DE102005017348A1 - An injection internal combustion engine and method for determining an emission value of an injection internal combustion engine - Google Patents

Abstract

The invention relates to an injection internal combustion engine having an emission determination device (1) for determining an emission value for the exhaust gas formed in the fuel combustion and a method for determining an emission value for the exhaust gas formed during a fuel combustion in a combustion chamber of a cylinder of an injection internal combustion engine. DOLLAR A According to the invention, at least one soot emission value can be determined by the emission determining device (1) as a function of the injection pressure (p¶E¶) and of the center of gravity (S) of the fuel combustion as emission value; for the method it is provided that at least one soot emission value is determined from the detected injection pressure (p¶Z¶) and the determined center of gravity (S) of the fuel combustion.

Description

The The invention relates to an injection internal combustion engine having an emission determination device for determining an emission value for the fuel combustion formed exhaust gas according to the preamble of claim 1 and a method for determining an emission value for that at a fuel combustion in a combustion chamber of an injection internal combustion engine formed exhaust gas according to the preamble of claim 7.

It is known that the combustion process of an air-fuel mixture significantly influences the emissions generated during combustion in an internal combustion engine. However, the combustion process is complicated in a manner dependent on a variety of operating parameters and the relationship between the operating parameters and the combustion process and the resulting emission levels is often insufficiently described by complex simulation models. For the realization of a low-emission operation, however, knowledge of these relationships is desirable in order to optimize the combustion process and to be able to influence their emissions in a targeted manner, for example, by changing operating parameters of the internal combustion engine. In individual cases, it has been possible to model nitrogen oxide emission values by means of comparatively simple calculations or correlations. So revealed the DE 100 43 383 A1 a method for mathematical determination of the nitrogen oxide content in oxygen-containing exhaust gases of internal combustion engines. In the method, the nitrogen oxide content is determined from the air mass and fuel mass used in the cylinder and from the center of gravity of the fuel combustion. The center of gravity of the fuel combustion is in turn determined by a measurement and evaluation of the combustion chamber pressure curve. However, other methods for determining the center of gravity of fuel combustion are also known. However, for other emission levels, particularly soot emission, such simple models are not available.

In contrast, is It is an object of the invention to provide an internal combustion engine and a method, which by simple means an improved determination of an emission value enable.

These Task is by an injection internal combustion engine with the features of claim 1 and by a method with the features of Claim 7 solved.

The Internal combustion engine according to the invention has a Emission determination device used to determine the center of gravity Fuel combustion on the basis of recorded operating variables of Internal combustion engine is designed. According to the invention of the emission detection device dependent on from the injection pressure and the center of gravity of the fuel combustion at least a soot emission value determined. Surprised was found that by a suitable link of Injection pressure and center of gravity of fuel combustion simple way reliable Information concerning at least the fuel combustion win in the combustion chamber of a cylinder resulting soot emissions. The internal combustion engine is as direct injection, preferably multi-cylinder reciprocating engine designed and under the center of gravity the fuel combustion is as usual the crank angle position to understand at which 50% of the burn in a work cycle the amount of fuel participating in the cylinder is implemented. Preferably is called the soot emission value determined per working cycle ejected from the cylinder soot mass. The emission determining device is preferably formed in the manner of a microcomputer and has one Input unit for sensory or otherwise recorded operating variables of the internal combustion engine, an arithmetic unit and a storage unit. The arithmetic unit processes in a predetermined manner stored in the memory unit with data some or all recorded operating variables such that the center of gravity the combustion of fuel and, together with it Injection pressure of the soot emission value is obtained. The injection pressure is typically sensory detected size of preferably executed as a common rail system Fuel injection device available.

What the basis of the determination of the focus of combustion As regards the principle, it is provided in an embodiment of the invention, that the center of gravity of the combustion from that of a pressure sensor detected pressure profile in the combustion chamber can be determined. In further Embodiment of the invention is the center of gravity of the combustion calculated from a calculated combustion history of fuel combustion.

In Another embodiment of the invention, the soot emission value is stored Characteristic curves or characteristic diagrams for the dependence the soot emission from the center of gravity of the fuel combustion and the fuel injection pressure taken.

