Fluid piping system for a rotor of an electric machine

Abstract

The invention relates to a fluid conduit device (16) for a rotor (10) of an electric machine, wherein the fluid conduit device (16) is arranged in a rotor core (12) and is configured to deliver a fluid (F) from a fluid-permeable rotor shaft (11) to at least one groove (14) formed in the rotor core (12) in order to cool the rotor (10).

Description

[0001] The invention relates to a fluid routing device for a rotor of an electric machine, wherein the fluid routing device is configured to deliver a fluid from a fluid-permeable rotor shaft to a rotor core in order to cool the rotor core. The invention further relates to a rotor for an electric machine and an electric machine with such a fluid routing device.

[0002] Electric machines can be used as working machines for electrically powered motor vehicles, such as electric and hybrid vehicles. Electric machines of various designs can be used for this purpose, with an electric machine typically having a stationary stator and a rotor that is movable relative to the stator.

[0003] In electrically excited electric machines, active components incorporate magnetic field-generating systems, for example, in the form of current-generating windings, to create a magnetic flux and set the rotor into rotational motion. During operation, these components can heat up, which can lead to the formation of local hot spots, for example, due to an uneven temperature distribution. Since heating of the electric machine can negatively affect its efficiency and continuous power output, cooling solutions are available. Hot spots are particularly problematic in the area around the permanent magnets of permanent magnet synchronous machines (PMSM), as they can increase the risk of temperature-induced demagnetization of the permanent magnets.

[0004] Against this background, an object of the invention is to improve the cooling of a rotor of an electric machine. In particular, the fluid flow within the rotor is to be improved in order to enable more uniform cooling of the rotor.

[0005] This problem is solved by a fluid line device for a rotor of an electric machine with the features of claim 1, a rotor for an electric machine with the features of claim 9, and an electric machine for a motor vehicle with the features of claim 10. The dependent claims relate to advantageous embodiments of the invention.

[0006] According to a first aspect, a fluid conduit device for a rotor of an electric machine is specified, wherein the fluid conduit device can be arranged between two axially spaced rotor core sections and is configured to deliver a fluid from a fluid-permeable rotor shaft to at least one groove formed in the rotor core in order to cool the rotor.

[0007] The fluid guidance device can be arranged on the rotor shaft and / or between the rotor core sections, thereby allowing fluid exiting the rotor shaft to be guided by the fluid guidance device in a substantially radial direction to be discharged in the area of ​​at least one groove, thus enabling heat transfer between the fluid and the rotor core. This allows the fluid to enter the at least one groove, which runs axially in the rotor core, flow there, and thus be directed directly or very close to the areas requiring cooling. Alternatively, a fluid flow can be generated that facilitates heat dissipation within the rotor core.

[0008] The electric machine can be used, for example, as an electric traction machine for an electrically powered vehicle. The electric machine is specifically designed as a permanent magnet synchronous machine (PMSM), a current-excited synchronous machine (SSM), or an asynchronous machine (ASM). The electric machine can have a stationary stator and a rotor that is movable, in particular rotatable, relative to the stator. The rotor has a rotor core, which can be formed, for example, by a lamination stack of axially stacked laminations. These laminations are made of a soft magnetic iron-silicon alloy material, which reduces magnetic losses. Furthermore, the rotor can have at least one electrically conductive winding or at least one permanent magnet, which is designed to generate or provide a magnetic field.

[0009] To cool the electric machine or rotor, the rotor shaft is designed to allow fluid flow through it, or is fluid-flowing through it during operation. It can, for example, be designed as a rotating hollow shaft through which a fluid or cooling medium flows, around which the rotor, rotor core, or fluid guide system is fixedly arranged. The fluid is, in particular, an electrically non-conductive coolant, such as oil. It can be taken from a coolant circuit or a lubricant circuit, especially to avoid impairing the functionality of the electric machine in direct contact with current-carrying components.

[0010] The rotor shaft can have at least one outlet or at least one outlet opening for releasing coolant from the hollow rotor shaft, with several outlets being arranged, for example, circumferentially around the rotor shaft. During rotation of the rotor, the fluid can flow radially outwards from the rotor shaft to the fluid piping system by centrifugal force and be transported radially outwards, particularly at predetermined locations relative to the rotor core, to be discharged into the at least one groove, thus enabling direct interaction with the areas of the rotor to be cooled and facilitating heat transfer. This improves the cooling capacity of the rotor and thus establishes a homogenized temperature level.

[0011] The invention is based, among other things, on the idea of ​​supplying fluid not at the end face, but within the rotor lamination or rotor core. For this purpose, it is proposed to provide a fluid supply unit that can be arranged, or is already arranged, between two axially spaced rotor core sections within a rotor core, in order to deliver fluid, particularly on both sides of the fluid supply unit, to the groove(s) located in the respective rotor core sections. This allows for shorter flow paths and thus shorter heat transfer paths for the fluid within the rotor core, resulting in improved cooling to dissipate heat generated during operation and remove it from the system. In some embodiments, several fluid supply units can also be provided between several rotor core sections and / or the fluid supply unit can be made of plastic or other materials.It must be made of a material that has similar properties to, for example, the electrical steel of the rotor core.

