Recording-Material Pre-Charging for High-Resistance Image Transfer
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Solution Overview
Problem
Image deterioration such as transfer void occurs due to insufficient transfer current, particularly when transferring toner images onto high-resistance recording materials like synthetic paper or ultra-thick paper, especially in low-humidity environments, where the secondary transfer bias voltage exceeds the high-voltage capacitance, leading to improper transfer.
Innovation Solution
An image forming apparatus with a recording material charging member that applies a bias of the same polarity as the secondary transfer bias, upstream of the secondary transfer portion, to effectively charge the recording material surface opposite to the normal toner charge polarity, minimizing current interference between the secondary transfer and pre-charging portions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the pre-charging portion is placed close to the secondary transfer portion to minimize charge attenuation, then the charging effectiveness is improved, but current interference occurs between the pre-charging and secondary transfer portions causing improper transfer
Solution Approach 1:
The patent divides the charging function into two separate portions: a pre-charging portion that charges the recording material before it reaches the secondary transfer portion, and a secondary transfer portion that performs the actual toner transfer. This segmentation allows each portion to be optimized independently - the pre-charging portion can be positioned upstream to ensure effective charging, while the secondary transfer portion maintains proper transfer conditions without current interference.
Solution Approach 2:
The pre-charging portion performs the charging action in advance, before the recording material reaches the secondary transfer portion. By applying charge to the recording material upstream, the system ensures that the charge is established before transfer occurs, eliminating the need to place the charging mechanism immediately adjacent to the transfer portion and thus avoiding current interference problems.
2Reliability
If a very large absolute value of secondary transfer bias voltage is applied to transfer toner onto high-resistance recording materials, then the transfer capability is improved, but the voltage exceeds the high-voltage capacitance causing transfer void due to insufficient transfer current
Solution Approach 1:
The system performs preliminary charging of the recording material in the pre-charging portion before the material reaches the secondary transfer portion. This advance charging ensures that the recording material has sufficient charge to work cooperatively with the secondary transfer bias, enabling effective transfer at lower voltage levels and preventing transfer void caused by excessive voltage requirements.
Solution Approach 2:
The patent changes the electrical parameters of the recording material by pre-charging it to an opposite polarity. This parameter modification allows the secondary transfer to occur at lower voltage levels while maintaining adequate transfer current, thus avoiding the transfer void problem that occurs when the required voltage exceeds the high-voltage capacitance.
3Reliability
If the secondary transfer bias voltage is increased to transfer onto synthetic paper or ultra-thick paper, then the transfer onto high-resistance materials is improved, but productivity decreases due to the need for higher voltage application
Solution Approach 1:
By pre-charging the recording material upstream before it reaches the secondary transfer portion, the system prepares the electrical conditions for transfer in advance. This allows the secondary transfer to proceed efficiently at optimized voltage levels without requiring excessive voltage increases that would slow down the overall image forming process, thus maintaining productivity.
Solution Approach 2:
The pre-charging portion modifies the electrical parameters of the recording material by imparting an opposite charge polarity. This parameter change enables the secondary transfer to occur at lower, more efficient voltage levels, allowing transfer onto high-resistance materials like synthetic paper and ultra-thick paper without compromising image forming speed or productivity.
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 solution ensures effective transfer of toner images onto high-resistance materials by enhancing the transfer current, reducing the likelihood of image defects like transfer voids without compromising productivity.
Implementation Method 1
a recording material charging member provided upstream of the secondary transfer portion with respect to a recording material conveying direction so as to contact a surface of the recording material on a side opposite from a surface of the recording material which is conveyed toward the secondary transfer portion and onto which the toner image is transferred
Implementation Method 2
a first applying portion configured to apply, to the inner roller, a secondary transfer bias of the same polarity as a normal charge polarity of toner
Data Source
AI summary
An image forming apparatus includes an image bearing member, an intermediary transfer belt, an inner roller, a secondary transfer member, a first applying portion for applying, to the inner roller, a secondary transfer bias of the same polarity as a normal charge polarity of toner, a recording material charging member provided upstream of a secondary transfer portion with respect to a recording material conveying direction so as to contact a surface of a recording material on a side opposite from a surface of the recording material which is conveyed toward the secondary transfer portion and onto which the toner image is transferred and for charging the recording material, and a second applying portion for applying, to the recording material charging member, a recording material charging bias of the same polarity as the polarity of the secondary transfer bias.