JP2003070279A - Electric power unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce in size an overall unit by effectively reducing a consumption of a battery and preventing an induction motor for driving a hydraulic pump from becoming large in size. SOLUTION: The hydraulic pump P for supplying hydraulic oil to a hydraulic actuator (a tiltable cylinder 23, an expansion cylinder 31, a turning motor 22, and a tilting motor 41) is driven by the induction motor M. An inverter 63 of a controller 60 outputs an AC current of a frequency corresponding to a rotational speed of the motor M set by a rotational speed setting means (operating lavers 51 to 54 and a rotational speed setter 62) to operate the motor M. An output control circuit 64 of the controller 60 controls the AC current outputted from the inverter 63 so that the output of the motor M obtained based on an amplitude of the AC current outputted from the inverter 63 and the speed of the motor M detected by a rotational speed detector S does not exceed a predetermined prescribed output.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric power unit having a structure in which a hydraulic pump is driven by an electric motor using a battery as a power source, and a hydraulic actuator is driven by the discharged hydraulic oil.

[0002]

2. Description of the Related Art In various work vehicles including construction work vehicles such as crane vehicles and aerial work vehicles, hydraulic power is often used to drive actuators such as booms and winches. As a power source for supplying hydraulic oil for driving such a hydraulic actuator, there is known a power source for driving a hydraulic pump by taking out power of a traveling engine by a power take-off device (generally called PTO). In addition, there is a type in which the hydraulic pump is driven by a small dedicated engine separately mounted instead of the traveling engine, and it is known as a low noise type power unit.

As described above, the power source for driving the hydraulic pump by the engine can constitute a small and lightweight power unit.
The problem of noise generation and the effect of exhaust on the environment has also arisen, and in recent years, electric power units have been used that operate a motor using a battery as a power source and thereby drive a hydraulic pump to obtain hydraulic power. Is coming. Since such an electric power unit uses a battery as a power source, an increase in weight is inevitable, but there is a great advantage that the problems of noise and exhaust, which are inevitable in a device that reduces the power of an engine, do not occur.

As an example of the configuration of a conventional electric power unit, there is known one in which a DC motor is operated by a battery to drive a hydraulic pump. Since the DC motor has a large starting torque, it is very advantageous in a construction work vehicle or the like in which the hydraulic actuator is frequently operated and stopped frequently, and is commonly used. Also, an inverter that converts the DC voltage of the battery into an AC voltage and operates the induction motor using an AC current with a frequency that corresponds to the rotational speed of the hydraulic pump that is set according to the amount of operation of the operating lever such as a boom or winch. Electric power units with circuits are also known.

[0005]

However, in the former electric power unit, the number of revolutions of the DC motor changes according to the load torque, and the flow rate of the hydraulic oil discharged from the hydraulic pump cannot be controlled as desired. could not. For this reason, it was not possible to save the flow rate of hydraulic oil that was released as an excess flow rate from the relief valve, and there was a lot of wasted power. In the latter electric power unit, it is easy to control the rotation speed of the electric motor (induction motor) and it is possible to reduce the surplus flow rate by changing it freely, but even if the load is large, the rated capacity of the electric motor is not exceeded. To prevent this, it was necessary to use an electric motor with a large rated capacity. Therefore, the electric motor becomes large in size, and there is a problem that the electric power unit as a whole becomes large in size.

The present invention has been made in view of the above problems, and it is possible to effectively reduce the consumption of the battery, prevent the induction motor that drives the hydraulic pump from becoming large, and reduce the size of the entire unit. It is an object of the present invention to provide an electric power unit having a configuration that can be realized.

[0007]

In order to achieve such an object, an electric power unit according to the present invention is provided with a hydraulic actuator (for example, the undulating cylinder 2 in the embodiment).
3, a telescopic cylinder 31, a swing motor 22, a swing motor 41), a hydraulic pump that supplies hydraulic oil, an induction motor that drives the hydraulic pump, and a rotation speed setting unit that sets the rotation speed of the induction motor (for example, implementation). Of the operating levers 51 to 54 and the rotation speed setting circuit 6 of the controller 60
2), a battery, and an inverter circuit for converting the DC voltage of the battery into an AC voltage and outputting an AC current having a frequency corresponding to the rotation speed of the induction motor set by the rotation speed setting means to operate the induction motor. A rotation speed detection means for detecting the rotation speed of the induction motor (for example, the rotation speed detector S in the embodiment), the magnitude of the alternating current output by the inverter circuit, and the rotation of the induction motor detected by the rotation speed detection means. Output current control means for controlling the output of the alternating current so that the output to the induction motor obtained based on the number does not exceed a predetermined output value (for example, the output control circuit 64 of the controller 60 in the embodiment). And is configured.

