| 摘要 |
<p>PURPOSE:To suppress the deformation such as a bite of a valve seal by forming a metal seal part at a valve stem, and forming the metal seal part in such a way as to close a communicating passage from the time before the adhesion of a valve seal to the piston seal face until the separation of the valve seal. CONSTITUTION:In valve mechanism 6, a pressure chamber 3 and a makeup chamber 4 separated by a piston 2 can be communicated with each other by an elongated hole 12 and a communicating passage 5, and a valve seal 7 is fitted to the pressure chamber 3 side protruding part of a valve stem 13 inserted through the communicating passage 5. A metal seal part 8 fitted into the communicting passage 5 is formed at the side end part of a stem seat face 14 formed at the valve stem 13. The metal seal part 8 closes the communicating passage 5 from the time before the adhesion of the valve seal 7 to the piston seal face 15 at the advance time of the piston 2 until both seals 7, 15 are spaced at the return time of the piston 2. The fluid pressure change inside and outside of the valve seal 7 becomes small, so that the valve seal 7 is not deformed by residual pressure and temporary pressure rise.</p> |
