Rotor arrangement for an electric machine, electric machine, and method for cooling a rotor

Abstract

The invention relates to a rotor arrangement (1) for an electric machine, having a rotor (3) and a spray device (7) for spraying a coolant (10) with a coolant outlet (8) which is arranged with respect to the rotor (3) such that a rotor face (4) can be sprayed with the coolant (10), wherein a baffle plate (11), which is fastened to the rotor (3), is shaped and is arranged on the rotor (3) such that the coolant (10) sprayed by the spray device (7) can be caught by the baffle plate (11) and guided on the rotor face (4).

Description

[0001] Rotor arrangement for an electrical machine and electrical machine and method for cooling a rotor

[0002] The invention relates to a rotor arrangement for an electrical machine, comprising a rotor and a spray device for spraying a coolant with a coolant outlet which is arranged with respect to the rotor such that a rotor surface can be sprayed with the coolant, as well as to an electrical machine comprising a rotor arrangement and a method for cooling a rotor of an electrical machine.

[0003] Electrical machines with a rotor and a stator are common. During operation, the electrical machine heats up due to losses. These can be divided into ohmic losses, iron losses, stray losses, and mechanical losses. Iron losses occur primarily in the stator and rotor and contribute significantly to the total losses. If the electrical machine heats up too much, it can be destroyed. Therefore, various cooling systems are known in the state of the art.

[0004] DE 102015 015 797 A1 discloses an electric machine with a rotor and a stator. The stator comprises at least one winding having a surface facing the rotor, which can be exposed to a cooling fluid sprayed radially outward from the rotor as the rotor rotates, to cool the winding. The surface extends at least in a partial region at an angle to the axial direction of the rotor.

[0005] WO 2022 / 001268 A1 discloses a motor with a motor cooling system for an electric vehicle. The motor comprises a rotor with a rotor iron core, a first end cover, and a second end cover. A liquid inlet channel is provided in one end cover, which is fluidly connected to a liquid flow channel in the rotor iron core, and a liquid outlet channel in the end cover faces a stator winding. The liquid inlet channel, the liquid flow channel, and the liquid outlet channel form a rotor channel through which a coolant can flow.

[0006] The invention is based on the object of providing more effective cooling for an electrical machine, in particular a rotor of the electrical machine.

[0007] The problem is solved by the subject matter of the independent patent claims. Advantageous developments of the invention are described by the dependent patent claims, the following description, and the figures.

[0008] The invention is based on the idea of ​​capturing a coolant from a spray cooling system by using a guide plate and guiding it along a rotor surface, so that the contact time between coolant and rotor is improved and extended, thereby enabling more effective cooling of the rotor without the need for complicated cooling channel structures.

[0009] One aspect of the invention relates to a rotor assembly for an electrical machine, comprising a rotor and a spray device for spraying a coolant with a coolant outlet arranged relative to the rotor such that a rotor surface can be sprayed with the coolant. The rotor assembly has a guide plate. The guide plate is attached to the rotor, in particular rigidly attached, for example by welding. The guide plate is shaped and arranged on the rotor such that the sprayed coolant from the spray device can be captured by the guide plate and guided over the rotor surface.

[0010] By specifically guiding a coolant flow along the rotor surface, which can also be referred to as the rear of the rotor or rotor disk surface, using the baffle, convective heat transfer between the rotor and the coolant can be improved. Without targeted guidance of the coolant by the baffle, only a significantly lower heat transfer from the rotor surface to the coolant can be achieved due to strong atomization and jet reflection. By attaching the appropriately designed baffle to the rear of the rotor, the coolant can be held and guided along the rotor surface. By specifically guiding the coolant along the rotor surface, both the contact time between the coolant and the rotor surface can be extended and the heat transfer coefficient can be increased, particularly compared to air-cooled rotor arrangements.As a result, the effectiveness of rotor cooling can be significantly improved by the rotor arrangement according to the invention, thereby enabling an increase in the continuous power of the electric machine and / or the use of more cost-effective magnetic materials, adhesives, etc. This is particularly possible because the improved cooling of the rotor leads to a lower temperature at the rotor magnets and adhesives, thus lowering the temperature requirements for the magnetic materials and adhesives.

