Electric motor with field winding arrangement shrink-fitted to stator body
The shrink-fitted field winding arrangement in electric motors enhances thermal conductivity and connection strength by using conductors with rectangular cross-sections and insulators, addressing the heat transfer challenge in conventional motors.
Patent Information
- Application Number
- JP2025550698
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2023-03-07
- Filing Date
- 2024-01-17
- Publication Date
- 2026-02-27
AI Technical Summary
Conventional electric motors with field windings formed from conductive bars face challenges in achieving high heat transfer between the conductive bars and the stator body, despite offering high slot filling factors and current conduction.
A field winding arrangement is shrink-fitted to the stator body, utilizing conductors with rectangular cross-sections and insulators, enhancing thermal conductivity and connection strength through a compressive fit, optionally with supplemental insulation.
The solution improves packing factor, connection strength, and thermal conductivity between the field windings and stator body, addressing the heat transfer challenge while maintaining high slot filling efficiency.
Smart Images
Figure 2026507178000001_ABST
Abstract
Description
[Technical Field]
[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Patent Application No. 63 / 450,483, filed March 7, 2023, the disclosure of which is incorporated herein by reference as if fully set forth in detail herein.
[0002] Technical Field The present disclosure relates to an electric motor having a field winding arrangement that is shrink-fitted to a stator body. [Background technology]
[0003] This section provides background information related to the present disclosure. This background information is not necessarily prior art.
[0004] A conventional polyphase alternating current (AC) electric motor includes a stator assembly including a stator core or stator body and a field winding device attached to the stator body. The field winding device may include multiple sets of field windings. The field windings may be formed of wire and wound into winding slots formed in the stator body. Alternatively, the field windings may be formed of conductive bars (sometimes referred to as hairpins) that are individually housed in winding slots in the stator body and then electrically and mechanically coupled in series with each other. Using wire to form the field winding sets has the advantage of being relatively quick and easy to wind and assemble onto the stator body compared to using conductive bars. However, conductive bars typically fit more easily into the winding slots, which allows for a relatively high slot filling factor and typically allows for greater current conduction.
[0005] While known stator assemblies having field winding arrangements utilizing field windings formed from conductive bars or hairpins are generally satisfactory for their intended applications, the inventors have noted that in some situations it is desirable to have a relatively high degree of heat transfer between the conductive bars and the stator body. Summary of the Invention
[0006] This section provides a summary of the disclosure and is not a comprehensive disclosure of its entire scope or all features.
[0007] In one aspect, the teachings of the present disclosure provide an electric motor having a stator body defining a rotor bore and a plurality of winding slots, and a field winding device having a plurality of sets of field windings. The rotor bore extends along a motor axis. The winding slots are formed circumferentially around the rotor bore and longitudinally through the stator body. Each of the field windings has a plurality of conductors having a generally rectangular cross-sectional area. Each of the conductors includes a pair of in-slot segments, a connector portion, and a pair of free ends. Each of the in-slot segments is received in a corresponding one of the winding slots. The connector portions connect the pair of in-slot segments to each other at first axial ends of the in-slot segments. Each of the free ends is mechanically and electrically connected 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 connected to each other in series. The field winding device is shrink-fitted 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. [Brief explanation of the drawings]
[0009] The drawings described herein are merely illustrative of selected embodiments, do not illustrate all possible embodiments, and are not intended to limit the scope of the present disclosure.
[0010] [Figure 1] FIG. 1 is a cross-sectional view of an exemplary electric motor constructed in accordance with the teachings of the present disclosure.
[0011] [Figure 2] FIG. 2 is a perspective view of a portion of the electric motor of FIG. 1 showing the stator assembly in greater detail.
[0012] [Figure 3] FIG. 3 is a cross-sectional view of a portion of the stator assembly showing the stator body in more detail.
[0013] [Figure 4] FIG. 4 is an enlarged view of FIG.
[0014] [Figure 5] FIG. 5 is a perspective view of a portion of the stator assembly showing the conductors of the field winding.
[0015] [Figure 5A] FIG. 5A is a cross-sectional view taken along line 5A-5A in FIG.
[0016] [Figure 6] FIG. 6 is a cross-sectional view of a portion of the stator assembly showing the various field winding conductors housed in the winding slots of the stator body.
