Inverter-Integrated Driving Module Cooling via Radial Axial Airflow
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Solution Overview
Problem
Conventional inverter-integrated AC motors with inner rotors face limitations in increasing torque per unit length due to constraints on magnetic flux, leading to insufficient cooling of bearings when an outer rotor is used, resulting in reduced service life.
Innovation Solution
An inverter-integrated driving module design that includes a stator with an annular core and a rotor with magnetic poles, a centrifugal fan, and a heatsink with radiating fins, forming ventilation channels to direct cooling airflow effectively through the bearing and inverter units, enhancing heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If an outer rotor is used to increase torque per unit length, then the magnetic flux and torque are improved, but the bearing heat generation increases and cooling becomes insufficient
Solution Approach 1:
The patent introduces a multi-dimensional cooling airflow path that moves cooling air from the inverter module through the bearing housing and into the bearing. This spatial arrangement creates a three-dimensional cooling network that effectively removes heat from the bearing without interfering with the outer rotor configuration, thereby resolving the temperature increase issue while maintaining high torque output.
Solution Approach 2:
The bearing housing serves as an intermediary component that facilitates heat transfer from the bearing to the cooling airflow. The housing includes a cooling airflow introduction portion that directs cooled air onto the bearing, acting as a mediator between the heat-generating bearing and the cooling system, thereby effectively managing bearing temperature in the outer rotor configuration.
2Device complexity
If the outside diameter of the motor is kept constant with an inner rotor, then the construction is simpler, but the surface area facing the stator is reduced and magnetic flux is limited
Solution Approach 1:
The patent inverts the conventional rotor configuration by using an outer rotor instead of an inner rotor. This inversion allows the rotor to have a larger diameter and greater surface area facing the stator, thereby increasing magnetic flux and torque output while maintaining constant motor outside diameter. The outer rotor configuration overcomes the magnetic flux limitation of inner rotors.
3Power
If the rotor diameter is increased to use an outer rotor, then torque per unit length increases, but the rotor weight increases and bearing burden increases
Solution Approach 1:
The patent changes the rotor configuration parameter from inner rotor to outer rotor, which fundamentally alters the weight distribution and magnetic flux characteristics. The outer rotor design increases the radius where magnetic flux is generated, allowing for higher torque per unit length despite the increased rotor weight, as the leverage effect compensates for the additional mass.
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 solution effectively cools both the inverter units and the bearing, extending their service life by suppressing excessive temperature increases even in modules using an outer rotor.
Implementation Method 1
a plurality of radiating fins that are each disposed so as to stand perpendicularly on a rear surface of the fin base so as to extend radially
Implementation Method 2
a radial ventilation channel that is formed between adjacent radiating fins so as to communicate between the first inverter ventilation aperture and a radially outer side of the heatsink, and through which a cooling airflow flows radially
Implementation Method 3
a cooling airflow ventilation channel that includes: a radial ventilation channel that is formed between adjacent radiating fins so as to communicate between the first inverter ventilation aperture and a radially outer side of the heatsink, and through which a cooling airflow flows radially due to rotational driving of the fan
Implementation Method 4
a heatsink including: a tabular fin base; and a plurality of radiating fins that are each disposed so as to stand perpendicularly on a rear surface of the fin base
Data Source
AI summary
A first inverter ventilation aperture is disposed so as to pass through a portion of a fin base that faces a bearing, a first rotor ventilation aperture is disposed so as to pass through a portion of a bottom surface portion that faces the bearing, and a first cooling airflow ventilation channel is formed in which a cooling airflow flows radially inward through radiating fins, then flows toward a first surface side of a mount portion through the first inverter ventilation aperture, flows axially through an interior portion of a stator core, and then flows out between the bottom surface portion and a base portion through the first rotor ventilation aperture, and subsequently flows radially outward between the bottom surface portion and the base portion due to rotational driving of a centrifugal fan.