EP2449242B1 - Control and regulation method of the fuel pressure of a common-rail of a combustion engine - Google Patents

Description

The invention relates to a method for controlling and regulating an internal combustion engine according to the preamble of claim 1.

In an internal combustion engine with a common rail system, the quality of the combustion is largely determined by the pressure level in the rail. The rail pressure is therefore regulated to comply with the statutory emission limit values. Typically, a rail pressure control circuit comprises a comparison point for determining a control deviation, a pressure regulator for calculating an actuating signal, the controlled system and a software filter for calculating the actual rail pressure in the feedback branch. The control deviation is calculated from a target rail pressure to the actual rail pressure. The controlled system includes the pressure actuator, the rail and the injectors for injecting the fuel into the combustion chambers of the internal combustion engine.

From the DE 197 31 995 A1 a common rail system with pressure control is known, in which the pressure regulator is equipped with different regulator parameters. The pressure control should be more stable due to the different controller parameters. The controller parameters in turn are calculated depending on operating parameters, here: the engine speed and the target injection quantity. Using the controller parameters, the pressure controller then calculates the control signal for a pressure control valve, via which the fuel outflow from the rail into the fuel tank is determined. The pressure control valve is consequently arranged on the high-pressure side of the common rail system. An electrical pre-feed pump or a controllable high-pressure pump are shown in this reference as alternative measures for pressure regulation.

Also the DE 103 30 466 B3 describes a common rail system with pressure control, in which the pressure regulator accesses a suction throttle via the control signal. About the Suction throttle in turn determines the inlet cross-section to the high pressure pump. The suction throttle is consequently arranged on the low pressure side of the common rail system. In addition, a passive pressure relief valve can be provided as a protective measure against excessive rail pressure in this common rail system. The fuel is then discharged from the rail into the fuel tank via the open pressure relief valve. A corresponding common rail system with a passive pressure relief valve is out of the DE 10 2006 040 441 B3 known.

Another fuel pressure control system is out DE 10 2007 059 352 B3 known.

Due to the design, a control and constant leakage occur in a common rail system. The control leakage is effective when the injector is controlled electrically, that is, during the duration of the injection. As the injection duration decreases, the control leakage also decreases. The constant leakage is always effective, that is, even if the injector is not activated. This is also caused by the component tolerances. Since the constant leakage increases with increasing rail pressure and decreases with falling rail pressure, the pressure vibrations in the rail are dampened. The opposite is true for tax leakage. If the rail pressure rises, the injection duration is shortened to display a constant injection quantity, which results in a decreasing control leakage. If the rail pressure drops, the injection duration is increased accordingly, which results in increasing control leakage. The control leakage means that the pressure vibrations in the rail are amplified. The control and constant leakage represent a loss volume flow, which is pumped and compressed by the high pressure pump. However, this loss volume flow means that the high-pressure pump must be designed larger than necessary. In addition, part of the drive energy of the high-pressure pump is converted into heat, which in turn heats up the fuel and reduces the efficiency of the internal combustion engine.

In practice, the components are cast together to reduce the constant leakage. However, reducing the constant leakage has the disadvantage that the stability behavior of the common rail system deteriorates and pressure control becomes more difficult. This becomes clear in the low-load range, because here the injection quantity, i.e. the volume of fuel withdrawn, is very small. This becomes just as clear with a load shedding from 100% to 0% load, since the injection quantity is reduced to zero here and therefore the rail pressure only slowly decreases again. This in turn causes a long settling time.

Starting from a common rail system with rail pressure control via a low-pressure suction throttle and with reduced constant leakage, the object of the invention is to optimize the stability behavior and the settling time.

This object is achieved by a method for controlling and regulating an internal combustion engine having the features of claim 1. The configurations are shown in the subclaims.

The method consists in that, in addition to the rail pressure control via the low-pressure suction throttle as the first pressure control element, a rail pressure disturbance variable for influencing the rail pressure is generated via a pressure control valve on the high pressure side as the second pressure control element. Fuel is diverted from the rail into a fuel tank via the pressure control valve on the high pressure side. An essential element of the invention therefore consists in that a constant leak is simulated via the control of the pressure control valve. The rail pressure disturbance variable is calculated on the basis of a corrected target volume flow of the pressure control valve, which in turn is calculated from a static target volume flow and a dynamic target volume flow.

