaps in the machinery. However, with the advancement of mechanical technology, oil seals are also needed to prevent the leakage of water and chemical liquids, as well as the intrusion of dust and sand.

As shown in Figure 1, sealing devices include not only oil seals but also O-rings, lip seals, packing seals, and mechanical seals. Oil seals are the most common and representative seal used on rotating shafts.

Let's use a car as an example to explain how oil seals are used. Figure 2 shows an example of an oil seal used in a car engine. The reciprocating motion of the piston is converted into rotational motion by the connecting rod. The crankshaft is supported by metal bearings. To lubricate these bearings and other similar sliding parts, engine oil is stored in the oil pan. Because the oil pan is fixed to the crankcase, there must be a "gap" between the stationary crankcase and the rotating crankshaft. The sealing device that prevents leakage in these "gaps" between the rotating shaft and the case and between the reciprocating shaft and the case is an oil seal.
 

(Figure 3.) shows an example of an oil seal being used in a geared motor.
 

■The function of each part of the oil seal

(Figure 4.) shows the names of the various parts of the oil seal, (and Table 1.) shows the functions of the various parts of the oil seal.

〈Table 1.〉 Functions of various parts of the oil seal