Abstract:
An injection valve for injecting fuel into an internal combustion engine may include an actuator, an injection needle associated with a sealing seat, and a transmission unit that establishes an effective connection between the actuator and the injection needle. The transmission unit may include a pressure chamber including two movable pistons that are guided within a movable pot. The first piston may be guided through a bottom of the pot while maintaining a first sealing gap, and the second piston may be guided within a sleeve section of the pot while maintaining a second sealing gap. One piston may be effectively connected to the injection needle, while the other piston may be effectively connected to the actuator.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a U.S. National Stage Application of International Application No. PCT/EP2010/058132 filed Jun. 10, 2010, which designates the United States of America, and claims priority to German Application No. 10 2009 024 595.2 filed Jun. 10, 2009, the contents of which are hereby incorporated by reference in their entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The invention relates to an injection valve comprising a transmission unit. 
       BACKGROUND 
       [0003]    Existing disclosures, for example, WO 2008/003347 A1, U.S. Pat. No. 6,575,138 B2 and U.S. Pat. No. 6,298,829, disclose injection valves in which a hydraulic transmission unit is provided between an actuator and the nozzle needle. 
         [0004]    In some existing disclosures, the deflection of the actuator is transmitted into a corresponding deflection of the nozzle needle. 
       SUMMARY 
       [0005]    In one embodiment, an injection valve for injecting fuel into an internal combustion engine includes an actuator, a nozzle needle associated with a sealing seat, and a transmission unit that establishes an effective connection between the actuator and the nozzle needle. The transmission unit has a pressure chamber bounded by two movable pistons which are guided in a movable pot, wherein the first piston is guided through a bottom of the pot with a first sealing gap, wherein the second piston is guided in a sleeve-shaped section of the pot with a second sealing gap, and wherein one piston is operatively connected to the nozzle needle and the other piston is operatively connected to the actuator. 
         [0006]    In a further embodiment, the first piston bounds the pressure chamber with a larger end face than an annular face, adjoining the first piston, of the pot. In a further embodiment, a spring element is arranged in the pressure chamber and is inserted between the second piston and the bottom of the pot. In a further embodiment, the second piston has a sleeve-shaped pot shape, wherein an end of the nozzle needle projects into the sleeve-shaped section of the second piston, wherein the nozzle needle is attached in a positively locking fashion to the pot via a connecting part. In a further embodiment, the connecting part is embodied in the form of a partial ring plate which is open on one side and which comprises in a positively locking fashion a notch of the nozzle needle in a central region and is connected to the pot in an external region. In a further embodiment, the sleeve-shaped section of the second piston has free-standing wall sections in a lower end region, wherein the wall sections are guided through the cutouts and rest on a stop face. In a further embodiment, the connecting part has a partial-ring-shaped web whose external diameter corresponds substantially to the internal diameter of the sleeve-shaped section of the pot, and wherein the sleeve-shaped section of the pot is plugged over the web. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    Example embodiments will be explained in more detail below with reference to figures, in which: 
           [0008]      FIG. 1  shows a schematic design of an example injection valve, according to certain embodiments; 
           [0009]      FIG. 2  shows a schematic design of an example transmission unit of the injection valve of  FIG. 1 , according to certain embodiments; 
           [0010]      FIG. 3  shows an end of the nozzle needle with a connecting part, according to certain embodiments; 
           [0011]      FIG. 4  shows an end of the nozzle needle with a mounted second piston, according to certain embodiments; 
           [0012]      FIG. 5  shows an end of the nozzle needle with a second piston and a spring element, according to certain embodiments; 
           [0013]      FIG. 6  shows an end of the nozzle needle with a mounted pot, according to certain embodiments; and 
           [0014]      FIG. 7  shows a cross section through the end of the nozzle needle with a mounted pot. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    Certain embodiments of the present disclosure provide an improved transmission unit for an injection valve. 
