| 摘要 |
PURPOSE:To maintain perfect sealing even if the temperature change is repeated, by inserting a soft metal sealing member into between a metal member and a ceramics member and attaching a sealing assisting member for offsetting the thermal expansion of metal onto the sealing member. CONSTITUTION:A ceramics valve seat 1B is constituted by inserting a soft metal ring 6 between a gas casing 5 which contacts the valve seat 1B and a standing base and installing a cylindrical sealing assisting member 7 consisting of an invar behind the metal ring 6. When stainless steel is used for metal member, Fe-Ni alloy having a low expansion rate is suitably used for the sealing assisting member. Though thermal expansion is generated in each part, and the expanded sealing material is introduced into the expanded sealing gap, and sealing is maintained, sealing material is introduced also into the generated gap, since the thermal expansion of the assisting material 7 is small, and the swelling-out rate into the parts between the ceramics valve seat 1B, metal member 5, and a member 8 is little. Therefore, the deformation applied onto the sealing member is small, and the sealing of the ceramics valve seat can be perfectly maintained for a long period.
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