Externally excited electric machine with slip ring module, method for manufacturing an externally excited electric machine and motor vehicle

Abstract

The invention relates to a separately excited electric machine (FEM) for a traction drive (TA) of an at least partially electrically powered motor vehicle (KFZ), comprising a rotor shaft (RW) of a rotor (RO) to which a shaft end section (WEA) adjoins, wherein the shaft end section (WEA) has a first opening (EO) and a second opening (ZO) spaced apart from the first opening (EO) in an axial direction of the rotor (RO), a potting body (VK) arranged in the shaft end section (WEA) in which an electrically conductive connecting element (VE) is embedded at least partially, wherein the connecting element (VE) has a distal first end (DEE) and a distal second end (DZE), and the distal second end (DZE) can be guided through the second opening (ZO).a slip ring module (SRM) arranged on a distal end section DE of the shaft end section (WEA) with a slip ring (SR) and a connecting section (VA) arranged on the slip ring (SR), which is electrically connected to the distal first end (DEE) of the connecting element (VE), and a bearing device (LE) which sits on an outer cylindrical surface (AM) of the shaft end section (WEA) between the slip ring module (SRM) and the second opening (ZO) and by means of which the rotor (RO) can be mounted in a housing, and no grooves or recesses are formed on the outer cylindrical surface (AM) of the shaft end section (WEA) in the area of ​​the bearing device (LE).

Description

[0001] The invention relates to a separately excited electric machine for a traction drive of an at least partially electrically powered motor vehicle, wherein the electric machine has a rotor shaft with a shaft end section. A slip ring module is mounted on the shaft end section, the slip ring of which is electrically connected to a connecting element extending through the shaft end section. A bearing device is arranged on an outer surface of the shaft end section. The invention also relates to a method for producing the separately excited electric machine according to the invention. A further subject of the invention is a motor vehicle having the separately excited electric machine according to the invention.

[0002] Separately excited electrical machines are generally known. Known separately excited electrical machines typically have a slip ring module on a shaft end section, which is plugged onto an outer side or outer surface of the shaft end section. Grooves running in the axial direction of the rotor are formed in the outer surface to accommodate connecting elements of the slip ring module. Furthermore, a bearing assembly is known to sit on the shaft end section. Due to the grooves in the outer surface in the area of ​​the bearing assembly, extensive sealing measures are required between the bearing assembly and the outer surface to prevent a cooling medium for cooling a rotor winding from reaching the slip rings of the slip ring module. These sealing measures could increase the cost of the electrical machine.

[0003] US 2004 / 0 119 369 A1 describes a slip ring module for an electrical machine, wherein the slip ring module has two slip rings arranged in an insulating body, each connected to an electrical wire. A wire guide is formed in the insulating body, extending in the axial direction of the slip ring module, through which the wire is guided. The entire slip ring module is arranged on a rotor shaft. A bearing device is provided on a distal end of the rotor shaft, so that the slip ring module is arranged between the bearing device and a laminated core of the rotor.

[0004] DE 10 2021 130 559 A1 describes a rotor shaft with a separate slip ring module for a rotor of an electric machine. The slip ring module is arranged on a support element of a rotor body region and has a bearing surface for a bearing device.

[0005] From DE 10 2020 102 891 A1, a slip ring module that can be plugged onto a motor shaft is known, wherein a connecting wire is guided inside the slip ring module.

[0006] It is an object of the invention to provide a separately excited electrical machine which can be produced inexpensively and has an increased tightness in the region of a bearing device to the rotor shaft.

[0007] This problem is solved by the subject matter of the independent patent claims. Preferred developments of the invention are the subject matter of the dependent claims, the following description, and the figures. Each feature can represent an aspect of the invention, both individually and in combination, unless explicitly stated otherwise in the description.

