Oldham Coupling Stabilizes Drum Speed in Laser Printers
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Solution Overview
Problem
The rotational speed of a photosensitive drum in image forming apparatuses, such as laser printers, can vary due to meshing conditions with the cleaning gear, leading to uneven image density and banding patterns.
Innovation Solution
An Oldham's coupling mechanism is employed, featuring a driving-force transmitting member, a driven member with a flange and engaging projections, and a rotational-member driving gear with a loose fit portion, which allows for stable transmission of driving force to the photosensitive drum, preventing variations in rotational speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the drum gear meshes with the cleaning gear to transmit driving force, then the cleaning roller can be rotated, but the rotation speed of the photosensitive drum varies due to meshing conditions causing banding
Solution Approach 1:
A speed stabilizing gear is introduced as an intermediary component between the drum gear and the cleaning gear. This mediator gear receives rotational motion from the drum gear and transmits it to the cleaning gear, isolating the photosensitive drum from speed variations caused by meshing conditions. The stabilizing gear acts as a buffer that maintains constant rotational speed for the photosensitive drum while still enabling power transmission to the cleaning roller.
2Ease of manufacture
If the cleaning roller is rotated by meshing with the drum gear, then the cleaning function is achieved, but uneven image density and banding patterns occur
Solution Approach 1:
The speed stabilizing gear serves as a mediator that decouples the cleaning function from the photosensitive drum's rotational speed stability. By introducing this intermediate gear, the system maintains the simple meshing-based cleaning mechanism while preventing the transmission of speed variations to the photosensitive drum, thereby ensuring uniform image density without compromising the ease of cleaning mechanism implementation.
Data Source
AI summary
An image forming apparatus is provided that may include a photosensitive drum configured to rotate around an axis and a first rotational member disposed proximate a periphery of the photosensitive drum and configured to rotate about an axis parallel to the rotational axis of the photosensitive drum. The image forming apparatus may also include a driving-force transmitting member and a driven member, which includes a transmitted portion and a first engaging projection. The driven member may rotate about the rotational axis of the photosensitive drum together with the photosensitive drum and the transmitted portion of the driven member may receive a driving force transmitted from the driving-force transmitting member. The image forming apparatus may also include a rotational-member driving gear which has a loose fit portion configured to engage with the first engaging projection and a transmission gear portion configured to transmit the driving force to the first rotational member.