Transfer Current Control for Image Density Uniformity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional image forming apparatuses face issues with irregular image density due to varying image area ratios, leading to defective transfer and reverse transfer of toner images, especially in color printing where the transfer current is not adequately adjusted based on the image area ratio.
Innovation Solution
An image forming apparatus that includes a latent image carrier, a developing unit, and a transfer current output unit, which determines a target transfer current value based on an algorithm representing the relationship between the image area ratio and the transfer current, performing distinct transfer steps to optimize toner image transfer and prevent reverse transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a constant transfer current is output regardless of the image area ratio, then the device operation is simple, but image density irregularity occurs depending on the image area ratio
Solution Approach 1:
The transfer current target value is dynamically adjusted based on the image area ratio detected from the latent image carrier. The control unit changes the transfer current according to the proportion of image areas, transforming a static constant current system into a dynamic adaptive system that optimizes transfer performance for different image densities
Solution Approach 2:
The system changes the transfer current parameter based on the image area ratio. By detecting the image area ratio and corresponding the transfer current target value appropriately, the system adapts the electrical parameter to match the specific printing conditions, ensuring consistent image density across varying image areas
2Reliability
If the transfer current target value is increased to ensure sufficient current flow in low image area ratio conditions, then adequate current is provided for small images, but excessive current flows causing reverse transfer of toner
Solution Approach 1:
The system applies different transfer current target values tailored to specific image area ratio conditions. Instead of using a uniformly high current that causes reverse transfer, the control unit selectively adjusts the current based on the actual image area, providing locally optimized current levels that prevent both insufficient transfer and excessive reverse transfer
Solution Approach 2:
The control unit detects the image area ratio from the latent image carrier and uses this feedback information to determine the appropriate transfer current target value. This closed-loop control prevents reverse transfer by adjusting the current based on real-time detection of image characteristics
3Object-generated harmful factors
If the transfer current target value is decreased to prevent reverse transfer, then reverse transfer is minimized, but insufficient current flows causing defective transfer in low image area ratio conditions
Solution Approach 1:
The system dynamically adjusts the transfer current target value based on the detected image area ratio. This dynamic control ensures that the current is never too low to cause defective transfer, as the system increases the current target value when small image areas are detected, while preventing reverse transfer when large image areas are present
4Adaptability or versatility
If superimposing transfer is implemented for color printing, then color images can be formed, but irregularity in image density occurs due to inadequate adjustment of transfer current based on image area ratio
Solution Approach 1:
The image area ratio detection and transfer current control mechanism is designed to work universally across different color printing scenarios. The control unit detects image area ratios for each color component and adjusts the transfer current accordingly, ensuring consistent performance whether printing single-color or multi-color images
Solution Approach 2:
The system changes the transfer current parameter based on image area ratio detection, applying this parameter adjustment strategy to each color component in superimposing transfer. This ensures that each color layer is transferred with appropriate current levels, maintaining image density uniformity across the entire color image
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 ensures stable and efficient transfer of toner images across varying image area ratios, minimizing defects and maintaining optimal image density by dynamically adjusting the transfer current, thereby enhancing the overall printing quality.
Implementation Method 1
A transfer bias having a polarity opposite to the normally charged polarity of toner is applied to the transfer roller. A toner image on the photosensitive element is transferred to a recording sheet serving as a recording member fed into the transfer nip.
Implementation Method 2
On the surface of the photosensitive element, all of a non-image portion and an image portion (latent image portion) are charged with the same polarity with the normally charged polarity of toner, and the potential of the non-image portion becomes higher than the potential of the image portion.
Data Source
AI summary
In an image forming apparatus, a transfer current output unit outputs a transfer current having a same value as a target value to a nip forming member to transfer a toner image on a latent image carrier to the nip forming member to determine the target value based on an algorithm representing a relationship between an image area ratio of the toner image and the target value and the image area ratio, and in an algorithm for a second transfer step in which the toner image is transferred to be superimposed on the toner image of the nip forming member to which the toner image has been transferred, a smaller target value is related to a same image area ratio compared to the algorithm for a first transfer step in which the toner image is transferred to the nip forming member to which no toner image is transferred.