Patent Publication Number: US-2009229575-A1

Title: Coupling device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to EP Patent Application No. 08003045 filed Feb. 19, 2008, the contents of which is incorporated herein by reference in its entirety. 
     TECHNICAL FIELD 
     The invention relates to a coupling device for hydraulically and mechanically coupling a fuel injector to a fuel rail of a combustion engine. 
     BACKGROUND 
     Coupling devices for hydraulically and mechanically coupling a fuel injector to a fuel rail are in widespread use, in particular for internal combustion engines. Fuel can be supplied to an internal combustion engine by the fuel rail assembly through the fuel injector. The fuel injectors can be coupled to the fuel injector cups in different manners. 
     In order to keep pressure fluctuations during the operation of the internal combustion engine at a very low level, internal combustion engines are supplied with a fuel accumulator to which the fuel injectors are connected and which has a relatively large volume. Such a fuel accumulator is often referred to as a common rail. 
     Known fuel rails comprise a hollow body with recesses in form of fuel injector cups, wherein the fuel injectors are arranged. The connection of the fuel injectors to the fuel injector cups that supply the fuel from a fuel tank via a low or high-pressure fuel pump needs to be very precise to get a correct injection angle and a sealing of the fuel. 
     SUMMARY 
     According to various embodiments, a coupling device for hydraulically and mechanically coupling a fuel injector to a fuel rail can be designed which is simply to be manufactured and which facilitates a reliable and precise connection between the fuel injector and the fuel injector cup without a resting of the fuel injector on the cylinder head. 
     According to an embodiment, a coupling device for hydraulically and mechanically coupling a fuel injector to a fuel rail of a combustion engine, the fuel injector having a central longitudinal axis, may comprise—a fuel injector cup being designed to be hydraulically coupled to the fuel rail and to engage a fuel inlet portion of the fuel injector,—a first ring element being fixedly coupled to the fuel injector cup, and—a second ring element being fixedly coupled to the fuel injector and being fixedly coupled to the first ring element to retain the fuel injector in the fuel injector cup in direction of the central longitudinal axis. 
     According to a further embodiment, the fuel injector cup may comprise a groove, a first snap ring being arranged in the groove and being designed to fixedly couple the first ring element to the fuel injector cup. According to a further embodiment, the groove and the first snap ring can be arranged and designed to form a positive fitting coupling between the first ring element and the fuel injector cup which is designed to prevent a movement of the first ring element relative to the fuel injector cup at least in a first direction of the central longitudinal axis. According to a further embodiment, a welding seam may be arranged between the first ring element and the fuel injector cup to fixedly couple the first ring element to the fuel injector cup. According to a further embodiment, the first ring element can be in one part with the fuel injector cup. According to a further embodiment, the fuel injector may comprise a groove, a second snap ring being arranged in the groove of the fuel injector and is designed to fixedly couple the second ring element to the fuel injector. According to a further embodiment, the groove of the fuel injector and the second snap ring can be arranged and designed to form a positive fitting coupling between the second ring element and the fuel injector which is designed to prevent a movement of the second ring element relative to the fuel injector at least in a second direction of the central longitudinal axis opposing the first direction of the central longitudinal axis. According to a further embodiment, a welding seam can be arranged between the second ring element and the fuel injector to fixedly couple the second ring element to the fuel injector. According to a further embodiment, the second ring element can be in one part with the fuel injector. According to a further embodiment, one of the ring elements can be designed and arranged to enable a screw coupling between the ring elements. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
       Embodiments are explained in the following with the aid of schematic drawings. These are as follows: 
         FIG. 1  an internal combustion engine in a schematic view, 
         FIG. 2  a longitudinal section through a fuel injector, 
         FIG. 3  a longitudinal section through a first embodiment of a coupling device, 
         FIG. 4  a longitudinal section through a second embodiment of the coupling device, and 
         FIG. 5  a longitudinal section through a third embodiment of the coupling device. 
