Photosensitive Drum Pre-Exposure Timing for Uniform Charging
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Solution Overview
Problem
The DC charging system for electrophotographic image forming apparatuses leads to non-uniform surface potential on the photosensitive drum, causing ghost images and reduced product life due to abrasion and overcharging, which existing solutions like pre-charge exposure attempt to mitigate but result in abnormal discharges and mesh-like images.
Innovation Solution
An image forming apparatus with a control unit that adjusts the timing of latent image formation based on the photosensitive layer thickness and environmental conditions, using a second exposing unit to pre-expose the drum after toner transfer and before re-charging, to prevent overcharging and extend product life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If pre-charge exposure is performed to average surface potential and prevent ghost images, then charging uniformity is improved, but abnormal discharges occur and product life is reduced
Solution Approach 1:
The patent applies preliminary action by performing pre-charge exposure before the main charging process to average out surface potential variations. This preliminary light irradiation prevents ghost images by ensuring uniform charging conditions, while the control unit carefully manages the timing and duration to avoid excessive discharge that would reduce product life.
2Reliability
If DC charging system is used to reduce discharge frequency and extend photosensitive drum life, then product life is improved, but surface potential becomes non-uniform causing ghost images
Solution Approach 1:
The patent uses preliminary action by implementing pre-charge exposure before DC charging to uniformize the surface potential. This preliminary light irradiation ensures that the photosensitive drum surface is evenly prepared for charging, preventing ghost images while maintaining the low discharge frequency advantage of DC charging systems.
Solution Approach 2:
The patent applies continuity of useful action by maintaining a continuous pre-charge exposure process that operates throughout the charging cycle. This continuous light irradiation ensures consistent surface potential uniformity across the entire photosensitive drum surface, preventing ghost images while working harmoniously with the DC charging system.
3Reliability
If photosensitive layer thickness is increased to extend product life and reduce abrasion, then product life is improved, but abnormal discharges and mesh-like images occur
Solution Approach 1:
The patent applies parameter changes by adjusting the timing and duration of pre-charge exposure based on the photosensitive layer thickness. For thicker layers that are more prone to abnormal discharges, the control unit modifies the exposure parameters to achieve uniform charging without causing excessive discharge, thus maintaining both product life and image quality.
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 prevents abnormal discharges and extends the product life of the photosensitive drum by ensuring uniform charging and minimizing abrasion, while avoiding ghost images and mesh-like patterns.
Implementation Method 1
a charging member which charges the photosensitive member
Implementation Method 2
a first exposing unit which exposes a surface of the charged photosensitive member to form a latent image
Implementation Method 3
a second exposing unit which exposes the surface of the photosensitive member after the surface of the photosensitive member passes a transfer position
Data Source
AI summary
An image forming apparatus includes: a first exposing unit exposing a surface of a charged photosensitive member to form a latent image; a second exposing unit exposing the surface of the photosensitive member after the surface of the photosensitive member passes a transfer position at which a toner image obtained by causing toner to adhere to the latent image is transferred to a transferred body and before the surface of the photosensitive member reaches a charging position; and a control unit varying a length of a period from a timing at which a portion of the photosensitive member exposed by the second exposing unit is initially charged by the charging member to a timing at which the first exposing unit starts formation of the latent image when performing image formation based on a print signal, based on information related to a photosensitive layer thickness of the photosensitive member.