Shielded Charging Roller for Electrophotographic Image Stability
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Solution Overview
Problem
Existing image forming apparatuses using electrophotographic systems face challenges with charging unevenness due to interference between charging and developing biases, leading to image quality issues like jitteriness and blurriness, and existing solutions for minimizing interference are either ineffective in achieving miniaturization or complicate maintenance.
Innovation Solution
A compact charging unit with a metal shield member surrounding an insulating casing, which is in close contact with the charging member, is used to reduce the influence of developing bias on the charging bias, preventing electromagnetic induction and improving image stability while allowing for easy maintenance and miniaturization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a contact charging unit is used to reduce ozone emission, then environmental friendliness is improved, but charging unevenness occurs due to microscopic irregularities on the charging roller surface
Solution Approach 1:
The patent applies pulsating current voltage to the charging roller, creating a time-varying electric field that compensates for local irregularities on the charging roller surface and photosensitive member, achieving uniform charging despite surface imperfections
Solution Approach 2:
The patent uses pulsating current with a specific frequency range (50-2000 Hz) to create periodic electric field variations, which prevents spot-like charging unevenness by continuously adjusting the charge distribution on the contact surfaces
2Volume of moving object
If the charging unit and developing unit are placed close together for miniaturization, then device size is reduced, but electromagnetic induction causes interference between charging bias and developing bias
Solution Approach 1:
The patent introduces a shield member as an intermediary component between the charging unit and developing unit. This shield member blocks electromagnetic induction and interference between the charging bias and developing bias, allowing close placement of units without image quality degradation
Solution Approach 2:
The shield member is grounded to create an equipotential barrier, preventing electromagnetic interference from affecting the charging process while maintaining compact device dimensions
3Stability of the object's composition
If alternating current components are applied to both charging bias and developing bias for stable image formation, then image stability is improved, but electromagnetic induction causes beats and charging unevenness
Solution Approach 1:
The grounded shield member acts as an intermediary that prevents electromagnetic induction between the alternating current components of the charging bias and developing bias, eliminating beats and charging unevenness while maintaining image stability
Solution Approach 2:
The shield member extracts or isolates the electromagnetic field of one unit from affecting the other, separating the alternating current components' electromagnetic influences while allowing both to function for stable image formation
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 interference between charging and developing biases, enhancing image quality by reducing charging unevenness and allowing for a more compact and easily maintainable charging unit, thereby stabilizing the charging process and improving image formation.
Implementation Method 1
a metal shield member surrounding the insulating casing... to reduce the influence of developing bias on the charging bias, preventing electromagnetic induction
Data Source
AI summary
A charging unit in an image forming apparatus includes a charging roller that charges a photosensitive drum using a charging bias, an insulating casing surrounding the charging roller, and a metal shield member. The shield member is positioned so as to surround the casing in close contact with the outer peripheral surface of the casing.