Patent ID: 8153321

Claim:
A fuel cell system comprising: a fuel cell stack having an anode and a cathode; a first supply passage and a second supply passage that communicate with each other in the fuel cell stack and supply fuel gas to the anode; an exhaust passage that is connected to the second supply passage and discharges exhaust gas from the anode; an opening and closing unit that opens and closes the exhaust passage; and a flow amount controlling unit that controls flow amounts of the fuel gas passing through the first supply passage and the second supply passage, wherein fuel gas supplied via the first supply passage and fuel gas supplied via the second supply passage meet each other in counter-directional flow within the anode to form an extreme downstream position of the fuel gas, and wherein the flow amount controlling unit executes a control for supplying fuel gas to the anode in simultaneous flow from both the first supply passage and the second supply passage and varies a ratio between the flow amounts passing through the first supply passage and the second supply passage over time when the exhaust passage is closed to actively control the location of the extreme downstream position of the fuel gas within the anode and controls the flow amount such that the extreme downstream position of the fuel gas coincides with a position at which the exhaust passage is connected to the second supply passage when the opening and closing unit is open.