Two-Piece Piston Thinned Wall Regions Reduce Solder Joint Stress
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Solution Overview
Problem
Existing multi-part pistons for internal combustion engines have weak soldered joints due to thin-walled components, leading to high tensile stress on the lower soldered connection when the piston crown expands under pressure and temperature loads, with no design measures to mitigate this stress.
Innovation Solution
The piston design features a funnel-shaped widening of the ring element with thinned peripheral wall regions that deform hinge-like, reducing tensile stress on the soldered connections, and includes specific soldering surfaces and recesses to enhance the strength of both upper and lower soldered connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the ring element and base body are made thin-walled, then the weight of the piston is reduced, but the strength of the soldered joints is reduced
Solution Approach 1:
The patent applies local quality by creating thinned wall regions specifically at the peripheral areas of the ring element near the soldered connections, while maintaining adequate wall thickness in other critical areas. This localized thinning reduces overall piston weight while preserving joint strength through strategic material distribution.
Solution Approach 2:
The patent introduces a new dimensional feature by creating funnel-shaped widenings that extend radially outward from the peripheral wall regions. This radial dimensionality change allows the thinned regions to deform in a hinge-like manner, providing an additional degree of freedom that reduces tensile stress on soldered joints while maintaining overall structural integrity.
2Weight of moving object
If the ring element is made thin-walled, then the piston weight is reduced, but the tensile stress on the lower soldered joint increases under pressure load
Solution Approach 1:
The patent changes the geometric parameters of the ring element by introducing funnel-shaped widenings with specific radial extensions. This parameter change allows the thinned peripheral wall regions to deform in a controlled hinge-like manner, transforming the stress distribution pattern and reducing peak tensile stresses on the lower soldered joint during combustion pressure cycles.
Solution Approach 2:
The patent introduces dynamic behavior by enabling the thinned peripheral wall regions to deform flexibly in a hinge-like manner during engine operation. This dynamic deformation capability allows the structure to adapt to varying pressure and temperature conditions, reducing stress concentration on the soldered joints while maintaining structural integrity throughout the combustion cycle.
3Volume of moving object
If the ring element expands radially under pressure and temperature load, then the piston crown volume increases, but the lower soldered joint is subjected to large tensile stress
Solution Approach 1:
The patent applies local quality by creating thinned wall regions specifically at the peripheral areas of the ring element near the soldered connections, while maintaining adequate wall thickness in other critical areas. This localized thinning reduces overall piston weight while preserving joint strength through strategic material distribution.
Solution Approach 2:
The patent introduces a new dimensional feature by creating funnel-shaped widenings that extend radially outward from the peripheral wall regions. This radial dimensionality change allows the thinned regions to deform in a hinge-like manner, providing an additional degree of freedom that reduces tensile stress on soldered joints while maintaining overall structural integrity.
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 significantly reduces the tensile stress on the soldered connections, ensuring a stronger and more durable joint even under prolonged engine operation, thereby enhancing the piston's structural integrity.
Implementation Method 1
thinned peripheral wall regions arranged near the soldered connections are deformed in a hinge-like manner, which results in a considerable reduction in the tensile stress acting on the soldered connections during engine operation
Implementation Method 2
a soldering welding process, i.e. a hard soldering process, to connect the base body to the piston skirt and to the ring element
Data Source
AI summary
The invention relates to a two-piece piston (1) for an internal combustion engine, comprising a piston base body (2) and a ring element (3), which is soldered to the piston base body (2) by an upper solder connection (23) having the length b, which is disposed on the radial inside of a piston crown (4) formed at least partially by the ring element (3), and by a lower solder connection (24) having the length c, which is disposed radially outside on the top of a center part (9). In order to improve the strength of the solder connections (23) and (24) due to pressure and temperature-related deformations of the upper piston part, the ring element (3) has a peripheral, upper, thinner wall region (49) in the region of the piston crown (4) radially outside the upper solder connection (23) and further a peripheral, lower, thinner wall region (50) between the ring section (5) and the lower solder connection (24), wherein the thickness a and b of the thinner wall regions (49) and (50) has a lower value than the length b and c of the solder connections (23) and (24).