Electric machine with a stator lamination stack, motor vehicle with an electric machine and method for assembling an electric machine

Abstract

The invention relates to an electric machine (1) with a stator core (2), wherein the stator core (2) is enclosed by a housing (6), and wherein the stator core (2) comprises a rotor (3), and wherein the stator core (2) is configured to receive a winding (7), the winding (7) being arranged between the stator core (2) and the rotor (3), and wherein the stator core (2) is clamped in a stator space (8) of the housing (6). According to the invention, to ensure a secure clamping between the housing (6) and the stator core (2), the stator core (2) has a distinctive surface structure (18) on its first end wall (16) opposite the housing (6). The invention further relates to a motor vehicle with an electric machine (1) and a method for manufacturing an electric machine (1).

Description

The invention relates to an electric machine with a stator laminated core according to the preamble of claim 1.Electric machines with stator laminated cores are known in principle. This is an electric machine which has a stator in the form of the stator laminated core and a rotor, wherein the stator is designed to include the rotor. The stator consists of numerous individual sheets which are arranged stacked one on top of the other. Usually, the stator is surrounded by a housing. The torque delivered by the rotor must be supported via the stator. The support is usually realized with the aid of a so-called transverse press fit, wherein, for forming the transverse press fit, the stator has an oversized dimension with respect to a housing opening in which it is arranged. The stator is joined thermally, i.e. with the aid of a temperature difference between the stator and the housing, and / or with the application of a longitudinal force into the housing. However, the cross-press fit produces mechanical stresses in the stator laminated core, which have a negative effect on consumption of the electric machine. In order to prevent the radial mechanical stresses in the stator laminated core, it is also possible to clamp the stator laminated core axially with the aid of long screws, wherein, however, in this case setting occurs due to joints formed between the individual individual sheets, with the result that the prestressing force of the screws is reduced and therefore the transmittable torque of the electric machine is also reduced.The laid-open specification DE 10 2020 119 442 A1 discloses an assembly method for an assembly which comprises a stator laminated core and a housing part of an electric machine connected thereto. The stator laminated core is screwed to the housing part, wherein the stator laminated core has been provided with a type of microtoothing for axial securing in the housing part by laser cutting.The published patent application DE 10 2020 106 798 A1 discloses an electric machine for motor vehicles, the fluid-cooled stator of which, which is separated in a fluid-tight manner from the rotor thereof, is constructed from individual sheets. The individual sheets are connected to a stator back by die-bonding or laser welding. Four clamping screws offset by 90° with respect to one another in pairs are provided.The laid-open specification DE 10 2014 018 745 A1 describes an electric machine for a motor vehicle having a bearing which is laser welded to the housing in order to reduce the production costs.The published patent application DE 10 2016 222 385 A1 discloses an electric machine whose stator windings consist of conductor bars which are laser-welded to one another at their ends.The laid-open specification EP 4 160 874 A1 discloses a two-part electric machine for driving a hybrid or purely battery-operated vehicle, the shape conductors of which are melted at points by laser.The laid-open specification DE 10 2019 114 958 A1 discloses an electric machine for driving a motor vehicle, wherein a stator and / or a rotor rotatably accommodated in the stator have surface structures on their surfaces formed facing one another, which surface structures reduce an aerodynamic resistance during operation of the electric machine. The surface structures are formed with the aid of a laser.The laid-open specification DE 10 2017 216 406 A1 discloses a laser-optical arrangement for laser interference processing of surfaces of all kinds.The object of the present invention is to provide an improved electric machine having a stator laminated core. Furthermore, the objects of the invention are to specify an improved motor vehicle having an electric machine and a method for assembling an electric machine.The object is achieved according to the invention by an electric machine having a stator laminated core having the features of patent claim 1. The further objects are achieved according to the invention by a motor vehicle having an electric machine with the features of claim 10 and a method for mounting an electric machine with the features of claim 11. Advantageous embodiments with expedient and non-trivial developments of the invention are specified in the respective dependent claims.A first aspect of the invention relates to an electric machine having a stator laminated core, wherein the stator laminated core is surrounded by a housing, and wherein the stator laminated core is designed to comprise a rotor. The stator laminated core is designed to receive a winding, wherein the winding is arranged between the stator laminated core and the rotor. The stator laminated core is arranged in a clamped manner in a stator space of the housing. According to the invention, in order to bring about a secured connection between the housing and the stator laminated core, the stator laminated core has a pronounced surface structure on its first end wall opposite the housing. It should be mentioned at this point that the term "predictable surface structure" is understood to mean a surface structure which changes a surface of the first end wall in such a way that it has a friction which is sufficient to bring about sufficient friction between the surface structure and the housing, in particular static friction, depressions and elevations in the form of grooves or craters, or the like. The advantage of the invention can be seen in the fact that the stator laminated core has improved contact with the housing on account of the predicted surface structure, with the result that a required bracing force, for example a screw force, and therefore the required mechanical stresses are reduced. The electric machine according to the invention thus has a high degree of efficiency over a high running time.The surface structure