     
    
    
     Elements of the same design and function that occur in different illustrations are identified by the same reference character. 
     DETAILED DESCRIPTION  
     The various embodiments are distinguished by a coupling device for hydraulically and mechanically coupling a fuel injector to a fuel rail of a combustion engine, the fuel injector having a central longitudinal axis, the coupling device comprising 
     a fuel injector cup being designed to be hydraulically coupled to the fuel rail and to engage a fuel inlet portion of the fuel injector, a first ring element being fixedly coupled to the fuel injector cup, and a second ring element being fixedly coupled to the fuel injector and being fixedly coupled to the first ring element to retain the fuel injector in the fuel injector cup in direction of the central longitudinal axis. 
     This has the advantage that a fast and secure coupling of the fuel injector in the fuel injector cup is possible. Furthermore, the coupling of the fuel injector with the fuel rail by the ring elements of the fuel injector and the fuel injector cup allows an assembly of the fuel injector and the fuel rail without a further metallic contact between the fuel injector and further parts of the combustion engine. Consequently, a noise transmission between the fuel injector and further parts of the combustion engine can be kept small. 
     In an embodiment the fuel injector cup comprises a groove, and a first snap ring is arranged in the groove and is designed to fixedly couple the first ring element to the fuel injector cup. This may allow a simple construction of the coupling device which enables to carry out a fast and secure but reversible coupling of the first ring element to the fuel injector cup. 
     In a further embodiment the groove and the first snap ring are arranged and designed to form a positive fitting coupling between the first ring element and the fuel injector cup which is designed to prevent a movement of the first ring element relative to the fuel injector cup at least in a first direction of the central longitudinal axis. By this a secure coupling of the first ring element to the fuel injector cup is enabled. 
     In a further embodiment the coupling device has a welding seam which is arranged between the first ring element and the fuel injector cup to fixedly couple the first ring element to the fuel injector cup. This allows a simple construction of the coupling device and carrying out a very secure coupling of the fuel injector to the fuel injector cup. 
     In a further embodiment the first ring element is in one part with the fuel injector cup. This has the advantage that a very secure coupling of the fuel injector to the fuel injector cup is possible. Furthermore, a simple machining of the first ring element together with the fuel injector cup is possible. 
     In a further embodiment the fuel injector comprises a groove, a second snap ring is arranged in the groove of the fuel injector and is designed to fixedly couple the second ring element to the fuel injector. This may allow a simple construction of the coupling device which enables to carry out a fast and secure but reversible coupling of the second ring element to the fuel injector. 
     In a further embodiment the groove of the fuel injector and the second snap ring are arranged and designed to form a positive fitting coupling between the second ring element and the fuel injector which is designed to prevent a movement of the second ring element relative to the fuel injector at least in a second direction of the central longitudinal axis opposing the first direction of the central longitudinal. By this a secure coupling of the second ring element to the fuel injector is enabled. 
     In a further embodiment a welding seam is arranged between the second ring element and the fuel injector to fixedly couple the second ring element to the fuel injector. This allows a simple construction of the coupling device and carrying out a very secure coupling of the fuel injector to the fuel injector cup. 
     In a further embodiment the second ring element is in one part with the fuel injector. This has the advantage that a very secure coupling of the fuel injector to the fuel injector cup is possible. Furthermore, a simple machining of the second ring element together with the fuel injector is possible. 
     In a further embodiment one of the ring elements is designed and arranged to enable a screw coupling between the ring elements. This has the advantage that a simple construction of the coupling device is possible which allows carrying out a fast and secure coupling of the fuel injector in the fuel injector cup. Furthermore, a defined positioning of the fuel injector relative to the fuel injector cup in axial and circumferential direction is enabled. 
