Patent Publication Number: US-2020303987-A1

Title: Electric machine, and method for producing an electric machine

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to an electrical machine, and to a method for producing such an electrical machine. 
     An electrical machine is known from DE 10 2011 084 763 A1, in which a stator is arranged in a pole pot. A cover part is arranged on the pole pot, in which a rotor shaft is supported. The cover part is formed of plastic, and comprises electrical conductor elements for the interconnection of the electric winding of the stator. The coil wire ends of the windings are routed axially through the cover part, and are connected to the conductor elements on the upper side of the cover part. The cover part incorporates a lateral extension, which is configured as a laterally-projecting plug-in connector, the pins of which are connected both to the conductor elements and to a circuit board. At one free end of the rotor shaft, a signal generator is arranged for the detection of the rotor position. In axial opposition to the signal generator, a circuit board is arranged, upon which a sensor element for the evaluation of signals is arranged, which is not represented in greater detail. A metal cover with cooling ribs is fitted to the plastic cover part by means of clamping elements. 
     A design of this type has a disadvantage in that, as a result of the lateral projection of the plug-in connector, the electrical machine occupies a large structural volume in the radial direction. The axial mounting of the circuit board in the plastic cover part, with the plug-in connector, does not permit any central axial connector outlet. 
     SUMMARY OF THE INVENTION 
     The device according to the invention and the method according to the invention, have the advantage in that, by the provision of a sealing ring, the plug-in connector can be reliably sealed in relation to the cut-out in the metal cover. In this manner, the connector outlet of the plug-in connector can be arranged on the axial cover surface of the metal cover, as a result of which the electrical machine, with no radial projections, can be employed in a relatively narrow cylindrical structural volume. Particularly advantageously, the cut-out in the metal cover is configured to a circular design, and is punched out of the metal cover in axial opposition to the rotor. This circular cut-out can be particularly advantageously sealed in relation to the plug housing by means of a sealing ring. 
     By means of the measures described in the dependent claims, advantageous further developments and improvements of the forms of embodiment disclosed in the independent claims are possible. The plug housing is advantageously formed of plastic, and incorporates the plug-in connector in the form of an axial projection. The plug pins are directly embedded as insert components during the injection-molding of the plug housing. The plug housing comprises a cylindrical circumferential wall, which is advantageously mounted axially to the open pole pot. The electrical contacts of the plug pins are arranged within the cylindrical circumferential wall. The outer side of the circumferential wall constitutes a radial sealing surface, to which the sealing ring can be fitted. 
     In order to permit the exact positioning of the sealing ring on the plug housing, an axial shoulder is molded onto the circumferential wall, with which the sealing ring engages axially. This arrangement also prevents any axial displacement or twisting of the sealing ring upon the fitting of the metal cover to the plug housing. Additionally, this axial bearing surface can simultaneously be configured as an axial sealing surface, such that the plug housing comprises both a radial and an axial sealing surface for the sealing ring. 
     For the constitution of a radial seal, a radial inner side of the metal cover compresses the sealing ring radially against the radial sealing surface of the plug housing. The metal cover can be cost-effectively configured as a deep-drawn part, the cylindrical inner side of which is directly configured as a radial mating sealing surface for the radial sealing ring. 
     For the achievement of an axial seal, the metal cover comprises a cover surface, which extends transversely to the rotor shaft, the inner side of which is configured as an axial bearing surface for the sealing ring. If the metal cover is axially attached to the plug housing, the annular axial inner surface of the metal cover can constitute an axial seal with the opposing axial shoulder of the plug housing and the intervening sealing ring. 
     The plug housing, on its axial upper side, comprises a base surface, onto which the plug-in connector is molded. This base is particularly advantageously configured to a circular design, and the radial circumferential side thereof engages with the inner radial edge of the circular cut-out in the metal cover. The sealing ring is thus reliably shielded by the annular cover surface of the metal cover, such that the sealing ring is not directly exposed to the impact of any water stream. In this manner, the plug housing can be reliably sealed in relation to the metal cover. 
