Rotor for an electric machine

Abstract

Rotor for an electrical machine, comprising a hollow rotor shaft rotatable about a longitudinal axis and having at least one radially extending opening, a rotor core with at least one axially extending cooling bore, a plurality of rotor coils distributed over the circumference of the rotor core, and end rings arranged at the axial ends of the rotor core.

Description

[0001] The application relates to a rotor for an electrical machine, comprising a hollow rotor shaft rotatable about a longitudinal axis and having at least one radially extending opening, a rotor core with at least one axially extending cooling bore, a plurality of rotor coils distributed over the circumference of the rotor core and end rings arranged at the axial ends of the rotor core.

[0002] DE 10 2021 102 430 A1 relates to a rotor for an electric machine of a drive train, in particular of a motor vehicle, having a rotor shaft and active parts surrounding the rotor shaft on the circumference, which active parts comprise a laminated core and star disks adjoining the respective end faces of the laminated core. The rotor shaft is connected to the active parts in a rotationally fixed manner, whereby a torque can be transmitted between the active parts and the shaft. For cooling, the rotor has at least one cooling channel comprising an inlet region extending from an inlet end of the rotor shaft through the rotor shaft, and a coolant flow flowing through the active parts. The coolant inflow is designed such that the coolant flowing into the cooling channel via the inlet end of the rotor shaft is directed towards another end of the rotor shaft opposite the inlet end of the rotor shaft.

[0003] KR 101967731 B1 relates to a structure capable of firmly supporting a coil wound on a core of a rotor and a structure for cooling the heat generated in the rotor, the rotor comprising a plurality of cores configured to be rotatable and projecting radially from the center, a field coil wound around each of the cores, and a plurality of cooling support members having a cooling structure for supporting the field coil wound between two adjacent cores and for dissipating the heat generated inside the rotor to the outside.

[0004] US 1 101 1960 B2 discloses a wound rotor motor in which a rotating shaft is arranged vertically to immerse lower coil portions of a stator and a rotor in cooling oil in which the lower coil portions are partially immersed. The cooling oil rises from the area below the rotor through a flow channel in the rotating shaft and is sprayed into the area above the rotor by the centrifugal force generated by the rotation of the rotor, thereby enhancing the cooling effect of the motor and reducing the friction loss of the rotor due to the cooling oil.

[0005] WO 2018 / 095842 A1 discloses a wound rotor comprising a shaft extending in a longitudinal direction and a circumferential sequence of teeth and grooves, each tooth receiving a longitudinal winding intended to create a rotor pole, each winding defining a projecting coil head at each longitudinal end of the rotor, the rotor being capable of being cooled by a coolant sprayed onto the coil heads, the rotor further comprising at least one collar for mechanically retaining the rotor windings, the collar being mounted at one longitudinal end of the rotor to define a central opening opening into the coil heads, the collar having at least one drainage channel allowing the coolant sprayed onto the coil heads into the central opening to drain away.

[0006] WO 2021 / 232835 A1 discloses an electric motor rotor, an electric motor, and a vehicle. The rotor of the electric motor consists of a wound rotor having a rotating shaft, a rotor core, and a plurality of rotor coils, the rotor core being fixedly connected to the rotating shaft by a casing. The rotor core is provided with a plurality of winding holes spaced at intervals around the rotating shaft, and each winding hole penetrates two ends of the rotor core arranged in the axial direction. Each rotor coil is wound on the hole wall between two adjacent winding holes, and two adjacent rotor coils share one winding hole.A gap is formed between two adjacent rotor coils, and a first shaft hole is formed in the rotating shaft. The gap is configured to be a first heat dissipation channel in communication with the first shaft hole. The first heat dissipation channel is used for a cooling fluid flowing into the rotating shaft. Thus, the cooling fluid introduced into the rotating shaft from the outside enters the first heat dissipation channel from the first shaft hole under the action of centrifugal force to dissipate heat from the rotor coils of the wound rotor.

[0007] One object may be to propose an improved rotor for an electrical machine, in particular a separately excited synchronous motor, with improved cooling properties.

[0008] The object is achieved by a rotor for an electrical machine according to claim 1. Advantageous embodiments are the subject of the dependent claims.

[0009] The rotor for an electric machine comprises a hollow rotor shaft rotatable about a longitudinal axis and having at least one radially extending opening, a rotor core with at least one axially extending cooling bore, a plurality of rotor coils distributed around the circumference of the rotor core, and end rings arranged at the axial ends of the rotor core. At least one cooling channel hydraulically connects the opening to the cooling bore to conduct coolant from the hollow rotor shaft into the rotor core. Cover rings are arranged radially outside the end rings at the axial ends of the rotor core and form coolant reservoirs for collecting the coolant escaping from the cooling bore.

