Abstract:
A dosing valve for administering a reducing agent into an exhaust stream within an exhaust manifold of an internal combustion engine. The dosing valve includes a valve needle internally coaxial to a valve body and held in a closed position by a force of compressed spring acting axially and held in relation to the valve needle and valve body. The negative impact of varnish and dehydrogenated compounds, or coking products, of hydrocarbon based reducing agents, is substantially reduced or eliminated. Additionally, this includes decreased sensitivity to the negative impact of the precipitates and crystals that come out of the solution due to temperature change with urea-based reducing agents.

Description:
FIELD OF THE INVENTION 
       [0001]    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) or urea dosing valve system that eliminates the requirement for water cooling in a high temperature environment. 
       BACKGROUND OF THE INVENTION 
       [0002]    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 both nitrogen and oxygen, as shown by the equation below: 
         [0000]      2NO x   →x O 2 +N 2    
         [0003]    These three-way catalysts are also used to oxidize carbon monoxide to carbon dioxide, which is shown by the second equation below: 
         [0000]      2CO+O 2 →2CO 2  
 
         [0004]    Furthermore, these three-way catalysts are also used to oxidize hydrocarbons into carbon dioxide and water, as shown by the third equation below: 
         [0000]      C x H y   +n O 2   →x CO 2   +m H 2 O 
         [0005]    In the case of an engine which uses compression ignition, such as a diesel engine, 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 the NO x  due to excess oxygen in the exhaust gas stream. 
         [0006]    One way of reducing NO x  emissions in a diesel engine utilizes a Selective Catalytic Reduction (SCR) Catalyst in the presence of a reducing agent such as ammonia (NH 3 ) to modify the engine exhaust. 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. 
         [0007]    An aqueous solution of urea is also commonly used as a reducing agent. The urea is stored in a reducing tank that associated with the system. A dosing valve disposed on the exhaust manifold upstream of a catalytic converter meters 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. 
         [0008]    Additionally, particulate-specific traps accumulate unburned hydrocarbons, and dehydrogenated material is not removed by combusting a reducing agent such as diesel fuel to supply heat to oxidize or burn off these materials, this results in the trap reducing exhaust flow and increasing exhaust back pressure on the engine cylinders, reducing engine efficiency. 
         [0009]    In either case, a dosing valve assembly is mounted directly on the exhaust manifold, and thus operates in a very high temperature environment that can reach temperatures as high as six-hundred degrees Celsius. Accordingly, the dosing valve is cooled to prevent decomposition or crystallization of the urea, or coking due to failure of diesel fuel reducing agent prior to delivery into the exhaust stream, and to maintain integrity of the dosing valve assembly. 
         [0010]    The problems associated with this high temperature environment have previously been addressed by water cooling the assembly. However, this requires specialized plumbing and systems that ultimately increase costs and reduce reliability. Geometrical configurations can increase or decrease the sensitivity to deposits. 
         [0011]    Additionally, there are challenges relating to the quality of the spray when the volume of exhaust in the after-treatment process required is less, such as for smaller engine classes as used in privately owned vehicles and commuter vehicles typically less than four liters, and usually near two liters in engine displacement. Accordingly, there exists a need for a dosing valve which overcomes problematic spray quality due to a smaller mass flow rate of a reducing agent. 
       SUMMARY OF THE INVENTION 
       [0012]    Fundamentally, exhaust from a diesel engine is communicated through an exhaust manifold including a particulate-trap, which is coupled to a catalytic converter. The catalytic converter could be of the 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. A reducing agent, which in one embodiment may be diesel fuel, is introduced into the exhaust manifold via a dosing valve that is physically attached to manifold. According to embodiments of the present invention, the dosing valve fluidly communicates with a control valve that is disposed away from the exhaust manifold of the engine. The control valve receives a supply of diesel fuel that is stored in a fuel tank via a pressure regulator. 
         [0013]    A fuel pump supplies diesel fuel under pressure from the vehicle storage tank to a regulator. The fuel pump and the control valve are electrically coupled to the vehicle electronic control unit (ECU). Another electronic unit may be employed, such as a dosing control unit (DCU) which could be disposed between ECU and control valve. 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 or particulate trap. Pressure sensors are disposed upstream and downstream of catalytic converter or particulate trap to enable these parameters to be communicated to ECT. In addition, temperature sensors and NOx sensors electrically communicate with ECU as is known in the art. The ECU monitors various parameters including temperature, pressure, and NOx 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 NOx emissions. 
