Arcuate Spring Tensioner for Compact Engine Packaging
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Solution Overview
Problem
Existing tensioners for flexible drives, such as serpentine belts, face challenges in maintaining robustness and dampening characteristics while requiring a reduced height due to the large forces carried by the spring and frictional dampening members, leading to increased packaging volume and potential downsizing issues in compact engine compartments.
Innovation Solution
A tensioner design featuring a pivot shaft, a frustoconical pivot bushing, an arcuate spring, and a wear take-up mechanism that maintains continuous contact between the bushing and tensioner arm, allowing for reduced height and improved dampening through a laterally arranged arcuate spring and a hydraulic actuator for adjustable dampening.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If robust spring and frictional dampening members are used to carry large forces, then reliability and dampening characteristics are improved, but the height of the tensioner increases
Solution Approach 1:
The spring is repositioned from a vertical arrangement (coaxial with pivot shaft) to a lateral arrangement (arcuate path following the spring guide on the tensioner arm). This dimensional change moves the spring force application from the height dimension to the radial dimension, allowing robust spring design without increasing tensioner height
Solution Approach 2:
The spring is designed with an arcuate shape that follows the curved path of the spring guide, rather than a straight linear configuration. This curved geometry allows the spring to engage the tensioner arm laterally while maintaining compact height, optimizing both dampening characteristics and spatial efficiency
2Volume of stationary object
If tensioner components are downsized to occupy less volume, then packaging volume is reduced, but robustness deteriorates
Solution Approach 1:
The spring force is applied laterally through the arcuate spring guide rather than vertically, allowing the spring to be longer and more robust while occupying less vertical space. This redistributes the spatial requirements from height to radial dimension, maintaining robustness within compact packaging volume
Solution Approach 2:
The spring guide on the tensioner arm provides a dynamic curved path that allows the spring to follow the motion of the tensioner arm during operation. This dynamic engagement ensures continuous optimal contact and force application throughout the range of motion, maintaining robust performance in a compact design
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 design effectively maintains specified tension in flexible drives with reduced height, enhanced robustness, and adjustable dampening, minimizing wear and off-axis movement while optimizing spring force for various operational conditions.
Implementation Method 1
a spring acting between the mounting plate spindle and the tensioner arm to bias the tensioner arm to a first pivotal position about the pivot shaft, the spring having an arcuate shape corresponding to the path followed by a spring guide on the tensioner arm as the tensioner arm pivots about the pivot shaft
Implementation Method 2
Tensioners can also include frictional members which ride on one another as the tensioner arm moves to provide a dampening force to the tensioner
Data Source
AI summary
A tensioner operable to substantially maintain a specified tension in a flexible drive, such as a belt or chain, includes a spring, mounted laterally to the pivot shaft of the tensioner, which biases the tensioner arm towards the flexible drive. The spring is arcuate in shape and is maintained in a correspondingly arc-shaped spring retainer on a mounting plate of the tensioner. The arcuate shape of the spring and spring guide on the tensioner arm follows as the tensioner arm pivots towards and away from the flexible drive. The tensioner also has a wear take up mechanism to maintain the friction bushing in continuous engagement with the tensioner arm.