Patent Publication Number: US-2004056120-A1

Title: Fuel injector temperature stabilizing arrangement and method

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
     [0001] This application is a continuation-in-part of U.S. application Ser. No. 09/259,168, filed Jun. 29, 1999; which is a continued prosecution application (CPA) of U.S. application Ser. No. 09/259,168, filed Feb. 26, 1999, now abandoned; which is a continuation application of U.S. application Ser. No. 08/795,672, now U.S. Pat. No. 5,875,972; which is a CPA of U.S. Ser. No. 08/795,672, filed Feb. 6, 1997. This application claims the right of priority to each of the prior applications. Furthermore, each of the prior applications is hereby in their entirety incorporated by reference. 
    
    
     
       BACKGROUND OF INVENTION  
       [0002] This invention relates to fuel injectors in general and particularly high-pressure direct injection fuel injectors. More particularly to high-pressure direct injection fuel injectors having a body with a seat disposed exposed to the extreme temperatures within the engine cylinder. Experimental testing has shown that these extreme temperatures can effect the operative performance characteristics of the fuel injector. First, the excessive temperatures of the engine cylinder can disproportionately distort the components of the fuel injector within the engine cylinder. For example, the body, which is preferably metal, can be distorted in an unequal quantity from a needle disposed within the body. Distorting of the components of the fuel injector disportionality can, for example, alter the dimensional tolerances between the components of the fuel injector, i.e., the body, the needle, and the seat, which is believed, under certain operative conditions, to render the fuel injector inoperative. Second, the excess temperatures of the engine cylinder can cause the fuel injector to overheat and coke unburned fuel on the components of the fuel injector, i.e., the tip components of the fuel injector, such as, the seat at an outlet portion of the body. Coking of the fuel injector tip components can block the outlet of the fuel injector, which is believed to affect the fuel spray patterns of the fuel injector. Thus, distorting and coking of the fuel injector components utilized in a direct inject application is believed to diminish the performance capability of the fuel injector. Thus, an arrangement of the fuel injector components is needed which minimizes the effects of the temperature within the engine cylinders on the operative performance of the fuel injection.  
       SUMMARY OF THE INVENTION  
       [0003] 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, an armature, a needle, a swirl generator, and a valve seat. The body has an inlet portion, an outlet portion, and a body passage extending from the inlet portion to the outlet portion along the longitudinal axis. The armature is located proximate the inlet portion of the body. The armature is operatively connected to a needle. The swirl generator is located proximate the needle and the seat. The needle engages the seat, which is disposed at the outlet portion of the body.  
       [0004] The body includes a neck portion. The neck portion is, preferably, a cylindrical annulus that surrounds the needle. The needle is, preferably, a substantially cylindrical needle. The cylindrical needle is centrally located within the cylindrical annulus. The cylindrical annulus has an inner diameter that is no more than 50% greater than a diameter of the cylindrical needle, and an outer diameter that is no less than 100% greater than the inner diameter.  
       [0005] The seat, preferably, includes a first surface exposed to the body passage and a second surface exposed to an exterior of the fuel injector. The first surface is spaced from the second surface a defined distance along the longitudinal axis. In an alternative embodiment of the seat, the first surface has at least one cut-out configuration that extends from the first surface for a fraction of the defined distance into an interior of the seat. The at least one cut-out, preferable, is at least one volume that defines at least one wall in the interior of the seat.  
       [0006] In a first preferred embodiment of the alternative seat, the at least one volume is a plurality of volumes arranged in the first surface to correspond to a plurality of fuel passage openings in the swirl generator. Each of the plurality of volumes is, preferably, a cylindrical volume having a first diameter, and each of the plurality of fuel passage openings is, preferably, a circular aperture having a second diameter. The first diameter of the cylinder is substantially equal to the second diameter of the circular aperture. The at least one wall defined by each of the cylindrical volumes has a cylinder side wall and a cylinder end wall. The cylinder side wall and the cylinder end wall are located in an interior of the seat.  
       [0007] In a second preferred embodiment of the alternative seat, the at least one volume is a channel arranged in the first surface, which corresponds to the plurality of fuel passage openings. The channel has a width on the first surface that is substantially equal to the diameter of one of the fuel passage openings. Preferably, each of the fuel passage openings has the same diameter. The channel is, preferably, a continuous channel that defines an inner side wall, an outer side wall, and a channel end wall, which engages both the inner side wall and the outer side wall.  
