DE102009010887B3 - Method and device for operating an internal combustion engine - Google Patents

Abstract

Method and device for operating an internal combustion engine, having at least one cylinder (Z1-Z4) with a combustion chamber (26) and an exhaust tract (14), in which a catalytic converter (34) and a binary exhaust gas probe (MS1) are provided ( 52) are arranged upstream of the catalyst (34). A binary lambda controller may output a regulator position signal (LAM_FAC_FB) for controlling an air-fuel ratio (LAM) in the combustion chamber (26). After the measurement signal (MS1) has a value which is less than or equal to a predetermined lean threshold value (THD_L), the regulator control signal (LAM_FAC_FB) is varied by means of an integral control component (I) of the lambda controller until the measurement signal (MS1) has a value which greater than a predetermined threshold value of fat (THD_R), and then varied by means of the integral control component (I) until the measurement signal (MS1) has a value which is less than or equal to the predetermined lean threshold value (THD_L). Depending on the variations, integrator strokes (P1, P2) are determined which serve to determine whether a center position of the regulator actuating signal corresponds to a switching point of the exhaust gas probe (52). If this is the case, the controller control signal is generated as a rectangular signal with an upper and a lower plateuwert. The upper plateau value is correlated with a maximum value of the control loop signal when reaching the rich threshold. The lower plateau value is correlated with a minimum value of the ...

Description

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

always stricter legal regulations regarding permissible pollutant emissions in motor vehicles, in which internal combustion engines are arranged, make it necessary to pollutant emissions in one operation Keep the internal combustion engine as low as possible. This can on the one hand done by reducing the pollutant emissions be that while the combustion of the air / fuel ratio in the respective Cylinder of the internal combustion engine arise. On the other hand are in internal combustion engines Exhaust aftertreatment systems in use, the pollutant emissions, the while the combustion process of the air-fuel ratio be generated in the respective cylinder, in harmless substances convert.

such Exhaust after-treatment systems regularly include an exhaust gas catalyst, for example, a three-way catalyst or a catalyst for selective catalytic reduction, wherein the exhaust aftertreatment system at a high efficiency the conversion of pollutant components, such as carbon monoxide, hydrocarbons and nitrogen oxides.

Either the targeted influencing of the generation of pollutant emissions while combustion, as well as the conversion of pollutant components with a high efficiency set by a catalyst very precise adjusted air / fuel ratio in the respective cylinder ahead.

Out the textbook "Handbook Engine " Publisher Richard von Basshuysen, Fred Schäfer, 2nd edition, Vieweg & Sohn publishing company mbH, June 2002, pages 559 to 561, a binary lambda control is known with a lambda probe, the upstream of the catalytic converter is arranged.

at the upstream the exhaust gas catalyst used lambda probes, due to their location also as a pre-catalyst lambda probe are so-called binary or jump probes. With these, the output voltage is in a lean air / fuel mixture (lambda> 1) at a lower voltage level, increases at a stoichiometric Combustion with Lambda = 1 almost leaps and arrives at a rich air / fuel mixture (Lambda <1) upper voltage level. Such behavior is called two-point behavior designated. Characteristic of this Two-point behavior of binary Lambda probe is that in the area in which the characteristic a strong slope, the signal emitted by the lambda probe very much depends on the lambda value of the exhaust gas. In the currently available binary lambda probes is the resulting kink of the curve just below lambda = 1. The slope of the curve flattens to a richer air / fuel mixture starting from a lambda value near 1 clearly.

The binary Lambda control includes a PI controller, with the P and I components in maps about Engine speed and load are stored. In the binary lambda control results in the excitation of the catalyst, as a lambda fluctuation implied by the two-step control. The amplitude the lambda fluctuation is set to approx. 3%.

Of the Operation of an internal combustion engine controlled by a lambda probe takes place in such a way that the output signal representing the lambda value of the raw exhaust gas the lambda probe oscillates by a predetermined mean, the is assigned approximately lambda = 1. Since the catalytic converter at Raw gas with a given lambda optimum catalytic Properties, the predetermined average should be the predetermined Lambda value correspond. Depending on the catalytic converter, the given Lambda value at which there is an optimal catalytic effect, slightly different from lambda = 1.

