Abstract:
A low pressure fuel injector capable of atomizing fuel at relatively low pressure is configured to have reduced hydraulic resistance. Reduction in the hydraulic resistance minimizes the pressure drop within the fuel injector and thereby improves atomization of the fuel for improved fuel economy and performance, and decreased emissions.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Technical Field 
         [0002]    This present invention is directed to fuel injectors for automotive engines and, more particularly, to fuel injectors capable of atomizing fuel at relatively low pressures. 
         [0003]    2. Discussion 
         [0004]    Fuel injected internal combustion engines are well known in the industry. In direct injected engines, the injection tip of the fuel injector extends into the combustion chamber and includes a perforated plate also known as a metering plate for dispersing and directing fuel from the injection valve. In a conventional gasoline engine with port fuel injection system, the injection tip of the injector extends into a cavity or rail of the engine&#39;s intake manifold where the injected fuel is mixed with intake air before being discharged into the engine&#39;s combustion chamber. 
         [0005]    A metering plate located on the end of the fuel injector includes a variety of fuel flow passages that are configured to provide extremely small fuel droplets to meet stringent emission standards for internal combustion engines. The fine atomization of the fuel reduces exhaust emissions and improves cold weather start capabilities as well as reduces fuel consumption and improves performance. Typically the optimization of the droplet size depends on the pressure of the fuel and requires high pressure delivery of roughly 7 to 10 MPa. However, a higher fuel delivery pressure causes greater dissipation of the fuel and propagates the fuel further outward from the injector which makes it more likely that fuel condenses on the walls of the cylinder and on the top surface of the piston thereby decreasing the efficiency of combustion and increasing emissions. 
         [0006]    To address these problems, fuel injector systems have been proposed which utilize low pressure fuel while at the same time providing sufficient atomization of the fuel. To generate sufficient atomization at such low pressure, fuel injectors typically employ sharp edges at the nozzle orifice for atomization and acceleration of the fuel. However, the relatively low pressure of the fuel and sharp edges result in the spray being difficult to direct and reduces the range of the spray. More particularly, the spray angle or cone angle produced by the injector is somewhat more narrow. At the same time, additional improvement to the atomization of the low pressure fuel injector would increase the efficiency and operation of the engine. 
       SUMMARY OF THE INVENTION 
       [0007]    In view of the above, the present invention is directed to a low pressure fuel injector capable of atomizing fuel at relatively low pressure is configured to have reduced hydraulic resistance. Reduction in the hydraulic resistance minimizes the pressure drop within the fuel injector and thereby improves atomization of the fuel for improved fuel economy and performance, and decreased emissions. 
         [0008]    The fuel injector generally includes a valve needle having at least one surface with an elongated portion extending approximately parallel to a longitudinal axis, and a valve seat defining a valve passage extending along the longitudinal axis and wherein the valve seat defines an inner surface having a first arcuate portion with a profile of an arcuate curve extending from approximate parallel alignment with the longitudinal axis toward the longitudinal axis. 
         [0009]    The arcuate portion has a portion approximately perpendicular to the longitudinal axis. A transition portion extends from the first arcuate portion and approximately perpendicular to the longitudinal axis, and the transition portion further extends to a second arcuate portion wherein the second arcuate portion includes a seal area for sealing engagement with the needle valve. More specifically, the second arcuate portion extends along an arcuate curve arranged approximately perpendicular to the longitudinal axis toward a nozzle outlet edge along a surface angled approximately between fifteen degrees and seventy five degrees from parallel with the longitudinal axis. 
         [0010]    The first arcuate portion is configured to not contact the valve needle. The needle valve includes a lower planar surface approximately perpendicular to the longitudinal axis, and wherein the at least one surface is an approximately planar surface aligned along the longitudinal axis. 
         [0011]    The present invention is directed to a low pressure fuel injector for delivering fuel to a cylinder of an engine having a valve needle having an approximately planar surface extending approximately parallel to a longitudinal axis and a lower surface being approximately planar and extending approximately perpendicular to the longitudinal axis. 
