Electric machine

Abstract

The present invention relates to an electrical machine (100) having a motor housing (10) which extends along a longitudinal axis (A2) and accommodates a stator (11) with winding heads (12) and a rotor (13) rotatably mounted therein, wherein the stator (11) has a lateral surface which is designed in the radial direction as a stator back (14), and a cooling device (15) which has at least one helical channel (16) for guiding a cooling fluid, wherein the helical channel (16) surrounds the stator (11) at least in sections and is introduced into the motor housing (10) in such a way that the helical channel (16) is delimited on the motor housing side by the motor housing (10) and on the stator side by the stator (11).In order to propose an electrical machine with a cooling device which eliminates the disadvantages of the prior art, the invention provides that the spiral channel (16) is designed without any projection in the longitudinal axial direction with respect to the stator (11) and is connected via transverse connections (181, 182) to outlet openings (191, 192) which are arranged and aligned in such a way as to guide a cooling fluid emerging from the outlet opening (191, 192) onto the winding heads (12) of the stator (11).

Description

[0001] The present invention relates to an electrical machine with a motor housing which extends along a longitudinal axis and accommodates a stator with winding heads and a rotor rotatably mounted therein, wherein the stator has a lateral surface which is designed as a stator back in the radial direction, and a cooling device which has at least one helical channel for guiding a cooling fluid, wherein the helical channel surrounds the stator at least in sections and is introduced into the motor housing in such a way that the helical channel is delimited on the motor housing side by the motor housing and on the stator side by the stator.

[0002] Electrical machines of the type mentioned above are regularly part of electrical drive modules, which are usually installed in electric and / or hybrid vehicles. Depending on the design of the electrical machine, the stator and rotor have separate windings of electrical conductors. So that by skillfully applying electrical current to the conductors, magnetic fields are induced. Due to their alternating polarity, these magnetic fields attract and repel each other in such a way that the rotor rotates and can transfer kinetic energy to a drive shaft of the vehicle. When such an electrical machine is used as intended, the high electrical currents and the rotation of the rotor generate heat. This heat must be effectively dissipated by the cooling system to enable continuous operation of the electrical machine and to prevent damage to components due to overheating.Various cooling devices are known from the prior art for this purpose, in particular those that have cooling fluid-carrying channels with outlet openings that directly supply the stator and / or rotor with cooling fluid. Oil is usually used as the cooling fluid, which is conducted within a cooling fluid circuit.

[0003] Known designs of cooling systems for electrical machines have proven to be disadvantageous because they require the use of cooling fluid guide rings and axial seals to seal the spiral channels. These are additional components that must be manufactured, maintained, assembled, and maintained in the event of wear. Furthermore, at least in some known designs, such a geometry is only feasible with a comparatively large stator outer diameter because the cooling fluid channels are located in the stator back, resulting in a significant increase in stator lamination.

[0004] A comparable electric machine is described in DE 10 2021 121 031 A1. This document provides a stator cooling jacket separate from the motor housing as an additional component.

[0005] DE 10 2008 001 621 A1, CN 109 510 402 A, and US 2011 / 0298318 A1 each disclose electrical machines of a different type, because in these machines the cooling fluid channels are completely incorporated in the motor housing and are not limited in sections by the stator or the stator back.

[0006] Starting with a generic electrical machine, the object of the present invention is to propose an electrical machine with a cooling device that eliminates the aforementioned disadvantages. In particular, the cooling device should be easy to manufacture, maintain, assemble, and maintain. Furthermore, the cooling device should enable the use of a stator with a relatively smaller outer diameter.

[0007] This object is achieved by the electrical machine according to claim 1. According to the invention, the helical channel is designed so as to be free of any projections in the longitudinal axial direction with respect to the stator and is connected via cross connections to outlet openings which are arranged and aligned in such a way as to direct a cooling fluid emerging from the outlet opening to the winding heads of the stator. This prevents leaks even without the use of cooling fluid guide rings and axial seals at the transition between the stator and the motor housing. The helical channel and the cross connections can be easily incorporated into the motor housing, for example by drilling or milling. This advantageously eliminates the manufacture, provision, assembly and maintenance of the aforementioned additional components, as required according to the prior art.Furthermore, the stator outer diameter can be reduced, which reduces the material used for high-quality stator sheet.

