axial flux machine

Abstract

Axial flux machines can be cooled with a coolant. This cooling is to be improved. The invention relates to an axial flux machine (1) comprising a stator (3) and a rotor (2) which is rotatable about an axis of rotation (A) relative to the stator (3), said rotor having a rotor disk (4, 5) and a rotor surface (6) arranged perpendicular to the axis of rotation (A), wherein the rotor (2) has a cooling structure (7) which is designed to guide a coolant (8) along the rotor surface (6), wherein an outlet (10) of the cooling structure (7) is located radially further outwards than an inlet (9) of the cooling structure (7), wherein a radial coordinate of a profile of the cooling structure (7) increases starting from the inlet (9) and then decreases again, at least in regions, towards the outlet (10).

Description

The invention relates to an axial flux machine, having a stator and a rotor which is rotatable about an axis of rotation relative to the stator and has a rotor disc and a rotor surface arranged perpendicular to the axis of rotation.Electric machines having a rotor and a stator are known. In operation, the electric machine heats up due to losses. These can be divided into ohmic losses, iron losses, stray losses and mechanical losses, for example. Iron losses occur mainly in the stator and rotor and contribute a substantial proportion to the total losses. If the electric machine heats up too strongly, it can be destroyed as a result. Various cooling systems are therefore known in the prior art.The object of the invention is to provide an improved cooling for an axial flow machine, in particular a rotor of the axial flow machine.The object is achieved by the subject matters of the independent claims. Advantageous refinements of the invention are described by the dependent patent claims, the following description and the figures.The invention is based on the idea of improving the cooling of the axial flow machine by a targeted radial to and fro guidance of a coolant along a rotor surface.One aspect of the invention relates to an axial flow machine. The axial flux machine has a stator and a rotor. The rotor is rotatable about an axis of rotation relative to the stator. The rotor has a rotor disk and a rotor surface of the rotor disk arranged perpendicular to the axis of rotation. The rotor has a cooling structure configured to guide a coolant along the rotor surface. The cooling structure has an inlet and an outlet. The outlet of the cooling structure is located radially further outward than the inlet of the cooling structure. A radial coordinate of a course of the cooling structure increases starting from the inlet and then decreases again at least in regions toward the outlet. The course of the cooling structure thus moves away from the inlet starting from the axis of rotation and subsequently approaches the axis of rotation again towards the outlet at least in regions.By means of a targeted guidance of a flow of the coolant on the rotor surface from the inlet to the outlet by means of the cooling structure, convective heat transfer between the rotor and the coolant can be improved. This allows a defined heat exchange from the rotor to the coolant. In addition, the rotor is cooled particularly uniformly, since the coolant leads from the inlet through the cooling structure first radially outwards and then radially inwards again to the outlet. As a result, coolant already heated by the rotor reaches radially inward again and still cool coolant reaches radially outward again. The rotor surface can also be referred to as the rotor rear side or rotor disc surface.With a purely radial flow of the coolant outwards, the rotor would be cooled radially very non-uniformly, namely with increasing radius less and less. As a result, an effectiveness of rotor cooling by the cooling structure with radial back and forth flow can be significantly improved, whereby an increase in a continuous power of the electric machine can be made possible and / or more cost-effective magnetic materials or adhesives and the like can be used. In particular, this is possible because the improved cooling of the rotor results in a lower temperature of the magnets of the rotor and the adhesives, thereby reducing temperature requirements on the magnet materials and adhesives.In particular, the rotor surface is arranged perpendicular to the axis of rotation. The normal direction with respect to the rotor surface thus runs parallel to the axis of rotation. In particular, the vertical rotor surface is thus cooled and not necessarily a circumferential surface of the rotor. This is particularly advantageous for axial flow machines in which most of the heat arises at the rotor surface.In some embodiments, the rotor surface is located in the axial direction on a side of the rotor disks facing away from the stator. When speaking of an axial or radial direction, this is always to be understood in the present document with reference to the axis of rotation of the rotor, unless another indication is given.The coolant is in particular a lubricating oil of bearings of the