Heater Control Circuit for Image Heating Device
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Solution Overview
Problem
Existing image heating devices face challenges in reducing the first print-out time (FPOT) and minimizing thermal stress on the heater's base substrate, due to asymmetrical heat distribution and temporary power supply interruptions.
Innovation Solution
The image heating device incorporates a heater with a base substrate and a heat generating unit comprising two heat generating elements extending in the long-side direction. A heater control circuit with multiple power supply channels and a switch unit allows for controlled power distribution, optimizing heat distribution and reducing thermal stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the relay is turned on to supply high power to the heater for warming up the fixing unit, then the heater temperature rises faster, but the power supply is temporarily stopped during switching which delays the temperature rise and increases FPOT
Solution Approach 1:
The control circuit pre-charges the capacitor before switching from the first power supply channel to the second power supply channel. This preliminary action ensures that when the switching occurs, the capacitor is already charged and can immediately supply current to the heater, preventing any interruption in power supply and avoiding delay in temperature rise.
Solution Approach 2:
A capacitor is introduced as an intermediary energy storage element between the power supply channels and the heater. The capacitor acts as a buffer that can immediately supply current during switching transitions, eliminating power supply interruptions and reducing FPOT while allowing high power to be supplied for rapid heating.
2Temperature
If high power is supplied to the heater to reduce FPOT, then the heater temperature rises faster, but asymmetrical heat distribution produces large thermal stress to the base of the heater
Solution Approach 1:
The heater is divided into multiple independent heating zones (first heating zone and second heating zone) with separate power supply channels. This allows different power levels to be supplied to different regions of the heater simultaneously, enabling localized temperature control that achieves rapid overall heating while maintaining symmetrical heat distribution and reducing thermal stress on the base substrate.
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 reduces the FPOT and minimizes thermal stress on the heater's base substrate, ensuring efficient and reliable image heating while protecting the heater from excessive thermal stress.
Implementation Method 1
a heat generating unit configured to generate heat when powered
Data Source
AI summary
An image heating device includes a fixing member, a heater configured to heat the fixing member, and a heater control circuit configured to control the heater. The image heating device is configured to heat a toner image formed on a sheet. The heater includes a base substrate and a heat generating unit, the heat generating unit being provided on the base substrate and configured to generate heat when powered. The heater control circuit includes a first power supply channel through which a first power is supplied to the heat generating unit, a second power supply channel through which a second power lower than the first power is supplied to the heat generating unit, and a switch unit. The switch unit includes a semiconductor switch including a plurality of semiconductors, and is configured to selectively switch between the first and second power supply channels with the operation of the semiconductor switch.