Method of forming an electric motor using a mandrel assembly
The encapsulation process using a mandrel assembly with a mandrel core and expandable sleeve addresses heat buildup in electric motor stators by sealing the stator core's bore and filling gaps with encapsulant, improving heat transfer and rotor assembly compatibility.
Patent Information
- Application Number
- JP2025550699
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2023-03-08
- Filing Date
- 2024-01-17
- Publication Date
- 2026-03-02
AI Technical Summary
Existing electric motor stators experience heat buildup due to voids between conductive windings, which inhibit effective heat transfer to the stator material.
A method involving an encapsulation process using a mandrel assembly with a mandrel core and expandable sleeve to seal the stator core's bore, followed by injecting a liquid encapsulant that hardens to fill gaps and form an encapsulated stator assembly, ensuring minimal encapsulant enters the bore.
The method enhances heat transfer by reducing voids and minimizing encapsulant in the bore, thereby preventing heat buildup and maintaining a smooth surface for rotor assembly rotation.
Smart Images
Figure 2026507352000001_ABST
Abstract
Description
[Technical Field]
[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Patent Application No. 63 / 450,767, filed March 8, 2023, the disclosure of which is incorporated herein by reference as if fully set forth in detail herein.
[0002] Technical Field FIELD OF THE DISCLOSURE The present disclosure relates to forming electric motors, and more particularly to forming stator assemblies for electric motors. [Background technology]
[0003] This section provides background information related to the present disclosure. This background information is not necessarily prior art.
[0004] In today's electric motors, the stator teeth are typically wrapped with conductive wire. The conductive wire is typically wound multiple times around each stator tooth. Sometimes, a circular cross-sectional shape is used, and sometimes, a ribbon-shaped wire is used. In either case, however, the winding process typically leaves multiple voids between adjacent sections of conductive wire. These voids are undesirable because they inhibit heat transfer from the conductive windings to the stator material. This can lead to unacceptable heat buildup within the stator. Summary of the Invention
[0005] This section provides a summary of the disclosure and is not a comprehensive disclosure of its entire scope or all features.
[0006] In one aspect, the present disclosure provides a method of forming an electric motor. The method includes providing a stator assembly having a stator core and a set of windings, the stator core defining a bore and the windings coupled to the stator core; assembling the stator assembly into an encapsulation fixture, thereby forming an encapsulated assembly, the encapsulation fixture having at least a mandrel assembly including a mandrel core and a sleeve, at least a portion of the mandrel assembly extending through the bore of the stator core; heating the encapsulation assembly, thereby causing the sleeve of the mandrel assembly to expand against the stator core, thereby sealing against at least a portion of an inner surface of the bore of the stator core; injecting a liquid encapsulant into the encapsulation assembly such that the encapsulant at least partially encapsulates the stator assembly; at least partially hardening the encapsulant, thereby forming an at least partially encapsulated stator assembly; and separating the at least partially encapsulated stator assembly from the encapsulation fixture. In another aspect, the present disclosure provides a method of forming an electric motor.The method includes the steps of: providing a stator assembly having a stator core and a set of windings, the stator core defining a bore, the windings being coupled to the stator core; providing a mandrel assembly including a mandrel core and a sleeve, the mandrel core being at least partially disposed within a cavity of the sleeve; assembling the mandrel assembly into the bore of the stator core such that a portion of the mandrel assembly extends through the bore of the stator core of the stator assembly; and heating the stator assembly together with at least the mandrel assembly, thereby heating the sleeve of the mandrel assembly. expanding against a stator core, thereby sealing against at least a portion of an inner surface of the bore of the stator core; injecting the liquid encapsulant into the stator assembly such that the encapsulant at least partially encapsulates the stator assembly; at least partially hardening the encapsulant, thereby forming an at least partially encapsulated stator assembly; and removing the at least partially encapsulated stator assembly from the mandrel assembly after at least one of the at least partially encapsulated stator assemblies and the mandrel assembly have cooled such that the sleeve no longer seals against the inner surface of the bore of the stator core.
