Hydraulic system

Patent metadata

Field	Value
Publication number	US-10907659-B2
Application number	US-201816652134-A
Country	US
Kind code	B2
Filing date	Sep 21, 2018
Priority date	Sep 29, 2017
Publication date	Feb 2, 2021
Grant date	Feb 2, 2021

Abstract

A hydraulic system includes: a single-rod hydraulic cylinder; a variable displacement pump driven by a rotating machine; a rod-side supply line and a head-side supply line that connect the pump to the hydraulic cylinder; a first tank line that is branched off from the rod-side supply line and connects to a tank; a second tank line that is branched off from the head-side supply line and connects to the tank; and a flow rate adjuster. The flow rate adjuster is configured to: switch a delivery capacity of the pump to a first setting value when a pressure of the head-side supply line is higher than a pressure of the rod-side supply line; and switch the delivery capacity of the pump to a second setting value less than the first setting value when the pressure of the rod-side supply line is higher than the pressure of the head-side supply line.

First claim

The invention claimed is:

1. A hydraulic system comprising:
a single-rod hydraulic cylinder including a rod-side chamber and a head-side chamber;
a variable displacement pump driven by a rotating machine, the pump including a first port and a second port;
a flow rate adjuster that switches a delivery capacity per rotation of the pump between a first setting value and a second setting value less than the first setting value;
a rod-side supply line that connects the first port to the rod-side chamber;
a head-side supply line that connects the second port to the head-side chamber in a manner to form a closed circuit together with the pump, the rod-side supply line, and the hydraulic cylinder;
a first tank line that is branched off from the rod-side supply line and connects to a tank;
a first pilot check valve provided on the first tank line, the first pilot check valve allowing a flow from the tank toward the rod-side supply line and preventing a reverse flow, but stopping exerting a function of preventing the reverse flow when a pressure of the head-side supply line is higher than a first setting pressure;
a second tank line that is branched off from the head-side supply line and connects to the tank; and
a second pilot check valve provided on the second tank line, the second pilot check valve allowing a flow from the tank toward the head-side supply line and preventing a reverse flow, but stopping exerting a function of preventing the reverse flow when a pressure of the rod-side supply line is higher than a second setting pressure, wherein
the pressure of the rod-side supply line and the pressure of the head-side supply line are led to the flow rate adjuster, and
the flow rate adjuster is configured to:
switch the delivery capacity of the pump to the first setting value when the pressure of the head-side supply line is higher than the pressure of the rod-side supply line; and
switch the delivery capacity of the pump to the second setting value when the pressure of the rod-side supply line is higher than the pressure of the head-side supply line.

2. The hydraulic system according to claim 1 , wherein
a ratio between the first setting value and the second setting value is equal to a ratio between a pressure receiving area of the head-side chamber and a pressure receiving area of the rod-side chamber of the hydraulic cylinder.

3. The hydraulic system according to claim 1 , wherein
the rotating machine is a servomotor, and
a delivery side and a suction side of the first and second ports of the pump are switched with each other in accordance with a rotation direction of the rotating machine.

4. The hydraulic system according to claim 1 , wherein
a delivery side and a suction side of the first and second ports of the pump are switched with each other by tilting a swash plate or a tilted axis of the pump bi-directionally over a reference line.

5. A hydraulic system comprising:
a single-rod hydraulic cylinder including a rod-side chamber and a head-side chamber;
a variable displacement pump driven by a rotating machine, the pump including a first port and a second port;
a flow rate adjuster that switches a delivery capacity per rotation of the pump between a first setting value and a second setting value less than the first setting value;
a rod-side supply line that connects the first port to the rod-side chamber;
a head-side supply line that connects the second port to the head-side chamber in a manner to form a closed circuit together with the pump, the rod-side supply line, and the hydraulic cylinder;
a first tank line that is branched off from the rod-side supply line and connects to a tank;
a check valve provided on the first tank line, the check valve allowing a flow from the tank toward the rod-side supply line and preventing a reverse flow;
a second tank line that is branched off from the head-side supply line and connects to the tank; and
a pilot check valve provided on the second tank line, the pilot check valve allowing a flow from the tank toward the head-side supply line and preventing a reverse flow, but stopping exerting a function of preventing the reverse flow when a pressure of the rod-side supply line is higher than a setting pressure, wherein
the pressure of the rod-side supply line and the pressure of the head-side supply line are led to the flow rate adjuster, and
the flow rate adjuster is configured to:
switch the delivery capacity of the pump to the first setting value when the pressure of the head-side supply line is higher than the pressure of the rod-side supply line; and
switch the delivery capacity of the pump to the second setting value when the pressure of the rod-side supply line is higher than the pressure of the head-side supply line.

Assignees

• Kawasaki Heavy Ind Ltd

Inventors

• Kondo Akihiro
• Mitsui Hiroaki
• Toyota Toshihisa
• Yamada Haruo

Classifications

• F15B2211/20553

  with pilot circuit, e.g. for controlling a swash plate · CPC title

• F15B11/055

  by adjusting the pump output or bypass · CPC title

• F15B2211/75

  Control of speed of the output member · CPC title

• F15B2211/3051

  Cross-check valves · CPC title

• F15B2211/27

  Directional control by means of the pressure source · CPC title