Fuel injection system

Abstract

A fuel injection system employing digital logic to generate injection command pulses of a time duration calculated to provide a precise quantity of fuel to meet presently existing, varying engine requirements is disclosed herein. The system employs a first or injector selection circuit operative to select an injector or injector group for injection and a second or adaptive delay circuit to generate an injection command. The circuits are electronically intercoupled to provide for substantially simultaneous application of the selection pulse and injection pulse to the proper injector group and to eliminate the need for a mechanical distributor arrangement to select the proper injector group. The time duration or delay signal is generated by a function generator producing an output as a known function of time with injection occurring during the time it takes for the output to reach a pre-determined, selected, threshold value. In order to compensate for varying supply voltages, the second circuit includes means for providing automatic voltage compensation.

I claim: 
     
       1. In a fuel control system for an internal combustion engine of the type having fuel injector valve means and a means to sense engine crank angle, the combination comprising: generating means responsive to engine crank angle to generate a first signal having a waveform with leading and trailing transitions said transistions being indicative of the occurrence of at least one selected engine crank angle;   adaptive delay means responsive to said first signal waveform operative to generate a second signal having a waveform with leading and trailing transitions and including means operative to delay in time the leading transitions of said second signal waveform relative to the leading transitions of said first signal waveform by a predeterminable variable amount which is dependent upon engine speed and load;   inverter means responsive to said second signal operative to generate a third signal having a waveform with leading and trailing transitions corresponding to the trailing and leading transitions, respectively, of said second signal waveform whereby said second signal waveform is inverted to produce said third signal waveform;   gating means receiving said first and third signal waveforms and operative to produce an output signal having a waveform with leading and trailing transitions, which waveform is produced only when said first and third signal waveforms overlap in time; and   injector control means responsive to said output signal to energize at least one injector valve means during the time interval between two consecutive output signal waveform transitions.   
     
     
       2. The system as claimed in claim 1 wherein said adaptive delay means comprise: function generator means operative to generate a signal having a characteristic which varies with elapsed time from a first value indicative of a selected engine crank angle to a second value; and   threshold detector means operative to produce a signal having a first level and a second level and operative to switch therebetween whenever said function generator means signal passes through a predeterminable threshold level intermediate said first and second values.   
     
     
       3. The system as claimed in claim 2 including further rapid switching means coupled to said detector means operative to facilitate rapid switching of said detector means signal between said first and second levels. 
     
     
       4. The system as claimed in claim 3 wherein said detector means comprise an emitter-coupled pair of transistors, each of said transistors having a base electrode and an emitter electrode, one of said base electrodes arranged to receive said function generator means signal and the other of said base electrodes arranged to receive a reference signal and said rapid switching means comprise a constant current source in series relationship with said emitters. 
     
     
       5. In a fuel injection system for an internal combustion engine having fuel injection valve means, control means to generate a signal indicative of engine fuel requirements and input signal generating means operative to generate a first signal waveform having leading and trailing transitions, the improvement to said control means comprising: adaptive delay means operative to receive said first signal and to produce, as output, a delay signal having a waveform with a leading transition produced in response to the leading transition of said first signal waveform but delayed in time relative thereto by a predeterminable variable amount dependent upon engine operating parameters;   inverter means operative to receive said delayed signal and to produce in response thereto an inverted output signal having a waveform with a trailing transition corresponding to the leading transition of said delayed signal waveform; and   gating means operative to receive said first signal and said inverted signal and to produce an output signal having a waveform with leading transitions corresponding to said first signal waveform leading transitions and trailing transitions corresponding to said inverted signal waveform trailing transitions.   
     
     
       6. The system as claimed in claim 5 wherein said adaptive delay means comprise: generator means for generating a signal having a characteristic which varies with elapsed time in a predeterminable manner from a first predetermined value to a second predetermined value; and   detector means operative to receive said generator means signal and to produce an output signal waveform having transitions which correspond to the generator means signal characteristic passing through a third value intermediate said first and second values;   said delayed signal variable time delay being determined by the time required for said generator means signal to vary from said first value to said third value.   
     
     
       7. The system as claimed in claim 6 wherein said generator means comprise electronic means for generating a ramp voltage. 
     