[0007] In yet another aspect, the present disclosure provides a method of forming an electric motor, the method including the steps of providing a stator assembly having a housing, a stator core, and a set of windings, the stator core defining a bore, the windings coupled to the stator core, the stator core and the windings disposed within the housing; assembling the stator assembly into an encapsulation fixture to form an encapsulated assembly, the encapsulation fixture having at least a mandrel assembly including a mandrel core and a sleeve, the mandrel core at least partially disposed within a cavity of the sleeve, at least a portion of the mandrel assembly extending through the bore of the stator core; and heating the encapsulation assembly, thereby forming an encapsulated assembly of the mandrel assembly. expanding the sleeve of the mandrel against the stator core, thereby sealing it against at least a portion of the inner surface of the bore of the stator core; injecting a liquid encapsulant into the encapsulation assembly such that the encapsulant at least partially encapsulates the stator assembly in a portion of a gap defined between the housing and an outer diameter of the mandrel assembly; at least partially hardening the encapsulant, thereby forming an at least partially encapsulated stator assembly; and separating the at least partially encapsulated stator assembly from the encapsulation fixture after the encapsulation assembly has cooled to a point where the sleeve no longer seals against the inner surface of the bore of the stator core.
[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 1A] FIG. 1A is a perspective view of a stator assembly with an encapsulation fixture in accordance with the teachings of the present disclosure. [Figure 1B] FIG. 1B is a perspective view of a stator assembly with an encapsulation fixture in accordance with the teachings of the present disclosure.
[0011] [Figure 2] FIG. 2 is a partial exploded view of an encapsulation fixture and stator assembly without a housing in accordance with the teachings of the present disclosure.
[0012] [Figure 3] FIG. 3 is a cross-sectional view of an encapsulation fixture and stator assembly without a housing in accordance with the teachings of the present disclosure.
[0013] [Figure 4] FIG. 4 is a partially exploded view of a stator assembly and a second embodiment of an encapsulation fixture in accordance with the teachings of the present disclosure.
[0014] [Figure 5] FIG. 5 is a cross-sectional view of a stator assembly and a second form of encapsulation fixture in accordance with the teachings of the present disclosure.
[0015] [Figure 6] FIG. 6 is a perspective view of a portion of a third embodiment of an encapsulation fixture in accordance with the teachings of the present disclosure.
[0016] Corresponding reference numerals indicate corresponding parts throughout the various views of the drawings. DETAILED DESCRIPTION OF THE INVENTION
[0017] 1 and 2 , a stator assembly 100 for an electric motor generally includes a stator core 102, a set of windings 104 coupled to the stator core 102, and, in some applications, one or more end caps 105A, 105B (i.e., also referred to as “stator caps”) disposed at opposite ends of the stator assembly 100. The stator core 102 defines a bore 103 for receiving a rotor assembly (not shown) and has a plurality of teeth defining a plurality of slots between adjacent teeth. The set of windings 104 is coupled to the plurality of teeth and, more specifically, is wound around the plurality of teeth. In some applications, the stator core 102 is provided as a monolithic structure. In other examples, the stator core 102 is formed by a plurality of laminated disks arranged in a stackable manner and rigidly secured to one another.
[0018] Typically, air gaps between the windings 104 and the stator core 102 inhibit heat transfer from the windings 104 to the stator core 102, potentially resulting in unacceptable heat buildup within the stator assembly 100. To improve heat transfer, the stator assembly 100 is at least partially encapsulated with an encapsulant, such as a polymer-based liquid, as part of an encapsulation process. The encapsulant is provided to fill the air gaps between the stator core 102 and the set of windings 104. The encapsulant may also be used to fill other air gaps in the stator assembly 100, including, but not limited to, the air gaps around a pair of end caps and end turns in the set of windings 104 of the stator assembly 100.
[0019] The bore 103 of the stator assembly 100 is typically not encapsulated to provide a smooth surface for the rotor assembly. More specifically, little or no encapsulant is provided on the surface of the bore 103 because the rotor assembly rotates within the bore 103 of the stator assembly 100. As described herein, the present disclosure provides an encapsulation method employing an encapsulation fixture 200 having a mandrel assembly 202 that inhibits or reduces the amount of encapsulant that enters the bore 103.