[0017] [Figure 7] FIG. 7 is a cross-sectional view similar to FIG. 6, but showing in-slot insulators received within the winding slots and positioned between the conductors of the field winding and the opposing side walls of the winding slot.
[0018] Corresponding reference numerals indicate corresponding parts throughout the various views of the drawings. DETAILED DESCRIPTION OF THE INVENTION
[0019] Referring to Figure 1, an electric motor constructed in accordance with the teachings of the present disclosure is generally designated by the reference numeral 10. Electric motor 10 includes a motor housing 12, a stator assembly 14 housed within motor housing 12, and a rotor assembly 16 rotatable relative to stator assembly 14 about a motor axis 18. Rotor assembly 16 can be constructed in a manner known in the art and need not be described in detail herein. Stator assembly 14 includes a stator body 20 and a field winding arrangement 22.
[0020] 2-4 , the stator body 20 defines a rotor bore 30 extending concentrically along the motor shaft 18 and a plurality of winding slots 32 arranged concentrically around the stator body 20. Each winding slot 32 has a radially outer end 36, a radially inner end 38, and a conductor receiving portion 40. In the illustrated example, the radially inner end 38 of each winding slot 32 intersects the rotor bore 30, and the conductor receiving portion 40 of each winding slot 32 extends between the radially outer end 36 of the winding slot 32 and a position radially outward of the radially inner end 38 of the winding slot 32. Optionally, the conductor receiving portion 40 has a first circumferential width, and a portion 44 of each winding slot 32 between the radially inner end 38 and the radially inner end of the conductor receiving portion 40 has a second circumferential width narrower than the first width. Alternatively, each of the winding slots 32 may be configured such that the portion of the winding slot 32 disposed between the radially inner end of the conductor receiving portion 40 and the radially inner end 38 has a width in the circumferential direction that is equal to or greater than the first width.
[0021] 2, 5, and 5A, field winding device 22 includes multiple sets of field windings 50, and may optionally include supplemental insulating means (not specifically shown). Each set of field windings 50 includes multiple conductors 54 having a generally rectangular cross-sectional area. Each conductor 54 may include a conductor member 56 and an insulator 58 that are unitarily and integrally formed from a conductive metallic material.
[0022] Each conductor member 56 may have a pair of in-slot segments 60, a connector portion 62, and a pair of free ends 64. Each in-slot segment 60 is sized to be received in 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 each other at first axial ends 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 set of field windings 50 are electrically coupled in series with each other. In the illustrated example, the conductors 54 are configured to be axially inserted into the winding slots 32 ( FIG. 6 ), each conductor 54 having two in-slot segments 60 and one connector portion 62, with the free ends 64 being bent into their final shape after the conductors 54 are inserted into the winding slots 32. However, it should be understood that the conductor 54 may be comprised of more than two in-slot segments 60 and more than two connector portions 62, and / or the free end 64 may be formed into its final shape before the conductor 54 is inserted into the winding slot 32, for example, if the conductor 54 is inserted radially rather than axially into the winding slot 32 (FIG. 6).
[0023] The insulator 58 is formed of an electrically insulating material and is disposed on at least a portion of the conductor member 56 that may include the inslot segment 60. The insulator 58 may be formed of any type of electrically insulating material, but in the example shown, it is formed of a resin material (i.e., varnish). The insulator 58 does not need to be applied to (or may be removed from) the portions of the conductors 54 that are electrically coupled to each other. 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 to each other (e.g., welded to each other).
[0024] 4-5A , if included, supplemental insulating means (not shown) may be interposed between the stator body 20 and the in-slot segments 60 of the conductors 54. In one form, the supplemental insulating means may comprise a coating of an electrically insulating material over the interior surface of the stator body 20, including appropriate surfaces of the winding slots 32. The coating may be formed of a ceramic material or a resin such as varnish, and may form an electrically insulating barrier over the surfaces of the winding slots 32, including the radially outer ends 36 ( FIG. 4 ) of the winding slots 32, and over portions of the sidewalls 70 associated with the conductor receiving portions 40.
[0025] 7 , the auxiliary insulating means may additionally or alternatively include a plurality of separate in-slot insulators 80, which may be formed, for example, from a paper material or a plastic sheet material. Each of the in-slot insulators 80 is received in a corresponding one of the winding slots 32 and is interposed between the stator body 20 and the in-slot segment 60 received in the corresponding one of the winding slots 32. Each of the separate in-slot insulators 80 has a generally U-shaped cross-sectional shape and may abut opposing side walls 70 and the radially outer end 36 of the corresponding one of the winding slots 32.
