Electric machine stator with internal cooling channel

Abstract

An electric machine stator has an axis and includes a stator core having a back iron portion, a plurality of teeth, and a plurality of slots, the teeth alternately extending radially inward from the back iron portion with respect to the axis. A plurality of internal cooling channels extend through the stator core parallel to the axis.

Description

Technical Field

[0001] The present application relates to a stator for an electric machine including a stator core having a back iron portion, a plurality of teeth, and a plurality of slots. Background Art

[0002] It is known that heat losses or copper losses occur in the operation of electric machines, such as generators or motors, for powering automotive vehicles. In order to avoid excessive heating which would lead to reduced efficiency or even damage or reduced life (in particular, insulation life of the corresponding electric machine), cooling devices are provided.

[0003] For example, US 6,954,010 B1 discloses a device, such as a motor, transformer, or inductor, utilizing a lamination stack, wherein a plurality of at least partially overlapping holes pass through the lamination stack and define a plurality of coolant passages. Manifold members located at opposite ends of the lamination stack are used to couple the coolant passages to a suitable coolant pump and radiator. A variety of hole designs are disclosed, including both holes of the same size forming straight passages and holes that differ in size, shape, and / or position to form non-axial passages.

[0004] US10,128,701B1 discloses an electric motor cooling system in which a plurality of axial coolant channels are integrated into the stator teeth. The axis of each of the axial coolant channels is parallel to the axis of the stator. A coolant manifold assembly integrated into the stator couples the coolant channels in the stator to a source of coolant.

[0005] US2021 / 351642 A1 discloses an electric motor cooling system that utilizes a stator-integrated axial coolant channel and a coolant manifold centrally located within the stator to efficiently remove heat. The coolant manifold includes: a mid-member that allows coolant to enter the axial coolant channel via a transition lamination, wherein the transition lamination includes a coolant distribution channel that directs the flow of coolant entering the manifold into the stator-integrated axial coolant channel.

[0006] US2022 / 0014062 A1 discloses an electric machine including a rotor and at least one cooling channel. The rotor is rotatable about an axis defining an axial direction and includes a stator having an electrically conductive stator winding. A coolant flows through the at least one cooling channel to cool the stator winding. The stator includes teeth extending in the axial direction. The cooling channel and the stator winding are arranged in an intermediate space formed between two adjacent stator teeth. Plastic for transferring heat from the stator winding to the cooling channel is arranged in the intermediate space.

[0007] US2022 / 0200382 A1 discloses an in-slot cooling system in a stator stack, comprising: two or more conductors of a hairpin winding provided in each slot of a first group of slots, each conductor extending axially across the stator stack and at a different predetermined radial distance from an air gap; and adjacent to each slot of the first group of slots at an end near the air gap, a bridge portion of a laminate material, which closes the slot and forms an axial cooling channel in the stator stack substantially adjacent to the conductor at the shortest predetermined distance from the air gap, allowing coolant to flow therein without leaking therefrom. Summary of the invention

[0008] An object may be to provide an electric machine stator with an improved flow path for a cooling fluid.

[0009] According to a first aspect, the object is achieved by an electric machine stator according to claim 1. The electric machine stator has an axis and comprises a stator core, the stator core having a back iron portion, a plurality of teeth and a plurality of slots, the teeth and the slots extending radially inwardly from the back iron portion alternately with each other relative to the axis. A plurality of internal cooling channels extend through the stator core parallel to the axis. At least one of the internal cooling channels is provided as an integrated cooling channel, the integrated cooling channel extending at least partially in one of the teeth and interconnecting with one of the slots.

