Curved Concave Piston Ring Undercut for Oil Seal Performance
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Solution Overview
Problem
In internal combustion engines, piston rings with undercuts can lead to increased oil consumption due to oil flowing onto the undercut surface and between the piston ring and the ring groove, resulting in oil leakage on the combustion chamber side.
Innovation Solution
A piston ring design featuring a curved concave surface on its outer peripheral end, with a specific inclination angle and curvature radius, that directs oil scraped off towards the crankcase side, reducing the likelihood of oil flowing between the piston ring and the ring groove.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a piston ring with an undercut (stepwise cutout) is used to improve oil scraping performance, then oil scraping performance is improved, but oil consumption increases due to oil flowing onto the undercut surface and between the piston ring and ring groove
Solution Approach 1:
The patent applies curvature by replacing the traditional straight-cut undercut surface with a curved concave surface. The cut surface includes a curved concave surface curved in a concave shape so as to approach a central axis of the piston ring toward the crankcase side. This curved geometry effectively directs oil flow toward the crankcase side, preventing oil from flowing onto the piston ring surface and into the ring groove, thus reducing oil consumption while maintaining scraping performance.
Solution Approach 2:
The patent specifies precise parameter ranges for the curved concave surface: an inclination angle of a tangent of the curved concave surface at a point located closest to the combustion chamber side is equal to or greater than 5° and equal to or less than 50°, and the axial direction width ratio H/h1 is equal to or greater than 0.2 and equal to or less than 0.4. These parameter optimizations ensure the curved surface effectively redirects oil flow while maintaining proper oil scraping function.
2Ease of operation
If an undercut is formed in the piston ring to enhance oil scraping, then oil scraping ability is improved, but oil seal performance deteriorates due to oil leakage between piston ring and ring groove
Solution Approach 1:
The curved concave surface geometry creates an effective oil flow redirection mechanism. By curving the cut surface to approach the central axis toward the crankcase side, the design guides oil away from the piston ring lower surface and prevents it from entering the gap between the piston ring and ring groove, thereby maintaining oil seal performance while preserving scraping ability.
Solution Approach 2:
The optimized parameters (inclination angle 5°-50° and axial width ratio H/h1 of 0.2-0.4) ensure that the curved surface provides sufficient oil redirection capability without compromising the structural integrity or sealing function of the piston ring.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design effectively reduces oil consumption by ensuring that oil is directed away from the gap between the piston ring and the ring groove, thereby minimizing oil leakage and improving oil seal performance.
Implementation Method 1
a cut surface that connects the outer peripheral end surface and the lower surface so as to form a cutout portion extending in the peripherally longitudinal direction of the piston ring between the outer peripheral end surface and the lower surface, the cut surface includes a curved concave surface curved in a concave shape so as to approach a central axis of the piston ring toward the crankcase side
Data Source
AI summary
An outer peripheral surface of a piston ring has a cut surface provided to form a cutout portion between an outer peripheral end portion and a lower surface, the cut surface includes a curved concave surface, an inclination angle of a tangent of the curved concave surface at a point closest to the combustion chamber side on the curved concave surface, with respect to a first virtual line extending in parallel to the lower surface is equal to or greater than 5° and equal to or less than 50°, and in a case where an axial direction width of the piston ring is set as h1, and an axial direction width of the cut surface is set as H, H/h1 is equal to or greater than 0.2 and equal to or less than 0.4.