ELECTRIC MACHINE

Abstract

An electric machine may include a rotor and at least one cooling channel. The rotor may be rotatable about an axis defining an axial direction and include a stator having electrically conductive stator windings. A coolant may flow through the at least one cooling channel to the cool the stator windings. The stator may include teeth extending along the axial direction. The at least one cooling channel and the stator windings may be arranged in at least one intermediate space formed between two adjacent stator teeth. A plastic for transmitting heat from the stator windings to the at least one cooling channel may be arranged in the intermediate space.

Claims

1. An electric machine, comprising: a rotor rotatable about an axis of rotation which defines an axial direction and including a stator having electrically conductive stator windings; and at least one cooling channel through which a coolant can flow to cool the stator windings, wherein the stator has stator teeth which extend along the axial direction, are arranged at a distance from one another along a circumferential direction of the rotor, and carry the stator windings, wherein the at least one cooling channel and the stator windings are arranged in at least one intermediate space formed between two adjacent stator teeth in the circumferential direction, wherein a plastic for transmitting heat from the stator windings to the at least one cooling channel is arranged in the intermediate space.

2. The electric machine as claimed in claim 1, wherein the plastic is arranged on surface portions of the two adjacent stator teeth bounding the intermediate space.

3. The electric machine as claimed in claim 1, wherein the stator includes a stator body from which the stator teeth protrude radially inward, and wherein the plastic is arranged on a surface portion of the stator body which bounds the intermediate space radially on the outside.

4. The electric machine as claimed in claim 3, wherein the plastic forms an electrically insulating insulation layer which covers the surface portions of the two adjacent stator teeth.

5. The electric machine as claimed in claim 2, wherein the at least one cooling channel is arranged in a region of a radially inner end portion of the intermediate space.

6. The electric machine as claimed in claim 5, wherein the plastic forms at least one phase insulation which divides the intermediate space into a radially inner and a radially outer partial space, and wherein first conductor elements of the stator winding are arranged in the radially inner partial space and form a first phase winding, and second conductor elements of the stator winding are arranged in the radially outer partial space and form a second phase winding electrically insulated from the first phase winding.

7. The electric machine as claimed in claim 6, wherein the at least one phase insulation extends along the circumferential direction and connects two insulation layers arranged on the adjacent stator teeth.

8. The electric machine as claimed in claim 6, wherein the stator winding includes first conductor elements and second conductor elements, the first conductor elements are arranged in the radially inner partial space and are electrically connected to one another for the connection to a common first phase of an electric power source, and wherein the second conductor elements are arranged in the radially outer partial space and are electrically connected to one another for the connection to a common second phase of the electric power source.

9. The electric machine as claimed in claim 8, wherein the first and second conductor elements are surrounded by the plastic in a cross section perpendicular to the axial direction.

10. The electric machine as claimed in claim 9, wherein the first and second conductor elements are formed as winding bars made from an electrically conductive material.

11. The electric machine as claimed in claim 10, wherein the winding bars have a geometry of a right angle including two narrow sides and two wide sides in the cross section perpendicular to the axial direction.

12. The electric machine as claimed in claim 11, wherein the first conductor elements are electrically insulated from the second conductor elements via the phase insulation.

13. The electric machine as claimed in claim 8, wherein an additional cooling channel is arranged in a region of a radially outer end portion of the intermediate space.

14. The electric machine as claimed in claim 13, wherein the at least one cooling channel is arranged in the radially inner partial space formed via the phase insulation of plastic, and wherein the additional cooling channel is arranged in the radially outer partial space formed via the phase insulation of plastic.

15. The electric machine as claimed in claim 14, wherein a gap is formed between two first conductor elements or between one first and second conductor element, and wherein the plastic forms a gap filling with which the gap (63) is at least partially filled.

16. The electric machine as claimed in claim 1, wherein the plastic comprises a plastics compound in which the stator winding is embedded.

17. The electric machine as claimed in claim 1, wherein the intermediate space has geometry of a trapezoid or a rectangle in a cross section perpendicular to the axial direction.

18. The electric machine as claimed in claim 7, wherein the plastic provided on the surface portions of the stator teeth is formed by an electrically insulating first plastic material, and wherein the plastic forming the at least one phase insulation is formed by a second plastic material, and wherein the plastic forming a protective coating is formed by the second plastic material or by a third plastic material.

