Rotor for electric machine

Abstract

The invention relates to a rotor for an electric machine, comprising: a hollow rotor shaft which can be rotated about a longitudinal axis and which has at least one radially extending opening; a rotor core, which is provided with at least one axially extending cooling hole; a plurality of rotor coils distributed on a circumferential portion of the rotor core; and an end ring disposed at an axial end of the rotor core.

Description

Technical Field

[0001] The application relates to a rotor for an electric motor, comprising: a hollow rotor shaft rotatable about a longitudinal axis, the rotor shaft having at least one radially extending opening; a rotor core having at least one axially extending cooling hole; a plurality of rotor coils distributed on the circumference of the rotor core; and an end ring arranged at the axial end of the rotor core. Background Art

[0002] DE 10 2021 102 430 A1 relates to a rotor for an electric motor of a drive train, in particular a motor vehicle, having a rotor shaft and an active component surrounding the rotor shaft on the circumference, the active component comprising a laminated core and a star disk connected to the respective end sides of the laminated core. The rotor shaft is connected to the active component in a rotationally fixed manner, whereby a torque can be transmitted between the active component and the shaft. For cooling, the rotor has at least one cooling channel, which comprises an inflow region extending from an inflow end of the rotor shaft through the rotor shaft and a cooling liquid flow flowing through the active component. The coolant inflow is designed in such a way that the coolant flowing into the cooling channel via the inflow end of the rotor shaft is guided in the direction of the other end of the rotor shaft opposite to the inflow end of the rotor shaft.

[0003] KR 101967731 B1 relates to a structure capable of firmly supporting a coil wound onto a core of a rotor and a structure for cooling heat generated in the rotor, wherein the rotor comprises: a plurality of cores which are constructed so that they are rotatable and extend radially from the center; a field coil which is wound around each of the cores; and a plurality of cooling carrier elements with cooling structures which are used to support the field coils wound between two adjacent cores and to conduct heat generated in the interior of the rotor away to the outside.

[0004] US 1 101 1960 B2 discloses a motor with a wound rotor, wherein the rotating shaft is arranged in the vertical direction so that the lower coil section of the stator and the rotor is immersed in the cooling oil, and the lower coil section is partially immersed in the cooling oil. The cooling oil rises upward from the area below the rotor through the flow channel in the rotating shaft, and is sprayed into the area above the rotor due to 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 an axis extending in a longitudinal direction and a surrounding series of teeth and slots, wherein each tooth accommodates a longitudinal winding intended to produce a rotor pole, wherein each winding defines a protruding coil head at each longitudinal end of the rotor, wherein the rotor can be cooled by a coolant sprayed onto the coil head, wherein the rotor also includes at least one shaft ring for mechanically retaining the rotor winding, wherein the shaft ring is arranged at the longitudinal end of the rotor so that the shaft ring defines a central opening leading into the coil head, wherein the shaft ring has at least one outflow channel, which enables the coolant sprayed onto the coil head to flow out in the central opening.

[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, wherein the rotor core is firmly connected to the rotating shaft through a sheath. The rotor core is provided with a plurality of winding holes at a distance around the rotating shaft, and each winding hole passes through the two ends of the rotor core, which are 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 axial hole is formed in the rotating shaft, and the gap is constructed so that the gap is a first heat dissipation channel connected to the first axial hole, and the first heat dissipation channel is used for cooling liquid flowing into the rotating shaft. In this way, the cooling liquid introduced into the rotating shaft from the outside enters the first heat dissipation channel from the first axial hole under the action of centrifugal force to dissipate heat from the rotor coil wound around the rotor.

[0007] DE 10 2021 213 807 A1 discloses a rotor (1, 22) for an electric machine (30), comprising: a rotor shaft (3); a lamination stack (2) arranged on the rotor shaft (3), the lamination stack having a plurality of stacked electrical laminations; a first end plate (4) arranged at an axial side of the lamination stack (2), the first end plate having a radial protrusion (6) arranged along its circumference; a second end plate (5) arranged at an opposite axial side of the lamination stack (2), the second end plate having a radial protrusion (7) arranged along its circumference; a plurality of rotor windings (8) The invention relates to a rotor having a plurality of rotor windings, each of which is wound around a projection (6) of a first end plate (4) and an axially opposite projection (7) of a second end plate (5); a central cooling channel (10) extending in the rotor shaft (3) for supplying coolant; radial cooling channels (11, 12) extending from the central cooling channel (10) in the first end plate (4); and an axial cooling channel (13) extending from the radial cooling channel (12) in the lamination stack (2) along the outside of the lamination stack (2). In addition, an electric machine (30) and a vehicle (29) having such an electric machine (30) are described. The rotor has two pot-shaped end caps, which axially cover the end plates. At the ends of the lamination stack, the axial cooling channel has an axial outflow opening, through which the coolant can flow out and then radially out of the rotor through the recesses of the end caps.

