Kubota Corporation

Kazuyoshi Arii

Yuji Fukuda

Ryohei Sumiyoshi

Ryosuke Kinugawa

Keisuke Miura

Hiroaki Nakagawa

Kunihiro Suzuki

Satoshi Tajima

Ikuhiro Uotani

Kazuhiko Tsuji

Shiro Watanabe

Isao Tanaka

Toshihiko Takemura

Keigo Honda

Kiyoshi Matsui

Akira Tsuda

Masaru Kumatani

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.

Hydraulic system for work machine, and work machine

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.

Hydraulic system for work machine

A hydraulic system for a working vehicle includes a first hydraulic pump to deliver pilot fluid to a control valve for a hydraulic actuator whose highest load pressure acts on a first fluid passage, and a second hydraulic pump to deliver hydraulic fluid whose pressure acts on a second fluid passage. A hydraulic controller is operable to control a load-sensing (LS) differential pressure between the highest load pressure and a delivery pressure of the hydraulic fluid from the second hydraulic pump. A third fluid passage to which the second hydraulic pump delivers the hydraulic fluid branches to a fourth fluid passage for flow of the pilot fluid. A solenoid valve is operable to change a pilot pressure of the pilot fluid for the hydraulic controller, and a controller is configured or programmed to control the solenoid valve to adjust the pilot pressure to change the LS differential pressure.

Hydraulic system for working machine

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 lower than the fourth pressure threshold. The pilot check valve is opened while the pilot pressure is higher than or equal to the fourth pressure threshold. The first hydraulic device is a ride control device.

Hydraulic system of work machine and work machine

A hydraulic system for a work machine includes a tank to store an operation fluid, a hydraulic device to be operated by the operation fluid, a control valve to control the hydraulic device, a first fluid tube connecting the hydraulic device and the control valve, the first fluid tube being to supply the operation fluid from the control valve to the hydraulic device, a second fluid tube branching from the first fluid tube and connected to the tank, a switch valve provided to the second fluid tube, the switch valve being to control a flow rate of the operation fluid, and an oil cooler provided to the second fluid tube between the switch valve and the tank.

Hydraulic system for work machine and work machine

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 lower than the fourth pressure threshold. The pilot check valve is opened while the pilot pressure is higher than or equal to the second pressure threshold. The first hydraulic device is an operation control valve.

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.

A hydraulic system for a work machine includes a prime mover, a setup member, a hydraulic pump, an operation valve, a hydraulic device, and a memory. The memory stores first control characteristics indicating relations between the first pressure and an actual revolution speed of the prime mover, and stores a second control characteristic indicating a relation between the first pressure and the actual revolution speed of the prime mover. The hydraulic system includes a controller to set the first pressure based on the second control characteristic when a dropping amount of the actual revolution speed from the target revolution speed is less than a threshold value and to set the first pressure based on the first control characteristics determined corresponding to the target revolution speed when the dropping amount of the actual revolution speed from the target revolution speed is the threshold value or more.

A hydraulic system of a work machine includes a first oil path which is connected to a hydraulic pump and though which hydraulic oil is to flow from the hydraulic pump. An operation valve is connected to the first oil path. An operation lever is to control the operation valve to control pressure of the hydraulic oil in accordance with an operation of the operation member. A hydraulic instrument is to be actuated by the hydraulic oil output from the operation valve. A second oil path connects the operation valve and the hydraulic instrument. The hydraulic oil in the second oil path is discharged through a discharge oil path. An actuation valve is provided in the discharge oil path. An actuation valve controller is to control the actuation valve to be opened and closed according to a temperature of hydraulic oil detected by a first sensor.

Hydraulic system of work machine

A hydraulic system of a work machine includes a first hydraulic actuator, a first control valve, a first oil passage, a second hydraulic actuator, a second control valve, a second oil passage, and a bypass oil passage. The first control valve is connected to the first hydraulic actuator to control the first hydraulic actuator. The first oil passage is connected to the first control valve to supply hydraulic oil to the first control valve. The second control valve connected to the second hydraulic actuator to control the second hydraulic actuator. The second oil passage connects the second control valve and the first hydraulic actuator via the first control valve. Hydraulic oil returning from the first hydraulic actuator to the first control valve is to be supplied to the second control valve through the second oil passage. The bypass oil passage connects the first oil passage and the second oil passage.

A hydraulic system includes a hydraulic pump to discharge an operation fluid, a hydraulic device to be operated by the operation fluid, a plurality of hydraulic pressure controllers each to change an operation state of the hydraulic pressure controller based on a pressure of the operation fluid so as to control the hydraulic device, and a proportional valve connected to the plurality of hydraulic pressure controllers. The proportional valve is configured to set a pressure of the operation fluid supplied to the hydraulic pressure controllers.

Hydraulic system and working machine including the same

A hydraulic system for a work machine includes an operation member, a prime mover, a hydraulic pump driven by the prime mover, the hydraulic pump configured to output an operation fluid, a first temperature sensor to measure a temperature of the operation fluid, a first fluid tube connected to the hydraulic pump, an operation valve connected to the first fluid tube, the operation valve configured to control, in accordance with an operation extent of the operation member, a pressure of the outputted operation fluid, a hydraulic apparatus driven by the operation fluid outputted from the operation valve, a second hydraulic tube connecting the operation valve to the hydraulic apparatus, a discharge fluid tube to discharge the operation fluid included in the second fluid tube; and an actuation valve disposed on the discharge fluid tube, the actuation valve configured to control an aperture of the actuation valve based on the temperature.

A hydraulic motor has a primary side and a secondary side. A hydraulic pump is to be driven by the engine to supply an operation fluid to the primary side. A bypass circuit is to connect the primary side and the secondary side. An electromagnetic valve is configured to control a flowing amount of the operation fluid in the bypass circuit to control an amount of the operation fluid supplied to the primary side. A filter is disposed in a fluid tube connected to the secondary side. A relief valve is disposed between the hydraulic pump and the primary side. A controller is to control the electromagnetic valve to drive the hydraulic motor in a case where a temperature of the operation fluid is low when the engine is started.

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Sakai, Japan

Kazuyoshi Arii