What is the function of the compression ring?
1 Answers
Compression rings, also known as piston rings, serve to ensure the seal between the piston and the cylinder wall, preventing high-temperature, high-pressure combustion gases in the cylinder from leaking into the crankcase. Additionally, they transfer the majority of the heat from the piston crown to the cylinder wall, which is then dissipated by cooling water or air. The four main functions of compression rings are as follows: 1. Oil control function: They evenly distribute the oil splashed or sprayed onto the cylinder wall and scrape off excess oil. The scraped oil flows back to the crankcase through the gap between the piston and cylinder liner and the oil drain holes in the piston grooves. The oil ring controls 70% to 90% of the oil, while the compression rings control 10% to 20%. 2. Support function: During the synchronous reciprocating motion of the piston and piston rings, the piston exerts a significant normal force (reciprocating inertia force) on the piston rings. When the connecting rod exerts a side force on the piston, causing it to tilt, the piston rings apply a frictional reaction force due to the normal force, thereby supporting the piston. 3. Heat conduction function: Approximately 70% of the heat from the piston is conducted through the piston ring faces to the cylinder wall, with the top and second rings playing the primary role in heat conduction, ensuring the piston's thermal balance. 4. Sealing function: During the compression and power strokes, the piston rings seal the downward-moving gases. The top ring seals 80% to 90% of the gases, the second ring seals 10% to 20%, and the third ring (oil ring) seals about 5% of the gases.
