EP4652662A1

EP4652662A1 - Electric motor with field winding arrangement that is shrunk-fit to a stator body

Info

Publication number: EP4652662A1
Application number: EP24767539.0A
Authority: EP
Inventors: James R. DERR; Tyler D. JEZOWSKI
Original assignee: American Axle and Manufacturing Inc
Current assignee: American Axle and Manufacturing Inc
Priority date: 2023-03-07
Filing date: 2024-01-17
Publication date: 2025-11-26
Also published as: KR20250161597A; CN120814152A; WO2024186406A1; JP2026507178A; MX2025010538A

Abstract

An electric motor that includes a stator body, which defines a plurality of winding slots, and a field winding arrangement having a plurality of sets of field windings that include a plurality of conductors. Each of the conductors has a generally rectangularly shaped lateral cross-sectional area, and includes a pair of in-slot segments, a connector portion, and a pair of free ends. Each of the in-slot segments is received into a corresponding one of the winding slots. The connector portion coupling the pair of in-slot segments to one another at a first axial end of the in-slot segments. Each of the free ends being mechanically and electrically coupled to a corresponding one of the in-slot segments. The free ends of the conductors in each of the sets of field windings are electrically coupled in series to one another. The field winding arrangement is shrunk-fit to the stator body.

Description

ELECTRIC MOTOR WITH FIELD WINDING ARRANGEMENT THAT IS SHRUNK-FIT TO A STATOR BODY

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 63/450483 filed March 7, 2023, the disclosure of which is incorporated by reference as if fully set forth in detail herein.

FIELD

[0002] The present disclosure relates to an electric motor with a field winding arrangement that is shrunk-fit to a stator body.

BACKGROUND

[0003] This section provides background information related to the present disclosure which is not necessarily prior art.

[0004] Conventional multi-phase alternating current (AC) electric motors have a stator assembly that includes a stator core or body and a field winding arrangement that is mounted to the stator body. The field winding arrangement can include a plurality of sets of field windings. The field windings can be formed of wire and can be wound into winding slots that are formed in the stator body. Alternatively, the field windings can be formed of conductive bars, which are sometimes referred to as being hairpins, that are separately received into the winding slots in the stator body and thereafter electrically and mechanically coupled to one another in series. The use of wire to form the sets of field windings has the advantage of being relatively quicker and easier to wind/assemble to the stator body than the use of conductive bars. However, conductive bars typically fit the winding slots to a better degree, thereby providing a relatively higher degree of slot fill, and also are typically able to conduct a higher amount of current.

[0005] While the known stator assemblies having field winding arrangements that utilize field windings formed of conductive bars or hairpins are generally satisfactory for their intended use, we have noted that a relatively higher degree of heat transfer between the conductive bars and the stator body would be desirable in some situations. SUMMARY

[0006] This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.

[0007] In one form, the teachings of the present disclosure provide an electric motor that includes a stator body, which defines a rotor bore and a plurality of winding slots, and a field winding arrangement having a plurality of sets of field windings. The rotor bore extends along a motor axis. The winding slots are formed longitudinally through the stator body circumferentially about the rotor bore. Each of the sets of field windings includes a plurality of conductors that have a generally rectangularly shaped lateral cross-sectional area. Each of the conductors has a pair of in-slot segments, a connector portion, and a pair of free ends. Each of the in-slot segments is received into a corresponding one of the winding slots. The connector portion couples the pair of in-slot segments to one another at a first axial end of the in-slot segments. Each of the free ends is mechanically and electrically coupled to a corresponding one of the in-slot segments. The free ends of the conductors in each of the sets of field windings are electrically coupled in series to one another. The field winding arrangement is shrunk-fit to the stator body.

[0008] Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

DRAWINGS

[0009] The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure.

[0010] Figure 1 is a section view of an exemplary electric motor constructed in accordance with the teachings of the present disclosure;

[0011] Figure 2 is a perspective view of a portion of the electric motor of Figure 1 illustrating a stator assembly in more detail;

[0012] Figure 3 is a section view of a portion of the stator assembly illustrating a stator body in more detail;

[0013] Figure 4 is an enlarged portion of Figure 3; [0014] Figure 5 is a perspective view of a portion of the stator assembly illustrating a conductor of a field winding;

[0015] Figure 5A is a section view taken along the line 5A-5A of Figure 5;

[0016] Figure 6 is a section view of a portion of the stator assembly illustrating the conductors of various field windings as received in a winding slot in the stator body; and

[0017] Figure 7 is a section view similar to that of Figure 6 but depicting an in-slot insulator received in the winding slot and disposed between the conductors of the field windings and the opposite sidewalls of the winding slot. [0018] Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.