         [0014]    In one embodiment, a dosing valve assembly according to an embodiment of the present invention includes a control valve assembly, a fuel injector, where the fuel injector is part of the control valve assembly, and a spray valve assembly having a spray valve which includes a valve needle and a valve body having an aperture. The valve needle is movably disposed within the aperture of the valve body. A capillary delivery tube places the fuel injector in fluid communication with the spray valve assembly. A tapered portion is formed as part of the valve needle, an upper surface is formed as part of the tapered portion, a lower tapered portion is formed as part of the valve body of the spray valve, and a lower surface is formed as part of the lower tapered portion. An angled interface is formed by the upper surface and the lower surface which a reducing agent passes through when the spray valve is in an open position, and the spray valve assembly delivers the reducing agent to at least a portion of an exhaust system. 
         [0015]    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 that is less sensitive to deposit or precipitate buildup on the internal functional components. Additionally, it is an object of the invention to provide a spray optimized design having lower delivery mass for use with smaller engine platforms. 
         [0016]    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 within an exhaust manifold of an internal combustion engine. The dosing valve assembly includes a control valve coupled to a source of the reducing agent, a spray valve assembly having a reducing agent delivery valve constructed and arranged for coupling to the exhaust manifold to enable a specified quantity of reducing agent to be administered into the exhaust stream, and an optimized elongated conduit disposed between the control valve and reducing agent delivery valve for fluidly communicating reducing agent from the control valve to the reducing agent delivery valve. The arrangement according to embodiments of the present invention enables the spray valve assembly to be coupled to the exhaust manifold, and the control valve to be displaced from the spray valve assembly and away from the high temperature environment associated with the exhaust manifold without sacrifice of spray quality and response time between control valve and spray valve. 
         [0017]    In one embodiment, a spray valve assembly for administering a reducing agent into an exhaust stream within an exhaust manifold of an internal combustion engine in accordance with the invention includes an electronic fuel injector that operates as a control valve which is coupled to source of the reducing agent; a poppet or dosing valve constructed and arranged for coupling to the exhaust manifold to enable a specified quantity of reducing agent to be administered into the exhaust stream, the poppet valve including an inlet communicating with an elongated, optimized volume conduit disposed between the electronic fuel injector and poppet valve for fluidly communicating reducing agent from the electronic fuel injector to the spray valve, whereby, the spray valve may be coupled to the exhaust manifold and displaced from the electronic fuel injector. The electronic 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. 
         [0018]    Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
           [0020]      FIG. 1  is a perspective view of a dosing valve assembly, according to embodiments of the present invention; 
           [0021]      FIG. 2  is a first perspective view of a spray valve assembly used with a dosing valve assembly, according to embodiments of the present invention; 
           [0022]      FIG. 3  is a second perspective view of a spray valve assembly used with a dosing valve assembly, according to embodiments of the present invention; 
           [0023]      FIG. 4A  is a side view of a spray valve assembly used with a dosing valve assembly, according to embodiments of the present invention; 
           [0024]      FIG. 4B  is a sectional side view of a spray valve assembly used with a dosing valve assembly, according to embodiments of the present invention; 
           [0025]      FIG. 5  is an exploded view of a spray valve which is part of a spray valve assembly used with a dosing valve assembly, according to embodiments of the present invention; 
           [0026]      FIG. 6A  is a side view of a spray valve which is part of a spray valve assembly used with a dosing valve assembly, according to embodiments of the present invention; 
           [0027]      FIG. 6B  is a sectional side view of a spray valve which is part of a spray valve assembly used with a dosing valve assembly, according to embodiments of the present invention; 
           [0028]      FIG. 7  is an enlarged sectional view of the lower end of the body portion and the tapered portion of a valve needle, which are part of a spray valve, according to the present invention; 
           [0029]      FIG. 8  is a greatly enlarged view of the circled portion of  FIG. 7 ; 
           [0030]      FIG. 9  is a greatly enlarged view of a section of the body portion and the tapered portion of a valve needle in an open position, which are part of a spray valve, according to the present invention; 
           [0031]      FIG. 10A  is a side view of a valve needle of a spray valve which is part of a spray valve assembly used with a dosing valve assembly, according to embodiments of the present invention; 
           [0032]      FIG. 10B  is a side view of another embodiment of a valve needle which is part of a spray valve assembly used with a dosing valve assembly, according to embodiments of the present invention; 
           [0033]      FIG. 10C  is a side view of another embodiment of a valve needle which is part of a spray valve assembly used with a dosing valve assembly, according to embodiments of the present invention; 
           [0034]      FIG. 10D  is sectional view taken along lines  10 D- 10 D of  FIG. 10A ; 
           [0035]      FIG. 10E  is sectional view taken along lines  10 E- 10 E of  FIG. 10B ; and 
           [0036]      FIG. 10F  is sectional view taken along lines  10 E- 10 F of  FIG. 10C . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0037]    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. 
