Fixing Heater Timing Control for High-Voltage Print Protection
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Solution Overview
Problem
Heaters in fixing devices of image forming apparatuses can be damaged by input voltages higher than the product rating, leading to reduced printing efficiency as the machine becomes unusable.
Innovation Solution
The image forming apparatus includes a voltage measuring unit and a control unit that determine a heating timing for the heating unit based on measured voltage, controlling its operation to prevent damage during high voltage input, using a zero crossing detection circuit to synchronize heating with AC voltage peaks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the heating unit is protected by making the machine unusable when high voltage is detected, then the heating unit is protected from damage, but the printing operation cannot be continued which reduces printing efficiency
Solution Approach 1:
The patent applies dynamics by making the heating timing adjustable based on voltage conditions. The control unit dynamically determines heating timing according to the detected voltage, switching between normal heating operation and protected heating operation. This dynamic adaptation allows the system to maintain printing operations while protecting the heating unit during high voltage events, resolving the contradiction between reliability and productivity.
Solution Approach 2:
The patent changes the heating timing parameter based on voltage detection. When high voltage is detected, the control unit modifies the heating timing to occur at specific points in the AC voltage cycle (at or near peaks) rather than continuous heating. This parameter change protects the heating unit from voltage spikes while maintaining printing functionality, thus improving both reliability and productivity simultaneously.
2Productivity
If the heating unit operates continuously during high voltage input, then printing efficiency is maintained, but the heating unit may be damaged by voltage spikes
Solution Approach 1:
The control unit performs preliminary detection of voltage conditions before initiating heating. By detecting the AC voltage state in advance and determining appropriate heating timing based on detected voltage levels, the system prevents damage before it occurs. This preliminary action allows continuous printing operation while preemptively protecting the heating unit from voltage spike damage.
Solution Approach 2:
The patent implements periodic heating action synchronized with the AC voltage cycle. Instead of continuous heating, the heating unit operates periodically at specific timing within each voltage cycle (at or near peaks when voltage is highest). This periodic operation maintains printing productivity while avoiding sustained exposure to high voltage conditions that could cause damage.
3Reliability
If additional protection circuits are added to protect the heating unit, then the heating unit is protected from high voltage damage, but the device complexity and cost increase
Solution Approach 1:
The control unit performs multiple functions: it controls the heating unit operation, detects voltage conditions, determines heating timing, and protects against high voltage damage. By making the control unit universal and multi-functional, the patent eliminates the need for separate dedicated protection circuits, reducing device complexity and cost while maintaining heating unit protection.
Solution Approach 2:
The control unit uses its existing voltage detection capability to protect the heating unit itself. The system performs self-protection by monitoring voltage conditions and adjusting heating timing accordingly, without requiring external protection circuits. This self-service approach reduces complexity and cost while ensuring heating unit protection.
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 approach prevents damage to the heating unit while maintaining printing operations, reducing efficiency impacts, and minimizing cost increases by avoiding the need for additional protection circuits.
Implementation Method 1
a zero crossing detection circuit that detects a zero crossing point of an AC voltage
Implementation Method 2
The fixing device includes a heating unit that heats the sheet
Data Source
AI summary
According to at least one embodiment, an image forming apparatus includes a heater and a controller. The heater is configured to generate heat. The controller is configured to control AC power to the heater so that a part of the AC power which exceeds a threshold voltage is not applied to the heater.