Fuel cell system

Abstract

When a request power for a fuel cell is smaller than a predetermined value, a fuel cell system stops the supply of an oxidizing gas to the fuel cell and lowers the output voltage of the fuel cell from a use upper limit voltage to a reduction voltage to perform catalyst activation processing. When the output voltage of the fuel cell lowers to an air blow voltage because of the shortage of the oxidizing gas, the fuel cell system re-supplies the oxidizing gas to recover the output voltage of the fuel cell.

1 . A fuel cell system comprising:
 a fuel cell which receives a supplied fuel gas and oxidizing gas to generate a power; and   a control device which stops the supply of the oxidizing gas to the fuel cell and lowers the output voltage of the fuel cell to perform catalyst activation processing, when a request power for the fuel cell is smaller than a predetermined value.   
     
     
         2 . The fuel cell system according to  claim 1 , further comprising:
 an accumulator device,   wherein the control device prohibits the catalyst activation processing, when where the power chargeable into the accumulator device is a predetermined value or less.   
     
     
         3 . The fuel cell system according to  claim 1 , wherein the control device prohibits the catalyst activation processing, when the running speed of a vehicle using the fuel cell system as a car-mounted power source is a predetermined value or more. 
     
     
         4 . The fuel cell system according to  claim 1 , further comprising:
 a plurality of block valves arranged in a piping system which supplies the fuel gas to the fuel cell,   wherein the control device closes the plurality of block valves to form a closed space in the piping system, and detects a gas pressure fluctuation in the closed space to prohibit the catalyst activation processing while gas leakage is detected.   
     
     
         5 . The fuel cell system according to  claim 1 , wherein the control device performs the catalyst activation processing, when the output performance of the fuel cell lowers. 
     
     
         6 . The fuel cell system according to  claim 1 , further comprising:
 a DC/DC converter which controls the output voltage of the fuel cell; and   a capacitor into which the power generated by the fuel cell is charged,   wherein when the request power for the fuel cell is smaller than the predetermined value, the control device connects an output terminal of the fuel cell to the DC/DC converter, and controls the output voltage of the fuel cell by the DC/DC converter, whereas when the request power for the fuel cell is the predetermined value or more, the control device connects the output terminal of the fuel cell to the capacitor to charge the power generated by the fuel cell into the capacitor.