Kobelco Construction Machinery Co., Ltd.

Hidekazu Oka

Yutaka Toji

Naoki Sugano

Etsujiro Imanishi

Takao Nanjo

Yoichiro Yamazaki

Koji Yamashita

Koji Ueda

Kazuhiko Fujii

Hiroshi Togo

Saburo Senoo

Yuuji Matsuura

Provided is a hydraulic drive apparatus for a construction machine capable of achieving both of cavitation prevention and improvement of regeneration efficiency. The apparatus includes a regenerative motor configured to regenerate energy of hydraulic fluid discharged from a slewing motor, a first regeneration tank line for returning regeneration discharge fluid from the regenerative motor to a tank through a back pressure valve which is provided in a makeup line, a second regeneration tank line for returning the regeneration discharge fluid directly to the tank so as to bypass the back pressure valve, a regeneration-tank-line selector valve, and a regeneration-tank-line-selection control section configured to shift the regeneration-tank-line selector valve to pass the regeneration discharge fluid through the first regeneration tank line during slewing deceleration and otherwise through the second regeneration tank line.

Hydraulic drive apparatus for construction machine

A construction machine, including: a hydraulic pump; a working attachment including a boom, a boom cylinder, and another fluid-supplied cylinder closer to a leading end than the boom cylinder; first and second operation devices for the boom cylinder and the fluid-supplied cylinder; first and second control valves; a flow-rate-limiting section; and an anti-cavitation circuit. The fluid-supplied cylinder receives fluid-supply from the hydraulic pump, together with the boom cylinder. A reaction force upon work accompanying extension of the fluid-supplied cylinder increases the rod-side pressure of the boom cylinder and reduces a head-side pressure. The flow-rate-limiting section limits a supply flow rate to a head-side fluid chamber of the boom cylinder only during a boom-raising-operation with the rod-side pressure higher than the head-side pressure in the boom cylinder. The anti-cavitation circuit replenishes hydraulic fluid from a tank to the head-side fluid chamber.

Construction machine with working attachment

A hydraulic drive device capable of utilizing return oil effectively while maintaining a driven speed of a hydraulic actuator, as well as a working machine having the hydraulic drive device, are provided. The hydraulic drive device includes a controller. During an external force applying period in which a return oil pressure exceeds a discharge pressure from a hydraulic pump, the controller specifies a regenerating flow rate capable of being conducted to a regeneration oil passage and a surplus flow rate other than the regenerating flow rate on the basis of power required of the hydraulic pump out of return oil other than return oil which is conduced to a tank through a control valve, then conducts the return oil of the regenerating flow rate to the regeneration oil passage and controls an MO valve and a regulator so that the return oil of the surplus flow rate is conducted to an outlet oil passage.

Hydraulic drive device and working machine with the same

A hydraulic circuit for actuating an electromagnetic proportional pressure reducing valve by a command current outputted from a controller based on an operation amount of a remote control valve, and by a secondary pressure of the pressure reducing valve, actuating a common bleed-off valve which is a hydraulic pilot type spool valve is provided. In the controller, as a correction processing for correcting characteristics of a proportional valve command value which is a current value given to the pressure reducing valve and the opening area of the spool valve, at an inflection point at which the degree of change of a pump pressure increases, an actual proportional valve command value at a time of obtaining the pump pressure is compared to a theoretical proportional valve command value of a case of no tolerance, and a correction to compensate for a difference between the both command values is performed.

Hydraulic circuit of construction machine

With respect to a method of controlling a pump flow rate of a hydraulic pump, a method having a small flow rate command value is selected between a pressure feedback control for controlling the pump flow rate based on a set pressure (a cutoff pressure) and a pump pressure, and, an ordinary control for controlling the pump flow rate based on operation information, and in a case that the pressure feedback control is selected, a flow rate increasing control for increasing the flow rate command value after the case with the passage of time is performed.

Hydraulic control apparatus of working machine

A hydraulic control device for a working machine includes control valves; hydraulic actuators controlled by corresponding control valves and divided into groups; unified bleed-off valves disposed on discharge lines of first and second hydraulic pumps; central bypass paths provided in the control valves, the central bypass paths of each group being connected in tandem so as to form a central bypass line; and bypass-cutting valves disposed on the central bypass lines, the bypass-cutting valves being automatically switched so as to open the central bypass lines when the unified bleed-off valves are not operated.

Hydraulic control device for working machine

There is provided a hydraulic controller for a working machine in which a pilot hydraulic pressure source is connected in common to a plurality of pilot-operated hydraulic devices each having a pilot pressure input unit, and a common pilot pressure input switching valve is adapted to control the switching between a pilot pressure input from the pilot hydraulic pressure source to each pilot pressure input unit and a relief of the input. The switching control of a pilot pressure input by the pilot pressure input switching valve is performed based on the operating state of the working machine and pilot pressure input conditions of the respective pilot-operated hydraulic devices.

Hydraulic controller for working machine

A first group is supplied with hydraulic power from a first hydraulic pump. In the first group, an arm control valve is disposed at the most downstream position. A throttle is provided at the entrance of the arm control valve. Thus, a circuit is configured to give priority to boom raising or bucket excavation. During a combined operation, according to the operation amount of boom pulling or bucket excavation, a controller decreases the upper limit of the discharge amount of the first hydraulic pump determined by the operation amount of arm pulling and increases the recycling rate of oil to the expansion side of an arm cylinder.