[0008] DE 10 2021 213 810 A1 discloses a rotor (1, 18) for an electric machine (24), comprising: a rotor shaft (3); a lamination stack (2) formed of stacked electrical laminations arranged on the rotor shaft (3); a first end plate (4) arranged at an axial side of the lamination stack (2), the first end plate having a radial protrusion (5) arranged along its circumference; a second end plate (6) arranged at an opposite axial side of the lamination stack (2), the second end plate having a radial protrusion (7) arranged along its circumference; a plurality of rotor windings (8), the rotor windings being wound around the protrusions (5) of the first end plate (4) and the axially opposite protrusions (7) of the second end plate (6), respectively; a central cooling channel (10) extending in the rotor shaft (3) for supplying a coolant; and a peripheral cooling channel (11) extending in the first end plate (4), the cooling channel extending outward from the central cooling channel (10). The first end plate 4 is covered by a cover 16. The peripheral cooling channel opens into an outflow opening arranged at the circumference of the rotor, to which an axially extending section in the cover adjoins according to one embodiment. The axially extending section causes the coolant to be deflected in the axial direction before exiting the rotor and thereby cools the outer region of the cover and the rotor winding. Summary of the invention

[0009] One object may be to specify an improved rotor for an electric machine, in particular an external-field synchronous motor, which has improved cooling properties.

[0010] This object is achieved by a rotor for an electric machine according to claim 1. Advantageous embodiments are the subject matter of the dependent claims.

[0011] The rotor for an electric machine has: a hollow rotor shaft rotatable about a longitudinal axis, the rotor shaft having at least one radially extending opening; a rotor core having at least one axially extending cooling hole; a plurality of rotor coils distributed on the circumference of the rotor core; and an end ring arranged at an axial end of the rotor core. At least one cooling channel hydraulically connects the opening to the cooling hole so as to guide coolant from the hollow rotor shaft into the rotor core. At the axial end of the rotor core, a cover ring is arranged radially outside the end ring, the cover ring forming a coolant reservoir for collecting coolant coming out of the cooling hole. The rotor end winding of the rotor coil extending from the rotor core is arranged in the coolant reservoir formed by the cover ring.

[0012] The proposed rotor can advantageously utilize the centrifugal forces caused by the rotation of the rotor in order to convey coolant from the hollow rotor shaft through radially extending openings and via cooling channels into cooling holes, through which the coolant flows axially through the rotor core and emerges at the opposite end, where it is collected by a cover ring forming a coolant reservoir. It is also advantageous that the rotor end windings of the rotor coils protrude from the rotor core and are located in the coolant reservoir formed by the cover ring and are therefore effectively cooled.

[0013] The electric machine can be an externally excited synchronous motor having a wound rotor coil mounted in a rotor core. The rotor can also be a hybrid externally excited synchronous motor having a wound rotor coil and permanent magnets mounted on the rotor. The rotor coil winding can consist of a wire winding or a hairpin winding. The rotor core has axially and radially extending teeth, which are distributed on the circumference of the rotor core, and the end ring has legs corresponding to the teeth, wherein the rotor coil is arranged on the teeth and the legs, i.e., is wound around the teeth and the legs. The rotor coils on the teeth form the poles of the rotor. Unless otherwise specified, descriptions such as axially, radially and in the circumferential direction in principle relate to the longitudinal axis.

