Image Forming Apparatus Edge Soiling Prevention
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Solution Overview
Problem
In direct transfer systems for image forming apparatuses, soiling occurs on recording media due to developer adherence at the non-sheet-passing portion, especially when transferring media of varying sizes, as the surface potential of the photosensitive member is oppositely charged, leading to incomplete transfer and edge soiling.
Innovation Solution
An image forming apparatus with a rotatable image bearing member, a charging member, a developing member, a transfer member, and a voltage applying unit, where the edge position of the recording medium is identified based on acquired size information, and the surface potential of the image bearing member is adjusted to prevent excessive reverse discharge during transfer, ensuring the toner image is formed within a region with a controlled potential difference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the surface potential of the photosensitive member is adjusted to reduce developer transfer on the non-sheet-passing portion, then developer adherence is reduced, but the surface potential becomes oppositely charged, causing incomplete transfer and edge soiling
Solution Approach 1:
The patent divides the photosensitive member surface into two distinct regions: a first region (image forming region) and a second region (non-sheet-passing portion). Different surface potentials are applied to each region, allowing independent control of developer transfer behavior in each area, thus preventing edge soiling while maintaining complete transfer.
Solution Approach 2:
The patent applies different surface potential characteristics to different spatial locations on the photosensitive member. The first region maintains a potential suitable for complete toner transfer, while the second region has a modified potential to prevent developer adherence. This local differentiation resolves the contradiction between preventing edge soiling and ensuring complete transfer.
2Productivity
If a voltage is applied to the transfer member to transfer developer to the recording medium, then transfer is achieved, but current flows to the non-sheet-passing portion, oppositely charging the surface and causing soiling
Solution Approach 1:
By segmenting the photosensitive member into regions with different surface potentials, the patent directs transfer current primarily through the first region (image forming region) while minimizing current flow through the second region (non-sheet-passing portion). This prevents opposite charging at the edges while maintaining efficient transfer.
Solution Approach 2:
The patent uses the surface potential distribution as an intermediary mechanism to control current flow paths. By creating a potential gradient between the first and second regions, the system guides transfer current through appropriate pathways, preventing harmful opposite charging while maintaining transfer efficiency.
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 reduces soiling on the recording media by suppressing excessive reverse discharge and maintaining the desired surface potential, preventing toner adherence and edge soiling, even with media of different sizes and varying resistance values.
Implementation Method 1
a charging member configured to charge a surface of the image bearing member
Implementation Method 2
a transfer member configured to form a nip portion by contacting with the image bearing member, and to transfer the toner image developed on the image bearing member at the nip portion to a recording medium
Data Source
AI summary
In an image forming apparatus of a direct transfer system, when in a region where a transfer nip portion of a photosensitive drum is formed, a region in which the toner image can be formed is defined as a first region, and a region where the recording medium does not pass while the recording medium is conveyed by the transfer nip portion is defined as a second region, in forming the toner image on the recording medium, the photosensitive drum enters the transfer nip portion in a state where the second region of the photosensitive drum includes a region in which an absolute value of a surface potential is smaller than an absolute value of a surface potential of a region in which the toner image is not formed in the first region.