Induction Heater Current Control via Curie Point Feedback
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Solution Overview
Problem
Existing fixing apparatuses with electromagnetic induction heating units face issues in maintaining output levels, as the auxiliary heating unit loses magnetism at high temperatures, leading to increased current levels that can damage the driving circuit.
Innovation Solution
A fixing apparatus with a ferromagnetic layer, a roller, and an induction heater, where a controller determines if the temperature of the ferromagnetic plate exceeds its Curie point, and reduces the high-frequency current to prevent excessive heating and potential damage to the driving circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the current level is increased to maintain output when auxiliary heating unit loses magnetism, then the output level is maintained, but the driving circuit may be damaged
Solution Approach 1:
The controller continuously monitors the temperature of the auxiliary heating unit and detects when it reaches the Curie point through resistance changes. Based on this feedback, the controller automatically adjusts the current supplied to the induction heating unit, reducing it when the auxiliary heating unit loses magnetism. This closed-loop feedback mechanism maintains output stability while preventing driving circuit damage by dynamically adapting current levels to actual operating conditions.
Solution Approach 2:
The system changes the operating parameters by monitoring resistance variations of the auxiliary heating unit as it approaches the Curie point. When the resistance change indicates loss of magnetism, the controller modifies the current parameter supplied to the induction heating unit. This parameter adjustment allows the system to maintain adequate output while operating safely within circuit limitations despite the auxiliary heating unit's magnetic property changes.
2Temperature
If the temperature of auxiliary heating unit increases, then heat generation is sufficient for fixing, but magnetism is lost and current must be increased
Solution Approach 1:
The controller uses resistance monitoring as feedback to detect when the auxiliary heating unit reaches temperatures where magnetism is lost. This feedback allows the system to distinguish between beneficial temperature increases for fixing and harmful temperature increases that cause magnetic loss. Based on this feedback, the controller adjusts current levels appropriately, maintaining heat generation effectiveness while preventing excessive current draw.
Solution Approach 2:
The system dynamically adjusts the current supplied to the induction heating unit based on the real-time temperature and magnetic state of the auxiliary heating unit. Rather than using a fixed current level, the system adapts current delivery to match the actual operating conditions, increasing current when needed for heat generation and reducing it when the auxiliary heating unit loses magnetism, thereby optimizing the balance between temperature and power consumption.
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 effectively maintains the output level of the fixing apparatus while preventing damage to the driving circuit by adjusting the current based on the temperature of the ferromagnetic plate, ensuring efficient and safe operation.
Implementation Method 1
an induction heater configured to cause heat generation in the magnetic layer and the ferromagnetic plate
Implementation Method 2
a ferromagnetic plate disposed inside the belt and having a Curie point that is lower than a Curie point of the ferromagnetic layer
Data Source
AI summary
A fixing apparatus includes a belt including a ferromagnetic layer. A ferromagnetic plate is disposed inside the belt and has a Curie point that is lower than a Curie point of the ferromagnetic layer. An induction heater causes heat generation in the ferromagnetic layer and the ferromagnetic plate. The induction heater includes a coil. A driving circuit outputs a high frequency current to the coil, and changes the high frequency current. A temperature sensor measures a temperature of the coil. A controller controls the driving circuit to decrease the high frequency current if the temperature of the coil measured by the temperature sensor is higher than a predetermined value.