Stator for an axial flux machine, axial flux machine and motor vehicle

Abstract

Stator (10) for an axial flux machine (12), comprising a stator winding (22) having a plurality of electrical coils (24), wherein the coils (24) are arranged circumferentially around an axis of rotation (18) of a rotor (14) of the axial flux machine (12) next to one another and with respective coil axes (26) parallel to the axis of rotation (18), wherein each of the coils (24) has a respective magnetizable core element (28) and a respective coil winding (30), wherein the coil winding (30) encloses at least a central region (32) of the core element (28) in the axial direction, wherein the stator (10) has a main cooling channel (34) extending radially outwardly around the coils (24), wherein each coil (24) has at least one radial cooling channel (36) extending radially with respect to the axis of rotation (18), which is fluidically connected to the main cooling channel (34) by a radially outer end,wherein the stator (10) has a connecting cooling channel (38) arranged radially inside the coils (24), wherein a respective radially inner end of a respective radial cooling channel (36) is fluidically connected to the connecting cooling channel (38), characterized in that a respective radial cooling channel (36) is arranged at least partially in a respective core element (28) of a respective coil (24), wherein at least the main cooling channel (34) or the connecting cooling channel (38) has at least one holding mandrel (46) for arrangement in a respective radial cooling channel (36) in a region adjacent to the coil windings (30), wherein the holding mandrel (46) has a through-opening (48) for guiding a coolant in its longitudinal direction.

Description

[0001] The invention relates to a stator for an axial flux machine, having a stator winding comprising a plurality of electrical coils, wherein the coils are arranged circumferentially around a rotational axis of a rotor of the axial flux machine next to one another and with respective coil axes parallel to the rotational axis, wherein each of the coils has a respective magnetizable core element and a respective coil winding, wherein the coil winding encloses at least a central region of the core element in the axial direction, wherein the stator has a main cooling channel extending radially outwardly around the coils, wherein each coil has at least one radial cooling channel extending radially with respect to the rotational axis, which is fluidically connected to the main cooling channel with a radially outer end, wherein the stator has a connecting cooling channel arranged radially inside the coils,wherein a respective radially inner end of a respective radial cooling channel is fluidly connected to the connecting cooling channel. The invention further relates to an axial-flow machine having a stator and a rotor, wherein the rotor is arranged axially spaced from the stator with respect to a rotational axis of the rotor via an air gap and rotatably mounted. Finally, the invention also relates to a motor vehicle having an axial-flow machine.

[0002] Motor vehicles with axial flux machines, axial flux machines, and stators for axial flux machines are extensively known in the prior art, so that in principle there is no need for written proof in this regard. Axial flux machines, in particular axial flux machines operated in motor mode, occasionally also called disc rotor motors, are a type of electrical machine in which the rotor is essentially in the shape of a disc that is rotatable about an axis of rotation located at the center of the disc. Depending on the design, a machine winding can be provided on the stator side and / or the rotor side. The winding usually has several coils, which may have a magnetizable core element. However, designs are also conceivable in which the coils can be designed without core elements.The axial flux machine is characterized, among other things, by the fact that the coils generate a magnetic field that is aligned essentially parallel to the rotor's axis of rotation, at least in the area of ​​the coils. The outer diameter of the axial flux machine is often significantly larger than its axial length (also known as an axial flux machine, pancake machine, disc machine, or printed machine).

[0003] Axial flux machines can be lightweight and / or have a small moment of inertia. This means that, among other things, high rotational accelerations can be achieved with axial flux machines. Furthermore, a high power density can be achieved with an axial flux machine, which can be achieved, among other things, by a specific design of the coils, which only need to have a small axial extension. By constructing the winding thinly on a disc, the respective coil can have a comparatively large surface area, which can be cooled accordingly. However, the fact that the heat capacity is low proves to be problematic. Even brief overloading can therefore result in damage to the axial flux machine, particularly in the winding area.

