Abstract:
Electrical contact arrangement for an electric motor and method for producing same. The present invention relates to an electrical contact arrangement for an electric motor, in particular for an EC drive of a motor vehicle fan, comprising an elongate contact which runs perpendicular to a planar basic conductor, wherein the basic conductor is in the form of a leadframe, and a conductive cohesive and/or form-fitting and/or force-fitting connection is provided between the leadframe and the contact. The present invention also relates to a method for the production of said electrical contact arrangement.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to an electrical contact arrangement for an electric motor and a method for the production thereof. 
       TECHNICAL BACKGROUND 
       [0002]    Electrical contact arrangements for electric motors exist in a wide range of variants and embodiments. In this case, the type of contact arrangements required depends inter alia on the construction of the electric motor. 
         [0003]    In the case of brushless direct current machines, known as EC (electronically commutated) motors or also referred to as BLDC (brushless DC) or BL motors, what are known as phase contacts are required. Said contacts usually extend perpendicularly from a base conductor (a circuit board or a lead frame) on which the power electronics necessary for activating the motor are often provided. In a contact arrangement known to the applicant, the phase contacts are perpendicularly soldered to a circuit board as an SMD (surface-mounted device) component. In another contact arrangement known to the applicant, the phase contacts are formed in one piece from a lead frame and are angled perpendicularly thereto. 
         [0004]    A further contact arrangement is described in the international patent application WO 2009/112097 A1. According thereto, a pin extends through a conductor and rests on the surface of the conductor by means of a shoulder. 
         [0005]    All of these contact arrangements can in each case be provided individually for specific power classes. 
       SUMMARY OF THE INVENTION 
       [0006]    Against this background, the object of the present invention is that of specifying an improved contact arrangement. 
         [0007]    According to the invention, this object is achieved by a contact arrangement having the features of claim  1  and/or by a method having the features of claim  11 . 
         [0008]    According thereto, the following is provided. 
         [0009]    An electrical contact arrangement for an electric motor, in particular for an EC drive of a motor vehicle fan, comprising an elongate contact which extends perpendicularly to a planar base conductor, characterised in that the base conductor is formed as a lead frame and in that a conductive integral and/or positive and/or non-positive connection is provided between the lead frame and the contact. 
         [0010]    A method for producing an electrical contact arrangement, in particular a contact arrangement according to the invention, comprising the steps of: providing a flat lead frame and an elongate contact; arranging the contact perpendicularly to the lead frame; producing a conductive integral and/or positive and/or non-positive connection between the contact and the lead frame. 
         [0011]    The concept on which the present invention is based consists in attaching a (phase) contact to a lead frame by means of an integral and/or positive and/or non-positive 90° connection. In this way, it is possible to use a universal lead frame in phase contacts and to interconnect said contacts in the modular system. Individual parts can advantageously be produced thereby in large quantities and more economically on account of economies of scale. 
         [0012]    Moreover, a consistent manufacturing process for different power classes, in particular for all power classes of motor vehicle fan drives, is provided thereby, as a result of which synergies can be better used when producing the different power classes. 
         [0013]    Advantageous embodiments and developments are found in the further dependent claims and in the description, with reference to the drawings. 
         [0014]    In one embodiment, the conductive connection comprises at least one plug extension on the contact and at least one recess on the lead frame, which recess corresponds to the plug extension, the plug extension being fastened in the recess by means of a press fit. A press fitting process is preferably used for fastening, the recess preferably being present in the form of a hole and the plug extension preferably having a rectangular cross-sectional area. As a result, the corners of the cross-sectional area of the plug extension are slightly deformed during the press fitting process, as a result of which a non-positive connection occurs between the plug extension and the recess of the lead frame. Alternatively, however, it is also conceivable to provide a classic cylindrical press fit. 
