Curved Developing Blade Radius for Toner Pressure Control
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Solution Overview
Problem
Existing developing devices in electrophotographic image forming apparatuses face challenges in maintaining effective contact pressure between the developing blade and the developing roller, leading to improper toner regulation due to dispersed contact pressure and uneven surface formation, which results in toner fusion and deposition issues.
Innovation Solution
A developing device with a regulating member having a curved surface portion that contacts the developer carrying member, where the Martens hardness of the toner is between 200 MPa and 1100 MPa, and the radius of curvature of the curved surface portion is between 0.08 mm and 0.3 mm, ensuring optimal contact pressure and preventing toner fusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the radius of curvature of the bent portion of the developing blade is increased, then the contact area between the developing blade and the developing roller expands, but the contact pressure disperses and decreases, leading to improper toner regulation
Solution Approach 1:
The patent applies parameter changes by precisely controlling the radius of curvature of the bent portion within a specific range (0.05mm to 0.5mm) and the blade thickness (0.03mm to 0.1mm). This optimization ensures that the contact area is sufficient for stable contact while maintaining high contact pressure for effective toner regulation, resolving the contradiction between expanding contact area and maintaining contact pressure.
2Length of moving object
If the radius of curvature of the bent portion is decreased, then the outer periphery side is extended, but uneven shapes (cracks) occur on the surface of the developing blade, causing toner deposition and fusion
Solution Approach 1:
The patent resolves this contradiction by establishing a lower limit for the radius of curvature (0.05mm to 0.5mm) that prevents surface unevenness and cracks while still extending the blade sufficiently. This parameter optimization ensures both adequate blade length for contact and maintenance of surface uniformity to prevent toner deposition.
Solution Approach 2:
The patent applies local quality by making the bent portion have different structural characteristics from the rest of the blade. The bent portion is specifically designed with controlled curvature and thickness to achieve both extension and surface uniformity, while the straight portion maintains overall blade integrity and prevents crack formation.
3Strength
If the developing blade is made with lower hardness material, then toner is more liable to be deposited on the blade, but higher hardness may cause blade damage
Solution Approach 1:
The patent resolves this contradiction by optimizing the blade thickness parameter (0.03mm to 0.1mm) and the curvature radius, which together determine the contact pressure distribution. This parameter optimization allows the use of materials with appropriate hardness that are durable enough to prevent damage while having sufficient friction characteristics to prevent toner deposition.
Data Source
AI summary
A developing device includes a developer carrying member, a developing frame, and a regulating member. The regulating member includes a curved surface portion contactable to a surface of the developer carrying member, and satisfies the following relationships: 200 MPa≤HM≤1100 MPa, and 0.08 mm≤Rb≤0.3 mm, where HM is a Martens hardness of toner contained in the developer under a maximum load of 2.0×10−4 N, and Rb is a radius of curvature of the curved surface portion.