Abstract:
A dosing valve assembly is disclosed for administering a reducing agent into an exhaust stream from an internal combustion engine upstream of a catalytic converter and diesel particulate filter. The dosing valve assembly includes a control valve coupled to a source of reducing agent, a delivery valve constructed and arranged for coupling to the exhaust stream to enable a quantity of reducing agent to be administered into the exhaust stream, and an elongated conduit connecting the control valve and delivery valve for fluidly communicating reducing agent from the control valve to the fuel delivery valve. The disclosed arrangement enables the control valve to be displaced from the delivery valve and thus away from the high temperature environment proximal to the exhaust stream.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part and claims the benefit of U.S. application Ser. No. 11/504,148, filed Aug. 15, 2006, which claims the benefit of U.S. Provisional Application Ser. No. 60/708,195, filed Aug. 15, 2005, both entitled “Automotive Diesel Exhaust HC Dosing Valve,” the contents of which are hereby incorporated by reference herein. 
     This application further claims the benefit of U.S. Provisional Application Ser. No. 60/828,305, filed Oct. 5, 2006, entitled “Diesel Particulate Filter Systems,” the contents of which are hereby incorporated by reference herein. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to a system for reducing particulates and nitric oxide (NO x ) emissions by diesel engines, and more particularly, to a novel hydrocarbon (HC) dosing valve system that eliminates the requirement for water cooling in a high temperature environment. 
     BACKGROUND OF THE INVENTION 
     Hydrocarbons and NO x  emissions are a direct result of the combustion process in an internal combustion engine. To reduce such harmful emissions, catalytic converters are employed to reduce their toxicity. For gasoline engines, “three-way catalysts” are used to reduce nitrogen oxides to nitrogen and oxygen (2NO x →xO 2 +N 2 ), oxidize carbon monoxide to carbon dioxide (2CO+O 2 →2CO 2 ); and oxidize hydrocarbons to carbon dioxide and water: C x H y +nO 2 →xCO 2 +mH 2 O. In the case of compression ignition or “Diesel” engines, the most commonly employed catalytic converter is the diesel oxidation catalyst. This catalyst employs excess O 2  in the exhaust gas stream to oxidize carbon monoxide to carbon dioxide and hydrocarbons to water and carbon dioxide. These converters virtually eliminate the typical odors associated with diesel engines, and reduce visible particulates, however they are not effective in reducing NO x  due to excess oxygen in the exhaust gas stream. 
     Another problem prevalent with diesel engines is the generation of particulates (soot). This is reduced through what is commonly referred to as a soot trap or diesel particulate filter (DPF). The catalytic converter itself is unable to affect elemental carbon in the exhaust stream. The DPF is either installed downstream of the catalytic converter, or incorporated within the catalytic converter itself. A clogged DPF can create undesired backpressure on the exhaust stream and thereby reduce engine performance. To alleviate this problem, the DPF can undergo a regeneration cycle when diesel fuel is injected via a dosing valve directly into the exhaust stream and the soot is burned off. The injection of diesel fuel can be stopped after the regeneration cycle is complete. 
     NO x  emissions in the exhaust from a diesel engine can be reduced by employing a Selective Catalytic Reduction Catalyst (SCR) in the presence of a reducing agent such as ammonia (NH 3 ). Existing technologies utilize SCR and NO x  traps or NO x  absorbers. The ammonia is typically stored on board a vehicle either in pure form, either as a liquid or gas, or in a bound form that is split hydrolytically to release the ammonia into the system. 
     An aqueous solution of urea is commonly used as a reducing agent. The urea is stored in a reducing tank coupled to the system. A dosing valve is disposed on the exhaust carrying structure upstream of the catalytic converter to meter the delivery of a selected quantity of urea into the exhaust stream. When the urea is introduced into the high temperature exhaust, it is converted to a gaseous phase and the ammonia is released to facilitate reduction of NO x . In lieu of ammonia, diesel fuel from the vehicle&#39;s fuel supply can be used as the reducing agent. In this expedient, a quantity of diesel fuel is administered directly into the exhaust via the dosing valve. 
     In either case, the dosing valve is mounted in close proximity to the exhaust, and thus operates in a harsh environment where temperatures can reach as high as 600 deg C. Accordingly, the dosing valve must be cooled to prevent decomposition or crystallization of the urea prior to delivery into the exhaust stream, and to maintain the integrity of the valve assembly. To alleviate this problem, prior art expedients have employed water cooling systems for the valve assembly. However, water cooling requires specialized plumbing and additional components that ultimately increase costs and reduce reliability. 
