Voltage Generating Apparatus for Electrophotographic Cleaning
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Solution Overview
Problem
In electrophotographic image forming apparatuses, the shortening of sheet interval time for faster image formation can lead to insufficient cleaning due to reduced time for applying a cleaning reverse bias, resulting in undershoot and instability of the reverse bias voltage.
Innovation Solution
A voltage generating apparatus that includes a first power supply unit for a cleaning voltage and a second power supply unit for a transfer voltage, with a control unit generating a clock signal to switch between the two voltages, allowing the capacitor to charge in advance and stabilize the cleaning voltage even with a shortened raising time, thereby preventing undershoot.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the sheet interval time is shortened to increase productivity, then the image formation speed is improved, but the cleaning time is reduced causing insufficient cleaning and back staining
Solution Approach 1:
The patent applies preliminary action by charging the capacitor in advance during the secondary transfer period before the cleaning reverse bias is needed. This allows the capacitor to be ready to immediately supply current when the cleaning phase begins, enabling effective cleaning even within the shortened sheet interval time.
Solution Approach 2:
The patent utilizes periodic action by switching between secondary transfer mode and cleaning mode in regular cycles. During each cycle, the capacitor charges during secondary transfer and discharges during cleaning, creating a rhythmic pattern that optimizes both image formation and cleaning within the available time.
2Loss of time
If the raising time for the reverse bias is shortened to enable faster switching, then the sheet interval time utilization is improved, but the reverse bias becomes unstable and undershoot occurs
Solution Approach 1:
The capacitor is charged in advance during the secondary transfer period, so when cleaning begins, the capacitor immediately supplies the required current. This preliminary charging action eliminates the need for a long raising time while ensuring stable reverse bias voltage from the start of the cleaning phase.
Solution Approach 2:
The patent uses the capacitor as an energy copy mechanism, storing electrical energy during secondary transfer and replicating it as the reverse bias during cleaning. This energy copying allows instant voltage establishment without the delays and instability associated with traditional voltage raising methods.
3Productivity
If the sheet interval time is shortened, then the productivity is improved, but the cleaning reverse bias cannot be applied sufficiently causing toner adhesion
Solution Approach 1:
The patent skips the traditional voltage raising period by using the pre-charged capacitor to immediately supply the required reverse bias current. This rushing through of the voltage establishment phase allows the cleaning process to begin instantly, maximizing the utilization of the shortened sheet interval time for actual cleaning rather than voltage buildup.
Solution Approach 2:
Energy is stored in the capacitor in advance during the secondary transfer phase, preparing the system for immediate cleaning action. This preliminary energy storage ensures that the full cleaning reverse bias is applied from the start of the cleaning period, making effective use of the limited available time.
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
The solution enables stable control of the bias voltage during short sheet interval times, ensuring effective cleaning and preventing undershoot, thus maintaining the quality of the image forming process.
Implementation Method 1
a capacitor that holds a voltage supplied to a primary side of a transformer of the first power supply unit is charged in advance
Data Source
AI summary
A negative bias circuit outputs a DC voltage of a negative polarity. A positive bias circuit outputs a DC voltage of a positive polarity. The DC voltage of the positive polarity is used, for example, as a transfer voltage, and the DC voltage of the negative polarity is used as a cleaning voltage for cleaning toner. A cycle of the clock signal in a period during which the DC voltage of the first polarity is output is longer than a cycle of the clock signal in the period during which the voltage supplied to the load transits from the DC voltage of the first polarity to the DC voltage of the first polarity.