Movable Piston Crown for Variable Compression Ratio
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Solution Overview
Problem
Internal combustion engines face challenges in efficiently varying the compression ratio in real-time, particularly in low temperature combustion engines, which affects starting performance and efficiency due to fixed compression ratios that balance between ignition reliability and preventing abnormal combustion.
Innovation Solution
A system featuring a longitudinally movable inner cylinder liner and a cylinder head assembly that allows for dynamic adjustment of the combustion chamber volume, enabling real-time control of the compression ratio through a linear translation mechanism and dynamic displacement sensing, allowing the compression ratio to be optimized based on operational conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a fixed compression ratio is used in the engine, then the engine structure is simple and reliable, but the engine efficiency and starting performance cannot be optimized under varying operational conditions
Solution Approach 1:
The patent implements a variable compression ratio system where the piston crown can dynamically change its position relative to the piston body during the compression stroke. This dynamic adjustment allows the compression ratio to vary in real-time based on operational conditions, resolving the contradiction between fixed structure reliability and adaptability to varying conditions.
Solution Approach 2:
The piston is divided into separate components: a piston body and a movable piston crown. This segmentation allows independent control of the compression ratio through the piston crown's longitudinal movement, enabling adaptability without requiring complete redesign of the entire piston assembly.
2Reliability
If the compression ratio is increased to improve starting performance and ignition reliability, then ignition is more reliable, but abnormal combustion and excessive noise may occur
Solution Approach 1:
The movable piston crown enables dynamic adjustment of the compression ratio during operation. During starting conditions, the piston crown position can be adjusted to achieve a higher compression ratio for reliable ignition. During normal operation, the compression ratio can be reduced to prevent abnormal combustion and excessive noise, thus resolving the contradiction between ignition reliability and harmful effects.
Solution Approach 2:
The system changes the compression ratio parameter in real-time based on operational conditions. By adjusting the piston crown's longitudinal position, the compression ratio can be varied to optimize ignition reliability when needed while preventing abnormal combustion and noise during other operating conditions.
3Adaptability or versatility
If variable valve timing is used to adjust effective compression ratio, then compression ratio can be varied, but the amount of trapped intake charge is reduced, thus reducing power generation
Solution Approach 1:
The movable piston crown provides a direct mechanical means to vary the compression ratio without altering valve timing. This dynamic adjustment of the piston crown's longitudinal position allows the compression ratio to be changed while maintaining normal valve operation, thus preserving the trapped intake charge and engine power output.
Solution Approach 2:
The piston crown acts as an intermediary element between the piston body and the combustion chamber. By moving the piston crown longitudinally, the compression ratio is adjusted without affecting the valve timing and intake charge trapping, thus resolving the contradiction between variable compression ratio control and power maintenance.
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 engine efficiency and starting performance by allowing precise control over the compression ratio, optimizing combustion timing and temperature, and reducing the risk of abnormal combustion, while also accommodating varying altitudes and load conditions.
Implementation Method 1
A biasing component 28 is disposed within a cavity 24a formed by the second skirt portion 24, and between the first and second skirt portions 20 and 24, which tends to bias the second skirt portion 24 into a predetermined position when no pressure is acting on the piston 12
Implementation Method 2
the spring 28 and/or dashpot 30, thus reducing the effective compression ratio of the engine 10
Data Source
AI summary
The present disclosure relates to a system for controlling ignition of an air/fuel mixture intake charge directed into an internal combustion engine. The system may have a longitudinally movable inner cylinder liner configured to fit within a cylinder wall portion of an internal combustion engine, and able to receive a piston of the engine therein. A portion of the inner cylinder liner defines an internal volume forming a combustion chamber, and the internal volume controls a compression ratio of the cylinder. The system also has a cylinder head assembly operatively associated with the inner cylinder liner and able to move linearly to cause longitudinal displacement of the inner cylinder liner relative to the cylinder wall portion. This enables the volume of the combustion chamber to be further varied, to thus further vary the compression ratio.