| 摘要 |
The invention relates to a method for leakage diagnosis in a fuel tank system (1) of an internal combustion engine (2) of a motor vehicle, wherein the fuel tank system (1) has a fuel tank (16) and a storage element (19) for the temporary storage of hydrocarbons (23), wherein the fuel tank (16) and the storage element (19) are connected to one another in such a way that the hydrocarbons (23) which outgas from a fuel (17) which is situated in the fuel tank (16) are stored temporarily in the storage element (19), wherein the storage element (19) can be emptied by way of a purge air pump (7), wherein fresh air (24) can be conveyed by way of the purge air pump (7) through a fresh air line (42) to the storage element (19), as a result of which the hydrocarbons (23) can be released from the storage element (19) and can be fed through a hydrocarbon/air mixture line (43) to the internal combustion engine (2) for combustion, wherein the fresh air line (42) can be closed by way of a first valve (10), and the hydrocarbon/air mixture line (43) can be closed by way of a second valve (15), and wherein a pressure sensor (8) is arranged in the fuel tank system (1). In order to obtain reliable statements about the state of the fuel tank system, a stationary period of the motor vehicle is waited for in a first method step, the first valve (10) and the second valve (15) are closed in a second method step, the pressure change in the fuel tank system (1) is measured by way of the pressure sensor (8) within a predefined first time interval in a third method step, the first valve (10) or the second valve (15) is opened, and a positive pressure is built up in the fuel tank system (1) by way of the purge air pump (7) until a predefined positive pressure is reached in a fourth method step, the valve (10, 15) which was opened in the fourth method step is closed again in a fifth method step, the pressure change in the fuel tank system (1) is measured by way of the pressure sensor (8) within a predefined second time interval in a sixth method step, and the pressure changes which were measured in the third method step and in the sixth method step are compared with one another in a seventh method step, and the results are derived from said comparison for leakage diagnosis. |
