EP1705355B1 - Method for determining operating parameters of an injection system - Google Patents

Abstract

The method involves calculating an average speed of an injector in the order of injection cycles of an engine cycle. An injection control signal including a test pulse with an adjustable parameter is applied to the injector to be tested. An average speed of the injector to be tested is calculated. A difference between the average speeds is calculated. The above steps are repeated for another engine cycle by varying the parameter. A value of the parameter is determined for which the average speed difference exceeds a preset threshold and the value is stored. The average speeds of the injector and the injector to be tested are equal to the speed of an internal combustion engine realized on measurement periods recovering injection cycles associated to the injector and the injector to be tested respectively.

Description

The subject of the present invention is a process for determining operating parameters, also called a learning method, of an injection device for a combustion engine.

An injection device conventionally comprises a plurality of injectors, each of the injectors being controlled in opening and closing by an electronic control means, by means of control signals making it possible to control one or more pilot injections and a main injection on each of the injectors. injectors. The injectors used may be of several types, for example of the solenoid type or of the piezoelectric type.

The document EP 0 740 068 describes a solenoid injector. The injector comprises an injector body. At its lower end, the injector body defines a seat in which the lower end of a needle is able to engage, the needle being able to slide between an open position in which it allows the ejection fuel nozzle of the injector and a closed position in which it closes the injector tightly. The injector body is supplied with fuel by a fuel source under high pressure, such as a common rail, through a feed passage opening into an annular gallery. The annular gallery surrounds the needle, near its upper end, the shape of the needle being adapted to allow the flow of fuel from the annular gallery between the bore and the needle. The high-pressure supply line also communicates with a control chamber via a "restrictor". At its upper end, the control chamber is closed by a plate. The plate cooperates with a sliding valve member having a hollow shaft, the interior of the hollow shaft being adapted to communicate with the interior of the chamber when the valve member is disengaged from the plate. The interior of the hollow stem also communicates with a low pressure return. An electronic control means makes it possible to control, by means of control signals, a solenoid actuator. When the solenoid is energized, the valve member disengages from the plate. At this time, fuel from the control chamber can escape to inside the hollow stem and then in the low pressure return. When the pressure inside the control chamber decreases to a certain extent, the force applied to the needle due to the pressure inside the control chamber is no longer sufficient to hold the needle in its closed position. At this moment, the needle takes its open position and fuel is ejected from the injector. When the solenoid is no longer powered, the valve member re-engages in the plate under the action of a spring. This has the effect of blocking the communication between the inside of the hollow rod and the control chamber. At this moment, the pressure in the control chamber increases and pushes the needle towards its closed position.

The document EP 0 937 891 describes a piezoelectric injector. The injector includes a piston, which defines a control chamber in combination with the upper surface of the needle. The injector comprises piezoelectric actuators. The actuators are electrically connected to a control circuit capable of transmitting control signals. The pressurized fuel present in the control chamber exerts a force on the upper part of the needle and keeps it in the closed position, in combination with a spring. To begin the injection, the piezoelectric material is discharged, in order to reduce its size. This causes the piston to move in the opposite direction to the needle and thus to decrease the pressure inside the control chamber. At this moment, the needle is in its open position. When charging the piezoelectric material, this has the effect of pushing the piston down. This movement increases the fuel pressure inside the control chamber thus increasing the force applied to the upper surface of the needle which has the effect of pushing it towards its closed position.

Even if the injectors used in the injection device are of the same type, each injector has specific parameters. In addition, mechanical wear can also affect the accuracy of the amount of fuel injected. Learning processes must therefore be performed to adapt the control signals to the specific characteristics of each of the injectors, in order to balance the maximum engine operation, optimize combustion noise and control gaseous emissions. These methods make it possible in particular to determine for each injector the minimum control time (MDP) causing the opening of the injector.

A first solution is to use an accelerometer. However, this solution is sensitive to vibrations, and this poses problems of precision, especially with piezoelectric injectors.

A second solution is to use a speed sensor to continuously determine the speed of the crankshaft.

The document FR 2,720,787 describes a method for determining the specific parameters of each of the injectors of an injection device of a combustion engine, in particular a device with pilot injection and main injection. For this, the curve of the instantaneous speed difference of the motor shaft is established between the moment of passage to the top dead center of combustion of the cylinder in question and a predetermined subsequent time, for example offset by 60 °, preceding the changeover to top dead point of combustion of the next cylinder, depending on the duration of the pilot injection, the other operating parameters being kept constant. This curve has a minimum level. The slope breaking point of this curve makes it possible to determine the opening time of the injector from which said injector starts to flow. This method is intended to be implemented for example during the end of assembly line check for the development of the engine or to perform tests in the event of malfunction of the engine as part of the after-sales service.

The method described in this document is not feasible when the engine is outside the idle zone, that is to say when the injectors are controlled by control signals corresponding to a request from a control member gases. This process, which was designed for idle operation of the engine, exploits an instantaneous speed difference that is very sensitive to the shape of the instantaneous engine speed curve at each injection cycle. The present inventors have found that this form loses its regularity at high operating speed, so that the difference considered depended as much on the rotational speed of the engine as on the quantity injected. As a result, it was impossible to exploit this process quantitatively out of the idle mode. In addition, the instantaneous speed difference that is used in this process is very dependent on the speed of the engine, and this results in a large margin of error if the engine speed is not constant over the entire duration of the engine. learning. A similar process is described in the document EP 1 350 941 .

The present invention aims to provide a method for determining the operating parameters of an injection device of a combustion engine which avoids at least some of the aforementioned drawbacks and which is more precise. Another object of the invention is to provide a learning method that can be operated at different speeds of the engine and / or at different injector supply pressures to determine the relevant parameters over an extended operating range.

