Fuel control system with calibration learning capability for motor vehicle internal combustion engine

• US 4,130,095 A
• Filed: 12/01/1977
• Issued: 12/19/1978
• Est. Priority Date: 07/12/1977
• Status: Expired due to Term

• Current Assignee: General Motors Corporation (General Motors Company)
• Original Assignee: General Motors Corporation (General Motors Company)
• Inventors: Lahiff, John E., Bowler, Lauren L.
• Primary Examiner(s): Cox, Ronald B.
• Application Number:
  US05/856,238
• Time in Patent Office: 383 Days
• Field of Search: 123/32 EB, 123/32 EC, 123/32 EE, 123/32 EA, 123/119 EC, 60/276, 60/285
• US Class Current: 123/675
• CPC Class Codes: F02D 41/2438 Active learning methods
• CPC Class Codes: F02D 41/2448 Prohibition of learning
• CPC Class Codes: F02D 41/2454 Learning of the air-fuel ratio control
• CPC Class Codes: F02D 41/26 using computer, e.g. microprocessor
• CPC Class Codes: F02M 2200/507 Adjusting spring tension by screwing spring seats
• CPC Class Codes: F02M 51/0667 the armature acting as a valve or having a short valve body attached thereto
• CPC Class Codes: F02M 51/08 specially for low-pressure fuel-injection
• CPC Class Codes: Y10S 261/74 Valve actuation; electrical
• CPC Class Codes: Y10S 261/82 Upper end injectors

Abstract

A memory type fuel control system and method of operating a motor vehicle internal combustion engine having a three-way catalytic converter. A fuel flow control system provides a fuel supply rate near the air/fuel ratio at which the catalytic converter has maximum three-way conversion efficiency. The fuel supply rate so determined is trimmed by a trim factor recalled from memory, the authority of this trim factor being sufficient to compensate for engine and controller variations with time, manufacturing tolerances, etc. In the preferred form, the trim factor is stored in memory at an address determined by the same engine operating conditions that control the fuel supply. The engine exhaust gas oxidizing/reducing conditions are sensed by exhaust gas sensors. In the preferred form, a closed loop controller is responsive to the deviation of the sensed oxidizing/reducing conditions from the condition at which the catalytic converter has maximum three-way conversion efficiency to adjust the trimmed fuel supply rate in a sense to produce the oxidizing/reducing condition at which the maximum conversion efficiency is obtained. A sampling circuit recurrently samples and momentarily stores the engine operating conditions, such as engine load and speed conditions, in a short term memory to form a history of those conditions extending back at least by the amount of the engine transport delay time. At a later time, the exhaust gas oxidizing/reducing conditions sensed by the exhaust gas sensor is sampled, the engine operating conditions that produced the sampled exhaust gas condition are recalled from the short term memory, a new trimming value is determined for the recalled vehicle conditions which more closely produce a desired oxidizing/reducing condition, and such value is inserted in the main memory at the address determined by the recalled conditions. Such trim factor is then available for recall and use as the trimming factor when the engine is next operated under such conditions.

Claims

1. A fuel control system for an internal combustion engine having combustion space into which an air/fuel mixture is supplied to undergo combustion and having means defining an exhaust gas passage from the combustion space into which spent combustion gases are discharged and are directed to the atmosphere comprising, in combination:

a sensor responsive to the oxidizing/reducing conditions at a predetermined point in the exhaust passage, and hence, after a transport time delay period dependent upon engine operating conditions, to the mixture supplied to the combustion space, the sensor having an output condition indicative of predetermined desired oxidizing/reducing conditions;

a memory having locations addressable in accordance with at least one engine operating condition and having a number at each such location determinative of a fuel supply rate as determined by the engine operating condition so as to produce the predetermined desired oxidizing/reducing conditions;

means effective to supply fuel to the combustion space at a rate determined at least by the number recalled from the memory at the location of the current value of the predetermined engine operating condition;

sampling means effective to sample and store at recurrent intervals at least the predetermined engine operating condition; and

means responsive to at least the engine operating condition stored by the sampling means at the beginning of a particular transport time delay period and to the output condition of the sensor at the end of the particular transport time delay period effective to store in the memory at the address according to the engine operating condition at the beginning of the particular transport time delay period a new number having a value differing from the value previously stored at such address in a sense tending to restore the sensor output to the desired output condition.