In the electric power unit having such a structure, the output of the induction motor does not exceed a predetermined output value, so that the predetermined output value is set to an appropriate value if necessary. By setting it, useless power consumption can be prevented and battery consumption can be reduced. Here, if the above-mentioned predetermined output value is set to the rated capacity of the induction motor, the induction motor will always be used below the rated capacity, so the optimum one according to the load of the hydraulic pump should be selected. Can be used. Therefore, it is not necessary to use a large induction motor having a large rated capacity as in the conventional case, and the entire unit can be downsized. Further, since the induction motor is not subjected to operating conditions of performance or higher, it is possible to avoid unsafe conditions such as slippage and motor stall peculiar to the induction motor.

Further, in the present electric power unit, low consumption mode setting means (for example,
The low-consumption mode setting switch 71, the battery voltage detector 72, the integrated discharge current detector 73, and the low-consumption mode setting circuit 65 of the controller 60) according to the embodiment are provided, and the output current control unit consumes less power by the low-consumption mode setting unit. When the mode is not set, the predetermined output value is set to the rated capacity of the induction motor, and when the low consumption mode is set by the low consumption mode setting means, the predetermined output value is set to be lower than the rated capacity of the induction motor. It is preferable to set it to a low output value. With such a configuration, when the low consumption mode is set by the low consumption mode setting means, the output of the induction motor will not exceed the predetermined output value set lower than the rated capacity of the induction motor. It is possible to prevent unnecessary power consumption and reduce battery consumption.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 2 shows a side view of an aerial work vehicle equipped with the electric power unit according to the present invention. The aerial work vehicle 1 has a loading platform 12 behind a driver's seat 11, and has a truck-type traveling body 10 that travels on roads by tire wheels 13, 13, ..., and a turntable 20 provided on the traveling body 10. The telescopic boom 3 vertically swingably attached to a column 21 extending upward from the swivel base 20.
0 and a workbench 40 for mounting a worker on the tip of the telescopic boom 30.

The swivel base 20 is attached to the rear portion of the traveling body 10 so as to be rotatable 360 degrees about the vertical axis.
It is possible to carry out a horizontal turning operation by hydraulically driving the turning motor 22 built in 0. The telescopic boom 30 has a structure in which a plurality of boom members are assembled in a nested manner, and can be telescopically moved in the longitudinal direction (axial direction) by hydraulically driving the built-in telescopic cylinder 31. A hoisting cylinder 23 is laid between the telescopic boom 30 and the support column 21, and by hydraulically driving the hoisting cylinder 23, the telescopic boom 30 as a whole can be hoisted in the vertical plane.

A vertical post 32, which is always held vertically by the action of a leveling device (not shown), is provided at the tip of the telescopic boom 30, and the workbench 40 is rotatably supported by the vertical post 32. A swinging motor 41 is provided in the workbench 40, and by hydraulically driving the workbench 40, the entire workbench 40 can be swung about the vertical post 32, that is, swung. Since the vertical post 32 is always held vertically as described above, the floor surface of the workbench 40 is always kept horizontal.

Outrigger jacks 14, 14, ... Are provided at the lateral, front, rear, left and right portions of the traveling body 10 so as to extend in the vertical direction. These outrigger jacks 14, 14, ...
Is for holding the traveling body 10 under operation in a stable state, and the piston rod 14a having the pad 14b attached to the lower end thereof can be projected downward to support the traveling body 10 in a lifted state. . Note that each outrigger jack 14 can be used by protruding to the side of the traveling body 10.