1. a) sélectionner un injecteur à tester parmi lesdits injecteurs ;
2. b) calculer une vitesse moyenne associée à un injecteur précédent disposé avant ledit injecteur à tester dans l'ordre desdits cycles d'injection, qui est égale à la vitesse dudit moteur moyennée sur une durée de mesure recouvrant essentiellement un cycle d'injection associé audit injecteur précédent ;
3. c) pour ledit cycle d'injection associé audit injecteur à tester, appliquer audit injecteur à tester un signal de commande d'injection incluant au moins une impulsion de test ayant un paramètre réglable ;
4. d) calculer une vitesse moyenne associée audit injecteur à tester, qui est égale à la vitesse dudit moteur moyennée sur une durée de mesure recouvrant essentiellement ledit cycle d'injection associé audit injecteur à tester ;
5. e) calculer une différence entre la vitesse moyenne calculée à l'étape d) et ladite vitesse moyenne calculée à l'étape b)
6. f) répéter les étapes b) à d) pour au moins un autre cycle moteur en faisant varier à chaque fois ledit paramètre de l'impulsion de test ;
7. g) déterminer une valeur dudit paramètre de l'impulsion de test pour laquelle ladite différence de vitesse moyenne franchit un seuil prédéterminé et mémoriser ladite valeur de paramètre.

For this purpose, the invention relates to a method for determining the operating parameters of an injection device of a combustion engine, said injection device comprising a plurality of fuel injectors, and a means of electronic control adapted to control said injectors by means of injection control signals, said electronic control means being connected to a sensor for continuously measuring a speed of said combustion engine, said engine operating according to a motor cycle including at least one injection cycle associated with each of said injectors, said injection cycles succeeding one another in a predetermined order, characterized in that it comprises the steps of:

1. a) selecting an injector to be tested from among said injectors;
2. b) calculating an average speed associated with a previous injector disposed before said injector to be tested in the order of said injection cycles, which is equal to the speed of said engine averaged over a measurement period essentially covering an injection cycle associated with said previous injector;
3. c) for said injection cycle associated with said injector to be tested, applying to said injector to be tested an injection control signal including at least one test pulse having an adjustable parameter;
4. d) calculating an average speed associated with said injector to be tested, which is equal to the speed of said engine averaged over a period of measurement essentially covering said injection cycle associated with said injector to be tested;
5. e) calculating a difference between the average speed calculated in step d) and the average speed calculated in step b)
6. f) repeating steps b) to d) for at least one other motor cycle by varying each time said parameter of the test pulse;
7. g) determining a value of said parameter of the test pulse for which said average speed difference crosses a predetermined threshold and storing said parameter value.

According to one embodiment of the invention, said injectors are direct actuated. These injectors make it possible to obtain a more precise result due to the absence of hydraulic interaction.

Advantageously, in step c), said control signal comprises several test pulses, the value of said parameter being the same for each of said test pulse.

According to one characteristic of the invention, said parameter is a pulse duration.

According to a particular embodiment, while said method is carried out, said injector injection control signals other than said injector to be tested are zero. This corresponds for example to an execution of the method when the accelerator pedal is raised.

According to another embodiment, while the method is performed, said electronic control means provides said injectors with injection control signals including a main pulse corresponding to a request from a gas control member. This corresponds for example to a process execution when the accelerator pedal is depressed.

Advantageously, before step g), a filtered average velocity difference is calculated by applying a convolution by a filter to the curve representing the average velocity difference as a function of said parameter of the test pulse and in step g) , said filtered average speed difference is used. Preferably, said filter is a sliding average.

According to a feature of the invention, said method comprises a first step of experiencing a stability condition predetermined to detect a stable operation of said engine, and a step of terminating said method when said stability condition is not satisfied. Verification of the stability condition is not essential for the realization of the learning process, but it makes it possible to simplify data processing. The stability condition is composed of one or more elementary conditions, which can be cumulative or alternative. In particular, it can be provided that the stability condition is verified when several of the elementary conditions are satisfied. The elementary conditions can be tested simultaneously or successively. A nonlimiting list of elementary conditions which can make it possible to detect a so-called stable zone is given below.

Advantageously, said stability condition includes a motor speed condition, which condition is verified when said motor speed is between two predetermined thresholds (minimum and maximum).

Advantageously, said stability condition includes a torque condition of the engine, which condition is verified when the engine torque is between two predetermined thresholds (minimum and maximum).

Advantageously, said stability condition includes a speed ratio condition, which condition is satisfied when said speed ratio is greater than a predetermined threshold.

Advantageously, said stability condition includes a vehicle speed condition, which condition is verified when said vehicle speed is greater than a predetermined threshold.

Advantageously, said stability condition includes a clutch condition, which condition is verified when the clutch is activated.

According to one characteristic of the invention, said method comprises, at each motor cycle, a step of calculating a difference between said average speed calculated in step b) for said engine cycle and the average speed calculated in step b) for a preceding motor cycle, a step of calculating a corrected mean speed difference by correcting said average speed difference calculated in step e).

According to a characteristic of the invention, the speed of the combustion engine corresponds to the speed of rotation of a crankshaft of said combustion engine, said measurement time associated with an injector extending each time between a delayed initial instant of an offset angle α of the crankshaft relative to the top dead center of a piston corresponding to said injector and a delayed final instant of said offset angle α relative to the top dead center of the piston corresponding to the next injector in the order said injection cycles. Advantageously, the offset angle α is less than or equal to 45 °.

Preferably, said injection device comprises a common rail provided with a high pressure valve, each of said injectors being connected to said common rail. The presence of a high pressure valve on the common rail is preferable but not necessary.

According to one characteristic of the invention, said method comprises a step of selecting a common ramp pressure in a range ranging for example from 200 to 2000 bar and performing said method by maintaining this common rail pressure in said common rail.

Advantageously, said method comprises the steps of detecting an actuation of a gas control member of said vehicle corresponding to a fuel demand, calculating a common ramp target pressure adapted to said fuel demand, and, when the target pressure is less than said selected common rail pressure, lowering the pressure in said common rail by opening said high pressure valve.

Preferably, said method comprises the steps of detecting an actuation of a gas control member of said vehicle corresponding to a fuel demand, calculating a common ramp target pressure adapted to said fuel demand, and, when the target pressure is less than said selected common rail pressure, providing said injectors with injection control signals including at least one pre-injection pulse and one main pulse.

The invention will be better understood, and other purposes, details, features and advantages thereof will become more clearly apparent in the art. course of the detailed explanatory description which follows, several embodiments of the invention given by way of purely illustrative and non-limiting example, with reference to the accompanying schematic drawings.

