Fuel injection control apparatus for alcohol engine

A fuel injection control apparatus of an engine for injecting a mixed fuel containing gasoline and alcohol, having a throttle opening degree sensor for detecting an actual throttle opening degree, a crank angle sensor for producing a crank pulse at a predetermined crank angle, an intake air amount sensor for detecting an intake air amount, a coolant temperature sensor for detecting a coolant temperature, engine speed calculating means responsive to said crank pulse for calculating an engine speed, a single point injector provided in a connecting portion of each intake pipes communicated with each cylinders of the engine, and a plurality of multi point injectors adjacently disposed at each intake port of said cylinders, respectively, for injecting the fuel, said apparatus comprising:

• an alcohol concentration sensor for detecting an alcohol concentration of the fuel;
• and
• engine low speed range discriminating means for discriminating an engine low speed range in accordance with said engine speed;
• throttle full-open range discriminating means responsive to said actual throttle opening degree for discriminating a throttle full-open range;
• reference throttle opening degree setting means for setting a reference throttle opening degree in accordance with said alcohol concentration;
• evaporation time constant setting means responsive to said engine speed, said intake air amount and said coolant temperature for setting an evaporation time constant;
• fuel deposition coefficient setting means responsive to said actual throttle opening degree and said coolant temperature for setting a fuel deposition coefficients;
• desired air-fuel ration setting means responsive to said coolant temperature for setting a desired air-fuel ratio;
• injection mode selecting means for comparing said actual throttle opening degree and said reference throttle opening degree, and for outputting a single-point injection mode signal indicating a mode to perform single-point injection when said actual throttle opening degree is smaller than said reference throttle opening degree, and for outputting a multi-point injection mode signal indicating a mode to perform multi-point injection when said actual throttle opening degree is larger than said reference throttle opening degree;
• single-point injection amount setting means responsive to said single-point injection mode signal for setting a single-point injection amount depending on said evaporation time constant, said fuel deposition coefficient, said desired air-fuel ratio and said intake air amount so as to start injecting the fuel of said single-point injection amount at a fixed injection timing;
• fuel injection start timing setting means for delaying a fuel injection start timing for the multi-point injection against said fixed injection timing in accordance with the increasing of said alcohol concentration when said throttle full-open range discriminating means discriminates said throttle full-open range and said engine low speed range discriminating means discriminates said engine low speed range;
• and
• multi-point injection amount setting means responsive to said multi-point injection mode signal for setting a multi-point injection amount for each of said multi-point injectors so as to start injecting the fuel of said multi-point injection amount at a timing set by said fuel injection start timing setting means.