         [0012]    The present invention is directed to a low pressure fuel injector for delivering fuel to a cylinder of an engine, the fuel injector having a valve seat defining a valve passage extending along the longitudinal axis and wherein the valve seat defines an inner surface having a first arcuate portion having a profile of an arcuate curve extending from approximate parallel alignment with the longitudinal axis toward the longitudinal axis, and a second arcuate portion having a substantially opposing arcuate curve. 
         [0013]    Further scope of applicability of the present invention will become apparent from the following detailed description, claims, and drawings. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    The present invention will become more fully understood from the detailed description given here below, the appended claims, and the accompanying drawings in which: 
           [0015]      FIG. 1  is a cross-sectional view of a prior art low pressure fuel injector; 
           [0016]      FIG. 2  is a cross-sectional view of a low pressure fuel injector constructed in accordance with the teachings of the present invention; 
           [0017]      FIG. 3  is a cross-sectional view of a low pressure fuel injector constructed in accordance with the teachings of the present invention; and 
           [0018]      FIG. 4  is a perspective view of the valve needle. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0019]    A low pressure fuel injector  20  is generally illustrated in a partial cross-sectional view in  FIG. 2 . The injector  20  is used to deliver fuel to a cylinder of an engine, such as an internal combustion engine of a vehicle. An injector body  22  defines a passageway  24  and located within the passageway  24  and capable of engaging a valve seat  28  is a needle  26 . The needle  26  cooperates with the valve seat  28  to form a needle valve to start and stop fluid flow through the injector  20 . The injector body  22  is generally aligned along a longitudinal axis  15  and the passageway  24  generally extends along or parallel to the longitudinal axis  15 . A lower end of the injector body  22  defines a nozzle body  32 . It should be recognized by those skilled in the art that the injector body  22  and nozzle body  32  may be formed separately or the nozzle body  32  may be attached to the distal end of the injector body  22  by welding or other known techniques. 
         [0020]    In either case, the nozzle body  32  defines a valve seat  28  leading to a valve outlet  36  of the needle valve. The needle  26  is generally moved along the longitudinal axis  15 , in and out of engagement with the valve seat  28 , and is usually controlled by an electromagnetic actuator (not shown). In this manner, fluid or fuel flowing through the internal passage  24  and around the needle  26  is permitted or prevented from flowing to the valve outlet  36  by engagement or disengagement of the needle  26  with the valve seat  28 . 
         [0021]    The injector  20  further includes a metering plate  40  which is attached to the nozzle body  32 . It should be recognized by those skilled in the art that the metering plate  40  may be integrally formed with the nozzle body  32  or separately formed and attached to the nozzle body  32  by welding or other known techniques. In either case, the metering plate defines a nozzle cavity  42  for receiving fuel from the valve outlet  36 . The nozzle cavity  42  may be generally defined by the metering plate  40  and the lower portion of the nozzle body  32 , which also defines at least a portion of the valve outlet  36 . As illustrated in  FIGS. 2 and 3 , the metering plate  40  defines a nozzle cavity  42  which is defined by at least a bottom wall  44 . In some embodiments, although not illustrated, the metering plate may further include a side wall with the nozzle cavity  42  taking on a wide variety of configurations. The metering plate  40  further includes exit cavities  50 . The exit cavities  50  may be formed in a variety of size, shapes, and configurations. The location of the exit cavities may depend upon the desired spray pattern formed by the metering plate  40 . The exit cavities  50  may be formed in a variety of sizes, shapes, and configurations. 
         [0022]    In addition to using the location, size, shape, and configuration of the exit cavities as well as sharp edges that the nozzle orifice includes, the present invention uses the contours and configuration of the needle valve and valve seat to reduce the hydraulic resistance in the valve passageway, which reduces the pressure drop caused by the passageway, which in turn allows for high turbulence of the fuel to improve atomization of the fuel in the cylinder thereby decreasing emissions while increasing performance and fuel economy. 