• la figure 1 est une vue schématique montrant un système d'alimentation en carburant comportant le dispositif d'injection selon un mode de réalisation de l'invention ;
• la figure 2 est une courbe montrant l'évolution de la vitesse instantanée du moteur en fonction du temps pendant un cycle moteur ;
• la figure 3 est une vue schématique montrant des courbes de signaux de commande et la réponse d'un injecteur à ces signaux ;
• la figure 4 est un schéma fonctionnel représentant les étapes du procédé d'apprentissage, selon un premier mode de réalisation de l'invention ;
• la figure 5 est un schéma fonctionnel représentant les étapes de détermination d'une zone stable ;
• la figure 6 est un graphique représentant une série de courbes montrant l'évolution de la vitesse moyenne du moteur à chaque fois sur les cycles d'injection d'un injecteur particulier, en fonction du temps ;
• la figure 7 est un graphique représentant une courbe montrant l'évolution de la différence entre deux courbes de la figure 6 ;
• la figure 8 est un graphique similaire à la figure 7 montrant les résultats du procédé d'apprentissage selon un deuxième mode de réalisation de l'invention ;
• la figure 9 est une courbe montrant la quantité de carburant injectée lors d'une injection principale en fonction de la durée de séparation entre l'injection principale et une injection pilote, pour un injecteur piézoélectrique et un injecteur à solénoïde ;
• la figure 10 est un graphique montrant l'évolution de la différence de vitesse moyenne du moteur sur des cycles d'injection associés à deux injecteurs pour des injecteurs à solénoïde, en fonction du temps ; et
• la figure 11 est un schéma fonctionnel représentant les étapes du procédé d'apprentissage, selon le deuxième mode de réalisation de l'invention.

On these drawings:

• the figure 1 is a schematic view showing a fuel supply system comprising the injection device according to one embodiment of the invention;
• the figure 2 is a curve showing the evolution of the instantaneous motor speed as a function of time during a motor cycle;
• the figure 3 is a schematic view showing control signal curves and the response of an injector to these signals;
• the figure 4 is a block diagram showing the steps of the learning method, according to a first embodiment of the invention;
• the figure 5 is a block diagram showing the steps of determining a stable area;
• the figure 6 is a graph representing a series of curves showing the evolution of the average engine speed each time on the injection cycles of a particular injector, as a function of time;
• the figure 7 is a graph representing a curve showing the evolution of the difference between two curves of the figure 6 ;
• the figure 8 is a graph similar to the figure 7 showing the results of the learning method according to a second embodiment of the invention;
• the figure 9 is a curve showing the amount of fuel injected during a main injection as a function of the separation time between the main injection and a pilot injection, for a piezoelectric injector and a solenoid injector;
• the figure 10 is a graph showing the evolution of the average engine speed difference over injection cycles associated with two injectors for solenoid injectors, as a function of time; and
• the figure 11 is a block diagram showing the steps of the learning method according to the second embodiment of the invention.

Referring to the figure 1 , we see a fuel supply system 1 for an internal combustion engine. The feed system 1 is disposed in a vehicle (not shown) and cooperates with a motor (not shown), the injectors 7 injecting fuel into cylinders (not shown) of the engine, for example diesel. The supply system 1 comprises a low-pressure pump 2, also known as a booster pump, whose output pressure is for example approximately equal to 6 bars. The pump 2 is arranged so as to take fuel from a fuel tank 3 and supply fuel to an inlet of a high pressure pump 4 via a filter 5. The output pressure of the pump 4 is adjustable in a range of the order of 200-1800 bars or more. The high pressure pump 4 is arranged to charge a common rail 6 with high pressure fuel. Injectors 7 are connected to the common rail 6, each of the injectors 7 being controlled in opening and closing by an electronic control unit 8, commonly called engine control unit, by means of control signals. The control unit 8 also controls the high pressure pump 4 by controlling a filling actuator 9, and the fuel pressure inside the common rail 6 by means of a high pressure valve 10. pressure 11 makes it possible to measure the pressure inside the common rail 6 and to communicate it to the control unit 8. The control unit 8 receives signals concerning engine parameters, such as the speed of the vehicle or the position of the acceleration pedal, by appropriate sensors 12. Among the sensors 12, a crankshaft sensor makes it possible to measure, for example magnetically, the speed of rotation of a crankshaft of the engine. The rotational speed of the crankshaft will subsequently be considered as engine speed. The sensor assembly also includes a top dead center detection (PMH) sensor, which synchronizes the injection with the movement of the pistons, and a sensor for detecting the position of the accelerator pedal.

The figure 2 shows the evolution of the instantaneous speed of the motor ω, axis 26, as a function of time t, axis 27, on a motor cycle of a six-cylinder engine. The origin of the axis 26 does not correspond to 0. For a four-stroke engine, a motor cycle corresponds to a crankshaft rotation of 720 °. Each injector 7 is associated with a cylinder comprising a piston (not shown). During an engine cycle, the engine injectors are activated successively in a predetermined order, which corresponds to the order in which the pistons reach their respective top dead centers, so as to produce a balanced drive of the crankshaft. For example, for a four-cylinder engine, the activation sequence is generally: first cylinder, third cylinder, fourth cylinder, second cylinder. The arc speed curve is traditional and comes from the fact that each piston tends to slow down by compressing the gases in the cylinder arriving at its top dead center and re-accelerate under the thrust of the gas leaving its top dead center. So, on the figure 2 , the engine cycle has six arches corresponding to six injection cycles 20, 21, 22, 23, 24 and 25, each cycle 20 to 25 being associated with an injector 7. In the following, these reference numbers designate either the arch itself, the corresponding time interval. Each injection cycle 20 to 25 is between the top dead centers (TDCs) of two pistons. In the following, the order of the injectors 7 refers to the order of the injection cycles 20 to 25 associated, which can be distinct from the geometric order of the engine cylinders. For example, a first injector 7 will be considered as preceding a second injector 7 if the injection cycle associated with the first injector is performed before the injection cycle associated with the second injector, for a given engine cycle.

