Fixing Device Nip Angle and Pressing Roller Heating
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Solution Overview
Problem
Electrophotographic image forming apparatuses face challenges in efficiently warming up fixing devices, leading to energy wastage and paper curling issues, particularly with lightweight papers, due to high heat conductivity and inadequate detachment properties.
Innovation Solution
A fixing device with an endless-shaped fixing belt, a heating roller, and a pressing roller with an elastic layer and internal heating, where the detachment angle is set at 23 degrees or more and the pressing roller's temperature is incrementally adjusted, improving heat conductivity and detachment properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the thickness of the elastic layer of the fixing roller is increased to widen the nip width, then the nip width is improved, but the warm-up time increases due to high heat conductivity
Solution Approach 1:
The fixing device is divided into two separate heating systems: one for the fixing roller and one for the pressing roller. This segmentation allows independent temperature control of each component, enabling the pressing roller to be pre-heated without waiting for the fixing roller to reach temperature, thereby reducing overall warm-up time while maintaining adequate nip width.
Solution Approach 2:
The pressing roller is equipped with an independent heating device that activates before copying operations begin. This preliminary heating of the pressing roller allows it to reach the required temperature in advance, reducing the total warm-up time of the fixing device while the fixing roller thickness can be optimized for nip width without compromising warm-up performance.
2Area of stationary object
If the diameter of the fixing roller is increased to widen the nip width, then the nip width is improved, but the power consumption increases
Solution Approach 1:
The heating function is segmented between two separate rollers rather than relying on a single large fixing roller. This allows each roller to have smaller diameter and lower individual power consumption, while collectively providing the necessary nip width through their combined arrangement.
Solution Approach 2:
Heating is applied locally to specific regions where needed - the fixing roller is heated where it contacts the paper, and the pressing roller is heated independently at its contact point. This localized heating approach reduces overall energy consumption compared to heating a large-diameter fixing roller throughout.
3Reliability
If the fixing roller temperature is maintained at predetermined temperature during waiting mode, then the fixing quality is improved, but energy is wastefully consumed
Solution Approach 1:
The temperature control system dynamically adjusts the heating of the pressing roller based on operational state. During waiting mode, the pressing roller temperature is reduced to save energy, while during active copying operations, full heating is activated. The fixing roller maintains its temperature through thermal retention, allowing the system to balance energy consumption with fixing quality.
Solution Approach 2:
The heating of the pressing roller is activated periodically only when copying operations are detected, rather than continuously. This periodic heating approach reduces energy consumption during waiting modes while ensuring the pressing roller reaches required temperature before actual fixing operations begin.
4Speed
If a sponge with small heat capacity is used for the rubber layer to achieve fast heat properties, then the warm-up speed is improved, but the detachment properties deteriorate
Solution Approach 1:
The detachment function is transferred from the fixing roller rubber layer to the pressing roller. The pressing roller is equipped with a release layer specifically designed for paper detachment, while the fixing roller can use a thinner rubber layer optimized for heat response. This functional segmentation allows each roller to be optimized for its specific purpose without compromise.
Solution Approach 2:
The release layer is applied locally to the pressing roller surface where paper contact occurs during the exit phase. This localized detachment function on the pressing roller compensates for the reduced heat capacity of the fixing roller rubber layer, maintaining both fast heat response and adequate detachment properties.
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 paper detachment, prevents curling, and reduces energy consumption by optimizing the temperature difference between the fixing belt and pressing roller, ensuring efficient image formation without satin-like luster unevenness.
Implementation Method 1
a heating roller for heating the fixing belt
Implementation Method 2
the pressing roller's temperature is incrementally adjusted, improving heat conductivity and detachment properties
Implementation Method 3
the above elastic layer of the pressing roller is elastically deformed, thereby forming a fixing nip area (fixing nip portion) between the fixing roller and the pressing roller
Data Source
AI summary
Provided are a fixing device and an image forming apparatus provided with the same, which prevent the winding of a small paper having a light weight on a fixing belt, and also prevents paper blockage and paper curling. A detachment angle, which is defined by a tangent line of a fixing roller and a paper conveying direction at a paper exit point of a fixing nip portion where the fixing roller and a pressing roller pressure-contact with each other, is kept at 23 degrees or more, and a sheet of paper passes through the fixing nip portion, and a setting temperature of the pressing roller is increased step by step in accordance with the number of the sheet of paper by a heater lamp provided in an inside of the pressing roller.