Method for manufacturing a stator, electric machine and motor vehicle

Abstract

Method for manufacturing a stator (1) for an electric machine (2) for driving a motor vehicle (3), comprising: - providing a stator base body (4) with a plurality of stator slots (5), - arranging hairpins (6) in the stator slots (5) such that the hairpins (6) are arranged in the stator slots (5) in the radial direction (R) of the stator base body (4) in several hairpin layers and hairpin ends (7) of the hairpins (6) project from the stator base body (4) in the axial direction (A) of the stator base body (4), wherein the hairpin ends (7) each have a hairpin end surface (8) limiting the hairpins (6) in the longitudinal direction (L) of the hairpins (6), wherein a hairpin end side (9) of the hairpins (6) has a concave end contour (10) which extends towards the hairpin end surface (8),and- twisting the hairpin ends (7) in a circumferential direction (U) of the stator base body (4) by engaging a twisting tool in the concave end contours (10) and exerting a twisting force on the hairpin ends (7) by the twisting tool in a circumferential direction (U) such that radial guidance of the hairpin ends (7) during twisting is ensured by the interaction of the twisting tool with the concave end contour (10), wherein a compressive force component in the circumferential direction (U) and a compressive force component in the radial direction (R) are transmitted to the concave end contour (10) by the twisting tool during twisting on the concave end contour (10).

Description

The present invention relates to a method for producing a stator for an electric machine for driving a motor vehicle. The invention further relates to an electric machine for driving a motor vehicle and to a motor vehicle having an electric drive system.A large number of different stators for electric machines for driving motor vehicles are known. For efficiency reasons, stators of electric traction transmissions frequently have stator windings which are designed as plug-in windings. Stators of this type are also referred to as "hairpin stators", since the stator wires used to produce the plug winding resemble the shape of a hairpin.Stator wires for hairpin stators are substantially divided into two different types, U-pins and I-pins. U-pins have two parallel-arranged legs which are connected to one another in a bent-over intermediate region. On a side facing away from the intermediate region, the legs each have a free end. I-pins are rod-shaped and correspond approximately to a leg of a U-pin. The free ends of the U pins and I pins each have a hairpin end face.When producing a hairpin stator, a stator base body with stator slots is first provided. In a next step, the hair pins are inserted into the stator grooves in such a way that the hair pins protrude from the stator base body on both sides. The free hairpin ends of the hair pins are then widened and twisted using a tool. Since end sections of the free hairpin ends are gripped by the tool during this process, they still project in the axial direction from the stator base body. Finally, the end sections are each welded together in pairs. In this way, a polyphase stator winding is produced. Such a method is known, for example, from the document US 2006 / 0 267 440 A1. An apparatus for carrying out such a method is disclosed in document DE 10 2019 130 534 A1. A disadvantage of such stators is that the protruding end portions of the free hairpin ends take up a relatively large amount of space.An alternative manufacturing method for stators is known from document WO 2023 / 233 618 A1. The end portions of the free hairpin ends are substantially shorter. In addition, only one hairpin end of a pair of hairpins to be welded to one another is twisted, while the other hairpin end protrudes from the stator base body in the axial direction. In this way, an additional radial guide is provided at the twist, so that less space is required for the tool to the twist. The document U.S. Pat. No. 11 710 999 B2 likewise discloses a method in which all free hairpin ends are twisted. After twisturing, protruding end portions of the hairpin ends are cut off. For welding together adjacent hairpin ends in pairs, a holding tool is provided. It is disadvantageous that a relatively high amount of material is produced by cutting the end regions to length. Documents JP 2021-45 027 A and U.S. Pat. No. 11 557 931 B2 disclose further methods for producing hairpin stators.It is therefore an object of the present invention to eliminate or at least partially eliminate the above-described disadvantages in a stator for an electric machine for driving a motor vehicle. In particular, it is the object of the present invention to provide a method for producing a stator for an electric machine for driving a motor vehicle, an electric machine for driving a motor vehicle and a motor vehicle having an electric drive system, which have a particularly compact structural size and / or avoid excessive waste of material in a simple and cost-effective manner.The above object is achieved by the claims. Accordingly, the object