Abstract:
A compact fuel injection nozzle includes a unitary nozzle body, a nozzle cap, a valve member and a spring sub assembly. The spring sub assembly provides a biasing force against a valve member that includes an integral lift stop. The biasing force holds the nose of the valve member against the valve seat of the nozzle body until the fuel pressure inside the injector exceeds a minimum opening pressure. The lift stop provides a stop limit, permitting the valve member to move away from the valve seat a predetermined axial distance. The minimum opening pressure and valve opening axial distance may be calibrated by selection and installation of shims.

Description:
This application is a National Stage Application under 371 of PCT/US00/31537 filed Nov. 17, 2000 which claims the benefit of U.S. Provisional Application 60/166,031 filed Nov. 17, 1999. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates generally to a fuel injection nozzle. More particularly, the present invention relates to a fuel injection nozzle for an internal combustion engine. 
     Fuel injectors of the type contemplated by the present invention have a plunger or valve which is lifted from its seat by the pressure of fuel delivered to the injector by an associated high pressure pump in measured charges in timed relation with the associated engine. Representative fuel injector assemblies are described in U.S. Pat. Nos. 3,829,014, 4,205,789, 4,790,055, and 4,938,193. 
     The improvements in fuel injection nozzles chronicled by the succession of patents identified above, have been performance related and/or manufacturing related. In the present competitive market for these types of devices, the need to reduce the cost of materials and fabrication without compromising performance continues to be a primary factor. Although some of the devices represented by the prior art provided for improvements in materials and fabrication, further improvements are required. 
     Many internal combustion engines that utilize fuel injection nozzles are found in automotive applications. A fuel injection nozzle provides the path for injecting fuel into the combustion chamber of the internal combustion engine. Extensive analysis of the combustion process reveals that the most efficient injection point (in some cases) is at the top and center of the combustion chamber. In overhead cam engines the area immediately above the combustion chamber is occupied by the overhead cam (or cams) valve assemblies and connecting mechanisms, such as rocker arms, etc. Placement of injector nozzles in the midst of the valve train makes severe constraints on the length, diameter and overall size of the injector nozzle. Consequently, any reduction in size in the injector nozzle component provides improved flexibility of use. 
     Additionally, the tip of an injector nozzle includes discharge apertures from which pressurized fuel is delivered into the combustion chamber. Typically, the inside surface of the injector nozzle tip forms a valve seat for sealing with the injector valve between injection pulses. This valve seat/valve interface must form a reliable seal over a useful life that will encompass many millions of injection cycles. Materials for injection valves and injection nozzle tips therefore must be extremely tough, durable, i.e. hard materials. Injector nozzle tips are also subjected to high temperatures and pressures present in the combustion chamber. In high output or turbo-charged engines the temperature in the vicinity of the nozzle tip may well exceed 500° F. for sustained periods of time. Materials used for fuel injection valves and nozzle tips must therefore meet the dual requirements of maintaining their toughness over millions of cycles at sustained high temperatures. This has meant the use of specialty alloy steels having high Rockwell hardness and high temperature tempering properties. 
     Materials having these properties are typically both expensive and notoriously difficult to work with. The result has been that only the critical portions of the fuel injection nozzle were made from the exotic alloy steels, with the balance of the injector nozzle being more conventional steel. Assembly of injector nozzles from multiple parts increases both the cost and complexity of the manufacturing process. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide a fuel injection nozzle assembly in which the component parts are simply fabricated, easily assembled by automated processes, and readily installed in an engine, without compromising the performance of the nozzles. 
     Another object of the present invention is to provide a fuel injection nozzle assembly that has a compact size in relation to conventional fuel injection nozzle assemblies. 
     A further object of the present invention is to provide a fuel injection nozzle assembly in which the entire fuel injection nozzle body, including valve guide and nozzle tip, is made from a single piece of homogeneous material. 
     A yet further object of the invention is to provide a compact fuel injection nozzle assembly requiring fewer parts. 
     These objects are accomplished in accordance with the invention through improvements in several aspects of the conventional fuel injection nozzle assembly. 
