Patent Publication Number: US-2009224079-A1

Title: Fuel injector, valve body remanufacturing process and machine component manufacturing method

Description:
TECHNICAL FIELD  
     The present disclosure relates generally to machine components and processes used in manufacturing and remanufacturing such components, and relates more particularly to a unique welding strategy for anchoring a first body component within a bore in a second body component. 
     BACKGROUND  
     Over many years of machine system design and manufacturing, engineers have developed many ways to form, fashion and couple together system components. Press fitting, threads and welding are familiar examples of joining techniques commonly used. It has long been recognized that service environment, design, materials and other factors may render certain components best suited to one joining technique as compared to others. In the context of fuel injectors, components such as body components are often coupled together with threads. Other relatively small and specialized internal components of fuel injectors are commonly welded together. Laser welding, or other types of welding such as electron beam welding have been used for some time to weld together certain fuel injector components. Certain hard materials which might advantageously be used in manufacturing and remanufacturing fuel injectors, however, are well known to be challenging to weld due to their inherent properties. Limitations in the ability of engineers to weld certain materials has hindered development of improved and more broadly applicable manufacturing and remanufacturing technologies. 
     U.S. Pat. No. 6,441,335 to Nagaoka is directed to one process for welding members different in hardness. In particular, Nagaoka describes welding joint surfaces of a high-hardness number and a low-hardness number to one another by use of a laser or electron beam. Irradiation of the beam is offset from the joint surfaces of the two members by a predetermined distance. This is stated to allow melting provided by the beam to spread from the low-hardness to the high-hardness member. Nagaoka purports to improve weld quality despite the different hardness of the members to be joined. Nagoaka thus represents one example where a specific joining technique was developed based on inherent properties of the materials. 
     SUMMARY  
     In one aspect, a fuel injector includes an injector body having a plurality of body components, one of the body components including an insert positioned at least partially within a bore defined by a second one of the body components. The insert includes a valve seat and an outer diameter abutting an inner diameter of the second one of the body components which defines the bore, at a perimetric interface. The fuel injector further includes a plurality of welds anchoring the insert within the bore, each of the welds including a stitch straddling the perimetric interface. 
     In another aspect, a method of manufacturing a component of a machine system includes, positioning a first body component to be subjected to axial loading in a machine system in a bore defined by a second body component and having a center axis. The method further includes anchoring the first body component in the bore at least in part by welding the first body component to the second body component. Positioning the first body component in the bore includes abutting an outer diameter of the first body component with an inner diameter of the second body component defining the bore, at a perimetric interface. Welding the first body component to the second body component includes forming a plurality of axial load reacting welds between the first body component and the second body component, each of the plurality of axial load reacting welds comprising a stitch straddling the perimetric interface. 
     In still another aspect, a valve body remanufacturing process includes removing a damaged valve seat from within a valve body, and positioning an insert including 52100 steel in place of the removed valve seat. The process further includes forming a substitute valve seat in the insert, and welding the insert to the valve body with a plurality of crack free welds, each of the welds including a stitch straddling a perimetric interface between the insert and the valve body. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         FIG. 1  is a partially sectioned side diagrammatic view of a fuel injector according to one embodiment; 
         FIG. 2  is a sectioned side view of a component of the fuel injector of  FIG. 1  at one stage of a remanufacturing process; 
         FIG. 3  is a sectioned side view of the component shown in  FIG. 2  at another stage of a remanufacturing process; 
         FIG. 4  is a partial sectioned side view of the component shown in  FIGS. 2-3  at yet another stage of a remanufacturing process; 
         FIG. 5  is a sectioned side view of a machine component according to one embodiment; 
         FIG. 6  is an elevational view of a machine component according to one embodiment; 
         FIG. 7  is a close-up view of a portion of the machine component shown in  FIG. 6 ; 
         FIG. 8  is another close up view of a portion of the machine component shown in  FIG. 6 ; 
         FIG. 9  is a sectioned side view through a portion of the machine component shown in  FIG. 6 ; and 
         FIG. 10  is a pulse diagram for a laser welding process according to one embodiment. 