is achieved by a method for producing a stator for an electric machine for driving a motor vehicle having the features of independent claim 1, an electric machine for driving a motor vehicle having the features of subordinate claim 8, and by a motor vehicle having an electric drive system having the features of subordinate claim 9. Further features and details of the invention are evident from the dependent claims, the description and the drawings. Features and details which are described in connection with the method according to the invention naturally also apply in connection with the electric machine according to the invention and the motor vehicle according to the invention and vice versa, so that with regard to the disclosure reference is or can always be made reciprocally to the individual aspects of the invention.According to a first aspect of the invention, the object is achieved by a method for producing a stator for an electric machine for driving a motor vehicle. The method comprises:providing a stator base body having a plurality of stator grooves,arranging hair pins in the stator grooves in such a way that the hair pins are arranged in a plurality of hair pin layers in the stator grooves in the radial direction of the stator base body and hair pin ends of the hair pins project out of the stator base body in the axial direction of the stator base body, wherein the hair pin ends each have a hair pin end surface delimiting the hair pins in the longitudinal direction of the hair pins, wherein a hair pin end side of the hair pins has a concave end contour which extends towards the hair pin end surface, andtwist of the hairpin ends in a circumferential direction of the stator base body by engaging a twisting tool in the concave end contours and applying a twisting force to the hairpin ends by the twisting tool in the circumferential direction in such a way that a radial guidance of the hairpin ends is ensured during twist by the interaction of the twisting tool with the concave end contour. With the twisting tool, during twistting on the concave end contour, a pressure force component in the circumferential direction and a pressure force component in the radial direction are transmitted to the concave end contour.First, the stator base body is provided. The stator base body is preferably produced from a multiplicity of sheet metal disks which are stacked coaxially and are connected to one another. The sheet metal disks are preferably formed from electric sheet metal and further preferably each have a coating, in particular an electrically insulating coating, such as baking lacquer or the like. The stator base body extends along a stator longitudinal axis.A plurality of stator grooves are arranged in the stator base body for receiving the hair pins. The stator grooves preferably extend parallel to the stator longitudinal axis and have a groove depth in the radial direction. The groove depth preferably corresponds to a multiple of a hairpine thickness of the hairpines, wherein the hairpine thickness is understood to mean a thickness of a wire from which the hairpines are formed. Thus, a plurality of hairpin layers can be arranged one above the other in a stator groove in the radial direction.A groove width of the stator grooves preferably corresponds to a hairpin width of the hair pins, wherein the hairpin width is to be understood as a width of the wire from which the hair pins are formed. In the assembled state, the hairpin width is aligned in the circumferential direction or tangential direction. Preferably, a slot insulation material is arranged in each of the stator slots for electrically insulating the stator slot with respect to the hair pins. The groove insulation material can be formed, for example, as insulation paper.The hair pins are arranged in a plurality of hair pin layers in the stator slots. Thus, in the stator grooves, a plurality of hair pins are arranged next to one another in the radial direction. The arrangement of the hair pins is also effected in such a way that the hair pin ends of the hair pins project out of the stator base body in the axial direction of the stator base body. In the case of I pins, the free hairpin ends of the hair pins accordingly protrude from the stator base body on both sides. In the case of U-pins, the free hairpin ends protrude on one side from the stator base body. The bent-over intermediate regions of the hair pins protrude from the other side of the stator base body.Hair pins are used for carrying out the method according to the invention, in which the hair pin ends each have a hair pin end surface delimiting the hair pins in the longitudinal direction of the hair pins. Moreover, a hairpin end side of the hair pins has a concave end contour which extends towards the hairpin end face. The concave end contour ensures that the twisting tool engages in the hairpin end region, in which the twisting tool is prevented from slipping laterally off the hairpin in a positive-locking manner during twistging. The concave end contour can therefore also be referred to as a guide geometry. Preferably, the concave end