EP2006521A1 - Method for controlling rail pressure during a starting process - Google Patents

Abstract

The method involves activating an adjustment after starting an internal combustion engine (1) when recognizing a negative offset with a subsequent positive offset of a target-rail pressure (pCR), and a correcting variable is temporarily changed in the sense of a larger fuel conveying amount by the adjustment. An offset is computed from the target-rail pressure and an actual-rail pressure. The correcting variable for the pressure admission of a suction throttle (4) is computed from the offset over a pressure control valve. A conveyed fuel amount is determined over the throttle.

Description

The invention relates to a method for regulating the rail pressure in an internal combustion engine with a common rail system during the starting process according to the preamble of claim 1.

To achieve a high injection quality and a low pollutant emissions of the rail pressure is controlled in an internal combustion engine with a common rail system. A corresponding control circuit is from the DE 103 30 466 B3 in which the actual rail pressure is calculated from the measured raw values of the rail pressure and compared with the desired rail pressure, the reference variable. From the resulting control deviation calculated by a pressure regulator as a manipulated variable a volume flow, which is then limited and converted into a PWM signal. With the PWM signal, the solenoid of a suction throttle is then applied. About the suction throttle, the flow is influenced by a low pressure to a high pressure pump, the latter promotes the fuel in the rail under pressure increase. In this control circuit, the two pumps, the suction throttle and the rail correspond to the controlled system. The not previously published German patent application with the official file number DE 10 2006 049 266.8 shows the same control circuit with the specification that the volume flow is converted via a pump curve into a nominal electrical current, which is then the input to the PWM calculation.

• Zur Berechnung des PWM-Signals wird der elektrische Soll-Strom mit dem ohmschen Widerstand der Saugdrossel-Spule und der Leitung multipliziert. Die Saugdrossel wird in negativer Logik angesteuert, das heißt, diese ist stromlos offen. Bei vollständig geöffneter Saugdrossel gelangt der von der Niederdruckpumpe geförderte Volumenstrom ungedrosselt zur Hochdruckpumpe. Wird die Saugdrossel bestromt, so verschließt diese die Kraftstoffleitung. Um ein sicheres Absteuern, also ein vollständiges Verschließen der Kraftstoffleitung zu gewährleisten, muss der ohmsche Widerstand der Saugdrossel-Spule und der Leitung als maximal vorgegeben werden. Der maximale Wert des Widerstands ergibt sich bei maximaler Temperatur der Saugdrossel. Bei einem zulässigen Temperaturbereich von zum Beispiel -20 °C bis 120 °C ändert sich der ohmsche Widerstand der Saugdrossel von circa 2 Ohm auf 4 Ohm, also um 100%. Um den Hochdruck bei allen möglichen Umgebungsbedingungen sicher absteuern zu können, muss im elektronischen Steuergerät der maximale Festwert von 4 Ohm abgelegt werden. Bei kalten Temperaturen verursacht dies jedoch eine Fehlberechnung, da bei tatsächlichem kleinem Widerstand ein zu großes PWM-Signal berechnet wird und daher die Saugdrossel in Richtung der Schließstellung gesteuert wird. Beim Starten der Brennkraftmaschine in kalter Umgebung bewirkt dies, dass der Ist-Raildruck nach dem ersten Überschwingen (negative Regelabweichung) unter den Soll-Raildruck abfällt (positive Regelabweichung) und immer mehr abnimmt, bis der Öffnungsdruck der Injektordüsen unterschritten wird und ein Abstellen der Brennkraftmaschine verursacht wird.

In practice, the following problem may arise with this pressure control loop during startup:

• To calculate the PWM signal, the setpoint electrical current is multiplied by the ohmic resistance of the suction inductor coil and the cable. The suction throttle is controlled in negative logic, that is, it is normally open. When the intake throttle is fully open, the volume flow delivered by the low-pressure pump flows unthrottled to the high-pressure pump. If the suction throttle is energized, this closes the fuel line. To a safe Absteuern, so a complete closing the To ensure fuel line, the ohmic resistance of the suction throttle coil and the line must be specified as maximum. The maximum value of the resistance results at maximum temperature of the suction throttle. At a permissible temperature range of, for example, -20 ° C to 120 ° C, the ohmic resistance of the suction throttle changes from approximately 2 ohms to 4 ohms, ie by 100%. In order to safely control the high pressure in all possible ambient conditions, the maximum value of 4 Ohms must be stored in the electronic control unit. At cold temperatures, however, this causes a miscalculation, since an actual small resistance is calculated to a large PWM signal and therefore the suction throttle is controlled in the direction of the closed position. When starting the engine in a cold environment, this causes the actual rail pressure after the first overshoot (negative control deviation) drops below the target rail pressure (positive control deviation) and decreases more and more until the opening pressure of the injector nozzles falls below and stopping the engine is caused.

