Rotor of an electrical machine

Abstract

The invention relates to a rotor (100) for an electrical machine (10) with a rotor shaft (12) extending along a rotor axis (A), a cylindrical rotor core (13) having two opposite end faces (141, 142) between which a plurality of coaxially arranged recesses (15) extend, and a plurality of rotor bars (16) resting in the recesses (15) and each connected to at least one short-circuit disk (17) on the end faces (141, 142) of the rotor core (13), wherein cooling fluid channels (21) are formed between the rotor bars (16) and the rotor core (13), which are designed to guide a cooling fluid (30), wherein the cooling fluid channels (21) each have a cooling fluid inlet (22) on one of the end faces (141, 142) of the rotor core (13) and a cooling fluid inlet (22) on the opposite end face (142, 141) of the rotor core (13) each have a cooling fluid outlet (23).According to the invention, a rotationally symmetrical cooling fluid collecting funnel (241, 242) is formed on each of the two end faces (141, 142) of the rotor laminated core (13), which increasingly tapers in the radial direction with increasing distance from the rotor axis (A) and opens into at least one cooling fluid inlet (22).

Description

[0001] The invention relates to a rotor for an electrical machine with a rotor shaft which extends along a rotor axis, a cylindrical rotor laminated core which has two opposite end faces between which a plurality of coaxially arranged recesses run, and a plurality of rotor bars which rest in the recesses and are each connected to at least one short-circuit disk on the end faces of the rotor laminated core, wherein cooling fluid channels are formed between the rotor bars and the rotor laminated core, which are designed to guide a cooling fluid, wherein the cooling fluid channels each have a cooling fluid inlet on one of the end faces of the rotor laminated core and a cooling fluid outlet on the opposite end face of the rotor laminated core.

[0002] Electrical machines of the type discussed here are used primarily as drive units in electric or hybrid vehicles. Asynchronous machines (ASM) have proven particularly advantageous for this purpose. In such machines, rotors of this type are mounted within a stator, which has winding overhangs for accommodating excitation coils. By applying three-phase current to the excitation coils, a rotating magnetic field is generated within the stator, which induces a current in the rotor bars and the short-circuit disks, which in turn generates another magnetic field. The magnetic fields of the stator and the rotor interact in such a way that the magnetic field of the rotor aligns with the rotating magnetic field of the stator, exerting a torque on the rotor. By controlling the frequency of the three-phase current, the rotational speed of the rotor can be specified or adjusted.

[0003] During operation of such asynchronous machines, heat is generated by mechanical friction and the electrical resistance of the rotor bars and short-circuiting disks. This heat must be effectively dissipated to ensure continuous and trouble-free operation of the electrical machine. Today's cooling concepts for asynchronous machines typically cool the short-circuiting disks and / or the rotor core near the rotor shaft with a cooling fluid applied to these components.

[0004] A cooling concept is known from the generic EP 2 919 367 A1, according to which the rotor core has additional cooling fluid channels through which cooling fluid is guided to dissipate heat. Similar proposals are known from DE 10 2015 204 872 A1 and EP 2 299 565 A1.

[0005] State-of-the-art cooling concepts are limited in terms of achievable heat dissipation, which adversely impacts the available power of electrical machines. Furthermore, electrical machines are designed to be comparatively large to allow additional heat dissipation via the large surface area of ​​the components, which adversely impacts installation space and material requirements.

[0006] It is therefore the object of the invention to propose a rotor for an electrical machine with a cooling device that provides a high achievable heat dissipation, so that the available power can be increased and the installation space and material requirements can be reduced.

[0007] This object is achieved by the rotor according to claim 1. According to the invention, a rotationally symmetrical cooling fluid collecting funnel is formed on each of the two end faces of the rotor core, which increasingly tapers in the radial direction with increasing distance from the rotor axis and opens into at least one cooling fluid inlet. This allows cooling fluid to be collected without loss and directed into the cooling fluid channels, so that heat is directly and effectively dissipated from the rotor bars, which heat up due to the induced current and friction. The effective heat dissipation allows the electric machines to be designed comparatively smaller, which has a positive effect on the installation space required and the required material usage.

[0008] Advantageous embodiments of the invention are specified below and in the subclaims.

[0009] It is preferably provided that the cooling fluid outlet of a cooling fluid channel opens into a radial guide, wherein the radial guide is arranged and aligned such that cooling fluid emerging there is thrown onto winding heads of a stator in the assembled and rotating state of the electrical machine, whereby the cooling fluid additionally dissipates heat from the winding heads.

[0010] According to an advantageous development of the invention, tangentially adjacent cooling fluid channels are aligned antiparallel to one another, whereby cooling fluid inlets and / or cooling fluid outlets of adjacent cooling fluid channels are formed on different end faces of the rotor core. This prevents the rotor from being mounted with an imbalance. Furthermore, it results in a uniform cooling flow both within the rotor and with regard to the preferential cooling of the stator winding heads.

