Description:TECHNICAL FIELD
[0001] The present disclosure relates to the field of axial flux machines, and more specifically, pertains to a stator assembly for an axial flux machine having enhanced cooling performance.

BACKGROUND
[0002] Axial flux permanent magnet machines, such as motors or generators, are typically recognized by their rotor and stator configurations in the form of discs or rings arranged concentrically around a central axis. The stator typically includes coils aligned parallel to this axis, while the rotor contains permanent magnets. Positioned on a bearing, the rotor rotates around the central axis, driven by the magnetic fields produced by the stator coils. Axial flux rotating electrical machines distinguish themselves from the conventional radial flux machines by the orientation of their magnetic flux, which aligns parallel to a mechanical shaft instead of perpendicular to it, as in radial flux machines. This orientation affords axial flux machines several advantages over radial ones, including a more compact design, increased power density, and greater robustness. However, such axial flux rotating electrical machines encounter specific challenges that require attention, with cooling being a notable concern.
[0003] Manufacturing an axial flux machine as a sealed unit could prove advantageous in terms of cooling performance. Such sealed units offer numerous benefits, such as reduced susceptibility to contamination and compatibility for integration into an electric axle. However, sealed machines encounter limitations in air cooling efficiency. Therefore, exploring alternative cooling methods becomes imperative. In particular, effectively cooling stator windings of a stator of such axial flux machines presents a significant challenge in these sealed designs.
[0004] Effectively handling heat poses a significant challenge in the axial flux permanent magnet machines primarily because of their capability to function at exceptionally high power densities. The rapid dissipation of heat frequently determines the maximum torque sustainable for such machines, particularly during prolonged periods of continuous operation. Consequently, the efficiency of the cooling mechanism plays a crucial role in influencing the motor's performance during prolonged usage.
[0005] As depicted in the FIG. 1, an axial flux machine 100 typically consists of a central stator 102 surrounded by a pair of rotors 104, 106. Each rotor 104, 106 maintains an air gap 108 with the stator 102, through which the magnetic flux primarily flows in the axial direction of the axial flux machine 100. The specific configuration of these machines varies depending on the positioning of the north and south poles on the rotors 104, 106.
[0006] FIG. 2 shows a stator holder or housing 200 for a conventional axial flux machine. Most of the prior art related to cooling mechanisms in axial flux machines concentrates on methods such as machining holes or guiding tubes to establish a pathway for coolant within the volume of the stator housing 200. Such techniques generally aim to direct flow of a coolant either along an outer and/or inner circumference/periphery of the housing 200. Additionally, these pathways may be interconnected through machined holes within stator spikes 202 formed in the housing 200. Accordingly, Most of the existing design of stators for axial flux machines require formation of contraptions with a stator holder to create coolant tubes/channels to move a cooling fluid/coolant around to facilitate cooling of the stator windings. However, such conventional techniques are both costly and time-intensive, and they often prove ineffective because they involve generation of coolant flow pathways that fail to directly contact the heat source, namely copper windings of the stator. Despite the potential volume within the stator spikes 202, the size of machined holes or channels therein is constrained by manufacturing limitations. Consequently, such channels must be small, restricting the rate of coolant flow. Moreover, if design requirements dictate thin stator spikes, such as 2 mm or 3 mm thickness, machining channels within such narrow dimensions of the stator spikes 202 becomes exceedingly challenging, expensive, and necessitates complex overall designs.
[0007] Hence, there exists a necessity within the field to address the drawbacks and limitations inherent in current solutions. This entails delivering a simple, reliable, and economical stator assembly for an axial flux machine having improved cooling characteristics, while eliminating the requirement for complex manufacturing processes for producing such stator assemblies.

