Hitachi Construction Machinery Tierra Co., Ltd.

Daisuke Oka

Yoshifumi Takebayashi

Natsuki Nakamura

Hajime Yoshida

Kiwamu Takahashi

Takeshi Ishii

Kazushige Mori

Taihei Maehara

Provided is a construction machine that can prevent a machine body from being lowered since a blade is not put into a float state even where a misoperation is made by an operator when the machine body is in a jacked-up state, and that can perform a favorable leveling operation by putting the blade into the float state in accordance with an operator's operation when the machine body is not in the jacked-up state. A hydraulic excavator includes a controllerthat determines whether or not the machine body is in a jacked-up state and controls a float valve. In the case where it is determined that the machine body is not in the jacked-up state, the controllerchanges over the float valveto a float position V and invalidates an operation of a blade control valve, in accordance with a float instruction. In the case where it is determined that the machine body is in the jacked-up state, the controllerholds the float valvein a reference position IV and validates the operation of the blade control valve, irrespectively of the presence or absence of the float instruction.

Construction machine

A hydraulic drive system for a hydraulic excavator that enables leveling work and a jack-up operation by a blade in a float state, that can prevent a body from falling even when an operator has falsely operated the hydraulic excavator during the jack-up operation by the blade, and that yet can perform favorable leveling work with the blade turned into the float state is provided. A float switch, a float valve, and a controllerare provided, the float valveis changed over to a float position VI upon operating the float switchwhen the blade is not in a jack-up state, the float valveis changed over from the float position VI to a normal position V when the float valveis in a state of being at the float position VI and an operation lever devicehas been operated, and the float valveis kept at the normal position V when the float valveis at the normal position V and the float switchhas been operated in the jack-up state.

Hydraulic drive system for construction machine

When a swing motor and a boom cylinder are driven simultaneously, a hydraulic drive system appropriately adjusts a distribution of torques between hydraulic pumps and feeds back a torque actually consumed by the hydraulic pump for actuating the swing motor accurately to the hydraulic pump for actuating the boom cylinder. To that end, when boom raising and swinging are performed simultaneously, the hydraulic drive system corrects an allowable torque of a hydraulic pumpthat supplies a hydraulic fluid to a swing motorso as to be lowered by a certain ratio, reducing allowable torques of hydraulic pumpsandthat supply a hydraulic fluid to a boom cylinderby torques consumed by the hydraulic pumpsandthat supply a hydraulic fluid to the swing motor

Provided is a construction machine that can prevent a machine body from being lowered without placing a blade in a floating state when the machine body is jacked up, even if the operator performs an erroneous operation, and that can perform favorable leveling work by placing the blade in the floating state when the machine body is not jacked up. A hydraulic excavator includes a pressure sensor that detects the pressure in a bottom-side oil chamber of a blade cylinder, and a controller that switches between validation and invalidation of a floating command and a lowering command for a blade operation device. In the case where the pressure detected by the pressure sensor is less than a predetermined value, the controller switches a solenoid selector valve to an interruption position to invalidate the floating command when a forward stroke of the operation lever is equal to or more than a reference value. In the case where the pressure detected by the pressure sensor is equal to or more than the predetermined value, the controller holds the solenoid selector valve in a communication position to validate the floating command when the forward stroke of the operation lever is equal to or more than the reference value.

A construction machine that can easily regulate a set maximum flow rate at a time of replacement of an attachment and that can improve an energy conservation performance is provided. A controller selects a corresponding map in response to an attachment designation signal from among maps each of which sets a relationship between an operation signal per type of the attachment and a flow rate of a hydraulic fluid supplied to an actuator, generates a control signal by causing the selected map to refer to the operation signal, and controls a flow control valve of an attachment flow rate regulation valve device in such a manner that a position of the flow control valve is switched over from a neutral position on the basis of the control signal. An unloading valve that maintains a differential pressure across the flow control valve is disposed in the attachment flow rate regulation valve device.

Growing community of inventors

Yasu, Japan

Daisuke Oka