     By the arrangement of the sealing ring in the axial upper region of the circumferential wall of the plug housing, radial cut-outs in the circumferential wall, which are arranged axially below the radial sealing surface, can also be reliably sealed. Thus, for example, radial windows can be molded into the circumferential wall for the execution of welded joints in the interior of the plug housing. By this arrangement, the electrical contacts of the plug pins can be electrically connected to the corresponding terminal pins or ground contacts of the stator, after the plug housing has already been fitted to the pole pot. As the metal cover is directly axially sealed in relation to the pole pot, no moisture can reach the entire axial lower region below the radial sealing surface of the plug housing. 
     Additionally to the axial shoulder for the sealing ring, a further axial bearing surface can be configured on the outer circumferential wall of the plug housing, to which an axial spring can be applied which exerts an axial tensioning force between the plug housing and the metal cover. To this end, a corresponding and axially opposing mating bearing surface is configured on the inner side of the metal cover. After the fastening of the metal cover to the pole pot, this socket-shaped spring continuously compresses the plug housing against the flange of the pole pot, in order to offset manufacturing tolerances and differential material expansions in the various components over a wide temperature range. 
     In the interests of an axially favorable assembly sequence for the electrical machine, the radial dimensions of the plug-in connector, with its associated base, are smaller than the clear span of the cut-out in the metal cover. As a result, the metal cover can be axially attached to the plug housing, directly above the plug-in connector. This applies specifically in the case where, although the electrical contacts on the base are routed axially upwards, the connector shroud is bent through a right angle, such that the plug pins extend in a radial direction. By this arrangement, a customer plug can be radially connected to the electrical machine, without the necessity for an additional radial structural volume to accommodate a plug-in connector configured as a radial projection from the electrical machine. 
     In order to achieve a reliable sealing action, the sealing ring comprises a plurality of sealing lips, in an axially adjacent arrangement to one another. It is particularly beneficial if at least two sealing lips respectively are arranged on the sealing ring, in both radially opposing directions. By the configuration of the radial seal, the interior space of the motor thus remains reliably sealed even if, on the grounds of vibrations or temperature expansions, the plug housing is subject to axial displacement in relation to the metal cover, within certain limits. Additionally, on one or both axial sides of the sealing ring, axial sealing lips are arranged which, additionally to the radial seal, provide an axial seal. 
     By the configuration of a plurality of sealing lips on one side of the sealing ring, “pressure-relief chambers” are constituted between the sealing lips which, in the event of the penetration of moisture or impurities, provide a barrier for the next sealing lip. 
     If the metal cover, over its entire circumference, is welded to the flange of the pole pot by means of a weld seam, a highly robust metal housing, incorporating the plug-in connector, is constituted down to the base, which is firstly of a vibration-resistant design, and secondly functions as electromagnetic shielding. If a radial step is configured on the cylindrical circumferential wall of the metal cover, the resulting axial bearing surface on the inner side of the metal cover can be employed as an axial support for the axial spring. Thus, by the production of the metal cover, the radial and, where applicable, the axial sealing surface for the sealing ring can simultaneously be constituted and, at the same time, the radial structural volume for the socket-shaped tubular spring can be provided between the circumferential wall of the plug housing and the inner side of the metal cover. 
     It is particularly advantageous if sensor pins are molded into the plug housing, which are connected to a sensor element which is arranged on the inner side of the plug housing. If a free end of the rotor shaft projects through the bearing plate into the interior of the plug housing, a signal generator can be fastened to the rotor shaft, the signals of which can be employed for the evaluation of the detection of the rotor position by the sensor element. A sensor arrangement of this type, without the use of a circuit board as a carrier, can also be employed, even in the event of very high temperatures and vibrations. 
     Advantageously, the plug housing engages directly with the flange of the pole pot. Thus, by the connection of the metal cover to the flange, the plug housing is axially compressed against the flange, by means of the metal cover. Particularly advantageously, the cylindrical inner wall of the metal cover is thus directly sealed in relation to the plug housing, by means of the sealing ring. In this embodiment, the bearing plate is radially fastened to the pole pot within the plug housing, independently of said plug housing. 