[0020] In one form, the mandrel assembly 202 includes a mandrel core 204 and a sleeve 206. The mandrel core 204 supports the sleeve 206 and may be made of a variety of suitable materials, such as, but not limited to, steel, aluminum alloy, or other alloys. In one form, the mandrel core 204 defines an opening 208 and includes a set of grooves 209 (i.e., hereinafter "grooves 209") that define a set of ridges 210 along the outer surface of the mandrel core 204. In the example shown in FIGS. 1A, 1B, 2, and 3, the mandrel core 204 is provided as a multi-piece structure in which the pieces are secured together to provide a core that accommodates thermal expansion and part variations. For example, the mandrel core 204 includes an inner core 212 that defines the opening 208 and an outer core 214 having the ridges 210. The inner core 212 includes a biasing element 216, such as a spring, disposed around the outside of the inner core 212, with one end secured to the inner core 212 and the other end secured by a fastener, such as a washer 218 and clip 220. The outer core 214 defines a hole 222 for receiving and accommodating at least a portion of the inner core 212 and a groove 224 for the clip 220. The biasing element 216 extends between and is compressible between the inner core 212 and the outer core 214, thereby allowing the inner core 212 to move along the longitudinal axis of the mandrel assembly 202. The longitudinal axis is typically provided by a wire 225. The outer core 214 of the mandrel assembly 202 extends to one end of the stator assembly 100, and the inner core 212 of the mandrel assembly 202 extends to the other end of the stator assembly 100. The mandrel core 204 is adjustable in length to accommodate stator assemblies of different lengths. Specifically, the length of the mandrel core 204 is adapted to maintain a clamping force on the stator assembly 100 while accommodating, for example, length variations and / or thermal expansion.
[0021] While the fasteners for securing the biasing element 216 are shown to include a washer 218 and a clip 220, other suitable fasteners may be provided, including, but not limited to, a plate welded to the outer core 214 or a plate formed with the outer core 214. Additionally, although the mandrel core 204 is provided as a multi-piece component, the mandrel core 204 may also be provided as a single, monolithic piece of material of a fixed length.
[0022] In one form, the sleeve 206 is made of an elastomeric material that expands when heated, such as, but not limited to, a silicone-based material. The sleeve 206 defines a cavity, and the mandrel core 204 is at least partially disposed within the cavity to support the sleeve 206. More specifically, the sleeve 206 is configured to be disposed over and removable from the mandrel core 204. The sleeve 206 is generally aligned with the ribs 210 of the mandrel core 204.
[0023] In some applications, the mandrel core 204 and the sleeve 206 may include additional features for aligning and connecting them to one another. For example, the mandrel core 204 includes a rim 230, and the sleeve 206 has a circumferential recess 232 along its inner surface for receiving, or engaging, the rim 230 of the mandrel core 204.
[0024] As described further below, with the sleeve 206 positioned on the mandrel core 204, the mandrel assembly 202 is assembled to the bore 103 of the stator core 102, i.e., inserted into the bore 103 with a portion of the mandrel assembly 202 extending through the bore 103. The stator assembly 100 and the encapsulation fixture 200 having at least the mandrel assembly 202 may collectively be referred to as an encapsulation assembly. The encapsulation assembly is provided in, for example, an industrial oven and heated therein to increase the temperature of the stator assembly 100 and seal the bore 103. Specifically, during the heating process, the sleeve 206 expands relative to the stator core 102 and seals against at least a portion of the inner surface of the bore 103 of the stator core 102. In some cases, the sleeve 206 may also expand into the groove 209 of the mandrel core 204 to seal the space between the inner surface of the stator core 102 and the mandrel assembly 202. The encapsulated assembly is heated based on one or more heating parameters, including, but not limited to, one or more temperature settings and heating time of an industrial oven employed to heat the encapsulated assembly.