contour extends as far as the hairpin end surface.The hair pins are preferably made of copper or the like. The hair pins preferably have an electrically insulating coating, for example made of wire enamel or the like. The end regions of the hairpin ends that are to be electrically coupled to one another and to be connected, for example by welding, soldering, crimping or the like, are preferably stripped or have at least no electrically insulating coating in order to ensure electrical contacting of the hairpins. The concave end contour is therefore preferably free of the electrically insulating coating.Preferably, the hairpin ends protruding from the stator base body on a base body side of the stator base body are additionally widened in the radial direction by a tool configured for this purpose. Widening ensures a higher process safety during twisturing and electrical coupling and also mechanical connecting, such as welding, soldering, crimping or the like. The twist can thus take place with particularly low friction, without adjacent hairpin ends sliding on one another. Welding or soldering is improved by widening to the extent that the generation of unintentional welding bridges or soldering bridges to adjacent pairs of hairpin ends is better avoided. Crimping is improved by providing more space for a crimping tool.The twisting tool then makes the twisting of the hairpin ends in the circumferential direction of the stator base body. For this purpose, the twisting tool engages in the concave end contours of the hairpin ends and exerts a force in the circumferential direction on the hairpin ends. The twisting is preferably effected in such a way that directly adjacent hairpin ends are twisted in opposite directions in the circumferential direction. A radial guidance of the hairpin ends at the twist is ensured by the interaction of the twisting tool with the concave end contour, so that in the twisting tool additional radial support devices, which are arranged laterally of the hair pins in the radial direction, can be dispensed with. The winding head of the stator can thus be designed in a particularly space-saving manner.A method according to the invention for producing a stator for an electric machine for driving a motor vehicle has the advantage over conventional methods that a stator can be produced with simple means and in a cost-effective manner, which has a particularly compact winding head. Due to the concave end contours, a direct force introduction from the twisting tool to the hairpin ends can be achieved during twisting, so that additional pressing, guiding and shaping steps can be dispensed with. Moreover, no additional protruding hair pin end regions are therefore required, for example for producing a clamping by the twisting tool, which either take up additional installation space or lead to an additional material consumption due to cutting to length.According to a preferred development of the invention, it can be provided in a method for producing a stator that hair pins having a rectangular cross section are used. In this case, it is preferred that the hairpin width, i.e. an extension of the hairpin wire of the hairpin in the circumferential direction or in the tangential direction, is greater than a hairpin thickness, i.e. an extension of the hairpin wire in the radial direction. The rectangular cross section makes it easier to avoid twisting of the hair pins during twisturing about a longitudinal axis of the hair pins. Furthermore, hair pins with a rectangular cross-section have side surfaces which can be joined more easily to other side surfaces of adjacent hair pin ends. This has the advantage that the production of the stator is further improved with simple means and in a cost-effective manner.It is preferred according to the invention that hair pins are used in which the hair pin end face has a trapezoidal cross section, a pentagonal cross section or a rectangular cross section with a concave side. The concave end contour preferably extends on a longitudinal side of the hair pin, which extends in the thickness direction of the hair pin and in the longitudinal direction of the hair pin. In the case of a rectangular cross section which is not encompassed by the subject matter of the invention, the concave end contour is preferably formed as a uniform recess on the longitudinal side, wherein the concave end contour extends about an axis which is oriented parallel to the thickness direction of the hair pin. In the case of a trapezoidal cross section, the concave end contour is preferably designed as an asymmetrical recess on the longitudinal side, for example by different depths with respect to the longitudinal side without a concave end contour. The concave end contour accordingly extends about an axis which is aligned obliquely with respect to the thickness direction of the hair pin. In the case of a pentagonal cross section, the concave end contour is preferably formed by a concave end contour with a directly adjoining chamfer or the like. In the case of a rectangular cross section with a concave side, the concave end contour is preferably