Electric machine

Abstract

Electrical machine (5) comprising a rotor (1) with a rotor core (2), a stator (20) with stator winding heads (22, 23) which are arranged on opposite end faces of the stator (20), and a housing (15, 17, 19) with a reservoir (25) for a cooling liquid, wherein - the rotor lamination stack (2) comprises a plurality of laminations (7) stacked in a stacking direction (L), - the sheets (7) each have at least one opening (8) which connects the end faces (S) of the respective sheet (7) to one another, and - the openings (8) of laminations (7) offset in the stacking direction (L) are arranged offset from one another in a circumferential direction (U) of the laminations (7) in such a way that at least one screw-spindle-shaped cooling channel (9) is formed which runs through the rotor lamination stack (2) and connects two opposite end faces of the rotor lamination stack (2), - the stator (20) and the housing (15, 17) form an outer cooling channel (K) between them, which runs along the stator (20) and the winding heads (22, 23) and connects two opposite end faces of the stator winding heads (22, 23), - the at least one screw-spindle-shaped cooling channel (9) is designed to form a suction side (35) on a first end face of the rotor (1) and a pressure side (34) on a second end face of the rotor (1) when the rotor (1) is rotating, so that an electrically insulating cooling liquid is sucked in from the reservoir (25) and conveyed through the at least one screw-spindle-shaped cooling channel (9) and the outer cooling channel (K).

Description

[0001] The invention relates to an electric machine, in particular for a drive train of a motor vehicle. Furthermore, the invention relates to a method for cooling such an electric machine.

[0002] Electric machines for a motor vehicle drive train, in particular for a hybrid drive, are known from the prior art. To cool the electric machines, it is common practice to use air or, if necessary, water to cool the electric machine and to direct this cooling medium through at least one area of the machine. Cooling of the electric machine can be limited because, for example, only certain areas, such as the stator core of the machine, can be cooled via a cooling heat exchanger through which cooling water flows, while such cooling is not possible in other areas of the machine.

[0003] Against this background, electrical machines cooled by an electrically insulating coolant, such as oil, have become established for this application. In addition to a heat exchanger through which oil flows, such oil-cooled electrical machines feature direct cooling, particularly of the winding heads or, to a limited extent, the rotor of the electrical machine. The electrically insulating coolant is thus openly directed over the winding heads within a housing of the electrical machine, enabling large-area heat dissipation within the electrical machine.

[0004] DE 10 2012 017 293 A1 discloses an electric motor for a motor vehicle drive train. To cool the stator, a cooling fluid is pumped via a pump through a cooling channel formed between the housing and the stator.

[0005] DE 10 2013 201 501 A1 describes an alternative cooling device for an electrical machine. The stator has a plurality of successively arranged metal sheets, through which a cooling channel is formed in the longitudinal direction of the stator. Starting from a starting reservoir, the cooling fluid is pumped into the stator's cooling channel via a pump.

[0006] DE 44 14 219 A1 describes a rotor for an electric machine with a plurality of laminations arranged one behind the other and offset from one another in the circumferential direction. A helical channel for conveying an air flow runs through the rotor.

[0007] DE 10 2012 022 452 A1 discloses an electrical machine in which a meander-shaped cooling channel is arranged on an outer side of the stator.

[0008] DE 38 85 477 T2 describes a lip structure for a stator in a dynamoelectric machine.

[0009] US 3 203 077 A describes a device for producing rotors.

[0010] Based on the prior art described above, the object of the invention is to provide a simple, space-saving and powerful electrical machine and a method of the type mentioned above, which enable improved cooling of the stator with its stator winding heads and the rotor.

[0011] The problem is solved by the subject matter of the independent patent claims. Advantageous embodiments are the subject matter of the subclaims, the following description, and the figures.

[0012] The electric machine, in particular a spray oil-cooled electric machine for a drive train of a motor vehicle, comprises a rotor with a rotor core, a stator with stator winding heads, which are arranged on opposite end faces of the stator, and a housing with a reservoir for a cooling liquid.