Further features and advantages of the present invention will become apparent from the dependent claims and from the following descrip tion Application of preferred embodiments.

there are the above and to be explained below Features not only in the specified feature combination, but also usable in other combinations or in isolation, without departing from the scope of the present invention.

following The invention will be apparent from the drawings and the accompanying examples explained in more detail.

there demonstrate:

1 1 is a schematic block diagram of an advantageous embodiment of an emission determination device for determining an emission value;

2a a schematic pressure curve diagram for the dependence of the cylinder pressure of the piston position,

2 B a schematic Brennverlaufs diagram for the dependence of a combustion curve of a piston position,

2c a schematic cumulative combustion curve diagram for the dependence of a cumulative combustion curve on a piston position,

3 a schematic map for the soot emission as a function of the center of gravity of the combustion and the fuel injection pressure,

4 a schematic map for the nitrogen oxide emission as a function of the center of gravity of the combustion and the fuel injection pressure and

5 a schematic diagram for the emission of unburned hydrocarbons as a function of the center of gravity of the combustion and the fuel injection pressure.

In the 1 schematically illustrated emission determination device 1 serves to determine an emission value of an exhaust gas of an internal combustion engine, not shown. Without limiting the generality, it is assumed below that the internal combustion engine is a multi-cylinder direct-injection diesel internal combustion engine. The internal combustion engine preferably has a common rail injection system, a charging unit and an exhaust gas recirculation system. Furthermore, means for detecting operating variables of the internal combustion engine are provided. These may be configured as sensors for detecting rotational speed, exhaust gas recirculation amount, air quantity, fuel injection timing, charge air temperature, and the like. In particular, a sensor for detecting the fuel injection pressure is provided. However, it can also be provided to detect operating variables indirectly, for example by an electronic control unit of the internal combustion engine. The explanation of details will be omitted here, as equipped with such operating size detection means internal combustion engines are common and known in the art.

The emission determining device 1 is preferably in the nature of a microcomputer with a computing unit R, a memory unit SP and an input / output unit I / A executed. It is provided that the individual components R, SP, I / O can exchange data via corresponding data lines. The input / output unit I / O receives as input values E values of the detected operating variables of the internal combustion engine and makes them available for calculations of the arithmetic unit R. Using these values and data stored in the memory unit SP, the arithmetic unit R can carry out calculations which ultimately result in emission values of exhaust components formed during the fuel combustion in the cylinders. The determined emission values can be output directly as output variables A via the input / output unit I / O, but it can also be provided an upstream conversion into control variables for the operation of the internal combustion engine. According to the invention of the emission detection device 1 Depending on the injection pressure and the center of gravity of the fuel combustion at least one soot emission value can be determined as the emission value. The determination of the emission values is preferably carried out online and in real time in parallel to the current internal combustion engine operation. The determined emission values therefore correspond to the currently available emission values. The central step here is the determination of the center of gravity of the fuel combustion, which will be discussed in more detail below.

A first advantageous method for determining the center of gravity of the fuel combustion comprises first carrying out a computational analysis of a pressure curve in a combustion chamber of a respective cylinder of the internal combustion engine by the computing unit R. To this end, the arithmetic unit R receives measured values of the corresponding internal combustion chamber pressure, which is detected by a pressure sensor and the on - / output unit I / O to be supplied. The arithmetic unit R processes these measured values by means of a mathematical model stored in the memory unit SP and first calculates a combustion profile and, further therefrom, a sums combustion profile. From the latter results the location of the combustion center of gravity is the piston or crank angle position at which 50% of the amount of fuel participating in the combustion in one cycle of the cylinder is converted. Such a computational model is described, for example, in Pischinger, R., Krassnig, G., Taucar, G., Sams, Th .; Thermodynamics of the internal combustion engine, Springer-Verlag, 1989 described. However, any other calculation model can be used. Without giving any details below, only the necessary connections for understanding, including the 2a to 2c Reference is made.

2a is merely exemplary and schematically a sensor-detected pressure curve p _Z = f (φ) of the combustion chamber pressure p _Z as a function of the crank angle position φ via a compression stroke and power stroke of a cylinder of the internal combustion engine. Taking into account the laws that follow essentially from the first law of thermodynamics and stored in the memory unit SP, the arithmetic unit R determines from this pressure curve p _Z = f (φ) the associated and in 2 B schematically shown combustion curve dQ / dφ = f (φ) of the fuel combustion. The combustion curve dQ / dφ = f (φ) indicates the amount of heat dQ released per combustion angle dφ as a function of the crank angle position φ by the fuel combustion. This results from integration of in 2c shown, to 100 normalized sum combustion curve as the value of the currently at the respective crank angle position φ already burned fuel component and the center of gravity S of the fuel combustion as a 50% value.

