Patent Publication Number: US-2019168243-A1

Title: Outward opening injector for exhaust aftertreatment systems

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application claims the benefit of U.S. provisional application 62/595,514, filed Dec. 6, 2017, and entitled “Outward Opening Injector for Exhaust Aftertreatment Systems,” the content of which is hereby incorporated by reference herein in its entirety. 
    
    
     FIELD OF INVENTION 
     The invention relates generally a fluid injector for a Reductant Delivery Unit (RDU) and/or Diesel Delivery Unit (DDU) and, more particularly, to such a fluid injector having an outwardly opening injector valve. 
     BACKGROUND 
     Stringent emissions legislation in Europe and North America is driving the implementation of new exhaust aftertreatment systems, particularly for lean-burn technologies such as compression-ignition (diesel) engines and stratified-charge spark-ignited engines (usually with direct injection) that are operating under lean and ultra-lean conditions. Exhaust aftertreatment technologies are currently in production that treat NOx under these conditions. One of these technologies comprises a catalyst that facilitates the reactions of ammonia (NH 3 ) with the exhaust nitrogen oxides (NOx) to produce nitrogen (N 2 ) and water (H 2 O). This technology is referred to as Selective Catalytic Reduction (SCR). Ammonia is difficult to handle in its pure form in the automotive environment, therefore it is customary with these systems to use a liquid aqueous urea solution, typically at a 32% concentration of urea (CO (NH 2 ) 2 ). The solution is referred to as AUS-32, and is also known under its commercial names of AdBlue (EU), and DEF-Diesel Exhaust Fluid (USA). The urea is delivered to the hot exhaust stream and is transformed into ammonia prior to entry in the catalyst. 
     Because of a combination of increasing engine efficiency (resulting in low exhaust gas temperatures) and the need to enable NOx reduction very early in the certification cycles, automakers are increasingly turning toward so-called “close-coupled” exhaust system architectures—meaning installation of the SCR catalyst, and therefore also the injection point, much closer to the engine itself. As a result, mixing lengths—the distance from the injection point to the catalyst—are becoming much shorter. In certain cases, this means that the injected fluid needs to spread out to a wide area very rapidly in order to provide a good homogeneous delivery to the catalyst face. 
     Alternatively, systems are under development whereby active direct exhaust injection of hydrocarbon fluids is employed. The injected fuel is typically delivered to an oxidation catalyst and the resulting exothermic oxidation reaction increases the exiting exhaust gas temperature. This process helps accelerate the lightoff of the catalyst and in low speed, low load operating conditions helps maintain the exhaust temperatures above the catalyst lightoff temperature for optimized emissions conversion rates. There is a concern with state-of-the-art injection technologies described below that tip coking can occur that would obstruct flow passages and degrade the functionality of the injector. 
     Today&#39;s RDUs and DDUs are typically equipped with spray generators having thin disks with multiple orifice holes. The delivery units are typically equipped with solenoid-actuated valves. The solenoids include an armature-pole piece configuration wherein the armature action moves a connected valve element upon energizing of the solenoid coil. The movement of the valve element is “inward”, or away from the injector outlet. The fluid then proceeds through a thin disk with orifice holes which generates the desired spray shape and fluid flow rates. The inward-opening orifice-disk approach is typically limited in the cone angle of the spray, or in other words, the effective spray footprint. A typical maximum value for these designs is a cone angle of 30°, within which 90% of the spray is contained. 
     SUMMARY 
     In contrast to existing DDU injector designs which utilize a passively controlled, outward-opening poppet and a remotely located solenoid control valve, example embodiments of the present disclosure describe the implementation of a solenoid-controlled, outward-opening needle configured to generate relatively wide cone angle sprays while also being capable to resist hydrocarbon coking effects. This should allow for more flexibility in the types of sprays that can be provided for close-coupled AUS-32 and exhaust hydrocarbon dosing applications. 
