KR20090111964A - Hydraulic system of energy saving type - Google Patents

Abstract

The disclosed contents, in construction equipment such as excavators, to control the rotational direction (refer to the forward and reverse rotation direction) and the speed of the electric motor integrally connected to the variable displacement hydraulic pump to drive the hydraulic pump, the hydraulic pump according to the load The hydraulic cylinder is driven by controlling the discharge flow rate of the hydraulic cylinder, and hydraulic energy is converted into electrical energy by driving the hydraulic motor and the generator by the returning oil when the hydraulic cylinder is loaded and contracted (in hydraulic operation of the hydraulic cylinder). To convert it to play

Energy saving hydraulic system according to an embodiment of the present invention,

An electric motor driven in the forward and reverse directions according to a control signal input from the outside, a variable displacement hydraulic pump connected to the electric motor and driven in the forward and reverse directions,

A hydraulic cylinder installed in a flow path of the hydraulic pump and expanded and driven by hydraulic oil from the hydraulic pump driven according to the rotational direction and speed of the electric motor;

A branch valve installed in a flow path between the hydraulic pump and the hydraulic cylinder, and the internal spool is switched according to a control signal input from the outside;

A hydraulic motor driven by hydraulic oil returned from the hydraulic cylinder through a branch valve, a generator axially connected to the hydraulic motor,

Charging means for charging the battery to be regenerated after converting the electrical energy generated by the generator into a direct current; And

Including an electronic control unit for outputting a control signal to drive the branch valve and the electric motor in accordance with the signal input from the outside,

When the hydraulic cylinder is subjected to the contraction of the load pressure, the electric motor is generated by driving the hydraulic motor and the generator by the hydraulic oil returned from the hydraulic cylinder via the branch valve when the branch valve is switched according to the control signal of the electronic control unit rotor. It converts electric energy into DC current and charges it to the battery to regenerate when driving electric motor.

Description

Hydraulic system of energy saving type

The present invention controls the driving of the hydraulic cylinder for driving the work equipment of construction equipment such as excavators, loaders, etc. by the electric motor, and the hydraulic energy during the shrinkage driving (loading operation of the hydraulic cylinder) applied to the hydraulic cylinder The present invention relates to an energy-saving hydraulic system that can be used to regenerate electric energy.

More specifically, the hydraulic pump is driven by controlling the rotational direction (referring to the forward and reverse rotation directions) and the speed of the electric motor integrally connected with the variable displacement hydraulic pump, and controlling the discharge flow rate of the hydraulic pump according to the load. The present invention relates to an energy-saving hydraulic system that drives a hydraulic cylinder and converts hydraulic energy into electrical energy by driving the hydraulic motor and the generator at a flow rate that is returned when the hydraulic cylinder is loaded.

Hereinafter, the above-described shrinkage driving of the hydraulic cylinder (in operation of the hydraulic cylinder) means a state in which the cross-sectional area of the small chamber of the hydraulic cylinder is expanded and the cross-sectional area of the large chamber is contracted. do.

In general, the hydraulic system is used in construction equipment such as excavators, cranes, etc., where the output per unit area is large, the overload is prevented and precisely adjusted, and the force is easily adjusted so that a large force is required. On the other hand, the hydraulic system is known to be more than 50% of energy loss because it is always driven even when the driving device (engine, motor) that drives the hydraulic pump for supplying hydraulic oil to the hydraulic actuator such as the hydraulic cylinder is not working.

In other words, the operating energy for driving the actuator is the energy efficiency of up to 25% assuming that the hydraulic pump discharge energy "100".

Embodiment of the present invention, by controlling the rotational direction and speed of the electric motor to control the hydraulic oil flow direction and operating flow rate supplied to the hydraulic cylinder from the variable displacement hydraulic pump, the hydraulic oil is returned when the load is applied to the hydraulic cylinder By driving the hydraulic motor and the generator by converting the hydraulic energy into electrical energy, the energy-saving hydraulic system that can significantly save energy by regenerating the regenerated energy when driving the electric motor.

An embodiment of the present invention, by using an electric motor and a variable hydraulic pump to supply hydraulic oil to the hydraulic cylinder, and an energy-saving hydraulic system to simplify the configuration of the hydraulic line to reduce the cost and maintenance costs Related.

