Electronic control device for detecting mixture differences in an internal combustion engine

Abstract

A method for determining a setting of a cylinder (103) from a plurality of cylinders (103) of an internal combustion engine, the method comprising - changing (401) a common lambda target value (210) for the plurality of cylinders (103) for a predefined period of time (201, 202); - determining (402) reactions (311, 312, 313, 314) of the plurality of cylinders (103) to the change (301, 302) of the common lambda target value (210); wherein determining (402) reactions (311, 312, 313, 314) comprises determining (402) rough running changes (311, 312, 313, 314) of the plurality of cylinders (103) in response to the change (301, 302) of the common lambda target value (210); and - determining (403) one or more indicia regarding a setting of at least one of the plurality of cylinders (103) based on the determined reactions (311, 312, 313, 314) of the plurality of cylinders (103); wherein the determining (403) of one or more indicia comprises, - determining a change reference value from the determined rough running changes (311, 312, 313, 314) of the plurality of cylinders (103); - determining the deviations of the determined rough running changes (311, 312, 313, 314) from the change reference value; and - Comparing the determined deviations with a predefined threshold.

Description

[0001] The invention relates to the detection of differences in the composition of fuel-air mixtures in the plurality of cylinders of an internal combustion engine.

[0002] Vehicles (particularly single- or dual-vehicles such as motorcycles, passenger cars, or trucks) typically have internal combustion engines. Internal combustion engines, particularly gasoline engines, typically comprise a plurality of cylinders. A fuel-air mixture is introduced (e.g., injected) into each of the plurality of cylinders, which is then ignited to move a piston of the cylinder. The plurality of cylinders typically ignite at different phases, and the pistons of the cylinders drive a common crankshaft during the different phases.

[0003] The exhaust gases are led from the cylinders through a vehicle exhaust system, from the combustion engine and out of the vehicle. The exhaust system typically comprises a plurality of pipes (e.g. a manifold, a Y-pipe, and a tailpipe), a plurality of silencers, a catalytic converter and a so-called lambda sensor. In particular, the lambda sensor is designed to determine the oxygen content of the exhaust gases. A target value for the exhaust gas mixture measured by the lambda sensor is typically λ=1. Values of λ>1 are typically referred to as lean mixtures, which contain too much air, i.e. too much oxygen, and thus indicate that the fuel-air mixture supplied to the cylinders contains too little fuel. Values of λ<1 are typically referred to as rich mixtures, which contain too much fuel.The measured values of the lambda sensor can thus be used to regulate the fuel-air mixture supplied to the cylinders of an exhaust bank, e.g. to set a value of λ=1.

[0004] Due to aging processes and / or defects, the fuel-air mixtures in the individual cylinders can differ from one another. This can lead to a satisfactory lambda value being measured at the lambda sensor (e.g., λ=1) even though individual cylinders have a fuel-air mixture that is either too rich or too lean. The different fuel-air mixtures in the cylinders lead to a so-called "cylinder imbalance," which should be eliminated by taking suitable measures to equalize the cylinders. In particular, a "cylinder imbalance" can lead to failure to comply with certain emissions standards even though the lambda sensor shows a satisfactory lambda value.

[0005] DE 10 2007 043 734 A1 describes a method for determining the deviation of the lambda value of at least one cylinder of an internal combustion engine from the total lambda value. DE 10 2009 027 822 A1 describes a method for determining cylinder trim.

[0006] This document addresses the technical task of detecting and diagnosing the presence of a cylinder imbalance in an efficient, particularly time-efficient manner. Once a cylinder imbalance is detected, appropriate countermeasures can be initiated to enable cylinder balancing, thus improving exhaust gas quality and / or reducing fuel consumption.

[0007] The object is achieved by the independent claims. Advantageous embodiments are described, inter alia, in the dependent claims.

[0008] According to one aspect, a method for determining a setting of one cylinder from a plurality of cylinders of an internal combustion engine is described. The internal combustion engine may be an internal combustion engine (in particular a gasoline engine) of a vehicle (e.g., a passenger car, a truck, or a motorcycle). The internal combustion engine may comprise one or more cylinder banks, each having a plurality of cylinders. The plurality of cylinders may comprise, for example, four, six, or eight cylinders.

[0009] The adjustment of a cylinder can, in particular, include the composition of the fuel-air mixture supplied to the cylinder. This composition is typically influenced by the adjustment of the cylinder's injection system. Thus, the method can be designed to determine one or more indicators regarding the composition of the fuel-air mixture of a cylinder.

