KR101643023B1

KR101643023B1 - Electric power system for an Excavator

Info

Publication number: KR101643023B1
Application number: KR1020120037257A
Authority: KR
Inventors: 이상훈; 구자진; 권영민; 오창은
Original assignee: 현대중공업 주식회사
Priority date: 2012-04-10
Filing date: 2012-04-10
Publication date: 2016-07-26
Also published as: KR20130114871A

Abstract

The present invention relates to a battery comprising: a battery; engine; Engine generator; An inverter for an engine generator for controlling a rotational speed and a torque of the engine generator; A main motor that receives power from the battery and the engine generator to generate a driving force; Hydraulic pump; A main motor inverter for controlling a rotation speed and a torque of the main motor; A hydraulic actuator that receives driving force from the hydraulic pump; An electric generator for rotation which operates as an electric motor when providing the swing drive force to the electric excavator and operates as a generator when generating electric power by using the swing motion of the electric excavator; A pivoting inverter for controlling a rotational speed and a torque of the pivoting electric motor; An upper revolving structure driven by the revolving motor generator; A main controller for instructing a rotational speed and a torque control to the main motor inverter, the engine generator inverter and the pivoting inverter; And an operation stick for operating the hydraulic system, wherein the main controller receives the amount of the joystick and the discharge pressure of the hydraulic pump, And the main motor inverter controls the main motor to rotate at a commanded rotation speed of the main motor, wherein the main motor inverter calculates the rotation speed of the main motor and instructs the calculated rotation speed to the main motor inverter, .

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an excavator,

The present invention relates to an excavator power system and a control method, and more particularly, to an excavator electric power system and a control method that improve energy consumption efficiency and work performance.

As the oil prices continue to rise in recent years, there has been an increase in sales of electric vehicles that use electric power systems to improve energy efficiency, such as hybrids or electric vehicles.

In the field of construction equipment, the application of such electric power system is increasing, and construction equipment using electric power system such as hybrid excavator and wheel loader is actively being developed.

On the other hand, construction equipment such as an excavator works on construction or industrial sites. Since the fuel consumption is very high per day compared to automobiles, there is a constant market demand for fuel efficiency due to the high proportion of fuel expenses in equipment maintenance costs. Environmental issues such as regulation.

In order to improve the fuel efficiency and to cope with environmental problems, the construction equipment manufacturer has developed and applied various engine and pump power control technologies. However, the energy efficiency efficiency is limited due to the low efficiency power system structure of engine power type construction equipment .

Therefore, in order to improve the energy efficiency efficiency and work performance, it is necessary to research and develop a relatively efficient and environmentally friendly electric power system (a system composed of a large capacity battery, an electric motor, and an inverter).

SUMMARY OF THE INVENTION The present invention provides an excavator electric power source system with improved energy efficiency and work performance and a control method thereof.

The technical object of the present invention is not limited to the above-mentioned technical objects and other technical objects which are not mentioned can be clearly understood by those skilled in the art from the following description will be.

In order to solve the above problems, the present invention provides a battery which is used as a main power source and has a battery management system (BMS); An engine used as a power source for assisting the battery; An engine generator connected to an output shaft of the engine to produce power; An inverter for an engine generator for controlling a rotational speed and a torque of the engine generator; A main motor that receives power from the battery and the engine generator to generate a driving force; A hydraulic pump connected to the main electric motor and provided with a driving force therefrom; A main motor inverter for controlling a rotation speed and a torque of the main motor; A hydraulic actuator that receives driving force from the hydraulic pump; An electric generator for rotation which operates as an electric motor when providing the swing drive force to the electric excavator and operates as a generator when generating electric power by using the swing motion of the electric excavator; A pivoting inverter for controlling a rotational speed and a torque of the pivoting electric motor; An upper revolving structure driven by the revolving motor generator; A main controller for instructing the main motor inverter, the engine generator inverter and the pivoting inverter to perform rotational speed and torque control; And an operation stick for operating the hydraulic system, wherein the main controller receives the operation amount of the joystick and the discharge pressure of the hydraulic pump, And the main motor inverter controls the main motor to rotate at a commanded rotation speed of the main motor, wherein the main motor inverter calculates the rotation speed of the main motor and instructs the calculated rotation speed to the main motor inverter, .

