Method for assembling an electric traction drive for a motor vehicle

Abstract

The invention relates to a method for assembling an electric traction drive (10) for a motor vehicle, which in the final assembly state has a housing (20) with an electric machine (30) arranged in its interior, wherein the electric machine (30) - a housing-fixed stator (321) and - a rotor (341) arranged radially inside the stator (321) and fixed on a rotor shaft (342) which is mounted on the housing (20) at least in two positions on both sides of the stator (321), includes. The invention is characterized by a special division of the components into two assemblies (61, 62) which are joined axially with the aid of one or two centering mandrels (81, 82) in order to enable a smaller dimensioning of the air gap between the rotor (341) and the stator (321) of the electrical machine (30).

Description

[0001] The invention relates to a method for assembling an electric traction drive for a motor vehicle, which in the final assembly state has a housing with an electric machine arranged in its interior, wherein the electric machine - a housing-mounted stator and - a rotor arranged radially inside the stator, which is fixed on a rotor shaft which is mounted on the housing at least two positions on both sides of the stator.

[0002] Electric traction drives for motor vehicles are becoming increasingly important. While fundamental design characteristics of such drives were once the subject of innovations, fundamental design concepts have now been established, which can, however, be further improved in terms of efficiency and cost-effectiveness.

[0003] Such an assembly method is known from DE 10 2016 223 964 A1.

[0004] Common to known electric traction drives is the arrangement of an electric machine designed as an internal rotor machine within a housing. The stator of the electric machine is fixed to the inner wall of the housing, possibly via a cooling water jacket surrounding it. Inside the stator is a rotor fixed to a rotatably mounted rotor shaft. The rotor shaft usually also serves as the input shaft of an adjacent gearbox, whereby the specific coupling between the rotor shaft and the gearbox can be of a different nature. For example, a drive pinion of the gearbox can be incorporated into an end region of the rotor shaft or joined to said end region as a separate component. To ensure stable operation of the rotor shaft, it is generally considered advantageous to mount the rotor shaft at two positions that are as far apart as possible axially. In particular, the above-mentionedThe generic publication describes the arrangement of two rotor shaft bearings in the immediate vicinity of the axial ends of the rotor shaft. In some embodiments, a third rotor shaft bearing is provided in the axial central region of the rotor shaft, in particular between the rotor and the aforementioned drive pinion.

[0005] The assembly method disclosed in the generic document cited above provides for the provision of a complex, pre-assembled first structural unit consisting of a pot-shaped housing open on one side, in which the rotor shaft, including its first terminal rotor shaft bearing and, if applicable, the middle rotor shaft bearing, is already pre-assembled. This structural unit is then supplemented with the stator. In particular, a housing already containing the stator and open on both sides can be flanged to the pot-shaped housing part of the first structural unit. In a next step, the rotor is then joined to the rotor shaft. In a final step, a housing cover closing the housing is then mounted with the second terminal rotor shaft bearing. This method has the disadvantage that the rotor shaft, which is only supported on one side, has considerable play during the press-on process of the rotor – a process that requires particularly high joining forces.Although the clearance caused by bearing clearance at the location of the bearing(s) is relatively small, it leads to a comparatively large tilting clearance at the free, still unsupported end of the rotor shaft. Here, however, the stator and the rotor, which is to be pressed together with high joining force, are located radially directly adjacent to one another. Contact between the two components during the joining process must be avoided at all costs. This can only be ensured by dimensioning the air gap between stator and rotor accordingly. In particular, the air gap must be chosen to be wide enough that mutual contact between rotor and stator can be ruled out despite the aforementioned tilting clearance. However, a large air gap is detrimental to the efficiency of the electric machine during operation.

[0006] It is the object of the present invention to provide an improved assembly method that allows a small dimensioning of the air gap between the rotor and stator of the electrical machine.

