Patent Publication Number: US-8991360-B2

Title: Coaxial quill assembly retainer and common rail fuel system using same

Description:
TECHNICAL FIELD 
     The present disclosure relates generally to dual fuel common rail systems, and more particularly to a coaxial quill assembly that includes a matched pair of outer and inner quills kept together during pre-installation handling with a retainer. 
     BACKGROUND 
     Co-owned U.S. Patent application publication 2012/0055448 shows a co-axial quill assembly for a dual fuel common rail system in which inner and outer quills sealingly engage a common conical seat on individual fuel injectors. That references teaches the utilization of separate loading devices to ensure that the inner and outer quills sealingly engage the fuel injector despite dimensional tolerance variations that would be expected during the manufacture of the individual inner and outer quills, fuel injector and other engine components. While such a strategy may permit any outer quill to be matched with any inner quill at the time the fuel system is assembled to an engine, the separate loading strategy for each quill may be cumbersome and occupy more space than desirable in and around the engine. 
     The present disclosure is directed toward one or more of the problems set forth above. 
     SUMMARY 
     In one aspect, a coaxial quill assembly includes an outer quill with a first dimension along a centerline. An inner quill is positioned inside the outer quill and has a second dimension along the centerline. The outer quill and the inner quill are a matched pair such that the first dimension and the second dimension have a difference corresponding to a fuel system dimensional specification. The inner quill defines a first fuel passage, and a second fuel passage is defined by and between the inner quill and the outer quill. A retainer is positioned in, but not obstructing, the second fuel passage in frictional contact with an interior surface of the outer quill and an exterior surface of the inner quill. The retainer permits movement of the first quill relative to the second quill along the centerline with an application of an adjustment force, but resists separation of the first quill from the second quill absent a forced disassembly. 
     In another aspect, a dual fuel common rail fuel system includes a first common rail, a second common rail, and a plurality of fuel injectors that each define a first fuel inlet and a second fuel inlet that open through a common conical seat. A plurality of quill assemblies each defines first and second fuel passages that fluidly connect the first common rail and the second common rail, respectively, to an individual one of the fuel injectors. Each of the quill assemblies includes matched inner and outer quills that are out of contact with each other but retained together during pre-installation handling by a retainer positioned in the second fuel passage. The match is based on a first dimension of the outer quill and a second dimension of the inner quill having a difference corresponding to a fuel system dimensional specification that causes both the inner and outer quills to sealingly engage the common conical seat. The retainer resists separation of the first quill from the second quill absent a forced disassembly during pre-installation handling, but is inert to operation of the fuel system. 
     In still another aspect, a method of assembling a fuel system includes pre-assembling a plurality of quill assemblies by matching inner and outer quills for each quill assembly. The match is based on a first dimension of the outer quill and a second dimension of the inner quill having a difference corresponding to a fuel system dimensional specification that causes both the inner and outer quills to sealingly engage a common conical seat of one of the fuel injectors. A first common rail and a second common rail are fluidly connected to the plurality of fuel injectors with a plurality of quill assemblies. The matched inner and outer quills are retained together during pre-installation handling with a retainer positioned between the inner and outer quills. The retainers are left in place between their respective inner and outer quills after the rails are fluidly connected to the fuel injectors. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic illustration of an engine and dual fuel common rail fuel system according to the present disclosure; 
         FIG. 2  is a side sectioned view through one of the coaxial quill assemblies shown in  FIG. 1 ; 
         FIG. 3  is a perspective see through image of the coaxial quill assembly of  FIG. 2 ; 
         FIG. 4  is a perspective sectioned view of the coaxial quill assembly of  FIG. 3  as viewed along section lines  4 - 4 ; and 
         FIG. 5  is a partial end sectioned view through the coaxial quill assembly of  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring initially to  FIGS. 1 and 2 , an engine  10  includes a dual fuel common rail fuel system  11  that includes individual fuel injectors  20  positioned for direct injection into engine cylinders  12 . For instance, engine  10  might be a V configuration multi-cylinder compression ignition engine, such as those that might find use in mining operations and other similar applications. Dual fuel common rail fuel system  11  includes a first common rail  13  connected to a liquid fuel supply  17 , and a second common rail  14  connected to a gaseous fuel supply  16 . In the illustrated embodiment, the pressure in common rails  13  and  14  may be controlled by an electronic controller  15  in a conventional manner. Each of the fuel injectors  20  defines a liquid fuel inlet  21  and a gaseous fuel inlet  22  that open through a common conical seat  23 . A plurality of quill assemblies  30  each define a first fuel passage  41  and a second fuel passage  51  that fluidly connect the first common rail  13  and the second common rail  14 , respectively, to an individual one of the fuel injectors  20 . Each of the quill assemblies  30  include a matched pair of an inner quill  40  and an outer quill  50  that are out of contact with each other but retained together during pre-installation handling by a retainer  60  positioned in the second fuel passage. Each matched pair of an inner quill  40  and outer quill  50  is based upon a first dimension D 1  of the outer quill  50  and a second dimension D 2  of the inner quill  40  having a difference S corresponding to a fuel system dimensional specification that causes both the inner and outer quills to sealingly engage the common conical seat  23 . 
