Axial flux machine with direct magnet cooling

Abstract

An axial flux machine comprising a stator (100) and a rotor wherein:-the stator (100) comprises a plurality of stator elements (204) surrounded by a stator housing comprising a first cover (103); the first rotor disc (101) comprising a magnet (107) located within the annular region (500); -the stator (100) comprises: one or more injection elements (800) arranged on the first cover (103), each injection element (800) comprising at least one outlet hole, and one or more cooling channels (900) adapted to direct a cooling fluid under pressure to one or more respective injection elements (800); -either spraying element (800) is adapted to spray a cooling fluid towards the annular magnet region (500), such that the magnets (107) are cooled by the cooling fluid sprayed directly on the respective magnet surface during rotating rotor operation.

Description

Technical Field

[0001] The present invention relates generally to the field of axial flux machines. In particular, a solution for improving rotor cooling is proposed, which solution is easy to integrate into axial flux machines and can increase the cooling efficiency of the rotor magnets. Background Art

[0002] An axial flux machine is an electric machine that generates magnetic flux in the axial direction, i.e. in the direction of the axis of rotation. Typically, an axial flux machine comprises a disc-shaped or annular rotor and a stator, both having a central axis corresponding to the axis of rotation of the machine, the stator and the rotor being axially separated by a narrow air gap. The rotor comprises magnetic material, usually permanent magnets, which generates an axial magnetic flux. The stator comprises a plurality of coils in which an electric current can flow. During operation of the machine, the rotor is driven by the magnetic field generated by the stator current, while in the generator state, an electric current is induced in the stator coils due to the rotation of the rotor. Axial flux machines are known in different topologies, for example comprising one rotor and stator, one rotor and two stators, or two rotor disks located on either side of the stator.

[0003] During operation of an axial flux machine, the rotor magnets and rotor structure heat up due to eddy current losses in the magnetic material and back iron structure. These high temperatures can negatively impact the mechanical and magnetic properties and reliability of the magnetic material, which can adversely affect the performance of the machine. In addition, magnetic materials with higher temperature ratings are more expensive and can significantly increase the overall cost of the machine. Since losses are proportional to speed, the high temperatures reached by the magnetic material in the rotor currently limit the motor speed.

[0004] Although cooling the stator will also cool the rotor to a certain extent, a large amount of heat may still remain in the rotor. Therefore, solutions specifically for cooling the rotor magnets are proposed in the prior art.

[0005] In US10630157B2 and WO2016185173A1, the axial flux machine rotor is cooled by air cooling provided by the impeller blades. Since the impeller blades are located on the side of the rotor facing away from the stator, it is not possible to directly cool the magnets (the latter face the air gap). Therefore, the heat generated in the rotor magnets first needs to be transferred through the back iron material and the rotor housing, which has a negative impact on the cooling efficiency.

[0006] The solution proposed in WO2015 / 019107A2 aims to provide improved cooling of the rotor magnets. The axial flux machine includes a sump in which a cooling fluid is provided. When the rotor rotates, the magnets are immersed in the sump with the cooling fluid in turn. The rotation of the rotor in the fluid further causes the fluid to be adsorbed by the disc, so that the fluid has a tendency to centrifuge outwards. As the cooling fluid contacts the rotor structure, improved cooling thereof can be obtained. However, since the sump with the cooling fluid may cause additional friction during the rotation of the rotor, it is necessary to limit the liquid level in the sump. Therefore, the magnets may only be partially immersed, thereby still limiting the cooling efficiency obtained.

[0007] The object of the present invention is to disclose an axial flux machine which solves one or more of the above mentioned disadvantages of the prior art solutions. More specifically, the object is to propose a solution for improved rotor cooling which is easy to integrate into an axial flux machine and which enables to improve the cooling efficiency of the rotor magnets. Summary of the invention

[0008] According to a first aspect of the invention, the above object is achieved by an axial flux machine as defined in claim 1, the axial flux machine comprising a stator and a rotor, the rotor having a central axis corresponding to the rotation axis of the axial flux machine in an axial direction, and the rotor comprising a first rotor disk axially spaced from the stator by an air gap, in: - the stator comprises a plurality of stator elements, the plurality of stator elements being surrounded by a stator housing, any one of the stator elements comprising a coil wound on a core, the stator housing comprising a first cover, the first cover having an inner side facing the upper side of the coil and an outer side facing the air gap; - the first rotor disk comprises a magnet, the magnet surface of which is located in an annular region on the side of the rotor disk facing the air gap, And wherein the stator comprises: - one or more ejection elements arranged on the first cover, each ejection element comprising at least one outlet opening, and - one or more cooling channels adapted to direct a cooling fluid under pressure to one or more respective injection elements, Wherein, any one of the spray elements is adapted to spray cooling fluid towards the annular magnet region, so that during operation of the rotating rotor, the magnet is cooled by the cooling fluid sprayed directly onto the corresponding magnet surface.

[0009] The present invention therefore relates to an axial flux machine, which may also be referred to as, for example, an axial air gap motor or generator, or an axial flux permanent magnet machine. An axial flux machine is an electric machine that generates magnetic flux in an axial direction, i.e. in the direction of the axis of rotation. Typically, the machine is suitable for operation as a motor and a generator, depending on the operating conditions. An axial flux machine has at least one stator and at least one rotor. During operation, the stator remains stationary, while the rotor is an assembly of components that rotate during operation of the machine. Typically, the stator and the rotor each comprise a disc-shaped or annular component, respectively referred to as a stator disk or a rotor disk. The stator disk and the rotor disk are axially spaced apart by a narrow air gap. Different topologies are possible. For example, the machine may comprise one rotor disk and one stator disk, one rotor disk and two stator disks, or two rotor disks and one stator disk. In the latter case, the two rotor disks are mounted on both sides of the stator disk, with a first air gap between the stator and the first rotor disk and a second air gap between the stator and the second rotor disk. The axial flux machine may be a ring-shaped machine with a stator yoke or a YASA-type machine without a stator yoke. The latter machine is also known as a yokeless segmented armature (YASA) motor or generator, or simply a yokeless axial flux machine.

[0010] The stator comprises a plurality of stator elements, which are usually arranged rotationally symmetrically with respect to a central axis. Each stator element comprises a coil wound on a core. One or more rotor disks are mounted on the shaft of the machine. Each rotor disk comprises magnetic material (usually permanent magnets) that produces an axial magnetic flux. During operation of the motor, the rotor is driven by the magnetic field generated by the stator current flowing in the coils, while in the generator state, current is induced in the stator coils due to the rotation of the rotor.

