Hydraulic drive device for cargo handling vehicle
First Claim
1. A hydraulic drive device for a 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,wherein, while the descent control of the up-and-down control lever is performed, the directional control valve is configured to be placed in the open position, unless the descent control of the up-and-down control lever is performed singly and a difference between a command rotation rate and an actual rotation rate of the electric motor is less than a predetermined value; and
a controller configured to control the solenoid-controlled proportional valve and the directional control valve.
1 Assignment
0 Petitions
Accused Products
Abstract
A hydraulic drive device for cargo handling vehicle has: a tank; a pump for drawing in a hydraulic oil from the tank and supplying the hydraulic oil to hydraulic cylinders; an electric motor for driving the pump; a solenoid-controlled proportional valve disposed between an inlet port of the pump and a bottom chamber of an up-and-down hydraulic cylinder and configured to open with a valve travel depending upon a control input of a descent control of an up-and-down control member; a pressure compensation valve disposed between a branch portion located between the pump and the solenoid-controlled proportional valve and the tank and configured to open with a valve travel depending upon a pressure difference between pressures upstream and downstream of the solenoid-controlled proportional valve; and a valve disposed between the pressure compensation valve and the tank and configured to be switched between an open position and a close position.
8 Citations
7 Claims
-
1. A hydraulic drive device for a 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, wherein, while the descent control of the up-and-down control lever is performed, the directional control valve is configured to be placed in the open position, unless the descent control of the up-and-down control lever is performed singly and a difference between a command rotation rate and an actual rotation rate of the electric motor is less than a predetermined value; and a controller configured to control the solenoid-controlled proportional valve and the directional control valve. - View Dependent Claims (2, 3, 4, 5, 6, 7)
-
Specification