Transfer Voltage Control for Image Density on Irregular Media
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Solution Overview
Problem
Existing image forming apparatuses face challenges in achieving sufficient image densities on both recesses and protrusions of recording materials with large surface irregularities, often resulting in shading patterns and white spots due to inadequate toner transfer and electric discharge.
Innovation Solution
A transfer device with a nip forming member and a transfer voltage application unit that applies an alternating voltage with a DC component and an AC component, where the time average value of the transfer voltage is set closer to the peak supply voltage, and the absolute value of the return voltage is larger than the time average value to ensure effective toner transfer without generating electric discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If an AC voltage with DC component is applied to transfer toner onto recesses of recording material, then image density on recesses is improved, but white spots are generated due to electric discharge
Solution Approach 1:
The patent applies parameter changes by carefully controlling the voltage parameters of the alternating voltage. Specifically, the peak value of the AC component is limited to prevent electric discharge, while the DC component is optimized to ensure sufficient toner transfer into recesses. This parameter optimization resolves the contradiction between achieving high image density on recesses and avoiding white spots from electric discharge.
2Manufacturing precision
If high transfer voltage is applied to ensure sufficient toner transfer, then image density is improved, but electric discharge occurs causing white spots
Solution Approach 1:
The patent resolves this contradiction by changing and optimizing voltage parameters. The peak value of the AC component is constrained to a specific range that prevents electric discharge, while the DC component is set to an optimal value that ensures sufficient toner transfer. This parameter optimization allows high image density to be achieved without causing electric discharge and white spots.
3Manufacturing precision
If AC component is added to transfer voltage to move toner into recesses, then toner transfer to recesses is improved, but control complexity increases
Solution Approach 1:
The patent simplifies the control complexity by establishing specific parameter ranges for the alternating voltage. Instead of complex dynamic control, the solution defines fixed constraints: the peak value of the AC component should not exceed a certain threshold, and the DC component should be within a specific range. This parameter-based approach achieves effective toner transfer to recesses while maintaining simple and manageable voltage control.
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 configuration ensures sufficient image densities on both recesses and protrusions without generating white spots, effectively addressing the issues of toner transfer and electric discharge in image forming apparatuses.
Implementation Method 1
a secondary transfer voltage is applied to the secondary transfer roller at the outer side of the loop. With this, a secondary transfer electrical field for moving the toner image electrostatically to the secondary transfer roller from the secondary transfer opposing roller is formed between the secondary transfer opposing roller and the secondary transfer roller
Implementation Method 2
by using the secondary transfer voltage, toner reciprocates between the surface recesses on the recording material and the image carrier, so that the toner can make contact with the surface recesses on the recording material
Data Source
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AI summary
According to an embodiment, provided is a transfer device including: a nip forming member (36) that abuts against a surface of an image carrier (31) carrying a toner image; and a transfer voltage application unit (39) that applies a transfer voltage including a DC component and an AC component. The transfer voltage is an alternating voltage in which a supply voltage having polarity in a transfer direction and a return voltage having polarity opposite. A time average value Vave of the transfer voltage is set to be at polarity in the transfer direction and is set to be closer to a peak value Vt of the supply voltage relative to a center value Voff between a maximum and minimum value. An absolute value of the peak value Vr of the return voltage is set to be larger than an absolute value of the time average value Vave.