Patent Publication Number: US-6701899-B2

Title: Fuel injection unit

Description:
FIELD OF THE INVENTION 
     The present invention relates to a fuel injection system for injection of fuel into an internal combustion engine, in particular for direct injection of fuel into the combustion chamber(s) of the internal combustion engine. 
     BACKGROUND INFORMATION 
     A fuel injection system is described in German Published Patent Application No. 197 25 076. It has a ring-shaped seal support for a sealing connection between a fuel injector and a respective connecting piece of a fuel distributor line, this seal support cooperating with a first sealing element for sealing the seal support with respect to an end face of an inlet section of the fuel injector and cooperating with a second sealing element for sealing the seal support with respect to the connecting piece of the fuel distributor line. A bushing insertable into a fuel inlet orifice of the inlet section passes through the ring-shaped seal support, so that the seal support is movably secured in the radial direction between an upstream collar of the bushing and the inlet section of the fuel injector. 
     One feature of the arrangement described in the aforementioned publication is that due to the total of two sealing elements, there are two components which may be subject to defects and may result in leakage in particular. The two sealing elements are installed one above the other and therefore may require vertical space. Since the sealing elements may not lie in direct contact with one another and sufficient material may be required to be available to fill out the ring grooves, the additional vertical space required for the seal support may not be insignificant. Another feature of the arrangement described in the aforementioned publication is that radial mobility of the seal support may be ensured only if it has a certain axial play and is not pressed by the bushing against the inlet section. Consequently, during installation the bushing may be required to be inserted into the fuel inlet orifice to a precisely defined depth and the bushing as well as the fuel inlet orifice in the fuel injector may be required to be manufactured to a very high precision. 
     A fuel injector which has an inlet section and is insertable into a receiving bore and is sealed by an O-ring on this inlet section with respect to a connecting piece of a fuel distributor line is described in Japanese Published Patent Application No. 08-312503. The O-ring is in sealing contact with an inside wall of the connecting piece. 
     One feature of this fuel injector may be that the deviations which may occur in the fuel injector relative to the fuel distributor line due to manufacturing tolerances may be compensated only by asymmetrical pinching of the O-ring inasmuch as the axes of the connecting piece of the fuel distributor line and the fuel injector are shifted relative to one another. This may result in leakage even with relatively minor pinching of the O-ring. 
     SUMMARY OF THE INVENTION 
     A fuel injection system according to the present invention may provide that deviations in the axial position of the connecting piece of the fuel distributor line and the fuel injector relative to one another may be compensated reliably. This may prevent unwanted warping of the fuel injector relative to the fuel distributor line. This may yield in particular a smaller vertical space required in comparison with the conventional seals, which may allow tolerances to be compensated. In an example embodiment, the inner sleeve and the outer sleeve may be connected by spiral springs. 
     Pressure equalizing bores may be provided in the outer sleeve to connect the fuel chamber to a clearance volume formed between the sealing edges of the sealing arrangement and the outer sleeve. The sealing arrangement may thus be acted upon by the pressure of the fuel over a larger extent of its cross section and the contact pressure of the sealing edges may be increased. 
     The seal support may be secured by a locking ring on the guide section of the fuel injector with its inner sleeve against the end face of the inlet section. A gap may remain between the end face of the inlet section and the outer sleeve of the seal support due to the elasticity of the sealing element even when acted upon by fuel under pressure. Even when the inner sleeve is pressed by the locking ring against the end face due to the manufacturing tolerances, the outer ring having the sealing element may retain its functionality. 
     In an example embodiment, the guide section is formed by a hollow screw which may be screwed into a threaded bore of the fuel injector and may hold the seal support against the fuel injector. 
     The outer ring may have an upstream peripheral conical chamfer arranged on the outside radially. This may facilitate insertion of the seal support into the connecting piece. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a section through an example embodiment according to the present invention in a detail of an illustration of the connecting area between the fuel injector and the fuel distributor line. 
     FIG. 2 shows a top view of a seal support of the example embodiment illustrated in FIG.  1 . 
     FIG. 3 shows a top view of an alternative example embodiment of a seal support. 
     FIG. 4 shows another example embodiment of a fuel injection system according to the present invention in a detail corresponding to detail IV in FIG.  1 . 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 shows, as a sectional diagram of a portion of an example embodiment according to the present invention of a fuel injection system, the connecting area between a fuel injector  1  and a fuel distributor line  2 . Fuel distributor line  2  is shown here only in the area of a connecting piece  3 , and fuel injector  1  is shown here only in the area of an inlet section  4  having a guide section  5 . 
