| 摘要 |
PROBLEM TO BE SOLVED: To facilitate the machining of an exhaust passage and to stabilize braking performance with respect to the temperature change of pressure oil. SOLUTION: An exhaust passage 17 is composed of a large diameter passage 18 for communicating a hydraulic chamber 11 and a drain chamber 3 with each other by a large passage area, and a restriction portion 19 provided in a position opposite the hydraulic chamber 11 and having a smaller passage area compared with the large diameter passage 18. Accordingly, the large diameter passage 18 is bored by using a large-diameter drill, the restriction portion 19 having a small longitudinal dimension in an axial direction is bored by a small-diameter drill, and the machining of the exhaust passage 7 is facilitated. Also, since the restriction portion 19 is set as a thin blade orifice, braking performance with respect to the temperature change of hydraulic oil is stabilized. Further, since the restriction portion 19 is provided in the position opposite the hydraulic chamber 11, even if the restriction portion 19 is clogged by a foreign object in the pressure oil, the foreign object is dropped into the hydraulic chamber and removed while a motor is stopped.
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