The operation of the telescopic boom 30 for ups and downs, extension and retraction, and the swinging motion of the workbench 40 are performed by an operator operating the workbench 40 and an upper operating device 50 installed on the workbench 40.
It can be done by operating the lever. FIG. 1 is a block diagram showing a part of a control system of the aerial work vehicle 1. As shown in FIG. 1, an upper operation device 50 provided on a workbench 40 is instructed to lift and retract the telescopic boom 30. A raising / lowering operation lever 51 for performing the operation, an extension / contraction operation lever 52 for performing an extension / contraction command of the telescopic boom 30, a revolving operation lever 53 for performing a revolving command (of the telescopic boom 30) of the revolving base 20, and a work platform 40. And a swinging operation lever 54 for issuing a swinging command. When the hoisting operation lever 51 is tilted, a command signal for expanding and contracting the hoisting cylinder 23 is output in response to the tilting operation of the hoisting operation lever 51.
When the tilting operation of 2 is performed, a command signal for expanding and contracting the expanding and contracting cylinder 31 is output accordingly. Further, when the turning operation lever 53 is tilted, the turning motor 22 is correspondingly operated.
Is output in the forward and reverse directions. When the swinging operation lever 54 is tilted, a command signal for rotating the swinging motor 41 in the forward and reverse directions is output accordingly.

Each command signal output by operating the operation levers 51 to 54 is input to the valve control unit 61 of the controller 60 provided on the traveling body 10. The induction motor M is used for the oscillating cylinder 23, which is a hydraulic actuator that undulates, extends and retracts, and swivels the telescopic boom 30, the telescopic cylinder 31, the swing motor 22, and the swing motor 41, which is a hydraulic actuator that swings the work table 40. Discharged oil from the driven hydraulic pump P is supplied via the control valves V1, V2, V3 and V4.

The valve control unit 61 of the controller 60 is
Operation levers 51 to 5 performed by a worker on the workbench 40
4 electromagnetically drive the control valves V1 to V4 in accordance with the command signals output by the operation of 4, and the above hydraulic actuators (the undulating cylinder 23, the telescopic cylinder 31, the swing motor 2).
2 and the swing motor 41) are supplied with hydraulic oil. For this reason, an operator who has boarded the workbench 40 can move the telescopic boom 30 up and down, extend and retract by operating a lever from the upper operation device 50.
It is possible to freely control the turning operation and the swinging operation of the work table 40, and it is possible to perform the necessary work by moving the work table 40 to a desired position.

Next, the structure of the electric power unit provided in the aerial work vehicle 1 will be described. As shown in FIG. 1, the present electric power unit includes the above-mentioned hydraulic pump P that supplies hydraulic oil to the above-mentioned hydraulic actuators (the undulating cylinder 23, the telescopic cylinder 31, the swing motor 22, and the swing motor 41), and this hydraulic pump. The aforementioned induction motor M that drives P
And the operation levers 51 to 54 and the controller 60 described above.
Rotation speed setting means including a rotation speed setting circuit 62, a battery B, an inverter circuit 63 of the controller 60,
A rotation speed detector S that detects the rotation speed of the induction motor M and an output current control circuit 64 of the controller 60 are included. The rotation speed detector S not only directly detects the rotation speed of the induction motor M, but also detects the working oil discharge flow rate of the hydraulic pump P, and converts the working oil discharge flow rate to convert the rotation speed of the induction motor M. May be required.

A rotation speed setting circuit 62 of the controller 60
Is a hydraulic actuator (elevating cylinder 23, telescopic cylinder 31, turning motor 22, swinging head) that is an operation target, based on the information on the operation amounts of the operation levers 51 to 54 input via the valve control circuit 61. The hydraulic oil flow rate required to operate the motor 41) at a speed corresponding to the operation amount of the operation lever is calculated, and the rotational speed required for the hydraulic pump P is set from the hydraulic oil flow rate.

Inverter circuit 63 of controller 60
Converts the DC voltage of the battery B into an AC voltage and outputs an AC current having a frequency corresponding to the rotation speed of the induction motor M set by the rotation speed setting means to operate the induction motor M. Specifically, the operation amount of the operating lever is large,
When the rotation speed setting circuit 63 sets a high rotation speed, an AC current of high frequency is output to the induction motor M so that the hydraulic oil discharge flow rate of the hydraulic pump P is increased, and the operation amount of the operation lever is reduced. , Rotation speed setting circuit 6
When the rotational speed of the small value is set in 3, the low-frequency alternating current is output to the induction motor M so that the hydraulic oil discharge flow rate of the hydraulic pump P becomes small. As a result, the discharge flow rate of the hydraulic oil discharged from the hydraulic pump P becomes the minimum flow rate required to operate the hydraulic actuator at the required speed, and the relief valve R provided near the discharge passage of the hydraulic pump P The amount of surplus oil discharged is reduced, and power is wasted.

