Variable-Pitch Toothed Belt Drive for Lower Meshing Noise
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Solution Overview
Problem
Existing toothed belt drives generate significant noise and vibrations due to regular tooth pitch and meshing frequencies, which are difficult to mitigate with current noise reduction methods, especially in high-speed applications with varying pulley sizes, and require precise installation, making them error-prone and challenging to assemble.
Innovation Solution
Designing at least one toothed belt or pulley with varying tooth pitches along the circumference, where the deviation from the nominal pitch is limited by the gap clearance, significantly reducing structure-borne noise and vibrations by spectrally pre-calculating tooth meshing sequences to minimize dominant frequencies and secondary order levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If regular tooth pitch is used in toothed belt drives, then manufacturing precision is improved, but noise and vibrations increase significantly
Solution Approach 1:
The patent applies local quality by varying the tooth pitch in specific local regions of the belt rather than maintaining uniform pitch throughout. Different sections of the belt have different pitch characteristics, allowing noise reduction in critical areas while maintaining manufacturing feasibility. The variation is localized to specific tooth groups rather than requiring complete redesign of the entire belt.
Solution Approach 2:
The patent changes the pitch parameter from a constant value to a variable value along the belt length. By modifying the pitch parameter in controlled ways (creating pitch variations within specified ranges), the patent reduces the regularity that causes resonant vibrations and noise while still maintaining functional performance of the timing drive.
2Object-generated harmful factors
If division groups with up to 20% pitch difference are used to reduce noise, then noise emissions are reduced, but installation precision requirements increase and assembly becomes error-prone
Solution Approach 1:
The patent modifies the pitch parameter with much smaller variations (within ±0.02mm of nominal pitch) compared to prior art solutions that used 20% pitch differences. This subtle parameter change achieves noise reduction through breaking regular vibration patterns while maintaining compatibility with standard manufacturing tolerances and installation procedures, thus avoiding increased assembly complexity.
3Object-generated harmful factors
If larger pitch variations are used to reduce tooth meshing frequency, then noise is reduced, but reliability decreases due to belt destruction on skipping
Solution Approach 1:
The patent applies local quality by implementing pitch variations only in specific sections of the belt rather than throughout the entire length. This allows the belt to maintain uniform pitch in critical load-bearing sections for reliability, while introducing pitch variations in other sections to reduce noise from regular meshing frequencies. The selective application preserves both noise reduction and structural integrity.
Solution Approach 2:
The patent changes the pitch parameter within very narrow limits (±0.02mm) rather than using large pitch variations. This subtle parameter modification reduces tooth meshing frequency noise by breaking regular vibration patterns while maintaining sufficient engagement geometry to prevent belt damage during skipping or overload conditions, thus preserving reliability.
4Manufacturing precision
If precise and uniform tooth pitch is manufactured on vulcanization molds, then manufacturing precision is improved, but noise from regular oscillation increases
Solution Approach 1:
The patent applies local quality by introducing pitch variations in specific localized regions of the belt rather than compromising overall manufacturing precision. The vulcanization molds can still manufacture teeth with high precision, but the pitch between tooth groups is varied in controlled sections. This maintains manufacturing feasibility while reducing the regular oscillation patterns that generate airborne and structure-borne noise.
Solution Approach 2:
The patent changes the pitch parameter by introducing small variations (±0.02mm) in specific sections of the belt. This parameter modification disrupts the regular oscillation patterns that cause noise while maintaining sufficient precision for functional operation. The changes are small enough to be achievable with standard manufacturing processes yet large enough to reduce resonant noise effectively.
Data Source
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AI summary
The invention relates to a toothed belt drive comprising a toothed belt and at least two toothed pulleys, the toothed belt having at least one drive side provided with a toothed profile, the toothed belt looping around the toothed pulleys over part of the circumference of the pulleys and the teeth of the toothed belt meshing with the gaps between the teeth of the toothed pulleys. At least one of the sets of teeth on the belt or pulley is designed as a sequence of tooth pitches varying along the circumference, where - the individual tooth pitches vary at most by 5% relative to the mean tooth pitch on the belt or pulley and - the absolute difference of a varied tooth pitch from the mean tooth pitch on the belt or pulley is limited by the play (backlash) of the teeth, the play E S resulting from the difference between the width e S of the play between the toothed pulley in question and the width e R of the teeth of the toothed belt in the middle of the tooth height of the teeth of the toothed belt.