Abstract:
A compressed natural gas fuel injector including a housing, an inlet, an outlet, a seat, a closure member, and an attached nozzle. In a preferred embodiment, the inlet and outlet communicate a flow of gaseous fuel regulated by the closure member. The gaseous fuel passes through the seat, which is coupled to a rim surface of a retainer portion of the attached nozzle, and into a flow passage that further communicates the flow of gaseous fuel into one or more flow channels. The orientation of the flow channels within the attached nozzle greatly affects the discharge pattern and mixing characteristics of the gaseous fuel within an intake manifold. A method of flowing gaseous fuel through the fuel injector is also described.

Description:
BACKGROUND OF INVENTION  
       [0001]    In the case of internal combustion engines having injection systems, fuel injectors are conventionally used to provide a precise amount of fuel needed for combustion. Compressed natural gas (hereinafter sometimes referred to as “CNG”) is a common automotive fuel for commercial fleet vehicles and residential customers. In vehicles, the CNG is delivered to the engine in precise amounts through fuel injectors, hereinafter referred to as “CNG injectors”, or simply “fuel injectors”. CNG injectors of this type are described in commonly assigned U.S. Pat. No. 5,494,224, the disclosure of which is incorporated by reference herein. Typically, the CNG injector is required to deliver the precise amount of fuel per injection pulse and maintain this accuracy over the life of the injector. In order to improve the combustion of fuel, certain strategies are required in the design of CNG injectors. These strategies are keyed to the delivery of gaseous fuel into the intake manifold of the internal combustion engine in precise amounts and flow patterns. 
         [0002]    It is believed that some conventional CNG injector designs have failed to achieve suitable the combustion of gaseous fuel injected into the intake manifold of an internal combustion engine. Specifically, such design of CNG injectors may reduce air flow or even cause back-flow of the air-fuel mixture into the internal combustion engine&#39;s intake plenum or into other engine cylinders thereby causing engine misfire and other drivability problems. 
       SUMMARY OF THE INVENTION  
       [0003]    The present invention provides improved gaseous fuel targeting and fuel distribution with an attached nozzle design for a CNG injector. Back-flow of the air-fuel mixture into the internal combustion engine&#39;s intake plenum or into other engine cylinders may be avoided by providing a discharge pattern that forms a cloud of CNG. The discharge pattern of CNG delivered to the intake manifold of the present invention is believed to improve the air-fuel mixture and drivability problems that are believed to be in the prior art. 
         [0004]    In one aspect of the present invention, the CNG injector is provided with a housing, an inlet, an outlet, a seat, a closure member, and an attached nozzle. The inlet and outlet communicate with a flow of gaseous fuel that is regulated by the closure member disposed in at least two positions along the longitudinal axis. The seat is disposed proximate to the outlet and includes a sealing surface contiguous to a portion of the closure member in one of the two positions of the closure member and a seat orifice extending through the seat from the sealing surface along the longitudinal axis to a tapered surface that extends obliquely from the seat orifice about the longitudinal axis. Below the seat orifice, the seat is coupled to a rim surface of a retainer portion to define the beginning of a flow passage within the attached nozzle. 
         [0005]    In a preferred aspect of the present invention, the attached nozzle includes both the retainer portion and a flow modifier portion. The retainer portion engages an outer surface of the CNG injector proximate to its outlet by employing e.g., a press-fit, snap-fit, welded, or screw-on connection. The flow modifier portion affects the flow distribution pattern of gaseous fuel through the attached nozzle. The flow modifier portion includes the flow passage and flow channel(s) of the attached nozzle. The flow channel(s) may extend along numerous axes to disperse the gaseous fuel in a particular pattern within the intake manifold. 
         [0006]    In another aspect of the present invention, the flow channel may be disposed about an oblique axis to the longitudinal axis, and gaseous flow discharged through a singular oblique flow channel. 
