Methods for NOx sensor offset correction

Abstract

The invention relates to a method for NOx sensor correction. In a first step, at least one NOx value is measured with a NOx sensor over a measurement period. In a second step, at least one exhaust gas temperature is recorded over a period of time, with the measurement of the respective NOx value and the recording of the respective exhaust gas temperature occurring simultaneously. In a third step, the driving state of the vehicle is recorded at the time the exhaust gas temperature and the NOx value are recorded. In a further step, the NOx value is corrected by a correction factor, the correction factor for the respective NOx value being selected based on the exhaust gas temperature and the driving state of the vehicle. In a fifth step, the corrected NOx value is stored in a memory unit.In a sixth step, the recorded and corrected NOx values ​​are evaluated over the measurement period.

Description

[0001] The present invention relates to a method for NOx sensor offset correction.

[0002] In today's modern vehicles, the requirements for exhaust aftertreatment systems are crucial due to stringent emissions regulations. With the introduction of the new Euro 7 standard, which aims to further reduce emissions of nitrogen oxides (NOx) and other pollutants, the need for precise and reliable sensors is increasing. NOx sensors play a central role in monitoring and controlling emissions to ensure that vehicles comply with the prescribed limits.

[0003] A crucial aspect of using NOx sensors is their behavior under different driving conditions. It has been observed that NOx sensors exhibit different offset values ​​under various operating conditions, such as idling, partial load, or full load. These varying offsets can significantly affect the accuracy of emissions measurements and lead to misinterpretations, which in turn impair the efficiency of exhaust aftertreatment systems.

[0004] DE10023072A1 discloses that during a deceleration shutdown, the signal of a NOx-sensitive measuring device is used for the calibration of the measuring device.

[0005] German patent DE 10 2021 213 171 A1 discloses a method for adjusting a measured NOx value during a steady state of an internal combustion engine supported by a vehicle. The method includes receiving a NOx sensor measurement from a NOx sensor positioned along an exhaust pipe and determining the state of the internal combustion engine.

[0006] DE 10 2010 026 867 A1 discloses various systems and methods for controlling an engine in a vehicle during engine operation, wherein the engine has an exhaust and a NOx sensor installed in the engine exhaust.

[0007] German patent DE 10 2010 017 360 A1 discloses a method for correcting a NOx sensor, wherein the method corrects a NOx concentration detected by a NOx sensor. The method comprises: creating a correction map that records the relationship between temperature, oxygen concentration, and the excess ratio between NO and NO2 gases; determining the excess ratio based on the actually detected temperature and oxygen concentration; and correcting the NOx concentration based on the excess ratio and the difference between NO2 and NO diffusion rates.

[0008] DE 10 2017 113 009 A1 discloses a method for correcting a sensor signal of a sensor in an exhaust system, wherein a dynamic correction of the sensor signal is carried out by correcting a measured sensor signal by a dynamic correction value, wherein the dynamic component corresponds to the difference between an estimated gas temperature and the signal of the sensor model.

[0009] DE 10 2021 214 192 A1 discloses a method for determining the functionality of an exhaust gas sensor in an exhaust system of an internal combustion engine, comprising heating the exhaust gas sensors, determining sensor signals, comparing the signals during an operating period in which the catalyst temperature does not exceed a threshold value, and determining an operating parameter based on the comparison result.

[0010] The state of the art is improved by the introduction of dynamic error correction. This adaptive calibration enables more precise NOx measurement.

[0011] According to the invention, a method for NOx sensor offset correction according to claim 1 is provided, as well as a motor vehicle according to claim 9, which is configured to carry out the method. Advantageous embodiments can be found in the dependent claims and the description.

[0012] The invention relates to a method for NOx sensor offset correction, comprising the following process steps. In a first step, at least one NOx value is measured with a NOx sensor over a measurement period. In a further step, at least one exhaust gas temperature is recorded over the measurement period, wherein the measurement of the respective at least one NOx value and the recording of the respective at least one exhaust gas temperature occur simultaneously. In a further step, the driving state of the vehicle is recorded at the time of recording the at least one exhaust gas temperature and the measurement of the at least one NOx value. In a further step, the at least one NOx value is corrected by a correction factor, wherein the correction factor for the respective NOx value is selected based on the exhaust gas temperature and the driving state of the vehicle.In a further process step, at least one corrected NOx value is stored in a memory unit. In a further process step, the stored and corrected NOx values ​​are evaluated over the measurement period.