[0011] The stator elements are surrounded by a stator housing, which may also be referred to as a clamshell housing. Typically, the stator housing comprises two parallel cover plates, wherein a first cover plate and a second cover plate are connected by a circumferential wall extending in an axial direction, one circumferential wall being located at the outer circumference and one circumferential wall being located at the inner circumference. The cover located on one side of the first air gap is referred to as the first cover. The cover located on the opposite side is referred to as the second cover. The first cover has an inner side and an outer side. The inner side faces the inside of the stator housing and thus faces the coil. The outer side faces the outside of the stator housing and thus faces the first air gap. The cover plate may have a hole through which the core extends. In this case, the top and bottom surfaces of the core are in contact with the corresponding air gap. In another embodiment, the cover plate does not include such a hole, but has a continuous surface. In this case, the core does not extend through the cover plate, but is completely located between two opposing cover plates. In addition to the cover plate and the circumferential wall, the stator housing may also include an internal structure. For example, the stator housing may include a wall located between adjacent stator elements, for example for guiding a stator cooling fluid. Typically, such a wall extends radially and axially. The wall may connect two opposing cover plates. In another embodiment, there is no such wall.

[0012] The rotor disk comprises magnetic material, which may also be referred to as magnets or rotor magnets, and which are usually arranged as permanent magnets. Usually, each magnet is connected to the rotor cover plate, wherein the back iron structure is located between the cover plate and the magnet. In this way, the top surface of the magnet faces the air gap, while the back side of the magnet is connected to the back iron structure. Therefore, the top surface of the magnet is in contact with the air gap. The magnet usually has a rotationally symmetrical arrangement with respect to the central axis. The top surface of the magnet is located in an annular region on the side of the rotor disk facing the air gap. This means that there is an annular or ring-shaped area on the rotor disk defined by the position of the magnets; any magnet is located in this annular or ring-shaped area.

[0013] The stator comprises one or more injection elements arranged on the first cover. The injection element is an element suitable for injecting a cooling fluid. The fluid is a liquid (such as water or oil) or a gas (such as air). Each injection element comprises at least one outlet hole through which the fluid can leave the injection element. The cooling fluid is under pressure so that under the action of pressure, the injection element can emit a jet or spray. In an embodiment, the injection element can be suitable for generating a jet in a well-defined direction, i.e., suitable for injecting the fluid in a coherent flow. For example, the injection element is a single hole through which the pressurized fluid is ejected, or the injection element is a nozzle. In another embodiment, the injection element can be suitable for generating a dispersed fluid spray. For example, the injection element is a nozzle suitable for generating a fine liquid spray.

[0014] The stator further comprises one or more cooling channels adapted to direct a cooling fluid under pressure to one or more corresponding injection elements. If the first stator cover comprises a single injection element, there is a single cooling channel to direct the cooling fluid from the inlet to the injection element. If the first stator cover comprises a plurality of injection elements, a plurality of cooling channels are provided, each of which directs the cooling fluid from the inlet to the corresponding injection element. The cooling channels may have different embodiments. The cooling channels may be channels penetrating the stator housing material, such as drilled channels completely surrounded by the stator housing material, or may be fluid channels within the stator housing, such as fluid channels defined by a cover plate and / or one or more stator elements. A combination of fluid channels and drilled channels is also possible to constitute the above-mentioned cooling channels.

[0015] During operation, a cooling fluid under pressure flows through one or more cooling channels. Therefore, the machine comprises a cooling fluid supply device, which is suitable for supplying or conveying such a cooling fluid under pressure. In an embodiment, the cooling fluid flowing through the one or more cooling channels can be extracted from the stator cooling circuit. In this case, the stator housing comprises an inlet to provide cooling fluid to the inside of the stator housing, and this cooling fluid is partly used to cool the stator and partly conveyed through the cooling channels for cooling the magnets of the rotor. Therefore, one or more cooling channels branch off from the stator cooling circuit. In another embodiment, separate circuits can be used for cooling the rotor and the stator.

[0016] Any of the injection elements is suitable for spraying cooling fluid into the annular magnet area of ​​the first rotor disk. This means that one or more injection elements are arranged so that the generated jet or spray is at least partially directed toward the rotor area where the magnet is located. Therefore, after injection, the cooling fluid passes through the air gap and at least a portion of the injected fluid reaches the annular rotor area where the magnet is located. In the stationary position of the first rotor disk, the cooling fluid may splash onto the surface of one or more magnets and / or onto the material located between adjacent magnets. During operation of the machine, when the rotor disk rotates, each magnet passes through the cooling fluid jet or spray in turn and is splashed by the injected cooling fluid. In this way, during operation of the rotating rotor, the magnets are cooled by the cooling fluid sprayed directly onto the corresponding magnet surface. Typically, due to the high rotational speed of the rotor, a single injection element on the first stator cover or a small number of injection elements on the first stator cover are sufficient to obtain continuous cooling of the rotor magnets.

[0017] Therefore, the cooling solution of the present invention utilizes one or more cooling channels through the stator and corresponding injection elements, allowing the injection of cooling fluid into the air gap towards the magnet top surface. This has a number of advantages.

[0018] Firstly, the rotor cooling technique of the invention is easy to implement and integrate in an axial flux machine. In fact, the invention only requires the provision of one or more cooling channels and corresponding injection elements, all of which are located in the stator; no adjustments to the rotor are required. Since the stator remains stationary during operation of the machine, it is easy to supply the stator with cooling fluid. The complexity of supplying the rotating part of the machine with cooling fluid, such as would be required if the cooling channels were provided in the rotor disk, is thus avoided.

[0019] Secondly, the cooling solution of the present invention allows cooling the rotor magnets in a direct way. In fact, the ejected cooling fluid directly contacts the magnet surface, allowing efficient heat transfer from the magnet to the cooling fluid. In this way, the cooling can be optimally concentrated on the components that need cooling, thus achieving high cooling efficiency.

[0020] Finally, the jet or spray can be generated in such a way that only the amount of coolant required for cooling the magnets is provided. As a result, no excess coolant is sprayed into the air gap, thereby preventing the air gap from being saturated with coolant. The latter is important in order to prevent excessive friction from being generated in the air gap, which could affect the overall performance of the machine.

[0021] Since the present invention can improve magnet cooling, the axial flux machine has better performance, higher maximum speed and lower cost.

[0022] In fact, the better the magnetic material of the magnet is cooled, the lower its operating temperature. This improves efficiency and increases torque. On the other hand, since eddy current losses are proportional to the rotational speed, higher rotational speeds are allowed if better magnet cooling is provided. Therefore, higher speed motor designs become possible.

[0023] Finally, when the temperatures reached in the magnetic material are reduced, lower magnet temperature grades can be used, thereby reducing magnet material costs because less or even no rare earth metals are used. In addition, since the size of the segments can be increased and the number of segments required can be reduced when magnet cooling is improved, manufacturing costs can be reduced. Since magnets are one of the most expensive components in an axial flux machine, reducing their cost significantly reduces the overall cost of the machine.