19. The electric machine as claimed in claim 18, wherein the second plastic material is configured to be electrically insulating or electrically conductive, and wherein the third plastic material is configured to be electrically insulating or electrically conductive.

20. The electric machine as claimed in claim 19, wherein the first, second, and third plastic materials are a thermoplastic or a thermosetting plastic.

21. The electric machine as claimed in claim 20, wherein the first, second, and third materials have identical heat have different heat conductivities.

22. The electric machine as claimed in claim 21, wherein the first, the second, and third plastic materials are identical materials.

23. The electric machine as claimed in claim 1, wherein the stator is windings are a part of a distributed winding.

24. The electric machine as claimed in claim 22, wherein the heat conductivity of the first, second, and third plastic materials are at least 0.5 W/m K.

25. The electric machine as claimed in claim 1, wherein the intermediate space is formed to be substantially free of gaps or air inclusions.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0052] In the drawings, in each case schematically:

[0053] FIG. 1 shows an example of an electric machine according to the invention in a longitudinal section along the axis of rotation of the rotor,

[0054] FIG. 2 shows the stator of the electric machine according to FIG. 1 in a cross section perpendicular to the axis of rotation of the rotor,

[0055] FIG. 3 shows a detailed illustration of the stator of FIG. 2 in the region of an intermediate space between two adjacent stator teeth in the circumferential direction,

[0056] FIG. 4 shows a development of the example according to FIG. 3 with an additional second cooling channel,

[0057] FIG. 5 shows a variant of the example according to FIG. 3, in which the stator windings are not formed by winding bars, but rather by winding wires formed in a plastics compound.

DETAILED DESCRIPTION

[0058] FIG. 1 illustrates an example of an electric machine 1 according to the invention in a sectional illustration. The electric machine 1 is dimensioned in such a manner that it can be used in a vehicle, preferably in a road vehicle.

[0059] The electric machine 1 comprises a rotor 3, illustrated only roughly schematically in FIG. 1, and a stator 2. For clarification, the stator 2 in FIG. 2 is illustrated in a separate illustration in a cross section perpendicular to the axis of rotation D along the intersecting line II-II from FIG. 1. According to FIG. 1, the rotor 3 has a rotor shaft 31 and can have a plurality of magnets, not illustrated specifically in FIG. 1, the magnetic polarizations of which change along the circumferential direction U. The rotor 3 is rotatable about an axis of rotation D, the position of which is defined by the center longitudinal axis M of the rotor shaft 31. The axis of rotation D defines an axial direction A which extends parallel to the axis of rotation D. A radial direction R is perpendicular to the axial direction A. A circumferential direction U rotates about the axis of rotation D.

[0060] As FIG. 1 reveals, the rotor 3 is arranged in the stator 2. The electric machine 1 shown here is therefore what is referred to as an internal rotor. However, a realization in the form of what is referred to as an external rotor, in which the rotor 3 is arranged outside the stator 2, is also conceivable. The rotor shaft 31 is mounted on the stator 2 rotatably about the axis of rotation D in a first shaft bearing 32a and, spaced apart axially therefrom, in a second shaft bearing 32b.

[0061] In addition, the stator 2 comprises in a known manner a plurality of stator windings 6 which can be electrically energized in order to generate a magnetic field. The rotor 3 is set into rotation by magnetic interaction of the magnetic field generated by the magnets of the rotor 3 with the magnetic field generated by the electrically conductive stator windings 6.

[0062] It is gathered from the cross section of FIG. 2 that the stator 2 can have an annular stator body 7, for example made of iron. In particular, the stator body 7 can be formed from a plurality of stator body plates (not shown) which are stacked one on another along the axial direction A and are adhesively bonded to one another. A plurality of stator teeth 8 are integrally formed radially on the inside of the stator body 7, the stator teeth extending along the axial direction A, protruding away radially inward from the stator body 7 and being spaced apart from one another along the circumferential direction U. Each stator tooth 8 carries a stator winding 6. The individual stator windings 6 together form a winding arrangement. Depending on the number of magnetic poles to be formed by the stator windings 6, the individual stator windings 6 of the entire winding arrangement can be electrically wired to one another in a suitable manner.

[0063] During the operation of the machine 1, the electrically energized stator windings 6 generate waste heat which has to be dissipated from the machine 1 in order to prevent overheating and associated damage or even destruction of the machine 1. The stator windings 6 are therefore cooled with the aid of a coolant K which is guided through the stator 2 and which, by transmission of heat, absorbs waste heat generated by the stator windings 6.

