Method for identifying the sensor type of a sensor element of an exhaust gas sensor

Abstract

Method for identifying the sensor type of a sensor element (114) of an exhaust gas sensor for detecting at least one property of an exhaust gas in an exhaust tract, wherein the sensor element (114) of the exhaust gas sensor comprises an electrical heating element (136) and a cell (118) consisting of two electrodes (120, 124, 126) and a solid electrolyte (122) connecting the electrodes (120, 124, 126), wherein the method comprises at least the following steps: • at least one first step, wherein in the first step at least one characteristic parameter is determined, namely a heater resistance of the heating element (136) and / or an internal resistance of the cell (118); • at least one second step, wherein in the second step the characteristic parameter is compared with at least one reference value, wherein, according to this comparison, at least one feature is assigned to the sensor element (114) or at least one part of the sensor element (114), namely the sensor type.

Description

Prior ArtFrom the prior art, sensor elements for detecting at least one property of a gas in a measurement gas chamber are known. The invention is described below, without limiting further possible configurations, substantially with reference to methods and devices which serve for quantitative and / or qualitative detection of at least one gas component in a measurement gas space. For example, the gas can be an exhaust gas of an internal combustion engine, in particular in the motor vehicle sector, and the measurement gas chamber can be an exhaust tract, for example. Such sensor elements are described, for example, in REIF, Konrad (Ed.): Sensors in the motor vehicle. Wiesbaden: Springer, 2010 (Bosch Fachiebieft Autobriken). Pages 98-111, 160-165. ISBN 978-3-8348-1315-2. https: / / doi.org / 10.1007 / 978-3-8348-9718-3, pages 98-111 and pages 160-165. In particular, they may be exhaust gas sensors having different tasks. Known are, for example, oxygen-jumping probes, in particular for measuring an oxygen content of the exhaust gas in the range of the air ratio λ=1, broad band oxygen probes for measuring in the range of the air ratio λ=1 and in the rich and in the lean exhaust gas, exhaust gas temperature sensors, nitrogen oxide sensors and particle sensors.Exhaust gas sensors are operated, for example, in a vehicle, in particular with an activation system, for example with a control unit. For this purpose, the control device, in particular the control device, has in particular a hardware module. The hardware module controls, for example, components of the exhaust gas sensor, in particular electrodes and / or heaters of the sensor element, in particular of the exhaust gas sensor. Depending on the complexity of the sensor element, this is generally effected, for example, by discrete electronic components, such as, for example, in the case of a jumping probe, and / or by integrated electronic components with discrete circuitry, such as, for example, in the case of broadband lambda probes or other exhaust gas sensors.The heater can be operated, for example, on the one hand by, in particular, permanently connecting a battery voltage to a vehicle ground, for example, by a relay, and on the other hand, for example, by clocked, in particular pulse-width-modulated, switching of the battery voltage with a semiconductor switch, for example, a low-side FET and / or a heater output stage, on the vehicle ground. The heater output stage can be, for example, a discrete component in the control, in particular in the control device, or can be contained in a multiple component. Such a multiple component can have, in particular, besides one or more output stage channels, further functions, such as, for example, a voltage supply and / or a power supply and / or a CAN communication and / or other functions.The hardware module, in particular in the control, can be controlled by a microcontroller of the control and in particular of the software contained therein, the so-called "hardware capsule". This software can optionally control the sensor element via a probe ASIC and / or can control the heater and / or can evaluate a probe signal and / or execute correction and / or calibration functions and / or can carry out diagnoses and / or can deliver the probe signal to, for example, downstream software functions of the exhaust gas aftertreatment system.Methods and devices are desired, for example, for preventing malfunction of sensor elements, in particular exhaust gas probes. A control, in particular a probe control, with, for example, incorrect heating voltage and / or pump voltage can lead in particular to corruptions and / or to destruction of the sensor element. Known measures, in particular methods according to the prior art, are limited in particular to a configuration of the plug connection between the sensor element, for example the exhaust gas probe, and the control, the control unit. Methods are known, for example, which function on the principle of the poka yoke, for example by "plug socket", in particular by shaping and / or coloring, for example, a plug and / or by plug coding by means of at least one chip and / or at least one barcode.For example, methods for detecting the sensor element, in particular a sensor chip, by a workshop test device are known. In a workshop environment, it is generally not possible, or only possible with difficulty, to ascertain the sensor type, in particular the sensor element. For example, the workshop inspection device can identify the sensor type in a first step, in particular independently, wherein the workshop inspection device can carry out an inspection