Control apparatus for internal combustion engines

Abstract

An internal combustion engine control apparatus has a digital arithmetic unit to which signals are inputted from a plurality of detectors such as detectors for detecting an operational state of the engine and air fuel ratio detector and controls a fuel air ratio and ignition timing according to output signals from the arithmetic unit. The apparatus comprises by a misfire detector for detecting a misfiring state of the engine, NOx concentration detector and a controller for controlling the fuel air ratio and the ignition timing so as to fall within a tolerable stable combustion range defined by a detected misfire boundary and a detected NOx limit. The misfiring state and/or NOx concentration can be detected through detection of temperature change in the combustion chamber by a detector. The detector comprises a black body disposed in the combustion chamber and a fused silica cable mounting the black body.

What is claimed is: 
     
       1. A lean-burn control apparatus, having a digital arithmetic unit to which signals are inputted from a plurality of detectors for detecting an operational state of an internal combustion engine and an air fuel ratio detector, and controlling a fuel air ratio and ignition timing according to output signals from said arithmetic unit, characterized by misfire detecting means for detecting a misfiring state of said engine;   means for detecting NOx concentration information of said engine; and   means for controlling said fuel air ratio and said ignition timing so as to fall within a tolerable stable combustion range which is defined based on signals from misfire detector and said NOx concentration information detector, and in which combustion is stable and produces NOx of a tolerable concentration.   
     
     
       2. A lean-burn control apparatus according to claim 1, wherein said misfire detecting means is a detector for measuring the intensity of the combustion light of said engine, and said NOx concentration detecting means is a detector for measuring the intensity of said combustion light of said engine having a specific wavelength. 
     
     
       3. A lean-burn control apparatus according to claim 1, wherein said misfire detecting means and said NOx concentration detecting means are detectors for converting said combustion light of said engine into a temperature. 
     
     
       4. A lean-burn control apparatus according to claim 1, wherein said misfire detecting means and NOx concentration detecting means are a temperature detector comprising an optical transmission element, and a black body disposed in a combustion chamber of said engine and mounted on said optical transmission element. 
     
     
       5. A lean-burn control apparatus according to claim 4, wherein said transmission element is of quartz, said black body is a thin film adhered to an end portion of said optical transmission element so as to cover said end portion and made of one element selected from a group consisting of iridium, platinum, zirconium nitride and graphite. 
     
     
       6. A combustion control apparatus for an internal combustion engine having a plurality of cylinders and means for generating a timing signal relating to the timing of firing of combustion in said cylinders, comprising: a plurality of combustion flame optical sensors, each associated with a respective cylinder, for detecting firing of combustion in said cylinders;   a plurality of optical fiber cables, each connected to a respective one of said combustion flame optical sensors;   an optical signal processing circuit connected to all of said optical fiber cables to produce an output signal having a series of pulses each corresponding to an optical signal of a respective optical sensor;   detecting means responsive to said timing signal and said output signal of said optical signal processing unit for detecting a condition of combustion in said cylinders on the basis of said series of pulses; and   means for controlling at least one of fuel air ratio and ignition timing in said internal combustion engine using detected conditions of combustion in said cylinders.   
     
     
       7. A combustion control apparatus according to claim 6, wherein said controlling means operates to control both fuel air ratio and ignition timing. 
     
     
       8. A combustion control apparatus for an internal combustion engine having a plurality of cylinders, comprising: a combustion flame optical sensor, associated with a cylinder for detecting firing combustion in said cylinder, said optical sensor having a non-linear characteristic;   optical signal processing means connected to said optical sensor for converting an optical output thereof to an electrical signal output;   linear processing means connected to said optical signal processing means for linearizing said electrical signal output thereof; and   means for controlling at least one of fuel air ratio and ignition timing in said internal combustion engine using an output of said linear processing means.   
     
     
       9. A combustion control apparatus according to claim 8, wherein filter means is connected to said linear processing means for filtering said linearized electrical signal. 
     
     
       10. A combustion control apparatus according to claim 8, wherein said controlling means operates to control both fuel air ratio and ignition timing. 
     
     
       11. A method of controlling fuel air ratio and ignition timing in an internal combustion engine so as to maintain values of fuel air ratio and ignition timing within a target range in which combustion is stable and NOx concentration is tolerable, comprising the steps of: (a) detecting a misfiring state of said engine;   (b) detecting NOx concentration information of said engine; and   (c) adjusting the value of at least one of fuel air ratio and ignition timing so that both fuel air ratio and ignition timing fall within a target range defined by a misfire boundary and a predetermined NOx concentration boundary.   
     
     
       12. A method according to claim 11, wherein said step (c) comprises adjusting the value of both said fuel air ratio and said ignition timing to cause both fuel air ratio and ignition timing to fall within said target range. 
     
