Transfer Apparatus Voltage Control for Separation Discharge
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Solution Overview
Problem
In image forming apparatuses using electrophotography, separation discharge can occur when a sheet is separated from a conveyance belt, leading to toner scattering due to a grounded roller, which affects conveyance stability and transfer quality.
Innovation Solution
Applying a voltage with a polarity opposite to the toner charge to the second roller and guide member during the separation process, along with a resistor in the energizing path to control current flow, suppresses separation discharge and maintains toner adhesion to the sheet.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a roller is grounded at the sheet separation position, then the sheet can be separated from the conveyance belt, but separation discharge occurs causing toner scattering
Solution Approach 1:
The patent changes the electrical parameter (voltage) of the roller from grounded (0V) to a negative voltage state. By applying a negative voltage to the roller at the separation position, the electrostatic potential difference that causes separation discharge is eliminated, thereby preventing toner scattering while maintaining reliable sheet separation.
2Reliability
If electrostatic attraction is used to convey the sheet, then conveyance stability and transfer property improve, but separation discharge occurs at the separation position
Solution Approach 1:
The patent applies a local quality change by specifically modifying the electrical state of the roller at the separation position while maintaining the electrostatic attraction mechanism elsewhere. The negative voltage is applied only to the separation position roller, creating a localized electrostatic environment that prevents discharge without interfering with the overall electrostatic conveyance and transfer process.
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 reduces toner scattering and maintains print density by preventing separation discharge and ensuring stable electrostatic adhesion of toner to the sheet during separation from the conveyance belt.
Implementation Method 1
a sheet is conveyed while being electrostatically attracted to the conveyance belt
Implementation Method 2
transfers electrostatically a toner image, formed on the image carrier, to the transfer material
Implementation Method 3
separation discharge may occur when the sheet is separated from the conveyance belt
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A transfer device (35) includes a conveyance belt (351), a transfer roller (352), and a stretch roller (354). The conveyance belt (351) is in contact with an image carrier (31) that carries a toner image, and conveys a sheet via a contact position with the image carrier (31). A voltage having a polarity opposite to a charging polarity of toner that forms the toner image is applied to the transfer roller (352), and the transfer roller (352) transfers the toner image carried by the image carrier (31) onto the sheet at the contact position. The stretch roller (354) stretches the conveyance belt (351) at a separation position in which the sheet is separated from the conveyance belt (351) and which is downstream of the contact position in a conveyance direction in which the sheet is conveyed by the conveyance belt (351), and the voltage having the polarity opposite to the charging polarity of the toner is applied to the stretch roller (354).