Connecting Rod Small-End Assembly for Twist-Limited Length Adjustment
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Solution Overview
Problem
Connecting rod twist in internal combustion engines leads to excessive wear and early failure of components, necessitating a solution to customize connecting rod length while minimizing twist for optimal engine performance.
Innovation Solution
A connecting rod assembly with a flat interfacing surface on the small end and a wrist pin notch, allowing for shim insertion to adjust length and control twist through a transition fit, ensuring minimal torsional movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the connecting rod length is customized by inserting shims between curved surfaces, then the connecting rod length can be adjusted, but fretting wear occurs reducing reliability
Solution Approach 1:
The invention inverts the conventional approach by using flat surfaces instead of curved surfaces. The small end of the connecting rod is provided with a flat surface, and the wrist pin is provided with a complementary flat surface, creating a flat-to-flat interface that eliminates fretting wear while allowing shim insertion for length adjustment.
2Adaptability or versatility
If shims are inserted to adjust connecting rod length, then piston-to-piston clearance can be optimized, but connecting rod twist increases causing excessive wear
Solution Approach 1:
The flat surface configuration inherently provides torsional stability while allowing length adjustment. The complementary flat surfaces on the small end and wrist pin create a rigid interface that resists twisting moments, maintaining connecting rod stability even when shims are inserted for clearance optimization.
Solution Approach 2:
The invention applies different surface characteristics to different locations: flat surfaces at the interface locations (small end and wrist pin) for stability and wear resistance, while maintaining the overall cylindrical shape of the connecting rod for structural integrity. This localized application of flat surfaces solves both the adjustment and stability requirements.
3Ease of manufacture
If a single-piece connecting rod design is used, then manufacturing is simple, but length customization is difficult
Solution Approach 1:
The invention segments the connecting rod assembly by providing a flat surface on the small end that interfaces with a complementary flat surface on the wrist pin, creating a modular interface that allows shim insertion. This segmentation enables length customization while maintaining the simplicity of a primarily single-piece design, as the core connecting rod remains intact.
Data Source
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AI summary
A connecting rod assembly has a connecting rod with a large end and a small end, a piston wrist pin, and fasteners to connect the connecting rod to the piston wrist pin and optionally one or more shims in between the connecting rod and piston wrist pin. A notch on the wrist pin allows for the seating of a flat surface on the small end of the connecting rod in the connecting rod assembly. Side walls on both the notch and the small end of the connecting rod limit twist. The connecting rod assembly allows for the adjustment of piston location in a cylinder while limiting connecting rod twist.