Hydraulic system for work machine, and work machine

Patent metadata

Field	Value
Publication number	US-10316496-B2
Application number	US-201615390536-A
Country	US
Kind code	B2
Filing date	Dec 26, 2016
Priority date	Sep 30, 2014
Publication date	Jun 11, 2019
Grant date	Jun 11, 2019

Abstract

A hydraulic system for a work machine includes a hydraulic pump to supply a pilot fluid, and a hydraulic switch valve to be switched to a plurality of switching positions based on a pilot pressure. The pilot pressure is a pressure of the pilot fluid supplied from the hydraulic pump. The hydraulic system includes a direction switch valve to apply a first pilot pressure to the hydraulic switch valve to switch the hydraulic switch valve into one of the plurality of switching positions. The hydraulic system includes a pressure applying device to apply a second pilot pressure to the hydraulic switch valve. The second pilot pressure is lower than the first pilot pressure.

First claim

What is claimed is:

1. A hydraulic system for a work machine, comprising:
a hydraulic pump to supply a pilot fluid;
a hydraulic switch valve to be switched to a plurality of switching positions based on a pilot pressure, the pilot pressure being a pressure of the pilot fluid supplied from the hydraulic pump;
a direction switch valve to apply a first pilot pressure to the hydraulic switch valve to switch the hydraulic switch valve into one of the plurality of switching positions; and
a pressure applying device to apply a second pilot pressure to the hydraulic switch valve, the second pilot pressure being lower than the first pilot pressure,
wherein the pressure applying device includes
a second fluid tube connecting the direction switch valve to the hydraulic switch valve,
a fourth fluid tube connecting the hydraulic pump to the direction switch valve, and
a fourth throttle to set the pilot pressure in the direction switch valve to the second pilot pressure.

2. The hydraulic system according to claim 1 , wherein
the pressure applying device includes
a first fluid tube connecting the hydraulic pump to the hydraulic switch valve, and
a first throttle to set the pilot pressure in the first fluid tube to the second pilot pressure.

3. The hydraulic system according to claim 1 , comprising:
a first check valve provided in the second fluid tube, the pilot fluid being to flow from the direction switch valve to the hydraulic switch valve through the first check valve, the pilot fluid being prevented from flowing from the hydraulic switch valve to the direction switch valve through the first check valve.

4. The hydraulic system according to claim 3 , comprising:
a coupler provided in the second fluid tube to couple an upper stream portion of the first check valve to a downstream portion of the first check valve; and
a fifth throttle provided in the coupler to reduce a speed at which the pilot fluid flows in the coupler.

5. The hydraulic system according to claim 4 , wherein the coupler is a branched fluid tube to couple the upper stream portion of the first check valve to the downstream portion of the first check valve, the branched fluid tube being arranged to be in a parallel connection with the first check valve.

6. The hydraulic system according to claim 1 , wherein the hydraulic switch valve includes a spool to be switched to a plurality of switch positions.

7. A work machine comprising the hydraulic system according to claim 1 .

8. A hydraulic system for a work machine, comprising:
a hydraulic pump to supply a pilot fluid;
a hydraulic switch valve to be switched to a plurality of switching positions based on a pilot pressure, the pilot pressure being a pressure of the pilot fluid supplied from the hydraulic pump;
a direction switch valve to apply a first pilot pressure to the hydraulic switch valve to switch the hydraulic switch valve into one of the plurality of switching positions; and
a speed reducing device to reduce a speed of changing the pilot pressure to be changed to the first pilot pressure,
wherein the speed reducing device includes
a second fluid tube connecting the direction switch valve to the hydraulic switch valve,
a second throttle to reduce the pilot pressure in the second fluid tube,
a third fluid tube connecting the hydraulic switch valve to a tank to which the pilot fluid is to be discharged from the hydraulic switch valve, and
a third throttle to reduce an amount of the pilot fluid flowing in the third fluid tube,

wherein the second throttle and the third throttle reduce the speed of changing the pilot pressure.

