US-20260128628-A1 - ELECTRIC MOTOR WITH MIXED MAGNET ROTOR HAVING SIMILAR MAGNET BLOCKS

US20260128628A1US 20260128628 A1US20260128628 A1US 20260128628A1US-20260128628-A1

Abstract

A permanent magnet rotor assembly for an electric motor, an electrified vehicle, and a method is provided. The assembly includes an annular stack of rotor lamination layers (“rotor lams”) constructed of a magnetic core material. The rotor lams have inner axial surfaces collectively defining a group of first openings through the magnetic core material and a group of second openings through the magnetic core material. The annular stack includes a first arrangement of permanent magnets and a second arrangement of permanent magnets.

Inventors

Ali Alqarni
Alireza Fatemi
Thomas W. Nehl

Assignees

GM Global Technology Operations LLC

Dates

Publication Date: 20260507
Application Date: 20241030

Claims (20)

1 . A permanent magnet rotor assembly for an electric motor, comprising: an annular stack of rotor lamination layers (“rotor lams”) constructed of a magnetic core material, the rotor lams having inner axial surfaces collectively defining a group of first openings through the magnetic core material and a group of second openings through the magnetic core material, wherein the annular stack includes at least one pole that includes a first arrangement of permanent magnets, wherein each respective permanent magnet of the first arrangement is disposed within a corresponding one of the group of first openings, and wherein the first arrangement of permanent magnets is arranged in a mixed magnet configuration having at least one low-coercivity magnet surrounded by at least two high-coercivity magnets; and a second arrangement of permanent magnets, wherein each respective permanent magnet of the second arrangement is disposed within a corresponding one of the group of second openings, wherein the second arrangement of permanent magnets is arranged in a mixed magnet configuration having at least one low-coercivity magnet surrounded by at least two high-coercivity magnets.
2 . The permanent magnet rotor assembly of claim 1 , wherein the at least two high-coercivity magnets include at least one of a neodymium-based magnet or a samarium cobalt magnet.
3 . The permanent magnet rotor assembly of claim 1 , wherein the at least one low-coercivity magnet includes a ferrite-based magnet.
4 . The permanent magnet rotor assembly of claim 1 , wherein the high-coercivity magnets have parallel magnetization.
5 . The permanent magnet rotor assembly of claim 1 , wherein the high-coercivity magnets are segmented.
6 . The permanent magnet rotor assembly of claim 1 , wherein the at least one low-coercivity magnet is curved and has radial magnetization.
7 . The permanent magnet rotor assembly of claim 1 , wherein at least one of the high-coercivity magnets is substantially parallel to a radius of the pole.
8 . The permanent magnet rotor assembly of claim 1 , wherein an inner layer of the at least one low-coercivity magnet has a V configuration.
9 . The permanent magnet rotor assembly of claim 1 , wherein two low-coercivity magnets are separated by a center post.
10 . The permanent magnet rotor assembly of claim 1 , wherein the high-coercivity magnets are a different size than the low-coercivity magnets, and wherein each pole includes only two to three magnet sizes.
11 . The permanent magnet rotor assembly of claim 1 , wherein the first arrangement of permanent magnets includes two low-coercivity magnets, and wherein the second arrangement of permanent magnets includes one low-coercivity magnet.
12 . An electrified vehicle, comprising: an electric drive system having an electric motor including a stator; and a permanent magnet rotor assembly for the electric motor configured to rotate due to a rotating magnetic field created by the stator, wherein the permanent magnet rotor assembly includes an annular stack of rotor lamination layers (“rotor lams”) constructed of a magnetic core material, the rotor lams having inner axial surfaces collectively defining a group of first openings through the magnetic core material and a group of second openings through the magnetic core material, wherein the annular stack includes at least one pole; a first arrangement of permanent magnets, wherein each respective permanent magnet of the first arrangement is disposed within a corresponding one of the group of first openings, and wherein the first arrangement of permanent magnets is arranged in a mixed magnet configuration having at least one low-coercivity magnet surrounded by at least two high-coercivity magnets; and a second arrangement of permanent magnets, wherein each respective permanent magnet of the second arrangement is disposed within a corresponding one of the group of second openings, wherein the second arrangement of permanent magnets is arranged in a mixed magnet configuration having at least one low-coercivity magnet surrounded by at least two high-coercivity magnets.
13 . The electrified vehicle in claim 12 , wherein the at least one high-coercivity magnet includes at least one of a neodymium-based magnet or a samarium cobalt magnet.
14 . The electrified vehicle in claim 12 , wherein the at least one low-coercivity magnet includes a ferrite-base magnet.
15 . The electrified vehicle in claim 12 , wherein the high-coercivity magnets are segmented.
16 . The electrified vehicle in claim 12 , wherein the low-coercivity magnets and the high-coercivity magnets are curved and have radial magnetization.
17 . The electrified vehicle in claim 12 , wherein at least one of the high-coercivity magnets is substantially parallel to a radius of the pole.
18 . The electrified vehicle in claim 12 , wherein an inner layer of the low-coercivity magnets has a V configuration.
19 . A method for manufacturing a permanent magnet rotor assembly, comprising: laminating a plurality of sheets of a magnetic core material to form an annular stack of rotor lams, wherein the sheets have inner axial surfaces collectively defining a group of first openings through the sheets of magnetic core material and a group of second openings through the magnetic core material; positioning a first arrangement of permanent magnets within a corresponding one of the group of first openings, and wherein the first arrangement of permanent magnets is arranged in a mixed magnet configuration having at least one low-coercivity magnet surrounded by at least two high-coercivity magnets; and positioning a second arrangement of permanent magnets within a corresponding one of the group of second openings, wherein the second arrangement of permanent magnets is arranged in a mixed magnet configuration having at least one low-coercivity magnet surrounded by at least two high-coercivity magnets.
20 . The method in claim 19 , further comprising: positioning a third arrangement of permanent magnets within a corresponding one of a group of third openings, wherein the third arrangement of permanent magnets is arranged in a mixed magnet configuration having at least one low-coercivity magnet surrounded by at least two high-coercivity magnets.

