Fixing Unit Metal Sheet Positioning for Temperature Stability
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Solution Overview
Problem
The existing fixing units in image forming apparatuses face instability in temperature detection due to changes in the pressing force of springs and relative displacement between the temperature sensor and the graphite sheet, leading to inaccurate temperature control.
Innovation Solution
A fixing unit configuration that includes a heater, an endless belt, a holder, and metal sheets in contact with the substrate, where the temperature sensor is positioned through holes in the holder to maintain consistent contact with the metal sheets, reducing positional deviation and enhancing temperature detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a graphite sheet is pressed toward the heater by a spring via the temperature sensor, then the heater is brought into close contact with the graphite sheet, but the pressing force changes instantaneously or over time causing displacement in relative position of the temperature sensor
Solution Approach 1:
The patent removes the spring component from the system and replaces it with a metal sheet that has inherent elastic properties. This extraction of the spring eliminates the source of pressing force fluctuations while maintaining the necessary contact pressure between the temperature sensor and the heat source.
Solution Approach 2:
The patent changes the material parameter from graphite to metal, and changes the mechanical parameter from spring-based pressing to elastic deformation-based pressing. The metal sheet's elastic modulus and thermal conductivity are optimized to provide stable contact pressure without the dynamic fluctuations characteristic of spring mechanisms.
2Temperature
If a graphite sheet is used as a thermally conductive member, then heat conduction is achieved, but displacement easily occurs in relative position of the temperature sensor with respect to the graphite sheet
Solution Approach 1:
The patent employs a composite structure where a metal sheet is combined with the graphite sheet. The metal sheet provides structural stability and positioning accuracy, while the graphite sheet maintains its thermal conduction function. This composite approach leverages the complementary properties of both materials.
Solution Approach 2:
The metal sheet acts as an intermediary between the temperature sensor and the graphite sheet. It provides a stable, rigid surface for the temperature sensor to contact, while still allowing thermal energy to be transmitted to the graphite sheet and subsequently to the heater.
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 stabilizes temperature detection, reduces positional deviation, and improves the accuracy of temperature control, ensuring consistent image quality and efficient operation of the image forming process.
Implementation Method 1
a heater including a substrate and a resistance heating element disposed on the substrate
Implementation Method 2
a metal sheet in contact with the substrate and a temperature sensor configured to detect a temperature of the heater
Data Source
AI summary
A fixing unit includes a heater including a substrate and a resistance heating element disposed on the substrate, an endless belt configured to move about the heater and having an inner peripheral surface in contact with the heater, and a holder holding the heater in a hole of the holder, a metal sheet in contact with the substrate and a temperature sensor configured to detect a temperature of the heater. The temperature sensor is in contact with the metal sheet through the hole, and an end portion of the metal sheet in a lateral direction of the substrate is inserted into the hole so that the metal sheet is positioned with respect to the heater in the lateral direction.