Outboard Motor Lower Case Split Surface Design
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Solution Overview
Problem
Conventional outboard motors face challenges in accurately installing bearings that support the propeller shaft due to insufficient assembly and machining accuracy, leading to potential misalignment and increased time in assembling internal components.
Innovation Solution
The outboard motor design features a lower case divided into a front case and a rear case, with the split surface extending only in a portion of the forward-rearward direction, allowing for easier and accurate installation of bearings and improved workability of internal components, including the propeller shaft, by displacing the split surface from bearing installation positions and enabling better machining of water and oil passages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the split surface extends in the horizontal direction along the central axis of the propeller shaft, then the lower case can be assembled from separate upper and lower housings, but steps or misalignment occur on the split surface due to insufficient assembly and machining accuracy
Solution Approach 1:
The lower case is divided into a front case and a rear case instead of upper and lower housings. The split surface extends in the forward-rearward direction only in a portion of the lower case, specifically forward of the drive shaft, rather than along the entire central axis. This segmentation approach maintains ease of assembly while avoiding steps or misalignment at the bearing installation positions.
2Ease of operation
If the split surface extends along the entire lower case in the forward-rearward direction, then complete disassembly is achieved, but bearing installation accuracy decreases due to steps or misalignment on the split surface
Solution Approach 1:
The split surface is positioned to extend in the forward-rearward direction only in a specific portion of the lower case (forward of the drive shaft), while the rear portion where bearings are installed maintains a continuous surface. This local differentiation ensures that the split surface provides ease of disassembly where needed, while the bearing installation positions maintain high precision without steps or misalignment.
3Manufacturing precision
If the lower case is divided into front case and rear case with split surface forward of drive shaft, then bearing installation accuracy is improved, but assembly complexity increases
Solution Approach 1:
The lower case is divided into a front case and a rear case that are assembled to each other. The front case contains the split surface extending in the forward-rearward direction forward of the drive shaft, while the rear case houses the propeller shaft and bearings. This segmentation achieves bearing installation accuracy while maintaining relatively simple assembly procedures through the use of standard fastening connections between the front and rear cases.
Data Source
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AI summary
An outboard motor (100, 200) includes an engine (E), a propeller shaft (P1) configured to rotate together with a propeller (P2) and extend in a forward-rearward direction, and a lower case (2) configured to house the propeller shaft. The lower case includes a front case (25) and a rear case (26) separate from the front case, the rear case being disposed rearward of the front case, and the front case and the rear case are assembled to each other.