         [0015]    In a further embodiment, the conductive connection comprises a fork formed in a planar manner in the lead frame, in which fork the contact is introduced and fastened. The contact is preferably staked in the fork. During staking, a permanent positive, non-positive and in addition in part integral connection is produced. In the process, the fork is fused on and shaped using pressing force and heat. As an alternative to staking, a soldered joint or a classic welded joint, for example by means of laser beam welding or resistance welding, would also be conceivable. 
         [0016]    In an advantageous embodiment, the fork is formed in one piece with the lead frame and comprises a strut, by means of which said fork is connected to the lead frame. Thus, advantageously, no further fastening means are required for attaching the contact to the lead frame. 
         [0017]    In a preferred embodiment, the strut is double-angled in a Z-shape. Optionally or in addition, the fork is arranged in parallel with the lead frame. The Z-shaped angling of the strut achieves an offset between the plane of the lead frame and the plane of the fork, as a result of which the accessibility of the fork for the fastening process, in particular the staking process, is improved. In the Z-shape, the bends can also be right-angled. The parallelism of the fork relative to the lead frame is preferred in this embodiment, since a perpendicular orientation of the contact to the lead frame is automatically achieved thereby. As an alternative to a spacing by means of a strut angled in a Z-shape, it would also be conceivable to provide an enlarged recess in the lead frame around the region of the fork, such that the fork can be reached by means of a tool in order to connect the fork to the contact. 
         [0018]    In a further embodiment, the conductive connection has a contact foot angled perpendicularly away from the contact. Said foot extends in parallel with the lead frame and is welded on the surface thereof. A connection surface is thus advantageously provided on the contact, in which a preferred orientation of the contact is already provided perpendicularly to the lead frame. In order to weld the contact foot onto the lead frame, a projection welding method is preferably used, in which a bulge-like extension is provided on the contact foot and the contact foot is welded on by means of resistance welding. The bulge-like extension provides a punctiform resting point, which results in only a very small resting surface of the bulge on the lead frame. The resistance of the transition is thus increased, with the result that the material of the contact foot, which preferably contains copper, can be more easily melted on in order to produce a welded joint. After welding, a very large contact surface between the contact and the lead frame is then advantageously available, which surface is in particular larger than the mathematical sectional surface area between the geometries of the contact and the lead frame. As an alternative to projection welding, it would also be conceivable to connect the contact foot to the lead frame by means of a different resistance welding method, a laser beam welding method, an MIG (metal inert gas) welding method, a soldering method or the like. Moreover, a connection by means of a fastener would also be conceivable, for example by means of a rivet driven through the contact foot and the lead frame. 
         [0019]    In one embodiment, the contact foot is guided through the lead frame and makes contact with the lead frame at the side of said foot which is oriented towards the contact. The side oriented towards the contact corresponds to the side which is oriented towards the extension direction of the contact. Advantageously, in particular tensile loads in the extension direction of the contact can thus be particularly well absorbed. Moreover, the connection point is thus shielded from the electric motor. This can be advantageous in particular in the case of an over-moulded lead frame, in which the surface provided for making contact is left free of the overmould. The overmould is formed as a plastics layer and is designed and provided for the purpose of corrosion protection and for insulation of the lead frame. The non-insulated contact point is then advantageously provided on the protected rear side of the lead frame. 
         [0020]    In a further embodiment, the contact foot is brought into contact vertically on the lead frame at the side of said foot which is oriented away from the contact. In this case, the “sole” of the contact foot, i.e. the side of the contact foot which is oriented away from the extension direction of the contact, stands on the lead frame. Advantageously, the contact foot can thus be freely positioned on the lead frame, the perpendicular angle always being maintained. Moreover, no opening is required in the lead frame. 
