Patent Publication Number: US-8528524-B2

Title: Fuel injection valve for arrangement in a combustion chamber of an internal combustion engine

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a U.S. National Stage Application of International Application No. PCT/EP2009/057590 filed Jun. 18, 2009, which designates the United States of America, and claims priority to German Application No. 10 2008 036 413.4 filed Aug. 5, 2008, the contents of which are hereby incorporated by reference in their entirety. 
     TECHNICAL FIELD 
     The invention relates to a fuel injection valve for mounting to a combustion chamber of an internal combustion engine, comprising a nozzle support with a nozzle body disposed thereon in a fixed manner via a nozzle clamping nut, said nozzle body designed to protrude into the combustion chamber and being provided for holding a nozzle needle, and at least one annular sealing element comprising an upper support surface facing the nozzle clamping nut and a lower support surface facing the combustion chamber, said sealing element surrounding the nozzle body and being provided for sealing the nozzle support from the combustion chamber. 
     BACKGROUND 
     A nozzle clamping nut holds the two main components of the fuel injector—an injection nozzle and a valve body—tightly together. When the fuel injector is mounted to the cylinder head, the injection nozzle protrudes into a combustion chamber of a motor vehicle engine, the valve body disposed thereabove actuating the injection nozzle. It is necessary here to seal off the fuel injector from the combustion chamber at the cylinder head. This is accomplished by appropriate design of the nozzle clamping nut acting in conjunction with a corresponding device, a seal seat, in the cylinder head. 
     Such a sealing arrangement must meet exacting requirements. On the one hand, the sealing arrangement is exposed to high thermal loads (−40° C. for cold starting in winter, to over +150° C.) during operating conditions and, on the other hand, the sealing device is subject to high mechanical stress, particularly vibration loads. In addition, the sealing arrangement must ensure a durable, long-lasting seal between fuel injector and cylinder head. 
     In the prior art there is embodied for this purpose, e.g. on the nozzle clamping nut, a horizontal rim which is seated on a likewise horizontal rim provided in the injector bore, and the nozzle clamping nut or rather the fuel injector is pressed with high static force against the cylinder head. By providing a large areal overlap of the two rims, it is intended to create a durable fluid-tight joint. 
     The injector is generally sealed off from the combustion chamber by a metal sealing washer. This sealing is necessary because of the hot exhaust gases and the pressure loss in the cylinder. Due to the high combustion temperatures and high cylinder pressures, sealing is only possible using a metal sealing washer, so that no combustion gases can flow directly past the injector and into the environment. 
     In DE 101 02192 A1, a nozzle clamping nut has, on a free end, a truncated cone shaped region which can be inserted in a corresponding truncated cone shaped injector bore section. In the preassembled state, i.e. when the fuel injector with nozzle clamping nut is inserted in the truncated cone shaped injector bore, there is a circumferential angular difference of 2° to max. 5° between the truncated cone on the nozzle clamping nut and the truncated cone bore in the cylinder head. This ensures that the fuel injector is centered in the injector bore, the fuel injector then being pressed with high static force into the bore and a common sealing surface being formed between the truncated cone of the nozzle clamping nut and conical arc in the cylinder head. 
     Mixture and the hot combustion gases flow as far as the sealing locations of nozzle clamping nut and nozzle body, and also the seal between injector and cylinder head. In this gap there is now a build-up of unburned mixture and exhaust gases, e.g. H 2 O and S. After the engine is turned off, condensation of electrolyte (water) may now occur in the cool-down phase. The electrolyte promotes ion exchange and therefore corrosion. 
     In the prior art it is also known to screw the nozzle tightly to the nozzle clamping nut without any additional sealing. Also known is protecting the nozzle body from heat by coating it and installing sleeves as heat sinks. However, new combustion methods appear to cause corrosion precisely in this area, so that direct sealing against corrosive substances from combustion gases is absolutely necessary in this region. 
