Piston Ring Width Configuration for Blow-By and Friction Balance
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Solution Overview
Problem
In diesel engines, increasing the number of compression rings to reduce blow-by gas leads to increased piston weight and friction, posing challenges for small engines where weight and friction reduction are crucial.
Innovation Solution
A configuration of three compression rings and one oil ring is used, with optimized axial widths and tension distribution, and a tapered shape for the third compression ring, to minimize friction and weight while reducing blow-by gas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the number of compression rings is increased to reduce blow-by gas, then gas seal performance is improved, but piston weight and friction increase
Solution Approach 1:
The patent changes the physical parameters of the compression rings, specifically making the third compression ring thinner in axial width compared to the first and second rings. This parameter change allows the third ring to have reduced mass and friction characteristics while still maintaining its gas sealing function, thereby resolving the contradiction between improving gas seal performance and increasing piston weight
Solution Approach 2:
The patent applies local quality by giving each compression ring different axial widths tailored to their specific functional requirements. The first and second rings have larger axial widths for primary sealing, while the third ring has a smaller axial width optimized for its position and secondary sealing role. This localized optimization allows the system to achieve overall gas seal performance without uniformly increasing the mass of all rings
2Reliability
If the number of compression rings is increased to reduce blow-by gas, then gas seal performance is improved, but friction increases
Solution Approach 1:
The patent changes the axial width parameter of the third compression ring to be smaller than that of the first and second rings. This parameter change directly reduces the contact area between the third ring and the cylinder bore, thereby reducing friction while maintaining the ring's gas sealing capability at its specific location
Solution Approach 2:
The patent applies local quality by optimizing the axial width of each compression ring according to its specific position and functional requirements. The third ring, positioned lower in the combustion chamber, has a reduced axial width that is sufficient for its local sealing needs, thereby minimizing its contribution to overall friction while maintaining system-wide gas seal performance
3Duration of action of stationary object
If three or more compression rings are used to maintain long-term function, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent applies local quality by assigning different axial widths to different compression rings based on their specific positions and functional requirements. The first and second rings have larger axial widths for primary sealing duties, while the third ring has a smaller axial width optimized for its secondary sealing role. This differentiated design allows the system to achieve enhanced reliability through multiple rings without uniformly increasing the complexity of each individual ring
4Weight of moving object
If the axial width of compression rings is reduced to decrease piston weight, then piston weight is reduced, but ring strength may be compromised
Solution Approach 1:
The patent applies local quality by giving each compression ring different axial widths matched to their specific structural and functional requirements. The first and second rings, which bear higher loads and perform primary sealing, have larger axial widths that ensure sufficient strength. The third ring, positioned lower and performing secondary sealing, has a reduced axial width that is sufficient for its lower load requirements, thereby reducing overall piston weight while maintaining adequate strength distribution
Solution Approach 2:
The patent changes the axial width parameter of the third compression ring to be smaller than the first and second rings. This selective parameter change reduces the mass of the third ring contributing to overall piston weight reduction, while the first and second rings maintain their larger dimensions to ensure sufficient strength for their critical sealing positions
Data Source
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AI summary
A combination of piston rings assembled to a piston includes a first compression ring, a second compression ring, a third compression ring and an oil ring. When an axial width of the first compression ring is h1(1), an axial width of the second compression ring is h1(2), an axial width of the third compression ring is h1(3) and an axial width of the oil ring is h1(4), h1(1) ≥ h1(2) and h1(1) ≥ h1(3), and when h1(TOTAL) = h1(1) + h1(2) + h1(3) + h1(4), h1(TOTAL) ≥ 3.9 mm.