REGISTER  |  SIGN IN
United States Patent4255789
Hartford , ; et al.March 10, 1981
Title
Microprocessor-based electronic engine control system
Abstract
A method and apparatus for controlling the various functions of an internal combustion engine using a program-controlled microprocessor having a memory preprogrammed with various control laws and associated control schedules receives information concerning one or more engine operating parameters such as manifold pressure, throttle position, engine coolant temperature, air temperature, and engine speed or period and the like. These parameters are sensed and then supplied to input circuits for signal conditioning and conversion to digital words usable by the microprocessor. The microprocessor-based electronic engine control system computes a digital word indicative of a computer-commanded engine control operation and output circuitry responds to predetermined computer-generated commands and to the computed digital command words for converting them to corresponding pulse-width control signals or the like for controlling such engine operations as fuel-injection ignition timing, proportional and/or on-off EGR control, and the like.
Inventors:Hartford; Thomas W. (Livonia, MI), Johnson; Edwin A.  (Clarkston, MI), Russo; Frank A.  (Williamsburg, VA)
Assignee:The Bendix Corporation (Southfield, MI)
Appl. No.:881321
Filed:February 27, 1978
Current U.S. Class:701/108 708/290 123/406.65 123/480 123/492 701/106 
Field of Search:364/424,431,442,200,900,550 123/32EB,32EE,32EH,32EC,32EA,117D,117R,119EC 340/347AD 235/304.1
U.S. Patent Documents
3553654January 1971Crane
3581304May 1971Paradise et al.
3636555January 1972Waaben
3661126May 1972Baxendale
3688221August 1972Fruhalf
3749065July 1973Rothfusz et al.
3835819September 1974Anderson, Jr.
3858561January 1975Aono
3867717February 1975Moehring et al.
3893432July 1975Krupp et al.
3919533November 1975Einolf, Jr. et al.
3969614July 1976Moyer et al.
3996911December 1976Canup
4008698February 1977Gartner
4009699March 1977Hetzler et al.
4020802May 1977Hattori et al.
4035780July 1977Kristick et al.
4099495July 1978Kiencke et al.
4100891July 1978Williams
4115864September 1978Vick et al.
4121554October 1978Sueishi et al.
4126107November 1978Harada et al.
4127091November 1978Leichle
4130095December 1978Bowler et al.
4132193January 1979Takase et al.
4132200January 1979Asano et al.
Foreign Patent Documents
2551639Jun., 1977DE
Primary Examiner: Gruber; Felix D.
Attorney, Agent or Firm:Haas, Jr.; Gaylord P. Wells; Russel C.
Claims

We claim:
1. In an internal combustion engine having an intake system an exhaust system, an engine block, a plurality of cylinders disposed in said engine block, a piston mounted for reciprocal movement in each of said plurality of cylinders in response to the combustion of air shaft responsive to the reciprocation of said pistons in said cylinders for being drivably rotated thereby, throttle means disposed in said intake system for controlling the air flow into said plurality of cylinders, means responsive to a fuel control signal for selectively supplying a controlled quantity of fuel into a selected one or more of said plurality of cylinders, means responsive to an ignition control signal for selectively controlling the time and duration of the ignition of said fuel in said selected one or more of said plurality of cylinders, means coupling said exhaust system to said intake system for establishing an exhaust gas recirculation path therebetween, means disposed at least partially within said recirculation path and responsive to an exhaust gas recirculation control signal for selectively varying the quantity of exhaust gas recirculated from said exhaust system back to said intake system, an improved electronic engine control system comprising:
means for sensing a plurality of selected engine operating parameters and generating a conditioned sensor output signal indicative of the value of each of said sensed plurality of selected engine operating parameters;
means for generating predetermined command signals to control the processing said output signal;
means responsive to said predetermined command signals for converting a selected one of said conditioned sensor output signals indicative of the value of a selected one of said sensed engine operating parameters into one or more digital words indicative thereof;
memory means for storing data representing look-up tables of control command modifier values for use in computing one or more engine control commands and program means for implementing at least one of preprogrammed fuel control law, ignition control law or exhaust gas recirculation control law;
means responsive to said one or more of said digital words representative of the value of said selected engine operating parameters for addressing said memory means for one or more of said stored look-up tables of modifier values;
computing means including means responsive to each of said addressed look-up tables for computing one or more desired modifier values, said computing means further including program execution means for generating said predetermined command signals and for implementing said at least one pre-programmed control law utilizing said computed modifier values for calculating one or more digital command words indicative of a desired control action to be taken for effecting a predetermined engine control function; and
means responsive to said one or more digital command words for generating a precisely controlled value of at least a selected one of said fuel control signal for selectively controlling the quantity of fuel supplied to a selected one or more of said plurality of cylinders, said ignition control signal for selectively controlling the time and duration of the ignition of said fuel in said selected one or more of said plurality of cylinders, and said exhaust gas recirculation signal for selectively varying the quantity of exhaust gas recirculated from said exhaust system back to said intake system.

2. In an internal combustion engine having an intake system, an exhaust system, an engine block, a plurality of cylinders disposed in said engine block, a piston disposed in each of said plurality of cylinders and mounted for reciprocal movement within each of said cylinders in response to combustion of fuel and air therein, means associated with at least a predetermined one of said cylinders and responsive to said piston reciprocating therein having attained a predetermined reference position for generating an engine position signal indicative thereof, means responsive to a fuel control signal for selectively controlling the quantity of fuel supplied to a selected one or more of said plurality of cylinders, means responsive to an ignition control signal for selectively controlling the time and duration of the ignition of said fuel in said selected one or more of said plurality of cylinders, an improved microprocessor-based engine control system comprising:
means for sensing a plurality of engine operating parameters and generating sensor output signals indicative of the value thereof;
means for generating command signals for processing said sensor output signals;
means for converting a selected one of said sensor output signals into one or more data words representative thereof in response to said processing signals;
means responsive to one or more of said data words for performing predetermined programmed operations thereon in accordance with pre-programmed fuel control laws and ignition timing laws and for generating digital commands indicative of a desired control action for effecting one or more predetermined engine control functions such as fuel pulse injection or ignition timing, the operation thereof being synchronized to the generation of said engine position signals;
means responsive to said digital commands for controlling the generation of a selected one of said fuel control signal or said ignition timing signal thereby accurately controlling the quantity of fuel supplied to a selected one or more of said plurality of cylinders or the time and duration of fuel ignition therein; and
means responsive to said engine position signals for altering the rate at which said digital commands are generated such that certain control functions such as fuel control are up-dated once each revolution until a predetermined engine speed is reached and then once every other revolution thereafter, and other control functions such as ignition timing and the like are updated once every other revolution at low engine speeds and once each revolution after the engine speed reaches a second predetermined level, thereby automatically proportioning the up-dating of said data commands to effectively compensate for changing computing power per engine revolution and hence the number of computations that can be performed per revolution which inherently occur with changes in engine speed.

3. In an internal combustion engine having an engine block, a plurality of cylinders disposed in said engine block, a piston disposed in each of said cylinders and mounted for reciprocal movement therein in response to the combustion of air and fuel in said cylinder, means responsive to a fuel control signal for selectively controlling the supply of fuel into a selected one or more of said plurality of cylinders, means responsive to a digital fuel control command for controlling the generation of said fuel control signal, and an electronic engine control means for implementing a pre-programmed fuel control law to generate said digital fuel control command, the improvement comprising:
external sensing means for generating a signal indicative of the value of engine temperature;
means responsive to said signal indicative of the value of engine temperature for converting said signal into an engine temperature data word representative thereof;
memory means for storing data representative of a look-up table having a predetermined finite number of basic fuel command modifier values representing a continuous control surface having an infinite number of such modifier values;
means responsive to at least said engine temperature data word for addressing said look-up table to obtain at least one predetermined basic fuel command modifier value;
means for interpolating between data representative of said addressed at least one predetermined basic modifier value and the basic modifier values adjacent thereto for accurately computing an optimal modifier value for use by said electronic engine control means in the implementation of said predetermined fuel control law; and
program means for implementing said fuel control law to generate said digital fuel control command, said program means being responsive to said accurately computed optimal modifier value for modifying the value of said digital fuel control command to insure the generation of a more accurate engine temperature-compensated digital fuel control command and hence a more accurate engine temperature-compensated fuel control signal thereby insuring a more accurately controlled supply of fuel into said selected one or more cylinders.

4. In an internal combustion engine having an intake system, an exhaust system, an engine block, a plurality of engine cylinders disposed in said engine block, a piston disposed for reciprocal movement within each of said plurality of cylinders, an output shaft responsive to the reciprocation of said pistons within said cylinders in response to the combustion of fuel and air therein for driveably rotating same, means for selectively supplying fuel into one or more of said cylinders, means responsive to an ignition control pulse for controlling the ignition of said fuel in said cylinders, means for sensing a predetermined position of said piston within said cylinder such as top-dead-center or the like for generating engine position pulses and for obtaining an indication of the speed or period of said engine, and a micro-processor-based electronic engine control system including memory means, the improvement in said microprocessor-based electronic engine control system comprising:
memory means for storing data representative of at least one look-up table for establishing a predetermined multi-dimensional control surface representing values of modifier variables;
means responsive to said engine speed or period for addressing said memory means for at least one look-up table and selecting a predetermined modifier variable stored therein;
program means responsive to the addressing of said look-up table memory means for interpolating between said addressed predetermined modifier value and adjacent values for computing an optimal modifier value for use in ignition timing calculations, said program means further including means responsive to said engine speed or period and to said computed optimal modifier values for generating an ignition control word indicative of a predetermined delay interval, said ignition timing being controlled thereby such that said ignition control pulse is initiated at the end of a delay represented by said ignition control word, said program means being further effective for terminating said ignition control pulse after a second predetermined period, thereby controlling the ignition timing of said engine.

5. In an internal combustion engine having an intake system, an exhaust system, an engine block, a plurality of engine cylinders disposed in said engine block, a piston disposed for a reciprocal movement within each of said plurality of cylinders, an output shaft responsive to the reciprocal movement of said pistons within said cylinders in response to the combustion fuel and air therein for drivably rotating same, means for controllably supplying fuel to a selected one or more of said cylinders, sensor means associated with one or more of said pistons or said output shaft for generating engine position pulses indicative of the piston having attained a predetermined position such as top-dead-center or the like, said engine position pulse being generally indicative of engine speed or period, and a microprocessor-based engine control system including a memory means, a means responsive to an ignition control pulse for controlling the ignition of said fuel within said cylinders, the improvement comprising:
memory means for storing data representative of at least one look-up table containing a predetermined finite number of modifier values stored in said memory means for establishing a predetermined at least two dimensional control surface representing an infinite number of modifier values which are a function of at least engine speed or period;
means responsive to at least said engine position pulses or a speed or period value derived therefrom for addressing said look-up table to select one of said finite modifier values therefrom;
program means for interpolating between said one selected modifier value and the addressable values adjacent thereto for computing an optimal modifier value, said program means further including means responsive at last to said accurately computed optimal modifier value for calculating a first digital ignition control word indicative of the pulse-width or duration of said ignition control pulse, said program means further including means responsive to each of said engine position pulses for initiating the start of said ignition control pulse upon receipt thereof for controlling both ignition timing and ignition dwell time.

