STATOR FOR AN ELECTRIC MACHINE, PRODUCTION METHOD FOR SUCH A STATOR IN AN ELECTRIC MACHINE

Abstract

A stator for an electric machine may include a ring-shaped stator body defining a longitudinal centre axis, a plurality of electrically conductive stator windings fixed radially internally on the stator body with respect to the longitudinal centre axis, and a plurality of radial cooling apertures through which coolant is flowable. The stator windings may be encased by a plastic injection moulded body. The stator windings may project on both sides with respect to the longitudinal centre axis axially beyond the stator body such that the stator body is flanked axially on a first side by a ring-shaped first axial overhang and on a second side by a ring-shaped second axial overhang. The cooling apertures may penetrate at least one of the first axial overhang and the second axial overhang.

Claims

1. A stator for an electric machine, comprising: a ring-shaped stator body defining a longitudinal centre axis; a plurality of electrically conductive stator windings fixed radially internally on the stator body with respect to the longitudinal centre axis, the plurality of stator windings encased by a plastic injection moulded body, the plurality of stator windings projecting on both sides with respect to the longitudinal centre axis axially beyond the stator body such that the stator body is flanked axially on a first side by a ring-shaped first axial overhang and on a second side by a ring-shaped second axial overhang; and a plurality of radial cooling apertures through which coolant is flowable and which penetrate at least one of the first axial overhang and the second axial overhang.

2. The stator according to claim 1, wherein the plurality of radial cooling apertures penetrate the at least one of the first axial overhang and the second axial overhang with respect to the longitudinal centre axis at least one of radially and in a direction of a vertical axis extending perpendicularly to the longitudinal centre axis.

3. The stator according to claim 1, wherein the plurality of radial cooling apertures are distributed in a circumferential direction around the longitudinal centre axis at least one of uniformly and with a uniform circumferential distance with respect to one another in the circumferential direction over an entire circumference of the at least one of the first axial overhang and the second axial overhang.

4. The stator according to claim 1, wherein: the plurality of radial cooling apertures are arranged adjacent to one another in a circumferential direction around the longitudinal centre axis; and between two immediately adjacent radial cooling apertures of the plurality of radial cooling apertures in the circumferential direction, at least one of a predetermined and a predeterminable angle is spanned.

5. The stator according to claim 1, wherein the plurality of radial cooling apertures disposed in the at least one of the first axial overhang and the second axial overhang extend respectively between two adjacent stator windings of the plurality of stator windings, encased by the plastic injection moulded body, in a circumferential direction around the longitudinal centre axis.

6. The stator according to claim 1, wherein: the encased plurality of stator windings forming the first axial overhang are formed by a plurality of free wire ends, encased by the plastic injection moulded body, of a plurality of wire strands forming the plurality of stator windings; the plurality of free wire ends are combined into a plurality of contact groups each including a subset of the plurality of free wire ends; the subset of the plurality of free wire ends of a contact group of the plurality of contact groups are connected to one another in an electrically conductive manner and are electrically insulated by the encasing plastic injection moulded body; the plurality of contact groups are arranged spaced apart with respect to one another in a circumferential direction around the longitudinal centre axis such that a plurality of clear intermediate spaces are delimited by the plurality of contact groups; each clear intermediate space of the plurality of clear intermediate spaces is delimited between two adjacent contact groups of the plurality of contact groups in circumferential direction; and the plurality of clear intermediate spaces form the plurality of radial cooling apertures.

7. The stator according to claim 1, wherein the plurality of radial cooling apertures at least one of i) include and ii) are formed by a plurality of cooling ribs around which the coolant is flowable.

8. The stator according to claim 1, wherein the plurality of radial cooling apertures are radially open.

9. The stator according to claim 8, wherein at least one radial cooling aperture of the plurality of radial cooling apertures forms a cooling tunnel that is at least one of delimited and bordered all around by the plastic injection moulded body and that is radially open.

10. The stator according to claim 8, wherein at least one radial cooling aperture of the plurality of radial cooling apertures forms a cooling slit that is delimited by the plastic injection moulded body in a u-shaped manner, is open radially, and is open axially on a side facing away from the stator body.

