In the mechanical operation, the friction between the bearing and oil seal will lead to oil temperature increasing and cracking and produce painting film by acidic substances and PTFE surface, resulting in failure of oil seal. In order to realize the temperature decreasing of the lubricating oil flowing andavoid oil seal failure due to the rise of temperature and improve the sealing performance of oil seal, thread groove is carved in the oil seal lip to let the oil film produce the inward suction.