BRPI1003069A2 - process and device for determining the composition of a fuel mixture for the operation of an internal combustion machine - Google Patents

Abstract

PROCESS AND DEVICE FOR DETERMINING THE COMPOSITION OF A FUEL MIXER FOR OPERATING AN INTERNAL FUEL MACHINE. The present invention relates to a process for determining the composition of a fuel mixture of a first fuel and of at least one second fuel for the operation of an internal combustion engine, wherein the fuels are they distinguish in their chemical or physical properties or combustion and, where parameters are determined, which depend on the chemical or physical properties or combustion of the fuel mixture. According to the invention it is provided that from a first parameter a first composition value of the fuel mixture is determined by the fact that from at least one second parameter at least a second value is determined the composition of the fuel mixture is determined from a combination of the first composition value and at least the second composition value. Furthermore, the invention relates to a corresponding device. The process and device enable a low cost and reliable determination of the composition of fuel mixtures for internal combustion machines.

Description

Report of the Invention Patent for "PROCESS AND DEVICE FOR DETERMINING THE COMPOSITION OF A FUEL MIXTURE FOR THE OPERATION OF AN INTERNAL COMBUSTION MACHINE".

description

The present invention relates to a process for determining the composition of a fuel mixture, a first fuel and at least a second fuel for the operation of an internal combustion engine, wherein: , fuels differ in their chemical, and / or physical and / or combustion properties and, where certain parameters are determined, which depend on the chemical, and / or physical and / or combustion properties of the fuel mixture.

The invention further relates to a device for determining the composition of a fuel mixture, a first fuel and at least a second fuel for the operation of an internal combustion engine. whereas fuels differ in their chemical, and / or physical and / or combustion properties, and parameters are determined depending on the chemical, and / or physical and / or combustion properties of the fuel mixture and where the internal combustion engine is coordinated with a control unit. State of the Art

Otto engine-based internal combustion engines are generally operated with a hydrocarbon fuel composed of refined petroleum-based fossil fuels. To this fuel is increasingly added alcohol produced from renewable raw materials (plants), for example ethanol or methanol in different mixing ratios. In the US and Europe, a mixture of 75% to 85% ethanol and 15 to 25% gasoline is generally employed under the trade name E85. Internal combustion engines are designed so that they can be operated with both pure gasoline and mixtures up to E85; This is referred to as "flex fuel operation".

For economical operation with low emission of toxic substances with simultaneous high engine power, the operating parameters in flex fuel operation need to be adapted to the respective existing fuel mixture. a stoichiometric air to fuel ratio of 14.7 parts air weight per parts of gasoline, in the use of ethanol, however, a 9 parts air weight must be adjusted.

In the case of flex fuel operation, due to the distinct evaporation properties dependent on temperature, ethanol and gasoline during the start-up of the internal combustion engine, a mixing factor shall be predetermined as a function of the mixing ratio. adapted enrichment. Similarly, the timing of ignition needs to be adapted to the fuel mixture. Therefore, knowledge of the available fuel mixture ratio is of crucial importance for the operation of the internal combustion engine.

To determine the composition of the fuel mixture various fuel type sensors may also be employed, also referred to as "fuel composition sensors". Fuel type sensors take advantage of the different properties of fuels used, for example, alcohol and gasoline, to determine fuel composition. Thus, for example, ethanol is a protic solvent, which contains hydrogen ions and has a large dielectric constant but is dependent on water content. Gasoline, by contrast, is an aprotic solvent with a small dielectric constant. Based on this, there are fuel type sensors which determine the fuel composition through the dielectric properties of the fuel mixture. Other fuel type sensors take advantage of the different electrical conductivity or optical properties of fuels, such as different refractive indices. In this case, it is disadvantageous that by employing fuel type sensors the system costs are increased. Another disadvantage lies in the fact that according to existing standards the correct

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The fuel-type sensor's operating capability needs to be monitored, which requires additional expenditure.

For this reason, software-based systems for the determination of fuel composition have been developed which do not employ any special fuel type sensor but which evaluate the signals from the sensors in the internal combustion engine. These systems can be realized at cheaper costs than systems with fuel type sensors.

