DE102005055952A1 - Method for operating internal-combustion engine, involves detection and determination of residual gas partial pressure of residual gas in combustion chamber - Google Patents

Abstract

Method, involves detection and determination of residual gas partial pressure of residual gas in a combustion chamber (8). Air partial pressure is determined at the time of closing the exhaust valve (10) of air as a function of the residual gas partial pressure, in the combustion chamber. Air mass is determined in the combustion chamber at the time, in which the intake valve (9) closes, as a function of the air partial pressure. Independent claims are also included for the following: (1) Internal-combustion engine; (2) Control unit for internal-combustion engine; (3) Computer program; and (4) Storage element for control unit.

Description

The The present invention relates to a method for operating an internal combustion engine, wherein the internal combustion engine has at least one inlet valve, at least an exhaust valve, an exhaust pipe and a suction pipe, wherein the inlet valve and the outlet valve a valve overlap and wherein exhaust gases are recirculated from the exhaust pipe into the intake manifold.

The The invention further relates to an internal combustion engine with at least an intake valve, at least one exhaust valve, an exhaust pipe and a suction pipe, wherein the inlet valve and the outlet valve a valve overlap and wherein exhaust gases are traceable from the exhaust pipe into the intake manifold.

The Invention further relates to a control unit for an internal combustion engine, wherein the internal combustion engine at least one inlet valve, at least one Exhaust valve, an exhaust pipe and a suction pipe, wherein the Inlet valve and the exhaust valve have a valve overlap and wherein exhaust gases are traceable from the exhaust pipe into the intake manifold. The invention relates also a computer program for such a control unit.

State of technology

The in the combustion chamber of the internal combustion engine after closing the Inlet valves located gas mixture is referred to as combustion chamber filling. The combustion chamber filling is composed of air, which via the intake manifold in the combustion chamber at open Inlet valves passes, and from so-called residual gas. The residual gas is due to the exhaust gas mass that remains in the cylinder after combustion and not while the opening time the exhaust valves is ejected formed.

Of the Residual gas in the combustion chamber can be further increased by means of a so-called exhaust gas recirculation. This may be desirable be, because the residual gas, the ignition and the course of combustion affected. In the so-called external exhaust gas recirculation connects an additional valve the suction pipe with the exhaust pipe, so that exhaust gas from the exhaust pipe over the Valve enters the suction pipe, there mixed with the air and when open Inlet valve returns to the combustion chamber.

at the so-called internal exhaust gas recirculation passes the exhaust gas due to simultaneously opened intake and exhaust valves, the so-called valve overlap, directly from the combustion chamber or from the exhaust pipe and over the Combustion chamber in the intake manifold. The combustion chamber filling can in internal combustion engines with valve overlap contain at certain operating points up to 30% residual gas.

Around one at any time optimal combustion regarding the pollutants generated, fuel consumption and performance must always be in line with the current operating condition Air-fuel ratio for the Combustion in the combustion chamber are available. For example is the ideal theoretical combustion at a mass ratio of 14.7: 1st Depending on the operating mode, however, this value may vary.

to Formation of the air-fuel mixture will vary depending on the time the combustion in the combustion chamber air a corresponding Quantity of fuel injected into the combustion chamber or into the intake manifold. The determination of the required amount of fuel is thus carried out dependent on from the existing in the combustion chamber air filling, so the proportion of air the combustion chamber filling. The air filling in turn depends on the so-called intake manifold pressure, which for example via a is determined in the suction pipe mounted pressure sensor. In systems with big ones camshaft overlap However, there is a non-linear one Relationship between the air filling in the combustion chamber and the intake manifold pressure measured by means of a sensor.

The air filling is also dependent from the atmospheric pressure and thus from the geographical altitude in which the internal combustion engine is operated.

Previous Use method to calculate the amount of fuel to be metered in an approximation process a linear relationship between air filling and intake manifold pressure, the however, systems with great Camshaft overlap due often insufficiently describes the influence of the internal residual gas recirculation.

It Furthermore, methods are known which are based on complex physical Models are based and, for example, findings of gas dynamics and hydrodynamics. However, these methods require a variety of model parameters, which in turn can be determined a variety of measurements is necessary. For evaluation of the model parameters Furthermore, a so-called optimizer is necessary, for example runs in the form of a computer program in a control unit and using the method of least squares of a given squares Set of parameters that determines model parameters.

