Kawasaki Jukogyo Kabushiki Kaisha

Caterpillar Sarl

Masahiro Ohira

Yoshiyuki Tode

Hideki Nakajima

Seiji Aoki

A hydraulic drive apparatus includes a hydraulic pump that discharges a working fluid; a flow dividing valve that divides a pump passage connected to the hydraulic pump into first and second passages, and changes an opening degree of each passage according to a signal that is input to the flow dividing valve; a travel system hydraulic circuit that is connected to the first passage and controls a flow of the working fluid to a travel motor; a loading system hydraulic circuit that is connected to the second passage and controls a flow of the working fluid to a loading actuator; a pressure sensor that detects a pressure supplied to the travel motor; and a control device that controls, by outputting the signal to the flow dividing valve, the opening degree of the first and second passages according to the pressure detected by the pressure sensor.

Hydraulic drive apparatus

Each of left and right direction switching valves includes: a pump port connected to a pump; a first compensation port connected to an upstream side of a corresponding pressure compensation valve; a second compensation port connected to a downstream side of the corresponding pressure compensation valve; a pair of supply/discharge ports connected to a corresponding travel motor; and a communication port. The communication ports of the left and right direction switching valves are connected by a communication line. When a spool shifts from a neutral position by the travel operation device, the pump port communicates with the first compensation port and the second compensation port communicates with one of the supply/discharge ports and the communication port. Each direction switching valve is configured wherein a degree of communication between the second compensation port and communication port increases in a shifting amount of the spool from the neutral position.

Hydraulic circuit of construction machine

A hydraulic circuit of a construction machine includes: a first pump line that connects a delivery port of a pump to a pump port of a first direction-switching valve; a second pump line that is branched off from the first pump line and is connected to a pump port of a second direction-switching valve; and a priority valve provided on the second pump line. The priority valve is configured to: fully open the second pump line when a pressure difference between a delivery pressure of the pump and a load pressure of a first actuator is greater than a setting value; and decrease an opening degree of the second pump line in accordance with decrease in the pressure difference when the pressure difference is less than the setting value.

Growing community of inventors

Kobe, Japan

Masahiro Ohira