Disclosed is a hydraulic control apparatus including a flow-path selector valve that switches a supply flow path and a flow-path switching control unit that operates the same, a regeneration valve and a regeneration release valve capable of the regenerative operation, and a regeneration control unit that operates the same. The flow-path switching control unit makes the flow-path selector valve form a flow-path providing communication between first and second pumps in a combined operation state. The regeneration control unit judges the propriety of the regenerative operation on the basis of the second pump pressure which is the discharge pressure of the second pump in a single operation state and judges the propriety of the regenerative operation on the basis of whether or not the driving state of the work actuator is within an allowable range corresponding to the target work operation amount in the combined operation state.

Provided is a construction machine. The construction machine includes a boom cylinder driving a boom, a rotation motor rotating a rotary body, an arm cylinder driving an arm, a bucket cylinder driving a bucket, a first main pump supplying working fluid to the boom cylinder and discharging the working fluid in opposite directions, a second main pump supplying working fluid to the rotation motor and discharging the working fluid in opposite directions, and a third main pump supplying working fluid to the arm cylinder or the bucket cylinder.

An object of the present invention is to provide a construction machine that is equipped with a pressure accumulating device, which accumulates the return oil of an actuator, and that is capable of adjusting the operation speed of the actuator according to the revolution speed of a prime mover. For this purpose, in a construction machine including a prime mover, a revolution speed setting device that sets a revolution speed of the prime mover, an actuator, a pressure accumulating device that can supply and discharge a hydraulic fluid to and from the actuator, a first control valve disposed on a hydraulic fluid line that connects the pressure accumulating device and the actuator to each other, an operation device that gives an instruction for operation of the actuator, and a controller that is inputted with an operation signal of the operation device and outputs a control signal to the first control valve, the controller controls the first control valve according to an operation amount of the operation device and the revolution speed set by the revolution speed setting device.

An hydraulic apparatus (100) for energy recovery in an operating machine comprising an hydro-pneumatic accumulator (14) able to accumulate, during the operation of lowering of an operative load (111) by an operating machine (1), a volume of oil with a fixed amount of an inert fluid, and the pre-charge pressure (Po) of which, before the beginning of the accumulation, is adjusted according to the variations of pressure of the oil inside the hydraulic cylinders (12,13) which act on the operative load (111), in such a way to accumulate the maximum hydraulic energy made available by the lowering of operating load (111), that is to maximize the average pressure of hydro-pneumatic accumulator (14) during the phase of accumulation of energy.

The object of the present invention resides in provision of a construction machine in which a hydraulic cylinder can be driven in a high efficiency by an accumulator. To this end, the construction machine including: a hydraulic cylinder; a first accumulator that accumulates return fluid from the hydraulic cylinder with a first set pressure; a tank that stores hydraulic fluid therein; a first hydraulic pump that delivers the hydraulic fluid sucked from the tank; a hydraulic actuator that is driven by the first hydraulic pump; and a second accumulator that accumulates return fluid from the hydraulic actuator with a second set pressure, includes a first control valve placed in a first hydraulic line that connects the first accumulator and the hydraulic cylinder to each other, and a second control valve placed in a second hydraulic line that connects the second accumulator and the hydraulic cylinder to each other. The second set pressure is set to a value higher than that of the first set pressure.

The present invention provides a construction machine equipped with a pressure accumulation device that accumulates return oil from an actuator, and that can implement both improvement in fuel efficiency with enhancement in workability. To achieve the foregoing, a controller sets an actuator upper limit output power that is an upper limit for an output power of the actuator according to a work mode selected by a work mode selection device, and controls a first control valve and a second control valve such that a sum of an output power of a hydraulic pump and an output power of the pressure accumulation device does not exceed the actuator upper limit output power.

It is an object of the present invention to provide a construction machine capable of efficiently driving a hydraulic cylinder by an accumulator. Thus, the construction machine includes a first control valve disposed in a first hydraulic fluid line connecting a bottom-side fluid chamber of a hydraulic cylinder with an accumulator, and a second control valve disposed in a second hydraulic fluid line connecting a rod-side fluid chamber of the hydraulic cylinder with a tank. The construction machine further includes a third control valve disposed in a third hydraulic fluid line connecting the rod-side fluid chamber with the accumulator, and a fourth control valve disposed in a fourth hydraulic fluid line connecting a line part of the first hydraulic fluid line, which connects the bottom-side fluid chamber with the third control valve, and a line part of the third hydraulic fluid line, which connects the rod-side fluid chamber with the third control valve, with each other.

A hydraulic system for a working machine includes a first electric machine connected to a first hydraulic machine; a second electric machine connected to a second hydraulic machine, an output side of the second hydraulic machine being connected to an input side of the first hydraulic machine; at least one hydraulic consumer hydraulically coupled to an output side of the first hydraulic machine via a supply line and configured to be powered by the first hydraulic machine; and a valve arrangement arranged between the hydraulic consumer and the first and second hydraulic machines, wherein the valve arrangement is configured to control a return flow of hydraulic fluid from the hydraulic consumer to either the input side of the first hydraulic machine or an input side of the second hydraulic machine based on a requested output pressure from the first hydraulic machine.

A hydraulic machine. A boom actuator includes a large chamber and a small chamber. A recovery unit receives fluid discharged from the large chamber and then recovers energy. A recovery line connects the large chamber and the recovery unit. An accumulator is connected to a first point on the recovery line. A discharge valve is disposed on the recovery line between the first point and the recovery unit. A first sensor measures a pressure in the accumulator. A controller controls opening and closing of the discharge valve. The controller performs anti-bouncing control of: determining a target pressure in the accumulator corresponding to a load pressure applied to fluid in the large chamber by a load according to a predetermined correspondence; and controlling the opening and closing of the discharge valve such that the pressure in the accumulator measured by the first sensor reaches the target pressure.

To make it possible to control supply, discharge, and recycled flow rates independently of each other for the stick cylinder in a construction machine comprising first and second stick spool valves respectively connected to first and second hydraulic pumps. [Solution] A poppet valve is provided at upstream side of the first stick spool valve for controlling a supply flow rate from first hydraulic pump, the first stick spool valve is configured to supply hydraulic flow from the poppet valve to the stick cylinder without restricting the flow, and when the stick cylinder is extended, the poppet valve is configured to control supply flow rate from the first hydraulic pump to head side oil chamber, the first stick spool valve is configured to control recycled flow rate from a rod side oil chamber to the head side oil chamber, and the second stick spool valve is configured to control the supply flow rate from second hydraulic pump to head side oil chamber and the discharge flow rate from the rod side oil chamber to an oil tank.