Belt Fixing Device Non-Contact Temperature Sensor and Reflection Sheet Detection
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Solution Overview
Problem
In electrophotographic image forming apparatuses, the use of belt type fixing devices faces issues with toner adhesion, jam detection, and temperature sensing, where sheets can adhere to the belt due to high toner ratios and oilless systems, leading to incorrect jam detection and potential damage from excessive heating.
Innovation Solution
A belt type fixing device employing a non-contact type temperature sensor within the sheet passing range and a contact type temperature sensor outside of it, with a controller ensuring accurate temperature sensing and preventing excessive heating, along with a reflection type sheet sensor for backup, to reliably detect sheet presence and prevent damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a non-contact type temperature sensor is used to avoid scratching the fluorine surface layer, then the belt surface integrity is improved, but the sensor may incorrectly sense sheet temperature as belt temperature causing excessive heating
Solution Approach 1:
A reflective sheet sensor is introduced as an intermediary detection device. When a sheet is present, it reflects light to the sensor, providing a signal that the sheet is in the heating zone. This allows the system to distinguish between sheet presence and actual belt temperature, preventing erroneous heating control while maintaining non-contact temperature sensing.
Solution Approach 2:
The system implements feedback control by continuously monitoring both temperature sensor output and sheet sensor output. The controller adjusts heating based on combined feedback: temperature data indicates thermal state while sheet sensor data confirms whether the sensed temperature belongs to the belt or a sheet, enabling accurate closed-loop temperature control.
2Device complexity
If a contact type temperature sensor is positioned in the sheet passing range, then temperature sensing is simplified, but the sensor scratches the fluorine surface layer of the belt
Solution Approach 1:
The contact type temperature sensor is replaced with a non-contact type temperature sensor. This substitution eliminates mechanical contact between the sensor and the fluorine surface layer, preventing scratches and surface damage while maintaining accurate temperature sensing capability through radiant heat detection.
3Productivity
If the sheet sensor determines no sheet is present, then the system operates normally, but sheets adhering to the belt due to high toner ratio are not detected causing continuous heating
Solution Approach 1:
The system uses feedback from the sheet sensor to monitor sheet presence in the heating zone. When the sensor detects a sheet (through light reflection), it signals the controller to maintain or adjust heating. This continuous feedback loop ensures that sheets with high toner ratios that adhere to the belt are detected and processed correctly, preventing erroneous operation.
Solution Approach 2:
The reflective sheet sensor acts as an intermediary detection mechanism that works in conjunction with the temperature sensor. It provides an additional layer of detection that can identify sheets based on light reflection properties, complementing the temperature-based detection and improving overall sheet presence detection reliability.
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 configuration enhances accurate jam detection and prevents damage by ensuring the heat source is not activated unnecessarily, maintaining the integrity of the belt and avoiding excessive heating, thus improving the reliability of sheet sensing and fixing operations.
Implementation Method 1
A non-contact type temperature sensor is positioned in a sheet passing range corresponding to the width of the minimum sheet size to be dealt with and assigned to the heat roller
Implementation Method 2
A reflection type sheet sensor determines whether or not a sheet is present on the belt
Data Source
AI summary
A belt type fixing device includes a fix roller, a press roller rotatable in pressing contact with the fix roller, a heat roller accommodating a heat source therein and a belt passed over the fix roller and heat roller. A non-contact type temperature sensor is positioned in a sheet passing range corresponding to the width of a minimum sheet size and assigned to the heat roller while a contact type temperature sensor is positioned outside of the sheet passing range. A controller prevents the heat source from being turned on if a temperature sensed by the non-contact type temperature sensor is short of a preselected temperature B when a temperature sensed by the contact type temperature sensor reaches a preselected temperature A assigned to the non-contact type temperature sensor. A reflection type sheet sensor determines whether or not a sheet is present on the belt.