WO-2026092937-A1 - METHOD AND DEVICE FOR DETERMINING NITROGEN OXIDES AND AMMONIA IN EXHAUST GAS, VEHICLE, COMPUTER PROGRAM PRODUCT, AND COMPUTER-READABLE STORAGE MEDIUM

WO2026092937A1WO 2026092937 A1WO2026092937 A1WO 2026092937A1WO-2026092937-A1

Abstract

In a method for determining nitrogen oxides and ammonia in the exhaust gas of a vehicle, the vehicle having a nitrogen oxide sensor, a lambda signal is received. On the basis of the lambda signal, a lambda value is determined which is representative of the combustion air ratio of the vehicle. A lambda gradient is determined which is representative of whether the lambda value has increased or decreased in comparison with a preliminary value. On the basis of the lambda value and the lambda gradient, it is determined whether a measured value of the nitrogen oxide sensor is representative of nitrogen oxides in the exhaust gas or whether the measured value of the nitrogen oxide sensor is representative of ammonia in the exhaust gas. An information signal is transmitted which comprises information as to whether the measured value of the nitrogen oxide sensor is representative of nitrogen oxides in the exhaust gas or whether the measured value of the nitrogen oxide sensor is representative of ammonia in the exhaust gas.

Inventors

Fink, Fabian
RODATZ, PAUL
HAFT, GERHARD
NIENHOFF, MICHAEL

Assignees

Schaeffler Technologies AG & Co. KG

Dates

Publication Date: 20260507
Application Date: 20250930
Priority Date: 20241029

Claims (10)

1. Method for determining nitrogen oxides and ammonia in the exhaust gas of a vehicle, wherein the vehicle has a nitrogen oxide sensor, wherein a lambda signal is received in the method, - depending on the lambda signal, a lambda value is determined that is representative of the combustion air ratio of the vehicle, - a lambda gradient is determined that is representative of whether the lambda value has increased or decreased compared to a previous value, - depending on the lambda value and the lambda gradient, it is determined whether a measured value from the nitrogen oxide sensor is representative of nitrogen oxides in the exhaust gas or whether the measured value from the nitrogen oxide sensor is representative of ammonia in the exhaust gas, and - an information signal is sent which includes information on whether the measured value of the nitrogen oxide sensor is representative of nitrogen oxides in the exhaust gas or whether the measured value of the nitrogen oxide sensor is representative of ammonia in the exhaust gas.
2. Method according to claim 1, wherein four lambda threshold values are provided and, depending on a comparison of the lambda value with the four lambda threshold values and the lambda gradient, it is determined whether a measured value of the nitrogen oxide sensor is representative for nitrogen oxides in the exhaust gas or whether the measured value of the nitrogen oxide sensor is representative for ammonia in the exhaust gas, wherein the first lambda threshold value (SW1) of the four lambda threshold values is greater than the third lambda threshold value (SW3), the third lambda threshold value (SW3) is greater than the second lambda threshold value (SW2), and the second lambda threshold value (SW2) is greater than the fourth lambda threshold value (SW4).
3. The method according to claim 2, wherein - in a first case, where the lambda value is greater than the first lambda threshold value (SW1 ), it is determined that the measured value of the nitrogen oxide sensor is representative of nitrogen oxides in the exhaust gas, - in a second case, where the lambda gradient is positive and the lambda value is greater than the second lambda threshold (SW2) and less than the first lambda threshold (SW1), it is determined that the measured value of the nitrogen oxide sensor is representative of nitrogen oxides in the exhaust gas, 202400918 32 - in a third case, where the lambda gradient is negative and the lambda value is smaller than the third lambda threshold (SW3) and larger than the fourth lambda threshold (SW4), it is determined that the measured value of the nitrogen oxide sensor is representative of ammonia in the exhaust gas, - in a fourth case, where the lambda value is smaller than the fourth lambda threshold (SW4), it is determined that the measured value of the nitrogen oxide sensor is representative of ammonia in the exhaust gas, - in all other cases, a final valid decision after the four cases remains active until one of the four cases is fulfilled again.
4. Method according to claim 2 or 3, wherein for the comparison of the lambda value with the four lambda thresholds an actual lambda value and a predicted lambda value are determined, wherein the actual lambda value is used to determine whether the lambda value is greater than the first lambda threshold (SW1 ) or less than the fourth lambda threshold (SW4) and the predicted lambda value is used to determine whether the lambda value is greater or less than the second or third lambda threshold (SW2, SW3).
5. Method according to any of the preceding claims, wherein the determined lambda value is a filtered lambda value.
6. Method according to one of the preceding claims, wherein, for determining the lambda value and the measured value, a lambda measurement signal and a measured value signal are received which was sent by the nitrogen oxide sensor and the two signals are synchronized before further processing.
7. Device, wherein the device is configured to perform the method according to any of the preceding claims.
8. Vehicle comprising the device according to claim 7.
9. Computer program product comprising instructions which, when the program is executed by a computer, cause it to execute the method according to any one of claims 1 to 6.
10. A computer-readable storage medium comprising instructions that, when executed by a computer, cause it to execute the method according to any one of claims 1 to 6. ...

