Crown-Shaped Developing Roller with Modulus-Controlled Elastic Layer
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Solution Overview
Problem
Developing rollers with a single layer of diene-based rubber and a crown shape experience density unevenness on electrophotographic images when used for a long period under low-temperature and low-humidity conditions due to variations in electric resistance and strain along the axial direction, leading to uneven nip width and inconsistent toner development.
Innovation Solution
The developing roller is designed with an elastic layer having a thickness of 0.30 mm or more, specific elastic moduli at defined positions, and a surface treatment to increase the elastic modulus of the outermost surface to 500 MPa or more, ensuring uniform nip width and consistent toner application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a single layer elastic layer containing diene-based rubber is used in the developing roller, then the impact resilience is improved, but density unevenness occurs on electrophotographic images when used for a long period under low-temperature and low-humidity conditions
Solution Approach 1:
The elastic layer is divided into multiple layers with different material compositions and properties. The first elastic layer contains diene-based rubber for impact resilience, while the second elastic layer contains polymeric material with specific glass transition temperature to maintain dimensional stability. This segmentation allows each layer to perform its specific function without interfering with the other's performance.
Solution Approach 2:
The patent uses a composite structure combining diene-based rubber and polymeric material in a multi-layer configuration. The diene-based rubber provides elasticity and impact absorption, while the polymeric material with controlled glass transition temperature provides dimensional stability and resistance to environmental conditions, creating a composite material system that achieves both impact resilience and long-term reliability.
2Shape
If the developing roller is formed into a crown shape to compensate for bending, then the nip width uniformity is improved, but the elastic layer still experiences strain variations along the axial direction under low-temperature and low-humidity conditions
Solution Approach 1:
The patent applies local quality by creating regions with different material properties within the elastic layer. The first elastic layer with diene-based rubber provides local elasticity where needed, while the second elastic layer with polymeric material provides local dimensional stability. This local differentiation of material properties allows the structure to maintain both nip width uniformity and strain consistency under varying environmental conditions.
3Productivity
If the developing roller is used for forming electrophotographic images on a large number of sheets, then the productivity is improved, but density unevenness occurs due to variations in electric resistance and strain
Solution Approach 1:
The patent implements preliminary action by pre-configuring the multi-layer elastic structure with specific material properties and thickness ratios before use. The glass transition temperature of the polymeric material is specifically selected to ensure dimensional stability under the operating conditions. This preliminary design prevents density unevenness from developing during extended use, allowing high productivity without sacrificing image quality consistency.
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
The solution stabilizes high-quality electrophotographic image formation over extended periods by suppressing density unevenness and resistance variations, even under low-temperature and low-humidity environments, by maintaining uniform electric resistance and nip width.
Implementation Method 1
the elastic layer having a thickness of 0.30 mm or more, specific elastic moduli at defined positions, and a surface treatment to increase the elastic modulus of the outermost surface to 500 MPa or more, ensuring uniform nip width
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
Provided is a developing roller comprising an electroconductive substrate and an electroconductive elastic layer constituted by a single layer on an outer periphery of the substrate. The elastic layer contains a diene-based rubber, has a thickness of 0.30 mm or more, and the elastic layer has a crown shape in which an outer diameter of a center portion in a longitudinal direction along an axis of the substrate is larger than an outer diameter of each of both end portions in the longitudinal direction. Elastic moduli E11, E12 and E13 in a first region of the elastic layer in cross-sections at positions P1, P2 and P3 of the elastic layer are each 500 MPa or more.