Rotor arrangement and electric machine

Abstract

The invention relates to a rotor arrangement (1) comprising: a rotor body (2) which forms a plurality of slots (3) in the axial direction for receiving a winding (4); rotor poles (5) which are each formed in the radial direction between two of the slots (3); windings (4) which extend in the slots (3) and enclose the rotor poles (5); slot closure elements (6) which close the slots (3) in the radial direction; at least one separating body (7) which is arranged in one of the slots (3) in the circumferential direction between two of the windings (4); wherein the separating body (7) comprises at least one continuous cooling channel (8) which extends in the axial direction and through which a cooling medium can flow, wherein the at least one cooling channel (8) has a plurality of cooling fins (12) which project into the cooling channel (8).

Description

[0001] Rotor arrangement and electrical machine

[0002] The present invention relates to a rotor arrangement comprising a rotor body which forms a plurality of slots in the axial direction for receiving a winding, rotor poles which are formed in the radial direction between two of the slots, windings which run in the slots and enclose the rotor poles, slot closure elements which close the slots in the radial direction, and at least one separating body which is arranged in one of the slots in the circumferential direction between two of the windings, wherein the separating body comprises at least one continuous cooling channel extending in the axial direction through which a cooling medium can flow. The invention further relates to an electrical machine.

[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 suitability of electric drives and also to offer users the same driving comfort they are accustomed to.

[0004] In the development of electrical machines, particularly those intended for electric axles or hybrid modules, there is a continuing need to increase their power density and efficiency while simultaneously reducing manufacturing costs. In this context, it is also known to design electrical machines as separately excited synchronous machines (SMMs). A separately excited synchronous machine is a special type of synchronous machine in which the magnetic field in the rotor is generated not by permanent magnets, but by energizable coils. These coils are often also referred to as field or excitation coils. To energize the coils in the rotating rotor, the power must be supplied via suitable transformer devices.

[0005] Due to the manufacturing process, gaps can occur between any two excitation windings of a rotor. Support or separating elements are typically inserted into these gaps, filling the gap completely or largely. Particularly for high-speed applications, these separating elements protect the windings of the excitation coils against unintentional movement in the centrifugal force field. EP 1 494 335 B1 discloses corresponding separating elements between adjacent excitation coils.

[0006] Particularly with regard to increased power densities and efficiency, there is a need to cool the rotor during operation and dissipate thermal energy, especially in separately excited synchronous machines. Air-cooled rotors or fluid-cooled hollow shafts, for example, are known from the prior art. DE102018220810A1 discloses a fluid-cooled rotor for an electric machine and a separately excited synchronous machine with a directly or near-loss-cooled rotor winding. A fluid-cooled hollow shaft with a conical wall is disclosed in EP3618241A1.

[0007] The object of the present invention is to provide a suitable device for dissipating thermal energy from a rotor for a separately excited synchronous machine, which has a compact design and a high level of operational reliability.

[0008] This object is achieved by a rotor arrangement comprising a rotor body which forms a plurality of slots in the axial direction for receiving a winding, rotor poles which are formed in the radial direction between two of the slots, windings which run in the slots and enclose the rotor poles, slot closure elements which close the slots in the radial direction, at least one separating body which is arranged in one of the slots in the circumferential direction between two of the windings, wherein the separating body comprises at least one continuous cooling channel which extends in the axial direction and through which a cooling medium can flow, wherein the at least one cooling channel has a plurality of cooling fins projecting into the cooling channel.

[0009] The advantageous effect of this aspect is that power loss in the form of heat can be dissipated as close to its source as possible thanks to the cooling channels in the separator. Furthermore, the integration of the cooling channel into the separator results in only a minimal impact on the rotor's electromagnetic design, in contrast to cooling between the slots in the rotor body itself.

[0010] This allows for improvements in speed stability, thermal behavior, efficiency and available torque density compared to the state of the art.

[0011] The cooling fins extending into the cooling channel can provide an increased surface area and, as a result, optimized heat transfer from the separator to the cooling medium. The cooling fins can be incorporated into the separator, for example, by an extrusion process.

