Planetary reducer is a transmission mechanism, which needs to transmit torque to the working machine through the shaft and bearing, so the relationship between transmission efficiency and quality is directly related to the bearing. The sliding quality and life of the bearing will affect the overall quality and performance of the planetary reducer. The bearing has the following functions in the planetary reducer: ① prevent the loss of lubricating oil when the gear is used inside the bearing, and ensure that the bearing is in a lubricating state; ② Prevent the dust or harmful gas outside the bearing from entering the bearing cavity to prevent bearing damage; ③ It can support the gear shaft or connecting rod between turns.
The following focuses on the impact of bearing water inflow on the planetary reducer bearing.
1. Corrosion and oil emulsification: water directly corrodes the bearing surface to form iron oxide. The water and the acid in the oil (produced by the presence of water) together increase the corrosion potential and increase the electrochemical corrosion of the bearing. When abrasive particles appear on the metal surface, rust and corrosion will lead to rapid deterioration of the surface. The base metal is exposed after the metal corrosion surface is worn, and it is easier to be corroded in the presence of water and acid. Etching and pitting on the bearing raceway and rolling body caused by corrosion damage the oil film structure, causing contact fatigue and wear of the bearing. Water promotes the emulsification of oil. After emulsification of oil, it will not only reduce the lubrication effect but also bring serious consequences. For example, the emulsion may break the oil film at the bearing and other parts, and increase the friction and cause the bearing to overheat.
2. Destroy the oil film strength. Rolling element bearings rely on the viscosity of oil to establish a key clearance to carry the load. The reason why the oil film can bear great load is that the viscosity of lubricating oil increases with the pressure, while water does not have this property. Therefore, when a small water droplet is brought into the load area, the oil film gap will be lost, and collision or dry friction will occur, which will lead to the possibility of fatigue cracks, pits and peeling on the rolling contact surface. Water can flash or explode superheated steam in the load area, which can rapidly damage the oil film and cause potential fracture surface, and worsen the lubrication effect. Water pollution also increases the ability of oil to carry air, which increases the cavitation in the oil, weakens the oil film, causes oxidation, and leads to local surface fatigue and corrosion.
3. Hydrogen embrittlement. In some cases, water will be decomposed into oxygen atoms and hydrogen atoms under the high pressure generated in the load area of rolling bearing, and hydrogen will be generated during hydrolysis and corrosion. The hydrogen produced in the process can be absorbed into the surface of the bearing raceway, resulting in the deterioration of the bearing material performance. After the bearing is corroded by hydrogen, the material under its raceway surface is easy to crack. When some cracks spread to the surface, it may cause pitting and peeling. Due to additives (extreme pressure additives, anti-wear additives, etc.), sulfide in lubricating oil and environment will accelerate the formation of cracks.
Through the above analysis, it is known that water entering the bearing will have a great impact on the planetary reducer bearing. Therefore, it is necessary to prevent water entering the bearing, so as to ensure the safe and stable operation of the planetary reducer bearing.