Stator for AC motor

A stator of an alternating current (AC) motor is disclosed. The stator includes a stator core having a divided structure including and an outer stator core fitted around the inner stator core while being connected to an inner circumference of the inner stator core. The inner stator core has a rotor insertion hole formed at the inner circumference of the inner stator core and a plurality of tooth members arranged in a circumferential direction at an outer circumference of the inner stator core. Since the coils are wound directly on the tooth members through intervals between the neighboring tooth members at the outer circumference of the inner stator core, manufacturing of the stator is facilitated. In addition, since insertion of the coils into the slots is not performed through gaps formed on an inner side of the inner stator core where the rotor insertion hole is formed, the gaps may be minimized. As a result, the performance of the AC motor is improved.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims the benefit of Korean Patent Application No. 2009-0012109, filed on Feb. 13, 2009 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.

BACKGROUND

Embodiments of the present disclosure relate to the structure of a stator for an alternating current (AC) motor, which is capable of improving the performance of the AC motor and also improving the manufacturing efficiency thereof.

2. Description of the Related Art

An alternating current (AC) motor is relatively inexpensive and has a long mechanical life, and therefore has been employed in various fields, for example, as a driving unit for a compressor of a freezing cycle in a refrigerator or an air-conditioner.

The AC motor includes a stator and a rotor. Upon application of electric power to the stator, the rotor is rotated by electromagnetic interaction between the stator and the rotor, thereby converting electric energy into mechanical energy.

The stator is constituted by a stator core, and a coil mounted to the stator core.FIG. 1is a plan view showing a conventional stator core.

As shown inFIG. 1, the stator core1of the AC motor is structured by a plurality of silicon steel plates2all having the same ring shape while being stacked in a plurality of layers along the length of the stator core1.

The stator core1includes a rotor receiving hole1acentrally formed through the stator core1to receive a rotor, and a plurality of slots1barranged around the rotor receiving hole1ato receive coils (not shown), respectively. A tooth member1cis formed in a radial direction between the respective neighboring slots1bso that the coil is wound on each tooth member1cand thereby forms a magnetic path. The coil is inserted in the slot1bthrough a gap1dformed on an inner circumference between the respective neighboring tooth members1cin a direction from the rotor receiving hole1a.

As a width of the gap1dis decreased, core loss and excitation current are reduced, thereby improving the performance of the AC motor. However, according to the conventional structure of the stator core1as described above, the coil is inserted in the slot1bthrough the gap1dformed between the tooth members1c. Therefore, the width of the gap1dneeds to be sufficient for insertion the coil, that is, about at least 1.70 mm in consideration of thickness of the coil.

In order to construct the stator of the conventional AC motor, first, a plurality of the silicon steel plates2are connected in a stacked manner, thereby forming the stator core1. In a state where an insulator (not shown) is mounted at an inner wall of each of the slots1b, the coil is inserted in the slot1b.

When the coil is inserted in the slot1b, the coil cannot be wound directly on the tooth member1cbecause the width of the gap1dis too narrow. Therefore, the coil is rolled into a ring shape in advance at the outside of the stator core1and then is inserted in the slot1bthrough the gap1d. According to such a conventional method, installation of the coil is complicated. As a result, manufacturing of the stator becomes inconvenient.

In order to solve such inconvenience, the gap1dmay be widened so that the coil is directly wound on the stator core1. However, core loss and excitation current will be increased in this case, thereby deteriorating the performance of the AC motor.

Furthermore, after the coils are mounted at the stator core1, a coil trimming process is additionally performed in a manner that the coils drawn along the length of the stator core1and exposed out of the slot1bare tied up using a fixing string, thus completing manufacturing of the conventional AC motor stator. As described so far, manufacture of the conventional AC motor stator has several inconveniences, for example, the coil trimming process additionally required after mounting of the coil.

SUMMARY

Therefore, it is an aspect of the present disclosure to provide a stator for an alternating current (AC) motor, capable of being more conveniently manufactured and improving the performance of the AC motor.

