| 摘要 |
PURPOSE:To enable an exact depressure-proportional-control according to the carrying condition of a vehicle by, on the basis of the non-occurrence or occurrence of a predetermined pressure step and a predetermined reference decelerated-speed at a time of braking, making a depressure control through making brake pressure toward a brake operating device vary step by step. CONSTITUTION:A tube passage 3 connected to an output port on one side of a brake valve 1 is made to branch off to tube passages 3a, 3b, and is connected to a rear wheel cylinder through a multi-step control valve 4 and an air-over hydraulic booster 5 along on the side of the tube passage 3a, and electromagnetic selector valves 7, 8 are connected to the tube passage 3b. The multi-step control valve 4 is so constituted as to have the first and second control chambers 23, 24 which are partitioned by putting slidably a step piston 16 in a step hole 15 in the mainbody 14, and is so provided as to have a depressure control done step by step through controlling the supply of liquid pressure to each control chamber 23, 24 by electromagnetic selector valves 7, 8. And electromagnetic selector valves 7, 8 control by means of a control device according to the output of a decelerated-speed detector and a brake pressure detector 11.
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