In normal operation, the engine computer 8 receives the control signal from the accelerator pedal and calculates fuel flow rates to be injected into each cylinder according to this signal (algorithm known per se). The computer 8 produces control signals of the injectors for injecting the calculated flows, each time in the form of one or more pulses, for example a pilot pulse and a main pulse. These flow rates correspond to the amount of fuel required for engine operation. The calculator 8 calculates and regulates the common ramp pressure as a function of the fuel demand (algorithm known per se). The calculated pressure is called the common ramp target pressure. For example, at 4500 rpm, the pressure inside the ramp 6 is approximately equal to 1800 bar. The calculator 8 also controls the idle, which corresponds to a predetermined minimum speed that the computer 8 maintains when no signal is transmitted by the accelerator pedal. These features obtained by programming the engine computer 8 are conventional and will not be described in detail.

The computer 8 contains a learning program whose execution controls the progress of a process which will now be described.

Realization of the process

Referring to Figures 2 to 4 the course of the training method will now be described to determine the value of a parameter of the control signal associated with an injector 7. This process is carried out while the engine is running. The parameter that one wishes to determine is, in this case, a minimum duration of a control signal pulse (MDP) which causes an effective opening of an injector 7.

In step 96 the process is initialized. This type of learning is intended to be performed during the use of the vehicle, for example the initialization takes place every fifteen minutes or hour. By performing this process regularly, it is possible to perform statistical processing of the values of minimum durations obtained at each execution, which makes it possible to obtain more precise values.

At step 97 the ramp pressure is set.

In step 98 the injector under test, that is to say the injector for which it is desired to determine the minimum control duration, is selected. On the figure 2 , which will serve to describe an example of the course of the process, it is the injector associated with the injection cycle 22.

In step 99 an initial control duration D0 is set. The initial control duration D0 corresponds to the duration of a test pulse that will be sent to the injector selected to perform the injection cycle 22, for example in the vicinity of the top dead center 33 of the engine cycle, in progress during the first pass through the loop 43 of the process. A control duration D is then incremented at each passage in the loop 43, a test pulse of a duration equal to the current control time in the loop 43 being sent to the selected injector to perform the injection cycle 22 , for example at the vicinity of the PMH 33, at each engine cycle during the process. The expression each motor cycle designates the cycles during which the loop 43 is executed. Two successive passages in the loop 43 may be optionally spaced from one another.

We will now describe steps 100 to 106, during a passage in the loop 43. The number of passages in the loop 43 is indexed by an index in the following description. For the illustration, reference is made below to three successive passages of rank n-1, n, n + 1.

In step 100 a stability condition, which will be described in detail later with reference to the figure 5 , is proven. In the first embodiment described below, this condition is defined to ensure that the engine operates in a phase where no fuel injection is required and where the control signals of all the injectors are therefore uniformly zero, except the signals generated specifically for the purposes of the learning process. This is why the arches 20, 21, 24 and 25 are not considered to change significantly from one engine cycle to another. If the stability condition is verified, it goes to step 101, otherwise the process is interrupted or at least it leaves loop 43 (arrow 44), which corresponds to going to step 106. This second possibility allows to exploit the measurements acquired during the previous passages in the loop 43, if any.

Step 101 consists of calculating an average speed ω _{21, n-1} ( figure 2 ) of the engine on the injection cycle 21, which immediately precedes the cycle 22. The average speed ω _{21, n-1} is calculated over a measurement period T which essentially covers the injection cycle 21, by an integral calculated between times t 1 and t 2: $${\mathrm{\omega }}_{21,\mathrm{not}-1}=1/\mathrm{T}\mathrm{.}\int \mathrm{\omega }\mathrm{.}$$

The initial moment t1 of the measurement time T is for example offset from the top dead center 31 by a duration 32 which corresponds to an offset angle α of rotation of the crankshaft. In this case, the final moment t2 of the measurement duration T is shifted by the same angle α relative to the top dead center 33 associated with the next injector.

Step 102 consists in calculating an average speed ω _{22, n-1} of the engine on the injection cycle 22. The average speed ω _{22, n-1} is calculated over a duration T 'which is shifted from the TDC 33 of the angle of offset α. This offset angle α makes it possible to wait for the test pulse sent to the selected injector, which takes place in the vicinity of the top dead center 33, to have its effect, namely to cause an effective injection of fuel into the engine. injection cycle 22, if any, and therefore a combustion. This offset angle α is for example of the order of 30 °. The test pulse of current duration D _n-1 , which has been generated in the vicinity of the PMH 33, is represented for illustrative purposes on the first line of the figure 3 . The figure 3 represents, in three successive passages in the loop 43, the shape of the test pulse (left column) and the corresponding effective displacement of the needle of the injector under test (right column). The displacement signal of the injector 45 _n-1 shows that the injector has not opened. This absence of injection is also visible on the figure 2 . The instantaneous speed of the engine on the injection cycle 22, represented by the arch 22 _n-1 being identical to the arch 21, that is to say that ω _{22, n-1} = ω _{21, n- 1} .

When the average speed ω _{22, n-1} has been calculated, proceed to step 103, which consists of calculating the average speed difference ΔΩ _n-1 = ω _{22, n-1} -ω _{21, n-1} .

It will be noted that the calculation of the average speed difference over two consecutive injection cycles 21, 22 makes it possible to limit the influence of external parameters on the average speed difference. In particular, the average speed variation due to the natural slowdown of the engine is negligible over such a short period. Torque (ΔΩ _n-1 , D _n-1 ) is stored. Step 103 can also be performed outside loop 43.

In step 104, a pulse duration D _n greater than the duration D _n-1 is selected. The pulse of duration D _n is represented for illustrative purposes on the second line of the figure 3 .

In step 105, the duration D _n is compared with a preselected maximum pulse duration D _max . If the duration D _n is less than the maximum duration, we return to step 100 for a new passage in the loop 43, otherwise we go to step 106. In this case, we consider that the duration D _n is less than the duration D _max .

At the next pass in the loop 43, the average speeds ω _{21, n} and ω _{22, n} are calculated in a similar manner. The figure 3 shows the displacement signal 45 _n of the selected injector in response to the pulse of duration D _n . The signal 45 _n shows that the injector has opened over an opening time τ _n . There is therefore an actual fuel injection on the injection cycle 22, the result of which is also visible on the figure 2 : the mean velocity ω _{22, n} corresponding to arch 22 _n is greater than the mean velocity ω _{21, n} corresponding to arch 21. Note that arch 23 _n is greater than arch 23 _n-1 although no injection occurred during the injection cycle 23 _n . This acceleration of the engine during the cycle 23 is due to the inertia of the engine. The average speed difference ΔΩ _n is calculated and the torque (ΔΩ _n , D _n ) stored. In step 104, a pulse duration D _{n + 1} greater than the duration D _n is selected. The duration D _{n + 1} is represented on the third line of the figure 3 . The duration D _{n + 1} being less than the duration D _max , it returns to step 100.