DE 3036107 C3 discloses a regulation device for a fuel metering system in an internal combustion machine consisting of a fuel supply device (fuel injection valve), a lambda probe, means (time element) for the formation of a basic measurement signal which, depending on the characteristic operating quantity, ultimately corrects the control signal (ti) of the fuel supply lambda which, starting from a signal (λ) measured by the lambda probe, determines a correction factor that multiplies the basic measurement signal (tp) with the correction factor. In this case, it is predicted that, in addition to the correction factor (KR λ), lambda correction is dependent on an additive correction quantity (ΚΑ λ) and / or a multiplicative correction quantity (KL λ) that is determined as a function of the correction factor and the operating quantity.

The regulating device makes it possible to compensate for systematic deviations from specific fuel measurements by means of the basic metering signal, hence the so-called pre-control, of the value determined by lambda regulation by means of an adjustment intervention with a corresponding long-term correction. Systematic deviations can be conditioned, for example, by aging or finishing influences. On average, the amount of fuel defined through the corrected pre-control corresponds to the amount actually required. Short-term deviations can be compensated for with the lambda regulator, which is now in the # # ν% x \?

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the entire adjustment range is available. The process based on it is also known under the term blend adaptation.

The determination of the fuel mixture ratio can be done without additional fuel type sensor by means of a fuel adaptation. Fuel adaptation is activated after a recognized refill through the tank level transmitter. A fuel composition changed through the fueling process leads to an altered stoichiometric fuel to air ratio. Through a corresponding intervention of the Iambda regulation on the operating parameters of the internal combustion engine, in particular on the adjusted fuel-air ratio and on the ignition time, this change in fuel properties. is considered in the context of fuel adaptation. Thus, from the intervention of the Iambda regulation or the fuel adaptation, it can be concluded on the stoichiometric relationship and, from this, on the composition of the fuel mixture. Correspondingly, the composition of the fuel mixture can be determined cheaply through a simple software solution.

In this case it is disadvantageous that, after a fueling process, during fuel adaptation, the mixture adaptation needs to be temporarily deactivated so that the altered combustion properties of the fuel mixture are not falsely regulated due to long-term correction of the adaptation of the mixture. Turning off mixture adaptation is undesirable and contradicts CARB's requirements in particular in the USA according to continuous monitoring and diagnostics of the fuel supply system.

Another disadvantage of the process lies in the fact that during a refueling process with small amounts of fuel, tank fill level sensors do not always reliably recognize this. If repeated refueling of such minimum quantities is performed, then in particular, in the case of low fuel tank fill, it may occur that a .j Fls. —W-

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The fuel composition changes significantly without this being recognized and regulated by the fuel adaptation. Then the change in combustion properties is falsely corrected by adapting the mixture.

Another system for determining the mixing ratio of

fuel without the use of a special fuel type sensor is described in the unpublished applicant publication R.312407. The publication describes a process for determining the ratio (z) of components of a fuel mixture which is transported through a fuel pump, the process being characterized by the fact that, a measure (p_KP) is recorded for the fuel pump power consumption and that, by means of the recorded measure (p_KP), the ratio (z) of fuel mixture components is determined.

Another method for determining the fuel mixture ratio without the use of a special fuel type sensor is described in the applicant's unpublished document R.318835. The publication describes a process for determining the composition of a fuel mixture from a first fuel and a second fuel for the operation of an internal combustion engine, with the first and second fuel having indices octane, and the internal combustion engine having at least one octane sensor and one octane setting. The process is characterized by the fact that the composition of the fuel mixture is determined by an initial octane sensor signal. Another process for determining the composition of a

Fuel mixture from a first and at least a second fuel for the operation of an internal combustion engine, with fuel mixtures of different compositions having a different octane index, is characterized by the fact that the composition of the fuel mixture is determined by the ignition angle at which no engine knocking occurs. The process is described in applicant's document R.320246, not yet published. r Fh

