2. The coarse filter is connected in series between the oil pump and the main oil passage, so it is also called the full-flow filter to remove the impurities in the oil. It is mainly composed of upper cover, shell, paper filter element and bypass valve. When the engine is working, the lubricating oil with pressure is fed into the cavity around the filter element. The larger impurities in the oil are blocked by the paper filter element, while the clean lubricating oil enters the inner cavity of the filter element and then enters the main oil passage of the cylinder through the oil outlet.
　　3, fine filter: its role is to filter out smaller impurities in the lubricating oil, usually with the main oil channel in parallel, there are centrifugal and board type two.
　　4. Structure of centrifugal fine filter: the hollow shaft is fixed on the shell, and the rotor body and end sleeve are connected together. It is located on the thrust bearing and can rotate freely around the rotor shaft. The compression nut fastens the rotor cover to the rotor body, and the upper part is pressed by a spring to restrict the axial movement of the rotor, which is equipped with two opposite nozzles. When the engine is running, a small part of the engine oil is pumped from the oil pump into the filter through the oil port. When the oil pressure is lower than 9s kpa, the inlet pressure limiting valve is closed, and the fine filter does not work. When the oil pressure exceeds 98 kpa, the pressure limit valve gradually opens, the oil through the central hole of the rotor shaft, from the oil hole. Then it enters the rotor body through the oil hole and sprays out from the two nozzles. When the oil pressure rises to 294 kpa, the rotor speed can reach more than 5000r/min. The proportion of impurities in the lubricating oil in the inner chamber of the rotor is larger than that of the lubricating oil. Under the action of rotating centrifugal force, it is thrown to the rotor wall and attached to the cover on the wall. Clean oil at the center, from the center into the two nozzles, constantly spray outward, ejected oil flow back to the lower crankcase.
　　This paper is sorted out by dongguan oneness filtration technology co., LTD