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Piston rings are metal rings that are embedded in the grooves of the piston. There are two types of piston rings: compression rings and oil rings. The compression ring is used to seal the combustible mixture in the combustion chamber; the oil ring is used to scrape excess oil from the cylinder.
Piston rings are metal rings that are embedded in the grooves of the piston. There are two types of piston rings: compression rings and oil rings. The compression ring is used to seal the combustible mixture in the combustion chamber; the oil ring is used to scrape excess oil from the cylinder.
The piston ring is a metal elastic ring with large outward expansion deformation, which is assembled into the annular groove corresponding to the cross section. Reciprocating and rotating piston rings rely on the pressure difference of gas or liquid to form a seal between the outer circular surface of the ring and the cylinder and one side of the ring and the ring groove. Among the parts of the engine, the role of the piston ring is very subtle, and a slight defect will affect the performance of the entire engine. Today, I will talk about those things about the piston ring.
What is a triple gap?
The piston ring works in a working environment of high temperature, high pressure, high speed and poor lubrication, and at the same time has good airtight function, oil scraping function and heat conduction function, not only to ensure its sealing performance, but also to prevent the piston ring from being stuck in the ring. groove and cylinder, so three clearances must be left when installing the piston ring.
There are three gaps to be measured when the piston ring is installed, referred to as the three gaps of the piston ring, one is the opening (ring mouth) gap, the other is the axial gap (side gap), and the third is the radial gap (back gap), also known as the end gap. , side clearance, back clearance. Now let's introduce the measurement method of the piston ring three clearance:
Measurement of end gap
The end gap is the gap at the opening after the piston ring is installed in the cylinder to prevent the piston ring from being stuck after thermal expansion. When checking the end clearance of the piston ring, put the piston ring into the cylinder flat, push it flat with the top of the piston, and then measure the clearance at the opening with a thickness gauge, generally 0.25~0.50mm. Due to the high working temperature of the first ring, its end gap is larger than that of the other rings.
Measurement of backlash
Backlash refers to the upper and lower clearance of the piston ring in the ring groove. If the side clearance is too large, the sealing effect of the piston will be affected. If the side clearance is too small, the piston ring will be stuck in the ring groove. When measuring, put the piston ring into the ring groove and measure with a thickness gauge. Due to the high working temperature of the first ring, the value is generally 0.04~0.10mm, and the other gas rings are generally 0.03~0.07mm. The clearance is small, generally 0.025~0.07mm, and the combined oil ring has no side clearance.
Measurement of backlash
Backlash refers to the gap between the back of the piston ring and the bottom of the piston ring groove after the piston is installed in the cylinder. It is generally expressed by the difference between the groove depth and the ring thickness, which is generally 0.30~0.40mm. The backlash of ordinary oil rings is relatively large. The general experience is to put the piston ring into the ring groove, if it is lower than the ring land, it is suitable to rotate freely without feeling stagnant.
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