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An unpublished applicant's document R.325517 describes a process for determining a fuel composition of a fuel mixture from a first and at least a second fuel for operating a machine. internal combustion in the known fuel-to-air ratio, or an Iambda value in a known fuel in which, through targeted interventions, the quietness of operation of the internal combustion engine is negatively influenced by less occasionally. In this case, it is envisaged that the influence will be effected by a variation of an ignition angle and / or by a variation of the fuel-air ratio, whereby a quiet operation resulting from this or a The resulting gradient for operating uneasiness derives a parameter for the current composition of the existing fuel mixture, or an Iambda value for the internal combustion engine cylinders. The applicant's unpublished document R.322638 states that

A process for determining the composition of a fuel mixture from a first and at least a second fuel for the operation of an automatic ignition internal combustion machine with at least one sensor having determines the course of combustion in at least one cylinder of the internal combustion engine, which is characterized by the fact that, from a quantity, which characterizes a combustion process in at least one cylinder of the combustion engine internal combustion, a measure is formed for the stability of the combustion process, and the determination of the composition of the fuel mixture takes place from the measure for the stability of the combustion process.

Applicant's not yet published application R.327499 describes a process for determining a fuel composition of a fuel mixture of a first and at least one second fuel for the operation of a combustion engine. whereby an initial signal from a broadband Iambda probe disposed in the outlet gas channel of the 7A6 is fed to a control unit; -rT

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internal combustion machine, the process of which is characterized by the fact that

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whereas the composition of the fuel mixture is determined by the flow characteristic of the wide band Iambda probe pump as a function of the Iambda value of the outlet gases.

The processes mentioned for determining the composition

of a fuel mixture based on various parameters and signals from the existing internal combustion engine or its control unit show the disadvantage that the inaccuracy of information obtained in determining the fuel composition in part is noticeably greater than the accuracy. necessary for the control of the internal combustion machine.

Applicant's not yet published application R.322094 describes a process for controlling an internal combustion engine which is operated with a fuel mixture of a first and at least a second fuel, whereby the machine The internal combustion system features a fuel metering device, a tank fill level gauge for the determination of tank content and a change in the tank content, a sensor for the cylinder fill register for the determination of an air mass driven to the internal combustion engine and at least one exhaust gas probe for determining and regulating the oxygen content of the exhaust gas. The process is characterized by the fact that, considering the oxygen content of the exhaust gas, in a first process step a first value is determined for the composition of the conducted air mass fuel mixture and the measured change in the content. that in a second stage of the process a second value is determined for the fuel mixture composition of the air mass driven at idle to the internal combustion engine, and the amount of fuel driven by the fuel metering device, because the first and second values are compared for agreement within a specified limit and that, in the case of deviating values, a - -ΉΛ * 3 ·

fuel metering, the determination of the air mass or tank fill level gauge. Accordingly, the process is for monitoring the fuel metering device, for monitoring the conducted air mass or for monitoring the tank fill level meter; The accuracy in determining the two values for the composition of the fuel mixture is limited to the accuracy of the individual processes that underlie the determination of the composition and thus subject to major inaccuracies of assertion accuracy.

The task of the invention is to prepare a process which makes it possible

Reliable, low-cost recognition of the composition of a fuel mixture from at least two fuels with a sufficiently low assertion accuracy is possible. Disclosure of the Invention The task of the invention relating to the process is solved by the

that from a first parameter a first composition value of the fuel mixture is determined by the fact that at least one second parameter is determined at least a second composition value and whereby the composition of the fuel mixture is determined from a combination of the first composition value and at least the second composition value.

