Transfer Device Alternating Bias for Irregular Sheet Defects
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Solution Overview
Problem
Transfer defects occur when using sheets with large irregularities due to insufficient transfer electric fields in recesses, and increasing transfer bias can lead to electrostatic discharge and reverse charging.
Innovation Solution
A transfer device with a voltage applying section that alternates between a first transfer bias greater than a reference bias and a second transfer bias equal to or smaller than the reference bias, ensuring adequate electric field for toner transfer while minimizing electrostatic discharge and reverse charging, using a direct current power source to apply these biases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If transfer bias voltage is increased to form sufficient electric field in recesses, then toner transfer to recess areas is improved, but electrostatic discharge and reverse charging occur causing transfer defects
Solution Approach 1:
The patent applies periodic pulse voltage with alternating positive and negative polarity to the transfer member. During the positive voltage period, toner is transferred to the sheet surface. During the negative voltage period, the electric field direction reverses, allowing toner to be drawn back from recesses where it may have accumulated. This periodic action prevents excessive toner accumulation in recesses that would cause transfer defects, while avoiding continuous high voltage that would cause electrostatic discharge.
2Manufacturing precision
If transfer bias is increased to move toner into recesses, then transfer completeness in recesses is improved, but transfer defects are caused due to excessive current
Solution Approach 1:
The patent employs periodic pulse voltage application where the voltage polarity alternates between positive and negative. The positive voltage phase transfers toner to the sheet, while the negative voltage phase draws toner back from recesses. This periodic action ensures that toner is not permanently trapped in recesses, preventing transfer defects while maintaining transfer completeness. The alternating polarity creates a dynamic equilibrium that prevents excessive toner accumulation.
3Device complexity
If constant DC voltage is applied for transfer, then simple transfer process is maintained, but insufficient electric field in recesses causes transfer defects
Solution Approach 1:
The patent replaces constant DC voltage with periodic pulse voltage that alternates polarity. This modification maintains relative simplicity in the voltage control system while dramatically improving transfer quality in recesses. The periodic positive voltage provides the necessary electric field to move toner into recesses, while the subsequent negative voltage phase prevents toner from becoming trapped, ensuring complete and defect-free transfer.
Solution Approach 2:
The patent changes the voltage parameter from constant DC to time-varying pulse voltage with alternating polarity. This parameter change transforms the electric field characteristics, allowing the system to dynamically control toner movement. The voltage magnitude and polarity are modulated over time to optimize both the initial transfer into recesses and the subsequent prevention of toner trapping, thereby improving transfer quality without significantly increasing system 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
Reduces transfer defects in recesses by maintaining an effective electric field for toner transfer while preventing electrostatic discharge and reverse charging, improving image quality on irregular surfaces.
Implementation Method 1
a transfer bias composed of a DC voltage having a constant value is applied to the second transfer member, and a transfer electric field is formed between the first transfer member and the second transfer member
Implementation Method 2
the toner image on the first transfer member is electrostatically moves to the sheet, and the toner image is transferred to the sheet
Implementation Method 3
the transfer bias including a first application period for applying a first transfer bias greater than a reference transfer bias in absolute value and a second application period for applying a second transfer bias equal to or smaller than the reference transfer bias in absolute value
Data Source
AI summary
A transfer device includes a voltage applying section configured to apply a transfer bias to a transfer member, and a control section configured to control the voltage applying section to apply a transfer bias in which a first application period for applying a first transfer bias and a second application period for applying a second transfer bias are alternately provided to the transfer member when a first sheet having a small surface smoothness passes through a nip.