Developing Bias Control for Toner Fogging Prevention
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Solution Overview
Problem
Toner deterioration leads to oppositely-charged toner particles adhering to the background area of electrostatic latent images, causing image fogging, which existing methods cannot prevent effectively.
Innovation Solution
An image forming apparatus and method that adjusts the developing bias by setting the developing voltage Vmin to ensure toner flies from the developing roller to the photoconductor in the image area but not in the background area, using a voltage application section to control the electric field intensity, preventing oppositely-charged toner from adhering to the background.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional developing bias is applied to attract toner to the electrostatic latent image, then toner adhesion to the image area is improved, but toner adheres to the background area causing image fogging
Solution Approach 1:
The patent applies a dynamic developing bias that alternates between a first voltage (attracting toner to image area) and a second voltage (repelling toner from background area). This dynamic voltage switching creates temporal separation between toner attraction and repulsion phases, allowing precise control of toner adhesion to prevent fogging while ensuring proper image formation.
Solution Approach 2:
The patent changes the voltage parameter of the developing bias between two distinct states: a first voltage level for attracting toner to the image area and a second voltage level for repelling toner from the background area. This parameter switching enables differential control of toner behavior in different spatial regions, resolving the contradiction between achieving sufficient toner adhesion and preventing unwanted background adhesion.
2Manufacturing precision
If the developing voltage is increased to ensure toner flies to the image area, then image density is improved, but oppositely-charged toner adheres to the background area
Solution Approach 1:
The patent employs periodic application of alternating voltages during the developing process. The first voltage (higher magnitude) is applied during the toner transfer phase to ensure sufficient image density, while the second voltage (lower or opposite polarity) is applied during the cleaning phase to repel oppositely-charged toner from the background area. This periodic action resolves the contradiction by separating the high-voltage requirement for image density from the low-voltage requirement for fogging prevention.
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
Effectively prevents low-charged and oppositely-charged toner from adhering to the background area, thereby reducing image fogging and maintaining print quality.
Implementation Method 1
The non-contact developing type development is conducted by applying a developing bias to attract the toner from the developing roller 340 onto the electrostatic latent image on the photoconductor 310
Implementation Method 2
a developing voltage Vmin for forming an electric field in a direction that causes the toner to fly from the developing roller to the image carrier
Implementation Method 3
the surface of the photoconductor 310 is uniformly charged by the charging device 320
Implementation Method 4
the exposure device 330 applies light corresponding to an image to the uniformly charged surface of the photoconductor 310. Thus, a potential of the light exposed portion is changed
Implementation Method 5
The transferred toner is fixed to the paper by a fuser unit 360 to prevent peeling of the toner
Data Source
AI summary
Developing bias is set as follows. An electric field intensity between a developing roller and a photoconductor is set to cause normally-charged toner to fly in an image area and not to cause the toner to fly in a background area. Thus, the normally-charged toner does not fly in the background area. The normally-charged toner caused to fly is therefore unlikely to flick low-charged toner and oppositely-charged toner. The low-charged toner and the oppositely-charged toner will not adhere to the background area and cause image fogging. Accordingly, an image forming apparatus can be provided to prevent the low-charged toner and the oppositely-charged toner from adhering to the background area of an electrostatic latent image on the photoconductor and to avoid the occurrence of image fogging in the background area on a printed material.