Abstract:
An injector for injecting a reagent includes an axially translatable valve member positioned within a housing. An electromagnet is positioned within the housing and includes a coil of wire positioned proximate the valve member such that the valve member moves between a seated position and an unseated position relative to an orifice in response to energizing the electromagnet. A connector coupled to the housing includes an inlet tube concentrically aligned with and surrounding a return tube. The inlet tube is adapted to receive pressurized reagent from a source of reagent. The return tube is adapted to return reagent to the source.

Description:
FIELD 
     The present disclosure relates to injector systems and, more particularly, relates to an injector system for injecting a reagent, such as an aqueous urea solution, into an exhaust stream to reduce oxides of nitrogen (NO x ) emissions from diesel engine exhaust. 
     BACKGROUND 
     This section provides background information related to the present disclosure which is not necessarily prior art. Lean burn engines provide improved fuel efficiency by operating with an excess of oxygen, that is, a quantity of oxygen that is greater than the amount necessary for complete combustion of the available fuel. Such engines are said to run “lean” or on a “lean mixture.” However, this improved or increase in fuel economy, as opposed to non-lean burn combustion, is offset by undesired pollution emissions, specifically in the form of oxides of nitrogen (NO x ). 
     One method used to reduce NO x  emissions from lean burn internal combustion engines is known as selective catalytic reduction (SCR). SCR, when used, for example, to reduce NO x  emissions from a diesel engine, involves injecting an atomized reagent into the exhaust stream of the engine in relation to one or more selected engine operational parameters, such as exhaust gas temperature, engine rpm or engine load as measured by engine fuel flow, turbo boost pressure or exhaust NO x  mass flow. The reagent/exhaust gas mixture is passed through a reactor containing a catalyst, such as, for example, activated carbon, or metals, such as platinum, vanadium or tungsten, which are capable of reducing the NO x  concentration in the presence of the reagent. 
     An aqueous urea solution is known to be an effective reagent in SCR systems for diesel engines. However, use of such an aqueous urea solution involves many disadvantages. Urea is highly corrosive and may adversely affect mechanical components of the SCR system, such as the injectors used to inject the urea mixture into the exhaust gas stream. Urea also may solidify upon prolonged exposure to high temperatures, such as temperatures encountered in diesel exhaust systems. Solidified urea will accumulate in the narrow passageways and exit orifice openings typically found in injectors. Solidified urea may also cause fouling of moving parts of the injector and clog any openings or urea flow passageways, thereby rendering the injector unusable. 
     Some reagent injection systems are configured to include a pump, a supply line and a return line such that aqueous urea is continuously pumped to minimize solidification and also transfer heat from the injector to the aqueous urea stored at a remote location. Typically, an injector is equipped with an inlet coupled to the supply line and a spaced apart outlet coupled to the return line. While injectors configured in this manner have functioned sufficiently in the past, packaging and cost concerns may arise regarding the provision and applying of more than one reagent flow line. Other considerations include ease of installation, reagent flow uniformity and a possible benefit regarding moving the reagent inlet further away from the heat source. Accordingly, it may be desirable to provide an improved injector system including a reagent injector having coaxial supply and return lines. 
     SUMMARY 
     This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features. 
     An injector for injecting a reagent includes an axially translatable valve member positioned within a housing. An electromagnet is positioned within the housing and includes a coil of wire positioned proximate the valve member such that the valve member moves between a seated position and an unseated position relative to an orifice in response to energizing the electromagnet. A connector coupled to the housing includes an inlet tube concentrically aligned with and surrounding a return tube. The inlet tube is adapted to receive pressurized reagent from a source of reagent. The return tube is adapted to return reagent to the source. 
     An injector for injecting a reagent includes including an axially translatable valve member positioned within a housing. An electromagnet is positioned within the housing such that the valve member moves between a seated position and an unseated position relative to an orifice in response to energizing the electromagnet. A connector is coupled to the housing and includes an inlet tube concentrically aligned with a return tube. The inlet tube is adapted to receive pressurized reagent from a source of reagent. The return tube is adapted to return reagent to the source. An inner body is positioned within the housing to at least partially define a flow path for reagent to pass between the inner body and the housing. The inner body includes a bypass passage and a plurality of swirl slots. Reagent flows from the inlet tube, through the flow path and the bypass passage to the return tube when the valve member is in the seated position. A portion of the reagent flows from the inlet tube, through the flow path, through the swirl slots and out of the orifice when the valve member is in the unseated position. 
     Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       DRAWINGS 
       The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure. 
         FIG. 1  is a schematic depicting an exemplary exhaust aftertreatment system including an electromagnetically controlled reagent injector constructed in accordance with the teachings of the present disclosure; 
         FIG. 2  is a perspective view of the electromagnetically controlled reagent injector; 
         FIG. 3  is an exploded perspective view of the reagent injector; 
         FIG. 4  is a cross-sectional view taken through the injector depicted in  FIGS. 2 and 3 ; 
         FIG. 5  is another cross-sectional view taken through the injector depicted in  FIGS. 2 and 3 ; 
         FIG. 6  is a perspective view of an inner lower body of the previously depicted injector; 
         FIG. 7  is another perspective view of the inner lower body of the previously depicted injector; 
         FIG. 8  is a perspective view of an alternate connector; and 
         FIG. 9  is a cross-sectional view taken through the alternate connector of  FIG. 8 . 
     
    
    
     Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings. 
     DETAILED DESCRIPTION 
     Example embodiments will now be described more fully with reference to the accompanying drawings. 
     It should be understood that although the present teachings may be described in connection with diesel engines and the reduction of NO x  emissions, the present teachings may be used in connection with any one of a number of exhaust streams, such as, by way of non-limiting example, those from diesel, gasoline, turbine, fuel cell, jet or any other power source outputting a discharge stream. Moreover, the present teachings may be used in connection with the reduction of any one of a number of undesired emissions. For example, injection of hydrocarbons for the regeneration of diesel particulate filters is also within the scope of the present disclosure. For additional description, attention should be directed to commonly-assigned U.S. Patent Application Publication No. 2009/0179087A1, filed Nov. 21, 2008, entitled “Method And Apparatus For Injecting Atomized Fluids”, which is incorporated herein by reference. 
     With reference to the Figures, a pollution control system  8  for reducing NO x  emissions from the exhaust of an internal combustion engine  21  is provided. In  FIG. 1 , solid lines between the elements of the system denote fluid lines for reagent and dashed lines denote electrical connections. The system of the present teachings may include a reagent tank  10  for holding the reagent and a delivery module  12  for delivering the reagent from the tank  10 . The reagent may be a urea solution, a hydrocarbon, an alkyl ester, alcohol, an organic compound, water, or the like and can be a blend or combination thereof. It should also be appreciated that one or more reagents may be available in the system and may be used singly or in combination. The tank  10  and delivery module  12  may form an integrated reagent tank/delivery module. Also provided as part of system  8  is an electronic injection controller  14 , a reagent injector  16 , and an exhaust system  18 . Exhaust system  18  includes an exhaust conduit  19  providing an exhaust stream to at least one catalyst bed  17 . 
     The delivery module  12  may comprise a pump that supplies reagent from the tank  10  via a supply line  9 . The reagent tank  10  may be polypropylene, epoxy coated carbon steel, PVC, or stainless steel and sized according to the application (e.g., vehicle size, intended use of the vehicle, and the like). A pressure regulator (not shown) may be provided to maintain the system at predetermined pressure setpoint (e.g., relatively low pressures of approximately 60-80 psi, or in some embodiments a pressure of approximately 60-150 psi) and may be located in the return line  35  from the reagent injector  16 . A pressure sensor may be provided in the supply line  9  leading to the reagent injector  16 . The system may also incorporate various freeze protection strategies to thaw frozen reagent or to prevent the reagent from freezing. During system operation, regardless of whether or not the injector is releasing reagent into the exhaust gases, reagent may be circulated continuously between the tank  10  and the reagent injector  16  to cool the injector and minimize the dwell time of the reagent in the injector so that the reagent remains cool. Continuous reagent circulation may be necessary for temperature-sensitive reagents, such as aqueous urea, which tend to solidify upon exposure to elevated temperatures of 300° C. to 650° C. as would be experienced in an engine exhaust system. 
     Furthermore, it may be desirable to keep the reagent mixture below 140° C. and preferably in a lower operating range between 5° C. and 95° C. to ensure that solidification of the reagent is prevented. Solidified reagent, if allowed to form, may foul the moving parts and openings of the injector. 
