Slip ring arrangement

Abstract

The invention relates to a slip ring arrangement for an electric machine, the slip ring arrangement comprising a first slip ring module having a first slip ring for making electrical contact, a first conductor which extends from the slip ring in the axial direction and is electrically conductively connected to the first slip ring, and a substantially hollow-cylindrical first carrier element. The first slip ring is arranged on a radial outer side of the carrier element in a first axial section. In a second axial section, the first conductor is enclosed by the first carrier element between a radial inner side and a radial outer side. Furthermore, a circumferential first flange is arranged on the outer side between the first axial section and the second axial section. The invention also relates to a rotor of an externally excited synchronous machine.

Description

[0001] SLIDE RING ARRANGEMENT

[0002] The present invention relates to a slip ring arrangement for an electric machine and a rotor of a separately excited synchronous machine, comprising a slip ring arrangement according to the invention.

[0003] Electric motors are increasingly being used for propulsion in motor vehicles to create alternatives to combustion engines that require fossil fuels. Considerable efforts have already been made to improve the everyday usability of electric drives and to offer users the familiar driving comfort.

[0004] In the development of electric motors for electric drives, there is a persistent need to increase their power density and efficiency while simultaneously reducing manufacturing costs, as the vehicle's cost and weight are largely determined by the battery size. In this context, it is also common to design electric motors as separately excited synchronous machines (FSMs). Here, electrical power must be transferred to the rotor of a separately excited synchronous machine to excite the rotor windings. For traction motors, a contact-based transformer is typically used for this purpose. When these windings are energized, a magnetic field is generated, which, in combination with the stator's magnetic field, produces a torque. The strength of the rotor field can be adjusted by varying the current applied. This allows the machine's behavior to be continuously optimized for efficiency in the respective driving situation.

[0005] US1870236A discloses a slip-ring assembly consisting of a plurality of separate units mounted axially on a shaft of an electrical machine, the units being mounted in axial contact. Each unit comprises a hub element engaging with the shaft, an annular slip ring concentric with the hub, and a body of insulating material that secures the ring to the hub and extends laterally from the plane of one end of the ring. The insulating body of each unit has projecting sections that engage with the slip ring and other projecting sections that engage with the hub to prevent relative axial movement of either element with respect to the body. Furthermore, the insulating body of each unit has a through-hole between the ring and the hub.

[0006] US2019140521A discloses a slip ring arrangement wherein an internally ventilated disk is arranged between adjacent slip rings for the purpose of cooling.

[0007] The object of the invention is now to provide an improved slip ring arrangement which has a compact design and thus addresses the high requirements for small footprint and high power density, particularly in the field of electric vehicle drives.

[0008] This problem is solved by the measures specified in the independent claims. Advantageous embodiments can be found in the dependent claims.

[0009] According to one aspect, a slip ring arrangement for an electric machine comprises a first slip ring module, having a first slip ring for electrical contact, a first conductor extending axially from the slip ring and electrically connected to the first slip ring, and a substantially hollow cylindrical first support element. The first slip ring is arranged on the support element in a first axial section on a radial outer surface. In a second axial section, the first conductor is enclosed by the first support element between a radial inner surface and a radial outer surface. Furthermore, a circumferential first web is arranged on the outer surface between the first axial section and the second axial section.

[0010] Advantageously, the first web forms an axial stop for subsequent installation in a hollow shaft. Furthermore, the web is designed to maximize air and creepage distances and electrical currents, thus minimizing the risk of an electrical short circuit.

[0011] The advantageous effect of arranging the first conductor between the radial inner and radial outer surfaces of the first support element lies, on the one hand, in the form-fit or material-fit fixation of the first conductor and, on the other hand, in the insulation of the conductor from its surroundings. Preferably, the first support element is made of an injection-moldable insulator, which is overmolded around the first conductor. It is particularly advantageous if the first support element is manufactured such that the first slip ring and the first conductor are overmolded in a single mold or operation step and thus fixed in their spatial arrangement. Advantageously, the first web is formed monolithically from the first support element. Preferably, the first slip ring is arranged coaxially with the radial outer and radial inner surfaces of the first support element.