[0011] In particular, the guide vane can capture the majority of the sprayed coolant, in particular more than 80%, in particular more than 90%. During operation of the electric machine, rotational forces carry the coolant outwards, away from a rotational axis of the rotor, over the rotor surface and hold and guide it on the rotor surface by the guide vane. When the coolant reaches the outer edge of the rotor, it can, for example, be thrown off and fed into a cooling circuit. In particular, the guide vane ensures that the majority of the rotor surface covered by the guide vane, in particular more than 80%, in particular more than 90%, in particular more than 95%, is wetted with the coolant. This results in particularly effective and efficient cooling of the rotor, since the rotor can be cooled very well and, for example, using less coolant.This also has the advantage that effective cooling is possible with simple spray cooling without the need for complex cooling channels in or on the rotor.

[0012] When referring to an axial or radial direction, this is always to be understood above and below in relation to the rotor's axis of rotation, unless otherwise stated. The coolant is, in particular, cooling oil.

[0013] In particular, the spray device comprises a coolant supply and a pump in addition to the coolant outlet. In particular, the coolant outlet sprays the coolant in a jet that is between 0° and 90° wide, in other words, has an opening angle of 0° to 90°.

[0014] According to the invention, the guide plate has a guide portion. The guide portion has a zero-gap portion. The zero-gap portion covers the rotor surface at least partially in the radial direction and completely tangentially circumferentially. The zero-gap portion rests against the rotor surface.

[0015] The zero-gap section serves to force a very thin coolant, also referred to as a cooling fluid film, onto the rotor surface under the strong centrifugal forces present during operation. The gap height between the rotor surface and the guide vane is determined solely by the surface roughness and flatness of the rotor surface and the guide vane. In the zero-gap section, the gap height is nominally 0, meaning the zero-gap section is flush with the rotor surface. In fact, however, the gap height is sufficient on a microscopic scale due to the surface structures of the rotor surface and the guide vane, allowing the coolant to spread.

[0016] It is possible for the zero-gap section to be directly connected to the retaining section. It is also possible for the zero-gap section to be directly connected to the retaining section and extend radially to the edge of the rotor. This allows the coolant to be guided particularly well over a large portion of the rotor side.

[0017] However, it is also possible for the zero-gap section to be directly connected to the catch section and not extend radially to the edge of the rotor, in particular so that the zero-gap section covers less than 50%, in particular less than 30%, in particular less than 20%, of the rotor surface. This arrangement can save weight and installation space, especially if the zero-gap section forms the entire guide section of the baffle.

[0018] In one embodiment, the guide plate is designed to guide the coolant radially and tangentially around the rotor surface. This allows the rotor to be cooled more effectively and efficiently. Tangentially around means along an imaginary circle with a specific radius around the axis of rotation that is smaller than a maximum outermost rotor radius. The imaginary circle lies on a plane perpendicular to the axis of rotation, for example, on the rotor surface. The direction can be clockwise or counterclockwise. For example, the guide plate can guide the coolant both radially and tangentially around the rotor surface within a circular ring region with the axis of rotation at its center.

[0019] In one embodiment, the rotor surface is arranged perpendicular to a rotational axis of the rotor. In other words, a normal direction on the rotor surface is parallel to the rotational axis.

[0020] In particular, the rotor surface that is arranged perpendicular to the axis of rotation of the rotor is cooled and not necessarily a lateral surface of the rotor. This is particularly advantageous for electrical machines where most of the heat is generated at the rotor surface, for example in axial flux machines. In one embodiment, the guide plate has a collecting part. The collecting part is raised in the axial direction from the rotor surface. The collecting part is open towards the axis of rotation in order to collect the coolant. The collecting part is a part of the guide plate that is arranged closest to the axis of rotation in the radial direction. In particular, the collecting part is further away from the axis of rotation in the radial direction than the coolant outlet, since the coolant is carried radially outwards by the centrifugal forces.

[0021] In particular, the catch part is designed to be tangentially completely circumferential in order to prevent the coolant from flowing past the outside of the catch part instead of between the catch part and the rotor surface.