         [0021]    In a further embodiment, the conductive connection comprises a tab formed in the lead frame and having a back which is positioned perpendicularly to the lead frame and two tab wings which are angled perpendicularly to the back. In this case, the contact is introduced into the tab between the tab wings and fastened therein, in particular staked. The tab advantageously provides a fastening guide which is oriented perpendicularly to the plane of the lead frame and which particularly advantageously provides a very large contact surface between the contact and the lead frame, which surface is in particular greater than the mathematical sectional surface area between the geometries of the contact and the lead frame. In this case, the tab wings and the back surround the contact in a U-shape. However, the staking also preferably closes the open side of the U-shape, with the result that the contact is surrounded, in particular completely surrounded. Of course, the above-mentioned alternative connection processes, which can be used as alternatives to staking, are also possible in this case. 
         [0022]    In a preferred embodiment, the tab is formed in one piece with the lead frame and comprises a strut which is connected to the back and by means of which said tab is connected to the lead frame. Particularly preferably, the tab can also be formed, in the unfolded surface thereof, during the lead frame production process. Subsequently, said tab is made into the final shape thereof by means of a shaping process. Advantageously in this case, the tab is already connected to the lead frame by means of the strut, with the result that no additional connection techniques are required. The production process for forming the tab is described in further detail below. 
         [0023]    In one embodiment of the method for producing an electrical contact arrangement, the connection between at least one plug extension formed on the contact and at least one recess provided in the lead frame is produced by means of a press fit. The press fitting method which has already been described above is preferably used in this case. A connection is thus produced without application of heat being required therefor. Moreover, no additional auxiliary materials (solder, flux, Sil-fos or the like) are required. Moreover, in this case the contour of the contact attached to the tool is advantageously provided directly, without any additional bending process. 
         [0024]    In a further embodiment of the method, the connection is produced using a fork, which is formed flat in the lead frame and comprises a strut by means of which said fork is connected to the lead frame, by means of the following steps: doubled, in particular Z-shaped, angling of the strut such that the fork is arranged so as to be spaced apart from and in parallel with the lead frame; introducing the contact into the fork; staking the fork and the contact. A particular advantage of this embodiment is that an annular contact can thus be attached and/or connected to the lead frame by means of very simple welding. Advantageously, in this case the contour of the contact attached to the tool can be provided without any additional bending process. In this case, the fork is preferably formed such that the contact can be inserted in the fork with a clearance fit prior to staking, so that the insertion is advantageously simple to carry out. During staking of the fork and the contact, a positive, non-positive and in addition in part also integral connection is preferably provided. For this purpose, a hot crimping tool is placed on the fork for example, by means of which tool heat and a pressing force can be simultaneously transferred to the fork. In the process, the material of the fork fuses and/or melts on in part and is simultaneously shaped in order to fasten the contact. 
         [0025]    In a further embodiment of the method, the connection is produced using a contact foot, which is formed on the contact and is perpendicularly angled thereto and extends in parallel with the lead frame, by means of the following steps: guiding the contact foot through an opening in the lead frame and placing the surface of the contact foot oriented towards the contact on the lead frame, or positioning the surface of the contact foot oriented away from the contact on the lead frame; welding, in particularly projection welding, the contact foot onto the lead frame. The contact can in particular be an annular contact element which has been shaped flat and has been angled in the region of the contact foot. The annular contact element is thus connected to the lead frame by means of a very large contact surface, as a result of which the connection obtains high mechanical stability and high electrical conductivity. Alternatively thereto, it would also be conceivable for the contact to have a rectangular cross-sectional area and for the contact foot to constitute merely an angled portion of the contact. In the first alternative of the method (guiding through), it is advantageous that the connection can absorb high tensile forces in the extension direction of the contact. In the second alternative of the method (positioning) it is particularly advantageous that the contact can be welded to the lead frame by means of a large contact surface without an opening in the lead frame. 
