US 6,637,197 B1 · Method for controlling a rich/lean combustion mixture in a defined manner

Abstract

A method for selective rich/lean control of a combustion mixture using an electrochemical gas sensor. The method makes possible the operation of an NOx adsorption catalyst, which stores excess NOx present in the exhaust gas in a storage phase, the exhaustion of the storage capacity of the catalyst being expressed as an increase in the NOx concentration in the exhaust-gas stream after the catalytic converter, and which converts the stored NOx in a subsequent regeneration phase using a rich exhaust-gas mixture, the end of this reaction being able to be seen in a reduction in the lambda value of the exhaust-gas stream after the catalytic converter. The electrochemical gas sensor underlying the method for operating the NOx adsorption catalyst is operated such that the NOx and the oxygen concentrations in the exhaust-gas stream can be alternately determined using one and the same gas sensor.

Claims12

Dependent claims

A method for selective rich/lean control of a combustion mixture for an operation of an NOx adsorption catalyst, comprising:

storing NOx in a storage phase when the combustion mixture is set to be lean;
converting the stored NOx in a regeneration phase when the combustion mixture is set to be rich;
using an NOx concentration and an oxygen concentration in combustion exhaust gases in a flow direction behind the NOx adsorption catalyst for monitoring the storage phase and for monitoring the regeneration phase, respectively;
determining the NOx concentration and the oxygen concentration by the same electrochemical gas sensor;
and
causing, using a measuring signal of the gas sensor, the storage phase to be initiated in response to a predetermined oxygen concentration not being attained, while a combustion mixture set to be rich is present.

3 more elements

A method for selective rich/lean control of a combustion mixture for an operation of an NOx adsorption catalyst, comprising:

storing NOx in a storage phase when the combustion mixture is set to be lean;
converting the stored NOx in a regeneration phase when the combustion mixture is set to be rich;
using an NOx concentration and an oxygen concentration in combustion exhaust gases in a flow direction behind the NOx adsorption catalyst for monitoring the storage phase and for monitoring the regeneration phase, respectively;
determining the NOx concentration and the oxygen concentration by the same electrochemical gas sensor, the gas sensor including a first pump cell, a second pump cell and a concentration cell;
causing, using a measuring signal of the gas sensor, the storage phase to be initiated in response to a predetermined oxygen concentration not being attained, while a combustion mixture set to be rich is present;
setting a low oxygen partial pressure by an oxygen transport via the first pump cell to determine the NOx concentration contained in the combustion exhaust gases during the storage phase;
using the concentration cell for monitoring the oxygen concentration and using the second pump cell for transporting free oxygen and oxygen resulting from a decomposition of NOx;
setting a low oxygen partial pressure by an oxygen transport via a pump cell to determine the oxygen concentration contained in the combustion exhaust gases;
and
using one of the first pump cell, the second pump cell and the concentration cell for monitoring the oxygen concentration.

7 more elements

A method for selective rich/lean control of a combustion mixture for an operation of an NOx adsorption catalyst, comprising:

storing NOx in a storage phase when the combustion mixture is set to be lean;
converting the stored NOx in a regeneration phase when the combustion mixture is set to be rich;
using an NOx concentration for monitoring the storage phase;
using an oxygen concentration in combustion exhaust gases in a flow direction behind the NOx adsorption catalyst for monitoring the regeneration phase;
determining the NOx concentration and the oxygen concentration by the same electrochemical gas sensor, the gas sensor including a first pump cell, a second pump cell and a concentration cell;
causing, using a measuring signal of the gas sensor, the storage phase to be initiated in response to a predetermined oxygen concentration not being attained, while a combustion mixture set to be rich is present;
setting a low oxygen partial pressure by an oxygen transport via the first pump cell to determine the NOx concentration contained in the combustion exhaust gases during the storage phase;
using the concentration cell for monitoring the oxygen concentration and using the second pump cell for transporting free oxygen and oxygen resulting from a decomposition of NOx;
setting a low oxygen partial pressure by an oxygen transport via a pump cell to determine the oxygen concentration contained in the combustion exhaust gases;
and
using one of the first pump cell, the second pump cell and the concentration cell for monitoring the oxygen concentration.

8 more elements

Dependencies are inferred from the claim text.

Method for controlling a rich/lean combustion mixture in a defined manner

Life of this patent

Method for controlling a rich/lean combustion mixture in a defined manner

Life of this patent

Abstract

Claims12