       [0008] The present invention also provides a method of stabilizing temperature of a fuel injector in a direct injection application. The fuel injector has a body; an armature proximate an inlet portion of the body; a needle operatively connected to the armature; a seat disposed at the outlet portion of the body; and a swirl generator proximate the seat. The method is accomplished by providing the needle with a substantially uniform cross-sectional area, and selecting the body to surround the needle and form a body passage that has an average cross-sectional area less than 2.25 times the substantially uniform cross-sectional area of the needle. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0009] 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.  
     [0010]FIG. 1 is a cross-sectional view of a fuel injector of the present invention taken along its longitudinal axis;  
     [0011]FIG. 2A is an enlarged cross-section; view of the body of the fuel injector shown in FIG. 1, which illustrates a first alternative embodiment of the seat of the present invention;  
     [0012]FIG. 2B is an enlarged cross-sectional view of the body of the fuel injector shown in FIG. 1, which illustrates a second alternative embodiment of the seat of the present invention;  
     [0013]FIG. 3A is a plan view of the seat illustrated in FIG. 2A; and  
     [0014]FIG. 3B is a plan view of the seat illustrated in FIG. 2B. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)  
     [0015]FIG. 1 illustrates a preferred embodiment of the fuel injector  10 , in particular a high-pressure, direct-injection fuel injector  10 . The fuel injector  10  has a housing, which includes a fuel inlet, a fuel outlet  14 , and a fuel passageway  16  extending from the fuel inlet to the fuel outlet  14  along a longitudinal axis  18 . The housing includes an overmolded plastic member  20  cincturing a metallic support member  22 .  
     [0016] 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  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 to vary the length of an armature bias spring  32 , which controls the quantity of fluid flow from the fuel outlet  14  of the injector  10 . The overmolded plastic member  20  also supports a socket that receives a plug (not shown) to operatively connect the fuel 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 inlet member. The o-ring  34  is supported by a backing ring  38  to sealingly secure the inlet source with a fuel supply member, such as a fuel rail (not shown).  
     [0017] 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 operatively connected to the socket through the overmolded plastic member  20 . An armature  46  is axially aligned with the inlet member by a spacer  48 , a body shell  50 , and a body  52 . The armature  46  has an armature passage  54  aligned along the longitudinal axis  18  with the inlet passage  26  of the inlet member.  
     [0018] The spacer  48  engages the body  52 , which is partially disposed within the body shell  50 . An armature guide eyelet  56  is located on an inlet portion of the body  60 . An axially extending body passage  58  connects the inlet portion of the body  60  with an outlet portion of the body  62 . The armature passage  54  of the armature  46  is axial aligned with the body passage  58  of the body  52  along the longitudinal axis  18 . A seat  64 , which is preferably a metallic material, is located at the outlet portion of the body  62 .  
     [0019] The body  52  has a neck portion  66 , which is, preferably, a cylindrical annulus that surrounds a needle  68 . The needle  68  is operatively connected to the armature  46 , and is, preferably, a substantially cylindrical needle  68 . The cylindrical needle  68  is centrally located within the cylindrical annulus. The cylindrical needle  68  is axially aligned with the longitudinal axis  18  of the fuel injector  10 . The cylindrical annulus of the neck portion  66  has an inner diameter  70  and an outer diameter  72 . The inner diameter  70  is, preferably, no more than 50% greater than a diameter  74  of the substantially cylindrical needle  68 , and the outer diameter  72  is, preferably, no less than 100% greater than the inner diameter  70 .  
     [0020] The relationship between the diameter  74  of the cylindrical needle  68 , the inner diameter  70  of the cylindrical annulus, and the outer diameter  72  of the cylindrical annulus provides the cylindrical needle  68  and cylindrical annulus, respectively, with a particular solid mass, which in the preferred embodiment is metal. The physical relationship of the cylindrical needle  68  and the cylindrical annulus are selected so that the body passage  58  assists in stabilizing the temperature of the fuel injector  10  components, and allows fuel flow from fuel inlet to fuel outlet  14  of the fuel injector  10 . The metal mass of the cylindrical needle  68  and the cylindrical annulus combined with the fuel in the body passage  58 , in addition to the mass of the seat  64 , which is also preferably metal, create a thermal mass that distributes the heat that the fuel injector  10  is exposed to within the engine cylinder. It is believed that the temperature of the engine cylinder is more uniformly distributed across the components of the fuel injector  10 , i.e., the body  52 , the fuel in the body passage  58 , the needle  68 , and the seat  64 , so that the fuel injector  10  withstands the operative temperatures of the cylinder without distorting the dimensional tolerance between the components of the fuel injector  10 . By maintaining the dimension tolerance of the fuel injector  10  components, performance operability and reliability of the fuel injector  10  under various operating conditions can be achieved.  
