Selective Pre-Exposure Device Placement for Ghost Image Suppression
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Solution Overview
Problem
Tandem-type image forming apparatuses using the DC charging type face issues with ghost image generation due to inadequate discharging of photosensitive members, leading to increased costs and potential deterioration, while the AC charging type reduces ghost images but is costly.
Innovation Solution
The image forming apparatus employs a configuration where the first and second image forming stations lack pre-exposure discharging means, while the third and fourth stations have pre-exposure devices to optically discharge photosensitive members, optimizing charging and reducing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pre-exposure device is provided in all image forming stations to discharge photosensitive members, then ghost image generation is suppressed, but costs and device complexity increase
Solution Approach 1:
The patent applies pre-exposure devices selectively only to downstream image forming stations (third and fourth stations) where ghost images are most likely to occur due to high toner density from preceding stations. Upstream stations (first and second stations) omit these devices since they don't receive toner images from previous stations, thus avoiding unnecessary complexity while targeting the specific problem location.
Solution Approach 2:
The image forming apparatus is segmented into upstream and downstream stations with different configurations. The downstream stations are equipped with pre-exposure functionality while upstream stations are not, creating a segmented approach that optimizes the balance between ghost image suppression and device complexity.
2Reliability
If a pre-exposure device is provided to discharge photosensitive members, then charging uniformity is improved, but photosensitive member deterioration accelerates and costs increase
Solution Approach 1:
Pre-exposure devices are applied locally only where necessary (downstream stations with high toner density) rather than universally across all stations. This localized application achieves sufficient charging uniformity improvement where needed while minimizing unnecessary light exposure that would accelerate photosensitive member deterioration in upstream stations.
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 ghost image generation while reducing costs by ensuring uniform potential of photosensitive members, thus improving image quality and extending the lifespan of the apparatus.
Implementation Method 1
a device for optically discharging the photosensitive member, a so-called pre-exposure device (discharging means), is mounted
Implementation Method 2
a DC charging type for (electrically) charging the photosensitive member by applying only the DC voltage
Implementation Method 3
toner images formed at the respective image forming stations are successively transferred superposedly onto an intermediary transfer member
Data Source
AI summary
In an image forming apparatus including a plurality of image forming stations, a pre-exposure device is not provided in at least a most upstream image forming station at which a toner image formed by the image forming station cannot arrive, and the pre-exposure device is provided in at least a most downstream image forming station at which the toner image formed by the image forming station can arrive.