Resin Shaft Drive Unit Design for Load Distribution
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Solution Overview
Problem
Existing drive units in image forming apparatuses face challenges in distributing rotational loads evenly across resin shafts, leading to potential damage and increased costs due to uneven contact pressures.
Innovation Solution
A design method for the drive unit that includes a sheet metal frame with bearing holes and a resin housing, where the resin shafts are designed to maintain a contact pressure below the minimum reference contact pressure to prevent damage, ensuring the relationship F/D×L < Fa, where F is the load, D is the shaft diameter, and L is the axial contact length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If resin shafts are used in the drive unit, then manufacturing cost is reduced and ease of manufacture is improved, but the shafts are susceptible to damage from uneven contact pressures and have lower reliability
Solution Approach 1:
The patent applies local quality by optimizing the contact pressure distribution at specific locations where the resin shafts interface with the gears and bearing holes. By controlling the local contact pressure to remain below the minimum reference contact pressure Fa, the design prevents damage at critical stress points while maintaining the overall simplicity of resin shaft construction.
Solution Approach 2:
The patent changes the contact pressure parameter by designing the shaft portions and gears to satisfy the relationship F/D×L < Fa, where F is the load, D is the shaft diameter, and L is the axial contact length. This parameter optimization ensures that the contact pressure remains within safe limits for resin materials, preventing damage while maintaining manufacturing advantages.
2Power
If the contact pressure on resin shafts is increased to transmit more power, then power transmission capability is improved, but the risk of shaft damage increases
Solution Approach 1:
The patent optimizes the power transmission by changing the contact pressure parameter through design of shaft portions and gears to satisfy F/D×L < Fa. This allows the system to transmit necessary power while maintaining contact pressure below the damage threshold for resin materials.
Solution Approach 2:
The patent uses composite construction with resin shaft portions integrated into a resin housing, creating a composite structure that distributes loads more effectively. This composite approach allows power transmission while maintaining reliability by preventing stress concentration at any single point.
3Ease of manufacture
If resin materials are used for shaft portions, then manufacturing cost is lowered and ease of manufacture is improved, but the shafts are more prone to damage from concentrated loads
Solution Approach 1:
The patent addresses concentrated loads by applying local quality optimization at the bearing holes and gear contact points. The shaft portions are designed with specific geometric features that distribute local loads evenly, preventing stress concentration while maintaining the manufacturing advantages of resin materials.
Solution Approach 2:
The patent distributes loads by extending the contact area in the axial dimension through the shaft portions projecting into the bearing holes. This dimensional approach transforms point loads into distributed loads along the axial direction, reducing stress concentration on the resin material.
Data Source
AI summary
A design method of a drive unit includes: deriving a minimum reference contact pressure Fa causing any of the shaft portion among the plurality of the shaft portions to result in damage; and designing the shaft portions or the gears to be of form such that the plurality of shaft portions and the plurality of gears satisfy the relationship F/D×L<Fa, given that, with the plurality of shaft portions and the plurality of gears linked to the drive source and the rotated components, the load acting on a single of the shaft portions among the plurality of shaft portions is F (N), the diameter of the single of the shaft portions is D (mm), and the length of axial contact between the single of the shaft portions and the gear mounted thereon is L (mm).