[0012] According to one embodiment, the slip ring arrangement comprises a second slip ring module, having a second slip ring for electrical contact, a second conductor extending axially from the second slip ring and electrically connected to the second slip ring, and a substantially hollow cylindrical second support element. The second slip ring is arranged on a radial outer surface of the second support element in a first axial section. In a second axial section, the second conductor is enclosed by the second support element between a radial inner surface and a radial outer surface.Between the first axial section and the second axial section, a continuous second web is arranged on the outside, wherein the second section of the second support element is arranged radially inside the first support element, and the second web rests against the first support element in the axial direction.

[0013] Advantageously, this results in a compact, nested slip ring arrangement for an electric machine, in particular a separately excited synchronous machine. Preferably, the second slip ring is arranged coaxially to the radial outer side and the radial inner side of the second support element.

[0014] Advantageously, the second web forms an axial stop for mounting in the first support element and thus defines the spatial position of the first and second support elements relative to each other. Particularly preferred is the radial inner and radial outer surfaces of both the first and second support elements being coaxial with each other, so that when the second support element is arranged within the first, it is centered relative to the first. This results in a coaxial arrangement of the slip rings. Furthermore, the web is designed to maximize air and creepage distances and thus minimize the risk of an electrical short circuit.

[0015] According to one embodiment, the first axial section of the first slip ring module forms an axial end face, and the second axial section forms a second axial end face opposite the first axial section. The first support element forms a rod-like extension on the second axial end face, which completely encloses the first conductor.

[0016] The first conductor preferably projects axially from the rod-like extension of the first support element at its distal end.

[0017] According to a further embodiment, the first axial section of the second slip ring module forms an axial end face, and the second axial section forms a second axial end face opposite the first axial section. The second support element forms a rod-like extension on the second axial end face, which completely encloses the second conductor.

[0018] The second conductor preferably protrudes axially from the rod-like extension of the second support element at its distal end.

[0019] According to an advantageous embodiment, the slip ring arrangement comprises a substantially cylindrical third support element, which forms an axial section with a radial outer surface, wherein a circumferential third web is arranged on the outer surface. The third web rests axially against the second support element.

[0020] Particularly preferably, the third web is arranged on an axial end face of the third support element. According to one embodiment, the first web has a radius R1, the second web a radius R2, and the third web a radius R3, where R1, R2, and R3 are identical.

[0021] This results in a design of the slip ring assembly that is easy to install. However, the minimum radius to be maintained, R1, R2, or R3, is determined by the requirements regarding clearance and creepage distance. Advantageously, the radii are chosen such that the minimum radius is the determining radius for all other radii, even if these could be dimensioned smaller.

[0022] According to one embodiment, the radial outer surface of the second axial section of the second support element has essentially the same diameter as the radial inner surface of the first support element. A sealing element is arranged between the radial outer surface of the second axial section of the second support element and the radial inner surface of the first support element.

[0023] According to a further embodiment, the radial outer surface of the axial section of the third support element has essentially the same diameter as the radial inner surface of the second support element. A sealing element is arranged between the radial outer surface of the axial section of the third support element and the radial inner surface of the second support element.

[0024] Thus, a nested structure with appropriate interference fits allows for the production of a fixed slip ring arrangement, which is sealed against any fluid, e.g. oil or oil-water mixtures for the purpose of cooling the rotor via the hollow shaft towards the shaft end.

[0025] According to one embodiment, the first conductor projects from the first support element at a distal end of the extension and forms a first contact surface there. A third conductor is arranged on this first contact surface, extending essentially radially outwards.

[0026] According to one embodiment, the second conductor projects from the second support element at a distal end of the extension, forming a second contact surface. A fourth conductor is arranged on this second contact surface, extending essentially radially outwards.

[0027] The first and second contact surfaces project radially beyond the radial inner surface of the first and second support elements and are thus accessible from an axial direction through the hollow shaft-like structure for a tool, so that after inserting the first support element into the hollow shaft, the second support element into the first support element, and the fourth support elements into the hollow shaft, the first and third conductors or the second and fourth conductors can be electrically contacted at the corresponding first or second contact surfaces, e.g. by means of laser beam welding or a welding gun passing through the first and second support elements.

[0028] According to another aspect, a rotor of a separately excited synchronous machine has a hollow shaft with a radial inner surface and a slip ring arrangement according to the above aspect and / or embodiments, wherein the second section of the first support element is arranged radially inside the hollow shaft, and the first web rests against the hollow shaft in the axial direction.

