US 12,312,770 B2
Construction machine
Seiji Hijikata, Tsukuba (JP); Yasutaka Tsuruga, Ryugasaki (JP); Masatoshi Hoshino, Tsuchiura (JP); and Ryou Yagisawa, Tsuchiura (JP)
Assigned to Hitachi Construction Machinery Co., Ltd., Tokyo (JP)
Appl. No. 17/908,084
Filed by Hitachi Construction Machinery Co., Ltd., Tokyo (JP)
PCT Filed Apr. 7, 2021, PCT No. PCT/JP2021/014785
§ 371(c)(1), (2) Date Aug. 30, 2022,
PCT Pub. No. WO2021/261051, PCT Pub. Date Dec. 30, 2021.
Claims priority of application No. 2020-107172 (JP), filed on Jun. 22, 2020.
Prior Publication US 2023/0099135 A1, Mar. 30, 2023
Int. Cl. E02F 9/22 (2006.01); F15B 1/02 (2006.01)
CPC E02F 9/2203 (2013.01) [F15B 1/024 (2013.01); F15B 2211/2658 (2013.01)] 4 Claims
OG exemplary drawing
 
1. A construction machine comprising:
a prime mover;
a revolution speed setting device for setting a revolution speed of the prime mover;
a cylinder;
a pressure accumulating device that accumulates a hydraulic fluid discharged from the cylinder and supplies the hydraulic fluid to the cylinder;
a hydraulic operating fluid tank;
a bottom side hydraulic fluid line that connects the pressure accumulating device and a bottom side oil chamber of the cylinder to each other;
a rod side hydraulic fluid line that connects a rod side oil chamber of the cylinder and the hydraulic operating fluid tank to each other;
a communication hydraulic fluid line that connects the bottom side hydraulic fluid line and the rod side hydraulic fluid line to each other;
a first control valve that is disposed on the bottom side hydraulic fluid line;
an operation device for giving an instruction for extension and contraction of the cylinder; and
a controller that is inputted with an operation signal corresponding to an operation amount of the operation device and outputs a control signal to the first control valve, wherein
the construction machine comprises:
a pressure increasing control valve that is disposed on the communication hydraulic fluid line and opens when the cylinder is operated to contract by the operation device;
a hydraulic pump that is driven by the prime mover, sucks the hydraulic fluid from the hydraulic operating fluid tank and delivers the hydraulic fluid;
a pressure sensor that senses a pressure of the pressure accumulating device; and
a second control valve that connects a delivery port of the hydraulic pump to one of the hydraulic operating fluid tank and the pressure accumulating device according to a control signal from the controller,
the controller is configured to
output the control signal to the second control valve such that the delivery port of the hydraulic pump is connected to the hydraulic operating fluid tank in a case where the pressure detected by the pressure sensor is equal to or higher than a predetermined pressure and such that the delivery port of the hydraulic pump is connected to the pressure accumulating device in a case where the pressure detected by the pressure sensor is lower than the predetermined pressure,
compute a target opening amount by multiplying an opening amount of the first control valve, the opening amount corresponding to the operation amount of the operation device, by a gain of 1 or less that continuously changes according to the revolution speed of the prime mover set by the revolution speed setting device, and
change the opening amount of the first control valve, thereby controlling a flow rate of the hydraulic fluid to be supplied from the pressure accumulating device to the cylinder or a flow rate of the hydraulic fluid to be regenerated from the cylinder to the pressure accumulating device.