This problem can be solved by the rail pressure control loop is a current control of the coil current is superimposed, as for example from the DE 10 2004 061 474 A1 is known for the control circuit described above. Due to the additional hardware, however, this solution is expensive.

From the DE 101 56 637 C1 Although a method for controlling and regulating the starting operation of an internal combustion engine is known, the aim of the method, however, is to suppress pressure oscillations by preventing oscillation between the control and regulating operation. With regard to the problem described above, no further information can be found from the reference.

The invention is based on the object, with little additional effort to make sure the starting process.

The object is solved by the features of the first claim. The embodiments are shown in the subclaims.

After the engine is started, it is first checked whether an adaptation-triggering event occurs. The triggering event is a detected negative control deviation with subsequent positive control deviation of the rail pressure, that is, the is-rail pressure initially swings beyond the desired rail pressure and then subverts the again Set rail pressure. Upon detection of the triggering event, the adaptation is activated, via which the manipulated variable is temporarily changed in the sense of a larger flow rate. This is done by either changing the manipulated variable indirectly via the change in the controller components or directly the desired electrical current or the PWM signal. The controller components are changed via a proportional coefficient to determine a P component and / or a reset time to determine an I component of the pressure regulator. For the calculation, adaptation characteristics for the proportional coefficient, the integral time, the nominal current and the PWM signal are provided. To increase the reliability, the adaptation is deactivated and locked until the restart of the internal combustion engine when the control deviation is less than a limit.

The adaptation compensates for the temperature dependence of the suction throttle resistance without additional sensors. The high pressure control is thus more robust against temperature fluctuations. In practice, a shutdown of the internal combustion engine at engine start no longer occurs.

Fig. 1

ein Systemschaubild,

Fig. 2

ein Blockschaltbild des Regelkreises mit Adaption,

Fig. 3

eine Kennlinie,

Fig. 4

eine Kennlinie,

Fig. 5A-5H

einen Startvorgang als Zeitdiagramm,

Fig. 6

einen Programm-Ablaufplan und

Fig. 7

einen Unterprogramm-Ablaufplan.

In the drawings, a preferred embodiment is shown. Show it:

Fig. 1

a system diagram,

Fig. 2

a block diagram of the control loop with adaptation,

Fig. 3

a characteristic

Fig. 4

a characteristic

Fig. 5A-5H

a start process as a time diagram,

Fig. 6

a program schedule and

Fig. 7

a subprogram schedule.

The FIG. 1 shows a system diagram of an internal combustion engine 1 with common rail system. The common rail system has the following components: a low-pressure pump 3 for conveying fuel from a fuel tank 2, a variable intake throttle 4 for influencing the fuel volume flow flowing through, a high-pressure pump 5 for conveying the fuel with pressure increase, a rail 6, (optional) individual storage 7 for storing the fuel and injectors 8 for injecting the fuel into the combustion chambers of the internal combustion engine. 1

The operation of the internal combustion engine 1 is determined by an electronic control unit (ADEC) 10. The electronic control unit 10 includes the usual components of a microcomputer system, such as a microprocessor, I / O devices, buffers and memory devices (EEPROM, RAM). In the memory modules relevant for the operation of the internal combustion engine 1 operating data in maps / curves are applied. About this calculates the electronic control unit 10 from the input variables, the output variables. In FIG. 1 the following input variables are exemplarily shown: the rail pressure pCR, which is measured by means of a rail pressure sensor 9, an engine speed nMOT, a signal START for activating the internal combustion engine 1 by the operator and an input quantity EIN. For example, the input variable ON summarizes the charge air pressure of the turbocharger and the temperatures of the coolant / lubricant and of the fuel.