[0010] Typically, the composition of the fuel-air mixture can be deduced from the composition of the exhaust gases from a cylinder. The composition of the exhaust gases from a cylinder can be determined, for example, using a lambda sensor. The lambda sensor provides a so-called lambda value or measured lambda value. Since a vehicle typically only has one common lambda sensor for the plurality of cylinders, only one common lambda value can be determined for the exhaust gases from the plurality of cylinders. The described method can be designed to determine one or more indices relating to the individual lambda value of an individual cylinder, even though only one common lambda value is measured for the plurality of cylinders.

[0011] The method comprises changing a common lambda target value for the plurality of cylinders for a predefined period of time. For example, for the predefined period of time, the lambda target value can be increased from a standard target value (e.g., λ=1) to a lean target value (e.g., λ>1). This typically results in the fuel-air mixtures of all cylinders of the plurality of cylinders being leaner. Alternatively or additionally, for the predefined or for a different period of time, the lambda target value can be reduced from the standard target value (e.g., λ=1) to a rich target value (e.g., λ<1). This typically results in the fuel-air mixtures of all cylinders of the plurality of cylinders being richer. The change in the common lambda target value can be controlled and / or regulated by a control unit (e.g., an engine control unit) (e.g., based on the lambda measured values of a common lambda sensor).

[0012] The method further comprises determining reactions of the plurality of cylinders to the change in the common lambda target value. Determining reactions may, in particular, include determining changes in the rough running of the plurality of cylinders in response to the change in the common lambda target value. The rough running values and / or changes therein can be determined, for example, using a crankshaft sensor.

[0013] The method further comprises determining one or more indices regarding a setting of at least one of the plurality of cylinders based on the determined reactions of the plurality of cylinders. As explained above, in particular one or more indices regarding the composition of the fuel-air mixture of at least one cylinder can be determined. Due to the change in the common lambda target value for all cylinders of the plurality of cylinders, it is possible to analyze each of the plurality of cylinders in a short time. In particular, it is possible to determine one or more indices for each individual cylinder of the plurality of cylinders by changing the common lambda target value only once. This provides a time-efficient diagnostic method.

[0014] Determining one or more indicators can include identifying at least one cylinder of the plurality of cylinders whose rough running change deviates from a rough running change of the other cylinders of the plurality of cylinders. In particular, determining one or more indicators can include the following steps: Determining a change reference value (e.g., a mean value, a median value, or an initial value) from the determined rough running changes of the plurality of cylinders. In addition, deviations of the determined rough running changes from the change reference value can be determined. Furthermore, the determined deviations can be compared with a predefined threshold value. Deviations that are greater than or equal to the predefined threshold value can represent an indication of incorrect adjustment of the corresponding cylinder.

[0015] In particular, based on the one or more indicators, it can be determined that a first of the plurality of cylinders has a fuel-air mixture that is too lean or too rich. In response, the fuel-air mixture supplied to the first cylinder can be changed. Alternatively or additionally, an ignition angle and / or a torque of the first cylinder can be changed. This can achieve equalization of the cylinders in a time-efficient manner. For this purpose, changes to the fuel-air mixture, the ignition angle, and / or the torque of the other cylinders of the plurality of cylinders can also be made if necessary.

[0016] As already explained above, a composition of the exhaust gases from the plurality of cylinders can be determined by a common lambda probe. Furthermore, the exhaust gases from the plurality of cylinders can be passed through a catalytic converter (e.g., a controlled catalytic converter). The method can further comprise performing a functional test of the catalytic converter in response to the change in the common lambda target value, in particular during the predefined period of time. An additional second lambda probe (also referred to as a trim probe) can be used for the functional test. In other words, both a diagnosis of the catalytic converter and a diagnosis of the plurality of cylinders can be performed during the predefined period of time.Alternatively or additionally, the method may further comprise performing a functional test of the common lambda sensor in response to the change in the common lambda target value, particularly during the predefined period. This means that during the predefined period, both a diagnosis of the common lambda sensor and a diagnosis of the plurality of cylinders can be performed. This can further shorten the time required to perform the various diagnostic procedures.