In accordance with an aspect of the present disclosure, a stator for an AC motor includes a stator core having a divided structure comprising an inner stator core and an outer stator core fitted around the inner stator core while being connected to an inner circumference of the inner stator core, the inner stator core having a rotor insertion hole formed at the inner circumference of the inner stator core and a plurality of teeth members arranged in a circumferential direction at an outer circumference of the inner stator core to wind coils thereon, wherein the inner stator core comprises a plurality of layer units stacked in a lengthwise direction while being coupled together, wherein the plurality of layer units comprise ring-shaped integrated layer units each having a plurality of integrally-connected teeth pieces, and separate layer units each having a plurality of separate teeth pieces, the integrally-connected teeth pieces of the integrated layer units and the separate teeth pieces of the separate layer units forming the plurality of teeth members, and wherein the integrated layer units are disposed at opposite longitudinal ends of the inner stator core, and the separate layer units are disposed between the integrated layer units.

The AC motor stator may further include a gap defined between circumferentially-neighboring ones of the teeth members, wherein the gap is twice an air gap defined between a rotor and the rotor insertion hole.

One or two of the integrated layer units may be disposed at each longitudinal end of the inner stator core.

The AC motor stator may further include an insulator connected to the inner stator core so as to insulate the coils from the stator core. The insulator may include guards to support exposed parts of the coils to the outer stator core. The guards may be formed at positions of the insulator corresponding to the inner and outer circumferences of the inner stator core, to extend in a lengthwise direction of the inner stator core.

DETAILED DESCRIPTION

Reference will now be made in detail to the embodiment of the present disclosure, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout.

As shown inFIGS. 2 to 4andFIG. 7, a stator of an alternating current (AC) motor according to the embodiment of the present disclosure includes a stator core10and coils40mounted to the stator core10.

The stator core10has a divided structure constituted by an inner stator core20and an outer stator core30. The inner stator core20includes a rotor insertion hole21formed at an inner circumference of the inner stator core20to receive a rotor, and a plurality of tooth members22circumferentially arranged at an outer circumference of the inner stator core20to wind coils40around the tooth members22. The outer stator core30has a hollow cylindrical shape so that the inner stator core20is fitted in an inner circumference of the outer stator core30. In the inner stator core20, a space defined between neighboring ones of the tooth members22forms a slot23to mount each coil40.

To achieve connection between the inner stator core20and the outer stator core30, connection grooves31are formed on an inner circumference of the outer stator core30for force-fit connection with connection parts22aformed at respective outer ends of the tooth members22of the inner stator core20. A sealing part32is formed between neighboring ones of the connection grooves31of the outer stator core30in order to seal a gap defined between neighboring ones of the connection parts22awhen the inner and the outer stator cores20and30are interconnected.

Therefore, the interval between the neighboring connection parts22aof the inner stator core20may be designed to be wide, irrespective of core loss or excitation current. As a result, the coils40may be wound directly on the tooth members22such that they are inserted into the slots23around the connection parts22a, before the inner stator core20is connected to the outer stator core30. Accordingly, winding of the coils40may be more rapidly performed.

The inner stator core20is formed by stacking a plurality of layer units50and60in a longitudinal direction. Here, the layer units50are disposed at opposite longitudinal ends of the inner stator core20, whereas the layer units60are disposed between the layer units50. The layer units50and the layer units50have different forms from each other, so as to define a gap24having a minimal size between the neighboring tooth members22at the side of the inner circumference of the inner stator core20defining the rotor insertion hole21.

More particularly, the layer units50and60constituting the inner stator core20include integrated layer units50having an integrated ring shape in which a plurality of teeth51are integrally connected, and separate layer units60in which a plurality of separate teeth61are separately and circularly arranged. The teeth51and61of the integrated and separate layer units50and60form the tooth members22.

Each of the integrated layer units50includes the teeth51, which form the tooth members22, and connection parts52each disposed between neighboring ones of the teeth51, to integrally connect the teeth51. The integrated layer units50are disposed at opposite longitudinal ends of the inner stator core20. Each of the separate layer units60includes the teeth61, which are circularly arranged. The separate layer units60are disposed between the opposite integrated layer units50in such a manner that the teeth61correspond to the teeth51. The teeth61forming the separate layer units60, and the integrated layer units50may be manufactured by punching a silicon steel plate according to their shapes. The layer units50and60are stacked and interconnected through caulking.

Reference numerals53and63denote caulking holes for caulking. However, not limited to the caulking, the layer units50and60may be interconnected through welding or bolt-connection.