     Inlet section  4  is formed in one piece with fuel injector  1 . An end face  6  is formed at the transition of inlet section  4  to guide section  5 . A fuel inlet bore  7  of fuel injector  1  passes through guide section  5  and inlet section  4 . A seal support  30  is composed of an inner sleeve  8  and an outer sleeve  9  which surrounds inner sleeve  8  radially and is elastically connected to inner sleeve  8  via plate springs  10  arranged in a spiral. Guide section  5  passes through and guides inner sleeve  8 . A locking ring  11  secures inner sleeve  8  in its position and presses it against end face  6  of inlet section  4 . 
     Locking ring  11  is inserted into a peripheral groove  12  of guide section  5 . An O-ring  14  is inserted as a sealing element into a rectangular step  13  which is formed on outer sleeve  9  and faces end face  6 . A clearance volume  15  between outer sleeve  9  and O-ring  14  communicates with fuel chamber  17  to be sealed via a pressure equalizing bore  16 . Clearance volume  15  is formed between sealing edges  18 ,  19  of O-ring  14  with respect to step  13  of outer sleeve  9 . With an axial sealing edge  20 , O-ring  14  rests on end face  6  and with a peripheral sealing edge  21  it rests on an inside wall  22  of connecting piece  3 . Outer sleeve  9  has a peripheral conical chamfer  23  on its downstream end. A central axis  24  through fuel injector  1  is shown for the sake of illustration. Likewise, a central axis  25  through connecting piece  3  is also shown. Axes  24 ,  25  may also have an offset by distance a due to manufacturing tolerances. 
     Outer sleeve  9  is connected to inner sleeve  8  only elastically by plate springs  10 , so that only minor forces are transmitted in the axial direction. Regardless of whether and with what force inner sleeve  8  is pressed against end face  6 , a gap b is formed between outer sleeve  9  and end face.  6 , the size of this gap depending on the elasticity of O-ring  14  and the prevailing pressure in fuel chamber  17 . Therefore, outer sleeve  9  may be easily displaceable radially. In conjunction with chamfer  23 , outer sleeve  9  is adjusted to offset a in assembly. This may be possible as long as axial sealing edge  20  is still resting completely on end face  6 . In operation of fuel injector  1 , the sealing effect of O-ring  14  is reinforced by pressure equalizing bore  16 . Due to pressure equalizing bore  16 , O-ring  14  is also acted upon by fuel under pressure in clearance volume  15  on its cross-sectional extent between sealing edges  18 ,  19  against outer sleeve  9 . Therefore, the contact pressure on axial sealing edge  20  and peripheral sealing edge  21  is reinforced. 
     FIG. 2 shows a top view of seal support  30  from FIG. 1 having a configuration of plate springs  26  according to an example embodiment of the present invention. Outer sleeve  9  concentrically surrounds inner sleeve  8 . The two are connected elastically via plate springs  26 , which are directed radially outward and have a fold in the example embodiment illustrated here. 
     FIG. 3 shows a view of seal support  30  from FIG. 1, illustrating another configuration of plate springs  27  according to an example embodiment of the present invention. Outer sleeve  9  concentrically surrounds inner sleeve  8 . The two are connected by plate springs  27 , which are configured as spiral plate springs directed radially outward. 
     FIG. 4 shows another example embodiment of a fuel injection system according to the present invention in a detail corresponding to detail IV in FIG.  1 . Since this example embodiment differs from the example embodiment illustrated in FIG. 1 only in this detail, the same reference numbers have been used for the same parts. Seal support  30  is composed of inner sleeve  8  and outer sleeve  9 , which surrounds inner sleeve  8  radially and is elastically connected to inner sleeve  8  via plate springs  10  arranged in a spiral. A locking ring  28  sitting in groove  12  holds inner sleeve  8  and outer sleeve  9  against end face  6 . O-ring  14  arranged in step  13  of outer sleeve  9  is supported by a supporting ring  29  arranged between O-ring  14  and end face  6 . O-ring  14  is in sealing contact with connecting piece  3 . 
     In the example embodiment of fuel injection system illustrated here, outer sleeve  9  is held more securely in its position. O-ring  14  may be deformed to a greater extent by supporting ring  29  without resulting in any leakage.