Hitachi Construction Machinery Co., Ltd.

Juri Shimizu

Kenji Hiraku

Hiromasa Takahashi

Teppei Saitoh

Mariko Mizuochi

Takamasa Kai

Shohei Sugiki

Teppei Saitou

Akinori Ishii

Yuki Akiyama

Shouhei Sugiki

Kazunori Ishihara

Takaaki Tanaka

Jun Ikeda

Hiroyuki Sadamori

Takashi Kusama

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.

Construction machine

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.

An engine () drives a variable capacity-type hydraulic pump (), discharged hydraulic oil is selectively supplied to a cooling fan () and a hoist cylinder () in accordance with switching of a selection valve (), thereby controlling the same on the basis of each target value. A pump discharge pressure (Pp) of the hydraulic oil discharged from the hydraulic pump () and a motor supply pressure (Pm) of the hydraulic oil supplied to a hydraulic motor () via the selection valve () are detected by sensors () and are compared with pressure determination values stored in advance as a pump discharge pressure (Pp) and an actuator supply pressure (Pm) generated when the target value is achieved. Presence/absence of abnormality in the hydraulic actuator control device () is determined on the basis of a result of the comparison, and when abnormality is determined to have occurred, control is performed to minimize the capacity of the hydraulic pump ().

Hydraulic actuator control device for dump truck

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.

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.

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.

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.

Work machine

Provided is a work machine that can selectively establish a closed circuit connection between a single rod-type hydraulic cylinder and a plurality of bidirectional-type hydraulic pumps, the work machine being capable of enhancing responsiveness of the single rod-type hydraulic cylinder when a high-speed lever switching operation is conducted in a state in which a rod pressure of the single rod-type hydraulic cylinder is higher than a bottom pressure. When a bucket lever () is operated to a side of extending the bucket cylinder in a state in which a pressure in a rod chamber () of the bucket cylinder () is higher than a pressure in a bottom chamber (), a controller () opens a rod-side proportional valve () and discharges a working fluid in the rod chamber to a working fluid tank () such that a differential pressure between the pressure in the rod chamber and the pressure in the bottom chamber is reduced below a switching pressure (Psw) of a flushing valve ().

Drive system for construction machine

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.

A drive system for a construction machine capable of appropriately controlling a distribution flow rate to each hydraulic actuator and improving operability by an operator is provided. A flow rate distribution section that computes a distribution flow rate of a hydraulic fluid supplied to each of a plurality of hydraulic actuators on the basis of a demanded flow rate, sets, within a distributable region set for computing a range of a distributable flow rate that is a flow rate of the hydraulic fluid suppliable to each of at least two hydraulic actuators driven by a combined operation among the plurality of hydraulic actuators from a plurality of hydraulic pump devices for the at least two hydraulic actuators, a distribution region for computing a range of the distribution flow rate of the hydraulic fluid actually supplied to each of the at least two hydraulic actuators, and computes the distribution flow rate in such a manner that the distribution flow rate falls within the distribution region and a ratio among the distribution flow rates of the plurality of hydraulic actuators is equal to a ratio among the demanded flow rates of the plurality of hydraulic actuators.

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Tokyo, Japan

Juri Shimizu