Method for operating an exhaust gas purification apparatus

1. A method for operating an exhaust gas purification apparatus for purifying an exhaust gas stream of a vehicle, the exhaust gas purification apparatus including a close-coupled catalytic converter apparatus and a non-close-coupled catalytic converter apparatus, the method comprising:

monitoring a first lambda value at a first position, the first position being upstream of the close-coupled catalytic converter apparatus,

operating the close-coupled catalytic converter apparatus with an excess of fuel,

monitoring a second lambda value at a second position, the second position being downstream of the close-coupled catalytic converter apparatus and upstream of the non-close-coupled catalytic converter apparatus,

selectively feeding external air or an external air mixture into an external air inlet of the exhaust gas purification apparatus downstream of the second position,

monitoring a third lambda value at a third position, the third position being downstream of the external air inlet and upstream of the non-close-coupled catalytic converter apparatus,

selectively cooling the exhaust gas stream between the third position and the non-close-coupled catalytic converter apparatus,

monitoring a fourth lambda value at the non-close-coupled catalytic converter apparatus, and

operating the non-close-coupled catalytic converter apparatus in a stoichiometric method of operation.

2. The method of claim 1 , wherein all of the method steps are carried out only in part load operation and/or in starting operation of an internal combustion engine of the vehicle.

3. The method of claim 1 , wherein the all of the method are carried out only in full load operation of an internal combustion engine of the vehicle.

4. The method of claim 1 , wherein the method is carried out only in part load operation of the internal combustion engine of the vehicle and when the close-coupled catalytic converter apparatus exceeds a limit temperature.

5. A method for operating an exhaust gas purification apparatus for purifying an exhaust gas stream of a vehicle, the vehicle having an internal combustion engine with first and second cylinder sections coupled respectively to first and second close-coupled catalytic converter apparatuses and a single non-close-coupled catalytic converter apparatus connected to the first and second close-coupled catalytic converter apparatuses, the method comprising:

monitoring first and second lambda values at first and second positions in proximity respectively to the first and second close-coupled catalytic converter apparatuses;

operating the first close-coupled catalytic converter apparatus so that the first lambda value is greater than 1 by a specified amount and operating the second close-coupled catalytic converter apparatus so that the second lambda value is less than 1 by the specified amount so that the first and second close-coupled catalytic converter apparatuses are operated to have complementary lambda values;

monitoring at least one lambda value in proximity to the non-close-coupled catalytic converter apparatus; and

operating the non-close-coupled catalytic converter apparatus in a stoichiometric method of operation.

6. An exhaust gas purification apparatus for purifying an exhaust gas stream from an internal combustion engine of a vehicle, the internal combustion engine having first and second cylinder sections, comprising:

first and second close-coupled catalytic converter apparatuses communicating respectively with the first and second cylinder sections;

a non-close-coupled catalytic converter apparatus communicating with the first and second close-coupled catalytic converter apparatuses;

a cooling apparatus between the first and second close-coupled catalytic converter apparatuses and the non-close-coupled catalytic converter apparatus for cooling the exhaust gas stream from the first and second close-coupled catalytic converter apparatuses to the non-close-coupled catalytic converter apparatus;

a first and second close-coupled sensor units for monitoring close-coupled lambda values of the first and second close-coupled catalytic converter apparatuses respectively;

at least one non-close-coupled sensor unit for monitoring non-close-coupled lambda values of the non-close-coupled catalytic converter apparatus; and

a controller configured to:

selectively operating the cooling apparatus to cool the exhaust gas stream between the first and second close-coupled catalytic converter apparatuses and the non-close-coupled catalytic converter apparatus,

selectively operating the first and second close-coupled catalytic converter apparatuses so that the first lambda value is greater than 1 by a specified amount and the second lambda value is less than 1 by the specified amount so that the first and second close-coupled catalytic converter apparatuses are operated to have complementary lambda values, and

selectively operating the non-close-coupled catalytic converter apparatus in a stoichiometric method of operation.

7. The exhaust gas purification apparatus of claim 6 further comprising at least one additional sensor unit between the close-coupled catalytic converter apparatuses and the cooling apparatus for determining at least one intermediate lambda value.

8. The exhaust gas purification apparatus of claim 6 further comprising at least one additional sensor unit between the close-coupled catalytic converter apparatuses and the non-close-coupled catalytic converter apparatus for determining at least one intermediate lambda value.