program, for example, in a second step, in particular without the need for an operator, for example a mechanic, to input a probe type, for example a sensor type. It can thus be ensured, for example, that the correct test program and / or correct test parameters can be used, in particular for the respective sensor type. As a result, for example, a number of misdiagnoses can be reduced; for example, it is possible to prevent an intact sensor element, in particular incorrectly, from being recognized as defective.A method and a device would therefore be desirable which make it possible in particular to detect the probe type and / or the sensor type, in particular the sensor element, particularly preferably the exhaust gas probe, and / or to detect another property, for example of activation, for example in a motor vehicle.Exhaust gas sensors and associated operating methods are also known from EP 1 707 950 A2, U.S. Pat. No. 2004 / 0 238 378 A1, JP H03-189 350 A and U.S. Pat. No. 5,513,522 A.Disclosure of the InventionTherefore, a method and a device for detecting the sensor type of a sensor element of an exhaust gas sensor are proposed, which at least largely avoid and / or mitigate the expected disadvantages of known methods and devices.The operation of a sensor element can be understood in particular to mean a method in which the sensor element is used for detecting at least one property of a gas in a measurement gas space, for example within the scope of a common use of the sensor element, for example during the operation of a motor vehicle. Alternatively or additionally, the operation can be, in addition to being used for detecting the property, also a diagnostic operation, for example in a workshop or during a test phase.The sensor element serves for detecting at least one property of an exhaust gas in an exhaust tract, for example an internal combustion engine. The sensor element may be, in particular, an exhaust gas sensor. The sensor element can be selected, for example, from the group consisting of: at least one exhaust gas temperature sensor; at least one broad band oxygen sensor; at least one oxygen burst sensor; at least one nitrogen oxide sensor; at least one particle sensor; at least one lambda sensor.According to the invention, it is provided that the sensor element ( 114) of the exhaust gas sensor comprises an electrical heating element ( 136) and a cell, consisting of two electrodes and a solid electrolyte connecting the electrodes.A detection can be understood in particular to mean a measurement in which the property is determined qualitatively and / or quantitatively. The property can in principle be any physical and / or chemical property of the gas. Preferably, it can be at least one property selected from the group consisting of: a temperature; a proportion of a gas component in the gas. The gas component can be, for example, oxygen and / or nitrogen oxides. The detection can be, in particular, a quantitative and / or qualitative detection. The gas can be, for example, an exhaust gas of an internal combustion engine, in particular in the motor vehicle sector. The measurement gas chamber can be, for example, an exhaust tract. The proportion of the gas component can also be, for example, a plurality of proportions of a gas component. The proportion of the gas component can be, in particular, a partial pressure and / or a percentage of the gas component.According to the invention, the method comprises at least the following steps:• at least one first step, wherein at least one characteristic variable is determined in the first step, namely a heater resistance of the heating element (136) and / or an internal resistance of the cell;• at least one second step, wherein in the second step the characteristic variable is compared with at least one comparison value, wherein corresponding to this comparison at least one feature, namely the sensor type, is assigned to the sensor element or at least a part of the sensor element.The terms "first" and "second", and if present also "third" or further similar terms, do not provide any information about whether, for example, further steps are still present. In principle, these terms likewise do not give any indication of a sequence. Particularly preferably, the method can be carried out in the sequence starting from the first step, subsequently the second step and subsequently, for example, further steps, wherein, however, a different sequence is also possible.A characteristic variable can be understood here in general to mean a property of the sensor element, for example a qualitative and / or a quantitative property. The characteristic variable can be, in particular, a characteristic variable. The characteristic variable can be selected, for example, from the group consisting of: an ohmic resistance; an operating temperature; an electric current, in particular a current characteristic curve; an electric voltage, in particular a voltage characteristic curve.A comparison value can generally be understood to mean at least one value or a set of values which are comparable to the characteristic variable in such a way that at least one comparison result, for example a qualitative and / or quantitative comparison result, can be generated, for example a comparison result of the type "corresponds", "is greater than", "is less than", "is greater than or equal", "is less than or equal", "deviates by not more than a predefined value" or a similar type. The comparison value can be, for example, at least one individual value and / or at least one tolerance range and / or at least one interval and / or at least one value table.The at least one part of the sensor element can be, for example, the entire