Development Bias Control for Image Density Uniformity
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Solution Overview
Problem
Image forming apparatuses face issues with periodic image density unevenness due to fluctuations in the development gap caused by eccentricity or low roundness of the development sleeve or photoconductor, leading to background staining and carrier adherence when switching from a constant to a periodically changing bias.
Innovation Solution
The apparatus periodically changes the development or charging bias based on pre-adjusted control data, maintaining a constant bias value initially and switching to a fluctuating value when the difference from the central value in the periodic fluctuation range is less than or equal to a threshold, ensuring a substantially constant electric field strength and reducing uneven image density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the development bias is periodically changed to compensate for development gap fluctuation, then image density uniformity is improved, but background staining and carrier adherence occur during switching
Solution Approach 1:
The patent applies preliminary action by gradually transitioning the development bias from a constant value to a periodically changing value through intermediate stages. Before implementing full periodic variation, the system first applies a constant bias to stabilize the electric field, then progressively introduces periodic components to compensate for development gap fluctuations without causing abrupt changes that lead to background staining and carrier adherence.
Solution Approach 2:
The patent implements dynamics by making the development bias adaptable and changeable based on operating conditions. The bias control unit dynamically adjusts the development bias between constant and periodically changing modes, and further adapts the periodic variation amplitude based on detected image density, transforming the static bias system into a dynamic one that responds to real-time conditions.
2Object-generated harmful factors
If the development bias is constantly maintained at a fixed value, then background staining and carrier adherence are suppressed, but periodic image density unevenness occurs
Solution Approach 1:
The patent applies periodic action by introducing periodic variation in the development bias to counteract the periodic fluctuation of the development gap caused by eccentricity or low roundness of the development sleeve or photoconductor. The bias control unit varies the development bias at the same frequency as the development gap fluctuation, creating a compensating effect that eliminates periodic image density unevenness while maintaining suppression of background staining and carrier adherence through controlled transition.
3Manufacturing precision
If the bias is switched from constant to periodically changing, then image density uniformity is improved, but image formation stability deteriorates during transition
Solution Approach 1:
The patent applies preliminary action by establishing a stable constant bias state before transitioning to periodic variation. The bias control unit first maintains a constant development bias to ensure stable image formation and carrier distribution, then progressively introduces periodic components after stabilization, preventing disruption to the image formation process during the transition phase.
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 effectively suppresses background staining and carrier adherence while maintaining consistent image density by adjusting the bias output to match the fluctuating development gap, ensuring stable image formation.
Implementation Method 1
a charging unit configured to uniformly charge a surface of the rotationally driven latent-image bearing body
Implementation Method 2
a latent-image writing unit configured to write a latent image to the surface after the charging unit uniformly charges the surface
Implementation Method 3
a development unit configured to develop the latent image to form a toner image; a development power source configured to output a development bias to be supplied to the development unit
Data Source
AI summary
An image forming apparatus includes a latent-image bearing body, a charging unit, a latent-image writing unit, a development unit, a development power, and a bias control unit. After a start of an image forming operation, the bias control unit performs a process of constantly maintaining an output of a development bias at an adjustment bias value. The adjustment bias value is a central value in a periodic fluctuation range of the output of the development bias. At a timing at which a difference of the development bias from the adjustment bias value in the periodic fluctuation range is less than or equal to a predetermined threshold value, the bias control unit performs switching from the process of constantly maintaining the output of the development bias at the adjustment bias value to a process of periodically changing the output of the development bias based on development bias control data.