[0007] This object is achieved in conjunction with the features of the preamble of claim 1 by the steps: a) Providing a first structural unit comprising a housing cover which is open axially on one side and has a wall opening in its axial end wall, wherein in the interior of the housing cover - a first housing-side bearing seat in which a first rotor shaft bearing is fixed via its outer bearing shell, and - a stator seat in which the stator of the electrical machine is fixed, b) providing a second structural unit comprising - the hollow rotor shaft, which is open axially on both sides and on which the rotor of the electric machine is fixed and which carries a first shaft-side bearing seat corresponding to the first housing-side bearing seat at a distance from the rotor, and - a housing body which is axially open at least on one side and has a second housing-side bearing seat arranged in a wall opening in an axial end or intermediate wall, in which an outer bearing shell of a second rotor shaft bearing is fixed, the inner bearing shell of which is fixed on a corresponding second shaft-side bearing seat which is arranged on the side of the rotor facing away from the first shaft-side bearing seat and spaced therefrom, wherein the two structural units are fixed in a coaxial alignment relative to one another and with their open sides facing one another on two supports of a joining device which are displaceable relative to one another in the axial direction, namely the first structural unit on a first support and the second structural unit on a second support, c) Join the components by moving the supports towards each other until the rotor shaft engages with its first shaft-side bearing seat in the first rotor shaft bearing in order to whose inner bearing shell is to be fixed force-fitting, the rotor is axially colocated with the stator and the housing cover is fixed to an edge or flange facing it of the housing body, wherein the second carrier carries a second carrier centering mandrel which coaxially penetrates the second rotor shaft bearing and engages positively in the hollow rotor shaft.

[0008] In short, the invention provides for the provision of a first structural unit, which can also be described as a “stator module”, and a second structural unit, which can also be described as a “shaft module”, and for both to be joined with the aid of an external stabilization, whereby any tilting play of the shaft is avoided during the joining process and therefore mutual contact between the rotor and stator is excluded.

[0009] The stator module provided as the first structural unit comprises a pot-shaped housing cover that is open on one side to allow the engagement of components of the shaft module provided as the second structural unit, in particular its rotor shaft and rotor. The first rotor shaft bearing is already pre-installed in the housing cover. In particular, its outer bearing shell is fixed to a first housing-side bearing seat, while its inner bearing shell is still awaiting connection to a corresponding first shaft-side bearing seat. Furthermore, the stator, possibly together with a surrounding water jacket, is also pre-installed.

[0010] The shaft module, provided as a second assembly, comprises a single- or multi-part housing body and the rotor shaft, including the rotor already fixed to it. The rotor shaft is already supported on one side and preferably largely at the end by a second rotor shaft bearing in said housing body. Naturally, this rotor shaft, even loaded with the weight of the rotor, is subject to significant tilting play relative to the housing cover. Designs are conceivable in which the pre-installed rotor shaft is already supported by two rotor shaft bearings (both on the same side of the rotor). This reduces the tilting play problem, but cannot eliminate it.

[0011] Therefore, the shaft module is fixed to a support of a joining device, referred to here as the second support, to which a centering mandrel, referred to here as the second support centering mandrel, is also fixed. This centering mandrel passes coaxially through the second rotor shaft bearing, engages positively with the hollow rotor shaft, and thus centers it perfectly (relative to the housing body). The stator module, on the other hand, is fixed to another support of the joining device, referred to here as the first support. Both supports are aligned relative to each other with high precision. The same applies to the housing parts, which are preferably precisely aligned to the supports via precise alignment contours and fixed to them. Due to the second support centering mandrel, the rotor shaft (including the rotor) cannot escape this precise alignment - despite its bearing clearance.To join the components, the carriers are axially moved toward each other. This allows the joining process to be carried out in a controlled manner and with minimal tolerances, particularly with a minimally dimensioned air gap between the rotor and stator. The inherent tilting play of the rotor shaft caused by the bearing clearance in the second rotor shaft bearing is completely eliminated by the stabilization provided by the second carrier centering mandrel.

[0012] In addition, the joining forces required for the joining process are significantly lower than in the prior art: All that is required is to press the first shaft-side bearing seat onto the inner bearing shell of the first rotor shaft bearing pre-assembled in the stator module. The joining force required for this is significantly lower than that required to press the rotor onto the rotor shaft. This pressing can be performed in isolation during the manufacture of the second assembly or shaft module, away from the stator, which is at risk of collision.

[0013] In the final assembly state, this results in a traction drive whose electric machine can have a significantly smaller air gap between the rotor and stator than would be possible with a state-of-the-art assembly process.

[0014] It is preferably provided that the axial end of the stator facing the second structural unit does not protrude, or protrudes less far, beyond the edge of the housing cover facing the second structural unit (62) than the edge of the housing body facing the first structural unit protrudes beyond the end of the rotor facing the first structural unit. This ensures that the shells of the housing parts, i.e. the housing cover and the housing body, already interact with each other, in particular engage with each other, before the rotor moves into the free space radially inside the stator during the joining process. This creates additional relative centering of the two modules to each other, which further supports the alignment precision already achieved by their fixation on the supports.

