Surface-Roughness Charging Roll for Uniform Photoconductor Discharge
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Solution Overview
Problem
Image forming apparatuses face challenges in achieving uniform image quality due to uneven discharge between the charging roll and the photoconductor element, which is influenced by the surface roughness of the charging roll.
Innovation Solution
A charging roll design featuring a core member, a rubber base material, and a surface layer with specific surface roughness characteristics, including an average height of convex portions between 0.8 and 2.1 micrometers and an average interval between 6.6 and 11.5 micrometers, to ensure uniform discharge and reduce image unevenness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the surface roughness of the charging roll is adjusted by use of fine particles in the surface layer, then the discharge uniformity is improved, but the image unevenness occurs due to excessive smoothness
Solution Approach 1:
The patent applies parameter changes by precisely controlling the surface roughness parameters (average height of convex portions: 0.8-2.1 μm, average interval: 6.6-11.5 μm) of the charging roll surface. This optimization of physical parameters ensures uniform discharge while preventing image unevenness, resolving the contradiction between discharge uniformity and image quality.
Solution Approach 2:
The charging roll employs a composite structure consisting of a rubber base material layer and a surface layer with specific roughness characteristics. This composite material design allows the surface layer to provide controlled roughness for uniform discharge, while the underlying rubber base material provides elasticity and charge storage capability, thereby achieving both uniform discharge and preventing image unevenness.
2Reliability
If the surface roughness is increased to improve discharge uniformity, then the charging performance is enhanced, but the image quality deteriorates due to surface irregularities
Solution Approach 1:
The patent optimizes the surface roughness parameters within specific ranges (average height: 0.8-2.1 μm, average interval: 6.6-11.5 μm) to achieve the best balance between charging performance and image quality. This precise parameter control ensures sufficient surface irregularities for uniform discharge while maintaining smoothness for high image quality.
Solution Approach 2:
The charging roll features local quality differentiation with a surface layer having controlled roughness characteristics on top of a rubber base material layer. The surface layer provides localized surface irregularities for improved discharge uniformity, while the overall surface remains sufficiently smooth to prevent image defects, thus resolving the contradiction between charging performance and image quality.
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
The described charging roll design effectively reduces image unevenness by maintaining uniform discharge between the photoconductor drum and the charging roll, resulting in high-quality images with minimized defects.
Implementation Method 1
An object of JP-A-2015-121769, JP-A-2012-14141, and JP-A-2005-91414 is to control a discharge between the charging roll and the photoconductor element to make the discharge as uniform as possible
Data Source
AI summary
A charging roll includes a core member, a rubber base material disposed around the core member, and a surface layer disposed around the rubber base material. The average of heights of contours of convex portions on a surface of the surface layer relative to an average cylindrical surface obtained by averaging surface irregularities of the surface layer is equal to or greater than 0.8 micrometers and is equal to or less than 2.1 micrometers. The average of intervals between apexes of the convex portions on the surface of the surface layer is equal to or greater than 6.6 micrometers and is equal to or less than 11.5 micrometers.