Developing Bias Control for Image Density Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing image forming apparatuses face issues with image defects due to speed variations in intermediary transfer members, leading to density variations and uneven images, especially when handling sheets of varying thicknesses and surface configurations, and current solutions are either costly, complex, or interfere with image quality by introducing moire patterns.
Innovation Solution
The proposed solution involves controlling the developing bias to adjust the toner amount on the intermediary transfer belt in real-time based on predicted speed variations, ensuring consistent image density by modifying the potential difference between the image portion and the developing bias, thereby stabilizing image quality across different paper types and print modes without increasing costs or introducing moire issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If secondary transfer pressure is increased to ensure sufficient transfer property for sheets with uneven surface configuration, then transfer efficiency is improved, but load variation on the intermediary transfer belt is increased causing impact-caused unevenness
Solution Approach 1:
The invention applies preliminary action by adjusting the developing bias before the sheet enters the secondary transfer nip to anticipate and compensate for the upcoming load variation. When it is predicted that the sheet leading end will enter or the trailing end will come out of the secondary transfer nip, the developing bias is adjusted in advance to control the toner amount, thereby preventing impact-caused unevenness before it occurs.
Solution Approach 2:
The invention changes the parameter of developing bias dynamically based on the sheet position and predicted load variation. By adjusting the developing bias voltage or current in real-time, the toner amount on the intermediary transfer belt is controlled to compensate for speed variations, maintaining uniform image density despite changes in transfer pressure and belt speed.
2Reliability
If the intermediary transfer belt speed is stabilized to prevent impact-caused unevenness, then image quality is improved, but additional complex mechanisms or costly components are required
Solution Approach 1:
The invention implements feedback control by using a sheet position detection mechanism to determine when the sheet leading end enters or the trailing end comes out of the secondary transfer nip. Based on this feedback information, the developing bias is automatically adjusted to compensate for predicted speed variations, creating a closed-loop control system that maintains image quality without requiring complex mechanical stabilization mechanisms.
Solution Approach 2:
The invention replaces mechanical speed stabilization mechanisms with an electrical/control-based approach. Instead of using additional mechanical components to stabilize the intermediary transfer belt speed, the invention uses developing bias adjustment to compensate for speed variations, substituting a complex mechanical system with a simpler electrical control system.
3Manufacturing precision
If developing bias is adjusted to control toner amount during speed variation, then density variation is minimized, but energy consumption increases due to frequent bias changes
Solution Approach 1:
The invention applies partial action by adjusting the developing bias only during specific critical periods when the sheet leading end enters or the trailing end comes out of the secondary transfer nip. Instead of continuously adjusting the bias, the control is applied selectively only when necessary to prevent impact-caused unevenness, thereby reducing overall energy consumption while maintaining image quality.
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 effectively stabilizes image quality by minimizing density variations caused by speed fluctuations, ensuring high-quality images irrespective of paper type or print mode, without the need for additional costly components or complex mechanisms, and avoids moire interference.
Implementation Method 1
the developer amount control means (101) changes the developing bias application amount by a predetermined value for a predetermined time period with timing when the intermediary transfer member (51) causes the speed variation
Data Source
AI summary
An image forming apparatus includes a rotatable image bearing member; a developing device, including a developer carrying member and developing bias application means for applying a developing bias for developing a developer image; a rotatable intermediary transfer member; a primary transfer member for forming a primary transfer nip and for transferring the developer image from the image bearing member onto the intermediary transfer member; a secondary transfer member for secondary-transferring the developer image from the intermediary transfer member onto a recording material; wherein an area of the image bearing member includes a first area at least containing an area located in primary transfer nip at a time when a speed of the intermediary transfer member is temporarily decreased and includes a second area located in the primary transfer nip when there is no temporary change in speed; and a control device for controlling a developing bias.