Piston Pin Assembly with Offset Axes for Compression Ratio Control
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Solution Overview
Problem
Existing solutions for dynamically adjusting the compression ratio in internal combustion piston engines are complex and unreliable, particularly in engines producing more than 150 kW per cylinder, as they require intricate mechanisms like eccentric bushings and locked pins for effective length adjustment.
Innovation Solution
A piston pin assembly with a power transmission system using a circular gear rim and a locking system, featuring offset central axes, allows for simple and reliable control of compression ratio adjustment by selectively locking or unlocking the rotational movement of the piston pin, enabling efficient power transmission and compression ratio changes during engine operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If eccentric bushing and locked pin mechanisms are used for dynamic compression ratio adjustment, then compression ratio can be adjusted during engine operation, but device complexity increases significantly
Solution Approach 1:
The piston pin assembly is segmented into distinct functional zones: first and second affixing areas for attaching to the piston, and a separate third affixing area at the center for attaching to the connecting rod. This segmentation allows the center area to be independently positioned with an offset second central axis relative to the common first central axis of the ends, enabling compression ratio adjustment without complex eccentric mechanisms
Solution Approach 2:
The invention introduces a dimensional offset between the first central axis (ending) and second central axis (center area) of the piston pin. This axial offset creates the effective length variation needed for dynamic compression ratio adjustment, replacing the traditional radial eccentric bushing approach with a more straightforward dimensional configuration
2Adaptability or versatility
If intricate mechanisms like eccentric bushings are used for compression ratio adjustment, then dynamic adjustment is achieved, but reliability decreases in high-power engines
Solution Approach 1:
Instead of using an eccentric bushing that requires rotation and locking mechanisms to achieve effective length change, the invention inverts the approach by positioning the third affixing area at an offset location along the piston pin's central axis. This allows the connecting rod to be attached at a predetermined offset position, achieving compression ratio adjustment through a simpler, more reliable geometric configuration that eliminates complex rotating and locking mechanisms
3Ease of operation
If floating piston pin is used, then rotational movement freedom is achieved, but compression ratio control becomes difficult
Solution Approach 1:
The piston pin exhibits different functional qualities at different locations: the first and second ends have affixing areas that allow rotational freedom similar to floating pins, while the center third affixing area is positioned with an offset second central axis to provide the compression ratio control function. This local differentiation of functional qualities allows both rotational freedom and controlled compression ratio adjustment
Data Source
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AI summary
Invention relates to apiston pin assembly for an internal combustion piston engine, which piston pin assembly comprises a piston pin having at its first end (14.1) and its second end (14.2) a first and a second affixing area and between the first and the second ends, at a center area (14.3),, and in which piston pin the first and the second ends having a common first central axis and the center area having a second central axis which axes are offset at a distance from each other. The assembly comprises a power transmission system (102) comprising a circular gear rim (104) arranged to transmit power to the third area of the piston pin, the gear rim being capable engage a connecting rod and the pistonpin to transmit work from rotational movement of the connecting rod in respect to a piston while installed to an engine and the engine is cranked or operated; a locking system (200) which selectively locks or unlocks the rotational movement of at least the third area (14.3) of the piston pin in respect to the piston.