In FIG. 1 are shown as output variables of the electronic control unit 10 is a signal PWM for controlling the suction throttle 4, a signal ve for controlling the injectors 8 and an output variable OFF. The output variable OFF is representative of the further control signals for controlling and regulating the internal combustion engine 1, for example for a control signal for activating a second exhaust gas turbocharger in a register charging.

In FIG. 2 a pressure control loop is shown. The input variables are a nominal rail pressure pCR (SL) as a reference variable, the engine speed nMOT and input variables E1 to E3. The output quantity corresponds to the raw value of the rail pressure pCR, which represents the controlled variable. From the raw value of the rail pressure pCR, an actual rail pressure pCR (IST) is determined by means of a filter 17. This is compared with the set point pCR (SL) at a summation point, resulting in a control deviation ep. From the control deviation ep, a manipulated variable is calculated by means of a pressure regulator 11. Typically, the pressure regulator 11 is designed as a PIDT1 controller. The manipulated variable corresponds to a volume flow VR. The physical unit of the volume flow is liters / minute. Optionally, it is provided that the calculated nominal consumption is added to the volume flow VR. The volume flow VR corresponds to the input variable for a limit 12. The limit 12 can be speed-dependent, input variable nMOT. The output of the boundary 12 corresponds to a desired volume flow VSL, which via a pump curve 13 a electrical target current iSL is assigned. At a point A, the target current iSL is multiplied by the input E1. The input value E1 stands for the ohmic resistance of the suction throttle coil and the cable. This calculated voltage value is converted via a function block calculation PWM signal 14 into a PWM signal PWM. During conversion, fluctuations in the operating voltage are taken into account as input quantity E2. With the PWM signal PWM then the controlled system 15 is acted upon. This consists of the suction throttle with high-pressure pump, reference numeral 16, and the rail 6 with the (optional) individual memories. The path of the magnetic core of the intake throttle is changed via the PWM signal, whereby the delivery flow of the high-pressure pump is influenced freely. The Saudrossel is controlled in negative logic, that is, this is completely open when de-energized. The input quantity E3 is representative of the engine speed nMOT and the form provided by the low-pressure pump 3. From the rail 6 and the individual memories 7, a consumption volume flow V3 is discharged via the injectors 8. This closes the control loop.

The invention now provides that the control loop is supplemented by a function block 18 for calculating the indirect adaptation or a calculation 21 for determining the current adaptation value di or a calculation 22 for determining a PWM adaptation value dPWM. About the function block 18, the controller shares and thus the manipulated variable are changed indirectly. The manipulated variable is changed directly via the calculation 21 or calculation 22. A calculation 19 for determining a proportional adaptation value dkp and a calculation 20 for determining an adjustment time adaptation value dTn are combined in the function block 18. The two calculations 19 and 20 may alternatively or together be arranged in the function block 18.

To illustrate the indirect adaptation by means of the function block 18, the proportional adaptation value dkp is determined via the calculation 19 as a function of the control deviation ep and an input variable E4 via a characteristic curve ADAP1, which is shown in FIG FIG. 3 is shown. The input quantity E4 includes the engine speed nMOT, two limit values of the system deviation and one sampling time. At a point C, the proportional adaptation value dkp is added with a constant value K1. The result corresponds to the proportional coefficient kp. The P component of the pressure regulator 11 is then calculated from the proportional coefficient kp and the control deviation ep. About the calculation 20 is dependent on the control deviation ep and a Input quantity E5 of the reset time adaptation value dTn via a characteristic curve ADAP2, which is determined in the FIG. 4 is shown. The input quantity E5 includes the engine speed nMOT, two limit values of the control deviation and the sampling time. At a point D, the reset time adaptation value dTn is added with a constant value K2. The result corresponds to the reset time Tn.

To illustrate the immediate adaptation, in a first embodiment, via the calculation 21, the current adaptation value di is determined as a function of the control deviation ep and an input variable E6 via the characteristic curve ADAP2 FIG. 4 , calculated. The input quantity E6 includes the engine speed nMOT, two limit values of the control deviation and the sampling time. At a point E, the desired current iSL calculated via the pump characteristic 13 and the current adaptation value di are added. Subsequently, the sum at the point A is multiplied by the input quantity E1, that is to say the ohmic resistance. In a second embodiment, via the calculation 22, the PWM adaptation value dPWM as a function of the control deviation ep and an input variable E7 via the characteristic curve ADAP2, see FIG FIG. 4 , calculated. The input quantity E7 includes the engine speed nMOT, two limit values of the control deviation and the sampling time. At a point B, the PWM value determined via the PWM calculation 14 and the PWM adaptation value dPWM are added.