[0008] Advantageous further developments of the invention are disclosed below and in the subclaims.

[0009] According to an advantageous embodiment of the invention, the spiral channel is connected to at least one cooling fluid inlet. Oil is preferably used as the cooling fluid.

[0010] Preferably, the spiral channel is designed to be free of cooling fluid outlets, except for the outlet openings, so that the amount of cooling fluid supplied per unit of time corresponds to the amount of cooling fluid discharged via the outlet openings. This means that the cooling fluid entering the spiral channel via the at least one cooling fluid inlet is completely directed to the winding heads, resulting in effective cooling performance.

[0011] During normal operation of the electric machine, the rotor rotates within the stator and thus also transmits torque to the stator. To prevent torque-induced rotation of the stator within the motor housing, it is preferably provided that the stator is positively mounted within the motor housing in a tangential direction, preferably using a tongue and groove connection. This ensures that the stator and the motor housing are securely connected to one another.

[0012] In order to achieve a constant cooling performance of the stator in the radial and longitudinal axial directions, an advantageous embodiment of the invention provides for the spiral channel to have at least one inner spiral and at least two outer spirals. The at least one inner spiral completely surrounds the stator, while the outer spirals surround the stator in sections. To achieve uniform cooling performance, particularly with a comparatively long stator, it is preferably provided that the spiral channel has several inner spirals, wherein the inner spirals are preferably connected to one another via longitudinal connections for conducting cooling fluid.

[0013] The cooling device is preferably part of a closed cooling fluid circuit that has a cooling fluid pump. Oil is used as the preferred cooling fluid.

[0014] According to an advantageous development of the invention, the cooling fluid circuit comprises a section of cooling fluid channels, which extend partially within a rotor shaft and partially within the rotor, where they open into outlet openings that are aligned and arranged to direct cooling fluid emerging from the outlet openings to the winding heads. As a result, the winding heads are also wetted with cooling fluid and cooled on their inner sides, which face away from the stator, thus resulting in consistent and uniform cooling of the winding heads across the entire surface.

[0015] Specific embodiments of the present invention are explained below with reference to the figures. They show: Fig. 1a: a longitudinal section of parts of an electrical machine according to the state of the art; Fig. 1b: a perspective view of a cooling fluid guide ring according to the prior art; Fig. 2: a longitudinal section of parts of an electrical machine; Fig. 3a-d: perspective views of different spiral ducts; Fig. 4a: a longitudinal section of an electrical machine; Fig. 4b-d: different cross-sectional views of the electrical machine; Fig. 5: a sectional plan view of an electrical machine.

[0016] Fig. 1a shows a longitudinal section of part of an electrical machine 1, as is known from the prior art. The electrical machine 1 has a motor housing 2 that extends along a longitudinal axis A1 and accommodates a stator 3 with winding heads 4. Cooling fluid channels 5 run within the motor housing 2 and are partially delimited by the stator 3 in the circumferential region thereof. In the longitudinal axial direction, the cooling fluid channels 5 each have a projection with respect to the stator 3, so that cooling fluid guide rings 6, axial seals 7, and radial seals 8 are incorporated in these regions. The cooling fluid guide rings 6 have openings 9 that are aligned such that cooling fluid escaping therefrom wets the winding heads 4, thereby cooling the winding heads 4. Fig. 1b shows a perspective view of a cooling fluid guide ring 6 with an axial seal 7, a radial seal 8 and openings 9.

