Induction Heating Coil Winding Density for Uniform Temperature
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Solution Overview
Problem
Electromagnetic induction heating type image forming apparatuses face challenges in maintaining uniform temperature distribution across the width of the image heating member, leading to potential overheating at non-contact portions and reduced productivity due to fluctuations in temperature.
Innovation Solution
The apparatus includes a rotatable image heating member with an electroconductive layer, a pressing member, an urging member, and an excitation coil, where the lengths of these components are specifically configured to satisfy the relationship LcoilA > Lb > Lr > LcoilB, ensuring optimal heat distribution and minimizing temperature fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the heating area extends to the non-contact portion of the pressing roller, then the heating coverage is improved, but the temperature of the non-contact portion gradually increases during continuous sheet passing, requiring heat to be stopped to prevent exceeding the heat-proof temperature, which lowers productivity
Solution Approach 1:
The excitation coil is designed with non-uniform winding density along the longitudinal direction, creating different magnetic flux densities at different positions. The coil has a first winding density in a first region and a second winding density in a second region, allowing localized control of heating intensity to prevent overheating at the non-contact portion while maintaining heating coverage
Solution Approach 2:
The patent changes the geometric parameters of the excitation coil by defining specific winding densities and spatial distributions of the coil windings. This parameter optimization allows the magnetic flux to be distributed non-uniformly, concentrating heat where needed and reducing heat in the non-contact portion, thereby enabling continuous operation without temperature-related shutdowns
2Stability of the object's composition
If the excitation coil is positioned to heat the entire image heating member, then the temperature uniformity is improved, but the heat may concentrate at the non-contact portion leading to overheating, while reducing the heating area causes temperature drop in the sheet passing area
Solution Approach 1:
The excitation coil employs different winding densities in different longitudinal regions, creating spatially varying magnetic flux densities. This local quality differentiation allows the coil to generate appropriate heat levels in the sheet passing area while minimizing heat concentration at the non-contact portion, achieving both uniformity and control
Solution Approach 2:
The system dynamically adjusts the excitation coil's magnetic flux distribution through optimized winding configurations, allowing adaptive heat generation that responds to the operational state. This dynamic characteristic enables the system to maintain temperature uniformity during continuous sheet passing without causing overheating
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 temperature fluctuations across the image heating member, preventing overheating and maintaining consistent heat application, thereby enhancing productivity and image quality.
Implementation Method 1
a device for generating a fluctuating magnetic field is disposed opposite to the electroconductive layer and generates magnetic flux which penetrates the electroconductive layer. As a result, an eddy current is generated in the electroconductive layer to cause heat generation
Implementation Method 2
an eddy current is generated in the electroconductive layer to cause heat generation
Data Source
AI summary
An image heating apparatus includes a rotatable image heater including: an electroconductive layer; a pressor, press-contacting the heater, for forming a nip in which an image on a recording material is to be heated; an urging member, provided inside the heater, for urging the heater toward the pressor; and an excitation coil for induction-heating the electroconductive layer. When the length of the heater with respect to a rotational axis direction thereof is Lb, the length of the pressor with respect to the rotational axis direction is Lr, the outside distance of bent portions of the coil at both end portions thereof with respect to the rotational axis direction is LcoilA, and the inside distance of the bent portions with respect to the rotational axis direction is LcoilB, the lengths Lb and Lr and the distance LcoilA and LcoilB satisfy the following relationship:LcoilA>Lb>Lr>LcoilB.