Abstract:
The invention relates to an electric motor, in particular a pump motor, comprising a permanent magnet rotor; a wound stator including a stator laminate package, insulating elements and a stator winding; a motor housing made of plastic material; and a component carrying a rotor bearing, in particular a pump head. The electric motor provides a generic motor with a reliable and economically feasible fastening of the stator to the motor housing, wherein heat expansion cracks are avoided and noise transmissions can be reduced.

Description:
BACKGROUND OF THE INVENTION 
     (1) Field of the Invention 
       [0001]    The invention relates to an electric motor, in particular a pump motor, having a permanent magnet rotor, a wound stator, with a stator laminate package, insulating elements and a stator winding, a motor housing made of plastic material and a component carrying a rotor bearing, in particular a pump head. 
         [0002]    (2) Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98 
         [0003]    In the case of combustion engines in the motor vehicle sector, mechanical pumps, which are driven by the crankshaft via a cam belt, are generally provided as main cooling water pumps. As a support or an alternative in a shut-off combustion engine, electric ancillary cooling water pumps are used, which are generally designed as electronically commutated direct-current motors. Main cooling water pumps can also be operated electrically. Likewise, cooling water pumps are also used in hybrid and electric vehicles. There, mainly in the cooling circuit of a battery cooling system. Electronically commutated DC motors are further used as a drive for blowers, air, fuel and oil pumps. From DE 10 2009 047 332 A1, a generic electric motor is known, in which the stator is welded to the motor housing. In the known pump, there is the danger that in case of severe temperature fluctuations, due to the different materials used (metal, plastic) and based on differences in thermal expansion damages to the welded joint can occur. In addition, undesired noise transmissions can occur due to the shown large-area installation of stator parts on the motor housing. 
       BRIEF SUMMARY OF THE INVENTION 
       [0004]    It is therefore the object of the invention to provide for a reliable and economically feasible fastening of the stator to the motor housing in a generic electric motor, whereby thermal expansion cracks are avoided and noise transmissions can be reduced. 
         [0005]    By welding an insulating element to the motor housing, sound sources or noise transmitters, for example a containment shell, can be decoupled from the stator. This makes a significant noise reduction possible. Furthermore, a shortening of tolerance chains and an exact positioning of further components such as electronics to the housing are possible. In addition, the welding allows a direct introduction of stator forces into the housing and thus a relief of connecting regions between the component bearing the rotor, e.g. the pump head, and the motor housing and possibly a containment shell. In addition, the number of connecting elements and thus the weight can be reduced. Owing to greater tolerances and a smaller number of parts, a particularly economical production is possible. The mentioned advantages can be achieved more clearly, if both insulating elements are welded to the motor housing. 
         [0006]    For the welded connection with the housing, additional fastening projections are provided, which extend radially in the direction of the motor housing. As a result, the stator can be kept at a small distance from the motor housing and noise transmissions can thereby be prevented or at least significantly reduced. As a result of the connection to the motor housing, the stator can also be decoupled from a containment shell. 
         [0007]    In order to ensure a fixed mechanical and play-free connection even in the case of large temperature differences, axial mirror balancing means are provided, which in particular can compensate for different longitudinal extensions between the plastic housing of the motor housing and the metal material of the stator laminate. 
         [0008]    These axial play balancing means are produced by means of a special geometrical shaping of the fastening projections and/or their transitional area, in particular bridge sections, to the insulating element by providing clearances and/or deflectable arms and/or the transitional areas are designed as compliant areas. 
         [0009]    However, it is also possible for the motor housing to comprise compliant fastening regions, to which at least one of the insulating elements is welded. A combination is also possible, in which both the insulating elements and the motor housing are provided with compliant regions. 
         [0010]    For a good insulating effect, a substantially annular cover disc often suffices. 
         [0011]    The insulating elements can be designed in different ways. Insulating elements, which, in addition to the annular covering disk, also have groove linings extending axially in stator slots, have been found to be particularly expedient. In addition to the insulating effect, the groove linings also contribute to a more stable mounting of the stator in the motor housing, because they engage deeply with the stator slots and effect a firm hold of the stator core, in particular of the stator lamination package, through the plurality of groove linings. Finally, the insulating elements are held on the stator core by the wire tension of the stator winding. 
         [0012]    The formation of axial projections on the second insulating element results in further advantageous embodiments of the invention. In particular, an axial mounting space for a circuit board can be limited by the axial projections. 
