DE102015219526B4 - Method and system for operating an internal combustion engine - Google Patents

Abstract

Method for operating an internal combustion engine having at least two cylinders (Z1, Z2, Z3), each of which is assigned at least one injection valve (18), an exhaust tract (4) comprising an exhaust gas catalyst (21) and a lambda probe (42) whose measurement signal (MS1) is representative of an air / fuel ratio in the cylinders (Z1, Z2, Z3), wherein - a provision unit (B42) is provided, which is designed to provide an estimated dead time (Tt_EST) of the lambda probe (42) A device is provided which is designed to determine cylinder-specific lambda signals (LAM_Z1, LAM_Z2, LAM_Z3) as a function of the measuring signal (MS1) of the lambda probe (42) and of the estimated dead time (Tt_EST) of the lambda probe (42); is designed to determine lambda deviation signals (D_LAM_Z1, D_LAM_Z2, D_LAM_Z3) for the respective cylinders (Z1 to Z3) depending on the cylinder-specific lambda signals (LAM_Z1, LAM_Z2, LAM_Z3) , based on a lambda signal (LAM_ZI_MW) averaged over the cylinder-specific lambda signals (LAM_Z1, LAM_Z2, LAM_Z3), an observer (B22) is provided which is supplied with the cylinder-individual lambda deviation signals (D_LAM_Z1, D_LAM_Z2, D_LAM_Z3) on the input side and observer output quantities (OBS_Z1, OBS_Z2, OBS_Z3) related to the respective cylinder (Z1 to Z3) are representative of deviations of the injection characteristic of the injection valve (18) of the respective cylinder (Z1 to Z3) from a predetermined injection characteristic, - respective cylinder-individual lambda regulators ( B36, B38, B40) are provided, which are designed such that the respective observer output variable (OBS_Z1, OBS_Z2, OBS_Z3) is supplied to them as an input variable, which is assigned to the respective cylinder (Z1, Z2, Z3) respective regulator control signal influencing the fuel mass to be metered into the respective cylinder (Z1 to Z3) st, in which - a dead time adaptation operation is carried out, in which - one of the cylinders (Z1, Z2, Z3) is specified as a selected cylinder, - for at least the selected cylinder a different from the other cylinders air / fuel ratio is given and that respective injection valve (18) is controlled accordingly, - depending on the cylinder-specific lambda signal, which is assigned to the selected cylinder, and free from the cylinder-specific lambda signals, which are the ...

Description

The invention relates to a method and a system for operating an internal combustion engine.

Ever stricter legal regulations regarding permissible pollutant emissions from motor vehicles, in which internal combustion engines are arranged, make it necessary to keep pollutant emissions during operation of the internal combustion engine as low as possible. On the one hand, this can be done by reducing the pollutant emissions that occur during the combustion of the air / fuel mixture in the respective cylinders. On the other hand, exhaust gas aftertreatment systems are used in internal combustion engines, which convert the pollutant emissions which are generated during the combustion process of the air / fuel mixture in the respective cylinder into harmless substances.

For this purpose, catalytic converters are used, which convert carbon monoxide, hydrocarbons and nitrogen oxides into harmless substances.

Both the targeted influencing of the generation of pollutant emissions during combustion, as well as the conversion of the pollutant components with a high efficiency by an exhaust gas catalyst require a very precisely adjusted air / fuel ratio in the respective cylinder.

From the textbook "manual internal combustion engine", editor Richard von Basshuysen, Fred Schäfer, 2nd edition, Vieweg & Sohn Verlagsgesellschaft mbH, June 2002, pages 559-561, a binary lambda control is known with a binary lambda probe, which is arranged upstream of the catalytic converter , The binary lambda control comprises a PI controller, the P and I components being stored in maps via engine speed and load. In the binary lambda control, the excitation of the catalytic converter, also referred to as lambda fluctuation, implicitly results from the two-step control. The amplitude of the lambda fluctuation is set to about 3%.

Furthermore, from the textbook "Manual combustion engine", editor Richard von Basshuysen, Fred Schäfer, 2nd edition, Vieweg & Sohn Verlagsgesellschaft mbH, June 2002, pages 559-561, a linear lambda control known with a linear lambda probe arranged upstream of the catalytic converter is. The linear lambda control comprises a PII ² D controller to which a control deviation is supplied which depends on the measurement signal of the linear lambda probe.

In order to meet future legal requirements in particular with regard to pollutant emissions, increasingly close-coupled catalytic converters are used. These require due to the small mixing distance from the exhaust valves to the catalytic converter in many cases a very low tolerance in the air / fuel ratio in the individual cylinders of an exhaust bank and indeed a much lower tolerance than in a remote engine arrangement of the catalytic converters. In this context, a cylinder-specific lambda control can be used.

The DE 10 2005 009 101 B3 discloses a method and corresponding apparatus for determining a correction value for influencing an air-fuel ratio in a respective cylinder of a multi-cylinder internal combustion engine.

The DE 10 2006 026 390 A1 discloses an electronic control device for controlling the internal combustion engine in a motor vehicle with a running irregularity determination unit and with an injection quantity correction unit, wherein a defined group of cylinders is associated with a lambda probe. The injection quantity of a cylinder of the defined group to be examined is adjusted in the direction of lean by a differential adjustment value assigned to a running differential value and the injection quantity of at least one of the remaining cylinders assigned to the same lambda probe is adjusted in the direction of rich, so that overall a predetermined lambda value of this group of at least almost 1 is achieved.

