Fuel injection control apparatus of internal combustion engine

#This application is based on Application No. 2002-33919, filed in Japan on Feb. 12, 2002, the contents of which are hereby incorporated by reference.

#1. Field of the Invention

#The present invention relates to a fuel injection control apparatus of an internal combustion engine, and particularly, to an air/fuel ratio feedback control of the internal combustion engine.

#In the accompanying drawings:

#FIG. 1 is a block diagram showing a construction of a fuel injection control apparatus of an internal combustion engine according to an embodiment of the present invention;

#FIG. 2 is a simplified graph showing the change of a compensation coefficient (gain) from when O2 feedback is performed for the first time by a feedback controlling means 20 of FIG. 1;

#FIG. 1 is a block diagram showing a construction of a fuel injection control apparatus of an internal combustion engine according to an embodiment of the present invention. In FIG. 1, a signal from an O2 sensor 1, and a signal from control conditions 8 such as a throttle opening, water temperature, and engine rotation speed, are inputted to a feedback determination means 3A of a feedback controlling means 20 according to the present embodiment. In the feedback determination means 3A, a feedback gain set at the time of starting the feedback control, which is used for imparting operation constant to perform the feedback control from when the feedback control is started until an optimum air/fuel ratio is achieved, is set to a value larger than that of a feedback gain for the normal operation period, which is used for imparting operation constant to perform the feedback control in a stable state. Thus, the feedback determination means 3A changes the feedback gain between the time of starting the feedback control and the normal operation time, in performing the feedback control. It makes the determination whether the O2 feedback has been performed, the judgement between a rich state and a lean state, and the determination whether the feedback is started for the first time.

#Specifically, when the feedback determination means 3A makes determination that the feedback is performed for the first time and that the current air/fuel ratio is in a rich state, a gain from a first-time rich-side gain calculating means 4a is selected as the compensation coefficient for the O2 feedback. The first-time rich-side gain calculating means 4a incorporates therein a gain correspondence table between the rotation speed and the rich or lean state, for example, and obtains from the table the gain for the rich or lean state that corresponds to the rotation speed, to thereby achieve output thereof.

#Also, in a similar manner, when the feedback determination means 3A makes determination that the feedback is not for the first time but for the normal operation time and the current air/fuel ratio is in the rich state, a gain from a normal rich-side gain calculating means 4b is selected. When it is determined that the feedback is for the first time and the current air/fuel ratio is in the lean state, a first-time lean-side gain calculating means 5a is selected. When it is determined that the feedback is not for the first time but for the normal operation period and the current air/fuel ratio is in the lean state, a normal lean-side gain calculating means 5b is selected. Each of the gain calculating means, as in the first-time rich-side gain calculating means 4a, the gain for the rich or the lean state which corresponds to the rotation speed, is obtained through the incorporated gain correspondence table establishing correspondence between the rotation speed and the rich or the lean state, to thereby attain output thereof.