DE102019203749A1 - Method for determining an error in an exhaust gas sensor of an internal combustion engine - Google Patents

Abstract

The invention relates to a method for determining a fault in an exhaust gas sensor (100) which has a pump cavity (120, 220) in which a pump electrode (114, 224) is arranged and a measurement cavity (140, 240) in which one Measuring electrode (144, 244) is arranged. The method according to the invention comprises introducing oxygen into the pump cavity (120, 220), flowing the oxygen into the measurement cavity (140, 240), generating a diagnostic measurement signal which indicates an amount of oxygen in the measurement cavity (140, 240), detecting a change in the diagnostic measurement signal, which results from the oxygen introduced, a determination of a time period between the introduction of oxygen and the change in the diagnostic measurement signal and a determination that the exhaust gas sensor (100) is faulty if the determined time period until the detected change in the diagnostic measurement value from a predetermined value Time reference value deviates by more than one time threshold.

Description

The present invention relates to a method for determining an error in an exhaust gas sensor of an internal combustion engine, in particular a method for determining an error in a combination exhaust gas sensor for selectively detecting the nitrogen oxide and ammonia content in the exhaust gas of the internal combustion engine.

Exhaust gas sensors, such as B. nitrogen oxide sensors, allow a measurement of the concentration of components in the exhaust gas of internal combustion engines, such as gasoline or diesel engines. As components, the exhaust gas from the internal combustion engine has i.a. Ammonia (NH3) and nitrogen oxides (NOx), whereby knowledge of the respective concentration can be advantageous for controlling the internal combustion engine.

The DE 10 2007 035 768 A1 discloses a method for diagnosing a nitrogen oxide sensor arranged in an exhaust gas system of an internal combustion engine, which has at least one setting device for adjusting the oxygen content of exhaust gas that has entered the sensor by means of an electrical variable and at least one measuring device that outputs a measurement value that characterizes the nitrogen oxide content of the exhaust gas.

Furthermore, from the DE 697 32 582 T2 a method and an apparatus for measuring the oxygen concentration and the nitrogen oxide concentration using a nitrogen oxide sensor are known.

In addition, the DE 103 12 732 B4 a method for operating a measuring probe for measuring a gas concentration in a measuring gas with an oxygen ion-conducting solid electrolyte, which has a measuring cavity for receiving the measuring gas, a measuring electrode and an outer electrode. A pump current flowing between the measuring electrode and the outer electrode transports oxygen ions from the measuring electrode to the outer electrode. The measuring electrode is checked by determining the electrode area effectively available for oxygen diffusion or a value dependent on it, by setting a predetermined oxygen concentration in the measuring cavity, impressing a predetermined constant pump current between the measuring electrode and the outer electrode and the resulting Nernst potential at the Measuring electrode is measured, the time period is measured until the measured Nernst potential jumps from small to large values, the measured time period is compared with a predetermined threshold value and a defect of the measuring electrode is determined when the measured time period falls below the predetermined threshold value.

The WO 2017/222001 A1 , WO 2017/222002 A1 and WO 2017/222003 A1 each disclose nitrogen oxide sensors that are provided with a pre-cavity in which a pre-electrode is provided. The ammonia component in the exhaust gas of the internal combustion engine can be qualitatively determined by controlling the pump electrode and the pre-electrode.

From the DE 10 2016 206 991 A1 a method for diagnosing a nitrogen oxide sensor is known. In this case, a predetermined oxygen concentration is set within the measuring cavity of a nitrogen oxide sensor, regardless of the composition of the exhaust gas present. This is essentially achieved in that the oxygen in the exhaust gas is almost completely drained off before reaching the measuring cavity, the predetermined oxygen content being set by introducing oxygen into the measuring cavity, so that a predetermined oxygen content is established within the measuring cavity.