     
    
    
     DETAILED DESCRIPTION  
     Referring to  FIG. 1 , there is shown a fuel injector  10  according to one embodiment. Fuel injector  10  may include an injector body  11  having a plurality of body components. In one example, injector  10  includes a first body component  12  such as a nozzle body having a needle check  30  positioned therein and configured to control fuel injection via a set of nozzle outlets  32 . A nozzle supply passage  28  extends in body component  12 , and into a second body component  14  coupled with body component  12 . A third body component  16  may be coupled with body component  14  and has a piston or plunger  26  positioned therein which is configured to pressurize a fuel for supplying to nozzle supply passage  28 . When the pressure of fuel in nozzle supply passage  28  is sufficient, needle check  30  will open to allow fuel to spray from nozzle outlets  32  into an engine cylinder (not shown) in a conventional manner. 
     Yet another body component  18  may be coupled with body component  16 . A control valve member  40  is positioned at least partially in body component  18  and is movable to control fluid communications between a first fluid passage  22  and a second fluid passage  24 . First fluid passage  22  may be configured to connect with a fuel supply or other fluid supply of an associated engine. Valve member  40  may move between a position blocking a first or upper seat  33  and a second position blocking a second or lower seat  36 . When valve member  40  contacts lower seat  36 , fluid communications past valve seat  36  and, hence, between passages  22  and  24  are blocked. When valve member  40  does not contact lower seat  36 , fluid communications exist between passages  22  and  24 . A timing face  35  may be formed on body component  18  to assist in timing the motion of valve member  40  in a manner known to those skilled in the art. An electrical actuator subassembly  20  may also be provided and coupled with valve member  40  to electrically actuate valve member  40 . Subassembly  20  and valve member  40 , along with various other components, may comprise a control valve assembly of fuel injector  10 . 
     Fuel injector  10  may be of the type where fuel pressurization is achieved by way of piston  26  within injector body  11 . In other words, an actuation fluid supplied via passage  22  may be selectively supplied to piston  26  to pressurize fuel by moving valve member  40  from its position blocking seat  36  to its position at which it does not block seat  36 , in a conventional manner. In other embodiments, fuel injector  10  need not include any internal pressurization mechanism, and fuel might be supplied to injector  10  at an already sufficiently pressurized state from a common rail or the like. It should further be appreciated that fuel injector  10  represents one type of machine system and associated machine components which fall within the scope of the present disclosure, however, the present disclosure is not limited to fuel injectors, engines or even hydraulic systems, as will be apparent from the following description. 
     It is nevertheless contemplated that one practical application of the present disclosure will be in the field of remanufacturing or salvaging hydraulically actuated devices, such as fuel injectors. In the past it was common to scrap many of the components used in hydraulically actuated devices. In particular, valve bodies such as valve body  18  were often scrapped when a valve seat such as seat  36  reached a state of wear or damage where performance was affected. While various techniques for remanufacturing valve bodies have been proposed over the years, in the context of fuel injectors there have existed certain barriers to commercial success. The present disclosure addresses these issues as further described herein by providing strategies for remanufacturing valve bodies such as valve body  18 , in an efficient and practicable manner which does not compromise future performance of the associated hydraulic device, such as fuel injector  10 . In spite of the practical application to the field of remanufacturing, it should be appreciated that new machine components such as fuel injectors, or components using at least some new parts, might be manufactured in the manner described herein. 
     Valve seat  36  may comprise a conical valve seat formed in another body component  34  which comprises an insert  34  positioned in valve body  18 . In one embodiment, insert  34  will comprise an annular ring and consist of a material having a hardness which is greater than a hardness of the material of which valve body  18  is made. In one further embodiment, insert  34  comprises 52100 steel or may consist essentially of 52100 steel. Where injector  10  comprises a remanufactured fuel injector, valve seat  36  may be a substitute valve seat in place of a valve seat originally formed in component  18 . Referring also to  FIG. 2 , there is shown a valve body  18  similar to component  18  of injector  10  at one stage of a remanufacturing process according to the present disclosure. Fuel injector components may be expected to actuate millions, or even billions, of times over the course of a service life. In the case of valve body  18 , the many impacts on its original valve seat with a valve member such as valve member  40 , can lead to several problems. Erosion due to fluid flow, cavitation, and “beat-in” of the original valve seat may result from valve member impacts. When fuel injector  10  is received after removing from service in an engine, its existing valve seat may be worn or otherwise damaged to the point that the injector no longer functions as desired. It should be understood that the term “damaged” should be broadly construed as used herein. Valve seats exhibiting wear, deformation, pitting, cavitation, scratches or any other type of condition developed over time and potentially affecting performance could be considered damaged, as that term is intended to be understood. 
