Hybrid induction motor

A hybrid induction motor comprises a stator fixedly installed in a casing, an induction rotor rotatably inserted into a center of the stator and having a shaft at a center thereof, a first synchronous rotor slid in a longitudinal direction of the shaft between the stator and the induction rotor and free-rotatably installed in a circumferential direction of the shaft, and a second synchronous rotor facing the first synchronous rotor, slid in a longitudinal direction of the shaft between the stator and the induction rotor, and free-rotatably installed in a circumferential direction of the shaft.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a hybrid induction motor, and more particularly, to a hybrid induction motor capable of improving a starting function and facilitating to implement a variable speed rotation.

2. Description of the Background Art

A hybrid induction motor refers to a motor in which a permanent magnet (hereinafter, will be referred to as a ‘synchronous rotor’) is free-rotatably installed between a stator and an induction rotor thus to be electro-magnetically coupled thereto.

FIG. 1is a longitudinal section view showing a hybrid induction motor in accordance with the conventional art, andFIG. 2is a sectional view taken along line I-I ofFIG. 1.

As shown, in a conventional hybrid induction motor10, a stator11is fixedly-disposed at an inner side of a casing10a, and a synchronous rotor14is rotatably disposed at an inner side of the stator11. An induction rotor13is rotatably disposed at an inner side of the synchronous rotor14. Also, a rotation shaft15for outputting a rotation force of the induction rotor13outwardly is press-fit into a center of the induction rotor13.

The stator11is formed of a laminated silicon steel, and a plurality of slots16afor winding a driving coil16that generates a rotating magnetic field are formed at an inner circumferential surface of the stator11.

The synchronous rotor14comprises a magnet portion14afreely rotatable between the stator11and the induction rotor13, a magnet support portion14bfor supporting the magnet portion14a, and a bearing portion14cfor supporting the magnet support portion14bto freely rotate around the rotation shaft15.

The induction rotor13is formed as a squirrel cage rotor comprising a plurality of through holes13aformed in the laminated silicon steel with, conductive bars13binserted into each through hole13a, and end rings13cformed at both ends of each conductive bar13b. An unexplained reference numeral15adenotes a shaft bearing.

An operation of the conventional hybrid induction motor will be explained.

Once a rotating magnetic field is formed as a first current is sequentially applied to the driving coil16of the stator11, the synchronous rotor14is synchronized by the rotating magnetic field thereby to be rotated at a synchronous speed. A magnetic flux generated from the magnet portion14aof the synchronous rotor14serves as a rotating magnetic field of the induction rotor13, so that the induction rotor13is rotated.

Herein, the rotation shaft15coupled to the induction rotor13is rotated together with the induction rotor13thereby to transmit a rotation force to other components such as a fan.

However, in the conventional hybrid induction motor10, a single synchronous rotor is implemented under a state that a magnetic flux density of an air gap between the induction rotor and the synchronous rotor is almost constant. Therefore, a starting torque of the synchronous rotor14is not sufficient, and thus a great current has to be applied to the driving coil16at the time of an initial driving of the induction motor.

Furthermore, even if a voltage applied to the driving coil16is varied, a varied amount of the magnetic flux density of the air gap is reduced, resulting in a difficulty in speed-varying the induction motor. Accordingly, an efficiency of the motor is degraded and the motor has limited functions.

BRIEF DESCRIPTION OF THE INVENTION

Therefore, an object of the present invention is to provide a hybrid induction motor capable of lowering a starting current required to start a synchronous rotor and thus enhancing an efficiency thereof.

Another object of the present invention is to provide a hybrid induction motor capable of varying a rotation speed of an induction rotor.

To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided a hybrid induction motor, comprising: a stator fixedly installed in a casing; an induction rotor rotatably inserted into a center of the stator and having a shaft at a center thereof; a first synchronous rotor slid in a longitudinal direction of the shaft between the stator and the induction rotor and free-rotatably installed in a circumferential direction of the shaft; and a second synchronous rotor facing the first synchronous rotor, slid in a longitudinal direction of the shaft between the stator and the induction rotor, and free-rotatably installed in a circumferential direction of the shaft.

The first synchronous rotor comprises a first support portion to a center thereof a shaft is rotatably coupled, a first magnet portion coupled to an end of the first support portion in a circumferential direction and rotated by a rotating magnetic field of the stator for rotating the induction rotor, and a first bearing portion disposed at the center of the first support portion for inserting the shaft.

