Eccentric rotor and vibration motor incorporating the eccentric rotor

1. Field of the Invention

The present invention relates generally to a vibration motor, and more particularly to an eccentric rotor of the vibration motor.

2. Description of Related Art

Mechanical vibrations are required for many different applications. Such as vibrations for material pulverization and selection in industrial use, vibration for home massage machines, and silent notification of incoming calls and messages for mobile phones, are but a few examples of mechanical vibration applications.

There are various methods that can be used to produce mechanical vibrations. One method involves the use of electric motors. A conventional type of vibration motor includes a casing receiving a stator therein, a shaft connected with the stator, and a rotor being rotatably disposed around the shaft. The rotor includes a bearing mounted around the shaft and an eccentric weight attached to the bearing. Vibration is produced by the rotation of the rotor as a result of the eccentric weight attached to the rotor. However, the eccentric weight is usually made of copper. A density of the copper is about 8.9 g/cm 3 , which is too small to enable the eccentric weight to generate a highly satisfied vibration effect.

According to a preferred embodiment of the present invention, a vibration motor includes a housing, a stator received in the housing and a rotor rotatably disposed in the stator. The stator includes two claw-pole assemblies arranged back-to-back, and a shaft fixedly connected with the two claw-pole assemblies. The rotor includes a bearing rotatably mounted around the shaft, a permanent magnet mounted around the bearing, and an eccentric weight fixedly attached to the permanent magnet. The eccentric weight includes a main body and at least one inserting portion having a density higher than that of the main body. The main body is made of plastic, bakelite, aluminum, copper, aluminum alloy or copper alloy, while the at least one inserting portion is made of tungsten or tungsten alloy. The at least one inserting portion is fixed to the main body at position near a periphery of the main body so that the at least one inserting portion is distant from a rotation center of the eccentric weight.

Other advantages and novel features of the present invention will be drawn from the following detailed description of a preferred embodiment of the present invention with attached drawings, in which:

Many aspects of the present vibration motor can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present vibration motor. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views:

FIG. 1 is an isometric, exploded view of a vibration motor in accordance with a preferred embodiment of the present invention;

FIG. 2 is an isometric, assembled view of the vibration motor of FIG. 1 ;

FIG. 3 is an isometric, assembled view of a stator of the vibration motor of FIG. 2 ;

FIG. 4 is an isometric view of an eccentric weight of a rotor of the vibration motor of FIG. 2 ;

FIG. 5 is similar to FIG. 4 , but shows the eccentric weight in accordance with a second embodiment of the present invention;

FIG. 6 shows an isometric view of a third embodiment of the eccentric weight; and

FIG. 7 shows an isometric view of a fourth embodiment of the eccentric weight.

Referring to FIGS. 1-2 , a vibration motor according to a preferred embodiment can be used in a communication equipment, such as a calling machine, a mobile phone or the like, which includes a housing 30 , a stator 10 received in the housing 30 , and an eccentric rotor 20 being rotatably supported by the stator 10 .

The housing 30 is cylindrical-shaped, including a lower portion 30 b and an upper portion 30 a located above and facing the lower portion 30 b . Alternatively the housing 30 can be integrally formed. Each of the lower and upper portions 30 a , 30 b defines a cutout 32 a , 32 b in a free end thereof. When assembled the free ends of the two portions 30 a , 30 b abut against each other, and cooperatively the cutouts 32 a , 32 b define a passage in the housing 30 for connecting the motor with a power source (not shown). It is to be understood that the passage can be only formed in one of the portions 30 a , 30 b of the housing 30 , according to the shape of the stator 10 , for conveniently connecting the motor to the power source.

