Patent Publication Number: US-2020295614-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/EP2018/081564, filed Nov. 16, 2018, designating the United States and claiming priority to German application DE 10 2017 221 835.5, 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 electrical 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 electrical machines to equip the latter with a cooling system for cooling the stator—in particular said stator windings. A cooling system of this type includes one or several cooling ducts, 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 as described herein. 
     It is a general idea of the disclosure to embed the stator windings of an electrical machine, together with a cooling duct through which coolant can flow, in an electrically insulating plastic, which is formed by two plastic masses made of different plastic materials, to cool the stator winding. 
     The plastic can thus act as heat-transferring medium to transfer heat from the stator windings to the coolant 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 simultaneously ensured that the stator windings, which are to be cooled, are not electrically short-circuited in an unwanted manner. 
     The use of two plastic masses made of different plastic materials 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 these two components in the 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 the cooling duct, are extrusion-coated with the plastic to form the two plastic masses. The embedding of the stator windings and of the cooling duct in the plastic masses is thus very simple, even though two different plastic materials are used. Significant cost advantages also result from this in the production of the electrical machine according to the disclosure. 
     According to another aspect of the disclosure, 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. The axis of rotation defines an axial direction of the electrical machine. The machine furthermore includes a stator, which has several 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 thereby communicates fluidically with the coolant collecting chamber with at least one cooling duct, through which a coolant can flow. Several cooling ducts of this type are typically provided between the coolant distribution chamber and the coolant collecting chamber. According to an aspect of the disclosure, the at least one cooling duct and the at least one stator winding are embedded in an electrically insulating plastic for thermal coupling to the coolant. The stator includes 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 electrically insulating plastic is arranged together with the at least one cooling duct and 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. 
     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 a further 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 and the at least one cooling duct are embedded in the second plastic mass made of the second plastic material or are arranged within the second plastic mass or are at least partially or even 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. 
     A first and a second plastic mass are particularly typically arranged in at least two intermediate spaces, typically in all intermediate spaces. The heat transfer can be optimized in this way. 
     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 comprises 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. 
     The at least one cooling duct is typically covered or surrounded by the first or 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, so 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 second 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 is 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. 
     In the case of an advantageous further development, 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 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. 
     According to a further aspect of the disclosure, the intermediate space is divided into a first and a second partial space. In the case of this design, the at least one stator winding is arranged in the first partial space. The at least one cooling duct is arranged in the second partial space. A positioning aid, with which the at least one cooling duct can be positioned in the second partial space, is formed between the two partial spaces. This measure allows for a precise and stable positioning of the cooling duct, which is typically a tube body or a flat tube, respectively, when said cooling duct, together with the stator windings, is extrusion-coated with the plastic, which results in the two plastic masses, in the intermediate space between the two stator teeth. 
     According to a further aspect of the disclosure, the positioning aid includes two protrusions, which are formed on two stator teeth, which are adjacent in the circumferential direction. The two protrusions face one another in the circumferential direction of the rotor and protrude into the intermediate space so as to position in the cooling duct. This design allows for a particularly exact alignment of the cooling duct in the intermediate space prior to the extrusion-coating with the plastic of the plastic mass. 
     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, such 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 achieved. 
     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, so 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 substantially 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, 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 is 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, 
         FIG. 4  shows a further development of the variation shown in  FIG. 3 , 
         FIG. 5  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. 6  shows a second variation of the electrical machine according to  FIG. 1 , which requires particularly little installation space, and 
         FIG. 7  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 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 figures. 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 the pertinent person of 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 ,  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 . 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 including identical heat conductivity can also be used for the first and second plastic mass  11   a  and  11   b.    
     As shown in  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 including the 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. As can be seen in  FIG. 3 , the cooling duct  10  is covered completely by the second plastic mass  11   b  in the cross-section perpendicular to the axial direction A. 
     The two plastic masses  11   a  and  11   b  are typically each injection molding masses made of the electrically insulating plastic. The use of an injection molding process simplifies and accelerates the production of the plastic mass. 
     It goes without saying that the stator winding  6 , which is arranged in the intermediate space  9  according to  FIG. 3 , in each case partially belongs to a first stator winding  6   a , which is borne by a first stator tooth  8   a , and is partially assigned to 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.    
     As shown in  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. 