     Example embodiments of the present disclosure overcome shortcomings of existing RDUs and DDUs and satisfy a significant need for an improved delivery unit having an enhanced spray cone angle. In accordance with an example embodiment, there is shown an after-treatment fluid dosing device, including a fluid injector having an inlet port for receiving a fluid, an outlet port for discharging the fluid received by the inlet port, and a valve body extending between the inlet port and the outlet port, the valve body having a through-bore defining a flow path for the fluid through the fluid injector. The fluid injector further includes a valve seat disposed at the outlet port, a valve needle having a first end and a second end and being movable within the valve body between a closed position in which the second end engages with the valve seat to block a flow of fluid from exiting the outlet port and an open position in which the second end is spaced apart disposed in a downstream direction, relative to the flow of fluid through the fluid injector, from the valve seat so as to allow fluid to exit the fluid injector at the outlet port. The valve body, the valve seat and the valve needle form an outwardly opening valve assembly. 
     The fluid injector further includes an actuator unit having a pole piece fixedly disposed within the valve body, an armature coupled to the valve needle, disposed upstream of the pole piece relative to the flow of fluid through the fluid injector, and axially movable within the valve body, and a coil coupled to the valve body and disposed around at least part of the pole piece and the armature such that the coil generates a force when energized to move the armature toward the pole piece so as to cause the valve needle to move from the closed position to the open position. A first spring is disposed between and contacting the pole piece and the armature so as to urge the armature away from the pole piece and move the valve needle to the closed position when the coil is no longer energized. 
     In an example embodiment, the valve seat may include a bore defined through the valve seat and the fluid flows through the bore and around the second end of the valve needle when the valve needle is in the open position, the bore having an inverse conical shape. The actuator unit may be disposed in a longitudinally central region of the fluid injector. 
     In an example embodiment, the valve needle includes a largely cylindrical shape and the second end of the valve needle includes a sealing surface which contacts the valve seat when the valve needle is in the closed position so as to prevent fluid from exiting the fluid injector, with the sealing surface being angled relative to a longitudinal axis of the needle valve. The valve seat includes a contact surface which at least partly defines the bore of the valve seat and engages with the sealing surface of the valve needle when the valve needle is in the closed position, and the contact surface is angled relative to the longitudinal axis of the needle valve. 
     In another example embodiment, a tube adjustably is disposed between the inlet port and the armature, and a calibration spring is disposed between the tube and the armature, the calibration spring urging the armature towards the pole piece. 
     The after-treatment fluid dosing device is a reductant delivery unit or a diesel delivery unit. A shield surrounds at least a part of the fluid injector, the shield including upper and lower shields and a mount coupled to a downstream end portion of the fluid injector, for mounting the along an exhaust pipe of a vehicle. 
     Other objectives, features and characteristics of the present invention, as well as the methods of operation and the functions of the related elements of the structure, the combination of parts and economics of manufacture will become more apparent upon consideration of the following detailed description and appended claims with reference to the accompanying drawings, all of which form a part of this specification. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be better understood from the following detailed description of the preferred embodiments thereof, taken in conjunction with the accompanying drawings, wherein like reference numerals refer to like parts, in which: 
         FIG. 1  is a cross-sectional view of a fluid injector for after-treatment dosing systems, according to an example embodiment; 
         FIG. 2  is an enlarged cross-sectional view of the fluid outlet of the fluid injector of  FIG. 1 ; 
         FIG. 3  is an enlarged elevational view of an end of a fluid valve needle of the fluid injector of  FIG. 1 ; 
         FIG. 4  is a cross-sectional view of an air-cooled after-treatment dosing unit having the fluid injector of  FIG. 1 ; and 
         FIG. 5  is a cross-sectional view of a liquid-cooled after-treatment dosing unit having the fluid injector of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. 