     The amount of reagent required may vary with load, exhaust gas temperature, exhaust gas flow, engine fuel injection timing, desired NO x  reduction, barometric pressure, relative humidity, EGR rate and engine coolant temperature. A NO x  sensor or meter  25  is positioned downstream from catalyst bed  17 . NO x  sensor  25  is operable to output a signal indicative of the exhaust NO x  content to an engine control unit  27 . All or some of the engine operating parameters may be supplied from engine control unit  27  via the engine/vehicle databus to the reagent electronic injection controller  14 . The reagent electronic injection controller  14  could also be included as part of the engine control unit  27 . Exhaust gas temperature, exhaust gas flow and exhaust back pressure and other vehicle operating parameters may be measured by respective sensors. 
     With reference to  FIGS. 2-7 , reagent injector  16  will be further described. Reagent injector  16  includes an outer body assembly  50  having an outer body upper section  52  and an outer body lower section  54 . Outer body lower section  54  may be fixed to outer body upper section  52  via welding or a mechanical fastening process. A mounting flange  56  may be fixed to outer body assembly  50  to couple injector  16  to conduit  19 . A washer  57  is positioned between mounting flange  56  and outer body assembly  50 . 
     A fluid sleeve assembly  58  is depicted as a three-piece assembly having a first flux bridge collar  60  and a second flux bridge collar  62  interconnected by a flux break  64 . Fluid sleeve assembly  58  is shaped as an elongated hollow cylindrical member sized and positioned to extend through outer body assembly  50 . First flux bridge collar  60  includes a counterbore  66  sized to receive a reduced outer diameter stepped portion of flux break  64 . Flux break  64  includes a counterbore  68  sized to cooperate with a reduced outer diameter portion  70  of second flux bridge collar  62 . First flux bridge collar  60  includes a reduced outer diameter portion  72  cooperating with a pocket  74  formed in outer body upper section  52 . 
     An elongated inner lower body  80  may be received within fluid sleeve assembly  58 . Elongated inner lower body  80  includes an elongated throughbore  82 . A plurality of circumferentially spaced apart upper protrusions  84  radially outwardly extend from a cylindrical portion  86 . A plurality of circumferentially spaced apart lower protrusions  88  radially outwardly extend from cylindrical portion  86 . The gaps between each of upper protrusions  84  and each of lower protrusions  88  are aligned with one another to define several axially extending flow channels or flow paths  90 . A plurality of circumferentially spaced apart apertures  94  radially extend through elongated inner lower body  80  interconnecting flow channels  90  and bore  82 . A flange  96  radially outwardly extends from cylindrical portion  86  at one end of elongated inner lower body  80 . A plurality of swirl slots  100  extend through flange  96  terminating at an inner volume or swirl chamber  102 . Swirl slots  100  are positioned to tangentially intersect swirl chamber  102 . Swirl slots  100  are in fluid communication with flow paths  90 . 
     An orifice plate  110  is fixed to fluid sleeve assembly  58  and engages inner lower body  80 . Orifice plate  110  includes a raised center hub portion  112  received within a recess  114  formed in inner lower body  80 . A surface  116  of center hub portion  112  defines a portion of swirl chamber  102 . An orifice  118  extends through orifice plate  110  and is in fluid communication with swirl chamber  102 . 
     A valve member  124  is slidably positioned within bore  82 . Valve member  124  includes an elongated pintle  126  having a conically shaped first end  128  and an opposite second end  129 . First end  128  is selectively engageable with a valve seat  130  of orifice plate  110  to define a sealed and closed position of valve member  124  when seated. An unsealed, open position exists when pintle  126  is spaced apart from valve seat  130 . Valve seat  130  surrounds orifice  118 . The valve seat may be conically or cone-shaped as shown to complement the conical end  128  of pintle  126  to restrict the flow of reagent through orifice  118 . Depending on the application and operating environment, pintle  126  and orifice plate  110  may be made from a carbide material, which may provide desired performance characteristics and may be more easily and cost-effectively manufactured. In addition, limitations or disadvantages associated with other materials may be avoided, such as those associated with manufacturing complex part shapes. Carbide may provide additional advantages, such as insensitivity to brazing temperatures that may range from 870-980° C., as opposed to carbon steels and tool steels, which may distemper. Carbide may also provide an increased surface hardness when compared to the hardness achievable with most other steels. Carbide may also be advantageous with regard to overall wear resistance. 
