Fixing Roller Temperature Control via ON/OFF to PID Switching
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Solution Overview
Problem
Existing image forming apparatuses face challenges in achieving early temperature convergence and minimizing undershoot and overshoot of the fixing member during the initial stages of image forming operations, particularly due to inadequate heat distribution and timing issues in switching between ON/OFF and PID control methods.
Innovation Solution
An image forming apparatus that employs a controller to switch between a first fixing control (ON/OFF control with a fixed duty ratio) and a second fixing control (PID control based on temperature differences) to manage the heating of the fixing member, ensuring efficient temperature regulation by adjusting the duty ratio of the heater power supply.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If ON/OFF control is used to heat the fixing roller, then the temperature can reach the target quickly, but temperature ripples with overshoot and undershoot occur
Solution Approach 1:
The patent applies dynamic control by switching from ON/OFF control to PID control based on the operational state. During warm-up, ON/OFF control provides rapid heating. During printing operations, PID control dynamically adjusts power based on temperature feedback, eliminating ripples while maintaining stability. This dynamic switching resolves the contradiction between fast heating and temperature stability.
Solution Approach 2:
The control parameters are changed based on operational conditions. The system transitions from fixed ON/OFF control parameters during warm-up to adaptive PID control parameters during printing. This parameter change allows the system to achieve both rapid initial heating and stable temperature maintenance without excessive oscillations.
2Stability of the object's composition
If PID control is used from the start, then temperature stability is improved, but undershoot becomes large at the initial stage when the pressing roller is not sufficiently heated
Solution Approach 1:
The system performs preliminary heating using ON/OFF control before switching to PID control. This preliminary action brings the pressing roller to an adequate temperature level first, preventing the undershoot problem that would occur if PID control were applied immediately to a cold system. The warm-up phase prepares the system for the more precise PID control phase.
Solution Approach 2:
The control strategy dynamically adapts to the thermal state of the system. Initially, when the pressing roller is cold, ON/OFF control provides aggressive heating. As the system warms up and thermal equilibrium approaches, the system transitions to PID control for precise regulation. This dynamic adaptation prevents both excessive undershoot and maintains stability.
3Stability of the object's composition
If switching from ON/OFF control to PID control is delayed, then initial temperature stability is maintained, but undershoot becomes larger at the initial stage
Solution Approach 1:
The system uses temperature feedback to determine when to switch control modes. A temperature threshold is monitored, and when the fixing roller reaches this threshold, the system automatically transitions from ON/OFF to PID control. This feedback-based switching optimizes the balance between initial stability and convergence speed, preventing excessive undershoot while minimizing time loss.
4Loss of time
If switching from ON/OFF control to PID control is done early, then convergence to target temperature is accelerated, but overshoot becomes larger
Solution Approach 1:
The switching decision is based on real-time temperature feedback and predictive timing. The system monitors the temperature rise rate and switches at the optimal moment when the pressing roller has accumulated sufficient heat but before thermal equilibrium is reached. This feedback-based timing prevents premature switching that would cause overshoot while still achieving rapid convergence.
Solution Approach 2:
The system performs preliminary heating with ON/OFF control to build up thermal mass in the pressing roller before transitioning to PID control. This preliminary action ensures that when PID control begins, the system is already warm and can converge quickly without excessive overshoot, as the thermal inertia is already established.
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 allows for early convergence to the target control temperature, minimizing undershoot and overshoot, and reducing temperature ripples, thereby improving the reliability and efficiency of the image forming process.
Implementation Method 1
the temperature control of the fixing apparatus controls electric power supply to a heater to heat the heating roller
Implementation Method 2
the detected temperature of a temperature sensor to detect the surface temperature of the heating roller
Implementation Method 3
the fixing apparatus conveys a sheet to a fixing nip portion formed between both the rollers, and performs heating and pressing treatment, thereby fixing a toner image onto the sheet
Data Source
AI summary
In an image forming apparatus according to the present invention, when an image forming operation is started from a standby state, electric power is supplied to a heater by switching to a first fixing control to turn on and off the heater to heat a heating roller with a fixed duty ratio based on the detected temperature of the heating roller, and thereafter, when detecting a state that the falling detected temperature reaches a lower limit value at which the detected temperature turns to rising, electric power is supplied to the heater by switching to a second fixing control which changes a duty ratio in accordance with a temperature difference between the detected temperature and a target control temperature.