[0013] In an advantageous further development, the exhaust gas temperature can be measured using a sensor or an exhaust gas temperature model. The exhaust gas temperature can be measured by the sensor and / or provided by the exhaust gas temperature model. The exhaust gas temperature model can be supplied with vehicle data and can be configured to calculate or predict the exhaust gas temperature based on this data. The exhaust gas temperature can be provided for various points in time or periods, particularly during or within the measurement period.

[0014] The exhaust gas temperature model can be implemented as a mathematical or numerical model to calculate or predict the temperature of the exhaust gases in an internal combustion engine or at the outlet. In a further development, the correction factor is loaded from a storage unit. By correcting the NOx values, a characteristic curve can be interpolated around the corrected NOx values.

[0015] In a training course, the average NOx value over the measurement period is determined during the evaluation. For this purpose, the measured NOx values ​​can be summed and divided by the time or by the number of measured NOx values.

[0016] The average NOx value can be determined from the corrected NOx values, in particular the NOx values ​​in the storage unit.

[0017] In a training course, the evaluation of at least one corrected NOx value takes place at different times, with the times being arranged sequentially.

[0018] In a beneficial advanced training, NOx values ​​can be measured at 5-second intervals. Subsequently, a series of measurements over time can be generated, for example, including NOx values ​​for 5s, 10s, 15s, and 20s. The measurement intervals can be varied depending on the application. The number of NOx values ​​within each measurement interval can also be varied.

[0019] In a further training course, the selection of the respective correction factor is configured by whether the motor vehicle is in powered operation or in unpowered thrust mode.

[0020] The term "fired operation" in motor vehicles refers to the state in which the engine is actively running and burning fuel to generate mechanical energy. This encompasses all operating conditions in which the engine is supplied with fuel, regardless of whether the vehicle is idling, driving at low speeds, or under high load. During fired operation, the combustion of fuel takes place in the engine, providing the necessary power to propel the vehicle. This process produces exhaust gases, which are cleaned by the exhaust system, including catalytic converters and particulate filters, to minimize emissions and comply with legal requirements, such as the Euro 7 standard. Fired operation is therefore central to the functionality and performance of motor vehicles and can be the focus of measures aimed at optimizing efficiency and reducing pollutant emissions.

[0021] Unfired thrust in motor vehicles refers to the operating condition in which the vehicle's engine is not burning fuel, but the vehicle continues to move due to its kinetic energy. This typically occurs when a driver releases the accelerator pedal and the vehicle continues to coast. In this state, the engine is not actively supplied with fuel, so no combustion takes place, but the vehicle's kinetic energy continues to provide propulsion. Unfired thrust is important for fuel efficiency, as no fuel is consumed in this state, and it contributes to reducing emissions, as no exhaust gases are produced.

[0022] According to the invention, at least one NOx value measured in a fired operation and / or in unfired thrust is checked by a control value.

[0023] The NOx measurement during unfired thrust can take place after a specific dead time. This dead time is necessary to purge the exhaust gases still present in the engine at the beginning of the unfired thrust with air. This ensures accurate measurements. The dead time can range from 10 ms to 10 s.

[0024] According to the invention, if the measured NOx value deviates from the corresponding control value by a factor greater than a predetermined value, the measured NOx value is replaced by the corresponding control value.

[0025] In a training course, if the measured NOx value deviates from the corresponding control value by a factor greater than a predetermined value, a fault in the exhaust system of a motor vehicle is detected and stored in the storage unit.

[0026] In a beneficial training process, this can indicate a fault in the exhaust system to the vehicle user and / or start a cleaning program for the exhaust system.

[0027] When the exhaust system cleaning program of a vehicle is initiated, several processes can be started to reduce the accumulation of pollutants such as soot and nitrogen oxides (NOx) and to ensure the efficiency of the exhaust system. First, the engine control unit increases the exhaust gas temperature, either by adjusting the combustion process or by injecting additional fuel into the exhaust manifold. This temperature increase is necessary to bring the catalytic converters and particulate filters up to their optimal operating temperature.

