Patent ID: 7105243

Claim:
A fuel cell system comprising: a fuel cell working to produce an electrical energy arising from chemical reaction of hydrogen with oxygen; a hydrogen supply line supplying a hydrogen gas from a hydrogen supply device to said fuel cell; an off-gas recirculating line extending from said fuel cell to said hydrogen supply line; an ejector vacuum pump designed to recirculate an off-gas, which is discharged from said fuel cell and includes hydrogen having unreacted with the oxygen in the chemical reaction, to said fuel cell through said off-gas recirculating line, said ejector vacuum pump being designed to be controllable of an amount of the off-gas recirculated, working to mix the off-gas flowing through said off-gas recirculating line with the hydrogen gas flowing through said hydrogen supply line to output a mixture gas to said fuel cell; an output demand determining circuit working to determine a demand for output of the electrical energy from said fuel cell; a pressure sensor working to measure an output pressure of said ejector vacuum pump; and a controller working to determine the amount of the off-gas to be recirculated through said ejector vacuum pump as a function of the demand for output of the electrical energy determined by said output demand determining circuit, said controller also regulating an open area of an outlet of said ejector vacuum pump based on the output pressure measured by said pressure sensor to control the amount of the off-gas recirculated through said ejector vacuum pump.