The dynamic and static properties of the lambda probe can become due to aging of the probe. This can change the situation of the predetermined lambda value corresponding voltage level shifted be. Furthermore, the predetermined lambda value, in which an optimal catalytic effect of the catalytic converter is present over the Shift the life of the catalytic converter.

The DE 102 20 337 A1 discloses a method of operating an internal combustion engine equipped with a three-way catalytic converter in which a lambda value of the air-fuel mixture supplied to the internal combustion engine is cyclically alternately alternately set below and above a stoichiometric desired value in a forced excitation, whereby the lambda value in rich Phases below the stoichiometric setpoint and in lean phases above the stoichiometric setpoint. In the forced excitation, the rich phases and the lean phases are matched with respect to the amount of oxygen stored in the catalytic converter or with regard to the air mass.

The object of the invention is a method and to provide a device for operating an internal combustion engine, by means of which an operation with very low pollutant emissions is made possible.

The Task is solved by the characteristics of the independent Claims. Advantageous embodiments of the invention are characterized in the subclaims.

The Invention is characterized by a method and a corresponding Device for operating an internal combustion engine, the at least one Cylinder having a combustion chamber and an exhaust tract, in which a catalyst and a binary Exhaust gas upstream at least a partial volume of the catalyst are arranged, wherein the binary Exhaust probe is designed to output a measurement signal, wherein a binary one Lambda controller with a proportional control component and an integral Control part is designed to output a controller control signal for regulating an air / fuel ratio in the combustion chamber of the cylinder.

at The method is in a conditioning phase after the measurement signal has a value less than or equal to a predetermined one Lean threshold is the regulator control signal by means of the integral Rule portion varies until the measurement signal has a value that bigger or is equal to a predetermined fat threshold, and dependent on This variation determines a first integrator stroke. The control signal is varied by the integral rule portion until the measurement signal has a value that is less than or equal to the predetermined lean threshold is, and dependent From this variation, a second integrator stroke is determined.

Depending on the integrator strokes it is determined whether a condition is met that is representative of a central position of the regulator control signal a switching point of the exhaust gas probe equivalent.

If this is the case, a diagnostic phase is initiated. In the diagnosis phase the control signal is a square wave signal with an upper plateau value and a lower plateau value. The upper plateau value is correlates with a maximum value of the servo control signal when Reaching the fat threshold, which is the value of the first integrator stroke correlates with the fulfillment of the Condition existed. The lower plateau value is correlated with one minimum value of the servo control signal when reaching the lean threshold, the is correlated to the value of the second integrator stroke used in the fulfillment of the Condition existed.

This has the advantage that a diagnosis of the catalyst in safer Way during Phases of limited dynamics of the air / fuel ratio are performed can. This is a rectangular Course of the controller control signal for controlling the air / fuel ratio realized. Shifts of the center position of the control signal and thus a lack of correspondence of the mid-position of the regulator control signal with the switching point of the exhaust probe can in the conditioning phase means detected by the first integrator stroke and the second integrator stroke become. After completing the conditioning phase, note the center position of the regulator control signal in the diagnostic phase, the regulator control signal assume a rectangular shape, with the reliable way under alternately fat and lean mixture on average for diagnosis the catalyst desired Air / fuel ratio adjusted can be. A setting of the control knob signal in the diagnostic phase, the not the one for the diagnosis of the catalyst may correspond to necessary specifications to be avoided.

According to one advantageous embodiment a first time period in which the regulator control signal is the upper plateau value assumes, depending from the first integrator stroke and another time period in which the regulator control signal assumes the lower plateau value, depending on the second integrator stroke. This can in the diagnostic phase a Diagnosis of the catalyst, each with a quantitatively suitable loading rich and lean air / fuel mixture.

