Developing Bias Control for Image Density Stability
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Solution Overview
Problem
Image density in electrographic image forming apparatuses fluctuates significantly between pages due to environmental changes and photoreceptor weariness, causing visual discomfort in readers when process control adjusts image density.
Innovation Solution
An image forming apparatus and method that determine a print-time developing bias based on previous adjustments, setting it between the reference developing bias for target image density and the previous print-time developing bias, to minimize density changes between pages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If process control adjusts image density by setting developing bias to reference developing bias, then image density approximation to target density is improved, but image density fluctuation between pages increases causing visual discomfort
Solution Approach 1:
The patent applies dynamics by making the developing bias adjustable and variable rather than fixed. The arithmetic section dynamically calculates appropriate developing bias values based on detected image density and previous developing bias, allowing the system to adapt to changing conditions (photoreceptor weariness, environmental changes) while maintaining stability through controlled adjustment.
Solution Approach 2:
The patent implements feedback control by using the density sensor to detect actual image density, comparing it with the target density, and using this information to adjust the developing bias. The arithmetic section continuously refines the developing bias based on feedback from density detection and previous settings, creating a closed-loop control system that maintains both accuracy and stability.
2Manufacturing precision
If developing bias is significantly adjusted to correct image density, then target image density is achieved, but image density change between successive pages becomes noticeable
Solution Approach 1:
The patent applies partial action by adjusting the developing bias only partially toward the reference developing bias rather than fully setting it to the reference value. The arithmetic section calculates a intermediate developing bias that is between the previous developing bias and the reference developing bias, achieving density correction while limiting the magnitude of change to avoid noticeable fluctuations.
Solution Approach 2:
The patent implements beforehand cushioning by using the detected image density and previous developing bias to predict and prepare an appropriate developing bias adjustment. This prevents excessive or abrupt changes by cushioning the transition, ensuring that density corrections are applied smoothly without causing noticeable visual discomfort to readers.
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 reduces image density fluctuations between pages, ensuring image density is approximated to the target level and preventing significant changes that cause reader discomfort.
Implementation Method 1
a photoreceptor (3); a developing device (2) that forms a toner image by visualizing an electrostatic image formed on the photoreceptor
Data Source
AI summary
An image forming apparatus includes a photoreceptor, a developing apparatus, a developing bias supply power source, a control section for controlling a developing bias, a density sensor, and an arithmetic section. When an image density adjustment operation is performed, the arithmetic section determines a print-time developing bias in accordance with a detection result obtained by detecting, by the density sensor, a plurality of image density adjustment toner images formed by changing a developing bias. The print-time developing bias is set by the control section when printing is performed. also, In a case where a previous print-time developing bias falls within at least a low range of a predetermined range of the developing bias, the arithmetic section determines the print-time developing bias to a value between a reference developing bias for a target image density and the previous print-time developing bias.