Abstract:
An electromagnet device includes at least one electromagnet having at least one coil and at least one core built up from laminations. At least individual laminations are connected and reinforced by at least one profiled element.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to an electromagnet device.  
         BACKGROUND INFORMATION  
         [0002]    To generate the strongest possible electromagnetic fields, generally electromagnets with a coil and a ferromagnetic core are used. The core is located in the coil and/or surrounds the coil. If a current is passed through the coil, a magnetic field with the field strength H builds up around the coil in accordance with Ampere&#39;s law. Under the effect of the force of the magnetic field, the magnetic dipoles present in the core material orientate themselves in the direction of the field, also referred to as diffusion, and increase the magnetic flux density or induction in comparison with an air coil from B 0  to B. The resulting magnetic field is consequently dependent on the field strength H and the flux density B. Self-induction acts in the coil, so that the current and the field strength H dependent on the current increase with a delay. Furthermore, the build-up of the magnetic field is delayed by eddy currents developing in the core material, which hinder the diffusion of the magnetic field in the core and result in losses.  
           [0003]    To achieve a short response time in an electromagnet, the electromagnetic field should be built up and also allowed to decay again quickly and, in spite of small dimensions of the electromagnet, a large final force should be achieved, in particular in very dynamic systems, such as, actuators for actuating gas-exchange valves of internal combustion engines.  
           [0004]    To avoid eddy currents, iron cores have been built up from thin laminations which are insulated from one another and the contact surfaces of which are aligned transversely in relation to electric flux lines occurring, i.e., perpendicular to the winding of the coil (cf. H. Linse, Elektrotechnik für Maschinenbauer (Electrical Engineering for Machine Makers), 8th, revised edition, Teubner 1987, page 66 et seq.). It is desirable that only small voltages, and consequently no eddy currents, occur in the laminations. The laminations are either welded or crimped to one another.  
         SUMMARY  
         [0005]    It is an object of the present invention to provide an electromagnet device with laminated iron cores and having improved efficiency.  
           [0006]    The above and other beneficial objects of the present invention are attained by providing an electromagnet device having at least one electromagnet, which has at least one coil and at least one core built up from laminations.  
           [0007]    At least individual laminations are connected and reinforced by at least one profiled element. Despite the core being built up from individual laminations, improved rigidity may be achieved and undesired deformations of the laminated core and an associated air gap between an armature and a pole face of the core may be substantially avoided and the efficiency may be increased.  
           [0008]    To achieve high torsional rigidity and/or flexural rigidity, the profiled element may include various profiles, such as, for example, a T profile, a U profile with indentations, beads, etc. Improved torsional rigidity may be achieved with a hollow profile, such as, for example, with a “D-box profile”, which includes a D-shaped cross-sectional surface. To achieve not only improved torsional rigidity but also improved flexural rigidity, the hollow profile may, furthermore, be combined with further profiles, for example, with a U profile, etc.  
           [0009]    The profiled element may at least partially bound a channel, such as, for example, a cooling channel. Other channels may also be bounded by the profiled element, such as, for example, cable ducts, etc. Additional components, installation space, weight and assembly effort may be reduced. A coolant may be passed directly over the laminations of the core or over a coil, whereby improved heat removal may be achieved. Furthermore, the channel may be made in a hollow profile of the profiled element, whereby direct contact between the coolant and the core may be avoided. A closed cooling system may be achieved in a simple way, and it is possible to avoid designing the core, in terms of its material, for the coolant, or vice versa.  
           [0010]    The core may be supported on at least one bearing surface by the profiled element. Bearing forces may be absorbed via the profiled element and additional components may be reduced. To allow compensation for play and to make contact of an armature against a pole face of the core possible, the core may be guided movably on a bearing surface by the profiled element. That is, the profiled element may include at least a round outer contour, by which the core is pivotably mounted. It is possible to compensate for an air gap between the armature and the pole face, and to increase the efficiency, by a pivoting movement of the core.  
           [0011]    The profiled element may be connected to the laminations by various integral, positive and/or non-positive connections, such as, for example, by a welded connection, a screwed connection, a clamping and/or engaging connection, etc. The profiled element may be connected non-positively and/or positively to the laminations, thereby allowing a propagation of eddy currents via the profiled element simply to be substantially avoided. The profiled element may be formed from various materials, such as, for example, from steel, a fibre composite material, etc.  