2. A fuel control system for an internal combustion engine having combustion space into which an air/fuel mixture is supplied to undergo combustion and having means defining an exhaust gas passage from the combustion space into which spent combustion gases are discharged and are directed to the atmosphere comprising, in combination:

a sensor responsive to the oxidizing/reducing conditions at a predetermined point in the exhaust passage, and hence, after a transport time delay period dependent substantially upon engine speed, to the mixxture supplied to the combustion space, the sensor having an output condition indicative of predetermined desired oxidizing/reducing conditions;

a memory having locations addressable in accordance with at least one engine operating condition and having a number at each such location determinative of a fuel supply rate as determined by the engine operating condition so as to produce the predetermined desired oxidizing/reducing conditions;

means effective to supply fuel to the combustion space at a rate determined at least by the number recalled from the memory at the location of the current value of the predetermined engine operating condition;

sampling means effective to sample and store at recurrent intervals at least the predetermined engine operating condition;

means effective to determine the transport time delay period, said last mentioned means including an engine speed sensor effective to generate an engine speed signal and means responsive to the engine speed signal effective to provide an output signal that substantially represents the engine transport delay; and

means responsive to at least the engine operating condition stored by the sampling means at the beginning of the determined transport time delay period and to the output condition of the sensor at the end of the determined transport time delay period effective to store in the memory at the address according to the engine operating condition at the beginning of the determined transport time delay period a new number having a value differing from the value previously stored at such address in a sense tending to restore the sensor output to the desired output condition.

3. In combination, an internal combustion motor vehicle engine effective to propel a vehicle at operator controllable speeds and accelerations and being of the type wherein fuel is supplied at an intake point to energize the engine and spent exhaust gases are discharged at a predetermined discharge point;

a three-way catalytic converter effective to treat the exhaust gases downstream of said discharge point;

means effective in response to the current value of at least one engine operating condition to supply fuel to said intake point;

trimming means including a read/write memory addressable in accordance with an engine operating parameter effective to trim the fuel supplied by said first means in accordance with a number recalled from said memory at the address of the current value of the engine operating parameter;

short term memory means recurrently effective to store the value of at least said operating parameter;

a sensor system responsive to a condition of the exhaust gases indicative of the three-way convertibility of the exhaust gases at the converter;

means responsive to at least one engine variable effective to compute an approximation of engine transport delay;

elements responsive to the short term memory, the sensor system and said last means effective to determine at least the sense of the deviation from three-way convertibility of said exhaust gases at a time delayed by the time determined by said last means from the time of storing the operating parameter on the short term memory; and

means effective to write on the read/write memory an adjustment of the prior number in accordance with at least the sense of the value determined by said elements.

4. A fuel control system for a motor vehicle internal combustion engine having an intake chamber from which an air/fuel mixture is drawn into a combustion space to undergo combustion and having means defining an exhaust gas passage from the combustion space into which the spent combustion gases are discharged and directed to the atmosphere, the system comprising:

means effective to recurrently generate a fuel control signal from the values of predetermined engine operating parameters and trim the fuel control signal by a trimming factor recalled from storage at an address location determined by the engine operating parameters;

fuel supply means effective to supply fuel to the intake chamber in accordance with at least the trimmed fuel signal;

sampling means effective to recurrently store at least the values of the engine operating parameters to form a history of operation of the engine;

sensor means effective to recurrently sense the condition of the exhaust gases at the discharge point in relation to a predetermined desired condition of the gases;

means effective to determine the transport time delay T between the intake point and the predetermined discharge point, the transport time delay T being equal to the sum of a first delay component that is inversely proportional to the absolute pressure in the intake chamber and a second delay component that is inversely proportional to the engine speed;

means effective to recurrently recall the values of the engine operating parameters stored at time J-T, where J is the time at which the most recent condition of the exhaust gases is sensed by the sensor means; and

means responsive to the sensed condition of the exhaust gases at time J and the values of the recalled engine operating parameters effective to determine and store a new trimming factor at the storage address location determined by the recalled engine operating parameters having a value differing from the trimming factor previously stored at such address in a sense such as to tend to restore the sensor output to the predetermined desired condition.

