WO2019011839A1

WO2019011839A1 - Method for regulating pressure in a high-pressure injection system of an internal combustion engine, and internal combustion engine for carrying out such a method

Info

Publication number: WO2019011839A1
Application number: PCT/EP2018/068500
Authority: WO
Inventors: Armin DÖLKER
Original assignee: Mtu Friedrichshafen Gmbh
Priority date: 2017-07-10
Filing date: 2018-07-09
Publication date: 2019-01-17
Also published as: DE102017211770A1; DE102017211770B4

Abstract

The invention relates to a method for regulating pressure in a high-pressure injection system (101) of an internal combustion engine (1), in which a high-pressure correcting variable (V̇PI(DT1)) is determined according to a high-pressure deviation (ep) between an actual high pressure (pist) in the high-pressure injection system (101) and a nominal high pressure (psoll) used as a high-pressure reference variable, the high-pressure correcting variable (V̇PI(DT1)) being offset against a high-pressure disturbance variable (V̇Stoer dyn), and the high-pressure disturbance variable (V̇Stoer dyn) being determined according to a nominal injection quantity (QSoll stat). A dynamic nominal injection quantity QSoll dyn) is determined from the nominal injection quantity (QSoll stat) by means of a differentiation body (139), and the high-pressure disturbance variable (V̇Stoer dyn) is determined on the basis of the dynamic nominal injection quantity (QSoll dyn).

Description

DESCRIPTION Pressure control method in a high-pressure injection system

Internal combustion engine, and internal combustion engine for carrying out such a method

The invention relates to a method for pressure regulation in a high-pressure injection system of an internal combustion engine and to an internal combustion engine which is set up for carrying out such a method.

If during operation of an internal combustion engine, which has a high-pressure injection system for injecting fuel into at least one combustion chamber of the internal combustion engine, to a sudden load shedding, for example because a propeller dives out of the water in a marine propulsion or load in an application of the internal combustion engine to drive a powered as a generator electric machine to a power grid - especially at the request of a power grid operator - is suddenly dropped, the pressure in the high-pressure injection system can suddenly rise sharply and in particular beyond a permissible level. In this case, typically opens a pressure relief valve of the high pressure injection system, or a pressure control valve is responsive to at least limit the pressure increase, preferably to reduce the pressure. In certain applications of

Internal combustion engines experience such load-shedding events with comparatively high frequency, in particular in the case of ship drives or regenerative applications. This has a particularly negative effect on the durability of a pressure relief valve and / or a pressure control valve, as this typically depends on how often and how long such a valve has responded. Operation of the internal combustion engine with an open pressure relief valve or with an open pressure control valve is disadvantageous, since in this operating mode a comparatively low pressure is established in the high-pressure injection system, which ultimately leads to reduced engine power and higher emissions.

The invention is based on the object, a method for pressure control in one

To provide high-pressure injection system of an internal combustion engine and an internal combustion engine, said disadvantages do not occur. The object is achieved by providing the subject matters of the independent claims. Advantageous embodiments emerge from the subclaims. The object is achieved in particular by a method for pressure regulation in one

High-pressure injection system of an internal combustion engine is provided, wherein in

Depending on a high pressure control deviation between an actual high pressure in the high pressure injection system and a high pressure command value used as a high pressure control variable is determined, the high pressure control variable is offset with a high pressure disturbance. The high-pressure disturbance variable is determined as a function of an injection setpoint. From the injection target amount is doing by means of a

Differentiating a dynamic injection target set determined, and the high-pressure disturbance variable is determined based on the dynamic injection target amount. In particular, the fact that the high-pressure disturbance variable is determined based on the dynamic injection target set, which in turn is determined by means of a Differentiationsglieds from the desired injection quantity, the high-pressure disturbance variable changes the injection target amount very quickly - especially compared to a determination of the high-pressure disturbance on the basis the

Injection set amount before the application of the differentiation member - follow and thus react very quickly to such changes. If the load is dropped, the controller responds

Internal combustion engine typically by rapid reduction of the target injection rate, this development in the high-pressure disturbance can be mapped particularly quickly and highly dynamically, if this on the basis of the dynamic, by means of the Differentiationsglieds

differentiated injection setpoint is determined. The pressure control of the high-pressure injection system can react in this way faster than previously known on a load shedding or a reduced load, whereby preferably an impermissible increase in the pressure in the high-pressure injection system can be prevented, so it is not even in the best case Opening the pressure relief valve or a response of the pressure control valve comes. In this way, on the one hand, the pressure relief valve and / or the pressure control valve are spared, so that their durability extends advantageous, on the other hand operation of the internal combustion engine with open pressure relief valve and / or open pressure control valve is avoided, thereby preventing a loss of power and a deteriorated emission behavior of the internal combustion engine can be. The high-pressure injection system preferably has a common high-pressure accumulator for a plurality of fuel injectors, wherein the fuel injectors are arranged to inject fuel directly into combustion chambers of the internal combustion engine. Such a high-pressure injection system is also referred to as a common rail system. The pressure control is in particular set up and designed to provide a high pressure in the common

High-pressure accumulator, thus in the rail of the common rail system to regulate.

The desired high pressure used for the pressure control is according to a preferred

Embodiment of the method chosen constant. According to another preferred

Embodiment of the method, the desired high pressure is determined in dependence on a current load point of the internal combustion engine, particularly preferably read from a map, wherein the load point of the internal combustion engine is in particular defined from a pair of values of a currently applied by the internal combustion engine target torque and a current actual Speed of the internal combustion engine. Additionally or alternatively, the desired high pressure can be determined as a function of the current nominal injection quantity.