         [0016]    In some embodiments, the transmission unit has a pressure chamber which is bounded by two movable pistons, wherein the movable pistons are guided in a movable pot. A first piston is guided through a bottom of the pot with a first sealing gap. The second piston is guided in a sleeve section of the pot with a second sealing gap. One of the pistons is operatively connected to the nozzle needle and the other piston is operatively connected to the actuator. On the basis of this embodiment, a robust transmission unit is made available which, for a brief activation, transmits the deflection of the actuator directly into a deflection of the nozzle needle and additionally permits, via the sealing gaps, a chronologically slow change in the volume of the pressure chamber. 
         [0017]    In one embodiment, the second piston is bound to the sealing chamber with a larger end face and an annular face of the bottom of the pot through which the first piston is guided. In this way, the deflection of the actuator is transmitted into a relatively large deflection of the nozzle needle. In this way, for example small deflections of a piezoelectric actuator can be converted into a sufficiently large deflection of the nozzle needle. 
         [0018]    In a further embodiment, a spring element is arranged in the sealing chamber, wherein the spring element is clamped in between the second piston and the bottom of the pot. In this way it is ensured that the second piston is in abutment with a stop of the injection valve and the pressure chamber has a maximum volume. The operative connection between the actuator and the nozzle needle is thereby defined precisely. 
         [0019]    In a further embodiment, the second piston has a sleeve-shaped pot shape, wherein an end of the nozzle needle projects into the sleeve-shaped section of the second piston. The nozzle needle is connected in a positively locking fashion to the pot via a connecting part. This permits simple attachment of the nozzle needle to the pot, wherein the installation space is also reduced. 
         [0020]    In a further embodiment, the connecting element is embodied in the form of a partial ring plate which is open on one side and comprises a notch of the nozzle needle in a central region and is connected to the pot in an external region, in particular welded thereto. In this way, simple and reliable attachment of the nozzle needle to the pot is made possible. 
         [0021]    In a further embodiment, the ring element has cutouts, wherein the sleeve-shaped section of the second piston has free-standing wall sections in a lower end region, wherein the wall sections are guided through the cutouts and rest on a stop face. Owing to this embodiment, reliable support of the second piston on the stop face is possible, and in addition an operative connection between the nozzle needle and the pot is made available with little installation space. 
         [0022]    In a further embodiment, the connecting part has a partial-ring-shaped web whose external diameter corresponds substantially to the internal diameter of the sleeve-shaped pot, wherein the sleeve-shaped wall of the pot is plugged onto the web and surrounds the web. This permits additional securement of the connecting part to the pot. In this way, the connection between the connecting part and the pot becomes less sensitive to mechanical influences. 
         [0023]      FIG. 1  shows, in a schematic illustration, an example injection valve  1  according to certain embodiments, which injection valve  1  has a housing  2  to whose lower end a nozzle body  3  is attached using a clamping nut  4 . A nozzle needle  5  may be mounted so as to be movable in the longitudinal direction in the nozzle body  3 . The nozzle needle  5  may be operatively connected to an actuator  7  via a transmission unit  6 . In the lower region of the nozzle body  2 , a fuel space  8  may be formed between the nozzle needle  5  and the nozzle body  3 , which fuel space  8  may be supplied with fuel via ducts (not illustrated), for example by means of a fuel accumulator and/or by means of a fuel pump. An annular sealing seat  10  may be formed on the inner side of the nozzle body  3  between the fuel space  8  and injection holes  9 . A sealing face  11  which runs around in an annular shape at the lower end of the nozzle needle  5  may be assigned to the sealing seat  10 . Depending on the position of the nozzle needle, which is set by the actuation of the actuator  7 , the nozzle needle  5  may lift off from the sealing seat  10  and clears a hydraulic connection between the fuel space  8  and the injection holes  9 . 
