Rotor arrangement for a separately excited synchronous machine and separately excited synchronous machine

Abstract

The present invention relates to a rotor arrangement (100) for a separately excited synchronous machine, comprising: - a rotor shaft (1) designed as a hollow shaft for an excitation winding; - a transmission unit (3) for contactless transmission of a current required for rotor field generation to the excitation winding, wherein the transmission unit (3) is arranged in the rotor shaft (1); - a hollow heat sink (9) for conducting a cooling medium, which is arranged in the rotor shaft (1) and comprises on its outer surface a rectifier unit (11a) for the transmitted current; and - a covering element (15) which is mounted on the heat sink (9) for supporting the heat sink (9) within the rotor shaft (1). Furthermore, the invention relates to a separately excited synchronous machine.

Description

[0001] The present invention relates to a rotor arrangement for a separately excited synchronous machine and a separately excited synchronous machine.

[0002] Separately excited synchronous machines can be used as drive devices in motor vehicles and, unlike permanent magnet synchronous machines, comprise a rotor-side excitation winding (rotor winding) that can be energized to generate an excitation field. The excitation field interacts with a stator field to generate a rotary motion of the rotor.

[0003] It is known from the prior art that an alternating current provided by the power electronics can be transmitted contactlessly by an inductive (current) transmission unit. Such an inductive transmission unit can be a (e.g., rotationally symmetrical) transformer comprising a primary unit and a secondary unit, wherein the primary unit comprises a primary ferrite core with an associated primary winding, and the secondary unit comprises a secondary ferrite core with an associated secondary winding. The primary ferrite core and the secondary ferrite core are separated from one another by an air gap and are designed to rotate relative to one another. As a rule, the primary unit is arranged in a fixed location within the electrical machine, e.g., on the housing, while the secondary unit is rotatable, e.g., through a rotationally fixed connection to the rotor.

[0004] The inductive transmission unit allows an alternating current to be transmitted contactlessly from the primary winding of the primary unit to the secondary winding of the secondary unit. A rectifier unit connected to the secondary winding taps the transmitted alternating current and converts it into a direct current to power the rotor winding.

[0005] For example, DE 10 2020 207 000 A1 is known from the prior art, which shows a separately excited synchronous machine with a hollow shaft and an internal, contactless power transmission for the excitation current. The stator of the power transmission is designed as a hollow heat sink for a coolant, and the rectifier elements are located on one end face of the rotor.

[0006] As a further example of the state of the art, DE 10 2021 213 736 A1 shows a separately excited synchronous machine with a hollow shaft and a contactless energy transfer system for the excitation current with rectifier elements arranged on one rotor end face. A coolant flow is directed radially outward from the hollow shaft, thus cooling the contactless energy transfer system and the rectifier elements.

[0007] DE 10 2022 201 589 A1, as another example of the state of the art, shows a separately excited synchronous machine with a hollow shaft and internal, contactless energy transfer for the excitation current. A stationary cooling lance extends into the hollow shaft, and rectifier elements are mounted on the inner wall of the hollow shaft so that they rotate with it.

[0008] US Patent No. 9,461,526 B2 also shows rectifier elements in a hollow shaft of an electrical machine as another example of the prior art. Here, the rectifier elements are apparently attached to the inner wall of the hollow shaft, while a hollow, co-rotating heat sink for a coolant is located in the center.

[0009] Previous cooling concepts have insufficient cooling performance of components of the rectifier unit and the transmission unit.

[0010] The object of the present invention is to improve cooling of components of the rectifier unit and / or the inductive transmission unit.

[0011] The object is achieved by a rotor arrangement according to claim 1 and a separately excited synchronous machine according to claim 7.

[0012] A first aspect of the invention relates to a rotor arrangement for a separately excited synchronous machine, comprising: - a rotor shaft designed as a hollow shaft for an excitation winding; - a transmission unit for contactless transmission of a current required for rotor field generation to the excitation winding, wherein the transmission unit is arranged in the rotor shaft; - a hollow heat sink for conducting a cooling medium, arranged in the rotor shaft and comprising on its outer surface a rectifier unit for the transmitted current; and - a covering element that is fitted onto the heat sink to support the heat sink within the rotor shaft.