[0013] The rotor lamination stack comprises a plurality of laminations stacked in a stacking direction. The laminations each have at least one opening connecting the end faces of the respective lamination. The openings of the laminations offset in the stacking direction are arranged offset from one another in a circumferential direction of the laminations such that at least one screw-spindle-shaped cooling channel is formed, extending through the rotor lamination stack and connecting two opposite end faces of the rotor lamination stack.

[0014] The stator and the housing form an outer cooling channel between them, which runs along the stator and the winding heads and connects two opposite end faces of the stator winding heads. The at least one screw-shaped cooling channel is configured to form a suction side on a first end face of the rotor and a pressure side on a second end face of the rotor when the rotor or rotor core is rotating, so that an electrically insulating cooling liquid or, in general, a cooling medium is sucked from the reservoir and conveyed through the at least one screw-shaped cooling channel and the outer cooling channel.

[0015] The stacking direction of the laminations of the rotor core runs in particular in a longitudinal direction of the rotor. The laminations are each individual laminations, in particular congruent laminations with identical surfaces. Particularly preferably, all laminations of the rotor core are structurally identical, i.e., they are identical components. Furthermore, the laminations are preferably substantially annular, so that the rotor core has, in particular, a substantially hollow-cylindrical shape.

[0016] The laminations preferably each comprise a plurality of recesses arranged in a circular ring to form winding slots of the laminated core. The winding slots are preferably arranged equidistant from one another and along an outer circumference of the laminations. Each lamination of the rotor laminated core comprises at least one opening, which can be arranged between the outer circumference of the lamination, in particular between the winding slots arranged there, and a central bore in the lamination for mounting the lamination on a rotor shaft.

[0017] Furthermore, the openings of the laminations offset in the stacking direction are arranged offset from one another in a circumferential direction of the laminations, with congruent winding slots. This leads to a twisting of the openings in the assembled laminated core, which are provided on the laminations offset or arranged spirally relative to one another in the stacking direction. In other words, the openings of the laminations offset in the stacking direction are arranged twisted or rotated relative to one another in such a way that at least one screw-spindle-shaped cooling channel is formed in the assembly, with the design of the cooling channel being based on the principle of the Archimedes screw.

[0018] Through the at least one cooling channel of the rotor, in particular the electrically insulating cooling liquid provided for cooling the electric machine, for example an oil or an oil mist, can be sucked from the coolant reservoir and conveyed through the at least one cooling channel.

[0019] If the rotor lamination stack rotates at a sufficient speed during operation of the electric machine, at least one screw-shaped cooling channel within the rotor lamination stack also rotates and can pump the electrically insulating coolant through the cooling channel according to the principle of a screw pump. The outer contour of the cooling channel is determined by the shape or contour of the openings in the individual laminations. The possible flow rate can be influenced in particular by the speed of the rotor lamination stack, the inner and outer diameters and the pitch of the cooling channel, as well as by the friction of the coolant on the inner walls of the cooling channel. The screw-shaped course of the cooling channel provides a particularly large heat transfer surface, which enables improved heat dissipation and cooling.

[0020] It is preferably provided that the laminations each have a plurality of openings arranged on a circular ring of the laminations, which connect the end faces of the respective lamination to one another, and that the openings of laminations offset in the stacking direction are arranged offset from one another in a circumferential direction of the laminations in such a way that a plurality of screw-spindle-shaped cooling channels running through the rotor lamination stack are formed. A particularly large amount of electrically insulating coolant can be conducted through the rotor lamination stack through the plurality of cooling channels, thus enabling particularly high heat dissipation in the region of the rotor lamination stack. The openings can in particular be arranged equidistant from one another, whereby cooling channels running parallel to one another can be formed, which enable particularly uniform heat dissipation from the rotor lamination stack. Between adjacent openings, the lamination forms a spoke in each case.The resulting spoke design according to this embodiment enables high rotor stiffness and rotor strength and the transmission of high torques.

