Patent Publication Number: US-2020295618-A1

Title: Electrical machine, in particular for a vehicle

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation application of international patent application PCT/EP2018/081566, filed Nov. 16, 2018, designating the United States and claiming priority to German application DE 10 2017 221 836.3, filed Dec. 4, 2017, and the entire content of both applications is incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The disclosure relates to an electrical machine, in particular for a vehicle, as well as a vehicle including a machine of this type. 
     BACKGROUND 
     An electrical machine of this type can generally be an electric motor or a generator. The electrical machine can be formed as external rotor or as internal rotor. 
     A generic machine is known, for example from U.S. Pat. No. 5,214,325. It includes a housing, which surrounds an interior and which has a jacket, which revolves in a circumferential direction of the housing and radially limits the interior, a rear side wall, which axially limits the interior axially on one side, and a front side wall, which axially limits the interior axially on the other side. A stator of the machine is firmly connected to the jacket. A rotor of the machine is arranged in the stator, wherein a rotor shaft of the rotor is rotatably supported via a front shaft bearing on the front side wall. 
     The stator of a conventional electric machine typically includes stator windings, which are electrically energized during operation of the machine. Heat is thereby created, which has to be dissipated in order to avoid an overheating and damages to or even destruction of the stator associated therewith. For this purpose, it is known from conventional electric machines to equip the latter with a cooling device for cooling the stator—in particular said stator windings. A cooling device of this type includes one or several cooling channels, through which a coolant flows and which are arranged in the stator in the vicinity of the stator windings. Heat can be dissipated from the stator by heat transfer from the stator windings to the coolant. 
     It turns out to be disadvantageous thereby that an efficient heat transfer from the stator to the coolant, which flows through the respective cooling duct, is associated with significant structural effort. However, this has a disadvantageous impact on the production costs of the electrical machine. 
     SUMMARY 
     It is thus an object of the present disclosure to provide an improved electrical machine, in the case of which this disadvantage is largely or even completely eliminated. An improved electrical machine includes an improved cooling of the stator windings of the stator with simultaneously low production costs. 
     This object is achieved by an electrical machine, in particular for a vehicle, and a vehicle, in particular a motor vehicle, including at least one electrical machine. 
     It is a general idea of the disclosure to embed the stator windings of an electrical machine in an electrically insulating plastic, which is formed by two different plastic masses of different thermal conductivity, to cool the stator winding. 
     The plastic can thus act as heat-transferring medium to transfer heat from the stator windings to the coolant, which flows through a cooling duct, on the one hand and as electrical insulator for the stator windings on the other hand. In particular a particularly good heat transfer between the stator windings and the coolant, which is guided through the cooling duct, is established in this way. By using an electrically insulating plastic, it is furthermore ensured that the windings, which are to be cooled, are not electrically short-circuited in an unwanted manner. 
     The use of two plastic masses made of plastic materials with different thermal conductivity allows resorting to an expensive plastic material including high thermal conductivity in areas, in which a particularly high thermal conductivity is required for the heat dissipation. In contrast, a plastic—which can typically be acquired more cost-efficiently—can be resorted to in areas, in which such a high thermal conductivity is not required. As a result, this course of action leads to significant cost advantages in the production of the electrical machine 
     The direct thermal coupling of the cooling duct including the coolant to the stator windings, which are to be cooled, with the help of the embedding of the stator winding(s) in an electrically insulating plastic leads to a particularly effective cooling of the stator windings. In a high load operation of the electrical machine, it can thus also be ensured that the generated waste heat can be dissipated from the stator. Damages to or even destruction of the electrical machine by overheating of the stator can thus be avoided. 
     The production of the electrically insulating plastic can typically take place with injection molding, in the case of which the stator windings, which are to be cooled, as well as optionally also the cooling duct, are extrusion-coated with the plastic to form the two plastic masses. The embedding of the stator winding in the plastic masses is thus very simple, even though two different plastic materials are used. Cost advantages also result from this in the production of the electrical machine according to an aspect of the disclosure. A further advantage of the solution described here is that the second plastic mass can act as additional electrical insulation between the stator windings and the stator body. In the event that—due to production—not all stator windings can be embedded completely in the first plastic mass, the second plastic mass prevents a possible electrical short-circuit with the electrically conductive material of the stator body in any case. 
     An electrical machine according to an aspect of the disclosure, in particular for a vehicle, includes a rotor, which can be rotated about an axis of rotation, which, in turn, defines an axial direction of the electrical machine. The machine furthermore includes a stator, which has stator windings. The stator has stator teeth, which extend along the axial direction and which are arranged spaced apart from one another along a circumferential direction and which bear the stator windings. The machine furthermore includes a coolant distribution chamber and a coolant collecting chamber, which is arranged axially at a distance thereto. The coolant distribution chamber communicates fluidically with the coolant collecting chamber with at least one cooling duct, through which a coolant can flow, to cool the stator windings. At least one stator winding is embedded in an electrically insulating plastic for thermal coupling. The electrically insulating plastic is thereby arranged together with the at least one stator winding in at least one intermediate space, which is formed between two stator teeth, which are adjacent in the circumferential direction. According to an aspect of the disclosure, the electrically insulating plastic is formed by a first plastic mass made of a first plastic material and by a second plastic mass made of a second plastic material, the thermal conductivity of which is greater than the thermal conductivity of the first plastic material. 
