Stretch Roller Crown Shapes for Transfer Belt Wrinkle Control
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Solution Overview
Problem
Image forming apparatuses face issues with wrinkles on low-rigidity recording media, such as thin sheets, when passing through the transfer portion, leading to uneven toner transfer and image quality degradation.
Innovation Solution
The apparatus incorporates a first stretch roller with a normal crown shape and a second stretch roller with an inverse crown shape, both having straight and tapered areas, to deform the transfer belt and reduce wrinkles by enhancing adhesion and tension distribution, thereby preventing wrinkles on the recording medium.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a transfer belt is used to convey low-rigidity recording media through the transfer portion, then the recording medium can be transported, but wrinkles are generated on the recording medium leading to uneven toner transfer
Solution Approach 1:
The patent changes the physical parameters of the transfer belt by introducing variable tension zones with different tension levels. The first tension zone applies higher tension to flatten and suppress wrinkles on low-rigidity recording media, while the second tension zone maintains appropriate tension for subsequent transfer operations. This parameter variation resolves the contradiction by dynamically adjusting belt characteristics to prevent wrinkles while ensuring reliable toner transfer.
Solution Approach 2:
The patent implements a dynamic tension control system where the transfer belt transitions from a first tension state in the first tension zone to a second tension state in the second tension zone. This dynamic adjustment allows the system to adapt to different recording medium rigidity levels, suppressing wrinkles on flexible media while maintaining operational flexibility for various media types.
2Object-affected harmful factors
If the transfer belt tension is increased to suppress wrinkles, then wrinkle formation is reduced, but adhesion between the transfer belt and recording medium decreases
Solution Approach 1:
The patent applies different tension levels to different zones of the transfer belt. The first tension zone located upstream applies high tension specifically for wrinkle suppression, while the second tension zone located downstream maintains lower tension to preserve adhesion strength for toner transfer. This localized quality differentiation resolves the contradiction by providing high tension only where needed for wrinkle prevention without compromising adhesion in the transfer zone.
Solution Approach 2:
The transfer belt system is segmented into multiple tension zones with distinct tension characteristics. The first tension zone and second tension zone operate with different tension levels, allowing independent optimization of wrinkle suppression and adhesion maintenance. This segmentation enables the system to simultaneously achieve both objectives that would be conflicting in a uniform tension system.
3Device complexity
If uniform tension is applied across the transfer belt, then the structure is simple, but wrinkles appear on thin sheets and waved recording media
Solution Approach 1:
The patent introduces variable tension parameters along the transfer belt length, transitioning from uniform tension to non-uniform tension distribution. The first tension zone implements higher tension to suppress wrinkles on thin and waved recording media, while the second tension zone maintains appropriate tension for transfer operations. This parameter change resolves the contradiction by accepting increased system complexity to eliminate wrinkle formation.
Data Source
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AI summary
A first stretch roller (21) stretches a secondary transfer belt at a position where a tip in a conveying direction of a recording medium (P) being conveying through a secondary transfer portion (T2) can reach thereto. The first stretch roller has a circumferential surface formed into a normal crown shape in which a straight area (21c) where a diameter of the first stretch roller is constant is provided at a center part in a direction of axis of rotation. A second stretch roller (22) has a circumferential surface formed into an inverse crown shape in which a straight area (22c) where a diameter of the second stretch roller is constant is provided at a center part in a direction of axis of rotation.