     The retainer  60  resists separation of the inner quill  40  from its matched outer quill  50  absent a forced disassembly during pre-installation handling. However, after installation, the retainer  60  may be inert to operation of the fuel system  11 . Forced disassembly means that the matched quill pair  40 ,  50  will not accidently separate, such as by being dropped or maybe even mishandled. The forced disassembly requires an intent and maybe a tool(s) to separate one of the inner quill  40  and outer quill  50  from the retainer  60 . Being inert to the operation of the fuel system  11  means that fuel flows through or past the retainer  60  without interfering with the flow to the fuel injectors  20 . 
     The inner quill  40  has a spherical end  46  that is in contact with the common conical seat  23  at a gage line  48 . In addition, the outer quill  50  includes a spherically shaped end  53  that is also in contact with common conical seat  23  at a gage line  54 . The previously identified fuel system dimensional specification that causes the inner and outer quills  40 ,  50  to sealingly engage the common conical seat  23  may be prescribed by a specific distance “b” along a centerline  25  between gage line  48  and gage line  54 . 
     In the illustrated embodiment, the inner quill  40  has another spherical end  45  that defines an inlet  43  to the first fuel passage  41 . As shown in  FIG. 2 , quill assembly  30  might also include a manifold/clamp  18  that includes a conical seat  19  in contact with spherical end  45  of inner quill  40  at gage line  47 . 
     As stated earlier, the first common rail  13  may contain a liquid fuel, such as distillate diesel fuel, and the second common rail  14  may contain a gaseous fuel, such as natural gas. Nevertheless, those skilled in the art will appreciate that first and second common rails  13  and  14  could include different liquid fuels, or possibly even the same liquid fuels at different pressures without departing from the present disclosure. 
     Referring more specifically to  FIGS. 2-5 , each coaxial quill assembly  30  includes an outer quill  50  with a first dimension D 1  along centerline  25 . An inner quill  40  is positioned inside the outer quill  50  and has a second dimension D 2  along centerline  25 . As described earlier, the outer quill  50  and the inner quill  40  are a matched pair such that the first dimension D 1  and the second dimension D 2  have a difference S corresponding to a fuel system dimensional specification. The inner quill  40  defines a first fuel passage  41 . A second fuel passage  51  is defined by and between the inner quill  40  and the outer quill  50 . A retainer  60  is positioned in, but not obstructing the second fuel passage  51  in frictional contact with an interior surface  52  of outer quill  50  and an exterior surface  42  of inner quill  40 . The retainer  60  permits relative movement of the first quill  40  relative to the second quill  50  along centerline  25  with an application of an adjustment force, such as what might occur during installation in a fuel system  11 . However, the retainer  60  resists separation of the first quill  40  from its matched second quill  50  absent a forced disassembly. 
     Depending upon the structure of coaxial quill assembly  30 , the difference S may include a distance “b” along centerline  25  between a first gage line  54  of the outer quill  50  and a second gage line  48  of the inner quill  40 . The outer quill  50  may include a spherically shaped end  53  that includes gage line  54 , and inner quill  40  may also have a spherically shaped end  46  that includes the gage line  48 . The dimension D 2 , of the example embodiment shown corresponds to the distance between gage line  48  and gage line  47  on inner quill  40  along centerline  25 . The first dimension D 1  may correspond to a distance along centerline  25  between a first end of outer quill  50  and the gage line  54  at outlet  55 . In this specific embodiment, the first dimension D 1  is less than a length L 1  of the outer quill  50  along centerline  25 . In addition in the specific embodiment, the second dimension D 2  is less than a length L 2  of the inner quill  40  along centerline  25 . 
     The inner quill  40  may have spherical shaped ends  45  and  46  that define an inlet  43  and an outlet  44 , respectively, to the first fuel passage  41 . The outer quill  50  also has a spherically shaped end  53  that defines an outlet  55  from the second fuel passage  51 . 