[0022] In particular, the catching part is funnel-shaped and / or truncated cone-shaped. This means, in particular, that the catching part protrudes from the rotor surface in the longitudinal section through the rotational axis. This shape is particularly suitable for catching the coolant and directing it to the rotor surface due to its wide opening angle. In particular, the opening angle relative to the rotor surface is between 10° and 60°.

[0023] In one embodiment, the guide part has a dam part. The dam part does not contact the rotor surface. In particular, the gap height between the dam part and the rotor surface is 0.1 mm to 1 mm. The dam part is arranged radially between the catch part and the zero-gap part.

[0024] The dam serves to retain the coolant collected by the catcher. This increases the contact time between the coolant and the rotor surface, resulting in improved heat transfer for rotor cooling.

[0025] A possible design of the guide vane, referred to as a full variant, comprises the following sections radially from the rotational axis to the edge of the rotor: a catch section, a retention area, a zero-gap area, and optionally an assembly centering device. The assembly centering device can be attached to a lateral surface of the rotor. It can be implemented over the entire circumference or only partially, in particular at at least three locations, around the circumference.

[0026] For example, the radial extent of the individual sections varies depending on the rotor topology and cooling requirements. Depending on the design, not all sections necessarily need to be present. In one embodiment, the guide section has beads in the zero-gap section. The beads extend axially away from the rotor surface. The beads extend radially from the dam section partially, in particular only partially, i.e., not completely, through the zero-gap section.

[0027] The fact that the beads run radially from the accumulation area partially through the zero-gap section means that the beads do not extend radially to the outer edge of the zero-gap section. The beads serve to improve a tangentially even coolant distribution on the rotor surface. In the zero-gap section, unforeseeable uneven gap heights can occur due to unevenness in the guide vane and the rotor surface. This can lead to an uneven distribution of the coolant in the zero-gap section. In particular, the beads are distributed evenly tangentially on the rotor surface, particularly in a star shape. The beads can accumulate the coolant and then release it evenly tangentially. This can ensure even cooling of the rotor surface.

[0028] The guide section has support studs in an area of ​​the dam section. The support studs extend axially toward the rotor surface. The support studs contact the rotor surface.

[0029] In particular, the support studs border the dam. These support studs ensure a minimum clearance between the dam and the rotor surface.

[0030] This gives the rotor arrangement more stability.

[0031] In particular, the guide plate is welded to the rotor. In particular, the guide plate is welded, in particular exclusively, to the support studs and / or the beads on the rotor. In particular, the guide plate is fixed to the rotor surface via spot welds, for example, in the zero-gap section and at the indentations in the dam section. In particular, the zero-gap section can be designed as a flat cone in its uninstalled state in order to achieve a defined contact pressure against the rotor surface after fixation.

[0032] Another aspect of the invention relates to an electric machine with a rotor assembly. The rotor assembly is designed to drive a vehicle as part of an electric drive train. In one embodiment, the electric machine is designed as an axial flux machine.

[0033] In particular, the rotor arrangement is a rotor arrangement for an axial flux machine.

[0034] In an axial flux machine, the electrical machine has an axial design, for example by sandwiching a stator disk between two rotor disks. In particular, the stator disk is arranged on only one rotor disk. In an axial flux machine, the magnetic flux flows parallel to the rotor's axis of rotation. Therefore, the heat generated in an axial flux machine on the rotor surface that is perpendicular to the axis of rotation is greater than in a radial flux machine. In a radial flux machine, more heat is generated on a lateral surface of the rotor. The rotor arrangement according to the invention is therefore 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 in particular there are exactly two rotor surfaces, each located on a rotor disk.

[0035] In particular, the axial flux machine is a drive torque-providing component of an electric drive train, for example of a motor vehicle.

[0036] In particular, the rotor arrangement according to the invention also makes it possible to cool a radial flux machine.

[0037] A further aspect of the invention relates to a method for cooling a rotor of an electrical machine, comprising the following steps:

[0038] - spraying a coolant onto a rotor surface of the rotor through a spray device having a coolant outlet;

[0039] - capturing the sprayed coolant by a baffle attached to the rotor; and

[0040] - Guide the captured coolant on the rotor surface through the baffle.

[0041] In particular, the coolant is sprayed from a fixed housing part onto the rotor surface in order to cool the rotor.