[0012] By arranging or designing the fluid flow system, for example, the mass flow rate of the fluid that is or is intended to be guided through the slot(s) can be predetermined in order to homogenize the temperature distribution in the electric machine and / or avoid local hotspots. This can, for example, increase the efficiency and / or the continuous power output of the electric machine. Furthermore, the targeted guidance of the fluid to predetermined areas of the rotor core can relieve the load on a coolant pump located outside the electric machine, allowing it to be smaller and lighter.

[0013] In one embodiment, at least one groove is designed to receive at least one permanent magnet. The electric machine can be a permanent magnet synchronous machine, with the groove(s) or longitudinal opening(s) in the rotor lamination stack or rotor core each accommodating at least one permanent magnet, or permanent magnets being arranged therein. The groove(s) can also be designed to mechanically stabilize the permanent magnet(s) and direct a magnetic flux within the rotor core to form desired magnetic poles and / or reduce eddy current losses or stray fields. By supplying fluid to such grooves, the permanent magnets can be directly wetted and thus cooled by the fluid, in particular to prevent overheating and thus demagnetization.

[0014] In one embodiment, the fluid flow device is designed as a disk. The fluid flow device, or disk, can have a diameter corresponding to the diameter of the rotor core, thus enabling a uniform circumferential geometry for the rotor or rotor core. The disk can have a predetermined width and, in particular, can be designed to allow fluid flow, enabling the fluid flowing from the rotor shaft to be received and discharged by the fluid flow device to allow targeted feeding into the at least one groove.

[0015] In one embodiment, the fluid piping device has at least one fluid channel designed to receive fluid from the rotor shaft. This fluid channel can be located inside the fluid piping device, or within a disk-shaped fluid piping device, and can have multiple openings corresponding to outlets on the rotor shaft to receive the fluid. In other embodiments, at least one fluid channel can be formed on each flat side of the fluid piping device, for example, in the form of a recess, to allow fluid to flow along a surface within the respective fluid channel. A flow rate of fluid can be predetermined, for example, by means of a predetermined cross-section of the fluid channel, in order to control the cooling effect within the rotor.

[0016] In one embodiment, the fluid conduit assembly has at least one discharge opening that can be assigned to at least one groove. Such discharge openings can be arranged on both sides of the fluid conduit assembly or disk to allow fluid discharge in both axial directions, thus enabling uniform cooling of the rotor core on both sides of the fluid conduit assembly. If a fluid channel is formed on a surface of the fluid conduit assembly, at least one discharge structure can be provided that is configured to effect fluid discharge towards or onto a groove, and a spatial assignment of at least one such discharge structure to a groove can be provided.

[0017] In one embodiment, the at least one fluid channel has at least one circular arc-shaped distribution section. This allows for targeted fluid flow in a circumferential direction to enable fluid distribution across the entire cross-section of the rotor core or any slots arranged therein. Such a distribution section can, for example, be designed as an annularly circumferential fluid channel section, and a fluidic connection between several such connecting sections can be provided to enable a uniform fluid distribution and / or delivery to the slots, particularly independent of the direction of rotation.

[0018] In one embodiment, the at least one distribution section can be arranged concentrically to the rotor axis. In particular, several such distribution sections of the fluid channel are provided so that multi-stage distribution and / or discharge of the fluid can occur across a cross-section or in a radial direction of the rotor core or the grooves arranged therein. In some embodiments, the fluid channel or the connecting section may have a spiral shape, at least in sections, to promote radial outward flow of the fluid.

[0019] In one embodiment, the at least one fluid channel has at least one radially arranged connecting section. Such a connecting section can connect two distribution sections, particularly if they are arranged concentrically, to allow fluid flow, thus enabling uniform fluid distribution across the cross-section of the fluid piping system. In some embodiments, at least one such connecting section can be connected to a receiving opening of at least one fluid channel, which can be arranged corresponding to at least one outlet of the rotor shaft, to enable fluid flow in a diametrical direction away from the rotor shaft. This allows the at least one fluid channel to have a labyrinth geometry to enable fluid discharge, which is particularly adapted to a groove arrangement in the rotor core or rotor core sections.

[0020] According to a further aspect, a rotor for an electric machine is proposed, comprising at least one fluid flow device as described herein, wherein the fluid flow device is arranged in the axial center of the rotor core. Both rotor core sections have the same axial length, allowing the fluid flow device to be arranged centrally in a space between the two rotor core sections. This enables fluid discharge in both axial directions, allowing homogeneous cooling from a central region of the rotor core to end regions. In contrast to an end-face inlet, this arrangement allows sufficient heat absorption by the fluid at the end of the axial flow path because the flow path can have a reduced length compared to an end-face inlet.

[0021] According to a further aspect, an electric machine for a motor vehicle is proposed, comprising at least one rotor and / or at least one fluid piping device as described herein. Furthermore, a motor vehicle comprising such an electric machine or permanent magnet synchronous machine is proposed, whereby the effects and advantages described herein can be utilized by such a motor vehicle or electric machine.

