EP2449242A1

EP2449242A1 - Method for controlling and regulating the fuel pressure in the common rail of an internal combustion engine

Info

Publication number: EP2449242A1
Application number: EP10732642A
Authority: EP
Inventors: Armin DÖLKER
Original assignee: MTU Friedrichshafen GmbH
Current assignee: Rolls Royce Solutions GmbH
Priority date: 2009-07-02
Filing date: 2010-06-17
Publication date: 2012-05-09
Anticipated expiration: 2030-06-17
Also published as: CN102510942B; WO2011000478A1; DE102009031527B3; US20120097134A1; CN102510942A; US9441572B2; EP2449242B1

Abstract

Proposed is a method for controlling and regulating an internal combustion engine (1), in which the rail pressure (pCR) is controlled via a suction throttle (4) on the low pressure side as a first pressure-adjusting element in a rail pressure control loop. The invention is characterized in that a rail pressure disturbance variable (VDRV) is generated in order to influence the rail pressure (pCR) via a pressure control valve (12) on the high pressure side as a second pressure-adjusting element, by means of which fuel is redirected in a controlled manner from the rail (6) into a fuel tank (2), the rail pressure disturbance variable (VDRV) being calculated using a corrected target volume flow (Vk(SL)) of the pressure control valve (12).

Description

METHOD FOR CONTROLLING AND REGULATING THE FUEL PRESSURE OF A COMMON RAIL OF AN INTERNAL COMBUSTION ENGINE

The invention relates to a method for controlling and regulating a

Internal combustion engine according to the preamble of claim 1.

In an internal combustion engine with common rail system, the quality of the combustion is largely determined by the pressure level in the rail. In order to comply with the statutory emission limit values, the rail pressure is therefore regulated. Typically, a rail pressure control loop comprises a reference junction for determining a control deviation, a pressure regulator for calculating a control 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 nominal rail pressure to the actual rail pressure. The controlled system comprises the pressure actuator, the rail and the injectors for injecting the fuel into the combustion chambers of the internal combustion engine.

From DE 197 31 995 A1 a common rail system with pressure control is known, in which the pressure regulator is equipped with different controller parameters. Due to the different controller parameters, the pressure control should be more stable. The

Controller parameters, in turn, are calculated as a function of operating parameters, here: the engine speed and the desired injection quantity. On the basis of the controller parameters, the pressure regulator then calculates the actuating signal for a pressure regulating valve, via which the fuel outflow from the rail into the fuel tank is determined. The pressure control valve is thus arranged on the high pressure side of the common rail system. As an alternative measures for pressure control, an electric prefeed pump or a controllable high-pressure pump are shown in this reference.

DE 103 30 466 B3 also describes a common rail system with pressure regulation, in which the pressure regulator, however, accesses a suction throttle via the control signal. About the Suction choke, in turn, the inlet cross section is set to the high pressure pump. The suction throttle is thus arranged on the low pressure side of the common rail system. In addition, in this common rail system, a passive

Pressure relief valve may be provided as a protective measure against too high a rail pressure. The fuel is then discharged from the rail into the fuel tank via the opened pressure relief valve. A corresponding common rail system with a passive pressure relief valve is known from DE 10 2006 040 441 B3.

Due to the design, a common rail system has a control and a

Constant leakage on. The control leakage is effective when the injector is electrically energized, that is, during the duration of the injection. As the injection duration decreases, so does the control leakage. 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 with rising

Raildruck increases and decreases with falling rail pressure, the pressure oscillations are damped in the rail. In contrast, the tax leakage is reversed. If the rail pressure increases, the injection duration is shortened to represent a constant injection quantity, which results in a sinking control leakage. If the rail pressure drops, the injection duration is increased accordingly, which results in an increasing control leakage. The tax leakage thus leads to the pressure vibrations in the rail to be amplified. The control and constant leakage represent a loss volume flow, which is promoted and compressed by the high-pressure pump. This

Leakage volume flow, however, means that the high-pressure pump must be designed to be larger than necessary. In addition, part of the drive energy of the high pressure pump is converted into heat, which in turn causes the heating of the fuel and an efficiency reduction of the internal combustion engine.

