Electrophotographic Roller Crown Shape for Blot Adhesion
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Solution Overview
Problem
Electrophotographic rollers with a crown shape often experience blot adhesion in their end regions due to toner or external additives, especially in high-speed electrophotographic apparatuses.
Innovation Solution
The electrophotographic roller features a specific crown shape design where the diameter decreases from the central portion to both ends, with defined relationships between the distances and decrements in the longitudinal direction, and an elastic layer with enhanced elastic deformation power to prevent blot adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a crown shape is adopted for the charging roller to uniformize nip width, then the nip width uniformity is improved, but blot adhesion occurs in the end region
Solution Approach 1:
The patent applies local quality by differentiating the outer diameter profile into distinct regions: a central portion with larger diameter and end portions with smaller diameter. This non-uniform distribution creates different functional zones - the central region maintains adequate nip width for charging, while the reduced end portion diameter prevents blot adhesion by reducing contact area and pressure at the ends where blots typically form.
2Reliability
If the charging roller is pressed against the photosensitive member to apply predetermined force, then the charging effectiveness is improved, but blot adhesion increases in high-speed apparatuses
Solution Approach 1:
The patent changes the geometric parameter of the charging roller by reducing the outer diameter at the end portions relative to the central portion. This parameter modification allows the roller to maintain sufficient pressing force for effective charging in the central region while the reduced end diameter automatically decreases contact pressure and area at the ends, preventing blot adhesion without requiring adjustment of the overall pressing force.
Data Source
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AI summary
An electrophotographic roller includes: a mandrel and an elastic layer on the mandrel, and having a crown shape in which a diameter decreases from a central position O in a longitudinal direction of the mandrel toward an end portion. When a position of the end portion in the longitudinal direction of the elastic layer is defined as X2, a position between the O and the X2 is defined as X1, a distance between the O and the X1 is defined as LI, and a distance between the X1 and the X2 is defined as L2, L1 = 0.6×(L1+L2). When outer diameters of the electrophotographic roller at O, X1 and X2 are defined as Do, DX1 and DX2, respectively, and Z1 = (Do - DX1)/2 and Z2 = (DX1 - DX2)/2 are defined, Z 1, Z2, L1 and L2 satisfy (Z2/L2) < 1.931 × (Z1/L1).