Hydraulic Excavator

Patent metadata

Field	Value
Publication number	US-2021348366-A1
Application number	US-201917272688-A
Country	US
Kind code	A1
Filing date	Dec 12, 2019
Priority date	Mar 20, 2019
Publication date	Nov 11, 2021
Grant date	—

Abstract

A hydraulic excavator is provided which can suppress the fuel consumption amount and improve the work efficiency by reducing the hydraulic pressure loss generated when a plurality of hydraulic actuators different in load are operated simultaneously. The hydraulic excavator includes a center bypass flow control valve that is arranged at the most downstream of a center bypass line and limits the flow rate of hydraulic fluid passing through the center bypass line in response to the operation amount of the second operation device in a case where a second operation device is operated, and a spool stroke limitation device that, in a case where a first operation device and the second operation device are operated simultaneously, limits the spool stroke amount of a second directional control valve in response to the operation amount of the first operation device in a state in which the spool stroke amount of a third directional control valve is controlled in response to the operation amount of the second operation device.

First claim

1 . A hydraulic excavator comprising:
a main body including an upper swing structure and a lower track structure; a boom pivotably coupled to the main body; an arm pivotably coupled to a distal end portion of the boom; a bucket pivotably coupled to a distal end portion of the arm; a first hydraulic pump; a second hydraulic pump; a boom cylinder or a bucket cylinder to which hydraulic fluid is supplied from the first hydraulic pump and the second hydraulic pump to drive the boom or the bucket; an arm cylinder to which hydraulic fluid is supplied from the first hydraulic pump to drive the arm; a first operation device that issues an instruction on operation of the boom cylinder or the bucket cylinder; a second operation device that issues an instruction on operation of the arm cylinder; a first directional control valve that controls a direction and a flow rate of hydraulic fluid to be supplied from the first hydraulic pump to the boom cylinder or the bucket cylinder in response to an operation amount of the first operation device; a second directional control valve that controls a direction and a flow rate of hydraulic fluid to be supplied from the first hydraulic pump to the arm cylinder in response to an operation amount of the second operation device; and a third directional control valve that controls a direction and a flow rate of hydraulic fluid to be supplied from the second hydraulic pump to the arm cylinder in response to an operation amount of the second operation device, the first directional control valve and the second directional control valve being tandem connected to a center bypass line of the first hydraulic pump and being connected in parallel to a parallel line branched from the center bypass line, the hydraulic excavator including a center bypass flow control valve that is arranged at a most downstream of the center bypass line and limits a flow rate of hydraulic fluid passing through the center bypass line in response to an operation amount of the second operation device in a case where the second operation device is operated, and a spool stroke limitation device that is configured to, in a case where the first operation device and the second operation device are operated simultaneously, limit a spool stroke amount of the second directional control valve in response to an operation amount of the first operation device in a state in which a spool stroke amount of the third directional control valve is controlled in response to an operation amount of the second operation device.

2 . The hydraulic excavator according to claim 1 , further comprising:
a pilot pump, wherein the first operation device includes a boom pilot valve and a bucket pilot valve that reduce delivery pressure of the pilot pump in response to the operation amount of the first operation device and output resulting pressure as operation pressure of the first directional control valve, and the second operation device includes an arm pilot valve that reduces delivery pressure of the pilot pump in response to the operation amount of the second operation device and outputs resulting pressure as operation pressure of the second directional control valve and the third directional control valve.

3 . The hydraulic excavator according to claim 2 , further comprising:
pressure sensors that detect arm crowding operation pressure outputted from the arm pilot valve, boom raising operation pressure outputted from the boom pilot valve, bucket crowding operation pressure outputted from the bucket pilot valve, and bucket dumping operation pressure outputted from the bucket pilot valve, wherein the spool stroke limitation device includes a first solenoid proportional pressure reducing valve that has a primary pressure port connected to a secondary pressure port on an arm crowding side of the arm pilot valve and a secondary pressure port connected to an operation pressure port on an arm crowding side of the second directional control valve, and a controller that is configured to control secondary pressure of the first solenoid proportional pressure reducing valve on a basis of a target meter-in opening area having a lowest value among target meter-in opening areas of the second directional control valve, the target meter-in opening areas being determined on a basis of the arm crowding operation pressure, the boom raising operation pressure, the bucket crowding operation pressure, and the bucket dumping operation pressure, respectively.

4 . The hydraulic excavator according to claim 3 , further comprising:
a second solenoid proportional pressure reducing valve that has a primary pressure port connected to a delivery line of the pilot pump and a secondary pressure port connected to an operation pressure port of the center bypass flow control valve, wherein the controller is configure to control secondary pressure of the second solenoid proportional pressure reducing valve on a basis of the arm crowding operation pressure.

5 . The hydraulic excavator according to claim 3 , wherein,
the controller is configured to set a target opening area of the first solenoid proportional pressure reducing valve to a maximum opening area in a case where all of the boom raising operation pressure, the bucket crowding operation pressure, and the bucket dumping operation pressure are equal to or lower than predetermined pressure.

6 . The hydraulic excavator according to claim 3 , wherein
the controller is capable of individually setting minimum values of a target meter-in opening area of the second directional control value, the minimum values being respectively corresponding to the arm crowding operation pressure, the boom raising operation pressure, the bucket crowding operation pressure, and the bucket dumping pressure.

Assignees

• Hitachi Construction Mach Co

Inventors

• Ogura Kohei
• Kodaka Katsuaki
• Kayane Masahiro
• Shirakawa Yoshihiro

Classifications

• E02F9/2242

  including an electronic controller · CPC title

• E02F9/2271

  Actuators and supports therefor and protection therefor · CPC title

• E02F3/32

  working downwardly and towards the machine, e.g. with backhoes · CPC title

• E02F9/2296

  Systems with a variable displacement pump · CPC title

• F15B2211/6316

  the pressure being a pilot pressure · CPC title