         [0038]    Referring now to  FIG. 1 , a dosing valve assembly according to embodiments of the present invention is shown generally at  10 . The dosing valve assembly  10  includes a control valve assembly, shown generally at  12 , and a spray valve assembly, shown generally at  14 . The control valve assembly  12  has a fuel injector  16  that includes an electronic control element (not shown) that couples the dosing valve to the ECU and DCU. The fuel injector  16  is mounted to and supported by a bracket  18  for mounting the assembly within the vehicle. A fuel inlet  20  on a first end, shown generally at  22 , of the fuel injector  16  receives a supply of diesel fuel from a fuel tank. 
         [0039]    The fuel injector  16  is fluidly coupled to the spray valve assembly  14  though a capillary or low volume connecting tube  24 , which has a length sufficient to displace the control valve assembly  12  from the high temperature environment in proximity to the exhaust manifold, and a volume small enough to be pressurized in a timely fashion to have the dosing valve assembly  10  operate within a useful delay from activation of the control valve assembly  12 . The tube  24  is connected to a fuel outlet  26  on a second end, shown generally at  28 , of the injector  16 . The spray valve assembly  14  of the dosing valve assembly  10  is mounted directly on the exhaust manifold and described in further detail below. 
         [0040]    Referring now to  FIG. 2-4B , a spray valve assembly is shown, which in one embodiment may be mounted on an exhaust manifold to deliver a reducing agent (e.g., diesel fuel) into the exhaust stream. The tube  24  is connected to an inlet  30  which is formed as part of a body portion  32 . The body portion  32  includes a circumferential lip  34  which contacts the upper flanges  36  of a mounting clip, generally shown at  38 , used for attaching and holding the body portion  32  for connection with a suitable exhaust boss, shown generally at  40 . The mounting clip  38  also includes lower flanges  42 , which contact the circumferential lip  34  and a base portion  44 . Also disposed between the flanges  36 , 42  is a flange  46  integrally formed as part of the exhaust boss  40 . The exhaust boss  40  also includes a channel  48 , through which the body portion  32  extends, a central portion  50 , and an enlarged base portion  52 . The flange  46  and the enlarged base portion  52  are integrally formed with the central portion  50 . 
         [0041]    The present invention is not limited for use only with the mounting clip  38 , other types of clips may be used with the dosing valve assembly  10 , such as a spring clip, quick-release clamp, or a crimp clamp, and may be within the scope of the invention. Some types of dosing valves have been mounted using the exhaust boss  40  in combination with threads; this requires additional precautions in manufacture and assembly that increases manufacturing cost compared to the mounting clip  38  or other types of clips mentioned above. The inlet  30  receives fuel from the control valve assembly  12 . In an embodiment, disposed within the body portion  32  is a spray valve, shown generally at  54 . The spray valve  54  includes a valve needle  58 , a valve body  60 , and a spring clip  62  that holds a spring  64  in compression axially along the valve needle  58  in relation to the valve body  60 . Assembled part locations are shown in  FIGS. 4B and 6B . 
         [0042]    The spray valve  54  is disposed in the body portion  32 , through a connection, such as a press-fit connection, as shown in  FIG. 4B . However, it is within the scope of the invention that other types of connections may be used to connect the spray valve  54  to the body portion  32 . The spray valve  54  partially extends out of the lower end, shown generally at  66 , of the body portion  32 , and is disposed in the body portion  32  below the inlet  30 . 
