Motor Shaft Cooling Using Passive Screw-Driven Coolant Flow
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Solution Overview
Problem
Existing systems for cooling electric motors fluidically coupled to a gearbox face inefficiencies in delivering coolant to all surfaces of the motor, particularly those opposite the gearbox, and may increase packaging size, complexity, and cost with active coolant pumps.
Innovation Solution
A passive coolant transport system using an inner shaft with external screw threads or propeller features within an outer shaft to draw coolant from a sump into the motor, distributing it through openings and channels, and returning it via gravity drainage and gear splashing, without significant increases in packaging, complexity, or cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed, passive coolant transport system is employed to deliver coolant from the gearbox to the electric motor, then packaging space and system complexity are reduced, but the system is unable to efficiently deliver coolant to surfaces of the motor opposite the gearbox
Solution Approach 1:
The patent transforms the static, passive coolant transport system into a dynamic one by utilizing the rotation of the inner shaft to drive coolant flow. The screw thread features on the inner shaft convert rotational motion into axial coolant movement, enabling active coolant delivery to remote motor surfaces without adding complex pump systems.
Solution Approach 2:
The system uses the motor's own operational rotation to drive coolant circulation. The inner shaft rotation, which occurs during normal motor operation, automatically drives the screw thread mechanism to pump coolant, eliminating the need for separate active pumping components while ensuring coolant delivery during operation.
2Reliability
If an active coolant pump is implemented to deliver coolant to all motor surfaces, then coolant delivery efficiency is improved, but packaging space, complexity, and cost increase
Solution Approach 1:
The inner shaft serves multiple functions: it transmits mechanical power from the motor to the gearbox while simultaneously acting as a rotating pump through its screw thread features to circulate coolant. This multi-functionality eliminates the need for separate dedicated coolant pumps, reducing overall system complexity and packaging requirements.
Solution Approach 2:
The patent combines the power transmission shaft and coolant pump functions into a single integrated component. The inner shaft that transmits mechanical power also incorporates screw thread features that pump coolant, merging two previously separate functions into one component to reduce complexity.
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
The system effectively distributes coolant throughout the electric motor, maintaining efficiency and reducing complexity and cost, with limited cooling during reverse operation, and can be supplemented by an auxiliary cooling jacket.
Implementation Method 1
an external screw thread disposed along a portion of the inner shaft extending within the outer shaft. Upon rotation of the inner shaft, a coolant in the first sump may be drawn through the outer shaft from the first sump into the electric motor. Specifically, rotation of the external screw thread may induce flow of the coolant along the outer shaft.
Implementation Method 2
the coolant may be directed back to a second sump of the gearbox. During operation of the electric motor, rotation of the inner shaft may rotate at least one gear partially submersed in the coolant collected in the second sump.
Implementation Method 3
rotation of the inner shaft may rotate at least one gear partially submersed in the coolant collected in the second sump. As a result, the coolant may be splashed against a housing of the gearbox, wherefrom the splashed coolant may be directed back into the first sump
Data Source
AI summary
Systems and methods are provided for cooling an electric motor, the electric motor being fluidically coupled to a coolant sump of a gearbox. In one example, a system may include the gearbox including the coolant sump, the electric motor coupled to the gearbox, an outer shaft fluidic ally coupling the electric motor to the coolant sump, an inner shaft extending through each of the coolant sump and the outer shaft, and one or more surface features disposed along a portion of the inner shaft extending within the outer shaft. Upon rotation of the inner shaft during operation of the electric motor, a coolant in the coolant sump may be drawn through the outer shaft from the coolant sump into the electric motor. In this way, the coolant may be passively directed to the electric motor with minimal cost, packaging size, and system complexity and without significant losses in overall system efficiency.