[0042] Further embodiments of the method according to the invention follow directly from the various embodiments of the rotor arrangement according to the invention and of the electrical machine according to the invention, and vice versa. In particular, individual features and corresponding explanations as well as advantages relating to the various embodiments of the rotor arrangement according to the invention and of the electrical machine according to the invention can be transferred analogously to corresponding embodiments of the method according to the invention. In particular, the rotor arrangement according to the invention and the electrical machine according to the invention are designed to carry out a method according to the invention. In particular, the rotor arrangement according to the invention and the electrical machine according to the invention carry out the method according to the invention.

[0043] Further advantages, features, and details of the invention will become apparent from the following description of preferred embodiments and from the drawings. The features and combinations of features mentioned above in the description, as well as 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 respective specified combinations, but also in other combinations or on their own, without departing from the scope of the invention.

[0044] Showing:

[0045] Fig. 1 is a schematic longitudinal sectional view of an embodiment of a rotor arrangement according to the invention;

[0046] Fig. 2 is a schematic longitudinal sectional view of an embodiment of an axial flow machine with a rotor arrangement according to the invention;

[0047] Fig. 3 is a schematic longitudinal sectional view of a further embodiment of a rotor arrangement according to the invention;

[0048] Fig. 4 is a schematic longitudinal sectional view of a further embodiment of a rotor arrangement according to the invention;

[0049] Fig. 5 is a schematic longitudinal sectional view of a further embodiment of a rotor arrangement according to the invention; Fig. 6 is a schematic plan view of an embodiment of a rotor arrangement according to the invention

[0050] Fig. 1 shows a schematic longitudinal sectional view of an embodiment of a rotor arrangement 1 according to the invention. The rotor arrangement 1 has a rotor 3, a spray device 7 for spraying a coolant 10, and a guide plate 11, so that active rotor cooling can be referred to in particular. The rotor 3 has a rotor surface 4, which can also be referred to as the rotor rear side, and a rotor outer surface 6. The rotor surface 4 is arranged perpendicular to a rotational axis 5a, and the rotor outer surface 6 is arranged parallel to the rotational axis 5a. The spray device 7 has a coolant outlet 8. From this outlet, a coolant 10, in particular a cooling oil, can be sprayed onto the rotor surface 4 in the direction of the arrow P1.

[0051] The guide plate 11 has, in particular, a catch part 12 and a guide part 13. The guide part 13 has a zero-gap part 14. The gap height of the zero-gap part 14 relative to the rotor surface 4 is determined by the surface roughness of the rotor surface 4 and the guide plate 11 in the zero-gap part 14. In particular, the zero-gap part 14 can also be referred to as a zero-gap region and adjoins the catch part 12 radially outwards as a surface-parallel ring adjacent to the rotor surface 4, in particular to the catch part 12. In the exemplary embodiment shown in Fig. 1, the zero-gap part 14 forms the entire guide part 13. The catch part 12 and the guide part 13 can completely cover the rotor surface 4 tangentially. An opening remains radially around the rotational axis 5a, into which opening the coolant 10 can be sprayed. On the rotor surface 6, an assembly centering 16 can be arranged adjacent to the guide part 13.The assembly centering 16 can be attached to the rotor surface 6 all the way around or only partially, in particular at three or at least three points.

[0052] During operation of the rotor 3, the spray device 7 sprays the coolant 10 through the coolant outlet 8 in the direction of the arrow P1 onto the rotor surface 4. Due to the shape, in particular the truncated cone shape, of the capture part 12, the coolant 10, in particular the majority of the coolant 10, in particular more than 80% of the coolant 10, is captured and brought onto the rotor surface 4. An opening angle of the capture part 12 to the rotor surface 4 is less than 90°, in particular between 10° and 60°. The microscopic gap height of the zero-gap part 14 is sufficient such that the coolant 10 is guided radially outwards through the zero-gap part 14 by centrifugal forces that prevail during operation. At an outer edge of the rotor surface 4 or at the rotor shell surface 6, the coolant is thrown radially outwards, in particular over the entire circumference of the rotor 3.