The high-pressure manipulated variable is a variable that is suitable for the actual high pressure

influence. By changing the high-pressure control variable, the actual high pressure can thus be changed and, in particular, adjusted or at least approximated to the desired high pressure, so that the high-pressure control deviation is reduced.

The calculation of the high-pressure control variable with the high-pressure disturbance, that is in particular the connection of the high-pressure disturbance on the pressure control leads in known per se to a more dynamic behavior of the pressure control, since this can already respond to changes in high-pressure disturbance before they actually manifest themselves in a manner sufficient to respond to the pressure regulation in the high-pressure control deviation. The injection target amount is also referred to as a static injection target amount before the application of the differentiation term. This static injection target quantity is an input variable of the differentiation element, which has as its output variable the dynamic injection target quantity. The dynamic injection target quantity represents in particular a signal which

Changes in the static injection target quantity in a particularly pronounced manner, in particular As signal peaks, maps, so that determined based on the dynamic injection target amount high-pressure disturbance value changes faster when changing the value of the static injection target set, as if the high-pressure disturbance variable would be determined based on the static injection target.

Under a Differentiationsglied is a computing device, a

Signal processing device and / or an algorithm understood, the / from a

Input signal detects an output signal, wherein the output signal at least also has a proportion based on a differentiation of the input signal. As a result, changes in the input signal in the output signal are mapped in a particularly concise manner.

According to one development of the invention, it is provided that a (PD) Ti element is used as the differentiation element. Such a member known from control engineering in its own right besides a proportional component and a delay time Ti also has a differential component. Such a (PD) Ti element is particularly suitable for generating from an input signal a more dynamic output signal, which changes the input signal succinctly. In particular, by the use of such a (PD) Ti -Gliedes thus the dynamics of the pressure control can be significantly increased in its application to the desired injection quantity.

According to one embodiment of the invention, it is provided that a desired fuel volume flow is used as a high-pressure control variable, as a high-pressure disturbance a

Fuel nominal consumption is determined. The fuel nominal volume flow used as a high-pressure control variable in particular describes a volume flow which is to be conveyed along a fuel delivery path from a fuel reservoir, for example a tank, into the common high-pressure accumulator in order to achieve the desired high pressure or

maintain. It is obvious that the fuel target consumption of

Internal combustion engine, that is, in particular, the amount of fuel which is removed via the injectors the common high-pressure accumulator, the high pressure in the common high-pressure accumulator significantly influenced. If this nominal fuel consumption switched on as a high-pressure disturbance variable of the pressure control, this can react particularly dynamically and quickly already to changes in the fuel target consumption, even before they are mapped in a relevant manner in the high-pressure control deviation. This procedure corresponds in itself taken known manner in about a pilot control of the pressure control loop with the

Target fuel consumption.

It is also readily apparent that the target injection quantity is an important quantity for determining the nominal fuel consumption. If the nominal fuel consumption is now determined on the basis of the dynamic nominal injection quantity instead of the static nominal injection quantity, this can react particularly quickly and flexibly to changes in the nominal injection quantity.

According to one embodiment of the invention, it is provided that the high-pressure disturbance variable itself is not subjected to a differentiation element. Such a procedure is not required if the high-pressure disturbance variable is determined on the basis of the dynamic injection target quantity. The high-pressure disturbance then already follows the dynamically dynamic dynamics

Injection setpoint and does not need in turn a further dynamization by another differentiation member. In principle, however, it is also not excluded that the high-pressure disturbance variable itself is again subjected to a differentiation element in order to possibly make the process even more dynamic.

According to one embodiment of the invention, it is provided that the desired injection quantity is determined as the output variable of a speed control of the internal combustion engine. In this case, the injection target amount itself can be determined as a speed control variable of the speed control, or it can be determined based on a directly resulting from a speed controller speed control variable for direct control of the internal combustion engine. For example, it is possible that a speed controller in response to a speed control deviation between a current actual speed and a predetermined target speed, a desired torque, which is also referred to as a speed controller torque, determined with the actuators of

Internal combustion engine, however, can not be controlled directly. Therefore, from the desired moment is preferred - in particular depending on other sizes - the

Injection setpoint determined by means of which in particular the injectors of

Internal combustion engine to be controlled.

According to one embodiment of the invention, it is provided that the high-pressure disturbance variable, in particular the fuel target consumption, is determined from a combustion chamber number or number of cylinders of the internal combustion engine, a current actual rotational speed of the internal combustion engine and the dynamic injection target quantity. Since the injection target amount in particular the represents fuel quantity to be introduced by means of an injector into a combustion chamber of the internal combustion engine, the fuel target consumption from the injection target amount in conjunction with the number of combustion chambers, thus the number of cylinders of the internal combustion engine, and the instantaneous actual speed, in particular as a product of the desired injection quantity, preferably the dynamic injection target , with the number of cylinders and the instantaneous actual speed, and preferably at least one additional factor. Such a factor can, in particular, take account of a conversion between different units used for the variables considered and / or a division of the combustion chambers of the internal combustion engine into different combustion chamber groups; the latter in particular when the same high-pressure disturbance variable is used for pressure control for all combustion chamber groups.

According to a development of the invention, it is provided that a suction throttle in a fuel delivery path of the high-pressure injection system is actuated on the basis of the high-pressure control variable. In particular, the fuel volume flow from the fuel reservoir into the shared high-pressure accumulator can be influenced via the intake throttle.