To reduce the constant leakage, the components are shed in practice. However, a reduction in the constant leakage has the disadvantage that the stability behavior of the common rail system deteriorates and the pressure control becomes more difficult. This is clear in the low load range, because here the injection quantity, ie the extracted fuel volume, is very low. This is just as clear with a load shedding of 100% after 0% load, since here the injection quantity is reduced to zero and therefore the rail pressure only slowly degrades again. This in turn causes a long settling time. Based on a common rail system with a rail pressure control via a low-pressure suction throttle and with reduced constant leakage, the invention is based on the object to optimize the stability behavior and the settling time.

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

The method consists in that in addition to the rail pressure control over the

Low-pressure-side suction throttle as the first pressure actuator, a rail pressure disturbance for influencing the rail pressure via a high-pressure side pressure control valve is generated as a second pressure actuator. Fuel is removed from the rail into a fuel tank via the high-pressure-side pressure control valve. An essential element of the invention is thus that a constant leakage is simulated via the control of the pressure control valve. The rail pressure disturbance variable is calculated on the basis of a corrected nominal volumetric flow of the pressure control valve, which in turn is calculated from a static setpoint volumetric flow and a dynamic setpoint volumetric flow.

The static nominal volumetric flow is calculated as a function of a desired injection quantity, alternatively a setpoint torque, and an engine speed via a setpoint volumetric flow characteristic diagram. The desired volume flow characteristic map is designed in such a way that in a low load range, a setpoint volume flow with a positive value, for example 2 liters / minute, and in a normal operating range a setpoint volume flow of zero is calculated. Under low load range is to be understood in the context of the invention, the range of small injection quantities and thus small engine power.

The dynamic setpoint flow rate of the pressure control valve is calculated via a dynamic correction as a function of the set rail pressure and the actual rail pressure by calculating a resulting control deviation and setting the dynamic setpoint flow to zero with a resulting control deviation smaller than zero , If, on the other hand, the resulting control deviation is greater than or equal to zero, the dynamic setpoint volumetric flow is set to the value of the product of the resulting control deviation and a factor. In other words, the dynamic setpoint volume flow is largely determined by the control deviation of the rail pressure. is this negative and falls below a threshold, so for example at a

Load shedding, the static setpoint volume flow is corrected via the dynamic set flow rate. Otherwise, there is no change in the static setpoint volume flow.

Since the stationary fuel is only diverted in the low load range and in a small amount, there is no significant increase in the fuel temperature and also no significant reduction in the efficiency of the internal combustion engine. The increased stability of the rail pressure control loop in the low load range can be recognized by the fact that the rail pressure remains approximately constant in overrun mode and the rail pressure peak value is significantly lower in load shedding. The increase in pressure of the rail pressure is counteracted by the dynamic set volume flow, with the advantage that the settling time of the system can be further improved.

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

FIG. 1 shows a system diagram,

FIG. 2 shows a rail pressure control loop,

3 shows a block diagram of the rail pressure control loop with control,

FIG. 4 shows a block diagram of the dynamic correction,

FIG. 5 shows a current control circuit,

FIG. 6 shows a current control loop with precontrol,

FIG. 7 shows a desired volume flow characteristic map,

Figure 8 is a timing diagram and

Figure 9 is a program flowchart.

FIG. 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 to influence the flowing through

Fuel volume flow, a high-pressure pump 5 for conveying the fuel under pressure increase, a rail 6 for storing 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 implemented with Einzelspeichem, in which case For example, in the injector 7, a single memory 8 as an additional buffer volume

is integrated. As a protection against an inadmissibly high pressure level in the rail 6, a passive pressure relief valve 11 is provided, which absteuert the fuel from the rail 6 in the open state. An electrically controllable

Pressure control valve 12 also connects the rail 6 to the fuel tank 2. About the position of the pressure control valve 12, a fuel flow is defined, which is derived from the rail 6 in the fuel tank 2. In the text below, this fuel volume flow is referred to as rail pressure disturbance variable VDRV.