     As substantiated by the detailed illustration of  FIG. 3 , the cooling ducts  10  can each 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 , respectively. As shown in the detailed illustration of  FIG. 3 , one or several separating elements  18 , which separate the cooling duct  10  into partial cooling ducts  19 , which are fluidically separated from one another, can optionally be integrally molded on the tube body  16 , as shown in  FIG. 3 . The flow behavior of the coolant K in the cooling duct  10  can be improved in this way, which is associated with an improved heat transfer to the coolant K. In addition, the tube body  16  is additionally mechanically reinforced in this way. Three separating elements  18  of this type are illustrated in an exemplary manner in  FIG. 3 , thus resulting in four partial cooling ducts  19 . It goes without saying that a different number of separating elements  18  is possible in variations of the exemplary embodiment. The tube body  16 , which forms the cooling duct  10 , is formed as flat tube  17 , which has two broad sides  20  and two narrow sides  21  in a cross-section perpendicular to the axis of rotation D of the rotor  3  (see  FIG. 3 ). In the cross-section perpendicular to the axial direction A shown in  FIG. 3 , the two broad sides  20  of the flat tube  17  extend perpendicular to the radial direction R. 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 the example of  FIGS. 1 to 3 , the cooling duct  10  is arranged radially outside the stator windings  6  in the respective intermediate space  9 . The radial distance of the cooling ducts  10  to the axis of rotation D of the rotor  3  is thus greater than the radial distance of the stator windings  6  to the axis of rotation D. However, an arrangement of the cooling duct  10  radially on the inside is also conceivable. 
     To produce an electrical machine  1  according to  FIGS. 1 to 3 , the cooling ducts  10  formed by tube bodies  16  or flat tubes  17 , respectively, are initially introduced into the intermediate spaces  9 . The surfaces of the stator body  7  limiting the intermediate spaces  9  are subsequently 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 electrically insulated towards the respective intermediate space  9  in this way. 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  7  can also be extrusion-coated with the first plastic material forming 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.    
     According to  FIG. 3 , the intermediate space  9  can include a first partial space  9   c , in which the stator winding  6  is arranged, and a second partial space  9   d , in which the cooling duct  10  is arranged and which supplements the first partial space  9   c  to form the intermediate space  9 . As can be seen in  FIGS. 3 and 4 , a positioning aid  27 , with which the cooling duct  10  is fixed in the second partial space  9   d , can be arranged between the two partial spaces  9   c  and  9   d . Said positioning aid  27  includes two protrusions  28   a  and  28   b , which are formed on the two stator teeth  8   a  and  8   b , which are adjacent in the circumferential direction U and limit the intermediate space  9 . The two protrusions  28   a  and  28   b  face one another in the circumferential direction U and protrude into the intermediate space  9  in order to position the cooling duct  10 . The protrusions  28   a  and  28   b  thereby act as radial stop for the cooling duct  10 , which is formed as tube body  16  or flat tube body  17 , respectively, which can prevent an unwanted movement of the cooling duct  10  radially to the inside, in particular in response to the production of the plastic masses  11   a  and  11   b  with injection molding. 
       FIG. 4  shows a further development of the example of  FIG. 3 . The further development of  FIG. 4  differs from the exemplary embodiment shown in  FIG. 3  in that a cooling duct  10 , which, as in the example of  FIG. 3 , can be formed as tube body  16  or as flat tube  17 , respectively, is provided not only radially on the outside, but additionally also radially on the inside in the intermediate space  9 . As an example, the radially inner cooling duct  10  is illustrated as flat tube  17  including two separating elements  18  and three partial cooling ducts  19 . Where sensible, the above descriptions with regard to the example of  FIG. 3  also apply mutatis mutandis for the example of  FIG. 4 . 
     Reference will be made below to  FIG. 1  again. As clearly 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 plastic mass  11 , 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 . 
     As shown in  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. 
     As shown in  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. 5  shows a variation of the example of  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 significant cost advantages. In the example of  FIG. 5 , 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 . However, a circumferential or radial arrangement, respectively, is also conceivable. In the case of the variation according to  FIGS. 5 and 1 , the stator windings  6  are arranged radially within the cooling ducts  10  with respect to 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 , so 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 example of  FIG. 6 , which shows an exemplary embodiment, which is simplified as compared to  FIG. 5 , 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. 6 , the stator windings  6  are arranged radially within the cooling ducts  10  with respect to 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 , so 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 the example of  FIG. 7 , a further development of  FIG. 5  is shown. In the longitudinal section along the axis of rotation D illustrated in  FIG. 7 , 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.