[0008] In a first aspect, the invention relates to a separately excited electric machine for a traction drive of an at least partially electrically powered motor vehicle, comprising a rotor shaft of a rotor, to which a shaft end section is adjacent and / or formed, wherein the shaft end section has a first opening and a second opening arranged at a distance from the first opening in an axial direction of the rotor, a potting body arranged in the shaft end section, in which an electrically conductive connecting element is embedded at least in sections, wherein the connecting element has a distal first end and a distal second end, and the distal second end is guided or can be guided through the second opening, a slip ring module arranged on a distal end section of the shaft end section, having a slip ring and a connecting section arranged on the slip ring,which is electrically conductively connected to the distal first end of the connecting element, and a bearing device which is seated on an outer surface of the shaft end section between the slip ring module and the second opening and via which the rotor can be mounted in a housing, and no grooves or recesses are formed on the outer surface of the shaft end section in the region of the bearing device.

[0009] In other words, according to the first aspect of the invention, it is provided that an externally excited electric machine is provided for a traction drive of an at least partially electrically powered motor vehicle. The externally excited electric machine has a rotor which comprises a rotor shaft. A shaft end section is arranged and / or formed adjacent to the rotor shaft. The shaft end section comprises a first opening and a second opening arranged at a distance from the first opening in an axial direction of the rotor. The first opening is preferably aligned coaxially to a longitudinal axis of the rotor and / or the rotor shaft. Particularly preferably, the first opening is designed as an edge-closed opening.The second opening is formed in a wall of the shaft end section. If the shaft end section is considered separately, the second opening on a side facing away from the first opening is preferably designed as a recess and / or slot and only acquires the formation of a closed-edge opening when combined and / or connected to the rotor shaft. A potting body is arranged in the shaft end section. An electrically conductive connecting element is embedded in the potting body, at least in sections. The connecting element has a distal first end and a distal second end. The distal second end can be guided or is preferably guided through the second opening. Thus, a winding wire of a rotor winding of the rotor can be electrically conductively connected to the second end of the connecting element in a simple manner.A slip ring module is arranged on a distal end section of the shaft end section, which has a slip ring and a connecting section arranged on the slip ring. The connecting section is electrically conductively connected to the distal first end of the connecting element. Furthermore, a bearing device is provided, which sits on an outer circumferential surface of the shaft end section, between the slip ring module and the second opening. Due to the fact that the connecting element is guided through the shaft end section and establishes an electrically conductive connection between the slip ring and the distal second end of the connecting element, which can be connected to the rotor winding, no grooves or recesses are required on the outer circumferential surface of the shaft end section in the area of ​​the bearing device, so that the media tightness in this area can be increased in a simple and cost-effective manner.This prevents a cooling medium for cooling a laminated core arranged on the rotor shaft from reaching the slip ring module in the area of ​​the bearing device.

[0010] In a preferred embodiment of the invention, it is provided that a shaft sealing ring is arranged adjacent to the bearing device. It is thus conceivable that the shaft sealing ring is arranged on a side of the bearing device facing the slip ring module and / or on a side of the bearing device facing away from the slip ring module. If the bearing device is self-lubricating, in other words, contains a lubricant, in particular a grease, it is preferably provided that the shaft sealing ring is arranged on a side facing away from the slip ring module. This can prevent fluids, in particular a cooling medium for cooling a laminated core arranged on the rotor shaft, from penetrating the bearing device and reaching the slip ring module via the bearing device. It is also conceivable that the shaft sealing ring is arranged on a side facing the slip ring module.This arrangement is preferably provided if lubrication of the bearing device is to be effected via the coolant for cooling the laminated core arranged on the rotor shaft.

[0011] An advantageous development of the invention is that the outer circumferential surface is designed to be uninterrupted in a region where the shaft seal sits on the shaft end section and / or seals against it. In other words, in the region where the shaft seal sits on the outer circumferential surface, no grooves or flutes are formed that extend in the axial direction of the rotor across a width of the shaft seal—relative to the axial direction of the rotor or the shaft end section. Thus, the media tightness in the area of ​​the shaft seal and thus also of the bearing device can be increased in a simple and cost-effective manner.