The DE 10 2012 223 129 B3 discloses a method of operating an injector for an internal combustion engine having a plurality of combustion chambers, comprising determining a curve of a value of a rotational speed of a crankshaft of the internal combustion engine within a predetermined period of time for each combustion chamber of the plurality of combustion chambers and comparing the respective courses with a predetermined comparison course Deviation between the respective power output of the combustion chambers to determine a predetermined power output.

From the DE 10 2009 027 822 A1 A method is known for determining a trimming of at least one cylinder of an internal combustion engine, wherein the at least one cylinder is operated in succession in at least one lean phase and at least one rich phase to provide on average exhaust neutrality, wherein a rough running signal is evaluated in a lean phase to obtain cylinder-specific characteristic concerning the trim.

From the DE 10 2004 004 291 B3 It is known, for a given crankshaft angle, based on a reference position of the piston of the respective cylinder, to detect the measurement signal in an exhaust gas probe and to assign it to the respective cylinder. The predetermined crankshaft angle is adjusted depending on an instability criterion of a controller. By means of the controller, a manipulated variable for influencing the air / fuel ratio in the respective cylinder is generated as a function of the measurement signal detected for the respective cylinder.

In the DE 103 04 245 B3 is a method for adapting the signal sampling of lambda probe signal values described for use in a cylinder-selective lambda control for a multi-cylinder internal combustion engine. A lambda probe measures the lambda values in exhaust gas for individual cylinders at predetermined times. For the lambda values of several cylinders, a parameter is calculated, which is a measure for the deviation of the lambda values of the individual cylinders. The times for detecting the lambda values of the individual cylinders are set in relation to a crankshaft angle position of the internal combustion engine such that the parameter assumes an extreme value.

From the DE 10 2004 026 176 B3 For example, an internal combustion engine is known having a plurality of cylinders having injectors associated with the cylinders which meter fuel, with an exhaust probe disposed in an exhaust tract and its measurement signal characteristic of the air / fuel ratio in the respective cylinder. A sampling crankshaft angle with respect to a reference position of the piston of each cylinder is detected for detecting the measurement signal depending on a variable characterizing the air / fuel ratio in the respective cylinder or an ambient pressure or an opening degree of a by-pass valve of a bypass a turbine, which is arranged in the exhaust tract. At the sampling crankshaft angle, the measurement signal is detected and assigned to the respective cylinder.

In the DE 102 06 402 C1 A method for cylinder-selective lambda control in a multi-cylinder internal combustion engine is described. A difference between a desired lambda value and a lambda actual value for one of the cylinders is used to determine an injection correction time for the cylinder. The lambda desired value is changed by a first excitation amplitude for the cylinder in first time segments and by a second excitation amplitude in second time segments. The lambda actual value for the cylinder is determined as the lambda actual value with missing excitation amplitude as a function of the first and the second excitation amplitude from the lambda actual values which correspond to the first and second time segments.

In DE 10 2006 061 117 B3 a method is described for the phase adaptation of a cylinder-selective lambda control in a multi-cylinder internal combustion engine. Two of the cylinders are dimmed in their lambda value. The signal of a high-resolution observer probe arranged in the exhaust tract of the internal combustion engine is analyzed in order to determine the lambda values of the individual cylinders. The lambda values of the individual cylinders are compared with one another in order to determine a phase shift range from the comparison result. A correction value is used from the phase shift range to the step phase adaptation.

From the DE 197 00 711 A1 a method is known in which by means of a cylinder-selective measurement method for detecting the uneven running in the lower speed range of the internal combustion engine, the actually injected fuel quantities are determined and from each a cylinder-specific correction factor is calculated and stored. At higher speeds and loads, the injection time and / or the injection start angle is then changed individually for each cylinder on account of the correction factors, thereby improving the smooth running of the internal combustion engine.

The DE 103 55 336 A1 discloses a method for monitoring a valve lift switching of an internal combustion engine with valve lift, in which an assignment of a faulty valve switching to a cylinder or combustion chamber is made possible by the fact that a comparison of combustion chamber pressures of several cylinders in certain working phases with a comparison value to a deviation of the valve lift switching individual cylinders is closed by a default value.

From the DE 10 2005 029 137 B3 For example, a method is known for diagnosing a gas exchange valve lift adjustment system of an internal combustion engine having at least one exhaust gas probe, which delivers an output signal that varies continuously with an exhaust gas component. The method is characterized in that a measure of a spread of the output signal is determined, the measure is compared with a reference value, and errors of the valve lift adjusting system are detected on the basis of the comparison.

In the DE 102 30 899 A1 is a method for diagnosing a defect of an adjusting mechanism for adjusting the valve lift of at least one intake valve of an internal combustion engine whose operation is controlled by an operation control device, described. This is a Operating parameters of the internal combustion engine, which is controlled at an actual adjustment of the valve from the operating control unit to a desired value, monitored and the operation control unit closes from occurring in a controlled valve lift deviation of the operating parameter of the desired value to a defect of the adjustment. As monitored operating parameters are indicated, the air / fuel ratio (lambda), the speed or the torque of the internal combustion engine or the pressure or the air mass flow in the intake manifold of the internal combustion engine.

