Combined Oil Ring Profile for Low-Friction Oil Control
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Solution Overview
Problem
In internal combustion engines, reducing piston ring tension to minimize friction leads to increased oil consumption at high speeds due to thicker oil films, and conventional oil ring tensions between 0.5 to 0.6 N/mm are inadequate for low friction and oil control.
Innovation Solution
A combination oil ring design with specific outer peripheral surface shapes and coatings, including chromium nitride and DLC coatings, is implemented to maintain low oil ring tension while reducing oil consumption and friction, featuring asymmetrical and symmetrical contours on the segments to optimize oil film thickness and scraping action.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If oil ring tension is reduced to minimize friction, then friction is reduced, but oil consumption increases due to thicker oil films at high speeds
Solution Approach 1:
The patent applies different surface profiles to different segments of the oil ring. The first segment has a first surface profile while the second segment has a second surface profile, creating local variations in oil film thickness control. This allows the oil ring to maintain low tension overall while locally optimizing oil control at high speeds.
Solution Approach 2:
The patent employs asymmetrical surface profiles where the distance from the outer peripheral vertex to the inflection point differs between segments. The first segment has a first distance and the second segment has a second distance, creating asymmetrical oil scraping action that improves oil control without requiring increased tension.
2Loss of substance
If conventional oil ring tension (0.5 to 0.6 N/mm) is used to control oil film thickness, then oil consumption is reduced, but friction increases
Solution Approach 1:
The patent changes the geometric parameters of the oil ring segments, specifically the surface profiles and inflection point positions. By optimizing these parameters, the oil ring achieves effective oil control at lower tensions (below 0.5 N/mm) than conventional designs, thereby reducing friction while maintaining oil consumption control.
3Loss of substance
If contact width between segment outer peripheral slide surface and bore is reduced to increase actual surface pressure, then oil consumption is reduced, but friction increases
Solution Approach 1:
The patent creates a dynamic oil control mechanism through the asymmetrical surface profiles with inflection points. As the oil ring rotates and experiences varying loads, the contact width dynamically adjusts, allowing the system to maintain optimal actual surface pressure without excessive friction. The inflection points create zones of varying contact pressure that adapt to operating conditions.
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
The design effectively reduces oil consumption and friction at high engine speeds by optimizing oil film thickness and scraping action, achieving oil consumption ratios below 85% compared to conventional designs, while maintaining low friction levels.
Implementation Method 1
a friction loss force by a single-cylinder motoring tester is reduced
Implementation Method 2
forming an abrasion-resistant coating of low friction on an outer peripheral surface
Implementation Method 3
The tension reduction of the oil ring may cause increase in thickness of the oil film in a high-speed range with high-speed rotation of the engine
Data Source
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Figure 6
AI summary
Provided is a combination oil ring capable of achieving reduction of oil consumption and reduction of friction at the time of sliding of the oil ring. A shape of an outer peripheral surface of an upper segment of a pair of segments which is arranged on an engine combustion chamber side has a symmetrical curved shape, which is formed of a pair toward a distal end portion of the outer peripheral surface which slides with the cylinder inner wall respectively, extending from end points at outer peripheral side end portions of two surfaces forming an upper segment width, and the outer periphery distal end portion has an asymmetrical shape in the upper segment width direction over a vertex of the outer peripheral surface. A shape of an outer peripheral surface of a lower segment arranged on a side away from the engine combustion chamber is a symmetrical curved shape, which is formed of a pair toward a distal end portion of the outer peripheral surface which slides with the cylinder inner wall respectively, extending from end points at outer peripheral side end portions of two surfaces forming a lower segment width, and the outer periphery distal end portion has a symmetrical shape in the lower segment width direction over a vertex of the outer peripheral surface.