[0012] Furthermore, because the connecting element is guided through the shaft end section, the shaft end section can have a reduced outer diameter in the area of ​​the bearing device and the shaft seal. Due to the reduced outer diameter, the circumferential speed in the area of ​​the shaft seal is reduced when the rotor rotates about its longitudinal axis, thus reducing wear on the shaft seal and thus increasing its longevity.

[0013] An advantageous development of the invention is that the potting body is fixed in the shaft end section in the longitudinal direction of the rotor by a material fit and / or a form-fitting manner. The form-fitting fixation provides that the potting body is designed such that it is held in the shaft end section in the longitudinal direction of the rotor by an internal geometry of the shaft end section on the one hand and the rotor shaft on the other.

[0014] It is conceivable that the encapsulated body has a section in which a maximum outer diameter or outer cross-section is larger than a minimum inner diameter of the shaft end section. This allows the encapsulated body to be fixed in position toward the slip ring module.

[0015] The encapsulated body is preferably made of an electrically insulating material. Particularly preferably, the encapsulated body can be made of a plastic material or comprise a plastic. Such a encapsulated body can be manufactured inexpensively.

[0016] In an advantageous embodiment of the invention, a sealing element is arranged between an inner circumferential surface of the shaft end section and the encapsulated body. The sealing element is preferably designed as an annular seal, in particular as an O-ring. Particularly preferably, the sealing element is made of a permanently elastic material. The sealing element can prevent a fluid for cooling a laminated core arranged on the rotor shaft from passing through the second opening and an annular gap between the encapsulated body and the inner circumferential surface of the shaft end section toward the slip ring module.

[0017] It is conceivable that the distal first end is not guided through the first opening, but is designed to be recessed toward the first opening. This then requires that the connecting section of the slip ring module protrudes through the first opening into the shaft end section in order to be electrically conductively connected to the distal first end of the connecting element. This can be advantageous for the axial installation space of the rotor or the separately excited electric machine.

[0018] Alternatively, a preferred development of the invention provides that the distal first end is guided through the first opening. In other words, the distal first end projects beyond the first opening. Thus, it is not necessary for the connecting portion of the slip ring module to project into the first opening in the shaft end portion in order to be electrically conductively connected to the distal first end of the connecting element. In this way, the electrically conductive connection between the connecting portion of the slip ring and the distal first end of the connecting element is not, or not significantly, impeded by the shaft end portion, so that the electrically conductive connection can be implemented in a simple and inexpensive manner.

[0019] An advantageous embodiment of the invention provides that the connecting section has a receiving opening for receiving the distal first end of the connecting element. In other words, the distal first end is preferably linear and runs in the axial and / or longitudinal direction of the rotor. The receiving opening of the connecting section is designed either as a closed-edge opening and / or as a loop into which the linear distal first end of the connecting element engages when the slip ring module is plugged onto the shaft end section. Thus, the connecting section and the distal first end of the connecting element can be brought together in a simple and cost-effective manner to be electrically connected to one another.

[0020] The receiving opening can be formed integrally in the connecting element. However, it is also conceivable for a pole piece having the receiving opening to be plugged onto the connecting section, with the distal first end engaging the receiving opening of the pole piece.

[0021] As an alternative to the receiving opening in the connecting section, it can be provided that the connecting section and the distal first end of the connecting element run parallel to one another at least in sections in the region of the electrically conductive connection, and the parallel regions of the connecting element and the connecting section are preferably connected to one another by a material fit. The parallel regions preferably run in a longitudinal direction of the shaft end section.

[0022] The electrically conductive connection between the connecting section and the distal first end of the connecting element is a material connection, a force-fitting connection, and / or a positive connection. The material connection is preferably a welded connection or an electrically conductive adhesive connection. The positive and / or force-fitting connection can be a press-fit connection.

