Rotor of electric motor

A rotor of an electric motor including a rotor core, two conductive end plates, a plurality of conductors and a casting metal is provided. The rotor core has a central hole and a plurality of slots surrounding the central hole at a predetermined interval. The two conductive end plates, disposed at two ends of the rotor core, have a plurality of fixing structures, respectively. A plurality of cavities is disposed between two neighboring fixing structures and the shape and the positions of the cavities correspond to that of the slots. The conductors are shaped as long bars and penetrate the slots. Two ends of the conductors are fixed by the fixing structures. The casting metal is injected into the cavities and the slots, and further covers the peripheral of the conductors and the fixing structures, two ends of the rotor core and outside of the two conductive end plates.

This application claims the benefit of Taiwan application Serial No. 104140571, filed Dec. 3, 2015, the disclosure of which is incorporated by reference herein in its entirety.

TECHNICAL FIELD

The disclosure relates in general to an electric motor, and more particularly to a rotor of an electric motor.

BACKGROUND

The most commonly seen electric motor is mainly composed of a rotor and a stator winded with induction coils. The rotor can have many different types and can be formed of different materials. The most common type of the rotor includes copper rotor, aluminum rotor and squirrel-cage rotor. The squirrel-cage rotor generates an induced current through the conductors and is driven to rotate by the induced magnetic field.

Although the copper rotor has high rotor efficiency, the copper rotor is subject to problems such as difficulty in casting and high mold loss. Although the aluminum rotor is easier to cast, the aluminum rotor has higher resistance and higher loss. As for the squirrel-cage rotor, the soldering quality of conductors is unstable, and the casting process still have problems such as the flow of liquid metal being unsmooth, the distribution of the current being non-uniform, and the dynamic balance of the rotor being difficult to calibrate. Thus, how to provide a rotor having satisfactory efficiency and manufacturability and at the same time meeting the high quality requirement has become a prominent task for the industries.

SUMMARY

The present disclosure is directed to a rotor of an electric motor. Each conductor is electrically connected by the end plate disposed on at least one side of the rotor, and the conductor is fixed in the rotor core by the fixing structures of the end plate, such that at least one end of the conductor is fixed on the end plate, the casting metal further covers the two sides of the rotor, and the efficiency and the assembly quality of the rotor can be improved.

According to one embodiment of the present disclosure, a rotor of an electric motor including a rotor core, two conductive end plates, a plurality of conductors and a casting metal is provided. The rotor core has a central hole and a plurality of slots penetrating in the peripheral of the central hole, wherein the slots are disposed on the rotor core at a predetermined interval. The two conductive end plates are disposed at two ends of the rotor core respectively and have a plurality of fixing structures respectively. A plurality of cavities is disposed between two neighboring fixing structures respectively and the shape and the positions of the cavities correspond to that of the slots. The conductors are shaped as long bars and penetrate the slots. The two ends of the conductors are fixed by the fixing structures of the two conductive end plates respectively. The casting metal is injected into the cavities and the slots and further covers the peripheral of the conductors and the fixing structures, the two ends of the rotor core and the outside of the two conductive end plates.

According to another embodiment of the present disclosure, a rotor of an electric motor including a rotor core, a conductive end plate, a plurality of conductors and a casting metal is provided. The rotor core has a central hole and a plurality of slots surrounding the central hole, wherein the slots are disposed on the rotor core at a predetermined interval. The conductive end plate is disposed at one end of the rotor core, and has a plurality of fixing structures. A plurality of cavities is disposed between two neighboring fixing structures respectively, and the shape and the positions of the cavities correspond to that of the slots. The conductors are shaped as long bars and penetrate the slots. One end of the conductors is fixed by the fixing structures of the conductive end plates, and the other end of the conductors is fixed on the rotor core. The casting metal is injected into the cavities and the slots, and further covers the peripheral of the conductors and the fixing structures, the two ends of the rotor core and the outside of the conductive end plate.

The following description is made with reference to the accompanying drawings.

