Abstract:
A fuel rail assembly of an internal combustion engine includes an axially extending non-round fuel conduit and at least one axially extending stiffening feature integral with said conduit. Integration of the stiffening features in the conduit enables reduction or elimination of the objectionable frequency noise radiated by the fuel rail assembly. By aligning the stiffening features axially relative to the conduit, panels having a relatively small surface area are formed and, thus, the noise radiating surface area is significantly reduced. The axial orientation of the added stiffening features allows the length of the stiffening features to be relatively large, which increases the stiffening effects to provide increased resistance to flexing, thus, reducing the noise radiated by the fuel system of the internal combustion engine.

Description:
TECHNICAL FIELD 
     The present invention relates to engine management systems and components of internal combustion engines; more particularly, to fuel injection systems; and most particularly, to an apparatus and method for fuel rail radiated noise reduction. 
     BACKGROUND OF THE INVENTION 
     It is generally known in the art of internal combustion engine design to use fuel rails to deliver fuel to individual fuel injectors. A fuel rail is essentially an elongated manifold connected to a fuel supply system and having a plurality of ports for mating in any of various arrangements with a plurality of fuel injectors to be supplied. 
     Typically, a fuel rail assembly includes a plurality of fuel injector sockets in communication with the fuel rail, the injectors being inserted into the sockets and held in place in an engine cylinder head or intake manifold by bolts securing the fuel rail assembly to the head or manifold. 
     Two types of fuel delivery systems exist, the return type system including a return pipe to the fuel supply system and the return-less system. In what is referred to as a return-less system, a fuel return line does not fluidly connect the fuel rail back to the fuel supply system at a rail outlet end. In a “return” system, a fuel line fluidly connects the end of the fuel rail opposite the inlet end back to the fuel supply system. For economic reasons, the use of return-less fuel delivery systems increased in recent years. Drawbacks with return-less fuel delivery systems arise from pressure pulsations and fuel reflecting waves generated during reciprocating movements of a fuel pump and fuel injector valve assemblies. 
     During operation of an internal combustion engine, fuel rail assemblies typically vibrate due to the reciprocating movements of a fuel pump and fuel injector valve assemblies. For example, opening and closing events of the fuel injectors create pressure waves in the fuel system. To absorb the pressure waves, flexing walled manifolds are often used as a fuel rail or internal dampers are installed within the fuel rails. While flexing walled manifolds are less expensive than internal dampers and do not require additional parts to be installed the amount of noise typically radiated by the fuel rail increases with the use of flexing walls. Such noise radiated by the fuel rail assembly is objectionable and undesirable. 
     One prior art approach to dampen the noise radiated by a fuel rail assembly during operation of an internal combustion engine includes placing an acoustic cover on top of each fuel rail. While this method may be effective to reduce fuel system noise, the acoustic cover is a separate part that needs to be manufactured and installed, which creates extra cost and requires additional cycle time. In modern engine design it is desirable to reduce the number of parts required in the assembly of a fuel injection system in order to reduce the manufacturing cost, cycle time, and to improve reliability of the engine. 
     Another prior art approach to dampen the noise radiated by a fuel rail assembly during operation of an internal combustion engine includes integration of stiffening ribs or cavities that are aligned perpendicular to the axis of the fuel rail. Panels formed between these ribs or cavities may have a relatively large surface area and, therefore, may still allow vibration of the fuel rail assembly and, consequently, noise radiation by the fuel rail assembly. 
     What is needed in the art is a more effective fuel rail radiated noise reduction that eliminates assembly of additional parts. 
     It is a principal object of the present invention to provide a modified fuel conduit that enables reduction or elimination of radiated frequency noise for a variety of fuel systems. 
     SUMMARY OF THE INVENTION 
     Briefly described, a fuel rail assembly in accordance with the invention includes a variety of axially extending stiffening features integrated into or attached to a non-round walled fuel conduit to reduce or eliminate fuel system radiated frequency noise. In one aspect of the invention, additional material, for example, in the form of structural components, is added to the fuel rail assembly along the axial length of the conduit. Such structural components may be placed either interior or exterior to the conduit and may be either continuous or in segments. In another aspect of the invention, indentations or protrusions are formed along the axial length of the conduit. The indentations or protrusions may be formed continuously or in segments. Additionally, the cross-sectional dimensions of the stiffening features may be varied to enhance the noise reduction effect of the stiffening features. 