5. A fuel control system for a motor vehicle internal combustion engine having an intake chamber from which an air/fuel mixture is drawn into a combustion space to undergo combustion and having means defining an exhaust gas passage from the combustion space into which the spent combustion gases are discharged and directed to the atmosphere, the system comprising:

means effective to recurrently generate a fuel control signal from the values of predetermined engine operating parameters adjusted by a trimming factor recalled from storage at an address location determined by the engine operating parameters;

fuel supply means effective to supply fuel to the intake chamber in accordance with at least the adjusted fuel control signal;

sampling means effective to recurrently store at least the values of the engine operating parameters at intervals substantially less than the smallest operating transport time delay between the intake point and the discharge point to provide a history of operation of the engine, the sampling means having at least a number of storage locations equal to the greatest operating transport delay divided by the sampling interval;

sensor means effective to recurrently sense once during each of the intervals the condition of the exhaust gases at the discharge point in relation to a predetermined desired condition of the gases;

means responsive to at least the value of engine speed effective once during each of the intervals to determine the value T of the transport time delay;

means effective once during each of the intervals to recurrently recall the values of the engine operating parameters stored at time J-T where J is the time of the last interval; and

means responsive to the sensed condition of the exhaust gases at time J and the values of the recalled engine opearating parameters effective to determine and store a new trimming factor at the storage address location determined by the recalled engine operating parameters, the new trimming factor having a value differing from the trimming factor previously stored at such address in a sense such as to tend to restore the sensor output to the predetermined desired condition.

6. In a method of operating a motor vehicle internal combustion engine having a catalytic converter, the steps of

(a) substantially continuously determining the fuel rate primarily on an open loop basis from engine operating conditions and a trimming value stored in memory at one address associated with said conditions,

(b) applying fuel at such rate substantially continuously,

(c) periodically sampling the oxidizing/reducing conditions at the catalytic converter,

(d) determining from such sampling and at least one engine operating condition earlier in time by substantially the engine transport delay the change in the trimming value required to more nearly provide the desired oxidizing/reducing conditions and

(e) storing a new trimming value at the address of the earlier engine operating conditions that gave rise to the sampled oxidizing/reducing conditions so as to make the engine operation more nearly that desired.

7. The process of operating an internal combustion engine in a motor vehicle, the engine being effective to propel the vehicle at operator controllable speeds and acceleration and being of the type wherein fuel is supplied at an intake point to energize the engine and spent exhaust gases are discharged at a predetermined discharge point, comprising the steps of:

determining the fuel requirements of the engine in response to certain fuel determining engine operating parameters, adjusted by a trimming factor separate from said parameters and recalled from storage at an address location determined by at least one of said parameters;

supplying fuel to the engine in accordance with at least said predetermined fuel requirements;

recurrently storing at least the values of said operating parameters;

recurrently sensing the condition of the exhaust gases at said discharge point in relation to a predetermined condition of said gases;

determining from at least the value of engine speed the value T of the transport time delay between said intake point and said predetermined discharge point;

recurrently recalling the values of said operating parameters that were stored at the time T prior to the last sensed exhaust gas condition;

determining at least the sense of change in the trimming factor determined by each of said recalled values that is required to shift the amount of fuel supply in a direction to provide the predetermined condition of the exhaust gases at said discharge point; and

storing a new trimming factor at the address determined by each of the recalled values of said operating parameters that is shifted in said direction in relation to the previously stored value.