sensor element and / or a part of the sensor element, for example, it can be at least one heating element and / or at least one electrode.Within the scope of the present invention, a feature can be understood to mean generally a property of the sensor element, in particular a property which characterizes the sensor element and / or the type of sensor element or a part thereof. For example, it may be a property which is not directly measurable, for example is not directly detectable via an electrical measurement. The feature can be, for example, a type designation, in particular a sensor type and / or a probe type, and / or an operating duration of at least a part of the sensor element.The comparison can be understood here to mean, for example, an analysis, for example an analysis which enables one or more of the following statements: the characteristic variable agrees with the comparison value or not; the characteristic variable is greater than the comparison value; the characteristic variable is less than the comparison value; the characteristic variable is greater than or equal to the comparison value; the characteristic variable is less than or equal to the comparison value; the characteristic variable lies within a tolerance range of the comparison value. The comparison can comprise in particular calculation methods.As explained above, according to this comparison, the at least one feature is assigned to the sensor element or to the at least one part of the sensor element. In the context of the present invention, an assignment according to the comparison is understood to mean that the assignment is dependent on at least one result of the comparison. For example, at least one comparison result can be generated during the comparison, wherein the assignment takes place according to a dependence between the comparison result and the feature to be assigned, for example according to a function, a table, a list or similar dependencies.The method can in particular comprise a third step, wherein at least one operating mode can be selected in the third step according to the at least one feature. The sensor element can then be operated in particular in the operating mode. Within the scope of the present invention, an operating mode can generally be understood to mean a specification or a group of specifications according to which the sensor element is operated. This specification can comprise, for example, a type of application of at least one voltage and / or at least one electric current to the sensor element and / or a type of detection of at least one measured value at or in the sensor element, for example a type of detection of at least one voltage and / or at least one current at or in the sensor element. Furthermore, the specification can also comprise a chronological sequence of these types of application and / or measurements. For example, the operating mode can also comprise operation at a defined temperature and / or a defined frequency, for example an electrical voltage and / or an electrical current. Furthermore, the operating mode can be understood to mean a circuit and / or a method for operating and / or outputting an item of information and / or communication of an item of information.If, for example, an exchange of the sensor element, in particular a probe exchange, is carried out, for example in a workshop, and / or another sensor element, in particular a sensor element of another probe type, is installed, the control system, in particular the control unit, can be set and / or switched, for example automatically, to the operating mode required for the new sensor element, in particular to a correct operating profile. The control, in particular the control device, can in particular independently identify which sensor type has been installed and / or can independently select a matching operating mode, in particular a matching operating profile.At least one step selected from the group consisting of the first step, the second step and the third step can be carried out at least partially by at least one control. In this case, a control can generally be understood to mean a device which is configured to operate the sensor element, for example for detecting the at least one property. The control can be configured centrally or else decentrally and can also be integrated, for example, completely or partially into another device, for example into a control unit and / or engine control unit. The control can be connected to the sensor element, for example, via an interface. However, the control can also be integrated completely or partially into the sensor element. However, the control can also be integrated, for example, completely or partially in other components, for example in a plug and / or in a motor controller. The control can comprise, for example, at least one application device in order to apply current and / or voltage to the heater and / or at least one electrode. The application device can be, for example, a voltage source and / or a current source. Furthermore, the control can optionally comprise a measuring device, for example a voltage measuring device and / or a current measuring device. Furthermore, the control can optionally comprise, for example, an evaluation device, for example a data processing device. The evaluation device can be configured in particular to carry out the first step and / or the second step, for example the determination of the characteristic variable and / or the comparison of the characteristic variable with the comparison value. Furthermore optionally, the control can comprise at least one signal generator. The control can additionally optionally comprise at least one regulator, for example at least one