Abstract:
An electromagnetically actuatable valve is described, for controlling fluids, having an inner pole and a magnetic armature, the inner pole having a first end face oriented to the magnetic armature, and the magnetic armature having a second end face oriented to the inner pole, a first contact line and a second contact line being present between the first and second end face when the inner pole and the magnetic armature come into contact with one another, and a damping volume being present between the first and second contact line when the inner pole and the magnetic armature come into contact with one another.

Description:
FIELD OF THE INVENTION 
     The present invention relates to an electromagnetically actuatable valve for controlling fluids, in particular fuel. 
     BACKGROUND INFORMATION 
     Valves are known from the existing art in various embodiments. In fuel injection valves, electromagnetically actuatable valves are often used in which a magnetic armature is attracted by an inner pole. When this happens, the magnetic armature can impact against the inner pole or against a stop. As a result, during operation wear can occur, so that the components subject to wear are often provided with a wear-resistant layer, for example made of chrome or nickel. In addition, from German Published Patent Application No. 198 33 461 a magnetic valve is known in which the components that impact one another, the magnetic armature and the inner pole, are made in such a way that one of the components that strike one another has a spherically curved surface. This design has proved effective, but it would be desirable if a further reduction of noise and of wear were possible, in order to ensure the longest possible lifespan of magnetic valves. 
     SUMMARY 
     The electromagnetically actuatable valve according to the present invention for controlling fluids has, in contrast, the advantage that an additional damping and reduction of an impact impulse is possible. In addition, according to the present invention an improved wear characteristic of the valve can be achieved. According to the present invention, this is achieved in that an inner pole and a magnetic armature each have an end face directed toward one another, the end faces being shaped in such a way that a first and second contact line are present between the two end faces when the inner pole and the magnetic armature come into contact. In addition, here a damping volume is present between the first and second contact line. According to the present invention, a damping fluid volume is therefore present between two contact lines, which significantly reduces an impact impulse and wear at the inner pole and at the magnetic armature. In particular, in the valve according to the present invention an expensive wear-resistant layer is no longer necessary; rather, the end faces of the inner pole and of the magnetic armature can be produced without an additional wear-resistant layer. This makes production of the valve significantly less expensive. 
     Preferably, the two contact lines are each circular lines. Here, it is further preferable that the two contact lines are preferably situated concentric to a center axis of the valve. In this way, a symmetrical realization of the valve is ensured. 
     In addition, preferably one of the end faces of the inner pole or of the magnetic armature is a multiple cone and the other end face is a spherical surface. In this way, the two contact lines between the inner pole and the magnetic armature can be obtained through a contact of the spherical surface with at least two cone surfaces of the multiple cone. Particularly preferably, the multiple cone can be provided with exactly one first and one second cone surface, and is thus particularly easy to produce. Here, the spherical surface respectively contacts one of the first and second cone surfaces. 
     In addition, preferably the end face of the inner pole is fashioned as a multiple cone having at least one first and second cone region, and the end face of the magnetic armature is fashioned as a spherical surface. 
     Alternatively, the end face of the inner cone is fashioned as a spherical surface, and the end face of the magnetic armature is fashioned as a multiple cone having at least a first and second cone region. 
     In addition, preferably the end faces on the inner pole and on the magnetic armature each have a flat region that is perpendicular to a longitudinal axis of the valve. The flat regions on the end faces are preferably situated radially outside the two contact lines between the inner pole and the magnetic armature. On the flat regions provided perpendicular to the longitudinal axis of the valve, the magnetic flux is conducted parallel to the direction of movement of the magnetic armature and thus perpendicular to the flat regions. In this way, a necessary magnetic force level can be obtained because in particular field lines that run over a spherical surface between the inner pole and the magnetic armature contribute only to a small degree to the production of force, because the field lines are not oriented to the direction of movement of the magnetic armature, but rather exit into the working air gap perpendicular to the surface of the sphere. 
     Particularly preferably, the end faces of the inner pole and magnetic armature are fashioned such that the inner pole and the magnetic armature come into contact with one another only at the two contact lines. 
     In addition, preferably the end face of the magnetic armature is fashioned as a spherical surface, and the magnetic armature has in addition a guide region, the guide region being situated in a plane perpendicular to the longitudinal axis of the valve, and a midpoint of the spherical surface of the end face of the magnetic armature being situated in the plane. In this embodiment, an armature-inner pole configuration can be ensured that is particularly robust against tilting. 
     A particularly compact design results if the magnetic armature is connected to a valve needle and the valve needle is guided in the inner pole. 
     Preferably, none of the end faces of the inner pole and magnetic armature has a wear-resistant layer, and also none of the end faces of the inner pole and magnetic armature has a magnetic separating layer. Because in the case of contact between the inner pole and the magnetic armature only two contact lines are present, given the presence of a spherical end face a magnetic separating layer can be omitted because a contribution of the field lines to the magnetic adhesive force in the region of the spherical end face is small, because the field lines run perpendicular to the spherical surface and therefore have only a small axial force component. 
     In addition, preferably the flat regions on the end faces of the inner pole and magnetic armature are fashioned such that even in the case of a maximum tilting of the magnetic armature there is no contact between the inner pole and the magnetic armature in the area of the flat regions. 
     Particular preferably, the valve according to the present invention is a fuel injection valve. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a schematic sectional view of an electromagnetically actuatable valve according to a first exemplary embodiment of the present invention. 
         FIG. 2  shows an enlarged schematic representation of a region of impact between an inner pole and a magnetic armature of the valve of  FIG. 1 . 