[0017] According to a further aspect, a control unit (e.g., an engine control unit) for a vehicle is described. The vehicle comprises an internal combustion engine with a plurality of cylinders. The control unit is configured to change a common lambda target value for the plurality of cylinders. The change typically occurs for a predefined period of time. For this purpose, the control unit can be configured to receive lambda measurement data relating to an actual lambda value of exhaust gases from the plurality of cylinders from a (common) lambda probe. One or more settings of fuel injection systems in the plurality of cylinders can be changed (in particular controlled) depending on the lambda measurement data in order to thus change the common lambda target value.

[0018] The absolute change in the common lambda target value can be equal to or greater than a predefined lambda threshold. Examples of lambda thresholds are 0.05, 0.1, 0.15, or 0.2. For example, the lambda target value can be increased from λ=1 to λ=1.05, λ=1.1, λ=1.15, or λ=1.2, or decreased from λ=1 to λ=0.95, λ=0.9, λ=0.85, or λ=0.8.

[0019] Furthermore, the control unit is configured to determine the reactions of the plurality of cylinders to the change in the common lambda target value. For this purpose, the control unit can be configured to receive noise measurement data from a crankshaft sensor of a crankshaft of the internal combustion engine, wherein the crankshaft is driven by the plurality of cylinders. The reactions of the plurality of cylinders can be determined based on the noise measurement data.

[0020] The control unit is further configured to determine one or more indicators regarding a setting of at least one of the plurality of cylinders based on the determined reactions of the plurality of cylinders. In particular, one or more indicators regarding the composition of the fuel-air mixtures (i.e., regarding the individual lambda values) of at least one of the plurality of cylinders can be determined. In principle, an anomalous situation can be determined for each of the plurality of cylinders in a time-efficient manner.

[0021] According to a further aspect, a vehicle having the control unit described in this document is described.

[0022] According to another aspect, a software (SW) program is described. The SW program can be configured to be executed on a processor (e.g., on the control unit) and thereby to carry out the method described in this document.

[0023] According to a further aspect, a storage medium is described. The storage medium can comprise a software program configured to be executed on a processor and thereby to carry out the method described in this document.

[0024] It should be noted that the methods, devices, and systems described in this document can be used both alone and in combination with other methods, devices, and systems described in this document. Furthermore, any aspects of the methods, devices, and systems described in this document can be combined in a variety of ways. In particular, the features of the claims can be combined in a variety of ways.

[0025] The invention will be described in more detail below using exemplary embodiments. Fig. 1 is a block diagram of an exemplary plurality of cylinders; Fig. 2 an exemplary lambda sequence for diagnosing cylinder settings; Fig. 3 exemplary measured values of rough running values of the plurality of cylinders; and Fig. 4 a block diagram of an exemplary diagnostic procedure.

[0026] As stated at the beginning, this document deals with the diagnosis of so-called “cylinder imbalances”, i.e. with the diagnosis of cylinder settings, particularly with regard to the composition of the fuel-air mixtures in the individual cylinders.

[0027] The settings of a cylinder can be determined in particular by changing the fuel-air mixture supplied to a cylinder (in particular by making it leaner), and adjusting the fuel-air mixture of the other cylinders of the internal combustion engine to a corresponding extent (in particular by making it richer) so that a desired lambda value (e.g. λ=1) is still achieved on average. Changing the fuel-air mixture typically changes the torque caused by the piston of the cylinder on the crankshaft, which can be represented by the so-called rough running of the cylinder. In particular, when the fuel-air mixture in a cylinder is leaner, the rough running of that cylinder typically decreases.

[0028] This allows the fuel-air mixtures of the individual cylinders to be leaned out sequentially, thus determining the roughness curves of each cylinder. The relative changes in the roughness can then be used to determine the settings of the individual cylinders. In particular, cylinders with either too rich or too lean fuel-air mixtures can be identified.

[0029] However, such sequential diagnostic procedures have the disadvantage of being time-consuming, particularly for engines with a relatively high number of cylinders. This, in turn, means that only a relatively small number of iterations of a diagnostic procedure can be performed within the framework of standardized approval or test procedures. As a result, adjustment of the cylinders, in particular equalization of the cylinders, may not be possible within a specified time window of the standardized approval / test procedure. Performing diagnostic procedures within a defined time window is made even more difficult by the fact that various energy-saving functions (e.g., hybrid vehicles / engine start-stop phases) lead to shortened running times of the combustion engine. This further shortens the time available for diagnosis.

