Lubrication is the use of oil, grease or other fluid materials to separate the contact surfaces between moving objects, so as to reduce friction, reduce wear, reduce temperature, prevent corrosion and damp vibration.
1、 Classification of lubrication
1. Liquid lubrication;
2. Semi liquid lubrication;
3. Boundary lubrication.
2、 General principles of lubricant selection
(1) First, choose according to the working conditions.Common Iubrication of Equipment
(2) Consider the environment around the lubricant.
(3) The specific characteristics of the friction surface cannot be ignored in the bearings selection of lubricating materials.Common Iubrication of Equipment
(4) It is also necessary to make a reasonable selection according to the actual lubrication method.Common Iubrication of Equipment
3、 Common lubrication methods
1. Manual lubrication
2. Drip lubrication
3. Splash lubrication
4. Lubrication of oil ring, oil chain and oil tanker
5. Lubrication of oil rope and oil pad
6. Forced oil lubrication
7. Pressure circulating lubrication
8. Centralized lubrication
4、 Application of common lubricating oil and grease
1. Application of lubricating oil
(1) General purpose of machine oil
1) Mechanical oils with viscosity grades of l-an5, l-an7 and l-an10 are light lubricating oils, which are mainly used for the lubrication of high-speed and light load mechanical friction parts.Common Iubrication of Equipment
2) L-an15 viscosity grade mechanical oil is mainly applicable to the lubrication of bearings and main shafts of light load mechanical equipment with rotating speed in the range of 1500 ~ 5000r / min. It can be used as the hydraulic system oil of small and medium-sized ordinary mechanical equipment with low system pressure in winter.Common Iubrication of Equipment
3) L-an22 viscosity grade mechanical oil is mainly applicable to the lubrication of bearings and main shafts of light load mechanical equipment with rotating speed in the range of 1200 ~ 1500r / min. It can be used as the hydraulic system oil of ordinary mechanical equipment with low system pressure.Common Iubrication of Equipment
4) L-an32 viscosity grade mechanical oil is mainly applicable to the lubrication of bearings, main shafts and gears of light and medium load mechanical equipment with rotating speed in the range of 1000 ~ 1200R / min. It is widely used as hydraulic system oil of ordinary mechanical equipment.Common Iubrication of Equipment
5) L-an46 viscosity grade mechanical oil is mainly applicable to the lubrication of bearings, main shafts, gears and other friction parts of medium load mechanical equipment with rotating speed below 1000r / min. It is widely used.Common Iubrication of Equipment
6) L-an68 viscosity grade mechanical oil is mainly suitable for the lubrication of mechanical equipment with low speed and heavy load.Common Iubrication of Equipment
7) L-an100 and l-an150 viscosity grades of machine oil are mainly applicable to the lubrication of transmission parts of heavy machinery and equipment with low speed and heavy load and friction parts with easy oil loss.Common Iubrication of Equipment
(2) Example of application of mechanical oil in ordinary mechanical equipment: ordinary mechanical equipment works at room temperature and does not contact with water vapor and corrosive gas. The main technical index of lubricating oil is viscosity. Therefore, mechanical oil is generally used for lubrication.Common Iubrication of Equipment
(3) Characteristics of oil lubrication for typical components
1) In the rolling bearing, there are not only the rolling friction of the rolling body in the raceway, but also the sliding friction between the rolling body and the raceway, between the rolling body and the cage, and between the cage and the inner and outer rings. If the bearing lubrication is poor, under the condition of high-speed rotation, the bearing will be worn, heated, burned, and even damaged. Common Iubrication of Equipment
If the oil is improperly selected and the viscosity is too small, when the pressure per unit area borne by the bearing rolling element is very large, it is easy to cause the fracture of the lubricating oil film and aggravate the wear. If the viscosity of lubricating oil is too large, it will increase the friction resistance of bearing and increase the oil temperature; More importantly, it will affect the flow to the friction surface, which is difficult to form oil film, but harmful to the bearing. Therefore, the main requirement of rolling bearing for lubricating oil is that it must have sufficient viscosity and good stability.Common Iubrication of Equipment
For ball and cylindrical roller bearings using mechanical oil, under medium, low speed and normal temperature conditions, oil with viscosity grades of l-an22, l-an32 and l-an46 can generally be selected. Bearings with high speed and large inner diameter can choose oil with slightly lower viscosity. Bearings with low speed and small inner diameter can choose oil with slightly higher viscosity.Common Iubrication of Equipment
For roller bearings, the viscosity is higher than that of tapered roller bearings under the same axial load as that of tapered roller bearings. Under the condition of constant speed and normal temperature, the oil viscosity of tapered roller bearing and self-aligning roller bearing is low, which is limited to the mechanical oil of l-an32 viscosity grade; The oil viscosity of thrust self-aligning roller bearing is low, which is limited to the mechanical oil of l-an46 viscosity grade.