During the next passage in the loop 43, the average speeds ω _{21, n + 1} and ω _{22, n + 1} are calculated in a similar manner. The figure 3 shows the response signal 45 _{n + 1} of the selected injector to the pulse of duration D _{n + 1} . The signal 45 _{n + 1} shows that the injector has opened over an opening time greater than τ _{n + 1} greater than the opening time τ _n , which is also visible on the figure 2 , the average speed ω _{22, n + 1} of the cycle 22 _{n + 1} being greater than the average speed ω _{22, n} of the cycle 22 _n . The average speed difference ΔΩ _{n + 1} is calculated and the torque (ΔΩ _{n + 1} , D _{n + 1} ) stored.

The loop 43 is similarly repeated until the pulse duration reaches the maximum duration D _max or the stability condition is no longer verified. When the process exits loop 43, it proceeds to step 106.

In step 106, the stored average speed differences ΔΩ _n-1 , ΔΩ _n , ΔΩ _{n + 1} are convolutionally filtered with a low-pass filter W, so as to smooth out the differences due to the noise, in particular to the uncertainties of measures. The filter W is for example a sliding average centered using preceding values and values according to the value to be verified, for example with a sinusoidal or Gaussian arc-shaped weighting. $$\mathrm{\Delta \Omega f}\mathrm{=}\mathrm{\Delta \Omega }\left(\mathrm{D}\right)\mathrm{*}\mathrm{W}\mathrm{=}\mathrm{\int }\mathrm{\Delta \Omega }\left(\mathrm{D}\mathrm{-}\mathrm{OF}\right)\mathrm{.}\mathrm{W}\left(\mathrm{OF}\right)\mathrm{dD\text{'}}\mathrm{.}$$

In practice, the convolution is calculated in a discrete manner. For the sake of clarity, we have shown on the figure 6 evolution of average speeds ω ₂₁ , ω ₂₂ , ω ₂₃ , depending on the duration of the test pulse D. When the control duration D is less than the minimum control duration MDP, the average speeds ω ₂₁ , ω ₂₂ , ω ₂₃ decrease in a similar way. It will be noted that, when the injectors 7 inject no flow during several engine cycles, which is for example the case during up-and-down operation, the crankshaft nevertheless continues to rotate by inertia. The average speed of the motor, the average being for example performed on each motor cycle, is at this time decreasing, this decrease being relatively slow. When the control duration D is greater than the duration CDM, the average speed ω ₂₁ continues to decrease in the same way, while the average speed ω ₂₂ begins to increase. At this time, the curve of the average speed ω _{23 is} bent because the acceleration experienced by the crankshaft during the injection cycle 22 is still noticeable during the injection cycle 23, by inertia.

The figure 7 shows a curve 57 representing the filtered mean velocity difference ΔΩf, axis 34, between the average velocity curve ω ₂₂ and the average velocity curve ω ₂₁ of the figure 6 . The curve 57 is close to zero as long as the duration D of the control pulses sent to the injector to be tested do not result in an injection, that is to say as long as the duration D is less than MDP.

Step 107 is to determine the CDM control time from which it is considered that there really was an injection. For this, the values of the curve 57 are compared with a predetermined threshold 58. The threshold 58 is chosen so that it is above the noise.

It will be noted that the minimum command duration MDP ₀ is initially known for each injector 7, with a tolerance range, since it is a specification of the new injector. The existence of a small error on the initial value is not a problem because the process finally makes it possible to correct it. The minimum CDM control time drifts when the injector 7 is aged. In order to find the minimum command duration MDP, one solution therefore consists of scanning the curve 57 in the direction of the duration of increasing commands D over an interval centered on the previously known minimum command duration MDP ₀ . For example, the scanned interval can have a range of 100μs to a few hundreds of μs. D ₀ and D _max are for example set such that D ₀ = MDP ₀ -50 μs and D _max = MDP ₀ +50 μs, the minimum command time MDP ₀ being of the order of 100 μs. Another solution is to proceed by dichotomy to scan this interval.

In step 108, the value of MDP is stored. When the value of MDP has been stored, it is possible to return to step 98, if the minimum control time of another injector has to be determined, to step 97 if the minimum control duration of an injector has to be determined for a different ramp pressure, or in step 96 if the learning process is completed. In this case, the method waits for an initialization signal to start again.

Determination of a stable zone

The figure 5 shows the steps of a routine that runs for example continuously, in parallel with the method described with reference to the figure 4 . This routine makes it possible to test the condition of stability, which is verified when the vehicle is in a so-called stable zone, that is to say an area in which the average speed of the engine is substantially constant.

In step 80, the first test, Test 1, is to verify that the accelerator pedal is fully released.

In step 81, the second test, Test 2, is to verify that the motor speed is within an acceptable range. This range is for example between 750 and 3000 rpm. Beyond that, a test pulse creates very little variation in engine speed ω, even if there is actually injection, because of the inertia of the engine. In addition, the crankshaft sensor 12 having a measurement period of the order of one microsecond, increasing the speed of the crankshaft increases the margin of error.

In step 82, the third test, Test 3, is to verify that the gearbox is in the right range. This corresponds for example to a speed ratio between the third and the fifth. Indeed, in the first or second, the acceleration or braking cause sudden changes in the speed of the engine and this leads to measurement accuracy problems. This test is about verifying that the speed of the vehicle is higher than 30km / h, a condition that could also be tested.

In step 83, the fourth test, Test 4, is to verify that the clutch is activated, that is to say that the motor is coupled to the wheels. At 2500 rpm, when a user disengages, the speed falls very quickly, which poses correction problems, as will be described in detail below.

In step 84, the fifth test, Test 5, is to verify that the temperature of the water, fuel oil, air and oil is within an acceptable range. At very low temperatures, combustion is unstable. When the engine is hot, friction is minimized. This test is therefore used to wait for the engine to be in steady state.

Additional tests may be added to these tests to check the correct operation of the equipment required by the process.