[0015] During assembly, the housing cover is preferably pushed into the housing body. This is particularly suitable in preferred cases in which the stator is designed as a component of a stator unit, which comprises the stator and a sleeve surrounding the stator with an open channel structure arranged on its outer side. In the final assembly state, said open channel structure rests against the inner side of the housing body and, together with it, forms a closed water jacket.

[0016] In order to minimize the shear forces acting on the second rotor shaft bearing, which is preferably designed as a floating bearing, during joining, it is preferably provided to support the preassembled rotor axis in the shaft module. For this purpose, in a particularly advantageous embodiment, the second carrier centering mandrel can have a centering section of a first diameter on the side of the second rotor shaft bearing facing the first structural unit and a contact section of a second, larger diameter on the side of the second rotor shaft bearing facing away from the first structural unit (61). The second diameter is larger than the inner diameter of the rotor shaft and the contact section bears against the associated axial end of the rotor shaft.

[0017] A further improvement in the relative centering of the two structural units can be achieved by, as preferably provided, the first carrier carrying a centering mandrel, which is inserted into the hollow rotor shaft during assembly. This stabilizes the rotor shaft at both ends by a centering mandrel inserted into each of them.

[0018] It is advantageous if the primary carrier centering mandrel engages the rotor shaft as early as possible during the joining step, especially before the rotor enters the free space radially within the stator. The moment of entry of the rotor, especially its end which is least stabilized by the secondary carrier centering mandrel, into this free space is particularly critical. Therefore, the dimensions of the elements involved are preferably such that the sum of - the length of a projection of the first carrier centering mandrel (81) facing the second structural unit (62) over the first housing-side bearing seat - and the length of a projection of the rotor shaft (342) facing the first structural unit (61) over the rotor (341) is greater than the distance between - the axial end of the stator (321) facing the second structural unit (62) - and the first housing-side bearing seat.

[0019] In order to minimize the shear forces acting on the first rotor shaft bearing, which is preferably designed as a fixed bearing, during joining, a support is preferably provided here as well. In cases in which a primary carrier centering mandrel is provided, this can be achieved in that the primary carrier centering mandrel has a centering section of a first diameter on the side of the first rotor shaft bearing facing the second structural unit and a contact section of a second, larger diameter on the side of the first rotor shaft bearing facing away from the second structural unit, wherein the second diameter is larger than the inner diameter of the first rotor shaft bearing and the contact section bears axially against an inner bearing shell of the first rotor shaft bearing.

[0020] A further improvement in the relative centering of the two structural units can be achieved by, as preferably provided, the centering mandrels mutually centering and stabilizing each other. This can be achieved by one of the centering mandrels, preferably the primary carrier centering mandrel, being hollow and open on its side facing the other centering mandrel, preferably the secondary carrier centering mandrel. During joining, said hollow centering mandrel is pushed onto said other centering mandrel in a form-fitting manner inside the rotor shaft.

[0021] As already mentioned, the inventive concept can be applied to both single-bearing and double-bearing preassembled rotor shafts. In the latter case, this means that the housing body has a third housing-side bearing seat arranged between the second rotor shaft bearing and the rotor, in which an outer bearing shell of a third rotor shaft bearing is fixed, the inner bearing shell of which is fixed to a corresponding third shaft-side bearing seat on the side of the rotor facing away from the first shaft-side bearing seat, spaced apart from the rotor. The second rotor shaft bearing and / or, if present, the third rotor shaft bearing are preferably designed as floating bearings.

[0022] Further details and advantages of the invention will become apparent from the following specific description and drawings.

[0023] They show: Fig. 1: a sectional view through an embodiment of an electric traction drive for a motor vehicle assembled by means of the method according to the invention and Fig. 2: two process steps of the inventive method for assembling the traction drive according to Fig. 1.

[0024] The same reference numerals in the figures indicate the same or analogous elements.

[0025] Fig. 1 shows a sectional view of an electric traction drive 10, as can be advantageously assembled using the method according to the invention. The traction drive 10 comprises a housing 20, which is constructed from a two-part housing body 22 and a housing cover 24. In the illustrated embodiment, the housing cover 24 is pot-shaped and, in particular, comprises a casing 241 and an end wall 242 having a central wall opening 243, which, in the illustrated final assembly state, is closed by a cap 244 or another closing component, e.g., a rotor position sensor.

