Separately excited rotor with winding head cooling, traction drive and motor vehicle

Abstract

The invention relates to a separately excited rotor (RO) for an electrical machine (EM) of an at least partially electrically driven motor vehicle (KFZ), comprising a rotor shaft (RW) having a shaft cavity (WHR) and an outer shell surface (AM), a laminated core (BP) that is arranged on the outer shell surface (AM) and that has at least one salient pole (AP), a rotor winding (RWI) that is arranged on the salient pole (AP) and that has a winding head (WK) that protrudes beyond an end face (SS), formed in the axial direction of the rotor (RO), of the laminated core (BP), an end cap (EK) that covers at least parts and / or sections of the winding head (WK), a reservoir (RV) that is arranged and / or formed between the end cap (EK) and the end face (SS) and that has at least one outlet opening (AOE), and a passage opening (DLO) formed in a shaft wall (WW) of the rotor shaft (RW), wherein a cooling medium (KM) is able to leave the shaft cavity (WHR) of the rotor shaft (RW) through the passage opening (DLO), be received by the reservoir (RV) and escape from the reservoir (RV) through the outlet opening (AOE) and reach the winding head (WK).

Description

[0001] Description

[0002] Separately excited rotor with winding head cooling, traction drive and motor vehicle

[0003] The invention relates to a separately excited rotor for an electric machine of an at least partially electrically powered motor vehicle, wherein a cooling medium, originating from a hollow shaft of a rotor shaft, is collected by a reservoir and guided against a winding head of the rotor shaft. The invention also relates to a traction drive for an at least partially electrically powered motor vehicle with the rotor according to the invention. A further subject of the invention is a motor vehicle with the traction drive according to the invention.

[0004] Separately excited rotors are generally known. Known rotors typically comprise a rotor shaft with a laminated core arranged on the rotor shaft, the laminated core comprising at least one salient pole. It is also known that a rotor winding is formed on the salient pole, which winding has a winding head at the end of the laminated core. It is also known that the winding head can preferably be cooled by a cooling medium. It has been shown that the cooling effect of known cooling concepts for cooling the winding head is insufficient. However, an increased cooling effect is advantageous for increasing the performance of the electric machine.

[0005] One object of the invention is to increase the cooling effect of the rotor and / or the traction drive, which ultimately also increases the performance of the traction drive.

[0006] 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 patent claims, the following description, and the drawings. Each feature can represent an aspect of the invention, both individually and in combination, unless explicitly stated otherwise in the description.

[0007] In a first aspect, the invention relates to a separately excited rotor for an electric machine of an at least partially electrically driven motor vehicle, comprising a rotor shaft with a shaft cavity and an outer circumferential surface, a laminated core arranged on the outer circumferential surface, which has at least one salient pole, a rotor winding arranged on the salient pole, which has a winding head that projects beyond an end face of the laminated core formed in the axial direction of the rotor, an end cap covering the winding head at least partially and / or in sections, a reservoir arranged and / or formed between the end cap and the end face, with at least one outlet opening, and a passage opening formed between the end cap and the end face in a shaft wall of the rotor shaft, wherein a cooling medium can exit from the shaft cavity of the rotor shaft via the passage opening,absorbed by the reservoir and escapes through the outlet opening from the reservoir and can reach the winding head.

