Patent Application
20150059322
The invention relates generally to providing active cooling for a reductant delivery unit for an automotive selective catalytic reduction system.
New emissions legislation in Europe and North America is driving the implementation of new exhaust after treatment systems, particularly for lean-burn technologies such as compression-ignition (diesel) engines, and stratified-charge spark-ignited engines (usually with direct injection) that are operating under lean and ultra-lean conditions. Lean-burn engines exhibit high levels of nitrogen oxide emissions (NOx), that are difficult to treat in oxygen-rich exhaust environments characteristic of lean-burn combustion. Exhaust after treatment technologies are currently being developed that treat NOx under these conditions.
One of these technologies includes a catalyst that facilitates the reactions of ammonia (NH3) with the exhaust nitrogen oxides (NOx) to produce nitrogen (N2) and water (H2O). This technology is referred to as Selective Catalytic Reduction (SCR). Ammonia is difficult to handle in its pure form in the automotive environment, therefore it is customary with these systems to use a liquid aqueous urea solution, typically at a 32% concentration of urea (CO(NH2)2). The solution is referred to as AUS-32, and is also known under its commercial name of AdBlue. The urea is delivered to the hot exhaust stream and is transformed into ammonia in the exhaust after undergoing thermolysis, or thermal decomposition, into ammonia and isocyanic acid (HNCO). The isocyanic acid then undergoes a hydrolysis with the water present in the exhaust and is transformed into ammonia and carbon dioxide (CO2), the ammonia resulting from the thermolysis and the hydrolysis then undergoes a catalyzed reaction with the nitrogen oxides as described previously.
In some systems, the reductant delivery unit (RDU) is mounted under the body of the vehicle, downstream of the exhaust line. This results in relatively low temperatures at the SCR catalyst, longer light-off times, and low conversion efficiency of the NOx. Attempts have been made to relocate the SCR catalyst and the RDU injector closer to the engine in order to provide higher temperature exhaust gas for quicker light-off and more efficient conversion of the NOx.
However, this close placement may result in a high ambient thermal environment for the injector. In this case, active cooling of the injector may be required to prevent excessive heating of the injector tip, and hence of the AUS-32 working fluid.
The present invention is a reductant delivery unit having active cooling which is constructed to have sufficient structural robustness, and to improve corrosion resistance of the assembly, where an attack on the base injector is conceivable with the use of incorrect coolant media.
In one embodiment the reductant delivery unit has an upper shield, a lower shield connected to the upper shield, and an inner sleeve. An outer surface of the inner sleeve is connected to an inner surface of the upper shield and an inner surface of the lower shield. The reductant delivery unit also includes a lower sleeve having an outer surface, where a portion of the outer surface of the lower sleeve is connected to the inner surface of the inner sleeve, and another portion of the outer surface of the lower sleeve is connected to outer surface of the lower shield. A liquid cooling cavity is formed by the connection between the inner sleeve and the lower shield, the lower sleeve and the lower shield, and the lower sleeve and the inner sleeve. A corrugated portion is formed as part of the lower sleeve, and an injector is partially located within the inner sleeve, and partially located within the lower sleeve. Coolant flows into the liquid cooling cavity to provide a cooling function to the injector, and the corrugated portion of the lower sleeve transfers heat away from at least a portion of the injector.
A first connection point is formed by the connection between the outer surface of the inner sleeve and the inner surface of the lower shield, a second connection point is formed by a portion of the outer surface of the lower sleeve connected to an inner surface of the inner sleeve, and a third connection point is formed by an area of the outer surface of the lower sleeve connected to the outer surface of the lower shield.
The injector includes a lower valve body, and a portion of the lower valve body is press-fit into the corrugated portion of the lower sleeve.
It is an object of the invention to provide delivery of AUS-32 to the engine exhaust for use in SCR exhaust after treatment systems on vehicles via an actively cooled reductant delivery unit (RDU).
It is another object of this invention to provide active cooling for an RDU from a separate liquid circuit. Although the source of the cooling liquid may be varied, it is within the scope of the invention that engine coolant from an existing engine coolant circuit is used with the RDU of the present invention.
It is another object of the invention to provide a solution to cooling the exhaust-mount injection units due to extreme high temperature mounting locations.
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.
The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:
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.
Referring to the
The cap 14 at least partially surrounds a hydraulic connector 22. The hydraulic connector 22 has an inlet pipe 24, and an inlet cup 26, which in this embodiment are integrally formed together, but it is within the scope of the invention that the inlet pipe 24 and inlet cup 26 may be formed separately. The inlet pipe 24 includes an aperture 28 which extends through the pipe 24 and is in fluid communication with an inner cavity, shown generally at 30, formed by the inlet cup 26, best seen in
The retaining cap 14 maintains the inlet cup 26 in place via a weld with the upper shield 16. The upper shield 16 is constructed so as to minimize heat transfer from the hot ambient environment to the inner volumes of the unit 10 and the AUS-32 fluid passages, particularly during heating transients (e.g., engine drop to idle after a mountain climb pulling a trailer). In so doing, the heat capacity of the upper shield 16 protects against short-term heating of the inner components of the injector 32. The upper shield 16 is joined to the lower shield 18, via a laser weld, but also possibly by brazing.
