Fixing Device Heater Non-Uniform Heat Distribution
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Solution Overview
Problem
Fixing devices with films used in electrophotographic image forming apparatuses experience temperature rise issues in sheet-non-passing areas, leading to potential fixing failures when handling large-sized recording media due to end portion temperature decreases.
Innovation Solution
A fixing device with a tubular film, a heater having a heat generating resistor with varying heat generation across its length, and a heat conductive member that contacts the heater, ensuring greater heat generation at the end portions to maintain consistent temperature and prevent fixing failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a metal plate is in contact with the heater over the entire length to suppress temperature rise of sheet-non-passing area, then temperature control of sheet-non-passing area is improved, but end portion temperature decreases causing fixing failure on large-sized recording media
Solution Approach 1:
The heater is designed with non-uniform heat generation distribution, where the heat generating resistor has higher resistance at the end portions and lower resistance at the middle portion. This creates locally differentiated heating characteristics: the end portions generate more heat to compensate for thermal loss, while the middle portion generates less heat to prevent overheating. This local quality variation resolves the contradiction by providing different heating intensities at different locations of the heater.
Solution Approach 2:
The resistance distribution of the heat generating resistor is optimized to change along the longitudinal direction of the heater. Specifically, the resistance value is set to be higher at the end portions and lower at the middle portion. This parameter change enables the end portions to generate more heat (compensating for thermal loss to the metal plate) while the middle portion generates appropriate heat, thereby maintaining reliable fixing performance across the entire recording medium width.
2Loss of time
If a film with small heat capacity is used to reduce warm-up time, then first print out time is reduced, but temperature rise of sheet-non-passing area occurs when small-sized recording media are processed
Solution Approach 1:
The heater incorporates a metal plate at the sheet-non-passing area to locally improve heat dissipation characteristics. This metal plate acts as a heat sink that prevents excessive temperature rise in the sheet-non-passing area, allowing the use of a film with small heat capacity while controlling thermal behavior during operation.
Solution Approach 2:
The heat generating resistor is designed with position-dependent resistance values to control heat generation distribution. By adjusting the resistance parameter along the longitudinal direction, the system generates appropriate heat in the sheet-passing area while the metal plate in the sheet-non-passing area dissipates excess heat, maintaining temperature within acceptable ranges.
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
The solution effectively suppresses temperature rise in sheet-non-passing areas while maintaining end portion fixing performance, ensuring reliable fixing of large-sized recording media without impairing continuous printing performance.
Implementation Method 1
a heat generating resistor formed on the substrate
Implementation Method 2
a heat conductive member configured to contact a surface of the heater opposite to a surface of the heater that contacts the film, the heat conductive member having a heat conductivity higher than that of the substrate
Data Source
AI summary
A fixing device includes a tubular film; a heater including a substrate and a heat generating resistor, the heater having a first region on which the heat generating resistor is formed and a second region, located outside of the first region in a longitudinal direction of the substrate, on which the heat generating resistor is not formed; and a heat conductive member configured to contact a surface of the heater opposite to a surface of the heater that contacts the film, the heat conductive member having a higher heat conductivity than the substrate. The heat conductive member contacts the heater in a region extending across the first region and the second region, and an amount of heat generated by the heat generating resistor at its end portion is greater than that at its middle portion in the longitudinal direction.