8. The process of operating an internal combustion engine, the engine being of the type wherein fuel is supplied at an intake point to energize the engine and spent exhaust gases are discharged at a predetermined discharge point, comprising the steps of:

scheduling a desired air/fuel ratio in response to predetermined engine operating conditions to provide desired engine operation;

determining from predetermined engine operating parameters the engine fuel requirement resulting in a predetermined air/fuel ratio determined to produce a predetermined exhaust gas condition, trimmed by a trimming factor separate from said parameters and recalled from storage at an address location determined by at least one of said parameters;

adjusting the trimmed engine fuel requirement in accordance with the scheduled air/fuel ratio;

supplying fuel to the engine in accordance with at least the adjusted engine fuel requirement;

recurrently storing at least the value of the address location determining engine operating parameters;

sensing the condition of the exhaust gases at said discharge point in relation to the predetermined condition of said gases;

determining the value of the transport delay time between the intake point and the predetermined discharge point;

recurrently recalling the values of the operating parameters that were stored at the determined transport delay time prior to the last sensed exhaust gas condition;

adjusting the stored trimming factor determined by each of the recalled values in response to the deviation of the sensed condition of the exhaust gases from the predetermined exhaust gas condition in a direction to provide an open loop determined engine fuel requirement that more closely results in the predetermined exhaust gas condition; and

inhibiting the step of adjusting the stored trimming factor when the scheduled air/fuel ratio deviates from the predetermined air/fuel ratio determined to produce the predetermined exhaust gas condition.

9. A fuel control system for a motor vehicle internal combustion engine having an intake chamber from which an air/fuel mixture is drawn into a combustion space to undergo combustion and having means defining an exhaust gas passage from the combustion space into which the spent combustion gases are discharged and directed to the atmosphere, the system comprising:

a three-way catalytic converter effective to treat the exhaust gases downstream of the discharge point, the converter having convering characteristics that are a function of the oxidizing/reducing conditions in the exhaust passage;

a sensor responsive to the oxidizing/reducing conditions at a predetermined point in the exhaust passage, and hence, after a transport time delay period dependent upon engine operating conditions, to the mixture supplied to the combustion space, the sensor producing a signal indicative of the oxidizing/reducing conditions of the exhaust gases;

means effective to recurrently generate a fuel control signal from the values of at least one predetermined engine operating parameter and trim the fuel control signal by a trimming factor recalled from storage at an address location determined by the engine operating parameter;

a closed loop circuit responsive to the sensor signal effective to adjust the trimmed fuel control signal in a direction tending to restore a predetermined oxidizing/reducing condition at which the converter has desired converting characteristics when the sensor signal represents a deviation of the exhaust gas oxidizing/reducing condition from the predetermined oxidizing/reducing condition;

fuel supply means effective to supply fuel to the intake chamber in accord with the closed loop adjusted trimmed fuel signal;

sampling means effective to sample and store at recurrent intervals at least the predetermined engine operating parameter and the valve of the closed loop fuel adjustment; and

means responsive to at least the engine operating parameter and the value of the closed loop adjustment stored by the sampling means at the beginning of a particular transport time delay period and at least the oxidizing/reducing condition represented by the sensor signal at the end of the particular transport time delay period effective to store at the storage address location determined by the engine operating parameter at the beginning of the particular transport time delay period a new number having a value differing from the value previously stored at such address location in a sense tending to restore the desired oxidizing/reducing condition.

10. A fuel control system for a motor vehicle internal combustion engine having an intake chamber from which an air/fuel mixture is drawn into a combustion space to undergo combustion and having means defining an exhaust gas passage from the combustion space into which the spent combustion gases are discharged and directed to the atmosphere, the system comprising:

a three-way catalytic converter effective to treat the exhaust gases downstream of the discharge point, the converter having converting characteristics that are a function of the oxidizing/reducing conditions in the exhaust passage;

a sensor responsive to the oxidizing/reducing conditions at a predetermined point in the exhaust passage, and hence, after a transport time delay period dependent upon engine operating conditions, to the mixture supplied to the combustion space, the sensor producing a signal indicative of the oxidizing/reducing conditions of the exhaust gases;

means effective to recurrently generate a fuel control signal from the values of at least one predetermined engine operating parameter and trim the fuel control signal by a trimming factor recalled from storage at an adress location determined by the value of the engine operating parameter;

