JP2007321541A - Power unit of construction machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power unit of construction machine capable of travelling even in a very bad road face condition with high energy efficiency. <P>SOLUTION: In a power unit of construction machine supplying hydraulic oil discharged from a first pump P1 to one travel system actuator and supplying hydraulic oil discharged from a second pump P2 to the other travel system actuator, an auxiliary P3 is connected to the first pump P1 and the second pump P2 and a confluent control valve 22 is arranged at a connection process between the first and second pump and the auxiliary pump. While the confluent control valve confluences the hydraulic oil discharged from the first and second pump and the hydraulic oil discharged from the auxiliary pump and guides to both travel system actuators, the power unit of construction machine is constituted that the hydraulic oil is narrowed down to supply to the lower pressure actuator when a pressure difference is generated in the travel system actuators. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a power device for a construction machine such as a power shovel.

As a power device for a construction machine, for example, a power shovel can be cited, and the power shovel circuit configuration shown in Patent Document 1 is generally used. The main structure and operation of this power shovel will be described below.
As shown in FIG. 3, in this power shovel, the first pump P1 and the second pump P2 are linked to an engine that is a drive source, and hydraulic oil is discharged from both the pumps P1 and P2 by the rotation of the engine. I am doing so.

The first pump P1 is connected to the left travel valve 2 via the first pump passage 1 and the first tandem passage 1a. In the first tandem passage 1a, the turning valve 3 and the arm I speed valve are connected. 4. Boom II speed valve 5 and spare valve 6 are connected. However, the first parallel passage 7 is connected to the first pump passage 1, and the valves 3 to 6 are connected in parallel via the first parallel passage 7.
The second pump P2 is connected to the second pump passage 8 and the second tandem passage 8a, and the second tandem passage 8a includes a right travel valve 9, a bucket valve 10, and a boom I speed valve 11. The valve for arm II speed 12 is connected. However, the second pump passage 8 is connected to the second parallel passage 13, and the bucket valve 10 and the boom I speed valve 11 are connected in parallel via the second parallel passage 13.
The left travel valve 2 and the right travel valve 9 are valves that control the travel system actuators. By switching these valves 2 and 9, the travel system actuators can be operated independently on the left and right. it can. The valves other than the valves 2 and 9 are valves for controlling the actuator of the work machine system.

A distribution passage 14 is connected to the second pump passage 8, and the distribution passage 14 is led to the left travel valve 2. A switching valve 15 is provided in the distribution passage 14 so as to communicate or block the second pump P2 and the left travel valve 2.
In the figure, reference numeral 16 is a switching valve, 17 to 19 are relief valves, and 20 is a pilot pump. The pilot pump 20 discharges pilot pressure for switching each valve, the switching valve 15 and the switching valve 16, and the maximum pressure of the pilot line is set by the relief valve 19.
The relief valve 17 has a higher set pressure than the relief valve 18. Therefore, when the switching valve 16 is at the illustrated communication position, the set pressure of the relief valve 18 is the maximum pressure of the circuit, and when the switching valve 16 is at the shut-off position on the left side of the drawing, the set pressure of the relief valve 17 is set. Is the maximum pressure of the circuit.

Next, the operation of this power shovel will be described.
When operating the actuator of the work machine system with the excavator stopped, the first pump P1 is rotated and any one of the turning valve 3, the arm I speed valve 4, and the boom II speed valve 5 is turned on. Switch. Now, assuming that the arm I speed valve 4 is switched to operate the arm actuator, the hydraulic oil discharged from the first pump P1 passes through the first parallel passage 7 and the arm I speed valve 4 for the arm. While being guided to the actuator, the arm actuator can be operated by the hydraulic oil. At this time, when the arm I speed valve 4 is switched, the first pump passage 1 is shut off, and the first pump P1 and the left travel valve 2 are shut off.

In the above state, the second pump P2 is rotated and the bucket valve 10 is switched while keeping the switching valve 15 in the illustrated cutoff position. Then, the hydraulic oil discharged from the second pump P2 is guided to the bucket actuator via the second pump passage 8, the second tandem passage 8a, the second parallel passage 13, and the bucket valve 10, and is also generated by the hydraulic oil. The bucket actuator can be controlled.
If the arm I speed valve 4 and the arm II speed valve 12 are switched in a state where the hydraulic oil is discharged from the first and second pumps P1 and P2, the arm actuator can be controlled at the second speed. .
Thus, by rotating the first and second pumps P1 and P2 and switching the valve for controlling the actuator of the work implement system, the arm and boom can be controlled at the second speed, or the boom, arm and bucket can be controlled. Can be controlled at the same time.