In the DE 103 55 335 A1 A method for operating an internal combustion engine is proposed in which a direct inference is made possible on a faulty lift of an intake valve of a cylinder. In this case, the stroke of the intake valve of at least one cylinder of the internal combustion engine is diagnosed. In a exhaust gas line of the internal combustion engine, a value is determined which is representative of the air / fuel ratio in the respective cylinder. At least one such value is compared with a predetermined value. Depending on the deviation of this at least one value from the predetermined value, a faulty lift of the intake valve is diagnosed. The at least one value is preferably determined by means of a lambda probe in the exhaust gas line.

The object on which the invention is based is to provide a method and a system for operating an internal combustion engine with a plurality of cylinders, which can be operated reliably.

The object is solved by the features of the independent claim. Advantageous embodiments are characterized in the subclaims.

The invention is characterized by a method for operating an internal combustion engine. The invention is further characterized by a system for carrying out the method for operating an internal combustion engine.

The internal combustion engine comprises at least two cylinders, to each of which at least one injection valve is assigned, an exhaust tract comprising an exhaust gas catalytic converter and a lambda probe whose measurement signal is representative of an air / fuel ratio in the cylinders.

The lambda probe in particular detects a residual oxygen of the exhaust gas and thus its measurement signal is characteristic of the air / fuel ratio in the respective combustion chamber of the respective cylinder and upstream of the lambda probe prior to the oxidation of the fuel, referred to as the air / fuel ratio in the respective cylinder is.

A provision unit is provided, which is designed to provide an estimated dead time of the lambda probe.

The estimated dead time is representative of a time required for an exhaust gas packet from top dead center, in particular top dead center during combustion, to reach the lambda probe and its response thereto. Alternatively, another reference point for the estimated dead time is possible, such as the start of the injection and / or the ignition timing. The estimated dead time can initially be determined empirically in advance.

Preferably, the estimated dead time is indicated in degrees crankshaft angle. In this case, the respective top dead center of the respective cylinder forms the reference angle, ie in particular 0 degrees.

Furthermore, a device is provided which is designed to determine cylinder-specific lambda signals as a function of the measuring signal of the lambda probe and of the estimated dead time of the lambda probe. Thus, in particular even after a long period of operation and thus in particular an aged lambda probe, the respective cylinder-specific lambda signal can still be determined very precisely, that is to say in particular have a small deviation from an actual lambda.

The device is designed to determine Lambda deviation signals for the respective cylinders as a function of the cylinder-specific lambda signals, based on a lambda signal averaged over the cylinder-specific lambda signals. An observer is provided which is embodied such that the cylinder-specific lambda deviation signals are supplied to it on the input side and observer output variables related to the respective cylinder are representative of deviations of the injection characteristic of the injection valve of the respective cylinder from a predetermined injection characteristic.

Respective cylinder-specific lambda regulators are provided, which are designed such that they are each supplied with the respective observer output variable as an input variable, which is assigned to the respective cylinder, and the respective regulator control signal influences the fuel mass to be metered into the respective cylinder.

In the method, a dead time adaptation operation is performed in which one of the cylinders is specified as a selected cylinder. For at least the selected cylinder, a different air / fuel ratio than the other cylinders is determined. Prescribed ratio and the respective injection valve driven accordingly.

Depending on the cylinder-specific lambda signal, which is assigned to the selected cylinder, and free from the cylinder-specific lambda signals, which are assigned to the different cylinders of the selected cylinders, a first dead time difference is determined, depending on a predetermined assignment rule. Depending on the first dead time difference, the estimated dead time is adjusted.

Depending on the cylinder-individual lambda signal associated with the selected cylinder after adjusting the estimated dead time, and free of the cylinder-individual lambda signals associated with the cylinders other than the selected cylinder after adjusting the estimated dead time, a second dead time difference is determined depending on the given assignment rule. If the second dead time difference is greater than the first dead time difference, the assignment rule is adjusted and the estimated dead time is adjusted depending on the adjusted assignment rule.

After performing the dead time adaptation operation, it is determined as a function of the cylinder-specific lambda signal whether there is an error during a valve lift changeover or another fault.

If the second dead time difference is smaller than the first dead time difference, for example, the assignment rule can not be adjusted and the estimated dead time can be adjusted depending on the unmatched assignment rule.

If the assignment rule is adjusted, the adapted assignment rule is stored, for example, and used in the future, for example, for a new dead-time adaptation mode as the assignment rule.

After performing a dead time adaptation operation, a fault can be detected in a very reliable manner depending on the cylinder-specific lambda signal. In this case, the knowledge is used that the cylinder-individual lambda signal changes in a fault-free system after deadtime adaptation operation in the case of a valve lift switching to predictable level due to changes in flow conditions and / or the different times for exhaust ports.

The error includes, for example, a faulty valve lift, incomplete valve lift and / or a faulty injector. The determination as to whether there is an error during a valve lift changeover or another fault occurs, for example, by threshold value comparison with a predefined threshold value.

According to an optional embodiment is determined depending on the respective observer output size, whether an error in a valve lift switching or another error exists. Just the respective observer output is very easy to check, for example by threshold comparison with a predetermined threshold.

