Hitachi Construction Machinery Tierra Co., Ltd.

Hitachi Construction Machinery Co., Ltd.

Shingo Kishimoto

Kiwamu Takahashi

Yoshifumi Takebayashi

Kazushige Mori

Natsuki Nakamura

Hironao Ishikawa

An electrically-operated hydraulic work machine drives an actuator with a hydraulic pump driven by an electric motor and exercises load sensing control by controlling the rotation speed of the electric motor. The useful life of an electrical storage device, which is an electrical power source for the electric motor, is increased by suppressing the horsepower consumption of the hydraulic pump. This prolongs the operating time of the electrically-operated hydraulic work machine, and reduces the size of the electric motor. A controller exercises load sensing control over a variable displacement main pump by controlling the rotation speed of the electric motor, and provides the main pump with a torque control device that reduces the delivery rate of the main pump when the delivery pressure of the main pump increases, or provides the controller with a control algorithm that performs the same function as the torque control device.

Hydraulic drive system for electrically-operated hydraulic work machine

An object of the invention is to achieve a travel speed known in the art during travelling operation, improve energy efficiency by reducing energy loss, and obtain favorable travel operability less susceptible to effects from variations in a travel load and changes in a pump delivery pressure when travelling operation is performed through operation of a travel lever over a half stroke range or less. A variable restrictor valveis disposed in parallel with a flow sensing valveof an engine speed sensing valve unitA travel pilot pressure is adapted to act in an opening direction of the variable restrictor valveThe variable restrictor valveis set to have a continuously increasing opening area from a full closure to a maximum with an increasing travel pilot pressure. Travel flow control valvesandhave an opening area that allows a predetermined flow rate QT required for traveling to be obtained even when a target LS differential pressure is decreased to a second specified value Pawhen the travel lever is fully operated. In a first half of a spool stroke, the travel flow control valvesandhave an opening area approximate to an opening area of comparative example 1.

Hydraulic drive system for construction machine

Pressure sensors are provided to detect the delivery pressure of a hydraulic pump, the output pressure of an engine revolution speed detecting valve, and the output pressure of a differential pressure reducing valve generating the differential pressure between the delivery pressure of the hydraulic pump and a maximum load pressure. A vehicle controller calculates virtually the displacement of the hydraulic pump by use of the detected pressures and an equation of motion about a swash plate of the hydraulic pump, calculates the power need of the hydraulic pump and the output of the engine using these values, and switches a motor between powering and generation control in accordance with the result of a comparison between the pump power need and the engine output. In this manner, the displacement of the hydraulic pump without using sensors to detect the tilting angle of the swash plate of the hydraulic pump.

Hybrid working machine

An upper boom is constituted by a box member having a shape like a box that includes an upper flange, a lower flange, a left web and a right web, and bosses that are welded to both ends of the box member. Bent plate portions which are bent inward are provided at both ends of the left web, and bent plate portions are also provided at both ends of the right web. Reinforcement plates are positioned at an outside of the bent plate portions and welded between the left web and the boss, and reinforcement plates are also welded between the right web and the boss at an outside of the bent plate portions. With these bent plate portions and the reinforcement plates, a double structure can be provided in the vicinities of the bosses, and these portions can be reinforced.

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Koka, Japan

Shingo Kishimoto