[0013] The rotor shaft carries the excitation winding. The excitation winding (rotor winding) can be energized to generate the rotor-side magnetic field (rotor field). The rotor field then interacts with a stator-side magnetic field (stator field), driving the rotor shaft and thus the rotor assembly.

[0014] The inductive transfer unit is designed to transfer the current for rotor field generation to the rotor winding. For this purpose, the transfer unit comprises a stator-side primary side, which includes a primary ferrite core with a primary winding (primary winding), and a rotor-side secondary side, which includes a secondary ferrite core with a secondary winding (secondary winding). The primary side is fixed to the stator, and the secondary side is rotationally fixed to the rotor shaft. The primary and secondary sides are separated by an air gap through which the cooling medium can flow to cool the transfer unit.

[0015] The transmission unit is located at one end of the rotor shaft and at least partially inserted into the rotor shaft. In some examples, the transmission unit is located entirely within the rotor shaft. The end of the rotor shaft with the transmission unit is referred to as the drive end (drive side). In contrast, there is an output end of the rotor shaft (output side).

[0016] The heat sink is hollow and elongated and conducts the cooling medium in a direction from the output-side end of the rotor shaft to the transmission unit. The heat sink comprises a cavity (e.g., a fluid line) for transmitting the cooling medium, which extends over the entire length of the heat sink, e.g., axially. In a cross-sectional view (in the direction of the longitudinal axis of the heat sink), the fluid line is arranged centrally. In some examples, the fluid line can be drilled. In other examples, the heat sink can be cast with a core for the fluid line to form the fluid line.

[0017] The heat sink is arranged at least partially in the rotor shaft and is located within the rotor shaft such that the fluid line is arranged coaxially to the rotation axis of the rotor shaft.

[0018] The rectifier unit for rectifying and transmitting the current from the secondary winding of the transfer unit to the rotor winding is located on the outer surface of the heat sink. In addition to the rectifier unit, other components (of an electronic circuit) can be located on the outer surface of the heat sink. These components include, for example, conductive tracks, contact elements (e.g., connectors for connecting the secondary winding of the transfer unit and the rotor winding to the rectifier unit), circuits (e.g., for smoothing the input current, rectifier circuit), components for limiting induced voltage peaks (e.g., varistors, suppressor diodes (TVS diodes)), and other active and / or passive components for implementing safety functions or transmitting signals.

[0019] In some examples, the rectifier unit is arranged on an outer peripheral surface of the heat sink (possibly distributed). The outer peripheral surface is a surface of the heat sink that faces radially outward (as viewed from the longitudinal axis of the heat sink).

[0020] By placing the rectifier unit directly on an outer surface of the heat sink, improved cooling of the rectifier unit can be achieved. Because the cooling path is within the heat sink, there is no need for cooling medium to wet the outer surface of the heat sink.

[0021] The covering element is fitted onto the heat sink. This means that the covering element has a receiving opening through which the heat sink can be guided and which holds the heat sink either radially or positively. In other words, the covering element is placed onto the heat sink. When installed, the heat sink is firmly arranged in the covering element, at least in the radial direction and in the circumferential direction of the rotor shaft. A positive connection, such as a tongue and groove connection between the covering element and the heat sink, is also possible to provide fixation in the circumferential direction.

[0022] The covering element can be connected to the heat sink in at least one of a material-to-material, friction-to-material, or form-fitting manner. Furthermore, the covering element can be formed from a plastic or other electrically non-conductive material.

[0023] The cover element supports the heat sink within the rotor shaft. This means that the heat sink is supported within the rotor shaft, at least in the radial direction, by the cover element.

[0024] Furthermore, the heat sink is rotationally coupled to the rotor shaft via the covering element. The outer diameter of the covering element can be dimensioned such that it can be pressed into the hollow rotor shaft. Alternatively or in addition to the press fit, an anti-twist device can also be provided for the covering element, for example, through a tongue-and-groove connection between the inside of the rotor shaft and an outside of the covering element.

