Coking resistant after-treatment dosing value

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.

FIELD OF THE INVENTION

The present invention relates generally to a system for reducing particulates and nitric oxide (NOx) 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

Hydrocarbons and NOxemissions 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:
2NOx→xO2+N2

These three-way catalysts are also used to oxidize carbon monoxide to carbon dioxide, which is shown by the second equation below:
2CO+O2→2CO2

Furthermore, these three-way catalysts are also used to oxidize hydrocarbons into carbon dioxide and water, as shown by the third equation below:
CxHy+nO2→xCO2+mH2O

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 O2in 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 NOxdue to excess oxygen in the exhaust gas stream.

One way of reducing NOxemissions in a diesel engine utilizes a Selective Catalytic Reduction (SCR) Catalyst in the presence of a reducing agent such as ammonia (NH3) to modify the engine exhaust. Existing technologies utilize SCR and NOxtraps or NOxabsorbers. 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 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 NOx. In lieu of ammonia, diesel fuel from the vehicle'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.

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.

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.

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.

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

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 NOxcontent 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.

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 NOxcontent 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.

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.

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.

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.

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.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now toFIG. 1, a dosing valve assembly according to embodiments of the present invention is shown generally at10. The dosing valve assembly10includes a control valve assembly, shown generally at12, and a spray valve assembly, shown generally at14. The control valve assembly12has a fuel injector16that includes an electronic control element (not shown) that couples the dosing valve to the ECU and DCU. The fuel injector16is mounted to and supported by a bracket18for mounting the assembly within the vehicle. A fuel inlet20on a first end, shown generally at22, of the fuel injector16receives a supply of diesel fuel from a fuel tank.

The fuel injector16is fluidly coupled to the spray valve assembly14though a capillary or low volume connecting tube24, which has a length sufficient to displace the control valve assembly12from 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 assembly10operate within a useful delay from activation of the control valve assembly12. The tube24is connected to a fuel outlet26on a second end, shown generally at28, of the injector16. The spray valve assembly14of the dosing valve assembly10is mounted directly on the exhaust manifold and described in further detail below.

Referring now toFIG. 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 tube24is connected to an inlet30which is formed as part of a body portion32. The body portion32includes a circumferential lip34which contacts the upper flanges36of a mounting clip, generally shown at38, used for attaching and holding the body portion32for connection with a suitable exhaust boss, shown generally at40. The mounting clip38also includes lower flanges42, which contact the circumferential lip34and a base portion44. Also disposed between the flanges36,42is a flange46integrally formed as part of the exhaust boss40. The exhaust boss40also includes a channel48, through which the body portion32extends, a central portion50, and an enlarged base portion52. The flange46and the enlarged base portion52are integrally formed with the central portion50.

The present invention is not limited for use only with the mounting clip38, other types of clips may be used with the dosing valve assembly10, 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 boss40in combination with threads; this requires additional precautions in manufacture and assembly that increases manufacturing cost compared to the mounting clip38or other types of clips mentioned above. The inlet30receives fuel from the control valve assembly12. In an embodiment, disposed within the body portion32is a spray valve, shown generally at54. The spray valve54includes a valve needle58, a valve body60, and a spring clip62that holds a spring64in compression axially along the valve needle58in relation to the valve body60. Assembled part locations are shown inFIGS. 4B and 6B.

The spray valve54is disposed in the body portion32, through a connection, such as a press-fit connection, as shown inFIG. 4B. However, it is within the scope of the invention that other types of connections may be used to connect the spray valve54to the body portion32. The spray valve54partially extends out of the lower end, shown generally at66, of the body portion32, and is disposed in the body portion32below the inlet30.

The valve body60includes a large diameter portion68and a smaller diameter portion70, which are connected by a tapered portion72. The large diameter portion68includes a thick sidewall74, and the smaller diameter portion includes a thin sidewall76. The large diameter portion68also includes a lower tapered portion78. Extending through the valve body60and both sidewalls74,76is an aperture, shown generally at80. The aperture80has two different inner diameters corresponding to the inner diameters of each of the sidewalls74,76. Disposed in the aperture80are the valve needle58and the spring64. The valve needle58is slidably disposed in the aperture80, and on a first end, shown generally at82, includes a groove84which receives the spring clip62. On a second end, generally shown at86, the valve needle58includes a tapered portion88.

The valve needle58also includes an upper portion90which includes the groove84, and is substantially disposed in the small diameter portion70. However, a portion of the upper portion90protrudes out of the small diameter portion70is shown inFIGS. 4B and 6Bsuch that the groove84is outside of the valve body60. The spring clip62is located in the groove84and contacts an upper ledge92formed as part of the small diameter portion70. Also disposed in the small diameter portion70of the valve body60(and in part of the aperture80) is the spring64. The spring64contacts the spring clip62, and also contacts a lower ledge94formed as part of the large diameter portion68. The spring64is compressed by the spring clip62and the lower ledge94, the function of which will be described later.