Here, in step 85, the sixth test, Test 6, is to verify that the voltage across the battery is correct.

In step 86, the seventh test, Test 7, consists in verifying that no sensor 12 indispensable to the proper functioning of the process is faulty.

The stability condition is verified when all tests are verified. For example, a logic variable S can be used. In this case, the stability variable S is set to 1 in step 79. If one of the above tests produces a negative result, the variable S is set to 0 to step 78. The value of this variable is used in step 100 to determine whether loop 43 should be performed.

Stopping the process

The value of the minimum duration MDP depends on the pressure of the common ramp 6. This value MDP varies when the pressure of the common ramp 6 varies. It is therefore desirable to carry out the learning process for ramp pressures 6 covering the widest possible pressure range. The stability condition defines at the figure 5 will typically be checked when the accelerator pedal is released after an acceleration phase and the vehicle continues to run under its momentum without requiring torque from the engine. Under these conditions, it is therefore possible to choose a ramp pressure at which it is desired to carry out the process, and maintain this pressure in the ramp 6 instead of letting it fall as would occur during normal operation of the vehicle. When a user supports again on the accelerator pedal during the course of the learning process, the engine computer 8 reacts by interrupting the training and producing the control signals of the injectors necessary for injecting fuel according to the demand signal produced by the pedal, according to an algorithm known per se. However, the pressure that has been maintained in the common rail during the training is not necessarily adapted to the amount of fuel that must be injected, that is to say that can be burned. This could result in combustion noise if this pressure is too high. Several means may be provided to cancel or at least to reduce the combustion noise generated by improper ramp pressure during the transition between the learning process and a re-acceleration phase of the vehicle.

For this, a high pressure valve 10 is opened to reduce the pressure in the common rail 6 when it must be decreased. The high pressure valve 10 allows a very rapid decrease in the pressure in the ramp 6. For example, a high pressure valve allows a reduction of the order of 2000 bar / s. The use of a high pressure valve 10 thus makes it possible to very quickly reduce the ramp pressure after learning at high pressure.

In addition, it is advantageous that the engine computer 8 controls the injectors with at least one pilot pulse in front of the main pulse, so as to produce an additional pilot injection, very close to the main injection, which also reduces the combustion noise. The additional pilot injection is placed so as to reduce the noise as much as possible, for example as close as possible to the main injection.

As indicated, the method described above works well in a wide range of engine operation, for example idle speed at 3000rpm. Since an averaged rate over an injection cycle is used to determine the MDP parameter, the method is not sensitive to the precise shape of the ark corresponding to each injection cycle. Even at high speeds, when the arches begin to be deformed by engine inertia, the process still produces reliable results.

The learning method, previously described in the case of a dead-foot operation, can also be performed during steady-state operation, when the accelerator pedal is supported substantially substantially, and the flow rates of fuel calculated by the engine computer 8 are stable and identical for all injectors. In this variant embodiment, Test 1 is replaced by a Test 1 which tends to test whether these conditions are satisfied. The process is for the remainder the same. In this case, all the injectors receive control signals from the engine computer 8, for example in the form of a main pulse preceded by one or more pilot injections. These pulses are calibrated with respect to the high dead points of the pistons according to the known technique. The injector under test additionally receives the test pulse or pulses, which can be placed for example in advance of the main pulse or, if appropriate, the pilot pulse.

The need to supply all injectors with power can impose limits on the range in which the ramp pressure can be set during learning. It is necessary to avoid excessive combustion noise. For this, it is preferable to perform the injection into the cylinders in the form of multiple pulses. The presence of one or more pilot injections prepares and warms the diesel and air mixture and tends to reduce the noise by lengthening the duration of the combustion.

A second embodiment will now be described in which the process may be carried out in a so-called unstable zone, that is to say in which, in addition to allowing the cylinders to be supplied with fuel, the engine speed is allowed to vary relatively quickly. Correction calculations make it possible to compensate for variations in the speed of the motor due to the influence of parameters outside the learning process, such as acceleration or braking. With reference to figure 11 the steps of the learning method will now be described. The steps similar to the first embodiment are designated by the same reference numeral increased by 100. The same steps as in the first embodiment will not be described again.

In this embodiment, the stability condition to be tested can be made much less restrictive (step 200). Of course, steps 81 to 86 of the figure 5 can be preserved. An additional condition of verifying that the engine is within an acceptable load range can be added.

The description of two passages in the loop 143 will be sufficient to understand the principle.

Step 201 consists of storing the instantaneous speed ω of the engine over a period T essentially covering the injection cycle 21, which immediately precedes the cycle 22. The acquisition time T is identical to the first embodiment. We call v _{21, n} this batch of measures.

Step 202 consists in memorizing the instantaneous speed ω of the engine over a period T1 essentially covering the injection cycle 22. This series of measurements is called v _{22, n} . The set (v _{21, n} , v _{22, n} , D _n ) is stored.

Step 204 is identical to step 104.

Step 205 is identical to step 105. In the present case, it is considered that the duration D _{n + 1} is less than the duration D _max .

On the next pass through the loop 143, the V _{21 velocities, n + 1} and v _{22, n + 1} are stored similarly. The set (v _{21, n + 1,} v _{22, n + 1,} D _{n + 1} ) is stored.

In this embodiment, the loop 143 includes only stages of acquisition of the instantaneous speeds of the engine on the injection cycles 21 and 22. When the process exits the loop 143, it goes to the step 203.

In step 203, the average speed ω _{21, n} of the engine on the injection cycle 21 is calculated from the instantaneous speed v _{21, n} , in a manner which has been described in detail in the first embodiment of FIG. realization, and the average speed ω _{22, n} of the engine on the injection cycle 22 is calculated from the instantaneous speed v _{22, n} . The average speed difference ΔΩ _n = ω _{22, n} - ω _{21, n} is calculated. Torque (ΔΩ _n , D _n ) is stored. In the same way, the average speed ω _{21, n + 1} of the engine on the injection cycle 21 is calculated from the instantaneous speed v _{21, n + 1} , the average speed ω _{22, n + 1} of the engine on the injection cycle 22 is calculated from the instantaneous speed v _{22, n + 1} , and then the difference of average speed ΔΩ _{n + 1} = ω _{22, n + 1} - ω _{21, n + 1} is calculated. The torque (ΔΩ _{n + 1} , D _{n + 1} ) is stored.