The DE 10 2010 042 701 A1 describes a method for measuring and / or calibrating a gas sensor, which is provided for determining, in particular, oxygen-containing gas components in gas mixtures, in particular in exhaust gases from internal combustion engines. The gas sensor has at least one inner pump electrode, at least one outer pump electrode and at least one decomposition electrode provided for the electrochemical decomposition of the gas component to be determined, the at least one inner electrode and the at least one decomposition electrode being arranged in mutually separate chambers or sections of the gas sensor and wherein one ionic current induced by the decomposition of the gas component to be determined is used to determine the gas component. The method describes that the measurement and / or calibration is carried out during the ongoing operation of the gas sensor by essentially removing the gas component and / or oxygen to be determined from at least one of the chambers or sections in one step by means of electrochemical pumping processes, in a further step Step by means of electrochemical pumping processes, oxygen is introduced in a targeted manner into at least one of the chambers or sections and the changes caused by the introduced oxygen can be measured with respect to a further electrode. The gas sensor can be measured and / or calibrated using the measured values.

In view of the prior art, it is an object of the present invention to provide a method for diagnosing an exhaust gas sensor arranged in an exhaust gas line of an internal combustion engine, with which the functionality and measurement accuracy of the exhaust gas sensor can be detected reliably and efficiently.

This object is achieved with a method according to claim 1. Further advantageous refinements are specified in the subclaims.

The present invention is based on the idea of determining an error in an exhaust gas sensor designed to measure the concentration of nitrogen oxide and ammonia by specifically introducing oxygen into the exhaust gas sensor, which is significantly reflected in the measurement signal of the exhaust gas sensor. Knowing the rate of diffusion of oxygen within the exhaust gas sensor, the time between the introduction of oxygen into the exhaust gas sensor and the significant increase in the measurement signal of the oxygen sensor can be used to determine the functionality, in particular to determine whether the diffusion paths are OK. With a properly functioning exhaust gas sensor, this time corresponds approximately to a predetermined time. However, if there is a fault in the exhaust gas sensor, such as a partially blocked diffusion path within the exhaust gas sensor, the time would be greater than the predetermined time, since the oxygen introduced is at least partially prevented from diffusing into the measuring chamber, which is why the significant rise in the measurement signal takes place only later is observable.

Accordingly, according to a first aspect of the present invention, a method for determining a fault of an exhaust gas sensor having a main body and arranged in an exhaust gas line of an internal combustion engine is disclosed, which has a pump cavity arranged in the main body and connected to the exhaust gas, in which a pump electrode is arranged, and a has arranged in the main body and connected to the pump cavity via a diffusion path, in which a measuring electrode is arranged. The method according to the invention in accordance with the first aspect comprises introducing oxygen into the pump cavity by means of the pump electrode, flowing or getting the oxygen introduced into the pump cavity through the at least one diffusion path at least partially into the measurement cavity, generating a diagnostic measurement signal by means of the measurement electrode, that indicates an amount of oxygen in the measuring cavity, detecting a change in the diagnostic measurement signal that results from the oxygen coming from the pump cavity through the at least one diffusion path into the measuring cavity, determining a period of time between the introduction of the oxygen into the pump cavity and the change in the Diagnostic measurement signal and a determination that the exhaust gas sensor is faulty if the determined period of time until the detected change in the diagnostic measurement value deviates from a predetermined time reference value by more than a time threshold value. In particular, the diagnostic measurement signal indicates the amount of oxygen that is in the immediate vicinity of the measurement electrode.

In particular, the predetermined time reference value represents an expected diffusion time that the oxygen introduced into the pump cavity requires to at least partially get into the measurement cavity from the pump cavity in the case of an error-free exhaust gas sensor. The predetermined time reference value thus represents the expected time value for a fault-free exhaust gas sensor. If the determined time period between introduction of the oxygen and the detected change in the diagnostic measurement value deviates from this predetermined time reference value by more than the time threshold value, a fault in the exhaust gas sensor can be determined.

In a preferred embodiment of the method according to the invention, a predetermined pump current is applied to the pump electrode in order to introduce oxygen into the pump cavity. In particular, the signs of the electrical pump current applied to the pump electrode are opposite in normal measurement mode and in self-diagnosis mode to determine the fault of the exhaust gas sensor. In normal measurement operation of the exhaust gas sensor, the oxygen is normally pumped out of the exhaust gas in the pump cavity, whereas in the self-diagnostic operation of the exhaust gas sensor a predetermined amount of oxygen is now pumped into the exhaust gas sensor, in particular into the pump cavity of the exhaust gas sensor.