[0026] The housing cover 24 is flanged to the housing body 22, which is open axially on both sides and is constructed from two flanged housing body elements 221, 222. The casing 241 of the housing cover 24 extends far into the second housing body element 222 of the housing body 22 facing it and, together with the latter, forms a double wall that can be used as a water jacket, which will be discussed in more detail in the following paragraph. The housing body 22 forms a housing body main chamber 223, which, together with the interior of the housing cover 24, forms that part of the housing interior in which an electric machine 30 is arranged. It also forms a radially offset housing body secondary chamber 224, in which a gear 40 driven by the electric machine 30 via its input gear 401 is arranged. In the final installed state in a motor vehicle, the Fig. 1 left, open side of the housing body 22 is of course closed by further attachments, which are not relevant in the context of the present invention and therefore in Fig. 1 are not shown.

[0027] The electric machine 30 essentially consists of a stator 321 and a rotor 341, which are arranged coaxially to one another. In the illustrated embodiment, the stator 321 is a component of a stator unit 32, which, in addition to the stator 321, also comprises a sleeve 322, which is structurally largely identical to the casing 241 of the housing cover 24 or is formed by it. The sleeve 322 or the casing 241 of the housing cover 24 has an outer, open channel structure 323, which, in the illustrated final assembly situation, together with the wall of the second housing body element 222, forms a water jacket for cooling the electric machine 30.

[0028] The rotor 341 is part of a rotor unit 34, which, in addition to the rotor 341, comprises a rotor shaft 342 on which the rotor 341 is rotationally and axially fixed.

[0029] In the embodiment shown, the rotor shaft 342 is mounted in two rotor shaft bearings, namely the first rotor shaft bearing 51 in the end wall 242 of the housing cover 24 and the second rotor shaft bearing 52 in the first housing body element 221. The first rotor shaft bearing 51 essentially consists of an inner bearing shell 511 and an outer bearing shell 512, between which rolling elements 513 are arranged. The second rotor shaft bearing 52 essentially consists of an inner bearing shell 521 and an outer bearing shell 522, between which rolling elements 523 are arranged. In addition, the rotor shaft 342 has a pinion 343 in the area between the second rotor shaft bearing 52 and the rotor 341, which pinion meshes with an input gear 401 of the transmission 40.

[0030] Fig. 2 shows in both Fig. 2a and Fig. 2b two method steps for the inventive assembly of a drive arrangement 10 according to Fig. 1. Provided are a first assembly 61, also referred to here as stator module 61, and a second assembly 62, also referred to here as shaft module 62. The stator module 61 comprises the housing cover 24 together with the first rotor shaft bearing 51 pre-installed therein and the stator unit 32. The stator module 61 is fixed to a carrier 71 of a joining device not shown in detail. The first carrier 71, only schematically indicated, has alignment contours not shown in detail, which interact with corresponding contours of the stator module 61 to ensure a reliable and reproducible alignment of the stator module 61 relative to the joining device.

[0031] Also fixed to the first carrier 71 or constituting a component thereof is a first carrier centering mandrel 81, which coaxially penetrates the first rotor shaft bearing 51. In the illustrated embodiment, the first carrier centering mandrel 81 essentially has two axial sections, namely a contact section 811 arranged on the first carrier 71 and a centering section 812 merging into the free end of the first carrier centering mandrel 81. The diameter of the centering section 812 is significantly smaller than that of the contact section 811. In particular, the latter is matched to the diameter of the inner bearing shell 511 of the first rotor shaft bearing 51, so that the contact section 811 bears against said inner bearing shell 511 and supports it against axial forces.

[0032] The second structural unit or shaft module 62 comprises the housing body 22, in which the rotor unit 34 is already pre-installed via the second rotor shaft bearing 52. The shaft module 62 is fixed to a second carrier 72 of the joining device. Here, too, alignment contours (not shown) can contribute to a secure and reproducible alignment of the shaft module 62 relative to the joining device and thus, in cooperation with the alignment contours of the first carrier 71, overall to a secure and reproducible relative alignment of the structural units 61, 62 to one another. Also fixed to the second carrier 72 or forming a component thereof is a second carrier centering mandrel 82. This engages coaxially and positively with the open end of the hollow rotor shaft 342. Furthermore, the shape of the free, open end of the rotor shaft 342 corresponds to the centering section 812 of the first carrier centering mandrel 81.