The functionality of FIG. 2 is that after an adaptation-triggering event has been detected, the manipulated variable for acting on the intake throttle is changed either directly or indirectly in the sense of a larger allowable delivery. The indirect change takes place via the proportional coefficient kp and / or the readjustment time Tn. The immediate change takes place via the current adaptation value di or the PWM adaptation value dPWM. The adaptation-triggering event occurs when, after the engine has started, the actual rail pressure pCR (IST) oscillates beyond the desired rail pressure pCR (SL) and then undershoots the latter.

The FIG. 3 shows the characteristic ADAP1, via which a control deviation ep is assigned a proportional adaptation value dkp. The characteristic curve ADAP1 is composed of a first straight line section identical to the abscissa, a second straight leg section with a positive gradient and a third straight line section parallel to the abscissa. In a range from the coordinate origin to the first limit value GW1, the control deviation ep is assigned a proportional adaptation value dkp of zero via the first straight line section. In the area between the first Limit value GW1 and the second limit value GW2 is assigned to an increasing control deviation ep an increasing proportional adaptation value dkp, for example the control deviation ep1 via the point A, the positive value dkp1. Instead of the rising straight line section, other mathematical functions (parabola, hyperbola) can also be provided. In the range above the second limit value GW2, the control deviation ep is always assigned the same maximum value MAX.

The FIG. 4 shows the characteristic ADAP2, via which a control deviation ep the reset time adaptation value dTn or the current adaptation value di or the PWM adaptation value dPWM is assigned. The characteristic ADAP2 consists of a first straight line section identical to the abscissa, a second straight leg section with a negative slope and an abscissa-parallel third straight line section. For example, a control deviation ep1 is assigned the value MIN via the third straight line section, point B. In practice, the characteristic ADAP2 for the different adaptation values (dTn, di, dPWM) can be implemented differently with respect to the limit values as well as the slope. Instead of the second straight line section, another mathematical function, for example parabola or hyperbola, can also be provided.

In the FIG. 5 a start and a stop process are shown. The FIG. 5 consists of the subfigures 5A to 5H. These show in each case over time: the engine speed nMOT ( FIG. 5A ), the rail pressure pCR ( FIG. 5B ), a status signal motor ON ( FIG. 5C ), a status signal of a first flag Mneg ( FIG. 5D ), a status signal of a second flag Mpos ( FIG. 5E ), a signal adaptation ( FIG. 5F ), the course of the proportional coefficient kp ( FIG. 5G ) and the course of the reset time Tn ( FIG. 5H ). In both FIGS. 5A and 5B two case studies are shown. The dashed line indicates a course according to the prior art. The solid line indicates a course according to the invention. In the further explanation, a constant target rail pressure pCR (SL) of 600 bar is assumed, which is shown as a dot-dash line in FIG FIG. 5B is drawn.