[0025] In some embodiments, the covering element may have a fluid guide section that tapers toward the transfer unit. Taper means that the diameter of the fluid guide section (as viewed in the axial direction) decreases toward the transfer unit or the drive side of the rotor shaft.

[0026] For example, the fluid guide section can be truncated cone-shaped or truncated pyramid-shaped. In the assembled state, the top surface of the fluid guide section can be directed toward the drive side of the rotor shaft, and the base surface of the fluid guide section can be directed toward the output side of the rotor shaft.

[0027] In this way, a cooling medium that exits the heat sink through radial through-holes on the heat sink side can be guided along the inclined outer surfaces (fluid guide section) of the covering element by radial through-holes on the rotor shaft side and thus in the direction of the excitation winding.

[0028] The fluid guide section allows for optimized cooling medium flow in the peripheral space around the heat sink and a reduction in the cavity within the entire assembly (rotor assembly). "Cavity" refers to the space between the rotor shaft and the heat sink with integrated rectifier unit located within it.

[0029] In some embodiments, the covering element can comprise a support section, via which the covering element rests against an inner wall of the rotor shaft. The support section serves to support or mount the heat sink within the rotor shaft. The support section can, for example, be sleeve-shaped. An outer diameter of the support section can be selected such that the support section is frictionally connected to the rotor shaft and thus rests against the inner wall. Supporting means that the support section (and thus the covering element and the heat sink) is fixed in the radial direction within the rotor shaft.

[0030] In some embodiments, the overcoat element can electrically insulate the rectifier unit from the transmission unit. The overcoat element thus serves as insulation to extend an air gap and / or a creepage distance. These distances can be between a conductor or a solder joint from the secondary side to other solder joints on a circuit board of the rectifier unit. Alternatively or additionally, the overcoat element serves to insulate between conductive points on the heat sink (or on the circuit board) and the rotor shaft. Thus, the overcoat element provides insulation between electrical components on the circuit board and / or between the heat sink (with the rectifier unit) and the rotor shaft.In some examples in which the covering element is formed from a metal, the covering element comprises, at least in some areas, a sheath of insulating material in order to be able to maintain required air and / or creepage distances.

[0031] In some embodiments, a potting compound can fill a gap between the overlay element and an outer peripheral side of the heat sink. Potting, for example, means that the gap is filled with a resin. The gap extends at least radially between the overlay element and the heat sink. In some examples, the gap can be only partially filled with the potting compound. The potting compound enables mechanical support or fastening of components of the rectifier unit.

[0032] In some embodiments, the covering element may be formed from an electrically insulating material. In some examples, a plastic may be used.

[0033] A second aspect of the invention relates to a separately excited synchronous machine with a rotor arrangement according to one of the embodiments described above. The separately excited synchronous machine can be used as a drive motor for a motor vehicle.

[0034] Embodiments of the invention will now be described by way of example and with reference to the accompanying drawings, in which: Fig. 1 schematically shows a rotor arrangement according to an embodiment; Fig. 2a, b perspective views of a heat sink of the rotor assembly; Fig. 3a, b schematically show cooling paths through the rotor arrangement of Fig. 1.

[0035] Fig. Figure 1 shows a rotor assembly 100 according to an embodiment for a separately excited synchronous machine. The rotor assembly 100 comprises a rotor shaft 1 designed as a hollow shaft, an inductive transmission unit 3 for contactless transmission of current to a rotor winding (not shown), and a heat sink 9 for conducting a cooling medium.

[0036] The transmission unit 3 is arranged within the rotor shaft 1 and comprises a primary side 5 with a primary ferrite core 5a and a primary winding 5b. The primary ferrite core 5a is rotationally symmetrical and firmly connected to a stator (not shown). In this case, the primary ferrite core 5a comprises an axial (sleeve-shaped) section and a radially outwardly projecting section. The primary winding 5b at least partially wraps around the primary ferrite core 5a at its axial section.