Hydraulic control apparatus for hydraulic excavator

A hydraulic control system for a working machine according to the present invention includes a regulator control valve for controlling an operation of a pump regulator and a controller for sending a control signal for changing a discharge quantity of the pump to the regulator control valve in accordance with an operation amount of an operating device. This system further includes a fail-safe valve disposed in a control line joining the pump regulator and the regulator control valve. The fail-safe valve is configured so as to switch from an ordinary position to a fail-safe position in accordance with a failure signal indicative of failure in the regulator control valve.

Hydraulic control system for working machine

A hydraulic control system for a hydraulic excavator of the present invention comprises a boom control valve in a first oil path for providing pressure oil from a first hydraulic pump with a boom cylinder according to operation of a boom operating means, an arm control valve in a second oil path for providing pressure oil from a second hydraulic pump with an arm cylinder according to operation of an arm operating means, a confluence switching valve having a confluence position for joining the paths and a confluence stop position for stopping the confluence, a flow control valve for returning pressure oil in the first oil path to a tank, and a control means for controlling the valves, so as to switch the confluence switching valve to the confluence position and close the flow control valve when the arm operating means is operated independently and so as to switch the confluence switching valve to the confluence stop position and open the flow control valve when both of the operating means are operated simultaneously, thereby, the arm pulling operation is performed independently, an arm cylinder speed increases and a leveling efficiency is improved.

Hydraulic control system for hydraulic excavator

A hydraulic control system of the present invention comprising control valves for controlling the direction and flow rate of pressure oil discharged from a hydraulic pump, hydraulic actuators which the pressure oil is fed to and controlled by the control valves, the hydraulic actuators including hydraulic cylinders and a hydraulic motor, and a first return passage provided as a passage for returning return oil present at the head side of one of the hydraulic cylinders to the tank, the first return passage being in communication with the tank, and a second return passage for returning return oil from each of the other hydraulic actuators including the hydraulic motor except for the hydraulic cylinders to the tank, the second return passage having a back pressure check valve and a replenishing passage, the replenishing passage being configured so as to provide a back pressure developed by the back pressure check valve to the low pressure side of each of the other hydraulic actuators to prevent cavitations.

Hydraulic control system and construction machine

A hydraulic control device for a working machine includes hydraulic actuators, a hydraulic pump which functions as a hydraulic power source, control valves which control the actuators on the basis of operations by an operating unit, a common bleed-off valve which returns excess oil to a tank via an unload passage on the basis of the operations by the operating unit, and a control unit which controls the common bleed-off valve. The common bleed-off valve is capable of setting a position for closing the unload passage when the common bleed-off valve is in a non-operating state. The control valves have center bypass passages which function as individual bleed-off passages which open when the control valves are in neutral states. Opening characteristics of the control valves are set such that the center bypass passages are closed in initial stroke periods in which the control valves move toward operating positions.

An option valve for controlling the operation of an option actuator added as an option is installed into each of first and second main valve blocks in each of which plural control valves, a pressure oil supply line connected to a pump and a tank line connected to a tank are incorporated, and plural types of connection blocks incorporating circuit elements to be added to the option valve are attached to the main valve blocks selectively to constitute a hydraulic valve device. According to this hydraulic valve device, it is possible to widely cope with various option attachments despite a built-in system with the option valve incorporated beforehand in the main valve blocks.

Hydraulic valve device and method for assembling the same

In a hydraulic controller for construction machine according to the present invention, wherein there are provided regulators for each of a first and a second capacity variable hydraulic pump, each of the regulators being controlled, detecting the discharge pressure of each pump, in such a manner that one of the pumps absorbs a part of torque while the other thereof absorbs the remaining torque, and wherein a boom raising operation causes pressure oil from the pumps to be joined together and then supplied to a boom cylinder, while also a rotating operation causes pressure oil from the second pump to be supplied to a rotating motor, is provided a flow rate distribution controller adapted to control the regulators in such a manner that a difference in flow rate is provided between the pumps so that the first pump shows a higher flow rate at the start of a combined operation of raising and rotating, and that, on a steady rotating state which results in an increase in the discharge pressure difference between the pumps, the difference in flow rate is reduced. This enables pump horsepower to be distributed optimally between the boom cylinder and rotating motor during the raising and rotating operation.

Hydraulic controller for construction machine

The present invention relates to a control system and method for a hydraulic working machine characterized by having a construction wherein a flow discharge control valve is disposed in a discharge-side pipe line of a main flow control valve, the amount of operation of an operating lever is converted to a pilot pressure by a remote controlled valve, the pilot pressure is then input to a controller and is calculated into a pressure change speed as operation speed, in a pressure change speed calculator, further, the operation speed is calculated into an electromagnetic valve current in an electromagnetic valve current calculator, then the electromagnetic proportional valve current is output to an electromagnetic proportional valve from a command unit, and the degree of opening of the discharge flow control valve is controlled with a secondary pressure in the electromagnetic proportional valve. According to this construction, it is possible to diminish impact and vibration which occur when there is performed a sudden operation, and also possible to improve the operability for braking and stopping an actuator.

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Hiroshima, Japan

Hidekazu Oka