[0024] Optionally, according to claim 2, one or more injection elements are arranged as one or more corresponding holes in the first cover plate, so as to be suitable for ejecting the cooling fluid as a jet directed to the magnet area. In an embodiment, a hole can be arranged in the first cover plate, which is used as a single injection element. In another embodiment, a plurality of holes can be arranged in the first cover plate, each of which is used as an injection element. Under the action of pressure, the cooling fluid is ejected from the hole in the form of a jet. The jet represents a coherent flow of the fluid with a clear direction. The jet is directed to the rotor area where the magnet is located when ejected. Arranging the injection element as a hole has the following advantages: the pressure of the cooling fluid can still be maintained at a conventional level; there is no need to increase the fluid pressure as when using a nozzle as an injection element.

[0025] Optionally, according to claim 3, one or more cooling channels branch off from a cooling circuit for cooling the stator elements. This means that the axial flux machine comprises a stator cooling circuit in which a cooling fluid is circulated to cool the stator elements. For example, the cooling fluid can be supplied to a circumferential channel via an inlet port and then flows radially between adjacent coils. One or more cooling channels for cooling the rotor magnets branch off from the stator cooling circuit. This means that the cooling fluid supplied to the stator via the inlet port is partly used to cool the stator by circulating between the stator elements and partly used to cool the rotor via cooling channels and injection elements. In other words, the cooling fluid for magnet cooling is extracted from a main cooling circuit, which is already used for stator cooling. Thus, both stator cooling and rotor magnet cooling use a common cooling fluid supply; no separate cooling circuits are used for rotor and stator cooling. This helps to reduce the complexity and cost of the axial flux machine.

[0026] Optionally, according to claim 4, the cooling fluid is a cooling liquid, such as oil.

[0027] Optionally, according to claim 5, the first cover plate has an outer circumference and an inner circumference, and any one of the one or more injection elements is located at a radial position closer to the inner circumference than the outer circumference. Typically, the first cover plate is annular, having a circular outer circumference and a circular inner circumference. Each injection element is located near the inner circumference of the first stator cover. In this way, the cooling fluid will be injected onto the annular magnet area at a radial position closer to the inner edge of the annular magnet area than to the outer edge. The advantage of this is that due to the effect of centrifugal force, the cooling fluid will be further dispersed, thereby helping to improve cooling efficiency.

[0028] Optionally, according to claim 6, any one of the one or more cooling channels is fluidly connected to a fluid inlet located at the outer circumference of the stator, so that during operation, the cooling fluid is guided from the outer circumference of the stator to the inner circumference of the stator and then ejected through one or more ejection elements. The stator housing includes an inlet for providing a cooling fluid to the stator. Typically, in order to allow a simple machine design, the inlet is located at the outer circumference of the stator disk. The one or more cooling channels for rotor cooling are fluidly connected to the fluid inlet at the outer circumference. This means that during operation of the machine, one or more cooling channels receive fluid from the inlet by being connected to the inlet directly or via an intermediate element. Therefore, when the fluid inlet is located at the outer circumference of the stator and the ejection element is located near the inner circumference, the cooling fluid first needs to be transmitted from the outer circumference to the inner circumference and then ejected through the ejection element. Therefore, the fluid is transmitted in the direction of the inner circumference through the cooling channel, and the cooling channel does not necessarily reach the inner circumference itself. Typically, the transmission from the outer circumference to the inner circumference is a fluid transmission in a radial or substantially radial direction.

[0029] Optionally, according to claim 7, any of the one or more cooling channels comprises a radial portion and an end portion, the radial portion being adapted to guide the cooling fluid from the outer circumference of the stator to the inner circumference, the end portion being arranged as a channel passing through the material of the first cover and terminating at the injection element, the end portion being in fluid communication with the radial portion. This means that the cooling channel comprises a radial portion followed by an end portion, the end portion terminating at the injection element in the first stator cover. The radial portion of the cooling channel is adapted to convey the fluid from the outer circumference of the stator to the inner circumference. Typically, this is a transmission in a radial or substantially radial direction, but in embodiments, such transmission may deviate from a radial direction. Therefore, the term "radial" in "radial portion" is only used to indicate the portion of the channel conveying from the outer circumference to the inner circumference. According to various embodiments, the radial portion of the cooling channel may be implemented in different ways. For example, the radial portion may be arranged as a channel drilled in the material of the stator housing, or may be arranged as a fluid channel inside the stator housing. The end portion is arranged as a channel passing through the material of the first cover and terminating in the injection element. This means that the end portion is a channel delimited by a surrounding surface (e.g. a cylindrical surface), the surface being made of the material of the stator housing. Thus, the end portion is a channel, hole, groove, recess, bore or duct applied in the material of the cover plate and thus completely surrounded by the stator housing material. The end portion is in fluid communication with the radial portion. This means that, during operation of the machine, the end portion receives fluid from the radial portion. In one embodiment, the end portion directly connects the radial portion to the injection element. In another embodiment, the radial portion is indirectly connected (i.e. via an intermediate element) to the injection element.

[0030] Optionally, according to claim 8, the radial portion is arranged as a passage through the material of the first cover, or as a passage through the material of the wall located between adjacent stator elements. The wall constitutes part of the internal structure of the stator housing and is therefore contained in the stator housing. In an embodiment, the stator housing may include a plurality of walls, each wall being located between adjacent stator elements. Typically, such a wall extends in a radial direction, for example for guiding a stator cooling fluid between the coils. In an embodiment, the wall is connected to the first cover plate. The radial portion is arranged as a passage through the material of the first cover, or as a passage through the material of the wall. This means that the radial portion is a channel delimited by a surrounding surface, for example a cylindrical surface, which is made of the stator housing material. Thus, the radial portion is a channel, a hole, a groove, a recess, a bore or a duct applied in the material of the cover plate or the wall and is therefore completely surrounded by the stator housing material. Thus, both the end portion and the radial portion of the cooling channel are arranged as a passage through the stator housing material. In an embodiment, the end portion is directly connected to the radial portion. Arranging the radial portion of the cooling channel as a passage through the stator housing material has the advantage that the transport of the cooling fluid from the outer circumference to the inner circumference does not heat the cooling fluid. In fact, the delivery of the cooling fluid for rotor cooling takes place in channels separate from the stator elements, thus avoiding any contact with hot stator elements and thus heating of the fluid for rotor cooling.

