Single Phase Motor And Electrical Device Using Same

A single phase motor and an electrical device are provided. The single phase motor includes a stator and a rotor. The stator includes a stator core and a winding wound around the stator core. The stator core includes a yoke and two opposed pole portions. Each pole portion includes short and long pole shoes. The rotor is received in a space defined by the short and long pole shoes of the two pole portions. The short pole shoe of each pole portion and the long pole shoe of the opposite pole portion are located adjacent to each other and define a slot opening therebetween. Each pole portion includes the short pole shoe and long pole shoe, which provides the motor with different startup capabilities along the clockwise and counter-clockwise directions.

FIELD OF THE INVENTION

The present invention relates to a motor, and in particular to a single phase motor and an electrical device using the single phase motor.

BACKGROUND OF THE INVENTION

Motors used in conventional ventilation fans are usually Shaded Pole Motors. This type of motor has low efficiency and low power factor, consumes a large amount of copper and iron, and has high cost.

SUMMARY OF THE INVENTION

Thus, there is a desire for a single phase motor and an electrical device using the single phase motor, which can overcome the above-mentioned shortcomings.

In one aspect, a single phase motor is provided which includes a stator and a rotor rotatable relative to the stator. The stator includes a stator core and a winding wound around the stator core. The stator core includes a yoke and two opposed pole portions connected to the yoke. A short pole shoe and a long pole shoe extend from two sides of each pole portion toward the opposite pole portion. The rotor is received in a space defined by the short pole shoes and long pole shoes of the two pole portions. The short pole shoe of each pole portion and the long pole shoe of the opposite pole portion are located adjacent to each other and define a slot opening therebetween.

Preferably, the two pole portions define two slot openings therebetween, and a line connecting centers of the two slot openings is inclined relative to an axis of symmetry of the stator core.

Preferably, the line connecting the centers of the two slot openings is inclined relative to the axis of symmetry of the stator core by an angle of 0 to 30 degrees.

Preferably, end faces of the short pole shoe and long pole shoe of each pole portion facing the corresponding slot openings are parallel to the line connecting the centers of the two slot openings.

Preferably, the long pole shoe of each pole portion has a beveled portion such that a radial thickness of the long pole shoe progressively decreases in a direction toward the corresponding slot opening.

Preferably, each pole portion defines a positioning groove facing the rotor, and the positioning groove is offset from a center of the pole portion and located in an inner surface of the short pole shoe.

Preferably, a bottom of the positioning groove is arc-shaped.

Preferably, an outer circumferential surface of the rotor is located on a same circumference, an air gap with an even thickness is defined between the rotor and inner surfaces of the short pole shoe and long pole shoe of each pole portion.

Preferably, the rotor comprises a rotor main body, the rotor main body comprises a magnetic member mounting bracket and a permanent magnet member, the permanent magnet member is mounted to an outer side of the magnetic member mounting bracket, and an outer circumferential surface of the permanent magnet member is located on a same circumference.

Preferably, an outer profile of the stator core overall is rectangular in shape.

Preferably, an outer diameter of the rotor is 50%-70% of a width of the stator core.

Preferably, the stator core comprises a first core part and a second core part, the two opposed pole portions are respectively integrally formed with a first end of the first core part and a first end of the second core part, and a second end of the first core part and a second end of the second core part are coupled to each other.

Preferably, the second end of the first core part and the second end of the second core part are coupled to each other by a magnetic-conductive connecting piece.

Preferably, two dovetail grooves are defined in the second end of the first core part and the second end of the second core part respectively, two opposite ends of the magnetic-conductive connecting piece are respectively formed with dovetail tenons, and the dovetail tenons are engaged in the dovetail grooves.

Preferably, the rotor comprises a rotary shaft, a rotor main body attached around the rotary shaft, and a buffering device received within the rotor main body. The rotor main body and the rotary shaft have a sliding fit with each other. The buffering device has two ends connected to the rotary shaft and the rotor main body, respectively, for time delay synchronizing rotation speeds between the rotor main body and the rotary shaft.

In another aspect, the present invention provides an electrical device comprising the single phase motor described in any of the above embodiments.