In a further advantageous embodiment of the method according to the invention, the diagnostic measurement signal is an electrode voltage which is present between the measurement electrode and a reference electrode, which is provided in a reference cavity which is arranged in the main body and is connected to the ambient air. In particular, the electrode voltage describes the so-called Nernst voltage, which results from the application of the electrical measuring current to the measuring electrode.

Preferably, the predetermined time threshold is about 50%, preferably about 30%, more preferably about 15%. That is, if the determined period of time until the detected change in the diagnostic measured value deviates from the predetermined time reference value by more than 15%, an error in the exhaust gas sensor is determined.

In a preferred embodiment of the method according to the invention, the error in the exhaust gas sensor indicates an error in the at least one diffusion path.

In particular, the diffusion time of the gas mixture within the main body depends on the properties of the at least one diffusion path. The diffusion path forms a diffusion barrier, for example, and can be filled with a porous filler material in order to provide a predetermined diffusion rate within the exhaust gas sensor. If the determined time period deviates from the time reference value by more than the predetermined time threshold value, an error can be recognized within the diffusion path.

For example, an at least partially blocked diffusion path can be determined when the determined time period until the detected change in the diagnostic measured value exceeds the predetermined time reference value by more than the time threshold value. A diffusion path blocked by exhaust gas particles, for example, can make it difficult for oxygen to get from the pump cavity into the measurement cavity. For this reason, the time period until the change in the diagnostic measured value is ascertained, which can be recognized here as an error in the diffusion path, in particular as a blocked diffusion path.

In a similar way, an at least partially exposed diffusion path can be determined if the determined time period until the detected change in the diagnostic measured value falls below the predetermined time reference value by more than the time threshold value. An at least partially exposed diffusion path can be, for example, a broken-out part of the main body, which leads to an undesired enlargement of the diffusion path. This, in turn, can make it easier for the oxygen to get from the pump cavity into the measurement cavity, which reduces the time until the diagnostic measurement value changes, since the oxygen can diffuse from the pump cavity into the measurement cavity more quickly. In this case, a partially exposed diffusion path is recognized, since the determined time period is significantly smaller than the expected predetermined time reference value.

According to a further aspect of the present invention, a method for operating an exhaust gas sensor arranged in an exhaust gas line of an internal combustion engine is disclosed, which method comprises determining an error in the exhaust gas sensor in accordance with the first aspect and, if an error in the exhaust gas sensor has been determined, actuating the electrodes in accordance with Emergency operation includes currents that differ from the currents of the fault-free measuring operation of the exhaust gas sensor. Alternatively or additionally, in the case of an exhaust gas sensor with two measuring paths, the exhaust gas sensor can be operated in emergency mode by using the measuring path diagnosed as error-free as the operating path and the faulty measuring path being inoperative. In such an emergency mode, the measurement signal of the exhaust gas sensor is at least partially faulty (the nitrogen oxide signal also includes the ammonia portion), but the exhaust gas sensor can still be operated until the next maintenance without the vehicle being left behind.

• 1 eine schematische Schnittansicht durch einen Abgassensor gemäß einer beispielhaften ersten Ausführungsform zeigt,
• 2 eine schematische Schnittansicht durch einen Abgassensor gemäß einer beispielhaften zweiten Ausführungsform zeigt, und
• 3 ein beispielhaftes Ablaufdiagramm eines erfindungsgemäßen Verfahrens zum Ermitteln eines Fehlers des Abgassensors der 1 oder 2 zeigt.

Other features and objects of the invention will become apparent to those skilled in the art upon practicing the present teaching and viewing the accompanying drawings, in which:

• 1 2 shows a schematic sectional view through an exhaust gas sensor according to an exemplary first embodiment,
• 2nd 2 shows a schematic sectional view through an exhaust gas sensor according to an exemplary second embodiment, and
• 3rd an exemplary flow chart of a method according to the invention for determining an error of the exhaust gas sensor of the 1 or 2nd shows.

Elements of the same construction or function are provided with the same reference symbols in all figures.

In the context of the present disclosure, the term “taxes” includes the technical terms “taxes” and “rules”. The person skilled in the art will recognize in each case when control engineering control and when control engineering control is to be used.

