Stator for an electric machine

Abstract

Stator for an electric machine, comprising a stator core, a stator winding attached to the stator core, a plurality of cooling channels extending through the stator core, and distributors for directing a fluid into the cooling channels.

Description

[0001] The application relates to a stator for an electrical machine, comprising a stator core, a stator winding attached to the stator core, a plurality of cooling channels extending through the stator core, and distributors for directing a fluid into the cooling channels.

[0002] It is known that heat or copper losses occur during the operation of electrical machines such as generators or electric motors used to power motor vehicles. Cooling devices are provided to prevent thermal overheating, which would lead to reduced efficiency or even damage or a reduction in the service life, particularly the insulation life, of the respective electrical machine.

[0003] CN 207475301 U discloses a cooling system for an electric motor in which a plurality of axial cooling channels are integrated into the stator teeth. The axis of each of the axial coolant channels runs parallel to the stator axis. A coolant distribution assembly integrated into the stator connects the coolant channels in the stator to the coolant source.

[0004] US 2021 / 351642 A1 discloses a cooling system for electric motors that utilizes axial coolant channels integrated into the stator and a coolant distributor located centrally within the stator for efficient heat dissipation. The coolant distributor includes a central element that allows coolant to enter the axial coolant channels via transition plates. The transition plates contain coolant distribution channels that direct the coolant flow entering the distributor into the axial coolant channels integrated into the stator.

[0005] CN 112886735 A discloses a motor stator assembly with a cooling flow channel.

[0006] The stator consists of a stator support and a stator lamination that are nested together, with the stator lamination being provided with a stator winding. The stator winding protrudes axially from the end portion of the stator lamination, and the stator support is provided with a fluid inlet opening that penetrates the peripheral wall of the stator support. A cooling groove is formed between the opposite peripheral walls of the stator support and the stator lamination. The cooling groove communicates with the fluid inlet opening and is open to both end portions of the stator lamination in the axial direction to form a fluid outlet. The cooling fluid flows into the cooling channel through the fluid inlet opening and out of the cooling channel through the fluid outlet, thereby cooling the stator lamination and the stator winding.

[0007] One object may be to provide a stator of an electrical machine with a more efficient and / or more uniform distribution of the cooling fluid.

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

[0009] A stator of an electric machine, comprising: a stator core, a stator winding attached to the stator core, a plurality of cooling channels extending through the stator core, and two distributors arranged at opposite axial ends of the stator core for directing a fluid into the cooling channels. Each of the two distributors has a distributor channel hydraulically connected to a portion of the cooling channels, wherein a flow cross-section of the distributor channel decreases along a circumferential main extension direction of the distributor channel.

[0010] The two distributors allow the cooling fluid to be advantageously directed from both axial ends of the stator to the cooling channels, rather than through a central inlet as is the case with prior art. The decreasing flow cross-sections of the distributor channels ensure a more even distribution of pressure and flow velocity of the cooling fluid.

[0011] The substantially cylindrical stator core may define a longitudinal axis. The terms axial, radial, or circumferential as used herein refer to the longitudinal axis of the stator core unless otherwise specified. The stator winding attached to the stator core may be a hairpin winding. The cooling channels may generally extend from one axial end of the stator core to the other. For example, the cooling channels may be straight and parallel to the longitudinal axis, or spiral around the longitudinal axis, or with decreasing or increasing radial distance from the longitudinal axis. The decreasing flow area of ​​the distribution channel is to be understood as a decrease in the cross-sectional area of ​​the distribution channel, where the cross-sectional area is defined in a plane to which a flow direction of the cooling fluid is perpendicular. The flow area of ​​the cooling channels may, for example, be round or square.The distributors can be made of plastic and are essentially annular. The distributor channel extends in the circumferential direction along the distributor. The flow cross-section of the distributor channel can be rectangular, for example, but other shapes are also conceivable. The reduction in the flow cross-section of the distributor channel can occur continuously or in a discrete number of stages. For example, the distributor channel can have a constant height in the radial direction and a decreasing width in the axial direction along the main extension direction. Those skilled in the art will know that, alternatively or additionally, the height of the distributor channel can decrease in the radial direction along the main extension direction running in the circumferential direction. The main extension direction in the circumferential direction corresponds to the flow direction of the cooling fluid.

[0012] The two manifolds may be identical. When features of the manifolds are referred to in the singular, this is to be understood as meaning that the feature is present in both manifolds. The two manifolds may also be referred to as a first manifold of the two manifolds having a first manifold channel hydraulically connected to a first portion of the cooling channels, and a second manifold of the two manifolds having a second manifold channel hydraulically connected to a second portion of the cooling channels, wherein a flow cross-section of the first manifold channel decreases along the circumferential main extension of the first manifold channel and a flow cross-section of the second manifold channel decreases along the circumferential main extension of the second manifold channel.