     By the production method according to the invention, both the stator, incorporating the bearing plate, and the plug housing can each be manufactured as prefabricated units, which are then axially fastened one inside the other. Accordingly, the electrical contacts can then be electrically connected to the corresponding mating contacts within the housing. Thus, all the electrical contacts, with the corresponding mating contacts, are arranged radially within the circumferential wall of the plug housing, and radially within the external diameter of the pole pot, such that the electrical machine assumes a slim cylindrical structural form, with no radial projections. Further to the completion of electrical connections, a metal housing can be fitted to the plug housing, which is sealed both with respect to the pole pot and with respect to the plug-in connector, which projects outwards through the axial cut-out in the metal housing. To this end, the sealing ring can be fitted to the plug housing on the radial outer sealing surface, onto which the inner side of the metal housing is then fitted to constitute a radial seal. As a result, the circular cut-out in the metal cover is reliably sealed, by means of the sealing ring, over a wide temperature range. The radial side wall of the metal housing entirely encloses the plug housing, and is welded to the pole pot over its entire circumference in a leak-tight manner. A weld seam of this type can be highly advantageously applied between the flange of the pole pot and the axial lower edge of the metal cover. 
     By this production method, the plug housing can be fully populated in advance with all electrical and electronic components, and the latter can be mutually electrically interconnected whereby, advantageously, electrical conductors can be molded into the plug housing in the form of insert components. If the rotary position sensor and corresponding interference suppression components are fastened directly to the inner wall of the plug housing, without the use of a circuit board, these electronic components can be employed even at very high ambient temperatures. By the axial tensioning of the plug housing in relation to the metal cover, by means of the tubular spring, differential material expansions can be compensated. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of the invention are represented in the drawings, and are described in greater detail in the following description. In the drawings: 
         FIG. 1  shows a sectional view of a first exemplary embodiment of an electrical machine according to the invention, 
         FIG. 2  shows a view according to  FIG. 1 , prior to the fitting of the metal cover, 
         FIG. 3  shows a view according to  FIG. 1 , after the fitting of the metal cover, 
         FIG. 4  shows a cross-sectional view of the sealing ring, in the unloaded state, 
         FIG. 5  shows a cross-sectional view of the sealing ring, in the installed state, 
         FIG. 6  shows a further exemplary embodiment according to the invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows an exemplary embodiment of a fully-assembled electrical machine  10 , in which a stator  16  is fitted in a housing  14  of an electrical machine  10 . The stator  16  comprises coil frames  36 , which are constituted, for example, of separate individual segments  62  and wound with electrical windings  17 . The housing  14  functions as a pole pot  15 , which constitutes a magnetic return path for the electrical windings  17 . The pole pot  15 , at its open end, incorporates a flange  32 , upon which further components are fitted. In the exemplary embodiment according to  FIG. 1 , the pole pot  15 , on its base surface  40 , incorporates an opening, through which a rotor shaft  20  projects, in order to transmit the torque of the electrical machine  10  via a drive element  64  to an unrepresented gearing element. On the base surface  40 , a first bearing seat  70  is molded, into which a first rolling bearing  72  is inserted. The inner ring  73  of the first rolling bearing  72  is securely attached to the rotor shaft  20 . The first rolling bearing  72  thus constitutes a locating bearing for the rotor  18 . The rotor  18  comprises a rotor body  65 , which carries permanent magnets  68  which interact with the electrical windings  17 . The rotor body  65  is comprised, for example, of individually stacked segmental plates  66 , in which cut-outs  67  are punched out for the permanent magnets  68 . The coil wire ends  19  of the windings  17  project above the electrical coils  63  in the axial direction  4 . An interconnection board  22  is axially mounted on the stator  16 , wherein conductor elements  23  which project from a plastic body  21  are bonded, on fastening sections  25 , to the coil wire of the coils  63 . Electrical connections between the coil wire and the fastening sections  25  are constituted, for example, by welding, soldering or crimping. In the exemplary embodiment described, exactly three conductor elements  23  respectively comprise a terminal pin  26  for the phases U, V and W. The plastic body  21  engages in the axial direction  4  with the stator  16 , by means of molded-on spacers  42 . The spacers  42  of the interconnection board  22  are molded onto the outer radial edge thereof. In the exemplary embodiment, the spacers  42  engage with the coil frame elements  36 , on which the electrical windings  17  are wound. In this case, the coil frame elements  36  are configured as individual segments  62  for each coil  63 . On each of the coil frame elements  36 , an insulating mask  61  for the electrical windings  17  is respectively arranged. The plastic body  21  is configured to an annular design, such that the rotor shaft  20  of the rotor  18  can project through a central cut-out  44  therein. 
