Patent Publication Number: US-2019170037-A1

Title: Diesel dosing unit having an anti-coking injector assembly, and methods of constructing and utilizing same

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application claims the benefit of U.S. provisional application 62/595,358, filed Dec. 6, 2017, and entitled “A Diesel Dosing Unit Having an Anti-Coking Injector Assembly, and Methods of Constructing and Utilizing Same,” the content of which is hereby incorporated by reference herein in its entirety. The present application is related to U.S. nonprovisional application Ser. No. 15/833,683, filed Dec. 6, 2017, and titled, “Anti-Coking Injector Assembly for a Diesel Dosing Unit, and Methods of Constructing and Utilizing Same,” 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 which combines with a housing for a reductant delivery unit for use in a diesel dosing system. 
     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 be 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/or complex thermal isolation of the DDU injector. 
     SUMMARY 
     Example embodiments are directed to a DDU that is robust, simple in design and inexpensive to manufacture. In an example embodiment, the DDU includes a fuel injector including a first housing, a fluid inlet disposed at a first end of the first housing for receiving fluid, a fluid outlet disposed at a second end of the first housing for exiting fluid from the first housing, the first housing defining at least in part a fluid path through the first housing between the fluid inlet and the fluid outlet. The fuel injector further includes an actuator unit and a valve assembly operably coupled thereto for selectively discharging fluid in the fluid path from the fluid outlet when the valve assembly is in an open state and for preventing fluid in the fluid path from exiting the fluid outlet when the valve assembly is in a closed state. The DDU also includes an attachment assembly having a second housing or body with a first end attached or attachable to the second end of the first housing and a second end. The second housing at least partly defines a fluid path between the first end of the second housing and the second end thereof. In addition, the DDU includes a reductant delivery unit (RDU) housing in which the fuel injector and the attachment assembly are disposed. The RDU housing is configured to directly attach to an exhaust pipe of a vehicle. 
     In an example embodiment, the attachment assembly further includes a seat fixedly disposed within the second housing; and an attachment assembly needle movably disposed within the second housing and including a first end portion, the attachment assembly needle movable between a first position in which the first end portion of the attachment assembly needle contacts and provides a sealing engagement with the seat of the attachment assembly so as to prevent fluid from exiting the second housing through the second end thereof, and a second position in which the first end portion of the attachment assembly needle extends outwardly from the second end of the second housing and is spaced from the seat of the attachment assembly. A spring member is disposed within the second housing and coupled to the attachment assembly needle so as to bias the attachment assembly needle towards the first position thereof and prevent fluid in the second housing from exiting the second housing through the second end thereof. In this way, when the valve assembly is in the open state, fluid in the fuel injector exits the fuel injector from the fluid outlet thereof and enters the fluid path of the second housing under pressure so as to cause the attachment assembly needle to overcome the bias of the spring member and move to the second position for allowing the fluid to exit the second housing from the second end thereof. When the valve assembly is in the closed state, fluid in the fuel injector is prevented from passing into the fluid path of the second housing so as to cause the spring member to bias the attachment assembly needle to move to the second position and prevent the fluid from exiting the second housing from the second end thereof. 
     In an example embodiment, the fuel injector and the attachment assembly are dimensioned to have a combined profile which matches a profile of an injector of an existing RDU, and the RDU housing is a housing for the existing RDU. 
     In an example embodiment, the DDU includes at least one gasket disposed downstream of the attachment assembly, relative to a direction of fluid flow through the injector assembly. The at least one gasket at least partly thermally isolates the fuel injector and the attachment assembly from the exhaust pipe. The DDU may further include a flange having a sidewall into which an end portion of the DDU housing is disposed, the flange including an inner surface extending in a radial direction, wherein the at least one gasket includes a first gasket disposed between a downstream end portion of the attachment assembly and the inner surface of the flange. In addition, the flange may further include a downstream-facing outer surface disposed in the radial direction of the DDU, and the DDU may further include a second gasket disposed between the outer surface of the flange and a boss of the exhaust pipe of the vehicle. 
     In an example embodiment, the DDU is an actively cooled DDU and the RDU housing includes a coolant inlet for receiving a coolant, a coolant outlet for returning a coolant, and a coolant jacket in fluid communication with the coolant inlet and the coolant outlet. The coolant jacket surrounds the attachment assembly and at least part of the fuel injector. 
    
