Abstract:
An injection valve for injecting fuel into an internal combustion engine may include an actuator and an injection needle associated with a sealing seat. A hydraulic transmission unit may establish an effective connection between the actuator and the injection needle. The transmission unit may include two movable pistons, between which a movable pot is arranged. The movable pot may be guided within another stationary pot. The first piston may be guided through the bottom of the other pot, and the second piston is guided within a sleeve section of the pot. A first chamber may be formed between the other pot and pot, and a second chamber may be formed between pot and the second piston. The two chambers may be interconnected via at least one duct. 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 
     This application is a U.S. National Stage Application of International Application No. PCT/EP2010/058158 filed Jun. 10, 2010, which designates the United States of America, and claims priority to German Application No. 10 2009 024 596.0 filed Jun. 10, 2009, the contents of which are hereby incorporated by reference in their entirety. 
     TECHNICAL FIELD 
     The invention relates to an injection valve, e.g., a transmission unit of a fuel injection valve. 
     BACKGROUND 
     In the prior art, for example WO 2008/003347 A1, U.S. Pat. No. 6,575,138 B2 and U.S. Pat. No. 6,298,829 discloses injection valves in which a hydraulic transmission unit is provided between an actuator and the nozzle needle. 
     In the known prior art, the deflection of the actuator is transmitted into a corresponding deflection of the nozzle needle. 
     SUMMARY 
     In an embodiment, an injection valve for injecting fuel into an internal combustion engine may include an actuator, including a nozzle needle which is assigned to a sealing seat, wherein a transmission unit is provided which establishes an operative connection between the actuator and the nozzle needle, characterized in that the transmission unit has two movable pistons, wherein a movable pot is arranged between the two pistons, wherein the movable pot is guided in a sleeve-shaped section of a further, fixed pot, wherein the first piston is guided through an opening in the bottom of the further pot with a third sealing gap, wherein the second piston projects into a sleeve-shaped section of the pot with a fourth sealing gap, wherein a first chamber is formed between the further pot and the pot, wherein a second chamber is formed between the pot and the second piston, wherein the two chambers are connected to one another via at least one duct, and wherein one piston is operatively connected to the nozzle needle, and the other piston is operatively connected to the actuator. 
     In a further embodiment, a spring element, which prestresses the movable pot in the direction of the first piston, is clamped in between the nozzle needle and the movable pot. In a further embodiment, the first piston rests on an upper side of a bottom of the movable pot. In a further embodiment, two ducts are provided which connect the two chambers, wherein the two ducts are formed in a bottom of the movable pot. In a further embodiment, the second piston bounds the second chamber with a second end face, wherein the further pot bounds the first chamber with a second annular face which surrounds the first piston, and wherein the second end face is smaller than the second annular face. In a further embodiment, the fixed pot is connected to the housing via a disk-shaped edge region, wherein a drilled hole is formed in the edge region, which drilled hole connects an upper interior space of the injection valve to a lower interior space of the injection valve. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Example embodiments will be explained in more detail below with reference to figures, in which: 
         FIG. 1  shows a schematic design of an injection valve, according to certain embodiments; 
         FIG. 2  shows a transmission unit, according to certain embodiments; 
         FIG. 3  shows a nozzle body with a nozzle needle, according to certain embodiments; 
         FIG. 4  shows a nozzle needle with a second pot, according to certain embodiments; 
         FIG. 5  shows a nozzle needle with a fixed pot, according to certain embodiments; and 
         FIG. 6  shows a nozzle needle with a transmission piston, according to certain embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     Certain embodiments provide an improved transmission unit for an injection valve. 
