EP0695865B1 - Method for correcting the dissymmetries of a sensor wheel - Google Patents

Description

The invention relates to a correction method, less partial, of any size, the values of which are linked, directly or indirectly, to the rotation of a internal combustion engine, in particular an engine injection, depending on asymmetries and / or fluctuations of rotation of a target, linked in rotation to this motor, and to using which the values of the quantity considered are defined by measurement and / or calculation.

By size is meant, in the present specification description, any engine operating parameter, or any quantity obtained by measuring at least one such parameter and / or calculation from at least one such parameter of engine operation, which is related to the rotation of the target driven with the rotary engine crew, at except the only scrolling time of at least one angular sector defined on said target.

The invention therefore relates to a method for to compensate, at least in part, for the effects of asymmetries and / or fluctuations in the rotation of a linked target in rotation to an internal combustion engine on the values of a magnitude, related to the rotation of the target, except only the scrolling time of at least one sector defined angularity of this target, these asymmetries and / or fluctuations in target rotation resulting from asymmetries and / or manufacturing irregularities and / or centering of all components of the assembly or rotary assembly comprising the target linked in rotation to the combustion engine internal.

The quantity corrected by the method according to the invention is therefore any quantity that can be represented by at minus a signal based on information from at least one position and / or rotation detector of a rotary target, linked in rotation to the crankshaft, to a flywheel engine or a combustion engine output shaft internal, with the exception of the scrolling time of at least one defined angular sector of the target opposite a sensor.

We know that certain operating parameters an internal combustion engine, in particular an engine injection, the values of which are obtained by measurement and / or calculation from an angular position signal of the shaft the engine provided by a sensor of a well known type, comprising a target presenting singularities (teeth or holes) integral in rotation with the crankshaft or the flywheel motor, are used as quantities taken into consideration to determine operating states of the engine.

As an example, it is known to use the engine operating parameter called gas torque, i.e. the torque produced by the combustion of the mixture fuel in a combustion chamber, during the phase combustion-expansion of the corresponding cylinder of the engine, during an engine cycle, as a quantity taken into account to detect the presence of engine misfires spark ignition, also called spark ignition engine sparks, in particular for a motor vehicle of which the engine is, on the one hand, associated with an exhaust pipe catalytic, and, on the other hand, equipped with an installation injection fuel supply, preferably type called "multipoint", and such as injection, and preferably also, the ignition of the engine are controlled by a electronic command and control system, called engine control.

For this type of engine, it is also known, for example by FR 2 681 425, to calculate the gas torque at from a speed or speed signal from the motor, provided by an angular position sensor of the crankshaft or flywheel.

However, when the angular position signal of the motor shaft is obtained using a known sensor, of the aforementioned type, comprising a rotating integral target crankshaft or flywheel, signal development representative of the quantity considered, namely the couple calculated gas, is disturbed by the machining tolerances and centering of the rotary target, and more generally of the rotating assembly comprising the target and the motor at which the target is linked in rotation, and the invention aims to propose a method to at least partially compensate for fluctuations of this quantity, resulting from the fluctuations themselves resulting from these tolerances.

Furthermore, document EP 583 496 describes a method for detecting misfire of a injection, in which we measure, during the injection phase of fuel, then in the injection cut-off phase, the times scrolling of angular sectors defined on the target linked in rotation to the crankshaft as corresponding to combustion-expansion phases of the different cylinders of the motor, and then compare the times measured with each other and to thresholds, in order to detect the occurrence of misfires of combustion.

But the lessons of EP 583 496 do not allow not, in general, to correct the values of any quantity linked, directly or indirectly, to the rotation of an internal combustion engine, consequences resulting from asymmetries and / or fluctuations in rotation of a target linked in rotation to this engine, and whose position and / or speed of rotation is taken into account for measure and / or calculate the values of this quantity, as this is precisely the aim of the invention.

GB-A-2 249 839 also discloses a process detection of engine misfire, according to which we consider to be a misfire if the difference between torques measured during the combustion phase and in the non-combustion phase exceeds a certain threshold, and this for each cylinder, regardless of the conditions of combustion or non-combustion in other cylinders. To this end, we define a torque value for each of the angular sectors of the corresponding target respectively to a combustion phase of each cylinder of the engine, on at least one engine cycle and in the engine ignition and / or power failure fuel to have no combustion, at least one given engine speed higher than a speed close to idling.

To take into account disturbances that may arise internal friction in the engine, various corrections are performed, which is not to correct measured couples, but to take into account a difference between an average of two torque measurements and a third torque measurement performed outside combustion, cylinder by cylinder, to modify at least one detection threshold for misfires.