[0025] After heating, the encapsulation assembly is injected with an encapsulant, which in some applications is provided at the bottom of the encapsulation assembly for pushing upward through the stator assembly 100. For example, the stator assembly 100 has a first axial end (shown generally by reference numeral 110) and a second axial end (shown generally by reference numeral 112) opposite the first axial end 110, and the encapsulation assembly is positioned such that the first axial end 110 of the stator assembly 100 is lower than the second axial end 112 of the stator assembly 100. The encapsulant is provided at the first axial end 110 of the stator assembly 100 and pushed through the stator assembly 100 to the second axial end 112 of the stator assembly 100. The bore 103 is sealed by a mandrel assembly 202 to prevent the encapsulant from entering the bore 103.
[0026] After injection, the encapsulant is at least partially cured, thereby forming an at least partially encapsulated stator assembly 100. Specifically, the encapsulation assembly is heated in an industrial oven, thereby at least partially curing the encapsulant. The encapsulation assembly is then cooled to a point where the sleeve 206 no longer seals against the inner surface of the bore 103 of the stator core 102. After cooling, the stator assembly 100 is removed from the encapsulation fixture 200. For example, the mandrel assembly 202 is removed from the stator assembly 100 to separate the at least partially encapsulated stator assembly 100 from the encapsulation fixture 200. The sleeve 206 and mandrel core 204 leave the bore 103 of the stator assembly 100 with little or no encapsulant, providing a substantially smooth surface for the rotor assembly.
[0027] 4 and 5, instead of the two-piece mandrel assembly 202, the encapsulation fixture 300 may include a mandrel assembly 302 having a mandrel 304 adapted to extend at least partially through the bore 103 of the stator assembly 100. In one form, the mandrel 304 is adapted for a snug fit with the stator core 102; more specifically, the outer diameter of the mandrel 304 is smaller than the inner diameter of the stator core 102, but as close to the stator core 102 as possible to inhibit or reduce the encapsulant from entering the bore 103. The mandrel 304 is adapted to inhibit adhesion with the encapsulant. For example, the outer surface of the mandrel 304 is substantially smooth to inhibit or reduce adhesion of the encapsulant to the surface of the mandrel 304. Mandrel assembly 202 further includes seals 306A, 306B between stator core 102 and mandrel 304 for containing an encapsulant. For example, the mandrel defines a plurality of seal grooves 308A, 308B at opposite ends, with seal 306A disposed in seal groove 308A at one end of mandrel 304 and seal 306B disposed in groove 308B at a second, opposite end of mandrel 304.
[0028] For mandrel assembly 302, the encapsulation process is similar to that of mandrel assembly 202. More specifically, mandrel assembly 302 with mandrel 304 is assembled to, i.e., inserted into, bore 103 of stator core 102. The encapsulation assembly with mandrel assembly 302 and stator assembly 100 is heated to increase the temperature of stator assembly 100. Because there is no sleeve here, the heating parameters for the encapsulation assembly with encapsulation fixture 300 may differ from the heating parameters for the encapsulation assembly with mandrel assembly 202.
[0029] After heating, the encapsulation assembly, similar to the encapsulation assembly with the mandrel assembly 202, is injected with an encapsulating agent through the bottom of the encapsulation fixture 300. The mandrel 304 inhibits or significantly reduces the ingress of the encapsulating agent into the bore 103 because the reduced gap between the mandrel 304 and the bore 103 provides sufficient movement to remove the mandrel 304 from the bore 103. After injection, the encapsulating agent is at least partially cured, thereby forming an at least partially encapsulated stator assembly. If the expanded sleeve 206 does not seal the bore 203, the encapsulating agent may be removed from the encapsulation fixture 300 at an appropriate time after the encapsulating agent has cured. This allows the stator assembly 100 to be removed from the encapsulation fixture 300.
[0030] The following are different variations that are applicable to an encapsulation fixture having mandrel assembly 202 or mandrel assembly 302.
[0031] 2 and 3, in some variations, encapsulation fixture 200 further includes one or more end plates 250A, 250B disposed on opposite ends of mandrel assembly 202. More specifically, end plates 250A, 250B are positioned to at least partially close opposite ends of stator assembly 100 when stator assembly 100 is assembled to the encapsulation fixture. In one form, end plates 250A, 250B may be secured via fasteners, such as, but not limited to, clips 251 and screws (not shown) on mechanism 252. It will be readily understood that one or more end plates may also be provided on encapsulation fixture 300.