     A fuel injection nozzle in accordance with the invention includes a one-piece integral nozzle member. The nozzle member has a lower portion that is mounted in a socket in the engine cylinder head such that the nozzle tip of the lower portion is positioned within the cylinder head. An upper portion of the nozzle member projects above the cylinder head. The nozzle member also includes an axial bore and a fuel inlet orifice intersecting the axial bore. The inside surface of the axial bore adjacent the nozzle tip defines a valve seat. A fuel inlet member has a fuel passage extending from an inlet end portion to an outlet end portion. The outlet end portion is affixed in fluid communication with the fuel inlet orifice of the nozzle member. The inlet end portion may be mounted directly to the fuel pump. A cap member has a lower portion mounted to the upper portion of the nozzle member. 
     A valve member received in the axial bore reciprocates in response to periodic pulses of pressurized fuel fed to the axial bore via the fuel inlet orifice. The valve is a one-piece member extending from a nose end configured to seal against the valve seat to an axially opposed lift stop. The valve member includes an actuating surface, a bearing surface and a spring seat. 
     An upper portion of the cap member and the upper portion of the nozzle member define a spring chamber. A spring subassembly disposed within the spring chamber includes a spring disposed around the lift stop and seated against the spring seat, a lift shim disposed adjacent the cap member, and an opening pressure shim disposed intermediate the lift shim and the nozzle member. The opening pressure shim has an axial opening. The upper end portion of the lift stop is received within the opening of the opening pressure shim. The upper end of the spring engages the opening pressure shim. 
     The minimum opening pressure and valve lift can be calibrated by installation of lift and opening pressure shims of different axial thicknesses. Measurements of injector nozzle components permit calculation of the correct shim thicknesses. 
     Other objects and advantages of the invention will become apparent from the drawings and specification. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention may be better understood and its numerous objects and advantages will become apparent to those skilled in the art by reference to the accompanying drawings in which: 
         FIG. 1  is an elevation view, partly in section, of a first prior art fuel injection nozzle; 
         FIG. 2  is an elevation view, partly in section, of a second prior art fuel injection nozzle; 
         FIG. 3  is an elevation view, partly in section, of a compact fuel injection nozzle in accordance with the present invention; 
         FIG. 4  is an exploded view, partly in section, of the nozzle of  FIG. 3 , more clearly illustrating the individual components and the manner in which the components are assembled; 
         FIG. 5  is an elevation view, partly in section of a second embodiment of a compact fuel injection nozzle in accordance with the present invention; 
         FIG. 6  is an elevation view, partly in section of a third embodiment of a compact fuel injection nozzle in accordance with the present invention; and 
         FIG. 7  is an enlarged elevation view of the compact fuel injection nozzle illustrated in FIG.  5 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 1  shows a first conventional fuel injection nozzle  10  having a nozzle body  12 , a nozzle cap  14 , a fuel inlet stud  16 , and a leak-off cap  18 . During operation, fuel is supplied through passages  20  in the fuel inlet stud  16 , to a valve chamber  22  in the upper portion of the nozzle body  12 . An elongated nozzle valve  24  is axially reciprocable within the nozzle body  12  and includes a conical nose  26  at its lower end for sealing against a valve seat  28  and intermittently providing flow through discharge apertures  30  in the nozzle tip. Fluid at low pressure exits the nozzle cap  18  through a channel  32  leading to channels  34  in the hydraulic connections  36  of the leak-off cap  18 . 
     The primary function of the spring chamber  38  in the nozzle cap  14  is to properly position the spring subassembly  40 . The spring subassembly  40  in the nozzle cap  14  includes a central lift stop  42 , a coil compression spring  44  and spring seats  46 ,  48 , arranged for biasing the valve  24  downwardly to close the valve and establish a minimum opening pressure. The spring seat  46  includes a generally disk-shaped base portion for contacting the upper end of the valve, and a pedestal portion projecting upwardly therefrom. The lift stop  42  includes a stem portion axially aligned with another spring seat  48  and an integral head portion which is received in abutting relation with the dome of the cap  14 . The radially outer portions of the spring seats  46 ,  48  are adapted to engage the ends of the coil spring  44  and to hold it in a compressed (preloaded) condition within the spring chamber  38 . 
