US 11,795,660 B2
Hydraulic system of construction machine
Akihiro Kondo, Kobe (JP); Hideyasu Muraoka, Kobe (JP); and Yoshiyuki Tode, Kobe (JP)
Assigned to KAWASAKI JUKOGYO KABUSHIKI KAISHA, Kobe (JP)
Appl. No. 17/637,676
Filed by KAWASAKI JUKOGYO KABUSHIKI KAISHA, Kobe (JP)
PCT Filed Jul. 31, 2020, PCT No. PCT/JP2020/029478
§ 371(c)(1), (2) Date Feb. 23, 2022,
PCT Pub. No. WO2021/039283, PCT Pub. Date Mar. 4, 2021.
Claims priority of application No. 2019-152658 (JP), filed on Aug. 23, 2019.
Prior Publication US 2022/0282453 A1, Sep. 8, 2022
Int. Cl. E02F 9/12 (2006.01); E02F 9/22 (2006.01); E02F 9/20 (2006.01); E02F 9/24 (2006.01); F15B 13/044 (2006.01); E02F 3/32 (2006.01); E02F 3/42 (2006.01)
CPC E02F 9/2228 (2013.01) [E02F 9/123 (2013.01); E02F 9/125 (2013.01); E02F 9/128 (2013.01); E02F 9/2004 (2013.01); E02F 9/2267 (2013.01); E02F 9/2271 (2013.01); E02F 9/2285 (2013.01); E02F 9/2292 (2013.01); E02F 9/2296 (2013.01); E02F 9/24 (2013.01); F15B 13/044 (2013.01); E02F 3/32 (2013.01); E02F 3/425 (2013.01)] 3 Claims
OG exemplary drawing
 
1. A hydraulic system of a construction machine, comprising:
hydraulic actuators including a slewing motor;
a brake including a brake release port, the brake being switched from a brake-applied state, in which the brake prevents rotation of an output shaft of the slewing motor, to a brake-released state, in which the brake allows the rotation of the output shaft, when a hydraulic pressure led to the brake release port becomes higher than a first setting value;
control valves interposed between a main pump and the hydraulic actuators, each control valve including pilot ports;
first solenoid proportional valves connected to the pilot ports of the control valves;
operation devices to move the control valves, each operation device outputting an electrical signal corresponding to an operating amount of the operation device;
a controller that controls the first solenoid proportional valves based on the electrical signals outputted from the operation devices;
a second solenoid proportional valve connected to the brake release port by a secondary pressure line and connected to an auxiliary pump by a primary pressure line; and
a switching valve interposed between the auxiliary pump and the first solenoid proportional valves, the switching valve including a pilot port connected to the secondary pressure line by a pilot line, the switching valve switching from a closed position to an open position when a pilot pressure led to the pilot port of the switching valve becomes higher than or equal to a second setting value that is lower than the first setting value.