Vertical Motor Cooling Oil Layout to Protect the Rotor-Stator Air Gap
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Solution Overview
Problem
Existing cooling structures for vertical electric motors, particularly in outboard engines, fail to prevent cooling oil from entering the air gap between the rotor and stator when the motor tilts, leading to increased friction and other issues due to pitching motions of the boat or trim adjustments.
Innovation Solution
A cooling structure with a cooling oil supply member having outlets arranged circumferentially above the stator, with a greater amount of cooling oil dropped on parts of the stator orthogonal to the vertical axis than on parts orthogonal to it, minimizing the likelihood of oil entering the air gap even when the motor is tilted.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If cooling oil is dripped onto the rotor via slits on the bottom of a hollow annular member, then cooling performance is improved, but cooling oil may enter the air gap between rotor and stator when the motor tilts
Solution Approach 1:
The cooling oil supply member is divided into multiple outlets arranged circumferentially around the stator, with each outlet positioned to drip cooling oil onto specific regions of the stator. This segmentation allows differential cooling oil distribution - with outlets on the first axis having smaller diameters or fewer outlets compared to outlets on the second axis, preventing excessive oil from entering the air gap when the motor tilts during pitching motions or trim adjustments
Solution Approach 2:
Different regions of the stator receive different amounts of cooling oil based on their local cooling needs and tilt vulnerability. The outlets on the first axis (fore-aft direction) are designed with smaller diameters or fewer outlets to reduce oil flow in directions more prone to tilting, while outlets on the second axis (lateral direction) provide adequate cooling. This local quality differentiation ensures effective cooling while minimizing oil entry into the air gap during operational tilting
2Manufacturing precision
If the electric motor is positioned precisely vertical, then cooling oil drips onto coils as designed, but the motor cannot accommodate pitching motion or trim adjustment
Solution Approach 1:
The cooling oil supply system is designed to dynamically adapt to tilting conditions through its circumferential outlet arrangement. The outlets are positioned and sized to provide optimal cooling when the motor is vertical, while also preventing excessive oil flow that would cause air gap contamination during tilting. This dynamic design allows the system to maintain cooling effectiveness across a range of operating angles without requiring precise vertical positioning
3Reliability
If cooling oil flows into the air gap between rotor and stator, then friction increases and motor performance deteriorates, but preventing this reduces cooling effectiveness
Solution Approach 1:
The outlet diameters on the first axis are specifically reduced compared to those on the second axis, changing the flow parameters to minimize oil entry into the air gap during tilting. This parameter modification maintains sufficient cooling oil flow to the stator for effective cooling while preventing excessive oil from contaminating the air gap, thus preserving both cooling effectiveness and motor performance reliability
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 effective cooling while preventing cooling oil from entering the air gap, reducing friction and minimizing the risk of foreign matter entry, even during pitching motions or trim adjustments, thus maintaining motor efficiency and performance.
Implementation Method 1
a cooling oil supply member (50) positioned above the stator and including a plurality of outlets (54) for dropping cooling oil on an upper surface of the stator
Data Source
AI summary
In an outboard motor including a vertical electric motor, a cooling structure for the vertical electric motor comprises a cooling oil supply member positioned above the stator and including a plurality of outlets for dropping cooling oil on an upper surface of the stator, the outlets being arranged circumferentially in a coaxial relationship to the stator, and the outlets are configured such that an amount of cooling oil that is dropped on a part of the stator located on a first axis on a plane orthogonal to the vertical axis is smaller than an amount of cooling oil that is dropped on a part of the stator located on a second axis which is orthogonal to the first axis on the plane orthogonal to the vertical axis.