Abstract:
This invention relates to a the tip structure of a fuel injector as used in a internal combustion engine. Internal combustion engines using Homogeneous Charge Compression Ignition (HCCI) technology require a tip structure that directs fuel spray in a downward direction. This requirement necessitates a tip design that is capable of withstanding mechanical stresses associated with the design.

Description:
[0001] This invention was made with Government support under DOE Contract No. DE-FC05-970R22605 awarded by the U.S. Department of Energy. The Government has certain rights to this invention. 
     
    
     
       TECHNICAL FIELD  
         [0002]    This invention relates generally to an nozzle and more specifically to a nozzle tip for a fuel injector used with the internal combustion engine.  
         BACKGROUND  
         [0003]    Manufacturers of internal combustion engines are continuously attempting to improve on the efficiency and emissions output of internal combustion engines. In diesel engines, a large amount of research has been done to reduce NOx output of an engine, through the use of improved fuel injectors and injection timing. Typically, combustion takes place over approximately 40 to 50 degrees of crankshaft rotation. A nozzle tip for a fuel injector in a typical modern diesel engine includes an end portion, the end portion includes a plurality of nozzle openings. High pressure fuel is forced into the end portion and sprayed into the combustion chamber as the piston nears top dead center. The nozzle openings are oriented to spray fuel at an angle of 60 to 80 degrees from a longitudinal axis of the injector.  
           [0004]    Research has revealed that NOx emissions can be greatly reduced at partial load through a Homogeneous Charge Compression Ignition (HCCI). This is accomplished by injecting fuel into the cylinder at a much earlier stage in the combustion cycle. In this case, earlier, refers to the piston being farther from the cylinder head during the compression stroke of the engine, as the piston moves toward the cylinder head. The early injection permits fuel and air to more thoroughly mix, because in part there is a larger area between the top of the piston and the cylinder head. Having fuel and air more thoroughly mixed creates more complete combustion.  
           [0005]    Using a conventional injector tip configuration to achieve Homogeneous Charge Compression Ignition operation of an internal combustion engine results in fuel being sprayed in an undesirable pattern causing inadequate mixing. For example fuel may cling to the cylinder walls and other surfaces and not properly mix with air. This is because of the direction of the nozzle openings is toward the cylinder walls and the piston is so far from the fuel injector. By changing the angle of the nozzles in relation to the longitudinal axis, fuel can be directed toward the top surface of the piston. Changing the angle of the nozzle openings creates a new problem, fatigue life of the nozzle cavity at the entrance of the nozzle opening may be reduced using conventional tip geometry.  
           [0006]    The present invention is directed to overcoming one or more of the above identified problems.  
         SUMMARY OF THE INVENTION  
         [0007]    In a one aspect of the present invention, a nozzle tip for a fuel injector is provided. The fuel injector includes a longitudinal axis. The nozzle tip includes the end portion having a inner surface and a outer surface. A plurality of nozzle openings are disposed through said end portion and have a central axis. Each of the nozzle openings at an angle between the central axis and longitudinal axis of between 5 and 10 degrees. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    [0008]FIG. 1 is a partial sectional illustration of an engine having a fuel injector embodying one aspect of the present invention.  
         [0009]    [0009]FIG. 2 is an enlarged partial section illustration of the nozzle assembly of FIG. 1.  
         [0010]    [0010]FIG. 3 is an enlarged partial sectional illustration of the nozzle tip of FIG. 2.  
         [0011]    [0011]FIG. 4 is an enlarged partial sectional illustration of a nozzle tip embodying another aspect of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0012]    Referring to FIG. 1 an engine  10  includes a block  12  having a plurality of cylinders  14  therein, of which only one is shown, and a cylinder head  16  includes and exhaust passage  18  and an intake passage  22 . An intake valve  24  is interposed the intake passage  22  and the cylinder  14 . An exhaust valve  26  is interposed the exhaust passage  18  and the cylinder  14 . A fuel injector  28  having a body  30 , a nozzle assembly  32 , and a end portion  33  is additionally positioned within the cylinder head  16 . The fuel injector  28  is substantially of conventional construction, such as the type use with a hydraulically actuated electronically controlled unit injector system  
         [0013]    The fuel injector  28  includes a body  30  having a longitudinal axis  34 , an upper end  36  and a lower end  38 . An electronically actuated solenoid  42  is removably attached to the upper end  36 . A nozzle assembly  44  is removably attached to the lower end  38 .  