As shown in FIG. 1, the output current control circuit 64 is supplied with the AC current output from the inverter circuit 63 and the information on the rotation speed of the induction motor M detected by the rotation speed detector S. The output to the induction motor M is calculated based on the magnitude of the alternating current output by the inverter circuit 63 and the actual rotation speed of the induction motor M detected by the rotation speed detector S. The output control of the alternating current output by the inverter circuit 63 is performed so that the output value does not exceed a predetermined output value.

FIG. 3 is a graph showing the relationship between the hydraulic oil discharge pressure of the hydraulic pump P and the hydraulic oil discharge flow rate when the induction motor M is operated within the rated capacity range. The line AB shown in the graph is a portion where the output of the induction motor M becomes the above-mentioned predetermined output value, and is a line showing the constant output state of the induction motor M. Like the path L1 shown in this graph, the operation amount of the operation lever is increased while the hydraulic oil discharge pressure of the hydraulic pump P is constant (that is, the constant load is applied to the hydraulic actuator). The hydraulic oil discharge flow rate of P was increased (the frequency of the alternating current driving the induction motor M was increased), and the output of the induction motor M reached the above-mentioned predetermined output value (indicating a constant output state of the induction motor M). Line), the output current control circuit 64 performs control to increase the frequency of the alternating current (increase the rotation speed of the induction motor M) so that the hydraulic oil discharge flow rate of the hydraulic pump P further increases. Instead, the frequency of the alternating current is maintained even though the operation amount of the operation lever is increased so that the hydraulic oil discharge flow rate at the time when the output of the induction motor M reaches a predetermined output value is maintained. To (and maintain the rotational speed of the induction motor) performs a control to maintain the hydraulic oil delivery rate of the hydraulic pump P constant.

On the other hand, as shown by the route L2 in the graph of FIG. 3, the load increases when the hydraulic oil discharge flow rate of the hydraulic pump P is constant (that is, the hydraulic actuator is operating at a constant speed). If the output of the induction motor M reaches the above-mentioned predetermined output value (reaches the line indicating the constant output state of the induction motor), the output current control circuit 64 maintains the hydraulic oil discharge flow rate up to that point. The output of the induction motor M at the time when the output of the induction motor M reaches the above-mentioned predetermined output value, instead of performing the control for holding the frequency of the alternating current (holding the rotation speed of the induction motor M) as described above. So that the hydraulic oil discharge pressure rises while holding the hydraulic pressure, the frequency of the alternating current is made small (the rotational speed of the induction motor M is made small) regardless of the operation amount of the operating lever being held, Reduce flow rate Performs control of.

As described above, in the present electric power unit, the output of the induction motor M does not exceed the predetermined output value. Therefore, the predetermined output value is set to an appropriate value as necessary. By setting it, useless power consumption can be prevented and consumption of the battery B can be reduced.
Here, if the above-mentioned predetermined output value is set to the rated capacity of the induction motor M, the induction motor M will always be used at the rated capacity or less. Therefore, the optimum value according to the load of the hydraulic pump P is obtained. Can be used. Therefore, it is not necessary to use a large induction motor having a large rated capacity as in the conventional case, and the entire unit can be downsized. Further, since the induction motor M is not subjected to operating conditions of performance or higher, it is possible to avoid unsafe conditions such as slippage and motor stall peculiar to the induction motor M.

Further, as shown in FIG. 1, the electric power unit is provided with a low-consumption mode setting switch 71 which can be operated externally, and the controller 60 is responsive to the operation of the low-consumption mode setting switch 71. The low consumption mode setting circuit 65 for setting the low consumption mode is provided. Here, the output current control circuit 6 of the controller 60
The low consumption mode setting circuit 65 sets the predetermined output value to the rated capacity of the induction motor M when the low consumption mode setting circuit 65 does not set the low consumption mode.
When the low consumption mode is set in, the predetermined output value is set to an output value lower than the rated capacity of the induction motor M. This corresponds to sliding the line AB showing the constant output state of the induction motor M shown in FIG. 3 to the left in the figure (see also FIG. 4).

In the state where the low consumption mode is set, the output of the induction motor M does not exceed the predetermined output value which is set lower than the rated capacity of the induction motor M, so that power is consumed more than necessary. It is possible to prevent the battery B from being consumed and to effectively reduce the consumption of the battery B. In addition,
In this way, the low consumption mode is set by operating the low consumption mode switch 71, for example, when operating the telescopic boom 30, the workbench 40, or the like by inching, or when the operating speed of the hydraulic actuator may be low. Is.

