Chamfered Guide Surface for Fixing Nip Charge Reduction
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Solution Overview
Problem
Existing fixing devices in image forming apparatuses face issues with irregularities in toner images due to electric charge accumulation at guide edges, leading to transfer process failures, and attempts to address this through conductive or non-conductive materials with added carbon increase costs and degrade moldability.
Innovation Solution
A guide with a chamfered downstream portion and guide surfaces parallel to the tangent line of the fixing and pressing rotators, reducing friction and charge accumulation, made from heat-resistant resin materials like liquid crystal polymer to maintain surface smoothness and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the guide edge contacts the recording medium to guide it to the fixing nip, then the recording medium is correctly guided, but electric charge accumulates at the guide edge causing toner image irregularities
Solution Approach 1:
The patent removes the problematic sharp edge from the guide by replacing it with a chamfered surface. The guide surface is formed with an inclined chamfer that eliminates the edge where charge accumulation occurs, while still maintaining the guiding function through the inclined surface geometry.
Solution Approach 2:
The guide surface is designed with different local properties: the chamfered portion has a specific inclination angle (e.g., 45 degrees) to reduce friction and prevent charge accumulation, while other portions of the guide maintain their original guiding geometry. This localized modification addresses the charge issue without compromising overall guiding accuracy.
2Object-generated harmful factors
If conductive or non-conductive materials with carbon are used to address charge accumulation, then charge issues are reduced, but costs increase and moldability degrades
Solution Approach 1:
Instead of using material additives to address charge accumulation, the patent converts the geometric design into the solution. The chamfered guide surface geometry itself prevents charge accumulation by eliminating the sharp edge, transforming a design feature into a functional solution that avoids material cost increases and moldability issues.
3Object-generated harmful factors
If the guide surface is chamfered to reduce friction and charge accumulation, then toner image quality improves, but manufacturing complexity increases
Solution Approach 1:
The patent modifies a single geometric parameter of the guide - the edge geometry - by introducing a chamfer with a specific inclination angle. This parameter change reduces friction and charge accumulation while maintaining the overall simplicity of the guide structure, avoiding significant increases in manufacturing complexity.
Data Source
AI summary
A fixing device includes a fixing rotator, a pressing rotator, and a guide. The pressing rotator forms a fixing nip with the fixing rotator. The guide guides a recording medium to the fixing nip. The guide includes a guide surface that contacts a surface of the recording medium against a guide the recording medium. The guide surface is provided parallel to a line tangent to the fixing rotator and the pressing rotator.