Electric machine with rotor cooling

Abstract

An electrical machine (1) comprising a machine housing (2), a stator (3) arranged in the machine housing (2), and a rotor (4) rotatable about a rotor rotational axis (8) relative to the stator (3) and arranged on a rotor shaft (5), wherein at least one rotor coolant channel (9) is formed in the rotor (4) for cooling, which is fluidically connected on the one hand to a coolant inlet of the electrical machine (1) and on the other hand to a rotor ring channel (24) which overlaps, in a coolant-transferring manner, a collecting ring channel (25) formed in the machine housing (2) and fluidically connected to a coolant outlet of the electrical machine (1), wherein the rotor (4) has two rotor disks (11, 12) and a rotor lamination stack (10) arranged between the rotor disks (11, 12), wherein the at least one rotor coolant channel (9) is formed in the rotor lamination stack (10), characterized in thatthat the rotor ring channel (24) is formed in a side of the second rotor disc (12) facing away from the at least one rotor coolant channel (9).

Description

[0001] The invention relates to an electrical machine, having a machine housing, a stator arranged in the machine housing and a rotor which is rotatable about a rotor rotation axis with respect to the stator and is arranged on a rotor shaft, wherein at least one rotor coolant channel is formed in the rotor for cooling, which is fluidically connected on the one hand to a coolant inlet of the electrical machine and on the other hand to a rotor ring channel which is in coolant-transferring overlap with a collecting ring channel formed in the machine housing and fluidically connected to a coolant outlet of the electrical machine, wherein the rotor has two rotor disks and a rotor laminated core arranged between the rotor disks, wherein the at least one rotor coolant channel is formed in the rotor laminated core.

[0002] From the prior art, for example, the document EP 3 028 888 A1 is known. This describes a motor assembly with an integrated cooling system, comprising: a stator mounted in a motor housing; a rotor shaft, wherein the rotor shaft extends between a first end cap and a second end cap of the motor housing; a rotor mounted on the rotor shaft, wherein the rotor shaft has a hollow region; a coolant pump for injecting a coolant into the motor assembly; a coolant reservoir in fluid communication with the coolant pump; a first coolant channel, wherein the first coolant channel forms a fluid coupling between the coolant pump and the hollow region of the rotor shaft, wherein the coolant flowing through the first coolant channel is injected into the hollow region of the rotor by means of the coolant pump;a second coolant channel, the second coolant channel forming a fluid coupling of a region within the motor housing with the coolant reservoir, and wherein the coolant within the region of the motor housing flows into the coolant reservoir via the second coolant channel; and a plurality of distribution through-holes integrated into the rotor shaft, each of the distribution through-holes forming a fluid coupling of the hollow region of the rotor shaft with the region within the motor housing, wherein the coolant flowing from the hollow region to the region within the motor housing is in direct contact with the stator and the rotor before flowing through the second coolant channel into the coolant reservoir.

[0003] The generic document DE 10 2011 084 083 A1 relates to a rotor rotor for an electric motor, comprising an axially arranged supply channel for supplying a coolant, at least one cooling channel which is radially spaced from a rotational axis of the rotor and is connected to the supply channel via a radial connection, a coolant outlet for discharging the supplied coolant, wherein the coolant outlet is radially spaced from the supply channel.

[0004] Furthermore, the prior art documents JP 2009- 232 535 A, CN 2 14 314 785 U, CN 1 13 364 184 A, CN 1 10 601 446 A and JP 2012- 223 075 A are known.

[0005] The object of the invention is to propose an electrical machine which has advantages over known electrical machines, in particular enabling more efficient cooling.

[0006] This is achieved according to the invention with an electric machine having the features of claim 1. It is provided that the rotor ring channel is formed in a side of the second rotor disk facing away from the at least one rotor coolant channel.

[0007] Basically, it is provided that at least one rotor coolant channel is formed in the rotor for cooling, which is fluidically connected on the one hand to a coolant inlet of the electric machine and on the other hand to a rotor ring channel, which overlaps with a collecting ring channel formed in the machine housing and fluidically connected to a coolant outlet of the electric machine in a coolant-transferring manner.

[0008] Advantageous embodiments with expedient further developments of the invention are specified in the dependent claims.

[0009] The electrical machine serves either to convert electrical energy into kinetic energy or, conversely, to convert kinetic energy into electrical energy. In the former case, the electrical machine is operated as a motor, in the latter case as a generator. The following only addresses the use of the electrical machine as a motor. However, the statements always apply analogously to its use as a generator. The electrical machine is particularly preferably in the form of a synchronous machine, in particular as a separately excited synchronous machine. However, other designs of the electrical machine, in particular as an asynchronous machine, for example as a squirrel-cage or cage rotor, are also possible.