[0030] This document therefore describes a diagnostic method that enables the diagnosis of all cylinders of an internal combustion engine within a short period of time. In particular, the described diagnostic method enables the parallel diagnosis of multiple (e.g., all) cylinders of the internal combustion engine. Furthermore, the described diagnostic method enables the combination of cylinder diagnosis with other diagnostic methods (particularly for catalytic converter and / or lambda sensor diagnosis), thus enabling a further reduction in diagnostic times.

[0031] Fig. Figure 1 shows a block diagram of selected components of an internal combustion engine and an exhaust system. In particular, Fig. 1 a plurality of cylinders 103, to which a fuel-air mixture is supplied via respective injection systems 102 (e.g. via respective valves). The injection systems 102 are typically designed to change a ratio between fuel and air in the fuel-air mixture. The fuel can be supplied to the injection systems, for example, via a fuel line 101. The injection systems 102 (in particular the composition of the fuel-air mixture) can be controlled by a control unit 100 (e.g. by an engine control unit of the internal combustion engine) (e.g. as a function of measured values from a lambda probe 106). In particular, the control unit 100 can be designed to determine and / or control an available air quantity. The air quantity can be changed, for example, by a throttle valve and / or a camshaft setting of the vehicle.Furthermore, the control unit 100 can be configured to change the amount of fuel supplied to the cylinders 103 via the injection systems 102. Thus, the control unit 100 can change the composition of the fuel-air mixture of a cylinder 103.

[0032] After combustion, the exhaust gases from the cylinders 103 are discharged via one or more exhaust pipes 104. The exhaust pipe 104 typically contains a lambda probe 106, which is designed to detect a proportion of oxygen in the exhaust gases. The lambda probe 106 typically determines a common lambda measurement value (from which the composition of the exhaust gases from the cylinders 103 can be determined) for the plurality of cylinders 103 of the internal combustion engine (e.g., for a cylinder bank of the internal combustion engine). Furthermore, the exhaust gases are passed over a catalytic converter 107. The catalytic converter 107 can reduce pollutant emissions in the exhaust gases. In particular, the proportions of carbon monoxide, nitrogen oxides, and unburned hydrocarbons can be reduced by the catalytic converter 107 (e.g., by a regulated three-way catalytic converter).

[0033] In order for the catalytic converter 107 to reliably and as completely as possible remove pollutants (i.e., in particular, carbon monoxide and nitrogen oxides) from the exhaust gases, it is typically necessary for the exhaust gases to have a specific composition. In particular, a catalytic converter 107 is designed for a specific lambda target value (typically λ=1).

[0034] To check the function of the catalytic converter 107, a vehicle can perform a catalytic converter diagnosis / lambda diagnosis. For this purpose, the fuel-air ratio supplied to the cylinders 103 is changed for a specific period of time (e.g., at the instruction of the control unit 100). In particular, the supplied fuel-air ratio is made leaner (λ>1) for a specific period of time and / or richer (λ<1) for a specific period of time. It can then be analyzed whether and to what extent the catalytic converter 107 can remove pollutants from the exhaust gases with the changed fuel-air ratio. For this purpose, an additional trim probe 108 can be used. The trim probe can be arranged in the catalytic converter 107 or downstream of the catalytic converter 107. Alternatively or additionally, it can be analyzed whether and with what time delay the shared lambda probe 106 detects the change in the fuel-air ratio.The catalyst diagnosis / lambda diagnosis can, for example, be carried out regularly as part of a driving cycle (e.g. after starting the combustion engine).

[0035] This document describes a diagnostic procedure for determining the cylinder timing, which can be combined with the catalyst diagnosis / lambda diagnosis described above. In particular, it is proposed to increase and / or reduce the lambda values determined by the lambda sensor 106 for predefined periods of time compared to a predefined target value (e.g., λ=1). This is Fig. 2 shown. Fig. Figure 2 shows lambda target values 210 over time 200. In the example shown, at time 201, the lambda target value 210 is increased from the standard target value 211 (e.g., λ=1) to a lean target value 212 (e.g., λ>1). The lambda target value 210 is then maintained at the lean target value 212 until time 202 and can be reduced back to the standard target value 211 at the subsequent time 202. Similarly, at a time 203, the lambda target value 210 can be reduced to a rich target value 213 (e.g., λ<1) and can be increased back to the standard target value 211 at the subsequent time 204. This results in time intervals [201, 202] and / or [203, 204], ie pre-defined time periods in which the lambda target value 210 deliberately deviates from the standard target value 211.The time intervals and target value deviations for the cylinder diagnostic procedure can correspond to the time intervals and target value deviations of the catalyst diagnostics / lambda diagnostics. The setting of the target values and compliance with the time intervals can be controlled and / or regulated by control unit 100.

