Hydraulic system of work machine and work machine

• US 10,641,388 B2
• Filed: 12/06/2016
• Issued: 05/05/2020
• Est. Priority Date: 12/07/2015
• Status: Active Grant

• Current Assignee: Kubota Corporation
• Original Assignee: Kubota Corporation
• Inventors: Fukuda, Yuji, Arii, Kazuyoshi, Sumiyoshi, Ryohei
• Primary Examiner(s): Lopez, F Daniel
• Assistant Examiner(s): Quandt, Michael
• Application Number:
  US15/369,890
• Publication Number:
  US 20170159679A1
• Time in Patent Office: 1,246 Days
• Field of Search: 60435, 60436
• CPC Class Codes: B60K 17/10 of fluid gearing of fluid clutches B60K17/02
• CPC Class Codes: E02F 9/2285 Pilot-operated systems
• CPC Class Codes: F15B 11/003 Systems with load-holding valves
• CPC Class Codes: F15B 11/20 controlling several interacting or sequentially-operating members
• CPC Class Codes: F15B 2211/20576 with multiple pumps
• CPC Class Codes: F15B 2211/30505 Non-return valves, i.e. check valves
• CPC Class Codes: F15B 2211/30525 Directional control valves, e.g. 4/3-directional control valve
• CPC Class Codes: F15B 2211/3058 having additional valves for interconnecting the fluid chambers of a double-acting actuator, e.g. for regeneration mode or for floating mode directional control valves having a regenerative position F15B2211/3133; directional control valves having a floating position F15B2211/3127
• CPC Class Codes: F15B 2211/329 actuated by fluid pressure
• CPC Class Codes: F15B 2211/355 Pilot pressure control
• CPC Class Codes: F15B 2211/613 Feeding circuits
• CPC Class Codes: F15B 2211/6355 having valve means
• CPC Class Codes: F15B 2211/7053 Double-acting output members
• CPC Class Codes: F15B 2211/7058 Rotary output members
• CPC Class Codes: F15B 2211/71 Multiple output members, e.g. multiple hydraulic motors or cylinders
• CPC Class Codes: F15B 2211/7741 with floating mode, e.g. using a direct connection between both lines of a double-acting cylinder
• CPC Class Codes: F15B 2211/782 Concurrent control, e.g. synchronisation of two or more actuators
• CPC Class Codes: F16H 61/4035 Control of circuit flow
• CPC Class Codes: F16H 61/4157 Control of braking, e.g. preventing pump over-speeding when motor acts as a pump
• CPC Class Codes: F16H 61/423 Motor capacity control by fluid pressure control means
• CPC Class Codes: F16H 61/433 : Pump capacity control by fluid pressure control means
• CPC Class Codes: F16H 61/44 : with more than one pump or motor in operation

Abstract

A hydraulic system of a work machine includes a first hydraulic device to operate in a first operation mode while pressure of hydraulic oil supplied from a hydraulic pump via a first oil passage is equal to or higher than a first pressure threshold. The hydraulic oil in the first oil passage is to be discharged via a second oil passage. A pilot check valve is provided in the second oil passage and has a pilot port to receive a pilot pressure of the hydraulic oil. The pilot check valve is closed to stop discharging the hydraulic oil in the first oil passage through the second oil passage while the pilot pressure is higher than or equal to the second pressure threshold. The pilot check valve is opened while the pilot pressure is less than the second pressure threshold.

Claims

1. A hydraulic system of a work machine, comprising:

a hydraulic pump to discharge hydraulic oil;

a first hydraulic device to operate in a first operation mode while pressure of the hydraulic oil supplied from the hydraulic pump is equal to or higher than a first pressure threshold;

a first oil passage which connects the first hydraulic device and the hydraulic pump and via which the hydraulic oil is to be supplied to the first hydraulic device from the hydraulic pump;

a second oil passage which is connected to the first oil passage and via which the hydraulic oil in the first oil passage is to be discharged; and

a pilot check valve provided in the second oil passage and having a pilot port to receive a pilot pressure of the hydraulic oil, the pilot pressure being controlled to be a pressure higher than or equal to a second pressure threshold when an operation mode of the first hydraulic device is changed to the first operation mode, the pilot check valve being closed to stop discharging the hydraulic oil in the first oil passage through the second oil passage while the pilot pressure is higher than or equal to the second pressure threshold, the pilot check valve being opened such that the hydraulic oil in the first oil passage is discharged through the second oil passage while the pilot pressure is less than the second pressure threshold,

wherein the first hydraulic device is a travelling motor whose speed is changeable in accordance with the pressure of the hydraulic oil.