     According to an aspect of the disclosure, the at least one stator winding has two axial end portions, on which an additional electrically insulating insulation is arranged. Even though the electrically conductive stator windings are usually already surrounded with an electrical insulation so as to prevent that electrical short-circuits are generated in response to contact of individual winding portions with one another, it cannot be ensured, however, that, after manufacture and assembly of the stator windings, all of these stator windings are equipped throughout with an insulation of this type. According to an aspect of the disclosure, it is thus ensured with a redundant, additional electrically insulating insulation that the axial end portions limit neither the coolant distribution chamber nor the coolant collecting chamber directly. An unwanted electrical short-circuit of the coolant, which is present in the coolant distribution chamber or in the coolant collecting chamber, respectively, with the electrically conductive stator windings can be prevented in this way. 
     According to an exemplary embodiment, the second plastic mass limits neither the coolant distribution chamber nor the coolant collecting chamber directly. 
     According to another exemplary embodiment, the thermal conductivity of the first plastic material is greater than the thermal conductivity of the second plastic material. 
     As an alternative, the thermal conductivity of the first plastic material is smaller than the thermal conductivity of the second plastic material according to another exemplary embodiment. 
     As an alternative, the thermal conductivity of the first plastic material is equal to the thermal conductivity of the second plastic material according to another exemplary embodiment. 
     In the case of an exemplary embodiment, at least one stator winding is embedded in the first plastic mass made of the first plastic material in at least one intermediate space. The first plastic mass together with the stator winding embedded therein is furthermore embedded in the second plastic mass made of the second plastic material or is arranged in the second plastic mass or is at least partially or completely surrounded by it. This measure ensures a particularly good heat transfer between the stator windings and the cooling duct. During the production of the plastic masses, said intermediate space between the stator teeth can furthermore be used in the manner of a casting mold, into which the two plastic masses are injected. This simplifies the production of the plastic masses, because the provision of a separate casting mold can be forgone. 
     The first and second plastic mass is particularly typically arranged in at least two intermediate spaces, typically in all intermediate spaces. 
     In the case of an exemplary embodiment, the at least one stator winding, typically all stator windings, including the respective two axial end portions thereof, is/are fixed to at least one stator tooth with the first plastic mass. The axial end portions can also be held on the stator body in a durably stable manner. 
     The thermal conductivity of thermosetting plastics as well as of thermoplastics can be set by the selection of the material composition. The thermal conductivity of a thermoplastic can thus be equal to or greater than the thermal conductivity of a thermosetting plastic and vice versa. A use of thermoplastics has various advantages as compared to the use of thermosetting plastics. For example, thermoplastics can be recycled better as a result of the reversible shaping process used in response to the processing thereof or have a lower brittleness and improved dampening properties as compared to thermosetting plastics, respectively. Due to the fact, however, that the acquisition of thermoplastics is usually more expensive than of thermosetting plastics, it is advisable to selectively use thermoplastics for cost reasons. 
     According to an exemplary embodiment, the first and/or the second plastic mass includes a thermoplastic or is a thermoplastic, in order to utilize the above-mentioned advantages. 
     A further exemplary embodiment provides that the first and/or the second plastic mass includes a thermosetting plastic or is a thermosetting plastic, whereby the above-mentioned cost advantages can be utilized. 
     The first plastic material advantageously includes a thermosetting plastic or is a thermosetting plastic. In the alternative or in addition, the second plastic material can include a thermoplastic or is a thermoplastic. The use of a thermosetting plastic including thermal conductivity, which is set to be reduced in those areas, which are to be considered to be less critical with regard to heat transfer, is associated with reduced production costs. 
     In the case of a further exemplary embodiment, at least one cooling duct is arranged in the plastic mass. This measure ensures a particularly effective heat transfer between the stator windings and the cooling duct, because the cooling duct arranged in the intermediate space is located in the immediate vicinity of the stator windings, which are to be cooled. 
     In the case of a further exemplary embodiment, the at least one cooling duct is formed by at least one aperture, typically by several apertures, which is/are provided in the electrically insulating plastic, typically in the second plastic mass, and through which the coolant can flow. This variation can be realized in a technically particularly simple manner and is thus particularly cost-efficient. 
     The second plastic mass particularly typically surrounds or covers at least one aperture, typically all apertures, completely in a cross-section perpendicular to the axial direction. The aperture forming the cooling duct can be thermally coupled to the stator windings particularly well in this way. 