[0014] In order to form a coolant reservoir, the cover ring can respectively have a first section extending in the axial direction and a second section extending in the radial direction, wherein the first section is radially arranged outside the end ring at the axial end of the rotor core, and wherein the second section is arranged on the side of the end ring facing away from the rotor core in the axial direction and at least partially covers these end rings. The cover ring is implemented continuously in the circumferential direction. The first and second parts are connected, for example, by a curved central part. The cover ring can be made of one piece. The radial extension of the second part can correspond to the radial extension of the rotor coil. The second part has an opening, which is arranged inside the rotor coil in the radial direction, so that the cover ring is not closed. Therefore, the coolant advantageously fills the reservoir and is retained therein due to the rotational force, and cools the end winding. When the reservoir is filled, the coolant comes out through the radial inner end of the second part and is again thrown from the cover ring to the stator end winding due to the rotational force, thereby advantageously also cooling the stator end winding.

[0015] According to one embodiment, the cooling channel can be at least partially configured in the end ring. In particular, the cooling channel is configured as a groove in the contact surface of the end ring facing the rotor core.

[0016] According to another embodiment, the cooling channel is partially constructed in at least one fastening ring arranged on the rotor shaft. The fastening ring forms an axial support for the rotor core. In particular, the cooling channel is constructed as a groove in the contact surface of the fastening ring facing the rotor core. The contact surfaces of the end ring and the fastening ring are in contact with the end surface of the rotor core, wherein the fastening ring is connected to the rotor shaft and the end ring surrounds the fastening ring so that the radial inner section of the cooling channel is formed in the fastening ring and the radial outer section of the cooling channel is formed in the end ring. If the end ring, the fastening ring and the cover ring are mentioned in the singular, this should in principle be understood that the features apply to the two end rings, the fastening ring and the cover ring, respectively.

[0017] According to another embodiment, at least one outflow channel can be formed in the end ring to guide the coolant coming out of the cooling hole into the coolant reservoir formed by the cover ring. In particular, the outflow channel is formed as a groove in the radial outer surface of the end ring.

[0018] According to another embodiment, a pole shoe is arranged at each tooth, wherein the pole shoe forms the outside of the rotor, wherein the cooling hole is constructed in the tooth and / or the pole shoe. Each pole can be provided with at least one cooling channel. In the case where the first end ring is arranged at the first axial end of the rotor core and the second end ring is arranged at the second axial end of the rotor core, the cooling channel can be distributed between the first axial end and the second axial end, so that the coolant flows from the first axial end to the first part of the cooling hole and flows from the second axial end to the second part of the cooling hole. In this way, each tooth can have a cooling hole, which is fed with coolant alternately via the cooling channels at the first axial end and the second axial end in the circumferential direction. In this way, the flow direction of the coolant changes from each cooling hole to the corresponding adjacent cooling hole. Therefore, such an outflow channel is constructed in the leg of the first end ring, and the outflow channel is connected to one of the following cooling holes, and the cooling hole is fed with coolant via one of the cooling channels at the second axial end of the rotor core. Vice versa, such an outflow channel is constructed in the leg of the second end ring, which is connected to one of the cooling holes which is fed with coolant via one of the cooling channels at the first axial end of the rotor core. In the case of more than one cooling channel per pole, cooling channels and outflow channels can be formed at both axial ends of each pole.

[0019] According to another embodiment, a static nozzle extends into the hollow rotor shaft, wherein coolant is supplied to the rotor shaft via the static nozzle, which advantageously enables a low-pressure coolant supply. Compared to a rotating nozzle, the coolant flow in the static nozzle is not affected by the rotation speed of the rotor, which enables better control of the coolant flow to the rotor shaft. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The invention is described in more detail with reference to exemplary embodiments shown in the drawings.

[0021] in:

[0022] Figure 1 One embodiment of a rotor is shown in a perspective exploded view;

[0023] Figure 2 The cross-sectional view shows Figure 1 The rotor of the motor;

[0024] Figure 3 The perspective half-section view shows Figure 1 The rotor. DETAILED DESCRIPTION