Energy saving hydraulic system according to an embodiment of the present invention,

An electric motor driven in the forward and reverse directions according to a control signal input from the outside, a variable displacement hydraulic pump connected to the electric motor and driven in the forward and reverse directions,

A hydraulic cylinder installed in a flow path of the hydraulic pump and expanded and driven by hydraulic oil from the hydraulic pump driven according to the rotational direction and speed of the electric motor;

A branch valve installed in a flow path between the hydraulic pump and the hydraulic cylinder, and the internal spool is switched according to a control signal input from the outside;

A hydraulic motor driven by hydraulic oil returned from the hydraulic cylinder through a branch valve, a generator axially connected to the hydraulic motor,

Charging means for charging the battery to be regenerated after converting the electrical energy generated by the generator into a direct current;

Including an electronic control unit for outputting a control signal to drive the branch valve and the electric motor in accordance with the signal input from the outside,

When the hydraulic cylinder is subjected to the contraction of the load pressure, the electric motor is generated by driving the hydraulic motor and the generator by the hydraulic oil returned from the hydraulic cylinder via the branch valve when the branch valve is switched according to the control signal of the electronic control unit rotor. It converts electric energy into DC current and charges it to the battery to regenerate when driving electric motor.

Energy-saving hydraulic system according to an embodiment of the present invention,

An electric motor, a variable displacement hydraulic pump connected to the electric motor and driven in the forward and reverse directions, a hydraulic cylinder installed in the flow path of the hydraulic pump, a branch valve installed in the flow path between the hydraulic pump and the hydraulic cylinder, and hydraulic oil from the hydraulic cylinder Hydraulic motor driven by a generator and a generator, a converter for converting the electrical energy generated by the generator into a direct current to charge the battery, an electronic control unit for outputting a control signal to drive the branch valve and the electric motor according to the signal input from the outside In the energy-saving hydraulic system comprising a,

A first step of driving the hydraulic pump by an electric motor driven by a control signal from the electronic controller;

A second step of measuring the actual discharge pressure of the hydraulic pump and the required pressure generated on the large chamber side of the hydraulic cylinder and outputting a detection signal to the electronic control unit;

A third step of comparing and judging the pressure difference between the discharge pressure of the hydraulic pump and the required pressure of the hydraulic cylinder;

If the required pressure is larger than the discharge pressure, the discharge speed of the hydraulic pump is calculated by controlling the rotational speed of the electric motor and the difference between the required pressure and the discharge pressure, and then the swash plate tilt angle of the hydraulic pump is controlled to correspond to the calculated value. To control the discharge flow rate of the hydraulic pump,

A fourth step of controlling to reduce the discharge flow rate of the hydraulic pump by lowering the rotation speed of the set electric motor when the required pressure is smaller than the discharge pressure;

A fifth step of stopping the extension driving by reducing the speed at which the hydraulic cylinder is driven;

A sixth step of determining whether the driving direction of the electric motor which can be driven in the forward and reverse directions is changed;

When switching the driving direction of the electric motor, the hydraulic cylinder is contracted and driven, and a control signal is output to switch the branch valve.

A seventh step of terminating if the driving direction of the electric motor is not changed;

An eighth step of determining whether the hydraulic motor is driven by the hydraulic oil returned through the branch valve when the hydraulic cylinder is contracted and driven;

When the hydraulic motor is driven by the hydraulic oil from the hydraulic cylinder that is shrink-driven, the generator is driven by the hydraulic motor to convert the generated electric energy into a DC current to charge the battery.

When the hydraulic motor is not driven by the hydraulic oil from the hydraulic cylinder that is shrink-driven, the ninth step of reducing the contraction-driven speed of the hydraulic cylinder is stopped.

According to a preferred embodiment, a pilot check valve is provided in each of the supply side and the return side flow paths between the hydraulic pump and the hydraulic cylinder, and prevents the hydraulic oil backflow when the electric motor and the hydraulic pump are stopped.

And a pressure sensor provided in the large chamber side flow path of the above-described hydraulic cylinder, which measures the pressure of the hydraulic oil during expansion and contraction operation of the hydraulic cylinder and outputs a detection signal to the electronic control unit.

And a capacitor connected to the aforementioned battery and preventing deterioration due to overcharge or discharge from the converter to the battery.

When the control signal is input from the above-described electronic controller, the electronic proportional pressure reducing valve controls the swash plate tilt angle of the hydraulic pump so as to correspond to the input signal value.