         [0007]    In yet another aspect of the present invention, a method of flowing gaseous fuel through the seat orifice, along the flow passage, and through the flow channel(s) of the attached nozzle is described. The resulting discharge pattern of the gaseous fuel improves the mixing characteristics of the gaseous fuel within the intake manifold. The method can be achieved by: flowing gaseous fuel through the seat orifice along the longitudinal axis; and dispersing the gaseous fuel into separate columns disposed either obliquely to the longitudinal axis or generally perpendicular to the longitudinal axis. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0008]    The accompanying drawings, which are incorporated herein and constitute part of this specification, illustrate presently preferred embodiments of the invention, and, together with the general description given above and the detailed description given below, serve to explain features of the invention. 
           [0009]      FIG. 1  illustrates a cross-sectional view of the preferred embodiment of the CNG injector and attached nozzle. 
           [0010]      FIG. 2  illustrates a close-up perspective view of the CNG injector and attached nozzle with spray distribution pattern from four flow channels. 
           [0011]      FIG. 3  illustrates a close-up cross-sectional view of the preferred embodiment of an attached nozzle that, in particular, shows the various relationships between various surfaces in the attached nozzle. 
           [0012]      FIG. 4  illustrates a cross-sectional view of the CNG injector and another attached nozzle with the four flow channels. 
           [0013]      FIG. 5  illustrates a cross-sectional view of another preferred embodiment of the CNG injector and attached nozzle wherein a flow channel is oblique to the longitudinal axis. 
           [0014]      FIG. 6  illustrates a cross-sectional view of another preferred embodiment of an attached nozzle wherein a retainer portion of the attached nozzle does not include a third retainer surface. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0015]      FIG. 1  illustrates a fuel injector, in particular a high-pressure CNG injector  10 . The CNG injector  10  has a housing, which includes a fuel inlet  12 , a fuel outlet  14 , and a fuel passageway  16  extending from the inlet  12  to the outlet  14  along a longitudinal axis  18 . The housing includes an overmolded plastic member  20  cincturing a coil housing  22 . 
         [0016]    A fuel filter  24  with an inlet passage  26  is disposed within the overmolded plastic member  20 . The inlet passage  26  serves as part of the fuel passageway  16  of the CNG injector  10 . A fuel filter retainer member  28  and an adjustable tube  30  is provided in the inlet passage  26 . The preload adjustment tube  30  is positionable along the longitudinal axis  18  before being secured in place, thereby varying the length of an armature bias spring  32 . In combination with other factors, the length of the spring  32 , and hence the bias force against the armature, control the quantity of gaseous fuel flow through the CNG injector  10 . The overmolded plastic member  20  also supports an electrical connector  20   a  that receives a plug (not shown) to operatively connect the CNG injector  10  to an external source of electrical potential, such as an electronic control unit ECU (not shown). An elastomeric O-ring  34  is provided in a groove on an exterior extension of the filter  24  or outlet  14 . The O-ring  34  sealingly secures the filter  24  to a gaseous fuel supply member (not shown), such as a fuel rail and the outlet  14  to an intake manifold. 
         [0017]    The coil housing  22  encloses a coil assembly  40  as shown in  FIG. 1 . The coil assembly  40  includes a bobbin  42  that retains a coil  44 . The ends of the coil assembly  40  are electrically connected to the connector  20   a  of the overmolded plastic member  20 . An armature  46  is supported for relative movement along the axis  18  with respect to the filter  24 . The armature  46  is supported by a body shell  50 , and a body  52 . The armature  46  has an armature passage  54  in fluid communication with the inlet passage  26 . 
         [0018]    The body shell  50  engages the body  52 . An armature guide eyelet  56  is located on an inlet portion  60  of the body  52 . An axially extending body passage  58  connects the inlet portion  60  of the body  52  with an outlet portion  62  of the body  52 . The armature passage  54  of the armature  46  is in fluid communication with the body passage  58  of the body  52 . A seat  64 , which is preferably a metallic material, is mounted at the outlet portion  62  of the body  52 . 
