Image Forming Apparatus Nip Voltage Control
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Solution Overview
Problem
Image forming apparatuses using direct transfer methods often experience abnormal discharge and defective images due to uneven potential differences between photosensitive and transfer members, especially when recording materials are caught between them, leading to voids and discontinuous discharge.
Innovation Solution
An image forming apparatus with a control unit that manages charging and transfer voltages to prevent abnormal discharge by applying specific voltage levels before and during the transfer process, ensuring a controlled potential difference across the nip portion, including a first, second, and third voltage level for the charging and transfer members.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a high transfer bias is applied to transfer the toner image onto the recording material, then the transfer efficiency is improved, but abnormal discharge occurs when a void is formed between the photosensitive member, transfer member, and recording material
Solution Approach 1:
The patent applies a preliminary bias (first bias) to the transfer member before the recording material enters the nip portion, and uses a different bias (second bias) when the recording material is present. This preliminary action prepares the electrical conditions to prevent abnormal discharge while maintaining transfer efficiency, resolving the contradiction between high transfer bias and abnormal discharge prevention
2Object-affected harmful factors
If the transfer bias is reduced to prevent abnormal discharge when no recording material is present, then abnormal discharge is prevented, but the transfer efficiency decreases
Solution Approach 1:
The patent dynamically adjusts the transfer bias based on the presence or absence of recording material in the nip portion. By switching between first bias (when no material is present) and second bias (when material is present), the system optimizes both abnormal discharge prevention and transfer efficiency, resolving the contradiction between these two requirements
3Ease of operation
If a recording material enters the nip portion and forms a void due to material thickness, then the recording material is caught between the photosensitive member and transfer member, but discontinuous discharge occurs in the void causing uneven potential on the photosensitive member surface
Solution Approach 1:
The patent applies different bias conditions to different regions and times: using first bias when no material is present and second bias when material is present. This local differentiation in electrical conditions prevents abnormal discharge in void regions while maintaining uniform potential distribution, resolving the contradiction between material conveyance and potential uniformity
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
Prevents defective images by maintaining a stable potential difference, reducing unevenness and abnormal discharge, thereby improving image quality by ensuring uniform toner transfer and surface potential leveling.
Implementation Method 1
a charging member (2) configured to charge a surface of the image bearing member (1)... a charging voltage applying unit (23) configured to apply charging voltage to the charging member (2)
Implementation Method 2
a transfer member (5) configured to transfer a toner image formed on the surface of the image bearing member (1) onto a recording material... a transfer voltage applying unit (53) configured to apply transfer voltage to the transfer member (5)... based on a potential difference occurring between a photosensitive member and a transfer member
Data Source
AI summary
A nip portion is formed between a transfer member and an image bearing member. During an image transfer operation, a first transfer voltage is applied so that a first charging voltage is applied to the surface of the image bearing member forming the nip portion. Before paper enters, a second transfer voltage is applied so that a third charging voltage is applied to the surface of the image bearing member forming the nip portion. A void is formed by the image bearing member, the transfer member and the paper within the nip portion. Before an image transfer operation and the void is formed, one of the first and second transfer voltages and a third transfer voltage is applied so that a second charging voltage having a same polarity as the first charging voltage and being lower in absolute value is applied to the surface of the image bearing member.