[0023] In an advantageous embodiment of the invention, the slip ring module comprises a slip ring carrier, wherein the slip ring and the connecting section are arranged at least partially and / or in sections in the slip ring carrier. In this way, the slip ring module can be easily prepared and then subsequently plugged onto the shaft end section of the rotor shaft. This allows the manufacturing times of the separately excited electrical machine and consequently also the manufacturing costs to be reduced, since only the slip ring module itself is plugged onto the shaft end section and electrically connected to the connecting element.

[0024] It is advantageously provided that the slip ring module is plugged onto the shaft end section, and the slip ring of the slip ring module is arranged radially spaced from the outer surface of the shaft end section. This allows the installation space of the separately excited electrical machine to be reduced in the axial direction.

[0025] In a second aspect, the invention relates to a method for producing the separately excited electrical machine according to the invention, comprising the steps: - Providing a shaft end section, - Arrangement of a casting body having the connecting section in the shaft end section, - Connecting the shaft end section to the rotor shaft, - Bearing of the rotor shaft via a bearing device in a housing, - Arrangement of a slip ring module on a distal end section of the shaft end section.

[0026] In other words, according to the second aspect of the invention, a method for producing the rotor according to the invention is provided. This method comprises at least the steps of providing a shaft end section. A potting body, in which the connecting element is arranged, is arranged in the shaft end section. In this way, the connecting element is guided within the shaft end section. After the potting body has been arranged in the shaft end section, the shaft end section is connected to the rotor shaft. The rotor shaft can be designed as a hollow shaft, but is not limited to this. It is also conceivable for the rotor shaft to have a solid cross-section. The rotor shaft is mounted in a housing via a bearing device. The bearing can be designed as a rolling bearing. The housing can be a housing wall or a bearing plate of the housing of the separately excited electrical machine.Furthermore, it is provided that the slip ring module is arranged, in particular plugged, onto a distal end section of the shaft end section. The plugging on preferably takes place in the axial direction of the rotor or the rotor shaft. Depending on the outer diameter of the slip ring module, it can be provided that the slip ring module is arranged on the distal end section of the shaft end section via the bearing device in the housing after the arrangement and / or mounting of the rotor. Alternatively, it can be provided that the slip ring module is plugged onto the distal end section of the shaft end section and subsequently the entire rotor, together with the slip ring module plugged onto the shaft end section, is mounted in the housing via the bearing device. In this way, a method is provided with which a rotor can be arranged within a housing in a simple and cost-effective manner and with increased media tightness in the area of ​​the housing orof the bearing seat can be achieved.

[0027] It is advantageously provided that a shaft sealing ring is arranged adjacent to and / or spaced from the bearing device, which seals against the housing on the one hand and the shaft end section on the other hand.

[0028] A preferred development of the invention provides that, for arranging the potting body containing the connecting element in the shaft end section, a separate potting body containing the connecting element is produced outside the hollow shaft and captively arranged in the shaft end section. In this way, the potting body can be easily inserted into the shaft end section, preferably in the case of an assembled rotor or assembled rotor shaft, and can be arranged in the shaft end section, preferably via a material-to-material connection and / or a form-fitting connection.

[0029] During the positive connection of the casting body in the shaft end section, it is preferably provided that the casting body is inserted into the shaft end section with the distal first end of the connecting element leading in a rectilinear movement over a side facing away from the first opening of the shaft end section. It is preferably provided that the second opening, if the shaft end section is considered as such, is formed as a recess and / or slot in a wall of the shaft end section. Thus, by inserting the casting body into the shaft end section, the distal second end of the connecting element can be easily guided through the second opening.

[0030] After the potting body has been inserted into the shaft end section, the rotor shaft and the shaft end section are connected to each other. The connection is preferably a material-to-material connection. The material-to-material connection is preferably a welded connection.

