Method and a control device for operating a tank venting system of an internal combustion engine

1. A method for determining the loading of a fuel vapor retention filter in a fuel vaporization restraint system of an internal combustion engine and accounting for that loading in operation of the internal combustion engine, the method comprising:

activating a scavenge air pump disposed in a regeneration line with the fuel vapor retention filter;

upon reaching a constant speed of an impeller of the scavenge air pump conveying the scavenge air, detecting a pressure upstream of the scavenge air pump and a pressure downstream of the scavenge air pump;

calculating a differential pressure across the scavenge air pump;

determining the degree of loading of the fuel vapor retention filter based at least in part on the differential pressure; and

adjusting a fuel injection time based on the degree of loading.

2. The method as claimed in claim 1 , wherein the degree of loading is determined when the internal combustion engine is stationary and a flow control valve is closed, and the stationary value for the degree of loading is already taken into account in the first injection time calculation when starting the internal combustion engine.

3. The method as claimed in claim 1 , wherein:

the degree of loading is determined with the internal combustion engine running and a flow control valve open;

the flow control valve is controlled by means of a pulse width modulated activation signal; and

evaluation of the differential pressure takes place at a sampling rate synchronous with the control of the flow control valve.

4. The method as claimed in claim 1 , further comprising referencing a characteristics map stored in a control device of internal combustion engine to determine the degree of loading.

5. The method as claimed in claim 4 wherein the values for the degree of loading stored in the characteristics map are determined on a test bed.

6. The method as claimed in claim 1 , wherein:

the pressure values are supplied by two separate pressure sensors; and

the value for the differential pressure comprises a difference between the two pressure values.

7. The method as claimed in claim 1 , wherein the value for the differential pressure is obtained by a differential pressure sensor with fluid connections open out into the regeneration line upstream and downstream of the scavenge air pump.

8. A control device for determining the loading of a fuel vapor retention filter in a fuel vaporization restraint system ( 6 ) of an internal combustion engine, the control device comprising a processor programmed to:

activate a scavenge air pump disposed in a regeneration line with the fuel vapor retention filter;

upon reaching a constant speed of an impeller of the scavenge air pump conveying the scavenge air, detect a pressure upstream of the scavenge air pump and a pressure downstream of the scavenge air pump;

calculate a differential pressure across the scavenge air pump;

determine the degree of loading of the fuel vapor retention filter based at least in part on the differential pressure; and

adjust a fuel injection time based on the degree of loading.

9. An internal combustion engine comprising:

a fuel storage tank for storing fuel;

a connecting line coupling the fuel storage tank to a fuel vapor retention filter;

a regeneration line coupling the fuel vapor retention filter to an intake manifold with an electrically controllable flow control valve;

a venting line coupling the fuel vapor retention filter to the atmosphere;

an electrically controllable scavenge air pump disposed in the regeneration line so that scavenge air can be led through the fuel vapor retention filter and supplied to the intake manifold for regeneration of the fuel vapor retention filter; and

an engine control unit including a processor programmed to:

activate a scavenge air pump disposed in a regeneration line with the fuel vapor retention filter;

upon reaching a constant speed of an impeller of the scavenge air pump conveying the scavenge air, detect a pressure upstream of the scavenge air pump and a pressure downstream of the scavenge air pump;

calculate a differential pressure across the scavenge air pump;

determine the degree of loading of the fuel vapor retention filter based at least in part on the differential pressure; and

adjust a fuel injection time based on the degree of loading.