[0037] The transmission unit 3 further comprises a secondary side 7 with a secondary ferrite core 7a and a secondary winding 7b. The secondary ferrite core 7a comprises an axial (sleeve-shaped) section and a radially inwardly projecting section. The secondary winding 7b is inserted into the secondary ferrite core 7a. The secondary ferrite core 7a is rotationally fixedly connected to the rotor shaft 1 and is thus rotatable relative to the primary ferrite core 5a. For example, the secondary ferrite core 7a can be rotationally fixedly coupled to an inner circumferential surface of the rotor shaft 1 along its outer circumferential surface along the axial section.

[0038] The primary winding 5b and the secondary winding 7b are framed by the axial and radial sections of the primary ferrite core 5a and the secondary ferrite core 7a and overlap at least partially axially (as viewed in the longitudinal direction of the rotor assembly 100 or rotor shaft 1). In other embodiments (not shown), the primary windings 5a and the secondary windings 7b can also completely overlap axially.

[0039] The heat sink 9 is elongated and arranged in the rotor shaft 1. The heat sink 9 is connected to the rotor shaft 1 in a rotationally fixed manner (via a covering element 15 described later). A hollow socket 9a is provided at an end of the heat sink 9 facing the transmission unit 3. The heat sink 9 further comprises a fluid line 9b that extends over the entire length of the heat sink 9. The fluid line 9b is arranged centrally in the heat sink 9 (in a cross-sectional view of the heat sink 9) and is designed such that, when the rotor assembly 100 is assembled, it runs coaxially to the longitudinal axis of the rotor shaft 1. This guides the cooling medium close to the axis of rotation. In an end region facing the transmission unit 3, the heat sink 9 comprises two heat sink-side radial through-bores 9c that are arranged diametrically to one another and are in fluid communication with the fluid line 9b.The cooling medium can be guided radially outward from the heat sink 9 via the radial through-bores 9c on the heat sink side. Furthermore, the heat sink 9 comprises an inlet opening 9d for introducing the cooling medium into the heat sink 9 at an end facing away from the transmission unit 3. In some examples, the two radial through-bores 9c can be arranged not diametrically, but rather offset from one another in the circumferential direction as desired. In other examples, the heat sink 9 can also have more than two radial through-bores 9c, which are distributed (optionally evenly) in the circumferential direction of the heat sink 9. In further examples, the heat sink 9 can also have only one radial through-bore 9c.

[0040] Fig. 2a and Fig. 2b show the heat sink 9 with the covering element 15. The Fig. 2b a sectional view along the longitudinal axis of the heat sink 9. As in Fig. 2a and Fig. As shown in Fig. 2b, the heat sink 9 is essentially cuboid-shaped and comprises on an outer peripheral surface a rectifier unit 11 for rectifying the alternating current transmitted by the transmission unit 3.

[0041] Fig. 1 and Fig. 2a and Fig. 2b show that the rectifier unit 11 is connected via a first contact element 11a to the output of the secondary winding 7b of the transmission unit 3 and via a second contact element 11b to the rotor winding (not shown). The first contact element 11a and the second contact element 11b are each present in pairs in order to contact both electrical poles of the secondary winding 7b and the rotor winding, respectively. The further first and second contact elements 11a are not visible due to the illustration. In other examples, depending on the design of the rectifier unit 11 and the secondary winding 7b, the first contact element 11a and the second contact element 11b can each be present four times. In some examples, the rectifier unit 11 can further comprise at least one of the following components and / or contact elements, such as, for example:Components for limiting induced voltage spikes (varistors, TVS diodes), active or passive components for implementing safety functions or transmitting signals, and a circuit for smoothing the input current (e.g., an RC snubber). By providing the rectifier unit 11 on the heat sink 9, particularly effective cooling of the rectifier unit 11 can be achieved.

[0042] Referring to Fig. 1 and Fig. 2a and Fig. 2b, the covering element 15 is described. The covering element 15 is mounted on the heat sink 9 and is thus arranged radially between the rotor shaft 1 and the heat sink 9. The covering element 15 comprises a guide section 15a, an intermediate section 15b, and a support section 15c.

[0043] The guide section 15a of the covering element 15 comprises a receiving opening 15d for receiving the heat sink 9. For this purpose, the receiving opening 15d has a contour that corresponds to the outer peripheral contour of the heat sink 9. The heat sink 9 is received in the covering element 15 in a form-fitting manner in the radial direction via the receiving opening.