[0004] Such an axial flux machine is disclosed, for example, in EP 3 764 526 A1. Even though this design has proven itself, a problem remains regarding cooling, particularly during overload, as previously explained. For the cooling of the winding to function as intended in EP 3 764 526 A1, it is necessary that the axial ends of the stator containing the stator winding be completely sealed with a fluid-tight plate. Otherwise, the functionality disclosed therein would not be feasible. However, this also increases the air gap, reducing efficiency. The achievable power density is therefore limited.

[0005] CN 112 910 183 B also discloses a prior art axial flux machine. This teaching has already recognized the thermal problems of EP 3 764 526 A1 and teaches the arrangement of a heat pipe in the winding of each coil to improve cooling of the winding. The heat pipes are radially aligned in the respective coil winding and connected to a main cooling channel running around the outside of the coils, so that their radially outer ends can be cooled by a coolant flowing through the main cooling channel. Nevertheless, this design also proves to be disadvantageous because the function of the heat pipes is tied to the use of gravitational force and thus requires a specific alignment of the axial flux machine with respect to the gravitational force to ensure the function of the heat pipes. However, this is unfavorable or not feasible for many applications.

[0006] Furthermore, it has proven disadvantageous that the space available for the coil windings is not optimally utilized by the designs known in the prior art. This affects, among other things, the power density as well as the dynamic properties of the electric machine.

[0007] The invention is based on the object of providing improved cooling functionality for an axial flow machine. Furthermore, it is an object of the invention to improve the dynamic properties of the axial flow machine, in particular the power density.

[0008] As a solution, the invention proposes a stator for an axial flux machine, an axial flux machine and a motor vehicle according to the independent claims.

[0009] Advantageous further training results from features of the dependent claims.

[0010] With regard to a generic stator for an axial flux machine, the invention proposes in particular that a respective radial cooling channel is arranged at least partially in a respective core element of a respective coil.

[0011] With regard to a generic axial flux machine, the invention proposes in particular that the stator is designed according to the invention.

[0012] With regard to a generic motor vehicle, the invention proposes in particular that the axial flux machine is designed according to the invention.

[0013] The invention is based, among other things, on the idea of ​​shifting the cooling function to the magnetizable core elements of the coils. Radial cooling channels can advantageously be used for this purpose. The radial cooling channels extend essentially radially between the main cooling channel and the connecting cooling channel. They are preferably linear. However, they can also be partially curved. The radial cooling channels are at least partially arranged or formed in the region of the core elements. Preferably, they are arranged or formed entirely in the core elements. This makes it possible to enlarge the space available for the respective coil winding or to utilize it better than is permitted by the prior art. Therefore, essentially no cooling measures or cooling-supporting elements need to be provided in the region of the coil winding.

[0014] Rather, coil cooling can be improved by making greater use of the core elements, while simultaneously increasing the fill factor. Overall, this can achieve improved cooling and / or power density of the axial flux machine. In particular, internal sections of the respective coil windings can be more effectively cooled via the respective core element. The increased cooling effect is supported by the radial cooling channels formed in the respective core elements according to the invention.

[0015] Because the radial cooling channels are formed in the respective core elements in the invention, separate cooling channels, in particular separate radial cooling channels, no longer need to be provided. This can save material, costs, and labor. The invention makes it possible to fluidically connect the radial cooling channels directly to the main cooling channel and the connecting cooling channel. This allows coolant to flow at least partially in a radial direction, for example, either from the connecting cooling channel to the main cooling channel or vice versa. The connecting cooling channel and the main cooling channel can be connected to a corresponding coolant source, which is designed to simultaneously provide the coolant flow and cooling the coolant. The coolant can, for example, be a liquid such as oil, water, or the like.However, the coolant may also be partially gaseous and may comprise, for example, air, nitrogen, a noble gas and / or the like.