     SUMMARY 
     According to various embodiment, a fuel injection valve for mounting to a combustion chamber of an internal combustion engine can be provided, said valve ensuring improved sealing of the nozzle shaft in the region of the nozzle clamping nut with respect to the combustion chamber. 
     According to an embodiment, a fuel injection valve for arrangement in a combustion chamber of an internal combustion engine, may comprise a nozzle support with a nozzle body disposed thereon in a fixed manner via a nozzle clamping nut, said nozzle body designed to protrude into the combustion chamber and being provided for holding a nozzle needle, and at least one annular combustion chamber sealing element comprising an upper support surface facing the nozzle clamping nut and a lower support surface facing the combustion chamber, said lower surface surrounding the nozzle body and serving to seal the nozzle support from the combustion chamber, characterized in that at least one additional sealing element is provided for sealing the nozzle body in the area of the nozzle clamping nut. 
     According to a further embodiment, the sealing element can be disposed on the nozzle clamping nut or/and the combustion chamber seal. According to a further embodiment, the sealing element can be embodied as a separate element. According to a further embodiment, the sealing element can be made from very soft metals, heat resistant polymers or other fuel resistant materials. According to a further embodiment, the sealing element can be embodied by vulcanizing a seal onto the nozzle clamping nut. According to a further embodiment, the sealing element can be embodied by vulcanizing a seal onto the combustion chamber seal. According to a further embodiment, a heat resistant potting compound can be provided in a gap region between nozzle clamping nut and nozzle body. According to a further embodiment, the sealing element can be formed by part of the nozzle clamping nut. According to a further embodiment, the sealing element can be formed by part of the combustion chamber seal. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be explained in greater detail on the basis of exemplary embodiments with reference to the accompanying drawings in which: 
         FIG. 1 : shows a nozzle body locked in place via a nozzle clamping nut, as known from the prior art; 
         FIG. 2 : shows the arrangement according to  FIG. 1  with a first additional separate seal according to various embodiments; 
         FIG. 2   a : shows a detail A of  FIG. 2 ; 
         FIG. 3 : shows a detail corresponding to  FIG. 2A  with a second variant of the additional separate seal according to various embodiments; 
         FIG. 4 : shows a detail corresponding to  FIG. 2   a  with a third variant of the additional separate seal according to various embodiments; 
         FIG. 5 : shows a detail corresponding to  FIG. 2   a  with a fourth variant of the additional separate seal according to various embodiments; 
         FIGS. 6-8 : each show a detail corresponding to  FIG. 2A  with in each case different geometric modifications of the combustion chamber seal, and 
         FIG. 9 : shows a detail corresponding to  FIG. 2A  with a geometric modification of the nozzle clamping nut. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a longitudinal section through part of a fuel injection valve  10  with a nozzle clamping nut  20  which tightly grips a nozzle body  30 . Schematically indicated at  40  is a combustion chamber into which the nozzle body  30  partially protrudes. Disposed at the interface of the nozzle clamping nut  20 , nozzle body  30  and combustion chamber  40  is a combustion chamber sealing element  50 . The combustion chamber sealing element  50  surrounds the part of the nozzle body  30  extending beyond the nozzle clamping nut  20 . The nozzle body  30  has a circular or more specifically annular cross section in the longitudinal direction, i.e. in the injection direction. The combustion chamber sealing element  50  likewise has a thereto corresponding annular cross section in the longitudinal direction. The external diameter of the nozzle body cross section approximately corresponds to the internal diameter of the opening of the combustion chamber sealing element  50  (annular opening). The combustion chamber sealing element  50  has two end faces or bearing surfaces, an upper bearing surface  60  facing the nozzle clamping nut  20  and a lower bearing surface  70  facing the combustion chamber  40 . 
