Charging Roller Hardness Control for Toner Integrity
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Solution Overview
Problem
The contact charging type in cleaner-less image forming systems faces issues with toner crack and deformation due to high loads at the contact portion between the photosensitive drum and charging roller, leading to image defects and reduced toner flowability over time.
Innovation Solution
The system employs a charging roller with a Martens hardness lower than the toner, and a peripheral speed difference between the charging roller and photosensitive drum to alleviate load and prevent toner deposition, while controlling the Martens hardness of both the toner and charging roller to ensure stable image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a contact charging type is employed in a cleaner-less system, then the apparatus can be downsized and waste toner can be eliminated, but the toner is liable to cause crack and deformation due to high load at the contact portion between the photosensitive drum and charging roller
Solution Approach 1:
The patent applies parameter changes by precisely controlling the Martens hardness of the charging roller surface (HMR) and toner surface (HMD) to satisfy HMD > HMR. This hardness parameter relationship prevents the charging roller from excessively deforming the toner particles during contact charging, thereby eliminating toner cracks and deformation while maintaining the compact cleaner-less system configuration.
2Ease of operation
If the toner passes through the contact portion between the photosensitive drum and charging roller, then charging can be performed, but the irregular-shaped toner is not readily transferred and image defect is liable to cause
Solution Approach 1:
The patent changes the physical parameter of toner particle shape by ensuring high circularity (0.960 or more) and controlling the Martens hardness relationship (HMD > HMR). These parameter changes result in regularly shaped toner particles that are easily transferred from the photosensitive drum to the transfer sheet, preventing image defects while maintaining effective charging function.
3Stability of the object's composition
If the charging roller is press-contacted to the photosensitive drum, then uniform electric charge can be imparted, but the toner is liable to cause crack and deformation by crush between the photosensitive drum and charging roller
Solution Approach 1:
The patent applies parameter changes by controlling the Martens hardness of the charging roller surface (HMR) to be lower than the toner surface hardness (HMD). This hardness parameter relationship allows the charging roller to impart uniform electric charge through press contact while being soft enough to avoid crushing and deforming the toner particles, thus maintaining both charging uniformity and toner shape integrity.
4Loss of substance
If residual toner is collected and used again in the cleaner-less system, then waste toner can be eliminated, but with repetition of consumption and collection, an amount of irregular-shaped toner in the developing device increases
Solution Approach 1:
The patent applies parameter changes by ensuring the Martens hardness relationship HMD > HMR and maintaining high toner circularity (0.960 or more). These parameter changes prevent toner particle deformation during repeated charging and transfer cycles, ensuring that collected residual toner maintains its regular shape and flowability, thus enabling sustainable waste toner elimination in the cleaner-less system.
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 reduces toner crack and deformation, maintaining image quality and extending the lifespan of the toner by ensuring effective charging and transfer without contaminating the charging roller.
Implementation Method 1
a contact charging type in which a photosensitive drum is electrically charged uniformly in contact with the photosensitive drum
Implementation Method 2
a fog-removing bias (a fog-removing potential difference Vback which is a potential difference between a DC voltage applied to the developing device and a surface potential of the photosensitive drum)
Data Source
Figure 1
Figure 2
Figure 3(a)~3(b)
AI summary
An image forming apparatus includes: an image bearing member (1); a charging member (2) for electrically charging the image bearing member in contact with the image bearing member; and a developing member (31) for supplying developer in contact with the image bearing member. The developer (T) remaining on the image bearing member after transfer is collected by the developing member. A Martens hardness HMR of a surface of the charging member and a Martens hardness HMD of a surface of the developer satisfy the following relationship: HMD > HMR.