Transfer Unit Charging Bias Control for Image Density Uniformity
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Solution Overview
Problem
Conventional electrophotographic image forming apparatuses face issues with transfer efficiency, image dropout, and image-density irregularity due to the limitations of corona and contact charging methods, as well as the variability in surface smoothness of recording media, leading to ozone generation, surface damage, and maintenance challenges.
Innovation Solution
The apparatus incorporates a combination of corona, contact, and proximate charging methods with optimized transfer conditions, including specific charging biases and lubricant application, along with controlled pressing forces and linear velocity differences between image carriers and transfer members to stabilize the transfer process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If corona charging method is used, then charging efficiency is improved, but ozone generation increases and surface damage occurs
Solution Approach 1:
The patent changes the charging method from corona charging to contact charging, fundamentally altering the charging parameter to eliminate ozone generation while maintaining charging efficiency through optimized contact pressure and surface properties
2Object-generated harmful factors
If contact charging method is used, then ozone generation is reduced, but transfer efficiency decreases and image dropout increases
Solution Approach 1:
The patent applies local quality by optimizing the contact surface properties at the charging interface, using specific surface treatments and pressure distributions to enhance charge transfer efficiency while maintaining the benefits of contact charging
Solution Approach 2:
The patent introduces dynamic control of contact pressure and charging parameters to optimize transfer efficiency, adjusting conditions in real-time to prevent image dropout while maintaining low ozone generation
3Device complexity
If uniform pressing force is applied, then transfer process is simplified, but image-density irregularity increases due to recording medium variability
Solution Approach 1:
The patent implements dynamic pressing force control that adjusts pressure distribution based on the specific recording medium being used, optimizing image density uniformity while maintaining relatively simple overall system design through automated feedback control
4Productivity
If high transfer efficiency is pursued, then image quality is improved, but maintenance needs increase due to surface damage and wear
Solution Approach 1:
The patent replaces harsh mechanical corona discharge with gentler contact charging mechanics, reducing surface damage and wear while maintaining transfer efficiency, thereby decreasing maintenance requirements
Solution Approach 2:
The patent optimizes contact pressure and surface interaction parameters to achieve high transfer efficiency with minimal surface damage, extending component life and reducing maintenance frequency
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 enhances transfer efficiency, reduces image dropout, and improves image-density uniformity, thereby maintaining high-quality image reproduction while minimizing ozone generation and maintenance needs.
Implementation Method 1
a charging member may have discharge electrodes, such as wire electrodes, and shield electrodes surrounding the discharge electrodes. Such corona charging member applies high voltages to the discharge electrodes and shield electrodes to generate a corona shower, and charges the surface of a charged body, such as an image carrier, by the corona shower to a certain electric potential.
Implementation Method 2
By action of transfer electric field generated at each primary transfer area, the toner image on each image carrier is transferred onto the intermediate transfer belt.
Implementation Method 3
To prevent such damage, lubricant may be applied to the surface of photoconductor. Such lubricant may prevent the curling of the surface of photoconductor
Data Source
AI summary
An image forming apparatus includes a plurality of image forming units and a plurality of transfer units. The image forming units have corresponding image carriers and charging units. The image forming units form toner images of different colors on the corresponding image carriers. The transfer units face the corresponding image carriers to form transfer areas between the transfer units and the image carriers, and press a transfer member to the corresponding image carriers to transfer the toner images onto the transfer member at the transfer areas. The charging units include at least one corona-type charger and at least one contact-type charger. The image forming apparatus sets a first transfer condition for the transfer unit(s) corresponding to the image carrier(s) charged by the at least one corona-type charger and a second, separate transfer condition for the transfer unit(s) corresponding to the image carrier(s) charged by the at least one contact-type charger.