Fixing Belt Heat Capacity Segmentation for Hot Offset Control
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Solution Overview
Problem
Image forming apparatuses face challenges in reducing hot offset in high temperature and high humidity environments due to the use of toner with amorphous polyester resin, which becomes plasticized and leads to overshoot in fixing units with high heat capacity.
Innovation Solution
The image forming apparatus incorporates a fixing unit with a fixing belt and a rotational member that contacts the toner image, along with a heater that directly heats the contact area between the fixing belt and the rotational member, reducing the heat capacity of the fixing belt and minimizing overshoot.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a fixing unit with high heat capacity is used to ensure stable temperature control, then temperature stability is improved, but hot offset occurs in high temperature and high humidity environments due to overshoot
Solution Approach 1:
The fixing belt is divided into a heat capacity reducing portion with lower heat capacity and other portions with normal heat capacity. This segmentation allows the specific region that contacts the toner image to respond quickly to temperature control, preventing overshoot and hot offset, while other portions maintain stable temperature for overall fixing performance.
Solution Approach 2:
The fixing belt has non-uniform heat capacity distribution, with the heat capacity reducing portion having specifically reduced heat capacity compared to other portions. This local quality change enables precise temperature control at the critical contact area without affecting the overall temperature stability of the fixing unit.
2Manufacturing precision
If toner with amorphous polyester resin is used to improve fixing properties, then fixing quality is improved, but the toner becomes plasticized in high temperature and high humidity environments leading to hot offset
Solution Approach 1:
The molecular weight of the amorphous polyester resin is controlled within a specific range (Mw: 25,000-60,000, Mw/Mn: 5-10). This parameter control optimizes the resin's plasticization resistance while maintaining good fixing properties, preventing hot offset in high temperature and high humidity environments.
3Object-affected harmful factors
If the heat capacity of the fixing belt is reduced to prevent overshoot, then hot offset is reduced, but temperature control stability may be affected
Solution Approach 1:
The fixing belt is segmented into regions with different heat capacities. The heat capacity reducing portion prevents overshoot and hot offset by responding quickly to temperature changes, while other portions with normal heat capacity provide thermal mass for overall temperature stability, achieving both goals simultaneously.
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 effectively reduces hot offset occurrences in high temperature and high humidity environments by ensuring the fixing belt reaches the intended temperature only in the contact area, thereby enhancing the fixing properties of the toner image.
Implementation Method 1
a heater that is disposed so as to face the inner surface of the fixing belt to heat the contact area formed between the rotational member and the fixing belt
Implementation Method 2
toner with amorphous polyester resin, which becomes plasticized and leads to overshoot in fixing units with high heat capacity
Data Source
AI summary
An image forming apparatus includes an image holding member, a charging device, an electrostatic charge image forming device, a developing device having a toner, a transfer device, and a fixing device, wherein the fixing device includes a fixing belt, a rotational member, and a heater; the toner contains an amorphous polyester resin as a binder resin; and the toner has a weight average molecular weight Mw and a number average molecular weight Mn, Mw is from 25000 to 60000, and Mw/Mn is from 5 to 10, and has an infrared absorption spectrometry, the ratio of absorbance for a wavelength of 1500 cm−1 to absorbance for a wavelength of 720 cm−1 is 0.6 or less, and the ratio of absorbance for a wavelength of 820 cm−1 to absorbance for a wavelength of 720 cm−1 is 0.4 or less.