EP0684376B1 - Electronic system for identifying the strokes of an internal combustion engine - Google Patents

Description

The present invention relates to an electronicsystem for identifying the strokes of an internal combustionengine.

There are known electronic injection systems forinternal combustion engines in which a microprocessor-basedelectronic controller receives at its input aplurality of data signals (for example, the number ofengine revolutions, the throttle position, the intake airtemperature, the cooling water temperature, etc.), andgenerates at its output the injection stroke and time forthe different injectors.

Certain electronic injection systems, for examplethe systems known as "Multipoint" (one injector percylinder) which are sequential (the fuel is injected intoone cylinder at a time) and stroke-dependent (the fuel isinjected in the suction stroke) also require angularreference systems permitting the recognition of theengine strokes (suction, compression, expansion, exhaust)present in the different cylinders of the engine.

The known angular reference systems use twoangular position sensors: a first sensor which can supplya signal of the angular position of the crankshaft (withan interval of 360°) and a second sensor (with an intervalof 720°) which can supply a signal of the angularposition of the camshaft.

In particular, the first angular position sensorconveniently consists of a toothed pulley keyed to thecrankshaft and a fixed sensor which can supply a pulse atthe moment at which one tooth of the pulley passes infront of the fixed sensor. The toothed pulley also has aflattened portion, formed for example by the omission oftwo teeth, which is used as a zero reference for identifyingthe upper dead centres of the different cylindersof the engine. In particular, the upper dead centre ofeach cylinder of the engine is found, with an indeterminacyof 360°, in a specified angular position with respectto the zero reference. The upper dead centres of thedifferent cylinders are then identified by countingspecified numbers of pulses following the detection ofthe zero reference.

The second sensor consists of a toothed pulleykeyed to the camshaft and a fixed sensor which can supplyat its output a first signal level corresponding to afirst zero reference detected by the first sensor and asecond signal level corresponding to a subsequent detectionof the zero reference. The second sensor is used toeliminate the 360° indeterminacy of the first sensor.

The known systems also have electronic controllerswhich receive the signals generated by the first andsecond sensors and process them to obtain the data on theengine strokes (suction, compression, expansion, exhaust)of the different cylinders.

According to what is described in European Patent Applications N° 576334, it is also knowna method for identifying the strokes of an internal combustion engine that uses only one sensor fordetecting the angular position of the crankshaft, and means for suppressing the fuel supply in onecylinder in order to identify the correct stroke of that cylinder by the detection of the delay afterwhich the missing ignition in that cylinder is detected. Nevertheless, during the detection of thestroke of the cylinders, this method produces a reduction of engine torque that may cause, inparticular conditions, the undesired stop of the engine.

The known angular reference systems entail a considerablecomplexity of construction and high costs.

The processing of the signals generated by thetwo sensors is also complex.

The object of the present invention is to providean electronic system for identifying the strokes of aninternal combustion engine which resolves the problems ofthe known systems. In particular, the object of thepresent invention is to provide an electronic system foridentifying the strokes of an engine which uses only oneangular position sensor.

The above object is achieved by the present invention in that it relates to anelectronic system for identifying the strokes of a four-stroke internal combustion engine;the said engine having an output crankshaft coupled to a sensor of the angular positionof said crankshaft; the said sensor generating a signal having an interval of 360° of thecrankshaft; the said signal having at least one zero reference corresponding to a zeroangular reference of the said crankshaft;

the said electronic system also comprises first detecting means capable ofdetecting the said zero reference, first calculating means capable of arbitrarily assigningthe strokes of the cylinders of the said engine according to said zero reference and atleast one specified angular relationship between the said zero reference and the angularposition in which the upper dead centre of a first cylinder is reached, and torquemonitoring means capable of monitoring the torque generated by said engine;

the said electronic system being caracterized in that said torque monitoring meanscomprises first monitoring means capable of detecting the time evolution of theinstantaneous torque of a first cylinder, second monitoring means capable of detectingthe time evolution of the instantaneous torque of a second cylinder, and comparisonmeans capable of comparing the time evolution of the torques of said first and saidsecond cylinder for determining whether the arbitrarily assignation of the engine stokesmade by said first calculating means is correct; if the said arbitrarily assignation of theengine stokes is wrong, said comparison means being able to select retiming meanscapable of correcting the arbitrarily assignation of the engine stokes made by said firstcalculating means.