[0010] The proposed rotor can advantageously utilize the centrifugal force caused by the rotation of the rotor to convey coolant from the hollow rotor shaft through the radially extending opening and via the cooling channel into the cooling bore, through which the coolant flows axially through the rotor core and exits at an opposite end, where it is captured by the cover ring forming the coolant reservoir. Furthermore, it is advantageous that the end windings of the rotor coils protrude from the rotor core and are located in the coolant reservoir formed by the cover ring, thus effectively cooling them.

[0011] The electrical machine may be a separately excited synchronous motor with wound rotor coils installed in the rotor core. The rotor may also be a hybrid separately excited synchronous motor with wound rotor coils and permanent magnets installed on the rotor. The rotor coil windings may consist of wire or hairpin windings. The rotor core has axially and radially extending teeth distributed around the circumference of the rotor core, and the end rings have legs that match the teeth, with the rotor coils arranged on the teeth and legs, i.e., wound around the teeth and legs. The rotor coils on the teeth form the poles of the rotor. Terms such as axial, radial, and circumferential always refer to the longitudinal axis, unless otherwise stated.

[0012] To form the coolant reservoirs, the cover rings can each have a first section extending in the axial direction and a second section extending in the radial direction, wherein the first sections are attached to the axial ends of the rotor core radially outside the end rings and wherein the second sections are arranged in the axial direction on a side of the end rings facing away from the rotor core and at least partially cover them. In the circumferential direction, the cover rings are continuous. The first and second parts are connected, e.g., by a curved central part. The cover rings can be made from a single piece. The radial extension of the second part can correspond to a radial extension of the rotor coils. The second part has an opening arranged in the radial direction within the rotor coils, so that the cover rings are not closed.The coolant thus advantageously fills the reservoir and is held there by the rotational force, cooling the end windings. When the reservoir is full, the coolant exits through the radially inner end of the second part and, again by the rotational force, is propelled by the cover rings to the stator end windings, which are thereby also advantageously cooled.

[0013] According to one embodiment, the cooling channel can be formed at least partially in the end ring. In particular, the cooling channel is formed as a groove in a contact surface of the end ring facing the rotor core.

[0014] According to a further embodiment, the cooling channel is partially formed in at least one fastening ring arranged on the rotor shaft. The fastening ring forms an axial abutment for the rotor core. The cooling channel is designed in particular as a groove in a contact surface of the fastening ring facing the rotor core. The contact surfaces of the end ring and the fastening ring are both in contact with the end face of the rotor core, wherein the fastening ring is connected to the rotor shaft and the end ring surrounds the fastening ring, so that a radially inner section of the cooling channel is formed in the fastening ring and a radially outer section of the cooling channel is formed in the end ring. When the end rings, the fastening rings, and the cover rings are referred to in the singular, this is generally to be understood to mean that the described feature applies to both end rings, fastening rings, and cover rings.

[0015] According to a further embodiment, at least one outlet channel can be formed in the end ring to guide the coolant exiting the cooling bore into the coolant reservoir formed by the cover ring. In particular, the outlet channel is formed as a groove in a radially outer surface of the end ring.

[0016] According to a further embodiment, a pole piece is arranged on each tooth, the pole pieces forming an outer surface of the rotor, the cooling bore being formed in the tooth and / or the pole piece. At least one cooling channel can be provided for each pole. With a first end ring arranged at a first axial end of the rotor core and a second end ring arranged at a second axial end of the rotor core, the cooling channels can be divided between the first axial end and the second axial end, such that the coolant flows from the first axial end into a first part of the cooling bores and from the second axial end into a second part of the cooling bores. Thus, each tooth can have a cooling bore which is supplied with coolant in the circumferential direction alternately via a cooling channel at the first axial end and at the second axial end.The flow direction of the coolant thus alternates from each cooling hole to the adjacent cooling hole. Accordingly, those outlet channels are formed in the legs of the first end ring that are connected to one of the cooling holes that is supplied with coolant via one of the cooling channels at the second axial end of the rotor core. Conversely, those outlet channels are formed in the legs of the second end ring that are connected to one of the cooling holes that is supplied with coolant via one of the cooling channels at the first axial end of the rotor core. If there is more than one cooling channel per pole, cooling channels and outlet channels can be formed at both axial ends of each pole.

[0017] According to another embodiment, a static lance extends into the hollow rotor shaft, with the coolant being supplied to the rotor shaft through the static lance, which advantageously enables a low-pressure coolant supply. Compared to a rotating lance, the coolant flow in the static lance is not affected by the rotation speed of the rotor, allowing for better control of the coolant flow to the rotor shaft.