     The stiffening features may be placed on any of the surfaces of the conduit that may be radiating the objectionable noise. Accordingly, the stiffening features may be placed on either side or the top of the fuel conduit as well as on the bottom of the conduit between the fuel injector sockets. Integration of these stiffening features in the fuel rail assembly enables reduction or elimination of the frequency noise radiated by the fuel rail assembly eliminating the need to place a prior art acoustic cover on top of the fuel rail conduit. 
     By aligning the stiffening features axially relative to the fuel conduit, panels having a relatively small surface area are formed and, thus, the noise radiating surface area is significantly reduced compared to prior art stiffening ribs or cavities that are arranged perpendicular to the axis of the conduit. The axial orientation of the added stiffening features allows the length of the stiffening features to be larger than one that is aligned perpendicular to the axis of the fuel conduit. The increased length of the stiffening features will increase the stiffening effects to provide increased resistance to flexing, thus, reducing the noise radiated by the fuel rail assembly. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: 
         FIG. 1  is an isometric view of a first fuel rail assembly including continuous structural components, in accordance with the invention; 
         FIG. 2  is an isometric view of the first fuel rail assembly including intermittent structural components, in accordance with the invention; 
         FIG. 3  is a partial side elevational view of the first fuel rail assembly, in accordance with the invention; 
         FIG. 4  is a cross-sectional view along line  4 - 4  in  FIG. 3  of the first fuel rail assembly including exterior positioned structural components, in accordance with the invention; 
         FIG. 5  is a cross-sectional view of the first fuel rail assembly including interior positioned structural components, in accordance with the invention; 
         FIG. 6  is an isometric view of a second fuel rail assembly including continuous indentations, in accordance with the invention; 
         FIG. 7  is an isometric view of the second fuel rail assembly including intermittent indentations, in accordance with the invention; 
         FIG. 8  is a cross-sectional view of the second fuel rail assembly including indentations, in accordance with the invention; 
         FIG. 9  is an isometric view of a third fuel rail assembly including continuous protrusions, in accordance with the invention; 
         FIG. 10  is an isometric view of the third fuel rail assembly including intermittent protrusions, in accordance with the invention; and 
         FIG. 11  is a cross-sectional view of the third fuel rail assembly including protrusions, in accordance with the invention. 
     
    
    
     Corresponding reference characters indicate corresponding parts throughout the several views. The exemplification set out herein illustrates preferred embodiments of the invention, in one form, and such exemplification is not to be construed as limiting the scope of the invention in any manner. 
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIGS. 1 through 5 , a first fuel rail assembly  100  includes a non-round fuel conduit  110  that axially extends along an axis  102  from a first end  112  to a sealed second end  114 . Conduit  110  may include a top wall  116 , two sidewalls  118  and  122 , and a bottom wall  124  as illustrated. Other configurations of the conduit may be possible. For example, conduit  110  may be tubular or may be created by stampings of various shapes that are brazed together. Conduit  110  has an exterior surface  126  and an interior surface  128  (shown in  FIG. 4 ). A fuel inlet  130  is shown to fluidly connect first end  112  of conduit  110  with a fuel supply system (not shown). Fuel inlet  130  does not need to be positioned at first end  112  but may be positioned anywhere along conduit  110 . A plurality of fuel injector sockets  140  is connected to bottom wall  124  of conduit  110 . Injector sockets  140  are axially spaced apart along bottom wall  124 . 
     Axially extending stiffening features in form of structural components  150  are added to fuel conduit  110 . Structural components  150  may be formed separately from conduit  110  and may be attached to either the exterior surface  126  (as shown in  FIGS. 1-4 ) or the interior surface  128  (as shown in  FIG. 5 ) such that structural components provide a resistance to flexing to conduit  110  and, thus, enable reduction of the noise radiated by fuel rail assembly  100 . Structural components  150  may be attached to conduit  110 , for example, by brazing or welding. Structural components  150  may be formed from the same material as conduit  110  or from a different material. 
