Patent Publication Number: US-2019170104-A1

Title: Anti-coking injector assembly  for a diesel dosing unit, and methods of constructing and utilizing same

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application is related to U.S. provisional application ______, filed ______, and having attorney docket number 2017P08478US, the content of which is incorporated by reference herein. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to an attachment to a fuel injector for creating a unitary, outward opening injector assembly for use in applications in which the injector is susceptible to coking. 
     BACKGROUND 
     In a diesel engine, exhaust gas temperature management is critical for meeting emissions requirements. One method of exhaust gas temperature management is known as “post-injection” which utilizes an additional injection of fuel from the in-cylinder fuel injector during the exhaust stroke. Post-injection is known to cause oil dilution and requires more frequent engine maintenance. Another method of exhaust gas temperature management is a dedicated system that injects fuel directly into the exhaust stream. In particular, diesel fuel is delivered or otherwise sprayed into the exhaust stream in front of a diesel oxidation catalyst in order to provide the thermal energy required to re-burn captured particulates at the diesel particulate filter or to thermally manage the exhaust system temperature conditions. The delivery device is referred to as a diesel dosing unit (DDU). Because dedicated systems for performing these methods are on-demand, there may extended periods of inactivity. Extended periods of high temperature and inactivity have been seen to cause the DDU injector to be stuck in the closed position. This leads to complicated injector designs, including remotely mounting DDU injectors from the diesel engine exhaust pipe and complex thermal isolation of the DDU injector. 
     SUMMARY 
     Example embodiments of the present disclosure overcome shortcomings of injectors and satisfy a need for an improved anti-coking injector with resistance to being stuck in the closed position. According to an example embodiment, there is provided a fluid injector assembly having an attachment assembly. The attachment assembly includes a housing having a first end and a second end, the housing at least partly defining a fluid path between the first end of the housing and the second end thereof; a seat fixedly disposed within the housing; and a needle movably disposed within the housing and including a first end portion. The needle is movable between a first position in which the first end portion of the needle contacts and provides a sealing engagement with the seat so as to prevent fluid from exiting the housing through the second end thereof, and a second position in which the first end portion of the needle extends outwardly from the second end of the housing and is spaced from the seat of the attachment assembly for allowing fluid in the housing to exit the housing through the second end thereof. The attachment assembly further includes a spring member disposed within the housing and coupled to the needle so as to bias the needle towards the first position and prevent fluid in the housing from exiting the housing through the second end thereof. The first end of the housing is attached to a fluid outlet of a fluid injector having an inward opening valve, with the fluid path of the housing being in fluid communication with a fluid path of the fluid injector. The resulting combination of the fluid injector and the attachment assembly is suitable for use in applications in which injectors are susceptible to coking and being stuck in a closed state. 
     In at least some example embodiments, the fluid injector includes an injector housing, a fluid inlet disposed at a first end of the injector housing for receiving fluid, and a fluid outlet disposed at a second end of the injector housing for exiting fluid therefrom. The injector housing defines at least in part an injector fluid path through the injector housing between the fluid inlet and the fluid outlet. The fluid injector further includes an actuator unit and a valve assembly operably coupled thereto for selectively discharging fluid in the injector fluid path from the fluid outlet when the valve assembly is in an open state and for preventing fluid in the injector fluid path from exiting the fluid outlet when the valve assembly is in a closed state. The first end of the housing of the attachment assembly is connected to the fluid injector at or near the fluid outlet thereof. 
     In an example embodiment, the fluid injector is a fuel injector and the fluid injector assembly is a fuel injector or a diesel dosing unit (DDU) injector. In another example embodiment, fluid injector is a gasoline based port fuel injector. 
     When the valve assembly of the fluid injector is in the open state, fluid in the fluid injector exits the fluid injector from the fluid outlet thereof and enters the fluid path of the housing of the attachment assembly so as to cause the needle to overcome the bias of the spring member and move to the second position, and when the valve assembly of the fluid injector is in the closed state, fluid in the fluid injector is prevented from passing into the fluid path of the housing of the attachment assembly so as to cause the spring member to bias the needle of the attachment assembly to move to the first position. 
     In an example embodiment, the housing of the attachment assembly is laser welded to the second end of the injector housing, and the seat of the attachment assembly is laser welded to the housing thereof. 