[0031] Optionally, according to claim 9, the radial portion is a fluid channel defined by the inner side of the first cover and the upper side of the coil, and the end portion branches from this fluid channel. During operation of the axial flux machine, when the cooling fluid flows from the outer circumference of the stator to the inner circumference, the cooling fluid is guided between the upper side of the coil and the inner side of the first cover. Therefore, the radial portion does not act as a channel through the stator housing material, but as a bypass running above and / or below the coil. Such a fluid channel or bypass channel is defined by the available space between the inner side of the cover plate and the upper side of the coil, but is not completely surrounded by the material surface. For example, grooves or grooves can be applied to the inner side of the cover plate, thereby creating some space between the upper side of the coil and the cover plate, through which the cooling fluid can flow. Typically, the cooling fluid for cooling the stator elements flows in a radial direction between adjacent stator elements. By providing a bypass between the cover plate and the coil, part of the stator cooling fluid will flow through the bypass. Since the end portion of the cooling channel for rotor cooling branches off from the bypass channel, some of the cooling fluid flowing through the bypass channel will enter the end portion and be ejected through the ejection element for cooling the rotor magnets. Therefore, the rotor cooling fluid is usually guided in a radial direction between the upper side of the coil and the inner side of the first cover, and then ejected through the ejection element. The advantage of this is that there is no need to provide a separate channel through the stator housing material for radial direction delivery. On the other hand, the rotor cooling fluid may generate some heating due to the contact of the fluid with the hot winding. However, due to the limited contact surface between the bypass fluid and the upper side of the coil, the heating of the rotor cooling fluid during delivery from the outer circumference to the inner circumference will also be limited.

[0032] Optionally, according to claim 10, the radial portion is a fluid channel defined by the inner side of the first cover and the plate, and the end portion branches from this fluid channel. The plate is positioned between the inner side of the first cover and the upper side of the coil. During operation of the axial flux machine, when the cooling fluid flows from the outer circumference of the stator to the inner circumference, the cooling fluid is guided between the plate and the inner side of the first cover. Therefore, the radial portion does not act as a channel through the stator shell material, but as a bypass running between the plate and the inner side of the cover. Such a fluid channel or bypass channel is defined by the available space between the inner side of the cover plate and the upper side of the plate, but is not completely surrounded by the material surface. For example, grooves or grooves can be applied to the inner side of the cover plate, thereby creating some space between the plate and the cover, through which the cooling fluid can flow. Usually, the cooling fluid for cooling the stator elements flows in a radial direction between adjacent stator elements. By providing a bypass between the plate and the cover, part of the stator cooling fluid will flow through the bypass. Since the end portion of the cooling channel for rotor cooling branches off from the bypass channel, some of the cooling fluid flowing through the bypass channel will enter the end portion and be ejected through the injection element for cooling the rotor magnets. Therefore, the rotor cooling fluid is usually guided in a radial direction between the plate and the inner side of the first cover and then ejected through the injection element. The advantage of this is that there is no need to provide a separate channel through the stator housing material for radial delivery. In addition, the rotor cooling fluid is guided in a radial direction without contacting the stator elements. Therefore, the plate isolates the cooling fluid from the hot winding, thereby limiting the rotor cooling fluid from being heated before being ejected through the injection element.

[0033] Optionally, according to claim 11, the radial portion is one of the fluid channels for cooling the stator elements between adjacent stator elements, so that during operation, the cooling fluid is directed between two adjacent stator elements when flowing from the outer circumference to the inner circumference of the stator, and the end portion branches from this fluid channel. This means that the stator cooling circuit includes a fluid channel extending between adjacent stator elements. Typically, the stator cooling fluid flows in a radial direction, and the cooling of the stator elements occurs by contact between the cooling fluid and the heating coil. In an embodiment, there may be a radial wall between two adjacent stator elements, so that the fluid channel is defined by the space between the stator elements and the radial wall. In another embodiment, there is no such radial wall, and the fluid channel is defined by the space between two adjacent stator elements. The fluid channel may also be defined by the inner sides of two opposing cover plates. Since the end portion of the cooling channel for rotor cooling branches out from the stator fluid channel, some of the cooling fluid flowing through the channel will enter the end portion and be ejected through the injection element for cooling the rotor magnets. Therefore, the rotor cooling fluid is usually guided in the radial direction between two adjacent stator elements or between a stator element and a radial wall and then ejected by the ejection element. This has the advantage that no separate channels need to be provided through the stator housing material for radial delivery. On the other hand, the cooling fluid is heated by contact with at least one stator element before being used to cool the rotor magnets.

[0034] Optionally, according to claim 12, the core of the stator element extends through the first cover so that the surface of the corresponding core is in contact with the air gap, and during operation of the machine, at least a portion of the cooling fluid ejected by one or more injection elements splashes onto the core surface, thereby cooling the core. This means that the cover plate of the stator housing includes a hole through which the core extends. Therefore, the top and bottom surfaces of the core are in contact with the corresponding air gap. When the cooling fluid is ejected through one or more injection elements and reaches the rotor magnets, at least a portion of the cooling fluid is splashed back onto the core surface. In this way, the core will also be cooled due to the ejected cooling fluid. This has the following advantages: in addition to improving the cooling of the rotor magnets, the cooling of the stator elements is also improved.

[0035] Optionally, according to claim 13, - the rotor comprises a second rotor disk axially spaced from the stator by a second air gap; - the stator housing comprises a second cover facing the second air gap; and - the second rotor disk comprises magnets, the magnet surfaces of which are located in an annular region on the side of the disk facing the second air gap, And, the stator includes: - a second set of one or more ejection elements disposed on the second cover, each ejection element comprising at least one outlet opening, and - a second set of one or more cooling channels adapted to direct cooling fluid under pressure to a second set of one or more corresponding injection elements, Wherein, any one of the injection elements is adapted to inject cooling fluid toward the annular magnet region of the second rotor disk, so that during operation of the rotating rotor, the magnets of the second rotor disk are cooled by the cooling fluid injected directly onto the corresponding magnet surfaces.

[0036] This means that the axial flux machine has a topological structure comprising a stator and two rotor disks. The two rotor disks are mounted on both sides of the stator disk, and there is a first air gap between the stator and the first rotor disk and a second air gap between the stator and the second rotor disk. The stator housing comprises a second cover facing the second air gap. A second set of one or more injection elements is arranged on the second cover, and a second set of one or more cooling channels passing through the stator allow the supply of cooling fluid under pressure to the injection elements of the second group. The injection elements and cooling channels of the second group are defined in a similar manner to the injection elements on the first cover. In addition, the injection elements and cooling channels of the second group can have various embodiments, similar to the above-mentioned embodiments. Providing injection elements in the two stator covers can improve the cooling effect of the rotor magnets of the two rotor disks. In an embodiment, one injection element is arranged on each stator cover at a relative axial position.

