External Rotor Motor Cooling via Centrifugal Particle Ejection
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Solution Overview
Problem
Existing electric motors with external rotors face issues of reduced efficiency and shortened lifespan due to heating, and the introduction of foreign particles through openings in the rotor bell and outflow openings can negatively impact cooling and component integrity.
Innovation Solution
A plate-shaped rotor cover with outflow openings positioned on the ring wall and radially extending inner wings enhances airflow by increasing centrifugal force, while a closed plate bottom prevents direct entry of foreign particles and aids self-cleaning through centrifugal ejection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If openings are provided in the rotor bell base and outflow openings are provided in the rotor cover, then cooling air flow through the motor is improved, but foreign particles such as dirt, dust or moisture can penetrate the motor and damage components
Solution Approach 1:
The patent utilizes the harmful centrifugal force that tends to throw particles outward and the negative pressure zone to create a self-cleaning effect. The flow chambers are designed to rotate with the rotor, generating centrifugal force that actively ejects foreign particles through the outflow openings, converting the potential harm of particle penetration into a beneficial self-cleaning mechanism that protects internal components
Solution Approach 2:
The rotor cover is divided into multiple flow chambers separated by radial partition walls, with each chamber having its own outflow opening. This segmentation allows independent control of air flow paths and particle ejection for each chamber, improving overall cooling efficiency while maintaining particle protection through the collective action of all chambers
2Productivity
If the rotor cover is designed with outflow openings to increase air flow, then cooling efficiency is improved, but the structural complexity of the rotor cover increases
Solution Approach 1:
The rotor cover is designed to perform multiple functions simultaneously: it acts as a fan wheel to generate negative pressure for air intake, provides structural support for the rotor assembly, creates flow chambers for optimized air circulation, and serves as a particle ejection system through its outflow openings. This multi-functionality reduces the need for separate cooling components, simplifying the overall motor structure while maintaining high cooling efficiency
Solution Approach 2:
The patent combines the cooling fan function, structural housing function, and particle ejection function into a single integrated rotor cover component. The flow chambers and outflow openings are incorporated directly into the rotor cover structure, eliminating the need for separate cooling housings or particle filtration systems, thus reducing overall device 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
This design improves airflow and cooling efficiency within the motor, effectively preventing foreign particles from entering and enhancing self-cleaning, thus protecting the motor's internal components and extending its service life.
Implementation Method 1
the outflow openings are located at the maximum radius of the rotor cover. This causes an increase in the centrifugal force acting on the air between the rotor cover and the bell bottom
Implementation Method 2
the rotational movement of the air in the flow chambers and thus the centrifugal force acting on the air is increased by the inner vanes, which in turn has a strengthening effect on the air flow inside the engine
Implementation Method 3
generates a negative pressure in the intake area in the vicinity of the bell bottom of the rotor bell. The negative pressure causes the air inside the electric motor to be sucked in through the openings in the base of the bell
Implementation Method 4
the increased centrifugal force also acts on foreign particles that have penetrated and thus improves a self-cleaning function of the air flow inside the electric motor by ejecting the foreign particles from the outflow openings
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
The present invention relates to an electric motor (1) with a stator (2) and an externally rotating rotor (3), consisting of a rotor housing (4) and a rotor cover (5) acting as a fan. The rotor housing (4) has several openings (18) in its base (6). The rotor cover (5) has several outlet openings. The rotor cover (5) is disc-shaped and consists of a base and an annular wall. The outlet openings are preferably evenly distributed in the annular wall. The inner surface of the base of the rotor cover (5), facing the rotor housing (4), has several radially extending inner fins firmly connected to it.