Image Forming Apparatus Voltage Control for Fogging Suppression
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Solution Overview
Problem
Image forming apparatuses using the electrophotographic method face challenges in maintaining image density and reducing fogging when printing speed decreases, as the circumferential speed ratio between the image bearing member and the developer bearing member changes, leading to increased toner adhesion in blank portions.
Innovation Solution
An image forming apparatus with a developer bearing member and a supply member rotating in opposite directions, where a control unit adjusts the voltage difference between the developer bearing member and the supply member to counteract the speed difference, stabilizing image density and suppressing fogging by shifting the voltage polarity and absolute value accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the printing speed is reduced without changing the circumferential speed ratio between the image bearing member and the developer bearing member, then the image forming speed is decreased, but the fogging in blank portions increases due to toner adhesion
Solution Approach 1:
The invention changes the circumferential speed ratio between the developer bearing member and the image bearing member as a parameter adjustment. Specifically, the circumferential speed ratio is made higher in low printing speed mode than in normal mode, which prevents toner from adhering to blank portions while maintaining the reduced printing speed, thus resolving the fogging issue without sacrificing speed reduction benefits
Solution Approach 2:
The invention makes the circumferential speed ratio dynamic rather than fixed. The speed ratio is adjusted according to the printing speed mode: in normal mode a first speed ratio is used, while in low printing speed mode a second, higher speed ratio is used. This dynamic adjustment allows the system to adapt to different operating conditions and prevent fogging at reduced speeds
2Object-generated harmful factors
If the circumferential speed ratio of the developer bearing member to the image bearing member is increased in low printing speed mode, then the fogging in blank portions is suppressed, but the image density stability may be affected
Solution Approach 1:
The invention carefully controls the change in circumferential speed ratio to achieve fogging suppression while maintaining image density stability. By optimizing the specific value of the higher speed ratio used in low printing speed mode, the invention ensures that toner transfer remains effective and consistent, preventing both fogging and density instability
Solution Approach 2:
The invention implements control mechanisms that monitor and adjust the developing process based on the operating mode. The control unit detects the printing speed mode and automatically adjusts the circumferential speed ratio accordingly, ensuring optimal performance for each mode while maintaining image quality consistency across different printing speeds
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 configuration allows for stable image density and reduced fogging across varying printing speeds without altering the circumferential speed ratio, ensuring high-quality images by effectively managing toner distribution and adhesion.
Implementation Method 1
a supply member, which includes a foam layer at a surface and is arranged in contact with the developer bearing member, configured to rotate in a direction opposite to a rotation direction of the developer bearing member... a second voltage application mechanism configured to apply a voltage Vrs to the developer supply member... a difference Vdif (=Vrs−Vdr) between Vrs and Vdr
Implementation Method 2
a supply member, which includes a foam layer at a surface and is arranged in contact with the developer bearing member... configured to rotate in a direction opposite to a rotation direction of the developer bearing member and to supply the developer to the developer bearing member
Data Source
AI summary
An image forming apparatus includes a control unit controlling first and second voltage application mechanisms and shifting a difference Vdif (=Vrs−Vdr) between Vrs and Vdr toward polarity opposite to normal charge polarity of a developer as S decreases, where S is an absolute value of a speed difference between a circumferential speed of an image bearing member, which rotates while bearing an electrostatic latent image and a circumferential speed of a developer bearing member, which rotates at a constant circumferential speed ratio with respect to the image bearing member to develop the electrostatic latent image while bearing the developer, Vdr is a voltage that the first voltage application mechanism applies to the developer bearing member, and Vrs is a voltage that the second voltage application mechanism applies to the developer supply member.