| 摘要 |
PURPOSE:To prevent separation, cracks due to the repetition of thermal stress and the like from occurring by a structure wherein a buffler layer consisting of epoxy resin composition, the volumetric shrinkage of which is small and at the same time the difference between the thermal expansion coefficient of ceramic and that of which is small, is arranged between a ceramic part and a molded resin outer tube. CONSTITUTION:An outer tube 21, which is molded of epoxy resin or the like in advance, sheathes the ceramic outer tube 1 of a vacuum valve with a proper gap between the outer periphery of the tube 1 and the inner periphery of the tube 2. A resin buffer layer 3 is formed in the gap by pouring epoxy resin composition in the gap integrating them by heating and hardening the resin. Liquid epoxy resin composition to form the buffer layer 3 consists of inorganic powder such as silica, alumina or the like, milled fibers such as glass, alumina or the like, hardening agent and coloring agent. Because the epoxy resin composition contains a large quantity of inorganic powder and milled fibers, its volumetric shrinkage during hardening reaction is small. At the same time, the thermal expansion coefficient of the epoxy resin composition is nearly equal to that of ceramic. Accordingly, the influence of thermal stress due to the thermal expansion coefficients of the ceramic outer tube and of the epoxy resin outer tube on the change of temperature becomes smaller, resulting in preventing separation and cracks from occurring. |