In this case, an electrical setpoint current for controlling the suction throttle is preferably determined from the nominal fuel flow rate, wherein this setpoint electrical current is supplied as current control variable to a current regulator which is subordinate to the pressure control. This preferably determines a function of a current control deviation between a current actual current and the target current, a target voltage as a control variable of the current control for the suction throttle, then preferably based on the target voltage a pulse width modulated signal for the control of the suction throttle is calculated. The suction throttle is controlled by the pulse width modulated signal, and it is thereby measured by the intake throttle current flowing current, which - preferably after filtering - the current controller is supplied as actual size for determining the current deviation.

According to one embodiment of the invention, it is provided that the internal combustion engine has at least two combustion chamber groups, wherein a separate high pressure injection system is provided for each combustion chamber group of at least two combustion chamber groups, wherein for each high pressure injection system of the at least two separate high pressure injection systems, a separate pressure control is performed and wherein the same high pressure disturbance is used for the at least two separate pressure controls of the at least two separate high pressure injection systems. The separate pressure control for each separate high-pressure injection system of a combustion chamber group makes it possible to respond flexibly to deviations, errors or errors To respond to problems that occur only in one of the at least two combustion chamber groups. The use of the same high-pressure disturbance variable for all combustion chamber groups enables a particularly timely, rapid response to load shedding and an efficient, simple

Execution of the procedure, whereby the conditions of the load shedding for all

Combustion chamber groups are the same and occur at the same time, so that the use of a same common high-pressure disturbance is justified.

The combustion chamber groups are in particular cylinder banks of

Internal combustion engine. It is possible that the internal combustion engine has two cylinder banks and in particular is designed as a V-engine. However, it is also possible, for example, that the internal combustion engine has three cylinder banks and is then preferably designed as a W engine.

The object is also achieved by providing an internal combustion engine which is set up for carrying out one of the previously described embodiments of the method.

In particular, the internal combustion engine preferably has a control device, in particular a control device, which is set up to carry out such an embodiment of the method. In connection with the internal combustion engine, the advantages which have already been explained in connection with the method result in particular.

The internal combustion engine is preferably designed as a reciprocating engine. It has a high-pressure injection system for direct injection of fuel into at least one

Combustion chamber of the internal combustion engine, wherein it is possible that the internal combustion engine for a plurality of combustion chamber groups each having separate high-pressure injection systems. The at least one high-pressure injection system is designed in particular as a common-rail system.

The invention will be explained in more detail below with reference to the drawing. 1 shows a schematic representation of an exemplary embodiment of an internal combustion engine with a high-pressure injection system;

Figure 2 is a schematic representation of a method not belonging to the invention

Pressure regulation in a single high pressure injection system; Figure 3 is a schematic representation of a not belonging to the invention method for pressure control in two separate high-pressure injection systems of a two combustion chamber groups having internal combustion engine;

Figure 4 is a schematic detail of an embodiment of a method for

Pressure regulation in a high pressure injection system;

FIG. 5 shows a further schematic detail representation of an embodiment of a method for pressure regulation in a single high-pressure injection system;

Figure 6 is a schematic detail view of an embodiment of a method for

Pressure control in two separate high-pressure injection systems one

Internal combustion engine with two combustion chamber groups;

Figure 7 is a schematic representation of itself in the implementation of a

Embodiment of the method for pressure control resulting effects, and

Figure 8 is a schematic representation of another embodiment of the method for

Pressure control in a high-pressure injection system in the form of a flow chart. Fig. 1 shows a schematic representation of an embodiment of an internal combustion engine 1 with a high-pressure injection system 101, which is preferably designed as a common rail system and is also referred to below as a common rail system.

The illustrated common rail system comprises the following mechanical components: A fuel delivery path 102 with a low-pressure pump 3 for conveying fuel from a fuel tank 2, a variable intake throttle 4 for influencing the

by a high-pressure pump 5 for conveying the fuel under pressure increase, also known as a rail common high-pressure accumulator 6 for storing the fuel, and injectors 7 for injecting the fuel into combustion chambers 103 of the internal combustion engine 1. Optionally, the common rail System be executed with individual memories, in which case, for example, in the injector 7, a single memory 8 is integrated as an additional buffer volume. As a protection against an inadmissibly high pressure level in the rail 6, a passive pressure relief valve 11 is provided which opens, for example, at a rail pressure of 2400 bar and absteuert the fuel from the rail 6 into the fuel tank 2 in the open state. The operation of the internal combustion engine 1 is determined by an electronic control unit 10 (ECU). 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 input variables output variables. In Figure 1 example, the following input variables are shown: a rail pressure pCR, which is measured by a rail pressure sensor 9, an engine speed _n, a signal FP power output desired by an operator of the internal combustion engine 1, optionally a single accumulator pressure pE, and an input size. Under the input variable ON further sensor signals are summarized, for example, a charge air pressure of an exhaust gas turbocharger. In FIG. 1, a first signal PWM for controlling the suction throttle 4, a second signal ve for controlling the injectors 7 (injection start / injection end) and an output variable OUT are shown as output variables of the electronic control device 10. The output variable OFF is representative of 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.

From the German patent DE 10 2008 036 299 B3 a common rail system is known, which consists of two separate rails. Each rail is associated with a high-pressure pump, which promotes fuel under pressure increase in the respective rail. Each rail is in turn protected by a pressure relief valve against impermissibly high rail pressures.

