Fuser Heating Power Limiting for Stable Temperature Recovery
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Solution Overview
Problem
Existing image forming apparatuses face issues with temperature overshoot and undershoot in the heating member, leading to damage, unstable temperature control, and potential image quality defects due to excessive power supply and insufficient convergence to the target temperature.
Innovation Solution
Implementing a controller that uses PID control to cut off power to the heating member when it reaches a cutoff temperature, resumes power supply with limited maximum power until a specific period elapses, and adjusts the upper limit power based on current conditions to stabilize temperature control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If power supply to the heating member is resumed after cutoff, then the temperature can be restored, but temperature overshoot may occur causing damage to parts
Solution Approach 1:
The patent implements dynamic power supply control by adjusting the maximum power limit based on the elapsed time since power resumption. The control mechanism transitions from a static on/off control to a dynamic control where the power supply amount varies continuously based on the cooling period elapsed, preventing both overshoot and undershoot conditions
Solution Approach 2:
The patent applies preliminary action by setting an upper limit on the maximum power supply amount before the heating member can cause damage. This preventive measure is implemented by calculating the elapsed time since power resumption and determining an appropriate power limit in advance, ensuring that even if temperature fluctuations occur, they remain within safe boundaries
2Reliability
If power supply is cut off when temperature reaches cutoff temperature, then overshoot is prevented, but temperature control stability deteriorates
Solution Approach 1:
The control system dynamically adjusts the maximum power supply amount based on the cooling period elapsed since power resumption. This dynamic adjustment allows the system to maintain stable temperature control by adapting the power supply characteristics to the current thermal state of the heating member, preventing both overshoot and excessive cooling
Solution Approach 2:
The patent implements periodic monitoring and control by continuously measuring the elapsed time since power resumption and adjusting the maximum power supply amount accordingly. This periodic control mechanism ensures that the temperature remains stable by applying appropriate power limits at appropriate intervals during the cooling period
3Reliability
If maximum power supply is limited during specific period, then temperature overshoot is prevented, but convergence speed to target temperature decreases
Solution Approach 1:
The patent resolves the time-stability contradiction by implementing dynamic power supply control that adapts to the thermal state. The maximum power supply amount is adjusted based on the elapsed cooling period, allowing rapid heating when appropriate while preventing overshoot when the heating member is still cooling, thus optimizing both convergence speed and temperature stability
Solution Approach 2:
The control mechanism changes the power supply parameter (maximum power amount) based on the elapsed time since power resumption. This parameter change strategy allows the system to optimize heating efficiency at different stages of the cooling period, achieving both rapid convergence and stable temperature control by adapting the power supply characteristics to current conditions
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
Stabilizes temperature control, prevents overshoot, and ensures rapid convergence to the target temperature, reducing the risk of damage and improving image quality.
Implementation Method 1
a heating member that heats the fixing member
Implementation Method 2
a temperature sensor that detects a temperature of the heating member or the fixing member
Data Source
AI summary
An image forming apparatus according to an aspect of the present disclosure includes a fixing device and a controller. The fixing device includes a fixing member, a pressure member, a heating member, and a temperature sensor. The controller cuts off power supply to the heating member when the temperature detected by the temperature sensor has risen to a cutoff temperature higher than the target temperature and thereafter resumes power supply to the heating member when the detected temperature has fallen below the cutoff temperature, and performs the PID control while limiting a maximum power supplied to the heating member to an upper limit power, which is a power supplied to the heating member at the time when the detected temperature has risen to the cutoff temperature, during a period from when power supply is resumed until a predetermined specific period of time elapses.