     A fuel feed device  10  is assigned to an internal combustion engine  22  ( FIG. 1 ) which can be a diesel engine or a gasoline engine. It includes a fuel tank  12  that is connected via a first fuel line to a fuel pump  14 . The output of the fuel pump  14  is connected to a fuel inlet  16  of a fuel rail  18 . In the fuel rail  18 , the fuel is stored for example under a pressure of about 200 bar in the case of a gasoline engine or of about 2,000 bar in the case of a diesel engine. Fuel injectors  20  are connected to the fuel rail  18  and the fuel is fed to the fuel injectors  20  via the fuel rail  18 . 
       FIG. 2  shows the fuel injector  20 . The fuel injector  20  has a fuel injector body  21  and is suitable for injecting fuel into a combustion chamber of the internal combustion engine  22 . The fuel injector  20  has a fuel inlet portion  24  and a fuel outlet portion  25 . 
     Furthermore, the fuel injector  20  comprises a valve needle  26  taken in a cavity  29  of the fuel injector body  21 . On a free end of the fuel injector  20  an injection nozzle  28  is formed which is closed or opened by an axial movement of the valve needle  26 . In a closing position a fuel flow through the injection nozzle  28  is prevented. In an opening position fuel can flow through the injection nozzle  28  into the combustion chamber of the internal combustion engine  22 . 
       FIGS. 3 to 5  show different embodiments of a coupling device  50  which comprises the fuel injector  20 . The coupling device  50  is designed to be coupled to the fuel rail  18  of the internal combustion engine  22 . The coupling device  50  has a fuel injector cup  30 , a first ring element  36  and a second ring element  38 . The fuel injector cup  30  comprises an inner surface  34  and an outer surface  35  and is hydraulically coupled to the fuel rail  18 . Furthermore, the fuel injector cup  30  is in engagement with the fuel inlet portion  24  of the fuel injector  20 . The fuel inlet portion  24  of the fuel injector  20  comprises a sealing ring  48  with an outer surface  49 . 
     The first ring element  36  is fixedly coupled to the fuel injector cup  30 . The second ring element is fixedly coupled to the fuel injector  20 . Preferably, the first ring element  36  has a through hole  44  and the second ring element  38  has a thread  46 . The first ring element  36  and the second ring element  38  are fixedly coupled with each other by a screw  47  which is received by the through hole  44  of the first ring element  36  and is screwed into the thread  46  of the second ring element  38 . 
     As the first ring element  36  is fixedly coupled to the fuel injector cup  30 , the second ring element  38  is fixedly coupled to the fuel injector  20  and the first ring element  36  is fixedly coupled to the second ring element  38  by the screw  47 , the fuel injector  20  is retained in the fuel injector cup  30  in direction of the central longitudinal axis L. 
       FIG. 3  shows an embodiment of the coupling device  50  wherein the fuel injector cup  30  has a groove  32  and the fuel injector  20  has a groove  27 . The coupling device  50  has a first snap ring  40  which is arranged in the groove  32  of the fuel injector cup  30  and a second snap ring  42  which is arranged in the groove  27  of the fuel injector  20 . The first ring element  36  is in engagement with the first snap ring  40  and the second ring element is in engagement with the second snap ring  42 . 
     The first snap ring  40  enables a positive fitting coupling between the first ring element  36  and the fuel injector cup  30  to prevent a movement of the first ring element  36  relative to the fuel injector cup  30  in a first direction D 1 . The second snap ring  42  enables a positive fitting coupling between the second ring element  38  and the fuel injector  20  to prevent a movement of the second ring element  38  relative to the fuel injector  20  in a second direction D 2 . The first direction D 1  and the second direction D 2  are opposing directions of the central longitudinal axis L. 