In a further preferred embodiment become the first integrator strokes and the second integrator strokes low pass filtered, and the lowpass filtered first integrator strokes and second Integratorhübe be checking the condition and used in the diagnostic phase. This is one reliable determination of a mid-ply shift of the controller control signal and a reliable diagnosis of the catalyst by means of a plurality of determinations of integrator strokes possible.

embodiments are explained in more detail below with reference to the schematic drawings.

It demonstrate:

1 an internal combustion engine with a control device,

2A a waveform in a conditioning phase plotted over time,

2 B a waveform in a diagnostic phase plotted over time,

3 a flow chart of a pro gram processed in the control device,

4 a flowchart of a subroutine of the program 3 which is processed in the control device,

5 a flowchart of a subroutine of the program 3 which is processed in the control device.

elements same construction or function are cross-figurative with the same Reference number marked.

In 1 An internal combustion engine is shown with an intake tract 10 , an engine block 12 a cylinder head 13 and an exhaust tract 14 , The intake tract 10 preferably includes a throttle 15 , a collector 16 , and a suction tube 17 , The suction tube 17 is toward a cylinder Z1 at the inlet port into a combustion chamber 26 of the engine block 12 guided. The engine block 12 includes a crankshaft 18 , which has a connecting rod 20 with a piston 21 of the cylinder Z1 is coupled.

The cylinder head 13 includes a valvetrain with a gas inlet valve 22 and a gas outlet valve 24 , The cylinder head 13 further comprises an injection valve 28 and a spark plug 30 , Alternatively, the injection valve 28 also in the intake manifold 17 be arranged.

In the exhaust tract 14 is a catalyst 34 arranged, which is formed for example as a three-way catalyst. The catalyst 34 may comprise one or more units and thus include, for example, a pre-catalyst and a main catalyst.

The internal combustion engine also has a control device 35 on, with sensors that can record different measured variables and in each case determine the value of the measured variables. The control device 35 determined in response to at least one of the measured variables manipulated variables, which can then be converted into one or more actuating signals for controlling actuators by means of corresponding actuators. The control device 35 may also be referred to as a device for operating the internal combustion engine. The actuators are, for example, the throttle 15 , the gas inlet and outlet valves 22 . 24 , the injection valve 28 or the spark plug 30 ,

The sensors include a pedal position transmitter 36 , the accelerator pedal position of an accelerator pedal 38 detected. Furthermore, the internal combustion engine has an air mass sensor 40 on, the upstream of the throttle 15 is arranged and detected there a mass air flow. A temperature sensor 42 upstream of the throttle 15 detects an intake air temperature. An intake manifold pressure sensor 44 downstream of the throttle 15 is in the collector 16 arranged and detects an intake manifold pressure in the collector 16 , Furthermore, the internal combustion engine comprises a crankshaft angle sensor 46 which detects a crankshaft angle to which a rotational speed of the internal combustion engine can be assigned.

It is a binary exhaust gas probe 52 provided upstream of the catalyst 34 or in the catalyst 34 is arranged. The binary exhaust gas probe 52 especially in the catalyst 34 be arranged to be part of the volume of the catalyst 34 upstream of the binary exhaust gas probe 52 located. The binary exhaust gas probe 52 detects a residual oxygen content of the exhaust gas. The binary exhaust gas probe 52 is designed to output a measurement signal MS1. The measuring signal MS1 of the binary exhaust gas probe 52 is characteristic of an air / fuel ratio LAM in the combustion chamber 26 of the cylinder Z1 and upstream of the binary exhaust gas probe 52 before the oxidation of the fuel, hereinafter referred to as the air-fuel ratio LAM in the cylinder Z1.

Furthermore, another exhaust gas probe 54 provided downstream of the catalyst 34 is arranged and detects a residual oxygen content of the exhaust gas. The further exhaust gas probe 54 is designed to output a measurement signal MS2. The further exhaust gas probe 54 especially in the catalyst 34 be arranged to be part of the volume of the catalyst 34 downstream of the further exhaust gas probe 54 located. The further exhaust gas probe 54 is preferably designed as a further binary exhaust gas probe.

Next the cylinder Z1 are preferably further cylinders Z2 to Z4 provided which also corresponding actuators and optionally sensors assigned. The internal combustion engine can thus be any Include number of cylinders.