[0010] The electric machine basically consists of the machine housing, the stator, and the rotor. Both the stator and the rotor are located within the machine housing. The stator is stationary relative to the machine housing; in particular, it is rigidly attached to the machine housing. The rotor is mounted so that it can rotate about the rotor axis relative to the stator and thus also relative to the machine housing. For this purpose, it is mounted on the rotor shaft, which is rotatably mounted within the machine housing.

[0011] Preferably, the rotor shaft is rotatably mounted on the machine housing. For this purpose, at least one bearing engages on the rotor shaft on one side and on the machine housing on the other. The bearing is preferably designed as a rolling bearing, although a plain bearing design is also possible. Preferably, the rotor shaft is rotatably mounted by means of several bearings, in particular on the machine housing. The several bearings are further preferably arranged on opposite sides of the rotor in order to achieve a reliable and tilt-stable rotary mounting of the rotor shaft.

[0012] During operation of the electrical machine, heat is generated, particularly in the rotor. To ensure a long service life of the electrical machine, it is necessary to dissipate the heat from the electrical machine or at least distribute it within the electrical machine so that the heat is transported from warmer areas of the electrical machine to cooler areas of the electrical machine. A coolant is used for this purpose, in particular a liquid coolant. Preferably, the electrical machine is designed and / or the coolant is selected such that the coolant is always liquid when the electrical machine is operated as intended, i.e. the coolant does not evaporate.

[0013] The coolant is circulated at least temporarily within the electric machine, absorbing heat from the warmer areas, particularly the rotor, and transporting it to the cooler areas. For example, the heat is transferred from the rotor to the machine housing, from where it is dissipated into the environment outside the electric machine. The electric machine is preferably a closed system in which the coolant is merely circulated to distribute the heat. The final dissipation of heat from the electric machine to the environment outside can occur via the machine housing.

[0014] Alternatively, it is of course possible for the coolant to be supplied to the electrical machine from the external environment, flow through the electrical machine, absorb heat, and then be released back into the external environment. For example, the coolant is circulated between the electrical machine and a heat exchanger located away from the electrical machine, with the heat exchanger being designed and configured to release heat from the coolant toward the external environment.

[0015] To cool the rotor, at least one rotor coolant channel is formed therein. The rotor coolant channel extends at least partially, preferably largely or predominantly, through the rotor in the axial direction with respect to the rotor rotation axis. Relative to a total extension of the rotor in the axial direction, the rotor coolant channel extends through the rotor in the same direction over at least 70%, at least 80%, or at least 90%. This ensures effective cooling of the rotor. Viewed in cross-section with respect to the rotor rotation axis, the rotor coolant channel is preferably arranged adjacent to slots in the rotor in which, for example, the winding or winding wires of the winding are arranged.

[0016] Of course, the rotor does not have to have a winding, but can also be designed without one. In this case, the electric machine is preferably designed as an asynchronous machine or a permanently excited synchronous machine. In particular, the rotor coolant channel is arranged at a distance from the slots, so that the rotor coolant channel is sealed along its entire length, meaning the coolant flowing through it cannot escape radially. This excludes unavoidable leaks, which almost inevitably occur during the technical implementation of the electric machine.

[0017] Preferably, a plurality of coolant channels are formed in the rotor, wherein the at least one rotor coolant channel forms a component of this plurality of coolant channels. The coolant channels are arranged spaced apart from one another; in particular, they are distributed uniformly within the rotor in the circumferential direction relative to the rotor rotation axis. The coolant inlet and the coolant outlet of the electric machine are fluidically connected to one another via each of the coolant channels. Where reference is made to the rotor coolant channel or the at least one rotor coolant channel within this description, the explanations are analogous and, moreover, always transferable to each of the plurality of coolant channels.

[0018] The rotor coolant channel is fluidically connected to the coolant inlet of the electric machine on the one hand and to the coolant outlet of the electric machine on the other. The rotor coolant channel is connected to the coolant outlet via the rotor ring channel and the collecting ring channel. Preferably, the rotor coolant channel opens directly into the rotor ring channel, but it can also be provided that there is a connecting channel between the rotor coolant channel and the rotor ring channel. The rotor ring channel is designed in the rotor of the electric machine and surrounds the rotor axis of rotation in a ring-like manner, i.e. at least partially in the circumferential direction. Preferably, the rotor ring channel completely and continuously surrounds the rotor axis of rotation in the circumferential direction. If there are multiple coolant channels, each of the coolant channels is fluidically connected to the rotor ring channel.In particular, each of the coolant channels opens directly into the rotor ring channel or is connected to the rotor ring channel via a respective connecting channel. The multiple coolant channels are fluidically connected to one another via the rotor ring channel.

