Abstract:
A common rail fuel injection device for internal combustion engines includes a housing, a high-pressure fuel connection, and a fuel return connection including a plug part for connection to a fuel return line. To make the fuel injection device easier to assemble, the fuel return connection includes a socket part, which is secured in fuelproof fashion in a fuel return opening in the housing and onto which the plug part is placed in fuelproof fashion.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a 35 USC 371 application of PCT/DE 02/01093 filed on Mar. 26, 2002. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a fuel injection device for internal combustion engines, in particular to a common rail injector, having a housing, having a high-pressure fuel connection, and having a fuel return connection that includes a plug part for connection to a fuel return line. 
     2. Description of the Prior Art 
     A known fuel injection device of the type with which this invention concerned is on the market. It is used in internal combustion engines for instance in which the fuel is injected directly into the combustion chamber of the engine. This can involve both Diesel engines and gasoline engines. The known fuel injection device is disposed directly on the cylinder head of the engine. Via a high-pressure pump and a fuel manifold, fuel is furnished to it under very high pressure. 
     Excessive fuel not delivered to the combustion chamber by the fuel injection device is carried away from the fuel injection device via a fuel return and reaches the fuel tank again, for instance, or the high-pressure pump. In the known fuel injection device, the connection of the return line is done on the axial end, remote from the cylinder head, of the fuel injection device. To that end, a plug part can be inserted into an opening in the housing of the fuel injection device. The fuel return line can then be connected in turn to this plug part. 
     In operation of the known fuel injection device, it has proved favorable to dispose the high-pressure fuel connection on the projecting end of the fuel injection device, which means that there is no longer any space at this point for the fuel return line. Moreover, because of the electrical connection, the injection device is seated deep in the cylinder head. As a result, known laterally insertable connections cannot be used. 
     It is therefore the object of the present invention to improve a fuel injection device of the type defined at the outset in such a way that it has an easily accessible return connection that can be adapted in a simple way to various installation situations. 
     This object is attained in that the fuel return connection includes a socket part, which is secured in fuelproof fashion in a fuel return opening in the housing and onto which the plug part is placed in fuelproof fashion. 
     SUMMARY OF THE INVENTION 
     The fuel injection device of the invention includes a two-part return connection, which comprises a socket part and a plug part. The presence of a separate socket part makes it possible to embody the return connection to suit individual installation conditions of a particular internal combustion engine, without having to make modifications in the overall fuel injection device. As a result, space is created for instance for the disposition of a high-pressure fuel connection on the projecting end of the fuel injection device. Moreover, by means of an advantageous embodiment of the socket part, it is possible to make the return connection easier to both install and remove, and thus also to improve the operating safety of the fuel injection device. 
     Advantageous refinements of the fuel injection device of the invention are also disclosed. In a first refinement, the socket part and the plug part are both plastic injection-molded parts. Such parts are extremely economical and can be produced easily even with a complex geometry. 
     Furthermore, the fuel return opening is disposed laterally in the housing, and the socket part can have one portion toward the device and one portion toward the plug, whose longitudinal axes are at an angle to one another, preferably of approximately 90°, such that the longitudinal axis of the portion toward the plug extends essentially parallel to the longitudinal axis of the housing of the fuel injection device. 
     This refinement is especially preferred, since with it the return opening can be disposed at a more or less arbitrary point on the housing of the fuel injection device. By means of a suitable embodiment of the socket part, it is possible to shift the connection position in the axial direction and thus make it readily accessible to the user. Also by means of this refinement, it is possible to dispose the high-pressure fuel connection on the projecting end of the fuel injection device and at the same time to design the return connection in such a way that it can be embodied axially accessibly and above all in the axial direction of the housing of the fuel injection device. 
     Advantageously, the plug part has at least one stub for connection of a fuel return hose. Alternatively, however, two stubs for connecting two fuel return hoses can be provided. In that case, the plug part can be connected to a return ring line. 
     In a particularly preferred refinement of the fuel injection device of the invention, the plug part is secured on the socket part via a detent connection. This detent connection is easy to produce, readily withstands the usual operating loads, and is easy to open, for instance for inspection. The plug part can have at least one detent arm, which cooperates with at least one detent lug on the socket part. 