OBJECTS OF THE PRESENT DISCLOSURE
[0008] An object of the present disclosure is to provide a simple and reliable stator assembly for an axial flux machine having improved cooling performance.
[0009] Another object of the present disclosure is to provide a cost-efficient stator assembly for an axial flux machine having improved construction and quality, and eliminates the requirement for intricate manufacturing processes for producing such stator assemblies.
[0010] Another object of the present disclosure is to provide improved and direct surface contact with stator windings of the stator assembly that are generally the main source of heat during operation of the axial flux machine.
[0011] Another object of the present disclosure is to envisage a cooling arrangement that is easy to manufacture and integrate within the stator assembly, while increasing mechanical strength of the stator assembly to keep stator windings in place.
[0012] Another object of the present disclosure is to provide a reliable and light-weight stator assembly for an axial flux machine, which is associated with a high percentage of effect volume for coolant flow, and provide higher flow rates for the coolant.
[0013] Another object of the present disclosure is to provide a stator assembly that can be manufactured with reduced time and costs.

SUMMARY
[0014] Aspects of the present disclosure relates to a stator assembly for an axial-flux permanent magnet machine, such as motor or generator. The stator assembly incorporates a cooling arrangement for increasing heat transfer from stator windings of the stator assembly by ensuring adequate contact surface of cooling channels with the stator windings. The stator assembly increases utilization of volume of stator spikes of the stator assembly for facilitating sufficient coolant flow, while ensuring adequate cooling of the stator windings. The stator assembly provides a reliable and light-weight cooling arrangement that prevents the requirement of designing thin cooling channels.
[0015] In an aspect, the present disclosure provides a stator assembly for an axial flux machine. The stator assembly includes a stator holder having a plurality of stator spikes radially arranged on an outer periphery of the stator holder. The plurality of stator spikes are spaced from one another to form a gap between adjacent stator spikes. Each gap is adapted to receive a stator segment. The stator assembly includes at least one multi-channel tube adapted to be fitted into the gap formed between the adjacent stator spikes, and directly contact the stator segment positioned within the gap to dissipate heat from the stator segment during operation of the axial flux machine.
[0016] In an embodiment, the plurality of stator spikes may be arranged on the outer periphery of the stator holder in two or more rows. The gap may be formed between adjacent rows of the two or more rows of the stator spikes.
[0017] In an embodiment, the stator segment may include a top pole shoe and a bottom pole shoe.
[0018] In an embodiment, the at least one multi-channel tube may include a plurality of first bent portions adapted to contact the bottom pole shoe of the stator segment positioned within the gap present between the adjacent stator spikes, and a plurality of second bent portions adapted to contact the top pole shoe of the stator segment positioned within the gap. The plurality of first bent portions and the plurality of second bent portions may be adjacently positioned with respect to one another. The at least one multi-channel tube may also include a plurality of channel connecting portions integrally connected to the plurality of first bent portions and the plurality of second bent portions. The plurality of channel connecting portions may be adapted to contact side surfaces of the stator segment positioned within the gap.
[0019] In an embodiment, the at least one multi-channel tube may include an inlet portion for receiving a fluid, an outlet portion for expelling the fluid, and a plurality of channels for defining passages for the fluid to pass from the inlet portion to the outlet portion. The fluid passing through the plurality of channels dissipate heat from each stator segment during operation of the axial flux machine.
[0020] In an embodiment, the inlet portion and the outlet portion of the at least one multi-channel tube may be connected to a heat exchanger unit configured to cool the fluid expelled from the outlet portion and supply the cooled fluid to the inlet portion.
[0021] In an embodiment, each first bent portion of the plurality of first bent portions may be sequentially positioned within the gap followed by insertion of the stator segment into the gap. After the stator segment is inserted into the gap, each second bent portion of the plurality of second of bent portions may be sequentially positioned over the top pole shoe of another stator segment positioned in an adjacent gap.
[0022] In an embodiment, the stator segment may be positioned in direct contact with the first bent portion of the at least one multi-channel tube, and the adjacent stator segment is positioned in direct contact with the second bent portion of the at least one multi-channel tube.
[0023] In an embodiment, the at least one multi-channel tube may be made of a thermally conductive material, such as aluminium, copper, and the like.
[0024] Various objects, features, aspects and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.