The static target volume flow is calculated as a function of a target injection quantity, alternatively a target torque, and an engine speed using a target volume flow map. The target volume flow map is designed in such a way that a target volume flow with a positive value, for example 2 liters / minute, is calculated in a low-load range and a target volume flow of zero is calculated in a normal operating range. In the context of the invention, the low-load range is to be understood to mean the range of small injection quantities and thus small engine output.

The dynamic set volume flow of the pressure control valve is calculated via a dynamic correction depending on the set rail pressure and the actual rail pressure, by calculating a resulting control deviation and by setting the dynamic set volume flow to zero if the control deviation is less than zero . If, on the other hand, the resulting control deviation is greater than or equal to zero, the dynamic set volume flow is set to the value of the product of the resulting control deviation and a factor. In other words: The dynamic target volume flow is largely determined by the control deviation of the rail pressure. Is this is negative and falls below a limit value, for example in the event of a load shedding, the static target volume flow is corrected via the dynamic target volume flow. Otherwise there is no change in the static target volume flow.

Since the fuel is only discharged stationary in the low-load range and in small quantities, there is no significant increase in the fuel temperature and no significant reduction in the efficiency of the internal combustion engine. The increased stability of the rail pressure control circuit in the low-load range can be recognized from the fact that the rail pressure remains approximately constant in overrun mode and the rail pressure peak value is significantly lower when the load is shed. The increase in the rail pressure is counteracted via the dynamic set volume flow, with the advantage that the settling time of the system can be improved again.

Figur 1

ein Systemschaubild,

Figur 2

einen Raildruck-Regelkreis,

Figur 3

ein Blockschaltbild des Raildruck-Regelkreises mit Steuerung,

Figur 4

ein Blockschaltbild der dynamischen Korrektur,

Figur 5

einen Stromregelkreis,

Figur 6

einen Stromregelkreis mit Vorsteuerung,

Figur 7

ein Soll-Volumenstrom-Kennfeld,

Figur 8

ein Zeitdiagramm und

Figur 9

einen Programm-Ablaufplan.

A preferred exemplary embodiment is shown in the figures. Show it:

Figure 1

a system diagram,

Figure 2

a rail pressure control loop,

Figure 3

a block diagram of the rail pressure control circuit with control,

Figure 4

a block diagram of the dynamic correction,

Figure 5

a current control loop,

Figure 6

a current control loop with pilot control,

Figure 7

a target volume flow map,

Figure 8

a timing diagram and

Figure 9

a program schedule.

The Figure 1 shows a system diagram of an electronically controlled internal combustion engine 1 with a common rail system. The common rail system comprises the following mechanical components: a low-pressure pump 3 for conveying fuel from a fuel tank 2, a variable, low-pressure suction throttle 4 for influencing the fuel volume flow flowing through it, a high-pressure pump 5 for conveying the fuel while increasing the pressure, and a rail 6 for storing of the fuel and injectors 7 for injecting the fuel into the combustion chambers of the internal combustion engine 1. Optionally, the common rail system can also be designed with individual stores, in which case for example, an individual memory 8 is integrated in the injector 7 as an additional buffer volume. To protect against an impermissibly high pressure level in the rail 6, a passive pressure relief valve 11 is provided which, in the open state, controls the fuel from the rail 6. An electrically controllable pressure control valve 12 likewise connects the rail 6 to the fuel tank 2. A fuel volume flow is defined via the position of the pressure control valve 12 and is derived from the rail 6 into the fuel tank 2. In the further text, this fuel volume flow is referred to as rail pressure disturbance variable VDRV.