     For easy release of the detent connection, it is also proposed that the detent arm has an actuating portion, by which it can be actuated by hand in such a way that it comes free of the detent lug. 
     In order after assembly to assure in a simple way that the plug part is locked on the socket part in the desired way, it is proposed that the detent lug has a different color than at least the detent arm, and the detent arm is disposed such that the detent lug is visible from outside, in the locked state. 
     To make it easier to assemble the fuel return connection, it is also proposed that there is one protrusion on either the plug part or the socket part, and on the respectively other part, there is a groove that is complementary to the protrusion, and the protrusion and the groove cooperate such that by them, the angular position of the plug part relative to the socket part is unambiguously defined. As a result of this refinement, it becomes impossible to mount the plug part on the socket part in the wrong way. 
     In another refinement, a simple fastening of the socket part to the housing of the fuel injection device is disclosed. Accordingly, the socket part is secured inseparably in the fuel return opening of the housing by means of spray coating with plastic. 
     To prevent liquid plastic, during the injection molding operation, from soiling the region toward the plug of the socket part and thus making the later assembly of the fuel return connection more difficult, it is proposed that the socket part has a collar substantially orthogonal to the portion toward the plug and encompassing the portion toward the plug. During the injection molding operation, the injection tool can seal off the socket part at this collar. 
     If the fuel injection device is actuated electrically, an electrical connection device must be provided at some point. In that case, it is advantageous if the socket part and the electrical connection device are secured to the housing by the same spray coating. Both connection devices are thus encapsulated in the same injection molding compound and are securely held on the housing of the fuel injection device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Below, exemplary embodiments of the invention are explained in detail in conjunction with the accompanying drawings, in which: 
       FIG.  1 : a fragmentary longitudinal section through a first exemplary embodiment of a fuel injection device, with a socket part and a plug part; 
       FIG.  2 : a side view of the socket part of  FIG. 1 ; 
       FIG.  3 : a plan view of the socket part of  FIG. 1 ; 
       FIG.  4 : a front elevation view of the socket part of  FIG. 1 ; 
       FIG.  5 : a section taken along the line V—V of  FIG. 3 ; 
       FIG.  6 : a view from below of the plug part of  FIG. 1 ; 
       FIG.  7 : a side view of the plug part of  FIG. 1 ; 
       FIG.  8 : a plan view on the plug part of  FIG. 1 ; 
       FIG.  9 : a section taken along the line IX—IX of FIG.  7  through the plug part of  FIG. 1 ; 
       FIG.  10 : a fragmentary longitudinal section through a second exemplary embodiment of a fuel injection device; 
       FIG.  11 : a perspective view of a third exemplary embodiment of a fuel injection device; 
       FIG.  12 : a perspective view of the plug and the socket of the fuel injection device of  FIG. 11 , in the uninstalled state; and 
       FIG.  13 : a view similar to  FIG. 12 , in the installed state. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In  FIG. 1 , a first exemplary embodiment of a fuel injection device is identified overall by reference numeral  10 . The fuel injection device  10  shown is a common rail injector. It serves in an internal combustion engine to inject the fuel directly into the combustion chamber of the engine. Neither the engine nor the combustion chamber is shown in FIG.  1 . 
     The injector  10  includes a housing  12 , which on its lower end, not shown in  FIG. 1 , is secured to the cylinder head of the engine. On the end of the injector  10  projecting from the cylinder head of the engine, that is, the end that is visible in  FIG. 1 , there is a high-pressure fuel connection (not visible). An electrical connection  14  is also provided there, by way of which the injector  10  can be connected to an engine control unit (not shown). 
     Laterally in the upper region of the housing  12  is a fuel return connection  16 , which comprises a socket part  18  and a plug part  20 . The socket part  18  is inserted into a return opening  22  in the housing  12  of the injector  10 . The longitudinal axis of the return opening  22 , in the present exemplary embodiment, extends in the radial direction, that is, perpendicular to the longitudinal axis of the housing  12  of the injector  10  (but in an exemplary embodiment not shown, there can also be an offset between the longitudinal axis of the housing and the longitudinal axis of the return opening). Via the return opening  22 , the fuel which was delivered to the injector via the high-pressure fuel connection but was not injected into the combustion chamber of the engine, is carried away from the injector  10 . 
