Stator with cooling of the winding heads by means of a swirl flow and an electric machine

Abstract

Stator (1) for an electrical machine, comprising a stator base body (2) with stator slots (3) formed therein and a coil (4) arranged at least partially in the stator slots (3), which coil (4) has a winding head (7) arranged axially at the end of the stator base body (2) in an annular chamber (6) formed by a cover (5), wherein the cover (5) further has an inlet region (8) designed to introduce a cooling fluid into the chamber (6), the chamber (6) is fluidically connected to fluid channels (9) formed by the stator slots (3), the inlet region (8) is designed such that it generates a swirling flow of the cooling fluid for flowing through the chamber (6) in a circumferential direction (10), and the inlet region (8) has a diversion region (30) generating the swirl flow or the inlet region (8) has a diversion region (30) generating the swirl flow and the inlet region (8) is aligned at least with its opening obliquely / angularly to an axial direction (11) of the stator (1), characterized in that the diversion region (30) is formed by means of a sheet metal (19) and is positioned between a front side (31) of the winding head (7) and an inner side (32) of the cover (5) opposite the front side (31).

Description

The invention relates to a stator for an electric machine according to the features of the preamble of claim 1, having a stator base body with stator grooves formed therein and having a coil arranged at least partially in the stator grooves, which coil has a winding head arranged axially on the end side of the stator base body in an annular chamber formed by means of a cover / a cap, wherein the cover further has an inlet region formed for introducing a cooling fluid into the chamber.In electric machines, power losses occur during active operation and thus a heat input in detail. If the cooling by free convection is no longer sufficient, an active cooling is required. Such cooling can be effected by a moving fluid which, in the case of an internal rotor, is guided, for example, through a cooling jacket lying around the stator. Novel cooling methods are concerned with the direct cooling in the stator for heat dissipation of the iron and the conductor. With direct cooling, for example within the stator groove or on the winding head, it is therefore possible to dissipate the heat in a targeted manner at the location of the formation. As a result, the general temperature level in electric machines can be lowered and a more homogeneous temperature distribution can be ensured. This allows, for example, the use of more cost-effective and lighter materials.The prior art is known from DE 10 2021 120 773 A1, in which an active component of an electric machine is disclosed, having a cooling channel, which has at least in sections a substantially axial extension, which has a substantially constant cross-sectional area, wherein a reducing element, which projects into the extension and is designed to reduce the cross-sectional area in such a way that turbulence of the cooling fluid occurs when a cooling fluid flows through it.Further relevant stators are known from the disclosures of DE 10 2014 207 468 A1, DE 20 2020 107 583 U1, DE 10 2021 205 864 A1, U.S. Pat. No. 10 084 355 B2 and DE 10 2019 113 159 A1.The object of the present invention is to provide a stator for an electric machine with improved cooling and performance.This is achieved in a generic stator by the characterizing features of claim 1. It is provided here that the chamber is fluidically connected to fluid channels formed by the stator grooves and the inlet region is formed in such a way that it generates a swirling flow of the cooling fluid for flowing through the chamber in a circumferential direction. In this case, the cooling fluid in the chamber moves helically / in a coil-shaped / swirl-shaped manner, with the result that the cooling fluid subsequently flows further from the chamber into the fluid channels of the stator grooves. The cooling fluid flows in one direction in the circumferential direction and in the process moves additionally in the axial direction through the chamber. The cooling fluid thus has a flow velocity with a circumferential component but also with an axial component. The cooling fluid flows into the fluid channels after it has degraded the circumferential component of the flow velocity during the swirling movement. Due to a pressure drop, the movement takes place into the fluid channels and thus through the stator grooves. This provides efficient cooling of the winding head, but also of the stator slots.According to the invention, it is provided that the inlet region has a diversion region / section generating the swirl flow or the inlet region has a diversion region / section generating the swirl flow and the inlet region is oriented at least with its opening obliquely / at an angle to an axial direction of the stator. With the aid of the diversion region, the cooling fluid is diverted, so that the swirling flow of the cooling fluid develops. If the inlet region is oriented obliquely / at an angle, the inlet region has an axial component and a radial component. The inlet region preferably comprises an inlet connection piece which is formed integrally on the cover and thus connects the chamber to the environment in which a coolant feed line can be connected to the inlet connection piece. If the inlet region has a bypass region, the inlet connection piece is shaped in the axial direction of the cover, extending straight in the axial direction. If the inlet region is oriented obliquely / at an angle, the inlet connection piece has an axial and radial extent, and is formed obliquely on the cover, so that the cooling fluid from the coolant feed line flows directly at an angle / at an angle into the chamber of the cover.According to the invention, it is further provided that the diversion region is formed by means of a metal sheet and is positioned