Sheet Conveyance Roller Control for Wrinkle Prevention
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Solution Overview
Problem
Existing sheet conveyance apparatuses in image forming devices face issues with sheet wrinkles and reduced throughput due to the need to frequently separate and re-contact conveyance rollers during skew correction, which can lead to inefficiencies and operational stops.
Innovation Solution
A sheet conveyance apparatus with a control system that acquires sheet length information and adjusts the operation of roller pairs, allowing for either continuous contact or separation of the pre-registration roller pair based on sheet length and grammage to prevent wrinkles and optimize throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the conveyance roller pair is separated and re-contacted every time one sheet is conveyed to prevent wrinkles, then the sheet quality is improved, but the throughput of the sheet conveyance apparatus deteriorates due to temporary stops in sheet conveyance operation
Solution Approach 1:
The patent changes the operational parameters of the conveyance roller pair based on sheet characteristics. Specifically, it switches between two modes: (1) separating the roller pair for sheets with high wrinkle risk (long sheets or sheets with small grammage), and (2) maintaining continuous contact for sheets with low wrinkle risk (short sheets or sheets with large grammage). This parameter-based approach resolves the contradiction by optimizing the balance between sheet quality and throughput based on actual sheet conditions.
Solution Approach 2:
The patent implements a dynamic control system that adjusts the conveyance roller pair operation in real-time based on sheet length and grammage information. The system dynamically selects the appropriate mode (separation or continuous contact) for each sheet, making the system adaptable rather than static. This dynamic approach allows the apparatus to prevent wrinkles when necessary while maintaining high throughput when possible.
2Productivity
If the conveyance roller pair is kept in continuous contact to maintain high throughput, then the productivity is improved, but sheet wrinkles are generated due to nipping of the twisted part by the roller pair
Solution Approach 1:
The patent applies parameter changes by setting specific thresholds for sheet length and grammage that determine when to switch between separation mode and continuous contact mode. This quantitative parameter-based control allows the system to automatically adjust its behavior to prevent wrinkles for vulnerable sheets while maintaining high throughput for robust sheets, effectively resolving the contradiction between productivity and sheet quality.
3Device complexity
If the driving source for rotating the conveyance roller pair is also used for separating the roller pair, then the device complexity is reduced, but the sheet conveyance operation is temporarily stopped during separation or contact operations
Solution Approach 1:
The patent applies the multi-functionality principle by designing the driving source to perform dual functions: rotating the conveyance roller pair for sheet conveyance and actuating the separating mechanism for roller pair separation. This universal design reduces device complexity by eliminating the need for separate driving mechanisms. The system accepts temporary stops during mode switching as a necessary trade-off for the simplified mechanical design, while minimizing these stops through intelligent mode selection based on sheet characteristics.
Data Source
AI summary
A first roller pair disposed upstream of a second roller pair is separated from each other by a separating mechanism. A control portion is configured to start rotating the second roller pair after a leading edge of a sheet in a sheet conveyance direction is abutted against the second roller pair in a stopped condition. The control portion is configured to execute, based on the information concerning the sheet length acquired by the acquisition portion, either one of a plurality of modes including a first mode of rotating an upstream roller pair and the first roller pair to convey the sheet while the first roller pair is in a contact condition and a second mode of operating the separating mechanism to separate the first roller pair and of rotating the upstream roller pair to convey the sheet while the first roller pair is in a separated condition.