[0016] The magnetizable core element can be formed from a magnetizable material such as iron, cobalt, nickel, a magnetizable iron compound, alloys thereof, or the like. The core element can be formed from a homogeneous material. However, it is also possible to provide the core element with a layered structure, for example, in the manner of a laminated core, in which individual sheets forming the core element are electrically insulated from one another, for example, to reduce eddy current formation, or also in the manner of a magnetizable ferrite or the like. Preferably, exactly one coil winding is arranged on each core element.

[0017] The connecting cooling channel and the main cooling channel can have corresponding connecting elements that enable a fluid-tight connection to be established with the respective radial cooling channel, wherein preferably no further connecting or sealing elements need be required. Preferably, a respective core element of a respective coil at least partially supports the respective coil winding. It can be provided that the coil winding is wound onto the core element to form the respective coil. The coil winding can be formed from a suitable electrical conductor, which can be formed from a material such as copper, aluminum, silver, alloys thereof, and / or the like.The coil windings can be connected to an electrical energy converter or energy transformer in order to be supplied with an electrical voltage or current in a suitable manner for intended operation. It can also be provided that the coils are at least partially electrically connected to one another within the axial flux machine in order to achieve a predetermined connection type of the stator winding.

[0018] Preferably, the respective radial cooling channel extends radially completely through the respective core element. Particularly advantageously, corresponding openings or connecting elements are provided at the radially inner and outer ends of the core element, which allow the radial cooling channel to be connected to the connecting cooling channel and the main cooling channel. The core element preferably extends at least over the axial extent of the winding. However, it can also extend beyond the axial extent of the winding.

[0019] According to a further development, it is proposed that the core element projects beyond at least one winding head of a respective coil winding of the respective coil in the axial direction and that the radial cooling channel is arranged outside a region of the axial extent of the respective coil winding. The radial cooling channel is thus preferably arranged outside the coil winding, specifically in a region that projects axially beyond the winding head, i.e., a region of the core element adjacent to the coil winding. The radial cooling channel therefore does not need to be arranged, at least partially, in the region of the coil winding in the core element. Nevertheless, it can of course be provided that the radial cooling channel does not need to be exclusively linear. The radial cooling channel can also be designed such that it extends at least partially within the core element into a region that is arranged within the respective coil winding.Combinations of these can also be provided. However, the radial cooling channel is preferably designed as a linear radial cooling channel. The radial cooling channel is therefore preferably formed entirely in the region of the core element that projects beyond the winding overhang outside the coil winding.

[0020] It is further proposed that the core element projects axially beyond opposite winding ends of the coil winding, and that at least one radial cooling channel is arranged in the core element outside the region of the axial extension of the respective coil winding. This creates the possibility of cooling the core element at two opposite ends, thereby further improving the cooling functionality.

[0021] Furthermore, this design also offers the possibility of simultaneously utilizing the radial cooling channels for a mechanical fixing function. This is because the radial cooling channels can be provided at least partially by the main cooling channel and / or the connecting cooling channel, so that correspondingly designed cooling channels of the core elements can be plugged onto the tubular cooling channels of the main cooling channel and / or the connecting cooling channel by inserting the tubes into the cooling channels of the core elements. In this design, the cooling channels of the core elements are therefore not directly exposed to the coolant. This also facilitates fluidic coupling. The individual coils can then also be mechanically fixed via the main cooling channel or the connecting cooling channel.This design not only allows for improved cooling but also simplifies the mechanical design.

[0022] It is further proposed that a region of the respective core element that axially projects beyond the respective winding head has a larger core cross-sectional area than in the area of ​​the respective coil winding. This refinement makes it possible to minimize the obstruction of the magnetic flux through the radial cooling channel during normal operation of the axial flux machine. It is thus possible, for example, to keep the cross-sectional area provided for the magnetic flux in the axial direction of the core element at least constant. This makes it possible to further improve the power density.Preferably, the radial cooling channel is arranged or formed substantially centrally in the core element in the circumferential direction, wherein the sum of the cross-sectional areas for the magnetic flux in the region of the radial cooling channel corresponds at least to the cross-sectional area of ​​the core element in the region of the coil winding.

