Variable Cycle Engine Phasing Mechanism for Atkinson Otto Transition
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Solution Overview
Problem
Existing multi-linkage systems for engines constrain piston movement to a single four-stroke working cycle, limiting adaptability to changing output demands and efficiency considerations, particularly in transitioning between Atkinson and Otto cycles.
Innovation Solution
An engine assembly with a multiple linkage system and a phased eccentric shaft that allows variation in piston movement between Atkinson and Otto cycles by adjusting the rotational position of the second shaft relative to the crankshaft, maintaining a relatively constant geometric compression ratio through minimal variation in the top dead center position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a multiple linkage system is used to constrain piston movement to a single four-stroke working cycle, then the engine can achieve efficient operation for that specific cycle, but the adaptability to changing output demands is limited
Solution Approach 1:
The patent applies the dynamics principle by making the linkage system adjustable rather than fixed. The linkage assembly can be reconfigured to operate in different four-stroke cycles (Atkinson, Otto, Miller, Dual-cycle) through adjustable components, allowing the engine to adapt to changing output demands while maintaining efficiency for each specific cycle mode
Solution Approach 2:
The patent implements universality by designing a single engine system that can perform multiple functions through different cycle operations. The same engine hardware can switch between Atkinson cycle for efficiency, Otto cycle for power, Miller cycle for turbocharging, and Dual-cycle for hybrid operation, making the engine versatile for various operating conditions
2Adaptability or versatility
If the compression stroke length is increased to achieve Otto cycle operation, then the expansion ratio decreases to one, but the top dead center position changes significantly affecting geometric compression ratio
Solution Approach 1:
The patent applies parameter changes by carefully adjusting the linkage geometry and piston position parameters to achieve the desired cycle characteristics. When transitioning to Otto cycle, the system changes the compression stroke length parameter while simultaneously adjusting the top dead center position parameter to maintain a relatively constant geometric compression ratio within ±0.3 CR of the nominal value
Solution Approach 2:
The patent implements local quality by making specific localized adjustments to the linkage system at critical points. The linkage assembly is designed with specific geometric relationships between connecting rod, crankshaft, and eccentric shaft that locally control the piston trajectory and dead center positions to achieve the desired balance between compression stroke length and compression ratio
Data Source
AI summary
An engine assembly includes a crankshaft having a first axis of rotation and a crankpin offset from the first axis of rotation. A second shaft is offset from the crankshaft and has a second axis of rotation. A piston is movable in a cylinder between a top dead center position and a bottom dead center position to drive the crankshaft. A connecting rod extends from the piston. A four-jointed linkage assembly pivotably connects the connecting rod, crankshaft, and second shaft. A drive system operatively connects the crankshaft and the second shaft to drive the second shaft via the crankshaft. A phasing mechanism connects the drive system and the second shaft and is controllable to vary the rotational position of the second shaft relative to the crankshaft.