Abstract:
A valve for metering a flowing, e.g. gaseous or liquid, medium, in particular a fuel injection valve for internal combustion engines, is described, which valve comprises a valve housing having an inflow for the medium, a valve body having a metering opening for the medium, a join present between the valve housing and valve body, and a seal sealing the join. In order to ensure a seal that is reliable and not susceptible to cracking, in which context the material of the valve housing and valve body can be selected without restriction, the seal has a clamping ring, covering the join, that sits with a press fit on end portions, facing toward one another at the join, of the valve housing and valve body.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention proceeds from a valve for metering a flowing, e.g. gaseous or liquid, medium, in particular a fuel injection valve for internal combustion engines. 
       BACKGROUND INFORMATION 
       [0002]    A known fuel injection valve (German Published Patent Application No. 10 2007 028 490) has a hollow-cylindrical housing having an inflow end and a spray-discharge end. The inflow end is closed off by a cover carrying an inflow fitting; and a hollow-cylindrical valve body or nozzle body, which projects in part out of the housing, is inserted into the spray-discharge end. A spray-discharge opening, and a valve seat surrounding the spray-discharge opening on the outlet side, are embodied at that end of the valve body which remote from the housing. The spray-discharge end of the valve housing surrounds the valve body, and the annular join between the valve housing and valve body is sealed in liquid-tight fashion by way of a weld seam that connects the valve housing and valve body to one another, so that a fuel under a system pressure of, for example, 200 bar in the valve housing cannot emerge from the join. 
       SUMMARY 
       [0003]    The valve according to the present invention has the advantage that the clamping ring covering the join with a press fit onto the valve housing and body produces a sealing of the join between the valve housing and valve body which, compared with a weld seam, is secure and not susceptible to cracking The press fit of the clamping ring is produced preferably by heat shrinking For this, the clamping ring is heated, for example inductively and to the highest possible temperature; and the clamping ring, its inside diameter thereby enlarged, is slid or pressed onto the end portions of the valve housing and valve body so as to cover the join. The clamping ring shrinks upon cooling, and pulls the valve body and valve housing axially together, thereby bringing about a nonpositive engagement between the valve housing and valve body, and radial and axial sealing of the join. Alternatively, the press fit can also be produced by mechanically pressing on the clamping ring that has been slid with an overdimension onto the end portions of the valve housing and valve body. In contrast to sealing by way of a weld seam, the material of the valve housing and valve body can be selected without restriction, since the obligation to use a very easily weldable material in order to achieve a mechanically stable, pressure- and break-resistant weld seam is eliminated. The valve housing and valve body can thus be manufactured from an economical material, and manufacturing costs are lowered. Unlike with welding, where welding distortion can occur between the valve housing and valve body, reliable and good placement positioning of the two parts is achieved. In contrast to the case with welding of the valve housing and valve body, reliable sealing of the join can be ensured, despite high pressures in the valve housing, even when the valve body has a large outside diameter. A large outside diameter in turn creates the possibility of eccentric fluid guidance, which is advantageous for certain design embodiments of the valve, in the valve housing with respect to the central metering opening in the valve body. In order to limit the energy used to heat the clamping ring, the clamping ring is designed with the smallest possible volume. 
         [0004]    According to an advantageous embodiment of the invention, the end portions of the valve housing and valve body in the coverage region of the clamping ring are equipped with radial sealing edges spaced apart from one another that are formed, in a simple manner in terms of production engineering, by the tooth flanks of a tooth set. As a result of the hooking, associated with production of the press fit of the clamping ring, of the clamping ring into the sealing edges, a positive engagement is additionally brought about and the radial and axial sealing of the join is further improved. 
         [0005]    According to an advantageous embodiment of the invention, the end portions of the valve housing and valve body are butted against one another at the join, and have an identical outside diameter. The valve body and valve housing abut against each other in the join with an annular first stop surface embodied on the valve body and an annular second stop surface embodied on the valve housing, which is preferably disposed set back with respect to the end surface of the valve housing. The first stop surface has an inner circumferential edge that demarcates a central recess, impinged upon by medium, in the valve body; and the second stop surface has a projection region protruding beyond the inner circumferential edge. The recess encloses an obtuse angle with the annular recess bottom, and is embodied to be flat or concavely curved. The recess reduces the stiffness of the valve body at the join, and the fluid pressure existing in the recess additionally presses the valve body radially against the clamping ring, thereby enhancing positive engagement and sealing at the join. 
         [0006]    This effect is even further enhanced by the fact that, in accordance with a further embodiment of the invention, there is disposed on the valve housing, in the projection region of the second abutment surface, a groove that is open toward the recess and that preferably has a groove flank extending toward the inner circumferential edge of the first abutment surface on the valve body at an obtuse angle with respect to the groove bottom. This groove also results in a reduction in stiffness in the end portion of the valve housing, so that the fluid pressure existing in the recess and groove also presses the valve housing radially against the clamping ring. 
