Color Image Alignment via Drive Speed Control
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Solution Overview
Problem
Image forming apparatuses with multiple photoreceptors face challenges in maintaining precise alignment of color toner images due to fluctuations in temperature and external forces, leading to misalignment issues that affect image quality, particularly in high-quality imaging demands.
Innovation Solution
A controller calculates the misalignment of overlapped images and adjusts the driving speeds of the drive sources to correct the start timing of image formation, ensuring accurate alignment by determining the middle value between maximum and minimum misalignment values and switching between different printing speeds as needed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple photoreceptors are driven by separate drive motors, then alignment precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent combines multiple drive motors into a single shared drive motor that rotates the intermediate transfer belt. This single motor drives all photoreceptors (yellow, magenta, cyan, and black) through the common intermediate transfer belt, eliminating the need for separate drive motors for each photoreceptor and reducing device complexity while maintaining alignment precision through centralized control
Solution Approach 2:
The intermediate transfer belt serves as an intermediary mechanism that couples the single drive motor to multiple photoreceptors. By rotating the intermediate transfer belt, the system indirectly drives all photoreceptors in a coordinated manner, allowing one motor to control multiple image carriers without direct mechanical connection to each
2Device complexity
If a single shared drive motor is used, then device complexity is reduced, but misalignment occurs due to temperature fluctuations and external forces
Solution Approach 1:
The system implements feedback control by detecting the actual rotational positions of photoreceptors and comparing them with target positions. When misalignment is detected (caused by temperature fluctuations or external forces), the control unit calculates correction amounts and adjusts the drive motor's rotation to compensate, ensuring alignment precision is maintained despite environmental variations
Solution Approach 2:
The system performs preliminary alignment correction by detecting misalignment before it significantly affects image quality. The control unit continuously monitors photoreceptor positions and makes proactive adjustments to the drive motor rotation, preventing misalignment from deteriorating to a level that would cause visible image defects
3Manufacturing precision
If timing correction is performed, then misalignment is reduced, but slight drift of 1 dot or less remains in the sub-scan direction
Solution Approach 1:
The system changes the control parameter from binary timing correction (corrected/not corrected) to continuous rotational position adjustment. By controlling the drive motor's rotational position with higher precision and making fine adjustments in the sub-scan direction, the system reduces residual misalignment from 1 dot or less to a level below visual detection thresholds, achieving sub-dot precision
Data Source
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AI summary
An image forming apparatus includes at least first (202K), second (202C) and third image (202M) carriers (202M), a first drive source (98), a second drive source (99), at least one visible image forming mechanism for forming a visible image on the image carriers, a transfer unit (15) for overlappingly transferring the visible images, an image detector (136), and a controller (150). The first drive (98) source transmits a driving force to at least the first image carrier (202K). The second drive source (99) transmits a driving force to at least two image carriers other than the first image carrier (202K). The controller (150) calculates an amount of misalignment of the overlapped visible images that remain at the start timing of image formation based on the start timing of image formation after the timing correction, and separately determines driving speeds of the first (98) and the second drive sources (99) based on the amount of misalignment of the overlapped visible images.