The second synchronous rotor comprises a second support portion to a center thereof a shaft is rotatably coupled, a second magnet portion coupled to an end of the second support portion in a circumferential direction and rotated by a rotating magnetic field of the stator for rotating the induction rotor, and a second bearing portion disposed at the center of the second support portion for inserting the shaft.

The first bearing portion is an oilless bearing, the first support portion is a non-magnetic substance, the second bearing portion is an oilless bearing, and the second support portion is a non-magnetic substance.

The first support portion and the first magnet portion are integrally formed, and the second support portion and the second magnet portion are integrally formed.

A length of the first magnet portion in a shaft longitudinal direction is relatively longer than a length of the second magnet portion in a shaft longitudinal direction.

The first magnet portion of the first synchronous rotor and the second magnet portion of the second synchronous rotor can maintain a predetermined gap therebetween by an intermediate part, or an end of the first magnet portion and an end of the second magnet portion can come in contact with each other.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, a hybrid induction motor according to the present invention will be explained with reference to the attached drawings.

FIG. 3is a longitudinal section view showing a hybrid induction motor according to a first embodiment of the present invention,FIG. 4is a sectional view taken along line II-II ofFIG. 3,FIG. 5is a perspective view showing a synchronous rotor and an induction rotor in the hybrid induction motor according to a first embodiment of the present invention,FIGS. 6 to 8are schematic views showing each position of a first synchronous rotor and a second synchronous rotor at the time of starting and speed-varying the hybrid induction motor according to a first to embodiment of the present invention, andFIG. 9is a longitudinal section view showing a hybrid induction motor according to another embodiment of the present invention.

As shown, a hybrid induction motor according to a first embodiment of the present invention100comprises a stator110fixedly installed in a casing110a, an is induction rotor120rotatably inserted into a center of the stator110and having a shaft121at a center thereof, a first synchronous rotor130slid in a longitudinal direction of the shaft121between the stator110and the induction rotor120and free-rotatably installed in a circumferential direction of the shaft121, and a second synchronous rotor140facing the first synchronous rotor130, slid in a longitudinal direction of the shaft121between the stator110and the induction rotor120, and free-rotatably installed in a circumferential direction of the shaft121.

A coil winding portion116for winding a driving coil111of the stator110so that the stator110can have a polarity of an N pole or an S pole is formed at one side of the stator110.

A hole123for inserting the shaft121is formed at a center of the induction rotor120, and a plurality of conductive holes124are formed at an outer periphery portion of the induction rotor120with the same interval in a circumferential direction. A conductive bar125is installed at the conductive hole124.

The conductive bar125is formed by a die casting, and is formed of aluminum or copper. An end ring125aformed of aluminum is formed at the end of the conductive bar125.

The first synchronous rotor130comprises a first support portion131to a center thereof the shaft121is rotatably coupled, a first magnet portion133having a cylindrical shape and coupled to the end of the first support portion131in a circumferential direction thus to be rotated by a rotating magnetic field of the stator110for rotating the induction rotor120, and a first bearing portion135disposed at the center of the first support portion131for inserting the shaft121.

The second synchronous rotor140comprises a second support portion141to a center thereof the shaft121is rotatably coupled, a second magnet portion143having a cylindrical shape and coupled to the end of the second support portion141in a circumferential direction thus to be rotated by a rotating magnetic field of the stator110for rotating the induction rotor120, and a second bearing portion145disposed at the center of the second support portion141for inserting the shaft121.

The first magnet portion133and the second magnet portion143are respectively constructed to have a plurality of poles. The first magnet portion133and the second magnet portion143are respectively mounted in a radial direction. An N pole and an S pole are alternately formed at the first magnet portion133and the second magnet portion along each circumferential direction.

A length of the shaft121of the first magnet portion133in a longitudinal direction is relatively longer than a length of the shaft121of the second magnet portion143in a longitudinal direction.

The first support portion131and the first magnet portion133are integrally formed by a molding, and the second support portion141and the second magnet portion143are integrally formed by a molding.

Preferably, the first bearing portion135and the second bearing portion145are respectively formed of an oilless bearing so that the shaft121can be smoothly rotated.

An end133aof the first magnet portion133and an end143aof the second magnet portion143come in contact with each other. Under a state that the end133aof the first magnet portion133and the end143aof the second magnet portion143come in contact with each other, the first synchronous rotor130and the second synchronous rotor140can be slid in a longitudinal direction of the shaft121and can be free-rotatable in a circumferential direction of the shaft121.