6. In an internal combustion engine having an engine block, a plurality of cylinders disposed in said engine block, a piston disposed in each of said cylinders and mounted for reciprocal movement in response to the combustion of air and fuel in said cylinder, an output shaft responsive to the reciprocation of said pistons within said cylinders for drivably rotating same, means for selectively controlling the supply of fuel to one or more of said plurality of cylinders, means for generating an ignition pulse for controlling the ignition timing and ignition dwell time and therefore the ignition of said fuel within said cylinders, and a microprocessor-based engine control system for controlling the generation of said ignition pulse, said engine control system further comprising:
sensor means operatively associated with said engine for generating an engine position pulse each time one of said pistons is near the top-dead-center position of its associated cylinder;
program means for computing a first digital ignition control word indicative of ignition delay time and a second digital ignition control word indicative of ignition pulse-width;
means responsive to said first and second digital ignition control words for electronically controlling the generation of said ignition control pulse for ignition timing purposes during normal engine operation; and
means for detecting an engine cranking mode of operation for automatically switching the ignition timing from the control of said microprocessor-based engine control system and generating a first command signal; and
means responsive to said first command signal for mechanically controlling the generation of said ignition control pulse and therefore ignition timing throughout said cranking mode of operation.

7. The microprocessor-based engine control system of claim 6 wherein said means for detecting an engine cranking mode of operation includes gate means for directing said engine position pulse to the means for generating an ignition pulse and bypassing the microprocessor, and said means for mechanically controlling includes positioning said sensor means relative to said engine to achieve substantially optimum ignition during cranking.

8. A microprocessor-based engine control system for use in an internal combustion engine having means responsive to fuel control commands for supplying a controlled quantity of fuel to said engine, said engine control system comprising means for sensing one or more engine operating parameters and generating a primary fuel command in response thereto, means for monitoring at least one of said engine operating parameters for detecting a need for acceleration enrichment and generating an acceleration enrichment command in response thereto and means responsive to said acceleration enrichment command for generating first an immediate acceleration enrichment fuel command signal and therefore a longer term programmed increase in said primary fuel command for effecting the desired acceleration enrichment.

9. The microprocessor-based engine control system of claim 8 wherein said means for monitoring includes means for detecting when the engine is in the acceleration mode including detecting the rate of change of movement of the fuel control commands, means for generating a trigger signal to the microprocessor indicative of said acceleration mode, and said last named means includes means for deriving an enrichment factor signal in response to said trigger signal.

10. A microprocessor based engine control system for use in internal combustion engines wherein fuel control commands are used to control the quantity of fuel supplied to the engine, said engine control system comprising a microprocessor, a memory means associated with said microprocessor, program means stored in said memory for controlling said microprocessor to implement a particular fuel control law including data representing a look-up table of modifier values which are a function of engine temperature stored in said memory means, means for measuring engine temperature and addressing said memory means look-up table to obtain one of a finite number of pre-programmed modifier values therefrom, means for interpolating between said addressed one of a finite number of stored modifier values and adjacent stored values for computing an accurate engine temperature modifier value, said program means being responsive to said computed engine temperature modifier value in implementing said fuel control law for generating a highly precise engine temperature-compensated fuel control demand.

11. A microprocessor-based engine control system wherein fuel is supplied to one or more cylinders of an engine and the ignition of said fuel therein is controlled, said engine control system comprising a microprocessor, a memory means associated with said microprocessor a look-up table of modifier values stored in said memory means, means for sensing engine speed and generating a data word indicative thereof, means responsive to said data word for addressing said memory means look-up table and obtaining an addressed modifier value, means for interpolating between said addressed modifier value and adjacent stored values computing an accurate ignition dwell time modifier, and program means stored in said memory means for operating said microprocessor, said program means being responsive to one or more engine operating parameters and to said ignition dwell time modifier value for computing an ignition pulse-width digital word, and means responsive to said digital word for controlling the ignition dwell time of said system.

12. A microprocessor-based engine control system for use in an internal combustion engine of the type having means for supplying a controlled quantity of fuel to the engine in response to a fuel control signal, means for igniting the fuel supplied to the engine in response to an ignition control signal, and means for controlling the recirculation of exhaust gases from the exhaust manifold of said engine back to the intake manifold in response to an EGR control signal, said microprocessor-based engine control system comprising:
means for sensing a plurality of engine operating parameters such as manifold absolute pressure, air temperature, engine coolant temperature, throttle position, EGR valve position, the concentration of oxygen in the exhaust system of said engine and the like and for generating a conditioned output signal indicative thereof;
analog-to-digital converter means including means for converting each of said conditioned sensor output signals into a corresponding DC voltage level;
a microprocessor system including memory means and program means for implementing various control laws, arithematic functions and the like and for generating various sets of computer control signals;
multiplexer means responsive to first computer control signals for selecting a predetermined one of said DC voltage levels;
pulse-width to binary converter means responsive to said selected one of said DC voltage levels for generating a pulse-width indicative of said selected level and converting same into a binary number indicative thereof, said pulse-width to binary converter means being responsive to second computer control signals for transmitting said binary number to said microprocessor system;
means responsive to the speed or period of said engine for generating various engine pulse position signals indicative thereof;
program means within said multiprocessor for utilizing said received binary words to calculate digital control words in accordance with pre-programmed look-up tables, control laws, and data supplied thereto;
a plurality of serial shift registers associated with predetermined control functions;
parallel to serial converter means responsive to third computer control signals for receiving said digital control word in parallel from said microprocessor and serially transferring said control word into a selected one of said shift registers;
means for detecting a plurality of system conditions and generating interrupt signals in response thereto, said interrupt signals being transmitted to said microprocessor unit for use therein;
means associated with said serial shift registers for converting said binary values stored therein into a pulse-width output signal; and
means responsive to predetermined ones of said pulse width output signals for generating said fuel control pulse, said ignition control pulse and said EGR control pulse for controlling the operation of the said internal combustion engine.

13. In an engine system having an internal combustion engine, a plurality of cylinders in said internal combustion engine, a piston mounted for reciprocal motion within each of said plurality of cylinders in response to the combustion of fuel therein, an output shaft operatively coupled to said piston and rotatably driven by the reciprocation of said pistons within said cylinders, at least one fuel injector means responsive to a fuel control pulse for injecting a controlled quantity of fuel into a selected one or more of said plurality of cylinders for combustion therein, at least one ignition means responsive to an ignition control signal for selectively controlling the timing and duration of ignition of said injected fuel within said cylinder, an improved electronic engine control system comprising:
computer means;
memory means operatively coupled to said computer means for storing data representative of a plurality of look-up tables representing multi-dimensional control surfaces of modifier values which are functions of at least one engine operating parameter;
first program data means stored in said memory means for implementing a predetermined fuel control law when executed by said computer means;
means for sensing a plurality of real time engine operating parameters, at least one of said engine operating parameters being a function of engine speed, and for generating digital words indicative of the actual measured value of said sensed engine operating parameter;
means for generating command signals for processing data in said computer;
second program means executable by said computer means in response to said command signals for utilizing said digital words indicative of the actual measured value of said sensed engine operating parameter for addressing said memory means for a predetermined value stored in said look-up table in said memory means and for interpolating between said predetermined stored value and addressable stored values adjacent thereto to compute an interpolated control surface value for use in executing said fuel control law to generate a compensated fuel control digital command; and
means responsive to said fuel control digital command for generating said fuel control pulse to operate said at least one fuel injector means, the duration of said fuel control pulse determining the specific quantity of fuel to be injected into said selected one or more of said plurality of cylinders.

14. The system of claim 13 wherein said means responsive to said fuel control digital command for generating said fuel control pulse includes two separate and distinct circuit means for generating first and second separate non-overlapping, electrical pulses, the initiation of said second electrical pulse being coincident with the end of said first electrical pulse to produce a single uninterrupted fuel control pulse.

15. The system of claim 13 wherein said sensing means includes means for sensing engine temperature and generating a first digital word indicative thereof, means for sensing manifold absolute pressure and generating a second digital word representative thereof, said plurality of look-up tables stored in said memory means including at least one look-up table representing a multi- dimensional control surface of temperature modifier values for use in more accurately implementing said fuel control law, said at least one look-up table of temperature modifier values being a function of engine temperature and manifold absolute pressure and being addressable by said first and second digital words such that said second program means is executed by said computer means for interpolating between the control surface comprising said temperature modifier values for calculating an optimal temperature modifier value corresponding to said actual readings of temperature and manifold absolute pressure, said computer means executing said first program means and utilizing said optimal temperature modifier value in implementing said pre-programmed fuel control law for more accurately computing a compensated value for said fuel control digital command.

16. The system of claim 13 further including means responsive to at least one of said real time sensed engine operating parameters for anticipating a need for acceleration enrichment and generating an acceleration enrichment command signal indicative thereof, said computer means being responsive to said acceleration enrichment command signal for implementing said first program means to compute (1) a first initial and immediate one-time special fuel control digital command for immediate acceleration enrichment purposes and then (2) a longer time, more gradual programmed increase in said fuel control digital command computed by said first program means as it implements said fuel control law under the direction of said computer means.

17. The system of claim 16 wherein said means responsive to said fuel control digital command for generating said fuel control pulse includes a single circuit means for generating the total fuel control pulse from both said first initial and immediate one-time special acceleration enrichment fuel control digital command and from said second longer time, more gradual programmed increase in said normally generated fuel control digital command.

18. In an engine system having an internal combustion engine, a plurality of cylinders in said internal combustion engine, a piston mounted for reciprocal motion within each of said plurality of cylinders in response to the combustion of fuel therein, an output shaft operatively coupled to said piston and rotatably driven by the reciprocation of said pistons within said cylinders, at least one fuel injector means responsive to a fuel control pulse for injecting a controlled quantity of fuel into a selected one or more of said plurality of cylinders for combustion therein, at least one ignition means responsive to an ignition control signal for selectively controlling the timing and duration of ignition of said injected fuel within said cylinder, an improved electronic engine control system comprising:
computer means;
memory means operatively coupled to said computer means for storing data representative of a plurality of look-up tables representing multi-dimensional control surfaces of modifier values which are a function of at least one engine operating parameter;
program means stored in said memory means for implementing a predetermined ignition control signal calculation when executed by said computer means;
means for sensing a plurality of real time engine operating parameters at least one of which is a function of degrees of engine revolution for establishing a reference position for piston whose associated cylinder is to have the injected fuel ignited therein and for generating a reference position pulse indicative thereof;
means for generating command signals for processing data in said computer means;
said computer means executing said program means in response to said command signals for computing a first digital word indicative of a calculated delay time from the receipt of said reference pulse until ignition is to occur and a second separate and distinct digital word indicative of the duration of ignition of said fuel injected into said cylinder.

