Charging Roller Surface Porosity for Drum Contact Stability
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Solution Overview
Problem
The existing charging devices for image formation apparatuses using electrophotographic processes face instability in the charging state of the photosensitive drum due to a small contact area, leading to printing defects like fogging.
Innovation Solution
A charging device with a rotatable charging member that includes a shaft, an elastic layer, and a surface layer with porous particles, where the ratio of convex portions on the surface layer to its surface area is 68.4% or more, to stabilize the charging state and reduce printing defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the contact area between charging roller and photosensitive drum is reduced, then streaks caused by elastic layer component exudation are suppressed, but charging state stability deteriorates resulting in fogging
Solution Approach 1:
The surface layer is designed with non-uniform hardness, having a first hardness in the bulk and a second hardness at the surface that is lower than the first hardness. This local quality variation allows the surface to have different mechanical properties from the bulk, enabling it to suppress component exudation while maintaining stable charging contact.
Solution Approach 2:
The charging roller is constructed as a composite structure with a surface layer having different hardness properties from the underlying elastic layer. This composite design combines the benefits of both layers: the surface layer suppresses exudation through its specific hardness, while the underlying elastic layer maintains the necessary flexibility and contact stability.
2Reliability
If the contact area between charging roller and photosensitive drum is increased, then charging state stability is improved, but streaks from elastic layer component exudation occur
Solution Approach 1:
The surface layer is designed with non-uniform hardness, having a first hardness in the bulk and a second hardness at the surface that is lower than the first hardness. This local quality variation allows the surface to have different mechanical properties from the bulk, enabling it to suppress component exudation while maintaining stable charging contact.
Solution Approach 2:
The charging roller is constructed as a composite structure with a surface layer having different hardness properties from the underlying elastic layer. This composite design combines the benefits of both layers: the surface layer suppresses exudation through its specific hardness, while the underlying elastic layer maintains the necessary flexibility and contact stability.
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 the occurrence of streaks and fogging by stabilizing the charging state, improving storage stability and reducing printing defects.
Implementation Method 1
a surface layer to be in contact with the contact member and containing porous particles
Implementation Method 2
an elastic layer provided between the shaft and the surface layer
Data Source
AI summary
A charging device according to one or more embodiments may include: a charging member that is rotatable and provided to be in contact with a contact member. The charging member includes: a shaft; a surface layer to be in contact with the contact member and containing porous particles; and an elastic layer provided between the shaft and the surface layer. A ratio of convex portions formed by the porous particles on the surface layer to a surface area of the surface layer is 68.4% or more.