9. The hydraulic system according to claim 8 , comprising:
a second check valve provided in the third fluid tube, the pilot fluid being to flow from the hydraulic switch valve to the tank through the second check valve, the pilot fluid being prevented from flowing from the tank to the hydraulic switch valve through the second check valve.

10. A hydraulic system for a work machine, comprising:
a hydraulic pump to supply a pilot fluid;
a hydraulic switch valve to be switched to a plurality of switching positions based on a pilot pressure, the pilot pressure being a pressure of the pilot fluid supplied from the hydraulic pump;
a direction switch valve to apply a first pilot pressure to the hydraulic switch valve to switch the hydraulic switch valve into one of the plurality of switching positions;
a pressure applying device to apply a second pilot pressure to the hydraulic switch valve, the second pilot pressure being lower than the first pilot pressure; and
a speed reducing device to reduce a speed of changing the pilot pressure, the pilot pressure being to be applied to the hydraulic switch valve and to be changed to the first pilot pressure.

11. The hydraulic system according to claim 10 , wherein
the pressure applying device includes
a second fluid tube connecting the direction switch valve to the hydraulic switch valve,
a fourth fluid tube connecting the hydraulic pump to the direction switch valve, and
a fourth throttle to set the pilot pressure in the direction switch valve to the second pilot pressure.

12. The hydraulic system according to claim 11 , comprising:
a first check valve provided in the second fluid tube, the pilot fluid being to flow from the direction switch valve to the hydraulic switch valve through the first check valve, the pilot fluid being prevented from flowing from the hydraulic switch valve to the direction switch valve through the first check valve.

13. The hydraulic system according to claim 12 , comprising:
a coupler provided in the second fluid tube to couple an upper stream portion of the first check valve to a downstream portion of the first check valve; and
a fifth throttle provided in the coupler to reduce a speed at which the pilot fluid flows in the coupler.

14. The hydraulic system according to claim 13 , wherein the coupler is a branched fluid tube to couple the upper stream portion of the first check valve to the downstream portion of the first check valve, the branched fluid tube being arranged to be in a parallel connection with the first check valve.

15. The hydraulic system according to claim 10 , wherein
the speed reducing device includes
a second fluid tube connecting the direction switch valve to the hydraulic switch valve,
a second throttle to reduce the pilot pressure in the second fluid tube,
a third fluid tube connecting the hydraulic switch valve to a tank to which the pilot fluid is to be discharged from the hydraulic switch valve, and
a third throttle to reduce an amount of the pilot fluid flowing in the third fluid tube,

wherein the second throttle and the third throttle reduce the speed of changing the pilot pressure.

16. The hydraulic system according to claim 15 , comprising:
a second check valve provided in the third fluid tube, the pilot fluid being to flow from the hydraulic switch valve to the tank through the second check valve, the pilot fluid being prevented from flowing from the tank to the hydraulic switch valve through the second check valve.

17. A hydraulic system for a work machine, comprising:
a hydraulic pump to supply a pilot fluid;
a hydraulic switch valve to be switched to a plurality of switching positions based on a pilot pressure, the pilot pressure being a pressure of the pilot fluid supplied from the hydraulic pump;
a direction switch valve to apply a first pilot pressure to the hydraulic switch valve to switch the hydraulic switch valve into one of the plurality of switching positions;
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Assignees

• Kubota Kk

Inventors

• Fukuda Yuji
• Arii Kazuyoshi
• Miura Keisuke
• Kinugawa Ryosuke
• Uotani Ikuhiro
• Tajima Satoshi
• Sumiyoshi Ryohei
• Suzuki Kunihiro

Classifications

• F15B2211/8606

  the abnormal condition being a shock · CPC title

• F15B2211/6316

  the pressure being a pilot pressure · CPC title

• F15B2211/30565

  having multiple valves for a single output member, e.g. for creating higher valve function by use of multiple valves like two 2/2-valves replacing a 5/3-valve · CPC title

• F15B2211/355

  Pilot pressure control · CPC title

• F15B2211/67

  Methods for controlling pilot pressure · CPC title