     Structural components  150  may be positioned on either wall, such as top wall  116 , sidewalls  118  and  122 , or bottom wall  124  as shown in  FIG. 3 . On top wall  116  and sidewalls  118  and  122 , structural components  150  may be attached as continuous features that continuously extend along axis  102  over the entire length of conduit  110  as shown in  FIG. 1  or may be attached intermittently as segments as shown in  FIG. 2 . On bottom wall  124 , structural components  150  may be attached as segments between fuel injector sockets  140  as shown in  FIG. 3 . The dimensions, such as width  152 , height  156 , and length  154 , may be varied to adjust the noise reduction effect. 
     While structural components  150  are shown in  FIG. 5  as attached to top wall  116 , both sidewalls  118  and  122 , bottom wall  124 , it may not be necessary to apply structural components  150  to each of those walls to achieve the desired stiffening effect for reducing the noise radiated by fuel rail assembly  100 . Structural components  150  may be applied to only one of the walls  116 ,  118 ,  122 , or  124  of conduit  110 , to all walls, or to any number in between. Continuously extending structural components  150  as shown in  FIG. 1  may be combined with intermittently extending structural components  150  as shown in  FIG. 2 . Segments of structural components  150  as shown in  FIG. 2  may be positioned on adjacent walls, such as top wall  116  and sidewall  118  or top wall  116  and sidewall  122 , such that segments of structural components  150  are arranged alternating. 
     While structural components  150  are shown either attached only to the exterior surface  126  of conduit  110  (as shown in  FIGS. 1-4 ) or attached only to the interior surface  128  of conduit  110  (as shown in  FIG. 5 ) combinations thereof are possible. 
     While the continuously extending structural components  150  are shown in  FIG. 1  to form a generally straight line, it may be possible for the structural components  150  to axially extend in a non-straight line, such as a curved line. While the structural components  150  are shown in  FIGS. 1-5  as being positioned centered on the walls, an off-centered position may be applicable. Only one structural component  150  applied to a single wall, such a top wall  116 , sidewalls  118  and  122 , and bottom wall  124 , is shown in  FIGS. 1-5 , but it may be possible to apply two or more structural components  150  extending axially in parallel to each of these walls. 
     Referring now to  FIGS. 6 through 8 , a second fuel rail assembly  200  includes a non-round fuel conduit  210  that axially extends along an axis  202  from a first end  212  to a sealed second end  214 . Conduit  210  includes a top wall  216 , two sidewalls  218  and  222 , and a bottom wall  224 . A fuel inlet  230  fluidly connects conduit  210  with a fuel supply system (not shown). Fuel inlet  230  is not limited to be positioned at first end  212  as shown in  FIGS. 6 and 7 . A plurality of fuel injector sockets  240  is connected to bottom wall  224  of conduit  210 . Injector sockets  240  are axially spaced apart along bottom wall  224 . 
     Axially extending stiffening features in form of indentations  250  are integrated into fuel conduit  210 . Indentations  250  may be, for example, formed as depressed slots or crimp dents. Indentations  250  provide an increased resistance to flexing to conduit  210  and, thus, enable reduction of the noise radiated by second fuel rail assembly  200 . Indentations  250  may be integrated into either wall, top wall  216 , sidewalls  218  and  222 , or bottom wall  224 . On top wall  216  and sidewalls  218  and  222 , indentations  250  may be formed as continuous features that continuously extend along axis  202  over the entire length of conduit  210  as shown in  FIG. 6  or may be formed intermittently as segments as shown in  FIG. 7 . In bottom wall  224 , indentations  250  may be formed as segments between fuel injector sockets  240 . The dimensions, such as width  252 , depth  256 , and length  254 , of indentations  250  may be varied to adjust the noise reduction effect. 
     While indentations  250  are shown in  FIG. 8  as formed in top wall  216 , both sidewalls  218  and  222 , and bottom wall  224 , it may not be necessary to form indentations  250  in each of those walls to achieve the desired stiffening effect for reducing the noise radiated by fuel rail assembly  200 . To achieve the desired stiffening effect to reduce the radiated noise, at least one indentation  250  is applied to at least one wall, such as top wall  216 , sidewalls  218  and  222 , or bottom wall  224 . Continuously extending indentations  250  as shown in  FIG. 6  may be combined with intermittently extending indentations  250  as shown in  FIG. 7 . Segments of indentations  250  as shown in  FIG. 7  may be positioned in adjacent walls, such as top wall  216  and sidewall  218  or top wall  216  and sidewall  222 , such that segments of indentations  250  are arranged alternating. 