[0029] Preferably, the radial inner surface extends from an axial end of the hollow shaft in the axial direction. The advantageous effect here is the reduction of radial and axial installation space compared to conventional designs, which are arranged radially outside the shaft and usually axially next to the actual rotor body. A further advantage lies in the reduced relative speed between the contact pin and the slip ring due to the sliding contact being located radially further inward compared to conventional systems, resulting in lower friction and thus reduced wear.

[0030] According to an advantageous embodiment, the radial outer surface of the second axial section of the first support element has essentially the same diameter as the radial inner surface of the hollow shaft. Preferably, a sealing element is arranged between the radial outer surface of the second axial section of the first support element and the radial inner surface of the hollow shaft.

[0031] Particularly preferred is the coaxial arrangement of the radial inner surface of the hollow shaft and the radial outer surface of the first support element, so that when the first support element is arranged in the hollow shaft, it is centered relative to the shaft. This results in a coaxial arrangement of the first slip ring. With the aforementioned advantageous configuration of the first and second support elements being coaxial to each other, the first and second slip rings are arranged coaxially with respect to the rotor shaft. The advantageous effect of this arrangement lies in the reduction of imbalances.

[0032] According to a further embodiment, the hollow shaft has a first radial opening that connects the radial inner side with a radial outer side of the hollow shaft, the third conductor passing through the hollow shaft through the first radial opening. According to a further embodiment, the hollow shaft has a second radial opening that connects the radial inner side with a radial outer side of the hollow shaft, the fourth conductor passing through the hollow shaft through the second radial opening. It is particularly advantageous for the first and second radial openings to be spaced apart from each other circumferentially such that they are opposite each other. In other words, they are particularly preferably spaced apart from each other circumferentially by 180°.

[0033] Preferably, the third or fourth conductor is secured relative to the first or second radial opening by means of a fourth support element in which the third or fourth conductor is positively embedded. This support element is preferably positively, materially, or force-fit connected to the hollow shaft to provide support against forces resulting from centrifugal forces occurring during operation.

[0034] Advantageously, the third conductor is thus guided and supported as far as possible inside the hollow shaft in a radial direction, so that the influence of unwanted forces, especially bending forces, is reduced or even completely avoided.

[0035] Advantageously, the fourth conductor is thus guided and supported as far as possible inside the hollow shaft in a radial direction, so that the influence of unwanted forces, especially bending forces, is reduced or even completely avoided.

[0036] The invention and its technical context are explained in more detail below with reference to the figures. It should be noted that the invention is not limited to the embodiments shown. In particular, unless explicitly stated otherwise, it is also possible to extract aspects of the concepts illustrated in the figures and combine them with other elements and findings from the present description and / or figures. It should be emphasized that the figures, and especially the depicted dimensions, are only schematic. Identical reference numerals denote identical objects, so that explanations from other figures may be consulted for supplementary information. Terms such as "radial," "axial," or similar refer to the axis of rotation of the electrical machine, unless a different reference is explicitly used.Furthermore, for the sake of better readability of the figures, only individual or a few identical elements of a reference symbol may be provided.

[0037] It shows

[0038] Fig. 1 shows a perspective view of a longitudinal section through a slip ring assembly,

[0039] Fig. 2 shows two detailed views of elements of the slip ring arrangement according to Fig. 1.

[0040] Fig. 3 shows two detailed views of the first slip ring module of the slip ring arrangement according to Fig. 1.