The control device 35 In one embodiment, it includes a binary lambda controller. The binary lambda controller is designed such that the control signal MS1 of the binary exhaust gas probe can be referred to as a controlled variable, which can also be referred to as a control input variable 52 is supplied. Due to the binary nature of the measurement signal MS1 of the binary exhaust gas probe 52 is the binary lambda controller designed as a two-step controller.

The binary lambda controller is designed to detect a lean phase LEAN because the measurement signal MS1 is smaller than a predetermined value low threshold THD_L at the binary exhaust gas probe 52 which may, for example, have a value of about 0.2V. In addition, the binary lambda controller is designed to detect a rich phase RICH because the measurement signal MS1 of the binary exhaust gas probe 52 has a value greater than a predetermined rich threshold THD_R at the binary exhaust gas probe 52 , The default grease threshold THD_R at the binary exhaust probe 52 For example, it may have a value of about 0.6V.

In 2A a curve of a regulator control signal LAM_FAC_FB of the binary lambda controller is plotted over time in a conditioning phase.

2 B shows a profile of the controller control signal LAM_FAC_FB the binary lambda controller over time in a diagnostic phase. The regulator control signal LAM_FAC_FB is a rectangular signal with an upper plateau value LAM_FAC_FB_T and a lower plateau value LAM_FAC_FB_B.

Of the binary Lambda controller is preferred as a PI controller with a proportional Control component P and an integral rule component I trained. The proportional Control component P is preferably formed so that the regulator control signal LAM_FAC_FB a first Proportionalsprung K1 or a second Proportionalsprung K2 run can. A characteristic diagram of the proportional jumps K1 is preferred, K2 provided, which can be permanently stored. The integral rule share I of the binary Lambda controller is preferably dependent determined by one or more integral increments. It can too a map of integral increments must be permanently stored.

Further details of 2A and 2 B be related to the description of the 3 to 5 explained.

To operate the catalyst 34 for an internal combustion engine can in a program memory of the control device 35 Programs are stored and processed during operation of the internal combustion engine.

A flowchart of a program is in 3 shown.

The program is started in a step S10 in which variables are initialized if necessary. The start preferably takes place when current information about the state of the catalyst 34 to be determined. This can for example be done during a motor run.

In a step S12, the integral control component I is first activated with suitable parameters and the function to be integrated. It is then checked whether the measurement signal MS1 has a value which is greater than or equal to the predetermined rich threshold value THD_R at the binary exhaust gas probe 52 is. As long as this is not the case, the program remains in step S12 and the integral control component I for the variation of the controller control signal LAM_FAC_FB remains activated.

If the condition of step S12 is fulfilled, a first integrator stroke P1 is determined in a further step S14 as a function of the variation effected in step S12. In 2A This part of the program in the conditioning phase corresponds to the rising part of the control loop signal LAM_FAC_FB until a maximum value is reached.

In a step S16, optionally, a subroutine of the program of 3 be processed during operation of the internal combustion engine, in 4 detailed and described below.

In a step S18, the integral control component I is activated with suitable parameters and the function to be integrated. It is then checked whether the measurement signal MS1 has a value which is less than or equal to the predetermined lean threshold value THD_L at the binary exhaust gas probe 52 is. As long as this is not the case, the program remains in step S18 and the integral control component I for variation of the controller control signal LAM_FAC_FB remains activated.

If the condition of step S18 is fulfilled, a second integrator stroke P2 is determined in a further step S20 as a function of this variation. In 2A This part of the program in the conditioning phase corresponds to the falling part of the control loop signal LAM_FAC_FB until a minimum value is reached.

In a step S22, optionally another subprogram of the program of 3 be processed during operation of the internal combustion engine, in 5 detailed and described below.

In In a further step S24, the first integrator strokes P1 and the second integrator strokes P2 low-pass filtered. For this purpose, the first integrator strokes P1 become first filtered integrator stroke P1_FIL and from the second integrator strokes P2 second filtered integrator stroke P2_FIL determined. This happens for example, by averaging from the first Integratorhüben P1 or by averaging from the second integrator strokes P2.