The operating mode of the internal combustion engine 1 is determined by an electronic control unit (ECU) 10. The electronic control unit 10 contains the usual components of a microcomputer system, for example a microprocessor, I / O modules, buffers and memory modules (EEPROM, RAM). The operating data relevant to the operation of the internal combustion engine 1 are applied in characteristic maps / characteristic curves in the memory modules. The electronic control unit 10 uses these to calculate the output variables from the input variables. In the Figure 1 The following input variables are shown as examples: the rail pressure pCR, which is measured by means of a rail pressure sensor 9, an engine speed nMOT, a signal FP for the power specification by the operator and an input variable IN. The other sensor signals are summarized under input variable IN, for example the charge air pressure of an exhaust gas turbocharger. In a common rail system with individual stores 8, the individual store pressure pE is an additional input variable of the electronic control unit 10.

In Figure 1 The output variables of the electronic control unit 10 are a signal PWMSD for controlling the suction throttle 4 as the first pressure control element, a signal ve for controlling the injectors 7 (start / end of spray), a signal PWMDV for controlling the pressure control valve 12 as the second pressure control element and an output variable OFF. The position of the pressure control valve 12 and thus the rail pressure disturbance variable VDRV is defined via the signal PWMDV. The output variable AUS represents the other actuating signals for controlling and regulating the internal combustion engine 1, for example an actuating signal for activating a second exhaust gas turbocharger when charging with a register.

In the Figure 2 a rail pressure control circuit 13 for regulating the rail pressure pCR is shown. The input variables of the rail pressure control circuit 13 are: a target rail pressure pCR (SL), a volume flow which characterizes the target consumption VVb, the engine speed nMOT, the PWM basic frequency fPWM and a variable E1. Size E1 includes, for example, the battery voltage and the ohmic resistance of the inductor with supply line, which are included in the calculation of the PWM signal. The output variables of the rail pressure control circuit 13 are the raw value of the rail pressure pCR, an actual rail pressure pCR (IST) and a dynamic rail pressure pCR (DYN). The actual rail pressure pCR (IST) and the dynamic rail pressure pCR (DYN) are in the in Figure 3 controller shown processed.

The actual rail pressure pCR (IST) is calculated from the raw value of the rail pressure pCR using a first filter 19. This is then compared with the setpoint pCR (SL) at a summation point A, which results in a control deviation ep. A pressure regulator 14 calculates its manipulated variable from the control deviation ep, which corresponds to a volume flow VR with the physical unit liter / minute. The calculated target consumption Wb is added to the volume flow VR at a summation point B. The target consumption VVb is calculated via a calculation 23, which is carried out in the Figure 3 is shown and explained in connection with this. The result of the addition at the summation point B corresponds to an unlimited target volume flow VSDu (SL) of the suction throttle. A limit 15 is then used to limit the unlimited set volume flow VSDu (SL) as a function of the engine speed nMOT. The output variable of the limitation 15 corresponds to a target volume flow VSD (SL) of the suction throttle. An electrical target current iSD (SL) of the suction throttle is then assigned to the target volume flow VSD (SL) via the pump characteristic curve 16. The target current iSD (SL) is converted into a PWM signal PWMSD in a calculation 17. The PWM signal PWMSD represents the duty cycle and the frequency fPWM corresponds to the basic frequency. The PWM signal PWMSD is then applied to the solenoid of the suction throttle. This changes the path of the magnetic core, which freely influences the flow rate of the high pressure pump. For safety reasons, the suction throttle is open when de-energized and is acted upon by the PWM control in the direction of the closed position. The calculation of the PWM signal 17 can be subordinated to a current control loop, such as this from the DE 10 2004 061 474 A1 is known. The high-pressure pump, the suction throttle, the rail and, if applicable, the individual stores correspond to a controlled system 18 Closed loop. From the raw value of the rail pressure pCR, the dynamic rail pressure pCR (DYN) is calculated via a second filter 20, which is one of the input variables of the block diagram of the Figure 3 is. The second filter 20 has a smaller time constant and a smaller phase delay than the first filter 19 in the feedback branch.

The Figure 3 shows as a block diagram the highly simplified rail pressure control circuit 13 of the Figure 2 and a controller 21. The rail pressure disturbance variable VDRV is generated via the controller 21, that is to say the volume flow which the pressure control valve controls from the rail into the fuel tank. The input variables of the controller 21 are: the target rail pressure pCR (SL), the actual rail pressure pCR (IST), the dynamic rail pressure pCR (DYN), the engine speed nMOT and the target injection quantity QSL. The target injection quantity QSL is either calculated via a map depending on the desired performance or corresponds to the manipulated variable of a speed controller. The physical unit of the target injection quantity is mm ³ / stroke. In the case of a torque-based structure, a target torque MSL is used instead of the target injection quantity QSL. The output variable of the controller 21 corresponds to the rail pressure disturbance variable VDRV.

