Abstract:
A first module ( 1 ) has an injector housing ( 4 ) and a lifting actuating drive. A second module ( 2 ) has a nozzle body ( 16 ), an injection needle ( 18 ), and a restoring means. At least one value of at least one characteristic number for the first module is determined by appropriate control of the lifting actuating drive, and the first module ( 1 ) is associated with a plurality of categories (CL) according to the at least one value of the at least one characteristic number. At least one value of at least one characteristic number for the second module ( 2 ) is determined by appropriate actuation of the injection needle ( 18 ), and the second module ( 2 ) is associated with one of the plurality of categories according to the at least one value of the at least one characteristic number. In each case, a first module ( 1 ) and a second module ( 2 ) of the same category are paired and mounted.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is a U.S. national stage application of International Application No. PCT/EP2005/050819 filed Feb. 25, 2005 which designates the United States of America, and claims priority to German application number DE 10 2004 021 652.5 filed May 3, 2004, the contents of which are hereby incorporated by reference in their entirety. 
     
    
     TECHNICAL FIELD  
       [0002]     The invention relates to a method for producing an injector, which is particularly appropriate for measuring fuel into a combustion chamber of a cylinder of an internal combustion engine.  
       BACKGROUND  
       [0003]     Increasingly stringent legal provisions governing permitted pollutant emissions from internal combustion engines disposed in motor vehicles mean that various measures have to be taken to reduce pollutant emissions. One approach is to reduce the pollutant emissions produced by the internal combustion engine during the combustion of the air/fuel mixture directly. This means that it is important for the fuel to be measured in very precisely, requiring an injector that can be activated in a very precise manner. Injectors comprise a number of components, each having certain production scatter. An injector regularly comprises an injector housing and a lift actuating drive, configured for example as a piezoactuator, as well as a nozzle lock nut, a nozzle body and a nozzle needle, which is guided in a recess of the nozzle body and releases or closes an injection nozzle as a function of its position. A reset means is also regularly provided, to pre-tension the nozzle needle into its closed position.  
       SUMMARY  
       [0004]     The object of the invention is to create a method for producing an injector, which makes it possible in a simple manner for the injector to be controlled precisely.  
         [0005]     The object can be achieved by a method for producing an injector, comprising the steps of assembling a first module comprising an injector housing and a lift actuating drive, assembling a second module comprising a nozzle body, a nozzle needle and a reset means for the nozzle needle, determining at least one value of at least one characteristic variable for the first module by appropriate activation of the lift actuating drive, assigning the first module to one of a number of classes as a function of the at least one value of the at least one characteristic variable, determining at least one value of at least one characteristic variable for the second module by appropriate actuation of the nozzle needle, assigning the second module to one of a number of classes as a function of the at least one value of the at least one characteristic variable, and pairing and assembling a first module with a second module of the same class, respectively.  
         [0006]     In an embodiment, a predetermined lift of the lift actuating drive can be set for the first module under the influence of a predetermined counter-force acting on the lift actuating drive and a variable, which is characteristic of the electrical energy that has to be supplied to the lift actuating drive for this purpose is determined as the characteristic variable. In an embodiment, a predetermined lift of the lift actuating drive can be set for the first module with a predetermined electrical energy being supplied and the counter-force required on the lift actuating drive for this purpose is determined as the characteristic variable. In an embodiment, at least one predetermined lift of the nozzle needle can be set for the second module with test fluid being supplied to the second module and a first characteristic variable can be determined as a function of the necessary force that has to be applied to act on the nozzle needle for this purpose. In an embodiment, the at least one predetermined lift of the nozzle needle can be set for the second module and a second characteristic variable can be determined as a function of a resulting throughflow of fluid through an injection nozzle of the nozzle body, with test fluid being supplied at a predetermined pressure. In an embodiment, at least one predetermined lift of the nozzle needle can be set for the second module and a predetermined throughflow of test fluid through the injection nozzle of the nozzle body can be set and a third characteristic variable can be determined as a function of the necessary pressure of the test fluid for this purpose. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]     Exemplary embodiments of the invention are described below based on the schematic drawings, in which:  
         [0008]      FIG. 1  shows a first and second module of an injector during the determination of at least one characteristic variable each for allocation to a class,  
         [0009]      FIG. 2  shows the finished injector,  
         [0010]      FIG. 3  shows a flow diagram of a program for determining a class of the first module,  
         [0011]      FIG. 4  shows a first embodiment of a program for determining the class of the second module and  
         [0012]      FIG. 5  shows a program of a second exemplary embodiment for determining the class of the second module. 
     
    
       [0013]     Elements with the same structure or function are shown with the same reference characters in all the figures.  