     The fabrication of the prior art nozzle  10  begins with the transverse attachment of the inlet stud  16  to the nozzle body  12 . The ring portion  50  has an inner diameter at ambient temperature that is smaller than the outer diameter of the nozzle body  12  portion to which it will be connected. The ring portion  50  is first heated to expand the inner diameter to a dimension greater than the outer diameter of the body portion. The ring  50  is then slipped over the body portion a predetermined distance relative to the upper end of the nozzle body  12 . The ring  50  is cooled to form a rigid, shrink-fit, annular connection with the body portion, in such a manner to prevent leakage path formation. A drilling tool is then inserted into passage  20  and is advanced to penetrate the remaining material in the ring portion  50  and the adjacent wall of the nozzle body  12 . The passage through the ring portion  50  into the chamber  22  is reamed, deburred and then burnished. The step of burnishing provides a fluid seal at the juncture of the second passage with the interface between the nozzle body exterior and the ring interior. 
     The outer, cylindrical mounting portion of the guide member  52  is machined to provide an appropriate interference fit against the wall of the valve chamber  22  upon insertion into the nozzle body  12 . The forward, or downward portion of the guide member  52  includes a recessed, annular space  54  which, after insertion of the guide member  52  into the valve chamber  22 , is in fluid communication with the passage  20  from the inlet stud  16 . The two annular edges defining the recess  54  provide an “edge filter” effect such that fuel entering the recess  54  must pass over the edges in order to reach the valve chamber  22 . 
     The next steps include: orienting and assembling the nozzle tip  56  into a press-fit and preferably staked relation with the tip cavity  58 ; measuring the dimensions of the interior of the guide member  52 ; selecting a valve  24  having a bearing surface of appropriate dimensions for proper diametrical clearance and inserting it into the nozzle bore; and assembling the spring subassembly  40 . 
     Before the spring subassembly  40  is assembled and inserted into the spring chamber  38  of the cap  14 , the critical dimensions are checked. In the case of a fuel injector, there are two primary critical dimensions. The first critical dimension is the “as assembled” distance between the upper end of the valve  24  and the dome of the cap  14 . “As assembled” is the distance between these two points in an assembled injector. This distance can be determined from automated measurement of the nozzle body  12  with valve  24  inserted at one station, and measurement of the cap  14  and internal components thereof at another station. When this distance is known, the correct axial dimension (length) for the lift stop  42  can be determined. A lift stop  42  having the correct axial length will accurately permit the valve member to open a predetermined distance. The consistent accuracy of the valve opening distance is critical to the proper functioning of the injector. 
     The second critical dimension is the axial length of the spring  44  when the spring is preloaded (partially compressed) to a tension that will hold the valve  24  closed until the desired minimum opening pressure is exerted on the actuating surface  25  of the valve  24 . The axial length of the preloaded spring is used to determine the correct axial dimension of the lift stop head, which in turn determines the axial position of the upper spring seat  48  with respect to the lower spring seat  46 . 
     The head and the nose on the lift stop  42  are ground as necessary for adjusting the critical dimensions. After grinding, the spring subassembly  40  is inserted into the nozzle cap  14 , which is then torqued onto the upper end of the nozzle body  12 . A plastic or metal leak-off cap  18  is snapped on over the upper end of the nozzle cap  14 . The leak-off cap  18  forms one or more annular recesses with the nozzle cap  14 , leading to radial flow channels in fluid communication with the leak-off channel in the nozzle cap  14 , whereby fluid at low pressure within the nozzle cap  14  can be diverted away and recycled if desirable. 
     In the second prior art fuel injection nozzle  10 ′ shown in  FIG. 2 , the critical dimensions may be threadably adjusted by the pressure screw  60  and the lift screw  62 . After the critical dimensions are set, the pressure screw  60  and lift screw  62  may be locked in place by a pressure locknut  64  and a lift locknut  66 , respectively. 
     These prior art assembly configurations and methods of assembly require many precision parts and the intervention of skilled personnel in the assembly process. Such skilled personnel add to the cost of producing a fuel injection nozzle. In addition, human intervention in the production process may produce variable results depending upon the skill and/or attentiveness of the individual. As can be seen from  FIGS. 1 and 2 , the prior art injector nozzle bodies  12  and  12 ′ required the insertion of a separate nozzle tip  56  and guide member  52 . A compact fuel injection nozzle as described below incorporates the nozzle tip and guide member into a unitary injector nozzle body and permits adjustment of critical dimensions by the selection of appropriately dimensioned shims. A compact fuel injection nozzle in accordance with the present invention can be assembled more efficiently and with less human intervention than prior art fuel injection nozzles. Ultimately, a compact fuel injection nozzle may be assembled in a fully automated process. 