[0019] The collecting ring channel, on the other hand, is formed in the machine housing. It is fluidically connected to the coolant outlet of the electric machine. The rotor ring channel and the collecting ring channel are arranged in such a way that they are in direct fluid communication with one another. For this purpose, they overlap with one another at least in some areas. The electric machine is designed such that the rotor ring channel and the collecting ring channel lie opposite one another and together form a rotor coolant channel chamber. Viewed in the radial direction, the rotor ring channel is delimited on opposite sides by walls formed by the rotor. The collecting ring channel, on the other hand, viewed in the radial direction, is delimited on opposite sides by walls formed by the machine housing.The walls defining the rotor ring channel and the walls defining the collecting ring channel are in contact with each other in such a way that the rotor ring channel and the collecting ring channel are fluidically directly connected to each other, namely tightly.

[0020] In other words, the rotor ring channel, viewed in longitudinal section relative to the rotor rotation axis, is open-edged in the rotor in the direction of the collecting ring channel and has an orifice facing the collecting ring channel. The collecting ring channel, however—again viewed in longitudinal section—is open-edged in the direction of the rotor ring channel and has an orifice facing the rotor ring channel. The orifice of the rotor ring channel and the orifice of the collecting ring channel are at least partially overlapping, so that coolant present in the rotor ring channel can flow into the collecting ring channel and vice versa.The electric machine is fundamentally designed in such a way that the flow connection between the coolant inlet and the coolant outlet via the at least one rotor coolant channel, the rotor ring channel and the collecting ring channel is sealed within the scope of technical possibilities, so that no coolant or at most a small amount of coolant escapes along the flow connection as part of an unavoidable leak and reaches other areas of the electric machine.

[0021] The described design of the electric machine enables particularly efficient cooling of the rotor with simultaneous low energy consumption. Due to the fluidic connection of the rotor coolant channel to the coolant outlet via the rotor ring channel and the collecting ring channel, there is no need to deflect the coolant inwards in a radial direction relative to the rotor rotation axis within the rotor. Accordingly, it is not necessary to subject the coolant to a pressure sufficient to guide the coolant radially inwards against the centrifugal force acting on it during operation of the electric machine. Instead, it can be provided that the coolant is only guided radially inwards via the rotor ring channel and the collecting ring channel after it has flowed over from the rotor into the machine housing.This can be achieved with a comparatively low coolant pressure and correspondingly low energy consumption.

[0022] The invention provides that the rotor has two rotor disks and a rotor core arranged between the rotor disks, wherein the at least one rotor coolant channel is formed in the rotor core. The rotor is thus constructed in several parts and comprises the rotor disks and the rotor core. The rotor disks are, for example, solid and made of a single material. The rotor core, in contrast, is composed of several rotor cores arranged side by side. The rotor cores are preferably electrically insulated from one another to prevent or at least reduce eddy currents in the rotor.

[0023] The rotor lamination stack has a greater extension in the axial direction relative to the rotor rotation axis than the rotor disks. Preferably, the extension of the rotor lamination stack in the axial direction is greater by a factor of at least 10, at least 15, or at least 20 than the extension of one of the rotor disks in the same direction. The rotor disks themselves preferably have the same extension in the axial direction.

[0024] The rotor disks accommodate the rotor lamination stack between them; in particular, they rest against the rotor lamination stack on opposite sides. The rotor disks can be constructed from the same material as the rotor lamination stack, i.e., they can be made of the same material. However, a different material is preferably used for them than for the rotor lamination stack. While the lamination stack is made of metal, or at least largely of metal, the rotor disks are made of plastic, for example. Alternatively, the rotor disks can of course also be made of metal, for example, of a different metal from the rotor lamination stack.

[0025] The rotor coolant channel is formed solely in the rotor core, not in the rotor disks. However, it can be fluidically connected to the coolant inlet and / or outlet via the rotor disks. For this purpose, corresponding channels are provided in the rotor disks. The rotor coolant channel preferably extends completely through the rotor core in the axial direction relative to the rotor rotation axis, in particular forming a respective opening. The rotor disks are arranged such that they overlap the opening.In particular, the channels formed in the rotor disks are in fluid communication with the orifices, so that they continue the rotor coolant channel on both sides of the rotor core. Such a design enables a compact design of the electric machine and a simple fluid connection of the rotor coolant channel to the coolant inlet and the coolant outlet.