Also referring to FIG. 3 , the stator 10 includes upper and lower claw-pole assemblies 11 having size and shape the same with each other. Each of the claw-pole assemblies 11 includes an outer yoke 10 a and an inner yoke 10 b facing towards each other. Each of the inner yokes 10 b of the claw-pole assemblies 11 is ring-shaped with a circular hole 14 defined therein. A plurality of pole teeth 16 a , 16 b extend perpendicularly from an inner circumference of each yoke 10 a , 10 b . Each tooth 16 a , 16 b forms an arc-shaped free end. In this embodiment, each yoke 10 a , 10 b forms five teeth 16 a , 16 b . It is to be understood that the number of the teeth 16 a , 16 b formed on the yokes 10 a , 10 b is decided by the precision requirement of the motor, being not limited to the disclosed embodiment. The pole teeth 16 a , 16 b of the yokes 10 a , 10 b are evenly spaced from each other along a circumferential direction thereof and thus define a plurality of slots 19 therebetween. Each pole tooth 16 a , 16 b has a shape and size the same as those of other teeth 16 a , 16 b . Each of the slots 19 has a size a little larger than that of the tooth 16 a , 16 b so as to receive a corresponding tooth 16 a , 16 b therein when the outer and inner yokes 10 a , 10 b are assembled together.

A circular-shaped mounting portion 14 a is formed at a central portion of each of the outer yokes 10 a . Five ribs 18 a extend outwardly and radially from each mounting portion 14 a to connect the mounting portion 14 a with a periphery (not labeled) of the outer yoke 10 a . The ribs 18 a are evenly spaced from each other along a circumferential direction of the mounting portion 14 a and are connected with the periphery of the outer yoke 10 a between each two neighboring teeth 16 a . The mounting portion 14 a has an axis coincidental with that of the outer yoke 10 a . A through hole 141 a is defined in the mounting portion 14 a with an axis coincidental with the axis of the mounting portion 14 a . Several mounting holes 140 a are defined in the mounting portion 14 a around the through hole 141 a and are evenly spaced from each other along the circumferential direction of the mounting portion 14 a . The inner yoke 10 b of each claw-pole assembly 11 forms two apertures 120 therein, and a pair of protrusions 122 . The protrusions 122 of the upper inner yoke 10 b extend downwardly therefrom, while the protrusions 122 of the lower inner yoke 10 b extend upwardly therefrom. The apertures 120 and the protrusions 122 are alternately arranged and evenly spaced from each other along the circumferential direction of the inner yokes 10 a . A pair of pins 13 b are integrally formed with and extend outwardly from an outer periphery of each inner yoke 10 b . The two pins 13 b of each inner yoke 10 b are spaced from and parallel to each other.

Each of the outer yokes 10 a combines with a corresponding inner yoke 10 b to form the claw-pole assembly 11 . The inner yoke 10 b and the outer yoke 10 a of each claw-pole assembly 11 face to each other. The teeth 16 a of each outer yoke 10 a insert into the slots 19 of the corresponding inner yoke 10 b , and the teeth 16 b of each inner yoke 10 b insert into the slots 19 of the corresponding outer yoke 10 a . Thus the pole teeth 16 a , 16 b of the two yokes 10 a , 10 b of each claw-pole assembly 11 are intermeshed with each other. Along the circumferential direction of yokes 10 a , 10 b , the teeth 16 a , 16 b of the outer and inner yokes 10 a , 10 b of the claw-pole assembly 11 are arranged alternatively, and are separated from each other by an electrical angle of 180°. The teeth 16 a , 16 b of the yokes 10 a , 10 b of the claw-pole assembly 11 cooperatively form a cylindrical-shaped sidewall (not labeled) for coils (not shown) wound thereon. A narrow gap is defined between each two neighboring pole teeth 16 a , 16 b . The gaps between the teeth 16 a , 16 b are filled with resin inserted through the mounting holes 140 a of the mounting portions 14 a of the outer yokes 10 a by insert molding; thus, the inner and outer yokes 10 a , 10 b are fixedly combined together to form the claw-pole assembly 11 .

