Variable Compression Ratio Engine Crankshaft Mechanism
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Solution Overview
Problem
Conventional internal combustion engines with fixed compression ratios face inefficiencies due to the limitations of pre-ignition and knocking, which restrict the ability to vary compression ratios during operation, leading to compromised fuel efficiency and increased complexity when attempting to move crankshafts for variable compression designs.
Innovation Solution
A crankshaft system that allows for vertical movement of the crankpins relative to the cylinder head while maintaining stationary power take-off points, utilizing flex joints and actuators to adjust compression ratio, enabling conventional manufacturing techniques and improved power-to-weight ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the compression ratio is increased to improve fuel efficiency, then thermal efficiency increases, but pre-ignition and knocking occur that damage the engine
Solution Approach 1:
The patent implements a movable crankshaft system that allows the compression ratio to be dynamically adjusted during engine operation. The crankshaft can be positioned at different heights relative to the cylinder head, enabling the compression ratio to be changed from high (for fuel efficiency) to low (for preventing knocking) based on real-time operating conditions such as load, temperature, and fuel quality.
2Adaptability or versatility
If a movable crankshaft system is implemented to enable variable compression ratio, then compression ratio adjustability improves, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The crankshaft system is divided into separable components: a stationary crankshaft portion that remains fixed in the engine block, and a movable crankshaft portion that can be raised and lowered. This segmentation allows the stationary portion to maintain simple manufacturing and sealing, while the movable portion enables compression ratio adjustment without requiring the entire crankshaft system to be complex.
Solution Approach 2:
The patent introduces an intermediary mechanism (such as a lift system or actuator) that mediates between the stationary crankshaft portion and the movable crankshaft portion. This intermediary allows controlled vertical movement of the crankpins relative to the cylinder head while maintaining the structural integrity and simplicity of the overall crankshaft system.
3Adaptability or versatility
If the crankshaft is moved vertically to vary compression ratio, then compression ratio changes, but power take-off and sealing become difficult
Solution Approach 1:
The crankshaft is segmented into a stationary portion that provides stable power take-off points and sealing surfaces, and a movable portion that adjusts compression ratio. The stationary portion remains fixed relative to the engine block, maintaining conventional sealing arrangements and power transmission interfaces, while the movable portion contains the adjustment mechanism.
Data Source
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AI summary
A system and method for providing a variable compression ratio internal combustion engine is disclosed. The system can include a crankshaft pivotally coupled to a standard engine block using a plurality of pivoting main bearing caps. The system can pivot the main bearing caps, and thus the crankshaft, to increase or decrease the compression ratio of the engine. The system can also include a plurality of actuators to move one end of the main bearing caps. The crankshaft can comprise one or more flexible joints to enable the crankshaft to move, while the output(s) of the crankshaft remain stationary to enable conventional sealing and power take-off. The compression ratio can be varied continuously during use and can be included in an overall engine management system.