Based on the engine speed nMOT and the target injection quantity QSL, the static target volume flow Vs (SL) for the pressure control valve is calculated via a target volume flow map 22 (3D map). The target volume flow map 22 is designed in such a way that a positive value of the static target volume flow Vs (SL) is calculated in the low load range, for example when idling, while in the normal operating range a static target volume flow Vs (SL) of Zero is calculated. A possible embodiment of the target volume flow map 22 is shown in FIG Figure 7 shown and explained in connection with this. The target consumption Wb, which is an input variable of the rail pressure control circuit 13, is also calculated on the basis of the engine speed nMOT and the target injection quantity QSL. The static desired volume flow Vs (SL) is corrected according to the invention by adding up a dynamic desired volume flow Vd (SL). The dynamic target volume flow Vd (SL) is calculated via a dynamic correction 24. The input variables of the dynamic correction 24 are the target rail pressure pCR (SL), the actual rail pressure pCR (IST) and the dynamic rail pressure pCR (DYN). The dynamic correction 24 is shown as a block diagram in FIG Figure 4 shown and described in connection with this. The sum of the static set volume flow Vs (SL) and dynamic Target volume flow Vd (SL) corresponds to a corrected target volume flow Vk (SL), which is limited by an upper limit 25 to a maximum volume flow VMAX and lower limit to the value zero. The maximum volume flow VMAX is calculated using a (2D) characteristic curve 26 as a function of the actual rail pressure pCR (IST). The output variable of the limitation 25 corresponds to a resulting target volume flow Vres (SL), which is one of the input variables of a pressure control valve map 27. The second input variable is the actual rail pressure pCR (IST). Via the pressure control valve map 27, the resulting set volume flow Vres (SL) and the actual rail pressure pCR (IST) are assigned a set current iDV (SL) of the pressure control valve. The target current iDV (SL) is converted via a PWM calculation 28 into the duty cycle PWMDV with which the pressure control valve 12 is activated. A current control, current control circuit 29, or a current control with feedforward control can be subordinate to the conversion. The current regulation is in the Figure 5 shown and explained in connection with this. The current control with pilot control is in the Figure 6 shown and explained in connection with this. The pressure control valve 12 is controlled with the PWM signal PWMDV. The electrical current iDV which arises at the pressure control valve 12 is converted into an actual current iDV (ACTUAL) via a filter 30 for current control and is fed back to the calculation PWM signal 28. The output signal of the pressure control valve 12 corresponds to the rail pressure disturbance variable VDRV, that is to say the fuel volume flow which is diverted from the rail into the fuel tank.

In the Figure 4 the dynamic correction 24 is off Figure 3 shown. The input variables are the target rail pressure pCR (SL), the actual rail pressure pCR (IST), the dynamic rail pressure pCR (DYN), a constant control deviation epKON and a constant factor fKON. The output quantity corresponds to the dynamic set volume flow Vd (SL). The set rail pressure pCR (SL) is assigned the limited control deviation epLIM via a characteristic curve 31. The value of the limited control deviation epLIM is negative. For example, a set rail pressure pCR (SL) = 2150 bar is assigned a limited control deviation epLIM = -100 bar via characteristic curve 31. A first switch S1 determines whether its output variable AG1 corresponds to the limited control deviation epLIM or the constant control deviation epKON. In switch position S1 = 1, AG1 = epLIM applies, while in switch position S1 = 2, AG1 = epKON applies. The constant control deviation can, for example, be set to the value epKON = -50 bar. On At a summation point A, the output variable AG1 is compared with the control deviation ep. The control deviation ep is calculated at a summation point B from the target rail pressure pCR (SL) and the actual rail pressure pCR (IST), alternatively from the dynamic rail pressure pCR (DYN). The selection is made via a second switch S2. In the first position S2 = 1, the actual rail pressure pCR (IST) is decisive for the calculation of the control deviation ep. In the second position S2 = 2, however, the dynamic rail pressure pCR (DYN) is decisive for the calculation of the control deviation ep. The difference calculated at summation point A corresponds to a resulting control deviation epRES. The resulting control deviation epRES is compared with the value zero via a comparator 32. If the resulting control deviation epRES is less than zero (epRES <0), a third switch S3 is set to position S3 = 2. In this case, the dynamic set volume flow Vd (SL) is zero (Vd (SL) = 0). If, on the other hand, the resulting control deviation epRES is greater than or equal to zero (epRES≥0), the third switch is switched to position S3 = 1. In this position S3 = 1, the dynamic set volume flow Vd (SL) is calculated by multiplying the resulting control deviation epRES by a factor f. The factor f in turn is determined by a fourth switch S4. If the fourth switch is in the position S4 = 1, then the factor f is via a characteristic curve 33 as a function of the actual rail pressure pCR (IST), switch S2 = 1, or as a function of the dynamic rail pressure pCR (DYN), switch S2 = 2, calculated. If, however, the fourth switch is in the position S4 = 2, the factor f is set to a constant value fKON, for example fKON = 0.01 liter / (min · bar).

