Fixing Heater Waveform Control for Power Factor Improvement
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Solution Overview
Problem
The increasing power consumption and complexity of low-voltage power sources in electrophotographic image forming apparatuses lead to higher costs and larger spaces, necessitating a solution to improve the power factor while reducing costs.
Innovation Solution
The implementation of an image forming apparatus with a power source that converts AC voltage to DC voltage, utilizing a controller to manage two independent heat generating elements within the fixing portion, adjusting the current waveform based on temperature and duty ratio to optimize power supply, and employing a current detecting portion to adjust control periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If a power factor improving circuit such as a step-up active filler is mounted in the low-voltage power source portion, then the power factor is improved, but the circuit structure becomes complicated and the cost increases
Solution Approach 1:
The invention extracts the power factor improvement function from the low-voltage power source portion by directly controlling the heater's power supply waveform. Instead of adding a power factor improving circuit to the power source, the control portion modifies the AC power supply waveform directly to the heater, separating the power factor improvement function from the voltage conversion function.
Solution Approach 2:
The control portion performs multiple functions: it controls the heater temperature and simultaneously improves the power factor by shaping the power supply waveform. The same control circuit that manages heater operation also generates the phase-controlled waveform to improve power factor, making the control portion multi-functional.
2Use of energy by stationary object
If a power factor improving circuit is mounted in the low-voltage power source portion, then the power factor is improved, but the space required for the power source portion increases
Solution Approach 1:
The invention removes the power factor improving circuit from the low-voltage power source portion, thereby reducing the space required for the power source. The power factor improvement function is transferred to the heater control system, which operates at a different location and uses existing control infrastructure.
3Use of energy by stationary object
If the current passes through one heat generating element from a halfway point of the half wave, then the power factor is improved, but the control complexity increases
Solution Approach 1:
The invention applies periodic phase-controlled switching to the heater elements, where current is supplied from the halfway point of each half-wave cycle. This periodic control pattern simplifies the complexity by using a regular, repeating waveform strategy rather than complex continuous control algorithms.
Solution Approach 2:
The control is segmented into independent half-wave periods, with each half-wave controlled independently by switching at the halfway point. This segmentation allows simple, repetitive control actions rather than complex continuous control, reducing overall control complexity.
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 enhances the power factor, reduces costs, and minimizes the size of the image forming apparatus by efficiently managing power distribution and heat generation.
Implementation Method 1
a first heat generating element which generates heat by electric power supplied from the commercial power source and a second heat generating element which is controlled independently of the first heat generating element and which generates the heat by the electric power supplied from the commercial power source
Data Source
AI summary
An image forming apparatus includes: a power source portion; a fixing portion; and a controller. The controller sets a waveform of a current to be passed through each of first and second heat-generating-elements of the fixing portion in one control period so that, in a synchronous half wave in one control period, the current passes through one heat-generating-element from a halfway point of the half wave and the current passes through or does not pass through the other heat-generating-element throughout a half wave period. The controller sets a current supply starting timing of the current passing through the one heat-generating-element, at timing when a current passing toward the power source portion stops.