         FIG. 3  shows an enlarged schematic representation of an impact of the magnetic armature on the inner pole. 
         FIG. 4  shows a schematic sectional view of an inner pole and a magnetic armature according to a second exemplary embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     In the following, a fuel injection valve  1  according to a first exemplary embodiment of the present invention is described in detail with reference to  FIGS. 1 through 3 . 
     As can be seen from  FIG. 1 , fuel injection valve  1  includes an inner pole  2 , a magnetic armature  3 , and a coil  5 . In addition, a valve needle  4  is provided that is connected to magnetic armature  3 . A resetting spring  6  resets valve needle  4  to the initial position shown in  FIG. 1 , in which fuel injection valve  1  is closed. Reference character  7  designates a housing of the fuel injection valve. 
     In order to actuate the fuel injection valve, in a known manner coil  5  is supplied with current, causing magnetic armature  3  to be drawn toward inner pole  2 , and, given a maximum opening demand of the injection valve, to impact against inner pole  2 .  FIG. 1  shows the closed state of the valve. 
     The construction of inner pole  2  and of magnetic armature  3  is shown in detail in  FIGS. 2 and 3 . As can be seen in  FIG. 2 , a first end face  20  has a multiple cone  21  and a flat region  24 . Multiple cone  21  includes a first cone region  22  and a second cone region  23 . Here, flat region  24  on the end face of inner pole  2  is situated further out radially, going out from a center axis X-X of the valve, than is multiple cone  21 . 
     A second end face  30  of magnetic armature  3  has a spherical region  31  and a flat region  32 . Flat region  32  is also provided radially further out from center axis X-X than is spherical region  31 . 
     In the open state of the valve shown in  FIG. 2 , in which magnetic armature  3  impacts inner pole  2 , the geometrical realization of end faces  20 ,  30  of inner pole  2  and magnetic armature  3  results in a first circular contact line  8  and a second circular contact line  9 . At first contact line  8 , first cone region  22  comes into contact with spherical region  31 , and at second contact line  9  second cone region  23  comes into contact with spherical region  31 . Here, in the contacted state a gap S still continues to be present between the two flat regions  24 ,  32 . 
     In this way, a contact between inner pole  2  and magnetic armature  3  is limited to the two contact lines  8 ,  9 . As can be further seen from  FIGS. 2 and 3 , in this way a damping volume  10  results between the two contact lines  8 ,  9 . In the case of contact, damping volume  10  encloses fuel, and can in this way provide a robust damping at a high level, thereby reducing an impact impulse. As is clear from  FIG. 3 , here damping volume  10  does not have to have a large volume, so that no additional space requirement results from the realization according to the present invention of end faces  20 ,  30  of inner pole  2  and of magnetic armature  3 . 
     As can also be seen from  FIGS. 2 and 3 , the two flat regions  24 ,  32  of inner pole  2  and of magnetic armature  3  are oriented parallel to one another and thus perpendicular to center axis X-X. In case of impact ( FIGS. 2 and 3 ), gap S is provided in such a way that even in the case of a slight tilting of magnetic armature  2  out of center axis X-X, no contact occurs in the region of flat regions  24 ,  32 . Even when there is a slight tilting of magnetic armature  2 , only two contact lines occur, due to the realization according to the present invention of end faces  20 ,  30 . In the case in which magnetic armature  3  is tilted, it is true that these contact lines are then no longer situated concentric to center axis X-X, but nonetheless the same advantages are obtained as in the case of the concentric situation of contact lines  8 ,  9 . 
     In order to avoid to the greatest possible extent a tilting, magnetic armature  3  also has a guide region  33  on its radial outer side. Guide region  33  is situated in a plane E that is perpendicular to center axis X-X. In this plane E there is also situated a midpoint M of spherical region  31  of magnetic armature  3 . Radius R is drawn in in  FIG. 2 . 
     Thus, through the idea according to the present invention of the realization of the two impact-side end faces  20 ,  30  of inner pole  2  and of magnetic armature  3  in the form of a partial sphere on the one hand and in the form of a multiple cone on the other hand, a stop at two contact lines  8 ,  9  is provided. Here, a damping volume  10  between the two contact lines  8 ,  9  is defined in the case of impact. Thus, in the case of impact an outstanding damping, and thus reduced wear, can be obtained between inner pole  2  and magnetic armature  3 . In this way, a lifespan of the valve can be significantly prolonged without requiring a wear-resistant coating on the inner pole or on the magnetic armature. 
     In addition, a magnetic adhesion between magnetic armature  3  and inner pole  2  can be additionally reduced, because only a minimal contact, along two lines, is present between the two components in the case of impact. 
       FIG. 4  shows a second specific embodiment of the present invention; here identical or functionally identical parts have been provided with the same reference characters as in the first exemplary embodiment. In the second exemplary embodiment, inner pole  2  has a spherical region  25  and magnetic armature  3  has a multiple cone  35  having a first cone region  36  and a second cone region  37 . Here, again a damping volume  10  is obtained between the two end faces of inner pole  2  and of magnetic armature  3 . Likewise, two circular contact lines  8 ,  9  are obtained in the case of impact shown in  FIG. 4 . In addition, the valve of the second exemplary embodiment also has a guide element  11  that is situated on the end of valve needle  4 . For this purpose, in inner pole  2  a guide opening  12  is provided in which guide element  11  is guided. In this way, valve needle  4 , which is connected fixedly to guide element  11  and to magnetic armature  3 , is guided in the interior of inner pole  2 . In this way, a particularly compact construction can be obtained. In other respects, this exemplary embodiment corresponds to the first exemplary embodiment, so that reference is made to the description given there.