         [0014]    Referring now to FIG. 2, the nozzle assembly  32  includes an attachment portion  33  and a nozzle tip  60 . The attachment portion  33  is a substantially cylindrical member having an inner wall  48 , an outer wall  50 , a first end  52  and a second end  56 . The first end  52  is generally opened and adapted to engage the lower end  38  of the injector body  30 . The second end  56  is partially closed and defines an opening  58  that is adapted to receive a nozzle tip  60  in a conventional manner.  
         [0015]    The nozzle tip  60  is a substantially cylindrical member having a first end  62 , a second end  64 , an outer surface  66  and an inner bore  68 . The inner bore  68  extends from the first end  62  toward the second end  64 . A seat  69  is defined within the inner bore  68 , preferably near the second end  64 . The inner bore  68  is adapted to receive a needle valve  70 . The needle valve  70  is moveable between a first and second position. The needle valve  70  includes a needle seat  71  that is adapted to engage the seat when in the first position. The outer surface  66  defines a shoulder portion  72  toward the first end  62  and a shank portion  74  interposed the shoulder portion  72  and the second end  64 . The second end  64  of the nozzle tip  60  includes the end portion  76  having an inner surface  78  and an outer surface  80 . A plurality of nozzle openings  86  extend through the end portion  76  and open at the inner surface  78  and the outer surface  80 . The nozzle openings  34  may be disposed about the longitudinal axis  34 .  
         [0016]    Referring to FIG. 3, an embodiment of a end portion  76  of the present invention is shown. The inner surface  78  and outer surface  80  form a cylindrical portion  91  that is defined about the longitudinal axis  34  of the fuel injector  28 . The cylindrical portion  91  includes the end portion  76  and joins the inner bore  68  of the nozzle tip  60  opposite the end portion  76 . The end portion  76  forms a substantially large radius on the inner surface  78  and the outer surface  80 . The inner surface  78  and the outer surface  80  are spaced a predetermined distance from one and other. The nozzle openings  86  may be disposed evenly about longitudinal axis  34 . Each nozzle opening  86  includes a central axis  98  and a inside wall  100 . An intersection  99  is formed by the longitudinal axis  34  and the central axis  98  of each nozzle opening  90 . An angle α is defined between the longitudinal axis  34  and the central axis  98 . The angle α is preferably between 5 and 10 degrees. The nozzle openings  86  and each of the inner surface  78  and the outer surface  80  are substantially perpendicular to one and other. A radius  102  may additionally be formed at the intersection of the nozzle opening  86  and the inner surface  78 .  
         [0017]    Referring to FIG. 4, another embodiment of a end portion  76 ′ is shown. The end portion  33 ′ joins the inner bore  68  of the nozzle tip  60  opposite the end portion  76 ′. The end portion  76 ′ forms a large radius on the outer surface  80 ′. A conical portion  106  is defined about the longitudinal axis  34  on the inner surface  78 ′. The nozzle openings  86  are disposed about longitudinal axis  34 . Each nozzle opening  86  includes a central axis  98  and a inside wall  100 . The central axis  98  of each nozzle opening  86  is substantially perpendicular to the conical portion  106 . An intersection  99 ′ is formed by the longitudinal axis  34  and the central axis  98  of each nozzle opening  86 . An angle α′ is defined between the longitudinal axis  34  and the central axis  98 . The angle α′ is preferably between 5 and 10 degrees. An angle β is defined between the longitudinal axis  34  and the conical portion  106 . Angle β is preferably between 100 and 110 degrees. A radius  102  may additionally be provided at the intersection of the inside wall  100  and the inner surface  86 ′.  
       INDUSTRIAL APPLICABILITY  
       [0018]    In operation, a fuel injector  28  facilitates HCCI combustion by directing early injection of fuel into the cylinders  14  at a desired angle and pattern. The fuel is sprayed in a substantially downward direction, toward the piston, as the piston is moving toward the cylinder head  16 . The early injection allows a more thorough mixing of fuel and air because of a larger mixing area and more time before combustion. The more thoroughly mixed fuel and air mixture facilitates combustion at multiple sites in the cylinder  14  simultaneously resulting in more complete combustion and a reduction in NOx production.  
         [0019]    The geometric design of the end portion  92  of and the orientation of the nozzles  90  directs a fuel spray in a substantially downward direction and appropriate pattern, preventing the fuel from clinging to the cylinder walls and promoting mixing of air and fuel. Additionally, the orientation of the nozzles  90  reduces the concentration of stresses in the end portion  76 ′, increasing the fatigue life of the nozzle tip  60 .