     With reference to  FIGS. 3 and 4 , wherein like numerals represent like parts throughout the figures, a compact fuel injection nozzle in accordance with the present invention is generally designated by the numeral  68 . The compact fuel injection nozzle  68  includes a nozzle body  70 , a valve member  82 , a spring subassembly, a nozzle cap  72 , and a fuel inlet  74 . Fuel is supplied through a passage  76  in the fuel inlet  74 , to a valve chamber  78  in the upper portion  80  of the nozzle body  70 . An elongated nozzle valve  82  axially reciprocates within an axial bore  84  in the nozzle body  70  such that a conical nose  86  at its lower end seals against a valve seat  88 , intermittently providing flow through discharge apertures  90  in the nozzle tip  92 . 
     A lower portion  93  of the nozzle body  70  is mounted within a socket in an engine cylinder head (not shown) such that the upper portion  80  of the nozzle body  70  projects outwardly from the cylinder head and the intermittent flow of fuel is discharged into the cylinder. Pressurized fuel is forced (leaks) into the gap  94  between the bearing surface  96  of the nozzle valve  82  and the inside surface  98  of the axial bore  84  and provides lubrication between the nozzle valve  82  and the nozzle body  70 . The valve  82  is reciprocated as a result of the intermittent fuel pulses entering the valve chamber  78 , which apply hydraulic pressure on the actuating surface  100  of the valve  82 . Hydraulic pressure from fuel pulses lift the valve nose  86  off the valve seat  88 , exposing the discharge apertures  90  to the high pressure fuel occupying the axial bore  84  of the nozzle body  70 . Fuel under high pressure is then forced through discharge apertures  90  into the cylinder for combustion. 
     An upper segment  102  of the upper portion  80  of the nozzle body  70  has an outside diameter  104  that is less than the outside diameter  106  of the lower segment  108  of upper portion  80 , forming an upwardly facing shoulder  110 . The outside surface of upper segment  102  has a thread surface  112 . The inner surface of the lower portion  114  of the nozzle cap  72  has a thread surface  116  that is complementary with the thread surface  112  on upper segment  102 . When the nozzle cap  72  is installed on the nozzle body  70 , the lip  118  of the nozzle cap  72  engages the shoulder  110  on the nozzle body  70 . The threaded engagement between the lower portion  114  of the nozzle cap  72  and the upper segment  102  of the nozzle body  70 , together with a compressed annular gasket or O-ring  71  provide a substantially leak-tight seal. Preferably, the outside diameter  120  of the nozzle cap  72  is substantially equal to the outside diameter  106  of the upper portion  80  of the nozzle body  70  such that the outside surface of the assembled fuel nozzle  68  has a uniform appearance. 
     With reference to the embodiment of the compact fuel injection nozzle illustrated in  FIGS. 3 and 4 , the fuel inlet  74  is a single unitary pipe-like or tube-like structure having an inlet end portion  122  removably mounted to a fuel pump (not shown) and an outlet end portion  124  which is fixedly mounted to the nozzle body  70 . In this embodiment, the outlet end portion  124  of the fuel inlet  74  is disposed within a transverse bore  126  which extends from the outer surface of the nozzle body  70  to an abutment face  128  positioned such that transverse bore  126  intersects valve chamber  78 . A fuel passage  76  provides fluid communication between the fuel pump and the valve chamber  78 . The transverse bore  126  may extend through the valve chamber  78  such that the abutment face  128  is positioned in the opposite wall, as shown in FIG.  3 . Alternatively, the abutment face  128  may be positioned at a point intermediate the outer edge of the valve chamber  78  and the mid-point of the valve chamber  78 . 
     A valve member  82  extends from a nose end  86  to the head  148  of the integral lift stop  138 . A stem  85  connects the nose end  86  to the actuating surface  100 , bearing surface  96  and spring seat  156  machined on the length of the valve member  82 . The valve member  82  is received in the axial bore of the nozzle body  70  with the nose end adjacent the valve seat  88 . The bearing surface  96  is closely received by the valve guide surface  98  so the valve member is supported for axial movement. 
