Obround Sprocket Timing Drive for Low Angular Vibration
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Solution Overview
Problem
Existing synchronous belt drive systems in automotive and industrial engines face challenges in managing angular displacement timing errors and cyclic torque fluctuations, which can lead to vibrations detrimental to engine operation and longevity.
Innovation Solution
A synchronous belt drive system incorporating an obround sprocket with a specific magnitude and phase, featuring arcuate and linear portions, is designed to minimize angular displacement timing errors to less than 1.5 degrees peak to peak, thereby reducing tension fluctuations and vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional circular sprocket is used, then the structure is simple and easy to manufacture, but angular displacement timing error exceeds 1.5 degrees peak to peak
Solution Approach 1:
The patent applies asymmetry by designing an obround sprocket with non-circular geometry, specifically with alternating radii (R1 and R2) that create an asymmetric profile. This asymmetric shape is specifically configured to counteract the cyclic torque fluctuations from camshaft lobes, reducing angular displacement timing error to less than 1.5 degrees peak to peak while maintaining manufacturing feasibility through standardized obround geometry.
2Object-affected harmful factors
If camshaft dampers or damped belt tensioners are used to attenuate fluctuating torque loads, then vibration is reduced, but device complexity and cost increase
Solution Approach 1:
The patent applies parameter changes by modifying the sprocket's geometric parameters (alternating radii R1 and R2, arc lengths, and angular positions) to create a variable transmission ratio that actively counteracts the cyclic torque fluctuations. This changes the operational parameters of the belt drive system to reduce vibration without adding separate damping components, thereby avoiding increased device complexity.
3Manufacturing precision
If the obround sprocket is properly phased, then angular displacement timing error is reduced to less than 1.5 degrees peak to peak, but the design and alignment requirements become more stringent
Solution Approach 1:
The patent applies preliminary action by pre-configuring the obround sprocket with specific phase relationships between its alternating radii and the camshaft lobe positions. The sprocket is designed and installed with predetermined phase angles that proactively align the maximum and minimum radius positions with the corresponding torque fluctuation cycles, thereby reducing angular displacement timing error before operation begins and simplifying alignment requirements during installation.
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
The obround sprocket system effectively reduces angular vibration and tension fluctuations, enhancing engine performance, efficiency, and extending belt lifespan by optimizing the belt span length and elastic modulus to counteract cyclic torque fluctuations.
Implementation Method 1
a synchronous belt drive system comprising an obround sprocket (10) having a toothed surface and at least one linear portion (16) disposed between two arcuate portions (14,15), the arcuate portions having a constant radius (R1, R2), the linear portion having a predetermined length
Data Source
AI summary
A synchronous belt drive system comprising a first obround sprocket having a toothed surface and at least one linear portion disposed between two arcuate portions, the arcuate portions having a constant radius, the linear portion having a predetermined length, a sprocket having a toothed surface, the sprocket engaged to the first obround sprocket by an endless toothed member, and the first obround sprocket having a magnitude and a phase such that an angular displacement timing error between the sprocket and the first obround sprocket is less than 1.5 degree peak to peak.