Referring to the 1 is a schematic sectional view through an exhaust gas sensor 100 According to an exemplary first embodiment, which is designed to be arranged in an exhaust line of an internal combustion engine (not shown) and to detect the nitrogen oxide, ammonia and / or oxygen content in the exhaust gas of the internal combustion engine.

The exhaust gas sensor 100 has a main body 112 from a solid electrolyte, which is preferably formed from a mixed crystal of zirconium oxide and yttrium oxide and / or by a mixed crystal of zirconium oxide and calcium oxide. In addition, a mixed crystal of hafnium oxide, a mixed crystal of perovskite-based oxides or a mixed crystal of trivalent metal oxide can be used.

Inside the main body 112 are two measurement paths 110 , 210 provided which are essentially independent of one another and which are each connected to the exhaust gas. The first measurement path 110 has a first cavity 130 , a first pump cavity 120 and a first measuring cavity 140 on. The first cavity 130 is about a first Connection path 115 with the exterior of the main body 112 connected. In particular, exhaust gas can pass through the first connection path 115 in the first cavity 130 enter. The first pump cavity 120 is with the first cavity 130 via a first diffusion path 125 connected. The first diffusion path 125 is provided, for example, in the form of a very thin slot through which the gas mixture can pass at a predetermined rate. Alternatively, the first diffusion path 125 be filled or padded with a porous filler to form a diffusion rate regulation layer.

The first measuring cavity 140 is with the first pump cavity 120 via a second diffusion path 135 connected. The second diffusion path 135 is provided, for example, in the form of a very thin slot through which the gas mixture can pass at a predetermined rate. Alternatively, the second diffusion path 135 be filled or padded with a porous filler to form a diffusion rate regulation layer. The diffusion rate layers can alternatively be referred to as diffusion barriers.

The first diffusion path 125 and the second diffusion path 135 are designed such that the gas mixture can only partially pass through them. By knowing the cross sections of the first and second diffusion paths 125 , 135 and / or by knowing the respective porous filler, the diffusion rate through the first and second diffusion path 125 , 135 be determined and fixed.

In an alternative embodiment of the exhaust gas sensor 100 points the first measurement path 110 only the first pump cavity 120 and the first measuring cavity 140 on that with the first pump cavity 120 over the second diffusion path 135 connected is. In such an alternative embodiment of the exhaust gas sensor 100 is then the first pump cavity 120 connected to the exhaust gas via a connection path that corresponds to the path through the first connection path 115 , the first cavity 130 and the first diffusion path 125 of the exhaust gas sensor 100 of the 1 corresponds. In such an alternative embodiment of the exhaust gas sensor 100 can the exhaust gas from the exhaust line through this connection path directly into the first pump cavity 120 enter.

The second measurement path 210 has a second pump cavity 220 , a second cavity 230 and a second measuring cavity 240 on. The second pump cavity 220 is over a second connection path 215 with the exterior of the main body 112 connected. In particular, exhaust gas can pass through the second connection path 215 into the second pump cavity 220 Enter the second cavity 230 is with the second pump cavity 220 via a third diffusion path 225 connected. The third diffusion path 225 is provided, for example, in the form of a very thin slot through which the gas mixture can pass at a predetermined rate. Alternatively, the third diffusion path 225 be filled or padded with a porous filler to form a diffusion rate regulation layer.

The second measuring cavity 240 is with the second cavity 230 via a fourth diffusion path 235 connected. The fourth diffusion path 235 is provided, for example, in the form of a very thin slot through which the gas mixture can pass at a predetermined rate. Alternatively, the fourth diffusion path 235 be filled or padded with a porous filler to form a diffusion rate regulation layer. The diffusion rate layers can alternatively be referred to as diffusion barriers.

The third diffusion path 225 and the fourth diffusion path 235 are designed such that the gas mixture can only partially pass through them. By knowing the cross sections of the third and fourth diffusion path 225 , 235 and / or by knowing the respective porous fillers, the diffusion rate can be determined by the third and fourth diffusion path 225 , 235 be determined and fixed.

