Transmitter in a hollow shaft, radial slip ring module comprising oil-pressure brushes, optimised cable feed-through, and electric machines

Abstract

The invention relates to a slip ring arrangement for an electric machine, the slip ring arrangement comprising: a first slip ring which has a radial inner side and a radial outer side; a first contact pin which, together with the first slip ring, forms an electrically conductive sliding contact; a first conductor which extends from the first slip ring in the axial direction and is electrically conductively connected to the first slip ring; and a substantially hollow-cylindrical first carrier element which has a radial inner side and a radial outer side. The radial outer side of the first slip ring is arranged on the radial inner side of the first carrier element. The first conductor is enclosed between the radial inner side and the radial outer side of the first carrier element. The first contact pin is guided so as to be radially displaceable within a second carrier element and is acted upon, or can be acted upon, by a force in a first radial direction. The second carrier element is arranged in a volume which is defined in the radial direction by the radial inner side of the first slip ring, the second carrier element being arranged rotatably relative to the first carrier element. Furthermore, the first contact pin can be acted upon by the force of a fluid on the side opposite the sliding contact in the radial direction. The invention also relates to a rotor of an externally excited synchronous machine.

Description

[0001] Transmitter in hollow shaft / radial slip ring module with oil pressure brushes / optimized cable routing / E-machines

[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] The object of the invention is to provide an improved slip ring arrangement that is compact and thus addresses the high demands for small footprint and high power density, particularly in the field of electric vehicle drives. This object is achieved by the measures specified in the independent claims. Advantageous embodiments can be found in the dependent claims.

[0006] According to one aspect, a slip ring arrangement for an electric machine comprises a first slip ring, which has a radial inner surface and a radial outer surface; a first contact pin, which forms an electrically conductive sliding contact with the first slip ring; a first conductor extending axially from the first slip ring, which is electrically connected to the first slip ring; and a substantially hollow cylindrical first support element, which has a radial inner surface and a radial outer surface. The first slip ring is arranged with its radial outer surface against the radial inner surface of the first support element. The first conductor is enclosed between the radial inner surface and the radial outer surface of the first support element.The first contact pin is guided radially displaceably within a second support element and is subjected to, or can be subjected to, force in a first radial direction. The second support element is arranged in a volume defined radially by the radial inner surface of the first slip ring, and the second support element is rotatably arranged relative to the first support element. Furthermore, the first contact pin can be subjected to force by a fluid on the side radially opposite the sliding contact.

[0007] Advantageously, this results in a compact, nested slip ring assembly for an electric machine, particularly a separately excited synchronous machine, in which the contact force of the contact pin acting on the first slip ring can be adjusted via a pressure generated by a fluid. In other words, the second support element and the contact pin form a system comparable to a hydraulic cylinder, in which the contact pin represents the piston. Particularly advantageous is the ability to vary the contact force by varying the pressure on the contact pin, thus providing the required contact force and extending the service life of the slip ring assembly.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.

[0008] According to one embodiment, the slip ring arrangement comprises a second slip ring, a second contact pin which forms an electrically conductive sliding contact with the second slip ring, and a second conductor extending axially from the second slip ring and electrically connected to the second slip ring. The second slip ring is arranged with its radial outer surface against the radial inner surface of the carrier element, and the second conductor is enclosed between the radial inner surface and the radial outer surface of the first carrier element. The second contact pin is guided radially displaceably within the second carrier element and is subjected to force in a second radial direction. The second contact pin can be subjected to force by a fluid on the side radially opposite the sliding contact.

[0009] By arranging both the first and second contact pins in a common second support element, and by arranging both the first and second slip rings in a common first support element, a compact, nested slip ring assembly is obtained. Preferably, the first radial direction and the second radial direction are identical; in other words, the contact pins are arranged parallel in the second support element. It is particularly advantageous to have several of the first or second contact pins per slip ring. The second support element and the second contact pin also form a system comparable to a hydraulic cylinder, in which the contact pin represents the piston. Particularly preferred are the hydraulic cylinders formed by the second support element and the respective contact pin connected in parallel to each other.In other words, the same pressure exerted by the fluid acts on both the first and second contact pins. The advantageous effect of arranging the second conductor between the radial inner and radial outer surfaces of the first support element is comparable to that of the first conductor, namely the positive or material-locking fixation of the second conductor and the insulation of the conductor from the environment. It is particularly preferred that the first and second conductors are arranged in the first support element such that they are sufficiently far apart to maximize air and creepage distances and thus minimize the risk of an electrical short circuit. It is particularly preferred that the conductors are offset from each other by 180° in the circumferential direction.

