Hitachi Construction Machinery Co., Ltd.

Teppei Saitoh

Kenji Hiraku

Hiromasa Takahashi

Juri Shimizu

Mariko Mizuochi

Akinori Ishii

Hidefumi Ishimoto

Ryu Narikawa

Yuki Akiyama

Kouji Fujita

Takamasa Kai

Shohei Sugiki

Tadashi Nishizawa

Hideaki Itou

Akira Nakayama

Mitsuo Aihara

Hiroyuki Sadamori

Takashi Kusama

Shouhei Sugiki

Syouhei Sugiki

Hiraku Kenji

Provided is a work machine that allows assisting a loading work without giving uncomfortable feeling to an operator. The control deviceof the work machineincludes an allowable range calculation sectionthat calculates an allowable range indicating a range in which the front work deviceis movable in a height direction allowed in a swing operation; an operation determining sectionthat determines whether the work machineis under a convey operation; and an operation control sectionthat controls a turn operation of a boomsuch that the position of the front work devicein the height direction remains within the allowable range when the work machineis determined to be under the convey operation.

Work machine

Provided is a construction machine configured such that a hydraulic actuator is driven by a hydraulic pump for a closed circuit, by which oil film breakage of the hydraulic pump for a closed circuit is prevented to improve the reliability and a high operation rate can be obtained. The construction machine includes a switching valve that is provided in a branch hydraulic line connecting one of suction/delivery ports of a closed circuit pump and a charge line to each other and is opened and closed according to a control signal from a controller. The controller is configured to, in a case where a state in which a delivery volume of the closed circuit pump is kept to zero continues for a predetermined time period or more, open the switching valve and keep the delivery volume of the closed circuit pump to a predetermined delivery volume or more, the predetermined delivery volume being greater than zero.

Construction machine

A work machine includes a second pilot line that introduces a hydraulic fluid from a pilot hydraulic fluid source to a pilot valve bypassing a first gate lock valve, a second gate lock valve that is disposed on the second pilot line and that is configured to be switched to an open position for allowing the supply of the hydraulic fluid to the pilot valve or a closed position for interrupting the supply of the hydraulic fluid, and a controller that controls the second gate lock valve on the basis of a second remote operation signal transmitted from a remote operation apparatus and that controls the pilot valve according to a first remote operation signal transmitted from the remote operation apparatus. In a state where the first gate lock valve is at a closed position, the second gate lock valve is allowed to be controlled by the controller when stairs are in a retracted state, and is kept at the closed position irrespective of the second remote operation signal when the stairs are in an extended state.

A construction machine makes it possible for an operator to linearly push a bucket by operating an arm in a pushing direction. A controller is configured to, in case a straight locus is selected by a bucket locus selecting device, calculate a constant flow rate ratio according to a boom initial angle that is an angle of a boom sensed by a boom angle sensor at a time point when an arm is operated in a pushing direction by an operation device, and control the delivery flow rate of a first hydraulic pump such that a hydraulic fluid is discharged from a boom cylinder cap chamber at a flow rate obtained by multiplying a flow rate of a flow supplied to an arm cylinder cap chamber by the flow rate ratio while the arm is operated in the pushing direction and there is no boom operating instruction.

Provided is a construction machine in which travel operability is not impaired when a combined operation is performed in which a single-rod hydraulic cylinder is driven during a travel operation. A hydraulic excavator includes a controller that controls the delivery direction and delivery flow rate of a closed-circuit pump, opens and closes a travel switching valve and an assist switching valve, and controls the delivery flow rate of the open-circuit pump, according to a travel operation lever and a work operation lever. The controller holds the assist switching valve in a closed position irrespective of whether or not the work operation lever is operated in a case where the travel operation lever is operated.

Provided is a construction machine on which a hydraulic closed circuit for driving a single rod-type hydraulic cylinder and a swing hydraulic motor is mounted and that has good swing deceleration responsiveness. In this construction machine that drives each of a single rod-type hydraulic cylinder and a swing hydraulic motor in a closed circuit, a minimum passage area from a second flushing valve to a tank in a case the second flushing valve is fully open is smaller than a minimum passage area from a first flushing valve to the tank in a case the first flushing valve is fully open.

To make it possible to prevent a decrease in work speed due to a decrease in the speed of a given actuator when an operator unintentionally performs a fine operation of the control lever of the other actuator in a state in which the given actuator is driven by the hydraulic fluid delivered from a plurality of pumps, a controller () sets, as a composite dead zone line serving as a boundary of a composite dead zone, a composite dead zone line such that as an operation amount in one direction of a control lever (L) or (L) of a control lever device () or () is increased, the width of the composite dead zone corresponding to an operation amount in the other direction of the control lever is widened, and corrects the operation amount in the other direction such that the demanded flow rate of an actuator increases from zero, when the control lever is operated in the other direction in a state in which the operation amount in the one direction of the control lever remains within a range of the composite dead zone, and the operation amount in the other direction exceeds the composite dead zone line.

It is an object of the present invention to provide a construction machine having a good engine starting property in a low temperature environment. The construction machine of the present invention includes: an electric pump having a delivery port connected to a line part of a pilot line, the line part connecting a pilot pump with a pilot control valve; a motor that drives the electric pump; and a temperature sensor that measures a temperature of a hydraulic working fluid delivered from the pilot pump. A controller starts driving of the motor in the case where a key switch is operated from a key OFF state to a key ON state and where the temperature of the hydraulic working fluid measured by the temperature sensor is lower than a predetermined temperature.

