Compression Ring Curvature Control for Gap Wear Reduction
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Solution Overview
Problem
Existing compression rings face excessive outer peripheral abrasion near the gap, leading to reduced lifespan, and existing countermeasures either complicate manufacturing or fail to uniformly distribute surface pressure, resulting in increased costs and insufficient abrasion reduction.
Innovation Solution
A compression ring design where the radius of curvature decreases gradually from the side opposite to the gap toward the gap end portions, with a specific relationship between the radius of curvature and nominal diameter to reduce surface pressure near the gap without altering the ring's modulus, combined with a self-tangential force and optional hard coatings like CrN or DLC films.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a hard coating is applied to the entire ring to increase abrasion resistance, then the abrasion resistance is improved, but the manufacturing cost increases and the coating thickness becomes unnecessarily large
Solution Approach 1:
The patent applies local quality by concentrating the hard coating only on the high-abrasion areas (gap end portions within ±35° from the gap) rather than coating the entire ring. This selective coating approach reduces material usage and manufacturing cost while maintaining abrasion resistance where it is most needed, directly resolving the contradiction between reliability and manufacturing cost
2Stress or pressure
If the inner peripheral face is machined to reduce surface pressure near the gap, then the surface pressure distribution is improved, but the manufacturing steps are complicated and costs increase
Solution Approach 1:
The patent employs preliminary action by pre-forming the outer peripheral face with a specific radius of curvature relationship during the ring manufacturing process itself, rather than requiring subsequent machining operations. The radius of curvature at the gap end portions is made smaller than at the opposite side, which preliminarily establishes the desired surface pressure distribution, thereby avoiding complex post-manufacturing steps
3Stress or pressure
If the radius of curvature of the outer peripheral face is adjusted to reduce surface pressure near the gap, then the surface pressure distribution is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The patent applies parameter changes by establishing specific quantitative relationships for the radius of curvature at different positions on the outer peripheral face. The radius of curvature at gap end portions (±35° from gap) is set to be smaller than at the opposite side (180° from gap), creating a controlled pressure distribution pattern that reduces surface pressure near the gap while maintaining manufacturability through defined geometric parameters
Data Source
AI summary
To provide a long-life compression ring without an increase in the outer peripheral abrasion near the gap regardless of the ring material or the presence or absence of the outer peripheral hard coating, in an annular compression ring having a pair of gap faces opposed to each other to form a free gap and a nominal diameter d1 equal to an inner diameter of a cylinder to which the compression ring is attached to along with a piston, a self tangential force is 5N to 50N, and a radius of curvature R1 and the nominal diameter d1 satisfy a relationship:−0.01≤(2R1−d1)/d1<0.002where the radius of curvature R1 is that of outer peripheral arcs of gap end portions in a free shape state before the compression ring is attached to the cylinder, and the gap end portions are defined in ranges between the gap faces and positions where a center angle from a midpoint of the free gap is 35°.