Hitachi Construction Machinery Tierra Co., Ltd.

Hitachi Construction Machinery Co., Ltd.

Natsuki Nakamura

Yoshifumi Takebayashi

Kazushige Mori

Kiwamu Takahashi

Hajime Yoshida

Daisuke Oka

Yasutaka Tsuruga

Taihei Maehara

Yasuharu Okazaki

Shingo Kishimoto

Kenji Yamada

Takeshi Ishii

Masamichi Ito

Hiroyuki Nobezawa

Provided is a construction machine that can prevent a machine body from being lowered since a blade is not put into a float state even where a misoperation is made by an operator when the machine body is in a jacked-up state, and that can perform a favorable leveling operation by putting the blade into the float state in accordance with an operator's operation when the machine body is not in the jacked-up state. A hydraulic excavator includes a controllerthat determines whether or not the machine body is in a jacked-up state and controls a float valve. In the case where it is determined that the machine body is not in the jacked-up state, the controllerchanges over the float valveto a float position V and invalidates an operation of a blade control valve, in accordance with a float instruction. In the case where it is determined that the machine body is in the jacked-up state, the controllerholds the float valvein a reference position IV and validates the operation of the blade control valve, irrespectively of the presence or absence of the float instruction.

Construction machine

A hydraulic drive system for a hydraulic excavator that enables leveling work and a jack-up operation by a blade in a float state, that can prevent a body from falling even when an operator has falsely operated the hydraulic excavator during the jack-up operation by the blade, and that yet can perform favorable leveling work with the blade turned into the float state is provided. A float switch, a float valve, and a controllerare provided, the float valveis changed over to a float position VI upon operating the float switchwhen the blade is not in a jack-up state, the float valveis changed over from the float position VI to a normal position V when the float valveis in a state of being at the float position VI and an operation lever devicehas been operated, and the float valveis kept at the normal position V when the float valveis at the normal position V and the float switchhas been operated in the jack-up state.

Hydraulic drive system for construction machine

To provide a small hydraulic excavator, which even may have an upperstructure formed such that at least its rear end swings within a body width range and having a limited installation space for devices, that allows an accumulator to be disposed and allows the accumulator to be protected from external force generated during work. The present invention relates to a rear small-swing type mini excavator that includes an accumulatoraccommodating and recovering potential energy and hydraulic energy used by at least one of drives of an undercarriage, an upperstructureformed such that its rear end swings within the body width range of the undercarriage, and a working device. In the rear small-swing type mini excavator, the accumulatoris disposed between a valve blockand a front longitudinal boardof a longitudinal board member included in a main framealong the front longitudinal board, and a pipe connected to the accumulatorand the valve blockis disposed closer to the accumulatorand the valve block

Small hydraulic excavator

When a swing motor and a boom cylinder are driven simultaneously, a hydraulic drive system appropriately adjusts a distribution of torques between hydraulic pumps and feeds back a torque actually consumed by the hydraulic pump for actuating the swing motor accurately to the hydraulic pump for actuating the boom cylinder. To that end, when boom raising and swinging are performed simultaneously, the hydraulic drive system corrects an allowable torque of a hydraulic pumpthat supplies a hydraulic fluid to a swing motorso as to be lowered by a certain ratio, reducing allowable torques of hydraulic pumpsandthat supply a hydraulic fluid to a boom cylinderby torques consumed by the hydraulic pumpsandthat supply a hydraulic fluid to the swing motor

Provided is a construction machine that can prevent a machine body from being lowered without placing a blade in a floating state when the machine body is jacked up, even if the operator performs an erroneous operation, and that can perform favorable leveling work by placing the blade in the floating state when the machine body is not jacked up. A hydraulic excavator includes a pressure sensor that detects the pressure in a bottom-side oil chamber of a blade cylinder, and a controller that switches between validation and invalidation of a floating command and a lowering command for a blade operation device. In the case where the pressure detected by the pressure sensor is less than a predetermined value, the controller switches a solenoid selector valve to an interruption position to invalidate the floating command when a forward stroke of the operation lever is equal to or more than a reference value. In the case where the pressure detected by the pressure sensor is equal to or more than the predetermined value, the controller holds the solenoid selector valve in a communication position to validate the floating command when the forward stroke of the operation lever is equal to or more than the reference value.

A construction machine that can easily regulate a set maximum flow rate at a time of replacement of an attachment and that can improve an energy conservation performance is provided. A controller selects a corresponding map in response to an attachment designation signal from among maps each of which sets a relationship between an operation signal per type of the attachment and a flow rate of a hydraulic fluid supplied to an actuator, generates a control signal by causing the selected map to refer to the operation signal, and controls a flow control valve of an attachment flow rate regulation valve device in such a manner that a position of the flow control valve is switched over from a neutral position on the basis of the control signal. An unloading valve that maintains a differential pressure across the flow control valve is disposed in the attachment flow rate regulation valve device.

In a hydraulic drive system of a work machine which drives a plurality of actuators using three or more pumps, for an operation not including traveling, a highly efficient combined operation in a front implement and excellent combined operability of a swing and the front implement are enabled, while for an operation including traveling, a highly efficient traveling operation and a highly efficient combined operation of traveling and the front implement are enabled, and a sufficient operation speed of the front implement is achieved. To this end, each of the flow rates of the first, second, and third pumps () can be controlled independently by performing the load sensing control, and in a combined operation for driving a boom () and an arm (), ether one of them is driven by the first pump while the other one is driven by the second pump, and the swing is driven by the third pump. In the traveling operation, the maximum capacity of the first and second pumps is switched to the maximum capacity for the traveling operation and driven by an open center circuit. In a combined operation of traveling and the front implement, the front implement is driven by performing the load sensing control using the third pump.