     The attachment assembly may further include a spring stop disposed in the housing of the attachment assembly. A first end of the spring member is coupled to the spring stop and a second end of the spring member is coupled to the seat of the attachment assembly. The spring stop is connected to an axial end of the needle, and the needle, the seat, the spring and the spring stop form a subassembly of the attachment assembly. 
     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
         FIG. 1  is a side view of a fluid injector according to an example embodiment; 
         FIG. 2  is a partial cross sectional side view of the fluid injector of  FIG. 1 ; and 
         FIG. 3  is a detailed cross sectional view of an attachment assembly of the fluid injector of  FIGS. 1 and 2 . 
     
    
    
     DETAILED DESCRIPTION 
     The following description of the example embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. 
     Example embodiments of the present disclosure are directed to an injector assembly which utilizes an existing inward-opening fluid injector, such as a fuel injector, as the metering device of the injector assembly, and an attachment assembly which is connected to the fuel outlet of the fuel injector and which includes an outward opening valve. The resulting injector assembly is suitable as an injector for a DDU (i.e., a DDU injector) or for other applications in which a fluid injector is susceptible to coking. For reasons of simplicity, the injector assembly will be described hereinbelow for use as a DDU injector for a diesel dosing system (DDS). 
     Referring now to the  FIGS. 1 and 2 , there is shown an injector assembly  10  which is resistant to coking. According to an example embodiment, injector assembly  10  includes a fluid injector  12  and an attachment assembly  14  attached to a downstream end of fluid injector  12 . Fluid injector  12  is an existing fluid injector, such as an existing fuel injector. In one example embodiment, fluid injector  12  is a gasoline based port fuel injector. Fluid injector  12  is an inward opening fluid injector and/or has a valve assembly which is inward opening. In the example embodiments, fluid injector  12  is utilized in injector assembly  10  as the metering device for controlling the flow of fluid exiting injector assembly  10 . In the context of injection assembly  10  forming a DDU injector, fluid injector  12  meters the flow of diesel fuel from fluid injector  12  for injection into the exhaust pipe of a diesel engine. Use of an existing, relatively low cost injector, such as an existing fuel injector and particularly an existing gasoline based port fuel injector, provides a simplified, inexpensive and more robust injector assembly  10 . 
     It is understood that fluid injector  12  may be any of a number of different inward opening fluid/fuel injectors. In general terms, fluid injector  12  includes components and/or parts commonly found in fluid injectors: a housing  15 ; a fluid inlet  16  in which fluid is received from a fluid source; and a fluid outlet  18  which provides a metered flow of fluid exiting fluid injector  2 . Housing  15  may at least partly define a fluid path between fluid inlet  16  and fluid outlet  18 . Fluid injector  12  may further include an actuator unit  20  disposed within housing  15 . In an example embodiment, actuator unit  20  includes a coil  20 A, pole piece  20 B and a movable armature  20 C disposed in proximity to coil  20 A. Energizing coil  20 A, such as by passing a current through the coil, causes armature  20 C to move in an axial direction within housing  15  towards pole piece  20 B. Fluid injector  12  may further include a valve assembly  22  having an axially movable valve needle  24  with one end coupled to armature  20 C and a second end; and a valve seat  26  disposed at or near the fluid outlet  18  of fluid injector  12 . Valve needle  24  is movable between a first (closed) position in which the second end of valve needle  24  sealingly contacts valve seat  26  so that fluid in fluid injector  12  is prevented from exiting through fluid outlet  18  (shown in  FIGS. 2 and 3 ), and a second (open) position in which the second end of valve needle  24  is moved in an upstream direction, relative to the flow of fluid through fluid injector  12 , so that the second end of valve needle  24  is spaced apart from valve seat  26  to allow fluid in the fluid path of fluid injector  12  to exit through fluid outlet  18 . A spring (not shown) is disposed in the housing  15  and coupled to armature  20 C to bias the armature away from pole piece  20 B, which biases the valve needle  24  to the first (closed) position. Energizing coil  20 A causes armature  20 C to move so that the valve needle  24  moves to the second (open) position. In this way, the inward opening valve assembly  22  is controlled via coil  20 A to open and close the valve assembly to selectively provide a metered amount of fluid from fluid injector  12 . 