     A pintle head  142  is fixed to second end  129  of pintle  126 . Pintle head  142  is slidably positioned within bore  82 . A running-class slip fit between pintle head  142  and bore  82  provides an upper guide for valve member  124 . A lower valve member guide is formed at the sliding interface between pintle  126  and a reduced diameter portion  146  of bore  82 . Based on this arrangement, valve member  124  is accurately aligned with valve seat  130  and orifice  118 . 
     A plurality of circumferentially spaced apart and radially extending apertures  150  extend through pintle  126 . A longitudinally extending blind bore  152  extends from second end  129  into fluid communication with apertures  150 . When pintle  126  is in the closed or seated position, apertures  150  are positioned in fluid communication with apertures  94  to define a portion of a reagent return passageway. 
     A pole piece  164  includes an enlarged diameter first end  166  sized to be received within bore  82 . First end  166  of pole piece  164  is fixed to inner lower body  80  using a process such as electron beam welding or laser welding. A reduced diameter opposite second end  168  of pole piece  164  is sealingly fitted within a bore  172  formed in a coupling  174 . A seal  176  is positioned within a groove  178  of coupling  174 . Elongated pole piece  164  includes a central bore  184  extending therethrough. Central bore  184  is coaxially aligned with bore  152  and bore  172 . An orifice  186  is positioned within central bore  184  at second end  168  of pole piece  164 . A counterbore  188  inwardly extends from second end  168  of pole piece  164 . A compression spring  194  is positioned within counterbore  188  in biased engagement with pintle head  142  to urge valve member  124  into engagement with seat  130 . 
     A tube  200  includes a first end  202  positioned within first flux bridge collar  60  and fixed thereto. First end  202  abuts circumferentially spaced apart stops  204  axially extending from inner lower body  80 . Tube  200  also includes a radially outwardly flared portion  206  and a second end  208 . 
     A coaxial connector  210  includes a housing  212  having an enlarged collar  214  at one end and an integrally formed inlet tube  216  at an opposite end. A return tube  218  extends through inlet tube  216  making a ninety degree turn within housing  212 . A first end  220  of return tube  218  extends beyond a terminal end of inlet tube  216 . A second opposite end  222  of return tube  218  engages a barbed external surface  224  of coupling  174 . 
     A retainer  230  and a clip  232  cooperate with collar  214  to removably secure housing  212  to tube  200 . More particularly, a cylindrical pilot  234  of retainer  230  is received within a stepped bore  236  of housing  212 . Portion  206  of tube  200  engages a land  238  of retainer  230 . Clip  232  retains portion  206  against land  238 . A tang  242  radially outwardly protrudes from retainer  230  and engages collar  214  in a snap fit engagement by protruding through an aperture  244  and engaging a surface  246 . Clip  232  is transversely inserted through an aperture  250  extending through collar  214 . Legs  252  extend through apertures  254  extending through retainer  230  to restrict relative motion between housing  212 , retainer  230  and clip  232 . A spacer  260  is positioned within housing  212  to provide a path for reagent flowing through inlet tube  216 . A cage  262  is positioned within tube  200  to retain an inlet filter (not shown) therein. 
     An electromagnet assembly  300  is positioned within outer body assembly  50  as depicted in the Figures. Electromagnet assembly  300  includes a coil of wire  302  wrapped around a bobbin  304 . Pintle head  142  is constructed from a magnetic material such as 430 stainless steel such that electrical energization of coil  302  produces a magnetic field urging pintle head  142  toward pole piece  164 . When coil  302  is energized, first end  128  of pintle  126  becomes disengaged from seat  130  to allow reagent to flow through orifice  118 . Power may be provided to coil  302  via access to a receptacle  311 , for example, in response to a signal from electronic injection controller  14 . 
     Flux bridge collars  60  and  62  are constructed from ferritic  430  stainless steel. Pole piece  164  is made from ferritic  430  stainless steel or a similar magnetic material. Pintle head  142  may be made from ferritic  430  stainless steel. Flux break  64  is made from non-ferritic and non-magnetic  304  stainless steel as is inner lower body  80 . Constructing the previously described components from magnetic and non-magnetic materials as well as closely positioning the magnetic materials adjacent to one another greatly improves the magnetic circuit performance associated with electromagnet assembly  300 . Benefits may include the use of a smaller coil wire, a lesser number of turns of wire, and a reduced quantity of electric current to provide an improved electromagnetic actuator having lower cost, reduced size and mass. Increased control regarding the position of valve member  124  is also realized. 