[0018] The invention will be described in more detail with reference to an exemplary embodiment shown in the accompanying drawings. Fig. 1 shows an embodiment of a rotor in a perspective exploded view; Fig. 2 an electrical machine with the rotor of Fig. 1 in a sectional view; Fig. 3 the rotor of Fig. 1 in a perspective half-section.

[0019] In Fig. 1 shows an embodiment of a rotor 1 for an electrical machine in a perspective exploded view. The electrical machine with the rotor 1 is shown in the Fig. 2 is shown in a sectional view. In Fig. 3 shows the rotor 1 in a perspective half-section. Fig. 1, Fig. 2 and Fig. 3 are described together. The rotor 1 has a hollow rotor shaft 2 which is rotatable about a longitudinal axis L. The longitudinal axis L is only Fig. 2. In all figures, terms such as axial, radial and circumferential refer generally to the longitudinal axis L, unless otherwise stated. The hollow rotor shaft 2 has radially extending openings 3 which connect a cavity 22 to a surface of the rotor shaft 2. A rotor core 4 is rotatably mounted on the rotor shaft 2 so that it rotates together with the rotor shaft 2 about the longitudinal axis L. The rotor core 4 has axially extending cooling bores 5 which run from one axial end to the other. Two end rings 6 are arranged at the axial ends of the rotor core 4. A plurality of rotor coils 11 are distributed over the circumference of the rotor core 4, with the rotor coils 11 being wound around teeth 17 of the rotor core 4 and legs 18 of the end rings 6. The teeth 17 extend axially and radially from a central part of the rotor core 4 and are evenly distributed over a circumference of the rotor core 4.The legs 18 of the end rings 6 have a corresponding shape matching the teeth 17. A pole piece 19 is arranged on each tooth 17, with the pole pieces 19 at least partially forming an outer surface of the rotor 1. Remaining cavities between adjacent rotor coils 11 are filled with wedge pieces 27, which also form part of the outer surface of the rotor 1. A cooling bore 5 is provided for each tooth 17, which can be formed in a transition region between the tooth 17 and the pole piece 19. Rotor end windings 21 protrude from the rotor core 4 at both axial ends.

[0020] Cooling channels 7 hydraulically connect the openings 3 with the cooling bores 5 to guide coolant from the hollow rotor shaft 2 into the rotor core 4. The coolant flow is in Fig. 2 by the arrows P. Cover rings 8 are attached to the axial ends of the rotor core 4, radially outside the end rings 6, which form coolant reservoirs for collecting the coolant emerging from the cooling channel 5. The cover rings 8 each have a first section 9 extending in the axial and circumferential directions and a second section 10 extending in the radial and circumferential directions, wherein the first sections 9 are attached to the axial ends of the rotor core 4 radially outside the end rings 6 and the second sections 10 are arranged in the axial direction on a side of the end rings 6 facing away from the rotor core 4 and at least partially cover them. A radial extension of the second part 10 corresponds to a radial extension of the rotor coils 11, wherein the rotor end windings 21 are advantageously immersed in the coolant collected in the cover rings 7.A slot 26 is formed between a radial inner edge of the second part 10 and the end ring 6, through which slot coolant can escape from the reservoir of the cover ring 8 when the coolant level exceeds the inner edge of the second part 10. Due to the rotational force, the coolant level rises in the radial direction toward the longitudinal axis L. The coolant escaping from the reservoir of the cover ring 8 is propelled by the rotor 2 in the direction of the stator end windings 24 of the stator 23 (. Fig. 2). The coolant then collects by gravity at the bottom of a housing 25 of the electric machine, from where it can be returned, for example, via a heat exchanger (not shown), to the cavity 22 of the hollow rotor shaft 2.

