Variable Asymmetrical Crank Mechanism for Atkinson Cycle Load Control
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Solution Overview
Problem
Existing internal combustion engines operating on the Atkinson cycle with classic or symmetrical crank drives face inefficiencies due to throttled back-and-forth flow through intake valves, limiting thermal efficiency gains, while asymmetrical crank drives face design constraints that restrict achievable stroke differences and mass balance, hindering optimal implementation of the Atkinson cycle.
Innovation Solution
A variable asymmetrical crank mechanism with a combination of shaft journals, crank webs, ring gears, and planetary spur gears allows for cylinder-specific control of compression ratio and stroke lengths, enabling efficient implementation of the Atkinson cycle by adjusting the eccentricity and ring gear positions to optimize piston strokes and load control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If classic or symmetrical crank drives are used in Atkinson cycle engines, then the mechanical structure is simple and easy to manufacture, but thermal efficiency is limited due to throttled back-and-forth flow through intake valves
Solution Approach 1:
The patent applies asymmetry by designing a crank mechanism where the compression stroke is geometrically shorter than the expansion stroke. This is achieved through an asymmetric crank geometry where the crank radius for compression differs from the crank radius for expansion, eliminating the need for throttled back-and-forth flow through intake valves and significantly improving thermal efficiency while maintaining manufacturing feasibility
Solution Approach 2:
The patent implements dynamic adjustment of the crank mechanism to vary the compression ratio and stroke lengths during engine operation. This allows the engine to optimize thermal efficiency across different operating conditions by dynamically changing the geometric parameters of the crank drive, transitioning from a static to a dynamic system
2Loss of energy
If asymmetrical crank drives are used to achieve real Atkinson cycle, then thermal efficiency is improved, but design constraints restrict achievable stroke differences and mass balance
Solution Approach 1:
The patent resolves the design constraints by creating a novel asymmetric crank geometry that achieves significant stroke differences between compression and expansion while maintaining reasonable mass balance. The asymmetric crank design allows the large connecting rod eye to be positioned optimally, achieving pronounced asymmetrical Atkinson cycles without the limitations of prior art
Solution Approach 2:
The patent addresses mass balance issues by incorporating counterweights in the asymmetric crank mechanism. The counterweights are strategically positioned to compensate for the uneven mass distribution caused by the asymmetric stroke lengths, reducing vibrations and maintaining dynamic balance while preserving the thermal efficiency benefits
3Loss of energy
If compression ratio is increased to counteract reduced cylinder charge, then thermal efficiency is improved, but device complexity increases due to additional adjustment mechanisms
Solution Approach 1:
The patent merges the compression ratio adjustment function with the existing asymmetric crank mechanism. By integrating the compression ratio variation directly into the crank geometry rather than adding separate adjustment mechanisms, the system achieves improved thermal efficiency while minimizing increases in device complexity. The asymmetric crank itself serves as the adjustment mechanism
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 solution enhances thermal and mechanical efficiency by allowing continuous variation of the compression ratio and stroke lengths, reducing throttling needs, and improving load control strategies, while maintaining a compact and balanced design.
Implementation Method 1
a combination of shaft journals, crank webs, ring gears, and planetary spur gears allows for cylinder-specific control of compression ratio and stroke lengths
Implementation Method 2
enabling efficient implementation of the Atkinson cycle by adjusting the eccentricity and ring gear positions to optimize piston strokes
Data Source
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AI summary
The internal combustion engine has a crankshaft of a crank drive, which comprises multiple components, and which is designed as an assembled crankshaft. An eccentric crank synchronizes against a directed crank throw, when the crank throw is directed against a top dead center and the pivotable lug (13) are in a zero position. Two ring gears (11) or two sun gears by specified features have the crank throw for the cylinder-specific control of the compression ratio. The control of the compression ratio and the piston strokes is carried out uniformly for the cylinders. Independent claims are included for the following: (1) a load control method for an internal combustion engine; and (2) a cylinder deactivation method for an internal combustion engine.