On-board diagnostics for an exhaust gas catalytic converter and detection of aging

A vehicle comprising:

• a combustion chamber;
• a tract for exhaust gas leaving the combustion chamber;
• a SCR catalytic converter for purifying the exhaust gas;
• an electronic control device for operating the catalyst measuring system and evaluating the measurement data;
• a high-frequency sensor for determining ammonia loading of the SCR catalytic converter;
• a NOx sensor for sensing the NOx concentration downstream of the SCR catalytic converter;
• and
• an ammonia dosing system for injecting ammonia into an exhaust system of the vehicle;
• wherein the electronic control device instructs the ammonia dosing system to inject ammonia selectively into the exhaust system at a plurality of different dosing rates;
• and
• the electronic control device evaluates data received from the NOx sensor and of the high-frequency sensor to calculate a highest possible dosing rate of ammonia which brings about a greatest possible reduction in the NOx concentration in the exhaust gas without ammonia being deposited in the SCR catalytic converter.

A vehicle comprising:

• a combustion chamber;
• an tract for exhaust gas leaving the combustion chamber;
• an SCR catalytic converter for purifying the exhaust gas;
• an electronic control device for operating the catalyst measuring system and evaluating the measurement data;
• a high-frequency sensor for determining ammonia loading of the SCR catalytic converter;
• a NOx sensor for sensing the NOx concentration downstream of the SCR catalytic converter;
• and
• an ammonia dosing system for injecting ammonia into an exhaust system of the vehicle;
• wherein the electronic control device instructs the ammonia dosing system to inject ammonia selectively into the exhaust system at a plurality of different dosing rates;
• and
• the electronic control device evaluates data received from the NOx sensor and of the high-frequency sensor to calculate a highest possible dosing rate of ammonia which brings about a greatest possible reduction in the NOx concentration in the exhaust gas with the result that only a minimal amount of ammonia is deposited in the SCR catalytic converter.

A method for on-board diagnostics and for determining the state of aging of an SCR catalytic converter, the method comprising:

• determining the NOx concentration during dosed ammonia injection of an SCR catalytic converter as a reference;
• initializing the measurement by operating the SCR catalytic converter at a constant operating point without ammonia injection, with the result that no orvery little ammonia is stored in the SCR catalytic converter;
• injecting ammonia into the exhaust system according to a defined dosing rate;
• measuring the NOx concentration downstream of the SCR catalytic converter and the ammonia loading of the SCR catalytic converter;
• determining the highest possible ammonia dosing rate at which the NOx concentration downstream of the SCR catalytic converter becomes minimal without ammonia loading occurring, or with only minimal ammonia loading occurring, in the SCR catalytic converter;
• and
• determining the state of aging of the SCR catalytic converter based on the highest possible dosing rate.

A non-transitory computer-readable medium storing instructions for on-board diagnostics and for determining the state of aging of an SCR catalytic converter, the instructions when executed by a processor, causing the processor to:

• determine the NOx concentration during dosed ammonia injection of an SCR catalytic converter as a reference;
• initialize the measurement by operating the SCR catalytic converter at a constant operating point without ammonia injection, with the result that no orvery little ammonia is stored in the SCR catalytic converter;
• inject ammonia into the exhaust system according to a defined dosing rate;
• measure the NOx concentration downstream of the SCR catalytic converter and the ammonia loading of the SCR catalytic converter;
• determine the highest possible ammonia dosing rate at which the NOx concentration downstream of the SCR catalytic converter becomes minimal without ammonia loading occurring, or with only minimal ammonia loading occurring, in the SCR catalytic converter;
• and
• determine the state of aging of the SCR catalytic converter based on the highest possible dosing rate.