[0021] The cooling channels 7 are formed partly in the end ring 6 and partly in fastening rings 15, which are arranged on the rotor shaft 2 radially inside the end rings 6. The cooling channels 7 are formed as grooves in a contact surface 12 of the end ring 6 facing the rotor core 4 and in a contact surface 20 of the fastening ring 15 facing the rotor core 4. Furthermore, outlet channels 14 are formed in the end rings 6 in order to guide the coolant emerging from the cooling bore 5 into the coolant reservoir formed by the cover ring 8, wherein the outlet channels 14 are formed as grooves in a radially outer surface 16 of the end rings 6. In the illustrated embodiment, the end rings 6 have the groove for the cooling channels 7 on every second leg 18 and the groove for the outlet channels 14 on the respective other legs 18. The legs 18 of the end rings 6 have the cooling channels 7 and the outlet channels 14 alternating in the circumferential direction.The coolant flows of adjacent cooling holes 5 thus have opposite directions and advantageously form a counterflow. Reference symbol 1 rotor 2 Hollow rotor shaft 3 Opening 4 rotor core 5 Cooling hole 6 end ring 7 Cooling channel 8 lid ring 9 Part One 10 Second Part 11 Rotor coil 12 Contact surface of the end ring 14 output channels 15 Mounting ring 16 Radial outer surface of the end ring 17 tooth 18 legs 19 Pole piece 20 Contact surface of the mounting ring 21 rotor end windings 22 Cavity 23 Stator 24 stator end windings 25 housings 26 slot 27 wedge pieces L Longitudinal axis P arrows 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] DE 10 2021 102 430 A1

[0002] KR 101967731 B1

[0003] US 1 101 1960 B2

[0004] WO 2018 / 095842 A1

[0005] WO 2021 / 232835 A1

[0006]

Claims

[1] Rotor (1) for an electrical machine, comprising a hollow rotor shaft (2) rotatable about a longitudinal axis (L) with at least one radially extending opening (3), a rotor core (4) with at least one axially extending cooling bore (5), a plurality of rotor coils (11) distributed over a circumference of the rotor core (4), end rings (6) arranged at the axial ends of the rotor core (4), wherein at least one cooling channel (7) hydraulically connects the opening (3) to the cooling bore (5) in order to conduct coolant from the hollow rotor shaft (2) into the rotor core (4), wherein cover rings (8) are mounted on the axial ends of the rotor core (4) radially outside the end rings (6), which form coolant reservoirs for collecting the coolant emerging from the cooling bore (5). [2] Rotor according to claim 1, characterized bythat the cover rings (8) each have a first section (9) extending in the axial direction and a second section (10) extending in the radial direction, wherein the first sections (9) are attached to the axial ends of the rotor core (4) radially outside the end rings (6) and wherein the second sections (10) are arranged in the axial direction on a side of the end rings (6) facing away from the rotor core (4) and at least partially cover them. [3] Rotor according to claim 2, characterized by that a radial extension of the second part (10) corresponds to a radial extension of the rotor coils (11). [4] Rotor according to one of the preceding claims, characterized by that the connecting channel (7) is at least partially formed in the end ring (6). [5] Rotor according to one of the preceding claims, characterized bythat the cooling channel (7) is designed as a groove in a contact surface (12) of the end ring (6) facing the rotor core (4). [6] Rotor according to one of the preceding claims, characterized by that the cooling channel (7) is partially formed in at least one fastening ring (15) arranged on the rotor shaft (2). [7] Rotor according to claim 6, characterized by that the cooling channel (7) is partly formed as a groove in a contact surface (20) of the fastening ring (15) facing the rotor core (4). [8] Rotor according to one of the preceding claims, characterized by that at least one outlet channel (14) is formed in the end ring (6) in order to guide the coolant emerging from the cooling bore (5) into the coolant reservoir formed by the cover ring (8). [9] Rotor according to claim 8, characterized by that the outlet channel (14) is designed as a groove in a radially outer surface (16) of the end ring (6). [10] Rotor according to one of the preceding claims, characterized by that the rotor core (4) has axially and radially extending teeth (17) which are distributed over a circumference of the rotor core (4), wherein the end rings (6) have legs (18) matching a shape of the teeth (17), and wherein the rotor coils (11) are arranged on the teeth (17) and the legs (18). [11] Rotor according to claim 10, characterized by that a pole piece (19) is arranged on each tooth (17), the pole pieces (19) forming an outer surface of the rotor (1), the cooling channel (5) being formed in the tooth (17) and / or the pole piece (19). [12] Rotor according to one of the preceding claims, characterized by that a first end ring (6) is arranged at a first axial end of the rotor core and that a second end ring (6) is arranged at a second axial end of the rotor core (4), wherein the cooling channels (7) are distributed between the first axial end and the second axial end. [13] Rotor according to claim 12, characterized by that a cooling channel (7) is provided per tooth (17), alternately in the circumferential direction at the first axial end and at the second axial end of the rotor core (4). [14] Rotor according to one of claims 12 or 13, characterized by that outlet channels (14) are formed in the legs (18) of the first end ring (6), which are connected to those cooling bores (5) which are supplied with coolant via one of the cooling channels (7) at the second axial end of the rotor core (4). [15] Rotor according to one of the preceding claims, characterized by that a static lance protrudes into the hollow rotor shaft (2), wherein the coolant is supplied to the rotor shaft (2) through the static lance.

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