JP2010265708A - Battery-driven work machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To minimize environmental pollution and noise during the operation and reduce fuel consumption using a small engine in a work machine on which an engine is mounted together with a battery. <P>SOLUTION: This battery-driven work machine includes traveling motors 11, 12 for a base carrier 1 and a hydraulic pump 21 for driving an actuator constituted of a boom cylinder 13, an arm cylinder 14, and a bucket cylinder 15. The hydraulic pump 21 is driven by an electric motor 22. The electric motor 22 and an electric motor for slewing 10 are driven by a battery 24. A power supply device 26 constituted of an engine 27, a generator 29, and a power storage control means 30 is further mounted on the work machine. The engine 27 is driven so that the rotational speed and the output torque are constant for power generation. The work machine further includes the controlled engine 27 and the generator 29 driven by the engine. The power generated by the generator 29 is stored in the battery 24 through the power storage control means 30. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a work machine such as a hydraulic excavator, and relates to a battery-driven work machine provided with a plurality of actuators using a battery as a power source.

  BACKGROUND ART A hydraulic excavator as an example of a work machine is installed in a lower traveling body having left and right crawler belts so that an upper swing body can be turned via a turning device. The upper swing body includes a boom, an arm and a bucket, and is provided with working means for performing work such as excavation of earth and sand. The upper swing body is also provided with a cab where an operator who operates the machine is boarded.

  The lower traveling body is driven by a traveling motor, and a turning motor is attached to the turning device. The working means are each driven by a hydraulic cylinder such as a boom cylinder, an arm cylinder, and a bucket cylinder. Accordingly, these motors and hydraulic cylinders constitute machine actuators, and by operating each actuator, the vehicle travels, the upper swing body turns, and the work by the working means is executed. Here, a plurality of motors as actuators may be electric motors or hydraulic motors. On the other hand, it is a hydraulic cylinder that drives the working means. Therefore, the hydraulic excavator is provided with a hydraulic pump.

    As a power source of a work machine, an engine drive type using an engine as a prime mover has been widely used. However, in recent years, an electrically driven type has been developed and put into practical use from the viewpoints of demands such as suppression of generation of exhaust gas containing environmental pollutants such as particulate matter PM and reduction of noise. Here, in the case of an electric drive type, there is an external power type that requires an external power source. However, in this method, the vehicle and the external power source must always be connected with a power cord, and workability is poor. There is a problem.

  From the above, there is a battery-driven work machine in which a battery is mounted on a vehicle instead of an engine and this battery is used as a drive source. However, since a work machine may operate for a long time under a high load condition, if a battery is used to cover the entire energy of the work machine, a large-capacity battery is required. In some cases, it cannot be placed on the upper rotating body of the work machine in terms of weight.

  Accordingly, hybrid work machines equipped with an engine and a battery have been developed and put into practical use. Thus, by sharing with the engine, the mounted battery can be reduced in size and weight. As a hybrid system, there is a parallel hybrid system that uses an engine as a main power source and also supplies power from a generator that uses a battery as a power source. This parallel hybrid system uses the engine as the main power source. Since it is used as a source, it is still unsatisfactory in terms of reducing exhaust gas.

  As another hybrid system, there is a series hybrid type work machine that uses an engine, an induction machine having a function as an electric motor and a generator as a power source, and drives the engine and the induction machine at the same time. Is shown in As is apparent from the description of Patent Document 1, in a series hybrid vehicle, an induction machine is installed in addition to the engine and battery, and the induction machine is operated using the engine and battery as a power source. Thus, the hydraulic pump that drives the hydraulic actuator is driven. That is, the power source for driving the work machine is divided into the engine and the battery, and the engine is also used for power generation. As a result, since the battery is a part of the power source, the burden on the engine is reduced and the exhaust gas is reduced. This series hybrid system is superior to the parallel hybrid system. Here, in patent document 1, in order to be able to perform work efficiently, it is set as the structure which has the maximum output capacity which can supply motive power required at the time of a maximum load by an engine and an induction machine independently.

Japanese Patent Laid-Open No. 2006-233811

  By the way, the work machine is operated under various circumstances. For example, when excavating a hard ground, the work machine operates under an extremely high load state. When performing such work, it is necessary to use a large engine if the engine can cover the power, and if the engine generates the required output torque at the maximum load, As exhaust gas is generated, environmental pollutants including a large amount of particulate matter PM are released to the outside, contaminating the surrounding environment and increasing noise. In addition, since the engine output torque changes in accordance with load fluctuations, there is a problem in that fuel consumption is reduced.