[0064] In order to guide the coolant K through the stator 2, the machine 1 comprises a coolant distributor chamber 4 into which a coolant K can be introduced via a coolant inlet 33. A coolant collector chamber 5 is arranged along the axial direction A at a distance from the coolant distributor chamber 4. The coolant distributor chamber 4 communicates fluidically with the coolant collector chamber 5 by means of a plurality of cooling channels 10, of which only a single one can be seen in the illustration of FIG. 1. The coolant distributor chamber 4 and the coolant collector chamber 5 can each have an annular geometry in a cross section, not shown in the figures, perpendicular to the axial direction A. A plurality of cooling channels 10 are arranged spaced apart from one another along the circumferential direction U and each extend along the axial direction A from the annular coolant distributor chamber 4 to the annular coolant collector chamber 5. The coolant K introduced into the coolant distributor chamber 4 via the coolant inlet 33 can therefore be distributed to the individual cooling channels 10. After flowing through the cooling channels 10 and absorbing heat from the stator windings 6, the coolant K is collected in the coolant collector chamber 5 and is discharged again from the machine 1 via a coolant outlet 34 provided on the stator 2.

[0065] As can be seen in the illustrations of FIGS. 1 and 2, the stator windings 6 and the cooling channels 10 are arranged in intermediate spaces 9 which are formed between in each case two adjacent stator teeth 8 in the circumferential direction U. Said intermediate spaces 9 are also known to a relevant person skilled in the art as “stator grooves” or “stator slots” which, like the stator teeth 8, extend along the axial direction A.

[0066] The illustration of FIG. 3 which shows an intermediate space 9 formed between two adjacent stator teeth 8 in the circumferential direction U—also referred to below as stator teeth 8a, 8b—in a detailed illustration, will be explained below.

[0067] As FIG. 3 shows, the intermediate space 9 has an opening 52 radially on the inside, i.e. is open radially on the inside. The intermediate space 9 can have the geometry of a trapezoid, in particular a rectangle, in the cross section perpendicular to the axial direction A. In the example of FIG. 3, the cooling channel 10 is arranged in the region of a radially inner end portion 56a of the intermediate space 9 or of the stator groove 54, i.e. in the region of the opening 52.

[0068] In order to improve the transmission of heat of the waste heat generated by the stator windings 6 to the coolant K flowing through the cooling channels 10, a heat-conductive plastic 11 is additionally arranged in the intermediate spaces 9 next to a cooling channel 10 and a stator winding 6 according to FIG. 3. Said plastic 11 is preferably introduced into the intermediate space 9 by injection molding.

[0069] As FIG. 3 reveals, the plastic 11 is arranged on surface portions 50b, 50c of two stator teeth 8 which are adjacent in the circumferential direction U and bound the intermediate space 9. Furthermore, the plastic 11 is arranged on a surface portion 50a of the stator body 7 that bounds the intermediate space 9 radially on the outside.

[0070] The plastic 11 arranged on the surface portions 50a, 50b, 50c is expediently an electrically insulating plastic. It is therefore ensured that both the cooling channel 10 arranged in the intermediate space 9 and the stator winding 6 arranged in the same intermediate space 9 are in each case electrically insulated from the stator teeth 8 by means of the plastic 11. Furthermore, the stator winding 6 is connected in a heat-conducting manner to the cooling channel 10 via the plastic 11 such that waste heat generated in or by the stator winding 6 can be transmitted via the plastic 11 to the coolant K flowing through the cooling channel 10 and can thus be removed from the stator winding 6.

[0071] The plastic 11 arranged on the three surface portions 50a, 50b, 50c forms an electrically insulating and heat-conducting insulation layer 51 which covers the surface portions 50a, 50b, 50c. For example, a layer thickness d of the insulation layer 51 can be between 0.2 mm and 0.5 mm.

[0072] According to FIG. 3, the plastic 11 can not only form the insulation layer 51 but—alternatively or additionally thereto—also a phase insulation 58 arranged in the intermediate space 9 or in the stator groove 54. The phase insulation 58 divides the intermediate space 9 into a radially inner and into a radially outer partial space 59a, 59b. First conductor elements 60a of the stator winding 6, which conductor elements form a first phase winding 70a, can thus be arranged in the radially inner partial space 59a. Similarly, second conductor elements 60b of the stator winding 6, which form a second phase winding 70b that is electrically insulated from the first phase winding 70a, can be arranged in the radially outer partial space 59b.