[0021] The outer cooling channel can be defined in the radial direction by an outer surface of the stator on the one hand and an inner wall of the housing opposite the surface on the other. In other words, the outer cooling channel can be formed by a gap between the housing, stator, and stator winding heads. In the axial direction, i.e., in the longitudinal direction of the stator, the outer cooling channel extends along the entire stator and the stator winding heads. Furthermore, the outer cooling channel can run spirally along the entire circumference of the stator.

[0022] When the electric machine is at a standstill, a sump can form, particularly at the bottom of the housing, an oil sump that serves as a reservoir for the coolant. In the following, the invention is described largely in connection with oil or an oil mist as the coolant, without being limited thereto.

[0023] When the electric machine is put into the operating state, a pressure side and a suction side are formed in the preferably closed housing of the electric machine upon rotation of the at least one screw spindle-shaped cooling channel of the rotor, preferably supported by an additional radial fan wheel.

[0024] The oil can be sucked in from the oil sump. In this case, oil can also be pumped into the upper area of the rotor and stator, whereby the oil can drip over the winding overhang and be pumped to the pressure side via the at least one helical spindle-shaped cooling channel of the rotor. Initially, oil and, after prolonged operation and a sufficiently high speed, predominantly oil mist can be sucked into the rotor via the winding overhangs of the stator, which are cooled as the oil or oil mist passes through, and can be pumped to the pressure side of the electrical machine via the at least one helical spindle-shaped cooling channel. From there, the oil or oil mist can pass through the pressure-side stator winding overhang over a large area in order to move to the suction side by means of the suction effect of the at least one helical spindle-shaped cooling channel. The oil or oil mist can also be sucked on the suction side.the oil mist flows around the stator winding head there over a large area, in order to then either be conveyed again through the at least one screw spindle-shaped cooling channel to the pressure side or to return to the oil sump.

[0025] The at least one screw-spindle-shaped cooling channel and the outer cooling channel can thus form an internal oil or oil mist cooling circuit of the electric machine, which can advantageously be a transmission-integrated or traction electric machine. The oil or oil mist can be pumped based on the rotor's pumping function according to the Archimedes screw principle. The screw-spindle design of the rotor offers the possibility of pumping highly viscous and air-foamed oils, such as gear oil.

[0026] The electric machine according to the invention can be realized in an extremely small and compact design while maintaining maximum continuous power consumption, since the stator winding heads, the stator, and the rotor are cooled by an electrically insulating coolant, such as oil or oil mist. The cooling principle includes the cooling of rotating and stationary components of the electric machine in a closed housing.

[0027] At sufficiently high speeds, the electrically insulating coolant transforms into a coolant mist. If oil is used as the electrically insulating coolant, this transforms into an oil mist or an aerosol made up of an oil-air mixture. The aerosol has the advantage that, on the one hand, shear stress on the components remains low, thus avoiding the friction losses that would occur when using oil. On the other hand, the aerosol has a much higher specific thermal conductivity than air, allowing for much better heat dissipation on the rotor side and via the stator winding overhangs. The aerosol or oil mist can also cool the stator and rotor over the largest possible surface area, so that the resulting waste heat can be dissipated from the electrical machine very efficiently.

[0028] The electric machine according to the invention, which can be constructed comparatively small with ideal heat dissipation and yet provide a high continuous electrical output or a correspondingly high continuous torque, is ideally suited for use in motor vehicles, particularly in electric or hybridized vehicle drivetrains, since high performance with minimal installation space is one of the core requirements here. The electric machine according to the invention therefore has its preferred application in an application environment in which it is used for drivetrains for motor vehicles, particularly as a motor, generator, and / or motor-generator in serial or parallel hybridized drivetrains as well as in purely electric drivetrains.The suitability of the cooling principle is also particularly advantageous in transmission-integrated electric machines (GEM), which support the combustion engine, and in traction electric machines (TEM), which can propel a motor vehicle on their own.