         [0024]    The actuator  7  can be embodied, for example, as a piezo-electric actuator or as a magnetic actuator. As a result of electrical energization of the actuator  7 , the actuator  7  may become longer and may therefore act on the transmission unit  6 . The transmission unit  6  may be embodied in such a way that the deflection of the actuator  7  is transmitted to the nozzle needle  5 . The deflection of the actuator  7  in the direction of the nozzle needle  5  may be advantageously converted into an opposing movement of the nozzle needle  5  in the direction of the actuator  7  using the transmission unit  6 . 
         [0025]      FIG. 2  shows an example embodiment of a transmission unit  6  which is arranged between the actuator  7  and the nozzle needle  5  in the housing  2 . The transmission unit  6  has a first piston  12  which projects through a bottom  13  of a sleeve-shaped pot  14 . The pot  14  may be movably mounted. The first piston  12  may be fixedly connected to the actuator  7 . Furthermore, a second piston  15  may be provided which projects from an underside into the sleeve-shaped section of the pot  14 . The second piston  15  may be also of sleeve-shaped design, wherein an end piece  17  of the nozzle needle  5  may project into a sleeve-shaped section  16  of the second piston  15 . The end piece  17  may be guided through a hole  30  of a stop plate  18 , which is fixedly clamped to the housing  2 . The end piece may have a notch  19  into which a connecting part  20  engages. The connecting part  20  may be additionally connected to the sleeve  14 , in particular welded, caulked or bonded thereto. 
         [0026]    The second piston  15  may be seated with lower edge faces  27  on an upper side of the stop plate  18 . The upper side of the stop plate  18  may constitute a stop face for the second piston  15 . 
         [0027]    The first piston  12  may bound a pressure chamber  24  with an end face  28 . The pot  14  may bound the pressure chamber  24  with an annular face  29 , wherein the annular face  29  may be formed on the inner side of the bottom  13 , adjacent to the first piston  12 . 
         [0028]    A spring element  21  may be clamped in between an inner side of the bottom  13  and a step on the second piston  14 . The first piston  12  may be guided through the bottom  13  via a first sealing gap  22 . The first sealing gap  22  may be of a magnitude in the range from 3 to 15 μm, in particular in the region of 8 μm. The second piston  15  may be spaced apart from the inner wall of the sleeve  14  by means of a second sealing gap  23 . The second sealing gap  23  may be of a magnitude from 3 to 15 μm, in particular in the range of 8 μm. The first piston  12 , the sleeve  14  and the second piston  15  bound the pressure chamber  24 . The pressure chamber  24  may be filled with fuel and is connected via the sealing gaps  22 ,  23  to the interior of the housing  2 , which is also filled with fuel. Fuel with a low pressure may be arranged between the housing  2  and the transmission unit  6 . A second spring element  26  may be clamped in between an underside of the stop plate  18  and a second step  25  on the nozzle needle  5 . The second spring element  26  may prestress the nozzle needle  5  in the direction of the sealing seat  10 . The second spring element  26  may have a larger spring force than the spring element  21 . The annular face  29  may be advantageously smaller than the end face  28 . In particular, the annular face  29  may be half as large as the end face  28 . The surface area ratio between the annular face  29  and the end face  28  may define a transmission ratio between the deflection of the actuator and of the nozzle needle and can be correspondingly selected. 
         [0029]    In some embodiments, the transmission unit  6  according to  FIG. 2  may function as follows: in the non-actuated state of the actuator  7 , the nozzle needle  5  is pressed, with the sealing face  11 , onto the sealing seat  10  owing to the second spring element  26 . As a result, no fuel can be put out of the fuel space  8  via the injection holes  9 . The pressure chamber  24  is filled with fuel. In this context, the first and second pistons  12 ,  15  have spacing. The second piston  15  is supported on the stop plate  18  with the edge face  27 . The first and second sealing gaps  22 ,  23  are so narrowly dimensioned that when there is a brief application of pressure, which takes place within the scope of an injection by the actuator  7 , no change in the volume of the pressure chamber takes place. The first and second sealing gaps ensure that the pressure chamber  24  is always filled with fuel. 
