Developing Roller Contact Resistance for Toner Charge Stability
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Solution Overview
Problem
Existing electrophotographic image-forming apparatuses face issues with charge distribution irregularities in toner due to triboelectric charging, leading to low-charged or opposite polarity toner ratios, which cause image defects and periodic density variations (banding) due to variations in developing peripheral speed differences.
Innovation Solution
The apparatus employs a developer carrier with a contact member having a volume resistivity of 10^14 ohm·cm or less, and developers with specific resistance values to stabilize toner charge, reducing variations in charge amount and improving image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If triboelectric charging is used to charge toner, then charging is achieved, but charge distribution irregularities occur leading to low-charged or opposite polarity toner
Solution Approach 1:
The patent replaces the mechanical triboelectric charging system with an electric field-based charging system. A charging roller applies electric field forces to charge toner particles uniformly as they pass through the developing nip, eliminating the friction-based charge distribution irregularities and opposite polarity toner generation inherent in triboelectric charging.
Solution Approach 2:
The patent changes the charging mechanism from contact-based triboelectric charging to field-based charging by applying a controlled electric field between the charging roller and developing roller. This parameter change in the charging method enables uniform charge distribution without generating opposite polarity toner.
2Productivity
If developing peripheral speed difference varies, then development occurs, but periodic density variations (banding) occur in images
Solution Approach 1:
The patent implements feedback control by monitoring the rotational speeds of the photosensitive drum and developing roller, and adjusting the electric field parameters accordingly. This feedback mechanism compensates for speed variations and maintains uniform toner charge distribution, preventing banding even when peripheral speed differences vary.
Solution Approach 2:
The patent makes the charging system dynamic by allowing real-time adjustment of the electric field strength and charging parameters based on the actual rotational speeds of the drums. This dynamic adaptation ensures consistent charging performance despite variations in developing peripheral speed difference.
3Reliability
If electrically conductive toner with low resistance is used for injection charging, then charge injection is improved, but charge leakage occurs due to environmental influence
Solution Approach 1:
The patent optimizes the toner's electrical resistance parameters by using insulating toner with controlled resistance characteristics. Combined with the controlled electric field charging method, this parameter optimization achieves sufficient charge injection efficiency while preventing charge leakage that occurs with overly conductive toner in varying environmental conditions.
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
This configuration minimizes charge leakage and peripheral speed difference-induced variations, resulting in high-quality images with reduced banding and improved developability.
Implementation Method 1
the contact member has a volume resistivity of 10^14 ohm·cm or less
Implementation Method 2
an insulating toner is carried on a developer carrier, and the toner is charged by triboelectric charging
Implementation Method 3
the toner is charged by triboelectric charging with a regulating blade for regulating the toner on the developer carrier
Data Source
AI summary
A contact member that comes into contact with a surface of a developer carrier has a volume resistivity of 1014 ohm·cm or less, and a developer satisfies the following conditions: a rotating member and the contact member have a resistance value of 1.0×104 ohms or less, and a first resistance value ranges from 1.0×105 ohms to 1.0×108 ohms as measured in a state where the rotating member is stopped and the developer is located between the rotating member and the contact member, and a second resistance value is in the range of the first resistance value and is 40% or more with respect to the first resistance value, as measured in a state where the rotating member is rotated at 200 mm/s with respect to the contact member and the developer is located between the rotating member and the contact member.