Method for determining a NOx concentration
AssigneeSiemens Aktiengesellschaft
InventorsBertrand Lemire, Tim Walde
Life of this patent
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Abstract
A thick-film measurement sensor includes two measurement cells and is used to measure the NOx concentration in the exhaust gas from an internal combustion engine. The 1/λ value of the exhaust gas is determined from an oxygen ion pump current flowing in the first measurement cell, for example, by a characteristic diagram, and, a measurement error, which can be used to correct the measured NOx concentration, is determined from this 1/λ value, for example, by a characteristic curve that has previously been determined in a calibration measurement. The invention is based on the discovery that the measurement error is dependent on the air ratio in the exhaust gas. If this is expressed by the 1/λ value, there is no need for a complex division calculation during the correction.
Claims5
A method for determining the NOx concentration in an exhaust gas from an internal combustion engine, which comprises:
- introducing some of the exhaust gas into a first measurement cell of a measurement sensor and establishing a first oxygen concentration in the first measurement cell through a first oxygen ion pump current;
- establishing a second reduced oxygen concentration in a second measurement cell through a second oxygen pump current, the second measurement cell being connected to the first measurement cell;
- measuring the NOx concentration by a third oxygen pump current from the second measurement cell;
- determining from the first oxygen ion pump current an air ratio signal representing a function of a λ value of the exhaust gas;
- determining from the air ratio signal a measurement error representing a deviation of the measured NOx concentration from a true NOx concentration;
- and
- correcting the measured NOx concentration with the measurement error.
Dependencies are inferred from the claim text.