Method for inspecting a tank ventilation device, control device, and internal combustion engine

1. A method for checking the proper operation of a tank ventilation device for an internal combustion engine, comprising the steps of:

detecting the position of a pressure switch of the tank ventilation device, wherein the pressure switch being in a low-pressure position if the pressure in the tank ventilation device is less than a specified threshold pressure, and otherwise being in a high-pressure position,

when the internal combustion engine is running, opening at least partially a controllable tank ventilation valve of the tank ventilation device, which is arranged in a connecting pipe between a fuel-vapor storage system and an intake pipe of the internal combustion engine, and pneumatically connects the fuel vapor storage system and the intake pipe when in an open state, and pneumatically disconnects the fuel vapor storage system and the intake pipe when in a closed state,

detecting the position of the pressure switch again after opening the tank ventilation valve,

assessing the proper operation of the tank ventilation device on the basis of a comparison of the position of the pressure switch before opening the tank ventilation valve with the position of the pressure switch after opening the tank ventilation valve.

2. The method according to claim 1 , wherein in the case that the pressure switch is in the high-pressure position both before opening and after opening the tank ventilation valve, a fault in the tank ventilation device is identified.

3. The method according to claim 1 , wherein in the case that the pressure switch is in the high-pressure position before opening the tank ventilation valve,

the tank ventilation valve is opened as far as a specified first degree of opening, the size of which is designed so that a pressure that is less than the threshold pressure is only established in the tank ventilation device when the tank ventilation device contains no leaks, and

the tank ventilation device is assessed as fault-free if the pressure switch is in the low-pressure position after opening the tank ventilation valve as far as the first degree of opening, otherwise a fault in the tank ventilation device is identified.

4. The method according to claim 3 , wherein on identifying a fault in the tank ventilation device

the tank ventilation valve is opened as far as a specified second degree of opening that is greater than the first degree of opening,

the position of the pressure switch is detected after opening the tank ventilation valve as far as the second degree of opening, and

if after opening the tank ventilation valve as far as the second degree of opening, the pressure switch is in the low-pressure position, the fault in the tank ventilation device is identified as a leak.

5. The method according to claim 4 , wherein

the size of the second degree of opening is designed so that a pressure that is lower than the threshold pressure is only established in the tank ventilation device when the size of the leak is smaller than a given threshold leak size, and

if the position of the pressure switch after opening the tank ventilation valve as far as the second degree of opening is detected as the low-pressure position, the fault in the tank ventilation device is identified as a leak having a size that is smaller than the threshold leak size.

6. The method according to claim 4 , wherein a functional check of the tank ventilation valve is performed before opening the tank ventilation valve as far as the second degree of opening, and the tank ventilation valve is then only opened as far as the second degree of opening if the result of the functional check of the tank ventilation valve is that it is fault-free.

7. The method according to claim 6 , wherein for the functional check of the tank ventilation valve, a check is made as to whether an operating parameter of the internal combustion engine changes after actuating the tank ventilation valve.

8. The method according to claim 7 , wherein the operating parameter is the oxygen content of the exhaust gas from the internal combustion engine, which is measured by a Lambda sensor arranged in the exhaust section of the internal combustion engine.

9. The method according to claim 5 , wherein a functional check of the tank ventilation valve is performed before opening the tank ventilation valve as far as the second degree of opening, and the tank ventilation valve is then only opened as far as the second degree of opening if the result of the functional check of the tank ventilation valve is that it is fault-free.

10. A control device for an internal combustion engine, which is operable to

detect the position of a pressure switch of a tank ventilation device of the motor vehicle, the pressure switch being in a low-pressure position if the pressure in the tank ventilation device is less than a specified threshold pressure, and otherwise being in a high-pressure position,

open, when the internal combustion engine is running, at least partially a controllable tank ventilation valve of the tank ventilation device, which is arranged in a connecting pipe between a fuel-vapor storage system and an intake pipe of an internal combustion engine of the motor vehicle , and pneumatically connects the fuel vapor storage system and the intake pipe when in an open state, and pneumatically disconnects the fuel vapor storage system and the intake pipe when in a closed state,

detect the position of the pressure switch again after opening the tank ventilation valve, and to

assess the proper operation of the tank ventilation device on the basis of a comparison of the position of the pressure switch before opening the tank ventilation valve with the position of the pressure switch after opening the tank ventilation valve.

11. The control device according to claim 10 , wherein in the case that the pressure switch is in the high-pressure position both before opening and after opening the tank ventilation valve, a fault in the tank ventilation device is identified.

12. The control device according to claim 10 , wherein in the case that the pressure switch is in the high-pressure position before opening the tank ventilation valve,

the tank ventilation valve is opened as far as a specified first degree of opening, the size of which is designed so that a pressure that is less than the threshold pressure is only established in the tank ventilation device when the tank ventilation device contains no leaks, and

the tank ventilation device is assessed as fault-free if the pressure switch is in the low-pressure position after opening the tank ventilation valve as far as the first degree of opening, otherwise a fault in the tank ventilation device is identified.

13. The control device according to claim 12 , wherein on identifying a fault in the tank ventilation device

the tank ventilation valve is opened as far as a specified second degree of opening that is greater than the first degree of opening,

the position of the pressure switch is detected after opening the tank ventilation valve as far as the second degree of opening, and

if after opening the tank ventilation valve as far as the second degree of opening, the position of the pressure switch is detected as the low-pressure position, the fault in the tank ventilation device is identified as a leak.

14. The control device according to claim 13 , wherein

the size of the second degree of opening is designed so that a pressure that is lower than the threshold pressure is only established in the tank ventilation device when the size of the leak is smaller than a given threshold leak size, and

if the position of the pressure switch after opening the tank ventilation valve as far as the second degree of opening is detected as the low-pressure position, the fault in the tank ventilation device is identified as a leak having a size that is smaller than the threshold leak size.

15. The control device according to claim 13 , wherein a functional check of the tank ventilation valve is performed before opening the tank ventilation valve as far as the second degree of opening, and the tank ventilation valve is then only opened as far as the second degree of opening if the result of the functional check of the tank ventilation valve is that it is fault-free.

16. The control device according to claim 15 , wherein for the functional check of the tank ventilation valve, a check is made as to whether an operating parameter of the internal combustion engine changes after actuating the tank ventilation valve.

17. The control device according to claim 16 , wherein the operating parameter is the oxygen content of the exhaust gas from the internal combustion engine, which is measured by a Lambda sensor arranged in the exhaust section of the internal combustion engine.

18. The control device according to claim 14 , wherein a functional check of the tank ventilation valve is performed before opening the tank ventilation valve as far as the second degree of opening, and the tank ventilation valve is then only opened as far as the second degree of opening if the result of the functional check of the tank ventilation valve is that it is fault-free.

19. An internal combustion engine containing a control device according to claim 10 .