     The dimension “a” in  FIG. 2  may correspond to a distance along centerline  25  between the end of outer quill  50  and the gage line  47  of inner quill  40 . Thus, these dimensions for the specific embodiment yield the equations that S=D 2 −D 1  which equals a+b. In one specific embodiment, manifold/clamp  18  and its conical seat  19  might also be a common conical seat such that small dimension “a” represents a distance between gage line  47  of inner quill  40  and another gage line on the proximal end of outer quill  50  that also seats on common conical seat  19 . Thus, dimension “a” and dimension “b” may be characterized as gage line differences, depending upon the specific embodiment and structure, especially at the proximal end near manifold/clamp  18 . Those skilled in the art will appreciate that, because the relative spring rates of the inner and outer quills  40 ,  50  they may require different load levels to ensure proper sealing at common conical seat  23 . If so, there might also need to be a differential length (d) that is needed to achieve the appropriate loading. Therefore, the equations might be expressed as S=D 2 −D 1  which equals a+b+d. The differential length “d” may be positive or negative or zero, depending upon the specific design, quill materials and geometries. Thus, depending upon the specific design, “a” “b” and “d” may all be part of the fuel system dimensional specification discussed above. 
     Referring specifically to  FIGS. 3-5 , one example embodiment of retainer  60  is shown as a piece of spring steel that is elastically deformed to be positioned between inner quill  40  and outer quill  50 . This deformation may produce interference frictional contact at the circled contact points shown in  FIG. 5 . In one specific example, the retainer  60  may have an open shape  61 , such as the incomplete square shape as shown in  FIGS. 3-5 . 
     Because achieving sealing contact of both inner quill  40  and outer quill  50  at common conical seat  23  of fuel injector  20  is sensitive to the geometry at the contact location(s), one might expect at least one outer quill  50  of at least one quill assembly  30  would not be a match for an inner quill  40  of at least one other quill assembly  30  in a typical engine  10 . Thus, although the inner quills  40  and the outer quills  50  in the fuel system  11  may have slightly different dimensions from one another, the matched pairs all have a common fuel system dimensional specification. The retainers  60  of each quill assembly  30  may comprise an identical piece, such as spring steel, that is elastically deformed between the inner quill  40  and the outer quill  50 . As stated earlier, in the specific embodiment illustrated, the retainer  60  is illustrated, for example, as each being an identical piece of spring steel that defines an open square shape  61  around centerline  25 . 
     INDUSTRIAL APPLICABILITY 
     The present disclosure relates generally to fuel systems which need to bring two fuels that differ in at least one of identification, pressure and liquid or gaseous state from each other. The present disclosure finds specific application to fuel systems that supply liquid compression ignition fuel and natural gas fuel for combustion in an engine  10 . The present disclosure is specifically applicable to supplying fuels to fuel injectors  20  through an individual opening, for instance, in the engine head of engine  10 . Finally, the present disclosure finds specific application to a strategy for matching inner and outer quills  40 ,  50  and retaining them together with a retainer  60  during pre-installation handling. 
     In one aspect, a method of assembling a fuel system  11  includes pre-assembling a plurality of quill assemblies  30 . Each preassembled quill assembly  30  includes a matching pair of an inner quill  40  with an outer quill  50  that is based on a first dimension D 1  of the outer quill  50  and a second dimension D 2  of the inner quill  40  having a difference S corresponding to a fuel system dimensional specification that causes both the inner and outer quills  40 ,  50  to sealingly engage a common conical seat  23  of one of the fuel injectors  20  in the fuel system  11 . A first common rail  13  and a second common rail  14  are fluidly connected to fuel injectors  20  with the plurality of quill assemblies  30 . Each matched inner and outer quill pair  40 ,  50  is retained together during pre-installation handling with a retainer  60  positioned between the inner and outer quills  40 ,  50 . The retainers  60  are left in place between the respective inner and outer quills  40 ,  50  after the fluid connect step is completed by installing fuel system  11  in an engine  10 . 
     By preassembling matched pairs of inner and outer quills  40 ,  50 , the assembly of the fuel system  11  to engine  10  can be simplified and streamlined by avoiding specific adjustment features, while still ensuring that each quill  40 ,  50  sealingly engages the common conical seat  23  of a fuel injector  20 . By having specific matched dimensional pairs, any pair should properly be installable and inter-changeable with any of the engine cylinders  12  of engine  10  despite the fact that one could expect at least one outer quill  50  of at least one quill assembly  30  to not match at least one inner quill  40  of another quill assembly  30 . 
     It should be understood that the above description is intended for illustrative purposes only, and is not intended to limit the scope of the present disclosure in any way. Thus, those skilled in the art will appreciate that other aspects of the disclosure can be obtained from a study of the drawings, the disclosure and the appended claims.