The Averages become for example by a moving averaging determines, for example, later determined integrator strokes P1, P2 stronger weighted as earlier determined integrator strokes P1, P2. Alternatively you can the average values, for example, in each case by using a predetermined number of last determined integrator strokes P1, P2 are determined.

In a further step S26 it is now checked whether an already reached number N_REP of determinations of the integrator strokes P1, P2 reaches or exceeds a predetermined minimum number N_REP_MIN of determinations of the integrator strokes P1, P2. If this is not the case, the system returns to step S12 and further integrator strokes P1, P2 are determined in steps S12 to S20. This part of the program in the conditioning phase corresponds to cycling the regulator control signal LAM_FAC_FB, as it does for two cycles in 2A is shown.

If the condition of step S26 is satisfied, it is checked in a step S28, depending on the integrator strokes P1, P2 or the filtered integrator strokes P1_FIL, P2_FIL, whether a condition CDN is met, which is representative of a center position of the regulator actuating signal LAM_FAC_FB being a switching point the binary exhaust gas probe 52 equivalent. During operation of the internal combustion engine, shifts in the center position of the regulator control signal LAM_FAC_FB can occur, in particular when the load request changes, which result in the latter no longer having the rich threshold value THD_R and the lean threshold value THD_L of the binary exhaust gas probe 52 is correlated. The condition CDN allows
that by means of the integrator strokes P1, P2 or the filtered integrator strokes P1_FIL, P2_FIL, such a shift of the center position of the regulator actuating signal LAM_FAC_FB can be detected. If the condition CDN is not fulfilled, then the mid-position of the regulator control signal LAM_FAC_FB does not correspond to the switching point of the binary exhaust gas probe 52 is returned to the step S12 and in steps S12 to S22 integrator strokes P1, P2 are again determined.

The Steps S12 to S28 are used as the conditioning phase of the process designated.

The Following steps of the program are called the diagnostic phase of the procedure designated.

If the condition of step S28 is satisfied, in a further step S30 a first time duration T_1, in which the control signal LAM_FAC_FB assumes the upper plateau value LAM_FAC_FB_T, is determined as a function of the first integrator stroke P1. Preferably, the first time period T_1 becomes dependent on a desired charge A_KAT of the catalyst, an associated air mass MAF and a time T_TRIM for the trim control intervention according to the formula T_1 = 2 × A_KAT / (0.23 × MAF × (P1 + K2)) + T_TRIM determined. The determination of the time T_TRIM for the trim control intervention is given in the description 4 described.

In the step S30 is further a further period of time T_2, in which the Control signal LAM_FAC_FB the lower plateau value LAM_FAC_FB_B assumes, depending determined by the second Integratorhub P2. The second time period T_2 is preferred depending on from the desired Loading A_KAT of the catalyst and the associated air mass MAF after the Formula T_2 = 2 × A_KAT / (0.23 × MAF × (P1 + K2)).

In further embodiments For example, the first time T_1 is determined depending on the first filtered one Integrator stroke P1_FIL. In further embodiments, the other Duration T_2 dependent determined by the second filtered Integratorhub P2_FIL. In the Formulas for determining the first time T_1 and the second Time T_2 is then in a corresponding manner instead of the first Integratorhubs P1 to use the first filtered Integratorhub P1_FIL.

In a step S31, the control signal LAM_FAC_FB is generated as a square wave signal having the upper plateau value LAM_FAC_FB_T in the first time period T_1 and the lower plateau value LAM_FAC_FB_B in the second time duration T_2 (see also FIG 2 B ).

The upper plateau value LAM_FAC_FB_T results as a function of a maximum value of the control signal LAM_FAC_FB or a filtered maximum value of the control control signal LAM_FAC_FB upon reaching the rich threshold THD_R of the binary exhaust gas probe 52 with respect to the value of the first integrator stroke P1 or the value of the first filtered integrator stroke P1_FIL which existed when satisfying the condition CDN. The type of filtering of the maximum value of the regulator control signal LAM_FAC_FB is preferably correlated to that with respect to the first integrator stroke P1. In 2 B This part of the program in the diagnostic phase corresponds to the areas in which the control signal LAM_FAC_FB is equal to the upper plateau value LAM_FAC_FB_T (rich phase RICH).