         [0023]    As part of the present invention, reduce hydraulic resistance and to enhance turbulence and thereby improve atomization of the fuel, the needle valve is formed with at least two planar surfaces  27 , preferably three planar surfaces, and more preferably at least four planar surfaces. The number of planar surfaces may vary depending upon the configuration of the passageway as well as the desired flow of the fuel. As illustrated in the prior art illustration of  FIG. 1 , needles  26  have generally a bulbous end  25 . In comparison, as illustrated in  FIGS. 2 and 3 , the present invention not only includes planar side surfaces  29 ′ but a planar lower surface  29 ″ which is also substantially planar. The planar surfaces  27  on the needle  26  are bounded by edges  21 . As illustrated in  FIGS. 2 and 3 , the needle  26  may further include transition points or transition edges  21  used to help increase the turbulence of the fuel flow. These transition points or edges  21  act in a similar manner as the sharp nozzle edge  33  used in the prior art. The edges  21  are configured to create upstream turbulence from the sharp nozzle edge  33 . Increasing turbulence of the fuel stream before reaching the sharp nozzle edge  33  increases atomization of the fuel. While all of the planar surfaces  27  and lower surface  29  are illustrated as being substantially planar, they may be formed with some variation from being planar. For example, some form of a convex or concave shape that is still approximately planar may be used. 
         [0024]    The valve seat when viewed in cross section includes a first arcuate shape  130 , a second arcuate shape  132 , and a transition area  134  therebetween. The first arcuate shape  130  has a radius or curved profile similar to the radius or profile of the transition portion  23  on the needle  26 . As illustrated in  FIG. 2 , the valve seat  28  and needle  26  as well as the nozzle body  32  and needle  26  work in conjunction to form a fluid passageway  16  at the end of the passage  24 . This fluid passage as it nears the lower portion  35  of the nozzle body  32  narrows. This narrowing occurs as the fluid passage  16  curves inward following the shape of the first arcuate shape  130  as illustrated in  FIG. 2 . The passage  16  then narrows further as the transition portion  134  extends inward almost perpendicular to the longitudinal axis  15  or at a rate much greater than the transitional portion  23  on the needle  26  extends inward. Therefore, as the fluid passage  16  narrows, it passes the edge  21  which creates turbulence and is forced into a narrower area between the second arcuate shape  132  and transition portion  23  or the needle  26 . Along the second arcuate shape  132 , the needle  26  contacts the valve seat  28 . This point of contact is labeled as the seal area  31 . In proximity to the seal area  31 , the fluid passageway  16  is at its narrowest point. As the fluid passes through the passageway  16  proximate to the seal point  31  it suddenly expands into the valve outlet  36 , an area of greater volume. Therefore, as the fluid flows through the passageway  16  past one of the transition points  21 , it is squeezed by the first arcuate shape  130  and transition area  134  toward the seal point  31  on the second arcuate shape  132  and then expanded into the valve outlet  36 . The turbulence of the fluid is increased through this design and the abrupt edges, which in turn helps with atomization of the fuel. The fuel is then squeezed past the shape nozzle edge  33  to exit one of the exit cavities  50 . In the present invention the sharp nozzle edge  33  is configured to have the fuel from the passage turn along a greater radius than normal as the second arcuate shape  132  is configured to continue sloping inward toward the longitudinal axis  15  to terminate at the sharp nozzle edge  33 . A lower end of the injector body  22  defines a nozzle body  32 . It should be recognized by those skilled in the art that the injector body  22  and nozzle body  32  may be formed separately or the nozzle body  32  may be attached to the distal end of the injector body  22  by welding or other known techniques. The arcuate shapes,  130 , 132  are designed to minimize hydraulic resistance, thereby minimizing the pressure drop caused by the hydraulic resistance. Minimizing the pressure drops allows for enhancement of turbulence, thereby improving the atomization of the fuel. 
         [0025]    The valve seat or lower nozzle body may be formed from an inverted frusto-conical shape with the inner surface of the valve seat including a ridge  150  extending around the perimeter of the valve seat, as illustrated in  FIG. 3 . The ridge  150  includes the seal point, which sealingly engages the needle  26  to stop the flow of fluid through the fuel injector. The ridge  150  is configured to create turbulence upstream from the nozzle point as the fluid within the passage  16  is forced through the narrower area between the ridge  150  and the needle  26  and then expands into an open area of the valve outlet. 
         [0026]    The foregoing discussion discloses and describes an exemplary embodiment of the present invention. One skilled in the art will readily recognize from such discussion, and from the accompanying drawings and claims that various changes, modifications and variations can be made therein without departing from the true spirit and fair scope of the invention as defined by the following claims.