         [0043]    The valve body  60  includes a large diameter portion  68  and a smaller diameter portion  70 , which are connected by a tapered portion  72 . The large diameter portion  68  includes a thick sidewall  74 , and the smaller diameter portion includes a thin sidewall  76 . The large diameter portion  68  also includes a lower tapered portion  78 . Extending through the valve body  60  and both sidewalls  74 , 76  is an aperture, shown generally at  80 . The aperture  80  has two different inner diameters corresponding to the inner diameters of each of the sidewalls  74 , 76 . Disposed in the aperture  80  are the valve needle  58  and the spring  64 . The valve needle  58  is slidably disposed in the aperture  80 , and on a first end, shown generally at  82 , includes a groove  84  which receives the spring clip  62 . On a second end, generally shown at  86 , the valve needle  58  includes a tapered portion  88 . 
         [0044]    The valve needle  58  also includes an upper portion  90  which includes the groove  84 , and is substantially disposed in the small diameter portion  70 . However, a portion of the upper portion  90  protrudes out of the small diameter portion  70  is shown in  FIGS. 4B and 6B  such that the groove  84  is outside of the valve body  60 . The spring clip  62  is located in the groove  84  and contacts an upper ledge  92  formed as part of the small diameter portion  70 . Also disposed in the small diameter portion  70  of the valve body  60  (and in part of the aperture  80 ) is the spring  64 . The spring  64  contacts the spring clip  62 , and also contacts a lower ledge  94  formed as part of the large diameter portion  68 . The spring  64  is compressed by the spring clip  62  and the lower ledge  94 , the function of which will be described later. 
         [0045]    The valve needle  58  also has a lower portion, shown generally at  96 , connected to the upper portion  90 . The lower portion  96  has a plurality of deformations  98 . In the embodiment shown in  FIGS. 6B ,  10 A, and  10 D, there are eight deformations  98  (four types of deformations, and two of each type of deformation  98 ), but it is within the scope of the invention that in other embodiments, more or less deformations  98  may be used. Each deformation  98  contacts a different area of the inside surface of the thick sidewall  74 , best seen in  FIG. 6B . 
         [0046]    As mentioned above, the lower portion  96  of the valve needle  58  includes the tapered portion  88 , and the large diameter portion  68  of the valve body  60  includes the lower tapered portion  78 . Referring to  FIGS. 7-9 , the tapered portion  88  includes an upper surface  100 , and the lower tapered portion  78  includes a lower surface  102 . The upper surface  100  and lower surface  102  are conical surfaces and are positioned at an angle  104  relative to one another when the spray valve  54  is in the closed position, as shown in  FIGS. 7 and 8 . The angle  104  formed between the two surfaces  100 , 102  creates an opening, or angled interface, shown generally at  106 , which allows for fluid flow when the spray valve  54  is in an open position, as shown in  FIG. 9 . 
         [0047]    The distance between the spring clip  62  and the lower ledge  94  is less than the length of the spring  64  when the spring  64  is in a completely relaxed position. Therefore, there is a constant force applied to the spring clip  62  and the lower ledge  94 , biasing the valve needle  58  upward, and therefore biasing the spray valve  54  toward a closed position. 
         [0048]    Under the control of the vehicle&#39;s ECU/DCU, the control valve assembly  12  releases a quantity of fuel to the spray valve assembly  14  via the connecting tube  24 . The fuel flows through the connecting tube  24 , the inlet  30 , the body portion  32 , and around the spring clip  62  and through the aperture  80 . The fuel flows through the aperture  80  through both the small diameter portion  70  and the large diameter portion  68 . The fuel also flows around the deformations  98  and applies pressure to each of the surfaces  100 , 102 . The fuel under pressure generates a force across an area of each of the surfaces  100 , 102  that biases the valve needle  58 , overcoming the force of spring  64 , placing the spay valve  54  in the open position shown in  FIG. 9 , thereby enabling a quantity of fuel to flow through the angled interface  106  between valve needle  58  and valve body  60 . When the control valve assembly  12  restricts the flow of fuel through the connecting tube  24 , the reduced fuel pressure is overcome by the force of spring  64  to move the valve needle  58  upwardly such that the outer edge  110  of the lower surface  102  contacts the outer edge  108  of the upper surface  100 , closing off the spray valve  54 , and the flow of fuel is prevented from entering the exhaust manifold. 
