Method for mounting an electric traction drive

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 inside it, wherein the electric machine (30) - a housing-mounted stator (321) and - a rotor (341) arranged radially inside the stator (321), which is fixed on a rotor shaft (342) which is supported at least two positions on both sides of the stator (321) on the housing (20). The invention is characterized by a special division of the components into two assemblies (61, 62) which are axially joined together with the aid of one or two centering mandrels (81, 82) in order to enable a smaller dimensioning of the air gap between rotor (341) and stator (321) of the electric 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] Such an assembly method is known from DE 10 2016 223 964 A1.

[0003] DE 10 2016 206 479 A1 relates to a method for assembling a drive unit for a vehicle, wherein the drive unit has an electric machine and a transmission device, comprising the following method steps: Assembly of the gear device in a gear housing; axially passing an assembly mandrel through a recess in the gear housing and through a pinion shaft designed as a hollow shaft, which is rotatably mounted in the gear housing; centering a rotor shaft designed at least partially as a hollow shaft on the assembly mandrel; axially sliding a rotor of the electrical machine onto the rotor shaft; axially inserting the rotor shaft into the pinion shaft, wherein a spline on the rotor shaft engages a spline on the pinion shaft; axially sliding a stator of the electrical machine onto the rotor of the electrical machine and fixing the stator to the gear housing; removing the assembly mandrel and closing the recess in the gear housing with a cover.

[0004] US 2020 / 0 230 754 A1 shows a device for assembling a turbine engine, which is configured to center a shaft of a second module relative to a longitudinal axis of a hollow hub placed in front of a first module. The first module comprises a longitudinal cavity opening toward the front of the hollow hub and extending through the first module to a rear end. The shaft is configured to be inserted into the longitudinal cavity. The device comprises a centering element and a guide tube. The centering element is configured to be inserted into the hollow hub. The guide tube is configured to enter at least a portion of the longitudinal cavity of the first module. The device is arranged such that the guide tube slides within the centering element. The disclosure also relates to the assembly formed by the device and a calibration gauge, as well as to an assembly method using the same.

[0005] DE 10 2021 129 779 A1 relates to a housing for a transmission with an electric drive motor, comprising at least the following components: a one-piece first receptacle for an electric drive motor, wherein the electric drive motor comprises a stator and a rotor shaft with a rotor winding; and a one-piece second receptacle for a transmission, wherein the transmission comprises a first gear stage with a first gear pinion on a transmission input shaft, wherein the second receptacle comprises a first bearing receptacle for a first transmission bearing and a second bearing receptacle for a second transmission bearing, wherein a rotor shaft received in the first receptacle and the first transmission pinion received in the second receptacle are aligned with one another on a common axis of rotation by means of the transmission bearings in the bearing receptacles.The housing is primarily characterized by the fact that the first housing includes a third bearing housing for a rotor bearing that supports the rotor shaft. The one-piece housing ensures precise alignment of the rotor shaft and the transmission input shaft, thus reducing humming.

[0006] DE 10 2022 114 473 A1 relates to an electric axle drive train for an electrically or hybrid-operated motor vehicle comprising an electric machine and a transmission arrangement operatively connected to the electric machine, wherein the electric machine has a stator and a rotor which is rotatable relative to the stator and which is connected in a rotationally fixed manner to a rotor shaft which is rotatably mounted via a rolling bearing arrangement and axially passes through the electric machine, wherein the integrally formed rotor shaft extends axially into the transmission arrangement and the rotor shaft is connected to at least one torque-transmitting transmission element, wherein the rolling bearing arrangement comprises a fixed bearing and a loose bearing, wherein the fixed bearing is positioned axially between the torque-transmitting transmission element and the rotor, while the loose bearing is arranged at the distal end of the rotor shaft facing away from the transmission element.

[0007] DE 10 2021 211 080 A1 relates to an electric drive device comprising an electric motor part and a transmission part. A rotor shaft is coupled to a transmission input shaft within a connecting region such that torque is transmitted. An axial connection is formed between the rotor shaft and the transmission input shaft in the connecting region. The invention further relates to the use of the electric drive device in an electrically powered vehicle, in particular an electrically powered passenger car or an electrically powered light commercial vehicle.

[0008] 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.

