Electric motor
An electric motor design for hub motors comprises a stator assembly, having an axle, a stator plate sector holder, fixed on the axle, at least one stator sector assembly, mounted on the stator plate holder, and electric coils, would around the plates of the stator plate assembly; and a rotor assembly, having a casing, a rotor magnet retainer assembly, placed inside of the casing, and at least one permanent magnet, mounted on plates of the rotor magnet retainer assembly; wherein the stator sector assembly and/or the rotor magnet retainer assembly have plates which are stacked on top of each other and which are each divided into at least two sectors, saving production cost.
This application is a continuation application of U.S. patent application Ser. No. 11/034,662 filed on Jan. 12, 2005.
BACKGROUND OF THE INVENTION1. Field of the Invention
The present invention relates to an electric motor, particularly to an brushless peripheral-rotor electric hub motor in which rotor and stator plates divided in several sections are substituted for a conventional rotor and stator plates in single pieces. Thereby cost of molding and waste material are greatly reduced and unused material of other processes is usable, resulting in a significant cost advantage.
2. Description of Related Art
In conventional art, brushless peripheral-rotor motors, in which rotors are placed outside stators, are widely used in hubs of electric vehicles and washing machines. Motors of this type have inner stators with a plurality of electric coils connected with power. During operation as an electric generator, a rotating external magnetic field results in the generation of electric current. In each motor of this type, the rotor has a larger diameter than the stator and is provided with a plurality of permanent magnets. Usually, the rotor is made of a curved rotor plate in which the stator is inserted. Various ways of placing the permanent magnets in the rotor are used, which are mainly decided by cost. Accurate positions of the permanent magnets in the rotor plate are important for proper functioning of the motor.
There are mainly two conventional methods of making rotors. In the first, a rotor body is made in a single piece on a lathe, with inner peripheral grooves being cut out. Into each of the inner peripheral grooves a permanent magnet is laid. Since cutting of the inner peripheral grooves and automatic inserting of the permanent magnets is difficult, the permanent magnets are usually glued to an inner periphery of the rotor body. This method, however, is expensive and often results in errors of production. Furthermore, since the permanent magnets are glued to metal, magnetic flux is reduced by some degree. In the second method, rotor plates are produced by punching. Using silicon steel leads to better magnetic properties and a higher magnetic flux. Several rotor plates are inserted in a casing. By the rotor having several plates, cutting grooves is facilitated and working is easy. Choosing appropriate shapes for the rotor plates results in good magnetic properties and high effectivity in conjunction with the stator coils. However, since the rotor plates have relatively large diameters, large punching machines are required, and punching produces large quantities of waste material, leading to high cost of production.
SUMMARY OF THE INVENTIONIt is the object of the present invention to provide an electric motor which is easy to produce and which is manufactured at low cost and with little waste material.
The electric motor of the present invention has a stator and a rotor, both of which have plates that are divided into several sectors. The sectors are made by punching at high precision and are automatically assembled, facilitating automatic inserting of permanent magnets.
The present invention can be more fully understood by reference to the following description and accompanying drawings.
As shown in
The stator assembly 10 has a stator axle 11 with two ends that are fastened to a stator frame 12. A stator plate sector holder 13 is by a bolt 131 fixed to the stator axle 11, and is made of material that allows for effective dissipation of heat, like aluminum. Moreover, cooling by gas or liquid is possible to dissipate heat generated in the stator assembly 10 during operation. The stator plate sector holder 13 carries a stator sector assembly 14. Electric coils 15 are wound on plates of the stator sector assembly 14 and on opposite sides fixed thereon. The plates of the stator sector assembly 14 are fastened by bolts 16 or screws on fastening plates 17 on the stator plate sector holder 13. The electric coils 15 are supplied with electric currents through holes 111 in the stator axle 11. Electric current flowing through the electric coils 15 generates a radially oriented magnetic field, which interacts with the magnetic field of the permanent magnets 21. Gaps are left between the electric coils 15 and the permanent magnets 21, so that the permanent magnets 21 are able to move unhindered by the stator sector assembly 14.
