Outboard Motor Shift Mechanism Segmentation for Gearbox Strength
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Solution Overview
Problem
Conventional marine outboard motor shift mechanisms require a large access hole in the gearbox casting, compromising its strength and making assembly difficult due to the need to align and fix the shift finger with the shift rod, leading to potential oil leakage and water ingress.
Innovation Solution
A shift mechanism with a support shaft and pivotally mounted shift finger, allowing the shift finger to be part of a sub-assembly with the shift shuttle, reducing the diameter and mass of the shift mechanism, enabling easier assembly and alignment, and requiring a smaller access hole for the shift rod, thereby increasing the gearbox's strength and reducing leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the shift finger is fixed to the shift rod during assembly, then the shift mechanism can be assembled, but the access hole in the gearbox casting must be large which compromises the strength of the gearbox
Solution Approach 1:
The shift mechanism is divided into separate components: the shift finger is no longer fixed to the shift rod but is instead a separate pivotally mounted component on the support shaft. This segmentation allows the shift rod to pass through a smaller access hole while the shift finger is positioned separately, eliminating the need for a large access hole that would compromise gearbox strength.
Solution Approach 2:
A support shaft is introduced as an intermediary component that carries the shift finger. The support shaft is fixed to the gearbox casing and provides a pivot point for the shift finger, allowing the shift finger to be positioned correctly without being attached to the shift rod. This intermediary structure enables the use of a smaller access hole.
2Reliability
If the shift finger and shift rod are aligned and fixed together, then the shift mechanism functions correctly, but assembly becomes difficult and time-consuming
Solution Approach 1:
The shift finger is separated from the shift rod assembly, allowing each component to be positioned and secured independently. The shift finger is pivotally mounted on the support shaft rather than being fixed to the shift rod, which eliminates the complex alignment procedure previously required and significantly reduces assembly time.
Solution Approach 2:
The support shaft provides a built-in pivot mounting for the shift finger, allowing the shift finger to be automatically positioned and secured when installed on the support shaft. This self-positioning feature eliminates the need for complex alignment procedures between the shift finger and shift rod.
3Ease of manufacture
If a large access hole is provided for the shift rod and shift finger, then assembly is possible, but oil leakage and water ingress increase
Solution Approach 1:
The shift mechanism components are segmented so that the shift finger is separately mounted on the support shaft rather than being attached to the shift rod. This allows the shift rod to pass through a smaller access hole, reducing the opening size and thereby minimizing oil leakage and water ingress while maintaining assembly accessibility.
Solution Approach 2:
The support shaft acts as an intermediary that allows the shift finger to be positioned without requiring the shift rod to accommodate both components. This enables a smaller access hole to be used, reducing harmful factors like oil leakage and water ingress.
Data Source
Figure 1
Figure 2a~2d
Figure 3
AI summary
A marine outboard motor (2) is provided with a gear casing (40), a propeller shaft (29) rotatable within the gear casing about a propeller shaft axis (34), a drive shaft (27) having a drive gear (35), a clutch mechanism (50) for selectively engaging the drive gear with the propeller shaft and a shift mechanism (60) configured to operate the clutch mechanism. The shift mechanism comprises a support shaft (70) which is fixed relative to the gear casing and which extends along or parallel with the propeller shaft axis, a shift shuttle (80) which is slidable along the support shaft and is connected to a clutch member (53) of the clutch mechanism, a shift finger (90) pivotally mounted on the support shaft, and a shift rod (61) coupled to the shift finger by a releasable coupling. The shift finger is configured to move the shift shuttle along the support shaft to operate the clutch member when the shift finger is rotated about the shift rod axis by the shift rod. A marine vessel including such a marine outboard motor is also provided.