a closed loop circuit responsive to the sensor signal effective to generate a closed loop signal for adjusting the trimmed fuel control signal in a direction tending to restore a predetermined oxidizing/reducing condition at which the converter has desired converting characteristics when the sensor signal represents a deviation of the exhaust gas oxidizing/reducing condition from the predetermined oxidizing/reducing condition, the closed loop signal including an integral term varying at a rate effecting an adjustment of about 0.9 air/fuel ratios per second in the trimmed fuel control signal;

fuel supply means effective to supply fuel to the intake chamber in accord with the closed loop adjusted trimmed fuel signal;

sampling means effective to sample and store at recurrent intervals at least the predetermined engine operating parameter and the value of the closed loop fuel adjustment; and

calibration learning means responsive to at least the engine operating parameter and the value of the closed loop adjustment stored by the sampling means at the beginning of a particular transport time delay period and at least the oxidizing/reducing condition represented by the sensor signal at the end of the particular transport time delay period effective to store at the storage address location determined by the engine operating parameter at the beginning of the particular transport time delay period a new number having a value differing from the value previously stored at such address location in a sense tending to restore the desired oxidizing/reducing condition and by an amount less than the amount required to restore the desired oxidizing/reducing condition determined by system parameters, the number at a particular address determined by a particular value of the engine operating parameter having a value approaching the value which produces the desired oxidizing/reducing condition in response to recurrent operation of the engine at the particular value of the operating parameter, whereby the closed loop circuit and the calibration learning means cooperate to achieve the desired oxidizing/reducing condition for all engine operating conditions.

11. A fuel control system for an internal combustion engine having combustion space into which an air/fuel mixture is supplied to undergo combustion and having means defining an exhaust gas passage from the combustion space into which spent combustion gases are discharged and are directed to the atmosphere;

comprising, in combination;

a sensor responsive to the oxidizing/reducing conditions at a predetermined point in the exhaust passage, and hence, after a transport time delay period dependent substantially upon engine speed, to the mixture supplied to the combustion space, the sensor having an output condition indicative of predetermined desired oxidizing/reducing conditions;

a memory having locations addressable in accordance with at least one engine operating condition and having a number at each such location determinative of a fuel supply rate as determined by the engine operating condition so as to produce the predetermined desired oxidizing/reducing conditions;

means effective to supply fuel to the combustion space at a rate determined at least by the number recalled from the memory at the location of the current value of the predetermined engine operating condition;

an engine speed sensor producing speed pulses at a frequency related to engine speed;

a counter effectively to recurrently count a predetermined number of speed pulses, the predetermined number having a value such that the time period during which the speed sensor produces the predetermined number of pulses generally equals the engine transport time delay;

means responsive to the count in the counter effective at substantially the beginning of the count to store at least the predetermined engine operating condition;

means responsive to the count in the counter effective at substantially the end of the count to sample the output condition of the sensor; and

means responsive to at least the engine operating condition stored at the beginning of the count and to the output condition of the sensor at the end of the count effective to store in the memory at the address according to the engine operating condition at the beginning of the count a new number having a value differing from the value previously stored at such address in a sense tending to restore the sensor output to the desired output condition.

12. In a method of operating a motor vehicle internal combustion engine having a catalytic converter, the steps of

(a) substantially continuously determining the fuel rate primarily on an open loop basis from engine operating conditions and a trimming value stored in memory at one address associated with said conditions,

(b) adjusting at a predetermined rate the open loop determined fuel rate in response to the deviation of the oxidizing/reducing conditions at the catalytic converter from a desired oxidizing/reducing condition in a direction tending to restore the desired oxidizing/reducing condition,

(c) applying fuel at the adjusted open loop determined fuel rate substantially continuously,

(d) determining from at least one engine operating condition earlier in time by substantially the engine transport delay and the oxidizing/reducing conditions at the catalytic converter a change in the trimming value that more nearly provides the desired oxidizing/reducing conditions and

(e) storing a new trimming value at the address of the earlier engine operating conditions that gave rise to the oxidizing/reducing conditions at the catalytic converter varying from the trimming value previously stored at said address in a sense tending to restore the desired oxidizing/reducing condition whereby the steps of adjusting the open loop determined fuel rate and storing a new trimming value cooperate to achieve the desired oxidizing/reducing conditions at the catalytic converter.