[0053] Fig. 2 shows a schematic longitudinal sectional view of an embodiment of an axial flux machine 2 as an example of an electric machine with a rotor arrangement 1 according to the invention. In particular, the axial flux machine 2 can serve as the drive machine of an electric drive train for driving a predominantly or exclusively electrically powered vehicle. The axial flux machine 2 has, in particular, two rotor disks and a stator disk 17. The rotor surfaces 4 are arranged perpendicular to the axis of rotation 5a and a side of the rotor disks facing away from the stator disk 17. A bearing plate 19 is arranged on a rotor bearing 18. The structure and function of the guide plate 11 correspond, for example, to the structure and function of the guide plate 11 in Fig. 1.

[0054] The coolant 10 can be pumped through a coolant supply 9 to the coolant outlet 8. In this exemplary embodiment, the coolant supply 9 is guided through the bearing shield 19. In another exemplary embodiment, the coolant supply can also be guided within a rotor shaft 5b of the rotor 3. For example, the coolant outlet 8, which can also be referred to as a nozzle, is angled, in particular at an angle radially outward, to the catch part 12. The rotor shaft 5b runs along the axis of rotation 5a. The coolant 10 is carried radially outward by the guide part 13 by centrifugal forces and is thrown radially outward towards the bearing shield 19 at the outer edge of the rotor surface 4. The coolant 10 can flow downward along the bearing shield 19 according to gravity. The coolant 10 is fed to a cooling circuit through a drain hole 20.In particular, the coolant 10 is collected in an oil pan and cooled via an oil-water heat exchanger and then fed back to the rotor assembly via pumps.

[0055] The figures Fig. 1 and Fig. 3 up to and including Fig. 5 always show the same sectional perspective with different embodiments of the guide plate 11 arranged on the rotor 3. These sectional perspectives can be a partial view of Fig. 2, as indicated in Fig. 3 by the additional representation of the stator disk 17.

[0056] Fig. 3 shows a further embodiment of a rotor arrangement 1 according to the invention. In this embodiment, the guide part 13 has a damming part 15 in addition to the zero-gap part 14. The damming part 15 can be arranged between the collecting part 12, which can also be referred to as a collecting funnel, and the zero-gap part 14. In particular, a ring adjoins the collecting part 12 radially outwardly, which is approximately surface-parallel to the rotor 3 and spaced from the rotor surface. This section of the guide plate 11, referred to as the damming part 15, serves to damming the coolant 10 absorbed by the collecting part 12. The gap height between the rotor surface 4 and the guide plate 11 is in particular 0.1 mm to 1 mm.

[0057] Fig. 4 shows a further embodiment of a rotor assembly 1 according to the invention. In this embodiment, there is no assembly centering 16, and the guide part 13 has only the zero-gap part 14 and no dam part 15. The guide part 13 is short in this embodiment and ends before the outer edge of the rotor surface 4, in particular, viewed radially, within the inner two-thirds, in particular within the inner half, of the rotor surface 4. In particular, this embodiment has beads 21. The beads 21 are open radially outward. This allows the rotor surface 4 to be wetted with the coolant 10 as a wall film after exiting the bead.

[0058] Fig. 5 shows a further embodiment of a rotor arrangement 1 according to the invention. In this embodiment, the guide plate 11 is shaped as described with reference to Fig. 3. In addition, this embodiment also has the beads 21 and support studs 22. In particular, the radial beads 21 are embossed into the guide plate 11 in the zero-gap part 14, which extend from the dam part 15 over at least a part of the zero-gap part 14. The beads 21 serve to ensure a uniform distribution of the coolant 10. The support studs 22 can be provided on the dam part 15 to ensure the gap height between the guide plate 11 and the dam part

[0059] 15 as impressions. In particular, the guide plate 11 is welded to the beads 21 and the support studs 22 on the rotor surface.

