Variable Compression Ratio Crank Web Guide Portion
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Solution Overview
Problem
Existing variable compression ratio apparatuses face challenges in achieving stable dynamic stability and structural rigidity, particularly in the motion of dual link type eccentric and swing links, which can lead to abnormal combustion and engine damage due to limitations in advancing ignition timing.
Innovation Solution
A variable compression ratio apparatus is designed with dual link type eccentric and swing links, featuring a crank web with a guide portion that expands radially and a balancing portion, both with smooth flat surfaces, to guide and stabilize the downward motion of the links, ensuring they remain on path and maintain structural rigidity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a rigid structure and stable operation are required for the eccentric swing member, then the structural rigidity is improved, but the device complexity increases
Solution Approach 1:
The crank web is divided into multiple functional portions: a guide portion for guiding downward motion, a balancing portion for load balancing, and a coupling portion for connecting components. This segmentation allows each portion to be optimized for its specific function, achieving rigid stable operation while maintaining manufacturing feasibility through modular design
Solution Approach 2:
The guide portion and balancing portion are integrally formed as a single crank web structure, merging the functions of guiding downward motion and load balancing into one component. This integration reduces the number of separate parts, simplifying the overall device structure while maintaining the required structural rigidity
2Stability of the object's composition
If the guide portion is formed to be expanded in radial direction, then the guidance stability is improved, but the manufacturing complexity increases
Solution Approach 1:
The guide portion is formed with a circular arc shaped inner surface that expands radially outwardly from the crankpin exterior diameter. This curved geometry provides smooth guidance for the downward motion of the eccentric and swing links, ensuring stability while being manufacturable using standard radial expansion processes
3Manufacturing precision
If the inner surface is formed as a smooth flat surface, then the surface roughness is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The crank web is designed with different surface qualities in different regions: the guide portion and balancing portion have smooth flat inner surfaces for low friction contact, while other external surfaces have standard finishes. This localized application of high precision machining only where required (on the inner surfaces contacting the links) achieves excellent surface roughness without unnecessarily increasing manufacturing complexity across the entire component
Data Source
AI summary
A variable compression ratio apparatus includes: a piston defining a combustion chamber, a connecting rod connected to the piston; an eccentric link eccentrically connected to the piston, a swing link connected to the eccentric link so as to rotate the eccentric link, a crankpin to which the connecting rod is connected, and a crank web disposed at both sides of the crankpin and provided with a guide portion for guiding downward motions of the eccentric link and the swing link when the eccentric link and the swing link move downward. Thereby, the downward motions of the eccentric link and the swing link are stabilized.