13. A fuel control system for an internal combustion engine having combustion space into which an air/fuel mixture is supplied to undergo combustion and having means defining an exhaust gas passage from the combustion space into which spent combustion gases are discharged and are directed to the atmosphere comprising, in combination:

a sensor responsive to the oxidizing/reducing conditions at a predetermined point in the exhaust passage, and hence, after a transport time delay period depending upon engine operating conditions, to the mixture supplied to the combustion space, the sensor having an output condition indicative of predetermined desired oxidizing/reducing conditions;

a memory having locations addressable in accordance with at least one engine operating parameter and having a number at each such location determinative of a fuel supply rate as determined by the engine operating parameter resulting in an air/fuel ratio to produce the predetermined desired oxidizing/reducing conditions;

means effective to supply fuel to the combustion space at a rate determined at least by the number recalled from the memory at the location of the current value of the predetermined engine operating parameter;

a fuel vapor trap effective to accumulate fuel vapors from fuel vapor sources during certain engine operating conditions and to discharge the accumulated fuel vapor into the combustion space during certain other engine operating conditions, the air/fuel ratio of the mixture provided to the combustion space when the fuel vapors are being discharged from the vapor trap having a value less than the air/fuel ratio determined by the number recalled from memory;

calibration learning means including sampling means effective to sample and store at recurrent intervals at least the predetermined engine operating parameter and means responsive to at least the engine operating parameter stored by the sampling means at the beginning of a particular transport time delay period and to the output condition of the sensor at the end of the particular transport time delay period effective to store in the memory at the address according to the engine operating parameter at the beginning of the particular transport time delay period a new number having a value differing from the value previously stored at such address in a sense tending to restore the sensor output to the desired output condition; and

means responsive to said certain other engine operating conditions during which the accumulated fuel vapor in the fuel vapor trap is discharged into the combustion chamber effective to disable the calibration learning means to inhibit the storing of a new number in the memory so that the numbers in the address locations in the memory are unaffected by the oxidizing/reducing conditions existing in the exhaust gases resulting from discharge of the fuel vapors from the fuel vapor trap.

14. A fuel control system for an internal combustion engine having combustion space into which an air/fuel mixture is supplied to undergo combustion and having means defining an exhaust gas passage from the combustion space into which spent combustion gases are discharged and are directed to the atmosphere comprising, in combination:

a sensor responsive to the oxidizing/reducing conditions at a predetermined point in the exhaust passage and hence, after a transport time delay period dependent upon engine operating conditions, to the mixture supplied to the combustion space, the sensor having an output condition indicative of predetermined desired oxidizing/reducing conditions;

a memory having locations addressable in accordance with at least one engine operating condition and having a number at each such location determinative of a fuel supply rate as determined by the engine operating condition so as to produce the predetermined desired oxidizing/reducing condition;

means effective to recurrently sample at least the value of the engine operating condition at intervals substantially less than the smallest operating transport time delay;

a memory having sequential adress locations, the number of address locations being at least equal to the greatest operating transport time delay period divided by the sampling interval;

means effective to store the sampled values of the engine operating condition repetitively at sequential address locations in the memory to form a circulating memory that contains the most recent history of the sampled values at time related addresses;

means effective once during each of the intervals to determine the value of the transport time delay period from at least one engine operating parameter;

means effective during each of the intervals to recurrently recall the stored engine conditions at the address location spaced from the address location at which the most recent sampled engine conditions were stored by a number of sequential address locations equal to the determined transport delay period divided by the sampling interval; and

means responsive to the recalled engine conditions and the condition of the sensor effective to store in the first memory at the location addressable in accordance with the recalled engine operating condition a new number having a value differing from the value previously stored at such address in a sense tending to restore the sensor output to the desired output condition.