Electric machine

Abstract

The invention relates to an electrical machine (1) having a hollow shaft rotatable about a rotational axis (RA), a rotor (3), and a stator (4). The electrical machine (1) comprises a cooling path (16) through which a coolant (KF) can flow, wherein the cooling path (16) leads radially outwards from the hollow shaft (2), through the rotor (3), and through the stator (4). The electrical machine (1) also has a conveying arrangement (23) for conveying the coolant (KF) from an air gap (6) formed between the rotor (3) and the stator (4) into the cooling path (16).

Description

[0001] The invention relates to an electrical machine, in particular a separately excited synchronous machine for a vehicle, with a stator and a rotor according to the preamble of claim 1.

[0002] An electrical machine typically comprises a rotor and a stator, with the rotor being mounted coaxially within the stator so as to be rotatable about a rotational axis. The rotor and stator each comprise a plurality of windings distributed around the rotational axis. During operation of the electrical machine, the rotor and stator interact electromagnetically, and heat is generated in the windings of the stator and rotor. The windings are typically cooled convectively. However, since the rotor windings are often secured by means of a potting compound to prevent displacement under the action of centrifugal force, sufficient convective cooling of the rotor windings is disadvantageously difficult.

[0003] US 3,684,906 A discloses an electric machine with a rotor and a stator. A coolant flows through the electric machine, with an axial gap formed in the rotor for additional convective cooling of the windings.

[0004] US Pat. No. 9,419,498 B2 discloses an electrical machine with a rotor and a stator. The machine is air-cooled, with two impellers driving the air into an air gap between the rotor and the stator. Furthermore, an axial gap is formed in the rotor for additional convective cooling of the windings.

[0005] DE 2 834 988 A1 discloses an electrical machine with a rotor and a stator. The machine is cooled with oil, with oil first passing through the rotor and then through the stator.

[0006] DE 10 2021 121 016 A1 discloses an electric machine with a rotor and a stator. The rotor is cooled by a cooling fluid.

[0007] The object of the invention is therefore to provide an improved or at least alternative embodiment for an electrical machine of the generic type in which the described disadvantages are overcome.

[0008] This object is achieved according to the invention by the subject matter of independent claim 1. Advantageous embodiments are the subject matter of the dependent claims.

[0009] The present invention is based on the general idea of ​​efficiently cooling a separately excited synchronous machine by segmenting the rotor and the stator. The electric machine according to the invention is, in particular, a separately excited synchronous machine for a vehicle. The electric machine has a rotor and a stator. The rotor has a hollow shaft rotatable about a rotational axis, a rotor core, and a plurality of rotor windings, wherein the rotor core is connected to the hollow shaft in a rotationally fixed manner and the rotor windings are carried by the rotor core. The stator has a stator core and a plurality of stator windings, wherein the stator windings are carried by the stator core. The rotor is arranged coaxially and radially spaced in the stator, whereby an air gap circumferentially surrounding the rotational axis is formed between the rotor and the stator.The electric machine also has a cooling circuit with at least one cooling path, which is aligned transversely to the axis of rotation and leads radially outward from the hollow shaft through the rotor core and, at least in some areas, through the stator core. According to the invention, the electric machine has a conveying arrangement with a first conveying unit at a first axial longitudinal end of the rotor and a second conveying unit at a second axial longitudinal end of the rotor. A cooling fluid can flow through the cooling circuit, and the conveying arrangement is designed to convey air into the air gap and coolant from the air gap into the respective cooling path.

[0010] In the context of the present invention, the terms “radial”, “axial” and “rotating” always refer to the axis of rotation of the hollow shaft.

[0011] In the cooling path, the coolant can flow radially outward from the hollow shaft-side part of the cooling path into the rotor-side part of the cooling path and then across the air gap into the stator-side part of the cooling path. As the rotor rotates, the coolant can be conveyed radially outward from the hollow shaft-side part of the cooling path into the rotor-side part of the cooling path and then propelled across the air gap into the stator-side part of the cooling path. In the respective cooling path, the coolant can thus flow through the hollow shaft, the rotor core, and the stator core, allowing them to be cooled particularly effectively. The coolant can, in particular, be oil.