lock-in regulator. The control can furthermore preferably comprise at least one microcontroller and / or at least one hardware module. The control can furthermore be equipped with appropriate software which supports and / or regulates the method according to the invention and / or serves for storing and / or storing the comparison value, for example in a memory.On the basis of the comparison of the characteristic variable with the comparison value, in particular a fault situation can be detected and preferably in the case of a fault being detected at least one fault message can be output. A fault case can be understood here in general to mean an event or a group of events which deviate from at least one predefined norm, for example a set of norm events. The fault case can be, for example, a case in which the type designation of the sensor element is not known, for example since required data are not stored in the control, and / or it can be a case in which the sensor element cannot be operated with the control. Alternatively or additionally, the fault case can also be a case or comprise a case in which it is determined in the comparison that the sensor element is defective or has a behavior deviating from a standard behavior, for example if the sensor element is aged.An error message is generally understood to mean information which is transmitted and / or provided to a user and / or another device, which includes the fact that an error has occurred and preferably also what type of error is involved. The error message can be output in particular acoustically and / or optically and / or haptically and / or electronically. The fault may occur, for example, if the type of sensor element, for example the probe type, is not detected and / or if it is detected that the type of sensor element cannot be operated using the existing hardware. In this case, for example, in particular electronically, an error can be "set", for example by setting an error bit in a data memory to a predefined value.As explained above, the characteristic variable can be compared, for example, with at least two, preferably with at least three, comparison values. The comparison value can be selected in particular from the group consisting of: a single comparison value; a comparison interval; a value table. The comparison value can be, in particular, an individual value and / or an individual value with a tolerance range. A comparison interval can be, in particular, an open interval and / or a semi-open interval and / or a closed interval. For example, it can be an infinitely extended interval on one side. The value table can be, in particular, a table with at least two comparison values.The sensor element can in particular comprise a heating element, which is also referred to below as a heater. For example, the heating element can comprise at least one heating resistor. The heating element can preferably be designed to set and / or regulate at least a part of the sensor element to a specific temperature. The heating element can be operated, for example, by application of electric current and / or electric voltage and / or electric power, for example, by the control. In one of the alternatives of the invention, the characteristic variable is a heater resistance of the heating element.The heater current can be, in particular, the electrical current with which the heating element can be supplied. The heater voltage can be, in particular, the electrical voltage with which the heating element can be supplied. The heater power can be, in particular, the electrical power with which the heating element can be supplied.A limit current of a sensor element or of a part of the sensor element can generally be understood to mean a saturation current of the sensor element or of a part thereof, for example a saturation current of a current-voltage characteristic curve detected under predefined conditions. This current-voltage characteristic curve can be detected, for example, at a cell of the sensor element which comprises at least two electrodes and at least one solid electrolyte connecting the electrodes. The physical cause of the saturation can consist, for example, in a transport on and / or off of at least one gas component to or from one or more of the electrodes, which can be limited, for example, by a diffusion process.The characteristic variable can be compared, for example, with at least three comparison values, in particular with three intervals, wherein a feature can be assigned to the sensor element in accordance with the comparison. The feature can comprise in particular at least one sensor element type, in particular a probe type, and / or at least one state of the sensor element, for example a defect and / or an age.In another alternative of the invention, the characteristic variable is an internal resistance of the cell. For example, this internal resistance can be an internal resistance of at least one cell according to the above definition and / or a heater resistance of at least one heating element of the sensor element. The characteristic variable can preferably be compared with two comparison values, in particular two intervals. For example, a feature or a plurality of features can be assigned to the sensor element according to the comparison, wherein the feature can in particular comprise at least one sensor element type.The internal resistance of the cell can be, in particular, an ohmic internal resistanceThe characteristic variable can be compared with at least one comparison value, in particular at least one value table.According to the invention, the sensor type is assigned to the sensor element or a part of the sensor element in accordance with the comparison.In a