Circuit for providing electronic warm-up enrichment fuel compensation which is independent of intake manifold pressure in an electronic fuel control system

Abstract

A circuit for recognizing and providing warm-up enrichment fuel compensation for an electronic fuel control system is described herein. The circuit is adapted to recognize and respond to an engine operating parameter indicative of engine operation at an engine temperature less than the normal operating temperature and to increase the duration of the fuel injection command pulse generated by the main electronic fuel control system. In those electronic fuel control systems which provide a fuel injection command pulse whenever a generated voltage wave shape is below a threshold value, the present invention contemplates altering the shape of the generated wave shape to delay its excursion through the threshold value.

I claim: 
     
       1. An internal combustion engine fuel control system comprising: current source means;   electrical storage means;   first control means responsive to one engine operating parameter for providing a threshold signal;   switching control means responsive to another engine operating parameter for switchingly connecting said current source means to said storage means to provide a timed series of .Iadd.sequentially varied initial levels and .Iaddend.variable level injection command signals;   .Iadd.each said command signal commencing at said initial level; .Iaddend.   transistor means for controlling current flow from said current source means to said storage means;   voltage level establishing means for supplying a normal operating bias voltage to said transistor control means;   means responsive to engine temperature for providing a secondary bias voltage to the transistor means in response to engine temperature below a preselected level to reduce the rate at which current is supplied from said source means to said storage means and thereby increase the durations of said command signals; and   fuel delivery means commanded only by said series of command signals for supplying fuel to the engine whenever a command signal has a predetermined relationship with respect to the value of said threshold signal. .Iadd.   
     
     
       2.  An internal combustion engine fuel control system comprising: current source means;   electrical storage means;   first control means responsive to an engine air consumption dependent parameter engine operating parameter for providing a threshold signal;   switching control means responsive to an engine speed for switchingly connecting said current source means to said storage means to provide a timed series of sequentially variable initial levels and variable level injection command signals, each said variable level injection command signal beginning at a said initial level;   transistor means for controlling current flow from said current source means to said storage means, said transistor means responsive to engine temperature to control the rate at which current is supplied from said source means to said storage means and thereby vary the durations of said command signals; and   fuel delivery means commanded only by said series of command signals for supplying fuel to the engine whenever a command signal has a predetermined relationship with respect to the value of said threshold signal. .Iaddend.  3. The circuit of claim 1 wherein said one engine operating parameter is one of an engine speed dependent parameter and an engine air comsumption dependent parameter. .Iadd. 4. In an internal combustion engine fuel injection control system of the type providing a ramp voltage for each engine cycle and increasing at a controllable rate from an initial value through a threshold value and for generating a fuel injection control signal having a duration determined by a first elapsed time defined between said initial value and said threshold value, a second elapsed time being defined between the time said ramp voltage crosses said threshold value and the time said ramp voltage is initiated, improved circuit means for controlling said controllable rate, said initial value, and said threshold value comprising:   a. first, second and third sensor means for providing output signals responsive to the magnitude of said respective first, second and third engine operating parameters, at least one of which varies with temperature;   b. ramp rate control means coupled to one of said sensor means for controlling the ramp of said ramp voltage in accordance with one of said engine operating parameters;   c. initial value control means coupled to a second of said sensor means for controlling said initial value in accordance with a second of said engine operating parameters;   d. threshold value control means coupled to a third of said sensor means for controlling said threshold value in accordance with a third of said engine operating parameters; and   e. cycle by cycle computation means responsive to one of said sensors means for recomputing one of said initial value, threshold value, and controllable rates during said second elapsed time of each engine cycle. .Iaddend. .Iadd. 5. The circuit of claim 4 wherein said first engine operating parameter is one of an engine speed dependent parameter and an engine air consumption dependent parameter. .Iaddend..Iadd. 6. In an internal combustion engine fuel injection control system, a circuit for generating a fuel injection command signal comprising:   a. means for generating a ramp voltage commencing at an initial value determined in accordance with a first engine operating parameter, varying from said initial value at a predetermined rate controlled in accordance with a second engine operating parameter, and crossing a threshold value determined in accordance with a third engine operating parameter;   b. means for recomputing one of said initial value, threshold value, and controllable rate intermediate the time said ramp crosses said threshold value and time said ramp commences from said initial value; and   c. means for generating a fuel injection command in accordance with the time elapsed between said initial value and said threshold value. .Iaddend..Iadd. 7. The fuel injection command circuit of claim 6 wherein one of said engine operating parameters is determined in accordance with engine speed, one of said initial value and said threshold value is determined in accordance with said one engine operating parameter, and trigger means provide trigger pulses switchable between first and second states at a frequency determined by engine speed. .Iaddend. .Iadd. 8. The fuel injection command circuit of claim 6 further comprising capacitor means; current source means selectively switchable to charge said capacitor means; first switching means coupled to said capacitor means and to said current source means operative to allow said current source means to charge said capacitor means at said controllable rate from the time said ramp voltage is initiated until after said ramp voltage crosses said threshold value; and second switching means coupled to said capacitor means operative between the time said ramp voltage is initiated and the time said ramp voltage crosses said threshold value to reset said ramp voltage to a predetermined level and thereafter selectively permit said current source to charge said capacitor means so as to establish said initial value in accordance with the time elapsed from the time said ramp voltage is reset to the time said ramp voltage is initiated. .Iaddend..Iadd. 9. The fuel injection command circuit of claim 8 wherein said second switching means comprises reset pulse generating means and first and second transistors of opposite types each having three electrodes, the first electrode of said first transistor coupled to said capacitor means and the second electrode of said first transistor coupled to a source of reference potential, said first electrode of said second transistor coupled to said third electrode of said first transistor, said second electrode of said second transistor coupled to said source of reference potential, and said third electrode of said second transistor coupled to said reset pulse generating means said reset pulse generating means being operative on a switch of said trigger signals to couple said first and second transistors to provide a predetermined voltage drop between said first electrode of said first transistor and said source of reference potential, said predetermined voltage drop corresponding substantially with said predetermined level. .Iaddend. .Iadd. 10. In an internal combustion engine fuel injection control system of the tupe having a control circuit to electrically control the open time of at least one fuel injection valve in response to the rotation of an engine crankshaft and the magnitudes of temperature and at least two other different engine operating parameters, an improved control circuit comprising:   a. capacitor means for generating a first pulse train which produces at least one pulse for each cycle of the engine crankshaft, said first pulse train having successive pulses defining an interval therebetween, each said pulse starting at an initial point and then increasing at a controllable rate therefrom;   b. means for varying the magnitude of said initial point in accordance with a first of said two other engine operating parameters;   c. means for varying said controllable rate in accordance with temperature;   d. means for generating a second pulse train having pulse durations which begin when a pulse from said first pulse train is initiated and ends when a pulse from said first pulse train reaches a threshold value established in accordance with the second of said two other engine operating parameters;   e. means responsive to the magnitude of one of said two other engine operating parameters and said interval between said first pulse train pulses for establishing the value of one of said initial point and threshold value in accordance with the magnitude of the corresponding one of said two other engine operating parameters during said interval;   f. means for applying said pulses of said second pulse train to said fuel injector valve to open said valve for the duration of a pulse of said second pulse train. .Iaddend.