Further, in the electric power unit, as shown in FIG. 1, a battery voltage detector 72 for detecting the voltage of the battery B is provided, and the low consumption mode setting circuit 65 of the controller 60 has this battery. The low power consumption mode is set when the voltage of the battery B detected by the voltage detector 72 is equal to or lower than a predetermined reference voltage. On the other hand, the output current control circuit 64 of the controller 60 sets the predetermined output value to the rated capacity of the induction motor M when the low consumption mode setting circuit 65 does not set the low consumption mode, and the low consumption mode setting circuit 65. When the low consumption mode is set in, the predetermined output value is set to an output value lower than the rated capacity of the induction motor M. Therefore, when the voltage of the battery B becomes lower than the predetermined reference voltage, the output of the induction motor M does not exceed the predetermined output value set lower than the rated capacity of the induction motor M, and the electric power is more than necessary. It is possible to prevent the situation in which the battery is consumed and to effectively reduce the consumption of the battery B.

Further, in the electric power unit, as shown in FIG. 1, an integrated discharge current detector 73 for detecting the integrated discharge current of the battery B is provided, and the low consumption mode setting circuit 65 of the controller 60 is The low consumption mode is set when the integrated discharge current of the battery B detected by the integrated discharge current detector 73 is equal to or greater than a predetermined reference amount. On the other hand, the output current control circuit 64 of the controller 60 sets the predetermined output value to the rated capacity of the induction motor M when the low consumption mode setting circuit 65 does not set the low consumption mode, and the low consumption mode setting circuit 65. When the low consumption mode is set in, the predetermined output value is set to an output value lower than the rated capacity of the induction motor M. Therefore, when the integrated discharge current of the battery B exceeds the predetermined reference amount, the output of the induction motor M does not exceed a predetermined output value set lower than the rated capacity of the induction motor M, which is necessary. As described above, it is possible to prevent the situation in which the power is consumed and effectively reduce the consumption of the battery B. The integrated discharge current detector 7
In addition to directly measuring the discharging current of the battery B and integrating the discharging current, the inverter 3 drives the induction motor M from the inverter circuit 63.
Alternatively, the discharge current of the battery B may be obtained by measuring the AC current output to the battery and integrating the AC current.

Further, in this electric power unit, the low consumption mode setting circuit 65 is also provided when an input for operating a plurality of hydraulic actuators is made at the same time, that is, when a plurality of operation levers 51 to 54 are simultaneously operated. The low consumption mode is set in. This requires a larger amount of hydraulic oil flow to operate a plurality of hydraulic actuators at the same time than when a single hydraulic actuator is operated, the rotational speed of the induction motor M increases, and the output of the induction motor M increases. This is because the rated capacity of the electric motor M may be exceeded.

FIG. 4 is a graph showing how the current consumption of the battery B is reduced by setting the low consumption mode. The broken line in FIG. 4 shows the relationship between the hydraulic oil discharge pressure and the hydraulic oil discharge flow rate of the hydraulic pump P. When the low consumption mode is not set (normal mode), the low consumption mode is set. Both cases are shown. The solid line in FIG. 4 shows the relationship between the hydraulic oil discharge pressure of the hydraulic pump P and the current consumption of the battery B. The low consumption mode is not set (communication mode) and the low consumption mode is set. Both cases are shown. As can be seen from these graphs, the consumption current of the battery B when the low consumption mode is set is suppressed to be lower than the consumption current of the battery B when the low consumption mode is not set.

Although the preferred embodiments of the present invention have been described above, the scope of the present invention is not limited to the above. For example, in the above-described embodiment, the controller 60
As an example of the case where the low consumption mode is set in the low consumption mode setting circuit 65, the low consumption mode setting switch 7
1 is operated, when the voltage of the battery B detected by the battery voltage detector 72 is equal to or lower than a predetermined reference voltage, the integrated discharge current of the battery B detected by the integrated discharge current detector 73. When the input is for simultaneously operating a plurality of hydraulic actuators when the value is greater than or equal to a predetermined reference amount, the low consumption mode may be set by other conditions. Good.

