Fixing Device Temperature Control via Discontinuous Duty Adjustment
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Solution Overview
Problem
The existing PID temperature control method for fixing devices in image forming apparatuses is ineffective in maintaining the target temperature of the fixing belt, leading to temperature deviations and inadequate toner fixation due to gentle heater duty adjustments when the temperature is close to the target, resulting in rapid temperature drops during the fixing process.
Innovation Solution
A novel temperature control method that includes a heater duty control mechanism, where the heater duty is adjusted discontinuously before the recording sheet enters the fixing nip, allowing for a larger heater duty value to be substituted in the PID algorithm, ensuring sufficient heat supply and maintaining the target temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If PID control is used to optimize heater parameters according to temperature deviation, then temperature control precision is improved, but the heater duty increases gently when temperature is close to target, causing rapid temperature drops during fixing
Solution Approach 1:
The patent applies preliminary action by detecting when a recording sheet is approaching the fixing nip and proactively increasing the heater duty before the sheet enters the fixing zone. This anticipatory heating ensures sufficient temperature is maintained despite the upcoming heat absorption from the recording sheet, preventing the rapid temperature drops that occur with conventional PID control alone.
2Temperature
If heater duty is increased to compensate for heat drawn by recording sheet, then temperature maintenance is improved, but response time is delayed due to gradual heater duty adjustment
Solution Approach 1:
By detecting the approach of a recording sheet and triggering a discontinuous, significant increase in heater duty in advance, the system achieves rapid temperature compensation before the sheet enters the fixing nip. This eliminates the delay inherent in gradual PID adjustments and ensures immediate heat supply when needed.
Solution Approach 2:
The patent implements periodic monitoring of recording sheet approach and applies periodic discontinuous heater duty adjustments at critical moments. This periodic intervention strategy ensures temperature maintenance occurs rhythmically in sync with recording sheet passage, providing timely heat compensation without continuous adjustment delays.
3Device complexity
If ON/OFF control method is used for temperature control, then device complexity is reduced, but temperature deviation from target increases significantly
Solution Approach 1:
The patent incorporates feedback mechanisms that detect both temperature deviation and recording sheet approach. This dual feedback system triggers discontinuous heater duty adjustments based on actual conditions, significantly improving temperature control accuracy compared to simple ON/OFF control while avoiding the complexity of continuous PID adjustment systems.
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 prevents temperature drops in the fixing belt during the fixing process, ensuring consistent temperature control and improved image quality by allowing for a more significant heater duty increase, thereby maintaining the target temperature effectively.
Implementation Method 1
The heating roller 120 has a heater 150 inside. By having the heater 150 generate heat so as to heat the heating roller 120, the fixing belt 130 is also heated.
Implementation Method 2
When a printing sheet P on which a toner image T has been transferred passes through the fixing nip N, the toner is melted and the image is fixed on the printing sheet P.
Data Source
AI summary
A temperature control method for use in a fixing device that fixes a toner image on a recording sheet by passing the recording sheet through a fixing nip defined between a fixing member and a pressure member includes temperature detection, heater control, and duty control execution. The temperature detection detects a temperature of the fixing member with a temperature detector. The heater control controls operation of a heater of the fixing device by changing a duty thereof according to the detected temperature. The duty control execution executes a heater duty control to change a heater duty for a current control cycle discontinuously from that for a previous control cycle when the current control cycle precedes entry of the recording sheet into the fixing nip by a given period of time.