The operation of the internal combustion engine 1 is determined by an electronic control unit (ECU) 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 chips are the relevant for the operation of the internal combustion engine 1 operating data applied in maps / curves. About this calculates the

electronic control unit 10 from the input variables the output variables. The following input variables are shown by way of example in FIG. 1: the rail pressure pCR, which is measured by means of a rail pressure sensor 9, an engine speed nMOT, a signal FP for output specification by the operator and an input variable EIN. Under the

Input variable ON, the other sensor signals are summarized, for example, the charge air pressure of an exhaust gas turbocharger. In a common rail system with

Single memories 8, the individual storage pressure pE is an additional input of the electronic control unit 10.

In FIG. 1, as output variables of the electronic control unit 10, a signal PWMSD for controlling the suction throttle 4 as first pressure actuator, a signal ve for controlling the injectors 7 (start of injection / injection end), a signal PWMDV for

Control of the pressure control valve 12 as a second pressure actuator and a

Output size OFF shown. Via the signal PWMDV the position of the

Pressure control valve 12 and thus the rail pressure disturbance VDRV defined. 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. FIG. 2 shows a rail pressure control loop 13 for controlling the rail pressure pCR. The input variables of the rail pressure control loop 13 are: a desired rail pressure pCR (SL), a volume flow which characterizes the desired consumption Wb, the

Motor speed nMOT, the PWM fundamental frequency fPWM and a size E1. Under the size E1, for example, the battery voltage and the ohmic resistance of Saugdrosselspule are combined with supply, which are included in the calculation of the PWM signal. The output variables of the rail pressure control loop 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 further processed in the control shown in FIG.

From the raw value of the rail pressure pCR is by means of a first filter 19 of the

Actual rail pressure pCR (IST) calculated. This is then compared with the setpoint value pCR (SL) at a summation point A, resulting in a control deviation ep. From the control deviation ep, a pressure regulator 14 calculates its manipulated variable, which corresponds to a volume flow VR with the physical unit liters / minute. To the

Volume flow VR is added at a summation point B, the calculated target consumption Wb. The target consumption Wb is calculated via a calculation 23, which is shown in FIG. 3 and explained in connection therewith. The result of the addition at summation point B corresponds to an unlimited nominal volumetric flow VSDu (SL) of the intake throttle. About a limit 15 is then the

unlimited nominal volumetric flow VSDu (SL) limited depending on the engine speed nMOT. The output variable of the limit 15 corresponds to a nominal volume flow VSD (SL) of the suction throttle. The desired volume flow VSD (SL) is then assigned to the intake throttle via the pump characteristic curve 16, a desired electric current iSD (SL). The desired current iSD (SL) is converted in a calculation 17 into a PWM signal PWMSD. The PWM signal PWMSD represents the duty cycle and the frequency fPWM corresponds to the fundamental frequency. With the PWM signal PWMSD then the solenoid of the suction throttle is applied. As a result, the path of the magnetic core is changed, whereby the flow rate of the high-pressure pump is influenced freely. For safety reasons, the suction throttle is normally open and is on the

PWM control applied in the direction of the closed position. The calculation of the PWM signal 17 may be subordinated to a current control loop, as this from the

DE 10 2004 061 474 A1 is known. The high-pressure pump, the intake throttle, the rail and possibly the individual memory correspond to a controlled system 18. Thus, the 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 Figure 3 is. The second filter 20 in this case has a smaller time constant and a lower phase delay than the first filter 19 in the feedback path.

FIG. 3 shows a block diagram of the greatly simplified rail pressure control circuit 13 of FIG. 2 and a controller 21. Via the controller 21, the rail pressure disturbance variable VDRV is generated, that is to say the volume flow which the pressure control valve discharges from the rail into the fuel tank. The inputs of the controller 21 are: the SoII rail pressure pCR (SL), the actual rail pressure pCR (IST), the dynamic rail pressure pCR (DYN), the engine speed nMOT, and the target injection amount QSL. The desired injection quantity QSL is either calculated via a characteristic map as a function of the power requirement or corresponds to the manipulated variable of a speed controller. The physical unit of the target injection quantity is mm ³ / stroke. In a torque-based structure, a setpoint torque MSL is used instead of the setpoint injection quantity QSL. The output of the controller 21 corresponds to the rail pressure disturbance VDRV.

