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.

Description

BACKGROUND OF THE INVENTION MOC 70/72, 72, 219,275 filed Jan. 20, 1972 for a Electronic FLE Switch for Fuel Injection. As current flow I₁ from current source 101 increases, the voltage will follow the portion of the graph designated B-C. Upon reaching the limiting value C, the voltage present across the capacitor will remain at a substantially level value until it reaches the time period denoted as D. Assuming graph 90 is the voltage appearing across capacitor 103, the time interval A- D represents the time during which a triggering pulse is present on triggering lead 40, illustrated as the voltage pulse identified as 92. Upon termination of the pulse 92, a similar pulse denoted as pulse 94 is applied to the triggering lead 42. The application of triggering pulse 94 on triggering lead 42 will cause a similar voltage waveshape to appear across capacitor 104. In the meantime, the voltage present on capacitor 103 will be increasing from a value established at time D to a limiting value under the influence of application of current I₂ from current source 102. At normal operating temperatures, the slope of this increase will be substantially as illustrated in graph 90 and the injection time will be determined by the total elapsed time required for the voltage present on capacitor 103 to go from the value existing on that capacitor at the time denoted as D until the voltage on capacitor 103 reaches a threshold value which may be determined for example by the pressure sensor 12 through the circuitry denoted as 107 in FIG. 3.

With reference now to the voltage waveshape 96 in FIG. 4, the effect of the present invention will be illustrated. The voltage waveshape 96 is essentially the same as the voltage waveshape 90 during the time interval A to D. However, from the time D until the limiting value is reached five various voltage slopes are illustrated and are denoted as a through e. These correspond to some of the slopes obtainable through the use of the present invention for varying operating temperatures. Slope e may represent the slope obtained by the lowest operating temperature while the slope a represents the slope obtained at normal operating temperature, as defined by the voltage divider resistances 114, 115, and the slopes b, c, and d represent various intermediate levels.

A representative threshold value has been applied to the voltage waveshape 96 and has been numbered 98. Referring now to the voltage waveshape identified as 100, the output of voltage present at amplifier 58 in response to the voltage waveforms 94 & 96 with threshold level 98 is indicated. The first portion of the voltage waveform 100 is identified as a and corresponds to the pulse which would be generated by the portion of the waveform also identified as a in response to threshold 98. For lower temperature conditions when the present invention would so control current source 102 that the voltage waveform appearing across capacitor 103 is as indicated by waveform b, the pulse duration also identified as b would be present. For decreasing temperatures which would produce the waveshapes c and d the pulse durations identified as c and d would also be generated. For the most extreme condition of engine temperature the second portion of the waveshape 96 would most closely resemble the waveshape identified as e and in this instance, the total output pulse duration present at the output of amplifier 58 would be as represented by the total pulse e.

It can now be seen that the present invention accomplishes its stated objectives in a desirably expeditious form by controlling the magnitude of a current used to controllably charge a timing capacitor in a system which utilizes the time required for that current to charge the timing capacitor to a preselected level as a temperature compensation device. While the specific implementation of my invention has been controlled by the nature of the associated electronics, it will be understood that other implementations are possible. For example, an additional current source or a current sink could readily be controlled to achieve the results of my specific embodiment and such variations are intended to be encompassed by the claims which follow.

Claims

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 sequentially varied initial levels and variable level injection command signals;

each said command signal commencing at said initial level;

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.

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. 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.

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.

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.

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.

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.

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.

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.

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.