It is installed in the flow path branched to the supply side and the return side flow path between the above-mentioned hydraulic pump and the hydraulic cylinder, respectively, and supplements the insufficient hydraulic fluid according to the cross sectional area of the large chamber and the small chamber of the hydraulic cylinder, and supplies to the hydraulic cylinder. The hydraulic fluid includes a directional valve for returning to the hydraulic tank.

As described above, the energy saving hydraulic system according to the embodiment of the present invention has the following advantages.

By controlling the operating flow rate and flow direction supplied from the variable displacement hydraulic pump to the hydraulic cylinder according to the rotational direction and speed of the electric motor (formerly, the hydraulic oil supplied from the hydraulic pump to the hydraulic cylinder by a directional control valve, a proportional control valve, etc.). Control the quantity and flow direction), the cost and maintenance cost can be reduced by simplifying the configuration of the hydraulic line.

In addition, as the flow rate is returned when the hydraulic cylinder is loaded, the hydraulic motor and the generator are driven to convert hydraulic energy into electrical energy. Thus, energy is regenerated and regenerated when the electric motor is driven. can do.

In addition, the hydraulic pump is driven by the electric motor only during operation (when the hydraulic cylinder is driven) to supply hydraulic oil to the hydraulic cylinder (in the past, the engine continues to run regardless of the working mode of the equipment) to minimize energy loss. have.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings, which are intended to describe in detail enough to enable those skilled in the art to easily practice the invention, and therefore It does not mean that the technical spirit and scope of the present invention is limited.

As shown in Figures 1 to 3, the energy-saving hydraulic system according to an embodiment of the present invention,

The electric motor 10 is driven in the forward and reverse directions according to the control signal input from the outside,

A variable displacement hydraulic pump 9 connected to the electric motor 10 and driven in the forward and reverse directions,

A hydraulic cylinder (1) installed in the flow path of the hydraulic pump (9) and stretched and driven by hydraulic oil discharged from the hydraulic pump (9) driven according to the rotational direction and speed of the electric motor (10);

Branch valves are installed in the flow path between the hydraulic pump 9 and the hydraulic cylinder 1 (refering to the large chamber 1a side of the hydraulic cylinder 1), and the internal spool is switched in accordance with the control signal input from the outside ( 3) with,

A hydraulic motor 17 driven by hydraulic oil returned from the hydraulic cylinder 1 through the branch valve 3,

A generator 16 (generator) axially connected to the hydraulic motor 17,

A converter 15 for converting the electrical energy generated by the generator 16 into a direct current;

A battery 14 for charging the DC current converted by the converter 15,

Including an electronic control unit 12 (ECU) for outputting a control signal to drive the branch valve 3 and the electric motor 10 in accordance with a signal input from the outside,

Hydraulic oil returned from the hydraulic cylinder (1) via the branch valve (3) at the time of contraction of the hydraulic cylinder (1) to which the load pressure is applied, and the switching of the branch valve (3) in accordance with the control signal of the rotor of the electronic control unit (12). By driving the hydraulic motor 17 and the generator 16 to generate electrical energy, and converts the electrical energy into a direct current to charge the battery 14 is used to regenerate when driving the electric motor 10.

Pilot check valves are respectively provided on the supply side and the return side flow paths between the hydraulic pump 9 and the hydraulic cylinder 1 and prevent the hydraulic oil from flowing back when the electric motor 10 and the hydraulic pump 9 are stopped. 6).

It is installed in the large chamber side flow path of the hydraulic cylinder 1 mentioned above, and measures the pressure of hydraulic fluid at the time of expansion-contraction driving of the hydraulic cylinder 1, and outputs an electrical detection signal to the electronic control part 12. FIG. And a pressure sensor 2.

And a capacitor 13 connected to the above-described battery 14 and preventing deterioration due to overcharging or discharging from the converter 15 to the battery 14.

When the control signal input from the above-described electronic control unit 12, the electronic proportional pressure reducing valve 19 for controlling the discharge flow rate by controlling the swash plate tilt angle of the hydraulic pump 9 to correspond to the input signal value (current value) do.