Fig. 3 shows a block diagram of two such pressure control loops 105, 105 '. Both

Pressure control loops 105, 105 'are constructed identically. The upper pressure control loop 105 describes an A-side high pressure control loop for a first rail of a first cylinder bank A, the lower pressure control loop 105 'describes a B side high pressure control loop for a second rail of a second cylinder bank B. The A side high pressure control loop will now be described whose description applies mutatis mutandis to the B-side high pressure control loop. In this case, the same and functionally identical elements in the B-side high-pressure control loop are provided with primed reference numerals that correspond in magnitude to the reference numerals, which in each case the associated same and functionally identical elements of the A-side

High-pressure control circuit are assigned. Both pressure control loops 105, 105 'have a same desired high pressure soii as a reference variable. The difference between the desired high-pressure soii and an actual high-pressure pi _st ^A , which is preferably the rail pressure pCR, results in a high-pressure control deviation e _p ^A. A high pressure regulator 107 calculates from the high pressure control deviation e _p ^A depending on various

Controller parameters, eg. B. a proportional coefficient kp _HD ^A , a high-pressure variable V _{PI (DT} I ₎ ^A The high-pressure control variable V _{PI (DT} I ₎ ^A is a high-pressure disturbance, here one

dynamic disturbance Vs _toer ^dyn added, which corresponds to a feedforward control. A sum V _Unbeg ^A represents an unlimited nominal volume flow. This is then limited in a first limiter 109 as a function of the engine speed ni _st . The limited set volume flow Vs _o ii ^A is the input of a pump characteristic 1 1 1. output of the pump characteristic 1 1 1 is an electrical Saugdrossel target current Is ₀ ii ^A , which is received in the sequence in a current controller 1 13, from the Saugdrossel target current I _So u ^A and a filtered actual current Ii _st ^A a target voltage Us ₀ n ^A as a reference variable for the current control of

Saugdrossel 4 determines which then in a first computing element 1 15 in a

Duty cycle PWM ^{A of} a pulse width modulated PWM signal is converted. With the PWM signal, a solenoid coil of the suction throttle 4 is applied. As a result, the path of a magnetic core is changed, whereby the flow of the high pressure pump 5 is freely influenced. A controlled system 1 17 of the pressure control loop 105 consists of suction throttle 4,

High-pressure pump 5 and rail 6. output of the controlled system 1 17 are measured

High-pressure raw values pR ₀ h ^A , which are filtered by a high-pressure filter 1 19. The high pressure filter 1 19 z. B. correspond to a PTi algorithm. Output variable of the high-pressure filter 1 19 is the filtered actual high-pressure pi _st ^A , which is calculated with the target high-pressure psoii to the high-pressure control deviation e _p ^A. Another output variable of the controlled system 17 is the measured instantaneous actual current I _R0 I _I ^A , which is filtered by a current filter 121. The current filter 121 may also correspond to a PTi algorithm.

Output variable of the current filter 121 is the filtered actual current Ii _st ^A , which in turn enters as an input to the current regulator 1 13.

From the engine speed n; _st , a combustion chamber or cylinder number z of the internal combustion engine 1, an injection target amount Qs _o ii ^stat and two factors fi and f ₂ is calculated by multiplication in a computing unit 123 a static fuel target consumption Vs _toer ^Stat , which a static high-pressure disturbance variable of the two pressure control loops 105th , 105 'corresponds. The first factor fi depends on which physical unit the engine speed n; _st , the injection target amount Q _so ii ^stat and the fuel target consumption Vstoer ^{Stat are} given. Is the unit the engine speed ni _st [1 / min], the injection _target amount Q _so ii ^stat [mm ³ / stroke] and the fuel _target consumption Vs _toer ^Stat [mm ³ / s], the first factor fi has the value 1/120. The second factor f ₂ preferably has the value 0.5, since the injectors 7 are each half connected to one of the two rails and each rail can be assigned half the fuel _target consumption Vs _toer ^Stat . The static _nominal fuel consumption Vs _toer ^Stat is subsequently amplified by a first differentiation element 125, here a (PD) Ti element. Output variable of this first differentiation element 125 is a dynamic fuel _target consumption Vs _toer ^dyn , which corresponds to the dynamic disturbance Vs _toer ^{dyn of} the two pressure control loops 105, 105 'and the outputs of the two high-pressure regulator 107, 107' is added additive.

FIG. 2 shows a pressure control loop 105 for an internal combustion engine 1 with a simple rail.

Identical and functionally identical elements are provided with the same reference numerals, so that reference is made to the preceding description. Also in this case, the dynamic fuel target consumption Vstoer ^dyn the output of the high-pressure regulator 107 V _PI ( _DT I) is added additive as a high-pressure disturbance. The dynamic fuel _target consumption Vs _toer ^dyn is also determined in this case from the static fuel _target consumption Vs _toer ^Stat with the aid of the first differentiation element 125, here a (PD) Ti algorithm. The static

Fuel _target fuel consumption Vs _toer ^Stat is in turn calculated from the engine speed ni _st , the cylinder number z, the injection target quantity Qs _o ii ^stat and the first factor fi by multiplication. In the case of a simple rail, the fuel target consumption is not divided into two disturbance variables as in the case of separate rails, so that the second factor f ₂ shown in FIG. 3 now has the neutral value 1 and is therefore not shown. This corresponds to the static

_Target fuel consumption Vs _toer ^{Stat of} the high pressure static disturbance variable and the dynamic fuel _target consumption Vs _toer ^{dyn of} the dynamic high pressure disturbance variable of the pressure control loop 105.

