Abstract:
A fuel feed device for attachment to a cylinder head of an internal combustion engine has at least one fuel distribution element extending along a longitudinal direction, and at least one connecting element extending transversely to the longitudinal direction, wherein the connecting element can be used to connect the fuel distribution element to the cylinder head. The fuel feed device further includes at least one reinforcing element which is connected, on one hand, to an outer surface of the fuel distribution element and, on the other hand, to the connecting element outside the fuel distribution element.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application is the U.S. National Stage of International Application No. PCT/EP2011/002110, filed Apr. 27, 2011, which designated the United States and has been published as International Publication No. WO 2011/134651 and which claims the priority of German Patent Application, Serial No. 10 2010 018 615.5, filed Apr. 28, 2010, pursuant to 35 U.S.C. 119(a)-(d). 
     BACKGROUND OF THE INVENTION 
     The invention relates to a fuel feed device for attachment to a cylinder head of an internal combustion engine, with at least one fuel distribution element extending along a longitudinal direction and at least one connecting element extending transverse to the longitudinal direction, via which the fuel distribution element is connectable to the cylinder head, and a method for producing such fuel feed device. 
     EP 1 772 60 B1 discloses a generic device for attaching a high-pressure fuel accumulator to a cylinder head, with a high-pressure fuel accumulator, which has a main pipe extending along a longitudinal axis. The device also includes several fluid-tight passageways which are formed to extend completely through the aforementioned high-pressure fuel accumulator and extend substantially perpendicular to the longitudinal axis, as well as several screws which can be inserted through the respective several fluid-tight passageways. The fastening elements can here be mounted on the cylinder head, by which the high-pressure fuel accumulator is mounted on the cylinder head. The fluid-tight passageways are entirely formed by the aforementioned main pipe of the high-pressure fuel accumulator. 
     This device disadvantageously has an increased risk for leaks, which would allow fuel to leak from the high-pressure fuel accumulator, unless other measures are implemented. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide a fuel feed device and a method for producing such a fuel feed device with improved and more secure functional performance. 
     An inventive fuel feed device for attachment to a cylinder head of an internal combustion engine having at least one fuel distribution element extending along a longitudinal direction and at least one connecting element extending transverse, in particular perpendicular, to the longitudinal direction, via which the fuel distribution element can be connected to the cylinder head, is characterized by at least one reinforcing element, which is connected, on one hand, to an outer surface of the fuel distribution element and, on the other hand, with the connecting element outside, in particular exclusively outside, the fuel distribution element. 
     With the reinforcing element, the connection between the fuel distribution element, which is also referred to as the fuel rail, and the connecting element is reinforced. As a result, the probability of an occurrence of a leak and thus a leakage of fuel received in the fuel distribution element is significantly reduced. 
     Because the reinforcing element is connected to an outer surface of the fuel distribution element, a particularly large connecting surface exists between the reinforcing element and the fuel distribution element. This leads to lower stresses in the connecting surface when the fuel in the fuel distribution element is under very high pressure. This is particularly advantageous when the reinforcing element is materially connected, in particular soldered, to the fuel distribution element and/or to the connecting element. Due to the available large connecting surface, the mechanical stress, for example in the weld seam, is low. The large connecting surface is under less stress even in the presence of a very high internal pressure in the fuel distribution element and biasing forces from injectors cooperating with the fuel feed device, which significantly reduces the probability of a failure, for example, of the weld seam, and thus destruction of the entire fuel feed device. 
     The aforementioned advantages can be attained without increasing a wall thickness of the fuel distribution element and thus also its weight. This keeps the total weight of the fuel feed device within a small range. The number of attachment points and connecting surfaces between the connecting element and the fuel distribution element can be kept low, which in turn leads to a low weight and low cost of the fuel feed device. 