A construction machine incorporates a hydraulic closed circuit system capable of suppressing, even where a selector valve is stuck in an open state by a failure of the selector valve or a control system therefor, unintended operation of a hydraulic actuator and continuing operation of a machine body. The construction machine includes first sensors that detect open-closed states of a plurality of switching valves, first compulsory valve closing devices that change over the plurality of switching valves to a closed position irrespective of open-close control by a machine body controller, and a valve device controller that controls, when it is detected based on the open-closed states of the plurality of selector values detected by the first sensors that one of the plurality of selector values is stuck in an open state, the first compulsory valve closing device such that other selector valve connected to one of the plurality of closed circuit pumps to which the one selector valve is connected is closed.

A construction machine is provided which includes a hydraulic closed circuit in which a single rod hydraulic cylinder is driven directly by a bidirectionally tiltable variable displacement pump and can stably speed up the contraction action of the single rod hydraulic cylinder. In the case where a contraction action of a hydraulic cylinderis instructed through an operation leverwhen a differential pressure obtained by subtracting the pressure of a cap chamberfrom the pressure of a rod chamberis equal to or lower than a first threshold value a set to a level equal to or higher than a selection setting pressure of a flushing valvea controllercloses a rod side selector valveto disable rod assist action for supplying hydraulic fluid from a second hydraulic pumpto the rod chamber, and when the differential pressure is higher than the first threshold value, the controlleropens the rod side selector valve to enable the rod assist action.

This construction machine includes a first hydraulic drive device that is driven by a first prime mover and a second hydraulic drive device that is driven by a second prime mover. The first hydraulic drive device has a first closed circuit that connects a first hydraulic actuator and a first closed-circuit pump and a first assist flow path that connects the first closed circuit and a first open-circuit pump and that supplies pressure oil from the first open-circuit pump to the first closed circuit. The second hydraulic drive device is provided with a second closed circuit that connects a second hydraulic actuator and a second closed-circuit pump. The present invention also includes a first emergency flow path that branches from the first assist flow path and connects to the second closed circuit and that supplies pressure oil from the first open-circuit pump to the second closed circuit.

A construction machine includes a bidirectionally tiltable type hydraulic pump, a hydraulic cylinderhaving a cap chamberand a rod chamber, a first flow pathconnecting the hydraulic pumpand the cap chamber, a second flow pathconnecting the hydraulic pumpand the rod chamber, a discharge flow pathbranched from the first flow path, a discharge valvethat is disposed in the discharge flow pathand controls a discharge rate of hydraulic working oil from the cap chamberto the discharge flow path, an operation devicethat instructs an action of the hydraulic cylinder, and a controller. The controllercontrols the hydraulic pumpand the discharge valvesuch that at least a part of hydraulic working oil discharged from the cap chamberis discharged to the discharge flow pathwhen an operation amount of the operation devicelies within a fine operation region during a pulling action of the hydraulic cylinderin a state that a load is applied in a contraction direction. Accordingly, operability improves during fine operation of the pulling action of the hydraulic cylinder in the state that the load is applied in the contraction direction.

Provided is a construction machine capable of detecting a stuck-open state of a surplus flow control valve in real time during operation without involving a reduction in the operational speed. The construction machine is equipped with: a surplus flow control valve control section configured to output a closing command to a first surplus flow control valve at the operation start when an operation amount signal of an operation lever device is detected; a pump delivery control section configured to output a delivery flow rate command to an adjustment section of an open circuit pump; an assist valve control section configured to continue to output a closing command from before to an assist valve; a sticking detection determination section configured to compare a pressure signal with a previously set threshold value and determining that the surplus flow control valve is in a stuck-open state when the pressure signal is less than the threshold value and determining that the surplus flow control valve is normal when the pressure signal exceeds the threshold value; and a stop signal generating section configured to input therein a sticking determination signal, output in the case of a stuck-open state a control signal maintaining a closed state of the assist valve to the assist valve control section, and output in the case of a normal state a control signal causing the assist valve to perform an opening operation to the assist valve control section.

A work machine includes a closed circuit system in which there is provided a flushing valve. The flushing valve is equipped with: a valve main body; a spool which can select, in accordance with a position where the spool is arranged in the valve main body, connection between a first flow line and a third flow line, connection between a second flow line and the third flow line, or interruption of the connection between the first flow line, the second flow line, and the third flow line; a first liquid chamber that is provided inside the valve main body and into which a hydraulic working fluid from the first flow line flows; a first piston pressurizing the hydraulic working fluid having flowed into the first liquid chamber and moving the spool to a position where the second flow line and the third flow line are connected together, by the hydraulic pressure of the first liquid chamber; a second liquid chamber that is provided inside the valve main body and into which the hydraulic working fluid from the second flow line flows; and a second piston pressurizing the hydraulic working fluid having flowed into the second liquid chamber and moving the spool to a position where the first flow line and the third flow line are connected together, by the hydraulic pressure of the second liquid chamber.

To provide a work machine capable of efficiently regenerating the energy owned by hydraulic fluid during a swing deceleration. In the present invention, when a swing deceleration detection sectiondetects the state of a revolving upperstructurebeing decelerated, when an operation judgment sectionjudges the state that a double-tilting pump/motoris not supplying hydraulic fluid to any of a boom cylinderand an arm cylinder, and when the number of double-tilting pumps/motorshaving supplied hydraulic fluid to a swing hydraulic motorin the state before the swing deceleration detection sectiondetects the state of the revolving upperstructurebeing decelerated is equal to one or more, a pump valve control sectioncontrols changeover valvesto open and increases the displacements of the double-tilting pumps/motorsto the side to make suction pressures become higher than discharge pressures of the double-tilting pumps/motorsso that the double-tilting pumps/motorsoperate as motors.

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Tokyo, Japan

Teppei Saitoh