electric machine. Optionally, the coolant is a specific cooling oil.The axial flux machine is an axially constructed electric machine, for example, in that a stator disk is arranged in a sandwich-like manner between two rotor disks. In particular, the stator disk is arranged on only one rotor disk. In the axial flux machine, the magnetic flux flows parallel to the rotation axis of the rotor. Therefore, the heat generation in the axial flow machine on the rotor surface, which is perpendicular to the axis of rotation, is greater than in a radial flow machine. In a radial flow machine, more heat is generated on a circumferential surface of the rotor. Therefore, the rotor arrangement according to the invention is particularly advantageous for axial flux machines. In particular, the rotor surface is a side of the rotor facing away from the stator. If there are two rotor disks, then there are in particular exactly two rotor surfaces which are each located on a rotor disk.In one exemplary embodiment, the rotor has a first rotor disk and a second rotor disk, which are connected in a rotationally fixed manner via an axis, so that the rotor has an H-shape in longitudinal section. The cooling structure is arranged at least on and / or in the first rotor disk. However, it is also possible that a cooling structure is arranged both on and / or in the first rotor disk and also on and / or in the second rotor disk.For example, the respective rotor disk is a magnet carrier. This means in particular that respective magnets, in particular permanent magnets, can be held on the respective rotor disc, so that the respective magnets are supported by the respective rotor disc. Thus, the respective magnets are co-rotatable with the respective rotor disc, on which the respective magnets are held, about the axis of rotation relative to the stator. It is furthermore conceivable for at least one or more coils to be held on the stator. The coil can be energized. This means that an electric current can flow through the coil. Thus, for example, the stator carries the coil. In particular, the axial flow machine can have a housing, wherein the rotor disks are rotatable about the machine rotation axis relative to the housing. In this case, it is provided in particular that the stator is fixed to the housing. This means that the stator is connected to the housing in a rotationally fixed manner. Since the stator is arranged between the rotor disks in the axial direction of the axial flux machine, the stator is also referred to as a central stator. In particular by energizing the coil, that is to say by an electric current being conducted through the coil or through the coils, the rotor disks can be driven and thereby rotated, in particular about the axis of rotation, relative to the stator and preferably also relative to the housing.Furthermore, it is preferably provided that a first air gap is arranged in the axial direction of the axial flux machine between the stator and a first of the rotor disks. Furthermore, it is preferably provided that a second air gap is arranged in the axial direction of the axial flux machine between the stator and a second of the rotor disks. In particular, the respective air gap can be at least substantially disk-shaped.In one exemplary embodiment, the cooling structure is formed as a continuous cooling channel, in particular as a single cooling channel. This results in a, in particular single, homogeneous cooling flow. As a result, the rotor surface can be cooled particularly uniformly.In one embodiment, the cooling structure extends within the rotor disc of the rotor. The cooling structure is thus introduced into a material of the rotor disk. For example, through groove-like recesses in the rotor disk. Space and weight can thereby be saved. In particular, the cooling structure extends completely within the rotor disk.In one exemplary embodiment, the axial flow machine has a housing with a hollow structure. The axial flow machine is designed such that the coolant flows from the outlet of the cooling structure into the hollow structure without contact.Preferably, the hollow structure is fluidically connected to the outlet, in particular only on a housing surface which is arranged substantially parallel to the rotor surface and faces the rotor surface. For example, the coolant enters the cooling structure from a rotor shaft of the rotor. In particular, after the coolant leaves the cooling structure, the coolant flows into the hollow structure, possibly due to gravity, in inlet openings of the hollow structure. Optionally, the coolant is guided through the hollow structure, in particular by means of a pump, back into a rotor shaft of the rotor. The axial flow machine is preferably designed in such a way that the coolant can flow in this circuit.In particular, in this exemplary embodiment, no trough is required for collecting the coolant. As a result, drag losses can be reduced, because the rotor is not braked by the coolant in a trough and / or installation space can also be saved, because no trough is required.Contactless means in particular that no seals