     At least one aperture can advantageously have the geometry of a rectangle including two broad sides and two narrow sides in a cross section perpendicular to the axial direction. In this way, the aperture is given the advantageous geometry of a flat tube, which, in turn, allows for an installation space-saving arrangement of the cooling duct in the immediate vicinity of the stator winding(s) to be cooled. 
     The at least one cooling duct is typically covered or surrounded by the second plastic mass. A particularly good thermal connection of the coolant, which flows through the cooling duct, with the stator winding is ensured in this way. 
     According to an exemplary embodiment, the coolant distribution chamber and/or the coolant collecting chamber are at least partially arranged in the electrically insulating plastic, typically in the first plastic mass, for thermal coupling to the stator windings. This provides for a particularly good heat transfer between the coolant distribution chamber or coolant collecting chamber, respectively, and the stator windings, such that the coolant distribution chamber or the coolant collecting chamber, respectively, can also be used for direct absorption of heat from the stator windings. 
     The surface portions of the stator, which limit the intermediate space, are advantageously coated with the first plastic mass. This measure improves the electrical insulation of the stator windings against the stator body. 
     Together, the first and the second plastic mass particularly typically fill the intermediate space completely. The formation of unwanted intermediate spaces, for instance in the manner of air gaps, which would lead to an unwanted reduction of the heat transfer, is prevented in this way. 
     In the case of another exemplary embodiment, the first and the second plastic mass are each an injection molding mass made of the first or second plastic material, respectively. The use of an injection molding process simplifies and accelerates the creation of the plastic masses. This leads to cost advantages in the production of the electrical machine. 
     According to a further aspect of the disclosure, the stator includes a, typically ring-shaped, stator body, from which the stator teeth can protrude. In the case of this further development, the first plastic mass is arranged at least on an outer circumferential side of the stator body. The stator can be insulated electrically against the external environment of the machine in this way. The provision of a separate housing for receiving the stator body can thus be forgone. A coating of at least one or of both front sides of the stator body with the first plastic mass is also conceivable in an optional variation. In a further variation, the plastic mass can cover the stator body, typically completely. Particularly typically, the first plastic mass forms an outer coating on the outer circumferential side. The stator body is electrically insulated on the outer circumferential side in this way. 
     The first plastic mass advantageously protrudes axially from the respective intermediate space, typically on both sides. The first plastic mass can thus also be used for partially limiting the coolant distribution chamber or the coolant collecting chamber. A removal of the part of the first plastic mass, which protrudes from the intermediate space, which is required as part of the production of the machine, can in particular be forgone, which is associated with cost advantages in the production of the machine. 
     According to a further aspect of the disclosure, the first plastic mass at least partially limits the coolant distribution chamber and/or the coolant collecting chamber. The provision of a separate limitation for the coolant distribution chamber or the coolant collecting chamber, for instance in the form of a housing, can thus be forgone. 
     At least one cooling duct as well as the first and second plastic mass can advantageously be provided in at least one, typically in each intermediate space, between two stator teeth, which are each adjacent in the circumferential direction. It is ensured in this way that waste heat, which is operatively generated, can be dissipated from all available stator windings. 
     According to another exemplary embodiment, the at least one cooling duct is arranged radially outside or radially within the respective stator winding in the intermediate space. This provides an installation space-efficient arrangement of the cooling duct close to the stator windings, which are to be cooled, so that the electrical machine requires only little installation space for cooling the stator windings. 
     In the alternative, at least one cooling duct can also be arranged radially outside and at least one further cooling duct can additionally be arranged radially within the respective stator winding in the intermediate space. In the case of this variation, at least two cooling ducts are thus provided for cooling the stator winding, whereby an increased cooling capacity is effected. 
     According to a further aspect of the disclosure, the at least one cooling duct is formed as a tube body, which surrounds a tube body interior. In the case of this variation, at least one separating element, which divides the tube body interior into at least two partial cooling ducts, which are fluidically separated from one another, is integrally molded on the tube body. The tube body can be reinforced with said separating elements, such that the mechanical strength thereof increases. The tube body can be formed by an electrically conductive material, in particular a metal or by an electrically insulating material, in particular a plastic. 
     According to a further aspect of the disclosure, the tube body is formed as a flat tube, which extends along the axial direction and has two broad sides and two narrow sides in a cross section perpendicular to the axial direction. At least one broad side of the flat tube advantageously extends essentially perpendicular to the radial direction in the cross-section perpendicular to the axial direction. A length of the two broad sides can thereby typically be at least four times, typically at least ten times, a length of the two narrow sides. 
     According to a further exemplary embodiment, at least one cooling duct is arranged in the stator body and is formed by at least one aperture, through which the coolant can flow. Said aperture can be realized in the form of a through bore, which is introduced into the stator body with a suitable boring tool as part of the production of the electrical machine. The provision of a separate tube body or the like to limit the cooling duct is foregone in the case of this variation. This is associated with reduced production costs. Particularly typically, several apertures of this type are provided. 