     A bearing plate  54  is arranged axially above the interconnection board  22 , the outer radial edge of which is welded to the pole pot  15 . For example, the bearing plate  54  engages with a cylindrical recess  89  in the flange  32  of the pole pot  15 . The bearing plate  54  incorporates a second bearing seat  55 , which engages axially with the central cut-out  44  in the interconnection board  22 , in the form of an axial projection  53 . The second bearing seat  55  accommodates a second rolling bearing  56 , by means of which the rotor shaft  20  is supported in the stator  16  in a rotatable manner. The second rolling bearing  56  is configured, for example, as a ball bearing, and constitutes a floating bearing for the rotor  18 . To this end, an outer ring  58  of the second rolling bearing  56  is secured in the second bearing seat  55  of the bearing plate  54  in a non-rotating manner. The inner ring  57  is supported on the rotor shaft  20  in an axially displaceable manner. The second rolling bearing  56  is thus axially arranged in the same plane as the interconnection board  22 , such that the electrical machine  10 , in the axial direction  4 , shows a highly compact design. In the exemplary embodiment, the bearing plate  54  incorporates individual radial webbings  59 , between which the fastening sections  25 , which are configured as receiving bushes  27 , project axially upwards. Coil wire ends  19  of the coils  63  are inserted in perforations in the receiving bushes  27 . The terminal pins  26  likewise extend from the plastic body  21  through the bearing plate  54 , in order to permit the bonding thereof to corresponding contacts  30  of the plug-in connector  37 . In the sectional representation of the plastic body  21 , connecting sections  24  of various conductor elements  23  can be seen in cross-section. The cross-sections, which are shown in a flattened representation, are arranged in a mutually offset manner, both with respect to the axial direction  4  and with respect to the radial direction  3 . Consequently, for example, four individual conductor elements  23  can be arranged in exactly two axial planes  8 ,  9 . In the cross-sectional representation, axial ducts  28  in the plastic body  21  can be seen, which originate from retaining tools for the conductor elements  23  which are arranged in the injection-molding tool. For the purposes of vibration damping, the interconnection board  22  is compressed axially downwards from the bearing plate  54  against the coil frame  36  by means of axial spring means  246 . The spring means  246  are configured, for example in the form of an axial spring washer, which encloses the rotor shaft  20 . The spring washer is preferably configured as a corrugated disk  250 , which engages axially with the bearing plate  54  and with the interconnection board  22 . The spring means  246  generate an axial tensioning force, which maintains the interconnection board  22  in an exact position, even over a wide temperature range and in the event of high vibratory loads. The rotor  18  is axially tensioned with respect to the second rolling bearing  56  by means of a compression spring  86 . The compression spring  86 —for example, a helical spring  87 —engages on one side with the rotor body  65 , and on the other side with the inner ring  57  of the second rolling bearing  56 . 
