Patent Publication Number: US-6334576-B1

Title: Fuel injector having a ball seat with multiple tip geometry

Description:
FIELD OF INVENTION 
     This invention relates to fuel injectors in general, and more particularly to a fuel injector assembly which includes a modified needle tip having a ball seat with multiple tip geometry for fuel mixing for maximizing fuel combustion. 
     BACKGROUND OF THE INVENTION 
     In the case of internal combustion engines having fuel injection systems, fuel injectors are conventionally used to provide a precise amount of fuel needed for combustion. The fuel 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 optimize the combustion of fuel, certain strategies are required in the design of fuel injectors. These strategies are keyed to the delivery of fuel into the intake manifold of the internal combustion engine in precise amounts and flow patterns. Conventional fuel injector designs have failed to optimize the combustion of fuel injected into the intake manifold of an internal combustion engine. 
     SUMMARY OF THE INVENTION 
     The present invention overcomes the disadvantages of conventional fuel injectors and provides a fuel injector which incorporates a needle with a novel ball seat design and multiple tip geometries, which can provide various flow patterns and improved spray atomization for fuel for improved combustion. 
     The present invention provides a fuel injector having a fuel inlet, a fuel outlet, and a fuel passageway extending from the fuel inlet to the fuel outlet along a longitudinal axis. The fuel injector includes a body, a cylindrical needle slidingly disposed within the body, the needle having a support portion and a flow control portion, and a seat disposed at the fuel outlet. The fuel injector also includes a ball operatively connected to the support portion of the needle such that the flow control portion protrudes from the ball toward the seat. 
     The present invention also provides a method of controlling a fuel spray pattern in a fuel injector, the fuel injector having a body, a cylindrical needle slidingly disposed within the body, the needle having a support portion and a flow control portion, and a seat disposed at the fuel outlet. The method includes the steps of providing a ball operatively connected to the support portion of the needle such that the flow control portion protrudes from the ball toward the seat and providing fuel to the fuel injector. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     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. 
     FIG. 1 is a cross-sectional view of a fuel injector of the present invention taken along its longitudinal axis; 
     FIG. 2 is a plan view of the ball seat of the present invention of FIG. 1; 
     FIG. 3A is a plan view of a needle tip with a concave tip geometry; and 
     FIG. 3B is a plan view of a needle tip with a linear tip geometry. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 illustrates a fuel injector assembly  10 , such as a fuel injector assembly  10 . The fuel injector assembly  10  has a housing, which includes a fuel inlet  12 , a fuel outlet  14 , and a fuel passageway  16  extending from the fuel inlet  12  to the fuel outlet  14  along a longitudinal axis  18 . The housing includes an overmolded plastic member  20  cincturing a metallic support member  22 . 
     A fuel inlet member  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 fuel injector assembly  10 . A fuel filter  28  and an adjustable tube  30  is provided in the inlet passage  26 . The adjustable 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 fuel flow through the fuel injector assembly  10 . The overmolded plastic member  20  also supports a socket  20   a  that receives a plug (not shown) to operatively connect the fuel injector assembly  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 inlet member  24 . The O-ring  34  is biased by a flat spring  38  to sealingly secure the inlet member  24  to a fuel supply member (not shown), such as a fuel rail. 
     The metallic support member  22  encloses a coil assembly  40 . 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 socket  20   a  of the overmolded plastic member  20 . An armature  46  is supported for relative movement along the axis  18  with respect to the inlet member  24 . The armature  46  is supported by a spacer  48 , a body shell  50 , and a body  52 . The armature  46  has an armature passage  54  in fluid communication with the inlet passage  26 . 
     The spacer  48  engages the body shell  50 , which 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 . 
     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 needle  68 . The needle  68  is operatively connected to the armature  46 , and can be a substantially cylindrical needle  68 . The cylindrical needle  68  is centrally located within and spaced from the neck portion so as to define a part of the body passage  58 . The cylindrical needle  68  is axially aligned with the longitudinal axis  18  of the fuel injector assembly  10 . A ball  81  is operatively connected to the cylindrical needle  68  proximate the fuel injector outlet  14  at needle support portion  90 . A needle control portion (tip)  79  protrudes out of a through passage  81 ′ (hidden) in the ball  81 . 
     Operative performance of the fuel injector assembly  10  is achieved by magnetically coupling the armature  46  to the end of the inlet member  26  that is closest to the inlet portion  60  of the body  52 . Thus, the lower portion of the inlet member  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 fuel injector assembly  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 needle  68 . As shown in FIGS. 1-3B, ball  81  is operatively connected to needle  68  and engages the seat  64 . Ball  81  opens and closes the seat passage  76  of the seat  64  of the present invention to permit or inhibit, respectively, fuel from exiting the outlet of the fuel injector assembly  10 . In order to open seat passage  76 , the seal between the ball  81  and the seat  64  is broken by upward movement of the needle  68 . The needle  68  moves upwards when the magnetic force is substantially higher then it needs to be to lift the armature needle assembly against the force of spring  32 . In order to close the seat passage  76  of the seat  64 , the magnetic coil assembly  40  is de-energized. This allows ball  81  to re-engage surface  80  of seat  64  and close passage  76 . The surface  78  of ball  81  is preferably a spherical surface. During operation, fuel flows in fluid communication from the fuel inlet source (not shown) through the fuel inlet passage  26  of the inlet member  24 , the armature passage  54  of the armature  46 , the body passage  58  of the body  52 , and the seat passage  76  of the seat  64  and is injected from the outlet  14  of the fuel injector assembly  10 . 
     The ball  81  and the needle flow control portion  79  will now be described in detail. As shown in FIGS. 3A and 3B, the ball  81  is attached to the needle  68  by means of welding, press fitting, or by any other means well known in the art. Because mating between the surface  78  of ball  81  and the surface  80  of seat  64  is the only means of preventing fuel from ejecting through the passage  76  of seat  64 , a highly accurate surface finish for the ball surface  78  is required. The needle flow control portion  79  however only affects the spray pattern and the particle sizes emitted from the passage  76  of seat  64 . Thus a highly accurate surface finish for needle flow control portion  79  is not required. The present invention therefore provides a ball  81  which has a highly accurate machined surface  78  that mates with the highly accurate surface  80  of seat  64 . Before or after welding or press fitting of ball  81  onto needle  68 , the exposed needle flow control portion  79  can be machined as necessary. FIG. 3A shows a machined needle flow control portion  79  that has concave sides  79 ′. Similarly, FIG. 3B shows a machined needle flow control portion  79  that has linear sides  79 ″. It can be appreciated that as the fuel passes through body passage  58  towards seat passage  76 , the concave sides  79 ′ of needle flow control portion  79  will disperse the fuel in a wider pattern than that for the linear sides  79 ″ of needle flow control portion  79 . Similarly, one of ordinary skill in the art could envision a variety of other flow control portion configurations (i.e. convex, notched, sloped and varying cross-sections relative to the needle longitudinal axis) that would yet further improve or alter spray atomization and the spray pattern, and reduce the sac volume in the area between the ball and seat sealing surfaces and the seat passage  76 , for fuel injectors and other such devices. 
     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 fall scope defined by the language of the following claims, and equivalents thereof.