Fig. 4 shows a speed control circuit 127, which in one embodiment of a

Pressure control method is used. A current actual speed n; _st is subtracted from a target speed ns ₀ n, which gives a speed control deviation e. This speed control deviation e is an input variable of a speed controller 129, here a PI (DTi) controller. The speed controller 129 has, among other things, a further input variables

Proportional _coefficient kp _Drz and as output variable a speed controller torque M _So u ^{PI (DT1)} . This is added with a load signal torque Ms ₀ n ^Load , wherein the load signal torque Ms ₀ n ^{Load represents} a disturbance. Through this feedforward control, a system signal for Improving the dynamics of the speed control loop 127 are used. The sum of the speed controller torque Ms ₀ n ^{PI <} " ^DT1 ' ⁾ and the load signal torque Ms ₀ u ^Load becomes

then limited in a second limiter 131 down to a minimum desired torque Msoii ^Mm and up to a maximum desired torque Ms ₀ n ^Max . Finally, a friction torque Ms ₀ n ^{friction is} added to the thus limited setpoint torque Msoii, resulting in a corrected setpoint torque Mk _on . This is next to other sizes like the

Engine speed n _is input to a motor controller 133. Output of the

Engine control 133 is the static injection target quantity Qsoii ^stat - This is injected into the combustion chambers 103 of the internal combustion engine 1, wherein the internal combustion engine 1 itself, in particular with their combustion chambers 103 and a crankshaft, here represents a speed control path 135. _Raw values n _{raw of} the engine speed are detected and with the aid of a speed fan 137 in the current actual speed n; _st converted.

If the load of the engine 1 abruptly dropped, z. B. in an engine with generator application, the engine speed n increases; _st very quickly. As a result, there is a negative speed control deviation e, which is always larger in magnitude at constant target speed ns ₀ u. As a result, the target torque Msoii and finally the static injection target amount Qsoii ^stat decrease very rapidly, thereby braking the increase of the engine speed ni _s t. In this case, the increase of the engine speed ni _st is less, the faster the injection target quantity Qsoii ^stat decreases.

According to the procedure shown in Figures 2 and 3, the

Fuel target fuel consumption Vstoer ^Stat calculated by multiplying the engine speed ni _st and the static injection target quantity Qsoii ^stat . In a load shedding occurs, as described above, to an increase in the engine speed n; _st and a drop in the static injection target amount Qsoii ^stat . Here, the static injection target amount Qsoii ^stat falls much stronger than the engine speed ni _st increases: In a generator engine increases

Engine speed n; _In the case of full load dumping from full load, it increases by about 10% to 15%, while the static injection target Qsoii ^stat drops by about 95%. As a result, the static fuel target consumption Vstoer ^Stat drops overall when the load sheds. This

Behavior is enhanced by applying a (PD) Ti algorithm according to FIGS. 2 and 3, so that the dynamic fuel target consumption Vstoer ^dyn , which corresponds to the

Pressure feedback loop 105 is connected as a disturbance, falls more sharply than the static

Nominal fuel consumption Vstoer ^Stat . As a result, the dynamics of the pressure control loop 105 amplified, the target volume flow Vsoii in the case of a simple rail according to Figure 2 or the target volume flows Vsoii ^A and Vs ₀ u ^B in the case of separate rails according to Figure 3 are reduced faster, so that there is a smaller increase in the rail pressure pi _st (simple rail) or pi _st ^A and pi _st ^B (separate Rails) comes.

The disadvantage of this approach is that the falling of the static

Fuel nominal consumption Vstoer ^{Stat is} delayed after dropping the load, because the

Engine speed n _is , which in the calculation of the static fuel target consumption Vstoer ^Stat multiplicatively, initially increases. As a result, the fall of the dynamic target fuel consumption Vstoer ^dyn is also delayed immediately after the load shedding. As a result, the potential to combat rail pressure rise after load shedding, especially complete load shedding, is only partially exploited.

According to the invention, the calculation of the disturbance variable is improved to the effect that in the case of a load shedding, in particular a complete load shedding, a faster drop in the disturbance variable, ie the dynamic fuel target consumption Vstoer ^dyn , is achieved, with the aim of minimizing the increase in the rail pressure. This protects the fuel rail against impermissibly high rail pressures and prevents opening of the pressure relief valve. The invention provides a method which improves the dynamics of a pressure control loop 105 in the event of load shedding, in particular not only in common rail systems with mechanical overpressure valve, but also in common rail systems with electrically controllable pressure control valve or common Rail systems, which have installed both a mechanical overpressure valve and an electric pressure control valve. The invention is intended to prevent in such common rail systems that it comes to the response of the mechanical and / or of the or the electrically controllable pressure control valves.

As a result, the mechanical pressure relief valve or the or the electrically controllable pressure control valves are protected and their durability extended because the durability of a

Overpressure or pressure control valve depends on how often and how long this has addressed.

In the method according to the invention for pressure control in a high-pressure injection system is provided in particular that depending on the high-pressure control deviation e _p between the actual high pressure pi _st and the desired high pressure p _so n the high-pressure control variable VPI (DTI) is determined, this being offset with the high-pressure disturbance Vstoer ^dyn , wherein the high-pressure disturbance Vstoer ^{dyn is determined} as a function of the - in particular static - injection target set Qsoii ^stat , however, from the static injection target set Qsoii ^stat by means of a Differentiating a dynamic injection target set Qsoii ^{dyn is} determined, and wherein the high-pressure disturbance Vstoer ^{dyn is} determined based on the dynamic injection target set Qsoii ^dyn .