[0008] In other words, according to the first aspect of the invention, a separately excited rotor is provided for an electric machine of an at least partially electrically powered motor vehicle. The separately excited rotor comprises a rotor shaft. The rotor shaft is designed as a hollow shaft and thus has a shaft cavity. On a side facing outwards in the radial direction of the rotor shaft, the rotor shaft has an outer circumferential surface. A laminated core is arranged on the outer circumferential surface. The laminated core has at least one salient pole. The laminated core usually has a plurality of salient poles which are arranged and / or formed at regular and / or irregular intervals from one another in the circumferential direction of the laminated core. A rotor winding is arranged and / or wound on the salient pole.The rotor winding has a winding head, wherein the winding head projects beyond an end face of the laminated core formed in the axial direction of the rotor. The winding head is covered at least partially and / or in sections by an end cap. The winding head is covered by the end cap, preferably in the axial direction of the rotor and / or in the circumferential direction of the rotor. A reservoir for holding a cooling medium is arranged and / or formed between the end cap and the end face. The reservoir has at least one outlet opening. It is thus conceivable that the reservoir can have a plurality of outlet openings. The outlet opening is preferably directed and / or formed in the direction of the winding head.A passage opening is formed in a shaft wall of the rotor shaft so that a cooling medium can emerge from the hollow shaft of the rotor shaft through the passage opening, be absorbed by the reservoir, escape from the reservoir through the outlet opening, and reach the winding head. The cooling medium is preferably a fluid, in particular an oil or a water-glycol mixture. By absorbing the cooling medium emerging from the hollow shaft in the reservoir and specifically discharging the cooling medium through the outlet opening onto the winding head, the flowing cooling medium can be guided directly to a surface to be cooled, thereby increasing the cooling effect. In other words, atomization of the cooling medium is reduced, and the cooling medium is guided to the winding head as a flowing cooling medium. The increased cooling effect can also increase the performance of the rotor and / or the traction drive.

[0009] The passage opening is oriented and / or configured such that the cooling medium can flow from the shaft cavity into the reservoir. Advantageously, the passage opening is formed in the shaft wall of the rotor shaft between the end cap and the end face, relative to a longitudinal direction of the rotor. The passage opening is preferably configured as a closed-edge bore. The passage opening thus connects the shaft cavity to the outer circumferential surface.

[0010] An advantageous development of the invention is that the rotor shaft has an axial end with an inlet opening that is fluidically connected to the shaft cavity. In other words, the rotor shaft has an axial end. This end can preferably face towards or away from a transmission of the traction drive. An inlet opening is formed in the end, which is fluidically connected to the shaft cavity. Thus, a cooling medium can be supplied to the shaft cavity either directly or indirectly. Direct means that the cooling medium flows directly into the shaft cavity. Indirect means that a lance is guided through the inlet opening, and the lance opens into the shaft cavity, wherein the cooling medium can be supplied to the shaft cavity via the lance.

[0011] In a preferred embodiment of the invention, the winding head has a winding head height relative to a radial direction of the rotor shaft, with an inner section directed inward in the radial direction and an outer section directed outward in the radial direction, and the outlet opening is directed toward the inner section. In other words, in this way, the cooling medium can be guided from the inside to a surface of the winding head—relative to the radial direction of the rotor. Under the influence of centrifugal force during operation of the rotor, the cooling medium is then guided radially outward along the surface of the winding head, thereby cooling the winding head.

[0012] According to an advantageous development of the invention, the reservoir is J-shaped at least in sections in a longitudinal section through the rotor, with an opening in the reservoir for receiving a cooling medium exiting the rotor shaft facing the rotor shaft. In other words, the opening between a long web and a short web of the J-shaped reservoir is directed toward the rotor shaft, so that the cooling medium exiting the hollow rotor shaft via the passage opening can be easily received by the reservoir.

[0013] In this context, a preferred embodiment of the invention is that a short web of the reservoir, which is J-shaped in longitudinal section, faces the winding head and / or the end face. Conversely, this means that the long web of the J-shaped reservoir is formed on a side facing away from the end face. The reservoir is thus open towards the winding head, so that the cooling medium, if it does not reach the winding head via the outlet opening from the reservoir, then at least via the short web. This ensures that the cooling medium is guided from the reservoir towards the winding head in order to cool it.

[0014] An advantageous development of the invention lies in the fact that the at least one outlet opening is formed in the short web of the reservoir which is J-shaped in longitudinal section and / or in a transition between the short web and a long web of the reservoir which is J-shaped in longitudinal section. It is therefore conceivable that the outlet opening is formed in the short web, whereby an essentially axial flow to the winding head is possible. Essentially this means an inclination relative to the longitudinal axis of the rotor of 0° to 20°, the limits being included. The further the outlet opening is formed in the direction of the transition, the steeper the inclination, so that it can be oriented at up to 45° relative to the longitudinal axis of the rotor.

