Technical Field
The present invention is related to a fuel tank system.
Related Art
A fuel tank system is known in which a valve member (a diaphragm valve) is provided to a vent pipe that places a fuel tank in communication with a canister (for example, see Japanese Patent Application Laid-Open (JP-A) No. 2013-144942). In this fuel tank system, during ordinary operation, the valve member is closed so as to seal the fuel tank. However, when detecting whether or not a perforation has developed in the fuel tank (referred to simply as “perforation detection” hereafter), negative pressure from a negative pressure pump is introduced into the fuel tank by causing a negative pressure to act on a back pressure chamber of the valve member so as to open the valve member. More specifically, negative pressure from a negative pressure pump is caused to act on the back pressure chamber by providing a canister side bypass route that places the vent pipe at the canister side in communication with the back pressure chamber of the valve member.
In some cases, negative pressure generated when driving the engine is caused to act on a canister in which a vaporized fuel is adsorbed onto an adsorbent, and vaporized fuel adsorbed onto the adsorbent of the canister is caused to desorb (is purged).
In such cases, when the negative pressure from the engine acts on the fuel tank through the vent pipe from the canister, it is difficult to efficiently purge the canister using the negative pressure from the engine.