     A connecting surface between the reinforcing element and the connecting element is particularly large, wherein low stresses, and thus also low loads in the connecting surface, exist due to the large connecting surface even at a high internal pressure in the fuel distribution element, even in the presence of mechanical bias forces due to attached injectors, as well as the fuel feed device connected to the cylinder head. Because the reinforcing element and the connecting member are soldered together, this reduces the load on the weld seam, which positively affects the functional performance and reliability of the fuel feed device. 
     Preferably, the reinforcing element is formed as a reinforcing plate which advantageously has a receptacle corresponding to an outer contour of the fuel distribution element in which the fuel distribution element is at least partially received, and which extends away from the fuel distribution element at an angle, in particular transversely, with respect to the longitudinal direction. The reinforcing element is thus shaped as a collar, by which the fuel feed device is reinforced in the connecting region between the fuel distribution element and the connecting element. 
     The functions of the fuel feed device are then safely met to a particularly high degree when the connecting element is materially connected to the fuel distribution element, in particular soldered. 
     A particularly strong and rigid connection with a long service life is realized in a particularly preferred embodiment of the invention, wherein a receiving space is formed between the reinforcing element and the connecting element and/or between the reinforcing element and the fuel distribution element, in which receiving space a connecting means, in particular a connecting means for materially connecting the reinforcing element to the connecting element and/or the reinforcing element to the fuel distribution element, such as solder, adhesive and/or the like, are received. In this case, a particularly large surface area for forming, for example, a solder joint, is available which significantly reduces stresses in the solder joint. 
     According to another embodiment, the reinforcing element may have at least one through-opening extending into the receiving space, through which the connecting means, such as the solder, may be introduced. In this way, liquid solder can also be introduced into the exception of the receiving space which is enclosed on all sides with the exception of the through-opening. 
     In a further advantageous embodiment, the fuel feed device includes two reinforcing elements, which are each connected, on one hand, to the outer surface of the fuel distribution element and, on the other hand, with the connecting element outside, in particular exclusively outside, the fuel distribution element. For example, the connecting element hereby passes through the fuel distribution element and protrudes by a certain distance from both sides of the connecting element in the axial direction, i.e., on both a top side and a bottom side. For example, one of the two connecting elements is now arranged on the top side of the fuel distribution element and connected, on one hand, to the outer surface of the fuel distribution element and, on the other hand, to the connecting element. The second of the reinforcing elements is then arranged at the bottom side and connected, on one hand, to the outer surface of the fuel distribution element and, on the other hand, to the connecting element. This provides a particularly strong connection between the connecting element and the fuel distribution element. In addition, the stresses in the corresponding connecting surfaces between the respective reinforcing elements and the connecting element and/or the fuel distribution element are very small, resulting in a long service life of the fuel feed device. 
     The invention also relates to a method of producing a fuel feed device for attachment on a cylinder head of an internal combustion engine having at least one fuel distribution element extending along a longitudinal direction and at least one connecting element extending transverse, in particular perpendicular, to the longitudinal direction, via which the fuel distribution element can be connected to the cylinder head, wherein in one step of the method, a receiving space is formed between an attachment piece and the fuel distribution element and/or the connecting element for a connecting means for connecting the attachment piece to the fuel distribution element and/or the connecting element. The connecting means can then be placed or introduced in this receiving space, producing a particularly large connecting surface between the attachment piece and the fuel distribution element and/or the connecting element. This also keeps the load on the connection surface, in particular in this tension, low, thereby providing a fuel feed device which has a high functional performance and reliability and therefore a long service life. 
