Outboard Motor Cooling Passage Layout for Low Pressure Loss
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Solution Overview
Problem
Existing outboard motors face pressure loss issues in the supply passage for cooling water due to the long annular flow path when the lower unit pivots relative to the upper unit, disrupting the flow of cooling water.
Innovation Solution
The outboard motor design incorporates a connecting mechanism with cylindrical shaft portions that allow the drive shaft to be inserted into a space between these shafts, forming a shorter annular supply passage for cooling water, reducing pressure loss by shortening the flow path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the lower unit pivots relative to the upper unit with a conventional connecting mechanism, then the outboard motor can steer the boat, but the supply passage for cooling water becomes long and causes pressure loss
Solution Approach 1:
The drive shaft is inserted into the space between the first shaft portion and the second shaft portion of the nested connecting mechanism. This nesting arrangement allows the cooling water supply passage to be formed within the existing structural space, shortening the passage length and reducing pressure loss while maintaining the steering function through relative pivoting of the lower and upper units.
Solution Approach 2:
The supply passage is formed in a radial direction between the drive shaft and the first shaft portion, rather than extending axially along the length of the connecting mechanism. This dimensional change in the passage layout significantly reduces the flow path length and associated pressure loss while still delivering cooling water to the upper unit.
2Loss of energy
If the supply passage for cooling water is shortened to reduce pressure loss, then cooling efficiency improves, but the connecting mechanism structure becomes more complex
Solution Approach 1:
The space between the first shaft portion and the second shaft portion in the connecting mechanism serves dual functions: it allows relative pivoting for steering while simultaneously forming the cooling water supply passage. This multi-functionality eliminates the need for separate passage components, reducing overall structural complexity while achieving short passage length and low pressure loss.
Solution Approach 2:
The connecting mechanism and the cooling water supply system are merged into a single integrated structure. The shaft portions and drive shaft that form the mechanical connection also define the flow path for cooling water, combining two previously separate functions into one unified component arrangement.
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
This design ensures smooth and efficient supply of cooling water to the upper unit, minimizing pressure loss and maintaining uninterrupted flow during pivoting of the lower unit.
Implementation Method 1
a drive shaft configured to transmit a rotation of the drive motor to the propeller shaft
Implementation Method 2
a cooling mechanism provided in the upper unit and configured to cool an equipment requiring cooling including the drive motor by using cooling water
Data Source
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AI summary
An outboard motor includes a cooling device which includes a supply passage supplying a cooling water taken into a lower unit to a cooling mechanism. A first shaft portion of the connecting mechanism has a cylindrical shape, is provided in an upper part of the lower unit, and has an axis coaxial with the axis of a drive shaft. A second shaft portion has a cylindrical shape, is provided in a lower part of an upper unit, and has an axis coaxial with the axis of the drive shaft. One shaft portion of the first and the second shaft portions is inserted into the other shaft portion to be pivotable relative to the other shaft portion. The drive shaft is inserted into the one shaft portion with a space. A part of the supply passage is formed of the space between the drive shaft and the one shaft portion.