Transfer Potential Control for Toner Adhesion Defects
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Solution Overview
Problem
In electrophotographic image forming apparatuses, the application of voltage from a common power supply to both the charging device and developing device can lead to toner being electrostatically pulled onto the photosensitive drum before it is fully charged, causing defects such as unintended toner adhesion to the recording material, especially during initial operation or paper jams.
Innovation Solution
A control unit is implemented to manage the potential at the transfer portion of a rotary member, ensuring it matches the polarity of the toner during the initial stages of operation, preventing toner from being transferred to the intermediate transfer belt until the photosensitive member is fully charged.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If voltage is applied from a common power supply to both the charging device and developing device simultaneously, then the apparatus can be downsized and operation simplified, but toner is electrostatically pulled onto the photosensitive drum before it is fully charged, causing unintended toner adhesion defects
Solution Approach 1:
The control unit delays activation of the developing device until after the charging device has completed charging the photosensitive drum. This preliminary sequencing ensures the drum surface is fully charged before toner is supplied, preventing electrostatic attraction of uncharged areas and resulting in clean, defect-free images.
Solution Approach 2:
The system dynamically controls the timing of voltage application to different devices based on operational state. During initial operation or paper jams, the control unit adjusts the sequence of activating charging and developing devices, ensuring proper charging occurs before toner development to maintain image quality.
2Loss of time
If the developing device is activated at the same time as the charging device, then the initial operation time is reduced, but toner adheres to unintended parts of the image and the back surface of recording material
Solution Approach 1:
The control unit implements a preliminary charging phase where the charging device operates alone to fully charge the photosensitive drum surface before the developing device is activated. This sequential approach prevents toner from being attracted to uncharged areas, ensuring precise image formation without unintended adhesion.
Solution Approach 2:
The control unit monitors the operational state of the photosensitive drum and adjusts the timing of device activation accordingly. By detecting when charging is complete, the system optimizes the transition to the developing phase, balancing operation time with image precision.
3Productivity
If voltage is applied to the developing device before the photosensitive drum is fully charged, then the developing process can start earlier, but the entire surface of the photosensitive drum becomes developed, causing toner defects
Solution Approach 1:
The control unit ensures the charging device completes its charging cycle as a preliminary step before activating the developing device. This sequencing prevents premature development of uncharged areas, maintaining both productivity and image quality by ensuring only properly charged regions receive toner.
Solution Approach 2:
The control unit prevents the harmful effect of premature toner attraction by delaying developing device activation until charging is complete. This preliminary protective measure ensures the photosensitive drum surface is fully charged, preventing the entire surface from being developed and avoiding toner defects.
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 effectively prevents toner defects during the initial operation of the image forming apparatus, ensuring high-quality image formation by controlling the potential at the transfer portion to match the toner's polarity, thus avoiding unwanted toner adhesion and improving image clarity.
Implementation Method 1
a charging device that charges the photosensitive member
Implementation Method 2
the voltage is applied to the developing unit that is in contact with a section of the surface of the photosensitive drum that is not charged... the toner is electrostatically pulled toward the photosensitive drum
Implementation Method 3
A voltage with opposite polarity to the charged polarity of the toner at the time of development is applied to a transfer device to transfer the toner image formed on the photosensitive drum to a recording material
Data Source
AI summary
The image forming apparatus includes a control unit that controls the potential at a transfer portion of a rotary member to be a potential of the same polarity as the charged polarity of the toner at development, when an image forming apparatus starts rotating a photosensitive member, after the start of output by a common power supply and before a charge area on the photosensitive member reaches the transfer portion.