Abstract:
A connecting element between a motor and a control unit includes a flat base plate having electrical bushings and an, in particular centered, opening. The base plate further includes a shaft around the opening. A first seal is provided at the edge of the base plate and a second seal is provided at the upper edge of the shaft.

Description:
[0001]    This application claims priority under 35 U.S.C. §119 to German patent application no. DE 102011004919.3, filed Mar. 1, 2011 in Germany, the disclosure of which is incorporated herein by reference in its entirety. 
       BACKGROUND 
       [0002]    The present disclosure relates to a connecting element which can be inserted between a motor and a control unit, and to an assembly comprising the motor, the connecting element and the control unit. 
         [0003]    When developing motors, the size is an important property, in addition to the expected power output. In order to produce electric motors which are as small as possible, it has proven advantageous to at least partially physically separate the mechanical and electronic components. However, in order to produce a complete assembly comprising a motor and control unit, it is necessary to develop suitable connecting elements which allow these two elements to be combined. 
         [0004]    DE 10 2006 026 403 A1 discloses a circuit mount on which actuation electronics for an electric motor are mounted. In order to accommodate a bearing of the electric motor, the circuit mount has a deep-drawn receptacle in the center. Together with a cover over the circuit mount, this design forms an end plate of the electric motor, which end plate closes off the housing of the electric motor on one side. 
         [0005]    A further design of an electric motor with associated electronics is described in DE 10 2008 054 527 A1. In this design, the connection between the motor housing and the bearing plate which contains the electronics is achieved by means of welding or a shrink-fitting process. 
       SUMMARY 
       [0006]    When electric motors are used for a very wide variety of applications, various requirements to have to be met. In addition to thermal and vibrational loads, a high level of resistance to media also has to be provided. For example, in the event of corresponding use of the electric motors, for example as a steering motor in a steering system, care should be taken that the mechanical and electronic components are protected by suitable measures (solid and/or liquid sealing). Care should be taken that the necessary requirements in respect of the protective class are complied with, particularly at the interfaces between these components. 
         [0007]    The present disclosure describes a connecting element which is suitable for providing appropriate protection against the undesired ingress and/or propagation of media at an interface of the above kind in order to meet the desired requirements in respect of leaktightness. 
         [0008]    This is achieved by the connecting element, which is provided between the motor and the control unit, having at least two seals in order to efficiently impede any possible flow of media. In this case, the connecting element has a flat base plate in which electrical bushings and a shaft which is arranged around an opening are provided. While the electrical bushings are used to actuate the electric motor, the opening is required for the position sensor which is mounted on the rotor to pass through. Therefore, in order to achieve the required sealing, a first seal is provided which is arranged at the edge of the base plate, while a second seal is fitted at the upper edge of the shaft. 
         [0009]    Simple and efficient sealing can be achieved by these seals by virtue of the connecting element being positioned in an upper recessed region of the motor with subsequent mounting of the control unit. This sealing operation creates a barrier which makes it difficult or impossible for a liquid to enter the control unit via the motor. 
         [0010]    A further refinement of the disclosure in which not only the outer region around the base plate and the opening but also the electrical bushings are sealed off is particularly advantageous. To this end, the base plate is used as an IDC adapter plate, that is to say as a base plate with insulation-displacement and welded connections. In this case, a third seal is optionally used, said third seal being specially arranged in the region of the electrical bushings. One option for this seal is the use of molded seals, for example in the form of press-in seals. These molded seals can be introduced into the passage holes and be of flexible design, and therefore the electrical contact-making means can be inserted from the upper face and lower face of the base plate. However, as an alternative, the press-in seals can also be introduced together with one of the electrical contacts from the upper face or lower face and then be fixed. The electrical contact is then made from the electric motor to the base plate in the form of a welded or clamping contact and from the base plate to the control unit in the form of an insulation-displacement contact. 
         [0011]    In one development of the disclosure, the third seal projects beyond the base plate. In this case, provision can be made for the seal to be enclosed at least on one side of the base plate. A refinement of this kind can be used to ensure that a sufficient amount of material is introduced into the passage opening in order to achieve the desired sealing effect. 
         [0012]    It is particularly advantageous for the base plate to be of round or at least oval shape. The edge of the base plate can optionally also be formed as a bead. In contrast, it is also advantageous for the shaft to likewise be of round design. 
         [0013]    O-rings can be used for the seals if said base plate and/or shaft have/has a round or oval shape. Said O-rings can be placed directly on the edge regions of the base plate or of the shaft. However, provision may also be made for receptacles, for example in the form of beads or recesses, to be provided, these preventing the O-rings from slipping when they are mounted. 
         [0014]    Overall, the static seals according to the disclosure present a more robust alternative compared to dynamic seals. Furthermore, any losses in torque which may occur are avoided in comparison to dynamic seals. 
