Axial slip ring module and optimised cable feed-through for electric machines

Abstract

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

Description

[0001] AXIAL SLIDE RING MODULE AND OPTIMIZED CABLE GROOVE FOR ELECTRICAL 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] US1870236A and US2006208599A each disclose a commutator arrangement, similar to a slip ring arrangement in an electrically driven pump, wherein the ring-shaped commutator segments are designed such that contact pins or carbon brushes make axial contact with the commutator segments. The commutator arrangement is located axially outside the electric machine and radially around the rotor shaft of the electric machine. 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.

[0006] This problem is solved by the measures specified in the independent claims. Advantageous embodiments can be found in the dependent claims.

[0007] According to one aspect, a slip ring arrangement for an electric machine comprises a first slip ring, a first contact pin which forms an electrically conductive sliding contact with the first slip ring, and a first conductor extending axially from the first slip ring and electrically connected to the first slip ring. The slip ring arrangement further comprises a substantially hollow cylindrical first support element which has a first axial inner surface at a first axial end, forming a first rib extending radially inwards, with the first slip ring being arranged on the first axial inner surface. The first conductor is enclosed between a radial inner surface and a radial outer surface of the first support element. The first contact pin is guided axially displaceably within a second support element and is subjected to force in a first axial direction, or is subjected to force.The second support element is arranged within a volume defined radially by the radial inner surface of the first support element. The second support element is rotatably arranged relative to the first support element.

[0008] Advantageously, this results in a compact, nested slip ring arrangement 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, especially via a spring element such as a coil spring. It is particularly advantageous that the characteristic curve of the spring element is as flat as possible, thus ensuring a constant contact force on the contact pin over its service life. 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 positive or material-locking 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.

[0009] According to one embodiment, a slip ring arrangement comprises a second slip ring, a second contact pin which forms an electrically conductive sliding contact with the second slip ring, a second conductor extending axially from the second slip ring and electrically connected to the second slip ring, and a locking element which forms a second axial inner surface at a second axial end opposite the first axial end. The second slip ring is arranged on the second axial inner surface, and the second conductor is enclosed between a radial inner surface and a radial outer surface of the first support element. The second contact pin is guided axially displaceably within the second support element and is subjected to force in a second axial direction opposite to the first axial direction.The second support element is arranged at least sectionally in a volume which is defined in the axial direction by the first axial inner side and the second axial inner side.

[0010] 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 achieved. Analogous to the first web, which is monolithically formed from the first support element, the locking element, which is rotationally fixed to the first support element, forms a second web relative to the first support element, on which the second slip ring is arranged. Particularly preferably, the first axial direction and the second axial direction are opposite; in other words, the contact pins are arranged parallel to a common axis of rotation of the first support element and a rotor shaft in the second support element, but the slip rings, and thus the sliding contacts, are arranged on opposite axial inner surfaces.It is particularly advantageous to have several first or second contact pins per slip ring. The beneficial 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 in terms of 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.

[0011] According to one embodiment, the first conductor and the second conductor protrude from the first support element on an axial outer side.

[0012] Preferably, the first conductor and the second conductor protrude from the first support element on the axial outside, which corresponds to the first axial end of the first support element.

[0013] 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.

[0014] 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.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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°. According to a further 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[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 fourth conductor.

[0027] 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.

[0028] 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.

[0029] 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 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.

[0030] It shows

[0031] Fig. 1 a perspective view of a longitudinal half-section through a slip ring assembly, Fig. 2 two top views of longitudinal sections of the slip ring assembly according to Fig. 1 ,

[0032] Fig. 3 shows several detailed views of various components of the slip ring assembly according to Fig. 1.

[0033] Figure 1 shows a perspective view of a longitudinal half-section through a slip ring arrangement.

[0034] 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 side as on the radial inner side 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 consisting of 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 to the rotating first support element.Within the slip ring assembly, 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 two slip rings are arranged axially spaced from each other within the first carrier element on its axial inner surfaces. The first slip ring 2 is arranged on a first web 21 of the first carrier element 5, the web defining a first axial inner surface of the first carrier element 5. Opposite this first axial surface, a second axial inner surface is formed by a locking element 22, on which the second slip ring 7 is arranged. In other words, the locking element 22, which is rotationally fixed to the first carrier element, forms a second web.Thus, the respective sliding contact is formed on an axial inner side of the respective slip ring 2, 7, wherein the axial inner side of a slip ring is the side which is oriented in the same direction as the associated axial inner side of the first support element 5.