[0026] A further development of the invention provides that the at least one rotor coolant channel runs obliquely in longitudinal section with respect to the rotor axis of rotation, so that a distance of the at least one rotor coolant channel from the rotor axis of rotation changes over the course of the at least one rotor coolant channel. Due to the oblique arrangement of the rotor coolant channel, a conveying effect on the coolant is achieved during operation of the electric machine. During operation, the coolant is forced outwards in the radial direction by the centrifugal force acting on it. Since the distance of the rotor coolant channel from the rotor axis of rotation changes over its course, the coolant is forced axially in the direction which is further outwards in the radial direction. This further reduces the pressure required to circulate the coolant.

[0027] It can be provided that a longitudinal central axis of the rotor coolant channel is angled with respect to the rotor axis of rotation, i.e. that it encloses an angle with it which is greater than 0° and less than 180°. Preferably, the angle is at least 5° and at most 25°, at least 10° and at most 20°, or approximately or exactly 15°. However, it can also be provided that the longitudinal central axis of the rotor coolant channel is skew to the rotor axis of rotation. In this case, not only does the distance of the at least one rotor coolant channel from the rotor axis of rotation increase over its length in longitudinal section, but the rotor coolant channel is also inclined in the circumferential direction. Alternatively, an arrangement of the rotor coolant channel parallel to the rotor axis of rotation is of course also feasible. In any case, the rotor coolant channel preferably runs straight throughout and has a constant flow cross-section throughout.However, it can also be provided that the flow cross-section of the rotor coolant channel widens in the flow direction toward the coolant outlet. The described design of the electric machine enables particularly effective operation and efficient cooling.

[0028] A further development of the invention provides that a supply channel is formed in a first of the rotor disks, which is fluidically connected on the one hand to the coolant inlet and on the other hand to the at least one rotor coolant channel, and a discharge channel is formed in a second of the rotor disks, which is fluidically connected on the one hand to the at least one rotor coolant channel and on the other hand to the rotor ring channel. As already pointed out above, the rotor coolant channel is fluidically connected to the coolant inlet and the coolant outlet via the rotor disks. For this purpose, the supply channel is provided in the first rotor disk and the discharge channel is provided in the second rotor disk. The coolant inlet is fluidly connected to the rotor coolant channel via the supply channel, and the rotor coolant channel is fluidly connected to the coolant outlet via the discharge channel.

[0029] Both the rotor ring channel and the discharge channel are formed in the second rotor disk. The discharge channel opens into the rotor ring channel. The discharge channel has a smaller extension in the circumferential direction than the rotor ring channel. For example, the discharge channel has the same flow cross-section as the rotor coolant channel or, at most, a slightly larger flow cross-section than the rotor coolant channel. In the latter case, a flow cross-sectional area of ​​the discharge channel amounts to at most 150% of a flow cross-sectional area of ​​the rotor coolant channel. The rotor ring channel is preferably continuous and uninterrupted in the circumferential direction. If there are multiple coolant channels, a separate supply channel and a separate discharge channel are preferably formed in the rotor disks for each of the coolant channels.In other words, the first rotor disk contains the same number of supply channels as the coolant channels, and the second rotor disk contains the same number of discharge channels as the coolant channels. This enables effective coolant flow.

[0030] The invention provides that the rotor ring channel is formed in a side of the second rotor disk facing away from the at least one rotor coolant channel. As already described, the rotor ring channel overlaps with the collecting ring channel, such that a fluidic connection exists between them. Since the rotor ring channel is provided in the second rotor disk, it is particularly provided that the second rotor disk interacts sealingly with the machine housing. In other words, a side wall of the second rotor disk facing the machine housing and facing away from the rotor laminated core, in which side wall the rotor ring channel is open at the edge, interacts sealingly with a side wall of the machine housing facing the second rotor disk. This ensures a simple design of the electrical machine.In addition, if the second rotor disk is worn, it is possible to replace only the second rotor disk without having to replace the entire rotor, in particular the rotor lamination stack.

[0031] A further development of the invention provides that the rotor shaft is designed as a hollow shaft and has a fluid guide chamber which is fluidically connected on the one hand to the coolant inlet and on the other hand to the supply channel via an opening formed in a casing of the rotor shaft. The coolant is supplied to the rotor or the rotor coolant channel via the rotor shaft, more precisely via the fluid guide chamber. During operation of the electric machine, lubricant is supplied to the fluid guide chamber at least temporarily, which can escape through the opening and flow towards the rotor coolant channel. In other words, the fluid guide chamber is connected to the rotor coolant channel via the opening.