[0010] According to one embodiment, the first conductor and the second conductor protrude from the first support element on an axial outer side.

[0011] This allows for particularly advantageous electrical contact between the first or second conductor and a third or fourth conductor on one axial side, without requiring the first support element to be repositioned axially to accommodate a tool used for contacting. It is especially advantageous for the first and second conductors to be spaced apart circumferentially such that they are opposite each other. In other words, they are preferably spaced 180° apart circumferentially.

[0012] According to a further embodiment, the first conductor projects out from the first support element on its axial outer side, forming a first contact surface. A third conductor is arranged on this first contact surface, extending essentially in the axial direction along the first support element.

[0013] Advantageously, the contacting of the first and third conductors can thus be realized on an axial side, wherein the third conductor also forms a contact surface at a first distal end and has a further contact surface at a second distal end for contacting the coils or necessary switching elements in the rotor, wherein the further distal end of the third conductor is arranged on a side of the first support element facing away from the axial side.

[0014] According to a further embodiment, the second conductor projects from the first support element on its axial outer side, forming a second contact surface. A fourth conductor is arranged on this second contact surface, extending essentially axially along the first support element. Advantageously, this allows the contacting of the second and fourth conductors to be realized on one axial side. The fourth conductor also forms a contact surface at a first distal end and has a further contact surface at a second distal end for contacting the coils or necessary switching elements in the rotor. This second distal end of the fourth conductor is located on a side of the first support element facing away from the axial side.According to a further embodiment, a first groove runs in the axial direction on the radial outside of the first support element, in which a third support element is arranged in a form-fitting manner in the circumferential direction, which at least partially encloses the third conductor.

[0015] The positive-locking arrangement of the third support element offers the advantage of a defined spatial arrangement of the third support element relative to the first support element. The first groove, which runs in the axial direction, provides a translational degree of freedom, allowing for the compensation of mechanical stresses resulting from the contact between the first and third conductors. The third support element is particularly advantageous as an insulator for the third conductor, especially in relation to a rotor shaft.

[0016] According to a further embodiment, a second groove runs in the axial direction on the radial outside of the first support element, in which a fourth support element is arranged in a form-fitting manner in the circumferential direction, which at least partially encloses the fourth conductor.

[0017] The positive-locking arrangement of the fourth support element offers the advantage of a defined spatial arrangement of the fourth support element relative to the first support element. The second groove, which runs in the axial direction, provides a translational degree of freedom, allowing for the compensation of mechanical stresses resulting from the contact between the second and fourth conductors. The fourth support element is particularly advantageous as an insulator for the fourth conductor, especially in relation to a rotor shaft.

[0018] It is particularly advantageous that the first and second grooves are spaced apart from each other circumferentially such that they are opposite each other. In other words, they are preferably spaced apart from each other circumferentially by 180°.

[0019] According to a preferred embodiment, a sealing element is arranged between one of the contact pins and the second support element, so that a pressure chamber is formed.

[0020] The sealing element is particularly advantageous in preventing unwanted leakage between the second support element and the contact pin. Especially with a circumferential rubber seal, a further advantage of the sealing element is the restoring force acting on the contact pin, which is directed radially away from the sliding contact. This reduces friction and ultimately wear in the system, thus increasing the service life of the slip ring assembly.

[0021] According to a particularly preferred embodiment, one of the contact pins has a round cross-section.

[0022] Advantageously, if one of the contact pins has a round cross-section, conventional sealing elements such as O-rings can be used as circumferential rubber seals. However, other sealing elements are also conceivable.

[0023] 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 first support element is arranged radially inside the hollow shaft.

[0024] 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 less friction and therefore less wear.

[0025] According to an advantageous embodiment, a third groove extends axially along the radial inner surface. The third support element is arranged in the first and third grooves, forming a positive-locking connection.

