Hydraulic drive system of construction machine

Patent metadata

Field	Value
Publication number	US-10294633-B2
Application number	US-201515513727-A
Country	US
Kind code	B2
Filing date	Oct 9, 2015
Priority date	Oct 10, 2014
Publication date	May 21, 2019
Grant date	May 21, 2019

Abstract

A bi-directional pump connected to a motor by a pair of supply/discharge lines; a regulator changes the bi-directional pump tilting angle; and a controller controls the regulator based on a turning signal outputted from a turning operation valve. At the turning acceleration, at which the signal increases, the controller calculates a motor flow rate passing through the motor and an instruction flow rate determined based on the turning signal. If the instruction flow rate is greater than a reference flow rate obtained by adding a predetermined value to the motor flow rate, the controller controls the regulator so the bi-directional pump tilting angle is adjusted to a tilting angle realizing the reference flow rate. If the instruction flow rate is not greater than the reference flow rate, the controller controls the regulator so the bi-directional pump tilting angle is adjusted to a tilting angle realizing the instruction flow rate.

First claim

The invention claimed is:

1. A hydraulic drive system of a construction machine, comprising:
a turning motor;
a variable displacement bi-directional pump connected to the turning motor by a pair of supply/discharge lines, such that a closed loop is formed;
a bridging passage connecting the pair of supply/discharge lines to each other and provided with a pair of relief valves that are directed opposite to each other;
a regulator that changes a tilting angle of the bi-directional pump;
a turning operation valve that receives a turning operation and outputs a turning signal whose magnitude corresponds to an amount of the turning operation; and
a controller that controls the regulator based on the turning signal outputted from the turning operation valve, wherein
at a time of turning acceleration, at which the turning signal increases, the controller calculates a motor flow rate passing through the turning motor and an instruction flow rate determined based on the turning signal,
if the instruction flow rate is greater than a reference flow rate obtained by adding a predetermined value to the motor flow rate, the controller controls the regulator such that the tilting angle of the bi-directional pump is adjusted to a tilting angle that realizes the reference flow rate, and
if the instruction flow rate is not greater than the reference flow rate, the controller controls the regulator such that the tilting angle of the bi-directional pump is adjusted to a tilting angle that realizes the instruction flow rate.

2. The hydraulic drive system of a construction machine according to claim 1 , further comprising a supply pump coupled to the bi-directional pump, the supply pump supplying hydraulic oil to an actuator different from the turning motor, wherein
at a time of turning deceleration, at which the turning signal decreases, the controller calculates a motor flow rate passing through the turning motor and an instruction flow rate determined based on the turning signal,
if the instruction flow rate is less than a reference flow rate obtained by subtracting a predetermined value from the motor flow rate, the controller controls the regulator such that the tilting angle of the bi-directional pump is adjusted to a tilting angle that realizes the reference flow rate, and
if the instruction flow rate is not less than the reference flow rate, the controller controls the regulator such that the tilting angle of the bi-directional pump is adjusted to a tilting angle that realizes the instruction flow rate.

3. The hydraulic drive system of a construction machine according to claim 1 , wherein
the bi-directional pump is a swash plate pump whose swash plate is tiltable from a center to both sides,
the regulator includes:
a servo mechanism including a servo piston coupled to the swash plate of the bi directional pump, a first chamber operable to apply hydraulic pressure to one end of the servo piston, and a second chamber operable to apply hydraulic pressure to another end of the servo piston; and
a switching valve including a first solenoid and a second solenoid, the switching valve being configured to lead hydraulic oil to the first chamber when an electric current is fed to the first solenoid, and lead hydraulic oil to the second chamber when an electric current is fed to the second solenoid, and

the controller feeds an electric current to the first solenoid or the second solenoid at a time of turning acceleration, at which the turning signal increases, the electric current corresponding to the reference flow rate or the instruction flow rate.

4. The hydraulic drive system of a construction machine according to claim 3 , further comprising a charge pump operable to replenish the pair of supply/discharge lines with hydraulic oil, wherein
the switching valve leads the hydraulic oil discharged from the charge pump to the first chamber or the second chamber when the electric current is fed to the first solenoid or the second solenoid.

5. A hydraulic drive system of a construction machine, comprising:
a turning motor;
a variable displacement bi-directional pump connected to the turning motor by a pair of supply/discharge lines, such that a closed loop is formed;
a supply pump coupled to the bi-directional pump, the supply pump supplying hydraulic oil to an actuator different from the turning motor;
a bridging passage connecting the pair of supply/discharge lines to each other and provided with a pair of relief valves that are directed opposite to each other;
a regulator that changes a tilting angle of the bi-directional pump;
a turning operation valve that receives a turning operation and outputs a turning signal whose magnitude corresponds to an amount of the turning operation; and
a controller that controls the regulator based on the turning signal outputted from the turning operation valve, wherein
at a time of turning deceleration, at which the turning signal decreases, the controller calculates a motor flow rate passing through the turning motor and an instruction flow rate determined based on the turning signal,
if the instruction flow rate is less than a reference flow rate obtained by subtracting a predetermined value from the motor flow rate, the controller controls the regulator such that the tilting angle of the bi-directional pump is adjusted to a tilting angle that realizes the reference flow rate, and
if the instruction flow rate is not less than the reference flow rate, the controller controls the regulator such that the tilting angle of the bi-directional pump is adjusted to a tilting angle that realizes the instruction flow rate.

6. The hydraulic drive system of a construction machine according to claim 5 , wherein
the bi-directional pump is a swash plate pump whose swash plate is tiltable from a center to both sides,
the regulator includes:
a servo mechanism including a servo piston coupled to the swash plate of the bi directional pump, a first chamber operable to apply hydraulic pressure to one end of the servo piston, and a second chamber operable to apply hydraulic pressure to another end of the servo piston; and
a switching valve including a first solenoid and a second solenoid, the switching valve being configured to lead hydraulic oil to the first chamber when an electric current is fed to the first solenoid, and lead hydraulic oil to the second chamber when an electric current is fed to the second solenoid, and

the controller feeds an electric current to the first solenoid or the second solenoid at a time of turning deceleration, at which the turning signal decreases, the electric current corresponding to the reference flow rate or the instruction flow rate.

7. The hydraulic drive system of a construction machine according to claim 6 , further comprising a charge pump operable to replenish the pair of supply/discharge lines with hydraulic oil, wherein
the switching valve leads the hydraulic oil discharged from the charge pump to the first chamber or the second chamber when the electric current is fed to the first solenoid or the second solenoid.

Assignees

• Kawasaki Heavy Ind Ltd

Inventors

• Kondo Akihiro
• Yudate yoji

Classifications

• E02F9/2235

  including an electronic controller · CPC title

• F04B49/22

  by means of valves (F04B49/03 takes precedence) · CPC title

• F15B7/008

  with rotary output · CPC title

• F15B2211/20561

  reversible · CPC title

• F15B2211/7058

  Rotary output members · CPC title