     The at least one cooling duct is advantageously arranged in the stator body in the area between two adjacent stator teeth with respect to the circumferential direction. This makes it possible to arrange the cooling duct close to the stator windings, which are to be cooled, which improves the heat transfer from the stator windings to the cooling duct. 
     In the case of a further exemplary embodiment, the aperture forming the cooling duct is formed to be open towards the intermediate space. Said aperture is thereby closed in a fluid-tight manner by the electrically insulating plastic arranged in the intermediate space, typically by the second plastic mass. In the case of this variation, the apertures can be created particularly easily, which is associated with cost advantages in the production. 
     According to a further exemplary embodiment, the coolant distribution chamber and/or the coolant collecting chamber are formed by a cavity, which is present at least partially, typically completely, in the first plastic mass. The provision of a separate casing or of a housing, respectively, for limiting the coolant distributor or coolant collecting chamber, respectively, can thus be forgone. This exemplary embodiment is also associated with significant cost advantages. 
     According to an exemplary embodiment, the electrically insulating insulation is formed at least partially, typically completely, by an insulating varnish. An insulating varnish of this type can be applied to the stator windings with spraying as part of the production of the stator. In the alternative, it is also conceivable, however, to realize the additional insulation with the electrically insulating plastic, typically with a third plastic mass, which is part of the electrically insulating plastic. This variation can be produced particularly easily and is thus cost-efficient. 
     The disclosure further relates to a vehicle, in particular a motor vehicle, including an above-introduced electrical machine. The above-described advantages of the electrical machine can thus also be transferred to the vehicle according to an aspect of the disclosure. 
     Further important features and advantages of the disclosure follow from the claims, from the drawings, and from the corresponding figure description on the basis of the drawings. 
     It goes without saying that the above-mentioned features and the features, which will be described below, cannot only be used in the respective specified combination, but also in other combinations or alone, without leaving the scope of the present disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure will now be described with reference to the drawings wherein: 
         FIG. 1  shows an electrical machine in a longitudinal section along the axis of rotation of the rotor according to an exemplary embodiment of the disclosure, 
         FIG. 2  shows the stator of the electrical machine shown in  FIG. 1  in a cross-section perpendicular to the axis of rotation of the rotor, 
         FIG. 3  shows a detailed illustration of the stator shown in  FIG. 2  in the area of an intermediate space between two stator teeth, which are adjacent in the circumferential direction, 
         FIGS. 4 to 6  show variations of the exemplary embodiment shown in  FIG. 3 , 
         FIG. 7  shows a first variation of the electrical machine shown in  FIG. 1 , in the case of which the coolant, which flows through the cooling ducts, is also used to cool the shaft bearings of the rotor, 
         FIG. 8  shows a second variation of the electrical machine shown in  FIG. 1 , which requires particularly little installation space, and 
         FIG. 9  shows a third variation of the machine shown in  FIG. 1 , which provides for a particularly effective cooling of the stator windings. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       FIG. 1  illustrates an example of an electrical machine  1  according to an exemplary embodiment of the disclosure in a sectional illustration. The electrical machine  1  is dimensioned such that it can be used in a vehicle, typically in a road vehicle. The electrical machine  1  includes a rotor  3 , which is only illustrated roughly schematically in  FIG. 1 , and a stator  2 . For reasons of clarity, the stator  2  is illustrated in  FIG. 2  in a cross-section perpendicular to the axis of rotation D along the sectional line II-II of  FIG. 1  in a separate illustration. According to  FIG. 1 , the rotor  3  has a rotor shaft  31  and can have several magnets, which are not illustrated in more detail in  FIG. 1  and the magnetic polarization of which alternates along the circumferential direction U. The rotor  3  can be rotated about an axis of rotation D, the position of which is defined by the central longitudinal axis M of the rotor shaft  31 . An axial direction A, which extends parallel to the axis of rotation D, is defined by the axis of rotation D. A radial direction R is perpendicular to the axial direction A. A circumferential direction U rotates around the axis of rotation D. 
     As can be seen in  FIG. 1 , the rotor  3  is arranged in the stator  2 . The electrical machine  1  shown here is thus a so-called internal rotor. A realization as so-called external rotor, in the case of which the rotor  3  is arranged outside of the stator  2 , is also conceivable. The rotor shaft  31  is supported on the stator  2  in a first shaft bearing  32   a  and, axially spaced apart therefrom, in a second shaft bearing  32   b,  so as to be rotatable around the axis of rotation D. 
     In a known manner, the stator  2  furthermore includes several stator windings  6 , which can be electrically energized, to generate a magnetic field. Due to magnetic interaction of the magnetic field, which is generated by the magnets of the rotor  3 , the rotor  3  is set in rotation with the magnetic field generated by the stator windings  6 . 