Due to the different properties of pure fuels result in different chemical and physical properties as well as different combustion properties for fuel mixtures composed in different mixing ratios. These properties influence several parameters, usually independent of each other, which are recorded for internal combustion engine control. Thus, from the individual parameters indices can be derived for the composition of the fuel mixture in the form of composition values. A composition value describes the composition of the fuel mixture as obtained by means of a parameter. According to the correlation between the underlying parameters and the fuel mixture composition, ■ Sr >>

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Tolerances and tolerances in determining the measurement values that are the basis, the individual composition values have assertion inaccuracies that may be markedly greater than the accuracy desired in determining the composition of the fuel mixture. Since the individual parameters are independent of each other, one can start from a stochastic distribution of the composition values derived from this and the lack of statement accuracy. By an appropriate combination of the individual composition values, the actual composition of the fuel mixture can therefore be more accurately determined than is possible by the individual composition values. This increases the number of compositional values that are available to increase the accuracy of the statement.

In the process it is advantageous that the determination of the composition values and thus the composition of the fuel mixture can take place from parameters already existing in modern internal combustion machines. No additional components such as additional fuel type sensors need to be provided, which makes cost-effective conversion of the process as a mere software solution possible. For carrying out the process according to the invention, no

The diagnostic functions required by the legislator, such as mixing adaptation, need to be deactivated, and acceptance for the process is noticeably greater than existing software solutions.

Another advantage over existing solutions is that

Determination of fuel composition is not linked to the recognition of a fueling process. If, in the case of existing processes, which presuppose recognition of a filling process, minimum quantities no longer recognized by the tank fill level sensor system are often supplied, then this may take - in particular, in the case of low tank fill level - a noticeable change in the composition of the fuel mixture without this being recognized by the process.

According to a particularly preferred embodiment of the invention it may be provided that the combination of the first composition value and at least the second composition value occurs through the formation of the average value of the first composition value and at least of the second composition value. With increasing numbers of independently determined composition values, then, the actual composition of the fuel mixture can be defined sufficiently accurately, although individual composition values deviate from the actual composition even more strongly. . In this case, the formation of the mean value represents a simple calculation operation, which can be performed using any composition values.

Modern internal combustion machines usually have octane sensors, the initial signal of which is used for octane regulation. If the fuels differ in their octane number, or their octane index, then the octane number and octane index of a obtained fuel mixture are defined by the mixing ratio of the participating fuels. From the initial signal of the octane sensor or. By means of a process for adjusting the octane setting, for example, the ignition angle edition, then, independently of other processes, it can be concluded to determine the composition values on the composition of the fuel mixture. It may therefore be envisaged that one of the parameters for determining one of the fuel mixture composition values is determined from an initial signal from an octane sensor or an octane setting of the combustion machine. internal buston.

Another composition value can be determined by the fact that, as a parameter for determining one of the fuel mixture composition values, the number of revolutions of an electronically switched fuel pump or the electric current being used is used. driven to the fuel pump. In this case, the physical distinguishing characteristic of blended fuels is the different viscosity and the temperature dependence different from the viscosity of the individual fuels and therefore of the resulting fuel mixture. The viscosity of the fuel mixture directly influences the number of revolutions and the electric current conducted to the fuel pump, so that from these parameters clues can be obtained for the composition of the fuel mixture. In this case, it is advantageous for the composi- tion value to be determined independently of other processes for determining the parameters from which other composi- tion values are derived, which is a prerequisite for a stochastic distribution. composition values.

According to a preferred embodiment of the invention, it may be envisaged that for the determination of one of the composition values of the fuel mixture, one of the parameters is determined by the fact that a prepressure pressure formed by a low-pressure fuel pump is reduced until, in the region between the low-pressure fuel pump and a later disposed high-pressure fuel pump, steam bubbles appear and the pressure is used as a parameter. pre-repression, from which steam bubbles arise. The process can be employed, particularly in direct injection internal combustion machines. The basis for this is the vapor pressure different from the fuels employed. Thus, for example, a mixture of ethanol fuel and gasoline at constant temperature and an ethanol content greater than 30% with increasing ethanol content shows a decrease in vapor pressure. If, for example, during a test run the pre-pressure pressure of the low pressure fuel pump for a short period drops so low that, due to the vapor pressure of the fuel mixture not being reached, vapor bubbles in the fuel mixture between the low pressure fuel pump and the high pressure fuel pump, so the high pressure discharge comes down. At a known temperature, from the preset pre-set pressure, it can now be concluded on the composition of the fuel mixture. Vj-