     A closed loop reagent fluid path is provided when pintle  126  of reagent injector  16  is in the closed position. Reagent is provided from reagent tank  10  via delivery module  12  to inlet tube  216  via an inlet passageway  320  of dual passageway connector  210  interconnecting delivery module  12  and injector  16 . It is contemplated that inlet passageway  320  coaxially extends within inlet tube  216  and along an outer surface of return tube  218 . A return passageway  322  is provided inside of return tube  218 . Reagent being supplied to reagent injector  16  travels through inlet passageway  320  formed between inlet tube  216  and return tube  218 . Reagent continues to flow past spacer  260 . A passageway is formed between tube  200  and coupling  174  to allow reagent to pass thereby. Reagent continues to flow downward as viewed in the Figures toward orifice  118  through filter cage  262 . Pressurized reagent continues to flow through flow paths  90  along an inner surface of fluid sleeve assembly  58  and around inner lower body  80 . Supplied reagent flows substantially to the bottom of fluid sleeve assembly  58  and passes through swirl slots  100  to enter swirl chamber  102 . When pintle  126  is seated, reagent does not flow through orifice  118 . Reagent flows through apertures  94  of inner lower body  80  and apertures  150  of pintle  126  to enter longitudinal bore  152 . Pintle head  142  includes an aperture  330  placing longitudinal bore  152  in fluid communication with central bore  184  of the return fluid passageway. Reagent flowing along the return path passes through orifice  186  and bore  172  of coupling  174 . As previously noted, return tube  218  is fixed to coupling  174 . When reagent is not being injected into the exhaust system, the reagent is continuously pumped to flow past coil  302  and through pintle  126  to transfer heat from orifice plate  110  and pintle  126  to the flowing reagent. 
     When electromagnet  300  is energized, pintle  126  is moved from seat  130 . Pressurized reagent positioned in communication with swirl slots  100  flows through each of the swirl slots to enter swirl chamber  102 . Based on the pressure differential between orifice  118  and swirl slots  100  as well as the tangential relationship of swirl slots  100  to swirl chamber  102 , a swirling reagent motion is induced. The low pressure at orifice  118  combined with pressurized reagent moving in a swirling or circular fashion creates a finely atomized spray exiting orifice  118 . Reagent that does not exit orifice  118  continues to be recirculated as previously described. 
       FIGS. 8 and 9  depict an alternate coaxial connector identified at reference numeral  400 . Coaxial connector  400  includes a monolithic, one-piece, housing  402 . Housing  402  includes an inlet tube portion  404  and a return tube portion  406 . A plurality of radially extending webs  408  support return tube portion  406  within inlet tube portion  404 . An inlet passageway  410  extends between an inner surface of inlet tube portion  404  and an outer surface of return tube portion  406 . A return passageway  412  extends from a nipple  414  of return tube portion  406 . A seal groove  416  is formed on an outer surface of return tube portion  406 . In similar fashion, a seal groove  418  is provided on an outer surface of inlet tube portion  404 . Both inlet tube portion  404  and return tube portion  406  are barbed to provide a secure hose connection. 
     A collar portion  420  of coaxial connector  400  is sized and shaped to receive an end of tube  200  or a similar portion of injector  16 . Return tube portion  406  makes a 90 degree turn and terminates at an open end  422 . A fluid connection such as previously described between second end  222  of coupling  174  and return tube  218  is provided with coaxial connector  400  as well. An exit port  424  is positioned at the end of inlet passageway  410  to provide pressurized reagent to orifice  118  as previously described. It should be appreciated that the remaining components of injector  16  may be used in combination with alternate coaxial connector  400  without departing from the scope of the present disclosure. 
     Furthermore, the foregoing discussion discloses and describes merely exemplary embodiments of the present disclosure. One skilled in the art will readily recognize from such discussion, and from the accompanying drawings and claims, that various changes, modifications and variations may be made therein without departing from the spirit and scope of the disclosure as defined in the following claims.