Transfer Belt Timing Correction for Image Alignment
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Solution Overview
Problem
Existing image-forming apparatuses face challenges in eliminating the AC component of landing misalignment due to unevenness in the thickness of a belt or the radius of a roller, as conventional methods are either ineffective, costly, or prone to errors from factors like paper dust and ink mist.
Innovation Solution
An image-forming apparatus is designed with a transfer unit, image-forming units, a transfer amount detecting unit, a reference position detecting unit, an ink landing position calculating unit, and a storage unit that creates a correction table to adjust the printing timing signal, synchronizing the ink heads to correct for landing misalignment by shifting the phase of the pulse signal based on measured correction values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the diameter of the roller is enlarged or the thickness of the belt is reduced to reduce landing misalignment, then the landing misalignment is reduced, but the image forming device becomes large and heavy
Solution Approach 1:
The invention changes the operational parameters (rotation speed, timing) rather than physical dimensions. It measures the actual rotation speed of the transfer belt using a laser Doppler measurement device and adjusts the ink ejection timing to compensate for speed variations, thereby reducing landing misalignment without modifying the roller diameter or belt thickness
Solution Approach 2:
The invention replaces mechanical modification (changing roller diameter or belt thickness) with a measurement and control system. It uses laser Doppler measurement to detect belt rotation speed and employs timing adjustment to achieve the same effect as mechanical changes would have, but without increasing device size or weight
2Measurement precision
If the pressure of the roller is increased to prevent slide during measurement, then measurement accuracy is improved, but the belt deforms
Solution Approach 1:
The invention introduces a laser Doppler measurement device as an intermediary that can measure belt rotation speed without physical contact. This eliminates the need for direct roller-belt contact during measurement, allowing accurate speed detection without applying pressure that would cause belt deformation
Solution Approach 2:
The invention replaces mechanical contact-based measurement with optical measurement using laser Doppler effect. This substitution allows rotation speed measurement without mechanical pressure on the belt, preventing deformation while maintaining measurement accuracy
3Measurement precision
If conventional measurement methods are used, then landing misalignment can be detected, but detection accuracy decreases due to paper dust or ink-mist
Solution Approach 1:
The invention replaces mechanical or contact-based measurement methods with laser Doppler measurement. This optical measurement system measures the rotation speed of the transfer belt by detecting the Doppler shift of reflected laser light, making it immune to interference from paper dust and ink-mist that would affect contact-based sensors
Solution Approach 2:
The laser beam acts as an intermediary that can penetrate or pass through the measurement environment without being significantly affected by paper dust or ink-mist. The measurement is performed optically rather than through direct contact, eliminating the harmful effects of contaminants on measurement accuracy
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 solution effectively eliminates the AC component of landing misalignment, improving image accuracy and reducing the impact of belt and roller unevenness without increasing the size or weight of the device, and is less susceptible to errors from environmental factors.
Implementation Method 1
Japanese Patent Publication Laid-open No. 2004-188921 discloses a method to measure the thickness of a belt using a laser Doppler measurement device
Data Source
AI summary
An image-forming apparatus has: a transfer belt transferring a sheet; an encoder outputting a pulse signal in response to a rotational motion of the transfer belt; a belt reference sensor detecting a belt reference mark provided on the transfer belt; a first accumulator measuring a rotational position of the transfer belt against the reference mark by counting a pulse signal; a storage unit storing a table of printing timing correction values for one rotational cycle of the transfer belt; a second accumulator generating a printing timing signal by shifting a phase of the pulse signal by a printing timing correction value read from the table; and a image-forming unit controlling ink heads to eject inks on the sheet in synchronization with the printing timing signal, wherein an error in transfer amount of the sheet is calculated from a fluctuation in an interval of the inks ejected from the ink heads.