Fuel injection control system for internal combustion engine

#The present invention relates to fuel injection control systems for engines such as engines of automobiles, and more specifically to fuel injection control systems for injecting fuel twice or more times in each engine operating cycle.

#Japanese patent provisional publications Nos. 60-195347, 60-233353, 59-211731 and 59-29733 disclose fuel injection control systems designed to meet recent demands for better fuel economy, speedier response, higher output and further improvement in emission control in all operating conditions.

#These conventional injection systems are arranged to determine the injection timing and the fuel injection quantity in accordance with engine rpm, engine load and other engine operating parameters, and advance the injection timing so that the fuel can be correctly introduced into the engine within the suction stroke even when the fuel is enriched.

#FIG. 1 is a block diagram schematically showing a fuel injection control system of the present invention.

#FIG. 2 is a schematic view of a fuel injection control system according to a first or second embodiment of the present invention.

#FIG. 3 is a block diagram showing an injector control circuit of the control system of FIG. 2.

#As schematically shown in FIG. 1, a fuel injection control system of the present invention basically includes a means 101 for sensing an engine load, a means 102 for sensing a crank angle of the engine, a means 103 for determining fuel injection timings of first and second injections to be performed in each cycle, a means 104 for determining fuel injection quantities of the first and second injections, an output means 105 for producing first and second injection signals, and an injector means 106 for supplying the fuel to the engine by spraying the fuel twice in each cycle in response to the first and second injection signals. The fuel injection quantity determining means 104 includes a first means 104a for determining a desired fuel quantity in accordance with the engine load, a second means 104b for determining te first injection quantity of the first injection from the desired quantity, a third means 104c for determining a compensation quantity for compensating for a change in the desired quantity between a time of the first injection and a time of the second injection, and a fourth means 104d for determining the second injection quantity from the compensation quantity.

#A first embodiment of the present invention is shown in FIGS. 2-9.

#An engine 1 of this example has six cylinders, each of which is supplied with intake air through an intake pipe 2 and an intake manifold 3. There are provided six fuel injectors 4a-4f. Each cylinder is provided with one injector 4a, 4b, . . . or 4f. Each injector 4 (i.e., 4a, 4b, . . . or 4f) injects fuel in response to one of six fuel injection signals Si. An exhaust pipe 5 conveys exhaust gas mixture from each cylinder to a catalytic converter (not shown) for emission control.