[0015] According to a preferred embodiment of the invention, the end cap and the reservoir are formed as a single piece. This has the advantage of reducing the number of parts. A reduced number of parts can have a beneficial effect on the parts costs and also on the manufacturing process of the rotor, thus reducing the manufacturing costs of the rotor.

[0016] Alternatively, an advantageous development of the invention is that the end cap and the reservoir are constructed in multiple parts. A multi-part design can be advantageous in the selection and design of the materials, thereby reducing material and / or manufacturing costs.

[0017] A particularly advantageous embodiment of the invention is that the reservoir is designed to be at least partially and / or sectionally galvanically insulating. It is thus conceivable that the reservoir is preferably designed to be completely galvanically insulating or only partially galvanically insulating. If the reservoir is designed to be partially and / or sectionally galvanically insulating, at least one reservoir outer side facing the winding head is designed to be galvanically insulating. Preferably, the reservoir outer side can be coated with a galvanically insulating coating, at least sectionally.

[0018] In this context, galvanically insulating means that the material is not electrically conductive or electrically insulating. A galvanically insulating material is preferably a plastic. The plastic can be a thermosetting or thermoplastic.

[0019] It is conceivable that the end cap is made of or comprises a plastic. The plastic can be a thermoplastic or a thermosetting plastic. Such an end cap can be manufactured inexpensively, preferably by means of an injection molding process or an additive process.

[0020] An advantageous embodiment of the invention is that the end cap is made of a metal and / or comprises a metal. An end cap made of a metal can preferably be formed as a deep-drawn part, so that the end cap can be manufactured inexpensively.

[0021] In a preferred embodiment of the invention, the following applies to a minimum distance d1 between the winding head and a reservoir outer side facing the winding head in the region of the outlet opening: 0.5 mm < d1 < 7 mm, preferably 0.5 mm < d1 < 5 mm, and particularly preferably 0.5 mm < d1 < 3 mm. The smaller the minimum distance between the surface of the winding head and the outlet opening, the better the cooling medium can be brought to the surface of the winding head in a fluid state, and then flow radially along the surface of the winding head under the influence of centrifugal force. This increases the cooling effect of the rotor.

[0022] According to a preferred embodiment of the invention, a ramp contour is formed between the reservoir and the outer surface, which ramp contour directs a cooling medium emerging from the passage opening directly and / or indirectly into the reservoir. Indirect means that the cooling medium preferably first flows from the ramp contour against an inner side of the end cap before the cooling medium reaches the reservoir. Direct means that the cooling medium flows from the ramp contour directly into the reservoir. By means of the ramp contour and by utilizing the surface tension of the cooling medium, the cooling medium emerging from the passage opening can be guided into the reservoir as a flowing medium.

[0023] In this context, a preferred embodiment of the invention is that the angle a of the ramp contour, relative to a radial direction of the rotor, is 30° < a < 60°, preferably between 35° < a < 55°, and particularly preferably between 40° < a < 50°. Due to the inclination of the ramp contour, the cooling medium can be guided into the reservoir in a flowable state.

[0024] According to an advantageous development of the invention, the ramp contour is arranged on the end face, and a distal end of the ramp contour is directed toward the end cap. In other words, the end of the ramp contour points away from the laminated core toward the end cap.

[0025] A preferred embodiment of the invention is that for a smallest distance d2 between the distal end of the ramp contour and the inner side of the end cap and / or the reservoir facing the ramp contour, the following applies: 0.5 mm < d2 < 7 mm, preferably 0.5 mm < d2 < 5 mm, and particularly preferably 0.5 mm < d2 < 3 mm. The smaller the distance d2 is, the more advantageous the transition of the cooling medium in the flowable state from the ramp contour into the reservoir. In an advantageous embodiment of the invention, it is provided that the end cap has at least one outlet opening. The cooling medium, which is guided along the surface of the winding overhang, can escape via this outlet opening and can preferably be sprayed against a stator winding of a stator surrounding the rotor.