• $$\mathrm{<figure-callout\; id="1"\; label="erster\; Schalter\; S"\; filenames="imgf0001.png,imgf0004.png"\; state="\{\{state\}\}">erster</figure-callout>}\mathrm{Schalter}\mathrm{S}\mathrm{}1=2\mathrm{mit}\mathrm{epKON}=-50\mathrm{bar},$$
  
• $$\mathrm{<figure-callout\; id="2"\; label="zweiter\; Schalter\; S"\; filenames="imgf0001.png,imgf0004.png"\; state="\{\{state\}\}">zweiter</figure-callout>}\mathrm{Schalter}\mathrm{S}\mathrm{}2=1\mathrm{mit}\mathrm{ep}=\mathrm{pCR}\left(\mathrm{SL}\right)-\mathrm{pCR}\left(\mathrm{IST}\right)$$
  
  und
• $$\mathrm{<figure-callout\; id="4"\; label="vierter\; Schalter\; S"\; filenames="imgf0001.png"\; state="\{\{state\}\}">vierter</figure-callout>}\mathrm{Schalter}\mathrm{S}\mathrm{}4=2\mathrm{mit}\mathrm{f}=\mathrm{fKON}=\mathrm{0,01}\mathrm{Liter}/\left(\min \cdot \mathrm{bar}\right).$$
  

The function of the dynamic correction 24 will be explained using an example. The following parameters were used:

• $$\mathrm{<figure-callout\; id="1"\; label="first\; counter\; S"\; filenames="imgf0001.png,imgf0004.png"\; state="\{\{state\}\}">first\; </figure-callout>}\mathrm{counter}\mathrm{S}\mathrm{}1=\mathrm{2nd}\mathrm{With}\mathrm{epKON}=-50\mathrm{bar},$$
  
• $$\mathrm{second}\mathrm{counter}\mathrm{S}\mathrm{2nd}=1\mathrm{With}\mathrm{ep}=\mathrm{pCR}\left(\mathrm{SL}\right)-\mathrm{pCR}\left(\mathrm{IS}\right)$$
  
  and
• $$\mathrm{fourth}\mathrm{counter}\mathrm{S}\mathrm{4th}=\mathrm{2nd}\mathrm{With}\mathrm{f}=\mathrm{fKON}=0.01\mathrm{liter}/\left(\min \cdot \mathrm{bar}\right).$$
  

If the control deviation is greater than -50 bar (ep> (- 50 bar)), the resulting control deviation epRES is less than zero (epRES <O). The third switch is thus set to position S3 = 2 via comparator 32, so that the dynamic set volume flow Vd (SL) = 0. However, the control deviation is less than / equal to -50 bar (eps (-50 bar)), then the resulting control deviation epRES> 0. The comparator 32 thus controls the third switch to the position S3 = 1. The dynamic target volume flow is now calculated as Vd (SL) = (- 50 bar-ep) · 0.01 liters / (min · bar).