The lower plateau value LAM_FAC_FB_B is dependent on a minimum value of the control loop signal LAM_FAC_FB or a filtered minimum value of the control loop signal LAM_FAC_FB upon reaching the lean threshold THD_L, and although with respect to the value of the second integrator stroke P2 or the value of the second filtered integrator stroke P2_FIL that existed when satisfying the condition CDN. The type of filtering of the minimum value of the regulator control signal LAM_FAC_FB is preferably correlated with respect to the second integrator stroke 22 , In 2 B This part of the program in the diagnostic phase corresponds to the areas in which the control signal LAM_FAC_FB is equal to the lower plateau value LAM_FAC_FB_B (lean phase LEAN).

In another step S32 ends the program.

In 4 is the optional subroutine shown. The subroutine describes a trim control for a rich air-fuel ratio LAM in the cylinder Z1. The subroutine is started in a step S40.

In a step S42, it is preferably checked whether the measurement signal MS2 at the further exhaust gas probe 54 has a value which is less than or equal to a predetermined rich threshold value THD_R_2 of the further exhaust gas probe 54 is. The time T_TRIM for the trim controller intervention is a function of the measurement signal MS2 at the further exhaust gas probe 54 , This function can be permanently saved as a map. The predetermined grease threshold value THD_R_2 of the further exhaust gas probe 54 may for example have a value of about 400 mV. As long as this has not been reached, the program remains in step S42, keeping the control loop signal LAM_FAC_FB constant over the time T_TRIM for the trimming control intervention in the rich phase RICH. In 2A This part of the program in the conditioning phase corresponds to the part of the control loop signal LAM_FAC_FB in which it assumes the maximum value (rich phase RICH).

If the condition of step S42 is satisfied, the optional ends Subroutine in a further step S44 and the program becomes continued in step S18.

In 5 is the optional further subroutine shown. The further subroutine describes a trim control for a lean air / fuel ratio LAM in the cylinder Z1.

The another subroutine is started in a step S50.

In a step S52, it is preferably checked whether the measurement signal MS2 at the further exhaust gas probe 54 has a value which is greater than or equal to a predetermined lean threshold value THD_L_2 of the further exhaust gas probe 54 is. The time T_TRIM for the trim controller intervention is a function of the measurement signal MS2 at the further exhaust gas probe 54 , This function can be permanently saved as a map. The predetermined lean threshold value THD_L_2 of the further exhaust gas probe 54 may for example have a value of about 750 mV. As long as it has not been reached, the program remains in the lean phase LEAN while the controller control signal LAM_FAC_FB is kept constant in step S52.

If the condition of step S52 is satisfied, the optional ends Subroutine in a further step S54 and the program becomes continued in step S24.

Claims (4)