[0026] 1, 2, 4, and 6, the field winding device 22 is shrink-fitted to the stator body 20, whereby a compressive force is exerted on the field winding device 22 by the stator body 20. Such a configuration allows for one or more improvements, such as an increased packing factor (i.e., the ratio of the cross-sectional area of the in-slot segments 60 of the conductors 54 to the cross-sectional area of the conductor receiving portions 40), an increased connection strength between the field winding set 50 and the stator body 20, and / or an increased thermal conductivity (i.e., heat transfer) between the field winding set 50 and the stator body 20. In situations where supplemental insulation means are not employed in the electric motor 10, each of the in-slot segments 60 directly engages opposite side walls of the conductor receiving portions 40 of a corresponding one of the winding slots 32 in a shrink-fit manner, whereby a compressive force is exerted by the stator body 20 through the side walls 70 of the winding slot 32 and against the sides of the in-slot segments 60 abutting the side walls 70. In situations where the electric motor 10 includes supplemental insulation means, the compressive force exerted by the stator body 20 is transmitted through the side walls of the winding slot 32 and the supplemental insulation means to the sides of the in-slot segment 60 located between the side walls 70. It should be appreciated that shrink fitting the field winding device 22 into the stator body 20 may be accomplished by heating the stator body 20 and / or by cooling the conductors 54 of the field winding device 22 prior to inserting the conductors 54 into the winding slots 32.
[0027] The description of the above-described embodiments has been provided for purposes of illustration and description. The description is not intended to be exhaustive or to limit the present disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment and, where applicable, may be interchangeable and usable in selected embodiments even if not specifically shown or described. The same may be modified in various ways. Such modifications are not considered a departure from the present disclosure, and all such modifications are intended to be included within the scope of the present disclosure.
Claims
1. An electric motor (10), comprising: a stator body (20) defining a rotor bore (30) and a plurality of winding slots (32), the rotor bore (30) extending along the motor shaft (18), the winding slots (32) formed circumferentially around the rotor bore (30) and longitudinally through the stator body (20); a field winding device (22) having a plurality of sets of field windings (50), each of the field windings (50) having a plurality of conductors (54), each of the conductors (54) having a generally rectangular 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) received in a corresponding one of the winding slots (32), the connector portions (62) connecting the pair of in-slot segments (60) to each other at first axial ends of the in-slot segments (60), each of the free ends (64) being mechanically and electrically connected to a corresponding one of the in-slot segments (60), and the free ends (64) of the conductors (54) in each of the sets of the field windings (50) being electrically connected to each other in series; It is equipped with The electric motor (10) has a field winding device (22) that is shrink-fitted to the stator body (20).
2. 2. The electric motor of claim 1, wherein each of the conductors comprises a conductor member formed of a conductive metallic material and an insulator formed of an electrically insulating material, the insulator being disposed over at least a portion of the conductor member corresponding to the pair of in-slot segments.
3. 3. The electric motor (10) of claim 2, wherein each of the in-slot segments (60) directly engages opposite side walls (70) of a corresponding one of the winding slots (32).
4. 3. The electric motor (10) of claim 2, wherein the field winding device (22) includes supplemental insulating means, the supplemental insulating means being interposed between the stator body (20) and the in-slot segments (60) housed in the winding slots (32).
5. 5. The electric motor (10) of claim 4, wherein the supplemental insulation means comprises a resin contained within the winding slots (32).
6. 5. The electric motor (10) of claim 4, wherein the supplemental insulating means comprises a plurality of separate in-slot insulators (80), each of which is received in a corresponding one of the winding slots (32) and is interposed between the stator body (20) and the in-slot segment (60) received in the corresponding one of the winding slots (32).
7. 7. The electric motor (10) of claim 6, wherein each of the separate in-slot insulators (80) is formed from a paper material or a plastic sheet material.
8. 2. The electric motor of claim 1, wherein each of the winding slots has a radially inner end intersecting the rotor bore and a conductor receiving portion radially outward of the radially inner end, the conductor receiving portion having a first circumferential width, and a radial portion of each of the winding slots between the inner end and the conductor receiving portion having a second circumferential width smaller than the first width.