[0017] Fig. Figure 2 shows a longitudinal section of parts of an electrical machine 100 with a motor housing 10 extending along a longitudinal axis A2. The longitudinal axis A2 defines a cylindrical coordinate system. Directional specifications within the scope of this application, in particular axial, radial, and tangential, refer to this cylindrical coordinate system. The motor housing 10 accommodates a stator 11 with winding heads 12 and a rotor 13 rotatably mounted therein, which is mounted on a rotor shaft 26. The outer surface of the stator 11 facing the motor housing 10 is designed as a stator back 14. Within the motor housing 10, a cooling device 15 is formed, which has a spiral channel 16 for guiding a cooling fluid, wherein the spiral channel 16 has six inner spirals 171, which completely surround the stator 11 in the tangential direction, and two outer spirals 172, which each surround the stator 11 in sections.The spiral channel 16 has a groove-shaped cross-section and is delimited on the motor housing side by the motor housing 10 and on the stator side by the stator 11. In the longitudinal axial direction, the spiral channel 16 is designed to be free of projections relative to the stator 11, whereby the spiral channel 16 does not project beyond the stator 11 in the longitudinal axial direction. Transverse connections 181, 182 in the form of transverse bores with outlet openings 191, 192 extend within the motor housing 10, starting from the respective outer spirals 172 of the spiral channel 16. These transverse connections are arranged and aligned such that cooling fluid emerging therefrom is guided to the winding overhangs 12 of the stator 11. In the illustrated embodiment, the spiral channel 16 has a single cooling fluid inlet 20. Furthermore, the spiral channel 16, apart from the outlet openings 191, 192, is designed without a cooling fluid outlet, which means that the cooling fluid is discharged exclusively at the outlet openings 191, 192.Thus, the amount of cooling fluid supplied per unit of time is identical to the amount of cooling fluid discharged via the outlet openings 191, 192. To prevent longitudinal axial displacement of the stator, a stop 31 is formed on the motor housing 10.

[0018] The Fig. 3a, b, c and d show different spiral channels 16, which differ in particular in the number of inner spirals 171. Fig. 3a shows an embodiment with two inner spirals 171, Fig. 3b shows an embodiment with four inner spirals 171, Fig. 3c shows an embodiment with six inner spirals 171 and Fig. Figure 3d shows an embodiment with eight inner spirals 171.

[0019] Fig. Figure 4a schematically shows a longitudinal section of the electric machine 100 with a motor housing 10, in which the cooling fluid circuit is fully illustrated. Starting from a cooling fluid pump 21, a cooling fluid channel 22 extends to a first branch 23, from which the cooling fluid channel 22 opens into a gear 24 having a plurality of meshing gears 25. Further along, the cooling fluid channel 22 opens into a (unnumbered) supply line for (unnumbered) transmission components or a corresponding bypass. The cooling fluid channel 22 then branches off and opens, on the one hand, into the spiral channel 16 in the manner already described and, on the other hand, into the rotor shaft 26 of the rotor 13. From there, the cooling fluid channel 22 leads over the rotor 13 to outlet openings 27. These outlet openings 27 are aligned such that escaping cooling fluid acts on the winding heads 12 of the stator 11.The cooling fluid then flows by gravity to a collecting basin 28 and from there is fed back to the cooling fluid pump 21 via the gear 24, thus closing the cooling fluid circuit.

[0020] Fig. Figure 4b shows a first cross-sectional view of parts of the electric machine 100 along the cross-sectional plane AA. In particular, it is shown that the inner spiral 171 of the spiral channel 16 completely surrounds the stator 11. Furthermore, Fig. 4b a plurality of stator slots 29 with wires of the winding heads 12. For the positive mounting of the stator 11 within the motor housing 10, a tongue and groove connection 32 is formed between the stator 11 and the motor housing 10.

[0021] In contrast, Fig. 4c shows a second cross-sectional view of parts of the electric machine 100 along the cross-sectional plane BB, which intersects one of the outer spirals 172. It is shown that the outer spiral 172 surrounds the stator 11 only partially and thus incompletely.

[0022] Fig. 4d shows a third cross-sectional view of parts of the electric machine 100 along the cross-sectional plane CC, which intersects the electric machine 100 in the region of the cross connections 182.