[0033] As indicated by the arrows in Fig. 2a, during a joining step, the two supports 71, 72 are axially displaced towards each other in coaxial alignment of the centering mandrels 81, 82, so that, as in Fig. 2b, the stator module 61 is inserted into the shaft module 62. The secondary carrier centering mandrel 82 stabilizes the rotor shaft 342, which is pre-installed via the second rotor shaft bearing 52 and is comparatively unstable due to its bearing clearance. Additionally, in the illustrated embodiment, the centering section 812 of the primary carrier centering mandrel 81 engages coaxially with the rotor shaft 342 in a form-fitting manner, so that both structural units 61, 62 are optimally centered and stabilized relative to one another. This eliminates the risk of the rotor 341 colliding with the stator 321 during the joining process. However, under normal circumstances, stabilizing the rotor shaft 342 by the secondary carrier centering mandrel 82 is sufficient.

[0034] By further pushing together the supports 71, 72 beyond the stage of Fig. 2b, the building units 61, 62 reach their Fig. 1. The input gear 401 of the gearbox 40 engages the pinion 343 of the rotor shaft 342 in a manner not shown, and the inner bearing shell 511 of the first rotor shaft bearing 51 is pushed onto the corresponding shaft-side bearing seat at the free end of the rotor shaft 342.

[0035] Of course, the embodiments discussed in the specific description and shown in the figures represent only illustrative embodiments of the present invention. In light of the disclosure herein, a broad spectrum of possible variations is available to those skilled in the art. In particular, embodiments can also be realized in which the rotor shaft 342, in the final assembly state, is supported at three bearing positions instead of only two, as shown in the figures. In particular, a third rotor shaft bearing can be provided at a bearing position axially between the pinion 343 and the rotor 342. The corresponding housing-side bearing seat could, in particular, be arranged in the second housing body element 222. Within the scope of the method according to the invention, therefore, only a shaft module 62 that is only slightly modified compared to the illustrated embodiment is provided. Otherwise, reference can be made in full to the above explanations. List of reference symbols 10 Traction drive 20 housings 22 Housing body 221 first housing body element 222 second housing body element 223 Housing body main chamber 224 Housing body side room 24 housing cover 241 coat of 24 242 end wall of 24 243 Wall breakthrough in 242 244 Cap 30 electric machine 32 Stator unit 321 Stator 322 case 323 open channel structure 34 Rotor unit 341 Rotor 342 rotor shaft 343 pinion 40 gearboxes 401 input wheel of 40 51 first rotor shaft bearing 511 inner bearing shell of 51 512 outer bearing shell of 51 513 rolling elements of 51 52 second rotor shaft bearing 521 inner bearing shell of 52 522 outer bearing shell of 52 523 rolling elements of 52 61 first assembly unit / stator module 62 second assembly unit / shaft module 71 first carrier 72 second carrier 81 Primary carrier centering mandrel 811 section of 81 812 Centering section of 81 82 Secondary carrier centering mandrel 821 section of 82 822 Centering section of 82 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 2016 223 964 A1

[0003]