     It can be gathered from the cross section of  FIG. 2  that the stator  2  can have a ring-shaped stator body  7 , for example made of iron. The stator body  7  can in particular be formed of several stator body plates (not shown), which are stacked on top of one another along the axial direction A and which are adhered to one another. Several stator teeth  8 , which extend along the axial direction A, protrude radially to the inside away from the stator body  7 , and are arranged spaced apart from one another along the circumferential direction U, are integrally molded to the stator body  7  radially on the inside. Each stator tooth  8  bears a stator winding  6 . Together, the individual stator windings  6  form a winding arrangement. Depending on the number of the magnetic poles, which are to be formed by the stator windings  6 , the individual stator windings  6  of the entire winding arrangement can be wired together electrically in a suitable manner. 
     During 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 an overheating and damages to or even destruction of the machine  1  associated therewith. The stator windings  6  are thus cooled with the help of a coolant K, which is guided through the stator  2 , and which absorbs the waste heat generated by the stator windings  6  with heat transfer. 
     To guide the coolant K through the stator  2 , the machine  1  includes a coolant distribution chamber  4 , into which a coolant K can be introduced via a coolant inlet  33 . A coolant collecting chamber  5  is arranged along the axial direction A at a distance from the coolant distribution chamber  4 . The coolant distribution chamber  4  communicates fluidically with the coolant collecting chamber  5  with several cooling ducts  10 , of which only a single one can be seen in the illustration of  FIG. 1 . The coolant distribution chamber  4  and the coolant collecting chamber  5  can each have a ring-shaped geometry in a cross section perpendicular to the axial direction A, which is not shown in the figure. Several cooling ducts  10 , which each extend along the axial direction A from the ring-shaped coolant distribution chamber  4  to the ring-shaped coolant collecting chamber  5 , are arranged along the circumferential direction U at a distance from one another. The coolant K, which is introduced into the coolant distribution chamber  4  via the coolant inlet  33 , can thus be distributed to the individual cooling ducts  10 . After flowing through the cooling ducts  10  and the absorption of heat from the stator windings, the coolant K is collected in the coolant collecting chamber  5  and is dissipated from the machine  1  again via a coolant outlet  34  provided on the stator  2 . 
     As can be seen in the illustrations of  FIGS. 1 and 2 , the stator windings  6  are arranged in intermediate spaces  9 , which are formed between two stator teeth  8 , which are each adjacent in the circumferential direction U. Said intermediate spaces  9  are also known to a person of ordinary skill in the art as so-called “stator grooves” or “stator slots”, which extend along the axial direction A, as do the stator teeth  8 . 
     Attention is to now be directed to the illustration of  FIG. 3 , which shows an intermediate space  9  formed between two stator teeth  8 —hereinafter also referred to as stator teeth  8   a  and  8   b —which are adjacent in the circumferential direction U, in a detailed illustration. To improve the heat transfer of the waste heat generated by the stator windings  6  to the coolant K flowing through the cooling ducts  10 , an electrically insulating plastic  11  is in each case provided according to  FIG. 3  in the intermediate spaces  9 . The electrically insulating plastic  11  is formed by a first plastic mass  11   a  made of a first plastic material and by a second plastic mass  11   b  made of a second plastic material, the thermal conductivity of which is greater than the thermal conductivity of the first plastic material. The first plastic material  11   a  is a thermosetting plastic. The second plastic material  11   b  is a thermoplastic. In the example scenario, a first and a second plastic mass  11   a  and  11   b  are in each case arranged in all intermediate spaces  9 . The two plastic masses  11   a  and  11   b  are each injection molding masses made of the electrically insulating plastic  11 . The use of an injection molding process simplifies and accelerates the production of the plastic mass. In variations of the example, it is conceivable to select the plastic materials of the two plastic masses  11   a  and  11   b  in such a way that thermal conductivity of the second plastic material is smaller than the thermal conductivity of the first plastic material. In a further variation, two plastic materials having identical heat conductivity can also be used for the first and second plastic mass  11   a  and  11   b.    
     According to  FIG. 3 , the stator windings  6  arranged in the intermediate space  9  and a cooling duct  10  are embedded in the first plastic mass  11   a  made of the first plastic material. The first plastic mass  11   a  together with the stator winding  6  embedded therein and a cooling duct  10 , in turn, are embedded in the second plastic mass  11   b  made of the second plastic material or are partially surrounded by it, respectively. 
     According to  FIG. 1 , the stator windings  6  each have two axial end portions  14   a  and  14   b,  on which an additional electrically insulating insulation is arranged. Even though the electrically conductive stator windings are usually already surrounded with an electrical insulation so as to prevent that electrical short-circuits are generated in response to contact of individual winding portions within another, it cannot be ensured that, after manufacture and assembly of the stator windings  6 , all of these stator windings  6  are equipped throughout with an insulation of this type. It is thus ensured with a redundant, additional electrically insulating insulation that the axial end portions  14   a  and  14   b  neither limit the coolant distribution chamber  4  nor the coolant collecting chamber  5  directly. An unwanted electrical short-circuit of the coolant, which is present in the coolant distribution chamber  4  or in the coolant collecting chamber  5 , respectively, with the electrically conductive stator windings can be prevented in this way. 