     Axially above the bearing plate  54 , a plug housing  33  is arranged, upon which an external plug-in connector  37 , which is not represented in greater detail, is arranged for the supply of electric power to the electrical machine  10 . In the plug housing  33 , on the inner side  29  thereof, electrical contacts  30  are arranged, which are connected to the terminal pins  26  of the interconnection board  22 . The interconnection board  22  is connected to both the coil wire ends  19  and to the electrical contacts  30  of the plug-in connector  37 . For example, the electrical contacts  30  extend axially downwards in the form of contact lugs  34 , such that they are arranged immediately adjacently to the terminal pins  26 , and can then, for example, be welded to one another. In order to ensure the correct positioning of the terminal pins  26  in the circumferential direction  2 , the interconnection board  22  incorporates positioning elements  60 , both with respect to the stator  16  and/or with respect to the bearing plate  54 , which cooperate with corresponding mating elements. The plug housing  33  is likewise positioned with respect to the bearing plate  54  by means of an anti-rotation mechanism  102 ,  103 . In the plug housing  33 , a sensor element  74  is fastened, which cooperates with a signal generator  75  on the rotor shaft  20 , in order to detect the rotor position thereof. The sensor element  74  is, for example, permanently adhered to a flat base surface  115  of a sensor housing  79  on the inner side  29  of the plug housing  33 . For the purposes of rotary position detection, further to the fitting of the bearing plate  54 , a magnet holder  78  is press-fitted to the free end  80  of the rotor shaft  20 , which accommodates a sensor magnet  76 . The rotating magnetic field thereof is detected by the sensor element  74 , which is configured as a high-resolution magnetic field sensor  77 . A metal cover  81  is attached above the plug housing  33 , which is welded to the flange  32  of the pole pot  15  in a leak-tight manner, by means of the weld seam  154 . Both the plug housing  33  and the metal cover  81  each comprise a circular circumferential wall  82 ,  83 , which are arranged radially adjacently to each other. Between the plug housing  33  and the inner side of the metal cover  81 , a radial sealing ring  84  is press-fitted, which seals the electrical machine  10  in relation to the plug-in connector  37 . Moreover, an axial spring element  85  is arranged between the plug housing  33  and the metal cover  81 , which axially compresses the plug housing  33  against the flange  32  of the pole pot  15 . 
       FIG. 2  shows an electrical machine  10 , in which the plug housing  33  has been fitted to the pole pot  15 , prior to the attachment of the metal cover  81  above the plug housing  33 . The plug housing  33 , on the open end thereof to the pole pot  15 , incorporates an edge  140  which is enclosed over the entire circumference thereof. From the lower edge  140  of the plug housing, which engages axially with the pole pot  15 , the circumferential wall  83  extends in the axial direction  4 , in which radial windows  110  are formed for the insertion of welding tools. For example, a free capacitor terminal  134  of a capacitor which is fastened in the plug housing  33  is compressed against a ground contact  95  of the bearing plate  54 , and is then bonded by welding through the window  110 . Further radial windows  110  are arranged adjacently in the circumferential direction  2 , through which, by means of welding tools, the terminal pins  26  are welded to the contact lugs  34  of the plug housing  33 . The terminal pins  26  extend in the axial direction  4 , parallel to the contact lugs  34 . The latter overlap in the axial direction  4 , and are arranged adjacently to one another in the circumferential direction  2 . During the welding process, the plug housing  33  is axially compressed against the pole pot  15  by an assembly device. In this embodiment, welded joints between the terminal pins  26  and the contact lugs  34 , and the welded joint between the ground contact  95  of the bearing plate  54  and the free capacitor terminal  134  can be executed, for example, using an identically configured welding tool. In place of the free second capacitor terminal  134 , alternatively, a separate contact spring or an integral spring arm can also be configured on a second contact element for the capacitor, such that the welded joint and the first window  110  for the free capacitor terminal  134  can be omitted. Conversely, the ground contact  95  can then be constituted directly, upon the axial fitting of the plug housing  33  to the pole pot  15 , by the sprung contact with the bearing plate  54 . In this embodiment, the plug housing  33  then comprises an exact total of only three windows  110  for the welds U, V and W. 
