Random Sprocket Pitch Radius Pattern for Low-Noise Chain Drives
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Solution Overview
Problem
Traditional random sprockets increase overall chain tensions in internal combustion engine chain drives, especially when external tension variations are present, leading to unacceptable tension levels and noise issues, as they amplify torsional resonance frequencies and add to existing tension fluctuations.
Innovation Solution
Designing a random sprocket with a radial variation pattern that avoids orders prominent in chain tensions, minimizing tension increases and resonance excitation, and combining it with tension reducing random sprockets to reduce both noise and maximum chain tensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If traditional random sprockets are used to reduce engagement noise, then engagement noise is spread out over many orders, but overall chain tensions increase beyond acceptable levels
Solution Approach 1:
The sprocket design applies local quality by creating non-uniform tooth spacing patterns where specific teeth are positioned at different radial distances from the sprocket center. This localized variation in tooth position spreads engagement noise across multiple frequency orders while the carefully controlled pattern ensures tension fluctuations remain within acceptable limits, resolving the contradiction between noise reduction and tension control.
Solution Approach 2:
The invention changes the geometric parameters of the sprocket teeth by varying the radial position of individual teeth relative to the sprocket center. This parameter variation creates the random-like engagement pattern that reduces noise, while the controlled magnitude of these parameter changes prevents excessive tension fluctuations, simultaneously addressing both noise reduction and tension control requirements.
2Object-affected harmful factors
If random sprockets create tension fluctuations at resonance frequencies, then tension fluctuations are amplified, but this leads to substantial variation in chain tensions
Solution Approach 1:
The sprocket design incorporates preliminary anti-action by pre-configuring the tooth spacing pattern to avoid creating tension fluctuations at the chain drive's resonance frequencies. The non-uniform tooth positions are deliberately arranged so that the resulting tension fluctuation spectrum does not overlap with resonance frequencies, preventing amplification and maintaining stable chain tensions throughout operation.
3Force
If tension reducing random sprockets use uniform repeating patterns, then tensions are reduced, but engagement noise reduction is limited
Solution Approach 1:
The invention applies asymmetry by using non-uniform, non-repeating tooth spacing patterns instead of uniform repeating patterns. This asymmetric arrangement of teeth at varying radial positions creates more effective noise reduction by spreading engagement frequencies across a broader spectrum, while the pattern is carefully designed to maintain acceptable tension levels, overcoming the limitations of uniform patterns.
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 solution effectively reduces engagement noise while maintaining acceptable chain tensions, even with external excitations, by minimizing the interaction between sprocket-induced tensions and existing tension fluctuations, and allowing for easier manufacturing and servicing due to reduced tension variation with sprocket orientation.
Implementation Method 1
Random sprocket or pulley with varying pitch radius are intended to reduce the engagement noise of the drive. The random sprocket or pulley uses a radial variation pattern made of orders that are not already prominent in the chain tension
Implementation Method 2
the radial variation of the random sprocket creates oscillating tensions in the chain drive - mostly at low orders (several times per sprocket revolution)
Implementation Method 3
a chain or toothed belt drive is subjected to oscillating excitations. For example, a chain or toothed belt drive can be used between an engine crank shaft and cam shaft
Data Source
Figure 1
Figure 2a
Figure 2b
AI summary
A non-prevalent order random sprocket for an internal combustion engine comprising a pattern of pitch radii, such that the radial variation of the pitch radii excite tensions at non-prevalent orders in a drive system of the internal combustion engine.