According to a further optional embodiment, it is determined as a function of the respective regulator control signal whether there is an error during a valve lift changeover or another fault. Also, the regulator control signal can be checked very well, for example by threshold comparison with a predetermined threshold.

In accordance with a further optional embodiment, an adaptation value is determined as a function of the respective regulator control signal, and depending on the respective adaptation value, it is determined whether there is an error during a valve lift changeover or another fault. The adaptation value can also be checked very reliably, for example by threshold value comparison with a predetermined threshold value.

According to a further optional embodiment, if it has been determined that there is an error in a valve lift switching or another error, the internal combustion engine is operated with a predetermined parameter set, which is representative of an operation without valve lift switching. Depending on the cylinder-individual lambda signal and / or the respective observer output variable and / or the respective regulator control signal and / or the adaptation value, it is again determined whether there is an error during a valve lift changeover or another fault.

If the internal combustion engine is operated with a predetermined parameter set, which is representative of an operation without a valve lift switchover, then a classification of the fault can be carried out. If, for example, the cylinder-specific lambda signal and / or the respective observer output variable and / or the respective regulator adjustment signal and / or the respective adaptation value are below the respective threshold value during a renewed comparison with the predefined threshold value, then there is an error during a valve lift changeover. If this is not the case, then there is another error.

According to a further optional embodiment, depending on the re-determination, whether an error in a valve lift or another error is present, the dead time adaptation operation again carried out and depending on the first dead time difference and / or the second dead time difference is determined whether an incomplete valve lift switchover is present or another cause of fault.

If the internal combustion engine is operated with the predetermined parameter set, which is representative of an operation without a valve lift switchover and, for example, a renewed comparison with the predefined threshold value, the cylinder-specific lambda signal and / or the respective observer output variable and / or the respective regulator control signal and / or respective adaptation value above the respective threshold, then there is another error that can be classified by the re-deadtime adaptation operation closer. If the value of the first and / or second dead time difference is plausible for the value corresponding to a valve lift switching, then it can not be a Ventilhubumschaltfehler, but to another error, such as an injector error. If the value is not plausible, there is probably an incomplete valve lift switchover.

Embodiments of the invention are explained in more detail below with reference to the schematic drawings. Show it:

1 an internal combustion engine with a control device,

2 a flowchart for operating the internal combustion engine

3 a block diagram in the context of a cylinder-specific lambda control,

4 to 12 Waveforms plotted over time.

13 an assignment rule and,

14 a state transition diagram for operating the internal combustion engine.

Elements of the same construction or function are identified across the figures with the same reference numerals.

An internal combustion engine ( 1 ) comprises an intake tract 1 , an engine block 2 , a cylinder head 3 and an exhaust tract 4 , The intake tract 1 preferably includes a throttle 5 and a collector 6 and a suction tube 7 leading to a cylinder Z1 via an inlet passage in the engine block 2 is guided. The engine block 2 further comprises a crankshaft 8th , which has a connecting rod 10 with the piston 11 of the cylinder Z1 is coupled.

The cylinder head 3 includes a valvetrain with a gas inlet valve 12 and a gas outlet valve 13 ,

The cylinder head 3 further comprises an injection valve 18 and a spark plug 19 , Alternatively, the injection valve 18 also in the intake manifold 7 be arranged.

In the exhaust tract 4 is an exhaust gas catalyst 21 arranged, which is preferably designed as a three-way catalyst and the example, very close to the outlet, the exhaust valve 13 is assigned, is arranged.

A control device 25 is provided, the sensors are assigned, which detect different parameters and each determine the value of the measured variable. Operating variables include not only the measured variables but also derived from these variables. The control device 25 is designed to determine, depending on at least one of the operating variables manipulated variables, which are then converted into one or more actuating signals for controlling the actuators by means of corresponding actuators. The control device 25 may also be referred to as a device for operating the internal combustion engine.

The sensors are a pedal position transmitter 26 , which is an accelerator pedal position of an accelerator pedal 27 detected, an air mass sensor 28 , which is an air mass flow upstream of the throttle 5 detected, a first temperature sensor 32 , which detects an intake air temperature, an intake manifold pressure sensor 34 , which is an intake manifold pressure in the collector 6 detected, a crankshaft angle sensor 36 , which detects a crankshaft angle, which then a speed N is assigned.

Furthermore, a first lambda probe 42 provided upstream of the catalytic converter 21 or in the catalytic converter 21 is arranged and detects a residual oxygen content of the exhaust gas and whose measurement signal MS1 is characteristic of the air / fuel ratio in the combustion chamber of the cylinder Z1 and upstream of the first lambda probe 42 before the oxidation of the fuel, hereinafter referred to as the air-fuel ratio in the cylinder Z1. The first exhaust gas probe 42 may be arranged in the catalytic converter so that a part of the catalyst volume upstream of the first exhaust gas probe 42 located. The first exhaust gas probe can be designed as a binary exhaust gas probe, for example also referred to as a jump probe, or as a linear lambda probe, also referred to as a broadband probe.

In principle, a second lambda probe can also be used 44 downstream of the catalytic converter 21 be arranged.

Depending on the embodiment of the invention, any subset of said sensors may be present, or additional sensors may be present.