further aspect of the present invention, as explained above, a device for detecting at least one property of a gas in a measurement gas space is proposed. The device comprises at least one sensor element.For example, this can be a ceramic sensor element, for example a ceramic sensor element having at least one layer structure.According to the invention, the sensor element comprises a cell which has at least two electrodes and at least one solid electrolyte connecting the electrodes. For example, at least one of the electrodes can be supplied with gas from the measurement gas chamber directly or via at least one gas-permeable porous element.Furthermore, according to the invention, the sensor element comprises an electrical heating element. For possible configurations of the sensor element, reference can be made, for example, to the above description and / or to Robert Bosch GmbH: Sensoren in Motor Vehicle, 1st Edition 2010, pages 98-111 and pages 160-165.The device further comprises at least one control. The control is configured to carry out the method according to the invention for operating a sensor element for detecting at least one property of a gas in a measurement gas space, as described above.The method and apparatus of the invention may have a variety of advantages over known methods and apparatus. For example, malfunction and damage to the sensor element, in particular to the exhaust gas sensor, by operation with a wrong operating profile can preferably be ruled out. In initial equipment, in particular in production, the method according to the invention can be used, for example, in order to facilitate exchangeability of different sensor types. In particular, for example, the different sensor types can be configured to be compatible on the hardware side, i.e. sensor elements of different sensor types can be operated on the same hardware module, for example. This can be advantageous for the vehicle manufacturer, for example, since, for example, effort can be dispensed with in order to ensure that the correct operating profile matching the respectively installed sensor type, in particular probe type, in particular a matching operating mode and / or information relating thereto, has been stored in the control system, in particular in the control device. For example, the method according to the invention and / or the device according to the invention make it possible for a different probe type to be able to be installed, in particular in the production, from vehicle to vehicle, without this being disadvantageous, for example later during operation or in repair. By developing new, in particular digital, and / or software configurable controls and / or control concepts (ASIC), it may be possible in the future, for example, to provide hardware-compatible "open" interfaces also for broadband probes.Brief Description of the DrawingsExemplary embodiments of the invention are illustrated in the following figures and are explained in more detail in the following description.The following are shown: FIG. 1 : shows an exemplary embodiment of a device according to the invention; FIG. 2 : an exemplary embodiment of a method according to the invention for operating at least one sensor element.Embodiments of the InventionFIG. 1 shows an exemplary embodiment of a device 110 according to the invention. The device 110 according to the invention for detecting at least one property of a gas in a measurement gas chamber 112 comprises at least one sensor element 114. The device 110 furthermore has at least one control 116. The control 116 is configured to carry out a method according to the invention for operating at least one sensor element 114 for detecting at least one property of a gas in a measurement gas space 112. Sensor element 114 may be designed, in particular, as a lambda probe. The sensor element 114 can be designed, for example, as a single-cell or multicellular sensor element 114. A cell 118 can be understood here to mean, for example, an arrangement of at least two electrodes 120 and a solid electrolyte 122. The solid electrolyte 122 can be, in particular, a ceramic solid electrolyte 122, such as, for example, zirconium dioxide, in particular yttrium-stabilized zirconium dioxide (YSZ) and / or scandium-doped zirconium dioxide (ScSZ). The solid electrolyte 122 can preferably be gas-impermeable and / or can ensure ionic transport, for example ionic oxygen transport. The sensor element 114 comprises at least one first electrode 124 and at least one second electrode 126. The first electrode 124 can be connected at least partially, in particular via a diffusion barrier 128, to the measurement gas space 112. The second electrode 126 can be connected at least partially to a further gas space, in particular a reference gas space, for example a reference channel 130. The reference channel 130 can be connected in particular to an air reservoir, in particular the outside air. The first electrode 124 can be charged with gas from the measurement gas space 112 in particular via a gas access path 132 and / or via the diffusion barrier 128. An electrical voltage, in particular a Nernst voltage, can be measured between the first electrode 124 and the second electrode 126. Starting from the Nernst voltage, it is possible to draw conclusions about the proportion of the gas component in the gas, in particular in the exhaust gas, for example. The proportion of the gas component can be, for example, a partial pressure of the gas component, in particular it can be an oxygen partial pressure and / or an oxygen proportion. The gas component can particularly preferably be oxygen. In principle, the gas component can also comprise at least one nitrogen oxide. The Nernst