[0023] Furthermore, it is proposed that the cross-sectional area in the axial direction outside the respective coil winding be at least equal to the cross-sectional area inside the coil winding. This ensures that the flux flow of the core element through the radial cooling channel is impaired as little as possible.

[0024] Preferably, the cross-sectional area of ​​the core element is constant in the axial direction. This allows for good flow guidance even in the area of ​​the radial cooling channel while simultaneously keeping the core element as compact as possible.

[0025] According to a further development, it is proposed that the radial cooling channel has a flow cross-section that is larger at a large radial distance from the axis of rotation than at a small radial distance from the axis of rotation. This makes it possible to take into account the geometry of the core element or a respective coil in order to form the radial cooling channel. For example, such a design makes it possible to automatically achieve a higher coolant flow in a radially inner region. This allows for better cooling of the radially inner region of the stator winding.

[0026] Furthermore, it is provided that at least the main cooling channel or the connecting cooling channel has at least one holding mandrel for arrangement in a respective radial cooling channel in an area adjacent to the coil windings. This development makes it possible to simplify the design of the stator as well as its manufacture. The radial cooling channel can thus not only provide a cooling function for the respective coil, but can also be used to fasten the core element. This proves to be particularly advantageous if the coil winding is simultaneously held by the core element. The holding mandrel can be designed to at least partially penetrate the radial cooling channel. Preferably, the holding mandrel completely penetrates the radial cooling channel. The holding mandrel can partially or completely fill the radial cooling channel transversely to its longitudinal extent.

[0027] The retaining mandrel has a through-hole for guiding a coolant along its longitudinal direction. This is particularly advantageous when the retaining mandrel essentially completely fills the radial cooling channel in its cross-section.

[0028] According to a further development, it is proposed that the radial cooling channel has a flow cross-section that is larger at a large radial distance from the axis of rotation than at a small radial distance from the axis of rotation. This makes it possible to further improve the cooling function. The radial cooling channel can, for example, be conical or similarly shaped.

[0029] The advantages and effects stated for the stator according to the invention naturally also apply equally to the electrical machine equipped with the stator according to the invention or to the motor vehicle equipped with the electrical machine according to the invention and vice versa.

[0030] The motor vehicle according to the invention is preferably designed as a motor vehicle, in particular as a passenger car or truck, or as a passenger bus or motorcycle.

[0031] The invention also encompasses combinations of the features of the described embodiments. The invention therefore also encompasses implementations that each comprise a combination of the features of several of the described embodiments, unless the embodiments are described as mutually exclusive.

[0032] Exemplary embodiments of the invention are described below. Shown are: Fig. 1 shows a schematic side view of an electrically driven motor vehicle with an electric drive device comprising an axial flux machine; Fig. 2 in a schematic side view the axial flow machine according to Fig. 1; Fig. 3 in a schematic perspective view a stator of the axial flow machine according to Fig. 2 with a stator winding having a plurality of coils, which is arranged between a radially inner connection cooling channel and a radially outer main cooling channel; Fig. 4 in a schematic view like Fig. 3 the stator with the coils arranged circumferentially on the radially inner connecting cooling channel without an outer main cooling channel; Fig. 5 in a schematic radial plan view a coil of the stator winding according to Fig. 4; Fig. 6 a schematic exploded view of one of the coils arranged on the connecting cooling channel; Fig. 7 is a schematic plan view of an axial end of the coil according to Fig. 5, Fig. 6; Fig. 8 a schematic sectional view of the coil according to Fig. 7 along a section line VIII-VIII in Fig. 7; Fig. 9 in a schematic perspective view of the connecting cooling channel with holding mandrels for the coils; and Fig. 10 in a schematic perspective view an arrangement of the coils on the connection cooling channel according to Fig. 9 in the manufacture of the stand.

