With the continuous accumulation of impurities on the filter paper, the passability of the filter paper continues to decrease, and the circulation resistance continues to increase, causing the oil pressure on the outside of the filter paper to continue to rise. When the oil pressure is sufficient to open the bypass valve, the oil is no longer filtered by the filter paper, but directly enters the center pipe from the bypass valve, and then enters the engine lubrication system from the oil outlet in the middle of the oil filter base plate to participate in lubrication.

The working principle of oil filter：

        1、When the engine is running, with the operation of the oil pump, the oil with impurities enters the oil filter from the oil inlet on the bottom plate assembly of the oil filter, and passes through the check valve to the outside of the filter paper for filtering. Under the action of oil pressure, the oil continuously passes through the filter paper and enters the center tube, while the impurities in the oil remain on the filter paper；

        2、The oil filter is located in the engine lubrication system. The upstream of the oil filter is the oil pump, and the downstream is the parts that need to be lubricated in the engine. The function of the oil filter is to filter out harmful impurities in the oil, and to supply the crankshaft, connecting rod, camshaft, supercharger, piston ring and other moving parts with clean oil to play the role of lubrication, cooling and cleaning, thereby Extend the life of these parts；

        3、The oil filter is mainly composed of filter paper and housing, as well as auxiliary parts such as sealing ring, support spring, and bypass valve. From the appearance, we see the oil filter as a whole, the filter paper, bypass valve and other parts are invisible. There are two kinds of oil filters in reality: coarse filters and fine filters. The lubrication system also has two filtering methods: full flow and split flow. The coarse oil filter and the fine filter correspond to the full flow type and the split flow type respectively.