Method for checking a three-way exhaust catalytic converter of an internal-combustion engine
AssigneeSiemens Aktiengesellschaft
InventorsJohannes Beer, Hong Zhang
Life of this patent
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Abstract
To check a three-way catalytic converter, a NOx sensor is used to determine the NOx concentration downstream of the catalytic converter that is to be diagnosed. On account of the close relationship between a NOx conversion and a HC conversion, the measured NOx concentration can be used to determine the HC conversion properties of the three-way catalytic converter.
Claims8
A method for checking a conversion ability of a three-way exhaust catalytic converter disposed in an exhaust pipe of an internal-combustion engine, the internal-combustion engine being operated with an air/fuel ratio corresponding to a conversion window of the three-way exhaust catalytic converter, which comprises the steps of:
- using an NOx sensor for recording an NOx concentration in the exhaust pipe downstream of the three-way exhaust catalytic converter;
- and
- using values of the NOx concentration to determine conversion properties of the three-way exhaust catalytic converter by performing the following steps while the internal-combustion engine is warming up with the air/fuel ratio:
- forming a sum value of the NOx concentration measured from a beginning of a starting of the internal-combustion engine until a time at which the NOx concentration falls below a predetermined threshold;
- comparing the sum value with the predetermined threshold;
- inferring that the three-way exhaust catalytic converter has aged if the predetermined threshold is exceeded;
- and
- performing at least one of activating a malfunction indication device and inputting an entry into a malfunction memory if the predetermined threshold is exceeded.
A method for checking a conversion ability of a three-way exhaust catalytic converter disposed in an exhaust pipe of an internal-combustion engine, the internal-combustion engine being operated with an air/fuel ratio corresponding to a conversion window of the three-way exhaust catalytic converter, which comprises the steps of:
- using an NOx sensor for recording an NOx concentration in the exhaust pipe downstream of the three-way exhaust catalytic converter;
- and
- using the values of the NOx concentration to determine conversion properties of the three-way exhaust catalytic converter by performing the following steps while the internal combustion engine is warming up and secondary air is being supplied:
- forming a sum value from the NOx concentration measured from a time at which a supply of the secondary air is terminated until a further time at which the NOx concentration falls below a predetermined threshold;
- comparing the sum value with the predetermined threshold;
- inferring that the exhaust catalytic converter has aged if the predetermined threshold is exceeded;
- and
- performing at least one of activating a malfunction indication device and inputting an entry into a malfunction memory if the predetermined threshold is exceeded.
Dependencies are inferred from the claim text.