| 摘要 |
PURPOSE:To make an on-off valve mechanism closable so speedily in time of antilock control, by making a cross section of a first piston smaller than that of a second piston as far as the degree that proportional decompression action is produced in the on-off valve mechanism is avoidable. CONSTITUTION:A first piston 17 is slidingly fitted in a first cylinder part 15 while a second piston 22, having a slightly larger cross section A2 than a cross section A1 of the first piston 17, is slidingly fitted in a second cylinder part 16. And, in a partition wall 9, there is provided with a first valve mechanism 53 which interconnects and intercepts an interval between an input hydraulic chamber 18 and an output hydraulic chamber 23, and a second valve mechanism 61 is installed in a piston rod 33. According to this method, in time of antilock control, a valve body 56 is situated in a position proximate to a valve seat 59 so that the first valve mechanism 53 is closed as quick as possible, and a wheel speed in time of antilock control starting slowly comes down, thus accurate antilock control takes place.
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