Preferably, the electrical device is a ventilation fan, the ventilation fan comprises an impeller, the impeller is mounted to a rotary shaft of the rotor of the single phase motor.

Preferably, the electrical device is a drain pump or a circulation pump.

In comparison with the prior art, each pole portion of the single phase motor of the present invention includes the short pole shoe and long pole shoe at two sides of the pole portion, thereby providing different startup capabilities along the clockwise direction and counter-clockwise direction. The short pole shoe of each pole portion and the long pole shoe of the other pole portion are located adjacent to each other and define the slot opening therebetween, which facilitates reducing the inductance and strengthening the unidirectional startup capability of the motor.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Below, embodiments of the present invention are described in further detail with reference to the drawings.

Referring toFIG. 1, a ventilation fan500of the present invention includes an impeller300and a motor assembly600. The motor assembly600includes a single phase motor100and a driving circuit. The impeller300includes a mounting portion301mounted to one end of a rotary shaft31of the single phase motor100, so that the impeller300is driven to rotate by the rotary shaft31. In this embodiment, the single phase motor100is a single phase synchronous alternating current motor. In comparison with the traditional shaded pole motor, the single phase motor of the present invention has a compact structure and is convenient to repair and replace. The driving circuit includes a PCB board200mounted to the single phase motor100. In this embodiment, the impeller300is a centrifugal impeller and has an outer diameter significantly greater than the size of the single phase motor100.

Referring toFIG. 2, the single phase motor100of the motor assembly600includes a stator20and a rotor30rotatable relative to the stator20. The stator20includes a stator core21, an insulating bracket22mounted to the stator core21, and a winding23wound around the insulating bracket22. In this embodiment, the PCB board200is mounted to the insulating bracket22adjacent the winding23. Preferably, the PCB board200is mounted to one side of the insulating bracket22facing away from the impeller300. This can make the structure of the single phase motor100more compact and reduce the size of the single phase motor100. In addition, during operation of the impeller300, a low pressure area is formed at a central region of the impeller300, which causes external air to flow to this low pressure area, and the single phase motor100, the PCB board200and the winding23are located in this low pressure area. Therefore, a flow passage exists between the PCB board200and the impeller300, which allows air to flow therethrough. This airflow may flow over and directly cool the PCB board200, thus prolonging the lifespan of the PCB board200. Because the outer diameter of the impeller300is significantly greater than the size of the single phase motor100, the PCB board200can be sufficiently cooled. In an alternative embodiment, the impeller300may also be an axial impeller.

The stator20further includes a first support bracket24and a second support bracket25respectively mounted to two axial sides of the stator core21. The stator core21is made from a magnetic-conductive material. The first support bracket24and the second support bracket25are configured to support the rotary shaft31of the rotor30. The first support bracket24and the second support bracket25are interconnected through an axial connecting mechanism26so as to sandwich the stator core21between the first and second support brackets24,25. In this embodiment, each of the first support bracket24and the second support bracket25is an integrally formed part, which is convenient to fabricate. Bearing seats are disposed in the first support bracket24and the second support bracket25, for mounting of bearings24a,25a(FIG. 7), respectively. The two bearings24a,25asupport the rotary shaft31such that the rotary shaft31is capable of rotating relative to the stator20.

The connecting mechanism26includes a screw261, an associated screw nut262, and a positioning sleeve263. The first support bracket24and the second support bracket25define through holes for allowing the screw261to pass therethrough. The positioning sleeve263is attached around the screw261and disposed between the first support bracket24and the second support bracket25for axially positioning and supporting the first support bracket24and the second support bracket25and improving the appearance.

Referring toFIG. 3, in this embodiment, the insulating bracket22includes a first insulating bracket221and a second insulating bracket226that are integrally formed. The first insulating bracket221and the second insulating bracket226include integrally formed main portions222,227, respectively. Side plates223a,223bare formed at two ends of the main portion222, and side plates228a,228bare fanned at two ends of the main portion227. The main portions222,227are attached around the stator core21. The winding23includes a first winding and a second winding that are wound around the main portions222,227, respectively.

