Helical Base Support Piston Reduces Groove Stress
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Solution Overview
Problem
Pistons for internal combustion engines face high stress and fatigue due to extreme loads, particularly in the lowermost annular groove, which is exacerbated by kinematic forces and temperature, necessitating improved fatigue strength without significant weight increase.
Innovation Solution
The piston incorporates base supports with a helical contour that connects to the piston crown, reducing stress in the lowermost groove by distributing loads more effectively, with a slope that can be expressed as x(t) = (r*cos(t)*r*sin(t)*h*2*π*t, allowing for a lighter yet stronger design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If pockets are formed radially outside the piston pin to reduce weight, then the weight of the piston is reduced, but the fatigue strength in the lowermost annular groove deteriorates due to high tensile stress
Solution Approach 1:
The base support is positioned specifically in the lowermost annular groove region where fatigue stress is highest, providing localized reinforcement without adding material throughout the entire piston. This targeted approach strengthens the critical area while maintaining overall weight reduction from the pockets.
Solution Approach 2:
The base support features a curved, arc-shaped contour that follows the cylindrical geometry of the piston. This curved design distributes stress more effectively compared to straight structural elements, reducing stress concentration in the lowermost groove while maintaining structural integrity.
2Adaptability or versatility
If the piston skirt is made resilient to react to lateral forces, then the piston can accommodate lateral forces, but high tensile stress occurs in the lowermost annular groove on the pressure side
Solution Approach 1:
The base support is positioned asymmetrically in the lowermost annular groove region, specifically on the pressure side where tensile stress from lateral forces is highest. This asymmetric placement provides targeted reinforcement where the combination of lateral force reaction and combustion pressure creates maximum stress.
Solution Approach 2:
The curved contour of the base support follows the cylindrical geometry of the piston and distributes the stress from lateral forces more evenly across the lowermost groove region, reducing peak tensile stress while maintaining the piston skirt's ability to react to lateral forces.
Data Source
AI summary
A piston (10) for an internal combustion engine, includes shaft wall sections (18) for supporting in a cylinder or a cylinder liner, and at least one base support (20) that is connected thereto in the circumferential direction, and which has at least one contour that forms a section of a helix.