[0060] Fig. 6 shows an embodiment of a rotor assembly 1 according to the invention in a plan view of the rotational axis 5a. In this illustration, the rotational axis 5a is oriented in the z-direction. In this embodiment, the guide plate 11 is configured as shown in Fig. 5. The dashed arrow P2 points in a tangential circumferential direction. The x-axis and the y-axis point in radial directions, and the z-axis points in an axial direction. List of Reference Symbols

[0061] 1 Rotor arrangement

[0062] 2 axial flux machine

[0063] 3 Rotor

[0064] 4 Rotor area

[0065] 5a axis of rotation

[0066] 5b Rotor shaft

[0067] 6 Rotor surface

[0068] 7 Spray device

[0069] 8 Coolant outlet

[0070] 9 Coolant supply

[0071] 10 Coolant

[0072] 11 Baffle

[0073] 12 Catch part

[0074] 13 Guide part

[0075] 14 Zero gap part

[0076] 15 storage section

[0077] 16 Assembly centering

[0078] 17 Stator disc

[0079] 18 rotor bearings

[0080] 19 Bearing shield

[0081] 20 drain hole

[0082] 21 beads

[0083] 22 support studs

[0084] P1 Arrow 1

[0085] P2 Arrow 2

Claims

Patent claims 1. A rotor arrangement (1) for an electrical machine, comprising a rotor (3) and a spray device (7) for spraying a coolant (10) with a coolant outlet (8) which is arranged with respect to the rotor (3) in such a way that a rotor surface (4) can be sprayed with the coolant (10), and a guide plate (11) which is fastened to the rotor (3), wherein the guide plate (11) is shaped and arranged on the rotor (3) in such a way that the sprayed coolant (10) of the spray device (7) can be captured by the guide plate (11) and guided on the rotor surface (4), characterized in that the guide plate (11) has a guide part (13) which has a zero-gap part (14) which completely covers the rotor surface (4) in the radial direction, at least in regions and tangentially circumferentially (P2), and rests against the rotor surface (4).

2. Rotor arrangement (1) according to claim 1, wherein the guide plate (11) is designed to guide the coolant (10) radially on the rotor surface (4).

3. Rotor arrangement (1) according to one of the preceding claims, wherein the rotor surface (4) is arranged perpendicular to a rotational axis (5a) of the rotor (3).

4. Rotor arrangement (1) according to claim 2 or 3, wherein the guide plate (11) has a catching part (12), wherein the catching part (12): - is raised in the axial direction from the rotor surface (4), - is open towards the axis of rotation (5a), - a part of the guide plate (11) arranged closest to the axis of rotation (5a) in the radial direction, and - is further away from the axis of rotation (5a) in the radial direction than the coolant outlet (8).

5. Rotor arrangement (1) according to claim 4, wherein the guide part (13) has a dam part (15) which does not bear against the rotor surface (4) and is arranged radially between the catch part (12) and the zero gap part (14).

6. Rotor arrangement (1) according to claim 5, wherein the guide part (13) has, in a region of the dam part (15), support knobs (22) which extend axially in the direction of the rotor surface (4) and contact the rotor surface (4).

7. Rotor arrangement (1) according to one of the preceding claims, wherein the guide part (13) in the zero gap part (14) has beads (21) which extend axially away from the rotor surface (4) and run at least partially through the zero gap part (14) in the radial direction.

8. Rotor arrangement (1) according to one of the preceding claims, wherein the guide plate (11) has an assembly centering part (16) which extends at least partially over the circumference of the rotor shell surface (6), in particular in individual elevations.

9. Rotor arrangement (1) according to one of the preceding claims, wherein the guide plate (11) is fixed to the rotor (3) via welding points in the zero gap region (14) and / or in the support knobs (22).

10. Rotor arrangement (1) according to one of the preceding claims, wherein the guide plate (11) in the unassembled state has a shape which differs from the assembled state in that the zero gap region (14) is at least partially not flat but frustoconical in shape and thus an axial prestress of the guide plate (11) on the rotor (3) is provided.

11. An electric machine having a rotor arrangement (1) according to any one of the preceding claims, which is designed to drive a vehicle as part of an electric drive train.

12. Electrical machine according to claim 11, which is designed as an axial flux machine (2).

3. A method for cooling a rotor (3) of an electrical machine with a rotor arrangement (1) according to one of claims 1 to 10, comprising the following steps: - spraying a coolant (10) onto a rotor surface (4) of the rotor (3) by means of a spray device (7) having a coolant outlet (8); - capturing the sprayed coolant (10) by a guide plate (11) which is attached to the rotor (3); and - Guiding the captured coolant (10) on the rotor surface (4) through the guide plate (11).

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