Method for testing the function of a pressure switch of a tank ventilation system, control device, and internal combustion engine

• US 20100071672A1
• Filed: 11/27/2007
• Published: 03/25/2010
• Est. Priority Date: 11/29/2006
• Status: Active Grant

• Current Assignee: Vitesco Technologies GmbH (INA-Holding Schaeffler GmbH & Co. KG), Audi AG (Volkswagen AG)
• Original Assignee: Continental Automotive GmbH (Continental AG), Audi AG (Volkswagen AG)
• Inventors: Köhler, Armin, Grunwald, Oliver
• Granted Patent: US 8,161,948 B2
• Time in Patent Office: Days
• US Class Current: 123/520
• CPC Class Codes: F02M 25/0818 having means for pressurising the evaporative emission space

Abstract

The switched state of a pressure switch in a tank ventilation system of a motor vehicle is used for testing the function of the tank ventilation system, the pressure switch being in a low-pressure position if the pressure in the tank ventilation system is lower than a predefined pressure limit while being in a high-pressure position if that is not the case. A defective pressure switch can result in wrong assessments. Disclosed is a method for testing the function of the pressure switch, the method encompassing the following steps: a switched state of the pressure switch is detected; a measure is carried out that increases the pressure in the tank ventilation system above the pressure limit if the pressure switch is in the low-pressure position; a defect of the pressure switch is identified if the pressure switch remains in the low-pressure position after carrying out the measure.

Claims

1. A method for testing the function of a pressure switch of a tank ventilation system for an internal combustion engine of a motor vehicle, the pressure switch being in a low-pressure position if the pressure in the tank ventilation system is lower than a predefined pressure limit, and the pressure switch being in a high-pressure position if that is not the case, wherein the method comprises the following steps:

detecting a switched state of the pressure switch,

carrying out a measure that increases the pressure in the tank ventilation system above the pressure limit if the pressure switch is in the low-pressure position,

identifying a defect of the pressure switch if the pressure switch remains in the low-pressure position after the measure has been carried out.

2. The method according to claim 1, wherein the measure comprises:

when the internal combustion engine is at a standstill, a tank ventilation valve of the tank ventilation system, which valve is arranged in a connecting line between a fuel vapor accumulator and an intake pipe of the internal combustion engine, is actuated such that the tank ventilation system is pneumatically connected to the intake pipe.

3. The method according to claim 2, wherein the tank ventilation valve is actuated such that the tank ventilation system and the intake pipe are pneumatically separated once the pressure switch switches to the high-pressure position after the measure has been carried out.

4. The method according to claim 1, wherein the measure comprises:

when the internal combustion engine is in operation, a tank ventilation valve of the tank ventilation system, which valve is arranged in a connecting line between a fuel vapor accumulator and an intake pipe of the internal combustion engine, is actuated such that the tank ventilation system and the intake pipe are pneumatically separated.

5. The method according to claim 4, wherein the acceleration of the motor vehicle is detected, and the defect of the pressure switch is identified, if the acceleration exceeds a predefined acceleration limit.

6. The method according to claim 5, wherein the defect of the pressure switch is identified only when the acceleration exceeds the predefined acceleration limit several times.

7. The method according to claim 5, wherein both the longitudinal acceleration and the lateral acceleration of the motor vehicle are detected.

8. The method according to claim 4, wherein a temperature that represents a measure of the temperature in the tank ventilation system is detected, and a defect of the pressure switch is identified, if the temperature exceeds a predefined temperature limit.

9. The method according to claim 8, wherein the temperature concerned is the coolant temperature of the internal combustion engine.

10. The method according to claim 8, wherein the temperature concerned is the temperature in a fuel tank of the motor vehicle.

11. The method according to claim 8, wherein the temperature concerned is the ambient temperature of the motor vehicle.

12. The method according to claim 8, wherein the temperature concerned is the exhaust gas temperature of the motor vehicle.

