Induction Heating Coil Parasitic Capacitance Resonance
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Solution Overview
Problem
Conventional image heating apparatuses using electromagnetic induction heating face issues with high-frequency power supply, leading to increased switching loss and noise due to parasitic capacitance, which can result in power source breakdown.
Innovation Solution
The image heating apparatus employs a cylindrical rotatable member with a conductive layer and a magnetic core, where a coil is helically wound around the magnetic core, and an inverter supplies an alternating current within a range of 20.5 to 100 kHz, optimizing the coil interval and resistance to reduce parasitic capacitance and maintain stable operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If high frequency alternating current is supplied to the exciting coil to reduce transformer size, then the magnetic core cross-sectional area can be reduced, but switching loss and switching noise increase due to parasitic capacitance
Solution Approach 1:
The patent extracts and addresses the parasitic capacitance problem by introducing a resonance capacitor connected in series with the exciting coil. This resonance capacitor compensates for the parasitic capacitance formed between adjacent coil wires, allowing high-frequency operation while reducing switching loss and switching noise. The extraction principle is applied by isolating and counteracting the harmful parasitic capacitance effect through the resonance circuit.
Solution Approach 2:
The patent changes the operating frequency parameter to a specific high-frequency range (20.5 kHz to 100 kHz) and adjusts the resonance capacitor value to match the parasitic capacitance at this frequency. By optimizing the frequency parameter and the resonance capacitor value, the system achieves reduced magnetic core volume while maintaining low switching loss through resonant operation that minimizes the impact of parasitic capacitance.
2Volume of moving object
If high frequency alternating current is supplied to the exciting coil, then transformer size can be reduced, but switching noise increases due to parasitic capacitance
Solution Approach 1:
The patent converts the harmful parasitic capacitance into a beneficial element by using it as part of a resonance circuit. The parasitic capacitance, which originally caused switching noise, is now utilized in conjunction with the resonance capacitor to create resonant operation at the desired frequency. This resonance enables efficient energy transfer while suppressing switching noise, effectively converting the harmful parasitic capacitance into a useful component of the power supply system.
3Power
If the coil is wound with many turns to produce high power, then power output increases, but parasitic capacitance increases leading to power source breakdown
Solution Approach 1:
The patent introduces the resonance capacitor as an intermediary element between the power source and the exciting coil. This resonance capacitor acts as a mediator that compensates for the parasitic capacitance caused by multiple coil turns. By placing the resonance capacitor in series with the coil, it creates a resonant circuit that cancels the harmful effects of parasitic capacitance, allowing high power output with many coil turns while maintaining power source reliability and preventing breakdown.
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 switching loss and noise, ensuring stable high-frequency operation and efficient heat generation for image fixation in image forming apparatuses.
Implementation Method 1
The conductive layer generates heat by electromagnetic induction due to an alternating magnetic field produced from the alternating current supplied to the coil
Data Source
AI summary
An image heating apparatus configured to heat an image formed on a recording material includes a cylindrical rotatable member including a conductive layer, a magnetic core inserted through the rotatable member, a coil helically wound around an outer side of the magnetic core within the rotatable member, and an inverter configured to supply an alternating current to the coil. A frequency of the alternating current supplied from the inverter is within a range of 20.5 to 100 kHz. The conductive layer generates heat by electromagnetic induction due to an alternating magnetic field produced from the alternating current supplied to the coil. The coil is wound at an interval of 1 mm or longer.