• Zum Zeitpunkt t0 wird der Startvorgang durch Bestromung des Anlassers aktiviert. Die Kurbelwelle der Brennkraftmaschine beginnt sich zu drehen. Es erfolgt jedoch noch keine Einspritzung. Nach dem Zeitpunkt t0 erhöht sich die Motordrehzahl nMOT, bis sie eine Anlasserdrehzahl n1 erreicht. Zum Zeitpunkt t1 erreicht die Motordrehzahl nMOT eine Drehzahlschwelle bei der das Drehzahlsignal vom Drehzahlsensor sicher erfasst werden kann. Das Signal Motor AN wird dann auf 1 gesetzt, siehe Figur 5C. Da die Hochdruckpumpe 5 mechanisch mit der Kurbelwelle verbunden ist, beginnt diese mit dem Drehen der Kurbelwelle den Kraftstoff in das Rail zu fördern. Hierdurch vergrößert sich der Raildruck pCR. Zum Zeitpunkt t2 ist die Synchronisierung abgelaufen, so dass die Einspritzung in die Brennräume der Brennkraftmaschine beginnt. Hierdurch vergrößert sich die Drehzahl nMOT der Brennkraftmaschine in Richtung des Leerlauf-Drehzahlniveaus von 600 Umdrehungen. Zum Zeitpunkt t3 überschreitet die Motordrehzahl nMOT das Leerlauf-Drehzahlniveau und schwingt über dieses hinaus. Der Grund hierfür ist die Reaktionszeit des Drehzahl-Regelkreises. Zum Verlauf der Motordrehzahl nMOT korrespondiert der Verlauf des Ist-Raildrucks pCR(IST), welcher im Zeitraum t2 bis t3 ebenfalls stark zunimmt und danach über das Soll-Raildruckniveau von 600 bar hinausschwingt. Da nunmehr der Ist-Raildruck pCR(IST) größer als der Soll-Raildruck pCR(SL) ist, liegt eine negative Regelabweichung ep vor. Auf Grund der negativen Regelabweichung ep reduziert der Druckregler die Stellgröße, wodurch die Saugdrossel in Richtung ihrer Schließstellung gesteuert wird. Da nunmehr von der Hochdruckpumpe weniger Kraftstoff gefördert wird, verringert sich der Ist-Raildruck pCR(IST) bis dieser nach dem Zeitpunkt t4 den Soll-Raildruck pCR(SL) unterschwingt. Auf Grund der niedrigen Umgebungstemperatur ist der ohmsche Widerstand der Saugdrossel-Spule geringer als der im elektronischen Steuergerät abgelegte Festwert. Dies führt dazu, dass für den Soll-Strom iSL und das PWM-Signal PWM zu kleine Werte berechnet werden. Als Folge wird der Durchlaufquerschnitt der Saugdrossel zu klein eingestellt. Dadurch wird durch die Hochdruckpumpe 5 weniger Kraftstoff in das Rail gefördert, wodurch der Ist-Raildruck pCR(IST) weiter sinkt. Beispielsweise sinkt nach dem Zeitpunkt t5 der Ist-Raildruck pCR(IST) unter das Druckniveau von 580 bar mit fallender Tendenz. Zum Zeitpunkt t6 fällt der Ist-Raildruck pCR(IST) unter den Öffnungsdruck der Injektoren, beispielsweise 300 bar. Die Injektoren können nun keinen Kraftstoff mehr in die Brennräume der Brennkraftmaschine einspritzen, wodurch ein Abstellen der Brennkraftmaschine bewirkt wird, siehe hierzu Figur 5A.

The process according to the prior art (dashed line) at low ambient temperature proceeds as follows:

• At time t0, the starting process is activated by energizing the starter. The crankshaft of the engine starts to rotate. It still happens no injection. After the time t0, the engine speed nMOT increases until it reaches a starter speed n1. At time t1, the engine speed nMOT reaches a speed threshold at which the speed signal from the speed sensor can be reliably detected. The signal motor ON is then set to 1, see FIG. 5C , Since the high-pressure pump 5 is mechanically connected to the crankshaft, this starts with the rotation of the crankshaft to promote the fuel in the rail. This increases the rail pressure pCR. At time t2, the synchronization has expired, so that the injection into the combustion chambers of the internal combustion engine begins. This increases the speed nMOT of the internal combustion engine in the direction of the idle speed level of 600 revolutions. At time t3, the engine speed nMOT exceeds and ramps beyond the idle speed level. The reason for this is the reaction time of the speed control loop. The profile of the actual rail pressure pCR (IST) corresponds to the course of the engine speed nMOT, which also increases sharply in the period t2 to t3 and then oscillates beyond the target rail pressure level of 600 bar. Since now the actual rail pressure pCR (IST) is greater than the target rail pressure pCR (SL), there is a negative control deviation ep. Due to the negative control deviation ep, the pressure regulator reduces the manipulated variable, whereby the suction throttle is controlled in the direction of its closed position. Since less fuel is now conveyed by the high-pressure pump, the actual rail pressure pCR (IST) is reduced until it drops below the set rail pressure pCR (SL) after time t4. Due to the low ambient temperature, the ohmic resistance of the suction throttle coil is lower than the fixed value stored in the electronic control unit. As a result, too small values are calculated for the desired current iSL and the PWM signal PWM. As a result, the flow area of the suction throttle is set too small. As a result, less fuel is conveyed into the rail by the high-pressure pump 5, as a result of which the actual rail pressure pCR (IST) continues to drop. For example, after the time t5, the actual rail pressure pCR (IST) drops below the pressure level of 580 bar with decreasing tendency. At time t6, the actual rail pressure pCR (IST) drops below the opening pressure of the injectors, for example 300 bar. The injectors can no longer inject fuel into the combustion chambers of the internal combustion engine, whereby a shutdown of the internal combustion engine is effected, see FIG. 5A ,

