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The role of motor bearing grease and lubrication method

by:JNSN     2021-12-26
Rolling bearing is an important mechanical component. Whether the performance of a motor can be fully utilized depends on whether the bearing is properly lubricated. It can be said that lubrication is a necessary condition to ensure the normal operation of the bearing. It is useful for improving the bearing capacity and use of the bearing. Life span plays an important role. Motor bearing models are generally lubricated with grease, but they are also lubricated with lubricating oil. 1 Lubrication purpose The purpose of bearing lubrication is to form a thin film of oil between the surface of the rolling element or the sliding surface to prevent direct metal contact. Lubrication reduces the friction between metals and slows down their wear; the formation of oil film increases the contact area and reduces the contact stress; ensures that the rolling bearing can operate normally for a long time under high-frequency contact stress and prolongs the fatigue life; eliminates frictional heat and reduces The working surface temperature of the bearing can prevent burns; it can prevent dust, rust and corrosion. Oil lubrication is suitable for high-speed bearings and can withstand a certain degree of high temperature, and it also plays a role in reducing bearing vibration and noise. Oil lubrication is roughly divided into: 3.3 Splash lubrication Splash lubrication is a commonly used lubrication method for rolling bearings in closed gear transmissions. It uses rotating parts such as gears and oil slingers to splash the lubricating oil. It is scattered on the bearing or flows into the pre-designed oil groove along the box wall into the rolling bearing to lubricate the rolling bearing, and the used lubricating oil can be recycled and reused in the box. Because rolling bearings do not require any auxiliary facilities when splash lubrication is used, they are often used in simple and compact gear transmissions. However, the following three points should be paid attention to when using splash lubrication: 1) The lubricating oil level should not be too high, otherwise the stirring oil will lose too much, and the oil will be lost. The orifice drips oil to the bearing to lubricate the bearing. The amount of oil used at the orifice root can be adjusted. The advantages of this lubrication method are: simple structure and easy to use; disadvantages: the viscosity is not easy to be too high, otherwise the oil will not drip smoothly, which will affect the lubrication effect. Therefore, it is generally used for low-speed and light-load rolling bearing lubrication. Oil bath lubrication is also called immersion oil lubrication, which is to immerse the bearing part in the lubricating oil, so that each rolling element of the bearing can enter the lubricating oil once during the operation, and bring the lubricating oil to other working parts of the bearing. Taking into account the stirring loss and temperature rise, in order to slow down the aging speed of lubricating oil, generally oil bath lubrication is not easy to use in high-speed bearings. The sediment in the pool, such as wear debris, is brought into the bearing part, causing abrasive wear. 2) The lubricating oil in the box should always be kept clean, and the magnetic adsorber can be used in the oil pool to remove the wear debris and foreign matter in time to reduce the occurrence of abrasive wear. 3) In the structural design, an oil storage tank and an orifice leading to the bearing can be set on the tank wall, so that the bearing is similar to the state of oil bath lubrication or drip lubrication, supplementary lubrication, and prevent insufficient oil supply. Oil circulating lubricating oil circulating lubrication is a way to actively lubricate the rolling bearing parts. It uses an oil pump to suck the lubricating oil from the oil tank, introduce it into the rolling bearing seat through the oil pipe and the oil hole, and then return the oil to the oil tank through the oil return port of the bearing seat, and use it after cooling and filtering. Therefore, this lubrication method can effectively dissipate frictional heat while dissipating more heat, so it is suitable for bearing support with large loads and high speeds. Oil injection lubrication is a kind of oil circulating lubrication. However, in order to allow the lubricating oil to fully enter the internal relative moving surface of the high-speed bearing, and at the same time to avoid excessive temperature rise and excessive frictional resistance due to the excessive circulating oil supply under high-speed operation conditions, the oil enters the bearing seat A nozzle is added to the port, and the oil supply pressure is increased, and the oil is sprayed onto the bearing by the nozzle to achieve lubrication and cooling of the bearing. Therefore, oil injection lubrication is a good lubrication method, mainly used for high-speed rolling bearings, and can be used for rolling bearings where the dmn value is greater than 2000000mm·r/min. The pressure of the oil pump for oil injection lubrication is generally about 3 to 5 bar. In order to overcome and avoid the wall effect under high-speed conditions, the injection speed of the nozzle outlet must reach more than 20% of the linear velocity of the rolling bearing. Oil mist lubrication is a kind of micro-lubrication, which uses a small amount of lubricating oil to meet the lubrication requirements of rolling bearings. Oil mist lubrication is to turn lubricating oil into oil mist in the oil mist generator, and lubricate the bearing through the oil mist. Because the oil mist condenses into oil droplets on the working surface of the rolling bearing, in fact the rolling bearing still maintains a thin oil lubrication state. When the linear velocity of the rolling element of the bearing is very high, oil mist lubrication is often used to prevent other lubrication methods from increasing the internal friction of the oil due to excessive oil supply and increasing the working temperature of the rolling bearing. Generally, the oil mist pressure is about 0.05 to 0.1 bar. However, the following two points should be paid attention to when using this lubrication method: 1) The viscosity of the oil should generally not be higher than 340mm2/s (40°C), because too high viscosity will not achieve the atomization effect. 2) The lubricated oil mist may partly escape with the air and pollute the environment. When necessary, an oil-gas separator can be used to collect oil mist, or a ventilation device can be used to remove exhaust gas. The oil-air lubrication uses a piston type quantitative distributor to send a small amount of oil to the compressed air stream in the pipe at regular intervals, forming a continuous flow of oil on the pipe wall and providing it to the bearing. Since new lubricating oil is often fed in, the oil will not age. Compressed air makes it difficult for external impurities to penetrate the inside of the bearing. The micro-supply of oil reduces the pollution to the surrounding environment. Compared with oil mist lubricating oil, oil-air lubrication has less and more stable quantity, small friction torque and low temperature rise. It is especially suitable for high-speed bearings.
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