[0031] The encapsulated body is preferably designed such that it cannot be fully extended through the shaft end section beyond the first opening. In other words, the encapsulated body has, at least in some sections, an outer cross-section that is larger than a smallest inner cross-section. In other words, the encapsulated body has an outer geometry that only allows the encapsulated body to be inserted into the shaft end section via a side facing away from the first opening. Thus, the encapsulated body can be securely fixed in position within the rotor, at least in the direction of the slip ring module in the axial direction.

[0032] In the direction of the rotor shaft, the potting body is preferably fixed and / or positioned in the axial direction by the rotor shaft. It is conceivable for the rotor shaft to be designed as a solid body. In this case, the rotor shaft itself serves as a stop for the potting body. However, it is also conceivable for the rotor shaft to be designed as a hollow shaft. In this context, it is then provided that an outer cross-section and / or outer diameter of the potting body adjacent to the rotor shaft is larger than an inner diameter of the hollow shaft that is aligned and / or formed adjacent to the potting body.

[0033] Alternatively, it is conceivable that, in order to arrange the potting body containing the connecting element in the shaft end section, the connecting element is first arranged in the shaft end section, and then the potting body is introduced into the shaft end section and cured therein. In other words, the potting body is formed "in-place." For this purpose, the connecting element is inserted into the shaft end section beforehand and then potted within the shaft end section. This allows a media-tight connection of the potting body to an inner side of the shaft end section to prevent fluid transport through the shaft end section.

[0034] In a third aspect, the invention relates to a motor vehicle with the separately excited electrical machine according to the invention.

[0035] The motor vehicle is preferably an at least partially, preferably completely, electrically powered motor vehicle.

[0036] The separately excited electric machine is preferably an integral component of a traction drive of the motor vehicle.

[0037] It should be noted that all features described above and below with respect to one aspect of the present invention apply equally to any other aspect of the present invention. Specifically, all features of the separately excited electrical machine can apply equally to the method for manufacturing the separately excited electrical machine and to the motor vehicle. This also applies vice versa.

[0038] Further features and advantages of the present invention emerge from the dependent claims and the following exemplary embodiments. The exemplary embodiments are not restrictive, but rather to be understood as examples. They are intended to enable the skilled person to implement the invention. The applicant reserves the right to make individual and / or several of the features disclosed in the exemplary embodiments the subject of patent claims or to incorporate such features into existing patent claims. The exemplary embodiments are explained in more detail with reference to drawings.

[0039] In these show: Fig. 1 shows a longitudinal section through a separately excited electrical machine in the region of a shaft end section of a rotor in a first embodiment; Fig. 2 a longitudinal section through the separately excited electrical machine in the region of the shaft end section of the rotor in a second embodiment; Fig. 3 an exploded view of the shaft end section in longitudinal section; Fig. 4 a motor vehicle with the separately excited electric machine.

[0040] In Fig. Figure 1 shows a longitudinal section through a separately excited electric machine FEM in the region of a shaft end section WEA of a rotor RO. The separately excited electric machine FEM is configured and / or designed for a traction drive TA of an at least partially electrically powered motor vehicle KFZ.

[0041] The separately excited electric machine FEM has a rotor RO that surrounds the rotor shaft RW. A laminated core BP with at least one salient pole (not shown) is arranged in a rotationally fixed manner on an outer circumferential surface AUF of the rotor shaft RW. A rotor winding RW is typically wound on the salient pole.

[0042] A shaft end section WEA is arranged and / or formed adjacent to the rotor shaft RW. The shaft end section WEA comprises a first opening EO and a second opening ZO arranged at a distance from the first opening EO in an axial direction of the rotor RO. A potting body VK is arranged in the shaft end section WEA. An electrically conductive connecting element VE is embedded at least in sections in the potting body VK. The connecting element VE has a distal first end DEE and a distal second end DZE. In the present exemplary embodiment, the distal second end DZE is guided through the second opening ZO of the shaft end section WEA. Thus, a winding wire of the rotor winding RW can be electrically conductively connected to the distal second end DZE.