     The detailed embodiment of the socket part  18  will now be explained in conjunction with FIGS.  2 - 5 : 
     The socket part  18  includes a portion  24  toward the injection device and a portion  26  toward the plug. The portion  24  toward the injection device is essentially cylindrically, and on its projecting end, somewhat spaced apart from it, it has an encompassing groove  28 . An O-ring, not shown in  FIGS. 2-5 , is inserted into the groove  28 . By this O-ring, the portion  24  toward the device of the socket part  18  is sealed off from the return opening  22 , in the installed position shown in  FIG. 1. A  flow conduit  30  (see  FIG. 5 ) extends in the interior of the portion  24  toward the injection device. 
     The portion  26  toward the plug is formed onto the end of the portion  24  toward the device projecting from the housing  12 , in the installed position. It includes a likewise essentially cylindrical conduit housing  32 , whose longitudinal axis extends at a right angle to the longitudinal axis of the portion  24  toward the device. The longitudinal axis of the portion  26  toward the plug is thus essentially parallel to the longitudinal axis of the housing  12  of the injector  10 . 
     A flow conduit  34  extends in the interior of the conduit housing  32  and communicates fluidically with the flow conduit  30  in the portion  24  toward the device of the socket part  18 . An encompassing groove  36  is also embodied in the portion  26  toward the plug, on its projecting end, spaced apart somewhat from it, and an O-ring, not shown in  FIGS. 2-5 , is placed in this groove. In the installed position, the sealing between the socket part  18  and the plug part  20  is effected by this O-ring. 
     Via four spacers  38 , protruding approximately radially from the conduit housing  32 , a guide ring  40  is formed onto the conduit housing  32 . The center axis of the guide ring  40  and the center axis of the conduit housing  32  are in alignment with one another. The guide ring  40  has an approximately quadrilateral cross section with greatly rounded corners. The rounding of the diagonally opposed corners is the same in each case, while rounded corners next to them differ from one another. The guide ring  40  extends axially to a height just before the groove  36 . 
     A narrow guide slot  42  extending in the axial direction is made in the guide ring  40  at one point. The guide slot  42  extends from the edge  44  of the guide ring  40  toward the plug, over approximately one-third of the length of the guide ring  40 . On the end of the guide ring  40  toward the portion  24  toward the device, spaced apart somewhat from this end, an encompassing collar  46  is formed onto the guide ring  40 . One detent lug  48  is formed onto each of two diametrically opposed regions of the guide ring  40 . The detent lug  48  are colored bright green, while conversely the other parts of the socket part  15  are left grayish black. 
     The plug part  20  will now be explained in detail in conjunction with FIGS.  6 - 9 : 
     It includes an approximately cylindrical base portion  50 . Formed onto the upper end of base portion  50  is a radially protruding connection stub  52 . A flow conduit  54  ( FIG. 9 ) extends in the interior of the base portion  50 . A fastening plate  56  is formed onto the upper region of the base portion  50 . The plane of the fastening plate  56  is orthogonal to the longitudinal axis of the base portion  50 . The fastening plate  56  has an elliptical basic outline overall. Recesses  58  are located in the region of the longer half-axes of the fastening plate  56 . 
     In diametrically opposed end regions of the fastening plate  56 , detent arms  60  are also provided, which extend parallel to the longitudinal axis of the base portion  50 . The portion of the detent arms  60  located at the level of the connection stub  52  is embodied as an actuating portion  62 . The portion of the detent arms  60  located at the level of the lower region of the base portion  50  in  FIGS. 7 and 9  has one detent hook  64 , oriented toward the base portion  50 , on each of its projecting ends. The detent hook  64  is colored bright red, while all the other parts of the plug part  20  are kept grayish black. 
     Guide aprons  66  extend downward parallel to the base portion  50  from the side regions of the fastening plate  56 , below the shorter half-axes. A riblike protrusion  68  is embodied between one of the two guide aprons  66  and the base portion  50 . 