[0035] Starting from the first slip ring 2, a first conductor 4 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 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 surface 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 surface into the hollow shaft 18 and parallel to the first conductor 4. The third conductor 11 extends axially along the first support element 5.The third support element 15 encloses the third conductor 11, at least partially, and functions as an electrical insulator as well as a support element that fixes the position of the third conductor. The third conductor 11 penetrates the hollow shaft 18 radially through a first radial opening 19, 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).

[0036] 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 along 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).

[0037] 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.

[0038] Figure 2 shows two top views of the longitudinal section according to Fig. 1, showing the slip ring assembly 1 from two perspectives at 90° to each other. In Figure 2a), two second contact pins 8 are shown, which are arranged offset from each other by 180° in the circumferential direction. By means of a spring element, which electrically connects the contact pins to a contact point, the second contact pins 8 are pressurized and pressed axially against the second slip ring 7, forming a sliding contact.

[0039] Figure 2b) shows two first contact pins 3, which, like the second contact pins 8, are also arranged offset from each other by 180°. Thus, in the illustrated embodiment, there is an offset of 90° between the contact pins in the circumferential direction. A spring element, which electrically connects the contact pins to a contact point, presses the first contact pins 3 under pressure and pressed them axially against the first slip ring 2, forming a sliding contact. The axial direction in which the first contact pins 3 are pressurized is opposite to the axial direction in which the second contact pins 8 are pressurized; therefore, they are also referred to as the first axial direction and the second axial direction.

[0040] Figure 3 shows several detailed views of various components of the slip ring assembly according to Fig. 1.

[0041] Figure 3a) shows the first support element 5 and the second support element 6 arranged within 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 apart circumferentially such that they are opposite each other. In other words, they are spaced 180° apart circumferentially.

[0042] Figure 3b) shows the first support element 5 without the second support element 6. The arrangement of the first slip ring 2 on the first web 21 and the arrangement of the second slip ring 7 on the locking element 22, which forms a second web with respect to the first support element 5, are clearly visible.

[0043] Figure 3c) shows the second support element 6 and the arrangement of the first and second contact pins 3, 8.

[0044] Figure 3d) 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.

[0045] List of reference signs

Claims

Patent claims 1. Slip ring arrangement (1 ) for an electric machine, comprising - a first slip ring (2), - a first contact pin (3) which forms an electrically conductive sliding contact with the first slip ring (1 ), - 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) which has a first axial inner surface at a first axial end forming a first web (21) extending radially inwards, wherein the first slip ring (2) is arranged on the first axial inner surface, and the first conductor (4) is enclosed between a radial inner surface and a radial outer surface of the first support element (5), wherein the first contact pin (3) is guided axially displaceably within a second support element (6) and can be subjected to force in a first axial 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 surface of the first support element (5), wherein the second support element (6) is rotatably arranged relative to the first support element (5).

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), and - a locking element (22) which forms a second axial inner surface at a second axial end opposite the first axial end, wherein the second slip ring (7) is arranged on the second axial inner surface, and the second conductor (9) is enclosed between a radial inner surface and a radial outer surface of the first support element (5), wherein the second contact pin (8) is guided axially displaceably within the second support element (6), and is subjected to force in a second axial direction opposite to the first axial direction, characterized in that the second support element (6) is arranged at least sectionally in a volume which is defined in the axial direction by the first axial inner surface and the second axial inner surface.

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 claim 3, wherein the first conductor (4) and the second conductor (9) project outwards from the first support element (5) on the axial outside, which corresponds to the first axial end of the first support element (5).

5. Slip ring arrangement (1) according to one of claims 3 to 4, 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 (4) protrudes from the first support element 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 essentially in the axial direction along the first support element (5).

6. Slip ring arrangement (1 ) according to claim 5, wherein a first groove (14) extends in the axial direction on the radial outside 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 surrounds the third conductor (11 ), or a second groove (16) extends in the axial direction on the radial outside 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 surrounds the fourth conductor (13).

7. 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 1 to 7, wherein the first support element (5) is arranged radially inside the hollow shaft (18), and a third groove extends in the axial direction in the radial inner surface, and the third support element (15) is arranged in the first groove (14) and in the third groove forming a positive-locking connection, or a fourth groove extends in the axial direction in the radial inner surface, and the fourth support element (17) is arranged in the second groove (16) and in the fourth groove forming a positive-locking connection.

8. Rotor of a separately excited synchronous machine according to claim 7, 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 through the second radial opening (20).

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