between a front side of the winding head and an inner side of the cover opposite the front side. When flowing in via a straight inlet connection piece, the flow movement of the cooling fluid can be influenced in such a way that the swirl flow is formed. Between the front side of the winding head and the opposite inner side of the cover, a free space is formed in which the sheet metal is positioned. The free space is thus used efficiently to form the swirl flow by diverting the cooling fluid. The sheet metal is preferably arranged toward a cover-side inner opening of the inlet region. If the cooling fluid flows through the inlet region and enters the chamber via the cover-side inner opening, the cooling fluid is directly diverted and the swirl flow is formed.Advantageous embodiments are claimed in the dependent claims and are explained in more detail below.It is expedient if the metal sheet is positioned inclined to an axial direction and / or has an angled contour. The sheet metal can have altogether different embodiments which make it possible to deflect the cooling fluid. Preferably, the sheet is configured to redirect the cooling fluid to flow in the circumferential direction in only one direction, clockwise or counter-clockwise. The flow direction of the cooling fluid is thus always predefined.It is advantageous if the chamber has two regions separated / separate / divided from one another, which are connected fluidically via a channel. This assists in generating the swirling flow of the cooling fluid. Preferably, the chamber is divided by means of an annular disc separate from the cover. Particularly preferably, the disc has a plurality of through holes for forming the channel. The regions divided in the chamber, a region on the end winding side and a flow-generating region, are thus fluidically connected. The channel is a kind of separating channel.In addition, a first winding head can be arranged in a first cover on a first axial end side and a further / second winding head can be arranged in a further / second cover / cap on a second axial end side, wherein the further / second cover is fluidically connected to the fluid channels of the stator grooves and the further / second cover has an outlet region on the radial top side for discharging the cooling fluid. The cooling fluid thus flows from the first cover via the fluid channels in the stator grooves into the further cover, and the cooling fluid can flow out of the stator via the discharge region.The invention also relates to an electric machine having a rotor and a stator described above.In other words, the invention describes a swirling flow at the winding head in a chamber of an electric machine, which is produced by a targeted introduction of the fluid flow in a cover / housing of the winding head. Dead zones in the flow are prevented by the swirling flow and the entire end winding is uniformly cooled, since a turbulent flow forms in the end winding due to the forced convection. The swirling flow also makes it possible to distribute the fluid flow uniformly over the stator grooves.Various advantageous embodiments of the invention are explained in more detail below with reference to a drawing with figures.The following are shown: FIG. 1 shows a stator of an electric machine in a first embodiment, FIG. 2 shows a sectional view of the stator according to FIG. 1, FIG. 3 shows the stator in a second embodiment, FIG. 4 shows a detail of the stator with a sheet metal, FIG. 5 shows a detail of a cover, FIG. 6 shows an annular disc in a front view, and FIG. 7 is a partial view of an inner surface of the cover with an annular disc.The figures are merely schematic in nature and serve exclusively for understanding the invention. The same elements are provided with the same reference numerals. Features of the individual embodiments can be interchanged and used alternatively / cumulatively.FIG. 1 shows a stator 1 according to the invention for an electric machine, having a stator base body 2 with stator grooves 3 formed therein and having a coil 4 (see FIG. 2 ) arranged at least partially in the stator grooves 3, which coil 4 has a winding head 7 (see FIG. 2 ) arranged axially on the end side of the stator base body 2, in an annular chamber 6 forming a cover 5 / a cap, wherein the cover 5 furthermore has an inlet region 8 formed for introducing a cooling fluid into the chamber 6. It should be emphasized that the chamber 6 is fluidically connected to fluid channels 9 formed by the stator grooves 3, and the inlet region 8 is designed such that it generates a swirling flow of the cooling fluid for flowing through the chamber 6 in a circumferential direction 10.For the sake of better clarity, an axial direction 11 and a radial direction 12 are defined. The axial direction 11 describes the direction along a central axis 13 of the stator 1. the radial direction 12 describes the direction oriented perpendicular to the axial direction 11.FIG. 1 shows the basic structure of the stator 1. A (first) and (second) cover 5, 14 are arranged on the stator base body 2 in the axial direction 11, and stator grooves 3 are formed in the stator base body 2, distributed over the circumferential direction 10, which extend in the axial direction 11. The first cover 5 is positioned on a first axial end side 42 and the second cover 14 is positioned on a second axial end side 43.The (first) winding head 7 is positioned in the first cover 5. As shown, the first cover 5 has the inlet region 8 on the front side. In the embodiment shown, the inlet region 8 is formed by means of an inlet connection 15 formed in the axial direction 11 and having two openings 16, 17, an outer opening 16 on the cover side and an inner opening 17 on the cover side. This inlet port 15 is prepared to be connected to a coolant supply pipe.A flow direction 18 of the cooling fluid is shown by arrows. For this purpose, the cooling fluid flows in the axial direction 11 through the inlet connection 15 and the two openings 16, 