Variable Stroke Engine Crank Mechanism for Part-Load Efficiency
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Solution Overview
Problem
Internal combustion engines, particularly gasoline engines, suffer from significant energy losses and poor part-load efficiency due to throttling, engine friction, and reduced compression and expansion ratios at low loads, leading to inefficient power production and high fuel consumption.
Innovation Solution
A variable stroke and compression ratio engine design featuring multiple pistons connected to a wobbler on a dual-angled crank, allowing for adjustment of piston stroke and compression ratio through sliding engagement with upper and lower journals, thereby minimizing throttling losses and maintaining full compression and expansion ratios even at partial loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If throttling is used to control power at part load, then power is reduced, but pumping losses and energy efficiency deteriorate significantly
Solution Approach 1:
The patent applies dynamics by making the engine stroke variable through a mechanism that adjusts piston displacement. The stroke length changes dynamically based on load requirements, allowing the engine to maintain high efficiency at part load by reducing the compression/expansion volume rather than throttling. This resolves the contradiction by enabling power control through geometric adjustment rather than flow restriction.
Solution Approach 2:
The patent changes the physical parameter of stroke length to control engine output. By varying the stroke parameter according to load conditions, the engine can operate efficiently at part load without the severe pumping losses associated with throttling. The compression ratio is simultaneously adjusted to maintain optimal combustion conditions across different operating points.
2Loss of energy
If stroke is reduced to improve part load efficiency, then compression ratio and expansion ratio are reduced, but thermodynamic efficiency deteriorates
Solution Approach 1:
The patent employs dynamic adjustment of both stroke length and compression ratio independently. The variable stroke mechanism is coupled with a compression ratio control system that ensures the compression ratio remains optimal even when stroke is reduced for part load operation. This dynamic coordination resolves the contradiction between reducing energy losses and maintaining thermodynamic efficiency.
Solution Approach 2:
The patent changes multiple parameters simultaneously - stroke length and compression ratio - to achieve part load efficiency without sacrificing thermodynamic performance. By coordinating changes in these parameters, the engine maintains high compression ratios during reduced stroke operation, preserving combustion efficiency while reducing overall energy losses.
3Loss of energy
If variable stroke mechanism is added to reduce pumping losses, then device complexity increases, but manufacturing cost and complexity worsen
Solution Approach 1:
The patent merges the variable stroke mechanism with the existing crankshaft and connecting rod system. The stroke control is integrated into the fundamental engine architecture rather than adding completely separate systems. This merging approach reduces the incremental complexity by reusing existing components and motion paths.
Solution Approach 2:
The patent designs the variable stroke mechanism to serve multiple functions: controlling power output, maintaining compression ratio, and reducing pumping losses. By making the mechanism multi-functional, the patent reduces the need for separate systems for each function, thereby limiting the increase in overall device complexity.
Data Source
AI summary
A variable stroke and compression ratio engine employs multiple pistons connected to a wobbler. A crank with an axis of rotation has an upper journal with a first angle relative to the axis and a lower journal with a second angle with respect to the axis. A cradle connected for rotational motion with respect to the wobbler is carried by the crank with sliding engagement to the upper and lower journals for translation between a first high eccentricity position and second low eccentricity position.