Dual Charging Rollers for Uniform Drum Potential
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Solution Overview
Problem
In high-speed image forming apparatuses, contact charging rollers experience instability and non-uniform charging due to contamination by toner or external additives, leading to image defects and reduced reliability.
Innovation Solution
An image forming apparatus with a first and second charging member, where the second member applies a controlled AC and DC voltage to maintain a predetermined DC current range, ensuring uniform charging and surface potential stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single contact charging roller is used, then the device complexity is low and space is saved, but charging uniformity deteriorates due to contamination by toner or external additives
Solution Approach 1:
The charging device is divided into two independent contact charging rollers (first charging roller and second charging roller) that sequentially charge the photosensitive drum. This segmentation allows each roller to function independently, and when one becomes contaminated, the other can compensate to maintain charging uniformity.
Solution Approach 2:
Different voltage parameters are applied to the first and second charging rollers. The first charging roller receives a DC voltage, while the second charging roller receives a voltage with both AC and DC components. This parameter differentiation optimizes charging effectiveness and compensates for contamination effects.
2Productivity
If the photosensitive drum rotates at high speed to increase productivity, then output per unit time increases, but contact stability between charging roller and photosensitive drum deteriorates
Solution Approach 1:
The charging system is designed to dynamically adapt to high-speed operation. The two charging rollers are positioned to maintain stable contact with the photosensitive drum even during high-speed rotation, and the voltage parameters are optimized for dynamic charging conditions.
3Reliability
If a cleaning member is added to remove deposited matter, then charging uniformity improves, but device complexity increases and cleaning power deteriorates over time
Solution Approach 1:
The two charging rollers themselves serve the dual function of charging and mutual cleaning. As they sequentially contact the photosensitive drum, they naturally remove deposited matter through the charging process, eliminating the need for separate cleaning members.
4Use of energy by moving object
If DC voltage is applied to the charging roller, then electric power consumption is low and device size is small, but charging uniformity deteriorates when contamination occurs
Solution Approach 1:
The voltage parameters are changed between the two charging rollers. The first charging roller uses DC voltage for low power consumption, while the second charging roller uses voltage with AC and DC components to maintain charging uniformity when contamination occurs, combining the advantages of both approaches.
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 solution enhances charging uniformity and reliability by minimizing contamination effects, reducing image defects and maintaining high-quality prints.
Implementation Method 1
a first charging member for electrically charging the image bearing member in contact with the image bearing member
Implementation Method 2
the photosensitive drum is charged by applying to the charging roller a voltage in the form of a DC voltage, corresponding to the necessary surface potential Vd of the photosensitive drum, biased with an AC (voltage) component
Data Source
AI summary
An image forming apparatus includes a rotatable image bearing member; a first charging member for electrically charging the image bearing member; a second charging member, provided downstream of the first charging member with respect to a rotational direction of the image bearing member, for electrically charging the image bearing member; an applying device for applying a voltage to the first charging member and the second charging member; a detecting device for a DC current passing through the second charging member; and a controller for controlling, when an AC voltage and a DC voltage are applied to the second charging member while a DC voltage is applied to the first charging member, the DC voltage applied to the second charging member so that an absolute value of the DC current detected by the detecting device is within a predetermined range.