    
     
       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 ; 
         FIG. 3  is a detailed cross sectional view of an attachment assembly of the fluid injector of  FIGS. 1 and 2 ; 
         FIG. 4  is a perspective view of an air cooled DDU having therein the fluid injector of  FIGS. 1-3 , according to an another example embodiment; 
         FIG. 5  is a side view of the air cooled DDU of  FIG. 4 ; 
         FIG. 6  is a partial cross sectional view of the DDU of  FIG. 4 ; 
         FIG. 7  is a side view of a liquid cooled DDU having therein the fluid injector of  FIGS. 1-3 , according to another example embodiment; and 
         FIG. 8  is a partial cross sectional view of the DDU of  FIG. 7 . 
     
    
    
     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 or body  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 or body  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. 
     As mentioned above, injector assembly  10  utilizes an existing, lower cost fuel injector as fluid injector  12 , which lowers the cost of manufacturing injector assembly  10  and results in a robust fluid injector design. In accordance with another example embodiment, injector assembly  10  is utilized in a DDU as a DDU injector. In the embodiment, the profile (and/or outer dimensions) of injector assembly  10  matches or nearly matches the profile (and/or outer dimensions) of a fluid injector used in existing reductant delivery units (RDUs) of a selective catalytic reduction (SCR) system. As a result of having the same or similar profile/outer dimensions of an existing RDU injector, a DDU having injector assembly  10  may utilize an existing RDU housing of the existing RDU fluid injector. Using, with injector assembly  10 , the existing RDU housing with proven thermal protection of the RDU fluid injector results in a further lowering of design and manufacturing costs and a faster time to market. With some DDUs having smaller sales volumes than RDU sales volumes, utilizing existing injector and RDU technology in DDU designs provides significant cost advantages for DDU manufacturers. 
     In example embodiment, fluid injector  12  is an existing gasoline based port fuel injector. The port fuel injector has an existing counterpart injector having an extended tip which is used as an existing RDU injector of an existing RDU SCR system. Among other things, the extended tip of the counterpart RDU fuel injector provided greater distance of some components of the injector from the heated exhaust path of a vehicle and resulted in an injector having a greater length. In the example embodiment, attachment assembly  14  is sized so that when combined with the gasoline based port fuel injector used for fluid injector  12 , the total length and other dimensions defining the profile of injector assembly  10  matches the total length and other dimensions defining the profile of the counterpart RDU injector. By utilizing an existing port fuel injector and sizing the attachment assembly  14  so that injector assembly  10  has the same dimensions as an existing RDU injector, the RDU housing of the existing RDU injector may be used as the housing for a DDU having injector assembly  10 . 
       FIGS. 4-6  illustrate a passive or air cooled DDU  100  according to an example embodiment. DDU  100  includes injector assembly  10  as the DDU injector as described above, with fluid injector  12  being an existing gasoline port fuel injector having an RDU injector counterpart with an elongated tip. DDU  100  allows for direct mounting of injector assembly  10  to the exhaust pipe of a vehicle.  FIGS. 4-6  illustrate DDU  100  having DDU housing formed as an upper housing  102  and a lower housing  104 . The DDU housing is the housing of an existing RDU. DDU  100  further includes a diesel fuel inlet  106  for receiving diesel fuel which passes through fluid injector  12  and attachment assembly  14  and is selectively discharged from the downstream end of attachment assembly  14 . Both upper housing  102  and lower housing  104  includes a plurality of through-holes defined along the housings for allowing air to pass though the housings and regulate temperatures internal to the housings. Injector assembly  10  is disposed in an interior carrier  106 . Upper housing  102  and lower housing  104  are connected to carrier  106 , such as by folding tangs of an end portion of lower housing  104  so as to surround and clamp in place end portions of upper housing  102  and carrier  106 . 
