Photosensitive Drum Positioning in Process Cartridge
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Solution Overview
Problem
In color laser printers, the positioning of photosensitive drums relative to the body casing is not directly stabilized due to the influence of housing tolerances, leading to potential instability in the image forming process.
Innovation Solution
A process cartridge design where the photosensitive drum is supported by both axial bearings, allowing it to be directly positioned within the image forming apparatus body, with a driving force input mechanism and bias supply system that ensures the drum and housing are movable and stable relative to each other, and the cartridge is positioned within the body casing using parallel pressing forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the photosensitive drum is positioned through the housing of the drum unit, then the drum unit can be removably mounted, but the positioning stability is degraded due to housing tolerance accumulation
Solution Approach 1:
The patent extracts the positioning function from the housing and transfers it to the drum shaft itself. The drum shaft is equipped with positioning protrusions that directly engage with positioning recesses in the body casing, eliminating the intermediate housing link that caused tolerance accumulation. This allows the drum unit to remain removable while achieving direct and stable positioning.
Solution Approach 2:
The patent introduces positioning protrusions and recesses as intermediary elements between the drum shaft and the body casing. These specialized positioning features act as mediators that directly establish the positional relationship, bypassing the housing's indirect positioning role and eliminating the compound tolerance effect.
2Speed
If the drum shaft is freely rotatable on fixed shafts, then the drum can rotate without friction, but the thrust causes positioning instability
Solution Approach 1:
The patent transforms the static fixed shaft arrangement into a dynamic adjustable bearing system. The bearing members can move axially and radially within the drum shaft, allowing the system to dynamically adapt to thrust forces while maintaining positioning stability. This dynamic capability enables the drum to rotate freely while the bearing members absorb and distribute mechanical stresses.
Solution Approach 2:
The patent changes the mechanical parameters of the support system by replacing fixed shafts with adjustable bearings that have specific clearance ranges. The bearing members are designed with predetermined clearance and adjustment mechanisms that allow them to move within specific parameter ranges, optimizing both rotation freedom and positioning stability under varying operational conditions.
3Manufacturing precision
If the bearing members are tightly fixed, then the positioning precision is improved, but the rotation freedom is reduced
Solution Approach 1:
The patent employs dynamically adjustable bearings that can adapt their clearance characteristics during operation. The bearing members are designed to move within controlled ranges, allowing the system to optimize the balance between positioning precision and rotation freedom based on actual operational requirements rather than being fixed during manufacturing.
Solution Approach 2:
The patent implements bearings with adjustable clearance parameters that can be modified during assembly or operation. By controlling the clearance ranges of the bearing members, the system achieves positioning precision when needed while maintaining rotation freedom during normal operation, effectively decoupling these two parameters that would traditionally be mutually exclusive.
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
An image forming apparatus includes an image forming apparatus body including a driving force transmitting portion and a process cartridge. The process cartridge includes a housing, a photosensitive drum disposed in the housing, a first bearing rotatably supporting an axial end portion of the photosensitive drum, a driving force input portion, which is provided on the axial end portion of the photosensitive drum and is configured to engage the driving force transmitting portion in order to drive the photosensitive drum by a driving force transmitted from the driving force transmitting portion when the driving force transmitting portion is pressed against the driving force input portion, and a second bearing, which rotatably supports the other axial end of the photosensitive drum, and which comprises a first contact portion which contacts the image forming apparatus body when the driving force transmitting portion is pressed against the driving force input portion.