[0032] Specifically, the opening is connected to the supply channel of the first rotor disk, via which the rotor coolant channel is ultimately fluidically connected to the opening and thus to the fluid guide space. For this purpose, the first rotor disk overlaps the opening in the rotor shaft. The opening is made in the casing of the rotor surface or in a casing surface of the rotor shaft. It penetrates the casing completely in the radial direction, so that the opening opens into the fluid guide space on the one hand and penetrates the outside of the casing of the rotor shaft on the other, forming an opening. The opening is fluidically connected to the supply channel via this opening. Overall, a simple structure of the electric machine is thus realized.

[0033] A further development of the invention provides that the rotor ring channel and the collecting ring channel are arranged, viewed in the radial direction relative to the rotor rotation axis, between sealing elements of a labyrinth seal, which are formed alternately on the rotor and the machine housing and cooperate to establish a tight flow connection between the rotor ring channel and the collecting ring channel. A labyrinth seal is provided to achieve reliable sealing of the flow connection between the rotor ring channel and the collecting ring channel. The labyrinth seal has the sealing elements, with some of the sealing elements being located on the rotor, in particular on the second rotor disk, and others on the machine housing.

[0034] The sealing elements interact to form a seal, in particular, they engage one another to form a seal. For example, there may be several sealing elements on the rotor, between which a sealing element of the machine housing engages, and / or vice versa. Preferably, several of the sealing elements are located on the rotor and several of the sealing elements are located on the machine housing to achieve particularly reliable sealing. The labyrinth seal can significantly reduce coolant leakage, resulting in extremely efficient cooling of the electric machine or rotor.

[0035] A further development of the invention provides that the collecting ring channel is fluidically connected to the coolant outlet via a drain channel formed in the machine housing and / or a stator coolant channel formed in the stator. The drain channel preferably has smaller dimensions in the circumferential direction than the collecting ring channel. For example, the drain channel is in the form of a bore, thus having a round cross-section. The collecting ring channel, on the other hand, is preferably continuous and uninterrupted in the circumferential direction. The drain channel enables targeted removal of the coolant present in the collecting ring channel toward the coolant outlet.

[0036] In addition to or alternatively to the drain channel, there is the stator coolant channel. This is formed in the stator and serves to conduct coolant through it. Naturally, there are preferably several stator coolant channels. These are arranged at a distance from one another in the circumferential direction. In particular, they are evenly distributed in the circumferential direction. With the help of the stator coolant channel, the stator can also be cooled using the coolant, so that both heat from the rotor and heat from the stator is dissipated by the coolant. The coolant first flows through the rotor coolant channel and then enters the stator coolant channel. After flowing through the stator coolant channel, the coolant reaches the coolant outlet. In other words, the rotor coolant channel is fluidly connected to the coolant outlet via the stator coolant channel.In such a design of the electric machine, the drain channel is preferably fluidically located between the rotor coolant channel and the stator coolant channel, thus connecting them fluidically with each other.

[0037] A further development of the invention provides that the drain channel is fluidically connected via the coolant outlet to a coolant sump formed in the machine housing. The electric machine or the cooling system is thus a closed system. This means that the coolant is continuously and completely present within the electric machine, in particular in the machine housing. The coolant sump serves as a coolant reservoir, from which coolant is at least temporarily withdrawn and fed to the rotor coolant channel. After passing through the rotor coolant channel, the coolant exits it and reenters the coolant sump.

[0038] In one embodiment of the electric machine, the drain channel opens into the coolant sump via the coolant outlet. In another embodiment, the drain channel is only indirectly fluidically connected to the coolant sump, in particular via the stator coolant channel. In such a variant, the coolant outlet is preferably fluidically connected to one or more stator coolant channels via an annular chamber.

[0039] For example, the coolant sump is delimited by a heat-transferring wall of the machine housing, so that heat present in the coolant is dissipated via the wall toward the outside environment. Preferably, the wall is provided with surface-enlarging elements, such as cooling fins or the like, on its side facing the coolant sump and / or the outside environment in order to intensify heat transfer. Additionally or alternatively, a heat exchanger is present in the coolant sump, to which an additional coolant from the outside environment is supplied, at least temporarily. The coolant and the additional coolant are completely separated from one another in terms of flow. This enables particularly effective cooling of the electric machine.

