What is the reason why the valve of gasoline micro-tiller injects oil into the air filter?

When the piston moves, the gas passes through the exhaust port of the engine and enters the filter through the pipeline to cause spray. The filter is responsible for filtering the air entering the carburetor or EFI mechanism. On different models, the positions are slightly different, but they are all located in front of the carburetor or throttle body. Generally, it is a plastic cover, and the filter element is replaceable and clean, which requires regular maintenance.