Piston ring.
Piston ring is used to insert the piston groove inside the metal ring, piston ring is divided into two types: compression ring and oil ring. The compression ring can be used to seal the combustible mixture gas in the combustion chamber; The oil ring is used to scrape excess oil from the cylinder. The piston ring is a kind of metal elastic ring with large outward expansion deformation, which is assembled in the profile 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 circle of the ring and the cylinder and one side of the ring and the ring groove.
Scope of application
Piston rings are widely used in a variety of power machinery, such as steam engines, diesel engines, gasoline engines, compressors, hydraulic presses, etc., widely used in cars, trains, ships, yachts and so on. Generally, the piston ring is installed in the ring groove of the piston, and it and the piston, cylinder liner, cylinder head and other components of the chamber to do work.
Piston ring is the core component inside the fuel engine, it and cylinder, piston, cylinder wall together to complete the seal of fuel gas. Commonly used automotive engines have two kinds of diesel and gasoline engines, due to their different fuel performance, the use of piston rings are not the same, the early piston rings are formed by casting, but with the progress of technology, steel high-power piston rings were born, and with the function of the engine, environmental requirements continue to improve, a variety of advanced surface treatment applications, such as thermal spraying, electroplating, chrome plating, etc. Gas nitriding, physical deposition, surface coating, zinc manganese phosphating treatment, etc., greatly improve the function of the piston ring.
Piston ring function includes sealing, regulating oil (oil control), heat conduction (heat transfer), guidance (support) four roles. Sealing: refers to sealing gas, do not let the combustion chamber gas leakage to the crankcase, the gas leakage is controlled at a minimum, improve thermal efficiency. Air leakage will not only reduce the power of the engine, but also make the oil deterioration, which is the main task of the gas ring; Adjust the oil (oil control) : the excess lubricating oil on the cylinder wall is scraped off, and the cylinder wall is covered with a thin oil film to ensure the normal lubrication of the cylinder and piston and ring, which is the main task of the oil ring. In modern high-speed engines, special attention is paid to the role of piston ring control oil film; Heat conduction: the heat of the piston is transmitted to the cylinder liner through the piston ring, that is, the cooling effect. According to reliable data, 70 ~ 80% of the heat received by the piston top of the uncooled piston is dispersed through the piston ring to the cylinder wall, and 30 ~ 40% of the cooling piston is dispersed through the piston ring to the cylinder wall; Support: The piston ring keeps the piston in the cylinder, prevents direct contact between the piston and the cylinder wall, ensures smooth movement of the piston, reduces friction resistance, and prevents the piston from knocking the cylinder. Generally, the piston of the gasoline engine uses two gas rings and one oil ring, while the diesel engine usually uses two oil rings and one gas ring.
Good and bad identification
The working surface of the piston ring shall not have nicks, scratches, peeling, the outer cylinder and the upper and lower end surfaces shall have a fixed finish, the curvature deviation shall not be greater than 0.02-0.04 mm, the standard subsidence of the ring in the groove shall not exceed 0.15-0.25 mm, and the elasticity and clearance of the piston ring meet the requirements. In addition, we should also check the light leakage of the piston ring, that is, the piston ring is flat in the cylinder, put a small lamp under the piston ring, put a light screen above, and then observe the light leakage gap between the piston ring and the cylinder wall, which shows whether the contact between the piston ring and the cylinder wall is good. Under normal circumstances, the light leak seam of the piston ring measured with a thickness gauge should not exceed 0.03 mm. The length of continuous light leakage seam should not be greater than 1/3 of the cylinder diameter, the length of a number of light leakage gaps should not be greater than 1/3 of the cylinder diameter, and the total length of a number of light leakage should not exceed 1/2 of the cylinder diameter, otherwise, it should be replaced. Piston ring marking GB/T 1149.1-94 specifies that all piston rings required to have a mounting direction shall be marked on the upper side, that is, the side close to the combustion chamber. The rings marked on the upper side include: cone ring, inner chamfer, outer cutting table ring, nose ring, wedge ring and oil ring requiring installation direction, and the upper side of the ring is marked.
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