[0010] Compared with the channel integrated only in the tooth or in the slot, it is an advantageous embodiment to interconnect the integrated cooling channel with the slot while extending at least partially in the adjacent tooth. The channel in the tooth has a strong limitation on the circumferential width due to the small circumferential extension of the tooth. The channel in the slot has a smaller contact surface to the stator core, which retains a significant amount of heat to be dissipated. The integrated cooling channel interconnected with the slot allows various positions and cross-sections, with, for example, a low aspect ratio of circumferential and radial extension than the channel extending only in the tooth. In the sense that the material of the stator core does not separate the integrated cooling channel from the slot but the integrated cooling channel extends beyond the slot (especially in the circumferential direction), when the blanks forming the integrated cooling channel and the slot are connected or partially overlapped but not completely overlapped, the integrated cooling channel is interconnected with the slot and extends at least partially in the tooth. For example, a slot and one or more integrated cooling channels are formed as a shared blank. Further, one or two integrated cooling channels can be provided for each pair of slots and teeth.

[0011] According to an embodiment, the integrated cooling channel is arranged in the transition zone between the back iron part and the slot, i.e. at the radially outward end of the slot. The integrated cooling channel may extend partly in one of the teeth and partly in the back iron part. In addition, certain internal cooling channels that are not integrated cooling channels may be arranged at the radially inward end of the slot. According to a further embodiment, the integrated cooling channel may be arranged to extend radially along one or both sides of the slot.

[0012] According to a further embodiment, the integrated cooling channel and optionally the internal cooling channel have an impermeable conduit separating the flow of the cooling fluid inside the conduit from the slot fluid. The impermeable conduit may be made of a plastic composite material. The plastic composite material of the impermeable conduit may extend into the slot, thereby closing the slot towards the inner diameter of the stator core, for example, if the slot is open towards the inner diameter and the internal cooling channel is arranged at the radially inward end of the slot.

[0013] According to a further embodiment, the motor stator further comprises: a winding having a plurality of conductors extending through the slots parallel to the axis; and an insulating material encapsulating the conductors, wherein the insulating material is formed integrally with the impermeable conduit.

[0014] According to a second aspect, the object is achieved by an electric machine stator according to claim 7. The electric machine stator has an axis and comprises a stator core, the stator core having a back iron portion, a plurality of teeth and a plurality of slots, the teeth and the slots extending radially inwardly from the back iron portion alternately relative to the axis. A plurality of internal cooling channels extend through the stator core parallel to the axis, and a plurality of external cooling channels extend radially outwardly from the internal cooling channels through the stator core, the external cooling channels being fluidly connected to the internal cooling channels via radially extending connecting channels, wherein the connecting channels are arranged at the distal axial end of the stator core. The internal cooling channels may be provided partially or completely as integrated cooling channels as described with respect to the first aspect.

[0015] Advantageously, the plurality of internal cooling channels, external cooling channels and connecting channels form a flow path for a cooling fluid that flows through the external cooling channels toward the distal axial end of the stator core, radially inwardly along the distal axial end of the stator core through the connecting channels, and into the internal cooling channels extending through the stator core parallel to the axis. A longer flow path through the stator core is provided by the proposed flow path.

[0016] According to an embodiment, the external cooling channel extends at the radially outward end of the back iron portion. The connecting channel can be arranged at both distal axial ends of the stator core, thereby advantageously allowing opposite flow directions in adjacent internal cooling channels. The external cooling channel can be formed as an open slot in the radially outer surface of the stator core. The external cooling channel can be closed by the outer shell of the stator.

[0017] According to a further embodiment, the outer cooling channel has an axially extending section and a circumferentially extending section, together forming a branching pattern of the outer cooling channel.

[0018] According to a further embodiment, the stator core is formed by a plurality of laminations stacked in an axial direction, wherein a first type of laminations has circumferentially distributed notches in the radially outer surface, the notches of the first type of laminations forming an axially extending section of the outer cooling channel when stacked, and wherein a second type of laminations has circumferentially distributed openings in the radially outer surface, the openings spanning a circumferential distance overlapping two adjacent notches of the first type of laminations, the openings of the second type of laminations forming a circumferentially extending section of the outer cooling channel when stacked. In a stack of laminations, for example, two laminations of the first type are followed by one lamination of the second type, each opening connecting two adjacent notches.

