DE102006022994A1 - Internal combustion engine operating method, involves evaluating lambda sensor signal for deriving information about combustion state of cylinder of combustion engine, and determining oxygen signal from sensor signal - Google Patents

Abstract

The method involves deriving information about a combustion state of a cylinder of an internal combustion engine from operating parameters such as lambda sensor signal of the combustion engine. The sensor signal is evaluated for deriving the information about the combustion state, and an oxygen signal is determined from the sensor signal, where the oxygen signal indicates the relative oxygen content of an exhaust gas of the combustion engine. Independent claims are also included for the following: (1) a computer program is programmed for executing an internal combustion engine operating method (2) an electronic memory for storing a computer program, which executes an internal combustion engine operating method (3) a controller for an internal combustion engine.

Description

State of technology

The The invention relates to a method for operating an internal combustion engine, at the information about a combustion position of at least one cylinder of the internal combustion engine from an operating size of the internal combustion engine be derived.

The The invention further relates to a control device for an internal combustion engine.

Known Procedures determine features the combustion position based on cylinders of an internal combustion engine on a cylinder pressure signal or a structure-borne sound signal. Leave it For example, the start of burning or other interesting Times in the course of combustion of the air-fuel mixture in a considered cylinder.

Even though the former known method per se a relatively accurate Determination of the combustion position, e.g. the start of burning and the Focal point of combustion, in particular, the need for one or more cylinder pressure sensors to provide, disadvantageous. Especially for less expensive smaller engines the application of such a method is out of the question.

The Combustion determination based on structure-borne sound signals is opposite to the analysis the cylinder pressure less accurate and also relatively expensive.

epiphany the invention

Accordingly, it is Object of the present invention, a method and a control device of the initially mentioned above in such a way that an alternative inexpensive possibility given for determining the combustion position.

These Task is in an operating method of the aforementioned Type according to the invention thereby solved, that a lambda probe signal is evaluated to obtain information about the Derive combustion position.

advantageous effects

investigations The Applicant has shown that a correlation exists between the Combustion and the lambda probe signal is made, so that advantageous without using a cylinder pressure sensor information about the time course of a in the combustion chamber of the cylinder in question occurring combustion can be obtained.

Under In the present case, a lambda probe signal is understood as any signal, the information about contains an oxygen content of the exhaust gas of the internal combustion engine. One such signal will usually by one or more in an exhaust tract of the internal combustion engine contained lambda probes provided.

Especially Advantageously, according to the invention from the Lambda probe signal detects an oxygen signal that directly the relative oxygen content of an exhaust gas of the internal combustion engine indicates.

Further advantageous embodiments of the present invention are the subject the dependent claims.

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.

Short description the drawings

1 shows a low pass filtered oxygen signal obtained from a lambda probe signal plotted against a crank angle of an internal combustion engine;

2a shows another low-pass filtered oxygen signal plotted against the crank angle,

2 B illustrates times of a start of combustion, with the oxygen signal according to 2a correspond,

2c indicates a correlation of a feature according to the invention characterizing the combustion position to a start of combustion of different cylinders of the internal combustion engine,

3a shows a further time profile of a low-pass filtered oxygen signal plotted against the crank angle,

3b shows the passage of time 3a corresponding times of a start of combustion of different cylinders of the internal combustion engine,

3c indicates a correlation of characteristics characterizing the combustion position at the times of the start of combustion according to FIG 3b again,

4 shows a functional diagram illustrating the implementation of an embodiment of the method according to the invention,

5 shows a flowchart of an embodiment of the method according to the invention, and

6 shows a simplified block diagram of an intended for carrying out the method according to the invention internal combustion engine.

embodiments the invention

The inventive method for deriving information about a combustion position of at least one cylinder of schematically in 6 shown internal combustion engine 10 is below with reference to the flowchart 5 explained.