       DETAILED DESCRIPTION  
       [0014]     In an embodiment of a method for producing an injector, a first module comprising an injector housing and a lift actuating drive is mounted and a second module comprising a valve body, a nozzle needle and a reset means for the nozzle needle is mounted. At least one value of at least one characteristic variable is also determined for the first module by appropriate activation of the actuating drive. The first module is assigned to one or more classes as a function of the at least one value of the at least one characteristic variable. At least one value of at least one characteristic variable is determined for the second module by appropriate actuation of the nozzle needle. The second module is assigned to one or more classes as a function of the at least one value of the at least one characteristic variable. A first module is paired and mounted with a second module of the same class.  
         [0015]     There is therefore no need to adjust the injector and adjustment elements that may otherwise be needed for this purpose can be dispensed with. It is also possible in a simple manner to ensure a low rejection rate during injector production. Also the first module is not exposed to a test fluid during determination of the characteristic variables, to which test fluid the second module is generally exposed during determination of the at least one value of its at least one characteristic variable. Such a test fluid has the disadvantage that it can in some instances damage the lift actuating drive, if this is not integrated in the injector housing in a hermetically sealed manner. This is particularly critical in respect of a lift actuating drive configured as a piezoactuator, which is cast using a silicon casting compound, which in some instances swells on contact with a test fluid, which is a fuel for example.  
         [0016]     In one embodiment of the invention a predetermined lift of the lift actuating drive can be set for the first module under the influence of a predetermined counter-force on the lift actuating drive and a variable, which is characteristic of the electrical energy that has to be supplied to the lift actuating drive for this purpose is determined as the characteristic variable. The variable that is characteristic of the electrical energy that has to be supplied to the lift actuating drive for this purpose characterizes the individual activation response of the first module very effectively and is simple to acquire or determine.  
         [0017]     In a further embodiment of the invention a predetermined lift of the lift actuating drive can be set for the first module with a predetermined electrical energy being supplied and the counter-force on the lift actuating drive required for this purpose is determined as the characteristic variable. This counter-force on the lift actuating drive required for this purpose also characterizes the individual activation response of the first module very effectively.  
         [0018]     In a further embodiment of the invention at least one predetermined lift of the nozzle needle can be set for the second module with a test fluid being supplied to the second module and a first characteristic variable can be determined as a function of the necessary force that has to be applied to act on the nozzle needle for this purpose. The necessary force that has to be applied to act on the nozzle needle for this purpose characterizes the individual rigidity of the reset means of the second module very effectively.  
         [0019]     According to a further embodiment of the invention the at least one predetermined lift of the nozzle needle can be set for the second module and a second characteristic value can be determined as a function of a throughflow of fluid then resulting through an injection nozzle of the valve body with test fluid being supplied at a predetermined pressure. The resulting throughflow characterizes the individual geometry of the second module very effectively. It is also simple to set the predetermined lift of the nozzle needle and to supply test fluid at the predetermined pressure.  
         [0020]     According to a further embodiment of the invention at least one predetermined lift of the nozzle needle can be set for the second module and a predetermined throughflow of test fluid through the injection nozzle of the nozzle body can be set and a third characteristic variable can be determined as a function of the necessary pressure of the test fluid for this purpose. The pressure of the necessary test fluid for this purpose characterizes the individual geometry of the second module very effectively.  
         [0021]      FIG. 1  shows a first module  1  and a second module  2  of an injector during production of the injector and during determination of the characteristic variables to classify the first and second modules.  
         [0022]     The first module  1  comprises an injector housing  4 , having a recess extending in an axial direction, in which a thrust bearing  6  is preferably compressed. Axially adjacent to this is a hydraulic equalizing element  8  and adjacent to this a lift actuating drive configured as a piezoactuator  10 . A high-pressure hole  12  is also provided, which is provided to convey fuel from a fuel connection (not shown) to an injection nozzle  22  of the injector.  
         [0023]     The second module comprises a nozzle lock nut  14 , into which a nozzle body is inserted. The nozzle body  16  has a recess, into which a nozzle needle  18  is inserted. A reset means  20  is also provided, preferably configured as a spring, which pre-tensions the nozzle needle  18  into a closed position, in which it prevents the flow of fuel through the injection nozzle  22 . A transmission element  24  is also provided, which is configured to transmit the lift of the piezoactuator  10 . The transmission element  24  can alternatively also be disposed in the first unit or not be present at all.  
         [0024]     A first unit  26  is provided, which is connected in an electrically conductive manner to the piezoactuator  10  and by way of which a predeterminable electrical energy can be supplied to the piezoactuator  10 .  
         [0025]     A second unit  28  is also provided, by way of which a counter-force against the piezoactuator  10  can be set or even determined.  
         [0026]     A fourth unit  32  is also provided, by way of which a nozzle needle lift of the nozzle needle  18  can be set or even determined. A third unit  30  is also provided, by means of which the second module can be subjected to a test fluid, the third unit being configured to set a predetermined pressure of the test fluid or to determine the pressure of the test fluid. A fifth unit  34  is also provided, to receive the test fluid exiting from the injection nozzle  22 , thereby determining the throughflow of test fluid through the injection nozzle needle.  