This method has the disadvantage that it is particularly complicated to implement and requires a high computing power. Furthermore, the Model parameters or the model itself be adapted to the underlying internal combustion engine consuming.

It Object of the present invention, a generic method for operating an internal combustion engine and an internal combustion engine and a control unit therefor in such a way that the connection between the air filling in the Combustion chamber and the intake manifold pressure as accurately as possible little effort can be determined and thus an optimized operation the internal combustion engine possible is. In particular, resources of the control unit should be spared become. Furthermore, the adaptation of the method to different Internal combustion engines are simplified.

• – ein Restgaspartialdruck des sich im Brennraum befindenden Restgases ermittelt wird;
• – ein Luftpartialdruck der sich zum Zeitpunkt des Schließens des Auslassventils im Brennraum befindlichen Luft in Abhängigkeit von dem Restgaspartialdruck ermittelt wird;
• – die Luftmasse in dem Brennraum für den Zeitpunkt, in dem das Einlassventil schließt, in Abhängigkeit von dem Luftpartialdruck ermittelt wird.

This object is achieved according to the invention in an operating method of the type mentioned in that

• A residual gas partial pressure of the residual gas in the combustion chamber is determined;
• - An air partial pressure is determined at the time of closing the exhaust valve in the combustion chamber air as a function of the Restgaspartialdruck determined;
• - The air mass in the combustion chamber for the time when the inlet valve closes, is determined in dependence on the air partial pressure.

Advantages of invention

The inventive method uses the partial pressure of the returned residual gas and the partial pressure the remaining in the combustion chamber residual gas to determine the in the combustion chamber located air mass. Here is the partial pressure the pressure in a gas mixture, such as the air, a given Gas can be assigned. The partial pressure corresponds to the Total pressure that the component will fill when filling in the entire volume would.

The partial pressures can for example, directly for the determination of the air mass in the combustion chamber be determined. This is a largely independent of individual properties of an internal combustion engine possible, so that an adaptation of the method to different internal combustion engines especially easy is.

For the implementation of the inventive method is therefore not a creation of a complex physical model necessary. Nevertheless, it allows a more accurate determination of itself in the combustion chamber at the time of closing the intake valve Air mass, as it is with the known methods, which is the nonlinearity of internal combustion engines with big ones valve overlap disregarding, possible is. Furthermore, the application of the method according to the invention for one Internal combustion engine also simplified by the fact that no complex physical models and no optimizers for the determination of model parameters must be adapted to the internal combustion engine.

• – ein erstes Partialdruckverhältnis ermittelt, wobei das erste Partialdruckverhältnis das Verhältnis des Partialdrucks des rückgeführten Abgases zu dem Abgasdruck beschreibt;
• – ein zweites Partialdruckverhältnis ermittelt, wobei das zweite Partialdruckverhältnis das Verhältnis des Partialdrucks des im Brennraum verbleibenden Restgases zu dem Abgasdruck beschreibt;
• – der Restgaspartialdruck des sich im Brennraum befindenden Restgases durch eine Addition des ersten Partialdruckverhältnisses mit dem zweiten Partialdruckverhältnis und Multiplikation mit dem Abgasdruck ermittelt.

According to a preferred embodiment of the method

• Determining a first partial pressure ratio, the first partial pressure ratio describing the ratio of the partial pressure of the recirculated exhaust gas to the exhaust gas pressure;
• A second partial pressure ratio is determined, wherein the second partial pressure ratio describes the ratio of the partial pressure of the residual gas remaining in the combustion chamber to the exhaust gas pressure;
• The residual gas partial pressure of the residual gas in the combustion chamber is determined by adding the first partial pressure ratio to the second partial pressure ratio and multiplying by the exhaust gas pressure.

