Multipart Rotor Shaft Cooling via Segmented Cavities
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Solution Overview
Problem
Existing multipart rotor shafts for electric machines face challenges in achieving lightweight construction while providing efficient cooling and media transport, as they either have inadequate cooling due to small passage bores or excessive weight due to large coolant volumes, leading to inefficiencies in power-to-weight ratio and increased mass inertia.
Innovation Solution
A multipart rotor shaft design featuring a hollow carrier with a line element forming a cooling channel and separating elements to create symmetrical partial cavities, allowing for efficient cooling medium distribution with minimal coolant use, reducing mass inertia and enabling lightweight construction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of stationary object
If small passage bores are used for cooling medium conduction, then the volume requirement is reduced, but the cooling efficiency deteriorates and the rotor shaft weight is not sufficiently reduced
Solution Approach 1:
The cooling system is segmented into multiple independent cooling channels distributed throughout the rotor shaft structure. Instead of a single large bore, multiple smaller channels are created, allowing the cooling medium to reach multiple heat generation zones simultaneously. This segmentation enables sufficient cooling efficiency while maintaining a compact overall volume requirement.
Solution Approach 2:
The cooling medium conduction is extended from a single axial dimension to multiple spatial dimensions by creating a network of cooling channels that extend radially and axially throughout the rotor shaft. This multi-dimensional channel distribution allows efficient heat removal from the rotor core without requiring large single-dimension passage bores.
2Weight of moving object
If large line cross-sections and cavities are used in the rotor shaft, then lightweight construction is enabled, but the moved mass increases due to complete filling with coolant
Solution Approach 1:
Instead of completely filling the rotor shaft cavity with coolant, the system uses partial filling where the cooling medium is introduced through controlled channels to specific zones. This partial action approach provides sufficient cooling to critical heat generation areas while minimizing the total coolant volume, thereby reducing the moved mass and maintaining lightweight construction benefits.
Solution Approach 2:
The rotor shaft structure itself serves as the cooling channel network, eliminating the need for separate large-volume coolant reservoirs. The integrated cooling channels are formed within the rotor shaft material, allowing the structure to provide both mechanical support and thermal management functions, thus reducing overall weight while maintaining efficient cooling with minimal coolant.
3Weight of moving object
If hollow shafts are used for media transport, then weight savings are achieved, but running irregularities occur due to medium expansion and turbulence
Solution Approach 1:
The media transport function is segmented into multiple small distributed channels rather than a single large hollow shaft. This segmentation breaks up the turbulent flow patterns and medium expansion effects that cause running irregularities, while still achieving weight savings through the elimination of large solid structural elements. The multiple small channels provide stable, laminar flow characteristics.
4Area of stationary object
If complete conduction of cooling medium over entire axial and radial path lengths is used, then heat transmission area is increased, but device complexity and structural complexity increase
Solution Approach 1:
The cooling channels are merged with the rotor shaft structural elements, eliminating the need for separate cooling components. The cooling channels are integrated directly into the rotor shaft manufacturing process, combining the structural support function and heat transmission function into a single unified structure. This merging approach increases the heat transmission area while avoiding additional device complexity.
Solution Approach 2:
The rotor shaft is designed to serve multiple functions simultaneously: it provides mechanical support for the rotor core, acts as a cooling medium conduit, and serves as a structural element for mounting other components. This multi-functionality approach increases the effective heat transmission area without requiring additional dedicated cooling structures, thereby avoiding increased 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
The design achieves efficient cooling with reduced mass and increased power-to-weight ratio, allowing for higher power output and improved drive efficiency with minimal coolant usage, while maintaining a lightweight and rigid structure.
Implementation Method 1
the cooling medium can only be conducted in small quantities to the components to be cooled, in particular to the rotor core which heats up greatly
Implementation Method 2
A cooling medium may be conducted through the hollow rotor shafts for the purpose of cooling the rotor
Data Source
AI summary
A multipart rotor shaft for an electric machine comprises a first shaft journal with a first end flange and a first axial passage bore, a second shaft journal with a second end flange. The rotor shaft also includes a hollow carrier for a laminated rotor core, a line element for conducting a cooling medium, and a separating element which divides a cavity between the carrier and the line element into a first partial cavity and a second partial cavity.