Image Forming Apparatus Bowing Control for Trailing End Smear
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Solution Overview
Problem
Image forming apparatuses face issues with 'trailing end smear' due to speed differences between the trailing end of the recording medium and the photosensitive drum or transfer roller, leading to image defects, especially in borderless printing where margins are small.
Innovation Solution
An image forming apparatus equipped with a bowing amount measuring unit and a speed controller that adjusts the feeding speed of the recording material to maintain a zero bowing state at the trailing end's exit from the transfer nip, preventing speed discrepancies and smearing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If borderless printing is performed with a toner image slightly larger than the sheet on the peripheral surface of the photosensitive drum, then the entire sheet can be covered with the image, but the trailing end portion of the sheet reduces in speed in the transfer nip causing tail end smear
Solution Approach 1:
The patent applies preliminary action by controlling the bowing amount of the sheet in advance before the trailing end reaches the transfer nip. The bowing amount is adjusted beforehand so that when the trailing end exits the transfer nip, the sheet is in a substantially flat state, preventing speed reduction and tail end smear. This proactive control ensures the sheet is ready for high-speed transfer at the critical moment.
Solution Approach 2:
The patent implements dynamics by making the bowing amount adjustable and variable during the transfer process. The bowing control unit dynamically adjusts the bowing amount based on the sheet's position and the transfer requirements. This dynamic adjustment allows the system to adapt to different printing conditions and maintain optimal transfer speed throughout the process, preventing tail end smear while ensuring complete image coverage.
2Productivity
If the sheet is conveyed through the transfer nip at high speed, then productivity is improved, but the trailing end portion reduces in speed causing smearing of the toner image
Solution Approach 1:
The system performs preliminary bowing control before the trailing end of the sheet reaches the transfer nip. By adjusting the bowing amount in advance, the sheet is prepared to exit the transfer nip in a substantially flat state, which prevents speed reduction at the critical moment of image transfer. This ensures high transfer speed is maintained throughout the process, improving productivity while preventing smearing.
Solution Approach 2:
The patent employs feedback control where the bowing amount is measured and used to adjust the sheet conveyance speed. The measurement unit continuously monitors the bowing amount, and the control unit adjusts the speed accordingly to maintain the sheet in a substantially flat state at the transfer nip exit. This closed-loop feedback ensures consistent transfer quality and maintains high productivity.
3Manufacturing precision
If the trailing end of the sheet is pulled by the fixation nip, then the sheet positioning is improved, but the sheet bows excessively causing misalignment in the transfer nip
Solution Approach 1:
The patent applies preliminary action by controlling the bowing amount before the sheet enters the fixation nip. The bowing control unit adjusts the bowing amount in advance so that when the sheet reaches the fixation nip, it is in a substantially flat state. This prevents excessive bowing during fixation and ensures proper alignment in the transfer nip, while still achieving good sheet positioning.
Solution Approach 2:
The system implements dynamic bowing control that adjusts the bowing amount based on real-time measurements and sheet position. The bowing control unit continuously modifies the bowing amount to maintain the sheet in a substantially flat state throughout the transfer and fixation process. This dynamic adjustment prevents excessive bowing while maintaining good sheet positioning and alignment.
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 prevents trailing end smear by ensuring the recording medium exits the transfer nip at the same speed as the drum, resulting in high-quality borderless prints without image defects.
Implementation Method 1
an electrostatic latent image is formed on the peripheral surface of the photosensitive drum 205 by electrophotographic processing devices
Implementation Method 2
the toner image on the drum 205 is transferred onto the transfer sheet P as if it is peeled away from the drum 205
Implementation Method 3
the unfixed toner image on the transfer sheet P is fixed to the transfer sheet P
Data Source
AI summary
An image forming apparatus includes a rotatable image carrying member, a rotatable transfer member cooperative with the image carrying member, and a fixing unit having a fixing nip for nipping and feeding the recording material discharged from the transfer nip while fixing the toner image. In addition, a bowing amount measuring unit measures a bowing amount of the recording material, a storing portion stores a target bowing amount, and a speed controller controls a feeding speed of the recording material. The storing portion stores a plurality of target bowing amounts, which are selectable depending on kinds of the recording material, and the speed controller controls the feeding speed in the fixing nip, and then controls the feeding speed so that the bowing amount is substantially zero at the time when a trailing edge of the recording material leaves the transfer nip.