To provide a traveling speed switch system that can strike a balance between the proper speed setting and the travel covering ability, in a hydraulic driving device having an LS system.
This travel two-speed switch device 60 includes a valve device 61 and makes the high-speed setting and the low-speed setting for travel motors 2 and 3. The setting is made by setting, as a target compensation differential pressure of pressure compensation valves 12 and 13 that relates to travel motors 2 and 3, selectively either the differential pressure between the discharge pressure of a hydraulic pressure pump 1 and the maximum load pressure of a plurality of actuators 2 to 6 or a value lower than the differential pressure. The valve device 61 incorporates a pressure-reducing valve 62. The valve 62 limits the flow of pressure oil of hydraulic oil lines 63a and 63b by restrictions 61a and 61c and releases part of the hydraulic oil of the hydraulic oil line 63a via restrictions 61a and 61c. The valve device 61 can switch the flow of the hydraulic lines 63a and 63b between the open position where the flow of the hydraulic oil of the hydraulic lines 63a and 63b and the position where the valve 62 functions. The switch is controlled by a solenoid 64.
KANAI TAKASHI
KAWAMOTO JUNYA