[0040] A further development of the invention provides a coolant pump arranged in the machine housing, which is provided and configured to remove coolant from the coolant sump and supply the coolant to the at least one rotor coolant channel via the coolant inlet. The coolant pump is thus operated at least temporarily to remove the coolant from the coolant sump and supply it to the rotor coolant channel. The coolant pump arranged in the machine housing, in turn, serves to implement the fully closed cooling system.

[0041] The features and feature combinations described in the description, in particular the features and feature combinations described in the following description of the figures and / or shown in the figures, can be used not only in the respective combination specified, but also in other combinations or on their own, without departing from the scope of the invention. Thus, embodiments are also considered to be encompassed by the invention that are not explicitly shown or explained in the description and / or the figures, but which follow from or can be derived from the explained embodiments.

[0042] The invention will be explained in more detail below with reference to the exemplary embodiments shown in the drawings, without limiting the invention. In the drawings: Fig. 1 a schematic longitudinal sectional view of an electrical machine in a first embodiment, and Fig. 2 a schematic longitudinal sectional view of the electrical machine in a second embodiment.

[0043] The Fig. 1 shows a schematic longitudinal sectional view of an electrical machine 1 in a first embodiment. The electrical machine 1 has a machine housing 2, in which both a stator 3 and a rotor 4 of the electrical machine 1 are arranged. The rotor 4 sits on a rotor shaft 5, which is rotatably mounted on the machine housing 2 by means of several bearings 6. The rotor shaft 5 protrudes from the machine housing 2 on one side, in particular only on one side. On this side, it has a drive flange 7, via which it can be connected to a device to be driven. Overall, the stator 3 is arranged stationary in the machine housing 2, while the rotor 4 sits non-rotatably on the rotor shaft 5 and, together with the latter, is rotatably mounted with respect to the stator 3 and the machine housing 2, namely about a rotor rotation axis 8.

[0044] To cool the rotor 4, at least one rotor coolant channel 9 is formed therein. More precisely, the rotor coolant channel 9 is located in a rotor laminated core 10 of the rotor 4 and extends completely through it in the axial direction. At the end of the rotor laminated core 10, the rotor 4 has a first rotor disk 11 and a second rotor disk 12, which accommodate the rotor laminated core 10 between them. A supply channel 13 is formed in the first rotor disk 11, and a discharge channel 14 is provided in the second rotor disk 12. Of course, several rotor coolant channels 9 are preferably formed in the rotor 4, in particular spaced from one another in the circumferential direction, preferably evenly distributed in the circumferential direction.

[0045] In the exemplary embodiment shown here, the supply channel 13 is composed of two sub-channels angled relative to one another. One of the sub-channels is directly aligned with the rotor coolant channel 9, thereby establishing fluid communication with it. The other of the sub-channels is connected to the rotor coolant channel 9 via the first-mentioned sub-channel. This sub-channel overlaps with an opening 15 formed in a casing 16 of the rotor shaft 5, which is designed as a hollow shaft. Via the opening 15, the supply channel 13 is fluidically connected to a fluid guide chamber 17 located in the rotor shaft 5, particularly centrally.

[0046] The fluid guide chamber 17 is delimited in the direction of the drive flange 7 by a partition wall 18. On the side opposite the drive flange 7, however, the rotor shaft 5 is open, so that a corresponding opening is present. A projection 19 of the machine housing 2 protrudes through this opening into the fluid guide chamber 17 in a sealing manner. A supply channel 20 opens into the fluid guide chamber 17 via the projection 19. On its side facing away from the fluid guide chamber 17, the supply channel 20 is fluidically connected to a coolant pump 21, in particular to a pressure side of the coolant pump 21.

[0047] During operation of the electric machine, the coolant pump 21 at least temporarily sucks in coolant from a coolant sump 22 formed in the machine housing 2, preferably via a filter 23. The coolant conveyed by the coolant pump 21 flows through the feed channel 20 into the fluid guide chamber 17 and from there via the opening 15 into the feed channel 13. From there, it in turn enters the rotor coolant channel 9 and passes through this into the discharge channel 14. The discharge channel 14 opens on its side facing away from the rotor coolant channel 9 into a rotor ring channel 24, which is preferably continuous and uninterrupted in the circumferential direction.

[0048] The rotor ring channel 24 overlaps with a collecting ring channel 25 formed in the machine housing 2, preferably also continuously and uninterrupted in the circumferential direction. The collecting ring channel 25 is in turn fluidly connected to the coolant sump 22 via a drain channel 26. The coolant supplied to the rotor coolant channel 9 enters the rotor ring channel 24, from there into the collecting ring channel 25, and is then fed back to the coolant sump 22 via the drain channel 26. The flow path of the lubricant is indicated by the arrow 27. A leakage channel 28 is formed in the machine housing 2 in the axial direction and overlaps with the second rotor disk 12. Through this leakage channel 28, lubricant which has escaped from the rotor ring channel 24 into the collecting ring channel 25 during its passage therefrom can again enter the lubricant sump 22, as indicated by the arrow 29.