The object of the invention is on the contrary to correct values of any magnitude, except the time of scrolling of at least one angular sector, and such by example that the engine torque, which is related to the rotation of the engine, depending on asymmetries and / or fluctuations of rotation of the target linked in rotation to the motor.

To this end, the method according to the invention, for the correction of a quantity, linked to the rotation of a motor internal combustion, in particular of an injection engine, depending on asymmetries and / or fluctuations in rotation of a target linked in rotation to the engine and using which are defined, by calculation and / or measurement, values size, with the exception of the scrolling time of minus an angular sector defined on the target, and which includes the steps of setting a value for the magnitude for each of the angular sectors of the target corresponding respectively to a combustion-expansion phase of each engine cylinder, and on at least one engine cycle, in ignition and / or power cut-off phase engine fuel, at least one engine speed given above a speed close to idling, is characterized in that it further comprises the steps of calculate the average of the values obtained for all angular sectors, to define for each sector a term compensation equal to the product of the difference between the average of the values and the value of the quantity for this sector by a proportionality coefficient, preferably less than or equal to 1, and to add, for each sector, the compensation term corresponding to the values of the defined quantity, in the ignition and supply phase in fuel, for this sector over at least a range of engine speed, containing the speeds for which the ignition and / or fuel supply cut off applied.

In the case of an engine with four cylinders and four time, and in a simple way, the process comprises the steps consisting in defining a value of the quantity for each at least two successive engine U-turns, in the ignition and / or fuel supply cut-off audit given engine speed, to calculate half the variation of value of the quantity resulting from a motor half-turn to the other, to define the term compensation as equal to the product of half the change in value by the proportionality coefficient, and to add the term of compensation for the values of the quantity obtained in phase ignition and fuel supply for U-turns motor providing the value of the most variable low during ignition and / or power cut-off or respectively to subtract the term of compensation of values of the quantity obtained during the ignition phase and fuel supply for engine U-turns providing the value of the largest quantity in the phase of ignition and / or fuel supply cut out said engine speed range.

The method of the invention thus proposes a step to compensate for the differences in the quantities which are attributable to manufacturing tolerances and centering the target of the position detector of the crankshaft, as well as components of the rotating assembly of the engine as mentioned above.

For an injection engine, it is clear that the power supply and power off phases engine fuel correspond respectively to the phases injection and fuel injection shutdown. But the invention also applies to configurations in which the supply and cut-off phases in fuel correspond to phases respectively ignition and ignition cut-off.

Advantageously, moreover, the coefficient of proportionality chosen to calculate the compensation term depends on the load and / or the engine speed, and can be drawn from a table with one or two entries, in function of this or these operating parameters of the engine.

A better correction is also ensured, if the method further consists, for each angular sector of the target or each of the engine U-turns, to define the term compensation and / or the corresponding value of the magnitude, or the difference between the mean of the values for the different sectors and the value for the sector considered, or the variation of values of the quantity between two consecutive U-turns, in several areas of successive regimes, preferably with a step noticeably constant, between the neighboring idle speed and a speed maximum engine operation.

Likewise, and always with the aim of improving the quality of the correction ensured, the process consists of addition, for each angular sector of the target or each engine U-turn, to define the corresponding value of the magnitude, or the difference between the mean of the values and the value of the angular sector considered, or the variation in value of the quantity between two U-turns consecutive engine, as itself being an average values, differences or variations respectively of values of the quantity over a given number of cycles consecutive engines.

In order to facilitate its implementation, the method can also consist in memorizing the difference between the average of the values and the value of the quantity for the sector considered or to memorize the variation of the value the size between two consecutive engine U-turns, in a table at an entry according to the regime, for each angular sector.

Other advantages and characteristics of the invention follow from the description given below, as nonlimiting, of an exemplary embodiment with reference to the single attached figure, which schematically represents a device for implementing the method of the invention, for correct a quantity such as the gas torque vis-à-vis fluctuations in rotation of a driven tachometer target rotating with a four-cylinder injection engine and four-stroke.

