Decoupler Clutch Surface Finish for Stress Reduction
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Solution Overview
Problem
Existing decouplers with wrap spring clutches face challenges in extending operating life due to high contact stresses and lubricant degradation, leading to premature failure from contamination and wear.
Innovation Solution
A decoupler design with a clutch engagement surface featuring peaks and valleys, where the peaks have a selected width based on material yield strength and lubricant working range, reducing contact stresses and lubricant degradation by enhancing the surface area of contact and minimizing stress beyond the yield strength of the material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If a smooth clutch engagement surface is used, then the contact area is small leading to high contact stresses, but increasing the surface area by using a textured surface may increase lubricant contamination and wear
Solution Approach 1:
The clutch engagement surface is provided with a localized textured pattern consisting of peaks and valleys, where only specific regions (the peaks) make contact with the wrap spring clutch. This creates localized contact zones that distribute stress across multiple peak elements while the valleys provide lubricant reservoirs to reduce wear and contamination.
Solution Approach 2:
The textured surface creates a porous-like structure with peaks and valleys that allows lubricant to be retained in the valley regions. This porous structure increases the effective contact area through multiple peak contacts while the lubricant in the valleys prevents direct metal-to-metal contact, reducing wear and contamination.
2Temperature
If lubricant is used to reduce heat buildup between the wrap spring clutch and clutch engagement surface, then heat management improves, but lubricant degradation and contamination occur leading to premature failure
Solution Approach 1:
The textured surface pattern is pre-formed on the clutch engagement surface before operation, with valleys designed to capture and retain lubricant. This preliminary preparation ensures that lubricant is already positioned in optimal locations to manage heat through lubrication, preventing the need for high lubricant volumes that would lead to degradation and contamination.
Solution Approach 2:
The textured surface structure acts as an intermediary between the wrap spring clutch and the lubricant. The peaks provide contact points for torque transmission while the valleys serve as intermediaries to hold and distribute lubricant, reducing direct contact and minimizing lubricant contamination and degradation.
3Stress or pressure
If the peak width is increased to reduce contact stress, then stress distribution improves, but the surface area available for lubricant retention decreases
Solution Approach 1:
The clutch engagement surface is segmented into multiple discrete peak elements distributed across the surface. Each peak is narrow enough to allow sufficient valley space for lubricant retention, but collectively the multiple peaks provide adequate stress distribution. This segmentation allows both narrow individual peaks for lubricant retention and sufficient total contact area for stress management.
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 modified surface finish reduces contact stresses, minimizes lubricant contamination, and extends the operating life of the decoupler by maintaining lower stress levels and preventing premature wear, allowing for a broader range of operating conditions without exceeding the yield strength of the material.
Implementation Method 1
The clutch engagement surface has a surface finish that includes peaks and valleys, wherein the peaks engage the wrap spring clutch and each have a selected width, and a selected peak-to-peak pitch
Implementation Method 2
a volume of lubricant is positioned to lubricate the wrap spring clutch and the clutch engagement surface
Implementation Method 3
The peaks each have a selected width that is based at least in part on one or more properties selected from: a yield strength of a material making up the clutch engagement surface
Data Source
AI summary
In an aspect, the invention is directed to a clutched device that includes a clutch input member, a clutch output member, and a wrap spring clutch. The wrap spring clutch is engageable with the clutch input member and the clutch output member and has a radially outer surface and a radially inner surface. One of the radially outer and inner surfaces is engageable with a clutch engagement surface on one of the clutch input member and the clutch output member. The clutch engagement surface has a surface finish that includes peaks and valleys, wherein the peaks engage the wrap spring clutch and each have a selected width.