Of the Exhaust gas pressure may, for example, by means of a mounted in the exhaust pipe Pressure sensor can be determined. From the partial pressure conditions becomes the Restgaspartialdruck, so the partial pressure for the whole, in the Combustion chamber at the time of closing the intake valve residual gas, determined. By using partial pressure ratios the determination of the Restgaspartialdrucks is particularly easy. The partial pressure conditions In turn, they can be determined independently of external influences. In particular, the residual gas partial pressure is thus independent of an ambient air pressure can be determined. Thus, an optimized Operation of the internal combustion engine in different geographical Heights possible without that a special adaptation of the method according to the invention is necessary.

• – eine Temperatur des Luft-Restgas-Gemisches in dem Brennraum zu einem Zeitpunkt, in dem das Einlassventil schließt, ermittelt;
• – ein Hubvolumenverhältnis eines Zylinderhubvolumens zu einem Nominalhubvolumen für den Zeitpunkt, in dem das Einlassventil schließt, ermittelt;
• – ein effektives Hubvolumenverhältnis ermittelt; und
• – die Luftmasse in dem Brennraum für den Zeitpunkt, in dem das Einlassventil schließt, ermittelt, wobei die Luftmasse in dem Brennraum als Produkt aus dem Luftpartialdruck, der Temperatur in dem Brennraum und dem effektiven Hubvolumenverhältnis ermittelt wird.

Preferably

• - Determines a temperature of the air-residual gas mixture in the combustion chamber at a time when the inlet valve closes;
• A stroke volume ratio of a cylinder stroke volume to a nominal stroke volume for the time when the intake valve closes is determined;
• - Determined an effective stroke volume ratio; and
• - Determines the air mass in the combustion chamber for the time when the inlet valve closes, wherein the air mass in the combustion chamber is determined as the product of the air partial pressure, the temperature in the combustion chamber and the effective Hubvolumenverhältnis.

In order to is a particularly efficient determination of the air mass in the combustion chamber with simultaneous independence from the geographical altitude, in the internal combustion engine is operated. The stroke volume ratio can For example, be determined in advance, so that the temporal complexity the determination of the air mass as possible is kept low. Furthermore allows this is a particularly cost-effective Realization of the method according to the invention.

advantageously, becomes the first partial pressure ratio dependent on from the ratio of an intake manifold pressure to an exhaust pressure and in dependence from the relationship from an overlap angle determined to an engine speed, wherein the overlap angle from the Difference of an angle in which the exhaust valve closes, and one Angle, in which the inlet valve opens, is determined.

modern Internal combustion engines are common already sensors for the measurement of intake manifold pressure, engine speed and crankshaft angle on. A use and evaluation of these sensor signals thus allows a particularly simple and inexpensive application or use the method according to the invention.

Of the Exhaust pressure may be approximate be equated to the ambient pressure. The ambient pressure can e.g. be determined from the intake manifold pressure sensor signal when the Throttle wide open is or in the start.

Preferably becomes the first partial pressure ratio determined by means of a map, wherein an input by a quotient of the intake manifold pressure and the exhaust pressure and another Input from one Quotients from the overlap angle and the engine speed is formed.

By the use of a map can be the determination of the first partial pressure performed very fast become. Furthermore, the application to a particular internal combustion engine is characterized that simplifies for This engine only a map can be determined got to. The formation of quotients also makes it possible with a two-dimensional map to work, although in the determination the first partial pressure ratio more than just two sizes are taken into account.

Preferably becomes the second partial pressure ratio dependent on determined from an angle. This angle describes the crankshaft angle, where the exhaust valve closes. Up to this point of time the same pressure prevails in the combustion chamber and the exhaust pipe. This Angle value already exists, since this is already for the determination of the overlap angle is used.

In an advantageous embodiment of the method is the second partial pressure determined by means of a characteristic, the characteristic curve depending on of the predeterminable angle the ratio of a Cylinder stroke volume to a Nominalhubvolumen describes.

The relationship the cylinder stroke volume to the Nominalhubvolumen corresponds to Ratio of the Partialdrucks of remaining in the combustion chamber residual gas to the Exhaust pressure and thus the second partial pressure ratio. The Determining the second partial pressure ratio by means of a characteristic curve allows on the one hand a particularly fast determination of the second partial pressure ratio and allows on the other hand, a simple application, since the cylinder stroke volume is predetermined by the geometry of the motor.

advantageously, the air partial pressure is calculated by taking the difference from the measured intake manifold pressure and the residual gas partial pressure determined. The ruling in the combustion chamber Pressure can not or only with great effort directly by means of a Sensors are detected. When open Inlet valve, however, corresponds to the intake manifold pressure to the total pressure in the combustion chamber. To determine the total pressure is thus the for example, again by means of the pressure sensor arranged in the suction pipe determined intake manifold pressure used.