On the other hand, when the actuator of the work machine system is controlled during traveling of the power shovel, in other words, when the traveling system and the work machine system are simultaneously controlled, the switching valve 15 is switched to the communication position on the left side in the drawing. When the second pump P2 is rotated and the left travel valve 2 and the right travel valve 9 are switched, the hydraulic oil discharged from the second pump P2 causes the second pump passage 8 and the right travel valve 9 to be switched. To the right traveling actuator via the distribution passage 14 and the left traveling valve 2. Thus, since the hydraulic oil discharged from the second pump P2 is guided to both actuators of the traveling system, the power shovel can travel.
In this state, if the first pump P1 is rotated and any one of the turning valve 3, the arm I speed valve 4, and the boom II speed valve 5 is switched, the operation is performed by the hydraulic oil discharged from the first pump P1. Mechanical actuators can be activated.

When the excavator is driven without operating the work machine system actuator, the first and second pumps P1 and P2 are rotated while the switching valve 15 is kept at the cut-off position shown in the drawing. The travel valve 2 and the right travel valve 9 are switched. Then, the hydraulic oil discharged from the first pump P1 is guided to the left travel actuator, and the hydraulic oil discharged from the second pump P2 is guided to the right travel actuator, so that the power shovel can travel.
Hydraulic Pneumatic Handbook (Edited by Japan Society of Hydraulic and Pneumatics) Hydraulic Excavator Application Examples P638 and 639

In the power shovel, the hydraulic oil discharged from the first pump P1 is guided to the left travel actuator, and the hydraulic oil discharged from the second pump P2 is guided to the right travel actuator so that the power shovel travels. ing.
However, in construction sites that use power shovels, mud and bumps are scattered, and the road surface condition is often very poor. When a power shovel runs on such mud or uneven ground, there is a problem that the crawler gets stuck in mud or uneven and cannot get out of there.

In order to solve the above-described problem, it is conceivable to increase the operating force acting on the actuator of the traveling system so that the crawler can come out of the crawler even if it becomes muddy or uneven. In other words, it is conceivable to increase the capacities of both pumps P1, P2.
However, if the capacity of both pumps P1 and P2 is increased so that the vehicle can run even in poor road surface conditions, the load of the drive source becomes larger than necessary when operating the actuator of the work implement system. This time, there was a problem that the energy efficiency became very bad.

  An object of the present invention is to provide a power device for a construction machine that is capable of traveling even when the road surface condition is poor and that has high energy efficiency.

  The present invention includes a travel system actuator that operates independently on the left and right sides, a work machine system actuator, and a first pump and a second pump that selectively supply hydraulic oil to the travel system or work machine system actuator. It is premised on a power device for a construction machine that travels by supplying hydraulic oil discharged from the first pump to one traveling system actuator and supplying hydraulic oil discharged from the second pump to the other traveling system actuator. .

  Assuming the above configuration, the first invention connects an auxiliary pump to the first and second pumps, and provides a merging control valve in the connection process between the first and second pumps and the auxiliary pump. The merging control valve joins the hydraulic oil discharged from the first and second pumps and the hydraulic oil discharged from the auxiliary pump to lead to both actuators of the traveling system, while a pressure difference occurs between both actuators of the traveling system. In this case, the hydraulic oil supplied to the actuator with the lower pressure is reduced.

  The second invention includes a generator motor that rotates integrally with the auxiliary pump, and a power storage unit that stores electric power generated by the rotation of the generator motor, and inertia energy and potential energy act on the actuator of the work machine system. The passage on the return side is sometimes connected to the suction side of the auxiliary pump, and the inertial or positional energy is converted into electrical energy by rotating the auxiliary pump and generator motor with the return fluid from the actuator of the work equipment system. However, it is characterized in that the generator motor is rotated by the stored electrical energy and hydraulic oil is discharged from the auxiliary pump.