[0044] The guide section 15a serves to guide the cooling medium, which emerges from the heat sink-side radial through-bores 9c, in the direction of the rotor shaft-side radial through-bores 1a. The diameter of the guide section 15a increases from the drive side (left) toward the output side (right) of the rotor shaft 1. In other words, the guide section tapers toward the drive side of the rotor shaft. The outer surfaces of the guide section 15a essentially extend like the lateral surfaces of a truncated pyramid, with the rectangular base and top surfaces of the truncated pyramid arranged perpendicular to a longitudinal axis of the covering element 15. In some examples, the outer surfaces of the guide section 15a can essentially extend like the lateral surfaces of a truncated cone.

[0045] The sleeve-shaped intermediate section 15b of the covering element 15 is arranged on the base surface side of the truncated pyramid. This means that the guide section 15a merges into the intermediate section 15b. An outer diameter of the sleeve-shaped intermediate section 15b is smaller than the inner diameter of the rotor shaft 15c. As shown in Fig. 1, the intermediate section 15b is designed such that in the (assembled state of the rotor arrangement 100) an air gap is formed between the rotor shaft 1 and the intermediate section 15b, which air gap is arranged in the axial direction at the level of the rotor shaft-side radial through-bores 1a.

[0046] The intermediate section 15b merges into the support section 15c of the covering element 15. The support section 15c is sleeve-shaped, and an outer diameter of the support section 15c is selected such that the covering element 15 can be pressed into the rotor shaft 1 and is thus connected in a rotationally fixed manner to the inner circumferential surface of the rotor shaft 1. Alternatively or additionally, a material-to-material connection, e.g., by gluing, can be provided between the rotor shaft 1 and the covering element 15 in the region of the support section 15. The covering element 15 provides mechanical support or mounting of the heat sink 9 within the rotor shaft 1 against centrifugal forces.

[0047] The covering element 15 is formed from a plastic material. Furthermore, the covering element 15 is formed as a single piece. In other examples (not shown), the covering element 15 may be formed as multiple pieces. This means that at least one of the guide portion 15a, the intermediate portion 15b, and the support portion 15c may be formed separately.

[0048] Returning to Fig. 1, the rotor assembly 100 further comprises an intermediate element 13, which is arranged axially between the transmission unit 3 and the heat sink 9. During assembly of the rotor assembly 100, the heat sink 9 with the electronic circuit 11 is inserted axially from the drive side (from the left) into the rotor shaft 1, followed by the transmission unit 3 with the intermediate element 13.

[0049] The intermediate element 13 is formed from a plastic material, for example, an electrically insulating one. The intermediate element 13 comprises an annular disc 13a with an edge 13d as a base and a receiving sleeve 13b, which extends away from the annular disc 13a and is arranged coaxially with the annular disc 13a. An inner hole of the annular disc 13a is aligned with the inner circumference of the receiving sleeve 13b. Thus, an edge of the inner hole and an end of the receiving sleeve 13b are connected to each other. At another (free) end, the receiving sleeve 13b comprises a radially inwardly projecting collar 13c. The collar 13c comprises a collar opening for receiving the hollow socket 9a of the heat sink 9.

[0050] The intermediate element 13 has an outer diameter at its base (annular disc 13a) that essentially corresponds to the inner diameter of the rotor shaft 1. The intermediate element 13 abuts axially with the transmission unit 3 with one side of the annular disc 13.

[0051] The radial through-bores 1a on the rotor shaft side are provided for guiding the cooling medium from the interior of the rotor shaft 1 to the outside of the rotor winding. Fig. 1 shows two radial through-bores 1a on the rotor shaft side, which are arranged diametrically opposite one another. Alternatively, the radial through-bores 1a on the rotor shaft side can also be distributed arbitrarily in the circumferential direction. In other examples, only a single radial through-bore 1a can be provided. In further examples, a plurality of radial through-bores 1a can be arranged (uniformly) distributed in the circumferential direction of the rotor shaft. A distribution of the radial through-bores 1a on the rotor shaft side in the axial direction is also possible.