         [0013]    Furthermore, the axial projections can have radial limiting surfaces. With these they can, for example, abut against radial limiting means of a carrier plate. The carrier plate can further have stop surfaces, which serve as an axial boundary for the mounting space of the printed circuit board. At the same time, the radial limiting means of the carrier plate can limit the radial installation space of the printed circuit board. All these measures serve to hold the circuit board positively and to hold it in the housing without play. For this purpose, the printed circuit board is clamped between the fastening projections of the insulating elements and the motor housing, with the carrier plate being interposed, and fixed in this position by welding the insulating elements or at least one insulating element to the motor housing. 
         [0014]    In a further development of this method, it is proposed that the welding of the insulating element to the motor housing is effected by means of laser transmission welding. This is a proven process for joining plastic parts together. For this purpose, the housing material consists of a material transparent to laser light, while the insulating element consists of a material which absorbs the laser light. The insulating element is preferably welded to the motor housing via preferably three welding regions. At least in a pre-assembly state, a circumference described by the outer contours of the insulating element is greater than the inner diameter of the motor housing in the welding region. This results in a press fit between the motor housing and the insulating element. 
         [0015]    A laser beam directed from the outside onto the motor housing penetrates it in only slightly weakened condition, and hits the welding region of the insulating element, where it is largely absorbed, thus heating the welding region and the adjacent motor housing until the plastic material melts. Due to the press fit, the motor housing and the insulating element move slightly towards one another in the welding region and closely join each other. In order to establish a good welded connection, the entire area, in which the welding partners are abutted against each other, must be heated. For this purpose, the width of the welding region is adapted to the diameter, in particular the effective diameter, of the laser beam. 
         [0016]    Alternatively to the use of plastic materials with different transmission properties, it is also possible to use the same semi-transparent materials, which are irradiated with one or more laser beam(s) concentrated on the welding region. Since the motor housing must not be melted on the surface, the intensity of the laser beam or the laser beams should be significantly lower in this area than in the welding area. For this purpose, it is proposed that a plurality of beam bundles coming from different directions overlap in the welding region. 
         [0017]    It is aimed at holding the stator laminate package by means of the insulating elements under axial pretensioning. As a result, any extensions or shrinking of the stator lamination relative to the motor housing caused by temperature fluctuations can be compensated for. 
         [0018]    In order to be able to absorb large axial forces, at least one of the insulating elements should be welded to the motor housing completely or over a large circumferential area or over large peripheral areas. 
         [0019]    Preferably, the insulating element, which is in axial contact with the circuit board, should be welded to the motor housing completely or over a large peripheral area or over large peripheral areas. This ensures that the printed circuit board is clamped and held axially securely by the insulating element. The centering is preferably effected via the carrier plate. 
         [0020]    The invention also comprises pump motors, in particular centrifugal pump motors, with the described characteristics and configurations. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0021]    The invention is better understood by reading the following Detailed Description of the Preferred Embodiments with reference to the accompanying drawing figures, in which like reference numerals refer to like elements throughout, and in which: 
           [0022]      FIG. 1  is a sectional view of an electric motor according to the invention; 
           [0023]      FIG. 2  is a second sectional view of the electric motor according to the invention; 
           [0024]      FIG. 3  is a sectional view through an insulating element; 
           [0025]      FIG. 4  is a front view of the insulating element; 
           [0026]      FIG. 5  is a side view of the insulating element; 
           [0027]      FIG. 6  is a spatial representation of the insulating element; 
           [0028]      FIG. 7  is a rear view of the insulating element; 
           [0029]      FIG. 8  is a stator of the electric motor; 
           [0030]      FIG. 9  is an enlarged detail A of  FIG. 8 ; and 
           [0031]      FIG. 10  is a spatial representation of the electric motor. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0032]    In describing preferred embodiments of the present invention illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the invention is not intended to be limited to the specific terminology so selected, and it is to be understood that each specific element includes all technical equivalents that operate in a similar manner to accomplish a similar purpose. 
