US 12,104,349 B2
Construction machine
Kenji Hiraku, Kasumigaura (JP); Akira Nakayama, Tsuchiura (JP); and Teppei Saitoh, Mito (JP)
Assigned to Hitachi Construction Machinery Co., Ltd., Tokyo (JP)
Appl. No. 17/637,726
Filed by Hitachi Construction Machinery Co., Ltd., Tokyo (JP)
PCT Filed Oct. 6, 2020, PCT No. PCT/JP2020/037923
§ 371(c)(1), (2) Date Feb. 23, 2022,
PCT Pub. No. WO2021/090627, PCT Pub. Date May 14, 2021.
Claims priority of application No. 2019-202551 (JP), filed on Nov. 7, 2019.
Prior Publication US 2022/0282448 A1, Sep. 8, 2022
Int. Cl. E02F 9/22 (2006.01); E02F 3/32 (2006.01); E02F 3/42 (2006.01); E02F 9/20 (2006.01); F15B 13/02 (2006.01); F15B 21/00 (2006.01)
CPC E02F 3/425 (2013.01) [E02F 3/32 (2013.01); E02F 9/2004 (2013.01); E02F 9/2242 (2013.01); E02F 9/2267 (2013.01); E02F 9/2271 (2013.01); E02F 9/2275 (2013.01); E02F 9/2289 (2013.01); E02F 9/2292 (2013.01); F15B 13/024 (2013.01); F15B 13/027 (2013.01); F15B 21/00 (2013.01); E02F 9/2296 (2013.01)] 4 Claims
OG exemplary drawing
 
1. A construction machine comprising:
a closed circuit pump consisting of a bidirectionally tiltable hydraulic pump having two suction/delivery ports;
a hydraulic actuator connected in a closed circuit manner to the closed circuit pump;
a charge pump;
a charge line connected to a delivery port of the charge pump;
a check valve that is provided in a hydraulic line connecting the charge line and the closed circuit pump to each other and permits hydraulic operating fluid to flow from the charge line into the closed circuit pump;
a charge relief valve provided in the charge line;
an operation lever for instructing an operation of the hydraulic actuator; and
a controller that controls a delivery volume of the closed circuit pump according to an input from the operation lever; wherein
the construction machine includes a switching valve that is provided in a hydraulic line connecting one of the suction/delivery ports of the closed circuit pump and the charge line to each other and is opened and closed according to a control signal from the controller, and
the controller is configured to, in a case where a state in which the delivery volume of the closed circuit pump is kept to zero continues for a predetermined time period or more, open the switching valve and keep the delivery volume of the closed circuit pump to a predetermined delivery volume or more, the predetermined delivery volume being greater than zero.