Developing Roller Speed Control for Fog Suppression
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Solution Overview
Problem
In electrophotographic image forming apparatuses, the contact developing process leads to premature wear of the developing roller due to excessive friction and can result in a 'fog' phenomenon where toner is transferred to non-image areas, reducing image quality and shortening the life of the developing roller.
Innovation Solution
The electrophotographic image forming apparatus separates the photosensitive drum and developing roller during non-image formation and synchronizes their rotation speeds such that the developer feed roller rotates more revolutions than the developing roller before contact, ensuring adequate triboelectrification of toner and minimizing friction and wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the photosensitive drum and developing roller are kept in continuous contact during non-image formation, then the developing roller rotates more to triboelectrify toner, but this causes excessive friction and premature wear of the developing roller
Solution Approach 1:
The patent applies the dynamics principle by making the contact state between the photosensitive drum and developing roller changeable rather than fixed. The system dynamically switches between contact and separation states based on operational needs: contacting during image formation for proper toner application, and separating during non-image formation to reduce friction and wear, thereby extending developing roller life while maintaining image quality.
Solution Approach 2:
The patent implements periodic action by alternately contacting and separating the photosensitive drum and developing roller. During image formation, they contact periodically to apply toner; during non-image formation, they separate to minimize friction. This periodic contact-separation cycle optimizes both image quality and developing roller durability.
2Duration of action of stationary object
If the photosensitive drum and developing roller are separated during non-image formation, then friction and wear are reduced, but toner may not be sufficiently triboelectrified before contact
Solution Approach 1:
The patent applies preliminary action by ensuring that during the separated state, the developing roller completes a sufficient number of revolutions (greater than the photosensitive drum) to triboelectrify the toner before contact occurs. This preliminary rotation prepares the toner with adequate electrostatic charge, preventing fog phenomenon and ensuring high image quality when contact is restored.
3Reliability
If the developing roller rotates more revolutions to triboelectrify toner, then fog phenomenon is suppressed, but friction and wear increase
Solution Approach 1:
The patent uses preliminary action by having the developing roller rotate more than the photosensitive drum during the separated state to complete toner triboelectrification before contact. This ensures sufficient toner charging to suppress fog phenomenon and maintain image quality, while the subsequent contact-separation cycle minimizes overall friction and wear.
Solution Approach 2:
The patent converts the potentially harmful continuous contact into a beneficial periodic process. By separating during non-image formation, the system eliminates unnecessary friction and wear, while the increased revolutions during separation positively contribute to toner triboelectrification. This transforms what would be harmful continuous operation into a beneficial periodic contact-separation cycle.
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 suppresses the 'fog' phenomenon and extends the life of the developing roller by optimizing toner charging and reducing unnecessary revolutions, leading to improved image quality and reduced maintenance downtime.
Implementation Method 1
the developer feed member is brought into contact with the developer carrying member
Implementation Method 2
a number of revolutions of the developer feed member is larger than a number of revolutions of the developer carrying member, thereby a fog phenomenon which may occur immediately after contact of a photosensitive drum and a developing roller can be suppressed, and also shortening of a life of the developing roller due to revolutions for triboelectrification of toner can be suppressed
Data Source
AI summary
An electrophotographic image forming apparatus includes an electrophotographic photosensitive member configured to bear an electrostatic latent image, and a developer carrying member configured to develop the electrostatic latent image. The electrophotographic photosensitive member and the developer carrying member are separated from each other during non-image formation and brought into contact with each other after the electrophotographic photosensitive member and the developer carrying member start to be rotated. During a time period between a time when the electrophotographic photosensitive member and the developer carrying member start to be rotated and a time when the electrophotographic photosensitive member and the developer carrying member are brought into contact with each other, a number of revolutions of the developer feed member is larger than a number of revolutions of the developer carrying member.