Image Forming Apparatus Position-Dependent Magnification Control
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Solution Overview
Problem
Existing image forming apparatuses struggle to properly process paper deformation caused by thermal fixing, particularly when forming images on both sides of a paper, as they cannot effectively control magnification in the main-scanning direction at different positions in the sub-scanning direction, leading to issues with trapezoidal paper shapes.
Innovation Solution
An image forming apparatus that includes a signal generator for creating a clock signal based on the relative position in the sub-scanning direction, an image processor for converting input data, a magnification setting unit for setting image magnification in the main-scanning direction, and a controller to adjust the clock signal frequency accordingly, allowing for precise control of magnification at various positions in the sub-scanning direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If uniform dot clock modulation is used for image forming on rear side, then entire image can be uniformly magnified, but magnification cannot be changed at different positions in sub-scanning direction, making it impossible to properly process trapezoidal paper deformation
Solution Approach 1:
The patent applies local quality by making the dot clock frequency position-dependent in the sub-scanning direction. Different regions of the paper (upper and lower portions) are assigned different magnification factors, allowing the system to compensate for thermal shrinkage variations at different positions. The controller adjusts the dot clock frequency based on the relative position in the sub-scanning direction, creating position-specific magnification control that matches the trapezoidal deformation pattern.
2Reliability
If thermal fixing is performed by pressing a roller with heater, then images are thermally fixed, but difference in shrinkage rate at different positions causes trapezoidal paper deformation
Solution Approach 1:
The patent applies preliminary anti-action by pre-calculating and applying compensatory magnification adjustments before image forming on the rear side. The controller determines the degree of thermal shrinkage based on paper thickness and other conditions, then sets appropriate magnification factors for different positions in the sub-scanning direction. This preliminary compensation counteracts the expected trapezoidal deformation that would otherwise occur during thermal fixing.
3Productivity
If image forming is performed on both sides of paper, then double-sided printing is achieved, but paper deformation by thermal fixing affects rear side image quality
Solution Approach 1:
The patent applies preliminary action by performing image processing to adjust for thermal shrinkage before the actual image forming on the rear side. The controller calculates the appropriate magnification compensation based on paper properties and thermal fixing conditions, then applies this compensation to the image data before it is written to the photosensitive drum. This ensures that even though thermal fixing causes deformation, the final rear side image maintains proper geometric 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 enables the formation of images with controlled magnification in the main-scanning direction at different positions in the sub-scanning direction, effectively addressing paper deformation and preventing image deterioration due to thermal shrinkage, even on trapezoidal paper shapes.
Implementation Method 1
the paper is deformed by thermal fixing when an image is formed on one side
Implementation Method 2
thermally fixes the same, thereby forming an image
Data Source
AI summary
An image forming apparatus comprises a signal generator generating a clock signal associated with image forming in a main-scanning direction, an image forming unit including a write unit performing the image forming in the main-scanning direction on a paper relatively moving in a sub-scanning direction, in synchronization with the clock signal generated at the signal generator, an image processor converting input image data into data for driving the write unit, a magnification setting unit setting a magnification of an image in the main-scanning direction associated with a position of the image in the sub-scanning direction, a controller controlling to generate the clock signal of a frequency corresponding to a relative position in the sub-scanning direction on the basis of the magnification set at the magnification setting unit when the write unit performs the image forming on the basis of the data for driving converted at the image processor.