In the single figure, 1 shows a angular position sensor of the engine crankshaft, of a well-known type, already fitted to most vehicles automobiles, associated with an electronic control circuit motor and comprising a tachometric target, produced under the shape of a wheel 2 with singularities, toothed in this example, integral in rotation with the flywheel or engine crankshaft, as well as a sensor 3 fixed on the motor, the detector 1 being of the variable reluctance type, in which the sensor 3 is sensitive to the passage opposite teeth of wheel 2 and delivers an electrical signal pulsating variable frequency proportional to the regime N of the motor, this signal being shaped in a circuit 4 delivering the engine position signal to the rest of the device. In particular, the position signal is delivered to the engine control unit 5, controlling the injection and engine ignition. In parallel, the position signal is sent to a stage 6 for calculating the gas torque Cg produced by each combustion-expansion phase in each cylinder of the engine, for all its cycles. Floor 6, called gas torque software sensor, so is a calculator which calculates the gas torque from the signal position. The engine being of the kind comprising marks of measures, such as the teeth of wheel 2, arranged on a wheel or crown integral with the flywheel or crankshaft, means, such as width teeth wheel 2, to define a reference for indexing the markers, and a sensor 3 for scrolling the marks, fixedly mounted in the vicinity of the wheel or crown 2, the signal processing circuit contained in stage 6 implements a production process of representative value of the gas torque Cg generated by each combustion of the gas mixture in combustion engine cylinders internal, this process being such as that, for example, described in patent FR 2 681 425, incorporated herein description by reference, and to which reference will be made for more details.

The device implementing the method of the invention also includes means for calculating and memory allowing him to ensure compensation by learning of the symmetry defects of the tachometric target 2 of the engine position sensor 1. Indeed, the gas torque Cg is calculated at each combustion-expansion phase on a corresponding engine U-turn, in this example of a four-cylinder, four-stroke engine, i.e. to half or to the other half of the periphery of the wheel 2 from a singularity identifying the passage to top dead center of a reference cylinder. Now the tolerances for manufacturing and centering wheel 2 (dispersions dimensional due to the machining of the teeth, offset on flywheel or crankshaft and dimensional dispersions and / or offset of the rotating parts of the motor) have as a consequence, even for two combustion-expansion phases strictly identical successive, the measurements resulting speed are not identical and fluctuate for two cylinders compared to those obtained for two other cylinders. The principle of learning work consists in appreciating the asymmetry of the target rotary 2 in injection cut-off phase, controlled by the engine control unit 5.

Stage 6, which receives the cut-off information ignition or injection of unit 5, calculates, in phase of ignition or injection cut-off, the gas torque Cg and transmits these values to stage 7 of identification of asymmetries of the target 2 as a function of the engine speed N, whose signal is received by stage 7 of the control unit motor 5. To ensure compensation calibration, stage 7 calculates the average value of the gas torque Cg in ignition or injection cut-off phase for each of the target U-turns 2, for example 50 engine U-turns in a diet area and then the variation of the average gas torque from one half-target 2 to the other, corresponding to the difference between the two values averages of Cg and then calculating half of that difference, and its memorization in a table 8 to a input, depending on engine speed N, over the entire range engine speed, between a speed close to idle (for example of 1200 rpm) and the maximum speed, with zones speed following steps of 200 rpm or 500 rpm per example. Compensating for symmetry defects of the target 2 can be ensured, in the injection and ignition phase and for a given speed N, by adding, in the adder stage 10, receiving the Cg values during the injection phase and of ignition of stage 6, the half-deviation of gas torque memorized in stage 8 for the regime zone containing N to the Cg measurements obtained in stage 6 with half of target 2 giving the value (average) of the highest gas torque low in injection or ignition cut-off, and by subtracting the half-torque deviation memorized at Cg measurements obtained with half of target 2 giving the value (average) of the greatest gas torque in injection cut-off or ignition. Alternatively, as shown in the single figure, the half-deviation of gas torque memorized in stage 8 is weighted, in multiplier stage 9 receiving the engine speed signal N from unit 5 and also an engine load signal (not represented), by a coefficient K which is a function of the load and / or engine speed N, and taken from a table corresponding to one or two entry (s) stored in this stage 9. The compensation therefore consists in applying in phase injection and ignition in stage 10 a correction proportional to the half-disconnection of the gas cut-off injection or ignition, and defined by a term of compensation equal to the product of this half-deviation memorized by a proportionality coefficient K, taken from stage 9, and which can be equal to 1 or depends on the load and / or the engine speed N.

