Image Forming Apparatus Voltage Polarity Control
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Solution Overview
Problem
In electrophotographic image forming apparatuses, it is challenging to independently control the potential polarity of the primary and secondary transfer portions, especially when the secondary transfer portion's current is used for both transfers, leading to potential toner adhesion issues on recording materials.
Innovation Solution
An image forming apparatus with a control unit that changes the voltage polarity applied to the secondary transfer member to control the intermediate transfer member's potential polarity, applying different voltages in distinct steps and using a detection device to synchronize with the recording material's position for precise timing of voltage switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the potential polarity of the primary transfer portion is controlled by voltage applied to the secondary transfer member, then the secondary transfer portion can be used for both transfers, but the primary transfer portion cannot independently control its potential polarity
Solution Approach 1:
The patent divides the voltage control into two independent segments: a first voltage applied to the secondary transfer member for secondary transfer, and a second voltage applied to the intermediate transfer member for primary transfer. This segmentation allows each transfer portion to be controlled independently despite sharing a common power supply structure, resolving the contradiction between simplified device configuration and independent control capability.
2Adaptability or versatility
If the voltage polarity is switched for toner ejection processing, then the primary transfer portion can perform adjustment processing, but toner may adhere to the recording material passing through the secondary transfer portion
Solution Approach 1:
The patent applies the second voltage to the intermediate transfer member in advance before the toner ejection processing begins. This preliminary action ensures that the primary transfer portion is already prepared with the correct potential polarity to receive toner for ejection processing, while the secondary transfer portion maintains its own voltage control to prevent toner adhesion to recording material.
Solution Approach 2:
The intermediate transfer member acts as an intermediary between the primary transfer portion and the secondary transfer portion. By applying voltage to the intermediate transfer member independently, the patent creates a mediator that can be controlled separately from the secondary transfer member, allowing toner ejection processing without affecting the secondary transfer process or causing toner adhesion to recording material.
3Ease of operation
If the image forming apparatus interrupts image formation for toner ejection processing, then the primary transfer portion can be controlled independently, but the process time increases
Solution Approach 1:
The patent enables continuous independent control of both transfer portions without interrupting image formation. By applying voltages to both the secondary transfer member and intermediate transfer member simultaneously and independently, the system maintains continuous useful action in both primary and secondary transfer processes, eliminating the need to interrupt image formation for toner ejection processing and thus reducing process time.
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 approach reduces process time and minimizes the influence on secondary transfer by allowing independent control of primary and secondary transfer portions, preventing toner contamination and ensuring efficient image formation.
Implementation Method 1
the control unit changes polarity of a potential of the intermediate transfer member in the primary transfer portion by changing polarity of the voltage to be applied to the secondary transfer member
Implementation Method 2
a detection device that detects the presence/absence of a recording material at a first position which is upstream of the secondary transfer portion on a conveyance path of the recording material
Implementation Method 3
an intermediate transfer member onto which the toner image is primarily transferred from the image bearing member in a primary transfer portion that contacts the image bearing member
Implementation Method 4
a secondary transfer member that constitutes, together with the intermediate transfer member, a secondary transfer portion, and secondarily transfers the toner image from the intermediate transfer member to a recording material in the secondary transfer portion
Data Source
AI summary
A control unit changes the polarity of a potential of an intermediate transfer member in a primary transfer portion by changing the polarity of voltage to be applied to a secondary transfer member, and applies first voltage in a first step of forming an image on a recording material by transferring a toner image. A detection device detects the presence/absence of the recording material at a timing when a rear end of the toner image reaches a second position which is upstream of a secondary transfer portion on a conveyance path of the toner image. The control unit determines a timing to switch the voltage to be applied to the secondary transfer member from the first voltage to second voltage having polarity opposite to that of the first voltage, based on the detection result by the detection device.