[0019] According to further embodiments, at least part of the internal cooling channel may be fully integrated into the slot and / or the internal cooling channel may be arranged at a radially inward end of the slot and / or two or more internal cooling channels may be provided per slot. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Exemplary embodiments are illustrated in the context of the accompanying drawings. In each of the drawings: Figure 1 An embodiment of a stator of an electric machine is shown in a perspective view; Figure 2 Shows Figure 1 Details; Figure 3 In different diagrams, Figure 2 Details; Figure 4 Shown in perspective Figure 1 The end cover of the stator core; Figure 5 In a further perspective view Figure 4 end cap; Figure 6a and 6b An electric machine having a motor stator is shown; Figure 7 Shows the formation Figure 1 a first type of laminations of a stator of an electric motor; Figure 8 Shows Figure 7 Details of the laminations; Fig. 9 Shows the formation Figure 1 a second type of laminations of a stator of an electric motor; Fig.10 Shows Fig. 9 Details of the laminations; Fig.11 A further embodiment of a motor stator is shown; Fig.12 Another embodiment of a motor stator is shown; Fig.13 Another embodiment of a motor stator is shown; Fig.14 Another embodiment of a motor stator is shown; Fig.15 A further embodiment of a stator for an electric machine is shown. DETAILED DESCRIPTION

[0021] Figure 1 An exemplary embodiment of a stator 1 of an electric machine is shown in perspective and partially in section. Figure 2 and Figure 3 Two different diagrams show Figure 1 Details of A. Describe together Figures 1 to 3 . The motor stator 1 has an axis L, which may also be referred to as a longitudinal axis L. It defines an axial direction. In the assembled motor including the stator 1, a rotor, not depicted, is arranged in the inner diameter 11 of the stator 1, rotatable about the axis L. The stator core 2 has a back iron portion 3, a plurality of teeth 4 and a plurality of slots 5, the teeth 4 and the slots 5 extending radially inwardly from the back iron portion 3 alternately relative to the axis L. The stator core 2 may be formed by a plurality of insulated ferromagnetic iron laminations 18 stacked in the axial direction. Those skilled in the art appreciate that the stator core 2 may alternatively be formed as a helically wound insulated ferromagnetic iron bar. The motor stator 1 further comprises: a winding 7, such as a distributed winding 7, whose winding head extends outwardly from an end cap 27 at the distal end of the stator 1 in the perspective view. The end cap 27 and the winding 7 are not depicted at the proximal end of the stator 1, wherein a cross-sectional view of a plurality of conductors 8 passing through the winding 7 is shown. The conductors 8 extending through the slots 5 parallel to the axis L are not depicted as individual wires, but may be inserted groups of wire coils or plug-in windings like a hairpin winding. Figure 2 Detail A in FIG. 1 shows the insulating material 10 surrounding the conductor 8 .

[0022] According to the first aspect, a plurality of internal cooling channels are provided as integrated cooling channels 6'. The integrated cooling channels 6' extend through the stator core 2 parallel to the axis L. Each of the integrated cooling channels 6' is interconnected with one of the slots 5, i.e. the integrated cooling channels 6' and the slots 5 are formed inside a common blank, such as Figure 3 As shown in the figure, Figure 3 Detail A is shown without the insulating material 10 of the conductor 8. The material of the stator core 2 does not separate the integrated cooling channel 6' from the slot 5. In the depicted embodiment, the integrated cooling channel 6' is arranged in the transition zone between the back iron part 3, the teeth 4 and the slot 5. The integrated cooling channel 6' extends partially in the teeth 4 and partially in the back iron part 3. The stator core 2 further has an external cooling channel 12 at the radially outward end of the back iron part 3. The external cooling channel 12 can be formed as an open slot in the radial outer surface of the stator core 2. The external cooling channel 12 can have an axially extending section 15 and a circumferentially extending section 16, which connects two parallel axially extending sections 15, thereby forming a channel pattern with multiple flow paths along the radially outward end of the back iron part 3. In the depicted embodiment, one internal cooling channel 6' is provided for each pair of slots 5 and teeth 6.