designed as a symmetrical recess on the longitudinal side, wherein the concave end contour extends about an axis which is oriented parallel to the longitudinal direction of the hair pin. This has the advantage that the production of the stator is further improved with simple means and in a cost-effective manner.More preferably, hair pins are used in which two adjacent hair pin end sides of the hair pins have a concave end contour which extends to the same hair pin end surface. The hairpin end face thus preferably has a pentagonal cross section. Further preferably, the two adjacent concave end contours have a common separating edge. Preferably, the two adjacent concave end contours are formed with different widths. This has the advantage that the production of the stator is further improved with simple means and in a cost-effective manner.In a particularly preferred embodiment of the invention, it can be provided in a method for producing a stator that hair pins are used which are designed as U pins, wherein the concave end contours of the hair pin ends face one another. The U-pins have two legs which are connected to one another by an intermediate region bent over by approximately 180°. The U-pins are preferably monolithically formed, such that the two limbs and the intermediate region are produced from an I-pin, for example, by a forming process. The concave end contours are thus arranged completely or at least partially on the inner sides of the legs. This has the advantage that the production of the stator is further improved with simple means and in a cost-effective manner.Preferably, the twisting tool rolls on the concave end contour during twistging. For this purpose, the twisting tool can have, for example, a rolling section which is preferably of convex design. The rolling section preferably has a smaller radius than the concave end contour. By exerting a compressive force from the twisting tool on the concave end section in the circumferential direction or tangential direction, the hairpin can be bent over in such a way that the rolling section rolls on the concave end contour. By engaging the roll-off section in the concave end contour, a deflection of the hair pin in the radial direction is additionally positively prevented. This has the advantage that the production of the stator is further improved with simple means and in a cost-effective manner.According to a preferred embodiment of the invention, the hairpin ends are electrically connected to one another in pairs in a welded position after twistaging, wherein the hairpin ends are held in the welded position by the twisting tool for connection. A welded layer is understood within the scope of the invention to mean a relative position of the hairpin ends, in which these are arranged for the electrically coupled connection in pairs to form the stator winding. A welded layer can also be understood within the scope of the invention to mean a relative position of the hairpin ends in which these are arranged for the purpose of welding, soldering, crimping or the like in pairs to form the stator winding. According to the invention, it can be provided that the stripped hairpin ends of the hair pins contact one another in pairs in the welded position. The holding of the hairpin ends in the welded position is preferably effected by the twisting tool remaining in an end position which the twisting tool assumes directly at the end of the twisting process if no further bending of the hairpins takes place. Accordingly, the holding in the welded position is preferably effected by providing an abutment by the twisting tool by maintaining a compressive force on the concave end contour. Further preferably, the pressure force brings about a mutual pressing of the hairpin ends to be welded to one another in the radial direction. Thus, the subsequent welding process, soldering process, crimping process, or the like is more easily and reliably performed. This has the advantage that the production of the stator is further improved with simple means and in a cost-effective manner.With the twisting tool, during twistting on the concave end contour, a pressure force component in the circumferential direction and a pressure force component in the radial direction are transmitted to the concave end contour. Particularly preferably, the concave end contour is designed in such a way that the transmission of these pressure force components is promoted. Accordingly, the concave end contour is preferably designed such that at least one surface normal at a location of the concave end contour, which is in engagement with the twisting tool during twisturing, has a directional component in the radial direction and a directional component in the circumferential direction or tangential direction. This ensures stable guidance of the hairpin ends and reduces the risk of the hairpin ends slipping off in the radial direction. Thus, further guiding devices of the twisting tool for guiding the hairpin ends during twisting can be dispensed with. This has the advantage that the production of the stator is further improved with simple means