       FIG. 2  shows a longitudinal section through a corresponding detail according to  FIG. 1 , wherein an additional sealing element  80  is provided. Said sealing element grips around the nozzle body  30  in the region of a shoulder  90  of the nozzle body  30  in the contact area of the nozzle clamping nut  20  and combustion chamber sealing element  50 . The sealing element  80  can be embodied as a separate annular element consisting of very soft metals, heat resistant polymers or other fuel resistant materials. The internal diameter of said annular sealing element  50  corresponds approximately to the external diameter of the nozzle body  30 , so that it can be mounted thereon from the combustion chamber end of the nozzle body.  FIG. 2A  shows the enlarged area A from  FIG. 2 . It should be noted that, in the assembled state of the fuel injection valve, the sealing element  80  bears against the nozzle body  30 , the nozzle clamping nut  20  and the combustion chamber sealing element  50 . 
       FIG. 3  shows the same detail as  FIG. 2   a , wherein the sealing element  180  is here formed by vulcanizing a sealing area onto the nozzle clamping nut  20 , the sealing element  180  being vulcanized-on prior to mounting of the combustion chamber sealing element  50 . As can be seen from  FIG. 3 , the sealing element  180  is only in contact with the nozzle body  30  and the nozzle clamping nut  20 . However, contact also with the combustion chamber sealing element  50  in the completely assembled state is not ruled out here. 
       FIG. 4  likewise shows a detail according to that of  FIG. 2A . In this exemplary embodiment also, a sealing element  280  is formed by vulcanization. In contrast to  FIG. 3 , however, the sealing element  280  is vulcanized onto the combustion chamber sealing element  50 , namely in the region between the outer circumference of the nozzle body and that in the inner circumference of the combustion chamber sealing element  50 . 
       FIG. 5  also shows the fuel injection valve detail corresponding to  FIG. 2A . In this exemplary embodiment, the gap formed by the shoulder of the nozzle body  30 , the nozzle clamping nut  20  and the combustion chamber sealing element  50  is filled with a heat resistant potting compound as a sealing element  380 . Said potting compound is introduced after the nozzle clamping nut  20  has been screwed together with the nozzle body  30 . Consequently, the sealing element  380  abuts the nozzle body  30  and the nozzle clamping nut  20 . 
       FIGS. 6 to 8  show examples in which, by modifying the geometry of the combustion chamber sealing element  150 ,  250 ,  350 , another additional seal is formed is order to seal against deposits due to unburned mixture and exhaust gases in the gap between nozzle clamping nut  20  and nozzle body  30 .  FIG. 6  shows an annular combustion chamber sealing element  150  which has, in the region of its internal diameter, radially inward, a tongue  100  formed in longitudinal section in the axial direction toward the combustion chamber. In the cross section of the combustion chamber sealing element  150 , said tongue  100  tapers radially inwardly downward (in the direction of the combustion chamber  40 ) to the extent that a sealing contact with the outer circumferential surface of the nozzle body  30  is established. 
       FIG. 7  likewise shows an annular combustion chamber sealing element  250  with a tongue  200  oriented away from the combustion chamber  40  in the axial direction of the fuel injection valve. Like the tongue  100  in  FIG. 6 , the tongue  200  tapers in the cross section of the combustion chamber sealing element  250  and forms a sealing contact with the nozzle body  30  in the region of the shoulder  90  of the nozzle body  30 . 
       FIG. 8  also shows an annular combustion chamber sealing element  350 . In the region of its radially internal diameter, this combustion chamber sealing element  350  narrows uniformly radially inward and tapers in cross section to the external diameter of the nozzle body, forming a sealing contact therewith. In this example, the seal is therefore established via a cross-sectionally rectangular tongue  300  of the combustion chamber sealing element  350 . 
       FIG. 9  shows a sealing element  400  which is formed by a tongue extending radially inward on the nozzle clamping nut  120 . For this purpose the nozzle clamping nut  120  has, on its region adjacent to the combustion chamber sealing element  50 , a projection  400  which projects radially inward to the extent that it comes into sealing contact with the nozzle body  30  in the region of the shoulder  90 . In this case the tongue  400  is shown as tapered, but can also have a cross-sectionally different shape therefrom. 
     The invention is not limited to the embodiments described above. Indeed, deviations therefrom are also conceivable without departing from the scope of protection sought in the subsequent claims.