5 shows the calculation of the high-pressure disturbance variable according to an embodiment of the method for a single-rail pressure-regulating loop 105. Here, a second differentiation element 139, here a (PD) Ti-member 141 or a (PD) Ti algorithm is ^stat to the static target injection quantity Qsoii applied, and not on the static target fuel consumption Vstoer ^Stat, which is so far not calculated. The static injection target quantity Qsoii ^stat is thus the input variable of the second differentiation element 139, the output variable of which is the dynamic injection target quantity Qsoii ^dyn. Characteristic variables of the (PD) Ti element 141 are a derivative time T _v and a delay time Ύ. From the engine speed n; _st , the number of cylinders z, the dynamic injection target amount Qsoii ^dyn and the first factor fi is performed

Multiplication in the computing unit 123, the dynamic fuel target consumption Vstoer ^dyn calculated and the pressure control loop 105 added as a high-pressure disturbance additive. The first factor fi depends on which physical unit the engine speed ni _st , the dynamic injection target amount Qsoii ^dyn and the dynamic fuel target consumption Vstoer ^{dyn are} given. Is the unit of engine speed n; _st [1 / min], the dynamic injection setpoint Qsoii ^dyn [mm ³ / stroke] and the dynamic fuel target consumption Vstoer ^dyn

[mm / s], the first factor fi again has the value 1/120. If the high pressure disturbance Vstoer ^dyn the pressure control loop 105 calculated in this way, a much higher dynamics of the high pressure disturbance Vstoer ^dyn can be achieved, ie in the case of a load shedding faster drop of the high pressure disturbance Vstoer ^dyn can be achieved. Thereby, the increase of the rail pressure in the case of the load shedding is reduced, and the rail is effectively protected against excessive load and reliably prevents opening of the pressure relief valve or a response of the pressure regulating valve.

Important here is the application of the differentiation member 139, in particular (PD) Ti-Algorithmusses, on the injection target amount Qsoii ^stat - This is the highly dynamic

Injection target quantity Qsoii ^dyn , which is then used to calculate the high pressure Disturbance Vs _toer ^{dyn is} used. The influence of the increasing engine speed ni _st on this calculation is thus minimized. The multiplication of the engine speed ni _st with the dynamic injection target set Qs _o ii ^dyn and the constant values of the number of cylinders z and the first factor fi leads to the high-dynamic high-pressure disturbance Vs _toer ^dyn des

Pressure control loop 105, which drops very quickly in the event of a load shedding. This results in a very fast falling setpoint volume flow Vs _o ii as a manipulated variable of the pressure control circuit 105. When de-energized open suction throttle valve 4, that is, a suction throttle valve 4, which is actuated in the closing direction is a rising electrical by means of the pump characteristic curve 111 at a falling setpoint volume flow Vs _o ii Target current Is _o ii and thus calculates an increasing PWM duty cycle PWM. Overall, the method thus allows a faster increase in the PWM duty cycle and thus a faster closing of the suction throttle 4. Thus, a strong increase in the rail pressure is effectively prevented and the

Internal combustion engine 1 protected. Compared to the procedure according to Figures 2 and 3, the increase in the rail pressure is reduced by 40 bar to 60 bar.

FIG. 6 shows the calculation of the high-pressure disturbance variable Vs _toer ^dyn according to an embodiment of the method for pressure-control loops 105, 105 'of two separate fuel rails. Identical and functionally identical elements are provided with the same reference numerals, so that reference is made to the preceding description. In this case, the desired injection quantity Qs _o ii ^{stat is} again amplified by the second differentiation element 139, in particular a (PD) Ti algorithm, so that the highly dynamic injection target quantity Qs _o ii ^dyn results. The disturbance Vs ^dyn _toer which two pressure control loops 105, 105 'is applied additively is, _st the product of the engine speed ni, the number of cylinders z, the dynamic target injection amount Qs _o ii ^dyn and the two factors fi and f _2. The same applies to the factors fi and f ₂ as already described in connection with FIGS. 3 and 5, ie the first factor fi depends on which physical units for the engine speed ni _st , the dynamic injection target quantity Qsoii ^dyn and the interference quantity Vstoer ^dyn be used. The second factor f ₂ preferably has the value 0.5, since with separate rails, an identical number of injectors 7 is generally connected to each of the two rails, and the disturbance variable Vs _toer ^{dyn is} therefore assigned to both rails in equal parts.

The high-pressure variable Vs _toer ^dyn is in each case the output of the pressure regulator 107, 107 ', ie the signals V _{PI (DT} I ₎ ^A and V _{PI (DT} I ₎ ^{B added} additive. The resulting sum is limited depending on the engine speed ni _st , so that the target volume flows Vs _o ii ^A or Vsoii ^B as manipulated variables of the pressure control loops 105, 105 'result. The nominal volume flow Vsoii ^A , Vsoii ^B is in each case the input variable of the pump characteristic 111, 111 '. Output variable of the pump characteristic 111, 111 'is the electrical target current Is ₀ ii ^A , Isoii ^B - From the electrical nominal current I _So u ^A , I _So u ^B finally the duty cycle PWM ^A , PWM ^{B of} the PWM signal, with which the respective Suction choke is applied, calculated.

Characterized in that the second differentiation member 139 to the injection target set Qsoii ^stat and not, as shown in Figures 2 and 3, the first differentiation member 125 to the static

Fuel nominal consumption Vstoer ^{Stat is} applied, even in the case of separate fuel rails in a load shedding a faster reduction of the disturbance Vstoer ^dyn achieved. As a result, the setpoint volumetric flow Vs ₀ n ^A , Vs ₀ n ^B is reduced more rapidly and, if the current is not current, open

Saugdrossel 4 - ie a suction throttle 4, which is operated in the closing direction, the target current Isoii ^A , Isoii ^B increases faster. As a result, the duty ratio increases PWM ^A , PWM ^{B of} the PWM signal, with which the suction throttle 4 is applied, faster, so that the suction throttle 4 closes faster. As a result, an overshoot of the rail pressure is reduced and the engine is effectively protected against overpressure. Above all, it can be prevented that a mechanical pressure relief valve opens or an electrically controllable pressure control valve responds or is opened. For the sake of completeness, it is noted that the separate fuel rails are preferably each assigned a separate intake throttle 4, these separate intake throttles 4 being separately controlled by the separate pressure control circuits 105, 105 '.