[0036] The vehicle may include a crankshaft sensor 105. The crankshaft sensor 105 is configured to detect rough running of the individual cylinders 103. In particular, the crankshaft sensor 105 is configured to detect a change in the rough running of the individual cylinders 103. A deviation of the lambda target value 210 from the standard target value 211 typically leads to a change in the fuel-air mixtures supplied to the respective cylinders. The change in the fuel-air mixtures also results in a change in the rough running of the individual cylinders 103. This document proposes detecting the change in the rough running of the individual cylinders 103 as a result of the deviation of the lambda target value 210 from the standard target value 211. The change in the rough running of the individual cylinders 103 can then be analyzed and used to determine the settings of the individual cylinders 103.

[0037] Fig. 3 shows exemplary changes in the rough running 310 of the individual cylinders 103 for different deviations 300 of the lambda target value 210 from the standard target value 211. In particular, Fig. 3 the changes in the rough running 310 with an increase 301 of the lambda target value 210 (e.g. to the lean target value 212) and with a reduction 302 of the lambda target value 210 (e.g. to the rich target value 213). In the example shown, an increase 301 of the lambda target value 210 leads to the rough running (LU) change 311 of a first cylinder 103, the LU change 312 of a second cylinder 103, the LU change 313 of a third cylinder 103, and the LU change 314 of a fourth cylinder 103. On the other hand, a reduction 302 of the lambda target value 210 leads to the rough running (LU) change 321 of the first cylinder 103, the LU change 322 of the second cylinder 103, the LU change 323 of the third cylinder 103, and the LU change 324 of the fourth cylinder 103.

[0038] The exemplary LU changes allow various observations: • Reducing 302 the lambda target value 210 (i.e., injecting richer fuel-air mixtures) typically results in smaller LU changes than increasing 301 the lambda target value 210 (i.e., injecting leaner fuel-air mixtures). This is to be expected, since an excess of fuel typically has a less pronounced effect on the energy generated during combustion in cylinder 103 than a lack of fuel. • The LU changes of the individual cylinders 103 are different. This indicates different compositions of the fuel-air mixtures in the individual cylinders 103. • For example, the second cylinder 103 shows an LU change 312 that is greater than the LU changes of the other cylinders 103. This increased LU change 312 with an increase 301 of the lambda target value 210 indicates that the fuel-air mixture in the second cylinder 103 is too lean. • In an analogous manner, the second cylinder 103 shows an LU change 322 that is significantly greater than the LU changes of the other cylinders 103. This increased LU change 322 when reducing 302 the lambda target value 210 also indicates that the fuel-air mixture in the second cylinder 103 is too lean. • The third cylinder 103 shows an LU change 313 that is significantly smaller than the LU changes of the other cylinders 103. This reduced LU change 313 when increasing 301 the lambda target value 210 indicates that the fuel-air mixture in the third cylinder 103 is too rich. • In an analogous manner, the third cylinder 103 shows an LU change 323 which is slightly smaller than the LU changes of the other cylinders 103. This reduced LU change 323 when reducing 302 the lambda target value 210 also indicates that the fuel-air mixture in the third cylinder 103 is too rich.

[0039] Thus, by analyzing the determined LU changes when increasing 301 and / or reducing 302 the lambda target value 210, information regarding the composition of the fuel-air mixtures of the individual cylinders 103 can be determined. The analysis may include, for example: • An averaging of the LU changes 311, 312, 313, 314 of the individual cylinders 103. The mean of the LU changes can be regarded as a change reference value. • Determination of deviations in the LU changes 311, 312, 313, 314 of the individual cylinders 103. In particular, a deviation of the LU changes from a change reference value can be determined. Absolute deviations that are greater than or equal to a predefined threshold can indicate an overly rich or too lean fuel-air mixture in the corresponding cylinder 103. • A positive deviation of the LU change 322 from the change reference value when reducing 302 the lambda target value 210 (where the positive deviation is, for example, greater than or equal to a positive threshold value) may indicate that the fuel-air mixture is too lean. • A negative deviation of the LU change 323 from the change reference value when increasing 301 the lambda target value 210 (where the negative deviation is, for example, less than or equal to a negative threshold value) may indicate that the fuel-air mixture is too rich.