The actuators are, for example, the throttle 5 , the gas inlet and outlet valves 12 . 13 , the injection valve 18 or the spark plug 19 ,

In addition to the cylinder Z1 also further cylinders Z2 to Z3 are provided, which then also corresponding actuators and optionally sensors are assigned. Thus, for example, the cylinders Z1 to Z3 may for example be associated with an exhaust bank and a common first lambda probe 42 have assigned. In addition, of course, other cylinders may be provided, such as those associated with a second exhaust bank. Thus, the internal combustion engine may comprise any number of cylinders.

The control device 25 comprises a lambda control, which may be a binary lambda control or, correspondingly, a linear lambda control depending on the design of the first lambda probe.

On the output side of the respective lambda control, a regulator control signal is output, which influences a fuel mass to be metered for all of the respective first lambda probe 42 associated cylinder. The control signal of the lambda control is linked in particular multiplicatively with a fuel mass to be metered in order to determine a corrected metered fuel mass.

The fuel mass to be metered is determined, for example, as a function of the rotational speed N and a load. For this purpose, for example, one or more maps may be provided, which are determined in advance, so for example on an engine test bench.

Depending on the corrected fuel mass, an actuating signal is determined, in particular for the respective injection valve 18 ,

A system preferably comprises a computing unit and a memory for storing data and programs. For operating the internal combustion engine, a program for operating the internal combustion engine is stored in the system, which can be processed during operation in the arithmetic unit. The software implemented the program below using the 2 described flowchart.

The program for operating the internal combustion engine is started in a step S1, in which variable can be initialized if necessary.

In a step S3, a dead time adaptation operation is performed, which is explained in more detail in the following figures.

In a step S5, depending on a cylinder-specific lambda signal LAM_Z1, LAM_Z2, LAM_Z3, which will be explained in more detail later, it is determined whether there is an error during a valve lift changeover or another fault.

For this purpose, for example, a threshold value comparison is carried out in a step S7. For example, an observer output OBS_Z1, OBS_Z2, OBS_Z3, which will be explained in more detail later, and / or the servo position signal and / or an adaptation value, which will be explained in more detail later, are compared with a predefined threshold value. Alternatively, it can also be determined in another way, depending on the observer output variable OBS_Z1, OBS_Z2, OBS_Z3 and / or the regulator control signal and / or the adaptation value, whether there is an error in a valve lift changeover or another fault.

If, for example, the predetermined threshold is not exceeded, the program is continued again in step S3. If the predetermined threshold value is exceeded, the program is continued in a step S9.

In step S9, the internal combustion engine is operated with a predetermined parameter set, which is representative of an operation without valve lift switching.

In a step S11, depending on the cylinder-specific lambda signal LAM_Z1, LAM_Z2, LAM_Z3 and / or the respective observer output OBS_Z1, OBS_Z2, OBS_Z3 and / or the respective controller control signal and / or the adaptation value, it is again determined whether an error occurs during a valve lift changeover or other error is present. This is done, for example, by another threshold comparison. If, for example, the predetermined threshold is not exceeded, then the program is continued in a step S13. If the predetermined threshold value is exceeded, the program is continued in a step S15.

In step S13, it is determined that the error is likely to be a faulty valve lift switching of all cylinders acts. Subsequently, the program is ended and can optionally be started again in step S1.

In the step S15, the dead time adaptation operation is performed again.

In a step S17, depending on a first dead time difference and / or a second dead time difference, which will be explained in more detail later, it is determined whether there is an incomplete valve lift changeover or if there is another cause of the fault. This is done, for example, by another threshold comparison. If, for example, the predetermined threshold value is not exceeded, then the program is continued in a step S19. If the predetermined threshold value is exceeded, the program is continued in a step S21.

In step S19, it is determined that the error is likely to be an incomplete valve lift switching to a position. Subsequently, the program is ended and can optionally be started again in step S1.

In step S21, it is determined that the error is likely to be another error, such as a faulty injector. Subsequently, the program is ended and can optionally be started again in step S1.

Based on 3 is a cylinder-specific lambda control explained in more detail. A block B16 comprises an allocation unit, which is designed to be dependent on the measurement signal MS1 of the first lambda probe 42 determine the cylinder-specific lambda signals LAM_Z1, LAM_Z2, LAM_Z3 and, depending on the cylinder-specific lambda signals LAM_Z1, LAM_Z2, LAM_Z3, determine cylinder-specific lambda deviation signals D_LAM_Z1, D_LAM_Z2, D_LAM_Z3 for the respective cylinders based on a lambda signal LAM_ZI_MW averaged over the cylinder-specific lambda signals LAM_Z1, LAM_Z2, LAM_Z3.

The allocation unit further comprises a block B18, which comprises a switch. The changeover switch is designed to perform a changeover, which is correlated to the respective times at which the respective exhaust gas package is representative of the respective cylinder Z1 to Z3. In this case, a respective switching of the switch is triggered by a trigger TRIG, which can also be referred to as a trigger and which is provided by a delivery unit, which is explained in more detail below with reference to a block B42. The trigger thus determines the respective sampling instant of the measurement signal MS1 and the respective assignment to the respective cylinder-specific lambda signal LAM_Z1, LAM_Z2, LAM_Z3.