     In this case, in the axial region of the radial window  110 , the circumferential wall  83  of the plug housing  33  incorporates a radial offset  146 , in order to constitute an annular axial shoulder  144  for the sealing ring  84 . The sealing ring  84  is axially fitted to this annular shoulder  144  such that, over the entire circumference, it engages radially with a cylindrical radial sealing surface  148  of the circumferential wall  83 . Axially above the radial sealing surface  148 , the circumferential wall  83  forms a transition to an axial cover wall  117  of the plug housing  33 , onto which the plug-in connector  37  is molded. A circular base  127  is thus constituted on the cover wall  117 , onto which the plug-in connector  37 , with its associated penetrations for the plug pins  41 ,  43 , is molded. The transition from the upper cover wall  117  of the plug housing  33  to the plug-in connector  37  is thus entirely radially located within the radial sealing surface  148 . The plug-in connector  37  projects out of the metal cover  81  through a cut-out  39  in the axial upper side. In this exemplary embodiment, the power pins  43  and the sensor pins  41  are angled in the radial direction  3 , such that a corresponding customer plug is insertable in a connector shroud  132  of the plug-in connector  37 , in the radial direction  3 . Thus, in the radial direction  3 , the plug-in connector  37 , in combination with the connector shroud  132 , does not project beyond the circular cut-out  39  in the metal cover  81 . In an alternative embodiment, the power pins  43  and the sensor pins  41  in the plug-in connector  37  can also extend in the axial direction  4 , such that the corresponding customer plug can be fitted from above to the connector shroud  132  in the axial direction  4 . On the continuous annular edge  140 , an axial rebate  152  is formed on the outer side of the plug housing  33 , with which the annular axial spring  85  can engage. The axial spring  85  is configured, for example, as a tubular spring  185 , which is axially attached to the plug housing  33  up to the axial rebate  152 . In the exemplary embodiment, axially-oriented ribs  141  are molded onto the edge  140 , by means of which the metal cover  81  is centered during the press-fitting thereof. In one variation of the embodiment, the windows  110  can also be configured to open axially downwards (represented by broken lines in  FIG. 2 ). The edge  140  is thus no longer configured continuously over the circumference, but incorporates interruptions in the region of the windows  110 . Thus, in these regions, the plug housing  33  only engages with axial webbings between the windows  110  on the pole housing  15 . 
     As can be seen in  FIG. 3 , the metal cover  81  is then fitted axially over the plug housing  33 , such that the cylindrical metal wall  82  thereof covers the radial windows  110 . The sealing ring  84  seals the radial sealing surface  148  of the plug housing  33  vis-à-vis the radial inner side  156  of the metal cover  81 . An annular cover surface  158  of the metal housing  81 , which constitutes a rim  159  of the cut-out  39 , entirely covers the sealing ring  84  in the axial direction  4 . The rim  159  engages radially with a radial lateral surface  137  of the base  127 , such that the sealing ring  84  is protected against a direct fluid stream. During the fitting of the metal cover  81 , the latter is axially compressed against the flange  32  of the pole housing  15 , against the axial spring force of the axial spring  85 , and is welded to the flange  32  by means of a fully-circumferential weld seam  154 . The tubular spring  185  engages axially on one side with the axial rebate  152  on the plug housing  33 , and on the other side with an axial counter-stop  153  in the metal housing  81 . To this end, a radial step  160  is formed in the cylindrical metal wall  82  of the metal cover  81 , which constitutes an annular axial shoulder in the form of an axial counter-stop  153 . 
       FIG. 4  shows a cross-sectional representation of a sealing ring  84  according to the invention which is formed, for example, of silicone or an elastomer. In this embodiment, the cross-section comprises a rectangular base shape  161 , which extends further in the axial direction  4  than in the radial direction  3 . On the right-hand side, two axially-adjoining radial sealing lips  162  are configured which, in the installed state, engage radially with the inner side  156  of the metal housing  81 . In radial opposition thereto on the rectangular base shape  161 , two further radial sealing lips  163  are configured, which extend radially inwards to the radial sealing surface  148  of the plug housing  33 . The radially outwardly-oriented sealing lips  162 , which engage with the metal housing  81 , are configured to larger dimensions, and specifically incorporate a larger radial extension than the radially inwardly-oriented sealing lips  163 . On the rectangular base shape  161 , moreover, an axial sealing lip  164  is formed, which extends axially downwards to the annular shoulder  144  of the plug housing  33 . In the axially opposing direction, a further axial sealing lip  165  extends upwards towards the annular cover surface  158  of the metal housing  81 . 