[0012] Each cooling path crosses the air gap between the stator and the rotor, allowing the coolant from each cooling path to enter the air gap. The conveying arrangement can generate pressure in the air gap, forcing the coolant from the air gap back into the cooling path. To do this, the conveying device can use the conveying units on both sides of the air gap to generate an air flow that conveys the coolant from the air gap back into the cooling path. The conveying arrangement can therefore prevent the coolant, which typically has a higher viscosity, from remaining in the air gap and increasing friction between the rotor and stator. This allows the rotor and stator to be effectively cooled by the coolant, while keeping friction losses between the stator and rotor low.The air conveyed into the air gap by the conveying arrangement can then be discharged, for example, together with the cooling liquid via the cooling path.

[0013] The respective conveying unit can, in particular, be arranged outside the air gap and axially opposite and spaced from the air gap. In other words, the conveying unit can be arranged such that the radial width of the air gap is not negatively affected, yet the air can still be conveyed into the air gap by means of the conveying unit. The respective conveying unit can, for example, be represented by a paddle wheel with several blades distributed around the rotational axis. The blades can, in particular, be evenly distributed around the rotational axis.

[0014] The respective conveyor unit can be fixed to the rotor in a rotationally fixed manner or can rotate with the rotor. For example, the rotor can have two balancing rings, and the balancing rings can be fixed to the axial longitudinal ends of the rotor. The respective conveyor unit can then be fixed to the respective balancing ring and rotate around the outside of the respective balancing ring. In particular, the respective conveyor unit—and in particular the respective impeller—can be pressed onto the respective balancing ring.

[0015] The respective cooling path or the hollow-shaft-side portion of the cooling path can be formed in some areas by a radially outward-facing bore in the hollow shaft. Alternatively, the respective cooling path or the hollow-shaft-side portion of the cooling path can be formed in some areas by several—for example, six—radially outward-facing bores in the hollow shaft. The respective bores can be distributed evenly or unevenly around the axis of rotation. The respective bore can, for example, have a diameter between 0.5 mm and 1 mm.

[0016] The respective cooling path or the rotor-side part of the cooling path can be formed in some areas by an axial gap between two adjacent rotor laminations of the rotor core. In other words, two adjacent rotor laminations of the rotor core can be arranged axially spaced from one another, and the rotor-side part of the cooling path can thus be formed between these rotor laminations in the form of the axial gap. The axial gap can, for example, have an axial height of between 1 mm and 2 mm. If the hollow-shaft-side part of the cooling path is formed by the at least one bore, the respective at least one bore expediently opens radially into the axial gap formed between the two rotor laminations. To form the axial gap, the rotor core can be formed in at least two parts or from at least two rotor core parts that are firmly connected to the hollow shaft separately from one another.The respective axial gap can then also be formed between the respective adjacent rotor core parts.

[0017] To form the axial gap, the rotor can have at least one spacer. The spacer can be arranged between the two adjacent rotor laminations of the rotor core or between the two rotor core parts. The respective cooling path can then be formed regionally around and / or in the respective spacer and regionally between the respective adjacent rotor laminations or between the two rotor core parts. The respective spacer can be formed by a separate element. The separate element can be arranged radially adjacent to the hollow shaft or radially spaced from the hollow shaft. The respective spacer can alternatively be formed by a radially outwardly directed step of the hollow shaft. In principle, several different spacers can be provided.

[0018] The respective cooling path can be formed in the spacer of the rotor by a bore leading radially outwards. Alternatively, the respective cooling path in the spacer of the rotor can be formed by a plurality of bores leading radially outwards. The respective at least one bore in the spacer is expediently fluidically connected to the axial gap in the rotor core. If the hollow shaft-side part of the cooling path is formed by the at least one bore in the hollow shaft, the respective at least one bore in the spacer corresponds fluidically to the respective at least one bore in the hollow shaft. The respective bores can be distributed evenly or unevenly around the axis of rotation. The respective bore can, for example, have a diameter between 0.5 mm and 1 mm.

[0019] The respective cooling path or the stator-side part of the cooling path can be formed in some areas by an axial gap between two adjacent stator laminations of the stator core. In other words, two adjacent stator laminations of the stator core can be arranged axially spaced from one another, and the stator-side part of the cooling path can thus be formed in the form of the axial gap between these stator laminations. The axial gap can, for example, have an axial height of between 1 mm and 2 mm. If the rotor-side part of the cooling path is formed by the axial gap in the rotor core, the respective axial gap in the stator core is expediently arranged radially opposite the respective axial gap in the rotor core. To form the axial gap, the stator core can be formed in at least two parts or from at least two stator core parts that are manufactured separately.The respective axial gap can then also be formed between the respective adjacent stator core parts.