BRIEF DESCRIPTION OF THE DRAWINGS
[0025] The accompanying drawings are included to provide a further understanding of the present disclosure, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure.
[0026] FIG. 1 shows a typical axial flux machine in accordance with prior art;
[0027] FIG. 2 depicts a stator holder for a conventional axial flux machine in accordance with prior art;
[0028] FIG. 3 illustrates a perspective view of a stator segment of a stator assembly for an axial flux machine, such as an axial flux motor or axial flux generator, in accordance with prior art;
[0029] FIGs. 4A and 4B show schematic representations of a cooling arrangement of conventional stator assemblies for an axial flux machine, in accordance with prior art;
[0030] FIG. 5 illustrates a perspective view of stator holder of the stator assembly in accordance with an embodiment of the present disclosure;
[0031] FIGs. 6A to 6C illustrate various representations of a multi-channel tube to be coupled to a stator holder of a stator assembly of an axial flux machine, in accordance with an embodiment of the present disclosure;
[0032] FIG. 7 illustrates a perspective view of multiple multi-channel tubes fitted to the stator holder of the stator assembly in accordance with an embodiment of the present disclosure;
[0033] FIGs. 8A to 8C illustrate various representations depicting the process of fitting the at least one multi-channel tube to the stator holder of the stator assembly, in accordance with an embodiment of the present disclosure; and
[0034] FIGs. 9A to 9D illustrate various representations of the stator assembly in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION
[0035] The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such details as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the scope of the present disclosures as defined by the appended claims.
[0036] Embodiments explained herein relate to a stator assembly designed for use in an axial-flux permanent magnet machine, such as a motor or generator. The stator assembly integrates a cooling arrangement aimed at enhancing heat transfer from the stator windings by ensuring sufficient contact surface area between a set of cooling channels and the stator windings. Moreover, the stator assembly maximizes the utilization of the stator spikes' volume to facilitate ample coolant flow, thereby ensuring effective cooling of the stator windings. Overall, the stator assembly offers a reliable, cost-efficient and lightweight cooling solution that eliminates the need for designing thin cooling channels.
[0037] FIG. 3 illustrates a single stator segment 300 for a typical stator assembly of an axial flux machine. An axial flux machine, such as a motor or a generator, may potentially incorporate numerous such stator segments 300 radially arranged with respect to one another to form the stator assembly. The stator segment 300 may include a winding 302 from of copper wires wound around laminated stator plates, which are stacked to form a trapezoidal shape. Additionally, the top and bottom sections 304-1, 304-2 of the laminated stator plates may include components known as pole shoes. These pole shoes 304-1, 304-2 serve the dual purpose of aligning the copper winding 302 and enhancing electromagnetic performance of the axial flux machine. The top and bottom pole shoes 304-1, 304-2 facilitate the spreading of magnetic flux for improved uniformity and help reduce reluctance of the magnetic path. Conventionally, the stator segments/windings 300 are positioned in an arc formed within stator spikes 402 of a stator holder 400, as shown in FIGs. 4A and 4B. Each stator spike 402 may also contain machined holes 404 to establish coolant channels 406. These coolant channels 406 can exit from an inner perimeter of the stator holder 400, as depicted in FIG. 4A, or from above or both sides. External cooling pipes 408, as shown in FIG. 4B, may be connected to holes 404 formed in each stator spike 402. As clearly evident, the coolant channels 406 enter the stator spikes 402 from the outer edge, requiring a complex and sophisticated mechanism to be machined within the stator holder 400 to enable the coolant/liquid to exit through a different channel.
[0038] The present disclosure addresses the aforesaid deficiencies and shortcomings of conventional stator assemblies by providing a stator assembly for an axial flux machine, which is configured to enhance and establish direct surface contact with the stator windings to dissipate heat generated by the stator windings during operation of the axial flux machine with the help of a coolant. The cooling arrangement of the stator assembly is simple to manufacture and seamlessly integrates within a stator holder of the stator assembly. The cooling arrangement offers mechanical stability to secure the stator windings in position, and optimizes the effective volume for coolant flow, resulting in a higher percentage of utilization. The proposed stator assembly enables increased flow rates for the coolant, while substantially reducing the time and cost associated with manufacturing of the stator holder. The stator assembly includes a circular stator holder 500, as shown in FIG. 5, having a plurality of stator spikes 502 radially arranged on an outer periphery of the stator holder 500. The stator spikes 502 are spaced from one another to form a gap 504 between adjacent stator spikes 502. Each of the stator spikes 502 may include a screw hole for fitment of a stator support structure (clearly shown in FIG. 9B). Each gap 504 is adapted to receive a stator segment 300. In an embodiment, the stator spikes 502 may be arranged on the outer periphery of the stator holder 502 in two or more rows. The gap 504 may be formed between adjacent rows of the stator spikes 502.
