| 摘要 |
PROBLEM TO BE SOLVED: To make a sliding characteristic of a fixing valve element and a movable element in a good condition, prevent change even if a device is used for a long time, sufficiently improve durability, and reduce costs by forming at least one of sliding contact surface by a ceramic body including compound oxide expressed in a specified chemical formula. SOLUTION: At least one of sliding contact surface of a fixing valve element and a movable valve element is formed of a ceramic body including zinc compound expressed in a chemical formula of ZnO.nAl2O3. The zinc compound is formed as a needle shaped compound oxide whose average aspect ratio is 3 or more and which is formed by temporarily burning serving a composition ratio of zinc oxide(ZnO) and aluminum oxide (nAl2O3)as 1:1 or more. The ceramic body includes zinc aluminate (nAl2O3). A main component of the ceramic body comprises ceramic oxide, and thereby, formability is facilitated, and manufacture is performed in low costs.
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