           [0012]    The profiled element may be integrally connected to at least one carrier part, whereby the rigidity of the core may be further increased. The integral connection may be achieved by various methods, for example, at the end face by an adhesive, soldered and/or welded connection. The profiled element and the carrier part may be configured in an overlapping manner and welded in a fillet weld. The fillet weld may be made with a large weld volume, and low material loading and a particularly solid connection may be achieved.  
           [0013]    The electromagnet device according to the present invention may be used in various devices, such as those subjected to high mechanical loads and required to meet high rigidity requirements, such as electromagnetic actuators for actuating gas-exchange valves in internal combustion engines. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    [0014]FIG. 1 is a schematic cross-sectional view through an actuator from above.  
         [0015]    [0015]FIG. 2 is a side view of the actuator illustrated in FIG. 1.  
         [0016]    [0016]FIG. 3 is a schematic cross-sectional view of an actuator with profiled elements having a hollow profile. 
     
    
     DETAILED DESCRIPTION  
       [0017]    [0017]FIG. 1 illustrates an electromagnetic actuator with an electromagnet  22  for actuating a gas-exchange valve (not illustrated in detail) of an internal combustion engine. The electromagnet  22  acts on a rotating armature  23 , which is pivotably mounted in a bearing  24 .  
         [0018]    The electromagnet  22  includes a coil  32  and a core  19 , which is built up from thin laminations  10  which are insulated from one another and the contact surfaces of which are arranged transversely in relation to electric flux lines (FIG. 2). According to the present invention, the laminations  10  are connected and reinforced by two profiled elements  11 ,  12 . The profiled elements  11 ,  12  engage positively in recesses  29 ,  30 ,  31  of the laminations  10  and with these are braced with the laminations  10  non-positively in addition to a positive engagement (FIG. 1).  
         [0019]    The profiled elements  11 ,  12  include a U profile with a bottom part and two legs. The bottom part is configured so that it curves outwardly and, as a result, has a round outer contour, by which the core  19  is pivotably mounted on bearing surfaces  20 ,  21  in a carrier device  27 . It is possible by a pivoting movement  25 ,  26  to compensate for an air gap between the rotating armature  23  and pole faces of the electromagnet  22 .  
         [0020]    Instead of making the core  19  constantly pivotable, prior to being put into operation for the first time, it may also be set to the rotating armature  23  or pivoted into a desired position and subsequently welded to carrier plates  36 ,  37 , as illustrated in FIG. 2. Like components are designated by the same reference numerals throughout the several views. In the finished assembled state, the carrier plates  36 ,  37  and the profiled element  12  are configured in an overlapping manner and are welded to one another by a curve-shaped fillet weld  38 ,  39 . In order to increase the rigidity further, indentations  28  may be made on a side of the profiled elements  12  facing away from the core.  
         [0021]    The profiled elements  11 ,  12  bound a cooling channel  15 ,  16  outwardly, one cooling channel  15  being bounded inwardly by the laminations  10  and one cooling channel  16  being bounded inwardly by the coil  32 .  
         [0022]    [0022]FIG. 3 illustrates another example embodiment of the present invention. With respect to features and functions which remain the same, reference can be made to the description of the example embodiments illustrated in FIGS. 1 and 2.  
         [0023]    The laminations  10  of the core  19  are connected and reinforced by two profiled elements  13 ,  14 , which engage positively in recesses  33 ,  34 ,  35  of the laminations  10  and, in addition to a positive connection, are non-positively braced with the laminations  10 . Both profiled elements  13 ,  14  include a hollow profile with a D-shaped cross-sectional surface, i.e., a “D box”, in which cooling channels  17 ,  18  are made. Other profile shapes are also possible. The D-shaped cross-sectional surface produces a round outer contour, by which the core  19  may be mounted in a pivotable manner. Furthermore, improved torsional rigidity is achieved. The terminating profiled element  13  with respect to the coil  32  additionally includes a U profile, with which it reaches around the coil  32 . The U profile achieves improved flexural rigidity in addition to improved torsional rigidity.