The invention will now be illustrated withparticular reference to the attached figures, whichrepresent a non-restrictive preferred embodiment, inwhich:

Figure 1 shows an internal combustion engine providedwith an electronic system for identifying thestrokes, made according to the principles of the presentinvention;

Figure 2 is a logical block diagram of the operationsperformed by the system according to the presentinvention; and

Figure 3 shows the variation with time of a monitoredvalue of the system according to the presentinvention.

Figure 1 shows a four-strokeinternal combustionengine 2 operating in an Otto cycle, provided with aninjection device 4 controlled by anelectronic controller7 operating according. to the electronic system of strokeidentification according to the present invention.

In particular, theelectronic controller 7receives a plurality of signals S1, S2, ... Sn of inputdata collected in the engine 2 (for example, signalsproportional to the engine coolant temperature, to theintake air temperature, to the throttle position, etc.)and generates at the output a plurality of injectiontimes Tj supplied to the injection device 4.

The injection device 4 is provided with fourinjectors 4a, 4b, 4c, 4d operating with corresponding first, second, third andfourth cylinders 9a, 9b, 9c, 9d(shown schematically) of the engine 2 ("Multipoint"system) and can inject the fuel into one cylinder at atime (sequential system) and in the suction stroke (timedsystem).

Theelectronic controller 7 is provided with anengine stroke reference unit 11 permitting recognition ofthe engine stroke (suction, compression, expansion,exhaust) in eachcylinder 9a, 9b, 9c, 9d of theengine 2.

The reference unit 11 receives at its input asignal from asensor 15 coupled to atoothed pulley 17mounted on one end of thecrankshaft 20 of theengine 2.Thesensor 15 can generate an electrical pulse when onetooth of thepulley 17 passes in front of thesensor 15.In particular, thetoothed pulley 17 is keyed to oneend20a of theshaft 20 close to thecylinder 9a. Thecylinder9d is also close to oneend 20b of theshaft 20opposite theend 20a.

Thetoothed pulley 17 is provided with sixtyteeth, with the omission of two, and therefore has aflattened portion formed by the absence of these twoteeth, which is used as the zero reference. The zeroreference is used to identify the upper dead centres ofthe different cylinders of the engine. In particular, theupper dead centre of eachcylinder 4a, 4b, 4c, 4d isfound, with an angular indeterminacy of 360°, in aspecified angular position αa, αb, αc, αd with respect tothe zero reference.

The signal R generated by thesensor 15 consistsof a sequence of pulses Di equally spaced by an intervalt. The signal R also has a flat portion Dz of width T(equal to approximately three times t) in which pulsescannot be detected; this flat portion Dz is producedduring the passage of the flattened portion in front ofthesensor 15.

The upper dead centre of each cylinder is identifiedwith the said indeterminacy of 360° by counting aspecified number of pulses Na, Nb, Nc, Nd after thedetection of the zero reference.

In particular, when the zero reference isdetected it is not possible to identify the timing of thedifferent cylinders 9a, 9b, 9c, 9d in an unambiguous way,since the interval of theengine 2, operating in the Ottocycle, is 720° of the rotation of the crankshaft and theinterval of the signal generated by thesensor 15 is 360°of the rotation of the crankshaft. Consequently it is notpossible to know whether the 360° following the zeroreference coincide with the first 360° of the cycle orwith the final 360° of the engine cycle. It is thereforenot possible to know whether the first specified angularposition αa following the zero reference corresponds tothe upper dead centre of thefirst cylinder 9a or to thatof thefourth cylinder 9d of theengine 2.

The reference unit 11 also interacts with adevice 25, for example the device described in FrenchPatent FR-9111273 with the title "Process and device formeasuring the torque of an internal combustion engine",capable of measuring the instantaneous torque developedindividually by the different cylinders of theengine 2.

The unit 11 generates at its output a signalwhich describes the engine strokes (suction, compression,expansion, exhaust) of eachcylinder 9a, 9b, 9c, 9d oftheengine 2.

With particular reference to Figure 2, the operationsperformed by the unit 11 operating according tothe system of the present invention will now be illustrated.

