BRIEF DESCRIPTION OF THE DRAWINGS
The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description made with reference to the accompanying drawings. In the drawings:
FIG. 1 is a schematic view showing a fuel vapor treatment apparatus according to a first embodiment;
FIG. 2 is a schematic view showing a flow passage when cutoff pressure of a pump is detected in the fuel vapor treatment apparatus;
FIG. 3 is a schematic view showing a flow passage when air pressure is detected in the fuel vapor treatment apparatus;
FIG. 4 is a schematic view showing a flow passage when pressure of mixture including air and fuel vapor is detected in the fuel vapor treatment apparatus;
FIG. 5 is a schematic view showing a flow passage when mixture is purged from both first and second canisters in the fuel vapor treatment apparatus;
FIG. 6 is a schematic view showing a flow passage when mixture is purged from the first canister in the fuel vapor treatment apparatus;
FIG. 7 is a schematic view showing a flow passage when reference pressure is detected in the fuel vapor treatment apparatus;
FIG. 8 is a schematic view showing a flow passage when a leak check operation is performed and a purge valve blocks therein, in the fuel vapor treatment apparatus;
FIG. 9 is a schematic view showing a flow passage when the leak check operation is performed and the purge valve communicates therein, in the fuel vapor treatment apparatus;
FIG. 10 is a time chart showing an operation of the fuel treatment apparatus;
FIG. 11 is a time chart showing an operation for measuring a fuel vapor concentration in the fuel vapor treatment apparatus;
FIG. 12 is a time chart showing an operation for purging mixture in the fuel vapor treatment apparatus;
FIG. 13 is a time chart showing the leak check operation in the fuel vapor treatment apparatus;
FIG. 14 is a time chart showing an operation of a fuel vapor treatment apparatus according to a modified embodiment;
FIG. 15 is a schematic view showing solenoid valves for a fuel treatment apparatus according to a second embodiment;
FIG. 16 is a schematic view showing solenoid valves for a fuel treatment apparatus according to a third embodiment;
FIG. 17 is a schematic view showing a fuel vapor treatment apparatus, according to a fourth embodiment; and
FIG. 18 is a time chart showing an operation according to the fourth embodiment.