FR2857057A1 - Fuel injection system controlling method for internal combustion engine, involves transforming one correction function, by using individual quality characteristics of injectors, to another function to correct injector control signals - Google Patents

Abstract

The method involves performing a collective correction of a pressure wave, for two injectors of an internal combustion engine, and determining a correction function. Individual quality characteristics of the injectors are projected. The correction function is transformed, by using the projected individual quality characteristics, to another correction function for correcting control signals of the injectors. An independent claim is also included for a device for controlling an injection system of an internal combustion engine having two injection units.

Description

The present invention relates to a method and a control device

  an injection system of an internal combustion engine equipped with at least two injection elements, wherein the fuel dosage is distributed between a first partial injection and at least

  a second partial injection, with means provided for correcting the control signal defining the amount of fuel to be injected as a function of a pressure wave influence on the at least two partial injections.

  STATE OF THE ART In current high-pressure fuel injection systems, in particular in non-controlled internal combustion engines, all the quantities or doses of fuel injected by injection valves (injectors) into the combustion chambers of the internal combustion engine are each distributed over a number of partial injections. These partial injections are frequently very close to each other in time and generally consist of one or more pre-injections preceding the actual main injection. A widely used injection system, described in DE 100 02 270 C1, of the type in question here, is called a common rail injection system. In this injection system the fuel is stored intermediately in a high pressure accumulator (ramp) before feeding the various injectors.

  The multiple partial injections mentioned above, make it possible to prepare the mixture better and individually they produce in particular a lower emission of exhaust gas from the internal combustion engine, a noise reduced to combustion and a greater power provided by the internal combustion engine.

  In the partial injections mentioned above, the precision of each quantity or dose injected is very important. However, it is also known that each injection using an injector results in a brief collapse of the fuel pressure in the supply line associated with the injection system between the ramp and the injector concerned and in the injector itself for the high-pressure connection adjacent to the boom and connected to the needle of the injector. Such a brief breakdown of the pressure produced, at the end of the control of the injector, a fuel pressure wave which occurs in particular between the ramp and the injector. This pressure wave produces uncomfortable variations in the amount of fuel to be injected; the effect of the pressurized wave is amplified even when the lifting frequency of the injector needle increases, thus the taking into account of this pressure wave, in particular in the future injection systems using actuators very fast piezoelectric as injection actuators to control the needle of the injector, will take a significant increasing.

  A known proposal for minimizing the evoked influence of the pressure wave consists in measuring this influence outside the running operation of the motor vehicle equipped with such an internal combustion engine (in a way, a measure out of line) on a test bench and take into account the results of these measurements for example when presetting the operating parameters of the internal combustion engine of the vehicle. But the model that must be used to calculate the influence of such a pressure wave composed of partial injections with partial injections that follow each other in time becomes very complicated. Thus, in this model, it is necessary to intervene a large number of operating parameters of the internal combustion engine such as the quantity or dose injected, the instantaneous pressure of the fuel prevailing in the ramp, the temperature of the fuel or the geometry of the pipes. of the entire injection system.

  These parameters are involved in the parametrization of the measurement of the pressure wave performed as above in a substantially offline manner. Correction of the pressure wave itself is effected by appropriate variation of the injector control time by applying a collectively defined correction for all injectors at each individual injector. By this correction the effect of a pressure wave on the injection of about +/- 4mm3 is reduced to about 1 ... 2 mm3.

  However, as soon as there are significant deviations between the injected doses or quantities and / or a dose balance adjustment by individual control times of the injectors, the amplitude of the triggered pressure waves can increase significantly and the correction of the pressure wave mentioned above can only be done with a rigid compensation function vis-à-vis a further deterioration of the preparation of the mixture and thus ultimately this results in an increase in emissions and combustion noise. Indeed, differences in injection quantities, important, that the end of the injection differs significantly from the respective set value. The pressure wave triggered by the respective end of the injection dominates all the pressure oscillations produced so that the evoked controlled correction results in considerable injection errors.

  OBJECT OF THE INVENTION The object of the present invention is to develop a method and a device of the type defined above, to allow a better correction of the pressure wave with respect to internal combustion engines and in particular to operating conditions thereof. DESCRIPTION AND ADVANTAGES OF THE INVENTION For this purpose, the invention relates to a process of the type defined above, characterized in that for the at least two injection elements a collective correction of the pressure wave is carried out and a first correction function is determined, the individual characteristic quantities of the at least two injection elements are recorded, and the first correction function is converted by means of the individual characteristic values of the at least two injection elements into a second correction function by means of which the control of the at least two injection elements is corrected for the pressure wave.

