Induction Heater Core Design for Uniform Temperature Distribution
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Solution Overview
Problem
Conventional electromagnetic induction heating methods for fixing devices in image forming apparatuses face inefficiencies due to magnetic flux leakage and increased costs from segmented cores, leading to non-uniform temperature distribution and reduced heat generation efficiency.
Innovation Solution
A fixing device with a rotary fixing member, pressure roller, and induction heater featuring an excitation coil, side core, and arch-shaped cores that cover the excitation coil without interfering with it, ensuring efficient magnetic flux transmission and uniform temperature distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the core is divided into multiple segments to improve assembly and reduce manufacturing difficulty, then the ease of manufacture is improved, but magnetic flux leaks from joint portions between adjacent cores, reducing heat generation efficiency
Solution Approach 1:
A magnetic flux guiding member (yoke) is introduced as an intermediary component to connect segmented cores. This mediator guides magnetic flux through the joint portions between adjacent cores, preventing flux leakage while maintaining the segmentation benefits for assembly and manufacturing. The yoke acts as a magnetic bridge that eliminates the harmful effect of segmentation on heat generation efficiency.
2Stability of the object's composition
If a gap is provided between all arch-shaped cores and side cores to afford unified contact status, then temperature uniformity in the longitudinal direction is improved, but heat generation efficiency decreases
Solution Approach 1:
Different gap configurations are applied to different regions of the core structure. A first gap is provided between arch-shaped cores and side cores to ensure unified contact status and temperature uniformity. A second gap is provided between end cores and side cores, but this gap is configured differently (smaller or without magnetic flux guiding member) to maintain high magnetic flux density at the ends for efficient heat generation. This local differentiation resolves the contradiction by applying different gap strategies to different locations.
3Loss of energy
If both side ends of arch-shaped cores are bent toward the heat generator to improve magnetic flux concentration, then heat generation efficiency is improved, but uniform temperature distribution along the axial direction cannot be maintained
Solution Approach 1:
Only the inner side portions of the arch-shaped cores are bent toward the heat generator, while the outer end portions extend in the longitudinal direction without bending. This localized bending approach concentrates magnetic flux at the critical inner regions for efficient heat generation, while the unbent outer portions maintain uniform temperature distribution along the axial direction by preventing excessive heat concentration.
4Device complexity
If segmented cores are used to reduce manufacturing complexity, then the device complexity is reduced, but the number of parts increases, resulting in cost rise
Solution Approach 1:
A magnetic flux guiding member (yoke) is used as an intermediary that connects multiple segmented cores into a unified magnetic circuit. While segmentation increases the number of core parts, the yoke integrates these segments functionally, reducing overall device complexity by providing a standardized connection mechanism and simplifying the assembly process.
Solution Approach 2:
The core is divided into multiple segmented parts (arch-shaped cores and side cores) that can be manufactured separately and assembled. This segmentation reduces manufacturing complexity for each individual part while the standardized interfaces and magnetic flux guiding members minimize the overall number of unique components required.
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
The solution enhances heat generation efficiency, reduces energy consumption, and maintains uniform temperature distribution along the fixing member, improving the energy-saving properties and operational speed of the fixing device.
Implementation Method 1
when a high frequency alternating current is supplied to the coil, an alternate magnetic field is formed around the coil, and an eddy current is generated near the surface of the support roller
Implementation Method 2
When the eddy current is generated to the support roller as a heat roller, joule heat is generated by the electrical resistance of the support roller itself and the fixing belt wound around the support roller is heated
Data Source
AI summary
A fixing device includes a rotary fixing member; a pressure roller pressed against the fixing member to form a nip in association with the fixing member; and an induction heater, as a heat source, to heat the fixing member. The induction heater includes an excitation coil to induction-heat the fixing member; a side core disposed along an outer circumference in a longitudinal direction of the excitation coil; and a plurality of arch-shaped cores disposed to cover the excitation coil in the longitudinal direction thereof. The arch-shaped cores include center portions corresponding to an inner side of the excitation coil and bent to the fixing member; and outer end portions extending in the direction leading to the side core without interfering with the excitation coil.