13. The method according to claim 2, wherein the time period from implementation of the measure is detected, and a defect of the pressure switch is identified, only when the time period exceeds a predefined time-period limit.

14. The method according to claim 2, wherein prior to identification of a defect of the pressure switch, testing of the function of the tank ventilation valve is carried out and the defect of the pressure switch is identified only when the testing of the function of the tank ventilation valve reveals that the tank ventilation valve does not clamp in a state in which the tank ventilation system is pneumatically separated from the intake pipe.

15. The method according to claim 4, wherein prior to identification of a defect of the pressure switch, testing of the function of the tank ventilation valve is carried out and the defect of the pressure switch is identified only when the testing of the function of the tank ventilation valve reveals that the tank ventilation valve does not clamp in a state in which the tank ventilation system is pneumatically connected to the intake pipe.

16. A control device for a motor vehicle which comprises a tank ventilation system, the tank ventilation system having a pressure switch that is in a low-pressure position if the pressure in the tank ventilation system is lower than a predefined pressure limit, and the pressure switch being in a high-pressure position if that is not the case, wherein the control device for testing the function of the pressure switch is operable:

to detect a switched state of the pressure switch,

to carry out a measure that increases the pressure in the tank ventilation system above the pressure limit if the pressure switch is in the low-pressure position, and

to identify a defect of the pressure switch if the pressure switch remains in the low-pressure position after the measure has been carried out.

17. The control device according to claim 16, wherein the measure comprises:

when an internal combustion engine of the motor vehicle is at a standstill, a tank ventilation valve of the tank ventilation system, which valve is arranged in a connecting line between a fuel vapor accumulator and an intake pipe of the internal combustion engine, is actuated such that the tank ventilation system is pneumatically connected to the intake pipe.

18. The control device according to claim 16, wherein the measure comprises:

when an internal combustion engine of the motor vehicle is in operation, a tank ventilation valve of the tank ventilation system, which valve is arranged in a connecting line between a fuel vapor accumulator and an intake pipe of the internal combustion engine, is actuated such that the tank ventilation system and the intake pipe are pneumatically separated.

19. The control device according to claim 18, wherein the acceleration of the motor vehicle is detected, and the defect of the pressure switch is identified, when the acceleration exceeds a predefined acceleration limit.

20. The control device according to claim 18, wherein the defect of the pressure switch is identified only when the acceleration exceeds the predefined acceleration limit several times.

21. The control device according to claim 19, wherein both the longitudinal acceleration and the lateral acceleration of the motor vehicle are detected.

22. The control device according to claim 18, wherein a temperature is detected which represents a measure of the temperature in the tank ventilation system, and a defect of the pressure switch is identified, if the temperature exceeds a predefined temperature limit.

23. The control device according to claim 22, wherein the temperature concerned is the coolant temperature of the internal combustion engine.

24. The control device according to claim 22, wherein the temperature concerned is the temperature in a fuel tank of the motor vehicle.

25. The control device according to claim 22, wherein the temperature concerned is the ambient temperature of the motor vehicle.

26. The control device according to claim 22, wherein the temperature concerned is the exhaust gas temperature of the motor vehicle.

27. The control device according to claim 17, wherein the time period from implementation of the measure is detected, and a defect of the pressure switch is identified only when the time period exceeds a predefined time-period limit.

28. The control device according to claim 17, wherein prior to identification of a defect of the pressure switch, testing of the function of the tank ventilation valve is carried out, and the defect of the pressure switch is identified, only if the testing of the function of the tank ventilation valve reveals that the tank ventilation valve does not clamp in a state in which the tank ventilation system is pneumatically separated from the intake pipe.

29. The control device according to claim 18, wherein prior to identification of a defect of the pressure switch, testing of the function of the tank ventilation valve is carried out, and the defect of the pressure switch is identified, only if the testing of the function of the tank ventilation valve reveals that the tank ventilation valve does not clamp in a state in which the tank ventilation system is pneumatically connected to the intake pipe.

30. An internal combustion engine comprising a control device according to claim 16.