Fuser Bias Voltage Control for Offset Prevention
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Solution Overview
Problem
Conventional image forming apparatuses experience offset issues due to continuous application of bias voltage, which attracts negatively charged toner to the heat roller, causing image abnormalities when printing papers are fed at varying intervals, especially in rapid and unstable paper feeding conditions.
Innovation Solution
An image forming apparatus with a controller that selectively applies a bias voltage to the pressure roller based on the time interval between printing papers, determining whether to apply the voltage when the paper is not in the nip, using a power supply unit and paper detector to manage the bias voltage application according to preset times in simplex and duplex printing modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the bias voltage is applied continuously to the pressure roller, then the image fixation is improved, but the offset occurs due to toner accumulation on the heat roller
Solution Approach 1:
The patent implements periodic action by controlling the power supply unit to apply the bias voltage only during specific time intervals when printing papers are present in the fuser, rather than continuous application. The controller measures the time interval between consecutive papers and adjusts voltage application accordingly, turning off the bias voltage when no paper is present to prevent toner accumulation on the heat roller while maintaining image fixation quality during actual printing operations
2Object-generated harmful factors
If the bias voltage is shut down when printing paper is not in the fuser, then the offset is minimized, but the paper feeding becomes unstable in rapid printing
Solution Approach 1:
The patent applies feedback by having the controller continuously monitor the time interval between printing papers entering the fuser. Based on this real-time feedback, the controller dynamically adjusts the bias voltage application state. When the time interval indicates rapid printing conditions, the controller maintains voltage application to ensure stable paper feeding, while shutting down voltage when paper intervals are long to prevent offset, thus adapting the system behavior to actual operating conditions
3Productivity
If the bias voltage is applied during rapid printing with short paper intervals, then the productivity is improved, but the toner accumulation on the heat roller increases
Solution Approach 1:
The patent implements dynamics by making the bias voltage application adaptive rather than static. The controller dynamically adjusts the voltage application state based on the measured time interval between printing papers. During rapid printing with short intervals, the controller maintains voltage application to support high productivity. When paper intervals extend beyond a threshold, the controller shuts down voltage to prevent toner accumulation, thus optimizing the balance between printing speed and offset prevention in real-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
This solution minimizes offset by accurately controlling the bias voltage application, preventing toner accumulation on the heat roller and ensuring consistent image quality even in high-speed printing operations.
Implementation Method 1
a heat roller heated to a preset temperature
Implementation Method 2
a pressure roller for having conductivity and forming a nip by pressure-contacting with the heat roller
Implementation Method 3
by applying the (+) voltage to a pressure roller, the force of attaching the charged toner of the (−) polarity to the printing paper is increased
Data Source
AI summary
An image forming apparatus includes a heat roller heated to a preset temperature; a pressure roller for having conductivity and forming a nip by pressure-contacting with the heat roller; a power supply unit to apply a bias voltage to the pressure roller; and a controller to, when a printing paper enters the nip, control the power supply unit to apply the bias voltage to the pressure roller. When a time interval is longer than a preset time, the controller can control the power supply unit not to apply the bias voltage when the printing paper is not placed in the nip, and when the time interval is shorter than the preset time, the controller can control the power supply unit to apply the bias voltage when the printing paper is not placed in the nip.