Charging Roller Projections and Helical Cleaning for Image Defects
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Solution Overview
Problem
In electrophotographic image forming apparatuses, contact charging types face issues with contaminant deposition on charging members, leading to vertical stripe image defects due to the accumulation of toner and external additives on the surface of charging rollers, especially when using cylindrical or helical cleaning members with surface projections.
Innovation Solution
The use of a charging roller with an electroconductive resin material surface layer containing first and second surface particles of specific sizes, forming projections that help in reducing contaminant deposition by facilitating easy removal, combined with a helical cleaning roller with a rectangular cross-section to effectively clean the charging roller surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a cylindrical cleaning member is contacted to a surface of a charging member having projections formed by dispersing particles, then cleaning function is provided, but contaminant is liable to deposit at base portions of the projections and accumulate over time
Solution Approach 1:
The surface layer is segmented into multiple particle size categories (first particles: 3-10 μm, second particles: 10-20 μm, third particles: 20-30 μm) to create projections with varied heights. This segmentation prevents contaminants from accumulating at uniform base portions, as the stepped projection structure creates multiple elevation levels that disrupt contaminant deposition patterns.
Solution Approach 2:
Different regions of the charging member surface have different projection heights created by the multi-size particle distribution. The local quality varies across the surface, with some areas having taller projections and others having shorter ones, preventing uniform contaminant accumulation and improving cleanability.
2Object-affected harmful factors
If particles are dispersed in a surface layer of the charging member to increase surface roughness and decrease contact area, then contaminant deposition is suppressed, but cleaning becomes less effective when using traditional cylindrical cleaning members
Solution Approach 1:
The cleaning member is designed with a helical structure that rotates during operation, creating dynamic cleaning action. This rotational movement allows the cleaning surface to continuously engage with different portions of the charging member, effectively removing contaminants from projections of varying heights that static cylindrical cleaners cannot address.
Solution Approach 2:
The cleaning member transitions from a simple cylindrical form to a helical structure, adding a dimensional aspect that enables the cleaner to access and clean projections at different heights and angles, thereby improving effectiveness on rough surfaces with multi-level projections.
3Productivity
If a charging roller is used for long term operation, then productivity is maintained, but contaminants accumulate on the surface causing vertical stripe image defects
Solution Approach 1:
The charging member surface is pre-configured with projections of multiple heights before operation begins. This preliminary structure prevents contaminant accumulation from occurring uniformly, thereby maintaining image quality throughout extended operation periods without requiring frequent cleaning or replacement.
Solution Approach 2:
The surface morphology parameter is changed from a uniform smooth or single-roughness surface to a multi-level projection structure with varying heights. This parameter change in surface topography fundamentally alters contaminant deposition behavior, preventing the accumulation that leads to vertical stripe defects during prolonged operation.
Data Source
AI summary
An image forming apparatus includes a photosensitive member, a charging roller, a cleaning roller, an urging member and an image forming portion. The charging roller has an outermost surface layer including an electroconductive resin material, first surface particles having an average particle size of more than 7 μm and less than 30 μm and second surface particles having an average particle size of more than 2 μm and less than 6 μm. The first and second surface particles are dispersed in the electroconductive resin material so as to form first projections and second projections, respectively. The cleaning roller cleaning roller includes a shaft portion and an elastic cleaning portion extending helically around the shaft portion and having a rectangular cross-section perpendicular to an extending direction thereof.