Electronically controlled regulator

An electronically controlled regulator comprising, inside a body formed with an introduction port and a discharge port, a pressure regulating valve including:

• a valve shaft that is coaxially disposed with a valve body on an outer peripheral portion at a middle position in a longitudinal direction and is able to reciprocate in an axial direction;
• a valve seat having a seat face capable of being in close contact with the valve body;
• and a discharge pressure regulating unit that regulates a pressure of a fluid by causing the valve shaft to reciprocate through driving of an electric motor electronically controlled to change a distance between the valve body and the valve seat, a high-pressure fluid introduced from the introduction port being discharged from the discharge port as a depressurized fluid at a set pressure on a side of a discharge pressure chamber while being depressurize and regulated by the pressure regulating valve, wherein:
• an inner portion of the body is sectioned into (i) a high-pressure chamber communicating with the introduction port, (ii) the discharge pressure chamber communicating with the discharge port, (iii) a pressure control chamber accommodating the electric motor, and (iv) an atmospheric pressure chamber communicating with atmospheric air;
• a proximal end side of the valve shaft is supported in a state of being inserted into a cylindrical support hole having a communication hole communicating with the atmospheric air;
• and
• a seat diameter of the valve seat as a boundary between the high-pressure chamber and the discharge pressure chamber, a first seal diameter of a first seal member on an atmospheric pressure chamber side as a boundary between the high-pressure chamber and the atmospheric pressure chamber, and a second seal diameter of a second seal member on a pressure control chamber side as a boundary between the discharge pressure chamber and the pressure control chamber are substantially the same.