11. The stator according to claim 1, further comprising a plurality of cooling tunnels and a plurality of cooling slits, wherein: the plurality of cooling tunnels are each formed by a respective radial cooling aperture of the plurality of radial cooling apertures, delimited by the plastic injection moulded body, and radially open; the plurality of cooling slits are each formed by a respective radial cooling aperture of the plurality of radial cooling apertures, delimited by the plastic injection moulded body in a u-shaped manner, open radially, and open axially on a side facing away from the stator body; the first axial overhang at least one of includes and forms a partial ring-shaped power connection portion and partial ring-shaped counter-portion arranged adjacent to the power connection portion in a circumferential direction around the longitudinal centre axis; the power connection portion includes three pin-shaped electric phase supply connections that are respectively aligned in a parallel manner with respect to the longitudinal centre axis, contacted electrically with the plurality of stator windings, and embodied encased by the plastic injection moulded body at least axially at a foot side with a formation of a foot base and with bare metal axially at a head side for an electric supply contacting; the plurality of cooling tunnels are associated with the power connection portion, are arranged axially between i) at least one of the three phase supply connections and the foot base and ii) the stator body, and penetrate the power connection portion radially; and the plurality of cooling slits are associated with the counter-portion, penetrate the counter-portion, and are radially and axially open.

12. The stator according to claim 1, further comprising a fluid path through which the coolant is flowable, wherein the fluid path extends at least in sections axially with respect to the longitudinal centre axis through the stator body and at least in sections radially with respect to the longitudinal centre axis in a radial manner through the plurality of radial cooling apertures.

13. A production method for the stator according to claim 1, comprising: providing the stator body; injecting a plastic insulator material, forming an insulating plastic injection moulded body onto a bare radial internal circumference side of the stator body; arranging the plurality of stator windings and a plurality of phase supply connections on the stator body; and injecting a plastic material forming the plastic injection moulded body onto the insulating plastic injection moulded body, the plurality of stator windings, and the plurality of phase supply connections to fix the plurality of stator windings and the plurality of phase supply connections on the stator body and, at the same time, at least one of form and introduce the plurality of radial cooling apertures.

14. An electric machine, comprising the stator according to claim 1, a machine housing, and a rotor, wherein the stator is arranged in the machine housing and cooperates with the rotor.

15. A stator for an electric machine, comprising: a ring-shaped stator body defining a longitudinal centre axis; a plurality of electrically conductive stator windings disposed radially inside of the stator body and connected to the stator body, the plurality of stator windings projecting axially beyond the stator body at each axial end such that the stator body is flanked axially on a first side by a ring-shaped first axial overhang and on a second side by a ring-shaped second axial overhang; a plastic injection moulded body at least partially encasing the plurality of electrically conductive stator windings; and a plurality of radial cooling apertures through which coolant is flowable, the plurality of radial cooling apertures penetrating at least one of the first axial overhang and the second axial overhang.

16. The stator according to claim 15, further comprising a plurality of cooling tunnels each of which is formed by a respective radial cooling aperture of the plurality of radial cooling apertures, delimited by the plastic injection moulded body, and radially open.

17. The stator according to claim 16, further comprising a plurality of cooling slits each of which is formed by a respective radial cooling aperture of the plurality of radial cooling apertures, delimited by the plastic injection moulded body in a u-shaped manner, open radially, and open axially on a side facing away from the stator body.

18. The stator according to claim 15, further comprising a plurality of cooling slits each of which is formed by a respective radial cooling aperture of the plurality of radial cooling apertures, delimited by the plastic injection moulded body in a u-shaped manner, open radially, and open axially on a side facing away from the stator body.

19. The stator according to claim 15, further comprising a fluid path through which the coolant is flowable, wherein the fluid path includes: at least one first section extending axially through the stator body; and at least one second section extending radially outward through at least one of the plurality of radial cooling apertures.

20. A stator for an electric machine, comprising: a ring-shaped stator body defining a longitudinal centre axis; a plurality of electrically conductive stator windings arranged on an inner circumferential surface of the stator body, the plurality of stator windings projecting axially beyond the stator body at each axial end such that the stator body is flanked axially on a first side by a ring-shaped first axial overhang and on a second side by a ring-shaped second axial overhang; a plastic injection moulded body at least partially encasing the plurality of stator windings and connecting the plurality of stator windings to the stator body; a plurality of radial cooling apertures through which coolant is flowable, the plurality of radial cooling apertures penetrating at least one of the first axial overhang and the second axial overhang; and a fluid path through which the coolant is flowable, the fluid path including i) at least one first section extending axially through the stator body and ii) at least one second section extending radially through at least one of the plurality of radial cooling apertures; wherein at least some of the plurality of radial cooling apertures are delimited by the plastic injection moulded body and are radially open.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0039] There are shown, respectively schematically

[0040] FIG. 1 a perspective view of a preferred example embodiment of a stator according to the invention,

[0041] FIG. 2 as FIG. 1 a perspective view of the preferred example embodiment of the stator according to the invention, however an axial overhang of the stator is illustrated in a partially transparent manner, so that stator windings can be seen, and finally

[0042] FIG. 3 in a top view, the stator of FIGS. 1 and 2 in the viewing direction of an arrow III drawn in FIG. 1.