19. The system of claim 18 wherein said means for generating said ignition control signal further includes means responsive to the occurrence of the next successive reference pulse for generating said ignition control signal even if said predetermined delay period from the receipt of said previous reference position pulse has not yet elapsed to enable smoother acceleration and the like.

20. The system of claim 18 wherein said means for generating said ignition control signal further includes means for initiating said ignition control pulse upon the occurrence of each successive reference position pulse whenever said engine is in a cranking mode of operation such as during warm-up or the like.

21. In combination with an internal combustion engine of the type having an engine block, a plurality of cylinders located in said engine block, a plurality of pistons each mounted in a respective cylinder for reciprocating movement therein, an output shaft operatively coupled to said plurality of pistons and rotatable upon the reciprocation of each of said pistons within said cylinders, an intake manifold common to all of said plurality of cylinders, said intake manifold having an opening therein for receiving air and means disposed within said opening for selectively varying the effective size of said opening, means for supplying fuel to a selected one or more of said plurality of engine cylinders, said fuel supply means including a fuel pump and at least one electromagnetically operated fuel injector valve adapted to operate in response to a fuel control signal, means for igniting the fuel supplied to said selected one or more of said plurality of engine cylinders, said fuel igniting means being responsive to an ignition control signal for controlling the timing and duration of admission of the fuel injected into said selected one or more of said plurality of engine cylinders, and an electrical system for controlling the operation of said fuel supply means and said igniter means to cause the combustion of fuel and air in each of said plurality of engine cylinders and thereby cause said pistons to reciprocate within said cylinders to rotate said output shaft, the improvement in said electrical system comprising:
means for sensing various engine operating parameters on a real time basis and for producing a corresponding plurality of digital signals indicative thereof, at least one of said digital signals representing operator-commanded changes in the size of said opening in said manifold intake;
means for generating said fuel control signal for controlling the operation of said fuel supply means in response to said plurality of digital signals, said fuel control signal generated means including means for receiving and processing said plurality of digital signals from said sensing means, said processing means including a digital data processor operating under the control of a program to convert said plurality of digital signals into a first electrical control signal for operating said fuel pump and controlling the supply of fuel to said fuel injection means, a second electrical control signal for opening said fuel injector valve for a predetermined time interval T1 for a given predetermined revolution of said output crankshaft, means responsive to said one of said digital signals representing a change in the effective size of said opening for anticipating an operator-commanded acceleration enrichment request and generating a fourth electrical control signal indicative thereof, a fourth electrical control signal responsive to said third electrical control signal for opening said fuel injector valve for at least one additional time interval T2 for each predetermined revolution period of said output shaft to increase the amount of fuel supplied to a selected one or more of said plurality of engine cylinders for acceleration enrichment purposes and then increase the rotational speed of said output shaft, another of said plurality of digital signals being representative of a sensed engine operating parameter indicative of one or more of said pistons having reached a predetermined reference position for generating successive engine position pulses, means responsive to the receipt of an engine position pulse for counting a delay time therefrom prior to generating said ignition control signal and causing the combustion of injected fuel within said selected one or more of said plurality of said cylinders, and means normally responsive to the end of said predetermined delay time interval for generating said ignition control pulse for a time interval T3 whose duration controls the time of combustion of said injected fuel within said selected engine cylinder.

22. The system of claim 21 wherein said means normally responsive to the termination of said predetermined delay count for automatically initiating the generation of said ignition control pulse upon the occurrence of the next successive engine position pulse regardless of the state of said delay counter whenever acceleration has been requested, the engine is in the cranking mode of operation, and the like.
Description
BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to a method and apparatus for controlling an internal combustion engine and more particularly to a microprocessor-based electronic engine control system having a memory preprogrammed with various control laws and control schedules and being responsive to one or more sensed engine-operating parameters for generating control signals for controlling one or more of such engine operating functions as, for example, fuel injection, ignition timing, EGR control, and the like.

2. Statement Of The Prior Art

Many of the patents of the prior art recognize the need for employing the enhanced accuracy of digital control systems for more accurately controlling one or more functions of an internal combustion engine.

U.S. Pat. No. 3,969,614 which issued to David F. Moyer, et al on July 13, 1976 is typical of such systems as are U.S. Pat. No. 3,835,819 which issued to Robert L. Anderson, Jr. on Sept. 17, 1974; U.S. Pat. No. 3,904,856 which issued to Louis Monptit on Sept. 9, 1975; and U.S. Pat. No. 3,906,207 which issued to Jean-Pierre Rivere, et al on Sept. 16, 1975. All of these Patents represent a break-away from the purely analog control systems of the past, but neither the accuracy, reliability, or number of functions controlled is sufficient to meet present day requirements.

Future internal combustion engines will require that emissions be tightly controlled due to ever-increasing governmental regulations, while fuel consumption is minimized and drivability improved over the entire operating range of the engine. None of the systems of the prior art provide a method and apparatus for controlling the operation of an internal combustion engine with sufficient accuracy to attain minimal emissions and minimal fuel consumption together with improved drivability.

The systems of the prior art attempt to control one or more of the engine operating functions but none attempts to control the operation of the fuel pump, fuel injection, engine ignition timing, on-off and/or proportional EGR control, and the like while using feedback from such devices as oxygen sensors for emission control purposes or for effecting a closed loop fuel control made of operation while including provisions for optimizing acceleration enrichment handling, and the like.

These and other problems of the prior art are solved by the microprocessor-based electronic engine control system of the present invention which eliminates most or all of the problems of the prior art and enables a commercially feasible implementation of a digital control system having a relatively low cost, and which is easy to repair and maintain. The system of the present invention is able to implement much more advanced and complex fuel control laws and expand the various control funtions performed thereby to include, in addition to fuel injection, ignition timing and on-off and/or proportional EGR control while, at the same time, reducing the cost and size of the unit and increasing reliability so as to render the system commercially feasible.

These and other objects and advantages of the present invention will be accomplished by the present method and apparatus for the electronic engine control of nearly all engine functions while simultaneously providing many safety features together with increased accuracy and ease of adaption to the internal combustion engines of modern vehicles.

SUMMARY OF THE INVENTION

A method and apparatus for controlling one or more of the operating functions of an internal combustion engine such as the on-off control of the fuel pump, the control of fuel injection, ignition timing and pulse-width control, on-off and/or proportional EGR control, and the like, as well as making provisions for implementing closed loop control of various engine-operating functions. The system of the present invention includes a program-controlled microprocessor which is entirely interrupt driven. Memory means associated with the microprocessor are used to store program routines for implementing various control laws and the subroutines required for the implementation thereof as well as look-up tables or schedules of control values required for implementation of said control laws. Means for sensing engine speed or period are provided and various clock-controlled operations are synchronized thereto so that the present system operates on a clock-normalized to the engine speed which is particularly useful in controlling the I/O circuitry associated therewith. The I/O input circuitry converts inputs from sensors monitoring one or more engine operating parameters into pulse-width modulated signals which are subsequently converted into binary codes for transfer to the microprocessor system. Based on the programs stored in the memory associated with the microprocessor, the microprocessor monitors the present engine operating conditions via the sensors and various hardware features for detecting failures and the like and, via interrupts supplied to the computer, controls the execution of the stored control laws to output the appropriate engine control commands.

Many independent yet inter-related novel features are present in the microprocessor-based electronic engine control system of the present invention including:

(1) The use of a programmable engine control system which can control fuel flow only, ignition timing only, on-off and/or proportional EGR control only, or any combination thereof, including all three combined;

(2) System partitioning whereby some of the very high speed simpler sensing and control operations are performed in I/O digital input circuitry and the more complex slower varying functions are performed in the microprocessor so as to maximize the use of a standard microprocessor while minimizing the custom interface and thereby reducing its attendant cost while increasing the system flexibility;

(3) The system provides for a variable allocation of the microprocessor computing capability to select the control functions on the basis of engine speed. The desired update rate for the control commands is generally based on engine revolutions and as the engine speed increases, the number of computations that can be performed per revolution decreases. Therefore, to effectively use the changing computing power per revolution, it is automatically apportioned such that certain control functions such as fuel control are updated once per revolution at lower engine speeds until a first predetermined engine speed is reached and then once every other revolution thereafter as the speed increases and other control functions such as ignition timing are updated once per firing (four times per revolution on an eight cylinder engine) at low engine speeds and reduced down to two times per revolution as the engine speed increases past a second predetermined value and then once per revolution as the engine speed increases beyond a third predetermined value of engine speed;

(4) The method and apparatus of the present invention teaches a mapping approach which reduces a ten-bit input variable down to eight bits while keeping a relatively constant accuracy throughout the measurement range;

(5) The fuel control commands of the present invention are derived from a combination of a look-up table and interpolation operations which are extremely complex and highly accurate;

(6) Extra fuel commands for acceleration enrichment are provided through the same output circuitry as the main fuel command;

(7) Acceleration enrichment accomplished through a combination of an immediately generated fuel command following the detection of an acceleration input request and then a longer term programmed increase in the main fuel pulse via the preprogrammed control laws;

(8) Fuel control commands are modified to compensate for engine temperatures using look-up tables and interpolation operations;

(9) The present system provides for closed loop fuel control using either an oxygen sensor in the exhaust system of the engine or for closed loop fuel control using any other feedback signal, and closed loop control of other engine control functions could also be implemented using the teachings of this invention;

(10) Ignition timing is controlled by means of electronic delays determined by table look-up and interpolate operations;

(11) Ignition dwell time is electronically controlled as a function of engine speed by means of a table look-up and interpolation approach;

(12) The system of the present invention automatically switches from electronic control of ignition timing to mechanical control during engine cranking if desired;

(13) The system of the present invention allows the ignition timing to be electronically varied from advance to retard and back to advance without loss of firing;

(14) The system of the present invention can either control on-off EGR or proportional EGR;

(15) The preferred embodiment of the present invention utilizes two separate fuel pulse output commands, but a single command or a number of command corresponding to the number of injectors could be used with only minor alterations in the output circuitry;

(16) Both group injection and simultaneous double fire modes of operation can be controlled with the system of the present invention;

(17) the microprocessor-based electronic engine control system of the present invention is automatically reinitialized if random noise results in the continuous execution of an errneous program loop and means are further provided for insuring that if reinitialization is ineffective, "a fail condition" is flagged; and

(18) Various system failures, such as clock failure, a stall condition, or the like are automatically flagged by the microprocessors and may be used for other purposes, as safety dictates. Furthermore, various failure indications may be used to activate a limp-home type circuit to enable the vehicle to travel a short distance for repairs even through the engine control system itself has failed.