• Nach dem Motorstart wird geprüft, ob eine negative Regelabweichung (ep<0) festgestellt wird. In der Praxis wird hierzu die Regelabweichung ep mit einem Grenzwert verglichen, zum Beispiel-10bar. Dies ist nach dem Zeitpunkt t3 der Fall, da der Ist-Raildruck pCR(IST) über den Soll-Raildruck pCR(SL) hinausschwingt. Mit Erkennen des Überschwingens des Ist-Raildrucks pCR(IST) über den Soll-Raildruck pCR(SL) wird der erste Merker Mneg gesetzt. In der Figur 5D wechselt dessen Status von Null nach Eins. Anschließend wird geprüft, ob eine positive Regelabweichung (ep>0) vorliegt. In der Praxis wird hierzu die Regelabweichung ep mit einem Grenzwert verglichen, zum Beispiel +10bar. Dies ist nach dem Zeitpunkt t4 der Fall. Mit Erkennen des Unterschwingens des Ist-Raildrucks pCR(IST) unter den Soll-Raildruck pCR(SL) wird der zweite Merker Mpos gesetzt. In der Figur 5E wechselt dessen Status von Null nach Eins. Ein Überschwingen des Ist-Raildrucks pCR(IST) mit anschließendem Unterschwingen des Ist-Raildrucks pCR(IST) wird als adaptionsauslösendes Ereignis interpretiert und daher die Adaption aktiviert. In der Figur 5F wechselt daher deren Status von Null nach Eins. Mit Aktivierung der Adaption wird die Stellgröße temporär im Sinne einer größeren Fördermenge verändert. Beim dargestellten Beispiel wird die Stellgröße über den Proportional-Beiwert kp (Fig. 5G) und die Nachstellzeit Tn (Fig. 5H) verändert. Die Veränderung dieser Reglerparameter erfolgt bei gesetzter Adaption über die Kennlinie ADAP1 der Figur 3 und die Kennlinie ADAP2 der Figur 4. Die aus der Adaption resultierenden Verläufe der beiden Reglerparameter sind im Zeitraum t5 bis t7 in den beiden Figuren 5G und 5H dargestellt. Beendet wird die Adaption, wenn die Regelabweichung ep wieder Null beträgt. Dies ist zum Zeitpunkt t8 der Fall. In der Figur 5F wird daher der Status der Adaption von Eins auf Null zurückgesetzt. Zum Zeitpunkt t9 wird die Brennkraftmaschine abgestellt, wodurch die Motordrehzahl nMOT in der Figur 5A abfällt. Zur Erhöhung der Betriebssicherheit bleibt die Adaption solange verriegelt, bis ein Motorstillstand erkannt wird. Ein Motorstillstand wird erkannt, wenn die Motordrehzahl nMOT während eines vorgebbaren Zeitraums, zum Beispiel 2.5 Sekunden, kleiner als 80 1/min wird. Mit Erkennen dieser Bedingung, Zeitpunkt t10, werden die beiden Merker und das Signal Motor AN auf Null gesetzt.