         [0026]    In a further embodiment of the method, the connection is produced using a tab, which is formed in one piece in the lead frame and comprises a back, in particular also a strut connected to the back, by means of which strut the tab is connected to the lead frame, and two tab wings which are angled perpendicularly to the back, by means of the following steps: positioning the back perpendicularly relative to the lead frame; angling the tab wings perpendicularly relative to the back; introducing the contact into the tab between the tab wings; staking the tab and the contact. When perpendicularly angling the tab wings relative to the back, a gap is preferably provided between the tab wings which are angled in the same direction, in which gap the contact can be inserted with a clearance fit. When staking the tab to the contact, a positive, non-positive and also at least in part integral connection is then produced between the tab and the contact. This connection technique also achieves a contact surface between the lead frame and the contact which is very large compared with the cross-sectional area of the contact, while also having a simple contact geometry, which provides an improved connection in terms of the mechanical strength and the electrical conductivity. 
         [0027]    The above embodiments and developments can be combined as desired, as far as this is reasonable. Further possible embodiments, developments and implementations of the invention also comprise combinations, not explicitly stated, of features of the invention described above or in the following, with reference to the embodiments. In particular, in this case, a person skilled in the art would also add individual aspects as improvements or supplements to the respective basic configurations of the present invention. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0028]    The present invention will be described in greater detail in the following, on the basis of the embodiments shown in the schematic figures, in which: 
           [0029]      FIG. 1  is a perspective front view of an electrical contact arrangement in the press fitted design; 
           [0030]      FIG. 2  is a perspective front view of an electrical contact arrangement comprising a fork formed in the lead frame; 
           [0031]      FIG. 3  is a perspective front view of a first variant of an electrical contact arrangement comprising a contact foot formed on the contact; 
           [0032]      FIG. 4  is a perspective view from below of a second variant of an electrical contact arrangement comprising a contact foot formed on the contact; 
           [0033]      FIG. 5 a    is a perspective front view of an electrical contact arrangement comprising a tab formed in the lead frame; 
           [0034]      FIG. 5 b    is a plan view of the tab formed in the lead frame, in an unfolded state. 
       
    
    
       [0035]    The accompanying drawings are intended to provide better understanding of the embodiments of the invention. The drawings show embodiments and, together with the description, explain principles and concepts of the invention. Other embodiments and many of the mentioned advantages can be found in the drawings. The elements of the drawings are not necessarily shown to scale relative to one another. 
         [0036]    In the drawings, elements, features and components which are identical, function in the same manner and have the same effect are, if not specified otherwise, provided with the same reference numerals in each case. 
       DESCRIPTION OF EMBODIMENTS 
       [0037]      FIG. 1  is a perspective front view of an electrical contact arrangement  1  in the press fitted design. The electrical contact arrangement  1  comprises a lead frame  3  and a contact  2 . The lead frame  3  is an insert-moulded lead frame, the base material being a conductive metal, in particular copper, preferably E-Cu, and this conductive layer being over-moulded with a plastics casing (not shown). The contact is also a conductive material, in particular copper, preferably E-Cu. In the embodiment shown, a conductive connection  4  comprises two plug extensions  5  on the contact  2 , which extensions each have a square cross-sectional area. In addition, two recesses  6 , designed so as to correspond to the plug extensions  5 , are provided in the lead frame  3 . In the embodiment shown, said recesses are holes or annular holes. Any plastics casing is omitted in the region of the connection  4 . 
         [0038]    In order to fasten the contact  2  to the lead frame  3 , the plug extensions  5  are pressed into the recesses  6 . A non-positive connection is thus produced between the lead frame  3  and the contact  2 , the material of the contact  2  and/or of the lead frame  3  being deformed in the region of the corners of the plug extensions  5  and thus a normal force being exerted on the contact surface, as a result of which a friction fit is produced. The connection thus consists in a non-positive fit at the contact surfaces, between the contact  2  and the lead frame  3 . 
