Method and device for diagnosing a leak in an evaporation system and in a tank ventilation line of an internal combustion engine

A device for a combined diagnosis of a leak in an evaporation system and in a tank ventilation line of an internal combustion engine supported by a vehicle, the device comprising:

• a fresh-air shut-off valve being part of the evaporation system and arranged between an activated carbon filter and a fresh-air filter;
• a pressure sensor system;
• and
• an engine controller configured to:
• diagnose the evaporation system using a fresh-air shut-off valve of the evaporation system and a pressure sensor system of the evaporation system;
• during the diagnosis on whether there is a leak in the evaporation system of the internal combustion engine, check different diagnosis regions of the evaporation system, the diagnosis regions include a tank region of the internal combustion engine and a filter region of the internal combustion engine;
• and
• during the diagnosis of the tank ventilation line, check a flow through the tank ventilation line,
• wherein during the check of the filter region, the engine controller is further configured to:
• close the fresh-air shut-off valve:
• after a predefined waiting time, evacuate the filter region including the tank ventilation line arranged in the filter region by opening a tank ventilation valve;
• close the tank ventilation valve after a predefined negative pressure has been reached, and
• calculate and evaluate an ensuing pressure gradient after the tank ventilation valve has been closed,
• wherein during the check of the tank region, the engine controller is configured to:
• evaluate a pressure change resulting from a temperature change of the gas volume in the fuel tank with a constant fuel tank volume after the internal combustion engine has been shut down and while the vehicle is at a standstill, and
• compare an expected pressure profile from a predefined temperature profile during the temperature change after an ignition terminal of the internal combustion engine has been switched on with a measured pressure profile from a previous vehicle standstill phase and then,
• recognize a presence of a leak-free tank region, if the measured pressure profile lies within a predefined tolerance range around the expected pressure profile.

A device for diagnosing a leak in an evaporation system and in a tank ventilation line of an internal combustion engine, the device comprising:

• a fresh-air shut-off valve being part of the evaporation system and arranged between an activated carbon filter and a fresh-air filter;
• a pressure sensor system;
• and
• an engine controller configured to:
• diagnose the evaporation system using a fresh-air shut-off valve of the evaporation system and a pressure sensor system of the evaporation system;
• during the diagnosis on whether there is a leak in the evaporation system of the internal combustion engine, check different diagnosis regions of the evaporation system, the diagnosis regions include a tank region of the internal combustion engine and a filter region of the internal combustion engine;
• and
• during the diagnosis of the tank ventilation line, check a flow through the tank ventilation line,
• wherein during the check of the tank region, the engine controller is further configured to:
• compare an expected pressure profile from a predefined temperature profile during a temperature change after an ignition terminal of the internal combustion engine has been switched on with a measured pressure profile from a previous vehicle standstill phase and then,
• recognize a presence of a leak-free tank region, if the measured pressure profile lies within a predefined tolerance range around the expected pressure profile.