Other advantages and meritorious features of the present invention will be more fully understood from the following detailed description of the drawings and the preferred embodiment, the appended claims and the drawings, which are briefly described hereinbelow.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an overall block diagram of an internal combustion engine provided with the mircroprocessor-based electronic engine control system of the present invention;

FIG. 2 is a broad block diagram of the microprocessor-based electronic engine control system of the present invention;

FIG. 3 is a block diagram of the analog-to-digital converter circuitry of block 121 of FIG. 2;

FIG. 3A is an electrical schematic diagram of the pressure sensor signal amplifier and comparator circuitry of block 141 of FIG. 3;

FIG. 3B is an electrical schematic diagram of the air temperature sensor signal amplifier and comparator circuitry of block 142 of FIG. 3;

FIG. 3C is an electrical schematic diagram of the engine coolant temperature sensor signal amplifier and comparator circuitry of block 143 of FIG. 3;

FIG. 3D is an electrical schematic diagram of the throttle position sensor signal amplifier and comparator circuitry of block 144 of FIG. 3;

FIG. 3E is an electrical schematic diagram of the preferred embodiment of the oxygen sensor signal conditioning system of block 146 of FIG. 3;

FIG. 3F is an electrical schematic diagram of the preferred embodiment of the ramp generator circuitry of block 147 of FIG. 3;

FIG. 3G is a timing diagram for explaining the operation of the ramp generator circuitry of FIG. 3F;

FIG. 3H is a block diagram illustrating the broad concept of the ratiometric feedback-compensated ramp-type analog-to-digital converter system of the present invention;

FIG. 3I is an electrical timing diagram used to illustrate the operation of the circuit of FIGS. 3H and 3J;

FIG. 3J is an electrical schematic diagram showing, in detail, portions of the circuit of FIG. 3H and for describing an alternate embodiment to the ramp generating circuit utilized in the preferred embodiment of FIG. 3F;

FIG. 4 is a block diagram of the binary encoder circuitry of block 122 of FIG. 2;

FIG. 4A is an electrical schematic diagram of the preferred embodiment of the differentiator and level detector circuitry of block 411 of FIG. 4;

FIG. 4B in an electrical schematic diagram of the multiplexer circuitry of block 412 of FIG. 4;

FIG. 4C is a block diagram of the pulse-width to binary converter system of block 413 of FIG. 4;

FIG. 4C1 is an electrical schematic diagram of the counter control logic circuitry of block 454 of FIG. 4C;

FIG. 4C2 is an electrical schematic diagram of the ramp reset control counter circuitry of block 455 of FIG. 4C;

FIG. 4C3 is a count state table for the eight stage counters of FIGS. 4C2, 4D7, and 4D9;

FIG. 4C4 is an electrical schematic diagram of the window control counter system of block 456 of FIG. 4C;

FIG. 4C5 is a ten-page count state table for the window counter of FIG. 4C4;

FIG. 4C6 is a combined block and schematic diagram of a window counter system with range selection which represents and alternate embodiment to the window control counter system of FIG. 4C4;

FIG. 4C7 is an electrical schematic diagram of the pulse-width counter number one circuitry associated with block 457 of FIG. 4C;

FIG. 4C8 is an electrical schematic diagram of the pulse-width counter number two circuitry associated with block 458 of FIG. 4C;

FIG. 4C9 is an electrical schematic diagram of the pulse-width counter number three circuitry associated with block 459 of FIG. 4C; FIG. 4D is a block diagram of the oxygen system integrator circuitry of block 414 of FIG. 4;

FIG. 4D1 is an electrical schematic diagram of the divide-by 16 counter of block 641 of FIG. 4D;

FIG. 4D2 is a count state table for the three stage counter of FIG. 4D1;

FIG. 4D3 is an electrical schematic diagram of the synchronizer circuitry of block 642 of FIG. 4D;

FIG. 4D4 is a count state table for the seven stage counter 715 of FIG. 4D3;

FIG. 4D5 is an electrical schematic diagram of the counter circuitry of block 643 of FIG. 4D;

FIG. 4D6 is a count state table for the four stage preset table counter 750 of FIG. 4D5;

FIG. 4D7 is an electrical schematic diagram of the counter circuitry associated with block 644 of FIG. 4D;

FIG. 4D8 is a count state diagram for the six stage counters of FIGS. 4D7, 4D11, 4D12 and 4D14;

FIG. 4D9 is an electrical schematic diagram of the sampler circuitry of block 645 of FIG. 4D;

FIG. 4D10 is an electrical schematic diagram of the sensor test control circuitry of block 646 of FIG. 4D;

FIG. 4D11 is an electrical schematic diagram of the channel number one sampling counter and register circuitry of block 647 of FIG. 4D;

FIG. 4D12 is an electrical schematic diagram of the channel number two sampling counter and register circuitry of block 648 of FIG. 4D;

FIG. 4D13 is an electrical schematic diagram of the sampling counter multiplexer of block 649 fo FIG. 4D;

FIG. 4D14 is an electrical schematic diagram of the binary to pulse-width converter of block 650 of FIG. 4D;

FIG. 4E is an electrical schematic diagram of the crankshaft position signal conditioner circuitry of block 415 of FIG. 4;

FIG. 4F is an electrical schematic diagram of the crankshaft position pulse processor circuitry of block 416 of FIG. 4;

FIG. 4G is an electrical schematic diagram of the engine time interval counter circuitry of block 417 of FIG. 4;

FIG. 5 is a block diagram of the microcomputer system of block 123 of FIG. 2 and various circuits associated therewith;

FIG. 5A is a block diagram of the reset control circuitry of block 1131 of FIG. 5;

FIG. 5A1 is an electrical schematic diagram of the power-on reset generator circuitry of block 1142 of FIG. 5A;

FIG. 5A2 is an electrical schematic diagram of the buffer logic circuitry of block 1143 of FIG. 5A;

FIG. 5A3 is an electrical schematic diagram of the clock fail detector circuitry of block 1144 of FIG. 5A;

FIG. 5A4 is an electrical schematic diagram of the MPU reset control circuit of block 1145 of FIG. 5A;

FIG. 5A5 is an electrical schematic diagram of the watchdog circuit of block 1146 of FIG. 5A;

FIG. 5A6 is a count state table for the shift counter of FIG. 5A5;

FIG. 5A7 is a count state table for the binary counter of FIG. 5A5;

FIG. 5B is a generalized block diagram of the MPU 6800 microprocessor of block 1132 of FIG. 5 and the various inputs and outputs associated therewith;

FIG. 5C is a block digram showing the various inputs and outputs associated with the memory circuitry of block 1133 of FIG. 5;

FIG. 5D is an electrical schematic diagram of the chip select circuitry of block 1134 of FIG. 5;

FIG. 5E is an electrical schematic diagram of the command signal generator circuitry of block 1135 of FIG. 5; FIG. 5F is an electrical schematic diagram of the secondary command signal generator circuitry of block 1136 of FIG. 5;

FIG. 5G is an electrical schematic diagram of the buffer circuitry of block 1137 of FIG. 5;

FIG. 5H is an electrical schematic diagram of the parallel-to-serial converter system of block 1138 of FIG. 5;

FIG. 5I is an electrical schematic diagram of the status input circuitry associated with block 1139 of FIG. 5;

FIG. 5J is an electrical schematic diagram of the camshaft sensor conditioning circuitry assiociated with block 1140 of FIG. 5;

FIG. 5K is an electrical schematic diagram of the interrupt control circuitry of block 1141 of FIG. 5;

FIG. 6 is a block diagram of the binary decoder system of block 124 of FIG. 2 and the circuitry generally associated therewith;

FIG. 6A is an electrical schematic diagram of the output port circuitry of block 2111 of FIG. 6;

FIG. 6B is an electrical schematic diagram of the first and second fuel pulse counters of block 2112 of FIG. 6;

FIG. 6C is an electrical schematic diagram of the ignition delay storage register of block 2113 of FIG. 6; FIG. 6D is an electrical schematic diagram of the transfer logic network associated with block 2114 of FIG. 6;

FIG. 6E is an electrical schematic diagram of the ignition delay counter circuitry of block 2115 of FIG. 6;

FIG. 6F is an electrical schematic diagram of the ignition pulsewidth storage register of block 2116 of FIG. 6;

FIG. 6G is an electrical schematic diagram of the transfer logic network of block 2117 of FIG. 6;

FIG. 6H is an electrical schematic diagram of the ignition pulsewidth counter circuitry of block 2118 of FIG. 6;

FIG. 6I is an electrical schematic diagram of the ignition control circuit of block 2119 of FIG. 6;

FIG. 6J is an electrical schematic diagram of the ignition timing generator circuitry of block 2120 of FIG. 6;

FIG. 6J1 is a count state table for the shift register counter of FIG. 6J;

FIG. 6K is an electrical schematic diagram of the proportional EGR counter circuitry and the output circuitry associated therewith a block 2121 of FIG. 6;

FIG. 6L is an electrical schematic diagram of the fuel pulse control flip-flops and the gating circuitry associated therewith of block 2122 of FIG. 6;

FIG. 6M is an electrical timing diagram for explaining the ignition timing effected by the circuitry of FIG. 6;

FIG. 7 is a block diagram generally illustrating the power control circuitry and analog output circuitry associated with block 125 of FIG. 2;

FIG. 7A is an electrical schematic diagram of the relay driver and relay circuitry of block 3001 of FIG. 7;

FIG. 7B is an electrial schematic diagram of the EGR valve driver circuitry of block 3002 of FIG. 7;

FIG. 7C is a block diagram of the injector driver circuitry of block 3003 (and block 3007 which is substantially identical thereto) of FIG. 7;

FIG. 7C1 is an electrical schematic diagram of the voltage-to-current converter circuitry of block 3011 of FIG. 7C;

FIG. 7C2 is an electrical schematic diagram of the precision current sink circuitry of block 3012 of FIG. 7C;

FIG. 7C3 is an electrical schematic diagram of a comparator circuitry of block 3013 of FIG. 7C;

FIG. 7C4 is an electrical schematic diagram of the SR flip-flop circuitry of the block 3014 of FIG. 7C;

FIG. 7C5 is an electrical schematic diagram of the injector clamp control circuitry of block 3015 of FIG. 7C;

FIG. 7C6 is an electrical schematic diagram of the driver circuitry associated with block 3016 of FIG. 7C; FIG. 7C7 is an electrical schematic diagram of the sensing resistor and short protection circuitry of block 3017 of FIG. 7C;

FIG. 7C8 is an electrical schematic diagram of the injector short protection circuitry of block 3018 of FIG. 7C;

FIG. 7C9 is an electrical schematic diagram of the bias circuitry of block 3019 of FIG. 7C;

FIG. 7C10 is an electrical schematic diagram of the injector current control circuit block 3020 of FIG. 7C;

FIG. 7D represents and electrical schematic diagram of the power amplifier circuit of block 3004 of FIG. 7 and the conventional ignition coil driver circuit of block 3005 associted therewith;

FIG. 7E is a schematic diagram with certain funcional block designations of the five volt section of the power supply regulator of block 3006 including the low voltage shutdown circuitry, the band gap reference circuitry, the five volt regulator circuitry, the circuit protection circuitry associated therewith;

FIG. 7F is an electrical schematic diagram of the +9.5 volt regulator section of the circuit of block 3006 including the 9.5 volt regulator circuitry and the short circuit protection network for the 9.5 volt supply;