In a first process step 100 is to be evaluated as the operating size of the internal combustion engine 10 first detects a lambda probe signal, for example, from one in an exhaust system (not shown) of the internal combustion engine 10 contained lambda probe to a the internal combustion engine 10 controlling controller 20 ( 6 ) is output. As well as the detection of the lambda probe signal, the implementation of the further method steps according to the invention also takes place in the control unit 20 , The control unit 20 For this purpose, it can be equipped with an electronic memory on which a corresponding computer program for carrying out the method according to the invention is stored.

After the detection of the lambda probe signal, this is first in the step 110 an oxygen signal which directly determines the relative oxygen content of the exhaust gas of the internal combustion engine 10 indicates. Advantageously, the oxygen signal according to the invention in a subsequent step 120 low-pass filtered, wherein preferably a low-pass filter with a cut-off frequency between about 100 Hz and about 500 Hz is used. Alternatively, the reverse order is possible, ie first a low-pass filtering of the lambda probe signal and then the formation of the oxygen signal thereof.

1 shows by way of example a time profile of the thus obtained low-pass filtered oxygen signal ro2_tp, the present case in percent and over a crank angle of a crankshaft, not shown, of the internal combustion engine 10 is applied.

According to the invention, in a subsequent process step 130 a global mean ro2_M of the low-pass filtered oxygen signal ro2_tp is formed. This averaging is carried out via the crank angle intervals I_1, I_2, I_3, I_4 of the presently considered four cylinders of the internal combustion engine 10 , The resulting global mean ro2_M is shown below 1 indicated by a dashed line and has a value of about 4.63%.

In a further step 140 of the method according to the invention are then for each of the considered cylinders of the internal combustion engine 10 cylinder-specific average values m1, m2, m3, m4 of the low-pass filtered oxygen signal ro2_tp formed. The cylinder-specific average values m1, m2,... Are formed by averaging those values of the low-pass filtered oxygen signal ro2_tp, which lie in the considered crank angle interval I_1, I_2,.

According to the in 1 given time profile of the low-pass filtered oxygen signal ro2_tp the cylinder-specific average values m1, m4 are arranged below the global mean ro2_M, while the cylinder-individual average values m2, m3 above the global mean ro2_M.

Hereinafter, in the process step 150 in each case the cylinder-specific combustion position characterizing features formed. According to the invention, the formation of these characterizing features takes place as a function of the global mean value ro2_M and the cylinder-specific average values m1, m2, m3, m4.

The characterizing features are preferably obtained as the difference .DELTA.1, .DELTA.2, .DELTA.3, .DELTA.4 between the global mean value ro.sub.2_M and the respective cylinder-specific mean value m.sub.1, m.sub.2, m.sub.3, m.sub.4, cf. the double arrows in 1 ,

For example, a first characterizing feature Δ1, which characterizes the combustion position in a cylinder assigned to the crank angle interval I_1, is obtained according to the invention by subtracting the global mean value ro2_M from the cylinder-specific mean value m1: Δ1 = m1 - ro2_M.

The Determination of further characterizing features or the differences Δ2, Δ3, Δ4 takes place in a similar way.

After the determination of the characteristics characterizing the combustion position, according to the invention in step 160 ( 5 ) Based on the characterizing features on a combustion position, that is, on the time course of combustion in the respective combustion chamber of the respective cylinder of the internal combustion engine 10 , closed.

The ones described below 2a to 2c exemplify a relationship between the combustion position and the low-pass filtered oxygen signal ro2_tp.

2a shows a further time course of the low-pass filtered oxygen signal ro2_tp, which, as in 1 in percent and above a crank angle of the crankshaft of the internal combustion engine 10 is applied.

The global mean ro2_M and corresponding individual cylinder averages are also shown as dashed and solid lines in FIG 2a however, only the cylinder-specific mean value m1 of a first considered cylinder ZZ1 in FIG 2a is provided with a reference numeral.