[0040] Increasing 301 or decreasing 302 the lambda target value 210 thus enables the simultaneous evaluation of all cylinders 103. Increasing 301 or decreasing 302 the lambda target value 210 thus enables a time-efficient diagnosis of the cylinder settings. Furthermore, the diagnosis of the cylinder settings can be performed as part of the catalyst diagnosis / lambda diagnosis (especially simultaneously), resulting in further time savings for the diagnostic procedure.

[0041] In other words, it is proposed to combine the catalytic converter and / or lambda sensor diagnoses (also referred to as "close-the-cap" diagnosis) with the diagnosis of "cylinder imbalance". In this case, a statement about the cylinder lambda (i.e. about the fuel-air mixture of a cylinder 103) is not achieved by adjusting a cylinder 103 individually, but by adjusting all cylinders 103 in a cylinder bank in parallel with respect to the bank lambda 210. This takes into account that particularly lean or rich cylinders 103 react specifically to a mixture jump, e.g. with regard to the rough running value of the cylinders 103. Other, particularly untrimmed, cylinders 103, in contrast, react to a lesser extent.

[0042] As in Fig. 3, the specific reaction of a cylinder 103 can be a varying change 311, 312, 313, 314 in the rough running values 310. From the determined reactions of the individual cylinders 103, a suspected fault can be derived, which can lead to a corresponding prioritization of the diagnostic function "Cylinder Imbalance". In other words, conspicuous cylinders (such as the second and third cylinders in the example of Fig. 3) can be analyzed in further diagnostic steps with higher priority. In particular, a diagnosis based on a gradual and / or sudden individual adjustment of the fuel-air mixture can be performed for the identified cylinder(s) 103. In particular, a diagnostic procedure can be performed for an identified cylinder 103 in which the common lambda target value 210 of the plurality of cylinders is left constant at the standard target value 211.

[0043] Depending on the engine design and the reliability of the correlation between the rough running value or change in rough running and cylinder lambda, intervention may go beyond simply triggering a suspected fault. In particular, an error may be stored in the fault log. For example, a driver may be prompted (e.g., via an in-vehicle display) to visit a workshop.

[0044] Fig.4 shows an exemplary sequence of steps in the method described in this document for determining the setting of the cylinders of an internal combustion engine (in particular for determining the setting with regard to the composition of the fuel-air ratio). In a first step 401, the lambda target value 210 of the cylinder bank is changed (e.g., increased or reduced). The rough running values are then determined (step 402). In particular, the changes in the rough running values (as reactions of the cylinders 103 to the change in the lambda target value 210) are determined. The determined reactions of the cylinders 103 can then be analyzed (step 403). In particular, indicators regarding the settings of the cylinders 103 can be determined. An exemplary indicator is, for example, a noticeable deviation in the LU change 313 of a cylinder 103 compared to the LU changes 311, 312, 314 of the other cylinders 103.

[0045] Additionally, interventions can be made to the cylinder bank. For example, the fuel-air mixture of a cylinder that is too rich or too lean can be adjusted. After an intervention has been performed, the process can be repeated (step 404: changing the lambda target value 210; step 405: determining the responses of the cylinders 103) to determine whether the intervention(s) had the desired effect.

[0046] Based on the determined change in rough running values, a ranking can be established (particularly with regard to suspected faults for specific cylinders). This suspected fault helps with prioritizing the diagnosis and targeting the critical cylinder. This has the advantage that, in multi-bank systems, the critical cylinder bank can be targeted first in order to identify a faulty cylinder in subsequent diagnostic steps. Furthermore, the identification of a suspected fault within the framework of the described parallel procedure enables the differential treatment of at least one identified cylinder and / or the cylinders identified as non-critical (e.g., with regard to a learning rate and / or repetitions).

[0047] Carrying out the described parallel method enables a reduction in diagnosis time, particularly if it is determined that no fault is suspected. It is also possible for test corrections to be carried out that are coordinated in an analysis and intervention function 403. These test corrections include options for influencing the engine torque and / or the rough running value of at least one cylinder. The test corrections can, for example, include a mixture or ignition angle correction in order to verify the behavior of the cylinders or to separate the cylinders if they react similarly. In other words, an intervention (step 403) can, for example, take the form of a change in the test conditions (e.g., a change in the composition of the fuel-air mixture in a cylinder and / or a change in the ignition angle in a cylinder).In a subsequent parallel diagnostic procedure (steps 404, 405) the influence of the change in the test conditions can then be determined.