     
       8. The system as claimed in claim 6 wherein said generator means include a resistive-reactive network and said output signal is controlled by the rate of change of a signal present in the reactive portion of said network. 
     
     
       9. The system as claimed in claim 6 wherein said threshold detecting means comprise a controllably variably biased unijunction transistor. 
     
     
       10. The system as claimed in claim 6 wherein said threshold detecting means comprise a controllably variably biased emitter-coupled pair of transistors, each of said transistors having an emitter electrode and a base electrode. 
     
     
       11. The system as claimed in claim 6 including further rapid switching means in series relationship with the emitters of said emitter-coupled pair operative to cause rapid regeneration at the emitters of the emitter-coupled pair of transistors when said generator means output signal reaches a predeterminable value. 
     
     
       12. The system as claimed in claim 11 wherein said rapid switching means comprise a constant current source coupled to the emitters of the emitter-coupled pair of transistors. 
     
     
       13. In a fuel injection system for an internal combustion engine having a plurality of fuel injectors, the combination comprising: input means operative to generate a first signal having a waveform with leading and trailing transitions, said transitions being indicative of at least one engine crank angle;   adaptive delay means operative to generate a second signal having a waveform with leading and trailing transitions, and including means operative to delay in time the leading transitions of said second signal waveform relative to the leading transitions of said first signal waveform by a predeterminable variable amount which is dependent upon engine speed and load and including further means operative to cause the second signal waveform trailing transitions to occur no later in time than said first signal waveform trailing transitions;   inverter means responsive to said second signal operative to generate a third signal having a waveform with leading and trailing transitions corresponding to the trailing and leading transitions, respectively, of said second signal waveform whereby said second signal waveform is inverted to produce a third signal waveform; and   gating means receiving said first and third waveforms and operative to generate an injection command signal for at least one injector whenever said first signal waveform and said third signal waveform overlap in time, said command signal having a waveform with leading and trailing transitions, with the command signal trailing transitions corresponding in time to said third signal trailing transitions.   
     
     
       14. The system as claimed in claim 13 wherein said adaptive delay means comprise: function generator means operative to generate a signal having a characteristic which varies with elapsed time from a first value indicative of a selected engine crank angle to a second value; and   threshold detector means operative to produce a signal having a first level and a second level and operative to switch therebetween whenever said function generator means signal passes through a predeterminable threshold level intermediate said first and second levels.   
     
     
       15. The system as claimed in claim 14 including further rapid switching means coupled to said detector means operative to facilitate rapid switching of said detector means signal between said first and second levels. 
     
     
       16. The system as claimed in claim 15 wherein said detector means comprise an emitter-coupled pair of transistors, each of said transistors having a base electrode and an emitter electrode, one of said base electrodes arranged to receive said function generator means signal and the other of said base electrodes arranged to receive a reference signal and said rapid switching means comprise a constant current source in series relationship with said emitters. 
     
     
       17. In an internal combustion engine fuel control system of the type having fuel injector valve means and a means to sense engine crank angle, the combination comprising: generating means responsive to engine crank angle to generate a first signal having a waveform with leading and trailing transitions, said transitions being indicative of the occurrence of at least one selected engine crank angle;   sweep generator means responsive to one of said first signal waveform transitions operative to generate a monotonically changing sweep signal having an initial point which corresponds to said one transition;   threshold comparison means responsive to said sweep signal operative to compare said sweep signal with a threshold level and to produce an output signal having a waveform with leading and trailing transitions, said transitions corresponding to sweep signal excursions through said level;   and injector control means receiving said output signal to control the actuation of the injector valve means during the time interval between two consecutive output signal waveform transitions.   
     
     
       18. The system as claimed in claim 17 wherein said sweep signal has a characteristic which varies as a function of engine operating parameters. 
     
     
       19. The system as claimed in claim 17 including further: threshold establishing means responsive to at least one engine operating parameter operative to establish a reference threshold level; and   means to communicate said threshold level to said threshold comparison means.   
     
     
       20. The system as claimed in claim 19 wherein said sweep generator means comprise electronic means for generating a ramp voltage. 
     
     
       21. The system as claimed in claim 19 wherein said sweep generator means include a resistive-reactive network and said threshold comparison means output signal is controlled by the rate of change of a signal present in the reactive portion of said network. 
     