[0028] The diesel particulate filter (DPF) undergoes a regeneration cycle in which accumulated soot is burned off and converted into CO2 and ash. This is achieved by increasing the exhaust gas temperature to approximately 600°C, which efficiently combusts the soot particles. Simultaneously, the SCR (Selective Catalytic Reduction) system, through the injection of AdBlue (a urea solution), ensures that NOx is converted into harmless nitrogen and water.

[0029] Additionally, special sensors and diagnostic programs can be activated to monitor the condition of the exhaust system and ensure that all components are functioning correctly. These measures help to comply with legal emission limits and extend the service life of the exhaust system. The cleaning program is started regularly or as needed, depending on operating conditions and the load on the exhaust system.

[0030] Exhaust system cleaning is also possible for gasoline-powered vehicles. Gasoline vehicles can be equipped with various exhaust aftertreatment systems to reduce pollutant emissions and comply with legal limits.

[0031] The three-way catalytic converter (TWC) can be the main component in gasoline vehicles for reducing nitrogen oxides (NOx), carbon monoxide (CO), and unburned hydrocarbons (HC). At optimal temperatures and air-fuel ratios, the catalytic converter can transform these pollutants into harmless substances such as nitrogen, water, and carbon dioxide.

[0032] In a beneficial further development, gasoline vehicles can be equipped with a secondary air injection system that introduces additional oxygen into the exhaust stream. This can help to increase exhaust gas temperatures and improve the efficiency of the catalytic converter, especially during the cold start phase.

[0033] In a beneficial further development, gasoline vehicles, especially those with direct injection, can be equipped with gasoline particulate filters (GPFs). These filters capture particles and soot that may be present in the exhaust stream. Similar to diesel particulate filters, the GPF can be periodically regenerated by increasing the exhaust gas temperature to burn off the accumulated particles.

[0034] In a beneficial upgrade, motor vehicles can be equipped with an on-board diagnostics (OBD) system that continuously monitors the condition of the exhaust aftertreatment components. OBD system sensors can collect data on exhaust gas temperatures, oxygen content, and other parameters to ensure that the exhaust aftertreatment systems are operating efficiently. If necessary, the OBD system can make adjustments or alert the vehicle user to potential problems.

[0035] These measures and technologies help to reduce vehicle emissions and minimize environmental impact.

[0036] In a further training course, a distinction is made during the evaluation whether the motor vehicle is in powered operation or in unpowered overrun, and these NOx values ​​are evaluated separately.

[0037] In an advantageous further training, a series of NOx measurements is used for this purpose, either during fired operation or during unfired thrust.

[0038] The invention also relates to a motor vehicle with at least one NOx sensor and a control / processing unit, wherein the control / processing unit is configured to carry out the method according to one of the preceding claims.

[0039] In an advantageous further development, the control / processing unit can include at least one microcontroller and / or FPGA and / or processor which is trained to perform the tasks described above.

[0040] In particular, the control / processing unit may be designed to process vehicle data and / or calculate the exhaust gas temperature model and output at least one output value of the exhaust gas temperature model.

[0041] The invention is described below by way of example only, with reference to the drawings. The drawings show: Fig. Figure 1 shows a method for NOx sensor correction according to an embodiment of the invention; and Fig. 2 an exhaust gas characteristic curve with NOx values ​​from a NOx sensor and corrected NOx values ​​according to an embodiment of the invention; and Fig. 3 two exhaust gas characteristic curves with NOx values ​​from a NOx sensor and corrected NOx values ​​according to an embodiment of the invention.

[0042] Fig. Figure 1 shows a method for NOx sensor correction, which comprises the following steps. In a first step, at least one NOx value 110 is measured with a NOx sensor over a measurement period, S1. In a second step, at least one exhaust gas temperature T is recorded over the measurement period, whereby the measurement of the respective at least one NOx value 110 and the recording of the respective at least one exhaust gas temperature T occur simultaneously, S2. In a third step, the driving state of the vehicle is recorded at the time of the measurement of the at least one exhaust gas temperature T and the recording of the at least one NOx value 110, S3. In a further step, the at least one NOx value 110 is corrected by a correction factor, wherein the correction factor for the respective NOx value 110 is selected based on the exhaust gas temperature T and the driving state of the vehicle, S4.In a fifth step, at least one corrected NOx value 120, 210 is stored in a storage unit, S5. In a sixth step, the stored and corrected NOx values ​​120, 210 are evaluated over the measurement period, S6.