[0041] Figure 1 shows a perspective view of a longitudinal section through a slip ring assembly 1. The slip ring assembly 1 comprises a first slip ring module 31, which is inserted axially into a hollow shaft 18, and a second slip ring module 32, which is inserted axially into the first slip ring module 31. The first slip ring module 31 comprises a first support element, which has a first web 21 and a first axial section, which is shown to the right of the web 21 in Figure 3b). A first slip ring 2 is arranged in this first axial section. This first slip ring 2 is electrically connected to a first conductor 4, which extends from the first axial section to a second axial section to the left of the first web 21 between a radial inner and a radial outer surface of the first support element 5.From the second axial section, the first conductor 4 extends into a rod-like extension, which is integrally formed from the first support element 5. The rod-like extension is formed at a second axial end face of the first support element 5, which is located at a distal end of the first axial section, and is opposite a first axial end face, which is also located at a distal end of the first axial section. Starting from the electrical contact with the first slip ring 2, the first conductor 4 is completely enclosed by the first support element in both radial and circumferential directions until it projects axially out of the rod-like extension. In the region of the second axial section, the first conductor 4 forms a U-shaped recess in the radial direction, thereby creating space within the first support element 5 for receiving a sealing element 40 (see also Fig. 40).2b). The sealing elements are not shown in Fig. 3. The first slip ring module 31 is inserted into the hollow shaft 18 with its second axial section, the first web 21 forming an axial stop. The slip ring assembly 1 further comprises the second slip ring module 32, which is inserted axially into the first slip ring module 31. The second slip ring module 32 comprises a second support element 6, which has a second web 22 and a first axial section, the arrangement of which with respect to the second web 22 is analogous to the arrangement of the first axial section of the first support element 5 and the first web 21. A second slip ring 7 is arranged in this first axial section.This second slip ring 7 is electrically connected to a second conductor 9, which extends from the first axial section into a second axial section between a radial inner and a radial outer surface of the second support element 6, with the second web 22 being arranged between the first and second sections. From the second axial section, the second conductor 9 extends into a rod-like extension that is integrally formed from the second support element 6. The rod-like extension is formed at a second axial end face of the second support element 6, which is located at a distal end of the second axial section, and is opposite a first axial end face, which is located at a distal end of the first axial section.The second conductor 9, starting from the electrical contact with the second slip ring 7, is completely enclosed radially and circumferentially by the second support element 6 until it projects axially out of the rod-like extension. The second slip ring module 32 is inserted into the first slip ring module 31 with its second axial section, the second web 22 forming an axial stop. A third support element 15 is inserted axially into the second slip ring module 32, forming a third web 23 on an axial outer side, which again serves as an axial stop. The third support element 15 also has a sealing element 40.Regarding the sealing concept, in the first slip ring module 31, sealing elements are attached to the radial outside towards the hollow shaft and to the radial inside towards the second slip ring module 32 in the first axial section; furthermore, a sealing element is attached to a radial outside of an axial section towards the second sealing element.

[0042] The first conductor 4 projects from the first support element at a distal end of the extension and forms a first contact surface 10 there; likewise, the second conductor 9 forms a corresponding second contact surface 12. The two contact surfaces are spaced 180° apart in the circumferential direction.

[0043] Figure 2 shows two detailed views of elements of the slip ring assembly according to Figure 1. The slip ring assembly 1 is shown without the hollow shaft 18 and without the support elements for receiving the first and second contact pins 3, 8 in Figure 2b) as a section and in Figure 2a) as a three-dimensional representation. Thus, Figure 2b) shows that a first conductor 4 extends axially from the first slip ring 2 within a wall formed between the radial outer and radial inner surfaces of the first support element 5, which is essentially designed as a hollow cylinder. The first conductor 4 is thus enclosed by the first support element 5, which therefore acts as an electrical insulator and as a support element that fixes the first conductor 4 in its position. The first conductor 4 projects out of the first support element 5 on an axial outer surface and forms a first contact surface 10 at its distal end.A third conductor 11 is arranged on this first contact surface 10. This conductor extends radially through a first radial opening 19 in the hollow shaft 18 (see Fig. 1), thus enabling electrical contact with the rotor windings (not shown), which are arranged on the radial outer side of the hollow shaft 18 in a rotor body (also not shown). A fourth support element 17 encloses the third conductor 11, at least partially, and functions as an electrical insulator and as a support element that fixes the position of the third conductor 11. Extending from the second slip ring 7, a second conductor 9 runs axially within a wall formed between the radial outer and radial inner sides of the second support element 6, which is essentially a hollow cylinder.The second conductor 9 is thus enclosed by the second support element 6, which therefore functions as an electrical insulator and as a support element that fixes the second conductor 9 in its position. The second conductor 9 projects from the second support element 6 on an axial outer side and forms a second contact surface 12 at its distal end. A fourth conductor 13 is arranged on this second contact surface 12. A further fourth support element 17 encloses the fourth conductor 13, at least partially, and functions as an electrical insulator and as a support element that fixes the position of the fourth conductor 13. The fourth conductor 13 penetrates the hollow shaft 18 radially through a second radial opening 20, thus ultimately enabling electrical contact with the rotor windings (not shown), which are arranged on the radial outer side of the hollow shaft 18 in a rotor body (also not shown).

[0044] Figure 3 shows two detailed views of the first slip ring module of the slip ring assembly according to Fig. 1. The depiction of sealing elements 40 has been omitted.