         [0033]      FIG. 1  shows a sectional view of an electric motor  1  according to the invention, with a wound stator  4 , a permanent magnet rotor  2 , a containment shell  3 , a pump head  11 , a printed circuit board  20 , a carrier plate  14  and a motor housing  10 . The stator  4 , the circuit board  20  and the carrier plate  14  are located in a dry space  25  (see  FIG. 2 ). The permanent magnet rotor  2  is rotatably mounted in a wet space  26  (see  FIG. 2 ) about an axis  49 , which, on the one hand, is fixed in the containment shell  3  and, on the other hand, in the pump head  11 . The stator  4  comprises a stator laminate package  38  and insulating elements  6 . A stator winding  40  (see  FIG. 8  and  FIG. 9 ) is not shown here. The stator laminate package  38  comprises a closed magnetic return ring  39  with radially inwardly extending poles  45 , which alternate with grooves, into which groove lining regions  17 ,  18  of the insulating elements  5 ,  6  are inserted. The insulating elements  5 ,  6  have axial covers  54  and  55 , respectively, which axially cover the magnetic return ring  39 . Fastening projections  7 ,  8  extend from the insulating elements  5 ,  6  in radial direction. The fastening projections  7 ,  8 , also referred to as attachment projections have welding regions  36 ,  37 , in which they are firmly connected to the motor housing  10 . 
         [0034]    The stator  4  is attached to the motor housing  10  via the insulating elements  5 ,  6  such that the stator laminate package  38  and the stator winding  40  ( FIGS. 8 and 9 ) are axially fixed. The second insulating element  6  is equipped with axially inserted winding connections  53 , which are mechanically and electrically connected to the printed circuit board  20  as press-fit contacts. The stator  4  is largely decoupled from the containment shell  3 . An insulating element  6  on the side of the circuit board comprises axial projections  9 , which axially abut against the printed circuit board  20 . The printed circuit board  20  is positively fixed between the axial projections  9  and the carrier plate  14 . The carrier plate  14  has a stop surface  19 , which serves the purpose of axially fixing the printed circuit board  20 . On the opposite side, the carrier plate  14  abuts against a bottom  34  (see  FIG. 2 ) of the motor housing  10 . Furthermore, the carrier plate  14  comprises radial limiting means  21 , which limit the radial mounting space of the printed circuit board  20 . 
         [0035]      FIG. 2  shows a second sectional view of the electric motor  1  according to the invention, with the wound stator  4 , the permanent magnet rotor  2 , the containment shell  3 , the pump head  11 , the circuit board  20 , the carrier plate  14  and the motor housing  10 . The containment shell  3  has a containment shell flange  22  and the pump head  11  has a pump head flange  23 . The motor housing  10  is of a pot-like design and has a housing flange  24  and a connector shaft  29 . The pump head flange  23 , the containment shell flange  22  and the housing flange  24  have fastening eyes  27  with screws  28 , by means of which the pump head  11  and the containment shell  3  are screwed to the motor housing  10 . On the other side of the containment shell flange  23 , O-rings  30  are arranged as sealing elements. The printed circuit board  20  is equipped with a plurality of SMD components. Larger components, such as an electrolytic capacitor  31  and an induction coil  32 , are mechanically held on the carrier plate  14 , but are electrically contacted on the printed circuit board  20 . The circuit board  20  and the carrier plate  14  are axially fixed between the stator  4  and the motor housing  10 . The printed circuit board  20  is fixed axially and radially between the stator  4  and the carrier plate  14 . A contact element  33 , which is likewise electrically connected to the circuit board  20 , is mechanically received in the carrier plate  14 . A bottom  34  of the pot-like motor housing  10  has a bulge  35 , which is adapted to the shape of the electrolytic capacitor  31 . A pump impeller  16  is shown, which is integrally formed with a hollow shaft  12 . The impeller  16  has a cover disc  52 . The permanent magnet rotor  2  with pump impeller  16  is rotatably mounted on the axis  49  via a fixed bearing  46  and a spherical sliding bearing  47  and between the pump head  11  and the containment shell  3 . The spherical bearing  47  abuts against a spherical counter bearing  48 . The fixed bearing  46  is arranged between a hollow-cylindrical permanent magnet  15 , which is made of a plastic-bound material and injected around the hollow shaft  12 , and the axis  49 . The fixed bearing  46  bears the impeller  16  radially as well as axially via the end of the hollow shaft  12  and a thrust washer  51 , which abuts against a bearing-receiving sleeve  13  integrally formed with the containment shell  3 . Further,  FIG. 2  shows the wet space  26 , the dry space  25 , a stator laminate package  38 , and the insulating elements  5 ,  6 . A stator winding  40  (see  FIG. 8  and  FIG. 9 ) is not shown here. The pump head  11  comprises a suction port  41  and a pressure connection port  42 . In the suction port  41 , spokes  43  create a permeable connection between the suction port  41  and the receptacle  50 . 
         [0036]      FIG. 3  shows a sectional view through the first insulating element  5 , with a fastening projection  7 , which is integrally formed with a ring section  58  via a bridge section  56  and has a welding area  36 . The annular sections  58  are partially separated from one another by means of clearances  61 . The groove lining regions  17  adjoin the annular sections  58 , which have axially projecting winding head retaining projections  57  in their central inner region. The groove lining regions  17  have wire guide grooves  60  on their outwardly pointing surface, which ensure an ordered wire laying. The bridge section  56  is dimensioned in such a way that it permits an anticipated thermal expansion compensation. For this purpose, the bridge sections  56  extend at an angle of approximately 45°+−15° with respect to the motor axis and are of a smaller width than the fastening projections  7 . 