FIG. 7G is an electrical block diagram of the fuel management control limp-home circuit which may be used as one embodiment of or a portion of the get-home circuit of block 135 of FIG. 2; FIG. 7H is an electrical diagram of an ignition limp-home circuit which may be utilized as one embodiment of or a portion of the get-home circuit of block 135 of FIG. 2;

FIG. 8 is a block diagram illustrating a conventional MC 6875 clock oscillator with the related inputs and outputs which is used in the preferred embodiment of the present invention and as the master-clock oscillator of block 134 of FIG. 2;

FIG. 9 is a schematic diagram illustrating the read-only memory (ROM) notion utilized throughout this application including the drawing symbol or notation, the actual transistor schematic diagram, and the logic element equivalent;

FIGS. 9.1A and B represent equivalent logic symbols for an inverter as used in the present application and an electrical circuit implementation thereof;

FIGS. 9.2A and B represent equivalent logic symbols for a two input NOR circuit and a schematic implementation thereof;

FIGS. 9.3A and B represent equivalent logic symbols for a three input NOR gate and an electrical schematic implementation thereof;

FIGS. 9.4A and B represent equivalent logic symbols for a four input NOR gate and an electrical circuit implementation thereof;

FIGS. 9.5 A and B represent equivalent logic symbols for a five input NOR gate and an electrical circuit implementation thereof;

FIGS. 9.6A and B represents equivalent logic symbols for a six input NOR gate and a circuit schematic implementation thereof; FIGS. 9.7A and B show equivalnet logic symbols for a two input NAND gate and the preferred circuit implementation thereof;

FIGS. 9.8A and B represent equivalent logic symbols for a three input NAND gate and the preferred circuit implementation thereof;

FIGS. 9.9A and B show equivalent logic symbols for a two input AND/ three input NOR gate network and the preferred circuit implementation thereof;

FIGS. 9.10A and B show two equivalent logic symbols for a three input AND/ three input NOR gate network and the preferred circuit implementation thereof;

FIGS. 9.11A and B show equivalent logic symbols for a three input AND, two input AND/ two input NOR gate configuration and the preferred circuit implementation thereof;

FIGS. 9.12A and B show a dual two input AND/ two input NOR gate configuration and the preferred circuit implementation thereof;

FIGS. 9.13A and B represent the logical designation for a two input AND/ two input OR/ two input NAND gate configuration and the preferred circuit implementation thereof;

FIGS. 9.14A and B show equivalent logical designations for a two input AND/two input NOR gate configuration and the preferred circuit implementation thereof;

FIGS. 9.15A and B show the logic symbol designation for a two input OR (two input AND), three input AND/ two input NOR gate configuration and the preferred circuit implementation thereof;

FIGS. 9.16A and B show equivalent logic diagrams of a two input OR/ two input NAND gate configuration and the preferred circuit implementation thereof;

FIGS. 9.17A and B show equivalent logic designations for a dual two input OR/ two input NAND gate configuration and the preferred circuit implementation thereof;

FIGS. 9.18A and B show equivalent logic symbols for a three input NOR, two input NOR/ two input AND gate configuration and the preferred circuit implementation thereof;

FIGS. 9.19A and B show the logical symbol for a two input NAND (two input OR), dual two input AND/ two input NOR gate configuration and preferred circuit implementation thereof;

FIGS. 9.20A and B show the logic designation for an RS clocked flip-flop and the preferred circuit implementation thereof;

FIGS. 9.21A and B show the logic designation for an RS, Dr clock flip-flop and the preferred circuit implementaion thereof;

FIGS. 9.22A and B show the logic designation of a two phase dynamic flip-flop and the preferred circuit implementation thereof;

FIGS. 9.23A and B show the logic designation for a "D" flip-flop and the preferred circuit implementation thereof;

FIGS. 9.24A and B show the logic designation for a two phase dynamic DS, DR, flip-flop and the preferred circuit implementation thereof;

FIGS. 9.25A and B show the logic designation for a static shift register stage and the preferred circuit implementation thereof;

FIGS. 9.26A and B show the logic designation for a static shift registier stage with preset and the preferred circuit implementation thereof;

FIGS. 9.27A and B show the logic designation for a dynamic shift register stage with preset and preferred circuit implementation thereof;

FIGS. 9.28A and B show the logic designation of a two phase dynamic flip-flop with DR and DS inputs and the preferred circuit implementation thereof;

FIGS. 9.29A and B show the logic designation of half adder or subtractor circuit and the preferred circuit implementation thereof;

FIGS. 9.30A and B show the logic designation of a comparator circuit and the preferred circuit implementation thereof;

FIG. 10 is a block diagram of the software utilized in the preferred eombodiment of the microprocessor based electronic engine control system of the present invention;

FIG. 10.1 is a diagramatic flow chart illustrating the basic fuel control law implemented by the hardware and software systems of the present invention;

FIG. 10.2 is a block diagram illustration of the basic software structure utilized in the preferred embodiment of the present system;

FIG. 10.3 is a detailed flow diagram of the start-up routine implemented in the present system;

FIG. 10.4 is a detailed flow diagram of the interrupt handling routine used in the system of the present invention;

FIG. 10.5 is a detailed flow diagram of the acceleration enrichment interrupt routine used in the present system;

FIG. 10.6 is a detailed flow diagram of the fuel pulse complete interrupt routine used in the present system;

FIGS. 10.7A through 10.7F illustrate a detailed flow diagram of the engine position interrupt routine used with the present system;

FIG. 10.8 is a detailed flow diagram of the ignition timing computation routine of the present system;

FIG. 10.9A through 10.9D illustrate a detailed flow diagram of the fuel pulse computation routine used in the present system;

FIGS. 10.10A through 10.10I illustrate an even more detailed flow diagram of the fuel pulse computation routine used in the present system;

FIGS. 10.11A through 10.11C represent the detailed flow diagram of the oxygen compensation routine used in the present system;

FIG. 10.12 is a detailed flow diagram of the acceleration enrichment factor computation routine used in the present system;

FIG. 10.13 is a detailed flow diagram of the acceleration enrichment modifier routine used in the present system;

FIGS. 10.14A and B form a detailed flow diagram of the analog-to-digital data mapping routine used in the present system;

FIG. 10.15 is a detailed flow diagram of the delay computation routine used in the present system;

FIG. 10.16 is a detailed flow diagram of the double precision multiplication routine used in the present system;

FIG. 10.17 is a detailed flow diagram of the double precision negation routine used in the present system;

FIG. 10.18 is a detailed flow diagram of the double precision four place rotation routine used in the present system;

FIG. 10.19 is a detailed flow diagram of the engine period input data test routine used in the present system;

FIG. 10.20 is a detailed flow diagram of the A/D input data test routine used in the present system;

FIGS. 10.21A and B form a detailed flow diagram of the engine period input mapping routine used in the present system;

FIG. 10.22 is a detailed flow diagram of the fuel cut-off test routine used in the present system;

FIG. 10.23 is a detaled flow diagram of the fuel pulse output routine used in the present system;

FIG. 10.24 is a detailed flow diagram of the "A"-curve decay factor computation routine used in the present system;

FIG. 10.25 is a detailed flow diagram of the input data integration routine used in the present system;

FIG. 10.26 is a detailed flow diagram of the double precision linear interpolation routine used in the present system;

FIG. 10.27 is a detailed flow diagram of the EGR constant multiplier computation routine used in the present system;

FIG. 10.28 is a detailed flow diagram of the ignition rate limiting routine used in the present system;

FIG. 10.29 is a detailed flow diagram of the 8.times.16 multiplication routine used in the present system;

FIG. 10.30 is a detailed flow diagram of the generalized X by 16 bit multiplication (or divide by 2X) routine used in the present system;

FIG. 10.31 is a detailed flow diagram of the single precision linear interpolation routine used in the present system;

FIGS. 10.32A and B form a detailed flow diagram of the two dimensional surface interpolation routine used in the present system;

FIG. 10.33 is a detailed flow diagram of the tip-in fuel pulse computation routine used in the present system;

FIG. 10.34 is a detailed flow diagram of the tip-in fuel pulse output routine used in the present system; and

FIG. 10.35 is a detailed flow diagram of the wide open throttle compensation computation routine used in the present system.

This application is one of fourteen applications filed on Feb. 27, 1978, all commonly assigned and having substantially the same specification and drawings, the fourteen applications being identified below:

______________________________________ Serial Num- ber Title ______________________________________ 881,321 Microprocessor-Based Electronic Engine Control System 881,322 Feedback-Compensated Ramp-Type Analog to Digital Converter 881,323 Input/Output Electronic For Microprocessor-Based Engine Control System 881,324 Switching Control of Solenoid Current in Fuel Injection Systems 881,921 Dual Voltage Regulator With Low Voltage Shutdown 881,922 Oxygen Sensor Qualifier 881,923 Ratiometric Self-Correcting Single Ramp Analog To Pulse Width Modulator 881,924 Microprocessor-Based Engine Control System Acceleration Enrichment Control 881,925 Improvements in Microprocessor-Based Engine Control Systems 881,981 Oxygen Sensor Feedback Loop Digital Electronic Signal Integrator for internal Combustion Engine Control 881,982 Improvements in Electronic Engine Controls System 881,983 Electronic Fuel Injection Compensation 881,984 Ignition Limp Home Circuit For Electronic Engine Control Systems 881,985 Oxygen Sensor Signal Conditioner ______________________________________

DESCRIPTION OF THE PREFERRED EMBODIMENT

I. Introduction

In the following description, the method and apparatus of the invention are embodied in a microprocessor-based electronic engine control system as applied to a General Motors Corporation 350 cubic inch, V-8 internal combustion engine installed in a standard 1976 Cadillac Seville automobile. The engine is a conventional reciprocating piston, throttled, electronic fuel injected, spark-ignition internal combustion engine, but any type of engine having any conventional number of cylinders "N" can also be used with the system of the present invention.

FIG. 1 shows an internal combustion engine 101 having an intake system 102, an exhaust 103, and an output shaft 104 which is operatively rotated by the reciprocation of the individual pistons produced by the combustion of fuel and air within the individual cylinders of the engine 101, as conventionally known.

The intake system 102 includes an intake manifold 105, an air inlet assembly 106 and a throat 107 communicating the air inlet assembly 106 with the intake manifold 105. A throttle valve 108, such as a conventional butterfly valve or the like, is operatively disposed within the throat 107 to control the air flow between the inlet 106 and the intake manifold 105 for varying the air/fuel ratio, as conventionally known. An accelerator pedal 109 is conventionally used to vary the position of the throttle valve 108, as indicated by the dotted line 110 from the accelerator pedal 109 to the throttle or throttle valve 108. As conventionally known, the operator controls or commands the position of the accelerator pedal 109 to vary the air flow into the intake manifold 105 and the electronic engine control system 111 which, as illustrated in FIG. 2, operates to automatically and nearly instantaneously adjust various controlled variables to control or determine the operating characteristics of the engine 101 as hereinafter described.