[0009] 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.

[0010] 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, are 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.

[0011] 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.

[0012] 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 body open axially on both sides, in the interior of which - a first housing-side bearing seat in which a first rotor shaft bearing is fixed via its outer bearing shell, and - an axially terminal 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 cover with a second housing-side bearing seat arranged in a wall opening in its axial end wall, in which an outer bearing shell of a second rotor shaft bearing is fixed, the inner bearing shell of which is fixed to a corresponding second shaft-side bearing seat on the side of the rotor facing away from the first shaft-side bearing seat, spaced therefrom, wherein the structural units are fixed in a coaxial alignment relative to one another and with the first rotor shaft bearing and the first shaft-side bearing seat facing one another on two supports of a joining device, namely the first structural unit on a first support and the second structural unit on a second support, c) Joining the structural units by sliding the supports towards one another until the rotor shaft engages with its first shaft-side bearing seat in the first rotor shaft bearing in order to fix its inner bearing shell in a force-fitting manner, the rotor is axially colocated with the stator and the housing cover rests against an edge of the housing body facing it, wherein the first support carries a first centering mandrel which coaxially penetrates the first rotor shaft bearing and onto which the hollow rotor shaft is pushed in a form-fitting manner during the joining process.

[0013] In short, the invention provides for the provision of a first structural unit, which can also be described as a "housing module", and a structural unit, which can also be described as a "shaft module", and for both to be joined with the aid of an external centering and stabilizing device, whereby any tilting play of the shaft is avoided during the joining process and therefore mutual contact between the rotor and stator is excluded.

[0014] The housing module provided as the first structural unit comprises a housing body that is open on both sides, both to allow the insertion of the shaft module provided as the second structural unit and to provide access for the centering mandrel, which will be described in more detail later. The first rotor shaft bearing is already pre-installed in the housing body. 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.

[0015] The shaft module, provided as a second assembly, comprises a housing cover 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 via a second rotor shaft bearing in the said housing cover. Naturally, this rotor shaft, which is still loaded with the weight of the rotor, is subject to considerable tilting play relative to the housing cover.

[0016] Therefore, the housing module is fixed to a first support of a joining device, to which a centering mandrel is also fixed, which coaxially penetrates the first rotor shaft bearing and extends its free end towards the shaft module. This is fixed to an opposite second support of the joining device. Both supports are moved axially towards one another to join the components, with the centering mandrel engaging positively in the entry opening of the hollow rotor shaft at a very early stage of the joining process, thereby stabilizing the shaft coaxially to the rotor shaft bearing and thus also the rotor coaxially to the stator. The rest of the joining process can then be continued in a controlled manner and with minimal tolerances, in particular with a minimally dimensioned air gap between the rotor and stator.The tilting play of the rotor shaft, which is still present due to the bearing clearance in the second rotor shaft bearing, is completely suppressed by the stabilization using the centering mandrel.

[0017] 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 housing 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.

[0018] 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.

[0019] In order to ensure that the centering mandrel already engages in the rotor shaft in a stabilizing manner before the rotor and stator come into direct radial proximity to each other during the joining process, in which a remaining tilting play of the rotor shaft could lead to mutual contact, it is preferably provided that the sum of - the length of a projection of the first centering mandrel facing the second structural unit over the first housing-side bearing seat - and the length of a projection of the rotor shaft facing the first structural unit over the rotor is greater than the distance between - the axial end of the stator facing the second structural unit - and the first housing-side bearing seat.

[0020] The greater the difference between the said sum and the said distance, the more robust the joining process. However, as the said difference increases, the required joining paths also increase, so the expert will find a healthy compromise between minimizing joining paths and maximizing process robustness.

[0021] As mentioned, the joining forces occurring in the method according to the invention are significantly lower than those in the prior art. Nevertheless, the first rotor shaft bearing in particular is exposed to a not inconsiderable shear force between its inner and outer bearing shell when the first shaft-side bearing seat is pressed into the inner bearing shell of the first rotor shaft bearing. In a further development of the invention, it is therefore provided that the first 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.