The valve needle58also has a lower portion, shown generally at96, connected to the upper portion90. The lower portion96has a plurality of deformations98. In the embodiment shown inFIGS. 6B, 10A, and 10D, there are eight deformations98(four types of deformations, and two of each type of deformation98), but it is within the scope of the invention that in other embodiments, more or less deformations98may be used. Each deformation98contacts a different area of the inside surface of the thick sidewall74, best seen inFIG. 6B.

As mentioned above, the lower portion96of the valve needle58includes the tapered portion88, and the large diameter portion68of the valve body60includes the lower tapered portion78. Referring toFIGS. 7-9, the tapered portion88includes an upper surface100, and the lower tapered portion78includes a lower surface102. The upper surface100and lower surface102are conical surfaces and are positioned at an angle104relative to one another when the spray valve54is in the closed position, as shown inFIGS. 7 and 8. The angle104formed between the two surfaces100,102creates an opening, or angled interface, shown generally at106, which allows for fluid flow when the spray valve54is in an open position, as shown inFIG. 9.

The distance between the spring clip62and the lower ledge94is less than the length of the spring64when the spring64is in a completely relaxed position. Therefore, there is a constant force applied to the spring clip62and the lower ledge94, biasing the valve needle58upward, and therefore biasing the spray valve54toward a closed position.

Under the control of the vehicle's ECU/DCU, the control valve assembly12releases a quantity of fuel to the spray valve assembly14via the connecting tube24. The fuel flows through the connecting tube24, the inlet30, the body portion32, and around the spring clip62and through the aperture80as shown by the arrowed lines inFIG. 6B. The fuel flows through the aperture80through both the small diameter portion70and the large diameter portion68. The fuel also flows around the deformations98and applies pressure to each of the surfaces100,102. The fuel under pressure generates a force across an area of each of the surfaces100,102that biases the valve needle58, overcoming the force of spring64, placing the spay valve54in the open position shown inFIG. 9, thereby enabling a quantity of fuel to flow through the angled interface106between valve needle58and valve body60. When the control valve assembly12restricts the flow of fuel through the connecting tube24, the reduced fuel pressure is overcome by the force of spring64to move the valve needle58upwardly such that the outer edge110of the lower surface102contacts the outer edge108of the upper surface100, closing off the spray valve54, and the flow of fuel is prevented from entering the exhaust manifold.

The conical surface100of the valve needle58and respective conical surface102of the lowered tapered portion78of the valve body60are designed such that as the fluid moves past the surfaces100,102to 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 angle104is selected not only for the decreasing area effect with increasing flow diameter, but for having the surfaces100,102converge such that the surfaces100,102meet at as close to a circular line as possible to reduce the area sensitive to deposit buildup. The angle104is 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.

While one embodiment of the valve needle58is described above, other embodiments of the valve needle58are also possible. Possible alternate embodiments of the valve needle58are shown inFIGS. 10B, 10C, 10E, and 10F. While the scope of the invention is not limited to these, three proposed manufacturing strategies are shown inFIGS. 10A, 10B, 10C, 10D, 10E, and 10F.

FIGS. 10A and 10Dshow an embodiment where the valve needle58is 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 deformations98, 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 wall74of the valve body60. The contact area formed between the deformations98and the inside diameter of the thick side wall74is very low, yet the length over diameter ratio is large enough to provide appropriate guiding for axial translation of the valve needle58within the valve body60. The low contact area increases the local force applied to the inner surface of the thick side wall74to overcome deposits that may form between the valve needle58and the area of the aperture80along the inside diameter of the thick side wall74of the valve body60.

FIGS. 10B and 10Eshow another embodiment and technique of manufacture from wire where the geometry of the valve needle58is made by creating another type of deformation, generally shown at112. Each deformation112has four guide protrusions114which contact the inside diameter of the thick side wall74during operation of the spray valve54. In this embodiment, there must be at least one deformation112in at least one location, and the deformation112must have at least three guide protrusions114to provide adequate centering and guiding. Three guide protrusions114provide 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 deformations112, each having four guide protrusions114which provide centering and guiding.

FIGS. 10C and 10Fshow another embodiment of a valve needle58, which has been machined, rather than deformed.FIGS. 10C and 10Fshow a valve needle58having two locations, shown generally at116with four contact areas118. In an alternate embodiment, there may be one location116having three contact areas118, because at least one location with three contact areas are needed to provide centering and guiding within the inside diameter of the thick side wall74of the valve body60. However, it is also within the scope of the invention that more locations116having more contact areas118may be used. Again, all embodiments ofFIGS. 10A, 10B, 10C, 10D, 10E, and10F show a reduced contact area and large length over diameter number for reducing sensitivity to deposits.

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 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.