The exhaust system 103 includes an exhaust manifold 112 and an exhaust outlet apparatus 113. A conduit 114 is provided for operatively connecting the exhaust manifold 112 of the exhaust system 103 back to the intake system 102 for supplying exhaust gases back to the intake system 102 for reducing the generation and emission of pollutants. An exhaust gas recirculation EGR) valve, generally represented by block 115, is operatively disposed in or at least partially within or operatively associated with the conduit 114 for regulating, controlling or metering the EGR flow back to the intake system 102.

The engine 101 of FIG. 1 is also provided with two groups of fuel injectors, represented generally by the singularly illustrated fuel injector 116 and each of the individual injectors 116 of both groups are operated simultaneously in parallel, via the mode of operation referred to as simultaneous double fire (SDF) in the prior art. In an alternate implementation, it is well known that each of the injectors 116 of a group may be operated simultaneously in parallel with each of the groups being operated on alternate engine revolutions and on different engine revolutions from the other groups referred to as two groups (TG) in the prior art. A fuel pump, not shown, but known in the art, is used via fuel lines 118 to the individual injectors 116
and to provide the necessary pressure so that the quantity of fuel injected into the individual cyclinders of the engine 101 is determined by the period of energization or operation of the injector 116 which is the primary controlled variable of the system of the present invention.

The controlled variables, that is, the variables which may be selectively adjusted or varied to control or determine the performance characteristic of the engine's energy conversion process include the fuel injection pulse-width which determines the period of energization of the injectors 116 and hence the quantity of fuel injected into the engine 101 and the timing thereof; the spark ignition, including advance angle in crankshaft degrees of rotation, firing and spark ignition dwell (time duration that the spark coil is energized); and the positioning of the EGR valve 115 to control exhaust gas recirculation.

Various sensors, detectors, etc. to be hereinafter described are positioned at various locations with respect to the internal combustion engine 101 and are used to measure or sense various engine operating parameters such as manifold absolute pressure; throttle position; coolant temperature; air temperature; the oxygen content of the exhaust gases; crankshaft and camshaft position for engine period information; ambient air pressure; engine cranking status; and the position of the EGR valve and the like. Signals indicative of these actual engine operating parameters are supplied to the microprocessor-based electronic engine control system 111 of the present invention which dynamically and continually computes the optimal controlled variables, e.g., the fuel-injection timing and pulse-width; the ignition firing advance and dwell; the EGR valve position, etc. These controlled variables are dynamically up-dated and recomputed to continually adjust the performance of the engine 101 so as to achieve an optimal balance between (a) minimizing the generation and emission of pollutants; (b) minimizing fuel consumption; and (c) optimizing vehicle drivability.

As hereinafter described, the microprocessor-based electronic engine control system 111 of the system of FIG. 1 utilizes programs and tables of optimal values stored in memory for optimizing the selection and adjustment of the controlled variables to obtain optimal engine performance under all operating conditions.

FIG. 2 is a broad block diagram of the microprocessor-based electronic engine control system of block 111 of FIG. 1 and illustrates the signal exhanges betwen the various blocks illustrating the system.

A plurality of sensors or detectors 126 to 133, as hereinafter described, supply signals to the analog to digital converter circuitry of block 121; to the binary encoder circuitry of block 122; or directly to the microprocessor system circuitry of block 123. Many of the outputs of the microprocessor system of block 123 are supplied to the binary decoder circuitry of block 124 which supplies decoded signals to the power control circuits of block 125 which then outputs signals to control the previously described controlled variables.

Block 126 represents a pressure transducer for sensing the absolute pressure existing within the intake system 102 of the internal combustion engine 101 of FIG. 1 and generates an analog output signal indicative of the absolute manifold pressure existing within the intake manifold 105. The pressure transducer of block 126 may be a conventional Gulton pressure transducer or, in the preferred embodiment of the present invention, a pressure transducer such as that disclosed in U.S. Pat. application Ser. No. 797,726 which was filed on May 17, 1977 and assigned to the assignee of the present invention, and incorporated by reference herein, but any conventional pressure transducer capable of accurately measuring the absolute manifold pressure existing within the intake system 102 may be used. The analog output of the pressure transducer 126 is an analog signal or voltage level represented by the letter "a" which is supplied to one input of the analog to digital converter circuitry of block 121 as hereinafter described.

The air temperature sensor of block 127 is preferably a thermistor-type device connected in an electrical circuit capable of producing a DC voltage having a variable level proportional to the ambient air temperature. A preferred location for the temperature sensor 127 is in the throat 107 of the air intake system 102 of the engine 101 somewhere upstream of the throttle valve 108. The DC electrical signal having a voltage proportional to the ambient air temperature existing in the throat 107
upstream of the throttle plate 108 is designated by the letter "b" and is transferred to another input of the circuitry of block 121.

The engine temperature sensor of block 128 is preferably a similar thermistor-type device mounted in the engine cooling system upstream of the usual engine control thermostat and having a negative temperature co-efficient. The thermistor of sensor 128 is connected in an electrical circuit capable of producing a DC voltage having a variable level proportional to the engine coolant temperature and this DC signal or voltage level is designated by the letter "c" which is supplied to a third input of the circuitry of block 121 as hereinafter described.

The throttle position sensor of block 129 may be any conventional device such as a strain gage, potentiometer or the like for generating a DC voltage proportional to the relative position of the throttle valve 108 from some reference position. For example, the transducer 129 may include a mechanical link, represented by the dotted line 117 of FIG. 1 and a one turn wire-wound potentiometer electrically connected in a voltage divider circuit for supplying a DC voltage level or signal proportional to the relative position of the throttle valve 108. The DC voltage is designated "d" and is supplied to still another input of the analog to digital converter circuitry of block 121. A similar transducer may be used as the EGR value position sensor of block 130 to supply a DC voltage signal "e" to a fifth input of the circuitry of block 21 which is proportional to the position of the EGR valve 115 of FIG. 1.

The exhaust gas oxygen content sensor or sensors of block 131 are conventional zirconia type oxygen sensors. These devices are electrochemical gas sensors which may, for example, include a hollow cylindrical tube of stabilized zirconium dioxide closed at one end. The outside of the tube is exposed to the exhaust gases and the inside of the tube is referenced to atmospheric oxygen. The zirconium dioxide acts as a solid electrolyte and the inside and outside surfaces are coated with platinum which serves as a catalyst and provides conductive electrodes which can be used to sense the electric potential produced by the sensor. The sensor has the unique characteric that the potential it produces varies characteristically from approximately 800
milivolts at a rich air/fuel ratio to 200 milivolts at a lean air/fuel ratio. In the rich condition, the outside of the sensor is exposed to gases containing near zero quantities of excess oxygen, allowing a maximum potential and at a point just slightly rich of stoichiometric however, appreciable amounts of excess oxygen appear in the exhaust gases and the potential drops abruptly in accordance with the Nernst equation D=(RT/K)ln(P.sub.1 /P.sub.2). The gain or slope of this voltage change is so sharp and so abrupt as to be nearly comparable to that of a switch. Particularly important, of course, is the fact that is occurs at the ideal operating point of a conventional "three-way-catalyst". Because this characteristic is an inherent property of the oxygen sensor, it is not subject to drift and does not change significantly with age. Moreover, there are no unit-to-unit differences in the characteristics.

In the preferred embodiment of the present invention, one oxygen sensor is provided in each bank of a V-8 engine immediately before the two banks join. In the event that a single oxygen sensor is used, it would preferably be located at or immediately below the point where the two banks join in the exhaust outlet 113 of the exhaust system 103 of the engine 101.

Because of the high gain characteristics of the zirconia type oxygen sensor of block 131 near the stoichiometric air/fuel ratio, the sensor is often referred to as an air/fuel ratio or lamda (.lambda.) sensor. In operation, the sensor or sensors of block 131 will produce a first DC level signal when a rich air/fuel ratio is detected and a second and distinct DC voltage when a lean air/fuel ratio is detected. These DC signal levels from the first and second oxygen sensors are designated by the letters "f.sub.1 " and "f.sub.2 ", respectively, and are supplied to the analog to digital converter circuitry of block 121 of FIG. 3.

A particularly important characteristic of the oxygen sensors of block 131 is that their impedence decreases exponentially with temperature. Therefore, a very small output voltage is produced at low temperatures when the internal impedance of the sensor is extremely high so that the sensor output becomes unreliable or invalid below some predetermined operating temperature such as 300 degrees Centigrade or the like where its internal impedance is approximately one megaohm. As hereinafter described with respect to the circuitry of block 121, means are provided for testing the validity of the oxygen sensor signals from block 131 before the output readings are used for control purposes.

II. General Description of the Microprocessor-Based Electronic Control System of FIG. 2

The analog to digital converter circuitry of block 121 of FIG. 2 is primarily a group of analog circuits used to perform an analog to pulse-width conversion as hereinafter described. Each sensor input channel of the analog to digital converter circuitry of block 121 has a signal conditioner to achieve the proper impedence matching, polarity changing, and scaling of the sensed parameter prior to its conversion into a pulse-width. The primary function of the converter circuitry of block 121 is to convert or transform the analog voltage signal or level into a pulse-width digital signal, hereinafter called digital signal, which is proportional to and indicative of the value of the analog input signal from the particular sensor associated with a given channel.

The binary encoder circuitry of block 122 includes the digital portion of the circuits required for the analog to digital conversion and the circuitry for multiplexing the pulse-width converted signals indicative of the various analog inputs into a pulse-width to binary converter which transforms the pulse-widths into corresponding binary numbers or digital words indicative of the sensed engine operating parameters. The binary encoder circuitry of block 122 also includes circuitry for digitally processing the oxygen sensor information and circuitry for measuring time intervals between engine position pulses so that the sampling frequency of each sensor may be determined in normalized real time rather than actual real time as hereinafter described.

The binary words indicative of the actual sensed engine operating parameters are supplied to the microprocessor system of block 123 wherein a standard, low-cost, off-the-shelf microprocessor and standard units of memory are programmed to manipulate the incoming data in accordance with various programs and memory-stored one, two and three dimensional optimal surfaces and look-up tables, determined experimentally or the like. The microprocessor system of block 123 performs the required control law computations and table look-ups and outputs digital control words to the binary decoder circuitry of block 124. The microprocessor system of block 123 further includes means for processing camshaft position signals, interrupt control circuitry, command signal generators, reset control logic, buffers, and parallel-to-serial converters for transferring data to the binary decoders of block 124.

The binary decoder circuitry of block 124 receives the binary words indicative of the required timing and pulse-width of the fuel injection pulses; the ignition firing delay from the last crankshaft position pulse and ignition pulse-width information; and the EGR control function, and converts these digital words into pulse-widths capable of driving or actuating the power control circuits of block 125. The circuits of block 125 respond to the pulse-width inputs and supply the necessary drive current to operate the fuel injectors, fuel pump, ignition coils, EGR actuators and the like. Additionally, the circuitry of block 125 includes the power supply regulator circuitry of the present invention.