Differences in the cross-sectional area between the large chamber 1a and the small chamber 1b of the hydraulic cylinder 1 are provided in the flow passages branched to the supply side and the return side flow passages between the hydraulic pump 9 and the hydraulic cylinder 1 described above. In accordance with the present invention, the hydraulic fluid is supplied to the hydraulic cylinder 1, and the excess hydraulic oil includes a directional valve 8 for returning the hydraulic tank.

In the figure, reference numeral 4 denotes a check valve, 5 denotes a relief valve for protecting hydraulic components in the hydraulic system by maintaining a set pressure in the hydraulic circuit, and 7 denotes a flow rate according to the load generated in the flow path of the hydraulic pump 9. Regulating throttle valve, 11 is hydraulic tank and 18 is power supply.

Hereinafter, with reference to the accompanying drawings an example of the use of the energy-saving hydraulic system according to an embodiment of the present invention will be described in detail.

FIG. 2 is a state diagram of an energy saving hydraulic system according to an exemplary embodiment of the present invention, which illustrates the operation of extending the hydraulic cylinder (hydraulic cylinder out operation).

As shown, power is supplied to the power supply 18 by a control signal from the electronic control unit 12 so as to extend and drive the hydraulic cylinder 1 described above, and a current is supplied to the electric motor 10 to be driven. As a result, the variable displacement hydraulic pump 9 integrally connected with the electric motor 10 is driven. At this time, the hydraulic pump 9 is driven according to the forward and reverse rotation control signals of the electric motor 10.

The hydraulic pressure set in the hydraulic system is formed by the hydraulic oil discharged from the hydraulic pump 9, and the operating oil amount that is insufficient according to the generated pressure is changed by the direction switching valve 8 along the pilot pressure to change the hydraulic tank ( 1) and the flow path of the hydraulic pump 9 is connected, it is possible to supply insufficient hydraulic fluid.

The hydraulic cylinder 1 is extended and driven by the hydraulic oil supplied from the hydraulic pump 9 to the large chamber 1a of the hydraulic cylinder 1. At the same time, the hydraulic oil returned from the small chamber 1b (small chamber) of the hydraulic cylinder 1 is supplied to the large chamber 1a via the hydraulic pump 9. At this time, the hydraulic oil returned from the hydraulic cylinder (1) is adjusted according to the driving speed of the hydraulic cylinder (1) by the hydraulic system based on the meter-out principle via the throttle valve (7).

The pilot check valve 6 described above is kept open by the pressure of the hydraulic oil formed in the discharge passage of the hydraulic pump 9.

On the other hand, when the drive signal of the hydraulic cylinder 1 is not applied to the electronic control unit 12 by the user, the pilot check valve 6 is kept closed, so that the hydraulic cylinder 1 is maintained in a neutral state. It will limit the flow of hydraulic fluid.

3 is a diagram showing a second state of use of the energy saving hydraulic system according to the embodiment of the present invention, which shows the contraction operation of the hydraulic cylinder (in hydraulic operation of the hydraulic cylinder).

As shown in the drawing, as a control signal is inputted to the electronic control unit 12 so as to deflate and drive the above-described hydraulic cylinder 1, the variable displacement hydraulic pump 9 is driven due to the driving of the electric motor 10. Let's do it. As a result, the hydraulic oil discharged from the hydraulic pump 9 is supplied to the small chamber 1b of the hydraulic cylinder 1 so as to shrink-drive the hydraulic cylinder 1.

At this time, the pressure sensor 2 provided in the flow path of the large chamber 1a side of the hydraulic cylinder 1 measures the required pressure Psensor of the large chamber 1a side, and outputs a detection signal to the electronic control unit 12. .

At this time, when the discharge pressure Pref of the variable displacement hydraulic pump 9 which drives the hydraulic cylinder 1 is relatively larger than the required pressure Psensor of the large chamber 1a side of the hydraulic cylinder 1 (hydraulic cylinder When no load or light load is generated in (1), the electronic control unit 12 determines that the hydraulic cylinder 1 is shrink-driven under no load or light load, and switches the internal spool to the branch valve 3. Control signal is not output.

That is, when light loads and no loads are generated in the hydraulic cylinder 1 to be contracted and driven, the hydraulic pumps may be reduced by reducing the set rotational speed of the electric motor 10 without controlling the discharge flow rate of the variable displacement hydraulic pump 9. By adjusting the discharge flow rate of 9) it is possible to control the drive speed of the hydraulic cylinder (1).

