Developer Bearing Member Elastic Layer Roughness for Image Smearing
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Solution Overview
Problem
Conventional electrophotographic image forming apparatuses experience image smearing due to discharge products adhering to the image bearing member, especially in cleaner-less systems, which complicates maintenance and increases apparatus size and cost, particularly under high humidity conditions.
Innovation Solution
A developer bearing member with an elastic layer on its surface, where the load per unit area of contact is 5.8 N/mm² or more and the ten-point average roughness is greater than the volume-average particle diameter of the developer, is used to effectively scrape discharge products from the image bearing member, preventing image smearing without requiring a dedicated cleaning member.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If an inter-shaft regulating member is provided to lower the drum contact pressure, then the developing roller penetration level is regulated, but the force of the developing roller scraping discharge products weakens and image smearing occurs
Solution Approach 1:
The patent applies local quality by creating a specific rough surface structure on the developing roller at the contact portion with the image bearing member. The ten-point average roughness Rz is controlled to be 3.0 μm or more, which locally enhances the scraping capability at the contact interface while maintaining regulated overall contact pressure through the inter-shaft regulating member. This local surface modification enables effective discharge product removal without requiring excessive drum contact pressure.
2Reliability
If a cleaning member is provided to remove discharge products, then image smearing is suppressed, but apparatus size and cost increase
Solution Approach 1:
The patent makes the developing roller multi-functional by endowing it with both its primary development function and a secondary cleaning function. The rough surface structure (Rz ≥ 3.0 μm) on the developing roller enables it to scrape and remove discharge products from the image bearing member during the normal development process. This eliminates the need for a separate cleaning member, reducing apparatus complexity while maintaining image quality stability.
Solution Approach 2:
The developing roller performs self-service by using its own rough surface structure to remove discharge products during the development operation. The developing roller automatically cleans the image bearing member surface as it rotates and contacts the drum, without requiring external cleaning mechanisms or additional operational steps.
3Reliability
If the surface of the image bearing member is hard and smooth, then charge retention is good, but discharge products cannot be scraped off and image smearing occurs
Solution Approach 1:
The patent applies local quality by creating a specific rough surface structure on the developing roller at the contact portion with the image bearing member. The ten-point average roughness Rz is controlled to be 3.0 μm or more, which locally enhances the scraping capability at the contact interface while maintaining regulated overall contact pressure through the inter-shaft regulating member. This local surface modification enables effective discharge product removal without requiring excessive drum contact pressure.
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 stabilizes image quality by reducing image smearing occurrences while maintaining user convenience and avoiding the need for frequent cleaning operations, even in high humidity environments.
Implementation Method 1
the surface of the image bearing member has a low surface friction coefficient μ and is hard, it is hard to scrape the surface
Implementation Method 2
a load per unit area of a contact portion between one surface of a flat glass plate and the surface of the elastic layer is to be 5.8 N/mm2 or more
Data Source
AI summary
A developer bearing member including: a rotational shaft; and an elastic layer on an outer circumference surface of the rotational shaft, developer being borne on a surface of the elastic layer, wherein the elastic layer is configured such that a load per unit area of a contact portion between one surface of a flat glass plate and the surface of the elastic layer is to be 5.8 N/mm2 or more, in a state that the one surface of the flat glass plate being parallel with an axis direction of the rotational shaft and the one surface of the flat glass plate coming into contact with the surface of the elastic layer with a predetermined penetration level, and wherein a ten-point average roughness Rzjis on the surface of the elastic layer is greater than a volume-average particle diameter of a particle of the developer.