     The electrically insulating insulation can be formed by an insulating varnish. An insulating varnish of this type can be applied to the stator windings  6  with spraying as part of the production of the stator  2 . In the alternative, it is also conceivable, however, to realize the additional insulation with the electrically insulating plastic  11 , for example with a further, third plastic mass, which is part of the electrically insulating plastic  11 . 
     The stator windings  6 , including their respective two axial end portions  14   a  and  14   b,  are fixed to the stator teeth  3  with the first plastic mass  11   a.  The axial end portions  14   a  and  14   b  can also be held on the stator body  3  in a durably stable manner in this way. 
     It goes without saying that the stator winding  6 , which, according to  FIG. 3 , is arranged in the intermediate space  9 , is in each case partially associated with a first stator winding  6   a,  which is borne by a first stator tooth  8   a  and which is partially associated with a second stator winding  6   b,  which is borne by a second stator tooth  8   b,  which is adjacent to the first stator tooth  8   a  in the circumferential direction U. To clarify this scenario, a virtual separating line  12  is delineated in  FIG. 3 . The winding wires  13   a  shown to the left of the separating line  12  in  FIG. 3  belong to the stator winding  6   a,  which is borne by the stator tooth  8   a.  The winding wires  13   b  shown to the right of the separating line  12  belong to the stator winding  6   b,  which is borne by the stator tooth  8   b.    
     According to  FIG. 3 , the cooling duct  10  formed in the intermediate space  9  is realized by several apertures  40 , which are arranged in the electrically insulating plastic  11  and through which the coolant K can flow. The second plastic mass  11   b  typically in each case surrounds the apertures  40  completely in a cross-section perpendicular to the axial direction A shown in  FIG. 3 . The apertures  40  forming the cooling duct  10  can be thermally coupled to the stator windings  6  particularly effectively in this way. 
     The apertures  40 —four apertures  40  of this type are shown merely in an exemplary manner in  FIG. 3 —are arranged spaced apart from one another along the circumferential direction U and in each case extend along the axial direction A. The apertures  40  can be realized as through bores, which are introduced into the second plastic mass  11   b  with a suitable boring tool. The apertures  40  can each have the geometry of a rectangle comprising two broad sides  20  and including two narrow sides  21  in the cross-section perpendicular to the axis of rotation D. A length of the two broad sides  20  is thereby at least twice, typically at least four times, a length of the two narrow sides  21 . The advantageous geometry of a flat tube is thus reproduced. 
     In the example of  FIG. 3 , the apertures  40  forming the cooling duct  10  are arranged in the plastic mass  11  radially outside of the stator windings  6  with respect to the radial direction R. The radial distance of the cooling duct  10  to the axis of rotation D of the rotor  3  is thus greater than the distance of the stator winding  6  to the axis of rotation D. However, an arrangement of the cooling ducts  10  radially on the inside is also conceivable. The two broad sides  20  of the apertures  40  each extend perpendicular to the radial direction R in the cross-section perpendicular to the axial direction A shown in  FIG. 3 . 
     To produce an electrical machine  1  according to  FIGS. 1 to 3 , the surfaces of the stator body  7  forming the intermediate spaces  9  are extrusion-coated with the second plastic material, typically a thermoplastic, and the second plastic mass  11   b  is formed in this way. The material of the stator body  7  is thereby electrically insulated towards the respective intermediate space  9 . The stator windings  6  are then introduced into the intermediate spaces  9  and are arranged on the stator teeth  8 . The stator windings  6  are then extrusion-coated with the first plastic material, typically a thermosetting plastic, which results in the first plastic mass  11   a.  The stator body  7  can also be extrusion-coated with the first plastic material, which forms the first plastic mass  11   a,  as part of the production of the electrically insulating plastic  11 , which consists of the two plastic masses  11   a  and  11   b.  Before or after this, the apertures  40  forming the cooling duct  10  can be introduced into the second plastic mass  11   b  with the help of a suitable boring tool. 
       FIG. 4  shows a variation of the example of  FIG. 3 . In the case of the machine  1  according to  FIG. 4 , the cooling duct  10  is not arranged in the first plastic mass  11   a,  but in the stator body  7  of the stator  2 . As can be seen in  FIG. 4 , the apertures  40  forming the cooling duct  10  are arranged in the stator body  7  radially outside of the intermediate space  9  and, with respect to the circumferential direction U, between two adjacent stator teeth  8   a  and  8   b.  Analogously to the example of  FIG. 3 , the cooling duct  10  is formed by apertures  40 , which, however, in the case of the variation according to  FIG. 4 , are arranged in the stator body  7 —and not in the plastic  11 . The cooling duct  10  can be formed by introducing the apertures  40 —typically in the form of bores with the help of a suitable boring tool—into the stator body  7  or into the stator body plates forming the stator body  7 , respectively, typically as part of the production of the stator body  7 . 