     The upper segment  102  of the nozzle body  70  forms a cavity  130 , which, together with the upper portion  132  of the nozzle cap  72 , define a spring chamber  134 . A spring subassembly  136  housed in the spring chamber  134  includes a coil compression spring  140 , a lift shim  142 , and an opening pressure shim  144 , arranged for biasing the valve  82  downwardly to close the valve and establish a minimum opening pressure. The spring  140  surrounds the lift stop  138  with the lower end  154  of the spring  140  bearing against the spring seat  156  of the valve member  82 . The disc-shaped lift shim  142  has a top surface  158  that abuts the inside surface  160  of the dome of the cap  72 . The washer-shaped opening pressure shim  144  has an axial opening  162  sized to slidably receive the head end  148  of the lift stop  138 . The pressure shim  144  has an upper surface  164  which abuts the bottom surface  166  of the lift shim  142  and a lower surface  168  which engages the upper end  170  of spring  140 . 
       FIGS. 5 and 6  illustrate alternative preferred embodiments of the compact fuel injection nozzle  68 ′ and  68 ″. With reference to  FIG. 5 , alternative embodiment  68 ′ incorporates an alternative configuration for attaching the fuel inlet member  74  to the nozzle body  70 . The middle segment  204  of the nozzle body  70 ′ has a diameter that is less than the upper portion  80  of the nozzle body, forming a downwardly facing shoulder  208 . A banjo-type fitting  200  includes an opening  202  to receive the middle portion  204  of the nozzle body  70  and an opening  206  orthogonal to the nozzle body to receive the outlet end portion  124  of the fuel inlet member  74 . 
     The fitting  200  is preferably brazed to the outlet end portion  124  of the inlet member  74 . The fitting  200  is then mounted to the nozzle body  70 ′ with the fitting abutting the downward facing shoulder  208 . The axial location of the shoulder  208  and the configuration of the fitting  200  serve to axially align the fuel passage  76  of the fuel inlet member  74  with the fuel inlet  210  in the injector nozzle  70 ′. Angular alignment of the fuel passage  76  and the fuel inlet  210  may be accomplished by any number of known methods. The fitting  200  is then preferably brazed to the nozzle body  70  to form a durable, sealed joint. 
       FIG. 6  illustrates a further preferred embodiment  68 ″ in which the outer diameter of the upper portion  80 ″ of the nozzle body  70 ″ is reduced, resulting in a narrowed downward facing shoulder  208 ′. The fitting  200  is assembled to the nozzle body  70 ″ and the outlet end portion  124  of the fuel inlet  74  in the same manner as described with respect to embodiment  68 ′. Fitting  200  extends radially beyond the narrowed downward facing shoulder  208 ′, forming an upward facing shoulder  110 ′. The configuration of the cap  72 ″ is altered to abut the new, lower upward facing shoulder  110 ′ when assembled. This alternative embodiment  68 ″ results in the use of less tool steel to form the nozzle body  72 ″, further reducing the cost of production. 
     In all respects other than those described, alternative embodiments  68 ′ and  68 ″ are configured and function substantially the same as embodiment  68 . 
     It will be noted that the cap  72 ′,  72 ″ of the compact fuel injection nozzle  68 ′,  68 ″ includes an external annular groove  230 . This groove  230  is used to facilitate removal of the fuel injection nozzle  68 ′,  68 ″ from the cylinder head of an engine (not illustrated) as explained in U.S. Pat. No. 4,790,055. 
     The nozzle body  70  is preferably manufactured from a single, unitary piece of M50 tool steel that can be heat-treated to a hardness of Rockwell C 60-C 64. The term “unitary” as used in this application refers to a single piece of homogeneous material, in this case M50 alloy tool steel. Of course, other alloy steels or materials may be appropriate. When purchased as bar stock, the M50 tool steel is of moderate hardness (approximately Rockwell C 20-25) and is readily machinable using standard machining methods. From bar stock, a nozzle body  70  is machined to include the required external dimensions, cavity  130  and a rough axial bore  84 . An appropriate transverse bore  126 , or fuel inlet orifice  210  is machined to intersect with axial bore  84 . 
     Assembly of the nozzle  68  begins with the transverse attachment of the fuel inlet  74  to the nozzle body  70 . The outlet end portion  124  of the fuel inlet  74  is inserted into the transverse bore  126  until the outlet end  172  engages the abutment face  128 . The outside surface of the fuel inlet  74  is brazed to the outside surface of the nozzle body  70  to fixedly mount the fuel inlet  74  to the nozzle body  70  and to prove a fluid-tight seal between the fuel inlet  74  and the nozzle body  70 . 
