Kobelco Construction Machinery Co., Ltd.

Yoshimi Saotome

Shota Oguma

Norifumi Shiraga

A construction machine including: a swivel motor; a working attachment having a boom, a boom cylinder, an arm and an arm cylinder; a hydraulic actuator circuit having a first circuit including the boom cylinder and a boom control valve, a second circuit including the arm cylinder and an arm control valve, and a third circuit including the swivel motor and a swivel control valve; first to third pumps for the first to third circuits; a merge valve having a first position for merge of third pump fluid into the first circuit and connection of an unload line of the third circuit to a tank, and a second position for prohibiting the merge; and a merge selecting control section which holds the merge valve at the first position either of when only a swivel operation is performed and when a boom raising operation is performed.

Construction machine

A construction machine includes a hydraulic actuator circuit including: a first circuit connected to one of travel motors and a boom cylinder; a second circuit connected to the other travel motor and arm cylinder; and a third circuit connected to a slewing motor; control valves for hydraulic actuators; and a merging valve having a first position for unloading hydraulic fluid discharged from a third pump upon no operation except for two travel motors; a second position for merging the hydraulic fluid into the first and second circuits upon a simultaneous operation of the travel motors and an operation of at least one remaining hydraulic actuator except for a boom raising operation; and a third position for merging the hydraulic fluid into the first circuit while blocking it from the second circuit upon the boom raising operation.

Construction machine having hydraulic circuit

Provided is a construction machine including a first circuit with a boom cylinder, a second circuit with an arm cylinder and a third circuit with a slewing motor, first to third pumps discharging respective first to third pump fluids, a first flow combining valve having a first combining position for the third and first pump fluids and a first combination limiting position, a second flow combining valve having a second combining position for the third and second pump fluids and a first combination and a second combination limiting position, and a flow combination switching control section which switches the flow combining valves to their respective combination limiting positions during an arm attracting operation and switches the combining valves to their respective combination limiting positions during a single slewing operation or during a boom raising operation with no arm operation.

Construction machine with hydraulic circuit

A throttle path for returning a part of pilot oil to a tank is formed by a tank path provided in a valve block of a control valve and a notch provided in a spool thereof. The above path is opened within a section from a vicinity of a stroke where a hydraulic actuator starts moving to right before a stroke end among a spool stroke of the control valve. An opening area of the above path is slowly reduced in accordance with an increase in the stroke at a final phase of the section.

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Hiroshima, Japan

Yoshimi Saotome