and in a cost-effective manner.According to a second aspect of the invention, the object is achieved by an electric machine for driving a motor vehicle. The electric machine has a stator with a stator base body and a stator winding made of hair pins and a rotor mounted rotatably with respect to the stator. According to the invention, the stator is produced by a method according to the invention for producing a stator for an electric machine for driving a motor vehicle.Accordingly, the stator has a stator base body with a multiplicity of stator slots. A plurality of hair pins are arranged in the stator grooves in such a way that the hair pins are arranged in a plurality of hair pin layers in the stator grooves in the radial direction of the stator base body and the hair pin ends of the hair pins protrude from the stator base body in the axial direction of the stator base body. On at least one end face of the stator base body, the hairpin ends are twisted and welded together in pairs, soldered, crimped or the like. On the other end face of the stator base body, the hairpin ends can likewise be twisted and welded together in pairs, soldered, crimped or the like. Alternatively, two hair pins can be connected to one another on an end face of the stator base body by an intermediate region which is formed monolithically with the hair pins. In both cases, the stator has a winding head on each of the two stator end sides. In this way, a polyphase stator winding is formed.The electric machine according to the invention differs from conventional electric machines in the design of the stator, in particular of the hair pins. The hairpin ends of the hair pins, which protrude from the stator base body and are electrically coupled to one another in pairs and are connected to one another in order to form the polyphase stator winding, for example welded, soldered, crimped or the like, each have a hairpin end surface delimiting the hair pins in the longitudinal direction of the hair pins, wherein a hairpin end side of the hair pins has a concave end contour which extends to the hairpin end surface. This configuration of the hairpin ends substantially improves the production of the stator.The electric machine according to the invention for driving a motor vehicle has all the advantages which have already been described with respect to a method for producing a stator for an electric machine for driving a motor vehicle according to the first aspect of the invention. Accordingly, the electric machine according to the invention has the advantage over conventional electric machines that a stator having a particularly compact winding head is provided with simple means and in a cost-effective manner. Due to the concave end contours, a direct force introduction from the twisting tool to the hairpin ends is achieved during twisting, so that additional pressing, guiding and shaping steps have been dispensed with. Moreover, no additional protruding hair pin end regions are therefore required, for example for producing a clamping by the twisting tool, which either take up additional installation space or lead to an additional material consumption due to cutting to length.According to a third aspect of the invention, the object is achieved by a motor vehicle. The motor vehicle has an electric drive system with a traction battery. According to the invention, the electric drive system for driving the motor vehicle has an electric machine according to the invention.The traction battery is configured to provide electrical energy for operating the electric machine.The motor vehicle according to the invention has all the advantages which have already been described with regard to a method for producing a stator for an electric machine for driving a motor vehicle according to the first aspect of the invention and with regard to an electric machine for driving a motor vehicle according to the second aspect of the invention. Accordingly, the motor vehicle according to the invention has the advantage over conventional motor vehicles that a stator having a particularly compact winding head is provided with simple means and in a cost-effective manner. Due to the concave end contours, a direct force introduction from the twisting tool to the hairpin ends is achieved during twisting, so that additional pressing, guiding and shaping steps have been dispensed with. Moreover, no additional protruding hair pin end regions are therefore required, for example for producing a clamping by the twisting tool, which either take up additional installation space or lead to an additional material consumption due to cutting to length.An electric machine according to the invention, a motor vehicle according to the invention and a method according to the invention are explained in more detail below with reference to drawings. They show in each case schematically: FIG. 1 shows a perspective view of a stator for an electric machine according to a preferred first embodiment of the invention, FIG. 2 shows a perspective view of a hairpin of the electric machine from FIG. 1 , FIG. 3 shows a side view of a stator during a first