  According to the invention, the device of the type defined above is characterized by means for performing a collective correction of the pressure wave for the at least two injection elements and for determining a first correction function, means for capturing individual characteristic quantities of the at least two injection elements, and means for converting the first correction function using the individual characteristic values entered from the at least two injection elements into a second correction function at the first using which the control of the at least two injection elements from the point of view of the pressure wave is corrected.

  The basic idea of the invention, namely the correction of the pressure wave for the injectors carried out individually by an individual amplitude modulation at each injector, is made with the correction data obtained collectively for all the injectors. In other words, in a first approximation, a collective correction of the pressure wave is proposed and the correction data thus obtained are adapted in second approximation, by amplitude modulation, by making an individual adaptation on each injector.

  According to a preferred development of the method of the invention, first of all for all injectors of the injection system, a collective correction of the pressure wave is made. A first representative correction function is deduced for all the injectors. With the aid of appropriate sensors or the engine control unit, specific characteristics of the injector or operating parameters are prepared. As individual quantity to the injector there is in particular the input / output adjustment ratio of an inlet / outlet throttling member or the opening pressure of the nozzle of an injector.

  Alternatively, in a manner known per se, it is possible to perform a compensation of the actual quantities of the different injectors and then use the individual balancing data per injector as described to have specific characteristic quantities of the injector.

  According to another development, the input characteristics specific to the injector are further normalized, and from these normalized correction quantities, the individual values per injector for the amplitude modulation thus evoked for the first function of FIG. correction. Starting from this first correction function, then, for each injector, an amplitude modulated correction function is subsequently calculated for each injector in order to finally correct the control duration of the various injectors as a function of the pressure wave.

  The correction function correction data calculated individually for each injector is preferably transmitted each time in the form of a control code to the engine control or control unit which in this embodiment carries out the evoked correction of the pressure wave.

  According to the invention, furthermore for the control device: the conversion means of the first correction function produce a scaling of the amplitude or an amplitude modulation of the first correction function the means for capturing individual characteristic quantities of the at least two injection elements cooperate with means for performing a real flow compensation for the at least two injection elements; the means for capturing individual characteristic quantities of the at least two injection elements; at least two injection elements cooperate with means which provide the ratio of the output throttle / inlet throttle of the respective injection element and / or the opening pressure of an injector of the respective injection element; means for intermediate storage of the first correction function in the form of a correction matrix in the control unit of the combustion engine; internal bustion.

  The method and the device according to the invention allow an individual correction of the behavior of the injection dose in the case of successive multiple partial injections, in particular regardless of the amplitude of the pressure wave which is established. . Thus, for stronger pressure oscillations, this allows a more accurate and efficient correction of the pressure wave, respecting very precise injection dose tolerances and also optimizing the operating characteristics of the internal combustion engine. and in particular emissions and noise development. The process according to the invention makes it possible to reduce the already mentioned dispersion of the quantities dosed with 1 to 2 mm 3 up to even 0.5 to 1 mm 3.

  The present invention is preferably applicable to a common rail injection system controlled by very fast piezoelectric actuators and this although for the auxiliary and main injections that follow in time and for separate pre-injections, and which follow one another .

  Drawings The present invention will be described in more detail below with the aid of preferred embodiments shown in the accompanying drawings, in which: FIG. 1 is a schematic view of a common rail injection system according to FIG. 2 is a schematic partial view in longitudinal section of an internal combustion engine fuel injector according to the state of the art, FIG. 3 shows the control signals of FIG. an injector actuator according to a known scheme of the state of the art with a main injection and a pre-injection, to explain the effect of the pressure wave at the base of the present invention, - Figures 4a, 4b show pressure wave curves in the common-rail injection system of FIG. 1 (curve shown in FIG. 4a) and fuel flow curves for explaining the correction of the pressure wave according to the invention (Figure 4b) - Figure 5 shows a flow chart to explain the invention. DESCRIPTION OF AN EMBODIMENT For the understanding of the invention, FIG. 1 shows the main elements of a high pressure fuel injection system, for example a common rail injection system. Reference 1 denotes the fuel tank. This tank 1 makes it possible to supply fuel through a first filter 5 and an upstream supply pump 10 through a second filter 15. The fuel leaving the second filter 15 passes through a pipe for supplying a high-pressure pump 25. The connecting line between the second filter 15 and the high pressure pump 25 is further connected by a connecting line provided with a low pressure limiting valve 45 to the tank 1. The high pressure pump 25 is connected to a ramp 30 The ramp 30, also called high pressure accumulator, is connected by fuel lines to different injectors 31 by pressure transmission links. A pressure relief valve 35 connects the ramp 30 to the fuel tank 1. The pressure relief valve 35 is controlled by means of a coil 36.