[0020] To form the axial gap, the stator can have at least one spacer. The spacer can be arranged between the two adjacent stator laminations of the stator core or between the two stator core parts. The respective cooling path can then be formed regionally around and / or in the respective spacer and regionally between the respective adjacent stator laminations or between the two stator core parts. The separate element can be arranged radially adjacent to a housing of the electrical machine or radially spaced from the housing of the electrical machine. The respective spacer can alternatively be formed by a radially inwardly directed step of the housing of the electrical machine. In principle, several different spacers can be provided.

[0021] The respective cooling path can be formed in the stator spacer by a radially outward-leading bore. Alternatively, the respective cooling path in the stator spacer can be formed by several radially outward-leading bores. The respective at least one bore in the spacer is expediently fluidically connected to the axial gap in the stator core. The respective bores can be distributed evenly or unevenly around the rotation axis. The respective bore can, for example, have a diameter between 0.5 mm and 1 mm.

[0022] The respective cooling path can be partially formed by a portion of the air gap between the rotor and the stator. The respective cooling path can bridge the air gap between the rotor and the stator or lead across the air gap between the rotor and the stator. The respective rotor-side part of the cooling path and the respective stator-side part of the cooling path can be arranged radially opposite one another, as already described above.

[0023] The respective stator windings and / or the respective rotor windings can be arranged in the respective cooling path so that the coolant can flow directly around them. The respective stator windings can be exposed in the respective axial gap in the stator core or in the respective stator-side part of the cooling path and / or the respective rotor windings can be exposed in the respective axial gap in the rotor core or in the respective rotor-side part of the cooling path. This allows the coolant flowing in the respective cooling path to flow directly around the rotor windings and / or the stator windings and thus cool them particularly effectively. The decisive factor here is that the rotor windings and / or the stator windings are usually made of copper and have good thermal conductivity in the wire direction and can therefore be effectively cooled over their entire length or completely.

[0024] The electric machine can have a housing, wherein the housing can accommodate the stator and the rotor coaxially. The respective cooling path can then be formed in some areas of the housing and lead radially outwards from the stator into the housing. The housing-side part of the cooling path can be connected to further channels of the cooling circuit inside the housing or outside the housing. The respective channels can expediently lead back to the hollow shaft-side part of the cooling path. The cooling circuit can have further components outside the cooling path - such as a cooler and / or a separator - which are fluidically connected to the cooling path via the respective channels.

[0025] Further important features and advantages of the invention emerge from the subclaims, from the drawing and from the associated description of the figures based on the drawing.

[0026] It is understood that the features mentioned above and those to be explained below can be used not only in the respective combination specified, but also in other combinations or on their own, without departing from the scope of the present invention. Components mentioned above and to be mentioned below of a higher-level unit, such as a device, an apparatus, or an arrangement, which are designated separately, may form separate parts or components of this unit or be integral areas or sections of this unit, even if this is shown differently in the drawing.

[0027] Preferred embodiments of the invention are illustrated in the drawing and are explained in more detail in the following description.

[0028] The only Fig. 1 shows a sectional view through an electrical machine 1 according to the invention. The machine 1 has a hollow shaft 2 rotatable about a rotation axis RA, a rotor 3, a stator 4 and a housing 5. The rotor 3 is coaxially and rotatably received in the stator 4. The rotor 3 and the stator 4 are arranged radially spaced from one another, so that an air gap 6 is formed between the rotor 3 and the stator 4. The stator 4 is coaxially and rotationally fixedly received in the housing 5. The housing 5 encloses the rotor 3 and the stator 4 from the outside and is in Fig. 1 is indicated purely schematically.

[0029] The rotor 3 has a rotor core 7 made up of a plurality of rotor laminations 8, wherein the rotor core 7 is connected to the hollow shaft 2 in a rotationally fixed manner—for example, pressed onto the hollow shaft 2. The rotor 3 also comprises two end caps 9a and 9b, which are fixed to the rotor core 7 at opposite axial longitudinal ends 3a and 3b of the rotor 3. The rotor 3 further comprises two balancing rings 10a and 10b, which externally surround the associated end caps 9a and 9b. Rotor windings 11 are arranged or wound on the end caps 9a and 9b. The stator 4 has a stator core 12 with a plurality of stator laminations 13, wherein the stator core 12 is fixedly and in particular rotationally fixedly connected to the housing 5. The stator 4 also comprises a plurality of stator windings 14, which are carried by the stator core 12.

