Abstract:
A fuel delivery rail assembly for supplying fuel to a plurality of fuel injectors in an engine is provided. The assembly comprises an elongate conduit having a longitudinal fuel passage therein, a fuel inlet pipe, and a plurality of sockets. One wall of the conduit opposite to the socket mounting wall includes a flat or arcuate flexible absorbing surface. High-frequency noise suppressing means such as a rib, a cavity or a clamp is applied to the one wall opposite to the absorbing surface. Thus, fuel pressure pulsations and shock waves are reduced by bending of the absorbing surface, and emission of high-frequency noise is eliminated.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    This invention relates to a fuel delivery rail assembly for an internal combustion engine, especially for an automotive engine, equipped with an electronic fuel injection system. The fuel delivery rail assembly delivers pressurized fuel supplied from a fuel pump toward intake passages or chambers via associated fuel injectors. The assembly is used to simplify installation of the fuel injectors and the fuel supply passages on the engine. In particular, this invention relates to sectional constructions of a fuel conduit (fuel rail) having a fuel passage therein and connecting constructions between the conduit and sockets for receiving fuel injectors.  
           [0002]    Fuel delivery rails are popularly used for electronic fuel injection systems of gasoline engines. There are two types of fuel delivery rails; one is a return type having a return pipe and another is a non-return (returnless) type. In the return type, fuel is delivered from a conduit having a fuel passage therein to fuel injectors via cylindrical sockets and then residual fuel goes back to a fuel tank via the return pipe. Recently, for economical reasons, use of the non-return type is increasing and new problems are arising therefrom. That is, due to pressure pulsations and shock waves which are caused by reciprocal movements of a fuel pump (plunger pump) and injector spools, the fuel delivery rail and its attachments are vibrated thereby emitting uncomfortable noise.  
           [0003]    U.S. Pat. No. 6,354,273 (Imura et al.) discloses a fuel delivery rail assembly including at least one flat or arcuate flexible absorbing surface. However, in case that one wall of the conduit opposite to the socket mounting wall is providing the absorbing surface, it tends to emit high-frequency noise, which may be caused by mechanical vibratory resonance.  
           [0004]    U.S. Pat. No. 4,660,524 (Bertsch et al.) discloses a fuel supply line having an elastic wall section connected to a rigid wall section.  
           [0005]    U.S. Pat. No. 4,649,884 (Tuckey) discloses a fuel rail having a flexible metal membrane which absorbs pulsations created by injectors.  
         SUMMARY OF THE INVENTION  
         [0006]    It is an object of the present invention to provide a fuel delivery rail assembly which can reduce the pressure fluctuations within the fuel passages caused by fuel injections, and also to reduce the vibrations caused by fuel reflecting waves (shock waves), to thereby eliminate emission of uncomfortable high-frequency noise.  
           [0007]    A conventional type of fuel delivery rail assembly comprises an elongate conduit having a longitudinal fuel passage therein, a fuel inlet pipe fixed to an end or a side of the conduit, and a plurality of sockets vertically fixed to the conduit adapted to communicate with the fuel passage and so formed as to receive tips of fuel injectors at their open ends.  
           [0008]    According to the characteristics of the invention, one wall of the conduit opposite to the socket mounting wall includes a flat or arcuate flexible absorbing surface. In addition, high-frequency noise suppressing means are applied to the outer surface of the conduit as follows:  
           [0009]    (A) A high-frequency noise suppressing rib is fixed to said one wall across the longitudinal direction of the conduit.  
           [0010]    (B) A high-frequency noise suppressing cavity is formed in said one wall across the longitudinal direction of the conduit.  
           [0011]    (C) A high-frequency noise suppressing clamp is located for holding the socket mounting wall and said absorbing surface between the clamp.  
           [0012]    As a result of the above construction of the invention, in a fuel delivery rail assembly having a fuel conduit made by steel, stainless steel or press materials, it has been found that it becomes possible to eliminate emission of uncomfortable noise including high-frequency noise. These noise are caused by the vibration and pressure pulsations due to the reflecting waves of injections and lack of dampening performance of the conduit.  
