Phase Detection for Reducing Periodic Image Density Unevenness
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Solution Overview
Problem
In image forming apparatuses, periodic density unevenness occurs due to variations in the roundness or eccentricity of the photosensitive drum and developing sleeve, leading to irregular density variations during image formation, which can result in detection misalignment and reduced accuracy of density correction.
Innovation Solution
The apparatus includes phase detection units for the photosensitive drum and developing sleeve, with a controller that adjusts image forming conditions based on detected phases and image density, and alters the circumferential velocity ratio between the two during phase detection and normal image formation to synchronize their rotation periods, thereby reducing periodic density unevenness and increasing detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the rotation periods of the photosensitive drum and developing sleeve are synchronized to detect periodic image density unevenness, then the detection accuracy of phase alignment is improved, but a periodic image density unevenness becomes more noticeable during normal image formation
Solution Approach 1:
The patent applies dynamics by making the circumferential velocity ratio between the developing sleeve and photosensitive drum adjustable rather than fixed. During phase detection mode, the ratio is set to synchronize rotation periods for accurate detection. During normal image formation, the ratio is changed to desynchronize the periods, preventing noticeable periodic density variations. This dynamic adjustment resolves the contradiction between detection accuracy and image quality.
Solution Approach 2:
The patent uses periodic action by implementing distinct operational modes: phase detection mode where synchronization occurs periodically to measure density unevenness, and normal image formation mode where desynchronization occurs periodically to prevent noticeable artifacts. The controller alternates between these modes, applying periodic synchronization only when measurement is needed, thus achieving both accurate detection and acceptable image quality.
2Measurement precision
If the circumferential velocity ratio of the developing sleeve to the photosensitive drum is changed during phase detection mode, then the synchronization of rotation periods is achieved, but the image forming conditions must be altered between detection and normal operation
Solution Approach 1:
The patent applies parameter changes by modifying the circumferential velocity ratio parameter between different operational modes. The controller adjusts this velocity ratio parameter to achieve synchronization during phase detection mode for accurate measurement, then changes it to a different value during normal image formation mode. This parameter adjustment resolves the technical contradiction while managing system complexity through controlled mode switching.
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 enhances the detection accuracy of phase angles, reduces the noticeability of periodic density unevenness during normal image formation, and prevents irregular density variations by synchronizing the rotation periods of the photosensitive drum and developing sleeve, improving the overall image formation process.
Implementation Method 1
an electric field occurring due to a potential difference between the surface potential of the developer bearing member with a development voltage applied thereto and the surface potential of the image bearing member causes toner to move from the developer bearing member to the image bearing member
Data Source
AI summary
A controller is able to, in a case where the controller receives a correction instruction for image density, execute a phase detection mode for detecting a phase of an image bearing member and detecting a phase of a developer bearing member and change an image forming condition for an image forming unit during an image formation mode based on respective phases of the image bearing member and the developer bearing member detected in the phase detection mode and an image density of a toner pattern, and a ratio of a circumferential velocity of the developer bearing member to a circumferential velocity of the image bearing member during the phase detection mode is different from a ratio of a circumferential velocity of the developer bearing member to a circumferential velocity of the image bearing member during the image formation mode.