voltage is generally dependent, in particular, on a difference in concentration of the gas component between first electrode 124 and second electrode 126. The sensor element 114 shown in FIG. 1 represents in particular a single-cell sensor element 114. In principle, single-cell or else multi-cell sensor elements 114 can be used, as described, for example, in Robert Bosch GmbH: Sensoren in Motor Vehicle, 1st Edition 2010, pages 160-165. The second electrode 126 can be configured in particular as a reference electrode. The first electrode 124 may be arranged in a cavity 134, but may also be connected to the cavity 134 in a fluidic and / or gas connection. Furthermore, the sensor element 114 can comprise a heating element 136, in particular a heater. The heating element 136 can be connected to the control 116 in particular via electrical lines 138. The control 116 can be designed in particular as a control device. The control 116 can be connected to the sensor element 114 via an interface 140, for example. However, the control 116 can also be integrated completely or partially into the sensor element 114. However, the control 116 can also be integrated, for example, completely or partially into other components, for example in a plug and / or in a motor controller. The control 116 can comprise, for example, at least one application device for applying current and / or voltage to the electrodes 120, for example the first electrode 124 and / or the second electrode 126. The application device can be, for example, a voltage source and / or a current source. The application device can in particular comprise electrical lines 138. For example, the application device can comprise in particular the electrical lines 138 to the heating element 136, in particular for supplying the heating element 136 with electrical voltage and / or electrical current. The control 116 can optionally comprise at least one measuring device, for example at least one voltage measuring device and / or at least one current measuring device. Furthermore, the control 116 can optionally comprise, for example, at least one evaluation device, for example at least one data processing device. Furthermore, optionally, the control 116 can comprise at least one signal generator. The control 116 can additionally optionally comprise at least one regulator, for example at least one lock-in regulator. Furthermore, the control 116 can contain, for example, at least one microcontroller and / or at least one hardware module and / or at least one software and / or a memory, in particular a data memory.The method according to the invention for operating a sensor element 114 for detecting at least one property of a gas in a measurement gas space 112 comprises at least the following steps: at least one first step, wherein in the first step at least one characteristic variable is determined, namely a heater resistance of the heating element 136 and / or an internal resistance of the cell 118; at least one second step, wherein in the second step the characteristic variable is compared with at least one comparison value, wherein corresponding to this comparison at least one feature, namely the sensor type, is assigned to the sensor element 114 or at least a part of the sensor element 114.The method can in particular comprise a third step, wherein in the third step an operating mode can be selected according to the feature, wherein the sensor element 114 is operated in the operating mode. In principle, the method can also comprise one or more further steps, wherein the steps can also be carried out, for example, multiple times and / or in different orders.At least one step selected from the group consisting of the first step, the second step, the third step and optionally a further step can be carried out at least partially by the at least one control 116. For example, on the basis of the comparison of the characteristic variable with the comparison value, a fault situation can be detected and, preferably, at least one fault message can be output in the case of a detection of a fault.In one exemplary embodiment, the characteristic variable is the internal resistance of the Nernst cell 142. The sensor type is detected via the internal resistance of a Nernst cell 142. A Nernst cell 142 is a cell 118 which comprises the first electrode 124 and the second electrode 126, and the solid electrolyte 122. The sensor types can differ, for example, in an ohmic resistance of the Nernst cell 142 RiN, in particular for the same heater voltages. A broadband lambda probe can have, for example, a resistance of the Nernst cell 142 RiN=300 Ω, wherein another broadband lambda probe, in particular with a different configuration, in particular another sensor type, can have a resistance of the Nernst cell 142 of RiN=800 Ω. When a constant voltage is applied across the Nernst cell 142, for example between two electrodes 120, in particular between the first electrode 124 and the second electrode 126, for example, particularly preferably between the reference electrode and the inner pump electrode, currents of different magnitude, in particular pump currents, may result, for example, due to different resistances. As a result, in particular the resistance, in particular the internal resistance, of the Nernst cell 142 is suitable as a characteristic variable. For example, a constant heating power, preferably when the vehicle is stationary, can be applied to the heating element 136. As a result, it is possible, for example, to prevent an incident flow on the probe, in particular on the sensor element 114. In this case and / or thereafter, for example after a waiting time, the resistance of the Nernst cell 142 RiN, in particular the