[0073] The phase insulation 58 expediently extends along the circumferential direction U. The phase insulation 58 preferably connects the two insulation layers 51 which are arranged on the adjacent stator teeth 8a, 8b and are made from the plastic 11 to each other.

[0074] It is seen that the plastic 11 not only forms the electric insulation layer 51, but also a first protective coating 75 which is arranged in the intermediate space 9 and bounds or surrounds the cooling channel 10. The provision of a tubular body or the like for the fluid-tight boundary of the cooling channel 10 in such a manner that no coolant K can emerge therefrom is thus superfluous.

[0075] In the example scenario of FIG. 3, the first protective coating 75 closes the opening 52 of the open intermediate space 9 or of the stator groove 54.

[0076] As FIG. 3 furthermore reveals, the stator winding 6 is not only electrically insulated from the cooling channel 10 via the plastic 11 forming the first protective coating 75, but is also connected in a heat-conducting manner to said cooling channel such that waste heat generated in or by the stator winding 6 can also be transmitted via the first protective coating 75 to the coolant K flowing through the cooling channel 10.

[0077] The first conductor elements 60a are arranged in the radially inner partial space 59a and the second conductor elements 60b in the radially outer partial space 59b.

[0078] The cooling channel 10 arranged in the region of the radially inner end portion 54a is arranged in the radially inner partial space 59a formed by means of the phase insulation 58 made from plastic 11.

[0079] As FIG. 3 reveals, the stator winding 6 arranged in the intermediate space 9 comprises first conductor elements 60a and second conductor elements 60b which are arranged next to one another along the radial direction R and at a distance from one another in the intermediate space 9. A gap 61 is formed between in each case two conductor elements 60a, 60b which are adjacent along the radial direction R, said gap preferably being able to extend along the circumferential direction U. The plastic 11 forms a gap filling 62 with which the gap 61 is completely filled.

[0080] In a similar manner, a gap 61 can be formed between the first and second conductor elements 60a, 60b and the electrical insulation arranged on the surface portions 50b, 50c of the stator teeth 8a, 8b. Also in this case, the plastic 11 forms a gap filling 62 by means of which the gap 61 is filled. It goes without saying that said gap 61 which is filled with the plastic 11 can also extend only in sections or can be present in the form of what is referred to as an air inclusion. It is also conceivable for there to be a plurality of gaps 61 or air inclusions which are filled with the gap filling 62 consisting of the plastic 11. All the first and second conductor elements 60a, 60b are thus surrounded by the electrically insulating and heat-conducting plastic 11 in the cross section perpendicular to the axial direction A, as illustrated in FIG. 3.

[0081] The first and second conductor elements 60a, 60b are in each case formed as first or second winding bars 65a, 65b from an electrically conductive and mechanically stiff material. In the cross section perpendicular to the axial direction A, the first and second winding bars 65a, 65b each have the geometry of a rectangle 66 with two narrow sides 67 and two wide sides 68.

[0082] According to FIG. 3, the first conductor elements 60a are arranged in the radially inner partial space 59a and are electrically connected to one another for the connection to a common first phase of an electrical power source. In a corresponding manner, the second conductor elements 60b are arranged in the radially outer partial space 59b and are electrically connected to one another for the connection to a common second phase of the electrical power source. Furthermore, first conductor elements 60a are electrically insulated from the second conductor elements 60b by means of the phase insulation 58.

[0083] FIG. 4 shows a development of the example of FIG. 3. The example of FIG. 4 differs from that of FIG. 3 in that an additional cooling channel 10 is arranged in the region of a radially outer end portion 56b of the intermediate space 9 or of the stator groove 54, said end portion running opposite the radially inner end portion 56a with respect to the radial direction.