[0037] Optionally, according to claim 14, any one of the one or more cooling channels of the second group includes a final portion, which is arranged to pass through the material of the second cover and terminate at the channel of the injection element of the second group. The final portion is fluidly connected to the radial portion, which is suitable for guiding the cooling fluid from the outer circumference of the stator to the inner circumference of the stator. Therefore, any cooling channel of the second group is suitable for supplying cooling fluid to the injection element in the second cover plate and includes a final portion. The final portion is arranged as a channel passing through the material of the second cover and is equivalent to the "end portion" arranged in the first cover. Therefore, the cooling channels of the first group are suitable for supplying cooling fluid to the injection element in the first cover, and the cooling channels of the second group are suitable for supplying cooling fluid to the injection element in the second cover, and they each have a corresponding end portion and a final portion. On the other hand, the radial portion suitable for guiding the cooling fluid from the outer circumference of the stator to the inner circumference of the stator is used by the first stator cover and the second stator cover. In other words, the second cooling channel for cooling the second rotor disk branches out from the radial portion of the first cooling channel for cooling the first rotor disk. In this way, only one delivery channel or channel from the outer circumference to the inner circumference is required to cool the two rotor disks, thereby reducing the complexity of the machine design and the manufacturing cost. In one embodiment, the final part of the second cooling channel can branch off from the fluid channel defined inside the stator housing. In another embodiment, the final part of the second cooling channel can be connected to the radial part through the intermediate part.

[0038] Optionally, according to claim 15, - the stator comprises at least one wall located between two adjacent stator elements and extending axially between the first cover and the second cover; the radial portion is arranged as a passage through the material of the first cover, or as a passage through the material of the wall, and - Any of the one or more cooling channels of the second group comprises an intermediate portion arranged as a passage through the material of the wall, the intermediate portion being in fluid communication with both the radial portion and the final portion.

[0039] The wall forms part of the internal structure of the stator housing. In an embodiment, the stator housing may include a plurality of walls, each wall being located between adjacent stator elements. Typically, such a wall extends in a radial direction, for example for guiding a stator cooling fluid between the coils. The wall extends in an axial direction and typically connects two cover plates. The radial portion is arranged as a channel through the material of the first cover, or as a channel through the material of the wall. Each of the one or more cooling channels of the second group includes an intermediate portion passing through the wall (for example in an axial direction) and a final portion passing through the second cover plate. The intermediate portion is in fluid communication with both the radial portion and the final portion. This means that the intermediate portion can receive fluid from the radial portion and supply fluid to the final portion. In an embodiment, the intermediate portion directly connects the radial portion with the final portion. In this way, also in order to cool the magnets of the second rotor disk, the cooling fluid only needs to be guided through a channel arranged in the stator housing material, thereby avoiding the fluid from being heated before being used for rotor cooling. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 A stator and two rotor disks according to an embodiment of the invention are shown.

[0041] Figure 2 A stator is shown with the second cover removed according to an embodiment of the invention.

[0042] Figure 3 Shows Figure 2 Top view of the opened stator.

[0043] Figure 4 yes Figure 3 Detailed view of the .

[0044] Figure 5 A rotor disk according to an embodiment of the invention is shown.

[0045] Figure 6 and Figure 8 A top view of a stator according to an embodiment of the present invention is shown.

[0046] Figure 7A cross section of a stator according to an embodiment of the invention is shown on a bending plane parallel to the axial direction.

[0047] Fig. 9 A cross-sectional view according to section CC is shown showing a cooling channel for rotor magnet cooling according to a first embodiment of the invention.

[0048] Fig.10 A cross-sectional view according to section AA is shown, illustrating a cooling channel for rotor magnet cooling according to a first embodiment of the invention.

[0049] Fig.11 and Fig.12 A radial cross section is shown, illustrating a cooling channel for rotor magnet cooling according to a first embodiment of the invention.

[0050] Fig.13 A cross-sectional view according to section AA is shown, illustrating a cooling channel for rotor magnet cooling according to a second embodiment of the invention.

[0051] Fig.14 A cross-sectional view according to section AA is shown, illustrating a cooling channel for rotor magnet cooling according to a third embodiment of the invention.

[0052] Fig.15 A cross-sectional view according to section AA is shown showing a cooling channel for rotor magnet cooling according to a fourth embodiment of the invention. DETAILED DESCRIPTION

[0053] Figure 1 The stator 100 and rotor of an axial flux machine are shown. Two rotor disks 101, 102 are located on either side of the stator disk 100. The stator disk 100 and the first rotor disk 101 are axially separated by a first air gap 105, while the stator disk 100 and the second rotor disk 102 are axially separated by a second air gap 106. The stator disk 100 and the rotor disks 101, 102 have a central axis along the X-direction or axial direction 115, corresponding to the rotation axis of the machine. The radial direction 116 is represented as the Y-direction in the figure. The first rotor disk 101 includes a magnetic material 107, also called a magnet 107 or a rotor magnet 107, and is typically a permanent magnet. The second rotor disk 102 includes a magnetic material 108, also called a magnet 108 or a rotor magnet 108, and is typically a permanent magnet. The magnets 107, 108 generate magnetic flux along the axial direction 115.

[0054] The stator housing or clamshell housing comprises a first cover 103 and a second cover 104. The cover plates 103, 104 are perpendicular to the axial direction 115 and form the bottom and upper limits of the stator housing, respectively. Figure 2The stator 100 is shown with the second cover 104 removed. The stator 100 comprises a plurality of stator elements 204 which are arranged rotationally symmetrically with respect to a central axis 115. Each stator element 204 comprises a coil or winding 110 which is wound around a ferromagnetic core 109 which extends in an axial direction 115. The first cover 103 has an inner side 202 and an outer side 203. The inner side 202 faces the inside of the stator housing and thus faces the coil 110. The outer side 203 faces the outside of the stator housing and thus faces the first air gap 105. The first cover 103 is disc-shaped and has a circular outer circumference 200 and a circular inner circumference 201. The first cover 103 and the second cover 104 are connected by circumferential walls 205, 205 located at the outer circumference and the inner circumference, respectively.

[0055] Figure 3 and Figure 4 Shows Figure 2 1 shows a top view of the stator 100 opened in FIG. The stator disk 100 has an outer circumference 300 and an inner circumference 301. The inner structure of the stator housing comprises a guide wall 111, wherein the guide wall 111 is located between each pair of adjacent stator elements 204 and extends in a radial direction 116. The radial wall 111 is connected to the outer circumferential wall 205 at one outer end. In the axial direction, the radial wall extends between the first cover 103 and the second cover 104, thereby connecting the two cover plates.