         [0037]      FIG. 4  shows a front view of the first insulating element  5 , the groove lining areas  17 , which also cover the front face of the poles, the winding head holding projections  57 , the ring sections  58 , the clearances  61 , the fastening projections  7  with their welding areas  36  and the bridge sections  56 . In the example shown, three fastening projections  7  are provided; they protrude radially over the annular sections  58  and prevent large-area contact between the insulating elements  5  and thus between the stator and the motor housing. 
         [0038]      FIG. 5  shows a side view of the first insulating element  5 , with the groove lining areas  17 , the ring sections  58 , the clearances  61  and the fastening projections  7 , with their welding areas  36  and the bridge sections  56 . 
         [0039]      FIG. 6  shows a three-dimensional representation of the first insulating element  5 , with the groove lining areas  17 , with their wire guide grooves  60 , the winding head holding projections  57 , the fastening projections  7 , with their welding areas  36 , the ring sections  58 , the clearances  61  and the bridge sections  56 . 
         [0040]      FIG. 7  shows a rear view of the first insulating element  5 , with the groove lining areas  17 , the cover disc  55 , the fastening projections  7 , with their welding areas  36  and the bridge sections  56 . 
         [0041]      FIG. 8  shows the stator  4  of the electric motor  1 , which is fixed in the motor housing  10 , with the first insulating element  5 , the second insulating element  6 , the stator laminate package  38 , the printed circuit board  20  and the carrier plate  14 . The stator laminate package  38  comprises the magnetic return ring  39 , which is axially covered by the first cover disc  54  of the first insulating element  5  and by the second cover disc  55  of the second insulating element  6 . The first insulating element  5  is shown with a fastening projection  7 , the bridge  56  and the welding region  36 . The first insulating element  5  is connected to the motor housing  10  firmly but compliantly via the welding region  36 . The yielding effect can provide both radial and axial thermal expansion compensation. Furthermore, the first insulating element  5  has the groove lining regions  17 , the annular sections  58  and the clearances  61 , carries the winding  40  and insulates the latter from the stator laminate package  38 . The winding  40  is electrically connected to the printed circuit board  20  via winding connections  53 . In the example shown, the second insulating element  6  has fastening projections  8 , which are connected to the second insulating element  6  without compliant bridge sections  56 . Alternatively, however, compliant bridge sections  56  can also be provided here. The second insulating element  6  is integrally formed with a wire laying ring  59 , which receives connecting wires, which are laid between the individual windings. 
         [0042]    The motor housing  10  comprises the containment shell flange  22 , the bottom  34  and the connector shaft  29 . The carrier plate  14  receives the electrolytic capacitor  31  and the induction coil  32  and, on the one hand, is supported on the bottom  34  of the motor housing  10  and, on the other hand, on the printed circuit board  20 . The printed circuit board  20  is accommodated axially between the axial projection  9  and the carrier plate  14 . The fastening projections  7  of the first insulating element  5  and the fastening projections  8  of the second insulating element  6  describe an outer circle whose diameter in a pre-assembly state is greater than the inner diameter of the motor housing  10  at the respective connection point. Since the motor housing  10  tapers slightly towards the bottom  34  for injection-molding reasons, the said diameters are not identical. A press connection exists between the motor housing  10  and the fastening projections  8  and  9  after assembly, but before welding. This is at least partially attenuated by the welding process. 
         [0043]      FIG. 9  shows an enlarged detail A from  FIG. 8 , with the motor housing  10 , the stator laminate package  38 , the magnetic return ring  39 , the first insulating element  5  and the winding  40 . The insulating element  5  is illustrated with the first cover disc  54 , the fastening projection  7 , with its welding region  36 , the bridge part  56  and the annular part  58 . Furthermore, the containment shell flange  22  is shown. 
         [0044]      FIG. 10  shows a three-dimensional view of the electric motor  1 , with the pump head  11 , with the suction port  41  and pressure port  42  and a pump head flange  23 , a containment shell flange  22  integral with the containment shell  3 , the motor housing  10  with the housing flange  24 , the bottom  34 ,  29  and the bulge  35  for receiving an electrolytic capacitor  31 . Furthermore, fastening eyes  27  can be seen, which are designed as extensions in the pump head flange  23 , the containment shell flange  22  and the housing flange  24  and allow a screw connection. On the motor housing  10 , an axial securing shape  44  is formed, which serves the purpose of axially securing an annular fastening device arranged around the motor housing  10 . 
         [0045]    It is to be understood that the present invention is not limited to the illustrated embodiments described herein. Various types and styles of user interfaces may be used in accordance with the present invention without limitation. Modifications and variations of the above-described embodiments of the present invention are possible, as appreciated by those skilled in the art in light of the above teachings. It is therefore to be understood that, within the scope of the appended claims and their equivalents, the invention may be practiced otherwise than as specifically described. 
       LIST OF REFERENCE SYMBOLS 
       [0046]      
         [0000]    
       