[0011] To supply the cooling fluid, the rotor shaft preferably has cooling fluid channels that open into radial bores with openings on the shell side. The openings of the radial bores are each radially aligned with one of the cooling fluid collecting funnels. Cooling fluid escaping from the openings is propelled in the direction of the cooling fluid collecting funnel due to pressure and / or the high rotation of the rotor. From there, the cooling fluid is guided into the cooling fluid channels of the rotor core. This negative pressure is created by the rotation-induced discharge of the cooling fluid at the openings of the radial guides of the rotor core, which maintains a uniform cooling fluid flow within the cooling fluid channels of the rotor core.

[0012] According to a preferred embodiment of the invention, the cooling fluid collecting funnels each have two funnel surfaces, namely one funnel surface on the rotor core side and one funnel surface on the short-circuit disk side. The funnel surfaces on the rotor core side are preferably formed by the end faces of the rotor core. The funnel surfaces on the short-circuit disk side, in contrast, are preferably formed by several disks, which have a smaller inner diameter with increasing distance from the funnel surface on the rotor core side, resulting in a stepped funnel surface. The disks are preferably designed as short-circuit disks and / or spacer disks.

[0013] According to an alternative embodiment of the invention, the funnel surfaces on the short-circuit disc side are each formed by at least one disc, the inner diameter of which decreases with increasing distance from the funnel surface on the rotor core side, resulting in a funnel surface that is inclined with respect to the rotor axis. The at least one disc is preferably designed as a short-circuit disc or spacer disc. Multiple discs can also be provided, the inner surfaces of which, facing the rotor axis, merge flush with one another.

[0014] Specific embodiments of the invention are explained below with reference to the figures. They show: Fig. 1 an electrical machine, Fig. 2a a rotor of the electric machine, Fig. 2b a first detailed view of the rotor with a cooling fluid collecting funnel, Fig. 2c a second detailed view of the rotor with a cooling fluid collecting funnel, Fig. 2d a third detailed view of the rotor with a radial guide, Fig. 2e a first cross-sectional view along the cross-sectional plane AA and Fig. 2f a second cross-sectional view along the cross-sectional plane BB.

[0015] Fig. 1 shows an electrical machine 10 mounted within a housing 11. The electrical machine 10 has a rotor 100 with a rotor shaft 12 extending along a rotor axis A and encompassed by a cylindrical rotor core 13 having two opposing end faces 141, 142. The rotor axis A defines a cylindrical coordinate system. Directional references within the scope of this application, in particular axial, radial, and tangential, refer to this cylindrical coordinate system. A plurality of coaxially arranged recesses 15 ( Fig. 2a, Fig. 2e), in which several rotor bars 16 rest, each of which is connected to at least one short-circuit disk 17 at the end faces 141, 142 of the rotor core 13. The rotor 100 is mounted relative to a stator 18 for rotation about the rotor axis A, wherein the stator 18 has a stator core 19 and winding heads 201, 202. By applying three-phase current to the winding heads 201, 202, a torque is exerted on the rotor 100 in the manner already described, which rotates about the rotation axis A.

[0016] Fig. 2a shows a detailed view of the rotor 100. To dissipate heat, the rotor bars 16 do not lie fully against the rotor core 13, but cooling fluid channels 21 ( Fig. 2a-e), which are designed to guide a cooling fluid 30, wherein the cooling fluid channels 21 each have a cooling fluid inlet 22 on one of the end faces 141, 142 of the rotor core 13 and a cooling fluid outlet 23 on the opposite end face 142, 141 of the rotor core 13. Rotationally symmetrical cooling fluid collecting funnels 241, 242 are formed on the two end faces 141, 142 of the rotor core 13, which increasingly taper in the radial direction with increasing distance from the rotor axis A and open into at least one cooling fluid inlet 22. The cooling fluid outlets 23 of the cooling fluid channels 21 each open into a radial guide 251, 252 ( Fig. 2a, d, f), wherein the radial guides 251, 252 are arranged and aligned such that cooling fluid 30 emerging therefrom is thrown off onto the winding heads 201, 202 of the stator 18 in the assembled and rotating state of the electrical machine 10. Fig. The cooling fluid channels 21 shown in Figure 2a are aligned antiparallel to one another, whereby the cooling fluid inlets 22 and / or the cooling fluid outlets 23 are formed on different end faces 141, 142 of the rotor core 13.

[0017] In the illustrated embodiment, the rotor shaft 12 has cooling fluid channels 26 that open into radial bores 27 with shell-side openings 28. The openings 28 of the radial bores 27 are each radially aligned with one of the cooling fluid collecting funnels 241, 242, so that cooling fluid 30 exiting the openings 28 of the radial bores 27 is directed into the cooling fluid collecting funnels 241, 242.