         [0019]    As shown in  FIG. 1 , the body  52  includes a neck portion  66  that extends between the inlet portion  60  and the outlet portion  62 . The neck portion  66  can be an annulus that surrounds a closure member  68 . The closure member  68  is operatively connected to the armature  46 , and can be a substantially cylindrical needle. The cylindrical closure member  68  is centrally located within and spaced from the neck portion so as to define a part of the body passage  58 . The cylindrical closure member  68  is axially aligned with the longitudinal axis  18  of the CNG injector  10  also includes an inward conical taper  68   a  on the bottom surface of the closure member  68 . Significant features of the closure member herein are also disclosed in U.S. Pat. No. 6,328,231 entitled “Compressed Closure member Gas Injector Having Low Noise Valve Closure member,” the disclosure of which is incorporated herein by reference. Features of the CNG injector  10  are also disclosed in commonly assigned, commonly filed (Application Serial No.  09 / 320 , 178 ) application entitled “Contaminant Tolerant Compressed Natural Gas Injector and Method of Directing Gaseous Fuel Therethrough,” the disclosure of which is incorporated herein by reference. 
         [0020]    Operative performance of the CNG injector  10  is achieved by magnetically coupling the armature  46  to the end of the filter  26  that is closest to the inlet portion  60  of the body  52 . Thus, the lower portion of the filter  26  that is proximate to the armature  46  serves as part of the magnetic circuit formed with the armature  46  and coil assembly  40 . The armature  46  is guided by the armature guide eyelet  56  and is responsive to an electromagnetic force generated by the coil assembly  40  for axially reciprocating the armature  46  along the longitudinal axis  18  of the CNG injector  10 . The electromagnetic force is generated by current flow from the ECU (not shown) through the coil assembly  40 . Movement of the armature  46  also moves the operatively attached closure member  68 . The closure member  68  opens and closes the seat orifice  76  of the seat  64  to permit or inhibit, respectively, gaseous fuel from exiting the outlet of the CNG injector  10 . In order to open the seat orifice  76 , the seal between the tip of closure member  68  and the seat  64  is broken by upward movement of the closure member  68 . The closure member  68  moves upwards when the magnetic force is substantially higher than necessary to lift the armature closure member assembly against the force of spring  32 . In order to close the seat orifice  76  of the seat  64 , the magnetic coil assembly  40  is de-energized. This allows the tip of closure member  68  to re-engage surface  80  of seat  64  and close passage  76 . During operation, gaseous fuel flows in fluid communication from the fuel inlet source (not shown) through the fuel inlet passage  26  of the filter  24 , the armature passage  54  of the armature  46 , the body passage  58  of the body  52 , and the seat orifice  76  of the seat  64  and is injected from the CNG injector  10 . 
         [0021]    As shown in  FIGS. 1 and 3 , an attached nozzle  100  is located proximate to the seat of the CNG injector  10  and, includes a retainer portion  110  and a flow modifier portion  120  as shown in  FIG. 3 . The attached nozzle may be made from a suitable material for gaseous fuel. Preferably, the attached nozzle may be made from a metallic material, most preferably stainless steel. 
         [0022]    The retainer portion  110  of the attached nozzle engages an outer surface  67  of the outlet  14  (shown in  FIG. 1 ) about the longitudinal axis  18  of the CNG injector  10 . A first retainer surface  112  of the retainer portion  110  couples with the outer surface  67  through e.g., a press-fit, snap-fit, welded, or screw-on connection. The first retainer surface  112  forms a cylindrical surface to surround the outer surface  67 . Substantially perpendicular to the first retainer surface is a rim surface  111  that can engage a bottom surface of the seat  64  as shown in  FIGS. 1 and 3 . Preferably, the first retainer surface  112  has an inner diameter of about 8 millimeters and a length along the longitudinal axis  18  of about 2 millimeters. Preferably, the rim surface  111  has an outer diameter of about 9 millimeters. 
         [0023]    A second retainer surface  113  and a third retainer surface  114  of the retainer portion  110  connect the first retainer surface  112  to the flow modifier portion  120  of the nozzle  100  as shown in  FIG. 3 . The second retainer surface  113  may be at an oblique angle to the longitudinal axis  18  while the third retainer surface  114  is planar and orthogonal to the longitudinal axis  18 , therein creating an annular pocket  115  about the longitudinal axis  18  as shown in  FIGS. 1 and 3 . The annular pocket  115  may enclose a flange portion  69  of the outlet  14  to secure the attached nozzle  100  to the outlet  14 . 