or rotary feedthroughs are required for transporting the coolant into the hollow structure, so that losses of the axial flow machine are also reduced as a result.In one exemplary embodiment, the axial flux machine has a rotor cover which is separate from the rotor disk. The rotor cover closes the cooling structure axially on a side facing away from the stator. This side facing away from the stator can be referred to in particular as the outer side of the rotor and a side facing the stator can be referred to in particular as the magnet side of the rotor.Optionally, the outlet faces the rotor cover and the inlet faces the magnet side. For example, the cooling structure is arranged in the rotor disk in a channel-like manner and is open axially on the outer side. The rotor cover closes the cooling structure on the outside.In an exemplary embodiment of an axial flow machine, a rotor cover separate from the rotor disk. The cooling structure extends within the rotor cover. For example, the cooling structure extends completely within the rotor cover. Then, the rotor disk preferably closes off the cooling structure in the axial direction.Optionally, the cooling structure extends partially within the rotor cover and partially within the rotor disc. Optionally, the cooling structure includes a first half-groove in the rotor cover and a second half-groove in the rotor disc.In one embodiment, the rotor cover has an outlet part. The outlet portion is axially raised from the rotor surface. An axial distance from the rotor surface increases with decreasing radius with respect to the axis of rotation. The outlet part is open towards the axis of rotation. The outlet part is a part of the rotor cover arranged closest to the axis of rotation in the radial direction. The outlet part is farther from the axis of rotation in the radial direction than the inlet of the cooling structure.In particular, the outlet part is designed to be completely circumferential with respect to the axis of rotation, in particular in order to conduct the coolant into the hollow structure.In one exemplary embodiment, the outlet part is funnel-shaped. This means in particular that the outlet part protrudes from the rotor surface in longitudinal section through the axis of rotation. This shape is particularly suitable for guiding the coolant into the hollow structure through a corresponding angle of slope. In particular, the angle of departure with respect to the rotor surface is between 10° and 80°, in particular between 40° and 60°.In one exemplary embodiment, the housing has a catch part. The catch part is raised in the axial direction from a housing surface of the housing facing the rotor surface. An axial distance from the housing surface increases with decreasing radius with respect to the axis of rotation. The catch part is open towards the axis of rotation. The catch part overlaps in the radial direction at least in regions with the opening of the rotor cover.In particular, the catching part is designed to be completely circumferential with respect to the axis of rotation in order to prevent the coolant from flowing past the outside of the catching part instead of into the hollow structure.In particular, the catching part is funnel-shaped. This means that the catch part protrudes from the housing surface in longitudinal section through the axis of rotation. This shape is particularly suitable for catching the coolant and in particular for guiding it further into the hollow structure. In particular, the angle of protrusion of the catch part relative to the housing surface is between 10° and 80°, in particular between 40° and 60°.For example, only a region of the capture part overlapping with the outlet part is funnel-shaped. Optionally, the catch part is v-shaped or z-shaped, wherein a first leg of the shape is arranged directly along the housing on the housing surface, which is arranged substantially parallel to the rotor surface and faces the rotor surface. Preferably, a second and / or a third leg of the mold forms the funnel-shaped, overlapping region.In one exemplary embodiment, the cooling structure is formed as two nested spirals. Radially outer ends of the spirals are connected to each other. Radially inner ends of the coils constitute the inlet and the outlet. The cooling structure thus has at least one loop. This results in a type of meander, for example. As a result of this shape of the cooling structure, the coolant can be guided radially outwards and then at least in regions radially inwards to the outlet. As a result, the rotor is cooled particularly uniformly.In one exemplary embodiment, the rotor shaft has a cavity. The cavity is fluidically connected to the cooling structure via the inlet for feeding the coolant into the cooling structure. The axial flow machine is designed such that the coolant can be injected, in particular injected, into the cavity of the rotor shaft in a contactless manner, in particular from the hollow structure.For this purpose, the axial flow machine has, for example, a spray tube. The axial flow machine preferably has a pump, with which the coolant