[0012] The separator thus essentially serves two functions. Firstly, the separator can help secure the windings in the slots even under the influence of centrifugal force, and secondly, it can provide fluid-based cooling within the slots through the cooling channel. Thus, the rotor windings are supported at a constant speed via this separator and are simultaneously cooled.

[0013] The separator is preferably made of a non-ferromagnetic material to avoid interference with the electromagnetic function of the rotor or the electrical machine. The separator is preferably made at least partially of a material with good thermal conductivity to ensure a good thermal connection between the rotor windings and the cooling medium. The separator can be manufactured, for example, using an aluminum extrusion process, plastic extrusion, or a plastic injection molding process. This allows for the creation of a hollow interior but closed exterior shape that can conduct a cooling medium and is leak-proof even under high pressure.

[0014] According to one embodiment, the cooling channel has a constant cross-section in the axial direction. Furthermore, the cooling channel has a substantially constant radial distance from a rotational axis in the axial direction. The advantageous effect of this embodiment is that the design of the cooling channel prevents a speed- and direction-dependent pumping effect through the cooling channel, since both the inlet and outlet of the cooling channel in the separating body are equally spaced from the rotational axis.

[0015] According to one embodiment, the rotor assembly comprises a rotor shaft, which is designed as a hollow shaft and has an opening in the radial direction for guiding the cooling medium. The opening is connected to the cooling channel for guiding the cooling medium. Advantageously, the opening is connected to the cooling channel via a further component, which, together with the opening and the cooling channel, forms a channel system. Thus, the cooling channel is connected to a cooling system via the channel system. Particularly advantageously, the cooling channel is connected to the cooling system on both sides via a respective further component, thus forming a closed cooling circuit.

[0016] According to one embodiment, a cavity is formed in the slot, which is delimited by one of the windings and the separator, wherein the cavity comprises a potting material. The advantageous effect of this embodiment is that the potting material in the cavity improves the thermal connection between the windings and the separator. The cavity results from manufacturing-related component tolerances of the windings and the separator.

[0017] According to one embodiment, the cooling medium is a cooling liquid. The advantageous effect of this embodiment is that cooling liquids have a higher heat capacity and higher thermal conductivity than gases, thus enabling better heat dissipation and dissipation of power losses. In particular, the cooling liquid contains oil and / or water.

[0018] According to one embodiment, the rotor body is designed as a laminated stack. The advantageous effect of this design is that eddy current losses in the rotor body are minimized. According to an advantageous embodiment of the invention, the cooling fins can be formed integrally, preferably monolithically, with the separating body. The advantage of this design is that it allows for particularly good heat transfer and a particularly favorable shape for the cooling fins from a manufacturing perspective.

[0019] Preferably, the cooling fins have a constant cross-section in the axial direction. Furthermore, the cooling fins have a substantially constant radial distance from a rotational axis in the axial direction.

[0020] The advantageous effect of this design lies in the fact that the design of the cooling fins prevents a speed- and direction-dependent pumping effect caused by the cooling fins extending into the cooling channel. Furthermore, this design allows the separator to be manufactured using extrusion and / or injection molding processes.

[0021] It is further preferred that the cooling fins have a substantially identical geometry, which is particularly advantageous in terms of manufacturing technology and simplifies the modeling of the heat transfer.

[0022] According to a further preferred development of the invention, the separating body can also comprise a plurality of cooling channels that are spaced apart radially and / or circumferentially. The advantageous effect of this design is that this improves heat dissipation and dissipation of power losses. A further advantage is that the multiple spaced cooling channels allow for more uniform heat dissipation and dissipation of power losses.