     Assembly of alternative embodiments  68 ′,  68 ″ begins with attachment of the fitting  200  (containing the outlet end portion  124  of the fuel inlet  74 ) to the nozzle body  70 ′,  70 ″. Preferably the fitting is brazed in place to provide a strong, fluid tight bond between the fitting  200  and the nozzle body  70 ′,  70 ″. 
     For all embodiments  68 ,  68 ′,  68 ″, the brazing process takes place in a furnace where the assembled nozzle body  70 ,  70 ′,  70 ″, fitting  200  (if appropriate) and fuel inlet  74  are heated to a temperature of approximately 2,100° F. Copper material, inserted between the parts during assembly, melts in the heat and flows to form the brazed joint. The alloy steel of the nozzle body  70 ,  70 ′,  70 ″ is hardened by the cycle of heating and cooling experienced in the furnace. The alloy steel, which was formerly Rockwell C (R c ) 20-25, is hardened to a Rockwell C (R c ) 60-64. The alloy steel nozzle body is then tempered at a temperature of approximately 1,100° F. to relieve internal stresses in the crystal structure that occur during the brazing/hardening process, as is known in the art. 
     The next step is to use an Electrical Discharge Machine to produce the fine discharge apertures  90  in the now hardened and tempered nozzle tip  92 . Precise grinding tools are then used to hone the valve guide surface  98  of the axial bore  84  where the bore will guide the axial movement of the nozzle valve  82 . The bore  84  in this location must be very precisely configured so the gap  94  between the bearing surface  96  of the valve  82  and the valve guide surface  98  meets strict tolerances. The valve seat  88  is also ground to a specified configuration. Cutting lubricant may be injected into the axial bore  84  through the discharge apertures  90  in the tip as well as from the direction of the honing/lapping tool (not illustrated) to cool and lubricate the honing/lapping tools. The lubricant is injected at high pressure to ensure adequate cooling and eject any removed material. The shortened length of the axial bore  84  in the compact fuel injection nozzle decreases the length of the lapping tool used to configure the valve seat  88 . A shorter tool has increased rigidity at its grinding tip, resulting in acceptable accuracy in the valve seat configuration. 
     Assembly of the internal parts of the compact fuel injection nozzle in accordance with the present invention will be described with reference to the embodiment illustrated in  FIGS. 3 and 4 . It will be understood by those of skill in this art that the methods described with reference to embodiment  68  are equally applicable to alternative embodiments  68 ′ and  68 ″. 
     Next, a nozzle valve  82  having a bearing surface  96  of appropriate dimensions for proper diametrical clearance (as described above) is inserted into the axial bore  84  and the distance between the head end  148  of lift stop  138  and a reference point  174  on the valve body  70  is measured. The relative position of the spring seat  156  with respect to reference point  174  is also measured. It will be understood by those of ordinary skill in the art that reference point  174  is arbitrary. All that is important about the reference point is that the same point be used consistently. 
     A lift shim  142  having a thickness determined by the measured distance between head end  148  and reference point  174  is selected from a family of lift shims  143 . The family of lift shims  143  comprises a number of lift shims having different predetermined thicknesses. The number of lift shims and the thickness of each lift shim in the family  143  are selected such that the selected lift shim  142  substantially corrects the accumulated tolerances for the spring subassembly components without requiring the machining of any such components. Selecting an appropriate lift shim  142  from a family of lift shims  143  thereby eliminates one or more machining steps that were required to manufacture the first prior art nozzle  10 . In addition, selecting an appropriate lift shim  142  from a family of lift shims  143  thereby eliminates the lift locknut  66  and pressure locknut  64  required to manufacture the second prior art nozzle  10 ′. 
     The relationships between the parts contained in the spring chamber  134  are best illustrated with reference to  FIG. 7. A  compact fuel injection nozzle  68 ′ is configured so that the valve member  82  moves axially away from the valve seat  88  by a predetermined valve lift distance in response to a predetermined fuel pressure (minimum opening pressure) in the axial bore  84 . The opening distance and the minimum opening pressure are determined by the components in the spring chamber  134  acting on the valve member  82 . 
     An assembled cap  72 ′ and nozzle body  70 ′ have a fixed relationship to one another, resulting in a fixed distance from the valve seat  88  to the inside surface  160  of the cap  72 ″. To establish the opening distance of the valve member  82 , the position of the head end  148  of a seated valve member  82  is measured with respect to some part of the nozzle body  70 ′. The “as assembled” relationship of the inside surface  160  of the cap  72 ′ relative to the part of the nozzle body are known and permit the calculation of the distance between the head end  148  of the valve member  82  and the inside surface  160  of the cap (shown in  FIG. 7  as B). Distance B minus the axial thickness of lift shim  142  equals the valve lift distance. The valve lift distance may be adjusted by selection of lift shims from a family of lift shims having various axial thicknesses. 
