Charging Roller Waviness Control for Image Quality
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Solution Overview
Problem
Image quality deterioration due to density unevenness caused by waviness on the surface of the cored bar member in thin-layer charging rollers, leading to oblique density unevenness in image forming apparatuses.
Innovation Solution
A charging device with a cored bar member coated with a conductive resin layer having a film thickness of 200 μm or less, and filtered maximum waviness of 8 μm or less in the axial direction over a 60 mm reference length, to ensure uniform charging and prevent surface grinding unevenness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a thin-layer charging roller is used to reduce cost and simplify configuration, then manufacturing cost and structural complexity are reduced, but image quality deteriorates due to density unevenness caused by cored bar surface waviness
Solution Approach 1:
The patent applies parameter changes by specifying precise control limits for the cored bar surface waviness (filtered maximum waviness of 8 μm or less over a 60 mm reference length) and the conductive resin layer thickness (200 μm or less). These parameter specifications resolve the contradiction by establishing manufacturing tolerances that ensure image quality while maintaining the cost advantages of thin-layer charging rollers.
2Ease of manufacture
If the conductive resin layer is made thin (200 μm or less) to reduce cost, then manufacturing cost is reduced, but surface irregularities from the cored bar are more directly transmitted to the charging surface
Solution Approach 1:
The patent applies preliminary action by pre-controlling the surface quality of the cored bar member before applying the conductive resin layer. By specifying that the filtered maximum waviness must be 8 μm or less over a 60 mm reference length before coating, the invention ensures that the thin resin layer (200 μm or less) will not amplify surface irregularities, thereby maintaining charging uniformity while reducing cost.
3Productivity
If cored bar surface waviness is not controlled, then manufacturing process is simpler and faster, but periodic density unevenness occurs in the charged image
Solution Approach 1:
The patent resolves this contradiction by establishing specific parameter thresholds for the cored bar surface: filtered maximum waviness of 8 μm or less over a 60 mm reference length. This parameter specification enables manufacturers to maintain high productivity while ensuring charging uniformity, as it provides a clear, measurable criterion for surface quality control without requiring excessive manufacturing complexity.
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 suppresses image quality deterioration by maintaining uniform charging performance, reducing oblique density unevenness and stripe noise, resulting in improved image quality.
Implementation Method 1
a conductive resin layer provided on a surface of the cored bar member... to apply electric charge to an image carrier
Data Source
AI summary
A charging device is configured to apply electric charge to an image carrier provided outside the charging device. The charging device includes: a cored bar member; and a conductive resin layer provided on a surface of the cored bar member. The conductive resin layer has a film thickness of 200 μm or less. Filtered maximum waviness in an axial direction of the cored bar member is 8 μm or less in a range of a reference length of 60 mm.