  In short, in a hybrid work machine including an engine with a battery, when the engine is used for driving the work machine, the rotational speed and output torque of the engine change according to the operating conditions of the work machine. For this reason, the installed engine has the ability to output the necessary power even at the maximum load of the work machine, so it will be large, and it will be subject to changes in engine speed and output torque. Accordingly, there is a limit to the effect of suppressing the generation of environmental pollutants contained in the exhaust gas and the generation of noise, and further dissatisfaction remains in terms of reducing fuel consumption.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a working machine equipped with an engine together with a battery by using a small engine with a small horsepower so that the environment during operation can be obtained. An object of the present invention is to minimize contamination and noise and to reduce fuel consumption.

  In order to achieve the above-described object, the present invention provides a plurality of actuators using a battery as a power source in order to provide working means for a traveling vehicle and drive at least the traveling means of the vehicle and the driving means of the working means. A battery-powered work machine having a power supply device for supplying power to the battery in the traveling vehicle, the power supply device having an engine controlled so that a rotational speed and an output torque are constant; It is characterized by comprising a generator driven by this engine.

  The working machine is provided with at least a vehicle traveling means and a working means for excavating earth and sand. In addition, the lower traveling body provided with the upper revolving body capable of swiveling is also provided with a turning means. The traveling means is driven by a traveling motor, the working means is driven by a hydraulic cylinder, and the turning means is driven by a turning motor. These are actuators, and at least a hydraulic cylinder is connected to a hydraulic pump. This hydraulic pump is driven by an electric motor. On the other hand, the traveling motor and the turning motor can be configured as an electric motor, and can also be configured as a hydraulic motor driven by a hydraulic pump. As the motor, it is desirable that at least the swing motor is configured as an electric motor from the viewpoint of regenerating energy.

  The work machine is equipped with a battery and an engine, but the only power source of the motor that consists of an electric motor or a swing motor that drives the hydraulic pump is the battery, and the engine is not connected to the motor. The engine and the generator constitute a power supply device for supplying power to the battery. Therefore, this work machine is not of a hybrid type, and is driven by a battery that uses a battery as a whole power source.

  During operation of the work machine, the engine is driven to continuously generate power. In this way, by continuously generating power while the work machine is in operation, the total amount of power generated by the engine is added to the power capacity of the battery. Therefore, the battery can be reduced in size and weight accordingly. It is assumed that the power supply capacity of the power supply apparatus, that is, the power generation capacity of the engine constituting the power supply apparatus depends on the battery mounted. If a battery with a large power capacity can be mounted in relation to the installation space of the battery, the engine may be smaller, but if the power capacity of the battery is reduced, the engine will be enlarged to some extent.

  Since the engine is not used as a drive source for the actuator in the work machine, the engine can be operated so as to output a constant torque at a constant rotational speed, and the engine load does not fluctuate. Here, if the rotational speed is constant and the output torque is constant, the engine noise is minimized, and environmental pollutants such as particulate matter PM contained in the exhaust gas can be suppressed. If the rotational speed of the engine is constant for driving the generator, the output torque is also constant. However, the amount of environmental pollutants contained in the exhaust gas changes according to the rotational speed of the engine, and the fuel consumption is not constant. Therefore, based on the structure of the engine mounted on the work machine, it is set to drive in the best operating state. Here, the best operating state can be set mainly based on the cleanliness of the exhaust gas and the fuel efficiency, so as to reduce noise. For example, the rotational speed is set so that the particulate matter PM of the exhaust gas becomes the minimum amount and is driven with the lowest fuel consumption.

  The engine constitutes a power supply means for charging the battery. If charging is performed in a state where the power capacity of the battery is equal to or greater than a predetermined value, the battery is overcharged and its life is reduced. Therefore, the battery is provided with a remaining charge detection means for detecting the remaining charge, and when the power capacity is less than or equal to the set value, the engine is driven to generate power, and when the set value is exceeded, the engine is driven. Stop. As a result, the battery is prevented from being overcharged and the service life is extended.

  The battery mounted on the traveling vehicle can be reduced in size, and the engine can make up for the power that is insufficient with this battery. In addition, environmental pollution during engine operation can be suppressed and noise can be reduced. it can.

