Belt Fixing Unit Sensor Orientation for Toner Soiling
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Solution Overview
Problem
In vertical-transport image forming apparatuses, the non-contact temperature sensor in the belt fixing unit is prone to soiling with toner and paper dust, leading to degraded sensing accuracy due to its orientation and exposure to falling debris.
Innovation Solution
The non-contact temperature sensor is positioned on the surface of the fixing belt facing upwards between the fixing and heating rollers, with a wind shield to prevent air flow interference and a gap from the belt surface, ensuring the sensing surface points downward to avoid soiling and maintain accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the temperature sensor is provided facing the fixing roller from the upstream side with the fixing belt passing therebetween, then the temperature sensing is enabled, but the sensing surface is prone to be soiled with toner and paper dust in vertical transport passage
Solution Approach 1:
The patent inverts the conventional temperature sensor arrangement by positioning the sensor on the fixing belt surface rather than facing the fixing roller from upstream. This inversion changes the sensing surface orientation to face downward, preventing toner and paper dust from soiling the sensor while maintaining temperature measurement capability through the fixing belt
2Measurement precision
If the temperature sensor is positioned close to the fixing belt for accurate sensing, then temperature control precision is improved, but air flow interference degrades sensing accuracy
Solution Approach 1:
The patent introduces a wind shield as an intermediary element between the temperature sensor and the air flow. The wind shield blocks the direct impact of air flow on the sensor while allowing the sensor to remain positioned close to the fixing belt for accurate temperature sensing, thus mediating between the conflicting requirements of proximity and air flow protection
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 the sensing accuracy by preventing soiling and reducing temperature sensing errors, allowing for precise control of the fixing temperature in vertical-transport image forming apparatuses.
Implementation Method 1
a non-contact temperature sensor for controlling the fixing temperature... The temperature sensor is provided on a non-contact basis in the paper passage region on the surface of the upper one of the parts of the fixing belt
Implementation Method 2
a wind shield may be provided that points away from the housing toward the fixing belt. This prevents the temperature sensing part of the sensing element from being directly influenced by the stream of air flowing along the surface of the fixing belt
Data Source
AI summary
A belt fixing unit has a fixing roller and a pressing roller that are provided in a pair midway along a transport passage through which paper having a toner image formed thereon is transported from bottom to top approximately in a vertical direction and that fix the toner image on the paper, a heating roller that is provided parallel to and in a position approximately horizontal to the fixing roller and that incorporates a heater for heating the fixing roller, and a fixing belt that is formed as an endless belt and that is wound around and between the fixing roller and the heating roller. A non-contact temperature sensor for controlling the fixing temperature is provided on a non-contact basis in the paper passage region on the surface of the upper one of the parts of the fixing belt facing each other up and down between the fixing roller and the heating roller.