Additionally, the microprocessor-based electronic engine control system of FIG. 2 includes a crankshaft position sensor 132 which may be, for example, a conventional reluctance pick-up or magnetic transducer, optical transducer or the like capable of detecting timing marks, holes or cogs on the crankshaft 104 of the engine 101 or on some member such as a pulley affixed thereto for rotation therewith. The analog output of the engine crankshaft position sensor of block 132 is indicated by the letter "G" which is supplied to an input of the binary encoder circuitry of block 122 which includes pulse processing logic for conditioning the crankshaft sensor signal "G" and synchronizing the engine position pulse to the logic clock to generate one and only one clock period wide pulse for each engine position pulse detected.

The engine crank-shaft position sensor outputs the signal "G" which is representative of a particular point in the operating cycle of each individual engine cylinder, for example, this pulse could be indicative of some fixed angular rotation ahead of top dead center of the compression stroke for each cylinder, four-cycle, or the like. Therefore, on an eight cylinder engine, four engine position pulses would occur during each engine revolution. Similarly, on the six cylinder engine, the sensor would generate three engine position pulses per revolution and on a four cylinder engine, two pulses per revolution, etc. These signals are used to normalize the logic clock to the engine cycle and the normalized pulses are used to control various engine events.

A similar magnetic transducer or reluctance pick-up may be included within the camshaft position sensor circuitry of block 133 which senses some predetermined camshaft position for generating the output signal "G6" and supplies this signal to the microprocessor system of bloc 123 for interrupt control and engine event timing purposes as hereinafter described.

In the preferred embodiment of this invention, a camshaft position sensor and conditioning circuit such as disclosed in U.S. Pat. application Ser. No. 828,806 which was filed on Aug. 29, 1977 and which is assigned to the assignee of the present invention, is contemplated.

A crystal controlled master clock oscillator is represented by the block 134 which supplies accurate clock signals to the circuitry of blocks 122, 123 and 124. Additionally, various "get-home" or limp-home circuits may be coupled between the microprocessor system of block 123 and the power control circuits of block 125, as represented by block 135 to generate the necessary fuel injection pulse-width and ignition advance timing and dwell time to enable the automobile to function long enough to get to a service station or the like in the event of a major systems failure. Lastly, an ignition switch 136 supplies an "ignition-on" signal and a "starting" signal to the power control circuits of block 125 as hereinafter described.

The signal "S10" is outputted from the power control circuits of block 125 and used to supply switched power to actuate a conventional fuel pump, such as that disclosed in U.S. Pat. No. 2,980,090 which issued on Apr. 18, 1961 to R. W. Sutton, et al and which is assigned to the assignee of the present invention and incorporated by reference herein. The fuel pump, not shown but conventionally known--is connected to the fuel injector 116 by a suitable conduit 118. Similarly, the fuel pump is connected to the fuel tank by another conduit and it may be electrically operated by the output of the signal S10 for maintaining sufficient pressure on the fuel into the injector for insuring its injection while the fuel injectors 116 are in the open position.

The power control circuits of block 125 also supply the signals S20 and S30 to control the operation of the first set of fuel injectors and the signals S40 and S50 to control the operation of the second set of fuel injectors. The fuel injectors
116 may be any conventional type of fuel injectors designed to be responsive to a pulse-width signal for opening a fuel injection valve or port for a period directly controlled by the duration or pulse-width of the signals supplied thereto. For example, the type of fuel injectors disclosed in the above-identified U.S. Pat. No. 2,980,090 or the type illustrated in U.S. Pat. No. 4,030,668 which issued to A. M. Kiwior on June 21, 1977, and which is assigned to the assignee of the present invention and incorporated by reference herein, may be used.

The output signal TU10 is supplied to a conventional ignition coil for controlling the spark timing as conventionally known and set forth in one or more of the above-referenced patents.

The output signal X30 may be supplied to an EGR actuator to control the positioning of the EGR valve 115 of FIG. 1 in any conventional manner. For example, the EGR valve 115 could include a butterfly valve connected by a mechanical linkage to a stepper motor with the stepper motor being electrically controlled by the electrical output signal X30. Similarly, the positioning of the EGR valve 115 could be controlled by standard on/off solenoid or a proportional actuator such as a servo motor as disclosed in U.S. Pat. application Ser. No. 855,493 filed on Nov. 28, 1977 which is assigned to the assignee of the present invention and which is incorporated by reference herein. See also commonly owned U.S. Pat. application Ser. No. 870,966
filed on Jan. 19, 1978 the disclosure of which is incorporated by reference herein.

III. Analog to Digital Converter Circuits

3.0 Broad Description of the Analog to Digital Converter Circuitry

The analog to digital converter circuitry of block 121 of FIG. 2 is illustrated in a more detailed block diagram in FIG. 3. The signal amplifier and comparator circuitry of blocks 141, 142, 143, 144 and 145 each have one input adapted to receive the corresponding analog sensor output signals "a", "b", "c", "d" and "e" from the sensors of blocks 126, 127, 128, 129 and 130 of FIG. 2, respectively; a second input connected to the output of the ramp generator of block 147; and a third reference input, also from the ramp generator circuitry of block 147. The ramp generator of block 147 produces an extremely accurate voltage ramp which is initiated by a first signal to start at a predetermined reference level and then its output is checked after one or more predetermined time intervals to verify the accuracy of the ramp and make corrections, if necessary, as hereinafter described.

The signal amplifier and comparator circuits of blocks 141 through 145 perform the required signal conditioning to provide impedence matching, scaling and signal inversion, if needed, depending upon the sensor output signal supplied to the particular A/D converter input.

The primary outputs of the signal amplifier and comparator circuits of blocks 141, 142, 143, 144 and 145 supply pulse-width output signals A, B, C, D and E, respectively, to the binary encoder circuitry of block 122 of FIG. 2. The primary signal output of each of the blocks 141 through 145 is normally low but goes high as soon as the sampling period is begun after the signal i.sub.0 is supplied from the binary encoder circuitry of block 122 to the ramp generator of block 147 to initialize the system to the reference level i.sub.2 and begin the generation of the ramp voltage i.sub.1. At this point, the outputs A, B, C, D, and E go high and remain high until the value of the ramp voltage becomes equal to the value of the corresponding analog input signals "a", "b", "c", "d", and "e". As soon as the ramp voltage i.sub.1 has become equal to the analog input level, the output signal goes low so that the pulse-width or pulse duration of each of the output signals A, B, C, D and E is proportional to and indicative of the magnitude of the corresponding analog input signals "a", "b", "c", "d" and "e", respectively.

Additionally, a second output of the pressure sensor signal amplifier and comparator circuit of block 141 may supply an amplified analog signal a.sub.1 and a second output of the throttle position sensor signal amplifier and comparator of block
144 may supply an amplified analog signal d.sub.1 to the binary encoder circuitry of block 122 for monitoring the rate of change of manifold absolute pressure and/or throttle position, as hereinafter described.

The oxygen sensor signal conditioning system of block 146 receives as its inputs, the output signals f.sub.1 and f.sub.2 from the first and second oxygen sensors of block 131 of FIG. 2. In addition to appropriate amplification circuitry, the oxygen sensor signal conditioning system of block 146 directs the current to the oxygen sensors for impedence monitoring; establishes a stoichiometric threshhold level; and sets an inhibit threshhold level against which the impedence monitoring current is compared for generating an inhibit signal whenever the sensor temperature is below the required operating temperature for valid and reliable readings.

In addition to generating the required ramp voltage signal i.sub.1, the ramp generator of block 147 establishes a reset or initial reference signal i.sub.2 which is offset a predetermined amount from ground and this reference signal i.sub.2 is also supplied to the amplifier circuitry of blocks 141 through 145 so that a ratiometric relationship is established between the ramp generator and the circuitry of blocks 141 through 145 so that their operation is relatively independent of fluctuations in power supply voltage as hereinafter described.

3.1 Pressure Sensor Signal Amplifier and Comparator Circuit

The pressure sensor signal amplifier and comparator circuit of block 141 of FIG. 3 is illustrated in the electrical schematic of FIG. 3A. The +9.5 volt regulated power supply of block 125 of FIG. 2 is connected via lead 147 to a node 148 which in turn is connected via lead 149 to the positive input terminal of the manifold absolute pressure sensor of block 126 of FIG. 2. The reference signal i.sub.2 is supplied from the ramp generator of block 147 of FIG. 3 to reference node 150. A first resistor 151 has one end connected to the +9.5 volt supply at node 148 and its opposite end connected to a positive input node 152. A second resistor 153 has one end connected to the positive input node 152 and its opposite end connected to the reference node 150. The positive input node 152 is connected directly to the non-inverting input of an operational amplifier 154. The combination of the resistors 151 and 153 establish a voltage divider so that the node 152 is established at some predetermined ratiometric voltage level between the reference node 150 and the + 9.5 volt supply.

The reference node 150 is also connected to the negative input terminal of the manifold absolute pressure sensor of block 126 of FIG. 2 via lead 155 and the output of the sensor supplies the signal "a" via lead 156 to the source input of the signal conditioning portion of the circuitry of FIG. 3A. Lead 156 is connected to the inverting input node 160 through a pair of series resistors 157 and 159. A high frequency transient shunt is provided by connecting a capacitor 161 between the sensor input and reference lead 155 by connecting one end of the capacitor 161 to the junction 158 of the resistors 157, 159 and its opposite end to the lead 155. Therefore, the combination of resistors 157, 159, and capacitor 161 provides a high frequency filter whose RC time constant should not substantially attentuate the analog input signal frequencies.

The inverting input node 160 is connected directly to the inverting input of the operational amplifier 154 and a feedback resistor 162 is connected between the inverting input node 160 and the output 165 of the operational amplifier 154 with one end of resistor 162 connected directly to the inverting input node 160 and the opposite end connected to a node 163. Node 163 is directly connected to the output node 165 via lead 164. The resistor 162 is a trim resistor which can be used for controlling the amount of gain or the slew rate of the operational amplifier 154.

In the preferred embodiment of the present invention, the circuits of FIG. 3 are implemented in LSI and the value of resistor 162 may be actively tailored or trimmed with a laser during live operation so that the gain of the amplifier 154 may be tailored along with offset so as to allow calibration for any specific manifold absolute pressure sensor to the present system with a high degree of accuracy. The resistor 153 is used to provide the necessary offset and the total signal conditioning circuit comprising the operational amplifier 154, the capacitor 161, and resistors 151, 153, 157, 159 and 162 provide a signal conditioning circuit which acts as an inverter and provides an amplified and inverted signal level at the circuit output 165.

The amplified and inverted signal level is supplied from the output node 165 as the output signal "a.sub.1 " via lead 164, node 163 and output lead 166. The output signal is also supplied through a resistor 167 to the non-inverting input node
168 of an operational amplifier 169 configured as a conventional comparator circuit. The non-inverting input node 168 is connected directly to the non-inverting input terminal of the comparator 169 and the ramp voltage signal i.sub.1 is supplied to the inverting input of the comparator 169 through a resistor 170. The resistors 167 and 170 provide isolation. The output of the comparator 169 is taken from output node 171 and output node 171 supplies the pulse-width output signal "A" to the binary encoder circuitry of block 122 of FIG. 2 via lead 172.

