| 摘要 |
PURPOSE: To improve reliability at trouble of an antilocking system in which a pressure modulator is interposed in a front axle brake system by connecting a bypass piping detouring the pressure modulator to the front axle brake system, and controlling a bypass valve in the piping according to the pressure of an auxiliary pressure source. CONSTITUTION: Within front axle and rear axle respective brake systems extending from two outlet pressure spaces 18, 19 of a tandem main cylinder 14, the front axle brake system is provided with a pressure modulator 21, a drive pressure space 44 defined in a casing 22 can be selectively connected to the pressure outlet 47 of a hydraulic auxiliary pressure source held in high pressure level through an ABS control valve 46. Further the front axle brake system is connected to a bypass piping detouring the pressure modulator 21 through check valves 53, 54, and a bypass valve 101 is interposed on the way. When the outlet pressure of an auxiliary pressure source 48 is lowered under the minimum prescribed value at antilocking control, the valve 101 is controlled so as to return to the release position.
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