     Further advantages, features and details of the invention will become apparent from the following description of a preferred exemplary embodiment and with reference to the drawings. The features and feature combinations mentioned above in the description and the features and feature combinations mentioned below in the description of the drawings and/or the features and feature combinations shown solely in the figures can be used not only in the respective described combination, but also in other combinations or in isolation, without deviating from the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       The drawings show in: 
         FIG. 1  a schematic diagram of a high-pressure fuel accumulator for a direct injection gasoline or diesel engine, which is connected via sleeves to a cylinder head of the gasoline or diesel engine; 
         FIG. 2  a section of a schematic cross-sectional view of the high-pressure fuel accumulator according to  FIG. 1 ; 
         FIG. 3  a section of a schematic longitudinal sectional view of the high-pressure fuel accumulator according to the preceding figures; 
         FIG. 4  a section of a schematic longitudinal sectional view of another embodiment of a high-pressure fuel accumulator according to the preceding figures; 
         FIG. 5  a schematic longitudinal sectional view and a schematic cross-sectional view of a reinforcement sheet for a high-pressure fuel accumulator according to the preceding figures; 
         FIG. 6  a schematic perspective view of the reinforcement sheet according to  FIG. 5 ; 
         FIG. 7A  a schematic plan view of a sleeve for a high-pressure fuel accumulator according to the preceding figures; 
         FIG. 7B  a detail of a schematic and enlarged plan view of the sleeve according to  FIG. 7A ; 
         FIG. 8A  a detail of a schematic plan view of a high-pressure fuel accumulator according to the preceding figures, with the sleeve according to  FIGS. 7A and 7B ; 
         FIG. 8B  a detail of a schematic and enlarged plan view of the high-pressure fuel accumulator according to  FIG. 8A ; 
         FIG. 9A  a schematic plan view of the high-pressure fuel accumulator according to  FIGS. 8A and 8B  with the reinforcing plate according to  FIG. 6 ; 
         FIG. 9B  a detail of a schematic and enlarged plan view of the high-pressure fuel accumulator according to  FIG. 9A ; 
         FIG. 10  a schematic plan view of another embodiment of a reinforcing panel according to  FIG. 6 ; 
         FIG. 11A  a schematic plan view of another embodiment of a sleeve according to  FIG. 7A , and 
         FIG. 11B  a detail of a schematic and enlarged plan view of the sleeve according to  FIG. 11 . 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIG. 1  shows a high-pressure fuel reservoir  10  with a fuel distribution pipe  12  for a direct-injection gasoline or diesel engine. During operation of the gasoline or diesel engine, fuel is pressurized by a high pressure pump and fed into the fuel distribution pipe  12 , which distributes the fuel to injectors. The injectors inject the fuel into each cylinder. For this purpose, receptacles  14 ,  16 ,  18  and  20  of the high-pressure fuel accumulator  10  are provided, with a corresponding injector inserted into each receptacle and for supplying the injector with fuel from the fuel distribution pipe  12 . 
     As seen clearly in the context of  FIGS. 2 and 3 , the high-pressure fuel accumulator  10  includes sleeves  22  and  24  connecting the high-pressure fuel accumulator  10  with a cylinder head of the gasoline or diesel engine. The sleeve  22  passes completely through the fuel distribution pipe  12 , i.e., is guided through corresponding through-openings in an outer surface  26  of the fuel distribution pipe  12  and extends through these through-openings. Moreover, the sleeve  22  is inserted into a corresponding receptacle of the sleeve  24 . To prevent fuel from exiting between the sleeves  22  and  24 , a sealing element  28  is provided between the sleeves  22  and  24  in the axial direction in the direction of arrow  27 . 
     The high-pressure fuel reservoir  10  further includes reinforcing plates  30 , wherein the respective reinforcing plate  30  is soldered, on one hand, to the outer surface  26  and, on the other hand, to the sleeve  24  exclusively on the outside of the fuel distribution pipe  12 . 
     Moreover, a receiving space  32 , in which the solder for soldering is received, is formed between the reinforcing plate  30  and the sleeve  24  and the fuel distribution pipe  12 . In this way, soldering surfaces  34  are available for soldering the reinforcing plate  30  to the fuel distribution pipe  12  and the sleeve  24 , ensuring a particularly strong connection of the fuel distribution pipe  12  with the sleeve  24 . Moreover, the sleeve  24  is connected with solder applied to additional soldering surfaces  36  with the fuel distribution pipe  12 , with solder applied at soldering surfaces  38  with the sleeve  22 . The sleeve  22  is connected, via solder applied to corresponding solder surfaces  40 , with fuel distribution pipe  12 . 