     A sealing ring  84  according to  FIG. 4  is represented, in the installed state, in  FIG. 5 . Upon installation, all the sealing lips  166  undergo deformation, such that the sealing lips  166  engage with their respective opposing sealing surfaces  148 ,  156 ,  144 ,  158  in a sealing manner. In the radial direction  3 , greater compression occurs between the radial sealing surface  148  and the inner side  156  than in the axial direction  4  between the annular shoulder  144  and the annular cover surface  158 . This is attributable to the fact that, in the event of high temperature differences, axial displacement occurs between the plug housing  33  and the metal housing  81 , which is compensated by the axial spring  85 . Consequently, an axial clearance  174  is constituted between the plug housing  33  and the metal housing  81 , which permits an axial movement of the plug housing  33  relative to the metal housing  81 . However, the sealing action of the axial seal is thus strongly dependent upon temperature variations. The radial seal constituted by the radial sealing lips  162  and  163 , however, is substantially independent of temperature, as no significant radial relative movement occurs between the plug housing  33  and the metal housing  81 . Between the sealing lips  166 , in the installed state, cavities  168  are constituted, into which the material of the sealing ring  84  can expand. The cavities  168  also function as pressure-relief chambers for the seal, in which dirt particles and moisture can accumulate. The pressure-relief chambers thus prevent any “infiltration” of the sealing lips  166 , which can specifically occur on sealing lips  162 ,  165  which engage with a sealing surface  156 ,  158  of metal construction. The metal housing  81  of the device represented in  FIG. 5  is radially centered by the press-fitting thereof onto the sealing ring  84  wherein, simultaneously, the sidewall  170  of the cut-out  39  engages radially with the radial lateral surface  137  of the base  127 . 
     A further exemplary embodiment of a fully-assembled electrical machine  10  is represented in  FIG. 6 . The plug-in connector  37  is arranged axially above the cover wall  117 , on the outer side of the plug housing  33 . The plug-in connector  37  is angled through a right-angle in the radial direction  3 , such that the power pins  41  and the sensor pins  43  are likewise oriented in the radial direction  3  within the connector shroud  132 . The power pins  43 , on the inner side  29 , terminate in the form of contact lugs  34 , which are welded to the terminal pins  26  on the interconnection board  22 . The sensor pins  41 , on the inner side  29 , terminate in the form of insert conductors  116 , which are electrically contacted with terminal lugs  106  on the sensor element  74 , which is configured as a magnetic field sensor  77 . The sensor pins  41  and the power pins  43  are respectively configured as one-piece bent stampings  116 —preferably of copper—which are inserted in the molding tool in conjunction with the injection-molding of the plug housing  33 . Further to the fitting of the plug housing  33  to the bearing plate  54  by means of the positioning elements  60 , a metal cover  81  is attached over the plug housing  33 , which is then fastened to the pole pot  15 . The metal cover  81  comprises a cylindrical sidewall  82 , which encloses the plug housing  33  over the entire circumference thereof. The sealing ring  84 , incorporating a plurality of radial sealing lips  162 , is arranged radially between the circumferential wall  82  of the metal cover  81  and the radial sealing surface  148  of the plug housing  33 . For example, exactly four axially-adjoining radial sealing lips  162  are formed on the radial sealing ring  84 , which engage with the inner side  156  of the sidewall  82 . The sealing ring  84  engages axially with the annular shoulder  144  which, in this case, is configured as a radial webbing  145  on the outer side of the circumferential wall  83 . On the axial upper side, the sealing ring  84  engages axially with the inner side of the annular cover surface  158  of the metal cover  81 . By means of a circumferential radial projection  138 , the sealing ring  84  projects radially below the base  127 , such that the gap between the lateral surface  137  of the base  127  and the radial inner side of the border  170  is sealed. The plug-in connector  37  projects out of the metal cover  81 , through the cut-out  39  which is formed on the axial side of said metal cover  81 . By means of the sealing ring  84 , the plug-in connector  27  is sealed vis-à-vis the metal cover  81 . The metal cover  81 , conversely, is welded to the flange  32  of the pole pot  15  in a leak-tight manner. The magnetic field sensor  77  is arranged in the center of the cover wall  117 , in direct axial opposition to the sensor magnets  76  which are attached at the free end  80  of the rotor shaft  20 . In this embodiment, no axial spring is arranged between the metal cover  81  and the plug housing  33 , such that a radial clear space  172  is constituted between the cylindrical sidewall  82  and the circumferential wall  83 . 