The injector 32 includes an upper valve body 34, which is hollow and in fluid communication with the inner cavity 30. Part of the upper valve body 34 is surrounded by a first seal, which in this embodiment is an upper o-ring 36 which is in contact with the inner wall 38 of the inner cavity 30, to provide a seal connection between the upper valve body 34 and the inlet cup 26, ensuring all fluid that flows through the inlet cup 26 passes into the upper valve body 34.
The upper valve body 34 is partially surrounded by a housing 40 having a connector 42. The connector 42 is in electrical communication with a coil 44, and the coil 44 is part of a solenoid portion, shown generally at 46. The solenoid portion 46 is part of the injector 32, and controls the movement of a valve portion, shown generally at 48, which is also part of the injector 32. In addition to the coil 44, the solenoid portion 46 also includes a pole piece 50 surrounded by the coil 44, and a moveable armature 52. The pole piece 50 and the armature 52 are substantially hollow such that a return spring 54 is disposed in a cavity, shown generally at 56, formed by the pole piece 50 and armature 52. The return spring 54 biases the armature 52 downward when looking at
The valve portion 48 includes a tube 60 connected to the armature 52 at a first end, shown generally at 62, and a ball 64 connected to a second end, shown generally at 66. The ball 64 is part of a valve, and the valve also includes a valve seat 68. The valve seat 68 is mounted in the lower end of a lower valve body 70, and the lower valve body 70 is connected to the pole piece 50, such that the lower valve body 70 is partially surrounded by the coil 44. Movement of the ball 64 is controlled by a guide 74. The guide 74 includes a guide aperture 92 through which the ball 64 moves, and also includes side apertures 76 which the fluid flows through. The valve seat 68 includes a conical-shaped portion 78, upon which the ball 64 rests when the valve is in the closed position. The valve seat 68 also includes a central aperture 80, through which the fluid passes as the fluid exits the injector 32.
During the operation of the injector 32, the valve, and more specifically the tube 60 and the ball 64, are biased by the return spring 54 to contact the valve seat 68, and therefore keep the valve in a closed position. When the coil 44 is energized, the armature 52 is drawn toward the pole piece 50. The energizing of the coil 44 generates enough force that the armature 52 overcomes the force of the return spring 54, and moves towards the pole piece 50. Because the tube 60 is connected to the armature 52, and the ball 64 is connected to the tube 60, the movement of the armature 52 towards the pole piece 50 moves the ball 64 away from the valve seat 68, opening the valve. When the valve is in an open position, the fluid flows from the aperture 28 through the inner cavity 30, the upper valve body 34, pole piece 50, armature 52, the tube 60 and out a plurality of exit apertures 72 formed as part of the tube 60. After the fluid flows out of the exit apertures 72, the fluid passes through the side apertures 76, and out the central aperture 80.
When the coil 44 is no longer energized, the return spring 54 forces the armature 52 away from the pole piece 50, and moves the armature 52, the tube 60 and the ball 64 such that the ball 64 is placed against the conical-shaped portion 78 of the valve seat 68, placing the valve in the closed position.
The solenoid portion 46 also includes a casing 82 which at least partially surrounds the coil 44 and the lower valve body 70. Surrounding part of the casing 82 is a second seal, which in this embodiment is a lower o-ring 84, and the lower o-ring 84 is surrounded by an inner sleeve 86. The inner sleeve 86 is disposed within the cavity 20, and part of the outer surface 88 of the inner sleeve 86 is connected (through the use of a weld) to both the inner surface 90 of the upper shield 16, and the inner surface 94 of the lower shield 18. The connection between the outer surface 88 of the inner sleeve 86 and the inner surface 94 of the lower shield 18 forms a first connection point 108. Part of the lower valve body 70 is also surrounded by a lower sleeve 96. The lower sleeve 96 includes an outer surface 98, and part of the outer surface 98 of the lower sleeve 96 is connected to an inner surface 100 of the inner sleeve 86 by a weld or brazing process forming a second connection point 102. Another area of the outer surface 98 of the lower sleeve 96 is connected to the outer surface 104 of the lower shield 18 by a weld or brazing process to form a third connection point 106.