     [0021] Operative performance of the fuel injector  10  is advanced by magnetically coupling the armature  46  to the inlet member near the inlet portion of the body  60 . A portion of the inlet member proximate 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  10 . The electromagnetic force is generated by current flow from the ECU through the coil assembly  40 . Movement of the armature  46  also moves the operatively attached needle  68 . The needle  68  engages the seat  64 , which opens and closes the seat passage  76  of the seat  64  to permit or inhibit, respectively, fuel from exiting the outlet of the fuel injector  10 . The needle  68  includes a curved surface  78 , which is preferably a spherical surface, that mates with a conical end  80  of a funnel  82  that serves as the preferred seat passage  76  of the seat  64 . During operation, fuel flows in fluid communication from the fuel inlet source (not shown) through the fuel inlet passage of the inlet member, 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  to be injected from the outlet of the fuel injector  10 .  
     [0022] A swirl generator  84  is located in the body passage  58  proximate the seat  64 . The swirl generator  84  allows the fuel to form a swirl pattern on the seat  64 . In particular, for example, the fuel is swirled on the conical end  80  of the funnel  82  in order to produce a desired spray pattern. The swirl generator, preferably, is constructed from at least one flat disk; however, various configurations of a swirl generator  84  could be employed. The swirl generator, as shown in FIG. 1, includes a pair of flat disks, a guide disk  86  and a swirl disk  88 .  
     [0023] The guide disk  86 , as shown in FIGS. 2A and 2B, has a perimeter  90 , a central aperture  92 , and a plurality of fuel passage openings  94  between the perimeter  90  and the central aperture  92 . The swirl disk  88  has a plurality of slots  100  that corresponds to the plurality of fuel passage openings  94  in the guide disk  86 . Each of the slots  100  extends tangentially from the respective fuel passage opening  94  to the central aperture  92 .  
     [0024] The needle  68  is guided in the central aperture  92  of the guide disk  86 . The plurality of fuel passage openings  94  supply fuel from the body passage  58  to the swirl disk  88 . The swirl disk  88  directs fuel from the fuel passage openings  94  in the guide disk  86  and meters the flow of fuel tangentially toward the seat passage  76  of the seat  64 . The guide disk  86  and swirl disk  88  that form the swirl generator  84  are secured to a first surface  102  of the seat  64 , preferably, by laser welding.  
     [0025] As shown in FIG. 1, the first surface  102  of the seat  64  is directed toward the body passage  58  of the body  52  and a second surface  104  of the seat  64  is exposed to an exterior of the fuel injector  10 . The first surface  102  is spaced from the second surface  104  a defined distance along the longitudinal axis  18  of the fuel injector  10 . As shown in FIGS. 2A and 3A, the first surface  102 , in an alternative embodiment of the seat  64 , has at least one cut-out  106  that extends from the first surface  102  for a fraction of the defined distance into an interior of the seat  108 . Preferably, the at least one cut-out  106  comprises at least one volume  110  that defines at least one wall  122  in the interior of the seat  108 .  
     [0026] The at least volume  110  within the interior of the body  52  allows for fuel to enter the interior of the seat  108 . Because, during operation, the fuel within the fuel injector  10  is typically at a lower temperature than the temperature of the seat  64 , the fuel tends to assist in stabilizing the temperature of the components of the fuel injector  10  within the engine cylinder. In particular, the at least one volume  110  allows for the fuel in the fuel passage of the fuel injector  10  to reduce the operative temperature of the seat  64 . Lower operative temperatures of the seat  64  are believed to reduce coking of fuel on the second surface  104  of the seat  64 .  