In an alternative embodiment of the exhaust gas sensor 100 points the second measurement path 210 only the second pump cavity 220 and the second measuring cavity 240 on that with the second pump cavity 220 is connected via a diffusion path that follows the path through the third diffusion path 225 , the second cavity 230 and the fourth diffusion path 235 of the exhaust gas sensor 100 of the 1 corresponds. In such an alternative embodiment of the exhaust gas sensor 100 can the exhaust gas from the second pump cavity 220 through this diffusion path directly into the second measuring cavity 240 enter.

In the main body 112 is also a reference cavity 50 formed directly with the exterior of the main body 12th communicates. Within the reference cavity 50 is a reference electrode 52 arranged. In particular, there is the reference cavity 50 with the ambient air, ie not with the exhaust gas, and is designed to provide an oxygen reference for those in the main body 112 of the exhaust gas sensor 100 arranged to form different electrodes.

On an outside of the main body 112 is an exhaust gas electrode in contact with the exhaust gas (also called "P +" electrode) 22 arranged. In particular, during a measuring operation of the exhaust gas sensor 100 by applying a reference current to the exhaust gas electrode 22 the oxygen in the exhaust gas is ionized and by the main body 112 as oxygen ions to the reference electrode 52 diffuse and be converted back into oxygen molecules to form an oxygen reference.

Within the first pump cavity 120 is a first pump electrode (also called "P -" electrode) 124 arranged. In particular, during the measuring operation of the exhaust gas sensor 100 by applying a first pump current IP0 on the first pump electrode 124 the oxygen in the exhaust gas within the first pump cavity 120 be ionized and by the main body 112 migrate or arrive or diffuse as oxygen ions. Because of the first pump cavity 120 applied oxygen ions form between the first pump electrode 124 and the reference electrode 52 indirectly a first electrode voltage or first Nernst voltage V0 out. More specifically, the first electrode voltage or the first Nernst voltage is formed V0 directly from the immediate vicinity of the first pump electrode 124 residual oxygen still present.

With IP0 can be an oxygen concentration in the pump cavity 120 Depending on the level of the oxygen concentration set, there may be a reduction in nitrogen oxides or oxidation of the ammonia.

Within the first measuring cavity 140 is a first measuring electrode (also called the first "M2" electrode) 144 arranged, which is designed during the measuring operation of the nitrogen oxide sensor 100 when applying a first measuring current IP21 within the first measuring cavity 140 to ionize existing oxygen and / or nitrogen oxides so that the oxygen ions pass through the main body 112 can hike or get there. Because of the first measurement cavity 140 ejected or pumped out oxygen ions form between the first measuring electrode 144 and the reference electrode 52 a first measuring electrode voltage or first measuring Nernst voltage V21 made by applying the first measuring current IP21 on the first measuring electrode 144 is kept at a constant value. More precisely, the first measuring electrode voltage or the first measuring Nernst voltage is formed V21 directly from the immediate vicinity of the first measuring electrode 144 residual oxygen still present. The first measuring current applied IP21 is then an indication of the nitrogen oxide content within the exhaust gas.

The one on the first pump electrode 124 applied first pump current IP0 is controlled in such a way that preferably only the oxygen is ionized, but not the nitrogen oxides. For this purpose, the first pump current is provided IP0 to be controlled such that the first electrode voltage or first Nernst voltage V0 is kept constant at a first voltage value, for example 220 mV. In particular, the first pump electrode 124 designed to do so during normal operation of the nitrogen oxide sensor 100 to pump almost all of the oxygen out of the exhaust gas, so that in the first measuring cavity 140 there are almost only nitrogen oxides. The first measuring electrode 144 is designed to ionize the nitrogen oxides, the on the first measuring electrode 144 applied first measuring current IP21 is a measure of the nitrogen oxide content in the exhaust gas.

Within the second pump cavity 220 is a second pump electrode (also called "M0" electrode) 224 arranged. Here, during the measurement operation of the exhaust gas sensor 100 by applying a second pump current IP3 on the second pump electrode 224 the oxygen in the gas mixture within the second pump cavity 220 be ionized and by the main body 112 migrate or arrive or diffuse as oxygen ions. Because of the second pump cavity 220 applied oxygen ions form between the second pump electrode 224 and the reference electrode 52 indirectly a second electrode voltage or second Nernst voltage V3 out. More specifically, the second electrode voltage or the second Nernst voltage is formed V3 directly from the in the immediate vicinity of the second pump electrode 224 residual oxygen still present.

