Electrostatic Toner Control for Ghost Reduction
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Solution Overview
Problem
Conventional electrophotographic image forming apparatuses face issues with development ghosts and image missing due to toner charge differences and insufficient toner supply, particularly when the inter-sheet distance is shortened, leading to increased mechanical friction and toner deterioration.
Innovation Solution
The apparatus employs a control unit to manage the electric potential difference between the developer bearing member and the supply roller, adjusting the bias to urge toner from the development roller to the supply roller during image non-forming regions and vice versa during image forming regions, ensuring sufficient toner supply and reducing development ghost occurrences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If measures to strengthen mechanical scraping-off of the supply roller are taken, then a development ghost is reduced, but mechanical sliding-contact and friction between the development roller and the supply roller increases, so that toner deterioration is accelerated
Solution Approach 1:
The patent replaces mechanical scraping-off with electrostatic force. A bias voltage is applied to the supply roller to create an electric field that electrostatically attracts and removes development residual toner from the development roller, substituting the mechanical sliding-contact system with an electrostatic field-based system. This resolves the contradiction by eliminating the need for strong mechanical friction while still achieving effective toner scraping-off.
Solution Approach 2:
The patent changes the operational parameters by applying a controlled bias voltage to the supply roller. By adjusting the voltage parameter, the system can dynamically control the electrostatic force for toner removal, replacing the fixed mechanical contact pressure system. This allows effective toner scraping-off without the harmful mechanical friction that causes toner deterioration.
2Reliability
If a bias to cause development residual toner to peel off is applied, then development ghost is reduced, but when an image with a high printing ratio is printed, image missing due to insufficiency of toner supply amount occurs
Solution Approach 1:
The patent makes the bias voltage applied to the supply roller dynamic rather than fixed. The control unit adjusts the voltage based on the printing conditions: applying a higher voltage during image non-formation to remove residual toner, and reducing or reversing the voltage during image formation to ensure sufficient toner supply. This dynamic adjustment resolves the contradiction by adapting the electrostatic force to the operational phase.
Solution Approach 2:
The patent implements periodic switching of the bias voltage polarity and magnitude based on the printing cycle. During image non-formation periods, a bias is applied to remove residual toner; during image formation periods, the bias is adjusted to facilitate toner supply. This periodic action pattern allows the system to achieve both development ghost reduction and sufficient toner supply at different times in the operational cycle.
3Reliability
If the inter-sheet distance is set to a distance equal to or longer than that corresponding to one cycle of rotation of the development roller, then toner charge amount can be controlled, but productivity is reduced due to longer cycle time
Solution Approach 1:
The patent replaces the mechanical timing-based toner charge control (which required long inter-sheet distances) with electrostatic field-based control. By applying bias voltage to the supply roller, the system can control toner charge amount and remove residual toner electrostatically during shorter inter-sheet distances, enabling faster continuous printing while maintaining toner charge control.
Solution Approach 2:
The patent changes the control parameter from mechanical timing (inter-sheet distance) to electrical parameter (bias voltage). By controlling the voltage applied to the supply roller, the system can achieve effective toner management within shorter time intervals, thereby reducing the inter-sheet distance requirement and increasing continuous printing productivity.
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 reduces development ghost phenomena and prevents image missing at the trailing edge, maintaining image quality and extending the operational life of the development device by optimizing toner distribution and supply.
Implementation Method 1
control is performed to change a bias between the development roller and the supply roller and cause development residual toner on the development roller to peel off due to electrostatic force
Implementation Method 2
mechanical sliding-contact and friction between the supply roller and the development roller causes toner to be supplied to the development roller while being subjected to triboelectric charging
Data Source
AI summary
An image forming apparatus includes a control unit that controls an electric potential difference between a development roller and a supply roller in such a manner that force in a direction from the supply roller toward the development roller acts on toner in a section of an image forming region extending from a leading edge of a first image forming region toward a trailing edge thereof. The control unit controls the electric potential difference in such a manner that force acting on the toner becomes smaller in a section extending from a switching point, which is located at a position obtained by returning from a leading edge of a second image forming region to the first image forming region by a distance equal to or greater than a circumferential length of the development roller, to the trailing edge of the first image forming region.