Induction Heating Cores for Uniform Temperature Distribution
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Solution Overview
Problem
The existing induction heating systems in image forming apparatuses face issues with temperature uniformity and core cost due to the need for different Curie point cores to manage temperature rises for varying sheet sizes, leading to reduced fixing device lifespan and increased costs.
Innovation Solution
A fixing device with plural cores of different shapes arranged along the rotating member, where main cores with a higher thickness are positioned for standard-sized sheets and thinner sub-cores for larger sheets, both made of the same material, to manage temperature distribution and prevent magnetic flux leakage, thereby maintaining uniform temperature and extending device lifespan without the need for multiple core materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If two kinds of cores with different Curie points are arranged in different positions, then temperature distribution is controlled, but manufacturing cost increases
Solution Approach 1:
The patent applies local quality by varying the thickness of cores at different positions along the rotating member. Thinner cores are placed in areas where sheets pass frequently to reduce heat generation and prevent excessive temperature rise, while thicker cores are placed in areas where sheets pass less frequently. This positional variation in core thickness allows temperature control without requiring multiple core materials with different Curie points, thereby resolving the contradiction between temperature distribution control and manufacturing cost.
2Temperature
If uniform high temperature is maintained across the rotating member, then fixing performance is improved, but elastic member hardness deteriorates prematurely
Solution Approach 1:
The patent implements local quality by creating non-uniform temperature distribution through varied core thickness. Areas with thinner cores generate less heat and prevent excessive temperature rise that would degrade elastic members, while areas with thicker cores maintain sufficient temperature for effective fixing. This localized temperature control ensures that elastic members in high-temperature zones do not experience premature hardening or degradation, thereby extending rotating member lifespan while maintaining fixing performance.
3Temperature
If core thickness is increased to maintain temperature, then heating performance is improved, but temperature uniformity deteriorates
Solution Approach 1:
The patent resolves this contradiction by applying local quality through positional variation in core thickness. Thicker cores are strategically placed in areas where sheets pass less frequently to maintain adequate heating performance, while thinner cores are placed in areas with frequent sheet passage to prevent excessive temperature rise. This creates a tailored temperature distribution that maintains overall heating effectiveness while achieving local temperature uniformity, preventing both under-heating and over-heating zones.
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 ensures uniform temperature distribution across the rotating member, preventing premature wear and maintaining optimal toner fixation, while reducing production costs by eliminating the need for cores with different Curie points.
Implementation Method 1
High-frequency current flows to the excitation coil, whereby a high-frequency magnetic field is generated from the excitation coil
Implementation Method 2
Eddy-current is generated in the rotating member by the high-frequency magnetic field
Implementation Method 3
The rotating member generates heat with Joule heat based on the eddy-current
Data Source
AI summary
Plural main cores and plural sub-cores are arranged spaced apart from each other along a direction orthogonal to a rotating direction of a heat belt. The plural main cores are opposed to a first area where a sheet having first width in the heat belt passes. The plural sub-cores are opposed to second areas that are areas excluding the first area in an area where the sheet having second width larger than the first width in the heat belt passes. The plural sub-cores have thickness in the direction orthogonal to the rotating direction of the heat belt smaller than the thickness of the plural main cores.