         [0007]    According to further embodiments of the invention, the radial and axial sealing of the join can be additionally improved by a variety of features. For example, a sealing ring covering the join and made of an elastomer, e.g. silicone, which presses radially onto the end portions of the valve housing and valve body, can additionally be placed into the clamping ring; or at least a part of that region of the end portions of the valve housing and valve body which is covered by the clamping ring can be coated with elastic sealing material, e.g. silicone; or a sealing ring made of an elastomer, e.g. silicone, can be disposed between the mutually abutting contact surfaces of the valve housing and valve body; or at least one of the two abutment surfaces on the valve housing and valve body can be coated with a sealing material, e.g. silicone. Welding of the clamping ring on the one hand to the valve body and on the other hand to the valve housing can moreover be additionally performed. In this case the two weld seams perform only a sealing function, since the axial forces of the fluid pressure are received by the clamping ring. Because the weld seams as a result do not need to have a high level of mechanical stability, a material that is less well suited for welding can also be used for the valve housing, valve body, and clamping ring. 
         [0008]    A material that is as hard as possible and has high strength, e.g. 1.4035 hardened steel, is preferably used for the valve housing and valve body; and a material having high strength and slightly lower hardness, e.g. 1.4035 hardened and annealed steel, is used for the clamping ring. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  shows portions of a longitudinal section of a valve for metering a liquid or gaseous medium, 
           [0010]      FIGS. 3 to 7  each shows what is depicted in  FIG. 2 , in accordance with further exemplifying embodiments. 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    The valve, depicted in longitudinal section in  FIG. 1 , for metering a flowing medium, i.e. a liquid or gaseous medium, is used preferably as an injection valve for injecting fuel into the combustion cylinder or air intake section of an internal combustion engine, but can also be utilized as a dispensing valve for injecting an aqueous solution, for example a urea-water solution, into the exhaust section of an internal combustion engine. The valve has a valve housing  11 , one of whose end faces is closed off by a valve body  12 . A metering opening  13  that is controlled, i.e. closed or opened, by an outwardly opening valve member  14  in conjunction with a valve seat  122  embodied on valve body  12  is embodied at that end of a through orifice  121  extending centrally in valve body  12  which is remote from the housing. Valve member  14 , having a valve needle  141  and a closure head  142  disposed at the end of valve needle  141 , is actuated in known fashion by an actuator (not depicted here), e.g. a piezoelectric actuator, against the return force of a valve closing spring  16  bracing against valve needle  141  and against valve body  12 . An axially extending inflow  17  for the medium is provided eccentrically in valve housing  11 ; through the inflow the medium travels into a cavity  15  that is embodied in valve body coaxially with through orifice  121  and receives valve closing spring  141 , and from there via through orifice  121 , which guides valve needle  141 , to a metering opening  13  closed by closure head  142 . 
         [0012]    A join  18 , at which the mutually facing end portions of valve housing  11  and  12 , which have the same outside diameter, abut against one another, is present between valve housing  11  and valve body  12 . Join  18  is sealed by a seal  20 . Seal  20  has, according to the present invention, a clamping ring  19  that covers join  18  and rests with a press fit on the end portions of valve housing  11  and valve body  12 . Clamping ring  19  is made from a material having high strength and a hardness slightly less than the hardness of the material of valve housing  11  and valve body  12 . Clamping ring  19  is made, for example, of 1.4035 hardened and annealed steel, and valve housing  11  and valve  12  of 1.4035 hardened steel. 
         [0013]    The press fit is preferably produced by heat-shrinking clamping ring  18  onto the end portions of valve housing  11  and valve body  12 . For this, clamping ring  19  is heated preferably, for example, inductively to the highest possible temperature, and clamping ring  19 , its inside diameter enlarged by the heating, is slid or pressed over join  18  onto the end portions of valve housing  11  and of valve body  12 . In order to shorten its heating process and in order to save energy, clamping ring  19  has a volume that is as small as possible. Clamping ring  19  shrinks upon cooling. Valve body  12  and valve housing  11  are thereby pulled axially together at join  18 , and a nonpositive engagement and a radial and axial seal are produced between valve body  12  and valve housing  11 . 
         [0014]    As is apparent from the portion of the valve depicted in enlarged fashion in  FIG. 2 , the end portions of valve housing  11  and valve body  12  are additionally equipped, in the coverage region of clamping ring  19 , with radial sealing edges spaced apart from one another that are formed, in the simplest case, by the tooth flanks of a tooth set  21 . The press fit causes clamping ring  19  to additionally hook into the sealing edges of tooth set  21 , with the result that an additional positive engagement and an enhanced sealing action are achieved. 
