SE2050510A1 - - Google Patents

Abstract

METHOD OF MANUFACTURING A STATOR FOR AN AXIAL FLUX MACHINEA method of manufacturing a stator (3) for an axial flux machine (1), wherein the method comprises: a) providing a stator frame structure (8) comprising an inner ring (9), a stator core support (11), and an outer ring (17) which are concentrically arranged, the stator core support (11) having a plurality of core slots (13) distributed along the circumferential direction of the stator core support (11), b) inserting cores into the core slots (13), c) providing coils around the cores, the coils forming part of a stator winding, and d) filling spaces between the stator core support, the inner ring, the outer ring and the coils with a potting material (23).

Description

1O METHOD OF MAN UFACTURING A STATOR FOR AN AXLÅL FLUXMACHINE TECHNICAL FIELD The present disclosure generally relates to axial flux machines.

BACKGROUND Axial flux machines are used in applications such as e-mobility, wind energy,robotics, fans and pumps etc, where high torque density, high efficiency andspecific form factor of short axial length is sought for. The benefits of axialflux machines are coming with a cost in manufacturing challenges, particularly for double rotor and single yokeless stator topology.

The construction of the stator in a yokeless stator topology is a challenge asthe stator comprises a plurality of independent core teeth with coils woundaround them. Such stator construction requires the use of fixtures thatposition and hold the cores in designated places. A known method is to use apotting material that fills in the spaces between the stator winding and thestator frame. However, this method requires the use of jigs that will hold thestator cores in place during the potting process. The jigs become part of thestator construction. Since the jigs are placed in the vicinity of the airgap, theymust be non-magnetic and non-conductive. Therefore, also their thermalconductivity is very low which blocks the heat inside the coils and reduces the rating of the electrical machine.

SUMMARY In view of the above, a general object of the present disclosure is to provide amethod of manufacturing a stator and a stator which solves or at least mitigates the problems of the prior art.

There is hence according to a first aspect of the present disclosure provided amethod of manufacturing a stator for an axial flux machine, wherein the method comprises: a) providing a stator frame structure comprising an inner 1O ring, a stator core support, and an outer ring which are concentricallyarranged, the stator core support having a plurality of core slots distributedalong the circumferential direction of the stator core support, b) insertingcores into the core slots, c) providing coils around the cores, the coils formingpart of a stator winding, and d) filling spaces between the stator core support, the inner ring, the outer ring and the coils with a potting material.

Thereby, easy assembly of the stator may be provided. Due to the stator coresupport no additional core fixtures or jigs are needed to position the cores.

Moreover, the stator core support eliminates the need for potting moulds.The stator may be a yokeless stator.

The stator frame structure may made of three separate components, namelythe inner ring, the stator core support provided radially outside the innerring, and the outer ring arranged radially outside the stator core support.Alternatively, the stator core support, the inner ring and the outer ring maybe integral, forming a single structure. In the latter case, the integral stator frame structure may for example be made by casting or 3D-printing.

According to one embodiment step c) involves placing the coils one by one around the cores.

According to one embodiment the step c) involves placing all the coils as a pre-assembled structure simultaneously around the cores.

According to one embodiment the stator core support is made of aluminium, stainless steel or a polymer.The stator core support may for example be made of laminated aluminium.

The stator core support may have a conductive tape on its outer surface orsurfaces. The heat flux from the stator core support to the outer ring may thereby be significantly improved. 1O There is according to a second aspect of the present disclosure provided astator for an axial flux machine, comprising: a stator frame structureincluding an inner ring, a stator core support having a plurality of core slotsdistributed along the circumferential direction of the stator core support, andan outer ring, which are arranged concentrically, a plurality of cores arrangedin a respective core slot, coils provided around the cores, the coils formingpart of a stator winding, and a potting material filling spaces between the stator core support, the inner ring, the outer ring and the coils.

The core slots extend in the axial direction of the stator. The core slots may extend through the stator core support.

The stator core support is an annular structure such as an annular plate,provided with the core slots distributed evenly along the circumferential direction of the annular structure.

The core slots may for example have a trapezoidal shape in cross-section. Thetip of these trapezoids may be pointing towards the central axis of the statorcore support. The base of each trapezoid may be facing the circumference of the stator core support.

According to one embodiment the stator core support is made of aluminium, stainless steel or a polymer.

There is according to a third aspect of the present disclosure provided an axial flux machine comprising the stator of the second aspect.

One embodiment comprises a double rotor having two rotor yokes, whereinthe stator is yokeless, and wherein the rotor yokes are arranged on a respective side of the stator.

Generally, all terms used in the claims are to be interpreted according to theirordinary meaning in the technical field, unless explicitly defined otherwiseherein. All references to "a/ an/ the element, apparatus, component, means, etc. are to be interpreted openly as referring to at least one instance of the 1O element, apparatus, component, means, etc., unless explicitly stated otherwise.

BRIEF DESCRIPTION OF THE DRAWINGS The specific embodiments of the inventive concept will now be described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 schematically shows a sectional view of an example of an axial flux machine;Fig. 2 is a perspective view of an example of a stator for an axial flux machine; Figs 3a-3g show perspective view of an example of various stages of assembly of a stator; and Figs 4a and 4b show a front view of a stator, and a longitudinal section A-A of the stator in Fig. 4a, respectively.

DETAILED DESCRIPTION The inventive concept will now be described more fully hereinafter withreference to the accompanying drawings, in which exemplifyingembodiments are shown. The inventive concept may, however, be embodiedin many different forms and should not be construed as limited to theembodiments set forth herein; rather, these embodiments are provided byway of example so that this disclosure will be thorough and complete, andwill fully convey the scope of the inventive concept to those skilled in the art.

Like numbers refer to like elements throughout the description.

