Image Forming Apparatus Humidity-Resistant Sheet Separation
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Solution Overview
Problem
The image forming apparatus faces instability in transfer medium conveyance due to humidity-induced changes in electrical resistance, leading to electrostatic adhesion issues between the transfer medium and guide components, which affects separation from the image bearing member and conveyance stability.
Innovation Solution
The apparatus incorporates a rotatable image bearing member and a transfer member with an electrostatic transfer mechanism, along with a fixing unit, a first current path between the fixing nip and ground, a feeding unit, and a second current path with lower electrical resistance between the feeding nip and ground, to control the potential level of the transfer medium and stabilize conveyance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the sheet of transfer medium absorbs humidity, then it reduces in electrical resistance, but it becomes electrostatically adhered to the sheet discharge guide
Solution Approach 1:
The patent applies equipotentiality by grounding the sheet discharge guide through a low electrical resistance path, making it equipotential with the humidified sheet. This eliminates the potential difference that causes electrostatic adhesion, allowing the sheet to be discharged smoothly without sticking to the guide components.
Solution Approach 2:
The patent changes the electrical resistance parameter of the sheet discharge guide by providing a grounding path with lower electrical resistance than the sheet itself. This parameter change ensures that when the sheet absorbs humidity and its resistance decreases, the guide remains at ground potential, preventing electrostatic adhesion.
2Object-affected harmful factors
If a component is placed on the upstream side of the sheet discharge guide to reduce sheet potential, then electrostatic adhesion to the guide is prevented, but separation from the image bearing member becomes unsatisfactory
Solution Approach 1:
The patent segments the grounding function into two distinct locations: one grounding path at the sheet discharge guide (downstream) and another at the image bearing member (upstream). This segmentation allows the downstream guide to be grounded for discharge stability while the upstream image bearing member maintains its charging function for effective sheet separation.
Solution Approach 2:
The patent applies local quality by providing different electrical characteristics at different locations: the sheet discharge guide is grounded through low resistance to prevent adhesion, while the image bearing member is charged to high potential to enable separation. Each location has the electrical property optimized for its specific function.
3Object-affected harmful factors
If the sheet of transfer medium is reduced in electrical potential, then adhesion to the sheet discharge guide is prevented, but the flat component's ability to separate the sheet reduces
Solution Approach 1:
The patent makes the sheet discharge guide equipotential with ground through grounding, so there is no potential difference between the guide and the sheet. This eliminates electrostatic adhesion without affecting the potential difference between the charged image bearing member and the sheet, preserving the separation force.
Solution Approach 2:
The patent segments the electrical potential management into two zones: the image bearing member zone maintains high potential for separation, while the sheet discharge guide zone is grounded to prevent adhesion. This segmentation allows both functions to operate simultaneously without interference.
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 ensures reliable separation of the transfer medium from the image bearing member and stable conveyance by managing the potential level, reducing friction and adhesion issues, thereby maintaining apparatus stability even with high-humidity transfer media.
Implementation Method 1
a transfer member configured to contact said image bearing member to form a transfer nip, said transfer member being capable of electrostatically transferring the toner image from said image bearing member onto a recording material using an electric field applied to said transfer portion
Implementation Method 2
applies heat and pressure to the toner image with the use of their fixing device to fix the toner image to the sheet of transfer medium
Implementation Method 3
If transfer medium is left unattended in an environment which is high in humidity for a substantial length of time, the transfer medium absorbs a substantial amount of humidity
Implementation Method 4
a first current path provided between said fixing nip and a ground potential; and a second current path provided between said feeding nip and the ground potential
Data Source
AI summary
An image forming apparatus comprises a drum for carrying a toner image; a transfer member for contacting the drum to form a transfer nip, the transfer member being capable of electrostatically transferring the toner image from the drum onto a sheet; a fixing unit provided, downstream of the transfer member with respect to a sheet feeding direction, for fixing the toner image on the sheet by a fixing nip; a first current path provided between the fixing nip and a ground potential; a feeding unit, provided downstream of the fixing unit, for feeding the sheet while nipping by a feeding nip; a guiding member, disposed downstream of the feeding unit, for feeding the sheet passing through the transfer nip; and a second current path provided between the feeding nip and the ground potential, the second path having an electric resistance which is lower than that of the first path.