[0026] In this context, it is preferably provided that the outlet opening is designed with a closed edge and / or as a recess in a terminal edge facing the end face. It is therefore conceivable for the recess to be designed with a closed edge, i.e., as a bore. However, it is also conceivable for the outlet opening to be designed as a cutout or recess in a terminal edge of the end cap, wherein the terminal edge preferably faces the end face of the laminated core and directly or indirectly abuts it.

[0027] An advantageous development of the invention is that the outlet opening is arranged offset in the circumferential direction from the outlet opening. Preferably, the outlet opening is directed directly toward the winding head in order to be able to direct the cooling medium to the surface of the winding head or so that the cooling medium can flow onto the surface of the winding head. The outlet opening, on the other hand, is arranged offset in the circumferential direction of the rotor from or next to the salient pole.

[0028] According to a preferred embodiment of the invention, a plurality of outlet openings are provided, which are arranged at regular and / or irregular intervals in the circumferential direction of the reservoir and / or the rotor. Thus, the distribution of the outlet openings allows the cooling medium to be directed to the winding heads in a targeted manner to cool them efficiently.

[0029] A preferred embodiment of the invention is that a plurality of outlet openings are provided, which are arranged at a distance from one another in the circumferential direction of the rotor and / or the end cap. Thus, the cooling medium can be directed specifically toward the stator winding to cool the stator, thereby increasing the performance of the traction drive.

[0030] In a preferred embodiment of the invention, a plurality of passage openings are provided, which are arranged at a distance from one another in the circumferential direction of the rotor shaft. Preferably, the number of passage openings corresponds to the number of salient poles. However, it is also conceivable that the number of passage openings is a multiple of the number of salient poles.

[0031] In a second aspect, the invention relates to a traction drive of an at least partially electrically driven motor vehicle with the rotor according to the invention.

[0032] The traction drive preferably comprises a cooling medium, in particular an oil or a water-glycol mixture, wherein the cooling medium flows from the hollow shaft via the passage opening into the reservoir and, starting from the reservoir, is guided via the outlet opening to the surface of the winding head in order to cool it.

[0033] In a third aspect, the invention relates to a motor vehicle with the traction drive according to the invention.

[0034] The motor vehicle is preferably partially and particularly preferably completely electrically powered.

[0035] 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. In particular, all features of the separately excited rotor can apply equally to the traction drive and the motor vehicle. This also applies vice versa.

[0036] 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.

[0037] In these show: Fig. 1 a longitudinal section through a separately excited rotor according to an embodiment of the invention;

[0038] Fig. 2 shows a longitudinal section through the rotor in the region of a winding head of a rotor winding;

[0039] Fig. 3 is a view of an end cap;

[0040] Fig. 4 a view of a star disk with ramp contour;

[0041] Fig. 5 a motor vehicle.

[0042] Fig. 1 shows a longitudinal section through a separately excited rotor RO for an electric machine EM of a traction drive TA. The separately excited rotor RO comprises a rotor shaft RW. The rotor shaft RW is designed as a hollow shaft HW and thus has a shaft cavity WHR. On a side facing outwards in the radial direction of the rotor shaft RW, the rotor shaft RW has an outer circumferential surface AM. A laminated core BP is arranged on the outer circumferential surface AM. The laminated core BP has at least one salient pole AP. Typically, the laminated core BP has a plurality of salient poles AP arranged at regular intervals from one another in the circumferential direction of the laminated core BP. A rotor winding RWI is arranged and / or wound on the salient pole AP. The rotor winding RWI has a winding head WK, wherein the winding head WK projects beyond an end face SS of the laminated core BP formed in the axial direction of the rotor RO.

