Image Density Control for Color Tone Stability in Printers
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Solution Overview
Problem
Existing image forming apparatuses suffer from cyclic changes in color tone when forming superimposed images of low-density and high-density images, leading to deteriorated image quality.
Innovation Solution
An image forming apparatus that includes a control system to adjust image formation conditions by cyclically changing developing bias, charging bias, and exposure light amount to reduce image-density cycle fluctuations, using toner adhesion amount sensors to detect and correct density unevenness in both high-density and low-density image parts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If image-density fluctuation-reduction control is performed by cyclically changing developing bias and charging bias, then image-density cycle fluctuation is reduced, but phase mismatch between high-density and low-density images causes cyclic color tone changes
Solution Approach 1:
The patent applies different control strategies to different image density regions. For high-density image parts, image-density fluctuation-reduction control is performed by cyclically changing developing bias and charging bias. For low-density image parts, phase matching control is performed to align the phase of image-density cycle fluctuations. This local differentiation resolves the contradiction by treating high-density and low-density regions differently, preventing cyclic color tone changes while maintaining image-density uniformity.
Solution Approach 2:
The patent dynamically adjusts control parameters based on image density characteristics. The control system switches between image-density fluctuation-reduction control (for high-density regions) and phase matching control (for low-density regions) depending on the local image characteristics. This dynamic adaptation allows the system to optimize for both image-density uniformity and phase alignment across different regions, eliminating cyclic color tone changes.
2Object-affected harmful factors
If phase matching control is performed to match phases of image-density cycle fluctuations, then cyclic color tone changes are reduced, but image-density fluctuation remains in individual color components
Solution Approach 1:
The patent applies different control strategies to different image density regions. For high-density image parts, image-density fluctuation-reduction control is performed by cyclically changing developing bias and charging bias. For low-density image parts, phase matching control is performed to align the phase of image-density cycle fluctuations. This local differentiation resolves the contradiction by treating high-density and low-density regions differently, preventing cyclic color tone changes while maintaining image-density uniformity.
3Manufacturing precision
If developing bias and charging bias are cyclically changed to correct image-density fluctuation, then high-density image quality improves, but low-density image phase alignment deteriorates
Solution Approach 1:
The patent applies different control strategies to different image density regions. For high-density image parts, image-density fluctuation-reduction control is performed by cyclically changing developing bias and charging bias. For low-density image parts, phase matching control is performed to align the phase of image-density cycle fluctuations. This local differentiation resolves the contradiction by treating high-density and low-density regions differently, preventing cyclic color tone changes while maintaining image-density uniformity.
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
The solution effectively reduces cyclic changes in color tone, improving the overall image quality of superimposed images by aligning the image-density fluctuations across different color components.
Implementation Method 1
toner adhesion amount sensors to detect and correct density unevenness
Implementation Method 2
a charging device 60 that charges the photoconductor 40
Implementation Method 3
an exposure device 21 that exposes the charged photoconductor 40 to form an electrostatic latent image
Implementation Method 4
a developing device 61 that develops the electrostatic latent image on the photoconductor 40 to form a toner image
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
An image forming apparatus (1) includes a plurality of image forming units (18), an exposure device (21), and a controller (500). Each image forming unit (18) includes an image bearer (40), a charger (60), and a developer bearer (61a). The controller (500) acquires an image-density cycle fluctuation in a visible image for each image forming unit and performs image-density fluctuation-reduction control to cyclically change image forming conditions to reduce the image-density cycle fluctuation. The controller performs: first fluctuation-reduction control to correct a developing bias to cancel an image-density cycle fluctuation of a highdensity image pattern; second fluctuation-reduction control to, after the first fluctuation-reduction control, correct a charging bias to cancel an image-density cycle fluctuation of a first low-density image pattern; and third fluctuation-reduction control to, after the first and second fluctuation-reduction controls, correct an exposure light amount to cancel an image-density cycle fluctuation of a second low-density image pattern.