1, float type oil collection filter, in order to make the oil pump work well, it is necessary to remove the large particles of impurities in the oil before entering the oil pump, this task is undertaken by the collection filter. It is connected to the oil inlet of the oil pump. When the oil pump works, the oil is inhaled from the slit between the cover and the float. After filtering out the coarse impurities through the filter net, the oil pipe welded on the float enters the oil pump. When the filter screen is silted up, the suction force of the inlet pipe increases to overcome the strength of the filter screen and make the bad mouth leave the cover. Then the oil enters the suction pipe directly from the ring mouth without going through the filter screen.
　　2, the coarse filter in series between the oil pump and the main oil channel, so it is also called the full flow filter, used to remove larger impurities in the oil. It is mainly composed of upper cover, outer shell, paper filter element and bypass valve. When the engine is working, the lubricating oil with pressure is sent into the cavity around the filter element and 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 channel of the cylinder body through the oil outlet.
　　3, fine filter: its role is to filter out smaller impurities in the lubricating oil, usually parallel with the main oil channel, there are centrifugal and board type two.