Fuel cell system

1. A fuel cell system, comprising:

a fuel cell having an anode to which fuel gas is supplied, and a cathode to which oxidant gas is supplied;

a first oxidant gas flowpath through which the oxidant gas is supplied to the fuel cell;

a second oxidant gas flowpath through which the oxidant gas is discharged from the fuel cell;

a first shut-off valve, being normally closed, disposed upstream from the fuel cell and connected to the fuel cell through the first oxidant gas flowpath, the first shut-off valve having a first valve body having a first engagement block connected via a first rod and disposed outside the first shut-off valve;

a second shut-off valve, being normally-closed, disposed downstream from the fuel cell and connected to the fuel cell through the second oxidant gas flowpath, the second shut-off valve having a second valve body having a second engagement block connected via a second rod and disposed outside the second shut-off valve;

a first opening/closing unit for opening and closing the first shut-off valve;

a second opening/closing unit for opening and closing the second shut-off valve;

a cathode control unit for sealing the cathode by closing the first shut-off valve and the second shut-off valve by using the first opening/closing unit and the second opening/closing unit after stopping electro-chemical reaction in the fuel cell and for releasing the sealed cathode by opening the first shut-off valve and the second shut-off valve by using the first opening/closing unit and the second opening/closing unit after starting the electro-chemical reaction in the fuel cell;

a first valve lock unit having a first lock member and locking the first shut-off valve in an open state by engaging the first lock member with the first engagement block of the first shut-off valve; and

a second valve lock unit having a second lock member and locking the second shut-off valve in an open state by engaging the second lock member with the second engagement block of the second shut-off valve,

wherein the first valve lock unit and the second valve lock unit include respectively a first locking section and a second locking section which keep respectively the first shut-off valve and the second shut-off valve opened and unable to be closed while the first shut-off valve and the second shut-off valve are mechanically locked.

2. The fuel cell system according to claim 1 , wherein the first opening/closing unit has a first electric drive unit for supplying electricity to the first shut-off valve to drive the first shut-off valve from a closed state to the open state, the second opening/closing unit has a second electric drive unit for supplying electricity to the second shut-off valve to drive the second shut-off valve from a closed state to the open state, and the cathode control unit stops supplying electricity to the first and second electric drive units after the first and second shut-off valves are locked in the open state by the first and second valve lock units.

3. The fuel cell system according to claim 1 or 2 , wherein, negative pressure produced in the cathode sealed by the cathode control unit sucks the first valve body of the first shut-off valve in the closed state toward the fuel cell; sucks the second valve body of the second shut-off valve in the closed state toward the fuel cell; and maintains the first shut-off valve and the second shut-off valve in the closed state.

4. The fuel cell system according to claim 1 , further comprising a

back-pressure-regulating valve disposed downstream from the second shut-off valve.

5. A fuel cell system according to claim 1 ,

wherein the first opening/closing unit includes:

a first rotational driving source driven by supplying electricity;

a first pinion connected to a first drive shaft of the first rotational driving source;

a first valve housing having a first inlet port, a first outlet port and a first chamber each communicating with the first oxidant gas flowpath and receiving a first valve body in the first chamber;

a first rod section connected to the first valve body for displacing integrally with the first valve body and exposed outside from the first valve housing; and

a first rack section provided to an outer periphery of the first rod section and meshing with the first pinion,

wherein the first locking section includes:

a first solenoid provided outside of the first valve housing;

the first lock member which extends or retracts by the first solenoid under the excitation effect or non-excitation effect; and

the first engagement block connected to a free end of the first rod section and which is lockable by the first lock member,

wherein after the first locking section keeps the first shut-off valve opened, the first rotational drive source is stopped from being energized,

wherein the second opening/closing unit includes:

a second rotational driving source driven by supplying electricity;

a second pinion connected to a second drive shaft of the second rotational driving source;

a second valve housing having a second inlet port, a second outlet port and a second chamber each communicating with the second oxidant gas flowpath and receiving a second valve body in the second chamber;

a second rod section connected to the second valve body for displacing integrally with the second valve body and exposed outside from the second valve housing; and

a second rack section provided to an outer periphery of the second rod section and meshing with the second pinion,

wherein the second locking section includes:

the second lock member which extends or retracts by the second solenoid under the excitation effect or non-excitation effect; and

the second engagement block connected to a free end of the second rod section and which is lockable by the second lock member, and

wherein after the second locking section keeps the second shut-off valve opened, the second rotational drive source is stopped from being energized.