Gear Shaft Alignment via Asymmetric Projection for Roller Driving
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Solution Overview
Problem
In electrophotographic image forming apparatuses, increased rotational variations of process units like developing rollers and toner supply rollers lead to image unevenness at intervals of roller rotation.
Innovation Solution
A roller driving apparatus with a gear fixed to the shaft of the roller, featuring a hole for press-fitting the shaft, and an inner peripheral surface with projections that deform to secure the shaft, ensuring alignment of the gear center with the shaft center to minimize rotational variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional gear-shaft connection is used, then the structure is simple, but rotational variations increase causing image unevenness
Solution Approach 1:
The gear hole is designed with an asymmetric structure featuring a projection that extends in the radial direction, causing the gear center to be positioned offset from the hole center. This asymmetric design ensures that when the shaft is press-fit into the hole, the gear center automatically aligns with the shaft center, thereby reducing rotational variations and improving rotational stability without requiring high manufacturing precision for alignment.
Solution Approach 2:
The invention changes the geometric parameters of the gear hole by introducing a projection with specific dimensional constraints (length L1 between 5-50 μm, width L2 between 5-30 μm). These parameter changes create a mechanical feature that guides the shaft during press-fit, automatically achieving center alignment and reducing rotational variations while maintaining manufacturing feasibility.
2Reliability
If the gear center is offset from the hole center, then rotational variations are reduced, but manufacturing complexity increases
Solution Approach 1:
The gear hole incorporates a projection that extends radially inward from the hole's inner peripheral surface. This asymmetric feature creates an offset between the hole center and the gear center, which automatically aligns the gear with the shaft during press-fit. The asymmetric design achieves rotational stability while adding only minimal structural complexity to the gear.
Solution Approach 2:
The projection is localized to a specific region of the gear hole's inner peripheral surface, concentrating the alignment function in a small area. This local quality approach ensures that the offset alignment is achieved through a focused geometric feature rather than requiring complex overall gear redesign, thus maintaining low device complexity while improving rotational stability.
3Manufacturing precision
If press-fit connection is used with projections, then alignment precision is improved, but assembly force increases
Solution Approach 1:
The projection extends radially inward from the hole's inner peripheral surface, creating an asymmetric geometry that guides the shaft into proper alignment during press-fit. This asymmetric feature achieves precise alignment through the mechanical interaction between the projection and shaft, while the controlled projection dimensions (L1: 5-50 μm, L2: 5-30 μm) ensure that the assembly force required is manageable and does not exceed material limits.
Solution Approach 2:
By carefully controlling the dimensions of the projection (length L1 between 5-50 μm, width L2 between 5-30 μm), the invention optimizes the balance between alignment precision and assembly force. These parameter changes ensure that the projection provides sufficient guidance for precise alignment while requiring only moderate press-fit force, avoiding excessive assembly forces that could damage the components.
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
The solution effectively reduces rotational variations of the rollers, preventing image unevenness and ensuring consistent image quality in electrophotographic image forming processes.
Implementation Method 1
the first end portion of the shaft is inserted into the hole of the gear in a press-fit state by at least a part of the projection of the gear being deformed
Data Source
AI summary
A roller driving apparatus includes a roller having a shaft, and a gear fixed to a first end portion of the shaft, wherein the gear includes a hole into which the first end portion is inserted and formed of an inner peripheral surface including an inner circumferential surface centering on a first center, a projection, in a case where two areas divided by a virtual line passing through the first center are first area and areas, disposed in the first area and projecting relative to the inner peripheral surface, and a gear portion, wherein the first end portion of the shaft is inserted into the hole of the gear in a press-fit state, and wherein, when viewed along the longitudinal direction, a second center, which is a center of a pitch circle of the gear portion, is disposed in the second area.