[0030] The machine 1 also has a closed cooling circuit 15 with a cooling path 16 aligned transversely to the rotation axis RA. The cooling path 16 bridges the air gap 6 and can be flowed through by a cooling liquid KF - for example oil. The cooling path 16 leads from the hollow shaft 2 through the rotor core 7 and the air gap 6 and the stator core 12 into the housing 5 and out of the housing 5 to the outside. The cooling path 16 is formed within the hollow shaft 2 by several radial bores 17 (only one is visible here), within the rotor core 7 by an axial gap 18 between two adjacent rotor laminations 8, within the stator core 12 by an axial gap 19 between two adjacent stator laminations 13, and within the housing 5 by several radial bores 20 (only one is visible here).The cooling circuit 15 can be closed via further flow-through channels - not shown here - and the cooling path 16 can be fluidically connected to other components of the cooling circuit 15.

[0031] The axial gap 18 in the rotor core 7 is formed by means of a spacer 21 arranged between the adjacent rotor laminations 8 of the rotor core 7. The cooling path 16 is formed within the spacer 21 by several bores 22 - only one is visible here. In this exemplary embodiment, the spacer 21 is a separate element. However, it is also conceivable that the spacer 21 can be represented by a radially outwardly directed step of the hollow shaft 2. The axial gap 19 in the stator core 12 is formed here without a spacer. However, it is also conceivable that a spacer for forming the axial gap 19 in the stator core 12 can also be arranged between the respective adjacent stator laminations 13 of the stator core 12. This spacer can be formed separately in the same way or by a radially inwardly directed step of the housing 5.

[0032] The cooling path 16 is aligned transversely to the rotation axis RA. In the cooling path 16, the bores 17 in the hollow shaft 2 correspond to the bores 22 in the spacer 21, the bores 22 in the spacer 21 correspond to the axial gap 18 in the rotor core 7, the axial gap 18 in the rotor core 7 corresponds to the axial gap 19 in the stator core 12, and the axial gap 19 in the stator core 12 corresponds to the bores 20 in the housing 5, fluidically in a radially outward direction. The rotor windings 11 are located within the axial gap 18 in the rotor core 7, and the stator windings 14 are exposed within the axial gap 19 in the stator core 12, allowing the cooling fluid KF to flow directly around them, thereby cooling them particularly effectively. Since the rotor windings 11 and the stator windings 14 have good thermal conductivity in the wire direction, the rotor windings 11 and the stator windings 14 can be heated over the entire length orbe cooled completely effectively.

[0033] The cooling path 16 crosses the air gap 6 between the stator 4 and the rotor 3, so that the coolant KF from the cooling path 16 can penetrate into the air gap 6. To prevent this, the electric machine 1 comprises a conveying arrangement 23 with two conveying units 24a and 24b. The conveying units 24a and 24b are arranged at the axial longitudinal ends 3a and 3b of the rotor 3 and are secured to the balancing rings 10a and 10b. The respective conveying units 24a and 24b are represented here by impellers 25a and 25b with multiple blades. The blades can be evenly distributed around the rotation axis RA. The conveying arrangement 23 conveys air L into the air gap 6 and thereby displaces the coolant KF that has penetrated into the air gap 6 from the air gap 6 back into the cooling path 16.This can prevent the cooling liquid KF with a usually higher viscosity from remaining in the air gap 6 and increasing the friction between the rotor 3 and the stator 4.

[0034] In the electrical machine 1, the rotor windings 11 and the stator windings 14 can therefore be effectively cooled by means of the cooling liquid KF, and the increase in friction between the rotor 3 and the stator 3 caused by the cooling liquid KF can be prevented. 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] US 3 684 906 A

[0003] US 9 419 498 B2

[0004] DE 2 834 988 A1

[0005] DE 10 2021 121 016 A1

[0006]