     In some embodiments, the transmission unit has two movable pistons, wherein a movable pot is arranged between the two pistons, wherein the movable pot is guided in a further fixed pot, wherein the first piston is guided through a bottom of the further pot with a first sealing gap, wherein the second piston is guided in a sleeve section of the pot with a second sealing gap, wherein a first chamber is formed between the further pot and the pot, wherein a second chamber is formed between the pot and the second piston, wherein the two chambers are connected to one another via at least one duct, and wherein one piston is operatively connected to the nozzle needle, and the other piston is operatively connected to the actuator. According to such embodiments, a transmission unit may reliably permit the deflection of the actuator to be transmitted to the nozzle needle. 
     In one embodiment, a spring element, which prestresses the movable pot in the direction of the first piston, is clamped in between the nozzle needle and the movable pot. Prestress of the nozzle needle in the direction of a sealing seat may therefore be made possible. 
     In a further embodiment, the first piston rests on an outer side of the bottom of the movable pot. Idle travel may therefore be set precisely. 
     In a further embodiment, two ducts are provided which connect the two chambers, wherein the two ducts are formed in the bottom of the movable pot. The formation of two ducts may permit rapid pressure equalization between the two chambers. 
     In a further embodiment, the second piston bounds the second chamber in a second end face, wherein the further pot bounds the first chamber with a second annular face which surrounds the first piston. The second end face of the second piston may be smaller than the second annular face of the further pot. In this way, transmission of the deflection of the actuator into a relatively large deflection of the nozzle needle may be made possible. As a result, small deflections, for example of a piezo-electric actuator, may be converted into relatively large deflections of the nozzle needle. 
       FIG. 1  is a schematic illustration of an example injection valve  1 , according to certain embodiments. The example 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  is mounted so as to be movable in the longitudinal direction in the nozzle body  3 . The nozzle needle  5  is operatively connected to an actuator  7  via a transmission unit  40 . A fuel space  8 , which is supplied with fuel via ducts (not illustrated), for example via a fuel accumulator and/or via a fuel pump, is formed in the lower region of the nozzle body  2 , between the nozzle needle  5  and the nozzle body  3 . An annular sealing seat  10  is formed on the inside 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  is assigned to the sealing seat  10 . Depending on the position of the nozzle needle, which is set by the activation of the actuator  7 , the nozzle needle  5  lifts off from the sealing seat  10  and clears a hydraulic connection between the fuel space  8  and the injection holes  9 . 
     The actuator  7  can be embodied, for example, as a piezo-electric actuator or as a magnetic actuator. Through electrical energization of the actuator  7 , the actuator  7  becomes longer and therefore acts on the transmission unit  40 . The transmission unit  40  is 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 converted into an opposing movement of the nozzle needle  5  in the direction of the actuator  7  by means of the transmission unit  40 . 
       FIG. 2  shows an enlarged illustration of the example transmission unit  40 , according to certain embodiments. In the transmission unit  40 , a cylindrical first piston  12  projects through an opening  15  in a bottom  13  of a pot  14 . The pot  14  is fixedly connected to the housing  2  by means of an edge region  41  which runs round in a disk shape. Drilled holes  6  are formed in the edge region  41 , through which drilled holes  6  fuel can flow from an upper interior space of the injection valve to a lower interior space of the injection valve. A second sleeve-shaped pot  42  is arranged in the pot  14 , said pot  42  being movably mounted in a sleeve-shaped section of the pot  14 . A cylindrical end piece  17  of the nozzle needle  5  is guided into the sleeve-shaped section of the second pot  42 . 
     The end piece  17  constitutes a piston. The first piston  12  rests with the end face  28  on an upper side of a second bottom  43  of the second pot  42 . Two ducts  44 ,  45  are formed in the second bottom  43 . A first chamber  46  is formed between the first and the second pots  14 ,  42  and the first piston  12 . A second chamber  47  is formed between the second pot  42  and the end piece  17 . 