DETAILED DESCRIPTION

[0019] With reference to Figure 1 , an electric motor constructed in accordance with the teachings of the present disclosure is generally indicated by reference numeral 10. The electric motor 10 includes a motor housing 12, a stator assembly 14, which is received in the motor housing 12, and a rotor assembly 16 that is rotatable relative to the stator assembly 14 about a motor axis 18. The rotor assembly 16 can be constructed in a conventional and well known manner and as such, need not be described in detail herein. The stator assembly 14 includes a stator body 20 and a field winding arrangement 22.

[0020] With reference to Figures 2 through 4, the stator body 20 defines a rotor bore 30 that extends concentrically along the motor axis 18 and a plurality of winding slots 32 that are disposed concentrically about the stator body 20. Each of the winding slots 32 has a radially outward end 36, a radially inward end 38 and a conductor receiving portion 40. In the example provided, the radially inward end 38 of each of the winding slots 32 intersects the rotor bore 30, and the conductor receiving portion 40 of each winding slot 32 extends between the radially outward end 36 of the winding slot 32 and a location that is radially outward of the radially inward end 38 of the winding slot 32. Optionally, the conductor receiving portions 40 have a first width in a circumferential direction, and wherein a portion 44 of each winding slot 32 that is radially between the radially inward end 38 and a radially inward end of the conductor receiving portion 40 has a second width in the circumferential direction that is smaller than the first width. Alternatively, each of the winding slots 32 could be configured such that the portion of the winding slot 32 that is disposed between the radially inward end of the conductor receiving portion 40 and the radially inward end 38 can have a width in the circumferential direction that is greater than or equal to the first width.

[0021] With reference to Figures 2, 5 and 5A, the field winding arrangement 22 has a plurality of sets of field windings 50 and can optionally have a supplementary insulation means (not specifically shown). Each of the sets of field windings 50 having a plurality of conductors 54 that have a generally rectangularly shaped lateral cross-sectional area. Each of the conductors 54 can include a conductor member 56, which is unitarily and integrally formed of a conductive metal material, and an insulator 58.

[0022] Each of the conductor members 56 can have a pair of in-slot segments 60, a connector portion 62, and a pair of free ends 64. Each of the in-slot segments 60 is sized to be received into the conductor receiving portion 40 of a corresponding one of the winding slots 32. The connector portion 62 couples the pair of in-slot segments 60 to one another at a first axial end of the in-slot segments 60. Each of the free ends 64 is mechanically and electrically coupled to a corresponding one of the in-slot segments 60. The free ends 64 of the conductors 54 in each of the sets of field windings 50 are electrically coupled in series to one another. In the example provided, the conductors 54 are configured to be inserted in an axial direction into the winding slots 32 (Fig. 6), each conductor 54 has two of the in-slot segments 60 and a single connector portion 62, and the free ends 64 are bent into the final shape after the conductors 54 have been inserted into the winding slots 32. It will be appreciated, however, that the conductors 54 could be configured with three or more in-slot segments 60 and two or more connector portions 62, and/or that the free ends 64 could be formed into their final shape before the conductors 54 are inserted into the winding slots 32 (Fig. 6), for example if the conductors 54 are inserted into the winding slots 32 (Fig. 6) in a radial direction rather than in an axial direction.

[0023] The insulator 58 is formed of an electrically insulating material and is disposed over at least the portion of the conductor member 56 that can include the in-slot segments 60. The insulator 58 can be formed of any type of electrically insulating material, but is formed of a resin material (i.e., varnish) in the example that is provided. The insulator 58 need not be applied to (or could be removed from) portions of the conductors 54 that are electrically coupled to one another. In the example shown, the insulator 58 is removed from the portions of the free ends 64 of the conductor members 56 that are fixedly and electrically coupled (e.g., welded) to one another.

[0024] With reference to Figures 4 through 5A, if a supplementary insulation means (not shown) were to be included, the supplementary insulation means could be interposed between the stator body 20 and the in-slot segments 60 of the conductors 54. In one form, the supplementary insulation means can comprise coating of an electrically insulating material over an interior surface of the stator body 20 that includes appropriate surfaces of the winding slots 32. The coating could be formed of a ceramic material or a resin, such as a varnish, and can form an electrically insulating barrier over surfaces of the winding slots 32 that include the radially outward end 36 (Fig. 4) of the winding slots 32 and the portions of the sidewalls 70 that are associated with the conductor receiving portions 40.