[0023] Furthermore, according to a likewise advantageous embodiment of the invention, it can be provided that at least two of the cooling channels have a substantially geometrically identical cross-sectional contour. Such cross-sectional shapes have proven particularly advantageous with regard to the necessary dimensional stability of the separating body under the influence of centrifugal force, as well as for providing high heat transfer performance. According to another particularly preferred embodiment of the invention, it can be provided that at least two of the cooling channels have a rectangular basic contour, wherein the respective longitudinal sides of the cooling channels are oriented in a radial extension, which has also proven particularly advantageous with regard to optimizing the dimensional stability and heat transfer performance of the separating body.In principle, however, it would also be possible for the cooling channels to have a contour that differs from the rectangular shape, for example trapezoidal.

[0024] The outer cross-sectional contour of the separator can also have a contour that deviates from rectangular. The cross-sectional contour of the separator is preferably shaped so that the distance between the winding and the separator is as small as possible. For example, it would be conceivable for the separator to have a trapezoidal section at its radially outer end, with a rectangular section adjoining it radially inward on its short side. This allows the heat transfer from the winding to the separator to be further optimized, since the thermal conductivity of the potting compound, which usually fills the cavity between the winding and the separator, is generally poorer than the thermal conductivity of the separator.

[0025] Furthermore, the invention can also be further developed such that the at least two cooling channels are separated from one another by a web extending tangentially through the separating body in cross-section. Within the separating body, such a web can help maintain dimensional stability under the influence of high external centrifugal forces. In particular, the separating body can thus also absorb centrifugal forces from the surrounding components without being deformed to a critical degree.

[0026] In a likewise preferred embodiment of the invention, the separating body can also be formed from aluminum. The separating body is preferably produced from aluminum by extrusion. The material properties of aluminum make it possible to achieve good mechanical properties as well as good thermal conductivity within the separating body. Since aluminum is not ferromagnetic, the electromagnetic function of the machine is not impaired. Alternatively, the separating body can be produced from plastic by extrusion, although this generally results in lower thermal conductivity.

[0027] It may also be advantageous to further develop the invention such that the separator has an electrically insulating coating on its outer surface, at least in sections. The separator can thus be electrically insulated from live parts, in particular to prevent electrical contact between excitation coils or between the excitation coil and the vehicle and thus meet the requirements of high-voltage safety. The coating can be realized, for example, by painting, overmolding, or an adhesively bonded layer. For electrical insulation with limited requirements, the aluminum separator can also be anodized, for example. In the case of more stringent requirements, it can be overmolded with plastic, coated with an alternative material, or covered with a film on the contact surfaces to the rotor coils.This ensures that no electrical short circuit occurs between excitation coils or between an excitation coil and the vehicle.

[0028] According to a further preferred embodiment of the subject matter of the invention, it can be provided that the separating body protrudes axially from the slot closure element at least with one end face

[0029] This enables simplified connection of the separating bodies to a fluidic cooling circuit. The separating body can also be machined at its ends, e.g. deburred, and smooth sealing surfaces can be created at the ends by removing material, e.g. by milling, grinding or polishing on the inner or outer contour. In the case of plastic overmolding, sealing surfaces can also be made of plastic. Seals can be joined or injection-molded onto the sealing surfaces so that the interface between the separating body and the adjacent components for the inlet and outlet of the cooling medium can be sealed even against high pressure of the cooling medium. The separating body is preferably connected to a slot closing element which closes the groove radially and supports the support body in a speed-fixed manner.The slot closure element is preferably made of a non-ferromagnetic and non-electrically conductive material, e.g., plastic, so that the electromagnetic behavior of the machine is not impaired and no additional eddy current losses occur in this component. The slot closure element can be manufactured using plastic injection molding or extrusion and joined to the separator by a form-fitting or adhesive bond. Alternatively, the slot closure element can be injection-molded directly onto the separator. In this case, it can be integrally connected to a plastic overmolding of the separator.

[0030] Finally, the invention can also be advantageously implemented such that the slot closure element and the separating body are integrally connected. The advantageous effect of this design lies in the fact that the integral connection allows the slot closure element and the separating body to be manufactured as a single component. This reduces the complexity of the rotor arrangement. A further advantage lies in the fact that an integral connection provides a more stable component. Particularly preferably, the slot closure element and the separating body are monolithically formed, for example, from aluminum or plastic.