     With reference to  FIG. 1 , a fluid injector according to an embodiment of the present disclosure is shown, generally at  10 . Fluid injector  10  is configured to connect to a source of reductant (not shown) when fluid injector  10  is configured as, and forms part of, an RDU of a Selective Catalytic Reduction (SCR) system of a vehicle. In addition or in the alternative, fluid injector  10  is configured to be connected to a supply of diesel fuel (not shown) when fluid injector  10  is configured as, and forms part of, a DDU of a diesel dosing system. 
     A portion of an inlet tube  17  is disposed within a body  20 . A primary seal member  26 , such as an elastomer O-ring, surrounds part of the inlet tube  17  so as to provide a seal between the inlet tube  17 , the inlet cup  16  ( FIG. 4 ), and body  20 . 
     The fluid injector  10  includes a fluid inlet  12  at an upstream end of the injector, a fluid outlet  14  at a downstream end of the injector, and a fluid passageway  16  extending from fluid inlet  12  to fluid outlet  14 . The fluid passageway  16  may be defined in part by inlet tube  17  and a valve body, as described in greater detail below. Fluid injector  10  is of the solenoid-operated type, having an armature  18  operated by a coil  21 . A pole piece  22  is fixedly disposed within fluid injector  10 , such as within at least part of inlet tube  17 . As shown in  FIG. 1 , armature  18  is disposed upstream of pole piece  22 , relative to a direction of fluid flow from fluid inlet  12  to fluid outlet  14 . An electromagnetic force is generated by electric current from a vehicle&#39;s electronic control unit (not shown) through coil  21  via an electrical interface  23  of fluid injector  10 . When the coil  21  is energized by passing an electric current, armature  18  moves in a downstream direction toward fixed pole piece  22 . The pole piece  22 , armature  18  and coil  21  may be considered to be part of, or otherwise form, an actuator unit, generally indicated  24 , that controls fluid flow exiting fluid injector  10  via fluid outlet  14 , as described in greater detail below. 
     Fluid injector  10  includes a valve assembly, generally indicated at  30 , which is coupled to and cooperates with the actuator unit for passing and blocking the flow of fluid out of fluid outlet  14 . Valve assembly  30  includes a valve body  32  having a cavity defined therethrough, a moveable valve needle  34  disposed at least partly in the cavity of valve body  32 , and valve seat  36  disposed at fluid outlet  14  of fluid injector  10 . The cavity of valve body  32  defines at least part of fluid passageway  16  through which fluid flows from fluid inlet  12  to fluid outlet  14 . Elongated valve needle  34  includes a first end portion  34 A, in this case the upstream end portion, which is connected to armature  18  so as to be movable therewith, and a second end portion  34 B which is engageable with valve seat  36 . Valve needle  34  and armature  18  are movably disposed within fluid injector  10  along the longitudinal axis thereof. Specifically, valve needle  34  is movable between a closed position in which second end portion  34 B of valve needle  34  is sealingly engaged with valve seat  36  so as to prevent fluid from exiting fluid injector  10  from fluid outlet  14 , and an open position in which second end portion  34 B of valve needle  34  is spaced apart from valve seat  36  so that fluid flows through valve seat  36  and around the second end portion  34 B of valve needle  34 . In an example embodiment, armature  18  is connected to valve needle  34  at or near first end portion  34 A thereof. 
     With continued reference to  FIG. 1 , fluid injector  10  includes a return spring  19 , which is disposed between pole piece  22  and armature  18  so as to present a bias force to armature  18  in an upstream direction towards fluid inlet  12 , relative to the direction of fluid flow through fluid injector  10 . In particular, armature  18  includes a pocket  18 A defined from a lower, downstream surface of armature  18 . In addition, pole piece  22  includes a pocket  22 A defined from an upstream surface of pole piece  22 . Pockets  18 A and  22 A may each be laterally (radially) centrally located and face each other in fluid injector  10 . Return spring  19  is disposed within pockets  18 A and  22 A, and is compressed against inner radial surfaces of pockets  18 A and  22 A so as to urge armature  18  towards fluid inlet  12 . In this way, return spring  19  moves armature  18  towards fluid inlet  12  when coil  21  is no longer energized, so that valve needle  34  is returned to the closed position to prevent fluid from further exiting fluid injector  10 . 
