| 摘要 |
An active charcoal filter (20) of a tank-venting system stores fuel vaporizing in a tank (10). In order to check the operability of the tank-venting system, a leakage diagnostic unit (60) having a pump (50) is provided wherein the pump (50) is connected downstream of a switchover valve (70). A reference leak (81) is arranged parallel to the switchover valve (70). The switchover valve (70) includes two switching positions I and II. In the position I, the pump (50) is pressure-conductively connected to the line (80) and then pumps ambient air into the line (80) through the reference leak (81). The pumped flow, which is present at the output (51) of the pump (50), is, in the position I of the switchover valve (70) pure ambient air and, in the position II of the switchover valve (70), is air cleaned by the active charcoal filter (20). The pumped flow can therefore be outputted to the ambient of the vehicle via a line (52) without problems for the environment. Alternatively, the pumped flow at the output (51) of the pump (50) can be supplied to the intake manifold (40) via a return line. The tightness check takes place by detecting the current, which is to be supplied to the pump motor, and by determining whether the pumped flow, which is to be pumped by the pump (50) into the tank-venting system, deviates from the pumped flow which is present when introducing the underpressure via the reference leak. |