     In the method for producing an electrical machine  10  according to the invention, the stator  16  is firstly fitted in the pole pot  15 . To this end, the coil frames  36 , configured of individual segments  62 , are fitted with an insulating mask  61  and are wound with electrical windings  17 , prior to the insertion thereof into the pole housing  15 . Thereafter, the rotor  18  is inserted axially into the pole pot  15 , such that the rotor shaft  20  is securely press-fitted into the first rolling bearing  72 . Thereafter, the interconnection board  22  is arranged axially on the coils  63 , and is electrically bonded to the coil wire ends  19 , preferably by welding. Thereafter, the compression spring  86 —specifically a helical spring  87 —is axially attached to the rotor body  65  wherein, by the fitting of the bearing plate  54 , the compression spring  86  is axially pre-tensioned by the inner ring  57 . Simultaneously, the bearing plate  54  is axially tensioned vis-à-vis the interconnection board  22  by means of the axial spring means  246 . Under the action of this tensioning, the bearing plate  54 , at the radial outer ends thereof, is welded to the pole pot  15 . The first centering lug of the bearing plate  54  engages with corresponding mating elements in the interconnection board  22 . Further to the attachment of the bearing plate  54  by welding, the rotor  18  is reliably supported in the pole pot  15 , both radially and axially, in an oscillation-damping manner. In this state, the terminal pins  26  and the second centering lug  102  project axially upwards, such that the plug housing  33 , with its associated mating element  103 , can be axially attached to the centering lug  102 . The plug housing  33  thus engages axially with the flange  32  of the pole pot  15 . Through the radial windows  110  in the plug housing  33 , the terminal pins  26  can be welded to the electrical contacts  30  of the plug housing  33 . Likewise, the interference suppression capacitor of the plug housing  33  can be welded to the ground contact  95  on the bearing plate  54 , or the contact spring can be compressed against the bearing plate  54 . Thereafter, the sealing ring  84  is attached to the radial sealing surface  148  of the plug housing  33 . Upon the fitting of the metal cover  81 , the sealing ring  84  is compressed between the metal cover  81  and the plug housing  33 , wherein at least one radial seal and, where applicable, also one axial seal are configured. The metal cover  81  in turn engages with the flange  32  and, over the entire circumference thereof, is welded to the pole pot  15  in a leak-tight manner. By this arrangement, the axially upwardly projecting plug-in connector  37 , above the base  127  thereof, is reliably sealed in relation to the border  159  of the cut-out  39  in the metal housing  81 . In order to offset differential material expansions of the individual components over a wide temperature range, an axial spring  85  is preferably tensioned between the metal cover  81  and the plug housing  33 , which axially compresses the plug housing  33  against the pole pot  15 . 
     It will be observed that, with respect to the exemplary embodiments represented in the figures and in the description, multiple mutual combinations of the individual characteristics are possible. Thus, for example, the number, the physical configuration and the arrangement of the sealing lips  166 , and of the opposing sealing surfaces  148 ,  156 ,  144   158 , can be varied. Optionally, an axial seal can be configured in addition to the radial seal. Likewise, the position and the configuration of the plug-in connector  37 , with its associated base  127 , the contact lugs  34  and the insert conductors  116  can be adapted in accordance with customer requirements for the plug housing  33 . The electrical machine  10  is preferably intended for application in a gearing and drive unit as an engine compartment actuator in a vehicle, for example for the actuation of moving parts or the operation of pumps in the engine compartment, but is not restricted to such applications.