In order to improve the reliability and accuracy of the center of gravity S calculated in this way, a smoothing or filtering of the detected pressure value p _{Z can be} provided. Additionally or alternatively, an averaging over several cycles and / or multiple combustion chambers may be provided. For the calculations of the combustion process dQ / dφ = f (φ), it is advantageous if the cylinder charge in terms of fresh air mass, residual gas mass, exhaust gas recirculation and possibly other factors such as wall heat losses, leakage and the like are taken into account. The variables mentioned can be present as measured variables and can be read in by the input / output unit I / O or can be made available as pre-stored empirically determined values in the memory unit SP.

When Another method for determining the center of gravity S of fuel combustion may alternatively or additionally a calculation based on an empirical stored in the memory unit SP Model or a phenomenological Model be provided. This is done in an empirical model the combustion process dQ / dφ = f (φ) by means of a mathematical Function from current operating variables of the internal combustion engine determined.

With regard to an empirical model that may be used, operating variables of the internal combustion engine are linked together via a mathematical function and result in a modeled combustion curve dQ / dφ = f (φ), which is represented graphically as a polygon corresponding to that in FIG 2 B shown cornering can be played. As operating variables, fuel injection pressure, rotational speed, quantity and position of fuel injection processes, cylinder charge, charge air temperature, exhaust gas recirculation quantity, ignition delay and possibly other variables can be taken into account. These variables can be available as measured values or as stored variables analogously to the above-explained pressure profile analysis. For details relating to a corresponding model, reference is made, by way of example, to the technical article by Schreiner, K .: Examinations of the replacement combustion process and heat transfer in high-speed high-speed diesel engines, MTZ 54, No. 11, 1993.

As regards a possibly used phenomenological model, a large number of models are known, which are based essentially on a physico-chemical description of the combustion process, optionally with special consideration of the course of the injection. Details relevant to a corresponding model are given by way of example in the technical paper by Chmela, F., Orthaber, G., Schuster, W .:
The forecast of the combustion history of diesel engines with direct injection based on the Einspritzveraaufs, MTZ 59, No. 7/8, 1998 directed.

In the cases mentioned in each case also the combustion process or a replacement combustion process dQ / dφ = f (φ) is determined, from which according to the explanations to the pressure curve analysis the center of gravity S of fuel combustion results.

The inventive approach for determining at least one soot emission value is based on the assumption that the soot emission essentially two times depending on the center of gravity S of the fuel combustion on the one hand and the injection pressure on the other hand determine leaves. Such a dependence could be confirmed experimentally are and will preferably be determined in advance empirically and in the memory unit SP deposited in the form of suitable maps.

In 3 a characteristic diagram typical of said dependence is shown. As can be seen, the emitted soot mass m _R stated here in grams per cycle Asp is a constant fuel injection pressure p _E approximately exponentially dependent on the center of gravity S fuel combustion. Another dependency, as indicated by the corresponding arrow, is given by the fuel injection pressure p _E. For increasing injection pressure p _E , decreasing soot emission values m _R result, as illustrated by the underlying curves. Overall, therefore, the dependence of the soot emission m _R of the center of gravity S of the fuel combustion on the one hand and the injection pressure p _E on the other hand in the form of in 3 sketch outlined parameter representation with the fuel injection pressure p _E as a parameter.

During operation of the internal combustion engine, the emission determination device is used 1 Therefore, as explained above, determines the center of gravity S of the fuel combustion, read the fuel injection pressure p _E and read from this data, the map stored soot emission value m _R. However, instead of the soot emission values stored in a map, the previously determined empirical dependency can also be described by a corresponding formulaic relationship that is stored in the memory unit SP and to which the arithmetic unit R uses to determine the soot emission value.