Top ends of one side plate223aand one side plate228aof the first insulating bracket221and the second insulating bracket226form protruding first mounting portions224,229, respectively. Top ends of the other side plate223band the other side plate228bof the first insulating bracket221and the second insulating bracket226form protruding second mounting portions225,230, respectively. The first mounting portions224,229and the second mounting portions225,230are configured for mounting of the PCB board200.

The first mounting portion224of the first insulating bracket221and the first mounting portion229of the second insulating bracket226include support portions224a,229aand connecting members224b,229bdisposed at top ends of the support portions224a,229a,respectively. The support portions224a,229aare flush with the side plates223a,228a.The connecting members224b,229bpass through first through holes of the PCB board200to position and fixedly connect the PCB board200. The top ends of the support portions224a,229aabut against an underside of the PCB board200to support the PCB board200.

The top end of the second mounting portion225of the first insulating bracket221abuts against the underside of the PCB board200to support the PCB board200. The second mounting portion230of the second insulating bracket226includes a support portion233and two parallel connecting members231,232disposed on the support portion233. The support member233abuts against the underside of the PCB board200to support the PCT board200. Ends of the two connecting members231,232are formed with two barbs234, respectively. The two connecting members231,232pass through second through holes of the PCB board200, with the barbs234engaged with a top side of the PCB board200to hold the PCB board200and prevent the PCB board200from becoming loosened.

Referring toFIG. 4, the stator core21includes a generally U-shaped yoke24, and two pole portions211extending toward each other from two opposing side portions of the yoke24. The first insulating bracket221and the second insulating bracket226are mounted to the two opposing side portions, respectively. Each pole portion211includes a short pole shoe211aand a long pole shoe211bextending from two sides of the pole portion211. Because of asymmetry of the pole portion211, the single phase motor100has different startup capability in opposite directions, i.e. the startup capability in one startup direction is greater than the startup capability in the other startup direction. Between the two pole portions211, the short pole shoe211aof each pole portion211and the long pole shoe211bof the other pole portion211are located adjacent to each other and define a slot opening212therebetween. As such, a center of the slot opening212is offset from a center line or an axis of symmetry L2of the stator core21along a length direction of the stator core21. A line L1connecting the centers of the two slot openings212is inclined relative to the axis of symmetry L2by an angle of 0 to 30 degrees. This design facilitates increasing the magnetic reluctance between the two pole portions211, which reduces the inductance, enhances the unidirectional startup capability and working efficiency, and increases the power factor. In this embodiment, end faces of the short pole shoe211aand long pole shoe211bof each pole portion211that face the respective slot openings212are parallel to the line Ll. The long pole shoe211bof each pole portion211has a beveled portion211csuch that a radial thickness of the long pole shoe211bprogressively decreases in a direction toward the respective slot opening212, thereby reducing the inductance and enhancing the unidirectional startup capability of the single phase motor100.

Referring toFIG. 5, the rotor30is received in a space defined by the short pole shoes211aand long pole shoes211bof the two pole portions211. Each pole portion211defines a positioning groove213facing the rotor30. The positioning groove213is offset from a center of the corresponding pole portion211and located away from the corresponding long pole shoe211b.This configuration makes the length difference between the long pole shoe211band short pole shoe211aof each pole portion211even greater, thereby better controlling the stop position of the rotor30to make the stop position of the rotor30offset from a dead point and make it easier for the rotor30to start in one direction than in the other direction. Preferably, a bottom of the positioning groove213is arc-shaped. It should be understood that the bottom of the positioning groove213can also be V-shaped.

An outer circumferential surface of the rotor30is located on a same circumference in an axial plan view of stator100. Inner surfaces of the short pole shoe211aand long pole shoe211bof each pole portion211are inwardly-recessed arc pole faces. The pole faces of the short pole shoe211aand long pole shoe211bare located on a same circumference in the axial plan view of the stator100. The pole faces of the short pole shoe211aand the long pole shoe211bare concentric with the outer circumferential surface of the rotor30, i.e. the pole faces of the short pole shoe211aand long pole shoe211band the outer circumferential surface of the rotor30are all centered at the center of the rotor30. Therefore, an air gap214with an even thickness is defined between the short pole shoe211a,the long pole shoe211band the rotor30, which can improve the smoothness and stability and hence reliability of the startup of the single phase motor100.

