Intermediate Transfer Belt Test Patch Length for Toner Soiling Prevention
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Solution Overview
Problem
In electrophotographic image forming apparatuses using an intermediate transfer system, the common power supply for primary and secondary transfer currents leads to toner soiling of the secondary transfer member, causing voltage polarity issues and resulting in insufficient transfer and defective images due to high electrical resistance and toner adherence.
Innovation Solution
The apparatus includes a configuration with a plurality of image bearing members, developing units, an intermediate transfer medium, primary and secondary transfer units, a common transfer current supply, and a test patch forming and detecting system, where the test patch length is shorter than the distance between primary and secondary transfer portions to prevent toner adherence to the secondary transfer member.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a common power supply is used for primary and secondary transfer currents, then cost and size are reduced, but toner soiling of the secondary transfer member occurs causing insufficient transfer and defective images
Solution Approach 1:
The patent segments the transfer process by introducing an intermediate transfer belt that separates primary transfer (from photoconductive drum to intermediate belt) and secondary transfer (from intermediate belt to recording material). This segmentation allows independent control of transfer currents and prevents toner soiling of the secondary transfer member by ensuring toner is fully transferred before reaching the secondary transfer portion.
2Measurement precision
If test patch length equals intermediate transfer member length, then complete color density detection is achieved, but toner adheres to secondary transfer member causing soiling
Solution Approach 1:
The patent applies partial action by forming test patches only in specific regions (non-secondary transfer regions) of the intermediate transfer member rather than across the entire surface. This allows sufficient color density detection in the required areas while avoiding toner adherence problems in the secondary transfer region.
Solution Approach 2:
The patent applies local quality by creating different functional zones on the intermediate transfer member: regions where test patches are formed for color density detection, and regions (secondary transfer portions) where no test patches are formed to prevent toner soiling. Each region has optimized properties for its specific function.
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 effectively prevents toner soiling of the secondary transfer member, ensuring reliable current supply and preventing defective images by maintaining the desired voltage polarity during transfer operations.
Implementation Method 1
a primary transfer current for performing primary transfer and a secondary transfer current for performing secondary transfer are supplied from a common power supply... applying a current from a secondary transfer portion to an intermediate transfer belt in a circumferential direction thereof
Implementation Method 2
with a tension roller of the intermediate transfer belt being grounded via a Zener diode or a varistor
Data Source
AI summary
Test patches are formed such that lengths of the test patches in a rotational direction of the intermediate transfer member are shorter than a length of the intermediate transfer member from a primary transfer portion located in the lowermost stream among the plurality of primary transfer portions to the secondary transfer portion.