Variable Renewal Cycle Heater Control for Image Fixing
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Solution Overview
Problem
Conventional image heating apparatuses face challenges in achieving a balance between rapid temperature rise and stable temperature control during the heater rise period and fixing period, leading to overshooting, undershooting, and temperature ripples, which affect image quality and print quality.
Innovation Solution
An image heating apparatus with a controller that adjusts the electric power supply to the heater based on detected temperature, using a shorter renewal cycle during the heater rise period and a longer cycle during the fixing period, employing PI control to optimize ON-duty and renewal cycle settings for both periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the renewal cycle is made longer to reduce temperature ripple during fixing period, then temperature stability is improved, but the heater rise period becomes longer and temperature response becomes slower
Solution Approach 1:
The patent applies dynamics by making the renewal cycle variable rather than fixed. The control device dynamically adjusts the renewal cycle length based on the heater's operational state: using a first renewal cycle during the heater rise period and a second renewal cycle during the fixing period. This dynamic adaptation allows the system to optimize temperature response speed during heating while ensuring temperature stability during operation, thereby resolving the contradiction between rise speed and stability.
2Speed
If the ON-duty is increased to accelerate heater temperature rise, then heater rise speed is improved, but temperature overshooting increases
Solution Approach 1:
The patent employs periodic action through pulse-width modulation (PWM) control where the heater is supplied with electric power in periodic pulses rather than continuously. By adjusting the duty ratio (ON-time proportion) of these periodic pulses, the system can control the average power input to achieve desired temperature rise rates while preventing overshooting. The periodic nature allows thermal mass to absorb and distribute heat evenly, avoiding temperature spikes.
3Speed
If the renewal cycle is made shorter to improve temperature response during heater rise period, then temperature control responsiveness is improved, but temperature ripple increases during fixing period
Solution Approach 1:
The system dynamically switches between two different renewal cycle settings based on operational phase. During the heater rise period, a first renewal cycle with shorter duration is used to provide frequent temperature measurements and rapid control adjustments, ensuring responsive temperature tracking. During the fixing period, a second renewal cycle with longer duration is used to reduce measurement frequency and minimize temperature ripple. This dynamic switching resolves the contradiction between responsiveness and uniformity.
4Measurement precision
If PI control or PID control is used to control heater temperature, then temperature control precision is improved, but control complexity increases
Solution Approach 1:
The patent segments the temperature control process into distinct phases (heater rise period and fixing period) with different control parameters for each phase. Rather than using complex PID control throughout, the system uses simplified PI control with phase-specific parameters: different renewal cycles and different duty ratio adjustment strategies for each phase. This segmentation reduces overall control complexity while maintaining precision where needed.
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 effectively suppresses temperature overshooting and undershooting during the heater rise period and reduces temperature ripples in the fixing period, enabling high-speed temperature rise and improved image quality by balancing ON-duty and renewal cycle settings.
Implementation Method 1
a heater (23) for generating heat by being supplied with electric power from an AC power source
Data Source
AI summary
An image heating apparatus for heating a toner image in a nip while conveying a recording material on which the toner image is held is provided. The image heating apparatus includes: a heater configured to generate heat by being supplied with electric power from an AC power source; a rotatable heating member configured to be heated by the heater; a pressing member configured to form the nip in contact to the rotatable heating member; a temperature detecting portion configured to detect a temperature of the heater or the rotatable heating member; and a controller configured to set the electric power supplied to the heater every renewal cycle depending on a detected temperature by the temperature detecting portion. The renewal cycle is shorter in a rise period of the heater than in a period in which the recording material is conveyed in the nip.