[0025] exist Figure 1 An embodiment of a rotor 1 for an electric machine is shown in a perspective exploded view. Figure 2An electric machine having a rotor 1 is shown in a sectional view. Figure 3 The rotor 1 is shown in a perspective half-section view. Figure 1 , Figure 2 and Figure 3 The rotor 1 has a hollow rotor shaft 2 which is rotatable about a longitudinal axis L. The longitudinal axis L is only Figure 2 . In all figures, unless otherwise specified, descriptions such as axially, radially and in the circumferential direction refer in principle to the longitudinal axis L. The hollow rotor shaft 2 has a radially extending opening 3, which connects the cavity 22 to the surface of the rotor shaft 2. The rotor core 4 is fastened to the rotor shaft 2 in a rotationally fixed manner so that the rotor core rotates around the longitudinal axis L together with the rotor shaft 2. The rotor core 4 has an axially extending cooling hole 5, which extends from one axial end to the other axial end. Two end rings 6 are arranged at the axial ends of the rotor core 4. A plurality of rotor coils 11 are distributed on the circumference of the rotor core 4, wherein the rotor coils 11 are wound around the teeth 17 of the rotor core 4 and the legs 18 of the end rings 6. The teeth 17 extend axially and radially from the central part of the rotor core 4 and are evenly distributed on the circumference of the rotor core 4. The legs 18 of the end rings 6 have a shape that matches the teeth 17 accordingly. A pole shoe 19 is arranged at each tooth 17, wherein the pole shoe 19 at least partially forms the outer surface of the rotor 1. The remaining cavities between adjacent rotor coils 11 are filled with wedges 27, which also form part of the outer surface of the rotor 1. A cooling hole 5 is provided for each tooth 17, which can be formed in the transition area between the tooth 17 and the pole shoe 19. The rotor end winding 21 protrudes from the rotor core 4 at both axial ends.

[0026] The cooling channel 7 hydraulically connects the opening 3 to the cooling hole 5 in order to guide the coolant from the hollow rotor shaft 2 into the rotor core 4. The coolant flows in Figure 26, which is indicated by arrows P. At the axial end of the rotor core 4, a cover ring 8 is arranged radially outside the end ring 6, which forms a coolant reservoir for collecting the coolant coming out of the cooling channel 5. The cover ring 8 has a first section 9 extending in the axial direction and the circumferential direction and a second section 10 extending in the radial direction and the circumferential direction, wherein the first section 9 is arranged radially outside the end ring 6 at the axial end of the rotor core 4, and the second section 10 is arranged on the side of the end ring 6 facing away from the rotor core 4 in the axial direction and at least partially covers these end rings. The radial extension of the second section 10 corresponds to the radial extension of the rotor coil 11, wherein the rotor end winding 21 is advantageously immersed in the coolant collected in the cover ring 7. A cutout 26 is formed between the radial inner edge of the second section 10 and the end ring 6, through which the coolant can come out of the reservoir of the cover ring 8 when the coolant level exceeds the inner edge of the second section 10. Due to the rotational forces, the coolant level rises in the radial direction towards the longitudinal axis L. The coolant coming out of the reservoir of the cover ring 8 is flung from the rotor 2 in the direction of the stator end windings 24 of the stator 23 ( Figure 2 The coolant then collects due to gravity at the bottom of the housing 25 of the electric machine, from where it can be fed back into the cavity 22 of the hollow rotor shaft 2 , for example via a heat exchanger (not shown).

[0027] The cooling channel 7 is partially constructed in the end ring 6 and partially constructed in the fastening ring 15, which is arranged radially inside the end ring 6 on the rotor shaft 2. The cooling channel 7 is constructed as a groove in the contact surface 12 of the end ring 6 facing the rotor core 4 and in the contact surface 20 of the fastening ring 15 facing the rotor core 4. In addition, an outflow channel 14 is constructed in the end ring 6 to guide the coolant coming out of the cooling hole 5 into the coolant reservoir formed by the cover ring 8, wherein the outflow channel 14 is constructed as a groove in the radial outer surface 16 of the end ring 6. In the embodiment shown, the end ring 6 has a groove for the cooling channel 7 at one of each two legs 18, and a groove for the outflow channel 14 at the other leg 18. The legs 18 of the end ring 6 have the cooling channel 7 and the outflow channel 14 alternately in the circumferential direction. Therefore, the coolant flows of adjacent cooling holes 5 have opposite directions and advantageously form a counterflow.