         [0027]     An evaluation unit  36  is also provided, which is configured to assign the first and second modules  1 ,  2  respectively to one class CL of several classes CL respectively. Three classes CL can for example be provided but another number of classes CL can also be provided. The classes CL are selected such that injectors, which are made up in each instance of a first module and a second module of the same class, correspond very closely to a predetermined activation response and therefore ensure the precise measuring in of fuel.  
         [0028]     A program for determining the class CL of the first module  1  is started in a step S 1  ( FIG. 3 ).  
         [0029]     In a step S 2  a predetermined lift AH_G of the piezoactuator is set under the influence of a predetermined counter-force AF_G on the piezoactuator  10 . This is done using the first and second units  26 ,  28 . The predetermined lift AH_G can for example be 40 μm. The predetermined counter-force AF_G can for example be 100 N in respect of the state of the piezoactuator  10 , in which it is not deflected.  
         [0030]     In a step S 3  the electrical energy E_V, which was required to set the predetermined lift AH_G with the counter-force AF_G acting on the piezoactuator  10  at the same time, is determined. Steps S 2  and S 3  can also be repeated and a corresponding mean value of the required electrical energy E_V can thus be determined.  
         [0031]     In a step S 5  a class CL is assigned to the first module  1  as a function of the required energy E_V determined in step S 3 . Three classes are provided for example, such that either the first, second or third class is assigned in step S 5  as a function of the respective value of the required electrical energy E_V. The program is then terminated in a step S 7 .  
         [0032]     As an alternative to the procedure according to the program in  FIG. 3 , a predetermined electrical energy can also be supplied to the first module  1  and the predetermined lift AH_G can be set and it can then be determined what value the counter-force required on the lift actuating drive for this purpose must have. The class of the first module  1  is then also determined correspondingly as a function of the required counter-force.  
         [0033]     A program ( FIG. 4 ) for determining the class CL of the second module  2  is started in a step S 9 . In a step S 11  the third unit  30  sets a predetermined pressure of the test fluid and a first predetermined lift DH_G 1  of the nozzle needle  18  in the second module  2 . In a step S 13  the necessary first force F_V 1  required for this purpose and the resulting first throughflow FL_V 1  of test fluid through the injection nozzle  22  are then determined. The necessary first force F_V 1  is determined in the fourth unit  32 . The first throughflow FL_V 1  of test fluid is determined in the fifth unit  34 . It is possible for steps S 11  and S 13  to be repeated here too, with corresponding mean values being determined.  
         [0034]     In a step S 15  the class CL of the second module is determined as a function of the necessary first force F_V 1  and the first throughflow FL_V 1  of test fluid. Alternatively the class can also be determined solely as a function of the necessary first force F_V 1  or alternatively the first throughflow FL_V 1 . The program is then terminated in a step S 17 .  
         [0035]     A step S 19  is also preferably provided, in which a further second predetermined lift DH_G 2  of the nozzle needle  18  is set and a corresponding second necessary force F_V 2  and a corresponding second throughflow FL_V 1  of test fluid are acquired or determined and optionally also a further third predetermined lift DH_G 3  of the nozzle needle  18  is set and then a corresponding third necessary force F_V 3  and a corresponding third necessary throughflow FL_V 3  of test fluid are determined. The class CL of the second module is then determined in a step S 21  as a function of the necessary first to third forces F_V 1  to F_V 3  and/or the first to third throughflows FL_V 1  to FL_V 3  of test fluid.  
         [0036]      FIG. 5  shows a second embodiment of the program for determining the class CL of the second module  2 . In contrast to the program according to  FIG. 4 , the program is started in a step S 25  and in a step S 27  a first predetermined lift DH_G 1  of the nozzle needle  18  and a predetermined first throughflow FL_G 1  of test fluid through the injection nozzle are set. In a subsequent step S 29  the necessary first force for this purpose F_V 1  and the necessary first pressure for this purpose P_V 1  are determined or acquired, in the fourth unit  32  and the third unit  30 . The steps S 27  and S 29  can be repeated here too, with corresponding mean values being determined in step S 29 .  
         [0037]     In a step S 31  a class CL is then assigned to the second module  2 , as a function of the necessary first force F_V 1  and/or the necessary first pressure P_V 1 . The program is then terminated in a step S 31 . In a step S 35  the predetermined second lift DH_G 2  of the nozzle needle  18  is then also preferably set and then the correspondingly necessary second force F_V 2  and a correspondingly necessary second pressure P_V 2  are determined. The third predetermined lift DH_G 3  of the nozzle needle  18  is also preferably set and the necessary third force for this purpose F_V 3  is acquired or determined and the necessary pressure for this purpose P_V 3  is acquired or determined.  
         [0038]     The class CL is then assigned to the second module  2  in a step S 37  as a function of the necessary first to third force F_V 1  to F_V 3  and/or the necessary first to third pressure for this P_V 1  to P_V 3 .  
         [0039]     After carrying out the programs, first and second modules  1 ,  2  of the same class CL are then paired and program-controlled and for example mounted onto each other by program-controlled tightening of the nozzle lock nuts.