2. The hydraulic system according to claim 1, further comprising:

a third oil passage connected to the pilot port; and

a first actuator provided between the first oil passage and the third oil passage to control an amount of hydraulic oil flowing to the third oil passage.

3. The hydraulic system according to claim 2, further comprising:

a second hydraulic device to operate in a second operation mode while pressure of the hydraulic oil supplied from the hydraulic pump is equal to or higher than a third pressure threshold;

a fourth oil passage which connects the second hydraulic device and the first oil passage and via which the hydraulic oil is to be supplied to the second hydraulic device from the hydraulic pump; and

a second actuator connected to the fourth oil passage to control an amount of hydraulic oil flowing to the fourth oil passage.

4. The hydraulic system according to claim 3,

wherein the second hydraulic device is a braking mechanism to brake the travelling motor and to release the braking in accordance with the pressure of the hydraulic oil.

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

6. A hydraulic system of a work machine, comprising:

a hydraulic pump to discharge hydraulic oil;

a first hydraulic device to operate in a first operation mode while pressure of the hydraulic oil supplied from the hydraulic pump is equal to or higher than a first pressure threshold;

a first oil passage which connects the first hydraulic device and the hydraulic pump and via which the hydraulic oil is to be supplied to the first hydraulic device from the hydraulic pump;

a second oil passage which is connected to the first oil passage and via which the hydraulic oil in the first oil passage is to be discharged;

a pilot check valve provided in the second oil passage and having a pilot port to receive a pilot pressure of the hydraulic oil, the pilot pressure being controlled to be a pressure higher than or equal to a second pressure threshold when an operation mode of the first hydraulic device is changed to the first operation mode, the pilot check valve being closed to stop discharging the hydraulic oil in the first oil passage through the second oil passage while the pilot pressure is higher than or equal to the second pressure threshold, the pilot check valve being opened such that the hydraulic oil in the first oil passage is discharged through the second oil passage while the pilot pressure is less than the second pressure threshold;

a third oil passage connected to the pilot port;

a first actuator connecting the third oil passage and the first oil passage to change an amount of hydraulic oil flowing to the third oil passage;

a second hydraulic device to operate in a second operation mode while pressure of the hydraulic oil supplied from the hydraulic pump is equal to or higher than a third pressure threshold;

a fifth oil passage connecting the first actuator, the second hydraulic device, and the third oil passage; and

a travelling motor,

wherein the first actuator is a remote control valve to control the pressure of the hydraulic oil in accordance with an operation of an operating member;

wherein the second hydraulic device operates in accordance with the pressure of the hydraulic oil that is output from the remote control valve;

wherein the first hydraulic device is a braking mechanism to brake the travelling motor and to release the braking in accordance with the pressure of the hydraulic oil, and

wherein the second hydraulic device is a travelling pump to operate in accordance with the pressure of the hydraulic oil that is output from the remote control valve and to supply the hydraulic oil to the travelling motor.

7. The hydraulic system according to claim 6, further comprising:

a sixth oil passage connected to the third oil passage to discharge the hydraulic oil in the third oil passage; and

a first switching valve connected to the sixth oil passage to be switchable.

8. A hydraulic system of a work machine, comprising:

a hydraulic pump to discharge hydraulic oil;

a first hydraulic device to operate in a first operation mode while pressure of the hydraulic oil supplied from the hydraulic oil is equal to or higher than a first pressure threshold;

a first oil passage which connects the first hydraulic device and the hydraulic pump and via which the hydraulic oil is to be supplied to the first hydraulic device from the hydraulic pump;

a second oil passage which is connected to the first oil passage and via which the hydraulic oil in the first oil passage is to be discharged;

a pilot check valve provided in the second oil passage and having a pilot port to receive a pilot pressure of hydraulic oil, the pilot pressure being controlled to be a pressure lower than a fourth pressure threshold when an operation mode of the first hydraulic device is changed to the first operation mode, the pilot check valve being closed to stop discharging the hydraulic oil in the first oil passage through the second oil passage while the pilot pressure is lower than the fourth pressure threshold, the pilot valve being opened such that the hydraulic oil in the first oil passage is discharged through the second oil passage while the pilot pressure is higher than or equal to the fourth pressure threshold;

a third oil passage connected to the pilot port;

a first actuator provided between the first oil passage and the third oil passage to control an amount of hydraulic oil flowing to the third oil passage;

a relief valve provided in the second oil passage; and

a travelling motor,

wherein the first hydraulic device is a braking mechanism to brake the travelling motor and to release the braking in accordance with the pressure of the hydraulic oil, and

wherein the first actuator is a second switching valve which is connected to the first oil passage between the braking mechanism and the hydraulic pump and which is connected to the third oil passage.

9. A work machine comprising the hydraulic system according to claim 8.