On the other hand, when the discharge pressure Pref of the variable displacement hydraulic pump 9 is relatively smaller than the required pressure Psensor of the large chamber 1a side of the hydraulic cylinder 1 (heavy load is generated in the hydraulic cylinder 1). And the electronic controller 12 determines that the hydraulic cylinder 1 is contracted and driven in a heavy load state, thereby controlling the rotational speed of the electric motor 10, and the required pressure Psensor of the hydraulic cylinder 1. The discharge pressure of the hydraulic pump 9 is controlled according to the difference in the discharge pressure Pref of the hydraulic pump 9 (ΔP = Psensor-Pref).

4 is a flowchart illustrating a method of controlling an energy saving hydraulic system according to an exemplary embodiment of the present invention.

As shown, the electric motor 10 is driven by the control signal from the electronic control unit 12 by inputting the control signal to the electronic control unit 12 to stretch-drive the hydraulic cylinder 1 described above. , Drives a variable displacement hydraulic pump 9 connected to the electric motor 10 (see S100).

The required pressure Psensor generated in the large chamber 1a by the pressure sensor 2 provided in the flow path of the large chamber 1a side of the hydraulic cylinder 1 described above, and the discharge pressure Pref of the hydraulic pump 9. ) And output the detection signal to the electronic control unit 12 (see S200).

The pressure difference (ΔP = Psensor-Pref) between the discharge pressure of the hydraulic pump 9 and the required pressure of the hydraulic cylinder 1 is compared and judged (see S300).

That is, when the required pressure Psensor of the hydraulic cylinder 1 is relatively larger than the discharge pressure Pref of the hydraulic pump 9 (Psensor > Pref), the electronic controller 12 has a central portion in the hydraulic cylinder 1. It is determined that the bottom has occurred, and proceeds to the next step 400A.

On the other hand, when the required pressure Psensor of the hydraulic cylinder 1 is relatively smaller than the discharge pressure Pref of the hydraulic pump 9 (Psensor < Pref), the electronic control unit 12 applies to the hydraulic cylinder 1 It is determined that light load or no load has occurred and the process proceeds to S400B.

When it is determined that the heavy load is generated in the hydraulic cylinder 1 in the third step (S300) (Psensor> Pref), the constant rotation speed control of the electric motor 10, and the required pressure of the hydraulic cylinder (1) The discharge flow rate of the hydraulic pump 9 is calculated based on the difference value of the discharge pressure of the hydraulic pump 9.

The current value applied to the electromagnetic proportional pressure reducing valve 19 for controlling the swash plate tilt angle of the hydraulic pump 9 is calculated so that the discharge flow rate of the variable displacement hydraulic pump 9 can be adjusted. At this time, the pressure difference (ΔP = Psensor-Pref) between the discharge pressure of the hydraulic pump 9 and the required pressure of the hydraulic cylinder 1 is calculated in proportional derivative to calculate the current value.

U (t) = (Kp × e (t)) + (Kd × de (t) / dt)

At this time, "Kp" is proportional gain, "Kd" is differential gain, "e (t)" is the required pressure (Psensor) of the hydraulic cylinder (1) and the discharge pressure (Pref) of the variable hydraulic pump (9) , "u (t)" is an operation value for adjusting the difference value (ΔP = Psensor-Pref) of the pressure described above, and is an amount of current applied to the electromagnetic proportional pressure reducing valve 19.

The swash plate tilt angle of the hydraulic pump 9 is controlled by a control signal output corresponding to the current value calculated by the electronic controller 12 to control the discharge flow rate of the hydraulic pump 9 (see S400A).

On the other hand, when it is determined that no load or light load is generated in the hydraulic cylinder 1 in the third step (S300) (Psensor <Pref), the discharge speed of the hydraulic pump 9 is lowered by lowering the rotational speed of the set electric motor 10. Control to reduce the flow rate (see S400B). At this time, the control signal is not output from the electronic controller 12 to the electromagnetic proportional pressure reducing valve 19 for controlling the swash plate tilt angle of the hydraulic pump 9 so that the discharge flow rate of the hydraulic pump 9 can be adjusted. In addition, a switching control signal is not applied from the electronic control unit 12 to the branch valve 3.

The extension driving of the hydraulic cylinder 1 is reduced (the out operation of the hydraulic cylinder 1 is reduced) to stop the extension driving (see S500).