Preferably is to determine the temperature of the air-residual gas mixture in the combustion chamber the Temperature of the air with the difference of the exhaust gas temperature and multiplied by the residual gas partial pressure, to which value the product added from the exhaust gas temperature and the residual gas partial pressure and the value thus obtained is divided by the intake manifold pressure.

With the knowledge of the air temperature and the exhaust gas temperature, for example by means of mounted in the intake manifold and the exhaust pipe temperature sensors be determined, the temperature of the entire combustion chamber filling is determined. This, together with the partial pressure, is reflected in the combustion chamber Air and the effective Hubvolumenverhältnis the Air mass determined in the combustion chamber.

The Exhaust temperature can also be modeled as a function of cooling water temperature, the injected fuel mass and the time after engine start.

This calculation is based on the so-called Mixture formula for temperatures with which the temperature of a gas mixture from the temperatures of the gases involved in the mixture can be determined. An application of the mixture formula within the method according to the invention is possible since the basic applicability of the mixture formula is based on the mass ratios of the gases involved. The masses of the individual gases in turn are divided according to their partial pressures. By already determined partial pressures of the gas components in the combustion chamber, it is thus possible to determine the temperature of the air-residual gas mixture located in the combustion chamber, without the combustion chamber is assigned a temperature sensor.

In a particularly advantageous embodiment of the method is the stroke volume ratio means a characteristic determined, the characteristic curve depending a predeterminable angle, the ratio of a Zylinderhubvolumens to a Nominalhubvolumen describes.

The Using a characteristic makes it possible to that the displacement is not constant must be recalculated. Rather, it will be from an example especially stored in a memory area of the controller characteristic determined quickly and sparing the computing time of the controller. Here, the same characteristic as for the determination of the second partial pressure ratio be used.

In an advantageous embodiment of the method is the effective Swept Volume Ratio from the stroke volume ratio determined by multiplication with a correction factor. The correction factor is taken into account the pressure differences of the combustion chamber pressure with respect to the average intake manifold pressure to the time when the inlet valve closes. This can, for example Pressure differences considered that are due to flow differences or due to vibrations prevailing in the suction pipe. This will make a higher Accuracy of the inventive method reached.

Preferably is the correction factor by means of a map depending on determined by an angle and an engine speed. These two sizes are on the one hand particularly suitable to describe the pressure differences On the other hand, they are particularly easy to use with existing sensors to investigate.

The Task is also by a control device of the type mentioned solved by that the controller Means of implementation the method according to the invention having.

The Task is further by an internal combustion engine of the aforementioned Sort of solved by the internal combustion engine has means for carrying out the method according to the invention.

From Of particular importance is the realization of this invention in the form a computer program. The computer program is at least a control unit, in particular on a microprocessor, executable and for carrying out the method according to the invention suitable. In particular, you can for execution the method according to the invention Parts of the computer program on different control units or Microprocessors expire. The invention is thus the computer program realized, so that this computer program in the same way the Invention represents as the method to the execution of the computer program suitable is.

The Computer program is preferably stored on a memory element. The memory element can in particular be a random access memory. be a read-only memory or a flash memory. The storage element Can also be used as a floppy disk, Compact Disk (CD), Digital Versatile Disk (DVD), and / or at least one at least one component of the control unit or be formed of the microprocessor associated memory area.

drawings

Further Features, applications and advantages of the invention will become apparent from the following description of exemplary embodiments of the invention, which are illustrated in the figures of the drawing. All described or illustrated features form for themselves or in any combination, the subject matter of the invention, regardless of their summary in the claims or their dependency as well as independently from their formulation or presentation in the description or in the drawing.

1 schematically shows an internal combustion engine according to the invention,

2 shows a schematic representation of the dependencies of the variables used for carrying out the method according to the invention according to an embodiment.