     SUMMARY OF THE INVENTION 
     In view of the foregoing, it is an object of the invention to provide a dosing valve assembly for an internal combustion engine that eliminates the need for water cooling of the dosing valve. 
     It is a further object of the invention to provide a dosing valve assembly which utilizes a control valve that is separated from a delivery valve mounted on the exhaust carrying structure to remove the control valve from the high temperature environment proximal to the exhaust stream. 
     It is yet another object of the invention to provide a dosing valve assembly in accordance with the above that can be utilized to provide both SCR for a catalytic converter and regeneration for a DPF. 
     In accordance with aspects of the invention, a dosing valve assembly is disclosed for administering a reducing agent, such as for example, diesel fuel, into an exhaust stream from an internal combustion engine upstream of a catalytic converter and DPF. The dosing valve assembly comprises a control valve coupled to a source of the reducing agent, a delivery valve constructed and arranged for coupling to the exhaust stream at a location upstream of the catalytic converter and DPF to enable a quantity of reducing agent to be administered into the exhaust stream, and an elongated conduit connecting the control valve and delivery valve for fluidly communicating the reducing agent from the control valve to the delivery valve. The disclosed arrangement enables the control valve to be displaced from the delivery valve and away from the high temperature environment proximal to the exhaust stream. 
     In accordance with one aspect of the invention, the control valve comprises an electronic fuel injector coupled to a source of the reducing agent, and the delivery valve comprises a poppet valve. The fuel injector is coupled to an electronic control unit that signals the fuel injector to permit or inhibit the flow of reducing agent to the poppet valve in response to various sensed parameters. 
     These and other advantages of the invention will be apparent to those of ordinary skill in the art by reference to the following detailed description and the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic of an illustrative dosing system; 
         FIG. 2  is a schematic of a dosing valve assembly in accordance with an aspect of the invention; 
         FIG. 3  is a schematic of an exemplary control valve in the dosing valve assembly in accordance with another aspect of the invention; and 
         FIG. 4  is a schematic of an exemplary reducing agent delivery valve in the form of a poppet valve in accordance with yet another aspect of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Embodiments of the invention will be described with reference to the accompanying drawing figures wherein like numbers represent like elements throughout. Before embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of the examples set forth in the following description or illustrated in the figures. The invention is capable of other embodiments and of being practiced or carried out in a variety of applications and in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. 
     Referring to  FIG. 1 , there is depicted a system schematic of an exemplary dosing system  100 . Exhaust from a diesel engine (not shown) is communicated through an exhaust pipe  102  including a P-trap, which is coupled to a catalytic converter  104  and diesel particulate filter (DPF)  105 . The catalytic converter  104  is of the SCR type that is well known in the art, which utilizes a selective catalytic reduction method to reduce the NO x  content in the exhaust stream. The DPF  105  is shown schematically as being part of the catalytic converter  104 . However, it will be understood by those skilled in the art that the DPF may be a separate unit disposed downstream of the catalytic converter  104 . A reducing agent, such as diesel fuel in the exemplary embodiment, is introduced into the exhaust pipe via a dosing valve  106  that is physically attached to pipe  102 . The diesel fuel injected via the dosing valve upstream of the catalytic converter  104  acts both as the reducing agent for the SCR process, and to support the regeneration cycle in the DPF to clean the filter. 
     The dosing valve  106  fluidly communicates with a control valve  108  that is disposed away from manifold  102 . The details of the dosing valve  106  and control valve  108  assembly are described in detail below. The control valve  106  receives a supply of diesel fuel that is stored in a fuel tank  110  via a pressure regulator  112 . A fuel pump  114  supplies diesel fuel under pressure from tank  110  to regulator  112 . The fuel pump  114  and the control valve  108  are electrically coupled to an electronic control unit (ECU)  116 . A dosing control unit (DCU)  118  is disposed between ECU  116  and control valve  108 . These components are operative to meter a quantity of diesel fuel that is injected into the exhaust stream to reduce the NO x  content in the exhaust stream. The reduction is effectuated by introducing a desired quantity of diesel fuel upstream of catalytic converter  104 . Pressure sensors are disposed upstream and downstream of catalytic converter  104  to enable these parameters to be communicated to ECU  116  as schematically depicted in  FIG. 1 . In addition, temperature sensors and NO x  sensors electrically communicate with ECU  116  as is known in the art. The ECU  116  monitors various parameters including temperature, pressure and NO x  content in the exhaust stream and consequently meters the introduction of diesel fuel into the exhaust stream to optimize the reduction of undesirable particulates and NO x  emissions. 