The first block encountered is theblock 100 inwhich the system detects the signal R generated by thesensor 15.

In particular, in theblock 100 the system isprepared to await the flat portion Dz of the signal R inorder to identify the zero reference of thepulley 17.

Detection of the zero reference results in apassage from theblock 100 to ablock 110.

Theblock 110 arbitrarily assigns the strokes oftheengine 2, assigning, for example, the upper deadcentre of thefirst cylinder 9a to the first specified angular position following the zero reference; theassignation of the positions of the upper dead centres ofthe other cylinders is carried out in a way compatiblewith the first assignation.

In this way, the angular position αa of the upperdead centre of thefirst cylinder 9a is assigned afterthe detection of a specified number (for example, twenty)of pulses Na following the zero reference.

For the reasons stated above, the angular positionfound on the twentieth pulse following the zeroreference may also correspond to the upper dead centre ofthefourth cylinder 9d.

In case of error, the operation of the engine isnot compromised, since the charge in the ignition coil(not illustrated) and the subsequent spark in thefirstcylinder 9a and in thefourth cylinder 9d are ensured;the performance of theengine 2 is, however, seriouslydegraded, since the injection and sparking are incorrectlyadvanced by 360°.

Theblock 110 is followed by ablock 130 whichdetects an error in the assignation of the strokes(mistiming by 360°) and consequently retimes the injection.

In particular, theblock 130 comprises ablock131 in which the instantaneous torque supplied by onecylinder of the engine, for example the cylinder recognizedby theblock 110 as thefirst cylinder 9a, ismonitored by thedevice 25. Thiscylinder 9a is physicallyclose to thepulley 17.

With particular reference to Figure 3, the letterA indicates a curve which represents the variation withtime of the torque supplied by the cylinder recognized asthefirst cylinder 9a; the variation of this torque hasan approximately sinusoidal form.

Theblock 131 is followed by ablock 132 in whichis stored the signal expressing the variation with timeof the torque supplied by the cylinder recognized as thefirst cylinder 9a.

Theblock 132 is followed by ablock 133 in which the instantaneous torque supplied by another cylinder ofthe engine, in particular the cylinder at the greatestdistance along theshaft 20 from thefirst cylinder 9a,is monitored.

Theblock 133 may conveniently measure theinstantaneous torque supplied by the cylinder recognizedby theblock 110 as thefourth cylinder 9d; thefirstcylinder 9a and thefourth cylinder 9d are coupled toopposite portions of theshaft 20. The torque supplied bythefourth cylinder 9d is also displaced by 360° of thecrankshaft from the torque supplied by thefirst cylinder9a.

With particular reference to Figure 3, the letterB indicates a curve representing the variation with timeof the torque supplied by the cylinder recognized as 9d;the variation of this torque is approximately sinusoidal.In Figure 3 the displacement of 360° between the torquesofcylinders 9a and 9d is also eliminated.

Theblock 133 is followed by ablock 134 in whichthe torque measured in theblock 131 is compared with thetorque measured by theblock 133; for this purpose, sincethe torque measured in theblock 133 is displacedangularly and in time from the torque measured in theblock 131, a time correction is made to the torque storedin theblock 132. In particular, the stored torque (curveA) is displaced by 360° in such a way that the torquessupplied by the first andfourth cylinders 9a, 9d can becompared, and these torques can be considered as ifsupplied simultaneously.

The torques supplied by the first andfourthcylinders 9a, 9d, given equal stoichiometric compositionof the fuel mixture, spark advance and engine load,should have substantially equal variations in time, andthe curves A and B should therefore coincide.

This does not happen in practice, owing to thetorsional elasticity of the section of crankshaft betweenthecylinders 9a and 9d. For this reason, the torquesupplied by the cylinder which is physically closest tothetoothed pulley 17 is in advance of the torque supplied by the cylinder which is furthest from thetoothed pulley 17. Therefore, if the assignations made bytheblock 110 are correct, the torque supplied by thecylinder 9a is in advance of the torque supplied by thecylinder 9d.

In order to determine the time relation betweenthe torques of thecylinders 9a, 9d, theblock 134calculates the times t1 and t2 taken by the torquesrepresented by the curves A and B to reach a specifiedthreshold value C_threshold (Figure 3).

