Oil seal is a common oil seal element, in the air compressor, oil seal is generally used for the main engine head oil seal. The general head cost of the main engine basically accounts for 1/3 of the air compressor, and the cost of oil seal or oil seal sleeve is relatively much lower. The sealing state of the oil seal, one is the static seal between the outer edge of the oil seal and the cavity, and ensure the reliable positioning of the outer edge of the oil seal between the cavity. The second is the sealing state between the oil seal lip and the shaft. When the shaft rotates, it is dynamic sealing, and when the shaft is static, it is static sealing. The oil seal is mainly composed of sealing body, reinforcing skeleton and self-tightening spiral spring. The sealing body is divided into bottom, waist, cutting edge and sealing lip according to different parts. The oil seal is mainly composed of sealing body, reinforcing skeleton and self-tightening spiral spring. The sealing body is divided into bottom, waist, cutting edge and sealing lip according to different parts.