     
       13. A method according to claim 11, wherein step (a) comprises measuring the intensity of combustion light in a cylinder of the engine, and step (b) comprises measuring the intensity of a specific wavelength of combustion light. .Iadd. 
     
     
       14.  A method of detecting misfire of an internal combustion engine, comprising the steps of: detecting combustion light intensity in respective combustion chambers of the engine;   converting the detected combustion light intensity of a combustion chamber into an electrical signal corresponding to a measure of the detected combustion light intensity;   comparing the level of said electrical signal with a predetermined slice level; and   detecting misfire when a signal level of the electrical signal is less than the slice level. .Iaddend. .Iadd.15. A method of detecting misfire of an internal combustion engine, according to claim 14, and further comprising the steps of counting a number of times of the misfire occurring for a prescribed number of power cycles;   calculating an average number of times of the misfire in one power cycle; and   comparing the average number of times of misfire with a predetermined value to judge that the engine is in a misfire condition when the average number of times is larger than the predetermined value. .Iaddend. .Iadd.16. A method of detecting misfire of an internal combustion engine, comprising the steps of:   detecting combustion temperature in respective cylinders of the engine;   converting the detected combustion temperature of a cylinder into an electrical signal corresponding to a measure of the detected combustion temperature;   comparing the electrical signal with a predetermined level; and   judging a misfire condition of the engine when the electrical signal is   
     
     
        less than the predetermined level. .Iaddend. .Iadd.17.  A method according to claim 16, wherein judgement of the misfire is effected at each power cycle. .Iaddend. .Iadd.18. A method according to claim 16, and further comprising the steps of: counting misfire signals each of which is an electrical signal having a level which is less than said predetermined level and is outputted for a prescribed number of power cycles;   calculating an average number of times of occurrence of the misfire signal;   comparing the calculated average number of times with a predetermined value; and   judging a misfire condition of the engine when the calculated average number of times is larger than the prescribed value. .Iaddend. .Iadd.19. A method of detecting a condition of operation of an internal combustion engine, comprising the steps of:   detecting combustion light intensity in respective combustion chambers of the engine:   converting the detected light intensity of a combustion chamber into the electrical signal corresponding to a measure of the detected combustion light intensity; and   comparing the electrical signal with a predetermined slice level and judging that the engine is operating outside of an allowable limit of NOx emission when the signal level of the electrical signal is less than said predetermined slice level. .Iaddend. .Iadd.20. A method of detecting a condition of operation of an internal combustion engine according to claim 19, wherein an average value of combustion light intensity is determined for a prescribed number of power cycles; and   said average value is compared with a predetermined level for judging a misfire condition of the engine. .Iaddend. .Iadd.21. A method of detecting a condition of an internal combustion engine, comprising the steps of:   detecting combustion light intensity in respective combustion chambers of the engine;   converting the detected combustion light intensity of a combustion chamber into an electrical signal corresponding to a measure of the detected combustion light intensity; and   detecting an amount of NOx emitted from the engine on the basis of said electrical signal. .Iaddend. .Iadd.22. An apparatus for controlling an internal combustion engine, comprising:   means for detecting combustion light intensity in respective combustion chambers of the engine;   means for converting detected combustion light intensity of a combustion chamber into an electrical signal corresponding to a measure of the detected combustion light intensity;   means for comparing the electrical signal with a predetermined slice level and judging that the engine is operating in a misfire condition when the signal level of the electrical signal is less than the predetermined slice level; and   means for controlling at least one of fuel air ratio and ignition timing   
     
     
        until no misfire takes place. .Iaddend. .Iadd.23.  An apparatus for controlling an internal combustion engine, comprising: means for detecting combustion temperature in respective combustion chambers of the engine;   means for converting detected combustion temperature of a combustion chamber into an electrical signal corresponding to a measure of the detected combustion temperature;   means for comparing the electrical signal with a predetermined level and judging that the engine is operating in a misfire condition when the signal level of the electrical signal is less than the predetermined level; and   means for controlling at least one of fuel air ratio and ignition timing until no misfire takes place. .Iaddend. .Iadd.24. An apparatus for controlling an internal combustion engine, comprising:   means for detecting combustion light intensity in respective combustion chambers of the engine;   means for converting detected combustion light intensity into an electrical signal corresponding a measure of the detected combustion light intensity;   means for comparing the electrical signal with a predetermined level corresponding to an allowable limit of NOx exhausted from the engine and judging the amount of NOx to be outside of the limit when a signal level of the electrical signal is equal to or larger than the predetermined level; and   means for controlling at least one of fuel air ratio and ignition timing until the amount of NOx is within an allowable limit. .Iaddend.