Patent ID: 9175456
Filing Date: 2015-11-03
Classification: B66F,E02F,F15B

Abstract:
1. A hydraulic control device for a working vehicle comprising: a hydraulic pump constituting a hydraulic source for said working vehicle together with a tank; at least one or more hydraulic actuators driven by pressurized oil discharged from said hydraulic pump; a directional control valve for controlling switching of the pressurized oil to be supplied to said hydraulic actuator from said hydraulic pump; a pair of main lines for establishing connection between said directional control valve and said hydraulic actuator; an accumulator connected via one communication line branched from one main line out of said pair of said main lines to said hydraulic actuator to absorb pressure pulsations generated in said hydraulic actuator; and a pulsation absorption control valve provided in the halfway point of said one communication line to establish or block communication between said hydraulic actuator and said accumulator, wherein said directional control valve is arranged in the halfway point of a center bypass line for connecting said hydraulic pump to said tank to control switching of said pair of said main lines together with said center bypass line, wherein said one main line out of said pair of said main lines is connected to said one communication line in a position between said directional control valve and said pulsation absorption control valve, and said other main line is connected to said other communication line which is communicated with or blocked off from said tank through said pulsation absorption control valve, wherein said pulsation absorption control valve is arranged in the halfway position of said center bypass line to be adjacent to said directional control valve and includes a plurality of switching positions for establishing or blocking communication of said one communication line positioned between said one main line and said accumulator and for establishing or blocking communication of said other communication line positioned between said other main line and said tank, wherein a bypass passage is provided between said hydraulic actuator and said accumulator for establishing communication therebetween even when said pulsation absorption control valve is in either one of said switching positions, wherein said bypass passage is provided with a switching valve for blocking the communication between said hydraulic actuator and said accumulator by said bypass passage when a pressure in the side of said hydraulic actuator exceeds a predetermined set pressure, and wherein said switching valve is provided inside said pulsation absorption control valve.