3 shows a flowchart of an exemplary implementation of the method according to the invention.

description the embodiments

In the 1 is an internal combustion engine 1 a motor vehicle shown in which a piston 2 in a cylinder 3 along a by a double arrow 4 indicated lifting movement is moved up and down. The stroke of the piston 2 is by means of a connecting rod 5 on a crankshaft 6 so transferred that the crankshaft 6 in one by the arrow 7 indicated rotational movement is offset. The cylinder 3 is with a combustion chamber 8th provided, inter alia, by the piston 2 , an inlet valve 9 and an exhaust valve 10 is limited. With the inlet valve 9 is a suction tube 11 and with the exhaust valve 10 is an exhaust pipe 12 coupled.

In the suction pipe 11 is a first pressure sensor 13 and in the exhaust pipe 12 is another pressure sensor 14 arranged in the area of the inlet valve 9 and the exhaust valve 10 protrude an injection valve 15 and a spark plug 16 in the combustion chamber 8th , About the injector 15 can fuel in the combustion chamber 8th be injected. With the spark plug 16 can the fuel in the combustion chamber 8th be ignited.

In the suction pipe 11 is a rotatable throttle 17 arranged over the suction pipe 11 Air can be supplied. The amount of air supplied depends on the angular position of the throttle 17 , In the exhaust pipe 12 is a catalyst 18 housed, which is used to clean the resulting from the combustion of the fuel exhaust gases.

The injection valve 15 is via a pressure line with a fuel tank 19 connected. Has the internal combustion engine 1 over more than one cylinder 3 , so are the injectors of other cylinders 3 with the fuel storage 19 connected in a corresponding manner. The fuel storage 19 is supplied via a supply line with fuel. For this purpose, a fuel pump, not shown, is provided, which is suitable, the desired pressure in the fuel tank 19 build.

Furthermore, on the fuel tank 19 a pressure sensor 20 arranged, with which the pressure in the fuel tank 19 is measurable. This pressure is the pressure exerted on the fuel, and therefore the fuel through the injector 15 in the combustion chamber 3 the internal combustion engine 1 is injected.

In operation of the internal combustion engine 1 fuel gets into the fuel tank 19 promoted. This fuel is delivered through the injectors 15 the single cylinder 3 in the associated combustion chambers 8th injected. The injected amount of fuel depends essentially on the injection time and the fuel pressure in the fuel tank 19 from.

With the help of spark plugs 16 burns in the combustion chambers 8th generated by the pistons 2 in through the in 1 illustrated arrow 4 indicated up and down movements are offset. These strokes are on the crankshaft 6 transmit, exert on this a torque and put them in by the arrow 7 illustrated rotational movement. By means of a speed sensor 21 can the speed of the crankshaft 6 be determined.

A control unit 22 is of input signals 23 acted upon, for example, by means of the sensors 13 . 14 . 20 and 21 measured operating variables of the internal combustion engine 1 represent. Furthermore, the control unit 22 connected to an accelerator pedal sensor, not shown, which generates a signal indicative of the position of a driver operable accelerator pedal and thus the requested torque.

The control unit 22 generates output signals 24 , with which, for example via actuators or actuators, the behavior of the internal combustion engine 1 can be influenced. For example, the controller 22 with the injector 15 , the spark plug 16 and a fuel pressure in the fuel tank 19 controlling, not shown, pressure actuator connected and generates the signals required to control them.

Among other things is the control unit 22 intended to the operating variables of the internal combustion engine 1 to control and / or to regulate. For example, that of the injection valve 15 in the combustion chamber 8th injected fuel mass from the controller 22 controlled and / or regulated with regard to low fuel consumption, low pollutant development and / or particularly reliable operation.

For this purpose, the controller 22 a microprocessor 25 on which a storage element 26 , in particular a flash memory, is assigned. In the memory element 26 a computer program is stored which is suitable for controlling and / or regulating the internal combustion engine 1 perform.

For, regulation of the fuel mass to be metered by the control unit 22 determines the control unit 22 First, the air mass in the combustion chamber at the time of injection. According to the invention for this purpose in the control unit 22 depending on in 2 displayed input variables also in 2 calculations performed.

