Fixing Device Dynamic Threshold Control for Overheating Prevention
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Solution Overview
Problem
Existing fixing devices in image forming apparatuses are prone to damage from excessive heating due to continuous power supply to the heater during motor deceleration, especially when the control system fails, leading to overheating of the fixing member.
Innovation Solution
A fixing device with a threshold setting mechanism that adjusts the temperature threshold from a first to a second higher temperature during motor acceleration and back to the first temperature during deceleration, using a power supply stopping portion to prevent overheating by stopping heater power supply when deceleration begins.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the heater continues to be supplied with power during motor deceleration, then energy efficiency is improved by maintaining temperature, but the fixing member is damaged by excessive heating
Solution Approach 1:
The patent applies dynamics by making the temperature threshold adjustable based on motor operation state. The threshold dynamically switches between a first threshold (during acceleration) and a second threshold (during deceleration), allowing the system to adapt power supply conditions to current operational needs rather than using a fixed threshold throughout all operation phases.
Solution Approach 2:
The patent changes the parameter of temperature threshold based on motor operation phase. During acceleration, a first temperature threshold is used; during deceleration, a second (higher) temperature threshold is used. This parameter change allows the system to tolerate higher temperatures during deceleration when the fixing member's rotational speed is decreasing, preventing excessive heating damage while maintaining energy efficiency.
2Reliability
If the temperature threshold is raised during motor deceleration, then the fixing member is protected from excessive heating damage, but temperature control precision is reduced
Solution Approach 1:
The system dynamically adjusts the temperature threshold based on motor operation state. During deceleration, the second (higher) threshold provides protection against excessive heating damage, while during acceleration, the first (lower) threshold maintains precise temperature control. This dynamic adjustment resolves the contradiction by applying different precision levels appropriate to different operational phases.
Solution Approach 2:
The system performs preliminary action by detecting the motor deceleration state in advance and switching to the second temperature threshold before excessive heating damage can occur. This proactive adjustment based on predicted operational conditions allows the system to prevent damage while maintaining appropriate control precision for each phase.
3Device complexity
If a fixed temperature threshold is used throughout operation, then the control system is simple, but the fixing member is damaged during deceleration phases
Solution Approach 1:
The patent implements a dynamic control system that adjusts the temperature threshold based on motor operation state (acceleration vs. deceleration). This dynamic approach increases control system complexity slightly but dramatically improves reliability by preventing excessive heating damage during deceleration phases while maintaining adequate protection during acceleration.
Solution Approach 2:
The control system performs preliminary detection of motor operation state and switches between different temperature thresholds in advance of potential damage conditions. This preliminary action allows the system to prevent excessive heating damage before it occurs, improving reliability without requiring overly complex real-time monitoring systems.
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 the fixing member from being damaged by excessive heating by dynamically adjusting the temperature threshold and stopping heater power during motor deceleration, ensuring the device's safety and longevity.
Implementation Method 1
a heater configured to heat the fixing member upon being supplied with power
Implementation Method 2
a temperature sensor configured to sense temperature of the fixing device
Data Source
AI summary
A fixing device includes a motor, a heater, a power supply stopping portion, and a threshold setting portion. The motor rotates a fixing member that fixes a toner image transferred to a sheet onto the sheet. The heater heats the fixing member upon being supplied with power. In a case where temperature of the fixing device exceeds a threshold, the power supply stopping portion stops supply of power to the heater. The threshold setting portion changes the threshold from a first temperature to a second temperature higher than the first temperature in an acceleration period in which rotation speed of the motor increases, and changes the threshold from the second temperature to the first temperature when a deceleration period in which the rotation speed of the motor decreases starts.