         [0030]    If the actuator  7  is then deflected, for example by energization, the actuator  7  presses the first piston  12  downward in the direction of the nozzle needle  5 , since the actuator  7  is supported in the upper region against the housing  2 . As a result of this, the end face  28  forces fuel in the pressure chamber  24 , as a result of which the increased fuel pressure acts on the annular face  29 , and the pot  14  moves upward counter to the direction of movement of the first piston  12 . The pot  14  is connected via the connecting part  20  to the nozzle needle  5 , with the result that the nozzle needle  5  is lifted off from the assigned sealing seat  10  by the movement of the pot  14 . As a result, fuel can be injected via the injection holes  9 . In this context, the second spring element  26  is compressed. In addition, the spring element  21  is deflected since the distance between the step on the second piston  15  and the annular face  29  increases. As stated above, the volume of the pressure chamber  24  is substantially constant during this process. 
         [0031]    In order to end the injection, the increase in length of the actuator  7  is shortened, with the result that the first piston  12  is moved upward out of the pressure chamber  24 , the pressure in the pressure chamber  24  decreases. Consequently, the pot  14  is moved downward in the direction of the stop plate  18 , with the result that the nozzle needle  5  moves again into abutment on the sealing seat  10  with the sealing face  11 . The injection is therefore interrupted. 
         [0032]      FIG. 3  shows a partial illustration of the nozzle needle  5  and the stop plate  18  through whose central hole  30  the end piece  17  of the nozzle needle  5  projects. The end piece  17  may have an annular notch  19  into which the connecting part  20  is inserted laterally. The connecting part  20  is illustrated on the left next to the stop plate  18  in a perspective illustration. The connecting part  20  may be embodied as a plate-shaped part which is in the shape of a pitch circle. An insertion opening  31  may be formed in the connecting part  20  and extends as far as the center of the pitch-circle-shaped connecting part  20 . The diameter of the insertion opening  31  may correspond substantially to the diameter of the nozzle needle  5  in the region of the notch  19 . Furthermore, the connecting part  20  may have three cutouts  32 . Furthermore, a web  33  which runs around a center point of the connecting part  20  in the form of a partial ring may be formed. 
         [0033]    The pressure chamber  24  may be supplied with fuel via the sealing gaps  22 ,  23 , said fuel being present in the housing of the injection valve. The pressure chamber  24  may therefore always be filled with fuel. The sealing gaps  22 ,  23  may be selected in such a way that the sealing gaps  22 ,  23  are sealed for chronologically short increases in pressure which occur during injection processes. Chronologically longer lasting pressure differences may lead to the flowing in or flowing out of fuel in or out of the pressure chamber via the sealing gaps, such that the volume of the pressure chamber can change. 
         [0034]    For the purpose of mounting, the connecting part  20  may be inserted upward with the web  33  into the notch  19 , as is illustrated in the right-hand region of  FIG. 3 . Then, in order to mount the injection valve the second piston  15  may be plugged onto the end piece  17  of the nozzle needle  5 , wherein web-like wall sections  34  may project through the cutouts  32 , and the wall sections  34  of the second piston  15  rest with edge faces  27  on the stop plate  18 , as is illustrated in  FIG. 4 . The spring element  21  may then be plugged onto the stepped, upper region of the second piston  15 , as is illustrated in  FIG. 5 . The sleeve  14  may then be fitted onto the second piston  15 , as is illustrated in  FIG. 6 . The sleeve  14  may then be welded in the outer edge region to the connecting part  20 , as is illustrated in cross section in  FIG. 7 . For further mounting, the first piston  12  may be plugged into an opening  35  in the bottom  13  of the sleeve  14 , as is illustrated in  FIG. 2 .