Description

202400918 1 Description Method and apparatus for determining nitrogen oxides and ammonia in exhaust gas, vehicle, computer program product and computer-readable storage medium A method for determining nitrogen oxides and ammonia in the exhaust gas of a vehicle is described. Furthermore, a device for determining nitrogen oxides and ammonia in the exhaust gas of a vehicle is described. A vehicle is also described. A computer program is also described. Finally, a computer-readable storage medium is described. Many vehicles are equipped with a catalytic converter, particularly a three-way catalytic converter. These vehicles also have one or more nitrogen oxide sensors, so-called NOx sensors. EU7 legislation makes it mandatory to measure and determine a vehicle's NOx emissions using an in-vehicle NOx sensor. Since an NOx sensor based on the amperometric measurement principle measures the sum of NOx and ammonia (NH3) concentrations in the exhaust gas, as it is cross-sensitive to NH3, it is necessary to separate the NOx and NH3 components from the measured total signal. One task to be solved is to help reliably distinguish whether a measured value from a vehicle's nitrogen oxide sensor is representative of nitrogen oxides or of ammonia. This task is solved by the method and the subject matter of the independent patent claims. Advantageous embodiments, implementations, and further developments are the subject of the respective dependent patent claims. First, the procedure for determining nitrogen oxides and ammonia in the exhaust gas of a vehicle is explained. The vehicle is equipped with a nitrogen oxide sensor. The nitrogen oxide sensor is typically located downstream of a three-way catalytic converter. The nitrogen oxide sensor, also known as a NOx sensor, is based on the amperometric measurement principle. The procedure determines a lambda value that is representative of the combustion air ratio of the vehicle. 202400918 2 The lambda value, for example, is representative of a linear lambda signal. Alternatively, any other signal representative of the oxygen content or lambda value of the exhaust gas can be used. Examples include a binary lambda signal (measured in volts) or an oxygen concentration (measured in ppm or %). The lambda value is determined based on a lambda signal. This signal is provided, for example, by the nitrogen oxide sensor. Lambda specifically represents the air-fuel ratio compared to a stoichiometric combustion mixture. Alternatively, it can also be provided by a second nitrogen oxide sensor. The procedure determines a lambda gradient that is representative of whether the lambda value has increased or decreased compared to a previous value. Depending on the lambda value and the lambda gradient, it is determined whether a measured value from the nitrogen oxide sensor is representative for nitrogen oxides in the exhaust gas or whether the measured value from the nitrogen oxide sensor is representative for ammonia in the exhaust gas. Subsequently, an information signal is sent, which includes information on whether the measured value of the nitrogen oxide sensor is representative of nitrogen oxides in the exhaust gas or whether the measured value of the nitrogen oxide sensor is representative of ammonia in the exhaust gas. In general, the following relationship applies between the emissions downstream of a three-way catalyst and the lambda condition of the three-way catalyst or downstream of the three-way catalyst: When operating the catalytic converter with a superstoichiometric air-fuel mixture (lambda > 1, so-called "lean operation" or "lean mixture"), not all nitrogen oxides from combustion can be broken down, as the required reducing agent (e.g., CO) has already been oxidized beforehand. As a result, a certain concentration of NOx is present downstream of the catalytic converter, which can be detected by a nitrogen oxide sensor. The nitrogen oxide sensor can also be referred to as a NOx sensor. NOx is used here as a synonym for nitrogen oxides and is a collective term for gaseous oxides of nitrogen, especially nitric oxide (NO) and nitrogen dioxide (NO2). 202400918 3 If the catalytic converter is operated with a substoichiometric air-fuel mixture (lambda < 1, so-called "rich operation"), not all hydrocarbons and carbon monoxide present can be broken down. Additionally, ammonia (NH3) is produced as a side reaction during this rich operation, resulting in an additional pollutant. Consequently, the nitrogen oxide sensor downstream of the catalytic converter measures a certain concentration of NH3. However, all NOx emissions are converted to N2 and CO2 because sufficient amounts of carbon monoxide (CO) are present. Therefore, only NH3 exists downstream of the catalytic converter, and no NOx remains. However, this simple approach to distinguishing between NOx and NH3 emissions does not allow for a correct separation between NOx and NH3 under all conditions. Firstly, NOx and NH3 formation are