[0013] According to one embodiment, the distribution channel is annular, and the flow cross-section of the distribution channel decreases from a position of maximum flow cross-section in both circumferential directions. Advantageously, the fluid can be supplied to the distribution channel at the position of maximum flow cross-section. According to a further embodiment, a position of the minimum flow cross-section of the distribution channel lies at an angular distance of approximately 180° from the position of the maximum flow cross-section on a circumference of the distribution channel. Each distributor can have an inlet located at the position of the largest flow cross-section, but the inlet can also be formed by a part other than the distributor. The position of the maximum flow cross-section is the position along the main extension direction of the distribution channel with the largest cross-sectional area.The position of the minimum flow area is the position along the main extension direction of the distribution channel with the smallest cross-sectional area.

[0014] According to a further embodiment, the cooling channels are evenly distributed around the circumference of the stator core and hydraulically connected to one of the two distributors in an alternating pattern. If, for example, the cooling channels are alternately connected to one of the two distributors, the coolant in each cooling channel flows countercurrently to the adjacent cooling channel. Since heat is transferred to the coolant as it flows through the cooling channel, the temperature of the coolant is lower on the inlet side and rises along the cooling channel. The interleaved first and second portions of the cooling channels have the advantage of balancing the cooling effect and enabling a more even temperature distribution along the stator core. Various alternating patterns of the first and second portions of the cooling channels can be implemented; instead of ABABAB, for example, AABBAABB, etc., or AABABBABA-AB-A, etc.be realized, where A stands for the first part and B for the second part.

[0015] According to a further embodiment, each of the two distributors has outlet channels that are hydraulically connected to that portion of the cooling channels that is hydraulically connected to the distributor channel of the other of the two distributors, in order to receive the fluid from that portion of the cooling channels, wherein the outlet channels have at least one opening for discharging the fluid. The first distributor has first outlet channels that are hydraulically connected to the second portion of the cooling channels, and the second distributor has second outlet channels that are hydraulically connected to the first portion of the cooling channels. The outlet channels can have one or more openings for discharging the fluid. The fluid can advantageously be used to cool the winding heads of the stator winding, which protrude from the stator core at both axial ends. The openings can be directed towards the winding heads in order to distribute the fluid to the winding heads.The distributors can be arranged radially outside the winding heads and axially overlapping them. Two or three openings can be provided per outlet channel at different axial positions to advantageously cover the winding heads in the axial direction. Furthermore, at least one of the openings can be oriented radially perpendicular to the axial direction, and at least one further opening can be oriented radially and angled relative to the axial direction.

[0016] According to a further embodiment, the distribution channel is formed as a groove in the distributor, wherein the groove is closed by a housing enclosing the stator core. The housing has at least one inlet that is hydraulically connected to at least one of the distribution channels. Cooling fluid is fed into the cooling channels via the at least one inlet. A single inlet can be hydraulically connected to both distribution channels via two supply channels that extend axially along or through the stator core. Alternatively, the housing can also have two inlets, each hydraulically connected to one of the distribution channels. Advantageously, the two supply channels or the two inlets can be arranged at the position of the largest flow cross-section of the distribution channel. Furthermore, the stator can be mounted with the at least one inlet in a position of maximum potential energy, i.e. in the installed position on top of the stator.A cooling circuit may advantageously be passive, without external pressurization, wherein the cooling fluid is directed from a reservoir at a position of higher potential energy through the inlets to the distribution channels into the cooling channels, further through the outlet channels and the openings to the winding heads.

[0017] According to a further embodiment, the distributors have positioning means to maintain a relative position in the circumferential direction with respect to the stator core. The distributors can each have a gap in the circumferential direction, so that the distributors accordingly have a C-shape. The gap can be located at an angular distance of approximately 180° from the position of the maximum flow cross-section. The C-shape facilitates the installation of the distributors in the housing. A resilient element can be arranged between two surfaces facing the gap, pressing the two surfaces apart. In this way, the radial dimension of the distributors can be reduced during installation, while the resilient element increases the radial dimension of the distributor again after installation. The resilient element can be a rubber seal arranged in grooves in the surfaces facing the gap.

[0018] According to another embodiment, the stator core consists of a plurality of identical laminations, which is advantageous during stator core manufacturing, as only one type of lamination needs to be produced. Alternatively, the stator core can also be manufactured in one piece, i.e., not from laminations, but as a solid stator core. A one-piece stator core offers simplicity in manufacturing and assembly, but also has disadvantages such as increased eddy current losses, which lead to lower efficiency.