In step 201A, the average speed ω _{21, n} is compared with the average speed ω _{21, n-1} and an offset κ _n is calculated from the difference ω _{21, n} - ω _{21, n-1} . In the same way a shift κ _{n + 1} is calculated from the difference ω _{21, n + 1} - ω _{21, n} .

In step 203A, the shift κ _n (respectively κ _{n + 1} ) is used to calculate a correction factor f (κ _n ) (respectively f (κ _{n + 1} )) subtracted from the difference in speed ΔΩ _n (respectively ΔΩ _{n + 1} ), so as to store a corrected average speed difference ΔΩc _n = ΔΩ _n - f (κ _n ) (respectively ΔΩc _{n + 1} = ΔΩ _{n + 1} - f (κ _{n + 1} )) . This corrective factor is used to compensate for engine speed variations due to braking and acceleration.

In step 206, the stored corrected average speed differences ΔΩc _n , ΔΩc _{n + 1} are convolutionally filtered with the low-pass filter W.

An example of the result obtained with this method is represented on the figure 8 , for which braking has been performed during the acquisition of average speeds.

The curves 60 and 61 represented on the figure 8 show, as a function of the duration D, the evolution of the average speed difference ΔΩ, curve 61, and the corrected average speed difference ΔΩc, curve 60. When the curve 61 drops, for example due to braking , this abrupt modification of the motor speed is measured by the offset κ and compensated by the corrective factor f (κ), so that it does not influence the evolution of the curve 60 and in particular its intersection with the threshold 58.

As the engine ages, the compression ratios of the different cylinders can be varied, which can result in different engine speeds on different injection cycles. This results in an imbalance of the engine. The purpose of step 209 is to measure the influence of this type of imbalance on the average speeds ω _{21, n} and ω _{22, n} and to correct the average speed difference ΔΩ _n to compensate for this influence. For this purpose, the value of the average speed difference ω _{21, i} - ω _{22, i is used} in the absence of a test pulse. This value can be determined before the execution of the learning process or during it, for example during a passage i in the loop 143 during which the test pulse is removed. A corrective factor is thus calculated from the average velocity difference ω _{21, i} - ω _{22, i} and applied the average velocity difference ΔΩ _n or ΔΩc _n .

In step 210, the average speed of the motor Ω _n on the motor cycle corresponding to the loop of rank n at which the process is carried out is taken into account. Due to the inertia of the motor, the average speed difference ΔΩ _n generated by a given test pulse depends on the speed of the motor. For example, when 1 mg of fuel is injected at 1000 rpm, the average speed difference ΔΩ _n generated is greater than that produced by a 1 mg injection at 3000 rpm. The average velocity differences ΔΩ _n obtained are then adjusted by a scale factor dependent on Ω _n . This scale factor is for example calculated before the execution of the method and stored in the engine computer 8. For this, one can plot a curve ΔΩ as a function of Ω over a wide range of speeds Ω for a corresponding test pulse to a predetermined injected amount and use the slope of this curve as a scale factor. This adjustment step makes it possible to obtain precise results without having to modify the value of the detection threshold 58. Another solution would be to adapt the threshold 58 in a similar way.

Step 207 is to determine the minimum duration of CDM command from which it is considered that there really was an injection. For this, the values of the curve 60 are compared with the predetermined threshold 58.

Step 208 is identical to step 108.

Steps 203A, 209 and 210 are corrective steps that are optional. Each of these steps is designed to compensate for a particular phenomenon and can be used separately or in combination. These corrective steps can also be applied in the first embodiment.

The methods described above can be performed with all types of injectors. However, direct-acting injectors provide better accuracy, especially when multiple injections have to be made.

The figure 9 shows the amount of fuel Q injected into the main injection, axis 70, as a function of the separation time δ between the pilot pulse and the main pulse, axis 71, in the case of a solenoid injector, curve 72, and a piezoelectric injector, curve 73. The pulses are fixed. Only their separation varies. These two types of injectors do not behave identically, this difference being able to modify significantly the results of the learning process.

In the case of the use of a solenoid injector, the opening takes place in two stages. At first, the valve member disengages from the plate, and then the needle rises. The opening of the valve member takes place about 150 μs before opening the needle. This opening in two stages is explained in particular by the fact that the power generated by the solenoid is not sufficient to lift the needle directly. For some durations of the pilot pulse, it may happen that the valve member disengages but the needle does not rise. In this case, a fuel flow is created from the control chamber to the low pressure return. This has the effect of creating pressure waves. In particular, in the case of a multi injection, the main injection is disturbed by the wave created by the pilot injection and this disturbance depends on the separation δ. This phenomenon is illustrated by the figure 9 . In this case, even if the pilot injection does not lift the needle, it changes the main injection, which is a hydraulic interaction. In general, the multi injection is more complicated to achieve with a solenoid injector because each pilot injection disrupts the following by the creation of pressure wave.

The figure 10 shows an average speed difference curve ΔΩ, as a function of time t. A reference curve 75 has also been drawn. The pressure wave generated by the pilot injection changes the average speed 29 of the engine on the cycle of the injector to be tested before the actual opening of the injector. This results in an increase in the average speed difference 34 which can pass above the threshold 58. This therefore risks generating detection errors of the minimum duration 43b.

This problem does not arise with the direct-acting injectors, such as the piezoelectric injectors 73. The learning method described in the present invention is therefore particularly suitable for direct-acting injectors, for example piezoelectric injectors 73, although it can also be performed on solenoid injectors 72 taking into account the difference in behavior.

Other variants are also possible. For example, in each embodiment, the control signal may comprise several test pulses of the same duration D. For example, a test pulse is placed so that the crankshaft is before the TDC and a second test pulse is placed so that the crankshaft is close to the PMH. Since the average speed difference ΔΩ is proportional to the difference in the quantity of fuel injected by the injectors associated with the two cycles 21, 22, this difference is thus multiplied by the number of pulses, which makes it possible to improve the detection accuracy by increasing the slope of the curve on the figure 7 or 8 .

Note that it is also possible to calculate the average speed on another injection cycle preceding cycle 22, for example on cycle 20.