       FIG. 5  shows a variation of the example of  FIG. 4 . In the case of the variation according to  FIG. 5 , the apertures  40  forming the cooling duct  10  are also arranged in the stator body  7  of the stator  2 . In the example of  FIG. 5 , however—in contrast to the variation of  FIG. 4 —the apertures  40  arranged in the stator body  7  are formed to be open towards the intermediate space  9 . As can be seen in  FIG. 5 , the apertures  40  are closed in a fluid-tight manner towards the intermediate space  9  and by the second plastic mass  11   b  provided in the intermediate space  9 . 
       FIG. 6  shows a further development of the example of  FIG. 5 . In the case of the further development according to  FIG. 6 , a cooling duct  10  is formed in the stator body  7  as well as in the first plastic mass  11   a.  The cooling duct  10  additionally provided in the stator body  7 —hereinafter also referred to as “radial outer cooling duct”  10   a —is formed analogously to the example of  FIG. 5 , so that reference is made to the above explanations with regard to  FIG. 5 . The cooling duct  10  arranged in the first plastic mass  11   a  will also be referred to below as “radially inner cooling duct”  10   b.  With respect to the radial direction R, the stator winding  6  is thus arranged between the two cooling ducts  10   a  and  10   b.  As shown by the detailed illustration of  FIG. 6 , the radially inner cooling duct  10   b  can be formed by a tube body  16 , for example made of aluminum, which surrounds a tube body interior  22 . An electrically conductive material, in particular a metal or an electrically insulating material, in particular a plastic, can generally be considered as material for the tube body  16  or for the cooling duct  10  and  10   a,  respectively. As shown in the detailed illustration of  FIG. 6 , one or several separating elements  18 , which separate the cooling duct  10   b  into partial cooling ducts  19 , which are fluidically separated from one another, can optionally be integrally molded on the tube body  16 . The flow behavior of the coolant K in the cooling duct  10   b  can be improved in this way, which is associated with an improved heat transfer to the coolant. In addition, the tube body  16  is additionally mechanically reinforced. Two separating elements  18  of this type are illustrated in an exemplary manner in the example of  FIG. 6 , thus resulting in three partial cooling ducts  19 . It goes without saying that a different number of separating elements  18  is also possible in variations of the example. The tube body  16 , can be formed as flat tube  17 , which has two broad sides  20  and two narrow sides  21  in the cross-section perpendicular to the axial direction A. A length of the two broad sides  20  is at least four times, typically at least ten times, a length of the two narrow sides  21  in this case. The broad sides  20  extend perpendicular to the radial direction R. 
     Where sensible, the above-described variations according to  FIGS. 3 to 6  can be combined with one another. 
     Reference will be made below to  FIG. 1  again. As shown in  FIG. 1 , the first plastic mass  11   a,  which is typically formed in one piece, can protrude axially from the intermediate spaces  9  on both sides. This also allows for the embedding of the cooling distribution chamber  4 , and, alternatively or additionally, the coolant collecting chamber  5  in the first plastic mass  11   a,  for thermal coupling to the two axial end portions  14   a  and  14   b  of the respective stator winding  6 , which are arranged axially outside of the respective intermediate space  9 . In the area of the axial end portions  14   a  and  14   b  of the respective stator winding  6 , which are usually specially loaded thermally, an effective heat transfer to the coolant K, which is present in the coolant distribution chamber  4  or coolant collecting chamber  5 , respectively, can also be established in this way. This measure allows for a particularly effective cooling of the two axial end portions  14   a  and  14   b  of the stator winding  6 . 
     According to  FIG. 1 , the stator  2  together with the stator body  7  and the stator teeth  8  is further arranged axially between a first and a second bearing shield  25   a  and  25   b.    
     As can be seen in  FIG. 1 , a part of the coolant distribution chamber  4  is arranged in the first bearing shield  25   a,  and a part of the coolant collecting chamber  5  is arranged in the second bearing shield  25   b.  The coolant distribution chamber  4  and the coolant collecting chamber  5  are thus each partially formed by a cavity  41   a  and  41   b,  which is provided in the first plastic mass  11   a.    
     The first cavity  41   a  is thereby supplemented by a cavity  42   a  formed in the first bearing shield  25   a  to form the coolant distribution chamber  4 . The second cavity  41   b  is accordingly supplemented by a cavity  42   b  formed in the second bearing shield  25   b  to form the coolant distributing chamber  5 . In the case of the above-described embodiment variation, the plastic mass  11   a —but not the second plastic mass  11   b —thus limits the coolant distribution chamber  4  as well as the coolant collecting chamber  5  at least partially. 