[0023] Finally, Fig.5 is a sectional top view of the electric machine 100. In particular, the spiral channel 16 with a cooling fluid inlet 20 is schematically shown. The spiral channel 16 is spirally introduced into the motor housing 10 and completely surrounds the stator (hidden here) at the periphery of the inner spirals 171. The inner spirals 171 are connected to one another by longitudinal connections 30. The outer spirals 172, in contrast, only partially surround the stator 11. The transverse connections 181, 182, which branch off from the outer spirals 172, are aligned such that cooling fluid is directed to the winding heads 12. List of reference symbols 100 Electric Machine 1 Electrical machine (state of the art) 2 engine housings 3 Stator 4 winding head 5 Cooling fluid channel 6 Cooling fluid guide ring 7 Axial seal 8 Radial seal 9 Opening A1 Longitudinal axis 10 engine housing 11 Stator 12 winding head 13 Rotor 14 Stator back 15 Cooling device 16 spiral channel 171 inner spiral 172 outer spiral 181 Cross connection 182 Cross connection 191 Exit opening 192 Exit opening 20 Cooling fluid inlet 21 Cooling fluid pump 22 Cooling fluid channel 23 Junction 24 gearboxes 25 gear 26 Rotor shaft 27 Outlet opening 28 collection basins 29 Stator slot 30 Longitudinal connection 31 stop 32 tongue and groove connection A2 Longitudinal axis QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2021 121 031 A1

[0004] DE 10 2008 001 621 A1

[0005] CN 109 510 402 A

[0005] US 2011 / 0298318 A1

[0005]

Claims

[1] An electrical machine (100) comprising a motor housing (10) extending along a longitudinal axis (A2) and accommodating a stator (11) with winding heads (12) and a rotor (13) rotatably mounted therein, the stator (11) having a lateral surface which is designed in the radial direction as a stator back (14), and a cooling device (15) having at least one helical channel (16) for guiding a cooling fluid, the helical channel (16) surrounding the stator (11) at least in sections and being introduced into the motor housing (10) in such a way that the helical channel (16) is delimited on the motor housing side by the motor housing (10) and on the stator side by the stator (11), characterized byin that the spiral channel (16) is designed to be free of projections in the longitudinal axial direction with respect to the stator (11) and is connected via transverse connections (181, 182) to outlet openings (191, 192) which are arranged and aligned in such a way as to guide a cooling fluid emerging from the outlet opening (191, 192) onto the winding heads (12) of the stator (11). [2] Electrical machine (100) according to claim 1, characterized by that the spiral channel (16) is connected to at least one cooling fluid inlet (20). [3] Electrical machine (100) according to one of claims 1 or 2, characterized by that the spiral channel (16), apart from the outlet openings (191, 192), is designed to be free of cooling fluid discharge, so that the amount of cooling fluid supplied per unit of time corresponds to the amount of cooling fluid discharged via the outlet openings (191, 192). [4] Electrical machine (100) according to one of claims 1 to 3, characterized bythat the stator (11) is positively mounted in the tangential direction within the motor housing (10), for which purpose a tongue and groove connection (32) is preferably formed. [5] Electrical machine (100) according to one of claims 1 to 4, characterized by that the spiral channel (16) has at least one inner spiral (171) and at least two outer spirals (172). [6] Electrical machine (100) according to claim 5, characterized by that the at least one inner spiral (171) surrounds the stator completely and the outer spirals (172) surround the stator (11) in sections. [7] Electrical machine (100) according to one of claims 5 or 6, characterized by that the spiral channel (16) has a plurality of inner spirals (171), wherein the inner spirals (171) are connected to one another via longitudinal connections (30). [8] Electrical machine (100) according to one of claims 1 to 7, characterized bythat the cooling device (15) is part of a closed cooling fluid circuit which has a cooling fluid pump (21). [9] Electrical machine (100) according to one of claims 1 to 8, characterized by in that the cooling fluid circuit has a section of cooling fluid channels (22) which run in sections within a rotor shaft (26) and in sections within the rotor (13) and open there into outlet openings (27) which are aligned and arranged in such a way as to guide cooling fluid emerging from the outlet openings (27) onto the winding heads (12). [10] Electrical machine (100) according to one of claims 1 to 9, characterized by that oil is used as the cooling fluid.

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