is advantageously produced with the aid of a laser. The advantage of machining the stator laminated core with a laser, thus with a laser technique, can be seen in the fact that the surface structure can be introduced in a defined manner. It can be formed at specific locations on the first end wall and / or it can be formed at any desired depth with the aid of the laser.In a preferred embodiment of the electric machine, the stator laminated core is clamped by means of a clamping means between a stop formed in the stator space and the housing along an axis of rotation of the electric machine. This brings about a further increase in the reduction of the sets. In particular, if the clamping means is designed in the form of a clamping screw which extends along the axis of rotation, thus axially through the stator laminated core, reliable operation of the electric machine is ensured at a high efficiency and over an entire operating range.The clamping of the stator laminated core between the housing and the stop can be realized in a simple manner by a shoulder being formed in the housing, which shoulder lies opposite the first end wall for bearing. In other words, this means that the stator laminated core can be supported on the shoulder in the axial direction, and in particular this shoulder can have a receiving opening for the secure reception of the clamping means, into which it is introduced and is secured there, for example, with the aid of a force fit and / or form fit.The stator laminated core is advantageously formed from a harder material than at least one housing surface of the housing formed opposite the first end wall. If the stator laminated core is braced with its first end face, thus on the end face against a softer surface, in particular an aluminum surface, the surface structure is transferred quasi like a negative to the softer surface, in particular the housing surface, on account of the different material characteristics of the stator laminated core, which is made in particular of steel, and the housing surface, which is made in particular of aluminum.The stator laminated core is further advantageously coated, in particular with a baking lacquer. Normally, a prestressing force loss of a clamping screw clamping the stator laminated core is already brought about by the construction of the individual laminations of the stator laminated core. Electrical sheets consist of sheet metal which is covered with a thin layer of paint for reasons of insulation. From a certain temperature, a so-called glass transition temperature, the lacquer expands thermally to a great extent, whereby the individual sheet and thus the stator laminated core axially enlarge relative to the clamping screw. As a result of this enlargement, the clamping screw is plastically deformed or, in other words, elongated, as a result of which a lower prestressing force is produced after a cooling process. This effect is enhanced in the case of the so-called baking lacquer coating. The baking lacquer coating is provided for the adhesion of the individual sheets, the coating being stronger than the conventional insulating lacquer. Thus, the length of the clamping screw is more pronounced here. This elongation can be counteracted with the electric machine according to the invention even when using the baking lacquer coating, in that the required prestressing force of the clamping screw can be considerably reduced by the laser structuring.A second aspect of the invention relates to a motor vehicle having an electric machine, wherein, according to the invention, the electric machine is designed according to one of Claims 1 to 9. The advantage is to be seen in the fact that a motor vehicle is provided which overall has a high operating reliability.A third aspect relates to a method for mounting an electric machine having a stator laminated core, wherein the stator laminated core is surrounded by a housing, and wherein the stator laminated core is arranged such that it is clamped in a stator space of the housing. According to the invention, in a first step for producing a predictive surface structure, the stator laminated core is machined by means of a laser on its first end wall which is to be arranged opposite a housing surface of the housing, and in a second step the stator laminated core is clamped in the housing by means of clamping means in the form of high-strength clamping screws which are arranged so as to penetrate the stator laminated core completely along an axis of rotation of the electric machine. The advantage of the method according to the invention is to be seen in the fact that an electric machine of a high performance class can be provided, the stator laminated core of which is reliably axially clamped, wherein a necessary required prestressing force is ensured over a large difference in length of the stator laminated core with the aid of the high-strength clamping screws to be designed for each application, over the entire operating range of the electric machine.An additional component in the form of a friction element could also be arranged on the first end wall between the first end wall and the housing surface, which is coated with small high-strength elements, for example, to roughen the surfaces opposite it. As a result, the necessary prestressing force of the clamping screws could be reduced, as a result of which safe operation of the electric machine over the entire operating range could likewise be ensured.However, the method according to the invention can be used to mount an electric machine in a cost-effective manner, which, without the use of the additional component, which would require a further mounting step, allows reliable operation of the electric machine over its entire operating range.Overall, costs of the electric machine and its assembly effort can be reduced. Their installation space requirement and their complexity can likewise be reduced.Further advantages, features and details of the invention are evident from the following description of preferred exemplary embodiments and with reference to the drawing. The features and combinations of features mentioned above in the description and the features and combinations of features mentioned below in the description of the figures and / or shown alone in the figures can be used not only in the respectively specified combination but also in other combinations or alone without departing from the scope of the invention. Identical or functionally identical elements are assigned identical reference numerals. The following are shown: FIG. 1 shows a longitudinal section of an electric machine with a stator according to the prior art, FIG. 2 shows a