[0023] According to the second aspect, the motor stator has a plurality of internal cooling channels 6 extending through the stator core 2 in parallel with the axis L and a plurality of external cooling channels 12 extending radially outwards from the internal cooling channels 6 through the stator core 2, the external cooling channels 12 being fluidly connected to the internal cooling channels 6 via radially extending connecting channels 14. The connecting channels 14 are arranged at the distal axial ends of the stator core 2. According to the first aspect, the internal cooling channels 6 may be provided partially or completely as integrated cooling channels 6'. The end caps 27 are attached to both axial distal ends of the stator core 2, although at Figure 1 Only one of them is depicted in . Figure 4 and 5 The end cap 27 is shown in different perspective views. Figure 5 from the side facing the stator core 2 and in Figure 4 from the opposite side. The end cover 27 has the same slots 5 as the rotor core 2, but the integrated cooling channel 6' is provided only at every second slot 5, wherein the corresponding integrated cooling channel 6' is open to the axial end of the stator core 2. The corresponding other half of the integrated cooling channel 6' is fluidly connected to the external cooling channel 12 via the radially extending connecting channel 14 formed in the end cover 27. The same end cover 27 is arranged at both axial distal ends of the stator core 2, wherein the connecting channel 14 is rotated by one slot pitch. Therefore, the integrated cooling channel 6' is alternately open to the axial end of the stator core 2 and connected to the external cooling channel 12 via the connecting channel 14.

[0024] Figure 6a and6b The motor is shown in two different cross-sectional views described together. The housing 24 has a Figure 1 The motor stator 1 of the embodiment of the present invention. The rotor 29 is mounted on a shaft rotating about the axis L inside the motor stator 1. The open slots forming the external cooling channel 12 are closed by the inner surface 17 of the cylindrical part of the housing 24. A cooling fluid 30 such as oil can be pumped or delivered by gravity to the inlet 25, which leads to the external cooling channel 12. Figure 6a and 6b The two sections of are rotated relative to each other to show a cross-sectional view of two adjacent internal cooling channels 6, which can be provided as an integrated cooling channel 6'. The cooling fluid 30 flows through a channel pattern having a plurality of flow paths formed by the external cooling channels 12, toward both lateral ends of the stator core 2, and via the connecting channels 14 into the internal cooling channels 6, which can be provided as an integrated cooling channel 6', and is passed alternately by the cooled fluid 30 in one and the other axial direction, as in Figure 6a Pointing in one direction and in Figure 6b 2 , as illustrated by arrows B pointing in opposite directions in FIG. At the respective open ends, the cooling fluid 30 emerges from the inner or internal cooling channels 6, 6' and falls onto the winding heads of the windings 7, from where it reaches the bottom of the housing 24, where it is withdrawn from the housing 24 via at least one outlet 26 to be further conveyed, for example, to a heat exchanger not depicted. The plurality of inner cooling channels 6 or integrated cooling channels 6', the outer cooling channels 12 and the connecting channels 14 form a flow path for the cooling fluid 30 coming from the inlet 25, the cooling fluid 30 flows through the outer cooling channels 12 toward both distal axial ends of the stator core 2, radially inwardly along the distal axial ends of the stator core 2 through the connecting channels 14, and into the inner cooling channels 6 or integrated cooling channels 6' extending through the stator core 2 parallel to the axis L.

[0025] like Figure 1 The embodiment of the stator core 2 shown in FIG. Figures 7 to 10 The stacked laminations 18 are further described to form a Figure 7 A first type of laminations 20 forming the stator core 2 is shown, and Fig. 9A second type of lamination 22 is shown. The first type of lamination 20 has circumferentially distributed notches 21 in the radially outer surface, the notches 21 of the first type of lamination 20 forming the axially extending section 15 of the outer cooling channel 12 when stacked. The second type of lamination 22 has circumferentially distributed openings 23 in the radially outer surface, which span a circumferential distance overlapping two adjacent notches 21 of the first type of lamination 20, the openings 23 of the second type of lamination 22 forming the circumferentially extending section 16 of the outer cooling channel 12 when stacked. The circumferential distance B of the notches 21 may be, for example, 15°, while the circumferential distance D of the openings 23 may be 30°. Figure 8 Shows Figure 7 Detail A of a first type of lamination 20 , wherein the notch 21 may have a circumferential width C of 6°. Fig.10 Shows Fig. 9 Detail A of a lamination, in which the opening 23 may have a circumferential width E of 21°, spanning two adjacent notches 21, since E is equal to B plus C.