The input variables are in 2 mostly shown on the left side. These include an intake manifold pressure ps, an exhaust gas pressure pabg, an angle wAS, an angle wEÖ, an engine speed nmot, an angle wES, a temperature Tluft and a temperature Tabg.

For example, the intake manifold pressure ps by means of in the intake manifold 11 arranged pressure sensor 13 and the exhaust pressure pabg by means of in the exhaust pipe 12 arranged pressure sensor 14 determined. The angle WHAT denotes the angle at which the exhaust valve 10 closes. This angle can, for example, with respect to the position of the crankshaft 6 be specified. The angle wEÖ analogously describes the angle at which the inlet valve 9 opens, and the angle wES denotes the angle at which the inlet valve 9 closes.

The temperature Tluft indicates the temperature of the fresh air, which is in the intake manifold 11 located. Accordingly, the temperature Tabg denotes the temperature of the exhaust gas in the exhaust pipe. The temperatures Tluft and Tabg can, for example, by means of a temperature sensor determining the outside air or by means of a in the exhaust pipe 12 arranged temperature sensor can be determined. The exhaust gas temperature can also be modeled.

The engine speed nmot is, for example, by means of the speed sensor 21 determined.

The determination of the air mass of the air fraction located in the combustion chamber at the time of injection becomes, for example, as in FIG 3 shown flowchart performed.

In one step 100 starts the procedure. In one step 101 the input quantities ps, pabg, wAS, wEÖ, wES, nmot, Tluft and Tabg recorded by the corresponding sensors are transmitted to the control unit 22 fed.

In one step 102 quotients Q1 and Q2 are determined. The quotient Q1 describes the ratio of the intake manifold pressure ps to the exhaust pressure pabg. The quotient Q2 describes the ratio of the angle overlap to the engine speed nmot. The angle overlap is formed by forming the difference of the angle wAS in which the exhaust valve closes and the angle wEÖ in which the intake valve opens.

In one step 103 a partial pressure ratio pprue / pabg is determined. The partial pressure ratio pprue / pabg describes the ratio of the partial pressure prue of the suction pipe 11 recirculated exhaust gas to the exhaust pressure pabg. The partial pressure ratio pprue / pabg can be determined, for example, by means of a characteristic field KFpprue from the quotients Q1 and Q2. The map KFpprue can do this in the memory element 26 of the control unit 22 be stored.

In one step 104 a partial pressure ratio ppverb / pabg is determined. The partial pressure ratio ppverb / pabg describes the ratio of the partial pressure pverb of the combustion chamber 8th remaining residual gas to the exhaust pressure pabg. This can be done, for example, by means of a characteristic curve Vbr in which, as a function of a predefinable angle, the ratio of the volume of the combustion chamber 8th , the so-called cylinder stroke volume, is stored at the Nominalhubvolumen. In the present case, the characteristic curve Vbr is addressed with the angle wAS and thus provides the ratio of the cylinder stroke volume to the nominal stroke volume at the time in which the outlet valve 10 closes.

The ratio of the cylinder stroke volume to the nominal stroke volume corresponds to the partial pressure ratio ppverb / pabg, since at the time of closing the exhaust valve 10 only exhaust gas in the combustion chamber 8th located and at this time in the exhaust pipe 12 and in the combustion chamber 8th the same pressure pabg prevails. After closing the exhaust valve 10 the partial pressure pverb of the combustion chamber changes 8th Remaining residual gas due to the subsequent change of the cylinder stroke volume, so that the partial pressure ratio ppverb / pabg corresponds to the ratio of the cylinder stroke volume to the Nominalhubvolumen.

In one step 105 a residual gas partial pressure pbrint is determined. The Restgaspartialdruck pbrint describes the partial pressure of itself in the combustion chamber 8th at the time of closing the exhaust valve 10 located residual gas. For this purpose, the partial pressure ratios pprue / pabg and ppverb / pabg are added and multiplied by the exhaust gas pressure pabg.

In one step 106 the air partial pressure pluft is determined by forming the difference between the measured intake pipe pressure ps and the residual gas partial pressure pbrint.