[0084] In the example of FIG. 4, the plastic 11—in an analogous manner to the first protective coating 75 of the cooling channel 10—forms a second protective coating 75 which is arranged in the intermediate space 9 and which bounds and thus encases the additional cooling channel 10. As FIG. 4 reveals, the additional cooling channel 10 arranged in the radially outer end portion 56b is arranged in the radially outer partial space 59b of the intermediate space 9 or of the stator groove 54, said partial space being formed by means of the phase insulation 58 formed by the plastic 11. In an analogous manner to the first protective coating 75, the second protective coating 75 can also bound the second cooling channel 10 radially on the inside and radially on the outside in the cross section perpendicular to the axial direction A. Similarly, the second protective coating 75 can surround, and thereby bound, the second cooling channel 10 in the circumferential direction U of the stator 2 in the cross section perpendicular to the axial direction A.

[0085] FIG. 5 shows a variant of the example of FIG. 3. In the example of FIG. 5, the plastic forms a plastics compound in which the stator winding 6 is embedded. In the example of FIG. 5, the conductor elements 65 of the stator winding 6 are formed by winding wires 72 which are part of a distributed winding.

[0086] The plastic 11 provided on the surface portions 50a, 50b, 50c of the stator teeth 8a, 8b can be formed by a, preferably electrically insulating, first plastics material Kl. The plastic 11 forming the phase insulation 58 can be formed by a second plastics material K2. The plastic 11 forming the first and second protective coating 75 can be formed by the second plastics material K2 or by a third plastics material K3 which differs therefrom. The second plastics material K2 is expediently electrically insulating or electrically conductive. The third plastics material K3 can also either be electrically insulating or electrically conductive. The first plastics material K1 can be a thermoplastic or a thermosetting plastic. The same is true of the second and the third plastics material K2, K3. In each case two or even all three plastics materials K1, K2, K3 can have identical heat conductivities. Alternatively thereto, the first and, alternatively or additionally, the second and, alternatively or additionally, the third plastics material K1, K2, K3 can have different heat conductivities. The first and, alternatively or additionally, the second and, alternatively or additionally, the third plastics material K1, K2, K3 can be identical materials. Alternatively thereto, the first and, alternatively or additionally, the second and, alternatively or additionally, the third plastics material K1, K2, K3 can be different materials.

[0087] Likewise expediently, the heat conductivity of the plastic 11, in particular of the first and, alternatively or additionally, of the second and, alternatively or additionally, of the third plastics material K1, K2, K3 is at least 0.5 W/mK, preferably at least 1 W/mK.

[0088] Reference is again made below to FIG. 1. Furthermore, according to FIG. 1, the stator 2 with the stator body 7 and the stator teeth 8 is arranged axially between a first and a second end plate 25a, 25b.

[0089] As FIG. 1 shows, part of the coolant distributor chamber 4 is arranged in the first end plate 25a and part of the coolant collector chamber 5 is arranged in the second end plate 25b. The coolant distributor chamber 4 and the coolant collector chamber 5 are therefore each partially formed by a cavity 41a, 41b provided in the plastic 11. The first cavity 41a is complemented here by a cavity 42a, formed in the first end plate 25a, to form the coolant distributor chamber 4. In a corresponding manner, the second cavity 41b is complemented by a cavity 42b, formed in the second end plate 25b, to form the coolant collector chamber 5. In the variant embodiment explained above, the plastic 11 therefore at least partially bounds the coolant distributor chamber 4 and the coolant collector chamber 5.

[0090] The first end plate 25a can furthermore contain a coolant feed 35 which fluidically connects the coolant distributor chamber 4 to a coolant inlet 33 provided on the outside, in particular, as illustrated in FIG. 1, on the circumferential side, of the first end plate 25a. A second end plate 25b can correspondingly contain a coolant drain 36 which fluidically connects the coolant collector chamber 5 to a coolant outlet 34 provided on the outside, in particular, as illustrated in FIG. 1, on the circumferential side, of the end plate 25b. This permits an arrangement of the coolant distributor chamber 4 and of the coolant collector chamber 5 in each case radially on the outside of the first and the second end portion 14a, 14b, respectively, of the relevant stator winding 6 and also along the axial direction A as an extension of said end portions 14a, 14b. The end portions 14a, 14b of the stator windings 6 that are particularly loaded thermally during the operation of the machine 1 are also particularly effectively cooled by means of this measure.

[0091] According to FIG. 1, the plastic 11 can also be arranged on an outer circumferential side 30 of the stator body 7 and can therefore form a plastics coating 11.1 on the outercircumferential side 30. The stator body 7 of the stator 2 that is typically formed from electrically conductive stator plates can therefore be electrically insulated from the surroundings. The provision of a separate housing for receiving the stator body 7 can therefore be omitted.