Pinless Piston-Connecting Rod Joint for Uniform Thermal Expansion
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Solution Overview
Problem
Existing reciprocating piston engines face inefficiencies due to the added mass of the piston pin, which increases pollutant emissions and frictional losses, and struggle with thermal management, particularly in diesel engines where pistons must be designed with an oval peripheral surface to accommodate thermal expansion.
Innovation Solution
A piston design with a circumferential surface and a connecting rod holder featuring undercuts to securely attach the connecting rod, ensuring a uniform cross-sectional area along the axis of movement, which simplifies thermal management and eliminates the need for an oval shape, thereby reducing friction and improving sealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a piston pin is used to pivotally connect the piston and connecting rod, then the connection is achieved, but the reciprocating mass increases and frictional losses increase
Solution Approach 1:
The invention extracts and eliminates the piston pin from the system by providing the connecting rod with a self-contained pivotable connection directly to the piston's circumferential surface. The connecting rod features a pivotable connection element that engages with a corresponding receptacle on the piston, removing the need for a separate piston pin component and reducing reciprocating mass.
Solution Approach 2:
The invention merges the connection function into the connecting rod itself by integrating the pivotable connection element as part of the connecting rod structure. This combines what were previously separate components (piston pin and connecting rod) into a unified assembly, reducing the number of parts and overall mass.
2Temperature
If the piston is designed with an oval peripheral surface to accommodate thermal expansion, then thermal management is improved, but the manufacturing complexity increases and sealing behavior deteriorates
Solution Approach 1:
The invention applies local quality by providing thermal management features specifically at the piston crown (upper side) where heat generation is most intense, while maintaining a round circumferential surface for sealing. The piston crown can have specialized cooling channels or thermal management structures, while the circumferential surface remains geometrically simple and round for optimal sealing against the cylinder bore.
Solution Approach 2:
The invention segments the piston into distinct functional zones: the upper side (piston crown) handles thermal management and combustion forces, while the circumferential surface maintains a simple round geometry for sealing and guidance. This segmentation allows each zone to be optimized independently for its specific function.
3Adaptability or versatility
If the piston has a non-uniform cross-sectional area, then the design flexibility increases, but the thermal expansion uniformity decreases
Solution Approach 1:
The invention changes the key parameter of cross-sectional area uniformity along the piston's axis of movement to achieve uniform thermal expansion behavior. By maintaining substantially uniform cross-sectional area, the piston expands uniformly in all radial directions during operation, ensuring consistent sealing and geometric stability while still allowing design flexibility in other aspects such as internal cooling channels and combustion chamber geometry.
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 enhances thermal expansion uniformity, simplifies production, reduces emissions, and minimizes oil losses by maintaining a round shape, improving engine efficiency and reducing wear and oil consumption.
Implementation Method 1
This geometric design of the piston, in particular by means of providing substantially uniform cross-sectional areas for every cross section taken through the axis of movement, results in a uniform thermal expansion behavior around the circumference of the piston
Data Source
AI summary
The invention relates to a piston, in particular for an engine, having a top side, a bottom side, a circumferential surface extending along a circumference and a movement axis extending essentially parallel to a tangent of the circumferential surface and through the top side and through the bottom side, the circumferential surface being designed for guiding the piston in a cylinder bore of a cylinder along the movement axis, the top side being designed for absorbing compressive forces of a gas and the bottom side having a connecting rod receptacle, wherein the connecting rod receptacle has one or more undercuts in a traction and a compression direction, so that the connecting rod receptacle is designed to receive a thickened portion of a connecting rod which corresponds to the connecting rod receptacle in a form-fitting manner and can be pivoted about a pivot axis, wherein the piston has any number of radially arranged, essentially flat cross-sectional surfaces extending through the axis of movement. The invention also relates to a crank drive and an internal combustion engine.