A block B20 is designed to determine a lambda signal LAM_ZI_MW averaged over the cylinder-specific lambda signals LAM_Z1, LAM_Z2, LAM_Z3. In addition, block B20 is designed to determine cylinder-specific lambda deviation signals D_LAM_Z1, D_LAM_Z2, D_LAM_Z3 in each case depending on a difference of the respective cylinder-specific lambda signal LAM_Z1, LAM_Z2, LAM_Z3 and on the other side of the averaged lambda signal LAM_ZI_MW. Depending on the current position of the changeover switch in the block B18, the respective cylinder-specific lambda deviation signal D_LAM_Z1, D_LAM_Z2, D_LAM_Z3 is determined for the respectively relevant cylinder Z1 to Z3.

The respective currently determined cylinder-individual lambda deviation signal D_LAM_Z1, D_LAM_Z2, D_LAM_Z3 is supplied to a block B22 which comprises an observer, wherein the feed to a subtraction point SUB1 takes place, in which the difference to a model lambda deviation signal D_LAM_MOD is determined. This difference is then amplified in an amplifier K and then fed to a block B24 which also includes a switch which is switched in synchronism with that of the block B18.

On the output side of the block B24 this is coupled depending on its switching position with a block B26, a block B28 or a block B30. The blocks B26, B28 and B30 each comprise an I-element, that is to say an integrating element which integrates the signals present at its input. The output of the block B26 is representative of a deviation of the injection characteristic of the injector 18 of the cylinder Z1 of a predetermined injection characteristic and represents the observer output OBS_Z1, which is representative of the deviation of the injection characteristic of the injection valve of the cylinder Z1 of a predetermined injection characteristic. For example, the predetermined injection characteristic has a mean injection characteristic of all injection valves 18 be the respective cylinder Z1, Z2, Z3. The same applies to the observer output variables OBS_Z2, OBS_Z3, which are the output variables of the blocks B28 and B30 with respect to the cylinders Z2 and Z3, respectively.

In addition, a further switch is provided in a block B32, to which the observer output variables OBS_Z1, OBS_Z2 and OBS_Z3 are supplied on the input side and whose changeover switch is synchronous to that of the blocks B18 and B24 is switched and the output signal is the input of a block B34.

The block B34 comprises a sensor model of the first lambda probe. This sensor model is realized, for example, in the form of a PT1 element but may also comprise further elements. On the output side of the block B34, the model lambda deviation signal D_LAM_MOD is then generated as the output of the sensor model. The sensor model described here is optional and thus not necessarily necessary for the realization of a cylinder-specific lambda control.

The respective observer output variables OBS_Z1, OBS_Z2 and OBS_Z3 are fed to cylinder-specific lambda controllers, which are each formed in a block B36, B38 and B40. The cylinder-specific lambda controllers can have, for example, an integral component. The respective regulator control signal LAM_FAC_ZI_Z1, LAM_FAC_ZI_Z2, LAM_FAC_ZI_Z3 influences the fuel mass MFF to be metered in the respective cylinder Z1, Z2, Z3, so that, for example, a respective individual correction of the fuel mass to be metered can take place multiplicatively relative to the respective cylinder Z1 to Z3. In addition, the corresponding adaptation values can also be determined as a function of the respective cylinder-specific control actuating signals LAM_FAC_ZI_Z1, LAM_FAC_ZI_Z2, LAM_FAC_ZI_Z3, as illustrated by the schematically indicated further blocks following the blocks B36 to B40.

An estimated dead time Tt_EST is provided by means of the provisioning unit formed in the block B42. The trigger TRIG is initially determined in particular for a nominal first exhaust gas probe, which is, for example, in a new state and / or was measured, for example, on an engine test bench or the like.

By means of the estimated dead time Tt_EST, the trigger TRIG is adjusted accordingly so as to sample the measurement signal MS1 of the first exhaust gas probe 42 to consider the estimated dead time Tt_EST.

The trigger TRIG can basically refer to a respective crankshaft angle of the crankshaft 8th be predetermined and then be triggered accordingly based on a respective crankshaft angle and / or converted to the respective time range. Alternatively, however, it may also be predetermined directly in the time domain, in particular in relation to the respective rotational speed.

The estimated dead time Tt_EST is determined, for example, in the dead time adaptation mode. The dead time adaptation operation is carried out in particular if an oscillation of the cylinder-specific lambda signals is detected and / or if it is detected that a phase shift of the lambda signal is present, for example by means of the observer.

In the dead time adaptation mode, the control device is 25 designed to specify one of the cylinders Z1, Z2, Z3 as a selected cylinder and to specify for at least the selected cylinder a different air / fuel ratio from the other cylinders and the respective injection valve 18 to control accordingly. Furthermore, the control device 25 adapted to determine, depending on the cylinder-specific lambda signal, which is assigned to the selected cylinder, and free of the cylinder-specific lambda signals, which are assigned to the different cylinders of the selected cylinders, the first dead time difference and depending on a predetermined assignment rule. Furthermore, the control device 25 adapted to adjust the estimated dead time depending on the first dead time difference. The assignment rule includes, for example, an arcsine function or an arccosine function.

The control device 25 is further configured, in the dead time adaptation mode, to be dependent on the cylinder-specific lambda signal associated with the selected cylinder after adjusting the estimated dead time and free of the cylinder-individual lambda signals associated with the cylinders other than the selected cylinder after adjusting the estimated dead time to determine the second dead time difference, depending on the given assignment rule. Furthermore, the control device 25 is adapted, if the second dead time difference is greater than the first dead time difference, to adjust the assignment rule and adjust the estimated dead time depending on the adapted assignment rule.