It is determined whether the driving direction of the electric motor 10 which can be driven in the forward and reverse directions is changed (see S600).

In other words, when the driving direction of the electric motor 10 is changed, the hydraulic cylinder 1 proceeds to the next step (S700) of shrinkage driving (in hydraulic operation of the hydraulic cylinder), and the driving direction of the electric motor 10. If you do not switch the function, terminate it.

When the driving direction of the electric motor 10 which is rotated forward and reverse in the sixth step S600 is switched, the hydraulic cylinder 1 is contracted and driven to switch the spool to the branch valve 3. A control signal is outputted from 12) (see S700).

When the hydraulic cylinder 1 is contracted and driven, it is determined whether the hydraulic motor 17 is driven by the hydraulic oil returned through the branch valve 3 (see S800).

That is, when driving the hydraulic motor 17 by the operating oil returned through the branch valve (3) proceeds to the next step (S900A) for converting the hydraulic energy into electrical energy. On the other hand, when the hydraulic motor 17 is not driven, the process proceeds to step S900B of stopping the shrinkage driving of the hydraulic cylinder 1.

When the hydraulic motor 17 is driven by the hydraulic oil returned from the hydraulic cylinder 1 via the branch valve 3 in the eighth step S800, the generator 16 axially connected to the hydraulic motor 17 is driven. To generate electrical energy. The alternating current generated by the generator 16 is converted into a direct current by the converter 15. The DC current converted by the converter 15 is charged in the battery 14 to be reproduced when the electric motor 10 is driven (see S900A).

On the other hand, when the hydraulic motor 17 is not driven by the hydraulic oil returned from the hydraulic cylinder 1 via the branch valve 3, the shrinkage driving speed of the hydraulic cylinder 1 is reduced to stop the shrinkage driving. (See S900B).

As described above, the energy-saving hydraulic system according to an embodiment of the present invention,

By driving the electric motor 10 only in an operation mode such as an excavator (when driving the hydraulic cylinder 1), energy loss is greatly reduced, and the constant rotational speed control and hydraulic pressure of the electric motor 10 during heavy work Since the discharge flow rate of the hydraulic pump 9 is adjusted by controlling the swash plate tilt angle of the pump 9, the driving of the hydraulic cylinder 1 can be controlled according to the load.

In addition, the hydraulic circuit can be simplified by controlling the forward and reverse rotation directions and the speed of the electric motor to drive the hydraulic pump (in the past, using a directional valve and a proportional control valve).

In addition, the hydraulic motor 17 and the generator 16 driven by the hydraulic oil returned from the hydraulic cylinder 1 at the time of shrinkage driving of the hydraulic cylinder 1 to which the load is applied convert the hydraulic energy into electrical energy to the battery 14. After charging to), the energy can be saved by regeneration when driving the electric motor (10).

1 is a hydraulic circuit diagram showing an energy-saving hydraulic system according to an embodiment of the present invention;

2 is a diagram showing a first use state diagram of an energy saving hydraulic system according to an embodiment of the present invention.

3 is a view showing a second use state of the energy-saving hydraulic system according to the embodiment of the present invention, which shows the contraction operation of the hydraulic cylinder;

4 is a flowchart illustrating a method of controlling an energy saving hydraulic system according to an exemplary embodiment of the present invention.

* Explanation of symbols used in the main part of the drawing

One; Hydraulic cylinder

2; Pressure sensor

3; Branch valve

6; Pilot Check Valve

8; Directional Valve

9; Variable displacement hydraulic pump

10; Electric motor

12; Electronic control unit (ECU)

13; Condenser

14; battery

15; Converter

16; generator

17; Hydraulic motor

Claims (7)

