Because the hyperbolic gear transmission has the characteristics of good meshing smoothness and large reduction ratio, it is widely used in the gear transmission of the automobile rear axle main reducer. However, due to the high transmission pressure (up to 4000MPA) of the hyperbolic gear in the meshing transmission process, the relative slip speed can reach 400M/MIN, which produces a high instantaneous temperature (600～800℃), while the general oily additives It will desorb from the friction surface at about 100°C, and the oil film will be destroyed. Under such extreme pressure conditions, in order to prevent wear, abrasion and adhesion, it is necessary to reduce the friction of the metal contact surface. Therefore, organic compounds containing chlorine, sulfur, phosphorus and other elements are added to the hyperbolic gear oil as extreme pressure additives. Under extreme pressure conditions, these additives react with the metal at the high temperature part of the friction surface, forming a compound whose shear stress and melting point are lower than those of pure metal, that is, a false lubricating layer is formed on the meshing tooth surface to prevent contact with the surface Bite or fusion. This kind of false lubricating layer is formed by the chemical action of various active genes in the friction surface metal and additive molecules. In most cases, the effect of extreme pressure additives depends on the formation of metal sulfides, chlorides, and phosphorus and metal compounds. It can be seen from this that: it relies on "corrosion" of the metal surface to play the role of extreme pressure and anti-wear. Among them, sulfur-containing additives have a strong corrosive effect on non-ferrous metals, especially copper and its alloys. The ferric chloride film formed when the chlorine additives are used is prone to hydrolysis, generating hydrochloric acid, and corroding metals.