Induction Heating Element Temperature Control via Dynamic Sampling
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Solution Overview
Problem
Conventional image heating apparatuses face challenges in maintaining stable temperature control of the image heating element when fixing speed varies, leading to inefficient power control and increased costs due to the use of multiple IGBTs for wide-range power control, resulting in unstable temperature fluctuations and potential hot or cold offset defects.
Innovation Solution
An image heating apparatus that employs a calorific value control section to switch between linear control and PWM control at predetermined reference power, allowing for stable temperature maintenance using a single IGBT, thereby reducing costs and improving efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If PID control is used with fixed sampling time, then temperature control is simple, but temperature control becomes unstable when fixing speed changes
Solution Approach 1:
The patent implements dynamic sampling time adjustment based on fixing speed. The control section calculates appropriate sampling times by considering the thermal capacity and heat production characteristics at different fixing speeds, transforming the static sampling time into a dynamic parameter that adapts to varying operating conditions, thereby maintaining stable temperature control across different speeds
Solution Approach 2:
The patent changes the sampling time parameter according to fixing speed variations. By adjusting the sampling time parameter dynamically rather than keeping it fixed, the system maintains optimal control performance across different operating speeds, resolving the contradiction between simple control design and stable temperature maintenance
2Adaptability or versatility
If multiple IGBTs are used for wide-range power control, then power control range is extended, but device complexity and cost increase
Solution Approach 1:
The patent makes a single IGBT perform multiple functions by dynamically adjusting its operation mode and parameters based on power control requirements. The control section manages the IGBT to handle both high and low power ranges through adaptive control strategies, eliminating the need for multiple dedicated IGBTs for different power ranges
Solution Approach 2:
The patent changes operational parameters of the IGBT (such as duty cycle, switching frequency, and gate drive characteristics) to extend its effective control range. By dynamically adjusting these parameters, a single IGBT can efficiently handle wide power ranges that would traditionally require multiple devices
3Manufacturing precision
If fixing speed is reduced to improve image quality, then glossiness and transparency improve, but temperature control stability deteriorates
Solution Approach 1:
The patent implements dynamic control parameter adjustment based on fixing speed. When fixing speed is reduced for improved image quality, the control section automatically adjusts sampling time and power delivery parameters to compensate for the changed thermal dynamics, maintaining temperature stability across different speed settings
Solution Approach 2:
The patent uses temperature feedback from the detection section to continuously monitor and adjust power supply to the heat source. This feedback mechanism ensures that even at reduced fixing speeds, the system can maintain stable temperature control by real-time adjustment based on actual temperature measurements
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
The solution enables stable temperature control of the image heating element at varying fixing speeds, achieving lower costs and higher efficiency by switching between linear and PWM control methods, thus preventing temperature fluctuations and defects.
Implementation Method 1
generates an eddy current through the action of a magnetic field generated by an induction heating apparatus upon an image heating element
Implementation Method 2
heats an unfixed image on a recording medium such as transfer paper or an OHP (Over Head Projector) sheet through Joule heating of the image heating element
Implementation Method 3
generates an eddy current through the action of a magnetic field generated by an induction heating apparatus upon an image heating element
Data Source
AI summary
An image heating apparatus that enables a temperature of an image heating element to be stably maintained at a target temperature as a fixing speed varies. A Proportional-Integral-Derivative (PID) controller determines whether a temperature control computation results in a range that allows temperature control with one IGBT, and a linear control is performed if the result is at least equal to a minimum power obtained as IH output. PWM control is performed at minimum power if the power is less than a required minimum power. Thus, a computation method of a supply power computator need not be switched according to the fixing speed, and a calorific value of a fixing belt can be controlled using one computation method.