Abstract:
A fuel-injection system for the injection of fuel into an internal combustion engine includes at least one fuel injector and a fuel-distributor line as well as for each fuel injector a corrugated-tube bellows, which is able to be connected to an inflow section of the fuel injector. Deformation-energy absorbing elastomeric material abuts with an initial stress against at least some sections of the corrugated-tube bellows.

Description:
FIELD OF THE INVENTION 
   The present invention relates to a fuel-injection system for injecting fuel into an internal combustion engine. 
   BACKGROUND INFORMATION 
   German Published Patent Application No. 28 29 057 describes a fuel-injection system which supplies fuel to a mixture-compressing internal combustion engine having external ignition as a function of operating parameters. The fuel-injection system encompasses a metal fuel-distributor line, which, via at least one branch line, is connected to at least one fuel injector, the branch line being embodied as a metal tube and connected to the fuel injector by manner of a threaded connection. Easily bendable metal is used as material for the branch line. Arranged between the threaded connection on the branch line and the fuel injector are thin-walled metal bellows in the form of a corrugated-tube bellows by which a lateral offset between the beginning of the branch line on the fuel-distributor line and the fitting position of the fuel injector is compensated; in addition, the operating noises emanating from the fuel injector are damped by the yielding of the bellows. 
   German Published Patent Application No. 28 29 057 describes a fuel-injection system such that while the flexurally soft bellows having thin material thickness does reduce a transmission of solid-borne noise to the fuel-distributor line, it is excited to oscillations itself and radiates noise. The natural resonance characteristic of the corrugated-tube bellows may be influenced only to a negligible degree. The corrugated-tube bellows, if it is made of an elastic sheet metal, has only low self-damping. 
   Finally, due to the vibrations of the internal combustion engine during operation, the corrugated-tube bellows are in danger of breaking or ripping if insufficient self-damping occurs. In the case of directly injecting fuel injectors and at the high pressures required in this context, the connection between a fuel injector and the fuel-distributor line is safety-relevant and must not break under any circumstances. 
   U.S. Pat. No. 2,014,355 describes a pipe connection in the form of a corrugated tube by which the transmission of vibrations is meant to be prevented or reduced. On the outside, the corrugated tube is surrounded by an envelope that does not touch the corrugated tube and is rigidly connected to one pipe section at one end. At its other end, the envelope is sealed from the other pipe section by a flexible seal, the envelope shielding from noise originating in the corrugated tube. 
   Other systems provide that the natural oscillation characteristic of the corrugated tube may not be influenced. The oscillation characteristic is merely influenced indirectly with respect to one another, via the stiffness of the two pipe sections, since these tube sections are damped in their relative movements via the sleeve and the seal. Moreover, the configuration consists of several parts and is complicated. 
   SUMMARY OF THE INVENTION 
   The fuel-injection system according to the present invention may provide that the natural resonance characteristic and the noise damping of the corrugated-tube bellows may be influenced to a wide extent. Also, the damping corrugated-tube bellows according to the present invention may be manufactured and adapted in its damping values in an uncomplicated and cost-effective manner. In addition, the tightness of the fuel-conveying components does not depend on the deformability of a seal, such as an O-ring seal. The safety, as it relates to a component malfunction during the service life, is increased. 
   Elastomeric rings are arranged, radially on the outside, in the inner folds of the corrugated-tube bellows. 
   This exemplary embodiment may be manufactured with O-rings, for example, and is able to be produced in a cost-effective manner. The inner folds are zones of great deformation during longitudinal oscillations of the corrugated-tube bellows. Elastomeric rings abutting there dampen these oscillations. 
   Alternatively, or in addition, an elastomeric hose may abut against the corrugated-tube bellows radially on the outside, this hose abutting solely against outer folds of the corrugated-tube bellows. 
   Only one additional component is mounted in the production. Since all outer folds are joined to each other in the longitudinal direction in a manner that provides damping, the damping is especially high. 
   Using a union nut, which presses a sealing cone radially against a cylinder section of the corrugated-tube bellows, the corrugated-tube bellows may be joined to the inflow section in a releasable manner. 
   As an alternative, the union nut sealingly presses a single fold of the corrugated-tube bellows against the inflow section. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows a section through an exemplary embodiment of a fuel-injection system configured according to the present invention, in the sectional plane of a fuel injector and a corrugated-tube bellows of a fuel-distributor line. 