     The assembly of the injector  10  is done as follows: 
     First, the electrical connection  14  is placed at the top on the housing  12 . Then the socket part  18  is inserted, with the portion  24  toward the injection device, into the return opening  22 . This is done in such a way that the portion  26  toward the plug of the socket part  18  extends upward, in terms of  FIG. 1 , parallel to the longitudinal axis of the housing  12  of the injector  10 . In an injection molding tool, the electrical connection  14  and the socket part  18  are now spray-coated with plastic compound  70 . The injection-molding tool is sealed off from the outside by the collar  46 , among other provisions. By means of the plastic spray coating  70 , the socket part  18  is fastened securely to the housing  12 . 
     After the injector  10  has been installed in the engine, the fuel return connection  16 , among other elements, is attached. This is done first by slipping the plug part  20  onto the socket part  18  in the axial direction, as indicated by the arrow  72 . For doing so, the user firmly holds the plug part by the actuating portions  62 . The user guides the plug part  20  in such a way that the protrusion  68  between the guide aprons  66  and the base portion  50  of the plug part engages the guide slot  42  in the portion  26  toward the plug of the socket part  18 . 
     Thus the protrusion  68  and the guide slot  42  assure that the plug part  20  is secured in a defined angular position relative to the socket part  18 . During the process of sliding the plug part on, the guide aprons  66  slide along the guide ring  40 . Because of the geometric shape of the guide ring  40 , with the differently rounded corners, and because of the guide aprons  66 , once again an unambiguous angular position of the plug part  20  relative to the socket part  18  is also defined. In addition, the plug part  20  is centered relative to the socket part  18  during the process of being slipped on, by means of the guide aprons  66  and the guide ring  40 . 
     During the process of sliding the plug part on, the detent hooks  64  slide on the detent arms  60  of the plug part  20  over the detent lugs  48  on the socket part  18 . From the standpoint of the user, initially only the red detent hooks  64  are then visible. As a result, the detent hooks  64  are pressed elastically radially outward on the detent arms  60 . At the end of the slipping-on operation, the detent hooks  64  on the ends of the detent arms  60  snap radially inward and rest with an axial retaining face (not shown) on the corresponding detent lugs  48  of the socket part  18 . In this way, the plug part  20  is securely fixed to the socket part  18 . The red detent hooks  64  are now concealed to the view of the user by the green detent lugs  48 . This gives the user visual feedback about the connection that has been made. 
     To release the plug part  20  from the socket part  18 , the user presses the actuating portions  62  of the detent arms  60  radially inward. This moves the detent hooks  64  radially outward, thus releasing them from the detent lugs  48 . The user can now pull the plug part  20  off again from the socket part  18 . 
     A leakage hose (not shown) is then slipped onto the connection stub  52 . By way of this hose, excess fuel can be returned. 
     In  FIG. 10 , a second exemplary embodiment of an injector  10  is shown. Parts and elements that have equivalent functions to parts and elements of the exemplary embodiment described above are identified by the same reference numerals. They will not be explained again in detail. 
     In a distinction from the injector  10  described in  FIGS. 1-9 , the injector  10  shown in  FIG. 10  has a plug part  20  which includes two connection stubs  52 , pointing diametrically away from one another, on the base portion  50 . In this way, it is possible to connect the injector  10  to an annular leakage line (not shown). 
     In  FIGS. 11-13 , a third exemplary embodiment of a fuel injection device  10  is shown. Parts and elements that have equivalent functions to parts and elements of the exemplary embodiments described above are identified by the same reference numerals. They are not explained again in detail. 
     Unlike the exemplary embodiments described above, in this exemplary embodiment there is only a single detent arm  60  on the plug part  20 . Moreover, this detent arm  60  is not produced integrally with the plug part  20  but instead comprises a separate sheet-metal part, which is clipped into the plug part  20 . For better manipulation, a plurality of retaining plates  74  are formed onto the projecting end of the plug part  20  and furthermore serve to protect the connection stubs  22 . 
     The foregoing relates to 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.