Fixing Device with External Heater Temperature Detection
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Solution Overview
Problem
Existing fixing devices in electrophotographic image forming apparatuses face challenges due to the large diameter of the fixing belt required to accommodate the thermistor, leading to increased size and inaccurate temperature detection of the heater, as the thermistor is easily affected by the temperature of the surrounding space within the film.
Innovation Solution
The fixing device incorporates a cylindrical fixing belt with a heater and a heat equalizing member, where the heater extends along the axial direction, and the temperature detection part is positioned outside the fixing belt to detect the heater's temperature via the exposed heat equalizing member, reducing the belt's diameter and improving temperature detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the thermistor is disposed in the space surrounded by the fixing belt, then the temperature detection is possible, but the diameter of the fixing belt becomes large and the fixing device size increases
Solution Approach 1:
The temperature detection function is extracted from the interior space of the fixing belt and relocated to the exterior side. The thermistor is positioned outside the fixing belt while still being able to detect heater temperature through thermal conduction via the heat equalizing member, thereby eliminating the need for increased belt diameter to accommodate the sensor internally.
Solution Approach 2:
The heat equalizing member serves as an intermediary between the heater and the thermistor. It conducts heat from the heater to the thermistor that is positioned outside the fixing belt, enabling temperature detection without requiring the thermistor to be placed inside the belt's interior space.
2Device complexity
If the thermistor is wrapped in the fixing belt, then the temperature detection structure is simplified, but the thermistor is easily affected by the temperature of the space in the film and proper heater temperature cannot be detected
Solution Approach 1:
The thermistor is extracted from the problematic position of being wrapped in or surrounded by the fixing belt. By positioning it on the exterior side with thermal contact to the heater through the heat equalizing member, the sensor is removed from the thermal environment that caused measurement errors while maintaining structural simplicity.
Solution Approach 2:
The direct thermal contact mechanism is replaced by conducting heat through the heat equalizing member to reach the thermistor. This substitution allows the thermistor to be positioned outside the fixing belt while still accurately detecting heater temperature through the thermal conduction path provided by the heat equalizing member.
3Device complexity
If the thermistor is positioned inside the fixing belt, then the detection structure is compact, but the outer diameter of the fixing belt increases due to the space required for the thermistor
Solution Approach 1:
The thermistor is taken out from the interior space of the fixing belt and positioned on the exterior side. This extraction eliminates the need to increase the belt's inner diameter to accommodate the sensor, while the detection structure remains compact through the use of the heat equalizing member for thermal conduction.
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 allows for proper temperature detection of the heater while minimizing the fixing device's size, ensuring accurate temperature control and efficient thermal fixation of toner on the medium.
Implementation Method 1
The heat equalizing member extends in the axial direction, comes into contact with one surface of the heater opposite to the fixing belt, absorbs heat emitted from the heater and moving the heat in the axial direction
Implementation Method 2
The temperature detection part is in contact with one surface of the heat equalizing member opposite to the heater and detects a temperature of the heater via the heat equalizing member
Implementation Method 3
The heater extends in the axial direction of the fixing belt, comes into contact with an inner surface of the fixing belt facing the pressure region, and heats the fixing belt
Data Source
AI summary
A fixing device includes a fixing belt, a pressing roller, a heater, a heat equalizing member and a temperature detection part. The heater comes into contact with an inner surface of the fixing belt facing the pressure region, and heats the fixing belt. The heat equalizing member extends in the axial direction, and comes into contact with one surface of the heater opposite to the fixing belt. The temperature detection part is in contact with one surface of the heat equalizing member opposite to the heater and detects a temperature of the heater via the heat equalizing member. At least one of end portions of the heater and the heat equalizing member in the axial direction is exposed to an outside of the fixing belt. The temperature detection part is provided in contact with the heat equalizing member exposed from the fixing belt.