[0043] The slip ring module SRM is arranged on a distal end section DE of the shaft end section WEA. The slip ring module SRM has a slip ring SR and a connecting section VA arranged on the slip ring SR. The connecting section VA is electrically conductively connected to the distal first end DEE of the connecting element VE.

[0044] Furthermore, a bearing device LE is provided, which sits on an outer surface AM of the shaft end section WEA, preferably between the slip ring module SRM and the second opening ZO. The bearing device LE is arranged in a housing GE of the separately excited electrical machine FEM. The housing GE can be configured and / or designed as a bearing shield, intermediate wall, or outer wall in the area of ​​the bearing device LE.

[0045] Because the connecting element VE is guided through the shaft end section WEA and creates an electrically conductive connection between the slip ring SR and the distal second end DZE of the connecting element VE, which can be connected to the rotor winding RW, no grooves or recesses are required on the outer surface AM of the shaft end section WEA in the area of ​​the bearing device LE, so that the media tightness in this area can be increased in a simple and cost-effective manner. The increased media tightness prevents a liquid cooling medium for cooling the rotor RO, in particular the rotor winding RW and / or the laminated core BP, from reaching the slip ring module SRM.

[0046] In addition, a shaft seal WDR is provided, which is arranged adjacent to the bearing assembly LE and seals between the housing GR and the outer surface AM. In this case, the shaft seal WDR is arranged on a side of the bearing assembly LE facing away from the slip ring module SRM. This prevents a cooling medium for cooling the laminated core BP or the rotor winding from passing through the bearing assembly toward the slip ring module SRM.

[0047] Preferably, the outer circumferential surface AM is designed to be uninterrupted in an area where the shaft seal rests on the shaft end section WEA. This can increase the media tightness in the area where the bearing device LE rests on the shaft end section WEA.

[0048] Furthermore, due to the fact that the connecting element VE is guided through the shaft end section WEA, the diameter of the shaft end section WEA can have a reduced outer diameter in the area of ​​the bearing device LE and the shaft seal WDR. Due to the reduced outer diameter, the circumferential speed in the area of ​​the shaft seal WDR is reduced when the rotor RO rotates about its longitudinal axis, so that wear on the shaft seal WDR can be reduced and the service life of the shaft seal WDR can be increased.

[0049] The second opening ZO is arranged or formed in the shaft end section WEA between the bearing device LE and the laminated core BP. Thus, the connecting element VE only needs to pass through the shaft end section WEA and not through the entire rotor shaft RW. Thus, the connecting element VE can have a reduced length, which can reduce material costs.

[0050] The distal first end DEE is guided through the first opening EO. In other words, the distal first end DEE projects beyond the first opening EO. Thus, it is not necessary for the connecting section VA of the slip ring module SRM to project into the first opening EO in the shaft end section WEA in order to be electrically conductively connected to the distal first end DEE of the connecting element VE. In this way, the electrically conductive connection between the connecting section VA of the slip ring SRM and the distal first end DEE of the connecting element VE is not, or not significantly, impeded by the shaft end section WEA, so that the electrically conductive connection can be implemented in a simple and cost-effective manner.

[0051] The connecting section VA has a receiving opening ANO for receiving the distal first end DEE of the connecting element VE. In other words, the distal first end DEE is linear and runs in the axial and / or longitudinal direction of the rotor RO. The receiving opening ANO of the connecting section VA is designed either as a closed-edge opening and / or as a loop into which the linear distal first end DEE of the connecting element VE engages when the slip ring module SRM is plugged onto the shaft end section WEA. Thus, the connecting section VA and the distal first end DEE of the connecting element VE can be brought together in a simple and cost-effective manner to be electrically connected to one another.