Fig. 1 shows an example of an axial flux machine (AFM) 1. The AFM 1 comprises a stator 3. The stator 3 is in this example a yokeless stator.

The AFM 1 comprises rotor 4. The rotor 4 is in the present example a doublerotor. The rotor 4 comprises a shaft 5 and two rotor yokes 7. The rotor yokes 7 are arranged on a respective side of the stator 4. 1O The stator 3 comprises a stator frame structure. Fig. 2 shows a perspectiveview of an example of a stator frame structure 8. The stator frame structure 8comprises an inner ring 9, and a stator core support 11 arranged radiallyoutside of and concentrically with the inner ring 9. The stator frame structure 8 thus has a central through-opening formed by the inner ring 9.

The stator 3 comprises an outer ring 17 arranged radially outside of and concentrically with the stator core support 11.

The stator core support 11 may for example be a disc-shaped plate with a central through-opening.

The shaft 5 extends through the inner ring 9 in the AFM 1. The stator 3 has alongitudinal axis defined by the central axis of the cylindrical inner ring 9.The shaft 5 of the rotor 4 is rotatable about the longitudinal axis of the stator3.

The stator core support 11 comprises a plurality of core slots 13 evenlydistributed along the circumferential direction of the stator core support 11.The core slots 13 extend through the stator core support 11 in the longitudinaldirection of the stator core support 11, i.e. along an axis parallel with the central axis of the inner ring 9.

The stator core support 11 has spokes 15 which extend from a radially innerend of the stator core support 11 to an outer circumferential end of the statorcore support 11. The core slots 13 are formed between the spokes 15. Thespokes 15 may extend along respective radial directions along their entire extension.

The stator frame structure 8 may be formed as a single unit, with the innerring 9, the stator core support 11 and the outer ring 17 being integral.Alternatively, the stator frame structure 8 may be formed by the inner ring 9, the stator core support 11, and the outer ring 17 as separate components.

Figs 3a-3g shows various stages of the manufacturing process of the stator 3 according to one example thereof. 1O Fig. 3a shows the stator core support 11, which has a central through-openingconfigured to receive the inner ring 9. In the next step of assembly, shown inFig. 3b, the inner ring 9 is placed in the central through-opening of the stator core support 11.

Fig. 3c shows a stage of the assembly when the outer ring 17 has beenarranged outside of the stator core support 11. The steps shown in Figs 3b and 3c may be reversed, if desired.

The stator 3 further comprises cores 19, shown in Fig. 3d, and coils 21 shown in Fig. 3e.

Fig. 3d shows the cores 19 being placed in the stator core slots 13 one after the other.

Fig. 3e shows the coils 21 being placed around the cores 19. In Fig. 3f, all thecoils 21 have been placed around respective cores 19. The coils 21 form part ofthe stator winding. The coils 21 may be placed one after the other aroundrespective cores 19, or all the coils 21 may form a pre-assembled structure that is placed around the cores 19.

The stator 3 comprises a potting material 23. Fig. 3g shows the pottingmaterial which has been applied, and which fills the spaces between the coils21 and the stator frame structure 8 formed by the inner ring 9, the stator core support 11 and the outer ring 17.

The above steps describe how one side of the stator 3 is assembled. Coils arealso provided in the same manner around the cores 19 on the opposite side ofthe stator core support 11, and a potting material is applied on that side too, to fill the spaces between the coils and the stator frame structure 8.

Fig. 4a shows a front view of one side of the stator 3. Fig. 4b shows a cross-section along lines A-A of the stator 3 in Fig. 4a. The cores 19 extend axiallyan equal amount on both sides from the stator core support 11, and coils 21 are provided on both sides.

The coils 21 are thus divided into two sets, one on each side. These may be connected into two parallel branches to form the stator winding.

The inventive concept has mainly been described above with reference to afew examples. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the inventive concept, as defined by the appended claims.

Claims (8)

1. A method of manufacturing a stator (3) for an axial flux machine (1), wherein the method comprises: a) providing a stator frame structure (8) comprising an inner ring (9), astator core support (11), and an outer ring (17) which are concentricallyarranged, the stator core support (11) having a plurality of core slots (13) distributed along the circumferential direction of the stator core support (11),b) inserting cores (19) into the core slots (13), c) providing coils (21) around the cores (19), the coils (21) forming part of a stator winding, and d) filling spaces between the stator core support, the inner ring, the outer ring and the coils with a potting material (23).

2. The method as claimed in claim 1, wherein step c) involves placing the coils (21) one by one around the cores (19).

3. The method as claimed in claim 1, wherein the step c) involves placingall the coils (21) as a pre-assembled structure simultaneously around the cores (19).

4. The method as claimed in any of the preceding claims, wherein the stator core support (11) is made of aluminium, stainless steel or a polymer.

5. A stator (3) for an axial flux machine, comprising: a stator frame structure (8) including an inner ring (9), a stator coresupport (11) having a plurality of core slots (13) distributed along thecircumferential direction of the stator core support (11), and an outer ring (17), which are concentrically arranged, a plurality of cores (19) arranged in a respective core slot (13), 1O coils (21) provided around the cores (19), the coils (21) forming part of a stator winding, and a potting material (23) filling spaces between the stator core support (11), the inner ring (9), the outer ring (17) and the coils (21).

6. The stator (3) as claimed in claim 5, wherein the stator core support (11) is made of aluminium, stainless steel or a polymer.

7. An axial flux machine (1) comprising the stator (3) according to claim 5 or 6.

8. The axial flux machine (1) as claimed in claim 7, comprising a doublerotor (4) having two rotor yokes (7), wherein the stator (3) is yokeless, and wherein the rotor yokes (7) are arranged on a respective side of the stator (3).