[0033] The exemplary embodiments explained below are preferred embodiments of the invention. In the exemplary embodiments, the described components of the embodiments each represent individual features of the invention that can be considered independently of one another, each of which also develops the invention independently of one another. Therefore, the disclosure is intended to encompass combinations of the features of the embodiments other than those shown. Furthermore, the described embodiments can also be supplemented by further features of the invention already described.

[0034] In the figures, the same reference symbols designate elements with the same function.

[0035] Fig. 1 shows a schematic side view of an electrically driven motor vehicle, which here is embodied as an electric vehicle 50. The electric vehicle 50 has an electric drive device 52, which includes an axial flux machine 12 for driving the electric vehicle 50 in a normal driving mode. The axial flux machine 12 is embodied here as a multiphase axial flux machine 12. The electric drive device 52 is further connected via a multiphase inverter 56 as an energy converter to a high-voltage battery 54, which serves to supply electrical energy to the drive device 52.

[0036] Fig. 2 shows in a highly simplified schematic side view the axial flow machine 12 according to Fig. 1. If necessary, the axial flux machine 12 can also be designed such that it can be arranged in a wheel of the motor vehicle or the electric vehicle 50. The axial flux machine 12 has a stator 10 and a rotor 14. The rotor 14 is arranged rotatably and axially spaced from the stator 10 with respect to a rotational axis 18 of the rotor 14 via an air gap 20. The rotor 14 is designed as a magnetic disk and, opposite the stator 10, has a connecting pin 16 which is fastened to the rotor 14 concentrically to the rotational axis 18. The connecting pin 16 serves to provide mechanical power in motor operation or to supply mechanical power in generator operation.

[0037] The stator 10 is arranged in a rotationally fixed manner and has a connecting flange 58 for supplying a fluid coolant (not further specified), in this case air. In a region of the rotational axis 18, a further connecting flange 60 is provided, through which the coolant can be discharged from the stator 10. The connecting flanges 58, 60 are connected to a cooling system (not shown in detail), which supplies coolant at the connecting flange 58, discharges the coolant from the stator 10 at the connecting flange 60, and cools the coolant in order to make it available again in a cooled state at the connecting flange 58. Even if a closed cooling circuit is provided in the present case, the invention is not limited to this. It can also be provided that there is an open cooling circuit in which only coolant is supplied at the connecting flange 58, which is only discharged from the stator 10 at the connecting flange 58.

[0038] Fig. 3 shows in a schematic perspective view a stator 10 of the axial flow machine 12 according to Fig. 2. The stator 10 has a stator winding 22 comprising a plurality of coils 24. The stator winding 22 is arranged between a radially inner connecting cooling channel 38 and a radially outer main cooling channel 34. The connecting cooling channel 38 is essentially annular and has a circumferential cavity 62 that is fluidly connected to the connecting flange 60. This makes it possible to drain the coolant from the stator 10.

[0039] Furthermore, Fig. 3 shows that the stator 10 has the radially outer main cooling channel 34. The main cooling channel 34 is also essentially annular and has a circumferential cavity 64, which is fluidically coupled to the connecting flange 58. In this way, it is possible to supply the coolant to the stator 10.

[0040] Fig. 4 shows a schematic view of how Fig. 3, in which the stator 10 is shown without the outer main cooling channel 34. From Fig. 4 shows that the coils 24 are arranged adjacent to one another circumferentially around the connecting cooling channel 38 or in the circumferential direction around the rotational axis 18 of the rotor 14. The coils 24 have respective coil axes 26, which are arranged parallel to the rotational axis 18 (see Fig. 5).

[0041] Fig. 5 shows in a schematic radial plan view from the outside a coil 24 of the stator winding 22 according to Fig. 4. From Fig. 5 further shows that each of the coils 24 has a respective magnetizable core element 28, which in this case is formed from a suitable iron-containing alloy. The core element 28 can, for example, be designed in the manner of a laminated core or the like. Each of the coils 24 further has a respective coil winding 30. The coil winding 30 is formed in this case from an insulated electrical conductor wound onto the core element 28. In alternative embodiments, the coil winding 30 can, of course, also be implemented differently, for example by means of a strip conductor, using rods, in the manner of a needle winding, or the like. The electrical conductor preferably comprises a material that provides high electrical conductivity, for example copper, aluminum, silver, alloys thereof, and / or the like. As can be seen from Fig. 5, the coil winding 30 envelops a central region 32 of the core element 28 in the axial direction.

