Hollow Rotating Shaft Joint Asymmetry for Torsional Rigidity
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Solution Overview
Problem
Hollow rotating shafts in charging rollers used in electrophotographic image forming apparatuses can suffer from reduced torsional rigidity due to dimensional errors in projections and recesses, leading to uneven contact with the photosensitive drum and image defects.
Innovation Solution
A cylindrical rotating shaft with a joint portion featuring projections and recesses, where the projections have a first corner portion with a larger radius of curvature than the recesses, forming a gap between the corner portions to enhance torsional rigidity and prevent interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If continuously toothed projections and recesses are used to increase torsional rigidity, then the hollow rotating shaft can maintain uniform contact with the photosensitive drum, but dimensional errors cause corner portions to fail to contact properly, reducing torsional rigidity
Solution Approach 1:
The patent applies asymmetry by making the first corner portions of the projections have a larger radius of curvature than the second corner portions of the recesses. This asymmetric design ensures that even with dimensional errors, the corner portions can properly contact and interlock, maintaining the torsional rigidity of the hollow rotating shaft while compensating for manufacturing variations
2Ease of manufacture
If rectangular or trapezoidal projections and recesses are used, then the structure is simple to manufacture, but corner portions may not properly contact due to dimensional errors, leading to reduced strength
Solution Approach 1:
The patent applies local quality by differentiating the radius of curvature between the first corner portions of projections and the second corner portions of recesses. This localized variation in geometric properties ensures proper contact and interlocking at the corner portions while maintaining the overall simplicity of the toothed structure, thus preserving both ease of manufacture and torsional rigidity
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 minimizes the reduction in strength of the hollow rotating shaft, ensuring uniform contact and improved image quality by maintaining the torsional rigidity and preventing interference between the projections and recesses.
Implementation Method 1
The continuous toothed shape of the joint part of both ends of the sheet metal increases the frictional force between one end and the other end of the sheet metal, whereby the torsional rigidity of the hollow rotating shaft is increased
Data Source
AI summary
One end portion and the other end portion of a rotating member, which face each other and form a joint portion, have a shape with projections and recesses. Projections of one end portion fit in recesses of the other end portion, while projections of the other end portion fit in recesses of the one end portion, so that the one end portion and the other end portion are interlocked. The projections have a first corner portion rounded in an arc, while the recesses have a second corner portion rounded in an arc in which the first corner portion fits. The first corner portion has a larger radius of curvature than that of the second corner portion.