  The lines between the outlet of the high pressure pump 25 and the inlet of the pressure relief valve 35 correspond to the so-called high pressure zone. In this zone, the fuel is at a high pressure. The pressure in the high pressure zone is detected by a sensor 40. The lines between the fuel tank 1 and the high pressure pump 25 correspond to the low pressure zone.

  A control 60 applies a control signal AP to the high pressure pump 25, a control signal A to the injectors 31 and / or a control signal AV to the pressure evacuation valve 35. The control 60 processes the various signals of the sensors 65 characterizing the operating state of the internal combustion engine and / or the vehicle driven by this engine. Such an operating state is for example characterized by the rotational speed or speed N of the internal combustion engine.

  The injection system of FIG. 1 operates in the following manner: the fuel of the tank 1 is supplied by the pre-supply pump 10 through the first filter 5 and the second filter 15. When the pressure in the range When the low pressure limit reaches an unacceptable level, the low pressure limiting valve 45 opens and releases the communication between the output of the front pump or upstream pump 10 and the tank 1.

  The high pressure pump 25 delivers a quantity of fuel Q1 from the low pressure zone to the high pressure zone. The high-pressure pump 25 thus establishes a very high pressure in the ramp 30. Usually, for injection systems equipped with a spark-ignition internal combustion engine, maximum pressure values of the order of 30.degree. 100 bars; for internal combustion engines with non-controlled ignition, maximum pressures of the order of 1000 to 2000 bars are reached. With the aid of the injectors 31, the fuel can be injected at high pressure into the combustion chambers (cylinders) of the internal combustion engine by dosing the fuel.

  The sensor 40 measures the pressure P prevailing in the ramp or in the entire high pressure zone. The high pressure pump 25, controlled, and / or the pressure relief valve 35 can regulate the pressure in the high pressure zone.

  As front-loading pump 10, electric fuel pumps are usually used. For higher flow rates, especially those required by commercial vehicles, it is also possible to connect several such frontloading pumps in parallel.

  Figure 2 shows, in more detail, in a sectional view, an injection valve or injector 101 with piezoelectric control. The injector 101 includes a piezoelectric module 104 for actuating a valve member 103 axially slidable in the bore 113 of the valve body 107. The injector 101 further includes an adjuster piston 109 adjacent to the piezoelectric module. and an actuating piston 114 on the side of the valve closure member or injector 115. Between the pistons 109, 114 there is a hydraulic chamber 116 with hydraulic reduction effect. The valve closure member 115 cooperates with a valve seat 118, 119 thereby separating a low pressure zone 120 from a high pressure zone 121. An electrical control unit 112, simply indicated schematically, provides the control voltage to the piezoelectric module 104 and this as a function of the pressure level prevailing respectively in the high pressure zone 121. In the high pressure zone 121 of the injector 101 there is further provided an outlet throttling member 130 and an inlet throttle 131. The output / inlet adjustment ratio for the two throttle members 130, 131 is adjusted by means of a control valve 132.

  FIG. 3 shows characteristic control signal curves for an injector such as that of FIG. 2 for the main injection 200 and for a pre-injection 205 which precedes the main injection. The five curves or chronograms represent different control states in time for which the time interval between the two control signals 200, 205 decreases to 0 step from top to bottom to arrive at a minimum A_t_min. It is assumed here that the time interval At departure from the application has been chosen so that the pressure wave produced by the preinjection 205 in the ramp is damped again at the time of the control of the main injection 200 The corresponding values are values obtained by tests. It is further assumed that the time difference Δtmin, represented by the lower curve, corresponds to the minimum time interval between the injections, the interval for which the pressure wave produced by the pre-injection 205 has already resulted in a measurable variation of a parameter, preferably a torque variation provided by the internal combustion engine.

  It should be noted that the two injections presented in FIG. 3 are only given to explain the situation and the method and the device according to the invention can also be applied to several injections, and obviously separate pre-injections, separated in time, can also be influenced by their pressure waves as has been described above.