[0029] According to one embodiment, the outer cooling channel comprises spiral grooves which are formed by cutouts on the inner circumference of the housing or by cutouts on the outer circumference of the stator. The spiral grooves allow oil to be easily guided from the oil sump along these grooves to the end faces of the stator at the beginning, i.e. when the rotor starts to rotate. Above an imaginary horizontal center axis of the rotor, the oil can drip off after passing the stator winding heads and is sucked into the rotor by suction. At very high speeds, the proportion of bubbles in the oil increases. The rotor conveys the oil or an oil-air mixture to the pressure side and is cooled in the process. In other words, the stator, its stator winding heads and the housing also form screw-spindle-shaped channels for the purpose of creating an internal cooling circuit. This enables active oil or air circulation.Oil mist cooling of the rotor, stator and stator winding heads.

[0030] The stator can comprise a stator lamination stack with a plurality of laminations stacked in a stacking direction, wherein the individual laminations each have a plurality of recesses distributed along the outer circumference, and the recesses of laminations offset in the stacking direction are arranged offset from one another in a circumferential direction of the laminations such that the recesses of all laminations form the spiral-shaped grooves. This leads to a twisting of the recesses in the assembled stator lamination stack. In other words, the recesses of laminations offset in the stacking direction are arranged twisted or rotated relative to one another such that the helical-spindle-shaped grooves of the outer cooling channel are formed as a whole.

[0031] According to a further embodiment, the electric machine has a circulating cooling circuit with a pump and a heat exchanger for cooling the electrically insulating coolant, in particular oil. The pump can draw the electrically insulating coolant from the coolant reservoir, convey it through the heat exchanger, where it is cooled by a second cooling medium, for example, cooling water from a main cooling circuit, and then convey it back into the coolant reservoir.

[0032] Alternatively or additionally, it can advantageously be provided that additional cooling channels for cooling the electrically insulating coolant are arranged in a wall of the housing. For example, cooling water from a main cooling circuit can be conveyed within the additional cooling channels to absorb heat from the electrically insulating coolant, in particular oil. According to this alternative, a pump for conveying the electrically insulating coolant can be dispensed with.

[0033] In other words, the electrically insulating liquid, in particular oil, can be transported in a circulating cooling circuit to a heat exchanger by means of an oil pump, or can be recooled through cooling channels in, for example, a wall of the housing.

[0034] According to a further embodiment, the openings of the laminations of the rotor core, which are offset in the stacking direction, are arranged offset from one lamination to an immediately adjacent lamination in the circumferential direction of the laminations. This arrangement allows the openings to form a cooling channel with a particularly small pitch angle. As a result, a volume flow of coolant guided through the at least one cooling channel can flow past a particularly large surface area of the cooling channel, thereby absorbing a particularly large amount of heat from the rotor.

[0035] Alternatively, it can be provided that the openings of laminations of the rotor laminated core that are offset in the stacking direction are arranged offset from one partial laminated core to an immediately adjacent partial laminated core in a circumferential direction of the laminations. A partial laminated core comprises a plurality of laminations stacked on top of one another. Within the partial laminated cores, the laminations, which are in particular congruent, are aligned identically in the circumferential direction, i.e. the openings of laminations that are offset in the stacking direction are not offset from one another in the circumferential direction of the laminations within the partial laminated core. This arrangement allows cooling channels with a particularly large pitch angle to be formed through the openings, such that a volume flow of cooling medium conducted through the at least one cooling channel can pass through the cooling channel particularly quickly.

[0036] The openings of the rotor core laminations offset in the stacking direction can be offset from one another in the circumferential direction of the laminations by one slot pitch. A slot pitch is the circumferential distance or the angular distance between two adjacent winding slots. This unit of measurement for displacement or offset arrangement enables particularly simple and precise production of the core lamination with screw-spindle-shaped cooling channels formed by the openings. Alternatively, the openings of the laminations offset in the stacking direction can also be offset from one another in the circumferential direction of the laminations by an integer multiple of a slot pitch, depending on the desired pitch of the cooling channel.

[0037] According to a further embodiment, a fan impeller is arranged on the pressure side of the rotor core. The at least one fan impeller can further increase the volume flow conveyed through the at least one cooling channel. The at least one fan impeller can be integrally formed on a short-circuit ring. In this context, "integrally formed" is understood to mean, in particular, that the fan impeller is integrated into a short-circuit ring of the rotor, i.e., the short-circuit ring and the fan impeller are connected to one another as a single piece. This enables lower manufacturing costs.