[0052] The electrically conductive connection between the connecting section VA and the distal first end DEE of the connecting element VE is a material connection, a force-locking connection, and / or a positive connection. The material connection is preferably a welded connection or an electrically conductive adhesive connection. The positive and / or force-locking connection can be a press-fit connection.

[0053] The slip ring module SRM has a slip ring carrier SRT, wherein the slip ring SR and the connecting section VA are arranged at least partially and / or sectionally in the slip ring carrier SRT. In this way, the slip ring module SRM can be easily prepared and then subsequently plugged onto the shaft end section WEA of the rotor shaft RW. This allows the production times of the separately excited electrical machine FEM and consequently also the production costs to be reduced, since only the slip ring module SRM as such is plugged onto the shaft end section WEA and electrically connected to the connecting element VE.

[0054] Fig. 2 shows a longitudinal section through the shaft end section WEA of the separately excited electrical machine FEM in a second embodiment and the Fig. Figure 3 shows an exploded view of the WEA shaft end section in longitudinal section. Fig. 2 and Fig. 3 simultaneously referred to.

[0055] The casting body VK is inserted into the shaft end section WEA with the distal first end DEE of the connecting element VE leading in a straight-line movement over a side facing away from the first opening EO of the shaft end section WEA. The second opening ZO, if the shaft end section WEA is considered as such, is formed as a recess and / or slot in a wall WA of the shaft end section WEA. Thus, by inserting the casting body VK into the shaft end section WEA, the distal second end DZE of the connecting element VE can be easily guided through the second opening ZO.

[0056] After the casting body VK has been inserted into the WEA shaft end section, the rotor shaft RW and the WEA shaft end section are connected. The connection is preferably a material-to-material connection. The material-to-material connection is preferably a welded connection.

[0057] The encapsulated body VK is designed such that it cannot be fully extended through the shaft end section WEA beyond the first opening EO. In other words, the encapsulated body VK has, at least in some sections, an outer cross-section that is larger than a smallest inner cross-section. In other words, the encapsulated body VK has an outer geometry that only allows the encapsulated body VK to be inserted into the shaft end section via a side facing away from the first opening EO. Thus, the encapsulated body VK can be securely fixed and / or positioned in the axial direction within the rotor RO, at least in the direction of the slip ring module SRM.

[0058] In the direction of the rotor shaft RW, the potting body VK is fixed and / or positioned in the axial direction by the rotor shaft RW. It is conceivable that the rotor shaft RW, as shown in the present embodiment, is designed as a solid body. In this case, the rotor shaft RW itself serves as a stop for the potting body VK. However, it is also conceivable that the rotor shaft RW is designed as a hollow shaft. In this context, it is then provided that an outer cross-section and / or outer diameter of the potting body VK, which borders the rotor shaft RW, is larger than an inner diameter of the hollow shaft, which is aligned adjacent to the potting body.

[0059] Furthermore, it can be seen that a sealing element DE is arranged between an inner circumferential surface IM of the shaft end section WEA and the encapsulated body VK. The sealing element DE is preferably designed as an annular seal, in particular as an O-ring. In this way, a fluid for cooling a laminated core BP arranged on the rotor shaft RW can be prevented from passing through the second opening ZO and an annular gap between the encapsulated body VK and the inner circumferential surface IM of the shaft end section WEA in the direction of the slip ring module SRM.

[0060] Fig. 4 shows the motor vehicle KFZ with the traction drive TA, in which the separately excited electric machine FEM is arranged