[0031] The object of the invention is further achieved by an electrical machine comprising a rotor arrangement according to one of claims 1-10, wherein the electrical machine is designed as a separately excited synchronous machine.

[0032] The invention will be explained in more detail below with reference to figures without limiting the general inventive concept.

[0033] It shows:

[0034] Figure 1 is a detail view of a rotor with a first separating body in a cross-sectional view, Figure 2 is a perspective view of the separating body,

[0035] Figure 3 is a detail view of a rotor with a second separating body in a cross-sectional view,

[0036] Figure 1 shows a rotor assembly 1 for a separately excited synchronous machine, comprising a rotor body 2, which forms a plurality of slots 3 in the axial direction for receiving a winding 4, as well as rotor poles 5, which are formed in the radial direction between each pair of the slots 3. The rotor assembly 1 also has windings 4, which run in the slots 3 and enclose the rotor poles 5.

[0037] The slots 3 are closed in the radial direction by slot closure elements 6. In the circumferential direction, a separating body 7 is arranged in each of the slots 3 between two of the windings 4. The separating body 7 has two parallel, continuous cooling channels 8, each extending in the axial direction, through which a cooling medium can flow.

[0038] The slot 3, which extends in the axial direction through the rotor body 2, is particularly clearly visible in Figure 1. Energizable windings 4 are arranged in the slot 3, each enclosing a rotor pole 5 formed between two slots 3. The slot 3 is closed off in the radial direction to the outside by the slot closure element 6, which is arranged in the circumferential direction between two adjacent rotor poles 5. The rotor poles 5 each form a stop in the radial direction, facing one of the slots 3 in the circumferential direction. Each two of the stops facing a slot 3 thus form a positive-locking receptacle for the respective slot closure element 6. The positive-locking receptacle formed in this way secures the slot closure element 6 against centrifugal forces during operation.In the radial direction towards the inside, the separating body 7 is arranged in the slot 3 adjacent to the slot closure element 6 in such a way that it is aligned essentially in the radial direction centrally between two adjacent windings 4. The separating body 7 has two side surfaces which are aligned in the circumferential direction with the windings 4 and are parallel to one another and to an imaginary plane oriented in the radial direction. The separating body 7 is connected to the slot closure element 6. In the embodiment shown, this is a positive connection, but alternatively non-positive or material connections as well as combinations thereof are also possible. In the axial direction, cooling channels 8 are formed in the separating body 7, which are arranged at equal distances from the side surfaces in the circumferential direction and are equally spaced in the radial direction. This enables uniform heat dissipation.

[0039] The cooling channels 8 extend over the entire axial length of the separator 7 and are traversed by a cooling fluid during operation. The cooling channels are aligned parallel to a rotational axis (not shown) of the rotor body 2. A cavity 9 is formed in the groove 3 in the circumferential direction between each of the windings 4 and the separator 7. This cavity is filled with a potting compound 10. The potting compound 10 allows for better thermal connection between the winding 4 and the separator 7.

[0040] The cooling channels 8 each have a plurality of cooling fins 12 projecting into the cooling channels 8, which are formed monolithically with the separating body 7. The cooling channels 8 are radially spaced from one another and have a substantially geometrically identical rectangular cross-sectional contour, with the respective longitudinal sides 13 of the cooling channels 8 oriented in a radial direction. The two cooling channels 8 arranged radially one above the other are separated from one another by a web 14 extending tangentially through the separating body 7 in cross-section.

[0041] In the embodiment shown, the separating body 7 is formed from aluminum and has an electrically insulating coating 15 on its outer surface, at least in sections.