A correction by means of the dynamic target volume flow Vd (SL) therefore takes place when the control deviation ep falls below the value ep = -50 bar. If the control deviation ep becomes even smaller (more negative), that is, if the actual rail pressure overshoots even more, the fuel volume flow controlled by the pressure control valve, i.e. the rail pressure disturbance variable, is increased via the dynamic set volume flow Vd (SL). This ultimately leads to the rail pressure being intercepted.

The Figure 5 shows a pure current control, which to the current control circuit 29 Figure 3 corresponds. The input variables are the target current iDV (SL) for the pressure control valve, the actual current iDV (IST) of the pressure control valve, the battery voltage UBAT and controller parameters (kp, Tn). The output variable is the PWM signal PWMDV, which is used to control the pressure control valve. From the target current iDV (SL) and the actual current iDV (IST), see Figure 3 , the current control deviation ei is first calculated. The current control deviation ei is the input variable of the current controller 34. The current controller 34 can be designed as a PI or PI (DT1) algorithm. The controller parameters are processed in the algorithm. These are characterized, among other things, by the proportional coefficient kp and the reset time Tn. The output variable of the current regulator 34 is a target voltage UDV (SL) of the pressure control valve. This is divided by the battery voltage UBAT and then multiplied by 100. The result corresponds to the duty cycle of the pressure control valve in percent.

The Figure 6 shows as an alternative to Figure 5 a current control with combined pilot control. The input variables are the target current iDV (SL), the actual current iDV (IST), the controller parameters (kp, Tn), the ohmic resistance RDV of the pressure control valve and the battery voltage UBAT. The output variable is also the PWM signal PWMDV, which is used to control the pressure control valve. First, the target current iDV (SL) is multiplied by the ohmic resistance RDV of the pressure control valve. The result corresponds to a pre-control voltage UDV (VS). The current control deviation ei is calculated on the basis of the target current iDV (SL) and the actual current iDV (IST). From the current control deviation ei, the current controller 34 then calculates the desired voltage UDV (SL) of the pressure control valve as a manipulated variable. The current controller 34 can also be designed here either as a PI or as a PI (DT1) controller. Then the target voltage UDV (SL) and the pilot voltage UDV (VS) are added, the sum then divided by the battery voltage UBAT and multiplied by 100.

In the Figure 7 The target volume flow map 22 is shown. This is used to determine the static target volume flow Vs (SL) for the pressure control valve. The input variables are the engine speed nMOT and the target injection quantity QSL. In the horizontal direction, engine speed values from 0 to 2000 1 / min are plotted. The nominal injection quantity values from 0 to 270 mm ³ / stroke are plotted in the vertical direction. The values within the map then correspond to the assigned static target volume flow Vs (SL) in liters / minute. A part of the fuel volume flow to be controlled is determined via the target volume flow map 22. The target volume flow map 22 is designed in such a way that a static target volume flow of Vs (SL) = 0 liters / minute is calculated in the normal operating range. The normal operating range is double-framed in the figure. The simply framed area corresponds to the low-load area. In the low-load range, a positive value of the static target volume flow Vs (SL) is calculated. For example, with nMOT = 1000 1 / min and QSL = 30 mm ³ / stroke, a static target volume flow of Vs (SL) = 1.5 liters / minute is specified.

The Figure 8 shows as a timing diagram a load shedding from 100% to 0% load in an internal combustion engine which drives an emergency power generator (60 Hz generator). The Figure 8 consists of the partial diagrams 8A to 8D. These show over time: the generator power P in kilowatts Figure 8A , the engine speed nMOT in Figure 8B , the actual rail pressure pCR (IST) in Figure 8C and the dynamic target volume flow Vd (SL) in Figure 8D . The dashed line is in the Figure 8C a curve of the actual rail pressure pCR (IST) is shown without dynamic correction. The representation of the Figure 8 the same parameters were used as in the example for Figure 4 . A constant target rail pressure of pCR (SL) = 2200 bar was also used.