The vertically extending double arrow in a crank angle range of approximately 540 ° to 720 ° assigned to the first considered cylinder ZZ1 corresponds in this case to a characteristic characterizing the combustion position of the first cylinder ZZ1, comparable to the double arrow Δ1 1 ,

In 2 B are according to the in 2a time sequence of the low-pass filtered oxygen signal ro2_tp times of a start of combustion of the various cylinders ZZ1, ZZ2, ZZ3, ZZ4 of the internal combustion engine 10 specified. The times of the start of combustion are each plotted in the form of a crank angle. For example, for a time of the start of combustion of the first considered cylinder ZZ1 of the internal combustion engine results 10 a crank angle of about 181.6 °. Starting from the top dead center (TDC) at 180 ° CA, the start of combustion of the cylinder ZZ1 is therefore about 1.6 ° CA after TDC.

For the other cylinders ZZ2, ZZ3, ZZ4 of the internal combustion engine 10 This results in times for the start of combustion, which are substantially at an average value SOCM of about 181.1 ° crank angle. This corresponds to the fact that in the 2a the cylinder-specific mean values of the cylinders ZZ2, ZZ3, ZZ4 are substantially identical, while the cylinder-specific mean value m1 of the cylinder ZZ1 is significantly smaller than the remaining cylinder-individual average values.

The characteristics characterizing a cylinder-specific combustion position, that is to say the differences Δ1, Δ2, Δ3, Δ4 between the global mean value ro2_M and a corresponding cylinder-specific mean value m1, m2,..., Are shown in the graph according to FIG 2c specified. For this purpose, the corresponding data points are provided with the respective cylinder identifier ZZ1, ZZ2, ZZ3, ZZ4. The differences according to the invention are shown in the illustration 2c plotted over a difference between the in 2 B represented by a dashed line mean SOCM the start of combustion timing of all cylinders and the respective cylinder-individual combustion start times, which also in 2 B are shown.

Out 2c It can clearly be seen that the feature according to the invention of the difference Δ1, Δ2, Δ3, Δ4 between a global average ro2_M and a cylinder-specific mean value m1, m2, m3, m4 correlates with a start of combustion and can therefore be used to characterize a combustion position of a considered cylinder ,

That is, through the in step 150 of the process according to the invention ( 5 ) determined differences Δ1, Δ2, Δ3, Δ4, it is aware of the in 2c mapped relationship between the start of combustion and the characterizing feature, the differences Δ1, Δ2, Δ3, Δ4, possible, the start of combustion and thus information about the combustion position of a cylinder of the internal combustion engine 10 derive. The determination of information about the combustion position of a cylinder is in 5 through the step 160 illustrated.

With knowledge of the inventively determined actual combustion position of different cylinders of the internal combustion engine 10 can be carried out particularly advantageous further process steps (not shown), for example, an equalization of the combustion positions of the various cylinders of the internal combustion engine 10 to the object and thus contribute to their smoothness and reduce emissions.

The use of such a cylinder equalization with regard to their combustion position also advantageously allows the use of (partially) homogeneous combustion, the so-called. (P) HCCI method, which are used in particular for internal engine emission reduction, and compared to conventional combustion process greatly increased EGR (exhaust gas recirculation ) Rate. Such emission-reducing methods already lead to steady-state operation of the internal combustion engine 10 to cylinder individual different filling or mixture compositions (inert gas / fresh air) and can by applying the inventive method for determining the combustion position and for subsequent cylinder equalization can be optimized.

In order to the inventive method is particularly efficient, is equality the cylinder individually injected amounts of fuel before the execution the method according to the invention desirable.

Such equality can for example be done by known per se, eg speed-based method that affect the cylinder individually injected amounts of fuel in an adaptive process until between individual work cycles of the internal combustion engine 10 occurring speed fluctuations below a predetermined limit.

Furthermore, for efficient implementation of the method according to the invention, an assignment of the cylinders of the internal combustion engine 10 to a certain crank angle interval I_1, I_2, I_3, I_4 ( 1 ) be known.

