Process Cartridge Developing Roller Drive Using Oldham Coupling
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Solution Overview
Problem
Conventional electrophotographic image forming apparatuses face challenges in achieving high rotational accuracy of the developing roller due to the engagement complexities between the input gear, idler gear, and main assembly gear, which affects the image quality and requires additional space within the process cartridge.
Innovation Solution
The process cartridge employs an Oldham coupling mechanism that allows independent transmission of rotational driving force to the developing roller, simplifying the retraction mechanism and eliminating the need for a large guide for engagement, thereby improving the rotational accuracy and downsizing the cartridge and apparatus.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an input gear and idler gear are used to transmit rotational driving force to the developing roller, then the drive transmission can be achieved, but the rotational accuracy of the developing roller is influenced by engagement complexities and additional space is required
Solution Approach 1:
The patent removes the idler gear from the drive transmission system, directly engaging the input gear with the main assembly gear. This extraction of the intermediate component eliminates the engagement complexity and potential error accumulation that occurred with multiple gear interactions, thereby improving rotational accuracy while reducing the number of parts.
2Reliability
If an input gear and idler gear are used to transmit rotational driving force, then the drive transmission can be achieved, but additional space is required within the process cartridge
Solution Approach 1:
By removing the idler gear from the transmission path, the patent eliminates the space that would be required for this intermediate component. The direct engagement between the input gear and main assembly gear reduces the overall volume occupied by the drive mechanism within the process cartridge.
3Ease of operation
If a large guide is provided for engagement between the shaft coupling member and main assembly driving force transmitting member, then smooth engagement can be achieved, but the process cartridge and apparatus size increase
Solution Approach 1:
Instead of providing a large guide structure to enable engagement, the patent inverts the approach by designing the shaft coupling member with a spherical portion that can engage with the main assembly driving force transmitting member through a simpler, more compact mechanism. This inversion of the engagement design allows smooth operation without requiring excessive space.
Data Source
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Figure 3a~3b
AI summary
A process cartridge detachably mountable to a main assembly of the electrophotographic image forming apparatus, the main assembly including a first rotatable main assembly driving force transmission member, a second rotatable main assembly driving force transmission member, a main assembly positioning portion for positioning the cartridge, a movable member movable between a first position for permitting the cartridge to enter the main assembly in a longitudinal direction of the cartridge and a second position for urging the cartridge in a direction crossing and the longitudinal direction to position the cartridge to the main assembly positioning portion, and a main assembly locking member, the cartridge includes an photosensitive drum; a developing roller for developing a latent image formed on the drum with a developer; a drum coupling member, provided on one axial end of the drum, for engaging with the first main assembly drive transmission member and transmitting a first rotational driving force to the drum, when the cartridge is mounted to the main assembly; a shaft coupling member, provided on one axial end of the developing roller, for transmitting a second rotational driving force from the second main assembly driving force transmission member with a deviation permitted between an axis of the second main assembly drive transmission member and an axis of the developing roller, wherein the shaft coupling member includes an engaging portion for engaging with the second main assembly drive transmission member and receiving the second rotational driving force, when the cartridge is mounted to the main assembly; the engaging portion is movable in a direction crossing with the axial direction of the developing roller; when the cartridge enters the main assembly, the engaging portion is positioned to a holding portion provided in the cartridge; when the cartridge is moved by movement the movable member from the first position to the second position , the engaging portion is positioned to the main assembly locking member; and a distance between an axis of the engaging portion and an axis of the developing roller is smaller when the cartridge is positioned to the main assembly positioning portion than when the engaging portion is positioned by the holding portion.