     In the example embodiment illustrated in  FIG. 1 , fluid injector  10  further includes a dynamic flow adjustment mechanism for regulating the movement speed of armature  18  (and thus valve needle  34 ) during opening and closing of valve assembly  30 . Specifically, the dynamic flow adjustment mechanism includes an adjustment tube  25  and calibration spring  27 . Adjustment tube  25  is disposed within fluid passageway  16  of inlet tube  17  proximal to fluid inlet  12 . Adjustment tube  25  may be adjustably positioned within inlet tube  17  but once positioned remains fixed within fluid injector  10 . Adjustment tube  25  may include or be otherwise associated with a filter for filtering fluid entering fluid inlet  12 . Calibration spring  27  is disposed between and contacts a lower (downstream) surface of adjustment tube  25  and an upper (upstream) surface of armature  18 . Calibration spring  27  is configured to present a downward (downstream) bias force on armature  18  such that the total spring force by return spring  19  and calibration spring  27  is relatively easily adjusted at the time of manufacture of fluid injector  10 . 
       FIG. 2  illustrates in greater detail fluid outlet  14 . As can be seen, valve needle  34  extends through a throughbore  36 A of valve seat  36 . Throughbore  36 A is defined longitudinally through valve seat  36  and forms part of fluid passageway  16  which extends from fluid inlet  12  to fluid outlet  14 . Valve seat  36  may include a surface  36 B forming an inverted conical shaped portion for throughbore  36 A, funneling the fluid to fluid outlet  14 , and a sealing surface  36 C forming an exit portion for sealingly engaging second end portion  34 B of valve needle  34 . 
     Best shown in  FIG. 3 , second end portion  34 B of valve needle  34  includes a sealing surface  34 C which sealingly engages with sealing surface  36 C of valve seat  36  when valve needle  34  is in the closed position. In an example embodiment, sealing surface  34 C of valve needle  34  extends laterally (radially) and/or is tapered outwardly in a downstream direction, forming a frusto-conical shape. Second end portion  34 B of valve needle  34  may further include a surface  34 D which is downstream of sealing surface  34 C and extends radially inwardly and/or is inwardly tapered from sealing surface  34 C in a downstream direction. In an example embodiment, surface  34 D has an inverted frusto-conical shape. In other words, sealing surface  34 C forms an oblique angle with respect to a longitudinal axis of injector  10 . In an example embodiment, the oblique angle is configured such that the output spray of fluid from injector  12  has a conical shape with a cone angle of at least 70 degrees, and particularly at least 80 degrees, such as at least 90 degrees. Surface  34 E is largely flat and/or planar and forms the end surface of valve needle  34 . 
     Sealing surface  34 C of valve needle  34  may include scribe lines  34 F defined along sealing surface  34 C. Each scribe line  34 F may have a largely annular shape on sealing surface  34 C. 
     The operation of fluid injector  10  is as follows. Fluid, whether a reductant when fluid injector  10  is configured as a RDU or diesel fuel when fluid injector  10  is configured as a DDU, enters fluid injector  10  from fluid inlet  12 . When coil  21  is not energized, there is no electromagnetic force acting on armature  18  such that return spring  19  biases armature  18  and moves the armature towards fluid inlet  12  and away from pole piece  22 , which also moves valve needle  34  towards fluid inlet  12  so that second end portion  34 B, and particularly sealing surface  34 C, sealingly engages with sealing surface  36 C of valve seat  36  so that valve needle  34  is in the closed position and prevents fluid from exiting fluid injector  10  via fluid outlet  14 . When coil  21  is energized, an electromagnetic force is generated by coil  21  which moves armature  18  in a downstream direction towards pole piece  22 . The downstream movement of armature  18  causes valve needle  34  to move so that sealing surface  34 C of valve needle  34  disengages from sealing surface  36 C of valve seat  36 , thereby allowing fluid in fluid injector  10  to pass through through-bore  36 A of valve seat  36  and exit fluid injector  10 . The fluid exiting fluid injector  10  through fluid outlet  14  has a generally conical shape, based in part upon the dimensions of valve seat  36  and sealing surface  34 C of valve needle  34 . 
