Offset Transfer Roller AC Field for Toner Charge Control
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Solution Overview
Problem
Charge buildup on toner images in intermediate transfer mechanism (ITM) type electrophotographic image forming devices leads to unpredictable toner placement and backtransfer during secondary transfer, affecting image quality due to high transfer voltages causing Paschen breakdown.
Innovation Solution
A toner transfer apparatus with a laterally offset transfer roller made of non-compressible conductive material, using AC current with a DC offset to generate an electrical field between the photoconductor drum and the transfer roller, reducing charge buildup by altering the electrical path resistivity and voltage requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high transfer voltage is used to transfer highly charged toner, then complete toner transfer is achieved, but Paschen breakdown occurs causing unpredictable toner placement and backtransfer
Solution Approach 1:
The patent changes the electrical parameters by using AC current with DC offset instead of pure DC voltage, and introduces a laterally offset transfer roller configuration. This modifies the electric field distribution and reduces peak voltage stress, preventing Paschen breakdown while maintaining effective toner transfer through optimized field distribution.
Solution Approach 2:
The laterally offset transfer roller acts as an intermediary element that redistributes the electric field between the photoconductor drum and the toner image. By positioning the transfer roller laterally offset from the drum center, it creates a more uniform electric field that transfers toner effectively without causing breakdown.
2Adaptability or versatility
If toner passes through multiple image transfer stations, then full-color image is formed, but charge buildup increases causing transfer voltage variability
Solution Approach 1:
The patent applies periodic AC current with DC offset to the transfer roller, creating a time-varying electric field that periodically refreshes the charge distribution on the toner image. This periodic action prevents cumulative charge buildup as toner passes through multiple transfer stations, maintaining consistent transfer voltage requirements.
Solution Approach 2:
The patent introduces dynamic control through AC current modulation, allowing the electric field to adapt to the changing charge state of the toner image. The dynamic field distribution compensates for charge buildup variations that occur as toner progresses through multiple color transfer stations.
3Reliability
If AC current with DC offset is used to generate electrical field, then charge buildup is reduced, but device complexity increases
Solution Approach 1:
The transfer roller serves multiple functions: it provides mechanical pressure for toner transfer, generates the electric field through AC current with DC offset, and acts as a charge management element. By combining these functions in a single component, the patent reduces overall device complexity while achieving charge buildup control.
Solution Approach 2:
The patent merges the electric field generation function with the mechanical transfer function by using the transfer roller for both purposes. The AC current with DC offset is applied directly to the transfer roller, combining electrical and mechanical roles in one element, thereby simplifying the overall system architecture.
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 minimizes charge buildup and prevents backtransfer, maintaining consistent toner transfer quality by optimizing the electrical field and voltage distribution, resulting in improved image fidelity and reduced defects.
Implementation Method 1
AC current may be used to generate an electrical field between the photoconductor drum and the transfer roller
Implementation Method 2
The transfer roller may be constructed of an essentially non-compressible conductive material
Implementation Method 3
Charge buildup may be reduced by laterally offsetting a transfer roller from a photoconductor drum
Data Source
AI summary
The present application is directed to methods and devices for controlling charge buildup on a toner image as the toner image passes through one or more transfer nips. Charge buildup may be reduced by laterally offsetting a transfer roller from a photoconductor drum. The transfer roller may be constructed of an essentially non-compressible conductive material. AC current may be used to generate an electrical field between the photoconductor drum and the transfer roller.