| 摘要 |
PROBLEM TO BE SOLVED: To return an intermediate member to a required level by utilizing inversion of pressure during stroke when the intermediate member of a multistage shock absorber deviates off the required level. SOLUTION: When the rod 4 of a small diametral unit 1 is advanced/retreated to/from a cylindrical body 3, hydraulic fluid flows between an expansion chamber 8 and the contraction chamber 17 of a large diametral unit 2 through a hole 3a by the volume part of the advance/ retreat of the rod 4 to/from the cylindrical body 3. Hydraulic fluid flow makes a piston 15 and the cylindrical body 3 advance/retreat to/from a cylindrical body 11, and the volumetric change of an expansion chamber 16 at this time is absorbed by gas in an auxiliary chamber 14. Load is supported by differential pressure between lower side hydraulic pressure PL and upper side hydraulic pressure PU, and in a relation of pressure receiving area, PL becomes smaller than PU, thus the piston 15 and the cylindrical body 3 are lifted by leakage from the chamber 17 to the chamber 16. However, during stroke, PL may become larger than PU by damping force. At this time, a communicating passage 21 and a check valve 22 make hydraulic fluid return from the chamber 16 to the chamber 17 so as to lower the piston 15 and the cylindrical body 3 toward their original positions. When the piston 15 is returned to a position to close the lower opening 21a of the communicating passage 21, the above returning of hydraulic fluid is not performed, and a level at this time is retained.
|
