Transfer Roller Offset Layout to Suppress Discharge Image Defects
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Solution Overview
Problem
Existing image forming apparatuses experience defects in transferred images due to electrical discharge, particularly affecting colors other than black, leading to noticeable stains and reduced image quality.
Innovation Solution
The rotation shaft of the transfer roller corresponding to black toner is offset downstream from the image carrying member, while other transfer rollers are offset upstream, and the contact surface pressure is adjusted to suppress electric discharge and reduce toner scattering, thereby improving image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the transfer roller is positioned directly above the image carrying member, then the transfer efficiency is improved, but electrical discharge occurs causing image defects and toner scattering
Solution Approach 1:
The transfer roller is positioned asymmetrically relative to the image carrying member, specifically offset in the sub-scanning direction by 1mm to 5mm. This asymmetric positioning prevents direct alignment that causes electrical discharge while maintaining effective contact for toner transfer, thus resolving the contradiction between transfer efficiency and electrical discharge prevention
2Manufacturing precision
If the transfer roller contact pressure is increased, then the toner transfer completeness is improved, but toner scattering and stains increase due to electrical discharge
Solution Approach 1:
The contact pressure between the transfer roller and image carrying member is locally optimized by adjusting the roller's pressing force to within 0.1N to 1N. This localized pressure control ensures sufficient toner transfer completeness while preventing excessive pressure that would cause electrical discharge and subsequent toner scattering
Solution Approach 2:
The asymmetric positioning of the transfer roller in the sub-scanning direction creates an optimized contact zone that achieves effective toner transfer without the direct alignment that causes harmful electrical discharge and toner scattering
3Manufacturing precision
If the transfer roller is positioned to prevent electrical discharge, then image quality is improved, but the transfer roller positioning complexity increases
Solution Approach 1:
A simple asymmetric offset positioning of 1mm to 5mm in the sub-scanning direction is implemented. This straightforward geometric modification achieves electrical discharge prevention and improved image quality without requiring complex positioning mechanisms or control systems
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 enhances image quality by reducing toner scattering and consumption, improving color rendering and reproduction, and optimizing image density and reproducibility across different colors.
Implementation Method 1
The transfer rollers are kept in pressed contact with the image carrying members via the intermediate transfer belt
Implementation Method 2
The charging device electrostatically charges the surfaces of the image carrying members
Implementation Method 3
The exposure device exposes to light the surfaces of the image carrying members electrostatically charged by the charging device to form electrostatic latent images
Data Source
AI summary
An image forming apparatus includes a plurality of image carrying members, a charging device, an exposure device, a developing device, an intermediate transfer belt, and a plurality of transfer rollers. On the image carrying member disposed most downstream in the traveling direction of the intermediate transfer belt, a black tonner image is developed. The rotation shaft of at least one transfer roller located upstream of the transfer roller disposed most downstream in the traveling direction of the intermediate transfer belt is offset upstream from directly above the rotation shaft of the corresponding image carrying member.