The two claw-pole assemblies 11 are then arranged back-to-back to form the stator 10 of the motor. The circular holes 14 of the inner yokes 10 b cooperatively define a space receiving the rotor 20 therein. The two claw-pole assemblies 11 are located at two opposite upper and lower ends of the motor symmetrically. The inner yokes 10 b of the two claw-pole assemblies 11 abut each other and are located approximately in a middle of the stator 10 . The protrusions 122 of each inner yoke 10 b extend into the apertures 120 of the other inner yoke 10 b to fixedly assemble the two claw-pole assemblies together. The outer yokes 10 a of the two claw-pole assemblies 11 are spaced from each other. The outer yoke 10 a of the upper claw-pole assembly 11 is located at a top end of the stator 10 , whilst the outer yoke 10 a of the lower claw-pole assembly 11 is located at a bottom end of the stator 10 . A shaft 23 is received in the space of the stator 10 with top and bottom ends thereof being fixedly received in the through holes 141 a of the mounting portions 14 a of the outer yokes 10 a of the claw-pole assemblies 11 . An axis of the shaft 23 is coincidental with that of the stator 10 .

The eccentric rotor 20 includes a bearing 22 mounted around the shaft 23 and rotatable in respect thereto, a permanent magnet 26 mounted around the bearing 22 , and an eccentric weight 24 . The bearing 22 is received in the space of the stator 10 and located between the mounting portions 14 a of the outer yokes 10 a . A pair of spacers 25 a , 25 b made of highly abrasion-resistant material are respectively arranged on top and bottom ends of the bearing 22 for avoiding friction or impact between the bearing 22 and the outer yokes 10 a during rotation of the rotor 20 . The permanent magnet 26 is ring-shaped, and is received in the space of the stator 10 . An outer diameter of the magnet 26 is approximately the same as or a little smaller than an inner diameter of the stator 10 . An inner diameter of the magnet 26 is much larger than an outer diameter of the bearing 22 and thus an interspace is defined therebetween. The eccentric weight 24 is received in the interspace and sandwiched between the magnet 26 and the bearing 22 . Alternatively, the eccentric weight 24 can be adhered to an outer surface of the magnet 26 . In this case, the inner diameter of the magnet 26 is approximately the same as the outer diameter of the bearing 22 and adhered to an outer surface of the bearing 22 .

The eccentric weight 24 includes a main body 240 and an inserting portion 244 received in the main body 240 . The main body 240 is made of plastic, bakelite, aluminum, copper or its alloy, including a cylinder 241 mounted around the bearing 22 through interference and a weight 242 integrally formed with the cylinder 241 . The cylinder 241 defines an axial hole 241 a receiving the bearing 22 therein. The weight 242 is substantially arc-shaped, and extends from an outer-periphery of the cylinder 241 . The weight 242 has a height larger than that of the cylinder 241 , and top and bottom ends of the weight 242 are located outside top and bottom ends of the cylinder 241 of the main body 240 . An outer surface of the weight 242 is adhered to an inner surface of the magnet 26 by adhesive. Thus the bearing 22 , the magnet 26 and the eccentric weight 24 are fixedly assembled together. A column-shaped slot 243 is defined in an outer periphery of the weight 242 of the main body 240 . Along a circumferential direction of the weight 242 , the slot 243 is located in a middle portion. The inserting portion 244 has a size and shape the same as that of the slot 243 of the weight 242 . A cross section of the inserting portion 244 along a direction perpendicular to an axial direction thereof is circular shaped. In other words, the inserting portion 244 has a configuration like an elongate, round shaft. When the inserting portion 244 is inserted into the slot 243 , top and bottom surfaces of the inserting portion 244 are coplanar with the top and bottom surfaces of the weight 242 , respectively. The inserting portion 244 is made of tungsten or tungsten alloy, which has a density about 19.36 g/cm 3 and being much larger than that of the main body 240 . The inserting portion 244 is fixedly mounted in the weight 242 of the main body 24 by interferential fit so that the inserting portion 244 rotates with the main body 24 when the motor is in operation. Alternatively, the inserting portion 244 can be fixedly attached to the weight 242 by riveting or soldering.

