Induction Heating Controller Frequency Control for Core Saturation
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Solution Overview
Problem
Fixing devices with electromagnetic induction heating face issues of magnetic core saturation, leading to insufficient electric power supply and image defects due to restricted magnetic flux, which limits the size reduction of rotational heating components and affects thermal efficiency.
Innovation Solution
An image heating apparatus with a cylindrical rotatable member, a helical coil, and a magnetic core, where a controller adjusts the frequency of the AC current based on the recording material size and print ratio to optimize magnetic flux and power supply, preventing core saturation while ensuring adequate power for image fixation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the amount of electrical power supplied to the coil is restricted to limit the amount of magnetic flux generated in the core, then the core saturation is prevented, but the fixing device is supplied with insufficient electric power, triggering image defects
Solution Approach 1:
The patent applies dynamics by making the coil's electrical characteristics variable through frequency control. The controller dynamically adjusts the AC current frequency based on operating conditions, allowing the system to adapt between power restriction modes (for saturation prevention) and full power modes (for adequate fixation), thereby resolving the static contradiction between limiting and supplying power
Solution Approach 2:
The patent changes the operating parameter of frequency to resolve the power contradiction. By varying the frequency of AC current supplied to the coil, the system can control the magnetic flux generation characteristics while maintaining adequate power supply. This parameter change allows the same core to operate safely at different power levels without saturation, eliminating the need to choose between power restriction and adequate power supply
2Volume of moving object
If the coil and core are reduced in size to reduce the fixing device in size, then the device compactness is improved, but the magnetic core becomes saturated with magnetic flux, causing the coil inductance to reduce and electric power source damage
Solution Approach 1:
The patent uses frequency as a control parameter to prevent core saturation in compact designs. By adjusting the frequency of AC current, the system can control the magnetic flux density within the reduced core, allowing small core dimensions without saturation. This enables the fixing device to be compact while maintaining reliability
Solution Approach 2:
The dynamic frequency control allows the compact core to handle varying magnetic flux requirements. The controller adjusts frequency based on the actual heating needs, preventing saturation in the reduced core while maintaining adequate power delivery, thus resolving the contradiction between device size and saturation prevention
3Loss of energy
If the frequency of AC current is increased to improve electric power conversion efficiency, then the thermal efficiency is improved, but the magnetic core saturation risk increases
Solution Approach 1:
The controller implements feedback control by monitoring the operating conditions and adjusting the frequency accordingly. This feedback mechanism allows the system to operate at high frequencies for improved efficiency while preventing core saturation through real-time adjustment, resolving the contradiction between efficiency and saturation risk
Solution Approach 2:
The patent dynamically changes the frequency parameter based on operating conditions to balance efficiency and saturation prevention. By adjusting frequency in response to load requirements, the system can achieve high power conversion efficiency when needed while maintaining safety margins to prevent core saturation, eliminating the trade-off between these two parameters
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 enhances electric power conversion efficiency, stabilizes heat generation, and prevents image defects by dynamically controlling the AC current frequency, allowing for smaller, more efficient fixing devices with improved thermal performance.
Implementation Method 1
heat is directly generated in the electrically conductive layer of their rotational heating component
Implementation Method 2
the image is heated by heat of the rotatable member heated by electromagnetic induction heat generation of the electroconductive layer
Data Source
AI summary
An image heating apparatus for heating an image includes a cylindrical rotatable member including an electroconductive layer; a helical coil provided in the rotatable member, the coil having a helix axis extending along a generatrix direction of the rotatable member; a magnetic core provided in the coil and having an end portion; and a controller configured to control a frequency of an AC current supplied to the coil; wherein the image is heated by heat of the rotatable member heated by electromagnetic induction heat generation of the electroconductive layer, wherein the controller sets the frequency to a first frequency corresponding to a size of a recording material, and wherein the controller sets the frequency to a second frequency higher than the first frequency when a print ratio of the image is larger than a predetermined value.