         [0024]    The flow modifier portion  120  affects the flow distribution pattern of gaseous fuel through the attached nozzle  100 , as shown in  FIG. 2 , by the dashed outline of a gaseous fuel cloud. The flow modifier portion  120  defines a flow passage  121  that is in fluid communication with the seat orifice  76  and extends along a first flow modifier surface  122  disposed about the longitudinal axis  18 . The first flow modifier surface  122  may have a tapered surface  123  about the longitudinal axis  18  creating a truncated conical surface contiguous to the flow passage  121 . The flow passage  121  extends to a first flow channel  124  located within the attached nozzle  100  as shown in  FIG. 3 . 
         [0025]    The first flow channel  124  is encompassed by a second modifier surface  125  and extends along a first axis  126   a  that is generally orthogonal to the longitudinal axis  18 . The first flow channel  124  directs gaseous fuel to a first discharge outlet  127  of the attached nozzle  100  as shown in  FIG. 4 . Preferably the first flow channel  124  is generally circular in cross-section and has an inside diameter of about 2 millimeters. 
         [0026]    In one preferred embodiment, a second flow channel ( 130  in  FIG. 4 ) may extend along the first axis  126   a,  but in a direction diametrically opposed to the first channel  124 . In another preferred embodiment of the present invention, a third flow channel  128  and a fourth flow channel  129  may be extended along a second axis  126   b  that is generally orthogonal to both the first axis  126   a  and the longitudinal axis  18  of the attached nozzle  100  as shown in  FIG. 3 . The third and fourth flow channels are diametrically opposed to each other and may be generally circular in cross-section as shown in  FIGS. 3 and 4 . 
         [0027]    Gaseous fuel flows through the seat orifice  76 , along the flow passage  121 , and may be dispersed through one, two, three, four, or other multiple flow channel configurations of the attached nozzle  100 . Thus, the resulting multiple columns of gaseous fuel are dispersed generally perpendicular to the longitudinal axis  18  of the CNG injector  10  to improve the mixing characteristics within the intake manifold (not shown). The above-mentioned singular oblique flow channel  141  delivers a single column of gaseous fuel to the intake manifold at the first angle θ with respect to the longitudinal axis  18  to that in conjunction with an intake manifold geometry, the fuel injector is able to improve its mixing characteristics with air flow in the manifold. The preferred pressure at which the CNG injector  10  operates is approximately 200 pounds per square inch gauge pressure and a pressure drop of no more than 5 pounds per square inch gauge is expected across the nozzle. 
         [0028]    As shown in  FIG. 5 , the second flow modifier surface  125  of nozzle  100  may be disposed about an oblique axis  140  to the longitudinal axis  18  and gaseous flow discharged through a singular oblique flow channel  141  as shown in  FIG. 5 . The oblique flow channel angled at a first angle θ oblique to the longitudinal axis  18  may vary in range from 10° to 30°. However, the preferred first angle θ is approximately 26°. 
         [0029]    In yet another preferred embodiment of a nozzle as shown here in  FIG. 6  as nozzle  100 , the retainer portion  110  may omit the third retainer surface  114 . Thus, the oblique second retainer surface  113  may taper contiguous to the flow passage  121  of the flow modifier portion  120 . The flow passage  121  may be cylindrical in shape and substantially wider than the flow channels located orthogonally below it. The bottom of the flow passage  121  may terminate in a conical portion  150  located slightly below the bottom surface of the flow channels as shown in  FIG. 6 . 
         [0030]    While the present invention has been disclosed with reference to certain preferred embodiments, numerous modifications, alterations, and changes to the described embodiments are possible without departing from the sphere and scope of the present invention, as defined in the appended claims. Accordingly, it is intended that the present invention not be limited to the described embodiments, but that it have the full scope defined by the language of the following claims, and equivalents thereof.