BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic diagram of a configuration of an internal combustion engine and an air-fuel ratio control system therefor according to one embodiment of the present invention;
FIGS. 2A and 2B are graphical representations showing a deterioration detection method of the catalyst;
FIG. 3 is a block diagram showing a configuration of a module which performs a response deterioration compensation of an oxygen concentration sensor, the air-fuel ratio control, and a catalyst deterioration detection;
FIG. 4 is a block diagram showing a configuration of the response deterioration compensation block which performs the response deterioration compensation of the oxygen concentration sensor;
FIG. 5 is a graph showing frequency characteristics of the first-order delay compensator shown in FIG. 4;
FIG. 6 is a flowchart of a process for implementing functions of the blocks which constitute the module shown in FIG. 3;
FIG. 7 is a flowchart of the response deterioration diagnosis process executed in the process of FIG. 6;
FIGS. 8A and 8B are graphical representations of the time charts for illustrating the process of FIG. 7;
FIG. 9 is a graphical representation of a table referred to in the process of FIG. 7;
FIG. 10 is a portion of a flowchart of the perturbation signal generation process executed in the process of FIG. 6;
FIG. 11 is the remainder of the flowchart of the perturbation signal generation process executed in the process of FIG. 6;
FIGS. 12A-12E are graphical representations of tables referred to in the process of FIG. 10 and FIG. 11;
FIG. 13 is a flowchart of the KCMD calculation process executed in the process of FIG. 6;
FIGS. 14A and 14B are graphical representations of the time charts for illustrating the process of FIG. 13;
FIG. 15 is a portion of a flowchart of the correction amount (PO2C) calculation process executed in the process of FIG. 6;
FIG. 16 is the remainder of the flowchart of the correction amount (PO2C) calculation process executed in the process of FIG. 6;
FIG. 17 is a graphical representation of a table referred to in the process of FIG. 15;
FIGS. 18A-18D are graphical representations of the time charts for illustrating the process of FIG. 15 and FIG. 16;
FIG. 19 is a portion of a flowchart of the deterioration determination process executed in the process of FIG. 6;
FIG. 20 is the remainder of the flowchart of the deterioration determination process executed in the process of FIG. 6; and
FIGS. 21A-21D are graphical representations of the time charts for illustrating problems of the conventional technique and the effects of the present invention.
Patent Application
20070227123
