Abstract:
A fuel injector with an injector body is disclosed which has at least two separate function units that are largely independent of one another. The function units are reversibly joined to one another by a connecting element and at least one positioning pin. The two function units can be produced and tested separately, which greatly simplifies both the production process and maintenance of the fuel injectors and lessens the vulnerability of the fuel injectors to malfunction.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application is a 35 USC 371 application of PCT/EP 2005/056850 filed on Dec. 16, 2005. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   In fuel injection systems for direct-injection internal combustion engines, fuel injectors that contain one or more electrically triggerable valves are employed. For instance, an electrically triggerable magnet valve or piezoelectric valve may be provided for controlling a needle valve and thus for controlling the course of injection. Further valves may be used, for instance for a pressure boost. Separately testing the functionality of the various valves and the components connected to these valves or controlled by these valves, however, is often a challenge. 
   2. Prior Art 
   Since the electrically triggerable valve or valves are typically accommodated in the interior of an injector body, the production, testing and electrical contacting of these electrically triggerable valves as well as maintenance of the electrically triggerable valves often present considerable technical difficulties. 
   In many cases, on top of the injector body there is an electrical contact that can be connected to a corresponding control system and power supply system located outside the injector body. Via this contact (which may be either a plug with multiple contacts, or a plurality of individual plugs), all the electrically triggerable valves received in the interior of the injector body are as a rule triggered. In the interior of the injector body, this electrical contact must be connected to corresponding contacts of the electrically triggerable valve or valves of the injection system. This connection is typically done by means of flexible electrical cables and a simple soldering process. 
   This method for electrically contacting the electrically triggerable valves is associated with various disadvantages, however. For instance, the method is technically quite labor-intensive, since typically the cables must be initially soldered by hand against the corresponding electrical contacts. In practice, this method step requires great effort and is very time-consuming. Moreover, the connection between the electrically triggerable valves and the electrical contact on the injector body can be undone again only with difficulty. For removing or disassembling the injector body, soldered or welded connections must typically be disconnected again. Such a labor-intensive process makes it uneconomical to repair the injectors or replace individual parts of the injector body. 
   Moreover, in this method, testing the various functionalities of the fuel injectors sometimes presents major problems. In many cases, if a malfunction occurs in testing in the installed state, the fuel injector must be disassembled again, which is labor-intensive. Once the repair or replacement of individual components (such as of an electrically triggerable valve) has been done and the parts have been installed again, the functionality must then be tested again. In many cases, this method is too labor-intensive and thus uneconomical. 
   SUMMARY AND ADVANTAGES OF THE INVENTION 
   According to the invention, a fuel injector for injecting fuel into a combustion chamber of an internal combustion engine and a method for producing such a fuel injector are therefore proposed which avoid the described disadvantages of the prior art. A fundamental concept of the present invention is that an injector body of the fuel injector has at least two separate function units, which (for instance at least with regard to at least one functionality) are functional independently of one another and can be tested independently of one another. For instance, one function unit may have a control module for controlling a pressure boost of a fuel pressure, and another function unit may have a nozzle module for triggering an injection event by an injection valve member. The function units are reversibly connected or joined to one another via at least one nonpositive-engagement connecting element (such as a union nut) and at least one positioning pin. Instead of one or more positioning pins, according to the invention means that function the same way may also be employed, such as protrusions in the housing of one function unit that engage corresponding grooves in the other function unit and thus prevent relative rotation of the function units and make positioning the function units relative to one another easier. 
   The two function units each have at least one electrically triggerable valve (such as a magnet valve). Moreover, the fuel injector may have at least one electrical injector body contact, which is accessible from outside the injector body, and the second electrically triggerable valve has at least one valve contact, and the at least one electrical valve contact and the at least one electrical injector body contact are joined at least in part via at least one electrical solid conductor that is substantially dimensionally stable under its own weight. This electrical connection between valve contacts and the injector body contact can advantageously also include at least one electric plug contact, into which the at least one electrical solid conductor for instance is plugged. 
   In comparison to the prior art, the fuel injector of the invention makes a highly simplified production process possible. For instance, in particular, a first function unit can first be produced and tested, for instance with regard to the functionality of an electrically triggerable valve. Next, or parallel to this, a second function unit is produced and tested, for instance again with regard to the functionality of an electrically triggerable valve. Finally, the function units are reversibly joined to one another by means of the nonpositive-engagement connecting element, and an electrical connection between the at least one injector body contact and the at least one valve contact is made, for instance by means of plugging into an electric plug contact. 
