In accordance with the principle of filter, air filter can be divided into filtering, centrifugal, oil bath type, compound type several. At present, the air filter used in the engine mainly has the inertia oil bath type air filter, the paper dry type air filter, the polyurethane filter element air filter and so on.
Inertial oil bath type air cleaner has after inertial filter, oil bath type filter, filter filtration tertiary filtration, two air filter mainly through the filtering type filter. Inertial oil bath type air cleaner has small air resistance, can adapt to dust sandy work environment, the use of long life and other advantages, before in a variety of models of automobile and tractor engine used. But the air filter filtration efficiency is low, heavy weight, high cost, inconvenient maintenance, in the automobile engine has been eliminated gradually.
Made by resin microporous filter paper by dry-type air filter paper filter, filter paper porous, loose, folding, certain mechanical strength and water resistance, has the advantages of high filtration efficiency, simple structure, light weight, low cost, maintenance is convenient wait for a, is currently used most widely used car air filter.
Polyurethane air filter element is made of soft, porous and spongy polyurethane, strong adsorption capacity, the air filter with paper dry-type air filter has the advantages of but low mechanical strength, in the car engine used more widely. After the two kinds of air filter, the disadvantage is that the service life is short, the work is not reliable in harsh environmental conditions.
All kinds of air filters have advantages and disadvantages, but inevitably there are contradictions between the intake and the filtering efficiency. With the in-depth study of the air filter, the requirement of the air filter is higher and higher. In recent years, the emergence of some new type of air filter, such as fiber air filter and complex V type air filter material filter, air filter, thermostatic air cleaner etc. to meet needs of engine.