In one step 107 is made using the so-called mixture formula as in 2 represented by the air temperature Tluft and the exhaust gas temperature Tabg, the intake manifold pressure ps and the partial pressures plv pbrint and the temperature Tbr of the air-residual gas mixture at the time in which the inlet valve 9 closes, determines. This is possible because only the ratios of the masses of the substances involved are crucial for the application of the mixture formula and these split in the ratio of the partial pressures, here the partial pressures and pbrint split.

In one step 108 is an effective stroke volume ratio Vheff / Vh at the time the intake valve 9 closes, calculates. For this purpose, first the characteristic Vbr is addressed with the angle wES. The characteristic Vbr describes a stroke volume ratio Vhwes / Vh of the cylinder stroke volume to the nominal stroke volume at a predetermined time, and in the present case provides the stroke volume ratio Vhwes / Vh at the time when the intake valve 9 closes, back. At this point, however, has the pressure in the combustion chamber 8th due to the upward movement of the piston 2 to the mean pressure ps in the suction tube 11 elevated. To compensate for this, the effective stroke volume ratio Vheff / Vh is multiplied by multiplying the volume ratio Vhwes / Vh by a correction factor fveff. The correction factor fveff can, for example, be in the form of a characteristic map KFVeff in the memory element 26 of the control unit 22 be stored, wherein the map KFVeff the correction factor fveff as a function of an angle, here the angle wES, and the speed nmot describes.

In one step 109 will be in the combustion chamber 8th at the time of closing the intake valve 9 located air mass rl determined. For this purpose, the in the step 106 determined air partial pressure pluft, the reciprocal 1 / Tbr in the step 107 determined temperature Tbr and that in the step 108 multiplied effective stroke volume ratio Vheff / Vh multiplied.

In one step 110 The method according to the invention ends, for example, with the fact that in dependence on itself in the combustion chamber 8th located air mass rl the amount of fuel to be injected is determined.

The characteristic curve Vbr can be applied to a specific internal combustion engine when the method is applied 1 based on the geometry of the internal combustion engine 1 , in particular the cylinder diameter, the piston stroke and the shape of the combustion chamber 8th be determined. The map KFVeff can then be determined, with no valve overlap, otherwise no linearity of the pressure conditions would be present. The map KFpprue can then be determined with existing valve overlap, ie in particular for the angle range between the angle wAS and the angle wEÖ.

The individual steps of the method according to the invention can be carried out in a sequence other than that shown, as long as possible dependencies are taken into account in such a way that the input values necessary for carrying out the calculations of a step are available. In particular, it is conceivable to execute several steps in parallel, to combine steps or to combine calculations within one step with calculations of other steps. For example, one or more of the steps in the step 101 recorded and the control unit 22 supplied input variables ps, pabg, wAS, wEÖ, wES, nmot, Tluft and Tabg only in the step in which the respective input variable is required, detected or the control unit 22 be forwarded.

Claims (16)