[0056] from Figure 1 and Figure 2 As can be seen, the outer circumferential wall 205 comprises outer channels 113 and 114, while the space between the outer end of the guide wall and the inner circumferential wall 206 defines the inner channel 112. The channels 113, 114 and 112 form part of a cooling circuit for stator cooling, for cooling the stator elements 204. Such stator cooling solutions are known in the prior art and are described, for example, in EP3764526A1. The outer and inner channels 113, 114, 112 are arranged to allow the stator cooling fluid to flow tangentially around the central axis. On the other hand, the guide wall 111 is arranged to allow the stator cooling fluid to flow in a radial direction. For this purpose, a radial fluid channel is provided between each coil 110 and the adjacent radial wall 111. In the embodiment shown, the cooling fluid is supplied to the cold channel 113 via a supply port, which is not shown in the figure. Figure 4The stator fluid circulation is schematically shown (as indicated by the arrows). In the channel 113, the cooling fluid circulates in a tangential direction. Next, the cooling fluid flows in a radial direction to the inner circumference (see arrow 401). When flowing through the radial fluid channel, the fluid is guided by the radial wall 111, so that it is forced to flow to the coil 110 and discharge the heat from the coil 110. The fluid is then collected in the inner channel 112. For adjacent stator elements, the radial flow occurs in the opposite direction, from the inner circumference to the outer circumference, see arrow 402. The heated fluid is collected in the hot channel 114, which is connected to the port for discharging the stator cooling fluid.

[0057] Figure 5 A top view of the first rotor disk 101 is shown. The first rotor disk 101 includes magnets 107 attached to a disk-shaped plate. The magnets 107 are arranged rotationally symmetrically around a central axis. As shown, the magnets 107 together define an annular or ring-shaped area 500 on the rotor disk. Any magnet 107 is located within the annular area 500. The area 500 is bounded by an inner limit 501 and an outer limit 502. When installed in an axial flux machine, the top surface of the magnet 107 faces the first air gap 105, so the top surface is in contact with the air gap 105. The second rotor disk 102 has a similar design to the first rotor disk 101.

[0058] Figure 6 103 or a similar-looking second stator cover 104 is shown in a top view. The figure shows that the stator cover plates 103, 104 include holes through which the core 109 extends. Figure 7 It can also be seen that Figure 7 Three adjacent stator elements 204 are shown, which have cores 109, the outer ends of which extend through the two cover plates 103 and 104. Therefore, the top surface of the core 109 is in contact with the corresponding air gaps 105 and 106. Note that Figure 7 The cross section is taken along the bending plane, similar to Figure 6 , but at another angular position different from that of the section AA. Figure 7 The cooling channels for rotor cooling are not visible. The cooling channels for rotor cooling are discussed further below. Figure 7 Again, it is shown that there are guide walls 111 between each pair of adjacent coils 110. The cooling fluid for stator cooling flows in a radial direction through the radial fluid channels 700 defined by the coils 110 and the guide walls 111.

[0059] Figures 8 to 15 The inventive solution for improving the cooling of the rotor magnets is shown. Four different embodiments of the rotor cooling channels are described. Figures 9 to 12 A first embodiment is shown. Fig.13, Fig.14 and Fig.15 A second, third and fourth embodiment are shown respectively. Figure 8 A top view of the first stator cover 103 is shown, and the first stator cover 103 is suitable for any one of the four embodiments.

[0060] like Figure 8 As shown, the first stator cover plate includes an injection element 800. In the embodiment shown, only one injection element 800 is provided in the first cover plate 103. In other embodiments, there may be more than one injection element 800. The second cover plate 104 also includes an injection element, which is opposite to the injection element 800 of the first cover plate 104. In the embodiment shown, the injection element is provided with a single outlet hole facing the first air gap 105. Through the injection element 800, the fluid under pressure can be injected into the first air gap 105, thereby generating a jet directed to the annular magnet area 500. From Figure 8 It can be seen that the ejection element 800 is located at a radial position close to the inner circumference 201 .

[0061] The stator also includes cooling channels for directing cooling fluid under pressure to the injection elements 800. Figures 9 to 12 In the first illustrated embodiment, the cooling passages 900 are passages (eg, drilled passages) through the stator housing material. Fig. 9 A cross section according to section CC is shown, see Figure 7 To show section CC. Fig.10 A cross section according to section AA is shown, see Figure 6 To show section AA. Fig.11 and Fig.12 shows a cross section according to the radial direction, similar to Figure 6 BB, but at an angular position corresponding to the injection element 800.

[0062] The cooling channel 900 includes a radial portion 901 and an end portion 902. The radial portion 901 and the end portion are both configured as a channel through the stator housing material. The radial portion 901 is a channel through the first cover 103 from the outer circumference 200, 300 toward the inner circumference 201, 301. In another embodiment, the radial portion 901 may pass through the guide wall 111 instead of through the first cover 103. In the embodiment shown, the radial portion 901 extends in a radial direction. The end portion 902 is a channel through the first cover 103, connecting the radial portion 901 to the injection element 800.

[0063] from Fig.11As can be seen in the figure, the radial portion 901 is in fluid communication with the cold channel 113 via the channel portion 1100. As mentioned above, the cold channel 113 forms part of a cooling circuit for stator cooling. Thus, the cooling channel 900 for rotor magnet cooling branches off from the circuit for cooling the stator elements 204. In this way, the cold cooling fluid which has not yet been heated by the stator elements is used to cool the rotor magnets.

[0064] During operation of the machine, the cooling fluid is first transferred through the radial portion 901, thereby flowing in the radial direction, from the outer circumference 300 to the inner circumference 301. This transfer from the outer circumference to the inner circumference is necessary because the cold channel 113 is located at the outer circumference 300 and the injection element 800 is located near the inner circumference 301. Next, the cooling fluid flows through the end portion 902 to the outlet hole 800 and is ejected from the outlet hole 800.

[0065] In this way, a jet directed toward the annular magnet region 500 is generated. Thus, after the injection, the cooling fluid passes through the first air gap 105, and at least a portion of the injected fluid reaches the rotor region 500 where the magnets 107 are located. During operation of the machine, when the rotor disk rotates, each magnet 107 passes through the cooling fluid jet in turn and is splashed by the injected cooling fluid. In this way, during operation of the rotating rotor, the magnets 107 are cooled by the cooling fluid injected directly onto the corresponding magnet surface. Due to the centrifugal force, the cooling fluid is dispersed, thereby further contributing to the cooling of the magnet surface. Afterwards, the cooling oil is radially discharged from the air gap to the outside and can be collected in a sump for extraction. Please note that the cooling oil, in addition to being used for cooling purposes, can also simultaneously contribute to the lubrication of the bearings.

[0066] Similarly, the magnets 108 arranged on the second rotor disk 102 are cooled by the jets ejected from the jet elements 1000 in the second stator cover 104. For this purpose, the stator comprises a second cooling channel adapted to direct the cooling fluid toward the jet elements 1000 of the second cover 104. In the illustrated embodiment, the second cooling channel comprises an intermediate portion 903 and a final portion 904. The intermediate portion 903 is a channel extending in the axial direction through the guide wall 111. A first outer end of the intermediate portion 903 is connected to the final portion 904, which passes through the second cover 104 and ends at the jet elements 1000. The other outer end of the intermediate portion 903 is connected to the radial portion 901. Therefore, the radial portion 901 is used in common to cool the first rotor disk and the second rotor disk. During operation, the cooling fluid first flows from the outer circumference to the inner circumference through the radial portion 901. Next, a portion of the fluid enters the end portion 902 and flows toward the first ejection element 800 , and another portion of the fluid enters the middle portion 903 and flows toward the second ejection element 1000 .