[0025] With reference to Figure 7, the supplementary insulation means could additionally or alternatively comprise a plurality of discrete in-slot insulators 80 that can be formed of a paper material or a plastic sheet material, for example. Each of the in-slot insulators 80 is received into a corresponding one of the winding slots 32 and is interposed between the stator body 20 and the in-slot segments 60 that are received into the corresponding one of the winding slots 32. Each of the discrete in-slot insulators 80 can have a generally U-shaped lateral cross-sectional shape and can abut the opposite sidewalls 70 and the radially outward end 36 of a corresponding one of the winding slots 32. [0026] With reference to Figures 1 , 2, 4 and 6, the field winding arrangement 22 is shrunk-fit to the stator body 20 such that a compressive force is exerted by the stator body 20 onto the field winding arrangement 22. Configuration in this manner can permit one or more improvements, such as an increased fill ratio (i.e. the ratio of the lateral cross-sectional area of the in-slot segments 60 of the conductors 54 to the lateral cross-sectional area of the conductor receiving portions 40), increased strength of the connection between the sets of field windings 50 and the stator body 20 and/or increased thermal conductivity (i.e., heat transfer) between the sets of field windings and the stator body 20. In situations where a supplementary insulation means is not employed in the electric motor 10, each of the in-slot segments 60 directly engages the opposite sidewalls of the conductor receiving portions 40 of a corresponding one of the winding slots 32 in a shrink-fit manner so that a compressive force is exerted by the stator body 20 through the sidewalls 70 of the winding slots 32 onto the sides of the in-slot segments 60 that abut the sidewalls 70. In situations where the electric motor 10 includes a supplementary insulation means, the compressive force that is exerted by the stator body 20 is transmitted through the sidewalls of the winding slots 32 and the supplementary insulation means to the sides of the in-slot segments 60 that are disposed between the sidewalls 70. It will be appreciated that the shrink fitting of the field winding arrangement 22 to the stator body 20 could be accomplished through the heating of the stator body 20 and/or the cooling of the conductors 54 of the field winding arrangement 22 prior to the insertion of the conductors 54 to the winding slots 32.

[0027] The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.

Claims

CLAIMS What is claimed is:

1 . An electric motor (10) comprising: a stator body (20) that defines a rotor bore (30) and a plurality of winding slots (32), the rotor bore (30) extending along a motor axis (18), the winding slots (32) being formed longitudinally through the stator body (20) circumferentially about the rotor bore (30); a field winding arrangement (22) having a plurality of sets of field windings (50), each of the sets of field windings (50) having a plurality of conductors (54), each of the conductors (54) having a generally rectangularly shaped lateral cross-sectional area, each of the conductors (54) having a pair of in-slot segments (60), a connector portion (62), and a pair of free ends (64), each of the in-slot segments (60) being received into a corresponding one of the winding slots (32), the connector portion (62) coupling the pair of in-slot segments (60) to one another at a first axial end of the in-slot segments (60), each of the free ends (64) being mechanically and electrically coupled to a corresponding one of the in-slot segments (60), wherein the free ends (64) of the conductors (54) in each of the sets of field windings (50) are electrically coupled in series to one another; wherein the field winding arrangement (22) is shrunk-fit to the stator body (20).

2. The electric motor (10) of Claim 1 , wherein each of the conductors (54) comprise a conductor member (56), which is formed of a conductive metal material, and an insulator (58) that is formed of an electrically insulating material, the insulator (58) being disposed over at least the portion of the conductor member (56) that corresponds to the pair of in-slot segments (60).

3. The electric motor (10) of Claim 2, wherein each of the in-slot segments (60) directly engages opposite sidewalls (70) of a corresponding one of the winding slots (32).

4. The electric motor (10) of Claim 2, wherein the field winding arrangement (22) comprises a supplementary insulation means, the supplementary insulation means being interposed between the stator body (20) and the in-slot segments (60) that are received into the winding slots (32).

5. The electric motor (10) of Claim 4, wherein the supplementary insulation means comprises a resin that is received into the winding slots (32).

6. The electric motor (10) of Claim 4, wherein the supplementary insulation means comprises a plurality of discrete in-slot insulators (80), each of the discrete in-slot insulators (80) being received into a corresponding one of the winding slots (32) and being interposed between the stator body (20) and the in-slot segments (60) that are received into the corresponding one of the winding slots (32).

7. The electric motor (10) of Claim 6, wherein each of the discrete in-slot insulators (80) is formed of a paper material or plastic sheet material.

8. The electric motor (10) of Claim 1 , wherein each of the winding slots (32) has a radially inward end (38), which intersects the rotor bore (30), and a conductor receiving portion (40) that is radially outward of the radially inward end (38), and wherein the conductor receiving portion (40) has a first width in a circumferential direction, and wherein a portion of each winding slot (32) that is radially between the inward end (38) and the conductor receiving portion (40) has a second width in the circumferential direction that is smaller than the first width.