Fixing Device Cylindrical Rotatable Member Induction Heating
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Solution Overview
Problem
Existing electromagnetic induction heating type fixing devices face challenges in downsizing while maintaining uniform heat generation distribution along the sleeve, as the lengths of magnetic core material and coil need to be shorter than the sleeve, and heat generation distribution must be stabilized.
Innovation Solution
A fixing device with a cylindrical rotatable member having an electroconductive layer, a magnetic member inserted into its hollow portion, and a helically wound coil outside to generate an AC magnetic field, ensuring uniform heat generation through electromagnetic induction heating, with specific resistance and frequency conditions to optimize heat distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the lengths of magnetic core material and coil are reduced to achieve downsizing, then the device size is reduced, but the heat generation distribution uniformity deteriorates
Solution Approach 1:
The patent applies local quality by positioning magnetic core materials at specific locations (both ends and center of the coil) rather than uniformly distributing them. This creates localized magnetic flux concentration points that compensate for the reduced overall length, ensuring uniform heat generation along the sleeve even with shortened magnetic core and coil lengths.
Solution Approach 2:
The magnetic core material is segmented into multiple pieces positioned at different locations along the coil length. This segmentation allows each magnetic core piece to independently generate and distribute magnetic flux to specific regions, achieving uniform overall heat distribution while maintaining a compact total length.
2Power
If the frequency of AC magnetic field is increased to improve heat generation efficiency, then the heating efficiency is improved, but the risk of image defects increases
Solution Approach 1:
The patent optimizes the frequency parameter of the AC magnetic field to a specific range (10 kHz to 100 kHz) where heat generation efficiency is maximized while avoiding frequencies that cause image defects. This parameter optimization balances heating performance with image quality reliability.
Solution Approach 2:
The patent implements temperature detection and feedback control to monitor the heat generation process in real-time. Based on the detected temperature, the system adjusts the AC magnetic field frequency and power to maintain optimal heating conditions, preventing image defects while ensuring efficient heat generation.
3Length of stationary object
If the magnetic core material length is reduced for downsizing, then the device becomes more compact, but the magnetic flux distribution uniformity deteriorates
Solution Approach 1:
The magnetic core is divided into multiple segments positioned at strategic locations (both ends and center of the coil). Each segment generates magnetic flux locally, and the combined effect of all segments creates uniform magnetic flux distribution along the entire sleeve length, compensating for the reduced individual segment lengths.
Solution Approach 2:
Magnetic core materials are placed at specific locations rather than continuously distributed. This localized placement creates concentrated magnetic flux paths that efficiently penetrate the electroconductive layer at critical points, ensuring uniform overall heat generation with shorter total magnetic core length.
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 enables downsizing of the fixing device while maintaining uniform heat generation along the sleeve, preventing image defects and ensuring efficient heat transfer, thus stabilizing the heat generation distribution.
Implementation Method 1
a coil helically wound outside the magnetic member at the hollow portion and forming an AC magnetic field by a flow of a current therethrough to cause the electroconductive layer to generate heat through electromagnetic induction heating
Implementation Method 2
a magnetic member inserted into a hollow portion of the rotatable member and not forming a loop outside the electroconductive layer
Data Source
AI summary
A fixing device includes a rotatable member having an electroconductive layer; a magnetic member which does not form a loop outside the electroconductive layer; a coil helically wound outside said magnetic member, wherein the coil forms an AC magnetic field by a flow of a current therethrough to cause the electroconductive layer to generate heat through electromagnetic induction heating; and a back-up member. When a circumferential direction resistance R of the electroconductive layer is represented by the following formula (1), a frequency f of the AC magnetic field and the circumferential direction resistance R satisfy the following formula (2):R=ρ×2πr/tw (1)f/R≧15 (kHz/milliohm) (2)where with respect to the electroconductive layer, ρ is a volume resistivity at a fixing temperature, t is a thickness, r is a radius, and w is a length with respect to a generatrix direction of the rotatable member.