     DDU  100  further includes an injector flange  108  which receives therein the downstream end of lower housing  104 . Specifically, flange  108  includes a sidewall  108 A which defines an inner space in which the downstream end of lower housing  104  is disposed. Injector flange  108  includes internal surface structure, generally indicated at  110 , that defines a flange outlet  112  that delivers fluid into an exhaust boss  114  of an exhaust flow path. Thus, as shown in  FIG. 6 , the flange  108  is coupled to an end of the exhaust boss  114  with the flange outlet  112  communicating with a bore of the boss  114 . The bore communicates with the exhaust flow path. 
     The internal surface structure  110  of flange  108  also includes a largely frusto-conical surface that is joined with at least one radius surface. In the embodiment, the conical surface defines the open end of the flange  38  and is joined with the radius surface, with the radius surface being joined directly with a gasket shelf surface  116  of the flange  108 . The gasket shelf surface  116  is disposed generally perpendicular with respect to a longitudinal axis of the injector assembly  10 . 
     DDU  100  further includes an isolating gasket  118  which rests on the gasket shelf surface  62  to seal the flange  108  with respect to the carrier  106 , and a second isolating gasket  120  disposed between a downstream end of flange  108  and an upstream end of exhaust boss  114 . Both isolating gaskets  118  and  120  serve to thermally isolate injector assembly  10  from high temperatures of the exhaust stream in the exhaust flow path of the vehicle, by blocking heat flow paths from the exhaust pipe through exhaust boss  114  and flange  108  to injector assembly  10 . DDU  100  thus uses isolating gaskets  118  and  120  as well as cooling airflow around DDU  100  to keep temperatures of injector assembly  10  from high temperatures which may damage injector assembly  10 . 
     Passively cooled DDU  100  is utilized for applications in which mounting locations along the exhaust pipe have lower temperatures and available cooling airflow. For mounting locations where the ambient temperature and the exhaust gas temperatures are higher, an actively cooled DDU may be used. Referring to  FIGS. 7 and 8 , there is shown an actively cooled DDU  200  according to another example embodiment. DDU  200  includes injector assembly  10  disposed in an existing RDU housing  201 . DDU  200  is actively cooled by passing coolant around injector assembly  10  so as to maintain temperatures thereof within a desirable temperature range. Housing  201  includes a diesel fuel inlet  202  for receiving diesel fuel which flows into injector assembly  10  for being selectively sprayed into the exhaust flow path of the corresponding vehicle. Housing  201  further includes a coolant inlet  204  for receiving coolant from a coolant source, and a coolant outlet  206  for returning coolant to the coolant source for recirculation. Housing  201  further includes a coolant jacket  208  which is fluidly coupled to coolant inlet  204  and coolant outlet  206 . Coolant jacket  208  is disposed around injector assembly  10 , and particularly around the portions of injector assembly  10  closest to the exhaust pipe, such as attachment assembly  14  and the downstream portion of fluid injector  12 . As shown in  FIG. 8 , coolant jacket  208  extends to or nearly to the bottom or downstream end of attachment assembly  14 . Actively cooled DDU  200  includes a V-clamp mount for mounting DDU  200  directly to the vehicle exhaust pipe. 
     It is understood that features of passively cooled DDU  100  and actively cooled DDU  200  may be utilized for providing further thermal protection to injector assembly  10 . For example, DDU  200  may include isolating gaskets  118  and/or  120  to disrupt any heat transfer path from the exhaust pipe to injector assembly  10 . 
     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.