Further, the hydraulic pump is provided with a pump controller for controlling the torque thereof, the pump controller is connected to the main controller, and the main controller receives the operation amount of the joystick and the discharge pressure of the hydraulic pump, And the pump controller may control the torque of the hydraulic pump by causing the hydraulic pump to discharge the commanded volume. In this case, it is also possible to control the torque of the hydraulic pump by calculating the volume of the pressure corresponding to the torque and the calculated volume to the pump controller.

The main controller may control the rotational speed command value of the main motor and the volume command value of the hydraulic pump to be corrected so that the main motor and the hydraulic pump operate at optimum efficiency points.

The main controller receives a state of charge (SOC) of the battery from the BMS and sends a drive command and a rotational speed signal to the engine when the charge state amount is less than a preset reference value, And the inverter for the engine generator may cause the engine generator to generate electric power according to the amount of electric power commanded from the main controller, and the produced electric power may be charged to the battery.

In addition, in the excavator electric power system, when the battery does not operate normally, power is prevented from flowing from the battery to the main electric motor and the turning-purpose electric motor, and the engine and the engine generator are operated to produce electric power , And the generated power may be used to drive the main electric motor and the electric generator for rotation and to perform the output reduction control for driving the main electric motor and the generator for rotation at an output lower than the rated output.

In addition, when the battery is not operating normally, the BMS sends a malfunction signal to the main controller, and when receiving a signal from the BMS, the main controller transmits power from the battery to the main motor and the generator It may be to block the inflow.

According to the present invention, energy efficiency and work performance of an excavator can be improved by improving a large-capacity battery of an excavator, a plurality of motors, a generator, an inverter, an engine control system, and a control method thereof.

In addition, it can respond to the demand for improvement of fuel efficiency for construction equipment due to the continuous increase of oil price, and to cope with environmental changes such as strengthening of exhaust gas regulation.

1 is a schematic diagram illustrating an excavator electric power system according to an embodiment of the present invention,
2 is a flow diagram illustrating the operation of an excavator electric power system in accordance with an embodiment of the present invention,
3 is a graph showing a main motor control curve of an excavator electric power system according to an embodiment of the present invention,
FIG. 4 is a graph showing the relation between the charged state of the battery and the engine operation of the excavator electric power system according to the embodiment of the present invention,
5 and 6 are schematic diagrams illustrating the operation of an excavator electric power system in accordance with an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The sizes and shapes of the components shown in the drawings may be exaggerated for clarity and convenience. In addition, terms defined in consideration of the configuration and operation of the present invention may be changed according to the intention or custom of the user, the operator. Definitions of these terms should be based on the content of this specification. It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventions. Of course.

1, an excavator electric power system according to an embodiment of the present invention includes an electric energy storage, an auxiliary engine generator, a main motor, a hydraulic system, a swivel, and a main controller 90.

The electric energy storage portion is a battery 10 used as a main driving force and charged by an external charging device (C). The battery 10 is typically provided with a BMS (Batch Management System) 100 for checking the state of charge of the battery 10 and the like.

The auxiliary engine generator includes an engine 20 used as a power source for assisting the battery 10, an engine generator 30 for generating electric power by the engine 20, an engine generator 30 for controlling the operation of the engine generator 30, And an inverter 31 for an engine generator.

The main motor unit includes a main motor 40 driven by the battery 10 and the engine generator 30, a main motor inverter 41 for controlling the operation of the main motor 40, And a hydraulic pump 50 provided with a driving force from the hydraulic pump 50.

The hydraulic system includes a hydraulic motor 600 for operation and a hydraulic cylinder 610 operated by the hydraulic pump 50 and a boom, an arm, a bucket, and the like.

