Dual Backlash Chain Tensioner for Noise Reduction
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Solution Overview
Problem
Existing chain drive tensioners often over-tension new chains, leading to 'chain whine' noise due to premature advancement of the ratchet tooth, while worn chains require increased tension to prevent skipping, necessitating a solution that balances initial slack management with long-term chain elongation.
Innovation Solution
A dual backlash tensioner that initially operates with large backlash values to prevent over-ratcheting in new chains, transitioning to standard small backlash values as the chain wears, ensuring controlled tensioning without over-tensioning and preventing chain skipping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a ratchet tensioner with small backlash is used, then worn chains are prevented from skipping teeth, but new chains become over-tensioned causing chain whine noise
Solution Approach 1:
The tensioner transitions from a static fixed-backlash design to a dynamic system that automatically adjusts backlash based on chain wear. The stop cam rotates relative to the toothed rack, changing the engagement position between cam teeth and rack teeth, thereby providing large initial backlash for new chains and reducing to small backlash for worn chains.
Solution Approach 2:
The invention changes the backlash parameter dynamically through the rotation of the stop cam. As the cam rotates, the effective backlash between the cam teeth and rack teeth changes, allowing the system to adapt to different chain wear states without manual intervention.
2Device complexity
If a fixed backlash tensioner is used, then the structure is simple, but it cannot adapt to both new and worn chain conditions
Solution Approach 1:
The tensioner incorporates a dynamic adjustment mechanism where the stop cam rotates to change the backlash value. This dynamic feature allows the simple ratchet structure to adapt to varying chain conditions while maintaining ease of manufacture and operation.
Solution Approach 2:
The tensioner system is self-adjusting through the interaction between the stop cam and toothed rack. As the chain wears and the plunger extends, the stop cam naturally rotates to a position where the backlash is reduced, providing automatic adaptation without external control.
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 dual backlash tensioner effectively reduces chain whine noise in new chains and maintains proper tension in elongated chains, preventing tooth skipping while allowing for gradual ratcheting as the chain wears, thus providing consistent and efficient chain management.
Implementation Method 1
A resilient member acts between the support and the plunger and urges the shoe outwardly. A resilient member urges the first tooth toward engagement with the plunger.
Implementation Method 2
A resilient member acts between the support and the plunger and urges the shoe outwardly.
Implementation Method 3
A latch, in the form of an oscillatable stop cam having first and second spaced teeth, is engagable with the plunger. The stop cam is pivotally mounted on the support.
Data Source
AI summary
A dual backlash tensioner includes a support having a recess therein. A plunger is slidable in the recess and includes a shoe extending outward from the recess. A first resilient member acts between the support and the plunger and urges the shoe outwardly. An oscillatable stop cam having first and second teeth spacedly disposed thereon is engagable with the plunger. The stop cam is pivotally mounted on the support. A second resilient member urges the first tooth toward engagement with the plunger. The plunger has a control portion opposing the stop cam that includes a toothed rack and an adjoining depression positioned toward the shoe. The stop cam teeth are adapted to engage the toothed rack.