     The first pot  14  bounds the first chamber  46  with a second annular face  52  which is formed on an inner side of the bottom  13 . The end piece  17  bounds the second chamber  47  with a second end face  53 . The second end face  53  may be smaller than the second annular face  52 . In particular, the second end face  53  is half as large as the second annular face. The surface area ratio between the second end face  53  and the second annular face defines a transmission between the deflection of the actuator and the deflection of the nozzle needle. A third spring element  48  is clamped between the second pot  42  and the nozzle needle  5 . The first and second ducts  44 ,  45  connect the first and second chambers  46 ,  47 . The first piston  12  is guided in a seal-forming fashion via a third sealing gap  49  in the bottom  13 . The second pot  42  is guided in a seal-forming fashion in a sleeve-shaped section of the fixed pot  14  via a fourth sealing gap  50 . The end piece  17  is guided in a seal-forming fashion in the sleeve-shaped section of the second pot  42  via a fifth sealing gap  51 . The third, fourth and fifth sealing gaps  49 ,  50 ,  51  may have a width of 2 to 20 μm, in particular in the region of 8 μm. The third, fourth and fifth sealing gaps  49 ,  50 ,  51  are dimensioned in such a way that the first and second chambers which are filled with fuel are sealed with respect to the interior space of the injection valve when there is a brief application of pressure, which occurs during injection processes. The third, fourth and fifth sealing gaps  49 ,  50 ,  51  ensure that the first and second chambers  46 ,  47  are always filled with fuel and that pressure differences which are present over relatively long time periods, i.e. for longer than injection processes, are equalized. 
     The transmission unit  40  functions as follows: in the non-actuated state of the actuator  7  the nozzle needle  5  is seated with the sealing face  11  on the sealing seat  10 , with the result that there is no connection between the fuel space  8  and the injection holes  9 . There is therefore no injection of fuel. The actuator  7  rests here on the first piston  12 . The first piston  12  rests on the second bottom  43  of the second movable pot  42  and therefore presses the nozzle needle  5  into the sealing seat via the third spring element  48 . The first and second chambers  46 ,  47  are completely filled with fuel, wherein the housing  2  in the region of the transmission unit  40  is also filled with fuel. 
     If an injection is then carried out, the actuator  7  is energized, with the result that the actuator moves downward in the direction of the transmission unit  40 . For this purpose, the actuator  7  is supported in the upper region against the housing  2  of the injection valve. The movement of the actuator  7  pushes the first piston  12  downward. The first piston  12  pushes the second pot  42  downward. The pressure in the second chamber  47  is therefore increased, with the result that fuel flows out of the second chamber  47  into the first chamber  46  via the first and second ducts  44 ,  45 . As a result the pressure in the second chamber  47  drops, with the result that the nozzle needle  5  moves upward and lifts off from the sealing seat  10 . Consequently, the injection starts. 
     If the injection is to be ended, the actuator  7  is actuated in such a way that it becomes shorter. As a result of this, the force acting on the first piston  12  and therefore also acting on the second pot  42  decreases. Consequently, the pressure in the second chamber  47  drops. In addition, the third spring element  48  causes the nozzle needle  5  to be pulled out of the second sleeve  42 . As a result, fuel flows back from the first chamber into the second chamber, and the nozzle needle  5  is pressed downward onto the sealing seat. 
       FIG. 3  shows a schematic illustration of the nozzle body  3  with the end piece  17  of the nozzle needle  5  and the third spring element  48  which rests on a step on the nozzle needle  5 , according to certain embodiments. 
       FIG. 4  shows a cross section through the second sleeve  42  which is fitted onto the end piece  17  of the nozzle needle, according to certain embodiments. The sleeve  14  is then fitted over the second sleeve  42 , as is illustrated in  FIG. 5 . The piston  12  is then pushed in through the opening in the bottom  13 , as is illustrated in  FIG. 6 . The actuator  7  is then mounted in the housing, and the structural unit as shown in  FIG. 1  is clamped to the housing  2  by means of the clamping nut  4 . The upper and lower interior spaces  18 ,  19  of the injection valve  1  are filled with fuel.