[0038] According to the method according to the invention for cooling an electrical machine described above, the rotor is operated such that an electrically insulating coolant is sucked from the coolant reservoir and conveyed through the at least one screw-spindle-shaped cooling channel and the outer cooling channel, wherein the rotation of the rotor generates a coolant-air mixture from the electrically insulating coolant. Regarding effects and advantageous embodiments of the method according to the invention, reference is made to the above statements in connection with the electrical machine according to the invention to avoid repetition.

[0039] In the following, exemplary embodiments of the invention are explained in more detail with reference to the schematic drawing. Herein: Fig. 1 a perspective view of a rotor with a rotor core, several screw spindle-shaped cooling channels and a fan impeller, Fig. 2 a plan view of a single lamination of the rotor core according to Fig. 1, Fig. 3 a perspective view of several stacked laminations of the rotor lamination stack according to Fig. 1 showing the formation of the cooling channels, Fig. 4 a partial longitudinal section through the rotor core according to Fig. 1, Fig. 5 a partial longitudinal section through another rotor lamination stack with several partial lamination stacks stacked on top of each other, Fig. 6 longitudinal sections through rotor lamination packages with up to 8 screw spindle-shaped cooling channels of different pitch, Fig. 9 a transmission-integrated electric machine, Fig. 10 a perspective view of a part of a stacked stator laminated core for use in the electrical machine according to Fig. 9, Fig. 11 an enlarged detail of the stator laminated core according to Fig. 10 and Fig. 12 a perspective view of a housing for use in the electrical machine according to Fig. 9.

[0040] Fig. 1 shows a rotor 1 comprising a laminated core 2 and a Fig. 1 first impeller 3 with blades 4 shown on the left. The rotor 1 is suitable for use in a Fig. 9 shown electrical machine 5 with an integrated gear 6. The rotor laminated core 2 comprises a plurality of identical laminations 7 stacked one above the other in a longitudinal direction L of the rotor 1, wherein the laminations 7 each have seven openings 8 and the openings 8 of all laminations 7 stacked one above the other form screw spindle-shaped cooling channels 9 running through the rotor laminated core 2.

[0041] Fig. 2 shows one of the identical laminations 7 of the rotor core according to Fig. 1. Each of the seven punched openings 8 in the sheet 7 connects opposite end faces S of the sheet 7 to one another and forms a section of the seven screw-spindle-shaped cooling channels 9 which run parallel to one another and are created by stacking the individual sheets 7 congruently in the longitudinal direction L of the rotor 1 to form the rotor laminated core 2, with either each individual sheet 7 or packages of several sheets 7 being arranged offset from one another in the circumferential direction U. The openings 8 are each arranged on an imaginary circular ring 10 of the sheets 7. Between adjacent openings 8, the sheet 7 forms a spoke 11. Furthermore, the sheet 7 has a plurality of identical winding slots 11 which extend radially outwards and are distributed equidistantly along an outer circumference 12 of the sheet 7 by a slot jump 13 each. The slot jump 13 is the circumferential distance orthe angular distance between two adjacent winding slots 11.

[0042] As is particularly evident from Fig. 3 and Fig. 4, the sheets 7 are stacked twisted relative to each other in such a way that the openings 8 of sheets 7 offset in the stacking direction L (exemplarily in Fig. 4 by the openings designated with reference symbols “8a” and “8b”) in a circumferential direction U of the sheets 7 from one sheet to an immediately adjacent sheet (exemplarily in Fig. 4 by the sheets designated by reference numerals “7a” and “7b”) are arranged offset from one another. The openings of the sheets offset in the stacking direction L (e.g. the openings 8a, 8b) are arranged offset from one another in the circumferential direction U of the sheets 7 by one groove step 13. This results in a relatively small pitch angle α of the cooling channel 9. The groove step 13 represents the angular distance between two adjacent winding slots 11. The openings 8 thus form screw spindle-shaped cooling channels 9, wherein the course of one of these cooling channels 9 is in the form of an Archimedean screw in Fig. 3 is shown partially without the associated sheets 7 for clarity. The cooling channels 9 run parallel to each other.

