Non-linear Element Guide Unit for Humidity-Resistant Toner Transfer
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Solution Overview
Problem
Conventional image forming apparatuses with grounded metal guide plates experience transfer defects due to reduced sheet resistance in humid environments, leading to inadequate toner transfer and sheet transport issues.
Innovation Solution
An image forming apparatus with a guide unit comprising an electrically conducting guide plate, an insulating support member, a conducting connecting member, and a non-linear element, such as a varistor or Zener diode, which reduces resistance when a predetermined voltage is applied, preventing transfer current flow and charging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a grounded metal guide plate is used to prevent charging of the guide plate, then the guide plate can be kept electrically neutral, but in highly humid environments the resistance value of the sheet is reduced and transfer current can flow to the guide plate through the sheet, causing transfer defects
Solution Approach 1:
A non-linear element (varistor or Zener diode) is introduced as an intermediary component between the guide plate and ground. This element has high resistance under normal conditions, preventing transfer current flow, but reduces resistance when voltage exceeds a predetermined value to dissipate excessive charge, thus mediating between charge prevention and current flow suppression
Solution Approach 2:
The electrical resistance parameter of the connection between guide plate and ground is made variable through the non-linear element. The resistance dynamically changes based on voltage conditions - maintaining high resistance during normal operation to prevent current flow, and reducing resistance when voltage exceeds thresholds to dissipate charge, thereby adapting to different environmental conditions
2Object-generated harmful factors
If a resin guide plate is used, then the guide plate can be electrically insulating, but it becomes charged as a result of friction with the sheets, and if dust adheres to the guide plate, defective sheet transport or defective toner transfer can be caused
Solution Approach 1:
The guide plate structure is divided into different functional zones: the guide plate surface itself remains electrically insulating (resin material) to prevent dust adhesion and friction charging, while the connection point to ground through the non-linear element provides selective charge dissipation. This local differentiation allows the insulating surface to prevent dust accumulation while the grounded connection manages electrical charge
Solution Approach 2:
The guide unit combines multiple materials with different electrical properties: an electrically insulating guide plate (resin) for dust prevention, an electrically conducting connecting member for charge management, and a non-linear element (varistor/Zener diode) with voltage-dependent resistance. This composite structure integrates the advantages of both insulating and conducting materials
Data Source
AI summary
A guide unit 24 includes an electrically conducting guide plate 25 disposed upstream of the transfer unit 20 that transports toner image transfer sheets between the image carrier 7 and the transfer unit 20, an electrically insulating support member 26 that supports the guide plate 25, an electrically conducting connecting member 30 installed on the support member 26, electrically connected to a ground plate 33, and a non-linear element 31 directly or indirectly electrically connected between the guide plate 25 and the connecting member 30. Further, if a voltage equal to or greater than a predetermined value is applied between the guide plate 25 and the connecting member 30, the resistance value is reduced.