Work machine

Patent metadata

Field	Value
Publication number	US-12325978-B2
Application number	US-202218683384-A
Country	US
Kind code	B2
Filing date	Oct 31, 2022
Priority date	Jan 21, 2022
Publication date	Jun 10, 2025
Grant date	Jun 10, 2025

Abstract

The present invention intends to provide a work machine that can execute speed control of an actuator and torque control of a swing motor by a simple configuration at the time of combined operation to simultaneously drive the swing motor and the other actuator. For this purpose, a controller calculates a pump target flow rate on the basis of an actuator target flow rate and a swing target flow rate and calculates a target meter-in opening area of an actuator directional control valve on the basis of the actuator target flow rate, a pump pressure, and an actuator meter-in pressure. The controller calculates target torque of the swing motor on the basis of the input amount of operation devices and output values of posture sensors and calculates a swing target meter-out pressure on the basis of the target torque and a swing meter-in pressure. The controller calculates a target meter-out opening area of a swing directional control valve on the basis of the swing target meter-out pressure and a swing meter-out pressure.

First claim

The invention claimed is:

1. A work machine comprising:
a track structure;
a swing structure swingably attached onto the track structure;
a work device attached to the swing structure;
a hydraulic operating fluid tank;
a hydraulic pump of a variable displacement type that sucks in a hydraulic operating fluid from the hydraulic operating fluid tank and delivers the hydraulic operating fluid;
a regulator that controls capacity of the hydraulic pump;
an actuator that drives the work device;
a swing motor that drives the swing structure;
an actuator directional control valve that controls flow of a hydraulic fluid supplied from the hydraulic pump to the actuator;
a swing directional control valve that controls flow of the hydraulic fluid supplied from the hydraulic pump to the swing motor;
operation devices to make an instruction of operation of the actuator and the swing motor; and
a controller that controls the regulator, the actuator directional control valve, and the swing directional control valve according to an input amount of the operation devices, wherein
the work machine includes
a first pressure sensor that senses a pump pressure that is a delivery pressure of the hydraulic pump,
second pressure sensors that sense an actuator meter-in pressure that is a pressure on a meter-in side of the actuator,
third pressure sensors that sense a swing meter-in pressure that is a pressure on a meter-in side of the swing motor and a swing meter-out pressure that is a pressure on a meter-out side of the swing motor, and
posture sensors that sense posture of the swing structure and the work device,
a meter-in opening and a meter-out opening are formed of a same valve disc in each of the actuator directional control valve and the swing directional control valve,
the actuator directional control valve is formed in such a manner that the meter-in opening becomes smaller than the meter-out opening with respect to valve displacement,
the swing directional control valve is formed in such a manner that the meter-out opening becomes smaller than the meter-in opening with respect to valve displacement, and
the controller is configured to
calculate an actuator target flow rate that is a target value of a flow rate of the hydraulic fluid supplied from the hydraulic pump to the actuator on a basis of the input amount of the operation devices,
calculate a swing target flow rate that is a target value of a flow rate of the hydraulic fluid supplied from the hydraulic pump to the swing motor on the basis of the input amount of the operation devices,
calculate a pump target flow rate that is a target value of a delivery flow rate of the hydraulic pump on a basis of the actuator target flow rate and the swing target flow rate,
calculate a target meter-in opening area that is a target value of a meter-in opening area of the actuator directional control valve on a basis of the actuator target flow rate, the pump pressure, and the actuator meter-in pressure,
calculate target torque that is a target value of input torque to the swing motor on a basis of the input amount of the operation devices and output values of the posture sensors,
calculate a swing target meter-out pressure that is a target of the swing meter-out pressure on a basis of the target torque and the swing meter-in pressure,
calculate a target meter-out opening area that is a target value of a meter-out opening area of the swing directional control valve on a basis of the swing target meter-out pressure and the swing meter-out pressure,
control the regulator according to the pump target flow rate,
control the actuator directional control valve according to the target meter-in opening area, and
control the swing directional control valve according to the target meter-out opening area.

2. The work machine according to claim 1 , wherein
the work machine includes a bleed-off valve that discharges the hydraulic operating fluid delivered from the hydraulic pump to the hydraulic operating fluid tank, and
the controller is configured to
calculate a bleed-off valve target opening area that is a target value of an opening area of the bleed-off valve on the basis of the input amount of the operation devices,
calculate an estimated bleed-off flow rate that is an estimated value of a passing flow rate of the bleed-off valve on the basis of the bleed-off valve target opening area and the pump pressure, and
calculate a sum of the actuator target flow rate, the swing target flow rate, and the estimated bleed-off flow rate as the pump target flow rate.

Assignees

• Hitachi Construction Mach Co

Inventors

• Kumagai Kento
• Imura Shinya
• Tsuruga Yasutaka
• Chiba Takaaki
• Yamamoto Shinjirou
• Amano Hiroaki
• Nishikawa Shinji
• Narazaki Akihiro

Classifications

• F15B11/16 Primary

  with two or more servomotors · CPC title

• F15B11/044

  by means in the return line {, i.e. "meter out"}(F15B11/046, F15B11/05 take precedence) · CPC title

• F15B11/042

  by means in the feed line {, i.e. "meter in"}(F15B11/046, F15B11/05 take precedence) · CPC title

• F15B11/028

  for controlling the actuating force (F15B11/024 takes precedence) · CPC title

• E02F9/22

  Hydraulic or pneumatic drives {(for dipper or bucket arm position control E02F3/43, for blade position control for graders E02F3/844; for turntables E02F9/121; for fork-lift trucks B66F9/22)} · CPC title