It is composition explanatory drawing of the hydraulic shovel as an example of the working machine of this invention. It is a circuit block diagram which comprises the drive mechanism of the hydraulic shovel of FIG. It is explanatory drawing which shows the relationship between the output waveform of the battery as a power source when a hydraulic excavator is operated under a certain condition, and energy consumption. Explanatory drawing which shows the relationship between the output waveform of the battery as a motive power source and energy consumption when it is made to operate | move on the condition similar to FIG. 3 by the structure of this invention which provided the engine as an electric power feeder in addition to a battery. It is. It is explanatory drawing which shows the generation | occurrence | production degree of particulate matter PM by the relationship between an engine rotational speed and axial torque. It is explanatory drawing which shows a fuel consumption efficiency by the relationship between an engine rotational speed and a shaft torque.

    Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, FIG. 1 shows a hydraulic excavator as an example of a work machine. The hydraulic excavator has a lower traveling body 1 provided with crawler-type traveling means on the left and right sides, and an upper revolving body 3 is installed on the lower traveling body 1 via a revolving device 2. The upper swing body 3 is equipped with excavation means 4 as a front structure, and is provided with a cab 5 and a building 6. The excavation work means 4 includes a boom 7 provided on the frame of the upper swing body 3 so as to be able to be lifted and lowered, an arm 8 connected to the boom 7 so as to be rotatable, and a bucket 9 provided at the tip of the arm 8. It is composed of

  In the hydraulic excavator having the above-described configuration, the movable mechanisms are the left and right crawler type traveling means and the excavation work means 4 in the turning device 2 and the lower traveling body 1. As shown in FIG. 2, the mechanism that drives each of these movable parts is an actuator. Among the actuators, the turning device 2 is driven by the turning electric motor 10, the left and right traveling means are driven by the traveling motors 11 and 12, and the boom 7 constituting the excavating work means 4 is the boom cylinder 13 and the arm. Reference numeral 8 denotes an arm cylinder 14 and the bucket 9 is driven by a bucket cylinder 15.

  The left and right traveling motors 11 and 12 are constituted by hydraulic motors, and the boom cylinder 13, the arm cylinder 14 and the bucket cylinder 15 are hydraulic cylinders. Accordingly, the hydraulic motor and the hydraulic cylinder are hydraulic actuators, and a hydraulic pump 21 is provided to drive the hydraulic motor and the hydraulic cylinder. The hydraulic pump 21 is driven by an electric motor 22 for driving the pump. It is. Therefore, a hydraulic control valve 23 is provided in the middle of the piping between the hydraulic pump 21 and the traveling motors 11 and 12, the boom cylinder 13, the arm cylinder 14, and the bucket cylinder 15. The hydraulic control valve 23 is controlled to be switched by an operation lever, and the operation control of each hydraulic actuator described above is performed by operating the operation lever. Here, since the turning motor 10 is configured to be directly driven by the electric motor 20, it functions as a power regenerative brake for regenerating inertia energy as electric power when turning is stopped. In addition to the turning, the regeneration can be configured to be performed, for example, in a boom lowering operation or the like.

  The electric motors 20 and 22 use a battery 24 as a power source, and the electric motors 20 and 22 are connected to the battery 24 via a power control means 25. The battery 24 is charged in advance. In addition, a power supply device 26 for supplying power to the battery 24 during operation of the hydraulic excavator is provided. For this purpose, an engine 27 is mounted on the hydraulic excavator, and a fuel tank 28 for supplying fuel to the engine 27 is provided. A generator 29 is connected to the engine 27, and the generator 29 is driven by the engine 27. Furthermore, the generator 29 is configured to supply power to the battery 24 via the power storage control means 30. Accordingly, the power feeding device 26 includes the engine 27, the generator 29, and the power storage control means 30.

  Here, the engine 27 is not connected to the power control means 25, and does not directly drive any movable mechanism of the hydraulic excavator, but only to generate power from the generator 29. The power storage control means 30 also constitutes a remaining power storage detection means for detecting the remaining power storage of the battery 24, and when the remaining power storage of the battery 24 is equal to or less than a predetermined value set as the power capacity. The engine 27 is operated, and when the power capacity exceeds the set value, the engine 27 is controlled to stop even though the excavator is in operation.