The swivel portion includes a swivel power generating motor 70 that operates as an electric motor and drives the swivel drive device 80 or plays a role of a generator in the regenerative braking operation therefrom, a swivel inverter 71 , And an upper revolving structure 80 driven by the revolving generation electric motor 70.

The main controller 90 is an upper control device for controlling the main motor inverter 41, the engine generator inverter 31 and the pivoting inverter 71.

On the other hand, it is possible to increase the working efficiency and the energy efficiency of the excavator by controlling the outputs of the main electric motor and the hydraulic pump according to the operation amount of the operation stick of the driver and the work load in the excavator.

That is, as the manipulation amount of the manipulation stick is increased, a higher working speed is required and the rotational speed of the main motor must be increased. As the work load is larger, the torque required for the main motor increases. Therefore, It is necessary to appropriately control the torque.

To this end, it is possible to control the speed of the main motor and the torque of the hydraulic pump, thereby controlling the number of revolutions and torque of the main motor. This will be described with reference to FIGS. 2 and 3. FIG.

The speed control of the main motor and the torque control method of the hydraulic pump are as shown in FIG.

First, when the amount of the operation stick is inputted to the main controller, the main controller determines the driver's operation amount of the excavator through the amount, and when the discharge pressure of the hydraulic pump is input to the main controller, To determine the workload of the excavator.

Next, the main controller calculates the rotational speed of the main motor by applying the determined driver manipulated variable and a predetermined weight to the work load, and instructs the calculated motor rotational speed to the main motor inverter, Controls the main electric motor to rotate at the commanded rotational speed.

The main controller calculates the volume of the pressure oil corresponding to the torque demanded by the hydraulic pump by applying the determined driver manipulated variable and the weight set in advance to the work load and instructs the calculated volume to the pump controller, The pump controller controls the torque of the hydraulic pump by causing the hydraulic pump to discharge the commanded volume.

In Fig. 3, a graph of the control curve of the electric motor is shown.

In FIG. 3, a plurality of curves drawn from the upper left to the lower right indicate that the main motor efficiency is constant. This curve increases the efficiency of the main motor as it goes to the right. Therefore, as the torque and the number of rotations of the main motor increase, the efficiency of the main motor increases.

However, since the torque and the number of revolutions required for the main motor vary depending on the working environment, the main controller needs to calculate the torque and the number of revolutions required for each working environment, and accordingly, the main motor needs to be controlled.

The main controller calculates a correction value of a rotation speed command value of the main motor and a volume command value of the hydraulic pump so that the main motor and the hydraulic pump operate at optimum efficiency points, And the torque and the number of revolutions of the main electric motor are controlled so as to correspond to the value of the main motor.

At this time, the reference value is required for the main controller to calculate the correction value. This set value refers to a criterion for allowing the main electric motor and the hydraulic pump to operate at an optimum efficiency point, and is represented by an electric motor control curve in Fig.

As a result, the main controller controls the main motor to have a torque and a speed according to the motor control curve.

At this time, the shape of the motor control curve is determined by combining the efficiencies of the main motor and the hydraulic pump, and may be changed depending on the working environment, the characteristics of the excavator, and the like.

4 is a graph illustrating the operation of the engine and the engine generator of the present invention.

The main controller receives a state of charge (SOC) of the battery from the BMS, sends a drive command and a rotational speed signal to the engine when the charge state amount is less than a preset reference value, And the rotational speed and the torque of the engine generator.

At this time, the engine is driven according to the command of the main controller, and the engine generator connected to the engine generates electric power.

The inverter for the engine generator causes the engine generator to generate electric power according to the amount of electric power commanded from the main controller, and the produced electric power is charged in the battery.

5 and 6 show a state in which the battery 10 does not operate normally, that is, the battery 10 fails to supply power to the main electric motor 40 and the electric motor 70 for rotation And shows a change in the power supply system of the excavator when the power supply is unstable or unstable.