According to the first aspect of the present invention, the hydraulic oil discharged from the first and second pumps and the hydraulic oil discharged from the auxiliary pump are merged and guided to both the travel system actuators. Can be applied.
Therefore, even when the vehicle travels at a high speed or gets stuck in the mud, it can be easily pulled out from there.
Moreover, since the hydraulic oil discharged from the auxiliary pump can be merged as necessary, it is not necessary to increase the capacities of the first and second pumps more than necessary. Therefore, the load of the drive source can be reduced and the energy efficiency can be increased.

  In addition, when there is a pressure difference between the two actuators in the traveling system, the hydraulic oil supplied to the actuator with the lower pressure is throttled, so a large amount of hydraulic oil can be supplied to the actuator with the higher pressure. Even if it is uneven, it can run without bending.

  According to the second invention, inertial energy or potential energy is converted into electric energy by the return fluid from the actuator of the work machine system, while the generator motor and the auxiliary pump are rotated by the electric energy stored in the power storage unit. Therefore, energy efficiency can be further increased.

A first embodiment of the present invention will be described with reference to FIG.
In the first embodiment, as in the conventional circuit configuration, hydraulic oil is applied to the traveling system actuators that operate independently on the left and right sides, the working machine system actuators, and the traveling system or working machine system actuators. The first and second pumps are selectively supplied, and the hydraulic oil discharged from the first pump is supplied to one traveling system actuator, and the hydraulic oil discharged from the second pump is supplied to the other traveling system actuator. Assuming a power device for a construction machine that travels.
And this 1st Embodiment has the characteristics in the point which connected the auxiliary pump via the merging control valve in the conventional circuit structure. Therefore, the above-described conventional circuit configuration is denoted by the same reference numeral, and here, the configuration and operation of the merging control valve and the auxiliary pump will be mainly described.

  FIG. 1 shows a circuit configuration of a power shovel that is one of the power devices for construction machines. In this power shovel, an auxiliary pump P3 having an electric motor M as a drive source is connected to a passage 21. Then, the passage 21 is branched into a first joining passage 23 and a second joining passage 24 by a joining control valve 22, the first joining passage 23 being the first pump passage 1, and the second joining passage 24 being the second pump passage. 8 are connected to each other.

The merging control valve 22 is provided in the connection process between the first and second pumps P1 and P2 and the auxiliary pump P3, and is discharged from the first and second pumps P1 and P2 and from the auxiliary pump P3. Although the hydraulic oil is merged, the merge control valve 22 will be described in detail.
The merging control valve 22 is a valve that can be switched to three positions, and holds the center position by the spring force of springs provided at both ends. The merging control valve 22 communicates the passage 21 with the first merging passage 23 and the second merging passage 24 at this center position, and equally distributes the hydraulic oil discharged from the auxiliary pump P3 to the merging passages 23 and 24.

When the merging control valve 22 is switched to the right position in the figure, the communication opening degree between the passage 21 and the first merging passage 23 gradually increases, and the communication opening degree between the passage 21 and the second merging passage 24 is increased. Gradually squeezed. On the other hand, when the merging control valve 22 is switched to the left side in the figure, the communication opening degree between the passage 21 and the second merging passage 24 gradually increases, and the communication opening degree between the passage 21 and the first merging passage 23 is increased. Gradually squeezed.
The merging control valve 22 guides the pilot pressure from the first merging passage 23 side to one end (right side in the figure) of the valve, and applies the pilot pressure from the second merging passage 24 side to the other end (left side in the figure). Guided.
Therefore, when the pressure on the first merging passage 23 side becomes higher than the pressure on the second merging passage 24 side, the merging control valve 22 is switched to the right position in the figure by the pilot pressure, and conversely on the second merging passage 24 side. When the pressure becomes higher than the pressure on the first merging passage 23 side, the merging control valve 22 is switched to the left position in the figure by the pilot pressure.

  In the first embodiment, based on the operation signal transmitted from each operation lever 25, the controller C rotates the electric motor M and the tilt angles of the first pump P1, the second pump P2, and the auxiliary pump P3. Is controlling.

Next, the operation of the first embodiment will be described.
When the excavator is driven without operating the work system actuator, the hydraulic oil is discharged by rotating the first and second pumps P1 and P2 while keeping the switching valve 15 in the illustrated cutoff position. In addition, the left travel valve 2 and the right travel valve 9 are switched. Then, the hydraulic oil discharged from the first pump P1 is guided to the left travel actuator, and the hydraulic oil discharged from the second pump P2 is guided to the right travel actuator, so that the power shovel travels.