Claims

[1] Electrical machine (1), in particular a separately excited synchronous machine for a vehicle, - wherein the electric machine (1) has a rotor (3) and a stator (4), - wherein the rotor (3) has a hollow shaft (2) rotatable about a rotation axis (RA), a rotor core (7) connected to the hollow shaft (2) in a rotationally fixed manner, and a plurality of rotor windings (11) carried by the rotor core (7), - wherein the stator (4) has a stator core (12) and a plurality of stator windings (14) carried by the stator core (12), - wherein the rotor (3) is arranged coaxially and radially spaced in the stator (4), thereby forming an air gap (6) surrounding the rotational axis (RA) between the rotor (3) and the stator (4), - wherein the electric machine (1) has a cooling circuit (15) with at least one cooling path (16), - wherein the respective cooling path (16) is aligned transversely to the axis of rotation (RA) and leads radially outwards from the hollow shaft (2) through the rotor core (7) and at least partially through the stator core (12), characterized by , - that the electric machine (1) has a conveyor arrangement (23) with a first conveyor unit (24a) at a first axial longitudinal end (3a) of the rotor (3) and a second conveyor unit (24b) at a second axial longitudinal end (3b) of the rotor (3), and - that the cooling circuit (15) can be flowed through by a cooling liquid (KF) and the conveying arrangement (23) is designed to convey the cooling liquid (KF) from the air gap (6) into the respective cooling path (16). [2] Machine (1) according to claim 1, characterized by that the respective conveyor unit (24a, 24b) is arranged outside the air gap (6) and axially opposite and spaced from the air gap (6). [3] Machine (1) according to claim 1 or 2, characterized by that the respective conveying unit (24a, 24b) is represented by a paddle wheel (25a, 25b) with several paddles distributed around the axis of rotation (RA). [4] Machine (1) according to one of the preceding claims, characterized by , - that the rotor (3) has two balancing rings (10a, 10b) and the balancing rings (10a, 10b) are fixed to the axial longitudinal ends (3a, 3b) of the rotor (3), and - that the respective conveyor unit (24a, 24b) is fixed to the respective balancing ring (10a, 10b) and rotates around the outside of the respective balancing ring (10a, 10b). [5] Machine (1) according to one of the preceding claims, characterized by that the respective rotor windings (11) and / or the respective stator windings (14) are arranged in the respective cooling path (16) so that the cooling liquid (KF) can flow directly around them. [6] Machine (1) according to one of the preceding claims, characterized by , - that the respective cooling path (16) bridges the air gap (6) between the rotor (3) and the stator (4), and / or - that the respective cooling path (16) leads across the air gap (6) between the rotor (3) and the stator (4), and / or - that the respective rotor-side part of the cooling path (16) and the respective stator-side part of the cooling path (16) are arranged radially opposite one another. [7] Machine (1) according to one of the preceding claims, characterized by , - that the rotor (3) has at least one spacer (21) and the spacer (21) is arranged between two adjacent rotor laminations (8) of the rotor core (7), wherein the respective cooling path (16) is formed in regions around and / or in the respective spacer (21) and in regions between the respective adjacent rotor laminations (8), and / or - that the stator (4) has at least one spacer and the spacer is arranged between two adjacent stator laminations (13) of the stator core (12), wherein the respective cooling path (16) is formed in regions around and / or in the respective spacer and in regions between the respective adjacent stator laminations (13) of the stator core (12). [8] Machine (1) according to claim 7, characterized by , - that the respective cooling path (16) in the spacer (21) of the rotor (3) is formed by a radially outwardly leading bore (22) in the spacer (21) or by a plurality of bores (22) in the spacer (21) distributed around the axis of rotation (RA) and leading radially outwards, and / or - that the respective cooling path (16) in the spacer of the stator (4) is formed by a radially outwardly leading bore in the spacer or by a plurality of bores in the spacer distributed around the axis of rotation (RA) and leading radially outwards. [9] Machine (1) according to one of the preceding claims, characterized by , - that the electrical machine (1) has a housing (5) coaxially accommodating the rotor (3) and the stator (4), and - that the respective cooling path (16) is formed in regions in the housing (5) and leads radially outwards from the stator (4) into the housing (5). [10] Machine (1) according to one of the preceding claims, characterized by that the respective cooling path (16) is formed in regions by a radially outwardly directed bore (17) in the hollow shaft (2) or by a plurality of bores (17) in the hollow shaft (2) distributed around the axis of rotation (RA) and leading radially outwards. [11] Machine (1) according to one of the preceding claims, characterized by that the respective cooling path (16) is partially formed by an axial gap (18) between two adjacent rotor laminations (8) of the rotor core (7). [12] Machine (1) according to one of the preceding claims, characterized by that the respective cooling path (16) is partially formed by a gap (19) between two adjacent stator laminations (13) of the stator core (12). [13] Machine (1) according to one of the preceding claims, characterized by that the respective cooling path (16) is partially formed by a region of the air gap (6) between the rotor (3) and the stator (4).

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