Patent Application
20090224079
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.
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.
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.
Referring to
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
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
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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.
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It may be noted from the
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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
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
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 52a 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 52b, 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 52a 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
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.
