Primary Transfer Roller Shift for Single Power Source Image Quality
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Solution Overview
Problem
The simplification and downsizing of image forming apparatuses are hindered by the need for multiple high-voltage power sources, which increases complexity and reduces image quality due to potential differences in current flow between photosensitive drums.
Innovation Solution
The image forming apparatus employs a single constant voltage source to charge multiple primary transfer rollers, with each roller shifted downstream to equalize current flow and reduce the number of power sources required, thereby preventing transfer memory and ensuring consistent image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single constant voltage source is used to charge multiple primary transfer rollers, then the number of power sources is reduced and device complexity is decreased, but potential differences in current flow between photosensitive drums may occur leading to transfer memory and image quality deterioration
Solution Approach 1:
The patent applies local quality by shifting each primary transfer roller downstream by a predetermined distance relative to its corresponding photosensitive drum. This creates asymmetric positioning where each transfer roller operates at a different location in the transfer path, allowing each to experience optimized local conditions for charge equalization. The shift distance is specifically designed to balance the current flow characteristics for each transfer roller, ensuring uniform charging despite using a single power source.
2Reliability
If multiple high-voltage power sources are used to charge each primary transfer roller individually, then image quality consistency is maintained through equalized current flow, but device complexity and size increase
Solution Approach 1:
The patent merges multiple power source functions into a single constant voltage source. Instead of using separate high-voltage power sources for each primary transfer roller, the invention combines all charging functions into one power source that supplies charge to all rollers simultaneously. The downstream shifting of rollers compensates for the loss of individual power source control, maintaining image quality while reducing complexity.
3Reliability
If primary transfer rollers are shifted downstream by a predetermined distance, then current flow is equalized and transfer memory is prevented, but the transfer mechanism becomes more complex
Solution Approach 1:
The patent introduces asymmetry by shifting each primary transfer roller downstream by a predetermined distance from its ideal alignment position with the corresponding photosensitive drum. This asymmetric positioning is deliberate and calculated to equalize current flow characteristics. The shift creates a non-uniform geometric relationship between transfer rollers and photosensitive drums that compensates for electrical field variations, preventing transfer memory while maintaining functional simplicity.
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 reduces the number of power sources needed while maintaining image quality by equalizing current flow and preventing transfer memory, thus simplifying the apparatus and enhancing its performance.
Implementation Method 1
The tandem-type image forming apparatus gives a potential to each photosensitive drums and causes the photosensitive drums to bear toner images in respective colors by electrostatic forces
Implementation Method 2
The toner images in the respective colors are transferred from the respective photosensitive drums to the transfer target by a potential difference (transfer field) between each photosensitive drum and a corresponding one of the transfer rollers
Implementation Method 3
static electricity is eliminated from the respective photosensitive drums after transfer of the toner images in the respective colors to the transfer target by for example irradiating the photosensitive drums with static elimination light
Data Source
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AI summary
An image forming apparatus (1) includes image bearing members (31), transfer members (52), and a power supply section (57). The image bearing members (31) each bear one of toner images in different colors from one another. The transfer members (52) are located opposite to the image bearing members (31). The power supply section (57) charges the transfer members (52). Through the above, the toner images on the respective image bearing members (31) are transferred to a moving transfer target (51). The power supply section (57) includes a power supply device (58 or 58a) connected to at least two of the transfer members (52). The transfer members (52) connected to the power supply device (58 or 58a) are each located at a position shifted upstream or downstream of a corresponding one of the image bearing members (31) in a moving direction (X) of the transfer target (51).