Theblock 134 is followed by ablock 135 in whichthe times t1 and t2 are compared with each other; inparticular, if the time t1 is less than t2 (with thetorque generated by the cylinder recognized as thefirstcylinder 9a in advance of the torque generated by thecylinder recognized as thefourth cylinder 9d) theblock135 is followed by ablock 136; otherwise (if the time t1is greater than t2 and therefore the torque generated bythe cylinder recognized as thefirst cylinder 9a lagsbehind the torque generated by the cylinder recognized as9d) theblock 135 is followed by ablock 137.

Theblock 137 retimes by 360° the timing set intheblock 110; consequently, the upper dead centre of thefourth cylinder 9d (whose position is displaced by 360°with respect to that of the first cylinder) is assignedto the first angular position of theshaft 20 followingthe detection of a specified number of pulses (forexample, twenty) from the zero reference.

Theblock 136 maintains the timing determined bytheblock 110.

Theblocks 136 and 137 lead to the exit from theprogram.

The advantages of the present invention will beclear from the above, since the described system detectsthe engine strokes precisely although only one angularposition sensor is used.

Claims (7)

1. Electronic system for identifying the strokes of a four-stroke internalcombustion engine (2); the said engine (2) having an output crankshaft (20) coupled to asensor (15, 17) of the angular position of said crankshaft (20); the said sensor (15, 17)generating a signal (R) having an interval of 360° of the crankshaft (20); the said signal(R) having at least one zero reference (Dz) corresponding to a zero angular reference ofthe said crankshaft (20);

   the said electronic system also comprises first detecting means (100) capable ofdetecting the said zero reference (Dz), first calculating means (110) capable ofarbitrarily assigning the strokes of the cylinders of the said engine (2) according to saidzero reference (Dz) and at least one specified angular relationship between the said zeroreference (Dz) and the angular position in which the upper dead centre of a first cylinderis reached, and torque monitoring means (130) capable of monitoring the torquegenerated by said engine (2);

   the said electronic system being characterized in that said torque monitoring means(130) comprises first monitoring means (131) capable of detecting the time evolution ofthe instantaneous torque of a first cylinder (9a), second monitoring means (133) capableof detecting the time evolution of the instantaneous torque of a second cylinder (9d), andcomparison means (135) capable of comparing the time evolution of the torques of saidfirst (9a) and said second cylinder (9d) for determining whether the arbitrarilyassignation of the engine stokes made by said first calculating means (110) is correct; ifthe said arbitrarily assignation of the engine stokes is wrong, said comparison means(135) being able to select retiming means (137) capable of correcting the arbitrarilyassignation of the engine stokes made by said first calculating means (110).
2. System according to Claim 1, characterized in that the said comparison means(135) are capable of detecting the displacement between the torques supplied by the first(9a) and second cylinder (9d); the said displacement being principally due to thetorsional elasticity of the section of crankshaft (20) lying between the said first (9a) andthe said second cylinder (9d).
3. System according to Claim 2, characterized in that the said comparison means(135) are capable of selecting the said retiming means (137) when the torque generatedby the said first cylinder (9a) lags behind the torque generated by the said secondcylinder (9d).
4. System according to Claim 2 or 3, characterized in that said torque monitoringmeans (130) comprises second calculating means (134) able to determine a firstreferring time (t1) in which the torque supplied by the said first cylinder (9a) reaches athreshold value (C_threshold), and a second referring time (t2) in which the torque suppliedby the said second cylinder (9d) reaches said threshold value (C_threshold); the saidcomparison means (135) being capable of comparing the said first (t1) and secondreferring time (t2) with each other in order to determine the displacement between thetorques supplied by the first (9a) and second cylinder (9d).
5. System according to Claim 4, characterized in that the said comparison means(135) are capable of selecting the said retiming means (137) when the said first time (t1)is greater than the said second time (t2).
6. System according to any of the preceding claims, caracterized that said firstcylinder (9a) is the cylinder of the engine (2) positioned along the crankshaft (20)physically close to said sensor (15, 17) of the angular position of crankshaft (20).
7. System according to any of the preceding claims, characterized that said secondcylinder (9d) is the cylinder of the engine (2) positioned along the crankshaft (20)physically at a maximum distance from said sensor (15, 17) of the angular position ofcrankshaft (20).

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