Abstract:
A fuel rail assembly is disclosed. The fuel rail assembly includes a generally hollow fuel rail having a longitudinal rail axis extending therethrough and a fuel damper element having a wall and a longitudinal damper element axis extending therethrough. The fuel damper element is located within the fuel rail. The damper axis is generally parallel with the rail axis. A method of forming the fuel rail assembly is also disclosed.

Description:
FIELD OF THE INVENTION 
     This invention relates to pressure dampers for use in fuel delivery systems for engines for motor vehicles. 
     BACKGROUND OF THE INVENTION 
     In fuel rails for injector-based fuel injection systems, the various devices associated with the fuel system cause pressure waves in the fuel to propagate through the fuel rails. Such pressure waves, if occurring at the wrong time, may have a small amount of fuel leaving the fuel rail and being injected into the engine at the time the injector is pulsed open. In addition, such pressure waves cause noise in the system that may be objectionable. Pressure pulses will give false readings to fuel pressure regulators by operating the regulator with a false indication of fuel pressure, which may result in fuel being bypassed and returned to the fuel tank. 
     A known pressure dampening system uses elastic walls forming the fuel supply line. As pressure pulses occur, the elastic walls function to dampen the pressure pulsations. Other pressure dampening systems use a pressure damper plugged in the end of a fuel rail with a pressure regulator at the other end. Still other pressure dampening systems use a compliant member operable to reduce peak pressure during injector firing events. The member is positioned in the fuel rail so as to not adversely affect the flow of fuel to an injector opening in the rail. The member is not free to rotate in the rail and the pressure pulses are dampened by the member, which is a pair of welded together shell halves with an enclosed airspace. Other pressure dampening systems use an in-line fuel pressure damper from the outlet of the fuel filter to the fuel rail. The damper is a pressure accumulator which operative to reduce transient pressure fluctuations induced by the fuel pump and the opening and closing of the fuel injectors. 
     Another dampening system utilizes an integral pressure damper that is attached to the fuel rail. The return tube is brazed to the rail and then at a convenient time in the assembly process the damper, which is a diaphragm, is attached to the return tube and crimped into position. The diaphragm operates to reduce audible operating noise produced by the injector pressure pulsations. 
     Still another dampening system uses a pulse damper in the fuel pump comprising a hollow body formed of a thin walled tube of flexible and resilient plastic material with heat sealed ends forming at least one chamber. The chamber carries a compressible gas to dampen pressure pulsations. Another dampening system uses a bellows modulator inside a gear rotor fuel pump for reducing pump noise by reducing the amplitude of fuel pressure pulses. Yet another system uses a bellows-like device at the junction of the lines of the flow path of the fluid from a fuel feed pump thereby forming a discontinuity in the flow path to reduce compressional vibrations of fuel being conveyed. 
     It would be beneficial to develop a dampening element that is relatively compact and inexpensive to manufacture and install. 
     BRIEF SUMMARY OF THE INVENTION 
     Briefly, the present invention provides a fuel rail assembly. The fuel rail assembly comprises a generally hollow fuel rail having a longitudinal rail axis extending therethrough and a fuel damper element having a wall and a longitudinal damper element axis extending therethrough. The fuel damper element is located within the fuel rail. The damper element axis is generally parallel with the rail axis. 
     The present invention also provides a dampening element for a fluid conduit. The dampening element comprises an elongated member adapted to be inserted into the fluid conduit. The elongated member has at least one generally rounded portion extending along a length of the member. 
     Additionally, the present invention provides a method of reducing pressure pulsations in a fluid conduit. The method comprises providing a fluid conduit with a dampening element located therein, the dampening element having an elongated member having at least one generally rounded portion extending along a length of the member; and flowing pressurized fluid through the fluid conduit. 
     Additionally, the present invention provides a method of forming a fuel rail assembly. The method comprises compressing a wall of an elongated member toward a longitudinal axis of the element in at least two locations along a length of the member, forming at least one generally rounded portion; and inserting the elongated member into a fuel rail. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are incorporated herein and constitute part of this specification, illustrate the presently preferred embodiments of the invention, and, together with the general description given above and the detailed description given below, serve to explain the futures of the invention. In the drawings: 
     FIG. 1 is a perspective view of a dampening element according to a first preferred embodiment of the present invention, installed in a fuel line; 
     FIG. 2 is a side view, in section, of the dampening element of FIG. 1, taken along line  2 — 2  of FIG. 1; 
     FIG. 3 is a side view, in section, of a dampening element according to a second preferred embodiment of the present invention; and 
     FIG. 4 is a side view, in section, of a dampening element according to a third preferred embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In the drawings, like numerals are used to indicate like elements throughout. A fuel dampening element  110  according to a preferred embodiment of the present invention is shown in FIGS. 1 and 2. The fuel dampening member or element  110  (hereinafter “element  110 ”) is adapted to be inserted into a generally hollow fluid conduit, such as fuel rail  20 , as shown in FIG.  1 . The element  100  inserted into the fuel rail  20  forms a fuel rail assembly  100 . The fuel rail  20  may be found in the fuel management system of a motor vehicle. In an integrated air-fuel module, the fuel rail assembly is a passageway or passageways for either or both a liquid such as gasoline or a non-liquid fluid, such as air or gas. This particular fuel rail  20  has a plurality of injector cups (not shown), each for receiving a fuel injector (not shown). The fuel rail  20  has an internal wall  201  which has an internal perimeter, and a longitudinal rail axis  203  extending therethrough. 