  The controller C is operated so as to drive the electric motor M when a large operating force is applied to the actuator of the traveling system in order to cause the power shovel to travel at a high speed or escape from the mud from the traveling state. Send a signal. The controller C that has received the operation signal rotates the electric motor M, and as the electric motor M rotates, the auxiliary pump P3 rotates and hydraulic oil is discharged.

At this time, since the merging control valve 22 holds the center position by the springs provided at both ends, the hydraulic oil discharged from the auxiliary pump P3 is transferred to the first merging passage 23 and the second merging passage 24 by the merging control valve 22. Equally distributed. Therefore, the hydraulic oil discharged from the first pump P1 and the auxiliary pump P3 merges in the first pump passage 1 and is guided to the left travel actuator, and the hydraulic oil discharged from the second pump P2 and the auxiliary pump P3 is They merge in the second pump passage 8 and are guided to the right traveling actuator.
Thus, a large operating force can be applied to the travel system actuator by joining the hydraulic oil discharged from the auxiliary pump P3 to the hydraulic oil discharged from the first and second pumps P1, P2. Therefore, the excavator can be run at a high speed as necessary, and even when the crawler gets stuck in the mud, it can be easily escaped from there.

  In the case where the hydraulic oil discharged from the auxiliary pump P3 is joined and traveling, for example, it is assumed that the left crawler gets stuck in mud. Then, the pressure of the left traveling actuator becomes higher than the pressure of the right traveling actuator, and the pressures of the first pump passage 1 and the first joining passage 23 are the pressures of the second pump passage 8 and the second joining passage 24. Higher than. When the pressure of the first merging passage 23 becomes higher than the pressure of the second merging passage 24, the merging control valve 22 is gradually switched to the right position in the figure by the pilot pressure.

  When the merging control valve 22 is switched to the right position in the figure, the communication opening degree toward the second merging passage 24 is gradually reduced, and the communication opening degree toward the first merging passage 23 is gradually increased. Therefore, a large amount of hydraulic oil discharged from the auxiliary pump P3 is guided to the first merging passage 23 side, and a large amount of hydraulic oil is guided to the actuator having the higher pressure among the actuators of the traveling system, that is, the left traveling actuator. Can do. In this way, the hydraulic oil that is guided to the lower pressure actuator of the traveling system actuator is throttled, so that a large flow rate does not flow to the lower pressure side, and the power shovel does not bend reliably. You can travel.

In addition, in this 1st Embodiment, although the case where the power shovel was drive | working was demonstrated, when operating the actuator of a working machine type | system | group, or when simultaneously controlling a driving | running | working system and a work machine system, The hydraulic oil discharged from the auxiliary pump P3 may be merged.
For example, when the traveling system and the work machine system are simultaneously controlled, if the hydraulic oil discharged from the auxiliary pump P3 is merged, even during simultaneous control, high-load work or high-speed traveling is performed. Can be.

According to the first embodiment, the hydraulic oil discharged from the first and second pumps P1 and P2 and the hydraulic oil discharged from the auxiliary pump P3 are merged and guided to both actuators in the traveling system. A sufficient operating force can be applied to the system actuator.
Therefore, even if the vehicle travels at a high speed during straight traveling or gets stuck in the mud, it can be easily removed from there.
Moreover, since the hydraulic fluid discharged from the auxiliary pump P3 can be merged as necessary, it is not necessary to increase the capacities of the first and second pumps P1 and P2 more than necessary. Therefore, the load of the drive source can be reduced and the energy efficiency can be increased.

A second embodiment of the present invention will be described with reference to FIG.
The circuit configuration of the second embodiment is characterized in that a regenerative circuit indicated by a two-dot chain line is connected to the circuit configuration of the first embodiment. The other circuit configurations are the same as those of the first embodiment. This is the same as the embodiment. Therefore, the same circuit configuration as that of the first embodiment is denoted by the same reference numeral, and here, the regenerative circuit will be mainly described.