  The effect of the pressure wave described above can be explained by means of FIG. 3. If the pre-injection VE 205 precedes the main injection HE 200 sufficiently far, in the present case, the The pressure corresponds to the Atd start interval, so at the time of the main injection 200, the pressure wave has already been damped and no longer affects the quantity of fuel injected at the time of the main injection. Because of the known known pressure velocity of the pressure, this time interval will depend mainly on the instantaneous pressure in the ramp. An appropriate starting value, obtained empirically,> 2 ms. If now the time interval is modified by leaving the beginning of the control of the main injection constant, but bringing the pre-injection closer to the main injection, we will have for a certain time interval an influence on the quantity of injection principle because the pressure wave, especially at the level of the needle of the nozzle, at the moment of opening and during the opening of the nozzle, increases because of a vertex of the pressure wave is decreases due to a depression of the pressure wave. This results in a quantity or moment effect which can be detected for example by means of the rotational speed signal of the internal combustion engine. In a variant, it is also possible to detect the quantitative effect in a manner known per se by a lambda probe or the control thereof.

  FIG. 4a shows characteristic curves of p_injector pressure waves in the zone of an injector of a common rail injection system according to FIG. 1; these curves are represented as a function of time (chronograms). The pre-injection applied before a main injection (or possibly another pre-injection) comprises two parts: a primary pressure oscillation 320 and a secondary pressure oscillation 330. Starting from an outlet pressure p_rampe 300, prevailing in the ramp the primary pressure swing 320 is produced by opening the switching valve 103 shown in FIG. 2 at time t1 305 and the ratio of the inlet / outlet throat of a throttle check valve (so-called A / Z value). The secondary pressure oscillation comes from the opening 310 and the closure 315 of the needle of the injector at times t2 and t3. Due to the closure of the injector needle at time t3, there is a brief pressure over-oscillation 325.

  The throttle valves or check valves, above, serve primarily to throttle the fuel flow into the injectors. They limit in a manner known per se the passage in one direction and allow the free return in the opposite direction. Depending on the mounting position of the check valve, the throttling effect will be either for the arrival or for the return. The transformation between the supply control and the return control is done for example by rotating the check valve 180 around a predefined axis.

  FIG. 4b shows characteristic injection fuel flow rates for the injection used to explain the correction of the pressure wave according to the invention. In the diagram is represented the instantaneous quantity injected by an injector as a function of the time difference t_diff. The difference in time t diff is defined by the interval of time between the falling edge of the previous rectangular injection flow curve and the rising edge of the rectangular injection-shaped injection curve. following. The solid line curve 400 represents the chronogram of the evoked collective average value, known per se, of the quantity injected by all the injectors. On the other hand, the two curves in broken lines 405, 410, represent two flow curves scaled, with amplitude modulation as described and which serve directly to the base to correct the quantities injected by the two injectors concerned. In the present exemplary embodiment, the flow curve 405 corresponds to a lowering of amplitude with respect to the average curve 400 and the flow curve 410 corresponds to a corresponding increase of the amplitude by serving, as already indicated, only to explain.

  The actual correction of the pressure wave for the control data or the control signals of the different injectors is done exclusively in a manner known per se by means of corresponding modifications of the control times. In FIG. 4b, in order to explain, there is also shown periodically variable rates 405, 410, also a median-median central line. The oscillations curves presented have been previously normalized on this value representing the non-influenced quantity curves of the pressure wave mentioned above; thus only the relative variations with respect to this median line are taken into account. At time t1, the flow curves 405, 410 for the two injectors describe a subsampling behavior with respect to the average line m_moyenne. That is why the control times at this moment for the injector corresponding to the curve 410 are corrected upwards, according to the arrow 415. Thus, according to the invention, there will be a much lower correction for the injector corresponding to the curve 415 following the arrow 420. At time t2, the situation is reversed and due to the behavior of over-oscillations at this point, it will be corrected with an inverted algebraic sign. Thus, for the curve 410 there will be a correction along the arrow 425 and for the curve 405, a correction according to the arrow 430 which again is much lower.

  Figure 5 shows a flowchart to further explain the process of the invention. For each of the injectors of the injection system which are shown only schematically, firstly, in a known manner, a collective correction of the pressure wave (500) is carried out. This collective correction of the pressure wave provides for the injectors controlled by hypothesis with respect to the pressure wave, medially, a first correction function fK (collective correction function) which depends mainly on the parameters: injected mass Am_injection and the control duration At. This correction function according to an exemplary embodiment will be standardized for the continuation of the treatment with respect to the average value of the injected quantity m_moyenne; this value corresponds to the value not influenced by the pressure wave. The normalized correction function fK, norm is stored intermediate (510) in a correction matrix of the control apparatus of the internal combustion engine.