At time t1, the load on the generator is suddenly dropped from the power P = 2000 kW to 0 kW. The missing load on the output of the internal combustion engine causes an increasing engine speed from time t1. At time t4, this reaches its maximum value nMOT = 1950 1 / min. Since the engine speed is regulated in a separate control loop, the engine speed swings back to the original initial value. Due to the increasing engine speed nMOT and the resulting reduction in the injection quantity from time t1, the high-pressure pump builds up a higher pressure level in the rail, so that the actual rail pressure pCR (ACTUAL) increases with a time delay to the engine speed nMOT. At time t2, the actual rail pressure pCR (IST) reaches the value pCR (IST) = 2250 bar. The control deviation ep is thus ep = -50 bar. The dynamic set volume flow Vd (SL), which is determined by the dynamic correction ( Fig. 3 : 24) is calculated, Vd (SL) = 0 liters / min. Since the actual rail pressure pCR (IST) continues to increase after the time t2, the control deviation ep decreases, that is to say it falls below the value -50 bar, as a result of which a positive dynamic set volume flow Vd (SL) is now calculated, see Figure 8D . At time t3, the actual rail pressure reaches the value pCR (IST) = 2300 bar. This results in a control deviation of ep = -100 bar. The dynamic target volume flow calculated from this is now Vd (SL) = 0.5 liters / min. An increasing dynamic target volume flow Vd (SL) corresponds to the increasing actual rail pressure pCR (IST). A decreasing dynamic target volume flow Vd (SL) corresponds to the decreasing actual rail pressure pCR (IST). At time t7, the actual rail pressure pCR (IST) again falls below the value pCR (IST) = 2250 bar, which results in a dynamic set volume flow of Vd (SL) = 0 liters / min, see Figure 8D .

A comparison of the two curves of the actual rail pressure pCR (IST) in the Figure 8C with dynamic correction (solid line) and without dynamic correction (dashed line) shows a reduction in overshoot, which also results in a shorter settling time.

• erster Schalter S1=1, womit die Berechnung der limitierten Regelabweichung epLIM aktiviert ist,
• der zweite Schalter S2=1, womit sich die Regelabweichung ep aus dem Soll-Raildruck pCR(SL) und dem Ist-Raildruck pCR(IST) berechnet, und
• der vierte Schalter S4=2, womit der Faktor f gleich fKON ist.

In the Figure 9 a program flow chart of the method for determining the rail pressure disturbance with correction is shown. The following parameters were used:

• first switch S1 = 1, which activates the calculation of the limited control deviation epLIM,
• the second switch S2 = 1, with which the control deviation ep is calculated from the set rail pressure pCR (SL) and the actual rail pressure pCR (IST), and
• the fourth switch S4 = 2, with which the factor f is fKON.

At S1, the target injection quantity QSL, the engine speed nMOT, the actual rail pressure pCR (IST), the battery voltage UBAT and the actual current iDV (IST) of the pressure control valve are read. The static target volume flow rate Vs (SL) is then calculated at S2 via the target volume flow characteristic map as a function of the target injection quantity QSL and the engine speed nMOT. At S3, the control deviation ep is calculated from the target rail pressure pCR (SL) and the actual rail pressure pCR (IST). The target rail pressure is converted to a characteristic curve ( Fig. 4 : 31) calculates the limited control deviation epLIM, which is negative, step S4. The resulting control deviation epRES is then calculated at S5. The resulting control deviation epRES is in turn determined from the control deviation ep and the limited control deviation epLIM. It is then checked at S6 whether the resulting control deviation epRES is negative. If this is the case, the dynamic set volume flow Vd (SL) is set to zero in S7. If the resulting control deviation epRES is not negative, the dynamic set volume flow Vd (SL) at S8 is calculated as the product of the costly factor fKON and the resulting control deviation epRES. At S9, the corrected target volume flow Vk (SL) is calculated from the sum of the static target volume flow Vs (SL) and the dynamic target volume flow Vd (SL). The actual rail pressure pCR (IST) is converted to a characteristic curve ( Fig. 3 : 26) the maximum volume flow VMAX is calculated at S10, to which the corrected desired volume flow Vk (SL) is then limited at S11. The result corresponds to the resulting target volume flow Vres (SL). At S12 the target current iDV (SL) is calculated depending on the resulting target volume flow Vres (SL) and the actual rail pressure pCR (IST) and finally at S13 the PWM signal for controlling the pressure control valve depending on the target current iDV (SL) calculated. The program sequence is now finished. Reference numerals 1 Internal combustion engine 33 curve 2nd Fuel tank 34 Current regulator 3rd Low pressure pump 4th Suction throttle 5 high pressure pump 6 Rail 7 Injector 8th Individual storage (optional) 9 Rail pressure sensor 10th electronic control unit (ECU) 11 Pressure relief valve, passive 12th Pressure control valve, electrically controllable 13 Rail pressure control loop 14 Pressure regulator 15 Limitation 16 Pump characteristic 17th Calculation of PWM signal 18th Controlled system 19th first filter 20 second filter 21 control 22 Set volume flow map 23 calculation 24th dynamic correction 25th Limitation 26 curve 27 Pressure control valve map 28 Calculation of PWM signal 29 Current control loop (pressure control valve) 30th filter 31 curve 32 Comparator