The control device 25 For example, it is configured to specify a maximum amplitude of the cylinder-specific lambda signal in the dead time adaptation mode for the selected cylinder and to determine the respective dead time difference as a function of the ratio of the cylinder-specific lambda signal of the selected cylinder to the predetermined maximum amplitude.

The control device 25 is formed, for example, in the dead time adaptation operation if the second dead time difference is smaller than one predetermined first threshold to incrementally adjust the estimated dead time subsequently.

The control device 25 For example, in the dead time adaptation mode, if the second dead time difference is greater than the first dead time difference and the amount of the difference of the first and second dead time differences is greater than a predetermined second threshold value, the assignment rule is adapted to change the direction in which the estimated dead time is adjusted.

The control device 25 For example, in the dead time adaptation mode, if the second dead time difference is larger or smaller than the first dead time difference and the amount of the difference of the first and second dead time differences is smaller than a predetermined second threshold value, it is configured to adjust the assignment rule such that the direction remains unchanged the estimated dead time is adjusted.

The dead time adaptation operation is terminated, for example, when the first and / or the second dead time difference is smaller than a respective Abbruchschwellenwert.

In the 4 a signal curve of a nominal measurement signal MS_NOM of the first lambda probe is plotted.

In the 5 is next to the waveform of the nominal measurement signal MS_NOM a waveform of the measurement signal MS1 of the first lambda probe 42 recorded in the case of an increased dead time, which can be interpreted as a phase shift of the measuring signal MS1. In the event that the corresponding change in the increased dead time is not taken into account, there is a deviation in the sampling of the measurement signal, which is indicated by the two arrows in the 6 is symbolized.

In other words, in the dead time adaptation mode, for example, a different air / fuel ratio for the selected cylinder, so that over a whole operating cycle of the internal combustion engine (for example, 720 ° crankshaft angle) a sinusoidal profile of the measuring signal MS1 is measured (see 7 - 10 ). For example, the selected cylinder is set to "bold" for this purpose. the other cylinders are for example set to "lean" or they are controlled by the lambda control in order, for example, to achieve a total lambda value of 1. As a selected cylinder, for example, the cylinder is selected which has the largest measured amplitude. For example, a phase angle of the observer can be set to the expected inflection point of the measurement signal MS1. Subsequently, an amplitude ratio is determined from the cylinder-specific lambda signal of the selected cylinder to a predetermined maximum amplitude. The predetermined maximum amplitude results for example from the predetermined deviating air / fuel ratio.

By means of the amplitude ratio can then be determined by means of the assignment rule, the respective dead time difference. For example, the assignment rule is an inverse function, as in 13 shown.

The estimated dead time can then be adjusted depending on the respective dead time difference in several adaptation steps (P-jump, I-loop) and stored in a non-volatile memory.

In the 7 - 10 Signal curves of the measuring signal MS1 are plotted. 7 shows the measurement signal MS1 in an exemplary dead-time adaptation operation with two cylinders, 8th shows the measurement signal MS1 in an exemplary dead-time adaptation operation with three cylinders and the 9 and 10 in each case the measurement signal MS1 in an exemplary dead time adaptation operation with four cylinders.

In the event that a balanced system results in extremely "lean" operation, the overall lambda setpoint may be set to a higher value (for example, in a two-cylinder engine). An exemplary control of an internal combustion engine with four cylinders with a possible offset of the selected cylinder is shown in FIG 11 shown.

12 shows the measurement signal MS1 in an exemplary dead time adaptation operation, wherein 13 a corresponding exemplary assignment rule is shown.

14 shows a possible state transition diagram for operating the internal combustion engine. The state Z0 indicates that the dead time adaptation mode is not active. The state Z1 stands for the fact that the observer checks whether the dead time adaptation mode should be started. The state Z2 stands for performing the above-described dead time adaptation operation. The state Z3 is to wait a predetermined time after completion of the dead time adaptation operation for the observer to stabilize. State Z4 is for checking that the dead time adaptation operation was successful. In particular, the determination of the second dead time difference can take place in the state Z4.

LIST OF REFERENCE NUMBERS

1

intake system

2

block

3

cylinder head

4

exhaust tract

5

throttle

6

collector

7

suction tube

8th

crankshaft

10

connecting rod

11

piston

12

Gas inlet valve

13

gas outlet

18

Injector

19

spark plug

21

catalytic converter

25

control device

26

Pedal position sensor

27

accelerator

28

Air mass sensor

32

first temperature sensor

34

intake manifold pressure sensor

36

Crank angle sensor

38

second temperature sensor

42

first lambda probe

44

second lambda probe

MS1

Measuring signal of the first lambda probe

MS_NOM

nominal measurement signal of the first lambda probe

LAM_Z1, LAM_Z2, LAM_Z3

cylinder-specific lambda signals

LAM_ZI_MW

averaged lambda signal

D_LAM_Z1, D_LAM_Z2, D_LAM_Z3

cylinder-individual Lambda deviation signals

D_LAM_MOD

Model Lambda deviation signal

B16

Block (allocation unit)

B18

Block (switch)

B20

K

amplifier

SUB1

subtraction point

B22

Block (observer)

B24

Block (switch)

B26, B28, B30

Block (I-member)

OBS_Z1, OBS_Z2, OBS_Z3

Observer size, which is related to the respective cylinder

B32

Block (switch)

B34

Block (sensor model)

B36, B38, B40

Block (cylinder-specific lambda controller)

B42

Block (deployment unit)

LAM_FAC_ZI_Z1

cylinder-individual regulator control signal, which is assigned to the cylinder Z1.