perspective illustration of a stator of an electric machine according to the invention, and FIG. 3 shows a longitudinal section of the electric machine according to the invention with the stator.An electric machine 1 with a stator laminated core 2 for a motor vehicle according to the prior art is constructed as depicted in FIG. 1. The electric machine 1 has a rotor 3 which is surrounded by the stator laminated core 2. The stator laminated core 2 is designed in the form of a stator of the electric machine 1, constructed from individual laminations 4 which are stacked one on top of the other or, in other words, are arranged lying next to one another.The electric machine 1 is designed in the form of a so-called internal rotor, wherein the rotor 3 is mounted rotatably in a housing 6 of the electric machine 1 with the aid of bearings 5 relative to the stator 4, which is designed to include the rotor 3, about an axis of rotation 24 of the electric machine 1. A winding 7 is arranged between the stator laminated core 2 and the rotor 3. The stator laminated core 2 and the winding 7 are accommodated in a stator space 8 of the housing 6, wherein coolant can flow through the stator space 8.In order to avoid a transfer of the coolant, which is used for cooling the electric machine 1, from the stator chamber 8 into a rotor chamber 9 of the electric machine 1 receiving the rotor 3, the stator chamber 8 and the rotor chamber 9 are designed to be separated from one another with the aid of a can 10. In other words, the stator chamber 8, which can also be referred to as a wet chamber, is separated from the rotor chamber 9, which can also be referred to as a dry chamber, by means of the split tube 10.The can 10, which is designed in the form of a hollow cylinder, has a support element 11 with a sealing element 12 each at its two ends for the secure separation of the two spaces 8, 9.The electric machine 1 embodied according to FIG. 1 is embodied to support a torque output by the rotor 3 having a so-called press fit between the housing 6 and the stator laminated core 2. For this purpose, the stator laminated core 2 has, prior to assembly, an excess in relation to a housing opening 13 forming the stator space 8 and the rotor space 9, and is joined into the housing 6 in the event of a temperature difference formed between the stator laminated core 2 and the housing 6 and / or by applying a longitudinal force.The press fit, in particular transverse press fit, exerts voltages in the stator laminated core 2 which have a negative effect on an efficiency of the electric machine 1.FIG. 2 illustrates a perspective illustration of the stator laminated core 2 of an electrical machine 1 according to the invention. The stator laminated core 2 is of hollow cylindrical design and has slot-shaped receiving openings 15 on its inner surface 14, in which the winding 7 can be arranged. The stator laminated core 2 has a first end wall 16 and a second end wall 17 formed facing away from the first end wall 16. In other words, this means that the first end wall 16 is not smooth, but rather has the predicted surface structure 18 for producing friction, in particular static friction, depressions and elevations in the form of grooves or craters, or the like. This surface structure 18 is produced with the aid of a laser. The second end wall 17 could also have the predicted surface structure 18.In FIG. 3, the machine 1 according to the invention with the stator laminated core 2 is shown. FIG. 2 illustrates a longitudinal section. The stator laminated core 2 is arranged with its first end wall 16 on a shoulder 19 of the housing 2 opposite thereto, wherein a contact is formed between the first end wall 16 and a housing surface 20 of the housing 6, wherein in the present exemplary embodiment the housing surface 20 is formed on the shoulder 19 which belongs to the housing 6.The shoulder 19 has a further receiving opening 22 for receiving a clamping means 21. The stator laminated core 2 has an opening 25 for receiving the clamping means 21, in which opening the clamping means 21 is positioned. With the aid of the clamping means 21, which is preferably designed in the form of a clamping screw, the stator laminated core 2 is clamped between a stop 23 arranged opposite its second end wall 17 and the shoulder 19, wherein with the aid of the clamping means 21, frictional contact is produced between the first end wall 16 and the housing surface 20 on account of the protruding surface structure 18. Advantageously, the stop 23 is designed in the form of a head of the clamping means 21, in the present exemplary embodiment in the form of the screw head.The stator laminated core 2 is preferably produced from a harder material, which is preferably steel, than the housing surface 20, which is preferably produced from an aluminum. Likewise, the entire housing 6 or only the shoulder 19 could be made of aluminum. The advantage of the different materials can be seen in the fact that the harder material can penetrate into the softer material when the clamping means 21 is caused to be prestressed and thus realizes a secured connection between the stator laminated core 2 and the housing 6.In addition, the stator laminated core 2 can be coated, in particular with a lacquer, in particular in the form of a baking lacquer.The electric machine 1 according to the invention is preferably produced with the aid of a method according to the invention, wherein the method for mounting the electric machine 1 with the stator laminated core 2 is characterized in that, in a first step for producing the predictive surface structure 18, the stator laminated core 2 is machined with the aid of a laser at its first end wall 16 which is to be arranged opposite the housing surface 20, and, in a second step, the stator laminated core 2 is clamped in the housing 6 with the aid of the clamping means 21, which are designed in the form of high-strength clamping screws which are arranged so as to penetrate the stator laminated core 2 completely. For this purpose, the stator laminated core 2 has openings 25 for each of the clamping screws to fully penetrate the clamping screws.List of reference characters1 Electric machine 2 Stator laminated core 3 Rotor 4 Individual sheet 5 Bearing 6 Housing 7 Winding 8 Stator chamber 9 Rotor chamber 10 Can 11 Carrier element 12 Sealing element 13 Housing opening 14 Inner surface 15 Receiving opening 16 First end wall 17 Second end wall 18 Surface structure 19 Shoulder 20 Housing surface 21 Clamping means 22 Further receiving opening 23 Stop 24 Axis of rotation 25 OpeningReferences included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedDE 10 2020 119 442 A1

