| 摘要 |
PURPOSE:To prevent the fluttering of a door by generating a large damping force in the vicinity of the perfect opening position of the door by installing a magnetic strain member for varying the passage area of a communication passage through extension and contraction and installing a magnet which is approached to the magnetic strain member by the slide of a piston. CONSTITUTION:When a door comes close to a perfect closure position, a magnetic strain member 18 approaches a permanent magnet 20 by the extension of a rod 10. Then, the magnetic strain member 18 is extended against the springy force of a spring 19 by the magnetic field of the permanent magnet 20, and a ring valve 16 is slidingly moved to close an opened port 15a, and a communication passage 15 is closed. Accordingly, a large damping force is generated by reducing the passage area by closing a part of a passage for the communication between the upper chamber 8a of e cylinder and the lower chamber 8b. Since the large damping force is generated in the vicinity of the perfect opening position of the door, the spring back of the door is prevented, and the fluttering of the door is prevented. Further, when the door is closed and the magnetic strain member 18 separates from the permanent magnet 20, the magnetic strain member is contracted, and the opened port part 15a is opened again. |
