PURPOSE: To eliminate a phase difference between the gas pressure fluctuation of primary side and the same fluctuation of secondary side surely and prevent the vibration of diaphragms for a regulating valve by a method wherein a secondary gas displacement chamber, communicated with a gas outflow path, and second air chamber, communicated with atmosphere through second diaphragm, are provided in the regulator.

CONSTITUTION: A valve port 3 is provided on the way of a gas path in the main body A of pressure regulator, having the gas inlet port 1 at one end and the gas outlet port 2 at the other end thereof, while an gas inflow path 4 and the gas outflow path 5 are provided through the valve port 3. The gas inflow path 4 is provided with the diaphragm 7, energized at all times by a spring 6, while first air chamber 9, communicated with atmosphere through a small hole 8, is defined and formed by the diaphragm 7. The regulating valve 10, which changes the opening degree thereof in conjunction with the movement of the diaphragm 7, is provided at the valve port 3. Further, the secondary gas displacement chamber 12, communicated with the gas outflow path 5 through the second small hole 11, is provided at the side of the gas outflot path 5. The secondary gas displacement chamber 12 is separated from the second air chamber 15, communicated with the atmosphere through the third small hole 14, by the second diaphragm 13.