[0026] Figures 11 to 14 1 and 2 show further embodiments of a stator 1 for an electric machine in a cross-sectional view, wherein the axis L is orthogonal to the projection plane. Only three adjacent slots 5 are depicted in the cut-out. A person skilled in the art realizes that the stator core 2 may have, for example, Figure 1 One of the notches 21 forming the axially extending section 15 of the external cooling channel 12 is depicted, which is closed at the radially outer end by the housing 24 .

[0027] Fig.11 The embodiment of the embodiment has two integrated cooling channels 6' per slot 5 arranged in the transition zone between the back iron part 3 and the slot 5. Further, the integrated cooling channels 6' each have: an impermeable conduit 9, separating the flow of the cooling fluid inside the conduit 9 from the slot 5 fluid. The impermeable conduit 9 can be made of a plastic composite material. The conductor 8 inside the slot 5 can have an insulating material 10, such as insulating paper. The slot 5 of the embodiment has a hole 28 towards the inner diameter 11 of the stator core 2.

[0028] Fig.12 The embodiment of the present invention has one internal cooling channel 6 per slot 5, wherein the internal cooling channel 6 is completely received in the slot 5 and is thus not an integrated cooling channel according to the first aspect. The internal cooling channel 6 is arranged at the radially inward end of the slot 5. The internal cooling channel 6 has an impermeable conduit 9 and the conductor 8 inside the slot 5 has an insulating material 10. The plastic composite material of the impermeable conduit 9 extends into the hole 28, thereby closing the slot 5 towards the inner diameter 11 of the stator core 2.

[0029] Fig.13The embodiment of the present invention has one internal cooling channel 6 per slot 5 at the radially inward end of the slot 5 which is completely received therein. The internal cooling channel 6 which is not an integrated cooling channel according to the first aspect has an impermeable conduit 9 and the conductor 8 inside the slot 5 has an insulating material 10 which is formed integrally with the impermeable conduit 9. The plastic composite material of the impermeable conduit 9 extends into the hole 28, thereby closing the slot 5 towards the inner diameter 11 of the stator core 2.

[0030] Fig.14 The embodiment of the present invention has one internal cooling channel 6 completely received in each slot 5 at the radially inward end of the slot 5. The internal cooling channel 6 which is not an integrated cooling channel according to the first aspect has an impermeable conduit 9, and the conductor 8 inside the slot 5 has an insulating material 10, wherein the insulating material 10 is formed integrally with the impermeable conduit 9. The slots 5 are closed towards the inner diameter 11 of the stator core 2.

[0031] Fig.15 The embodiment of has one internal cooling channel 6 per slot 5 which extends completely in the adjacent tooth 4 and is thus not an integrated cooling channel according to the first aspect.

[0032] Combination Figure 1 and 11 All features described with respect to embodiments 1 to 15 may be separately transferred to any other embodiment.

[0033] Reference numerals 1 Motor stator 2 Stator core 3. Guard iron part 4 Teeth 5 slots 6 Internal cooling channels 6' integrated cooling channel 7 Winding 8 Conductor 9. Impermeable Catheter 10. Insulation Materials 11 inner diameter 12 External cooling channels 14 Connection Channels 15 Axis extension section 16 Circumferential extension section 17 Inner surface 18 stacking 20 First type of lamination 21 Gap 22 Second type of lamination 23 Opening 24 Housing 25 Import 26 Exit 27 End cap 28 holes 29 Rotor 30 Cooling fluid B Arrow L axis

Claims

1. A motor stator (1) having an axis (L) and comprising: A stator core (2) having a back iron portion (3), a plurality of teeth (4) and a plurality of slots (5), the teeth and the slots extending radially inwardly from the back iron portion in alternation with respect to the axis, a plurality of internal cooling channels (6) extending through the stator core (2) parallel to the axis (L), Features At least one of the internal cooling channels (6) is provided as an integrated cooling channel (6'), which extends at least partially in one of the teeth (4) and is interconnected with one of the grooves (5).