It is envisaged that by the emission determination facility 1 in addition to the soot emission value, a nitrogen oxide emission value can be determined. It was possible to confirm the assumption that the nitrogen oxide emission also depends essentially on the center of gravity S of the fuel combustion on the one hand and on the injection pressure p _E on the other hand. 4 shows the determined ratios in the form of a map, analogous to in 3 shown map for the soot emission. In contrast to the soot emission m _R results in a reverse dependence on the fuel injection pressure p _E , ie at a constant center of gravity S occurs with increasing injection pressure p _E an increasing nitrogen oxide emission m _NOx . However, the procedure for determining the nitrogen oxide emission m _NOx is analogous to the above-explained procedure for determining the soot emission m _R , which is why it will not be discussed again at this point.

It could also be determined that the emission of unburned hydrocarbons also depends decisively on the center of gravity S of the fuel combustion on the one hand and on the injection pressure p _E on the other hand. In 5 the determined relationships are schematic in a map similar to that of 3 and 4 shown. As shown, with increasing center of gravity S with increasing injection pressure p _E a decreasing emission m _{uHC of} unburned hydrocarbons _results . It is inventively provided to determine the emission m _uHC unburned hydrocarbons in analogy to the procedure described above for determining the soot emission m _R from the center of gravity S of the fuel combustion and the injection pressure p _E , which is why details are omitted here at this point.

It It goes without saying that these are only examples in grams Working cycle Asp indicated emission values also by other units expressed can be being the basic dependencies unchanged stay. In particular, it can be provided that the emission values the gaseous Emissions of nitrogen oxide NOx and unburned uHC in volume fractions of the exhaust gas are determined in total.

The particles emitted by an internal combustion engine generally consist of soot particles to which unburned hydrocarbons have accumulated. For the estimation of a particle emission, it is therefore provided to determine from the soot emission value and the emission value of unburned hydrocarbons, preferably a mass-related particle emission value. For this purpose, for example, empirically determined maps may also be stored in the memory unit SP. In these, weighted sum values from soot emission and emission of unburned hydrocarbons are preferably stored for different operating points of the internal combustion engine. From the emission determination facility 1 Therefore, the current particulate emission can be determined for each operating point of the internal combustion engine.

According to the invention, it is provided that the not insignificant influence of the exhaust gas recirculation quantity or the exhaust gas recirculation rate on the emission values is taken into account. For this purpose, map sets are preferably analogous to those in the 3 . 4 and 5 maps stored for the soot emission, the nitrogen oxide emission and the emission of unburned hydrocarbons for different amounts of exhaust gas recirculation in the storage unit SP. Depending on the exhaust gas recirculation amount, which is detected, for example, by a Venturi sensor and fed to the input / output unit I / O, the arithmetic unit R accesses data of the corresponding characteristic field. If necessary, it interpolates between the values of two characteristic diagrams.

As from the maps of the 3 and 4 As can be seen, the soot emission and the nitrogen oxide emission have opposite dependencies on both the center of gravity S of the fuel combustion and the fuel injection pressure p _E. In many cases, the ratio of nitrogen oxide emissions is used to assess fuel combustion to the soot emission of interest. According to the invention, it is therefore intended to determine a ratio of nitrogen oxide emission and soot emission and / or particle emission.

The invention thus allows the determination of the essential emission values (soot, particles, nitrogen oxide and / or unburned hydrocarbons) of an internal combustion engine. The maps or calculation models in the storage unit SP of the emission determination device 1 Deposited dependencies therefore make it possible to influence the operation of the internal combustion engine in terms of a target value specification for one or more of the emission values. In this way, with regard to the emission of soot, particles, nitrogen oxide and / or unburned hydrocarbons optimum operation of the internal combustion engine can be adjusted. For this purpose, one or more operating variables of the internal combustion engine are changed such that there is a shift of the respective emission value in the direction of the target value.

Continuous detection of the ratio of nitrogen oxide emission and soot emission and / or particulate emission can be used to assess, for example, a wear-related change in engine operating parameters or, conversely, to have a corrective effect on changes in engine operating parameters that have occurred, so that the cleaning function of an exhaust gas purification system is largely retained. In this context, a networking of the emission detection device 1 with an on-board diagnostic device for the determination of malfunctions of all kinds advantageous. If, for example, a defect in the fuel circuit of the fuel injection device is reported with lowering of the fuel injection pressure, the effect on pollutant formation can be determined and the operation of the exhaust gas purification system can be adjusted and / or other engine operating parameters changed in such a way that the corresponding effects on tailpipe emissions remain as low as possible until the defect is corrected. Similarly, a variety of changes in engine characteristics may be responded which affect the fuel injection pressure and / or the CG of the combustion. In particular when detecting the internal combustion chamber pressure, changes in the center of gravity of the combustion system that occur, for example, due to injection nozzle coking, valve seat or piston ring wear can be detected, and deterioration of the tailpipe emissions can largely be avoided by adapting engine operating parameters.