The process according to the invention (solid line) proceeds as follows:

• After the engine is started, it is checked whether a negative control deviation (ep <0) is detected. In practice, the control deviation ep is compared with a limit value, for example -10 bar. This is the case after time t3, since the actual rail pressure pCR (IST) oscillates beyond the setpoint rail pressure pCR (SL). Upon detection of the overshoot of the actual rail pressure pCR (IST) via the setpoint rail pressure pCR (SL), the first flag Mneg is set. In the FIG. 5D its status changes from zero to one. Then it is checked whether there is a positive control deviation (ep> 0). In practice, the control deviation ep is compared with a limit value, for example + 10 bar. This is the case after time t4. Upon detection of the undershoot of the actual rail pressure pCR (IST) below the target rail pressure pCR (SL), the second flag Mpos is set. In the FIG. 5E its status changes from zero to one. An overshoot of the actual rail pressure pCR (IST) with subsequent undershooting of the actual rail pressure pCR (IST) is interpreted as an adaptation-triggering event and therefore the adaptation is activated. In the FIG. 5F therefore their status changes from zero to one. When the adaptation is activated, the manipulated variable is temporarily changed in the sense of a larger delivery rate. In the example shown, the manipulated variable is calculated via the proportional coefficient kp ( Fig. 5G ) and the reset time Tn ( Fig. 5H ) changed. The change of these controller parameters takes place with set adaptation via the characteristic ADAP1 of the FIG. 3 and the characteristic ADAP2 of the FIG. 4 , The resulting from the adaptation curves of the two controller parameters are in the period t5 to t7 in the two Figures 5G and 5H shown. The adaptation ends when the control deviation ep is zero again. This is the case at time t8. In the FIG. 5F Therefore, the status of the adaptation is reset from one to zero. At time t9, the engine is turned off, whereby the engine speed nMOT in the FIG. 5A drops. To increase operational safety, the adaptation remains locked until a motor standstill is detected. An engine stall is detected when the engine speed nMOT becomes less than 80 rpm for a predetermined period of time, for example 2.5 seconds. Upon detection of this condition, time t10, the two flags and the signal motor ON are set to zero.

The comparison of the two curves of the actual rail pressure pCR (IST) according to the prior art (dashed line) and according to the invention (solid line) clearly shows that the actual rail pressure pCR (IST) is less when using the adaptation after engine start drops, whereby a shutdown of the internal combustion engine is prevented.

In the FIG. 6 a program flow chart is shown. After the program start, the two markers, the adaptation and the motor AN are initialized with the value zero. At S1 it is checked whether the signal engine AN is equal to one, that is, whether the internal combustion engine is running. If this is not the case, the program path is traversed with the steps S13 and S14, otherwise the program part is traversed with the steps S2 to S11.

If the test at S1 indicates that the signal motor ON is not set, result S1: no, it is checked at S13 whether the engine speed nMOT is greater than / equal to a limit value GW, for example 80 rpm. If this is not the case, result S13: no, then this program part is finished. If, on the other hand, it is determined that the engine speed nMOT is greater than or equal to the limit value GW, result S13: yes, the signal motor ON is set at S14 and this program part is left. If the check at S1 indicates that the signal motor ON is set, result S1: yes, then S2 checks whether the adaptation is activated. If this has not yet been activated, result S2: no, then in S12 a subroutine Check Adaptation is branched, which in the FIG. 7 is shown and explained in connection with this. If the check in S2 indicates that the adaptation has already been activated, result S2: yes, then the manipulated variable is indirectly changed in S3 via the proportional coefficient kp and / or the reset time Tn or directly via the nominal electrical current or the PWM signal. At S4, it is checked whether the control deviation ep is smaller than a limit value ep3, for example -10 bar. If this is not the case, result S4: no, the program will continue at point A. If the test at S4 shows that the control deviation is smaller than the limit value ep3, the adaptation is deactivated at S5 and then it is checked at S6 whether the engine speed nMOT is less than a limit value GW, for example 80 rpm. If this is not the case, result S6: no, a time step t is set to zero at S15 and the program is ended. If the check at S6 reveals that the engine speed nMOT is less than the limit value GW, result S6: yes, the time step t is incremented by a time dt at S7. Thereafter, their current status is checked at S8. If the time step t is smaller than a limit value GW, the program is ended. If the test at S8 reveals that the time step t is greater than or equal to the limit value GW, result S8: yes, the two flags Mpos, Mneg and the signal motor ON are set to zero at S9, S10 and S11. This completes the program run.