[0067] The end portion 902 of the cooling channel may be straight, such as Fig.11 As shown, it can also be inclined, such as Fig.12 The end portion 1200 is shown. For ease of description, Fig.12 Only the first rotor disk 101 and the corresponding cooling channels are shown in FIG. The use of outlet holes 800, 1000 as injection elements allows the cooling fluid to be provided at a relatively low pressure (e.g., between 1 bar and 2 bar). Typically, the radial portion 901 of the cooling channel is relatively wide to allow unimpeded flow in the radial direction and a sufficient flow rate. On the other hand, the end portions 902, 904 and the outlet holes 800, 1000 must be specially designed to obtain the desired injection shape and the preferred flow rate and flow rate of the injection spray. For this purpose, outlet holes 800, 1000 with a relatively small diameter can be used. Please note that it is very important to inject the right amount of fluid into the rotor magnets: on the one hand, sufficient heat needs to be extracted from the magnets, and on the other hand, the air gap should not be saturated with the cooling fluid. The situation in which the air gap is saturated with the cooling fluid will cause undesirable friction during rotation. For example, a flow rate of 1 liter per minute can be provided for rotor cooling, of which 0.5 liters per minute are injected into the first rotor disk 101 and 0.5 liters per minute are injected into the second rotor disk 102. For example, 10% to 30% of the primary cooling fluid may be extracted for rotor cooling.

[0068] Finally, when the cooling fluid is ejected through the ejection elements 800 and 1000 and reaches the rotor magnets 107 and 108, respectively, at least a portion of the cooling fluid is splashed back onto the top surface of the core 109. Thus, by providing the core 109 extending through the apertures in the stator covers 103, 104, the cooling of the stator elements is also improved.

[0069] Fig.13 , Fig.14 and Fig.15 The second, third and fourth embodiments are shown respectively. These embodiments differ from the first embodiment in that the radial fluid transmission from the outer circumference to the inner circumference is different before the fluid enters the end portion 902. The end portion 902 (arranged as a passage through the first cover 103) and the injection element 800 are Figures 9 to 12 Likewise, the final portion 904 and the corresponding ejection element 100 are similar to those of the first embodiment.

[0070] Fig.13A second embodiment is shown. In the embodiment shown, grooves or channels 1300 are applied at the inner side 202 of the first cover plate 103, thereby creating some space between the upper side 1302 of the coil 110 and the cover plate 103. The space provided serves as a bypass channel 1300 under the winding; for the purpose of stator cooling, part of the fluid flowing in the radial direction will not flow along the side of the coil, but will flow in the radial direction through the bypass channel 1300. Therefore, when the cooling fluid flows from the outer circumference 300 to the inner circumference 301 of the stator, the cooling fluid is guided between the upper side 1302 of the coil 110 and the inner side 202 of the first cover 103. In other words, in this embodiment, the radial part is the fluid channel 1300 defined by the inner side 202 of the first cover 103 and the upper side of the coil 110.

[0071] The end portion 902 branches off from the fluid channel 1300 so that part of the fluid in the bypass channel 1300 flows to the injection element 800 for cooling the rotor magnets 107. During the radial transport, the cooling fluid comes into contact with the upper side of the winding. Therefore, the cooling fluid is heated to a certain extent before being ejected through the injection element 800. Similar to the cooling of the first rotor disk 101, the bypass channel or fluid channel 1301 is used for cooling the second rotor disk 102. The final portion 904 branches off from the fluid channel 1301 and ends at the injection element 1000.

[0072] Fig.14 A third embodiment is shown. The third embodiment differs from the second embodiment only in that a plate 1402 separates a bypass channel 1400 from the coil 110. The plate 1402 is perpendicular to the axial direction and substantially parallel to the upper side 1302 of the coil 110. Similar to the second embodiment, a groove or a groove 1400 is applied at the inner side 202 of the first cover plate 103. The plate 1402 is located between the inner side 202 of the first cover plate 103 and the upper side 1302 of the coil 110. Thus, the bypass channel 1400 or the fluid channel 1400 is defined by the plate 1402 and the inner side 202 of the first cover plate 103. During operation, the cooling fluid will be directed between the plate 1402 and the inner side 202 of the first cover plate 103 when flowing in the radial direction. In other words, in this embodiment, the radial portion is a fluid channel 1400 defined by the inner side 202 of the first cover 103 and the plate 1402.

[0073] The end portion 902 branches out from the fluid channel 1400 so that part of the fluid in the bypass channel 1400 flows to the injection element 800 for cooling the rotor magnets 107. The plate 1402 isolates the cooling fluid from the hot winding, thereby limiting the heating of the rotor cooling fluid before being ejected through the injection element 800. Similar to the cooling of the first rotor disk 101, the bypass channel or fluid channel 1401 is used for cooling the second rotor disk 102. The final portion 904 branches out from the fluid channel 1401 and ends at the injection element 1000.

[0074] Fig.15 A fourth embodiment is shown. In this embodiment, no dedicated radial cooling channel is provided for rotor cooling. Instead, the existing radial fluid channel 700 is used for cooling the stator element 204. Figure 7 As shown, the cooling fluid for stator cooling flows in the radial direction through the radial fluid channel 700 defined by the coil 110 and the guide wall 111. Fig.15 As shown, in the fourth embodiment, the end portion 902 and the final portion 904 branch out from one of the radial fluid channels 700. Therefore, in this embodiment, the radial portion of the cooling channel for rotor cooling corresponds to one of the fluid channels 700 between adjacent stator elements 204, and the fluid channel 700 is used for cooling the stator elements 204. Due to the contact with at least one coil 110, the cooling fluid is heated to a certain extent before being sprayed by the spray elements 800 and 1000.

[0075] Although the present invention has been described by specific embodiments, it will be understood by those skilled in the art that the present invention is not limited to the details of the above illustrative embodiments, and that the present invention can be embodied by various changes and modifications without departing from its scope. Therefore, the present embodiment should be regarded as illustrative and not restrictive in all aspects, and the scope of the present invention is indicated by the attached claims rather than the above description, and therefore, all changes within the meaning and equivalent scope of the claims should be included in the claims. In other words, this patent application covers any and all modifications, variants or equivalents that fall within the scope of the basic principles, and its basic attributes have been declared in this patent application. The reader of this patent application should also understand that the words "comprising" or "comprise" do not exclude other elements or steps, and the words "a" or "an" do not exclude multiple, and a single element (such as a computer system, a processor or another integrated unit) can implement the functions of several devices described in the claims. Any figure mark in the claims should not be interpreted as a limitation on the relevant claims. The use of the terms "first", "second", "third", "a", "b", "c", etc. in the specification or claims is to distinguish similar elements or steps, and does not necessarily describe a continuous or chronological order. Similarly, the terms "top", "bottom", "above", "below", etc., are introduced for descriptive purposes and do not necessarily indicate relative positions. It should be understood that the terms used are interchangeable under appropriate circumstances, and embodiments of the present invention may be implemented in other orders or orientations than described or illustrated in accordance with the present invention.