[0026] This advantageously results in the first support element being fixed relative to the hollow shaft, so that in particular no unintended forces act on the third conductor.

[0027] According to an advantageous embodiment, a fourth groove extends axially along the radial inner side. The fourth support element is arranged in the second and fourth grooves, forming a positive-locking connection.

[0028] This advantageously results in the first support element being fixed relative to the hollow shaft, so that in particular no unintended forces act on the fourth conductor.

[0029] Particularly advantageous is the circumferential spacing of the first and second grooves such that they are opposite each other. In other words, they are preferably spaced 180° apart circumferentially. Furthermore, it is particularly advantageous that the third and fourth grooves are spaced 180° apart circumferentially.

[0030] 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, with the third conductor passing through the hollow shaft through this first radial opening. Advantageously, the third conductor is thus guided and supported as far as possible within the hollow shaft in the radial direction, so that the influence of unwanted forces, in particular bending forces, is reduced or even completely avoided. 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, with the fourth conductor passing through the hollow shaft through this second radial opening.Advantageously, the fourth conductor is thus guided and supported as far as possible inside the hollow shaft in the radial direction, so that the influence of unwanted forces, especially bending forces, is reduced or even completely avoided. 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 preferably spaced 180° apart circumferentially.

[0031] 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 the same objects, so that explanations from other figures may be consulted for further clarification. 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.

[0032] It shows

[0033] Fig. 1 shows a perspective view of a longitudinal section through a slip ring assembly,

[0034] Fig. 2 shows two top views of the longitudinal section according to Fig. 1.

[0035] Fig. 3 shows two perspective views of the slip ring arrangement according to Fig. 1.

[0036] Fig. 4 shows several detailed views of various components of the slip ring assembly according to Fig. 1.

[0037] Figure 1 shows a perspective view of a longitudinal section through a slip ring assembly 1. The slip ring assembly 1 is arranged radially in the hollow shaft 18. The first support element 5 has essentially the same radius on its radial outer surface as on the radial inner surface of the hollow shaft 18. In the illustrated embodiment, the first support element 5 is secured against rotation, in particular, by means of an interference fit in the hollow shaft 18. Alternatively, a positive-locking anti-rotation device can be formed consisting of a first groove 14 in the first support element 5 and a corresponding groove in the hollow shaft 18, as well as a third support element 15, in which the third support element 15, similar to a key in a shaft-hub connection, orients the two grooves in the first support element 5 and the hollow shaft 18 relative to each other and secures them against rotation.On the circumferentially opposite side, a further positive-locking anti-rotation device can be formed by a second groove 16 in the first support element 5, a corresponding further groove in the hollow shaft 18, and a fourth support element. A second support element 6 is arranged radially inside the first support element 15 and is rotatable relative to the first support element 15. For the purpose of exciting rotor windings and thus energizing the magnetic field-generating rotor windings (not shown), contact pins 3, 8 together with slip rings 2, 7 form electrically conductive sliding contacts, so that electrical power can be transferred from the stationary second support element 6 to the rotating first support element 5.Within the slip ring arrangement 1, two electrically conductive sliding contacts are formed. Several first contact pins 3 form a first sliding contact with a first slip ring 2, and several second contact pins 8 form a second sliding contact with a second slip ring 7. The respective sliding contact is formed on a radial inner surface of the respective slip ring 2, 7. The two slip rings 2, 7 are arranged axially spaced apart from each other within the first support element 5 on its radial inner surface. A first conductor 4 extends axially from the first slip ring 2 within a wall formed between the radial outer surface and the radial inner surface 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 from the first support element 5 on an axial outer side and forms a first contact surface 10 at its distal end. A third conductor 11 is arranged on this first contact surface 10, extending axially from the axial outer side into the hollow shaft 18 and parallel to the first conductor 4. The third conductor 11 extends axially beyond the first support element 5. The third support element 15 encloses the third conductor 11, at least partially, and acts as an electrical insulator and as a support element that fixes the position of the third conductor.The third conductor 11 penetrates the hollow shaft 18 in a radial direction through a first radial opening 19 and thus ultimately enables electrical contact with the rotor windings (not shown), which are arranged on the radial outside of the hollow shaft 18 in a rotor body (also not shown).

