Variable Compression Ratio Engine Link Pin Diameter Optimization
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Solution Overview
Problem
In variable compression ratio internal combustion engines, the large load in the axis inclining direction causes excessive bending/torsion vibration and abrasion at the bearing portion of the first link pin, while the second link pin experiences reduced load and low surface pressure, leading to potential abrasion issues.
Innovation Solution
A variable compression ratio internal combustion engine design featuring a link mechanism with a first link pin of larger diameter than the second link pin, where the first link pin is positioned near the piston to handle the combustion load and the second link pin is positioned farther away with a smaller diameter to reduce motion trajectory and improve engine mountability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the first link pin has a larger diameter to handle combustion load, then abrasion resistance is improved, but device complexity increases
Solution Approach 1:
The patent applies different diameters to different link pins based on their specific functional requirements. The first link pin has a larger diameter to handle combustion loads and bending/torsion vibrations, while the second link pin has a smaller diameter for reduced motion trajectory. This local differentiation optimizes each component for its specific role rather than using a uniform design.
2Ease of operation
If the second link pin has a smaller diameter to reduce motion trajectory, then engine mountability is improved, but surface pressure decreases leading to potential abrasion issues
Solution Approach 1:
The patent differentiates the diameters of link pins according to their specific operational conditions. The second link pin uses a smaller diameter to reduce motion trajectory and improve engine mountability, while the first link pin uses a larger diameter to handle higher loads and vibrations, ensuring each component is optimized for its specific function.
3Productivity
If the first link pin handles large combustion load, then compression ratio control is improved, but bending/torsion vibration increases
Solution Approach 1:
The patent changes the physical parameter (diameter) of the first link pin to a larger size, which increases its moment of inertia and structural stiffness. This parameter change allows the link pin to better withstand bending and torsion vibrations generated during compression ratio control while maintaining effective load handling capability.
Data Source
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AI summary
There is provided a link mechanism (22) which connects a variable compression ratio mechanism (10) arranged to vary an engine compression ratio in accordance with a rotation position of a first control shaft (13), and an actuator (20), which includes a lever (25) connecting a first control shaft (13) and a second control shaft (24), a combustion load acted to the first control shaft (13) being transmitted through the lever (25) to the second control shaft (24). There are provided: a first link pin (28) connecting a tip end of the first arm portion (27) extending from the first control shaft (13) in a radially outward direction, and one end of the lever (25) so that the first arm portion and the lever are rotated relative to each other; and a second link pin (30) connecting a tip end of the second arm portion (29) extending from the second control shaft (24) in a radially outward direction, and the other end of the lever (25) so that the second control shaft and the lever are rotated relative to each other. A diameter (D1) of the first link pin (28) is set to be greater than a diameter (D2) of the second link pin (30).