The following is with reference to the 3a to 3c described by way of example an adaptation method for determining the cylinder assignment of the various cylinders of the internal combustion engine 10 to the oxygen signal or the low-pass filtered oxygen signal ro2_tp is used.

3a shows an example of a further time course of a low-pass filtered oxygen signal ro2_tp. In the present example, the two cylinders ZZ1, ZZ3 have been selectively injected or supplied fuel quantities deviating from a desired value, which is reflected in a correspondingly small or large cylinder-specific mean value m1 or m3. The cylinder ZZ1, for example, has been metered with an amount of fuel which is above the desired value or above averaged over all cylinders average value.

3b shows the start of combustion times of the cylinders ZZ1, ZZ2, ZZ3, ZZ4 of the internal combustion engine 10 , referring to the above with reference to 3a result in fuel metering. How out 3b can be seen, a combustion start time of the first cylinder ZZ1 with about 183 ° crank angle is significantly behind averaged over all four cylinders combustion start time SOCM, which is mapped at about 182.1 crank angle as a dashed line.

The relative delay of the start of combustion time of the cylinder ZZ1 results from the previously purposefully increased fuel quantity that has been supplied to the cylinder ZZ1, and also compare the cylinder-specific mean value m1 of the low-pass filtered oxygen signal ro2_tp 3a ,

Accordingly, a combustion start time of the cylinder ZZ3 is according to 3b clearly prior to the averaged over all cylinders burning time SOCM, because the cylinder ZZ3 like out 3a Obviously a too small amount of fuel has been supplied.

From the into the 3a and 3b Information displayed may be in the controller 20 ( 6 ) of the internal combustion engine 10 be determined accordingly, which cylinder of the internal combustion engine 10 is actually assigned to the respective crank angle intervals. 3c FIG. 2 illustrates the correlation of the difference features m1-ro2_M, m2-ro2_M,... (ordinate) according to the invention with a deviation (abscissa) of the cylinder-specific start of combustion time from the mean value SOCM of all start-of-combustion points.

4 gives in a schematic block diagram the functional relationships of a controller to which the inventive method for determining or regulating the combustion position of several cylinders ZZ1, .., ZZ4 of the internal combustion engine 10 underlying.

The cylinders of the internal combustion engine 10 are shown as function blocks ZZ1, .., ZZ4 and output at their output in each case a moment M1, .., M4, which acts on a functional block KW, the crankshaft of the internal combustion engine 10 modeled. Further, at the output of the cylinders ZZ1, .., ZZ4 a lambda probe signal λ1, .., λ4 available, for example by means of a in the exhaust gas tract of the internal combustion engine 10 integrated lambda probe is determined. The assignment of the lambda probe signal λ1, .., λ4 to the respective cylinder ZZ1, .., ZZ4 can be effected in the manner already described by means of an adaptation method.

As a result of the moments M1, .., M4 acting on it, the crankshaft KW has at its output a resulting speed n, which in the present case is fed to a function block FBC as an input variable. The function block FBC performs a cylinder-related and speed-based equalization of the fuel quantities to be injected, which is known per se. That is, the function block FBC determines the amounts of fuel Δmk1, .., Δmk4, the different cylinders ZZ1, .., ZZ4 of the internal combustion engine 10 be supplied, so that taking into account any variations or tolerances with respect to the control or fuel metering in all cylinders ZZ1, .., ZZ4 actually injected the same amount of fuel.

to Realization of the method according to the invention Furthermore, a function block designated PosMC is provided, the present example, designed as a proportional member is. The function block PosMC receives the different ones Cylinders ZZ1, .., ZZ4 assigned lambda probe signals and determined From this cylinder-specific variables ΔABMI1, .., ΔABMI4, the the driving times of the fuel injections in the different Cylinder ZZ1, .., ZZ4 influence or determine and thus on the combustion position of the respective cylinder ZZ1, .., ZZ4 act.