Within the second measuring cavity 240 is a second measuring electrode (also called a second "M2" electrode) 244 arranged, which is designed during the measuring operation of the nitrogen oxide sensor 100 when applying a second measuring current IP22 within the second measuring cavity 240 to ionize existing oxygen and / or nitrogen oxides so that the oxygen ions pass through the main body 112 can hike or get there. Because of the second measuring cavity 240 ejected or pumped out oxygen ions form between the second measuring electrode 244 and the reference electrode 52 a second measuring electrode voltage or first measuring Nernst voltage V22 made by applying the second measuring current IP22 on the second measuring electrode 244 is kept at a constant value. More precisely, the second measuring electrode voltage or the second measuring Nernst voltage is formed V22 directly from the in the immediate vicinity of the second measuring electrode 244 residual oxygen still present. The first measuring current applied IP21 is then an indication of the nitrogen oxide content within the exhaust gas. From the applied second measuring current IP22 and the applied first measuring current IP21 the proportion of ammonia in the exhaust gas can then be determined, especially since the ammonia in the exhaust gas is in the two measurement paths 110 , 210 is oxidized at different points and thus before and covers different diffusion distances after oxidation

The one on the second pump electrode 224 applied second pump current IP3 is set in such a way that only the ammonia and oxygen present in the exhaust gas are preferably ionized. For this purpose, the second pump current is provided IP3 to be controlled such that the second electrode voltage or second Nernst voltage V3 is kept constant at a second voltage value, for example 230 mV. In particular, the second pump electrode 224 designed to do so during normal operation of the nitrogen oxide sensor 100 to pump almost all of the oxygen out of the exhaust gas, so that in the second measuring cavity 240 there are almost only nitrogen oxides. The second measuring electrode 244 is designed to ionize the nitrogen oxides, the at the second measuring electrode 244 applied second measuring current IP22 is a measure of the nitrogen oxide content in the exhaust gas.

The different diffusion capabilities of ammonia (NH3) and nitrogen oxide (NO) result from the diffusion coefficients of ammonia and nitrogen based on the molar masses. Because ammonia molecules are lighter than nitrogen oxide molecules, ammonia can do better through the main body 112 , ie through the diffusion paths 115 , 125 , 215 , 225 , diffuse as nitrogen oxide. The diffusion of ammonia and nitrogen oxide takes place in particular due to the concentration gradient between the several cavities. As a result, the ammonia in the exhaust gas can better escape from the first cavity 130 into the first pump cavity 120 or from the second pump cavity 120 into the second cavity 230 pass as the nitrogen oxide in the exhaust gas.

The exhaust gas sensor according to the invention 100 also has a control unit (not explicitly shown) which is connected to the first pump electrode 124 , the exhaust gas electrode 22 , the second pump electrode 224 , the first measuring electrode 144 , the second measuring electrode 244 and the reference electrode 52 is connected and designed to each of these electrodes with the currents IP0 , IP3 , IP21 and IP22 to apply and the respective Nernst voltages V0 , V3 , V21 and V22 capture. The control unit is thus for controlling the operation of the exhaust gas sensor 100 educated.

In further alternative configurations of the exhaust gas sensor 100 it may be advantageous between the first pump cavity 120 and the first measuring cavity 140 to provide a further pump cavity, in which a further pump electrode is arranged, with which possibly still from the first pump cavity 120 oxygen can now be completely pumped out of the gas mixture. Similarly, it may be advantageous to use the second cavity 230 and the second measuring cavity 240 to provide a further pump cavity, in which a further pump electrode is arranged, possibly with the second pump cavity 220 oxygen can now be completely pumped out of the gas mixture.

Inside the main body 112 is also a heater 60 arranged, which is designed to the main body 112 to heat to a predetermined operating temperature and to maintain it, for example at approximately 850 ° C. The heater too 60 can be controlled and operated by the control unit.

