Silent Chain Link Plate Material and Height Design
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Solution Overview
Problem
Conventional double-sided engagement type silent chains suffer from reduced strength and fatigue due to stress concentrations at the tooth gap bottoms of outermost link plates, leading to cracks and increased wear, particularly when engaging with sprockets, and exhibit poor wear resistance, resulting in chain elongation and reduced rotational fatigue strength.
Innovation Solution
The silent chain employs link plates with a higher bainite mixing ratio in outermost link plates for enhanced impact resistance and fatigue strength, and a higher martensite mixing ratio in inner and adjacent outer link plates for improved wear resistance, along with a chromium carbide layer on pin hole surfaces to reduce contact wear and adhesion, while maintaining a higher back surface height in outermost link plates to mitigate stress concentrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional double-sided engagement type silent chains are used with outermost link plates having standard height, then the chain structure is simple and manufacturing is easier, but the impact resistance and fatigue strength are reduced due to stress concentrations at tooth gap bottoms
Solution Approach 1:
The patent applies local quality by differentiating the back surface height of link plates based on their position and function. Outermost link plates have a greater back surface height to increase impact resistance and fatigue strength, while inner link plates maintain a standard height. This localized structural modification optimizes strength where needed without unnecessarily complicating the entire chain structure.
2Strength
If uniform material composition is used throughout all link plates, then manufacturing is simpler and cost is lower, but wear resistance is insufficient in regions subjected to high contact stress
Solution Approach 1:
The patent implements local quality through differentiated material composition across different link plate positions. Link plates containing pin holes (outermost and adjacent outer link plates) use a steel material with 0.15-0.35% carbon content for enhanced wear resistance in high-contact-stress regions, while other link plates use standard material. This selective material application improves wear resistance where critical without unnecessarily complicating manufacturing throughout the entire chain.
3Strength
If connecting pins are fitted into pin holes of outermost link plates without additional strengthening measures, then assembly is simpler and manufacturing is easier, but contact wear between pin holes and connecting pins increases leading to chain elongation
Solution Approach 1:
The patent applies parameter changes by modifying the material composition parameter of link plates containing pin holes. By using steel with 0.15-0.35% carbon content in outermost and adjacent outer link plates, the wear resistance of pin holes is significantly improved, reducing contact wear with connecting pins and preventing chain elongation. This material parameter change provides enhanced durability without adding structural complexity to the pin hole design.
4Strength
If standard chain design is used without differentiated link plate heights, then the chain maintains a compact overall width, but the central portions of links have insufficient strength particularly when load is applied to outermost link plates
Solution Approach 1:
The patent applies local quality by selectively increasing the back surface height only of outermost link plates and adjacent outer link plates, while maintaining standard height for inner link plates. This localized height increase strengthens the central portions of links where loads are applied to outermost link plates, without unnecessarily increasing the overall chain width. The differentiated height design optimizes strength-to-volume ratio.
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 configuration significantly enhances the impact resistance and fatigue strength of outermost link plates, reduces wear elongation, and improves overall chain durability by suppressing crack generation and wear, even under high loads, while maintaining a compact design.
Implementation Method 1
a chromium carbide layer on pin hole surfaces to reduce contact wear and adhesion
Implementation Method 2
link plates composed of a bainite and martensite-mixed plate material
Data Source
AI summary
In a double-sided engagement silent chain having inner link plates with inwardly protruding teeth, outermost link plates with outwardly protruding teeth, and outer link plates with outwardly protruding teeth, adjacent the outermost link plates, the plates are composed of a bainite and martensite mixed plate material. The bainite mixing ratio in the outermost link plates is higher than the bainite mixing ratio of the inner link plates and the adjacent outer link plates. The martensite mixing ratio of the inner link plates and of the adjacent outer link plates is higher than the martensite mixing ratio in the outermost link plates. The heights of the backs of the outermost link plates, measured from the tooth gap bottoms, are greater than the corresponding heights of the backs of the inner link plates, and may be equal to or greater than the heights of the backs of the adjacent outer tooth plates.