[0032] In some variations, the encapsulation assembly with end plates 250A, 250B is connected via support rods. For example, referring to FIG. 5, an encapsulation fixture 400 usable with mandrel assembly 202 or mandrel assembly 302 includes two end plates 402 and a plurality of support posts 404 extending between the end plates 402. After assembly, the encapsulation assembly with encapsulation fixture 400 provides a clamping force acting against stator assembly 100 and mandrel assemblies 202, 302 via the end plates 402.
[0033] 2 and 3, in some variations, an end plate 250A at the bottom end of the encapsulation assembly defines an inlet port 256 for connecting to an encapsulant supply system (not shown) to receive the encapsulant. Although one inlet port 256 is provided, multiple inlet ports may be used.
[0034] In some applications, at least one of end plates 250A, 250B of encapsulation fixture 200 may include features for alignment with stator caps 105A, 105B of stator assembly 100. For example, end plate 250A includes feature 252 that aligns with feature 120 of stator cap 105A.
[0035] 1A and 1B, in some applications, the stator assembly 100 further includes a housing 128 within which the stator core 102 and the set of windings 104 are disposed. When the encapsulant is injected into the encapsulation assembly, the encapsulant is also supplied to a portion of the gap defined between the housing 128 and the outer diameter of the mandrel assemblies 202, 302.
[0036] 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. 1. A method of forming an electric motor, comprising: providing a stator assembly having a stator core and a set of windings, the stator core defining a bore, the set of windings coupled to the stator core; assembling the stator assembly into an encapsulation fixture, thereby forming an encapsulation assembly, the encapsulation fixture having at least a mandrel assembly including a mandrel core and a sleeve, at least a portion of the mandrel assembly extending through the bore of the stator core; heating the encapsulation assembly, thereby expanding the sleeve against the stator core, thereby forming a seal between the sleeve and at least a portion of an inner surface of the bore of the stator core; injecting a liquid encapsulant into the encapsulation assembly such that the encapsulant at least partially encapsulates the stator assembly; at least partially curing the encapsulant within the encapsulation assembly, thereby forming an at least partially encapsulated stator assembly; separating the at least partially encapsulated stator assembly from the encapsulation fixture; A method comprising:
2. The method of claim 1 , wherein the sleeve is made of an elastomeric material.
3. The method of claim 2 , wherein the elastomeric material is a silicone-based material.
4. The method of claim 1 further comprising providing the mandrel assembly having the mandrel core disposed at least partially within a cavity of the sleeve that supports the sleeve.
5. 2. The method of claim 1, wherein the stator assembly further includes a stator cap disposed at an axial end of the stator core, the encapsulation fixture further includes an end plate, and assembling the stator assembly to the encapsulation fixture further includes aligning the stator cap of the stator assembly with the end plate of the encapsulation fixture.
6. The encapsulation fixture further includes two end plates; The step of assembling the stator assembly into the encapsulation fixture comprises: at least partially closing opposite ends of the stator assembly with the two end plates; providing a clamping force to the stator assembly and the mandrel assembly via the two end plates; The method of claim 1 further comprising:
7. the stator assembly has a first axial end and a second axial end opposite the first axial end; The step of injecting the encapsulating agent into the encapsulation assembly comprises: positioning the encapsulation assembly such that the first axial end of the stator assembly is lower than the second axial end of the stator assembly; providing the encapsulant at the first axial end of the stator assembly such that the encapsulant is forced through the stator assembly to the second axial end of the stator assembly; The method of claim 1 further comprising:
8. The stator assembly further includes a housing in which the stator core and the set of windings are disposed; 2. The method of claim 1, wherein injecting the encapsulating material into the encapsulation assembly further comprises delivering the encapsulating material into a portion of a gap defined between the housing and an outer diameter of the mandrel assembly.
