Hydraulic drive device for cargo handling vehicle

A hydraulic drive device for cargo handling vehicle provided with a plurality of hydraulic cylinders including an up-and-down hydraulic cylinder for moving an object up and down with supply and discharge of hydraulic oil, and a plurality of manual control members including an up-and-down control lever configured so as to actuate the up-and-down hydraulic cylinder, the hydraulic drive device comprising:

• a tank reserving the hydraulic oil;
• a hydraulic pump having an inlet port for drawing in the hydraulic oil and an outlet port for discharging the hydraulic oil;
• an electric motor for driving the hydraulic pump;
• a first oil passage connecting the tank and the inlet port;
• a second oil passage connecting the outlet port and the plurality of hydraulic cylinders;
• a third oil passage branching off from the first oil passage and connecting the first oil passage and a bottom chamber of the up-and-down hydraulic cylinder;
• a solenoid-controlled proportional valve disposed on the third oil passage and configured to open with a valve travel depending upon a control input of a descent control of the up-and-down control lever;
• a pressure compensation valve disposed between a branch portion of the third oil passage and the tank on the first oil passage and configured to open with a valve travel depending upon a pressure difference between pressures upstream and downstream of the solenoid-controlled proportional valve on the third oil passage;
• a directional control valve disposed between the pressure compensation valve and the tank on the first oil passage and configured to be switched between an open position and a close position;
• and
• a controller configured to control the solenoid-controlled proportional valve and the directional control valve.