Charging Roll Surface Texture for Uniform Discharge and Image Quality
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Solution Overview
Problem
Image forming apparatuses face challenges in achieving uniform image quality due to uneven charging roll surface roughness, which affects discharge consistency and image quality.
Innovation Solution
A charging roll design featuring a core member, electroconductive rubber base material, and a surface layer with specific surface roughness parameters (RZ between 3.9 and 6.1 micrometers and S m between 12.5 and 13.5 micrometers) to ensure uniform discharge and reduce image unevenness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the surface roughness of the charging roll is adjusted by use of fine particles in the surface layer, then discharge uniformity is improved, but image unevenness occurs due to insufficient control of specific roughness parameters
Solution Approach 1:
The patent applies parameter changes by precisely controlling the surface roughness parameters RZ (3.9-6.1 μm) and Sm (12.5-13.5 μm) of the charging roll surface. This specific parameter range optimizes the discharge characteristics between the charging roll and photoconductor, achieving uniform charging while preventing image unevenness. The controlled particle size distribution in the surface layer further refines these surface parameters to the optimal range.
Solution Approach 2:
The charging roll employs a composite structure with multiple layers including an electroconductive support, electroconductive elastic layer, and electroconductive resin layer containing controlled particles. This composite material structure allows independent optimization of each layer's properties - the support provides mechanical strength, the elastic layer provides compliance, and the resin layer with controlled particles provides the precise surface roughness needed for uniform discharge without causing image unevenness.
2Ease of manufacture
If the surface roughness parameters are not precisely controlled, then manufacturing is easier, but discharge consistency deteriorates leading to poor image quality
Solution Approach 1:
The patent establishes specific parameter ranges for surface roughness (RZ: 3.9-6.1 μm, Sm: 12.5-13.5 μm) and particle size (5-10 μm for inorganic particles, 3-7 μm for organic particles) that balance manufacturability with discharge consistency. These parameters are optimized to be achievable through conventional manufacturing processes while ensuring reliable and consistent discharge characteristics across production batches.
Solution Approach 2:
The patent applies local quality by creating a surface layer with specifically controlled particle distribution and size only at the charging roll surface, while the underlying layers maintain their bulk properties. This allows the surface to have the precise roughness characteristics needed for consistent discharge, while the core structure retains its mechanical strength and electroconductive properties, making the overall manufacturing process more feasible.
3Manufacturing precision
If fine particles are used in the surface layer to control discharge, then image quality improves, but the surface roughness becomes too high causing image unevenness
Solution Approach 1:
The patent resolves this contradiction by precisely controlling the particle size parameters in the surface layer - using inorganic particles of 5-10 μm and organic particles of 3-7 μm, with the particle diameter being 0.03-0.07 times the thickness of the electroconductive resin layer. This specific parameter control ensures that particles are fine enough to improve image quality through controlled discharge, but not so fine that they create excessive surface roughness causing image unevenness.
Solution Approach 2:
The patent uses a composite particle system combining both inorganic and organic particles in the electroconductive resin layer. This composite approach allows the inorganic particles to provide structural support and controlled roughness, while the organic particles fill gaps and smooth the surface, achieving a balance that improves image quality through controlled discharge while maintaining image uniformity by preventing excessive roughness.
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 specified surface roughness of the charging roll leads to consistent discharge between the photoconductor element and the charging roll, enhancing image quality by minimizing image unevenness and ensuring accurate toner adhesion during the image formation process.
Implementation Method 1
discharge between the photoconductor element and the charging roll
Data Source
Figure 1~2
Figure 3
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 ten point height of irregularities Rz of a surface of the surface layer is equal to or greater than 3.9 micrometers, and is equal to or less than 6.1 micrometers. The mean spacing between peaks Sm of the surface of the surface layer is equal to or greater than 12.5 micrometers and being equal to or less than 13.5 micrometers.