[0043] The winding head WP is at least partially and / or sectionally covered by an end cap EK. The winding head WK is at least partially covered by the end cap EK in the axial direction of the rotor RO and in the circumferential direction of the rotor RO. A reservoir RV for holding a cooling medium KM is arranged and / or formed between the end cap EK and the end face SS. The reservoir RV has at least one outlet opening AOE. The outlet opening AOE is directed and / or formed toward the winding head WK.

[0044] A passage opening DLO is formed in a shaft wall WW of the rotor shaft RW, so that a cooling medium KM can emerge from the shaft cavity WHR of the rotor shaft RW via the passage opening DLO, be absorbed by the reservoir RV, escape from the reservoir RV via the outlet opening AOE and reach the winding overhang WK. The cooling medium is preferably a fluid, in particular an oil or a water-glycol mixture. By absorbing the cooling medium KM emerging from the hollow shaft HW in the reservoir RV and specifically discharging the cooling medium KM via the outlet opening AOE to the winding overhang WK, the flowing cooling medium can be guided directly to a surface OF of the winding overhang WK ​​that is to be cooled, thereby increasing the cooling effect. In other words, atomization of the cooling medium KM is reduced, and the cooling medium KM is guided to the winding overhang WK ​​as a flowing cooling medium KM.The increased cooling effect can also increase the performance of the rotor RO and / or the traction drive TA.

[0045] Fig. 2 shows a longitudinal section through the rotor RO in the region of the winding head WK of the rotor winding RW. As can be seen from the detailed view, the reservoir RV is J-shaped at least in sections in a longitudinal section through the rotor RO, with an opening OE of the reservoir RV facing the rotor shaft RW for receiving a cooling medium KM escaping from the rotor shaft RW. In other words, the opening OE between a long web LS and a short web KS of the J-shaped reservoir RV is directed towards the rotor shaft RW, so that the cooling medium KM escaping from the hollow rotor shaft RHW via the passage opening can be easily received by the reservoir RV.

[0046] It can also be seen that a ramp contour RK is formed between the reservoir RV and the outer surface AM, which ramp contour directs a cooling medium KM emerging from the passage opening DLO directly and / or indirectly into the reservoir RV. Indirect means that the cooling medium KM preferably first flows from the ramp contour RK against an inner side IS of the end cap EK before the cooling medium KM reaches the reservoir RV. Direct means that the cooling medium KM flows from the ramp contour RK directly into the reservoir RV. By means of the ramp contour RK and by utilizing a surface tension of the cooling medium KM, the cooling medium KM emerging from the passage opening DLO can be guided as a flowing medium into the reservoir RV.

[0047] The ramp contour RK is designed at an angle. For an angle a of the ramp contour RK, relative to a radial direction of the rotor RO, a = 45° applies in the present embodiment. Due to the inclination of the ramp contour RK, the cooling medium KM can be guided into the reservoir RV in a flowable state.

[0048] A distal end DE of the ramp contour RK is directed toward the end cap EK. In other words, the distal end DE of the ramp contour RK points away from the laminated core BP toward the end cap EK.

[0049] The following applies to a minimum distance d1 between the winding overhang WK ​​and a reservoir outer surface RAS facing the winding overhang WK ​​in the area of ​​the outlet opening AOE: 0.5 mm < d1 < 5 mm. The smaller the minimum distance between the surface OF of the winding overhang WK ​​and the outlet opening AOE, the better the cooling medium KM can be brought in a fluid state to the surface OF of the winding overhang WK, and then flow radially along the surface OF of the winding overhang WK ​​under the influence of centrifugal force. This can increase the cooling effect of the rotor RO.

[0050] For a minimum distance d2 between the distal end DE of the ramp contour RK and the reservoir RV or the inner side IS, the following applies: 0.5 mm < d2 < 5 mm. The smaller the distance d2 is, the more favorable the transfer of the cooling medium KM in the flowable state from the ramp contour RK into the reservoir RV.