DETAILED DESCRIPTION

A rotor of an electric motor is provided in an embodiment of the present disclosure. The rotor of the electric motor can be a squirrel-cage rotor whose conductors are formed of copper bars or aluminum bars. In general, the squirrel-cage rotor includes a rotor core and a plurality of conductors penetrating the rotor core. The rotor core is a cylinder composed of a plurality of stacked silicon steel plates whose outer diameters are identical. The induction coil wound on the stator generates a rotating magnetic field which drives the squirrel-cage rotor to rotate. When the rotating magnetic field of the stator coil is started up, the rotating magnetic field will cut the conductors of the squirrel-cage rotor and generate an induced current on the conductors. When the squirrel-cage rotor generates the induced current, the induced magnetic field of the squirrel-cage rotor will be generated at the same time, such that the squirrel-cage rotor will be driven by the rotating magnetic field and start to rotate.

According to the rotor of the present embodiment, the end plate disposed on at least one side of the rotor electrically couples to each conductor which is further fixed inside the rotor core by the fixing structure of the end plate, such that at least one end of each conductor is fixed on the end plate, and the casting metal further covers the two sides of the rotor to increase the efficiency and the assembly quality of the rotor.

Detailed descriptions of a rotor of an electric motor are disclosed below. However, the embodiments disclosed below are for explanatory and exemplary purposes only, not for limiting the scope of protection of the present disclosure.

Refer toFIGS. 1 and 2.FIG. 1shows an explosion diagram of a rotor100of an electric motor according to an embodiment of the present disclosure.FIG. 2shows an assembly diagram of a rotor100of an electric motor according to an embodiment of the present disclosure. The rotor100includes a rotor core110, two conductive end plates120and a plurality of conductors130and a casting metal140. In the present embodiment, the two ends of the conductors130are fixed by two conductive end plates120. However, the present disclosure is not limited to the said exemplification. For example, as shown inFIG. 5, in another embodiment, one end of the conductor130can be fixed by one single conductive end plate120, and the other end of the conductor130can be fixed on the rotor core110by the retaining structure or a solder structure; or, one end of the conductor130can be fixed on the rotor core110by way of extrusion deformation.

The rotor core110can be a cylinder composed of a plurality of silicon steel plates110a(only one silicon steel plate is illustrated in the diagram). The rotor core110has a central hole111and a plurality of slots112penetrating in the peripheral of the central hole111and surrounding the cylinder. Each slot112is extended outwards in a radial direction from the peripheral of the central hole111. The slots112are disposed on the rotor core110at a predetermined interval. In an embodiment, the spindle (not illustrated) of the electric motor can be fixed in the central hole111through a snap ring. Besides, the center of each silicon steel plate110ahas a first via111afor forming the central hole111shaped as a long bar, and a plurality of second vias112afor forming the slots112shaped as long bars are disposed in the peripheral of the first via111a. The size and shape of the first vias111aare identical to each other, and the size and shape of the second vias112aare identical to each other.

Moreover, the two conductive end plates120are disposed at two ends of the rotor core110, respectively. The conductive end plates120can be formed of copper or aluminum to increase the conductivity of the conductive end plates120. The two conductive end plates120have a plurality of fixing structures121for fixing each conductor130in a corresponding slot112.

The conductors130can be a copper rod or an aluminum rod, and shaped as a long bar penetrating a corresponding slot112. Each slot112can be a fan-shaped hole. The outer diameter of the conductor130is slightly smaller than the outer width but slightly larger than the inner width of the slot112, such that each conductor130can penetrate a corresponding slot112, and the two ends of the conductor130can be fixed by the fixing structures121of the two conductive end plates120.