           [0013]    In a theoretical principle, when shock waves produced by the fuel injections flow into the fuel inlet of the sockets or flow away therefrom by momentary back streams, the flexible absorbing surface absorbs the shock and pressure pulsations. In addition, when thin plates having small spring constant are deflected and deformed, the space of contents varies, namely expands or shrinks, thereby absorbing pressure fluctuations.  
           [0014]    Further, the high-frequency noise suppressing means work to prevent the absorbing surface from vibrating freely and emitting high-frequency noise. Thus, a high-frequency sound component contained in the noise is minimized and diffusion of high-frequency noise is considerably eliminated.  
           [0015]    Under the continuous experiments, following arrangements are found to be most preferable to obtain best results.  
           [0016]    (1) The rib is fixed near one end or each end of the conduit in its longitudinal direction in order to deviate from the maximum bending position of the absorbing surface.  
           [0017]    (2) The height of the rib is within a range from one half to four times of thickness of said absorbing surface.  
           [0018]    (3) The number of the rib is one to three.  
           [0019]    (4) The depth of the cavity is less than half of the total height of the conduit, and the width of the cavity is less than two times of the total height of the conduit.  
           [0020]    (5) The clamp is located near one end or each end of the conduit in its longitudinal direction.  
           [0021]    (6) The thickness of the absorbing surface is equal to or less than the thickness of other surfaces of the conduit.  
           [0022]    (7) The radius of a curvature at an edge of the absorbing surface is more than two times of the thickness of the absorbing surface.  
           [0023]    In this invention, thickness of each wall of the conduit, ratio of the horizontal size to the vertical size, and the range of clearance between the fuel inlet of the socket and its confronting surface are preferably defined by experiments or calculations such that, especially during idling of the engine, the vibrations and pressure pulsations are minimized.  
           [0024]    Since the present invention is directed essentially to the sectional construction of the conduit and connecting construction of the conduit and the sockets, interchangeability with the prior fuel delivery rails are maintained as far as the mounting dimensions are kept constant.  
           [0025]    Other features and advantages of the invention will become apparent from descriptions of the embodiments, when taken in conjunction with the drawings, in which, like reference numerals refer to like elements in the several views. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0026]    [0026]FIG. 1A is a perspective view, and FIG. 1B is a side view and FIG. 1C is a vertical sectional view of a first type fuel delivery rail assembly according to the invention.  
         [0027]    [0027]FIG. 2 is a perspective view of a modified assembly.  
         [0028]    [0028]FIGS. 3A to  3 C are perspective views of further modified assemblies.  
         [0029]    [0029]FIG. 4 is a perspective view of a second type fuel delivery rail assembly.  
         [0030]    [0030]FIG. 5 is a side view of a third type fuel delivery rail assembly.  
         [0031]    [0031]FIG. 6 is a side view of a modified assembly.  
         [0032]    [0032]FIG. 7A is a perspective view, and FIG. 7B is a vertical sectional view and FIG. 7C is a side elevational view of a further modified embodiment.  
         [0033]    [0033]FIGS. 8A to  8 C are perspective views of further modified assemblies.  
         [0034]    [0034]FIGS. 9A and 9B are vertical sectional views of further modified assemblies. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0035]    Referring to FIGS. 1A to  1 C, there is shown a first type embodiment of the present invention, a fuel delivery rail assembly  10  of the so called “top feed type”, adapted to an automotive four-cylinder engine. The fuel conduit (rail)  11  comprised of flat steel pipes extends along a longitudinal direction of a crank shaft (not shown) of an engine.  
         [0036]    At the bottom side of the conduit  11 , four sockets  4  for receiving tips of fuel injectors are located corresponding to the number of cylinders at predetermined angles and distances from each other. To the conduit  11 , two thick and rigid brackets  4  are fixed transversely so as to mount the assembly  10  onto the engine body. Fuel flows along the arrows thereby being discharged from the socket  3  and fuel injectors (not shown) into an air intake passage or cylinders of the engine.  
         [0037]    At the side of the conduit  11 , a fuel inlet pipe  5  is fixed by brazing or welding. Although at an end of the conduit  11  it is possible to provide a fuel return pipe for transferring residual fuel back to a fuel tank, the present invention is directed to a non-return type having fuel pressure pulsation problems, so that the fuel return pipe is not provided.  