[0022] Further advantages and application possibilities of the invention will become apparent from the following description in conjunction with the figures. Fig. Figure 1 shows a schematic representation of a rotor for an electric machine with a fluid line device for a rotor of an electric machine according to an exemplary embodiment of the invention. Fig. Figure 2 shows a further schematic representation of the rotor for an electric machine with a fluid line device for a rotor of an electric machine according to an exemplary embodiment of the invention. Fig. Figure 3 shows a further schematic representation of the rotor for an electric machine with a fluid line device for a rotor of an electric machine according to an exemplary embodiment of the invention. Fig. Figure 4 shows a schematic representation of a fluid piping device for a rotor of an electric machine according to an exemplary embodiment of the invention.

[0023] Fig. Figure 1 shows a rotor 10 for an electric machine according to an embodiment of the present disclosure in a schematic exploded view.

[0024] The rotor 10 has a fluid-flowable rotor shaft 11 and a rotor lamination stack or rotor core 12, in the hub or central opening of which the rotor shaft 11 is received or can be received. The rotor 10 is designed for use in an electric machine and is rotatably mounted relative to a stator about a rotational axis of the rotor 10. In the illustrated embodiment, the rotor lamination stack 12 has two rotor core sections 13, each of which has several axially extending grooves 14 designed to receive permanent magnets 15.

[0025] The rotor core sections 13 have the same axial length, so that a space is formed between the two axially spaced rotor core sections 13 in an axial center of the rotor core 12, in which a fluid line device 16 is arranged or can be arranged.

[0026] The fluid conduit assembly 16 has at least one fluid channel 18 configured to receive fluid from the rotor shaft 11 or from outlets 111 of the rotor shaft 11 and to discharge it on both sides to the slots 14 of the rotor core 12 or the two rotor core sections 13 in order to cool the rotor 10. In the slots 14, the fluid can flow axially to both end faces of the rotor core 12, which are closed in this case by means of two covers 17, thereby absorbing and dissipating heat from the rotor core 12 or the permanent magnets 15. For this purpose, the rotor shaft 11 can have outlets 111 to discharge the fluid, and the fluid conduit assembly 16 is designed such that the fluid channels 18 can be arranged to receive the fluid, in particular directly, from the outlets 111 and direct it to the slots 14.

[0027] Fig. Figure 2 shows the rotor 10 for an electric machine according to the embodiment shown in Figure 2. Fig. 1 in a schematic perspective representation.

[0028] It can be seen that at least one fluid line assembly 16 is arranged in the axial center of a rotor core 12 of the rotor 10. This allows the fluid, when the rotor 10 rotates, to leave the rotor shaft 11 through the outlets 111 due to centrifugal force and flow radially outwards into the fluid line assembly 16, which is designed to allow fluid flow, and to be discharged to the grooves 14 on both sides of the fluid line assembly 16 or the flow disk for cooling.

[0029] Fig. Figure 3 shows the rotor 10 for an electric machine according to the embodiment shown in Fig. 1 and Fig. 2 in a schematic sectional view.

[0030] During operation, the fluid F can flow in the hollow rotor shaft 11 and exit it via the outlets 111, entering the fluid piping system 16 or the fluid channels 18. The fluid piping system 16 or the fluid channels 18 can guide the fluid F radially outwards and discharge it at points where the slots 14 of the rotor core 12 adjoin the fluid piping system 16. There, it enters the slots 14 and flows towards the end faces of the rotor core 12, cooling the rotor core 12 and the permanent magnets 15 arranged in the slots 14.

[0031] Fig. Figure 4 shows a fluid line device 16 for a rotor 10 for an electric machine according to an embodiment of the present disclosure in a schematic cross-sectional view.

[0032] In some embodiments, the at least one fluid channel 18 can be designed as a trench or depression on both sides of the disc-shaped fluid conduit assembly 16; in the present case, the at least one fluid channel 18 is designed as a flowable conduit within the fluid conduit assembly 16.

[0033] In this embodiment, the fluid piping device 16 or fluid channel 16 has several circularly shaped, concentrically arranged distribution sections 118, which are fluid-carryingly connected by means of several radially extending connecting sections 188. In the illustrated embodiment, discharge openings 19 are provided at the connection points of the distribution sections 118 and connecting sections 188 to discharge the fluid F to the slots 14. If the at least one fluid channel 18 has a surface design, discharge structures can be provided to improve fluid discharge to the slots 14. The design of the fluid channels 18, distribution sections 118, connecting sections 188, and discharge openings 19 can be adapted to a cross-section of the rotor core sections 13 and the slots positioned therein to improve fluid discharge and thus the cooling effect. REFERENCE MARK LIST 10 Rotor 11 Rotor shaft 12 rotor core 13 Rotor core section 14 Nut 15 permanent magnet 16 Fluid piping system 17 Cover 18 Fluid channel 19. Drop-off opening 111 Outlet 118 Distribution section 188 Connecting section F Fluid R Rotor axis

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