Caterpillar Sarl

Sei Shimahara

Hiroyasu Nishikawa

Manabu Nakanishi

Masashi Shibata

Yusuke Shimizu

Yuya Kanenawa

Seiichi Akiyama

Isao Konishi

Kazuya Miyamori

Shinya Ohmura

Genta Mine

Atsunobu Doi

Problem to be solved: To provide a hydraulic circuit for the construction machine which enables to use the relief valve of low capacity in the work tool circuit. Solution: The hydraulic circuitfor a construction machine has: a hydraulic pumpof variable capacity, a work tooloperated by hydraulic oil delivered by the hydraulic pump, a work tool operating deviceto output a signal for operating the work tool, a control valveallowing the hydraulic pumpto supply the hydraulic oil to the work toolbased on the signal output from the work tool operating device, a tool's relief valveto release the hydraulic oil flowing between the control valveand the work tool, a pressure sensorto detect a pressure of hydraulic oil flowing into the work tool, and a controllerto reduce a delivery rate from the hydraulic pumpwhen the pressure detected by the pressure sensorexceeds a predetermined value.

Hydraulic circuit for a construction machine

A work machine equipped with an automatic hammering function is capable of preventing breakage of the hammer caused by blank firing. Hydraulic oil fed to a hydraulic breaker at the distal end of a work machine is controlled by first and second spools. Operating an operation lever so as to contract single rod type boom cylinders to press the hydraulic breaker against an object to be crushed. Head-side pressure and rod-side pressure of the boom cylinders are respectively detected by pressure sensors. Any one of switches is used to switch the mode of automatic hammering operation between an automatic hammering inhibiting mode and an automatic hammering authorizing mode. In the automatic hammering authorizing mode, a controller controls the first and second spools of the hydraulic breaker so as to open them only when head-side pressure and rod-side pressure of the boom cylinders are in a given range of pressing force.

Work machine

A controller controls the solenoid-operated variable pressure relief valves that are provided to control, at set pressures that can be electrically commanded, pressure of hydraulic oil fed to an attachment cylinder. The controller is provided with a control logic that is capable of controlling the aforementioned solenoid-operated variable pressure relief valves. The control logic performs the aforementioned calculation by compensating for pressure override characteristics of each solenoid-operated variable pressure relief valve based on input signals related to the set relief pressure for and a relief valve passing flow rate of the solenoid-operated variable pressure relief valve, and outputting to the solenoid-operated variable pressure relief valve command signals related to the adjusted set relief pressure resulting from the compensation of the pressure override characteristics.

Hydraulic circuit control device and work machine

A hydraulic pump driven by an engine, a hydraulic actuator, and a negative control circuit are provided on an open center hydraulic circuit, for guiding the hydraulic pressure in the center bypass to the hydraulic pump, as a negative control pressure. A negative control pressure control device controls the negative control pressure to an arbitrary value is also provided. The pump characteristic of the hydraulic pump is set such that the discharge flow rate is minimized when the negative control pressure in the negative control circuit is equal to or greater than a first predetermined pressure. Furthermore, an idling detection device that detects whether the hydraulic actuator is in a non-operated state or not is provided. The negative control pressure is forcefully controlled to the first predetermined pressure or higher when the non-operating state is detected.

Hydraulic control apparatus for work machine

A fluid pressure circuit that can, in either case where a first actuator that is fed from a first pump or a second actuator that is fed from a second pump is operated, by allowing feeding of the hydraulic fluid to a specific actuator from either the first or second pump, improve interlockability with the specific actuator. A control valve is incorporated with a plurality of first-group spools fed from a drive pump and a plurality of second-group spools fed from an idle pump. A solenoid selector valve unit switches a pilot line of a second-group tool controlling spool to a communicating state at the time of detection of a spool operation by a first pressure switch and switches a pilot line of a first-group tool controlling spool to a communicating state at the time of detection of a spool operation by a second pressure switch.

Fluid pressure circuit

A control unit for a work machine that allows automatically obtaining optimal operability even when the weight of a work arm in the work machine is changed. In a work machine where at least a part of a work arm to be operated by a fluid pressure actuator is provided so as to be replaceable, a control unit for a work machine includes: a pilot-operated control valve that controls the fluid pressure actuator; a proportional solenoid valve that pilot-controls the pilot-operated control valve by a pilot control pressure according to an electrical signal corresponding to a manual operation amount; a measuring means that measures a weight of at least the part of the work arm; and a controller that converts characteristics between the manual operation amount and the pilot control pressure of the proportional solenoid valve to characteristics according to the weight of the work arm measured by the measuring means.

Control unit for work machine

A valve control unit that prevents a decline in interlocking operation performance when pilot pressure control of a plurality of pilot-operated control valves is carried out by proportional solenoid valves. First and second proportional solenoid valves include a Common Operation Table of lever operation amount/boom-up pilot pressure characteristics and are inputted with a common boom-up lever operation amount. A third proportional solenoid valve also includes the Operation Table and is inputted with a stick-in lever operation amount common to the fourth proportional solenoid valve. The fourth proportional solenoid valve includes an Operation Table of lever operation amount/stick-in pilot pressure characteristics different from that of the first, second, and third proportional solenoid valves and is inputted with the stick-in lever operation amount common to the third proportional solenoid valve.

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Tokyo, Japan

Sei Shimahara