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Fuels differ in their energy density. Correspondingly, the energy density of a fuel mixture depends on the mixture ratio and the respective energy densities of the fuels employed. The power requirement of an internal combustion engine when idling can be known or determined according to the temperature of the cooling medium, the degree of efficiency, the ignition angle and the auxiliary consumers such as a compressor. air conditioner, generator, coolant pump, oil pump and speed. In the case of a low energy density fuel, when idling, more fuel must be driven compared to a high energy density fuel from the internal combustion engine. The amount of fuel driven to the internal combustion engine, therefore, is in direct relation to the mixture ratio of the fuel mixture and can be used as a parameter for determining a composition value. It may therefore be envisaged that as a parameter for determining one of the fuel mixture composition values the fuel mixture consumption in idling is employed. In this case, it is advantageous that the fuel volume current driven to the internal combustion engine in idle speed exists as a parameter over the duration of injection into the control apparatus.

A reduction in the fuel / air mixture, ie an increase in lambda value, in internal combustion engines leads to increased operating agitation. In this case, different fuels and fuel mixtures composed thereof have a so-called typical poor operating limit and, in addition, a limit to the amount of exhaust gas to be recirculated in an exhaust gas recirculation. If the mixture of fuel and air fed to the internal combustion engine is reduced, then both the ignition delay and the ignition delay are greatly delayed, or the ignition does not start at all. This leads to extremely retarded combustion, or combustion failures, which then result in markedly increased operating agitation. Knowledge of the poor operating limit, and the limit for exhaust gas recirculation is a clue to the mixing ratio of the fuel mixture employed. Therefore, it is envisaged that as a parameter for determining one of the composition values of the fuel mixture a poor operating limit and / or an exhaust gas return compatibility limit is employed. In this case, it is advantageous that the poor operating limit and exhaust gas return compatibility can easily be determined by a corresponding variation in the fuel / air ratio or the amount of exhaust gas. reappointed. An altered stochastic combustion system can be determined by evaluating the number of crankshaft rotations, for example by corresponding operating rest algorithms.

It is envisaged that as a parameter for the determination of one of the composition values of the fuel mixture the use of a pumping current from a broadband Iambda probe disposed in the exhaust gas of the internal combustion engine is employed, in accordance with As a function of the Iambda value of the exhaust gas, the determination of the composition of the fuel mixture may therefore be made using another independently determined composition value. The composition of the exhaust gas has a direct influence on the behavior of the broadband Iambda probe pumping current. Exhaust gases from different fuels, eg from ethanol and gasoline, for example, are characterized by different ratios of carbon monoxide and hydrogen. Exhaust gas from a gasoline-ethanol fuel mixture with a high quota of ethanol, in this case, has a higher carbon monoxide-hydrogen ratio than the exhaust gas that arises during combustion of a mixture. of gasoline and ethanol fuel with a small part of ethanol. The carbon monoxide and hydrogen ratio of the exhaust gas directly influences the pumping current behavior of the broadband Iambda probe. If the fuel / air ratio to the internal combustion engine is altered. · .. «* i Oi-. .Ov%.

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Accordingly, the characteristic curve of the pumping current of the broadband Iambda probe shows, in particular, in a range of Iambda <1, therefore, a pumping current behavior dependent on the mixing ratio of the fuels employed. With the help of the pumping current behavior of the broadband Iambda probe as a function of lambda, it can then be concluded on the composition of the fuel mixture. In this case, it is advantageous that a composite broadband lambda probe can be used to determine the composition value, and no other components are required, so that only a suitable software adaptation is required. - in the control device of the internal combustion engine.