[0049] It can be seen that the rotor coolant channel 9 is arranged obliquely in longitudinal section, so that its distance from the rotor axis of rotation 8 increases, in particular increases continuously, from the direction of the first rotor disk 11 towards the second rotor disk 12. The rotor coolant channel 9 is straight throughout and preferably has a constant flow cross-section throughout. During operation of the electric machine 1, the coolant is initially forced radially outwards due to the centrifugal force acting on it and, due to the oblique arrangement, in the axial direction towards the second rotor disk 12. This significantly reduces the pressure required by the coolant pump 21 to convey the coolant.

[0050] To seal a flow connection between the rotor ring channel 24 and the collecting ring channel 25, a labyrinth seal 30 is designed, which is composed of sealing elements 31 of the second rotor disk 12 and sealing elements 32 of the machine housing 2. The sealing elements 31 of the second rotor disk 12 originate from a base body of the second rotor disk 12 and each extend in the manner of a projection toward the machine housing 2, namely on the side facing away from the rotor coolant channel 9. The sealing elements 32 of the machine housing 2, on the other hand, project beyond a wall of the machine housing 2 and extend from there toward the second rotor disk 12.

[0051] The sealing elements 31 and 32 engage between one another, thus forming the labyrinth seal 30. Preferably, the sealing elements 31 and 32 are arranged on both sides of the rotor ring channel 24 and the collecting ring channel 25, viewed in the radial direction, so that the sealing effect is sufficiently realized in both directions. The sealing elements 31 and 32 are preferably in the form of annular projections that are continuous and uninterrupted in the circumferential direction. Preferably, viewed in the radial direction, there are at least two sealing elements 31 on each side of the rotor ring channel 24 and the collecting ring channel 25, between each of which a sealing element 32 of the machine housing 2 engages. In other words, there are at least four sealing elements 31 and two sealing elements 32, but preferably more.

[0052] The Fig.2 shows a schematic representation of the electric machine 1 in a second embodiment. This is similar to the first embodiment, so reference is made to the explanations relating to this embodiment, and only the differences will be discussed below. These lie in the fact that, in addition to the rotor cooling by means of the rotor coolant channel 9, stator cooling is realized. For this purpose, at least one stator coolant channel 33 is formed in the stator 3. Naturally, a plurality of stator coolant channels 33 are preferably realized in the stator 33, in particular spaced from one another in the circumferential direction, particularly preferably evenly distributed in the circumferential direction. The stator coolant channel 33 is arranged in terms of flow between the rotor coolant channel 9 and the coolant sump 22.The coolant is therefore first supplied to the rotor coolant channel 9 and flows through the rotor ring channel 24 and the collecting ring channel 25 into the stator coolant channel 33, in particular via the drain channel 26, which now does not open into the coolant sump 22, but is arranged fluidically between the collecting ring channel 25 and the stator coolant channel 33.

[0053] The stator coolant channel 33 is fluidically connected to the coolant sump 22 via an annular chamber 34 on its side facing away from the rotor coolant channel 9. Preferably, the leakage channel 28 also opens fluidically into the stator coolant channel 33, namely upstream of the stator coolant channel 33 or fluidically between the collecting ring channel 25 and the stator coolant channel 33. The lubricant, which has passed from the rotor ring channel 24 into the collecting ring channel 25 during its passage therefrom, thus enters the stator coolant channel 33 and flows through it toward the lubricant sump 22.

[0054] The rotor coolant channel 9 extends over the entire longitudinal extent of the rotor 4 or at least over a large part of the longitudinal extent, in particular over at least 80%, at least 90%, or at least 95% of the longitudinal extent. Similarly, the stator coolant channel 33 extends over the entire longitudinal extent of the stator 3 or at least over a large part of the longitudinal extent, in particular over at least 80%, at least 90%, or at least 95% of the longitudinal extent. Preferably, the rotor coolant channel 9 is connected to the fluid guide chamber 17 on a first side of the rotor 4, viewed in the axial direction.

[0055] The flow connection between the rotor coolant channel 9 and the stator coolant channel 33 is located on a second side of the rotor 4, opposite the first side. The connection of the stator coolant channel 33 to the coolant sump 22 is again provided on the first side. The coolant therefore initially flows through the rotor coolant channel 9 in a first axial direction and then through the stator coolant channel 33 in a second axial direction opposite the first axial direction.