In the above embodiment, the undulating cylinder 22 and the telescopic cylinder 3 are examples of hydraulic actuators.
1, the swing motor 22 and the swing motor 41 are shown.
In addition, a hydraulically driven winch, a booster, etc. provided near the workbench 40 are also included in the hydraulic actuator operated by the hydraulic fluid discharged from the hydraulic pump P. Further, in the above-described embodiment, an aerial work vehicle is exemplified as a target to which the electric power unit according to the present invention is applied, but the electric power unit is not limited to such an aerial work vehicle and other work vehicles, Further, the hydraulic actuator can be widely applied to all things which are driven.

[0032]

As described above, in the electric power unit according to the present invention, since the output of the induction motor does not exceed the predetermined output value set in advance, the output value of the induction motor can be set as required. By setting the value to an appropriate value, it is possible to prevent wasteful power consumption and reduce battery consumption. Here, if the above-mentioned predetermined output value is set to the rated capacity of the induction motor, the induction motor will always be used below the rated capacity, so the optimum one according to the load of the hydraulic pump should be selected. Can be used. Therefore, it is not necessary to use a large induction motor having a large rated capacity as in the conventional case, and the entire unit can be downsized. Further, since the induction motor is not subjected to operating conditions of performance or higher, it is possible to avoid unsafe conditions such as slippage and motor stall peculiar to the induction motor.

[Brief description of drawings]

FIG. 1 is a block diagram showing a part of a control system in an aerial work vehicle equipped with an electric power unit according to the present invention.

FIG. 2 is a side view of the aerial work vehicle.

FIG. 3 is a graph showing an example of a relationship between a hydraulic oil discharge pressure of a hydraulic pump and a hydraulic oil discharge flow rate.

FIG. 4 is a graph showing how the consumption current of the battery is reduced by setting the low consumption mode.

[Explanation of symbols]

1 Aerial work vehicle 22 Swing motor (hydraulic actuator) 23 Lifting cylinder (hydraulic actuator) 31 Telescopic cylinder (hydraulic actuator) 41 Swing motor (hydraulic actuator) 51-54 Operation lever (rotation speed setting means) 60 Controller 61 Valve control Circuit 62 Rotation speed setting circuit (rotation speed setting means) 63 Inverter circuit 64 Output current control circuit (output current control means) 65 Low consumption mode setting circuit (low consumption mode setting means) 71 Low consumption mode setting switch (low consumption mode setting) Means) 72 Battery voltage detector (low consumption mode setting means) 73 Integrated discharge current detector (low consumption mode setting means) B Battery M Induction motor P Hydraulic pump S Rotation speed detector (rotation speed detection means)

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takashi Morota             41-1, Higashimine Sugawa, Shinji Village, Tone-gun, Gunma Prefecture               Aichi Corporation Shinjiko             Inside the hall (72) Inventor Shunichi Nakazawa             41-1, Higashimine Sugawa, Shinji Village, Tone-gun, Gunma Prefecture               Aichi Corporation Shinjiko             Inside the hall (72) Inventor Masao Yoshida             41-1, Higashimine Sugawa, Shinji Village, Tone-gun, Gunma Prefecture               Aichi Corporation Shinjiko             Inside the hall F-term (reference) 3F205 AA05 KA10                 3F333 AA08 AB04 DB07 FA32 FE04                       FE05 FE09 FE10                 5H576 AA06 BB02 BB03 CC04 DD04                       GG02 GG04 HB02 JJ28 LL01                       LL22

Claims (3)

[Claims] 1. A hydraulic pump that supplies hydraulic oil to a hydraulic actuator, an induction motor that drives the hydraulic pump, a rotation speed setting unit that sets the rotation speed of the induction motor, a battery, and a DC voltage of the battery. To an AC voltage, an inverter circuit for operating the induction motor by outputting an AC current having a frequency corresponding to the rotation speed of the induction motor set by the rotation speed setting means, and the rotation speed of the induction motor. Rotation speed detection means for detecting, the output to the induction motor obtained based on the magnitude of the alternating current output by the inverter circuit and the rotation speed of the induction motor detected by the rotation speed detection means is predetermined. And an output current control means for controlling the output of the alternating current so as not to exceed the predetermined output value. unit. 2. The electric power unit according to claim 1, wherein the predetermined output value is set to a rated capacity of the induction motor. 3. A low consumption mode setting means for setting a low consumption mode, wherein the output current control means sets the predetermined output value to the predetermined output value when the low consumption mode is not set by the low consumption mode setting means. The rated capacity of the induction motor is set, and when the low consumption mode is set by the low consumption mode setting means, the predetermined output value is set to an output value lower than the rated capacity of the induction motor. The electric power unit according to claim 1.