     Remanufacturing of a hydraulic machine component such as a fuel injector which includes valve body  18  may commence by disassembling valve body  18  from other components of fuel injector  10 , after fuel injector  10  is removed from service in an engine system. The components may be cleaned, inspected for severe damage and the like, and then advanced for further processing. In one embodiment, material of valve body  18  which includes the original valve seat  136  may be removed from valve body  18  by machining a bore in valve body  18 . In  FIG. 2 , a machining tool  120  having a rotating cutting or grinding element  122  may be used to machine damaged valve seat  136  from valve body  18  for this purpose. 
     Referring to  FIG. 3 , there is shown valve body  18  at one stage of a remanufacturing process after machining a new bore  44  in valve body  18 , as depicted in  FIG. 2 . In one embodiment, new bore  44  is defined by an inner diameter of valve body  18  and may be formed so that it is coaxial with another bore  42  of valve body  18 . Insert  34  may be press-fit in bore  44 , having a perimetric interface  48  therewith, in place of the material removed when bore  44  is formed. In one embodiment, the press-fit between insert  34  and bore  44  may form a fluid seal or at least substantially form a fluid seal between insert  34  and bore  44 . Flowable curable sealing material such as Loctite, or other materials might be used to create or ensure a fluid seal between insert  34  and bore  44 . Insert  34  may have an outer diameter  46  which abuts bore  44  at perimetric interface  48 . Outer diameter  46  defines a width W of insert  34 , and may further comprise a thickness T perpendicular width W which is less than width W. Thickness T may be less than one-fifth width W. Once insert  34  is press-fit in bore  44 , it may be anchored in bore  44  by forming a plurality of welds between insert  34  and valve body  18 . Welds formed via a beam of coherent light, such as a laser, may be used. In  FIG. 3 , a laser welding apparatus  100  is shown having a base or housing  102  and a laser  104 . Line X represents a beam path of a laser beam generated with laser  104  to weld insert  34  in place. 
     Turning now to  FIG. 4 , there is shown valve body  18  at another stage of a remanufacturing process after insert  34  has been welded to valve body  18 . Another grinding or machining tool  110  having a rotatable grinding or machining element  112  may be used to machine a new seat  36  in insert  34 . Timing face  35  is also shown in  FIG. 4 . Those skilled in the art will appreciate that a relative distance between timing face  35  and seat  36  may be a distance specified based on a desired timing of a valve member such as valve member  40 . It has been discovered that properly locating seat  36  relative to timing face  35  may best be accomplished by forming seat  36  in insert  34  after press-fitting insert  34  with valve body  18 , and after welding insert  34  to valve body  18 . In other embodiments where valve timing precision is less of a concern, or where other means are used to locate seat  36  relative to timing face  35 , seat  36  might be formed in insert  34  prior to press fitting insert  34  with valve body  18 . In some instances, it may also be desirable for timing face  35  to be oriented relatively precisely in a plane perpendicular to an axis G of insert  34 . Axis G may also be a center axis defined by bore  44 . The desire for perpendicularity of time face  35  relative to axis G is due at least in part to an inner diameter  38  of insert  34  serving as a guide for valve member  40  during operation of fuel injector  10 . Where timing face  35  is not perpendicular to axis G, problems relating to valve travel or timing may occur. To avoid these issues, one or both of timing face  35  and inner diameter  38  may be ground or reground during remanufacturing valve body  18  as described herein. 
     Referring also to  FIG. 5 , there is shown another valve body  218  remanufactured according to the present disclosure. Valve body  218  is similar to valve body  18  in that it includes an insert  234  positioned therein which has a valve seat  236  which comprises a substitute for a worn or damaged valve seat previously existing in valve body  218 . Valve body  218  may be used in a fuel injector (not shown) which functions similarly to injector  10  described above, but is constructed differently such that a valve alternately blocking and opening valve seat  236  actuates in a travel direction aligned with a longitudinal axis of the fuel injector, instead of normal to a longitudinal axis of the fuel injector as is the case with fuel injector  10 . 
     Once insert  34  has been welded into valve body  18 , and seat  36  machined in insert  34 , valve body  18  may be reassembled with other remanufactured or new fuel injector components and returned to service in an engine system. 
     Turning now to  FIG. 6 , there is shown valve body  18  in elevation, viewed approximately along a common center axis of bores  42  and  44 . It will be recalled that welding insert  34  to valve body  18  may include anchoring insert  34  in bore  44  of valve body  18  with a plurality of welds  50 . Each of welds  50  may comprise a stitch straddling perimetric interface  48 . Welds  50  may be equally radially distributed about perimetric interface  48 . In one embodiment, at least four welds  50  will be used and in other embodiments a larger number of welds such as at least eight welds may be used. 