[0028] Reference numerals list

[0029] 1 Rotor

[0030] 2 Hollow rotor shaft

[0031] 3 Opening

[0032] 4 Rotor core

[0033] 5 Cooling holes

[0034] 6 End rings

[0035] 7 Cooling channels

[0036] 8 Cover ring

[0037] 9 Part 1

[0038] 10 Part 2

[0039] 11. Rotor Coil

[0040] 12 Contact surface of end ring

[0041] 14 Exit Channel

[0042] 15 Fastening ring

[0043] 16 Radial outer surface of end ring

[0044] 17 teeth

[0045] 18 feet

[0046] 19 Pole Shoes

[0047] 20 Contact surface of the fastening ring

[0048] 21 Rotor end winding

[0049] 22 Cavity

[0050] 23 Stator

[0051] 24 Stator end winding

[0052] 25 Shell

[0053] 26 Incision

[0054] 27 Wedge

[0055] L Longitudinal axis

[0056] P Arrow

Claims

1. A rotor (1) for an electric motor, comprising: A hollow rotor shaft (2) rotatable about a longitudinal axis (L), the rotor shaft having at least one radially extending opening (3), A rotor core (4) having at least one axially extending cooling hole (5), a plurality of rotor coils (11) distributed on the circumference of the rotor core (4), an end ring (6) arranged at an axial end of the rotor core (4), in, At least one cooling channel (7) hydraulically connects the opening (3) to the cooling hole (5) in order to conduct coolant from the hollow rotor shaft (2) into the rotor core (4), A cover ring (8) is arranged radially outside the end ring (6) at the axial end of the rotor core (4), and the cover ring forms a coolant reservoir for collecting coolant coming out of the cooling hole (5), wherein the rotor end winding (21) of the rotor coil (11) extending from the rotor core (4) is arranged in the coolant reservoir formed by the cover ring (8).

2. The rotor according to claim 1, characterized in that The cover ring (8) has a first section (9) extending in the axial direction and a second section (10) extending in the radial direction, wherein the first section (9) is arranged radially outside the end ring (6) at the axial end of the rotor core (4), and wherein the second section (10) is arranged on the side of the end ring (6) facing away from the rotor core (4) in the axial direction and at least partially covers the end ring.

3. The rotor according to claim 2, characterized in that The radial extension of the second portion (10) corresponds to the radial extension of the rotor coil (11).

4. A rotor according to any one of the preceding claims, characterised in that The connecting channel (7) is at least partially formed in the end ring (6).

5. A rotor according to any one of the preceding claims, characterised in that 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. A rotor according to any one of the preceding claims, characterised in that The cooling channel (7) is partially formed in at least one fastening ring (15) which is arranged on the rotor shaft (2).

7. The rotor according to claim 6, characterized in that The cooling channel (7) is partially designed as a groove in a contact surface (20) of the fastening ring (15) facing the rotor core (4).

8. A rotor according to any one of the preceding claims, characterised in that At least one outflow channel (14) is formed in the end ring (6) in order to guide the coolant coming out of the cooling bore (5) into a coolant reservoir formed by the cover ring (8).

9. The rotor according to claim 8, characterized in that The outflow channel (14) is designed as a groove in the radial outer surface (16) of the end ring (6).

10. A rotor according to any one of the preceding claims, characterised in that The rotor core (4) has axially and radially extending teeth (17), which are distributed on the circumference of the rotor core (4), wherein the end ring (6) has legs (18) matching the shape of the teeth (17), and wherein the rotor coil (11) is arranged on the teeth (17) and the legs (18).

11. The rotor according to claim 10, characterized in that A pole piece (19) is arranged on each tooth (17), wherein the pole piece (19) forms an outer surface of the rotor (1), wherein the cooling channel (5) is formed in the tooth (17) and / or the pole piece (19).

12. A rotor according to any one of the preceding claims, characterised in that A first end ring (6) is arranged at a first axial end of the rotor core, and a second end ring (6) is arranged at a second axial end of the rotor core (4), wherein the cooling channels (7) are distributed on the first axial end and the second axial end.

13. The rotor according to claim 12, characterized in that A cooling channel (7) is provided for each tooth (17), alternately at a first axial end and a second axial end of the rotor core (4) in the circumferential direction.

14. A rotor according to any one of claims 12 or 13, characterized in that An outflow channel (14) is formed in a leg (18) of the first end ring (6), which is connected to a cooling hole (5) which is supplied with coolant via one of the cooling channels (7) at the second axial end of the rotor core (4).

15. A rotor according to any one of the preceding claims, characterised in that A static nozzle protrudes into the hollow rotor shaft (2), wherein the coolant is supplied to the rotor shaft (2) via the static nozzle.

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