First, when the battery 10 is not operating normally, the BMS 100 senses an abnormal signal of the battery 10 and sends it to the main controller 90.

The main controller 90 receives an abnormal signal from the BMS 100 and cuts off power input from the battery 10 to the main electric motor 40 and the electric generator 70 for turning. At this time, a switch device, a relay device, or the like is usually used as the circuit breaker (S).

The reason for interrupting the power inflow is that if unstable electric power is supplied to the main electric motor 40 and the electric motor for swing due to the failure of the battery 10, it may cause failure of each electric motor.

Next, the main controller 90 drives the engine 20 and the engine generator 30. At this time, an engine control unit connected to the main controller 90 and driving or stopping the engine 20 according to the command may be added to the engine 20 and used.

5, when the power supply to the battery 10 is cut off by the main controller 90, the engine 20 and the engine generator 30 are operated to produce electric power.

The generated electric power is supplied to the main motor inverter 41 and the pivoting inverter 71 through the inverter for the energization generator to drive the main electric motor 40 and the pivoting electric motor 70 connected thereto.

Further, the main electric motor 40 drives the hydraulic pump 50, and the hydraulic pump 50 drives the hydraulic actuator 60.

On the other hand, the engine 20 used as an auxiliary power source typically has an output of about half of the output supplied by the battery 10. [ Therefore, in this case, the output reduction control is required.

The output reduction control is performed based on the rotation speeds of the main electric motor 40 and the rotation electric power generating motor 70 via the main controller 90 and the main electric motor inverter 41 and the pivoting inverter 71, This is done in a way that limits the torque.

The main electric motor 40 and the electric generator 70 for revolutions are driven at an output lower than the rated output through the output reduction control so that the operation of the excavator is limited, but the operation can be continued even in an emergency.

6, when the power supply from the battery 10 is cut off by the circuit breaker S, the inverter 31 for the engine generator, the inverter 41 for the main motor, , The electric power generated by the engine generator 30 is supplied to the main motor inverter 41 and the pivoting inverter 71 through the inverter 31 for the engine generator.

While the invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined by the appended claims. Accordingly, the true scope of the present invention should be determined by the following claims.

10: Battery 20: Engine
30: Engine generator 31: Inverter for engine generator
40: main motor 41: main motor inverter
50: Hydraulic pump 60: Hydraulic actuator
70: a generator motor for turning 71: an inverter for turning
80: Upper revolute 90: Main controller
100: BMS 600: Hydraulic motor
610: Hydraulic cylinder

Claims

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A battery used as a main power source and equipped with a battery management system (BMS);
An engine used as a power source for assisting the battery;
An engine generator connected to an output shaft of the engine to produce power;
An inverter for an engine generator for controlling a rotational speed and a torque of the engine generator;
A main motor that receives power from the battery and the engine generator to generate a driving force;
A hydraulic pump connected to the main electric motor and provided with a driving force therefrom;
A main motor inverter for controlling a rotation speed and a torque of the main motor;
A hydraulic actuator that receives driving force from the hydraulic pump;
An electric generator for rotation which operates as an electric motor when providing the swing drive force to the electric excavator and operates as a generator when generating electric power by using the swing motion of the electric excavator;
A pivoting inverter for controlling a rotational speed and a torque of the pivoting electric motor;
An upper revolving structure driven by the revolving motor generator;
A main controller for instructing a rotational speed and a torque control to the main motor inverter, the engine generator inverter and the pivoting inverter; &Lt; RTI ID = 0.0 >
If the battery does not operate normally,
Wherein the main motor and the generator for rotation are connected to each other to block power input from the battery to the main electric motor and the electric generator for rotation and to generate electric power by operating the engine and the engine generator, And an output reduction control for driving the electric motor and the generator for rotation is performed at an output lower than the rated output.

6. The method of claim 5,
Wherein the BMS sends a malfunction signal to the main controller, and the main controller, when receiving a signal from the BMS, interrupts the power inflow from the battery to the main motor and the turning power generation motor. system.