Dynamic Transfer Voltage Control for Image Banding in Direct Transfer
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Solution Overview
Problem
In direct transfer image forming systems, large current spikes occur when media sheets enter and exit the transfer nip, leading to print defects due to non-uniform charge distribution on the photoconductive member, causing either light or dark bands.
Innovation Solution
The method involves controlling the transfer voltage by ramping it up or down with alternating positive and negative steps to offset these current spikes, ensuring a smooth transition and preventing overcharging of the photoconductive member.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If constant transfer voltage is applied during media sheet transfer, then simple voltage control is achieved, but large current spikes occur when media sheet enters and exits the transfer nip causing print defects
Solution Approach 1:
The patent applies dynamics by transitioning from constant voltage control to dynamic voltage control where the transfer voltage is continuously adjusted based on real-time current feedback. The controller modifies the voltage level in response to detected current spikes, creating a dynamic system that adapts to the changing electrical conditions during media sheet entry and exit from the transfer nip.
Solution Approach 2:
The patent implements feedback control by monitoring the current flowing through the transfer nip and using this information to adjust the transfer voltage. When current spikes are detected during media sheet entry or exit, the controller responds by modifying the voltage to compensate for the spike, thereby preventing print defects while maintaining overall transfer efficiency.
2Productivity
If transfer voltage is increased to improve toner transfer efficiency, then faster transfer is achieved, but current spikes are amplified causing more severe print defects
Solution Approach 1:
The patent applies preliminary anti-action by detecting current spikes before they cause significant damage and immediately counteracting them with voltage adjustments. The feedback control system anticipates the harmful effects of current spikes by monitoring current levels and preemptively modifies the transfer voltage to neutralize the spike's impact, preventing light or dark bands on the printed image.
Solution Approach 2:
The patent implements parameter changes by dynamically adjusting the transfer voltage parameter in response to current conditions. Rather than maintaining a fixed high voltage for maximum transfer efficiency, the system varies the voltage parameter in real-time, reducing it during media sheet entry/exit to minimize current spikes while maintaining higher levels during stable transfer periods to ensure productivity.
3Manufacturing precision
If transfer voltage is reduced to minimize current spikes, then print defects are reduced, but toner transfer efficiency decreases
Solution Approach 1:
The patent resolves this contradiction through dynamic voltage adjustment, allowing the transfer voltage to be high during stable transfer periods for maximum productivity while automatically reducing it during media sheet entry and exit to maintain print quality. This dynamic approach enables the system to optimize both transfer efficiency and print quality at different moments in the transfer cycle.
Solution Approach 2:
The patent applies periodic action by implementing a control cycle that continuously monitors current and adjusts voltage in periodic intervals. The feedback control operates in cycles, detecting current conditions and applying appropriate voltage adjustments periodically, thereby maintaining both high transfer efficiency and acceptable print quality through rhythmic optimization rather than static settings.
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
This approach effectively mitigates the print defects by stabilizing the charge on the photoconductive member, maintaining consistent image quality by managing the transfer current spikes during media sheet entry and exit from the transfer nip.
Implementation Method 1
The electrophotographic process uses electrostatic voltage differentials to promote the transfer of toner from component to component. This voltage vector helps promote the transfer of toner from the developer roll to the latent image
Implementation Method 2
A separate voltage vector may exist within a transfer nip formed between the photoconductive member and a transfer member to promote the transfer of a developed image onto a media sheet. The toner transfer occurs in part because the toner itself is charged and is attracted to surfaces having an opposite charge or a lower potential
Data Source
AI summary
The present application is directed to methods of controlling the transfer voltage in a transfer nip formed between the photoconductive member and the transfer member. The methods offset the effects of large transfer current spikes caused when a media sheet enters and exits the transfer nip. The control may include either ramping up or ramping down the transfer voltage. The ramped transfer voltage may include a series of alternating positive and negative steps that generally trend to ramp up or down. The size of the steps may further be adjusted to provide a smooth transition.