The coarse filter is connected in series between the oil pump and the main oil passage, which is called the full-flow filter, mainly used to remove greater impurities in the oil, and paper filters are widely used at home and abroad.

Paper filter
The paper filter is mainly composed of an upper cover, a shell, a paper filter element and a bypass valve. When the engine works, the lubricating oil with pressure is fed into the cavity around the filter element, and the impurities in the oil will be blocked by the paper filter element, and the cleaner lubricating oil will enter the inner cavity of the filter element, and then enter the main oil passage of the cylinder block through the oil outlet.

The oil filter makes the lubricating oil flow more unimpeded, to avoid impurities scratching the surface of the brushed parts, the oil must be filtered more strictly before it is sent to the friction surface. In order to achieve the filtration effect without increasing the oil resistance, the coarse filter is usually connected to the main oil passage in series, and the fine filter is connected to the main oil passage in parallel.

Centrifugal fine filter
The hollow shaft shall be fixed on the shell, and the rotor body and the end sleeve shall be connected into one, and shall be located on the thrust bearing, which can rotate freely around the rotor shaft. The compression nut fastens the rotor cover and rotor body together, and the upper part is pressed with a spring to limit the axial movement of the rotor, and the rotor is equipped with two opposite nozzles under the rotor. When the engine is running, a small part of the oil is pumped from the oil pump into the filter through the oil port.

Float type oil filter
In order to make the oil pump work better, to remove the large particle impurities in the lubricating oil before entering the oil pump, this task is undertaken by the filter collector. It is connected to the oil inlet of the oil pump, the oil pump is working, the oil is sucked from the narrow gap between the cover and the float, and it will filter out the coarse impurities through the filter, and enter the oil pump through the tubing welded on the float. When the filter is silted, the suction of the inlet pipe increases, and the wire equipment can overcome the strength of the filter screen and make the bad mouth leave the cover, and the oil enters the suction pipe directly from the ring without the filter screen.