     Referring also to  FIG. 7 , there is shown a close-up view of a portion of valve body  18 , illustrating two of welds  50 . Each of welds  50  may have a weld direction W which is transverse to perimetric interface  48 , and in one embodiment may be perpendicular perimetric interface  48 . Referring also to  FIG. 8 , there is shown an even closer view of a portion of valve body  18 . It may be noted that the illustrated weld  50  or stitch includes a set of overlapping solidified weld pools, including a first weld pool  52   a  located at least predominantly in insert  34  and a last weld pool  52   b  located at least predominantly in valve body  18 . Other weld pools may lie between pools  52   a  and  52   b , represented approximately by each weld “ripple”  53  visible in  FIG. 8 . A length of each weld  50  may be about 0.080 inches in one embodiment. The set of weld pools which includes welds  52   a  and  52   b  will typically include at least three weld pools and defines weld direction W. In the embodiment shown, the set of weld pools are formed in essentially a straight line, and result from the path traversed by laser  104  during welding insert  34  to valve body  18  as further described herein. 
     It may be noted from the  FIG. 8  illustration that insert  34  includes a first land area  37  having an edge which comprises outer diameter  46  of insert  34  located at perimetric interface  48 . Valve body  18  may include a second land area  39  having an edge comprising the portion of the inner diameter of valve body  18  which defines bore  44 . The edges  44  and  46  of land areas  39  and  37 , respectively, are aligned at perimetric interface  48 . It may further be noted that the illustrated weld  50  extends from a position within land area  37  to another position within land area  39 . 
     Turning to  FIG. 9 , there is shown a cross section through a portion of valve body  18  and insert  34 , as well as through a weld  50 . Weld  50  includes a first weld portion  54  within insert  34 , a second weld portion  55  which is within each of insert  34  and valve body  18  and straddles perimetric interface  48 , and a third weld portion  56  which is within valve body  18 . In one embodiment, first weld portion  54  may consist of melted then solidified material of insert  34 , third weld portion  56  may consist of melted then solidified material of valve body  18 , and second weld portion  55  may consist of a mixture of melted then solidified material of insert  34  and valve body  18 . 
     INDUSTRIAL APPLICABILITY  
     The fields of remanufacturing and salvaging have expanded in recent years, yet viable strategies for restoring certain types of machine components to original specifications have been elusive. Valve bodies are one example of a class of machine components which it is known to salvage and return to service, but largely by strategies having various drawbacks. Valve seat regrinding in various forms has been known for many years, but changes in a distance between the reground valve seat and a timing face for the associated valve member tend to occur from regrinding and may be difficult to remedy. The timing face itself may be reground to return the distance to the valve seat to a specified distance, however, regrinding of the timing face can shorten the valve body, particularly causing problems where the valve seat and timing face are reground multiple times. Eventually, regrinding may also expose un-hardened material not suitable as a valve seat. It may also be difficult to locate machine tools during regrinding a valve seat precisely enough to maintain the valve seat location relative to other features within specified tolerances. Further still, in some instances valve seat damage, wear, etc., may be severe enough that regrinding cannot cure the defects without altering the valve body to the point that operation is compromised. Where applied in the context of remanufacturing, the present disclosure overcomes the problems and shortcomings associated with many earlier strategies for valve seat repair or refurbishing. In many instances it will be unnecessary to regrind a valve timing face of a valve body, as a valve seat newly formed in an insert can be located at a specified distance from the valve timing face. Since inserts contemplated herein may be formed from 52100 steel, the valve seat in the insert will tend to be relatively highly resistant to wear and damage. Should a valve body remanufactured as described herein be removed from service for another round of remanufacturing, its valve seat may be reground to give the valve body yet another service life, without exposing soft material. 
     Another feature of the present disclosure applicable in remanufacturing valve bodies, particularly those of hydraulically actuated control valves for fuel injectors, is the welding strategy disclosed herein. When a valve member, such as poppet valve member  40  shown in  FIG. 1  actuates, it tends to subject valve seat  36  to relatively high axial loading. Over the course of a service life, valve member  40  may hit valve seat  36  many times, as described herein, with relatively high axial force. A desire to use relatively hard materials for insert  34 , and the need to react relatively high, repetitive axial loads on insert  34 , is answered by the presently described welding strategy. 