[0019] Exemplary embodiments are described with reference to the accompanying drawings, in which Fig. 1 shows an embodiment of a stator of an electrical machine in a perspective view; Fig. 2 the embodiment of Fig. 1 in a perspective sectional view; Fig. 3 an enlarged detail of the Fig. 2 in a sectional view; Fig. 4 a part of an oil path through the embodiment of Fig. 1 in a perspective sectional view; Fig. 5 two distributors of the embodiment of Fig. 1 in a side view; Fig. 6 an enlarged detail of the distributor in a perspective view.

[0020] In Fig. 1 shows an embodiment of a stator of an electrical machine 1 according to the invention in a perspective view. The stator 1 of the electrical machine consists of a stator core 2, to which a stator winding is attached. Of the stator winding, only the winding heads 11 are visible, which protrude from the stator core 2 at the axial ends 4. The essentially cylindrical stator core 2 defines a longitudinal axis L, which only Fig. 1. Terms such as “axial”, “radial” or “circumferential” used to describe a figure refer to the longitudinal axis L of the stator core 2 in Fig. 1, unless otherwise stated. A housing 12 according to the embodiment has two inlets 14 for a cooling fluid, wherein the housing 12 encloses the stator core 2 and the winding heads 11. At opposite axial ends 4 of the stator core 2, two distributors 3 are attached, of which Fig. 1, only one is visible. The distributors 3 are arranged radially outside the winding heads 11, axially overlapping them, and radially inside the housing 12. The distributors 3 each have a gap 16 in the circumferential direction, with a resilient element 17 arranged between two surfaces facing the gap 16, which urges the two surfaces apart. The distributors 3 can be installed by reducing their radial dimension when inserting them into the housing 12. The preload force of the resilient element 17 ensures that the distributors 3 are firmly seated in the housing 12.

[0021] In Fig. 2 is the embodiment of Fig. 1 in a longitudinal section along the longitudinal axis L in a perspective view. A plurality of cooling channels 6 extend through the stator core 2, and the two distributors 3 are attached to the opposite axial ends 4 of the stator core 2 to direct the cooling fluid into the cooling channels 6. The seals 18 seal the distributors against the housing 12. Each of the two distributors 3, which may also be referred to as first distributor 3' and second distributor 3", has a distributor channel 5 that is hydraulically connected to a portion of the cooling channels 6. The flow cross-section of the distributor channels 5 decreases along a circumferential main extension direction of the distributor channels 5. The cooling fluid is supplied to the distributor channel 5 at a position with a maximum flow cross-section 7.A position of minimum flow cross-section 8 of the distribution channel 5 is located at an angular distance of approximately 180° from the position of the maximum flow cross-section 7 on a circumference of the distribution channel 5.

[0022] The cooling channels 6 are evenly distributed around the circumference of the stator core 2 and hydraulically connected to one of the two distributors 3 according to an alternating pattern, for example ABABAB- etc., or AABBAABB- etc., or AAB-AB-BABAABA- etc., where A represents a first portion of the cooling channels 6 and B represents a second portion of the cooling channels 6. In the illustrated embodiment, the distributor channel 5 of the first distributor 3' is connected to one of the cooling channels 6 at the position of the smallest flow cross-section 8. The distributor channel 5 of the second distributor 3" is connected to one of the cooling channels 6 at the position of the largest flow cross-section 7, where the inlet 14 is located. The inlets 14 are offset from one another in the circumferential direction by the distance between two adjacent cooling channels 6, which also applies to the respective positions of the maximum and minimum flow cross-sections 7, 8.The stator core 2 can be mounted such that the inlets 14 are approximately in a position of maximum potential energy to enable passive conveyance of the cooling fluid by gravity. The stator core 2 can consist of a plurality of laminations, which are advantageously identical.

[0023] Each of the two distributors 3 has outlet channels 9. The outlet channels 9 of the first distributor 3' are hydraulically connected to that part of the cooling channels 6 which is hydraulically connected to the distributor channel 5 of the second distributor 3", and vice versa. The outlet channels 9 receive the cooling fluid from the respective cooling channels 6, which is discharged from the outlet channels 9 through at least one opening 10, which with reference to Fig. 3 is described.

[0024] In Fig. 3 is an enlarged detail of Fig. 2 in a sectional view without the housing 12. The openings 10 of the outlet channel 9 are directed towards the winding heads 11 protruding from the stator core 2 in order to distribute the cooling fluid to the winding heads 11. The openings 10 of each outlet channel 9 have different axial positions in order to advantageously cover the winding heads 11. In the embodiment shown, two openings 10 are provided in different axial positions per outlet channel 9, wherein one of the openings 10 is directed in the radial direction perpendicular to the axial direction and the other of the openings 10 is directed in the radial direction and obliquely to the axial direction. However, the two openings 10 can also be directed in the radial direction perpendicular to the axial direction. The distribution channel 5 is designed as a groove in the distributor 3, wherein the groove is closed by the housing 12 enclosing the stator core 2.The seal 18 is also located in a groove axially outside the distribution channel 5.