internal resistance, can be measured. In this way, in particular the characteristic variable, in this case the internal resistance, can be detected. During the second step, in particular, an evaluation can be carried out. For example, if RiNis less than a threshold, it may be a broadband lambda probe of a particular sensor type, for example. If RiN is greater than a threshold, it can be, in particular, a broadband lambda probe of another probe type. A comparison value can in principle also comprise a threshold, in particular a threshold value, for example as in this exemplary embodiment. In this exemplary embodiment, the feature is in particular a sensor type. The sensor type can be detected, for example, via the internal resistance of the Nernst cell 142. This can serve, for example, to select an operating mode in a third step according to the feature, i.e. the sensor type, wherein the sensor element 114 can be operated in particular in this operating mode.In FIG. 2, a development of the above exemplary embodiment is illustrated by way of example. The characteristic variable is furthermore the internal resistance of the Nernst cell 142, for example an AC resistor, in particular an impedance and / or a reactance and / or an active resistor, and / or a DC resistor. Aging of the internal resistance, in particular of the AC internal resistance, of the Nernst cell 142 (RiAC) can lead, in particular, to the internal resistance increasing with the operating duration and / or the aging at the same temperature, in particular at the same ceramic temperature. In a broadband lambda probe, the internal resistance in the new state at 780° ceramic temperature can be nominally 300 Ω, for example. After operation, in particular in a continuous motor operation, for example for 3000 h with the preferably same, in particular constant, ceramic temperature, the internal resistance can be in particular up to 500 Ω. With the device 110 according to the invention and the method according to the invention, it can be determined, in particular in the control unit with this characteristic variable, in particular with this property, whether, for example, an old sensor element 114, in particular an old probe, has been replaced by a new sensor element 114, in particular a new probe. If necessary, the operating mode, in particular an operating profile, can be changed and / or adapted. In the first step, for example, a heating power, which is in particular constant, can be applied when the vehicle is stationary. In this case, for example, an incident flow of the sensor element 114 can be prevented. The characteristic variable, in particular the AC internal resistance of the Nernst cell 142 RiAC, can be detected. This embodiment can be carried out in particular with a broadband lambda probe. A broadband lambda probe can comprise in particular at least two cells 118, preferably at least one Nernst cell 142 and / or at least one pump cell. The pump cell can preferably have at least one outer electrode 120, wherein the Nernst cell 142 can preferably have at least one inner electrode 120. In principle, this exemplary embodiment can also be carried out with other sensor elements 114, in particular with a two-point lambda probe, for example a jump probe, for example a jump probe with rapid control readiness and / or a strong heating element 136. In the second step, a dependence of the internal resistance RiAC on the service life, in particular the service life of the sensor element 114, can be taken in particular from a value table, in particular with a constant heating power of the heating element 136 and without or with inflow to the sensor element 114. From the characteristic variable, in particular the internal resistance, it is possible to draw conclusions in particular as to the operating duration of the sensor element 114, in particular of the probe.An even more accurate determination of the aging can preferably be effected by determining the aging of a direct current internal resistance RiDC, in particular of the electrodes 120, in particular of the electrodes located on the outside and inside, for example of a pump cell and / or of a Nernst cell 142. In this case, for example, the following basic principles can be utilized: The RiAC, which can describe in particular an electrode degradation, ages in particular generally more quickly and / or with a higher factor, in particular an aging factor A, than the RiAC. In the first step, an alternating current with a frequency of, for example, 4 kHz can be applied in this case. In this case, as a rule, only the electrolyte degradation is measured. The reason for this can be, in particular, that the electrode / electrolyte transitions, described in particular as a parallel connection of a capacitor and a resistor, can preferably be "bridged" by the capacitor, since in an alternating current measurement the resistance, in particular the real part of the resistor, cannot be measured at the same time.FIG. 2 shows in particular an aging factor A with respect to an operating time B in hours (h). The operating time is shown here in particular divided into three different phases, which are identified by I, II, III. The top curve 144 describes in particular the aging factor of an Ri, for example one or more external electrodes 120, in particular the electrodes 120 of a pump cell, wherein the middle curve 146 can represent the aging factor of an RiDC, for example one or more internal electrodes 120, in particular electrodes 120 of the Nernst cell 142. The lower curve 148 shows in particular the aging factor of the RiAC, in particular in the case of an AC voltage and / or an AC current of 4 kHz, for the inner electrodes 120 and / or the outer