     
       22. The system as claimed in claim 19 wherein said threshold comparison means comprise a controllably variably biased unijunction transistor. 
     
     
       23. In an internal combustion engine fuel control system of the type having fuel injector valve means and a means to sense engine crank angle, the combination comprising: generating means responsive to engine crank angle to generate a first signal having a waveform with leading and trailing transitions, said transitions being indicative of the occurrence of at least one selected engine crank angle;   sweep generator means responsive to one of said first signal waveform transitions operative to generate a monotonically changing sweep signal having an initial point which corresponds to said one transition;   threshold comparison means responsive to said sweep signal operative to compare said sweep signal with a threshold level and to produce an output signal having a waveform with leading and trailing transitions, said transitions corresponding to sweep signal excursions through said level;   injector control means responsive to said output signal to control the actuation of the injector valve means during the time interval between two consecutive output signal waveform transitions;   threshold establishing means responsive to at least one engine operating parameter operative to establish a reference threshold level;   and means to communicate said threshold level to said threshold comparison means;   said threshold comparison means comprising a controllably variably biased emitter-coupled pair of transistors, each of said transistors having an emitter electrode and a base electrode.   
     
     
       24. The system as claimed in claim 23 including further rapid switching means in series relationship with the emitters of said emitter-coupled pair operative to cause rapid regeneration at the emitters of the emitter-coupled pair of transistors when said generator means output signal reaches a predeterminable value. 
     
     
       25. The system as claimed in claim 24 wherein said rapid switching means comprise a constant current source coupled to the emitters of the emitter-coupled pair of transistors. 
     
     
       26. In an internal combustion engine fuel control system of the type having fuel injector valve means and a means to sense engine crank angle, the combination comprising: first generating means responsive to the crank angle sensing means operative to generate a first signal having a waveform with leading and trailing transitions, selected transitions having a preselected relationship to at least one selected engine crank angle;   second generating means responsive to said first signal selected transitions operative to generate a second signal having a waveform with leading and trailing transitions, said transitions occurring in timed relationship to the occurrence of said first signal selected transitions;   sweep generator means responsive to one of said second signal waveform transitions operative to generate a monotonically changing sweep signal having an initial point which corresponds to said one transition;   threshold comparison means responsive to said sweep signal operative to compare said sweep signal with a threshold level and to produce an output signal having a waveform with leading and trailing transitions, said transitions corresponding to sweep signal excursions through said level;   and injector control means receiving said output signal to control the actuation of the injector valve means during the time interval between two consecutive output signal waveform transitions.   
     
     
       27. The system as claimed in claim 26 wherein said second signal leading transitions occur in timed relationship to alternate ones of the first signal selected transitions and said second signal trailing transitions occur in timed relationship to the first signal selected transitions which occur intermediate said alternate transitions. .Iadd. 
     
     
       28.  A multivibrator circuit including in combination: comparator means having a reference input, first and second signal inputs, and an output;   means for supplying a reference voltage to the reference input of the comparator means;   timing capacitor means coupled across the first and second signal inputs of the comparator means at first and second junctions, respectively;   means for supplying operating potential;   first and second charging circuits coupled between the means for supplying operating potential and the first and second junctions, respectively, and;   switch means connected to said first and said second charging circuits for alternatively shunting a portion of the current in one of said charging circuits to provide supplementing current in the other of said charging circuits. .Iaddend. .Iadd.   
     
     
       29.  A circuit for generating a fixed pulse duration comprising: complementary pulse generator means for generating first and second normally complementary signals at respective first and second pulse generator outputs and for switching said complementary signals between first and second substantially constant output levels;   logic gate means having first and second gate inputs coupled respectively to said first and second pulse generator outputs operative to provide a logic gate output having a first and second logic levels; and   capacitor means coupling said first and second logic gate inputs for causing a predetermined overlap in the magnitudes of said pulse generator outputs by increasing the time required for said pulse generator outputs to switch between said first and second levels;   whereby said logic gate means generates one of said first and second output levels only during said predetermined overlap. .Iaddend. .Iadd.30. The circuit of claim 29, wherein said logic gate means comprises an AND gate. .Iaddend.