Excavating – Scoop or excavating and transporting container – Dipper-type
Reexamination Certificate
1999-05-28
2001-03-13
Pezzuto, Robert E. (Department: 3671)
Excavating
Scoop or excavating and transporting container
Dipper-type
C060S420000
Reexamination Certificate
active
06199307
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a working machine such as an excavator which is operated using a battery as a drive source.
2. Description of the Prior Art
Usually, in a conventional working machine such as a hydraulic excavator, a hydraulic pump is actuated by utilizing the power of an engine mounted for traveling and a hydraulic oil discharged from the hydraulic pump is fed to various hydraulic actuators such as a rotating motor, a boom cylinder and an arm cylinder to actuate various portions. However, in such a machine utilizing the engine power, there is a fear that noises and exhaust gases generated from the engine may exert a bad influence on the working site environment. For this reason it is the present situation that strict restrictions are placed on operations in cities and towns and in tunnels, further, on night operations.
In an effort to eliminate such bad influence there has recently been proposed a working machine wherein an electric motor is rotated by utilizing the electric power of a battery mounted on the working machine and a hydraulic pump is actuated by the electric motor (see, for example, Japanese Patent Laid Open No. 9-144061).
The battery mounted on the above working machine is lower in energy density (energy capable of being stored per unit mass) than fossil fuels such as gasoline and gas oil which are engine fuels. Thus, battery-powered working machine is disadvantageous in that the continuous working time is short as compared with working machines which utilize the engine power. As an example of means for increasing the continuous working time there is mentioned a means wherein energy is recovered when a negative work such as boom lowering or rotation braking work is performed and it is regenerated in the battery (that is, the attainment of a high efficiency is intended by energy regeneration). However, a large number of valves, including electromagnetic proportion valves, are mounted on a hydraulic excavator or the like and there occurs a large pressure loss or relief loss in those valves, so that it is very difficult to effect an efficient recovery of energy to the battery through the medium of such a hydraulic circuit.
If the operation of the boom and the rotation are conducted directly with use of an electric motor which is driven by a battery, without using such a hydraulic circuit, it will be possible to effect an efficient recovery of energy. However, in comparison with the hydraulic actuator, such an electric motor is smaller in the force and torque which it can generate per unit weight; besides, a reduction mechanism is required. Thus, the use of such a battery-powered electric motor is disadvantageous in that moving portions becomes more complicated in structure than in the use of a hydraulic actuator. The weight of moving portions also increases. Therefore, if the electric motor in question is provided at the front end of a boom, not only the moment of inertia of the boom and that of the entire swing structure will become larger, but also the weight balance of the entire working machine will become unstable.
SUMMARY OF THE INVENTION
The present invention has been accomplished in view of the above-mentioned circumstances and it is an object of the invention to provide a battery-powered working machine capable of keeping low the moment of inertia of a boom, etc. and capable of effecting a highly efficient recovery of energy to increase the continuous working time while maintaining the entire working machine in good weight balance.
According to the present invention, for achieving the above-mentioned object, there is provided in one aspect thereof a battery-powered working machine including a boom attached to a body of the working machine so as to be capable of rising and falling, a working portion attached to the boom, and a battery as a drive source, the working machine further including a boom actuating electric motor which is supplied with electric power from the battery and which actuates the boom directly, a hydraulic pump actuating electric motor which is supplied with electric power from the battery and which actuates a hydraulic pump, the hydraulic pump which is actuated by the hydraulic pump actuating electric motor and which discharges a hydraulic oil, and a hydraulic actuator which is supplied with the hydraulic oil discharged from the hydraulic pump and which actuates the working portion attached to the boom.
According to the present invention there is provided in another aspect thereof a battery-powered working machine including a rotatable superstructure carried rotatably on a lower carriage, a boom attached to the rotatable superstructure so as to be capable of rising and falling, a working portion attached to the boom, and a battery as a drive source, the working machine further including a rotating electric motor which is supplied with electric power from the battery and which directly causes the rotatable superstructure to rotate, a hydraulic pump actuating electric motor which is supplied with electric power from the battery and which actuates a hydraulic pump, the hydraulic pump which is actuated by the hydraulic pump actuating electric motor and which discharges a hydraulic oil, and a hydraulic actuator which is supplied with the hydraulic oil discharged from the hydraulic pump and which actuates the working portion attached to the boom.
According to the present invention there is provided in a further aspect thereof a battery-powered working machine including a rotatable superstructure carried on a lower carriage rotatably, a boom attached to the rotatable superstructure so as to be capable of rising and falling, a working portion attached to the boom, and a battery as a drive source, the working machine further including a boom actuating electric motor which is supplied with electric power from the battery and which actuates the boom directly, a rotating electric motor which is supplied with electric power from the battery and which directly causes the rotatable superstructure to rotate, a hydraulic pump actuating electric motor which is supplied with electric power from the battery and which actuates a hydraulic pump, the hydraulic pump which is actuated by the hydraulic pump actuating electric motor and which discharges a hydraulic oil, and a hydraulic actuator which is supplied with the hydraulic oil discharged from the hydraulic pump and which actuates the working portion attached to the boom.
In these working machines, since the boom and the rotatable superstructure are actuated directly by electric motors (that is, they are actuated through mechanical means such as reduction gears without through any hydraulic means), the mechanisms associated with the said actuation can be simplified. Besides, when a negative work is performed such as moving down the boom at a predetermined speed against its own weight or braking the rotatable superstructure during rotation, the boom actuating electric motor or the rotating electric motor are allowed to function as a generator, thereby converting the said negative work into an electric energy, which can be recovered in the battery. On the other hand, a hydraulic actuator, which is less heavy than the electric motors, is used for actuating the working portion located farther from the centroid position of the working machine than the boom and the rotatable superstructure. Further, a hydraulic pump is actuated by a hydraulic pump actuating electric motor which uses the battery as a drive source, to supply the hydraulic actuator with hydraulic oil. In this way it is possible to avoid a great increase in inertia moment of the rotatable superstructure and the boom and avoid deterioration of the weight balance of the entire working machine.
The working portion attached to the boom comprises, for example, an arm connected rotatably to the front end portion of the boom and a bucket connected rotatably to the front end portion of the arm. In this connection, it is preferable for the working machine to be provided with an arm actuat
Kagoshima Masayuki
Kinugawa Hideki
Kabushiki Kaisha Kobe Seiko Sho
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Pezzuto Robert E.
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