Patent ID: 7919211

Claim:
An on-board fuel cell system adapted to be installed on a motor vehicle, comprising: a hydrogen-gas storage device including a hydrogen-gas absorbing alloy capable of absorbing or releasing a hydrogen gas; a fuel cell that is supplied with the hydrogen gas discharged from the hydrogen-gas storage device, so as to generate electric power, while discharging a remaining portion of the hydrogen gas; a first passage that connects an outlet of the hydrogen-gas storage device with an inlet of the fuel cell, and allows the hydrogen gas discharged from the hydrogen-gas storage device to flow therethrough to be supplied to the fuel cell; a second passage that connects an outlet of the fuel cell with a first point in the first passage, and allows the hydrogen gas discharged from the fuel cell to flow therethrough to be returned to the first passage; a pump that is disposed in the second passage, and is operable to force the hydrogen gas in the second passage to flow toward the first point in the first passage; a third passage that connects a second point located in the first passage between an outlet of the hydrogen-gas storage device and the first point, with a third point located in the second passage between the outlet of the fuel cell and the pump, the third passage allowing the hydrogen gas diverting from the first passage to flow therethrough to be fed to the second passage; a first valve that is disposed in the first passage between the second point and the first point, and is able to permit and inhibit flow of gas therethrough upon opening and closing thereof, respectively; a second valve that is disposed in the second passage between the outlet of the fuel cell and the third point, and is able to permit and inhibit flow of gas therethrough upon opening and closing thereof, respectively; a third valve that is disposed in the third passage, and is able to permit and inhibit flow of gas therethrough upon opening and closing thereof, respectively; and a controller that controls the pump and the first, second and third valves, wherein: when a pressure of the hydrogen gas discharged from the hydrogen-gas storage device is higher than a reference pressure, the controller opens the first and second valves and closes the third valve, so that the hydrogen gas discharged from the hydrogen-gas storage device is supplied to the fuel cell through the first passage, and the hydrogen gas discharged from the fuel cell is returned to the first passage through the second passage, with the pump circulating the hydrogen gas; and when the pressure of the hydrogen gas discharged from the hydrogen-gas storage device is lower than the reference pressure, the controller closes the first and second valves and opens the third valve, and causes the pump to draw the hydrogen gas out of the hydrogen-gas storage device and feed the hydrogen gas from the first passage to the second passage through the third passage, so that the hydrogen gas is supplied from the second passage to the fuel cell through the first passage.