[0039] The stator assembly includes at least one multi-channel tube adapted to be fitted into the gap 504 formed between the adjacent stator spikes 502. FIGs. 6A and 6B illustrate various representations of a multi-channel tube 600 to be coupled to the stator holder 500 of the stator assembly. FIG. 6C shows multiple multi-channel tube 600 to be coupled to the stator holder 500. The at least one multi-channel tube 600 is adapted to directly contact the stator segment 300 positioned within the gap 504 to dissipate heat from the stator segment 300 as well as the stator holder 500 during operation of the axial flux machine. The multi-channel tubes 600 may be made of a thermally conductive material, such as aluminium, copper, and the like. The multi-channel tubes 600 may be coated with an insulation material to make them electrically non-conductive.
[0040] As shown in FIG. 3, the stator segment 300 may include a top pole shoe 304-1 and a bottom pole shoe 304-2. Each of the multi-channel tube 600 may include an inlet portion 604 for receiving a fluid, an outlet portion 606 for expelling the fluid, and a plurality of channels 602 for defining passages for a fluid/coolant to pass from the inlet portion 604 to the outlet portion 606. The fluid passing through the channels 602 dissipate heat from each stator segment 300 during operation of the axial flux machine. The inlet portion 604 and the outlet portion 606 of the multi-channel tube 600 may be connected to a heat exchanger unit (not shown) configured to cool the fluid expelled from the outlet portion 606 and supply the cooled fluid to the inlet portion 604 for re-circulation of the fluid through the channels 602.
[0041] Referring now to FIG. 7, where a perspective view of multiple multi-channel tubes 600 fitted to the stator holder 500 of the stator assembly is shown. One, two, three, or multiple multi-channel tubes 600 may be necessary to form a complete coolant flow circuit for the stator assembly. The multi-channel tubes 600 can be arranged in an arc, as depicted in FIG. 7. The multi-channel tubes 600 may either touch the bottom or top surface of the stator holder 500, along with always being in direct contact with the stator windings of the stator segment 300 positioned within the gap 504.
[0042] Each of the multi-channel tube 600 may include a plurality of first bent portions 608 adapted to contact the bottom pole shoe 304-2 of the stator segment 300 positioned within the gap 504 present between the adjacent stator spikes 502 of the stator holder 500, and a plurality of second bent portions 610 adapted to contact the top pole shoe 504-1 of the stator segment 500 positioned within the gap 504. The first bent portions 608 and the second bent portions 610 may be adjacently positioned with respect to each other. The multi-channel tube 600 may also include a plurality of channel connecting portions 612 integrally connected to the first bent portions 608 and the second bent portions 610, and adapted to contact side surfaces of the stator segment 300 positioned within the gap 504. Thus, during operation of the axial flux machine, the coolant passing through the channels 602 of the multi-channel tube 600 take heat away from the top pole shoe 504-1, the bottom pole shoe 504-2 and the side surfaces of each stator segment 300 due to direct physical contact of the first bent portions 608, the second bent portions 610 and the channel connecting portions 612 with the bottom pole shoe 504-2, the top pole shoe 504-1, and the side surfaces of the stator segments 300, respectively. The stator holder 500 includes the stator spikes 502 that secure and direct the multi-channel tubes 600 to form the coolant flow circuit for the stator assembly.
[0043] Each of the multi-channel tubes 600 can be pre-bent into serpentine or any other configurations to facilitate convenient installation to the stator holder 500. The multi-channel tubes 600 may contain one or more channels within themselves. The multi-channel tubes 600 may be readily manufactured in various shapes and sizes. Moreover, current manufacturing processes enable the production of the multi-channel tubes 600 with extremely small, capillary-like holes, some as tiny as 1 mm, while the multi-channel tubes 600 themselves may be 1.4 mm in diameter. The manufacturing simplicity of such tubes allows for the design of an axial flux machine that optimizes torque, potentially necessitating very thin tubes (1-2 mm). Additionally, the multi-channel tubes 600 may be made of ductile materials, thereby facilitating bending with ease.