[0043] Fig. Figure 5 illustrates how individual sheets 7 can be stacked on top of each other as an alternative to a laminated core 2 according to the invention. After individual sheets 7, for example those according to Fig. 2, have been provided, these are stacked successively in a stacking direction L such that the openings 8 of sheets 10 offset in the stacking direction L are arranged offset from one another in a circumferential direction U of the sheets 7. According to the embodiment according to Fig. 5, for example, the openings designated by reference numerals "8a" and "8b" of sheets 7 offset in the stacking direction L from a partial sheet stack 14a to an immediately adjacent partial sheet stack 14b are arranged offset from one another by a groove pitch 13 in a circumferential direction U of the sheets 7. This results in a relatively large pitch angle α of the cooling channel 9. Each partial sheet stack 14a, 14b comprises three individual sheets 7.

[0044] Fig. 6 to 8 show a comparison of screw spindle-shaped cooling channels 9 with different pitch angles α. In Fig. 6 are the openings 8 of sheets 7 offset in the stacking direction L - similar to Fig. 4 - from one sheet to an immediately adjacent sheet in the circumferential direction of the sheets 7 are arranged offset from one another, resulting in a relatively small pitch angle α of the cooling channel 9. In Fig. 7 and Fig. 8 are the openings 8 of sheets offset in the stacking direction L - similar to Fig. 5 illustrates - from one partial laminated core to an immediately adjacent partial laminated core in a circumferential direction of the laminations offset from one another, which results in comparison to the rotor laminated core according to Fig. 6 a larger pitch angle α of the cooling channel 9 results. The pitch angle α of the cooling channel 9 according Fig. 8 is larger than the one after Fig. 7, since the partial laminated cores 14 arranged offset from one another in the circumferential direction Fig. 8 contain a larger number of individual sheets than the sheet packages 14 according to Fig. 7.

[0045] Fig. Figure 9 shows an electrical machine 5 with a housing 15 and an oil cooling circuit 16, the flow direction of which is illustrated by arrows within the housing 15. In a Fig. A rotor shaft 18 is rotatably mounted in the first section 17 of the housing 15 shown on the left in Figure 9. In a Fig. 9, the second section 19 of the housing 15, shown on the right, houses the gear 6, which is driven by the rotor shaft 18. On the rotor shaft 18, a rotor 1 is mounted according to one of the Fig. 1 to 8 are mounted in a rotationally fixed manner, so that when the rotor shaft 18 rotates, the rotor 1 also rotates. The rotor 1 is surrounded radially at a small distance by a fixed stator 20, which comprises a stator laminated core 21 ( Fig. 10 and Fig. 11) and on its two opposite end faces each has a stator winding head 22 and 23, which protrude in the axial direction beyond two opposite axial end faces of the rotor 1. The stator 20 is completely surrounded by the first section 17 of the housing 15 at a distance in the radial direction. The first section 17 of the housing 15 and the stator 20 form spiral grooves 24 between them, as shown by Fig. 10 to 12. The spiral grooves 24 form part of an outer cooling channel K between the stator 20 and the housing 15. The outer cooling channel continues on both sides of the spiral grooves 24 between the stator winding heads 22, 23 and the first section 17 of the housing 15. In its lower region, the housing 15 further forms a sump 25 for oil, which serves in particular to cool the rotor 1, stator 20, and gear 6.

[0046] After the oil has absorbed heat, in particular from the rotor 1 and the stator 20, as described below, it is recooled in a circulating cooling circuit 26. The circulating cooling circuit 26 comprises a coolant line 27, which is connected to the sump 25 on the inlet side 28 and the outlet side 29. A feed pump 30 is arranged within the coolant line 27, which draws oil from the sump 25 and conveys it back to the sump 25 via a heat exchanger 31. To cool the oil within the heat exchanger 31, cooling water also flows through it, which circulates in a main cooling circuit 32 and is in turn cooled by a main water cooler 33.

