Charging Voltage Control for Electrophotographic Memory Phenomenon
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Solution Overview
Problem
The existing image forming apparatuses using electrophotographic printing methods face the issue of 'memory phenomenon' due to charging unevenness on the photosensitive member, leading to image defects like lateral black streaks, which are difficult to suppress with existing solutions that require additional components and increased costs.
Innovation Solution
The apparatus employs a controller to adjust the peak-to-peak voltage of the charging voltage applied to the charging member, increasing it for specific areas during the transferring process to alleviate charging unevenness and prevent memory phenomenon, thereby stabilizing the potential on the photosensitive member.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a separation electric discharge prevention electrode is provided in the vicinity of the separation position, then the memory phenomenon caused by separation electric discharge is suppressed, but the device complexity and cost increase due to additional components and drive circuits
Solution Approach 1:
The invention extracts and eliminates the need for the separation electric discharge prevention electrode and its drive circuit by using the existing charging portion to remove positive charges. This removes the harmful component while maintaining the suppression effect on memory phenomenon.
Solution Approach 2:
The charging portion, which already exists in the system, is utilized to perform the additional function of removing positive charges from the photosensitive member. This self-service approach eliminates the need for separate components dedicated to preventing separation electric discharge.
2Reliability
If a separation electric discharge prevention electrode is provided with a drive circuit generating opposite polarity voltage, then the memory phenomenon is suppressed, but the manufacturing cost increases
Solution Approach 1:
The charging portion is designed to perform multiple functions: primary charging of the photosensitive member and secondary removal of positive charges caused by separation electric discharge. This multi-functionality eliminates the need for separate components and reduces manufacturing cost.
Solution Approach 2:
The invention removes the need for the separation electric discharge prevention electrode and its associated drive circuit by utilizing the existing charging portion, thereby reducing component count and manufacturing cost while maintaining effectiveness.
3Reliability
If the charging portion removes positive charges effectively, then the memory phenomenon is suppressed, but the charging uniformity may be affected
Solution Approach 1:
The charging portion applies charging voltage locally to specific areas of the photosensitive member where positive charges need to be removed. This localized action suppresses memory phenomenon while maintaining overall charging uniformity by targeting only the affected regions.
Solution Approach 2:
The charging portion performs preliminary removal of positive charges from the photosensitive member before the main charging process, ensuring that the subsequent charging creates uniform potential distribution without being affected by residual positive charges.
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 approach effectively suppresses the memory phenomenon and charging defects, ensuring consistent image quality without the need for additional components, thereby reducing costs and improving the longevity of the photosensitive drum.
Implementation Method 1
a charging member configured to charge the photosensitive member at a charging portion
Implementation Method 2
a charging voltage being obtained by superimposing an alternate-current voltage on a direct-current voltage
Implementation Method 3
an exposure device configured to expose the charged photosensitive member with light to form an electrostatic image on an image area on the photosensitive member
Implementation Method 4
a developing device configured to supply toner to the electrostatic image on the photosensitive member to form a toner image
Implementation Method 5
a transfer member to which a voltage is applied to transfer the toner image on the photosensitive member to a recording material at a transfer portion
Data Source
AI summary
An image forming apparatus including: a charging member configured to charge a photosensitive member at a charging portion by a charging voltage in which an alternate-current voltage is superimposed on a direct-current voltage; a transfer member configured to transfer a toner image formed on the photosensitive member to a recording material at a transfer portion; and a controller configured to control the charging voltage, a predetermined area of the photosensitive member passing through the transfer portion during a trailing edge of the recording material passing through the transfer portion, wherein the controller controls a value of a peak-to-peak voltage of the alternate-current voltage when the predetermined area passes through the charging portion to be larger than a value of a peak-to-peak voltage when an area that becomes the image area other than the predetermined area passes through the charging portion.