During assembly, the rotor 20 and the stator 10 are received in the housing 30 . The two claw-pole assemblies 11 are separated from each other by an electrical angle of 90°. The pins 13 b of the two inner yokes 10 b are alternatively arranged; one pin 13 b of each inner yoke 10 b is located between the two pins 13 b of the other inner yoke 10 b . The four pins 13 b are parallel to each other and located at a same plane. Two coils (not shown) respectively wind around the sidewalls formed by the intermeshed pole teeth 16 a , 16 b . Each coil has two ends connected to the two pins 13 b of a corresponding inner yoke 10 b to be electrically connected to the power source. The rotor 20 is rotatably mounted around the shaft 23 . During operation, currents are applied to the coils by the power source. An alternating magnetic field is thus generated by the stator 10 to interact with the magnetic field established by the permanent magnet 26 to drive the rotor 20 of the motor into rotation. As the weight 242 of the eccentric weight 24 is arc shaped, a center of gravity of the rotor 20 is offset from an axis of rotation, thereby vibration is produced due to the eccentricity of weight of the rotor 20 . As the inserting portion 244 has much larger density than that of the main body 240 , the weight of the eccentric weight 24 of the rotor 20 is increased. Accordingly, when the rotor 20 is rotated, the vibration motor in accordance with the present invention will have a better vibration effect. Moreover, since the inserting portion 244 is located adjacent to an outer periphery of the weight 242 which is far from the axis of the rotation, the vibration effect can be enhanced.

FIG. 5 shows an alternative embodiment of the eccentric weight of the rotor of the motor. The difference of the second embodiment over the first embodiment is that the weight 242 a of the main body 240 a of the eccentric weight 24 a defines three slots 243 a therein. The slots 243 a are evenly spaced from each other along the circumferential direction of the weight 242 a . Three inserting portions 244 are respectively received in the slots 243 a . Also the inserting portions 244 are made of tungsten or tungsten alloy to increase the weight of the eccentric weight 24 a and further move a center of weight of the eccentric weight 24 a away from the rotation center. It is to be understood that the number of the inserting portions 244 can be changed according to the vibration intensity requirement of the vibration motor, being not limited to the disclosed embodiments.

FIGS. 6-7 shows the inserting portions of the eccentric weights have different shapes. In these embodiments, the inserting portions 244 b , 244 c of the eccentric weights 24 b , 24 c have cross sections being irregular shaped. Alternatively, the inserting portions 244 b , 244 c can be cones or cuboids. As shown in FIG. 6 , the eccentric weight 24 b includes a cylinder 241 and a weight 242 b . The weight 242 b defines a slot 243 b therein. The inserting portion 244 b is fixedly received in the slot 243 b . The inserting portion 244 b has a shape approximately the same as, but has a size larger than that of the slot 243 b . When the inserting portion 244 b is assembled with the main body 240 b , the inserting portion 244 b has a smaller part extending radially to an outside of the weight 242 b . FIG. 7 shows a fourth embodiment of the eccentric weight. The main body 240 c of the eccentric weight 24 c includes a cylinder 241 c and three weight 242 c extend radially and outwardly from the cylinder 241 c . The cylinder 241 c and the weights 242 c have the same height. The three weights 242 c are evenly spaced from each other along the circumferential direction of the cylinder 241 c and thus define three slots 243 c each between two neighboring weights 242 c . The inserting portion 244 c has a height larger than that of the main body 240 c . When the inserting portion 244 c is mounted into a slot 243 c of the main body 240 c , top and bottom surfaces are located outside top and bottom ends of the main body 240 c.

It is understood that the invention may be embodied in other forms without departing from the spirit thereof. Thus, the present example and embodiment is to be considered in all respects as illustrative and not restrictive, and the invention is not to be limited to the details given herein.