         [0049]    The conical surface  100  of the valve needle  58  and respective conical surface  102  of the lowered tapered portion  78  of the valve body  60  are designed such that as the fluid moves past the surfaces  100 , 102  to the exhaust atmosphere, the flow area decreases even though the flow geometry increases in average diameter. This has the effect of increasing fluid velocity and simultaneously the conical liquid sheet formed is decreasing in thickness as the conical liquid sheet flows outward. This creates a fluid momentum that has a radial vector force to overcome the viscous forces of the liquid that have a force vector pointing toward the axis of the conical liquid sheet. The contact angle  104  is selected not only for the decreasing area effect with increasing flow diameter, but for having the surfaces  100 , 102  converge such that the surfaces  100 , 102  meet at as close to a circular line as possible to reduce the area sensitive to deposit buildup. The angle  104  is generally in the range of ten degrees to thirty degrees, but it is within the scope of the invention that greater or lesser angles may be used. 
         [0050]    While one embodiment of the valve needle  58  is described above, other embodiments of the valve needle  58  are also possible. Possible alternate embodiments of the valve needle  58  are shown in  FIGS. 10B ,  10 C,  10 E, and  10 F. While the scope of the invention is not limited to these, three proposed manufacturing strategies are shown in  FIGS. 10A ,  10 B,  10 C,  10 D,  10 E, and  10 F. 
         [0051]      FIGS. 10A and 10D  show an embodiment where the valve needle  58  is made from suitable wire, such as Inconel 718 or Pyromet 718, 200, or 300 series Austenitic Stainless, and is used in the embodiment described above. The wire is deformed in four different ways to create the deformations  98 , each rotated one-hundred-eighty degrees circumferentially from the other, creating an effective eight-point guide that rides within the inside diameter of the thick side wall  74  of the valve body  60 . The contact area formed between the deformations  98  and the inside diameter of the thick side wall  74  is very low, yet the length over diameter ratio is large enough to provide appropriate guiding for axial translation of the valve needle  58  within the valve body  60 . The low contact area increases the local force applied to the inner surface of the thick side wall  74  to overcome deposits that may form between the valve needle  58  and the area of the aperture  80  along the inside diameter of the thick side wall  74  of the valve body  60 . 
         [0052]      FIGS. 10B and 10E  show another embodiment and technique of manufacture from wire where the geometry of the valve needle  58  is made by creating another type of deformation, generally shown at  112 . Each deformation  112  has four guide protrusions  114  which contact the inside diameter of the thick side wall  74  during operation of the spray valve  54 . In this embodiment, there must be at least one deformation  112  in at least one location, and the deformation  112  must have at least three guide protrusions  114  to provide adequate centering and guiding. Three guide protrusions  114  provide three contact points, which is required because at least three contact points are necessary to define a circle geometrically on a two dimensional surface. In this embodiment, there are two deformations  112 , each having four guide protrusions  114  which provide centering and guiding. 
         [0053]      FIGS. 10C and 10F  show another embodiment of a valve needle  58 , which has been machined, rather than deformed.  FIGS. 10C and 10F  show a valve needle  58  having two locations, shown generally at  116  with four contact areas  118 . In an alternate embodiment, there may be one location  116  having three contact areas  118 , because at least one location with three contact areas are needed to provide centering and guiding within the inside diameter of the thick side wall  74  of the valve body  60 . However, it is also within the scope of the invention that more locations  116  having more contact areas  118  may be used. Again, all embodiments of  FIGS. 10A ,  10 B,  10 C,  10 D,  10 E, and  10 F show a reduced contact area and large length over diameter number for reducing sensitivity to deposits. 
         [0054]    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 form the description of the invention, but rather from the claims as interpreted according to the full breath permitted by the patent laws. For example, while the method is disclosed herein with respect to tubular components of a fuel injector, the techniques are configurations of the invention may be applied to other tubular components where a hermetric weld is required. It is to be understood that he 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. 
         [0055]    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.