Diesel EGR control

#1. Field of the Invention

#The field of the invention relates to control of diesel engines having exhaust gas recirculation.

#2. Background Art

#The advantages of the invention claimed herein will be more readily understood by reading an example of an embodiment in which the invention is used to advantage with reference to the following drawings wherein:

#FIGS. 1a and 1b are a block diagrams of an embodiment in which the invention is used to advantage;

#FIG. 2 is a high level flowchart which perform a portion of operation of the embodiment shown in FIGS. 1a and 1b; and

#Direct injection compression ignited internal combustion engine 10, comprising a plurality of combustion chambers, is controlled by electronic engine controller 12. Combustion chamber 30 of engine 10 is shown in FIG. 1a including combustion chamber walls 32 with piston 36 positioned therein and connected to crankshaft 40. In this particular example, piston 36 includes a recess or bowl (not shown) to help in forming stratified charges of air and fuel. Combustion chamber or cylinder 30 is shown communicating with intake manifold 44 and exhaust manifold 48 via respective intake valves 52a and 52b (not shown), and exhaust valves 54a and 54b (not shown). Fuel injector 66A (in this example a diesel fuel injector) is shown directly coupled to combustion chamber 30 for delivering liquid fuel directly therein in proportion to the pulse width of signal fpw received from controller 12 via conventional electronic driver 68. Fuel is delivered to fuel injector 66A by a high-pressure fuel system (not shown) including a fuel tank, fuel pumps and a fuel rail.

#Intake manifold 44 is shown communicating with throttle body 58 via throttle plate 62. In this particular example, throttle plate 62 is coupled to electric motor 94 so that the position of throttle plate 62 is controlled by controller 12 via electric motor 94. This configuration is commonly referred to as electronic throttle control (ETC), which is also utilized to control fresh airflow and EGR flow as described later herein.

#Nitrogen oxide (NOx) catalyst 70 is shown positioned upstream of particulate filter 72. NOx catalyst 70 reduces NOx when engine 10 is operating lean of stoichiometry.