     As mentioned, fluid injector  10  is adapted for use in after-treatment dosing units, such as RDUs and DDUs.  FIG. 4  illustrates fluid injector  10  forming part of a passive or air-cooled dosing unit  100 . Dosing unit  100  includes a housing formed as an upper housing  102  and a lower housing  104 . Dosing unit  100  further includes a fluid inlet  106  for receiving fluid, e.g., a reductant or diesel fuel, which passes through fluid injector  10  and is selectively discharged from fluid outlet  14  thereof. Both upper housing  102  and lower housing  104  include a plurality of through-holes defined along the housings for allowing air to pass though the housings and regulate temperatures internal to the housings. Fluid injector  10  is disposed in an interior carrier  107 . Upper housing  102  and lower housing  104  are connected to carrier  107 , such as by folding a tang  104 A of an end portion of lower housing  104  so as to surround and clamp in place end portions of upper housing  102  and carrier  107 . 
     Dosing unit  100  further includes an injector flange  108  which receives therein the downstream end of lower housing  104 . Injector flange  108  includes an internal surface structure, generally indicated at  110 , that defines a flange outlet  112  that delivers fluid into a vehicle exhaust flow path. Flange  108  interfaces with a boss (not shown) that is welded to the vehicle exhaust. A bracket  114  is disposed over a portion of flange  108  and is secured to the vehicle exhaust line via bolts or other fasteners (not shown) so as to fix dosing unit  110  to the exhaust line. 
     The internal surface structure  110  of flange  108  also includes a largely frusto-conical surface  108 A that is joined with at least one radial surface  108 B. In the embodiment, the frusto-conical surface  108 A defines the open end of the flange  108  and is joined with the radial surface  108 B, with the radial surface  108 B 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 . 
     Dosing unit  100  further includes an isolating gasket  118  which rests on the gasket shelf surface  116  to seal flange  108  with respect to carrier  107 , and a second isolating gasket  120  disposed between a downstream end of flange  108  and an upstream end of the exhaust boss. Both isolating gaskets  118  and  120  serve to thermally isolate fluid injector  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 the exhaust boss and flange  108  to fluid injector  10 . Dosing unit  100  thus uses isolating gaskets  118  and  120  as well as cooling airflow around dosing unit  100  to keep temperatures of fluid injector  10  from high temperatures which may damage fluid injector  10 . 
     Passively cooled dosing unit  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 dosing unit may be used. Referring to  FIG. 5 , there is shown an actively cooled dosing unit  200  according to another example embodiment. Dosing unit  200  includes fluid injector  10  disposed therein. Dosing unit  200  is actively cooled by passing coolant around fluid injector  10  so as to maintain temperatures thereof within a desirable temperature range. Dosing unit  200  includes a housing  201  having a fluid inlet  202  for receiving fluid, e.g., a reductant or diesel fuel, which flows into fluid injector  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 (not shown in  FIG. 5 ) for returning coolant to the coolant source for recirculation. Housing  201  also includes a coolant jacket  208  which is fluidly coupled to coolant inlet  204  and the coolant outlet. Coolant jacket  208  is disposed around fluid injector  10 , and particularly around the portions of fluid injector  10  closest to the exhaust pipe. As shown in  FIG. 5 , coolant jacket  208  extends to or nearly to the bottom or downstream end of fluid injector  10 . Actively cooled dosing unit  200  includes a V-clamp mount for mounting dosing unit  200  directly to the vehicle exhaust pipe. 
     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.