With the continuous enhancement of the engine, the piston's thermal load is higher and higher, and the conventional cooling cannot meet the requirements. In order to ensure the performance of the engine, the structural measures of oil injection cooling on the top of the piston are adopted. In recent years, it has been widely used to install special cooling nozzles on the lubricating oil channel of the body, and the forced injection of oil cooling on the top of the piston inner cavity. In use to ensure that the cooling nozzle flow, effective, otherwise they will not spray cooling and make the piston at the top and raise the temperature of the first ring groove, causing the piston at the top of the unusual expansion, ablation, even cylinder; The temperature of the ring groove increases the oil cementation, causing the engine failure.