Transfer Voltage Control for Fog Suppression in Image Formers
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Solution Overview
Problem
The image forming apparatus experiences 'fog at startup' due to toner transfer from the developing roller to the photosensitive drum without an electrostatic latent image, leading to toner scattering and contamination in the transfer nip.
Innovation Solution
The apparatus includes a controller that manages the transfer voltage, applying a voltage of opposite polarity to the normal charge polarity during a specific period after startup, and gradually increasing the voltage to transfer toner from the transfer roller back to the photosensitive drum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the developing roller is separated from the photosensitive drum at startup, then the fog at startup is suppressed, but the device complexity increases due to the contact and separation mechanism
Solution Approach 1:
The patent replaces the mechanical contact and separation mechanism with an electrical field control system. By applying a voltage of opposite polarity to the transfer roller, the invention creates an electrostatic field that prevents fog toner transfer without requiring physical separation of the developing roller from the photosensitive drum, thereby eliminating the need for complex mechanical switching mechanisms
Solution Approach 2:
The patent changes the electrical parameter (voltage polarity) of the transfer roller to suppress fog at startup. By applying a voltage of opposite polarity to the normal charge polarity during a specific period after startup, the invention dynamically controls the electrostatic field to prevent unwanted toner transfer while maintaining normal operation parameters when needed
2Reliability
If a voltage of opposite polarity is applied to the transfer roller during startup, then toner scattering is suppressed, but the energy consumption increases
Solution Approach 1:
The patent applies voltage of opposite polarity only during a specific period after startup rather than continuously. The controller manages the transfer voltage to apply opposite polarity voltage temporarily during the critical startup phase when fog occurs, then switches to normal operating voltage, thereby reducing overall energy consumption while maintaining effective fog suppression
Solution Approach 2:
The patent applies opposite polarity voltage in advance during the startup period before normal operation begins. By preemptively suppressing fog toner transfer during the vulnerable startup phase, the invention prevents toner scattering before it can occur, reducing the need for subsequent cleaning operations and associated energy consumption
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 solution effectively suppresses toner scattering by transferring the fog toner onto the transfer roller and then back to the photosensitive drum, reducing contamination and improving print quality.
Implementation Method 1
a transfer voltage of an opposite polarity to a normal charge polarity of the toner is applied, so that the toner image on the image bearing member is electrostatically transferred onto the recording material
Implementation Method 2
a surface of a photosensitive drum as an image bearing member is electrically charged uniformly to a dark-portion potential by a charging means
Implementation Method 3
the charged surface of the photosensitive drum is exposed to light by an exposure means, so that a light-portion potential is formed on the surface of the photosensitive drum
Data Source
AI summary
A controller of an image forming apparatus controls a transfer voltage applying portion so that a voltage is not applied to a transfer member or a voltage of an opposite polarity to a normal charge polarity of toner is applied to the transfer member, in a first period including at least a period, after rotation of a photosensitive member and a developing member, from first arrival of a first region at a transfer portion to first arrival of a second region at the transfer portion, and so that at least a first voltage of the same polarity as the normal charge polarity and a second voltage of the same polarity as the first voltage and larger in absolute value than the first voltage are applied to the transfer member in a second period after the first period and before a toner image reaches the transfer portion.