[0038] Starting from the second slip ring 7, a second conductor 9 extends axially within a wall formed between the radial outer and radial inner surfaces of the first support element 5, which is essentially a hollow cylinder. The second conductor 9 is thus enclosed by the first support element 5, which therefore acts 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 first support element 5 on an axial outer surface and forms a second contact surface 12 at its distal end. A fourth conductor 13 is arranged on this second contact surface 12, extending axially from the axial outer surface into the hollow shaft 18 and parallel to the second conductor 9. The fourth conductor 13 extends axially beyond the first support element 5.The fourth support element 17 encloses the fourth conductor 13, at least partially, and functions as an electrical insulator as well 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 outside of the hollow shaft 18 in a rotor body (also not shown).

[0039] The electrical path thus extends from an electrical contact of the first contact pins 3 via the first sliding contact to the first slip ring 2 via the first conductor 4, which is electrically connected to the first slip ring 2 and is in turn electrically connected to the third conductor 11, to the rotor windings not shown, via the fourth conductor 13, which is electrically connected to the second conductor 9, to the second slip ring 7, which is electrically connected to the latter, and via the second sliding contact via the second contact pins 8 to a further electrical contact.

[0040] Figure 2 shows two top views of the longitudinal section according to Figure 1, with the slip ring assembly 1 shown from two perspectives at 90° to each other. In Figure 2a), an axially extending volume is shown in the plane of the image above the contact pins 3, 8. This volume can be connected to a hydraulic system via an opening in the axial outer surface of the second support element 6, located to the right in the plane of the image. The opening is also clearly visible in Figure 3a). The contact pins 3, 8 are arranged to be radially displaceable within the second support element 6, but are electrically connected to a terminal element. The electrical connection is implemented, for example, via spring elements or flexible cables, such that any length compensation due to radial movement of the contact pins, for example, due to wear, can be compensated for.If a pressurized fluid is introduced into the axially extending volume, the second support element 6 and the contact pins 3, 8 form a system comparable to a hydraulic cylinder. The pressure acting on each of the individual contact pins 3, 8, and thus exerting a contact force on the respective slip ring 2, 7 in the sliding contact, can therefore be varied. Corresponding systems that allow for potentially automated adjustment or control are not shown further and are therefore not described. Figure 3b) shows a top view of a section plane that runs centrally through the rotor shaft along the axial direction; the radial direction in which the contact pins 3, 8 are displaceable extends into the plane of the image. The first and second contact pins 3, 8 are designed here as pins with a substantially rectangular cross-section.

[0041] Figure 3 shows two perspective views of the slip ring assembly 1 according to Figure 1. In Figure 3a), only the slip ring assembly 1 is shown, whereas in Figure 3b), the slip ring assembly 1 is shown arranged in the hollow shaft 18. Both the third support element 15 and the fourth support element 17 run in the first and second grooves 14 and 16, respectively, and do not project beyond them in the radial direction, since in the embodiment shown in Figure 3a), the first support element is secured against rotation in the hollow shaft 18 according to Figure 3b) by means of an interference fit. Furthermore, it can be seen in Figure 3b) that

[0042] Figure 4 shows several detailed views of various components of the slip ring assembly 1 according to Fig. 1.

[0043] Figure 4a) shows the first support element 5. The first groove 14, which is designed to receive the third support element 15, extends along the radial outer surface of the first support element 5 over its entire axial length. The first groove 14 is located radially outside the first conductor 4 and is positioned circumferentially in the same direction as the first conductor 4. The second groove 16 is spaced circumferentially from the first groove 14 such that they are opposite each other. In other words, they are spaced 180° apart circumferentially. The second groove 16 is designed to receive the fourth support element 17 and also extends over the entire axial length of the first support element 5. The second groove 16 is also positioned circumferentially in the same direction as the second conductor 9. Thus, the first and second conductors 4, 9 are spaced circumferentially such that they are opposite each other.In other words, they are spaced 180° apart in the circumferential direction. Figure 4b) shows the second support element 6.

[0044] Figure 4c) shows several first and second contact pins 3, 8, which are connected in pairs via electrical contacts. Not shown is the flexible connection of the contact pins 3, 8 to the contacts, which allows radial displacement of the contact pins.