point in time when carrying out a method according to the invention, FIG. 4 shows a side view of a stator during a second point in time when carrying out a method according to the invention, FIG. 5 shows a side view of a stator during a third point in time when carrying out a method according to the invention, FIG. 6 is a perspective view of a hairpin end according to a preferred first embodiment of the invention, FIG. 7 shows a perspective view of a hairpin end according to a second embodiment, which does not comprise the subject matter of the invention, FIG. 8 is a perspective view of a hairpin end according to a preferred third embodiment of the invention, FIG. 9 is a perspective view of a hairpin end according to a preferred fourth embodiment of the invention; and FIG. 10 shows a side view of a preferred embodiment of a motor vehicle according to the invention.Elements with the same function and function are provided with the same reference numerals in each of FIGS. 1, 2, 3, 4, 5, 6, 7, 8, 9 to 10.FIG. 1 schematically shows a stator 1 for an electric machine 2 for driving a motor vehicle 3 according to a preferred first embodiment of the invention in a perspective view. The stator 1 has a stator base body 4 which has a multiplicity of stator slots 5. The stator slots 5 have a slot depth in the radial direction R and extend through the stator base body 4 in the axial direction A. A plurality of hair pins 6, which are designed as U pins, are arranged in the stator slots 5 in such a way that the hair pins 6 are arranged in a plurality of hair pin layers in the stator slots 5 and protrude from the stator base body 4 on both sides in the axial direction A.The hair pins 6 have hair pin ends 7 which protrude from the stator base body 4 on one side in the axial direction A. The hair pins 6 have an electrically insulating coating, wherein no electrically insulating coating is arranged at end regions of the hair pin ends 7. The hairpin ends 7 are twisted in the circumferential direction U and welded together in pairs.FIG. 2 shows a hairpin 6 of the electric machine 2 from FIG. 1 schematically in a perspective illustration. The hair pin 6 is designed as a U-pin and has two parallel legs 13 extending in the longitudinal direction L, which are connected to one another via an intermediate region 14 bent by 180°. The legs 13 are monolithically formed with the intermediate region 14. The hair pin 6 has a rectangular cross section. Two free hair pin ends 7 of the hair pin 6 are each bounded by a hair pin end face 8. On mutually opposite hairpin end sides 9, a concave end contour 10 is formed in each case, which extends as far as the hairpin end face 8.FIG. 3 schematically shows a side view of a stator 1 during a first point in time when carrying out a method according to the invention. At the first time, a stator base body 4 with a plurality of stator slots 5 is provided, in which hair pins 6 are arranged in a plurality of hair pin layers. Free hair pin ends 7 of the hair pins 6 project out of the stator base body 4 in the axial direction A. At end regions of the hairpine ends 7, a concave end contour 10 is formed in each case.FIG. 4 shows the stator 1 during a second point in time when carrying out a method according to the invention schematically in a side view. At the second time, the hairpin ends 7 are widened in the radial direction R. FIG. 5 schematically shows a side view of the stator 1 during a third point in time when carrying out a method according to the invention. At the third time, the hairpin ends 7 are twisted in the circumferential direction U and arranged in a welded position V for welding in pairs.FIG. 6 shows a hairpin end 7 according to a preferred first embodiment of the invention schematically in a perspective view. The hairpin 6 (cf. FIG. 2 ) has a rectangular cross section. The hairpin end 7 is bounded by a hairpin end surface 8 in the longitudinal direction L. On two adjacent hairpin end sides 9, a concave end contour 10 is formed, which extends as far as the hairpin end face 8. The hairpin end face 8 is thus trapezoidal. The concave end contour 10 is curved about an axis which is formed obliquely to the longitudinal direction L.In FIG. 7, a hairpin end 7 according to a second embodiment, which does not comprise the subject matter of the invention, is schematically shown in a perspective view. The hairpin 6 (cf. FIG. 2 ) has a rectangular cross section. The hairpin end 7 is bounded by a hairpin end surface 8 in the longitudinal direction L. On a hairpin end side 9, a concave end contour 10 is formed, which extends as far as the hairpin end surface 8. The hairpin end face 8 is thus rectangular. The concave end contour 10 is curved about an axis which is formed perpendicularly to the longitudinal direction L.FIG. 8 shows a hairpin end 7 according to a preferred third embodiment of the invention schematically in a perspective view. The hairpin 6 (cf. FIG. 2 ) has a rectangular cross section. The hairpin end 7 is bounded by a hairpin end surface 8 in the longitudinal direction L. On a hairpin end side 9, a concave end contour 10 is formed, which extends