Secondary Transfer Roller Bias Control for Toner Cleaning
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Solution Overview
Problem
Conventional image forming apparatuses face difficulties in sufficiently removing toner from the transfer member, leading to staining and inefficiencies due to incomplete toner removal.
Innovation Solution
An image forming apparatus that employs a controlled bias voltage application process, using a negative bias voltage followed by a positive bias voltage of lower absolute value to effectively transfer and remove toner from the secondary transfer roller, ensuring complete cleaning without causing discharge-induced re-polarization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a reverse polarity current having a larger absolute value than the same-polarity current is applied to remove toner, then toner removal capability is improved, but discharge occurs and re-polarizes the toner causing incomplete removal
Solution Approach 1:
The patent applies bias currents in a periodic sequence: first a same-polarity current to charge the transfer member, then a reverse-polarity current to remove toner, and repeats this cycle multiple times. This periodic application allows toner to be gradually removed without excessive discharge, as each cycle builds upon the previous state. The control unit increments the same-polarity current value in each cycle while limiting the reverse-polarity current to prevent harmful discharge effects.
Solution Approach 2:
The patent dynamically adjusts the same-polarity current value in each cycle, incrementing it by a predetermined amount from the initial value. This dynamic adjustment optimizes the charging effect in each successive cycle, ensuring sufficient toner adhesion before removal attempts while adapting to the changing state of the transfer member and toner during the cleaning process.
2Productivity
If the same-polarity current value is increased to improve toner adhesion, then toner removal efficiency is improved, but discharge occurs decomposing air and generating ions that re-polarize toner
Solution Approach 1:
The patent applies the reverse-polarity current with an absolute value that is equal to or greater than the same-polarity current value, which is sufficient to remove toner effectively. This partial excessive action ensures complete toner removal in each cycle without needing to excessively increase the same-polarity current, thereby avoiding the harmful effects of air decomposition and ion generation that would occur with much higher current values.
Solution Approach 2:
By repeating the cycle of same-polarity and reverse-polarity current application multiple times, the patent achieves cumulative toner removal效果. Each cycle removes a portion of the toner, and the repetition ensures complete removal without requiring any single cycle to use excessively high currents that would cause discharge and ion generation.
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 apparatus achieves thorough toner removal from the secondary transfer roller, reducing staining and power consumption by strategically applying bias voltages to manage toner charge and movement between the transfer roller and intermediate transfer belt.
Implementation Method 1
The bias application device 506 sequentially applies to the transfer member 504 bias currents with different polarities from each other while the transfer member is not present at a transferred position
Implementation Method 2
the bias application device 506 applies a same-polarity current having the same polarity as toner constituting the toner image
Implementation Method 3
discharge occurs due to the same-polarity current. When air in the vicinity of the transfer member 504 is decomposed by the discharge, a same-polarity ion with the same polarity as the toner and a reverse-polarity ion with a reverse polarity to the toner are generated
Data Source
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AI summary
An image forming apparatus (1) having an image carrier (11; 4) that carries a toner image; an opposed member (14; 5; 18) that is provided so as to be opposed to the image carrier (11; 4); an application device (32; 5) that applies a bias to the opposed member (14; 5; 18); and a control device (30) that controls the application device (32; 5) to apply a first bias and thereafter a second bias to the opposed member (14; 5; 18) so as to remove toner from the opposed member (14; 5; 18). The first bias has an absolute value that is large enough to cause discharge from the opposed member (14; 5; 18) into air. The second bias has an absolute value that is too small to cause discharge from the opposed member (14; 5; 18) into the air, and has a reverse polarity to the first bias.