Patent ID: 7028706

Claim:
A gas decompression device which decompresses gas to be supplied to a fuel cell in fuel cell system, the gas decompression device comprising: a body which includes an inlet, an outlet, and an internal space; a diaphragm which divides the internal space into a measuring room and a back pressure room; a valve seat which is provided for the measuring room and arranged between the inlet and the outlet; a valve body which is provided for the valve seat and interlocked with the diaphragm; working pressure supply means which supplies working pressure to the back pressure room; a pressure control spring which urges the diaphragm in a direction to make the valve body separate from the valve seat; working pressure adjust means which adjusts working pressure to be supplied to the back pressure room; gas flow rate detect means which detects flow rate of gas from the outlet or a value corresponding to the flow rate; stop detect means which detects a stop of the fuel cell system, wherein the control means controls the working pressure adjust means so as to lower the working pressure to atmospheric pressure level when a stop of the fuel cell system is detected by the stop detect means; and control means which controls the working pressure adjust means so as to adjust the working pressure depending on the flow rate or the value corresponding to flow rate detected by the gas flow rate detect means, wherein the diaphragm is displaced in a direction to make the valve body come close to the valve seat when gas pressure works on the measuring room side of the diaphragm, the diaphragm is displaced in a direction to make the valve body separate from the valve seat when working pressure works on the back pressure room side of the diaphragm, and gas flowing in the measuring room through the inlet and out from the outlet is decompressed by such that collaboration of at least the diaphragm and the pressure control spring makes the valve body move with reference to the valve seat.