[0018] Fig. Figure 2b shows a detailed view of a first embodiment of a cooling fluid collecting funnel 241. The cooling fluid collecting funnel 241, 242 each has two funnel surfaces 29, namely a funnel surface 291 on the rotor core side and a funnel surface 292 on the short-circuit disk side. The funnel surface 291 on the rotor core side is formed by the end faces 141, 142 of the rotor core 13. The funnel surface 292 on the short-circuit disk side is formed by a plurality of short-circuit disks 17, which have a smaller inner diameter with increasing distance from the funnel surface 291 on the rotor core side, resulting in a stepped funnel surface 29.

[0019] Fig.2c, in contrast, shows a second embodiment of the short-circuit disk-side funnel surface 292, which is formed by a plurality of short-circuit disks 17, the inner diameter of which becomes increasingly smaller with increasing distance from the rotor core-side funnel surface 291, so that a funnel surface 29 is obtained which is inclined with respect to the rotor axis A. List of reference symbols 100 rotors 10 electric machine 11 housings 12 Rotor shaft 13 Rotor lamination package 141 front sides 142 front side 15 Recess 16 rotor bar 17 Short-circuit disc 18 Stator 19 Stator laminated core 201 winding head 202 winding head 21 Cooling fluid channel 22 Cooling fluid inlet 23 Cooling fluid outlet 241 Cooling fluid collecting funnel 242 Cooling fluid collecting funnel 251 Radial guide 252 Radial guide 26 Cooling fluid channel 27 Radial bore 28 Opening 29 funnel area 291 rotor core side funnel surface 292 short-circuit disc-side funnel surface 30 cooling fluid QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] EP 2 919 367 A1

[0004] DE 10 2015 204 872 A1

[0004] EP 2 299 565 A1

[0004]

Claims

[1] Rotor (100) for an electrical machine (10) with a rotor shaft (12) extending along a rotor axis (A), a cylindrical rotor core (13) having two opposite end faces (141, 142) between which a plurality of coaxially arranged recesses (15) extend, and a plurality of rotor bars (16) resting in the recesses (15) and each being connected to at least one short-circuit disk (17) on the end faces (141, 142) of the rotor core (13), wherein cooling fluid channels (21) are formed between the rotor bars (16) and the rotor core (13), which are designed to guide a cooling fluid (30), wherein the cooling fluid channels (21) each have a cooling fluid inlet (22) on one of the end faces (141, 142) of the rotor core (13) and a cooling fluid inlet (22) on the opposite end face (142, 141) of the rotor core (13) each have a cooling fluid outlet (23), characterized bythat a rotationally symmetrical cooling fluid collecting funnel (241, 242) is formed on each of the two end faces (141, 142) of the rotor laminated core (13), which increasingly tapers in the radial direction with increasing distance from the rotor axis (A) and opens into at least one cooling fluid inlet (22). [2] Rotor (100) according to claim 1, characterized by in that the cooling fluid outlet (23) of a cooling fluid channel (21) opens into a radial guide (251, 252), wherein the radial guide (251, 252) is arranged and aligned such that cooling fluid (30) emerging therefrom is thrown off onto winding heads (201, 202) of a stator (18) in the assembled and rotating state of the electrical machine (10). [3] Rotor (100) according to one of claims 1 or 2, characterized bythat tangentially adjacent cooling fluid channels (21) are aligned antiparallel to one another, whereby cooling fluid inlets (22) and / or cooling fluid outlets (23) of adjacent cooling fluid channels (21) are formed on different end faces (141, 142) of the rotor laminated core (13). [4] Rotor (100) according to one of claims 1 to 3, characterized by that the rotor shaft (12) has cooling fluid channels (26) which open into radial bores (27) with shell-side openings (28), wherein the openings (28) of the radial bores (27) are each aligned in the radial direction with one of the cooling fluid collecting funnels (241, 242). [5] Rotor (100) according to one of claims 1 to 4, characterized by that the cooling fluid collecting funnels (241,242) each have two funnel surfaces (29), namely a funnel surface (291) on the rotor core side and a funnel surface (292) on the short-circuit disk side. [6] Rotor (100) according to one of claims 1 to 5, characterized bythat the rotor sheet side funnel surfaces (291) are formed by the end faces (141, 142) of the rotor sheet stack (13). [7] Rotor (100) according to one of claims 1 to 6, characterized by that the funnel surfaces (292) on the short-circuit disc side are formed by a plurality of discs which have a smaller inner diameter with increasing distance from the funnel surface (291) on the rotor core side, so that a stepped funnel surface (292) is produced. [8] Rotor (100) according to claim 7, characterized by that the discs are designed as short-circuit discs (17) and / or spacer discs. [9] Rotor (100) according to one of claims 1 to 8, characterized bythat the funnel surfaces (292) on the short-circuit disc side are formed by at least one disc, the inner diameter of which becomes increasingly smaller with increasing distance from the funnel surface (291) on the rotor core side, so that a funnel surface (292) is obtained which is inclined with respect to the rotor axis (A). [10] Rotor (100) according to claim 9, characterized by that the at least one disc is designed as a short-circuit disc (17) or spacer disc.

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