can be transported from the hollow structure of the housing via the injection tube into the rotor shaft.A further aspect of the invention relates to a vehicle having an axial flow machine according to the invention. The axial flow machine is designed to drive the vehicle as part of an electric drive train of the vehicle.In particular, the axial flow machine is a component of the electric drive train, for example of a motor vehicle, which provides driving torque. This means that the axial flow machine, also referred to as a disk rotor machine, can be used for a drive train of a motor vehicle, so that the motor vehicle can be electrically driven, in particular purely, by means of the axial flow machine. The axial flow machine is thus in particular a traction machine, by means of which the motor vehicle can be driven electrically, in particular purely. The motor vehicle is thus, for example, a hybrid vehicle or else an electric vehicle, in particular a battery-electric vehicle (BEV).Further embodiments of the vehicle according to the invention follow directly from the various embodiments of the axial flow machine according to the invention and vice versa. In particular, individual features and corresponding explanations and advantages with respect to the various embodiments can be transferred analogously to the axial flow machine according to the invention to corresponding embodiments of the vehicle according to the invention and vice versa.Further advantages, features and details of the invention are evident from the following description of preferred exemplary embodiments and on the basis of the drawings. The features and combinations of features mentioned above in the description and the features and combinations of features mentioned below in the description of the figures and / or shown alone in the figures can be used not only in the respectively specified combination but also in other combinations or alone without departing from the scope of the invention.The following are shown: FIG. 1 shows a schematic longitudinal sectional illustration of a detail of an exemplary embodiment of an axial flow machine according to the invention; FIG. 2 shows a schematic cross-sectional illustration of a further exemplary embodiment of an axial flow machine according to the invention in a detail; and FIG. 3 shows a schematic longitudinal sectional illustration of a further exemplary embodiment of an axial flow machine according to the invention in a detail.FIG. 1 shows a schematic longitudinal sectional illustration of a detail of an exemplary embodiment of an axial flow machine 1. In particular, the axial flow machine 1 is an axial flow machine for a motor vehicle. This means, for example, that the motor vehicle, which is preferably designed as a motor vehicle, in particular as a passenger vehicle, can have the axial flow machine 1 in its completely produced state. The axial flow machine 1 is an electric machine which can provide torques. In particular, vehicle wheels of an axle of the motor vehicle can be driven by means of the respective torque provided by the axial flow machine 1, as a result of which the motor vehicle can be driven, in particular purely electrically.The axial flux machine 1 has a rotor 2 and a stator 3 (FIG. 3 ). The rotor 2 has, in particular, a first rotor disk 4 and a second rotor disk 5 (FIG. 3 ).The rotor disks 4, 5 are rotatable, in particular jointly or simultaneously, about a machine rotational axis, also referred to simply as rotational axis A, relative to the stator 3. In particular, the axial flux machine 1 can provide the aforementioned torques via the rotor 2. The axis of rotation A is, for example, an axis of symmetry with respect to which, for example, the respective rotor disk 4, 5 and / or the stator 3 is configured rotationally symmetrically. In addition, the axis of rotation A is also referred to as the axis of rotation, since the rotor disks 4, 5 and the axis of rotation are rotatable relative to the stator 3. In particular, the stator 3 is arranged between the rotor disks 4, 5 in the axial direction of the axial flux machine 1.The rotor 2 has a rotor surface 6 arranged perpendicular to the axis of rotation. The rotor 2 has a cooling structure 7 configured to guide a coolant 8 (FIG. 3 ) along the rotor surface 6. The cooling structure 7 has an inlet 9 and an outlet 10. The outlet 10 of the cooling structure 7 is located radially further outward than the inlet 9 of the cooling structure 7. the cooling structure 7 extends radially outward starting from the inlet 9 and then at least in regions radially inward toward the outlet 10.In the exemplary embodiment shown in FIG. 1, the rotor 2 has a rotor cover 11. For example, the first rotor disk 4 and / or the second rotor disk 5 has the cooling structure 7. In other exemplary embodiments not shown here, the rotor cover 11 can have the cooling structure 7.Preferably, the rotor cover 11 has an outlet part 11 a. The outlet part 11 ais optionally funnel-shaped and projects in particular from the rotor surface 6 in the axial direction.FIG. 2 shows a schematic cross-sectional