The method proposed here allows the dynamic behavior of the

Pressure control loop 105, 105 'to improve. This applies both, as described, in the event of a load shutdown, as well as in the case of a load application. In a load application, the application of the method causes the high-pressure disturbance Vstoer ^dyn des

Pressure control loop 105, 105 'and thus the set volume flow Vsoii, Vs ₀ n ^A and Vs ₀ n ^B increases faster. As a result, the setpoint current Is _d i _, or Is ₀ n ^A and Is _o ii ^B , and the duty cycle PWM, or PWM ^A and PWM ^B - in the case of a normally open suction throttle 4 - reduced faster. This results in that the intake throttle 4 is opened faster and therefore the rail pressure drops less sharply, which is favorable for the emission behavior and the efficiency and thus the dynamics of the engine. Fig. 7 illustrates the resulting in the arrangement of the method proposed here advantages in the form of five timing diagrams. The first time diagram at a) shows the

Consumption P of the internal combustion engine 1, the second time chart at b) the

Engine speed n _is , the third timing diagram at c) the injection target amount Qs _o ii, the fourth timing diagram at d) the high pressure disturbance Vs _toer , and the fifth timing diagram at e) the rail pressure pi _st , respectively plotted against the time t.

At a first time ti, the consumption power P of the internal combustion engine 1, z. B. in the case of a generator application abruptly reduced from the initial value Ps _tart to the value 0 kW, ie the engine load is abruptly dropped completely. The engine speed ni _st , shown in the second _{timing diagram} , increases as a result of this load shedding, starting from an initial value ns _tart - in the third _{timing diagram} , two curves are shown. The solid curve shows the static injection target quantity Qsoii ^stat as the manipulated variable of the

Speed control loop 127 corresponding to Figure 4. The dotted curve shows the dynamic injection target amount Qs _o ii ^dyn according to Figures 5 and 6, ie the static

Injection set amount Qs _o ii ^stat is the input quantity, and the dynamic injection set amount Qs _o ii ^dyn is the output of the (PD) Ti gate 141. It can be seen that the

Injection set amounts Qs _o ii ^stat and Qs _o ii ^{dyn become} smaller after the load is dropped, with the dynamic injection target set Qs _o ii ^dyn decreasing much faster than the static one

Injection setpoint Qs _o ii ^stat - The static injection setpoint Qs _o ii ^stat reaches the value 0 mm ³ / stroke at a fourth time t ₄ , the dynamic injection setpoint Qs _o ii ^dyn already at an earlier, third time t ₃ . The dynamic injection target set Qs _o ii ^dyn can also assume negative values, but for the sake of simplicity, a curve in the positive range is shown. The fourth time diagram shows a total of three curves. The solid curve represents the static fuel _target consumption Vs _toer ^Stat according to FIGS. 2 and 3.

This is calculated as the product of the engine speed ni _st , the number of cylinders z, the static injection target quantity Qs _o ii ^stat , the first factor fi and, in the case of separate rails, the second factor f ₂ . This static fuel _target consumption Vs _toer ^Stat has a falling course after the load has dropped, ie after the first time t _ls . The dashed curve represents the high-pressure disturbance Vs _toer ^dyn (nE) of the pressure control loops (105, 105 ') corresponding to FIGS. 2 and 3. Since the dashed curve is the output and the solid curve is the input of the first differentiation element 125, the dashed line falls Curve, starting from an initial value Vs _tart , faster than the solid curve. The dotted curve shows the high pressure disturbance Vs _toer ^dyn (E) of the pressure control loops 105, 105 'in the sense of here proposed method, that is, in the case that this is calculated by previously the second differentiating member 139 is applied to the static injection target set Qsoii ^stat . It can be seen that the dotted curve drops faster than the dotted curve, ie the high-pressure disturbance drops faster when calculated by the proposed method than in FIGS. 2 and 3. The fifth time diagram again shows three curves. The solid curve shows the course of the rail pressure pi _st , when a static disturbance Vstoer ^Stat the additive control loop 105, 105 'is added additive, without additional gain by a Differentiationsglied. It can be seen that the rail pressure p _{actual rises} at a second time t ₂ , and thus with a time delay to the engine speed _{n i} _st , and reaches its maximum value at a fifth time t s. The dashed curve shows the course of the rail pressure pi _st when the high-pressure disturbance Vstoer ^dyn the pressure control loops 105, 105 'is calculated according to Figures 2 and 3, that is, when the high-pressure static disturbance Vstoer ^Stat amplified by the first differentiation member 125 and the Pressure control loops 105, 105 'as a dynamic high-pressure disturbance Vstoer ^dyn additive is switched. It can be seen that the rail pressure in this case does not increase so much and its maximum value is smaller by the value dpi (nE). The dotted curve shows the course of the rail pressure when the high pressure disturbance Vstoer ^dyn the pressure control loops 105, 105 'is calculated according to the method proposed here, ie in the case that it is calculated by previously the second differentiating 139 to the static Injection target quantity Qsoii ^{stat is} applied. It can be seen that the maximum value of the rail pressure pi _st in this case compared to

Procedure according to Figures 2 and 3 can be additionally lowered by the value dp ₂ (E). As described above, dp ₂ (E) is in practice 40 bar to 60 bar.