Conversely, if a malfunction is reported by the onboard diagnostic device for an exhaust aftertreatment component, then the emission determining device can act as a countermeasure measure 1 an effect on the emission values compensatory acting intervention in the engine operation can be caused.

Claims (17)

Injection internal combustion engine having a combustion chamber in which fuel for driving the internal combustion engine can be burned and with - an injection device for direct injection of fuel into the combustion chamber, - operating size detection means for detecting operating variables of the internal combustion engine, the at least one injection pressure (p _E ) for in the Combustion chamber, and - an emission determining device ( 1 ) for determining an emission value for the exhaust gas formed in the fuel combustion in the combustion chamber, wherein the emission determination device ( 1 ) for determining a center of gravity (S) for fuel combustion in the combustion chamber on the basis of the recorded operating variables, characterized in that the emission determining device ( 1 ) as a function of the injection pressure (p _E ) and of the center of gravity (S) of the fuel combustion as the emission value at least one soot emission value can be determined. An injection internal combustion engine according to claim 1, characterized in that a with the emission detecting means ( 1 ) communicating pressure sensor for detecting a pressure curve in the combustion chamber is provided and the center of gravity (S) of the combustion can be determined from the pressure profile detected by the pressure sensor. An injection internal combustion engine according to claim 1, characterized characterized in that the center of gravity (S) of the combustion a calculated combustion history of the fuel combustion can be determined. Injection-type internal combustion engine according to one of claims 1 to 3, characterized in that with the emission determination device ( 1 ) means are provided for detecting an exhaust gas recirculation amount, and a corrected as a function of the detected exhaust gas recirculation amount soot emission value can be determined. Injection-type internal combustion engine according to one of claims 1 to 4, characterized in that the emission determination device ( 1 ) In addition, a nitrogen oxide emission value can be determined. Injection-type internal combustion engine according to one of claims 1 to 5, characterized in that the emission determination device ( 1 ) additional an emission value for unburned hydrocarbons can be determined. Method for determining an emission value for the exhaust gas formed during fuel combustion in a combustion chamber of an injection internal combustion engine, in which - fuel is injected into the combustion chamber, - operating variables of the internal combustion engine, which at least a fuel injection pressure (p _Z ) include detected, - fuel in the combustion chamber is burned and - from detected operating variables of the internal combustion engine, a center of gravity (S) of the fuel combustion is determined, characterized in that from the detected injection pressure (p _Z ) and the determined center of gravity (S) of the fuel combustion at least one soot emission value is determined. Method according to claim 7, characterized in that that determines a combustion course of the fuel combustion in the combustion chamber and from the combustion process, the center of gravity (S) of fuel combustion is determined. Method according to claim 8, characterized in that that the burning process from a sensory recorded pressure curve be determined in the combustion chamber. Method according to claim 8, characterized in that that the combustion curve calculated from the recorded operating variables of the Internal combustion engine can be determined. Method according to one of claims 7 to 10, characterized in that the soot emission value stored characteristic curves or maps for the dependence of the soot emission from the center of gravity (S) of the fuel combustion and the fuel injection pressure (p _E ) is taken. Method according to one of claims 7 to 11, characterized that an exhaust gas recirculation amount is determined and the determined soot emission value depending from the exhaust gas recirculation amount is corrected. Method according to one of claims 7 to 12, characterized that in addition a nitrogen oxide emission value is determined. Method according to one of claims 7 to 13, characterized that in addition an emission value for unburned hydrocarbons is determined. Method according to claim 14, characterized in that that, from the soot emission value and the emission value for unburned hydrocarbons determined a particle emission value becomes. Method according to one of claims 10 to 15, characterized that a ratio value out Nitrogen oxide emission and soot emission and / or particle emission is determined. Method according to claim 16, characterized in that that a target value for the ratio of Nitrogen oxide emission and soot emission and / or particulate emission is predetermined and an operating variable of the internal combustion engine changed like that will that shift the ratio of nitrogen oxide emission and soot emission and / or particle emission towards the target value.