| 摘要 |
PURPOSE:To contrive to lessen pedal operating force and to speed up the response by a structure wherein, when the working fluid pressure at oil pressure source is higher than the predetermined working fluid pressure, a hydraulic piping to engage a clutch through a back pressure valve is communicated to the oil pressure source, while, when lower, said piping is communicated to a reservoir. CONSTITUTION:An oil hydraulic pipe 5a in the delivery side of an oil hydraulic pump 5 is connected on one hand to the displacement chamber 1f of an oil hydraulic actuator 2 through a back pressure valve 8, an oil hydraulic directional control valve 3 and an oil hydraulic pipe 3a and on the other hand to the displacement chamber 1e of the oil hydraulic actuator 2 through a pressure control circuit 4 and an oil hydraulic pipe 7a. Further, the oil hydraulic pipe 7a is connected through a back pressure valve 7 to a reservoir 5d. Furthermore, an unloader valve 6 is interposed between the oil hydraulic pipes 5a and 7a. One pilot pipe 5c of the oil hydraulic directional control valve 3 is communicated to the oil hydraulic pipe 5a, while the other pilot pipe 7b of the valve 3 is communicated to the oil hydraulic pipe 7a. |