This compensation by addition or subtraction a correction proportional to the half-deviation of gas torque between the two halves of the rotating target 2 in phase of injection or ignition shutdown is simple application to four-cylinder and four-stroke engines of the most general compensation. The latter consists for a z-cylinder engine, to be calculated during the shutdown phase ignition and / or injection, the value (average over by example 100 consecutive engine cycles) of Cg on each angular combustion-expansion sector of a cylinder, value 2 engine revs / z, , if the engine is at four-stroke, or 1 engine revolution / z if the engine is two time, calculating the average of the values (means) of Cg on all sectors, then calculate, for each sector, the difference between this mean and the (mean) value of Cg for this sector, possibly to weight this difference by a coefficient K depending on the load and / or the engine speed, and then to compensate, at least partially, the calculated value of Cg during the injection phase and for each sector by adding this possibly weighted difference. The most compensation general therefore consists in applying, for each sector, to Cg values obtained during injection and ignition phase for this sector, a compensation or correction term additive proportional to the difference between the mean of couples Cg, calculated for all sectors in phase of injection and / or ignition cut-off, and the torque Cg calculated for the sector considered also in cutoff injection and / or ignition.

Stage 10 thus delivers on its output, for each combustion-expansion phase in each engine cylinder, a signal representative of the value of the gas torque Cg produced in the corresponding cylinder by combustion corresponding, and corrected for the asymmetry of target 2.

Claims (9)

1. A method for the correction, at least partially, of a quantity (Cg) linked to the rotation of an internal combustion engine, in particular an injection engine, as a function of the dissymmetries and/or fluctuations in the rotation of a target (2) linked in rotation to the engine and with the help of which are defined, through measurement and/or calculation, values of the quantity (Cg), with the exception of the time for at least one angular sector defined on the said target to pass, comprising the stages consisting of defining a value of the quantity (Cg) for each of the angular sectors of the target (2) corresponding respectively to a combustion-expansion phase of each cylinder of the engine, and on at least one engine cycle, in a phase of cut-off of ignition and/or fuel supply at at least one given engine speed greater than an engine speed close to idling speed, characterised in that it comprises furthermore the stages consisting of calculating the mean of the values obtained for all the angular sectors, in defining for each sector a compensation term equal to the multiplication of the difference between the mean of the values and the value of the quantity for that sector by a coefficient of proportionality (K), preferably less or equal to 1, and in adding, for each sector, the compensation term corresponding to values of the quantity defined in the ignition and fuel supply phase for that sector in at least one range of engine speed, that includes speeds for which the cut off of ignition and/or fuel supply has been applied.
2. Method according to claim 1, for a four cylinder four stroke engine, characterised in that it comprises the stages consisting of defining a value of the quantity (Cg) for each of at least two successive half revolutions of the engine, in a phase of cut off of ignition and/or fuel supply at the said given engine speed, in calculating half of the resulting variation in the value of the quantity from one half engine revolution to another, in defining the compensation term as being equal to the product of half the variation in the value and the coefficient of proportionality (K), and adding the compensation term to the values of the quantity (Cg) obtained in the ignition and fuel supply phase for the half engine revolutions producing the smallest value of the quantity in the cut off of ignition and/or fuel supply phase or respectively in subtracting the compensation term from the values of the quantity (Cg) obtained in the ignition and fuel supply phase for the half engine revolutions producing the greatest value of the quantity (Cg) in the cut off of ignition and/or fuel supply phase, in the said range of engine speed.
3. Method according to one of the claims 1 and 2, characterised in that it consists furthermore in choosing a coefficient of proportionality (K) that is a function of the load of the engine.
4. Method according to one of the claims 1 to 3, characterised in that it consists furthermore in choosing a coefficient of proportionality (K) that is a function of the engine speed (N).
5. Method according to any of the claims 1 to 4, for an injection engine, characterised in that the phases of fuel supply and fuel supply cut off correspond to phases of fuel injection and cut off of fuel injection respectively.
6. Method according to any of the claims 1 to 4, characterised in that the phases of supply and supply cut off correspond respectively to phases of ignition and ignition cut off respectively.
7. Method according to any of the claims 1 to 6, characterised in that it comprises also the stage consisting, for each angular sector of the target (2), or engine half revolution, of defining the said compensation term and/or the said value, or difference, or variation in values of the quantity (Cg) over several successive zones of engine speed (N), preferably at an approximately constant rate, between the said engine speed close to idling speed and a maximum engine operating speed.
8. Method according to any of the claims 1 to 7, characterised in that it comprises the stage consisting, for each angular sector of the target (2) or every half engine revolution, of defining the said value or difference or variation of values of the quantity (Cg) as being itself a mean of values, or of differences, or of variations of values of the quantity (Cg) over a given number of consecutive engine cycles.
9. Method according to any of the claims 1 to 8, characterised in that it comprises furthermore the stage consisting of storing the said difference or variation of the values of the quantity (Cg) in a table with one entry as a function of the engine speed (N), for each angular sector.

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