Transfer Device Superimposed Bias Embossed Media
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Solution Overview
Problem
Image forming apparatuses using secondary transfer devices experience transfer failures when dealing with recording media having coarse or embossed surfaces, resulting in uneven image density due to inadequate toner transfer, especially in recessed portions.
Innovation Solution
A transfer device incorporating a direct current (DC) and alternating current (AC) power source to generate a superimposed bias, which is used in conjunction with a contact-and-separation mechanism to control the distance between the image bearer and the nip forming device, ensuring a larger space during transfer to prevent electrical discharge and ensure adequate toner transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a DC bias is applied to the transfer nip, then the transfer process is simple and stable under constant current control, but transfer failures occur on embossed surfaces due to inadequate toner transfer to recessed portions
Solution Approach 1:
The patent applies a superimposed bias consisting of a DC voltage and an AC voltage to the transfer nip. The AC voltage component creates periodic electric field variations that enable toner particles to reach recessed portions of embossed surfaces during the transfer process, while the DC voltage maintains overall transfer stability. This periodic action resolves the contradiction by ensuring both transfer stability and image density uniformity on embossed surfaces.
2Force
If the space between the image bearer and nip forming device is reduced for better contact, then transfer pressure increases, but electrical discharge occurs with superimposed bias causing transfer failures
Solution Approach 1:
The patent optimizes the space between the image bearer and nip forming device specifically for use with superimposed bias. By maintaining an appropriate space rather than reducing it to maximum contact, the invention prevents electrical discharge while still ensuring sufficient transfer pressure. This parameter optimization resolves the contradiction by balancing transfer pressure and electrical discharge prevention.
3Reliability
If a larger space is maintained between image bearer and nip forming device, then electrical discharge is prevented with superimposed bias, but transfer pressure decreases reducing transfer efficiency
Solution Approach 1:
The patent determines an optimal space value that prevents electrical discharge while maintaining sufficient transfer pressure for efficient toner transfer. This optimized space parameter resolves the contradiction by ensuring both transfer stability and acceptable transfer efficiency when using superimposed bias.
Solution Approach 2:
The AC voltage component of the superimposed bias creates periodic electric field variations that enhance toner transfer effectiveness even with the optimized space, maintaining transfer efficiency while preventing electrical discharge.
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
The solution effectively prevents transfer failures by maintaining a sufficient transfer bias and ensuring consistent image density across the recording medium, even on embossed surfaces, by utilizing a superimposed bias and controlled separation mechanism.
Implementation Method 1
The transfer bias power source includes a direct current (DC) power source and an alternating current (AC) power source electrically connected to each other, to output a transfer bias including at least one of a DC bias and a superimposed bias in which a DC voltage and an AC voltage are superimposed to transfer a toner image
Implementation Method 2
The contact-and-separation device causes the image bearer and the nip forming device to contact and separate from each other. The controller controls the contact-and-separation device to increase a size of a space between the image bearer and the nip forming device upon transfer using the superimposed bias
Data Source
AI summary
A transfer device includes an image bearer to bear a toner image, a nip forming device to contact the image bearer to form a transfer nip, a transfer bias power source including a direct current (DC) power source and an alternating current (AC) power source electrically connected to each other to output a transfer bias including at least one of a DC bias and a superimposed bias to transfer the toner image from the image bearer onto a recording medium interposed in the transfer nip, a contact-and-separation device to cause the image bearer and the nip forming device to contact and separate from each other, and a controller to control the contact-and-separation device to increase a size of a space between the image bearer and the nip forming device upon transfer using the superimposed bias such that the space is larger than the space upon transfer using the DC bias.