[0043] Fig. Figure 2 shows an exhaust gas curve 100, where a vehicle is in unpowered overrun. The Y-axis represents the NOx value in ppm. The X-axis represents the exhaust gas temperature T. An exhaust gas curve 100 in unpowered overrun shows NOx values ​​of 110, which are corrected to a corrected NOx value of 120 depending on the exhaust gas temperature T by a correction factor.

[0044] Fig.Figure 3 shows a first exhaust gas curve 100, representing a vehicle in unfired overrun mode, and a second exhaust gas curve 200, representing a vehicle in fired operation. The Y-axis represents the NOx value in ppm. The X-axis represents the exhaust gas temperature T. The exhaust gas curve 100 in unfired overrun shows corrected NOx values ​​of 120, which are adjusted by a correction factor depending on the exhaust gas temperature T. The exhaust gas curve 200 in fired operation shows corrected NOx values ​​of 220, which are adjusted by a correction factor depending on the exhaust gas temperature T. The difference between the two exhaust gas curves 100 and 200 allows conclusions to be drawn about the effectiveness of the exhaust gas aftertreatment system.

[0045] The invention is not limited to the described embodiments. Within the scope of the invention, all described and / or drawn features can be combined with one another as desired, unless otherwise stated. Reference sign S1 - S6 process steps Temperature NOx exhaust gas quantity 100 Exhaust gas characteristic curve 110 NOx value 120 Corrected NOx value 200 exhaust gas characteristic curve 210 Corrected NOx value 250 distance

Claims

[1] Method for NOx sensor correction comprising the following process steps: - Measuring at least one NOx value (110) with a NOx sensor (S1) over a measurement period; - Recording at least one exhaust gas temperature (T) over the measurement period, wherein the measurement of the respective at least one NOx value (110) and the recording of the respective at least one exhaust gas temperature (T) are carried out simultaneously (S2); - Recording the driving condition of the motor vehicle at the time of recording at least one exhaust gas temperature (T) and measuring at least one NOx value (110), (S3); - Correcting at least one NOx value (110) by a correction factor, wherein the correction factor for the respective NOx value (110) is selected based on the exhaust gas temperature (T) and the driving condition of the motor vehicle (S4); - Storing at least one corrected NOx value (120, 210) in a storage unit (S5); - Evaluating the recorded and corrected NOx values ​​(120, 210) over the measurement time (S6); characterized by , that at least one NOx value (110) measured in a fired operation and / or in unfired thrust is checked by a control value, wherein If the measured NOx value (110) deviates from the corresponding control value by a factor greater than a predetermined value, the measured NOx value (110) is replaced by the corresponding control value. [2] Method for NOx sensor correction according to claim 1, according to claim 1, characterized by , that the correction factor is loaded from a memory unit. [3] Method for NOx sensor correction according to one of the preceding claims, characterized by , that when evaluating, the average NOx value (120, 210) is determined over the measurement period. [4] Method for NOx sensor correction according to one of the preceding claims, characterized by , that the evaluation of at least one corrected NOx value (120, 210) takes place at different times, with the times being arranged sequentially. [5] Method for NOx sensor correction according to any one of the preceding claims, characterized by , that the selection of the respective correction factor is configured by whether the motor vehicle is in powered operation or in unpowered thrust mode. [6] Method for NOx sensor correction according to any one of the preceding claims, characterized by , that the NOx value (110) measured in a fired operation and / or in unfired thrust is checked by a control value. [7] Method for NOx sensor correction, according to claim 6, characterized by, that if the measured NOx value (110) deviates from the corresponding control value by a factor greater than a predetermined value, a fault in the exhaust system of a motor vehicle is detected and stored in the storage unit. [8] Method for NOx sensor correction according to any one of the preceding claims, characterized by , that the evaluation differentiates between whether the motor vehicle is in powered operation or in unpowered thrust mode, and that these NOx values ​​are evaluated separately. [9] Motor vehicle with at least one NOx sensor and a control / processing unit, wherein the control / processing unit is configured to perform the method according to one of the preceding claims.

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