Developing Roller Surface Conductivity for Stable Toner Transport
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Solution Overview
Problem
Existing developing rollers in electrophotographic image forming apparatuses face issues with toner transport failure due to insufficient toner transporting force when used for extended periods in varying environmental conditions, particularly in high-temperature and high-humidity environments, despite efforts to reduce drive torque for energy efficiency.
Innovation Solution
A developing roller design with a conductive outer surface featuring a first region (insulating portion) and a second region (conductive portion) of higher conductivity, where the impedance at specific frequencies is maintained above a certain threshold and the surface potential of the conductive portion is controlled to prevent charge leakage and accumulation, ensuring stable toner transport.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the contact area of the toner supply roller is reduced or the peripheral speed difference is reduced to reduce drive torque, then energy consumption is reduced, but the amount of toner supplied from the toner supply roller to the developing roller becomes insufficient
Solution Approach 1:
The developing roller surface is divided into insulating portions and conductive portions with different electrical properties. The insulating portions are charged by triboelectric charging or injection charging to create microelectric fields that generate gradient forces, attracting toner to the developing roller and ensuring sufficient toner supply even when the contact area or peripheral speed difference is reduced.
Solution Approach 2:
The invention changes the electrical parameters of the developing roller surface by creating regions with different conductivity. The insulating portions have high resistance to maintain charge, while the conductive portions have low resistance to dissipate charge. This parameter differentiation enables the roller to generate the necessary electric fields for toner attraction without requiring increased mechanical contact or speed difference.
2Temperature
If the insulating portion is charged by injection charging in a high-temperature and high-humidity environment for a long period, then the resistance of the insulating portion is reduced, but the insulating portion is not sufficiently charged and toner transport failure occurs
Solution Approach 1:
The developing roller incorporates both insulating portions and conductive portions in specific patterns. The conductive portions serve to dissipate accumulated charges and prevent excessive charge buildup that would occur in high-temperature and high-humidity environments. This local differentiation of electrical properties ensures that the insulating portions remain sufficiently charged for toner transport even under adverse environmental conditions.
Solution Approach 2:
The conductive portions act as charge dissipation paths that provide feedback control to the charging process. When the insulating portions become overly charged or when environmental conditions cause resistance reduction, the conductive portions automatically dissipate excess charge, maintaining the optimal charge level needed for reliable toner transport.
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 enables high process speed with reduced drive torque while preventing toner transport failure across diverse environments, maintaining consistent toner transport performance over time.
Implementation Method 1
the insulating portion on the surface is charged by triboelectric charging between the developing roller and the toner
Implementation Method 2
injection charging for injecting charges by a potential difference between the developing roller and another contact member, mainly, a developing blade
Implementation Method 3
a microelectric field due to a potential difference is formed between the charged insulating portion and a conductive portion which has high conductivity and is not charged. Due to this microelectric field, a gradient force, which is a force in the direction of the outer surface of the developing roller, is generated around the developing roller. Since the toner around the developing roller is attracted to the developing roller by this gradient force
Data Source
AI summary
A developing roller includes a substrate having a conductive outer surface and a conductive layer on the outer surface of the substrate, an outer surface of the developing roller is formed of at least a first region and a second region having higher conductivity than the first region, the first region and the second region are placed adjacent to each other, the first region is placed on an outer surface of the conductive layer, the outer surface of the developing roller has an impedance of 1.0×106Ω or more, and a potential of the outer surface of the developing roller satisfies a predetermined relationship.