[0045] Figure 4d) shows the third support element 15 and the third conductor 11 contained therein. For the sake of readability, the reference numerals for the fourth support element 17 and the fourth conductor 13 have been omitted from Figure 4d), since in the illustrated embodiment the support elements 15, 17 and the conductors 11, 13 are identical.

[0046] List of reference signs

Claims

Patent claims 1. Slip ring arrangement (1 ) for an electric machine, comprising - a first slip ring (2) which has a radial inner surface and a radial outer surface, - a first contact pin (3) which forms an electrically conductive sliding contact with the first slip ring (2), - a first conductor (4) extending axially from the first slip ring (2), which is electrically connected to the first slip ring (2), and - a substantially hollow cylindrical first support element (5) having a radial inner side and a radial outer side, wherein the first slip ring (2) is arranged with its radial outer side on the radial inner side of the first support element (5), and the first conductor (4) is enclosed between the radial inner side and the radial outer side of the first support element (5), wherein the first contact pin (3) is guided radially displaceably within a second support element (6) and can be subjected to force in a first radial direction, characterized in that the second support element (6) is arranged in a volume which is defined in the radial direction by the radial inner side of the first slip ring (2),wherein the second support element (6) is rotatably arranged relative to the first support element (5) and wherein the first contact pin (3) on the side radially opposite the sliding contact can be subjected to force by a fluid.

2. Slip ring arrangement (1) according to claim 1, comprising - a second slip ring (7), - a second contact pin (8) which forms an electrically conductive sliding contact with the second slip ring (7), - a second conductor (9) extending axially from the second slip ring (7), which is electrically connected to the second slip ring (7), wherein the second slip ring (7) is arranged with its radial outer side on the radial inner side of the support element, and the second conductor (9) is enclosed between the radial inner side and the radial outer side of the first support element (5), wherein the second contact pin (8) is guided radially displaceably within the second support element (6), and can be subjected to force in a second radial direction, wherein the second contact pin (8) can be subjected to force by a fluid on the side opposite the sliding contact in the radial direction.

3. Slip ring arrangement (1 ) according to claim 2, wherein the first conductor (4) and the second conductor (9) project outwards from the first support element (5) on an axial outer side.

4. Slip ring arrangement (1 ) according to one of claims 2 to 3, wherein the first conductor (4) projects out of the first support element (5) on the axial outside 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 the axial direction along the first support element (5), or the second conductor (9) projects out of the first support element (5) on the axial outside 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 the axial direction along the first support element (5).

5. Slip ring arrangement (1) according to claim 4, wherein a first groove (14) extends in the axial direction on the radial outer side of the first support element (5), in which a third support element (15) is arranged in a form-fitting manner in the circumferential direction, which at least partially encloses the third conductor (11), or a second groove (16) extends in the axial direction on the radial outer side of the first support element (5), in which a fourth support element (17) is arranged in a form-fitting manner in the circumferential direction, which at least partially encloses the fourth conductor (13).

6. Slip ring arrangement (1 ) according to one of the preceding claims, wherein a sealing element is arranged between one of the contact pins (8, 10) and the second support element (6) so that a pressure chamber is formed.

7. Slip ring arrangement (1 ) according to claim 6, wherein one of the contact pins (8, 10) has a round cross-section.

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 one of claims 5 to 7, wherein the first support element (5) is arranged radially inside the hollow shaft (18).

9. Rotor of a separately excited synchronous machine according to claim 8, wherein a third groove extends in the axial direction in the radial inner side and the third support element (15) is arranged in the first groove (14) and in the third groove (19) forming a positive locking connection, or a fourth groove extends in the axial direction in the radial inner side and the fourth support element (17) is arranged in the second groove (16) and in the fourth groove forming a positive locking connection.

10. Rotor of a separately excited synchronous machine according to claim 8 or 9, wherein the hollow shaft (18) has a first radial opening (19) which allows the radial connects the inner side with a radial outer side of the hollow shaft, 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 inner side with a radial outer side of the hollow shaft, wherein the fourth conductor (13) penetrates the hollow shaft through the second radial opening (20).

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