         [0039]      FIG. 2  is a perspective front view of an electrical contact arrangement  1  comprising a fork  11  formed in the lead frame  3 . For this purpose, the lead frame  3  is already formed in the same plane as the fork  11  integrated therein during punching out. The fork  11  comprises two fork extensions  13 ,  13 ′ and a strut  12 . In the unprocessed state (not shown) of the lead frame  3 , the fork  11  extends in the plane of the lead frame  3 , the strut  12  extending flat and the fork extensions  13 ,  13 ′ likewise extending flat and so as to be spaced apart from one another in the plane of the lead frame  3 . Subsequently, the strut  12  of the fork  11  is bent twice, into a Z-shape, in the manner shown in  FIG. 2 , such that the fork  11  extends in a plane which is in parallel with the plane of the lead frame  3 . This serves to improve accessibility of the fork  11  by a staking tool. The Z-bends are preferably right-angled bends. 
         [0040]    By means of a fork  11  of this kind, a contact  2 , in particular an annular contact, which extends perpendicularly to the plane of the lead frame  3 , can be fastened to the lead frame  3  at a 90° angle. For this purpose, the contact  2  is introduced between the two fork extensions  13 ,  13 ′. Subsequently, the fork  11 , in particular the fork extensions  13 ,  13 ′, is/are heated and crimped by means of a staking tool, such that a positive, non-positive and also at least in part integral connection is then produced between the contact  2  and the fork  11 . The state shown in  FIG. 2  is thus achieved, in which state the contact  2  is fastened in the fork  11  by means of staking and thus a conductive connection  4  is produced between the contact  2  and the lead frame  3 . 
         [0041]      FIG. 3  is a perspective front view of a first variant of an electrical contact arrangement  1  comprising a contact foot  21  formed on the contact  2 . The contact  2  is designed as an annular contact and is arranged at a 90° angle to the lead frame  3 . The contact foot  21  is formed on a flattened end of the annular contact  2  and is angled perpendicularly to the extension direction  22  of the contact  2 . The contact foot  21  comprises a side  23  which faces the contact and/or the extension direction  22  of the contact  2 , and a side  24  which is remote from the contact and/or the extension direction thereof. In the embodiment shown, the contact  2  is positioned having the remote side  24 , which forms the sole of the contact foot  21 , as it were, on the lead frame  3 . The electrically conductive connection  4  between the contact foot  21  and the lead frame  3  is produced by welding the contact foot  21  onto the lead frame  3 . Particularly preferably, a projection welding method is used for this purpose. Alternatively thereto, a different resistance welding method, a laser beam welding method, or a soldering method can also be used to integrally connect the contact foot  21  to the lead frame  3 . Preferably, in the process, the remote side  24  is welded to the lead frame over a large surface area, such that a large contact surface is produced which has high mechanical strength and high electrical conductivity. 
         [0042]      FIG. 4  is a perspective view from below of a second variant of an electrical contact arrangement  1  comprising a contact foot  21  formed on the contact  2 . In this case, the contact  2  extends perpendicularly to the plane of the lead frame  3  and comprises a contact foot  21  formed in a similar manner to the contact foot  21  shown in  FIG. 3 . Differently from the arrangement shown in  FIG. 3 , in the embodiment shown the contact foot  21  is guided through the lead frame  3  via a recess  25  in the lead frame  3  and fastened to the rear side of the lead frame  3 . For this purpose, the side  23  of the contact foot  21  which faces the contact  2  and/or the extension direction  22  of the contact  2  rests on the lead frame  3  and is welded thereto over a large surface area. Similarly to the embodiment described with reference to  FIG. 3 , here too a wide range of joining techniques can be used, a projection welding process preferably being used. The recess  25  through which the contact foot  21  is guided is preferably already made when punching the lead frame  3 , meaning that no additional manufacturing step is required therefor. 
