Fixing Heater Protection Using Time-Varying Temperature Thresholds
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing fixing apparatuses with heat fixing systems experience rapid temperature rises at the end portion of the fixing member, leading to overheating, which is not effectively addressed by current safety devices that cause delays in stopping energization, potentially resulting in further temperature increases.
Innovation Solution
An image forming apparatus with a temperature detection system that includes a controller, a reference voltage generator, and a breaker to quickly stop power supply to the heating portion by adjusting the reference voltage based on elapsed time since heating initiation, ensuring the temperature does not exceed predetermined thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a safety device with a fixed threshold temperature is used to detect abnormal heating, then the safety device can prevent overheating in normal operation, but it causes a delay in stopping energization when the temperature rises rapidly, leading to continued temperature increase during the delay period
Solution Approach 1:
The patent applies dynamics by making the reference voltage variable rather than fixed. The reference voltage generator produces a reference voltage that changes over time since heating start, allowing the threshold for abnormal heating detection to adapt dynamically. This resolves the contradiction by enabling rapid detection when temperature rises quickly while maintaining appropriate thresholds during normal operation.
Solution Approach 2:
The patent changes the parameter of reference voltage from a constant value to a time-dependent value. The reference voltage generator modifies the reference voltage based on elapsed time since heating initiation, allowing the detection threshold to adjust dynamically. This enables the safety device to respond appropriately to both normal and abnormal heating scenarios without fixed-delay limitations.
2Reliability
If the reference voltage is changed in accordance with the amount of current of the heater to prevent malfunction, then the safety device can distinguish normal from abnormal heating, but a delay time occurs from when the current changes until the reference voltage changes and the circuit state is changed
Solution Approach 1:
The patent applies preliminary action by pre-generating a time-varying reference voltage that anticipates the heating process. Instead of waiting for current changes to calculate and adjust the reference voltage, the system has the reference voltage generator continuously provide an appropriate reference voltage based on elapsed time. This eliminates the delay between current change and reference voltage adjustment.
Solution Approach 2:
The patent implements feedback by continuously monitoring the temperature detector output voltage against the time-varying reference voltage. The breaker receives feedback about whether the temperature exceeds the dynamic threshold and immediately stops energization when abnormal heating is detected, creating a rapid closed-loop response system that eliminates delay.
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
The solution effectively prevents rapid temperature rises by rapidly stopping power supply to the heating portion, thereby preventing overheating and maintaining the fixing member at a safe temperature, enhancing operational safety and reliability.
Implementation Method 1
a temperature detector configured to output an output voltage that corresponds to a temperature of the fixing member or a temperature of the heating portion
Implementation Method 2
a heating portion configured to heat the fixing member by being supplied with electric power
Data Source
AI summary
An image forming apparatus includes a fixing member, a heating portion configured to heat the fixing member by being supplied with electric power, a power source configured to supply electric power to the heating portion, a temperature detector, a controller configured to control power supply from the power source to the heating portion based on the output voltage from the temperature detector, a reference voltage generator configured to generate a reference voltage, and a breaker configured to stop the power supply from the power source to the heating portion. The reference voltage generator is configured to output the reference voltage that changes with time having elapsed since a start of heating at which the power supply to the heating portion was started by the controller.