Photosensitive Drum Charging Voltage Control for Attenuation
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Solution Overview
Problem
In electrophotographic image forming apparatuses, variations in the dark attenuation amount of the photosensitive drum's surface potential can lead to inappropriate charging, resulting in image defects like image density fluctuations and scattering fog, especially when the photosensitive drum is replaced.
Innovation Solution
An image forming apparatus that includes a photosensitive member unit with an information storage portion to store the attenuation amount of the surface potential, and a setting portion that adjusts the voltage applied to the charging member based on the current flowing when a preset voltage is applied, allowing for proper charging by setting the applying voltage to either a first or second voltage depending on the attenuation amount.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If the attenuation amount of the surface potential is increased to extend the lifetime of the photosensitive drum, then the dark attenuation amount varies greatly among photosensitive drums, but the surface potential at the development position becomes inappropriate, causing image defects
Solution Approach 1:
The patent applies parameter changes by adjusting the applying voltage to the charging roller based on the measured dark attenuation amount. The control unit reads the attenuation amount from the storage unit and dynamically changes the voltage parameter to compensate for variations in dark attenuation, ensuring the surface potential at the development position remains appropriate even when lifetime is extended through increased attenuation.
2Ease of operation
If a fixed voltage is applied to the charging roller based on the discharge start voltage, then the charging process is simple, but the surface potential cannot be properly charged when the dark attenuation amount varies
Solution Approach 1:
The patent implements feedback by measuring the dark attenuation amount, storing this information, and using it to adjust the applying voltage. The control unit continuously monitors the attenuation characteristics and feeds this information back into the voltage control system, allowing the charging process to adapt to individual photosensitive drum characteristics while maintaining operational simplicity.
3Reliability
If the applying voltage is increased to compensate for high dark attenuation, then the surface potential may be sufficient, but image density fluctuation and scattering fog occur due to potential overshoot
Solution Approach 1:
The patent applies partial action by adjusting the voltage to provide just enough compensation for the measured dark attenuation without excessive overcompensation. By reading the specific attenuation amount from storage and setting the applying voltage accordingly, the system avoids both insufficient charging and overshoot conditions that would cause image defects, achieving precise partial adjustment.
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 ensures that the surface potential of the photosensitive drum is accurately maintained at the appropriate potential, preventing image defects even when the dark attenuation amount varies, thus ensuring consistent and high-quality image formation.
Implementation Method 1
The photosensitive drum is charged by applying a DC voltage to the charging roller and generating a discharge in the vicinity of the nip (so-called DC charging system)
Data Source
AI summary
An image forming apparatus includes a photosensitive member unit, a charging member, an exposing unit, a developing unit, an information storage portion, and a setting portion. The information storage portion stores information on an attenuation amount of a surface potential of the photosensitive member by which the surface potential is attenuating until the photosensitive member rotates from a contact position of the photosensitive member to a development position of the photosensitive member. If the attenuation amount is a first attenuation amount, the setting portion sets an applying voltage to be applied to the charging member at the time of image formation to a first voltage. If the attenuation amount is a second attenuation amount greater than the first attenuation amount, the setting portion sets an applying voltage to be applied to the charging member at the time of image formation to a second voltage higher than the first voltage.