Electric Motor Cooling via Rotor Negative Pressure
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Solution Overview
Problem
Conventional electric motor cooling systems face inefficiencies at low speed rotations due to high viscosity resistance of the cooling medium and require external pumps, which are costly and prone to air leaks.
Innovation Solution
An electric motor design featuring a stator, rotor, and a cooling medium channel with a discharge port positioned close to the rotor, where the cooling medium storing portion is lower than the discharge port, utilizing negative pressure to suck in the cooling medium and enhance cooling efficiency without an external pump, and incorporating a variable air gap mechanism to manage viscosity resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If an external oil pump is used to supply cooling medium, then rotor cooling efficiency is improved during high speed rotation, but device complexity and cost increase
Solution Approach 1:
The rotor itself generates the negative pressure needed for cooling medium supply through its rotation, eliminating the need for external pumps. The rotating rotor creates a pressure difference that automatically draws cooling medium from the storing portion through the channel to the rotor surface, making the system self-servicing without additional mechanical components.
Solution Approach 2:
The external oil pump is completely removed from the system. Instead of adding a pumping mechanism, the invention extracts the cooling function directly from the rotor's rotational motion, using the rotor's own movement to create the necessary pressure differential for cooling medium circulation.
2Temperature
If cooling medium is supplied during low speed rotation, then rotor cooling is provided, but viscosity resistance increases and cooling efficiency deteriorates
Solution Approach 1:
The cooling medium supply is made dynamic and speed-dependent. The system automatically adjusts cooling medium flow based on rotor speed - at low speeds, negative pressure is insufficient and cooling medium is not supplied, avoiding viscosity resistance issues. At high speeds, sufficient negative pressure naturally draws cooling medium, providing effective cooling when needed most.
Solution Approach 2:
The invention changes the operational parameters of the cooling system based on rotor speed. The negative pressure parameter varies with rotation speed, creating a threshold effect where cooling medium supply is activated only when rotor speed generates sufficient negative pressure, thereby avoiding the viscosity resistance problems associated with low-speed operation.
3Device complexity
If discharge port is positioned away from rotor, then cooling medium flow is simplified, but cooling efficiency decreases
Solution Approach 1:
The discharge port is repositioned from a remote location to be in close proximity to the rotor surface. This spatial repositioning in the radial dimension enables direct impingement of cooling medium onto the rotor, dramatically improving cooling efficiency. The cooling medium is discharged almost immediately adjacent to the rotor surface it needs to cool, eliminating long flow paths and energy losses.
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 cools the rotor across various speed ranges without external pumps, maintaining efficiency by minimizing viscosity resistance and reducing costs.
Implementation Method 1
a negative pressure caused between the rotor and the discharge port sucks the cooling medium in the cooling medium storing portion
Data Source
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AI summary
An electric motor (10) of the present invention includes: a stator (11); a rotor (12) axially supported to a rotational shaft (13) in such a configuration as to rotate relative to the stator (11), the rotor (12) being adapted to be cooled by a cooling medium (L); a cooling medium storing portion (60) disposed on the stator (11) side and storing therein (60) the cooling medium (L); and a cooling medium channel (22) for leading the cooling medium (L) from the cooling medium storing portion (60) to the rotor (12), wherein a discharge port (23a) for discharging the cooling medium (L) of the cooling medium channel (22) is disposed close to a rotational portion (18a) of the rotor (12), the cooling medium storing portion (60) is disposed lower than the discharge port (23a), and a negative pressure caused between the rotor (12) and the discharge port (23a) sucks the cooling medium (L) in the cooling medium storing portion (60).