Patent ID: 8728674

Claim:
A fuel cell system comprising: a fuel cell including an electrolyte membrane, an anode and a cathode sandwiching the electrolyte membrane, an anode gas passage through which a fuel gas is supplied to and discharged from the anode, and a cathode gas passage through which an oxidizing gas is supplied to and discharged from the cathode; a fuel gas channel including the anode gas passage and through which the fuel gas is supplied to and discharged from the anode, the fuel gas channel comprising a fuel gas supplying passage connected to an entrance of the anode gas passage, a fuel gas supplying valve disposed on the fuel gas supplying passage to open and close the fuel gas supplying passage, the anode gas passage, a fuel gas discharging passage connected to an exit of the anode gas passage, and a fuel gas discharging valve disposed on the fuel gas discharging passage to open and close the fuel gas discharging passage; an oxidizing gas channel including the cathode gas passage and through which the oxidizing gas is supplied to and discharged from the cathode, the oxidizing gas channel comprising an oxidizing gas supplying passage connected to an entrance of the cathode gas passage, an oxidizing gas supplying valve disposed on the oxidizing gas supplying passage to open and close the oxidizing gas supplying passage, the cathode gas passage, an oxidizing gas discharging passage connected to an exit of the cathode gas passage, and an oxidizing gas discharging valve disposed on the oxidizing gas discharging passage to open and close the oxidizing gas discharging passage; and a controller including at least one of a microcomputer and a CPU and a storage unit storing a program, the program, when executed by the at least one of the microcomputer and the CPU, causing the controller to control opening and closing of each of the fuel gas supplying valve, the fuel gas discharging valve, the oxidizing gas supplying valve and the oxidizing gas discharging valve, wherein: the program, when executed by the at least one of the microcomputer and the CPU, further causes the controller to control the fuel gas supplying valve, the fuel gas discharging valve, the oxidizing gas supplying valve and the oxidizing gas discharging valve, when the fuel cell system performs a stop process in a daily shut-down operation, such that: the fuel gas channel and the oxidizing gas channel are closed by closing the fuel gas supplying valve, the fuel gas discharging valve, the oxidizing gas supplying valve and the oxidizing gas discharging valve, and when negative pressure is generated in the cathode, with the oxidizing gas supplying valve closed, the oxidizing gas discharging valve is open to supply a discharged oxidizing gas in the oxidizing gas discharging passage from the exit of the cathode gas passage to the cathode.