Resistance Heating Element Power Control for Current Surge Suppression
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Solution Overview
Problem
In image forming apparatuses using electrophotography, fixing devices with resistance heating elements face high initial currents due to low electrical resistance at room temperature, leading to complex configurations when pre-heating the resistance heating element before power supply is started.
Innovation Solution
A power supply control method that gradually increases input power to the resistance heating element when the heating timing arrives, using a power supply control portion to manage power input based on a predetermined upper limit value, and determines if the commercial power source voltage meets a threshold value to optimize current flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If power supply to resistance heating element is started immediately, then heating efficiency is improved, but large current flows due to low electrical resistance at room temperature
Solution Approach 1:
The control portion performs preliminary assessment of the resistance heating element's temperature before full power supply. It determines whether preheating is necessary by checking if the current temperature is below the target temperature, and only then applies power gradually. This preliminary check prevents immediate full power supply that would cause large current surges.
Solution Approach 2:
The power supply to the resistance heating element is made dynamic rather than static. The control portion adjusts the power supply level based on real-time temperature feedback, gradually increasing power as the element heats up. This dynamic adjustment allows the system to achieve high heating efficiency while avoiding large initial current flows by adapting power levels to the element's thermal state.
2Object-affected harmful factors
If resistance heating element is preheated before power supply, then initial current surge is suppressed, but device configuration becomes complex
Solution Approach 1:
The resistance heating element serves its own temperature sensing function through its inherent electrical resistance characteristics. Since the resistance of the heating element changes with temperature, the control portion can determine the element's temperature state by monitoring its resistance, eliminating the need for separate temperature sensors or complex preheating circuits. This self-service approach suppresses initial current surges while keeping the device configuration simple.
Solution Approach 2:
The control portion implements a feedback mechanism by continuously monitoring the electrical resistance of the heating element to infer its temperature state. Based on this feedback, it dynamically adjusts the power supply level - applying power gradually when resistance indicates low temperature, and full power when resistance indicates sufficient heating. This feedback-based control suppresses initial current surges without requiring complex device configuration.
3Object-affected harmful factors
If gradual power increase is implemented, then current flow is controlled, but heating response time increases
Solution Approach 1:
The control portion implements periodic measurement of the resistance heating element's temperature through its electrical resistance. It periodically checks whether the element has reached the target temperature and adjusts power supply in periodic cycles. This periodic action allows gradual power increase to control current flow while maintaining efficient heating response by continuously monitoring and adjusting power levels based on real-time thermal state.
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 approach suppresses initial current surges during heating without complicating the device configuration, ensuring efficient power management and stable operation of the fixing device.
Implementation Method 1
a resistance heating element which is used for heating the fixing member and in which an electrical resistance increases as a temperature increases
Data Source
AI summary
A fixing device includes a fixing member, a resistance heating element, and a power supply control portion. The fixing member fixes a toner image transferred onto a sheet. The resistance heating element is used for heating the fixing member, and an electrical resistance thereof increases as a temperature increases. The power supply control portion gradually increases, when a heating timing of the fixing member arrives, input power to be input to the resistance heating element toward a predetermined upper limit value.