Fuel cell system

A fuel cell system comprising:

• a fuel cell to which fuel gas and oxidant gas are fed and which generates electric power;
• an oxidant feed path to the fuel cell;
• an oxidant pump of a turbo type in which a shaft is supported by an air bearing, and which takes in and sends out the oxidant gas by rotary motion;
• an actual-flow-rate detection means for the oxidant gas;
• a pressure control means for the oxidant gas;
• a rotational-speed confirmation means for the oxidant pump;
• a control means which increases the pressure of the oxidant gas through the pressure control means when the actual flow rate of the oxidant gas is greater than a target flow rate while the rotational speed of the oxidant pump is within a lowest range of the rotational speed in which the air bearing can support the shaft;
• a humidifier arranged between the oxidant pump and the fuel cell;
• a humidifier bypass which bypasses the humidifier;
• and
• an oxidant-flow regulating means which controls proportions of the oxidant gas between the humidifier and the humidifier bypass;
• wherein the control means sets the target flow rate and a target pressure on the basis of a value of current requested from the fuel cell, and sets the target pressure according to the proportions controlled by the oxidant-flow regulating means, and when the actual flow rate is greater than the target flow rate the control means sets a sum of a first predetermined value and the target pressure as a new target pressure.

A fuel cell system comprising:

• a fuel cell to which fuel gas and oxidant gas are fed and which generates electric power;
• an oxidant feed path through which the oxidant gas to be fed to the fuel cell flows;
• an oxidant exhaust path through which fuel off-gas exhausted from the fuel cell flows;
• an oxidant pump of a rotary type which takes in and sends out the oxidant gas by rotary motion;
• an actual-flow-rate detection means which detects an actual flow rate of the oxidant gas;
• a rotational-speed confirmation means which confirms a rotational speed of the oxidant pump;
• a back pressure valve which is arranged in the oxidant exhaust path and controls a pressure of the oxidant gas fed to a cathode of the fuel cell;
• and
• a control means which controls the back pressure valve to decrease an aperture of the back pressure valve in steps smaller than steps in which the aperture of the back pressure valve is controlled to increase, in the case where the actual flow rate is greater than the target flow rate even when the rotational speed of the oxidant pump is lowered to a lowest range of the rotational speed after the back pressure valve is controlled to increase the aperture.