     Best seen in  FIG. 2  and, in an enlarged view, in  FIG. 3 , attachment assembly  14  includes a housing having a first (upstream) end  30  and a second (downstream) end  32 . Attachment assembly  14  further includes, disposed in housing  34 , an outward opening valve subassembly including a needle  36 , seat  38 , return spring  40  and spring stop  42 . Needle  36  and seat  38  each includes a sealing surface which when engaged with each other, provides a seal which prevents fluid in housing  34  from exiting through second end  32  thereof. Spring stop  42  includes a pocket  42 A defined along one axial side thereof which receives an end portion of spring  40 . A second end portion of spring  40  engages with seat  38 . An axial end portion of needle  36  is connected to spring stop  42 , and a central portion of needle  36  is disposed within spring  40 . The second axial end portion of needle  36  is connected to spring stop  42 . Spring  40  biases needle  36  so that needle  36  sealingly engages with seat  38 . Needle  36  and seat  38  are dimensioned so that fluid exiting housing  34  has a largely cone shaped pattern. Once needle  36 , seat  38 , spring  40  and spring stop  42  are connected to each other in this way to form the valve subassembly, the valve subassembly is inserted into and fixed within housing  34 . In particular, seat  38  is welded within the inner surface of housing  34 , such as with a laser weld. The components of the valve subassembly—needle  36 , seat  38 , spring  40  and spring stop  42 —may be constructed from stainless steel or comparable materials. 
     As mentioned, attachment assembly  14  is connected to the downstream end of fluid injector  12  near fluid outlet  18  thereof. In one embodiment, first end  30  of housing  34  of attachment assembly  14  is laser welded to the downstream end of housing  15  of fluid injector  12 . The connected end of housing  34  may be configured so that the connected end is press fit into the inner surface of the end of housing  15  before the laser welding. Alternatively, attachment assembly  14  may be attached to fluid injector  12  using other techniques, such as crimping, threaded engagement, brazing, etc. 
     With attachment assembly  14  connected to fluid injector  12 , injector assembly  10  is formed as an outward opening injector, with fluid injector  12  utilized as the metering valve of injector assembly  10 . Fluid injector  12  controls the flow of fluid through injector assembly  10 , with the fluid discharged from injector assembly  10  having a spray pattern defined by attachment assembly  14  and particularly the dimensions of needle  36  and seat  38  of attachment assembly  14 . 
     In use, fluid which entered the fluid path of fluid injector  12  via fluid inlet  16  is prevented from exiting the fluid path through fluid outlet  18  when coil  20 A of fluid injector  12  is de-energized, which allows for the spring within fluid injector  12  to bias valve needle  24  so as to contact and sealingly engage with valve seat  26 , thereby placing valve assembly  22  in the closed state. With no fluid build-up or pressure within housing  34  of attachment assembly  14  due to valve assembly  22  being closed, spring  40  urges needle  36  against seat  38  so as to prevent fluid from exiting attachment assembly  14  through second end  32 . In this state, injector assembly  10  is closed. When coil  20 A is energized, armature  20 C is urged in the upstream direction towards fluid inlet  16 , thereby separating the end of valve needle  24  from valve seat  26  so as to allow the fluid in the fluid path of fluid injector  12  to exit fluid injector  12  through fluid outlet  18 . Such exiting fluid enters housing  34  of attachment assembly  14  which causes fluid pressure in housing  34  to build against spring stop  42  and/or needle  36  until the pressure overcomes the bias forces on needle  36  by spring  40  and causes needle  36  and spring stop  42  to move downwardly so that needle  36  separates from seat  38  and allows fluid in attachment assembly  14  and fluid injector  12  to exit injector assembly  10  via seat  38 . In this state, injector assembly  10  is in the open position. The exiting fluid has a spray pattern dependent upon the dimensions of needle  36  and seat  38 . 
     With injector assembly  10  using fluid injector  12  as a metering device and attachment assembly  14  providing a flow pattern for fluid exiting attachment assembly  14 , injector assembly  10  utilizes an existing fluid injector having an inward opening injector valve and attachment assembly  14  to result in an integrated, unitary injector assembly. Attachment assembly  14  having an outward opening valve subassembly formed by needle  36 , seat  38 , spring  40  and spring stop  42  advantageously prevents coking at or around seat  38  and prevents needle  36  from sticking thereto. Injector assembly  10  finds use in applications in which injectors are susceptible to coking and/or valves sticking, such as DDUs. 
     The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.