[0022] In this further development, the centering mandrel fulfills a dual function: firstly, to stabilize the rotor shaft as explained above, and secondly, to support the inner bearing shell of the first rotor shaft bearing against the axial force occurring when the first shaft-side bearing seat is inserted. On the side of the first rotor shaft bearing facing the first carrier, the centering mandrel is thickened and supports the first rotor shaft bearing, at least its inner bearing shell. Radially within the first rotor shaft bearing and on its side facing the shaft module, however, the profile of the centering mandrel is adapted to the smallest clear width of the area of ​​the hollow interior of the rotor shaft facing it. This smallest clear width is preferably located at the inlet of the hollow rotor shaft facing the housing module.

[0023] As a special measure in the context of this embodiment, the contact section of the centering mandrel is preferably provided with an undercut. This means that the contact section has an annular groove in the transition area to the centering section, the inner diameter of which corresponds to the outer diameter of the centering section and the outer diameter of which is naturally smaller than the diameter of the inner shell of the first rotor shaft bearing. Such an embodiment allows the first shaft-side centering seat to be placed slightly axially spaced (up to the depth of said annular groove) behind the axial end of the rotor shaft. In other words, in this embodiment, the tip of the rotor shaft can protrude slightly axially beyond the first rotor shaft bearing in the final assembly position.

[0024] The free end of the centering pin, facing the shaft module, is preferably pointed. The tip provides a guide bevel that facilitates the insertion of the centering pin into the hollow rotor shaft.

[0025] In a preferred development of the invention, it can be provided that the second carrier of the joining device also carries a centering mandrel, which is referred to here as the second centering mandrel and which engages in a form-fitting manner from the other side into the hollow interior of the rotor shaft during joining. In particular, it can engage in the interior of the rotor shaft even before the actual joining process. For example, the second centering mandrel can be fixed to the second carrier of the joining device, with the hollow rotor shaft of the shaft module fixed to the second carrier being slipped onto said second centering mandrel. Unlike the first centering mandrel in the housing module, the second centering mandrel in the shaft module already has a stabilizing effect in this pre-joining state and already ensures an initial, at least partial suppression of the tilting play of the rotor shaft in the second rotor shaft bearing.

[0026] Embodiments with two centering mandrels can be further optimized by the interaction of the centering mandrels not only with the rotor shaft but also with each other. For this purpose, one of the centering mandrels can be hollow and open on the side facing the other centering mandrel, wherein, during joining, said hollow centering mandrel is pushed positively onto said other centering mandrel inside the rotor shaft. Preferably, it is the second centering mandrel that is hollow, and it is preferably the first centering mandrel onto which it is pushed positively inside the rotor shaft. Of course, such a design presupposes that the minimum clear widths at the two ends of the rotor shaft are different.In particular, in the described embodiment, the end of the rotor shaft interacting with the first centering mandrel has a smaller minimum clear width than the end of the rotor shaft facing the second centering mandrel.

[0027] As mentioned at the beginning, embodiments with three rotor shaft bearings are known. In addition to the two end rotor shaft bearings, i.e. the above-mentioned first rotor shaft bearing and the above-mentioned second shaft bearing, a third rotor shaft bearing can be provided in an axially central region. For the housing module provided before the joining process, i.e. the first structural unit, this means that the housing body has a third housing-side bearing seat arranged between the first rotor shaft bearing and the stator. For the shaft module provided before the joining process, i.e. the second structural unit, it means that the rotor shaft has a corresponding third shaft-side bearing seat between the first shaft-side bearing seat and the rotor, on which third rotor shaft bearing is fixed via its inner bearing shell.In other words, the third rotor shaft bearing is already mounted on the rotor shaft prior to the joining process. During the joining process, its outer bearing shell is inserted into the third housing-side bearing seat simultaneously with the first shaft-side bearing seat being pressed into the inner bearing shell of the first rotor shaft bearing.

[0028] To stabilize the inner bearing shell of the third rotor shaft bearing during the joining process, the third shaft-side bearing seat can have a step that supports it against the joining force. Nevertheless, there is a risk of damage to the third rotor shaft bearing if excessive joining forces are applied. Therefore, it is preferred that the third housing-side bearing seat and the third rotor shaft bearing be dimensioned to be joined with a loose fit relative to each other. This means that the joining forces required to join the third rotor shaft bearing are significantly lower than those required to join the well-supported first rotor shaft bearing.