         [0043]      FIG. 5 a    is a perspective front view of an electrical contact arrangement comprising a tab  31  formed in the frame. In this embodiment, the contact  2 , which is designed as an annular contact, is likewise oriented perpendicularly to the lead frame  3 . The tab  31  is formed in one piece with the lead frame  3  and is produced integrally during the process of producing the lead frame  3 . For this purpose, an unfolded surface of the tab  31  is also punched out when punching the lead frame  3  and is subsequently bent into a tab  31  by means of shaping. The tab  31  comprises two tab wings  33 ,  33 ′, a back  32  and a strut  34 . The strut  34  is connected to the back  32  and to the remainder of the lead frame  3 . The back  32  is angled perpendicularly to the strut  34  and extends in parallel with the contact  2 . The tab wings  33 ,  33 ′ are angled in the same direction, again perpendicularly to the back, and likewise extend in parallel with the contact  2 . In order to produce an electrically conductive connection  4  between the lead frame  3  and the contact  2 , the contact  2  is introduced into the tab  31  between the tab wings  33 ,  33 ′. For this purpose, the tab wings  33 ,  33 ′ are preferably provided at a spacing from one another which is greater than the diameter of the contact  2 , such that the contact  2  can be introduced easily into the tab  31  with a clearance fit. Subsequently, the tab wings  33 ,  33 ′ and/or the tab  31  are staked to the contact  2 , the tab wings  33 ,  33 ′ in particular being shaped. A non-positive and positive, and in part integral, connection is thus produced between the contact  2  and the tab  31 . 
         [0044]    Due to the fact that, in the fully assembled state, the tab mostly, or preferably even completely, surrounds the contact  2 , a particularly large contact surface between the contact  2  and the lead frame  3  is provided, as a result of which the mechanical stability of the connection  4  and the electrical conductivity are advantageously relatively high. 
         [0045]      FIG. 5 b    is a plan view of the lead frame  3  and the tab  31  according to  FIG. 5 a    in an unshaped and unfolded state. This unfolded state corresponds to an unprocessed state, which exists before the tab  31  is shaped. In order to produce the tab  31 , this folded shape is formed during punching of the lead frame  3 . In this case, the strut  34 , the back  32  and the tab wings  33 ,  33 ′ are arranged in a plane together with the remainder of the lead frame  3 . In order to form the tab  31 , initially the back  32  is then bent perpendicularly relative to the strut  34  along a first bending line  35 , such that the back  32  extends perpendicularly from the plane of the lead frame  3 . Subsequently, the tab wings  33 ,  33 ′ are angled perpendicularly relative to the back  32  along second bending lines  36 , both tab wings  33 ,  33 ′ being angled away from the strut  34  in the same direction. A U-shape of the tab  31  is thus produced, which tab is oriented perpendicularly to the plane of the lead frame  3 . In order to connect the contact  2  to the lead frame  3 , the contact  2  is introduced into the tab  31  between the tab wings  33 ,  33 ′, perpendicularly to the lead frame  3 . Subsequently, said contact is fastened to the tab  31  as described with reference to  FIG. 5   a.    
         [0046]    Although the present invention has been fully described above on the basis of preferred embodiments, it is not restricted thereto but rather can be modified in a wide variety of ways. 
       LIST OF REFERENCE NUMERALS 
       [0047]      1  Contact arrangement 
         [0048]      2  Contact 
         [0049]      3  Base conductor, lead frame 
         [0050]      4  Connection 
         [0051]      5  Plug extension 
         [0052]      6  Recess 
         [0053]      11  Fork 
         [0054]      12  Strut 
         [0055]      13 ,  13 ′ Fork extensions 
         [0056]      21  Contact foot 
         [0057]      22  Extension direction of the contact 
         [0058]      23  Side facing the contact 
         [0059]      24  Side facing away from the contact 
         [0060]      25  Recess 
         [0061]      31  Tab 
         [0062]      32  Back 
         [0063]      33 ,  33 ′ Tab wing 
         [0064]      34  Strut 
         [0065]      35  first bending line 
         [0066]      36  second bending lines