Method for operating an internal combustion engine, which has at least one cylinder (Z1-Z4) with a combustion chamber ( 26 ) and an exhaust tract ( 14 ), in which a catalyst ( 34 ) and a binary exhaust gas probe ( 52 ) upstream of at least a partial volume of the catalyst ( 34 ), wherein the binary exhaust gas probe ( 52 ) is designed for outputting a measurement signal (MS1), wherein a binary lambda controller with a proportional control component and an integral control component (I) is designed for outputting a regulator control signal (LAM_FAC_FB) for regulating an air / fuel ratio (LAM) in the combustion chamber ( 26 ) of the cylinder (Z1-Z4), such that - in a conditioning phase - after the measurement signal (MS1) has a value that is less than or equal to a predetermined lean threshold (THD_L), the regulator control signal (LAM_FAC_FB) by means of the integral control component (I) is varied until the measurement signal (MS1) has a value which is greater than or equal to a predetermined rich threshold (THD_R), and depending on this variation, a first Integratorhub (P1) is determined, - the regulator control signal (LAM_FAC_FB) means of the integral control component (I) is varied until the measurement signal (MS1) has a value which is less than or equal to the predetermined lean threshold value (THD_L), and depending on this variation, a second integrator stroke (P2) is determined, and - the Integratorhüben (P1, P2) is determined whether a condition (CDN) is met, which is representative that a center position of the control loop signal (LAM_FAC_FB) a switching point t of the exhaust gas probe ( 52 ), and if so, a diagnostic phase is initiated, wherein - in the diagnostic phase, the control loop signal (LAM_FAC_FB) is generated as a square wave signal having an upper plateau value (LAM_FAC_FB_T) and a lower plateau value (LAM_FAC_FB_B), wherein - the upper plateau value ( LAM_FAC_FB_T) is correlated with a maximum value of the control loop signal (LAM_FAC_FB) when the rich threshold is reached value (THD_R), which correlates to the value of the first integrator stroke (P1) that existed when the condition (CDN) was satisfied, and - the lower plateau value (LAM_FAC_FB_B) is correlated with a minimum value of the control loop signal (LAM_FAC_FB) when the Lean threshold (THD_L), which correlates to the value of the second integrator stroke (P2) that existed when the condition (CDN) was met. The method of claim 1, wherein a first period of time (T_1), in which the controller control signal (LAM_FAC_FB) the upper plateau value (LAM_FAC_FB_T) assumes, depending from the first integrator stroke (P1) and another time period (T_2), in which the controller control signal (LAM_FAC_FB) the lower plateau value (LAM_FAC_FB_B), depending from the second integrator stroke (P2). The method of claim 1 or 2, wherein the first Integratorhübe (P1) and the second integrator strokes (P2) are low-pass filtered, and the low-pass filtered first Integratorhübe (P1) and second integrator strokes (P2) during testing condition (CDN) and in the diagnostic phase. Device for operating an internal combustion engine, which has at least one cylinder (Z1-Z4) with a combustion chamber ( 26 ) and an exhaust tract ( 14 ), in which a catalyst ( 34 ) and a binary exhaust gas probe ( 52 ) upstream of at least a partial volume of the catalyst ( 34 ), wherein the binary exhaust gas probe ( 52 ) is designed to output a measurement signal (MS1), wherein a binary lambda controller with a proportional control component and an integral control component (I) is designed for outputting a regulator control signal (LAM_FAC_FB) for regulating an air / fuel ratio (LAM) in the combustion chamber ( 26 ) of the cylinder (Z1-Z4), wherein the device is designed - for varying the controller control signal (LAM_FAC_FB) by means of the integral control component (I) after the measurement signal (MS1) has a value which is less than or equal to a predetermined lean threshold (THD_L ) is, until the measurement signal (MS1) has a value which is greater than or equal to a predetermined rich threshold value (THD_R), and for determining a first Integratorhub (P1) depending on this variation, - for varying the Reglerstellsignal (LAM_FAC_FB) means the integral control component (I) until the measurement signal (MS1) has a value which is less than or equal to the predetermined lean threshold value (THD_L), and for determining a second integrator stroke (P2) depending on this variation, and - for determining depending on the Integratorhüben (P1, P2), whether a condition (CDN) is met, which is representative that a center position of the control loop signal (LAM_FAC_FB) a switching point of the exhaust assonde ( 52 ), and if this is the case for initiating a diagnostic phase, wherein - in the diagnostic phase, the controller control signal (LAM_FAC_FB) is designed as a square wave signal having an upper plateau value (LAM_FAC_FB_T) and a lower plateau value (LAM_FAC_FB_B), wherein - the upper plateau value (LAM_FAC_FB_T ) is correlated with a maximum value of the control loop signal (LAM_FAC_FB) upon reaching the rich threshold (THD_R), which correlates to the value of the first integrator stroke (P1) that existed when the condition (CDN) was met, and - the lower plateau value (LAM_FAC_FB_B) is correlated with a minimum value of the control loop signal (LAM_FAC_FB) upon reaching the lean threshold (THD_L) that correlates to the value of the second integrator stroke (P2) that existed when the condition (CDN) was met.