In the FIG. 7 a subroutine is shown, which checks whether the adaptation is activated. At S1 it is checked whether the first flag Mneg is set. If this is not the case, result S1: no, then at S7 the control deviation ep is compared with a limit value ep1, for example -10 bar, and either this program part is left, result S7: no, or at S8 the first flag Mneg is set to one set and then to the main program of FIG. 6 , Point A returned. If the check at S1 indicates that the first flag Mneg is set, result S1: yes, the status of the second flag Mpos is checked at S2. If this is already set to one, result S2: yes, then this program part is terminated and it becomes the main program of the FIG. 6 , Point A returned. If, on the other hand, the test at S2 shows that the second flag Mpos has not yet been set, result S2: no, the control deviation ep is compared with a limit value ep2, for example +10 bar, at S3. If this is not greater than the limit value ep2, this program part is left and the main program of the FIG. 6 , Point A returned. If the check at S3 shows that the control deviation ep is greater than the threshold value ep2, result S3: yes, the second flag Mpos is set to one at S4 and the adaptation is activated at S5. At S6, the manipulated variable is then changed in the sense of a larger flow rate. Thus the subroutine is finished and it becomes the main program of the FIG. 6 , Point A, returned.

• die Temperaturabhängigkeit des Saugdrossel-Widerstands wird kompensiert, ohne dass eine Erweiterung der Elektronik-Hardware erforderlich ist;
• Beim Startvorgang wird ein zu starkes Absinken des Ist-Raildruck verhindert, wodurch die Hochdruckregelung robuster gegenüber Temperaturschwankungen ist;
• Ein unbeabsichtigtes Abstellen der Brennkraftmaschine beim Motorstart tritt in der Praxis nicht mehr auf.

From the previous description, the following advantages result for the adaptation according to the invention:

• the temperature dependence of the Saugdrossel resistance is compensated, without an expansion of the electronics hardware is required;
• During the starting process, an excessive drop in the actual rail pressure is prevented, whereby the high pressure control is more robust to temperature fluctuations;
• An inadvertent shutdown of the engine when starting the engine no longer occurs in practice.

reference numeral

1

Internal combustion engine

2

Fuel tank

3

Low pressure pump

4

interphase

5

high pressure pump

6

Rail

7

Single memory

8th

injector

9

Rail pressure sensor

10

electronic control unit (ADEC)

11

pressure regulator

12

limit

13

Pump curve

14

Calculation PWM signal

15

controlled system

16

Suction choke with pump

17

filter

18

Function block for calculating the indirect adaptation

19

Calculation dkp

20

Calculation dTn

21

Calculation di

22

Calculation dPWM

Claims (8)

Method for regulating the rail pressure (pCR) in an internal combustion engine (1) with a common rail system during the starting process, in which a control deviation (ep) from a desired rail pressure (pCR (SL)) and an actual rail pressure (pCR (IST) ) is calculated, in which from the control deviation (ep) via a pressure regulator (11) a manipulated variable for acting on a suction throttle (4) is calculated and in which via the suction throttle (4) the subsidized fuel quantity is set,
characterized,
that an adaptation is activated after the engine has started upon detection of a negative control deviation with subsequent positive control deviation of the rail pressure (pCR), via which the control variable is temporarily changed in the sense of a larger flow rate. Method according to claim 1,
characterized,
that the manipulated variable is indirectly changed via the change of the controller components (PI) or directly. Method according to claim 2,
characterized,
that, when the adaptation is activated, the P component of the pressure regulator (11) is changed by means of a proportional coefficient (kp) and / or the I component of the pressure regulator (11) over a readjustment time (Tn). Method according to claim 3,
characterized,
in that the proportional coefficient (kp) is calculated as a function of a proportional adaptation value (dkP) and the reset time (Tn) as a function of a reset time adaptation value (dTn). Method according to claim 2,
characterized,
that the manipulated variable is changed directly by changing a desired electrical current (iSL) or a PWM signal (PWM). Method according to claim 5,
characterized,
in that the desired electrical current (iSL) is changed via a current adaptation value (di) and the PWM signal via a PWM adaptation value (dPWM). Method according to one of the preceding claims,
characterized,
in that the proportional adaptation value (dkp), the reset time adaptation value (dTn), the current adaptation value (di) and the PWM adaptation value (dPWM) are calculated via an adaptation characteristic (ADAP1, ADAP2) as a function of the control deviation (ep). Method according to one of the preceding claims,
characterized,
that the adaptation is deactivated and locked until the restart of the internal combustion engine when the control deviation (ep) becomes negative.

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