[0045] List of reference signs

Claims

Patent claims 1. Slip ring arrangement (1 ) for an electric machine, comprising a first slip ring module (31), having - a first slip ring (2) for electrical contact, - a first conductor (4) extending axially from the slip ring (2), which is electrically connected to the first slip ring (2), and - a substantially hollow cylindrical first support element (5) on which the first slip ring (2) is arranged in a first axial section on a radial outer side, and in a second axial section the first conductor (4) is enclosed between a radial inner side and a radial outer side by the first support element (5), characterized in that a circumferential first web (21) is arranged on the outer side between the first axial section and the second axial section.

2. Slip ring arrangement (1) according to claim 1, comprising a second slip ring module (32), comprising - a second slip ring (7) for electrical contact, - a second conductor (9) extending axially from the second slip ring (7), which is electrically connected to the second slip ring (7), and - a substantially hollow cylindrical second support element (6) on which, in a first axial section, the second slip ring (7) is arranged on a radial outer side, and in a second axial section, the second conductor (9) is enclosed between a radial inner side and a radial outer side by the second support element (6), and between the first axial section and a second web (22) is arranged around the outside of the second axial section, wherein the second section of the second support element (6) is arranged radially inside the first support element (5), and the second web (22) rests against the first support element (5) in the axial direction.

3. Slip ring arrangement (1) according to claim 2, wherein the first axial section of the first slip ring module (31) forms an axial end face and the second axial section forms a second axial end face opposite the first axial section, wherein the first support element (5) forms a rod-like extension on the second axial end face which circumferentially surrounds the first conductor (4), or the first axial section of the second slip ring module (32) forms an axial end face and the second axial section forms a second axial end face opposite the first axial section, wherein the second support element (6) forms a rod-like extension on the second axial end face which circumferentially surrounds the second conductor (9).

4. Slip ring arrangement (1 ) according to one of claims 2 to 3, comprising a substantially cylindrical third support element (15) which forms an axial section with a radial outer surface, wherein a circumferential third web (23) is arranged on the outer surface, and the third web (23) abuts the second support element (6) in the axial direction.

5. Slip ring arrangement (1) according to claim 4, wherein the first web (21) has a radius R1, the second web (22) has a radius R2, the third bridge (23) has a radius R3, wherein R1, R2, and R3 are identical.

6. Slip ring arrangement (1) according to any one of claims 2 to 5, wherein the radial outside of the second axial section of the second support element (6) has substantially the same diameter as the radial inside of the first support element (5), wherein a sealing element (40) is arranged between the radial outside of the second axial section of the second support element (6) and the radial inside of the first support element (5), or the radial outside of the axial section of the third support element (15) has substantially the same diameter as the radial inside of the second support element (6), wherein a sealing element (40) is arranged between the radial outside of the axial section of the third support element (15) and the radial inside of the second support element (6).

7. Slip ring arrangement (1 ) according to one of claims 3 to 6, wherein the first conductor (4) projects out of the first support element (5) at a distal end of the extension and forms a first contact surface (10) there, and a third conductor (11 ) is arranged on this first contact surface (10), which extends substantially in a radial direction outwards, or the second conductor (9) projects out of the second support element (9) at a distal end of the extension and forms a second contact surface (12) there, and a fourth conductor (13) is arranged on this second contact surface (12), which extends substantially in a radial direction outwards.

8. Rotor of a separately excited synchronous machine, comprising a hollow shaft (18) with a radial inner surface, and a slip ring arrangement (1 ) according to any one of claims 1 to 7, wherein the second section of the first support element (5) is arranged radially inside the hollow shaft (18), and the first web (21) rests against the hollow shaft (18) in the axial direction.

9. Rotor of a separately excited synchronous machine according to claim 8, wherein the radial outside of the second axial section of the first support element (5) has substantially the same diameter as the radial inside of the hollow shaft (18), wherein a sealing element (40) is arranged between the radial outside of the second axial section of the first support element (5) and the radial inside of the hollow shaft (18).

10. Rotor of a separately excited synchronous machine according to one of claims 8 to 9, wherein the hollow shaft (18) has a first radial opening (19) which connects the radial inside with a radial outside of the hollow shaft (18), wherein the third conductor (11) penetrates the hollow shaft (18) through the first radial opening (19), or the hollow shaft (18) has a second radial opening (20) which connects the radial inside with a radial outside of the hollow shaft (18), wherein the fourth conductor (13) penetrates the hollow shaft (18) through the second radial opening (20).

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