[0003] DE 10 2020 106 798 A1

[0004] DE 10 2014 018 745 A1

[0005] DE 10 2016 222 385 A1

[0006] EP 4 160 874 A1

[0007] DE 10 2019,114 958 A1

[0008] DE 10 2017 216 406 A1

[0009]

Claims

Electric machine (1) having a stator laminated core (2), wherein the stator laminated core (2) is surrounded by a housing (6), and wherein the stator laminated core (2) is designed to comprise a rotor (3), and wherein the stator laminated core (2) is designed to accommodate a winding (7), wherein the winding (7) is arranged between the stator laminated core (2) and the rotor (3), and wherein the stator laminated core (2) is arranged such that it is clamped in a stator space (8) of the housing (6), characterized in that, in order to bring about a secured clamping between the housing (6) and the stator laminated core (2), the stator laminated core (2) has a predictive surface structure (18) on its first end wall (16) opposite the housing (6).Electric machine (1) according to Claim 1, characterized in that the surface structure (18) is produced with the aid of a laser.Electric machine (1) according to Claim 1 or 2, characterized in that the stator laminated core (2) is clamped by means of a clamping means (21) between a stop (22) formed in the stator space (8) and the housing (6) along an axis of rotation (24) of the electric machine (1).Electric machine (1) according to Claim 3, characterized in that the clamping means (21) is designed in the form of a clamping screw which extends through the stator laminated core (2) along the axis of rotation (24).Electric machine (1) according to one of the preceding claims, characterized in that the housing (6) has a shoulder (19) which is formed opposite the first end wall (16) for bearing.Electric machine (1) according to Claim 5, characterized in that the shoulder (19) has a further receiving opening (22) for the secure reception of the clamping means (21).Electric machine (1) according to one of the preceding claims, characterized in that the stator laminated core (2) is formed from a harder material than at least one housing surface (20) of the housing (6) formed opposite the first end wall (16).Electric machine (1) according to Claim 7, characterized in that the stator laminated core (2) is produced from steel and at least the housing surface (20) is produced from aluminium.Electric machine (1) according to one of the preceding claims, characterized in that the stator laminated core (2) is coated.Motor vehicle having an electric machine (1), wherein the electric machine (1) is designed according to one of Claims 1 to 9.Method for mounting an electric machine (1) with a stator laminated core (2), wherein the stator laminated core (2) is surrounded by a housing (6), and wherein the stator laminated core (2) is arranged in a clamped manner in a stator space (8) of the housing (6), characterized in that, in a first step for producing a predictive surface structure, the stator laminated core (2) is machined by means of a laser on its first end wall (16), which is to be arranged opposite a housing surface (20) of the housing (6), and, in a second step, the stator laminated core (2) is clamped in the housing by means of clamping means (21) in the form of high-strength clamping screws, which are arranged in a fully penetrating manner along an axis of rotation (24) of the electric machine (1).Method according to Claim 11, characterized in that the electric machine (1) is designed according to one of Claims 1 to 9.

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