   The separate testing of the individual function units enhances the process stability in the production of the fuel injectors considerably, and makes it possible to detect defects (such as electrical defects of the individual valves) early and eliminate them if applicable. The function units may thus also be produced separately and independently of one another. Simple removal and repair for maintenance purposes is possible. This lowers the overall costs of production and repair and enhances the reliability of the fuel injectors. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is described in further detail below in terms of the exemplary embodiments shown in the drawings. Identical reference numerals designate components that are the same as one another or correspond to one another in their function. Individually, the drawings show: 
       FIG. 1 , a sectional view of a fuel injector that has a first function unit (control unit) and a second function unit (nozzle unit); 
       FIG. 2A , a perspective view of the disconnection of the control unit and nozzle unit; 
       FIG. 2B , a perspective view of the control unit; 
       FIG. 2C , a perspective fragmentary view of the nozzle unit; 
       FIG. 3A , a perspective view of a control unit positioned relative to a nozzle unit by means of positioning pins; 
       FIG. 3B , a perspective view of the function units of  FIG. 3A , after the control unit and nozzle unit have been put together; 
       FIG. 3C , a perspective view of a nonpositive-engagement connection of the two function units of  FIG. 3B  by means of a union nut; and 
       FIG. 4 , a flow chart of a method according to the invention. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   In  FIG. 1 , an overall view of a preferred exemplary embodiment of an injector body  110  for a common rail injection system is shown. The injector body  110  can be disassembled at the butt joints  124 ,  126 ,  128  and  130  into essentially five function modules, namely one control module  132 , one sealing plate  134 , one line connection module  136 , one pressure booster module  138 , and one nozzle module  140 . The pressure booster module  138  serves essentially to boost a fuel pressure (for instance, 1000 bar), which is made available at the fuel injector from an external pressure source, for instance via a high-pressure collection chamber (common rail) to a second pressure (for instance 2200 bar), so that two operating pressures are available for the injection event. The nozzle module  140  has an injection valve member  146  (shown only symbolically in  FIG. 1 ), such as a nozzle needle, which controls the actual injection event into the combustion chamber of an internal combustion engine (for instance via injection openings). 
   The modules  132 ,  134 ,  136 ,  138  and  140  are grouped in this exemplary embodiment into two function units, namely one control unit  148  including the control module  132  and the sealing plate  134 , and one nozzle unit  150  including the line connection module  136 , the pressure booster module  138 , and the nozzle module  140 . These two function units  148  and  150  are separated or disconnected from one another by the second butt joint  126  and are reversibly joined together by a union nut  152 . The function units  148 ,  150  are furthermore joined together via the positioning pins  154  (in the sectional view of  FIG. 1 , only one of the positioning pins  154  can be seen), which are each received in corresponding positioning bores  156  in the control module  132 , in the sealing plate  134 , and in the line connection module  136 . 
   The injector body  110  furthermore has two magnet valves  111 ,  112 : a first magnet valve  111 , disposed in the control module  132 , for controlling the pressure boost in the pressure booster module  138 , and a second magnet valve  112 , disposed in the nozzle module  140 , for controlling the actual injection event via the injection valve member  146 . 
   Because two function units  148 ,  150  are separable or disconnectable along the second butt joint  126 , the (“dry”) control module  132  and the (“wet”) part of the injector body  110  located below the first butt joint  124  can be designed, produced and tested separately, and then put together. Moreover, because of this separability, individual components of the injector body  110  can easily be replaced for maintenance purposes, for instance, which is in accordance with the “system repair concept” (SRC). 
   The magnet valve  112  in the nozzle module  140  is electrically triggerable via two electrical valve contacts  114 . The injector body  110 , on its upper end, has an electrical injector body contact  116  that is accessible from above. In the modular construction of the injector body  110  as shown, the capability of breaking down the injector body  110  and of simple modular assembly is achieved by providing that the valve contacts  114  be connected electrically to the injector body contact  116  in such a way that simple assembly and capability of breaking down the injector body continue to be assured. 
   In this exemplary embodiment, for connecting the two electrical valve contacts  114  to the injector body contact  116 , two conductor conduits  120  are provided, which extend through the modules  138 ,  136  and  134 . The conductor conduits  120  are formed by bores in the pressure booster module  138 , in the line connection module  136 , and in the sealing plate  134 . Once the injector body  110  has been put together, these bores are each aligned at the butt joints  128  and  126 , so that the result is a single, continuous conductor conduit  120 . 