[0025] In Fig. 4 is an oil path through the embodiment of Fig. 1 is shown partially in a perspective sectional view. Shown are the walls or surfaces that define the oil path of the first distributor 3', which is fed via the inlet 14 and distributes the fluid into one of the portions of the cooling channels 6, forming one half of the cooling channels 6. The downstream end is formed by the outlet channels with openings 10 formed in the second distributor 3". The distributor channel 5 is substantially circular and is interrupted by the gap 16. The flow cross-section of the distributor channel 5 decreases from the inlet 14 or the position of the maximum flow cross-section 7 in both circumferential directions.

[0026] In Fig. 5 are the two distributors 3 of the embodiment of Fig. 1 in a side view. The flow cross-section of the distribution channels 5, which can be referred to as the first distribution channel 5' in the first distributor 3' and as the second distribution channel 5" in the second distributor 3", decreases from a position with maximum flow cross-section 7 in both circumferential directions to the position with minimum flow cross-section 8. The distribution channel 5 can have a constant height in the radial direction and a decreasing width in the axial direction along the main extension direction running in the circumferential direction. The distributors 3 have positioning means 15 for maintaining a relative circumferential position with respect to the stator core 2.

[0027] In Fig.Figure 6 shows an enlarged detail of the distributor 3 in a perspective view. An elastic element 17, for example in the form of a rubber seal, is arranged in the gap 16 between the two surfaces facing the gap 16. The elastic element 17 sits in respective grooves 19 of the surfaces. The openings 10 of the outlet channels are visible on an inner side of the distributor. Reference symbol 1 Stator of an electrical machine 2 Stator core 3 distributors 3' First distributor 3" Second distributor 4 Axial end 5 Distribution channel 5' First distribution channel 5" Second distribution channel 6 cooling channel 7 Position of maximum flow area 8 Position of minimum flow cross-section 9 Exhaust channel 10 Opening 11 winding heads 12 housings 14 inlets 15 positioning devices 16 gap 17 Elastic element 18 Seal 19 grooves L Longitudinal axis 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] CN 207475301

[0003] US 2021 / 351642 A1

[0004] CN 112886735 A

[0005]

Claims

[1] Stator (1) of an electrical machine, comprising: a stator core (2), a stator winding attached to the stator core, a plurality of cooling channels (6) extending through the stator core (2), and two distributors (3) arranged at opposite axial ends (4) of the stator core (2) to direct a fluid into the cooling channels (6), wherein each of the two distributors (3) has a distribution channel (5) which is hydraulically connected to a portion of the cooling channels (6), wherein a flow cross-section of the distribution channel decreases along a main extension direction of the distribution channel (5) running in the circumferential direction. [2] Stator according to claim 1, characterized bythat the distribution channel (5) is annular and the flow cross-section of the distribution channel decreases from a position of maximum flow cross-section (7) in both circumferential directions, wherein the fluid is supplied to the distribution channel (5) at the position of maximum flow cross-section (7). [3] Stator according to claim 2, characterized by that a position of the minimum flow cross-section (8) of the distribution channel (5) is at an angular distance of approximately 180° from the position of the maximum flow cross-section (7) on a circumference of the distribution channel. [4] Stator according to one of the preceding claims, characterized by that the cooling channels (6) are evenly distributed over the circumference of the stator core (2) and are hydraulically connected to one of the two distributors (3) according to an alternating pattern. [5] Stator according to one of the preceding claims, characterized bythat each of the two distributors (3) has outlet channels (9) which are hydraulically connected to that portion of the cooling channels (6) which are hydraulically connected to the distributor channel (5) of the other of the two distributors in order to receive the fluid from this portion of the cooling channels, wherein the outlet channels (9) have at least one opening (10) for discharging the fluid. [6] Stator according to one of the preceding claims, characterized by in that the distribution channel (5) is designed as a groove in the distributor (3), wherein the groove is closed by a housing (12) enclosing the stator core (2), wherein the housing (12) has at least one inlet (14) which is hydraulically connected to at least one of the distribution channels (5). [7] Stator according to claim 6, characterized by that the at least one inlet (14) is arranged in an installation position in a position of maximum potential energy. [8] Stator according to one of the preceding claims, characterized by that the distributors (3) have positioning means (15) to obtain a relative position in the circumferential direction with respect to the stator core (2). [9] Stator according to one of the preceding claims, characterized by that the distributors (3) each have a gap (16) in the circumferential direction, wherein an elastic element (17) is arranged between two surfaces facing the gap, which holds the two surfaces apart under prestress. [10] Stator according to one of the preceding claims, characterized by that the stator core (2) consists of a plurality of identical laminations.

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