         [0015]    Further advantages can be found in the following description of exemplary embodiments. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  shows the customary assembly of an assembly comprising a motor, a connecting element and a control unit. 
           [0017]    In contrast,  FIG. 2  shows the assembly with the connecting element according to the disclosure. 
           [0018]      FIGS. 3   a  and  3   b  show a detailed illustration of the connecting element. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    Splitting the mechanical electric motor component and electronic control components into different elements makes it necessary to provide suitable connecting elements for connecting these components. 
         [0020]      FIG. 1  shows, by way of example, a possible design of an assembly according to the prior art comprising an electric motor  110  and a control unit  120 , in which design the control unit is at least partially recessed in the upper region of the electric motor and is screw-connected to said electric motor. A base plate  100  which has three contact elements  130  to  134 , for example for a three-phase electric motor, is used for the internal assembly. Electrical contact-connections between the control unit  120  and the electric motor  110  can be established through corresponding holes  140  in the base plate. An opening  105  is provided in the center of the base plate  100 , the rotor with the position sensor positioned on it passing through said opening. This rotor, as part of the shaft of the electric motor, is used, together with the position sensor which can obviously also be positioned in the control unit  120 , to establish the position of the rotor in order to control, in an optimum manner, start-up of the motor by means of actuation via the three phases. 
         [0021]    As can therefore be seen in  FIG. 1 , various ways (edge region of the base plate, central opening and passage opening in the contact-making means) for liquid which has entered to pass from the motor, along the shaft, to the connections of the control unit  120  are present between the electric motor  110  and the control unit  120 . 
         [0022]    Seals according to  FIGS. 2 and 3   a  and  3   b  are provided in order to close these points of possible media passage. Firstly,  FIG. 2  shows that substantially no modifications have to be made to the electric motor  210  or to the control unit  200 . Major modifications are made only to the base plate  200  used which is in the form of an IDC adapter plate. 
         [0023]    A first seal  260  in the form of an O-ring is fitted in the edge region of the base plate  200 . A bead into which the O-ring is recessed can optionally be provided for the purpose of better guidance. This O-ring provides lateral sealing in the recessed region between the base plate  200  and the housing of the electric motor  210 . Furthermore, the central opening  205  is provided with a shaft  250  in contrast to the version according to  FIG. 1 . Said shaft is used to arrange the second seal  270 , which is intended to seal off this opening  205 , at a level which is elevated in relation to the base plate  200 , in order to allow sealing between the base plate and the control unit. To this end, an O-ring is likewise arranged in the upper region of the shaft  250 . In this case, the second seal  270  can be provided both in the interior of the shaft  250  and outside. Fitting the second seal  270  on the outside has purely practical advantages since the second seal  270  or the O-ring can be press-fitted in a simple and force-fitting manner by corresponding shaping of the lower face of the control unit  220 . 
         [0024]    The third possible seal  280  relates to the through-plating which is necessary for the electrical connection between the electric motor  210  and the control unit  220 . To this end, three contact elements  230  to  234 , one for each (actuation) phase, are mounted on the base plate  200  according to the present exemplary embodiment, said contact elements establishing a welded connection to the electric motor and an insulation-displacement connection to the control unit  220 . Openings  240  and  242  (the opening for the contact element  234  is concealed) are provided in order to pass the electrical connections through the base plate  200 , said openings being closed by means of the third seal  280 . The sealed-off bushings can be clearly seen on the lower face of the base plate  200  according to  FIG. 3   b.  These third seals are designed such that a sealed-off electrical connection from the electric motor to the contact elements  230  to  234  can be established on the other side. 
         [0025]    Suitable third seals  280  are molded seals which are inserted or pressed into the opening. In this case, provision can be made for the seals to be of flexible design and to be matched to the shape of the contact elements  230  to  234  of the front face and/or to the corresponding contact pins of the electric motor. However, as an alternative, provision can also be made for the third seals  280  to be introduced from the front face together with the contact elements  230  to  234  and then to be hardened. Care should be taken here that contact can be made with the contact elements on the front face from the rear face without damaging the seal. The third seals can also optionally be designed as O-rings. 
         [0026]      FIG. 3   b  further shows that the third seals  280  are provided with a collar. This collar is used firstly to gather any excess sealing material and/or to ensure that a sufficient amount of sealing material can be introduced into the passage openings. Secondly, this collar also serves to protect the electrical contact-making means from the ingress of moisture or liquid between the connecting element  200  and the motor  210 . 
         [0027]    A fourth seal  290  can be provided in a further exemplary embodiment, said fourth seal being introduced into the recess at the base of the shaft  250  on the rear face of the base plate  200 . Placing this fourth seal of the base plate on the base of the recessed region of the motor  210  can additionally or alternatively seal the contact-making means from the shaft or from the rotor.