  The boom actuator A shown in FIG. 2 divides the inside of the cylinder into a rod side chamber A1 and a piston side chamber A2 by a piston to which a rod is fixed. When the boom operation lever is operated to the lower side, the boom I speed valve 11 and the boom II speed valve 5 are switched to one side, and the first parallel path 7 and the second parallel path 13 are connected via the connection path 26. To communicate with the rod side chamber A1. At this time, the piston side chamber A2 communicates with the tank via the connection passage 27, and the rod contracts into the cylinder and lowers the load acting on the rod. On the other hand, when the boom operating lever is operated to the up side, the boom I speed valve 11 and the boom II speed valve 5 are switched to the other side, and the first parallel path 7 and the second parallel path 13 are connected to the connection path. Communicating with the piston side chamber A <b> 2 through 27. At this time, the rod side chamber A1 communicates with the tank through the connection passage 26, and the rod extends from the cylinder and increases the load acting on the rod. As described above, the boom actuator A switches the boom I speed valve 11 and the boom II speed valve 5 to expand and contract the rod and raise or lower the load, or hold the load. .

The connection passage 27 is connected to the suction side of the auxiliary pump P <b> 3 through the return flow path 28 and the suction side flow path 29. However, a regenerative switching valve S is provided between the return flow path 28 and the suction side flow path 29, and switching the regenerative switching valve S allows the return flow path 28 and the suction side flow path 29 to communicate with each other. I try to block it.
Further, the discharge side flow path 30 is connected to the discharge side of the auxiliary pump P3 and the regenerative switching valve S is switched so that the discharge side flow path 30 communicates with the passage 21 or communicates with the tank. Like to do.

  The regeneration switching valve S is a valve that can be switched to three positions, and the discharge-side flow path 30 is communicated with the tank at the center position. Further, when the regenerative switching valve S is switched to the upper position in the drawing, the tank and the suction side flow path 29 are communicated with each other, and the discharge side flow path 30 and the passage 21 are communicated. On the other hand, when the regenerative switching valve S is switched to the lower position in the drawing, the discharge side flow path 30 and the tank are communicated, and the return flow path 28 and the suction side flow path 29 are communicated.

The regenerative switching valve S is switched by the pilot pressure acting on both ends. The controller C controls the pilot pressure. That is, the controller C controls the pilot solenoid valves 31 and 32 based on the operation signal of each operation lever 25 and controls the pilot pressure acting on the regeneration switching valve S to switch the regeneration switching valve S. Yes.
A short-circuit passage 33 is connected between the suction-side passage 29 and the discharge-side passage 30, and a two-position switching valve 34 is provided in the short-circuit passage 33. The two-position switching valve 34 normally holds a position where the suction side flow path 29 and the discharge side flow path 30 are communicated with each other by the spring force of a spring. It switches to the position which interrupts | blocks 29 and the discharge side flow path 30. FIG. The pilot pressure for switching the two-position switching valve 34 is controlled by the pilot solenoid valve 32. That is, at the same time when the regeneration switching valve S is switched to the upper position in the figure, the two-position switching valve 34 is switched to the left position in the figure.
Further, a power converter G and a power storage unit U that stores electric energy generated by the rotation of the generator motor MG are connected to the generator motor MG that is a drive source of the auxiliary pump P3. When the generator motor MG is driven, the generator motor MG is driven by the electric energy stored in the power storage unit U.

Next, the operation of the second embodiment will be described.
When lowering the load from the state in which the load is applied to the boom actuator A, the boom operation lever 25 is operated to the lower side to switch between the boom I speed valve 11 and the boom II speed valve 5. Then, the controller C that has received the operation signal controls the tilt angles of the first pump P1 and the second pump P2 and also controls the pilot solenoid valve 31 to bring the regenerative switching valve S to the lower position in the figure. Switch. Therefore, the hydraulic oil is guided from the first pump P1 and the second pump P2 to the rod side chamber A1 via the boom II speed valve 5 and the boom I speed valve 11, and the return oil from the piston side chamber A2 is connected. It is guided to the suction side of the auxiliary pump P3 via the passage 27 → the return flow path 28 → the regeneration switching valve S → the suction side flow path 29. Here, the connection passage 27 is a passage on the return side when inertia energy or potential energy acts on the actuator of the work machine system.

  The auxiliary pump P3 is rotated by the return oil guided from the return side passage, and the generator motor MG is rotated along with the rotation of the auxiliary pump P3. The return oil that has rotated the auxiliary pump P3 is returned to the tank via the discharge-side flow path 30 and the regeneration switching valve S. Thus, when lowering the boom actuator A, the generator motor MG converts the inertial energy and the potential energy acting on the boom actuator A into electrical energy, and the electrical energy is stored in the power storage unit U. can do.

