Abstract:
Apparatus and method for substantially reducing or eliminating pressure pulsations caused by the opening and closing of fuel injectors. A preferred embodiment provides a restriction orifice adjacent the inlet end of a fuel injector filter of a respective fuel injector.

Description:
TECHNICAL FIELD  
       [0001]     The present invention relates to fuel injectors for internal combustion engines; more particularly, to a fuel injector with a built-in orifice for reducing pressure pulsations.  
       BACKGROUND OF THE INVENTION  
       [0002]     Fuel injectors for controllably metering fuel to the combustion cylinders of internal combustion engines are well known. For ease and reliability in manufacturing, the fuel injectors typically are mounted by their inlet ends at appropriate intervals into a rigid fuel supply line harness, appropriately configured to place the injection end of each fuel injector into its corresponding injection socket in the manifold runner. Such a harness is known as a fuel injector rail, or simply a fuel rail.  
         [0003]     In a typical direct injector fuel injection system, each injector is programmed to pulse or open every other revolution of the engine crankshaft. During an injector opening event in a direct injector fuel injection system, the measured fuel pressure in the fuel rail can instantaneously drop by more than 30 kPa, then can increase by more than 50 kPa after the injector closes. Although such high and low pressures can vary widely depending on rail volume, injector open/close time, and inlet line inner diameter, for example, in a typical four cylinder engine operating at 2000 RPM, the combined injectors can pulse at a rate of 66 pulses per second. In such injector-based systems, these pulses cause high frequency pressure waves of significant amplitude to propagate through the fuel rail(s) potentially causing erratic delivery of fuel to the cylinders.  
         [0004]     The fuel rails themselves are typically bolted to the cylinder head. In one prior art design, the fuel rail is laterally offset from the position of the bolts which are secured to the cylinder head through brackets. The fuel rail is offset so the bolts are accessible when attaching or removing the fuel rail from the cylinder head. In this design, the brackets extend around a respective fuel injector socket, into which the inlet ends of the injectors are placed. This prior art design requires a jump tube leading from the rail to the respective injector socket.  
         [0005]     One known method for reducing injector pressure pulsations is to include a restriction orifice in the fuel line leading to the injector. Due to the narrowing of the flow area, the restriction orifice breaks up and thus reduces the pressure pulsations. The location of the restriction orifice should be somewhere between the fuel rail and injector. In one known design, the restriction orifice is placed inside the jump tube. While this method is effective at reducing pressure pulsations, it also adds cost and complexity to the fuel system.  
         [0006]     It would therefore be desirable to have a design and method for reducing pressure pulsations in a fuel line that does not increase cost or complexity to the system.  
       SUMMARY OF THE INVENTION  
       [0007]     The present invention addresses the above need by providing a design and method for reducing pressure pulsations in a fuel line caused by the opening and closing of the fuel injectors. In a preferred embodiment, a restriction orifice is provided in the fuel injector filter of a respective fuel injector. The restriction orifice acts to break up and thus reduce or eliminate pressure pulsations through the fuel injector. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]     The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:  
         [0009]      FIG. 1  is an isometric view of a fuel rail and associated fuel injectors;  
         [0010]      FIG. 2  is a partial cross-sectional view of a fuel injector as taken generally along the line  2 - 2  in  FIG. 1 ; and  
         [0011]      FIG. 3  is an enlarged detail view of the portion of the injector as indicated by the circled dash line labeled  FIG. 3  in  FIG. 2 . 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0012]     Referring to  FIG. 1 , there is seen a fuel rail  10  for mounting to an engine (not shown) via bracket  12 . The fuel rail  10  is laterally offset from the injector sockets  14  to provide access to the bolts  13  which pass through openings in bracket  12 . With the fuel rail  10  laterally offset from the injector sockets  14 , jump tubes  16  are required to provide a fluid path from the rail  10  to a respective injector socket  14 . Injector sockets  14  are known in the art and provide a coupling between a respective fuel injector  18  and the fuel rail  10 .  
         [0013]     It is noted that fuel rail  10  and bracket  12  are shown for purposes of environment only, and the present invention may be used in any fuel delivery system having one or more fuel injectors.  
         [0014]     Fuel injectors  18  each have a fuel inlet end  18   a  and fuel outlet end  18   b . Fuel is thus directed through fuel outlet end  18   b  upon the opening of the injector. As stated above, fuel injectors open and close very rapidly in order to provide the correct amount of fuel to the engine depending on the engine load condition. Without corrective measures being taken, unacceptable amounts of noise and vibration are created due to the rapid opening and closing of the fuel injectors as they pass fuel into the engine.  
         [0015]     Referring to  FIGS. 2 and 3 , a preferred embodiment of the invention is shown wherein a restriction orifice  20  is molded or otherwise formed in injector filter  22 . Fuel injector filters are known and include a filter media  24  disposed within a filter body  26  for removing small particulate from the fuel as the fuel enters the inlet end  18   a  of the fuel injector  18 . The fuel injector filter body  26  may further include ribs  28  or other means for connecting the filter body to the fuel injector directly or via a filter connector  30 .  
         [0016]     The fuel injector filter is positioned within the longitudinal passageway  18   c  of the injector  18  to intercept and filter the fuel flowing therethrough prior to the fuel exiting the injector at outlet end  18   b . As seen best in  FIG. 3 , a restriction orifice  20  is provided at the inlet end  22   a  of filter  22 . The restriction orifice may be integrally molded with filter body  26  or may be a separate component which is connected to the filter body  26  adjacent filter inlet end  22   a  or other suitable location within filter body  26 . Filter outlet end  22   b  is generally positioned along the longitudinal axis of the injector passage  18   c.    
         [0017]     It is noted that fuel filter bodies are typically injection molded from a plastic such as Nylon 66, for example. In a preferred embodiment, the restriction orifice  20  is between about 0.75 to about 2 mm in diameter although the final size will depend on the particular injector design employed. This restriction orifice is sufficient to substantially reduce or eliminate pressure pulsations in the fuel lines occurring as a result of the opening and closing of the fuel injectors.  
         [0018]     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.