Three-Compression-Ring Piston Structure for Low Blow-By Sealing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In spark ignition engines, reducing blow-by gas while minimizing friction and piston weight is challenging, especially in high-output gasoline engines where increasing the number of compression rings is difficult due to weight and friction concerns.
Innovation Solution
A configuration of three compression rings and one oil ring is assembled to the piston, with specific tension and diameter ratios, and a tapered outer peripheral surface on the third compression ring, along with a spacer expander in the oil ring, to enhance sealing and reduce friction.
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 applies parameter changes by specifying precise tension relationships between rings (Ft(1) > Ft(3) and Ft(TOTAL)/d1 ≤ 0.68 N/mm) and geometric parameters (torsional angle of 20' ± 40' for the third ring). This allows three compression rings to achieve effective sealing while controlling total tension to minimize friction and weight impact, resolving the contradiction between seal performance and weight/friction.
Solution Approach 2:
The third compression ring features a tapered outer peripheral surface with specific torsional angle (20' ± 40'), creating local quality enhancement at the sealing interface. This localized geometric optimization improves gas seal performance without requiring additional rings, thereby avoiding increased piston weight and friction.
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 controls friction by limiting the total tension parameter Ft(TOTAL)/d1 to ≤ 0.68 N/mm while maintaining effective sealing with three rings. This parameter optimization ensures adequate gas seal performance while keeping friction within acceptable limits, resolving the contradiction between seal quality and friction.
3Reliability
If three compression rings are assembled to the piston, then blow-by gas is reduced, but piston axial length and weight increase
Solution Approach 1:
The patent optimizes axial length by controlling ring thickness parameters (h1(1), h1(2), h1(3)) and land portion lengths (Lp2, Lp3, Lp4) to satisfy specific relationships. This allows effective sealing with three compression rings while minimizing the increase in piston axial length and weight, resolving the contradiction between seal performance and dimensional constraints.
Data Source
Figure 1
Figure 2
Figure 3
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 hl(2), an axial width of the third compression ring is hl(3) and an axial width of the oil ring is h1(4), h1(1) ≥ h1(2) and h1(1) ≥ h1(3), and when hl(TOTAL) = h1(1) + h1(2) + h1(3) + h1(4), h1(TOTAL) ≥ 3.1 mm.