Image-Forming Fixing Device with External Heater Temperature Sensing
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Solution Overview
Problem
Existing fixing devices in electrophotographic image forming apparatuses face issues with large size due to the placement of the thermistor within the fixing belt, leading to inaccurate temperature detection of the heater, as it is easily affected by the temperature of the surrounding space in the film.
Innovation Solution
The fixing device incorporates a heat equalizing member and temperature detection part positioned outside the fixing belt, with the temperature detection part contacting the heat equalizing member exposed from the belt, allowing for accurate temperature detection of the heater while reducing the belt's diameter and device size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the thermistor is disposed in the space surrounded by the fixing belt, then the temperature detection is easier to implement, but the fixing belt diameter becomes large and the device size increases
Solution Approach 1:
The temperature detection part is extracted from the internal space of the fixing belt and positioned on the external surface. This allows the thermistor to detect heater temperature without being enclosed by the fixing belt, thereby reducing the belt diameter while maintaining detection functionality.
Solution Approach 2:
A heat conduction member is introduced as an intermediary between the heater and the temperature detection part. This member conducts heat from the heater to the thermistor externally, enabling accurate temperature detection without requiring the thermistor to be positioned inside the fixing belt.
2Device complexity
If the thermistor is wrapped in the fixing belt, then the temperature detection structure is simplified, but the detection accuracy decreases due to influence from the surrounding space temperature
Solution Approach 1:
The heat conduction member serves as a dedicated thermal pathway that isolates the temperature detection from the influence of the fixing belt's surrounding space temperature. By conducting heat directly from the heater to the thermistor, it ensures accurate heater temperature measurement despite the thermistor's external position.
Solution Approach 2:
The temperature detection function is separated from the fixing belt structure itself. The thermistor and heat conduction member form an independent detection system that interfaces with the heater separately, allowing accurate measurement without being affected by the belt's thermal environment.
3Device complexity
If the thermistor is positioned inside the fixing belt, then the detection setup is simpler, but the fixing device overall size becomes large
Solution Approach 1:
The temperature detection components are taken out from the internal configuration and repositioned on the external surface of the fixing belt. This extraction eliminates the need for additional internal space, thereby reducing the overall device size while maintaining detection functionality through the heat conduction member.
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 enables precise temperature control of the heater, reducing the fixing device's size and ensuring proper thermal fixation of toner onto the medium by accurately detecting and regulating the heater's temperature.
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
Figure 1
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AI summary
A fixing device (7) includes a fixing belt (20), a pressing roller (21), a heater (23), a heat equalizing member (26) and a temperature detection part (27). The heater (23) comes into contact with an inner surface of the fixing belt (20) facing the pressure region, and heats the fixing belt (20). The heat equalizing member (26) extends in the axial direction, and comes into contact with one surface of the heater (23) opposite to the fixing belt (20). The temperature detection part (27) is in contact with one surface of the heat equalizing member (26) opposite to the heater (23) and detects a temperature of the heater (23) via the heat equalizing member (26). At least one of end portions of the heater (23) and the heat equalizing member (26) in the axial direction is exposed to an outside of the fixing belt (20). The temperature detection part (27) is provided in contact with the heat equalizing member (26) exposed from the fixing belt (20).