Heater Current Detection Stabilization for Image Forming Apparatus
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Solution Overview
Problem
Existing image forming apparatuses face challenges in accurately detecting electric current changes in resistive heat generators due to phase control and temperature changes, making it difficult to determine abnormal conditions like disconnection, which affects temperature control and energy efficiency.
Innovation Solution
A heater system with resistive heat generators connected in parallel, featuring an electric current detector that stabilizes current measurement by ensuring an identical alternating current waveform for a predetermined time, allowing precise detection of resistance changes and enabling accurate control through a controller that adjusts power supply based on detected voltage and current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If phase control is used to supply power to the resistive heat generator, then power supply control is achieved, but accuracy in detecting the electric current value degrades substantially
Solution Approach 1:
The patent introduces an intermediary conversion process where the alternating current is first rectified into direct current, and then converted into a voltage value for detection. This mediator approach allows phase control to be maintained while enabling accurate current measurement through voltage detection, which is not affected by the phase control waveform distortions.
Solution Approach 2:
The patent replaces direct electric current detection with a voltage detection system. By converting the current measurement problem into a voltage measurement problem through rectification and conversion, the system achieves accurate detection without being affected by the phase control waveform, effectively substituting one detection mechanism for another more suitable one.
2Temperature
If the resistive heat generator is shortened to increase the number of heat generators, then temperature increase in the non-conveyance span is suppressed further, but it becomes difficult to install the temperature detecting sensor for each heat generator
Solution Approach 1:
The patent merges the temperature detection function into a single shared sensor that monitors the overall temperature of the fixing belt, rather than requiring separate sensors for each resistive heat generator. This combining approach reduces the number of sensors needed while still achieving effective temperature control and suppression of temperature increase in non-conveyance spans.
Solution Approach 2:
The patent implements a universal temperature detection system where a single temperature detecting sensor serves multiple resistive heat generators simultaneously. This multi-functional sensor approach eliminates the need for individual sensors for each generator, reducing device complexity while maintaining effective temperature monitoring across all heating zones.
3Reliability
If one of the resistive heat generators suffers from disconnection, then other heat generators continue to receive electric current, but this results in abnormal temperature increase of the resistive heat generators
Solution Approach 1:
The patent implements a feedback mechanism where the temperature detecting sensor continuously monitors the temperature of the fixing belt and provides this information to the control unit. When disconnection of a resistive heat generator causes abnormal temperature increase, the feedback signal triggers the control unit to interrupt power supply to the remaining connected heat generators, preventing overheating while allowing continuous operation capability.
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 enhances the accuracy of electric current detection and resistance monitoring, improving temperature control and preventing abnormal temperature increases, thus ensuring reliable operation and energy efficiency in image forming apparatuses.
Implementation Method 1
a laminated heater constructed of a base and a plurality of resistive heat generators. The laminated heater heats the fixing belt
Implementation Method 2
A positive temperature coefficient (PTC) heater having a positive temperature coefficient is employed as the resistive heat generator to suppress temperature increase in the non-conveyance span of the fixing belt further
Data Source
Figure 1A
Figure 1B
Figure 2A
AI summary
A heater (91) includes an electric current detector (430) that detects an electric current that flows through a plurality of resistive heat generators (364, 368). A voltage detector (450) detects a voltage applied to the resistive heat generators (364, 368). An electric current controller (400) controls the electric current that flows through the resistive heat generators (364, 368) based on the electric current detected by the electric current detector (430) and the voltage detected by the voltage detector (450). The electric current detector (430) detects the electric current in a state in which, after a power supply (410) starts supplying power to the resistive heat generators (364, 368), an identical waveform of an alternating current supplied to the resistive heat generators (364, 368) continues for a predetermined time period or longer taken for the electric current detector (430) to detect the electric current.