Hydraulic system for work machine

Patent metadata

Field	Value
Publication number	US-12006659-B2
Application number	US-202217860279-A
Country	US
Kind code	B2
Filing date	Jul 8, 2022
Priority date	Jun 7, 2016
Publication date	Jun 11, 2024
Grant date	Jun 11, 2024

Abstract

A hydraulic system for a work machine, which includes a first hydraulic pump to deliver operation fluid, a second hydraulic pump to deliver pilot fluid, a first hydraulic actuator configured to control flow rate of the operation fluid based on the pilot pressure applied to the pressure receivers, a manual operator configured to operate the first hydraulic actuator, having an operation lever to move toward both directions, operation valves to change pressure of the pilot fluid in accordance with movement of the operation lever, and a discharge fluid tube to drain the pilot fluid from the operation valves. The hydraulic system includes an actuating valve in the discharge fluid tube and configured to reduce pressure of the pilot fluid in the discharge fluid tube.

First claim

What is claimed is:

1. A hydraulic system for a work machine, comprising:
a first hydraulic pump to deliver operation fluid;
a second hydraulic pump to deliver pilot fluid;
a first hydraulic device including first and second pressure receivers to receive the pilot fluid, the first hydraulic device configured to control a flow rate of an operation fluid based on the pilot pressure applied to the first and/or second pressure receivers;
a first manual operator configured to operate the first hydraulic device, the first manual operator including
a first operation lever for a user to move toward one direction and another direction opposite to the one direction,
a first operation valve configured to change first pressure of the pilot fluid in accordance with movement of the first operation lever toward the one direction, and
a second operation valve configured to change second pressure of the pilot fluid in accordance with the movement of the first operation lever toward the another direction;

at least one discharge fluid tube configured to drain the pilot fluid from the first operation valve and/or the second operation valve;
at least one actuating valve disposed in the at least one discharge fluid tube and configured to reduce pressure of the pilot fluid in the at least one discharge fluid tube, the at least one actuating valve including a relief valve having a setting pressure configured to be adjusted, which allows the pilot fluid to drain from the at least one discharge fluid tube through the relief valve when the pressure of the pilot fluid upstream of the relief valve is greater than the setting pressure; and
a proportional valve connected to a pressure-receiver of the relief valve, which is configured to adjust the setting pressure of the relief valve by changing pressure of the pilot fluid applied to the pressure-receiver of the relief valve.

2. The hydraulic system according to claim 1 , comprising:
a second hydraulic device including third and fourth pressure receivers to receive the pilot fluid, the second hydraulic device configured to control a flow rate of an operation fluid based on the pilot pressure applied to the third and/or fourth pressure receivers;
a second manual operator configured to operate the second hydraulic device, the second manual operator including
a second operation lever for the user to move toward one direction and another direction opposite to the one direction,
a third operation valve configured to change third pressure of the pilot fluid in accordance with the movement of the second operation lever toward the one direction, and
a fourth operation valve configured to change fourth pressure of the pilot fluid in accordance with the movement of the second operation lever toward the another direction, wherein

the at least one discharge fluid tube is configured to drain the pilot fluid from at least one of the first operation valve, the second operation valve, the third operation valve and the fourth operation valve,
the at least one actuating valve is disposed in the at least one discharge fluid tube, and is configured to reduce the pressure of the pilot fluid in the at least one discharge fluid tube.

3. The hydraulic system according to claim 2 , comprising:
a first pair of second fluid tubes connecting the first operation valve and the second operation valve to the first hydraulic device and to the at least one discharge fluid tube; and
a second pair of second fluid tubes connecting the third operation valve and the fourth operation valve to the second hydraulic device and to the at least one discharge fluid tube; and
at least one check valve disposed in the at least one discharge fluid tube, the at least one check valve being configured to allow the pilot fluid to flow from the first pair of the second fluid tubes and the second pair of the second fluid tubes to the at least one actuating valve and to block the pilot fluid to flow from the at least one actuating valve to the first pair of the second fluid tubes and the second pair of the second fluid tubes.

4. The hydraulic system according to claim 2 , wherein
each of the first hydraulic device and the second hydraulic device includes a travel pump configured to control the flow rate of the operation fluid.

5. The hydraulic system according to claim 1 , comprising:
a first pair of second fluid tubes connecting the first operation valve and the second operation valve to the first hydraulic device and to the at least one discharge fluid tube; and
at least one check valve disposed in the at least one discharge fluid tube, the at least one check valve being configured to allow the pilot fluid to flow from the first pair of the second fluid tubes to the at least one actuating valve and to block the pilot fluid to flow from the at least one actuating valve to the first pair of the second fluid tubes.

6. A hydraulic system for a work machine, comprising:
a first hydraulic pump to deliver operation fluid;
a second hydraulic pump to deliver pilot fluid;
a first hydraulic device including first and second pressure receivers to receive the pilot fluid, the first hydraulic device configured to control a flow rate of an operation fluid based on the pilot pressure applied to the first and/or second pressure receivers;
a first manual operator configured to operate the first hydraulic device, the first manual operator including
a first operation lever for a user to move toward one direction and another direction opposite to the one direction,
a first operation valve configured to change first pressure of the pilot fluid in accordance with movement of the first operation lever toward the one direction, and
a second operation valve configured to change second pressure of the pilot fluid in accordance with the movement of the first operation lever toward the another direction;

at least one discharge fluid tube configured to drain the pilot fluid from the first operation valve and/or the second operation valve; and
at least one actuating valve disposed in the at least one discharge fluid tube and configured to reduce pressure of the pilot fluid in the at least one discharge fluid tube, wherein
the at least one actuating valve includes a pilot-operated check valve having a pressure receiver, which prevents or allows the pilot fluid to flow from the at least one discharge fluid tube through the pilot-operated check valve in accordance with pressure applied to the pressure receiver thereof.

7. The hydraulic system according to claim 6 , comprising:
a switch valve connected to the pressure-receiver of the pilot-operated check valve and configured to be switched between a first position and a second position,
the first position preventing the pilot fluid to flow from the at least one discharge fluid tube through the pilot-operated check valve, and
the second position allowing the pilot fluid to flow from the at least one discharge fluid tube through the pilot-operated check valve.

8. A hydraulic system for a work machine, comprising:
a first hydraulic pump to deliver operation fluid;
a second hydraulic pump to deliver pilot fluid;
a first hydraulic device including first and second pressure receivers to receive the pilot fluid, the first hydraulic device configured to control a flow rate of an operation fluid based on the pilot pressure applied to the first and/or second pressure receivers;
a first manual operator configured to operate the first hydraulic device, the first manual operator including
a first operation lever for a user to move toward one direction and another direction opposite to the one direction,
a first operation valve configured to change first pressure of the pilot fluid in accordance with movement of the first operation l

Assignees

• Kubota Kk

Inventors

• Fukuda Yuji
• Arii Kazuyoshi

Classifications

• E02F9/2292

  Systems with two or more pumps · CPC title

• E02F9/2285

  Pilot-operated systems · CPC title

• E02F9/2025

  Particular purposes of control systems not otherwise provided for (E02F3/16, E02F3/26, sub-groups of E02F3/43, E02F3/651, sub-groups of E02F3/84, E02F3/907, E02F5/145 take precedence) · CPC title

• E02F9/166

  movable, tiltable or pivoting, e.g. movable seats, dampening arrangements of cabins (seats for vehicles in general B60N2/00) · CPC title

• E02F3/3414

  the arms being pivoted at the rear of the vehicle chassis, e.g. skid steer loader · CPC title