Outboard Motor Shift Shaft Segmentation for Weight Reduction
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Solution Overview
Problem
Existing outboard motor designs that prevent submersion during tilting up by positioning the outboard motor body rearward of the hull increase the mechanical strength and weight of the bracket, leading to a heavier outboard motor.
Innovation Solution
The outboard motor design includes a shift shaft with a first shift shaft extending upward-downward and a second shift shaft positioned below and rearward of the first shift shaft, with a shift force transmitter to transmit forces, and a drive shaft with a similar configuration, keeping the center of gravity closer to the hull to prevent submersion while minimizing weight increase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the outboard motor body is positioned rearward of the hull to prevent submersion during tilting up, then submersion is prevented, but the mechanical strength and weight of the bracket increase
Solution Approach 1:
The shift shaft is divided into two segments: a first shift shaft extending upward-downward and a second shift shaft positioned below and rearward of the first shift shaft. This segmentation allows the lower portion (second shift shaft) to be positioned rearward to prevent submersion, while the upper portion (first shift shaft) remains forward, keeping the overall center of gravity closer to the hull and reducing bracket weight requirements
Solution Approach 2:
Only the lower portion of the shift shaft (second shift shaft) is positioned rearward of the hull, while the upper portion (first shift shaft) remains forward. This localized positioning achieves the submersion prevention function where needed without moving the entire outboard motor body rearward, thereby minimizing the increase in bracket mechanical strength and weight
2Reliability
If the outboard motor body is positioned rearward of the hull, then submersion is prevented, but the size of the bracket increases
Solution Approach 1:
The shift shaft is segmented into two parts with different positions: the first shift shaft extends upward-downward in a forward position, while the second shift shaft is positioned below and rearward of the first shift shaft. This segmentation enables the lower control mechanism to be positioned rearward for submersion prevention while keeping the upper structure forward, thus avoiding the need to increase bracket size
Solution Approach 2:
The shift shaft transitions from a single linear upward-downward extension to a two-dimensional configuration with the first shift shaft and the second shift shaft positioned at different horizontal locations (forward and rearward respectively). This dimensional change allows the lower portion to be positioned rearward without requiring the entire structure to move rearward, preventing bracket size increase
Data Source
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AI summary
An outboard motor (100, 200) includes an engine (E), a drive shaft (3, 203), and a shift shaft (4a) disposed forward of the drive shaft. The shift shaft includes a first shift shaft (41) configured to extend in an upward-downward direction, a second shift shaft (42) disposed below the first shift shaft and spaced apart from and rearward of the first shift shaft, the second shift shaft being configured to extend in the upward-downward direction, and a shift force transmitter (43) configured to transmit, to the second shift shaft, a shift force applied to the first shift shaft.