[0029] The housing module is preferably designed such that the stator protrudes beyond the edge of the housing body facing the shaft module, and the housing cover is correspondingly pot-shaped. Such a design has proven particularly useful for embodiments in which the stator is formed as part of a stator unit, which comprises the stator and a sleeve surrounding the stator with an open channel structure arranged on its outer side. Said open channel structure, in the final assembly state, rests against the inner side of the housing body and, together with it, forms a closed water jacket.

[0030] Further features and advantages of the invention will become apparent from the following specific description and drawings.

[0031] They show: Fig. 1 a sectional view through a first embodiment of an electric traction drive for a motor vehicle mounted by means of the method according to the invention, Fig. 2 a sectional view through a second embodiment of an electric traction drive for a motor vehicle mounted by means of the method according to the invention, Fig. 3 two process steps of the method according to the invention for assembling the traction drive according to Fig. 1, Fig. 4 two process steps of the method according to the invention for assembling the traction drive according to Fig. 2.

[0032] The same reference numerals in the figures indicate the same or analogous elements.

[0033] 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.

[0034] 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 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 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.

[0035] The electric machine 30 essentially consists of a stator 321 and a rotor 341, which are arranged coaxially with one another. In the illustrated embodiment, the stator 321 is part of a stator unit 32, which, in addition to the stator 321, also includes a sleeve 322. The sleeve 322 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 and the casing 241 of the housing cover 24, forms a water jacket for cooling the electric machine 30.

[0036] 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.

[0037] In the embodiment shown, the rotor shaft 342 is mounted in two rotor shaft bearings, namely the first rotor shaft bearing 51 in the first housing body element 221 and the second rotor shaft bearing 52 in the end wall 242 of the housing cover 24. 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 first rotor shaft bearing 51 and the rotor 341, which pinion meshes with an input gear 41 of the transmission 40.

[0038] Fig. 2 shows an alternative embodiment of an electric traction drive for a motor vehicle, which differs from the embodiment according to Fig. 1. In addition, the above-mentioned Fig. 1 What has been said is referred to.

[0039] Fig. 3 shows 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 the housing module 61, and a second assembly 62, also referred to here as the shaft module 62. The housing module 61 comprises the housing body 22 including the first rotor shaft bearing 51, stator unit 32, and gear 40 pre-installed therein. The housing module 61 is fixed to a carrier 71 of a joining device not shown in detail.

[0040] Also fixed to the first carrier 71 or constituting a component thereof is a first centering mandrel 81, which coaxially penetrates the first rotor shaft bearing 51. In the illustrated embodiment, the first centering mandrel 81 essentially has two axial sections, namely a contact section 811 arranged on the first carrier 71 and a centering section 812 that merges into the free end of the 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. At the transition between the contact section 811 and the centering section 812, the centering mandrel 81 is provided with a relief 813.

[0041] The second assembly or shaft module 62 comprises the housing cover 24, 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 support 72 of the joining device. Also fixed to the second support 72 or forming a component thereof is a second centering mandrel 82. This engages coaxially and positively with the open end of the hollow rotor shaft 342. In the illustrated embodiment, the second centering mandrel 82 is hollow in the region of its free end and open at its free end, with the corresponding cavity 821 corresponding in shape to the centering section 812 of the first centering mandrel. Furthermore, the free, open end of the rotor shaft 342 also corresponds in shape to the centering section 812 of the first centering mandrel 81.

[0042] As indicated by the arrows in Fig. 3a, 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. As shown in Figure 3b, the shaft module 62 is inserted into the housing module 61. The centering section 812 of the first centering mandrel 81 engages coaxially with the rotor shaft 342 in a form-fitting manner, so that both assemblies 61, 62 are centered and stabilized relative to each other. This eliminates the risk of the rotor 341 colliding with the stator 321 during the joining process.

[0043] By further pushing together the supports 71, 72 beyond the stage of Fig. 3b, the building units 61, 62 reach their Fig. 1. The input gear 41 of the gearbox 40 engages the pinion 343 of the rotor shaft 342, 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.