Thus, in the inner stator core20according to the above embodiment, the gap24between the neighboring tooth members22at the side of the rotor insertion hole21is defined by an interval between the neighboring teeth61of the separate layer units60stacked between the opposite longitudinal ends of the inner stator core20. The separate layer units60are combined with the annular integrated layer units50into an integral body, accordingly constructing the inner stator core20. Therefore, mounting of the coil40in the slot23may be performed through the intervals between the neighboring connection parts22aforming the outer circumference of the inner stator core20. That is, the gap24between the tooth members22may be designed to have a minimal width, without taking into consideration insertion of the coil40. As a consequence, the performance of the AC motor may be improved compared to the conventional art.

The width of the gap24may be twice an air gap defined between a rotor (not shown) and the rotor insertion hole21, in order to maximize the performance of the AC motor. Also, the gap24may be formed merely by adjusting the interval between the teeth61of the separate layer unit60, without a dedicated process. For example, when the air gap formed between the rotor (not shown) and the rotor insertion hole21is about 0.3 mm, the width of the gap24may be about 0.6 mm.

Meanwhile, the integrated layer units50having no gap along the inner circumference become leakage parts where a magnetic path is not formed. In this regard, the number of the integrated layer units50at each longitudinal end of the inner stator core20may be minimized to be, for example, one or two. In the illustrated embodiment, a single integrated layer unit50is provided at each longitudinal end of the inner stator core20.

Referring toFIG. 5andFIG. 6, the stator of this embodiment further includes first and second insulators70and80connected to the stator core10so as to insulate the coils40from the stator core10. For more convenient manufacturing of the stator, the first insulator70includes guards72and73, and the second insulator80includes guards82and83, respectively. The guards72,73,82, and83function to support the coils40, and are connected to the inner stator core20before the inner stator core20is connected with the outer stator core30.

The first insulator70is mounted to one end of the inner stator core20, whereas the second insulator80is mounted to the other end of the inner stator core20. The first and the second insulators70and80include pluralities of first and second insulating members71and81, respectively. The first and second insulating members71and81are arranged in a circumferential direction to surround the tooth members22, except for the outer side where the connection parts22aare formed and the inner side where the rotor insertion hole21is formed.

The first and second insulating members71and81of the first and second insulators70and80surround the tooth members22at respective longitudinal half portions of the inner stator core20. In a state where the inner stator core20is completely coupled, corresponding ones of the first and the second insulating members71and81are in contact with each other at facing ends thereof so that the inner walls of the slot23and the coil40are completely insulated from each other.

The guards72,73,82and83are formed at positions of the insulators70and80, corresponding to the inner and outer circumferences of the inner stator core20, while extending to a predetermined length in a lengthwise direction of the inner stator core20. Each of the inner guards72and82has a single annular structure. The inner guards72and82are arranged at the upper and lower inner circumferences of the inner stator core20, respectively. The outer guards73and83are disposed in plural at the upper and lower outer circumferences of the inner stator core20, respectively, such that they correspond to the first and the second insulating members71and81one by one.

Accordingly, as shown inFIG. 6, when the coils40are wound directly on the tooth members22of the inner stator core20to which the first and the second insulating members70and80are mounted, parts of the coils40exposed outwardly of the slots23in the lengthwise direction of the inner stator core20may be stably supported by the inner guards72and82and the outer guards73and83. That is, it is unnecessary to dedicatedly trim the coils40wound on the inner stator core20. Thus, the stator may be manufactured more efficiently and rapidly.

After the insulators70and80and the coils40are mounted to the inner stator core20, the inner stator core20is connected to the outer stator core30by force-fitting the connection parts22aof the inner stator core20to the connection grooves31of the outer stator core30. Thus, assembly of the AC motor stator is completed.

As is apparent from the above description, in the stator of the AC motor according to the embodiment of the present disclosure, the stator core has a divided structure including and an outer stator core fitted around the inner stator core while being connected to an inner circumference of the inner stator core. The inner stator core has a rotor insertion hole formed at the inner circumference of the inner stator core and a plurality of tooth members arranged in a circumferential direction at an outer circumference of the inner stator core.

According to this structure, a coil may be wound directly on each tooth member through intervals between the neighboring tooth members at the outer circumference of the inner stator core. Therefore, manufacturing of the stator is facilitated.

Furthermore, since insertion of the coils into the slots is not performed through gaps formed at the inner side of the inner stator core where the rotor insertion hole is formed, the gaps may have a minimal size. As a result, the performance of the AC motor is improved.