Induction Heating Fixing Belt Temperature Control
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Solution Overview
Problem
In image forming apparatuses using induction heating systems, temperature unevenness occurs in fixing devices with divided coils, leading to fixing failures due to incomplete heating of all portions of the fixing belt or roller, resulting in inconsistent toner fusion.
Innovation Solution
A power control circuit that dynamically adjusts the output power of the induction heating system by comparing temperatures at the center and ends of the fixing belt, shifting power from a minimum to 0 W only when temperatures deviate from a set range, and alternately controlling the excitation time ratio of center and side coils to maintain uniform temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If power on and off control is performed in divided IH coils, then electric power consumption is reduced, but temperature unevenness occurs causing fixing failure
Solution Approach 1:
The patent changes the control parameter from binary on/off to continuous duty cycle adjustment. The duty cycle is varied based on temperature feedback from multiple sensors, allowing precise control of average power while maintaining temperature uniformity across different coil regions.
Solution Approach 2:
The patent applies different duty cycles to different coil groups based on their local temperature conditions. Temperature sensors are placed at the center and ends of the fixing belt, and each coil group receives customized power control to compensate for thermal gradients and ensure uniform temperature distribution.
2Loss of energy
If minimum power is set to 0 W for power saving, then energy consumption decreases, but temperature control precision deteriorates
Solution Approach 1:
The patent employs periodic pulsed power supply with variable duty cycles instead of continuous or binary on/off control. By adjusting the ratio of on-time to total cycle time, the system achieves intermediate power levels that maintain temperature precision while reducing average power consumption compared to continuous operation.
Solution Approach 2:
The patent implements feedback control using temperature sensors that continuously monitor the fixing belt temperature. The detected temperature is fed back to the power control circuit, which adjusts the duty cycle dynamically to maintain the target temperature, ensuring precision even when operating at reduced average power levels.
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 ensures consistent temperature distribution across the fixing device, preventing fixing failures and optimizing energy usage by minimizing power consumption and reducing temperature ripples.
Implementation Method 1
an induction heating power supply that supplies a high-frequency magnetic field generated by a high-frequency current to an excitation coil with a predetermined waveform to a fixing member
Implementation Method 2
causing an induction current (an eddy-current) in a fixing roller or a fixing belt, causing the fixing roller or the fixing belt to generate heat
Data Source
AI summary
A fixing device includes a fixing belt, exercitation coils for induction-heating the fixing belt, power supplies that supply high-frequency power to the excitation coils, an output power detecting circuit that detects output electric energy of the power supplies, a power control circuit that controls the output electric energy of the power supplies, and temperature sensors that detect the temperature of a surface portion of the fixing belt. When electric energy applied to the excitation coils during the power fall reaches minimum power set in advance larger than 0 W, the power control circuit maintains the minimum power while the temperature detected by the temperature sensors is within a predetermined control temperature range and controls output power of the induction heating power supplies to shift from the minimum power to 0 W when the detected temperature deviates from the predetermined control temperature range.