[0044] Fig. 4 shows two analogous process steps for assembling a traction drive 10 according to Fig. 2. As already explained above, this essentially differs from the embodiment according to Fig. 1. As in Fig. 4, this third rotor shaft bearing 53 is a component of the shaft module 62. In particular, its inner bearing shell 531 is pressed onto a corresponding shaft-side bearing seat of the rotor shaft 342. During the joining process, its outer bearing shell 532 is inserted into a corresponding housing-side bearing seat of the housing body 22, preferably with a loose fit in order to avoid excessive joining forces. Furthermore, reference can be made to the explanations for Fig. 3.

[0045] Naturally, the embodiments discussed in the specific description and shown in the figures represent only illustrative embodiments of the present invention. A person skilled in the art will have a wide range of possible variations in light of the disclosure herein. In particular, as shown in the Fig. 3 and Fig.4, the stator unit 32 protrudes axially beyond the edge of the housing body 22. This projection is then inserted into the casing 241 of the housing cover 24 during the joining process. In other embodiments, it is possible for the housing cover 24 to be flat and essentially consist only of its end wall 242; in such embodiments, a projection of the stator unit 32 beyond the housing body 22 is obviously prohibited. 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 41 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 53 second rotor shaft bearing 531 inner bearing shell of 53 532 outer bearing shell of 53 533 rolling elements of 53 61 first assembly unit / housing module 62 second assembly unit / shaft module 71 first carrier 72 second carrier 81 first centering mandrel 811 section of 81 812 Centering section of 81 813 undercut 82 second centering mandrel 821 cavity

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 body (22) open axially on both sides, in the interior of which - a first housing-side bearing seat in which a first rotor shaft bearing (51) is fixed via its outer bearing shell (512), and - an axially terminal 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 cover (24) with a second housing-side bearing seat arranged in a wall opening (243) in its axial end wall (242), 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 on the side of the rotor (341) facing away from the first shaft-side bearing seat, wherein the structural units (61, 62) are fixed in a coaxial alignment relative to one another and with the first rotor shaft bearing (51) and the first shaft-side bearing seat facing one another on two supports (71, 72) of a joining device that 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 moving the supports (71, 72) towards each other 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 (521) in a force-fitting manner, the rotor (341) is axially colocated with the stator (321) and the housing cover (24) rests against an edge of the housing body (22) facing it, wherein the first carrier (71) carries a first centering mandrel (81) which coaxially penetrates the first rotor shaft bearing (51) and onto which the hollow rotor shaft (342) is pushed in a form-fitting manner during joining. [2] Method according to claim 1, characterized by , that the sum of - the length of a projection of the first 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. [3] Method according to one of the preceding claims, characterized bythat the first 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). [4] Method according to claim 3, characterized in that the contact section is provided with a relief cut (813). [5] Method according to one of the preceding claims, characterized by that the end of the first centering mandrel (81) facing the second structural unit (62) is pointed. [6] Method according to one of the preceding claims, characterized bythat the second carrier (72) carries a second centering mandrel (82) which engages positively in the hollow interior of the rotor shaft (342) during joining. [7] Method according to claim 6, characterized by that one of the centering mandrels (81; 82) is hollow and open on its side facing the other centering mandrel (82; 81), wherein during the joining said hollow centering mandrel (81; 82) is pushed positively onto said other centering mandrel (82; 81) in the interior of the rotor shaft (342). [8] Method according to claim 7, characterized by that the second centering mandrel (82) is hollow and open on its side facing the first structural unit (61), wherein during the joining the second centering mandrel (82) is pushed positively onto the first centering mandrel (81) in the interior of the rotor shaft (342). [9] Method according to one of the preceding claims, characterized bythat the housing body (22) has in its interior a third housing-side bearing seat arranged between the first rotor shaft bearing (51) and the stator (321), and the rotor shaft (342) has a corresponding third shaft-side bearing seat between the first shaft-side bearing seat and the rotor (341), on which third rotor shaft bearing (53) is fixed via its inner bearing shell (531). [10] Method according to claim 9, characterized by that the third housing-side bearing seat and the third rotor shaft bearing (53) are dimensioned to be joined with a loose fit relative to one another. [11] Method according to one of the preceding claims, characterized by that the stator (321) projects beyond the edge of the housing body (22) facing the second structural unit (62) and the housing cover (24) is correspondingly pot-shaped. [12] 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.

Images