On the basis of the engine speed nMOT and the target injection quantity QSL, the desired static volume flow Vs (SL) for the pressure control valve is calculated via a nominal volume flow characteristic map 22 (3D characteristic map). The desired volume flow characteristic map 22 is designed in such a way that in the low load range, for example at idle, a positive value of the static target volume flow Vs (SL) is calculated, while in

Normal operating range a static set flow rate Vs (SL) is calculated from zero. A possible embodiment of the desired volume flow characteristic map 22 is shown in FIG. 7 and will be explained in more detail in connection therewith. Also on the basis of the engine speed nMOT and the target injection quantity QSL the desired consumption Wb is calculated via the calculation 23, which is an input of the rail pressure control loop 13. The static setpoint volume flow Vs (SL) is inventively corrected by adding up a dynamic setpoint volume flow Vd (SL). Calculated is the

dynamic set flow Vd (SL) via a dynamic correction 24. The

Input variables of the dynamic correction 24 are the desired rail pressure pCR (SL), the actual rail pressure pCR (IST) and the dynamic rail pressure pCR (DYN). Dynamic correction 24 is shown as a block diagram in FIG. 4 and will be described in connection therewith. The sum of nominal static volumetric flow Vs (SL) and dynamic Nominal volumetric flow Vd (SL) corresponds to a corrected nominal volumetric flow Vk (SL), which is delimited above a limit 25 to a maximum volumetric flow VMAX and down to the value zero. The maximum is calculated

Volume flow VMAX over 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 setpoint volume flow Vres (SL), which is one of the input variables of a pressure control valve characteristic map 27. The second input is the actual rail pressure pCR (IST). Via the pressure regulating valve characteristic map 27, the target volume flow Vres (SL) and the actual rail pressure pCR (IST) are assigned a nominal current iDV (SL) of the pressure regulating valve. The desired current iDV (SL) is converted by a PWM calculation 28 into the duty cycle PWMDV with which the pressure regulating valve 12 is actuated. The conversion can be subordinated to a current control, current control loop 29, or a current control with feedforward control. The current regulation is shown in FIG. 5 and will be explained in connection therewith. The current control with pilot control is shown in FIG. 6 and will be explained in connection therewith. With the PWM signal PWMDV the pressure regulating valve 12 is activated. The electric current iDV which adjusts itself to the pressure regulating valve 12 is converted into an actual current iDV (IST) for current regulation via a filter 30 and fed back to the calculation PWM signal 28. The output signal of the pressure regulating valve 12 corresponds to the rail pressure disturbance variable VDRV, that is to say that fuel volume flow which is diverted from the rail into the fuel tank.

FIG. 4 shows the dynamic correction 24 from FIG. The

Input variables are the nominal 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 setpoint volume flow Vd (SL). The nominal 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. Thus, for example, a set rail pressure pCR (SL) = 2150 bar via the characteristic curve 31 becomes a limited control deviation

epLIM = -100 bar assigned. A first switch S1 determines whether its output variable AG 1 corresponds to the limited control deviation epLIM or the constant control deviation epKON. In switch position S1 = 1, AG1 = epLIM, while in switch position S1 = 2, AG1 = epKON. The constant control deviation can be set to the value epKON = -50 bar, for example. At a summation point A, the output variable AG1 is compared with the control deviation ep. The control deviation ep at a summation point B is calculated from the desired 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. A comparator 32 compares the resulting control deviation epRES with the value zero. If the resulting control deviation epRES is less than zero (epRES <0), then a third switch S3 is set to the position S3 = 2. In this case, the dynamic setpoint volumetric flow Vd (SL) is equal to zero (Vd (SL) = O). Is, however, the resulting

Control deviation epRES greater than or equal to zero (epRES≥O), the third switch is changed to position S3 = 1. In this position S3 = 1, the dynamic setpoint volume flow Vd (SL) is calculated by multiplying the resulting control deviation epRES by a factor f. The factor f in turn is set via a fourth switch S4. If the fourth switch in the position S4 = 1, then the factor f is a characteristic curve 33 depending on the actual rail pressure pCR (IST), switch S2 = 1, or depending on the dynamic rail pressure pCR (DYN), switch S2 = 2, calculated. If, on the other hand, 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 / (bar).

