Random Sprocket Pitch Radii to Cut Noise Without Chain Resonance
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Solution Overview
Problem
Traditional random sprockets increase overall chain tensions in chain drives with external tension variations, often exceeding acceptable levels, while attempting to reduce engagement noise, and fail to effectively minimize tension fluctuations that resonate with the chain drive.
Innovation Solution
A random sprocket with a radial variation pattern using orders not prominent in the chain tension, avoiding resonance with oscillating excitations and external sources, combined with tension reducing random sprocket patterns to minimize tension increases and enhance noise reduction.
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 reduced, but overall chain tensions increase beyond acceptable levels
Solution Approach 1:
The patent applies local quality by creating a random sprocket where only specific radial variation patterns (those not prominent in external tension sources) are used at specific locations in the radial direction, while other patterns are avoided. This selective application of radial variation locally reduces noise without globally increasing chain tension.
Solution Approach 2:
The patent changes the parameters of the radial variation pattern by selecting specific orders that are not prominent in external tension sources. By modifying which frequency orders are present in the radial variation and avoiding those that would resonate with external excitations, the patent achieves noise reduction without excessive tension increase.
2Object-affected harmful factors
If random sprockets with radial variation are used to break up engagement noise, then noise is spread over many orders, but tension fluctuations occur at low orders causing resonance with chain drive
Solution Approach 1:
The patent changes the frequency domain parameters of the radial variation by performing a Fourier analysis to identify which orders are prominent in external tension sources. It then designs the radial variation pattern to avoid these specific frequency orders, preventing resonance while still achieving noise reduction through radial variation.
Solution Approach 2:
The patent uses feedback by analyzing the external tension sources (crankshaft torques, cam torques, fuel pump torques) to determine which frequency orders are already prominent. This information feeds back into the design of the random sprocket's radial variation pattern, ensuring that the sprocket does not add tension at resonant frequencies.
3Force
If tension reducing random sprockets use uniform repeating patterns to cancel tensions, then overall maximum tension is reduced, but engagement noise reduction is minimal
Solution Approach 1:
The patent applies asymmetry by using a non-uniform, random radial variation pattern instead of a uniform repeating pattern. The random pattern lacks symmetry and repetition, which prevents it from effectively canceling tensions through phase opposition while still achieving noise reduction by varying the timing of tooth engagement.
Data Source
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.