Fuser Temperature Estimation for Contaminated Sensor Detection
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Solution Overview
Problem
Temperature sensors in fixing devices of image forming apparatuses may become contaminated, leading to inaccurate temperature detection and subsequent control of the fixing rotator surface temperature, resulting in deviations from the intended target value.
Innovation Solution
A fixing device with a temperature sensor that estimates temperature based on a heater control circuit, using weighted average estimation (WAE) control to determine abnormalities by analyzing differences in estimated temperature values stored in a memory, ensuring accurate temperature control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a temperature sensor is used to detect the surface temperature of the fixing rotator, then the controller can control the surface temperature to be a target value, but the temperature sensor may become contaminated and cannot accurately sense the temperature
Solution Approach 1:
The patent introduces a thermal model as an intermediary between the heater control circuit and the temperature sensor. The thermal model estimates the actual surface temperature of the fixing rotator by processing the output from the temperature sensor, compensating for measurement errors caused by contamination. This intermediary layer allows the system to maintain accurate temperature control even when the sensor itself becomes contaminated.
Solution Approach 2:
The patent implements a feedback mechanism where the controller continuously monitors the temperature sensor output, processes it through the thermal model, and adjusts the heater control circuit accordingly. The system uses the estimated temperature values from the thermal model to determine whether abnormalities exist and to maintain the surface temperature at the target value, creating a closed-loop feedback system that compensates for sensor degradation.
2Measurement precision
If the temperature sensor becomes contaminated, then the detected temperature is inaccurate, but adding complex contamination detection mechanisms increases device complexity
Solution Approach 1:
The patent replaces complex mechanical or physical contamination detection mechanisms with a computational thermal model. Instead of adding physical sensors or mechanical probes to detect contamination, the system uses mathematical modeling and signal processing to estimate the actual temperature and detect abnormalities. This substitution maintains measurement precision while avoiding increased device complexity.
Solution Approach 2:
The thermal model serves as a computational intermediary that processes the raw temperature sensor data and outputs corrected temperature estimates. This intermediary layer filters out errors caused by contamination without requiring additional physical components, thereby maintaining simple device architecture while improving measurement accuracy.
Data Source
AI summary
According to one embodiment, a fixing device includes a fuser including a fixing member with a surface to contact a printable medium and a heat source for heating the fixing member. A temperature sensor is provided having a sensing part that contacts the surface of the fixing member. A heater control circuit is configured to estimate a temperature of the surface of the fixing member based on a temperature measured by the sensing part of the temperature sensor. A memory is provided for storing estimated temperature values obtained over a prior time period by the heater control circuit. A controller is configured to determine whether there is an abnormality in the fixing device based on a difference between a maximum value and a minimum value of the estimated temperature values stored in the memory.