Electric Machine Rotor Magnet Retention via Elastic Holding Devices
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Solution Overview
Problem
In electric machines with rotors and permanent magnets, large manufacturing tolerances can lead to poor retention of magnets under centrifugal force, causing them to shift or become dislodged during rotation, especially in applications like range extenders and refrigerant compressors.
Innovation Solution
The use of holding devices within the rotor housings, featuring a combination of rounded and flat portions that apply radial and axial forces to secure the magnets, along with elastically deformable parts and retaining flanges, ensures the magnets remain in place regardless of rotor speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If large manufacturing tolerances are used to reduce manufacturing costs, then manufacturing cost decreases, but magnet retention under centrifugal force deteriorates
Solution Approach 1:
The holding devices are pre-installed in the rotor housings before the magnets are placed. These devices are already in position to apply retaining forces, so when magnets are installed with large tolerances, the holding devices immediately engage and secure them, preventing displacement under centrifugal force during rotation.
Solution Approach 2:
The holding devices act as intermediary elements between the rotor housing and the permanent magnets. They transmit and distribute the retaining forces (radial and axial) to the magnets, ensuring secure retention even when the magnets have manufacturing tolerances that would otherwise cause poor retention.
2Reliability
If holding devices are added to secure magnets, then magnet retention improves, but device complexity increases
Solution Approach 1:
The holding devices are designed as thin, flexible elastic elements that can deform to apply retaining forces. This flexible membrane structure provides the necessary retention functionality while occupying minimal space and adding minimal structural complexity to the rotor assembly.
Solution Approach 2:
The holding devices utilize elastic deformation as their working mechanism. By changing the physical state of the elastic material (deforming it), the devices generate the necessary radial and axial forces to retain magnets, providing a simple yet effective solution without complex mechanical structures.
3Reliability
If elastic deformation is used to apply retaining forces, then magnet retention improves, but manufacturing precision requirements increase
Solution Approach 1:
The holding devices are made from elastic materials whose mechanical properties (elastic modulus, deformation characteristics) are optimized to provide sufficient retaining forces. By carefully selecting and tuning these material parameters, the devices can compensate for manufacturing tolerances in other components while maintaining reliable magnet retention.
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 solution effectively secures permanent magnets, reducing sensitivity to shocks, vibrations, and centrifugal forces, allowing for wider manufacturing tolerances and increased performance by maintaining magnetic flux and reducing iron losses, while enabling the use of multiple magnets or non-magnetic elements for enhanced power and reliability.
Implementation Method 1
the rounded portions whose convex side is turned towards the permanent magnets apply by deformation a radial force on each permanent magnet of the housing from the inside towards the outside of the rotor
Implementation Method 2
the second part having a shape such that it exerts an axial force by deformation on the column of magnets
Implementation Method 3
they are subjected to the action of the centrifugal force
Data Source
Figure 1~2a
Figure 2b~2c
Figure 2d~2e
AI summary
The invention essentially concerns a rotor (1) having permanent magnets (14) comprising a stack of laminations forming the core (3) of the rotor, and housings (9) receiving permanent magnets (14). At least some of the housings (9) contain a plurality of magnets (14) stacked in an axial direction and forming a column of magnets. The rotor (1) further comprises holding devices (17) each comprising a first portion positioned axially between a face (91) of a housing (9) and a face of the magnets and shaped such that it exerts a radial force by deformation on each magnet (14) of the column of magnets, from the inside towards the outside of the rotor. The holding device can also comprise a second radial portion having a shape such that it exerts an axial force by deformation on the permanent magnets (14), as well as a third flat portion and a folding zone located between the first and third portions. The invention also concerns a holding device associated with the rotor.