The lower sleeve 96 surrounds a lower end, shown generally at 110, of the lower valve body 70. More specifically, the lower sleeve 96 is shaped such that the lower sleeve 96 includes a corrugated portion 112 having ridges which contact the lower end 110 of the lower valve body 70, such that the lower valve body 70 is press-fit into the lower sleeve 96. The corrugated portion 112 functions to transfer heat away from the portion of the lower valve body 70 surrounded by the corrugated portion 112. The connection between the inner sleeve 86 and the lower shield 18, the connection between the lower sleeve 96 and the lower shield 18, and the connection between the lower sleeve 96 and the lower shield 18 forms a liquid cooling cavity, shown generally at 114.
The lower shield 18 has various contours and shapes, which not only forms the lower end 110 used for connection with the lower sleeve 96, but also forms the shape of the liquid cooling cavity 114. There are also two apertures formed as part of the lower shield 18, into which two hydraulic connectors are fixedly mounted. More specifically, there is an inlet hydraulic connector 116 mounted in a coolant inlet aperture (not shown), and an outlet hydraulic connector 118 mounted in a coolant outlet aperture 120. The coolant outlet aperture 120 and the coolant inlet aperture are substantially similar, therefore only one is shown.
The lower shield 18 is joined hermetically to the inner sleeve 86 via laser weld or brazing. The outer surface 88 of the inner sleeve 86 and the inner surface 94 of the lower shield 18 comprise the principal boundary surfaces of the liquid cooling cavity 114. Liquid is brought to and evacuated from the cavity 114 via the inlet aperture and outlet aperture 120 in the lower shield 18 equipped with hydraulic connectors 116,118, also joined to the lower shield 18, preferably by brazing.
The inner sleeve 86 is designed so as to minimize the space between the inside of the inner sleeve 86 and the various injector overmold surfaces. It is also understood that this volume could also be filled with a conductive compound to improve heat transfer to the liquid coolant in the cavity 114. Additionally, the inner sleeve 86, lower sleeve 96, and the lower shield 18 are shaped such that the stress on the connection points 108,102,106 is minimized. The lower sleeve 96 includes an outwardly extending flange 122 which contacts and connects to the outer surface 104 of the lower shield 18. More particularly, the lower shield 18 includes an inwardly extending flange 124 which is connected to the outwardly extending flange 122 through a weld or brazing process to form the third connection point 106. The outer surface 104 is part of the inwardly extending flange 124. The lower sleeve 96 also includes an upwardly extending flange 126 which contacts and connects to the inner surface 100 of the inner sleeve 86. In this embodiment, the inner sleeve 86 includes a downwardly extending flange 128 which connects to the upwardly extending flange 126 through a weld or brazing process to form the second connection point 102. The inner surface 100 of the inner sleeve 86 is part of the downwardly extending flange 128.
Mounted to the outer surface of the lower shield 18 is a v-clamp flange 130 which is used for mounting the reductant delivery unit 10 somewhere along the exhaust system. In one embodiment, the reductant delivery unit 10 may be mounted to an exhaust pipe, but it is within the scope of the invention that the reductant delivery unit 10 may be mounted to an exhaust manifold, or other exhaust system component. During the operation of the unit 10, engine coolant is pumped to the inlet hydraulic connector 116 and flows through the inlet hydraulic connector 116 into the liquid cooling cavity 114. The coolant then circulates through the liquid cooling cavity 114 and exits the liquid cooling cavity 114 through the outlet hydraulic connector 118. The coolant is prevented from contacting the solenoid portion 46 of the injector 32 because of the welds at the three connection points 108,102,106. This circulation of coolant into and out of the liquid cooling cavity 114 cools the reductant delivery unit 10, and provides the reductant delivery unit 10 with a more consistent operating temperature.
The interface with the exhaust line is shown here as one suited for the v-clamp flange 130. Other mounting configurations are also possible, including flanges with bolts. The v-clamp flange 130 (or other flange configurations) is joined to the lower shield 18, also preferably by brazing. It is understood that a number of the braze operations could be accomplished simultaneously with one operation. The flanges 130 would then provide suitable surfaces and geometries for implementation of a sealing gasket to prevent exhaust gas leakage through the flange/boss interface.
An additional advantage of providing the reductant delivery unit 10 with liquid cooling is the unit 10 then has the ability to maintain a constant fluid temperature of the urea, as defined by the liquid cooling circuit. In this way, temperature corrections to adjust for density and viscosity changes in the working fluid can be greatly simplified, or even eliminated, as can be any temperature feedback systems that would be normally required (e.g. coil current measurements).
When in use, urea solution is fed through the inlet pipe 24, such that the urea solution passes through the inner cavity 30 and into the upper valve body 34 of the injector 32. In this embodiment, the inlet pipe 24 is depicted as being substantially perpendicular to the injector 32, which presents certain packaging advantages for some installations. However, the radial orientation of the inlet pipe 24 may be varied, as well as the axial orientation. In this embodiment, the inlet pipe 24 and the inlet cup 26 are integrated as one piece; however, a two piece construction (inlet pipe 24 and inlet cup 26) is also possible which may be advantageous from a construction standpoint.
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.