Refer toFIGS. 3A and 3B.FIG. 3Ashows a front view of a conductive end plate120and a rotor core100.FIG. 3Bshows a partial enlargement of a region A in theFIG. 3A. As indicated inFIG. 3A, the rotor core110has a central hole111, the center of the conductive end plate120has a hole125, the diameter of the central hole111is smaller than the diameter of hole125, and the central hole111and the hole125have the same central position C. Additionally, the fixing structures121are extended outwards along the radial direction from the peripheral of the hole125, and a plurality of cavities122are disposed between two neighboring fixing structures121, wherein the fixing structures121basically composed of cross-shaped sheets, and the shape and the positions of the cavities122correspond to that of slots112. In an embodiment, each cavity122can be a fan-shaped hole whose inner width w1is smaller than the outer width w2; the fixing position of the conductor130is close to the outside of the cavity122, and the outer diameter of the conductor130is slightly smaller than the outer width w2of the cavity122.

Refer toFIG. 3B. Each slot112is exposed in a corresponding cavity122and slightly smaller than the corresponding cavity122. For example, the ratio of the area of the cavity122to the area of the slot11is larger than 1.3, but the shape and size of each slot112correspond to that of the corresponding cavity122, such that the casting metal140can be injected into the rotor core110in subsequent casting process and the generated pores will be reduced.

Refer toFIG. 3B. Two latches123are disposed oppositely on two neighboring lateral sides (long sides) of the fixing structures121and are protruded towards a corresponding cavity122, such that each conductor130is engaged between the two latches123. In an embodiment, the shape of the two latches123matches the shape of the conductor130. For example, if the outer surface of the conductor130is a circle, each of the two latches123will have an indented surface matching the outer surface of the conductors130, such that the conductors130can be engaged between the two latches123to reduce processing error. Moreover, after the conductor130is engaged between the two latches123, the conductor130can further be fixed by way of soldering to enhance the structural strength. Also, the two conductive end plates120and the rotor core110can be fixed together by the latches or by way of soldering.

As indicated inFIG. 3B, the area of the conductor130is less than ¼ of the area of each slot112, and most area of the slots112can be used as a space allowing the casting metal140to be injected into the rotor core110. The fixing structures121not only fix the conductors130, but further reduce the volume of the rotor100. Thus, the casting metal140can be smoothly injected into the rotor core110and more amount of casting metal140can be injected to fill the slots112.

Refer toFIGS. 3A, 3B and 4.FIG. 4shows a partial cross-sectional view of a casting metal140injected into a rotor100. After the two conductive end plates120, the rotor core110and each conductor130are fixed, the liquid metal (such as liquid aluminum or liquid copper) is injected into the slots112of the rotor core110to form a casting metal140through a rotor injection process. The casting metal140is injected into the rotor core110and further covers the peripheral of each conductor130and the fixing structures121. The casting metal140exposed outside can further cover the two ends of the rotor core110and the outside of two conductive end plates120to reinforce the overall structure of the rotor.

In an embodiment, details of the rotor injection process are disclosed below. Firstly, a rotor assembly is placed into a casting mold. Then, liquid metal is injected into the casting mold from one side of the casting mold and fills up the rotor through the slots112of the rotor core110, and extra liquid metal is drained from the other side of the casting mold. Then, the casting mold is removed after the liquid metal cools and cures, and surface treatment and turning process are applied to the rotor to remove extra parts until the outer diameter of the rotor reaches a predetermined goal. Meanwhile, the two conductive end plates120on the two sides of the rotor100and each conductor130penetrating the rotor core110are covered and fixed by the casting metal140to complete the final rotor product.

According to the rotor of an electric motor disclosed in above embodiment of the present disclosure, the conductors of the rotor are fixed by the fixing structures, and the peripheral of the conductors has larger spaces, such that the casting metal can be uniformly injected into the rotor and the pores can be reduced. Besides, the two conductive end plates disposed on the two sides of the rotor (or the single conductive end plate disposed on one side of the rotor) have better conductivity and more stable quality than the conventional way implemented by solder fixing or aluminum ring, such that the efficiency of the rotor can be increased, and the dynamic balance of the rotor is easier to calibrate, and the current distribution of the conductors inside the magnetized rotor becomes more uniform.