[0042] The slot closure element 6 and the separating body 7 are integrally connected. As can be seen from Figure 2, the separating body 7 protrudes axially from the slot closure element 6 at least with one front end 16. The separating body 7 can be machined at its front end 16, in particular to produce smooth and particularly dimensionally accurate sealing surfaces 17 by removing material, e.g., by milling, grinding, or polishing on the inner or outer contour. In the case of plastic overmolding, the sealing surfaces 17 can also be made of plastic. Seals can also be joined or injection-molded onto the sealing surfaces 17 so that the interface between the separating body 7 and the adjacent components for the introduction or discharge of the cooling medium can be sealed even against high pressure of the cooling medium.

[0043] Figure 3 shows a further development of the rotor arrangement 1 already known from Figure 1. In this case, one or more filler bodies 11 made of a non-ferromagnetic material are positioned in the cooling channels 8 inside the separating body 7, which filler bodies reduce the volume of the cooling channels 8 inside the separating body 7 and thus promote guidance of the cooling medium along the outer walls of the cooling channels 8, which can improve the heat transfer into the cooling medium.

[0044] The invention is not limited to the embodiments illustrated in the figures. The above description is therefore not to be considered restrictive, but rather explanatory. The following claims are to be understood as meaning that a stated feature is present in at least one embodiment of the invention. This does not exclude the presence of further features. Where the claims and the above description define 'first' and 'second' features, this designation serves to distinguish between two similar features without establishing a priority. List of reference symbols

[0045] 1 Rotor arrangement

[0046] 2 rotor bodies

[0047] 3 grooves

[0048] 4 windings

[0049] 5 rotor poles

[0050] 6 slot closure elements

[0051] 7 separating bodies

[0052] 8 cooling channel

[0053] 9 Cavity

[0054] 10 Casting compound

[0055] 11 packing

[0056] 12 cooling fins

[0057] 13 long sides

[0058] 14 jetty

[0059] 15 Coating

[0060] 16 End

[0061] 17 sealing surfaces

Claims

Claims 1. Rotor arrangement (1 ), comprising - a rotor body (2) which forms a plurality of slots (3) in the axial direction for receiving a winding (4), - rotor poles (5) which are formed in the radial direction between two of the slots (3), - windings (4) which run in the slots (3) and enclose the rotor poles (5), - slot closure elements (6) which close the slots (3) in the radial direction, - at least one separating body (7) which is arranged in one of the slots (3) in the circumferential direction between two of the windings (4), - wherein the separating body (7) comprises at least one continuous cooling channel (8) extending in the axial direction, through which a cooling medium can flow, characterized in that the at least one cooling channel (8) has a plurality of cooling fins (12) projecting into the cooling channel (8).

2. Rotor arrangement (1) according to claim 1, characterized in that the cooling fins (12) are formed integrally, preferably monolithically, with the separating body (7).

3. Rotor arrangement (1) according to claim 1 or 2, characterized in that the separating body (7) comprises a plurality of cooling channels (8) which are spaced apart from one another radially and / or in the circumferential direction.

4. Rotor arrangement (1) according to claim 3, characterized in that at least two of the cooling channels (8) have a substantially geometrically identical cross-sectional contour.

5. Rotor arrangement (1) according to claim 3 or 4, characterized in that at least two of the cooling channels (8) have a rectangular basic contour, wherein the respective longitudinal sides (13) of the cooling channels (8) are oriented in radial extension.

6. Rotor arrangement (1) according to one of claims 3-5, characterized in that the at least two cooling channels (8) are separated from one another by a web (14) extending tangentially through the separating body (7) in cross section.

7. Rotor arrangement (1) according to one of the preceding claims, characterized in that the separating body (7) is formed from aluminum.

8. Rotor arrangement (1) according to one of the preceding claims, characterized in that the separating body (7) has an electrically insulating coating (15) on its outer surface at least in sections.

9. Rotor arrangement (1) according to one of the preceding claims, characterized in that the separating body (7) protrudes axially from the slot closure element (6) at least with one end face (16) 10. Rotor arrangement (1) according to one of the preceding claims, characterized in that the slot closure element (6) and the separating body (7) are integrally connected. 1 . Electrical machine comprising a rotor arrangement (1) according to one of the preceding claims, wherein the electrical machine is designed as a separately excited synchronous machine.

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