Transfer Roller Voltage Polarity Control for Sheet Separation
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Solution Overview
Problem
In image forming apparatuses, poor separation of sheets occurs due to burrs at the leading edge, leading to incomplete transfer of toner images and potential winding around the image carrier, despite existing solutions that do not fully prevent this issue.
Innovation Solution
A transfer device with a control system that applies a voltage of opposite polarity to the transfer section until a predetermined non-image area of the sheet has passed through the nip portion, then switches to the transfer polarity to prevent sheet sticking and ensure proper toner image transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If transfer voltage is applied to the transfer roller from the beginning of the sheet leading edge, then toner image transfer density is improved, but sheet poor separation and winding occur due to burrs at the sheet leading edge
Solution Approach 1:
The patent applies a preliminary action by applying transfer voltage before the sheet leading edge enters the nip portion. Specifically, voltage is applied to the transfer roller from a timing when the sheet leading edge has not yet entered the nip portion until a predetermined time after entry. This preliminary voltage application ensures that the electric field is already established when the sheet enters, preventing poor separation while maintaining transfer density.
Solution Approach 2:
The patent implements dynamics by making the voltage application timing adjustable and adaptive. The control unit dynamically adjusts the voltage application timing based on the sheet conveyance speed and nip portion characteristics. The voltage is applied from a timing when the sheet leading edge has not yet entered the nip portion until a predetermined time after entry, creating a dynamic voltage application window that adapts to different operating conditions.
2Reliability
If voltage is not applied in the leading edge area of the sheet, then sheet poor separation is prevented, but toner image transfer density decreases
Solution Approach 1:
The patent applies local quality by differentiating the voltage application timing for different regions of the sheet. The voltage is applied from a timing when the sheet leading edge has not yet entered the nip portion until a predetermined time after entry, creating a localized voltage application window that prevents poor separation at the leading edge while ensuring sufficient voltage application for proper toner transfer in the image area.
3Device complexity
If the sheet leading edge enters the nip portion before voltage is applied, then voltage application timing is simplified, but electric discharge occurs at burrs causing poor separation
Solution Approach 1:
The patent applies preliminary action by establishing voltage application before the sheet leading edge enters the nip portion. The control unit is configured to apply voltage to the transfer roller from a timing when the sheet leading edge has not yet entered the nip portion, ensuring that the electric field is already established when the sheet enters, thereby preventing electric discharge at burrs and poor separation.
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 approach effectively prevents poor separation and ensures the full density of the toner image is transferred onto the sheet, even with burrs at the leading edge, by managing the electric field direction and voltage application timing.
Implementation Method 1
voltage (transfer voltage) having a polarity which is opposite to the polarity of toner is applied to a transfer roller T to move the toner onto the sheet S from the photoreceptor K
Implementation Method 2
the direction of an electric field points toward the photoreceptor K from the transfer roller T. Therefore, electric discharge occurs in the opening which is formed at the leading edge of the sheet between the transfer belt B and the sheet S
Data Source
AI summary
A transfer device comprising: a transfer section which forms a nip portion between the transfer section and an image carrier and transfers a toner image on an image carrier onto a sheet passing through the nip portion; an application section which applies a voltage to the transfer section; a determining section which determines a timing of applying voltage from the application section to the transfer section, wherein the control section controls the application section to apply a voltage having an opposite polarity to a transfer polarity to the transfer section until the timing determined by the determination section in a period since a leading edge of the sheet in a conveyance direction advances into the nip portion until a predetermined non image area of the sheet has passed through the nip portion, and then, at a timing determined, switch to apply a voltage having the transfer polarity.