17 into the (first) chamber 6. After the cooling fluid has reached the first chamber 6, the cooling fluid flows counterclockwise in the circumferential direction 10 as shown and moves through the first chamber 6 according to an axial velocity component in the axial direction 11, When the cooling fluid has arrived axially at the end of the first chamber 6, it flows via the fluid channels 9 of the stator grooves 3 in the axial direction 11 into a (second) chamber 20 of the second cover 14.Arranged axially on the rear side, on the second axial end side 43, is the second cover 14, which forms the second chamber 20 for a (second) winding head 21 (see FIG. 2 ). The second cover 14 has an outlet region 22 which is prepared for draining the cooling fluid. In the present case, the outlet region 22 is formed with the aid of an outlet connection 23. The outlet connection piece 23 is arranged in the radial direction 12 and has an inner and outer opening 24, 25 which are oriented radially upwards. The second cover 14 also has the necessary connections 26 for supplying current to the stator 1.Projections 27 rounded in the circumferential direction 10 with bores formed in the axial direction 11 are formed on the stator 1 in order to fasten the two covers 5, 14 to the stator base body 2. For this purpose, the covers 5, 14 have tabs 28 which are arranged in the circumferential direction 10 and extend in the radial direction 12 and have axial through-holes which are arranged on these elevations 27 and are fixed by means of fastening means 29.The stator base body 2 is formed from a plurality of individual sheets stacked in the axial direction 11. The stator base body 2 is thus a stator laminated core.FIG. 2 shows the stator 1 according to FIG. 1 in a perspective sectional view. In this illustration, the winding heads 7, 21 already mentioned above are now shown, which have been covered by the covers 5, 14 in FIG. 1. The bobbin 4 has a total of two winding heads 7, 21, wherein, according to the illustration, the first winding head 7 is positioned on the front side in the axial direction and the second winding head 21 is positioned on the rear side according to the illustration.FIG. 3 shows a sectional view with a section of the stator 1 according to FIG. 1, with focus on the first cover 5 with the first chamber 6. The inlet region 8 has a bypass region 30, which is formed in the present case from the metal sheet 19. The sheet metal 19 is arranged between a front side 31 of the first winding head 7 and an opposite inner side 32 of the first cover 5. The sheet 19 is positioned directly behind the inner opening 17 of the inlet connection 15 on the cover side in the axial direction 11 and ensures a diversion of the cooling fluid at which time it impinges on the sheet 19. This is illustrated in accordance with the illustration with reference to the flow direction 18 of the cooling fluid. At the axial end of the first chamber 6, the cooling fluid flows over into the fluid channels 9.FIG. 4 shows the stator 1 in a second embodiment with a first cover 5 different from FIG. 1. In comparison to the embodiment according to FIG. 1, the inlet region 15 of the first cover 6 is not completely shaped in the axial direction 11, but in the present case has, in addition to an axial component, also a radial component, as a result of which an orientation / position angled with respect to the axial direction 11 is present. Thus, the cooling fluid does not flow completely from the axial direction 11 but obliquely / at an angle 33 into the first chamber 6, whereby a separate diversion of the cooling fluid for generating the swirl flow is dispensed with.FIG. 5 shows a schematic view of the first chamber 6 in a further embodiment. In the present embodiment, the first chamber 6 is divided into two regions 34, 35 by means of an annular disc 36. In the axial direction 11, the disk 36 is positioned such that it is positioned with its rear side 37 toward the front side 31. The disk 36 has a plurality of axial through holes 38 which are formed distributed on the disk 36 in the circumferential direction 10. These through holes 38 form a channel 39; the free flow movement is disturbed by means of the channel 39 and an axial movement is necessary for reaching the second region 35. The disk 36 has two rows of through-holes 38 in the radial direction 12, so that two through-holes 38 are always positioned at a distance from one another in the radial direction 12. The sheet 19 is positioned between the inner side 32 and a front side 40 of the disc 36 in the present embodiment.For the specific configuration of the disc 36, reference is made to FIG. 6, which illustrates a front view of the disc 36. The through-holes 38 are shown in FIG. 6 by way of example on one section.For a further view, reference is made to FIG. 7, which shows a detail of an inner lateral surface 41 of the first cover 5 with the first winding head 7 arranged therein. Here, the flow movement of the cooling fluid according to the flow direction 18 through the inlet region 8 is illustrated, wherein the cooling fluid spreads in the circumferential direction 10 and the axial direction 11 and flows through the separating channel 39 from the first region 34 into the second region 35.List of reference characters1 Stator 2 Stator base body 3 Stator groove 4 Coil 5 First cover 6 First chamber 7 First winding head 8 Inlet region 9 Fluid channel 10 Circumferential direction 11 Axial direction 12 Radial direction 13 Central axis 14 Second cover 15 Inlet connection piece 16 Outer opening 17 Inner opening 18 Flow direction 19 Sheet 20 Second chamber 21 Second winding head 22 Outlet region 23 Outlet connection piece 24 Inner opening 25 Outer opening 26 Connections 27 Elevations 28 Tabs 29 Fastening means 30 Bypass region 31 Front side 32 Inner side 33 Angle 34 First region 35 Second region 36 Disk 37 Rear side 38 Through hole 39 Channel 40 Front side 41 Inner jacket surface 42 First axial end side 43 Second axial end side

