Patent Abstract:
The invention relates to a fuel injection system having a return line connector, having a return inlet and at least two return outlets. To improve the service life of the fuel injection system, a check valve device, which prevents the passage of a fluid from the return outlets to the return inlet is integrated with the return line connector. A return line connector is provided for each fuel injector in the fuel injection system.

Full Description:
REFERENCE TO RELATED PATENT APPLICATION 
       [0001]    This application is a continuation-in-part based on U.S. patent application Ser. No. 11/774,684 filed on Jul. 9, 2007. 
     
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
       [0002]    The invention relates to a return line connector having a return inlet and at least two return outlets. The invention further relates to a fuel injection system having a high-pressure fuel reservoir for supplying fuel to fuel injectors that are connected to a return line device. The returning fuel quantity from the fuel injectors is collected and pumped back into a fuel tank via the return line device. 
       OBJECT AND SUMMARY OF THE INVENTION 
       [0003]    The object of the invention is to create a return line connector by which the service life of a fuel injection system can be improved. 
         [0004]    In a return line connector, having a return inlet and at least two return outlets, this object is attained in that a check valve device, which prevents the passage of a fluid from the return outlets to the return inlet is integrated with the return line connector. This affords the advantage that reflected pressure waves are not propagated back through the return outlets into a fuel injector connected to the return inlet of the return line connector. 
         [0005]    A preferred exemplary embodiment of the return line connector is characterized in that the check valve device includes a check valve body, which as a function of the pressure difference between the return inlet and the return outlets opens a variably sized flow cross section from the return inlet to the return outlets. This offers the advantage that when a defined pressure difference is attained, a flow cross section that is optimal for the flow can be opened. 
         [0006]    A further preferred exemplary embodiment of the return line connector is characterized in that the flow cross section opened by the check valve body increases with the pressure difference. As a result, unwanted pressure surges in the return system can be markedly reduced. 
         [0007]    A further preferred exemplary embodiment of the return line connector is characterized in that the return line connector has a screwlike base body with a screw-headlike head, at which a sleevelike valve receiving body originates, whose end remote from the head is open and forms the return inlet. The screwlike base body makes it simple to mount the return line connector on or in a cylinder of an internal combustion engine. 
         [0008]    A further preferred exemplary embodiment of the return line connector is characterized in that the check valve body is received, such that it is movable back and forth, in the sleevelike valve receiving body. The check valve body is designed such that, depending on its position in the sleevelike receiving body, it opens a more or less large flow cross section from the return inlet to the return outlets. 
         [0009]    A further preferred exemplary embodiment of the return line connector is characterized in that between the check valve body and the head of the return line connector, a check valve spring device is disposed in the interior of the sleevelike valve receiving body. Via the spring characteristic of the check valve spring device, the opening performance of the check valve device can be adjusted precisely. 
         [0010]    A further preferred exemplary embodiment of the return line connector is characterized in that the sleevelike valve receiving body, between the head and the check valve body, has two through holes, which form the return outlets. Preferably, a connection piece to which return lines can be connected is disposed in the region of the through holes. 
         [0011]    A further preferred exemplary embodiment of the return line connector is characterized in that a stop sleeve is secured in the end, remote from the head, of the sleevelike valve receiving body. The stop sleeve forms a sealing seat for the check valve body. 
         [0012]    A further preferred exemplary embodiment of the return line connector is characterized in that the sleevelike valve receiving body is provided with a male thread on its end remote from the head. As a result, it becomes possible to fasten the return line connector by means of screwing it in. 
         [0013]    In a fuel injection system having a high-pressure fuel reservoir for supplying fuel to fuel injectors that are connected to a return line device, this object is attained in that per fuel injector, the return line device has one above-described return line connector. By means of the return line connector of the invention, the number of pressure peaks in a valve, especially a magnet valve, that is integrated with the fuel injector can be reduced. The maximum intensity of the pressure peaks can furthermore be lessened. As a result, the service life of the valves and hence of the fuel injectors can be increased. Accommodating the check valve device in the return line connector furthermore offers the advantage that the modularity of the fuel injection system is not restricted. In addition, no additional masses that could cause unwanted fluctuations are introduced into the fuel lines. Because the check valve is disposed in the immediate vicinity of the fuel injector, extensive propagation of pressure waves is effectively prevented. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    The invention will be better understood and further objects and advantages thereof will become more apparent from the ensuing detailed description of a preferred embodiment, taken in conjunction with the drawings, in which: 
