Piston rings are metal rings that are used to fit inside the grooves of pistons. There are two types of piston rings: compression rings and oil rings. The compression ring can be used to seal the combustible gas mixture in the combustion chamber; the oil ring is used to scrape excess oil from the cylinder.
A piston ring is a metal elastic ring with a large outward expansion deformation, which is assembled into a section and its corresponding annular groove. Reciprocating and rotating piston rings rely on the pressure difference of gas or liquid to form a seal between the outer surface of the ring and the cylinder and one side of the ring and the ring groove.
By structure A. Monolithic structure: Through casting or monolithic forming. B. Combined ring: Piston ring composed of two or more parts in a ring groove. C. Slotted oil ring: The oil ring is parallel on the side, has two contact ring banks, and has oil return holes. D. Slotted spiral spring oil ring: The oil ring of the spiral spring is placed in the slotted oil ring. The supporting spring can increase the specific pressure in the radial direction, and its acting force on the inner surface of the ring is equal. Common in diesel engines. E. Steel belt combined oil ring: An oil ring composed of a liner ring and two scraper rings. The design of the lining ring varies from factory to factory and is commonly found in gasoline engine rings.
Section shape Bucket ring, cone ring, inner chamfered ring, wedge ring and trapezoidal ring, nose ring, outer shoulder twist ring, inner chamfered ring, steel belt combination oil ring, counter chamfered oil ring, same Chamfered oil ring, cast iron spiral spring oil ring, steel oil ring, etc.
By material Cast iron, steel.
Surface treatment Nitriding ring: The nitride layer has a hardness of more than 950HV and a brittleness of grade 1, and has good wear resistance and corrosion resistance. Chrome-plated ring: The chromium-plated layer has fine and smooth crystals, hardness above 850HV, very good wear resistance, and crisscross micro-crack network, which is conducive to the storage of lubricating oil. Phosphate ring: Through chemical treatment, a layer of phosphate film is generated on the surface of the piston ring, which can prevent the product from rusting and improve the initial running-in of the ring. Oxidation ring: Under the condition of high temperature and strong oxidant, an oxide film is formed on the surface of steel materials, which has corrosion resistance, anti-friction lubrication and good appearance. There are also PVD and so on.
Come by Piston rings include air rings and oil rings. The role of the air ring is to ensure the seal between the piston and the cylinder. Prevent a large amount of high-temperature and high-pressure gas in the cylinder from leaking into the crankcase. At the same time, most of the heat at the top of the piston is conducted to the cylinder wall, and then taken away by cooling water or air. The oil ring is used to scrape off the excess oil on the cylinder wall, and apply a uniform oil film on the cylinder wall. Friction resistance.
Force The forces acting on the piston ring include gas pressure, the elastic force of the ring itself, the inertial force of the ring’s reciprocating motion, and the friction between the ring and the cylinder and the ring groove, as shown in the figure. Due to these forces, the ring will produce basic motions such as axial motion, radial motion, and rotary motion. In addition, due to its motion characteristics, piston rings inevitably appear suspended and axial vibrations caused by axial irregular motions, radial irregular motions and vibrations, twisted motions, etc., along with irregular motions. These irregular movements often prevent the piston ring from functioning. When designing the piston ring, it is necessary to give full play to the favorable movement and control the disadvantage.
Thermal conductivity The high heat generated by combustion is transmitted to the cylinder wall through the piston ring, so it can cool the piston. The heat dissipated to the cylinder wall through the piston ring can generally reach 30 to 40% of the heat on the top of the piston.
Air tightness The first function of the piston ring is to maintain the seal between the piston and the cylinder wall, and to control air leakage to a minimum. This effect is mainly borne by the air ring, that is, under any operating conditions of the engine, the leakage of compressed air and gas must be minimized to improve thermal efficiency; prevent the leakage between the cylinder and the piston or between the cylinder and the ring Bite it; prevent malfunction caused by deterioration of lubricating oil, etc.
Oil control The second role of the piston ring is to properly scrape off the oil attached to the cylinder wall and maintain normal fuel consumption. When too much lubricating oil is supplied, it will be sucked into the combustion chamber, which will increase the fuel consumption, and because of the coke produced by combustion, it will have a bad effect on engine performance.
Supportive Because the piston is slightly smaller than the inner diameter of the cylinder, if there is no piston ring, the piston is unstable in the cylinder and it is impossible to move freely. At the same time, the ring also needs to prevent the piston from directly contacting the cylinder to play a supporting role. Therefore, the piston ring moves up and down in the cylinder, and its sliding surface is all borne by the ring.
Piston rings are widely used in various power machinery, such as steam engines, diesel engines, gasoline engines, compressors, hydraulic machines, etc., and are widely used in automobiles.
Trains, ships, yachts, etc. Generally, the piston ring is installed in the ring groove of the piston, and it forms a chamber with the piston, the cylinder liner, the cylinder head and other components to perform work.