2. The motor stator according to claim 1, characterized in that: The at least one integrated cooling channel (6') is arranged in a transition zone between the back iron portion (3) and the slot (5).

3. The stator of an electric machine according to any one of the preceding claims, characterized in that The internal cooling channel (6) has an impermeable conduit (9) separating the flow of cooling fluid inside the conduit from the groove (5) fluid.

4. The motor stator according to claim 3, characterized in that: The impermeable conduit (9) is made of a plastic composite material.

5. The motor stator according to claim 4, characterized in that: The plastic composite material of the impermeable conduit (9) extends into the hole (28), the composite material in the hole closing the slot (5) towards the inner diameter (11) of the stator core (2).

6. The stator of an electric machine according to any one of the preceding claims 3 or 4, characterized in that: The motor stator further comprises a winding (7) having a plurality of conductors (8) extending through the slots (5) parallel to the axis (L), with an insulating material (10) encapsulating the conductors, wherein the insulating material is formed integrally with the impermeable conduit (9).

7. An electric machine stator (1), preferably an electric machine stator according to any one of the preceding claims, having an axis (L) and comprising: A stator core (2) having a back iron portion (3), a plurality of teeth (4) and a plurality of slots (5), the teeth and the slots extending alternately radially inwardly from the back iron portion relative to the axis (L), a plurality of internal cooling channels (6) extending through the stator core (2) parallel to the axis (L), a plurality of external cooling passages (12) extending radially outwardly from the internal cooling passages (6) through the stator core (2), wherein the outer cooling channel (12) is fluidically connected to the inner cooling channel (6) via a radially extending connecting channel (14), Features The connecting channel (14) is arranged at the distal axial end of the stator core (2).

8. The motor stator according to claim 7, characterized in that: The plurality of internal cooling channels (6), the external cooling channels (12) and the connecting channels (14) form a flow path for a cooling fluid (30), the cooling fluid flowing through the external cooling channels (12) toward the distal axial end of the stator core (2), radially inward along the distal axial end of the stator core (2) through the connecting channels (14), and into the internal cooling channels (6) extending through the stator core (2) parallel to the axis (L).

9. The stator of an electric machine according to any one of the preceding claims 7 or 8, characterized in that The external cooling passage (12) extends through a radially outward extent of the back iron portion (3).

10. The stator of an electric machine according to any one of the preceding claims 7 to 9, characterized in that The connecting channel (14) is arranged at both distal axial ends of the stator core (2).

11. The stator of an electric machine according to any one of the preceding claims 7 to 10, characterized in that The external cooling passage (12) is formed as an open slot in the radially outer surface of the stator core (2).

12. The stator of an electric machine according to any one of the preceding claims 7 to 11, characterized in that The outer cooling channel (12) has an axially extending section (15) and a circumferentially extending section (16), forming a branching pattern of the outer cooling channel.

13. The stator of an electric machine according to any one of the preceding claims 7 to 12, characterized in that The stator core is formed by a plurality of laminations (18) stacked in an axial direction, wherein laminations of a first type (20) have circumferentially distributed notches (21) in a radially outer surface, the notches of the laminations of the first type forming an axially extending section (15) of the outer cooling channel (12) when stacked, and The laminations of the second type (22) have circumferentially distributed openings (23) in the radial outer surface, the openings spanning a circumferential distance overlapping two adjacent notches (21) of the laminations of the first type (20), the openings (23) of the laminations of the second type forming a circumferentially extending section (16) of the external cooling channel (12) when stacked.

14. The stator of an electric machine according to any one of the preceding claims 7 to 13, characterized in that The internal cooling channel (6) is completely integrated into the groove (5).

15. The stator of an electric machine according to any one of the preceding claims 7 to 14, characterized in that The internal cooling channel (6) is arranged at the radially inward end of the slot (5).

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