     In the following, the assembly and disassembly of the fuel injector  20  with the fuel injector cup  30  according to the embodiment of  FIG. 3  will be described: 
     For assembling, the first ring element  36  is shifted over the fuel injector cup  30 , the first snap ring  40  is shifted into the groove  32  of the fuel injector cup  30 , the second ring element  38  is shifted over the fuel injector  20  and the second snap ring  42  is shifted into the groove  27  of the fuel injector  20 . Additionally, the first ring element  36  is shifted on the fuel injector cup  30  until it is in a positive fitting coupling with the fuel injector cup  30  to prevent a movement of the first ring element  36  relative to the fuel injector cup  30  in the first direction D 1  of the central longitudinal axis L. Furthermore, the second ring element  38  is shifted over the fuel injector  20  until it is in a positive fitting coupling with the fuel injector  20  to prevent a movement of the second ring element  38  relative to the fuel injector  20  in the second direction D 2  of the central longitudinal axis L opposing the first direction Dl of the central longitudinal axis L. 
     Furthermore, the fuel inlet portion  24  of the fuel injector  20  is shifted into the fuel injector cup  30  in a way that the first ring element  26  and the second ring element  38  are in engagement with each other. Then, the screws  47  are screwed into the threads  36  of the second ring element  38  and a state as shown in  FIG. 3  is obtained. As can be seen in  FIG. 3 , the inner surface  34  of the fuel injector cup  30  is in sealing engagement with the outer surface  49  of the sealing ring  48 . After the assembly process fuel can flow through the fuel injector cup  30  into the fuel inlet portion  24  of the fuel injector  20  without fuel leakage. 
     To disassemble the fuel injector  20  from the fuel injector cup  30 , the screws  47  are removed and the fuel injector  20  can be shifted away from the fuel injector cup  30  in axial direction and the fuel injector cup  30  and the fuel injector  20  can be separated from each other. 
     In the embodiment of  FIG. 4  the coupling device  50  has a welding seam  52  between the first ring element  36  and the fuel injector cup  30  and a welding seam  54  between the second ring element  38  and the fuel injector  20 . By the welding seams  52 ,  54  the ring elements  36 ,  38  are rigidly coupled to the fuel injector cup  30  and the fuel injector  20  respectively. 
     In the following the assembly and disassembly of the fuel injector  20  with the fuel injector cup  30  of the embodiment of  FIG. 4  will be described: 
     For assembling the fuel injector  20  with the fuel injector cup  30 , the first ring element  36  is shifted over the fuel injector cup  30  and the welding seam  52  is attached to fixedly couple the first ring element  36  to the fuel injector cup  30 . Furthermore, the second ring element  38  is shifted over the fuel injector  20  and is rigidly coupled to the fuel injector  20  by the welding seam  54 . The fuel inlet portion  24  of the fuel injector  20  is pushed into the fuel injector cup  30 . By shifting the fuel injector  20  in axial direction into the fuel injector cup  30 , the inner surface  34  of the fuel injector cup  30  is in sealing engagement with the outer surface  49  of the sealing ring  48 . The screws  47  are screwed into the second ring element  38  as described e embodiment of  FIG. 3 . 
     In the embodiment of the coupling device  50  of  FIG. 5  the first ring element  36  is in one part with the fuel injector cup  30  and the second ring  38  is in one part with the fuel injector  20 . By this a very rigid and very secure coupling between the fuel injector cup  30  and the fuel injector  20  is possible. 
     For assembling the fuel injector  20  with the fuel injector cup  30  according to the embodiment of  FIG. 5 , the fuel inlet portion  24  of the fuel injector  20  is pushed into the fuel injector cup  30  and the first ring element  36  and the second ring element  38  are screwed together by the screws  47 . 
     The coupling of the fuel injector  20  with the fuel rail  18  by the ring elements  36 ,  38  and the screws  47  allows an assembly of the fuel injector  20  and the fuel injector cup  30  without a further metallic contact between the fuel injector  20  and the further parts of the internal combustion engine  22 . A sealing between the fuel injector body  21  and a combustion chamber of the internal combustion engine  22  can be carried out by a plastic element, in particular by a PTFE element. Consequently, noise transmission between the fuel injector  20  and further parts of the internal combustion engine can be kept small.