A feedback resistor 173 is connected between the comparator output 171 and the non-inverting input 168. One terminal of the feedback resistor 173 is connected directly to the non-inverting input 168 of the comparator 169 and the opposite terminal of the resistor 173 is connected to a node 174. Node 174 is connected directly to the output node 171 via lead 175 so as to establish a positive feedback path from the output terminal 171 back to the non-inverting input of the operational amplifier 169 via lead 175, node 174, resistor 173 and node 168. This positive feedback provides the necessary hysteresis so that the output of the comparator 169 provides a snap-action type effect as soon as the ramp voltage i.sub.1 reaches the threshhold level established at the non-inverting input. A resistor 176 connects the +5-volt regulated power supply from the power control circuitry of block 125 of FIG. 2 to the node 174 to act as a pull-up resistor. The +5-volt signal level is compatible with the digital logic circuitry of the binary encoder of block 122 of FIG. 2 and insures the proper output transitions as the comparator 169 sinks currents from the positive supply of voltage.

In operation, the analog signal level "a" provided from the output of the pressure sensor circuit of block 126 of FIG. 2 is supplied to the sensor input of the signal conditioning circuit of FIG. 3A via lead 156. This signal is filtered to eliminate high speed transients and the ratio established by resistor 151 and 153 together with the gain of the amplifier 154, which is controlled by the value of the feedback resistor 162, provides a properly amplified and conditioned signal a.sub.1 at the output 165.

The amplified signal level is also supplied from the output 165 of the operational amplifier 154 through the isolation resistor 167 to the non-inverting input of the comparator 169. So long as the voltage level of the ramp signal i.sub.1 being supplied through the isolation resistor 170 to the inverting input of the comparator 169 remains below the voltage level of the signal present at the non-inverting input, the output of the comparator 169 will be high. As soon as the comparator voltage i.sub.1 becomes equal to the signal at the non-inverting input, the output of comparator 169 will go low. The hysteresis resistor 173 insures that the output changes rapidly in a snap-action manner so that as soon as the ramp voltage i.sub.1 becomes equal to the signal present at the non-inverting input of the comparator 169, the output from the comparator will immediately go low. This terminates the analog to pulse-width conversion such that the signal A is a pulse-width signal whose width or time duration is proportional to and indicative of the value of the output signal "a" from the pressure sensor 126 of FIG. 2 and this pulse-width signal A is supplied to an input of the analog to digital comparator circuitry of block 121 of FIG. 2 for conversion into a binary number as hereinafter described.

3.2 Air Temperature Sensor Signal Amplifier and Comparator Circuit

The air temperature sensor signal amplifier and comparator circuit of block 142 of FIG. 3 is illustrated in the electrical schematic diagram of FIG. 3B. The +9.5-volt supply is connected to the positive input of the air temperature sensor of block 127 of FIG. 2 through a resistor 177 and the reference level i.sub.2 is connected to a reference node 178 and then to the opposite terminal of the air temperature sensor of block 127 via lead 179. The air temperature sensor could be a thermistor type device or some similar temperature responsive device which would appear as a resistance between the input sensing node 180 and the reference lead 179. The characteristics of the sensor would be such that its resistance would vary, although not in a truly linear manner, with changes in temperature so that the sensor output signal "b" would be supplied to the input node 180 of the signal amplifier and signal conditioning circuitry of FIG. 3B and the node 180 would act, in effect, as the tap point on a voltage divider comprising the resistor 177 and the air temperature sensing device 127.

The signal "b" is supplied to the inverting input node 181 of an operational amplifier 182 through a pair of series resistors 183 and 184. A capacitor 185 is connected in shunt between a junction 186 between the series resistors 183, 184 and the reference lead 179 to form a high frequency filter. The combination of resistors 183 and 184 with the capacitor 185 forms a high frequency filter whose time constant does not substantially attenuate the "b" input signal but which does serve to filter out high frequency transients and the like.

The +9.5-volt supply is also connected to the reference node 178 through a pair of resistors 187, 188. The junction 189 of the resistors 187, 188 is connected directly to the non-inverting input of the operational amplifier 182 and the resistors
187, 188 establish a voltage divider configuration between the +9.5-volt source and the reference potential ramp i.sub.2 at node 178 so as to establish a predetermined threshhold level at the non-inverting input with the value of the resistor 188
establishing the offset voltage for the operational amplifier 182 as conventionally known.

A feedback resistor 190 is connected between the inverting input node 181 and the amplifier output node 191 to determine the gain of the amplifier 182. As previously described, the value of the gain resistor 190 may be actively tailored during live operation of the sensor so that the operation of the circuit of FIG. 3B is not dependent upon the use of the particular type of air temperature sensor 127 but may be used with any such sensor. The output of the operational amplifier 182 is taken directly from output node 191 and represents an amplified and inverted version of the analog input signal "b" from the air temperature sensor 127 of FIG. 2.

The amplified and inverted signal from the output 191 of the amplifier 182 is supplied to the non-inverting input node 192 through an isolation resistor 193. The non-inverting input node 192 is connected directly to the non-inverting input of another operational amplifier 194 configured as a conventional comparator circuit. The ramp of voltage signal i.sub.1 is supplied to the inverting input of the comparator 194 through a second isolation resistor 195. A feedback resistor 196 is connected between the non-inverting input node 192 and the comparator output node 197 through a resistor 196, node 198, and lead 199. The feedback path from the output 197 through lead 199, node 198 and resistor 196 back to the non-inverting input 192 provides the necessary hysteresis so that the output of the comparator reacts in a snap-action manner to provide a sharp transition as soon as the comparator threshhold voltage is attained. The node 198 is connected to a +5-volt DC supply through a pull-up resistor 200 as previously described and the output of the comparator 194 is taken from node 197 and supplies the signal "B" to one input of the binary encoder circuitry of block 122 of FIG. 2 via lead 201.

In operation, the output signal level "b" from the air temperature sensor 127 of FIG. 2 is supplied to input node 180 and high frequency transients and the like are filtered out. The filtered signal is supplied to the inverting input of operational amplifier 182 whose gain is controlled by a feedback resistor 190 and a properly conditioned, amplified and inverted output signal is supplied to one input of a comparator 194. The opposite comparator input is supplied with the ramp voltage signal i.sub.1 and the output of the comparator 194 will go high and remain high until the ramp voltage becomes equal to the value of the amplified sensor signal voltage present at the non-inverting input node 192. As soon as equality of inputs is attained, the output of the comparator 194 immediately goes low to terminate the output pulse and the signal B which is outputted to the binary encoder circuitry of block 122 is a pulse-width signal whose width or time duration is proportional to and indicative of the value of the sensed air temperature.

3.3 Engine Coolant Temperature Sensor Signal Amplifier and Comparator Circuit

The engine coolant temperature sensor signal amplifier and comparator circuit of block 143 of FIG. 3 is illustrated in the electrical schematic of FIG. 3C. The +9.5-volt supply is connected to the positive terminal of the engine temperature sensor device of block 128 of FIG. 2 through a resistor 202 and the reference level signal i.sub.2 is supplied to reference node 203 and to the opposite terminal of the engine temperature sensor 128 via lead 204. As indicated previously, the engine temperature sensor 128 is a thermistor type device similar to that used in the air temperature sensor but normally having a slower response time and would normally appear as a resistor between the input node 205 and the reference lead 204. Therefore, the resistor 202 and the engine temperature sensor 128 would establish a voltage divider such that the signal present at the node 205 represents the sensor output signal "c" which is proportional to and indicative of the engine temperature since the resistance of the sensor with changes in the engine coolant temperature.

The engine coolant temperature signal "c" is supplied to the inverting input node 206 through a pair of series resistors 207 and 208. A shunt capacitor 210 is connected between the junction 209 between the resistors 207, 208 and the reference lead 204 so as to establish a filter configuration from resistors 207, 208 and capacitor 210 which filters out the high frequency components presented to the input node 205 without significantly attenuating the input signal "c".

The +9.5-volt source is also connected to the reference node 203 through a pair of series resistors 211, 212. The junction 213 of resistors 211 and 212 is connected directly to the non-inverting input of an operational amplifier 214 whose inverting input is connected directly to the input node 206. The resistors 211, 212 form a voltage divider between the +9.5-volt source and the reference node 203 and the value of the resistor 212 establishes the offset potential presented to the non-inverting input of the amplifier 214.

The inverting input node 206 is connected directly to the output node 215 of the amplifier 214 through a feedback resistor 216. As previously described, the value of feedback resistor 216 may be actively tailored during live operation of the sensor 128 so as to calibrate the gain for any specific temperature sensor with the required degree of accuracy.

A properly conditioned, amplified and inverted signal indicative of the engine temperature is present at the output node 215 of the amplifier 214 and this condition signal is presented to the non-inverting input node 217 through an isolation resistor 218. Node 217 is connected directly to the non-inverting input of an operational amplifier 219 configured as a conventional comparator. The ramp voltage signal i.sub.1 is supplied through an isolation resistor 220 to the negative comparator input and a feedback resistor 221 has one terminal connected directly to the positive input node 217 and its opposite terminal connected to a node 222. Node 222 is connected directly to the output node 223 of the comparator 219 through a lead 224 so as to establish a feedback path from the output node 223 of the comparator 219 to the positive input node 217 via lead 224, node 222 and resistor 221. The resistor 221 provides the necessary hysteresis so that the output of the comparator will abruptly change as soon as the established threshhold is attained as conventionally known. A +5-volt source of potential is connected to node 222 through a pull-up resistor 225, as previously described, and the output of the comparator is the pulse-width signal "C" which is suppied to another input of the binary encoder circuitry of block 122 of FIG. 2 via lead 226.

In operation, the analog signal level "c" from the engine temperature sensor of block 128 of FIG. 2 is taken from the input node 205 and high frequency transients and the like are filtered out by the filter comprising resistors 207, 208 and capacitor 210. The offset of the operational amplifier 214 is established by resistor 212 and the gain is controlled by the value of resistor 216 so that a properly conditioned, amplified and inverted signal indicative of the actual engine coolant temperature is presented to one input of a comparator 219. The other input of the comparator 219 receives the output of the ramp generator i.sub.1 so that the output of the comparator will initially go high to generate the signal C which will remain high until the ramp voltage i.sub.1 becomes equal to the value of the signal present at the non-inverting input node 217 of the comparator 219. As soon as equality exists, the output of the comparator 219 will immediately go low to terminate the generation of the signal C whose pulse-width or time duration will be proportional to and indicative of the actual measured value of the engine coolant temperature and this signal C is supplied to the binary encoder circuitry of block 122 for conversion into a binary number for further processing as hereinafter described.

3.4 Throttle Position Sensor Signal Amplifier and Comparator Circuit

A voltage-to-current transformer circuit indicated generally by the reference numeral 227 in the schematic of FIG. 3D is used to supply a source of current to the potentiometer of the throttle position sensor of block 129 of FIG. 2. FIG. 3D illustrates the circuit detail of block 144 of FIG. 3. The voltage-to-current transformer circuit 227 has an input reference node 228