     While the continuously extending indentations  250  are shown in  FIG. 6  to form a generally straight line, it may be possible for indentations  250  to axially extend in a non-straight line, such as a curved line. While the indentations  250  are shown in  FIGS. 6-8  as being positioned centered on the walls, an off-centered position may be applicable. Only one indentation  250  formed in a single wall, such a top wall  216 , sidewalls  218  and  222 , and bottom wall  224 , is shown in  FIG. 6 , but it may be possible to form two or more indentation  250  that axially extend in parallel in each of these walls. 
     Referring now to  FIGS. 9 through 11 , a third fuel rail assembly  300  includes a non-round fuel conduit  310  that axially extends along an axis  302  from a first end  312  to a sealed second end  314 . Conduit  310  includes a top wall  316 , two sidewalls  318  and  322 , and a bottom wall  324 . A fuel inlet  330  fluidly connects conduit  310  with a fuel supply system (not shown). Fuel inlet  330  is not limited to be positioned at first end  312  as shown in  FIGS. 9 and 10 . A plurality of fuel injector sockets  340  is connected to bottom wall  324  of conduit  310 . Injector sockets  340  are axially spaced apart along bottom wall  324 . 
     Axially extending stiffening features in form of protrusions  350  are integrated into fuel conduit  310 . Protrusions  350  may be, for example, formed as protruded slots. Protrusions  350  provide an increased resistance to flexing to conduit  310  and, thus, enable reduction of the noise radiated by second fuel rail assembly  300 . Protrusions  350  may be integrated into either wall, top wall  316 , sidewalls  318  and  322 , or bottom wall  324 . On top wall  316  and sidewalls  318  and  322 , protrusions  350  may be formed as continuous features that continuously extend along axis  302  over the entire length of conduit  310  as shown in  FIG. 9  or may be formed intermittently as segments as shown in  FIG. 10 . In bottom wall  324 , protrusions  350  may be formed as segments between fuel injector sockets  340 . The dimensions, such as width  352 , height  356 , and length  354 , of protrusions  350  may be varied to adjust the noise reduction effect. 
     While protrusions  350  are shown in  FIG. 11  as formed in top wall  316 , both sidewalls  318  and  322 , and bottom wall  324 , it may not be necessary to form protrusions  350  in each of those walls to achieve the desired stiffening effect for reducing the noise radiated by fuel rail assembly  300 . To achieve the desired stiffening effect to reduce the radiated noise, at least one protrusion  350  is applied to at least one wall, such as top wall  316 , sidewalls  318  and  322 , or bottom wall  324 . Continuously extending protrusions  350  as shown in  FIG. 9  may be combined with intermittently extending protrusions  350  as shown in  FIG. 10 . Segments of protrusions  350  as shown in  FIG. 10  may be positioned in adjacent walls, such as top wall  316  and sidewall  318  or top wall  316  and sidewall  322 , such that segments of protrusions  350  are arranged alternating. 
     While the continuously extending protrusions  350  are shown in  FIG. 9  to form a generally straight line, it may be possible for protrusions  350  to axially extend in a non-straight line, such as a curved line. While the protrusions  350  are shown in  FIGS. 9-11  as being positioned centered on the walls, an off-centered position may be applicable. Only one protrusions  350  formed in a single wall, such a top wall  316 , sidewalls  318  and  322 , and bottom wall  324 , is shown in  FIG. 9 , but it may be possible to form two or more protrusions  350  that axially extend in parallel in each of these walls. 
     By aligning a variety of stiffening features, such as added structural components  150 , indentations  250 , or protrusions  350 , axially relative to a fuel conduit, such as fuel conduit  110 ,  210 , or  310 , each wall where a stiffening feature is integrated is divided into panels. Each of such panels has a reduced radiating surface area, which results in a reduction of objectionable frequency noise. 
     While in  FIGS. 1-11  either added structural components  150 , indentations  250 , or protrusions  350  are shown, respectively, it may be possible to combine added structural components  150 , indentations  250 , and/or protrusions  350  in a single fuel conduit, such as conduit  110 ,  210 , or  310 . 
     While only added structural components  150 , indentations  250 , or protrusions  350  are shown as axially extending stiffening features, other forms of axially extending structures may be used as stiffening features. 
     While the invention has been described by reference to various specific embodiments, it should be understood that numerous changes may be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the described embodiments, but will have full scope defined by the language of the following claims.