[0051] Furthermore, it can be seen that the winding overhang WK, relative to a radial direction of the rotor shaft RW, has a winding overhang height with an inner section IA directed inward in the radial direction and an outer section directed outward in the radial direction, and the outlet opening AOE is directed towards the inner section IA. In other words, in this way, the cooling medium KM - relative to the radial direction of the rotor RO - can be guided from the inside to a surface OF of the winding overhang WK. Under the influence of centrifugal force during operation of the rotor RO, the cooling medium KM is then guided outward in the radial direction along the surface OF of the winding overhang WK, thereby cooling the winding overhang WK.

[0052] Fig. 3 shows a view of the end cap EK. It is conceivable that the end cap EK and the reservoir RV are formed as a single piece, as indicated in Fig. 1. This has the advantage of reducing the number of parts. A reduced number of parts can have a beneficial effect on the parts costs and also on the manufacturing process of the rotor RO, thus reducing manufacturing costs.

[0053] In this case, the end cap EK and the reservoir RV are constructed in multiple parts. A multi-part design can be advantageous in the selection and design of materials, thereby reducing the material and / or manufacturing costs of the rotor RO.

[0054] In the exemplary embodiment, the end cap EK is made of a metal or comprises a metal. An end cap EK made of a metal can preferably be formed as a deep-drawn part, so that the end cap EK can be manufactured inexpensively.

[0055] The reservoir RV is galvanically insulating. In this case, galvanically insulating means that the reservoir RV comprises a material that is not electrically conductive or electrically insulating. A galvanically insulating material can preferably be a plastic. The plastic can be a thermosetting or thermoplastic plastic. The plastic can be a thermoplastic or a thermosetting plastic. With a galvanically insulating reservoir RV, the distance to the electrically conductive winding head WK can be reduced. The reduced distance d1 can reduce atomization of the cooling medium KM. This can have a beneficial effect on the cooling effect.

[0056] Furthermore, it can be seen that the reservoir RV has a plurality of outlet openings AOE, which are arranged at regular and irregular intervals along the circumference of the reservoir RV and / or the rotor RO. Thus, the distribution of the outlet openings AOE allows the cooling medium KM to be directed specifically to the winding heads EK for efficient cooling.

[0057] In this case, a group of first outlet openings (AOE) is provided, arranged at regular intervals. The number of groups of first outlet openings (AOE) depends on the number of salient poles (AP) of the rotor (RO).

[0058] A plurality of outlet openings ALO are provided in the end cap EK, which are arranged at a distance from one another in the circumferential direction of the rotor RO and / or the end cap EK. Thus, the cooling medium KM can be directed specifically toward the stator winding (not shown) to cool the stator (not shown), thereby increasing the performance of the traction drive TA.

[0059] The outlet opening ALO is designed as a closed-edge recess, i.e., a bore. Conceivably and particularly advantageously, the recess is formed in a terminal edge ASK facing the end face SS. This design has the advantage that the end cap EK is not weakened by the bore.

[0060] The outlet opening ALO is offset from the outlet opening AOE in the circumferential direction of the rotor RO. In particular, the outlet opening AOE is directed directly toward the winding head WK to allow the cooling medium KM to reach the surface OF of the winding head WK and to allow the cooling medium KM to flow onto the surface OF of the winding head WK. The outlet opening ALO, on the other hand, is offset from or adjacent to the salient pole AP in the circumferential direction of the rotor RO.

[0061] Fig. 4 shows a view of a star disk STS with the ramp contour RK. It is conceivable that the ramp contour RK is manufactured and / or formed as a separate component. However, it is particularly advantageous if the ramp contour RK is an integral part of the star disk STS, which can also be referred to as a routing cap. The routing cap is arranged on the end face SS of the laminated core BP, and the rotor winding RWI is wound thereafter. The rotor winding RWI is guided around the routing cap in the area of ​​the end face SS and is guided within it.

[0062] The STS star disk is made of a galvanically insulating material, in particular a plastic.

[0063] Fig. 5 shows an at least partially electrically driven motor vehicle KFZ with the traction drive TA, which comprises the electric machine EM, wherein the rotor RO is arranged in the electric machine EM of the traction drive TA.

