To prevent the seal surface of a valve element from becoming a condition stuck on a valve seat by carrying out non-sticky coating on the valve seat.
A gas flow-in chamber 33, a gas flow-out chamber 34, and a valve seat 35 on which a valve hole 35a for communicating both chambers 33, 34 with each other is arranged, are formed on a valve cabinet 30, and a valve element 31 and a needle 32 are stored in the gas flow-in chamber 33. Non-sticky coating is carried out on the valve seat 35. The non-sticky coating is carried out by coating, for example, fluorocarbon resin such as Teflon on the valve seat 35. In the case where non-sticky coating is applied on the valve seat 35, fluorocarbon resin liquid is sprayed from a nozzle N into the valve cabinet 30 after the valve cabinet 30 is degreased, and then the fluorocarbon resin is heated and cured At this time, fluorocarbon resin is coated on not only the valve seat 35 but also the inside of a guide cylinder 37. Even if the seal surface of the valve element 31 is brought into push-contact with the valve seat 35 for a long time, the seal surface is not kept stick on the valve seat 35, and a gas passage is ensured surely in the case where an overturning condition is released.
ITOU YOSHIYASU
ONO MASAFUMI