Description

INTRODUCTION The present disclosure relates to a rotor for an electric motor, and more particularly, to an electric motor with an arrangement of mixed magnets. A rotary electric machine of the type used in an electric drive system of an electric vehicle operates in a motoring mode in which output torque is delivered to a coupled load (e.g., one or more road wheels of a motor vehicle) and/or a generating mode in which machine rotation is used to generate electricity. In a typical configuration, the electric machine includes a cylindrical rotor formed from an annular stack of thin magnetic rotor lamination layers or “rotor lams.” The magnetic material of a rotor lam is typically an alloy of iron and silicon generally referred to in the art as electrical steel. Permanent magnets may include, for example, neodymium (Nd) magnets, also known as NdFeB, NIB, or Neo magnets. Nd magnets are rare-earth magnets made from an alloy of neodymium (Nd), iron (Fe), and/or boron (B). Nd magnets have high-coercivity (i.e., resistance to being demagnetized) and a high magnetic energy density. Permanent magnets can be disposed within openings or slots in a rotor to generate motor flux having a flux field that follows a predefined path, which can be boosted and/or opposed. Boosting the flux field increases torque production of the electric machine, while opposing the flux field will limit torque production of the electric machine. The configuration and/or topology of the permanent magnets disposed within the rotor can determine the electric machine's power density. While present rotors for an electric motor achieve their intended purpose, there is a need for new and improved permanent magnet arrangements within rotors that offer improved torque production and power density within the electric motor. SUMMARY According to several aspects of the present disclosure, a permanent magnet rotor assembly for an electric motor is provided. The permanent magnet rotor assembly includes an annular stack of rotor lamination layers (“rotor lams”) constructed of a magnetic core material. The rotor lams have inner axial surfaces collectively defining a group of first openings through the magnetic core material and a group of second openings through the magnetic core material. The annular stack includes a first arrangement of permanent magnets and a second arrangement of permanent magnets. Each respective permanent magnet of the first arrangement is disposed within a corresponding one of the group of first openings, and the first arrangement of permanent magnets is arranged in a mixed magnet configuration having at least one low-coercivity magnet surrounded by at least two high-coercivity magnets. Each respective permanent magnet of the second arrangement is disposed within a corresponding one of the group of second openings, and the second arrangement of permanent magnets is arranged in a mixed magnet configuration having at least one low-coercivity magnet surrounded by at least two high-coercivity magnets. In accordance with another aspect of the disclosure, the at least two high-coercivity magnets include at least one of a neodymium-based magnet or a samarium cobalt magnet. In accordance with another aspect of the disclosure, the at least one low-coercivity magnet includes a ferrite-based magnet. In accordance with another aspect of the disclosure, the high-coercivity magnets have parallel magnetization. In accordance with another aspect of the disclosure, the high-coercivity magnets are segmented. In accordance with another aspect of the disclosure, the at least one low-coercivity magnet is curved and has radial magnetization. In accordance with another aspect of the disclosure, at least one of the high-coercivity magnets is substantially parallel to a radius of the pole. In accordance with another aspect of the disclosure, an inner layer of the at least one low-coercivity magnet has a V configuration. In accordance with another aspect of the disclosure, two low-coercivity magnets are separated by a center post. In accordance with another aspect of the disclosure, the high-coercivity magnets are a different size than the low-coercivity magnets, and each pole includes only two magnet sizes. In accordance with another aspect of the disclosure, the first arrangement of permanent magnets includes two low-coercivity magnets, and the second arrangement of permanent magnets includes one low-coercivity magnet. According to several aspects of the present disclosure, an electrified vehicle is provided. The electrified vehicle includes an electric drive system having an electric motor including a stator and a permanent magnet rotor assembly for the electric motor configured to rotate due to a rotating magnetic field created by the stator. The permanent magnet rotor assembly includes an annular stack of rotor lamination layers (“rotor lams”) constructed of a magnetic core material. The rotor lams have inner axial surfaces collectively defining a group of