Hydraulic drive system of work machine

Pressure compensating valves not fully closing at the stroke end are employed, and upon the operator's operation for the traveling, pilot primary pressure is reduced and supplied to remote control valves-of non-travel operating devices. Thus, the inflow of the hydraulic fluid into non-travel actuators is suppressed and a necessary amount of hydraulic fluid for travel motors is secured in travel combined operation. Accordingly, when saturation occurs in a construction machine's hydraulic drive system performing the load sensing control due to combined operation with a great load pressure difference between two actuators, deceleration/stoppage of an actuator on the low load pressure side is prevented by preventing full closure of the pressure compensating valve on the low load pressure side, while also preventing deceleration/stoppage of a high load pressure actuator by securing a necessary amount of hydraulic fluid for the high load pressure actuator.

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

To make it possible to efficiently utilize rated output torque of a prime mover by performing total torque control with high precision through precise detection of absorption torque of another hydraulic pump by use of a purely hydraulic structure and feedback of the absorption torque to the side of one hydraulic pump, delivery pressure of a main pump and a load sensing drive pressure are supplied to a torque feedback circuit, which modifies the delivery pressure of the main pump to achieve a characteristic simulating the absorption torque of the main pump, and outputs the modified pressure. An output pressure of the torque feedback circuit is supplied to a torque feedback piston, which controls displacement of the main pump so as to decrease the displacement of the main pump and thereby decrease maximum torque as the output pressure increases.

To cope with a variety of flow rate balance required of two actuators flexibly in combined operations driving two actuators of high maximum demanded flow rates at the same time while suppressing the wasteful energy consumption caused by the throttle pressure loss in a pressure compensating valve, the arrangement is such that when the demanded flow rate of a boom cylinderis lower than a prescribed flow rate, the boom cylinderis driven only by hydraulic fluid delivered from a single flow type main pumpand when the demanded flow rate of the boom cylinderis higher than the prescribed flow rate, the hydraulic fluid delivered from the single flow type main pumpand hydraulic fluid delivered from a first delivery portof a split flow type main pumpare merged together and the boom cylinderis driven by the merged fluids. Further, when the demanded flow rate of an arm cylinderis lower than a prescribed flow rate, the arm cylinderis driven only by hydraulic fluid delivered from a second delivery portof the split flow type main pumpand when the demanded flow rate of the arm cylinderis higher than the prescribed flow rate, hydraulic fluid delivered from the first delivery portand hydraulic fluid delivered from the second delivery portare merged together and the arm cylinderis driven by the merged fluids.

In a hydraulic driving system for construction machines, when track motorsandare operated and the delivery pressure of a main pumpincreases to a second value PSof the set pressure of a main relief valve, the set pressure of a signal pressure relief valveincreases from a third value PAto a fourth value PA, which is smaller than the second value PSof the set pressure of the main relief valve, the difference between the second value PSand the fourth value PAbeing smaller than the target LS differential pressure. With such a structure, even if one of actuators reaches the stroke end and the delivery pressure of the hydraulic pump rises to the set pressure of the main relief valve, the other actuators do not stop, and further when the main relief valve is configured to increase the set pressure during operation of a specific actuator, the load pressure of the specific actuator does not increase to the increased set pressure of the main relief valve.

Hydraulic driving system for construction machine

The object is to make it possible to efficiently utilize rated output torque of the prime mover by performing total torque control with high precision through precise detection of absorption torque of the other hydraulic pump by use of a purely hydraulic structure and feedback of the absorption torque to the one hydraulic pump's side. For this purpose, the hydraulic drive system is equipped with: a torque feedback circuitwhich is supplied with delivery pressure of a main pumpand load sensing drive pressure, modifies the delivery pressure of the main pumpto achieve a characteristic simulating the absorption torque of the main pump, and outputs the modified pressure; and a torque feedback pistonwhich is supplied with output pressure of the torque feedback circuit and controls displacement of a main pumpso as to decrease the displacement of the main pumpand thereby decrease maximum torque Tas the output pressure increases. The torque feedback circuitincludes first and second variable pressure reducing valvesand

An object to achieve favorable operability, in a combined operation that involves a specific actuator and involves a great difference in load pressure and when an operation of an operating unit for the specific actuator is a fine operation, by reducing energy consumption arising from wasted restricting pressure loss of a pressure compensating valve and by flexibly varying a flow rate of a hydraulic fluid supplied to the specific actuator depending on the load pressure. To achieve this object, a boom cylinder () is provided with an open center type flow control valve () that controls a hydraulic fluid from a main pump () and a closed center type flow control valve () that controls a hydraulic fluid from a main pump (). The main pump () is subject to load sensing control. The flow control valve () is opened to control a supply flow rate up to an intermediate zone of an operating range of an operating unit for the boom cylinder (). Both the flow control valves () and () are opened to control the supply flow rate after the intermediate zone.

In addition to a main pumphaving two delivery portsandand performing the load sensing control, two subsidiary pumpsandfor the load sensing control for respectively performing assist driving on a boom cylinderand an arm cylinderare provided. When driving the boom cylinderor the arm cylinder, a selector valveoris switched and flows of hydraulic fluid are merged together and supplied to the boom cylinderor the arm cylinder. When driving actuators other than the boom cylinderor the arm cylinder, only the hydraulic fluid from the main pump is supplied to the actuators. In short, the hydraulic drive system is configured so that two specific actuators having great demanded flow rates and tending to have a great load pressure difference between each other when driving at the same time can be driven with hydraulic fluid delivered from separate delivery ports. With this configuration, wasteful energy consumption due to pressure loss in a pressure compensating valve can be suppressed, and in cases of driving an actuator of a low demanded flow rate, the hydraulic pump can be used at a point where the volume efficiency is high.

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Koka, Japan

Natsuki Nakamura