       FIG. 2  is a schematic of a dosing valve assembly  200 , which generally comprises a control valve assembly  202  and poppet valve assembly  204 . The control valve assembly  202  includes a fuel injector  206  that, for this application, has been modified to omit an orifice disk that atomizes a fuel charge that is delivered to an internal combustion engine in the usual manner. The fuel injector  206  is described in greater detail below. In general terms, the fuel injector  206  comprises an electronic connector  208  that couples fuel injector  206  to the ECU  116  and DCU  118  as described above and depicted in  FIG. 1 . The fuel injector  206  is disposed on a bracket  210  for mounting the assembly within the vehicle. A fuel inlet  212  on a first end of the fuel injector  206  receives a supply of diesel fuel from fuel tank  110  ( FIG. 1 ). The fuel injector  206  is fluidly coupled to poppet valve assembly  204  through a connecting tube  214 , which has a length sufficient to displace the control valve assembly  202  from the high temperature environment in proximity to the exhaust stream. The poppet valve assembly  204  is mounted directly on the exhaust structure and described in further detail below. 
       FIG. 3  is a schematic an exemplary fuel injector  306  (corresponding to  206  in  FIG. 2 ), that may be used as a control valve for the present invention. Fuel injector  306  extends along a longitudinal axis A-A between a first injector end  308 A and a second injector end  308 B, and includes a valve group subassembly  310  and a power group subassembly  312 . The valve group subassembly  310  performs fluid handling functions, e.g., defining a fuel flow path and prohibiting fuel flow through the injector  306 . The power group subassembly  312  performs electrical functions, e.g., converting electrical signals to a driving force for permitting fuel flow through the injector  306 . 
     The valve group subassembly  310  includes a tube assembly  314  extending along the longitudinal axis A-A between the first fuel injector end  308 A and the second fuel injector end  308 B. The tube assembly  314  can include at least an inlet tube  316 , a non-magnetic shell  318 , and a valve body  320 . The inlet tube  316  has a first inlet tube end  322 A proximate to the first fuel injector end  308 A. The inlet tube  316  can be flared at the inlet end  322 A into a flange  322 B to retain an O-ring  323 . A second inlet tube end  322 C of the inlet tube  316  is connected to a first shell end  324 A of the non-magnetic shell  318 . A second shell end  324 B of the non-magnetic shell  318  can be connected to a generally transverse planar surface of a first valve body end  326 A of the valve body  320 . A second valve body end  326 B of the valve body  320  is disposed proximate to the second tube assembly end  308 B. A separate pole piece  328  can be connected to the inlet tube  316  and connected to the first shell end  324 A of the non-magnetic shell  318 . The pole piece may comprise a stainless steel material such as SS 430FR (ASTM A838-00). The non-magnetic shell  318  can comprise non-magnetic stainless steel, e.g., 300-series stainless steels such as SS 305 (EN 10088-2), or other materials that have similar structural and magnetic properties. 
     As shown in  FIG. 3 , inlet tube  316  is attached to pole piece  328  by weld bead  330 . Formed into the outer surface of pole piece  328  are pole piece shoulders  332 A, which, in conjunction with mating shoulders of a bobbin of the coil subassembly, act as positive mounting stops when the two subassemblies are assembled together. The inlet tube  316  can be attached to the pole piece  328  at an inner circumferential surface of the pole piece  328 . Alternatively, an integral inlet tube and pole piece can be attached to the inner circumferential surface of a non-magnetic shell  318 . 
     An armature assembly  334  is disposed in the tube assembly  314 . The armature assembly  334  includes a first armature assembly end having a ferromagnetic or armature portion  336  and a second armature assembly end having a sealing portion. The armature assembly  334  is disposed in tube assembly  314  such that a shoulder  336 A of armature  336  confronts a shoulder  332 B of pole piece  328 . The sealing portion can include a closure member  338 , e.g., a spherical valve element, that is moveable with respect to the seat  340  and its sealing surface  340 A. The closure member  338  is movable between a closed configuration (depicted in  FIG. 3 ) and an open configuration (not shown). In the closed configuration, the closure member  338  contiguously engages the sealing surface  340 A to prevent fluid flow through the opening. In the open configuration, the closure member  338  is spaced from the seat  340  to permit fluid flow through the opening. The armature assembly  334  may also include a separate intermediate portion  342  connecting the ferromagnetic or armature portion  336  to the closure member  338 . The intermediate portion or armature tube  342  may be attached to armature  336  and closure member  338  by weld beads  344 ,  346 , respectively. 
