Internal Combustion Engine Piston Skirt Wall Thickness Optimization
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Solution Overview
Problem
Modern pistons for internal combustion engines face a challenge in achieving both high rigidity and reduced weight, as existing designs either maintain constant or decreasing wall thickness towards the center, which does not effectively distribute stress for optimal performance.
Innovation Solution
The piston features a skirt wall with increased thickness in the central region and lateral regions, with a constant curvature and stress distribution, treating the skirt wall as a bending beam to manage load, resulting in a weight reduction of up to 25% or a 25% increase in rigidity without adding weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the wall thickness of the skirt walls is increased to improve rigidity, then the rigidity is improved, but the weight increases
Solution Approach 1:
The patent applies local quality by varying the wall thickness of the skirt wall according to the stress distribution pattern. The wall thickness is increased in regions of higher stress (near the connecting walls and piston crown) and decreased in regions of lower stress (central region), creating a non-uniform thickness profile that optimizes rigidity where needed while reducing weight where less support is required. This is achieved through the formula t(φ) = t₀ + a·cos(φ) + b·cos(2φ), which creates localized thickness variations matching the stress distribution.
Solution Approach 2:
The patent employs parameter changes by modifying the wall thickness parameter t(φ) as a function of the circumferential angle φ. The thickness parameter varies continuously around the circumference according to a mathematical function that reflects the stress distribution, allowing optimization of both rigidity and weight by adjusting the coefficients a and b in the thickness formula to match specific loading conditions.
2Weight of moving object
If the wall thickness decreases towards the centre to reduce weight, then the weight is reduced, but the rigidity deteriorates
Solution Approach 1:
The patent applies local quality by varying the wall thickness of the skirt wall according to the stress distribution pattern. The wall thickness is increased in regions of higher stress (near the connecting walls and piston crown) and decreased in regions of lower stress (central region), creating a non-uniform thickness profile that optimizes rigidity where needed while reducing weight where less support is required. This is achieved through the formula t(φ) = t₀ + a·cos(φ) + b·cos(2φ), which creates localized thickness variations matching the stress distribution.
Solution Approach 2:
The patent employs parameter changes by modifying the wall thickness parameter t(φ) as a function of the circumferential angle φ. The thickness parameter varies continuously around the circumference according to a mathematical function that reflects the stress distribution, allowing optimization of both rigidity and weight by adjusting the coefficients a and b in the thickness formula to match specific loading conditions.
3Strength
If a rib is added in the centre of the skirt wall to improve rigidity, then the rigidity is improved, but the weight increases and device complexity increases
Solution Approach 1:
The patent applies local quality by varying the wall thickness of the skirt wall according to the stress distribution pattern. The wall thickness is increased in regions of higher stress (near the connecting walls and piston crown) and decreased in regions of lower stress (central region), creating a non-uniform thickness profile that optimizes rigidity where needed while reducing weight where less support is required. This is achieved through the formula t(φ) = t₀ + a·cos(φ) + b·cos(2φ), which creates localized thickness variations matching the stress distribution.
Solution Approach 2:
The patent inverts the conventional approach of adding material (ribs) to improve rigidity. Instead of adding a central rib that would increase weight, the invention removes material from the central region where stress is lowest, while maintaining or increasing thickness in high-stress regions. This inverse approach achieves rigidity optimization through strategic material removal and redistribution rather than addition.
Data Source
AI summary
The invention relates to a piston for an internal combustion engine having two skirt wall (10), which are connected by connecting walls (14), which bear piston-pin bosses, wherein at least one skirt wall (10) has a greater wall thickness in a region (12) that is central along the piston periphery and in the lateral regions than between the central region (12) and each lateral region and is continuously curved on the inside of the piston in a section perpendicular to the piston axis, and wherein the wall thickness distribution is substantially constant in the direction of the piston axis.