In this embodiment, the slot opening212has a width (i.e. a distance between the short pole shoe211aand long pole shoe211bat opposite sides of the slot opening212) greater than a thickness d3of the air gap214.

In this embodiment, the outer profile of the stator core21overall is rectangular in shape. A width of the stator core21is indicated by W, an outer diameter of the rotor30is indicated by D, and the outer diameter D of the rotor30is 50%-70% of the width W of the stator core21. This configuration reduces the size and the cost of the single phase motor100, which makes the single phase motor100more cost-effective.

Referring toFIG. 6, the stator core21is frame shaped with an opening. The stator core21includes a first core part215and a second core part216that are connected by a magnetic-conductive connecting piece217. The main portion222of the first insulating bracket221and the main portion227of the second insulating bracket226are attached around the first core part215and the second core part216, respectively.

A first end215aof the first core part215and a first end216aof the second core part216are respectively formed with dovetail grooves218a,218b.Two opposite ends of the magnetic-conductive connecting piece217are respectively formed with dovetail tenons219a,219b.The dovetail tenons219a,219bare engaged in the dovetail grooves218a,218b,such that the first core part215, the second core part216and the magnetic-conductive connecting piece217are connected and locked. A second end215bof the first core part215and a second end216bof the second core part216form the two opposed pole portions211, respectively.

In this embodiment, both the first core part215and the second core part216are F-shaped.

In an alternative embodiment, both the first core part215and the second core part216are E-shaped.

It should be understood that the first core part215and the second core part216may also be directly connected by engagement between a dovetail groove/dovetail tenon at the first end215aof the first core part215and a dovetail tenon/dovetail groove at the first end216aof the second core part216, without using the magnetic-conductive connecting piece217.

Referring toFIGS. 7 to 9, the rotor30includes a rotary shaft31, a rotor main body32and a buffering device35. The rotor main body32is attached around the rotary shaft31. The rotary shaft31is supported by the two bearings24a,25a.The two bearings24a,25aare located outside two ends of the rotor main body32. The rotor30is rotatable relative to the stator20. The rotor main body32includes a magnetic member mounting bracket33and a permanent magnet member34. The magnetic member mounting bracket33is an injection-molded part. The permanent magnet member34is mounted to an outer side of the magnetic member mounting bracket33, and an outer circumferential surface of the permanent magnet member34is located on a same circumference in an axial plan view of the rotor.

In particular, the rotor main body32and the rotary shaft31have a sliding fit with each other to allow for a rotation speed difference therebetween. The buffering device35is disposed within the rotor main body32and attached around the rotary shaft31. The buffering device35has one end connected to the rotor main body32, and the other end of the buffering device35is connected to the rotary shaft31, for synchronizing with time delay the rotation speeds between the rotor main body32and the rotary shaft31, which can effectively reduce or eliminate the occurrence of the startup failure or stall of the motor100. The buffering device35is disposed in the interior of the rotor main body32and hence one end of the rotary shaft31of the single phase motor100is directly connected to a load, which results in a more compact structure of the motor100and facilitates repairmen and replacement of the motor100.

The magnet member mounting bracket33of the rotor main body32includes a hollow cylindrical portion36, a lower cover37fixedly attached around a lower end of the hollow cylindrical portion36, and a sleeve ring38formed on an upper end of the hollow cylindrical portion36. The hollow cylindrical portion36and the sleeve ring38is injection-molded integral part which can be convenient to fabricate. The permanent magnet member34is formed by two arcuate permanent magnet members34a,34battached to the outer side of the hollow cylindrical portion36. Two bearings32a,32bare respectively mounted within two ends of the hollow cylindrical portion36. The two bearings32a,32bhave a sliding fit with the rotary shaft31, which allows the rotor main body32to freely rotate relative to the rotary shaft31. The buffering device35is disposed between the two bearings32a,32b,which can prevent axial displacement of the rotor main body32.

The sleeve ring38and the lower cover37have opposed grooves, and the groove37aof the lower cover37is opposed to the groove (which is invisible in the figures) of the sleeve ring38. Two ends of the permanent magnet member34are engaged in the grooves to axially position the permanent magnet member34.

