Lubricating oil is a kind of liquid lubricant used in various types of machinery to reduce friction and protect machinery and processing parts. It mainly plays the role of lubrication, cooling, rust prevention, cleaning, sealing and buffering.
1. cooling, it is required to discharge the friction heat out of the machine at any time;
2. reduce friction and wear resistance, reduce friction resistance to save energy, reduce wear to extend the mechanical life and improve economic benefits;
3. sealing, it is required to prevent leakage, dust and gas leakage;
4. anti corrosion and rust prevention, and it is required to protect the friction surface from oil deterioration or external erosion;
5. clean and wash, and clean and remove the scale of friction area;
6. stress dispersion buffer, decentralized load, mitigation of impact and shock absorption;
kinetic energy transmission, hydraulic system, remote control motor and stepless friction speed change, etc.
When the engine is running, dry friction will occur if some friction parts are not properly lubricated. The practice shows that the heat produced by dry friction in a short time is enough to melt the metal, and cause the damage of the machine parts and even jam (the main reason is that many leaking or leaking vehicles have problems such as cylinder pulling and axle holding). Therefore, the friction parts in the engine must be well lubricated. When the lubricating oil flows to the friction part, it will adhere to the friction surface to form a layer of oil film, reducing the resistance between friction parts, and the strength and toughness of the oil film is the key to play its lubrication role.
Only a small part of the heat generated by fuel combustion in the engine is used for power output, friction resistance consumption and auxiliary mechanism driving; the rest of the heat is discharged to the atmosphere with exhaust gas, and will be taken away by the cooling medium in the engine. The excess heat in the engine must be discharged from the engine body, otherwise the engine will burn out due to excessive temperature. On the one hand, it is done by the engine cooling system, on the other hand, it is carried out by lubricating oil after absorbing heat from the surface of cylinder, piston, crankshaft and so on.
Many dirt will be produced during engine operation. For example, sand and dust brought by inhalation air, carbon deposit formed after combustion of mixed gas, rubber formed after oxidation of lubricating oil, metal debris generated by friction between machine parts, etc. These dirt will be attached to the friction surface of the machine, if not cleaned, it will increase the wear of the machine. In addition, a large amount of gum will make the piston ring bond and stick, which will cause the engine to not work normally. Therefore, these dirt must be cleaned in time, and the cleaning process is completed by circulating the lubricating oil in the body.
There is a certain gap between the cylinder and piston, piston ring and ring groove of the engine, as well as between the valve and the valve seat, so as to ensure that the movement pairs will not jam. But these gaps can cause the cylinder seal to be bad, and the combustion chamber leakage results in the reduction of cylinder pressure and engine output power. The oil film formed by lubricating oil in these gaps ensures the sealing of the cylinder, maintains the cylinder pressure and engine output power, and can prevent the exhaust gas from flowing down into the crankcase.
When the engine is running or stored, the air, lubricating oil, water in fuel and the acid gas produced by combustion will cause corrosion and corrosion to the parts, thus increasing the damage of friction surface. The oil film formed by lubricating oil on the surface of the machine can avoid direct contact between the parts and water and acid gas, and prevent corrosion and corrosion.
Eliminate impact load
At the end of compression stroke, the mixture starts to burn and the cylinder pressure rises sharply. At this time, the lubricating oil in the bearing clearance will ease the impact load on the piston, piston pin, connecting rod, crankshaft and other parts, so that the engine can work smoothly, and prevent direct metal contact and reduce wear.