Piston Second Land Tapered Face for Gas Pressure Stability
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Solution Overview
Problem
Existing engine designs experience increased oil consumption and blow-by gas leakage due to reduced rigidity and deformation of ring grooves, leading to unstable sealing performance over prolonged operation.
Innovation Solution
The engine incorporates a tapered face on the second land with a diameter reducing towards the second ring groove, maintaining rigidity and preventing deformation, along with optimized indentation dimensions to suppress gas pressure variations and enhance sealing performance of pressure and oil rings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a groove is formed in the intermediate portion of the outer peripheral face of the second land to create an indentation, then the capacity of the space facing the second land increases and gas pressure variation is suppressed, but the rigidity of the second land is significantly reduced causing piston vibration and ring groove deformation
Solution Approach 1:
The patent applies local quality by forming the indentation only at the corner portion of the second land rather than across its entire surface. This localized approach allows the indentation to increase space capacity and suppress gas pressure variation while preserving the rigidity of the main second land structure. The corner-specific placement ensures that the structural integrity of the second land is maintained while still achieving the desired pressure stabilization effect.
2Stability of the object's composition
If the second land rigidity is reduced due to indentation formation, then gas pressure variation is suppressed, but the piston vibrates and ring grooves become deformed and abnormally worn
Solution Approach 1:
By concentrating the indentation formation specifically at the corner portion of the second land, the patent achieves gas pressure stabilization without compromising the overall structural integrity. The localized corner indentation provides sufficient space capacity increase and pressure variation suppression while leaving the main body of the second land and ring grooves sufficiently rigid to maintain stable sealing performance over prolonged operation.
3Volume of stationary object
If the indentation is formed to increase space capacity, then gas pressure variation during piston movement is suppressed, but the first and second oil rings exhibit unstable behavior and sealing performance degrades
Solution Approach 1:
The patent resolves this contradiction by forming the indentation exclusively at the corner portion of the second land rather than across its entire surface. This localized approach increases the space capacity sufficient to suppress gas pressure variation while preserving the rigidity needed to maintain stable oil ring behavior and sealing performance. The corner-specific placement prevents the structural weakening that would otherwise cause oil ring instability.
Data Source
Figure 1(A)~1(B)
Figure 2(A)~2(B)
AI summary
An engine in which an oil consumption and a leakage of blow-by gas can be stably reduced for a long period of time has a piston including a first land 3, a first ring groove 4, a second land 5, a second ring groove 6, a third land 7, a third ring groove 8, and a piston skirt 9 formed on a piston peripheral wall 1 in this order from the head of the piston. A first pressure ring 10 is fitted in the first ring groove 4; a second pressure ring 11 is fitted in the second ring groove 6; an oil ring 12 is fitted in the third ring groove 8. A corner at a boundary between an outer peripheral face 5a of the second land 5 and a second-land-side end face 6a of the second ring groove 6 is bevelled, with a tapered face 14 having a diameter reducing toward the second ring groove 6 to form an indentation for the suppression of variation in gas pressure in the space 17 facing the second land during upward and downward movements of the piston.