[0042] The Fig. 6 to 8 show the structure of the stator winding 22 more clearly, particularly with respect to a single one of the coils 24. Fig. 6 to 8, it can be seen that each coil 24 has two radial cooling channels 36 extending radially with respect to the rotational axis 18. A respective radial cooling channel 36 is fluidically connected with a radially outer end to the main cooling channel 34. A respective radially inner end of a respective radial cooling channel 36 is fluidically connected to the connecting cooling channel 38. As can be seen from the Fig. 5 to 8, the respective radial cooling channel 36 is arranged substantially in the respective core element 28 of the respective coil 24. This makes it possible to keep a groove area for the coil windings free of elements required for cooling. At the same time, it is possible to ensure that the coil winding 30 can substantially completely enclose the core element 28 in the axial direction. The respective radial cooling channel 36 therefore extends completely through the respective core element 28. In particular, this configuration therefore makes it possible to achieve a high fill factor.

[0043] As can be seen from the Fig. 5 to 8, a respective coil winding 30 has two opposing winding heads 40, 42 that are axially spaced from one another. The core element 28 projects beyond the winding heads 40, 42 in the axial direction. Outside the region of the axial extension of the respective coil winding 30, a radial cooling channel 36 is arranged or formed in the core element 28. This means that the radial cooling channels 36 are formed or arranged outside the region of the coil windings 30, viewed in the axial direction. This makes it possible, on the one hand, to achieve a high fill factor and, on the other hand, to simultaneously achieve an improved cooling effect compared to the prior art. This makes it possible to at least improve the power density or efficiency. The load capacity in the event of an overload can also be improved.

[0044] As further shown by the Fig. 5 and Fig. 8, the region 44 of the respective core element 28 that projects axially beyond the respective winding overhang 40, 42 has a larger core cross-sectional area than in the region of the respective coil winding 30. This makes it possible to impair the guidance of the magnetic flux through the radial cooling channels 36 arranged axially beyond the winding overhangs 40, 42 as much as possible. Preferably, the core cross-sectional area available for the magnetic flux in the region 44 is equal to or larger than the core cross-sectional area within the coil winding 30. Particularly advantageously, the region 44 is widened such that, with respect to the coil axis 26, on each side of the coil axis 26, at least half the core cross-sectional area is available that is available in the region of the coil winding 30.

[0045] Viewed in the axial direction, the core cross-sectional area outside the respective coil winding 30 corresponds at least to the core cross-sectional area inside the respective coil winding 30. In particular, it can of course be achieved that the core cross-sectional area of ​​the core element 28 is essentially constant when viewed in the axial direction.

[0046] The Fig. 9 and Fig. 10 further illustrate the structure of the stand 10. In particular, Fig. 9 and Fig. 10 also shows how the stand 10 can be manufactured. Fig. 9 it can be seen that the connecting cooling channel 38 has, in an area adjacent to the coil windings 30, holding mandrels 46 for arranging in the respective radial cooling channels 36, as can be seen from Fig. 10. Each retaining mandrel 46 has a through-opening 48 for guiding the coolant in its longitudinal direction. The through-opening 48 is fluidly connected to the cavity 62, so that the coolant flowing through the radial cooling channels 36 or the through-openings 48 can be collected and discharged in the cavity 62.