Claims

Patent claims 1. A separately excited rotor (RO) for an electric machine (EM) of an at least partially electrically powered motor vehicle (KFZ), comprising a rotor shaft (RW) with a shaft cavity (WHR) and an outer circumferential surface (AM), a laminated core (BP) arranged on the outer circumferential surface (AM) and having at least one salient pole (AP), a rotor winding (RWI) arranged on the salient pole (AP) and having a winding head (WK) projecting beyond an end face (SS) of the laminated core (BP) formed in the axial direction of the rotor (RO), an end cap (EK) covering the winding head (WK) at least partially and / or in sections, a reservoir (RV) arranged and / or formed between the end cap (EK) and the end face (SS), having at least one outlet opening (AOE), and a passage opening (DLO) formed in a shaft wall (WW) of the rotor shaft (RW),wherein a cooling medium (KM) emerges from the shaft cavity (WHR) of the rotor shaft (RW) via the passage opening (DLO), is absorbed by the reservoir (RV) and escapes from the reservoir (RV) via the outlet opening (AOE) and can reach the winding head (WK).

2. Separately excited rotor according to claim 1, characterized in that the winding head (WK) has a winding head height with respect to a radial direction of the rotor shaft (RW) with an inner section (IA) directed inwards in the radial direction and an outer section directed outwards in the radial direction, and the outlet opening (AOE) is directed towards the inner section (IA).

3. Separately excited rotor according to one of the preceding claims, characterized in that the reservoir (RW) is at least partially J-shaped in a longitudinal section through the rotor (RO), wherein an opening (OE) of the reservoir (RV) for receiving a cooling medium (KM) emerging from the rotor shaft (RW) faces the rotor shaft (RW).

4. Separately excited rotor according to claim 3, characterized in that a short web (KS) of the reservoir, which is J-shaped in longitudinal section, faces the winding head (WK) and / or the end face (SS).

5. Separately excited rotor according to claim 4, characterized in that the at least one outlet opening (AOE) is formed in the short web (KS) of the reservoir which is J-shaped in longitudinal section and / or in a transition between the short web (KS) and a long web (LS) of the reservoir which is J-shaped in longitudinal section.

6. Separately excited rotor according to one of the preceding claims, characterized in that for a smallest distance d1 between the winding head (WK) and a reservoir outer side (RAS) facing the winding head (WK) in the region of the outlet opening (AOE), the following applies: 0.5 mm < d1 < 7 mm.

7. Separately excited rotor according to one of the preceding claims, characterized in that a ramp contour (RK) is formed between the reservoir (RV) and the outer circumferential surface (AM), which ramp contour directs a cooling medium (KM) emerging from the passage opening (DLO) directly and / or indirectly into the reservoir (RV).

8. Separately excited rotor according to one of the preceding claims, characterized in that for an angle a of the ramp contour (RK), based on a radial direction of the rotor, the following applies: 30° < a < 60°.

9. Separately excited rotor according to claim 8, characterized in that the ramp contour (RK) is arranged on the end face (SS), and a distal end of the ramp contour (RK) is directed towards the end cap (EK).

10. Separately excited rotor according to claim 8 or 9, characterized in that for a smallest distance d2 between the distal end of the ramp contour (RK) and an inner side (IS) of the end cap (EK) or the reservoir (RV) facing the ramp contour (RK), the following applies: 0.5 mm < d2 < 7 mm. 11 . Separately excited rotor according to one of the preceding claims, characterized in that the end cap (EK) has at least one outlet opening (ALO).

12. Externally excited rotor according to claim 11, characterized in that the outlet opening (ALO) is closed at the edge and / or is designed as a recess in an end edge (ASK) facing the end face (SS).

13. Externally excited rotor according to claim 11 or 12, characterized in that the outlet opening (ALO) is arranged offset in the circumferential direction relative to the outlet opening (AOE).

14. Traction drive (TA) of an at least partially electrically driven Motor vehicle (KFZ) according to one of the preceding claims.

15. Motor vehicle (KFZ) with a traction drive (TA) according to claim 14.

Images