In the lubrication system, the oil filter in order to make the lubricating oil flow unimpeded, avoid impurities from scratching the surface of the parts, the oil must be strictly filtered before it is sent to the friction surface. In order to achieve a satisfactory filtering effect without increasing the resistance of the oil passage, the coarse filter is generally connected in series with the main oil passage, and the fine filter is connected in parallel with the main oil passage.

1. Float type oil filter, in order to make the oil pump work well, the large particles in the lubricating oil must be removed before entering the oil pump. This task is undertaken by the filter. It is connected to the oil inlet of the oil pump. When the oil pump is working, the oil is sucked in from the slit between the cover and the float, filtered through the filter screen to remove coarse impurities, and then enters the oil pump through the oil pipe welded to the float. When the filter screen is blocked, the suction force of the oil inlet pipe increases. Overcoming the strength of the filter screen, the broken port leaves the cover, and the oil enters the oil suction pipe directly from the ring port without passing through the filter screen.

2. The coarse filter is connected in series between the oil pump and the main oil passage, so it is also called a full-flow filter to remove larger 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 sent into the cavity around the filter element, the larger impurities in the oil are blocked by the paper filter element, and the clean lubricating oil enters the inner cavity of the filter element and then passes through the oil outlet Enter the main oil passage of the cylinder block.

3. Fine filter: Its function is to filter out smaller impurities in the lubricating oil. It is usually connected in parallel with the main oil passage and has two types: centrifugal and cardboard.

4. The structure of the centrifugal fine filter: the hollow shaft is fixed on the shell, and the rotor body and the end sleeve are connected as a whole, which is located on the thrust bearing and can rotate freely around the rotor shaft. A compression nut fastens the rotor cover and the rotor body together. The upper part is compressed by a spring to limit the axial movement of the rotor. Two nozzles that are opposite to each other are installed under the rotor. When the engine is running, a small part of the oil is pumped from the oil pump and enters the filter through the oil port. When the oil pressure is lower than 9s kPa, the oil inlet pressure limiting valve is closed and the fine filter does not work. When the oil pressure exceeds 98 kPa, the pressure limiting valve is gradually opened, and the oil is sprayed from the oil outlet through the center hole of the rotor shaft. Then it enters the rotor body through the oil hole and ejects from the two nozzles, so the jet reaction force pushes the rotating hand to rotate. When the oil pressure rises to 294 kPa, the rotation speed of the rotor can reach 5000r/min or more. The impurity in the lubricating oil in the rotor cavity has a larger specific gravity than the lubricating oil. Under the action of the rotating centrifugal force, it is thrown to the rotor wall and Attach the cover to the wall. The clean lubricating oil at the center enters the two nozzles from the center and continuously sprays outward, and the sprayed lubricating oil flows back to the lower crankcase.

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