The 2nd represents a schematic sectional view through an exhaust gas sensor 200 according to an exemplary second embodiment, which is different from the exhaust gas sensor 100 of the 1 differs in that only one measurement path 110 is present, which is from the second pump cavity 220 in which the second pump electrode 224 is arranged, the first pump cavity 120 in which the first pump electrode 124 is arranged, and the (first) measuring cavity 140 in which the (first) measuring electrode 144 is arranged, is formed. In the design of the exhaust gas sensor according to 2nd become the two measurement paths 110 , 210 realized that the two pump electrodes 124 , 224 be operated selectively and alternately. This means that in a first operating mode, the first pump current IP0 on the first pump electrode 124 is applied, the second pump electrode 224 is deactivated and thus the second pump cavity 220 the first cavity 130 represents, and in a second operating mode, the second pumping current IP3 on the second pump electrode 224 is applied, the first pump electrode 124 is deactivated and thus the first pump cavity 120 the second cavity 230 represents. The first measuring current is in the first operating mode IP21 on the measuring electrode 144 applied, the second measuring current in the second operating mode IP22 on the measuring electrode 144 is created.

Referring to the 3rd FIG. 4 is an exemplary flow diagram of a method according to the invention for determining a fault in the exhaust gas sensor of FIG 1 disclosed. In particular, the following is the first measurement path 110 of the exhaust gas sensor 100 of the 1 Reference, whereby it is expressly stated that the second measurement path 210 of the exhaust gas sensor 100 of the 1 can be examined accordingly for errors. The same applies to the diffusion path 110 of the exhaust gas sensor 200 of the 2nd .

The procedure of 3rd starts at step 300 , where the exhaust gas sensor 100 is switched from normal measuring mode to self-diagnosis mode. In a subsequent step 310 will oxygen into the pump cavity 120 by means of Pump electrode 124 brought in. It should be noted that, as already described above, in normal measurement operation of the exhaust gas sensor 100 a current at the pump electrode IP0 is applied to oxygen from the pump cavity 120 bring out. As a result, oxygen is introduced into the pump cavity 120 on the pump electrode 124 a current is applied, which causes oxygen to enter the pump cavity 120 is introduced. It is preferred to add a significant amount of oxygen to the pump cavity 120 bring in.

In a subsequent step 320 gets into the pump cavity 120 oxygen introduced through the diffusion path 135 at least partially in the measuring cavity 140 . In the next step 330 is by means of the measuring electrode 144 generates a diagnostic measurement signal that shows an amount of oxygen in the measurement cavity 140 displays. In particular, the diagnostic measurement signal corresponds to the first measurement current IP21 which is used to control the first measuring electrode voltage V21 on the first measuring electrode 144 is applied to a constant voltage value.

In a subsequent step 340 a change in the diagnostic measurement signal is detected, which is due to the pump cavity 120 through the diffusion path 135 into the measuring cavity 140 coming oxygen results. In particular, this leads to the measuring cavity 140 entering oxygen to a significant increase in the first measuring current IP21 .

After the change in the diagnostic measurement signal has been detected, there is a period of time between the introduction of the oxygen into the pump cavity 120 and the change in the diagnostic measurement signal in a further step 350 determined. For this purpose, it is preferred that the step 310 a time signal is started, which ends when the change in the diagnostic measurement signal is detected.

In a further step 360 it is checked whether the step 350 determined time period deviates from a predetermined time reference value by more than a time threshold. Will at the crotch 360 If the determined time period does not deviate from the predetermined time reference value by more than one time threshold value, the method returns to the step 310 and the diagnostic procedure can be performed again.

However, at the crotch 360 determined that the determined time period deviates from the predetermined time reference value by more than the time threshold value, the method proceeds to the step 370 on which a fault in the exhaust gas sensor is determined before the method in step 380 ends.

A deviation of the determined time period from the predetermined time reference value by more than the time threshold value is namely an indication that the in the pump cavity 120 introduced oxygen into the measuring cavity as expected 140 can diffuse, which is why an error in the diffusion path 135 can be closed. Possible errors are, for example, a blocked diffusion path 135 or an at least partially exposed diffusion path 135 . In both cases, the oxygen can either be slower or faster from the pump cavity 120 into the measuring cavity 140 arrive, which can be seen in the deviation from the time reference value.