     Surface treatments can be applied to at least one of the end portions  332 B and  336 A to improve the armature&#39;s response, reduce wear on the impact surfaces and variations in the working air gap between the respective end portions  332 B and  336 A. The surface treatments can include coating, plating or case-hardening. Coatings or platings can include, but are not limited to, hard chromium plating, nickel plating or keronite coating. Case hardening on the other hand, can include, but is not limited to, nitriding, carburizing, carbo-nitriding, cyaniding, heat, flame, spark or induction hardening. 
     Fuel flow through the armature assembly  334  is facilitated by at least one axially extending through-bore  336 B and at least one aperture  342 A through a wall of the armature assembly  334 . The apertures  342 A, which can be of any shape, are preferably non-circular, e.g., axially elongated, to facilitate the passage of gas bubbles. The apertures  342 A provide fluid communication between the at least one through-bore  336 B and the interior of the valve body  320 . Thus, in the open configuration, fuel can be communicated from the through-bore  336 B, through the apertures  342 A and the interior of the valve body  320 , around the closure member  338 , and through outlet end  308 B of injector  306 . 
     In another embodiment, a two-piece armature having an armature portion directly connected to a closure member can be utilized. Although both the three-piece and the two-piece armature assemblies are interchangeable, the three-piece armature assembly is preferable due to its ability to reduce magnetic flux leakage from the magnetic circuit of the fuel injector  306 . It will be appreciated by those skilled in the art that the armature tube  342  of the three-piece armature assembly can be fabricated by various techniques, for example, a plate can be rolled and its seams welded or a blank can be deep-drawn to form a seamless tube. 
     In the case of a spherical valve element providing the closure member  338 , the spherical valve element can be connected to the armature assembly  334  at a diameter that is less than the diameter of the spherical valve element. Such a connection is on the side of the spherical valve element that is opposite and contiguous contact with the seat  340 . A lower armature assembly guide  348  can be disposed in the tube assembly  314 , proximate the seat  340 , and slidingly engages the diameter of the spherical valve element. The lower armature assembly guide  348  facilitates alignment of the armature assembly  334  along the longitudinal axis A-A. 
     A resilient member  350  is disposed in the tube assembly  314  and biases the armature assembly  334  toward the seat  340 . A filter assembly  352  comprising a filter  354  and a preload adjuster  356  is also disposed in the tube assembly  314 . The filter assembly  352  includes a first filter assembly end  352 A and a second filter assembly end  352 B. The filter  354  is disposed at one end of the filter assembly  352  and also located proximate to the first end  308 A of the tube assembly  314  and apart from the resilient member  350  while the preload adjuster  356  is disposed generally proximate to the second end of the tube assembly  314 . The preload adjuster  356  engages the resilient member  350  and adjusts the biasing force of the member  350  with respect to the tube assembly  314 . In particular, the preload adjuster  356  provides a reaction member against which the resilient member  350  reacts in order to close the injector  306  when the power group subassembly  312  is de-energized. The position of the preload adjuster  356  can be retained with respect to the inlet tube  316  by an interference press-fit between an outer surface of the preload adjuster  356  and an inner surface of the tube assembly  314 . Thus, the position of the preload adjuster  356  with respect to the inlet tube  316  can be used to set a predetermined dynamic characteristic of the armature assembly  334 . 
     The power group subassembly  312  comprises an electromagnetic coil  358 , at least one terminal  360 , a coil housing  362 , and an overmold  364 . The electromagnetic coil  358  comprises a wire that that can be wound on a bobbin  314  and electrically connected to electrical contacts  368  on the bobbin  314 . When energized, the coil  358  generates magnetic flux that moves the armature assembly  334  toward the open configuration, thereby allowing the fuel to flow through the opening. De-energizing the electromagnetic coil  358  allows the resilient member  350  to return the armature assembly  334  to the closed configuration, thereby shutting off the fuel flow. The housing, which provides a return path for the magnetic flux, generally includes a ferromagnetic cylinder surrounding the electromagnetic coil  358  and a flux washer  370  extending from the cylinder toward the axis A-A. The flux washer  370  can be integrally formed with or separately attached to the cylinder. The coil housing  362  can include holes, slots, or other features to break-up eddy currents that can occur when the coil  358  is energized. 
     The overmold  364  maintains the relative orientation and position of electromagnetic coil  358 , the at least one terminal  360 , and the coil housing  362 . The overmold  364  includes an electrical harness connector  370  portion in which a portion of the terminal  360  is exposed. The terminal  360  and the electrical harness connector portion  372  can engage a mating connector, e.g., part of a wiring harness (not shown), to facilitate connecting injector  306  to ECU  116  ( FIG. 1 ) for energizing the electromagnetic coil  358 . 
