Fixing Device Cooling Unit for Non-Sheet Region Temperature Control
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Solution Overview
Problem
The existing image forming apparatuses with resistance heating elements face issues of increased power consumption and image quality defects due to temperature differences between the sheet passing and non-sheet passing regions, especially when switching between small and large-sized recording sheets, leading to inefficient heating and potential damage to the fixing device components.
Innovation Solution
A fixing device with a temperature monitoring unit, power supply unit, and control unit that maintains the sheet passing region at a target temperature and cools the non-sheet passing region to manage electrical resistivity and temperature differences, using a resistance heating element whose electrical resistivity varies with temperature, ensuring the electrical resistivity is lower in the non-sheet passing region and the temperature difference does not exceed an allowable limit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the non-sheet passing region is excessively cooled to prevent overheating, then the temperature in the non-sheet passing region is reduced, but the power consumption rate per unit area becomes higher in the non-sheet passing region than in the sheet passing region
Solution Approach 1:
The patent applies local quality by differentiating the thermal management approach between the sheet passing region and non-sheet passing region. The cooling unit is controlled to cool the non-sheet passing region selectively, while the sheet passing region maintains its temperature through normal heating operation. This localized cooling approach addresses the overheating issue in the non-sheet passing region without adversely affecting the sheet passing region's thermal conditions, thereby preventing the paradoxical increase in power consumption rate that would result from uniform cooling across the entire heating rotating body.
2Reliability
If the temperature difference between sheet passing region and non-sheet passing region increases, then the electrical resistivity decreases in the non-sheet passing region, but the amount of current flowing through the resistance heating element exceeds the standard value
Solution Approach 1:
The patent implements feedback control through the control unit that monitors temperature conditions and adjusts the cooling unit's operation accordingly. The control unit receives temperature information from both the sheet passing region and non-sheet passing region, and based on this feedback, regulates the cooling intensity to maintain the temperature difference within a range that prevents excessive current flow. This closed-loop control ensures that the electrical resistivity in the non-sheet passing region is managed properly without causing harmful excessive current conditions.
3Reliability
If a PTC resistance heating element is used, then the electrical resistivity increases with increasing temperature in the non-sheet passing region, but the power consumption rate per unit area becomes higher in the non-sheet passing region
Solution Approach 1:
The patent extracts the thermal management function for the non-sheet passing region by introducing a separate cooling unit that selectively cools this area. This extraction of the heating function's thermal side effect allows the PTC resistance heating element to operate with its inherent temperature-stability characteristics in the sheet passing region, while the cooling unit independently manages the thermal conditions in the non-sheet passing region, preventing the power consumption increase that would otherwise result from uncontrolled heating in this area.
4Adaptability or versatility
If thermal fixing is performed on small-sized recording sheets, then the area of the non-sheet passing region increases relative to the entire region, but the total power consumption in the entire region increases accordingly
Solution Approach 1:
The patent applies dynamics by making the cooling unit's operation adaptive and controllable based on the actual thermal conditions. Rather than having a fixed cooling intensity, the cooling unit's operation is dynamically adjusted by the control unit according to the temperature difference between the sheet passing region and non-sheet passing region. This dynamic control allows the system to efficiently manage power consumption when processing small-sized sheets, where the non-sheet passing region occupies a larger proportion of the total area, by cooling only when and where necessary to maintain optimal thermal conditions.
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 reduces power consumption in the non-sheet passing region, prevents image quality defects, and extends the durability of the fixing device components by maintaining appropriate temperature differences and controlling cooling operations based on the non-sheet passing region's temperature.
Implementation Method 1
a resistance heating element whose electrical resistivity varies with temperature
Implementation Method 2
a positive temperature coefficient (PTC) resistance heating element, whose electrical resistivity increases with increasing temperature
Implementation Method 3
a negative temperature coefficient (NTC) resistance heating element, whose electrical resistivity decreases with increasing temperature
Implementation Method 4
a cooling unit configured to cool the non-sheet passing region
Data Source
AI summary
A fixing device thermally fixing an unfixed image by pressing a recording sheet against a heating rotating body using a resistance heating element as a heat source, comprising: a temperature monitoring unit monitoring temperature in a sheet passing region and in a non-sheet passing region of the heating rotating body; a power supply unit supplying power to the resistance heating element so that the temperature in the sheet passing region is maintained at a target temperature during thermal fixing; a cooling unit cooling the non-sheet passing region; and a control unit controlling cooling so that (i) electrical resistivity of the resistance heating element is lower in a region corresponding to the non-sheet passing region than in a region corresponding to the sheet passing region and (ii) an absolute value of a temperature difference between the sheet passing region and the non-sheet passing region does not exceed an allowable temperature difference.