Claims

[1] Separately excited electrical machine (FEM) for a traction drive (TA) of an at least partially electrically driven motor vehicle (KFZ), comprising a rotor shaft (RW) of a rotor (RO), to which a shaft end section (WEA) adjoins, wherein the shaft end section (WEA) has a first opening (EO) and a second opening (ZO) arranged at a distance from the first opening (EO) in an axial direction of the rotor (RO), a casting body (VK) arranged in the shaft end section (WEA), in which an electrically conductive connecting element (VE) is embedded at least in sections, wherein the connecting element (VE) has a distal first end (DEE) and a distal second end (DZE), and the distal second end (DZE) can be guided through the second opening (ZO), a slip ring module (SRM) arranged on a distal end section DE of the shaft end section (WEA) with a slip ring (SR) and a connecting section (VA) arranged on the slip ring (SR), which is electrically conductively connected to the distal first end (DEE) of the connecting element (VE), and a bearing device (LE) which is seated on an outer circumferential surface (AM) of the shaft end section (WEA) between the slip ring module (SRM) and the second opening (ZO) and via which the rotor (RO) can be mounted in a housing, and no grooves or recesses are formed on the outer circumferential surface (AM) of the shaft end section (WEA) in the region of the bearing device (LE). [2] Separately excited electrical machine according to one of the preceding claims, characterized by that a shaft sealing ring (WDR) is arranged adjacent to the bearing device (LE). [3] Separately excited electrical machine according to claim 2, characterized bythat the outer surface (AM) is designed without interruption in an area in which the shaft sealing ring (WDR) sits on the shaft end section (WEA). [4] Separately excited electrical machine according to one of the preceding claims, characterized by that the casting body (VK) is positively fixed in the shaft end section (WEA) in the longitudinal direction of the rotor (RO). [5] Separately excited electrical machine according to one of the preceding claims, characterized by that the casting body (VK) has a section in which a maximum outer diameter or outer cross-section is larger than a smallest inner diameter of the shaft end section WEA. [6] Separately excited electrical machine according to one of the preceding claims, characterized by that a sealing element (DE) is arranged between an inner circumferential surface (IM) of the shaft end section (WEA) and the casting body (VK). [7] Separately excited electrical machine according to one of the preceding claims, characterized by that the distal first end (DEE) of the connecting element (VE) is guided through the first opening (EO). [8] Separately excited electrical machine according to one of the preceding claims, characterized by that the connecting section (VA) has a receiving opening (ANO) for receiving the distal first end (DEE) of the connecting element (VE). [9] Separately excited electrical machine according to one of the preceding claims, characterized by that the slip ring module (SRM) has a slip ring carrier (SRT), wherein the slip ring (SR) and the connecting section (VA) are arranged at least partially and / or sectionally in the slip ring carrier (SRT). [10] Separately excited electrical machine according to one of the preceding claims, characterized bythat the slip ring module (SRM) is plugged onto the shaft end section (WEA), and the slip ring (SR) of the slip ring module (SRM) is arranged at a distance in the radial direction from the outer surface (AM) of the shaft end section (WEA). [11] Method for producing a separately excited electrical machine (FEM) according to one of the preceding claims, comprising the steps: - Providing a shaft end section, - Arrangement of a casting body (VK) having a connecting element (VE) in the shaft end section (WEA), - Connecting the shaft end section to the rotor shaft, - Bearing of the rotor shaft (RW) via a bearing device (LE) in a housing (GE), - Arrangement of a slip ring module (SRM) on a distal end section (DE) of the shaft end section (WEA). [12] Method according to claim 11, characterized byin that, in order to arrange the casting body (VK) having the connecting element (VE) in the shaft end section (WEA), a separate casting body (VK) having the connecting element (VE) is produced outside the rotor shaft (RW) and is then arranged captively in the shaft end section (WEA). [13] Method according to claim 11, characterized by in that, in order to arrange the casting body (VK) having the connecting element (VE) in the shaft end section (WEA), the connecting element (VE) is first arranged in the shaft end section (WEA), and then the casting body (VK) is introduced into the shaft end section (WEA) and hardens therein. [14] Method according to one of claims 11 to 13, characterized by that after the arrangement of the casting body in the shaft end section, the shaft end section is connected to the rotor shaft. [15] Motor vehicle (KFZ) with a separately excited electrical machine (FEM) according to one of claims 1 to 10.

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