     The reinforcing plate  30  provides very large solder surfaces  34 , which in particular greatly relieves a solder seam between the fuel distribution pipe  12  and the sleeve  22 , thereby lowering the probability for crack formation and formation of leaks in the high-pressure fuel accumulator  10 . 
     When the fuel distribution pipe  12  has a high internal pressure and when the high-pressure fuel accumulator  10  is screwed to the cylinder head with bolts passing through the sleeves  22  and  24 , the stresses and thus loads remain low in the solder surfaces  34 ,  36 ,  38  and  40 , resulting in a very low risk for cracking. Since the reinforcing plate  30  is connected to the outer surface  26  and extends in the axial direction away from the fuel distribution pipe  12 , the size especially of the soldering surface  34  does not depend on the wall thickness of the fuel distribution pipe  12 , as is the case, for example, with the soldering surface  40 . This produces a rigid connection between the fuel distribution pipe  12  and the sleeves  22  and  24 , without increasing the weight of the fuel distribution pipe  12 . 
     For arranging solder in the receiving space  32 , the reinforcing plate  30  has at least one through opening  46  ( FIG. 5 ) facing the receiving space  32 , into which liquid or viscous solder paste, for example copper paste, may be introduced. For soldering the sleeve  22  with the sleeve  24 , a solid solder ring is provided, which is melted in the soldering process in a continuous furnace, thereby soldering the sleeve  22  to the sleeve  24 . The remaining solder seems and solder joints are shown here with the solder paste. 
     In other words, the high-pressure fuel accumulator  10  is produced by first plugging the sleeves  22  and  24  and the reinforcing plate  30  together, whereby the seal  28  and any solid solder rings are also mounted. The pre-assembled high-continuous pressure fuel accumulator  10  is then transported into and conveyed through the furnace for forming the respective solder joint. Thereafter, in a final assembly of the gasoline or diesel engine, the high-pressure fuel accumulator  10  is attached to the cylinder head, whereby the screws are guided through the sleeves  22  and  24  and screwed into the cylinder head. 
     Instead of the two sleeves  22  and  24  shown in the figures, only the sleeve  22  may be provided, whereby the seal  28  and a corresponding solder joint between the sleeve  22  and  24  is omitted. In this case, the connecting plate  30  is soldered, on one hand, to the outer surface  26  of the fuel distribution pipe  12  and, on the other hand, to the sleeve  22 . The stresses on the corresponding solder surfaces during operation are also low in this embodiment of the high-pressure fuel accumulator  10 , which results in a highly functional and reliable performance of the high-pressure fuel accumulator  10  and a very low probability for the occurrence of leaks. 
       FIG. 4  shows another embodiment of the high-pressure fuel accumulator  10  in accordance with the preceding figures, wherein only the sleeves  24  are now provided to connect the high-pressure fuel accumulator  10  to the cylinder head. An exemplary sleeve  24  representing the sleeves  24  is shown in  FIG. 4 . The sleeve  22  like the sleeve  24  penetrates the fuel distribution pipe  12  and is guided through and passes through corresponding through-holes in the outer surface  26  of the fuel distribution pipe  12 . The sleeve  24  protrudes from the fuel distribution pipe  12  in the axial direction of the sleeve  24  according to the direction of arrow  27 , both on a top side  42  of the fuel distribution pipe  12  as well as on a bottom side  44  of the fuel distribution tube  12 . The reinforcing plate  30  is arranged on the bottom side  44 , which like the high-pressure fuel accumulator  10  in accordance with  FIGS. 1 to 3  is soldered, on one hand, to the outer surface  26  of the fuel distribution pipe  12  and, on the other hand, to the sleeve  24  exclusively outside of the fuel distribution pipe  12 . 