     Preferably, the element  110  is constructed from an elongated single piece of hollow, thin walled stainless steel tubing, Inconel, or electrodeposited nickel, although those skilled in the art will recognize that the element  110  can be constructed from other suitable materials as well, so long as the material can withstand the fluids or fuels that are transported by the fuel rail  20 . Additionally, the element  110  can be other shapes instead of tubular, including box-shaped, or other suitable shapes. In the preferred embodiment, the element  110  originates as a tubular piece having an exterior wall  101 , shown by the dashed lines in FIG.  2 . The exterior wall  101  is compressed toward a longitudinal axis  103  of the element  110  at four locations  102  along the length of the element  110 , as shown by the dashed arrows A. Preferably, the wall  101  is compressed by pinching the wall  101  toward the longitudinal axis  103  using pins and rollers, although those skilled in the art will recognize that other tools and techniques, such as using interior and exterior dies, can be used. Alternatively, the element  110  can be formed by extrusion, as is well known in the art. 
     By compressing the wall  101  at four locations, four generally rounded or semi-elliptical portions or lobes  104  which extend from the longitudinal axis  103  are formed along the length of the element  110 , such that a cross-section of the element  110 , as shown in FIG. 2, gives the appearance of a cross. A tip  105  on the wall  101  of each lobe  104  is preferably approximately a same first distance from the longitudinal axis  103  as the tip  105  on the wall  101  of each other lobe  104 , and all locations on the wall  101  between adjacent lobe tips  105  are less than the first distance from the longitudinal axis  103 . Free ends  106  of the element  110  are pinched together and sealed, preferably by a laser weld, although those skilled in the art will recognize that the free ends  106  can be sealed by other methods, such as, for example, chemical bonding, as well. 
     Preferably, the element  110  has a nominal outside diameter of approximately 9.5 mm (⅜ inches), a wall  101  thickness of approximately 0.15 mm (0.006 inches) and a length of approximately 127 mm (5 inches). However, those skilled in the art will recognize that the thickness and length of the wall  101  can be other dimensions as well. The wall  101  is very thin, hence very sensitive to pulsed pressure signals. The function of the element  110  is to receive the pulsed fuel pressure signals in compression by compressing or when in tension by expanding, to smooth out pressure peaks so as to reduce the pressure pulsations in the fuel rail  20  and to provide a relatively laminar flow of the fuel or fluid in the fuel rail  20  and into each injector as the respective injector is opened. The element  110 , having its lobes  104  formed from the wall  101 , provides the resiliency necessary to absorb the pressure pulses. The pressure pulses, acting on the plurality of the lobes  104 , operate to compress or stretch the lobes  104 , which thereby absorb the pulsed pressure. The lobes  104  may be in either a compression mode or in a tension mode. The relatively large amount of surface area of the wall  101  within a small volume inside the fuel rail  20  provides a large surface area for absorbing the pulsed pressure signals. 
     The element  10  is installed in an open end of the fuel rail  20  such that the longitudinal axis  103  of the element  110  is generally parallel to the longitudinal axis  203  of the fuel rail  20 . The element  110  can be secured to the fuel rail  20  by a clip (not shown), or can be freely inserted in the fuel rail  20 , allowing the element  110  to float within the fuel rail  20 . Preferably, the fuel rail  20  has a nominal 19 mm (¾ inch) diameter. When using an element  110  having an outside diameter of approximately 9.5 mm, the ratio of the diameter of the fuel rail  20  to the element  110  is approximately 2:1. Pressurized fuel flows through the fuel rail  20  in the areas  202  within the fuel rail  20  which are not occupied by the element  110 . 
     An additional benefit of the preferred embodiment of the element  110  is that the element  110  provides internal structural support to the fuel rail  20 . In the event that an external compression force is applied to the fuel rail  20 , the element  110  acts as a stiffener which may prevent the fuel rail  20  from totally collapsing. 
     Preferably, the element  110  is used in non-return fuel systems, although those skilled in the art will recognize that the element  110  can be used in any type of fuel system in which pressure pulsations would potentially occur. 
     Although four lobes are preferred, other embodiments with less than or more than four lobes can be used. For example, FIGS. 3 and 4 show elements  210  and  310  having three lobes  204  and two lobes  304 , respectively, which can be used. Preferably, the lobes  104 ,  204 ,  304  are all symmetrically spaced about the longitudinal axis, although those skilled in the art will recognized that the lobes  104 ,  204 ,  304  need not be symmetrically spaced. Additionally, although the lobes  104 ,  204 ,  304  are preferably the same size as respective lobes  104 ,  203 ,  304  in the same element  110 , those skilled in the art will recognize that the lobes  104 ,  204 ,  304  need not be the same size. Further, although the lobes  104 ,  204 ,  304  are preferably rounded or semi-elliptical in shape, those skilled in the art will recognize that the lobes  104 ,  204 ,  304  can be other shapes as well. 
     The use of element  110  has been shown in a fuel rail  20 , although such a damper may be positioned in other parts of a fuel or fluid systems such as in cooperation with molded passageways. Such other areas are in pressure regulator, fuel pump motors or any place wherein pressure pulses occur. 
     It will be appreciated by those skilled in the art that changes could be made to the embodiment described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined in the appended claims.