Pulley Assembly Coil Spring Groove Design for Noise Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing pulley systems in alternators experience noise and reduced durability due to belt slippage and resonance caused by crankshaft rotational speed fluctuations, and coil springs prone to fatigue from stress concentration at fixed ends.
Innovation Solution
A pulley assembly with a coil spring interconnecting two members, where the coil spring is clamp-fitted into grooves with a gradual radial gap increase and undulating surfaces to distribute stress and allow for large angular displacement, reducing stress concentration and enhancing durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the coil spring ends are fixed in grooves with sharp transition corners to allow large angular displacement, then the belt resonance and noise are suppressed, but the coil spring corners experience stress concentration leading to fatigue and potential fracture
Solution Approach 1:
The groove is designed with different geometric characteristics at different locations: the transition corners are rounded to eliminate stress concentration for the coil spring, while the groove maintains sufficient depth and curvature to allow large angular displacement and suppress belt resonance. This local differentiation resolves the contradiction between durability and noise suppression.
2Productivity
If the coil spring is allowed to undergo large elastic deformation to absorb crankshaft speed fluctuations, then the belt slippage is reduced, but the stress on the spring increases leading to potential breakage
Solution Approach 1:
The groove geometry is designed in advance to provide stress distribution and protection. The rounded transition corners and optimized groove curvature预先 (in advance) cushion the stress that would otherwise concentrate on the spring, allowing the spring to undergo large deformations for absorbing crankshaft fluctuations without risking breakage.
3Power
If the coil spring is rigidly fixed to the pulley and shaft to transmit torque efficiently, then the power transmission is improved, but the ability to absorb rotational speed fluctuations is reduced
Solution Approach 1:
The coil spring is designed to be dynamically connected to both the pulley and shaft through the groove mechanism. The groove geometry allows the spring to rotate and deform freely enough to absorb crankshaft speed fluctuations, while still maintaining sufficient contact and geometric constraint to transmit torque effectively from the alternator shaft to the pulley.
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 absorbs rotational fluctuations, reduces noise, and increases belt durability by distributing stress evenly across the coil spring, preventing premature fatigue and maintaining system efficiency.
Implementation Method 1
the elastic deformation permissible within the limit of the elasticity of the rubber member
Implementation Method 2
A viscous fluid is also utilized, the viscosity of which increases in response to the generation of a shear force resulting from rotational speed fluctuations
Implementation Method 3
capable of generating a shearing stress in excess of the elastic limit of the elastic member, a relative angular displacement between the pulley and member is suppressed by reason of an increase in viscosity of the viscous fluid
Data Source
AI summary
A pulley assembly having first and second members. The first member is capable of cooperating with a power transmission belt to drive/be driven by the belt. The first member is movable guidingly relative to the second member around a first axis. A coil spring has a length and a circumference and a first portion attached to the first member and a second portion attached to the second member so that a force tending to move the first/second member around the first axis is transmitted through the coil spring to the second/first member. At least one of the first and second members has a groove bounded by a surface into which the respective portion of the coil spring is fit. The respective portion of the coil spring is clamp fit within the groove.