   The individual bores of the conductor conduit  120 , in this exemplary embodiment, in the various modules  138 ,  136 ,  134  each have a rectilinear course. With the provisions of the invention, a curved course of the bores can also be achieved. However, the bores in the individual modules  138 ,  136 ,  134  do have a different inclination relative to an injector axis  142 . While the conductor conduit  120  in the pressure booster module  138  has an inclination of 1° to the injector axis  142 , the inclination in the line connection module  136 , in this exemplary embodiment, is 2.2°. These different angles of inclination relative to the injector axis  142  are due to the fact that the injector body  110  tapers in its cross section toward the bottom, that is, from the control module  132  to the nozzle module  140 . 
   The connection between the two electrical valve contacts  114  of the magnet valve  112  and the injector body contact  116  is effected, in this exemplary embodiment, in part via two solid conductors  118 . The solid conductors  118  extend through the two conductor conduits  120  and connect the valve contacts  114  to electric plug contacts  122 , which in turn are connected to the injector body contact  116  via an electrical connection  144  (for instance, two cables each soldered at one end to an electric plug contact  122  and at another end to the injector body contact  116 ). The solid conductors  118  are thus fixedly or detachably connected electrically to the valve contacts  114  of the magnet valve  112 . 
   The connection of the solid conductors  118  to the plug contacts  122  is done reversibly, so that this connection can be made upon assembly of the injector body  110 , or in other words when the control unit  148  and nozzle unit  150  are put together, by simply pressing the solid conductors  118  into the plug contacts  122 . Conversely, in the event of maintenance, the solid conductors  118  can be easily removed from the plug contacts  122  again, and thus the injector body  110  can be broken down into the two function units  148 ,  150  again without having to unsolder electrical connections. 
   The solid conductors  118  are selected to be rigid enough that on the one hand they do not substantially change their shape under their own weight, and can thus be easily threaded through the conductor conduits  120  with their different inclinations to the injector axis  142  and plugged into the plug contacts  122 . The solid conductors should have a certain plasticity, so that no mechanical stresses arise either at the transition between portions of the conductor conduits  120  that have different angles of inclination. The term “solid conductor” does not necessarily narrow the choice of materials to solid elements; on the contrary, hollow conductors (tubes) may for instance also be used as solid conductors  118 , as long as they have sufficient mechanical rigidity. 
   In the exemplary embodiment shown in  FIG. 1 , the solid conductors  118  have as their material CuSn6 with a Brinell hardness of between 80 and 90 HB, a material that is otherwise used as a welding additive, for instance. Alternatively, however, CuAl8, CuAl8Ni2, CuAl8Ni6, CuAl9Fe, CuMn13Al7, CuSi3, CuSn, copper, or nickel silver, for instance, can also be used. These materials meet the aforementioned requirements in terms of hardness and plasticity and moreover are easily joined to the valve contacts  114  by welding. The hardness of the materials should be between 50 and 100 HB, preferably between 60 and 95 HB, and especially advantageously between 75 and 90 HB. 
   In  FIGS. 2A through 2C , the assembling of the fuel injector from the two individual function units  148  and  150  is shown in perspective. Particularly in  FIG. 2A , it can be seen how the control unit  148  and the nozzle unit  150  can be disconnected from one another along the butt joint  126  by loosening the union nut  152 . It can also be seen in  FIG. 2A  that the nozzle unit  150  has a fuel delivery stub  210 , by way of which the nozzle unit  150  can be supplied with fuel. This fuel delivery stub  210  may for instance be in communication with a high-pressure collection chamber (common rail). In particular, in this exemplary embodiment, the sealing plate  134  (see  FIG. 1 ), which is disposed in the control unit  148 , may be designed such that it prevents fuel from the nozzle unit  150  from getting into the control unit  148  via the butt joint  126 . Thus the butt joint  126 , as already described above, separates the “wet” nozzle unit  150  from the “dry” control unit  148 . This furthermore contributes to the fact that the two function units  148 ,  150  can be produced separately and tested separately. 
   In  FIG. 2B , a control unit is shown in perspective. It can be seen here that the injector body contact  116 , which is disposed on the top of the control unit  148 , has four individual connection pins or bolts  212  in this exemplary embodiment. Via two at a time of these connection bolts  212 , a given one of the two magnet valves  111 ,  112  can each be triggered. 