The function of dynamic correction 24 will be explained by way of example. The following parameters were used as a basis:

- first switch S1 = 2 with epKON = -50 bar,

second switch S2 = 1 with ep = pCR (SL) - pCR (IST) and

- fourth switch S4 = 2 with f = fKON = 0.01 liter / (min. bar).

If the control deviation is greater than -50 bar (ep> (- 50 bar)), the resulting control deviation epRES is less than zero (epRES <O). This is about the

Comparator 32, the third switch is controlled in the position S3 = 2, so that the dynamic target volume flow Vd (SL) = O is. Is the control deviation, however less than or equal to -50 bar (ep≤ (-50 bar)), the resulting control deviation epRES> 0. Thus, the comparator 32 controls the third switch in the position S3 = 1. The dynamic set flow rate is now calculated to Vd (SL) = (- 50 bar-ep) ^• 0.01 liter / (min bar).

A correction by means of the dynamic setpoint volume flow Vd (SL) thus takes place when the control deviation ep falls below the value ep = -50 bar. If the control deviation ep is even smaller (negative), that is, if the actual rail pressure oscillates even more strongly, the fuel volume flow, ie the rail pressure disturbance variable, which is controlled by the pressure control valve, is increased via the dynamic set volume flow Vd (SL). This eventually causes the rail pressure to be absorbed.

FIG. 5 shows a pure current regulation, which corresponds to the current control circuit 29 of FIG. The input variables are the nominal current iDV (SL) for the pressure regulating valve, the actual current iDV (IST) of the pressure regulating valve, the battery voltage UBAT and the controller parameters (kp, Tn). The output variable is the PWM signal PWMDV, with which the pressure regulating valve is controlled. From the desired current iDV (SL) and the actual current iDV (IST), see FIG. 3, the current control deviation ei is first calculated. The current control deviation ei is the

Input of the current controller 34. The current controller 34 may be implemented as a PI or PI (DTI) - algorithm. The algorithm processes the controller parameters. These are characterized inter alia by the proportional coefficient kp and the reset time Tn. The output of the current regulator 34 is a desired voltage UDV (SL) of the pressure regulating valve. This is through the

Battery voltage UBAT divided and then multiplied by 100. The result corresponds to the duty cycle of the pressure control valve in percent.

FIG. 6 shows, as an alternative to FIG. 5, a current control with combined pilot control. The input quantities are the setpoint 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 here also the PWM signal PWMDV, with which the pressure regulating valve is controlled. First, the desired current iDV (SL) is multiplied by the ohmic resistance RDV of the pressure regulating valve. The result corresponds to a pilot control voltage UDV (VS). On the basis of the desired current iDV (SL) and the actual current iDV (IST), the current control deviation ei is calculated. From the current control deviation ei, the current controller 34 then calculates the setpoint voltage UDV (SL) of the

Pressure control valve. The current regulator 34 can also be embodied here as either a PI or PI (DTI) controller. Thereafter, the desired voltage UDV (SL) and the pilot voltage UDV (VS) are added, the sum then by the

Battery voltage UBAT divided and multiplied by 100.

In the figure 7, the desired volume flow map 22 is shown. This determines the nominal static volumetric 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 are plotted from 0 to 2000 rpm. In the vertical direction, the nominal injection quantity values from 0 to 270 mm ³ / stroke are plotted. The values within the map then correspond to the

assigned static nominal flow rate Vs (SL) in liters / minute. About the desired volume flow map 22 is a part of the abzusteuernden

Fuel flow defined. The desired volume flow characteristic map 22 is designed such that in the normal operating range a static setpoint volume flow of Vs (SL) = 0 liters / minute is calculated. The normal operating range is doubly framed in the figure. The simple framed area corresponds to the low load area. In the low load range, a positive value of the static setpoint volumetric flow Vs (SL) is calculated. For example, at nMOT = 1000 1 / min and QSL = 30 mm ³ / stroke, a static set flow rate of Vs (SL) = 1.5 liters / minute is set.

