The functions and working principles of different types of oil filters

The oil filter plays a crucial role in the engine. It can effectively filter out metal shavings, mechanical impurities and oxides from the engine oil. Once these impurities enter the lubrication system randomly with the oil, they will accelerate the wear of engine components and may even lead to the blockage of oil pipes or oil passages.

First, let's introduce the oil filter. It usually adopts a filter screen design and is installed before the oil pump to prevent large particle impurities from entering the oil pump. The filter collector is divided into two types: floating type and fixed type. The floating oil filter can draw in relatively clean engine oil from the oil surface, but the foam on the oil surface is also prone to being sucked in, thereby affecting the oil pressure and making the lubrication effect less stable. The fixed type oil filter is installed below the oil surface. Although the cleanliness of the oil it sucks is slightly inferior to that of the floating type, it can prevent foam from being sucked in, provide stable and reliable lubrication, and has a simple structure. Currently, it has become the first choice for automotive engines.

Next comes the full-flow oil filter, which is connected in series between the oil pump and the main oil passage to ensure that all the engine oil is filtered through it. At present, most car engines adopt full-flow oil filters. There are various types of filter elements for this type of filter, among which paper filter elements are widely used due to their highly efficient filtration performance. Paper filter element oil filters are divided into two structures: detachable and integral, which respectively have the characteristics of easy replacement and overall replacement. In addition, the full-flow oil filter is also equipped with a bypass valve. When the filter element is severely clogged with impurities, the oil pressure rises. Once it reaches a certain pressure value, the bypass valve opens, allowing the unfiltered oil to directly enter the main oil passage to ensure the normal operation of the lubrication system.

For large trucks, especially heavy-duty ones, the engine usually adopts a combination of full-flow and split-flow oil filter layout. The full-flow filter is mainly responsible for filtering impurities with a particle diameter of 0.05mm or more, while the split-flow filter further filters out tiny impurities with a particle diameter of 0.001mm or more, and only processes 5% to 10% of the oil supply from the oil pump. The split type fine filter is further divided into two types: the filtering type and the centrifugal type. Among them, the centrifugal type oil fine filter is widely used due to its highly efficient centrifugal separation technology. This type of filter is equipped with a rotor inside, which is supported on the shaft by rolling bearings. The rotor is driven to rotate at high speed by the working pressure of the lubrication system itself. Under the action of centrifugal force, solid impurities are separated and accumulated on the inner wall of the rotor.

Finally, let's introduce the centrifugal oil filter. Its features lie in stable performance, reliable structure and no need to replace the filter element. Just disassemble the rotor regularly and clean the accumulated dirt to reuse it, and it has a relatively long service life. However, its drawbacks are also obvious, including complex structure, high price and heavy weight, etc. At the same time, it has high requirements for the technical level of maintenance personnel.