   It can also be seen in  FIG. 2B  that in this exemplary embodiment, two positioning pins  154  are let into the control unit  148 . These positioning pins  154  can for instance be let into corresponding positioning bores  156  of the control unit  148  (see  FIG. 1 ) either fixedly or detachably. As already described above, according to the invention, instead of positioning pins  154 , still other devices may be employed which make it easier to position the function units  148 ,  150  relative to one another and prevent the function units  148 ,  150  from rotating relative to one another. In particular, protrusions and corresponding grooves may be named in this respect. 
   In  FIG. 2C , in a fragmentary perspective view, the upper end of the nozzle unit  150  is shown. It can be seen here that the upper ends of the solid conductors  118  protrude from the line connection module  136 . For insulation from the injector body  110 , the solid conductors  118  are sheathed with shrink-fit hoses  214 , but the upper ends are stripped of insulation for the sake of contacting. As can be seen in conjunction with  FIG. 1 , when the function units  148 ,  150  are put together, the upper ends of the solid conductors  118  are thrust through conductor conduits  120  in the sealing plate  134  and are plugged into the plug contacts  122 . In addition, in this exemplary embodiment, O-rings  216  are slipped onto the ends of the solid conductors  118  at the top and are additionally meant to prevent fuel from the nozzle unit  150  from getting into the control unit  148  along the solid conductors  118 . 
   In  FIG. 2C , the orifices of the positioning bores  156  can also be seen, into which the positioning pins  154  of the control unit  148  are thrust when the two function units  148 ,  150  are joined together, in order to assure exact positioning of the control unit  148  relative to the nozzle unit  150  and thus to make it possible to plug the solid conductors  118  “blind” into the plug contacts  122 . 
   In  FIGS. 3A through 3C , the joining together of function units  148 ,  150  is shown in perspective. First, as shown in  FIG. 3A , the positioning pins  154 , which as can be seen in  FIG. 2B  are fixedly connected to the control unit  148  in this exemplary embodiment, are thrust into the positioning bores  156  in the nozzle unit  150 . As a result, the control unit  148  is positioned relative to the nozzle unit  150 , and thus the two function units  148 ,  150  can no longer rotate relative to one another. The plug contacts  122  thus already have the correct position relative to the upper ends of the solid conductors  118  as well. “Blindly” joining the two function units  148 ,  150  together by a motion of the control unit  148  in the joining direction  310  is thus possible, in which the upper ends of the solid conductors  118  are plugged into the plug contacts  122  and an electrical connection between the valve contacts  114  of the second magnet valve  112  and the injector body contact  116  is thus made (see  FIG. 1 ). The status of the two function units  148 ,  150  after the two function units  148 ,  150  have been put together is shown in perspective in  FIG. 2B . The union nut  152  has been left out of  FIGS. 3A and 3B  for the sake of simplicity. Once the two function units  148 ,  150  have been put together, the two function units are connected by nonpositive engagement to one another by screwing down the union nut  152 . For maintenance purposes, this connection by the union nut  152  can easily be undone again, so that the two function units  148 ,  150  can for instance be tested and repaired separately from one another. 
   In  FIG. 4 , a schematic flow chart of a method according to the invention for producing a fuel injector is shown. The method steps shown need not necessarily be performed in the order shown, and still other method steps not shown in  FIG. 4  may also be performed. 
   In a first method step  410 , a first function unit  148  of a fuel injector is produced; it has at least one injector body contact  116  and at least one first electrically triggerable valve  111 . In method step  412 , a first functionality of the first function unit  148 , in particular an electrical function of the first electrically triggerable valve  111 , is tested. 
   Independently of method steps  410  and  412 , in method step  414  a second function unit  150  is produced, which has at least one second electrically triggerable valve  112  with at least one electrical valve contact  114 . In method step  416 , a second functionality of this second function unit  150 , in particular an electrical function of the second electrically triggerable valve  112 , is tested. In the (optional) method step  418 , the two function units  148 ,  150  are then positioned relative to one another by means of at least one positioning pin  154 . Next, in method step  420 , the first function unit  148  and the second function unit  150  are reversibly connected to one another at a butt joint  126  by means of at least one nonpositive-engagement connecting element  152 , whereupon an electrical connection is made between the at least one injector body contact  116  and the at least one valve contact  114 . 
   The foregoing relates to a preferred exemplary embodiment of the invention, it being understood that other variants and embodiments thereof are possible within the spirit and scope of the invention, the latter being defined by the appended claims.