     When the appropriate lift shim  142  has been selected, distance E between the bottom surface  166  of the lift shim  142  and the spring seat  156  of the valve member  82  can be calculated. The axial length of a correctly preloaded spring is preferably determined by bench testing. Knowing the axial length of the preloaded spring  140  and distance E, the axial thickness D of opening pressure shim  144  can be determined and the appropriate opening pressure shim selected from a family of opening pressure shims  145  having various axial thicknesses. 
     Thus, by simple and reliable bench measurements, it is possible to match a lift shim  142  and opening pressure shim  144  to a given nozzle body  70 ′, valve member  82 , cap  72 ′ and spring  140 . A matched set of parts will accurately produce the desired opening distance and opening pressure in the assembled compact fuel injection nozzle  68 ′. This manufacturing process requires no grinding or intervention by highly skilled personnel to achieve consistently acceptable quality. 
     It should be appreciated that a compact fuel injection nozzle  68 ,  68 ′,  68 ″ in accordance with the invention replaces the nozzle body  12 ,  12 ′, nozzle tip  56 ,  56 ′ and guide member  52 ,  52 ′ of the prior art nozzles  10 ,  10 ′ with a single, unitary nozzle body  70 ,  70 ′,  70 ″. This eliminates the manufacturing steps required to manufacture each of the three components separately, measuring the guide member  52 ,  52 ′ and nozzle tip  56 ,  56 ′ for fit with the nozzle body  12 ,  12 ′, and press-fitting and staking the guide member  52 ,  52 ′ and nozzle tip  56 ,  56 ′ to the nozzle body  12 ,  12 ′. The use of three separate components to form a complete prior art nozzle body was necessitated by limitations within the prior art manufacturing process. 
     The nozzle tip  56 ,  56 ′ and guide member  52 ,  52 ′ must be composed of a relatively hard metal to provide the proper operating characteristics. The prior art machining process could not machine the axial bore if the valve body  12 ,  12 ′ was composed of the same material as the nozzle tip  56 ,  56 ′ and guide member  52 ,  52 ′. Consequently, the nozzle body  12 ,  12 ′ of prior art nozzles  10 ,  10 ′ is composed of carbon steel. The manufacturing process which has been developed to produce the compact fuel injection nozzle  68  utilizes coolant at a higher pressure (up to 2000 psi) in a manner which had not been envisioned before. The subject manufacturing equipment and process directs a stream of this high pressure coolant into the nozzle body  70  as the axial bore  84  is machined to cool the work area, provide lubrication, and to eject chips out of the work area. As a consequence, an accurate axial bore  84  and valve seat  88  can be ground in the hard material, allowing the entire nozzle body  70  to be manufactured from the same material as a unitary member. In addition, the manufacturing process can manufacture the components to tighter tolerances. 
     The overall length of the compact injection nozzle  68 ,  68 ′,  68 ″ is only 3.00 inches as compared to an overall length of 4.00 inches for the prior art nozzles. The tip shank minimum diameter of the compact injection nozzle is slightly greater (0.220 inches) than that of the prior art nozzles (0.214 inches) and the injector minimum shank diameter is substantially the same as that of the prior art nozzles (0.374 inches). It should be appreciated that the reduced length of the compact nozzle provides increased flexibility of use. It should also be appreciated that the small difference in the tip shank minimum diameter has substantially no impact on the use of the compact injection nozzle  68 . 
     Prior art nozzles  10 ,  10 ′ require a leak-off path to allow the nozzles to be properly tuned in a cost-effective manner. The use of tighter tolerances in conjunction with a fuel injection pump assembly that permits pressures in the fuel inlet  74  to bleed down between injection cycles has eliminated the need to provide a fuel leak-off path. Consequently, the leak-off cap  18 ,  18 ′ of the prior art nozzles  10 ,  10 ′ has been eliminated. This feature is particularly advantageous when the injector nozzle is located in the midst of the valve train, because several possible sources of fuel leaks are eliminated. 
     While preferred embodiments have been shown and described, various modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the present invention has been described by way of illustration and not limitation.