Induction-Heated Fuser Roller Control Using Detection Coil Feedback
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Solution Overview
Problem
Existing image heating apparatuses with electromagnetic-induction heating systems face challenges in accurately controlling the temperature distribution of the rotary member due to frequency-dependent changes, making it difficult to prevent overheating and ensure uniform heating across the longitudinal direction.
Innovation Solution
The apparatus incorporates a cylindrical rotary member with a magnetic core and an exciting coil, an inverter to generate alternating magnetic flux, and detection coils to monitor induced electromotive force and temperature, allowing for precise control of the heating process by adjusting the driving frequency and power supply based on detected conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the frequency of alternating current supplied to the exciting coil is changed to adjust temperature distribution, then the temperature uniformity of the rotary member is improved, but the control complexity and risk of overheating increase
Solution Approach 1:
The patent employs a detection coil that generates an electromotive force signal proportional to the alternating magnetic flux in the rotary member. This feedback signal is used by the control portion to monitor the heating state and adjust the inverter's driving frequency and power output, creating a closed-loop control system that maintains temperature uniformity while preventing overheating.
Solution Approach 2:
The control portion dynamically adjusts the driving frequency and power output of the inverter based on the electromotive force signal from the detection coil. By changing these parameters in response to real-time feedback, the system optimizes temperature distribution across the rotary member without requiring complex additional hardware.
2Reliability
If the electric power supplied to the heating element is limited to prevent overheating, then the safety is improved, but the heating efficiency and productivity decrease
Solution Approach 1:
The detection coil provides real-time feedback on the magnetic flux state, allowing the control portion to precisely regulate power delivery. This enables the system to operate at high power levels when appropriate while automatically reducing power when overheating is detected, thus maintaining both safety and heating efficiency without arbitrary power limits.
Solution Approach 2:
The system dynamically adjusts the inverter's power output based on the electromotive force signal, transitioning between different power levels as needed. This dynamic control allows the heating element to operate efficiently during normal conditions while automatically preventing overheating, eliminating the need for fixed power limitations.
3Temperature
If the temperature detection portion is used to control heating, then the temperature control is improved, but the system becomes vulnerable to detection errors causing excessive heating
Solution Approach 1:
The detection coil acts as an intermediary sensor that indirectly measures the magnetic flux state rather than directly measuring temperature. This intermediary measurement provides a more reliable indicator of heating conditions, as it is less susceptible to errors and can detect anomalies before they result in overheating, enhancing system reliability.
Solution Approach 2:
The control portion uses the electromotive force signal from the detection coil to predict and prevent potential overheating conditions before they occur. By monitoring the magnetic flux state in advance, the system can adjust power delivery proactively, preventing detection errors from leading to excessive heating.
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 enables accurate temperature control of the rotary member, preventing overheating and ensuring uniform heating across the rotary member, even in the presence of errors in temperature detection, thereby enhancing the reliability and efficiency of the image heating process.
Implementation Method 1
an exciting coil wound around the magnetic core along the axis direction of the rotary member, an inverter configured to flow alternating current in the exciting coil, a control portion configured to control the inverter to cause alternating current to flow through the exciting coil so that alternating magnetic flux is generated in the magnetic core and the rotary member is induction-heated
Implementation Method 2
the heat-generating rotary member is heated by Joule heat generated by the eddy-current loss that occurs in the heat-generating rotary member
Implementation Method 3
the rotary member is heated by Joule heat generated by the eddy-current loss that occurs in the heat-generating rotary member
Implementation Method 4
a detection coil in which induced electromotive force is produced by the induced electromotive force being electromagnetically induced by the alternating magnetic flux
Data Source
AI summary
An image heating apparatus includes a cylindrical rotary member, a magnetic core, an exciting coil wound around the magnetic core along the axis direction of the rotary member, an inverter configured to flow alternating current in the exciting coil, a control portion configured to control the inverter to cause alternating current to flow through the exciting coil so that alternating magnetic flux is generated in the magnetic core and the rotary member is induction-heated, and a detection coil in which induced electromotive force is produced by the induced electromotive force being electromagnetically induced by the alternating magnetic flux. The control portion is configured to change driving frequency of the inverter. The control portion is configured to stop or reduce electric power supplied from the inverter to the exciting coil, in a case where a value of the induced electromotive force becomes greater than a predetermined value.