The buffering device35includes an elastic member351, and a first connecting base352and a second connecting base353connected to two ends of the elastic member351. The first connecting base352is movably attached around the rotary shaft31, and the second connecting base353is fixedly attached around the rotary shaft31. The hollow cylindrical portion36surrounds an outer circumferential side of the buffering device35. The first connecting base352is connected to the hollow cylindrical portion36. Specifically, in this embodiment, the first connecting base352includes four circumferentially arranged protruding blocks352a,and an inner wall surface of the hollow cylindrical portion36includes grooves36aengaged with the protruding blocks352aso as to connect the first connecting base352to the hollow cylindrical portion36.

The rotor30further includes a limiting ring39fixedly attached to the rotary shaft31and disposed outside one end of the rotor main body32away from the second connecting base353. As such, the two ends of the rotor main body32are respectively position-limited by the second connecting base353and the limiting ring39. During operation of the single phase motor100, the limiting ring39axially limits the rotor main body32, which prevents axial movement of the rotor main body32.

In this embodiment, the buffering device35further includes an elastic sleeve354. The sleeve354is disposed at an inner side of the hollow cylindrical portion36and surrounds an outer circumferential side of the elastic member351. Two ends of the sleeve354are fixedly connected to the first connecting base352and the second connecting base353, respectively. Preferably, the material of the sleeve354is a soft material such as rubber or foamed plastic, which on one hand achieves shock-absorbing and noise reduction results and, on the other hand, prevents the elastic member351from directly striking on the hollow cylindrical portion36when an outer diameter of the elastic member351increases.

In this embodiment, the elastic member351is a helical spring movably attached around the rotary shaft31. When the motor10begins starting, the rotor main body32rotates under the driving of the electromagnetic force of the stator20. One end of the rotary shaft31is directly connected to a load so that the rotary shaft31has a large inertia, and the rotary shaft31has a sliding fit with the rotor main body32. Therefore, at this time, the rotation speed of the rotor main body32is greater than the rotation speed of the rotary shaft31, i.e. a rotation speed difference exists between the rotor main body32and the rotary shaft31. The helical spring is pulled by the rotation of the rotor main body32, such that the end of the helical spring that is connected to first connecting base352is tightened with its inner diameter gradually decreasing. As a result, the end of the helical spring that is connected to the second connecting base353is also gradually tightened, and the rotation speed of the rotary shaft31is eventually synchronous with the rotation speed of the rotator main body32, which effectively reduces the inertia of the single phase motor100brought by the load at the startup. When the motor100stops from an operation state, because of the large rotational inertia of the load, the rotation speed of the rotary shaft31is greater than the rotation speed of the rotor main body32, i.e. a rotation speed difference exists between the rotor main body32and the rotary shaft31, such that the end of the helical spring that is connected to the second connecting base353is gradually loosened with its inner diameter gradually increasing. As a result, the end of the helical spring that is connected to the first connecting base352is also gradually loosened, and the rotation speed of the rotator main body32is eventually synchronous with the rotation speed of the rotary shaft31, such that the load can be effectively reduced. During this course, the sleeve354surrounds the helical spring, which prevents the helical spring from being damaged due to over-increasing of its inner diameter.

The single phase motor100of the present invention has a compact structure and has the advantages of strong unidirectional startup capability, high working efficiency, high power factor and low cost. Therefore, the ventilation fan500using the single phase motor100of the present invention has high working efficiency, low cost and long lifespan.

It should be understood that the single phase motor100of the present invention can also be used in electrical devices having a unidirectional startup requirement of the single phase motor100, such as a warm-air machine, an air conditioner drain pump900, or a circulation pump800(seeFIGS. 11-12).

FIG. 10illustrates an electrical device700using the ventilation fan500of the present invention. The electrical device700includes an outer housing701and a mounting bracket702disposed in an interior of the outer housing701. The ventilation fan500is mounted to the mounting bracket702. The electrical device700using the ventilation fan500of the present invention has high work efficiency, long lifetime and low cost. The electrical device700can be, for example, an air ventilation device, a ventilation and cooling device, a range hood, or the like.