Photosensitive Drum Charging for Transfer Memory Suppression
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Solution Overview
Problem
The existing image forming apparatuses, particularly those using electrophotographic technology, face challenges in suppressing the occurrence of image defects due to 'transfer memory', which results from non-uniform charging of the photosensitive drum caused by electric discharge during the transfer process.
Innovation Solution
The image forming apparatus incorporates a rotatable photosensitive member, multiple charging members, and a transfer member, with a controller managing the charging and transfer voltages. The first charging position is downstream of the transfer position and upstream of the second charging position, allowing for controlled surface potential uniformization by injecting electric charges in the first charging position with a voltage less than the discharge start voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a large transfer voltage is applied to the transfer roller, then the transfer efficiency is improved, but electric discharge occurs between the photosensitive drum and the transfer roller causing non-uniform charging
Solution Approach 1:
The patent applies a preliminary action by introducing a first charging member that charges the photosensitive drum surface before the transfer process. This pre-charging ensures uniform surface potential distribution before the high-voltage transfer occurs, preventing electric discharge and non-uniform charging while allowing the use of large transfer voltages for efficient transfer.
2Speed
If the transfer voltage is applied to the transfer roller without a recording material interposed, then the transfer speed is increased, but electric discharge occurs causing transfer memory
Solution Approach 1:
The first charging member performs preliminary charging of the photosensitive drum surface before the transfer operation. This ensures that even when transfer voltage is applied without a recording material interposed, the surface potential remains uniform, preventing electric discharge and transfer memory while maintaining high transfer speed.
Solution Approach 2:
The first charging member acts as an intermediary that mediates between the transfer roller and the photosensitive drum. By providing controlled pre-charging, it enables the transfer roller to apply high voltages without causing harmful electric discharge, thus maintaining both speed and reliability.
3Manufacturing precision
If a pre-exposure means is used to uniformize surface potential, then the surface potential uniformity is improved, but the complexity of the device increases
Solution Approach 1:
The patent extracts the essential function of potential uniformization from the complex pre-exposure system and implements it through a simple first charging member. This eliminates the need for additional exposure means while achieving the same goal of uniform surface potential distribution, thereby reducing device complexity.
Solution Approach 2:
The patent replaces the optical mechanism of pre-exposure with an electrical charging mechanism. Instead of using light to uniformize surface potential, a first charging member directly applies electrical charge, achieving the same effect with simpler mechanics and fewer components.
4Manufacturing precision
If the first charging voltage is increased to compensate for potential non-uniformity, then the charging uniformity is improved, but electric discharge occurs during charging
Solution Approach 1:
The first charging member applies a partial charging action with a voltage lower than the discharge start voltage. This sufficient but controlled charging ensures uniform surface potential without reaching the threshold for electric discharge, achieving charging uniformity while avoiding harmful discharge effects.
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 effectively suppresses the occurrence of image defects due to transfer memory by ensuring uniform surface potential of the photosensitive drum, even under high transfer voltages, thereby maintaining image quality and reducing potential non-uniformities.
Implementation Method 1
a first charging member configured to electrically charge a surface of the photosensitive member in contact with the surface of the photosensitive member in a first charging position
Implementation Method 2
a second charging member configured to electrically charge the surface of the photosensitive member in a second charging position
Implementation Method 3
a transfer member contacting the surface of the photosensitive member in a transfer position and configured to transfer the toner image from the photosensitive member onto a recording material passing through between the photosensitive member and the transfer member
Implementation Method 4
a controller configured to control the first charging voltage applying portion, the second charging voltage applying portion, and the transfer voltage applying portion
Data Source
AI summary
An image forming apparatus includes a photosensitive member, first and second charging members, a developing member, a transfer member, first and second charging voltage applying portions, a transfer voltage applying portion, and a controller. The controller controls the transfer voltage applying portion so that a region of at least a part of the photosensitive member surface contacting the transfer member in a transfer position has a potential of an opposite polarity to the predetermined polarity, controls the first charging voltage applying portion so that the surface of the photosensitive member is charged in a first charging position by applying a first charging voltage of less than a discharge start voltage, and controls the second charging voltage applying portion so that the surface of the photosensitive member is charged in a second charging position by applying a second charging voltage of not less than the discharge start voltage.