Needle roller bearing needs more effective lubrication due to its large sliding friction. Therefore, the viscosity grade of the oil should generally be lower than that of ball bearings with the same specification and speed.
As for the oil consumption, if the oil tank is used for lubrication, for the bearing with the speed below 1500r / min, the oil level is allowed to reach the center line of a rolling element below the center of a rolling element below, but only when it contacts the rolling element. If oil dripping lubrication is carried out, under normal circumstances, the low temperature shall not be less than 3 ~ 4 drops per minute.
2) When the sliding bearing is lubricated with oil, the viscosity grade of the oil is related to the diameter of the journal, the rotation speed of the shaft and the load per unit area of the bearing.
3) The lubrication of gear transmission mainly considers the correct lubrication between gear teeth. As for other parts in the gearbox, such as bearings, they are usually lubricated with the same oil as the gear.
4) Reasonable lubrication of the machine tool guide rail can maintain the geometric accuracy of the guide rail for a long time, prolong the service life of the guide rail, improve the motion accuracy of the machine tool, improve the accuracy of the machined parts, and reduce the surface roughness of the machined parts.
Under general working conditions, the sliding guide rail is lubricated with mechanical oil. The oil viscosity shall be selected according to the load and speed of the guide rail, whether it is horizontal or vertical, and whether the ambient temperature is low or high. Table 1-15 shows the viscosity grades of common oils for ordinary machine tools and heavy machine tools, which can be used for reference.
When selecting the oil for the guide rail, one problem worthy of attention is to help overcome the crawling phenomenon of the guide rail under the condition of low-speed movement. Although there are many reasons for crawling phenomenon, the large difference between dynamic friction coefficient and static friction coefficient between guide rails is an important factor. In terms of lubrication, appropriately increasing the viscosity of the oil or adding some additives to make the lubricating oil have good oiliness and adsorption, and improving the strength of the oil film can significantly reduce the difference between dynamic and static friction coefficients and improve the creep resistance of the guide rail. The commonly used anti creeping oil is to add 5% sulfurized cottonseed oil, 5% sulfurized whale oil, or 0.3% stearic acid and other oily additives to the l-an68 viscosity grade mechanical oil.
5) The characteristics of chain lubrication are many lubrication points and large impact load. If the speed is high in the transmission, it is easy to throw out the oil, and the lubricating oil can only enter between the pin shaft and the roller through the gap between the chain pieces and between the chain pieces and the end face of the roller, which increases the difficulty of lubrication. Therefore, the requirements of the transmission chain for oil are: it must have good oiliness, high permeability and anti-oxidation stability. In this way, the oil can not only penetrate into each friction surface, but also not be thrown out and squeezed out, and the oxidation speed can be delayed in case of contact with air.
For transmission chains with different lubrication methods, it should be noted during maintenance that manual lubrication is only applicable to unimportant transmission with chain speed less than 4m / s, and oil should be filled with oil pot or brush every 15 ~ 25h. Oil dripping lubrication is only applicable to the transmission with chain speed less than 10m / s. It is required to adjust the position of oil dripping needle valve accurately so that the oil must drip on the chain piece. Oil bath lubrication is applicable to the transmission with chain speed of 6 ~ 12m / s. The depth of the chain immersed in the oil pool shall not exceed the height of the chain piece or the tooth height of the sprocket.
When selecting oil, it shall be comprehensively determined according to the transmission speed, working temperature and oil feeding method of the chain. Generally, refer to table 1-16 to determine the viscosity grade of oil.