Hitachi Construction Machinery Co., Ltd.

Teppei Saitou

Kenji Hiraku

Juri Shimizu

Hiromasa Takahashi

Takamasa Kai

Shouhei Sugiki

To provide a construction machine that has a hydraulic system mounted thereon in which a closed-circuit pump, and an open-circuit pump and a proportional valve are arranged as a pair, and that makes it possible to use an unused open-circuit pump or proportional valve to accelerate the speed of a single rod hydraulic cylinder when the single rod hydraulic cylinder and a hydraulic motor are driven simultaneously. A controller () controls a cap-side selector valve () and a rod-side selector valve () such that a particular open-circuit pump () not connected to a single rod hydraulic cylinder () is connected to the single rod hydraulic cylinder, and controls an opening area of a particular proportional valve () provided on a flow line that connects a delivery port of the particular open-circuit pump to a tank, when the single rod hydraulic cylinder and a hydraulic motor () are driven simultaneously.

Construction machine

An object of the present invention is to provide a construction machine capable of suppressing lugging down of an engine irrespective of contents of operation of an operator and the load state of a hydraulic actuator. A controllerincludes: a demanded torque estimating sectionconfigured to estimate demanded torque as torque demanded from an engineby the first hydraulic pump on the basis of a demanded velocity of a first hydraulic actuatorand a load pressure on the first hydraulic actuator; a demanded velocity limiting sectionconfigured to, in a case in which a demanded torque change rate as a change rate of the demanded torque exceeds a predetermined change rate, limit the demanded velocity such that the demanded torque change rate becomes equal to or lower than the predetermined change rate; and a command calculating sectionconfigured to calculate a delivery flow rate of the first hydraulic pump on the basis of the demanded velocity of the first hydraulic actuator, the demanded velocity being limited by the demanded velocity limiting section.

An object of the present invention is to provide a construction machine that has a hydraulic closed-circuit system mounted therein and capable of selectively connecting some of a plurality of hydraulic pumps driven by two engines to any one of a plurality of hydraulic actuators and that can downsize the engines while maintaining high work efficiency. A controllerincludes an actuator/engine allocation computing section Fthat, at the time of connecting closed-circuit pumps that are not connected to any of the hydraulic actuators, andto any one of the hydraulic actuators, allocates closed-circuit pumps driven by a right engineto the one hydraulic actuator in a case in which an estimated maximum load on a left engineis heavier than an estimated maximum load on the right engine, and allocates closed-circuit pumps driven by the left engine to the one hydraulic actuator in a case in which the estimated maximum load on the right engine is heavier than the estimated maximum load on the left engine.

Provided is a work machine which makes it possible, in a hydraulic closed-circuit system, to prevent occurrence of cavitation when reverse lever operation which is an instruction for a swing in a direction opposite to a swing direction is performed during swing deceleration. A controller is configured to perform control such that a rate of a flow supplied from a bidirectionally tiltable hydraulic pump to a swing motor becomes lower than a pump flow rate according to an operation amount of the swing operation lever when a swing direction corresponding to a swing velocity sensed at a velocity sensor is different from a swing direction corresponding to operation of a swing operation lever.

Growing community of inventors

Tsuchiura, Japan

Teppei Saitou