DETAILED DESCRIPTION

[0043] FIGS. 1 to 3 show a preferred example embodiment of a stator, designated as a whole by reference number 1, which can be integrated in an electric machine and can cooperate there with a rotor in operation of the electric machine. Here, in particular the stator 1 heats up, so that the electric machine or respectively the stator 1 must be cooled, for which in the present case radial cooling apertures 8, able to be flowed through by coolant, are provided.

[0044] In FIGS. 1 and 2 perspective views of a preferred example embodiment of a stator 1 according to the invention are illustrated. In FIG. 2 an axial overhang 6 of the stator 1, which is explained further below, is illustrated in a partially transparent manner, so that its inner workings can be seen. FIG. 2 shows these inner workings again in an enlarged view, bordered by a frame of dashed lines.

[0045] With reference to FIGS. 1 and 2, it is to be explained that the stator 1 has a ring-shaped stator body 3 which defines a longitudinal centre axis 2, which is indicated here by a dot-and-dash line. An insulating plastic injection moulded body 22 of plastic insulator material is injected on a, by way of example bare, radially internally lying inner circumference side 23 of the stator body 3, viewed with respect to the longitudinal centre axis 2, which inner circumference side cannot be seen in FIG. 1, however is indicated in FIG. 2 at least in the enlarged view. On this insulating plastic injection moulded body 22, electrically conductive stator windings 5 or coils are arranged, which can be produced from individual electrically conductive wire strands or hairpin wires or by a plurality of solid wires or conductors, not illustrated here, which are bent in a u-shaped manner. The wire strands have respectively two free wire ends 12 and, at the opposite end, a bending portion. Within the mounting of the stator windings 5 (I-pins, U-pins or wave winding, essentially all type of hairpins) these wire strands are inserted or respectively pushed in with their free wire ends 12 ahead into the stator body 3, so that the free wire ends 12 project axially with respect to the longitudinal centre axis 2 on one side of the stator body 3 and the said bending portions of the wire strands on the other side of the stator body 3. The free wire ends 12 are furthermore soldered or welded to one another, so that the separate wire strands are connected in an electrically conductive manner and form cohesive stator windings 5. Preferably, all type of hairpin windings 5 comprises at least phase connection busbars (and star or delta connection busbars), where bulk of material would dramatically increase the thermal hotspots in those areas, hence implemented cooling apertures within the winding heads improves thermal performance (and thus also continuous power) for e.g. more than 30%.

[0046] In order to insulate the stator windings 5 electrically and to fix them permanently on the stator body 3, the stator windings 5 are injected around completely with an injection moulding compound of plastic material, designated in the hardened state as plastic injection moulded body 4, whereby they are completely encased by way of example and are permanently fixed on the stator body 3. Here, the wire ends 12, which are encased by the plastic injection moulded body 4, are grouped into a plurality of contact groups 13. Each of these contact groups 13 has several electrically connected wire ends 12, stacked on one another in a radially touching manner, which, as mentioned, are encased by the plastic injection moulded body 4. The contact groups 13 are, furthermore, spaced apart with respect to one another in a circumferential direction 9 around the longitudinal centre axis 2, so that a clear intermediate space 14 is delimited between two immediately adjacent contact groups 13 in circumferential direction 9. The stator body 3, the stator windings 5 and the plastic injection moulded body 4 thereby preferably form an integral structural unit.

[0047] The free wire ends 12 and bending portions of the wire strands protruding axially over the stator body 3 are also completely encased by the plastic injection moulded body 4, so that, as can be seen in FIGS. 1 and 2, it can be stated that the encased stator windings 5 form ring-shaped overhangs on both sides of the stator body 3. For simpler designation, these are designed below as first axial overhang 6 and second axial overhang 7.

[0048] In order to be able to realize a relatively good cooling of the stator 1 in operation of an electric machine which is equipped with a stator 1 according to the invention, the above-mentioned radial cooling apertures 8, which are able to be flowed through by coolant, are provided in the area of the overmolded busbars and/or first axial overhang 6 and/or second axial overhang 7, which in the present case penetrate the first axial overhang 6 radially with respect to the longitudinal centre axis 2 or respectively in the direction of a vertical axis 24, standing perpendicularly on the longitudinal centre axis 2, which is indicated in FIGS. 1 and 2 respectively by a dash double dotted line. The radial cooling apertures 8 are therefore radially open, so that coolant can flow from radially internally to radially externally, or vice versa. Basically, it is of course conceivable that alternatively or additionally the second axial overhang 7, which is oriented opposed to the first axial overhang 6 axially, is equipped with such radial cooling apertures 8.

