Work machine

Patent metadata

Field	Value
Publication number	US-9212469-B2
Application number	US-201214367000-A
Country	US
Kind code	B2
Filing date	Dec 18, 2012
Priority date	Dec 22, 2011
Publication date	Dec 15, 2015
Grant date	Dec 15, 2015

Abstract

There is provided a hydraulic excavator including a hydraulic pump ( 6 ) driven by an engine ( 7 ), a boom cylinder ( 3 a ) driven by hydraulic fluid delivered from the hydraulic pump ( 6 ), a swing motor ( 16 ) driven electrically, an operating device ( 4 A) for operating the boom cylinder ( 3 a ), an operating device ( 4 B) for operating the swing motor ( 16 ), and a vehicle body controller ( 11 ) which limits the power of the swing motor ( 16 ) in accordance with the operation amount of the operating device ( 4 A) when the two operating devices ( 4 A, 4 B) are operated in combination. The power limit value of the swing motor ( 16 ) varies depending on the output of the engine ( 7 ). This allows a good operational feeling to be retained in combined operation regardless of the operating state of the engine.

First claim

The invention claimed is:

1. A work machine comprising:
an engine;
a hydraulic pump driven by the engine;
a hydraulic actuator driven by hydraulic fluid delivered by the hydraulic pump;
an electric actuator driven electrically;
a first operating device which operates the hydraulic actuator; a second operating device which operates the electric actuator, and
a control device configured to calculate a target speed of the electric actuator in accordance with an operation amount of the second operating device, calculate a speed limit value of the electric actuator by correcting the target speed in accordance with an operation amount of the first operating device, calculate a torque limit value in accordance with the operation amount of the first operation device, the torque limit value used as a maximum torque of the electric actuator during the operation of the electric actuator, control a torque generated by the electric actuator to be lower than the torque limit value, and control a speed of the electric actuator to be lower than the speed limit value, wherein
the control device is further configured to calculate a power required to drive the hydraulic actuator in accordance with the operation amount of the first operating device, calculate a power limit value in accordance with the power required to drive the hydraulic actuator, the power limit value capable of being supplied to the electric actuator for driving the electric actuator, select the smaller of the torque limit value and a torque resulting from torque conversion of the power limit value, generate a torque command for the electric actuator in accordance with the selected value, and output the torque command to the electric actuator.

2. A work machine according to claim 1 , wherein
the first operating device is operable in two directions, and
the power limit value of the electric actuator has characteristics corresponding to a direction in which the first operating device is operated.

3. A work machine according to claim 1 , wherein
the electric actuator is a motor, and
the power limit value of the electric actuator is set independently depending on whether the motor is in a powering or regenerative operation.

Assignees

• Hitachi Construction Machinery

Inventors

• Udagawa Tsutomu
• Fujishima Kazuo
• Ishikawa Koji
• Satake Hidetoshi
• Kunitomo Yuichi

Classifications

• B60L2240/443

  Torque · CPC title

• B60L2240/423

  Torque · CPC title

• B60L7/14

  for vehicles propelled by AC motors · CPC title

• B60L2240/421

  Speed · CPC title

• B60L2200/40

  Working vehicles · CPC title