illustration of a further exemplary embodiment of the axial flux machine 1 in a fragmentary manner. For example, the first rotor disk 4 is shown in an axial plan view of the cooling structure 7 without the rotor cover 11 in FIG. 2.For example, the cooling structure 7 includes a cooling passage 7 cand a passage 7 d. The passage 7 d leads from a collecting basin 15 a(FIG. 3 ) in the interior of a rotor shaft 15 (FIG. 3 ) of the rotor 2 axially away from the stator 3 and radially outwards to the cooling channel 7 c.A side facing the stator 3 can be referred to in particular as a magnetic side. In particular, the first rotor disk 4 has a first magnet side and the second rotor disk 5 has a second magnet side. If appropriate, the respective opposite side can be referred to as the first outer side of the first rotor disk 4 and as the second outer side of the second rotor disk 5. In particular, the respective outer side corresponds to the respective rotor surface 6. The passage 7 dpreferably leads from the collecting basin 15 ain each case from the magnet side to the outer side of the respective rotor disk 4, 5.For example, the cooling channel 7 cextends from the passage 7 d, in particular in the form of a spiral or worm, radially outwards, in particular as far as a turning loop 7 a. This can be referred to as meandering, for example. Preferably, the cooling structure 7 runs from the turning loop 7 a, in particular in the form of a worm, radially inward as far as the outlet 10. This means in particular that a radius of the helical cooling structure 7 increases uniformly. A change in the radius of the cooling structure 7 can therefore be constant, for example, with the exception of the turn-over loop 7 a.In other embodiments not shown, the cooling structure has a plurality of turn loops 7a.Preferably, a width 7 bof the cooling structure 7 is between 1 mm and 4 mm, in particular between 2 mm and 3 mm, in particular 2.5 mm. An axial depth of the cooling structure 7 preferably has between 1 mm and 4 mm, in particular between 1.5 mm and 2.5 mm, in particular 2 mm.FIG. 3 shows a schematic longitudinal sectional illustration of a further exemplary embodiment of the axial flow machine 1 in a detail. For example, the housing 12 encloses an interior 1 aof the axial flow machine. Optionally, the stator 3 and the rotor disks 4, 5 are each arranged at least partially, in particular completely, in the interior 1 a. The stator 3 is preferably mounted fixed to the housing, i.e. connected to the housing 12 in a rotationally fixed manner. In particular, the rotor disks 4, 5 are rotatable about the axis of rotation A relative to the housing 12 and relative to the stator 3. Magnets 13, 14 are held, for example, on the rotor disks 4, 5, in particular in such a way that the rotor disks 4, 5 each at least partially accommodate the magnets 13, 14.In particular, the magnets 13 and 14 are designed as permanent magnets. For example, the rotor 2 includes the rotor shaft 15. The rotor shaft 15 runs in particular parallel to the axis of rotation A.Preferably, the housing 12 has a hollow structure 12 a, not shown completely in FIG. 3. The hollow structure 12 acomprises in particular an opening 12 binto the interior 1 aof the axial flow machine 1. For example, the opening 12 bis disposed at a side part 12 cof the housing 12. The side part 12 cis preferably arranged perpendicular to the axis of rotation A and in particular has a housing surface facing the rotor disc 4, 5. It is possible for the hollow structure to have a plurality of openings 12 b. For example, the hollow structure 12 aextends in a tube-like or shaft-like manner radially outwards, in particular in the side part 12 c. For example, the housing 12 has a shell part 12 d. The hollow structure 12 apreferably runs, in particular additionally, in the casing part 12 d. In particular, the hollow structure 12 aextends in a region of the casing part 12 dwhich is located at the bottom when the axial flow machine 1 is installed as intended.Optionally, the housing 12 has a catch part 12 e. The catch part 12 eis optionally funnel-shaped and projects in particular from the side part 12 cin the axial direction. For example, the catching part 12 eand the outlet part 11 aadcreate radially. In particular, the outlet part 11 ais arranged at least partially radially further inward than the catch part 12 e.A circuit of the coolant 8 can be configured, for example, as follows. The coolant 8 can pass from the rotor shaft 15 into the cooling channel 7 c,for example, through the passage 7 d. In the cooling channel 7 c, the coolant is preferably first guided radially outwards, in particular up to the turn loop 7 a, and then guided radially inwards again to the outlet 10. The capture part 12 eadpossibly guides the coolant through the opening 12 binto the hollow structure 12 a, through the side part 12 cand optionally into the jacket part 12 d.Preferably, a pump not shown in FIG. 3 pumps the coolant 8 out of the hollow structure 12 a, in particular from the jacket part 12 d, into the rotor shaft 15. Optionally, the coolant 8 is sprayed into the rotor shaft 