  In step (515) the specific characteristic quantities of the injector are entered. This is in a manner known per se of the compensation of the actual quantity and the data resulting therefrom will be used as characteristic quantities. As a variant, the individual control data of the injectors, the A / Z ratio (inlet throat / inlet throat) of the respective injector or the opening pressure for opening an injection nozzle of the injector are used. the respective injector for such characteristic quantities. The raw data obtained for the various individual characteristic quantities of the injectors are then normalized (520) on the average value already mentioned m_moyenne and are transmitted in the form of command to the control unit already indicated (525) to be there if necessary also recorded intermediately. The values thus stored intermediate for the normalized corrections function are amplitude modulated or scaled in amplitude, preferably using the individual characteristic values entered for the injectors. However, it is noted that the correction function can also be changed in another way with the indicated characteristic quantities, for example by performing a weighted scaling.

  With the aid of the data transmitted from the standardized characteristics of the injectors, the control unit calculates a fixed scale factor or variable fixed factor as a function of time (530); using the scale factor, the standard correction function fK, norm for each separately selected injector is adapted by inverse scaling (535); this gives a new correction function FK, norm, inj.-indiv. Finally, with the aid of this new correction function F1, norm, inj.-indiv., The correction of the pressure wave of the control data of the different injectors is carried out as already described above.

  The method described above can be implemented either in the form of a circuit in a control apparatus for this purpose or in the form of a control code integrated in the engine control or management apparatus. Such a device comprises control or calculation means by means of which it first performs a prescribed collective correction of the pressure wave for the injection elements and determines the first evoked correction function. . The first correction function is stored in the form of a correction matrix in an appropriate memory of the control device. Sensors are further provided to capture the individual parameters of the injection elements. In a variant, these characteristic quantities may be provided directly by the control or engine management apparatus insofar as the actual quantity compensation described is relied upon. Calculation and control means are also provided for a prescribed conversion of the first correction function using the characteristic variables entered. The device also comprises calculation or control means with which the injector control signal is corrected, which signal determines the quantity or dose of fuel to be injected at the moment.

Claims (11)

  1) A method of controlling an injection system of an internal combustion engine having at least two injection elements, wherein a fuel dose is divided between a first partial injection and at least a second partial injection and the signal which defines the fuel dose injected by the at least two injection elements is corrected according to the influence of the pressure wave on the at least two partial injections, characterized in that for the at least two injection elements, a collective correction of the pressure wave is performed and a first correction function is determined, the individual characteristic quantities of the at least two injection elements are recorded and the first correction function is converted using individual characteristic quantities entered from the at least two injection elements into a second correction function by means of which corrects for the ond e pressure, the control of the at least two injection elements.   2) Method according to claim 1, characterized in that the first correction function with the aid of the individual characteristic values entered of the at least two injection elements, is converted into the second correction function by scaling the d amplitude or amplitude modulation of the first correction function.   3) Process according to claim 1 or 2, characterized in that the individual characteristic quantities of the at least two injection elements are formed from the actual quantitative compensation performed each time for the at least two injection elements.   4) Method according to claim 1, characterized in that the individual characteristic quantities of the at least two injection elements are formed by the ratio of an inlet throttle / inlet throttle member of the respective injection element and / or by the opening pressure of an injector of the respective injection element.   5) Method according to claim 1, characterized in that the first correction function is recorded intermediate way in a control apparatus of the internal combustion engine in the form of a correction matrix.   6) Process according to claim 1, characterized in that the individual characteristic values obtained from the at least two injection elements in the form of a control code are transmitted to a control apparatus of the internal combustion engine.   7) Control device of an injection system of an internal combustion engine equipped with at least two injection elements, wherein the fuel dosage is distributed between a first partial injection and at least a second partial injection , with means provided for correcting the control signal defining the quantity of fuel to be injected as a function of a pressure wave influence on the at least two partial injections, characterized by means for effecting a collective correction of the pressure for the at least two injection elements and for determining a first correction function, means for capturing individual characteristic quantities of the at least two injection elements, and means for converting the first correction function to the using the individual characteristic quantities entered from the at least two injection elements into a second correction function using the e of which the control of the at least two injection elements from the point of view of the pressure wave is corrected.   8) Device according to claim 7, characterized in that the conversion means of the first correction function produce an amplitude scaling or amplitude modulation of the first correction function.   9) Device according to claims 7 or 8,   characterized in that the means for capturing individual characteristic quantities of the at least two injection elements cooperate with means for effecting actual flow compensation for the at least two injection elements.   10) Device according to claim 7 or 8, characterized in that the means for capturing individual characteristic quantities of the at least two injection elements, cooperate with means which provide-the report output throttle body / body the inlet restriction of the respective injection element and / or the opening pressure of an injector of the respective injection element.   11) Device according to one of claims 7 to 10, characterized by intermediate storage means of the first correction function in the form of a correction matrix in the control apparatus of the internal combustion engine.