Claims (6)

1. A method for controlling and regulating an internal combustion engine (1), in which the rail pressure (pCR) is regulated via a first pressure adjusting member in a rail pressure control loop (13), wherein
   a rail pressure disturbance value (VDRV) is generated in order to influence the rail pressure (pCR) via a pressure regulating valve (12) on the high pressure side as second pressure adjusting member, via which fuel is discharged from the rail (6) into a fuel tank (2), wherein the rail pressure disturbance value (VDRV) is calculated using a corrected target volume flow (Vk(SL)) of the pressure regulating valve (12), wherein
   the corrected target volume flow (Vk(SL)) is calculated from a static target volume flow (Vs(SL)) and a dynamic target volume flow (Vd(SL)), wherein the dynamic target volume flow (Vd(SL)) of the pressure regulating valve (12) is calculated via a dynamic correction (24) as a function of a target rail pressure (pCR(SL)) and of an actual rail pressure (pCR(IST)),
   characterised in that a suction throttle (4) on the low pressure side is used as first pressure adjusting member, and that the dynamic target volume flow (Vd(SL)) is calculated in that a resulting control deviation (epRES) of the rail pressure (pCR) is calculated and in that, if a resulting control deviation (epRES) is smaller than zero (epRES<0), the dynamic target volume flow (Vd(SL)) is set to the value of zero (Vd(SL)=0)) or if a resulting control deviation (epRES) is greater than/equal to zero (epRES≥0), the dynamic target volume flow (Vd(SL)) is set to the value of the product of resulting control deviation (epRES) and a factor (f), and wherein the resulting control deviation (epRES) is calculated in that a control deviation (ep) of the rail pressure (pCR) is calculated from the difference of target rail pressure (pCR(SL)) and actual rail pressure (pCR(IST)), in that a limited control deviation (epLIM) is calculated from the target rail pressure (pCR(SL)) via a characteristic curve (31) and in that the resulting control deviation (epRes) is calculated as the difference of the limited control deviation (epLIM) and the control deviation (ep).
2. The method according to claim 1,
   characterised in
   that the static target volume flow (Vs(SL)) of the pressure regulating valve (12) is calculated via a target volume flow characteristic field (22) as a function of a target injection amount (QSL), alternatively to a target moment (MSL), and a motor speed (nMOT).
3. The method according to claim 1,
   characterised in
   that the factor (f) is calculated via a characteristic curve (33) as a function of the actual rail pressure (pCR(IST)).
4. The method according to any one of the preceding claims,
   characterised in
   that alternatively to the actual rail pressure (pCR(IST)), a dynamic rail pressure (pCR(DYN)) is used in the calculation, wherein the actual rail pressure (pCR(IST)) is calculated from the rail pressure (pCR) via a first filter (19), and the dynamic rail pressure (pCR(DYN)) is calculated from the rail pressure (pCR) via a second filter (20).
5. The method according to any one of the preceding claims,
   characterised in
   that the limited control deviation (epLIM) and/or the factor (f) are set to a constant value (epKON, fKON).
6. The method according to claim 1,
   characterised in
   that the rail pressure disturbance value (VDRV) is calculated via a pressure regulating valve characteristic field (27).

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