Variable-Relief Piston Ring for Oil Film and Wear Control
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Solution Overview
Problem
Existing piston rings face uneven radial pressures due to heat expansion differences, leading to increased surface pressure, reduced oil film thickness, and subsequent wear and friction, especially in shock areas.
Innovation Solution
A piston ring design featuring a pressure reduction floor on the outer edge with a varying axial dimension of the contact area along the circumference, which compensates for the varying radial pressures by adjusting the gas attack surface height.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ground chamfers are provided uniformly around the entire circumference to counteract radial pressure, then the load-bearing area is relieved and tribological damage is prevented, but the circumferentially varying radial pressures due to thermal expansion differences are not adequately compensated
Solution Approach 1:
The patent applies local quality by providing ground chamfers only in specific circumferential regions where thermal expansion differences cause higher radial pressures. The chamfers are positioned at the joint area and opposite the joint area, while leaving the mid-section without chamfers. This localized approach compensates for the circumferentially varying radial pressures while maintaining reliability in the critical high-stress regions.
2Force
If the axial height of the contact surface is increased to compensate for radial pressure variations, then the gas attack surface height increases to counteract gas pressure, but the oil film thickness is further reduced in already critical areas
Solution Approach 1:
The patent applies local quality by varying the axial height of the contact surface according to the circumferential position. The contact surface has maximum axial height at the joint area and opposite the joint area where radial pressures are highest, and reduced axial height in the mid-section. This localized variation allows the gas attack surface to generate sufficient counteracting force precisely where needed without excessively reducing oil film thickness in areas where it is already adequate.
3Ease of manufacture
If uniform pressure relief is applied around the entire circumference, then the structure is simple and easy to manufacture, but it does not account for the extreme variability of radial pressures caused by thermal expansion differences
Solution Approach 1:
The patent applies local quality by providing pressure relief features only in specific circumferential regions rather than uniformly around the entire ring. The ground chamfers are positioned at the joint area and opposite the joint area, creating a non-uniform pressure relief distribution that adapts to the variable radial pressures caused by thermal expansion differences, while maintaining reasonable manufacturing simplicity.
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 counteracts gas pressure on the ring, reducing wear and friction by maintaining optimal oil film thickness and distributing radial pressures more evenly across the piston ring.
Implementation Method 1
the gas attack surface height, which counteracts the gas pressure at the ring's inner diameter
Implementation Method 2
a specifically defined axial dimension of the contact surface around the circumference of the ring compensates for the circumferentially varying radial pressures or effective radial pressures
Implementation Method 3
reduces the oil film thickness... resulting in increased wear, scuffing and reinforcement layer disruption
Data Source
Figure 1~2
AI summary
Disclosed is a piston ring (2), comprising a ring outer side (4), a ring upper flank (6) and a ring lower flank (8), the ring outer side (4) having, at an upper edge (10), a pressure relief chamfer (12) so that only a lower part of the ring outer side forms a contact surface (14), characterized in that an axial dimension of the contact surface (14) varies in the circumferential direction (18).