Method for determining a NOx concentration
First Claim
1. 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 an oxygen ion pump current;
establishing a second oxygen concentration in a second measurement cell connected to the first measurement cell;
measuring the NOx concentration in the second measurement cell;
determining from the 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.
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Accused Products
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.
2 Citations
14 Claims
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1. A method for determining the NOx concentration in an exhaust gas from an internal combustion engine, which comprises:
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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 an oxygen ion pump current;
establishing a second oxygen concentration in a second measurement cell connected to the first measurement cell;
measuring the NOx concentration in the second measurement cell;
determining from the 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. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method for determining the NOx concentration in an exhaust gas from an internal combustion engine, which comprises:
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providing a measurement sensor having a first measurement cell and a second measurement cell connected to the first measurement cell;
introducing some of the exhaust gas into the first measurement cell and establishing a first oxygen concentration in the first measurement cell through an oxygen ion pump current;
establishing a second oxygen concentration in the second measurement cell;
measuring the NOx concentration in the second measurement cell;
determining from the 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. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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Specification