FIG. 8 shows as a time diagram a load shedding from 100% to 0% load in an internal combustion engine which drives an emergency power generator (60 Hz generator). FIG. 8 consists of the partial diagrams 8A to 8D. These show in each case over time: the generator power P in kilowatts in FIG. 8A, the engine speed nMOT in FIG. 8B, the actual rail pressure pCR (IST) in FIG. 8C and the dynamic setpoint volume flow Vd (SL) in FIG. 8D. A dashed line in FIG. 8C shows a profile of the actual rail pressure pCR (IST) without dynamic correction. The illustration of FIG. 8 was based on the same parameters as in the example of FIG. 4 described above. A constant nominal rail pressure of pCR (SL) = 2200 bar was also used. At time t1, the load on the generator of the power P = 2000 kW

abruptly dropped to 0 kW. The missing load at 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 controlled in its own control loop, the oscillates

Engine speed to the original initial value again. Due to the increasing engine speed nMOT and the resulting reduction of the injection quantity from time t1, the high pressure pump builds a higher one

Pressure level in the rail on, so that the actual rail pressure pCR (IST) increases with time delay to the engine speed nMOT. At time t2, the actual rail pressure pCR (IST) reaches the value pCR (actual) = 2250 bar. The control deviation ep is thus ep = -50 bar. The dynamic setpoint volumetric flow Vd (SL), which is calculated via the dynamic correction (FIG. 3: 24), is therefore Vd (SL) = O liter / min. Since the actual rail pressure pCR (IST) continues to increase after the time t2, the control deviation ep decreases, that is, it falls below the value -50 bar, whereby a positive dynamic setpoint volume flow Vd (SL) is now calculated, see FIG 8D. To the

At time t3, the actual rail pressure reaches the value pCR (actual) = 2300 bar. This results in a control deviation of ep = -100 bar. The calculated dynamic volume flow is now Vd (SL) = O, 5 liters / min. For the increasing actual rail pressure pCR (IST) corresponds to an increasing dynamic setpoint volume flow Vd (SL). For the decreasing actual rail pressure pCR (IST), a decreasing dynamic setpoint volume flow Vd (SL) corresponds. At time t7

the actual rail pressure pCR (IST) again falls below the value pCR (actual) = 2250 bar, which results in a dynamic setpoint volume flow of Vd (SL) = 0 liter / min, see FIG. 8D.

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

FIG. 9 shows a program flow chart of the method for determining the rail pressure disturbance variable with correction. The following parameters were used: first switch S1 = 1, with which the calculation of the limited control deviation epLIM is activated,

the second switch S2 = 1, with which the control deviation ep is calculated from the SoII rail pressure pCR (SL) and the actual rail pressure pCR (IST), and

the fourth switch S4 = 2, whereby the factor f is fKON.

At S1, the target injection amount QSL, the engine speed nMOT, the actual rail pressure pCR (IST), the battery voltage UBAT and the actual current iDV (IST) of the pressure regulating valve are read. Then, at S2, the desired static volume flow Vs (SL) is calculated via the desired volume flow characteristic field as a function of the desired injection quantity QSL and the engine speed nMOT. At S3, the

Control deviation ep calculated from the target rail pressure pCR (SL) and the actual rail pressure pCR (IST). From the nominal rail pressure, the limited control deviation epLIM is calculated via a characteristic curve (FIG. 4: 31), which is negative, step S4. Then the resulting control deviation epRES is calculated at S5. The resulting control deviation epRES, in turn, is 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, then the dynamic setpoint volume flow Vd (SL) is set to zero at S7. If the resulting control deviation epRES is not negative, the dynamic setpoint volumetric flow Vd (SL) is calculated at S8 as the product of the costing factor fKON and the resulting control deviation epRES. At S9, the corrected target volumetric flow Vk (SL) is calculated from the sum of the static volumetric flow Vs (SL) and the dynamic volumetric flow Vd (SL). From the actual rail pressure pCR (IST), the maximum volume flow VMAX at S10 is calculated via a characteristic curve (FIG. 3: 26), to which the corrected setpoint volume flow Vk (SL) is then limited at S11. The result corresponds to the resulting desired volume flow Vres (SL). At S12, the setpoint current iDV (SL) is calculated as a function of the resulting setpoint volume flow Vres (SL) and the actual rail pressure pCR (IST), and finally the PWM signal for actuating the pressure control valve in S13 is calculated in S13