         [0038]    As shown in FIG. 1C, the conduit  11  has a flat rectangular section such that a circular steel pipe or stainless steel pipe is pressed into a flat form. The vertical and horizontal dimensions of the conduit  11  can be defined such that each wall thickness is 1.2 mm, the height is 10.2 mm, the width is 28 to 34 mm.  
         [0039]    Based upon the charasteristics of the present invention, one wall  11   a  of the conduit  11  opposite to the socket mounting wall  11   b  provides a flat flexible absorbing surface  11   a . Since the absorbing surface  11   a  faces to the fuel inlet port  13  of the socket  3 , it can absorb shock and vibration during fuel injection timing.  
         [0040]    In addition, two ribs  15 ,  16  are fixed to the wall  11   a  by brazing or welding across the longitudinal direction of the conduit  11 . The dimensions of each rib  15 ,  16  can be defined such that its length is about 80 to 90 percent of the width of the conduit  11 , and its height is within a range about one half (50 percent) to four times (400 percent) of the thickness of the absorbing surface  11   a , and its width is within a range about 30 to 40 percent of the total height of the conduit  11 .  
         [0041]    As it is understood from FIG. 1C, shock waves emitted from a fuel supply port  6   a  of the injection nozzle  6  pass through the fuel inlet port  13  of the socket and run againt the absorbing surface  11   a , thereby being dampened. During this action, the ribs  15 ,  16  work to minimize a high-frequency sound component from the vibration noise. Thus, diffusion of high-frequency noise is considerably eliminated.  
         [0042]    [0042]FIG. 2 illustrates a fuel delivery rail assembly  20  according to a modified embodiment of the invention. In this embodiment, only one rib  25  is located near the midpoint of the conduit  11 . Further, the fuel inlet pipe  5  is fixed to a distal end of the conduit  11 .  
         [0043]    Depending upon a configuration of the fuel rail, the number of the rib can be selected and optimized by continuous experiments.  
         [0044]    [0044]FIGS. 3A to  3 C illustrate further modified embodiments in which one rib or two ribs are located near one end or each end (both ends) of the conduit  11 . In FIG. 3A, two ribs  26 ,  27  are located near each end of the conduit  11 . In FIG. 3B, one rib  26  is located near the free end of the conduit  11 . In FIG. 3C, one rib  27  is located near fuel inlet end of the conduit  11 . According to some experiments, it has been found that the rib position near the end of the conduit  11  can provide the most effective performance.  
         [0045]    Referring to FIG. 4, there is shown a second type embodiment of the present invention, a fuel delivery rail assembly  30 . Based upon the charasteristics of the present invention, one wall  11   a  of the conduit  11  opposite to the socket mounting wall provides a flat flexible absorbing surface  11   a . Since the absorbing surface  11   a  faces to the fuel inlet port of the socket  3 , it can absorb shock and vibration during fuel injection timing.  
         [0046]    In addition, two cavities  35 ,  36  are formed to the wall  11   a  across the longitudinal direction of the conduit  11 . The dimensions of each cavity  35 ,  36  can be defined such that its length is about 90 to 100 percent of the width of the conduit  11 , and its depth is within a range about 30 to 40 percent of the total height of the conduit  11 , and its width is within a range about 100 to 200 percent of the total height of the conduit  11 .  
         [0047]    The cavities  35 ,  36  also work to minimize a high-frequency sound component from the vibration noise. Thus, diffusion of high-frequency noise is considerably eliminated.  
         [0048]    Referring to FIG. 5, there is shown a third type embodiment of the present invention, a fuel delivery rail assembly  40 . Based upon the charasteristics of the present invention, one wall  11   a  of the conduit  11  opposite to the socket mounting wall  11   b  provides a flat flexible absorbing surface  11   a . Since the absorbing surface  11   a  faces to the fuel inlet port  13  of the socket  3 , it can absorb shock and vibration during fuel injection timing.  
         [0049]    In addition, a snap-ring type clamp  45  is located for holding the socket mounting wall  11   b  and the absorbing surface  11   a  between the clamp  45 . The clamp  45  comprises a semi-circular head  45   a , flat retaining portions  45   b  and expanded tails  45   c.    
