Charging Roller Surface Roughness for Film Resistance
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Solution Overview
Problem
Existing charging rollers in electrophotographic systems face challenges in maintaining long-term filming resistance while suppressing degradation in halftone uniformity, particularly due to external additive filming, which cannot be effectively addressed by conventional surface roughness control methods.
Innovation Solution
A charging roller with a direct current voltage application, featuring a shaft member, elastic layer, and a surface layer with particles of 2 μm to 15 μm in diameter, where the maximum height (Sz) and autocorrelation length (Sal) are within specific ranges (8≤Sz≤16 and 13≤Sal≤30) to enhance filming resistance and halftone uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If the surface roughness of the charging roller is increased to suppress toner filming, then the lifetime of the charging roller is extended, but the uniformity of halftone decreases in DC charging systems
Solution Approach 1:
The patent changes the surface roughness parameters from conventional Rz (10-point height) to Sz (maximum height) and Sal (autocorrelation length), establishing new parameter ranges (8≤Sz≤16 μm, 13≤Sal≤30 μm) that simultaneously achieve filming resistance and halftone uniformity in DC charging systems
Solution Approach 2:
The charging roller employs a composite structure with a shaft member, elastic layer, and surface layer containing dispersed particles (2-15 μm diameter), creating a multi-layer composite material that provides both durability and controlled surface properties for optimal charging performance
2Reliability
If the surface roughness of the charging roller is increased to suppress external additive filming, then the filming resistance is improved, but the contact area between the charging roller and photosensitive drum decreases
Solution Approach 1:
The patent introduces new surface roughness parameters (Sz and Sal) with specific ranges that balance filming resistance and contact area, replacing conventional Rz-based specifications and enabling optimal performance in DC charging 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
The solution effectively maintains improved filming resistance and halftone uniformity over a long period, reducing image defects caused by external additive filming and toner contamination, while optimizing the contact area between the charging roller and the photosensitive drum.
Implementation Method 1
a charging roller to which a direct current voltage is applied and which is configured to charge a surface of an image bearing member... an elastic layer formed around the shaft member
Data Source
AI summary
An image forming apparatus includes an image bearing member configured to bear an image and a charging roller to which a direct current voltage is applied and which is configured to charge a surface of the image bearing member. The charging roller includes a shaft member, an elastic layer formed around the shaft member, and a surface layer formed around the elastic layer. Particles having particle diameters within a range of 2 μm or larger and 15 μm or smaller are dispersed in the surface layer. A maximum height Sz (μm) and an autocorrelation length Sal (μm) with respected to the surface layer of the charging roller satisfy 8≤Sz≤16 and 13≤Sal≤30.