     A coolant supply  35 , which fluidically connects the coolant distribution chamber  4  to a coolant inlet  33 , which is provided on the first bearing shield  25   a  on the outside, in particular circumferentially as illustrated in  FIG. 1 , can further be formed in the first bearing shield  25   a.  A coolant discharge  36 , which fluidically connects the coolant collecting chamber  5  to a coolant outlet  34 , which is provided on the bearing shield  25   b  on the outside, in particular circumferentially, as illustrated in  FIG. 1 , can accordingly be provided in the second bearing shield  25   b.  This provides for an arrangement of the coolant distribution chamber  4  or of the coolant collecting chamber  5 , respectively, in each case radially on the outside of the first or second end portion  14   a  and  14   b,  respectively, of the respective stator winding  6  and also in the extension of these end portions  14   a  and  14   b  along the axial direction A. The end portions  14   a  and  14   b  of the stator windings  6 , which are specially loaded thermally during operation of the machine  1 , are also cooled particularly effectively with this measure. 
     According to  FIG. 1 , the first plastic mass  11   a  made of the electrically insulating plastic  11  can also be arranged on an outer circumferential side  30  of the stator body  7  and can thus form a plastic coating  11 . 1  on the outer circumferential side  30 . The stator body  7  of the stator  2 , which is typically formed of electrically conductive stator plates, can thus be electrically insulated against the surrounding area. The provision of a separate housing for receiving the stator body  7  can thus be forgone. 
       FIG. 7  shows a variation of the exemplary embodiment shown in  FIG. 1 . To also cool the rotor shaft  31  as well as the two shaft bearings  32   a  and  32   b  during operation of the machine  1 , the coolant supply  35  can be thermally coupled to the first shaft bearing  32   a,  which is arranged in the first bearing shield  25   a.  The coolant discharge  36  can likewise be thermally coupled to the second shaft bearing  32   b,  which is arranged in the second bearing shield  25   b.  A separate cooling device for cooling the shaft bearings  32   a  and  32   b  can be forgone in this way, which results in cost advantages. In the exemplary embodiment shown in  FIG. 7 , the coolant inlet  33  and the coolant outlet  34  are provided on the outer front side  26   a  and  26   b  of the respective bearing shield  25   a  and  25   b.  In the case of the variation according to  FIGS. 7 and 1 , the stator windings  6  are arranged radially within the cooling ducts  10  along the radial direction R. The stator windings  6  are guided out of the stator  2  to the outside with an electrical connection  50  through a lead-through  39  provided in the second bearing shield  25   b,  such that they can be electrically energized from the outside. The lead-through  39  is arranged radially between the coolant distribution chamber  4  or the coolant collecting chamber  5 , respectively, and the axis of rotation D. 
     In the exemplary embodiment shown in  FIG. 8 , which is simplified as compared to the exemplary embodiment shown in  FIG. 7 , the coolant distribution chamber  4  and the coolant collecting chamber  5  are arranged only in the axial extension of the cooling ducts  10 . This variation requires particularly little installation space for the coolant distribution chamber  4  and for the coolant collecting chamber  5 . In the case of the variation according to  FIG. 8 , the stator windings  6  are arranged radially within the cooling ducts  10  along the radial direction R. The stator windings  6  are guided out of the stator  2  to the outside with an electrical connection  50  through a lead-through  39  provided in the second bearing shield  25   b,  such that they can be electrically energized from the outside. The lead-through  39  is arranged in the second bearing shield  25   b  radially outside of the coolant distribution chamber  4  or of the coolant collecting chamber  5 , respectively, with respect to the radial direction R. 
     In  FIG. 9 , a further development of the exemplary embodiment shown in  FIG. 7  is illustrated. In the longitudinal section along the axis of rotation D illustrated in  FIG. 9 , the coolant distribution chamber  4  surrounds the first axial end portion  14   a  of the respective stator winding  6  in a U-shaped manner, thus axially on the end side as well as radially on the inside and radially on the outside in the case of this further development. The coolant collecting chamber  5  accordingly surrounds the second axial end portion  14   b  of the respective stator winding  6  in a U-shaped manner, thus axially on the end side as well as radially on the inside and radially on the outside in the longitudinal section along the axis of rotation D. In the case of this variation, cooling ducts  10  are provided radially within as well as radially outside of the stator winding  6 . The respective stator windings  6 , including the axial end portions  14   a  and  14   b  thereof, are thus in direct thermal contact with the coolant K via the cooling ducts  10  as well as via the coolant distribution chamber  4  as well as the coolant collecting chamber  5 . This allows for a particularly effective cooling of the stator winding  6 , including the axial end portions  14   a  and  14   b,  which are subjected to thermally special loads. 
     It is understood that the foregoing description is that of the exemplary embodiments of the disclosure and that various changes and modifications may be made thereto without departing from the spirit and scope of the disclosure as defined in the appended claims.