Without additional components a composition value can be determined by the fact that one of the parameters for determining one of the fuel mixture composition values is derived from a film thickness of the suction pipe wall. In internal combustion engines with injection of the suction pipe, a film forms on the wall of the suction pipe of the respective fuel or its fuel mixture. The film thickness of the suction pipe wall is dependent on the vaporization enthalpy of the fuel employed. Since fuels, for example, gasoline and ethanol differ in their enthalpy from vaporization, the film thickness of the suction pipe wall depends directly on the mixture ratio of the fuels employed. In the event of a change provided by a driver's wish, or engine control of the fuel-air ratio, the suction pipe wall film must first be formed and reduced to the new equilibrium density. For this reason, the composition value can be determined by observing the lambda intervention during the passage of a thrust shutdown for fuel conduction and combustion restart. Another embodiment of the invention provides that one of the

parameters for the determination of one of the fuel mixture composition values is determined from the adjustment of the sound mixture

frog. The combustion properties of fuel mixtures are directly dependent on the respective composition of the fuel mixture. By adapting the lambda controlled mixture, the operating parameters of the internal combustion engine are adapted to an altered fuel composition such that the exhaust gas composition is within the predetermined range, for example. , in a lambda = 1. From the passive observation of the mixture adaptation, therefore, without an intervention during the diagnosis or a blocking of the mixture adaptation in a fuel supply diagnosis, another clue may be be obtained on the fuel composition of the fuel mixture and thereby another composition value.

Another fuel mixture composition value can be determined regardless of the fact that as a parameter for determining one of the fuel mixture composition values a signal from a fuel type sensor is employed.

The task of the invention concerning the device is solved by the fact that the control unit is provided with parameters and / or signals for parameter determination, and that in the control unit a program operation is provided for the determination of at least one parameter. - for two parameter composition values, and for the determination of the composition of the fuel mixture from at least two composition values. Thus, the composition of a fuel mixture can be determined by a mere software solution without additional components, without the legislator having to temporarily deactivate predetermined diagnostic functions. The number of composition values considered for the determination of the fuel mixture composition can be increased by corresponding to the number of parameter signals in the control unit that depend on the fuel mixture properties, so that the objectivity of the fuel mixture can be reduced. statement of the determined composition of the fuel mixture.

The process and the device may be employed, preferably:

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for determining the composition of a gasoline and alcohol fuel mixture, preferably a gasoline and ethanol fuel mixture.

BRIEF DESCRIPTION OF THE INVENTION The invention will be explained below with the aid of an example.

example shown in the figure. It is shown:

Figure 1 is a diagram for determining the composition of a fuel mixture.

Figure 1 shows a diagram for the determination of composition 10 of a fuel mixture composed of various characteristic parameters for composition 10, in the example of a mixture of gasoline and ethanol fuel. Along a first axis 11 the percentage of ethanol is applied to the fuel mixture. In order to obtain a total deviation 16 desired in determining composition 10, the characteristic parameters are determined by a first composition value 12, a second composition value 13, a third composition value 14 and a fourth composition value. 15. Composition values 12, 13, 14, 15 are shown as expected values with standard deviation, and are arranged along a second axis 17 next to each other. Composition values 12, 13, 14, 15 may be determined, for example, from an octane index or a vapor pressure of the fuel mixture as a characteristic parameter. Instead of four values, according to the invention another number of two or more than two composition values may also be used. The standard deviation of the composite values 12, 13, 14, 15 in this case may be greater than the maximum total deviation 16 desired for the determination of the composition 10 of the fuel mixture.

According to the invention the composition 10 of the fuel mixture is determined by a combination of the composition values 12, 13, 14, 15. In the embodiment shown, the combination occurs by means of formation of average value through the values of composition 12, 13, 14, 15.. Á Λ & A® '"Hi ·.

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Since the composition values 12, 13, 14, 15 were de-

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independent of each other and therefore can be derived from a stochastic distribution of composition values 12, 13, 14, 15 around composition 10, in determining the composition 10 of the fuel mixture the required accuracy can be obtained and represented by the total deviation 16, even though the inaccuracies of assertion accuracy that underlie the composition values 12, 13, 14, 15 are markedly larger.

With an increasing number of composition values 12, 13, 14, 15 considered, the average value formed approximates the actual composition 10 and thus the ethanol content of the fuel mixture, and the failure during the determination of the composition. composition 10 is reduced.