     Moreover, an additional reinforcing plate  31  is arranged on the top side  42 , which like the reinforcing plate  30  is soldered, on one hand, to the outer surface  26  of the fuel distribution pipe  12  and, on the other hand, to the sleeve  24  exclusively outside of the fuel distribution pipe  12 . A respective receiving space  32 , in which the solder for soldering is received, is formed once more between the reinforcing plates  30  and  31  and the sleeve  24  and the fuel distribution pipe  12 . In analogy to the reinforcing plate  30 , the reinforcing plate  31  also has solder surfaces  34  for soldering the reinforcing plate  30  to the fuel distribution pipe  12  and the sleeve  24  in order to provide a particularly strong connection. The sleeve  24  is also soldered to the fuel distribution pipe  12  with solder applied to other solder surfaces  40 . By providing two reinforcing plates  30  and  31  on both the top side  42  and on the bottom side  44 , the solder surfaces  34  and  40  are subjected to very low loads and stresses during the operation of the gasoline or diesel engine, resulting in a long service life of the high-pressure fuel accumulator  10 . 
       FIG. 5  shows the reinforcing plate  30 ,  31 ; the through-opening  46  which opens into the receiving chamber  32  and through which the solder paste can be introduced is also seen in  FIG. 5 .  FIG. 5  also shows that the reinforcing plate  30 ,  31  has in a connecting region  48  a receiving contour  50  which corresponds to the outer contour of the outer surface  26  of the fuel distribution pipe  12  schematically shown in  FIG. 5 . This ensures a defined contact the reinforcing plate  30  with the fuel distribution pipe  12  and to the outer surface  26 . A diameter D of the reinforcing plate  30 ,  31  for passage of the sleeve  24  is, for example, at least substantially in a range from 11 mm to 12 mm and in particular in a range from 11.8 mm to 11.95 mm, with both end values included. The diameter D should hereby be matched to an outer diameter of the sleeve  24  so as to be able to introduce, on one hand, a sufficient quantity of solder paste between the reinforcing plate  30 ,  31  and the sleeve  24  and, on the other hand, not to make a gap too large for the formation of a which it connection between the reinforcing plate  30 ,  31  and the sleeve  24   
       FIG. 6  shows the reinforcing plate  30 ,  31  in a perspective view with the through-opening  46 . 
       FIGS. 7A and 7B  illustrate an alternative embodiment of the sleeve  24 . The sleeve  24  has knurls  50  in the region of the solder surfaces  40 , i.e. in a connecting region between the sleeve  24  and the fuel distribution pipe  12 . Moreover, the sleeve  24  has in the axial direction in accordance with the direction arrow  27  an outer diameter step between the knurls  50 , wherein an outer diameter of the sleeve  24  is at least substantially less by 0.1 mm than the other outer diameter of the sleeve  24   
       FIGS. 8A and 8B  show the sleeves  24  with the knurls  50 , which are inserted through corresponding through-holes in the outer surface  26  of the fuel distribution pipe  12 . Solder paste for soldering the sleeves  24  to the fuel distribution pipe  12  is then applied in the region of the knurls  50 . 
       FIGS. 9A and 9B  show the high-pressure fuel accumulator  10  with the reinforcing sheets  30  and  31  and the sleeves  24  with the knurls  50 , wherein the sleeves  24  are soldered to the fuel distribution pipe  12  by way of the solder applied to the solder surfaces  40 . The reinforcing plates  30  and  31  are also soldered by way of solder applied to the solder surfaces  34  to the sleeve  24  and/or the fuel distribution pipe  12 . In addition, the reinforcing plates  30  and  31  are soldered to the fuel distribution pipe  12  by way of solder applied to solder surfaces lands  52  and  54 . 
       FIG. 10  shows an additional embodiment of the reinforcing plate  30 ,  31 , which now has four through-openings  46 , via which solder can be introduced into the receiving space  32 . 
       FIGS. 11A and 11B  show another alternative embodiment of the sleeve  24  with the knurls  50 . Notches  56  are formed in the axial direction of the sleeve  24  according to the direction of arrow  27  both between the knurls  50  and on the upper side and the lower side.