Curved-Undercut Piston Ring for Lower Oil Consumption
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Solution Overview
Problem
In internal combustion engines, oil consumption increases due to oil flowing from the cylinder inner wall onto the undercut surface of piston rings, leading to potential leakage into the combustion chamber.
Innovation Solution
A piston ring design with a curved concave surface on its outer peripheral surface, angled between 5° and 50° relative to the lower surface, and a cutout portion with specific dimensions, facilitating oil drainage into the crankcase.
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 leaking into the combustion chamber
Solution Approach 1:
The patent applies curvature by replacing the conventional sharp-edged undercut 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, with a controlled inclination angle (5°-50°) of the tangent at the point closest to the combustion chamber side. This curved geometry allows oil to follow the contour and drain properly into the crankcase rather than flowing onto the piston ring's lower surface and leaking into the combustion chamber, thus maintaining oil scraping performance while reducing oil consumption.
2Ease of operation
If the undercut depth and angle are increased to improve oil scraping, then oil scraping performance improves, but the risk of oil flowing onto the chamfered portion of the ring groove and increasing oil consumption increases
Solution Approach 1:
The patent applies parameter changes by precisely controlling the inclination angle of the curved concave surface's tangent (5°-50° relative to a virtual line parallel to the lower surface) and the axial direction width ratio of the cut surface (H/h1 between 0.2-0.4). These parameter optimizations ensure that oil is effectively directed away from the ring groove's chamfered portion while maintaining reliable oil sealing, preventing the harmful effect of oil flowing into the combustion chamber even as oil scraping performance is enhanced.
Data Source
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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.