[0047] The retaining pins 46 also allow for the coils 24 to be fixed in place, thus allowing for easy assembly of the stand 10. No additional components need to be provided. Rather, the coils 24 with their cooling channels 36 can simply be pushed onto the retaining pins 46, as shown in FIG. Fig. 6 and Fig.10. Once the coils 24 are arranged on the connecting cooling channel 38, the main cooling channel 34 can be arranged, wherein at the same time the radially outer ends of the retaining mandrels 46 are connected to the main cooling channel 34 in such a way that the through openings 48 are fluidically connected to the cavity 64. This makes it possible for coolant supplied to the cavity 62 to flow into the through openings 48, flow radially inward through them, to be collected again in the cavity 62 and discharged. In this way, a very compact and cost-effective design for the axial flow machine 12 can be achieved.

[0048] Overall, the invention makes it possible to provide an improved axial flux machine that is not only characterized by high efficiency and high performance, but also enables a particularly simple design, particularly with regard to manufacturing. The invention achieves this by improving the fill factor because separate cooling elements do not need to be provided in the area of ​​the respective coil windings. The cooling function is realized, among other things, by means of the core elements, which have radial cooling channels 36 outside the area of ​​the coil windings for this purpose.

[0049] The description of the figures serves only to explain the invention and is not intended to limit it.

Claims

[1] Stator (10) for an axial flux machine (12), comprising a stator winding (22) comprising a plurality of electrical coils (24), wherein the coils (24) are arranged circumferentially around an axis of rotation (18) of a rotor (14) of the axial flux machine (12) next to one another and with respective coil axes (26) parallel to the axis of rotation (18), wherein each of the coils (24) comprises a respective magnetizable core element (28) and a respective coil winding (30), wherein the coil winding (30) encloses at least a central region (32) of the core element (28) in the axial direction, wherein the stator (10) comprises a main cooling channel (34) extending radially outwardly around the coils (24), wherein each coil (24) comprises at least one radial cooling channel (36) extending radially with respect to the axis of rotation (18), which is fluidically connected to the main cooling channel (34) by a radially outer end is,wherein the stator (10) has a connecting cooling channel (38) arranged radially inside the coils (24), wherein a respective radially inner end of a respective radial cooling channel (36) is fluidically connected to the connecting cooling channel (38), , characterized by in that a respective radial cooling channel (36) is arranged at least partially in a respective core element (28) of a respective coil (24), wherein at least the main cooling channel (34) or the connecting cooling channel (38) has at least one holding mandrel (46) for arrangement in a respective radial cooling channel (36) in a region adjacent to the coil windings (30), wherein the holding mandrel (46) has a through-opening (48) for guiding a coolant in its longitudinal direction. [2] Stand according to claim 1, characterized by that the respective radial cooling channel (36) extends radially completely through the respective core element (28). [3] Stand according to one of the preceding claims, characterized by that the core element (28) projects beyond at least one winding head (40, 42) of a respective coil winding (30) of the respective coil (24) in the axial direction and the radial cooling channel (36) is arranged outside a region of the axial extent of the respective coil winding (30). [4] Stand according to one of the preceding claims, characterized by that the core element (28) projects beyond opposite winding heads (40, 42) of the coil winding (30) in the axial direction and the at least one radial cooling channel (36) is arranged outside the region of the axial extension of the respective coil winding (30) in the core element (28). [5] Stand according to one of the preceding claims, characterized by that a region (44) of the respective core element (28) projecting axially beyond the respective winding head (40, 42) has a larger core cross-sectional area than in the region of the respective coil winding (30). [6] Stand according to one of the preceding claims, characterized by that the radial cooling channel has a flow cross-section which is larger at a radially large distance from the axis of rotation than at a radially small distance from the axis of rotation. [7] Axial flux machine (12), comprising a stator (10) and a rotor (14), wherein the rotor (14) is arranged axially spaced and rotatable relative to the stator (10) with respect to an axis of rotation (18) of the rotor (14) via an air gap (20), characterized by that the stand (10) is designed according to one of the preceding claims. [8] Motor vehicle (50) with an axial flow machine (12), characterized by that the axial flow machine (12) is designed according to claim 7.

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