Claims

Stator (1) for an electric machine, having a stator base body (2) with stator grooves (3) formed therein and having a coil (4) arranged at least partially in the stator grooves (3), which coil (4) has a winding head (7) arranged axially on the end side of the stator base body (2) in an annular chamber (6) formed by means of a cover (5), wherein the cover (5) furthermore has an inlet region (8) formed for introducing a cooling fluid into the chamber (6), the chamber (6) is fluidically connected to fluid channels (9) formed by the stator grooves (3), the inlet region (8) being formed in such a way that it generates a swirling flow of the cooling fluid for flowing through the chamber (6) in a circumferential direction (10), and the inlet region (8) has a diversion region (30) generating the swirl flow or the inlet region (8) has a diversion region (30) generating the swirl flow and the inlet region (8) is oriented at least with its opening obliquely / at an angle to an axial direction (11) of the stator (1), characterized in that the diversion region (30) is formed by means of a metal sheet (19) and is positioned between a front side (31) of the winding head (7) and an inner side (32) of the cover (5) opposite the front side (31).Stator (1) according to Claim 1, characterized in that the sheet (19) is arranged with respect to a cover-side opening (17) of the inlet region (8).Stator (1) according to Claim 1 or 2, characterized in that the sheet (19) is positioned inclined with respect to an axial direction (11) and / or has an angled contour.Stator (1) according to one of Claims 1 to 3, characterized in that the chamber (6) has two regions (34, 35) which are divided from one another and are fluidically connected via a duct (39).Stator (1) according to Claim 4, characterized in that the chamber (6) is divided by means of an annular disc (36).A stator (1) according to claim 5, characterized in that the disc (36) for forming the channel (39) has a plurality of through holes (38).Stator (1) according to one of the preceding claims, characterized in that a first winding head (7) is arranged in a first cover (5) on a first axial end side (42) and a second winding head (21) is arranged in a second cover (14) on a second axial end side (43), wherein the second cover (14) is fluidically connected to the fluid channels (9) of the stator grooves (3) and the second cover (14) has an outlet region (22) on the radially upper side for discharging the cooling fluid.Electric machine having a rotor and a stator (1) according to one of Claims 2 to 9.

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