JP3067627B2 - How to drive the earth auger - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for driving an earth auger mounted on a ground excavator.

[0002]

2. Description of the Related Art An excavator is provided with an AC generator, an AC motor for a ground auger driven by the AC generator, and an auger screw driven to rotate by the motor.

[0003] In this case, the output of the AC generator during normal operation is used in a state lower than the rated value, whereas a very large current must flow when the AC motor is started. An alternator with a standard several times the rated capacity is required, and the generator efficiency deteriorates.

It is necessary to change the rotation speed of the auger screw depending on the hard or soft condition of the ground to be excavated. When a conventional induction motor is used, the rotation speed is changed by changing the number of poles of the AC motor. The number, that is, the rotational torque is changed. However, the range in which the number of rotations can be changed is about two steps, and it has been difficult to obtain an optimum rotation speed. That is, since the starting current of the induction motor is several times the rated current, the voltage drop in the power supply is large when the power supply impedance as viewed from the induction motor side is high, and the necessary starting current cannot be flown. There was a drawback that it took time.

[0005] It is an object of the present invention to solve these problems and to be able to operate with a relatively small-scale alternator and to operate the generator with high efficiency.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention relates to an electric power supplied from an AC generator 10.
And by a converter 20 the output voltage can be varied arbitrarily
Te into a stabilized DC power supply, drives the AC motor 40 provided in the ground auger to the DC power supply output via a sine wave <br/> inverter 30, the speed control system 50
Of the converter 20 based on the rotation speed setting data of
Output voltage and output voltage of sine wave inverter 30
This adopts a configuration in which the wave number is changed to a desired value .

[0007]

FIG. 1 is a block diagram showing an embodiment of the present invention, in which a three-phase AC generator 10, a converter (constant voltage rectifier) 20 and a three-phase inverter (variable AC conversion) are shown. ) 30 and a three-phase induction motor 40. Converter 20 is a device that converts the output of three-phase AC generator 10 into a DC power supply. The converter 20
Is composed of a rectifier 21 and a controller 22, and the output voltage of the converter 20 can be set by the controller 22. If it is necessary to change the setting of the control unit 22 to a voltage corresponding to the frequency of the three-phase inverter 30, the setting can be made by a command from the rotation control device 50 as necessary. I have.

The converter 20 is a device for supplying DC power to the three-phase inverter 30 for generating a three-phase AC sine wave power supply as described above. Supply from the energy stored in When the energy is insufficient, the voltage drops, and the control unit 22 operates to operate the rectification unit 21.
It has a negative feedback function that controls so that more power can be supplied from. Therefore, the output voltage of converter 20 is maintained at a constant value, and a voltage drop can be prevented. That is, since the output voltage of the converter 20 is held by the negative feedback function, the internal impedance of the power supply is equivalently reduced, and the output voltage of the converter 20 is maintained at a constant value even with an overcurrent at the time of starting or the like. Can be held.

The three-phase inverter 30 is a device for converting the DC power of the converter 20 into a three-phase AC sine wave power. 3
Examples of the phase inverter 30 include a sine wave inverter such as a multiplex phase modulation type and a pulse width modulation type, including the simplest rectangular wave inverter. Here, the induction motor 40 is a simple
When driven by an AC power supply based on the voltage output of a square-wave pulse, an impact torque is generated, and in addition to the problem of becoming a vibration source, the power factor is deteriorated, and effective torque cannot be obtained. Requires a current generator and inverter. Therefore, even a three-phase rectangular wave inverter having different purposes of the present invention
Therefore, it cannot be adopted. Therefore, the third embodiment
As the phase inverter 30, the pulse is proportional to the sine wave change.
A modulating sine wave inverter, such as the above three-phase sine wave
A pulse width modulation type inverter is applied.

The three-phase inverter 30 includes a frequency controller 31,
It comprises a function generator 32, a waveform generator 33, and an output circuit 35. The frequency and voltage data of the three-phase inverter 30 are sent from the rotation speed controller 50 to the frequency controller 31. The frequency controller 31 calls out the frequency and voltage data designated by the rotation speed control device 50 from the data stored in the function generator 32 and supplies them to the waveform generator 33. The waveform generator 33 converts the DC power of the converter 20 into a sine wave of the designated data according to the instruction of the frequency controller 31 and removes the high frequency component via the output circuit 34 to the three-phase induction motor 40. Then, the three-phase induction motor 40 is rotated.

The rotation speed control device 50 comprises a rotation speed controller 51 and a rotation speed setting device 52. The rotation number setting device 52 is a dial type or the like,
Alternatively, it can be set by the synchronous speed of the three-phase induction motor 40 or the like. The signal from the rotation speed setting device 52 is converted into a signal by the rotation speed controller 51 and supplied to the frequency controller 31 of the three-phase inverter 30. If the DC voltage supplied to the three-phase inverter 30 is also changed, necessary data is also supplied to the control unit 22 of the converter 20 at the same time. Thus the operator when the time to change the rotation of the 3-phase induction motor 40 is set to the rotational speed desired by operating the rotational speed controller 52, the data is three-phase inverter 30
It sent in the frequency controller 31 Rutotomoni, converter 2
The three-phase inverter 30 is fed simultaneously to the control unit 22 of 0 is changed to the power supply frequency and the desired voltage, it is possible to easily change the rotational speed of the three-phase induction motor 40.

FIG. 2 shows a voltage waveform of a power supply according to an embodiment of the present invention. AC is a one-phase voltage waveform of the three-phase AC generator 10, DC is a voltage waveform of the converter 20, and AC1 is a one-phase voltage waveform of the three-phase inverter 30.
At a frequency higher than the power supply frequency of the phase alternator 10,
2 indicates a low frequency. Even if the converter 20 and the three-phase inverter 30 as a load of the converter require a large amount of current in a short time, the output voltage operates to maintain a constant voltage by negative feedback. In other words, converter 20 has 3
Also serves as a buffer function between the phase AC generator 10 and the three-phase inverter 30.

[0013]

According to the present invention, since the rotation speed can be continuously changed, the operation can be performed at a rotation speed suitable for the excavated object. Furthermore, there is no reduction in motor efficiency due to an increase in the number of poles, and there is no impact torque or torque ripple due to the square wave inverter,
It can be operated without any problems with a generator with a capacity standard that is about several percent higher than the motor standard to be used.

That is, according to the present invention, the operation can be performed in a state of high efficiency close to the standard of a normal generator, and the operation cost is reduced. Furthermore, since the rotation speed suitable for the hardness of the ground to be excavated can be selected, work efficiency is increased, energy is saved, and the economic effect is large.

[Brief description of the drawings]

FIG. 1 shows an embodiment of the present invention in a block diagram.

FIG. 2 shows a power supply waveform of each unit according to the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 AC generator 20 Converter (constant-voltage rectifier) 30 Inverter 40 AC motor (3-phase induction motor) 50 Revolution control device

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) E21B 3/02 E21B 7/00 H02M 3/00-3/44

Claims (1)

(57) [Claims] An electric power supplied from an AC generator is output.
Voltage is converted to a stabilized direct-current power supply by any variable can converter and drives AC motor provided in the ground auger to the DC power supply output via a sine wave inverter
Both are based on the speed setting data from the speed controller.
Output voltage of said converter and a sine wave inverter
Changing the output voltage and output frequency of the
Characteristic method of driving earth auger.