Dependence of the desired current iDV (SL) calculated. This completes the program. reference numeral

Internal combustion engine 33 characteristic curve

Fuel tank 34 Current regulator

Low pressure pump

interphase

high pressure pump

Rail

injector

Single memory (optional)

Rail pressure sensor

electronic control unit (ECU)

Pressure relief valve, passive

Pressure control valve, electrically controllable

Rail pressure control circuit

pressure regulator

limit

Pump curve

Calculation PWM signal

controlled system

first filter

second filter

control

Target volumetric flow-map

calculation

dynamic correction

limit

curve

Pressure control valve map

Calculation PWM signal

Current control circuit (pressure control valve)

filter

curve

comparator

Claims

claims

1. A method for controlling and regulating an internal combustion engine (1), wherein the rail pressure (pCR) via a low-pressure suction throttle (4) as the first

Pressure actuator in a rail pressure control loop (13) is controlled,

characterized,

in that a rail pressure disturbance variable (VDRV) for influencing the rail pressure (pCR) is generated via a high-pressure-side pressure regulating valve (12) as a second pressure actuator, via which fuel from the rail (6) into a fuel tank (2).

is the rail pressure disturbance variable (VDRV) on the basis of a

corrected nominal volume flow (Vk (SL)) of the pressure regulating valve (12) is calculated.

2. The method according to claim 1,

characterized,

the corrected nominal volume flow (Vk (SL)) is calculated from a static setpoint volume flow (Vs (SL)) and a dynamic setpoint flow rate (Vd (SL)).

3. The method according to claim 2,

characterized,

in that the nominal static volumetric flow rate (Vs (SL)) of the pressure regulating valve (12) is dependent on a desired injection quantity (QSL), alternatively a setpoint torque (MSL), and an engine speed (nMOT) via a nominal volumetric flow characteristic map ( 22).

4. The method according to claim 2, characterized,

in that the dynamic setpoint volume flow (Vd (SL)) of the pressure regulating valve (12) is calculated via a dynamic correction (24) as a function of a setpoint rail pressure (pCR (SL)) and an actual rail pressure (pCR (IST)).

5. The method according to claim 4,

characterized,

in that the dynamic setpoint volume flow (Vd (SL)) is calculated by calculating a resulting control deviation (epRES) of the rail pressure (pCR) and, in the case of a resulting control deviation (epRES) smaller than zero (epRES <0), the dynamic setpoint volumetric flow (Vd (SL)) is set to the value zero (Vd (SL) = O)) or with a resulting control deviation (epRES) greater than or equal to zero (epRES≥O), the dynamic setpoint volume flow (Vd (SL)) the value of the product of resulting control deviation (epRES) and a factor (T) is set.

6. The method according to claim 5,

characterized,

the resulting control deviation (epRES) is calculated by calculating a control deviation (ep) of the rail pressure (pCR) from the difference between the target rail pressure (pCR (SL)) and the actual rail pressure (pCR (IST)), from the Target rail pressure (pCR (SL)) is calculated via a characteristic curve (31), a limited control deviation (epLIM) is calculated, and the difference between the limited control deviation (epLIM) and the control deviation (ep) is calculated.

7. The method according to claim 5,

characterized,

the factor (f) is calculated as a function of the actual rail pressure (pCR (IST)) via a characteristic curve (33).

8. Method according to one of the preceding claims,

characterized,

that as an alternative to the actual rail pressure (pCR (IST)) a dynamic rail pressure

(pCR (DYN)) is used in the calculation, where the actual rail pressure

(pCR (IST)) is calculated via a first filter (19) from the rail pressure (pCR) and the dynamic rail pressure (pCR (DYN)) is calculated from the rail pressure (pCR) via a second filter (20).

9. Method according to one of the preceding claims,

characterized,

that the limited control deviation (epLIM) and / or the factor (T) are set to a constant value (epKON, fKON).

10. The method according to claim 1,

characterized,

in that the rail pressure disturbance variable (VDRV) is calculated via a pressure regulating valve characteristic map (27).