The aforementioned self-diagnosis method can, for example, at periodic intervals, such as every 100 operating hours of the internal combustion engine, and / or in predetermined operating states of the internal combustion engine, such as. B. during a fuel cut-off phase.

It may also be preferred that the step 370 if there is a fault in the exhaust gas sensor 100 was determined the operation of the exhaust gas sensor 100 switches to emergency operation. In such an emergency mode, the measurement signal is partially faulty, but this emergency mode can serve to extend the time until the exhaust gas sensor is replaced 100 to bridge. Consequently, the exhaust gas sensor can 100 be operated in emergency mode at least for this period of time without the vehicle coming to a standstill.

QUOTES INCLUDE IN THE DESCRIPTION

This list of documents listed by the applicant has been generated automatically and is only included for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 102007035768 A1 [0003]
• DE 69732582 T2 [0004]
• DE 10312732 B4 [0005]
• WO 2017/222001 A1 [0006]
• WO 2017/222002 A1 [0006]
• WO 2017/222003 A1 [0006]
• DE 102016206991 A1 [0007]
• DE 102010042701 A1 [0008]

Claims (8)

Method for determining an error of an exhaust gas sensor (100) which has a main body (112) and is arranged in an exhaust gas line of an internal combustion engine, which has a pump cavity (120, 220) which is arranged in the main body (112) and is connected to the exhaust gas and in which a pump electrode (114 , 224) and has a measuring cavity (140, 240) arranged in the main body (112) and connected to the pump cavity (120, 220) via a diffusion path (125, 135, 225, 235), in which a measuring electrode (144 , 244), the method comprising: Introducing oxygen into the pump cavity (120, 220) by means of the pump electrode (114, 224), The oxygen introduced into the pump cavity (120, 220) at least partially enters the measurement cavity (140, 240) through the at least one diffusion path (125, 135, 225, 235), Generating a diagnostic measurement signal by means of the measurement electrode (144, 244), which indicates an amount of oxygen in the measurement cavity (140, 240), Detecting a change in the diagnostic measurement signal which results from the oxygen entering the measurement cavity (140, 240) from the pump cavity (120, 220) through the at least one diffusion path (125, 135, 225, 235), - Determining a time period between the introduction of oxygen into the pump cavity (120, 220) and the change in the diagnostic measurement signal, and - Determine that the exhaust gas sensor (100) is faulty if the determined time period until the detected change in the diagnostic measured value deviates from a predetermined time reference value by more than a time threshold value. Procedure according to Claim 1 A predetermined pump current (IP0, IP3) is applied to the pump electrode (124, 224) to introduce oxygen into the pump cavity (120, 220). Method according to one of the preceding claims, wherein the diagnostic measurement signal is an electrode voltage (V2) which is present between the measurement electrode (144, 244) and a reference electrode (52) which is arranged in a main body (112) and is connected to the ambient air Reference cavity (50) is provided. Method according to one of the preceding claims, wherein the predetermined time threshold value is approximately 50%, preferably approximately 30%, more preferably approximately 15%. Method according to one of the preceding claims, wherein the error of the exhaust gas sensor (100) indicates an error of the at least one diffusion path (125, 135, 225, 235). Procedure according to Claim 5 , wherein an at least partially blocked diffusion path (125, 135, 225, 235) is determined when the determined time period until the detected change in the diagnostic measured value exceeds the predetermined time reference value by more than the time threshold value. Procedure according to Claim 5 , wherein an at least partially exposed diffusion path (125, 135, 225, 235) is determined if the determined time period until the detected change in the diagnostic measured value falls below the predetermined time reference value by more than the time threshold value. Method for operating an exhaust gas sensor (100) arranged in an exhaust line of an internal combustion engine, comprising: - determining an error of the exhaust gas sensor (100) according to one of the preceding claims, and - If a fault in the exhaust gas sensor (100) has been determined, actuating the electrodes (114, 214, 144, 244) in accordance with an emergency operation with currents which differ from the currents of the fault-free measuring operation of the exhaust gas sensor (100).

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