The is called, the function block PosMC determined by means of the method according to the invention from the lambda probe signal a combustion position of the respective Cylinder ZZ1, .., ZZ4 or characterizing a combustion position Differences Δ1, Δ2, .. and forms in dependence hereof the quantities ΔABMI1, .., ΔABMI4, the set the activation times of the various cylinders ZZ1, .., ZZ4.

The exact relationship between the control variables .DELTA.ABMI1, .., .DELTA.ABMI4 predetermined by the function block PosMC and a combustion position in the respective cylinder ZZ1,..., ZZ4 or the differences .DELTA.1, .DELTA.2, .. characterizing the combustion position is usually dependent on a plurality of parameters internal combustion engine 10 and can be determined, for example, by means of a systematic measurement. The connection may then be for future use in a memory of the controller 20 ( 6 ), eg in the form of one or more proportionality factors or one or more characteristic curves or characteristic diagrams.

All in all allows the inventive method Advantageously, the determination of a combustion position in one or multiple cylinders of an internal combustion engine, without the need for separate sensors must be provided monitor the combustion chamber pressure of the cylinder concerned. Based on the inventively obtained information about the actual Combustion position of individual cylinders may e.g. a combustion position control carried out become.

Claims (11)

Method for operating an internal combustion engine ( 10 ), in which information about a combustion position of at least one cylinder of the internal combustion engine ( 10 ) from an operating variable of the internal combustion engine ( 10 ) are derived, characterized in that a lambda probe signal is evaluated in order to derive information about the combustion position. A method according to claim 1, characterized in that from the lambda probe signal, an oxygen signal is determined which determines the relative oxygen content of an exhaust gas of the internal combustion engine ( 10 ) indicates. Method according to claim 1 or 2, characterized that the lambda probe signal and / or the oxygen signal of a Be subjected to low pass filtering, wherein a cutoff frequency of the low pass preferably between about 100 Hz and about 500 Hz. Method according to one of claims 2 to 3, characterized in that for several, preferably all, cylinder of the internal combustion engine ( 10 ) a global mean (ro2_M) of the oxygen signal and the low-pass filtered oxygen signal (ro2_tp) is formed. Method according to Claim 4, characterized in that cylinder-specific mean values (m1, m2, m3, m4) of the oxygen signal or of the low-pass filtered oxygen signal (ro2_tp) are formed, the oxygen signal or the low-pass filtered oxygen signal (ro2_tp) being respectively measured over a crank angle interval (I_1 , I_2, I_3, I_4), which corresponds to the corresponding cylinder of the internal combustion engine ( 10 ) assigned. Method according to claim 5, characterized in that a characterizing the cylinder-specific combustion position Feature in dependence the global mean (ro2_M) and the cylinder-specific mean (m1, m2, m3, m4), in particular as difference (Δ1, Δ2, Δ3, Δ4) between the global mean (ro2_M) and the cylinder-specific mean (m1, m2, m3, m4). Method according to Claim 6, characterized that characterizes the cylinder-specific combustion position Feature is used to control the timing of a particular the start of the drive, a fuel injection, in particular the Main injection to influence the cylinder. Method according to one of the preceding claims, characterized in that an assignment of a cylinder of the internal combustion engine ( 10 ) is determined at a specific crank angle interval (I_1, I_2, I_3, I_4) by selectively reducing or increasing an amount of fuel allocated to the cylinder, and by evaluating a resulting deviation of the lambda probe signal or of the oxygen signal. Computer program, characterized in that it for execution A method according to any one of claims 1 to 8 is programmed. Electronic storage on which a computer program that is to execute a Method according to one of the claims 1 to 8 is programmed. Control unit ( 20 ) for an internal combustion engine ( 10 ), characterized in that it is designed for carrying out a method according to one of claims 1 to 8.