           [0015]      FIG. 1  is a schematic illustration of a fuel injection system in which the return line connector of the invention may be used; 
           [0016]      FIG. 2  shows a return line connector of the invention in longitudinal section; and 
           [0017]      FIG. 3  shows the return line connectors being connected to the fuel injectors and being disposed in a return line of the fuel injection system 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0018]    In  FIG. 1 , a fuel injection system  1  with a central high-pressure fuel reservoir  2 , also known as a common rail, is schematically shown. Five fuel injectors  4 ,  5 ,  6 ,  7 ,  8  are connected to the high-pressure fuel reservoir  2 . The fuel injectors  4  through  8  serve to inject fuel into combustion chambers of an internal combustion engine. 
         [0019]    The fuel to be injected passes via high-pressure lines from the high-pressure fuel reservoir  2  to the individual fuel injectors  4  through  8 . Excess fuel or control leakage is pumped back into a fuel tank via a return line  10 . The return line  10  includes six return connection portions  11  through  16 . Between each two return connection portions  11  through  16 , a respective fuel injector  4  through  8  is connected to the return line  10 . Each of the fuel injectors  4  through  8  is connected to the return line  10  via a respective return line connector. 
         [0020]    In  FIG. 2 , a return line connector  20  is shown in longitudinal section. The return line connector  20  includes a screwlike base body  21  with a screw-headlike head  22 . The head  22  is in the form of a hexagon. A sleevelike valve receiving body  24  originates at the head  22  and is hollow on the inside and is provided on its free end  26  with an opening  27 . The opening  27  forms a return inlet for a fuel injector. In the region of the free end  26 , the sleevelike valve receiving body  24  is provided on the outside with a male thread  28 . The male thread  28  serves to screw the base body  21  into a hole  29  (shown only schematically in  FIG. 3 ), equipped with a complementary female thread, of a cylinder or cylinder head  46  of the engine. 
         [0021]    Between the male thread  28  and the head  22 , the sleevelike valve receiving body  24  has two through holes  31 ,  32 . The through holes  31 ,  32  are disposed in the vicinity of the head  22  and form two return outlets. With the aid of a connection piece, portions of a return line ( 10  in  FIG. 1 ) can be connected to the return outlets  31 ,  32 . 
         [0022]    A valve body  35  is received, such that it is movable back and forth, in the interior of the sleevelike valve receiving body  24 . The valve body  35  is also known as a valve piston or valve ball and preferably has a star-shaped cross section. In the longitudinal section shown, it can be seen that the valve body  35  has a longitudinal groove  36 , which enables the passage of fuel from the return inlet  27  to the return outlets  31 ,  32 . The valve body  35  does not have merely a single longitudinal groove  36  but rather a plurality of longitudinal grooves, which are distributed uniformly over the circumference of the valve body  35 , producing the preferred star-shaped cross section. 
         [0023]    On its end toward the head  22 , the valve body  35  has a collar  38 , which is interrupted by the longitudinal grooves  36 . A check valve spring  40  is fastened between the valve body  35  and the head  22 . The end of the valve body  35  remote from the head  22  contacts a stop sleeve  44 , which is press-fitted into the opening  27  on the free end  26  of the base body. The stop sleeve  44  forms a stop and a sealing seat for the valve body  35 . 
         [0024]      FIG. 3  shows the connection of the fuel injectors  4  through  6  to the return line  10  via return line connection devices  20  that are assigned to the respective fuel injectors  4  through  6 . The connection of the further fuel injectors  7  and  8  is done in the same way and is not shown in  FIG. 3  for reasons of space. 
         [0025]    The return line connection devices  20  are screwed into holes the cylinder or the cylinder head  46 . The through holes  31  and  32  of the return line connection devices  20  communicate with the return connection portions  11  through  13 . The return connection portions  11  through  13  communicate directly with the through holes  31 ,  32 , where they have an interruption. Fuel from the part of the return connection portion  11  oriented toward the injector  4  reaches the interior of the return line connection devices  20  via the through hole  31  and, through the through hole  32 , it reaches the part of the return connection portion  11  remote from the injector  4 . Via the return line  10 , fuel is fed back into the fuel tank. 
         [0026]    For example, the fuel injector  4  will be considered below; the procedure described is effected precisely the same way for the other injectors, but the reference numerals have to be adapted. Excess fuel from the fuel injector  4  or control leak fuel from the fuel injector  4  passes via a line  50  from the fuel injector  4  to reach the opening  27 , which forms the return inlet of the return line connection devices  20 . Depending on the fuel pressure in the line  50 , the valve body  35  moves upward and opens up a communication between the line  50  and the return connection portion  11 . As a result of the opened communication, excess fuel from the fuel injector  4  or control leak fuel from the fuel injector  4  can reach the return connection portion  11  via the through holes  31  and  32  and proceed onward to reach the fuel tank. 
         [0027]    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.

Technology Classification (CPC): 8