US 11,859,367 B2
Construction machine
Teppei Saitoh, Mito (JP); Hiromasa Takahashi, Abiko (JP); and Kenji Hiraku, Kasumigaura (JP)
Assigned to Hitachi Construction Machinery Co., Ltd., Tokyo (JP)
Appl. No. 17/275,064
Filed by Hitachi Construction Machinery Co., Ltd., Tokyo (JP)
PCT Filed Nov. 5, 2019, PCT No. PCT/JP2019/043331
§ 371(c)(1), (2) Date Mar. 10, 2021,
PCT Pub. No. WO2020/152937, PCT Pub. Date Jul. 30, 2020.
Claims priority of application No. 2019-011592 (JP), filed on Jan. 25, 2019.
Prior Publication US 2022/0056667 A1, Feb. 24, 2022
Int. Cl. E02F 9/22 (2006.01); F15B 11/17 (2006.01); E02F 9/12 (2006.01); E02F 3/32 (2006.01)
CPC E02F 9/123 (2013.01) [E02F 3/32 (2013.01); E02F 9/2289 (2013.01); E02F 9/2292 (2013.01); E02F 9/2296 (2013.01); F15B 11/17 (2013.01); F15B 2211/7135 (2013.01)] 4 Claims
OG exemplary drawing
 
1. A construction machine comprising:
a lower track structure;
an upper swing structure swingably mounted to the lower track structure;
a work device provided on the upper swing structure;
a tank reserving a hydraulic operating oil;
a single rod-type hydraulic cylinder that drives the work device;
a swing hydraulic motor that drives the upper swing structure;
an operating device that gives instructions on operations of the work device and the upper swing structure;
a first closed circuit pump including a bidirectionally tiltable pump;
a second closed circuit pump including a bidirectionally tiltable pump;
a cylinder closed circuit that connects the first closed circuit pump to the single rod-type hydraulic cylinder in a state of a closed circuit;
a swing closed circuit that connects the second closed circuit pump to the swing hydraulic motor in a state of a closed circuit;
a first flushing valve that permits a line on a low pressure side of the cylinder closed circuit to communicate with the tank;
a second flushing valve that permits a line on a low pressure side of the swing closed circuit to communicate with the tank;
a first selector valve that switches between communication and interruption of communication between the first closed circuit pump and the single rod-type hydraulic cylinder; and
a second selector valve that switches between communication and interruption of communication between the second closed circuit pump and the swing hydraulic motor, and
openings and closings of the first selector valve and the second selector valve and delivery rates of the first closed circuit pump and the second closed circuit pump being controlled according to operation signals inputted from the operating device,
wherein a minimum passage area from the second flushing valve to the tank in a case the second flushing valve is fully open is smaller than a minimum passage area from the first flushing valve to the tank in a case the first flushing valve is fully open.