Claims

[1] Method for assembling an electric traction drive (10) for a motor vehicle, which in the final assembly state has a housing (20) with an electric machine (30) arranged in its interior, wherein the electric machine (30) - a housing-fixed stator (321) and - a rotor (341) arranged radially inside the stator (321) and fixed on a rotor shaft (342) which is mounted on the housing (20) at least in two positions on both sides of the stator (321), includes, characterized by the steps: a) providing a first structural unit (61) comprising a housing cover (24) that is open axially on one side, wherein in the interior of the housing cover (24) - a first housing-side bearing seat in which a first rotor shaft bearing (51) is fixed via its outer bearing shell (512), and - a stator seat in which the stator (321) of the electrical machine (30) is fixed, b) providing a second structural unit (62) comprising - the hollow rotor shaft (342) which is open axially on both sides and on which the rotor (341) of the electrical machine (30) is fixed and which carries a first shaft-side bearing seat corresponding to the first housing-side bearing seat at a distance from the rotor (341), and - a housing body (22) which is open axially at least on one side and has a second housing-side bearing seat arranged in a wall opening in an axial end or intermediate wall, in which an outer bearing shell (522) of a second rotor shaft bearing (52) is fixed, the inner bearing shell (521) of which is fixed on a corresponding second shaft-side bearing seat which is arranged on the side of the rotor (341) facing away from the first shaft-side bearing seat at a distance therefrom, wherein the structural units (61, 62) are fixed in a coaxial alignment relative to one another and with open sides facing one another on two supports (71, 72) of a joining device which are displaceable relative to one another in the axial direction, namely the first structural unit (61) on a first support (71) and the second structural unit (62) on a second support (72), c) joining the structural units (61, 62) by sliding the supports (71, 72) towards one another until the rotor shaft (342) engages with its first shaft-side bearing seat in the first rotor shaft bearing (51) in order to fix its inner bearing shell (511) in a force-fitting manner, the rotor (341) is axially colocated with the stator (321) and the housing cover (24) rests against an edge or flange of the housing body (22) facing it, the second support (72) carrying a second support centering mandrel (82) which passes coaxially through the second rotor shaft bearing (52) and engages in a form-fitting manner in the hollow rotor shaft (342). [2] Method according to claim 1, characterized by that the axial end of the stator (321) facing the second structural unit (62) does not protrude, or protrudes less far, beyond the edge of the housing cover (24) facing the second structural unit (62) than the edge of the housing body (22) facing the first structural unit (61) protrudes beyond the end of the rotor (341) facing the first structural unit (61). [3] Method according to one of the preceding claims, characterized bythat the second carrier centering mandrel (82) has a centering section (822) of a first diameter on the side of the second rotor shaft bearing (52) facing the first structural unit (61) and a contact section (821) of a second, larger diameter on the side of the second rotor shaft bearing (52) facing away from the first structural unit (61), wherein the second diameter is larger than the inner diameter of the rotor shaft (342) and the contact section (821) bears against the associated axial end of the rotor shaft (342). [4] Method according to one of the preceding claims, characterized by that the first carrier (71) carries a first carrier centering mandrel (81) which is inserted into the hollow rotor shaft (342) in a form-fitting manner during joining. [5] Method according to claim 4, characterized by that the sum of - the length of a projection of the first carrier centering mandrel (81) facing the second structural unit (62) over the first housing-side bearing seat - and the length of a projection of the rotor shaft (342) facing the first structural unit (61) over the rotor (341) is greater than the distance between - the axial end of the stator (321) facing the second structural unit (62) - and the first housing-side bearing seat. [6] Method according to one of claims 4 to 5, characterized by in that the first carrier centering mandrel (81) has a centering section (812) of a first diameter on the side of the first rotor shaft bearing (51) facing the second structural unit (62) and a contact section (811) of a second, larger diameter on the side of the first rotor shaft bearing (51) facing away from the second structural unit (62), wherein the second diameter is larger than the inner diameter of the first rotor shaft bearing (51) and the contact section (811) bears axially against an inner bearing shell (511) of the first rotor shaft bearing (51). [7] Method according to one of claims 4 to 6, characterized by that one of the centering mandrels (81; 82), in particular the first carrier centering mandrel (81), is hollow and open on its side facing the other centering mandrel (82; 81), in particular the second carrier centering mandrel (82), wherein during the joining process said hollow centering mandrel (81; 82) is pushed positively onto said other centering mandrel (82; 81) inside the rotor shaft (342). [8] Method according to one of the preceding claims, characterized byin that the housing body (22) has in its interior a third housing-side bearing seat arranged between the second rotor shaft bearing (52) and the rotor (341), in which an outer bearing shell (532) of a third rotor shaft bearing (53) is fixed, the inner bearing shell (531) of which is fixed on a corresponding third shaft-side bearing seat on the side of the rotor (341) facing away from the first shaft-side bearing seat at a distance therefrom. [9] Method according to claim 8, characterized by that the second rotor shaft bearing (52) and / or, if present, the third rotor shaft bearing (53) is designed as a loose bearing and the first rotor shaft bearing (51) is designed as a fixed bearing. [10] Method according to one of the preceding claims, characterized byin that the stator (321) is designed as a component of a stator unit (32) which comprises the stator (321) and a sleeve (322) surrounding the stator (321) and having an open channel structure (323) arranged on the outside thereof, wherein said open channel structure (323) in the final assembled state rests against the inside of the housing body (22) and together with this forms a closed water jacket.

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