Fixing Unit Temperature Control Against Sensor Contamination
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Solution Overview
Problem
Foreign matters or toner dirt adhering to the temperature sensor in an image forming apparatus can lead to inaccurate temperature detection, causing a discrepancy between the heat roller's actual temperature and the detected temperature, resulting in inappropriate temperature control and potential hot offset issues.
Innovation Solution
A temperature control device that includes a temperature sensor, first and second storage circuits, and a temperature correction circuit to estimate and correct the target temperature based on a calculated temperature difference, ensuring accurate temperature control of the fixing unit by adjusting power supply to the heater.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the temperature sensor directly contacts the heat roller to detect temperature, then the temperature detection responsiveness is improved, but foreign matters or toner dirt can adhere to the sensor causing inaccurate detection
Solution Approach 1:
A pressing member is introduced as an intermediary between the temperature sensor and heat roller. The pressing member applies pressure to ensure thermal contact for accurate detection while preventing foreign matters from adhering to the sensor surface, thus resolving the contradiction between detection responsiveness and accuracy
Solution Approach 2:
The pressing member is designed to automatically maintain contact pressure between the temperature sensor and heat roller during operation. This self-adjusting mechanism ensures continuous accurate temperature detection without manual intervention, while the pressure prevents contaminant accumulation on the sensor
2Measurement precision
If the target temperature is increased to compensate for temperature detection errors, then the temperature control accuracy is improved, but hot offset occurs due to excessive temperature
Solution Approach 1:
The system continuously monitors the temperature sensor output and compares it with the actual heat roller temperature. When a discrepancy is detected (indicating sensor contamination), the control algorithm automatically adjusts the target temperature downward rather than increasing it, preventing hot offset while maintaining accurate temperature control
Solution Approach 2:
The control system proactively detects temperature discrepancies before they cause hot offset by comparing sensor readings with expected temperature values. When contamination is detected, the system preemptively corrects the target temperature to prevent the harmful effect of excessive heating
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
Prevents temperature discrepancies by correcting the target temperature, thereby preventing hot offset and ensuring stable operation of the image forming apparatus.
Implementation Method 1
a temperature sensor that detects a temperature of the heat roller
Implementation Method 2
an amount of power supplied to a heat member (a lamp, an IH heater, or the like)
Data Source
AI summary
A temperature control device controls power supplied to a heater based on a temperature estimate value estimated over time so that a temperature control target to which heat propagates from the heater of the fixing unit reaches a preset target temperature. The temperature control device includes a temperature sensor, first and second storage circuits, a temperature difference detection circuit, and a target temperature correction circuit. The temperature sensor detects a temperature of the heater. The first storage circuit stores the temperature estimate value. The second storage circuit stores a sensor temperature. The temperature difference detection circuit calculates an actual temperature rise amount from a temperature difference between the temperature estimate value and the temperature of the heater from the respective storage circuits. The temperature correction circuit performs control such that a target temperature is lowered in accordance with the actual temperature rise amount.