On the other hand, as already described in the first embodiment, when the hydraulic oil discharged from the auxiliary pump P3 is merged with the first pump P1 and the second pump P2 to run the power shovel, each operation lever 25 is operated. Based on the operation signal, the controller C controls the pilot solenoid valve 32 and the generator motor MG.
Under the control of the controller C, the generator motor MG is rotated by the electric energy stored in the power storage unit U, and the auxiliary pump P3 rotates and discharges hydraulic oil as the generator motor MG rotates.

  At this time, the regenerative switching valve S is switched to the upper position in the drawing and the two-position switching valve 34 is switched to the left position in the drawing by the pilot pressure introduced from the pilot solenoid valve 32. Therefore, the hydraulic oil discharged from the auxiliary pump P3 is equally distributed to the first pump passage 1 and the second pump passage 8 via the discharge side flow passage 30 → the regeneration switching valve S → the passage 21 → the merging control valve 22. The Then, the hydraulic oil discharged from the auxiliary pump P3 merges the same amount in the first pump P1 and the second pump P2, and the merged hydraulic oil is guided to both travel actuators.

Even when the hydraulic oil discharged from the auxiliary pump P3 is guided to the work machine system actuator or to the travel system and work machine system actuators at the same time, the pumps P1 and P2 are joined together in the same manner as described above. That's fine.
Further, when there is a difference in pressure between the first merging passage 23 and the second merging passage 24, the communication opening degree in the lower pressure is reduced by the pilot pressure as described above.

According to the second embodiment, inertial energy or potential energy is converted into electric energy by the return fluid from the boom actuator A, while the generator motor MG and the auxiliary pump P3 are rotated by the electric energy stored in the power storage unit U. As a result, energy efficiency can be further improved.
In the second embodiment, the inertia energy and potential energy acting on the boom actuator are converted into electric energy. However, the work machine system actuator is subject to inertia energy or potential energy. Any actuator may be used as long as it is present. Therefore, the actuator of the work machine system is not limited to the cylinder but may use a motor.

Moreover, although each pump in the said 1st, 2nd embodiment can make discharge amount variable by controlling a tilt angle with a controller, you may use a constant discharge pump.
In the first and second embodiments, the circuit configuration of the power shovel has been described. However, the present invention is not limited to the power shovel, and includes a travel system and work machine system actuators. It can be widely used in power units operated by separate pumps.

It is a circuit diagram of a 1st embodiment. It is a circuit diagram of a 2nd embodiment. It is a circuit diagram used for the power unit of the conventional construction machine.

Explanation of symbols

22 Merge control valve 28 Return flow path G Power conversion device M Electric motor MG Generator motor P1 First pump P2 Second pump P3 Auxiliary pump U Power storage unit

Claims (2)

  A travel system actuator that operates independently on the left and right; a work machine system actuator; and a first pump and a second pump that selectively supply hydraulic oil to the travel system or work machine system actuator. In the power equipment for a construction machine that travels by supplying the hydraulic oil discharged from the pump to one traveling system actuator and supplying the hydraulic oil discharged from the second pump to the other traveling system actuator, the first and second An auxiliary pump is connected to the pump, and a merging control valve is provided in the connection process between the first and second pumps and the auxiliary pump, and the merging control valve includes hydraulic oil discharged from the first and second pumps. While the hydraulic fluid discharged from the auxiliary pump is merged and guided to both actuators of the traveling system, when a pressure difference occurs between the actuators of the traveling system, There way construction machine power unit was configured to narrow the operating oil supplied to the actuator of.   A generator motor that rotates integrally with the auxiliary pump, and a power storage unit that stores electric power generated by the rotation of the generator motor, and becomes a return side when inertial energy or potential energy acts on the actuator of the work machine system The passage is configured to be connected to the suction side of the auxiliary pump, and the auxiliary pump and the generator motor are rotated by the return fluid from the actuator of the work machine system to convert the inertial energy or potential energy into electric energy and store the electric energy, 2. The power device for a construction machine according to claim 1, wherein the generator motor is rotated by the stored electric energy and the hydraulic oil is discharged from the auxiliary pump.

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