活塞环作用包括密封、调节机油（控油）、导热（传热）、导向（支承）四个作用。 密封：指密封燃气，不让燃烧室的气体漏到曲轴箱，把气体的泄漏量控制在最低限度，提高热效率。漏气不仅会使发动机的动力下降，而且会使机油变质，这是气环的主要任务； 调节机油（控油）：把气缸壁上多余的润滑油刮下，同时又使缸壁上布有薄薄的油膜，保证气缸和活塞及环的正常润滑。在现代高速发动机上，特别重视活塞环控制油膜的作用； 导热：通过活塞环将活塞的热量传导给缸套，即起冷却作用。据可靠资料认为，活塞顶所受的的热量中有70～80%是通过活塞环传给缸壁而散掉的； 支承：活塞环将活塞保持在气缸中，防止活塞与气缸壁直接接触，保证活塞平顺运动，降低摩擦阻力，而且防止活塞敲缸.

The functions of piston rings include sealing, oil regulation (oil control), heat conduction (heat transfer), and guidance (support). Sealing: refers to sealing the gas, preventing the gas in the combustion chamber from leaking to the crankcase, controlling the gas leakage to a minimum, and improving thermal efficiency. Leakage will not only reduce the power of the engine, but also deteriorate the oil, which is the main task of the gas ring; Oil regulation (oil control): scrape off the excess lubricating oil on the cylinder wall, and at the same time make a thin oil film on the cylinder wall to ensure the normal lubrication of the cylinder, piston and ring. In modern high-speed engines, special attention is paid to the role of piston rings in controlling the oil film; Heat conduction: The heat of the piston is transferred to the cylinder liner through the piston ring, which plays a cooling role. According to reliable information, 70-80% of the heat received by the piston top is dissipated by transferring it to the cylinder wall through the piston ring; Support: The piston ring keeps the piston in the cylinder, preventing the piston from directly contacting the cylinder wall, ensuring the smooth movement of the piston, reducing friction resistance, and preventing the piston from knocking the cylinder