     [0027] In a first preferred embodiment, the at least one volume  110  is a plurality of volumes  110 P arranged in the first surface  102  to correspond to the plurality of fuel passage openings  94  of the guide disk  86 . As illustrated in FIG. 2A, each of the plurality of volumes  110 P is, preferably, a cylindrical volume  114  having a first diameter  116 , and each of the plurality of fuel passage openings  99  is, preferably, a circular aperture  118  having a second diameter  120 . The first diameter  116  of the cylindrical volume  114  is substantially equal to the second diameter  120  of the fuel passage opening in order to maximize fuel flow efficiency.  
     [0028] Each of the cylindrical volumes  114  includes a wall  112  that includes a cylinder side wall  122  and a cylinder end wall  124  in the interior of the seat  108 . The cylinder end wall  124  is located between the first surface  102  and the second surface  104  so that fuel in the fuel passageway  16  assists in reducing the operative temperature of the seat  64  during use of the fuel injector  10  in an engine cylinder as compared to a seat  64  without at least one cut-out  106 . Preferably, the cylinder end wall  124  is located between the second surface  104  and a midpoint along the defined distance from the first surface  102  and the second surface  104 .  
     [0029] In a second preferred alternative embodiment, the at least one volume  110  is a channel  126  arranged in the first surface  102  to correspond to the plurality of fuel passage openings  94 . The channel  126  has a width  128  on the first surface  102 , and each of the plurality of fuel passage openings  94  is, preferably, a circular aperture  118  with a diameter  130 . The diameter  130  of one of the fuel passage openings  94  is substantially equal to the width  128  of the channel  126 . The channel  126  is, preferably, a continuous channel  126 , such as the circular channel illustrated in FIG. 3. The continuous channel  126  defines an inner side wall  132 , an outer side wall  134 , and a channel end wall  136 . The channel end wall  136  engages both the inner side wall  132  and the outer side wall  134 .  
     [0030] The inner side wall  132 , the outer side wall  134 , and the channel end wall  136  can have various configurations. For example, as shown in FIGS. 2B and 3B, the preferred embodiment has an inner side wall  132  and an outer side wall  134  are substantially parallel to the longitudinal axis  18  of the fuel injector  10 , and the channel end wall  136  is substantially perpendicular to the inner side wall  132  and the outer side wall  134  . Alternatively, the channel end wall  136  could have a parabolic cross-section that connects to substantially parallel or non-parallel inner and outer side walls  134 .  
     [0031] The channel end wall  136  extends into the interior of the seat  108  so that fuel in the fuel passageway  16  assists in reducing the seat  64  temperature during use of the fuel injector  10  in an engine cylinder. Preferably, the channel end wall  136  is located between the second surface  104  and a midpoint along the defined distance from the first surface  102  and the second surface  104 .  
     [0032] The present invention also provides a method of stabilizing temperature of a fuel injector  10  in a direct injection application. The fuel injector  10  has a body  52 ; an armature  46  proximate an inlet portion of the body  60 ; a needle  68  operatively connected to the armature  46 ; a seat  64  disposed at the outlet of the body  52 ; and a swirl generator  84  proximate the seat  64 . The method is accomplished by providing the needle  68  with a substantially uniform cross-sectional area, and selecting the body  52  to surround the needle  68  and to form a body passage  58  proximate the needle  68  that has an average cross-sectional area less than 2.25 times the substantially uniform cross-sectional area of the needle  68 . The body passage  58  forms part of the fuel passageway  16  of the fuel injector  10 .  
     [0033] In a preferred embodiment of the method, a substantially cylindrical member is provided as the needle  68  and a cylindrical annulus is provided as part of the body  52  to form the body passage  58 . The cylindrical annulus has an inner diameter  70  that is no more than 50% greater than a substantially uniform diameter of the substantially cylindrical needle  74 , and an outer diameter  72  that is no less than 100% greater than the inner diameter  70 . The seat  64  has a first surface  102  exposed to the fuel passageway  16  and a second surface  104  exposed to an exterior of the fuel injector  10 , and at least one cut-out  106  is configured in the first surface  102  to form a wall  112  that extends for a fraction of the defined distance into an interior of seat  108 . As an example according to the present invention, the diameter of a needle can be 2.085 millimeters, the inner diameter of the valve body can be 3.00 millimeters, and the outer diameter of the valve body can be 7.68 millimeters.  
     [0034] 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.