Condensation protection AECD for an internal combustion engine employing cooled EGR

#The present invention relates generally to systems for controlling exhaust emissions produced by an internal combustion engine, and more specifically to such systems including an auxiliary emission control device for accommodating control of condensation effects resulting from cooled EGR.

#When combustion occurs in an environment with excess oxygen, peak combustion temperatures increase which leads to the formation of unwanted emissions, such as oxides of nitrogen (NOx). This problem is aggravated through the use of turbocharger machinery operable to increase the mass of fresh air flow, and hence increase the concentrations of oxygen and nitrogen present in the combustion chamber when temperatures are high during or after the combustion event.

#One known technique for reducing unwanted emissions such as NOx involves introducing chemically inert gases into the fresh air flow stream for subsequent combustion. By thusly reducing the oxygen concentration of the resulting charge to be combusted, the fuel burns slower and peak combustion temperatures are accordingly reduced, thereby lowering the production of NOx. In an internal combustion engine environment, such chemically inert gases are readily abundant in the form of exhaust gases, and one known method for achieving the foregoing result is through the use of a so-called Exhaust Gas Recirculation (EGR) system operable to controllably introduce (i.e., recirculate) exhaust gas from the exhaust manifold into the fresh air stream flowing to the intake manifold valve, for controllably introducing exhaust gas to the intake manifold. Through the use of an on-board microprocessor, control of the EGR valve is typically accomplished as a function of information supplied by a number of engine operational sensors.

#FIG. 1 is a diagrammatic illustration of one preferred embodiment of a system for controlling exhaust emissions produced an internal combustion engine employing cooled EGR including a condensation protection AECD, in accordance with the present invention.

#FIG. 2 is a diagrammatic illustration of one known embodiment of at least a portion of the emission manager block of the control computer illustrated in FIG. 1.

#FIG. 3 is a diagrammatic illustration of one known embodiment of at least a portion of the AECD protection logic block illustrated in FIG. 2.

#For the purposes of promoting an understanding of the principles of the invention, reference will now be made to a number of preferred embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated embodiments, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.

#Referring now to FIG. 1, one preferred embodiment of a system 10 for controlling exhaust emissions produced by an internal combustion engine 12, in accordance with the present invention, is shown. System 10 includes an internal combustion engine 12 having an intake manifold 14 fluidly coupled to a compressor 16 of a turbocharger 18 via intake conduit 20, wherein the compressor 16 receives fresh air via intake conduit 22. Optionally, as shown in phantom in FIG. 1, system 10 may include an intake air cooler 24 of known construction disposed in line with intake conduit 20 between the turbocharger compressor 16 and the intake manifold 14. The turbocharger compressor 16 is mechanically coupled to a turbocharger turbine 26 via drive shaft 28, wherein turbine 26 is fluidly coupled to an exhaust manifold 30 of engine 12 via exhaust conduit 32, and is further fluidly coupled to ambient via exhaust conduit 34. An EGR valve 36 or other suitable flow restriction mechanism is disposed in fluid communication with intake conduit 20 and exhaust conduit 32 via an EGR conduit 38, an EGR cooler 40 of known construction disposed in-line with EGR conduit 38 between EGR valve 36 and intake conduit 20. Although not shown in FIG. 1, EGR cooler 40 is, in one preferred embodiment, cooled via engine coolant circulating through a cooling system 44 associated with engine 12, in a manner well-known in the art, although the present invention contemplates cooling the EGR cooler 40 via other known cooling arrangements employing other known cooling fluids. In any case, those skilled in the art will recognize that “coolant temperature”, as this term is used herein, generally refers to the temperature of the particular cooling system, or coolant fluid, used to cool the EGR cooler 40.

#System 10 includes a control computer 42 that is preferably microprocessor-based and is generally operable to control and manage the overall operation of engine 12. Control computer 42 includes a memory unit (not shown) as well as a number of inputs and outputs for interfacing with various sensors and systems coupled to engine 12. Computer 42, in one embodiment, may be a known control unit sometimes referred to as an electronic or engine control module (ECM), electronic or engine control unit (ECU) or the like, or may alternatively be any control circuit capable of operation as described hereinafter.