Charging Roller Contact Control for Photosensitive Member Charge Injection
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Solution Overview
Problem
In electrophotographic image forming apparatuses, the DC charging type struggles with charge injection phenomena due to discharge products deposited on the photosensitive member, leading to image defects, especially in high-humidity environments, where the surface resistance is lowered, and the charge injection phenomenon occurs, disturbing the image formation.
Innovation Solution
A DC charging type image forming apparatus with a rotatable photosensitive member having an elastic deformation power of 47% or more, featuring a charging roller with an elastic layer that forms a nip with elastic deformation along the photosensitive member's surface, and a specific contact width and contact area ratio between the charging roller and the photosensitive member are controlled to minimize the charge injection phenomenon.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If the surface layer of the photosensitive member is increased in hardness to suppress abrasion, then the lifetime of the photosensitive member is extended, but the surface resistance is lowered and charge injection phenomenon occurs causing image defects
Solution Approach 1:
The invention changes the elastic deformation rate parameter of the photosensitive member surface layer to 47% or more, which maintains surface resistance and prevents charge injection phenomenon while suppressing abrasion. This parameter optimization resolves the contradiction between extending lifetime and maintaining image quality.
Solution Approach 2:
The invention introduces dynamic elastic deformation characteristics to the photosensitive member surface layer, allowing it to deform elastically under the charging roller pressure. This dynamic response maintains proper contact conditions and surface resistance, preventing charge injection while protecting against abrasion.
2Manufacturing precision
If the contact area between charging roller and photosensitive member is increased to improve charging uniformity, then charging quality is improved, but charge injection phenomenon is exacerbated causing image defects
Solution Approach 1:
The invention creates localized independent contact portions rather than continuous contact, distributing the charging function across multiple discrete points. This local quality approach maintains charging uniformity while reducing the total contact area, thereby preventing charge injection phenomenon.
Solution Approach 2:
The contact interface between the charging roller and photosensitive member is segmented into multiple independent contact portions. This segmentation reduces the continuous contact area that causes charge injection while maintaining sufficient charging points for uniform charging across the photosensitive member surface.
3Duration of action of stationary object
If a protective layer is added to the photosensitive member surface to reduce abrasion, then lifetime is extended, but discharge product deposition increases causing surface resistance reduction and image defects
Solution Approach 1:
The invention uses a composite surface layer structure with specific elastic deformation characteristics (47% or more) that combines abrasion resistance with proper discharge product management. This composite material approach prevents both excessive wear and harmful discharge product deposition.
Solution Approach 2:
The invention converts the potential harm of discharge product deposition into a beneficial effect by optimizing the elastic deformation rate. The optimized surface properties allow controlled interaction with discharge products that maintains surface resistance and prevents image defects while still providing abrasion protection.
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 controlled contact width and contact area ratio between the charging roller and the photosensitive member effectively suppress the charge injection phenomenon, reducing image defects and extending the lifespan of the photosensitive member by maintaining surface resistance and preventing excessive abrasion.
Implementation Method 1
the surface of the photosensitive member is charged by electric discharge generating in a small gap between the photosensitive member and the charging member
Implementation Method 2
the charging roller forms a nip with elastic deformation along the surface of the photosensitive member by being urged against the photosensitive member with a predetermined urging force
Data Source
AI summary
An image forming apparatus includes a photosensitive member having a surface having elastic deformation power of 47% or more, a charging roller forming a nip between itself and the photosensitive member, and an image forming portion. When a nip region corresponding to the nip is formed and then an area of independent contact portions between the charging member and a measuring contact member is measured, the following relationship is satisfied: (contact width X)×(Contact area ratio α)≤0.1, where a length from a position of one end to a position of the other end of the nip region with respect to a direction perpendicular to a longitudinal direction of the charging roller is the contact width X, and a ratio of a sum of areas of the independent contact portions to an entire area of a measuring region is the contact area ratio α.