Transfer Power Source Control for AC Banding Prevention
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Solution Overview
Problem
In electrophotographic image forming apparatuses, the superimposition of alternating-current (AC) voltage on the transfer voltage via a transfer medium with low electric resistance, often due to high humidity, leads to non-uniform toner transfer and image defects known as AC banding, as the current flowing from the transfer member to the image bearing member is deflected by the AC waveform component, resulting in uneven image shades.
Innovation Solution
An image forming apparatus equipped with a detection unit to monitor the current flowing in the transfer member and a control unit that adjusts the transfer voltage based on the detected frequency of the AC waveform component, ensuring the current remains within an appropriate range to prevent AC banding by setting a lower limit voltage and switching between constant current and constant voltage control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a transfer medium with low electric resistance (due to moisture absorption) is used, then the transfer medium can be handled under high-temperature, high-humidity conditions, but AC voltage superimposition occurs via the transfer medium causing non-uniform toner transfer and AC banding
Solution Approach 1:
The patent employs a detection unit to detect the current flowing in the transfer member and feeds this information back to a control unit. The control unit compares the detected frequency with a predetermined frequency range including the AC power source frequency, and adjusts the transfer voltage accordingly to prevent AC banding while maintaining adaptability to humid environments
Solution Approach 2:
The patent dynamically changes the transfer voltage parameter based on detected AC waveform components. When AC banding is detected through frequency comparison, the control unit adjusts the transfer voltage to compensate for the low electric resistance condition caused by moisture absorption, thereby maintaining uniform toner transfer
2Manufacturing precision
If the transfer voltage is increased to compensate for low electric resistance, then uniform toner transfer can be maintained, but AC voltage superimposition causes current deflection and AC banding
Solution Approach 1:
The detection unit continuously monitors the current in the transfer member and provides feedback to the control unit. The control unit compares the detected frequency with the predetermined frequency range and dynamically adjusts the transfer voltage to eliminate AC waveform components, thereby preventing AC banding while maintaining uniform toner transfer
Solution Approach 2:
The patent transitions from a static transfer voltage approach to a dynamic control system that continuously adjusts the transfer voltage based on real-time detection of AC waveform components. This dynamic adjustment allows the system to maintain uniform toner transfer while actively suppressing AC banding
3Reliability
If a detection unit is added to detect current in the transfer member, then AC banding can be detected and prevented, but the device complexity increases
Solution Approach 1:
The control unit performs multiple functions: it detects the current frequency, compares it with the predetermined frequency range, determines the presence of AC waveform components, and adjusts the transfer voltage accordingly. This multi-functionality reduces the need for separate dedicated components for each function
Solution Approach 2:
The detection unit is positioned between the transfer member and transfer power source, utilizing the existing current path without requiring additional external sensors or complex measurement circuits. The system uses its own operational current for detection purposes
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 effectively prevents AC banding by maintaining a stable current flow, ensuring uniform toner transfer and preventing image defects, even when the transfer medium has low electric resistance due to moisture absorption.
Implementation Method 1
a transfer voltage is applied to a transfer member situated to face an image bearing member, such as a drum-shaped photosensitive member or intermediate transfer member, to electrostatically transfer a toner image borne on the image bearing member onto a transfer medium
Implementation Method 2
An alternating-current (AC) power source applies an AC voltage to the heating member so that the heating member is heated to a temperature at which the toner image is transferable onto the transfer medium
Implementation Method 3
the transfer medium onto which the toner image is transferred at a transfer nip portion formed by the image bearing member and the transfer member is conveyed to a fixing unit and then heated and pressed by the fixing unit so that the toner image is fixed to the transfer medium
Data Source
AI summary
A heating member of a fixing unit is situated in a fixing portion, and a commercial power source applies an alternating-current voltage to the heating member so that the heating member heats a transfer medium held in the fixing portion. In a case of transferring the toner image from an image bearing member onto the transfer medium in a transfer portion, a control unit controls a transfer power source based on a result of a comparison between a frequency obtained from a first detection result input from a detection unit with a predetermined frequency range including the frequency of the alternating-current voltage.