FIG. 8 shows an embodiment of the method in the case of a simple fuel rail in the form of a flow chart. In a first step S1, the raw values p are _raw

Rail pressure detected and filtered by the high-pressure fan 119. In a second step S2, the desired high pressure ps _d i is calculated. In a third step S3, the high pressure control deviation e _p as the difference between target high pressure is _set and p is filtered high pressure p _is calculated. In a fourth step S4, the high-pressure control variable V _{PI (DT} I _{) is} calculated as the output of the high-pressure regulator 107. In a fifth step S5, the dynamic

Injection set amount Qsoii ^dyn calculated by applying to the manipulated variable of the speed control loop 127, the static injection target set Qsoii ^stat , in particular a (PD) Ti algorithm. In a sixth step S6, the high-pressure disturbance Vstoer ^{dyn of} the pressure control loop 105 as a product of the engine speed ni _st , the number of cylinders z, the dynamic injection target amount Qs _o ii ^ and the first factor f calculated. In a seventh step S7, the unlimited nominal volume flow Vunbeg is calculated as the sum of the output variable V _PI ( _DT I) of the high-pressure regulator 107 and the high-pressure disturbance variable Vs _toer ^dyn (feedforward control). In an eighth step S8, the duty ratio PWM of the PWM signal applied to the suction throttle 4 is calculated. This eighth step S8 includes in particular the

speed-dependent limitation of the unlimited nominal volumetric flow Vu _nbeg , the calculation of the suction dosing setpoint current Is _o ii, the calculation of the intake throttle setpoint voltage Us ₀ u as

Manipulated variable of the Saugdrosselstrom-locked loop, as well as the calculation of the duty cycle PWM of the PWM signal of the suction throttle command voltage Us _o ii- Thus, the program flow is ended.

The method proposed here has the following advantages in particular:

The dynamics of the pressure control loop 105, 105 'under load changes is significantly increased.

With load drops, the overshoot of the rail pressure is significantly reduced. As a result, the rail is protected from excessive pressure and thus too much stress.

At the same time opening of the mechanical pressure relief valve or a response of the electrically controllable pressure control valve is prevented, whereby the Überduckventil or the pressure control valve is protected and the activation of the Hochdruckregler- emergency operation is prevented. In the high-pressure controller emergency operation is the

Internal combustion engine 1 operated with open pressure relief valve or open pressure control valve. In this mode of operation, a low rail pressure sets in, resulting in reduced engine power at higher emissions.

- The fact that an opening of the mechanical pressure relief valve or a response of the electrically controllable pressure control valve is prevented when Lastab throw, the internal combustion engine 1 can be used in systems with highly dynamic load behavior in the first place. These are in particular marine propulsion systems with constantly expanding and submerging propellers, as well as generator applications.

When a load is applied, the rail pressure lessens under. As a result, the efficiency and the emission behavior of the internal combustion engine 1 is improved.

Claims

1. A method for pressure control in a high-pressure injection system (101) of a

Internal combustion engine (1), wherein

- as a function of a high-pressure control deviation (e _p ) between an actual

High pressure (p _is ) in the high-pressure injection system (101) and a desired high pressure (p _so ii) used as a high-pressure reference variable, a high-pressure control variable (V _{PI (DT} I ₎ ) is determined,

- the high-pressure manipulated variable (Vpipn)) is offset with a high-pressure disturbance variable (Vstoer ^dyn ),

- wherein the high-pressure disturbance variable (Vs _toer ^dyn ) is determined as a function of an injection target quantity (Qsoii ^stat ), and wherein

from the injection target quantity (Qsoii ^stat ) by means of a differentiation member (139)

dynamic injection target set (Qs _o ii ^dyn ) is determined, and wherein

- The high-pressure disturbance variable (Vstoer ^dyn ) based on the dynamic injection target quantity

(Qsoii ^dyn ) is determined.

2. The method according to claim 1, characterized in that a (PD) Ti member (141) is used as the differentiation member (139).

3. The method according to any one of the preceding claims, characterized in that as a high-pressure control variable (V _{PI (DT} I ₎ ) a nominal fuel flow rate is used, as a high-pressure disturbance variable (V _Stoer ^dyn ) a fuel target consumption is determined.

4. The method according to any one of the preceding claims, characterized in that the high-pressure disturbance variable (Vs _toer ^dyn ) itself is not subjected to a differentiation member.

5. The method according to any one of the preceding claims, characterized in that the injection target amount (Qs _o ii ^stat ) as the output variable speed control (127) of the

Internal combustion engine (1) is determined.

6. The method according to any one of the preceding claims, characterized in that the high-pressure disturbance variable (V _Sto er ^dyn ) from a cylinder number z of the internal combustion engine (1), an actual speed (n _is ) and the dynamic injection target rate (Qs _o ii ^dyn ) is determined.

7. The method according to any one of the preceding claims, characterized in that based on the high-pressure control variable (V _{PI (DT} I ₎ ) a suction throttle (4) in a fuel delivery path (102) of the high-pressure injection system (101) is driven.

8. The method according to any one of the preceding claims, characterized in that the internal combustion engine (1) has at least two combustion chamber groups, wherein for each

A separate high-pressure injection system (101) is provided for combustion chamber group, wherein for each high pressure injection system (101) a separate pressure control is performed, and wherein the same high pressure disturbance (Vstoer ^dyn ) for the at least two separate

Pressure control of the high pressure injection systems (101) is used.

9. internal combustion engine (1), adapted for carrying out a method according to one of the preceding claims 1 to 8.