     According to a preferred embodiment, the magnetic flux generated by electromagnetic coil  358  flows in a circuit that includes pole piece  328 , armature assembly  334 , valve body  320 , coil housing  306 , and flux washer  370 . The magnetic flux moves across a parasitic air gap between the homogeneous material of the magnetic portion or armature  336  and valve body  320  into the armature assembly  334  and across a working air gap between end portions  332 B and  336 A towards the pole piece  328 , thereby lifting closure member  338  away from seat  340 . 
     In an illustrative embodiment, wire is wound onto a preformed bobbin  366  having electrical connector portions  368  to form a bobbin assembly. The bobbin assembly is inserted into a pre-formed coil housing  362 . To provide a return path for the magnetic flux between the pole piece  328  and the coil housing  362 , flux washer  370  is mounted on the bobbin assembly. 
     In operation, the electromagnetic coil  358  is energized, thereby generating magnetic flux in the magnetic circuit. The magnetic flux moves armature assembly  334  (along the axis A-A, according to a preferred embodiment) towards the integral pole piece  328 , closing the working air gap. Such movement of the armature assembly  334  separates the closure member  338  from the seat  340  and allows fuel to flow from the fuel tank  110  ( FIG. 1 ), through inlet tube  368 , through-bore  336 B, apertures  342 A and valve body  320 , thereafter between seat  340  and closure member  338 , through the opening, and finally through the outlet end  308 B and into connecting tube  214  ( FIG. 2 ). When the electromagnetic coil  358  is de-energized, the armature assembly  334  is biased by the resilient member  350  to contiguously engage closure member  338  against seat  340 , thereby blocking fluid flow through the injector  306 . 
       FIG. 4  is a schematic an exemplary poppet valve assembly (PVA)  404  (corresponding to  204  in  FIG. 2 ), that is mounted on the exhaust carrying structure to deliver a reducing agent (e.g., diesel fuel) into the exhaust stream. PVA  404  comprises an inlet  406  having a threaded portion  408  for attaching the connecting tube  214  ( FIG. 2 ). The inlet  406  receives fuel from the control valve assembly (see  FIG. 3 ). The fuel is delivered to first chamber  410  defined in a housing  412  of the poppet valve assembly  404 . In the illustrative embodiment, the housing  412  includes a first portion  414   a  and second portion  414   b  that are joined by welding at  416 . Seals may be provided in the assembly, but are omitted here for clarity. A moveable valve plate  418  is disposed within housing  412  and includes at least one aperture  420  to enable fluid flow from first chamber  410  to a second chamber  422 . Valve plate  418  is normally biased by spring  424  against annular surface  426  bounding first chamber  410 . A valve stem  428  is attached at a first end  430  to valve plate  418  and is axially elongated along a central axis B-B to a flared portion  432  at a second end  434 . The flared portion has a surface  436  that is normally biased against a complimentary surface  438  that defines a valve seat in housing  412  to block fluid flow through to an outlet end  440  of poppet valve PVA  404 . An orifice plate  442  is disposed in the outlet end  440  to provide for a uniform distribution of fuel into the exhaust stream as is well known in the art of fuel injector design. The PVA  404  is mounted on the exhaust carrying structure shown generally by the reference numeral  444 , by a clamping assembly (omitted for clarity). In operation, control valve assembly  306  ( FIG. 3 ), under the control of ECU  116 /DCU  118 , releases a quantity of fuel to PVA  404  via connecting tube  214  ( FIG. 2 ). The fuel under pressure biases the valve plate  418  downwardly against the force of spring  424 , thereby enabling a quantity of fuel to flow through aperture(s)  420  into second chamber  422 . The movement of valve plate  418  translates the flared portion  432  of valve stem  428  away from surface  438 , which permits fuel to flow through the orifice plate  442  and out of the PVA  404  into the exhaust manifold. When the control valve assembly  306  restricts the flow of fuel through the connecting tube  214 , the reduced fuel pressure in first chamber  410  is overcome by the force of spring  424  to move the valve plate  418  (and stem  428 ) upwardly to close off the PVA  404 , and the flow of fuel is prevented from entering the exhaust stream. 
     The foregoing detailed description is to be understood as being in every respect illustrative and exemplary, but not restrictive, and the scope of the invention disclosed herein is not to be determined from the description of the invention, but rather from the claims as interpreted according to the full breadth permitted by the patent laws. For example, while the method is disclosed herein with respect to tubular components of a fuel injector, the techniques and configurations of the invention may be applied to other tubular components where a hermetic weld is required. It is to be understood that the embodiments shown and described herein are only illustrative of the principles of the present invention and that various modifications may be implemented by those skilled in the art without departing from the scope and spirit of the invention.