       FIG. 2  shows an exemplary embodiment of a corrugated-tube bellows and an inflow section of a fuel injector in a sectioned view. 
       FIG. 3  shows an additional exemplary embodiment of a corrugated-tube bellows and an inflow section of a fuel injector in a sectioned view. 
   

   DETAILED DESCRIPTION 
     FIG. 1  shows a section through an exemplary embodiment of a fuel-injection system  1  according to the present invention in the sectional plane of a fuel injector  2  and a corrugated-tube bellows  3  of a fuel-distributor line  4 . Fuel injector  2  is shown only in the region of an inflow section  5 , which is provided with a thread  6  for a union nut  7 . When tightened, union nut  7  presses on an upper conical surface  8  of a sealing cone  9 , which is moved into inflow section  5  by manner of a lower conical surface  10 , thereby radially compressing sealing cone  9  and pressing it against a cylinder section  11  of corrugated-tube bellows  3 . Due to the high surface pressure acting on lower conical surface  10  and on cylinder section  11 , a fuel inflow  12  is sealed, without an elastomer coming into contact with the fuel. 
   At its other end, corrugated-tube bellows  3  is sealingly joined to fuel-distributor line  4  by a welded seam  13 . 
   Inserted in inner folds  14  of corrugated-tube bellows  3 , with an initial stress, are elastomeric rings  15 , these elastomeric rings lying at the outside of corrugated-tube bellows  3 , in the rounded grooves formed by inner folds  14 , and are not in contact with the fuel. 
   If corrugated-tube bellows  3  is incited to expansions and contractions, especially in its longitudinal axis, by the vibrations occurring during operation of an internal combustion engine, elastomeric rings  15  absorb energy and damp this movement. The noise characteristic and the natural oscillation characteristic of corrugated-tube bellows  3  are thus influenced in an effective manner. This damping may be effected in a cost-effective manner. Above all, an adaptation is easily accomplished by using elastomeric rings  15  that have a different modulus of elasticity and/or by using a different number of elastomeric rings  15 . For instance, only every second inner fold  14  may be provided with an elastomeric ring  15  in order to reduce the damping of corrugated-tube bellows  3 . 
     FIG. 2  shows a section through an exemplary embodiment of a fuel-injection system  1  configured according to the present invention. The exemplary embodiment deviates from the configuration in  FIG. 1  only in the region of an inflow section  16  to fuel injector  2 , and with respect to a union nut  17 . 
   Identical components bear matching reference numerals. Shown is the sectional plane of fuel injector  2  and corrugated-tube bellows  3  as well as of fuel-distributor line  4 . 
   Formed on inflow section  16  is thread  6  for union nut  17 . Corrugated-tube bellows  3  is held in this position in that a flange  18  of union nut  17  presses an edge  19  against inflow section  16 . 
   Fuel inflow  12  is sealed by the surface pressure of the edge in a sealing line  20  with respect to inflow section  16 , without an elastomer coming into contact with the fuel. 
   At its other end, corrugated-tube bellows  3  is sealingly connected to fuel-distributor line  4  by a welded seam  13 . Inserted with an initial stress in inner folds  14  of corrugated-tube bellows  3  are elastomeric rings  15 . 
   This configuration effects a sealing and a releasable affixation of corrugated-tube bellows  3  on inflow section  16  of fuel injector  2  in an effective manner. 
     FIG. 3  shows another exemplary embodiment of the present invention. The configuration corresponds to that of  FIG. 2 , with the only difference that no elastomeric rings  15  are present, but a elastomeric hose  22  is used instead. Corrugated-tube bellows  3  and inflow section  16  of fuel injector  2  as well as fuel-distributor line  4  are shown in a sectional view. Union nut  17 , which engages with thread  6  at inflow section  16 , retains edge  19  of corrugated-tube bellows  3  at inflow section  16  by manner of flange  18 . 
   At its other end, corrugated-tube bellows  3  is sealingly connected to fuel-distributor line  4  by a welded seam  13 . 
   Elastomeric hose  22  is drawn over corrugated-tube bellows  3 , for example by shrink-fitting a shrink tube. In an effective manner, elastomeric hose  22  also damps the relative movements of adjacent outer folds  21 . In doing so, elastomeric hose  22  in each case abuts against corrugated-tube bellows  3  only in the region of outer folds  21 . 
   Noise damping may thus be achieved in a cost-effective configuration. 
   It is also possible to provide elastomeric rings, as shown in  FIGS. 1 and 2 , in addition to elastomeric hose  22 .