[0048] The present invention is not limited to the embodiments shown. In particular, it should be noted that the description and figures are intended only to illustrate the principle of the proposed methods, devices, and systems.

Claims

[1] A method for determining a setting of a cylinder (103) from a plurality of cylinders (103) of an internal combustion engine, the method comprising - changing (401) a common lambda target value (210) for the plurality of cylinders (103) for a predefined period of time (201, 202); - determining (402) reactions (311, 312, 313, 314) of the plurality of cylinders (103) to the change (301, 302) of the common lambda target value (210); wherein determining (402) reactions (311, 312, 313, 314) comprises determining (402) rough running changes (311, 312, 313, 314) of the plurality of cylinders (103) in response to the change (301, 302) of the common lambda target value (210); and - determining (403) one or more indicia regarding a setting of at least one of the plurality of cylinders (103) based on the determined reactions (311, 312, 313, 314) of the plurality of cylinders (103); wherein the determining (403) of one or more indicia comprises, - determining a change reference value from the determined rough running changes (311, 312, 313, 314) of the plurality of cylinders (103); - determining the deviations of the determined rough running changes (311, 312, 313, 314) from the change reference value; and - Comparing the determined deviations with a predefined threshold. [2] Method according to claim 1, wherein the change (301, 302) of the common lambda target value (210) comprises: - an increase (301) of the lambda target value (210) from a standard target value (211) to a lean target value (212); and / or - a reduction (302) of the lambda target value (210) from the standard target value (211) to a rich target value (213). [3] The method of any preceding claim, wherein determining (403) one or more indicia comprises identifying at least one cylinder (103) of the plurality of cylinders (103) whose rough running change (313) differs from a rough running change of the other of the plurality of cylinders (103). [4] A method according to any preceding claim, the method further comprising - determining, based on the one or more indicia, that a first of the plurality of cylinders (103) has a fuel-air mixture that is too lean or too rich; and - in response thereto, changing (403) the fuel-air mixture supplied to the first cylinder (103) and / or changing (403) an ignition angle of the first cylinder (103) and / or changing (403) a torque of the first cylinder (103). [5] A method according to any preceding claim, wherein - a composition of exhaust gases from the plurality of cylinders (103) is determined by a common lambda probe (106); - the exhaust gases of the plurality of cylinders (103) are passed through a catalyst (107); and - the method further comprises performing a functional test of the catalyst (107) and / or performing a functional test of the common lambda probe (106) in response to the change (301, 302) of the common lambda target value (210) during the predefined period (201, 202). [6] Control unit (100) for a vehicle, the vehicle comprising an internal combustion engine having a plurality of cylinders (103), the control unit (100) being arranged - to change a common lambda target value (210) for the plurality of cylinders (103) for a predefined period of time (201, 202); - to determine reactions (311, 312, 313, 314) of the plurality of cylinders (103) to the change (301, 302) of the common lambda target value (210); wherein the reactions (311, 312, 313, 314) comprise rough running changes (311, 312, 313, 314) of the plurality of cylinders (103) in response to the change (301, 302) of the common lambda target value (210); and - to determine one or more indicia relating to a setting of at least one of the plurality of cylinders (103) on the basis of the determined reactions (311, 312, 313, 314) of the plurality of cylinders (103); wherein the control unit (100) is configured to determine one or more indicia, - to determine a change reference value from the determined rough running changes (311, 312, 313, 314) of the plurality of cylinders (103); - to determine deviations of the determined rough running changes (311, 312, 313, 314) from the change reference value; and - to compare the determined deviations with a predefined threshold. [7] Control unit (100) according to claim 6, wherein the control unit (100) is arranged - to receive lambda measurement data relating to an actual lambda value of exhaust gases from the plurality of cylinders (103) from a lambda probe (106); and - depending on the lambda measurement data, to change one or more settings of injection systems (102) of fuel in the plurality of cylinders (103) and thus to change the common lambda target value (210). [8] Control unit (100) according to one of claims 6 to 7, wherein the control unit (100) is arranged - to receive unrest measurement data from a crankshaft sensor (105) of a crankshaft, the crankshaft being driven by the plurality of cylinders (103); and - to determine the reactions (311, 312, 313, 314) of the plurality of cylinders (103) on the basis of the restlessness measurement data.

Images