  In FIG. 3, assuming that the excavator is operated for a time T, and the output waveform during that time is P, the total output energy output over this time T is Etol. Here, the power output is negative when the regeneration is being performed. Therefore, the required output energy is Edem obtained by subtracting the regenerative energy Ereg from the total output energy Etol. This required output energy Edem is covered by the remaining amount of electricity stored in the battery 24. In this case, a large battery having a large power capacity must be mounted.

  From the above, the hydraulic excavator is equipped with the engine 27 as the power feeding device 26, and the generator 29 can be driven by operating the engine 27. Here, the engine 27 that constitutes the power feeding device 26 is for power generation, and there is no load fluctuation, so it is driven at a constant rotational speed. Then, the electric power generated by the generator 29 is stored in the battery 24 via the power storage control means 30. Thereby, the battery 24 can ensure a predetermined power capacity. As a result, as shown in FIG. 4, the stored energy Eadd derived from the engine 27 is added. Therefore, if the output energy from the battery 24 is Enet, the total output energy for the entire time T is obtained by Etol. Will be.

  By the way, by mounting the engine 27 together with the battery 24 and operating the engine 27 for power generation, the burden on the battery 24 is reduced, and a small and lightweight battery can be used. However, when the engine 27 is driven, exhaust gas is generated and engine noise is also generated. In this sense, it is inferior to an all-electric work machine driven by a battery.

  Incidentally, the problem of noise generated from the engine 27 becomes large when the rotational speed of the engine 27 is changed. When the engine 27 is driven at a constant rotational speed, noise is minimized, It will not be a nuisance to the surroundings.

  And about exhaust gas, according to the rotational speed of the engine 27, the quantity of environmental pollutants, such as particulate matter PM contained in exhaust gas, changes. Specifically, as shown in FIG. 5, when the engine 27 is driven in a predetermined output torque state, the discharge amount of the particulate matter PM changes according to the rotational speed, but proportionally according to the rotational speed. Although the amount of discharge is small within a certain rotational speed range, the amount of particulate matter PM discharged is low even when the rotational speed is increased or the rotational speed is decreased. Become more. Therefore, the particulate matter PM is discharged at the minimum rotational speed.

  Further, the fuel consumption of the engine 27 can be reduced by driving at a constant rotational speed. Further, as shown in FIG. 6, there is a low fuel consumption region even when the engine 27 is driven with a predetermined output torque.

  From the above, the output torque and the rotation speed are controlled so that the engine 27 can be driven at a constant rotational speed, and the particulate matter PM shown in FIG. 5 can be driven at a low fuel consumption as shown in FIG. Choosing speed allows the engine 27 to be efficient and minimize environmental pollution. At this time, the rotational speed of the engine 27 is lower than the rated rotational speed.

  Further, in order to prevent the battery 24 from being overcharged, the remaining amount of electricity stored in the battery 24 is detected by the remaining amount of electricity detecting means constituting the electricity storage control means 30, and the remaining amount of electricity stored is set as the power capacity. The engine 27 is driven when it is equal to or less than the predetermined value, and the engine 27 is controlled to stop when the set value of the power capacity is exceeded. As a result, the battery 24 is protected, and there is no situation where the life of the battery 24 is shortened.

DESCRIPTION OF SYMBOLS 1 Lower traveling body 2 Swivel device 3 Upper revolving body 4 Excavation work means 10 Electric motor 11 for turning drive 11, 12 Travel motor (hydraulic motor)
DESCRIPTION OF SYMBOLS 13 Boom cylinder 14 Arm cylinder 15 Bucket cylinder 21 Hydraulic pump 22 Electric motor 24 Battery 25 Electric power control means 26 Electric power feeder 27 Engine 29 Generator 30 Electric power storage control means

Claims (3)

In a battery-powered work machine having a plurality of actuators that use a battery as a drive source in order to provide working means on a traveling vehicle and drive at least the traveling means of the vehicle and the driving means of the working means.
The traveling vehicle is provided with a power supply device that supplies power to the battery,
The battery-powered work machine is characterized in that the power supply device includes an engine controlled so that a rotational speed and an output torque are constant, and a generator driven by the engine. The remaining battery level detection means for detecting the remaining battery charge level of the battery is provided. When the power capacity is equal to or lower than a set value, the remaining power level detection means drives the engine to generate power, and when the set value is exceeded. The battery-driven work machine according to claim 1, wherein the driving of the engine is stopped. The battery-driven work machine according to claim 1 or 2, wherein the rotational speed of the engine is set based on a relationship between an emission amount of an environmental pollutant of exhaust gas and fuel consumption.

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