[0047] When the rotor 1 is stationary, the oil collects in the sump 25. When the electrical machine 5 is put into operation, the rotor shaft 18 rotates and with it the rotor 1 and the screw-shaped cooling channels 9. By rotating the screw-shaped cooling channels 9, which each form a conveyor spiral in the sense of a screw pump, and the fan impeller 3 ( Fig. 1), a pressure side 34 and a suction side 35 are formed within the closed housing 17 of the electrical machine 5 on opposite end faces of the rotor 1. Due to the suction effect of the screw spindle-shaped cooling channels 9 on the suction side 35, oil is sucked in from the sump 25 via the spiral grooves 24 between the first section 17 of the housing 15 and the stator 20 and thus over the entire circumference of the stator 20. In this case, oil can also be conveyed into the upper area of the rotor 1 and stator 20, wherein the oil is particularly drawn in via the Fig. 9 can drip off the stator winding head 23 shown on the right and be conveyed to the pressure side 34 via the screw-spindle-shaped cooling channels 9 of the rotor 1. Initially, oil and, after prolonged operation, predominantly oil mist are sucked into the rotor 1 via the stator winding head 22 and 23, which are cooled as the oil or oil mist passes through, and are conveyed via the screw-spindle-shaped channels 9 to the pressure side 34 of the electrical machine 5. From there, the oil mist passes the stator winding head 22 and 23 of the other stator side to return to the suction side 35 via the circumference of the stator laminated core. Due to the spiral grooves 24 on the outer circumference of the stator laminated core 21 ( Fig. 10, Fig. 11) or on the inner circumference of the housing 15 ( Fig. 12), the oil from the oil sump 25 is initially guided easily along these grooves 24 to the end faces of the stator laminated core 21.

[0048] Above an imaginary central axis or longitudinal axis L of the rotor shaft 18, the oil can drip off after passing the winding overhangs 22 and 23 and is sucked into the screw-spindle-shaped cooling channels 9 of the rotor 1 by suction. At very high speeds, the proportion of bubbles in the oil increases. The rotor 1 conveys the oil or oil-air mixture to the pressure side 34 and is cooled in the process. The oil is recooled via the circulating cooling circuit 26. Alternatively, cooling channels can also be arranged in a wall of the housing 15, through which cooling water from the main water cooling circuit 32 flows, for example, and ensure recooling of the oil within the housing 15.

[0049] Fig. 10 and Fig. 11 show a part of a stator laminated core 21 for use in the electrical machine according to Fig. 1. The stator laminated core 21 has been assembled by stacking identical laminations 36. The laminations 36 have a plurality of recesses 37 extending radially outward from an inner circumference 38 of the lamination 36. Several of these laminations 36 have been stacked in a stacking direction L, which may be identical to a stacking direction L of the laminations 7 of the rotor laminated core 2 ( Fig. 1 and 3 to 5), stacked one above the other. As a result, the recesses 37 form winding slots 39 of the stator lamination stack 21 arranged in a circular ring. The laminations 36 furthermore each have a plurality of recesses 40 arranged in a circular ring around the recesses 37 or winding slots 39, which are arranged along an outer circumference 41 of the laminations 36 and extend radially inward from the outer circumference 41. The laminations 36 were each rotated relative to one another by a slot pitch 42, so that the recesses 40 of laminations 36 offset in the stacking direction L and immediately adjacent to one another form spiral-shaped slots 24, which each run obliquely to the stacking direction L and can serve as an outer channel K within the electrical machine 5. The course of a slot 24 is shown in Fig. 11 is exemplary traced with a dash-dot line 24a. Between two grooves 24, the outer circumference 41 of the laminations 36 or of the stator lamination stack 21 forms a spiral-shaped cooling fin 43, wherein the course of one of the cooling fins 43 is exemplary in Fig. 11 is traced by a dashed line 43a.

[0050] Fig. 12 shows a first section 17 of a hollow cylindrical housing 15 for use in the electrical machine 5 according to Fig. 9. The first section 17 of the housing 15 has, on its inner circumference 44, which serves as a mating surface for installing the stator 20, screw spindle-shaped recesses 45 which can form spiral grooves 24 of the cooling channel K.

