Heater Phase Control for Harmonic Reduction in Image Formers
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Solution Overview
Problem
Existing image forming apparatuses face challenges in reducing harmonic current while maintaining temperature followability, especially with high-output heaters and varying basis weights of print materials, as the fixed prohibited section for phase control limits harmonic current reduction and affects temperature control.
Innovation Solution
The apparatus employs a controller that dynamically adjusts the start phase angles for alternating current supply to the heater, ensuring they are outside the prohibited section and vary for each control period, and stops the current at zero cross points, thereby reducing harmonic currents and maintaining temperature followability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a fixed prohibited section is used in phase control to reduce harmonic current, then harmonic current is reduced, but temperature followability is lowered
Solution Approach 1:
The patent applies dynamics by making the prohibited section variable rather than fixed. The controller dynamically adjusts the prohibited section based on the supply rate, shifting it toward the advance side as supply rate increases. This dynamic adjustment allows the system to reduce harmonic current at low supply rates while maintaining temperature followability at high supply rates, resolving the contradiction between harmonic current reduction and temperature control performance.
Solution Approach 2:
The patent changes the parameter of the prohibited section position based on the supply rate. By making the prohibited section position a variable parameter that depends on the supply rate, the system can optimize harmonic current reduction at different operating conditions. This parameter change approach allows the prohibited section to be positioned optimally for each supply rate level, preventing the degradation of temperature followability that occurs with a fixed prohibited section.
2Object-generated harmful factors
If the prohibited section is widened to reduce harmonic current, then harmonic current is reduced, but the range of usable phase angles is reduced
Solution Approach 1:
The patent makes the prohibited section position dynamic by shifting it according to the supply rate. Instead of using a single wide fixed prohibited section that limits all phase angle choices, the system adjusts the prohibited section position to match the current operating conditions. This dynamic approach reduces harmonic current effectively while preserving the availability of appropriate phase angles for temperature control across different supply rates.
Solution Approach 2:
The patent applies local quality by making the prohibited section position dependent on the local operating condition (supply rate). Different regions of the operating range (different supply rates) have different prohibited section positions optimized for their specific conditions. This allows the system to reduce harmonic current locally at each operating point without globally restricting the range of usable phase angles.
3Loss of energy
If low power is continuously supplied to a high output heater, then energy consumption is reduced, but harmonic current increases due to consecutive use of the same start phase angle
Solution Approach 1:
The patent applies periodic action by introducing variation in the start phase angle across consecutive control periods. Instead of using the same start phase angle continuously when low power is required, the system periodically changes the start phase angle by applying different prohibited sections at different supply rates. This periodic variation reduces harmonic current while maintaining low energy consumption, as the system can still operate at low supply rates but with varying phase angles that prevent harmonic buildup.
Solution Approach 2:
The patent makes the start phase angle selection dynamic by adjusting the prohibited section position based on the supply rate. When low power is supplied, the system dynamically selects start phase angles that are outside the dynamically positioned prohibited section, ensuring that the same phase angle is not used consecutively. This dynamic approach reduces harmonic current while allowing continuous low power operation for energy efficiency.
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 effectively reduces harmonic currents while enhancing temperature followability by varying the start phase angles and adjusting the prohibited sections, improving the efficiency of heat application for diverse print materials.
Implementation Method 1
A fixing unit has a heater and is configured to fix a toner image to a sheet by applying heat from the heater
Implementation Method 2
A fixing unit has a heater and is configured to fix a toner image to a sheet by applying heat from the heater
Implementation Method 3
A temperature detector configured to detect a temperature of the fixing unit
Implementation Method 4
A controller controls a supply of alternating current to the heater... decides a start phase angle that is a reference for a supply start corresponding to the supply rate... starts supply of the alternating current to the heater at the start phase angle
Implementation Method 5
Transform Electrical Energy to Thermal Energy... applying heat from the heater... controls a supply of alternating current to the heater
Data Source
AI summary
An apparatus decides a supply rate for each control period that comprises a plurality of half periods in an alternating current based on a difference between a target temperature and a temperature detected by a detector. In a case where the same supply rate over a plurality of the control period is decided, a start phase angle that is a reference for a supply start corresponding to the supply rate is decided so that the start phase angle is located outside a prohibited section and a combination of the start phase angle differs for each control period. For each of a plurality of half periods configuring the control period, supply of the alternating current to a heater is started at the start phase angle. When a zero cross point of the alternating current arrives, the supply of the alternating current is stopped.