Pre-Charging Exposure Light Control for Drum Ghost Suppression
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Solution Overview
Problem
The existing cleaner-less system in electrophotographic image forming apparatuses experiences voltage fluctuations due to surface potential displacement of photosensitive drums during pre-charging exposure, leading to image density non-uniformity, especially in color image forming apparatuses with common power sources.
Innovation Solution
The apparatus includes a controller that adjusts the light emission quantity of the pre-charging exposure device to gradually change the surface potential of the photosensitive drum, ensuring stable charging voltage by stepwise rising and falling light emission control, thereby minimizing potential fluctuations and preventing transfer residual toner deposition on charging rollers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If pre-charging exposure is performed to discharge the photosensitive drum surface, then transfer residual toner deposition on charging roller is suppressed, but charging voltage fluctuates due to surface potential displacement
Solution Approach 1:
The pre-charging exposure device performs preliminary discharge action on the photosensitive drum surface before the charging process. This preliminary action removes surface potential that would otherwise cause transfer residual toner to deposit on the charging roller, while the exposure timing and light quantity are controlled to avoid charging voltage fluctuations
Solution Approach 2:
The invention changes the light quantity parameter of the pre-charging exposure device dynamically. By adjusting the light quantity based on the operational state, the system achieves effective surface discharge to prevent toner deposition while maintaining charging voltage stability within a predetermined range
2Object-affected harmful factors
If light quantity of pre-charging exposure is increased to discharge surface potential, then drum ghost is suppressed, but charging voltage fluctuates due to load change
Solution Approach 1:
The invention dynamically adjusts the light quantity parameter of the pre-charging exposure device. By controlling the light quantity to be within a predetermined range, the system effectively suppresses drum ghost caused by surface potential while preventing excessive load changes that would cause charging voltage fluctuations
Solution Approach 2:
The system implements feedback control by monitoring the charging voltage and adjusting the pre-charging exposure light quantity accordingly. When charging voltage approaches the upper limit, the light quantity is reduced to prevent voltage fluctuation, thereby maintaining both drum ghost suppression and voltage stability
3Device complexity
If common power source is used for multiple charging devices, then device complexity and cost are reduced, but voltage fluctuation affects multiple image forming portions
Solution Approach 1:
The invention implements a common power source device that serves multiple charging members simultaneously. This universal power source configuration reduces device complexity and cost while the pre-charging exposure control ensures that voltage fluctuations do not affect image density uniformity across different image forming portions
4Productivity
If pre-charging exposure light quantity is abruptly changed, then surface potential discharge is efficient, but charging voltage fluctuates due to load fluctuation
Solution Approach 1:
The invention makes the pre-charging exposure light quantity dynamic rather than fixed. The light quantity is adjusted in real-time based on the charging voltage state, transitioning smoothly between different levels to maintain surface potential discharge efficiency while preventing abrupt load changes that would cause voltage fluctuations
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 suppresses charging voltage fluctuations and prevents image density non-uniformity, ensuring high-quality image formation without the need for additional cleaning mechanisms in the cleaner-less system.
Implementation Method 1
a pre-charging exposure device... for discharging (removing a potential of) the surface of the photosensitive drum by irradiating the photosensitive drum surface with light
Implementation Method 2
a charging roller... for electrically charging the surface of the photosensitive drum to a uniform potential
Implementation Method 3
an electrostatic latent image is formed by irradiating a surface of the photosensitive drum with light depending on image data
Implementation Method 4
toner as a developer is deposited by a developing means on the electrostatic latent image formed on the photosensitive drum
Implementation Method 5
the toner image formed on the photosensitive drum is transferred onto a recording material such as recording paper by a transfer means
Data Source
AI summary
An image forming apparatus includes a first image forming portion, a second image forming portion, a power source portion, and a controller. The power source portion is constituted so that when the power source portion applies a charging voltage to a first charging member of the first image forming portion, the charging voltage is also applied to a second charging member of the second image forming portion. The controller carries out control so that an emitted light quantity of a light emitting element is changed from a first light quantity to a second light quantity larger than the first light quantity and is changed from the second light quantity to a third light quantity larger than the second light quantity.