Image-Forming Fixing Device Resistance Sensing for Heater Breakdown
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Solution Overview
Problem
Existing image forming apparatuses face challenges in detecting localized dielectric breakdown in the heater of the fixing device, which can lead to abnormal heating and potential safety hazards due to the slow response of temperature sensors in detecting temperature changes.
Innovation Solution
Incorporating a resistance measuring circuit to measure the electrical resistance of the metal portion of the holding member, which is used to control the power supply to the heater based on the measured resistance values and the rotation state of the pressure roller, allowing for immediate shutdown when dielectric breakdown occurs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If temperature sensors are used to detect abnormal heating in the heater, then temperature monitoring is achieved, but the response speed is slow due to the thermal inertia of the sensor
Solution Approach 1:
The patent replaces the mechanical/thermal temperature sensing system with an electrical resistance measurement system. The holding member's electrical resistance is measured to detect temperature changes, providing immediate electrical signal response without the thermal inertia inherent in temperature sensors. This substitution of measurement methodology resolves the contradiction between reliable detection and fast response.
Solution Approach 2:
The holding member serves as an intermediary element that experiences temperature changes from the heater and translates them into measurable electrical resistance changes. This intermediary approach allows indirect but rapid detection of temperature abnormalities through resistance measurement, bypassing the slow direct temperature sensing method.
2Productivity
If power supply to the heater is not interrupted quickly when dielectric breakdown occurs, then continuous operation is maintained, but abnormal heating and safety hazards occur
Solution Approach 1:
The patent implements a feedback control system where the resistance measurement of the holding member continuously monitors heater temperature conditions. When dielectric breakdown occurs, the resistance change provides immediate feedback to the control device, which then interrupts power supply to prevent abnormal heating, thus resolving the contradiction between maintaining continuous operation and preventing harmful effects.
Solution Approach 2:
The system performs preliminary monitoring through resistance measurement to detect dielectric breakdown before it leads to dangerous overheating. By detecting the breakdown event early through resistance changes and immediately interrupting power supply, the system takes preliminary protective action that prevents the development of harmful abnormal heating conditions.
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 solution enables rapid detection and prevention of dangerous overheating by promptly stopping power supply to the heater, thereby ensuring safety and preventing potential hazards.
Implementation Method 1
The resistance measuring circuit measures electrical resistance of the metal portion of the holding member
Implementation Method 2
The heater is a planar heater having a substrate and a plurality of resistors formed on the substrate
Data Source
AI summary
The fixing device includes a heater, a holding member, a fixing member, a pressure roller, a drive mechanism, and a resistance measuring circuit. The holding member includes a metal portion and holds the heater. The pressure roller is rotatably supported, and applies pressure to a toner image on a sheet by sandwiching the fixing member and the sheet between the pressure roller and the heater. The resistance measuring circuit measures electrical resistance of the metal portion of the holding member. The control device controls whether to allow or prohibit a supply of power to the heater in accordance with a rotation state of the pressure roller and a measured resistance value of the resistance measuring circuit.