An electric motor driven in a forward and reverse direction according to a control signal input from the outside, and a variable displacement hydraulic pump connected to the electric motor and driven in a forward and reverse direction; A hydraulic cylinder installed in a flow path of the hydraulic pump and expanded and driven by hydraulic oil from the hydraulic pump driven according to the rotational direction and speed of the electric motor; A branch valve installed in the flow path between the hydraulic pump and the hydraulic cylinder, the branch spool being switched according to a control signal input from the outside; A hydraulic motor driven by hydraulic oil returned from the hydraulic cylinder through a branch valve, and a generator axially connected to the hydraulic motor; Charging means for charging the battery to be regenerated after converting the electrical energy generated by the generator into a direct current; And Including an electronic control unit for outputting a control signal to drive the branch valve and the electric motor in accordance with the signal input from the outside, When the hydraulic cylinder under load pressure is contracted and driven, the hydraulic motor and generator are driven by hydraulic oil returned from the hydraulic cylinder via the branch valve when the branch valve is switched according to the control signal of the electronic control unit rotor to generate electric energy. And converting the electric energy into a DC current and charging the battery to regenerate the electric motor when the electric motor is driven. The energy supply system of claim 1, further comprising a pilot check valve disposed at a supply side and a return side flow path between the hydraulic pump and the hydraulic cylinder, and preventing a hydraulic oil backflow when the electric motor and the hydraulic pump are stopped. Reduced hydraulic system. The pressure sensor of claim 1 or 2, further comprising: a pressure sensor provided in the large chamber side flow path of the hydraulic cylinder, the pressure sensor measuring the pressure of the hydraulic oil during expansion and contraction operation of the hydraulic cylinder and outputting a detection signal to the electronic control unit. Energy-saving hydraulic system. 4. The energy saving hydraulic system according to claim 3, comprising a condenser connected to said battery and preventing deterioration due to overcharge or discharge from said converter to said battery. The energy saving type of claim 4, further comprising an electronic proportional pressure reducing valve controlling the discharge flow rate by controlling the swash plate tilt angle of the hydraulic pump so as to correspond to the input signal value when the control signal is input from the electronic controller. Hydraulic system. The hydraulic oil supply system according to claim 4 or 5, wherein the hydraulic oil is provided in a flow passage branched to a supply side and a return side flow path between the hydraulic pump and the hydraulic cylinder, respectively, and supplements the insufficient hydraulic fluid according to the cross sectional area difference between the large chamber and the small chamber of the hydraulic cylinder. Energy-saving hydraulic system, characterized in that it comprises a directional valve to supply to the hydraulic cylinder, the excess hydraulic fluid is returned to the hydraulic tank. An electric motor, a variable displacement hydraulic pump connected to the electric motor and driven in the forward and reverse directions, a hydraulic cylinder installed in the flow path of the hydraulic pump, a branch valve installed in the flow path between the hydraulic pump and the hydraulic cylinder, and hydraulic oil from the hydraulic cylinder Hydraulic motor driven by a generator and a generator, a converter for converting the electrical energy generated by the generator into a direct current to charge the battery, an electronic control unit for outputting a control signal to drive the branch valve and the electric motor according to the signal input from the outside In the energy-saving hydraulic system comprising: A first step of driving a hydraulic pump by the electric motor driven by a control signal from the electronic controller; A second step of measuring the actual discharge pressure of the hydraulic pump and the required pressure generated on the large chamber side of the hydraulic cylinder and outputting a detection signal to the electronic control unit; A third step of comparing the pressure difference between the discharge pressure of the hydraulic pump and the required pressure of the hydraulic cylinder; When the required pressure is larger than the discharge pressure, the discharge flow rate of the hydraulic pump is calculated based on the rotational speed control of the electric motor and the difference between the required pressure and the discharge pressure, and then the swash plate tilt angle of the hydraulic pump is set to correspond to the calculated value. Control the discharge flow rate of the hydraulic pump, A fourth step of controlling to reduce the discharge flow rate of the hydraulic pump by lowering the rotation speed of the set electric motor when the required pressure is smaller than the discharge pressure; A fifth step of stopping the stretch driving by reducing the speed at which the hydraulic cylinder is stretched and driven; Determining whether the driving direction of the electric motor capable of driving in the forward and reverse directions is changed; When the driving direction of the electric motor is changed, the hydraulic cylinder is contracted and driven, and a control signal is output to switch the branch valve. A seventh step of terminating if the driving direction of the electric motor is not changed; An eighth step of determining whether the hydraulic motor is driven by the hydraulic oil returned through the branch valve when the hydraulic cylinder is contracted and driven; And When driving the hydraulic motor by the hydraulic oil from the hydraulic cylinder that is shrink-driven, by driving the generator by the hydraulic motor to convert the electrical energy generated by the direct current to charge the battery, And a ninth step of reducing the contraction driving speed of the hydraulic cylinder to stop the contraction drive when the hydraulic motor is not driven by the hydraulic oil from the contraction-driven hydraulic cylinder.

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