[0056] The described configuration of the electric machine 1 enables particularly efficient cooling of the rotor 4 using at least one rotor coolant channel 9. This is achieved, on the one hand, by the oblique arrangement of the rotor coolant channel 9 and, on the other hand, by the fluidic connection of the rotor coolant channel 9 to the discharge channel 26 via the rotor ring channel 24 and the collecting ring channel 25. This prevents the coolant from being returned radially inward within the rotor 4. Accordingly, a comparatively low pressure is sufficient to pump the coolant, which pressure must be provided by the coolant pump 21. LIST OF REFERENCE SYMBOLS: 1 Electric machine 2 machine housings 3 Stator 4 Rotor 5 Rotor shaft 6 warehouses 7 Drive flange 8 Rotor rotation axis 9 Rotor coolant channel 10 rotor lamination stack 11 1. Rotor disc 12 2. Rotor disc 13 Feed channel 14 discharge channel 15 Breakthrough 16 coat 17 Fluid guide chamber 18 Partition wall 19 lead 20 flow channel 21 Coolant pump 22 Coolant sump 23 filters 24 rotor ring channel 25 Collecting ring channel 26 Drain channel 27 Arrow 28 Leakage channel 29 Arrow 30 Labyrinth seal 31 Sealing element 32 Sealing element 33 Stator coolant channel 34 Annular chamber

Claims

[1] An electrical machine (1) comprising a machine housing (2), a stator (3) arranged in the machine housing (2), and a rotor (4) which is rotatable about a rotor rotational axis (8) relative to the stator (3) and arranged on a rotor shaft (5), wherein at least one rotor coolant channel (9) is formed in the rotor (4) for cooling, which is fluidically connected on the one hand to a coolant inlet of the electrical machine (1) and on the other hand to a rotor ring channel (24) which overlaps, in a coolant-transferring manner, a collecting ring channel (25) formed in the machine housing (2) and fluidically connected to a coolant outlet of the electrical machine (1), wherein the rotor (4) has two rotor disks (11, 12) and a rotor lamination stack (10) arranged between the rotor disks (11, 12), wherein the at least one rotor coolant channel (9) is formed in the rotor lamination stack (10), characterized bythat the rotor ring channel (24) is formed in a side of the second rotor disk (12) facing away from the at least one rotor coolant channel (9). [2] Electrical machine according to claim 1, characterized by that the at least one rotor coolant channel (9) runs obliquely in longitudinal section with respect to the rotor rotation axis (8), so that a distance of the at least one rotor coolant channel (9) from the rotor rotation axis (8) changes over the course of the at least one rotor coolant channel (9). [3] Electrical machine according to one of the preceding claims, characterized byin that a supply channel (13) is formed in a first of the rotor disks (11, 12) which is fluidically connected on the one hand to the coolant inlet and on the other hand to the at least one rotor coolant channel (9), and in a second of the rotor disks (11, 12) a discharge channel (14) is formed which is fluidically connected on the one hand to the at least one rotor coolant channel (9) and on the other hand to the rotor ring channel (24). [4] Electrical machine according to claim 3, characterized by that the rotor shaft (5) is designed as a hollow shaft and has a fluid guide chamber (17) which is fluidically connected on the one hand to the coolant inlet and on the other hand to the feed channel (13) via an opening (15) formed in a casing (16) of the rotor shaft (5). [5] Electrical machine according to one of the preceding claims, characterized bythat the rotor ring channel (24) and the collecting ring channel (25) are arranged, viewed in the radial direction with respect to the rotor rotation axis (8), between sealing elements (31, 32) of a labyrinth seal (30) which are formed alternately on the rotor (4) and the machine housing (2) and cooperate to produce a tight flow connection between the rotor ring channel (24) and the collecting ring channel (25). [6] Electrical machine according to one of the preceding claims, characterized by that the collecting ring channel (25) is fluidically connected to the coolant outlet via a drain channel (26) formed in the machine housing (2) and / or a stator coolant channel (33) formed in the stator (3). [7] Electrical machine according to claim 6, characterized by that the drain channel (26) is fluidically connected via the coolant outlet to a coolant sump (22) formed in the machine housing (2). [8] Electrical machine according to one of the preceding claims, characterized by a coolant pump (21) arranged in the machine housing (2), which is provided and designed to remove coolant from the coolant sump (22) and to supply the coolant to the at least one rotor coolant channel (9) via the coolant inlet.

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