electrodes 120. The RiDC, in particular the RiDC of at least one outer electrodes 120, in particular one or more electrodes 120 of the pump cell, ages in particular more quickly than that of one or more inner electrodes 120, in particular of the electrodes 120 of a Nernst cell 142. A high aging factor can be interpreted in particular as high aging. The difference between the DC internal resistances of the external electrodes 120 and the internal electrodes 120 may be caused in particular by an ingress of harmful exhaust gas constituents, since, for example, the ingress is limited substantially only by a protective layer and not by a diffusion barrier 128. The aging of the RiAC can take place in particular in the interior of the electrolyte, in particular of the solid electrolyte 122, and can thus be independent of damage due to exhaust gas constituents in particular. This aging may in particular be mainly a temperature effect and may thus proceed almost the same, for example, for the electrodes 120 and / or the cells 118, in particular for both cells 118 of a dual-cell sensor element 114. In principle, the aging can be a factor, in particular the aging factor A, relative to the new value, in each case independently of the new value. In particular from this knowledge, a rough classification and / or assignment of the service life and / or of the operating duration, for example to the sensor element 114, can be achieved. FIG. 2 shows comparative values for service lives <500 h, for example for service lives between 500 and 100 h, and for service lives >1000 h, for example. In phase I, in particular the Ri of one or more external electrodes 120, in particular the RiDC of the pump cell, can already be aged. Phase I can extend, for example, between 0 h to 500 h. In phase II, in particular the RiDC of one or more internal electrodes 120, in particular the RiDC of the Nernst cell 142, can be aged, that is to say after an operating time of, for example, 500 h to 1000 h. In phase III, in particular the RiAC, in particular for all electrodes 120, for example for the external electrodes 120 and the internal electrodes 120, can be heavily aged, for example after an operating time of more than 1000 h. This refinement requires, in particular, for example as a comparison value, an empirical factor for the RiDC aging, which can describe, for example, a strength of poisoning by the respective application.

Claims

Method for detecting the sensor type of a sensor element (114) of an exhaust gas sensor for detecting at least one property of an exhaust gas in an exhaust tract, wherein the sensor element (114) of the exhaust gas sensor comprises an electrical heating element (136) and a cell (118) consisting of two electrodes (120, 124, 126) and a solid electrolyte (122) connecting the electrodes (120, 124, 126), wherein the method comprises at least the following steps: • at least one first step, wherein at least one characteristic variable is determined in the first step, namely a heater resistance of the heating element (136) and / or an internal resistance of the cell (118); • at least one second step, wherein in the second step the characteristic variable is compared with at least one comparison value, wherein corresponding to this comparison at least one feature, namely the sensor type, is assigned to the sensor element (114) or at least a part of the sensor element (114).Method according to the preceding claim, wherein the method comprises a third step, wherein in the third step an operating mode is selected according to the feature, wherein the sensor element (114) is operated in the operating mode.Method according to the preceding claim, wherein at least one step selected from the group consisting of the first step, the second step and the third step is carried out at least partially by at least one control (116).Method according to one of the preceding claims, wherein a fault event is detected on the basis of the comparison of the characteristic variable with the comparison value and preferably at least one fault message is output in the case of a detection of a fault event.Method according to one of the preceding claims, wherein the characteristic variable is compared with at least two, preferably with at least three, comparison values.Method according to one of the preceding claims, wherein the comparison value is selected from the group consisting of: a single comparison value; a comparison interval; a value table.Method according to one of the preceding claims, wherein the determination of the heater resistance comprises the determination of a heater current at a predetermined heater voltage, wherein the characteristic variable is compared with at least two, preferably with at least three comparison values, in particular two intervals and a single value.Method according to one of the preceding claims, wherein the characteristic variable comprises at least one limit current of the sensor element (114) or at least part of the sensor element (114).Method according to one of the preceding claims, wherein the feature comprises aging of the sensor element (114) and / or an operating duration.Device (110) for detecting the sensor type of a sensor element (114) of an exhaust gas sensor for detecting at least one property of an exhaust gas in an exhaust tract, wherein the sensor element (114) of the exhaust gas sensor comprises an electrical heating element (136) and a cell (118) consisting of two electrodes (120, 124, 126) and a solid electrolyte (122) connecting the electrodes (120, 124, 126), wherein the device (110) has at least one control (116), wherein the control (116) is configured to carry out a method according to one of the preceding claims.

Images