     Conventional wisdom in the welding arts has for many years been that successful welding of 52100 steel and certain other materials is nearly or totally impossible. Even where some degree of fusion between a component formed from 52100 steel and another component is achieved, cracks tend to form almost immediately after welding ceases. Development of cracks has prevented engineers from welding 52100 steel in most, if not all industrial applications. Returning to  FIGS. 7 ,  8  and  9 , it may be noted that each weld  50  is crack free. Formation of welds  50  without cracks is believed to result at least in part from the manner in which laser  104  is operated during welding insert  34  to valve body  18 . 
     In one embodiment, each weld  50  will be initiated by first applying a beam from laser  104  to insert  34 . In general, laser  104  may form first weld pool  52   a  which is at least predominantly and typically entirely in insert  34 , and then form a string of successive overlapping weld pools which progress to last weld pool  52   b , at least predominantly and typically entirely in valve body  18 . It will be recalled that insert  34  may consist essentially of 52100 steel in one embodiment, and may be relatively homogeneous. Thus, formation of first weld pool  52   a  may result from melting of the relatively homogeneous 52100 steel. As welding of a particular weld  50  progresses, material comprising the weld pools as welding approaches and then traverses perimetric interface  48  may gradually begin to include material of valve body  18 . When welding has passed across perimetric interface  48  material comprising the weld pools may eventually consist entirely of material of valve body  18 . 
     It is believed that initiating welding in first weld portion  54 , relatively homogeneous material of insert  34 , then relatively gradually moving into second weld portion  55 , mixed material of both insert  34  and valve body  18 , and then completing welding in third weld portion  56 , relatively homogeneous material of valve body  18 , allows a more gradual heating up and cooling down of the material which eventually solidifies to form each weld  50 . This differs from earlier welding strategies along a cylindrical perimetric interface where heating and/or cooling of the materials to be joined was relatively more rapid. Circumferential stitch welds, in contrast to the radial stitch welds  50  described herein, would be one such example. It is further believed that the relatively gradual temperature changes in the second weld portion  55  comprising a mixture of material of insert  34  and material of valve body  18  inhibits the formation of cracks upon cooling, as the material appears to experience relatively less thermal stress associated with welding. 
     Laser  104  may comprise a Lumonics JK 701H YAG Laser having a max power of 500 Watts in one embodiment, capable of pulsed operation to form the sets of weld pools comprising each weld  50 , as described herein. The spot size of laser  104  may be about 0.5 millimeters in one embodiment, pulse duration may be about 20 milliseconds and frequency may be about 10 Hz. Laser speed may be about 1.96 millimeters per second. In other embodiments, differing laser parameters may be used. Turning now to  FIG. 10 , there is shown a laser pulse diagram illustrating one exemplary power curve for laser  104  according to the present disclosure and representing one pulse P. It will be recalled that laser  104  may have a maximum power output of about 500 Watts. Pulse P may include a plurality of pulse segments, including a first segment A having a duration of about 6 milliseconds at about 10% of max power, a second segment B having a duration of about 9 milliseconds at about 35% of max power and a third segment C having a duration of about 5 milliseconds at about 20% of max power. Each of the pulses used in forming each weld  50  may have the same power profile as that shown in  FIG. 10 . 
     The present description is for illustrative purposes only, and should not be construed to narrow the breadth of the present disclosure in any way. Thus, those skilled in the art will appreciate that various modifications might be made to the presently disclosed embodiments without departing from the full and fair scope of the present disclosure. For example, while much of the foregoing description emphasizes the context of fuel injectors, and in particular remanufacturing fuel injectors, the present disclosure is not thereby limited. Other machine systems such as engine systems other than fuel systems, and even technologies unrelated to engines may have body components which are subjected to axial loading, and thus need to be securely anchored in a second body component, such as in a bore. 
     Welding and potentially press fitting of one body component of a machine system within a second body component of a machine system, as described herein, can provide a means for reacting axial loads to provide a robust anchoring strategy for machine components in a wide variety of technologies. Welds  50  may thus comprise axial load reacting welds of a type suitable for use in a broad variety of applications. One example outside the context of fuel systems would be in the field of actuators where mechanical stops of relatively hard material are often used to react axial loads on actuators rods and the like. Such stops can wear over time and need to be replaced. Inserting an insert as described herein into certain actuator bodies, and welding it therein, could provide a means for remanufacturing some systems which were previously scrapped. Other aspects, features and advantages will be apparent upon an examination of the attached drawings and appended claims.