LAM_FAC_ZI_Z2

cylinder-individual regulator control signal, which is assigned to the cylinder Z2.

LAM_FAC_ZI_Z3

cylinder-individual regulator control signal, which is assigned to the cylinder Z3.

T

Time constant (of the PT1 element)

Tt_EST

estimated dead time

TRIG

Trigger (Sampling)

t

Time

V

tension

[°]

angle

Z0-Z4

Status

Z1-Z3

cylinder

Claims (7)

Method for operating an internal combustion engine having at least two cylinders (Z1, Z2, Z3), to each of which at least one injection valve ( 18 ), an exhaust tract ( 4 ), which is an exhaust gas catalyst ( 21 ) and a lambda probe ( 42 ) whose measurement signal (MS1) is representative of an air / fuel ratio in the cylinders (Z1, Z2, Z3), wherein - a provision unit (B42) is provided, which is adapted to an estimated dead time (Tt_EST) of the lambda probe ( 42 ), - a device is provided which is designed to be dependent on the measuring signal (MS1) of the lambda probe ( 42 ) and the estimated dead time (Tt_EST) of the lambda probe ( 42 ) to determine cylinder-specific lambda signals (LAM_Z1, LAM_Z2, LAM_Z3), the device is designed to determine Lambda deviation signals (D_LAM_Z1, D_LAM_Z2, D_LAM_Z3) for the respective cylinders (Z1 to Z3) as a function of the cylinder-specific lambda signals (LAM_Z1, LAM_Z2, LAM_Z3) , based on a lambda signal (LAM_ZI_MW) averaged over the cylinder-specific lambda signals (LAM_Z1, LAM_Z2, LAM_Z3), an observer (B22) is provided which is supplied with the cylinder-individual lambda deviation signals (D_LAM_Z1, D_LAM_Z2, D_LAM_Z3) on the input side and observer output quantities (OBS_Z1, OBS_Z2, OBS_Z3) related to the respective cylinder (Z1 to Z3) are representative of deviations in the injection characteristic of the injection valve ( 18 ) of respective cylinder (Z1 to Z3) of a predetermined injection characteristic, - respective cylinder-individual lambda controllers (B36, B38, B40) are provided, which are each supplied to the respective observer output variable (OBS_Z1, OBS_Z2, OBS_Z3) as an input variable , which is associated with the respective cylinder (Z1, Z2, Z3), and the respective control position signal influences the fuel mass to be metered into the respective cylinder (Z1 to Z3), in which - a dead time adaptation operation is carried out, in which - one of the cylinders (Z1, Z2, Z3) is specified as a selected cylinder, - for at least the selected cylinder a different from the other cylinders air / fuel ratio is given and the respective injection valve ( 18 ) is driven accordingly, - a first dead time difference is determined depending on the cylinder-specific lambda signal, which is assigned to the selected cylinder, and free of the cylinder-individual lambda signals, which are assigned to the different cylinders of the selected cylinders, depending on a predetermined assignment rule, Depending on the first dead time difference, the estimated idle time is adjusted, depending on the cylinder-specific lambda signal associated with the selected cylinder after adjusting the estimated dead time, and free of the cylinder-individual lambda signals, after adjusting the cylinders different from the selected cylinder are associated with the estimated dead time, a second dead time difference is determined and depending on the predetermined assignment rule, - if the second dead time difference is greater than the first dead time difference, the assignment Vorschr ift is adapted and the estimated idle time is adjusted as a function of the adapted assignment rule and - after performing the dead time adaptation operation depending on the cylinder-specific lambda signal (LAM_Z1, LAM_Z2, LAM_Z3) it is determined whether there is an error in a valve lift switching or another error. Method according to Claim 1, in which it is determined as a function of the respective observer output variable (OBS_Z1, OBS_Z2, OBS_Z3) whether there is an error during a valve lift changeover or another error. A method according to claim 1 or 2, wherein it is determined depending on the respective controller control signal, whether an error in a valve lift switching or another error exists. Method according to one of the preceding claims, in which an adaptation value is determined as a function of the respective regulator control signal and, depending on the respective adaptation value, it is determined whether there is an error in a valve lift changeover or another fault. Method according to one of the preceding claims, in which If it has been determined that there is a fault in a valve lift switchover or another fault, the engine is operated at a predetermined set of parameters which is representative of an operation without valve lift switching and - Is determined again depending on the cylinder-individual lambda signal (LAM_Z1, LAM_Z2, LAM_Z3) and / or the respective observer output variable (OBS_Z1, OBS_Z2, OBS_Z3) and / or the respective control signal setting, if there is an error in a valve lift or another error. The method of claim 5, wherein depending on the re-determination whether an error in a Ventilhubumschaltung or another error, the dead time adaptation operation is performed again and is determined depending on the first dead time difference and / or the second dead time difference, if an incomplete valve lift switching is present or another cause of the error. System for carrying out a method according to one of the preceding claims.

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