         [0015]    The radial sealing and the positive engagement are additionally reinforced by the fluid pressure existing in the interior of valve body  12  and valve housing  11 , by the fact that a reduction in the stiffness of valve body  12  and valve housing  11  is performed. For this, an annular first abutment surface  22  is embodied on valve body  12 , and an annular second abutment surface  23  on valve housing  11 . First abutment surface  22  and second abutment surface  23  abut against one another in join  18 . First abutment surface  22  has an inner circumferential edge  25  demarcated by a central recess  24  in valve body  12 , and second abutment surface  23 , which is disposed on valve housing  11  with a setback with respect to the end face of valve housing  11 , has a projection region  26  that protrudes beyond inner circumferential edge  25  and is thus located over recess opening  243 . Recess  24  has an annular recess bottom  241  through which valve needle  141  of valve member  14  passes, a recess wall  242 , and a recess opening  243  surrounded by recess wall  242 . Inflow  17  for the medium opens into recess opening  243 , so that recess  24  is impinged upon by medium under system pressure. Recess wall  242  preferably encloses an obtuse angle with recess bottom  241 , and in the exemplifying embodiment is embodied with a concave curvature ( FIG. 2 ). A flat or planar embodiment of recess wall  242  is possible. A groove  27  open toward recess  24  is disposed in projection region  26  of second abutment surface  23  on valve housing  11 . groove  27  has a groove flank  271  that extends toward inner circumferential edge  25  of first abutment surface  22  on valve body  12 , preferably at an obtuse angle with respect to groove bottom  272  ( FIG. 2 ). The system pressure of the medium acting on recess wall  242  and on groove flank  271  additionally presses the end portions of valve body  12  and valve housing  11  radially against the shrunk-on clamping ring  19 , and thus reinforces the radial sealing and positive engagement between valve housing  11  and valve body  12  at join  18 . 
         [0016]    In the portions depicted in  FIGS. 3 to 7  of modified exemplifying embodiments of the valve, seal  20  at join  18  between valve housing  11  and valve body  12  is also supplemented with further design features in addition to the shrunk-on clamping ring  19 . 
         [0017]    In the exemplifying embodiment according to  FIG. 3 , seal  20  also has, in addition to clamping ring  19 , a sealing ring  28  that is made of an elastomer, e.g. silicone, and axially covers join  18 , and that is placed into clamping ring  19  and presses radially onto the end portions of valve housing  11  and valve body  12 . Sealing ring  28  is received in a groove  29 , recessed into the inner annular wall of clamping ring  19 , that is preferably disposed symmetrically with respect to join  18 . 
         [0018]    In the exemplifying embodiment according to  FIG. 4 , seal  20  also has, in addition to clamping ring  19 , a coating  30  that is made of an elastomer, e.g. silicone, and that extends, in that region of the end portions of valve housing  11  and valve body  12  which is covered by clamping ring  19 , at least over a part of both the end portion of valve housing  11  and the end portion of valve body  12 . The two parts of coating  30  (which are preferably of the same size) are applied onto the end portions of valve housing  11  and valve body  12  before clamping ring  19  is pressed on. 
         [0019]    In the exemplifying embodiment according to  FIG. 5 , seal  20  also has, in addition to clamping ring  19 , a sealing ring  31  that is made of an elastomer, e.g. silicone, and that is disposed between abutment surfaces  22 ,  23  of valve body  12  and valve housing  11 . 
         [0020]    In the exemplifying embodiment according to  FIG. 6 , seal  20  also has, in addition to clamping ring  19 , a coating  32  that is made of an elastomer, e.g. silicone, and is applied onto one of the two abutment surfaces  22 ,  23 , or both, of valve body  12  and valve housing  11 . 
         [0021]    The exemplifying embodiment according to  FIG. 7  differs from the exemplifying embodiment according to  FIGS. 1 and 2  only in that clamping ring  19 , shrunk onto the end portions of valve housing  11  and valve body  12 , is also welded at its two end faces on the one hand to valve housing  11  and on the other hand to valve body  12 . The weld seams thereby produced are labeled  33  and  34  in  FIG. 7 . These weld seams  33 ,  34  serve exclusively for additional sealing of join  18  and do not receive any axial forces, so that more stringent demands do not need to be made in terms of their mechanical strength, and a material less suitable for welding can also be used for valve housing  11 , valve body  12 , and clamping ring  19 . 
         [0022]    Except for the modified seal  20 , the exemplifying embodiments of the valves depicted in part in  FIGS. 3 to 7  correspond to the exemplifying embodiment of the valve according to  FIGS. 1 and 2 , so that identical components are labeled with the same reference characters.