9. 2. The method of claim 1, further comprising removing the stator assembly from the encapsulation fixture including the mandrel assembly after the encapsulation assembly has cooled to a point where the sleeve no longer seals against the inner surface of the bore of the stator core.
10. 1. A method of forming an electric motor, comprising: providing a stator assembly having a stator core and a set of windings, the stator core defining a bore, the windings coupled to the stator core; providing a mandrel assembly including a mandrel core and a sleeve, the mandrel core being at least partially disposed within a cavity of the sleeve; assembling the mandrel assembly into the bore of the stator core such that a portion of the mandrel assembly extends through the bore of the stator core of the stator assembly; heating the stator assembly together with at least the mandrel assembly, thereby causing the sleeve of the mandrel assembly to expand against the stator core, thereby sealing against at least a portion of an inner surface of the bore of the stator core; injecting a liquid encapsulant into the stator assembly such that the encapsulant at least partially encapsulates the stator assembly; allowing the encapsulant to at least partially cure, thereby forming an at least partially encapsulated stator assembly; removing the at least partially encapsulated stator assembly from the mandrel assembly after the at least one of the at least partially encapsulated stator assemblies and the mandrel assembly have cooled such that the sleeve no longer seals against the inner surface of the bore of the stator core; A method comprising:
11. The method of claim 10 , wherein the sleeve is made of an elastomeric material.
12. The method of claim 11 , wherein the elastomeric material is a silicone-based material.
13. at least partially closing opposite axial ends of the stator assembly with two end plates; providing a clamping force to the stator assembly and the mandrel assembly via the two end plates; The method of claim 10 further comprising:
14. The stator assembly further includes a stator cap provided at an axial end of the stator core of the stator assembly, 14. The method of claim 13, wherein at least partially closing opposite axial ends of the stator assembly further comprises aligning a first of the two end plates with the stator cap of the stator assembly.
15. the stator assembly has a first axial end and a second axial end opposite the first axial end; The step of injecting the encapsulating agent comprises: positioning the stator assembly such that the first axial end of the stator assembly is lower than the second axial end of the stator assembly; providing the encapsulant at the first axial end of the stator assembly such that the encapsulant is forced through the stator assembly to the second axial end of the stator assembly; The method of claim 10 further comprising:
16. The stator assembly further includes a housing in which the stator core and the set of windings are disposed; The method of claim 10 , wherein the step of injecting the encapsulant further comprises delivering the encapsulant into a portion of a gap defined between the housing and an outer diameter of the mandrel assembly.
17. 1. A method of forming an electric motor, comprising: providing a stator assembly having a housing, a stator core, and a set of windings, the stator core defining a bore, the windings coupled to the stator core, the stator core and the windings disposed within the housing; assembling the stator assembly into an encapsulation fixture, thereby forming an encapsulation assembly, the encapsulation fixture having at least a mandrel assembly including a mandrel core and a sleeve, the mandrel core being at least partially disposed within a cavity of the sleeve, and at least a portion of the mandrel assembly extending through the bore of the stator core; heating the encapsulation assembly, thereby expanding the sleeve of the mandrel assembly against the stator core, thereby sealing against at least a portion of an inner surface of the bore of the stator core; injecting the encapsulant in liquid form into the encapsulation assembly such that the encapsulant at least partially encapsulates the stator assembly in a portion of a gap defined between the housing and an outer diameter of the mandrel assembly; allowing the encapsulant to at least partially cure, thereby forming an at least partially encapsulated stator assembly; separating the at least partially encapsulated stator assembly from the encapsulation fixture after the encapsulation assembly has cooled to a point where the sleeve no longer seals against the inner surface of the bore of the stator core; A method comprising:
18. The method of claim 17 , wherein the sleeve is made of an elastomeric material.
19. The method of claim 18 , wherein the elastomeric material is a silicone-based material.
20. The encapsulation fixture further includes two end plates; The step of assembling the stator assembly into the encapsulation fixture comprises: at least partially closing opposite ends of the stator assembly with the two end plates; providing a clamping force to the stator assembly and the mandrel assembly via the two end plates; 20. The method of claim 17, further comprising: