Dynamic Transfer Bias Control for Image Forming Apparatus
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Solution Overview
Problem
Existing image forming apparatuses face challenges in maintaining stable transfer of toner images due to variations in environmental conditions and sheet properties, leading to defective transfers, as conventional methods either fail to provide sufficient transfer current at low temperatures and humidities or result in excessive current flow when dealing with narrow sheets.
Innovation Solution
An image forming apparatus that includes a voltage detecting means to calculate a transfer member correction voltage and a sheet correction voltage based on detected conditions, combining these to determine a transfer bias voltage for stable image transfer, ensuring appropriate toner image transfer onto sheets regardless of environmental and sheet-specific factors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If constant-voltage control is used to maintain stable voltage to transfer means, then voltage stability is improved, but transfer current becomes insufficient when resistance increases in low temperature and humidity environments
Solution Approach 1:
The patent implements dynamic control by switching between constant-voltage control and constant-current control based on environmental conditions. A temperature-humidity sensor detects environmental parameters, and a control unit adjusts the control mode accordingly: using constant-voltage control in normal conditions and constant-current control in low temperature and humidity conditions where resistance increases, thereby ensuring reliable transfer across varying environments.
2Reliability
If constant-current control is used to maintain appropriate transfer current, then transfer reliability is improved, but excessive current flows when transfer means directly contacts image carrying member with narrow sheets
Solution Approach 1:
The control unit dynamically switches between constant-current control and constant-voltage control based on sheet width detection. When narrow sheets are detected, the system uses constant-voltage control to prevent excessive current flow during direct contact between transfer means and image carrying member. For standard width sheets, constant-current control is applied to ensure reliable transfer, thus avoiding harmful effects while maintaining transfer quality.
3Ease of operation
If a fixed coefficient R is used to calculate transfer bias voltage (V2 = RV1), then control simplicity is maintained, but transfer bias voltage becomes inaccurate when sheet kind and intra-apparatus humidity vary
Solution Approach 1:
The patent changes the control parameter from a fixed coefficient R to dynamic parameters including temperature, humidity, and sheet width. The control unit adjusts the transfer bias voltage based on real-time detection of these parameters, replacing the simplistic V2 = RV1 formula with a multi-parameter control strategy that adapts to varying sheet kinds and environmental conditions, thereby improving voltage accuracy while maintaining reasonable control complexity.
4Ease of manufacture
If theoretical transfer bias voltage is used based on predetermined formulas and tables, then control implementation is simplified, but actual transfer bias voltage may not match requirements due to use history and sheet quality variations
Solution Approach 1:
The patent implements feedback control by using sensors to detect actual environmental conditions (temperature, humidity, sheet width) and feeding this information back to the control unit. The control unit continuously adjusts the transfer bias voltage based on real-time feedback, rather than relying solely on predetermined theoretical values. This closed-loop control ensures consistent transfer quality despite variations in use history and sheet quality, while maintaining ease of implementation through automated sensor-based adjustment.
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 enables stable and efficient transfer of toner images by dynamically adjusting the transfer bias voltage, addressing issues of insufficient current at low temperatures and excessive current flow, thereby improving transfer quality across varying conditions and sheet types.
Implementation Method 1
a voltage detecting means for detecting a voltage generated at the transfer position by applying the predetermined current to the transfer member or opposite member
Data Source
AI summary
An image forming apparatus that transfers a toner image from includes a transfer belt to a sheet via to carry a toner image, a transfer roller. The image forming apparatus transfers the toner image by applying a transfer bias voltage to either the transfer roller or to make contact with the transfer belt to transfer the toner image onto a sheet from the transfer belt, an opposite roller facing the transfer roller across the transfer belt. The transfer bias voltage is decided by adding a transfer roller correction voltage, based on a voltage detected by a voltage detection unit when a predetermined current is applied to either the transfer roller or the opposite roller by a current application unit when no sheet is present in a transfer position, and a sheet correction voltage, based on a sheet kind and an intra-apparatus humidity.