To reduce the overall size of a hydraulic damper for vibration control by controlling the flow of working fluid between a first working chamber and a second working chamber by means of a single pilot-operated stop valve.
A pilot-operated stop valve 21 has in a valve body 47, a small-diameter hole 77 and a large-diameter hole 79 connected via a valve seat 81. A main valve element 51 with a seat surface 83 seated on the valve seat 81 is slidably fitted in the large-diameter hole 79. The small-diameter hole 77 and the large-diameter hole 79 are connected to a first working chamber 15 and a second working chamber 17 respectively At the back of the main valve element 51, an acting chamber 85 is formed, which is connected to the low-pressure side by a pilot passage 75 in which a pilot valve 55 is interposed. The main valve element 51 has a first pressure receiving surface S1 and a second pressure receiving surface S2 for respectively receiving the pressures of working fluid in the small-diameter hole 77 and the large-diameter hole 79 in the unseated direction. A restriction 61 and a first check valve 65 are interposed in series in a first connecting passage 62 connecting the small-diameter hole 77 and the acting chamber 85. A restriction 63 and a second check valve 67 are interposed in series in a second connecting passage 64 connecting the large-diameter hole 79 and the acting chamber 85.
SAKAI MITSUO
FUJISAKA MASAHIRO
KOTAKE YUJI
KURINO HARUHIKO
HITACHI METALS TECHNO LTD
KAJIMA CORP