The rotor assembly 20 comprises the permanent magnets 21, a rotor magnet retainer assembly 22, and a casing 23. The permanent magnets 21 are mounted on the inward surface of the rotor magnet retainer assembly 22, and the rotor magnet retainer assembly 22 is fitted into the casing 23, forming an integral body. The casing 23 has two sides that are mounted on a shaft 231, allowing the rotor assembly freely to rotate on the stator axle 11. A brake drum 24 is attached to an opposite side of the rotor assembly 20, having a brake shoe (not shown) for stopping a rotating movement of the rotor assembly 20.
In the interaction between the stator assembly 10 and the rotor assembly 20, the permanent magnets 21 are driven by the rotating magnetic field generated by the electric coils 15. On the other hand, if the casing 23 is rotated against the stator assembly 10, the rotating magnetic field of the permanent magnets 21 generates an electric current in the electric coils 15.
Referring to
For each of the rotor plate sectors 221, the protrusions 222 and a recess 223 are of any suitable shape. As shown in
Referring to
Furthermore, each of the stator plate sectors 141 has a fixing hole 147, allowing a bolt or a screw to be led through for fastening the stator plate assembly 14 on the stator plate holder 13.
Referring to
To summarize, the present invention has a stator plate assembly and a rotor magnet retainer assembly having single plates which are further divided into sectors. Production thereof by punching is fast and allows for precise and easy accommodating of permanent magnets. Furthermore, waste material during production is minimized, even waste material from other production processes is usable, so that costs are greatly reduced.
While the invention has been described with reference to preferred embodiments thereof, it is to be understood that modifications or variations may be easily made without departing from the spirit of this invention which is defined by the appended claims.
Claims
1. An electric motor comprising:
- a stator assembly, further comprising a stator axle, a plurality of electric coils, forming a plurality of electric coil magnetic poles, a stator plate holder, fixed on said stator axle, at least one stator plate assembly, mounted on said stator plate holder, having a plurality of stator plates that are stacked on one another in the axial direction, each of said stator plates being divided into at least two stator plate sectors, each of said stator sector plates having at least one elongated alignment ridge diametrically oriented on a first major surface, at least one matching alignment valley opposingly positioned on a second major surface for nesting with said alignment ridge of an adjacent rotor sector plate, thereby maintaining alignment within said stack of stator sector plates, and at least one fixing hole centrally located for fixing the stacked said stator sector plates to said stator plate holder, and at least one of said a plurality of electric coils being wound around said stator plates of said stator plate assembly; and
- a rotor assembly, further comprising a casing, a rotor magnet retainer plate assembly, placed inside of said casing, and a plurality of permanent magnets, forming a plurality of permanent magnet poles, said plurality of magnet poles being substantially equal in number to the number of said plurality of electric coil magnetic poles, mounted on an inward surface of said rotor magnet retainer assembly.
2. The electric motor according to claim 1, wherein said stator plate sectors of said stator plate assembly have edges with mating protrusions and recesses to be mutually fitted.
3. The electric motor according to claim 1, wherein said stator plate sectors of said stator plate assembly have alignment ridges and valleys for stacking plates of said stator plate assembly on each other.
4. The electric motor according to claim 1, wherein said stator plate assembly has seats for holding said electric coils.
5. The electric motor according to claim 1, wherein said stator plate sectors have fixing holes, allowing to be fastened to said stator plate holder by bolts or screws.
6. The electric motor according to claim 1, wherein the number of permanent magnet poles of the rotor magnet retainer plate assembly is 16.
Type: Application
Filed: Mar 24, 2009
Publication Date: Jul 16, 2009
Inventors: Chun-Hsien LU (Hsinchu City), Huan-Lung Gu (Hsinchu), Chi-Tang HSU (Hsinchu City)
Application Number: 12/409,897
International Classification: H02K 1/18 (20060101); H02K 21/22 (20060101);