Charging Roller Pitch Design for Uniform Image Formation
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Solution Overview
Problem
In image forming apparatuses using cleaner-less systems, uneven charging of the image bearing member occurs due to post-black fogging, which leads to defective charging and soiling of the charging roller, affecting the uniformity of the charging process and the quality of the printed images.
Innovation Solution
The solution involves configuring the image forming apparatus such that the developing roller pitch and charging roller pitch are made equal or the charging roller pitch is longer than the developing roller pitch, ensuring that post-black fogging toner is not continuously adhered to the charging roller, thereby preventing uneven charging by adjusting the circumferential velocities and pitches of the rollers to inhibit toner adhesion and facilitate uniform charging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the charging roller continuously contacts the image bearing member to charge it, then charging efficiency is improved, but post-black fogging toner adheres to the charging roller causing uneven charging
Solution Approach 1:
The patent applies periodic action by creating a cyclic pattern of toner adhesion and removal on the charging roller. The roller pitch is designed to be longer than the developing roller pitch, causing toner to adhere during certain rotation periods and be removed in subsequent periods when fresh surfaces contact the image bearing member. This periodic renewal prevents continuous adhesion and maintains charging uniformity.
Solution Approach 2:
The patent changes the geometric parameters of the system, specifically setting the charging roller pitch to be longer than the developing roller pitch. This parameter change alters the interaction pattern between the rollers, creating conditions where post-black fogging toner is not continuously adhered to the charging roller surface, thereby preventing uneven charging while maintaining charging efficiency.
2Productivity
If the circumferential velocity of the charging roller is increased to improve charging speed, then productivity is improved, but toner adhesion to the charging roller increases causing defective charging
Solution Approach 1:
By designing the charging roller pitch to be longer than the developing roller pitch, the system creates periodic cycles where toner adheres to the charging roller during high-speed rotation and is subsequently removed when the roller surface renews its contact with the image bearing member. This periodic action prevents continuous toner buildup even at increased charging speeds.
Solution Approach 2:
The patent introduces asymmetry in the pitch lengths of the charging roller and developing roller. This asymmetric design creates a mismatch in their rotational patterns, ensuring that the charging roller surface is periodically renewed and does not continuously accumulate toner, thereby reducing toner adhesion problems while maintaining high charging speed.
3Object-generated harmful factors
If a cleaner-less system is used to eliminate waste toner, then environmental performance is improved, but post-black fogging occurs causing uneven charging
Solution Approach 1:
In the cleaner-less system, the periodic action principle ensures that while untransferred toner is retained and reused, post-black fogging toner is periodically removed from the charging roller through surface renewal. The charging roller pitch being longer than the developing roller pitch creates cycles where toner is adhered and then removed, preventing continuous accumulation and maintaining charging uniformity without requiring a cleaner.
Solution Approach 2:
The patent changes the operational parameters by setting specific pitch relationships between rollers in the cleaner-less system. By making the charging roller pitch longer than the developing roller pitch, the system achieves automatic periodic removal of post-black fogging toner, resolving the contradiction between waste elimination and charging uniformity.
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 effectively reduces uneven charging and prevents post-black fogging, ensuring consistent and uniform charging of the image bearing member, thereby improving the quality and reliability of the image forming process.
Implementation Method 1
a contact DC charging system, in which the surface of the photosensitive drum is uniformly charged to inhibit the generation of ozone by allowing an electrically conductive charging apparatus to make direct contact instead of a corona charging device
Implementation Method 2
untransferred toner on the photosensitive drum following the transfer step can be collected and reused as a result of carrying out so-called 'simultaneous development and cleaning'. Simultaneous development and cleaning is carried out by collecting untransferred toner on the photosensitive drum following the transfer step with a fog removal bias (fog removal potential difference Vback, which is potential difference between direct current voltage applied to the developing apparatus and surface potential of the photosensitive drum)
Implementation Method 3
A regulating blade arranged in contact with the developing roller imparts a charge to the toner due to triboelectric charging between the regulating blade and the developing roller
Data Source
Figure 1
Figure 2
Figure 3A~3F
AI summary
When the outer diameter of a charging member (3) is defined as Hc, the ratio of the circumferential velocity of the charging member to the circumferential velocity of an image bearing member (1) is defined as Rc, the outer diameter of a developer bearing member (9) is defined as Hd, and the ratio of the circumferential velocity of the developer bearing member to the circumferential velocity of the image bearing member is defined as Rd, the relationship Hc/Rc ≥ Hd/Rd is satisfied.