Fixing Device Relay Switch Temperature Control
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Solution Overview
Problem
Conventional fixing devices in image forming equipment face issues with excessive temperature rise during sudden stops or power-offs, leading to misjudgment by the overheat protection circuit, resulting in prolonged downtime and difficulty in restarting safely.
Innovation Solution
A fixing device with a relay switch and temperature detection sensors that control the heat source, keeping the relay switch off when the fixing member's temperature exceeds a predetermined level, preventing abnormal stops and allowing safe restarts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the fixing member is made with low heat capacity (thin-walled roller or belt) to reduce warm-up time and energy consumption, then energy efficiency is improved, but the fixing member becomes excessively sensitive to residual heat and prone to false overheat detection
Solution Approach 1:
The patent changes the thermal parameters of the fixing member by using a thin-walled structure with low heat capacity, which allows rapid temperature changes and quick warm-up. This parameter change enables energy savings while the control system compensates by using hysteresis in temperature threshold judgment to prevent false overheat detection.
2Device complexity
If the overheat protection circuit uses a fixed temperature threshold to detect excessive heat, then the detection simplicity is maintained, but the system cannot distinguish between actual overheat conditions and temporary temperature rises during restart, leading to false alarms
Solution Approach 1:
The patent transforms the static temperature threshold into a dynamic threshold that changes based on operational state. By introducing hysteresis with different threshold values for heating and cooling phases, the system adapts to temporary temperature variations during restart while maintaining simple circuit design. This dynamic adjustment prevents false overheat detection during normal operation cycles.
Solution Approach 2:
The control unit performs preliminary judgment about the operational state before activating the overheat protection. By detecting whether the fixing member has recently been heated and is currently in a cooling phase, the system prepares to use a higher temperature threshold for overheat detection, preventing false alarms during restart without requiring complex real-time analysis.
3Reliability
If the image forming device stops operation due to false overheat detection during restart, then the overheat protection function is maintained, but the downtime increases and productivity decreases
Solution Approach 1:
The patent implements dynamic temperature threshold adjustment based on operational history. When the system detects that the fixing member has been recently heated and is in a cooling phase, it temporarily raises the overheat detection threshold. This dynamic adaptation allows the device to restart successfully without false overheat protection activation, maintaining productivity while preserving reliable overheat detection when actually needed.
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 prevents unnecessary shutdowns and allows for safe continuation of operations by managing temperature thresholds, reducing downtime and avoiding false alarms from the overheat protection circuit.
Implementation Method 1
the heat source is formed by a halogen heater heating the fixing member by radiation heat
Implementation Method 2
heat from the fixing member and the pressing member is absorbed by a recording medium, for example paper, passing through a nip portion between the two members
Data Source
AI summary
According to an embodiment, provided is a fixing device that includes: a rotatable fixing member that heats a recording medium on a side carrying an unfixed image; a rotatable pressing member that is pressed and is contacted with the fixing member to form a nip portion between the pressing member and the fixing member; a heat source heating the fixing member; a relay switch provided in an energizing path for the heat source; a temperature detection sensor detecting a temperature of the fixing member; and a control unit that controls energization of the heat source according to the temperature detected by the temperature detection sensor. The control unit keeps the relay switch in an off state if the temperature of the fixing member is equal to or more than a predetermined temperature when the fixing member has stopped rotation.