Claims

[1] Electrical machine (5) comprising a rotor (1) with a rotor core (2), a stator (20) with stator winding heads (22, 23) which are arranged on opposite end faces of the stator (20), and a housing (15, 17, 19) with a reservoir (25) for a cooling liquid, wherein - the rotor lamination stack (2) comprises a plurality of laminations (7) stacked in a stacking direction (L), - the sheets (7) each have at least one opening (8) which connects the end faces (S) of the respective sheet (7) to one another, and - the openings (8) of laminations (7) offset in the stacking direction (L) are arranged offset from one another in a circumferential direction (U) of the laminations (7) in such a way that at least one screw-spindle-shaped cooling channel (9) is formed which runs through the rotor lamination stack (2) and connects two opposite end faces of the rotor lamination stack (2), - the stator (20) and the housing (15, 17) form an outer cooling channel (K) between them, which runs along the stator (20) and the winding heads (22, 23) and connects two opposite end faces of the stator winding heads (22, 23), - the at least one screw-spindle-shaped cooling channel (9) is designed to form a suction side (35) on a first end face of the rotor (1) and a pressure side (34) on a second end face of the rotor (1) when the rotor (1) is rotating, so that an electrically insulating cooling liquid is sucked in from the reservoir (25) and conveyed through the at least one screw-spindle-shaped cooling channel (9) and the outer cooling channel (K). [2] Electrical machine (5) according to claim 1, characterized bythat the outer cooling channel (K) comprises spiral grooves (24) which are formed by recesses (45) on the inner circumference (44) of the housing (15) or by recesses (40) on the outer circumference (41) of the stator (20). [3] Electrical machine (5) according to claim 2, characterized by that the stator (20) comprises a stator laminated core (21) with a plurality of laminations (36) stacked in a stacking direction (L), wherein - the individual sheets (36) each have a plurality of recesses (40) distributed along the outer circumference (41) and - the recesses (40) of sheets (36) offset in the stacking direction (L) are arranged offset from one another in a circumferential direction of the sheets (36) such that the recesses (40) of all sheets (36) form the spiral grooves (24). [4] Electrical machine (5) according to one of the preceding claims, characterized bythat the electrical machine (5) has a circulating cooling circuit (26) with a pump (30) and a heat exchanger (31) for cooling the electrically insulating cooling liquid. [5] Electrical machine (5) according to one of the preceding claims, characterized by that further cooling channels for cooling the electrically insulating cooling liquid are arranged in a wall of the housing (15, 17, 19). [6] Electrical machine (5) according to one of the preceding claims, characterized by that the openings (8a, 8b) of laminations (7) of the rotor laminated core (2) offset in the stacking direction (L) are arranged offset from one lamination (7a) to an immediately adjacent lamination (7b) in the circumferential direction (U) of the laminations (7). [7] Electrical machine (5) according to one of claims 1 to 5, characterized bythat the openings (8) of laminations (7) of the rotor laminated core (2) offset in the stacking direction (L) are arranged offset from one partial laminated core (14a) to an immediately adjacent partial laminated core (14b) in a circumferential direction (U) of the laminations (7) relative to one another. [8] Electrical machine (5) according to one of the preceding claims, characterized by that the openings (8) of laminations (7) of the rotor laminated core (2) offset in the stacking direction (L) are arranged offset from one another in the circumferential direction (U) of the laminations (7) by a groove jump (13). [9] Electrical machine (5) according to one of the preceding claims, characterized by that a fan impeller (3) is arranged on the pressure side (34) of the rotor core (2). [10] Method for cooling an electrical machine (5) according to one of the preceding claims, wherein the rotor (1) is operated in such a way that an electrically insulating cooling liquid is sucked in from the coolant reservoir (25) and conveyed through the at least one screw-spindle-shaped cooling channel (9) and the outer cooling channel (K), wherein a cooling liquid-air mixture is generated from the electrically insulating cooling liquid by the rotation of the rotor (1).

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