Method for operating an internal combustion engine ( 1 ), wherein the internal combustion engine ( 1 ) at least one inlet valve ( 9 ), at least one outlet valve ( 10 ), an exhaust pipe ( 12 ) and a suction tube ( 11 ), wherein the inlet valve ( 9 ) and the exhaust valve ( 10 ) have a valve overlap and wherein exhaust gases from the exhaust pipe ( 12 ) in the suction pipe ( 11 ), characterized in that - a residual gas partial pressure (pbrint) of the combustion chamber ( 8th ) is determined; An air partial pressure (pluft) at the time of closing the exhaust valve ( 10 ) in the combustion chamber ( 8th ) is determined in dependence on the Restgaspartialdruck (pbrint); - the air mass (rl) in the combustion chamber ( 8th ) for the moment in which the inlet valve ( 9 ), is determined as a function of the air partial pressure (pluft). A method according to claim 1, characterized in that - a first partial pressure ratio (pprue / pabg) is determined, wherein the first partial pressure ratio (pprue / pabg) describes the ratio of the partial pressure (pprue) of the recirculated exhaust gas to the exhaust gas pressure (pabg); A second partial pressure ratio (ppverb / pabg) is determined, the second partial pressure ratio (ppverb / pabg) describing the ratio of the partial pressure (ppverb) of the exhaust gas remaining in the combustion chamber to the exhaust gas pressure (pabg); and - the residual gas partial pressure (pbrint) of the combustion chamber ( 8th ) is determined by adding the first partial pressure ratio (pprue / pabg) to the second partial pressure ratio (ppverb / pabg) and multiplying by the exhaust gas pressure (pabg) A method according to claim 1 or 2, characterized in that - a temperature (Tbr) of the air-residual gas mixture in the combustion chamber ( 8th ) at a time when the inlet valve ( 9 ), is determined; A stroke volume ratio (Vhwes / Vh) of a cylinder stroke volume (Vhwes) to a nominal stroke volume (Vh) for the time when the intake valve ( 9 ) is determined. - An effective stroke volume ratio (Vheff / Vh) is determined; and - the air mass (rl) in the combustion chamber ( 8th ) as the product of the air partial pressure (pluft) of the air, the reciprocal (1 / Tbr) of the temperature (Tbr) in the combustion chamber ( 8th ) and the effective stroke volume ratio (Vheff / Vh) is determined. A method according to claim 2 or 3, characterized in that the first partial pressure ratio (pprue / pabg) is dependent on the ratio of an intake manifold pressure (ps) to an exhaust pressure (pabg) and depending on the ratio of an overlap angle to an engine speed (nmot ), where the overlap angle is the difference between an angle (wAS) in which the exhaust valve ( 10 ) and an angle (wEÖ) in which the inlet valve ( 9 ) opens, is determined. Method according to one of claims 2 to 4, characterized that the first partial pressure ratio (pprue / pabg) is determined by means of a map, wherein a Input size through a quotient of the intake manifold pressure (ps) and the exhaust gas pressure (pabg) and another input from one Quotients from the overlap angle and the engine speed (nmot) is formed. Method according to one of claims 2 to 5, characterized that the second partial pressure ratio (ppverb / pabg) depending is determined by an angle (WHAT). Method according to one of claims 2 to 6, characterized that the second partial pressure ratio (ppverb / pabg) is determined by means of a characteristic curve (Vbr), where the characteristic in dependence a predeterminable angle, the ratio of a Zylinderhubvolumens to a Nominalhubvolumen describes. Method according to one of the preceding claims, characterized characterized in that the air partial pressure (pluft) by education the difference between the measured intake manifold pressure (ps) and the residual gas partial pressure (pbrint) is determined. Method according to one of claims 3 to 8, characterized in that for determining the temperature (Tbr) of the air-residual gas mixture in the combustion chamber ( 8th ) the temperature of the air (Tluft) is multiplied by the difference between the exhaust gas temperature and the residual gas partial pressure (pbrint), the product of the exhaust gas temperature (Tabg) and the residual gas partial pressure (pbrint) is added to this value, and the value thus obtained by the intake manifold pressure (ps) is divided. Method according to one of claims 3 to 9, characterized that the stroke volume ratio (Vhwes / Vh) is determined by means of a characteristic curve (Vbr), wherein the Characteristic in dependence from a predeterminable angle the ratio of a Zylinderhubvolumens to a Nominalhubvolumen describes. Method according to one of claims 3 to 10, characterized the effective stroke volume ratio (Vheff / Vh) is calculated from the stroke volume ratio (Vhwes / Vh) multiplied by a correction factor (fveff) becomes. Method according to claim 11, characterized in that that the correction factor (fveff) is determined by means of a characteristic map (KFVeff) dependent on is determined from an angle and an engine speed (nmot). Internal combustion engine ( 1 ) with at least one inlet valve ( 9 ), at least one outlet valve ( 10 ), an exhaust pipe ( 12 ) and a suction tube ( 11 ), wherein the inlet valve ( 9 ) and the exhaust valve ( 10 ) have a valve overlap and wherein resulting exhaust gases by means of an internal feedback from the exhaust pipe ( 12 ) in the suction pipe ( 11 ), characterized in that the internal combustion engine ( 1 ) is prepared for use in a method according to one of claims 1 to 12 Control unit ( 22 ) for an internal combustion engine ( 1 ), characterized in that it is prepared for use in a method according to one of claims 1 to 12. Computer program, characterized in that it for use in a method according to one of claims 1 to 12 is programmed. Memory element for a control unit, thereby characterized in that on the storage element a computer program stored for use in a method according to a the claims 1 to 12 is programmed.