Since individual composition values 12, 13, 14, 15 can be determined by an internal combustion engine control unit of existing sensor parameters and signals, the determination of composition 10 of the fuel mixture This can be done by simply expanding the control unit with no additional components and sensors. For the determination of composition values 12, 13, 14, 15 and composition 10 no diagnostic routines need to be interrupted, for example mixing adaptation.

Claims (13)

1. Method for determining the composition (10) of a fuel mixture of a first fuel and at least one second fuel for the operation of an internal combustion engine, where fuels are distinguished by chemical and / or physical and / or combustion properties and, where certain parameters are determined that depend on the chemical and / or physical and / or combustion properties of the fuel mixture, characterized by the fact that the From a first parameter, a first composition value (12) of the fuel mixture is determined by the fact that from at least one second parameter at least a second value is determined. composition (10) and the fact that the composition (10) of the fuel mixture is determined from a combination of the first composition value (12) and at least the second composition value (13). Process according to Claim 1, characterized in that the combination of the first composition value (12) and at least the second composition value (13) occurs by forming the average value of the first composition. composition value (12) and at least the second composition value (13). Process according to Claim 1 or 2, characterized in that one of the parameters for determining one of the composition values (12, 13, 14, 15) of the fuel mixture is determined from: an initial signal from an octane sensor or an octane setting of the internal combustion engine. Method according to any one of Claims 1 to 3, characterized in that as the parameters for determining one of the composition values (12, 13, 14, 15) of the fuel mixture, the number of revolutions is used. from an electronically switched fuel pump, or the electrical current that is driven to the fuel pump. Process according to any one of Claims 1 to 4, characterized in that one of the parameters for determining one of the fuel mixture composition values (12, 13, 14, 15) is determined by: by the fact that a prepressure pressure formed by a low pressure fuel pump is reduced until, in the region between the low pressure fuel pump and a later disposed high pressure fuel pump, steam bubbles appear and as a parameter the pre-pressure pressure from which steam bubbles appear is used. Process according to any one of Claims 1 to 5, characterized in that as a parameter for determining one of the composition values (12, 13, 14, 15) of the fuel mixture the consumption of the mixture is employed. of fuel when idling. Method according to any one of Claims 1 to 6, characterized in that as a parameter for determining one of the composition values (12, 13, 14, 15) of the fuel mixture a running limit is used. and / or an exhaust gas return compatibility limit. Process according to any one of Claims 1 to 7, characterized in that, as a parameter for determining one of the composition values (12, 13, 14, 15) of the fuel mixture, a pumping current of a broadband Iambda probe disposed in the exhaust gas of the internal combustion machine as a function of the Iambda value of the exhaust gas. Process according to any one of Claims 1 to 8, characterized in that one of the parameters for determining one of the fuel mixture composition values (12, 13, 14, 15) is derived from: a film thickness of the suction pipe wall. Process according to any one of claims 1 to 9, characterized in that one of the parameters for determining one of the fuel mixture composition values (12, 13, 14, 15) is determined from the adjustment of mixture adaptation. Process according to any one of claims 1 to 10, characterized in that as a parameter for determining one of the composition values (12, 13, 14, 15) of the fuel mixture a signal is used. of a fuel type sensor. 12. Device for determining the composition (10) of a fuel mixture of a first fuel and at least one second fuel for the operation of an internal combustion engine, whereby fuels differ in their chemical properties. and / or physical and / or combustion of the fuel mixture and, where certain parameters are determined, which depend on the chemical and / or physical and / or combustion properties of the fuel mixture and, where, to the internal combustion engine A control unit is coordinated, characterized in that the control unit is supplied with parameters and / or signals to determine the parameters and that a program execution is provided for the determination of at least , two composition values (12, 13, 14, 15) from the parameters, and for the determination of the composition (10) of the fuel mixture from, eg and minus two, composition values (12, 13, 14, 15). Use of the process as defined in claim 11 and the device as defined in claim 12 for determining the composition (10) of a preferred gasoline-alcohol fuel mixture of a fuel mixture of gasoline and ethanol.