US 11,753,798 B2
Hydraulic system for working machine
Yuji Fukuda, Sakai (JP); Ryota Hamamoto, Sakai (JP); Jun Tomita, Sakai (JP); and Yuya Konishi, Sakai (JP)
Assigned to KUBOTA CORPORATION, Osaka (JP)
Filed by KUBOTA CORPORATION, Osaka (JP)
Filed on Jun. 15, 2022, as Appl. No. 17/840,680.
Claims priority of application No. 2021-152394 (JP), filed on Sep. 17, 2021.
Prior Publication US 2023/0092677 A1, Mar. 23, 2023
Int. Cl. E02F 9/22 (2006.01); F15B 21/0427 (2019.01); F15B 21/08 (2006.01); E02F 9/20 (2006.01)
CPC E02F 9/2225 (2013.01) [E02F 9/2083 (2013.01); E02F 9/2246 (2013.01); E02F 9/2278 (2013.01); F15B 21/0427 (2019.01); F15B 21/082 (2013.01)] 20 Claims
OG exemplary drawing
 
1. A hydraulic system for a working machine, comprising:
a hydraulic pump to deliver hydraulic fluid;
a first hydraulic device to be activated by the hydraulic fluid;
a second hydraulic device to be activated by the hydraulic fluid separately from the first hydraulic device;
a first activation valve to control the hydraulic fluid to be supplied to the first hydraulic device;
a second activation valve to control the hydraulic fluid to be supplied to the second hydraulic device;
a first fluid passage connecting the first activation valve and the first hydraulic device;
a second fluid passage connecting the second activation valve and the second hydraulic device;
a third fluid passage connecting the first fluid passage and the second fluid passage;
a first discharge fluid passage connectable to the first fluid passage to discharge the hydraulic fluid;
a second discharge fluid passage connectable to the second fluid passage to discharge the hydraulic fluid; and
a controller to control operation of the first activation valve and operation of the second activation valve; wherein
the controller is configured or programmed to set an output-port pressure of one activation valve to a preloading pressure having a predetermined value, and set an output-port pressure of the other activation valve to a pressure lower than the preloading pressure to discharge the hydraulic fluid in any one of the first fluid passage and the second fluid passage to the first discharge fluid passage or the second discharge fluid passage, the one activation valve being one of the first activation valve and the second activation valve, the output-port pressure of the one activation valve being a pressure of the hydraulic fluid at an output port of the one activation valve, the other activation valve being the other of the first activation valve and the second activation valve, and the output-port pressure of the other activation valve being a pressure of the hydraulic fluid at an output port of the other activation valve;
the controller is configured or programmed to increase at least either one of the output-port pressure of the one activation valve or the output-port pressure of the other activation valve to a normal pressure higher than the preloading pressure from a state where the one activation valve is controlled such that the output-port pressure thereof is equal to the preloading pressure and the other activation valve is controlled such that the output-port pressure thereof is lower than the preloading pressure, by performing control on the one activation valve such that the output-port pressure of the one activation valve becomes lower than the preloading pressure and performing control on the other activation valve such that the output-port pressure of the other activation valve is increased to the normal pressure.