as far as the hairpin end face 8 and has a decreasing depth in the longitudinal direction L away from the hairpin end face 8. The hairpin end face 8 is thus formed in a rectangular shape with a concave side. The concave end contour 10 is curved about an axis which is formed approximately parallel to the longitudinal direction L.In FIG. 9, a hairpin end 7 according to a preferred fourth embodiment of the invention is schematically shown in a perspective view. The hairpin 6 (cf. FIG. 2 ) has a rectangular cross section. The hairpin end 7 is bounded by a hairpin end surface 8 in the longitudinal direction L. On two adjacent hairpin end sides 9, a concave end contour 10 is formed in each case, which extends as far as the hairpin end face 8 and have a common side edge. The concave end contours 10 have different widths. The hairpin end face 8 is thus pentagonal. One of the concave end contours 10 is curved about an axis which is formed perpendicularly to the longitudinal direction L. The other of the concave end contours 10 is curved about an axis which is formed obliquely to the longitudinal direction L.FIG. 10 shows a preferred embodiment of a motor vehicle 3 according to the invention schematically in a side view. The motor vehicle 3 has an electric drive system 11 having an electric machine 2 according to the invention for driving the motor vehicle 3 and a traction battery 12 for providing electrical energy for operating the electric machine 2.List of reference characters1 Stator 2 Electric machine 3 Motor vehicle 4 Stator base body 5 Stator groove 6 Hairpin 7 Hairpin end 8 Hairpin end surface 9 Hairpin end side 10 Concave end contour 11 Electric drive system 12 Traction battery 13 Limb 14 Intermediate region A Axial direction L Longitudinal direction R Radial direction U Circumferential direction V Welded position

Claims

Method for producing a stator (1) for an electric machine (2) for driving a motor vehicle (3), having: - providing a stator base body (4) having a multiplicity of stator grooves (5), - arranging hair pins (6) in the stator grooves (5) in such a way that the hair pins (6) are arranged in a plurality of hair pin layers in the stator grooves (5) in the radial direction (R) of the stator base body (4) and hair pin ends (7) of the hair pins (6) project out of the stator base body (4) in the axial direction (A) of the stator base body (4), wherein the hair pin ends (7) each have a hair pin end surface (8) delimiting the hair pins (6) in the longitudinal direction (L) of the hair pins (6), wherein a hairpin end side (9) of the hair pins (6) has a concave end contour (10) which extends towards the hairpin end surface (8), and - twist of the hairpin ends (7) in a circumferential direction (U) of the stator base body (4) by engaging a twisting tool in the concave end contours (10) and exerting a twisting force on the hairpin ends (7) by the twisting tool in the circumferential direction (U) in such a way that a radial guidance of the hairpin ends (7) during twist is ensured by the interaction of the twisting tool with the concave end contour (10), wherein, with the twisting tool during twistting on the concave end contour (10), a pressure force component in the circumferential direction (U) and a pressure force component in the radial direction (R) are transmitted to the concave end contour (10).Method according to claim 1, characterised in that hair pins (6) with a rectangular cross-section are used.Method according to claim 2, characterised in that hair pins (6) are used, in which the hair pin end face (8) has a trapezoidal cross-section, a pentagonal cross-section or a rectangular cross-section with a concave side.Method according to one of the preceding claims, characterized in that hair pins (6) are used in which two adjacent hair pin end sides (9) of the hair pins (6) have a concave end contour (10), which extend to the same hair pin end face (8).Method according to one of the preceding claims, characterized in that hair pins (6) are used which are designed as U pins, the concave end contours (10) of the hair pin ends (7) facing one another.Method according to one of the preceding claims, characterized in that the twisting tool rolls on the concave end contour (10) during twistaging.Method according to one of the preceding claims, characterized in that the hairpin ends (7) are connected to one another electrically coupled in pairs in a welded position (V) after the twist, wherein the hairpin ends (7) are held in the welded position (V) by the twisting tool for connection.Electric machine (2) for driving a motor vehicle (3), having a stator (1) with a stator base body (4) and a stator winding made of hair pins (6) and a rotor mounted rotatably with respect to the stator (1), characterized in that the stator (1) is produced by a method according to one of the preceding claims.Motor vehicle (3) having an electric drive system (11) with a traction battery (12), characterized in that the electric drive system (11) has an electric machine (2) according to Claim 8 for driving the motor vehicle (3).

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