[0052] Fig. 3a and Fig. 3b each schematically show a cooling (medium) path indicated by arrows in the rotor arrangement 100 of Fig. 1. This shows Fig. 3a a “serial connection” in which a cooling path from a transfer point on the output side of the rotor shaft 1 (in Fig. 3 on the right) is directed toward the rotor winding and does not cool the transfer unit 3. The cooling path toward the transfer unit 3 is blocked by a plug 9e arranged in the hollow socket 9a. Alternatively, the cooling path can be blocked by not having a through-hole in the hollow socket 9a. In this case, the plug 9e is formed integrally with the hollow socket 9a or with the heat sink 9.

[0053] In Fig. 3a, the cooling medium is transferred via a stator-side cooling medium supply line (not shown) through the inlet opening 9d of the heat sink 9 into the fluid line 9b. Due to the rotation generated during operation of the separately excited synchronous machine, the cooling medium flows through the heat sink-side radial through-bores 9c—guided by the guide section 15a—in the direction of the inner wall of the rotor shaft 1. Finally, the cooling medium flows through the rotor shaft-side radial through-bores 1a in the direction of the rotor winding.

[0054] Fig. 3b shows a “parallel connection” in which, in addition to the cooling path in the direction of the rotor winding, a cooling path is also provided in the direction of the transmission unit 3. For this purpose, the plug in Fig. 3b is omitted. As a result, the cooling medium flows through the hollow nozzle 9a and opens into the receiving sleeve 13b of the intermediate element 13. From there, the cooling medium flows via the air gap between the primary ferrite core 5a and the secondary ferrite core 7a to the primary winding 5b and the secondary winding 7b and then to a side opposite the output side of the rotor arrangement 100 (in Fig. 3 to the left).

[0055] As from Fig. 3a, b, the cooling medium is little to not at all influenced in terms of flow by the external shape and design of the heat sink 9, which results in a reduction of drag torques caused by the cooling medium. Reference symbol 1 rotor shaft 1a Rotor shaft side radial through holes 3 transmission unit 5 Primary page 5a Primary ferrite core 5b Primary windings 7 Secondary side 7a Secondary ferrite core 7b Secondary windings 9 heat sinks 9a Hollow socket 9b Fluid line 9c Radial through holes on the heat sink side 9d plug 11 electronic circuit 11a first contact element 11b second contact element 13 Intermediate element 13a annular disc 13b Receptacle 13c collar 13d collar opening 15 Cover element 15a Fluid guide slope 15b Intermediate section 15c support section 15d Recording opening

Claims

[1] Rotor arrangement (100) for a separately excited synchronous machine, comprising: - a rotor shaft (1) designed as a hollow shaft for an excitation winding; - a transmission unit (3) for contactless transmission of a current required for rotor field generation to the excitation winding, wherein the transmission unit (3) is arranged in the rotor shaft (1); - a hollow heat sink (9) for conducting a cooling medium, arranged in the rotor shaft (1) and comprising on its outer surface a rectifier unit (11a) for the transmitted current; and - a covering element (15) which is fitted onto the cooling element (9) to support the cooling element (9) inside the rotor shaft (1). [2] Rotor arrangement (100) according to claim 1, wherein the coating element (15) has a fluid guide section (15a) which tapers towards the transmission unit (3). [3] Rotor arrangement (100) according to claim 1 or 2, wherein the covering element (15) comprises a support section (15c) by which the covering element (15) is supported against an inner wall of the rotor shaft (1). [4] Rotor arrangement (100) according to one of claims 1 to 3, wherein the covering element (15) electrically isolates the rectifier unit (11a) from the transmission unit (3). [5] Rotor arrangement (100) according to one of claims 1 to 4, wherein a potting compound fills a space between the coating element (15) and an outer circumferential side of the cooling body (9). [6] Rotor arrangement (100) according to one of claims 1 to 5, wherein the covering element (15) is formed from an electrically insulating material. [7] Externally excited synchronous machine with a rotor arrangement (100) according to any one of claims 1 to 6.

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