Claims

1. An axial flux machine, comprising a stator (100) and a rotor, the rotor having a central axis corresponding to the rotation axis of the axial flux machine in an axial direction (115), and the rotor comprising a first rotor disk (101), the first rotor disk (101) being axially separated from the stator (100) by an air gap (105), in, - the stator (100) comprises a plurality of stator elements (204) surrounded by a stator housing, each stator element (204) comprising a coil (110) wound on a core (109), the stator housing comprising a first cover (103), the first cover (103) having an inner side (202) facing an upper side (1302) of the coil (110) and an outer side (203) facing an air gap (105); - the first rotor disk (101) comprises a magnet (107), the magnet surface of the magnet (107) being located in an annular region (500) on the side of the rotor disk facing the air gap (105), It is characterized in that The stator (100) comprises: - one or more ejection elements (800) arranged on the first cover (103), each ejection element (800) comprising at least one outlet hole, and - one or more cooling channels (900) adapted to direct a cooling fluid under pressure to one or more corresponding injection elements (800), Wherein, any one of the spray elements (800) is adapted to spray cooling fluid toward the annular magnet region (500), so that during operation of the rotating rotor, the magnets (107) are cooled by the cooling fluid sprayed directly onto the corresponding magnet surface.

2. An axial flux machine according to any one of the preceding claims, One or more ejection elements (800) are arranged as one or more corresponding holes in the first cover (103), thereby being suitable for ejecting the cooling fluid as a jet directed towards the magnet area (500).

3. An axial flux machine according to any one of the preceding claims, One or more cooling channels (900) branch off from a cooling circuit for cooling the stator elements (204).

4. An axial flux machine according to any one of the preceding claims, The cooling fluid is a cooling liquid, such as oil.

5. An axial flux machine according to any one of the preceding claims, The first cover (103) has an outer circumference (200) and an inner circumference (201), and any one of the one or more injection elements (800) is located at a radial position closer to the inner circumference (201) than to the outer circumference (200).

6. An axial flux machine according to any one of the preceding claims, Any one of the one or more cooling channels (900) is fluidly connected to a fluid inlet located at the outer circumference (300) of the stator (100), so that during operation, the cooling fluid is guided from the outer circumference (300) of the stator to the inner circumference (301) of the stator and then sprayed through one or more spray elements (800).

7. An axial flux machine according to any one of the preceding claims, Any one of the one or more cooling channels (900) comprises a radial portion (901) and an end portion (902), wherein the radial portion (901) is adapted to guide the cooling fluid from the outer circumference (300) of the stator to the inner circumference (301) of the stator, and the end portion (902) is arranged as a channel passing through the material of the first cover (103) and terminating at the injection element (800), and the end portion (902) is in fluid communication with the radial portion (901).

8. The axial flux machine according to claim 7, The radial portion (901) is configured as a passage through the material of the first cover (103), or as a passage through the material of the wall (111) between adjacent stator elements (204).

9. The axial flux machine according to claim 7, wherein the radial portion is a fluid channel (1300) defined by the inner side (202) of the first cover (103) and the upper side (1302) of the coil (110), so that during operation, when the cooling fluid flows from the outer circumference (300) of the stator to the inner circumference (301) of the stator, the cooling fluid is guided between the upper side (1302) of the coil (110) and the inner side (202) of the first cover (103), And wherein the end portion (902) branches out from the fluid channel (1300).

10. The axial flux machine according to claim 7, in, The radial portion is a fluid channel (1400) defined by the inner side (202) of the first cover (103) and a plate (1402), the plate (1402) being located between the inner side (202) of the first cover (103) and the upper side (1302) of the coil (110), so that during operation, when the cooling fluid flows from the outer circumference (300) of the stator to the inner circumference (301) of the stator, the cooling fluid is guided between the plate (1402) and the inner side (202) of the first cover (103), And wherein the end portion (902) branches out from the fluid channel (1400).

11. The axial flux machine according to claim 7, wherein the radial portion is one of the fluid channels (700) between adjacent stator elements (204) for cooling the stator elements, so that during operation, when the cooling fluid flows from the outer circumference (300) of the stator to the inner circumference (301) of the stator, the cooling fluid is guided between two adjacent stator elements (204), And wherein the end portion (902) branches out from the fluid channel (700).

12. An axial flux machine according to any one of the preceding claims, wherein the core (109) of the stator element (204) extends through the first cover (103) such that a surface of the corresponding core (109) is in contact with the air gap (105), And among them, During operation of the machine, at least a portion of the cooling fluid sprayed by the one or more spray elements (800) splashes onto the core surface, thereby cooling the core (109).

13. An axial flux machine according to any one of the preceding claims, in: - the rotor comprises a second rotor disk (102) axially spaced apart from the stator (100) by a second air gap (106); - the stator housing comprises a second cover (104) facing the second air gap (106); the second rotor disk (102) comprises magnets (108) whose magnet surfaces are located in an annular region (500) on the side of the disk facing the second air gap (106), And wherein the stator (100) comprises: - a second set of one or more ejection elements (1000) disposed on the second cover (104), each ejection element (1000) comprising at least one outlet hole, and - a second set of one or more cooling channels adapted to direct a cooling fluid under pressure to a second set of one or more corresponding injection elements (1000), Any one of the spray elements (1000) is suitable for spraying cooling fluid toward the annular magnet region of the second rotor disk (102), so that during operation of the rotating rotor, the magnets (108) of the second rotor disk (102) are cooled by the cooling fluid sprayed directly onto the corresponding magnet surfaces.

14. An axial flux machine according to claims 13 and 7, wherein any cooling channel of the second set of one or more cooling channels comprises a final portion (904) arranged to pass through the material of the second cover (104) and terminate at a channel of the second set of injection elements (1000), Wherein the final portion (904) is in fluid communication with a radial portion (901), the radial portion (901) being adapted to direct cooling fluid from an outer circumference (300) of the stator towards an inner circumference (301) of the stator.

15. An axial flux machine according to claims 14 and 8, in: The stator (100) comprises at least one wall (111) located between two adjacent stator elements (204) and extending axially between the first cover (103) and the second cover (104); the radial portion (901) is arranged as a passage through the material of the first cover (103), or as a passage through the material of the wall (111), and - Any cooling channel of the one or more cooling channels of the second group comprises an intermediate portion (903) arranged as a passage through the material of the wall (111), the intermediate portion (903) being in fluid communication with both the radial portion (901) and the final portion (904).

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