Pumpvorrichtung für ein Brennstoffverdunstungs-Rückhhaltesystem und Brennstoffverdunstungs-Rückhaltesystem

摘要

Known pumping devices that generate an overpressure in a fuel vapour control system for diagnostic purposes have in common that the connection between an adsorption filter and the environment is shut off during the whole diagnosis process. In the event of a malfunction of the shut off valve, that may for example get jammed, a negative pressure may build up that is dangerous for the fuel tank. In the state of the art, this danger is avoided by protective valves arranged on the fuel tank. In the disclosed pumping device (2), the valves (24, 25) required to generate the overpressure are designed in such a way that in an open position of a regenerating valve (10) and in a closed position of a shut off valve (20) the cross section of flow Aprotection through the valves (24, 25) is sufficient to ensure such a small resistance to flow that no negative pressure capable of damaging the fuel tank (4) can be reached. The disclosed pumping device is provided for a fuel vapour control system of an internal combustion engine.