Hydraulic drive system of construction machine

Patent metadata

Field	Value
Publication number	US-10370825-B2
Application number	US-201615573497-A
Country	US
Kind code	B2
Filing date	Apr 28, 2016
Priority date	May 11, 2015
Publication date	Aug 6, 2019
Grant date	Aug 6, 2019

Abstract

Pump controller: when operation device receives neither first or second operation, outputs standby rotation speed as command rotation speed to engine controller, standby rotation speed being lower than selected reference rotation speed; when operation device receives first operation, changes command rotation speed from standby rotation speed to first target rotation speed in such a manner that as an amount of first operation increases, increasing rate of command rotation speed decreases gradually; when operation device receives second operation, changes command rotation speed from standby rotation speed to second target rotation speed in such a manner that as an amount of second operation increases, increasing rate of command rotation speed increases gradually; and feeds command current to a solenoid proportional valve that outputs secondary pressure to regulator that adjusts tilting angle of a pump, such that a discharge flow rate of the pump is proportional to amount of first and second operation.

First claim

The invention claimed is:

1. A hydraulic drive system of a construction machine, the hydraulic drive system comprising:
an operation device that receives a first operation for moving an actuator in a first direction and receives a second operation for moving the actuator in a second direction, in which a load on the actuator is lower than the load on the actuator moved in the first direction;
a variable displacement pump that supplies hydraulic oil to the actuator and that is driven by an engine;
a solenoid proportional valve that outputs a secondary pressure corresponding to a command current;
a regulator that adjusts a tilting angle of the pump in accordance with the secondary pressure outputted from the solenoid proportional valve;
an engine controller that controls a fuel injector of the engine;
a rotation speed selector that receives a selection of a reference rotation speed of the engine; and
a pump controller that outputs a command rotation speed to the engine controller and feeds the command current to the solenoid proportional valve, wherein
the pump controller:
when the operation device receives neither the first operation nor the second operation, outputs a standby rotation speed as the command rotation speed, the standby rotation speed being lower than the selected reference rotation speed;
when the operation device receives the first operation, changes the command rotation speed from the standby rotation speed to a first target rotation speed lower than or equal to the selected reference rotation speed in such a manner that as an amount of the first operation increases, an increasing rate of the command rotation speed decreases gradually;
when the operation device receives the second operation, changes the command rotation speed from the standby rotation speed to a second target rotation speed lower than or equal to the selected reference rotation speed in such a manner that as an amount of the second operation increases, the increasing rate of the command rotation speed increases gradually; and
feeds the command current to the solenoid proportional valve, such that a discharge flow rate of the pump is proportional to the amount of the first operation and the amount of the second operation.

2. The hydraulic drive system of a construction machine according to claim 1 , wherein
the actuator is at least one of a boom cylinder, an arm cylinder, and a bucket cylinder.

3. The hydraulic drive system of a construction machine according to claim 2 , wherein
the second target rotation speed is lower than the first target rotation speed.

4. The hydraulic drive system of a construction machine according to claim 3 , wherein
the pump controller feeds the command current to the solenoid proportional valve, such that a maximum value of the tilting angle of the pump when the amount of the first operation is at its maximum is the same as a maximum value of the tilting angle of the pump when the amount of the second operation is at its maximum.

5. The hydraulic drive system of a construction machine according to claim 1 , wherein
the second target rotation speed is lower than the first target rotation speed.

6. The hydraulic drive system of a construction machine according to claim 5 , wherein
the pump controller feeds the command current to the solenoid proportional valve, such that a maximum value of the tilting angle of the pump when the amount of the first operation is at its maximum is the same as a maximum value of the tilting angle of the pump when the amount of the second operation is at its maximum.

Assignees

• Kawasaki Heavy Ind Ltd

Inventors

• Kondo Akihiro
• Muraoka Hideyasu

Classifications

• F02D41/3005

  Details not otherwise provided for · CPC title

• F15B2211/20523

  Internal combustion engine · CPC title

• F15B13/0442

  with proportional solenoid allowing stable intermediate positions · CPC title

• E02F3/32

  working downwardly and towards the machine, e.g. with backhoes · CPC title

• F15B2211/6346

  representing a state of input means, e.g. joystick position · CPC title