It should be noted that the higher the speed, the more frequent the injections. At 2000rpm, we inject every 60ms and it takes about 2s to perform the learning. When the number of revolutions per minute increases the learning time decreases.

Some steps of the learning process may be performed in a different order or simultaneously without changing the result.

In addition, the described learning methods can be immediately adapted to the determination of any other parameter of the control signal. For this, the test pulse can be modified according to another parameter than its duration, for example slope, amplitude or other.

Although the invention has been described in connection with several particular embodiments, it is obvious that it is not limited thereto and that it includes all technical equivalents described means and combinations thereof if they fall within the scope of the invention.

Claims (21)

1. Method for determining the operating parameters of an injection device of an internal combustion engine, said injection device comprising a plurality of fuel injectors (7), and an electronic control means (8) for controlling said injectors by means of injection control signals, said electronic control means being connected to a sensor (12) for constantly measuring a speed of said combustion engine, said engine operating according to an engine cycle that includes at least one injection cycle (21, 22, 23) associated with each of said injectors, said injection cycles succeeding one another in a predetermined sequence, characterized in that it comprises the steps of:

   a)selecting (98, 198) an injector to be tested from said injectors;

   b)calculating (101, 201) an average speed associated with a previous injector (ω_21,n-1, ω_21,n, ω_21,n+1) located in front of said injector to be tested in the sequence of said injection cycles, said speed being equal to the speed of said engine averaged over a measurement duration (T) covering essentially an injection cycle associated with said previous injector;

   c)for said injection cycle associated with said injector to be tested, applying an injection control signal to said injector to be tested, the signal including at least one test pulse having an adjustable parameter (D_n-1, D_n, D_n+1);

   d)calculating (102, 202) an average speed associated with said injector to be tested (ω_22,n-1, ω_22,n, ω_22,n+1) which is equal to the speed of said engine averaged over a measurement duration (T1) covering mainly said injection cycle associated with said injector to be tested;

   e)calculating (103, 203) a difference between the average speed calculated at step d) and said average speed calculated at step b);

   f)repeating steps b) to d) for at least another engine cycle while varying, on each occasion, said parameter of the test pulse; and

   g) determining a value of said parameter of the test pulse for which said average speed difference exceeds a predetermined threshold (58) and storing said parameter value.
2. Method according to Claim 1, characterized in that said injectors are directly actuated.
3. Method according to either of Claims 1 and 2, characterized in that, at step c), said control signal comprises several test pulses, the value of said parameter being the same for each of said test pulses.
4. Method according to any one of Claims 1 to 3, characterized in that said parameter is a pulse duration (D_n-1, D_n, D_n+1).
5. Method according to any one of Claims 1 to 4, characterized in that while the method is carried out, said injection control signals for the injectors other than said injector to be tested are zero.
6. Method according to any one of Claims 1 to 4, characterized in that while the method is carried out, said electronic control means provides said injectors with injection control signals including a main pulse corresponding to a request coming from a throttle control unit.
7. Method according to any one of Claims 1 to 6, characterized in that, prior to step g), a filtered average speed difference (ΔΩ_f) is calculated by applying a convolution by a filter (W) to the curve representing the difference in average speed as a function of said parameter of the test pulse and in that, at step g), said filtered average speed difference is used.
8. Method according to Claim 7, characterized in that said filter (W) is a running average.
9. Method according to any one of Claims 1 to 8, characterized in that it comprises a first step consisting in testing (100, 200) a predetermined stability condition in order to detect a stable operation of said engine, and a step consisting in ending said method when said stability condition is not met.
10. Method according to Claim 9, characterized in that said stability condition includes an engine speed condition, the condition being verified when said engine speed is between two predetermined thresholds.
11. Method according to Claim 9 or 10, characterized in that said stability condition includes an engine torque condition, the condition being verified when the engine torque is between two predetermined conditions.
12. Method according to any either of Claims 9 to 11, characterized in that said stability condition includes a gear ratio condition, the condition being verified when said gear ratio is greater than a predetermined threshold.
13. Method according to any either Claims 9 to 12, characterized in that said stability condition includes a vehicle speed condition, the condition being verified when said vehicle speed is greater than a predetermined threshold.
14. Method according to any one of Claims 9 to 13, characterized in that said stability condition includes a clutch condition, the condition being verified when the clutch is activated.
15. Method according to any one of Claims 1 to 14, characterized in that it comprises, at each engine cycle, a step of calculating (201A) a difference between said average speed calculated at step b) for said engine cycle (ω_21,n) and said average speed calculated at step b) for a previous engine cycle (ω_21,n-1), a step of calculating (203A) a corrected average speed difference (ΔΩ_c) by correcting said average speed difference calculated (203) at step e).
16. Method according to any one of Claims 1 to 15, characterized in that said speed of said combustion engine corresponds to the rotating speed of a crankshaft of said combustion engine, said measurement duration (T, T1) associated with an injector extending on each occasion between an initial moment (t1) delayed by an offset angle α of the crankshaft in relation to the combustion top dead centre (31) of a piston corresponding to said injector and a final moment (t2) delayed by said offset angle α in relation to the top dead centre (33) of the piston corresponding to the next injector in the sequence of said injection cycles.
17. Method according to Claim 16, characterized in that the offset angle α is less than or equal to 45°.
18. Method according to any one of Claims 1 to 17, characterized in that said injection device includes a common rail (6) provided with a high-pressure valve (10), each of said injectors being linked to said common rail.
19. Method according to Claim 18, characterized in that it comprises a step consisting in selecting (97, 197) a common rail pressure within a range from 200 to 2000 bar and in carrying out said method by maintaining this rail pressure in said common rail.
20. Method according to Claim 19, characterized in that it comprises the steps consisting in detecting an actuation of a throttle control unit of said vehicle corresponding to a fuel demand, in calculating a common rail target pressure suited to said fuel demand, and, when the target pressure is less than said selected common rail pressure, in reducing the pressure in said common rail by opening said high-pressure valve.
21. Method according to Claim 19, characterized in that it comprises the steps consisting in detecting an actuation of a throttle control unit of said vehicle corresponding to a fuel demand, in calculating a common rail target pressure suited to said fuel demand, and, when the target pressure is less than said selected common rail pressure, in providing said injectors with injection control signals including at least a pre-injection pulse and a main pulse.

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