         
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 1  
                 electric motor 
               
               
                   
                 2  
                 permanent magnet rotor 
               
               
                   
                 3  
                 containment shell 
               
               
                   
                 4 
                 stator 
               
               
                   
                 5  
                 first insulating element 
               
               
                   
                 6  
                 second insulating element 
               
               
                   
                 7 
                 first fastening projection 
               
               
                   
                 8  
                 second mounting peojection 
               
               
                   
                 9  
                 axial projection 
               
               
                   
                 10  
                 stator housing 
               
               
                   
                 11  
                 pump head 
               
               
                   
                 12 
                 hollow shaft 
               
               
                   
                 13  
                 bearing-receiving sleeve 
               
               
                   
                 14  
                 carrier plate 
               
               
                   
                 15  
                 permanent magnet 
               
               
                   
                 16  
                 pump impeller 
               
               
                   
                 17  
                 first groove lining area 
               
               
                   
                 18 
                 second groove lining area 
               
               
                   
                 19 
                 stop surface 
               
               
                   
                 20 
                 circuit board 
               
               
                   
                 21 
                 radial limiting means 
               
               
                   
                 22 
                 containment shell flange 
               
               
                   
                 23  
                 pump head flange 
               
               
                   
                 24  
                 housing flange 
               
               
                   
                 25  
                 dry space 
               
               
                   
                 26 
                 wet space 
               
               
                   
                 27  
                 fastening eye 
               
               
                   
                 28  
                 screw 
               
               
                   
                 29  
                 connector shaft 
               
               
                   
                 30 
                 O-ring 
               
               
                   
                 31  
                 electrolytic capacitor 
               
               
                   
                 32 
                 inductor coil 
               
               
                   
                 33  
                 contact element 
               
               
                   
                 34  
                 bottom 
               
               
                   
                 35  
                 protrusion 
               
               
                   
                 36  
                 first welding area 
               
               
                   
                 37  
                 second welding area 
               
               
                   
                 38  
                 stator laminate package 
               
               
                   
                 39  
                 magnetic return ring 
               
               
                   
                 40  
                 stator winding 
               
               
                   
                 41  
                 suction port 
               
               
                   
                 42  
                 pressure port 
               
               
                   
                 43  
                 spoke 
               
               
                   
                 44  
                 axial securing shape 
               
               
                   
                 45  
                 pole 
               
               
                   
                 46  
                 fixed bearing 
               
               
                   
                 47  
                 spherical sliding bearing 
               
               
                   
                 48 
                 spherical counter bearing 
               
               
                   
                 49  
                 axis 
               
               
                   
                 50  
                 intake 
               
               
                   
                 51  
                 stop disk 
               
               
                   
                 52 
                 cover disc 
               
               
                   
                 53  
                 winding connection 
               
               
                   
                 54  
                 first cover disc 
               
               
                   
                 55  
                 second cover disc 
               
               
                   
                 56  
                 bridge section 
               
               
                   
                 57  
                 winding head holding projection 
               
               
                   
                 58  
                 ring section 
               
               
                   
                 59  
                 wire laying ring 
               
               
                   
                 60  
                 wire guide groove 
               
               
                   
                 61  
                 clearance