A first air gap (t1) is formed between the first synchronous rotor130and the stator110, and a second air gap (t2) is formed between the first synchronous rotors130and the induction rotor120.

Hereinafter, an operation of the hybrid induction motor according to the first embodiment of the present invention will be explained with reference toFIGS. 3 to 8.

Once a rotating magnetic field is formed as a first current is sequentially applied to the driving coil111of the stator110, the first synchronous rotor130and the second synchronous rotor140are synchronized by the rotating magnetic field thereby to be rotated at a synchronous speed.

A magnetic flux generated from the first magnet portion133and the second magnet portion143serves as a rotating magnetic field of the induction rotor120, so that the induction rotor120is rotated. An output of the induction rotor120is transmitted outwardly through the shaft121fixed thereto.

Before the first synchronous rotor130and the second synchronous rotor140are synchronized, the first synchronous rotor130and the second synchronous rotor140are rotated up to a speed prior to a synchronous speed with a state except states shown inFIGS. 6 and 7where each pole of the first synchronous rotor130and the second synchronous rotor140are arbitrarily facing each other.

When the firs synchronous rotor130and the second synchronous rotor140have been synchronized, a voltage applied to the driving coil111is great and thus a magnetic force from the stator110is much greater than an attractive force between different poles of the first synchronous rotor130and the second synchronous rotor140. In this case, as shown inFIGS. 6 and 7, the first synchronous rotor130and the second synchronous rotor140are facing to each other with a state of N-N and S-S or a state of N-S and S-N, and are rotated at a synchronous speed. Herein, the rotating magnetic field formed at each inner side of the first synchronous rotor130and the second synchronous rotor140becomes maximum, and thus the induction rotor120has a maximum rotation speed.

On the contrary, when a voltage applied to the driving coil111is less and thus a magnetic force from the stator110is not greater than an attractive force between different poles of the first synchronous rotor130and the second synchronous rotor140, the first synchronous rotor130and the second synchronous rotor140are rotated at a synchronous speed with same poles thereof being overlapped a little as shown inFIG. 8. Herein, the rotating magnetic field formed at each inner side of the first synchronous rotor130and the second synchronous rotor140becomes weak, and thus the induction rotor120has a decreased rotation speed.

In the hybrid induction motor according to the first embodiment of the present invention, if the rotating magnetic field generated from the driving coil111is weak while a state conversion fromFIG. 6intoFIG. 7is performed, the first synchronous rotor130and the second synchronous rotor140are alternately synchronized with the rotating magnetic field of the driving coil111. Accordingly, the number of poles of the first synchronous rotor130and the second synchronous rotor140is increased by approximately two times. As the result, the rotating magnetic field for rotating the first synchronous rotor130and the second synchronous rotor140at a synchronous speed can be greatly lowered at the time of an initial driving of the hybrid induction motor. In a process that the first synchronous rotor130and the second synchronous rotor140are alternately synchronized, vibration can be generated in a direction of the shaft121. However, the vibration can be prevented by controlling a shaft-direction length of an intermediate270part that will be later explained or a shaft-direction length of an over hang portion130aof the first synchronous rotor130, that is, a portion exposed more outwardly than the stator110.

FIG. 9is a longitudinal section view showing a hybrid induction motor according to another embodiment of the present invention.

As shown, in a hybrid induction motor200according to another embodiment of the present invention, a first magnet portion233of a first synchronous rotor230and a second magnet portion243of a second synchronous rotor240can have a predetermined gap therebetween by an intermediate part270. Preferably, the intermediate part270is a non-magnetic substance.

One surface of the intermediate part270is fixed to an end233aof the first magnet portion233, and another surface of the intermediate part270is in contact with an end243aof the second magnet portion243.

An operation of the hybrid induction motor according to another embodiment of the present invention is the same as that of the hybrid induction motor according to the first embodiment of the present invention, and thus its detail explanation will be omitted.

In the hybrid induction motor having a double permanent magnet structure according to the present invention, a starting current is greatly lowered at the time of initially driving the hybrid induction motor thus to reduce noise and to enhance an efficiency of the motor. Furthermore, since a magnetic flux of the synchronous rotor is varied according to a variation of an applied voltage, a rotation speed of the hybrid induction motor can be freely varied and thus the hybrid induction motor can be applied to various products.