[0044] FIGs. 8A to 8C illustrate various representations depicting the process of fitting each of the multi-channel tube 600 to the stator holder 500 of the stator assembly. As shown in FIG. 8A, a first bent portion 608 adjacent to the inlet portion 604 of the multi-channel tube 600 may be positioned within the gap 504 followed by insertion of the stator segment 300 into said gap 504 such that the bottom pole shoe 504-2 of the stator segment 300 is placed over the first bent portion 608. The multi-channel tube 600 may be placed in the gap 504 in such a way that the multi-channel tube 600 sits between the spikes 502. The stator holder 500 may be coated with a thermal adhesive on all or a few surfaces where the multi-channel tubes 600 are in contact. After the first bend portion 608 of the multi-channel tube 600 is placed in the gap 504, the stator segment 300 may be placed within the gap 504. After the stator segment 300 is inserted into the gap 504, another stator segment 300 may be inserted to an adjacent gap 504. The stator segments 300 may be held without movement at corresponding positions within the gaps 504 either due to the mechanical press-fit, friction between the tubes and the stator windings, or by use of a thermal adhesive. Thereafter, a second bent portion 610 adjacent to the first bent portion 608 may be positioned over the top pole shoe 304-1 of the other stator segment 300 positioned in the adjacent gap 504, as depicted in FIG. 8B. In an embodiment, after one such stator segment 300 is placed, another stator segment 300 may directly be placed into an adjacent gap 504 of the stator holder 500, and the second bent portion 410 of the multi-channel tube 600 may be wrapped around it. This process can be reiterated until all first bent portions 608 and second bent portions 610 are coupled to corresponding bottom pole shoe 304-2 and top pole shoe 304-1 of the stator segments 300. In this state, the outlet portion 610 adjacent to a first bent portion 608 of the multi-channel tube 600 is available to be coupled to the heat exchanger unit for re-circulation of the coolant, as shown in FIG. 8C.
[0045] FIGs. 9A to 9D illustrate various representations of the stator assembly 900. The inlet portions 604 and the outlet portions 606 of the multi-channel tubes 600 may emanate radially outwards from the installed configuration of the multi-channel tubes 600 to the stator holder 500. A plurality of holders (stator support structure) 902 may be fastened to the screw holes present on the stator spikes 502 to securely hold the stator segments 300 in position, and allow secure fitting of the multi-channel tubes 600 with the stator holder 500. As shown in FIG. 9D, the stator assembly 900 may be provided with an outer casing 904 having a coolant inlet 906 in fluidic communication with the inlet portions 604 of all the multi-channel tubes 600 through coolant inlet guiding tubes 908. The outer casing 904 may also include a coolant outlet 910 in fluidic communication with the outlet portions 606 of all the multi-channel tubes 600 through coolant outlet guiding tubes 912. The coolant inlet 906 and the coolant outlet 910 may be in fluidic communication with external pipes/channels or heat exchanger units that configured to provide low temperature coolant and expel the high temperature coolant to effectively take away heat from the stator segments 300 and the stator holder 500.
[0046] The outer casing 904 may be formed from three or more identical parts, each installed in such a way that the multi-channel tubes 600 are inserted into a slot or cavity of each of said parts of the outer casing 904. In an implementation, a first outer casing part may be assembled to the stator assembly 900. Said first outer casing part may include a recessed slot that corresponds with the multi-channel tubes 600. After installation of the outer casing part, the recessed slot may be filled with insulating adhesive or resin to seal any gaps between the multi-channel tubes 600 and the slot or cavity of the first outer casing part. Additionally, the first outer casing part may include screw holes at their two ends where they may be coupled to other components. Other outer casing parts may be assembled to the stator assembly 900 in a similar manner. The recessed slots of the outer casing parts may covered with caps, which connect with the coolant inlet or outlet guiding tubes 908, 912.
[0047] While the foregoing describes various embodiments of the disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof. The scope of the disclosure is determined by the claims that follow. The disclosure is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the disclosure when combined with information and knowledge available to the person having ordinary skill in the art.
, Claims:WE CLAIM:

1. A stator assembly for an axial flux machine, comprising:
a stator holder (500) comprising a plurality of stator spikes (502) radially arranged on an outer periphery of the stator holder (500), the plurality of stator spikes (502) being spaced from one another to form a gap (504) between adjacent stator spikes (502), each gap (504) adapted to receive a stator segment (300); and
at least one multi-channel tube (600) adapted to be fitted into the gap (504) formed between the adjacent stator spikes (502), and directly contact the stator segment (300) positioned within the gap (504) to dissipate heat from the stator segment (300) during operation of the axial flux machine.

2. The stator assembly as claimed in claim 1, wherein the plurality of stator spikes (502) are arranged on the outer periphery of the stator holder (500) in two or more rows, and wherein the gap (504) is formed between adjacent rows of the two or more rows of the stator spikes (502).

3. The stator assembly as claimed in claim 1, wherein the stator segment (300) comprises a top pole shoe (504-1) and a bottom pole shoe (504-2).

4. The stator assembly as claimed in claim 3, wherein the at least one multi-channel tube (600) comprises:
a plurality of first bent portions (608) adapted to contact the bottom pole shoe (504-2) of the stator segment (300) positioned within the gap (504) present between the adjacent stator spikes (502);
a plurality of second bent portions (610) adapted to contact the top pole shoe (504-1) of the stator segment (300) positioned within the gap (504), wherein the plurality of first bent portions (608) and the plurality of second bent portions (610) are adjacently positioned with respect to one another; and
a plurality of channel connecting portions (612) integrally connected to the plurality of first bent portions (608) and the plurality of second bent portions (610), wherein the plurality of channel connecting portions (612) are adapted to contact side surfaces of the stator segment (300) positioned within the gap (504).
5. The stator assembly as claimed in claim 1, wherein the at least one multi-channel tube (600) comprises:
an inlet portion (604) for receiving a fluid;
an outlet portion (606) for expelling the fluid; and
a plurality of channels (602) for defining passages for the fluid to pass from the inlet portion (604) to the outlet portion (606), wherein the fluid passing through the plurality of channels (602) dissipate heat from each stator segment (300) during operation of the axial flux machine.

6. The stator assembly as claimed in claim 5, wherein the inlet portion (604) and the outlet portion (606) of the at least one multi-channel tube (600) are connected to a heat exchanger unit configured to cool the fluid expelled from the outlet portion (606) and supply the cooled fluid to the inlet portion (604).

7. The stator assembly as claimed in claim 4, wherein each first bent portion of the plurality of first bent portions (608) is sequentially positioned within the gap (504) followed by insertion of the stator segment (300) into the gap (504).

8. The stator assembly as claimed in claim 7, wherein after the stator segment (300) is inserted into the gap (504), each second bent portion of the plurality of second of bent portions is sequentially positioned over the top pole shoe (504-1) of another stator segment (300) positioned in an adjacent gap (504).

9. The stator assembly as claimed in claim 8, wherein the stator segment (300) is positioned in direct contact with the first bent portion of the at least one multi-channel tube (600), and the adjacent stator segment (300) is positioned in direct contact with the second bent portion of the at least one multi-channel tube (600).

10. The stator assembly as claimed in claim 8, wherein at least one multi-channel tube (600) is made of a thermally conductive material.