[0049] In FIG. 1 to 3 it can be seen that the said radial cooling apertures 8 are distributed in a circumferential direction 9 around the longitudinal centre axis 2 uniformly and with a uniform circumferential distance 10 with respect to one another in circumferential direction 9 over the entire circumference 25 of the first axial overhang 6, wherein each radial cooling aperture 8 is formed by or delimited by one of the said intermediate spaces 14. Thereby, the radial cooling apertures 8 are oriented radially with respect to the longitudinal centre axis 2 and extend respectively between two stator windings 5, adjacent in a circumferential direction 9 around the longitudinal centre axis 2 and encased by the plastic injection moulded body 4, wherein between two radial cooling apertures 8 immediately adjacent in circumferential direction 9, by way of example an angle 11 of 7.5 is spanned. Thereby, in operation of an electric machine equipped with the stator 1, an effective cooling can be realized. Preferably, the said cooling apertures 8 are integrated in space between the welding are of the hairpins and busbars, where otherwise would be a lot of bulk plastic material with low thermal conductivity. Hence hot spots in this area would limit the performance of electric motor. By implementing the said cooling apertures 8 in this particular area the performance is improved by e.g. more than 30%.

[0050] Furthermore, thereby a fluid path 21 for coolant is created, which is indicated in FIGS. 1 and 3 by a dotted line. The fluid path 21 extends axially along the longitudinal centre axis 2 through the entire stator body 3 and then radially with respect to the longitudinal centre axis 2 radially through the radial cooling apertures 8 from radially internally through the first axial overhang 6 to radially externally, or vice versa. Preferably, the key is, that radial cooling apertures 8 enables the flow of the coolant from the inner side to the outer side of the axial overhang 6, 7. Hence interconnecting a first set of channels 26 with a second set of channels 27 and/or a third set of channels 28 being in serial connection. The stator 1 preferably comprises all three channels 26, 27, 28. However, for some simplified embodiments, the second set of channels 27 could be avoided for sake of reducing the complexity of the tool being used for overmolding. Preferably, the radial cooling apertures 8 are used to provide a passage between at least two set of channels 26, 27, 28 in serial connection.

[0051] With reference to FIG. 1 it is to be explained in addition that the first axial overhang 6 is divided into a partial ring-shaped power connection portion 17 and into a partial ring-shaped counter-portion 18, adjacent in this respect in circumferential direction 9. The power connection portion 17 has three pin-shaped electric phase supply connections 19, which are embodied respectively aligned in a parallel manner with respect to the longitudinal centre axis 2, contacted electrically with the stator windings 5, encased by the plastic injection moulded body 4 at least axially at the foot side with the formation of a foot base 20, with busbars within, and with bare metal for an electric supply contacting, not illustrated here, axially at the head side. It can be seen that several radial cooling apertures 8 are associated with the power connection portion 17, which are realized as so-called cooling tunnels 15. These cooling tunnels 15 are distinguished in that respectively in the circumferential direction 9 towards both sides they are delimited or bordered all around by the plastic injection moulded body 4 and with respect to the longitudinal centre axis 2 axially towards both sides by the plastic injection moulded body 4, and are only open in radial direction. These cooling tunnels 15 are arranged axially between the phase supply connections 19 or respectively the foot base 20 and the stator body 3, and penetrate the power connection portion 17 radially completely. Preferably, the radial cooling apertures are arranged in the space between overmolded busbars (i.e. phase connections and star connection busbars) and between welded area of hairpin wires within the axial winding head overhang 6, 7. Thereby, this portion can be cooled relatively well. For example, if there are no cooling apertures, the hotspots in this area limiting the complete performance of the stator 1 or an electric motor comprising the stator 1. Furthermore, also several radial cooling apertures 8 are associated with the counter-portion 18, however these are realized as cooling slits 16. These cooling slits 16 are distinguished in that they are axially open on a side facing away from the stator body 3, and furthermore on both sides in the circumferential direction 9 are delimited or bordered by the plastic injection moulded body 4 and axially with respect to the longitudinal centre axis 2 on a side facing the stator body 3 by the plastic injection moulded body 4, whereby a u-shaped plastic injection moulded delimitation is produced.