         [0050]    The clamp  45  also works to minimize a high-frequency sound component from the vibration noise. Thus, diffusion of high-frequency noise is considerably eliminated. The clamp  45  can be made in a removable type as shown in FIG. 5 or made in a rigid type which is fixed to the conduit  11 .  
         [0051]    Referring to FIG. 6, there is shown a modified embodiment of the present invention, a fuel delivery rail assembly  50 . Based upon the charasteristics of the present invention, one wall  11   a  of the conduit  11  opposite to the socket mounting wall  11   b  provides a flat flexible absorbing surface  11   a . Since the absorbing surface  11   a  faces to the fuel inlet port of the socket  3 , it can absorb shock and vibration during fuel injection timing.  
         [0052]    In addition, a rigid U-shape clamp  55  is fixed to the conduit  11  by brazing or welding for holding the socket mounting wall  11   b  and the absorbing surface  11   a  between the clamp  55 . The width of the clamp  55  along the longitudinal direction of the conduit  11  can be about 12 mm.  
         [0053]    [0053]FIGS. 7A to  7 C illustrate a further modified embodiment in which a rigid C-shape clamp  65  is fixed to the conduit  11  by brazing or welding for holding the socket mounting wall  11   b  and the absorbing surface  11   a  between the pad portions  65   a  of the clamp  65 .  
         [0054]    [0054]FIGS. 8A to  8 C illustrate further modified embodiments in which one clamp or two clamps are located near one end or each end (both ends) of the conduit  11 . In FIG. 8A, two clamps  66 ,  67  are fixed to each end of the conduit  11 . In FIG. 8B, one clamp  66  is fixed near the free end of the conduit  11 . In FIG. 8C, one clamp  67  is fixed near the fuel inlet end of the conduit  11 . According to some experiments, it has been found that the clamp position near the end of the conduit  11  can provide the most effective performance.  
         [0055]    [0055]FIGS. 9A and 9B illustrate further modified embodiments in which modified clamps are comprised of end caps  75 ,  76  each extending along the longitudinal direction and closing an end portion of the conduit  11 . These clamps  75 ,  76  work to prevent the end portions from freely vibrating such that high frequency noise is eliminated. In FIG. 9A, the end cap  75  is connected to the fuel inlet pipe  5  at an end thereof. In FIG. 9B, the end cap  76  is closing the free end of the conduit  11 .  
         [0056]    As shown in FIGS. 9A and 9B, the end caps  75 ,  76  are overlapping on the conduit  11 . The dimension of the overlapping portion of the end caps  75 ,  76  can be defined such that its wall thickness is about 50 to 400 percent of the thickness of the absorbing surface  11   a , and its overlapping length is within a range about five to twenty times of the thickness of the absorbing surface  11   a.    
         [0057]    Several experiments were done for proving the effects of the inventive clamp associated with an actual engine.  
         [0058]    (1) Fuel delivery rail: width 34 mm, height 10.2 mm, length 300 mm, wall thickness 1.2 mm, material “Japanese industrial standard STKM11A steel pipe” 
         [0059]    (2) Fuel supply pipe from a fuel tank to an engine: outer diameter 8 mm, wall thickness 0.7 mm, material “Japanese industrial standard STKM11A steel pipe” 
         [0060]    (3) Engine: six cylinders gasoline engine  
         [0061]    (4) measuring points: Variations of acceleration were measured by an acceleration pickup which is located under the floor of an automobile near a connecting portion between a steel fuel supply pipe and a connecting plastic hose which is connected to the fuel inlet pipe  5 .  
         [0062]    Under the conventional phase in which the inventive clamp is not located, it was found that peak frequency components exist near 600 Hz and 1.3 kHz. Under the inventive phase in which one clamp is located near the midpoint of the longitudinal conduit, it was found that a vibration level (acceleration) was decreased by 55 percent at 600 Hz, and 30 percent at 1.3 kHz. Under the second inventive phase in which two clamps are located near both ends of the longitudinal conduit, it was found that a vibration level was decreased by 70 percent at 600 Hz, and 45 percent at 1.3 kHz.  
         [0063]    It should be recognized that various modifications are possible within the scope of the invention claimed.