15 via the spray tube 16. Preferably, the rotor shaft 15 has a funnel-shaped collecting part 15 a. The collecting part 15 ain particular projects radially inward from the rotor shaft 15 and conducts the coolant 8 axially in the direction of the inlet 9.In the exemplary embodiment shown in FIG. 3, the axial flow machine 1 has a planetary gear 17. For example, the coolant 8 is guided from the hollow structure 12 athrough a rotary feedthrough 19 into an output shaft 17 aof the planetary gearing 17. For example, the coolant 8 is then injected into the rotor shaft 15 from the output shaft 17 avia the injection tube 16.The rotor shaft 15 is optionally designed as a differential shaft and the coolant 8 passes through the differential shaft into the inlet 9.List of reference characters1 Axial flux machine 1 a Innenraum 2 Rotor 3 Stator 4 First rotor disk 5 Second rotor disk 6 Rotor surface 7 Cooling structure 7 a Wende loop 7 b Breite 7 c Kühlkanal 7 d Durchführung 8 Coolant 9 Inlet 10 Outlet 11 Rotor cover 11 a Auslass part 12 Housing 12 a Hohl structure 12 bOpening 12 cSide part 12 d Mantel part 12 e Fang part 13 Magnet 14 Magnet 15 Rotor shaft 15 a Sammel part 16 Injection tubes 17 Planetary gear

Claims

Axial flow machine (1) comprising a stator (3) and a rotor (2) rotatable about an axis of rotation (A) relative to the stator (3) and having a rotor disc (4, 5) and a rotor surface (6) of the rotor disc (4, 5) arranged perpendicular to the axis of rotation (A), characterized in that - the rotor (2) has a cooling structure (7) which is configured to guide a coolant (8) along the rotor surface (6); - an outlet (10) of the cooling structure (7) is located radially further outwards than an inlet (9) of the cooling structure (7); and - a radial coordinate of a course of the cooling structure (7) increases starting from the inlet (9) and then decreases again at least in regions towards the outlet (10).Axial flow machine (1) according to claim 1, characterised in that the cooling structure (7) extends within the rotor disc (4, 5) of the rotor (2).Axial flow machine (1) according to Claim 1 or 2, characterized in that - the axial flow machine (1) has a housing (12) with a hollow structure (12a), and - the axial flow machine (1) is designed in such a way that the coolant (8) flows from the outlet (10) of the cooling structure (7) into the hollow structure (12a) without contact.Axial flux machine (1) according to one of the preceding claims, characterized in that the axial flux machine (1) has a rotor cover (11) which is separate from the rotor disc (4, 5) and which closes off the cooling structure (7) axially on a side facing away from the stator (3).Axial flow machine (1) according to one of Claims 1 to 3, characterized in that the axial flow machine (1) has a rotor cover (11) which is separate from the rotor disc (4, 5), wherein the cooling structure (7) runs within the rotor cover (11).Axial flow machine (1) according to claim 4 or 5, characterised in that the rotor cover (11) has an outlet part (11a), wherein the outlet part (11a): - is raised from the rotor surface (6) in the axial direction, wherein an axial distance from the rotor surface (6) increases with decreasing radius with respect to the axis of rotation (A), - is opened towards the axis of rotation (A) and has a corresponding opening (12b), - is a part of the rotor cover (11) arranged closest to the axis of rotation (A) in the radial direction, and - is further away from the axis of rotation (A) in the radial direction than the inlet (9) of the cooling structure (7).Axial flow machine (1) according to Claim 3 and Claim 6, characterized in that the housing (12) has a capture part (12e), wherein the capture part (12e): - is raised in the axial direction from a housing surface of the housing (12) facing the rotor surface (6), wherein an axial distance from the housing surface increases with decreasing radius with respect to the axis of rotation (A), - is open towards the axis of rotation (A), and - overlaps at least in regions in the radial direction with the opening (12b) of the rotor cover (11).Axial flow machine (1) according to one of the preceding claims, characterized in that the cooling structure (7) is formed as two nested spirals, the radially outer ends of which are connected to one another and the radially inner ends of which represent the inlet and the outlet.Axial flow machine (1) according to one of the preceding claims, characterized in that - the rotor shaft (15) has a cavity which, for feeding the coolant (8) into the cooling structure (7), is fluidically connected to the cooling structure (7) via the inlet (9), and - the axial flow machine (1) is designed in such a way that the coolant (8) is injected into the cavity of the rotor shaft (15) in a contactless manner, in particular from the hollow structure (12a), during operation.Vehicle having an axial flow machine (1) according to one of the preceding claims, wherein the axial flow machine (1) is designed to drive the vehicle as part of an electric drive train of the vehicle.

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